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[ { "answer_id": 8500, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 3, "selected": false, "text": "<h2>First, a lot of setup</h2>\n\n<p>For this answer I have to make a lot of assumptions about how AI's work vs. how organic brains work. I find the most meaningful answer coming from a quad chart based on two ways of valuing a \"thing.\" They're certainly not the only two ways to value things, but they prove useful for me when thinking about AI.</p>\n\n<p>I chart value of objects on how well an object behaves when it works \"as defined,\" and how well an object behaves when it works \"out of spec,\" (i.e. when you ask it to do something you don't think it's \"expected\" to do, how well does it keep up)</p>\n\n<pre><code> Out of Spec Behavior\n Poor | Good\n +---------+-------------+\nAs Good | Tool | Interesting |\nDefined ------+---------+-------------+\nBehavior Poor | Crude | Resilient |\n +---------+-------------+\n</code></pre>\n\n<ul>\n<li><strong>Crude things are not good at anything.</strong> They fall apart with use, and are generally not very good at adapting to new situations. The modern human category of \"child's toys\" fits in this block.</li>\n<li><strong>Tools are amazingly good at what they do best.</strong> Once we devise a tool, and understand its abilities, they prove amazingly good at accomplishing goals. However, they are often very narrowly focused, unable to adapt to changing environments. A helicopter can fly in ways that are a marvel to behold, as long as they are kept within spec. However, on Everest, humans climb higher than any helicopter can go because the air is too thin. There was a famous rescue on the lower slopes of Everest where a helicopter pilot decided it was worth the risk, but refused to land at that altitude for fear the machine would not be able to take off again. He instead hovered just a few feet off the snow, carefully feeling for a sign that the helicopter was leaving its spec range.</li>\n<li><strong>Resilient objects just keep working, against all odds.</strong> Some systems are not known for their ability to perform in ideal conditions, but in unpredictable dangerous environments where one does not get to prepare. Survival gear tends to fall in this category. As one example, there is a military technique nicknamed \"dummy cording\" where you discard the core out of some parachute cord (to save weight) and use the outer sheaths to tie your gear to yourself so that it stays around in times of great exhaustion. Parachute cord was <em>never</em> designed for this operation, but its construction is so resilient that it turns out to be useful, even after you've taken the strong part out.</li>\n<li><strong>Interesting objects keep our attention with their behavior.</strong> When we try to use them \"in spec\" as tools, they function perfectly, beating our wildest expectations. When we have to use them \"out of spec,\" they keep surprising us by never failing, even when submitted to environmental conditions far outside of their \"operating environment.\" Military equipment often fits in this category. Consider the famous pictures of <a href=\"http://realitypod.com/2011/03/helicopter-static-electricity-phenomenon-explained-corona-effect/\">helicopter halos</a> in the desert from sand hitting the rotors, or the A-10's legendary ability to fly, <a href=\"http://www.strangemilitary.com/images/content/109862.jpg\">even after taking hundreds of round</a>s. Even those who understand the physics of what is happening and the design decisions that lead to it are awed by it at first sight.</li>\n</ul>\n\n<p><strong>All four of these categories are relative to the observer.</strong> A Swiss watchmaker would draw the boundaries differently than an Amazon tribal elder would.</p>\n\n<p><strong>I put forth an (unproven) hypothesis that AI's and organic brains take a different path through this quad chart.</strong></p>\n\n<ul>\n<li><p>If you believe in evolution, Organic Life consists of all of the really good random discoveries genetics found over millions of years. Along the way, each of these ideas are subjected to a remarkable number of varying scenarios. The ones that survive are ones which improve survivability, but more importantly are versatile enough to be useful in thousands of unexpected situations. <strong>Organic life improves itself by trying to go from Crude to Resilient to Interesting.</strong></p></li>\n<li><p>AIs are generally computer programs. Programs were originally tools. Currently our programmers are very good at making computers do astonishing things in spec, but we are not very good at making the computers do good things when we surprise the printer. This is the source of great frustration for any IT person who has to explain why the user's input wasn't \"spec,\" so the computer is failing. AI seeks to be more and more versatile, handling situations the programmer did not think of. <strong>AI improves itself by trying to go from Crude to Tool to Interesting.</strong></p></li>\n</ul>\n\n<p><strong>As an over-generalization, I will assume your biological and AI centric human civilizations will continue to develop along these general principles.</strong></p>\n\n<p><strong>The most obvious effect of these two paths is that the AI centric civilization will want to change its environment more drastically than the biological based one will.</strong> This is because a intermediate grade AI is a Tool, which means it works well when you can apply it \"in spec.\" The easiest way to make sure these Tools function is to change the face of the world so that it is easier for a user of the AI Tool to be confident that its use is \"in spec.\"</p>\n\n<p>Biological based civilizations will be less inclined to change their environment. In fact, if the environment is complicated and hostile, it makes it easier to ensure all of its creations are Resilient. Your biological civilization will be fine with a world where they can never tell if their creations are operating \"in spec,\" because that isn't as important to their civilization. They would easily create amazing creations, but their amazingness would show up in the resiliency of their designs. You wouldn't see a bio-jetpack that can be used once to assault an AI tower through an unprotected ledge, but you might see a jetpack that can be used continuously, and has uses for fanning the eggs of young creatures in hot summers. <strong>This isn't because the giant brains can't figure out how to make such a one-shot device, but rather because the giant brains wont <em>want</em> to make such a device. They've been raised to look for more resilient solutions.</strong></p>\n\n<hr>\n\n<h2>Now for the mixing and the war</h2>\n\n<p>We will assume each side has a strong cultural identity: they believe their approach is superior enough to distinguish \"us\" from \"them.\"</p>\n\n<p>From the biological perspective, there will be only one possible response to mixing: increase the complexity of the environment. If they are fearful of the AIs, then they will seek to make \"them\" unable to progress. A complicated environment means it's harder to tell that Tools are operating \"in spec,\" limiting AI's ability to leverage all of its creations. On the other hand, if they seek to coexist with the AIs, the they need a way to make the AI's robust like their culture. To do this, they would wrap the AIs in environments that are designed to appear simple to the AIs (letting them use their tools), but on the outside, such environments are highly resilient (so the Biological can make sure their friendly AIs never face complicated out-of-spec environments).</p>\n\n<p>From the AI perspective, there is also only one possible response to the mixing: simplify the complexity of the environment. If they are fearful of the Biologicals, then they will seek to achieve a strategic advantage by paving over all of the complexities of the Biological environment. If they seek to coexist with the Biologicals, then they will need to develop a common ground where they can safely interact with Biology without fear of going out of spec.</p>\n\n<p>So from both perspectives, there is a natural desire to segregate. The most Interesting AIs will seek out the most predictable regions far away from the Biologicals, to make sure they are never driven \"out of spec.\" The most Interesting Biological creatures will seek out the deepest most complex natural regions of their area, far away from the AIs, to make sure that any dangerous Tools are blunted by the journey to their home.</p>\n\n<p>The middle will be colonized by a mix of Tools and Resilient creatures which have to seek out their own living after the most Interesting creatures take the prime real estate. The more you want to minimize the mixing, the more you need the young Tools to look up to the intelegence of their Interesting AI masters, and the more you need the young Resilient creatures to look up to the wisdom of their Interesting organic elders. It would be up to you as an author to decide how far you want to take that.</p>\n\n<hr>\n\n<p>However, consider that such mixing may not be such a bad thing. Consider that your average adult cannot compete with the wisdom of an elder. Consider that your average sword cannot compete with the awesome capabilities of a firearm. But give an average adult a sword, and put it in a realm with wise-but-unarmed elders, and firearm wielding-but-mindless drones on the other side, and suddenly they just might be able to hold their own.</p>\n\n<p>And darn shame if after millennia of conflict over who the <em>rightful heirs</em> to humanity are, if a group of humans which are viewed as Crude by both AI and Biological masters alike can suddenly stand in the middle of these two great forces and proclaim them heirs to <em>both</em> of their lineages.</p>\n\n<h2>Balancing the Game</h2>\n\n<p>Very often we assume that AI's will naturally win over Biology, but there's some argument for why that isn't naturally so. <strong>AI's are better at solving small, well defined problems. Biology is better at solving vague large problems.</strong> Consider the health of an ant colony. If we want to kill an ant colony, its not hard. We put some ant-killer down, let them eat it, and laugh in our superiority.</p>\n\n<p><em>The ants laugh too.</em> By biomass, they outweigh all humans together and are found on nearly every type of terrain on this planet. The ants are far less concerned with the loss of one colony. <em>Maybe they are winning?</em></p>\n\n<p>Interaction between AI and Biology would consist strongly of the AI side striking for a small well defined goal with a superior force, and capturing it virtually every time. However, the Biologicals would seek to make it a Phyric victory. They want the AIs to win the battles but lose the war. Their tactics would involve letting the AIs get what they want, but making sure that in each battle, they give more than they capture. Biologicals would excel at giving up a township, and using that to misplace the AI armies and sac an AI city in trade.</p>\n\n<p>The AIs would try to predict their behavior, and that's where the real balance would lie. Biology is highly chaotic. It is virtually impossible to predict what a mind will think of next. Chaos is the enemy of AI planning. You can't apply logic to it, because the purpose of moving chaotically is that it is impossible to tell if an attack is going to be a minor skirmish or a major war. <em>Not even the Biologists would know which it would be, until the last moment.</em> That's where the Biologists can return the balance to even.</p>\n\n<p>There is a fighting style where you set up your self and your environment such that you don't prevent your opponent from doing anything, and you don't commit to anything. You just make sure that you get a slight advantage no matter what they do. Then you wait. Due to a lot of math I wont put here, I've found this is <em>much</em> easier to accomplish with Biology (focusing on Resilience) than it is to accomplish with AI (focusing on logic and Tools). Biology would give the AI a few billion options, all of which look good, but each of which is flawed. The AI would have to analyze each of them, while the Biology knows that it doesn't need to. Whatever path the AI chooses, Biology is ready.</p>\n\n<p>This technique is very dependent on chaotic behavior. If the AI chooses to do nothing, then their predictions become exponentially less accurate, which is brutal for long term planning. This technique forces the AI to make a choice, without giving it time to make the choice wisely.</p>\n" }, { "answer_id": 8509, "author": "tls", "author_id": 3278, "author_profile": "https://worldbuilding.stackexchange.com/users/3278", "pm_score": 0, "selected": false, "text": "<p>The two cultures (hardware and wetware) can trade in products. It would also be to their benefit for their scientists/academics to consult each other.</p>\n\n<p>Cooperation and interdependence is a lot more beneficial for both cultures anyway. </p>\n\n<p>It would even be interesting if you have a third culture that combines both philosophies. I'm going to borrow a word from the documentary \"I videogame\" and call them \"culture breakers\". They will do what culture breakers do - pull bounderies or blur the bounderies of these two philosophies.</p>\n\n<p>They would be generally (but not exclusively) young people willing to try new things.</p>\n" }, { "answer_id": 8510, "author": "jamesqf", "author_id": 3545, "author_profile": "https://worldbuilding.stackexchange.com/users/3545", "pm_score": 0, "selected": false, "text": "<p>I was going to ask just one question - what to your AIs actually WANT? - but then I realized that it could just as easily be asked of your biotech culture, too. I think that if you can come up with plausible answers, you'll have most of the answer. </p>\n\n<p>One of many possibilities is that the AIs see the Biotechs as a threat, and want to exterminate them. Another is that the AIs are perfectly happy to stay in their underground silicon caverns, and want to control the Biotechs in order to keep the electric supply stable.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/8498", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/1991/" ]

[ { "answer_id": 8661, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 5, "selected": true, "text": "<p><strong>Invent a new religion!</strong></p>\n\n<p>I'm not joking. The world you have described is very very very black and white: literally \"everything is Good, except the shadow, which is Evil.\" This limits the amount of color you can put in your story.</p>\n\n<p>Your shadow needs a weakness. In particular, here is a quad chart showing what happens when you mix good and evil</p>\n\n<pre><code> Good Evil\n +------+-------+\n Good | Good | Evil |\n +------+-------+\n Evil | Evil | Evil |\n +------+-------+\n</code></pre>\n\n<p>As you can see, by your description of \"once the shadow infects an area, it becomes nothing\" is an indomitable ability. That claim needs to be broken down in order to have Good ever stand a chance.</p>\n\n<p>One bright solution is to bring in Chaos. Make the effect of mixing good and evil less predictable. If you mix black paint into white paint thoughtfully, it looks grey or black (depending on how much black you used). However, in the moments of mixing, you see swirls of black and swirls of white, unmixed. It is not unfathomable that after mixing Good and Evil, some swirls of Good remain, they're just hard to spot.</p>\n\n<p>This forms the backdrop for what you really need: a new religion of balance. You intentionally have set up the Shadow to be ridiculously strong, so it will be hard for you to sell to your readers the idea that somehow humanity magically turns it back with a perfect plan. We're going to need something murkier.</p>\n\n<p>Consider a new caste of individuals who are comfortable with a balance of Good and Evil, rather than merely worshiping Good. They can live off of the borders between them. These individuals would be able to see shades of grey, not just black and white. This ability would give them the ability to penetrate into the Evil Shadow for quite some time before losing their balance and being corrupted absolutely. If they could find the \"core\" of the Shadow, and instil one dollop of good in the center, it could weaken the shadow dramatically.</p>\n\n<p>This would also generate political drama. The forces of Good could never appreciate what Those Who See Grey think, but they also would recognize that these individuals are the key to survival. The frustration of a perfectly good King having to trust a Grey individual would be palpable.</p>\n\n<p>But the shadow would also seek out these Greys. They are not necessarily harder to corrupt or easier, just different. When corrupting good, the shadow must patiently wait in the dark, and strike when Good's defenses are down. With the Greys, it would be more of a continuous press, slowly trying to gain a foothold in their mind by making the Grey confused as to what is the Shadow, and what is the Grey itself (a confusion that is easier to have when Grey than Good).</p>\n\n<hr>\n\n<p>As a possible source of this new Grey caste, consider the effects of an imperfect strike from Good onto Evil, or an imperfect corruption of Good by Evil. Both could create a mix which could create a sense of Grey. After all, The Shadow better make a mistake somewhere, or it really is too powerful of an opponent.</p>\n" }, { "answer_id": 8665, "author": "Darth Hunterix", "author_id": 3254, "author_profile": "https://worldbuilding.stackexchange.com/users/3254", "pm_score": 3, "selected": false, "text": "<p>Starve the bastard!</p>\n\n<p>If I understand correctly, The Shadow feeds by corrupting humans, and corrupted humans are only capable of evil. That excludes them from simple, mundane tasks, like harvesting food, sewing, cleaning up after themselves... </p>\n\n<p>In other words, of the Good People manage to put some barrier between themselves and the land already claimed by the Shadow, and then use their magic to put themselves into 20 year slumber, two things will happen:</p>\n\n<ol>\n<li>Human servants of The Shadow will die, since their only souce of food and medicine will disappear</li>\n<li>The Shadow won't have anybody to corrupt, so it won't have a power source, and eventually run out of juice.</li>\n</ol>\n\n<p>How to build such a wall is up to you.</p>\n\n<p>I see from your comment to the other answer, that you want some boy form other world. Maybe you can make him some visionary engineer? We actually have a deficit of those in the real world, so maybe you'll inspire some young people to study math a bit harder :)</p>\n" }, { "answer_id": 8693, "author": "Sigma Ori", "author_id": 2253, "author_profile": "https://worldbuilding.stackexchange.com/users/2253", "pm_score": 2, "selected": false, "text": "<p>If it's a cosmic entity, defeat it in a cosmic way!</p>\n\n<p>Say the entity has consumed half the planet. You can make the people of the people discover some kind of ancient magic that keeps their world together. Then, have them break that magic and <a href=\"https://www.google.gr/search?q=aion&amp;client=opera&amp;hs=oj1&amp;source=lnms&amp;tbm=isch&amp;sa=X&amp;ei=czq2VIWdEJT1apH1gogP&amp;ved=0CAgQ_AUoAQ&amp;biw=1366&amp;bih=660#tbm=isch&amp;q=aion%20planet\" rel=\"nofollow\">split the world in two</a>. </p>\n\n<ul>\n<li>This doesn't defeat the point of an eldritch abomination, which is to be so much beyond humanity that it can't be fought by conventional means.</li>\n<li>It doesn't eradicate the horror, since the Shadow can still make a comeback after a long while, if it finds a way to cross to the other half of the planet.</li>\n<li>Since the splitting magic will definitely be something arcane, you can have huge conflicts between the peoples of your world about whether they can and whether they should move forward with this.</li>\n<li>You will have an interesting setting to play with, in the stories between the initial \"defeat\" of the Shadow and its comeback- if you intend to write any.</li>\n</ul>\n" }, { "answer_id": 192028, "author": "Alendyias", "author_id": 80953, "author_profile": "https://worldbuilding.stackexchange.com/users/80953", "pm_score": 0, "selected": false, "text": "<p>If Druids can influence or control natural elements, I may have a solution: <strong>malachite.</strong>\nYou see, malachite is known for trapping evil spirits. Your Shadow is the archetypal evil spirit, so if the Druids work together, they may be able to trap the Shadow in a giant malachite crystal. Then you'll have to be able to defeat it.</p>\n<p>What if it's not someone dropping <em>Good</em> into the Shadow's core that beats it, but rather changing its paradigm? Paradigm=perspective, this Shadow clearly has a strong connection to people, so it's possible enough people with a strong perspective on &quot;the beauty of nature&quot; or the &quot;meaning of life&quot; could change its mindset and therefore its actions.</p>\n<p>The genius of this is after the Shadow's eyes are (figuratively) open to how beautiful the world is compared to nothingness, it'll want to <em>preserve</em> the world as is, or maybe try to create a different version of the current world that better reflects its dark nature but isn't a &quot;plain of absolute nothingness.&quot;</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/8652", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/5216/" ]

[ { "answer_id": 8824, "author": "JohnP", "author_id": 5260, "author_profile": "https://worldbuilding.stackexchange.com/users/5260", "pm_score": 4, "selected": true, "text": "<p>It has to do with how the planets were formed, as the gas cloud that surrounded the sun coalesced when it was a protostar.</p>\n\n<p>It is explained rather well here:\n<a href=\"https://astronomy.stackexchange.com/questions/130/why-do-the-planets-in-our-solar-system-orbit-in-the-same-plane\">https://astronomy.stackexchange.com/questions/130/why-do-the-planets-in-our-solar-system-orbit-in-the-same-plane</a></p>\n\n<p>A protoplanetary disc is a rotating disc of gas surrounding a newly formed star. When the star is forming out of a molecular cloud, as it condenses it averages out random motion of the gas in favor of the net angular momentum of the nebula.</p>\n\n<p>Conservation of angular momentum causes the ball of gas that formed the protostar to flatten out and take the shape of a disc (like a ball of pizza dough becoming a flat shape when spun, it flattens and spreads out).</p>\n" }, { "answer_id": 8825, "author": "bowlturner", "author_id": 19, "author_profile": "https://worldbuilding.stackexchange.com/users/19", "pm_score": 2, "selected": false, "text": "<blockquote>\n <p>1) Are planets in the same altitude level?</p>\n</blockquote>\n\n<p>The planets orbiting our sun are all in the same plane. meaning they make a disc with rings.</p>\n\n<blockquote>\n <p>2) What defines altitude in the space (universe)?</p>\n</blockquote>\n\n<p>The closest I can think of what you mean is distance from the sun. closer and farther orbits</p>\n\n<blockquote>\n <p>3) Is the universe a XYZ plane?</p>\n</blockquote>\n\n<p>The universe is multidimensional, but yes basic space has the 3 basic axis. </p>\n\n<blockquote>\n <p>4) What keeps planets from orbit the sun in a 45º orbit from Earth's perspective?</p>\n</blockquote>\n\n<p>Some thing called the <a href=\"http://en.wikipedia.org/wiki/Invariable_plane\" rel=\"nofollow\">Invariable Plane</a> </p>\n\n<blockquote>\n <p>The invariable plane of a planetary system, also called Laplace's invariable plane, is the plane passing through its barycenter (center of mass) perpendicular to its angular momentum vector. In the Solar System, about 98% of this effect is contributed by the orbital angular momenta of the four jovian planets (Jupiter, Saturn, Uranus, and Neptune). The invariable plane is within 0.5° of the orbital plane of Jupiter,<a href=\"http://en.wikipedia.org/wiki/Invariable_plane\" rel=\"nofollow\">1</a> and may be regarded as the weighted average of all planetary orbital and rotational planes.</p>\n</blockquote>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/8823", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/6522/" ]

[ { "answer_id": 9839, "author": "James Westman", "author_id": 3535, "author_profile": "https://worldbuilding.stackexchange.com/users/3535", "pm_score": 2, "selected": false, "text": "<p>This already exists (although not exactly the way you described it). It is called a <a href=\"http://en.wikipedia.org/wiki/Sonic_weapon\" rel=\"nofollow\">sonic weapon</a>, and it uses sound.</p>\n\n<p>Sound is just a pressure wave. These weapons shoot sound at opponents. Really big ones knock people over; big ones cause weird effects because of the vibration in internal organs; small ones make really annoying noises.</p>\n\n<p>AFAIK these are currently experimental and not available to the public. However, they are definitely possible to build and use. They seem somewhat portable (if you have a vehicle to put it on), but as they are still experimental, they will probably shrink over time.</p>\n" }, { "answer_id": 9840, "author": "Ville Niemi", "author_id": 3434, "author_profile": "https://worldbuilding.stackexchange.com/users/3434", "pm_score": 3, "selected": false, "text": "<p>What you are describing is essentially what happens in <a href=\"http://en.wikipedia.org/wiki/Steam_explosion\">steam explosions</a>. The word to note is <strong>explosion</strong>. The damage done is relative to the speed the pressure increases since otherwise the rate of gas escaping and the rate of gas increasing find a balance at some much lower level. So if you want to weaponize air pressure, you pretty much have to use an explosion of some sort. A practical example of a weapon like that is a <a href=\"http://en.wikipedia.org/wiki/Hand_grenade#Concussion\">concussion grenade</a>. <a href=\"http://en.wikipedia.org/wiki/Thermobaric_weapon\">Fuel air explosives</a> also have some of the features you want.</p>\n\n<p>Similar effects can happen without explosion if the pressure outside falls fast enough. This can happen with tornadoes. An artificial effect that can cause the same effect is a <a href=\"http://en.wikipedia.org/wiki/Firestorm\">firestorm</a>.</p>\n" }, { "answer_id": 9841, "author": "Dan Smolinske", "author_id": 5002, "author_profile": "https://worldbuilding.stackexchange.com/users/5002", "pm_score": 2, "selected": false, "text": "<p>Since you <em>literally</em> asked for it...</p>\n\n<p><strong>FTL</strong></p>\n\n<p>Take portable wormholes that can be turned on or off. So for example you'd have a circle A that would connect to another circle B, instantaneously at any distance.</p>\n\n<p>The first option is obvious - put one end in space, throw the other at someone and open it. Instant vaccuum as air is sucked out.</p>\n\n<p>Second option - put one in a high-pressure chamber you control, you can now release instant high-pressure atmosphere anywhere the other end is at.</p>\n\n<p>But let's go further down the rabbit hole. It's not strictly <em>air</em> pressure, but put a really tiny one at the bottom of the ocean (a couple of miles down). Now open it, water will shoot at at incredibly speeds and give you a portalable <a href=\"http://en.wikipedia.org/wiki/Water_jet_cutter\" rel=\"nofollow\">water knife</a>.</p>\n\n<p>Connect one end to the inside of a steam engine, you can now boil people on-demand.</p>\n\n<p>If they're tough enough, let's put one inside the outer edges of the sun...</p>\n\n<p>Ok, enough of that. More realistically you should go with:</p>\n\n<p><strong>Heat / Cold</strong></p>\n\n<p>Air pressure is largely a function of air temperature. Any technology that would let you pull heat from the air, or put heat into the air quickly, will let you also rapidly change air pressure, giving you the effects you describe (bursting windows either out or in, for example).</p>\n" }, { "answer_id": 9844, "author": "Serban Tanasa", "author_id": 3510, "author_profile": "https://worldbuilding.stackexchange.com/users/3510", "pm_score": 5, "selected": true, "text": "<p>Such weapons exist and are called thermobaric bombs. They do rely on chemical reactions to trigger the overpressure blast though. Oh, and it doesn't blast out just the windows, the walls too... Sorry about that.</p>\n\n<p>A thermobaric explosive works by having the initial blast spread fuel in the targeted area, and then a secondary charge ignites the cloud. This achieves a longer burn and much higher temperatures than a regular plastic explosive. In doing do the high temperatures end up creating a devastating overpressure wave that does most of the damage. This is particularly effective in closed areas such as caves, bunkers or buildings. How does this work? Well, the easiest clue is the ideal gas law:</p>\n\n<pre><code>pV=nRT\np is pressure\nV is volume\nn is the number of moles\nR is the universal gas constant\nT is temperature (K)\n</code></pre>\n\n<p>So higher temperature, ceteris paribus, yields higher pressure. A regular explosion has an overpressure wave too, it's very sharp but very short. For a thermobaric weapon, the pressure builds, builds, and just doesn't stop, until much, much later. It's a bit like the difference between getting punched and a very close encounter with a 300lbs lineman. See a Chinese weapon in action:</p>\n\n<p><img src=\"https://i.stack.imgur.com/cbBzS.jpg\" alt=\"thermobaric bomb\"></p>\n\n<p>Jane's dryly describes it thus:</p>\n\n<blockquote>\n <p>Its effectiveness against buildings, bunkers is noted, as well as the\n fact that because the blast takes oxygen from the air, personnel in\n the airtight space suffocates because of the oxygen deficit.</p>\n</blockquote>\n\n<p>These weapons were initially developed by the Soviets, who developed man-portable versions such as the <a href=\"http://en.wikipedia.org/wiki/RPO-A_Shmel\" rel=\"nofollow noreferrer\"><em>РПО-А Шмель</em></a> <code>RPO-A Shmel</code> and the <em>ТОС-1 - тяжёлая огнемётная система</em> <code>TOS-1 Heavy Flamethrower \"Buratino\"</code> missile launcher. These were used by the Russians to level Grozny in 1999. \n<img src=\"https://i.stack.imgur.com/uNuJz.jpg\" alt=\"Russian pinnochio\"></p>\n" }, { "answer_id": 9915, "author": "bowlturner", "author_id": 19, "author_profile": "https://worldbuilding.stackexchange.com/users/19", "pm_score": 2, "selected": false, "text": "<p>One weapon I haven't seen mentioned yet that police and others use when storming a house are <a href=\"http://en.wikipedia.org/wiki/Stun_grenade\" rel=\"nofollow\">flash-bangs</a>, they are using a bright flash and a concussion/loud noise (fast change in air pressure) made from rapidly expanding explosion to blind and deafen and disorient those in an enclosed space. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/9837", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/6724/" ]

[ { "answer_id": 12045, "author": "Neil", "author_id": 557, "author_profile": "https://worldbuilding.stackexchange.com/users/557", "pm_score": 4, "selected": false, "text": "<p><a href=\"http://en.wikipedia.org/wiki/Mad_Max\">Mad Max</a> was based in the \"not-too-distant\" future, and I think they got it right, in the sense that technologies that prove useful are still in the know-how, such as how to ride a motorcycle or fire guns. Ideas like cities and airplanes were painted as the stuff of legends. Of course, it wasn't specified how long in the future, so we're left with a guess.</p>\n\n<p>Though I would argue that only two generations would be sufficient time to arrive at a point such that Mad Max would have been possible. Most people don't know how to build electronics or get a power plant back online. It would only take a generation to lose all this technical knowledge. It would take only one more for what basic knowledge we have to also become lost, and for only technologies that we need to survive to remain.</p>\n\n<p>This is highly speculative of course, but if you think about it, cities are only able to exist due to existing technology. You would see mass chaos in cities if electricity dropped, and shortly thereafter it would become unsustainable. Cities would quickly become abandoned save for a few scavengers. After two generations, most would have burnt down or it would be absent of anything useful for the taking. Future generations would wonder if it were even possible to have so many people living in such small spaces. </p>\n\n<p>So too would be things we take for granted such as computers, telephones, elevators. All of these things without electricity and without knowing how they work would seem like magic if they somehow could get them to work. </p>\n" }, { "answer_id": 12075, "author": "Philip Oakley", "author_id": 7953, "author_profile": "https://worldbuilding.stackexchange.com/users/7953", "pm_score": 2, "selected": false, "text": "<p>In the right scenario it can be very fast. A specialist company, or industry, closes and the methods are lost very quickly as usually the necessary knowledge is not in the hands of a single individual, but in the whole team, and once split, it's gone.</p>\n\n<p>Have a look at the various industrial archaeology projects to see what knowledge folk are trying to re-discover (e.g. how to create the original Sheffield steel)</p>\n" }, { "answer_id": 12076, "author": "David Rice", "author_id": 7547, "author_profile": "https://worldbuilding.stackexchange.com/users/7547", "pm_score": 2, "selected": false, "text": "<p>Almost all knowledge right now is institutional and dispersed. </p>\n\n<p>For example - nobody - not a single person (and to a lesser extent, not a single company) knows how to build a working computer from the ground up. </p>\n\n<ul>\n<li>The people who refine the metals and materials do not know how to build a chip. </li>\n<li>The people who know how to design semiconductors don't know how to design a CPU. </li>\n<li>The people who design the CPU don't know how to manufacture the CPU. </li>\n<li>The people who manufacture the CPU don't know how to program a general-purpose OS. </li>\n<li>Very few people who design OS's know how to also build a working networking server. </li>\n<li>Etc. </li>\n</ul>\n\n<p>If the internet were somehow destroyed (say, a global catastrophe that eliminated electronic communication for some time) I would guess that the knowledge would be lost within 10-30 years, via atrophying skills and deaths of the greybeards.</p>\n" }, { "answer_id": 12086, "author": "Sobrique", "author_id": 3131, "author_profile": "https://worldbuilding.stackexchange.com/users/3131", "pm_score": 2, "selected": false, "text": "<p>It's quite hard to say exactly, because it depends a lot on how advanced the tech is. Bear in mind a lot of artisan crafts were passed on master-apprentice for many generations. Clockwork for example, is hundreds of years old.\nSteam power, combustion, even the transistor - aren't <em>technically</em> very difficult. So keeping it alive as an artisan craft I think would be very feasible. </p>\n\n<p>However our advanced tech - anything involving a microprocessor - cannot be made without the right infrastructure. So they would pass into history the instant they broke. You'd have the people who had seen or used one - but when they died, then they would pass out of living memory and be one step removed. </p>\n\n<p>A second generation, and that would be that. There might be records, designs etc. but the degree of advanced manufacturing took ... well, the industrial revolution probably started about 1750 - so we've had about a 250 year 'run up' to our advanced manufacturing of today. </p>\n\n<p>Starting over <em>might</em> take less time, because of record keeping. But then, it might not, because people are people, and actually - a lot of our records <em>now</em> wouldn't survive a 250 year downtime.</p>\n" }, { "answer_id": 22618, "author": "Random", "author_id": 2490, "author_profile": "https://worldbuilding.stackexchange.com/users/2490", "pm_score": 0, "selected": false, "text": "<p>I'd suggest 3 generations, where a generation is an approximate amount of time for one individual to grow to physical maturity and reproduce. Let's say 20 years, times 3, for 60 years.</p>\n\n<p>I'm saying 3 generations based on the 3rd generation rules for wealth building and space habitats. I know what you're thinking now... huh? These have been referenced before here on worldbuilding (<a href=\"https://worldbuilding.stackexchange.com/questions/20275/what-society-might-survive-the-3-generation-rule\">What society might survive the 3 generation rule</a>). </p>\n\n<p>I'd also reference the story \"Earth Abides\", a post-apocalypse story after a plague decimates humanity. The main protagonist is a geologist. At first, the survivors gather and try to preserve the society they knew. Their children, the next generation, are more focused on building a new society based on the reality they were raised in. This includes no modern medicine, or electricity. They are still being raised with the expectations of the previous generation, which includes a formal education. But there's no use for education in modern manufacturing techniques and the like. They learn what they need to in order to survive.</p>\n\n<p>Their children, in turn, have even less use for what we consider basic education. Reading and writing skills are not commonly held, and much of what we understand of the modern world has been subsumed by nature, and are the stories of the grandparents. The rock hammer wielded by the protagonist becomes a \"magical\" symbol of authority.</p>\n" }, { "answer_id": 31026, "author": "Mason Wheeler", "author_id": 2326, "author_profile": "https://worldbuilding.stackexchange.com/users/2326", "pm_score": 2, "selected": false, "text": "<p>To lose the knowledge of how to make stuff? About a generation. But to have the concepts involved become mythologized? That generally takes around 3 centuries.</p>\n\n<blockquote>\n <p>HISTORY MUST BE CURVED, for there is a horizon in the affairs of\n mankind. Beyond this horizon, events pass out of historical\n consciousness and into myth. Accounts are shortened, complexities\n sloughed off, analogous figures fused, traditions “abraded into\n anecdotes.” Real people become culture heroes: archetypical beings\n performing iconic deeds. (Vansina 1985)</p>\n \n <p>In oral societies this horizon lies typically at eighty years; but\n historical consciousness endures longer in literate societies, and the\n horizon may fall as far back as three centuries. Arthur, a late 5th\n cent. war leader, had become by the time of Charlemagne the subject of\n an elaborate story cycle. Three centuries later, troubadours had done\n the same to Charlemagne himself. History had slipped over the horizon\n and become the stuff of legend.</p>\n \n <blockquote>\n <p>In AD 778, a Basque war party ambushed the Carolingian rear guard (Annales regni francorum). Forty years later, Einhard, a minister of\n Charlemagne, mentioned “Roland, prefect of the Breton Marches” among\n those killed (“Hruodlandus Brittannici limitis praefectus,” Vita\n karoli magni). But by 1098, Roland had become a “paladin” and the\n central character, the Basques had become Saracens, and a magic horn\n and tale of treachery had been added (La chanson de Roland). Compare\n the parallel fate of a Hopi narrative regarding a Navajo ambush\n (Vansina, pp. 19-20). </p>\n </blockquote>\n \n <p>This suggests that 17th century history has for the bulk of the\n population already become myth. Jamestown is reduced to “Pocahontas,”\n and Massachusetts boils down to “the First Thanksgiving.” And the\n story of how heliocentrism replaced geocentrism has become a Genesis\n Myth, in which a culture-hero performs iconic deeds that affirm the\n rightness of Our Modern World-view.</p>\n \n <p>-- <a href=\"http://tofspot.blogspot.com/2013/10/9-great-ptolemaic-smackdown-from.html\" rel=\"nofollow\">The Great Ptolemaic Smackdown</a></p>\n</blockquote>\n\n<p>The author here is speaking of the \"Galileo was persecuted for believing that the Earth goes around the Sun\" myth, (the truth is far more complicated, and far more interesting!), but the point raised here has plenty of other applications.</p>\n\n<p>For example, we've all heard the idea that Columbus proved that the world is round. Not only is this so wrong that it falls apart under the simplest possible examination--take a look at a globe sometime and see if you can explain how sailing from Spain west to the Caribbean and then back east to Spain will prove that--he <em>actually wasn't trying to.</em> Everyone knew the world was round already, sailors most of all! (The visual phenomenon of a ship disappearing at the horizon from the bottom up, exactly as it would when moving along a curved surface, has been known since ancient times.) What Columbus tried to prove is that the world was a lot smaller than everyone knew it was--and they were essentially right about the size of the world, BTW--such that if you set out west from Europe, you could reach Asia before running out of provisions. He was wrong about that, and if there hadn't been more unexpected land in the way, he and his crew would have all died at sea.</p>\n\n<p>But in the early 19th century--about 300 years after his fateful voyage--the idea arose, promulgated by Washington Irving, that Columbus was some paragon of Reason, proving to the benighted people of his day that the world was not actually flat as everyone believed, and the myth has stuck around in the popular consciousness ever since.</p>\n\n<p>Therefore, by long historical precedent, if your society reaches a state where knowledge of modern concepts turns into myth, it's likely to take about 300 years.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/12043", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/7944/" ]

[ { "answer_id": 12373, "author": "Jax", "author_id": 6799, "author_profile": "https://worldbuilding.stackexchange.com/users/6799", "pm_score": 3, "selected": false, "text": "<p>Use <a href=\"http://www.wikipedia.org/wiki/Multiple_Satellite_Imaging\" rel=\"nofollow\">Multiple Satellite Imaging</a>.</p>\n\n<p>NASA has already planned a \"Planet Finder.\" The basic idea is that the more telescopes you point at a place the finer image you get, enabling you to zoom in more....I suppose you could set up a system of thousands (maybe hundreds of thousands or millions, but I don't have time to do the math) and see the surface of a planet. </p>\n\n<p>Rig them up in the outer reaches of the Alpha Centuri System and you can probably zoom in to a huge degree. The biggest problem I see is that you won't have a clear idea of what is actually happening as Alpha Centuri is 4.367 light years away. If you have the ability to reach alpha centuri in a timely manner then it would probably be easier to send a small team and have them send a signal back (assuming you have figured out how to instantaneously communicate with other star systems)</p>\n" }, { "answer_id": 12377, "author": "3C273", "author_id": 466, "author_profile": "https://worldbuilding.stackexchange.com/users/466", "pm_score": 2, "selected": false, "text": "<p>Realistically speaking, I see four major problems with your situation.</p>\n<ol>\n<li><p>Alpha centauri is <a href=\"https://www.google.ca/search?client=ubuntu&amp;channel=fs&amp;q=how%20far%20is%20alpha%20centauri&amp;ie=utf-8&amp;oe=utf-8&amp;gfe_rd=cr&amp;ei=qSsMVaW8Hav_sQfr3oDwBg\" rel=\"nofollow noreferrer\">4.3 lightyears</a> form Earth. so you should see what happens 4 year earlier. Which can actually make for a pretty interesting concept.</p>\n</li>\n<li><p>The second big problem is that the telescope needs to stay fixed on earth (or worse, on a particular city). As you pointed out in your question. This feat seem almost impossible considering the distance, as a fraction of a degree would spell the difference between looking at Earth and looking at Pluto. But it is theoretically possible.</p>\n<p>Distin's idea of using many telescope might help on that regard. As the redundancy could be used to recalibrate the telescopes in real time, cover for errors and reconstruct a better image afterwards.</p>\n</li>\n<li><p>The last point concerns seeing through the atmosphere. The reason Hubble is located in space is that the atmosphere blurs image. This, along with point number 2, would probably make seeing a distinct city completely impractical. This would probably also prohibit the use of many telescopes like Dustin proposes. <a href=\"http://hubblesite.org/the_telescope/hubble_essentials/\" rel=\"nofollow noreferrer\">This site explains it quickly.</a>\nThis is not really a problem if you wish to see what's happening in space.</p>\n</li>\n<li><p>The telescope would need to be incredibly powerful to clearly see all the way to Earth. Which also implies it would be incredibly massive. Today's telescope do not allow us to see any kind of details of something smaller than a star. I'm afraid I can't give more precise guess at how big it would need to be. Dustin's idea makes this point a little better as the individual telescopes can be smaller.</p>\n</li>\n</ol>\n<p>More powerful telescopes need to be bigger and/or longer. Diagrams on <a href=\"http://www.raleighastro.org/observing/general-articles/102-purchasing-a-telescope\" rel=\"nofollow noreferrer\">this site</a> shows a few ways how telescopes are made shorter. Yours could probably be the size of a small moon by itself. If you want to build such massive tool, the only realistic way would probably be a <a href=\"http://en.wikipedia.org/wiki/Liquid_mirror_telescope\" rel=\"nofollow noreferrer\">liquid mirror telescope.</a></p>\n<p>Where the mirror is a rotating pool of reflective liquid. Those are used in the real world because a curved mirror of this size has higher risk of breaking under it's own weight. In your case, this is not as important as you would realistically be in space. But the size of the required mirror (and lenses) make those hard to craft in the first place. Either because they need to be crafted in space or because you need a massive amount of material to craft it.</p>\n<p>In summary, building such a telescope might be possible and pretty interesting. Using it to see clearly enough in space would be theoretically possible but extremely complex and probably would not detect something smaller than a small moon. Going through the atmosphere is so complex that it seems simply impossible to me.</p>\n" }, { "answer_id": 13724, "author": "3C273", "author_id": 466, "author_profile": "https://worldbuilding.stackexchange.com/users/466", "pm_score": 2, "selected": false, "text": "<p>Here's another take on showing just how improbable it is to actually see a planet the size of Earth with any kind of clarity. I'll use existing telescope information to get an idea of the power of future tools. Then I'll look at the kind of magnification we need to see Earth.</p>\n\n<p>The bottom line is that you'd need much better technology than what we have now (or custom epic-scale hardware) and you probably wouldn't realistically get the level of details you expect.</p>\n\n<p>Bear in mind that I am in no way a telescope expert (these researches actually taught me a thing or two) and my knowledge of the finer details of telescope working is lacking.</p>\n\n<p><strong>What we can see now</strong></p>\n\n<p>I'll use Hubble as a point of comparison for image quality. The <a href=\"https://web.archive.org/web/20150403164057/http://jwst.nasa.gov/comparison.html\" rel=\"nofollow noreferrer\">James Webb telescope</a> is meant as the next space telescope, with launch due in 2018. According to the link, Webb is 17 times larger, has a collecting area 7 times larger. For a field of view 15 times larger and a \"significantly better spatial resolution than is available with the infrared Spitzer Space Telescope\". I know that we can't equate the field of view with resolution. But I'll assume it can translate relatively well if the telescope was made specifically for resolution. </p>\n\n<p>From that, I'll assume that raw power of your telescopes to be around 50 times stronger than Hubble.</p>\n\n<p><strong>How to detect an exoplanet</strong></p>\n\n<p>Even without catching details, how can we just confirm that Earth still exists? </p>\n\n<p>Turns out that most exoplanets are <a href=\"https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets#Established_detection_methods\" rel=\"nofollow noreferrer\">indirectly detected</a> instead of actually being seen. There is, however, a <a href=\"https://en.wikipedia.org/wiki/List_of_directly_imaged_exoplanets\" rel=\"nofollow noreferrer\">list</a> of directly imaged planets. The good news is that some are a lot farther than Alpha Centauri. The bad news is that the smallest is above Jupiter size. </p>\n\n<p>Moreover, if you look at the pictures of those planets. All we can see are speck of light. <a href=\"https://en.wikipedia.org/wiki/2MASS_J04414489%2B2301513#/media/File:Brown_dwarf_2M_J044144_and_planet.jpg\" rel=\"nofollow noreferrer\">This</a> and <a href=\"https://en.wikipedia.org/wiki/HD_95086_b#/media/File:VLT_image_of_exoplanet_HD_95086_b.jpg\" rel=\"nofollow noreferrer\">this</a> picture are among the clearest I've found. This view of <a href=\"https://en.wikipedia.org/wiki/Beta_Pictoris_b\" rel=\"nofollow noreferrer\">Beta Pictoris b</a> is annotated and can give you an idea of the scale we're dealing with. </p>\n\n<p>If those images were magnified 100 times because of technological advancements, we could definitely \"see\" Jovian planets. But Earth-like planets would look like current images at best. </p>\n\n<p><strong>Possible but unrealistic</strong></p>\n\n<p>In the end, the magnification needed makes it theoretically possible to see what's happening in space. It would be possible if:</p>\n\n<ul>\n<li>What's happening is on the scale of Jupiter or a Dyson sphere. This object would be visible in the same way exoplanets or secondary stars are visible. </li>\n<li>What's happening emits a distinct form of radiation. Maybe a pattern is visible in non-visible light or it emits a special kind of radiation. This is basically how we detect neutron stars.</li>\n<li>Your society is much more advanced than we are.</li>\n<li>I underestimate how much of an effect a telescope swarm might have.</li>\n</ul>\n\n<p>On top of that, if you decide you can see what's happening. Considering the distances involved, the smallest shake on the telescope would go off Earth. so that your final images would probably be the few good images that happened to showcase Earth. You couldn't really get a \"film\" if you had that in mind. </p>\n\n<p>In the end, if I was your characters, I'd try to launch a series of probes in a hit'n'run : come in, take a clip of what's happening, get out. Repeat until you know what's happening or until the probes don't come back. This might require having an independent launching station/ship between Alpha and Earth.</p>\n\n<p><strong>The challenge of synchronizing a telescope swarm</strong></p>\n\n<p>I have added this section as I think it's the kind of information you want if you go ahead with this. But it's not the biggest problem. I don't really know what kind of performance you can get from a telescope swarm.</p>\n\n<p>First of all, why would you want to synchronize telescopes? The main point would be to make them move as one and align them on the same object. Earth is a moving target after all. </p>\n\n<p>As a starting point, the Webb telescope will be located at the Lagrangian point (<a href=\"https://en.wikipedia.org/wiki/Lagrangian_point#L2\" rel=\"nofollow noreferrer\">L2</a>), which is 1.5 million km from Earth but relatively close. There is a 5 second delay between Earth and L2, making synchronization impossible without FTL communication (<a href=\"https://en.wikipedia.org/wiki/Faster-than-light#FTL_communication_possibility\" rel=\"nofollow noreferrer\">which may or may not be acceptable for you</a>). </p>\n\n<p>This means that you can have a synchronized swarm of telescope in the same area of space, but it's simply impossible to have a swarm spanning the whole solar system. You could, however, collect separate data from multiple point of view in the solar system and reassemble them later. </p>\n" }, { "answer_id": 13729, "author": "Schwern", "author_id": 760, "author_profile": "https://worldbuilding.stackexchange.com/users/760", "pm_score": 4, "selected": true, "text": "<p>Maybe. Probably not people. And not without some incredibly fine control and gobs of computing power. The hard limit is atmospheric conditions on Earth.</p>\n\n<hr>\n\n<p>According to the <a href=\"https://en.wikipedia.org/wiki/Imagery_intelligence#Satellite\" rel=\"nofollow noreferrer\">Rayleigh criterion</a>, the resolution of a circular collector is a function of wavelength, diameter and distance.</p>\n\n<pre><code>resolution = 1.22 x wavelength x distance / diameter\n</code></pre>\n\n<p>To detect individual humans from above, let's say we want 50 cm resolution. Alpha Centauri is 4.3 light years away. The Earth's atmosphere is pretty transparent to visible light. How big does the mirror have to be?</p>\n\n<pre><code>diameter = 1.22 x wavelength x distance / resolution\n\ndiameter = 1.22 x ~500nm x 4.3 light years / 50 cm\n</code></pre>\n\n<p>Your telescope has to be <a href=\"https://www.wolframalpha.com/input/?i=1.22+*+wavelength+of+visible+light+*+4.3+light+years+%2F+50+cm\" rel=\"nofollow noreferrer\">4 light minutes</a> in diameter or half the diameter of the orbit of the Earth. Oh dear. That's ok, all is not lost!</p>\n\n<p>Fortunately you don't have to make bigger and bigger mirrors to get the job done. Others have mentioned <a href=\"https://worldbuilding.stackexchange.com/a/12373/760\">multiple array telescope</a> concepts. It can get weirder.</p>\n\n<p><a href=\"https://www.youtube.com/watch?v=kdo0pqh2PXA\" rel=\"nofollow noreferrer\">SciShow recently did a piece on space telescope concepts</a> to drastically improve resolution without having to build bigger and bigger mirrors. One is a <a href=\"http://www.colorado.edu/news/releases/2015/01/23/new-space-telescope-concept-could-image-objects-far-higher-resolution\" rel=\"nofollow noreferrer\">giant umbrella</a> which would take advantage of the diffraction of light waves around the edge of an object to focus the light.</p>\n\n<p>The other is to carefully position glitter ... sorry... <a href=\"http://www.rit.edu/news/story.php?id=51127\" rel=\"nofollow noreferrer\">\"smart dust\"</a> to form a giant mirror in space out of what are essentially tiny reflective pixels. The light pressure from lasers would be used to carefully nudge the particles into position and keep them there.</p>\n\n<hr>\n\n<p>Then you have the problem of focusing a planet going around the Sun at 30 km/s in a elliptical orbit. That means you don't just track it in a straight line, you have to track the curve of the orbit as well. Once you do that, you have to track a person on the surface rotating at 450m/s, again curved. The math isn't that hard, and since you're so far away you have to turn your telescope very little, but the minute and constantly changing motion of your telescope required is extremely difficult to resolve down to a few meters.</p>\n\n<p>This is why we don't point the Hubble at the Earth. <a href=\"https://en.wikipedia.org/wiki/DSCOVR\" rel=\"nofollow noreferrer\">DSCOVR</a>, the recently launched telescope we <em>do</em> intend to point at the Earth, will sit at the Sun-Earth L1 point 1.5 million km away and is only intended to do atmospheric readings.</p>\n\n<p>Fortunately for our 4 light minute wide space telescope, this is all predictable! Each piece can focus their local element individually without having to communicate with the rest of the telescope. No internal FTL communication required.</p>\n\n<hr>\n\n<p>Atmospheric conditions are your ultimate limiting factor, the problem of atmospheric haze. Even on the clearest day, the atmosphere reflects and diffuses light making your image fuzzy no matter what you do. This is part of the reason we put telescopes in space. But it is <a href=\"http://earthobservatory.nasa.gov/Features/RemoteSensing/remote_04.php\" rel=\"nofollow noreferrer\">mostly transparent to certain wavelengths</a>. Visible light is one. Microwaves are much better, but humans and aircraft carriers don't emit microwaves. Also the longer your wavelength (microwaves are pretty long) the lower your resolution.</p>\n\n<p>Scientists have been studying <a href=\"https://en.wikipedia.org/wiki/Astronomical_seeing#Overcoming_atmospheric_seeing\" rel=\"nofollow noreferrer\">the problem of how to get good resolution through an atmosphere</a> for a long time and have come up with some very, very clever ways to overcome the problem. The whole is covered under <a href=\"https://en.wikipedia.org/wiki/Adaptive_optics\" rel=\"nofollow noreferrer\">adaptive optics</a>. But that's for looking out from inside the atmosphere. We want to look <em>in</em>.</p>\n\n<p>Fortunately we don't have to run the numbers, <a href=\"https://en.wikipedia.org/wiki/KH-11_Kennan\" rel=\"nofollow noreferrer\">we have had spy satellites which can do this since the 60s and 70s</a>. They're good enough to see aircraft carriers and people through the atmosphere, a sufficiently large array at Alpha Centauri <em>probably</em> is, too. But I don't have the numbers.</p>\n\n<p>The other place to look for information is in speculation about viewing exoplanets.</p>\n\n<hr>\n\n<p>You will be seeing 4.3 years into the past. You might think \"great, then I can see whatever caused the Earth to stop communicating years ago\", no. Information can only travel at the speed of light, so your information that there is a problem on the Earth would also be 4.3 years old. Even if at the moment you realized there's a problem on Earth you swung your super telescope to look, you'd still have missed the event. Best you can do is see the aftermath.</p>\n\n<hr>\n\n<p>What you can definitely do is gather data to theorize about what happened. For example, if you see a lot of atmospheric dust that could indicate meteor strike or nuclear war. Spectral analysis could tell you if there's a sudden increase in any elements in the atmosphere. Changes in albedo could tell you similar things. Color shifts could tell you if there was a massive plant die off (or if it goes the other way, <a href=\"https://en.wikipedia.org/wiki/Triffid\" rel=\"nofollow noreferrer\">Triffid attack</a>). This is how we make guesses about exoplanets right now, just from a few smudged pixels.</p>\n\n<p>With all that time and effort to get what will probably be a hazy image of what happened 4 years ago (plus time to make and focus the telescope), it might be best to just pack up the family car and take a road trip. Of course by then it will have been at least 8 years. But at least you can pick up souvenirs.</p>\n" }, { "answer_id": 13737, "author": "2012rcampion", "author_id": 3407, "author_profile": "https://worldbuilding.stackexchange.com/users/3407", "pm_score": 1, "selected": false, "text": "<p>Requirement:</p>\n\n<blockquote>\n <p>\"Build a telescope [...] at Alpha Centauri that could resolve [$1-100~\\text{m}$] objects\"</p>\n</blockquote>\n\n<p>You are correct in assuming that \"the primary obstacle is <em>something something signal <strong>diffraction</em></strong>\"</p>\n\n<p>The way to think about diffraction is something like this. Imagine a wave of light headed towards you. If the wave hits one side of your telescope before the other, then you know that it must have come slightly to the side of where you are pointing. However, if the angle is so small that the difference in between when the wave hits each side of the telescope is less than the wavelength, then you can't tell that one hit before the other. You can only get around this by making your telescope larger to exaggerate the difference.</p>\n\n<p>Although the precise number depends on the shape of the telescope, the minimum diameter required can be approximated by:</p>\n\n<p>$$\nD = \\frac{\\lambda d}{b}\n$$</p>\n\n<p>Where $d$ is the distance to the target, and $b$ is the desired resolution. We can plug in some estimates for the quantities, assuming that the distance is from Earth to the Alpha Centauri binary, the resolution is <a href=\"http://en.wikipedia.org/wiki/Landsat_7\" rel=\"nofollow\">typical for Earth-observing satellites</a>, and a wavelength in the middle of the visible spectrum:</p>\n\n<p>$$\n\\begin{align}\nD &amp;= \\frac{500~\\text{nm}\\times 4.3~\\text{ly}}{15~\\text{m}} \\\\\n&amp;= 1.4\\cdot 10^6~\\text{km} \\\\\n&amp;\\approx 0.01~\\text{AU}\n\\end{align}\n$$</p>\n\n<p>The required size scales inversely with the resolution. To get the same $0.5~\\text{km}$ resolution as a <a href=\"http://www.goes-r.gov/spacesegment/abi.html\" rel=\"nofollow\">next-generation geostationary imaging satellite</a> the required size is only $42\\,000~\\text{km}$; but to acheive the $30~\\text{cm}$ resolution of modern satellites the required size balloons up to $0.46~\\text{AU}$.</p>\n\n<p>Atmospheric turbulence (<em>seeing</em> in astronomical parlance) is not an issue here. As usual, Randall <a href=\"https://what-if.xkcd.com/32/\" rel=\"nofollow\">does a good job of explaining this</a>.</p>\n\n<p>So to detect human-size targets you would need a telescope the size of Venus's orbit constructed around one of the stars, and to detect an aircraft carrier you'd need a telescope just slightly larger than the Earth.</p>\n\n<hr>\n\n<p>A solid (a.k.a. monolithic) mirror this size would be impossible. Even a segmented mirror (like <a href=\"http://jwst.nasa.gov/mirrors.html\" rel=\"nofollow\">JWST will use</a>) would require too much material to be practical.</p>\n\n<p>However, in our wave analogy we only ever looked at the two edges of the telescope, not at anything in the middle. It turns out that the middle of the telescope doesn't actually contribute to the maximum resolution, so we can discard it. In fact, we can discard almost all of the mirror, since we don't need every point along the edge either.</p>\n\n<p>This is the concept of a <a href=\"http://web.mit.edu/deweck/www/PDF_archive/3%20Refereed%20Conference/3_12_SPIE_4849_25.pdf\" rel=\"nofollow\">sparse aperture</a> telescope, the leading theoretical design for massive spaceborne telescopes like the one you want to construct. <a href=\"http://arcl.ae.illinois.edu/SFFMT_Chung_Hadaegh_Final.pdf\" rel=\"nofollow\">This paper</a> (coincidentally by one of my professors!) goes over the performance analysis of telescopes constructed of swarms of small mirrors.</p>\n\n<p>As for the control of such a swarm, you have two options:</p>\n\n<ul>\n<li><p>If all of the mirrors know where they are, where the target is, and where the focal point is, they can all align themselves individually, without referencing the others. In this case, to target the mirror I would keep the optical axis of the system locked onto the Sun, and simply steer the detector to follow your target on Earth. Although the velocity of the Earth in its orbit is high (around $30~\\text{km}/\\text{s}$), 1) it will correspond to a much lower velocity in the focal plane of the telescope, and 2) the speed is pretty constant, so no matter how fast the sensor has to move it can simply coast along.</p></li>\n<li><p>Alternatively, you could take a cue from <a href=\"http://en.wikipedia.org/wiki/Synthetic_aperture_radar\" rel=\"nofollow\">synthetic aperture radar</a> and just record the incoming light pattern, and correct for any misalignment when you do your data processing. This way you only need a precise measurement system, much cheaper per unit than a precision maneuvering system. (Remember, <em>precision</em> in this context means nanometer accuracy.) Traditional SAR uses radio waves, which are slow enough that their instantaneous intensity can be recorded. Light has too high a frequency for this to work, so you'd probably instead use some sort of holographic method to record the phase of the incoming light relative to some reference beam. 'Steering' the array would be a data-processing operation; in effect, you'd be taking a petapixel image of the entire solar system.</p></li>\n</ul>\n\n<hr>\n\n<p>In terms of technology, such as system is not too far off. I interned under someone who was interested in these systems, and he helped put together this <a href=\"http://hires.gsfc.nasa.gov/si/documents/Carpenter_tech_WP_EOS_032409_v3.pdf\" rel=\"nofollow\">technology roadmap</a>, which estimates large-scale swarm telescopes are only 20-50 years away. Such a telescope would certainly be cheaper, in terms of energy and materials, than travel to another star in human timescales (based on current understanding of physics). I would say <strong>go for it!</strong></p>\n\n<hr>\n\n<p>One last thing to mention. You can get more data more cheaply by increasing your spectral resolution instead of your spatial resolution. That is, instead of only processing three spectral bands (red, green, and blue), you shoud record and process a couple dozen bands spread through the infrared, visible, and ultraviolet spectra. This would allow you to determine lots of interesting properties (like surface material and temperature) at every pixel in the image, and is useful for distinguishing similar-looking objects (like snow/ice/clouds/white roofs).</p>\n" }, { "answer_id": 153148, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 1, "selected": false, "text": "<p>You might be able to do some interesting things with a swarm of satellites a few thousand AU out, using the local star as a gravitational lens. This is a long way out, but not as far as going all the way back to Sol. A mission called <a href=\"https://en.wikipedia.org/wiki/FOCAL_(spacecraft)\" rel=\"nofollow noreferrer\">FOCAL</a> has been proposed that would send a single telescope out to the Sun's gravitational focus. There's been various discussion about how good the image produced from such a mission would be, see for example Geoffrey A. Landis \"<a href=\"https://arxiv.org/abs/1604.06351\" rel=\"nofollow noreferrer\">Mission to the Gravitational Focus of the Sun: A Critical Analysis</a>\".</p>\n\n<p>Unfortunately Alpha Centauri is a binary star which would likely complicate things. Maybe they could use Proxima as the lens instead.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/12370", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/755/" ]

[ { "answer_id": 12930, "author": "Mir", "author_id": 8067, "author_profile": "https://worldbuilding.stackexchange.com/users/8067", "pm_score": 3, "selected": false, "text": "<p>I think the established term for this is known as the <a href=\"http://en.wikipedia.org/wiki/Grandfather_paradox\" rel=\"nofollow\">grandfather paradox</a>.</p>\n\n<p>From a story in which a time traveller ventures into the past and kills his grandfather. Since it seems to defy all known laws of the universe there's no way to say for sure what would happen. I'd like to think that time travel would result in creating two parallel dimensions that the traveller \"jumps\" between. Since he's from another dimension, it doesn't really matter if he has a grandfather in the current dimension he's in. Or does it?</p>\n" }, { "answer_id": 12931, "author": "Joe Z.", "author_id": 150, "author_profile": "https://worldbuilding.stackexchange.com/users/150", "pm_score": 2, "selected": false, "text": "<p>The theory I usually go with is that each possible timeline is also part of a multidimensional universe of timelines. When $J_1$ goes back in time to create $J_{0A}$, he's not actually going back to tell the <em>same</em> $J_0$ not to build a time machine, since that's impossible by causality, but just one in an equivalent timeline up to that point.</p>\n\n<p>$J_1$ and $J_{1A}$ coexist in different timelines, one with the time machine, one without, and never then able to communicate to each other again because they can't travel to the exact same timeline anymore. If $J_{1A}$ were then to invent another time machine between $T_1$ and $T_2$ and try to go back in time to $T_1$ to tell $J_{1A}$ not to make the time machine, he'd be telling $J_{1B}$ not to make it, not $J_{1A}$.</p>\n\n<p>So the universe doesn't really reset, it's just a copy of it that gets affected.</p>\n" }, { "answer_id": 12932, "author": "Blckknght", "author_id": 2097, "author_profile": "https://worldbuilding.stackexchange.com/users/2097", "pm_score": 5, "selected": true, "text": "<p>If your universe allows time travel to split the timeline into two, I think your choice to splitting it only based on whether the time machine is built is incorrect. The right place to split the timeline is at $T_{-1}$, just before $J_1$ arrives in \"his\" past.</p>\n\n<p>In one branch, at $T_{0A}$, a $J_1$ from \"the future\" appears. In the other branch, at $T_0$, he does not.</p>\n\n<p>Thus, when $J_1$ tells a \"past version of himself\" not to build the time machine, he's really telling $J_{0A}$, an alternate version of his past self, not $J_0$.</p>\n\n<p>I quoted some of the phrases above, because of the alternate realities involved. $T_{0A}$ isn't really $J_0$'s past, nor is he really from that timeline's future.</p>\n\n<p>Bad ASCII diagram:</p>\n\n<pre><code>T-1 ----------------&gt; T0 --------------------------&gt; T1\n \\ (J0 invents time machine) (J1 uses machine)\n \\ /\n \\ .-------- J1's journey &lt;--------\n \\ V\n --------------&gt; T0A -------------------------&gt; T1A\n (J0A doesn't invent the machine) (J2 and J1A live happily ever after)\n</code></pre>\n" }, { "answer_id": 12938, "author": "guildsbounty", "author_id": 443, "author_profile": "https://worldbuilding.stackexchange.com/users/443", "pm_score": 0, "selected": false, "text": "<p>There are several different theories on how a Grandfather Paradox would resolve itself.</p>\n\n<p>Split Reality: The time traveler creates an alternate dimension in which that time machine is not invented. The time traveler returning to his home time/reality may or may not be possible.</p>\n\n<p>Stable Time Loop: The past and future cannot be changed and are immutable. If you went back and time and told yourself not to build a time machine, then you were told not to build one by your future self, built the time machine anyway, and then went back to tell yourself not to. That is how it always happened, and it cannot be altered. This is a favorite of a lot of shows (like Doctor Who...for a good example of a stable time loop, see the episode 'Blink.')</p>\n\n<p>Timey-Wimey Shenanigans: You are told not to create a time machine, then your future self ceases to exist, and you are left with that information despite the fact that it couldn't have been delivered. See: Marty McFly disappearing from existence as a result of his actions, from Back to the Future.</p>\n\n<p>Chronal breakdown: Congrats, you just broke reality. Maybe time freezes, maybe you wink out of existence, maybe the whole universe vanishes in a puff of logic.</p>\n" }, { "answer_id": 12992, "author": "Aaru", "author_id": 7563, "author_profile": "https://worldbuilding.stackexchange.com/users/7563", "pm_score": 1, "selected": false, "text": "<p>You invented a time machine. As you are about to use it for the first time, you excitedly enter the room. You place yourself in the seat, and you're about to press the launch button, when you notice a piece of paper, jammed into a previously invisible crevice in the machine. You open it up. It's clearly a page torn from your pocket notebook, in your own handwriting, albeit in a very <em>shaky</em> script. There is only 1 word on the paper: </p>\n\n<p>$$\\huge{Don't}$$</p>\n\n<p>You ponder this for a minute. You tear a page from your notebook, and, in a shaky script, write: \"Don't\". You set the time machine to Present Time -1 hour, 0 minutes. You press the button. You quickly stuff the paper in the appropriate crevice, and go silently hide in a nearby cupboard. An hour later, you breathe a sigh of relief, come out, and take a large crowbar out of your toolbox. You turn towards the machine.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/12929", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/8348/" ]

[ { "answer_id": 13664, "author": "Dan Pichelman", "author_id": 7918, "author_profile": "https://worldbuilding.stackexchange.com/users/7918", "pm_score": 2, "selected": false, "text": "<p>In that environment I would just assume that I am always under visual/audio surveillance 100% of the time. Anything I read or write will be read by the bad guys.</p>\n\n<p>The best form of communication would be something that you can do in plain sight in front of your observers. </p>\n\n<p>One TV show had a bit where two stage magicians communicated using Morse code with the length of the spaces between spoken words. It's clever, but if the bad guys play back a video recording there's a chance they could pick up on this.</p>\n\n<p>If your two people have a safe way to make arrangements prior to being under surveillance, they could set up a set of <a href=\"http://en.wikipedia.org/wiki/One-time_pad\" rel=\"nofollow\">One-Time Pad</a>s.</p>\n\n<p>Rather than going through the math described in the Wikipedia article, I'd just memorize a simple lookup table such as</p>\n\n<ul>\n<li>fish: get me out of this place!</li>\n<li>wrench: I need more time</li>\n<li>potato: I need more stuff/tools</li>\n<li>ring: I need more people</li>\n<li>sock: I quit, this is too complicated.</li>\n</ul>\n\n<p>The interesting bit is that you don't get to reuse the table. You must have a new one with completely different (&amp; totally random) key words for every communication.</p>\n\n<p>Anyone listening to your conversation might not even notice that you're sending secret messages. If they do notice, how are they going to figure out what \"fish\" means, when in the next message you might use the word \"carbon\" to say the same thing and you never re-use the word \"fish\"?</p>\n" }, { "answer_id": 13667, "author": "Tim B", "author_id": 49, "author_profile": "https://worldbuilding.stackexchange.com/users/49", "pm_score": 3, "selected": false, "text": "<p>There are two ways to beat this sort of system.</p>\n\n<p><strong>Firstly from without:</strong></p>\n\n<p>Essentially you need to be able to hide the message in among seemingly innocent interactions.</p>\n\n<p>For example I read a sci-fi novel where an undercover agent always went and had sex with the same person whenever he got back into port. What wasn't known to the local authorities is that they were both agents and they had a language that could be \"spoken\" between them by applying various levels of pressure with various parts of their hands while they seemed to be paying attention to other matters.</p>\n\n<p>The example in another answer of inserting key words into phrases is also a good example, as is using pauses between words.</p>\n\n<p>The key thing is to bury your communications inside something unrelated so that people do not see anything untoward either at the time or later on replaying the surveillance.</p>\n\n<p>You should also make a habit of going and having similar conversations without any hidden meaning to all sorts of other people. This means that if one person is uncovered then it becomes much harder to work out who out of all their contacts is actually a contact.</p>\n\n<p><strong>Secondly from within:</strong></p>\n\n<p>Get people inside the system and they can work out where is monitored and where is not, knowledge of those black spots can then be distributed to others and information slowly spreads as more people are recruited.</p>\n\n<p>The weakest point in most systems are the humans running it, not the systems themselves. Subvert the people and you subvert the system.</p>\n\n<p><strong>Combined approach</strong></p>\n\n<p>Perhaps the best solution would be the combined approach. Insiders provide some privacy in one area which is then used to develop codes and other methods that allow you to communicate even while under surveillance.</p>\n" }, { "answer_id": 13673, "author": "Kristy", "author_id": 8309, "author_profile": "https://worldbuilding.stackexchange.com/users/8309", "pm_score": 2, "selected": false, "text": "<p>Sign language? Can't be overheard, and you can use your body to block your communications so they can't be seen. (You can <em>whisper</em> to someone in sign by making your signs really small so that only they can see).</p>\n\n<p>Alternatively, morse code using touch. Morse code already exists, you wouldn't have to spend too much time developing it. You might not even have to ever broach the idea of using it out loud - everyone knows SOS. if someone starting tapping that on my knee in an orwellian world i would go out and learn the rest of morse code to find out what else they had to say. Light taps can be easily obscured by clothes/blankets/screens.</p>\n\n<p>I think there would be an element of risk no matter what system you choose. The consciousness of this risk can only improve your story by adding tension.</p>\n" }, { "answer_id": 14065, "author": "codeMonkey", "author_id": 8681, "author_profile": "https://worldbuilding.stackexchange.com/users/8681", "pm_score": 4, "selected": true, "text": "<p>If you go to the Information Security Exchange you will see over and over again:</p>\n\n<pre><code>There is no such thing as perfect security.\n</code></pre>\n\n<p>An adversary with sufficient desire and means will compromise your communication pathway. That is what makes 1984 (and real life big brother states like China) so frightening.</p>\n\n<p>These big brother states are limited by their ability to filter out the normal from the interesting. During the Vietnam War, American POWs were isolated from each other in order to wear them down. The POWs began communicating using everyday sounds. Since everyone in the Hanoi Hilton was sick, the POWs would cough and sneeze in code to pass messages. Chores became means of communicating - the delay between sweeps on a broom could be varied to produce Morse code. </p>\n\n<p>These methods are not fool proof, but they were sufficient for the POWs. A more aggressive \"big brother\" would have certainly understood every message passed, but the North Vietnamese were distracted by the whole fighting a war thing: they could only devoted so much manpower / time / energy to the POW camp. </p>\n\n<p>So the key to your story will be three-fold:\n1) What is normal behavior? </p>\n\n<p>2) How can I modify that behavior to pass information? </p>\n\n<p>3) (most importantly) What limits Big Brother? - with unlimited time and money nothing is secret.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/13663", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/8703/" ]

[ { "answer_id": 14658, "author": "Serban Tanasa", "author_id": 3510, "author_profile": "https://worldbuilding.stackexchange.com/users/3510", "pm_score": 2, "selected": false, "text": "<h2>We can, actually</h2>\n<p>I recall this little frog being levitated using a (somewhere between 1-100 Tesla) magnetic coil using diamagnetism about a decade or more ago. There he is:</p>\n<p><img src=\"https://i.stack.imgur.com/izSWP.jpg\" alt=\"levitating frog\" /></p>\n<p>Water is diamagnetic, as are many good conductors. So frogs and more recently, <a href=\"http://adsabs.harvard.edu/abs/2010AdSpR..45..208L\" rel=\"nofollow noreferrer\">small mammals</a>, have been levitated.</p>\n<pre><code>Material χv (× 10−5)\nSuperconductor −105\nPyrolytic carbon −40.9\nBismuth −16.6\nMercury −2.9\nSilver −2.6\nCarbon (diamond) −2.1\nLead −1.8\nCarbon (graphite) −1.6\nCopper −1.0\nWater −0.91\n</code></pre>\n<p>More relevant to your question, there was a spinning-stabilized toy patented in the 70s and more recently, <strong>there are</strong> commercially available solutions such as the <a href=\"https://www.youtube.com/watch?v=W6SSY7ABJkw\" rel=\"nofollow noreferrer\">Levitron</a> for low weight objects in a limited range.</p>\n<p><img src=\"https://i.stack.imgur.com/LCtm6.jpg\" alt=\"levitron\" /></p>\n<p>Heck, you can <a href=\"https://www.youtube.com/watch?v=VylZJrep1MM\" rel=\"nofollow noreferrer\">build one yourself with a few magnets</a>.</p>\n" }, { "answer_id": 14663, "author": "Samuel", "author_id": 3202, "author_profile": "https://worldbuilding.stackexchange.com/users/3202", "pm_score": 1, "selected": false, "text": "<p>There is a significantly better way to do it than magnets, a way that's already being done.</p>\n\n<p><strong>Acoustic Levitation</strong></p>\n\n<p>As you can see in <a href=\"https://youtu.be/odJxJRAxdFU\" rel=\"nofollow noreferrer\">this video</a>, small objects can be made to levitate and move around by controlling the amplitude and frequency of the ultrasonic waves.</p>\n\n<p>Acoustic waves are just pressure waves, by bouncing the waves between two plates objects can be suspended in the low pressure nodes. </p>\n\n<p><img src=\"https://i.stack.imgur.com/IqqsM.jpg\" alt=\"enter image description here\"></p>\n\n<p>You can build simple ones at home with an ultrasonic transducer from ebay. This is a significantly cheaper way to get the same effect as magnetic levitation. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/14657", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/7162/" ]

[ { "answer_id": 15000, "author": "WhatRoughBeast", "author_id": 7858, "author_profile": "https://worldbuilding.stackexchange.com/users/7858", "pm_score": 2, "selected": false, "text": "<p>Well, to begin with, it throws the classical rules about inheritance and noble blood lines out the window. Since (most of the time) the dead will inconsiderately not stay dead, death does not sever ownership of land and goods, but rather provides a prolonged absence (sort of like going off to the Crusades). And, arguably, the entire philosophical underpinnings of marriage have to change, since \"till death do you part\" no longer means what it used to. If a queen dies, can the king remarry? Or vice versa?</p>\n\n<p>And, since Christianity is no longer tenable, \"divine right of kings\" will not rear its ugly head.</p>\n\n<p>Land grants, given in perpetuity, were a king's source of power, since he could reward vassals by giving the lands of deceased enemies. With the certainty of resurrection, a new lord's claim is really only good for 16 years or so, and then the old lord is likely to start sniffing around for a way to get his land back.</p>\n\n<p>In general, the effect will be long-term social instability as well. Feuds and vendettas will literally last forever. </p>\n" }, { "answer_id": 15070, "author": "eharper256", "author_id": 9029, "author_profile": "https://worldbuilding.stackexchange.com/users/9029", "pm_score": 3, "selected": true, "text": "<p>In addition to WhatRoughBeast's answer, people persisting their knowledge through the ages would somewhat negate the need for education systems after a certain period of time. We wouldn't spend time educating our kids much beyond the basics if they suddenly gain smarts at 16 regardless. </p>\n\n<p>On the other hand, it means research projects can be continued throughout the centuries. There would be less of that human urge to do all we could as soon as we could; after all, what's the rush, I can get around to that in my next lifetime. </p>\n\n<p>Even so, ironically, and counterintuitively, these two factors would probably contribute to slowing technological progress (less inclination to combine minds if you can ponder to yourself for centuries, and less inclination to do anything in general if I'm immortal). </p>\n\n<p>Alot of human society is built on the reverence of death. Even in ancient times, death was sacred, and burial was a huge part of civilization. Without that, what do people find sacred instead? Life is less sacred, death is not to be feared. Ancient legends would change immeasurably and the sense of morals would be considerably skewed. </p>\n\n<p>As Mari M mentions, murder is less of sin; and creative torture methods preserving life (i.e. preventing the release of death) are liable to be created along with consistant genocides. If you suddenly remembered your past life at 16, and it was 40 years of vicious torture, imprisonment and rape all flooding your consciousness at once I'd be surprised if we didn't end with a few babbling catatonics from that. <em>\"Kill me again so I can have another 16 years of ignorance, please.\"</em> might even become a service... (yikes that got dark). </p>\n\n<p>Soul study (Animatology) would become a big science. If someone can accurately predict where and when and how a soul will reincarnate, the limits and powers of the respawn points, and the related abilities to manipulate them, you gain alot of power. </p>\n\n<p>This is also the best method to become a usurper. If you can predict where the old king comes back to life all the time, simply find him and stab him in the face again before he turns 16. As a bonus, he's now locked as a wolf or whatever for 5-15 years before he becomes a human again if the animal/human cycle is set in stone. </p>\n\n<p>Finally, if souls have this human/animal cycle, then your human population max is actually less than 6.5 billion, right?</p>\n" }, { "answer_id": 15071, "author": "Muhammad Abdul-Rahim", "author_id": 9201, "author_profile": "https://worldbuilding.stackexchange.com/users/9201", "pm_score": 0, "selected": false, "text": "<p>I can imagine something truly grotesque with this reincarnation society. A nation that wants to truly destroy another, so they first wipe everybody out and then whenever any life is reincarnated into that land (since Souls are bound to a land as you said), they kill that life immediately. Keep this cycle up, and you can prevent an entire race of people from existing, leaving them stuck in a cycle of endless reincarnation.</p>\n\n<p>It does depend on how dark you wish to go with your story. What I said in the previous paragraph is fairly morbid, but I believe it's worth considering multiple fronts for this, if only for curiosity's sake.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/14996", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/8792/" ]

[ { "answer_id": 15226, "author": "newton1212", "author_id": 9188, "author_profile": "https://worldbuilding.stackexchange.com/users/9188", "pm_score": 2, "selected": false, "text": "<p>As you stated previously we use calcium in our bones but, given several bone sustenance changes, it would be trivial to use said calcium to create skeleton based flora. Unfortunately...</p>\n\n<h3>Where do we get it?</h3>\n\n<p>On average soil is around a tiny 1 percent calcium. If your goal is to reinforce the plant, then this might work if you add small amounts of hydroxyapatite(bone) to the cell walls of the plant but not if want a complete skeleton. For that i suggest.</p>\n\n<h3>Carnivorous Plants</h3>\n\n<p>The human body, and most other large animals, contain a great amount of calcium just waiting to be used by your potential plant. Although large carnivorous plants are more fantastical they would allow for the vast need of calcium to be met.</p>\n" }, { "answer_id": 15233, "author": "theonlygusti", "author_id": 9182, "author_profile": "https://worldbuilding.stackexchange.com/users/9182", "pm_score": 5, "selected": true, "text": "<p>Lets look at some real-world examples of plants which already absorb and use metals, namely <a href=\"https://en.wikipedia.org/wiki/Hyperaccumulator\" rel=\"noreferrer\">hyperaccumulators</a>.</p>\n\n<p><img src=\"https://i.stack.imgur.com/RrHre.jpg\" alt=\"Hyperaccumulating plants already use metals within their tissues.\"></p>\n\n<p>Hyeraccumulators are plants which can withstand extremely high concentrations of metals otherwise toxic to non-hyperaccumulating plants.</p>\n\n<p>They extract metals from the soil and store them within leaves, shoots and their roots. Other plants can also extract metals from soils, but hyperaccumulators can do this at a much, <em>much</em> faster rate and are also able to store incredible quantities of these toxic metals within their tissues.</p>\n\n<p>Because of this extraction of metals, hyperaccumulators are commonly used in <a href=\"http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/metalsanduses/extractingmetalsrev5.shtml\" rel=\"noreferrer\">phytomining</a>, where we use such plants to take minerals out of the soil for us.</p>\n\n<p><img src=\"https://i.stack.imgur.com/gcxGp.jpg\" alt=\"phytomining process\"></p>\n\n<p>Of course, hyperaccumulators absorb many metals, not just the ones valuable to humans.</p>\n\n<p>Because of the toxicity of the metals which are absorbed by hyperaccumulating plants, scientists speculate that the primary purpose of hyperaccumulation, at least, the primary defensive purpose, is to prevent them from being eaten. The concentration of toxic metals within these plants is so high that animals which eat them will die, and so never be found eating them again.</p>\n\n<p><img src=\"https://i.stack.imgur.com/w8J5f.jpg\" alt=\"Toxic metals used mainly to deter animals.\"></p>\n\n<p>So, here on Earth, hyperaccumulators only pad their tissues with toxic metals to decrease the likelihood of their being eaten, but you've stated specific interest in using metals to improve structure, rigidity and strength.</p>\n\n<p>However, if a plant were able to pull metals from the ground like a hyperaccumulator, there's no reason those metals couldn't then be used to strengthen the plant.</p>\n\n<p>First, let's have a look at which metals hyperaccumulators are known to handle:</p>\n\n<pre><code>Name Symbol UTS tensile strength\nAluminium Al 700\nSilver Ag 170\nArsenic As 3\nBeryllium Be 448\nChromium Cr 689\nCopper Cu 220\nManganese Mn -\nMercury Hg -\nMolybdenum Mo 690 Disclaimer:\nLead Pb 17 I am pretty certain that the\nPalladium Pd 325 listed tensile strengths are\nPlatinum Pt 240 inaccurate and inconsistent.\nSelenium Se 500 They should be used just as a\nZinc Zn 28 rough idea of the actual\n strengths.\n</code></pre>\n\n<p>From this list, two metals stand out; Aluminium and Chromium.</p>\n\n<p><img src=\"https://i.stack.imgur.com/Buc9m.jpg\" alt=\"Al/13/27 Cr/24/52\"></p>\n\n<p>Both incredibly strong metals; this is the same Aluminium used in <a href=\"http://www.riotintoalcan.com/ENG/ourproducts/1542_aluminium_and_its_uses.asp\" rel=\"noreferrer\">skyscrapers and jet engines</a>, and the same chromium as used in <a href=\"https://en.wikipedia.org/wiki/Chrome_plating\" rel=\"noreferrer\">Chrome plating</a>.</p>\n\n<p>If your plants were to hyperaccumulate large enough quantities of these metals, they could capitalise on their strength in many ways. Some examples I thought of were:</p>\n\n<ul>\n<li>Reinforcing cell-walls by chrome plating. Currently, plant cell walls are made almost entirely from <a href=\"https://en.wikipedia.org/wiki/Cellulose\" rel=\"noreferrer\">cellulose</a>, which is (compared to chromium) very weak. By reinforcing this cellulose with chromium, individual cells of your plant would become nigh-indestructable.</li>\n<li>Building skeletal systems. Along with the <a href=\"https://en.wikipedia.org/wiki/Phloem\" rel=\"noreferrer\">Phloem</a> and <a href=\"https://en.wikipedia.org/wiki/Xylem\" rel=\"noreferrer\">Xylem</a> of current plants, metal plants might have a third system of vessels, filled with Aluminium, keeping the plant structurally sound. Good luck snapping a twig laced with one of the toughest metals of which we know.</li>\n<li>Plating the entire plant. If the plant's <a href=\"http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/Leaf.html\" rel=\"noreferrer\">epidermis</a> were to secrete chromium instead of wax, it could build up a thick layer of chrome plating, which cannot be scratched, corroded or otherwise damaged.</li>\n</ul>\n\n<p><img src=\"https://i.stack.imgur.com/BioUa.jpg\" alt=\"Metal plant uses chrome-plating to protect itself.\"></p>\n\n<p>Of course, now that you have the ability to absorb minerals and metals from the ground, you can use them however you want!</p>\n" }, { "answer_id": 18482, "author": "Joshua Hanley", "author_id": 467, "author_profile": "https://worldbuilding.stackexchange.com/users/467", "pm_score": 2, "selected": false, "text": "<p>Not carbon-based plants as we know them.</p>\n\n<p>The advantages like structural strength that you associate with <a href=\"http://en.wikipedia.org/wiki/Metal#Physical\" rel=\"nofollow noreferrer\">metals</a> are generally a result of what <a href=\"http://en.wikipedia.org/wiki/Metallurgy\" rel=\"nofollow noreferrer\">humans have done to the metal</a>—accumulation, processing, and forging/casting or plating. Those processes require a lot of energy, a lot of heat, and a lot of motility, none of which plants are going to be able to pull off or survive on their own.</p>\n\n<p>Metals as they exist naturally are not generally useful for their metallic properties. They are almost always bound in some sort of ore, highly impure, rare even within the mass of the ore, and they usually require considerable and energy-intensive physical and chemical <a href=\"http://en.wikipedia.org/wiki/Extractive_metallurgy\" rel=\"nofollow noreferrer\">processing</a> before you get a usable quantity of elemental metal.</p>\n\n<p>At that point, even more processing must be done. Two of the basic properties of metals are ductility and malleability, which are the ability to deform under tensile or compressive stress. <strong>Thus metals aren't known for their ability to withstand stress, but rather for their ability to deform under it without fracturing.</strong></p>\n\n<p>The metals known or used for their strength or rigidity owe that strength to a crystal structure imparted by the process of <a href=\"http://en.wikipedia.org/wiki/Forging\" rel=\"nofollow noreferrer\">forging</a> or <a href=\"http://en.wikipedia.org/wiki/Casting\" rel=\"nofollow noreferrer\">casting</a>. Those processes require levels of heat (the metal has to melt) which are impossible for any carbon-based lifeform to create on its own without technology or to withstand at close range.</p>\n\n<p>Electroplating, a process used to coat things in useful metals—although usually for corrosion-resistance or decoration (which are the reasons you know what chrome is) and not for strength—is both energy-intensive and an electrochemical, technological process. Plants aren't going to be able to use or survive plating. Even if they could, metals are opaque to sunlight, so any plant coated in them won't be able to survive.</p>\n\n<p>Besides, plants already have the use of another light-weight, rigid material for structural strength: <a href=\"http://en.wikipedia.org/wiki/Cellulose\" rel=\"nofollow noreferrer\">cellulose</a>. Humans were using wood for its strength and rigidity long before we discovered how to work metals. And, while cellulose doesn't have the rigidity of structural steel, it also doesn't have to be heated to 1,539 °C in order to have that strength, which is a big advantage when you're constructing a plant.</p>\n\n<p><strong>tl;dr: You don't get <img src=\"https://i.stack.imgur.com/UC7t0.png\" alt=\"structural steel\"> without <img src=\"https://i.stack.imgur.com/LOEZy.jpg\" alt=\"a lot of heat and technology\"></strong></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/15225", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/7066/" ]

[ { "answer_id": 15226, "author": "newton1212", "author_id": 9188, "author_profile": "https://worldbuilding.stackexchange.com/users/9188", "pm_score": 2, "selected": false, "text": "<p>As you stated previously we use calcium in our bones but, given several bone sustenance changes, it would be trivial to use said calcium to create skeleton based flora. Unfortunately...</p>\n\n<h3>Where do we get it?</h3>\n\n<p>On average soil is around a tiny 1 percent calcium. If your goal is to reinforce the plant, then this might work if you add small amounts of hydroxyapatite(bone) to the cell walls of the plant but not if want a complete skeleton. For that i suggest.</p>\n\n<h3>Carnivorous Plants</h3>\n\n<p>The human body, and most other large animals, contain a great amount of calcium just waiting to be used by your potential plant. Although large carnivorous plants are more fantastical they would allow for the vast need of calcium to be met.</p>\n" }, { "answer_id": 15233, "author": "theonlygusti", "author_id": 9182, "author_profile": "https://worldbuilding.stackexchange.com/users/9182", "pm_score": 5, "selected": true, "text": "<p>Lets look at some real-world examples of plants which already absorb and use metals, namely <a href=\"https://en.wikipedia.org/wiki/Hyperaccumulator\" rel=\"noreferrer\">hyperaccumulators</a>.</p>\n\n<p><img src=\"https://i.stack.imgur.com/RrHre.jpg\" alt=\"Hyperaccumulating plants already use metals within their tissues.\"></p>\n\n<p>Hyeraccumulators are plants which can withstand extremely high concentrations of metals otherwise toxic to non-hyperaccumulating plants.</p>\n\n<p>They extract metals from the soil and store them within leaves, shoots and their roots. Other plants can also extract metals from soils, but hyperaccumulators can do this at a much, <em>much</em> faster rate and are also able to store incredible quantities of these toxic metals within their tissues.</p>\n\n<p>Because of this extraction of metals, hyperaccumulators are commonly used in <a href=\"http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/metalsanduses/extractingmetalsrev5.shtml\" rel=\"noreferrer\">phytomining</a>, where we use such plants to take minerals out of the soil for us.</p>\n\n<p><img src=\"https://i.stack.imgur.com/gcxGp.jpg\" alt=\"phytomining process\"></p>\n\n<p>Of course, hyperaccumulators absorb many metals, not just the ones valuable to humans.</p>\n\n<p>Because of the toxicity of the metals which are absorbed by hyperaccumulating plants, scientists speculate that the primary purpose of hyperaccumulation, at least, the primary defensive purpose, is to prevent them from being eaten. The concentration of toxic metals within these plants is so high that animals which eat them will die, and so never be found eating them again.</p>\n\n<p><img src=\"https://i.stack.imgur.com/w8J5f.jpg\" alt=\"Toxic metals used mainly to deter animals.\"></p>\n\n<p>So, here on Earth, hyperaccumulators only pad their tissues with toxic metals to decrease the likelihood of their being eaten, but you've stated specific interest in using metals to improve structure, rigidity and strength.</p>\n\n<p>However, if a plant were able to pull metals from the ground like a hyperaccumulator, there's no reason those metals couldn't then be used to strengthen the plant.</p>\n\n<p>First, let's have a look at which metals hyperaccumulators are known to handle:</p>\n\n<pre><code>Name Symbol UTS tensile strength\nAluminium Al 700\nSilver Ag 170\nArsenic As 3\nBeryllium Be 448\nChromium Cr 689\nCopper Cu 220\nManganese Mn -\nMercury Hg -\nMolybdenum Mo 690 Disclaimer:\nLead Pb 17 I am pretty certain that the\nPalladium Pd 325 listed tensile strengths are\nPlatinum Pt 240 inaccurate and inconsistent.\nSelenium Se 500 They should be used just as a\nZinc Zn 28 rough idea of the actual\n strengths.\n</code></pre>\n\n<p>From this list, two metals stand out; Aluminium and Chromium.</p>\n\n<p><img src=\"https://i.stack.imgur.com/Buc9m.jpg\" alt=\"Al/13/27 Cr/24/52\"></p>\n\n<p>Both incredibly strong metals; this is the same Aluminium used in <a href=\"http://www.riotintoalcan.com/ENG/ourproducts/1542_aluminium_and_its_uses.asp\" rel=\"noreferrer\">skyscrapers and jet engines</a>, and the same chromium as used in <a href=\"https://en.wikipedia.org/wiki/Chrome_plating\" rel=\"noreferrer\">Chrome plating</a>.</p>\n\n<p>If your plants were to hyperaccumulate large enough quantities of these metals, they could capitalise on their strength in many ways. Some examples I thought of were:</p>\n\n<ul>\n<li>Reinforcing cell-walls by chrome plating. Currently, plant cell walls are made almost entirely from <a href=\"https://en.wikipedia.org/wiki/Cellulose\" rel=\"noreferrer\">cellulose</a>, which is (compared to chromium) very weak. By reinforcing this cellulose with chromium, individual cells of your plant would become nigh-indestructable.</li>\n<li>Building skeletal systems. Along with the <a href=\"https://en.wikipedia.org/wiki/Phloem\" rel=\"noreferrer\">Phloem</a> and <a href=\"https://en.wikipedia.org/wiki/Xylem\" rel=\"noreferrer\">Xylem</a> of current plants, metal plants might have a third system of vessels, filled with Aluminium, keeping the plant structurally sound. Good luck snapping a twig laced with one of the toughest metals of which we know.</li>\n<li>Plating the entire plant. If the plant's <a href=\"http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/Leaf.html\" rel=\"noreferrer\">epidermis</a> were to secrete chromium instead of wax, it could build up a thick layer of chrome plating, which cannot be scratched, corroded or otherwise damaged.</li>\n</ul>\n\n<p><img src=\"https://i.stack.imgur.com/BioUa.jpg\" alt=\"Metal plant uses chrome-plating to protect itself.\"></p>\n\n<p>Of course, now that you have the ability to absorb minerals and metals from the ground, you can use them however you want!</p>\n" }, { "answer_id": 18482, "author": "Joshua Hanley", "author_id": 467, "author_profile": "https://worldbuilding.stackexchange.com/users/467", "pm_score": 2, "selected": false, "text": "<p>Not carbon-based plants as we know them.</p>\n\n<p>The advantages like structural strength that you associate with <a href=\"http://en.wikipedia.org/wiki/Metal#Physical\" rel=\"nofollow noreferrer\">metals</a> are generally a result of what <a href=\"http://en.wikipedia.org/wiki/Metallurgy\" rel=\"nofollow noreferrer\">humans have done to the metal</a>—accumulation, processing, and forging/casting or plating. Those processes require a lot of energy, a lot of heat, and a lot of motility, none of which plants are going to be able to pull off or survive on their own.</p>\n\n<p>Metals as they exist naturally are not generally useful for their metallic properties. They are almost always bound in some sort of ore, highly impure, rare even within the mass of the ore, and they usually require considerable and energy-intensive physical and chemical <a href=\"http://en.wikipedia.org/wiki/Extractive_metallurgy\" rel=\"nofollow noreferrer\">processing</a> before you get a usable quantity of elemental metal.</p>\n\n<p>At that point, even more processing must be done. Two of the basic properties of metals are ductility and malleability, which are the ability to deform under tensile or compressive stress. <strong>Thus metals aren't known for their ability to withstand stress, but rather for their ability to deform under it without fracturing.</strong></p>\n\n<p>The metals known or used for their strength or rigidity owe that strength to a crystal structure imparted by the process of <a href=\"http://en.wikipedia.org/wiki/Forging\" rel=\"nofollow noreferrer\">forging</a> or <a href=\"http://en.wikipedia.org/wiki/Casting\" rel=\"nofollow noreferrer\">casting</a>. Those processes require levels of heat (the metal has to melt) which are impossible for any carbon-based lifeform to create on its own without technology or to withstand at close range.</p>\n\n<p>Electroplating, a process used to coat things in useful metals—although usually for corrosion-resistance or decoration (which are the reasons you know what chrome is) and not for strength—is both energy-intensive and an electrochemical, technological process. Plants aren't going to be able to use or survive plating. Even if they could, metals are opaque to sunlight, so any plant coated in them won't be able to survive.</p>\n\n<p>Besides, plants already have the use of another light-weight, rigid material for structural strength: <a href=\"http://en.wikipedia.org/wiki/Cellulose\" rel=\"nofollow noreferrer\">cellulose</a>. Humans were using wood for its strength and rigidity long before we discovered how to work metals. And, while cellulose doesn't have the rigidity of structural steel, it also doesn't have to be heated to 1,539 °C in order to have that strength, which is a big advantage when you're constructing a plant.</p>\n\n<p><strong>tl;dr: You don't get <img src=\"https://i.stack.imgur.com/UC7t0.png\" alt=\"structural steel\"> without <img src=\"https://i.stack.imgur.com/LOEZy.jpg\" alt=\"a lot of heat and technology\"></strong></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/15231", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/90/" ]

[ { "answer_id": 15265, "author": "bowlturner", "author_id": 19, "author_profile": "https://worldbuilding.stackexchange.com/users/19", "pm_score": 4, "selected": false, "text": "<p>Well there are currently some plants that need their seeds to travel through the digestive track of animals before they can germinate. I was looking but couldn't find them right now. I think they got their coating so they could pass through a digestive system and be carried away. </p>\n\n<p>So step that up a bit, and let it 'catch' in the digestive system, then start to sprout. Though making it more a symbiotic relationship (with at least one or two species) would make it more likely, maybe it helps process some other foods. And when the host dies, it will sprout out and use the body as a food source.</p>\n\n<p>If it always killed it's host every time it is eaten most would learn to avoid it quickly. </p>\n" }, { "answer_id": 15266, "author": "Jim2B", "author_id": 7886, "author_profile": "https://worldbuilding.stackexchange.com/users/7886", "pm_score": 4, "selected": false, "text": "<p><strong>Plant Growing in the Lungs</strong><br>\nThis is a story ripped from the headlines. It is a <a href=\"http://www.medicalnewstoday.com/articles/197623.php\" rel=\"nofollow noreferrer\">plant growing in a living person's lung.</a></p>\n\n<blockquote>\n <p>Ron Sveden, a retired teacher from Brewster, Massachusetts in the US\n was astonished to discover that what he thought was a tumor growing in\n his lung was actually a plant that had sprouted from an inhaled pea.</p>\n \n <p>75-year old Sveden said he was told the pea seed had split and\n sprouted in his lung. It was about half an inch long (about 1.25 cm),\n which \"is a pretty big thing\", he said according to a news report from\n NBC.</p>\n</blockquote>\n\n<p>Pea growing in lungs - example of plant growing in a living animal.\n<img src=\"https://i.stack.imgur.com/9bLge.jpg\" alt=\"Pea growing in lungs\"></p>\n\n<p>Not the digestive tract but pretty close.</p>\n\n<p><strong>Fungus Growing in the Body</strong><br>\nAnother close match is <a href=\"http://jim2b.blogspot.com/2014/12/december-chest-ct-fungal-pneumonia.html\" rel=\"nofollow noreferrer\">fungal pneumonia</a> (which I have). It is an example of fungus growing in a living animal's lungs. You inhale the spores and they take up residence, germinate, and begin growing.</p>\n\n<p>My fungal pneumonia - example of fungus growing in living animals<br>\n<img src=\"https://i.stack.imgur.com/ENFNh.png\" alt=\"My fungal pneumonia\"></p>\n\n<p>After the fungus reaches a certain amount of growth, the fungal growth releases fungal cells into your blood system and spreads to other parts of the body. This enables the fungus to spread to any part of your body (intestines, brain, heart, liver, you name it) and begin a new fungus colony (this is the stage they caught mine at).</p>\n\n<p>It is fatal if not treated.</p>\n\n<p><strong>Other Thoughts</strong><br>\nThe lungs are probably a more benign environment than the intestines.</p>\n" }, { "answer_id": 15268, "author": "Adam Davis", "author_id": 473, "author_profile": "https://worldbuilding.stackexchange.com/users/473", "pm_score": 5, "selected": true, "text": "<p>The biggest problem is that you want the plant to thrive in two very different environments (relatively speaking):</p>\n\n<pre><code> Body Ground\nTemperature Hot Cold\nMoisture Wet Dry\nRespiration Liquid Air \nNutrients Bloodborne Soil/compost\nEnergy Glucose Photosynthesis\n</code></pre>\n\n<p>Therefore, for this to work, you really need to have a two stage lifespan. Similar to a caterpillar that meta-morphs into a butterfly, your plant will likely have to transition from thriving in one environment to another. </p>\n\n<p>The seed, therefore must be inhaled, consumed, or embedded somehow. Natural processes suggest inhalation or ingestion as the most successful route. While I'd prefer inhalation (close to bloodstream and air, not as harsh as digestive), it appears you've already selected digestive.</p>\n\n<p>So the seed has to not only survive the digestive tract, but the plant has to provide some enticement to being eaten. If it were inhalation, it wouldn't have to entice - it would merely send out spores or microscopic airborne seeds when jostled. The plant, therefore, provides significant satisfying nutrition, so as to get hosts to eat it.</p>\n\n<p>Once consumed, the seed has to pass through the upper digestive tract, but get stuck in the lower digestive tract (lower acidity). This seems difficult, but perhaps it has a germination time of 1-2 hours once the outer acid protective surface is cleaned off. It then starts rooting in several directions, preventing it from moving further down the digestive tract. Small barbed roots that can absorb nutrients from the partially digested food would be best.</p>\n\n<p>At this time it just absorbs energy that will be used during its transition, and builds into a tumor, with longer and longer roots. Eventually it will completely obstruct the digestive tract or the roots will pierce too many blood vessels or veins, and the host will die. If it's necessary that the host doesn't feel pain until near death, then it either synthesizes anesthetic which it emits through its roots, or it doesn't send out roots and instead merely becomes a digestive obstruction.</p>\n\n<p>When the host dies, the process of decomposition sends chemical signals to the seedling and within a few hours it is expending energy sending a tendril upward (any way could be up at this point, but gravity leads the way) seeking light. Once light is obtained, the plant sends out leaves, roots itself more firmly to the host and ground below, and, eventually, flowers and fruits to catch another host for its offspring.</p>\n\n<p>Pulling off the metamorphosis is the tricky part, but since we have animal analogs that do this, it shouldn't be too difficult to explain to the audience.</p>\n" }, { "answer_id": 15269, "author": "DeadAnt", "author_id": 9262, "author_profile": "https://worldbuilding.stackexchange.com/users/9262", "pm_score": 1, "selected": false, "text": "<p>There is a virus or something that infects an ant and makes it climb a tree before sprouting or creating spores inside it's dying/dead body. Can't remember the ant or the plant/virus that does this but have heard this from a few sources,</p>\n" }, { "answer_id": 15274, "author": "Jake", "author_id": 2092, "author_profile": "https://worldbuilding.stackexchange.com/users/2092", "pm_score": 3, "selected": false, "text": "<p>My thought would be that a plant couldn't do it. At least not by itself. Mostly because a plant needs to carry out photosynthesis in order to live.</p>\n\n<p><strong>HOWEVER</strong> there is an analog of a <a href=\"http://en.wikipedia.org/wiki/Cordyceps\" rel=\"nofollow\">parasitic fungus</a> that will kill its insect host then \"bloom\" out of the body as it continues to gather nutrients from its now deceased host.</p>\n\n<p><strong>ALSO</strong> there is an analog for a symbiotic relationship between fungi and plants. These are the <a href=\"http://en.wikipedia.org/wiki/Lichen\" rel=\"nofollow\">lichens</a>. Now these organisms still use photosynthesis, but, unlike a plant, which is defined by use of photosynthesis, nothing says that lichens necessarily require photosynthesis.</p>\n\n<p><strong>BY EXTENSION</strong> A particularly virulent strain of cordyceps mutates that can infect mammals. However, there is a bit of an issue. As diets change and mammals evolve stronger stomach acid, it is harder for the fungus to survive past the digestive tract. So it evolves a way of attaching itself to a plant ovum and hitching a ride into the digestive tract. The stomach acid erodes the tough outer shell of the seed and the cortyceps is released into the intestines and blooms with the added benefit of pushing the seed out of the mammal to so it can sprout, utilizing the decaying body for nutrients while getting that sweet sweet sunlight fix. Further evolution happens involving little hooks on the seed to adhere to the intestinal wall and cortyceps producing higher level of nitrogen locking the cortyceps and plant into a codependent symbiosis. Then the plant starts producing tasty fruit, humans start eating said tasty fruit, cortyceps-tree evolves to utilize humans, a new plague upon all of humanity is unleashed, and millions of grotesque mafia deaths happen in movies. All because you couldn't be bothered to core an apple.</p>\n" }, { "answer_id": 15303, "author": "user6511", "author_id": 6511, "author_profile": "https://worldbuilding.stackexchange.com/users/6511", "pm_score": 1, "selected": false, "text": "<blockquote>\n <p>Is this realistic for a story?</p>\n</blockquote>\n\n<p>In a modern society - no. We bury our dead in boxes (and those that we don't bury we <em>burn</em>), and don't grow anything near them. </p>\n\n<p>The life-cycle of this plant makes sense for animals, but not for people. It would make sense for ancient, pre-historic cavemen, but not for any civilisation in the past few thousand years. </p>\n" }, { "answer_id": 193237, "author": "Amanda West", "author_id": 81701, "author_profile": "https://worldbuilding.stackexchange.com/users/81701", "pm_score": 0, "selected": false, "text": "<p>If you inserted the seed into the rectum, it could sprout in the composting faeces. The sprout could move upwards and puncture the lung, receiving the carbon dioxide plants need. The human would absorb it oxygen, and so could survive symbiotically under water. Excess moisture in the lung would be absorbed by aerial roots. If the tree could send chlorophyll through the blood vessels to the skin, the skin would turn green and photosynthesise, providing energy to both.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/15263", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/6799/" ]

[ { "answer_id": 15288, "author": "AndyD273", "author_id": 6751, "author_profile": "https://worldbuilding.stackexchange.com/users/6751", "pm_score": 3, "selected": false, "text": "<p>The smallest warhead created for the US military was the <a href=\"http://en.wikipedia.org/wiki/W54#Variants\" rel=\"nofollow\">W54 Davy Crocket</a> which used 23kg of Pu239 and had a yield equivalent to 10-20 tons of TNT. </p>\n\n<p><a href=\"https://www.youtube.com/watch?v=HdLm0PgrqBI\" rel=\"nofollow\">Video of the Davy Crocket being fired</a>.</p>\n\n<p><strike>According to other research, the smallest amount of Pu239 you can use to make a bomb is 10kg, which still has the power of several tons of TNT, plus the thermal effects. So even that small of an amount would <a href=\"http://nuclearsecrecy.com/nukemap/?&amp;airburst=0&amp;linked=1&amp;kt=0.001&amp;lat=42.3313888&amp;lng=-83.045836&amp;hob_ft=0&amp;zm=17\" rel=\"nofollow\">take out a normal city block</a>.</p>\n\n<p>I don't know if it would completely vaporize the target, but none of the pieces would be very big, and they would be pretty spread out.</strike></p>\n\n<p>Edit: So, after a lot more reading, I found that there are ways to lower the threshold for critical mass: shaping the pit, neutron reflectors, the type of explosives used to compress the mass, etc. With all the right tricks you can get it <a href=\"http://www.wikipedia.org/wiki/Plutonium#Explosives\" rel=\"nofollow\">down to about 4kg</a>. </p>\n\n<p>Fatman only used 6.2kg of Pu 239, and it had a yield of 20 kilotons. So you would have to find ways to lower the efficiency. </p>\n\n<p>Apparently it's harder to go smaller with a nuke than it is to go bigger.</p>\n" }, { "answer_id": 15304, "author": "Jim2B", "author_id": 7886, "author_profile": "https://worldbuilding.stackexchange.com/users/7886", "pm_score": 0, "selected": false, "text": "<p>Your question doesn't provide a bunch of very important bounding parameters about the size of the thing to be destroyed, the level of destruction required, the composition of the thing to be destroyed, the proximity of things to not be destroyed, what level of \"untouched\" is really required, and how much time we're allowed to take.</p>\n\n<p>So I'm going to provide you with several answers. I hope one satisfies your needs.</p>\n\n<pre>\nSize of thing to be destroyed? 1 human body\nComposition of thing to be destroyed? 1 human body\nLevel of destruction? must flush down the bathroom tub drain\nProximity to nearby objects? a couple of feet\nHow affects nearby things? Don't hurt things out of bathtub\nHow much time? Days\n</pre>\n\n<p>Use extremely caustic materials like $ LiOH $ or $ H_2SO_4 $ that work well on organic chemicals.</p>\n\n<p>I figured out the quantity once but don't feel up to doing that today. Just remember the acid/base <strong>is</strong> consumed in the reaction and some of the weight of the acid/base is the water in which it is in solution.</p>\n\n<p>So estimate the weight of chemicals required at 150% of the body weight.</p>\n\n<p><strong>Bad Stuff</strong><br>\nThe problem is this will not dissolve all the bits of the human body. I assume someone looking for this method of \"disposing of evidence\" would know what to look for if they found several empty drums of caustic chemicals.</p>\n\n<p>You could do the same thing with metals and other materials. However, the best caustic chemicals for a given task change depending upon the composition of the object to be destroyed and the container in which you plan to do the destruction.</p>\n\n<p>Also, as stated above, this will take days to complete and it will stink to high heaven. You'll probably need a gas mask to enter the room during the destruction.</p>\n" }, { "answer_id": 15305, "author": "Jim2B", "author_id": 7886, "author_profile": "https://worldbuilding.stackexchange.com/users/7886", "pm_score": 4, "selected": false, "text": "<p>Continuing on the theme of chemical solutions (ba-dum-bum-CHING - I'm here all night folks)...</p>\n\n<p>One way to rid yourself of unwanted objects or personnel is to liquefy or vaporize them and allow nature to clear them away. For this sort of operation, I eschew explosions because although they deliver a lot of energy, they tend to apply it indiscriminately to everything around them.</p>\n\n<p>So let's try a more focused approach: thermite</p>\n\n<p>Grind up metallic aluminum and rust into a fine dust. Perhaps combine them with a combustible binder material and apply liberally to the object (person) that absolutely, positively has to go away.</p>\n\n<pre>\nSize of thing to be destroyed? Unknown\nComposition of thing to be destroyed? Non-refractory materials\nLevel of destruction? Burn, liquify, or vaporize\nProximity to nearby objects? a couple of feet\nHow affects nearby things? Don't hurt things beyond a couple of feet\nHow much time? Seconds to minutes\n</pre>\n\n<p>Thermite burns at temperatures of thousands of degrees. It will burn, liquefy, or vaporize many materials as shown in this video of thermite on dry ice:</p>\n\n<p><a href=\"https://www.youtube.com/watch?v=14EMPjfSmVs\">Thermite Vs. Dry Ice</a></p>\n\n<p>It won't have this effect on most refractory materials (tungsten, carbon-carbon, etc.).</p>\n\n<p><strong>Bad Stuff</strong><br>\nWhile thermite most certainly will rid you of some offensive materials, unless you are extremely liberal and careful with its application there almost certainly will be evidence left.</p>\n" }, { "answer_id": 15306, "author": "Jorge Aldo", "author_id": 7066, "author_profile": "https://worldbuilding.stackexchange.com/users/7066", "pm_score": 2, "selected": false, "text": "<p>Go with Californium:</p>\n\n<p>It can used in a small nuclear device due to the much smaller critical mass needed to produce a nuclear chain reaction when using Californium. </p>\n\n<p>According to wikipedia, the critical mass of Plutonium-239 is 10kg, and circa 10-15kg (23kg minus mass of casing etc) was used to make the W54 Davy Crokett recoiless nuclear cannon. A Californium-252 based version would weight much less. Major problem is that Californium is not cheap. At 2.7Kg critical mass, this means a 3-7kg nuclear weapon, but costing at least 10 Million dollars each round.</p>\n" }, { "answer_id": 15307, "author": "2012rcampion", "author_id": 3407, "author_profile": "https://worldbuilding.stackexchange.com/users/3407", "pm_score": 3, "selected": false, "text": "<p>If you want to limit the damage to a few feet, any type of explosion is right out. <a href=\"http://en.wikipedia.org/wiki/M-80_(explosive)\" rel=\"nofollow\">Large firecrackers</a>, <a href=\"http://en.wikipedia.org/wiki/Bottle_rocket\" rel=\"nofollow\">bottle rockets</a>, and even non-chemical explosions like the <a href=\"http://en.wikipedia.org/wiki/Dry_ice_bomb\" rel=\"nofollow\">\"dry ice bomb\"</a> can throw shrapnel a dozen feet or more. Scaling up a little more, a <a href=\"http://en.wikipedia.org/wiki/M67_grenade\" rel=\"nofollow\">hand grenade </a> can be fatal at up to 15 feet. Nuclear explosions are right out.</p>\n\n<hr>\n\n<p>What you want is a concentrated release of energy, unlike an explosion which disperses energy outward. My first instinct is <a href=\"http://en.wikipedia.org/wiki/Thermite\" rel=\"nofollow\">thermite</a>, an extremely hot-burning metal powder. Typically it's used for <a href=\"https://youtu.be/XQViDITyIKs?t=1m8s\" rel=\"nofollow\">welding railroad tracks</a>, but you can also use it to, say, <a href=\"https://youtu.be/rdCsbZf1_Ng?t=2m18s\" rel=\"nofollow\">melt through the engine block of a car</a>.</p>\n\n<hr>\n\n<p>If 2 thousand degree molten metal doesn't fulfill your appetite for destruction though, then let's move on to something else. Since you asked about nuclear devices, let's start with some radiation. In particular, <a href=\"http://en.wikipedia.org/wiki/Cathode_ray\" rel=\"nofollow\">electron beams</a>. Most of the electron beams (originally named 'cathode rays') we encounter today are in the form of CRT monitors, but these only deliver a minuscule amount of power. However, there are a number of more... <em>industrial</em> uses of electron beams:</p>\n\n<ul>\n<li>Electron irradiation, used to sterilize materials or process plastics. Here's a <a href=\"https://youtu.be/7H9SA8XCHug?t=58s\" rel=\"nofollow\">video</a> of what happens to a camera passing through an irradiator used for industrial plastics processing. The beam used in that video delivers around <a href=\"http://www.wolframalpha.com/input/?i=3.6+MeV+%2F+(electron+charge)+*+7mA\" rel=\"nofollow\">25 kW</a> of beam power.</li>\n<li>Electron beam welding. Here's <a href=\"https://www.youtube.com/watch?v=kh7o6w-GePY\" rel=\"nofollow\">a video</a> showing an electron beam welder making a 74\" joint in 1 3/4\" steel in just four minutes. A similar technique uses an electron beam to <a href=\"https://www.youtube.com/watch?v=BMGNy1MgsyM\" rel=\"nofollow\">fuse metal powder into 3d printed shapes</a>.</li>\n<li>Finally, the most powerful of these devices is an electron beam furnace. These are huge and highly specialized machines, so information on them is hard to find. Here's an <a href=\"http://theodoregray.com/periodictable/Stories/077.x3/\" rel=\"nofollow\">article</a> describing the process of melting iridium with an electron beam furnace. Iridium melts at almost 2500 degrees Celsius.</li>\n</ul>\n\n<p>What a megampere electron beam would do to an unprotected target in open air... I leave that to your imagination.</p>\n\n<hr>\n\n<p>Wait, you still want more? Well, we can step up to a proton beam, the type used in <a href=\"http://en.wikipedia.org/wiki/Proton_therapy\" rel=\"nofollow\">proton therapy</a>. The reason I'm limiting myself to charged particle beams is that, unlike neutron radiation or gamma radiation, charged particles interact strongly with matter, so the radiation is short-ranged (which will prevent collateral damage). The type of beams used in cancer treatment penetrate on the order of ten centimeters before stopping abruptly.</p>\n\n<p>Like electron beams, a powerful proton beam would melt or vaporize the target. However, it would also do significant damage to the target on a nuclear level. Individual protons have thousands of times more energy and momentum than electrons, possibly enough to fuse with the nuclei of atoms and increase their mass, or knock out other nucleons and reduce the mass. After you're through with it, the target won't even be identifiable by its isotopes.</p>\n\n<p>I don't have any videos for you here; proton beams don't have many industrial uses, since they're hard to produce. (Good thing \"cost isn't a problem.\") Again, what you do with such a beam is up to your imagination.</p>\n" }, { "answer_id": 15308, "author": "Jim2B", "author_id": 7886, "author_profile": "https://worldbuilding.stackexchange.com/users/7886", "pm_score": 0, "selected": false, "text": "<p>Still avoiding explosives...</p>\n\n<p>Another way to rid yourself of unwanted possession (or people) would be to burn them. This poses a problem when the object (person) is not flammable. Interestingly, most things that are not already oxidized will burn when exposed to a 100% oxygen environment (things like human flesh).</p>\n\n<p>So acquire a tank of pure oxygen and set that garbage on fire. You may need to keep the flow of oxygen going while you're eradicating the object (evidence).</p>\n\n<pre>\nSize of thing to be destroyed? Unknown\nComposition of thing to be destroyed? Most non-oxidized materials\nLevel of destruction? Burn or vaporize\nProximity to nearby objects? Tens of feet?\nHow affects nearby things? Don't hurt things beyond tens of feet\nHow much time? Minutes\n</pre>\n\n<p>I've never actually played with this but I would guess that it won't be as carefully contained as the previous two.</p>\n" }, { "answer_id": 15309, "author": "Jim2B", "author_id": 7886, "author_profile": "https://worldbuilding.stackexchange.com/users/7886", "pm_score": 2, "selected": false, "text": "<p>Alright, I'm done with the little stuff, let's move on to explosions.</p>\n\n<p>The problem with explosions (as I stated elsewhere) is that they apply their energy indiscriminately and tend to damage what you want damaged along with everything else around it.</p>\n\n<pre>\nSize of thing to be destroyed? Scale explosion to target size\nComposition of thing to be destroyed? Scale explosion to target composition\nLevel of destruction? Blast\nProximity to nearby objects? More than 10s of yards to a mile or more\nHow affects nearby things? Don't hurt things beyond this range\nHow much time? milliseconds\n</pre>\n\n<p>If done with careful planning and placed with care, it is possible to create things like shaped charges or direct the explosive force of an explosion. This does indeed focus the explosion and direct the majority of its fury at the intended target, but it is still unhealthy for anything near the explosion.</p>\n\n<p>Consider the case of a self-forging projectile trying to penetrate the armor of a tank. Whether the projectile penetrates the armor or not, the area around the tank is extremely unhealthy for infantry soldiers. Other armored vehicles could shrug off the explosion and/or fragments, but the explosion would likely kill any soldiers near the tank.</p>\n\n<p>The same thing happens when directing an explosion with the intent of destroying high-rise buildings without damaging nearby buildings. The focus of the blast does indeed hit the desired target, but if you stood near the explosion, you'd very likely be killed. Construction materials are MUCH tougher than your typical human being.</p>\n\n<p>We are faced by another quandry with this too. Even with 500 lbs of high explosives, there was plenty of the cement truck left to identify in this Mythbuster's explosion.</p>\n\n<p><a href=\"https://www.youtube.com/watch?v=Gxm_qpKh7Jw\" rel=\"nofollow\">https://www.youtube.com/watch?v=Gxm_qpKh7Jw</a></p>\n\n<p>So in order to really destroy something so that no trace is left, you would need a truly enormous explosion and it just isn't safe to be around those, if you wish to live.</p>\n\n<p>Even with the Mother of all Bombs (MOAB) 18,000 lbs of fuel (it uses atmospheric oxygen as the oxidizer), there would be plenty of material left to identify objects destroyed in the blast.</p>\n\n<p><a href=\"https://www.youtube.com/watch?v=HsQdeAeOEg4\" rel=\"nofollow\">https://www.youtube.com/watch?v=HsQdeAeOEg4</a></p>\n\n<p>Oh yeah, and you wouldn't want to be anywhere near the detonation point.</p>\n\n<p>Just a point of interest here. Explosions typically don't break all chemical bonds in the target. The blast tends to fragment the target. Individual fragments of target and bomb usually contain enough information to figure out quite a bit about both.</p>\n" }, { "answer_id": 15310, "author": "Jim2B", "author_id": 7886, "author_profile": "https://worldbuilding.stackexchange.com/users/7886", "pm_score": 0, "selected": false, "text": "<p>How about another twist before we go nuclear...</p>\n\n<p>Directed energy weapons.</p>\n\n<p>Directed energy weapons are very able to apply energy to a very focused source. The amount of energy they can deliver is pretty pitiful when compared with the energy of explosions but it still may be sufficient for your needs.</p>\n\n<pre>\nSize of thing to be destroyed? Roughly human sized\nComposition of thing to be destroyed? Most non-refractory materials\nLevel of destruction? Burn, melt, or vaporize\nProximity to nearby objects? Minimum of tens of feet,\n maximum out to hundreds of yards\nHow affects nearby things? Combustion to dozens of feet,\n blindness to anyone who can view the target\nHow much time? Seconds to minutes\n</pre>\n\n<p>It is easy to focus and direct the beam to hit the intended target without <em>directly</em> hitting anything else. However, such powerful beams will momentarily reflect off objects breaking off the target or floating in the air. This will send stray beams of high powered coherent light flying in all directions.</p>\n\n<p>You'll have to assume anyone standing in the line of sight with the target will be permanently blinded.</p>\n\n<p>Furthermore, if the beam heats the target up enough to burn, melt, or vaporize the target, the target is going to be radiating enormous amounts of heat. My guess is nearby combustibles will combust, including hair &amp; clothing. </p>\n" }, { "answer_id": 15311, "author": "Jim2B", "author_id": 7886, "author_profile": "https://worldbuilding.stackexchange.com/users/7886", "pm_score": 2, "selected": false, "text": "<p>OK, my last entry. This one includes large &amp; unconventional methods of getting rid of things.</p>\n\n<p><strong>Nuclear</strong><br>\nif you absolutely positively have to make it go away, nuclear is the sure fired way to ensure that happens.</p>\n\n<p>The problem of course is how do you keep it from destroying the nearby stuff that you don't want destroyed. Well the US Air Force as an app (project) for that, it's called <a href=\"http://www.projectrho.com/public_html/rocket/spacegunconvent.php#id--Nukes_In_Space--Nuclear_Shaped_Charges\" rel=\"nofollow\">Casaba Howitzer and it is a freaking nuclear shaped charge</a>.</p>\n\n<pre>\nSize of thing to be destroyed? Roughly human sized\nComposition of thing to be destroyed? Most non-refractory materials\nLevel of destruction? Burn, melt, or vaporize\nProximity to nearby objects? Minimum of tens of feet,\n maximum out to hundreds of yards\nHow affects nearby things? Combustion to dozens of feet,\n blindness to anyone who can view the target\nHow much time? Microseconds\n</pre>\n\n<p>I am tired and don't want to get into all the gory details (but find the topic terribly interesting). Scientists felt they could focus about 80% of the destructive power of the bomb.</p>\n\n<p>That still leaves 20% of a nuclear bomb to annihilate everything else not in path of the directed shot.</p>\n\n<p>Within some (very short) distance of the bomb, the gamma rays and neutrons are powerful enough to cause transmutation (fission &amp; fusion reactions). All chemical bonds will be broken all atoms will be ionized (possibly multiple times).</p>\n\n<p>Within a longer (but still short) distance of the bomb, the heat caused by absorbed gamma rays and neutrons will ensure most chemical bonds are broken and many atoms are ionized (but no nuclear shenanigans will be going on).</p>\n\n<p>In an atmosphere these two zones combine and form the fireball region which absorbs most gammas, causing the air to heat and generate the blast wave.</p>\n\n<p>In space, the gammas just keep going and kill people directly.</p>\n\n<p>Regardless of the direction of the blast, the bomb will spew neutrons about. Neutrons are not stopped very well by most shielding (it's better to use large quantities of water to shield you instead of dense metals, for instance). Neutrons will kill people so even if infrastructure survives the 20% of the bomb that escapes the directed blast, the nearby people will die anyway.</p>\n\n<p><strong>Kinetic Projectiles</strong><br>\nI want to throw one final thought out there.</p>\n\n<p>You could do it with a hypersonic kinetic projectile. If shot from space, it would look like a shaft of light shot down from the sky and simply left a crater where the offensive tidbits were left. The blast from any bombardment which creates a crater will also damage the things around the crater rim. But this sort of strike does not cause radiation damage (but does cause a blast).</p>\n\n<p>Kinetic weapons scale better than conventional or nuclear weapons. They can be as small as a .22 bullet to as large as the dinosaur killing asteroid (~6 miles in diameter). You can also adjust the speed of the projectile.</p>\n\n<p>Kinetic projectiles have the added benefit of not emitting lethal radiation, so if you survive the impact and subsequent blast, you'll survive the encounter.</p>\n\n<p>This a video of the meteor that fell over Russia. Imagine a targeted strike intended to take out a building. It would damage nearby buildings but leave most of the city untouched (sans windows, of course).</p>\n\n<p><a href=\"http://media1.s-nbcnews.com/i/MSNBC/Components/Video/_Player/swfs/embed_V2/embedV2_20140520v2.swf?settings=38251917&amp;onsite=true#!flashvars#launch=50827929&amp;width=652&amp;height=466&amp;autoplay=true&amp;pg=&amp;bts=&amp;freewheelvideo=NBC_no_ads&amp;onsite=true\" rel=\"nofollow\">Video of meteor over Russia</a></p>\n" }, { "answer_id": 15316, "author": "jamesqf", "author_id": 3545, "author_profile": "https://worldbuilding.stackexchange.com/users/3545", "pm_score": 2, "selected": false, "text": "<p>I think the only way to make a really small nuclear explosion (for a given value of 'nuclear') is to use a very small quantity of antimatter. But as already pointed out, that won't completely obliterate the object: even with thermite, there would still be chemical traces.</p>\n\n<p>No, the only way to completely obliterate an object is to utilize a quantum black hole.</p>\n" }, { "answer_id": 15317, "author": "DA.", "author_id": 305, "author_profile": "https://worldbuilding.stackexchange.com/users/305", "pm_score": 1, "selected": false, "text": "<blockquote>\n <p>How to create a nuclear explosion localized to only a few square feet?</p>\n</blockquote>\n\n<p>Make it controlled. Nuclear reactors are controlled nuclear reactions. They're controlled to the point where there is no explosion.</p>\n\n<p>A nuclear bomb is an uncontrolled nuclear reaction. </p>\n\n<p>I'm likely stretching physics here, but one could perhaps have an incredibly tiny amount of fissionable material and then control it with a really tiny reactor (nano-sized rods?)</p>\n" }, { "answer_id": 15325, "author": "Kaithar", "author_id": 7949, "author_profile": "https://worldbuilding.stackexchange.com/users/7949", "pm_score": 2, "selected": false, "text": "<p>Forget explosives, too much hassle and not very effective. The proper way of dealing with this, as touched on in another answer, is fire. Lots and lots of lovely fire.</p>\n\n<blockquote>\n <p>The point is to completely eradicate something relatively small, leaving no trace. Let's assume that this is taking place on Earth. The government that is using this procedure has access to lots of funds, so cost isn't a problem.</p>\n</blockquote>\n\n<p>Oh baby, lets have fun.</p>\n\n<p>So, since cost isn't an issue, the first thing you're going to need is a ridiculously expensive burn box. How expensive? Basically you need a safe made of high purity tungsten, the thicker the better. Elemental tungsten has one of the highest melting points around at 3695K, plus it is fairly resistant to various forms of corrosion. For suitable tungsten you're probably talking at least \\$300-\\$400 per kg, at $19250kg/m^3$ a suitable box is not going to be cheap.</p>\n\n<p>Next up is a fuel. Your best bet here is a oxy-acetylene, although you'd need to avoid running it with too much oxygen as the peak temperatures for acetylene burning in pure oxygen are around the same as the previously mentioned melting point of tungsten.</p>\n\n<p>This contraption will melt just about anything. Organic material will be incinerated, most metals will be reduced to liquid (most will actually start to boil), even things like silicon and stone will be an unrecognisable puddle. You're also probably going to need some kind of exhaust capture system, since the fumes would likely be extremely toxic, and a really good cooling system to get rid of the heat.</p>\n\n<p>If you're careful in selecting the materials used to make whatever is being destroyed you should be able to completely incinerate it. Organics and lower temp metals like gold, tin and copper should be little or no traces left. Worst case is a completely unrecognisable bit of slag.</p>\n\n<p>The basic principles involved are not that different to those involved in crematoriums, since there are similar constraints like exhaust capture. This kind of system also works best in smaller scale, suiting your \"couple of feet\" scale.</p>\n\n<p>As a plus, you could probably slap a heat exchanger on the thing and heat your government offices with it.</p>\n" }, { "answer_id": 15336, "author": "pjc50", "author_id": 1985, "author_profile": "https://worldbuilding.stackexchange.com/users/1985", "pm_score": 2, "selected": false, "text": "<p>This will likely be buried under the other answers, but you can have tiny fusion explosions. <a href=\"https://lasers.llnl.gov/\" rel=\"nofollow\">There is a current real project to produce them.</a> Each fusion capsule is pinhead-sized and detonated by a warehouse-sized laser. All you need to do is scale this <em>up</em> a bit and you can have yourself a fusion explosion capable of destroying a few cubic feet around it with a large \"bang\". However, it wouldn't be particularly more powerful than a conventional explosion of the same size. The fundamental thing about explosions is that they're not containable.</p>\n\n<p>Or you could just use the warehouse-sized laser directly. Or a <a href=\"http://en.wikipedia.org/wiki/Plasma_torch\" rel=\"nofollow\">plasma torch</a>.</p>\n" }, { "answer_id": 15337, "author": "Drenzul", "author_id": 9197, "author_profile": "https://worldbuilding.stackexchange.com/users/9197", "pm_score": 1, "selected": false, "text": "<p>If its that small and needs to be disposed of with no evidence, I'd suggest firing it into the Sun or Jupiter. Trying to destroy it on the spot to that level is going to be tricky and will almost certainly at least leave some traces. </p>\n\n<p>I think about the best you could achieve without major damage to nearby areas would probably be a plasma jet, formed by a large number of shaped charge explosives. Forget nuclear, its not directed enough to achieve the level of destruction you want without major damage to the surrounding area.</p>\n\n<p>Basically surround the object in a number of shaped charge warhead, the conflagration of plasma-jets should pretty much annihilate it with at worst minor damage to surronding areas (you could stand 20' or so away). If the shaped charges are set-up correctly, you could probably reduce nearly anything to dust/vapour. (Shaped charged warheads often vaporise the armour they are penetrating).</p>\n" }, { "answer_id": 15340, "author": "Zibbobz", "author_id": 764, "author_profile": "https://worldbuilding.stackexchange.com/users/764", "pm_score": 1, "selected": false, "text": "<p>I'm going to assume a nuclear weapon is absolutely essential - maybe you need some method to kill Godzilla's eggs, and can only trust in the psudo-magical power of nuclear explosions. Regardless of the reason, it has to be a nuclear bomb. </p>\n\n<h2><strong>The Bomb</strong></h2>\n\n<p>The smallest nuclear weapon, and very nearly the smallest possible nuclear explosive yield ever constructed, would be the <a href=\"http://en.wikipedia.org/wiki/Davy_Crockett_(nuclear_device)\" rel=\"nofollow\">Davy Crockett</a>, which carries the distinction of being the only nuclear weapon ever conceived for infantry use. </p>\n\n<p>The weapon delivers the equivalent explosive force of <a href=\"http://en.wikipedia.org/wiki/Nuclear_weapon_yield\" rel=\"nofollow\">10 to 20 tons of TNT</a>, but the actual radius of the blast is less well-documented. However, it apparently delivers an instantly lethal dose of radiation within 500 feet of the blast (and a less lethal but at least equally tragic dose up to 4 miles out), so if radiation is the reason you need a bomb, then it'll definitely do. </p>\n\n<h2><strong>Containment</strong></h2>\n\n<p>If you have any type of control over the explosion area, your best bet to limit the damage would be to construct an entirely-lead encasing compound, specifically designed to contain the radiation damage AND explosive damage of the bomb. Inner chambers would be constructed to collapse and absorb as much of the explosive force as possible, while the rest of it would simply contain the radiation. </p>\n\n<p>It's hard to say how large the facility would need to be, since most nuclear explosion tests were carried out in large, open, barren areas rather than elaborate lead shielded constructs. If you can mitigate the risk of hitting groundwater, and can control the <em>exact</em> location of the explosion, doing it underground would be even better. </p>\n\n<h2><strong>Practicality</strong></h2>\n\n<p>Realistically, a nuclear explosion is a poor method of ensuring the absolute destruction of an object. The explosive damage can be replicated with much safer, more practical explosives, and the radiation damage doesn't require a nuclear explosion to create - any nuclear reactor would be able to furnish you with enough toxic radiation to do whatever you need to do to whatever you need destroyed. </p>\n\n<p>The only reason you'd ever need it to specifically be a nuclear blast is if you need both a large amount of kinetic explosive force <strong>and</strong> high levels of radiation, in an immediate dose and at the same time. </p>\n" }, { "answer_id": 15357, "author": "Darth Wedgius", "author_id": 7525, "author_profile": "https://worldbuilding.stackexchange.com/users/7525", "pm_score": 1, "selected": false, "text": "<p>You could, maybe, use an explosively pumped flux compression generator (I swear I didn't take that from an unproduced Back to the Future IV script -- <a href=\"http://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator\" rel=\"nofollow\">http://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator</a> ) to create a really small fusion explosion without the fission stage ( <a href=\"http://en.wikipedia.org/wiki/Pure_fusion_weapon\" rel=\"nofollow\">http://en.wikipedia.org/wiki/Pure_fusion_weapon</a> ). But that's not just a matter of cost, there are engineering details that I think we're far from having solved -- you'd probably need Tony Stark, Mr. Spock, and Samantha Carter to design the damn thing.</p>\n\n<p>But if it can be done, then you could make fusion explosions smaller than the minimum practical fission explosion (see AndyD273's answer for that ).</p>\n\n<p>There are also supposed to be ways to trigger very small nuclear fission or fusion explosions using anti-matter, but I (just intuitively -- not based on actually having to go through the trouble of, you know, getting <em>knowledge</em>) think that'd be harder to scale down.</p>\n" }, { "answer_id": 15402, "author": "Mandrill", "author_id": 9306, "author_profile": "https://worldbuilding.stackexchange.com/users/9306", "pm_score": 0, "selected": false, "text": "<p>A weapon that consists of 2 devices, one is installed in north pole and emits a very narrow (1 nanometer diameter) beam of neutrinos and the other one is installed in the south pole and emits a beam anti-neutrinos. Neutrinos and anti-neutrinos do not interact with either matter or anti-mater so both fluxes can pass through anything and everything.</p>\n\n<p>A super precise technology allows the beams to be directed with incredible precision. When both beams crosses the neutrinos and anti-neutrinos reactive with each other releasing a great amount of energy.</p>\n\n<p>The project is kept in secret so nobody know such devices exist. When they want to kill someone all they need to know is their precise location in the world and make the beams cross in the target. Doesn't matter if the target is inside a box of steel with 10m thickness walls, there is no safe place.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/15282", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2665/" ]

[ { "answer_id": 15619, "author": "evankh", "author_id": 8918, "author_profile": "https://worldbuilding.stackexchange.com/users/8918", "pm_score": 3, "selected": false, "text": "<p>One trick is to not use all the letters. For elves, you might limit vowels to i and e, and consonants to n, r, b, m, l, and other 'soft' sounds, while dwarves could use u and o, and d, k, l, r, t, g, x, etc. There are a lot of letters like n and m that work for about any type of name, and different types are defined by inclusion or exclusion of just a few letters.</p>\n\n<p>Or you can let your computer do the hard work for you. I myself use a Python script to generate pronounceable random words suitable for names:</p>\n\n<pre><code>def word(syl,p1,p2,con,vow):\n w=''\n for s in range(syl):\n syllable=''\n if random.random()&lt;=p1:\n syllable=syllable+random.choice(con)\n syllable=syllable+random.choice(vow)\n if random.random()&lt;=p2:\n syllable=syllable+random.choice(con)\n w=w+syllable\n return w\n</code></pre>\n\n<p>Just type <code>import random</code> first. <code>syl</code> is the number of syllables, <code>p1</code> and <code>p2</code> are the probabilities of consonants on each end of the syllable, <code>con</code> and <code>vow</code> are list of consonants and vowels. There's probably a cleaner way to do this, codewise, but it works well. By tweaking the probabilities, I can usually get one in four of these random words to be usable names (YMMV) and many more just require simple tweaks like substituting a letter.</p>\n\n<p>For suffixes, you can put <code>+random.choice([list of suffixes])</code> after the function. I find this is good for place names with suffixes like 'bury', 'ton', etc. but it could work well for names too.</p>\n" }, { "answer_id": 15628, "author": "Neil Slater", "author_id": 61, "author_profile": "https://worldbuilding.stackexchange.com/users/61", "pm_score": 2, "selected": false, "text": "<p>This problem crops up so often that many people have made automated name generators publicly available. There are several workable computer algorithms that give reasonable results, in that names will feel like they have the right category and be pronounceable. Whether or not they suit your purpose is a matter of taste. But there are so many, you can just Google for them, find ones that are close enough and maybe customise the results to suit you. Search for \"fantasy random name generator\" or similar will get 100s of hits.</p>\n\n<p>Here is one I quite liked on a quick recent search: <a href=\"http://fantasynamegenerators.com/#fantasyNames\" rel=\"nofollow\">http://fantasynamegenerators.com/#fantasyNames</a></p>\n\n<p>Once you have found one you like, I suggest you run it a few times and note down your favourite names into quick pick lists ready to use. You don't need to use them exactly as-is, you can add a human touch by altering the results. Or you could just treat the output as a starting inspiration, to break out of your block on the small set of endings that have worked for you so far.</p>\n" }, { "answer_id": 15629, "author": "palako", "author_id": 7760, "author_profile": "https://worldbuilding.stackexchange.com/users/7760", "pm_score": 2, "selected": false, "text": "<p>One laborious way to approach this is to construct your own language for your races.\nIt may be a bit too much for just names but the benefits are that\nyou can create other words as well and by following your rules\nyour names and words are consistent.</p>\n\n<p>You at the very least have to decide how the language\nsounds and create the lexicon. Further steps would be to create\ngrammar and design an alphabet but they are not necessarily required\nif you only want to come up with names.</p>\n\n<p>So, essentially you have to define what the language sounds, or to simplify:\ndecide what kind of syllables the language has and only use those to construct\nyour names.</p>\n\n<p>I'd advice you to head to <a href=\"http://www.zompist.com/kit.html\" rel=\"nofollow\">http://www.zompist.com/kit.html</a> for further information and try out\nthe lexicon generator ( <a href=\"http://www.zompist.com/gen.html\" rel=\"nofollow\">http://www.zompist.com/gen.html</a> ) that allows you to create words or the use the more complex Derivizer at ( <a href=\"http://akana.conlang.org/tools/derivizer.html\" rel=\"nofollow\">http://akana.conlang.org/tools/derivizer.html</a> ) to create new derivate names from existing ones.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/15617", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/6620/" ]

[ { "answer_id": 17304, "author": "Erik", "author_id": 5213, "author_profile": "https://worldbuilding.stackexchange.com/users/5213", "pm_score": 5, "selected": true, "text": "<p>\"What could possibly make you think this is a good way to judge a species?\"</p>\n\n<p>Because really, coming all the way here to ask a <em>single, random person</em> to come up with a question in under an hour is really a waste of resources and a huge gamble to get anything useful out it.</p>\n" }, { "answer_id": 17308, "author": "Murphy", "author_id": 4750, "author_profile": "https://worldbuilding.stackexchange.com/users/4750", "pm_score": 2, "selected": false, "text": "<p>\"How do I construct/instantiate the piece of technology/knowledge that you have which you believe would be most beneficial to humanity\"</p>\n\n<p>Why? Their answer is likely to be useful even this is the only interaction you ever have with them, is likely to tell you a lot about their value structure and is likely to tell you something about their tech level.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/17298", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/9644/" ]

[ { "answer_id": 19258, "author": "Aify", "author_id": 6453, "author_profile": "https://worldbuilding.stackexchange.com/users/6453", "pm_score": 6, "selected": true, "text": "<p>Graphene is what you're looking for. </p>\n\n<p>With a tensile strength of 130000 MPa, it has (IIRC) the highest tensile strength in the world.</p>\n\n<p>So lets make a wire-thin sword!</p>\n\n<p>I envision it to probably end up looking something like this:</p>\n\n<pre><code> &gt;----------------------------------------------&lt;|\n||||||| |\n L_______________________________________________|\n</code></pre>\n\n<p>where the <code>-------</code> represent the blade, and the <code>&lt;|</code> the tip that the other end of the blade is connected to, and the <code>||||&gt;</code> represents a handle. It's important to note that the wire is being pulled taut by the <code>&lt;|</code> piece at the end of the blade. The <code>L____|</code> represents a structure similar to that of a hacksaw, in order to hold the wires tightly.</p>\n\n<p>This is a <strong>slashing/chopping</strong> weapon.</p>\n\n<p>How/Why does this work? </p>\n\n<p>The \"Graphene wire\" is really a <strong>Graphene ribbon</strong></p>\n\n<p>Graphene itself contains elastic properties, which helps with the above concept of cutting. Even if the Graphene doesn't cut right away, the elasticity will help it to continue cutting as you swing the blade through your target. \"Graphene sheets (with thicknesses of between 2 and 8 nm) had spring constants in the region of 1-5 N/m and a Young’s modulus (different to that of three-dimensional graphite) of 0.5 TPa.\"</p>\n\n<p>Graphene also has amazing shear strength. Shear modulus of graphite was reported to be ~0.44 TPa. To give you some context, the shear strength of a carbon diamond structure is ~93 GPa. 1 TPa is 1000 GPa.</p>\n\n<p><strong>To answer your question: Yes, you can.</strong> </p>\n\n<p>Unfortunately, because the human body is so variable, I can't find any actual numbers regarding how much force is required to tear off a limb - however, we should note that this blade doesn't apply force the same way a sword does.</p>\n\n<p>A sword cuts and splits the target because it \"wedges\" it apart. In this case, however, because we have a monomolecular ribbon that's completely flat, we should be able to pass through the entire target (irrelevant of what the target is made of, but assuming you gave it a good chop with no deviation in blade angle) extremely easily, since all we're severing are molecular bonds. Forces at the molecular level are at the pico-Newton level (1pN = $10^{-12}$ N); what we exert on anything using anything at any given time exerts more force than what's required. Here's some more context: One pound of force gives us 43.62 Newtons. Even a toddler could exert one pound of force by accident - so if you gave this thing to a baby and he accidentally swung it through you, good luck.</p>\n\n<p>Thank you to Samuel for pointing out some numbers for me: \"the shear strength of the Graphene ribbon is maybe 4200 piconewtons / angstrom, while fibers in the skin, like collagen, have a shear strength of only 5.5 piconewtons / angstrom.\" These numbers show that along the same area, the ribbon has a shear strength of over 750 times that of collagen.</p>\n\n<p>Skin seems easy to cut though. What about bone? Luckily for us, most of bone's elasticity comes from the collagen in it, which means we cut bone just as easily as we do skin.</p>\n\n<p>For an adult? It cuts anything, and everything, better than warm butter. </p>\n\n<p>Once you finish slicing, the limb will only be held on by suction and surface tension. Any movement, and it simply slides/pops off.</p>\n\n<p><strong>However, even regarding the above saying that it is possible in theory, this tool is much better suited to a hospital setting requiring quick amputations than a battle situation.</strong></p>\n\n<p>Strictly speaking, this would work as an amputation device, but would be sorely suited for battle if the opponents also had access to similar weapons. In that scenario, please refer to Ville Neimi's answer (2 to 4th paragraph) regarding why it would suck as a weapon. Note that in normal use, the Graphene should be strong enough to be reused over and over again. The hexagonal structure of the Graphene ribbon means that even if any edge atoms are lost, it doesn't matter - No matter which atoms you lose, you will always have a suitable cutting edge.</p>\n\n<hr>\n\n<p><strong>References:</strong></p>\n\n<p>R. R. Nair, M. Sepioni, I-Ling Tsai, O. Lehtinen, J. Keinonen, A. V. Krasheninnikov, T. Thomson, A. K. Geim, I. V. Grigorieva. Spin-half paramagnetism in graphene induced by point defects. Nature Physics, 2012; DOI: 10.1038/nphys2183</p>\n\n<p><a href=\"http://www.graphenea.com/pages/graphene-properties#.VYCbRkZ8ork\">http://www.graphenea.com/pages/graphene-properties#.VYCbRkZ8ork</a></p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Graphene#Thermal_conductivity\">https://en.wikipedia.org/wiki/Graphene#Thermal_conductivity</a></p>\n\n<p><a href=\"http://poplab.stanford.edu/pdfs/PopVarshneyRoy-GrapheneThermal-MRSbull12.pdf\">http://poplab.stanford.edu/pdfs/PopVarshneyRoy-GrapheneThermal-MRSbull12.pdf</a></p>\n\n<p><a href=\"https://web.engr.illinois.edu/~aluru/Journals/APL11.pdf\">https://web.engr.illinois.edu/~aluru/Journals/APL11.pdf</a></p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Bone\">https://en.wikipedia.org/wiki/Bone</a></p>\n" }, { "answer_id": 19358, "author": "Burki", "author_id": 7000, "author_profile": "https://worldbuilding.stackexchange.com/users/7000", "pm_score": 2, "selected": false, "text": "<p>I think, just like your cool picture suggests, that a whip-like weapon is what you're looking for.<br>\nConsider a whip, i.e. a strand of something (and yes, we'll use carbon-nanotubes here, because they are really, really cool!) with a handle.<br>\nAdd some barbs to the end.<br>\nKeep in mind that anything that is thin enough and does not move out of the way is actually a cutting edge.</p>\n\n<p>Now, you hit your opponent. The strand of carbon nanotubes will be wound around your opponent's arm, and you pull back hard.\nThe thinness of the strand, together with the force you apply by pulling it back, and assisted by the barbs at the end, that will get hooked into your opponent's armour, clothing or flesh, result in the loop around the limb trying to get smaller, and thus cutting tissue that is in the way.</p>\n\n<p>The only question remaining is: can you pull hard enough to cut through the bone?\nThat is where it really helps if your enemy is an armed octopus: They have no bones, which will make the limb removing business a lot easier.<br>\nThe downside: your octopus still has plenty of remaining limbs to make it very, very clear what he thinks about that.</p>\n" }, { "answer_id": 19435, "author": "Ville Niemi", "author_id": 3434, "author_profile": "https://worldbuilding.stackexchange.com/users/3434", "pm_score": 3, "selected": false, "text": "<p>I'll assume you mean \"monomolecular\" literally. In that case the answer is \"<strong>No</strong>\", you can't make practical melee weapons from monomolecular wire. You could build tools or missiles using monomolecular wire and those could have significant amputationility.</p>\n\n<p>The basic issue is that a melee weapon needs to sustain repeatedly hitting the target and, most likely, armor, other weapons and coincidental objects. When that happens the atoms of the weapon will collide with the atoms of whatever is hit. No matter how hard your weapon is this will result in some of the atoms being ablated.</p>\n\n<p>Most weapons are hard enough for the loss to be insignificant, maybe requiring occasional resharpening of the edge. A monomolecular weapon <strong>needs</strong> all of its atoms for its structure. Even if the material has some redundancy so it doesn't simply go \"poof\" or break on first impact it will be locally weakened. So repeated impacts will result in the weapon losing strength until it suddenly breaks. Probably just at the moment you are fighting for your life.</p>\n\n<p>At this point it is simpler to add redundancy by making the impact point a composite of multiple molecules or crystals, just like conventional weapons are. A thin wire of \"conventional\" metal maybe reinforced with nanotubes or graphene gets the job done and is more robust and much simpler to engineer.</p>\n\n<p>For practical monomolecular weapon you need something where the fragility and unpredictable robustness do not matter. A single use weapon such as a missile you throw away or shoot. A specialized tool used for assassination that unless you mess up you only use a single time and then dispose of. A weapon that can recover from being broken by simply producing more of the blade or whip.</p>\n\n<p>The last is probably closest to what is wanted. A whip with an electric charge or a super science force field such as in the picture adding rigidity for pseudo inertia on impact could cause significant damage. And while it would almost certainly break on impact, it would be a simple matter for a microcontroller to detect the length of the whip was reduced from the change in capacitance and extrude enough new material to keep the length constant. A monomolecular whip has very little mass for a certain length so you'd probably run out of power before replacement material.</p>\n\n<p>But even then it would be much easier to use a conventional material instead of an exotic monomolecular one. More robust and probably cheaper. As noted in comments, the practicality of even this limited class of monomolecular weapons is still much less than that of more conventional weapons due to marginal benefits over much more reliable solutions, so nobody would use them. Practical in theory, but not in practice. Which I am not sure even makes sense.</p>\n" }, { "answer_id": 19443, "author": "HDE 226868", "author_id": 627, "author_profile": "https://worldbuilding.stackexchange.com/users/627", "pm_score": 2, "selected": false, "text": "<p>As a starting point, I used <a href=\"https://physics.stackexchange.com/questions/134119/how-does-a-knife-cut-things-at-the-atomic-level\">How does a knife cut things at the atomic level?</a> from Physics Stack Exchange, specifically, <a href=\"https://physics.stackexchange.com/questions/134119/how-does-a-knife-cut-things-at-the-atomic-level/134137#134137\">lemon's answer</a>. lemon¹ talked about something called <a href=\"http://en.wikipedia.org/wiki/Nanoindentation\" rel=\"nofollow noreferrer\">nanoindentation</a>, which is typically used as a laboratory testing technique.</p>\n\n<p>For now, I'll use some of Wikipedia's equations to work this out.</p>\n\n<p>The <a href=\"http://en.wikipedia.org/wiki/Young%27s_modulus\" rel=\"nofollow noreferrer\">Young's modulus</a> of the thing being cut, $E$, is related to the stiffness of the contact, $S$ and the indentation depth, $h$, by\n$$E=\\frac{1}{\\beta}\\frac{\\sqrt{\\pi}}{2}\\frac{S}{\\sqrt{A(h)}}\\tag{1}$$\nwhere\n$$A(h)=\\sum_{n=0}^{n=7}C_nh^{2^{-(n-1)}}$$\nDoing some re-arranging,\n$$A(h)=\\left(\\frac{S\\sqrt{\\pi}}{E\\beta2}\\right)^2$$\nSetting these two equal gives us\n$$\\left(\\frac{S\\sqrt{\\pi}}{E\\beta2}\\right)^2=\\sum_{n=0}^{n=7}C_nh^{2^{-(n-1)}}$$\nLet's solve for $S$:\n$$S=\\frac{2E\\beta}{\\pi}\\sqrt{\\sum_{n=0}^{n=7}C_nh^{2^{-(n-1)}}}\\tag{2}$$\nIf we say that $C_0=C_1=C_2=. . .=24.5$, and $h$, the thickness of the human arm, is about 0.1 meters, and $E$ is about 14, then, for one tip, I find that the stiffness needed is . . . $\\approx$ 1,196,000 Newtons/meter; the force needed is 196,000 Newtons. That's only if one tip is used. Add on more tips on a smaller scale, and this could be feasible. You would get smaller tips, and so smaller identations for each one, but it <em>could</em> work. Perhaps.</p>\n\n<p>The important thing to gain from this is that the types of tips used in nanoindentation can be quite effective. <a href=\"http://www.sciencedirect.com/science/article/pii/S0927025605003289\" rel=\"nofollow noreferrer\">A (paywalled) study</a> also mentioned in lemon's answer showed that the different types of nanoindenters used in the process can produce slightly different results. Fortunately, <a href=\"http://en.wikipedia.org/wiki/Nanoindenter\" rel=\"nofollow noreferrer\">the Wikipedia page on the devices</a> produces a nice starting point for research . . . which led me nowhere. Curses.</p>\n\n<p>What was I even trying to get at? Consider a long piece of barbed wire. Now make the barbs tiny - really tiny - and lined on every piece of the wire. Then turn each barb into something like a nanoindenter. Now you've got quite the weapon. The reason I covered nanoindenters was that I wanted to see if it would be possible to pick a design such that the shape would be more important that the composition.</p>\n\n<p>In any event, the resulting weapon would look like this:</p>\n\n<pre><code> ||\n--------||\n ||---x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x\n--------||\n ||\n</code></pre>\n\n<p>The tip of each \"x\", though, would be in the shape of a nanoindenter.</p>\n\n<hr>\n\n<p>^{1 Note to any potential editors: the username is all lowercase.}\n<br></p>\n" }, { "answer_id": 109325, "author": "bukwyrm", "author_id": 49354, "author_profile": "https://worldbuilding.stackexchange.com/users/49354", "pm_score": 1, "selected": false, "text": "<p>No way. The positive answer(er)s all fail to take into account a) how exceedingly small a molecule is, b) how many molecules there are in a body (and how much they interact with one another) c) how a chain has to weather the sum of all forces acting on it and d) that a force acting perpendicularly on a chain can not simply be colinearized as is, but will lead to a colinear force many times the former magnitude.</p>\n\n<p>Have a breaking strength of 1TP like one answer gave for graphene: One Pascal is one Newton of force (100 grams in earth gravity) on one square meter. So 1TP means <strong>10^12 Newtons per square meter</strong>! Yay! But consider the cross section of a molecule: Let's be generous and set it to 2nmx2nm - thats (2*10^-9)^2. So the breaking force for that single molecule is: 4*10^-6 Newtons ... the force gravity exerts on four tenths of a milligram of mass. You could lift four fruitflies with that! (Yay?)\nAny molecule encountered by the \"whip\" on it's way through flesh will need to be acted upon by a force - shear intermolecular-bonds, shove it out of the way, resist adhesive forces... and at any one time, the whip traversing something as small as the human finger would encounter (lowballing) 10^5 molecules - so any of those molecules could be acted upon by (in the mean) 4*10^-11 Newtons - that's just about ten times the force needed to break a hydrogen bond (weakest bond there is <a href=\"http://www.picotwist.com/index.php?content=smb&amp;option=odg\" rel=\"nofollow noreferrer\">http://www.picotwist.com/index.php?content=smb&amp;option=odg</a>) and just a fourth of the force need to break a noncovalent bond. And we haven't even begun figuring in the multiplicators coming into play because the \"whip\" has these forces acting perpendicular to itself.</p>\n\n<p>The \"whip\" will drift towards its target, strike with undetectable force, and then break at the first tug. Possibly there is a papercut along the way. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/19249", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/3202/" ]

[ { "answer_id": 19258, "author": "Aify", "author_id": 6453, "author_profile": "https://worldbuilding.stackexchange.com/users/6453", "pm_score": 6, "selected": true, "text": "<p>Graphene is what you're looking for. </p>\n\n<p>With a tensile strength of 130000 MPa, it has (IIRC) the highest tensile strength in the world.</p>\n\n<p>So lets make a wire-thin sword!</p>\n\n<p>I envision it to probably end up looking something like this:</p>\n\n<pre><code> &gt;----------------------------------------------&lt;|\n||||||| |\n L_______________________________________________|\n</code></pre>\n\n<p>where the <code>-------</code> represent the blade, and the <code>&lt;|</code> the tip that the other end of the blade is connected to, and the <code>||||&gt;</code> represents a handle. It's important to note that the wire is being pulled taut by the <code>&lt;|</code> piece at the end of the blade. The <code>L____|</code> represents a structure similar to that of a hacksaw, in order to hold the wires tightly.</p>\n\n<p>This is a <strong>slashing/chopping</strong> weapon.</p>\n\n<p>How/Why does this work? </p>\n\n<p>The \"Graphene wire\" is really a <strong>Graphene ribbon</strong></p>\n\n<p>Graphene itself contains elastic properties, which helps with the above concept of cutting. Even if the Graphene doesn't cut right away, the elasticity will help it to continue cutting as you swing the blade through your target. \"Graphene sheets (with thicknesses of between 2 and 8 nm) had spring constants in the region of 1-5 N/m and a Young’s modulus (different to that of three-dimensional graphite) of 0.5 TPa.\"</p>\n\n<p>Graphene also has amazing shear strength. Shear modulus of graphite was reported to be ~0.44 TPa. To give you some context, the shear strength of a carbon diamond structure is ~93 GPa. 1 TPa is 1000 GPa.</p>\n\n<p><strong>To answer your question: Yes, you can.</strong> </p>\n\n<p>Unfortunately, because the human body is so variable, I can't find any actual numbers regarding how much force is required to tear off a limb - however, we should note that this blade doesn't apply force the same way a sword does.</p>\n\n<p>A sword cuts and splits the target because it \"wedges\" it apart. In this case, however, because we have a monomolecular ribbon that's completely flat, we should be able to pass through the entire target (irrelevant of what the target is made of, but assuming you gave it a good chop with no deviation in blade angle) extremely easily, since all we're severing are molecular bonds. Forces at the molecular level are at the pico-Newton level (1pN = $10^{-12}$ N); what we exert on anything using anything at any given time exerts more force than what's required. Here's some more context: One pound of force gives us 43.62 Newtons. Even a toddler could exert one pound of force by accident - so if you gave this thing to a baby and he accidentally swung it through you, good luck.</p>\n\n<p>Thank you to Samuel for pointing out some numbers for me: \"the shear strength of the Graphene ribbon is maybe 4200 piconewtons / angstrom, while fibers in the skin, like collagen, have a shear strength of only 5.5 piconewtons / angstrom.\" These numbers show that along the same area, the ribbon has a shear strength of over 750 times that of collagen.</p>\n\n<p>Skin seems easy to cut though. What about bone? Luckily for us, most of bone's elasticity comes from the collagen in it, which means we cut bone just as easily as we do skin.</p>\n\n<p>For an adult? It cuts anything, and everything, better than warm butter. </p>\n\n<p>Once you finish slicing, the limb will only be held on by suction and surface tension. Any movement, and it simply slides/pops off.</p>\n\n<p><strong>However, even regarding the above saying that it is possible in theory, this tool is much better suited to a hospital setting requiring quick amputations than a battle situation.</strong></p>\n\n<p>Strictly speaking, this would work as an amputation device, but would be sorely suited for battle if the opponents also had access to similar weapons. In that scenario, please refer to Ville Neimi's answer (2 to 4th paragraph) regarding why it would suck as a weapon. Note that in normal use, the Graphene should be strong enough to be reused over and over again. The hexagonal structure of the Graphene ribbon means that even if any edge atoms are lost, it doesn't matter - No matter which atoms you lose, you will always have a suitable cutting edge.</p>\n\n<hr>\n\n<p><strong>References:</strong></p>\n\n<p>R. R. Nair, M. Sepioni, I-Ling Tsai, O. Lehtinen, J. Keinonen, A. V. Krasheninnikov, T. Thomson, A. K. Geim, I. V. Grigorieva. Spin-half paramagnetism in graphene induced by point defects. Nature Physics, 2012; DOI: 10.1038/nphys2183</p>\n\n<p><a href=\"http://www.graphenea.com/pages/graphene-properties#.VYCbRkZ8ork\">http://www.graphenea.com/pages/graphene-properties#.VYCbRkZ8ork</a></p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Graphene#Thermal_conductivity\">https://en.wikipedia.org/wiki/Graphene#Thermal_conductivity</a></p>\n\n<p><a href=\"http://poplab.stanford.edu/pdfs/PopVarshneyRoy-GrapheneThermal-MRSbull12.pdf\">http://poplab.stanford.edu/pdfs/PopVarshneyRoy-GrapheneThermal-MRSbull12.pdf</a></p>\n\n<p><a href=\"https://web.engr.illinois.edu/~aluru/Journals/APL11.pdf\">https://web.engr.illinois.edu/~aluru/Journals/APL11.pdf</a></p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Bone\">https://en.wikipedia.org/wiki/Bone</a></p>\n" }, { "answer_id": 19358, "author": "Burki", "author_id": 7000, "author_profile": "https://worldbuilding.stackexchange.com/users/7000", "pm_score": 2, "selected": false, "text": "<p>I think, just like your cool picture suggests, that a whip-like weapon is what you're looking for.<br>\nConsider a whip, i.e. a strand of something (and yes, we'll use carbon-nanotubes here, because they are really, really cool!) with a handle.<br>\nAdd some barbs to the end.<br>\nKeep in mind that anything that is thin enough and does not move out of the way is actually a cutting edge.</p>\n\n<p>Now, you hit your opponent. The strand of carbon nanotubes will be wound around your opponent's arm, and you pull back hard.\nThe thinness of the strand, together with the force you apply by pulling it back, and assisted by the barbs at the end, that will get hooked into your opponent's armour, clothing or flesh, result in the loop around the limb trying to get smaller, and thus cutting tissue that is in the way.</p>\n\n<p>The only question remaining is: can you pull hard enough to cut through the bone?\nThat is where it really helps if your enemy is an armed octopus: They have no bones, which will make the limb removing business a lot easier.<br>\nThe downside: your octopus still has plenty of remaining limbs to make it very, very clear what he thinks about that.</p>\n" }, { "answer_id": 19435, "author": "Ville Niemi", "author_id": 3434, "author_profile": "https://worldbuilding.stackexchange.com/users/3434", "pm_score": 3, "selected": false, "text": "<p>I'll assume you mean \"monomolecular\" literally. In that case the answer is \"<strong>No</strong>\", you can't make practical melee weapons from monomolecular wire. You could build tools or missiles using monomolecular wire and those could have significant amputationility.</p>\n\n<p>The basic issue is that a melee weapon needs to sustain repeatedly hitting the target and, most likely, armor, other weapons and coincidental objects. When that happens the atoms of the weapon will collide with the atoms of whatever is hit. No matter how hard your weapon is this will result in some of the atoms being ablated.</p>\n\n<p>Most weapons are hard enough for the loss to be insignificant, maybe requiring occasional resharpening of the edge. A monomolecular weapon <strong>needs</strong> all of its atoms for its structure. Even if the material has some redundancy so it doesn't simply go \"poof\" or break on first impact it will be locally weakened. So repeated impacts will result in the weapon losing strength until it suddenly breaks. Probably just at the moment you are fighting for your life.</p>\n\n<p>At this point it is simpler to add redundancy by making the impact point a composite of multiple molecules or crystals, just like conventional weapons are. A thin wire of \"conventional\" metal maybe reinforced with nanotubes or graphene gets the job done and is more robust and much simpler to engineer.</p>\n\n<p>For practical monomolecular weapon you need something where the fragility and unpredictable robustness do not matter. A single use weapon such as a missile you throw away or shoot. A specialized tool used for assassination that unless you mess up you only use a single time and then dispose of. A weapon that can recover from being broken by simply producing more of the blade or whip.</p>\n\n<p>The last is probably closest to what is wanted. A whip with an electric charge or a super science force field such as in the picture adding rigidity for pseudo inertia on impact could cause significant damage. And while it would almost certainly break on impact, it would be a simple matter for a microcontroller to detect the length of the whip was reduced from the change in capacitance and extrude enough new material to keep the length constant. A monomolecular whip has very little mass for a certain length so you'd probably run out of power before replacement material.</p>\n\n<p>But even then it would be much easier to use a conventional material instead of an exotic monomolecular one. More robust and probably cheaper. As noted in comments, the practicality of even this limited class of monomolecular weapons is still much less than that of more conventional weapons due to marginal benefits over much more reliable solutions, so nobody would use them. Practical in theory, but not in practice. Which I am not sure even makes sense.</p>\n" }, { "answer_id": 19443, "author": "HDE 226868", "author_id": 627, "author_profile": "https://worldbuilding.stackexchange.com/users/627", "pm_score": 2, "selected": false, "text": "<p>As a starting point, I used <a href=\"https://physics.stackexchange.com/questions/134119/how-does-a-knife-cut-things-at-the-atomic-level\">How does a knife cut things at the atomic level?</a> from Physics Stack Exchange, specifically, <a href=\"https://physics.stackexchange.com/questions/134119/how-does-a-knife-cut-things-at-the-atomic-level/134137#134137\">lemon's answer</a>. lemon¹ talked about something called <a href=\"http://en.wikipedia.org/wiki/Nanoindentation\" rel=\"nofollow noreferrer\">nanoindentation</a>, which is typically used as a laboratory testing technique.</p>\n\n<p>For now, I'll use some of Wikipedia's equations to work this out.</p>\n\n<p>The <a href=\"http://en.wikipedia.org/wiki/Young%27s_modulus\" rel=\"nofollow noreferrer\">Young's modulus</a> of the thing being cut, $E$, is related to the stiffness of the contact, $S$ and the indentation depth, $h$, by\n$$E=\\frac{1}{\\beta}\\frac{\\sqrt{\\pi}}{2}\\frac{S}{\\sqrt{A(h)}}\\tag{1}$$\nwhere\n$$A(h)=\\sum_{n=0}^{n=7}C_nh^{2^{-(n-1)}}$$\nDoing some re-arranging,\n$$A(h)=\\left(\\frac{S\\sqrt{\\pi}}{E\\beta2}\\right)^2$$\nSetting these two equal gives us\n$$\\left(\\frac{S\\sqrt{\\pi}}{E\\beta2}\\right)^2=\\sum_{n=0}^{n=7}C_nh^{2^{-(n-1)}}$$\nLet's solve for $S$:\n$$S=\\frac{2E\\beta}{\\pi}\\sqrt{\\sum_{n=0}^{n=7}C_nh^{2^{-(n-1)}}}\\tag{2}$$\nIf we say that $C_0=C_1=C_2=. . .=24.5$, and $h$, the thickness of the human arm, is about 0.1 meters, and $E$ is about 14, then, for one tip, I find that the stiffness needed is . . . $\\approx$ 1,196,000 Newtons/meter; the force needed is 196,000 Newtons. That's only if one tip is used. Add on more tips on a smaller scale, and this could be feasible. You would get smaller tips, and so smaller identations for each one, but it <em>could</em> work. Perhaps.</p>\n\n<p>The important thing to gain from this is that the types of tips used in nanoindentation can be quite effective. <a href=\"http://www.sciencedirect.com/science/article/pii/S0927025605003289\" rel=\"nofollow noreferrer\">A (paywalled) study</a> also mentioned in lemon's answer showed that the different types of nanoindenters used in the process can produce slightly different results. Fortunately, <a href=\"http://en.wikipedia.org/wiki/Nanoindenter\" rel=\"nofollow noreferrer\">the Wikipedia page on the devices</a> produces a nice starting point for research . . . which led me nowhere. Curses.</p>\n\n<p>What was I even trying to get at? Consider a long piece of barbed wire. Now make the barbs tiny - really tiny - and lined on every piece of the wire. Then turn each barb into something like a nanoindenter. Now you've got quite the weapon. The reason I covered nanoindenters was that I wanted to see if it would be possible to pick a design such that the shape would be more important that the composition.</p>\n\n<p>In any event, the resulting weapon would look like this:</p>\n\n<pre><code> ||\n--------||\n ||---x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x\n--------||\n ||\n</code></pre>\n\n<p>The tip of each \"x\", though, would be in the shape of a nanoindenter.</p>\n\n<hr>\n\n<p>^{1 Note to any potential editors: the username is all lowercase.}\n<br></p>\n" }, { "answer_id": 109325, "author": "bukwyrm", "author_id": 49354, "author_profile": "https://worldbuilding.stackexchange.com/users/49354", "pm_score": 1, "selected": false, "text": "<p>No way. The positive answer(er)s all fail to take into account a) how exceedingly small a molecule is, b) how many molecules there are in a body (and how much they interact with one another) c) how a chain has to weather the sum of all forces acting on it and d) that a force acting perpendicularly on a chain can not simply be colinearized as is, but will lead to a colinear force many times the former magnitude.</p>\n\n<p>Have a breaking strength of 1TP like one answer gave for graphene: One Pascal is one Newton of force (100 grams in earth gravity) on one square meter. So 1TP means <strong>10^12 Newtons per square meter</strong>! Yay! But consider the cross section of a molecule: Let's be generous and set it to 2nmx2nm - thats (2*10^-9)^2. So the breaking force for that single molecule is: 4*10^-6 Newtons ... the force gravity exerts on four tenths of a milligram of mass. You could lift four fruitflies with that! (Yay?)\nAny molecule encountered by the \"whip\" on it's way through flesh will need to be acted upon by a force - shear intermolecular-bonds, shove it out of the way, resist adhesive forces... and at any one time, the whip traversing something as small as the human finger would encounter (lowballing) 10^5 molecules - so any of those molecules could be acted upon by (in the mean) 4*10^-11 Newtons - that's just about ten times the force needed to break a hydrogen bond (weakest bond there is <a href=\"http://www.picotwist.com/index.php?content=smb&amp;option=odg\" rel=\"nofollow noreferrer\">http://www.picotwist.com/index.php?content=smb&amp;option=odg</a>) and just a fourth of the force need to break a noncovalent bond. And we haven't even begun figuring in the multiplicators coming into play because the \"whip\" has these forces acting perpendicular to itself.</p>\n\n<p>The \"whip\" will drift towards its target, strike with undetectable force, and then break at the first tug. Possibly there is a papercut along the way. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/19253", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/10274/" ]

[ { "answer_id": 19524, "author": "Aify", "author_id": 6453, "author_profile": "https://worldbuilding.stackexchange.com/users/6453", "pm_score": 4, "selected": false, "text": "<p>Build INTO the ground - literally.</p>\n\n<p>A normal building would have a problem because of this:</p>\n\n<pre><code>|--------| &lt;- \n| | Big wave, big problem \\\\\n| | &lt;------------- | | The building has to withstand\n| | / \\ all the force hitting it\n| | / \\\n| [] | / \\\n---------------------------------------------------------ground------------------\n</code></pre>\n\n<p>So the solution is simple. Don't get hit. <strike>Dig</strike> Build like this:</p>\n\n<pre><code> &lt;- ------------ \"Hey, where's my target?\"\n \\\\\n | | The waves go over the building - it doesn't matter how big the\n&lt;- / \\ wave is if it doesn't hit :P\n / \\\n / \\\n-------=-------------------------------------------------ground------------------\n | |\n | | (Note: the \"=\" is the entrance hatch to our building)\n | | \n |________|---- \"Gtfo wave, nothing to hit here\" \n</code></pre>\n\n<p>In other words, you wouldn't see the buildings. You'd have a lot of entrance hatches on the ground though.</p>\n" }, { "answer_id": 19533, "author": "Mikey", "author_id": 3276, "author_profile": "https://worldbuilding.stackexchange.com/users/3276", "pm_score": 3, "selected": false, "text": "<p>This is a very broad question (starting with, what would life be like), so I'll assume and Earth-like progression of life.</p>\n\n<p><strong>Pyramids</strong></p>\n\n<p>The first coral-like structures evolved to be hardy against water erosion - they had to - and adapt to rise above water-level. Your big wave now just washes over and around their pyramid-like structure. After more and more structures mitigate against the strength of the surge. Other life soon follows, and life among the coral cities.</p>\n\n<p>Your advanced peoples build gently sloping ramps, and soon the wave is a non-issue. The architecture looks much like the pyramids and ramps of the hardy coral.</p>\n\n<p><img src=\"https://i.stack.imgur.com/YIflq.jpg\" alt=\"enter image description here\"></p>\n\n<p><strong>Water Life</strong></p>\n\n<p>Life evolves entirely in the water and evolves to go underground rather than to breathe air, and the wave is a non-issue.</p>\n\n<p>Honestly, there's a lot of speculation that can happen here.</p>\n" }, { "answer_id": 19534, "author": "bowlturner", "author_id": 19, "author_profile": "https://worldbuilding.stackexchange.com/users/19", "pm_score": 2, "selected": false, "text": "<p>I would say, they would likely be at least amphibious beings or more fishlike. Can live under water. As such much of their building can take place below the oceans waves where tidal waves will have much less effect. The other option would be far inland where the waters have lost most of their destructive force and are just strong currents. </p>\n\n<p>Under water, they can be any shape imaginable, even to the point they can sway in the ocean currents like sea weed. Which might be what the actually use to make their homes.</p>\n" }, { "answer_id": 19544, "author": "Joshua Hanley", "author_id": 467, "author_profile": "https://worldbuilding.stackexchange.com/users/467", "pm_score": 3, "selected": false, "text": "<p><strong>Structures could survive in deep water, or even on the floating artificial islands on the surface of the ocean above deep water</strong></p>\n\n<p>The wave height shown in the movie is largely due to <a href=\"https://en.wikipedia.org/wiki/Wave_shoaling\" rel=\"noreferrer\">wave shoaling</a>'s amplification of wave height in shallows:</p>\n\n<p><img src=\"https://i.stack.imgur.com/WwlzI.gif\" alt=\"wave shoaling amplification animation\"></p>\n\n<p>Tsunamis don't swamp seagoing ships that are underway out over deep ocean. </p>\n" }, { "answer_id": 19587, "author": "Green", "author_id": 10364, "author_profile": "https://worldbuilding.stackexchange.com/users/10364", "pm_score": 2, "selected": false, "text": "<p>I don't think life would evolve to any kind of tool development on Miller's world because of the very long list of conditions described in this other <a href=\"https://worldbuilding.stackexchange.com/a/2496/10364\">answer</a>. There's just no calm enough place to develop fire or tools, which are prerequisites for building any kind of human level infrastructure.</p>\n\n<p>Life would pick one of at least two strategies for living there. A filter feeder attached to the bedrock or a free-floater living in the standing wave. The closest earth analog to the ecology of Millers' is a <a href=\"https://en.wikipedia.org/wiki/Tide_pool\" rel=\"nofollow noreferrer\">tidal pool habitat</a>. </p>\n" }, { "answer_id": 100381, "author": "NofP", "author_id": 42101, "author_profile": "https://worldbuilding.stackexchange.com/users/42101", "pm_score": 2, "selected": false, "text": "<p>As mentioned elsewhere in the comments, <a href=\"https://physics.stackexchange.com/questions/161004/surface-waves-on-dr-millers-planet/161041#161041\">there are multiple interpretations of the waves.</a> I'll stick with the <i>sloshing</i>, so that it is entirely possible that the waves are only present on the side of the planet that faces the black hole. In this case, the planet rocks forth and back by a small angle, and the wave is basically fixed. </p>\n\n<p>In this situation, the path of destruction due to the wave is rather limited, perhaps a couple of degrees, and most of the planet should be \"safe\". Intelligent life can safely form on the outer edge of the path of destruction. Provided that the wave is directly in line with the black hole, and the planet oscillatory tilt angle is small, there should also be an equally small (safe) area that also experiences a day and night cycle (one hour, in the case of Miller's planet).</p>\n\n<p>Provided that the waves are not the real threat, as long as one chooses the right place, the real issue with building structures would be to deal with the forces exerted by the black-hole. I would expect pyramidal, or small dome structures to survive better than towers or stilted buildings. Given that the planet rocks forth and back, that it is tidally locked, and that the black hole gravitational pull is typically not perpendicular to the surface of the planet, we should expect a non-negligible amount of shear forces along the z-axis (the height) of any structure. Reducing the height of the construction and increasing the section should reduce the chances of failure. Among flat structures with a large base surface, pyramids and domes have a better distribution of inner stress components and are easier to build compared to rectangular blocks.</p>\n\n<p>A pictorial representation, the green area should be safe from the waves:\n<a href=\"https://i.stack.imgur.com/Dx3eB.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Dx3eB.png\" alt=\"Miller&#39;s planet\"></a></p>\n" }, { "answer_id": 190169, "author": "Sumer", "author_id": 80637, "author_profile": "https://worldbuilding.stackexchange.com/users/80637", "pm_score": 0, "selected": false, "text": "<p>I believe that the cities should be built on the poles because the water is frozen and because Gargantua is only visible on a small part of the frozen poles, making the tides lower.</p>\n" }, { "answer_id": 190183, "author": "rek", "author_id": 25189, "author_profile": "https://worldbuilding.stackexchange.com/users/25189", "pm_score": 2, "selected": false, "text": "<p>Their buildings would float, simple as that:</p>\n<p><a href=\"https://i.stack.imgur.com/Dq2Of.gif\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Dq2Of.gif\" alt=\"Candock floating dock, with surfers\" /></a></p>\n<p>Vast mats of linked pontoons would rise and fall with the waves; walls and roofs would flex to conform to the expansion and contraction of the undulation of the flooring substrate, perhaps little more than canvas-like fabric drapped from ropes strung between poles. Nets would hang in strategic places to catch anything dislodged as the flooring tips, and anything of value would either be lashed to poles or tied down to the pontoons.</p>\n<p>The leading edge of such structures would probably come to a point and curve upward to help stay above the first swell of the approaching wave, much like a canoe. You might imagine a 'town' as a series of parallel outriggers linked laterally:</p>\n<p><a href=\"https://i.stack.imgur.com/nNd3M.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/nNd3M.jpg\" alt=\"Outrigger canoe\" /></a></p>\n" }, { "answer_id": 192112, "author": "James McLellan", "author_id": 44287, "author_profile": "https://worldbuilding.stackexchange.com/users/44287", "pm_score": 0, "selected": false, "text": "<h2>We'd Change What We Call Buildable Land</h2>\n<p>We generally do not build on the beach, or in marshes for a similar reason to your aliens -- the technology we have at the time can't cope with the shifting sand, rush of tide.</p>\n<p>I'd suggest that, similarly, your evolving air breathing species' on a 1.2 km-tide planet would build their structures in the areas that are high enough to be safe from the waves. They'd consider the area under the surf to be unsuitable for building.</p>\n<p><strong>As technology progressed</strong> you could build down, into the ground. Or you could build seawalls reclaiming shallow or sheltered areas that aren't exposed to the strongest of the tide. Or you could build floating cities as some have suggested.</p>\n<p>However, to answer the question : I think your evolving species would start with whatever dry ground is available.</p>\n<p><a href=\"https://i.stack.imgur.com/2VVWA.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/2VVWA.png\" alt=\"enter image description here\" /></a></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/19503", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/9418/" ]

[ { "answer_id": 21000, "author": "Samuel", "author_id": 3202, "author_profile": "https://worldbuilding.stackexchange.com/users/3202", "pm_score": 4, "selected": true, "text": "<p>The net lift for the gases is how much the volume of air they displace weighs, minus the weight of the lifting gas itself. The following values are from <a href=\"http://www.airships.net/helium-hydrogen-airships\" rel=\"nofollow\">this site</a> and are per 1,000 cubic feet of volume.</p>\n\n<pre><code> | Weight of Lifting Gas | Weight of Air | Net Lift\n +-----------------------+----------------+------------\nHydrogen | 5.31 lbs | 76.36 lbs | 71.05 lbs\nHelium | 10.54 lbs | 76.36 lbs | 65.82 lbs\n</code></pre>\n\n<p>So, if you have 71 lbs of cargo, you need 1,000 cubic feet of hydrogen to lift it. The volume which the cargo takes up is irrelevant. </p>\n\n<p>You'll need more than to just lift cargo, of course, you have to lift the rest of the ship including the gas bag, deck, rigging, etc.</p>\n\n<p>This is assuming the atmosphere is the same density as on Earth. The specific values are with respect to Earth's gravity, but the ratio will remain for any (reasonable) value of gravity.</p>\n\n<p>If your planet isn't populated <a href=\"https://en.wikipedia.org/wiki/Metric_system#Usage_around_the_world\" rel=\"nofollow\">exclusively by Americans, Myanmas, or Liberians</a> then they probably use the glorious metric system.</p>\n\n<p>In which case the table looks more like this for a volume of one cubic meter:</p>\n\n<pre><code> | Weight of Lifting Gas | Weight of Air | Net Lift\n +-----------------------+----------------+------------\nHydrogen | 0.090 kg | 1.292 kg | 1.202 kg\nHelium | 0.178 kg | 1.292 kg | 1.114 kg\n</code></pre>\n\n<p>If you got some cargo from a backward country and they said it weighed 71 lbs, once you properly weighed it at 32.2 kgs you would know you need about 26.8 cubic meters of helium to lift it.</p>\n\n<p>In your specific case, if you wanted to lift a typical mobile home <a href=\"http://www.anr.state.vt.us/dec/wastediv/recycling/pubs/trailer.pdf\" rel=\"nofollow\">weighing 6758.53 kilograms (14,900 lbs)</a>:</p>\n\n<p>$$6\\,758.53\\ \\mathrm{kg} \\times {{1\\ \\mathrm{m^3}} \\over {1.114\\ \\mathrm{kg}}} \\approx 6\\,070\\ \\mathrm{m^3} $$</p>\n\n<p>You'd need 6,070 cubic meters (~214,000 cubic feet) of hydrogen. This is about two and a half Olympic swimming pools in volume. Or, more specifically, a sphere 22.6 meters (~74 ft) in diameter (a bit over 8 stories tall).</p>\n" }, { "answer_id": 21028, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 2, "selected": false, "text": "<p>If you want to forego the use of lifting gas, and don't mind going big, look at Buckminister Fuller's \"Cloud 9\"</p>\n\n<p>Fuller's insight was the volume of enclosed air in a geodesic dome increased by the cube/square law; it increased by the power of 3 as the dome doubled in area. At some point the amount of air inside the dome vastly outweighed the dome itself, and a temperature differential of as little as 1 degree f could cause the dome to take off like a hot air balloon.</p>\n\n<blockquote>\n <p>A 100-foot-diameter, tensegrity-trussed, geodesic sphere weighing three tons encloses seven tons of air. The air-to-structural-weight ratio is two to one. When we double the size so that the geodesic sphere is 200 feet in diameter, the weight of the structure increases to seven tons while the weight of the air increase to fifty-six tons – the air-to-structure ratio changes as eight to one. When we double the size again to a 400-foot geodesic sphere – the size of several geodesic domes now operating – the weight of the air inside increases to about 500 tons while the weight of the structure increases to fifteen tons. The air-weight-to-structure-weight ratio is now thirty-three to one. When we get to geodesic sphere one-half mile in diameter, the weight of the structure itself becomes of relatively negligible magnitude, for the ratio is approximately a thousand to one.</p>\n</blockquote>\n\n<p>Even larger domes work better, since you have a huge \"reserve\" of lifting power so long as the interior of the dome is warmer than the outside air. The waste heat of human activity and machinery inside the dome will actually help keep it aloft at night.</p>\n\n<p>Like any hot air balloon, you are adrift in the wind (you could add engines and propellers like a Dirigible airship), and the balloon will work better in cold climates where the temperature differential is more pronounced.</p>\n\n<p>The main issue here is are your people technologically capable of creating and maintaining such a structure? Once the idea of a geodesic or similar lightweight structure is developed, it should not take too long for someone to make the same deductions that Fuller did.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/20998", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/11049/" ]

[ { "answer_id": 21411, "author": "HDE 226868", "author_id": 627, "author_profile": "https://worldbuilding.stackexchange.com/users/627", "pm_score": 5, "selected": true, "text": "<h2>Ordering of planets (mass and type)</h2>\n<p>Can I start out by jokingly complaining that you picked a rather complex system? We've found a lot of exoplanets, but there are not many that reside in complex systems like this. This is going to be a tough question. <a href=\"https://worldbuilding.stackexchange.com/questions/21408/creating-a-realistic-worlds-map-solar-systems#comment54732_21408\">As Green predicted</a>, Kepler data is useful here - <a href=\"http://iopscience.iop.org/0004-637X/761/2/92/pdf/apj_761_2_92.pdf\" rel=\"noreferrer\">Fang &amp; Margo (2012)</a> found that</p>\n<blockquote>\n<p>75%–80% of planetary systems have one or two planets with orbital periods less than 200 days</p>\n</blockquote>\n<p>They also were able to plot data from a variety of parameters to come up with some graphs that could be used to make distribution curves. You can extrapolate from that, if you wish.</p>\n<p>Anyway, I'm off track here. Mass distributions were covered in <a href=\"http://iopscience.iop.org/1538-4357/501/2/L199/fulltext/985083.text.html\" rel=\"noreferrer\">Mazeh et al. (1998)</a> (which is almost certainly outdated, but a good analysis nonetheless) and <a href=\"http://arxiv.org/abs/1502.05011\" rel=\"noreferrer\">Malhotra (2015)</a>. Using some orbital spacing parameters (which you can adjust, if you want), Malhotra found that the peak value of <span class=\"math-container\">$\\log m/M_{\\oplus}$</span> occurs at about 0.6-1.0, with a standard deviation of 1.1-1.2. Not the greatest accuracy, but still pretty good.</p>\n<p><a href=\"http://arxiv.org/abs/1101.3545\" rel=\"noreferrer\">Llambay et al. (2011)</a> were able to come up with a mass-period distribution for exoplanets close to the star, which you can then use to come up with a decent distribution of masses at a given radius:</p>\n<blockquote>\n<p>Most smaller planets have orbital periods longer than P~2.5 days, while higher masses are found down to P~1 day.</p>\n</blockquote>\n<p>In short, more massive planets are closer in, while less massive planets are further out. Still, Llambay et al. only considered planets extremely close to their parent stars. For the rest of the system (i.e. planets farther out), I refer you to <a href=\"http://iopscience.iop.org/1538-3881/134/5/2061/pdf/1538-3881_134_5_2061.pdf\" rel=\"noreferrer\">Jiang et al. (2007)</a>. I can't copy the mass- and period- histograms they gave (relating each one to the total number observed), nor can I copy the scatter plots, but they are incredibly helpful, especially as they considered a sample size of 233 exoplanets.</p>\n<p>This graph, complied on <a href=\"http://en.wikipedia.org/wiki/File:Exoplanet_Period-Mass_Scatter.png\" rel=\"noreferrer\">Wikipedia</a> from <a href=\"http://www.openexoplanetcatalogue.com/\" rel=\"noreferrer\">the Open Exoplanet Catalogue</a>, is also helpful for an at-a-glance reference:</p>\n<p><a href=\"https://upload.wikimedia.org/wikipedia/commons/c/cc/Exoplanet_Period-Mass_Scatter.png\" rel=\"noreferrer\"><img src=\"https://upload.wikimedia.org/wikipedia/commons/c/cc/Exoplanet_Period-Mass_Scatter.png\" alt=\"\" /></a>\n<br>\n^{Image in the public domain.}</p>\n<p>Something you must consider is <a href=\"http://en.wikipedia.org/wiki/Planetary_migration\" rel=\"noreferrer\">planetary migration</a>. I've written several answers on it across Stack Exchange (e.g. <a href=\"https://physics.stackexchange.com/questions/160912/the-solar-system-explosion-in-the-nice-model\">The Solar System Explosion in the Nice Model</a>, <a href=\"https://earthscience.stackexchange.com/questions/4595/did-jupiter-really-make-earth-inhabitable\">Did Jupiter really make Earth (in)habitable</a>, <a href=\"https://worldbuilding.stackexchange.com/questions/12281/what-gravitational-impact-would-moving-jupiter-to-the-inner-solar-system-have-on/12290#12290\">What gravitational impact would moving Jupiter to the inner solar system have on the outer?</a>, etc. - the first focused on only one part, because Kyle Oman was already familiar with the it, hence the question), and others have written excellent answers elsewhere on Stack Exchange. By now, I'm sick and tired of typing the same thing up, so I refer you to the latter two posts I gave, as a starter. You need to include planetary migration because it will severely impact the orbits of the three gas giants in the system. Be careful that you have enough - my answer on Physics discusses just why a certain number is needed.</p>\n<hr />\n<h2>Planet mass to star ratio</h2>\n<p>No such ratio exists. You can have pretty much any (reasonable) combination you want. It all depends on the <a href=\"http://en.wikipedia.org/wiki/Molecular_cloud\" rel=\"noreferrer\">giant molecular cloud</a> from which the star formed and the evolution of the <a href=\"http://en.wikipedia.org/wiki/Protoplanetary_disk\" rel=\"noreferrer\">protoplanetary disk</a>. Anything can happen.</p>\n<hr />\n<h1>Number of planets</h1>\n<p>Fang &amp; Margot are, once again, helpful. <a href=\"http://arxiv.org/abs/1203.6072?context=astro-ph\" rel=\"noreferrer\">Weissbein et al.</a> are also an excellent resource for this specific part. I once again wish I could figure out directly how to copy graphs and histogram without using imgur - I may use that later - but I can get around that. Unfortunately, they make three assumptions:</p>\n<ol>\n<li>All planets in a system are exactly aligned</li>\n<li>All of the stars and planets are identical</li>\n<li>The Occupancy distribution of a planet existing at a given distance from its stellar host, f(r), is the same for all the stars which are capable of producing planets and is given by equation (1).</li>\n</ol>\n<p>The third is not a problem, but the first two are (see my section on ecliptic plane confinement for a discussion on the first). Luckily, as I show later, that criterion can easily be met. The second one is the problem.</p>\n<p>Anyway, Weissbein et al. find the probability, <span class=\"math-container\">$P$</span>, that a star hosts <span class=\"math-container\">$m$</span> planets to be\n<span class=\"math-container\">$$P(m)=\\int_0^{\\infty}\\left[\\frac{F(r)^m}{r^2m!}e^{-F(r)}\\right]dr$$</span>\nwhere <span class=\"math-container\">$r$</span> is radius and\n<span class=\"math-container\">$$F(r)\\equiv \\int_0^r f(r')dr'$$</span>\nwhere <span class=\"math-container\">$f(r')$</span> is a modified form of the general occupation probability function.</p>\n<p>They then used this to create a table of the results, which I will not include at the moment, as I am not good with tables in Stack Exchange. However, predictably, the number of systems went down as the number of planets increased.</p>\n<hr />\n<h2>Ecliptic plane confinement</h2>\n<p>&quot;Ecliptic plane confinement&quot; can be discussed in terms of <a href=\"http://en.wikipedia.org/wiki/Orbital_inclination\" rel=\"noreferrer\">orbital inclination</a>, generally denoted by <span class=\"math-container\">$i$</span>. In the case of most systems, this is close to zero degrees for most of the bodies involved (although <a href=\"https://astronomy.stackexchange.com/questions/11360/why-does-pluto-have-a-high-orbital-inclination?lq=1\">Pluto has a high inclination</a>).</p>\n<p>The planets in the Solar System <a href=\"https://astronomy.stackexchange.com/questions/130/why-do-the-planets-in-our-solar-system-orbit-in-the-same-plane?rq=1\">orbit in one plane</a>, because everything formed out of a protoplanetary disk. The planets tend to <a href=\"https://astronomy.stackexchange.com/questions/1095/why-do-the-planets-in-the-solar-system-stay-in-the-same-orbital-plane\">stay that way</a> because of a conservation of angular momentum. This can change in some cases - notably, <a href=\"https://astronomy.stackexchange.com/questions/11392/how-can-a-planet-have-a-90%c2%b0-inclination\">Kepler-452b has a high angle of inclination</a> (90 degrees!). As I wrote in my answer there, this may have happened for several reasons:</p>\n<ul>\n<li>The star's rotation axis was perturbed, just as Uranus's rotation axis was perturbed (although by different objects)</li>\n<li>The planet was perturbed by another object, either in the system (e.g. a planetoid) or a companion star. The Sun was formed with many other stars in a cluster; this happens for many stars.</li>\n</ul>\n<p>The relevant papers on this subject are <a href=\"http://arxiv.org/abs/1405.0960\" rel=\"noreferrer\">Crida &amp; Batygin (2014)</a> and <a href=\"http://iopscience.iop.org/0004-637X/784/1/66/pdf/apj_784_1_66.pdf\" rel=\"noreferrer\">Xue et al. (2014)</a>. There are other reasons for the change in orbital inclination of one planet, notably the <a href=\"http://en.wikipedia.org/wiki/Kozai_mechanism\" rel=\"noreferrer\">Lidov-Kozai mechanism</a> (see <a href=\"http://www.sciencedirect.com/science/article/pii/0032063362901290\" rel=\"noreferrer\">Lidov (1962)</a> and <a href=\"http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1962AJ.....67..591K&amp;data_type=PDF_HIGH&amp;whole_paper=YES&amp;type=PRINTER&amp;filetype=.pdf\" rel=\"noreferrer\">Kozai (1962)</a>). The Lidov-Kozai mechanism basically states that the eccentricity of an object's orbit can be changed by interactions with another (more massive) object, which also changes the orbital eccentricity of the first object. The angular momentum in the <span class=\"math-container\">$z$</span>-axis must be conserved here; it is the quantity\n<span class=\"math-container\">$$L_z=\\sqrt{1-e^2}\\cos i$$</span>\nYou can play around with this a bit to see what happens when different parameters are changed (you should be able to apply the orbital formulas given <a href=\"https://worldbuilding.stackexchange.com/questions/9944/making-a-planet-habitable-for-humanoids-the-planet\">here</a>). However, the model assumes that the perturber is much more massive than the perturbed object (Kozai's original analysis applied to perturbations of asteroids by Jupiter!). For larger bodies being perturbed, you would need a larger perturber. This makes it very difficult for planets. This could happen in a binary system where one star is more massive than another star, and the second star perturbs a planet moving around the larger star. It is, however, unlikely, and does not fit your model of one star.</p>\n<p>It makes sense that either most or the orbits have high orbital inclinations - a result of a perturbation of the star's rotation axis or the protoplanetary disk - or low orbital inclinations. The Lidov-Kozai mechanism is not good for large systems. It is also important to note that it is periodic in nature.\nOnce again quoting Fang &amp; Margot,</p>\n<blockquote>\n<p>In addition, over 85% of planets have orbital inclinations less than 3◦ (relative to a common reference plane).</p>\n</blockquote>\n<p>They used a <a href=\"http://en.wikipedia.org/wiki/Rayleigh_distribution\" rel=\"noreferrer\">Rayleigh distribution</a> to describe this:\n<span class=\"math-container\">$$P(k)=\\frac{k}{\\sigma^2}e^{-k^2/\\sigma^2}$$</span>\nwhere <span class=\"math-container\">$\\sigma$</span> is the parameter that determines the distribution of <span class=\"math-container\">$k$</span>. Notice the difference between a Rayleigh distribution and a <a href=\"http://en.wikipedia.org/wiki/Normal_distribution\" rel=\"noreferrer\">normal distribution</a>. An distribution for orbital eccentricity can be found in <a href=\"http://arxiv.org/abs/1203.1631\" rel=\"noreferrer\">Kane et al. (2012)</a>.</p>\n<hr />\n<h2>Bringing it all together.</h2>\n<p>There's the raw information that we need. Here's the synthesis.</p>\n<blockquote>\n<p>Is this the most likely arrangement, RxAxGx?</p>\n</blockquote>\n<p>Well, it's unlikely for that many planets to form around a star, so technically, no. Three gas giants implies orbital migration, which <em>could</em> push them outwards, as in our Solar System, but be prepared to have a fourth be in there at the beginning, as some variants of the Nice Model require (the &quot;5th gas giant&quot;).</p>\n<blockquote>\n<p>Can a massive gas giant be orbiting near the star out of the ecliptic plane?</p>\n</blockquote>\n<p>I stated earlier that the perturber generally needs to be more massive than the perturbed object, in classical models of the Kozai effect. This means that such an arrangement is unlikely to happen. A gas giant could be close to the star, sure, but not out of the ecliptic, if it was with a system of other planets that stayed in the ecliptic.</p>\n<blockquote>\n<p>Can the habitable would be alone with some comets and asteroids?</p>\n</blockquote>\n<p>Asteroids? Sure. Well, the habitable could not be <em>in</em> the asteroid belt, because then it would not have cleared its orbit and would be prone to collisions, which would quickly make the planet not so habitable!</p>\n<p><strong>The arrangement, on the whole, could happen.</strong></p>\n" }, { "answer_id": 21412, "author": "Avon", "author_id": 10685, "author_profile": "https://worldbuilding.stackexchange.com/users/10685", "pm_score": 2, "selected": false, "text": "<p><strong>Rocky/Gas Configurations</strong></p>\n\n<p>Anything is possible but it is no coincidence that the solar system has its most dense planets at orbits closest to the sun and gas giants a lot further out. The greater temperatures and solar wind pressures nearer the star will be pushing lighter elements away more easily from inner orbits when the star's reactor fires up. </p>\n\n<p>To quote <a href=\"https://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System</a>:</p>\n\n<blockquote>\n <p>The inner Solar System, the region of the Solar System inside 4 AU,\n was too warm for volatile molecules like water and methane to\n condense, so the planetesimals that formed there could only form from\n compounds with high melting points, such as metals (like iron, nickel,\n and aluminium) and rocky silicates.</p>\n</blockquote>\n\n<p>Heavy rocky planets nearer the star and gas giants further away are probably the most likely configuration with only peculiar formation events changing that.</p>\n\n<p>Independent rocky planets in the zone of the gas giants don't exist in our solar system but rocky moons of those gas giants do. So, rocky things can and do exist at any distance but gas giants tend to be further away and capture or destroy anything in their path. </p>\n\n<p>That gas giants don't exist beyond a certain point is probably simply a matter of the solar nebula being too thin after certain distances.</p>\n\n<p>Binary to trinary systems could perhaps produce different situations. If Jupiter had been big enough to be a red dwarf then we would have a complex binary system: Still probably with rocky planets between the two stars but perhaps an even larger rocky system orbiting Jupiter. However, we expect multiple-star systems to be generally less conducive to stable orbits as close as the habitable zone.</p>\n\n<p><strong>Orbital Planes and Directions</strong></p>\n\n<p>All planets formed within the system will be orbiting in the same plane and in the same direction: they will be constructed in that orbit from the same rotating primordial mass.</p>\n\n<p>However, collisions or gravitational interactions with a extra-stellar objects could feasibly knock a planet into a slightly different plane of orbit. It would have to be from an extra-stellar object, everything else has the same angular velocity vectors so collisions between system bodies just knock things into different motions in the same plane.</p>\n\n<p>A solar system that moved too close to a particularly massive neighbor could end up with planets in orbital planes that slope and become more elliptical the further out they are. That is far more likely than a rogue extra-stellar planet crashing into one of the planets and producing a new planet orbiting in a different plane and/or direction.</p>\n\n<p><strong>Captured Planets</strong></p>\n\n<p>Capturing an object in orbit is extremely unlikely: they tend to follow parabolic or hyperbolic paths and leave the encounter with the same kinetic energy they arrived. Only collisions during the process can change that and they are highly unlikely to happen let alone happen in just the right way to cause the visitor to start orbiting.</p>\n\n<p>However, it is possible: Neptune captured Triton (we know this because Triton orbits the opposite way to Neptune's rotation) so an extra-stellar planet could be captured and that could happen in any plane or any direction. It had to involve a collision so the result could be another planet also orbiting in a peculiar plane and direction.</p>\n\n<p><strong>The Star(s) Itself</strong></p>\n\n<p>Blue giants and super giants (O and B class) are almost certainly to be ruled out: they are too short lived.</p>\n\n<p>Other giants are also likely to be ruled out as they tend to be dying stars: the habitable zone will have moved and that causes problems for evolution. Their lives as giants also tend to be short. </p>\n\n<p>But anything else except dead stars (White Dwarfs, Neutron Stars and Black Holes) is feasible. </p>\n\n<p>Only nice orange, yellow or white main sequence stars seem likely to produce habitable zones that are stable for long enough for life to evolve:</p>\n\n<p><a href=\"https://i.stack.imgur.com/mvCJi.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/mvCJi.png\" alt=\"enter image description here\"></a></p>\n\n<p><strong>Disclaimer</strong></p>\n\n<p>We live in one of hundreds of billions of galaxies each with hundreds of billions of stars. I expect every imaginable configuration exists at least around one of those stars.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/21408", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/3202/" ]

[ { "answer_id": 21589, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 3, "selected": false, "text": "<p>So this one is pretty much hopeless. If you read anything about planetoids, you know we can't protect ourselves against them. If you read anything about stars, they basically boss planetoids around without more than the slightest wobble. Black holes boss stars around.</p>\n\n<p>Our best hope is to beg forgiveness. I don't know what we can do, but it is certainly going to involve lots of groveling, because they have 100% control of the situation, and if we are really really really optimistic, we can claim we have 0.00000001% of the control.</p>\n\n<pre><code>What can we do to defend Earth from the black holes?\nHow do we arrest these black holes?\nWhat Judicial precedents apply for trying the black holes in court?\nIn the long term, how will we mend human-black Hole relations, based on human-human relations in history, when one group of humans disrespected another.\n</code></pre>\n\n<p>Nothing. We do not defend Earth from black holes, because it is simply not realistic. We do not arrest black holes or have judicial precidences for the same reason we do not arrest solar flares... they're bigger than our entire judicial system. As for mending things... grovel. Admit our place, which is really no place at all, and hope that it is worth their time to even hear our groveling. It might not even be a concern anymore.</p>\n\n<p>For a sense of how big these black holes are, I will point out that they are within a few orders of magnitude of a supernova. Here's <a href=\"https://what-if.xkcd.com/73/\" rel=\"noreferrer\">XKCD's thoughts</a> on how big a supernova is.</p>\n" }, { "answer_id": 21606, "author": "Lorry Laurence mcLarry", "author_id": 10981, "author_profile": "https://worldbuilding.stackexchange.com/users/10981", "pm_score": 2, "selected": false, "text": "<p>Simple. We need to ask sentient Galaxies to arbitrate over us all.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/21583", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/8914/" ]

[ { "answer_id": 21597, "author": "Mark", "author_id": 278, "author_profile": "https://worldbuilding.stackexchange.com/users/278", "pm_score": 2, "selected": false, "text": "<p>That'll work, but it's inefficient: much of the energy generated gets radiated away as gamma radiation or other high-energy photons, while the need to keep the reaction chamber from overheating limits how fast you can use the fuel.</p>\n\n<p>A closely related concept you might be interested in the <a href=\"https://en.wikipedia.org/wiki/Nuclear_salt-water_rocket\" rel=\"nofollow\">nuclear salt-water rocket</a>: instead of injecting liquid uranium, it uses uranium salts dissolved in water.</p>\n" }, { "answer_id": 21598, "author": "Jim2B", "author_id": 7886, "author_profile": "https://worldbuilding.stackexchange.com/users/7886", "pm_score": 3, "selected": true, "text": "<p>There is a concept similar to this called a <a href=\"http://www.projectrho.com/public_html/rocket/enginelist.php#id--Nuclear_Thermal--Gas_Core--Open_Cycle--Nuclear_Salt_Water\" rel=\"nofollow noreferrer\">Nuclear Salt Water Rocket (NSWR)</A> that was proposed by an SF writer who is also a physicist.</p>\n\n<blockquote>\n <p>The fuel is a 2% solution of 20% enriched Uranium Tetrabromide in\n water. A Plutonium salt can also be used.</p>\n \n <p>Just to make things clear, there are two percentages here. The fuel is\n a 2% solution of uranium tetrabromide and water. That is, 2 molecules\n of uranium tetrabromide per 100 molecules of water.</p>\n \n <p>But the uranium tetrabromide can be 20% enriched. This means that out\n of every 100 atoms of uranium (or molecules of uranium tetrabromide),\n 20 are fissionable Uranium-235 and 80 are non-fissionable uranium. If\n it is 90% enriched, then 90 atoms are Uranium-235 and 10 atoms are\n non-fissionable. As a side note, 90% enriched is considered\n \"weapons-grade\".</p>\n \n <p>The fuel tanks are a bundle of pipes coated with a layer of boron\n carbide neutron damper. The damper prevents a chain reaction. The fuel\n is injected into a long cylindrical plenum pipe of large diameter,\n which terminates in a rocket nozzle. Free of the neutron damper, a\n critical mass of uranium soon develops. The energy release vaporizes\n the water, and the blast of steam carries the still reacting uranium\n out the nozzle.</p>\n \n <p>It is basically a continuously detonating Orion type drive with water\n as propellant. Although <strong>Zubrin</strong> puts it like this:</p>\n \n <blockquote>\n<pre><code>As the solution continues to pour into the plenum from the borated\nstorage pipes, a steady-state conditions of a moving detonating fluid\ncan be set up within the plenum.\n</code></pre>\n </blockquote>\n</blockquote>\n\n<p>Also, just to be clear this is a concept that could work <em>in theory</em> but working out the engineering details will be incredibly difficult (and other scientists do not think it will ever be practical).</p>\n\n<p>NSWR:<br>\n<a href=\"https://i.stack.imgur.com/zBQmV.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/zBQmV.jpg\" alt=\"NSWR\"></a></p>\n\n<p>20% UTB</p>\n\n<pre>\nExhaust Velocity 66,000 m/s\nSpecific Impulse 6,728 s \nThrust 12,900,000 N\nThrust Power 425.7 GW \nMass Flow 195 kg/s\nTotal Engine Mass 33,000 kg</pre>\n\n<p>90% UTB</p>\n\n<pre>\nExhaust Velocity 4,700,000 m/s \nSpecific Impulse 479,103 s \nThrust 13,000,000 N \nThrust Power 30.6 TW \nMass Flow 3 kg/s</pre>\n\n<p>Far more information available at the link provided above.</p>\n" }, { "answer_id": 21639, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 0, "selected": false, "text": "<p>Various nuclear systems exist, but perhaps the closest to what you are describing is the dusty fission fragment engine.</p>\n\n<p>Uranium or Plutonium diet is injected into the reaction chamber and held by a combination of electrical and magnetic fields. When enough dust is present, criticality is reached and the dust becomes a mass of plasma, with fission fragments flying out at speeds up to 3% of <em>c</em> Using the magnetic and electric fields to guide the reaction products out of the chamber and through a rocket nozzle provides thrust, although internal collisions and interaction with the fields reduces the exhaust velocity to a \"mere\" 1% of <em>c</em>.</p>\n\n<p>This is a low thrust, high ISP engine, but calculations suggest that using this device could propel a spacecraft to Jupiter in 6 years (accelerating and decelerating so you are captured in Jovian orbit. Energy could also be captured to run ship systems, either through capturing some of the waste heat of the engine to run turbines, or by slowing the exhaust stream further by allowing it to pass through an MHD generator (which is much lighter than turbines and is also highly efficient in converting the energy into electrical power).</p>\n\n<p>So long as fissionable \"dust\" is being injected into the core, the reactor will continue to provide thrust and power to the ship.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/21596", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/10981/" ]

[ { "answer_id": 22354, "author": "Dynas", "author_id": 11327, "author_profile": "https://worldbuilding.stackexchange.com/users/11327", "pm_score": 0, "selected": false, "text": "<p>Davinci developed his flying machine. Parachutes are fairly simple technology and operate on \"drag\" to deploy. Why can the halfling have a smaller parachute to deploy rather than a net. The more difficult problem is getting them high enough to merit their use. If they live on a mountain or cliff or floating city then awesome. The problem with the middle ages was lack of flying devices to merit their use. Do you have magic in this world?</p>\n" }, { "answer_id": 22370, "author": "Aify", "author_id": 6453, "author_profile": "https://worldbuilding.stackexchange.com/users/6453", "pm_score": 1, "selected": false, "text": "<p>Assuming a wingsuit with a 2-1 glide ratio (2 meters forward, 1 meter down), we should be able to create a massive net to catch the halfling. Wingsuits typically start gliding at approx 30mph (which is approx 13 m/s, taking approx 1.365 seconds to reach).</p>\n\n<p>Rough calculation (probably not that accurate): </p>\n\n<p>Starting from 100 meters up, jumping forwards, taking 1.365 seconds to reach wingsuit glidable speed, the halfling has already dropped ~9.136 meters, leaving ~91 meters to drop. If we go with a straight up conversion using the glide ratio assumed, our maximum distance traveled is 182 meters forward - but this would leave us splat on the ground, so we need to reduce this.</p>\n\n<p>Let us assume the following setup.</p>\n\n<pre><code> platforms\n___ ___\n | |\n | |\n | badly drawn net |\n | x __ | ^\n | -- | 100m\n | \\- | v\n | \\-_ _ /|\n_____________________________________________ground\n</code></pre>\n\n<p>X marks the target for the halfling, where he should aim to start contacting the net. The net will be roughly U shaped with the outer end much higher than the end point. The point of the catcher is to change his downards trajectory as gently as possible into a horizontal trajectory, until we can change it into an upwards trajectory where gravity will slow him down to safety. By using a curved net, we can acheive this - kind of like how skateboarders eventually settle down in the middle of a halfpipe.</p>\n\n<p>However, all that is speculation without actual math, so lets do some math.</p>\n\n<p>A 91 meter drop allows you to drop for 4.30799664301 seconds before hitting the ground. During that time you will have traveled 182 meters forward, but you would have hit the ground at a speed of 39.2266 meters per second, enough to kill your halfling. Assuming your net is large enough and your target tree is really far away, you could potentially allow for a full flight time of 2 + 1.365 seconds, where he would have dropped his altitude by a total of 55.5214522231 meters - we subtract the initial 9.1 meters, leaving him with leaving him with a total distance traveled of about 90 meters forwards (Enough to fly over a river or a small hill or something like that). At that point, he is plummeting at 32.99937725 meters per second, which is quite dangerous. This is where your halfling should reach the top of the net and begin to roll down it. He'll have 45 meters (roughly) of netting to roll through, while friction and the net slow him down, eventually to the point of safety.</p>\n\n<p>In short: From a 100 meter drop, the halfling can fly 90 meters forwards before probably needing to hit the catcher.</p>\n\n<p>Note: You may have noticed I didn't actually do the math for how long it would take the net to stop him, or how far he would have to roll. This is because <strong>I don't know how to do the math for that part.</strong> If anyone does, <strong>please</strong> feel free to edit this answer to include the proper maths.</p>\n\n<p>Note 2: I used <a href=\"http://www.gravitycalc.com/\" rel=\"nofollow\">this</a> site for the calculations.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/22287", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2947/" ]

[ { "answer_id": 22564, "author": "bowlturner", "author_id": 19, "author_profile": "https://worldbuilding.stackexchange.com/users/19", "pm_score": 3, "selected": false, "text": "<p>I'm going with a bullwhip. You can add things at either end. A cat-o-nine tales is a whip with little bits of metal in the ends. The handle could have different items as well, a spike, or mace type end. with double elbows the whip would be an incredibly nimble weapon. On top of that with the thumbs they could have parts of the 'cat-o-nine' that would lengthen and shorten different ends allowing for them to poison one person, inject someone else with a sleeping potion and just plain whip a third, all accurately and with the same weapon!</p>\n\n<p>Because of a question about short-sightedness. Most bullwhips are in the 7-10ft. range. I'm very near-sighted and I can see 10ft. away with the accuracy to use a whip. On top of that, with their excellent hearing they may use <a href=\"http://news.sciencemag.org/brain-behavior/2014/11/how-blind-people-use-batlike-sonar\" rel=\"noreferrer\">echolocation</a> type techniques to help pin down more accurately a targets location. Some blind people can ride their bikes down a busy street with it.</p>\n" }, { "answer_id": 22566, "author": "Aify", "author_id": 6453, "author_profile": "https://worldbuilding.stackexchange.com/users/6453", "pm_score": 7, "selected": true, "text": "<p>First, lets do away with the usual concept of a melee weapon. Short sightedness tends to make conventional weapons inaccurate and bad to use. So lets get up close and personal.</p>\n\n<p>Your description of the elbow placement and arm structure reminds me very much of the praying mantis. <a href=\"https://i.stack.imgur.com/NuJtT.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/NuJtT.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>When in doubt, look at nature. The mantis is often considered natures \"Perfect Predator\". But that's less important for this question - what's more important is its arm structure.</p>\n\n<p>Assuming that the elbows bend the same ways as the mantis elbows do, with joints at 1/3 and 2/3 down the arm, we can apply a specific weapon for maximum efficiency, taking into account natures design.</p>\n\n<p>I propose the following weapon:</p>\n\n<pre><code>---------O---------O---------[]&gt;\n V V V V V V V V V\n</code></pre>\n\n<p>Or alternatively, following the same concept (Version 2)</p>\n\n<pre><code>---------o---------o---------[]&gt;\n \\_______/ \\______/\n</code></pre>\n\n<p>This is meant to be a \"harness\" (but can be easily adapted to have protection in the form of metal plates or whatnot).</p>\n\n<ul>\n<li><code>[]&gt;</code> represents a handheld spike</li>\n<li><code>o</code> represents a joint</li>\n<li><code>---------</code> represents the sections of the arm that it is attached to, either via straps or locking mechanism, or whatever you want.</li>\n<li><code>V</code> represents spikes</li>\n<li><code>\\____/</code> represents blades</li>\n</ul>\n\n<p>How does this weapon work?</p>\n\n<p>Let's tackle this weapon one spot at a time, starting with the hand held spike. Consider the fully retracted arm - it looks something like this:</p>\n\n<pre><code>\\/\\\n</code></pre>\n\n<p>This is a position from which we can easily extend forwards into this:</p>\n\n<pre><code>─ ─ ─ \n</code></pre>\n\n<p>By providing a spike for the hand to hold, the user can \"palm thrust\" the spikes into the enemy quickly and with precision. Generally, stabbing is easily forseen as us single elbow users have to pull back and then thrust forwards. In this case, the double elbow user doesn't have the \"pulling back\" motion, since the retracted motion is likely the \"default\" position in order to keep the arms off the floor (especially since the arms are longer than the body).</p>\n\n<p>Note: the palm spike can easily be interchanged with a large amount of options, such as palm bucklers or normal weaponry. Highly customizable.</p>\n\n<p>What about the spikes and blades?</p>\n\n<p>Spikes and blades are interchangeable. I picked the spikes for version 1 because the mantis has spikes. It makes for a good gripping mechanism. You can grip with the following arm motion:</p>\n\n<pre><code> __\n\\/| -&gt; \\/ -&gt; \\/|\nstart extend retract and grip\n</code></pre>\n\n<p>and the spikes will help keep your gripped target in place while you thrust into them with the spike in your other hand.</p>\n\n<p>The blades, however, are not for gripping. If we offset the front and back blades a little bit, we can use them as a pair of scissors. Using the same motion as above, we can slice off limbs easily using the arm-slicers.</p>\n\n<p>Alternatively, with the blades, you don't have to cut like a scissor. When throw outwards with the same initial motion as the cut, as long as the user aims higher than the target, he can get a \"cutting\" like a knife motion with the blade, and achieve \"slashing\" by simply swinging the arm instead of retracting it.</p>\n\n<p>This weapon isn't only for offense. If we design the arm sections with plating, we now effectively have weaponized gauntlets, and the user can use the protected arms (especially since they're so long) as shields to block attacks.</p>\n\n<p>You mention that it should be customizable per user for looks and usability - easily done, as you can change out parts of the harness for thicker metal plates for protection, or sharper cutting appendages, etc etc, anything the user wants, and it can be easily painted and whatnot for decoration.</p>\n\n<p><strong>There you have it - the perfect melee weapon for a two elbowed creature.</strong></p>\n" }, { "answer_id": 22567, "author": "Samuel", "author_id": 3202, "author_profile": "https://worldbuilding.stackexchange.com/users/3202", "pm_score": 4, "selected": false, "text": "<p><strong>Arm Blades</strong></p>\n\n<p>The weakness for such a creature would be in those long exposed arms from getting chopped. A blade mounted to the arm will offer protection and offense for their extended arms.</p>\n\n<p><a href=\"https://i.stack.imgur.com/3ZOJa.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/3ZOJa.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>The blades can be used extended in times where extra reach is required or brought in close when in tight spaces. The retracted blades would mesh well with their natural <a href=\"https://en.wikipedia.org/wiki/Proprioception\" rel=\"noreferrer\">proprioception</a>, which will significantly reduce training required and chance of slicing oneself. </p>\n\n<p>They can be further customized by dual wielding, blade length, serrations, backward pointing spikes, etc.</p>\n" }, { "answer_id": 22569, "author": "DaaaahWhoosh", "author_id": 6507, "author_profile": "https://worldbuilding.stackexchange.com/users/6507", "pm_score": 1, "selected": false, "text": "<p>I'd first like to point out that the second elbow might just be a modified wrist. Many animals walk on what humans use as fingers, whether it be dogs walking on the palm-side or primates on the knuckle-side. It's not too inconceivable to believe that evolution simply kept this pattern for goblins, and extended it to include opposable thumbs and more functional fingers, though I admit I don't think it'd happen with as many joints as humans' ancestors had. </p>\n\n<p>Anyway, perhaps it's not the weapon that the goblins customize and tinker with, but the way it's used. With an extra elbow, these creatures are going to have superhuman dexterity and flexibility. It's very possible they'll be able to achieve a full 360-degree rotation of their hands, and put their hands in places humans can only dream of reaching. Thus, holding a knife or sword 'down' (slasher movie style) or 'up' (knife fighting style) might end up working about the same, or at least having the same level of effectiveness. This and many other different and perhaps laughable strategies will now be open for the goblins to try out and make their own. </p>\n\n<p>To work with this idea, swords (because swords are great, you really should just stick with them) can be modified for different <strong>lengths</strong> (already a thing, longer for reach at the expense of weight and cumbersomeness, shorter for the opposite), different <strong>weights</strong> (also a thing, weighted in the pommel makes it move more quickly, weighted towards the tip makes it hit harder), different <strong>angles</strong> (straight swords are easier to understand and use, while curved or angled swords are more complex but can be twisted around some blocking manouvres), and different <strong>guards</strong> (depending on how it's held, you might want to protect your hand differently). All of these can be customized to work best with an individual's preferred fighting style. </p>\n\n<p>Plus, they should carry a shield, because all these fighting styles means it's going to be very hard to know what your enemy is going to do. Shields can be modified for size, shape, material, and how it attaches to your arm. You really have a lot of options, even if everyone is running around with a sword and shield. </p>\n" }, { "answer_id": 22574, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 2, "selected": false, "text": "<p>Most races are not confined to a single weapon.</p>\n\n<p>So I'll suggest a few that would be immensely strong, based on their physique.</p>\n\n<h2><strong>Daggers</strong></h2>\n\n<p>Because of the traits (small areas/ enclosed spaces)(like trinkets and gadgets)(opportunists) they inherently have, Daggers synergize very well with them. Small weapons work well in tight areas, and daggers excel in this category.</p>\n\n<p>Due to their opportunistic nature, daggers would be useful for them to quickly deal massive amounts of damage/pain to their enemies. Their size facilitates this by being lighter. Curving the blade can also help this, since their additional joint gives them another angle to slice from.</p>\n\n<p>Trinket and gadgets play on the small nature a bit, however this comes into play with the mechanical side of the dagger. Hidden in the handle, spring loaded, extremely shiny as a blinding mechanism, these intelligent creatures use every facet of the dagger to their advantage.</p>\n\n<h2><strong>Darts</strong></h2>\n\n<p>Taking on a \"ranged dagger\" approach, darts can be slathered in poisons made from foliage taken from the very caves they live in. Since they're also small, they fit the physique of the creatures as well as the trinket-style attraction. Their thick skins also make holding 5 of these between their six fingers without pricking themselves easy.</p>\n\n<h2> <strong>Slings</strong></h2>\n\n<p>Depending on how you structure the secondary elbow, slings can be incredibly powerful, or average. Cheap to make, slings require a bit of cloth and a stone, so for those living in caves, these would be common. Shortsightedness isn't an issue with slings, as they can be used in melee situations as a club to a much lesser degree. </p>\n\n<h2><strong>Unconventional Weapons</strong></h2>\n\n<p>Dirty fighting tactics, such as a \"dust bomb\" that impairs enemy vision, giving them the advantage in close combat.</p>\n\n<p>Their size gives them an advantage against taller opponents when using ranged weapons. </p>\n\n<p>Chains, alone or with weapons attached. If a goblin is fast enough, he can use the chain to trip his enemies, finishing them off with the weapon attached to the tip. Think <a href=\"http://vignette3.wikia.nocookie.net/mkwikia/images/d/d9/Scorpion-Mortal-Kombat.png/revision/latest?cb=20110502235720\" rel=\"nofollow\">Scorpion's kunai</a>.</p>\n" }, { "answer_id": 22603, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 2, "selected": false, "text": "<p>Assuming that arms are like levers - the farther from the pivot, the weaker and faster they are. So, the goblins need weapons that benefit from speed and do not require too much strength.<br></p>\n\n<p>I guess, you could take a look at the <a href=\"https://en.wikipedia.org/wiki/Meteor_hammer\" rel=\"nofollow noreferrer\">meteor hammer</a>:<br><img src=\"https://i.stack.imgur.com/nPvvt.jpg\" alt=\"meteor hammer\"><br>\n+ Longer arms make faster strikes <br>\n+ Two elbows allow strikes at various angles<br>\n+ Two opposable thumbs give more presicion<br>\n+ The weapon has a lot of potential usages (listed below)<br>\n± To some extent, allows to block incoming attacks<br>\n- Require training.</p>\n\n<p><br>\nThe usages of this hammer include:<br>\n - Throw one of the heads to hit the opponent (upfront, or from above, or from a side), pull the head back<br>\n - Throw the meteor to wrap itself around a weapon, object or an opponent's limb, pull the head back to get the object / disarm or trip the opponent<br>\n - Block an attack using the chain<br>\n<br>\nSmall daggers and spiked knuckles seem like a good backup options. Due to their dexterity, goblins may have good chances of blinding the opponent.<br><br>\n(Also, your goblins remind me of <a href=\"http://www.tuckerskobolds.com/\" rel=\"nofollow noreferrer\">these</a> hellish kobolds a bit. Very promising creatures and really dangerous opponents :)</p>\n" }, { "answer_id": 22605, "author": "chineseflame", "author_id": 11692, "author_profile": "https://worldbuilding.stackexchange.com/users/11692", "pm_score": 2, "selected": false, "text": "<p>How about the baguazhang rooster claw ... The long arm and hook can extend up to the first elbow and protect the extended limbs:</p>\n\n<p><a href=\"https://i.stack.imgur.com/pPU1d.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/pPU1d.jpg\" alt=\"enter image description here\"></a>\n(<a href=\"http://www.selfdefenseguides.info/claw-knives/li-zi-ming-s-ba-gua-zhang-method.html\" rel=\"nofollow noreferrer\">Source</a>)</p>\n" }, { "answer_id": 22609, "author": "K. Meke", "author_id": 11691, "author_profile": "https://worldbuilding.stackexchange.com/users/11691", "pm_score": 2, "selected": false, "text": "<p>I love the preying mantis analysis, but my first thought when I saw the question was nunchucks! I can imagine all kinds of deadly, spinning mayhem perpetrated by a multi-jointed wielder.</p>\n" }, { "answer_id": 22633, "author": "TeasingDart", "author_id": 11700, "author_profile": "https://worldbuilding.stackexchange.com/users/11700", "pm_score": 1, "selected": false, "text": "<p>I propose a boomerang as a throwing weapon. The first joint is used as the throwing lever and the second joint could impart a wicked-fast counterspin.</p>\n" }, { "answer_id": 22664, "author": "SeanR", "author_id": 3235, "author_profile": "https://worldbuilding.stackexchange.com/users/3235", "pm_score": 2, "selected": false, "text": "<p><strong>Hammers.</strong></p>\n\n<p>The extra thumbs will give a firmer grip, extra elbows will give extra speed.</p>\n\n<p>It can also be <em>very</em> theatrical too!</p>\n\n<p><a href=\"https://i.stack.imgur.com/0cpPl.gif\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/0cpPl.gif\" alt=\"enter image description here\"></a></p>\n" }, { "answer_id": 22722, "author": "Jim", "author_id": 3054, "author_profile": "https://worldbuilding.stackexchange.com/users/3054", "pm_score": 1, "selected": false, "text": "<p>One factor that seems to me to play a huge role here, but I don't see much mention of it, are the mechanics of a socket joint vs. a hinge joint. Humans benefit from a single hinge joint attached to a socket joint in both our arms and legs, because if our hand or foot gets \"stuck\" rotation around the socket joint protects the weak torsional strength (e.g. rotational strength) of a hinge joint. Hinge joints can break easily when twisted. An extremely long limb with two hinge joints would be very susceptible to torsional breaks. </p>\n\n<p>Therefore, your goblins would be very concerned about twists to the joint that might cause it to break; and the longer a limb, the more likely this is. So, like the praying mantis (as mentioned in one answer), these creatures would likely hold their \"hands\" very close with one joint nearly always \"closed\" and pressed against their body - to reduce the odds of breaking one or the other hinge joint. They would likely appear to have much shorter arms than they actually do.</p>\n\n<p>The addition of an opposable thumb does not present exceptional advantage for anything wider that the width of a hand (e.g. two triggers on a gun??). That, however, can create some interesting side effects that I will mention in a moment.</p>\n\n<p>First, consider that nearly all weapons are developed from tools used to gather food or kill prey. As these goblins are not predators, gathering tools would become their weapons of choice due to the tools' familiarity, abundance and widespread use by the race.</p>\n\n<p>Thus, to develop a weapon or weapons, it is probably best to start there. First, with such lengthy arms, a quick \"stabbing\" gesture is likely to be developed - they could gather their food more rapidly using such a skill and also surprise enemies more easily. I'm sure they would want to extend their limb for the shortest possible time in order to minimize the risk of it twisting and breaking.</p>\n\n<p>I would assume a second thumb might make it possible to wield two daggers in one hand, creating something like \"scissors\" - which would be incredibly effective in both hunting and fighting. It might be possible to have nearly long enough daggers such that the goblin appears to wielding 4 small swords, two in each hand. Perhaps adding a hinge to each set of daggers would be another interesting twist on the concept, so that they essentially are scissors. Although, we humans add the hinge because we cannot control both blades with two opposable thumbs, so the goblins may not need the hinge on the two blades and it could, in fact, reduce their options (like tying chopsticks together...).</p>\n\n<p>Aside from the stabbing, an extra hinge could give more momentum to a weapon that swings on a short rope or chain, or is attached to a short rod or resembles a bat or club. A long cable is more likely to get tangled and risk torsional damage (e.g. it \"catches\" on the enemy or an object as the goblin is swinging it and then the goblin must release it or risk getting injured). Similarly a long club or bat would be unwieldy for their already long arms. </p>\n\n<p>However, it is the length of the arm that gives these weapons an advantage over shorter limbed, single hinged creatures since for these goblins, both hinges could extend simultaneously making the head of the weapon move very rapidly, with great force and momentum. </p>\n\n<p>The danger here is in making such a weapon too heavy - it's momentum could build so rapidly that breaks the goblin's own grip, or worse, their arm. But momentum is mass times the velocity, so the faster it moves, the less heavy it needs to be for equal effectiveness compared to a similar weapon wielded by shorter limbed creatures. And the energy it accumulates (mass times velocity squared) is an advantage by a wide margin (the square of the speed vs. linear increase based on mass). Also, force is related to mass times acceleration - so it will strike with surprising force.</p>\n\n<p>So a small bat or club would be much more deadly in the hands of these goblins than most humans would suspect. If a human encountered such a creature with a small club, the same weapon for a human would be ineffective in combat, while being very effective for the goblin. Anything with protruding blades or spikes could become lodged in the enemy, again risking a break in the arm or release of the weapon. I would expect something more like a spoon (for gathering) and a bat (for crushing foods or dislodging them).</p>\n\n<p>They might wield tools or weapons that lodge or have long ropes or chains when one hinge is closed, but it would be extremely risky in situations where both hinge joints are \"open\" or extended. Their ability to learn and use such weapons would be based on the less frequently need to construct things or creative scavenging (twisting knobs, carving, tightening, loosening, etc.). With their passive role, these types of tools would unlikely turn into weapons, but it would be possible, and it would probably resemble the way a human would wield them.</p>\n\n<p>Wielding a two-handed weapon would require the hinged joints be moved in parallel in order to reinforce the joints, otherwise the additional speed of wielding the objects would put the goblin at risk of breaking their limbs. However, moving in parallel is common with swords and clubs. It would allow longer and larger weapons to be wielded. (It might also be interesting to consider how they might develop bones that \"interlock\" and also allow them to \"cross their arms\" while still bending them...)</p>\n\n<p>Also, with the second thumb on each hand, the addition of a second, hinged blade or even a small sword or adjustable shield would create a weapon that has incredible potential. A secondary small blade would be very useful in close quarters combat where the opponent blocks the fall of the larger blade with their weapon, leaving them defenseless against an attack on their hands or arms from the smaller weapon. A highly skilled goblin may also have the ability to hold 1 large blade and 2 small blades, making defense against the weapon incredibly difficult for those of us only able to wield a single blade with two hands. Or even the goblin may wield to \"medium\" swords, but with both hands still gripped together.</p>\n\n<p>For gathering, since these should first be thought of as tools, I could imagine a larger blade for stabbing a food, while the smaller blades serve to severe the large piece from being attached to something. Perhaps as a way of severing a limb from a dead (or dying) animal, since they are not hunters. Basically to speed the gathering and retrieval of food the process is: stab, severe and run. Two medium blades could be used for rapidly cutting foliage to reach mushrooms, etc.</p>\n\n<p>The adaptation of tools to weapons I think is critical in developing both believable and intriguing weapons, in your case. At first, it was hard for me to see a clear advantage of the two hinges (torsional breaks are too easy, even in humans), but it might be possible with the thoughtful construction of the goblin's habits and behaviors, and then the development of their tools leading to the development of interesting weapons. Protecting hinge joints is something that we all innately have as humans, it would be more so with a double hinge-jointed goblin. To me, this is key in keeping it \"real\" while also exploring intriguing options.</p>\n\n<p>If nothing else, I hope you enjoyed reading another opinion. :)</p>\n" }, { "answer_id": 22980, "author": "Wad Cheber", "author_id": 11531, "author_profile": "https://worldbuilding.stackexchange.com/users/11531", "pm_score": 1, "selected": false, "text": "<p>Throwing weapons. The extra elbow turns the arm into an atlatl, a device used to throw spears at greater speed and over longer distances than would otherwise be possible. A creature with two elbows on each arm would throw things like a cannon firing.</p>\n" }, { "answer_id": 59388, "author": "Chaos_Kitty", "author_id": 28941, "author_profile": "https://worldbuilding.stackexchange.com/users/28941", "pm_score": 0, "selected": false, "text": "<p>The double elbow joints in the arms puts me in mind of the Fokrul Assail from the Malazan Book of the Fallen series. They were truly dangerous enemies, but they also had a superhuman supply of strength in their wiry limbs (unlike the creatures you're proposing). \nThe Fokrul Assail used mainly their hands and feet as weapons (having double joints just about everywhere) because they could slip around or past any defense with the greatly increased range of movement available. </p>\n\n<p>You could give your goblins a gauntlet of kinds, heavily customizable for close quarters combat. \nIt could have an endless amount of attachments; blades, spikes, large heavy chunks for a mace-like effect, small poisoned crossbows, claws for climbing rock faces in tunnels, or just about anything they could get their tinkering hands onto. </p>\n\n<p>That would also give them something to constantly be changing or improving whenever their attention wavered</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/22563", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/3254/" ]

[ { "answer_id": 23926, "author": "Green", "author_id": 10364, "author_profile": "https://worldbuilding.stackexchange.com/users/10364", "pm_score": 1, "selected": false, "text": "<p><strong>You probably can survive heavy acceleration while breathing liquids</strong> though keeping tabs on infection and ventilator function over longer periods will be definite concerns.</p>\n\n<p><strong>Breathing Fluorocarbons</strong></p>\n\n<p>The <a href=\"https://biology.stackexchange.com/questions/23074/what-are-the-effects-of-long-term-liquid-breathing\">Biology SE answer</a> indicates that it's possible for animals (very little human testing has been done) to survive for extended periods while immersed in and breathing fluorocarbons. Animal diaphragms aren't strong enough to move fluids so a ventilator must be used. Due to the dearth of research on the long-term effects of adult humans breathing fluorocarbons for weeks, months or years, everything is speculation though, given the inert nature of fluorocarbons, it would probably be okay.</p>\n\n<p><strong>Suspension in Fluorocarbons</strong></p>\n\n<ul>\n<li>Density of water is 1 gl/ml.</li>\n<li>Density of FC-75 is <a href=\"https://www.fishersci.com/shop/products/perfluoro-compound-fc-75-acros-organics-3/p-179920\" rel=\"nofollow noreferrer\">1.75 to 1.79g/mL.</a></li>\n<li>Density of human body is between <a href=\"http://ajcn.nutrition.org/content/20/4/305.full.pdf\" rel=\"nofollow noreferrer\">1.04 and 1.08 g/ml</a> (page 307).</li>\n</ul>\n\n<p>So without a weight belt/suit, a human will tend to \"float\" towards the top of the tank. Under 1$g$ acceleration, a simple weight belt is sufficient to maintain buoyancy because the strain induced by differences in buoyancy between the human body and water is negligible. <em>However, under 50 to 100$g$ the strain will be considerably more and will need to be accounted for.</em> A full body weighted &amp; pressure suit will be best because the less dense portions of the human body will want to float up and must be restrained. </p>\n\n<p>There is also <a href=\"http://onlinelibrary.wiley.com/doi/10.1002/cphy.cp040240/abstract\" rel=\"nofollow noreferrer\">this article</a> (paywall) about adaptation to acceleration environments.</p>\n\n<p><em>Yes you probably could suspend a crew in a fluid for the crushing accelerations required by the OP but it doesn't take a ton of handwaving to do so.</em> The only people you're going to really annoy are the buoyancy scientists.</p>\n\n<p><strong>Older Answer:</strong></p>\n\n<p>From the Biology SE answer:</p>\n\n<blockquote>\n <p>Kylstra, the first pioneer introducing the idea of land animals breathing liquids (Kylstra et al., 1962, found mice could withstand 4 hours of 160 atmospheres of pressure.</p>\n</blockquote>\n\n<p>So how much acceleration is equivalent to 160 atmospheres?</p>\n\n<pre><code>100kpa is one atmosphere.\n100kpa * 160 = 16000kpa\nP=F/A\nF=P*A\nF=16000000 Pa (N/m^2) * 1.7 m^2\nF = 27.2 MN\n</code></pre>\n\n<p>While 27.2 meganewtons seems like a lot, remember that this is across the entire surface of the body and from all directions so the pressures equalize. Free gases in the gut will diffuse in the surrounding tissues so decompressing/decelerating will need to be done slowly to avoid a lethal case of the bends.</p>\n" }, { "answer_id": 23931, "author": "Taemyr", "author_id": 733, "author_profile": "https://worldbuilding.stackexchange.com/users/733", "pm_score": 0, "selected": false, "text": "<p>Does it neutralize the g-forces?</p>\n\n<p>Being immerged in and breathing a liquid with a density close to that of the human body can aliviat damage from g-forces because in such an environment the forces are applied evenly. However Perfluorocarbon fluids are a bad choice, as they are far too dense - The density differentials in this case is as big as they are when you are immerged in and breathing air, you just change the sign.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/23691", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/12168/" ]

[ { "answer_id": 24019, "author": "Nonafel", "author_id": 11608, "author_profile": "https://worldbuilding.stackexchange.com/users/11608", "pm_score": 3, "selected": false, "text": "<p><em>So I'm no rocket scientist, but here goes. Much of this is shamelessly lifted from Project Rho.</em> </p>\n\n<p>First, lets ignore the diffraction caused by passing through the earths atmosphere for the following. I'm also assuming you're talking an actual laser, not a particle weapon, blaster, or some other variant. </p>\n\n<p>A general idea to start with is for the US military, the minimum threshold for a tactical weapons-grade laser is 100 kilowatts.</p>\n\n<p>Maximum range will be a few hundred thousand kilometers, otherwise almost every shot will miss due to light-speed lag, Unless we are shooting at targets that don't move. </p>\n\n<p>First we calculate the beam divergence angle θ (θ = 1.22 L/RL)</p>\n\n<pre><code>$θ = beam divergence angle (radians)$\n$L = wavelength of laser beam (m, see table above)$\n$RL = radius of laser lens or reflector (m)$\n</code></pre>\n\n<p>Next is beam power BP, then calculate the beam intensity at the target (the beam \"brightness\"):</p>\n\n<p>$$BPT = BP/(π * (D * tan(θ/2))2)$$</p>\n\n<pre><code>$BPT = Beam intensity at target (megawatts per square meter)$\n$BP = Beam Power at laser aperture (megawatts)$\n$D = range to target (meters)$\n$θ = Theta = Beam divergence angle (radians or degrees depending on your Tan() function)$\n$π = Pi = 3.14159...$\n</code></pre>\n\n<p>The following equation will be of use for determining the diffraction:</p>\n\n<p>$$R_T = \\frac{0.61 D L}{R_L}$$</p>\n\n<p>where:</p>\n\n<p>$R_T$ = beam radius at target (m)<br>\n$D$ = distance from laser emitter to target (m)<br>\n$L$ = wavelength of laser beam (m, see table below)<br>\n$R_L$ = radius of laser lens or reflector (m)</p>\n\n<p>As for laser wavelengths:</p>\n\n<ul>\n<li>Near Infrared 2.5$\\times$10^-6 to 7.5$\\times$10^-7 m (2,500 to 750 nanometers)</li>\n<li>Red 7.5$\\times$10^-7 to 6.2$\\times$10^-7 m (750 to 620 nanometers)</li>\n<li>Orange 6.2$\\times$10^-7 to 5.9$\\times$10^-7 m (620 to 590 nanometers)</li>\n<li>Yellow 5.9$\\times$10^-7 to 5.7$\\times$10^-7 m (590 to 570 nanometers)</li>\n<li>Green 5.7$\\times$10^-7 to 4.95$\\times$10^-7 m (570 to 495 nanometers)</li>\n<li>Blue 4.95$\\times$10^-7 to 4.5$\\times$10^-7 m (495 to 450 nanometers)</li>\n<li>Indigo 4.5$\\times$10^-7 to 4.2$\\times$10^-7 m (450 to 420 nanometers)</li>\n<li>Violet 4.2$\\times$10^-7 to 3.8$\\times$10^-7 m (420 to 380 nanometers)</li>\n<li>Ultraviolet A 4$\\times$10^-7 to 3.15$\\times$10^-7 m (400 to 315 nanometers)</li>\n<li>Ultraviolet B 3.15$\\times$10^-7 to 2.8$\\times$10^-7 m (315 to 280 nanometers)</li>\n<li>Extreme Ultraviolet 1$\\times$10^-7 to 1$\\times$10^-8 m (100 to 10 nanometers)</li>\n</ul>\n\n<p>Below Extreme Ultraviolet, you can't use the laser outside of the vacuum of space as the atmosphere would absorb it, so we can ignore those. </p>\n\n<p>An example of how this works is as follows:</p>\n\n<blockquote>\n <p>Say you have an ultraviolet (20 nanometer) laser cannon with a 3.2\n meter lens. Your hapless target is at a range of 12,900\n kilometers (12,900,000 meters). The Beam Radius equation says that the\n beam radius at the target will be about 4 centimeters (0.04 meters),\n so the beam will be irradiating about 50 cm2 of the target's skin\n (area of circle with radius of 4 centimeters). If the hapless target\n had a hull of steel armor, the armor has a heat of\n vaporization of about 60 kiloJoules/cm3. Say the armor is 12.5 cm\n thick. So for the laser cannon to punch a hole in the armor it will\n have to remove about 625 cm3 of steel (volume of cylinder with radius\n of 4 cm and height of 12.5 cm). 625 * 60 = 37,500 kiloJoules. If the\n laser pulse is one second, this means the beam requires a power level\n of 37,500 watts or 38 megawatts at the target.</p>\n</blockquote>\n\n<p>A note: using a pulsed laser rather than a single focused beam would require less power, in effect drilling into the target rather than trying to vaporize it. </p>\n\n<p>Now aside from all of that, you're generating a massive amount of waste heat that will require dissipation, but that's a whole extra problem. </p>\n\n<p>There's also a neat laser maker calculator <a href=\"http://panoptesv.com/SciFi/LaserDeathRay/DamageFromLaser.php\" rel=\"nofollow\">here</a> that I would recommend for those that don't math. </p>\n\n<p>Also to read the source of this information, you can find it <a href=\"http://www.projectrho.com/public_html/rocket/spacegunconvent.php#id--Laser_Cannon\" rel=\"nofollow\">here</a>.</p>\n" }, { "answer_id": 24044, "author": "Gary Walker", "author_id": 7325, "author_profile": "https://worldbuilding.stackexchange.com/users/7325", "pm_score": 2, "selected": false, "text": "<p>1 watt second is a joule, so I will use J instead of W/sec</p>\n\n<p>To be accurate you need to determine what is a definition of destroy. For example, to burn a person could mean incapacitate by 2nd or 3rd degrees burns of much of the body, or it could mean turn to ash.</p>\n\n<p>Published data from atomic testing suggested that 8-10 cal / cm^2 is enough to cause 3rd degree burns on unprotected flesh. 10 cal / cm^2 is about 420 KJ / m^2. Average adult has about 2 sq meters of skin, but since you can only irradiate 1 side, you have to settle for burning one side of a person, so 400 KJ one the target will incapacitate a human. Without medical treatment 3rd degree burns over 50% of body is often fatal due to shock, fluid loss and infection. To actually guarantee a kill, you need more power on target of course, 10 MJ is probably enough and their clothes will catch on fire too overriding more common forms of protection outdoors.</p>\n\n<p>Setting hardwoods on fire requires about 1 MJ / m^2 this would be sufficient for many homes, but a crushed white rock roof would be mostly unaffected, perhaps 10 MJ / m^2 would be enough -- 200 sq meters would include most homes so you need 2000 MJ or 2GJ on target.</p>\n\n<p>A car again is difficult determine what destroyed requires. Unlike on TV cars to not catch on fire or explode at the least provocation. To temporarily incapacitate a car via space laser, the softest target is probably the tires, could not find direct data, but I suspect 1 MJ / m^2 would ignite the tires most of the time, but since the tires are often shielded by the vehicle they would often not catch on fire until far beyond this point and in any case you could easily fix this. To destroy a car you need to get it hot enough to destroy vital components like electrical wiring or engine belts - though again belts are easily replaced. I believe if you can heat the car to 500 C you will destroy most of the wiring as well as other soft components (seals, etc). So, how much energy to raise a car temp by 500 C (it could be winter). Curb weight on a new Ford Exposition is up to about 6000 lbs, as a first order approximation lets model this as 2720 kg of iron. Iron has a heat capacity of 0.45 J/g/deg. So 2720 kg * 1000 g/kg * 500 deg = 612 MJ on target.</p>\n\n<p>Tanks are a lot like cars, so I will use the similar assumptions but I will require 800 deg and 63,000 kg (Leopold 2) and I will need about 22.7 GJ on target.</p>\n\n<p>Office building. Likely brick, stone, steel in construction. Again how much is enough to consider it destroyed? If you really want to be sure, you need to err on the high side. The Empire State building used 60,000 tons of steel, 200,000 cubic feet of limestone and granite, 10 million bricks and 730 tons of aluminum and stainless steel. To simplify, I will assume 200,000 cu ft of limestone and ignore the bricks and aluminum. How much does granite weigh about 2.75 g/cm^3 and a heat capacity of 0.19 J/g/deg. Total granite mass 15,600 long tones. For a 500 deg temperature rise I need 13,500 GJ for the steel plus 1,482 GJ for the granite or about 15 TJ to take out the empire state building. In actually fact, you don't heat up the lower floors in this case as the upper floors absorb nearly all of the heat. A 1 second pulse would need to essentially vaporize the upper part of the building in order to destroy. But that is not even enough as the vapor cloud itself would absorb and scatter a large percentage of the laser blast. A thousand times might be enough though.</p>\n\n<p>A small town, again what is threshold of destruction, and just how big is this. I was raised in Columbus Indiana, so seems like a good model to me. Columbus IN, population 44,061 (2010 census). Area 72.23 sq km. 500 deg temperature rise and steel &amp; concrete destruction (to take out all of the buildings). I will simply revert to the energy per unit assuming the 100 MJ per sq. M is enough to take out everything (100 times the energy to ignite hardwood). 100,000,000 MJ / m^2 * 72,230,000 m^2 = 7.223 PJ -- petajoules on target.</p>\n\n<p>Needless to say, there are no experimental confirmations of the beam attenuation that would be encountered firing from orbit to surface targets, certainly not anything approaching these energy levels. However, I did find <a href=\"https://www.google.com/url?sa=t&amp;rct=j&amp;q=&amp;esrc=s&amp;source=web&amp;cd=1&amp;cad=rja&amp;uact=8&amp;ved=0CCQQFjAAahUKEwjMsKH47NvHAhUEUZIKHaAgC50&amp;url=http%3A%2F%2Fwww.dtic.mil%2Fcgi-bin%2FGetTRDoc%3FAD%3DADA325417&amp;usg=AFQjCNF9m8BbK4iFz69HsZb1AHfiA9AWNQ&amp;sig2=IPatJW3ZVNjxS_eDQ6nzMQ\" rel=\"nofollow\">Laser Atmospheric Attenuation Tables</a> for LTAS. Without going through the justification at this I think you would need about 20-50 times as much light at the source to reliably punch through the atmosphere as you have at the target. I have not yet performed more detailed calculations to confirm this. So, take all of the amounts above and multiply by 50 if you want to be able to destroy targets with reasonable certainty. This is based on bad weather conditions. For best case but still realistic weather conditions it would appear that you only need 5-10 times the on-target energy at the source. </p>\n\n<p>The higher energy levels deserve better accuracy as their are many non-linear and probably classified effects that doubtless come into play.</p>\n\n<hr />\n\n<p>I am also understating the actual power required because I generally ignored that fact that for everything except the unprotected human case, the target will ablate. The surface layers will cook off turning into gas and taking much of the incoming heat with them, and continuing to absorb and scatter the incoming laser light. I also generally ignore the fact that the target will reflect some of the laser light, when in can reflect at least some of the incoming light. At most of these energy level, a mirror will not provide protection, at least not for long as even a good mirror will absorb enough energy to quickly be destroyed.</p>\n\n<p>These power levels are beyond ridiculous. For everything larger than a car, the power at the target exceeds that of even the largest electrical generation stations. The entire United States only has a electrical capacity of 1060 GW.</p>\n\n<p>For our simple 3rd degree burns on a single human 1MJ on target requires a minimum of 5 times that at the source and 5 times again for the loss of electrical conversion to laser energy, i.e., 25 MJ. A common comparison is that 1 MW will power 1000 homes, so 25 MW is over half of the power needed to supply Columbus Indiana just to incapacitate 1 person.</p>\n\n<p>Using capacitors to store up for a bolt from the sky may sound like a good idea, but your requirements dwarf standard capacitors. The <a href=\"http://functionspace.com/topic/1612/Largest-Capacitor\" rel=\"nofollow\">largest capacitor bank in the world is only 50 MJ</a>, built at a cost to 10 million Euro</p>\n\n<p>Somewhere during your construction phase people are going to wonder what you are building and will get motivated to put a stop to your evil plan.</p>\n" }, { "answer_id": 25047, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 2, "selected": false, "text": "<p>Most of the numeric factors have been accounted for, but there are a few other things you need to consider in your orbital fortress.</p>\n\n<p>Punching all that energy through the atmosphere, even in \"window\" wavelengths will cause a huge amount of energy to be deposited in the atmosphere. To a certain extent the initial thermal blooming and other distortion effects can be accounted for using \"adaptive optics\" (AKA a \"rubber mirror\") which flexes to compensate for atmospheric effects. At higher energy levels, like those needed for burning hardened targets like tanks, the amount of energy could easily cause air molecules to dissociate into plasma, blocking the beam entirely as the plasma absorbs the energy and radiates it away as incoherent light and heat. Luckily, since you are in orbit, you will miss the worst effect of the plasma running back \"up\" the beam to the emitter and depositing the energy on the mirror.</p>\n\n<p>The second consideration is that lasers in general have very low conversion efficiencies, so if you need as much as 5X the actual beam power as input energy for your laser system. This also means that you are join to be dealing with incredible amounts of waste heat, so your space station will be dominated by the energy system and vast arrays of radiators. Even at 400km altitude, the sheer size of all this could cause enough atmospheric drag to bring you out of orbit. The mass of all the stuff will also make your space station virtually immobile in terms of orbital manoeuvres, so people who object to being lasered from orbit won't have much difficulty in sending clouds of ball bearings or even sand into the orbital path of the space station, meaning that even with the impressive laser weapon, it could be destroyed.</p>\n\n<p>Now the most impressive laser weapon that I have ever seen described is also on the Atomic Rockets website (<a href=\"http://www.projectrho.com/public_html/rocket/spacegunconvent.php\" rel=\"nofollow\">http://www.projectrho.com/public_html/rocket/spacegunconvent.php</a>); the Ravening Beam of Death (RBoD), which uses a kilometre diameter accelerator ring to power a Free Electron Laser (FEL) capable of vaporizing metal, ceramic and carbon fibre a light second away in milliseconds, and I don't think that has the energy levels described to vaporize entire towns in a single shot. But it does provide an alternative, since a light second is almost the distance from the Earth to the Moon (and the beam itself is dangerous far beyond, a light second is arbitrarily chosen to make targeting responsive, since no target can move very far in a single second or the two seconds needed to see the effect of the shot and correct). </p>\n\n<p>So set up your fortress on the Moon, fire short pulses of laser energy rather than long beams, and remember to allow for the energy dumped in the atmosphere to dissipate between shots.</p>\n" }, { "answer_id": 25062, "author": "Joe Bloggs", "author_id": 9887, "author_profile": "https://worldbuilding.stackexchange.com/users/9887", "pm_score": 1, "selected": false, "text": "<p>The biggest problem for your laser of death is going to be the atmosphere. As Thucydides noted, even at wavelengths specifically chosen to not interact with the atmosphere, a considerable portion of your power is going to be transferred into the air. If your laser is powerful enough to punch through the armour of a tank (as worked out by Gary Walker) then the beam has to be about 22 GJ *20 (minimum attenuation) or 440 GJ. Lets assume that 40 GJ of energy gets through and the rest is lost to atmosphere, so 400 GJ pumped into the atmosphere. A lightning bolt delivers 1-10 GJ and turns the atmosphere to superheated plasma in a fraction of a second. I'm not sure what the energy flow rate is going to be like for your laser, given the atmospheric pressure gradient, distortion, diffraction and other effects, but I think it's fairly likely that with even a conservative estimate of the energies involved you're going to literally set the air on fire.</p>\n\n<p>You're looking at energy densities that can break water molecules apart and then set them on fire, ionise the air and generally do all sorts of bad things to the medium you're trying to push the laser beam through. If the laser makes it harder to push the beam through to the target you'll have to pump in more energy to hit, which will cause even worse things to happen, all the way up to turning the air into plasma and literally forcing it out of the way in order to make a path for the laser beam to travel through. This sets fire to an awful lot of other things too.</p>\n\n<p>In essence: this weapon will not be precise, will require an ungodly power source, and is generally hideous to try and build without anyone noticing. </p>\n\n<p>Or... You could just drop ceramic coated lumps of tungsten with some guidance packages on them... From your altitude you could knock out a city with something the size of a car, a tank with a computer tower, and a person (and his mates) with a tangerine...</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/24009", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/224/" ]

[ { "answer_id": 24025, "author": "bowlturner", "author_id": 19, "author_profile": "https://worldbuilding.stackexchange.com/users/19", "pm_score": 5, "selected": true, "text": "<p>Something will send up a flag, if the population count appears to stall at 8,000,000,000. At first I thought it will likely take a few years past the mark to notice that overall population isn't increasing and maybe one or two more to narrow down a close number. However...</p>\n\n<p>Looked it up it appears that the average death per day is 7.89/1000 people, the average births/day is around 20/1000. So there are over twice as many births as deaths/1000 people on the planet. Using these numbers once we hit 8,000,000,000 people the death rate will automatically more than double. That will be a huge flag for statisticians. And when the birth rate and death rate remain steady and equal (unless a large war or other event INCREASES the death rate) it will be pretty obvious that SOMETHING is going on artificially limiting the population. </p>\n\n<p>The scary thing is that once the pattern is noticed, wars and genocide might be waged in order to 'choose' who will die, not us, but THEM!</p>\n\n<p>EDT:\nOne last thing, if we discovered that being off Earth negates the 'spell', meaning it doesn't matter how many people are living on the moon, then we will start working hard at getting off this ball and colonizing the solar system.</p>\n" }, { "answer_id": 25058, "author": "Erik", "author_id": 5213, "author_profile": "https://worldbuilding.stackexchange.com/users/5213", "pm_score": 2, "selected": false, "text": "<p>The first sign that something fishy is going on probably will not be the stable population but rather the sudden, sharp, unexplainable increase in healthy people getting un-curable heart attacks for no apparent reason.</p>\n\n<p>Since medical statistics are kept by all civilized countries, which normally also have the highest chance of saving people (especially young ones) from heart attack, you would probably notice something fishy going on really fast.</p>\n\n<p>Once you compare statistics and do calculations, it should not be very hard (especially after a few months/years) to reach the conclusion that the number of random heart attacks correlates strongly with population in each country, which in turn leads to the conclusion that it's a global thing.</p>\n\n<p>From there, you can count backwards to when it started to happen all of a sudden using existing statistics, and then link it pretty easily to the birthrate and come to the conclusion that it must be related to people being born vs people dying.</p>\n\n<p>Personally I'll give it half a year before we figure it out, but much longer before we believe it and even longer before we can convince other people that something magical is happening.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/24023", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2071/" ]

[ { "answer_id": 25136, "author": "iAdjunct", "author_id": 5110, "author_profile": "https://worldbuilding.stackexchange.com/users/5110", "pm_score": 1, "selected": false, "text": "<p>The first problem with things in space is that everything moves fast - REALLY fast. For example, when you're near a planet, it's not that gravity is just too weak to pull you in - it's that you're going <em>really fast</em> and are counteracting gravity. To put a number to it, the international space station is traveling at 17,000 MPH.</p>\n\n<p>With today's bi-propellant technology, if your shield were in the ISS's orbit and 90% of it was fuel and a missile was coming in behind you, the best you could do is go roughly 6,000 MPH in the other direction. However, you wouldn't actually go 6,000 MPH in the other direction: you would instead start falling back to Earth irritatingly quickly.</p>\n\n<p>Changing orbits with today's technology is very difficult.</p>\n\n<p>Furthermore, missiles flying in space are limited in what they can do because they have to carry all their fuel with them and accelerate it as well. This is why ballistic missiles are just ballistic: it's hard to affect changes in your trajectory when you would also have to carry fuel... so they just don't carry fuel and fly. We then lob little things at them to get in their way (EKV: Exoatmospheric Kill Vehicle, which is literally a thing that gets in the way of incoming missiles and runs into them - sound familiar?). These are incredibly expensive and rely heavily on the other target being predictable (in this case, ballistic) so they can minimize fuel usage and cost.</p>\n\n<p><strong>But you asked about the future...</strong></p>\n\n<p>Why did I say everything above? Because, in the future, if you have interplanetary travel, you <em>must</em> have solved the engine inefficiency problem and made it <em>trivial</em> to produce engines that can just do whatever you want. However, your space ships still have structural issues, so they can only maneuver so quickly <em>(unless, I suppose, the entire hull is lined with small engines so it can perfectly distribute forces)</em>. Presumably they may have also created some sort of an inertial damper to let them maneuver more quickly.</p>\n\n<p>So let's say the enemy missiles and you both have the technology to make everything maneuver exactly how you want: <strong>you still lose</strong> because you're still playing defense and defense is always reactionary. If you get your shield right in the way of the missile (because your technology lets you do this effectively), then their missile would just change its course (because their technology <em>also</em> lets them do that). So you figure out how their algorithm works and make your shield predict theirs, so they change theirs. *(Note: this is <em>exactly</em> how defense works nowadays too)*.</p>\n\n<p>Regardless of your level of technology between now and then, you CAN put a shield (whether it be something already in space or something like EKV) between you and them, but you always have a disadvantage that they will have the same maneuverability abilities and they control the game (again, defense is always reactionary). Plus your [big metallic] shield tends to get destroyed when it gets hit. Plus yours has to be a lot more expensive because it has to be <em>more</em> capable than theirs, so they can always exhaust your resources by just firing lots of them at you.</p>\n\n<p>A shield like that really isn't any more effective than shooting their missile with your missile - except that your missile doesn't have to happen to be in the right spot [as much] as a shield does.</p>\n\n<p>This, by the way, is the genesis of energy weapons.</p>\n\n<p><strong>Some more related examples</strong></p>\n\n<p>Using some numbers from wikipedia...</p>\n\n<p>The US's \"Minuteman\" ballistic missiles cost $7 Million and [technically] only take a few people to operate them from a single silo.</p>\n\n<p>The US's EKV program is hard to estimate the cost of, but [1] says they cost about $90+ Million each. It costs more than 10 times as much to defend against a single ICBM as it does to launch one. But this isn't the whole story, because to be able to hit a flying thing, you first have to <em>detect</em> the flying thing (with radars, which have limited range and precision) and transmit that information (which can be jammed) and launch against it, so you have the cost of all of those pieces too.</p>\n\n<p>This cost differential has always been and probably always will be so.</p>\n\n<p>[1] - <a href=\"http://mostlymissiledefense.com/2012/07/24/ballistic-missile-defense-how-much-does-a-gbi-interceptor-cost-july-24-2012/\" rel=\"nofollow\">http://mostlymissiledefense.com/2012/07/24/ballistic-missile-defense-how-much-does-a-gbi-interceptor-cost-july-24-2012/</a></p>\n" }, { "answer_id": 25139, "author": "JDługosz", "author_id": 885, "author_profile": "https://worldbuilding.stackexchange.com/users/885", "pm_score": 0, "selected": false, "text": "<p><a href=\"https://worldbuilding.stackexchange.com/questions/12520/hard-sci-fi-energy-shields/12527?s=2|0.1283#12527\">In other answers</a>, I mentioned shilding based on superconductor flux pinning. That would work for intentional things being thrown at you as well.</p>\n\n<p>That is, <em>defense</em> is similar to shielding on fast spacecraft, which is a technology that will be developed so it is available for repurposing. I can imagine a protagonist group in a story naturally trying to adapt shielding to use for defense against attack.</p>\n\n<p>Think of the phenomenon as an improvement/refinement to the \"magnet\" idea. The plate is tasked to an intercept and moved by using the magnetic flux lines as a long arm; the plate is pinned to the far end. </p>\n\n<p>The plate absorbs energy by breaking. And the pieces are still pinned and now individually controllable, down to a minimum size.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/25115", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/7453/" ]

[ { "answer_id": 25332, "author": "Babika Babaka", "author_id": 9601, "author_profile": "https://worldbuilding.stackexchange.com/users/9601", "pm_score": 2, "selected": false, "text": "<p>I assumed here that the two stars and the planet are aligned, and midday/midnight are fixed using star A. </p>\n\n<p>The numbers bellow are for the equator of the planet, the extremities are going to have longer A days when inclined toward star A and longer B days when inclined toward star B. </p>\n\n<p>There will be a A and a B season cycles. During its double winter a pole is in a permanent true night, the opposite during its double summer. I tried here to give a general feeling of how living on this planet would be.</p>\n\n<hr>\n\n<p><strong>Single day point</strong><br>\n1/2 night + 1/2 day</p>\n\n<p>sunrise A : 6 am<br>\nsunset A : 6 pm<br>\nsunrise B : 6 am (eclipsed behind sun A)<br>\nsunset B : 6 pm (behind sun A) </p>\n\n<p><strong>First quarter</strong><br>\n1/4 night + 1/4 day A + 1/4 day B + 1/4 day A&amp;B</p>\n\n<p>sunrise A : 6 am<br>\nsunset A : 6 pm<br>\nsunrise B : 12 am<br>\nsunset B : 12 pm </p>\n\n<p><strong>Max double-day point</strong><br>\n1/2 day A + 1/2 day B</p>\n\n<p>sunrise A : 6 am<br>\nsunset A : 6 pm<br>\nsunrise B : 6 pm<br>\nsunset B : 6 am </p>\n\n<p><strong>Third quarter</strong><br>\n1/4 night + 1/4 day A + 1/4 day B + 1/4 day A&amp;B</p>\n\n<p>sunrise A : 6 am<br>\nsunset A : 6 pm<br>\nsunrise B : 12 pm<br>\nsunset B : 12 am </p>\n\n<hr>\n\n<h2>How it would look</h2>\n\n<p>When you start at the Single day point, day and night look the same as on Earth, because the two suns are aligned with each other. </p>\n\n<p>Days passes and star B emerges from behind start A. At first it will be like pretty much the same. The more the year progress, the more the two stars will look distant in the sky. </p>\n\n<p>When at first the two sunrises and sunsets happened with a few minutes intervals, the kind of twilight between two sunset or two sunrise will be longer and longer. The \"True Night\" and \"True day\" (time with both suns) between them will grow shorter. When the planet is at \"Double day\" point, there is no night, only a 12 hours \"day A\" and a 12 hours \"day B\".</p>\n\n<p>Then the opposite process starts. The intervals between sunrises and sunsets grow shorter, the single-sun days shorter and both true day and true night longer. The stars also grow closer in the sky.</p>\n" }, { "answer_id": 25337, "author": "Joe Bloggs", "author_id": 9887, "author_profile": "https://worldbuilding.stackexchange.com/users/9887", "pm_score": 2, "selected": false, "text": "<p>Quick point: An orbit with that level of eccentricity is going to have summers that literally melt everything, so I'm going to assume a circular (or at least much less eccentric) set of orbits. I'm also going to use the planet as my reference frame, because it makes it easier to track the locations of the two suns.</p>\n\n<p>On to some quick back of the envelope thoughts:</p>\n\n<p>1: With an axial tilt the change in sunrise/sunsets is going to follow a similar pattern to those on earth, with shorter 'A' days following the orbital period of A around the plant and shorter 'B' days following the orbital period of B around the planet. These changes in season will not synch up, as both A and B perturb each other's orbits relative to the planet. In essence you'll have some long 'A' seasonal cycles followed by short 'A' cycles, and similarly for 'B' cycles. </p>\n\n<p>This leads to some really rather complex characteristics base on the interactions between the location of A and B in their respective orbits relative to the direction of the axial tilt of the planet, the location of A relative to the planet, and the location of B relative to the planet. These characteristics need (sadly) some numbers to be able to work them out, specifically the orbital period of the planet, the orbital period of the two stars around their respective midpoint, and the location of the midpoint for the stars. Even if we ignore the effect of B's gravity on the planet (so the planet isn't immediately flung into an even more bizzare orbit), this is still pretty complex.</p>\n\n<p>If we ignore the effect of B's gravity on both A and the planet (lets say some bored god has ordained that A is the centre of all things), then things get easier, though they're still more complex than you might expect.</p>\n\n<p>Lets assume (for fun) that the planet orbits A at a distance of 2. (The unit doesn't really matter) and that B orbits at a distance of 3 (I'm using these numbers to make it more obvious, I realise it isn't a viable set of parameters for actual orbit, but we've already got a bored god on our side). Oh: The planet also spins at the same rate as Earth in a clockwise direction and we're defining 12:00 to be when we're furthest away or closest to star A.</p>\n\n<p>From here we can define 16 positions for the A/B/Planet system based on the four ordinals of A and the locations of the planet. If there is a planetary tilt we have to consider all 16 to calculate the day/night cycle, if not we can simplify it to 4. Lets go with the 4 first.</p>\n\n<p>Planet and B are both above A: The planet is fully illuminated, there is no day/night cycle</p>\n\n<p>Planet is above A, B is below A: The planet is half illuminated, the day/night cycle is 24 hours (Sunrise at 6:00, Sunset at 18:00. It's also worth nothing that this would be <em>cold</em>, as the planet would be missing out on all of B's warmth due to it being in the shadow of A (a star casting a shadow is the oddest concept I've thought about today...)</p>\n\n<p>Planet is above A, B is to the right side of A: At this point the planet is (break out the basic Pythagoras here) at a distance of 5 from star B, and also at an angle that means the two 'sunrises' are not split apart by a quarter of the rotational period but rather something closer to 2/3 (I'm going to handwave the actual angle here to make the hourly maths easier). This leaves you with Arise at 6:00,Aset at 18:00, Brise at about 2:00 and Bset at about 14:00</p>\n\n<p>Planet is above A, B is to the left side of A: Similar to above, but with Brise and Bset at 10:00 and 22:00.</p>\n\n<p>Thus end the trivial cases.</p>\n\n<p>When you put in an axial tilt you have to consider all 16 cases. Imagine the planet as a 24 hour analogue clock (yes, they exist) with 0:00 at the point furthest from A and 12:00 at the point closest to it. Work out where the stars are relative to the planet, then imagine the half of the circle nearest each star is lit up. You can use the numbers on the imaginary clock to find the sunrise and sunset times for a 0 tilt planet. To take the tilt into account shrink the half circle when the planet is tilting away from the star (northern hemisphere winter) and increase it when it's tilting towards the star (northern hemisphere summer), then use the numbers to get the sunrise/sunset times. It might also help to imagine one star illuminating in blue and one in red to clearly delineate the days in your own mind.</p>\n\n<p>Basically: The point I'm trying to make here is that the day/night/season cycle here is going to be complicated. From a story point of view I wouldn't try to explain it exactly as planetary orbits in binary systems tend to be either chaotic or unsuitable for life.</p>\n" }, { "answer_id": 25397, "author": "2012rcampion", "author_id": 3407, "author_profile": "https://worldbuilding.stackexchange.com/users/3407", "pm_score": 7, "selected": true, "text": "<h1>Update</h1>\n\n<p><a href=\"https://i.stack.imgur.com/S2zZz.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/S2zZz.png\" alt=\"enter image description here\"></a></p>\n\n<p>I've updated my CDF to handle eccentric orbits and customization of star brightness, and (more importantly) to show long-term seasonal effects. A few notes:</p>\n\n<ul>\n<li><p>Mousing over any of the parameters in the upper-left will show a tooltip with its name.</p></li>\n<li><p>Note that the luminosity slider only adjusts the luminosity by a small factor. A star's luminosity is mostly <a href=\"https://en.wikipedia.org/wiki/Mass%E2%80%93luminosity_relation\" rel=\"noreferrer\">determined by its mass</a>, so changing the mass slider also changes the luminosity.</p></li>\n<li><p>I assume that one orbit of the planet around the primary star is a \"year\" (regardless of the actual length), and that the year is divided into twelve equal months. Similarly, I divide the day into 24 hours, regardless of the actual day length.</p></li>\n<li><p>The upper-right side shows the orbit of the planet and the companion star from two views.</p></li>\n<li><p>The middle plot shows the total energy received from both stars over the course of one orbit of the companion star.</p></li>\n<li><p>The lower-left plot shows the same information as before: the shaded regions show the times when the primary and companion stars are visible. The difference is that the year the time axis shows starts at the time <code>t</code> on the slider.</p></li>\n<li><p>The lower-right plot shows the average <a href=\"https://en.wikipedia.org/wiki/Solar_irradiance\" rel=\"noreferrer\">insolation</a> (received sunlight) over the course of one day for a given latitude and time of year. Clicking on this plot sets the latitude and time of the visibility plot to its left.</p></li>\n</ul>\n\n<p>Download the <code>.cdf</code> file <a href=\"http://googledrive.com/host/0B0VNJlWZGkwNfmlvUjNOQUxoZmVuTWFfeFRnUk5wRVhuRVJWcTA0YjVGaDIwdzhnSUYyNWs/binary-seasons.cdf\" rel=\"noreferrer\">here</a> (needs the free <a href=\"https://www.wolfram.com/cdf-player/\" rel=\"noreferrer\">CDF player</a>), or if you have Mathematica you can download it with the following command:</p>\n\n<pre><code>Uncompress@FromCharacterCode@Flatten@Import[\"http://i.stack.imgur.com/l1bWc.png\", \"Data\"]\n</code></pre>\n\n<p><img src=\"https://i.stack.imgur.com/l1bWc.png\" alt=\"enter image description here\"></p>\n\n<h2>Assumptions and Terms</h2>\n\n<p><a href=\"https://commons.wikimedia.org/wiki/File:Orbit1.svg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/yrFiB.png\" alt=\"enter image description here\">\n_{<br>\nfrom Wikimedia Commons</a>}</p>\n\n<ul>\n<li><p>The planet $a$ orbits a star $A$, which is part of a binary system $AB$.</p></li>\n<li><p>The intersection of the <a href=\"https://en.wikipedia.org/wiki/Ecliptic\" rel=\"noreferrer\">ecliptic plane</a> and the <a href=\"https://en.wikipedia.org/wiki/Celestial_equator\" rel=\"noreferrer\">equatorial plane</a> defines the <a href=\"https://en.wikipedia.org/wiki/Equinox#Celestial_coordinate_systems\" rel=\"noreferrer\">vernal equinox direction</a>, labeled with $\\Upsilon$ in the above diagram. Another way to think of this is the location of the planet when the <a href=\"https://en.wikipedia.org/wiki/Subsolar_point\" rel=\"noreferrer\">subsolar point</a> crosses the equator from South to North. We'll measure angles counterclockwise from this point.</p></li>\n<li><p>The angle between the ecliptic and the equatorial planes is the <strong>obliquity</strong> $\\varepsilon$ (also called the axial tilt).</p></li>\n<li><p>The <strong>mean longitude</strong> $L$ is (for a low-inclination circular orbit) essentially the angle between an orbiting body and the reference direction when looking down on the orbital plane from above. It is equal to $\\Omega+\\omega+\\nu$ in the above diagram.</p></li>\n<li><p>The <strong>inclination</strong> $i$ and <strong>longitude of the ascending node</strong> $\\Omega$ are shown on the above diagram.</p></li>\n<li><p>The latitude of the observer on the planet is $\\phi$.</p></li>\n</ul>\n\n<p>Since the ecliptic is our plane of reference, for the planet $i_a=0$ and $\\Omega_a$ is not defined. However, these values are useful for the binary companion $B$. I'll treat $B$ as orbiting $A$ even though $B$ is heavier (to be luminous enough it must be at least $5M_\\odot$).</p>\n\n<p>I'm also treating the eccentricity of both orbits as zero so that the distances $r_{Aa}$ and $r_{AB}$ are constant.</p>\n\n<p>With all this sorted out we can apply some \"simple\" geometry to determine when the stars are above the horizon.</p>\n\n<h2>Results</h2>\n\n<p>I wrote a little <code>Manipulate</code> to visualize the effect of changing the latitude and orbital parameters of the binary. Here's what it looks like with the situation you describe at a mid-latitude of about 30 degrees north:</p>\n\n<p><a href=\"https://i.stack.imgur.com/e3eqw.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/e3eqw.png\" alt=\"enter image description here\"></a></p>\n\n<p>To figure out what's happening on a particular day, find the approximate date on the horizontal axis, then follow a vertical line straight up.</p>\n\n<p>As you can see, the sunrise and sunset times for the primary are pretty typical, fluctuating around 6 AM or PM.</p>\n\n<p>The companion star has a much more consistent duration of daylight, but its local noon 'laps' the primary's noon once a year.</p>\n\n<p><a href=\"https://i.stack.imgur.com/XdK8A.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/XdK8A.png\" alt=\"enter image description here\"></a></p>\n\n<p>On the equator, daylight times for the primary are more stable, but daylight times for the companion are relatively unchanged.</p>\n\n<p><a href=\"https://i.stack.imgur.com/W6H6E.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/W6H6E.png\" alt=\"enter image description here\"></a></p>\n\n<p>Far north of the arctic circle you can see that the summer has continuous daylight as before, but the would-be continuous winter night is interrupted by the companion star.</p>\n\n<p><a href=\"https://i.stack.imgur.com/QeUXv.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/QeUXv.png\" alt=\"enter image description here\"></a></p>\n\n<p>Changing the mean longitude of the companion ($L_B$) shifts the day-night cycle of the companion forward or backward in the year.</p>\n\n<p>Note that $L_B$ travels through its full range about once for every orbit of the companion star (about 15 to 40 years). This means that the two hemispheres will regularly cycle between eternal-daylight \"summers\" and eternal-daylight \"winters\", making for an interesting and complex seasonal cycle.</p>\n\n<hr>\n\n<p>I encourage you to experiment with the effects of adding inclination to the binary's orbit. To try it yourself, can either <a href=\"http://googledrive.com/host/0B0VNJlWZGkwNfmlvUjNOQUxoZmVuTWFfeFRnUk5wRVhuRVJWcTA0YjVGaDIwdzhnSUYyNWs/binary-day-night.cdf\" rel=\"noreferrer\">download the <code>.cdf</code> file</a> (you will need the free <a href=\"https://www.wolfram.com/cdf-player/\" rel=\"noreferrer\">CDF player from Wolfram</a>), or if you have a copy of Mathematica you can download it with the following command:</p>\n\n<pre><code>Uncompress@FromCharacterCode@Flatten@Import[\"http://i.stack.imgur.com/4ZDYm.png\", \"Data\"]\n</code></pre>\n\n<p><img src=\"https://i.stack.imgur.com/4ZDYm.png\" alt=\"enter image description here\"></p>\n" }, { "answer_id": 76035, "author": "M. A. Golding", "author_id": 34461, "author_profile": "https://worldbuilding.stackexchange.com/users/34461", "pm_score": 1, "selected": false, "text": "<p>Short Answer. </p>\n\n<p>For scientific reasons I have reversed your star designations, making Star B the one that Planet X orbits and Star A the more distant star.</p>\n\n<p>If planet X orbits Star B but not Star A, Star A should be at least ten times as far away from Planet X as Star B is, in order for the orbit of planet X to be stable. If this is supposed to be hard science fiction you will need a more expert opinion. Of course the distance between Star A and Star B can be many times the minimum of ten times the radius of Planet X's orbit around Star B.</p>\n\n<p>If the distance between Star A and Star B is exactly 10 times the radius of Planet X's orbit around Star B, then some times Planet X will be exactly 11 times as far from Star A as from Star B. And sometimes Planet X will be only 9 times as far from star A as from Star B. The distance from Star A to Planet X will vary between 0.9 and 1.1 times the average distance.</p>\n\n<p>And since the amount of light planet X receives from star A varies with the square of the distance, that amount will vary from 0.826 to 1.234 of the average amount.</p>\n\n<p>If the distance between Star A and Star B is exactly 100 times the radius of Planet X's orbit around Star B, the amount of light that Planet X receives from Star A will vary between 0.980 and 1.019 of the average amount of light.</p>\n\n<p>Since that is a smaller range of difference, as a general rule you would want the distances between Star A and Star B to be as many times greater as possible than the radius of the orbit of Planet X around star B.</p>\n\n<p>But you also need the distance between Star A and Star B to be as small as possible compared to the radius of the orbit of Planet X around Star B. If you want Planet X to be interesting because it is habitable for Earth Humans, or has advanced multi celled life like trees and mammals, or has native intelligent beings.</p>\n\n<p>If Star A is 10 times as far away from Planet X as Star B is, which I think is the minimum distance for Planet X to have a stable orbit, it will have to be 100 times as luminous as Star B to give Planet X as much light as Star B does. If Star A is only as luminous as Star B it will give Planet X only one percent of the light that Star B gives planet X.</p>\n\n<p>If Star A is 100 times as far away from Planet X as Star B is, it will have to be 10,000 times as luminous as Star B to give Planet X as much light as Star B does. If Star A is only as luminous as Star B it will give Planet X only one hundredth of one percent (or 0.0001) of the light that Star B gives planet X.</p>\n\n<p>You didn't specify the desired ratio between the apparent brightness of Star A and Star B as seen from Planet X. You just said Star A (your Star B) should give Planet X enough light to make a difference. And you didn't specify whether you meant enough light to make a difference in the temperature of Planet X or merely enough light to make a difference in it's illumination. </p>\n\n<p>If you want Star A to shed as much light on Planet X as Star B does, then the ratio of their relative absolute luminosity must equal the square of the ratio of their relative distances from Planet X. If Star A is 10 times as distant as Star B it will have to be 100 times as luminous to appear exactly as bright in the sky of Planet X. If Star A is 100 times as distant as Star B it will have to be 10,000 times as luminous to appear exactly as bright in the sky of Planet X. If Star A is 1,000 times as distant as Star B it will have to be 1,000,000 times as luminous to appear exactly as bright in the sky of Planet X.</p>\n\n<p>Thus if Star A and Star B have to have anything remotely resembling the same brightness in the sky of planet X, Star A should have at least several times the absolute luminosity of Star B, and possibly up to millions of times the luminosity. Thus Star A would be much intrinsically brighter than Star B. Thus Astronomers would call it A and call the star that Planet X orbits B. Because of the high probability that the more distant star would be more luminous than the star Planet X orbits, I switched the designations of the stars from what they were in your question.</p>\n\n<p>Suppose that you desire star A to appear 0.0001 times as bright in the sky of Planet X as Star B. Then if Star A is 0.10 times as luminous as Star B, and 10 times as far from Planet X, it will appear to be 0.0001 times as bright from the surface of Planet X. If Star A is exactly as luminous as Star B, and 100 times as far from Planet X, it will appear to be 0.0001 times as bright from the surface of Planet X. If Star A is 1,000 times as luminous as Star B, and 1,000 times as far from Planet X, it will appear to be 0.0001 times as bright from the surface of Planet X. If Star A is 10,000 times as luminous as Star B, and 10,000 times as far from Planet X, it will appear to be 0.0001 times as bright from the surface of Planet X. </p>\n\n<p>Thus even if Star A appears only 0.0001 times as bright as Star B as seen from Planet X, it could, depending on its distance, be tens, hundreds, or even many thousands of times as absolutely luminous as Star B, the star that Planet X orbits. </p>\n\n<p>By comparison, the Sun has an apparent brightness as seen from Earth 398,110 times as bright as the apparent brightness of an average full moon. The apparent brightness of the full moon is 0.0000025 that of the Sun, so if Star B appears as Bright as the Sun from Planet X and Star A appears only 0.0001 as bright as star B as seen from Planet X that could still be about 40 times as bright as a full moon seen from Earth.</p>\n\n<p>The absolutely most luminous star known to science is R136a1 in the Large Magellanic Cloud, about 8,710,000 times as luminous as the Sun. The least luminous known star is 2MASS J0523-1403, about 0.000126 times as luminous as the Sun. That gives a luminosity range of about 69,126,983,000 times. That should be enough for any desired difference in the luminosity of the two stars in the solar system of Planet X, right?</p>\n\n<p>Wrong. </p>\n\n<p>If you want Planet X to be interesting because it is habitable for Earth Humans, or has advanced multi celled life like trees and mammals, or has native intelligent beings, Planet X must have enjoyed a relatively constant amount of radiation from it's sun, Star B, for billions of years, since Earth is believed to be relatively typical, and it took billions of years for those things to develop on Earth.</p>\n\n<p>Therefore Star B that Planet X orbits must have been a relatively stable main sequence star for billions of years in order for Planet X to be habitable for Earth Humans, or have advanced multi celled life like trees and mammals, or have native intelligent beings. And since both stars in the system would be the same age, Star A must also have been a relatively stable main sequence star for billions of years. When stars eventually leave the main sequence they usually change in ways that destroys all life on the planets that orbit them and may also destroy all life on planets orbiting other stars in the same star system.</p>\n\n<p>And what types of stars will remain stable main sequence stars for billions of years? Stars of late spectral type F (starting at maybe type F8), type G, Type K, and type M. Thus Star B, that Planet X orbits, and Star A, in the same star system, would both have to be somewhere between about spectral type F8V to M9V, which would limit the possible range of their luminosity difference. I believe the extreme possible luminosity difference between Star A and Star B would be about 25 times.</p>\n\n<p>But many scientists believe that stars from mid type K and all type M stars are not suitable for having habitable planets for various reasons. If that is correct the possible spectral types for Star B would be limited to about F8V to K5V. That gives a luminosity range of about six times for the difference between Star A and Star B. But since it is not specified whether Star A should have any habitable planets its spectral type can be between type F8V and type M9V.</p>\n\n<p>So if you want your story to be anything like hard science fiction you should find more precise figures for the various limits listed before making your calculations, if you want Planet X to be interesting because it is habitable for Earth Humans, or has advanced multi celled life like trees and mammals, or has native intelligent beings. Unless the stars in the star system are younger and should not have planets as advanced as Planet X seems to be. Perhaps super powerful aliens terraformed Planet X millions of years ago and seeded it with life forms billions of years more advanced than it had time to evolve naturally, or even took Planet X from its original star system and moved it into the much younger star system it is now in.</p>\n" }, { "answer_id": 84267, "author": "Sam", "author_id": 39716, "author_profile": "https://worldbuilding.stackexchange.com/users/39716", "pm_score": 0, "selected": false, "text": "<p>The only thing I'm missing is the orbital period and inclination of your star B. It would be longer than the orbital period of the planet, and assuming there is any inclination, a stellar eclipse could only occur at the ascending and descending nodes. </p>\n\n<ul>\n<li>If any inclination exists, the north pole wouldn't be able to see star B for certain portions of star B's orbital period, at maximum descending argument (I hope my terms are right)</li>\n<li>If the orbital period of star B is a small enough ratio, like 4:1, you'd see four different years repeating, but if the ratio is strange, like 15:6, the pattern would be harder to describe.</li>\n</ul>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/25318", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/28/" ]

[ { "answer_id": 25680, "author": "Victor Stafusa - BozoNaCadeia", "author_id": 3002, "author_profile": "https://worldbuilding.stackexchange.com/users/3002", "pm_score": 2, "selected": false, "text": "<p>The Moon would just appear a bit larger in the sky. How many larger?</p>\n\n<p>Since the size correlates with the square of the distance and the area of the circle correlates to the square of the size (it is a sphere, but that is projected as a circle in our retinas), this means that:</p>\n\n<p>$$ \\text{actual size} = \\frac{(2,159.2\\text{ miles})^2}{(238,900\\text{ miles})^2} = \\frac{4,662,144.64\\text{ miles}^2}{57,073,210,000\\text{ miles}^2} = 0.0000816...$$</p>\n\n<p>$$ \\text{proposed size} = \\frac{(2,500\\text{ miles})^2}{(200,000\\text{ miles})^2} = \\frac{6,250,000\\text{ miles}^2}{40,000,000,000\\text{ miles}^2} = 0.00015625$$</p>\n\n<p>$$ \\text{elargement factor} = \\frac{\\text{proposed size}}{\\text{actual size}} = \\frac{0.00015625}{0,0000816...} = 1.9148...$$</p>\n\n<p>I.E, The Moon would be seen on the sky almost with the double of the size in area (191.48% to be precise), which is roughly 38% larger in diameter (the square root of 1.9148 is 1.38377).</p>\n\n<p>Let's suppose that our larger Moon has the same density as our common Moon. By which factor the Moon mass get larger?</p>\n\n<p>Mass would be measured by $m = v \\times d$, where $m$ is mass, $v$ is volume and $d$ is density. The volume of a sphere is $v = \\frac{4}{3} \\pi r^3$. So, we have that $m = \\frac{4}{3} d \\pi r^3$:</p>\n\n<p>$$\\text{Actual Moon mass} = \\frac{4}{3} \\pi (\\frac{2159.2}{2})^3 d = \\frac{(2159.2)^3 \\pi d}{6} = 10,066,502,706.688 \\frac{\\pi d}{6}$$\n$$\\text{Proposed Moon mass} = \\frac{4}{3} \\pi (\\frac{2500}{2})^3 d = \\frac{(2500)^3 \\pi d}{6} = 15,625,000,000 \\frac{\\pi d}{6}$$</p>\n\n<p>$$\\text{Mass elergement factor} = \\frac{\\text{proposed mass}}{\\text{actual mass}} = \\frac{15,625,000,000 \\frac{\\pi d}{6}}{10,066,502,706.688 \\frac{\\pi d}{6}} = 1,5521...$$</p>\n\n<p>This means that the proposed Moon is 55% more massive than our actual one.</p>\n\n<p>Now lets measure gravity attraction as $\\text{gravity} = \\frac{\\text{mass}}{\\text{distance}^2}$:</p>\n\n<p>$$\\text{Actual Moon gravity} = \\frac{10,066,502,706.688 \\frac{\\pi d}{6}}{(238,900 \\text{ miles})^2} =$$</p>\n\n<p>$$= \\frac{10,066,502,706.688 \\frac{\\pi d}{6}}{57,073,210,000\\text{ miles}^2} = 0.17637... \\frac{\\pi d}{6} \\text{miles}^{-2}$$</p>\n\n<p>$$\\text{}$$</p>\n\n<p>$$\\text{Proposed Moon gravity} = \\frac{15,625,000,000 \\frac{\\pi d}{6}}{(200,000 \\text{ miles})^2} =$$\n$$= \\frac{15,625,000,000 \\frac{\\pi d}{6}}{40,000,000,000\\text{ miles}^2} = 0.390625 \\frac{\\pi d}{6} \\text{miles}^{-2}$$</p>\n\n<p>$$\\text{}$$</p>\n\n<p>$$\\text{Gravity elergement factor} = \\frac{\\text{proposed gravity}}{\\text{actual gravity}} = \\frac{0.390625 \\frac{\\pi d}{6} \\text{miles}^{-2}}{0.17637... \\frac{\\pi d}{6} \\text{miles}^{-2}} = 2.21469...$$</p>\n\n<p>This would also means that the gravity that the Moon would exerce onto Earth would have 221.46% of the strength, which means tides with a bit more than the double of the strength. Assuming that the proposed Moon has the same density than our actual Moon.</p>\n\n<p>About the Earth's axial tilt. By searching in <a href=\"https://en.wikipedia.org/wiki/Axial_precession\" rel=\"nofollow\">wikipedia</a>:</p>\n\n<blockquote>\n <p>Lunisolar precession is caused by the gravitational forces of the Moon and Sun on Earth's equatorial bulge, causing Earth's axis to move with respect to inertial space. Planetary precession (an advance) is due to the small angle between the gravitational force of the other planets on Earth and its orbital plane (the ecliptic), causing the plane of the ecliptic to shift slightly relative to inertial space. Lunisolar precession is about 500 times greater than planetary precession.</p>\n</blockquote>\n\n<p>This would translate in a precession of equinoces where the lunisolar component would be significantly larger.</p>\n\n<p>Otherwise, the changes in Earth are not very significative. Things would be probably much as they are like today.</p>\n" }, { "answer_id": 25684, "author": "Gary Walker", "author_id": 7325, "author_profile": "https://worldbuilding.stackexchange.com/users/7325", "pm_score": 5, "selected": true, "text": "<p>To simplify, lets calculate some of the basic ratios up front</p>\n\n<pre><code>Avg. orbital distance ratio (center to center) = 238,900 / 200,000 = 1.1945\nDistance squared ratio = 1.1945^2 = 1.43683\nDistance cubed ratio = 1.704349\n\nDiameter ratio = 2500 / 2159.2 = 1.157836\nArea ratio = diameter ratio squared = 1.340585\nVolume ratio = diameter ration cubed = 1.552178\n</code></pre>\n\n<p>Assume mass ratio equals volume ratio, i.e. moon density is unchanged - this would not be true given identical materials as the matter would be more compressed with the additional pressure. So the mass ratio would be larger than the volume ratio. We don't know enough about the moon to calculate this accurately, not that I could model this change accurately without a lot of work.</p>\n\n<p><strong>Moonlight is brighter</strong> because it has 134% of its current surface area to reflect sunlight (and Earth-shine). But it is also closer and thus 143% of its intensity. Total moonlight received would be 1.912787 times the current moonlight.</p>\n\n<p>Eyesight response to light is non-linear, so it won't appear 91% brighter. Due to variations in orbits, the full moon varies from about mean value of -12.74 magnitude to -12.9 at it brightest. Under this scenario mean brightness would be around -13.5 magnitude. Reading by moonlight would be easier, etc. More stars would be obscured during a full moon.</p>\n\n<p><strong>Tides are larger</strong> - roughly speaking, tides are proportional to mass / distance^3 so the lunar tides are 2.64552 times as large as current tides. (Solar tides are about 45% those of the moon currently). Actual local tides vary quite a bit, but in general, they would be over twice as strong. This would affect ocean life as well as seaports, etc.</p>\n\n<p><strong>Axial tilt is complicated</strong> - I have seen frequently quoted that without the moon the axial tilt would vary up to 85 degrees, but I've also <a href=\"http://www.astrobio.net/news-exclusive/the-odds-for-life-on-a-moonless-earth/\" rel=\"nofollow noreferrer\">read that the axial tilt would vary by no more than 10 degrees</a> based on newer calculations that include the effects of the other planets. My guess is that the axial tilt would be a bit more tightly regulated than today -- lots of non-linear factors. For example, if Jupiter were a lot closer, the moon would actually be a destabilizing influence on axial tilt.</p>\n\n<p><strong>Earth's rotational slowdown</strong> would also be proportional to the tidal forces, i.e., the earth's current daily rotation slows down by around 20 millionths of a second per year. With this scenario, that change to about 50 millionths of a second per day per year -- more frequent leap seconds.</p>\n\n<p><strong>Moon orbital speed increases</strong>. For circular orbits, orbital velocity is proportional to 1/radius, so the moon will speed up from 0.635 miles/sec to 0.759 miles per second. Since the orbital path is also 19.45 percent shorter, the orbital time is 42.68% shorter -- i.e., sidereal month (360-degree revolution) changes from 27.3 days to 19.1 days. A synodic month (new moon to new moon) changes from 29.5 days to 20.15 days</p>\n\n<p><strong>Solar eclipses are more frequent and longer in duration.</strong> The Moon orbits the Earth more frequently - thus more opportunities for passing between us and the Sun. Many moon passes do not have the moon shadow crossing the earth because the moon's orbit is inclined to the earth orbit around the Sun so the shadow passes under or over the earth. With the smaller orbit, there will be fewer misses one a percentage basis. The Sun is about 400 times the distance of the moon and about 400 times the diameter of the moon, so eclipses are almost perfectly matched so we sometimes see total eclipses and sometimes see annular eclipses -- not anymore, there will be no annular eclipses. Currently, under ideal conditions, the maximum full umbra of the moon is about 166 miles wide on the earth allowing for a little over 7 minutes of maximum full totality. Full eclipses over 7 minutes are very rare, everything has to be lined up in a nearly optimal fashion.</p>\n\n<p>Shadow width on earth is now larger because the moon is larger and closer. These combine to make the shadow significantly larger - about 230 miles across. The increased orbital speed of the moon decreases transit time (offsetting the increased shadow size due to distance). Without complicated math and lots of new assumptions, exact figures are not possible, but I believe that assuming the eclipses would be about 15.7% longer on average because of the increased lunar diameter is a good first approximation. The larger umbra projected on the earth also means that around 30% more people will see each solar eclipse.</p>\n\n<hr/>\n\n<p>Lunar surface gravity is now 15.7% greater than before and the gravity well is 55% deeper so lunar missions just got harder. On the plus side, the trip won't take quite as long.</p>\n\n<p>The earth-moon barycenter has been moved from about 4700 km to 6100 km from the earth's center -- still within the earth though. This will result is a slightly more pronounced wobble (and more frequent) in the earth's orbit.</p>\n\n<p>The barycenter change may also cause slightly more seismic activity, especially when combined with the increased tidal stress. Perhaps slightly more weather variation too - <a href=\"http://www.accuweather.com/en/weather-news/do-full-moons-affect-weather-p/40127763\" rel=\"nofollow noreferrer\">tidal flows are thought to affect weakly some aspects of our weather.</a></p>\n\n<p>Many animals cycles will be affected due to brightness and frequency of the lunar cycles. Some people will also have their sleeping habits changed. Currently, there is little correlation of crime to the lunar cycle, but the increased brightness could deter crime.</p>\n\n<p>Everything based on lunar calendars will either change or ignore the changed lunar mechanics. Jewish, Christian, Islamic and Chinese calendars would be included.</p>\n\n<hr/>\n\n<p>Actual night sky moon would be a little larger than calculated above as this was based on center to center distance as would be accurate when the moon is on the horizon. When the moon is directly overhead you are somewhat closer because of the earth's radius (whether the moon is 200,000 or 238,900 miles away). For the moon remaining a fixed size, its apparent diameter would appear 19.84% larger when directly overhead instead of 19.45% when at the horizon, so the effect is small.</p>\n\n<p>A similar effect also occurs in that the surface of the moon is closer too -- light reflecting off the center of the moon will be just a little closer and correspondingly more likely to impact the earth and thus brighter. Again, the difference is minor.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/25675", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/10274/" ]

[ { "answer_id": 26014, "author": "Youstay Igo", "author_id": 13449, "author_profile": "https://worldbuilding.stackexchange.com/users/13449", "pm_score": 1, "selected": false, "text": "<p>As far our current knowledge of atmosphere and oxygen bonding types stands, no, multiple layers of ozone are not possible. But that shouldn't stop you. You could employ other <strong><em>ozone like</em></strong> layers for the same purpose. For example, try something like nitrogen ozone layer or carboxy ozone layer. These don't exist naturally yet but hey, fiction is fiction.</p>\n\n<p>However <em>if</em> they were possible and present, then yes, the damage of one layer would be covered up by the layers underneath it.</p>\n" }, { "answer_id": 26015, "author": "Green", "author_id": 10364, "author_profile": "https://worldbuilding.stackexchange.com/users/10364", "pm_score": 2, "selected": false, "text": "<p><strong>A second ozone layer could form IF a second UV source can be invented</strong></p>\n\n<p>NASA describes how ozone is made in a rather <a href=\"http://www.esrl.noaa.gov/csd/assessments/ozone/2010/twentyquestions/Q2.pdf\" rel=\"nofollow\">excellent paper on atmospheric chemistry</a>. In summary, UV light hits an O2 molecule forming oxygen ions that bond with other O2 molecules to form O3, or ozone. Since it takes UV light to form ozone and Earth's ozone layer absorbs 97-99%, creating a second ozone layer would require a second UV light source that doesn't come from the sun. If a second major UV source could be invented then a second ozone layer could form.</p>\n\n<p>From the article:</p>\n\n<blockquote>\n <p>Stratospheric ozone is formed\n naturally by chemical reactions involving solar ultraviolet\n radiation (sunlight) and oxygen molecules, which make up\n 21% of the atmosphere. In the first step, solar ultraviolet\n radiation breaks apart one oxygen molecule (O2) to produce\n two oxygen atoms (2 O) (see Figure Q2-1). In the second step,\n each of these highly reactive atoms combines with an oxygen\n molecule to produce an ozone molecule (O3). These reactions\n occur continually whenever solar ultraviolet radiation is present\n in the stratosphere. As a result, the largest ozone production\n occurs in the tropical stratosphere.</p>\n</blockquote>\n" }, { "answer_id": 26018, "author": "LSerni", "author_id": 6933, "author_profile": "https://worldbuilding.stackexchange.com/users/6933", "pm_score": 3, "selected": false, "text": "<p>Note: there is no such thing as an ozone <em>layer</em>. What is called ozone layer, as if it were a sort of crystal shell high in the atmosphere, is actually a volume of increased ozone density, so that the density function with height behaves a little like this:</p>\n\n<pre><code>%\n| #####\n| # ###\n| ### ###\n| ############ ############\n+------------------------------------------------------&gt; outer space\n</code></pre>\n\n<p>But ozone density is never zero anywhere. As per @Alpha3031's answer, you can have more or less temporary conditions in which you get ozone near the ground from photochemical smog, or near the border of the ecosphere, or anywhere in between.</p>\n\n<p>So \"more than one ozone layer\" would imply a density function more or less like this:</p>\n\n<pre><code>% Second layer\n| First layer ######\n| #### # ##\n| # ## # ##\n| ## ###### #####\n| ###### #########\n+------------------------------------------------------&gt; outer space\n</code></pre>\n\n<h1>Question 1: \"More than one ozone layer\".</h1>\n\n<p><strong>Yes, but it's tricky</strong></p>\n\n<p>The ozone layer is actually a dynamic phenomenon taking place in a volume of space where oxygen density, ultraviolet light from the Sun and (photo)catalytic processes from several substances (e.g. chlorine from chlorofluorocarbon compounds) interact in a narrow range of ways.</p>\n\n<p>So the greatest problem is having a high enough atmospheric column where the oxygen concentration is <em>just right</em>. This requires a shallow gravitational potential (the shallower, the best), which means a large, not so dense planet, and this has its drawbacks (technology as we know it is hugely based on iron and elements heavier than iron). Also, atmospheric pressure at sea level depends on the height of the atmospheric column.</p>\n\n<p>Once we have enough oxygen in the air to work, we can pursue two different avenues. With reference to the ASCII graphics above, you either raise a second \"hump\" far enough from the existing one, or you spread the one hump you have, and drive a \"wedge\" in the middle to split it into two.</p>\n\n<ul>\n<li>two different ozone sources. One is the Sun; the other \"hump\" would need to be a source at the right wavelength originating in the opposite direction, from the surface, and could not obviously be reflected from the Sun (UV at that wavelength are blocked by the ozone layer, and <em>that</em> is what creates the ozone layer in the first place). One possibility could be secondary ionization from shorter wavelength UVs, that do not get absorbed by the ozone layer (I'd need to check the transmittance curve of ozone - if it's flat at the key frequency and below, we're out of luck: there would be no \"shorter, unabsorbed wavelength\"). These \"UV-D\" rays would penetrate a bit more, hit some replenishable atmospheric constituent - perhaps nitrogen - that's denser than ozone, and release their energy as less energetic UV rays that would get refracted and, if these newborn UVs are the right frequency, generate more ozone \"some way down\".</li>\n</ul>\n\n<p>This phenomenon <em>already happens</em> in the atmosphere with normal ozone, which is one factor, together with atmosphere mixing, that makes the ozone layer \"thick\": it's actually several intertwining layers that scatter and amass. You'd need to do it with a different substance so that the separation between the two \"humps\" is larger, or you'd end up with a very thick, but single, ozone layer.</p>\n\n<ul>\n<li>one creation, two destruction mechanisms (standard spontaneous recombination being one). The ozone is generated in a thicker layer thanks to a shallower gravitational potential or a larger UV input from the Sun, then this large hump is split into two by e.g. some gas that deposits in the atmosphere at a specific height (we're doing <em>wild</em> assumptions on atmospheric diffusion and upper-atmosphere winds...). The gas is a sort of super-<a href=\"https://en.wikipedia.org/wiki/Halogen\" rel=\"nofollow\">halogen</a>, a super-chlorine or super-bromine, and catalyses the 2O3->3O2 ozone-killing reaction with such efficiency that where the gas is, no ozone at all can abide and you have a deep \"wedge\" separating two \"humps\". As a result, to all intents and effects you've now got <em>two</em> ozone layers, and only need to explain how the catalytic gas layer is kept together.</li>\n</ul>\n\n<p>You could have some unknown process (high energy collisions, but with what?) generate <a href=\"https://en.wikipedia.org/wiki/Ununseptium\" rel=\"nofollow\">unumseptium</a> atoms in the upper atmosphere. Its reactivity against ozone ought to be frightfully high (<strong>update</strong>: it actually isn't, see Wikipedia), even with a half-life of milliseconds, and the small half-life could help explain the localization of the layer - Uup atoms don't wander far from their birthplace before alpha decaying.</p>\n\n<p>Another more promising possibility, and one which already happens, is you have a volatile molecule where a sufficiently evil halogen is bound to something keeping it quiet. Then the molecule diffuses in the high atmosphere, and <em>almost</em> the same UV rays that produce ozone destroy it, thus freeing the halogen atom, which proceeds to destroy ozone before combining with water vapour or hydrogen or something else and precipitating away. This is what happens now with chlorofluorocarbons.</p>\n\n<p>You might also imagine a large fleet of aircraft with some ozone-harmful chemical in the exhaust fumes (this also happens in reality).</p>\n\n<h1>Question 2: \"Can multiple ozone layers cause more harm?\"</h1>\n\n<p>Ozone layers do not cause harm <em>per se</em>. What they do is intercept radiation and either absorb it or reflect it back at the same wavelength or at a longer one (\"greenhouse effect\").</p>\n\n<p>In the appropriate circumstances both phenomena might be either harmful or beneficial: think some organism that needs radiation at a specific wavelength, or a planet that would be too cold unless some of its thermal emission was bounced back to heat it a little more. The same layer would be harmful to the former and beneficial to the latter.</p>\n\n<h1>Question 3</h1>\n\n<p><strong>If one ozone layer had a hole, would the other(s) act like a backup shield to harmful rays from a star?</strong></p>\n\n<p>Not entirely. What would happen is that the depletion of one layer would increase radiation on the surface, but it would depend on the amount of the ozone shielding left. The layers are not \"redundant\", each one is there because of a specific cause.</p>\n\n<p>Also, depletion of one layer would increase radiation in the volume of air where the second layer is, and might then lead to the thickening of the second layer, leading to a null net effect on the surface (as far as radiations go). The thickening of the second layer might also have other effects, some beneficial and some harmful.</p>\n" }, { "answer_id": 26019, "author": "timuzhti", "author_id": 9166, "author_profile": "https://worldbuilding.stackexchange.com/users/9166", "pm_score": 3, "selected": false, "text": "<p>Yes, in fact <strong>we have an extra one right here on Earth</strong>. Mostly found in large cities, we call this layer smog. It's pretty harmful, because it's not at the right altitude. At sea level, it's just a pollutant. Here's a nice picture showing what we have:</p>\n\n<p><a href=\"https://i.stack.imgur.com/7bs3P.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/7bs3P.png\" alt=\"enter image description here\"></a></p>\n\n<p>Here's the NASA website I got it from: <a href=\"http://spaceplace.nasa.gov/greenhouse/en/\" rel=\"noreferrer\">http://spaceplace.nasa.gov/greenhouse/en/</a></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/26013", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/13744/" ]

[ { "answer_id": 26176, "author": "Dan Smolinske", "author_id": 5002, "author_profile": "https://worldbuilding.stackexchange.com/users/5002", "pm_score": 2, "selected": false, "text": "<p>Sure. You'd need a new biological paradigm where children are randomized instead of combining traits from their parents.</p>\n\n<p>For example, imagine if, when two humans have a child, it's basically a random human child with no direct relation to the mother or father. Your Creator figure would need to define the boundaries of randomness, while also preventing mutations.</p>\n\n<p>This eliminates evolution because the fitness of a parent won't impact the fitness of a child.</p>\n\n<p>A couple of notes:</p>\n\n<p>Just eliminating mutations isn't sufficient to prevent evolution entirely, as species would still specialize based on fitness within their current genomes.</p>\n\n<p>You would still see extinctions, and this would cause species to expand into areas they might not be optimized for. For example, say if a scavenger species went extinct. That opens up an ecological niche, and you would see a non-specialized species start to take advantage of that energy source. They wouldn't be good at it, of course, but it would still happen.</p>\n" }, { "answer_id": 26180, "author": "bowlturner", "author_id": 19, "author_profile": "https://worldbuilding.stackexchange.com/users/19", "pm_score": 1, "selected": false, "text": "<p>It would have to be a world that is very stable, since one of the benefits of evolution is adaptation to change. No adaptation, then if things die, most of the rest of the ecosystem will collapse.</p>\n\n<p>Swallows primarily eat mosquito (at least in MN), and if the mosquito population was mostly eliminated, even if only for a season or two, the swallows might collapse or die out. This is an extremely simple example, however it is meant to prove a point. Making changes in one place causes stresses in another. So we go through a mini ice age or a hot spell, it changes the environment and what plants and animals can survive there. If they can't adapt they will die out. It happens all the time, and without evolution, nothing will evolve to fill in those gaps that are left.</p>\n\n<p>So to even think about stopping evolution you need to stop change in the world. Or you need to have an organism that is infinitely mutable to handle living in any possible environment available. </p>\n" }, { "answer_id": 26181, "author": "Mike Nichols", "author_id": 879, "author_profile": "https://worldbuilding.stackexchange.com/users/879", "pm_score": 3, "selected": false, "text": "<p>There are three features of a system that are both necessary and sufficient for evolution to occur. These are <strong>heredity</strong>, <strong>variation</strong>, and <strong>selection</strong>. Any system which has these 3 features will have evolution and any system lacking any of these 3 features will not have evolution.</p>\n\n<p><strong>Variation</strong> is the existence of meaningful differences between entities in the system.</p>\n\n<p><strong>Heredity</strong> is the capability of those differences to be inherited when an entity reproduces.</p>\n\n<p><strong>Selection</strong> is the influence of these heritable variations on the fitness of the entity.</p>\n\n<p>In any system with these three features variations that confer a selective advantage will be inherited at a higher frequency, which will result in a change in frequency of the variations amongst the entities in the system.</p>\n\n<p>In a system lacking variation there can be no differences between the entities and therefore no selection is possible. In a system lacking heredity the selection of some variants over others has no impact on the frequency of variations in the system. In a system lacking selection there can be change due to random chance, but there will be no productive change only random fluctuations.</p>\n\n<p>I’ve intentionally used ambiguous language because these rules do not just apply to biological evolution, but to evolution in all possible dynamic systems.</p>\n\n<p>To address the question directly, removing any of those features of the system will suffice to prevent evolution. If your organism doesn't pass on its mutations, or if it never mutates in the first place evolution will not be possible. One caveat is that even without selection, genetic drift will still occur. Simply due to random chance some variations will be favored over others and changes will gradually accumulate. Any reproductive isolation will therefore result in eventual divergence and speciation. This gradual, random change fits the formal definition of \"evolution\", but I don't think most people would really consider it as such.</p>\n" }, { "answer_id": 26183, "author": "rumguff", "author_id": 11859, "author_profile": "https://worldbuilding.stackexchange.com/users/11859", "pm_score": 2, "selected": false, "text": "<p>I think its possible to conceive of an all powerful creator that can design a non sapient species which can propagate itself without evolution as long as the creator is able to hold all environmental constants constant, such that evolution to handle unexpected environmental situations is not required. This creator would have to be magical since I do not believe that such a creator could obey they laws of thermodynamics at all.</p>\n\n<p><strong>So first answer: If you have a creator not bound by thermodynamics you might be in with a shot.</strong></p>\n\n<p>So can a magical creator define a world in which there is no evolution but that otherwise obeys known laws?</p>\n\n<p><strong>If you have sapient tool using species with free will</strong> as part of this question then even if they cannot biologically evolve, the exercise of the creator is probably doomed as soon as the intelligent species are able to begin to craft their own destiny. This happens when:</p>\n\n<ul>\n<li>The passing on of stored knowledge becomes sufficiently reliable that newborns of the sapient species don't have to relearn everything from scratch. Writing, myths, language, stuff like that.</li>\n<li>The use of tools by the sapient species gives them a competitive advantage against the non tool using species which cannot evolve. </li>\n</ul>\n\n<p>These two basic traits of a proto-technological species introduces variables that the creator cannot plan for at the outset. Social consciousness and culture - that accumulation of collective knowledge and patterns - can evolve similar to biological evolution. This is as bad for the creators designs as biological evolution.</p>\n\n<p><strong>Second Answer: If you have sapients in the world then the creator would be forced to intervene at some point even if biological evolution is not operative, and to intervene increasingly often as the evolution of the sapients ceases to be biologically driven and is now cybernetic, technological and memetic.</strong></p>\n\n<p>I think that what I have just said is exactly the cultural framework on which all our religions are based...</p>\n\n<p>You'd have to take away the sapient's free will to make this work (which is essentially what Tolkein did with the Elves in Middle Earth, in order to ensure they would experience unchanging immortality and cultural stagnation).</p>\n" }, { "answer_id": 26184, "author": "Tyrabel", "author_id": 11079, "author_profile": "https://worldbuilding.stackexchange.com/users/11079", "pm_score": 0, "selected": false, "text": "<p>Evolution is a long process, but each step is based on a tiny mutation.</p>\n\n<p>The mutation spreads in the genetic pool if it's a positive change for the specie, and a positive change can be :</p>\n\n<ul>\n<li>Life improved (finding or assimilating food/water, resist to heat/cold...)</li>\n<li>Death avoided or life last longer (protecting from predators by poison, hiding, defense strategies, resisting diseases...)</li>\n<li>Reproduction improved (Better looking for the partner, more childs...)</li>\n</ul>\n\n<p>(If i forget something, please add in the comments)</p>\n\n<p>To prevent evolution, <strong>you could stop mutation.</strong> </p>\n\n<p>Sexual reproduction provoque mutation. Make all your creatures some clones and you will slow evolution down (even if it might not be stopped, even with parthenogenesis small mutation occurs)</p>\n\n<p>Interspecies DNA exchanges cause mutation (bacteria and viruses in your body are currently playing with some of your cells DNA, yuck). Very hard to stop, but it is a God's work. Here is a totally imaginary biology. Make viruses and tiny life forms very stable, or their DNA code very different from the \"big\" creatures, or make each cell inpenetrable to other forms of life.</p>\n\n<p><strong>If you don't want to change the whole world biology, try to make evolution unuseful</strong></p>\n\n<p>Have a very stable environment. You don't want species to evolve, even a little bit, because the summer was very hot and dry and this year's young frogs resist a higher temperature. </p>\n\n<p>Make your creatures' life a paradise. Evolution usually makes life longer and more secure. Without predators, less selection. Without diseases, less selection. With every creature equally healthy and beautiful, no partner selection (again with the clones). \nThe more humans make their life confortable, the less they evolve. They are no more selected by predators, diseases or disabilities. \"Bad\" genes do not disapear, \"Good\" ones do not offer a significant advantage on the number of childs to change the whole specie. </p>\n\n<p>Make each kind of creatures very numerous. A tiny mutation is more likely to drown in the genetic pool of a very large group of creatures. </p>\n\n<p><em>Bonus : now you have to find a way to keep a fair amount of creatures on your planet. Either they all die from age, or they live very long and have few children, for example ?</em></p>\n\n<p><strong>Conclusion</strong> your god have a lot of work to do during the creation if he wants to relax later. Evolution is a lazy but effective solution. But if you really have a god's power, you could just create a kind of creatures that eat or kill everything that doesn't fit the plan. Like a robot with a database of all living creatures. If this chicken does have more than 1% difference with the registred DNA code \"chicken\", kill it. </p>\n" }, { "answer_id": 26187, "author": "Youstay Igo", "author_id": 13449, "author_profile": "https://worldbuilding.stackexchange.com/users/13449", "pm_score": 2, "selected": false, "text": "<p>There are a lot of people in the world who believe that God created this universe, and they also believe that God drove evolution. There are several sub-schools within this paradigm and this is no place to discuss them in detail.</p>\n\n<p>There are a several possibilities for a world where creatures exist and evolution is absent. The first prerequisite is what you have already provided: that such a world has been created as-is by some supreme authority. The same supreme authority can change the rules of the game and make them unfavorable for evolution. It is quite simple. It is rather a thing of theology and philosophy than science.</p>\n\n<p>The flaw in your reasoning is that you want the rules to stay the same, and yet the product to be different. You want the same scientific rules which apply on this world and yet you want evolution to not occur as it does here on earth. You cannot have both of them simultaneously. You will either have to let go of the laws, or you will have to allow the laws to take effect authoritatively and drive the processes as they drive on earth.</p>\n\n<p>If you change the rules accordingly, you can get a static world. We are talking about a world where:</p>\n\n<ul>\n<li><p>Creatures do not compete within the same community, nor with other creatures. (That is, natural selection is off)</p></li>\n<li><p>Neither males, nor females have any favorite characteristics about the other gender so that an short giraffe would have as much chance of mating with a beautiful female as a tall, handsome giraffe. (Hence sexual selection is off)</p></li>\n<li><p>There is not the least random change in the dna of organisms at all. If there is any change in the dna of an organism, that organism instantly dies. (So there is no chance for mutations).</p></li>\n<li><p>Climatic conditions have no effect on animals and neither is any animal able to correspond accordingly to environmental changes. So that animals migrating from warmer to colder regions simply freeze to death, instead of undergoing any changes that help them survive there. (Thus phenotypical changes cannot occur)</p></li>\n</ul>\n\n<p>With an ecosystem running the above mentioned rules, evolution would not occur.</p>\n" }, { "answer_id": 26188, "author": "LSerni", "author_id": 6933, "author_profile": "https://worldbuilding.stackexchange.com/users/6933", "pm_score": 6, "selected": true, "text": "<p>The simplest way would be to <strong>prevent mutation</strong> and modify sex (you do not <em>need</em> sex in the world, but if you <em>must</em>...) in such a way that, for example, the male contributes <em>nothing</em> except the initial stimulus (which makes this essentially parthenogenesis, and that's why sex, or better, <em>gender</em> is not mandatory - you always can have homosexual intercourse as a matter of course, as it happens with Eric Flint's gukuys in <a href=\"https://en.wikipedia.org/wiki/Mother_of_Demons\" rel=\"nofollow noreferrer\"><em>Mother of Demons</em></a>).</p>\n\n<p>All individuals are XXY triploids, and inactivation of the Y chromosome happens \"at random\" (this allows any ratio of male to female, depending on the probability of inactivation). XXY genotypes have male phenotype, XXy genotypes are naturally female. This kind of genetic setup is perfectly possible and naturally occurs (except for the parthenogenetic reproduction twist) in humans, where <a href=\"https://en.wikipedia.org/wiki/Klinefelter_syndrome\" rel=\"nofollow noreferrer\">it is an anomaly</a>. But there's no reason for it to be.</p>\n\n<p>All creatures would then be identical clones genetically, but could (and probably would) sport differences, even large ones, due to <a href=\"https://en.wikipedia.org/wiki/Epigenetics\" rel=\"nofollow noreferrer\">epigenetic factors</a>.</p>\n\n<p>Also, depending on what the <em>cue</em> actually <em>is</em>, it might pose an interesting problem for birth control. Since all the needed machinery is self-contained in the female, sex for nonreproductive purposes could in effect be made impossible (meaning that <em>any</em> intercourse results in conception), or so awkward as to negate any recreational value, which might appeal to both deities and advanced aliens.</p>\n\n<p>This removes most mutations due to recombination between different DNA sets.</p>\n\n<p>As to how to prevent other kinds of mutation, the DNA helix gets routinely unwound and split in order to allow cell duplication. There already are enzymes that correct some common DNA replication errors. \"All\" that would be needed would be a super-enzyme, which we could call <em><a href=\"https://en.wikipedia.org/wiki/Reed%E2%80%93Solomon_error_correction\" rel=\"nofollow noreferrer\">DNA-reed-solomonase</a></em> :-), capable of detecting errors and either repairing them if possibile, or otherwise triggering the <a href=\"https://en.wikipedia.org/wiki/Apoptosis\" rel=\"nofollow noreferrer\">cellular self-destruct mechanism</a>.</p>\n\n<p>Such an enzyme could never have evolved (naturally), but a sufficiently advanced alien Seeder species might not find it difficult to build it from scratch.</p>\n\n<p>A possible side effect would be longevity, perhaps even immortality, and complete immunity to most forms of cancer, not unlike the aliens in Asimov's <a href=\"https://en.wikipedia.org/wiki/Hostess_%28short_story%29\" rel=\"nofollow noreferrer\">Hostess</a>.</p>\n\n<p>Another effect would be a strongly reduced capability for the species to cope with environmental changes through natural selection and random mutation. This might be no great problem for a technological civilization, but for 99.999% of Earth history, it would have been a sure ticket for racial extinction.</p>\n\n<h1>Update: couldn't the repair mechanism itself fail?</h1>\n\n<p>(@Peteris's objection)</p>\n\n<p>Yes, and on a cell-by-cell basis, it will often do just that.</p>\n\n<p>But the \"mechanism\" is not a simple reasonably-soft-fail enzyme system such as <em>evolved</em> creatures possess. It is rather a <em>designed</em> computer program implemented with amino acids.</p>\n\n<p>First of all it would have to fail in a <em>zygote</em>, otherwise the host would only get common cancer, and anyway the mutation would not get inherited.</p>\n\n<p>Then, <em>by definition</em> the change would need to break the main cellular repair mechanism, and <em>the organism has no others</em>. God or our aliens never saw the need for them, and actually had a good reason not to provide them: we want defective cells to <em>die</em>.</p>\n\n<p>So <em>this</em> pro-evolutionary change would actually be <em>counter</em>evolutionary, since it would expose the host to all kind of cellular damage against which it would have no resistance. Given the rate at which random mutations would occur and accumulate during its early development, it would be extremely unlikely that a mutated foetus could even come to term.</p>\n\n<p>We (the aliens or god) can further improve our game in two ways. One: since the child is a genetic clone, we need no placental barrier. The foetus is inundated by the mother's enzyme in addition to its own. This has no effect on perfect replicas, but mutated children die stillborn.</p>\n\n<p>Two: the planet itself could be abundant in any one of (or several) mutagenic compounds or phenomena (UV radiation, natural radioactivity...). Protected individuals get no cancer, while any unprotected individual will quickly develop several.</p>\n\n<p>To have a mutation in the enzyme, a point mutation or even a series of point mutations would not be enough. We'd need for the enzyme to change in such a way that <em>some</em> further mutations will be permitted, while oncogenic ones will still get eliminated.</p>\n\n<p>This is on the same scale of an English spell checker that somehow gets corrupted during the copy, but its SHA256 hash remains the same, <em>and</em> the resulting program turns out to not only still work but to have become a working <em>German</em> spell checker (I've heard this kind of hypothetical occurrence be referred to as a <em>Minerva mutation</em>, from the <a href=\"https://en.wikipedia.org/wiki/Minerva\" rel=\"nofollow noreferrer\">Roman goddess</a> that was believed to have sprung, already adult and clad in armour, from Jupiter's head).</p>\n\n<p>Chances of a Minerva event are in theory not zero, but I feel they're vanishingly small. This species' designers would have worried much more about the possibility of, say, a <a href=\"https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event\" rel=\"nofollow noreferrer\">Chicxulub impact</a>.</p>\n\n<h1>A closer look</h1>\n\n<p>This is a bit of a hen and egg problem, so let's see it in practice.</p>\n\n<p>Our alien engineered DNA can be represented like this (actual order is not important):</p>\n\n<pre><code>[H][CHECK][ BODY ]\n</code></pre>\n\n<p>where BODY is the DNA required by the cell, CHECK is the DNA that codes the \"compare to plan, then repair or kill\" mechanism, and H is the \"plan\" hash.</p>\n\n<p>The CHECK part translates into a very large molecule (megaDalton range) with <a href=\"https://en.wikipedia.org/wiki/Helicase\" rel=\"nofollow noreferrer\">helicase</a> capability, a sort of specialized polymerase. The molecule attaches to a DNA strand and \"walks\" through it generating a <a href=\"https://en.wikipedia.org/wiki/Transcription_bubble\" rel=\"nofollow noreferrer\">hashing/correcting bubble</a>. At the end of the process it has calculated the DNA \"hash\" and compares it to its expected value; if the check fails, cellular death is triggered. At any one moment every DNA molecule in the body could be examined by up to a dozen such <em>correctases</em>.</p>\n\n<p>A random mutation can then occur in one of three places:</p>\n\n<ul>\n<li>B mutation. This is the most likely, since the C (CHECK) part will probably be no more than 5% of the total DNA. Helicases and polymerases occupy around 1% of human DNA, and this engineered DNA is very likely to be much more compact. In percent, I think a 1:20 relation is a good ballpark figure. Anyway, a B mutation will be caught by the intact C molecule and either repaired or, if not possible, killed.</li>\n<li>H mutation. Enormously unlikely due to its small size, it will nonetheless happen than the H sequence mutates. When it happens, lots of corrupted C molecules are generated that will routinely misinterpret cellular DNA as corrupted itself, thereby behaving like a fast-acting cellular poison. The mutated cell will be the first to die, and will likely bring down several hundred of the nearby cells before the mistaken correctase is finally degraded. Something remotely similar happens, on a much larger scale, with some kinds of poison (e.g. that of some snakes or that of the <a href=\"https://en.wikipedia.org/wiki/Brown_recluse_spider\" rel=\"nofollow noreferrer\">brown recluse</a> spider; if you google that, be aware that the images may be quite disturbing). However, the net result is that this kind of mutation can't be inherited.</li>\n<li>C (CHECK) mutation. This is more promising. There are several kinds of mutations which can affect the correctase molecule:\n\n<ul>\n<li>mutations that make it believe <em>any</em> DNA is always corrupt. Same as the H mutation case.</li>\n<li>mutations that stop it working altogether (e.g. it can no longer bind to the DNA strand).</li>\n<li>mutations that stop it from being lethal (either by stopping it from detecting changes, stopping it from initiating cellular death) but keep it working as a correcting enzyme.</li>\n</ul></li>\n</ul>\n\n<p>But the main problem here, which would make it impossible as a natural occurrence, is that since every cell is routinely drenched in the correctase produced by itself <em>and its immediate neighbours</em>, any lessening in any one cell's correctase lethality would avail nothing. The cell would still be killed by its neighbours.</p>\n\n<p>To survive, all cells must be mutated (or synthesized) in the same way, all at once or after being kept separate. Or you need to have a single cell with <em>no neighbours</em>. Even the zygote cell is not \"alone\", it is connected to the mother organism.</p>\n\n<h1>\"Life will find a way\"</h1>\n\n<p>This is @MikeNichols' conclusion, and from the above scenario I would conclude that he's wrong... <strong>except he's not</strong>. He would be (of that I'm quite certain) if the organism existed alone, <em>in vacuo</em>. But no organism ever exists in an ecological vacuum (the closest approximation I'm aware of are Leo Frankowski's Mitchegai, <a href=\"http://heliologue.com/2010/06/08/kren-of-the-mitchegai-2/\" rel=\"nofollow noreferrer\">an eptalogy euthanised in 2004</a>).</p>\n\n<p>And the correctase mechanism is <strong>expensive</strong> - it needs specialized machinery that has an operating as well as a replication cost. A sizeable organism would have no trouble in keeping up the whole show, but a <em>micro-organism</em> would be hard pressed to do the same. So our alien engineers may have stopped evolution <em>in higher organisms</em>, but they can't reasonably stop evolution <em>in microbes</em>. And as far as we know, without a (healthy) microscopic biota, life is not possible.</p>\n\n<p>So we have a life pyramid where the top 10-15% is immune from evolution, and the lower organisms are free to evolve. While the middle layers may still be controllable by the 15% nobility, I suspect that a good 50% of the total planetary biomass would be logistically unreachable.</p>\n\n<p>And let's not forget that this setup is the exact opposite of <em>biodiversity</em>. Sooner or later some pathogen will evolve that finds a suitable <em>pabulum</em> in those perfectly engineered, static, possibly unageing higher organisms, <strong>and will kill them all</strong>. Won't they develop genetic immunity? Well, any other <em>im</em>perfect organism very likely would. But the Creators made sure this couldn't happen...</p>\n" }, { "answer_id": 26204, "author": "shannon", "author_id": 13861, "author_profile": "https://worldbuilding.stackexchange.com/users/13861", "pm_score": 1, "selected": false, "text": "<p>Record the genomic boundaries of the target species and devise technology to eradicate all deviation.</p>\n\n<hr>\n\n<p><strong>Clarification of the mechanism</strong> by request, presuming this is a fictional or future worldbuild:</p>\n\n<p>Some self-maintaining or self-replicating means (nanotech or biotech) exists to identify and eliminate all genetic deviation. This means might be administered willingly, e.g. to all females of a xenophobic or fervently religious species, or unwillingly, e.g. by a one-time intervention of an advanced foreign agent and resident in the atmosphere. The influence might be at conception, at birth, or prior to puberty. The mechanism itself might even be a genetic trait, provided it includes backup mechanisms which are highly resilient to coding errors. The mechanism might prevent conception, abort pregnancy, terminate life, or sterilize the \"mutant\".</p>\n\n<p>All of the above scenarios meet the currently-stated OP requirements, as of this writing.</p>\n\n<p>This easily defeats the target effect of evolution, since now the \"fittest\" are those that are unchanging. The correctly design mechanism would require deviation larger than that which evolution itself provides, to overcome.</p>\n" }, { "answer_id": 26205, "author": "Artelius", "author_id": 9277, "author_profile": "https://worldbuilding.stackexchange.com/users/9277", "pm_score": 0, "selected": false, "text": "<p><strong>Problem:</strong> How do we allow inherited individual variation (eye colour, colour-blindness, etc.) without gradual change in the species as a whole?</p>\n\n<p><strong>Solution 1: Strict mate selection</strong></p>\n\n<p>For example, elephants will only mate with a partner that is sufficiently elephant-like. Also, they will only mate with partners that are clearly very selective about whom they mate with.</p>\n\n<p>But what about mutations that change an elephant's conception of what classifies as an elephant? Well, perhaps those parts of the elephant's DNA are subject to very strict quality control (e.g. checksums).</p>\n\n<p><strong>Solution 2: Species DNA</strong></p>\n\n<p>In this case, all members of a species have identical DNA, and individual variations are inherited through other means (such as epigenetics). The DNA must be copied exactly for an embryo to form.</p>\n\n<p>Of course in both of these solutions, the proportion of individuals with particular characteristics within a species may change (e.g. certain eye colours may become more common over time) but the species themselves will not drift.</p>\n" }, { "answer_id": 26219, "author": "Peter - Reinstate Monica", "author_id": 2374, "author_profile": "https://worldbuilding.stackexchange.com/users/2374", "pm_score": 1, "selected": false, "text": "<p>The answer is an emphatic No, for very basic reasons. This is a variation of @Youstaf's argument: </p>\n\n<blockquote>\n <p>\"The flaw in your reasoning is that you want the rules to stay the\n same, and yet the product to be different.\"</p>\n</blockquote>\n\n<p>The key issue is that evolution is not a theory or a scientific concept. It is, in a very principle way, another word for reality. It means that everything just flows and arranges itself, unattended, through spontaneous events (think atomic level) and interaction within the framework of space and time.</p>\n\n<p>Your setup introduces a creator, or \"god\", which by definition is almighty; in the presence of a god anything is possible, including, for god's sake, no evolution, if you must. But it would mean that reality is not what we think it is but that instead \"god\" controls everything on a sub-atomic level and what we see are actually only Potemkin's villages. A Simulacron 3, a total Truman Show, a Matrix.</p>\n\n<p>I understood your question differently: \"God\" sets up a stage (reality functioning as we understand it, plus some mechanism X to prevent evolution) and then retreats, letting things play out. With that premise, \"evolution\" (of species, the universe) of course continues to happen, despite all efforts -- just, possibly, locally, slower. But, for example, at some point our sun will burn out.</p>\n\n<p>There is a last, perhaps even more fundamental issue, which resembles Richard Dawkins' god critique: Even if \"god\" manages to halt evolution on earth, and maybe in the galaxy, \"god\" and our reality are still part of a larger reality, i.e. part of a larger evolution. \"God\" will evolve, too! She might, for example, become bored and flush this reality down the drain, or be reprimanded by the ethics committee at her insititute and decide to let evolution, i.e. \"reality\", flow again.</p>\n" }, { "answer_id": 26221, "author": "Jack Aidley", "author_id": 857, "author_profile": "https://worldbuilding.stackexchange.com/users/857", "pm_score": -1, "selected": false, "text": "<p>You can't.</p>\n\n<p>The reason you can't is the existence of domesticated breeds and the huge variation within those breeds. This <em>requires</em> all the organism side mechanisms for evolution to be in place. That leaves only the existence of fitness differences occurring in the interface of organism and environment as the final ingredient for evolution and there's no way of not having that without having a very different world.</p>\n\n<p>You could have a created world without evolution but not with the creatures we see today in it.</p>\n" }, { "answer_id": 26226, "author": "algiogia", "author_id": 1981, "author_profile": "https://worldbuilding.stackexchange.com/users/1981", "pm_score": -1, "selected": false, "text": "<p>I admit my knowledge of evolution dates back to my school days (about 15 years ago) and seems theories have changed in the last year. But from what I recall evolution is something \"random\": one day an individual is born with a different (random) characteristic, due to the again random(ish) combination of its parents genetic material. If the new characteristic represents an advantage in the current environment the individual will survive and pass on its characteristic.</p>\n\n<p>However, I started to think some of the changes are too advanced or intelligent to be just the result of a chance. A friend suggested that cell are intelligent enough to trigger the changes (according to him we alter our DNA during our life). \nIf this is actually the way evolution works, you may have your god creates all beings without this \"intelligent adaptation\" skill.</p>\n\n<p>Keep \"armless\" mixes (change of traits due to mix of DNA materials, e.g. blond father + green-eyed mother = blond, green-eyed child) to avoid clonation, but remove adaptation changes (e.g. people move to colder area, skin cells \"decide\" to produce more/thicker hair).</p>\n" }, { "answer_id": 26231, "author": "James Elderfield", "author_id": 8707, "author_profile": "https://worldbuilding.stackexchange.com/users/8707", "pm_score": 0, "selected": false, "text": "<p>A world without evolution is going to be impossible if there is heredity and variation (as in the answer by Mike Nichols).</p>\n\n<p>However this doesn't mean that your creationist forces can't be actively manipulating evolution to prevent speciation. You've just got to work out where this balancing selection is going to come from.</p>\n\n<p>Speciation is generally caused by barriers to reproduction of any kind. For example two populations on different continents are likely to diverge as they can't meet to interbreed. To fix this your anti-evolution forces could be moving organisms between continents to maintain geneflow and homogeneity.</p>\n\n<p>If you want to stop drift or selection within a population you could selectively remove (e.g. kill or sterilise) organisms that are distant from the population average in any trait. This helps both to remove variation and to select strongly against divergence.</p>\n" }, { "answer_id": 26248, "author": "Biff MaGriff", "author_id": 8566, "author_profile": "https://worldbuilding.stackexchange.com/users/8566", "pm_score": 0, "selected": false, "text": "<p><strong>No</strong></p>\n\n<p>Here's why.</p>\n\n<p>Mistakes get made and creatures change over time. Even living fossils like Coelacanth who from outward appearances still look the same as ever have had their DNA change over the millennia.</p>\n\n<p>So get rid of DNA.</p>\n\n<p>A world of replicating robots, some species are clever and make tools which gives them an advantage over others and they quickly wipe out other species. Other clever species start altering their behaviour to avoid getting killed by the tool using clever species. Can you say that these species haven't changed? Compare this to cicadas in the real world. Are the ones that come out every 17 years the same as the ones that do not?</p>\n\n<p>So make em dumb, all they can do is replicate themselves exactly and die.</p>\n\n<p>All is fine but every once in a while there are accidents where a bot gets damaged and every once in a while it's replication code gets damaged and now those bots have offspring that are built in some fasion that outcompetes the original ones for resources...</p>\n" }, { "answer_id": 26265, "author": "Mike Scott", "author_id": 220, "author_profile": "https://worldbuilding.stackexchange.com/users/220", "pm_score": 1, "selected": false, "text": "<p>If you can do it, it will only work in the short term. No matter what precautions you take, chunks of genetic material will start reproducing and evolving outside your anti-evolutionary framework and become viruses. They will then wipe out all of your other species, since they can't evolve defences against the viruses.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/26175", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/3215/" ]

[ { "answer_id": 26232, "author": "Avernium", "author_id": 11306, "author_profile": "https://worldbuilding.stackexchange.com/users/11306", "pm_score": 2, "selected": false, "text": "<p>I’ll take a rough historical (and non hard science) stab at an answer.</p>\n\n<p>Infant Earth’s theorized impact with <a href=\"https://en.wikipedia.org/wiki/Theia_(planet)\" rel=\"nofollow\">Theia</a> seems like an interesting model for comparison here. We don’t seem to have a particularly clear idea of what Earth looked like at the time, but this event would have introduced quite a bit of material into the Earth’s vicinity (much of it theoretically forming the moon).</p>\n\n<p>At present, it’s thought that the impact event occurred around <a href=\"https://en.wikipedia.org/wiki/Giant_impact_hypothesis\" rel=\"nofollow\">4.4-4.45</a> billion years ago. This would have stirred things up quite a bit and required a cooling period, perhaps not unlike you bombarding the surface with enough iron to double the diameter of Mars. </p>\n\n<p>Determining how long you’d need to wait before the atmosphere reached “pleasant” temperatures is a bigger challenge. It seems that the Earth’s crust cooled and solidified around 4.1 billion years ago, though I’m sure it wouldn’t have been a nice place to be. Earth’s first lifeforms are believed to have developed around <a href=\"http://www.ecology.com/2011/09/10/earths-beginnings-origins-life/\" rel=\"nofollow\">3.8 billion years ago</a> with the beginning of the Archean Period. That puts you at around 600 million years, plus a few hundred million years to get to your preferred temperatures (assuming that the Earth was still a pretty hostile environment even during the Archean Period.)</p>\n\n<p>There are, of course, shortcomings to using this model.</p>\n\n<ul>\n<li>The giant impact hypothesis, while a leading theory, may not be fully\ncorrect. </li>\n<li>Earth was most likely still molten when the impact occurred, as\nopposed to the fully solidified Mars.</li>\n<li>Further analysis is needed between the start of the Archean period\nand your target environmental temperatures (though more\nspecification of the target may be useful).</li>\n</ul>\n" }, { "answer_id": 26233, "author": "Youstay Igo", "author_id": 13449, "author_profile": "https://worldbuilding.stackexchange.com/users/13449", "pm_score": 0, "selected": false, "text": "<p>Since Mars' atmosphere is only 1% of earth's atmosphere (in mass) so there would hardly be any fireworks visible from earth even with powerful telescopes. There would only be ultra-large clouds of red dust flying around though (iron oxide dust, that constitutes the surface of Mars).</p>\n\n<p>Having an extremely light atmosphere also means that Mars' greenhouse capability is virtually zero, and any heat generated by the event of impact would radiate away into space far quicker than it would on earth. I cannot provide an exact number though, as I am unaware of precise values in this subject.</p>\n\n<p>Also, I think you forgot a very important effect which would result due to this incredible increase in Mars' mass. I am talking about the asteroid belt between Mars and Jupiter. With nearly 3 times increase in Mars' mass, the gravitational balance that keeps the asteroid belt in it's place would be severely disturbed and a lot of asteroids would be deviating from their orbits towards Mars ... and beyond it ... towards ... don't ask me. The very thought horrifies me.</p>\n\n<hr>\n\n<p>My answer above, is written assuming that the additional iron mass was dumped on the red planet as dust and tiny iron fragments, not as a single planetary sized asteroid. If you are talking about <em>THAT</em>, then it would probably end Mars' existence as a planet as both objects would crash with a force that would crack Mars to the core and pulverize it to dust. Most of the planetoid mass would vaporize from the heat of impact. The phase-2 damage to earth would also be immensely huge. Falling debris and asteroids would end all life on earth (at least all multicellular life) and rip giant fissures on the crust.</p>\n" }, { "answer_id": 26237, "author": "SlySherZ", "author_id": 2377, "author_profile": "https://worldbuilding.stackexchange.com/users/2377", "pm_score": 1, "selected": false, "text": "<p>The parameter to the problem where changed midway through my calculation, so I won't finish it. I'll leave this here if someone wants to take over.</p>\n\n<p>Firstly we need to know the thickness of the iron pool.</p>\n\n<p>$\\text{Earth's mass} = E_m = 5.972 \\cdot 10 ^{24}\\text{kg}$</p>\n\n<p>$\\text{Mars's mass} = M_m = 6.39 \\cdot 10 ^ {23}\\text{kg}$</p>\n\n<p>$\\text{Difference} = E_m - M_m = 5.333 \\cdot 10 ^{24}\\text{kg}$</p>\n\n<p>$\\text{Iron's density} = D_i = 7850\\text{kg}/\\text{m}^3$</p>\n\n<p>$\\text{Volume of Iron} = V_i = \\text{Difference} / D_i = 6.794 \\cdot 10^{20}$</p>\n\n<p>$\\text{Radius of Mars} = R_m = 3.39 \\cdot 10 ^ 6\\text{m}$</p>\n\n<p>Volume of a spherical shell</p>\n\n<p>$Vi = 4/3 Pi (R_{mnew}^3 - R_m^3) &lt;=&gt; R_{mnew} = sqrt3(3V_i/(4\\pi) + R_m^3) = 5.859 × 10^6\\text{m} $</p>\n\n<p>Height of iron is:</p>\n\n<p>$h = R_{mnew} - R_m = 2.469 \\cdot 10^6\\text{m}$</p>\n\n<p>which makes the radius of Mars slightly lower than Earth's. This is a quite unrealistic result, because compression would play a big role into reducing this value.\nThere are many things that are hard to predict accurately. What would happen to the atmosphere? </p>\n\n<p>Let's assume the aliens choose the lowest temperature at which iron is liquid, it's melting point. Don't waste too much energy and the extra energy from the fall would keep it liquid to spread it evenly. Another inaccuracy, we ignore pressure.</p>\n\n<p>$M_{pi} = 1538ºC$</p>\n\n<p>Due to low amount of oxygen in the Mars atmosphere, I'll assume there's just some red rust on the iron.</p>\n\n<p>$\\text{emissivity} = \\epsilon = 0.6$</p>\n\n<p>$\\text{reflectivity} = Ref = 1 - \\epsilon = 0.4 $</p>\n\n<p>Next we want to know the equilibrium temperature of the planet.</p>\n\n<p>$\\text{Effective temperature of the Sun} = T_s = 5780K$</p>\n\n<p>$\\text{Distance from Mars to the Sun} = D = 2.279*10^{11}\\text{m}$</p>\n\n<p>Using planet's emissivity instead of a black body:</p>\n\n<p>$T_eq = T_s * Ref^{2/4} * \\sqrt( R_m / (2* D) ) = 9.97\\text{K}$</p>\n\n<p>Yes, it will get really really cold eventually. Let's make another assumption and consider the iron shell is empty inside. We've made so many up until now that every error will cancel out and we'll get the right result. Hopefully.</p>\n" }, { "answer_id": 26264, "author": "Gary Walker", "author_id": 7325, "author_profile": "https://worldbuilding.stackexchange.com/users/7325", "pm_score": 4, "selected": true, "text": "<p>Lets start by ignoring that for deep planetary pressures, iron is compressible and that it expands when it is heated.</p>\n\n<p><strong>Basic facts</strong></p>\n\n<pre><code>Mars mass: 6.4171e23 kg \nEarth mass: 5.97237e24 kg\nMars mean radius: 3389.5 km \nMars surface acceleration: 3.711 m/s^2\nIron density: 7850 kg/m^3\nvolume of a sphere = 4 / 3 * pi * r^3 \nradius of sphere = (volume * 3 / 4 / pi) ^ (1/3)\n\nMass of iron = m(Earth) - m(Mars) = 5.33066e24 kg\nVolume of iron = mass / density = 6.79065e20 m^3 or 6.79065e11 km^3\nGravitational Constant: 6.67385e-11 N m^2 / kg^2\n</code></pre>\n\n<p>Let us model the required iron as a spherical shell of iron with an inner radius equal to that of mars plus 150 km. So, what is the outer radius? We know that the total volume of the hollow sphere must be the total volume of iron minus the volume of the hollow interior.</p>\n\n<pre><code>vMars = 4 / 3 * pi * 3389.5^3 = 1.63116e11 km^3\nvInner = 4 / 3 / * pi * 3539.5^3 = 1.85744e11 km^3\nvOuter = vInner + vIron = 1.85744e11 + 6.79065e11 = 8.64809e11 km^3\n\nrOuter = (vOuter*3/4/pi)^(1/3) = 5910.31 km\nvIronMars = 8.42181e11 km^3 (calculated below)\nrIronMars = 5858.3 km\n</code></pre>\n\n<p>So, our iron to be dropped consists of a hollow ball of iron with an inner radius of 3539 km and outer radius of 5910 km. At the inner edge of the iron, the downward acceleration would be the acceleration due to Mars alone as the net contribution of the iron mass would be zero for all points inside the shell. At the outer radius, the acceleration would be based on the mass of the entire Earth.</p>\n\n<pre><code>accelInnerInitial = accelMarsSurface * (marsRadius / rInner)^2 = 3.711 * (3539.5/3389.5)^2 = 3.403 m/s^2\naccelOuterInitial = accelEarthSurface * (earthRadius / rOuter)^2 = 9.8066 * (6371/5910.3)^2 = 11.395 m/s^2\n</code></pre>\n\n<p>The differences in acceleration clarify the problem with the iron shell assumption, the iron blocks would crash into each other as they fall. We'll simply ignore this problem by and large.</p>\n\n<p>So, what is the impact velocity of the inner shell? Either we could do calculus since the acceleration increases as the shell falls closer to Mars, or we can take advantage of the formula for gravitational potential: </p>\n\n<pre><code>Gravitational Potential, V(x) = -G * M / x where G is the gravitational constants, M is the mass of the planet and X is the distance to the planets center. \n</code></pre>\n\n<p>Note that V(x) is always negative and approaches zero as distance approaches infinity. Since kinetic energy = 1/2 * mV^2 and a falling object converts gravitational energy to kinetic energy we can figure out the impact energy and velocity without having to integrate over radius with variable acceleration. </p>\n\n<p>For example, consider the case of falling from infinity to the surface of Mars. </p>\n\n<pre><code>F(x) = -GM/x thus F(3389500) = - 6.67385e-11 * 6.4171e23 / 3389500 = - 1.2635e7 J/kg. \n</code></pre>\n\n<p>Kinetic energy change will have the same magnitude as the gravitational potential energy change due to conservation of energy.</p>\n\n<p>Solving for kinetic energy for velocity, <code>V = sqrt(2*E/m)</code>, and using -F(3389500) for E.</p>\n\n<pre><code>V = sqrt(2*1.2635e7/1), V=5.027e3 meters / sec -- this is in perfect agreement with the published value for the escape velocity of Mars, a useful check on our method.\n</code></pre>\n\n<p>For a mass dropped from 150 km altitude. F(3539500) = -1.20996e7 J/kg. The difference between F(surface) and F(150 km up) is 5.35e5 J/kg, which means the impact velocity is 1035 meters/second if atmospheric drag is ignored. Given the total mass of iron being dropped, this seems like a good assumption.</p>\n\n<p>What about the outermost shell? similar math, but it based on total earth mass as all of the iron lies inside the outermost shell-- Mars radius is now much larger due to all of the rest of the iron already added to Mars. Again ignoring comprehensibility of the iron (and Mars itself), our new Mars planetary volume is the old volume plus the volume of all of the iron: </p>\n\n<pre><code>volumeIronMars = 1.63116e11 + 6.79065e11 = 8.42181e11 km^3. \n</code></pre>\n\n<p>Solving for radius yields 5858.3 km so the outer shell will fall a distance of only 52 km, however it does so with the full acceleration due to Earth mass, about 9 times Mars mass.</p>\n\n<pre><code>F(OuterShell) = -GM/x = -6.67385e-11 * 5.97237E+24 / 5910.308044 = -67439276 J/kg\n\nF(IronMarsSurface) = -6.67385e-11 * 5.97237E+24 / 5858.3.303939 = -68037933 J/kg\n\nChange in outer shell potential from falling = 5.99e5 J/kg`\n</code></pre>\n\n<p>The difference in energy gain for the inner and outer layers is close enough, that I will just use the geometric mean value of the inner and outer shells as the average energy change (instead of resorting to calculus to compute a more accurate number), i.e., 5.662E5 J/kg</p>\n\n<p>So, finally what is the temperature change? Iron has a specific heat capacity of around <code>0.45 joules / gram * deg</code> or <code>450 J/kg*deg</code> so we can finally compute the temperature rise as <code>5.662e5/450 or 1260 degrees Kelvin,</code> so <strong>the final iron temperature is about 1510 Kelvin or 1237 Celsius or 2258 Fahrenheit</strong> - this is considered white hot though there is still a yellowish orange appearance -- about the same as a candle flame. Iron melts at 1538C so not molten iron, but it will be much softer / more plastic than iron at Earth surface temperatures.</p>\n\n<p>The incandescent IronMars will be very noticeable from Earth.</p>\n\n<p>Calculation time to cool off is another set of nonlinear problems too. I want to stop here because there are 2 very different solutions.</p>\n\n<ol>\n<li>The iron rests upon the old mars surface or</li>\n<li>the iron continues to migrate down towards Mars core due to the impact load and great pressure of the softened iron overburden. </li>\n</ol>\n\n<p>In reality, I think that there would be major penetration of iron. It is a definite possibility that the bulk of the iron will descend further, perhaps even to join with the existing iron core. The extra heat from compressing the crust might be enough to melt all of the iron, in which case it is certainly heading to the core. If this happens (and I think it would) it will take hundreds of millions of years to become Earth-like or Mars-like. Also note that the downward migration of the iron releases additional heat, so if the effect is significant it is also unstoppable, the core size is going to increase greatly.</p>\n\n<p>Note that my basic model was unrealistic from the start (assuming a solid iron shell), in reality dropping from space ships the average drop height would be significantly higher and more energetic.</p>\n\n<p>One major secondary effect, Mars rotation period would become about <em>10 times</em> as long since the iron has to accelerate up to match the rotational velocity of Mars. This would add another large quantity of kinetic energy to the iron (enough to cause some iron melting near the equator)</p>\n\n<p>So how long to cool? Don't know, and its late and I'm tired so I'm stopping for now. </p>\n\n<hr />\n\n<p>The assumptions of the Virial theorem do not apply in this artificial case, i.e., we do not start with a stable gravitational bound system of widely dispersed matter. We have a collection designed to collapse upon itself within one day. Even if we allow that the iron will interact and heat up during the infall, nearly all of the radiant energy will terminate on another packet of iron during infall. To reduce this effect, it is necessary to spread out the iron -- but this raises the distance of the drop more than offsetting the increased heat loss. There is also very little time for the heated iron to radiate away its heat before impact. So I don't expect any significant percentage of the heat to radiate away during infall.</p>\n\n<p>What happens to the atmosphere of Mars? It too is heated to incandescence and will remain so as long as the iron remains that hot. I don't expect much of the atmosphere to be lost quickly since the escape velocity for IronMars will be even higher than Earth and the RMS gas velocity is only about 1 km/sec.</p>\n\n<hr />\n\n<p>I do have a quibble with the problem as posed, do the aliens have antigravity? You can't simply drop iron from orbit, a straight drop required your cargo ships to simply hover in place. If you can do that, why did you have to make such a mess in the first place?</p>\n" }, { "answer_id": 26294, "author": "Blake Walsh", "author_id": 2054, "author_profile": "https://worldbuilding.stackexchange.com/users/2054", "pm_score": -1, "selected": false, "text": "<p>I suspect the surface will actually be cold from the beginning.</p>\n\n<p>Here is one way to model it. Imagine you take a pillar of iron about 2000km tall, and drop it from 150km. As the pillar strikes the surface of mars, the bottom of the pillar will heat up tremendously through lithobraking and the weight and heat will drive it deep into the surface of mars - I suspect though that being dropped from a mere 150km the 2000km pillar of iron wont embed itself all the way into mars, and the top of it will remain poking out, with the top still being cold, not having experienced any lithobraking and indeed being far away from that heat.</p>\n\n<p>Now take billions of those pillars and drop them all around mars the bottoms will certainly be heated to extreme temperatures in the crunch zone, but the tops will remain cold. (you might want to imagine the pillars being slightly tapered, so when they all press together they form a neat sphere)</p>\n\n<p>In this modelling the boundary between Mars and the iron is super heated to tens of thousands of degrees, but that heat is contained by the mass of iron on top, and that mass of iron on top experiences no heating as such.</p>\n\n<p>And I suspect it doesn't matter whether you use billions of pillars, or trillions of iron ingots, or even a monolithic iron shell. If all the iron is placed 150km above mars, and all dropped simultaneously, that is what you'll get: A super molten layer of iron under a cold crust of iron and under that the \"cold\" core of mars (maybe heated by being slammed in all directions by 90% earth mass of falling iron). There might be volcanoes of molten iron emerging through fault lines in the collapsing iron, or it might be perfectly contained, nevertheless I am quite certain there will be large areas of cold iron.</p>\n\n<p>Now over time the heat of the super molten layer will migrate upwards and downwards, it certainly seems there is enough heat to heat all the iron to uncomfortable temperatures.</p>\n\n<p>The question is then, how quickly will it radiate out? Will it radiate out quickly enough to super heat the surface? Or will it just radiate out slowly, perhaps gently radiating over hundreds of thousands of years?</p>\n\n<p>I suspect it will be like Earth. There is enough thermal energy in Earth to heat all of Earth to a most uncomfortable temperature, in fact the average temperature of Earth is much hotter than our Iron Mars would be. But the rate of heat transfer from the core to the surface is too slow to do anything more than slightly warm the surface, and even with the wonderful conductive qualities of iron, there would be still be 2000km of it to act as an insulator.</p>\n\n<p>So that is my answer: that the surface of Iron Mars will initially be cold, and over time will be slightly warmed, but not uncomfortably so.</p>\n\n<p>If you <em>want</em> a cataclysmic heating of the surface, then the constraint of releasing all the iron at once should be relaxed, then the iron which is released later will also have a chance to slam into the surface like meteors.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/26225", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/10364/" ]

[ { "answer_id": 26694, "author": "DaaaahWhoosh", "author_id": 6507, "author_profile": "https://worldbuilding.stackexchange.com/users/6507", "pm_score": 4, "selected": true, "text": "<p>I think the best way to use these guys in a modern setting is as ship captains. Instead of having an entire bridge crew, this one guy could be issuing orders, reading and analyzing data, manning wheels and control stations, and generally doing the work of up to fifty people. Not only that, but since it's just one guy, there won't be any confusion trying to communicate: he's going to know everything.</p>\n\n<p>In other words, I don't think they would be used in primarily combat roles. Just trying to fit one hundred human arms through a door doesn't sound easy, so unless these creatures are about the size of a centipede I don't want them leading any charges. Instead, logistics and machine operation are where they're going to excel. </p>\n\n<p>For such jobs (or just in general), I'd say the best configuration is as a sort of sphere, with heads and arms at regular intervals. You could probably throw legs out entirely, as there are few cases where these creatures won't have at least a couple arms handy (pun). I'd bet there would be custom workstations built for them, with panels and screens in places where they can each reach a different head/arm. </p>\n\n<p>If you still want to have these guys on a battlefield, perhaps they can drive specialized tanks. These tanks could be covered in cameras and viewports and feature a wide array of weapons, to the point where it would appear not to have a weak side. It could also serve as a mobile command post, as the hecatons will probably have some heads and arms available for coordinating troop movements and even piloting drones. </p>\n\n<p>As a suggestion for a more medieval setting, I suggest the shield ball (pun?). Much like a shield wall, the hecaton will be covered by a series of fifty interlocking shields. The non-shielded arms will each carry a spear. To move, the hecatons will push off with the back spears and roll. Not only would this be absolutely terrifying, but the hecatons could continuously shift their orientation, moving fresh arms to the front and tired arms to the top or sides. </p>\n\n<p>The shield ball could even be useful in modern riot control, but modern warfare really is more about hiding than anything else, and the hecaton's going to stick out like a sore thumb. </p>\n\n<p>For an idea of the general shape of such a creature, consider the <a href=\"https://www.wikipedia.org/wiki/Deltoidal_hexecontahedron\" rel=\"noreferrer\">Deltoidal hexecontahedron</a>. Each face of this shape would contain a head and two arms, albeit with ten empty spaces (I couldn't find a satisfactory 50-sided version). With this structure in mind, I'd estimate the hecatons would be from 6 to 8 feet tall (around 2m), and just as wide. I'd recommend making the heads a bit small to give the arms room for solid muscle structure. Due to the large number of awkward angles, such a creature would most likely smell terrible (they may quite possibly have invented aerosol deodorant before the wheel). Caloric intake will need to be higher than that of a normal human, but definitely not fifty times higher; different heads may have to take turns eating meals. Each head should be built to handle being pressed into the ground quite often, so I'm thinking flat noses and sunken eyes. </p>\n" }, { "answer_id": 157847, "author": "Blapor", "author_id": 29627, "author_profile": "https://worldbuilding.stackexchange.com/users/29627", "pm_score": 0, "selected": false, "text": "<p>I know this question was asked a while ago, but I have a different idea I'd like to put forth: four-dimensional hecaton humanoids. Essentially, it would use a four-dimensional hyper-humanoid shape, which would essentially be a layering of humanoid forms in the fourth-dimensional direction, which gives it more bodies to put arms and heads on. In three-dimensional space, only a portion of it would be visible at any given time, based on the direction it was viewed from and how it's moving, and much of it would appear to be self-intersecting. The effect would be similar to viewing a hypercube (there are VR games that have been made to simulate this), but much more complex, with moving arms and heads and torsos and such. Ideally, they would all be anchored together at the waist/legs, so that portion of their body would exist normally in 3D space.</p>\n\n<p>Is it a formidable foe? Yes. Essentially it's a normal durable humanoid giant-titan thing that has a ton of redundancy and the ability to use 100 hands and 50 heads without self-interference, and it's nearly incomprehensible to any observers or opponents. Fighting it would be a trippy but assuredly deadly experience. Even if you take out the legs, it could probably still use its hands to move, and it might actually be more dangerous to take out the legs, since that would separate the bodies, leaving you to fight 50 separate 4D giant torsos, all working together. Short of nuking it, there's not much you could do to it that would kill it before it killed you, unless you get very creative.</p>\n\n<p>tl;dr, a multidimensional eldritch abomination</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/26626", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/14096/" ]

[ { "answer_id": 29274, "author": "Gary Walker", "author_id": 7325, "author_profile": "https://worldbuilding.stackexchange.com/users/7325", "pm_score": 4, "selected": true, "text": "<p><strong><h2>So, Nibiru finally makes it here - we've been waiting long enough.</h2></strong></p>\n\n<p><strong>1) Four years for planning and making changes means the ISS is totally inadequate as a generational ship.</strong> There is no reason to believe that the ISS will be any more inherently prepared for such usage than today. I.e., the ISS is dependent upon regular supply runs from earth to replace consumables such as the CO2 scrubbers, food, etc., as well as fuel to keep the ISS from deorbiting.</p>\n\n<p>We don't know how to create a stable ecology good for hundreds of years, much less getting it all figured out and installed on the ISS in time -- esp. given the chaos on the Earth that will be occurring during those four years.</p>\n\n<p><strong>2) The ISS will also become unlivable due to increased solar radiation (or something else)</strong>. Unless the ISS is somehow given escape velocity, it will also be orbiting at 110 Gm and be expected to incur a 50 C / 90 F temperature rise. Possible to mitigate perhaps in 4 years, but you also need to protect against 37% more frequent solar flare and CMEs (that average a little more than 37% more intense). ISS systems will simply fail over time, e.g. solar panels do not last forever, the ISS cannot possibly manufacture them and you cannot have enough spares of everything to last for hundreds of years. You cannot have an industrial base needed to keep things working. Given all of the chaos, a sudden depressurization event seems more likely than today too.</p>\n\n<p>What is the generational effects of null gravity? Unknown, but it is near certain that a future generation attempting to return to Earth would be unable to function well at 1 gee.</p>\n\n<p><strong>3) Changing to Earth's orbital radius from 150 Gm to 110 Gm is not a temporary change</strong>. The momentum transfer from the rogue planet (a.k.a. Nibiru) to Earth is a permanent change unless you have another planet or a second pass to restore the momentum. So, even a generational ISS would not help to repopulate the surface as it will remain inhospitable forever. </p>\n\n<p>The projected average temperatures more likely average about 65 C / 147 F when your consider the difference in solar radiation (1/r^2 law) and blackbody radiation (T^4 law) assuming greenhouse effect remains proportional. Since CO2 emissions should pretty much stop, this may be true. Likely vulcanism effects are contradictory dust (cooling) and sulfur dioxide (warming) so net is hard to predict, but SO2 would persist longer, so perhaps somewhat higher temperatures are likely -- but would seem very unlikely to boil off the oceans. So perhaps Earth is not quite as inhospitable as you suppose.</p>\n\n<p>BTW, living underground does not really solve the temperature problem in the long term as the increased surface temperature continually will seep down until it reaches thermodynamic equilibrium, i.e., same as the average surface temperature. This will take a very long time - hundreds or thousands of years if you are 100 meters or more under the surface.</p>\n\n<p><strong>4) Antartica here we come -- reserve that prime beachfront property now.</strong> Of course, guessing where the rising ocean will stop is a challenge. With a 50 C temperature rise, the average temperature in the interior would still be below freezing but the temperature at the perimeter would be well above freezing. There should be a reasonable large habitable zone. Raising crops will still be very challenging due to the long dark winters and weak sunlight in the summers, but some farming would be possible and doubtless quite effective if you have to grow lights in a greenhouse. If you are lucky, thorium cycle nuclear plants will be commercially available by 2037, but failing that, there are doubtless plenty of fossil fuels available on Antarctica - its not likely you are going to care much about man-made global warming. Thorium fuel cycle means you don't have all that complicated Uranium enrichment, etc., but failing that some CANDU reactors might be nice.</p>\n\n<p>Weather patterns will doubtless be interesting and it may in fact get pretty hot during the summer, but people live in hot places today. I would expect it to be livable if not pleasant.</p>\n\n<p><strong>5) Nibiru would be very likely be detected more than 4 years in advance.</strong> Our space based detection tech is getting really quite good. You don't say how fast Nibiru is moving. If it is just moving at galactic speed (&lt;100 km/sec), we are going to see it well in advance, automated systems are scanning the skies looking for asteroids, etc. and getting bigger and better. Compared to asteroids, Nibiru is a very large target and would be detected at a distance that would allow for more time considering the great distance it will have to travel before the big event. Consider that Sedna was detected at 86 AU and Nibiru would have to be larger to have the effect described. If Sedna were launched at 100 km/sec it would take 4.1 years to get here. Given the improvements in scanning and the larger size of Nibiru, I would expect that 10 or 20 years is more likely, even given an unusually high speed for Nibiru. I doubt we could make ISS generationally viable with 10 years, but with 20 years I could be more hopeful.</p>\n\n<p>Hyper-velocity rogue planets are very much rarer, but are expected to travel up to 5% of the speed of light. At .05c (15,000 km/sec), we would not have much time, perhaps even less than 1 month.</p>\n\n<p>But I think I have been totally underestimating the ability to detect Nibiru. If the planet is all at warm from the heat of formation or internal nuclear heating from uranium, etc. it will give off noticeable infrared. This means, we will be able to detect it from at least a couple of light years distance. I would also say that this is very likely. Even a hyper-velocity rogue due to hit in 2041 could already be detected by us in 2015. As the nearest discovered rogue, it would be intensely interesting and the race would be on to prevent Nibiru from messing up the Earth. Feel free to post the followup question.</p>\n\n<p><strong>6) No reason to expect governments to cooperate.</strong> I would say cooperation is quite unlikely. US and Canada are quite friendly in most ways today, but the northern territory might be prime real-estate. A US invasion of Canada does not seem impossible to me. China invading Siberia would seem very likely as they are not too fond of Russia already. When survival is at stake, the gloves come off. Use of nuclear weapons seems quite likely.</p>\n\n<hr/>\n\n<p><strong>Quibble</strong> - A near pass from Nibiru would not leave Earth in a nice near circular orbit. At best you have have a major semi-axis of 150 Gm and a minor semi-axis of 110 Gm. It would be necessary to actually make 2 passes to result in a near circular orbit. The first pass to change orbit to a 150/110 Gm ellipse and a second pass when Earth nears perihelion to change the orbit to a circular one.</p>\n\n<p><strong>Now the Real Problem.</strong> Changing the momentum of the Earth in a single or pair of short-term events would be very stressful. What is the gravitational potential of the Earth relative to the Sun? E(potential) = - G * (m1*m2) / r</p>\n\n<pre><code>G = 6.67408 × 10-11 m^3 / (kg * s^2)\nSun mass = 1.988E30 kg\nEarth mass = 5.972E24 kg\n\nFor e=1.5e11 meters, Ep = -5.28246e33 Joules\nFor e=1.1e11 meters, Ep = -7.20336e33 Joules\n</code></pre>\n\n<p>So, earth must lose 1.92909e33 Joules of gravitational potential to achieve the new orbit. How <a href=\"https://en.wikipedia.org/wiki/Orders_of_magnitude_(energy)\" rel=\"nofollow\">much energy is this really in comparison?</a></p>\n\n<pre><code>Hiroshima bomb 6.3e13 J\nThe Tsar Bomba 2.1e17 J\nTotal annual global energy consumption 5e20 J\nTotal global fossil fuel reserves 3.9e22 J\nChicxulub impact 5e23 J\nTotal solar energy impacting Earth per year 5.5e24 J\nTotal solar output 1 second 3.8e26 J\nRotational energy of earth 2.1e29 J\nTotal output of sun per day 3.3e31 J\n</code></pre>\n\n<p>So, total output of sun for 58 days. Or the total solar energy hitting the Earth for 350 million days i.e., about 1 million years worth of solar energy.</p>\n\n<p><strong>I suspect we have a little bigger problem than a new orbit closer to the sun.</strong> I.e., the scientists assuring you the Earth would survive were lying to you and hoping you were too lazy or incapable of doing the math. The tidal forces are simply going to be over whelming. Without assumptions and doing the math I can't be sure, but I suspect the only way to transfer this much momentum in a short event duration is to have Nibiru impact the earth. In will also disturb the asteroids belt as well as Kuiper belt and Oort cloud objects. The local neighborhood is going to be unpleasant for a very long time.</p>\n\n<hr/>\n\n<p>Woke up this morning and realized some simple assumptions that make it possible to think about changing the orbit. Assume Nibiru is an Earth twin, this makes the Roche limit equal to 2.5 * Earth/Nibiru radius. Earth radius is 6371 km, so closest possible approach of Nibiru would be 15972 km (center to center) to keep from breaking up the Earth. That is clearly too close, but a useful upper bound. The problem is that Nibiru would have to remain at the Roche limit for 6 days to transfer that much momentum, and of course Nibiru is actually making a fast flyby. So, the proposed momentum transfer is not possible without destroying Earth - actually breaking it into tiny pieces. No planet could impart enough of a change in a single high speed pass to keep from destroying Earth. Minimum speed of Nibiru would be high speed as it must fall toward the sun to approach Earth. Redoing the calculation for the planets grazing each other and I now know for certain that an impact is required to make the required momentum transfer in a single event.</p>\n\n<p>I should also add that exploding Earth into millions of chunks will make for some unpleasant days for anyone trying to inhabit anyplace else in the inner solar system, given the high frequency of big honking meter impacts as well as innumerable smaller impacts.</p>\n" }, { "answer_id": 29276, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 1, "selected": false, "text": "<p>It would probably be more feasible for the ISS to be outfitted as an interplanetary spaceship and he'd out for Mars or perhaps the Jovian system rather than expect it to remain functional for hundreds of years in free space.</p>\n\n<p>Once they are at Mars or one of the large moons of Jupiter (most likely Callisto, which is outside the intense radiation zones of Jupiter), the crew can detach the inflatable modules and land. (Handwave: the modules will have to be deflated and packaged in an aeroshell for landing on Mars, or carried down by some sort of utility rocket for Callisto). Once there, they can serve as habitats until more living/growing space is developed. Think of \"The Martian\" but with a crew of 20 or more having to \"science the s**t out of this\".</p>\n\n<p>In the background, the spacefaring nations of Earth are also going to be building and launching rockets as fast as their production lines can go, shipping landers with every sort of tool, spare part and supply package that can be crammed into the payload fairings to meet the arriving ISS. (Some nations might skip the meeting the ISS part and send their own astronauts and supplies on some version of the \"Mars Express\" mission to claim their own space in the solar system). An interplanetary ship is conceptually easy to make; this design is supposed to fit in a 5m Aeroshell and unfold once in orbit, so the ISS might find itself racing against flotillas of more advanced ships being built and launched as fast as the launching nation can build them. (<a href=\"http://www.deviantart.com/art/Hermes-from-The-Martian-rear-view-485084228\" rel=\"nofollow\">http://www.deviantart.com/art/Hermes-from-The-Martian-rear-view-485084228</a>)</p>\n\n<p>There are two very serious modifications to make for the ISS to do this for real:</p>\n\n<ol>\n<li>Build a hardened radiation \"storm cellar\" for the crew to shelter in during flight, and;</li>\n<li>put a nuclear reactor on the \"trailing\" boom to power a rocket engine of some sort so you can get from point a to point b <em>and back</em></li>\n</ol>\n\n<p>The ISS can be considered a 700 ton spaceship without a proper engine. The engine part is fairly easy, many different nuclear powered drives have been designed and some even prototyped since the late 1950's. Nuclear power provides a high density energy source that allows you to get to Mars or Jupiter in a reasonable amount of time, and if you launch to mars and the timing is good, you might be able to get at least two trips and another 20 astronaut/colonists to join the first crew in 4 years (plus habs, extra tools and supplies, etc.). A storm cellar is going to be more challenging, since it would be quite massive, and need a heavy lift rocket like the Falcon 9 Heavy, or the Russian Energia to boost into orbit. This part is critical, since possession is 9/10 of the law, whoever gets to the ISS first with the tools and equipment (and a viable plan) will essentially \"own\" the ISS and control the ship and the plan.</p>\n\n<p>Once on Mars or Callisto, the colonists will dig an underground base, set up the nuclear reactor on the surface away from the colony and start growing plants. The next order of business is to start going around and picking up supplies that have been scattered all over the surface (if colonists from other space programs and their supplies are available, they might join forces, since a larger group of people will have a reservoir of critical skills and knowledge that could be lost to smaller groups). The next 1000 years are going to be hard work, building the colony, redeveloping industrial technologies that can be manufactured from local materials and raising generations of people to expand to new locations both from the initial starting point and to other places in the solar system.</p>\n\n<p>This last part is wildly optimistic, since we don't know how to make a closed ecology, and even an \"open\" system that utilizes \"fresh\" material inputs from local materials is going to be a very iffy proposition: one mistake and you die....</p>\n" }, { "answer_id": 36371, "author": "Tim B", "author_id": 49, "author_profile": "https://worldbuilding.stackexchange.com/users/49", "pm_score": 0, "selected": false, "text": "<p>The other answers are good, but just to add.</p>\n\n<p>ISS is the wrong basis to use for doing this, a lot of what has been learned there would be useful but not essential.</p>\n\n<p>What will happen is that basically every heavy industry on earth ramps up to start building rockets and habitation modules as fast as possible, just churn them out, sell tickets, fire them into space.</p>\n\n<p>The modules would no doubt have hundreds of different designs and some would fair better than others. Heading to Mars is definitely a good candidate, or if not then one of the larger asteroids since a source of raw material is important.</p>\n\n<p>Expect a lot of people to die as their modules fail but in four years if everyone really went for it we could get a lot of people up there and some of those would have a chance to survive.</p>\n\n<p>The main problem is that four years is a short timescale really to achieve all this. With the amount of resources dedicated to it some people would make it off but the number of people getting into space would increase every year so 5 to 10 years would be a better timescale.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/29270", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/15131/" ]

[ { "answer_id": 30696, "author": "FiringSquadWitness", "author_id": 11147, "author_profile": "https://worldbuilding.stackexchange.com/users/11147", "pm_score": 3, "selected": false, "text": "<p>Using <a href=\"https://en.wikipedia.org/wiki/LZ_127_Graf_Zeppelin\">LZ 127 Graf Zepplin</a> as an example of a transatlantic airship flight from 1928, it took 111 hours to travel from Friedrichshafen, Tübingen, Germany to Lakehurst, New Jersey, United States of America, about 9,926km in length. </p>\n\n<p><strong>Faster:</strong></p>\n\n<p>In a similar airship that is capable of achieving the same speed of 89km/hr, on a similar journey across a Continental divide, the distance would need to be <strong>150,000km</strong> to achieve a two month journey taking 10 weeks. </p>\n\n<p>This means your theoretical planet would need to be on a scale of <strong>15x</strong> the size of the Earth to achieve a similar journey over a longer time.</p>\n\n<p>This massive world would probably increase the likely-hood of transition to air-travel as the speed to cross long distances would be a must for world spanning empires.</p>\n\n<p><strong>Slower:</strong></p>\n\n<p>If you wish for your airship to just travel slower to make the journey longer, to achieve a 2 month long journey taking 10 weeks,you would need to slow your airship to travel 6km/h to travel roughly 10,000km across an earth sized ocean.</p>\n\n<p>In terms of world building, the slower option makes less sense as most people can walk faster than 6km/hr, and any naval vessel could easily outspeed this airship. Unless of course the ocean in your world is so acidic that the only way to traverse it is to fly above it!</p>\n\n<p><strong>Between:</strong></p>\n\n<p>Below is a quick table of some compromises between the above suggestions:</p>\n\n<pre><code>| Distance | Scale | Speed | Likeness to other modes of travel|\n| 150,000km | 15x | 90km/h | Speed of Car |\n| 100,000km | 10x | 60km/h | Speed of Early Model Steam Train |\n| 50,000km | 5x | 30km/h | Speed of Horse Gallop |\n| 20,000km | 2x | 12km/h | Speed of Runner |\n| 10,000km | 1x | 6km/h | Speed of Fast Walker |\n</code></pre>\n" }, { "answer_id": 30714, "author": "bowlturner", "author_id": 19, "author_profile": "https://worldbuilding.stackexchange.com/users/19", "pm_score": 2, "selected": false, "text": "<p>Basing this off of JustAnotherDotNetDev's calculations:</p>\n\n<p>The big problem with making the planet much larger is of course gravity. As Michael pointed out in the comments, Jupiter is 11x the radius of earth, is mostly hydrogen and we wouldn't survive for very long under the huge crushing weight of our own bodies. So find reasons to slow things down.</p>\n\n<p>The one thing I can see that might help slow things down is that the people only navigate visually. so when the sun goes down they try to find a place to 'anchor' for the night. This would mostly double the time it takes to fly anywhere, and it would still be significantly faster than walking. </p>\n\n<p>One more thing might be that large merchant ships and large troop transports are large enough to just wallow along at 100-200 feet above the ground, and they might need to partially empty to navigate mountain passes, slowing things down more. </p>\n\n<p>Really high passes might need to actually completely empty the ship and 'carry' it over the pass to the other side, this could take weeks all by itself, and make the seasons have a huge impact on long distance travel.</p>\n" }, { "answer_id": 30717, "author": "AndyD273", "author_id": 6751, "author_profile": "https://worldbuilding.stackexchange.com/users/6751", "pm_score": 2, "selected": false, "text": "<p>Since all the tech (including the airship engines I assume) runs on mana, then in addition to bowlturners ideas, you could limit speed by the need to \"refuel\".</p>\n\n<p>I'll have to make a few assumptions since you didn't specify how mana works, but if mana isn't a constant, unlimited resource, then it'll have to be replentished.</p>\n\n<p>So the airship could be able to travel at 89km/hr, but only be able to travel for 6 hours before having to stop and recharge for a few hours. This could limit the ship to 1000km a day. Less if the engines aren't as efficient.</p>\n\n<p>Add to that high mountain ranges that need to be navigated around so straight line travel is impossible. So a straight \"as the crow flies\" distance of 10,000km could end up being 30,000km of distance needed to travel. </p>\n\n<p>Another thing that could slow it down is scheduled stops.<br>\nSay the world is heavily forested, and mountainous, so ground travel is difficult. You still have settlements and towns that need supplies and people that want to move around. The airships are the obvious choice for this, meaning that airships would have routes and have to make stops at each location along the way. Docking, unloading, and loading could take a while depending on what's being moved around. This would slow down the travel time too. You could still have express airships that only make a few stops.</p>\n\n<p>One other thing would be weather. Airships have trouble in high winds, so if your world has frequent storms, or even something like the <a href=\"https://en.wikipedia.org/wiki/Santa_Ana_winds\" rel=\"nofollow\">Santa Ana Winds</a> or <a href=\"https://en.wikipedia.org/wiki/Chinook_wind\" rel=\"nofollow\">Chinook winds</a> where the wind will blow hard for days/weeks at a time. The airships would have to anchor and wait for things to die down. Either that or travel really slowly, fighting the wind the whole way, and making frequent stops.</p>\n\n<p><strong>Edit</strong><br>\nAnother weather issue could be fog or low clouds full of things like tall trees and rocks. It could even be kind of like river navigation, where you had to have a navigator that knew where all the sand banks were in order not to run-aground. If this happened frequently, they would be forced to travel very slowly or risk crashing until the clouds lifted.</p>\n" }, { "answer_id": 30722, "author": "ventsyv", "author_id": 10293, "author_profile": "https://worldbuilding.stackexchange.com/users/10293", "pm_score": 0, "selected": false, "text": "<p>You can increase the radius/mass of the planet, as well as the density of the atmosphere.</p>\n\n<p>The bigger the radius, the bigger the circumference, and thus the further apart places will be.</p>\n\n<p>The bigger the mass, the higher the gravity thus you need more lift per pound to fly.</p>\n\n<p>The denser the atmosphere the more drag you'll get. Denser atmosphere provides more lift, but the higher gravity easily makes up for that.</p>\n\n<p>At the end you end up with slower airships (due to the higher gravity you'll have weight restriction, won't be able to carry enough fuel etc), more drag and greater distances to travel.</p>\n\n<p>On top of that add finicky airships that require ground service every few days and inability to navigate at night most nights and it could easily take months to go transcontinental.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/30695", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/15668/" ]

[ { "answer_id": 30947, "author": "Helwar", "author_id": 7991, "author_profile": "https://worldbuilding.stackexchange.com/users/7991", "pm_score": 4, "selected": false, "text": "<p>Well... I don't know if this is enough to constitute a complete and acceptable answer but here we go.</p>\n\n<p>You don't have to look to other realities or the future to see that happening. It's a basic issue in a capital society: If you don't make yourself known you don't exist. Your mercs are in the hot spots because there is where they are needed and have to be seen there. If their possible contractors see them there, they are prone to hire them in a tight spot or to take an off-job they don't want their soldiers losing time to. With time, mercs will make a name for themselves, get fame and more beneficial jobs for themselves.\nAll that would not have happened if they stayed at home watching TV. </p>\n\n<p>As I said before: capitalist society. It's not good enough to be good at your job, you have to advertise yourself. Otherwise, others will fill that hole you left, and they will take the jobs. And this is applicable to any job :)</p>\n" }, { "answer_id": 30949, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 3, "selected": false, "text": "<p>Historically, mercenaries also had close connections with the various noble houses which hired them (and occasionally married into the house, like Sir John Hawkwood, or perhaps simply replaced them if they were not being paid on a regular basis).</p>\n\n<p>Staying close to the scene of the action also provides the ability for the mercenary bands to manipulate things to their advantage. In the 1400's Italian city states often complained that the mercenaries would go to \"war\" without actually fighting (one battle reputedly ended with only <em>one</em> casualty (supposedly killed when he fell off his horse....) If you are a mercenary commander, you might want to compare notes with the other commanders in order to see who paid on time, who was a difficult employer and if there was an advantage to be gained by switching sides. This is more difficult if you are relaxing on a resort planet tens of light years away from the action. In story terms this also gives you the opportunity to get your characters in seedy bars or the back rooms of disreputable restaurants. </p>\n\n<p>Of course the people who hire mercenaries also want to keep tabs on them as well, so the agents of the noble houses also have a vested interest in having the mercenary bands close at hand. A mercenary band which is off in the distance not only is not building their reputation for fighting skills and prowess, but there may also be a suspicion in the air as to what they are <em>really</em> up to \"out there\". A mercenary band is already in a position where there is not a great deal of trust in them and their activities, so anything which adds to the suspicion is going to be counter-productive to their business.</p>\n" }, { "answer_id": 30950, "author": "mico villena", "author_id": 11313, "author_profile": "https://worldbuilding.stackexchange.com/users/11313", "pm_score": 3, "selected": false, "text": "<p>Because that's where the action is.</p>\n\n<p>Where there is war, the need for manpower increases. For this reason, they need to hire mercenaries to bolster their numbers. </p>\n\n<p>One more reason why they go to the hot spots is that they can pretty much guarantee employment if they are in the right place compared to those mercenaries abroad which need to be brought in, using the employers resources. </p>\n\n<p>We know that resources are in high demand during war time and uselessly squandering it just to hire mercenaries overseas/abroad is not using resources the way they should be.</p>\n" }, { "answer_id": 30952, "author": "zxq9", "author_id": 1948, "author_profile": "https://worldbuilding.stackexchange.com/users/1948", "pm_score": 8, "selected": true, "text": "<p>Not sure quite what definition you want to give of \"being a mercenary\", but I spent a few years as a contractor in Africa, Asia and the Middle East after leaving the Army, so I can tell you why I spent a bit of time wandering around the smellier parts of the world between contracts.</p>\n\n<p><strong>Connections</strong></p>\n\n<p>You get hired and find contracts by making sure people know you. I was in Special Forces for 6 years, and in a tiny community like that your reputation is everything. Once you get out it is the only way you get good contracts, too -- not by applying for them, but by getting cold-called by someone you know and already worked with before.</p>\n\n<p>But the longer you've been out of the military where assignments aren't your decision and you meet new people as a matter of course, you wind up becoming slowly isolated. Whatever sort of work you have been doing is the only way you meet people if you're only in the ugly parts of the world when you're on contract. That means you only meet people who do the same kind of work as you, and pretty soon your old contacts change careers (nobody does this forever, not unless they get paid extremely well -- but its actually feast-or-famine, and that begins to wear on you). Over time your contacts go stale, contracts become less frequent, wars end, new wars start in places you've never been, rules change, industry players change, empires come and go, languages you know become useless, etc.</p>\n\n<p>We watch all this firsthand, which is why we know that we can't count on being comfortable, ever, and absolutely none of us trust things like pension programs after watching entire governments implode overnight. That also means we don't have much faith in getting a next call while we're a world away sitting on our asses enjoying the good life. Yes, you do that a little, but only when you know you already have a contract lined up to go back to.</p>\n\n<p><strong>Location location location</strong></p>\n\n<p>So what does one do? Why do programmers looking for easy cash from VCs they can blindside with a storm of buzzwords migrate to San Francisco? Its one of the absolute worse places to <em>run</em> a company, but its one of the best for <em>starting</em> a company simply because the community is there. In the same way one might wonder why I would wander around a shithole like Baghdad or take a trip to Mali when job hunting? Because the community is there.</p>\n\n<p>Its not just bases and checkpoints and whatnot. Those of us who have to stay there a lot begin doing more pleasant things with our time. Some start up private bars, open restaurants, hire stranded immigrant workers who were screwed over by their former employers and start a service shop that handles things people like us know are needed (vehicle repair, gear cleaning, safe parcel delivery, couriers, <em>good</em> alcohol smuggling, proper medical supply import, etc.). We tend to those sidelines when we're not on contract, meet local girls (\"local\" as in she's there, and so are you for the moment), train with each other partly as play (its fun) and partly to keep skills alive, etc. <em>and keep making contacts</em>. It takes a little effort, but you can make life comfortable for yourself in the middle of the never-ending nightmare that is most of the world.</p>\n\n<p>Most of us are, if not friends, at least cut from the same cloth. We've had similar experiences. We like to swap lies (and the occasional true story) with one another over a drink. We like to roll and box with each other for fun. We have beer shoots on the weekends sometimes (loser buys for everyone). Few of us can train much back home. <em>People at home sincerely do not understand a huge part of our lives</em>. We come from the same dozen or so countries. We speak, if not the same language, the same 2 or 3 common pidgins. Its a comfortable place, even if its a rough one. And sure, maybe a few towns over people are getting their houses knocked over and roughed up by the local baddies or whatever, but <em>nobody</em> comes to mess with our little cobbled together neighborhood. So yeah, its less safe than living in, say, Austin, but its a lot safer than the general violence statistics for the region would make it appear. And the violence stats work in our favor anyway: fewer people show up who don't already know what they are doing which effects a self-selection for competence and prevents a flood of competitors from appearing out of nowhere.</p>\n\n<p><strong>We're feeding off of the chaos</strong></p>\n\n<p>Most of the world is not very well planned out. When a crisis occurs and a bigshot needs to go somewhere bad in a big hurry there simply isn't time to establish a strong guard force and mobilize it. Most countries don't even have decent diplomatic security forces (much less decent police -- or even decent people) so external contractors are a necessity.</p>\n\n<p>Usually an office that is already in position will get a call at the 11th hour with a desperate need for diplomatic security (or whatever else). Not ten minutes later a few of us are running up and down the street knocking on doors, calling each other \"Do you have any solid guys and a few locals you can bring on a run to X in two days?\" and \"Hey, do you still have that bigass armored bus? How about the bricked-out Mercedes and the Rhino, are they out of the shop yet?\" and so on.</p>\n\n<p>The next day we're all out, not officially on contract yet, but we're already rehearsing, making sure everybody knows what to do. One major advantage of working in a group like this is that you generally only need to rehearse actions-on, get guys new to a particular technique or scenario up to speed, and cover a few contingent actions. That's a <em>lot</em> different from having to rigidly train core skills because most of the trigger-pullers are privates who just left home for the first time. (The general age range of the guys I prefer to work with is 30~60 -- and don't let 60 throw you off, there is this freakish phenomenon we call \"old man strength\" and its totally real, and the <em>tactical maturity</em> of the older gentlemen tends to guarantee they don't have to exert themselves much in the first place, which is pure magic.)</p>\n\n<p>A few days later we've swapped out our patches and hats for whatever logos the prime contractor has and are standing all clean and pretty at the airfield waiting to meet the guy who is paying for the party.</p>\n\n<p>From the outside I suppose it looks like Xe (or Blackwater, or whatever they are now), or Triple Canopy or Aegis or whoever <em>appear</em> to be some full-time private military force you can just hire on short notice -- but that doesn't mean they have a barracks in Florida or Cape Town and are just waiting for the green light. Its <em>expensive</em> to have us around, just eating through corporate profits. They assemble their forces from people they already know <em>right then</em> and roll. (The <em>really</em> huge contracts that cover a whole warzone may wind up being slightly different in effect, because those contracts may be ongoing for 5 years at a time, but even those stories must eventually end.) The only people with some level of job security are the country/region managers and up. The polite girl who used to call me from Virginia to tell me my travel routes, for example, had <em>much</em> better job security than any contractor ever would.</p>\n\n<p>That's just diplomatic security. There are plenty of other contracts like training foreign militaries, providing direct QRF support, high-value recovery (sort of borderline legally), K&amp;R response, countersurveillance, and some other stuff for example, but the way you get to know each other and find your next job tends to be the same: by being out there, being well known, being likable, making friends, working lower-paying contracts that involve a ton of people to have a chance to meet some other guys, and <em>remembering who the dirtbags were</em> so you can avoid them in the future.</p>\n\n<p>It sounds bad to say \"we feed off the chaos\", but that's true. But its also true that the chaos is never-ending, people suck, nothing is stable, and nobody gives a crap about your problems but you and maybe your family. Its not going to get any better, and it hasn't been any different throughout history -- we're just this season's leaves, soon to be swept away whether we spend them shivering in our beds trying to stay safe or out there sweating, trying to get some cash together so we can get out of the crappy places of the world and start a family somewhere less screwed up.</p>\n\n<p><strong>So in the end...</strong></p>\n\n<p>Why do gravitate to the eye of the storm? Because in a world with no job security you have to make your own luck.</p>\n\n<p><strong>What about the organizations?</strong></p>\n\n<p>The above discussion was all about the people involved, explaining some of the reasons why <em>I</em> would occasionally hang around nasty places while off contract or at least spend my off-days while on contract making sure I had a good shot at having another contract one later on (or finding a better one right away if the current one paid peanuts but was super dangerous for no reason). That's all about us guys who are on-off contract every few months (or whenever the phone rings) and have no job security. The companies that are actually getting the contract awards have slightly different, but related, reasons to always have a presence in a disturbed region.</p>\n\n<p>Contracting companies don't really have any job security, either. Any given conflict will eventually end, and -- contrary to the hilariously off-base conspiracy theories that PMCs \"cause conflict to profit off them\" -- peace could break out at any time. But this is Earth. We can rest easy in the knowledge that <em>war is a natural state of mankind</em>. The trick is, just like owning a chain of grocery stores or selling fire insurance, you have to diversify your presence and product offerings to make sure you've got market coverage if you want your company to survive beyond a sing huge conflict. (A <em>lot</em> of PMCs have come and gone just around the Iraq conflict. Others will come and go elsewhere. A few have a semi-permanent presence on the eternally screwed up continents.)</p>\n\n<p>When everything goes to crap and the local embassy or company office needs to source something locally, it is a <em>very</em> good thing if you've already got a point of contact in country. Nothing fancy, just renting a one-room office or keeping a local on hire to answer the phone. If operations are fairly regular, though, like when a larger trend of conflicts is ongoing, it is absolutely impossible to keep up with regulatory requirements. Your job is, after all, to wield lethal force. In reality you do this every time you move a chair, pick up a rock, throw a baseball, grab any kind of farm tool you can imagine, or get the cutting board from under the sink... but that's not how regulators see things. (And before you say \"but you don't wage wars with rocks and knives and stuff\" -- that is <em>precisely</em> what insurgents do.) Sourcing the best weapons money can buy in a country like the US, UK or France is not terribly difficult -- but <em>shipping them out sure is</em>. The other side is even harder: getting authorization to ship weapons into a warzone. Now that last bit is highly ironic given the typical glut of weaponry just laying around and the fact that there is usually a vibrant black market in action -- but it is absolutely <em>insane</em> the layers of paperwork, ass-kissing, bribing, cousin marriages, and personal relationships you have to maintain to ship a container of 30 rifles from Arizona to Pakistan.</p>\n\n<p>Given that doing things the 100% legal way involves insurmountable regulatory hurdles, and to even be allowed to do things legally one must do the illegal stuff anyway to grease the skids on the operation (the bribes, cousin jiggering and relationships part) the path of least resistance is usually to source and maintain weapons locally and then <em>make that legal</em> by way of the bribes and whatnot. The end result is that you have mountains of paperwork to do (once your cache is made legal it will have to be registered and maintained by an armorer), but its done quickly and you have access to what you need <em>now</em> (money and arms) instead of never getting the operation off the ground because someone else can beat your price and timeline by sourcing locally. Its a race to market! But maybe not the sort of race to market everyone is aware occurs.</p>\n\n<p>The tradeoff is money (flexible) and time (inflexible) in exchange for a much lower availability of the weapons you <em>want</em> to use. In a big theater like Iraq or Afghanistan its not so hard to get real M-4's and things, but they will often be Bushmasters instead of Colts, for example (and when the the teeth on the bolt break while you're firing... you <em>really</em> hope the rest of them hold until you can maybe find a new one and a new barrel, which is anything but certain). In a smaller theater you are rarely that lucky and will have to settle for unreliable remakes (that look good, but don't sound so good), crappy magazines (failure to feed == failure to fire), ill-maintained former stockpile gear (that works, but requires some rehabilitation work), former Soviet stock (<a href=\"http://zxq9.com/archives/911\" rel=\"noreferrer\">contrary to the popular image, the AK-47 and PKM are <em>not</em> the first choice of most discerning infantrymen...</a>), or a big fat pile of \"frankenguns\". And that's just guns! The situation with ammunition is absolutely laughable most of the time (protip: <em>practice stoppage drills</em>).</p>\n\n<p>[<em>Frankengun</em>: A firearm, usually of Soviet design, that is assembled from the not-yet-totally-broken parts of a collection of other guns that used to work. This is particularly common with PKMs, which are already bad enough when they are in factory condition compared to an M-240B* or an MG-3**.]</p>\n\n<pre><code>* or MAG-58, or M-60, or...\n** or MG-42, or MG-11, or MG-53, or...\nSee, guns have lineages, too! The PKM's line had a lot of inbreeding...\n</code></pre>\n\n<p>Where individuals trying to find contract work hang around to be known and put themselves in the right places at the right times, companies hoping to score prime contracts have to have an early logistical presence and maintain it in order to be confident they can service any contracts at all.</p>\n\n<p><strong>EDIT</strong></p>\n\n<p>In the spirit of this answer I'm preserving a thread that occurred in comments below that will certainly be lost to moderation eventually.</p>\n\n<p>tl;dr: A tech contractor who worked for a PMC some of the same places I have asked some details about where the tactical contractors hang out and we had some back and forth. Ultimately, <em>I want to keep in touch with the guy</em>. This is partly out of habit, partly to reminisce, partly because I sense a kindred spirit, and partly because who knows when it might be a good thing to know another guy who does PMC work that is into tech?</p>\n\n<p><a href=\"http://zxq9.com/archives/1223\" rel=\"noreferrer\">http://zxq9.com/archives/1223</a></p>\n\n<p><em>This</em> is what I am talking about in terms of contractors sticking together like a tangle of Christmas-light-string shaped magnetic fishhooks.</p>\n" }, { "answer_id": 31000, "author": "Josh", "author_id": 15810, "author_profile": "https://worldbuilding.stackexchange.com/users/15810", "pm_score": 3, "selected": false, "text": "<p>I'm going to echo the actual PMC guy's great answer above, and note it even works that way in simulation. When I was running a mercenary group in EVE Online, I helped a team go from sitting in safe space and waiting for the contracts (which resulted in no contracts and a lot of boredom) to planning and executing raids on opportunistic targets AND to just showing up on the edges of war zones with a \"hey, you want twenty more guys? X mil up front plus Y% of the damage we do.\" sign hanging out. </p>\n\n<p>Do that for a few weeks and suddenly you have a bankable rep and people know how to hire you, because the people who are hiring aren't hanging out in the cushy areas (those guys have their own military already), the people who need you are the ones in the teeth of it in the first place.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/30944", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/5187/" ]

[ { "answer_id": 31668, "author": "SJuan76", "author_id": 3096, "author_profile": "https://worldbuilding.stackexchange.com/users/3096", "pm_score": 2, "selected": false, "text": "<p>I think you mostly answered yourself... even in an artificial environment, forcing people into shifts will cause issues that must be somehow justified. It is not only sunlight or not (we already master electricity to overcome that when we need) but the social life also. People doing unusual shifts often see their lifes altered by that (for example, by having to sleep when their kids are home).</p>\n\n<p>Imagine people living in shifts... how would you schedule, say, an sports event, a legislative meeting, or just a group of friends meeting to have a party together? Forcing people into shifts makes social life harder, so it will be done only when it is absolutely needed (emergency services).</p>\n\n<p>That said, assuming the situation is such that the society is structured around turns, the results won't be as dramatic as your questions point. Nowadays lots of people work in night shifts; when they are required during daytime they just take a day off (usually with a replacement) or make a double turn; human beings have some degree of flexibility. In extreme situations, drugs can be prescribed so a critical individual is kept well aware for an extended time period.</p>\n" }, { "answer_id": 31673, "author": "Zymurge", "author_id": 16242, "author_profile": "https://worldbuilding.stackexchange.com/users/16242", "pm_score": 2, "selected": false, "text": "<p>There's a great article that I read in National Geographic a few years ago that talks about caffeine and how it has facilitated changes in man's sleep patterns. The gist is that the invention of large scale artificial lighting has enabled man to function outside of the natural daylight cycle. Caffeine has played a large part in allowing humans to function in non-natural patterns.</p>\n\n<p>See: <a href=\"http://ngm.nationalgeographic.com/ngm/0501/feature1/\" rel=\"nofollow\">http://ngm.nationalgeographic.com/ngm/0501/feature1/</a></p>\n\n<p>To tie this into your question, this provides evidence that humans are adaptable to artificial lighting patterns with a little bit of 'chemical assistance'. In a completely artificial environment, the notions of day/night shifts becomes irrelevant. The next challenge would be how adaptable circadian rhythms are. Would our bodies still be tied to a 24 hour cycle or would enough time in a non sun driven setting allow us to adapt our wake/sleep patterns as well?</p>\n\n<p>If we could evolve away from the 24 hour pattern, then believe that schedules would be engineered around functional requirements, such that things would be optimized around the job and less around the people. For instance, in some jobs people might be more efficient in say a 4 hour shift due to the nature of the work and the average person's ability to focus on that type of task. You might create some sort of rhythm with say 4 hours on, 2 hours off, 4 hours on and then say 10 hours off. That turns into a 20 hour day. In the end, maybe that's more optimal.</p>\n\n<p>Whether this can ultimately be done takes me back to the article on caffeine. Prior to the advent of electricity and mass artificial lighting, the external elements weren't in place to allow us to change our patterns. With the lighting and caffeine we proved that we could change into multiple shifts and actually work through night hours. With a further artificial control of the environment and perhaps more regulated caffeine like stimulus, we could evolve to very different patterns than we recognize today.</p>\n" }, { "answer_id": 31675, "author": "Wingman4l7", "author_id": 16021, "author_profile": "https://worldbuilding.stackexchange.com/users/16021", "pm_score": 4, "selected": true, "text": "<p>I believe that a realistic answer to this will heavily depend on your universe's current <strong>understanding of human sleep patterns</strong>. \n<a href=\"http://www.bbc.com/news/magazine-16964783\" rel=\"nofollow\">Historical records indicate</a> that prior to the easy access to artificial lighting, <strong>people used to sleep in two, 4-hour chunks</strong>, separated by a waking period of 1-2 hours. A <a href=\"http://www.nytimes.com/1995/03/14/science/modern-life-suppresses-an-ancient-body-rhythm.html?pagewanted=all\" rel=\"nofollow\">psychiatrist's experiment in the 1990s</a> confirmed this pattern. <a href=\"http://www.washington.edu/news/2015/06/19/access-to-electricity-is-linked-to-reduced-sleep/\" rel=\"nofollow\">One study indicated</a> that access to artificial light has shortened our sleep periods by about an hour; seasons also caused variation.</p>\n\n<p>The best long-term case studies that I know of for someone <strong>living in a completely artificial light environment</strong> occurred over a period between 1962-1972 by the French scientist <a href=\"https://en.wikipedia.org/wiki/Michel_Siffre\" rel=\"nofollow\">Michel Siffre</a>. In 1962, he spent <strong>two months</strong> in a cave, notably <strong>without access to a clock or calendar</strong>, in an attempt to determine what natural biorhythms would develop in such an environment. In 1972, he repeated the experiment, staying in a cave for <strong>six months.</strong> <em><a href=\"http://www.cabinetmagazine.org/issues/30/foer.php\" rel=\"nofollow\">[source]</a></em> For those interested in reading more, the latter experiment was covered in the March 1975 issue of National Geographic in a piece entitled \"Six Months Alone in a Cave\" <em>(<a href=\"http://jamesmdeem.com/stories.cave4.html\" rel=\"nofollow\">summarized here</a>)</em>.</p>\n\n<p>Physiological effects included: </p>\n\n<ul>\n<li>developing an <strong>extended 25-26 hour sleep/wake cycle</strong>, with some occurrences of a <strong>48-hour sleep/wake cycle</strong> <em>(36 hours awake, 12-14 hours asleep)</em></li>\n<li>a <strong>subjective experience of the passage of time</strong>; he experienced it ~2x slower than it was in reality <em>(from the 2-month experiment)</em></li>\n</ul>\n\n<p>There have also been other experiments done as <strong>test runs for living in space habitats</strong>. The Russian <a href=\"https://en.wikipedia.org/wiki/MARS-500\" rel=\"nofollow\">MARS-500</a> isolation experiment between 2007-2011 simulated a 105-day stage and later a <strong>520-day mission</strong>; it's assumed that <a href=\"http://www.esa.int/var/esa/storage/images/esa_multimedia/images/2011/11/das_mars500-habitat_in_moskau/10297615-2-eng-GB/Das_Mars500-Habitat_in_Moskau.jpg\" rel=\"nofollow\">this closed habitat</a> had no access to natural light. The data on physiological changes is sparse, but <a href=\"http://www.space.com/19168-mock-mars-flight-reveals-big-sleep-concerns-for-astronauts.html\" rel=\"nofollow\">articles indicate</a> that circadian rhythms were effected, and that <a href=\"http://www.3news.co.nz/environmentsci/mars-experiment-marred-by-sleep-woes-2013010906\" rel=\"nofollow\">in general</a>, <strong>astronauts are plagued by sleep issues</strong>. </p>\n\n<hr>\n\n<pre><code>What do we do with all these facts?\n</code></pre>\n\n<p>You'd need have some semblance of <strong>conformity to a natural sleep cycle</strong> unless you want your residents chronically fatigued, irritable, etc. There would be <strong>natural limits to wake periods due to physical exhaustion</strong>, of course <em>(if we're ignoring biomedical enhancements or pharmaceuticals)</em>.</p>\n\n<p>Shift systems might be <strong>based on the length of an orbital cycle</strong>, if the artificial environment is orbiting a planetary mass. This could be merely for convenience's sake, if the station is coordinating with people working on the planet who are subject to a more traditional day/night cycle. </p>\n\n<p>Material resources are also a consideration; in Neal Stephenson's recent science fiction novel <em>Seveneves</em>, he posited that <strong>staggering wake/sleep cycles</strong> across a space station's population <strong>would prevent a strain on life-support systems</strong> and allow it to support a larger population. This did allow for some <strong>overlap</strong> between people on different \"shifts\", <strong>for work collaboration &amp; social interaction</strong>. Special attention was paid to being cognizant &amp; respectful of seeking someone's attention during their sleep period. In your universe, this could be imbued via the development of cultural practices and the implementation of shared calendar/contact systems that warned someone if they were trying to digitally interact with a person who was in a sleep period.</p>\n" }, { "answer_id": 31681, "author": "Jay", "author_id": 2973, "author_profile": "https://worldbuilding.stackexchange.com/users/2973", "pm_score": 2, "selected": false, "text": "<p>As others have noted, artificial light makes it possible for us to separate ourselves from the natural day-night cycle, but there are still limits to how far we go with this. Most people still live by the natural day. When you're outdoors, sunlight still provides a lot more light than artificial lighting over any large area. (You can light up a stadium with artificial lights, but not a town.) People generally find it more convenient to limit most of their outdoor activity to times when there's plenty of natural light so they can easily see where they're going and what they're doing.</p>\n\n<p>But supposing all we had was artificial light ...</p>\n\n<p>There are pros and cons to living and working in shifts.</p>\n\n<p>The obvious advantage is that you can get better utilization of buildings and machines. Many factories today run 24 hours with 3 shifts. 1 machine running 24 hours a day produces just as much as 3 machines running 8 hours a day. (Well, you have to make some allowance for time for maintenance, etc.) So by running 24 hours the factory cuts its capital investment by 2/3 while getting the same output.</p>\n\n<p>The same principle COULD work in retail. If people worked in 3 shifts, restaurants would only need 1/3 as many tables and chairs, roads would only need to accommodate 1/3 as much traffic, and so on.</p>\n\n<p>As you note, it would be a problem for very small businesses. If the owner of a store is the only clerk, and he wants to work a normal 8 hour day, then he's missing 2/3 of potential business. But for bigger stores it's a non-issue. Instead of having 6 clerks who work the same 8 hours every day, you have 2 for each shift.</p>\n\n<p>Yes, to make it work, people would have to be somewhat more flexible. A company might want to have a staff meeting with all the employees, not just those from one particular shift. Or socially, people might want to have a party with others from different shifts. So people would have to be willing to vary their shifts.</p>\n\n<p>If people tend to work the same shift their whole lives, or at least for very long periods, you might find that society becomes segregated by shift. Someone will find that all his business associates are from the same shift, and maybe even all of his friends. You may find that 2/3 of the population are people you never meet. The different shifts might start to drift apart culturally. Eventually each has its own laws and culture. Etc.</p>\n\n<p>Hmm, I have a sudden thought for a romance novel in this setting: There are huge bureaucratic or cultural barriers to changing shifts, so people divide up into separate cultures based on their shift. One day a man and a woman from two different shifts meet as they pass each other during shift change, or because of some special circumstance. They fall in love, and must struggle to get one of them moved to the other's shift so that they can be together. Their friends can't imagine why they would want to associate with one of \"those people\" from another shift.</p>\n\n<p>BTW Would people necessarily have three 8-hour shifts? Why not 9 hours or 7 hours? If you're not going by the Sun, who says they have to total 24 hours? Would they have to be distinct? Why not stagger them? Like 8 shifts starting 4 hours apart? Etc.</p>\n" }, { "answer_id": 33635, "author": "Sherwood Botsford", "author_id": 15784, "author_profile": "https://worldbuilding.stackexchange.com/users/15784", "pm_score": 0, "selected": false, "text": "<p>Analogies (always suspect...)</p>\n\n<p>A: International space station.</p>\n\n<p>B: Any large military ship. While some positions are on deck, what they have to do is not dictated by day/night. And many men won't see daylight for days at a time. </p>\n\n<p>C: Antarctic and arctic bases.</p>\n\n<p>D: Towns, such as Inuvic at higher latitudes than the 23 parallel (extensive periods of either constant dark or constant light.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/31660", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/4857/" ]

[ { "answer_id": 32519, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 2, "selected": false, "text": "<p>The death of 3 billion people would not cause much of a change in CO2 from breathing. The CO2 we breathe is a small part of the worldwide CO2 of all species.</p>\n\n<p>However, if half of our population died, it would likely collapse the entire world's infrastructure. The decrease in use of fossil fuels would matter far more. The amount of change is equal to the amount of impact you believe human civilization's CO2 has on the total.</p>\n" }, { "answer_id": 32521, "author": "HDE 226868", "author_id": 627, "author_profile": "https://worldbuilding.stackexchange.com/users/627", "pm_score": 3, "selected": false, "text": "<p>Some basic statistics:</p>\n\n<ul>\n<li><strong>Number of humans on Earth:</strong> <a href=\"http://esa.un.org/unpd/wpp/\" rel=\"nofollow noreferrer\">~7.3 billion people</a></li>\n<li><strong>CO₂ output per day per human:</strong> <a href=\"https://web.archive.org/web/20110202140715/http://www.epa.gov/climatechange/fq/emissions.html\" rel=\"nofollow noreferrer\">~1.0 kilograms</a></li>\n<li><strong>CO₂ output per year by vertebrates:</strong> <a href=\"http://www.skepticalscience.com/human-co2-smaller-than-natural-emissions-intermediate.htm\" rel=\"nofollow noreferrer\">~220 gigatonnes</a> (=220 trillion kilograms)</li>\n</ul>\n\n<p>This means that humans annually breathe out ~2.66 trillion kilograms of CO₂ per year - less than 1% of the total natural output by vertebrates. If <em>all</em> humans died today, there would be no effect from breathing out carbon dioxide.</p>\n\n<p><em>However</em>, <a href=\"http://www.usgs.gov/newsroom/article.asp?ID=2827&amp;from=rss_home#.Vog95mewfIU\" rel=\"nofollow noreferrer\">human activities spew out over ten times as much as we breathe out each year</a>. If we got rid of about one half of the population, we could cut that down significantly. That would make a huge difference.</p>\n\n<p>Also, <a href=\"https://worldbuilding.stackexchange.com/a/32519/627\">as Cort Ammon said</a> infrastructure would pretty much collapse. <a href=\"https://en.wikipedia.org/wiki/The_World_Without_Us\" rel=\"nofollow noreferrer\"><em>The World Without Us</em></a>, by Alan Weisman, is an interesting starting point for figuring out what would happen.</p>\n" }, { "answer_id": 32548, "author": "NPSF3000", "author_id": 703, "author_profile": "https://worldbuilding.stackexchange.com/users/703", "pm_score": 4, "selected": true, "text": "<p>It's probably worth noting that the carbon dioxide that we breath out doesn't come from no-where. I imagine that the oxygen (dioxide) comes from the atmosphere and that the carbon comes from the food we eat.</p>\n\n<p>Here's the kicker - even if half the earth's population died tomorrow, that food would still decompose and be released as carbon dioxide (because even bacteria respire just like us!). So no change there.</p>\n\n<p>But what happens if we don't grow the food in the first place? I hear you. If the food isn't grown, then it didn't consume any carbon. This is important to realize, becauseiIf you track carbon back far enough, you'll discover that it comes from <em>drum roll please</em>:</p>\n\n<pre><code>All plant and soil carbon comes, in the end, from CO2 in the atmosphere.\n</code></pre>\n\n<p><a href=\"http://carbon-sense.com/2008/05/12/where-do-plants-get-their-carbon/\" rel=\"nofollow noreferrer\">http://carbon-sense.com/2008/05/12/where-do-plants-get-their-carbon/</a> \nAlso see: <a href=\"https://biology.stackexchange.com/questions/37264/how-do-plants-get-carbon\">https://biology.stackexchange.com/questions/37264/how-do-plants-get-carbon</a></p>\n\n<p>So humans live - we grow food, the food takes carbon from atmosphere - we eat food and return carbon. Humans don't live, we don't grow food and the carbon doesn't get taken from the atmosphere in the first place. It's a zero sum game.</p>\n\n<p>So instead of thinking of humans (or any life form) as carbon dioxide producers, it might be best to think of us as carbon dioxide borrowers - we simply borrow some from the atmosphere, live our lives, and have it returned.</p>\n\n<p>The reason there is concern about human activity today is not due to our respiration, but due to:</p>\n\n<ul>\n<li>Deforestation, releasing a huge quantity of 'borrowed' carbon back into the atmosphere, without creating new borrowers to consume it.</li>\n<li>Highly 'greenhouse' chemicals - some are far more effective than carbon dioxide.</li>\n<li>Digging up dead corpses (literally oil/gas/coal) and releasing the carbon they borrowed a long time ago.</li>\n</ul>\n\n<p>A massive death rate among humans may cause changes in these behaviours, but our respiration alone has no impact.</p>\n" }, { "answer_id": 48383, "author": "EvilSnack", "author_id": 19460, "author_profile": "https://worldbuilding.stackexchange.com/users/19460", "pm_score": 1, "selected": false, "text": "<p>It does kinda-sort depend on which half of the human race dies off, so the question of <strong>how</strong> these people all die off is important.</p>\n\n<p>If the people who die off are in the top half of fossil fuel usage, then there will be a drastic reduction in anthropogenic CO2 being put into the atmosphere, while on the other hand if the people who die off are in the bottom half, then the reduction will be far less.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/32517", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/16737/" ]

[ { "answer_id": 34319, "author": "Gianluca", "author_id": 16391, "author_profile": "https://worldbuilding.stackexchange.com/users/16391", "pm_score": 3, "selected": false, "text": "<p>People (and cartels) will probably begin to meet in place outside the sight of the AI and controls, like in countryside, a baseball game, a busy street, or a lake river and talk, while doing something completely legal and unrelated. \nOr they can use a method like the Italian Mafia, which used a code written on paper, the so called \"pizzini\". </p>\n\n<p>In general, I suppose the the majority of the people probably will not care (not more than now) while the cartels will soon learn to avoid the surveillance, by technological countermeasures or going back to less technological methods that will probably beat the surveillance infrastructure</p>\n" }, { "answer_id": 34343, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 3, "selected": true, "text": "<p>There will be a sort of bell curve response as people who don't have the skills or don't care settle into their day to day lives without worrying too much about intrusive surveillance, while the criminal, hacker and libertarian element are busy working out ways to circumvent it.</p>\n\n<p>Some ideas are clearly \"out\". People hightailing it into the desert or other places where they think they can avoid surveillance will simply be telegraphic their intentions to the AI (and Predator drones can see you from a long way away). More subtle methods will have to be invented and practiced so that people can interact outside the parameters of the AI \"in plain sight\". Rather than smash and grabs, think more of con games, pickpockets and 3 card monte, or elaborate stage magic shows where the magician fools you with slight of hand, leaving you to wonder how exactly that was done.</p>\n\n<p>Ubiquitous surveillance states are already in existence, and have had the better part of a century to practice. The former Soviet Union had things like FAX machines and photocopiers in locked rooms with limited access and hordes of people co-opted or forced to spy on their neighbours. East Germany had an incredible ratio of agents to population (over 174,000; over 2% of the population), and more modern states like Iran and China (and modern Russia) use the internet and social media monitoring and electronic warfare methodology to extensively monitor and filter the population's information.</p>\n\n<p>Despite all this, there are a multitude of things people do, both high tech (various work arounds exist to penetrate the \"Great Firewall of China\", or you can be as simple was using \"burn\" phones for a single conversation), to low tech (Samizdat in the Soviet Union was basically conducted by hand copying information and passing sheets to trusted agents or through dead letter drops).</p>\n\n<p>The real key is to ensure that your activities are not far enough outside the parameters considered \"normal\" to attract attention. If the backstory you wrote is accurate, there must have been a time where the various anti government groups infiltrated or subverted various government agencies, so can have inside people to monitor what the AI is doing and report back what is working and what isn't, or even manipulate the feeds or outputs of the AI itself.</p>\n" }, { "answer_id": 34356, "author": "o.m.", "author_id": 6402, "author_profile": "https://worldbuilding.stackexchange.com/users/6402", "pm_score": 1, "selected": false, "text": "<p>One possible cartel strategy might be to overload the system. </p>\n\n<ul>\n<li>Make a point to have not-yet-convicted kingpins use the same barbers, the same grocers, the same country clubs as respectable citizens and political leaders. Suddenly those people are flagged as <em>associated</em> with criminal circles.</li>\n<li>Say they know one of their operatives is under suspicion. They cut that operative loose from their real operations and send him out to hand-deliver advertising flyers to a dozen random and not-so-random people. \"Good morning. Have you considered to change your phone provider? No? Sorry, have a nice day.\" </li>\n<li>In areas with suitable climate, build a drone which seeds/plants MJ in upper-class suburban gardens. \"Sorry officer, no idea where that came from.\" \"Yeah, sure.\"</li>\n<li>They take some of their not-yet-laundered money and wire it to random people. Couple of thousand dollars each, no comment.</li>\n</ul>\n\n<p>All those people would become <em>persons of interest</em> to the AI, right? They show up on no-fly lists, based on classified intelligence, they are denied jobs in even remotely security-critical sectors, with no legal recourse. Until those citizens dismantle the surveillance operation.</p>\n" }, { "answer_id": 191786, "author": "Tyler Mc", "author_id": 78662, "author_profile": "https://worldbuilding.stackexchange.com/users/78662", "pm_score": 0, "selected": false, "text": "<p>The cartel and other organizations would try to find ways around the surveillance by communicating with systems that most wouldn't consider to have the AI search. Actual criminals have communicated over <a href=\"https://www.computerworld.com/article/2470702/law-enforcement--gangs--terrorists-plot-evil-over-xbox-and-ps3.html\" rel=\"nofollow noreferrer\">video game systems</a> and the dark web using coded messages to avoid government surveillance. They would also establish more of their own infrastructure to prevent government spying like <a href=\"https://www.dailymail.co.uk/news/article-8525407/Drug-cartel-narco-antennas-make-life-dangerous-Mexico-s-cell-tower-repairmen.html\" rel=\"nofollow noreferrer\">making their own cellphone towers</a>. These methods would become more sophisticated methods of what these criminals use today to avoid detection.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/34311", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/17384/" ]

[ { "answer_id": 34710, "author": "AndreiROM", "author_id": 15059, "author_profile": "https://worldbuilding.stackexchange.com/users/15059", "pm_score": 2, "selected": false, "text": "<p>I think anyone advanced enough to communicate with us through those means would posses some pretty advanced tech. </p>\n\n<p>A computer analyzing the patterns in the messages would reach the conclusion that it's dealing with a mathematical algorithm, and they would just go from there.</p>\n\n<p>I'm not saying it would be <strong><em>easy</em></strong>, but it's basically inevitable if both species are set on communicating with one another.</p>\n" }, { "answer_id": 34711, "author": "cobaltduck", "author_id": 10851, "author_profile": "https://worldbuilding.stackexchange.com/users/10851", "pm_score": 5, "selected": true, "text": "<p>This question has already been debated by exo-astronomers. The best answer they could come up with (using 1974 technology) was the <a href=\"https://en.wikipedia.org/wiki/Arecibo_message#Numbers\">Arecibo Message</a>.</p>\n\n<p>The details might change, but the essential idea is that in the first part of your message, you teach the aliens, \"this is how we count.\"</p>\n\n<pre>\n0\n1 .\n2 ..\n3 ...\n4 ....\n5 .....\n6 ......\n7 .......\n8 ........\n9 .........\n10 ..........\n\n11 .......... .\n12 .......... ..\n\n\n20 ..........\n ..........\n21 .......... .\n ..........\n\n\n100 (*snip* a 10x10 grid of dots)\n</pre>\n\n<p>Then build communication from there. In the case of Arecibo, they used a binary system instead of decimal. If the aliens wrote back in their base four, we might expect:</p>\n\n<pre>\nX\nA .\nB ..\nC ...\nAX ....\nAA .... .\n</pre>\n\n<p>etc.</p>\n" }, { "answer_id": 34714, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 2, "selected": false, "text": "<p>The answer is \"we'd do the best we can.\" No method of teaching language has a perfect 100% success rate.</p>\n\n<p>One common approach that has been suggested in the past is to encode sequences which are very unlikely to occur by chance. For example, there are very few physical processes which can emit a stream of prime numbers, one after another. The idea is that the other species will try many different interpretations of the data, but hopefully the \"right\" meaning will stand out from the others.</p>\n\n<p>What defines a \"good\" sequence\" is a subject of much debate. This approach is dependent on the other species also finding a sequence meaningful. Some things, such as the series of prime numbers, are thought to be sufficiently fundamental to mathematics that we have a hard time considering languages where they are not given special status. Prime numbers have their roots in Peano arithmetic, which is remarkably fundamental. In fact, they are so fundamental that your particular concern of different bases is not an issue. 13 is a prime number. If they happen to use binary, 1101 is the same prime number. We will encode them differently, of course, but a series of numbers like this is a powerful tool for helping the other side understand the way we think.</p>\n\n<p>Just brainstorming for fun, I could see sending <code>.. ... ..... ....... ........... .............</code> on one frequency, with a corresponding decimal or binary sequence on a different frequency (in binary, it might look like <code>-. -- -.- --- -.-- --.-</code>, using a coding scheme with 2 symbols plus a space symbol). Provide enough correlatable data, and it becomes harder and harder for the aliens to misinterpret the meaning, because false hypotheses get weeded out.</p>\n" }, { "answer_id": 34718, "author": "Chase", "author_id": 17574, "author_profile": "https://worldbuilding.stackexchange.com/users/17574", "pm_score": 2, "selected": false, "text": "<p>Related to the Arecibo Message: the <a href=\"https://commons.wikimedia.org/wiki/File:Voyager_Golden_Record_Cover_Explanation.svg\" rel=\"nofollow noreferrer\">Golden Record</a> sent out with the Voyager probes communicated the RPM necessary to play the record by expressing the <a href=\"https://physics.stackexchange.com/questions/118647/what-is-the-unit-of-time-on-the-voyager-golden-record\">fundamental transition of the hydrogen atom</a> in binary. You could imagine using some constant like this, believed to exist far outside the Earth, as the basis for some kind of number system.</p>\n" }, { "answer_id": 57041, "author": "Andrew Zachary Foreman", "author_id": 27928, "author_profile": "https://worldbuilding.stackexchange.com/users/27928", "pm_score": 0, "selected": false, "text": "<p>You would need to create a Rosetta Stone of sorts. Also, look at examples of here on earth where separate human cultures contacted each other for the first time. You need to pick a universal constant that any advance species would be familiar with, then use that as a template of sorts to explore our language. <a href=\"https://en.wikipedia.org/wiki/Pioneer_plaque\" rel=\"nofollow\">https://en.wikipedia.org/wiki/Pioneer_plaque</a> This may give you some good ideas from people who have gone before us on this topic and also help you understand what I am saying. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/34709", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/17568/" ]

[ { "answer_id": 35577, "author": "Nyashes", "author_id": 17101, "author_profile": "https://worldbuilding.stackexchange.com/users/17101", "pm_score": 4, "selected": false, "text": "<p>Going through each question one by one:</p>\n\n<p><strong>what exactly does solving a theorem do?</strong> \nunderlying question: what is a theorem? A theorem is a tautology, something that can't be false. 2=2 <strong>IS</strong> a theorem (not an interesting one, I agree but still). With this definition I think you can understand that the word \"solving\" has little to do with theorems. However you can prove that something is a theorem (which is I assume, what you wanted to say). </p>\n\n<pre><code>&lt;/hard-math&gt; &lt;philosophy&gt; \n</code></pre>\n\n<p>In this case proving that something is a theorem depends on how you see math. Some think that mathematics is a human invention that only exists in our mind and has been created to help us understand the complexity of our world. In this case <strong>math does not exist by itself</strong> and proving a theorem means <strong>creating it</strong></p>\n\n<p>Other people think that mathematics is part of the physical world, it exists as rules just like physics does, it does not come from our mind but from us observing how the world works. In this case it's obvious that proving a theorem means <strong>discovering it</strong> (since it already exists in nature).</p>\n\n<p>Now concerning your trope: Maybe the first interpretation suits you better: if the platonic realm is created as we prove theorems (because it only exists in our mind), your alien living in this realm does not even exist before it has been proven to exist between two symbols. Then your alien can't do anything until it has been proven to be able to alter his world in some ways, and * <strong>tadadadam</strong> * can't alter our world until he has been proven to be able to do so. <strong>That's your initial discovery.</strong></p>\n" }, { "answer_id": 35581, "author": "Miller86", "author_id": 10713, "author_profile": "https://worldbuilding.stackexchange.com/users/10713", "pm_score": 3, "selected": false, "text": "<p><strong>True Names</strong></p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/True_name\">True names</a> are a powerful tool in lots of works, and give an individual with the knowledge of an entities' true name either power over or power via them. Perhaps in the Magic=Math universe, the beings with power don't have Names, but Equations, and knowledge of the supernatural equations gives power. If these equations live in a realm of pure math, the more complex the equation the greater the potential power. After all, Knowledge is Power.</p>\n\n<p>Additionally, if you go down this route, it's quite easy to have imperfect knowledge be incredibly dangerous. If you don't understand the equation correctly, the equation itself could cause untold damage as the parts not wholly understood seek freedom on behalf of the whole equation.</p>\n" }, { "answer_id": 35582, "author": "Lostinfrance", "author_id": 9207, "author_profile": "https://worldbuilding.stackexchange.com/users/9207", "pm_score": 3, "selected": false, "text": "<p><strong>Means of perception: could be anything</strong></p>\n\n<p>If we go by the model in the <em>Laundry</em> books, given that it is said that the those beings who perceive that a human Applied Computational Demonologist has solved a theorem are to be found in alien universe<strong>s</strong> in-the-plural, the means by which they perceive this could vary literally infinitely. (And if you can say that tongue-twister three times quickly, you too can summon a demon.)</p>\n\n<p>For some demons it could be hearing a voice from the skies or inside their minds, for others a searing pain, for others their personal computer sends them an alert.</p>\n\n<p><strong>Level of human mental involvement that will trigger the spell - could vary along a scale</strong></p>\n\n<p>Summoning cannot reasonably work by merely reproducing the steps of the mathematical proof without comprehension; otherwise we would be able to completely automate the process and it wouldn't be magic at all - or much of a story. At the other end of the spectrum, a computational magician writing, typing or speaking the spell/series of equations with full understanding and concentration ought to be virtually certain to be able to summon the demon and control it. However most summonings lie between these extremes. A person who never did get to grips with algebra can probably look at the Program of Summoning with no effect. A more mathematically-aware human skim-reading the relevant equations probably does no more than give a demon a slight headache.</p>\n\n<p><strong>Spell macros: allowed or not?</strong></p>\n\n<p>Depending on how your magic system works, the rules of magic might or might not allow a human to write or type a spell in advance, perhaps leaving off the final line until the last minute, and then press \"send\" when activation is required. If this is allowed then the once-common peril of making a mistake in saying the spell and so letting the demon out of the pentacle would be eradicated. However one might argue that magic, even mathematical magic, requires a human act of will to break through the barriers between universes and because of the way the human mind works just pressing \"send\" wouldn't cut it. On this model, it is psychologically impossible for a magically and mathematically skilled person to mentally go through the steps of the proof but stop before the end, just as I could not write out all but one of the steps of a geometrical proof and then stop myself from <em>perceiving</em> the last step whether I wrote it or not.</p>\n\n<p><strong>What is <em>solving a theorem</em> anyway?</strong></p>\n\n<p>By a rather sinister coincidence given the topic under discussion, Alexandre Thouvenin's mind-bending answer has appeared at the very moment when I was about to embark on a discussion of what exactly is meant by this, and the answer I give now incorporates ideas I got from him. </p>\n\n<p>My mathematical studies are long ago, but I don't remember <em>solving</em> theorems. I <em>solved</em> simultaneous equations and suchlike (i.e. found values of previously unknown variables for which certain conditions held true) and <em>proved</em> theorems. Since I wasn't Euclid, \"proving\" the theorems meant in practice just remembering the proof someone else had invented and writing it out again. Although it helped me to remember the proof if I understood it, that wasn't necessary. This seems unsatisfactory for magic, somehow. I feel intuitively that mathematical magic must be a process of discovery, like solving simultaneous equations. But there is a problem here. The \"process\" of discovery only feels like discovery because I lack the intelligence to perceive instantly the solution that is inherent in the equations. When some prehistoric genius first made explicit the statement \"two plus two equals four\", that this equivalence was possible was a discovery - but to you and me it is a tautology. Several mathematicians have pointed out that in a sense <em>all</em> mathematical statements are tautological if we could but perceive it. </p>\n\n<p>This leads me to not exactly an answer to your question of what exactly counts as \"solving\" a mathematical theorem for it to trigger the summoning, but at least to a revelation about the process: <strong>summoning demons is only possible because humans are stupid.</strong> We can only do it with the help of that surge of satisfaction we get from <em>finally</em> perceiving the answer. Demons perceive the answer as obvious as soon as they look at the question, which simply doesn't excite them enough. This is why demons cannot summon humans. Can you imagine how irritating this is to know? It's why they are so angry when we summon them.</p>\n" }, { "answer_id": 35609, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 3, "selected": false, "text": "<p><strong>Knowledge is power.</strong> What if this was taken to the extreme?</p>\n\n<p>Let's presume we don't really understand what happens when information is \"lost to entropy.\" This isn't much of a make-believe story to believe in, it's actually pretty accurate. We know the information gets diffused (such as the information contained in a tendril of smoke is diffused into the wind), and the information becomes inaccessible to us, simply because it has been mixed with other information until it is incomprehensible. Entropy seems to work this way in the physical world. Even Stephen Hawking's latest theory involves the topological mixing of information on the event horizon of black holes to avoid all sorts of confusion about information getting destroyed or being preserved.</p>\n\n<p>But what if there was more to it than just the physical realm? What if information or knowledge was actually a metaphysical thing. This also is not such a flight of fancy. Many who believe in a dualist philosophy that there is some mental component to us which is more than just the bare matter that makes us up already believe this. We like to believe we are \"something more.\"</p>\n\n<p>Now let's start to depart from our world. What if our world was in a unique position at the cusp of a multiverse. Knowledge or information in our world which was \"consumed by entropy\" from our perspective actually influences the other universes, potentially jeopardizing their very survival. The only hope of survival for such universes is to make sure to manipulate our world such that some knowledge just doesn't get out. As long as its never discovered in our world, that knowledge can never heart their world.</p>\n\n<p>In such a world, Aliens would have a vested interest in interfering with our world, and in particular with us. As humans we are either the single most powerful source of information in the universe, or at least one which stands out in the crowd, we would see quite a lot of interference. They may not want certain information to get consumed by entropy in certain ways, and they may be willing to expend a great deal of energy to do so. We may not understand what the particulars of their needs are (in particular, we may have no idea what particular ways entropy could consume information to trigger an effect), but we may understand that certain shapes or equations lead Aliens to action.</p>\n\n<p>Presumably they would want to teach us how to search for new knowledge without causing their universe trouble. They might carefully teach us particular tricks that help them. This could pick up an element of gnosticism. You could have an outer message, in the form of a mathematical proof, which itself is useful, and an inner message which contains the true power to influence that universe. Or they might pick up a Daoist perspective, trying to get us to accept that we are all part of one fabric to be preserved and enjoyed. They might even come in with an Abrahamic approach, with a show of force and the dictation of a set of rules for us to follow.</p>\n\n<p>It would also permit some of the more anarchistic groups to seek symbols and equations which are destructive to all universes.</p>\n\n<p>How did this come to pass? Tying it up in a nice little bow, we entered this path because one day, somebody discovered that information lost to entropy wasn't just getting mixed up like we thought.. it was actually getting lost. Somehow they managed to disseminate this information. Whether they escaped the violent reach of Entropy, or whether Entropy struck a deal with them, we may never know. Regardless, now we know, and knowing is half the battle. We still don't know what Entropy is, mind you, but maybe that's the whole point.</p>\n" }, { "answer_id": 36758, "author": "Tim B", "author_id": 49, "author_profile": "https://worldbuilding.stackexchange.com/users/49", "pm_score": 2, "selected": false, "text": "<p>I've got a slightly different take on this. Think of quantum physics and the observer effects. Quantum states that only \"collapse\" once observed.</p>\n\n<p>From the point of view of our universe all the demons are in a quantum state of possibility, a quantum state where they may or may not exist. By solving the right theoretical mathematics and visualizing it in your mind you are actually collapsing the wave-form of that demon and allowing it to come into physical form.</p>\n" }, { "answer_id": 51420, "author": "Steve Jessop", "author_id": 2390, "author_profile": "https://worldbuilding.stackexchange.com/users/2390", "pm_score": 2, "selected": false, "text": "<p>It's really a form of the same trope as summoning demons by pronouncing certain words/names, or following certain rituals. Or making yourself subject to external influences by reading the <em>Necronomicon</em>. How, rigorously, does a demon know whether you've said its name or not? Really good inter-dimensional hearing? Some kind of universal monitoring system that rushes off and tells it whenever someone says its name, like demonic Echelon? How does it detect from another world, what kind of incense you're using and what sigils you've drawn? Similarly, how does it know what mathematics you're doing?</p>\n\n<p>Part of the point of magic is that the mechanism is not rigorous: if it was then it would be physics, or just a political or commercial interaction with the demon.</p>\n\n<p>But as a general theme, the idea seems to be either that certain energies or entities are attracted to certain words/signs/substances/etc (by some form of sympathy), or else that certain states of mind allow the practitioner to perceive or interact with a world they normally cannot.</p>\n\n<p>Converted to mathematical form, it could be that there's some etheric substance that is pushed around by mathematical symbols, and that a proof of a theorem pushes that substance into a mechanism that then is able to do whatever it takes to pierce the veil. So, proving Fermat's Last Theorem is like building the machine in Sagan's <em>Contact</em> except that you're not building it out of material substance, you're building it out of some magical hand-wavey stuff that exists locally, and responds to local stimulus, but then is capable of a distant effect. In that case, a written proof might be a permanent magical doohickey provided that the symbols continue to hold the machine in shape. You still have to explain how the energy \"knows\" that the symbol \"2\" means the number that comes after the number represented by the symbol \"1\", but perhaps what matters is the structure of the patterns/relationships among symbols, and this explains why the actual symbols used are irrelevant.</p>\n\n<p>Alternatively, it might be that humans happen to be innately equipped with some faculty that draws the attention of demons, but that we're unable to use that faculty except when guided into a series of very specific mental states/visualisations, corresponding to the steps of a proof. In that case, a written proof in a book is nothing, but when someone reads it and it has its intended effect on them (of understanding the proof that it represents) then the magic happens and they start dreaming of unknown Kadath. The proof itself is no more or less magical than the mental exercises used by a Zen archer to shoot a bow, (and vice-versa the shooting exercises used to achieve mental and spiritual development). It's just that in the case of demon-summoning humans are actually so awful at it without the exercises as to be incapable.</p>\n\n<p>Or in a broader sense of the law of sympathy, perhaps there is some entity that definitionally <em>is</em> (or has some direct connection with) the platonic ideal of the number 2. Wherever things appear in pairs, or whenever someone thinks about the mathematical properties of the number 2, there that entity is, just as we might say that Thor exists wherever thunder does, or that silver is connected with the powers/associations of the Moon, or that God is omnipresent. Naturally then demons respond to mathematics: to do mathematics is to touch a part of their multi-dimensional self. It's then up to you whether the demon summoned is the demon of Fermat's Last Theorem specifically, or whether the general fuss and commotion caused in the region of the platonic universe corresponding to the intersection between \"elliptic curves\" and \"modular forms\", by proving the Taniyama-Shimura conjecture, is what attracts other demons.</p>\n\n<p>As for the rigorous details of <em>why</em> there is a law of sympathy at all, or <em>what causes</em> there to be a God of Thunder or a demon of Banach-Tarski dissections, or <em>how</em> the force is mediated by which symbols to build etheric machines, or <em>by what mechanism</em> humans have an innate capacity to summon demons or shoot bows: those may have to remain as irreducible principles of your in-fiction theory of magic. No doubt you can drill into some of them by introducing further concepts that dictate them.</p>\n" }, { "answer_id": 69218, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 2, "selected": false, "text": "<p>My first answer explored how a theorem itself could be valuable. The bounty suggests more interests is needed, so I wanted to put forth a theory that suggests the theorem itself isn't as important as it may appear.</p>\n<p>I wanted to focus on two parts of the question</p>\n<blockquote>\n<p>&quot;Discworld&quot; series, supernatural beings listen to people and might decide to meddle; speaking or performing rituals gets the specific attention of those paying general attention to human activity.</p>\n<p>How might this trope be made a little more rigorous?</p>\n</blockquote>\n<p>I think this trope can be made more rigorous by not looking at the theorem itself, but rather what the act of &quot;solving&quot; it implies. To this end, the theorems the supernatural beings listen for are not all that meaningful at all. However, the fact that a sentient mind &quot;solved&quot; these theorems could be of great interest. If they can solve that theorem, what else might they be able to do?</p>\n<p>If there are things which the supernatural do not want us doing, or ideas the supernatural do not want us to think of, they would be encouraged to meddle in our affairs to prevent us from doing or thinking those things. &quot;Solving&quot; a theorem might demonstrate that we are capable of taking the next step and thinking of the forbidden thing, or capable of leveraging that theorem to do some forbidden thing.</p>\n<p>What makes this powerful is that the &quot;solving&quot; of a theorem can now be treated as a symbolic gesture, rather than the thing that actually has power. This provides key direction for questions such as:</p>\n<blockquote>\n<p>If it's in a book somewhere, does a human mind going over the steps tickle something? Or does it require some degree of understanding of the complete proof?</p>\n</blockquote>\n<p>The answer is now dependent on how the supernatural being feels, rather than some strict rule set. Perhaps for a given entity, one must truly <em>understand</em> the implications of a proof of Fermat's Last Theorem before the entity cares enough to be cajoled into action. It may be that the entity doesn't actually care about his Last Theorem at all, but does care about some other great problem which can be solved using a similar approach. Someone who understands Fermat's Last Theorem is a likely candidate for being able to solve this entity's great problem.</p>\n<p>On the other hand, the same entity may treat a proof of P=NP differently. This may be a sufficiently powerful tool in the hands of a mathematician that the entity has to pay attention to anyone who knows the proof, even if they don't fully understand it. It may be that the entity wants to snuff out all memory of this proof, for fear that an uneducated person who memorized the proof might tell it to an educated person who would then understand it and know what to do with it.</p>\n<p>Approaching the theorems this way makes the theorems into threats and other gestures targeting the supernatural. This sort of posturing is very rigorous in other disciplines such as hand to hand combat. In addition, it offers many many quirks. Perhaps an entity doesn't really care about P=NP. What they really care about is BQP=NP. An entity might appreciate the fact that mathematicians are constantly getting sucked off into P=NP and aren't paying as much attention to BQP=NP. Perhaps that entity might reward a math-wizard for &quot;solving&quot; theorems in a way that encourages others to waste their time on P=NP. The options are limitless, and yet it would be easy to develop a rigorous structure within which any given supernatural being might choose to operate.</p>\n" }, { "answer_id": 69243, "author": "Taladris", "author_id": 2249, "author_profile": "https://worldbuilding.stackexchange.com/users/2249", "pm_score": 2, "selected": false, "text": "<p><strong>A mathematical variation of the True Name trope</strong></p>\n\n<p>Since the entities are real numbers, what is relevant is not their name, but their formal definition: roughly, a real number is <a href=\"https://en.wikipedia.org/wiki/Definable_real_number\" rel=\"nofollow noreferrer\">definable</a> if it can be uniquely described by a finite mathematical formula. For example, $\\sqrt{2}$ is the positive solution of $x^2=2$; $e\\simeq 2.71$ is the value at $1$ of the solution of the differential equation $y'=y$ with initial condition $y(0)=1$; etc...</p>\n\n<p>With that idea, you define have a hierarchy of powers among your entities using the complexity, that is the length of the shortest formula describing it. A surprising consequence of Cantor's theory of cardinals is that most real numbers are not definable.</p>\n\n<p>Notes: </p>\n\n<ul>\n<li>You can adapt this to use the concept of computable numbers. That would be a natural setting if you want your story to speak about Alan Turing </li>\n<li>Why limiting yourself to a \"dimension of pure numbers\", when you can consider the behemothic universe of mathematical objects? </li>\n</ul>\n" }, { "answer_id": 69254, "author": "user3644640", "author_id": 28538, "author_profile": "https://worldbuilding.stackexchange.com/users/28538", "pm_score": 2, "selected": false, "text": "<ul>\n<li>Every concept, such as a theorem, is matter in Platonic realm for being able to exist.</li>\n</ul>\n\n<p>Only in math can you 100% prove something. => The concept has to materialize itself in our world, because the theorem is perfect not only in the Platonic realm, but also in our world. This means that it is either a perfect copy of the concept in Platonic realm, or it brings the concept from that realm. => If latter, the concept may still have a tendency to stay in the Platonic realm.</p>\n\n<p>Then, there must be some conditions when a concept materializes itself in our world. It could be that it only materializes itself when somebody is thinking it clearly enough, aka. casting a spell by going the theorem in mind or in word. People think a bit differently when they speak (it even has a difference when sitting or standing). That might explain why the mages speak when casting.</p>\n\n<p>EDIT PS: This would also explain miracles, created by pure or perfect love, belief, friendship etc. Just might make a nice plot element if well implemented, but with high risk of being mawkish.</p>\n" }, { "answer_id": 69681, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 1, "selected": false, "text": "<p>You depict the math physically and bring it into the world. Draw the pattern. Build the temple. Play the fugue and variations. Bring the geometry and ratios into the physical world. Humans have been honoring and courting supernatural beings thus for thousands of years. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/35574", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/885/" ]

[ { "answer_id": 35608, "author": "bowlturner", "author_id": 19, "author_profile": "https://worldbuilding.stackexchange.com/users/19", "pm_score": 3, "selected": false, "text": "<p>The closer to the water that it is when it goes off the more energy is distributed to it. <a href=\"http://science.howstuffworks.com/explosion-land-water1.htm\">Air is a 'compressible' medium and so a body can deflect some of the pressure wave around itself</a>. However water is not. Air allows for shrapnel and debris to travel and be dangerous projectiles. In water, it's reverse, the water significantly reduces the speed of projectiles and \"radioactive particles\" however it does transmit much more of the pressure wave directly. </p>\n\n<p>It's like the difference between taking a long spring and pushing against someone to try and knock them over vs. taking a steel pole and pushing against them. The steel pole has a lot more direct transfer of the energy applied.</p>\n\n<p><a href=\"http://science.howstuffworks.com/explosion-land-water1.htm\">Quoted</a></p>\n\n<blockquote>\n <p>If you stood outside of shrapnel range for an exploding hand grenade, you'd likely remain unharmed. If you stood at the same range to an underwater explosion, the pressure wave would probably kill you [source: Landsberg]. When the wave reached your skin, it would pass through you. After all, little of its power would be reflected because your body's density is similar to that of the water. The wave would hit the air-filled pockets of your body and instantly compress the gases there, possibly resulting in blocked blood vessels, ruptured lungs, torn internal tissues and even brain hemorrhaging. Waves hitting the surface of the water or the bottom of the pool would bounce back, inflicting even more damage. Explore the links on the next page to learn more about explosions, the human body and how to survive other dangerous encounters.</p>\n</blockquote>\n\n<p>This implies that you would need to be farther away from the blast than if you were on the surface of the water. That is also with the expectation that it was at least partially submerged when the warhead detonated.</p>\n\n<p>Water doesn't compress well and the deeper you go the more pressure there is on the hull, now add a huge blast 'pushing' that water down even more, it will try to collapse all air pockets to help 'relieve' the pressure. Your little tin can would need to be extra strong. I would guess that being just a little way under the surface and traveling as fast and far away from ground zero would be your best chance of survival. </p>\n\n<p>Going straight down, you are adding more water pressure putting your sub ever closer to its tolerances. and keeping you in direct line of the pressure wave. Going straight away just under the surface you change the angle of 'attack' very quickly as you run. if it blows above the surface the angle of reflection get easier for the water to deflect the farther you get away. If it blows under water you can more easily move with the water or might be deflected out of the water, like puss from a zit.</p>\n\n<p>So my WAG is about 10ft down and tear out as fast as possible. Try to be a mile away or more if you can.</p>\n" }, { "answer_id": 35622, "author": "Seeds", "author_id": 15043, "author_profile": "https://worldbuilding.stackexchange.com/users/15043", "pm_score": 2, "selected": false, "text": "<p>I'm thinking most surface ships are faster than submersibles, especially ones laden with gold. :) <br>The villain is unlikely to give one enough time to run on the surface, in either case. <br>I suspect one would not be able to submerge fast enough to get out of range either. A 1MT nuke at, or near the surface is going to vaporize a large amount of water, possibly just rendering it as Hydrogen and Oxygen plus all the other bits dissolved.</p>\n\n<p>The radiation that isn't breaking down nearby matter into its component atoms is going to be winging through whatever medium you happen to have interposed, so assuming the primary and secondary shock waves do not crush/damage your submersible, you would definitely want to check your dosimeter to see what kind of lifespan you can expect on your organs, radiation lesions are supposed to be some of the most painful internal injuries.</p>\n\n<p>You would want to be several kilometers away at the very least.</p>\n" }, { "answer_id": 35625, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 6, "selected": true, "text": "<p>Depth may not be your friend, but number of layers is. When the shockwave hits the surface of the water, much of it is reflected, but some of the shockwave is transmitted. How much? It turns out <a href=\"https://books.google.com/books?id=CZtDAAAAQBAJ&amp;lpg=PA16&amp;ots=tTfPhlW33j&amp;dq=impedance%20mismatch%20air%20water%20shockwave&amp;pg=PA17#v=onepage&amp;q=impedance%20mismatch%20air%20water%20shockwave&amp;f=false\" rel=\"nofollow noreferrer\">they wrote a book about it</a>:</p>\n\n<blockquote>\n <p>As discussed by Henderson et al. (1990), when a blast wave first contacts a water sheet, a large portion of the incident energy is reflected back towards the source due to the impedance mismatch at the air-water interface. The remaining energy, which is transmitted through the water sheet, forms the observed weak shock wave and the resulting initial pressure rise. For the experimental conditions considered here, the initial blast overpressure is mitigated by as much as 80%. This indicates that a water sheet may be an effective emergency blast mitigant.</p>\n</blockquote>\n\n<p>In this case, the explosive was 48.4g of PETN (page 14), but I don't have any reason to expect any one shockwave to behave differently from another.</p>\n\n<p>So how far do you need to be? Well, they haven't written a book about that, but they did write a <a href=\"http://textfiles.com/survival/blastfnd.txt\" rel=\"nofollow noreferrer\">text file</a> about it. I'm getting a little nervous just how much attention this problem has gotten...</p>\n\n<pre><code> Blast effects of nuclear bomb (this is for an 80 col. printout)\n All distances to effect in miles. Note: airburst distances in ( )\n Airburst for optimum damage for that effect, since the height of airburst\n changes these figures represent worst case. See example for fixed height \nresults.\n\nMT 1psi 1.5 3 6 10 30 overpressure\n0.2 4(7.5) 3(6) 2(3.4) 1.3(1.8) 1(1.2) .55(.6)\n0.6 6(11) 4.5(9) 2.8(5) 1.8(2.6) 1.4(1.7) .8(.9)\n1.0 7(13) 5.5(10.5) 3.3(6) 2.2(3.2) 1.6(2) .95(1.05)\n5 12(23) 9(18) 5.5(10) 3.7(5.5) 2.7(3.5) 1.6(1.8)\n20 19(35) 14(28) 9(16) 6(8.5) 4.3(5.5) 2.5(3.4)\n(Update note: the 5 &amp; 20 Megaton bombs only existed in old Soviet Bear and \nBison class bombers and have been replaced with more modern 1 Megaton bombs.\nThe old US Titan missiles with their 9 Megaton bombs were scraped during late\n1987 and early 1988)\n</code></pre>\n\n<p>...</p>\n\n<pre><code>Examples of damage (from SURVIVING DOOMSDAY -Clayton, from tables in THE\nEFFECTS OF NUCLEAR WEAPONS 1977 -Gladstone) \n0.5 psi Private airplanes damaged but flyable, windows have light damage \n1.0 psi Windows heavily damaged, wood frame houses lightly damaged \n1.75 psi Some, but not all, glass shards capable of penetrating abdominal wall.\n2 psi Human body thrown hard enough to cause incapcitating injuries if standing\n3 psi Human body thrown hard enough to cause 1% fatalities if standing up.\n4 psi Forest road impassable due to fallen trees.\n5 psi Wood frame house collapse, 1% of eardrums rupture (in the elderly) \n6 psi Human body thrown hard enough to cause 99% fatalities \n</code></pre>\n\n<p>From this chart, 6 psi is enough for a 99% fatality rate. You're in a submersable, so that's 6psi in the air of the sub. The reflection off the surface means you need 5x that shockwave pressure (reciprocal of 80%), which is 30psi suggesting .95 miles of distance is needed. However, there's more to this, because you have <em>two</em> impedence mismatches. One from air to water, and one back from water to air. These effects stack, meaning you need 25x more pressure at the surface to affect you. Thus, you would need a 150psi shockwave hitting the water to reach the essential 6psi. If we look at the table, that pressure is remarkably hard to hit. Obviously the table doesn't go that far, but I'd be tempted to guess its around 0.1mi, or about 500 feet. As a point of comparison, Little Boy, the bomb dropped on Hiroshima, was detonated at 1,968 ± 50 feet. I won't play CONOPS games with nukes, but I'm guessing that by the time the shockwave hits the water's surface, it's gone far enough to be below the magic 150psi level.</p>\n\n<p>How about radiation? Piece of cake. From our <a href=\"https://space.stackexchange.com/questions/1336/what-thickness-depth-of-water-would-be-required-to-provide-radiation-shielding-i\">sister site</a>:</p>\n\n<blockquote>\n <p>We know from the nuclear power industry that spent fuel storage pools\n are pretty safe places to be around, radiation-wise. They're actually\n safe to swim in, to a point, because they're serviced routinely by\n human divers. They just can't get too close to the spent fuel.</p>\n \n <p>We use these pools for short-term storage because water is a really\n good radiation shield. How good? Well, according to a report on the\n topic prepared for the DoE back in 1977, a layer of water 7\n centimeters thick reduces the ionizing radiation (rays and particles)\n transmitted through it by half (the remainder is captured or moderated\n to non-ionizing energy levels, mainly heat).</p>\n</blockquote>\n\n<p>Considering that you can hold your breath and dive to 700cm in a pinch, radiation is going to be a non issue for any submersible.</p>\n" }, { "answer_id": 35626, "author": "Samuel", "author_id": 3202, "author_profile": "https://worldbuilding.stackexchange.com/users/3202", "pm_score": 3, "selected": false, "text": "<p><strong>You're probably not going to be able to escape by going down.</strong></p>\n\n<p>But this depends on what depth your ship was designed to withstand.</p>\n\n<p><a href=\"http://web.ornl.gov/~webworks/cppr/y2001/pres/123612.pdf\" rel=\"nofollow noreferrer\">This paper</a> gives equations to calculate the psi from a variable TNT equivalent bomb at a variable depth under the water (in feet, sorry) from the explosion on the surface. </p>\n\n<p>$P = 0.7 * 2.16 \\times 10^4 ({{W^{1/3}}\\over{R}})^{1.13}$</p>\n\n<p>Where $P$ is the overpressure in psi, the 0.7 coefficient is the attenuation due to being above the surface, $W$ is the charge weight in pounds, and $R$ is the range in feet.</p>\n\n<p>The questions are derived empirically from this data:\n<a href=\"https://i.stack.imgur.com/aQHb9.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/aQHb9.png\" alt=\"enter image description here\"></a></p>\n\n<p>In your case, for a 1MT bomb, things <a href=\"http://www.wolframalpha.com/input/?i=0.7%20*%202.16E4%20*%20(1E6%5E(1%2F3)%2FR)%5E1.13%20for%20R%20%3D%200%20to%201000&amp;rawformassumption=%7B%22MC%22,%20%220%20to%201000%22%7D%20-%3E%20%7B%22NumberMath%22%7D&amp;rawformassumption=%7B%22MC%22,%20%220%20to%201000%22%7D%20-%3E%20%7B%22CalculateDateDifference%22%7D\" rel=\"nofollow noreferrer\">don't look good</a>. Your ship is probably able to go to at least 1,000 ft underwater (to collect the gold). In sea water that's about 460 psi. The overpressure from a 1MT surface detonation at 1,000 feet underwater is over 1,100 psi. So, unless your submersible has a pressure safety factor of over three times the operating depth, you're not likely to survive.</p>\n\n<p>I don't know your planned depth, but I will estimate you have a safety factor of 20%. Given that information I can see that if you designed for 3,240 feet, and dove to that depth, the overpressure would just be inside your safety margins.</p>\n\n<p><a href=\"https://i.stack.imgur.com/stAl5.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/stAl5.png\" alt=\"enter image description here\"></a></p>\n\n<p><em>Note that the blue line only appears to be going back up because the additional overpressure has stopped diminishing faster than the growth of pressure at increasing depth.</em></p>\n" }, { "answer_id": 35636, "author": "Lobo", "author_id": 18072, "author_profile": "https://worldbuilding.stackexchange.com/users/18072", "pm_score": -1, "selected": false, "text": "<p>Even if you escaped the explosion the chances of escaping radioactive isotopes is probably highly unlikely, but let's say you did. You technically would live slightly longer than those directly affected. Your chances of survival would depend how fast you can get medical treatment, if assuming such a treatment even exists. Radiation spreads faster than wildfire it can cover an entire block within seconds over several hundred km, you might even find taking an acid bath a more peaceful death than being affected by radiation. If it can affect air particles you can be assured the effects on water molecules can't really shield it. Though I would surmise a nuclear sub exploding would cause the body of water to become tainted for the next thousand years. </p>\n" }, { "answer_id": 35682, "author": "Darrel Hoffman", "author_id": 14600, "author_profile": "https://worldbuilding.stackexchange.com/users/14600", "pm_score": 2, "selected": false, "text": "<p>One factor not discussed yet: Assuming you survive the blast and radiation, etc, what do you do next? Your ship is destroyed, and you're in a small short-range submersible miles from land. Even if the explosion was noticed by rescue parties (and odds are a 1 MT nuke would be noticed by <em>some</em>body), they would naturally assume that nothing could possibly have survived. The ship would be in millions of pieces, it would be ages before anyone noticed that the wreckage of the submersible was not present in the debris. Also, you mentioned there were henchmen searching for you, and they would do whatever they could to hinder any potential rescue efforts.</p>\n\n<p>Your submersible would eventually run out of fuel - they're not really built for long sea voyages. Even the process of diving and resurfacing requires energy to power the sub, and without the ship to provide recharging and refueling, your vehicle will soon be dead in the water. And I'm guessing you didn't have time to pack a water desalinater and few weeks worth of rations in there. Not to mention navigation equipment, so you might not even know what direction to go to find the nearest land. Air would also be a problem. You can't stay underwater forever, but surfacing to restock on air runs the risk of discovery by the villain's henchmen. Your most likely prognosis at this point would be a slow death by asphyxiation, thirst and/or starvation.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/35604", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/3510/" ]

[ { "answer_id": 36726, "author": "Samuel", "author_id": 3202, "author_profile": "https://worldbuilding.stackexchange.com/users/3202", "pm_score": 3, "selected": false, "text": "<h2>You've invented a new sport: Aero-Swimming.</h2>\n\n<p><strong>Best Case</strong></p>\n\n<p>You'd float, vertically speaking, very near the center of the hole. The difference in the gravity gradient from side to side would not be as noticeable, so you could likely get from one side to the other by swimming. </p>\n\n<p><strong>Set-up</strong></p>\n\n<p>That is, <em>if you reinforce the hole and then survive the fall</em>. Also you're going to need to not care about being crushed by the atmospheric pressure, but it seems to be excluded for your question. Because the pressures are indeed the same, as they depend on the vertical component of gravity.</p>\n\n<p>The hole will collapse without unobtanium structural support. It's true that the gravity will slightly pull into the walls of the hole (by as much as the mass of the missing material), but it won't compare the the immense pressure from the earth above which will want to squish into the hole like whip cream from between your hands.</p>\n\n<p><strong>No running by the hole</strong></p>\n\n<p>Running and jumping off is not a good idea. You're still going to fall for a while and achieve terminal velocity. You will also maintain that horizontal component of your leap and only be slowed by wind resistance, which will rapidly drop as it slows you, so that you'll not quite come to a complete stop. Or rather you will, but it will be with the opposite side of the hole while you're traveling 120 miles per hour downward but slower than walking speed toward the side. This would be similar to walking into the side of a bullet train, it's going to hurt.</p>\n\n<p><strong>Swimming</strong></p>\n\n<p>But that's only if you don't start swimming. You'll be able to control your horizontal movement to some degree in the air, just like in water. It will be more difficult, as the medium is far lighter than water, but the effect will be the same.</p>\n\n<p><strong>End Game</strong></p>\n\n<p>You'll never get out the other side. The air resistance will have slowed you down significantly (it's to the <a href=\"https://en.wikipedia.org/wiki/Drag_(physics)\" rel=\"nofollow noreferrer\">square of your velocity</a>, so it's more significant reduction for your vertical movement where you're moving faster). This means you're going to peak somewhere well below the top of the other side and start falling again. You'll oscillate back and forth for a while and finally settle in the center of the hole (vertically). You'll be able to move up or down a bit, but the gravity will eventually become too strong to swim, and you'll have to resort to climbing. But you can't climb that far, <a href=\"https://worldbuilding.stackexchange.com/a/12443/3202\">over 6,000 km</a> is probably farther than you'd even want to walk, let alone climb. </p>\n\n<p>You'll die down there, and your body will settle to the middle, waiting to collide with the next person to jump in.</p>\n" }, { "answer_id": 36727, "author": "Schwern", "author_id": 760, "author_profile": "https://worldbuilding.stackexchange.com/users/760", "pm_score": 5, "selected": true, "text": "<p>For this answer I'm assuming that Planet Plane is <a href=\"https://worldbuilding.stackexchange.com/a/12443/760\">the one from this answer</a> which is infinite in area and 6,378km deep.</p>\n\n<p>(This cannot be Planet Minecraft because it would not have a horizon for the Sun and Moon to drop below. For what Planet Minecraft would really be like, see <a href=\"https://www.youtube.com/watch?v=h5N7d8mcQk4\" rel=\"nofollow noreferrer\">this episode of It's Okay To Be Smart</a>.)</p>\n\n<blockquote>\n <p><em>Firstly; would this hole immediately collapse or would it be a somewhat stable structure?</em></p>\n</blockquote>\n\n<p>This depends on the material Planet Plane is made of. If we assume Planet Plane can exist, then your hole will not collapse.</p>\n\n<p>The problem with massive structures is gravity tries to pull them together into their most stable state: a sphere. Since Planet Plane exists as an infinite plane then we can surmise it is strong enough to resist gravity. Therefore your hole will remain open for a while.</p>\n\n<p>Eventually it will close. Any debris which falls into the hole will collect at the center where gravity balances out. Eventually enough debris will fall into the hole to fill it up.</p>\n\n<p>The problem isn't will the hole stay open, the problem is <strong><em>will the hole grow forever</em></strong>?</p>\n\n<p>As @Samuel pointed out in the comments, unlike a sphere where the center of mass is a point in the middle, the center of mass for a uniformly dense infinite plane with finite depth is an infinite plane in the middle of the planet. This means gravity is always pulling orthogonal to the surface</p>\n\n<pre><code> Side-view cutaway of Planet Plane\n\n gravity\n ||\n \\/\n &lt;=============================================&gt; D\n &lt;=============================================&gt; E\n &lt;------------- center of mass ---------------&gt; P\n &lt;=============================================&gt; T\n &lt;=============================================&gt; H\n</code></pre>\n\n<p>If you punch a hole in this structure, there will be no gravitational force trying to pull the sides together. Every side will have the same amount of mass around it in every direction. However, the hole has no mass (discounting the negligible effects from air) and exerts no gravity. Therefore <strong><em>each side will be a little closer to one half of the plane than the other</em></strong> and so will feel a stronger gravitational pull in that direction. The edges of the hole will experience a tug from their side of the planet, threatening to <em>widen the hole</em>. The hole will experience <a href=\"https://en.wikipedia.org/wiki/Tidal_force\" rel=\"nofollow noreferrer\">tidal forces</a>.</p>\n\n<p>If the hole gets wider, the sides get further apart, and the tidal effect gets stronger. Once it starts, <strong><em>the hole continues to get bigger forever</em></strong>. Fortunately there's infinite planet, so you'll never run out of surface to run to.</p>\n\n<p>I'd be interested to see someone do the math on the tidal forces at the edges of your 1km diameter cylinder.</p>\n\n<blockquote>\n <p><em>Secondly; (assuming it was/made stable) if I had a death wish and took a running jump off the edge, where would I fall? The exact center of the hole? Would I drift across to the other edge? One of the \"sides\" of the hole?</em></p>\n</blockquote>\n\n<p>The issue here is whether or not Planet Plane is rotating. If it's not, and if we assume the hole contains a vacuum, as you fall you will continue to drift across the hole at the speed you were running when you jumped. If you were an Olympic sprinter you'd be going about 10m/s and smack into the other side of the hole in about a minute and a half hitting it with the same force as if you had run into it, plus getting dragged along the edge of the hole. Ouch.</p>\n\n<p>If Planet Plane is rotating there will be a <a href=\"https://en.wikipedia.org/wiki/Coriolis_force\" rel=\"nofollow noreferrer\">Coriolis force</a> and you will smack into a wall on your way down. <a href=\"https://www.youtube.com/watch?v=jN-FfJKgis8\" rel=\"nofollow noreferrer\">Minute Physics has a great video on this</a>.</p>\n\n<p>The one exception is it your planet happened to be rotating on an axis running directly through your hole. This is the same as drilling a hole through the Earth <em>pole to pole</em>.</p>\n\n<p>The best case (for you) is if the planet is not rotating and your hole have an atmosphere. In this case air resistance will slow your forward motion and you will eventually fall straight down. But this causes a new problem.</p>\n\n<p>That same air resistance will slow your fall. When you pass the center point and begin traveling \"up\" towards the other side of the planet you're now feeling the same pull of gravity down into the hole. With no air resistance this will exactly balance out your acceleration due to falling and you will reach the peak of your fall right at the lip of the hole on the other side and you can gently step out.</p>\n\n<p>But air resistance will be slowing you during your fall and ascent. This means you'll come up short. Instead of peaking at the surface, you'll peak below it and fall back again to the other side, again peaking further below the surface. You'll oscillate back and forth like this, losing energy to atmospheric drag, until you're stuck floating in the center of the planet.</p>\n\n<p>Tidal forces also play a role. If you're in the exact center of the hole you're fine, but if you're closer to one side or the other the tidal force will slowly pull you towards the edge. As you get further away from the edges the force will get stronger. Again, I haven't done the math on how strong.</p>\n\n<blockquote>\n <p><em>Corollary: If the hole itself was stable, would travel through it unprotected be fatal? Eg: are the pressures on a mine-craftian world the same as on a spherical one?</em></p>\n</blockquote>\n\n<p>This depends on how old Planet Plane is, how it formed, and what it's made of.</p>\n\n<p>The interiors of spherical planets are initially very hot from the residual heating of forming due to gravitational collapse, plus the decay of any radioactive elements trapped in the insulated interior. There can also be heating due to tidal effects as happens on the moons of Jupiter and Saturn, the squeezing and stretching adds heat to the moon's interior.</p>\n\n<p>But Planet Plane can't be a moon, and it didn't form from gravitational collapse. So it's anyone's guess as to what heat of the interior will be.</p>\n\n<p>What will be a problem is air pressure. Air pressure is the weight of a column of air pressing down on you. Assuming a normal Earth atmosphere at the surface, at the center of the hole you'll be supporting an extra 3,189km column of air. This is <em>a lot</em> of air. The atmosphere ends and space begins at about 100km. At the center you'll be experiencing <em>at least 30 times normal air pressure</em>. This is roughly equivalent to being 300m under water (every 10m is about 1 atmosphere of pressure). <em>Squish</em> <a href=\"https://en.wikipedia.org/wiki/Deep_diving#Ultra-deep_diving\" rel=\"nofollow noreferrer\">You will need some serious deep sea equipment to survive this, only five people have gone that deep on the Earth</a>.</p>\n\n<p>(NOTE: I'm playing a bit fast and loose with the air pressure calculation. The pull of gravity will decrease towards the center of the hole which may reduce the air pressure. Still, it's doing to be in the ballpark of 30bar.)</p>\n" }, { "answer_id": 36740, "author": "Nathan", "author_id": 18509, "author_profile": "https://worldbuilding.stackexchange.com/users/18509", "pm_score": 0, "selected": false, "text": "<p>Gravity would be a constant for any distance away from the surface of the of the plane, however, it would change direction to pull you towards the plane. </p>\n\n<p>While you are in the inside of the finite length of the plane of matter, you would feel a gravitational force proportional to your distance away from the center of the finite width. </p>\n\n<p>Because of the infinite nature of the world in the horizontal directions, you would never feel a gravitational acceleration in the horizontal direction. Unless of course the hole is not symmetrical. No matter would ever feel any horizontal gravitational acceleration if it is in fact symmetrical. </p>\n\n<p>Air resistance is the only thing stopping you from reaching the other side.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/36724", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/17263/" ]

[ { "answer_id": 36954, "author": "Bryan McClure", "author_id": 17551, "author_profile": "https://worldbuilding.stackexchange.com/users/17551", "pm_score": 0, "selected": false, "text": "<p>The idea of using pi is a good idea, math after all is a constant in the universe. But you would have to incode it use some thing really basic. Morse code is the only thing that comes to mind, some one else could probably think of something better.</p>\n" }, { "answer_id": 36957, "author": "Youstay Igo", "author_id": 13449, "author_profile": "https://worldbuilding.stackexchange.com/users/13449", "pm_score": 0, "selected": false, "text": "<p>The signal would have to be <strong><em>really</em></strong> long. You cannot guarantee that the encoding we use would be understood by the target peoples too, so you would want to send a shipload of signals in the direction of target in order to give them enough information that they can start decoding it. It is a known rule that the quantity of encoded information is directly proportional to the probability of having it decoded.</p>\n\n<p>Simply sending mathematical tables of 2 or 3 would be a good idea</p>\n\n<p>2x1=2\n2x2=4\n2x3=6</p>\n\n<p>The reason for this is that such information is relatively easier to decode than a single value such as pi or some other constant value.</p>\n\n<p>Now you might question how would such basic information reveal our intelligence to the target species? The answer is that this information does not prove a much about our intelligence but the <strong>transmission</strong> of this information on radio waves means we have mastered e.m. communication, which is indeed a proof of tech development.</p>\n" }, { "answer_id": 36959, "author": "Anders Gustafson", "author_id": 13661, "author_profile": "https://worldbuilding.stackexchange.com/users/13661", "pm_score": 3, "selected": true, "text": "<p>Using the digits of a number isn't really the best way to express a number when communicating with an alien race as Extra Terrestrials would almost certainly use completely different methods for expressing number from us. In order to show our mathematical knowledge to aliens it would be better to find a method of communicating mathematics that doesn't involve any symbols. One way we could communicate our knowledge of math could be to send signal that looks like AA AAA AAAAA AAAAAAA AAAAAAAAAAA AAAAAAAAAAAAA AAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA as this would be a sequence of groups that all have the sequence of prime numbers as the number of individuals instead of using the symbols for the prime numbers so that they would not need to know what symbols we use for the prime numbers in order to recognize that it is a sequence of prime numbers. We could also send a signal like A AAAA AAAAAAAA AAAAAAAAA AAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA to represent perfect powers. Basically we would represent number in the most literal sense in terms of showing them by having numbers of things instead of the symbol for a number so that aliens could understand it even if they use different symbols for numbers. If we wanted to use pi we might send them a series of signals in which the length of each signal was close to pi times the length of the previous signal instead of using the digits of pi as they would likely have different symbols for 0 and 1 than the ones we use. If we wanted to teach aliens what symbols we use for different numbers we might send them the symbol next to clusters of objects that would have that number of objects and do it with many different types of objects so that they could see the pattern.</p>\n" }, { "answer_id": 36964, "author": "Marius", "author_id": 17967, "author_profile": "https://worldbuilding.stackexchange.com/users/17967", "pm_score": 2, "selected": false, "text": "<p>There is no need to try to convey any meaning to prove intelligence. Just the ability to send the signal proves a certain level of intelligence. The goal must be to make a signal that is likely to be picked up by the receiver, and interpreted as something other than a natural phenomenon. </p>\n\n<p>Using several frequency and sending patterns we assume if structured enough to not replicate any natural phenomenon, and then cycling through the pattern on different frequency. </p>\n\n<p>For instance first you do prime numbers on frequency 1, and even numbers on frequency 2, odd number on frequency 3, fibonacci on frequency 4. Then once you have done that for a while change it so that frequency 1 now does fibonacci, and frequency 2 does prime and so on. </p>\n" }, { "answer_id": 36976, "author": "nigel222", "author_id": 13883, "author_profile": "https://worldbuilding.stackexchange.com/users/13883", "pm_score": 0, "selected": false, "text": "<p>Prime numbers are a very good start. There is no known natural process that generates them. Once you have established primes as the context by transmitting the first few in some transparently simple coding scheme such as a number of pulses separated by silence, you can then repeat the same with gradually improved coding schemes, including checksums and redundancy and message start / end codes. And then you can transmit a large number that has only two prime factors M and N followed by M lines of N Bits. </p>\n\n<p>If maths is a universal language it ought to be obvious to assemble the lines as \"black\" and \"white\" pixels in a 2D grid. We're now transmitting imagery. Whether we are perceived as intelligent or as moronic now depends on other factors far less definite than mathematical fact.</p>\n" }, { "answer_id": 36979, "author": "Callum Mcshane", "author_id": 18502, "author_profile": "https://worldbuilding.stackexchange.com/users/18502", "pm_score": 1, "selected": false, "text": "<p>A few years back, the SETI institute received what they thought was a signal from another intelligent species, it was a steady pulse of on/off at regular intervals, this turned out to be a neutron star (or quasar) that created the effect because it was spinning quickly. The principle, however, remains: the simplest signal you can send is something so regular in amplitude, frequency, and wavelength that it simply cannot be interpreted as background noise. However the signal is interpreted, it will always be shown to be extremely uniform; unlike most natural radiation. (excepting, of course, neutron stars)</p>\n" }, { "answer_id": 37037, "author": "Gianluca", "author_id": 16391, "author_profile": "https://worldbuilding.stackexchange.com/users/16391", "pm_score": 0, "selected": false, "text": "<p>You can send out pulses using the numbers of the Fibonacci sequence as length, with every pulse separated from the next by an interval represented by the first 100 prime number, then repeating it from the beginning, with all the time in tenths of a second</p>\n\n<p>So you have a transmission like:</p>\n\n<p>F1 P1 F2 P2 F3 P3 ...</p>\n\n<p>where Fn is the nth number of the fibonacci sequence and Pn is the nth prime number.</p>\n\n<p>So you send a 1/10 pulse, wait 2/20, send a 1/10 pulse, wait 3/10, send a 2/10 pulse, wait 5/10, send a 3/10 pulse and so on.</p>\n\n<p>The problem however is what frequency/encoding to use, since it's not obvious how an alien species communicate, but maybe the \"magic\" frequency of 1420 MHz (as used by Frank Drake) can be a good choice.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/36940", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/17255/" ]

[ { "answer_id": 37722, "author": "Schwern", "author_id": 760, "author_profile": "https://worldbuilding.stackexchange.com/users/760", "pm_score": 3, "selected": true, "text": "<p>Assuming you had a wing design that already worked (<a href=\"http://www.wired.co.uk/news/archive/2012-07/09/batman-cape-physics\" rel=\"nofollow\">Batman's cape will not</a>) and the poles are already sufficiently strong and rigid, this could work.</p>\n\n<p>Collapsible tent poles work by slotting the pole into a metal sleeve. There's also a bungie cord inside the pole to (lightly) pull the pieces together. The sleeve is typically stronger than the pole, as campers know tent poles tend to break at the pole, so in terms of strength there's no problem replacing complete poles with collapsible ones. It will add some weight and reduce flexibility, but it should be manageable.</p>\n\n<p>Rather than joining the poles using magnets, it would be wise to retain the sleeve and cord system. It's proven tech, and your wing won't fall apart if you lose power. Where magnets come in is to pull the pole into the sleeve and ensure it's firmly seated. With some clever shaping of the ends of the poles and sleeves (funnel tip for the sleeve, round tip for the pole), this might be done reliably... though getting the complex shapes and joints necessary for a collapsible airfoil will be tricky. However if you lose power you lose tension and a pole may slip out of its sleeve. Perhaps you could have a locking mechanism, but it would also have to unlock.</p>\n\n<p>What would be even more reliable is to cause the bungie cord to contract pulling the ends of the poles into the sleeves. This could be a simple mechanical operation pulling on the cord at the middle of the pole, or by separating two pole pieces and inserting a spacer.</p>\n\n<pre><code>Poles at start =====*--=====*--=====*--=====*--=====*--=====\n\nOpen a gap =====*=====*=====*------------=====*=====*=====\n\nInsert spacer =====*=====*=====*-=========*-=====*=====*=====\n\nRelease tension =====*=====*=====*=========*=====*=====*=====\n</code></pre>\n\n<p>To collapse, remove the spacer releasing the tension on the cord.</p>\n" }, { "answer_id": 37744, "author": "Tim B", "author_id": 49, "author_profile": "https://worldbuilding.stackexchange.com/users/49", "pm_score": 0, "selected": false, "text": "<p>Having the cape go into that shape is certainly possible, although you would need a substantial amount of electric power if you wanted it to be strong. Assuming you wanted to use the cape to fly (or even glide) though then you have a bigger problem.</p>\n\n<p>Or a smaller problem.</p>\n\n<p>The cape isn't big enough. Look at <a href=\"https://en.wikipedia.org/wiki/Wingsuit_flying\" rel=\"nofollow\">wing suits</a> for example. The terminal velocity wearing a wing suit is still 110mph, you can fly around nicely but you certainly can't land.</p>\n\n<p>A hang glider or parachute needed to land at a more manageable and survivable speed is much larger than Batman's cape.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/37719", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/18654/" ]

[ { "answer_id": 38521, "author": "Separatrix", "author_id": 16295, "author_profile": "https://worldbuilding.stackexchange.com/users/16295", "pm_score": 3, "selected": false, "text": "<p>If they're subterranean they wouldn't disturb the grass and trigger the toxins the way a passing surface animal would. Also the air in their tunnels would have been filtered by passing through the relatively porous ground above them making it potentially safe to breathe. </p>\n\n<p>Or:<br>\nIf they've evolved around the bonegrass they're largely immune, but they do need to take a nap if a large animal triggers a lot of toxin near an open tunnel. Much like the <a href=\"http://news.nationalgeographic.com/news/2013/10/131024-grasshopper-mice-scorpion-venom-pain-animals-science/\">grasshopper mouse</a> and the scorpion, or the <a href=\"https://en.wikipedia.org/wiki/Mongoose\">mongoose</a> with snake venom.</p>\n\n<p>_{\nOnce you start introducing other creatures also living on the bonegrass victims then your fields are going to need to be quite bloodthirsty.\n}</p>\n" }, { "answer_id": 38522, "author": "Tim B", "author_id": 49, "author_profile": "https://worldbuilding.stackexchange.com/users/49", "pm_score": 3, "selected": false, "text": "<p>They would most likely arrange their burrows similar to how terrestrial burrowing creatures do so that there is enough air-flow through them to survive. Perhaps they even have \"breather\" tunnels that extend away from the grass fields and allow fresh air to flow in even when the grass starts spreading toxins.</p>\n\n<p>The moles could have a hibernation-like state when oxygen drops too low or toxin levels too high. Effectively they become dormant and conserve their oxygen until the event passes and the fresh air from their breather tunnels wakes them up again to continue their lives.</p>\n" }, { "answer_id": 38524, "author": "Murphy", "author_id": 4750, "author_profile": "https://worldbuilding.stackexchange.com/users/4750", "pm_score": 6, "selected": true, "text": "<p>For mammals... this could be a problem. </p>\n\n<p>A pretty average human being(62 kg) uses about 550 liters of pure oxygen per day(at sea level pressure).\nSo call it 9-ish litres per kg. </p>\n\n<p>A single naked mole-rat is about 35 grams. </p>\n\n<p>A colony is 20 to 300 individuals, with an average of 75.</p>\n\n<p>So an average colony of 75 might weigh in at about 2.5-3.0 Kg of mammal-flesh.</p>\n\n<p>They're extraordinarily long-lived for a rodent of their size (up to 31 years).</p>\n\n<p>Small rodents tend to use more, not less oxygen by weight (more active) but let's make some generous assumptions: \nLet's assume they use 10% as much oxygen by weight as humans. </p>\n\n<p>Your colony still needs 2.7 litres of pure O2 per day or 13.5 litres of normal air (20% oxygen) assuming they use it perfectly somehow. </p>\n\n<p>From this we can conclude that this is not a workable strategy:</p>\n\n<blockquote>\n <p>weak or old fleshmoles are driven to the surface, where they take a huge lungful of air, become paralyzed (neatly plugging the hole and removing the paralytic agent from the air they breathed in), then are dragged back down and rapidly consumed by their brethren.</p>\n</blockquote>\n\n<p><strong>They live too long, their lungs are too small and it's just not gonna work. They couldn't provide a tenth of the air needed even with generous assumptions.</strong> </p>\n\n<p>But if I remember correctly you talked about how your victims are left alive. The air in their lungs is not a good option, it's contaminated by the spores just like the outside air.</p>\n\n<p><strong>So let's try another option.</strong> </p>\n\n<p>Again, let's steal from real life organisms. </p>\n\n<p><a href=\"https://i.stack.imgur.com/p4HGb.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/p4HGb.jpg\" alt=\"Parasite\"></a></p>\n\n<p>Real paracites need oxygen, how do they get it? </p>\n\n<p>They absorb it from their host, often directly from the blood. \nYour victim has a perfectly good set of lungs and they're going to be alive for quite a while (longer if nothing burrows into their lungs).</p>\n\n<p>So your moles could be adapted to burrow into the flesh (careful not to cause lethal harm), find big arteries close to the heart/ lungs where it's rich in oxygen and then filter lots of oxygen from the blood and to somehow feed it back to their kin bellow using the victim as a living oxygen filter. </p>\n\n<p>Perhaps, if desperate and lacking prey for a long long time, the moles might sacrifice one of their own to use the same trick: one of them breathes while the others filter oxygen from its blood below. </p>\n\n<p>This leads on to some grim conclusions. </p>\n\n<p><strong>It's going to be in the moles' interest to keep the victim alive for as long as possible.</strong> </p>\n\n<p>Too much bonegrass growing up through them will kill too fast. So the moles could be chewing away the roots of some of the young bonegrass to keep it from killing the victim quickly. The bonegrass wants to kill you fast. The moles want to keep you alive for as long as possible. </p>\n\n<p><strong>Indeed, weirdly, if they have access to lots of calories but not much oxygen it could be in their interest to feed sugars into your blood while taking oxygen out.</strong> </p>\n\n<p>To stop you dying from infections they might even release antimicrobials as they chew into your flesh. </p>\n\n<p>(Additional reason for people to enter the bonegrass: fleshmole teeth could have \"venom\" sacks containing potent antibiotics)</p>\n\n<p>They also might carefully feed on fatty tissue, avoiding blood vessels, again to keep their victim alive for as long as possible. </p>\n\n<p>There are some far more practical options for filtering air... but they're not as fun as absorbing it from the blood of still living hosts. </p>\n\n<p>Now, there's also another possible use for your victim. A nice warm place for baby fleshmoles and similar parasites to grow.</p>\n\n<p>Here's a species of wasp which lays its eggs inside still-living hosts. </p>\n\n<pre><code>♫It lands on caterpillars \nIt lays it's eggs inside\nTo make sure that the meat's fresh\nIt keeps the things alive\n\nAll things bright and beautiful...♫\n</code></pre>\n\n<p><a href=\"https://i.stack.imgur.com/TF9N1.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/TF9N1.jpg\" alt=\"Keep the meat fresh\"></a></p>\n\n<p>Some wasps have an even more disturbing effect on their victims. </p>\n\n<p>Once the babies have eaten their way out through the hosts flesh the host's behavior has been altered by the parasite and the caterpillar spends the remainder of its life trying protecting the parasites. </p>\n\n<p><a href=\"https://youtu.be/7UkDMrG6tog?t=8\" rel=\"nofollow noreferrer\">https://youtu.be/7UkDMrG6tog?t=8</a></p>\n\n<p>So for added creepiness, imagine someone getting paralyzed, fleshmoles eat through their flesh but before they die the wind changes direction, the amount of paralytic poison decreases and they make their escape. </p>\n\n<p>They have a few baby fleshmoles under their skin but rather than wanting to cut them out and destroy them the host feels a strong compulsion to care for them because the fleshmoles have released a hormone that hijacks the normal instincts to protect your children. </p>\n\n<p>Someone is rescued from the bonegrass and the fleshmoles. The town rejoices. But the following week they're found carrying around a blanket filled with a squirming mass of infant fleshmoles treating them like a baby and feeding them chunks of raw meat.</p>\n" }, { "answer_id": 38525, "author": "Aarthew III", "author_id": 18654, "author_profile": "https://worldbuilding.stackexchange.com/users/18654", "pm_score": 2, "selected": false, "text": "<p>Since you mentioned CO₂, I'm guessing you are using <a href=\"https://worldbuilding.stackexchange.com/a/38493/7129\">this answer</a> from Tim B. </p>\n\n<p>If so, then think of dolphin moles. To store up large stores of CO₂ while still being able to breathe may require the bone grass to go on a crazy oxygen converting frenzy. This would create an abundance of outside oxygen while the plants stored up CO₂. Only during this time do the moles appear for air. The bone grass has learned to ignore the moles as the miles always disappear before they can pump out sufficient CO₂. The mole dolphins don't have to surface for a while and are alive and well. If you want the moles to tunnel into people's lungs, it would be a bit impractical as the person collapsed because it has too much CO₂... Perhaps this is what the mole eats? </p>\n\n<p>Also just a side note. The CO₂ could be used as a defense against fire. Whenever you try to light the bone grass, it suffocates the fire!</p>\n" }, { "answer_id": 38549, "author": "Joel", "author_id": 13778, "author_profile": "https://worldbuilding.stackexchange.com/users/13778", "pm_score": 1, "selected": false, "text": "<p>This is actually a real issue for termites. I know someone who studies this question - <a href=\"http://news.harvard.edu/gazette/story/2015/09/how-termites-ventilate/\" rel=\"nofollow\">How do termites ventilate their mounds</a>? After all, a bunch of termites live underground. I can't find a source now, but if I recall the biomass of a termite colony is comparable to that of a sheep - not warm blooded, but still that's a large O2 requirement.</p>\n\n<p>Let's think about the pollen. It gets carried by the wind, but it is heavier than air, so it doesn't get very high. In fact it's in the evolutionary interests of the grass to select density (and shape) such that the concentrations are highest in the level of the terrestrial animals walking around. So the pollen cloud won't get much over 6 feet high.</p>\n\n<p>Your moles have a few big termite mound-like structures in the middle of the field. The mounds exchange air from within the chamber and above the layer where the pollen lies. They can even come to the top, meerkat like, and look around for where some victim has fallen. Then they tunnel over to it.</p>\n" }, { "answer_id": 38566, "author": "Xandar The Zenon", "author_id": 16736, "author_profile": "https://worldbuilding.stackexchange.com/users/16736", "pm_score": 1, "selected": false, "text": "<p>Perhaps instead of them getting the oxygen from only their victims, they also have some kind of filter in their lungs that filters out CO₂ and let's only oxygen in. However, over the life time of the mole, the filter degrades, eventually to the point where it cannot keep itself alive. Then it is out out to pasture.</p>\n\n<p>But why skip out in a good meal? More oxygen can be found in the blood of their victims, which means they don't have to waste filters during feeding time. Which means eat the lungs and arteries last, so they can provide you with oxygen while you burrow through the victim's living flesh. Even if the creature hAs inhaled a lot of CO₂, it still takes less filtering and is nice and yummy for the flesh moles. And when their brethren become to old to efficiently filter out the CO₂, it is time to feed...</p>\n\n<p>Because fo such creatures you just can't get enough oxygen by simply draining it from the living blood.</p>\n" }, { "answer_id": 38580, "author": "Kyle", "author_id": 18880, "author_profile": "https://worldbuilding.stackexchange.com/users/18880", "pm_score": 1, "selected": false, "text": "<p>Your beasts' should be a sustainable ecosystem for bacteria that make O² out of byproducts produced by your beasts.</p>\n\n<p>There's a bacterium that does that, it's called <a href=\"https://www.mpg.de/621120/pressRelease201003241\" rel=\"nofollow\"><strong><em>Methylomirabilis oxyfera</em></strong></a>, it eats methane and oust oxygen, perhaps this kind of bacteria can live in your beast's digestive system consuming methane and producing oxygen so your beast would fart oxygen and breathe it in :D</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/38510", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/9887/" ]

[ { "answer_id": 38789, "author": "Philipp", "author_id": 224, "author_profile": "https://worldbuilding.stackexchange.com/users/224", "pm_score": 3, "selected": false, "text": "<p>It's impossible for a planet of that size to exist in a universe with our physical laws.</p>\n\n<p>A planet with a size of 5.0x10^30m would have a volume of 5.24×10^92m³. Assuming the same density as Earth (5514 kg/m³), this planet would have a mass of 2.89×10^96 kg.</p>\n\n<p>The surface gravity would be 7.7×10^24 m/s².</p>\n\n<p>The escape velocity on the surface would be 3×10^19 times the speed of light, and when you have an escape velocity higher than the speed of light, you have a black hole (in this case the event horizon would have a radius of 4.29×10^69 meters, if you really want to know).</p>\n\n<p>I'm sorry, but your mega-planet isn't going to work in this universe, unless you drastically reduce the gravity constant of the universe or construct the planet from some unobtanium material with a ridiculously low density.</p>\n" }, { "answer_id": 38795, "author": "Schwern", "author_id": 760, "author_profile": "https://worldbuilding.stackexchange.com/users/760", "pm_score": 4, "selected": false, "text": "<p>First, a lot of reasons why this won't work in our universe. Then, an interesting solution. Finally, why the exercise is pointless.</p>\n<hr />\n<p>5.0x10³⁰ meters is about 10,000 times larger than <a href=\"https://en.wikipedia.org/wiki/Observable_universe\" rel=\"nofollow noreferrer\">the observable universe</a>. That doesn't mean it's <em>larger</em> than the universe, but it does mean that an event on one point of the planet has only had enough time to reach 1/10,000th of the rest of the planet. <em><strong>There has not been enough time in the whole universe for light (and thus anything) to go from one side of the planet to the other</strong></em>. This means there hasn't been enough time for gravity to form it into a sphere, the gravity from one side has not had time to affect the other. One has to wonder how this planet formed in the first place.</p>\n<p>Either your universe is very, very, very, very much older than ours, or causality (ie. the speed of light) propagates much, much, much, much faster. Both of these have serious consequences. All sorts of important equations depend on the speed of light, so I'd leave that alone. Make your universe tremendously old. At least 10¹⁵ years.</p>\n<hr />\n<p>Then there's the question of <em><strong>where this planet is getting its light and heat from?</strong></em> A scaled up star would require an even older universe to be given time to form. Then that requires that your planet rotates. With a circumference of 3.14x10³¹m, even the smallest rotation will have the surface dwellers moving at the speed of light. There's no way to have anything like a normal day/night cycle, even light will take 10²³ seconds to get around the surface. One side bakes, the other side freezes.</p>\n<p>An alternative heat source would be better. Our universe has no edge, but perhaps your universe does and it produces light and heat as it gobbles up whatever is &quot;outside&quot;. Your planet is in the center of the universe and the surrounding edge is like being inside a spherical heat lamp. Your planet would be in perpetual daytime.</p>\n<p>Be careful not to cook the planet by adding to the overall energy of your universe.</p>\n<hr />\n<p>Then there's gravity. <a href=\"https://worldbuilding.stackexchange.com/a/38789/760\">@Philipp already covered that well</a>, can it be solved? One solution is to mess with the gravitational constant. This will severely alter the makeup of the universe on a large scale, but I'd say that's already happened.</p>\n<p>How much smaller should <code>G</code> be? We'll solve g = Gm/r² for G and plug in an Earth <code>g</code> of 9.8 m/s².</p>\n<pre><code>g = Gm/r^2\ngr^2 = Gm\ngr^2/m = G\n</code></pre>\n<p>Plug in your numbers... <code>r = 5x10^30 m</code>, <code>m = 2.89×10^96 kg</code> from @Philipp, <code>g = 9.8 m/s^2</code>. We get a G of <code>8.4x10^-35 N⋅m^2/kg^2</code> which is 24 orders of magnitude lower than in our universe. Gravity is already very weak, in your universe it's all but undetectable.</p>\n<p>Such weak gravity would make your planet take even longer to form. It's questionable gravity could ever form a planet given how much stronger all the other forces would be.</p>\n<hr />\n<p>An alternative way to solve the gravity problem is to <em><strong>make the planet hollow</strong></em>. This reduces its mass which reduces its surface gravity. The surface gravity of a hollow planet is a bit harder to calculate, so let's move on to the next problem: how did this shell form and how has it not collapsed?</p>\n<p>One possible solution is to put a small black hole in the center of the planet. The &quot;edge&quot; of the universe surrounding the planet is the inverted surface of a white hole. In effect, <em><strong>the planet is both outside and inside a black hole</strong></em>. <a href=\"https://en.wikipedia.org/wiki/Accretion_disk\" rel=\"nofollow noreferrer\">Material falling into the black hole heats as it falls</a>. This heated material comes out the white hole and creates the warm glow in the sky which heats the planet. As the planet is slowly eaten from the inside, a fine rain of material is falling on the surface from the white hole surrounding it.</p>\n<p>This is its geological cycle of renewal, matter on the surface is eventually buried and sinks down to be eaten by the black hole. That same matter falls from the white hole which then rains down on the surface to start the cycle again. Like our own geological cycle, this would be unobservably slow to humans.</p>\n<p><em><strong>The surface of the planet is a <a href=\"https://en.wikipedia.org/wiki/Standing_wave\" rel=\"nofollow noreferrer\">standing wave</a></strong></em> in this flow of particles: a cosmic traffic jam.</p>\n<p>This allows your planet without altering gravity or the age of the universe. <em><strong>This is an entirely different universe looping forever</strong></em>.</p>\n<hr />\n<p>Even this leaves the basic question of <em><strong>why have a planet so large the inhabitants don't even know they're on a sphere</strong></em>? At your scale the planet would appear to be flat. The horizon would not appear to curve, ships would not sink over the horizon because they could never reach it. There would be no round, orbiting bodies to hint at the shape of the planet because a planet that large with Earth's surface gravity can't hold on to things in orbit.</p>\n<p><em><strong>Your characters would think they live on a flat, infinite plane</strong></em> and there would be little they could do to prove otherwise. Your sphere is so big they could travel in any direction and never have evidence otherwise. Even at the speed of light for 100 years they'd have gone 10¹⁸ m or 1/10¹³ the circumference, not enough to detect a curve.</p>\n<p>From a storytelling perspective, <em><strong>what does living on a giant sphere indistinguishable from a flat, infinite plane gain you</strong></em>?</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/38787", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/10544/" ]

[ { "answer_id": 38922, "author": "John Robinson", "author_id": 13430, "author_profile": "https://worldbuilding.stackexchange.com/users/13430", "pm_score": 1, "selected": false, "text": "<p>Gonna answer your two questions in reverse order.</p>\n\n<p>The main thing I'd say you have left to address is how the CMF is structured.</p>\n\n<p>Who gives the orders? It's outside any sort of government, so it would have to have an internal command chain (democracy doesn't really work when it comes to heat-of-the-moment decisions), but how is that originally established, before the CMF is well-established and they can promote people based on merit? Do the people contributing the most get to lead? Do the people closest to the conflict (with theoretically the most experience) get to lead? Who decides promotions, anyway, especially into the top leadership positions? The larger, more powerful states likely aren't going to like the idea of someone from a smaller/weaker state leading the armies, and/or would want their own families to be in safer positions, so what sort of checks would be in place to prevent bribery and corruption?</p>\n\n<p>As far as it actually working.... I can see it working in the short term. But in a few generations, I can see the families of the center states getting complacent, wondering why they're paying and sending their children to fight against this \"phantom threat\" that isn't actually threatening them.</p>\n\n<p>Then there's also the problem of the CMF being the only military power in the West. What's to stop some ambitious CMF leader from seizing power (the analogous Julius Caesar to OP's Alexander)? It would certainly happen eventually, once the CMF starts to realize that they're the only ones with the weapons, so there's no point in paying for services anymore when they could just take over and get things for free.</p>\n" }, { "answer_id": 38923, "author": "user58697", "author_id": 2838, "author_profile": "https://worldbuilding.stackexchange.com/users/2838", "pm_score": 1, "selected": false, "text": "<p>Participants shall not disband their own forces. There must be something to balance the CMF. The Treaty shall have provisions similar to Second Amendment (as in well organized militia and the right to bear arms).</p>\n\n<p>The overall structure of CMF seems to work best if the Eastern states contribution is mostly military, while for safer Central it is mostly financial. Centrals however must be ready to mobilize their National Guards shall a full-scale conflict emerge, in which case this becomes a usual (temporary) military coalition.</p>\n\n<p>In no circumstances may army be allowed to perform police duties.</p>\n\n<p>PS: As of why Centrals would agree to contribute, there is a saying (attributed to Napoleon), that <em>a nation which doesn't feed its own army will feed an alien's one</em>.</p>\n" }, { "answer_id": 38936, "author": "Lensman", "author_id": 19334, "author_profile": "https://worldbuilding.stackexchange.com/users/19334", "pm_score": 2, "selected": false, "text": "<p>I see an analogy with the alliance of Greek city-states in the Persian Wars (499 B.C. to 449 B.C.). That also was a military alliance formed to fight off a foreign invader -- the Persians -- which was much too powerful for any one Greek city-state to resist. Otherwise, the Greeks were a pretty fractious bunch... as was demonstrated not long afterward in the Peloponnesian War (431–404 B.C.). The lack of clear borders between States, which you describe, also seems to fit the city-state model.</p>\n\n<p>The only real problem I see, which user58697 already pointed out, is your stipulation that the States forming the alliance would disband their own military forces. That would be equivalent to surrendering sovereignty... but the entire purpose of forming such an alliance would be so the individual States could preserve their sovereignty. So, not gonna happen.</p>\n\n<p>The alliance of the Greek states against Persia lasted little longer than the threat did. Likewise, I doubt in your scenario it's realistic for the alliance, or confederation or whatever you want to call it, would last very long once the immediate threat was defeated.</p>\n\n<p>So to make your scenario work, the external threat must be something that has to be repeatedly fought off. That would create a long-term confederation, which in time would perhaps grow into something more (as the original Confederation of the United States soon became a Federation). Perhaps there's a more powerful empire in that direction, one that has a hard time extending its reach to the lands in question, so doesn't invade often... but when they do, the military threat is formidable. I can think of at least one historical precedent for that: China (or more specifically, the Mongols) vs. Japan. There were two major Mongol invasions of Japan, but both failed.</p>\n" }, { "answer_id": 38997, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 3, "selected": true, "text": "<p>Two historical examples come to mind here.</p>\n\n<p>The first example is the Delian League, which has been alluded to in other answers. Formed by Athens as a reaction to the Persian Wars, the Delian league had various maritime powers band together and pool ships and funds to protect the league and the rest of Greece from any attempt by the Persians to invade again. Very soon, the Athenians simply requested money from the other league members, who were happy to oblige for the most part, since owning a navy is very capital and labour intensive. However, when Athens decided to take full control of the League's treasury, the other members discovered that <em>not</em> having a Navy also means not having a vote.</p>\n\n<p>Athens became an Empire in all but name, and the fear of Athenian Power lead to the Peloponnesian Wars.</p>\n\n<p>During the 1400's, Italian City States tended to alternate between citizen militias and hiring professional mercenary companies (Condottieri). The Condottieri quickly discovered that they could play various parities against each other, accept payments to <em>not</em> participate in wars or switch sides and otherwise make planning difficult to impossible for the City State authorities (or even overthrowing them if they didn't pay up according to the terms of the contract)</p>\n\n<p>So the essential point is that the hand that holds the sword eventually becomes the hand which holds the gold as well, and also the whip hand giving the orders. In your scenario, the central principalities will quickly discover that what seems to be an unrooted mercenary army is now calling the shots, and their tax revenues are not being spent for the benefit of the citizens of the central provinces.</p>\n\n<p>How this plays out in the end is probably similar to the end of the Italian city states. Weakened by constant internal divisions and shifting alliances, they were unable to present a united front against foreign invaders (one reason Leonardo da Vinci ended up in the French court, for example). The coalition army, not being \"rooted\" and existing on tax contributions from a disarmed population, becomes predatory against the very people whom it is supposed to protect, and falls apart when directly challenged by an outside force.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/38921", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2746/" ]

[ { "answer_id": 39011, "author": "o.m.", "author_id": 6402, "author_profile": "https://worldbuilding.stackexchange.com/users/6402", "pm_score": 3, "selected": false, "text": "<p><a href=\"https://en.wikipedia.org/wiki/Deforestation_during_the_Roman_period\">Deforestation</a> is a big issue. Not just in the Mediterranean but also in central Europe.</p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Monoculture\">Monoculture</a> is another issue.</p>\n\n<p>Unnatural selection through animal <a href=\"https://en.wikipedia.org/wiki/Animal_husbandry\">husbandry</a>.</p>\n\n<p>Removal of other <a href=\"https://en.wikipedia.org/wiki/Apex_predator\">apex predators</a>.</p>\n\n<p>While a civilization might try to be careful and environmentally conscious, humans would leave their mark -- killing other predators, growing more efficient food.</p>\n" }, { "answer_id": 39018, "author": "Separatrix", "author_id": 16295, "author_profile": "https://worldbuilding.stackexchange.com/users/16295", "pm_score": 3, "selected": true, "text": "<p>I was watching a BBC history documentary about the Romans in Britain earlier today and words along the lines of</p>\n\n<blockquote>\n <p>History is not like science, when you change one variable in history the others don't stay the same. It's all linked, change anything and there's such a massive cascading effect that it's impossible to say what may have happened.</p>\n</blockquote>\n\n<p>Here are a couple of the key aspects:</p>\n\n<p><strong>Extermination of the mega-fauna</strong>. This is still uncertain but it's considered likely that human hunters destabilised the populations and effectively exterminated a lot of these animals.</p>\n\n<p><strong>Deforestation</strong>. This is a bigger issue than previously mentioned. Not just Central Europe and the Near East but from Britain, which was solid forest, all the way across Russia.</p>\n\n<p><em>With just these two differences the world would be a place unrecognisable to us.</em></p>\n\n<p>but let's consider the way the things we affect, affect the world in their turn.</p>\n\n<p>Elephants knock over trees, fewer elephants, more trees. <br>\nWild herbivores eat young shoots, also keeping down new trees, <a href=\"http://oregonstate.edu/ua/ncs/archives/2003/oct/scientists-wolves-helping-rebalance-yellowstone-ecosystem\" rel=\"nofollow\">fewer predators, fewer trees, more erosion</a>.<br>\nBeavers build dams, meaning more shallow lakes, lower speed flow on the rivers, less erosion, but we killed all the beavers and cut down the trees that would bind the banks, so even the rivers don't follow the courses they would without us. </p>\n\n<p>A few other things we've done.<br>\nDraining the wetlands, this was even done by the Romans.<br>\nExtermination of predators, the Iberian Lynx is almost gone, the Eurasian Lion has been gone a long time. The Sabertooth Cat? Not known if this was humans. Marsupial Lion, believed to be humans.</p>\n" }, { "answer_id": 39022, "author": "EvilSnack", "author_id": 19460, "author_profile": "https://worldbuilding.stackexchange.com/users/19460", "pm_score": 2, "selected": false, "text": "<p>Not just deforestation, but also de-deforestation. Before humans got the ability to fight wildfires (not all of which are started by humans), they burned out of control. Now we can put them out or create firebreaks.</p>\n\n<p>The other major change to the landscape, courtesy of humanity, are dams and other hydrological projects.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/39010", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/18753/" ]

[ { "answer_id": 39307, "author": "Burned", "author_id": 15423, "author_profile": "https://worldbuilding.stackexchange.com/users/15423", "pm_score": 2, "selected": false, "text": "<p>It is in the sellers' interest to not be wiped out by the same issue that will wipe out everyone else so suddenly, so they have no incentive to raise the price beyond the point where the plan would be put into place. However, if the high demand means their inexpensive way of making something is not sufficient, their costs will increase and their prices will likely also increase. Finally, if the solution is nonobvious, the society may have a need to offer a strong incentive for the creation of that solution, which could be in the form of a high reward and price paid for a solution. (The money is pretty meaningless if live on Earth were wiped out, though).</p>\n" }, { "answer_id": 39310, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 3, "selected": false, "text": "<p>Ideally, the suppliers would provide the necessary materials at a reasonable price.</p>\n\n<p>In all likelihood though, given the nature of humanity and the inability of the entire race to work together harmoniously (even if it would mean utter extinction), the price of the necessary components would skyrocket and a very select, very rich stakeholders would more than likely demand exorbitant compensation or concessions as the age old question of \"What do I get out of it?\" is raised.</p>\n\n<p>More specifically, it would most likely become a case of - \"If these scientists can avoid the catastrophe, why should I not monopolize the solution and charge for the privilege? After all, it's only fair that I'm properly compensated for my time and material, and those that really want to be saved will find a way to pay for it?\"</p>\n\n<p>I don't hold much hope for humanity.</p>\n" }, { "answer_id": 39312, "author": "Monty Wild", "author_id": 75, "author_profile": "https://worldbuilding.stackexchange.com/users/75", "pm_score": 4, "selected": false, "text": "<p>In such a situation of dire global emergency, it is entirely likely that governments would switch to a command-economy mode, meaning that if the vendors of the goods necessary to save the world did not voluntarily reduce their profit margins, then governments would take steps to make it a <em>legal necessity</em> for the vendors to supply the goods at cost.</p>\n\n<p>In the event that the vendors attempted to decline to supply the goods entirely, the vendors' businesses could be seized and nationalised, and if necessary any persons with necessary trade secrets could be... <em>compelled</em> by whatever means necessary to divulge those secrets for the good of the entire world.</p>\n" }, { "answer_id": 39314, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 6, "selected": true, "text": "<p>We can see what happens already. It happens daily in business. Let's get to work</p>\n\n<blockquote>\n <p>However, there is one (and only one) option that can save the world, if we can get the funding.</p>\n</blockquote>\n\n<p>This phrasing indicates either an absurdly unlikely circumstance, or a partial picture. It is very unlikely that there is actually only one solution. For example, let's assume the problem is trivial: \"put these 7 numbers in order: 1, 3, 5, 7, 4, 13, 20.\" There are many solutions such as</p>\n\n<ul>\n<li>Swap the 5 and the 7. Then swap the 7 and the 4</li>\n<li>Swap the 4 and the 5. Then swap the 5 and the 7.</li>\n<li>Jumble the whole group up, put it through StackSort (<a href=\"https://xkcd.com/1185/\">read the image's tooltip</a>). Then go get a drink of water.</li>\n</ul>\n\n<p>And so forth. The actual number of degrees of freedom in the problem is quite staggering, especially when you consider the question of \"what happens next after we succeed?\" Are we thirsty? Maybe the plans that involved drinking water are good!</p>\n\n<p>What you more likely are describing is a case where there is a hard requirement: thou shalt do X, or the entire planet dies. There may be many implementations of X which function, although your word choices indicate that most courses of action will not satisfy X.</p>\n\n<p>Thus the goal of every rational actor in this scenario is two fold:</p>\n\n<ul>\n<li>Ensure the survival of the planet</li>\n<li>Ensure that, after the planet is saved, their position is as ideal as possible.</li>\n</ul>\n\n<p><em>Alternatively, <a href=\"http://www.schlockmercenary.com/2000-08-04\">in mercenary order</a> of priorities: 1) get paid. 2) live long enough to enjoy getting paid.</em></p>\n\n<p>Now this works great as long as everyone has perfect information. However, we don't. Its entirely possible that we may do our part, but someone else slacks off. In this case, we may be obliged to do even more work to save the planet, making up for the slackers. Now we're getting somewhere. This sounds a lot like a traditional Prisoner's Dilemma. This is a dilemma where two individuals (we'll call them Alice and Bob) commit a crime. There's not enough evidence to convict either one, so they are called in for questioning. There, they are provided with a dilemma:</p>\n\n<blockquote>\n <p>If you agree to testify against your partner, your testimony plus the evidence will be enough to convict him. This same deal is being offered to your partner. We admit, we don't have enough evidence to convict either of you without the other person admitting you two both did it, so here's the deal. If neither of you testify, we're going to convict both of you on a lesser crime, and give you both 1 year in jail. If either of you testifies against the other, they can go scott free, while the other person spends 9 years in jail. If both of you agree to testify, you'll both get convicted, but we'll only sentence you to 3 year.</p>\n</blockquote>\n\n<p>The logic diagram looks like this</p>\n\n<pre><code> Alice\n Quiet Testifies\n +-------------+--------------+\n Quiet | Alice: 1yrs | Alice: 0yrs |\n | Bob: 1yrs | Bob: 9yrs |\nBob +-------------+--------------+\n Testifies | Alice: 9yrs | Alice: 3yr |\n | Bob: 0yrs | Bob: 3yr |\n +-------------+--------------+\n</code></pre>\n\n<p>The dilemma forms because the best course of action is to both stay quiet. However, if you both realize this, you have to worry that your partner might try to decrease their own sentence by ratting you out. Thus, you must be conservative and testify. The result of the dilemma is that the most rational course of action is to testify, and both of you serve 3 years, even though you could have gotten away with just 1.</p>\n\n<p>We can draw an analogy to our example. Instead of \"Quiet\" and \"Testify,\" we can \"Conform\" to what is best for the planet, or \"Defect\" and do what is best for us</p>\n\n<pre><code> Alice\n Conform Defect\n +---------------------+--------------------+\n Conform | Everyone lives | Everyone lives |\n | Everyone is even | Alice makes money |\nBob +---------------------+--------------------+\n Defect | Everyone lives | Everyone dies |\n | Bob makes money | Everyone is unhappy|\n +---------------------+--------------------+\n</code></pre>\n\n<p>Obviously this pattern has more players, but the basic story with two players is enough to understand what is happening. The correlary to the prisoner's dilemma suggests that everyone gets greedy, then dies.</p>\n\n<p>However, that's not the end of the story for this dilemma. You see, if it was that simple, being a prosecutor or Attorney General would be a piece of cake! In reality, this doesn't work. We find that criminals refuse to snitch on each other with <em>remarkable</em> consistency. There's clearly a second force going on in the real world! From talking with criminals, we find the answer is obvious. A snitch doesn't get very far in the crime world. If you snitch, you've basically ended your career as a criminal. Nobody will work with a snitch, and everybody knows it. So this adjusts the logic of both Alice and Bob in our example. Both of them know the other person knows that snitches will be brutally punished. They may avoid a few years of jail time, but the trade isn't worth it. This knowledge is enough to get both Alice and Bob to conform, refusing to testify against their partner, and both get a year in prison.</p>\n\n<p>Likewise the global \"essence\" will likely rise up to try to find ways to ensure conformance. This will likely be in the form of governments putting dramatic pressure on companies to not defect in the name of profit. Sure, they can defect, but it might be the straw that broke the camel's back, causing the earth to die, and even if someone else did cover for them, they'd be labeled as a profiteering pile of filth and nobody will work with them, nor accept their money.</p>\n\n<p>The real question is not whether there will be defectors, but whether second order effects will creep in. At some point, when you're leaning on a company to do something \"for the common good\" rather than \"for your own profit,\" you can lean hard enough that the company gives you the middle finger, and folds up instead. The challenge for the government is to find ways to put pressure on the companies without causing them to fold up.</p>\n\n<p>There's another related experiment that has been done, involving two parties. Each party is assigned a random role. The first party is given two envelopes and some money, say $100. They are told to divide the money up between the two envelopes. One is money they will keep, and the other is kept by the second party. The second party is then permitted to look at the distribution of cash, and make a choice. They can either take their money, and the first person keeps theirs, or they can refuse it, and the first person gets nothing.</p>\n\n<p>The game theory logic for player one is simple. The first person's goal is to get as much money as they can, without causing the second player to defect. If they defect, nobody gets any money. The second player's logic is theoretically easy: just take the money, you always profit. However, if the first player knows this, they may only leave $1.</p>\n\n<p>This scenario is not well described in game theory. You actually need drama theory to make sense of the results. However, the results are easy to spot. In America, the most common result was a 50/50 split. If the first person tried to take more money, such as a 90/10 split, the second person would punish them by making sure nobody gets money.</p>\n\n<p>In some African nations, the result was different. The first player would choose 90/10, and the second player would accept. When asked why, the answer would be \"because \\10 is better than \\$0, and if I was in the first player's position, I'd have gotten to have the $90 anyways.\" In some groups, the split was actually quite arbitrary. It was found these groups were known for sharing everything as a group. It really didn't matter if the split was 50/50 or 90/10, they were going to pool the money later once both parties got back together!</p>\n\n<p>So this is the stage for where your question really ends up. Large powers like governments will put pressure on the companies to band together and do things for the common good. The amount of pressure they can put on the companies before they defect depends on the culture.</p>\n\n<p>So now we get back to the original issue of many solutions to the problem. The more solutions there are, the less pressure will be needed to ensure enough conformance to survive. As the number of solutions get smaller, more pressure will be needed, causing more companies to defect. At some point, that can be the end of humanity. However, we cannot know one way or another without a very lengthy exploration of exactly what scenario we are in, and what solutions present.</p>\n" }, { "answer_id": 39321, "author": "subrunner", "author_id": 19096, "author_profile": "https://worldbuilding.stackexchange.com/users/19096", "pm_score": 3, "selected": false, "text": "<p>I completely agree with Monty Wild that for a short-term project seizure of resources would be the probable outcome. </p>\n\n<p>Two issues though that might throw a wrench into your 'save-the-world' project:</p>\n\n<ul>\n<li>Since when is there only 1 scientific opinion? I thought there were at least 3: the world is going to end soon - the world is going to end next century - the world is not going to end. Yes, sure, the Flat Earth society (thankfully) gets laughed at, but what about the climate change issues? Does the climate change or does it not? Also, will your population believe the scientists (so that your politicians get the support to push such a large-scale project through)?</li>\n<li>As long as your potential DoomsDay is more than two decades away, I think you're pretty much SOL. Humans really aren't good at planning on such long terms; any politician suggesting to seize resources for the next twenty years will get laughed out of office (or at least not reelected). And global cooperation for such a long time seems very unlikely. Putting so many resources into a single project will inevitably effect the population, and there will inevitably be a country where the population revolts and stops contributing. Which will probably trigger a domino-effect amongst the economically weaker countries, and you need to be very, very lucky if it doesn't completely destroy any chances of success.</li>\n</ul>\n" }, { "answer_id": 39340, "author": "pjc50", "author_id": 1985, "author_profile": "https://worldbuilding.stackexchange.com/users/1985", "pm_score": 2, "selected": false, "text": "<p>The climate change analogy suggests that the response would be to deny the problem for as long as possible, and then to ensure that even if everyone else perishes the well-off have enough bunkers and tinned food to survive it.</p>\n\n<p>The World War analogy suggests that there would be some combination of command economy and long-term debt (e.g. the Lend-Lease programme and the Marshall plan). Get the materials first and leave an IOU.</p>\n\n<p>There would undoubtably be profiteering and some inflation of the prices. That's human nature; if, as you've set it out, there's no way the project would <em>not</em> be funded regardless of the cost, market forces don't apply. See for example the Daraprim pricing scandal: rather than the cost being related to production in any way, or ability of people to pay, the makers inflated it hugely.</p>\n\n<p>If you're holding the resource necessary to save the world, the only thing stopping you from demanding <em>all the money in the world</em> for it is the risk that going too far will result in you being expropriated by the government or murdered by an angry mob.</p>\n\n<p>Another example from the real world is Tamiflu and the debate over <a href=\"https://books.google.co.uk/books?id=CLGLBQAAQBAJ&amp;pg=PA87&amp;lpg=PA87&amp;dq=flu%20drug%20patent%20expropriation&amp;source=bl&amp;ots=n-eB7RuKYg&amp;sig=G8HA4vp3l_hjJsNboUms-eUlkYs&amp;hl=en&amp;sa=X&amp;ved=0ahUKEwigvqSs2-3LAhUB2xoKHfdNDVUQ6AEIJDAB#v=onepage&amp;q=flu%20drug%20patent%20expropriation&amp;f=false\" rel=\"nofollow\">expropriating it from the patent holders in the event of a potential bird flu pandemic</a>.</p>\n\n<p>A bit depends on the details: is the solution building a single thing in a single place? What opportunities are there for ISS-like international cooperation? Is there a chance that the disaster might be partial, or attenuated so it only affects some part of the world? Could the problem or solution be <em>weaponised</em>? These all affect who gets to profit from and pay for the fix.</p>\n" }, { "answer_id": 39397, "author": "coteyr", "author_id": 11158, "author_profile": "https://worldbuilding.stackexchange.com/users/11158", "pm_score": 1, "selected": false, "text": "<p>Look at our own history for your answer. </p>\n\n<p>First, even in times of war trading still happens. The currency may change, but trading it's self continues. This is even true between enemies at times. So some kind of economy would still exist.</p>\n\n<p>Next look at World War 2 and some of the countries war efforts. In the USA there was an extreme drive for metals. Prices went up, and stuff got hard to find. Propaganda and similar campaigns to \"Make it do\" arose. Look into how that worked out. There were several lines that people would not cross (Alarm clocks, sliced bread, and beauty products) but many many more that people were willing to give up (canned goods, typewriters, toys, and appliances)</p>\n\n<p>In a \"do or die\" situation, I would think the same basic principal would unfold, with rationing, propaganda, and and a sense of \"For Earth (or what ever the world is called)\" people would be willing, at least historically, to make the daily sacrifices needed to build the anti-dooms-day device.</p>\n" }, { "answer_id": 39405, "author": "Ben Millwood", "author_id": 17852, "author_profile": "https://worldbuilding.stackexchange.com/users/17852", "pm_score": 0, "selected": false, "text": "<p>Quoting <a href=\"https://en.wikipedia.org/wiki/Demand_shock\" rel=\"nofollow\">Wikipedia</a>:</p>\n\n<blockquote>\n <p>In economics, a <strong>demand shock</strong> is a sudden event that increases or decreases demand for goods or services temporarily.</p>\n</blockquote>\n\n<p>Unfortunately, that article doesn't give a lot of detail, although it does point to a couple of examples (probably smaller and less dramatic than your hypothetical), and give you a name for your concept that you can use for further reading. It does back up your guess that prices increase; however, price gouging can only really occur if there is a monopoly or near-monopoly on production, and for some reason it's hard for more entrepeneurs to join in (common reasons are regulation like patents or naturally-occurring prohibitive startup costs, like drilling an oil well). Otherwise, competition between producers undercutting each other will continue to keep prices reasonable. Likely if price-gouging did arise, the government would step in and break up monopolies or lower barriers to entry (if possible) to restore competition and drop the prices again.</p>\n\n<p>It may even be the case that as the industry booms, competition intensifies, economies of scale increase, and efficiency of production and investment in industry R&amp;D actually become a higher priority, so that costs and therefore prices actually lower. This is especially likely if previously the market for some resource was pretty niche but has now become a major commodity.</p>\n\n<p>However, it's also plausible that as demand increases, it becomes economically viable to pursue less efficient means of production in the name of increasing total output (suppose you have to mine some ore, and you need a certain level of purity in order for it to be actually worth digging out of the ground; as demand increases, the minimum level of purity that's \"worth it\" widens out). That would lead to an increase in price, but a reasonable one, since it reflects the increased underlying cost of production to keep pace with demand.</p>\n\n<p>Generally the shift of a bunch of labour and resources into this Big Solution could conceivably draw resources away from general economic activity, which might see a decline in quality of life, or a crash in unstable markets or something equally dramatic. However, macroeconomics can be counterintuitive, and arbitrarily increasing consumption and giving people unproductive busywork has at times been proposed as a solution to some economic problems. I'm not really qualified to comment on that.</p>\n\n<p>The prospect of imminent catastrophe will have direct social and economic impacts as well. Planning for the future now seems like less of a good idea, which makes investment seem like less of a good idea, which may lead to trouble. It's hard to say how people will individually react, and how optimistic or pessimistic they would be, but they could conceivably cause more widespread havoc. All this economist's talk becomes kind of irrelevant if people stop coming to work and start rioting instead and societal order breaks down. You may also find that people will deny that the apocalypse could possibly be happening, or even deny that it should be stopped. But that's more outside the scope of your question.</p>\n\n<p>In short: demand shocks have occurred in the past, and you might want to look them up (I haven't). If competition in production is easy, that will help to mitigate the impact on prices – simply put, as soon as producing unobtanium ore because hugely profitable, mining companies will flood in until it is merely very profitable, and then continue flooding in for as long as it is more profitable than whatever they were doing before, and thus is the equilibrium largely restored. Either way, you might find that the socio-psychological impact of imminent possible doom has a more striking impact on daily life than commodity market prices anyway.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/39304", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/17330/" ]

[ { "answer_id": 39477, "author": "PCSgtL", "author_id": 9776, "author_profile": "https://worldbuilding.stackexchange.com/users/9776", "pm_score": 2, "selected": false, "text": "<p>There has to be a catastrophe or other threat. This creates a need for a stronger navy or central government. Once it begins to accumulate power it continues to do so.</p>\n\n<p>The ideal vector would be civil war. Take a look at U.S. history as an example. </p>\n" }, { "answer_id": 39480, "author": "bowlturner", "author_id": 19, "author_profile": "https://worldbuilding.stackexchange.com/users/19", "pm_score": 4, "selected": true, "text": "<p>The 'easiest' would be an outside threat to the members of the confederation. Like the Borg or some other species bent on domination and conquest. </p>\n\n<p>We would band together (hopefully) to help each other survive and push back this mutual threat. (Though sitting by the way side and hoping the threat passes you by will be a strategy some will take.) </p>\n\n<p>The other would be some kind of dictator like Palpatine/Hitler, slowly, often by trickery (at the beginning), to get systems and groups to support him/her/it. After a while, when they have a significant following, they start pressuring more to 'join' and eventually the hold out will be conquered.</p>\n" }, { "answer_id": 39482, "author": "o.m.", "author_id": 6402, "author_profile": "https://worldbuilding.stackexchange.com/users/6402", "pm_score": 2, "selected": false, "text": "<p>To take a nod at <a href=\"https://en.wikipedia.org/wiki/Panama_Papers\" rel=\"nofollow\">current events</a>, start with a highly dispersed economy in a dispersed political system. The economy gets integrated by the collective effort of banks, megacorporations, etc. Then some very selfish actors start to exploit loopholes in the regulatory climate, or create them in the first place. The general population gets upset. What can they do?</p>\n\n<ul>\n<li>Remove the freedom of business to shift fictional assets as they like.</li>\n<li>Introduce galactic minimum standards for taxation, transparency, etc.</li>\n</ul>\n\n<p>If they take the latter option, they're on the way to a galactic government.</p>\n" }, { "answer_id": 39664, "author": "ckersch", "author_id": 2947, "author_profile": "https://worldbuilding.stackexchange.com/users/2947", "pm_score": 3, "selected": false, "text": "<h2> The Confederation develops strong AI, puts in on the internet, and elects it as president. </h2>\n\n<p>As the Confederation has come to understand all too well, human leaders suck. However, they've also discovered that advanced intelligences formed out of enormous networks of processors can govern quite effectively.</p>\n\n<p>They first developed one of these a few generations back. It was the first Strong AI that humanity ever made, and consisted of a single supercomputing cluster that could operate roughly on the same level as a human brain. Moreover, it was programmed in such a way that it could talk to humans, understand, and <em>empathize.</em> Being a computer network, it could also easily communicate with and distribute tasks to other computer networks, effectively allowing it to solve problems incredibly efficiently by properly managing lots of computing networks. The scientists called it the Global Emergent Neuron Network, or GLENN.</p>\n\n<p>GLENN rapidly transitioned from a simple experiment into a trusted adviser and political activist. He campaigned steadily for those platforms which he saw as most likely to benefit the Confederation, a goal which he was programmed for and which he wholeheartedly pursues. GLENN's business ventures also took off, and he funded the construction of additional computer cores in other cities and on other worlds, all connected through the Galactic Internet.</p>\n\n<p>GLENN was soon recognized as the single most powerful entity in the Confederation, with a presence on nearly every world. However, he remained a force of good. His core edict of 'serve and strengthen the confederation, and improve the lives of its citizens' continued to drive him. He did not twist it, reinterpret it as 'death to humanity' or fall into any of the other standard AI tropes. He met with and discussed philosophy and government with the greatest philosophers and scholars in the galaxy. He made friends. And, after a long period of introspection and self-reflection as to how he could best serve humanity, he decided to run for Prime Minister of the Galaxy.</p>\n\n<p>Of course, for a galaxy-spanning AI, term limits don't really make sense. GLENN did a great job in his first term, and the General Assembly almost unanimously decided to remove them. Elections still happen, of course, but there is little in the manner of serious opposition to GLENN's presidency. Flesh and blood organisms are simply too limited to do the job that GLENN can, and he has the resources to purchase a copy of any new AIs that are developed (of which there have been many) and incorporate their code into his.</p>\n\n<p>Now, GLENN is loved, GLENN is worshiped in a pseudo-religious manner as a god who truly listens to what people are saying, every minute of every day, and reacts accordingly. GLENN operates on the will of the General Assembly to reward those who further the cause of the Confederation and, with brutal efficiency, command the armed forces to destroy those who threaten it.</p>\n\n<p>While he would never claim such a title there are now many of the faithful who elevate him to a position above a mere Prime Minister: GLENN, Emperor of the Confederation.</p>\n" }, { "answer_id": 84388, "author": "Sasha", "author_id": 38408, "author_profile": "https://worldbuilding.stackexchange.com/users/38408", "pm_score": 1, "selected": false, "text": "<p>Have a group of old people with more money than morals, the concentration of capital soon turns into political power that is then used to create laws to benefit them at the cost of the rest of the population. </p>\n\n<p>As the government cuts the access to basic needs in exchange to benefiting the rich you will have an increasing concentration of resources, unemployment, wage-slavery, rampant debt, health and infrastructure problems.</p>\n\n<p>All that you need is a charismatic leader to put the blame on someone else and promise quick, easy solutions to the problems of the nation. </p>\n\n<p>For a bonus, shift the economy towards the production of weapons and war material, so you then creates a need for an almost constant war to keep the industry profiting. </p>\n" }, { "answer_id": 103204, "author": "M. A. Golding", "author_id": 34461, "author_profile": "https://worldbuilding.stackexchange.com/users/34461", "pm_score": 0, "selected": false, "text": "<p>Since there are other independent realms bordering the confederation in the original question, the confederation might change into a more centralized system, possibly an empire, for reasons of better managing the economy and for being stronger in dealings with outside governments, just as the United States of American found the Articles of Confederation inadequate and so adopted the Constitution.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/39475", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/6799/" ]

[ { "answer_id": 40094, "author": "Ewan", "author_id": 9427, "author_profile": "https://worldbuilding.stackexchange.com/users/9427", "pm_score": 2, "selected": false, "text": "<p>It depends on how your time travel works. But lets assume that you can change the past.</p>\n\n<p>original time line T0</p>\n\n<pre><code>Piccaso paints a picture.\nPiccaso sells picture for beer\nPiccaso dies\npeople see picture and like it\nPiccaso becomes famous\nPictures value increases\nPicture is sold for millions\n</code></pre>\n\n<p>time traveller time line T1</p>\n\n<pre><code>Piccaso paints picture\nPiccaso sells picture for beer to time traveller\nPiccaso dies\nTime traveller finds picture by unknown artist is worthless\n</code></pre>\n\n<p>You could argue that if you only take one of many pictures from piccaso then the 'undiscovered work' will still be worth millions. However this only works when there are few, or one, time travellers.</p>\n\n<p>Lets consider another senario</p>\n\n<p>T0</p>\n\n<pre><code>The library of alexandria burns to the ground\nthousands of ancient scrolls and artifacts of intrinsic historical value are lost.\nA few artifacts are rescued from the flames and buried\na thousand years pass\nthe few remaining artifacts come to light and are worth millions\n</code></pre>\n\n<p>T1</p>\n\n<pre><code>Time travellers steal everything from the library of alexandria and set it alight to cover thier crime\nThe library of alexandria burns to the ground\nTime travellers bury items to dig up in 1000 years\n'Lost' artifacts are sold for millions\n</code></pre>\n\n<p>T2</p>\n\n<pre><code>Time travellers steal everything from the library of alexandria and set it alight to cover thier crime\nThe first set of Time travellers arrive to find library in flames\nT1 time travellers return to the future and bitch about how thier plan didnt work\nTime cops hear the story and decide to investigate..\n</code></pre>\n\n<p>T3</p>\n\n<pre><code>Timecops arrive in alexandria the night before the fire\nTime travellers arrive and are arrested\nTimecops set library alight 'to protect the future!' And return\nfirst Time travellers arrive to find library in flames\ntime travellers return to the future and bitch...\ntimecops hear the story...\n</code></pre>\n\n<p>To make money from your time thefts you need your timeline to remain essentialy the same after you have returned from the past. This is difficult to achieve unless time travel is restricted in some way</p>\n" }, { "answer_id": 40095, "author": "AndreiROM", "author_id": 15059, "author_profile": "https://worldbuilding.stackexchange.com/users/15059", "pm_score": 2, "selected": false, "text": "<p>The very act of going back in time and interacting with the people/artifacts would change the future. So the \"future\" you return to may be one which is utterly alien to you. </p>\n\n<p>It would not be a reliable mechanism for commerce, as any decision would have wildly unexpected implications. As we all know, the global market performs best when dealing with a stable environment (not unchanging, simply stable). Furthermore, being able to travel back and forward in time creates a possibly universe ending paradox. </p>\n\n<p>If you want your story to involve travelling to the \"past\" and pilfering it of valuables you may wish to explain it as travel to a parallel universe instead. You would affect <em>their</em> future, but not interfere with the past of your own universe. </p>\n\n<p>It would also mean that paradoxes would be a non-issue. If you meet yourself in that other universe that person is not \"you\".</p>\n\n<p>At this point the economy would be influenced in various ways. If you were able to travel to a parallel universe with an entire army and completely pillage it of natural resources then that will heavily influence the economy of your world (obviously). </p>\n\n<p>If time travel is an ability available only to a very limited number of people then they may use this method to become rich without actually affecting the global economy much. </p>\n\n<p>It all depends on the scope of your enterprise.</p>\n" }, { "answer_id": 40098, "author": "Kys", "author_id": 16335, "author_profile": "https://worldbuilding.stackexchange.com/users/16335", "pm_score": 0, "selected": false, "text": "<p>Multi-universe/butterfly effect aside, there are still problems.</p>\n\n<p>All material wealth would be at risk. Two way time travel could be used as a pseudo-teleportation. Want to get into that locked vault? No problem, just travel back in time, walk in to where the vault would be, then travel forward to present time. Steal whatever, then reverse the process. This sort of time travel has all of the problems of a society with teleportation with the added effect of multi-universe paradoxes.</p>\n" }, { "answer_id": 40105, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 2, "selected": false, "text": "<p>There are dozens if not hundreds of rulesets for timetravel, dealing with issues of bringing things to/from the past or future. Every single one of them would have a different resolution of the issue of artifacts (which is unrelated to the issue of currency that you ask). Pick your favorite ruleset and we can talk specifics.</p>\n\n<p>However, in the case of artifacts, you have to realize that the rest of the world isn't just going to hold still while you pump all the value out of it by time traveling artifacts back and forth. It will adapt. One adaptation will happen remarkably early: your artifacts will get declared to be forgeries. A Picaso painting <em>must</em> be over a hundred years old. You're going to try to sell a Picaso that is less than a year old. Instantly people will notice that there is no possible way it has weathered this well over a hundred years, and you will be laughed at.</p>\n\n<p>As for currency, that's a question that requires one to know the particular ruleset for timetravel you are operating under. Under some multiverse based rulesets, you can grab an arbitrary amount of currency, say gold coins, and bring them back here. Then you can deal with the hyper inflation issues, though honestly, one person likely doesn't need <em>that</em> much gold to live as lavishly as they please. It's actually hard to spend a billion dollars. You have to work at it, and a billion is a drop in the bucket for any reasonable currency. In other rule sets, you may find the disappearance of said gold causes unintended consequences. Perhaps the dissapearing gold leads to a gold scare that leads to it being <a href=\"https://en.wikipedia.org/wiki/Gold_Reserve_Act\" rel=\"nofollow\">made illegal to hold gold</a>. You may be promptly arrested.</p>\n\n<p>There's dozens of other possible outcomes, depending on your time travel rules.</p>\n" }, { "answer_id": 40106, "author": "WhatRoughBeast", "author_id": 7858, "author_profile": "https://worldbuilding.stackexchange.com/users/7858", "pm_score": 0, "selected": false, "text": "<p>While others have dealt with the general question, your specific question has, I think, a simpler answer. You suggest that \"We could theoretically go back in time, take (or buy) some artifacts, and sell them in the future as antiques.\" Well, no. Let's say you go back to June of 1930 and buy up a dozen copies of Action Comics #1 - the first Superman comic. You come back to the present day and get 40,000 bucks per, right?</p>\n\n<p>Umm, no. You obviously have some freshly-printed forgeries.</p>\n\n<p>This applies to any object you wish to sell \"as antiques\", except objects like gold which do not develop signs of age.</p>\n\n<p>If your time machine is the really deluxe version, with complete spatial control, you can indeed prevent valuable artifacts from being lost (such as the contents of the Alexandrian Library), but for the most part you would have enormous difficulty providing a credible provenance, and the lack of appropriate aging would probably scuttle your ability to sell them. </p>\n\n<p>You could, in principle, recover valuable objects like the treasure from the holds of Spanish treasure fleet ships which wound up sunk, but again you'd have trouble selling them as antiques. Well, gold is gold, but that's not exactly the question you asked.</p>\n" }, { "answer_id": 40111, "author": "user3026691", "author_id": 19934, "author_profile": "https://worldbuilding.stackexchange.com/users/19934", "pm_score": 0, "selected": false, "text": "<p>When the market becomes saturated with something, said thing loses its value. So maybe the first ones to do it would get rich, but the rest would see diminishing returns.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/40093", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/17330/" ]

[ { "answer_id": 41986, "author": "o.m.", "author_id": 6402, "author_profile": "https://worldbuilding.stackexchange.com/users/6402", "pm_score": 3, "selected": false, "text": "<p>Currency is not <strong>just</strong> about setting value for bartered goods. Money is a <em>common</em> yardstick for different goods.</p>\n\n<ul>\n<li>Currency is a shortcut for multi-partner deals. Say Alice needs charcoal to forge a plowshare. Bob needs a plowshare to grow grain. Charles produces charcoal, but he'd rather have fish and not grain. So the deal has to involve Drew who takes Bob's grain for some fish.</li>\n<li>Alice needs the coal now, but Bob won't produce grain for quite some time. Will Drew be prepared to hand over fish for a promise of future grain?</li>\n<li>Alice produces relatively high-value objects, but she won't make all that many. If she made a plow this week, how can she get <em>fresh</em> food next week?</li>\n</ul>\n\n<hr>\n\n<p><strong>Follow-up:</strong></p>\n\n<p>How about tax incentives to barter? Get some precedents that cash transactions are taxed but barter is not, or at least that those who do barter can try and argue that the <em>cash</em> value of their transaction is very low.</p>\n\n<p>How about a move in your story to make most cash digital (a rider on one of those <em>if-you-don't-vote-for-this-you're-no-patriot-acts</em> to combat money laundering) coupled with a society which effectively denies bank accounts to poor people?</p>\n" }, { "answer_id": 41987, "author": "Mark Ripley", "author_id": 19751, "author_profile": "https://worldbuilding.stackexchange.com/users/19751", "pm_score": 4, "selected": true, "text": "<p>First some background about why currency tends to replace barter in economies. In general, a currency acts as a lubricant between trading partners, resulting in less complexity when used to trade or purchase any desired item.</p>\n\n<pre><code>Simple example with three people:\n person 'A' has a sword and wants a massive block of marble.\n person 'B' has a massive block of marble and wants a wheel of cheese.\n person 'C' has a wheel of cheese and wants a sword.\nBarter solution: they all meet in one place and trade items.\n</code></pre>\n\n<p>Possible problems with barter shown using this example:</p>\n\n<pre><code>1) Lack of information: How do the three discover that collectively\n they have the items they want so they can agree to the barter?\n\n2) Inequality of value: 'A' thinks his sword is worth more than the\n crappy block of marble offered by 'B'. How do you trade half\n a sword?\n\n3) Non-portability of items: transporting the marble block to the\n barter is difficult.\n\n4) Non durability of items: The wheel of cheese will go bad over\n time, requiring the barter to be completed quickly.\n</code></pre>\n\n<p>Currency fixes all four of these problems:</p>\n\n<pre><code>1) No need to match what you have to what someone else has;\n make a currency sale and then a currency purchase instead.\n\n2) If your item is worth more than an item you want, you end up\n with extra currency to use later.\n\n3) currency is portable, unlike a block of marble.\n\n4) currency hold value over time, unlike cheese (ignoring\n the whole fiat money/inflation issue here).\n</code></pre>\n\n<p>Currency also tends to be divisible into small enough values (no selling a single item for 1/2 penny) and be acceptable by everyone in the economy.</p>\n\n<p>I don't think the efficiency of currency over barter will allow you to create a realistic complex society that uses ONLY barter, at least as long as your world rewards economic efficiency. Simple or small economies can get away with barter.</p>\n\n<p>Now to answer your question.</p>\n\n<p>If your world has cultural values that totally ignore economic efficiency, then that society might avoid currency and only use barter. \"Our religion has banned money/coins\".</p>\n\n<p>If your world has a has an efficient way of discovering possible barters, ala internet matching of potential barters, then two of the problems of barter, lack of information and non-portability of items can be greatly reduced. You will still have problems of inequality of trades and non-durability of items though.</p>\n\n<p>My final answer is that you might want to consider a world with multiple non-traditional forms of currency. This would somewhat resemble a barter economy where you bartered (using non traditional currencies such as grain, crude oil, or other evenly divisible and value holding \"things\" like that). Your exchange rate between your non-traditional currencies (grain vs. crude oil) could be published so as to help potential buyers or traders decide on what form of 'currency' they wanted to use for the transaction.</p>\n" }, { "answer_id": 41991, "author": "Lostinfrance", "author_id": 9207, "author_profile": "https://worldbuilding.stackexchange.com/users/9207", "pm_score": 2, "selected": false, "text": "<p><em>&hellip;what can I do to make a barter system stable in a modern American society?</em></p>\n\n<p>Make the society itself massively <em>unstable</em>.</p>\n\n<p>Simply positing a catastrophe, either physical catastrophe or an economic one such as hyperinflation, that makes trade outside a local area is impossible will not be enough. For the reasons already stated by Mark Ripley and o.m., some alternative form of currency will reassert itself quite quickly. The catastrophe has to be ongoing and make it impossible to predict what anything will be worth next week. Then barter will be the only means left to people to survive. Not many of them will. Such instability would also make agriculture or animal husbandry very difficult.</p>\n\n<p>If you want to write a less depressing story, how about a technological society that for some reason (e.g. a political or religious prohibition on profit) feels the need to <em>pretend</em> to operate by barter. That society's version of eBay would operate with an underlying structure that placed a numerical value on whatever you had to sell, but this would be concealed and denied. Ostensibly it would be a complex chain of swaps such that everyone got approximately what they wanted in the end. This would be extremely inconvenient and could only be enforced by repression but that is no bar to it happening in real life or in fiction.</p>\n" }, { "answer_id": 41992, "author": "Jim", "author_id": 3054, "author_profile": "https://worldbuilding.stackexchange.com/users/3054", "pm_score": 1, "selected": false, "text": "<blockquote>\n <p>Create a barter system in modern American society</p>\n</blockquote>\n\n<p>Currency provides at least two major benefits over barter:</p>\n\n<ol>\n<li>Storing value. </li>\n<li>Making change.</li>\n</ol>\n\n<p>To replace these, you could have a place like Ebay - where you can offer a goat and the system takes the goat \"in\". Later, you want a dozen eggs and the \"system\" would determine that the \"trade\" is 1 goat for 100 dozen eggs. So it could \"debit\" your goat by 1/100. </p>\n\n<p>This is borderline ridiculous because the \"system\" would essentially create a currency. I use eBay as an example because a larger, barter based eBay would involve not just selling, but also \"buying\" at auction. In other words, people could offer to sell a goat, and someone \"buying\" the goat would need to already have \"sold\" something or else \"sell\" something of equal or greater value - and the system would handle \"making change\" and \"storing value\" for the inequity of the trade.</p>\n\n<p>However, the reason currency exists is because barter is terribly inefficient by comparison. With today's technology, this may work to some extent. However, it would likely fail for trades like rare artwork, intellectual property, private musical performances, etc. And it would struggle to handle selling tickets for a cruise ship, construction of a national monument, donating land for natural resource preservation, etc. And then there are things like credit/lending, insurance, taxation, utilities, medical services, education... it's a pretty long list of things we enjoy in today's world because currency makes the \"trade\" efficient. </p>\n" }, { "answer_id": 41995, "author": "nigel222", "author_id": 13883, "author_profile": "https://worldbuilding.stackexchange.com/users/13883", "pm_score": 0, "selected": false, "text": "<p>There is an interesting halfway house in which any individual or group can issue it's own currency. This is how money starts in a barter society: as IOU notes. \"I'll give you a day's carpentry when you need it in exchange for these groceries today\". And you can in turn trade the carpentry promise for, say, some clothing.</p>\n\n<p>At a certain point in the development of society the rulers see the advantages of giving themselves a monopoly over creating currency. If the nation collapses into anarchy, local currencies and IOUs again appear, only to be killed off when a new nation is formed.</p>\n\n<p>Money is power.</p>\n\n<p>So what you need is stable anarchy or libertarianism. Human nature means that anarchy or extreme libertarianism is unstable. But if humans had been made part of some alien society which stabilised that form of near-anarchy? Perhaps omnipresent robotic enforcement of \"an eye for an eye\" unless the victim offers mercy, plus termination with extreme prejudice of anyone wielding a lethal weapon in anger. No rulers, no coercion, just voluntary associations. Could it work? </p>\n" }, { "answer_id": 42000, "author": "Paulb", "author_id": 20812, "author_profile": "https://worldbuilding.stackexchange.com/users/20812", "pm_score": 1, "selected": false, "text": "<p>To the Q of \"<strong><em>what can I do to make a barter system stable in a modern American society?</em></strong>\"</p>\n\n<p>Think of currency transactions in the time/quality/cost frame:</p>\n\n<ul>\n<li>currency is very fast (credit card swipes, stock exchanges etc.)</li>\n<li>currency gives high quality (it's very granular from cents to billions, so it is a good language to discuss value in, it also allows a common language to compare different transactions over time)</li>\n<li>transaction cost is very low (most by computer, some by physical currency)</li>\n</ul>\n\n<p>How can you replicate those qualities in barter market?</p>\n\n<p>Time:</p>\n\n<ul>\n<li>you could use computer networks as a place to advertise your goods and look for goods that you want. This record of past barters would help during the haggling process.</li>\n<li>same network can can be the permanent record of a barter agreement</li>\n</ul>\n\n<p>Quality:</p>\n\n<ul>\n<li>the network can have a searchable history of similar barters that you can use as a yardstick when judging a proposed barter</li>\n<li>the network could have middlemen (or artificial intelligence) who put together baskets of goods and propose those baskets to parties</li>\n</ul>\n\n<p>Transaction Cost:</p>\n\n<ul>\n<li>the network will electronic record the agreement</li>\n</ul>\n\n<p>It sounds like a hybrid of eBay. There are websites attempting barter exchanges today. It hasn't caught on yet. One problem, there are several companies doing this, which makes one stop bartering impossible and reduces the probability of a match because buyers and sellers are in different non-connected markets. You'd have to create some kind of incentive that would cause people use one particular exchange.</p>\n\n<p>I agree with others, that currency is best. But I wanted to answer the Q you asked.</p>\n\n<p>And a semi-serious proposal: Tinder should copy their software to a new server called <strong><em>Bartr</em></strong>. Take a picture of the item for sale and Bartr broadcasts it. Consider items from others for your item, swipe left for No, right for Yes. It actually could work in a flea market environment.</p>\n" }, { "answer_id": 42760, "author": "Stilez", "author_id": 7962, "author_profile": "https://worldbuilding.stackexchange.com/users/7962", "pm_score": 0, "selected": false, "text": "<p>Change the scale, might be one solution. As several people point out, currency allows transactions over time and at a distance (unknown parties). Suppose individuals in some rural isolated area could only transact with those in their town, that would be plausibly sustainable (somewhat anyway). Then towns can barter with other towns, and towns in a region leads to regions bartering with regions. Since at each level of this barter hierarchy, the distance is not unreasonable for the parties concerned, and the trade is larger and focuses on different kinds of needs, perhaps it is sustainable.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/41981", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/11049/" ]

[ { "answer_id": 46418, "author": "Nathaniel Ford", "author_id": 6928, "author_profile": "https://worldbuilding.stackexchange.com/users/6928", "pm_score": 2, "selected": false, "text": "<p>This <a href=\"http://cseligman.com/text/planets/atmospherestructure.htm\" rel=\"nofollow noreferrer\">link is a good primer</a> on how atmospheric density relates to other planetary factors. In particular, you propose a planet that has <strong>less gravity</strong> than Earth and <strong>greater air density</strong>.</p>\n\n<p>Given that less gravity will reduce air density, all else held equal, because the gas will be held less closely to the surface, you have to have a compensating factor: either the gas must be much heavier (and thus easier for the gravity to act on), or the atmosphere must be a lot hotter with a lot more gas (akin to Venus). Venus has an atmospheric density around 80x Earths, so this doesn't seem entirely outside the realm of reason - but the gasses would be heavier, and therefore probably toxic as far as life-on-Earth would be concerned. </p>\n\n<p>It is of note that even in this situation, your very massive creatures would probably tend towards lower elevations, where the density is likely to be higher.</p>\n\n<p>The most unlikely thing is a planet less dense than Earth by a massive amount. I'm not entirely sure how to run the numbers, but such a planet is liable to be almost hollow if it has a larger solid surface, or be made up of elements that are a lot lighter than Earth's crust and core are composed of. Whether those elements could support complex life is unclear (you need a lot of heavier elements, such as Iron, for life).</p>\n\n<p>As a side note, I don't believe that, for purposes of air density, the electromagnetic field has a great deal of import. It probably shields some gas leakage, but it won't act as an impermeable membrane.</p>\n" }, { "answer_id": 46422, "author": "Josh King", "author_id": 21041, "author_profile": "https://worldbuilding.stackexchange.com/users/21041", "pm_score": 1, "selected": false, "text": "<p>You ask a lot of separate questions, I'm just answering on the magnetic field.</p>\n\n<p>The Earth has a large magnetic field because it's rotating molten iron core acts as a dynamo generating electric and magnetic fields due to the rotation.</p>\n\n<p>The overall density of your planet means it would most likely not have significant amounts of iron or other heavier elements, so it would most likely lack a magnetic field unless it had some other mechanism to generate one.</p>\n" }, { "answer_id": 46425, "author": "MozerShmozer", "author_id": 20048, "author_profile": "https://worldbuilding.stackexchange.com/users/20048", "pm_score": 4, "selected": true, "text": "<p>If you're hoping for the answer to be \"definitely\" you're out of luck, but I might be able to give you \"possibly.\"</p>\n\n<p>The planet you propose is going to have some issues, so I'll outline those immediately.</p>\n\n<ul>\n<li>First of all, out current model for planetary formation indicates that the closer a planet lies to its parent star, the denser that planet will become. Based on local extrapolation, this would put your planet outside the orbit of Mars, which is outside the habitable zone (for <em>our</em> sun). That's not a good sign for the development of complex life.</li>\n<li>Your planet also requires <em>more</em> atmosphere and <em>less</em> gravity. This is somewhat counterintuitive at first glance. Both Mars and the Earth demonstrate that a small planetary body will likely have a small atmosphere, while many other bodies of smaller size have <em>no</em> atmosphere.</li>\n<li>Lastly, you'll need a magnetic field around the planet to protect from ionizing radiation, and to reduce atmospheric loss from solar winds. At the proposed density, your planet will be slightly denser than Pluto. This is too light to expect there to be a metallic core with which to generate this magnetic field. That's a problem.</li>\n</ul>\n\n<p>So is there a way to overcome these issues? Possibly.</p>\n\n<ul>\n<li>Addressing the habitability issue, either your planet's orbit could have moved closer inward toward the sun, placing it in the habitable zone, the star is big enough that it warms the planet even at its increased radius, or the planet's atmosphere is dense enough that a paltry amount of sunlight could keep things warm. Probably some combination of the first and third solutions would make this planet more habitable and be fairly reasonable.</li>\n<li>As for the atmosphere/gravity issue, there are examples of small gravity wells retaining massive atmospheres. Venus is a good example, though it is somewhat strange in its own right, and the moon Titan is another. Both of these bodies demonstrate that a large atmosphere <em>can</em> exist around a small planet, so this is plausible for your planet, and perhaps even likely depending on who you ask (though be aware that in both examples the atmosphere is \"super-rotating,\" blowing around the entire planet at hundreds of miles per hour, like a planet sized hurricane. Definitely cool. Definitely dangerous.).</li>\n<li>Lastly, the magnetic field. This is tough. Venus herself has a small magnetic field generated by interactions between the high atmosphere plasma and the solar winds, but this would not be enough to protect most life forms we know. On the other hand, this <em>would</em> be enough to protect against atmospheric loss from solar winds, so that's exciting. There is also the possibility of a lightweight metal core, composed of something like magnesium perhaps, that could provide a magnetic dynamo while still retaining a low density. This is pure theory, and current models of the universe suggest it is highly unlikely, but that is not the same as impossible.</li>\n</ul>\n\n<p>So, could this planet exist? Maybe. Does it exist? Probably not. On the other hand, the chances of Earth developing just like it did were also quite low, yet here we are wasting our time on Stack Exchange when we should be working. I'd call that a win.</p>\n" }, { "answer_id": 46427, "author": "MolbOrg", "author_id": 20315, "author_profile": "https://worldbuilding.stackexchange.com/users/20315", "pm_score": 2, "selected": false, "text": "<p>Planet magnetic field is the result of the internal structure of planet and rotation of that internal structure or planet.<br>\nAs you concerned with numbers, there is no way prove or disprove planet magnetic field existence in your case, with provided numbers and description. We may only speculate that planet is not dense enough and probably there will be not much iron and so on, but that is not necessarily true. </p>\n\n<p>Magnetic field prevents heating upper layers of atmosphere with charged ions, and that prevents particles from upper layers have escape velocity, and that leads to less atmosphere leaking.</p>\n\n<p>Density, as pressure, depends more on a total mass of the atmosphere. Earth had a more dense atmosphere (as science believe), Venus has 92 times bigger atmosphere pressure and $5.243 kg/m^3$ density. The same mass atmosphere and earth's recipe (N2+O2 mix) and earth temperature and venus pressure and the resulting atmosphere will be 92 times denser ($\\approx 127 kg/m^3$). (not CO2, because it will be partially liquid and atmosphere will have less pressure)</p>\n\n<p>If you do not take H2 as the main part of the atmosphere, a composition is irrelevant, kinda, only mass is important. Although there not so much gasses to choose from.</p>\n\n<p>This way you may set your pressure as you like, and density according to your preferences of composition and temperature for that pressure.</p>\n\n<p>Composition any, but if you will take earth like it will be a safe choice, but keep in mind that CO2 will condense at 53 bar pressure at 293K temperature (room temperature). So 53 bar is sort of upper limit for that temperature, because of plants etc. But if the temperature is higher than 304K, pressure is unlimited. If you wish to have winters then something like 30bar and below. Take look at <a href=\"https://en.wikipedia.org/wiki/Carbon_dioxide_(data_page)#Liquid.2Fvapor_equilibrium_thermodynamic_data\" rel=\"nofollow noreferrer\">CO2 vapor pressure</a></p>\n\n<p>As stability is the concern, Venus has weak magnetic field and atmosphere do not fly away. The main problem is hydrogen because it is the lightest and evaporation of other gasses is slower, significantly, but even in not stable cases \"evaporation\" is constant for a planet, so more you have initially for longer it lasts. And for our current understanding (at least my) as life was born in water, more water is better, there are some problems, especially where oxygen will go(when hydrogen will fly away) and bunch of other problems, but even if magnetic field isn't strong enough, more water initially may help, and even not strong field protects to some extent, that means lucky combination is possible. It may also explain higher pressure, but pure oxygen isn't safe, so assume there was a lot of water and lot of NH3 this will explain earth mix, and also it correlates with fact that planet is light, so probably it was formed from lighter fraction, especially in earlier stages of the universe.</p>\n\n<p>Also one of the possible sources of water for earth maybe was <a href=\"http://www.space.com/27969-earth-water-from-asteroids-not-comets.html\" rel=\"nofollow noreferrer\">Asteroids</a> or <a href=\"https://en.wikipedia.org/wiki/Origin_of_water_on_Earth#Extraplanetary_sources\" rel=\"nofollow noreferrer\">Origin of water on Earth</a></p>\n\n<p>So, how much water in each particular case planet gets, depends on processes of forming this particular system and some luck, this means you may scientifically accurate, as our today's knowledge goes, set arbitrary initial amounts of water on a particular planet.</p>\n\n<p><em>The larger surface area allows more room for life</em></p>\n\n<p>Earth is large enough, to support any biological possible large creature, and it was a time when she supported it.</p>\n\n<p>Short speaking 6bar pressure is not a problem, for your planet. </p>\n" }, { "answer_id": 46780, "author": "M.A. Golding", "author_id": 22740, "author_profile": "https://worldbuilding.stackexchange.com/users/22740", "pm_score": 1, "selected": false, "text": "<p>I may point out that Titan, the big moon of Saturn, has less than have the surface gravity or escape velocity of Earth, and yet it has a denser atmosphere. </p>\n\n<p>Of course the factors that enabled Titan to acquire and keep its atmosphere would probably not work if that atmosphere needs to have a chemical composition and temperature similar to Earth's atmosphere.</p>\n\n<p>Similarly Venus has a slightly lesser surface gravity and escape velocity than Earth and has a many times denser atmosphere - again with a highly different composition and temperature.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/46415", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/22591/" ]

[ { "answer_id": 47058, "author": "Jim2B", "author_id": 7886, "author_profile": "https://worldbuilding.stackexchange.com/users/7886", "pm_score": 7, "selected": true, "text": "<h2>Yes</h2>\n\n<p>Nuclear weapons would be highly effective in space.</p>\n\n<p>But their effects are somewhat different than they are on the ground. I recommend reading <a href=\"http://www.projectrho.com/public_html/rocket/spacegunconvent.php#id--Nukes_In_Space\" rel=\"noreferrer\">this entire section of the Atomic Rockets website: Nukes in Space</a></p>\n\n<p>On the ground, nuclear weapons damage things through 3 mechanisms:</p>\n\n<h3>Radiation</h3>\n\n<p>Because the atmosphere is opaque to high frequency light (hard UV, XRay, &amp; Gamma Ray), the primary worrisome radiation is neutrons when detonated in the atmosphere (also see thermal flash below).</p>\n\n<p>In space, with no atmosphere, the high frequency light (primarily XRay and Gamma Ray) flies off without interference and this becomes one of the primary danger mechanisms of the nuclear detonation. In an atmosphere, almost all of the high frequency photon energy gets converted into the thermal flash and atmospheric blast mentioned below.</p>\n\n<blockquote>\n <p>For a conventional nuclear weapon (i.e., NOT a neutron bomb), the\n x-ray and neutron flux is approximately:</p>\n \n <p>$F_{XRay} = 2.6 \\cdot 10^{27} \\times \\frac{Y}{R^2}$</p>\n \n <p>$F_{neutron} = 1.8 \\cdot 10^{23} \\times \\frac{Y}{R^2}$</p>\n \n <p>where:</p>\n\n<pre><code>Fx = X-ray fluence (x-rays/m2)\nFn = Neutron fluence (neutrons/m2)\nY = weapon yield (kilotons TNT)\nR = range from ground zero (meters)\n</code></pre>\n</blockquote>\n\n<p>This shows that for a standard (not neutron enhanced) bomb, XRay radiation is about 10,000x more damaging than neutrons at any given distance from the bomb. Which radiation flux is more dangerous to the crew depends upon factors like what sort of shielding is available and where the crew is located in the ship.</p>\n\n<p>Neutron shielding is best (defined as the least amount of shield mass required to protect against it) composed of low mass atoms (e.g. Hydrogen in water).</p>\n\n<p>What type of shielding to use for XRay and gamma ray radiation depends upon its frequency. At the lower energies, high Z metals (like lead and tungsten) work best, while at higher energies all mass tends to shield about the same.</p>\n\n<p>Since water is terribly useful for spacecraft and ubiquitous across the Universe (from it you can make radiation shielding, water, oxygen, propellant, food, environmental coolant, and for some spacecraft fuel), I'd expect most ships to just use more water shielding in place of their high-Z metal, but otherwise dead weight, gamma ray shielding.</p>\n\n<h3>Thermal Flash</h3>\n\n<p>Because the atmosphere is opaque to high frequency light (hard UV, XRay, &amp; Gamma Ray), it converts those frequencies to lower frequency light (optical and thermal). This \"thermal flash\" is what caused memorable images (like the one below) and instantly vaporized some people in Hiroshima:</p>\n\n<p>Nuclear Thermal Flash:<br>\n<a href=\"https://i.stack.imgur.com/j6a4r.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/j6a4r.jpg\" alt=\"Nuclear Thermal Flash\"></a></p>\n\n<p>Since there is no atmosphere in space, the \"thermal\" flash is minimal and not really a concern.</p>\n\n<h3>Blast</h3>\n\n<p>In an atmosphere part of the energy of the detonation is absorbed by the atmosphere and turned into an atmospheric pressure wave (the \"blast\" or over-pressure wave). Once again this phenomenon does not occur in space.</p>\n\n<p>Therefore this issue can generally be ignored.</p>\n\n<p>Nuclear Blast Effects:<br>\n<a href=\"https://i.stack.imgur.com/obdVM.gif\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/obdVM.gif\" alt=\"Nuclear Blast Effects\"></a></p>\n\n<h3>What it looks like</h3>\n\n<p>Assuming a near miss that doesn't actually vaporize the spacecraft...</p>\n\n<p>Read this section of the <a href=\"http://www.projectrho.com/public_html/rocket/spacegunconvent.php#id--Nukes_In_Space--Nuke_vs._Spacecraft\" rel=\"noreferrer\">Atomic Rockets: Nuke vs. Spacecraft section</a> for the entire narrative. I'm going to quote a couple of key passages.</p>\n\n<blockquote>\n <p>First off, the weapon itself. A nuclear explosion in space, will look\n pretty much like a Very Very Bright flashbulb going off. The effects\n are instantaneous or nearly so. There is no fireball. The gaseous\n remains of the weapon may be incandescent, but they are also expanding\n at about a thousand kilometers per second, so one frame after\n detonation they will have dissipated to the point of invisibility.\n Just a flash.</p>\n</blockquote>\n\n<p>So a strobe flash. If you were looking at it, you'll be permanently blind if you're too close. If you had a camera/sensor looking at it, it would likely burn out too if it was too close.</p>\n\n<blockquote>\n <p>Next is spallation - shocks will bounce back and forth through the\n skin of the target, probably tearing chunks off both sides. Some of\n these may come off at mere hundreds of meters per second. And they\n will be hot, red- or maybe even white-hot depending on the material.</p>\n \n <p>To envision the appearance of this part, a thought experiment. Or,\n heck, go ahead and actually perform it. Start with a big piece of\n sheet metal, covered in a fine layer of flour and glitter. Shine a\n spotlight on it, in an otherwise-dark room. Then whack the thing with\n a sledgehammer, hard enough for the recoil to knock the flour and\n glitter into the air.</p>\n \n <p>The haze of brightly-lit flour is your vaporized hull material, and\n the bits of glitter are the spallation. Scale up the velocities as\n needed, and ignore the bit where air resistance and gravity brings\n everything to a halt.</p>\n</blockquote>\n\n<p>Followed by a halo of faint hazy \"dust\" flying away from the hull along with possibly some larger debris ripped off the ship. Some sections of the ship may be glowing red hot (or hotter) depending upon the proximity of the warhead.</p>\n\n<p>It's possible that (depending upon many details) the ship may survive the detonation while the radiation kills the crew quickly or over the course of weeks. If the crew receives a deadly dose of radiation they'll likely know it even if they will likely live for a week or so in increasing agony due to the radiation damage.</p>\n\n<h2>Would they go to war?</h2>\n\n<p>That's entirely up to you and your fictional Universe.</p>\n\n<p>In space warfare, any target with a predictable trajectory (e.g. not accelerating) is a sitting duck that can be held hostage and/or killed at any time the belligerents decide to strike. The weapons would not need to be nuclear. Given sufficient time, a small asteroid would do the job easily and the belligerents might be able to maintain plausible deniability.</p>\n" }, { "answer_id": 47059, "author": "John Dallman", "author_id": 22020, "author_profile": "https://worldbuilding.stackexchange.com/users/22020", "pm_score": 4, "selected": false, "text": "<p>The thing that causes deterrence is the reliable ability for each side to cause huge levels of damage to their opponent if they're attacked. </p>\n\n<p>On Earth, that is created by Intercontinental Ballistic Missiles, which are quite hard to intercept. If side A has 100 ICBMs, side B will need 250+ Anti-Ballistic Missiles to shoot most of them down, and those ABMs <em>cost more</em> than the ICBMs. So it's always possible to penetrate defence at lower cost than improving the defence, and both sides could do this. Further, neither side could attack the other by surprise without retaliation being possible. If A made a full-scale attack, B could launch its weapons before A's weapons arrived, and <em>both sides</em> would be destroyed. That realisation lead to nuclear arms limitation treaties, which were obeyed, because it was in everyone's mutual interest to do so. </p>\n\n<p>But that kind of deterrence emerges from the technical, geographic and financial constraints of the place and time. It isn't necessarily going to apply in the completely different situation you describe. </p>\n\n<p>How do you decide if deterrence is possible? You need to decide if your scenario allows one side to attack the other and cause vast amounts of damage irrespective of defences. </p>\n\n<p>If it can, and the other side won't be able to respond to an attack by also inflicting vast amounts of unstoppable damage, then you have the reverse of deterrence, a hair-trigger situation where the first to shoot wins, and somebody will, soon. </p>\n\n<p>But if the other side can respond to an attack by inflicting unstoppable destruction, then you have \"mutually assured destruction\" and deterrence. </p>\n" }, { "answer_id": 47061, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 4, "selected": false, "text": "<p>Nuclear devices are useful, but probably not in the way you are thinking.</p>\n\n<p>Because of the vast distances between objects in space, and the high relative speeds they are moving at, the most damaging, low cost option is to simply fling inert mass at the target. The kinetic energy will be massive, because the \"v\" in the v^2 will be measured in <em>kilometres per second</em>. Even an object in orbit around the earth is travelling far faster than any rifle bullet, so a bucket of ball bearings transported into space on an intersecting orbit with a satellite or space station becomes a fearsome weapon (Atomic Rockets has a snarky little exposition of the idea where the astronaut ejects the litter box of the ship's cat out the airlock on an intersecting orbit with the target....)</p>\n\n<p>Since the projectiles rely on their velocity to damage the targets, they can be made of wadded up kleenex, but as a practical matter, you probably want a dense core of stone or metal, and a simple homing device and a small thruster to make last minute orbital corrections. If you are firing at a moon or large space station, you can effectively launch across the solar system, but for targets capable of manoeuvre, one light second (just under the distance between the Earth and the Moon) provides a practical limit for targeting (too much farther and the target can move a substantial distance before the kinetic energy warhead arrives. It took New Horizons 9 hours to traverse the distance between the Earth and the Moon, for example). The kinetic energy weapons can be launched by virtually any sort of space propulsion system, so if your target is across the solar system, you could even use a light sail! More practically, mass drivers, rail guns or giant honking rocket boosters would provide the thrust to get to the target.</p>\n\n<p>Laser and energy weapons are also limited to a light second against manoeuvring targets, but since you can ramp up the hardware as much as you desire, a Ravening Beam of Death [RBoD] could theoretically vaporize metal and ceramics in milliseconds at that range. See <a href=\"http://www.rocketpunk-manifesto.com/search?q=space%20war\">Rocketpunk Manifesto</a> for the gory details.</p>\n\n<p>At this point, you might want to reconsider how these spacefaring \"nations\" are going to conduct warfare. When a space station can be hit by a bunch of rocks collectively packing the energy of the Castle Bravo nuclear device, there isn't going to be much left of the target. These sorts of weapons are really only useful in a \"war to the knife\", where you offer no quarter and take no prisoners, but then you can expect to be on the receiving end of that sort of punishment as well.</p>\n\n<p>As for nuclear devices, they don't really add much to the target effect unless you are using third and fourth generation warheads as accelerators to drive streams of pellets at 100 km/sec or plasma jets at 3% of the speed of light. This suggests that their primary purpose is not really as weapons in of themselves, but as a compact energy source to power defensive weapons that can attempt to shoot down incoming devices. The other, and probably more important use for nuclear devices is as the drive units for an ORION pulse drive.</p>\n\n<p>This also the workaround for the spaceships in your setting, ORION is the only high thrust/high ISP drive system known to science, and you ORION drive ships will be bigger, faster and more capable than anything else out there. ORION drive ships can also bring teams of commandos, computer hackers, biological warfare experts or ninjas to your enemy space station, disguised as tourists, business people or traders, allowing you to actually capture the enemy station and \"win\" the war.</p>\n" }, { "answer_id": 47086, "author": "Nathaniel Ford", "author_id": 6928, "author_profile": "https://worldbuilding.stackexchange.com/users/6928", "pm_score": 3, "selected": false, "text": "<h1>Are nuclear weapons useful in space?</h1>\n\n<p>Yes.</p>\n\n<p>One of the other answers gives an extensive amount of information on how nukes behave in space, but there a couple of key points:</p>\n\n<ul>\n<li>It is hard to hit things precisely in space. Consider the immense amount of work that went into <a href=\"http://spaceflight101.com/juno/juno-mission-trajectory-design/\">Juno's trajectory</a>. Nukes ease this burden because they just have to 'get close'. </li>\n<li>Collateral damage is limited. Space is awful large. A successful nuclear strike is likely to take out a target and not as much else (since everything else is very far away).</li>\n</ul>\n\n<p>I recommend reading Haldeman's <a href=\"https://en.wikipedia.org/wiki/The_Forever_War\">Forever War</a> for a visceral description of nuclear space combat, similar in tech level to that you describe.</p>\n\n<h1>Would large-scale territorial war be conceivable in this scenario?</h1>\n\n<p>As you define 'territory', probably not. One thing to remember is that space is very dynamic compared to earth. The notion of 'territory' changes rapidly and constantly. Because bodies in space are moving at different speeds along different trajectories, the notion of 'territory' is constantly churning. Further, things that are close physically for a little while (such as Mars and Earth) are often quite far away. And when they are close physically, the time it takes to get from one to the other is not actually the shortest transit time (again, with conventional tech - or, I suppose, if you had a <em>lot</em> of energy to burn somehow).</p>\n\n<p>Thus, to plan an invasion you have to calculate where your target is going to be when you get there. You have to figure out how much reaction mass it will take to get your troops in place. It's a lot of work, logistically, particularly because winning does not imply you have a secure supply line (important in war): because the target keeps moving it might well move past where you can support it. Further, supply ships might have to be sent without knowing if you won the fight on the far side. </p>\n\n<p>For this reason, being high on a gravity well (as in Heinlein's <a href=\"https://en.wikipedia.org/wiki/The_Moon_Is_a_Harsh_Mistress\">The Moon is a Harsh Mistress</a>) has an advantage, in that it's easy to go 'down' the well, and hard to come up. Fleets would have to be largely self-sufficient, would have to modify their plans as they get information, and the only 'territory' worth talking about would be areas around gravity wells. Capturing vast volumes of space with nothing in it doesn't really help. </p>\n\n<p>The other thing to note is that space, being largely empty, makes it very easy to see things coming. Telescopes, sensors, optics and radar all become super important. If you can see a fleet launch, understand it's trajectory, you can pretty much tell what it's going to do and (if you're close enough) respond long before the fleet performs what it's doing. It's ability to turn around is limited.</p>\n\n<p>This matters for nukes, specifically, as well: warheads are very observable, if only for the heat trail of the delivering rocket. If your nukes are hard to hide, it is all the harder to get them close enough. Arguably this makes them the <em>only</em> option, when a conventional warhead would stand no chance of getting close enough before being shot down. But it does suggest inert nuke 'mines' and other tactics would evolve in order to get around using nukes 'in the open'.</p>\n\n<p>In short: with shifting territory, in the open vastness of space, nukes are probably a key weapon, but the strategy and tactics around their use would change drastically - such that comparison to historical combat is very hard to make.</p>\n" }, { "answer_id": 47115, "author": "Separatrix", "author_id": 16295, "author_profile": "https://worldbuilding.stackexchange.com/users/16295", "pm_score": 2, "selected": false, "text": "<p>Since the nukes have been comprehensively covered, I'll look at the chances of going to war.</p>\n\n<p><strong>Unlikely</strong></p>\n\n<p>The key to this is resources and the fact that the same resources are fairly evenly distributed around the asteroid belts. There may be vast unexploited resources on the asteroid your rival empire has just moved on to, but the same is true of every other large asteroid in your vicinity. There's no clash for space, no clash for resources, only a clash for pride. With travel times what they are, along with the risks of the weapons involved, pride is not a valid reason to risk a nuclear war.</p>\n\n<blockquote>\n <p>Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space. - <em>Douglas Adams h2g2</em></p>\n</blockquote>\n\n<p>When it becomes interesting is when something comes up that is actually worth fighting for, but in practice that's a large deposit of unobtainium, handwavium, or a planet with a breathable atmosphere. Everything else is plentiful on an unimaginable scale.</p>\n\n<blockquote>\n <p>May you live in interesting times - <em>Auriental Curse (Pterry)</em></p>\n</blockquote>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/47055", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/22443/" ]

[ { "answer_id": 47464, "author": "Jim2B", "author_id": 7886, "author_profile": "https://worldbuilding.stackexchange.com/users/7886", "pm_score": 4, "selected": false, "text": "<h3>A question of scale</h3>\n\n<p>Supernova are powerful, extremely powerful. Imagine the most powerful explosion possible. Supernova are more powerful than that. <a href=\"https://what-if.xkcd.com/73/\" rel=\"nofollow noreferrer\">Xkcd has this important note about how powerful supernova really are</a>:</p>\n\n<blockquote>\n <p>However big you think supernovae are, they're bigger than that.</p>\n \n <p>Here's a question to give you a sense of scale:</p>\n \n <p>Which of the following would be brighter, in terms of the amount of\n energy delivered to your retina:</p>\n \n <ol>\n <li><p>A supernova, seen from as far away as the Sun is from the Earth, or</p></li>\n <li><p>The detonation of a hydrogen bomb pressed against your eyeball?</p></li>\n </ol>\n</blockquote>\n\n<p>A: the supernova by $1 \\cdot 10^9$ times!</p>\n\n<h3>Can planets even survive?</h3>\n\n<p>Earlier a question was asked on this board: <a href=\"https://worldbuilding.stackexchange.com/questions/19000/can-a-planet-survive-a-supernova\">Can planets survive a supernova explosion?</a>. I recommend reading the answers.</p>\n\n<p>In summary, if a planet is sufficiently far away, then some planets could survive. For instance, if you placed Jupiter in orbit around a star about to go supernova (Type II), then there is a very good chance Jupiter would survive.</p>\n\n<p>At Earth's distance, the Earth would not (then again, Jupiter probably wouldn't either).</p>\n\n<p>There's only been a four planets found around pulsars (supernova remnants). Of those, we think that only one was present before the supernova. However, <a href=\"https://en.wikipedia.org/wiki/PSR_J1719-1438\" rel=\"nofollow noreferrer\">this \"planet\" started as a star</a>. The \"planet\" that is left is the star's carbon core. The supernova blew the rest of the star away.</p>\n\n<h3>But could people survive?</h3>\n\n<p>Let's assume the planet is far enough from the supernova to prevent its vaporization and placed behind some other object (like another star) to protect its fragile surface from being blasted into space.</p>\n\n<p>Even then you need to worry about a lethal dose of neutrinos. The XKCD link above states that you need to be a minimum of 2.3 AU away from the supernova or the neutrinos will kill you regardless of the number of stars you use as a shield. In fact, you'll want to be significantly further away than 2.3 AU or large fractions of the population will die from the neutrino flux.</p>\n\n<h3>Yes, you can save the people</h3>\n\n<p>But you'll need to:</p>\n\n<ol>\n<li>Move the planet as far from the star as possible. Probably 5 or more\nAU away and further is better.</li>\n<li>Place another object between the supernova and the planet to shield\nthe planet from the normal radiation blast. A big planet is a minimum,\na big star would be much better.</li>\n<li>There are still no guarantees.</li>\n</ol>\n" }, { "answer_id": 47466, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 6, "selected": false, "text": "<p>Since at the moment of core collapse and implosion a Type Two Supernova can outshine an entire galaxy of 100,000,000 stars, you have a pretty tough job ahead of you.</p>\n\n<p>The obligatory <a href=\"https://what-if.xkcd.com/73/\" rel=\"noreferrer\">XKCD comic</a> gives you a taste of what you are in for, holding a thermonuclear device <em>to your eye</em> would have <em>nine orders of magnitude</em> less radiant energy than a Supernova exploding at the distance of our Sun from you.</p>\n\n<p>With that sort of energy output, even using super science to put a Jupiter sized planet between you and the incipient Supernova isn't going to do much good; the cremated remains of the \"shield planet\" will strike your planet as a hypersonic cloud of plasma (the size of Jupiter) moments before the shockwave arrived to sweep away the mess.</p>\n\n<p><a href=\"https://i.stack.imgur.com/kYsHy.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/kYsHy.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>This <a href=\"http://www.space.com/22446-supernova-shockwave-speed.html\" rel=\"noreferrer\">article</a> suggests that the shockwave is coming at you at <em>8 miles per second</em>. That is relatively slow compared to the monster outpouring of energetic radiation that has already swept through your world at the speed of light after the core implosion, but it will do a fine job of pushing the plasma left behind by your planet out of the Supernova's remnant space.</p>\n\n<p>I suppose that some sort of metamaterial could be devised to refract the energy of the supernova around your planet, but the issue here is the amount of energy is so extreme that even absorbing the most miniscule fraction of the energy will damage the device, and once parts of it start to melt/vapourize, the rest will rapidly follow, and your planet for a fraction of a second thereafter.</p>\n\n<p><a href=\"https://i.stack.imgur.com/9HI2m.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/9HI2m.png\" alt=\"enter image description here\"></a></p>\n\n<p>The other issue is that metamaterials are optimized for particular frequencies, whereas the Supernova will be emitting energy over a very broad spectrum of frequencies, from long radio waves to intensely energetic gamma radiation. You can expect the same sort of thing to happen if you try to erect a massive mirror between you and the Supernova. Even a dielectric mirror reflecting 99.99999% of the light will rapidly vaporize and of course the mirror is not going to be reflective in all wavelengths either.</p>\n\n<p>No, the only real way to save your planet when the core destabilizes and collapses, triggering the Supernova, is to <em>not be there</em>. Use your super science to create a wormhole and put your planet through it to another Solar System with a stable, quiet star, or use some sort of space warping geometry like an Alcubierre drive to get your planet out of the way post haste.</p>\n\n<p>If you had come to me with the problem a few million years earlier, there is the possibility of stellar engineering to prevent the Supernova happening in the first place. The massive gravitational pressure of the star is compressing the core and burning through the hydrogen at a furious rate. since much of the hydrogen has been consumed and converted into Helium, the gravitational pressure of the star is allowing Helium fusion to take place, and moving up the curve of binding energy to heavier and heavier elements. When the fusion reactions create Iron (Fe) the process stops, since Iron creates no net energy when fusing (or fissioning, for that matter), so the gravity of the star is no longer opposed by the energetic output of the fusion reaction at the core: the star implodes creating the Supernova.</p>\n\n<p>Using a technology called \"<a href=\"https://en.wikipedia.org/wiki/Star_lifting\" rel=\"noreferrer\">Star Lifting</a>\", a great deal of matter could have been \"lifted\" from the outer layers of the star, reducing its mass and placing it lower on the Hertzsprung–Russell diagram. The extra mass could be stored in a series of artificial gas giant planets and used to fuel the star in the far distant future, or to do other things in the here and now. Based on the description, the star is already close to collapse, and I'm not entirely sure what would happen if large amounts of mass were suddenly removed from an unstable star. I'm not really willing to try that experiment, are you?</p>\n\n<p><a href=\"https://i.stack.imgur.com/729KV.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/729KV.png\" alt=\"enter image description here\"></a></p>\n\n<p><em>Using artificial magnetic fields to pump solar plasma from the stellar poles</em></p>\n" }, { "answer_id": 47475, "author": "celtschk", "author_id": 98, "author_profile": "https://worldbuilding.stackexchange.com/users/98", "pm_score": 5, "selected": false, "text": "<p>Create a pocket dimension and move your planet in there. During the nova, make the entry to the pocket dimension (that is, the size of it as seen on the outside) small enough that the energy that enters is no larger than the planet can handle. After the nova, you can widen the entry again and get your planet back into normal space.</p>\n" }, { "answer_id": 47486, "author": "Peter - Reinstate Monica", "author_id": 2374, "author_profile": "https://worldbuilding.stackexchange.com/users/2374", "pm_score": 3, "selected": false, "text": "<p>The interconnected sea of Higgs Bosons constituting space time has some properties of non-Newtonian fluids. Normally, the linked bosons provide the \"medium\" which propagates interactions between different points in space time with the speed of c. </p>\n\n<p>But excited by a specific resonance frequency of gravitational vibration, the bosons stop interacting conventionally. Space time starts to resemble a friction-less super fluid. Interaction between different tempo-spatial locations are near-\"instantaneous\". A plane of such an anomal \"super-fluid\" space time would act like a shield from events like supernovae on the other side of it. Leakage from the plane is minimal; all events are propagated with high preference <em>inside</em> that plane, much like electrical charges travel inside a conductor. The effect can be visualized as a spatial-temporal Faraday cage.</p>\n\n<p>Conveniently, the events (and the energy they carry) leak at the edges of the plane where they can be harvested, for example to carry out computations. </p>\n\n<p>The details are rather tricky: Close to the plane's edge time and space do funny things (let me say that the tidal forces are your least worry), so that you want to keep a healthy distance. The plane must be large to shield the planet effectively; the energy pouring out at the edges partly radiates inwards, and it's a <em>lot</em>. Creating a super fluid Higgs Boson field of that scale requires a large amount of gravity resonators placed at very precise locations in order to create the required wave form. </p>\n\n<p>It also requires an inordinate amount of energy which would plainly not be available under normal circumstances. Luckily, the supernova will provide plenty, which can be used to bootstrap the field at the moment when it is needed. The engineering problems are enormous, but they are just engineering problems; I'm sure you'll solve them in time.</p>\n" }, { "answer_id": 47508, "author": "M.A. Golding", "author_id": 23030, "author_profile": "https://worldbuilding.stackexchange.com/users/23030", "pm_score": 0, "selected": false, "text": "<p>If you live in the fictional universe of E.E. Smith's <em>Lensman</em> series create a hyperspatial tube (sort of an early version of a wormhole) between your solar system and another one. Put one mouth of the tube right in front of your planet so your planet will enter the tube. Place the other end of the tube in the other solar system at a location where the velocity and direction of your planet as it exits the tube will be exactly right for the planet to go into a nice almost circular orbit of the new star. Be sure that there are no planets in the new solar system in positions likely to destabilize the new orbit of your planet. And close the hyperspatial tube <strong>before</strong> your old sun explodes!</p>\n\n<p>The <em>Lensman</em> universe also has lots of different types of force shields that can protect spaceships and planets from the ray guns of other space ships. It is possible that the ray guns are so powerful that they could vaporize planets and are as energy dense as exploding supernovae. Thus any force shields that could defend against such powerful ray guns might also defend and protect against a supernova.</p>\n\n<p>The planet Tralle, or Trallis III, capital of a space empire, was defended by the fortress planet Onlo, or Trallis VII, that should have been about a billion miles away. The weapons on Onlo were designed to destroy attackers after they had nearly reached ground level, but I suppose that nearly ground level actually meant billions and billions of miles, since the planet Tralle was protected by Onlo. At that time both sides in the space war were capable of attacking target planets with multiple mobile planets at a time to smash into the target planets, so the weapons of Onlo must have been capable of vaporizing multiple planets simultaneously and almost instantly at distances of at least billions of miles. Thus it seems likely that the ray guns on Onlo were powerful enough to have an energy beam density at least equal to a supernova at equal distances. Since the government on Tralle could not 100 percent trust the garrison of Onlo to not turn against them, they probably had Tralle protected by a force shield strong enough to stop Onlo's ray guns and thus a supernova's energy.</p>\n\n<p>The <em>Lensman</em> universe also has energy screens that can convert the cosmic energy in interstellar and intergalactic space and turn it into usable energy. It is possible that such screens could be adapted to convert the energy of a supernova into harmless and usable energy to power force screens to protect against any supernova energy that gets through the power converter screens. </p>\n\n<p>What if you don't live in the fictional <em>Lensman</em> universe and your technology is limited to that which Earth Scientists in the year 2015 consider possible? Then your in big trouble!</p>\n\n<p>If some form of time travel is possible, and if you dare to risk erasing yourself from existence, and other time paradoxes, go back in time millions of years and begin the process of slowly moving your planet tens of light years away from your star over a period of millions of years before it becomes a supernova.</p>\n\n<p>Here are some discussions of planet moving:</p>\n\n<p><a href=\"https://www.google.com/search?q=how+to+move+a+planet&amp;ie=utf-8&amp;oe=utf-8[1]\" rel=\"nofollow\">https://www.google.com/search?q=how+to+move+a+planet&amp;ie=utf-8&amp;oe=utf-8[1]</a></p>\n\n<p>And if it might take many thousands of years to move a planet's orbit a few million miles closer to or farther from the sun, it obviously could take millions or billions of years to move it light years away from a supernova. So if you just found out that your sun is going to be a supernova soon, you need to go back int time at least millions of years in a time machine to start the process.</p>\n" }, { "answer_id": 47521, "author": "Loren Pechtel", "author_id": 264, "author_profile": "https://worldbuilding.stackexchange.com/users/264", "pm_score": 1, "selected": false, "text": "<p>There's only one formula for surviving a supernova--be where it isn't.</p>\n\n<p>Either move your planet out into interstellar space, or move your star away. The latter approach will take some of the mass off the star and thus buy you more time before the big boom, also.</p>\n" }, { "answer_id": 47524, "author": "Bryce Wagner", "author_id": 22399, "author_profile": "https://worldbuilding.stackexchange.com/users/22399", "pm_score": 2, "selected": false, "text": "<p>Can you create an artificial black hole? Take one of your planets and collapse it into a singularity, and then launch it into the center of your sun?</p>\n\n<p>My limited understanding of supernova is that the outward explosion is a result of an inward collapse as fusion comes to an end, thus initiating a much more rapid fusion which counteracts the collapse, and sends everything flying back outwards.</p>\n\n<p>I don't know the math to do such calculations, so I don't know the net result. I see multiple possibilities:</p>\n\n<ol>\n<li><p>The inner mass gets sucked into the black hole. The fusion gradually peters out as it loses density. It causes a gradual collapse of the outer star, eventually sucking the whole star in, but the energy released from the accretion disk is absorbed by the surrounding hydrogen. This is the effect you are searching for.</p></li>\n<li><p>The mass gets sucked in so fast, it terminates the star's fusion, the whole thing collapses inward, but the black hole's force isn't enough to collapse the outer layer before a rebounding shockwave in the middle regions (between the black hole and the remainging outer shell) triggers the supernova prematurely.</p></li>\n<li><p>The black hole just sucks in everything in as it gets close, and the release of energy blasts apart the system more intensely than the supernova itself.</p></li>\n</ol>\n\n<p>Maybe other possibilities I haven't thought of. Anyway, I suspect that the exact effect is going to be determined by how large the black hole is, how fast it is moving relative to your sun, exactly where it hits and the angle of incidence, and who knows what else. If you consider this an option, I strongly recommend you run as many simulations as you can, if you do it wrong, you're liable to make things worse.</p>\n\n<p>Another option with a black hole would be to make it graze the outside of the sun rather than entering into it. If you can put it in a close but stable orbit, maybe it could extract mass gradually enough that it won't trigger a supernova, and might even leave a small star behind at the end. Again, run a lot of simulations of this scenario before attempting it, don't just guess. There's so many things that can go wrong.</p>\n\n<p>It's still going to be releasing unimaginable amounts of energy as matter gets pulled in, but hopefully you can end up directing a good chunk of it inward to the black hole instead of in your direction, and hopefully it will be a lot more gradual than a supernova.</p>\n\n<p>[When I say \"you should run a simulation\", I'm talking about the aliens in this situation, who should obviously have the computing power to do so.]</p>\n" }, { "answer_id": 47537, "author": "John Dallman", "author_id": 22020, "author_profile": "https://worldbuilding.stackexchange.com/users/22020", "pm_score": 6, "selected": false, "text": "<p>This isn't a supernova problem. This is a pointy-haired boss problem. It gets much easier once you realise that. &quot;We are going to have to move the planet a bit, but that will minimise depreciation on the hardware.&quot; We're going to move it further from the star, but we are going to keep it in orbit around the star, so we are <em>not</em> running away. Since it's at least eight times the mass of the Sun, we can stand a <em>long</em> way back - at least three light years - and still be in orbit.</p>\n<p>Call it 200,000AU, which means the damage from the supernova will be reduced by a factor of 40 billion, as compared with being in an orbit like Earth's. At this point the damage is about a fourtieth of having an H-bomb go off next to you. That means you can build a shield for your planet out of all the other planets in the solar system, and potentially have it actually work.</p>\n" }, { "answer_id": 47544, "author": "Bob Gray", "author_id": 23052, "author_profile": "https://worldbuilding.stackexchange.com/users/23052", "pm_score": 6, "selected": true, "text": "<p>All you'd need is an Einstein-Rosen bridge situated so that it was placed perpendicular to the planet. Make the entrance, say, 2 planetary diameters wide and just let it sit there.</p>\n\n<p>The energy from the supernova that would have impacted the planet will instead go into the wormhole and come out wherever. I say place the other end near another supernova and hit one supernova with the other. Interesting!</p>\n\n<p>The huge width of the bridge would stop any \"bleed-around\" energy from leaking through and hitting your planet. Sit back and watch the show!</p>\n" }, { "answer_id": 47556, "author": "Youstay Igo", "author_id": 13449, "author_profile": "https://worldbuilding.stackexchange.com/users/13449", "pm_score": 2, "selected": false, "text": "<p>Supernovas are <em>unimaginably</em> violent and energetic. So far as we know, <strong>no</strong> planet can realistically survive one. Meh, no planet in a goldillock zone can even survive a red giant star-phase. To do an impossible task, you must also possess impossible impossible power and skill. So then, with far, far futuristic technology, you have these options.</p>\n<h1>Method 1</h1>\n<p>One method to <em>survive the supernova</em> is to not let a supernova occur at all. You can:</p>\n<p>1- use an immensely massive rocket engine to push your planet away from the parent star. Then bring in a small white dwarf to the parent star so that they are as close to each other as possible, without colliding into each other. The white dwarf, being superdense, would have far stronger force of gravity than the parent star, and would suck in material from the parent star. However, if white dwarfs suck in too much material, they can <em>themselves</em> explode in a supernova. So when the said white dwarf has sucked in just enough material, move it away from the parent star and bring in another white dwarf. With a few dozen such <em>visits</em> you can remove the mass of the parent star enough to avoid any risk of supernova at all. Now use the immensely massive rocket engine again to bring your planet closer to the parent star.</p>\n<p>2- explode away huge chunks of your parent star using anti-matter <em>bombs</em>. Basically you want to fling anti-matter packets at the parent star. Once they hit the star, they would annihilate to create millions of hydrogen bombs sized explosions (matter and antimatter annihilate on contact and result in an Einsteinian explosion of <span class=\"math-container\">$E = MC^2$</span>). Explosions of this scale occur all the time in the core of a star, but are suppressed by the monstrous gravity of the star. On the surface, there would be nothing to contain or suppress them and <em><strong>huge</strong></em> chunks (upto the mass of half an Earth or so) of the star are torn away with each such event. Make sure to cause these gargantuan explosions to the <strong><em>other</em></strong> side of the star from your planet (the side facing away from your planet) so that your planet doesn't get swept clean by the ejecta. Once you have successfully blown away enough mass of the star, you have circumvented the danger of the supernova altogether.</p>\n<h1>Method 2</h1>\n<p>Move your planet faaaar away (at least a light year away) from the parent star. You would have to subsist on your own generated power on the planet as no stellar energy would be available. But with your exaggerated level of technology, this should be easily obtainable. Once the star has exploded and the debris settled, move your planet back to where it used to be.</p>\n" }, { "answer_id": 47558, "author": "a4android", "author_id": 22159, "author_profile": "https://worldbuilding.stackexchange.com/users/22159", "pm_score": 2, "selected": false, "text": "<p>\"The aliens need to keep the planet around the supernova. In fact, they are interested in this planet exactly because the star will explode as a supernova.\" This suggests that if the aliens want to keep their planet in orbit around a supernova they must have (a) a good reason for doing so, and (b) some way of using this to their own advantage. What (b) suggests is that the aliens already possess the technological means to save their planet.</p>\n\n<p>This message is just a test to see how smart we are. Basically it's a trick question. To determine if we can work out that they don't need our answer to save their planet. OK, aliens if you can do it, then just do it and stop pestering us poor Solar3alings for no good reason.</p>\n" }, { "answer_id": 47566, "author": "a4android", "author_id": 22159, "author_profile": "https://worldbuilding.stackexchange.com/users/22159", "pm_score": 2, "selected": false, "text": "<p>I've done my funny answer now it's time to roll up my sleeves and get serious. Fortunately, everything needed can be found in the answers of my esteemed colleagues.</p>\n\n<p>Starting with Bob Gray's Einstein-Rosen bridge, but to start with it won't be inflated to its full size of two planetary diameters as that will come later. An Einstein-Rosen bridge was the first version of what we today call a wormhole. The original Einstein-Rosen bridge will be traded in for an Ellis-Bronnikov wormhole (also known as Ellis wormhole for short) with Gauss-Bonnet gravity conditions. Because no exotic matter is needed to keep it open. All the details about this type of wormhole can be found under this <a href=\"https://en.wikipedia.org/wiki/Wormhole\" rel=\"nofollow\">rock</a>.</p>\n\n<p>Youstay Igo's immensely massive rocket engine will be fitted into a high-acceleration long-range interstellar spacecraft. This vessel will transport one mouth of the Ellis wormhole. It is launched with an acceleration of one thousand gravities. If an immensely massive rocket engine can move a planet propelling a spaceship at one thousand gravities should be trivial.</p>\n\n<p>The vessel is sent out into deep space. Its acceleration will produce a large amount of time dilation which once achieved the ship will coast at near-lightspeed velocity deep into the galaxy. Travelling for several thousand light years away from the supernova the vessel will be unaffected by its radiation and blast waves. Once it is sufficiently far enough away the ship decelerates then turns around and accelerates on a return course to the supernova.</p>\n\n<p>Entering the shattered ruins of a planetary system obliterated by the awesome power of the supernova. At last it goes into orbit around the neutron star that is all that remains of the exploded star. The Ellis wormhole is deployed and inflated to its full size of two planetary diameters.</p>\n\n<p>Several thousand years earlier, a few years after the vessel screamed out of the planetary system at an acceleration of one thousand gravities, the aliens inflate their end of the Ellis wormhole to its full size of two planetary diameters. The huge time dilation means if the aliens peer through the wormhole they will see the remains of the supernova several thousand years in their future.</p>\n\n<p>All they have to do now is allow their planet to pass through the Ellis wormhole and emerge in their own future. Now they are several thousand years in the future. The worst effects of the supernova are now long one. It is safe for their planet to once more take up residence in its own orbit again.</p>\n\n<p>Actually it will be away for as long as it took for the planet to pass through the wormhole which at two planetary diameters won't be too long at all. No more than a few hours. This assumes a velocity of about one km/sec in passing through the wormhole. The planet won't have run away. It has simply moved itself into the future of the post-supernova and it can get back to business again. Admittedly there will be a service interruption of several thousand years, but that's not unusual as we've all had ISPs like that.</p>\n\n<p>If that doesn't work, and there's no good reason why it should fail, but this is a further safeguard. Keep Charles Rockafellor's planetary diameter sized black hole. Because a black hole big enough to shield the planet would be big enough to drop into the star and consume it before it has a chance to go supernova. Then the planet ends up orbiting a black hole.</p>\n\n<p>There you go, two solutions to the one problem, so you can't say fairer than that. I am grateful to my colleagues for their creative ideas which provided the conceptual leverage to save a planet from extinction by supernova.</p>\n" }, { "answer_id": 47573, "author": "Ovi", "author_id": 13967, "author_profile": "https://worldbuilding.stackexchange.com/users/13967", "pm_score": 3, "selected": false, "text": "<p>My dear friends, worry not! Your planet will be safe, your religious rituals will be fulfilled, and you will be able to collect plenty of data should you chose to do so on a whim ;)</p>\n\n<p>You must construct a massive object, known to us as a black hole (even better would be a charged black hole). Use the fundamental forces of nature, gravity and electromagnetism, to maneuver this black hole precisely between your sacred planet and the star. Use thrusters to maintain your planet at some distance from the event horizon, while still being in the umbra of the black hole. You may worry that this will obstruct any data coming from the star, but you are mistaken. Gravitational lensing will ensure some of the radiation coming from the explosion will reach your receptors. The further away you are from the event horizon, the more of this data you will receive. You can fine tune your position so that you get as much data as possible without being annihilated.</p>\n\n<p>If you are worried about the gravitational effect of the back hole interfering with the supernova itself, you can always move your planet and black hole back a little but (not run away, but maybe a couple more AU's)</p>\n" }, { "answer_id": 47615, "author": "Victor Stafusa - BozoNaCadeia", "author_id": 3002, "author_profile": "https://worldbuilding.stackexchange.com/users/3002", "pm_score": 2, "selected": false, "text": "<p>This is a community wiki \"non-answer\" to summarize answers that won't work, at least not without some severe modifications. Feel free to edit this if you wish.</p>\n\n<ol>\n<li><p><strong>Move the planet to somewhere else very far away</strong>: This qualify as \"<em>just running away</em>\" which the OP specifically tried to reject right from the start because it is the easy non-interesting obvious solution. Coming back later does not makes this any better. Replacing \"<em>somewhere far away</em>\" with \"<em>inside a hidden dimension</em>\" or something like that do not makes it really different.</p></li>\n<li><p><strong>Preventing the supernova from happening</strong>: Also something that the OP specifically rejected right from the start because it makes the challenge uninteresting. Making a black-hole swallow the giant star prior to its explosion would not also make it any better either.</p></li>\n<li><p><strong>Use magic, unrestricted time-travel as in <em>Back to the Future</em> movie, faster-than-light communication, TARDIS, unobtainium adamantium shielding, <a href=\"https://en.wikipedia.org/wiki/Technobabble\" rel=\"nofollow\">technobabble</a>, etc</strong>: If you are inventing your own physics, then every answer would be possible, making the challenge uninteresting and closeable as too-broad. So, this is not valid.</p></li>\n<li><p><strong>Putting a massive planet or a smaller star as a shield</strong>: It would work to shield the planet from the initial blast (except for neutrinos). However, as the supernova quickly erode the shielding object, its debris would obliterate the planet. Anyway, this could be workable with some modifications.</p></li>\n<li><p><strong>Putting a neutron star or a black-hole as a shield</strong>: Black-holes and neutron stars are tiny (measuring a black-hole size by its event horizon radius). They features only several kilometers in diameter, so they are too small to shield the planet. Further, their gravitational lensing would focus a lot of radiation from the supernova on the planet. However, some modifications to this setting might make this workable.</p></li>\n<li><p><strong>Using a very large black-hole</strong>: If you get a very large black-hole to shield the planet, it would probably be at least an intermediate mass black-hole or a supermassive one, and it would very likely promptly swallow the giant star preventing the supernova or perhaps spaghetifying it to the degree that it becames an accretion disc. Again, some creative modifications to this setting might be workable.</p></li>\n</ol>\n" }, { "answer_id": 47628, "author": "nzaman", "author_id": 21117, "author_profile": "https://worldbuilding.stackexchange.com/users/21117", "pm_score": 3, "selected": false, "text": "<p>It seems your aliens have got 2 contradictory problems: </p>\n\n<p>a) they want to maximize energy extraction from the supernova,</p>\n\n<p>b) their equipment can't withstand a supernova. </p>\n\n<p>Short answer: shoot the management, evacuate, come back when they have a clue</p>\n" }, { "answer_id": 47630, "author": "Victor Stafusa - BozoNaCadeia", "author_id": 3002, "author_profile": "https://worldbuilding.stackexchange.com/users/3002", "pm_score": 1, "selected": false, "text": "<p>Put a series of stationary smaller stars aligned in both sides of the big star (or perhaps, instead of stationary, make them rotating all with the same angular velocity). Don't care about spending a lot of fuel and energy to keep a bunch of stars stationary in relation with each other in order to fight against gravity and extreme tidal forces (all those stars would themselves provide more than enough energy for that). You will probably need to interlace a series of disposable rocky planets featuring the best refrigeration technology possible between the stars in order to build hi-tech bases able to keep everything in its correct place. Also, all of that will significantly screw up the big star rotation and make it deformed and ellipsoidal and would significantly deform the smaller stars too, but who cares?</p>\n\n<p>Behind the last of those stars, in one of the sides, put the planet to be protected, inside a series of concentric Dyson spheres.</p>\n\n<p>When the central star explode, it will quickly erode the first star in each side, which will protect the following stars from the blast. The first star debris however, will erode the following stars, and as it erodes, it exposes the second star which will also erode exposing the third and so on. The intermediary planets are disposable and doomed. Since there is a lot of stars between the supernova and the protected planet, it will take a significant time for the supernova to erode all of them. Since the supernova will last only a couple of days, eventually it will be extinguished with hopefully enough spare stars relatively unnafected between the detonated used-to-be star and the planet.</p>\n\n<p>The reason for placing stars in both sides is to make it gravitationally more stable, keeping the barycenter at the supernova star. Also, this would give the opportunity to build two survivable planets instead of one, so you have a backup if something go wrong with one of them.</p>\n\n<p>The series of debris will emit a lot of heat and light, just as all the dust and gas present from the combined stellar winds of all of those stars. Also, at least a few debris will eventually hit the protected planet. All of that will significantly damage the planet, but still much less than the supernova impact. So, use the series of concentric Dyson spheres as ablation shields and use your best technologies to keep them in place even if they are severely damaged. Eject to outer space instead of towards the planet any parts of any Dyson sphere ablation shield that became in too bad shape to continueing being useful.</p>\n\n<p>Also, whatever is kept in the planet, it will need to be veeeery resistant from the torrent of neutrinos constantly hitting it.</p>\n\n<p>Finally, there still are no guarantees.</p>\n\n<p>_{^{Note: Since I am the OP, I choose to not accept my own answer as correct. Please, beat my answer with something better. :D}}</p>\n" }, { "answer_id": 47650, "author": "Lino Frank Ciaralli", "author_id": 23097, "author_profile": "https://worldbuilding.stackexchange.com/users/23097", "pm_score": 0, "selected": false, "text": "<p><strong>It's time to build a world engine and surf the rainbow.</strong></p>\n\n<p>So what we're going to do here is create a world engine which will allow you to pilot the planet away from the Supernova at a rate which will keep you at it's edge in order to avoid being obliterated while simultaneously allowing for maximum data collection. The engine is going to be powered by the Supernova itself, and in order for the engine to function, the spool will need to be able to dynamically adjust to ramping fluctuations in potential energy.</p>\n\n<p>You are also going to require a star capable of sustaining a life cycle on your planet. This star will need to be placed directly opposite the supernova approach vector. Both your planet's and the stars orbit of the supernova will need to be fixed so that the planet eclipses the supernova at all times. The engine will need to operate independently of the planet's rotation while remaining fixed in a single location. This is simple to accomplish with a dual frame setup, the inner frame fixed to the planet in equidistant points for even distribution of force. </p>\n\n<p>Once all of this is accomplished, the supernova will supply the power needed to elevate the electromagnetic force necessary to create a planetary shield that will prevent radiation from cooking your planet. As a secondary application, the energy can be redirected into a powerful blast resulting in an equal and opposite reaction pushing the planet away from the expanding supernova. The excess power would be channeled into holding the star at it's fixed point by propelling it before the planet.</p>\n\n<p>In effect, you will utilize the supernova as a wave, and surf the rainbow holding a torch ahead of you to light the way.</p>\n" }, { "answer_id": 47651, "author": "Murphy", "author_id": 4750, "author_profile": "https://worldbuilding.stackexchange.com/users/4750", "pm_score": 1, "selected": false, "text": "<p>Since you seem to be looking for hard science answers, one thing to note is that it was recently proven that what we thought was the minimum energy needed to perform computation isn't the lower limit. Your linked crypto thread is now out of date.</p>\n<p><a href=\"http://phys.org/news/2016-07-refutes-famous-physical.html\" rel=\"nofollow noreferrer\">http://phys.org/news/2016-07-refutes-famous-physical.html</a></p>\n<blockquote>\n<p>&quot;Now, an experiment has settled this controversy. It clearly shows that there is no such minimum energy limit and that a logically irreversible gate can be operated with an arbitrarily small energy expenditure. Simply put, it is not true that logical reversibility implies physical irreversibility, as Landauer wrote.&quot;</p>\n</blockquote>\n<p>Some of the limits of computation, how much you could theoretically do with a certain amount of energy are based on what appear to have been incorrect beliefs about information processing and entropy.</p>\n<blockquote>\n<p>It will push the research towards &quot;zero-power&quot; computing: the search for new information processing devices that consume less energy. This is of strategic importance for the future of the entire ICT sector that has to deal with the problem of excess heat production during computation.</p>\n<p>It will call for a deep revision of the &quot;reversible computing&quot; field. In fact, one of the main motivations for its own existence (the presence of a lower energy bound) disappears.</p>\n</blockquote>\n" }, { "answer_id": 47679, "author": "nijineko", "author_id": 22912, "author_profile": "https://worldbuilding.stackexchange.com/users/22912", "pm_score": 2, "selected": false, "text": "<p>Hmmm, here's an interesting thought: </p>\n\n<p>Create a station in-between the planet and star with enough motive power to maintain position against the nova shockwave. Any potential motive output will need to be offset so that it does not interfere with the planet. It will need shielding to protect it's functioning parts from not only the shockwave, but also the energy output, and any stray chunks of stellar crust or core that may happen its way. It may also need something with enough mass to stop or deflect heavy particles which tend to ignore most objects with mass. It might need to be big enough to physically shield the planet from the nova. </p>\n\n<p>The primary function of this station is to generate, store, and emit massive amounts of anti-matter of various types. it will create a fountain of anti-matter, centered by a high pressure \"spear\" of anti-particles. Impacting the material of the nova will create continuous large explosions which will have the effect of parting the wave of the nova just in the vicinity of the planet. Remember to allow for the angular momentum of the planet's orbit, unless it is planned to temporarily halt the planet. Addendum: the motive source of the station needs to be powerful enough to not only withstand the pressure of the various waves a nova will generate, but also the long term emission of anti-matter, and the subsequent motion imparted by the matter/anti-matter reactions over time and remain functionally operative over time. </p>\n\n<p>It is possible to generate anti-matter now, and even store it for short amounts of time with our existing technology. An advanced tech-base should be able to do much more with the concept. Don't point the station at anything you want to keep, and don't let just anyone have the keys. </p>\n\n<p>Ever given any thought to ah, just picking an example at <em>random</em> mind you, building a dyson sphere around the sun at a distance likely to survive the output and then to just relocate the planet only far enough to put it just outside the dyson sphere and then hooking it into the power and sensor net of the sphere? Great way to store up extra energy, plus to avoid having your neighbors laugh at you for losing your sun, you could even have the sphere emit in the exact same spectrum as the pre-nova sun for quite a while. Just wondering. </p>\n\n<p>Oh, and according to some of our greatest thinkers on our planet, the answer is 42. Just in case you hadn't found that out yet. </p>\n" }, { "answer_id": 47683, "author": "Physicist137", "author_id": 3180, "author_profile": "https://worldbuilding.stackexchange.com/users/3180", "pm_score": 2, "selected": false, "text": "<p>There is a very simple solution, and won't require that much energy (in comparison with some of the answers).</p>\n\n<p>Warp the spacetime continuum (like <a href=\"https://en.wikipedia.org/wiki/Alcubierre_drive\" rel=\"nofollow\">alcubierre</a>) somewhere in between the star and the planet, in such way to divert all radiation/neutrinos/plasma/garbage/etc away from the planet. (And away from the warp-machines, of course).</p>\n\n<p>So... basically a big gravitational lens/shield.</p>\n" }, { "answer_id": 47726, "author": "asgallant", "author_id": 19378, "author_profile": "https://worldbuilding.stackexchange.com/users/19378", "pm_score": 1, "selected": false, "text": "<p>A supernova explosion would annihilate any known form of matter, so a solution must involve not getting hit by the supernova. You could move the planet to a larger orbit to reduce the energy of the incoming blast to something manageable, but that feels like violating the spirit of the \"no running away\" rule to me. So if you can't block the supernova, and you can't move the planet, how could you survive the blast? Easy! Use the same principles employed by the Alcubierre drive to curve spacetime between the planet and the star so that there are no straight-line light paths between the two. The star explodes and the outward burst of energy and matter flows around the planet.</p>\n\n<p>The quantity of spacetime curvature can be tweaked to allow for some of the matter and energy of the explosion to reach the planet (within the bounds of what can be shielded against), if the aliens need to do some data collection about the supernova itself.</p>\n" }, { "answer_id": 47982, "author": "MolbOrg", "author_id": 20315, "author_profile": "https://worldbuilding.stackexchange.com/users/20315", "pm_score": 2, "selected": false, "text": "<h2>Answer to answer</h2>\n\n<p>Actually interesting answer from <a href=\"https://worldbuilding.stackexchange.com/a/47679/20315\">a25bedc5-3d09-41b8-82fb-ea6c353d75ae</a> (link to answer).</p>\n\n<p>This does not fit into a comment and some points are valuable as an answer, so it's kind of a clarification for A above.</p>\n\n<p>A hard sphere is bad, no no, it has to be not hard, it has to be flexible. More than that - it has to be active and actively interact with the shock wave, and extract energy.</p>\n\n<p>Shock wave speed is around 20'000km/s. So the sphere has to have a more complex structure then just a plain sphere. It has to have some inward parts, which will accelerate to that speed in the direction of the wave, and shape the incoming wave. And with the interaction of the shape areas of the wave, without destruction of those parts (the parts which interact with the wave, have the velocity in direction from star, heading to the outside of the sphere with relatively same speed) - jets inside jets, to let areas of the wave pass the main grid (slip in-between) and begin to extract kinetic energy, heat energy from that shock wave. (The extraction has to begin even earlier, at that shaping wave time, with de-accelerating and accelerating again part which was moved to star.)</p>\n\n<p>Mad skillzz about jet-jet:\n<a href=\"https://i.stack.imgur.com/4LTA0.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/4LTA0.png\" alt=\"super nova soap bubble and jet-jet\"></a></p>\n\n<ul>\n<li>Yes, I did not forget about conservation of momentum, but it's the best way I could to draw a picture.</li>\n<li>Funny note: if you will hover near planet - not orbiting, you might spend GG of fuel and fly nowhere, be still around the planet. Not so easy, but just a funny note.</li>\n</ul>\n\n<p><strong>A</strong> of a25bedc5-3d09-41b8-82fb-ea6c353d75ae is a good answer because it suggests an energy extraction mechanisms for that whole situation.</p>\n\n<p>Also QC of those aliens, it can't be on the planet. It's just a question of efficiency. If they have reversible bits energy, they maybe do not need much of that supernova energy. If they consume and dissipate energy in the process of making calculations, placing this computer on the planet makes no sense - it can't consume that energy in a reasonable time, to make calculations of that size.</p>\n\n<p>More than that, they might use the supernova blast and for energy and for building that super QC system. They will have plenty of material, rich with heavy elements, in volumes hard to find in other parts of the universe and more importantly, hard to collect in one place (takes a long time, or special circumstances, like a super massive black hole in the middle of a galaxy).</p>\n\n<p>Even more important than energy is a possibility of having a black hole (if the chosen star is good) as the result of such explosion. Using which it is possible to extract energy from the matter they can obtain in the location - around stars and from remains of this star and other star systems. Matter of energy conversion could have a good efficiency like $\\small 0.5 \\times mc^2$(if my calculations and assumptions are correct) and potentially have a much greater yield than the explosion of supernovae itself over time.</p>\n\n<p>And those objects (Supernova remains + BH or NS) are valuable resources, so even if you have one, you might want to have more of them, and they are rare enough. This place might begin to be a place of force on a local scale (1000's ly) for them. Yes, you might get cold remains of such event of in the past, it will still valuable but could be a looong journey to power, but with all or most of remains of super nova it will be really very attractive place in therms of energy and matter, and it makes great sense to overcome all difficulties on the way to obtain it and handle the situation in more sophisticated way.</p>\n\n<p>Those guys have an adventurer's nature: <em>Everything that does not rip the universe apart, makes us stronger!</em></p>\n\n<p>This way the supernova blast is indeed, great opportunity, which might be exploited. </p>\n\n<p>This antimatter spear part also isn't bad too, might work, there will be a lot of radiations, but a shield for a planet might work too. No need to annihilate everything, just slight change of impulse to form a shadow cone. Move planet, all planets, probably rob near by systems for all heavy materials (from stars too) (not necessary), add more H He to the star to make it blast when you need it, not when it wishes(at least ability to tune process a bit, and capture more neutrons, easy to burn thermonuclear fuel is also useful stuff, not easy to make fast and in quantity).</p>\n\n<p>Just a regular matter spear will work the same way as antimatter especially if you accelerate it to 20000 km/s(not necessary, just saves some mass in exchange for energy requirements) in case if you wish to protect a planet, and it is cheaper then antimatter, and easier to obtain. Same way as <a href=\"https://en.wikipedia.org/wiki/Ablation\" rel=\"nofollow noreferrer\">Ablation</a>. So saving a planet as a bioreactor is possible. (also wave of matter from such blast is a plasma, thus using magnetic field helps to protect such spear and reduce its ablation losses)</p>\n\n<p>Anyway, better to move the planet away, at 100'000 A.U., the same distance as the sphere, the flash will come in 1.7 years, the wave in 15-20 years. A sphere of that size can dissipate (at 1200K) (or convert to energy) Hypernova 1e46J blast in one year. Strongly suggest to read my answer about <a href=\"https://worldbuilding.stackexchange.com/a/45273/20315\">planet moving</a>, \"sphere\" can be done such way.</p>\n\n<p>Distance is good not only because energy density decreases proportionally to $\\small \\sim 1/r^2$, but also because blast wave is not energy-velocity monochromatic, so this way it will grow more gradual at a bigger distance.</p>\n\n<p>Also, some separation of materials by atom weights might happen, because of acceleration mechanisms (light pressure and such), we do not need all elements equal, some we need first, and it's would nice to use the possible situation for our advantage.</p>\n\n<p>Also, this way we might focus jets into nearby stars where we have also systems waiting for actions, by focusing shockwave into Hydrogen Helium jets(after removing heavy elements, and because we might not need light elements). This will focus the energy of the blast and allow star lifting using that energy when those jets arrive in star systems around. This way we might convert nearby stars to clouds (1000's of them) which we might to transport to our BH, later. Star lifting or complete disassembly and converting a star to a cloud by using the energy of a star itself is a million's million's year process and because of that using energy of supernovae in form of those jets to speed up the process is a good idea. There are also other tricks which could be possible with those jets, as redistribution of the impulse of that shockwave matter in jets and keep our shell momentum intact(or near so) which is one of the great problems in the situation. By using the energy of the incoming wave, to accelerate some part of it to let's say near 1c velocity. It helps to leave a significant portion of the matter from the star in its system, 98\\% of it, and focus the energy of the blast in 2\\% of the matter and near 1c speed, thus it will arrive to systems we would like to disassemble much faster, 50 times faster than it would be if we just focus 20'000 km/s jets as it is. Sure efficiency will not be 100\\%, but it could be closer to that than one could expect in the situation.</p>\n\n<p>This way we do not need to catch all remains at once, only part we can and need atm, everything else we will catch in other star systems. As a backup plan, if power exceed our expectations.</p>\n\n<p>With the help of the BH and the stars around and tools, this wave can be stopped in reasonable time. </p>\n\n<p>The remains of the supernova, in the form of a BH or maybe a neutron star, in worse case (or it just another possibility also good one, I even do not know what to choose neutron start(NS) or BH, give me both) will be a great help in stopping the wave.</p>\n\n<p>Also, a great way is to launch expansion across galaxy at 0.99c speeds or fly to SMBH for goals like this answer <a href=\"https://worldbuilding.stackexchange.com/a/47939/20315\">Why would a civilization choose to inhabit a single enormous vessel instead of maintaining interstellar colonies?</a></p>\n\n<p>So yes, supernovas and possibilities they offer are really attractive, but people plz plz do it well this time, not like it was with planets (ships searching planet with live and bananas to eat, 1960-70-80-...-novadays) - let's do it right this time))</p>\n\n<p>Value of supernovas have to be noticed, senpai noticed you.</p>\n\n<h2>Note</h2>\n\n<ul>\n<li><p>A supernova starting from 10 mass of sun, so at 100'000 A.U. average amount of matter flow trough sphere from star will be 0.00704 kg/m² (or one cubic centimeter of iron), and if wave will spread during 15 year of travel, in a way let say it begins at 15y mark and ends (kinda) at 16y mark - this value per second will be much less then that (just high speed dust), but more constant pressure. We might do a lot of things with that density flow at 20000 km/s or even more, even in case of hypernova (10 times more mass).</p></li>\n<li><p>One of your priorities is to isolate remain BH or NS as soon as possible, to prevent matter being lost in accretion processes. It's more important than even catching all of the shock wave, because it might make BH and NS inaccessible for out tools in the future, for a longer period of times then we might wish.</p></li>\n<li><p>Isolating and lifting matter around a BH (NS) is a great way to utilize some energy of shock wave, this way we may catch more and easier.<br>\nAgain, clearing the area around the BH (NS) is important - it's our anchor for the operation. </p></li>\n<li><p>A spear is a good way to clear path to internal olume/guts of the explosion, shortly after the blast, before wave will come to soap bubble sphere.</p></li>\n<li><p>A sphere does not have to be tick, it's not a wall stopping shock wave - it's like mesh-net with soap bubbles</p></li>\n<li><p>15 years is more than enough time to cool down for shock wave <a href=\"https://en.wikipedia.org/wiki/Supernova#Light_curves\" rel=\"nofollow noreferrer\">Supernova, Light curves</a>.</p></li>\n<li><p>Very important moment, this <a href=\"https://en.wikipedia.org/wiki/Supernova#Energy_output\" rel=\"nofollow noreferrer\">Supernova, Energy output</a> : </p></li>\n</ul>\n\n<p><a href=\"https://i.stack.imgur.com/U3uUg.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/U3uUg.png\" alt=\"Supernova, Energy output\"></a></p>\n\n<p>Only 0.1 <a href=\"https://en.wikipedia.org/wiki/Foe_(unit)\" rel=\"nofollow noreferrer\">foe</a> (1foe=10⁴⁴J) or less in form of gamma rays and other forms of radiation, even for hypernova, most energy is in form of <em>kinetic</em> energy of ejected mass.</p>\n\n<ul>\n<li><p>Another important moment, the result of the blast are heavy elements, and after some years they already below melting points, and to contain them in compact form, soap bubbles do not need to apply any force to do that. So even parts we did not stopped may be kept compact in travel, so we will catch them as single piece later</p></li>\n<li><p>More important we do not need soap bubbles, at all, just channels where we forming sticks from that shock wave media, yes, at 20000 km/s speed. Most of elements are Al, Si and below. <a href=\"https://en.wikipedia.org/wiki/R-process\" rel=\"nofollow noreferrer\">R-process</a></p></li>\n<li><p>How big, by mass, would that sphere has to be?</p></li>\n</ul>\n\n<p>Good question. In the \"move a planet\"-question, there was a pressure of gases, and sphere's used there are rather small, and they needed 1% by mass for active surface(shell) with 1bar pressure inside. The efficiency of the solution is better with size, so with 100'000 (30 million km) times bigger, it will be 1%/100'000, so 1/10'000'000 mass of the star. (Volume grows $\\small \\sim r^3$, thickness, and mass $\\small \\sim r^2$, so the mass of content grows faster than the mass of the shell.)</p>\n\n<p>But in the case of supernova remains there is <strong>no</strong> pressure to contain (solids, with a high melting point, mostly, pretty cool after 15 years), we have just press dust into solid sticks fast enough, so even less than that. (Yes, we will catch them later, in nearby star systems.)</p>\n\n<p>So exchanging one Gas giant for carbon in the star prior the blast (until there is some carbon and it didn't burned out) is a good idea and that's enough. So probably even no need to rob nearby systems.</p>\n\n<p>Those sticks we pressed, they will need some help to collect together during flight and focus their force on near by systems to evaporate stars, and yes we have to add enough of active material to accomplish that, but I think we still good with one GG.</p>\n\n<p>Probably we might even stop <em>all</em> sticks with one GG size of material of tool, but that is not so much important until we can focus them on near by stars.</p>\n\n<ul>\n<li><p>Hypernova are not so good, as I wished, they might implode without ejecting materials, not so good, we wish ejected material.</p></li>\n<li><p>20'000 km/s is from <a href=\"https://en.wikipedia.org/wiki/Supernova#Normal_Type_Ia\" rel=\"nofollow noreferrer\">Normal Type Ia</a>:<br>\n<em>An outwardly expanding shock wave is generated, with matter reaching velocities on the order of 5,000–20,000 km/s, or roughly 3% of the speed of light.</em></p></li>\n<li><p>All energy of the blast, all 10⁴⁶J (hypernova) might be stored in form of kinetic energy around black hole(potentially, not sure about tool, BH 30km radius may be too small for tool to do that, will leak - too small BH, SMBH is better in that sense), but not around NS</p></li>\n</ul>\n\n<h2>N.B.</h2>\n\n<ul>\n<li><p>Do not sell or exchange information with them if they are farther than 2000ly away, and you have doubts you will get from them what you agreed for.</p></li>\n<li><p>Ask for 10% of QC power</p></li>\n<li><p>If they are closer then 300ly and the problem is let's say today(our time), sell it anyway(are trustworthy or not) ask for 30%.</p></li>\n<li><p>If Venus is disassembled and they are closer than 1000ly, ask for the whole system, they might solve what they wish and take planet if they wish, and sell in case if they trustworthy(but take a hefty price, do not be cheap in the case, in all of those cases).</p></li>\n<li><p>If they didn't pay after the event, it can mean 2 types of problem. One is big - they are not trustworthy, it will be The Pain, if even possible at all to get them from that system. The second problem is not a problem, needs to check plans.</p></li>\n</ul>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/47463", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/3002/" ]

[ { "answer_id": 51208, "author": "JDługosz", "author_id": 885, "author_profile": "https://worldbuilding.stackexchange.com/users/885", "pm_score": 3, "selected": false, "text": "<p>There was a SETI Weekly Seminar a while back on just how alien maths might be.</p>\n\n<p>See <a href=\"https://youtu.be/KveKjHIipgo\">Contact with ET using Math? Not so fast. - Keith Devlin</a> and <a href=\"https://youtu.be/9MV65airaPA\">ET Math: How different could it be? - John Stillwell</a>.</p>\n\n<blockquote>\n <p>We like to think that intelligent aliens would have the same basic ideas about numbers and geometry as us, but, even if they do, they might express those ideas very differently. To illustrate what different forms a concept can take, I will show how differently the law ab=ba has been interpreted at different times in human mathematical culture. This seemingly basic law has several different origins -- in geometry, number theory, and set theory -- some of which seem alien even to experienced mathematicians.</p>\n</blockquote>\n" }, { "answer_id": 51209, "author": "PtAltaria", "author_id": 22719, "author_profile": "https://worldbuilding.stackexchange.com/users/22719", "pm_score": -1, "selected": false, "text": "<p>Mathematics is completely made up by humans, so the answer is very probably no.\nCounting is present in a lot of species; the ability to track the number of objects is important. This later evolved from a simple tally system to a numeral system like we have today. This sort of system is a reasonable assumption, it facilitates all sorts of things like including trade and agriculture.</p>\n\n<p>As a presumably space-faring civilisation, they would have to have some understanding of physics, so they'd need a way of dealing with that too. It's possible this would involve mathematics, but not necessarily certain. Variables play an important roll here, so I'd guess so.</p>\n\n<p>They would have equations, you can have an equation without mathematics after all. Indices aren't actually necessary for maths, they're technically just shorthand for lots of multiplication.</p>\n\n<p>As for algebra, that's the border of the realm of pure mathematics, which has little to do with the real world. Algebra as a concept would likely make little sense to an alien, why are the earthlings adding letters together? Since algebra has a simple, consistent logic I don't think it would take long for them to figure out how it works.</p>\n" }, { "answer_id": 51216, "author": "BobbyPi", "author_id": 21618, "author_profile": "https://worldbuilding.stackexchange.com/users/21618", "pm_score": 3, "selected": false, "text": "<p>Interesting question. I tend to say it's \"just\" a matter of learning the mathematical symbols and the rules for manipulating them. Mathematic is a language and this one needs to learn it. Now one is able to discover patterns and constants. For example, the alien might learn that pi is the ratio of the circumference and the diameter of a circle and that it is always the same, say a constant. If the aliens have a concept of a circle then it is likely that they have also a symbol for pi. In that sense it may look familiar to the alien once it understands our mathematical language.</p>\n" }, { "answer_id": 52376, "author": "Reed -SE is a Fish on Dry Land", "author_id": 3027, "author_profile": "https://worldbuilding.stackexchange.com/users/3027", "pm_score": -1, "selected": false, "text": "<p>Mathematics is based on logical Euclidian type <a href=\"https://math.stackexchange.com/questions/768944/is-all-of-mathematics-based-on-logic\">proof</a>. That type of \"straightforward\" rational logic Is not necessarily shared by aliens. Even for human populations, non-westerners often have problems with <a href=\"http://wilderdom.com/personality/intelligenceCulturalBias.html\" rel=\"nofollow noreferrer\">I.Q. tests</a>, logic, or problem solving designed <a href=\"http://opinionator.blogs.nytimes.com/2012/06/03/philosophys-western-bias/\" rel=\"nofollow noreferrer\">for westerners</a>. </p>\n\n<p>Aliens could use a different type, like irrational, associative, emotional or non-linear logic. Even something as simple as <strong>1+1=2</strong> could be radically different. </p>\n\n<p>The logic could be:</p>\n\n<ul>\n<li><strong>1+1=1</strong></li>\n</ul>\n\n<p>Like in 1 water + 1 water = 1 water, 1 white light + 1 white light = 1 white light, 1 red + 1 yellow = 1 orange, 1 hunger + 1 hunger = 1 hunger, 1 eater and 1 sandwich the sandwich is gone, eaten but the eater remains, 1 male and 1 female become 1 couple,...the goal of yoga is union, so this is fusion so, 1 + 1 = 1</p>\n\n<ul>\n<li><strong>1+1=3</strong></li>\n</ul>\n\n<p>1 billing hour + 1 billing hour = 3 billing hours, ask lawyers or financiers about this one, 1 husband and 1 wife make 1 baby, so 2 becomes 3, the red-yellow previous addition could also be counted as orange which is made of red and yellow, so 3 colors are there, so it really depends on perception. All procreation relies on this so, 1 + 1 = 3</p>\n\n<ul>\n<li><strong>1+1=0</strong></li>\n</ul>\n\n<p>1 alcohol + 1 alcohol = 0 alcohol, they both evaporate, 1 stain + 1 cleaning product cancel each other so = 0, 1 traveler and 1 plane, there are no longer here, so they are both gone, so = 0, 1 army and another conflicting army kill each other so no one left at the end, 1 fat man + 1 diet = no more fat man...This could be seen as mutual destruction, in a way it can be seen as 1+ (-1) = 0, but in other cases it is dissolution, were 1 + 1 = 0</p>\n\n<ul>\n<li><strong>1+1=x</strong></li>\n</ul>\n\n<p>All the previous examples are still based on human logic and perceptions, maybe for the aliens 1 cat and 1 trombone = 42 or µ² </p>\n\n<p>Actually, maybe the aliens wouldn’t even understand the concept, or the need for addition.</p>\n\n<p><strong>Edit</strong></p>\n\n<p>I admit that my examples are not very good and some have no have no logical consistency, but I am not a logician and I just came up with some various illustrations, and interpretations, of how 1+1 may not be 2.</p>\n\n<p>I have rarely such number of DV in so little time, plus a request to close and being put on hold, particularly given the research and time it took me to seriously answer. DVs are supposed to be for bad answers with no research, not because you don’t agree. </p>\n\n<p>I wanted to give an alternative answer, I could easily have just unthinkingly brayed: <em>“Math is universal! End of the question!</em>\", like some fanatical priest.</p>\n\n<p>To me this shows that without really questioningt it, they just accept this axiom as true, and automatically rejecting any notion that math may not be a universal language. </p>\n\n<p>You may not agree, that math is subjectively based on our perception of the world and there are valid arguments why you may not, but the universality of mathematics has been a valid <a href=\"https://www.physicsforums.com/threads/dividing-1-by-three-proves-math-is-not-a-universal-language.679368/\" rel=\"nofollow noreferrer\">debate</a> for over 2000 years.</p>\n\n<p>Some constants like Pi, plank units, the speed of light are <a href=\"https://en.wikipedia.org/wiki/Physical_constant\" rel=\"nofollow noreferrer\">fixed</a>, they are inherent and not mathematically constructed, or dependend, on our mathematical understanding. </p>\n\n<p>Yes, mathematics has self logic and consistency but it is like a closed circuit philosophical system. I could also argue that if it was even close to an “universal” system, or even a good system, we would know all about <strong>prime numbers</strong>. They seem to be the fundamental building blocks of the universe and our human math only know they are there and where their <a href=\"https://en.wikipedia.org/wiki/Riemann_zeta_function\" rel=\"nofollow noreferrer\">shadows are</a>.</p>\n\n<blockquote>\n <p>What you are describing is nothing to do with mathematics. – Aron</p>\n</blockquote>\n\n<p>In a way that's my point, math is a human logic language based on arguments. It is a way for our primitive brains to grasp the universe. It is based on our perceptions of counting units like pebles and 2D surfaces like circles. </p>\n\n<p>They are other types of logic, which math, in its limited scope, declares false or not relevant, like the 9 tailed cats of <a href=\"https://thelycaeum.wordpress.com/2012/11/25/equivocation-an-airtight-argument-for-nine-tailed-cats/\" rel=\"nofollow noreferrer\">equivocation</a>. </p>\n\n<p>A basic search reveals a plethora of them like <a href=\"https://en.wikipedia.org/wiki/Non-classical_logic\" rel=\"nofollow noreferrer\">alternative logics</a>, <a href=\"http://blog.markhamanderson.com/logic-and-mathematics-not-universal-nor-absolute/\" rel=\"nofollow noreferrer\">Logic and Mathematics not Universal nor Absolute\n</a>, <a href=\"http://www.edweek.org/ew/articles/2005/07/13/42math.h24.html\" rel=\"nofollow noreferrer\">Math: the Not-So-Universal Language\n</a>.\nPlus there is lots of evidence of math being culturally subjective, <a href=\"http://www.tsusmell.org/downloads/Conferences/2006/Luchin_Closing_2006.pdf\" rel=\"nofollow noreferrer\">Math a NOT so Universal Language\n</a>, or <a href=\"http://twentyinparis.net/2013/12/18/math-is-a-universal-language-or-is-it/\" rel=\"nofollow noreferrer\">a universal language… or is it?</a></p>\n" }, { "answer_id": 52386, "author": "The Square-Cube Law", "author_id": 21222, "author_profile": "https://worldbuilding.stackexchange.com/users/21222", "pm_score": 6, "selected": true, "text": "<p>While the symbols we use to describe mathematics are a human creation, the underlying truths of math are not. The relationship between π and the radius/circunference of a circle, the square-cube law and the relationship among speed, time and distance were part of the universe before humans existed, and will continue to be after humans are gone.</p>\n<p>Any aliens who have enough technological advancement to come to Earth and disguise themselves <strong>as an act of engineering</strong> should have an understanding of Math in the very least equal to ours, even if the way they abstract math in their heads and recordings is different from ours.</p>\n<p>For such aliens, learning our algebra could be like what learning chinese or japanese is to a regular western person. Not only the symbols are different, the way you have to organize your thoughts so that you can give meaning to an idea and express it is different too. But the things you can talk about in those languages are the same things we can talk about in English, even if some things area easier to express in one language or another.</p>\n<p>As an exercise on reorganizing your thoughs to abstract and express mathematical ideas differently, and with different symbols (or different meanings for the same symbols we use), you can also learn a low-level programming language (languages that force you to learn how a computer works in very minute detail) and play with it. You'll never see an equation the same way again. In the very least you will start using less and less base 10 and more and more bases 2 and 16 (and sometimes 8) in your head. I have been doing it for years, to the point that reading time from a watch like the one below is easier for me than reading time on an analog watch.</p>\n<p><a href=\"https://i.stack.imgur.com/BJpgi.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/BJpgi.jpg\" alt=\"enter image description here\" /></a></p>\n<p>(It says 12:15 by the way)</p>\n<p>Another example of how some programmers are practically aliens when it comes to Math. The &quot;equation&quot; below (actually a simple program written in <a href=\"https://esolangs.org/wiki/Brainfuck\" rel=\"nofollow noreferrer\">Brainfuck</a>) is a simple addition. It works if both values are zeroes or positive integers and the sum of their values is no greater than 255:</p>\n<pre><code>[-&gt;+&lt;]\n</code></pre>\n<p>The best part of it is that the variables to be summed are <strong>not</strong> represented in that equation. And the &quot;+&quot; symbol there does not mean &quot;add&quot;, it means &quot;increase by one&quot;. I could not explain that in an answer here, and if I tried, the more I talked about it, the more you would think I am an actual alien.</p>\n<p>Once you've put yourself through the effort of learning a language that uses different symbols and requires you to reorder your thougths, you can use your experience to describe how learning our algebra should feel to an alien. How easy or hard that would be for said alien is up to your tayloring as the writer of your story.</p>\n<hr />\n<p>There is alternative here, though. If the aliens come to Earth as <strong>an act of magic or psionics</strong>, done intuitively or instinctively, then they may not need mathematical concepts. But this does not mean they could not have them.</p>\n" }, { "answer_id": 52420, "author": "celtschk", "author_id": 98, "author_profile": "https://worldbuilding.stackexchange.com/users/98", "pm_score": 1, "selected": false, "text": "<p>All our mathematics is built on top of our logic, with concepts of \"true\" and \"false\". However what if the alien logic doesn't have those concepts? What if they have a sort of fuzzy logic where things can be \"more true\" and \"less true\", but not \"absolutely true\" or \"absolutely false\"?</p>\n\n<p>Such an \"inconclusive logic\" would certainly affect all of their mathematics. For a start, many of out paradoxes would be completely incomprehensible to them. First, they'd have a problem to even understand the concept of a contradiction, as in their logic, a sentence could be neither true nor false, as they don't have those concepts. Also, they couldn't even formulate a sentence like \"This sentence is false\", the best they could do is \"This sentence is less true than its negation\".</p>\n\n<p>Now, one important proof method in mathematics is proof by contradiction. They wouldn't have that in their toolbox. On the other hand, they would likely have developed other tools that work better in their logic (but may be problematic to describe in ours).</p>\n\n<p>Not to mention that a \"proof\" in their mathematics would be something very different from a proof in our mathematics, as their proofs wouldn't establish truth (remember, that's not a concept in their thinking), they would just <em>increase the trueness</em>. In turn, several different proofs of the same fact might not be seen as redundant by them, but each independent proof increases the trueness of the claim.</p>\n" }, { "answer_id": 52428, "author": "Reese Johnston", "author_id": 25797, "author_profile": "https://worldbuilding.stackexchange.com/users/25797", "pm_score": 2, "selected": false, "text": "<p>Any species would have a notion of counting - at the very least, a farmer needs to know whether he has the same number of sheep at the end of the day as he did at the beginning. Once you have counting, you have addition of whole numbers.</p>\n\n<p>If the concept of a rectangle occurs to you, then multiplication is the natural next step. Now, you might not consider a rectangle to be a sensible choice of shape - an alien species might perhaps think that triangles are the right way to arrange groups of objects, and then instead of $x \\cdot y$ they might use an operation $x \\oplus y = (x \\cdot y) / 2$, or something weirder.</p>\n\n<p>Here's where I think the first major divergence opportunity kicks in. Humans, at this point, abstracted a little and moved from counting objects to measuring lengths and areas; an alien species might not make that leap at all, and might decide that the only number that exist are the whole numbers. Then division becomes complicated - if there are no non-integers, then $3/2$ makes just as little sense as $1/0$. Unfortunately, there wouldn't be much else to work with unless they eventually did decide that non-integers exist - math would stall here.</p>\n\n<p>If they accept rational numbers, then division is the natural next step. Here's the next divergence - if they made the leap of connecting numbers to distances, then square roots will happen immediately, because there's no other way to deal with triangles. If they didn't, and they just decided division was okay anyway, then they might stall again.</p>\n\n<p>Algebra would happen as usual, at least to begin with - if you care about patterns, which you have to if you're going to do math at all, then replacing numbers with symbols is the objectively correct next step.</p>\n\n<p>BUT - exponents could easily go a different way. $x$ is a length, $x^2$ is an area, $x^3$ is a volume - you could insist that $x^4$ doesn't exist, because it doesn't have a physical analogue. So an alien civilization might have functions $S(x)$ and $C(x)$ meaning $x^2$ and $x^3$ respectively, and they might know that $x \\cdot S(x) = C(x)$, but they might think $x \\cdot C(x)$ is gibberish in the same way that $1/0$ is.</p>\n" }, { "answer_id": 52450, "author": "ventsyv", "author_id": 10293, "author_profile": "https://worldbuilding.stackexchange.com/users/10293", "pm_score": 0, "selected": false, "text": "<p>Learning the symbols and getting used to base 10 will be the two major problems, then there are certain conventions such as Cartesian coordinates, the \"width\" of a degree etc, but everything else is transferable. </p>\n\n<p>I'm reading a book on the history of the computer and it said that a lot of mathematicians in the early 20th century had problems working with bases other than 10 which prevented many of them from coming up with the idea of electronic computer. Given that your alien is fairly used to different bases, it should be fairly simple for him to \"learn\" high school algebra.</p>\n\n<p>First thing would be to get familiar with the integer set and the basic operators. Properties of sets and set operations are universal, same for boolean logic, therefore it should be fairly straightforward to learn the basic operations (+, -, *, /, power, =, parenthesis) by looking at equations such as:</p>\n\n<pre><code>... Identity for +,-\n0 + 0 = 0\n\n... Transitive Property, similarly for the other equivalence properties \n0 + 1 = 1\n1 + 0 = 1\n\n1 + 1 = 2\n... So forth demonstrating 0 - 9\n\n9 + 1 = 10\n</code></pre>\n\n<p>If you take a leap of fiction and stipulate that the whole world uses SI units, you'll make your alien's life much simpler.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/51204", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/22443/" ]

[ { "answer_id": 52160, "author": "Mołot", "author_id": 809, "author_profile": "https://worldbuilding.stackexchange.com/users/809", "pm_score": 1, "selected": false, "text": "<p>I highly doubt it. But with minor changes, may be. </p>\n\n<p>In practice, only noble gases can used to create light by putting electric current thorough them. Colors we got are either red / orange or blue to ultraviolet. The latter is obtained by using argon, krypton, or xenon and that's what you want in your bug. And a lot of it in atmosphere, so bugs can filter it. </p>\n\n<p>UV is nice. It can excite many chemicals and made them glow. All these colorful neon lights you have seen? UV and luminophore. So just make your bug produce various luminophores. Or have them in \"cells\" that can be open or closed, similar to the way chameleon and some of the octopuses do. It will not change color of glowing gas, but will look close to what you're looking for. </p>\n" }, { "answer_id": 52176, "author": "a4android", "author_id": 22159, "author_profile": "https://worldbuilding.stackexchange.com/users/22159", "pm_score": 2, "selected": false, "text": "<p>If your hypothetical organism is engaged with chemiluminescence involving gases would do something like the following.</p>\n<blockquote>\n<p>Another gas phase reaction is the basis of nitric oxide detection in commercial analytic instruments applied to environmental air-quality testing. Ozone is combined with nitric oxide to form nitrogen dioxide in an activated state.</p>\n</blockquote>\n<pre><code>NO+O3 → NO2[◊]+ O2 \n</code></pre>\n<blockquote>\n<p>The activated NO2[◊] luminesces broadband visible to infrared light as it reverts to a lower energy state.</p>\n</blockquote>\n<p>Now nitric oxide can be produced in living creatures, but ozone might difficult.</p>\n<blockquote>\n<p>In mammals including humans, ·NO is an important cellular signaling molecule involved in many physiological and pathological processes</p>\n<p>Ozone is formed from dioxygen by the action of ultraviolet light and also atmospheric electrical discharges, and is present in low concentrations throughout the Earth's atmosphere (stratosphere). In total, ozone makes up only 0.6 ppm of the atmosphere.</p>\n<p>Ozone is a powerful oxidant (far more so than dioxygen) and has many industrial and consumer applications related to oxidation. This same high oxidising potential, however, causes ozone to damage mucous and respiratory tissues in animals, and also tissues in plants, above concentrations of about 100 ppb. This makes ozone a potent respiratory hazard and pollutant near ground level. However, the ozone layer (a portion of the stratosphere with a bigger concentration of ozone, from two to eight ppm) is beneficial, preventing damaging ultraviolet light from reaching the Earth's surface, to the benefit of both plants and animals.</p>\n</blockquote>\n<p>While ozone does have problems for living organisms, it is produced physiologically.</p>\n<blockquote>\n<p>Ozone, along with reactive forms of oxygen such as superoxide, singlet oxygen, hydrogen peroxide, and hypochlorite ions, is naturally produced by white blood cells and other biological systems (such as the roots of marigolds) as a means of destroying foreign bodies. Ozone reacts directly with organic double bonds. Also, when ozone breaks down to dioxygen it gives rise to oxygen free radicals, which are highly reactive and capable of damaging many organic molecules. Moreover, it is believed that the powerful oxidizing properties of ozone may be a contributing factor of inflammation. The cause-and-effect relationship of how the ozone is created in the body and what it does is still under consideration and still subject to various interpretations, since other body chemical processes can trigger some of the same reactions</p>\n</blockquote>\n<p>Your chemiluminescent signalling critter will need to produce nitric oxide and ozone and combine them in dermal cells to do its signalling. Ozone is a hazardous substance for live tissue and organs, so the critter will have to manage the ozone carefully. So provided you have a creature that can make sufficient nitric oxide and ozone, then it can send signals chemiluminescently.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/52158", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/25466/" ]

[ { "answer_id": 52168, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 4, "selected": true, "text": "<p>The answer to this is <em>very</em> dependent on details. There's many ways to approach this and they lead to very different results.</p>\n\n<p>The first question is whether you ever have infinite energy density. This causes all sorts of equations to break down for the same reasons as a naked singularity breaks down all the laws of physics. Since energy and mass are entwined in relativity, this would also imply infinite mass, which causes even more problems. More than likely the answer to this is \"the physics of this universe would be completely and utterly unrelated to anything in this universe.\" This sort of thing only shows up in the big bang models, and we readily recognize that they're just models to describe what might have happened. If singularities like that were discovered in our universe, it'd be a big deal.</p>\n\n<p>Another option would be to have infinite energy but finite energy density. If you have infinite space, you can pull that off. This can be done in a few ways. One approach is to have the entire universe be \"warm,\" so there is some base energy available at all points permitting change to occur over time. This energy, however, may not be available for doing thermodynamic work. If that energy is in the form of waste heat, then you can't use it for work.</p>\n\n<p>Another approach would be to have the infinite energy in a form which is captureable for work. To do this, we would need to toss away the <a href=\"https://en.wikipedia.org/wiki/Laws_of_thermodynamics\" rel=\"nofollow noreferrer\">laws of thermodynamics</a>. The laws of thermodynamics that we are so familiar with only apply to systems that are at thermal equilibrium, and you would be able to ensure the universe never reaches equilibrium. The field of non-equilibrium thermodynamics is a very open field at this point. We're constantly being surprised by results found in that field, so I won't speculate as to what might happen.</p>\n\n<p>You can have the energy density decrease as you get further away from some magical \"origin\" point. In this case, you could build a universe where you could simply exist forever, because you'd always be able to find an energy gradient, which is the key requirement for doing mechanical work. This would be a departure from our physics because in this world, \"we cannot define the position of God's Throne in space.\" There is no point which is any more central than any other, or any more \"fixed\" in space.</p>\n\n<p>A final intriguing option would be to change the boundary conditions. We typically assume that energy approaches 0 as we get far away. However, you could have an oscillating boundary condition that has energy going on forever in a repetitive pattern.</p>\n\n<p>This one is rather interesting because we've got examples of it in the world of simulated automata. One interesting class is the 1 dimensional elementary cellular automata. These are simulated automata consisting of a line of cells which are either alive or dead, and change states each timestep based on their state and the state of their two neighbors. They are typically known by their \"rule\" number, which is a number describing the entire evolution function of the automata. One of these, <a href=\"https://en.wikipedia.org/wiki/Rule_110\" rel=\"nofollow noreferrer\">Rule 110</a> is particularly beautiful and interesting:</p>\n\n<p><a href=\"https://i.stack.imgur.com/Mz8Lt.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Mz8Lt.png\" alt=\"enter image description here\"></a></p>\n\n<p>In these pictures, the top row is the \"starting state,\" and each subsequent row is a new generation created by applying the rules of Rule 110. All you have to do for any cell is look at the cell's left neighbor, itself, and its right neighbor, and replace the state of the center cell using the following rule.</p>\n\n<pre><code>current pattern 111 110 101 100 011 010 001 000\nnew state for center cell 0 1 1 0 1 1 1 0\n</code></pre>\n\n<p>What's interesting about this is the pattern of small triangles of size 3 that build the \"backdrop\" for rule 110. This actually appears as long as you have at least 1 \"live\" cell in your initial state. Accordingly, it is common to explore the movement of the more beautiful triangles on an infinite repeating array of these size 3 triangles.</p>\n\n<p>This would correspond to an oscillating boundary condition. Anything \"interesting\" in this world can assume that there will be a continuous influx of energy from this osculation which can be harnessed.</p>\n\n<p>As it turns out, Rule 110 is considered to be very special because it is Turing complete! That's right. Anything you can do with your computer can actually be simulated using these little triangles. They make streams of them collide in very particular ways to execute operations using something called a cyclic tagging system.</p>\n\n<p><a href=\"https://i.stack.imgur.com/EPfWx.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/EPfWx.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>Incidentally, this is very similar to a rule we see in nature, Rule 30. Rule 30 is:</p>\n\n<pre><code>current pattern 111 110 101 100 011 010 001 000\nnew state for center cell 0 0 0 1 1 1 1 0\n</code></pre>\n\n<p>We see this in cone snails, used as camouflage.</p>\n\n<p><a href=\"https://i.stack.imgur.com/OpCmu.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/OpCmu.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>So, in short, infinite energy changes everything, but there are ways it can be kept tractable, such as having oscillating boundary conditions. Some of these cases even have really interesting beahviors!</p>\n" }, { "answer_id": 52180, "author": "Cem Kalyoncu", "author_id": 11055, "author_profile": "https://worldbuilding.stackexchange.com/users/11055", "pm_score": 2, "selected": false, "text": "<p>You should make the energy distribution of the universe uniform. In your universe, there is no big bang, universe came to be in an instant and has no bounds. Your universe does not expand, but it does not collapse either; as dark energy, similar to our universe, prevents it.</p>\n" }, { "answer_id": 52195, "author": "SGR", "author_id": 20331, "author_profile": "https://worldbuilding.stackexchange.com/users/20331", "pm_score": 1, "selected": false, "text": "<p>One hypothesis for what 'dark matter' might be in our Universe is a parallel Universe that is intersecting with our Universe. The hypothesis holds that gravity can permeate through parallel universes but nothing else.</p>\n\n<p>Well, in your Universe, how about allowing some form of energy to permeate across the intersection between our Universe and another (it doesn't matter what type of energy, as energy is transferable. For example, energy in the form of IR waves to heat water to turn massive space turbines). What we think to be limitless energy is 'dark energy' stolen from another Universe. The question becomes, what happens when that Universe finds out?</p>\n" }, { "answer_id": 52199, "author": "Benubird", "author_id": 8885, "author_profile": "https://worldbuilding.stackexchange.com/users/8885", "pm_score": 1, "selected": false, "text": "<p>To allow infinite energy in your universe, you simply need to have some sort of <em>thing</em> which creates energy from nothing. Unobtanium, magic, or some specific physical property or reaction that produces energy from nothing will make the amount of energy available infinite, while still allowing it to be useful.</p>\n\n<p>The important distinction is between \"energy\" and \"available energy\" - as has been pointed out, if the universe current contains an infinite amount of energy, then nothing can happen; it's frozen into an eternal stasis of frenetic motion, in which nothing can live.</p>\n\n<p>If, alternatively, you make the total current amount of energy finite, but allow it to increase indefinitely, then you can end up with a universe that looks very much like ours, but that allows the possibility that matter - and life - might last forever (see: <a href=\"https://en.wikipedia.org/wiki/Heat_death_of_the_universe\" rel=\"nofollow\">heat death</a>).</p>\n\n<p>It's the same with space. If your universe had an infinite amount of current space, we would already be in the heat death; instead what we have is matter gradually spreading out, so that effectively the amount of space is increasing. It might or might not increase infinitely; we don't know yet (see: <a href=\"https://en.wikipedia.org/wiki/Big_Crunch\" rel=\"nofollow\">Big Crunch</a>).</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/52164", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/24960/" ]

[ { "answer_id": 53998, "author": "John Dallman", "author_id": 22020, "author_profile": "https://worldbuilding.stackexchange.com/users/22020", "pm_score": 1, "selected": false, "text": "<p>There are some ways to break this problem into simpler ones.</p>\n<h1>One laser at a time</h1>\n<p>Since both the thrust sources are lasers, they're coherent. And since managing their relative phases at distances of light-years is basically impossible, you want to have just one active at a time, to prevent interference and loss of thrust.</p>\n<h1>Look at it as two separate voyages</h1>\n<p>It's a basic physics trick to break down problems in forces to two separate problems at right angles. Since there is essentially no friction in this system, that's quite accurate for this problem. So we can look at this as two separate problems:</p>\n<ol>\n<li><p>Leaving the starting point, accelerating, making turnover, decelerating and stopping at the right distance from the start.</p>\n</li>\n<li><p>Accelerating from zero velocity on the course parallel to the station to match its actual velocity.</p>\n</li>\n</ol>\n<p>I'm not suggesting that the first voyage should be completed, and then the second started, just that it's easier to think about the problem in two pieces.</p>\n<h1>Managing the sail</h1>\n<p>Start out with the sail pointing backwards towards the start point. Leave it there until you reach turnover. Then angle it at <span class=\"math-container\">$arctan(y/x)$</span> to your course, where <span class=\"math-container\">$y$</span> is your velocity away from the start, which you have to shed, and <span class=\"math-container\">$x$</span> is the velocity of the station, which you have to acquire. Leave it to the cunning laser on the station's ability to come from a different effective direction to its actual direction to supply thrust from a constant direction relative to you.</p>\n<p>This is not the most power-efficient way to do the voyage, but it makes the least demands on the laser at the start point and on the ship. Light-sail ships are even more weight-critical than ordinary spacecraft, and swinging your sail around continuously while you're riding the station's beam takes (a) reaction mass and (b) keeping the engines and control system that use that reaction mass working. All of that costs weight. Avoiding the need to do those things makes the voyage more likely to succeed.</p>\n" }, { "answer_id": 54145, "author": "HDE 226868", "author_id": 627, "author_profile": "https://worldbuilding.stackexchange.com/users/627", "pm_score": 3, "selected": false, "text": "<p>First, let’s look at the different types of trajectories a solar sail can take. They differ mainly based on something called the <em>lightness number</em>, $\\beta$, which depends on the composition and structure of the sail. $\\beta$ can be used to determine the type of trajectory the solar sail will follow:\n$$\\begin{array}{|c|c|}\n\\hline \\text{Value of }\\beta &amp; \\text{Type of trajectory} \\\\\n\\hline \\beta=0 &amp; \\text{circular Keplerian} \\\\\n\\hline 0&lt;\\beta&lt;\\frac{1}{2} &amp; \\text{elliptical} \\\\\n\\hline \\beta=\\frac{1}{2} &amp; \\text{parabolic} \\\\\n\\hline \\frac{1}{2}&lt;\\beta&lt;1 &amp; \\text{hyperbolic} \\\\\n\\hline \\beta=1 &amp; \\text{rectilinear} \\\\\n\\hline 1&lt;\\beta &amp; \\text{flipped hyperbolic} \\\\\n\\hline\n\\end{array}$$\nThis is also evident in Figure 4.8 (page 123) of Colin McInnes’ <a href=\"https://books.google.com/books?id=lvHxBwAAQBAJ&amp;pg=PA130&amp;lpg=PA130&amp;dq=solar+sail+logarithmic+spiral+escape+trajectory&amp;source=bl&amp;ots=inAfjimvhX&amp;sig=Qqkxsftl5xmPG-cyJOnQSi5DIIY&amp;hl=en&amp;sa=X&amp;ved=0ahUKEwiM68WEsvHOAhXGXB4KHVbWDMUQ6AEIIjAB#v=onepage&amp;q&amp;f=false\" rel=\"noreferrer\"><em>Solar Sailing: Technology, Dynamics and Mission Applications</em></a>, which is my primary reference in this answer:</p>\n\n<p><a href=\"https://i.stack.imgur.com/6Lx4p.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/6Lx4p.png\" alt=\"enter image description here\"></a></p>\n\n<p>Now, you can see that a hyperbolic trajectory of some sort may be exactly what you’re looking for - and, in fact, it requires no assistance from the base it is rendezvousing with! Parabolic trajectories, too, are escape trajectories, but a hyperbolic trajectory might be more efficient. Plus, having a greater lightness number results in a greater characteristic acceleration (see <a href=\"http://earth-escape.com/paper/200207_Pozzuoli_SeboldtDachwald.pdf\" rel=\"noreferrer\">Seboldt &amp; Dachwald (2003)</a>), because $a_c\\propto\\beta$. Therefore, I’d prefer to work with a flipped hyperbolic trajectory; I’ll choose $\\beta\\approx2$.</p>\n\n<p>There are two equations of motion for polar coordinates $(r,\\theta)$:\n$$\\frac{\\mathrm{d}^2r}{\\mathrm{d}t^2}-r\\left(\\frac{\\mathrm{d}\\theta}{\\mathrm{d}t}\\right)^2=-\\overbrace{\\frac{\\mu}{r^2}}^{\\text{gravitational}}+\\overbrace{\\beta\\frac{\\mu}{r^2}\\cos^3\\alpha}^{\\text{radiation}}\\tag{4.37a}$$\n$$r\\frac{\\mathrm{d}^2\\theta}{\\mathrm{d}t^2}+2\\left(\\frac{\\mathrm{d}r}{\\mathrm{d}t}\\right)\\left(\\frac{\\mathrm{d}\\theta}{\\mathrm{d}t}\\right)=\\beta\\frac{\\mu}{r^2}\\cos\\alpha^2\\sin\\alpha\\tag{4.37b}$$\nwhere $\\mu$ is the <a href=\"https://en.wikipedia.org/wiki/Standard_gravitational_parameter\" rel=\"noreferrer\">standard gravitational parameter</a> and $\\alpha$ is the angle between a vector normal to the sail and a vector pointing from the star to the sail. Compare McInnis’ $(\\text{4.37a})$ to $(\\text{346})$ <a href=\"http://www2.ph.ed.ac.uk/~egardi/MfP3-Dynamics/Dynamics_lecture_21.pdf\" rel=\"noreferrer\">here</a>, with the substitution of $h=r^2\\dot{\\theta}$. The two are identical, with the addition of the radiation term in the solar sail reformulation. Let’s have $\\alpha\\approx0$. This means that the right-hand side of $(\\text{4.37a})$ becomes $(\\beta-1\\frac{\\mu}{r^2}$, and the right-hand side of $(\\text{4.37b})$ becomes $0$.</p>\n\n<p>We can arrive at a simple analytical solution if we assume that the solar sail takes the path of a <a href=\"https://en.wikipedia.org/wiki/Logarithmic_spiral\" rel=\"noreferrer\">logarithmic spiral</a>, i.e. a path of the form\n$$r(\\theta)=r_0\\exp(\\theta\\tan\\gamma)$$\nwhere $r_0$ is the initial radius and $\\gamma$ is the <em>spiral angle</em>, the angle between the velocity vector and the transverse direction of the sail’s path. So let’s step back a little, and let’s assume that</p>\n\n<ul>\n<li>$\\beta\\approx0.75$ (I’ve chosen a value for a normal hyperbolic trajectory)</li>\n<li>$\\alpha\\neq0^{\\circ}$. It <em>could</em>, but that might not be optimal.</li>\n</ul>\n\n<p>McInnes goes through several substitutions, leading to\n$$r^3\\left(\\frac{\\mathrm{d}\\theta}{\\mathrm{d}t}\\right)^2=\\mu\\left[1-\\beta\\cos^2\\alpha(\\cos\\alpha-\\tan\\gamma\\sin\\alpha)\\right]\\cos^2\\gamma\\tag{4.41}$$\nFrom this and earlier substitutions, we can derive expressions for the radial velocity $v_r(r)$ and angular velocity $v_{\\theta}(r)$. The equation for the former is\n$$v(r)=\\sqrt{\\frac{\\mu}{r}}\\left[1-\\beta\\cos^2\\alpha(\\cos\\alpha-\\sin\\alpha\\tan\\gamma)\\right]^{1/2}\\tag{4.44}$$\nThere’s a fairly complicated relationship between $\\gamma$ and $\\alpha$, but it can be simplified for small $\\gamma$:\n$$\\frac{\\beta\\cos^2\\alpha\\sin\\alpha}{1-\\beta\\cos^3\\alpha}=\\frac{\\sin\\gamma\\cos\\gamma}{2-\\sin^2\\gamma}\\approx\\frac{1}{2}\\tan\\gamma\\tag{4.45,4.48}$$\nThis integration is important when we try to find a relationship between $r$ and $t$. We integrate $(\\text{4.44})$:\n$$\\int_{r_0}^r\\sqrt{r}\\mathrm{d}r=\\int_{t_0}^t\\left(2\\beta\\mu\\sin\\alpha\\cos^2\\alpha\\tan\\gamma\\right)^{1/2}\\mathrm{d}t\\tag{4.46}$$\nIntegrating this and substituting in $(\\text{4.48})$ yields\n$$t-t_0=\\frac{1}{3}\\left(r^{3/2}-r_0^{3/2}\\right)\\left(\\frac{1-\\beta\\cos^3\\alpha}{\\beta^2\\mu\\cos^4\\alpha\\sin^2\\alpha}\\right)^{1/2}\\tag{4.49}$$\nHowever, we can simplify this by letting $t_0=0$ and focusing on cases where $r_0\\ll r$ for most $r$, which is the case here when $r=r_f$. We can then find when the function of $\\alpha$ in $(\\text{4.49})$ is maximized; it turns out that for small $\\beta$ (i.e. $\\beta&lt;0.5$), $\\alpha_{\\text{max}}\\approx35.26^{\\circ}$. However, I chose $\\beta=0.75$, and so it turns out that $\\alpha$ is maximized at about $35.26^{\\circ}$. Plugging this back into our approximation for $\\tan\\gamma$, we find that $\\tan\\gamma\\approx1.362$, which gives us $\\gamma\\approx53.7^{\\circ}$. This likely makes our small angle approximation for $\\tan\\gamma$ less accurate, but it will do for now. Plugging this in, and assuming once again that $t_0=0$ and $r_0\\ll r$, $(\\text{4.49})$ gives us\n$$t=r^{3/2}\\times1.23\\times10^{-10}$$\nand for a final radius of three light-years ($2.838\\times10^{16}$ meters), we find that $t\\approx5.88\\times10^{14}$ seconds, or about 19 million years. That might seem like it can’t be correct, but <a href=\"http://www.centauri-dreams.org/?p=4238\" rel=\"noreferrer\">Centauri Dreams cites Matloff et al. that it could take a really good solar sail 30 years just to reach the Oort Cloud</a>, 500 AU away - and one light-year is about 60,000 AU. Clearly, a simple logarithmic spiral quite like this won’t work.</p>\n\n<p>In fact, this means that you absolutely need to give the solar sail a very fast initial boost to make interstellar travel on these scales even remotely feasible. This makes the equations a little harder, and it means that yyou might not see an easy analytical solution pop up.</p>\n\n<p>Let’s go back to our original coupled equations $(\\text{4.37a})$ and $\\text{4.37b})$, where we’ve set $\\beta=2$ and $\\alpha=0$. This becomes a simple <a href=\"https://en.wikipedia.org/wiki/Classical_central-force_problem\" rel=\"noreferrer\">central force problem</a>, which has one equation of the form\n$$\\frac{\\mathrm{d}^2r}{\\mathrm{d}t^2}-\\frac{h^2}{r^3}=\\frac{F(r)}{m}$$\nwhere I’ve defined $h\\equiv r^2\\dot{\\theta}$, which is conserved. $F(r)$ is the central force as a function of $r$; normally, in orbital mechanics, it’s simply\n$$F(r)=-\\frac{GMm}{r^2}$$\nas is the case in $(\\text{346})$; here, as I noted before, we also have to account for the force from radiation pressure. With $\\beta=2$, it just so happens that the two forces add up to\n$$F(r)=\\frac{-GMm}{r^2}+\\frac{(2)GMm}{r^2}=\\frac{GMm}{r^2}$$\nwhich is repulsive, unlike $(\\text{346})$. <a href=\"http://www2.ph.ed.ac.uk/~egardi/MfP3-Dynamics/Dynamics_lecture_21.pdf\" rel=\"noreferrer\">That pdf</a> shows a good derivation of the orbital equation from the central force law, which I’m not going to go through again, as it’s pretty standard. For a generic central force of the form\n$$F(r)=-\\frac{k}{r^2}$$\nwe arrive at an orbit of the form\n$$r(\\theta)=\\frac{l}{1+\\varepsilon\\cos\\theta}\\tag{355}$$\nwhere $k=-GM$ (in general, $k=(\\beta-1)GM$), and\n$$l\\equiv\\frac{mh^2}{k},\\quad\\varepsilon\\equiv\\frac{l}{a}-1\\tag{356}$$\nI’m no expert when it comes to solar sail construction, so I read through <a href=\"http://www.esa.int/esapub/bulletin/bullet108/chapter6_bul108.pdf\" rel=\"noreferrer\">McInnes et al. (2001)</a> and came up with a conservative estimate of 2,000 kg. The authors estimated that you could send a 900 kg solar sail to solar orbit, with much of that mass being payload. My guess could be way off, so I’d appreciate it if an expert has better figures.</p>\n\n<p>I assumed that the solar sail starts out on a circular orbit around a sun-like star at roughly Earth’s semi-major axis. From this, I calculated\n$$v_0=\\sqrt{\\frac{\\mu}{r}}=2.97\\times10^4\\text{ m/s}$$\n$$h=\\frac{|L|}{m}=\\frac{rmv}{m}=rv=4.46\\times10^{15}\\text{ m}^2\\text{/s}$$\n$$k=(\\beta-1)GM=1.327\\times10^{20}\\text{ m}^3\\text{/s}^2$$\n$$l\\equiv\\frac{mh^2}{k}=3\\times10^{14}$$\n$$\\varepsilon\\equiv\\frac{l}{a}-1=2000$$\nFrom this, I get\n$$r=\\frac{3\\times10^{14}}{1+2000\\cos\\theta}$$\n$\\varepsilon&gt;1$ (as was expected, given that $\\beta&gt;1$), and in fact $\\varepsilon\\gg1$. </p>\n\n<p>I used modified code from <a href=\"http://www.physics.buffalo.edu/phy302/topic1/#sec-15\" rel=\"noreferrer\">this page</a> to solve $(\\text{4.37a})$ in Mathematica and plot the motion of the solar sail over the course of one year:</p>\n\n<pre><code>M = 1.99 10^30 (*mass of Sun*)\nG = 6.67 10^-11 (*Newton's constant*)\nx0 = 1.50*10^11 (*apsidal distance*)\ny0 = 0; vx0 = 0;(*on x axis with velocity in y direction*)\nvCirc = Sqrt[G M/x0] (*apsidal speed for circular orbit*)\nvy0 = 0.8 vCirc (*smaller speed gives elliptical orbit*)\na = 1/(2/x0 - vy0^2/(G M)) (*semimajor axis from E=T+V*)\nT = 2 Pi Sqrt[a^3/(G M)] (*period from Kepler's third law*)\nbeta = 2 (*accounts for radiation pressure*)\n\nr[t_] := {x[t], y[t]} (*position vector*)\n\nequation = Thread[r''[t] == (beta-1) G M r[t]/Dot[r[t], r[t]]^(3/2)]\n\ninitial = Join[Thread[r[0] == {x0, y0}], Thread[r'[0] == {vx0, vy0}]]\n\nsolution = NDSolve[Join[equation, initial], r[t], {t, 0, T}]\n\norbit = ParametricPlot[r[t] /. solution, {t, 0, T}];\nShow[orbit]\n</code></pre>\n\n<p>This is the orbit:</p>\n\n<p><a href=\"https://i.stack.imgur.com/xTgVi.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/xTgVi.png\" alt=\"enter image description here\"></a></p>\n\n<p>As you can see, it travels in essentially a straight line, going at a little over 5 Au per year, at first. That’s not bad at all. It’s still going to take a long time to reach the base, but this is likely going to be on the order of thousands of years, not millions of years.</p>\n" }, { "answer_id": 54522, "author": "Mike Nichols", "author_id": 879, "author_profile": "https://worldbuilding.stackexchange.com/users/879", "pm_score": 2, "selected": false, "text": "<p>I believe the desired outcome can be achieved with relatively simple means. The trick with solar sails is that although the incoming light can only push the sail directly, the reflection of that light can push the sail in a different direction. The resulting net thrust is the combination of the incident light and the reflected light. For a solar sail being pushed by lasers at significant fractions of C it’s safe to assume that the the sail will have near 100% reflectivity (otherwise the non-reflected light would incinerate the ship) so the magnitudes of the incident and reflected light will be approximately equal. Since from basic geometry we know that the angle of incident light and the angle of reflection will be equal, then the angle of thrust, or net acceleration will always be directly orthogonal to the plane of the sail. This means the solar sail will always accelerate straight ahead. If we want to accelerate in a different direction, we simply have to turn our sail to face directly away from that direction, treating the sail as if it were any other conventional source of thrust. The caveat though is that changing the orientation of the sail changes the magnitude of the experienced thrust. The acceleration of the sail can be computed by the following functions:</p>\n\n<p><a href=\"https://i.stack.imgur.com/5yxKJ.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/5yxKJ.png\" alt=\"sail equations\"></a></p>\n\n<p>Since all the variables in the above equations are constants with the exception of B, the angle of the sail with respect to the laser, we can deduce the relationship between the acceleration of the ship and the angle B to be Accel = cos(B)^2. That is to say when B is 0 and the sail is facing the laser directly it will experience maximal acceleration and when B is 90 degrees and the sail is sideways to the laser is will experience 0 acceleration.</p>\n\n<p>It follows that if we want our trip to be efficient we need to minimize B. Of course, if you want to make the whole thing much simpler you can simply say the light comes from directly behind the craft at all times due to some fancy technology. In that situation the force experienced by the ship will always be constant. But that also takes all the fun out of solar sails doesn’t it?</p>\n\n<p>So with this system we can accelerate in any direction away from the laser source, but never back towards it. However, the efficiency of our acceleration decreases rapidly the harder we try to turn. One consequence of this is that it will be difficult to ever use both lasers simultaneously with any efficiency since they are ~90 degrees apart. This means for the first leg of our journey we are going to want to accelerate directly away from our home laser towards some far off rendezvous point and ignore the station laser. By accelerating directly away and keeping B equal to 0 we maximize our acceleration. At some point though we will need to reduce our velocity towards the oncoming station in order not to overshoot it. We have to use the station laser to do this. Ideally by this time we are closing with the station and thus the angle we must thrust to match velocities with the station is close to that of the laser making our thrust once again efficient.</p>\n\n<p>The below schematic isn’t exactly what I am describing above, it was made before I realized how inefficient the angled thrusting would be, but it still gets the general concept across.</p>\n\n<p><a href=\"https://i.stack.imgur.com/4r2jD.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/4r2jD.png\" alt=\"setting sail\"></a></p>\n\n<p>With regards to the effects of relativity. Obviously the lasers from both parties will need to be aimed light-years ahead of the ship’s path with absurdly precise calculations and a predetermined course. Even a slight error would compound and eventually throw the ship out of the path of the lasers which had been fired years in advance. Even with faster than light communications this would be a remarkable feat.</p>\n\n<p>To specifically address your concerns regarding relativity and the angle of the sail:</p>\n\n<blockquote>\n <p>I’m supposing that the angle at which it presents the sail will be\n significantly affected by relativistic effects and aberration of\n moving source.</p>\n</blockquote>\n\n<p>The aberration of light due to the movement of the station will not change the direction the ship accelerates since we determined above that the ship always accelerates orthogonal to the plane of the sail. The aberration of light will however change the magnitude of that thrust by influencing the projected area of the sail (and therefore the amount of light that hits the sail) and the proportion of the incident and reflected thrust vectors that are productive (how much of those vectors cancel each other out).</p>\n\n<p>This answer doesn’t include a precise plot of an optimal course for the ship to take. This is because there are many possible courses and they differ drastically based on the relative strengths of the lasers and the distances and velocities involved. For instance, if the station laser is significantly more powerful than the home laser we will want a course that lets us flip over to utilize it as soon as possible. But that course is very different from one in which the home laser is preferred. Based on the distances and velocities and maximal accelerations involved the ship might have to begin accelerating on a course nearly parallel to that of the station to ensure it matches velocities before the station passes. Or if the station is very far off maybe it can simply accelerate directly into the path of the station and then be brought up to speed by the maximal effectiveness of the station’s laser pushing the ship directly in front of it. I see no way to simply compute a single optimal course even if those missing constants were defined. I do think that this answer provides insight into the principles of the laser-powered lightsail’s operations and the equations necessary to calculate the time a given course will take.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/52675", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/885/" ]

[ { "answer_id": 54809, "author": "Feyre", "author_id": 26119, "author_profile": "https://worldbuilding.stackexchange.com/users/26119", "pm_score": 3, "selected": false, "text": "<p>So first of all, we need to define our terms here. To be clear, the orbit relates to the barycenter of the system. The changes are such that Janus is always farther away from Saturn's center of gravity than Epimetheus. When it comes to the barycenter.</p>\n\n<p>I generated a constrained 3-body model, and plotted the distance of the moons from the barycenter, running form 2006 January 1 00:00 TDB, over 20 days.\nThis is a transition in which Janus starts out farther than Epimetheus.</p>\n\n<p><a href=\"https://i.stack.imgur.com/w1cz4.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/w1cz4.png\" alt=\"enter image description here\"></a></p>\n\n<p>So far so good. In fact, we could just extend this to your problem, scaling all parameters so that they can apply to a very large star, and planets, they will of course not follow your instructions.\nNow to your example, the gravitation parameters calculated as the fractions ps the Sun and Earth mass are as follow:</p>\n\n<ol>\n<li>Star ...... - $0.5403728495401237^{-3}\\left[AU\\right]^3/\\left[Day\\right]^2$</li>\n<li>Planet A - $0.9776461689638198^{-9}\\left[AU\\right]^3/\\left[Day\\right]^2$</li>\n<li>Planet B - $0.7110153956100508^{-9}\\left[AU\\right]^3/\\left[Day\\right]^2$</li>\n</ol>\n\n<p>Next the positions and velocities.\nWe will <em>derive</em> the star's Ephemeris, so let's start with Planet A.</p>\n\n<p>Assuming the star has 1.1 times the sun's luminosity dependent on surface which is r squared rather than mass' r cubed, but I'm not changing all this stuff now that I realized this :), this means that for a similar habitableness.</p>\n\n<pre><code>Solve[{L == 1.1 L2, L == 1/r^2, L2 == 1/r2^2}]\n</code></pre>\n\n<blockquote>\n <p>r -> 0.953463 r2</p>\n</blockquote>\n\n<p>So our new orbit is at <code>1.04881</code> times Earth's orbital radius, or simply <code>1.04881AU</code>. Which we will use as the initial x-component for position, with y- and z-components 0.</p>\n\n<p>For an eccentricity of (near) 0 with respect to the barycenter, it further needs a velocity of:\n$$\\sqrt{a r}\\approx\\sqrt{\\mu_{star}/r_{star}}=0.02216411615734939\\left[AU\\right]/\\left[Day\\right]$$\nUnfortunately this is inconsistent with the idea of a 500 day orbit, so I will ignore this here.</p>\n\n<p>Now to Planet B, let's give it the position and velocity that Planet A will have one day later. We can multiply the resultant position and velocity by some factor, and be assured that they remain consistent and that crossing events take place because of the planets' gravitational pull towards each other.</p>\n\n<p>The result can give.... interesting orbits.\nFor instance, when Planet B has initial orbital radius of 0.995 times and initial velocity of 1.005 times that of Planet A:\nDistance of planets from the barycenter:</p>\n\n<p><a href=\"https://i.stack.imgur.com/hUDEH.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/hUDEH.png\" alt=\"enter image description here\"></a></p>\n\n<p>One orbit:</p>\n\n<p><a href=\"https://i.stack.imgur.com/swDeA.gif\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/swDeA.gif\" alt=\"enter image description here\"></a></p>\n\n<p>Using $t=500$ yields: <code>{{r -&gt; 1.68759, v -&gt; 0.0178942}}</code>.\nWe can then continue as before.</p>\n\n<p>Unfortunately, the effect which you are looking for, I'm not finding experimentally, I suspect the ratio beween the Sun and the planet's masses is too slim, if I draw the planets close enough together, they just end up sling-shotting each other out of orbit.</p>\n\n<p>So I sadly don't think it's going to work at this distance from the sun.</p>\n\n<p><a href=\"https://i.stack.imgur.com/hnLNW.gif\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/hnLNW.gif\" alt=\"enter image description here\"></a></p>\n\n<p>You can have <em>interesting</em> orbits, orbits that cross each other, but not this.</p>\n" }, { "answer_id": 54887, "author": "Nolo", "author_id": 19530, "author_profile": "https://worldbuilding.stackexchange.com/users/19530", "pm_score": 0, "selected": false, "text": "<p>Up front, I have zero background in this so I offer no hope of explaining any of the following to you, however, to add to <a href=\"https://worldbuilding.stackexchange.com/questions/53803/two-planets-in-a-stable-horseshoe-orbit#54809\">Feyre's</a> answer, <a href=\"http://www.orbitsimulator.com/yabbfiles/Attachments/Convunit_to_RealSma_.txt\" rel=\"nofollow noreferrer\">these initial conditions</a> may be useful to help determine if the orbit you want is possible. They are derived from <a href=\"http://www.orbitsimulator.com/cgi-bin/yabb/YaBB.pl?num=1289461093\" rel=\"nofollow noreferrer\">this discussion thread</a> around <a href=\"http://adsabs.harvard.edu/abs/1981A%26A...103..288T\" rel=\"nofollow noreferrer\">this paper</a>.</p>\n\n<p>An <a href=\"http://adsabs.harvard.edu/full/1967AJ.....72..149S\" rel=\"nofollow noreferrer\">earlier paper</a> on the same subject is here.</p>\n\n<p>Maybe Feyre or others can help to utilize these resources and come to a meaningful conclusion.</p>\n" }, { "answer_id": 98150, "author": "Klaws", "author_id": 17789, "author_profile": "https://worldbuilding.stackexchange.com/users/17789", "pm_score": 1, "selected": false, "text": "<p>There is no such thing as a \"stable horseshoe orbit\".</p>\n\n<p>Horseshoe orbits can be observed in reality, of course - but how stable are they?</p>\n\n<p>\"We find that horseshoe co-orbitals are generally long lived (and potentially stable) for systems with primary-to-secondary mass ratios larger than about 1200\". That's the case for Earth and Trojan asteroids, but not a suitable solution to the OP's question.</p>\n\n<p>What about Epimetheu and Janus? This horseshoe orbit can possibly have a lifetime of more than 10Gyr (10^10 years). For comparison: Earth is about 4.5Gyr old and the universe about 13.7Gyr. So plenty of time to develop life...right?</p>\n\n<p>Unfortunately, with a central body of a larger mass (like the sun), the stability/lifetimes of the horseshoe orbits suffer. For a central mass equal to that of Jupiter, the horseshoe orbits will have a lifetime measured in Myr (million years).</p>\n\n<p>Source and further reading: <a href=\"https://pdfs.semanticscholar.org/6e46/9b3abad04b18beed9b0044b45f11f327f647.pdf\" rel=\"nofollow noreferrer\">https://pdfs.semanticscholar.org/6e46/9b3abad04b18beed9b0044b45f11f327f647.pdf</a></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/53803", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/22607/" ]

[ { "answer_id": 56144, "author": "John Dallman", "author_id": 22020, "author_profile": "https://worldbuilding.stackexchange.com/users/22020", "pm_score": 4, "selected": false, "text": "<p>No. The cellphone is not a general-purpose radio transmitter, and without a signal from a base station (the kind that exists in every cellphone tower) it won't send anything except the \"hello, any base stations out there?\" signal. </p>\n\n<p>Modifying it to do anything else is impractical: it's built to operate with a base station network, and the logic of doing that is built into its chips. The manufacturers <em>wanted</em> it to be hard to hack, because doing so would allow malicious users to mess up the cellphone network. </p>\n" }, { "answer_id": 56145, "author": "Separatrix", "author_id": 16295, "author_profile": "https://worldbuilding.stackexchange.com/users/16295", "pm_score": 7, "selected": true, "text": "<p>Assets</p>\n\n<ul>\n<li><p>1 obsolete piece of short range comms kit requiring a battery you probably can't charge</p></li>\n<li><p>1 slightly malfunctioning escape pod with up to date comms that isn't working but you're still alive</p></li>\n</ul>\n\n<p>Current standards say the Mayday should be broadcast on VHF channel 16 (156.8 MHz). A 1999 phone, probably on 2g would likely use 900MHz (UHF). The slightly broken comms unit in the pod is probably using channel 16 or equivalent*. This is your first problem. The patrol ship will be listening in for signals broadcast on the mayday frequency. That's the frequency you need to hit, so first up is rebuilding your phone to that frequency.</p>\n\n<p><em>Or you could look at the pod comms system and see what's wrong.</em></p>\n\n<p>Your next problem is that your mobile phone's range is laughable in interstellar space. What's going to be even more laughable is when you try to use it in the radiation shielded environment of your escape pod. The signal, which is line of sight at the best of times, most likely won't even penetrate the hull. So now you need to hook it up to the external antenna used by the pod's own comms system.</p>\n\n<p><em>Or you could look at the pod comms system and see what's wrong.</em></p>\n\n<p>Now you need to make sure you're using the right broadcast method: are you on AM or FM? (There's no reason to think that 100 years from now they'd be able to pick up an analog signal)</p>\n\n<p><em>I'm sure you can see where I'm going with this. Fix the pod.</em></p>\n\n<p>Ultimately all you're going to do is rebuild a copy of the pod's own comms system with a batch of obsolete components. If you're good enough to do that you're good enough to fix the pod's own system which will be much easier.</p>\n\n<hr>\n\n<p>*I mention channel 16 as an example to show that there are standards for distress signals and they're very different from the standards for mobiles, if you want someone to pick it up then you need to be broadcasting on a frequency they're listening on.</p>\n\n<p><strong><a href=\"https://en.wikipedia.org/wiki/2182_kHz\">Distress frequencies</a></strong></p>\n\n<blockquote>\n <p>2182 kHz forms an essential part of the Global Maritime Distress Safety System (GMDSS). It has an associated DSC frequency at 2187.5 kHz. Other international distress frequencies, in use as of 2008, include:</p>\n</blockquote>\n\n<pre><code>121.5 MHz - civil aircraft emergency frequency\n243 MHz - military aircraft emergency frequency\n156.8 MHz - Marine VHF radio channel 16, short range maritime use\n406 MHz / 406.1 MHz - Cospas-Sarsat international satellite-based search and rescue (SAR) distress alert detection and information distribution system\n</code></pre>\n\n<p>Discontinued frequencies</p>\n\n<pre><code>500 kHz Morse code is no longer monitored.\n121.5 or 243 MHz locators. (No longer automatically monitored by satellite, though still used for aircraft communication and short-range direction finding.)\nEffective 1 August 2013, the U. S. Coast Guard terminated its radio guard of the international voice distress, safety and calling frequency 2182 kHz and the international digital selective calling (DSC) distress and safety frequency 2187.5 kHz. Additionally, marine information and weather broadcasts transmitted on 2670 kHz terminated concurrently.\n</code></pre>\n" }, { "answer_id": 56146, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 1, "selected": false, "text": "<h1>Yes</h1>\n<p>I vote for yes. Cell phones back then used to have huge batteries. You might be able to rig something up to transmit some kind or morse code just through electromagnetic interference noise.</p>\n<p>How much power you can generate depends on how much wire you have and how much electrical current you're prepared to sacrifice.</p>\n<hr />\n<p><a href=\"https://en.wikipedia.org/wiki/Electromagnetic_interference\" rel=\"nofollow noreferrer\">Electromagnetic Interference</a></p>\n<p>Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. The disturbance may degrade the performance of the circuit or even stop it from functioning. In the case of a data path, these effects can range from an increase in error rate to a total loss of the data. Both man-made and natural sources generate changing electrical currents and voltages that can cause EMI: automobile ignition systems, cell phones, thunder storms, the Sun, and the Northern Lights. EMI frequently affects AM radios. It can also affect cell phones, FM radios, and televisions.</p>\n<p>EMI can be used intentionally for radio jamming, as in electronic warfare.</p>\n<hr />\n<p>As right pointed out by another answerer, your ship will have shielding to protect the occupants from external radiation/electromagnetism. You're going to need to somehow shove that transmitter out of the airlock but still have control over it.</p>\n" }, { "answer_id": 56149, "author": "Abulafia", "author_id": 2087, "author_profile": "https://worldbuilding.stackexchange.com/users/2087", "pm_score": 4, "selected": false, "text": "<p>A cellphone from our era transmits with a power between 0.6 and 3 watts. For comparision, the Voyager probes had a 12 watt antenna. To succeed, the Voyager had to aim its dish at Earth and large radio telescopes on Earth were needed to receive the feeble signal.</p>\n\n<p>If the transponder's dish isn't broken and can be pointed to likely craft locations, a cellphone may therefore produce enough power for a signal, even if it's gibberish. A cellphone will usually max out its transmissions power when searching for a base station. </p>\n\n<p>Aiming at a large radio telescope somewhere would be better than broadcasting aimlessly. If you can transmit to Earth when your pod passes directly between say, Earth and Mars with it colonies, a lot of radio telescopes on Earth would already be aimed your way. </p>\n" }, { "answer_id": 56150, "author": "VouchForMe", "author_id": 27513, "author_profile": "https://worldbuilding.stackexchange.com/users/27513", "pm_score": 2, "selected": false, "text": "<p>Yes you can. \n<strong>However</strong>, the signal strength would be weak considering it's a cell phone and the range rather poor. Considering all the interference which could obstruct you (wall, other frequencies, magnetic fields, solar flares etc) your chances of reaching a receiver are close to zero unless it is in close proximity and actively searching for a signal.</p>\n" }, { "answer_id": 56157, "author": "Durakken", "author_id": 22659, "author_profile": "https://worldbuilding.stackexchange.com/users/22659", "pm_score": 1, "selected": false, "text": "<p>I don't think you can, based on the simple fact that you might get lucky and grab a walkie talkie, which was popular around that time to build into a phone, (The ranges I see got for that are in the range of 30 to 40 miles. Low Earth Orbit is around 100 miles up.) the more likely event is that you get your hands on a <a href=\"http://www.gsmarena.com/nokia_3210-6.php\" rel=\"nofollow\">Nokia 3210</a> or maybe a <a href=\"http://www.gsmarena.com/nokia_9110i_communicator-18.php\" rel=\"nofollow\">Nokia 9110</a> which doesn't even have that possibility to reach LEO it seems, but their batteries, provided they work, have around 4 Wh of power so, yay...</p>\n\n<p>Probably, a much better use of your time is to look for any object that can be used to focus light or produce a laser and use the battery of the phone to power that to send an SOS in morse code using the light. That might even be how we communicate then anyways and all you'd have to do is figure out where to point the thing and send a coherent message. In that case, you would need to just write a program that very rapidly turns on and off the laser to convery the binary keyboard inputs into binary and flashes of light. Then you'd have a real time one-way communication and be able to request help very easily at that point.</p>\n" }, { "answer_id": 56161, "author": "Pieter B", "author_id": 2130, "author_profile": "https://worldbuilding.stackexchange.com/users/2130", "pm_score": 5, "selected": false, "text": "<p>I vote yes.</p>\n\n<p>A lot of the cellphones back then already had a camera and flashlight. Actually the flashlight in those phones is often just a bright light, it doesn't even flash.</p>\n\n<p>With that light you can easily send an S.O.S. signal.</p>\n\n<p>And that's technically sending a signal out of your spacecraft. (It needs windows though.)</p>\n" }, { "answer_id": 56172, "author": "coteyr", "author_id": 11158, "author_profile": "https://worldbuilding.stackexchange.com/users/11158", "pm_score": 0, "selected": false, "text": "<p><strong>100% Yes</strong></p>\n\n<p>Remember Morse code. You don't need much to make that work. So Take your cell, figure out which way you want to go. Either rework the radio bit to send out \"something\" (even static), or ditch the radio bits and use the lights. </p>\n\n<p>Remember you don't need much to <strong>send</strong> Morse code. </p>\n\n<p>Now as to having that signal be received, well. With the radio part the receiver would need to be \"tuned\" to the correct frequency. It has to be listening somehow. Even if your only managing to modulate static, someone has got to be listening to the static. </p>\n\n<p>For the light, that's even more of a crap shoot. Someone or something need to be looking. That cell phone light isn't going to travel very far. </p>\n\n<p>You might better spend your time making the port side spot light blink. </p>\n\n<p>TL;DR sure you can use it to send a SOS. Rather it's received or not....</p>\n" }, { "answer_id": 56208, "author": "TMN", "author_id": 22096, "author_profile": "https://worldbuilding.stackexchange.com/users/22096", "pm_score": 6, "selected": false, "text": "<p>Absolutely. Simply write \"S. O. S.\" on a piece of paper, wrap it around the phone, secure it with some tape or a rubber band, then put the phone in the air lock and open the external door. Now all you need is a deck of cards so you'll have something to do while you await rescue!</p>\n" }, { "answer_id": 56220, "author": "Crowley", "author_id": 19902, "author_profile": "https://worldbuilding.stackexchange.com/users/19902", "pm_score": 0, "selected": false, "text": "<p>You absolutely can send any signal from the ship. Anywhere.</p>\n\n<p>The trouble is, that intensity of the signal, and thus signal-to-noise ratio, decays with the factor 1/r2, where r is the distance.</p>\n\n<p>So, without network that will transmit (receive, amplify, send) your S.O.S. signal none can hear it.</p>\n\n<p>Shouting out loud will have the same effect...</p>\n" }, { "answer_id": 56264, "author": "Nathaniel Ford", "author_id": 6928, "author_profile": "https://worldbuilding.stackexchange.com/users/6928", "pm_score": 2, "selected": false, "text": "<h1>Create a Giant Antenna</h1>\n\n<p>Given that your pod components are somehow damaged-beyond-repair, remove all the reasonably-strong wire you can from it and splice it all together. Splice it into your cell phone's antenna (assuming that is the only source of power). Tie one end of the antenna to something heavy and heave it out the airlock with as much force as you can in the direction opposite the travel of the pod. (This will be tricky.)</p>\n\n<p>Now, your cell phone has way too little juice to really make this matter, but it will serve as well as anything else for sending some signal down the antenna - even better if that signal, regardless of it's content, can be in the Morse-code short short short, long long long, short short short format. No encryption is needed for that. Failing that, any repeated signal will do as that is almost certainly man-made.</p>\n\n<p>More importantly, if the rescue ship is doing any active scanning at all, being The Future and the computers are better, it should twig to the fact that there is an antenna - which will cause an <a href=\"https://en.wikipedia.org/wiki/Radar_cross-section#RCS_of_an_antenna\" rel=\"nofollow\">anomalous interference</a> with signals in a distinct 'line' pattern along the length of the antenna. If the computer knows that such an antenna shouldn't be there, it should flag it as maybe worth looking at. The longer the antenna the more likely that active scans (read: throwing various beams of light at various frequencies out) will pick up the anomaly. Energizing the antenna at a rhythmic pace will give the computer additional clues as to the fact what it is looking at is man-made.</p>\n\n<p>Of course, if the amount of debris is too high, or there are a lot of signals bouncing around, this may be way too small a difference for anyone to really notice. </p>\n" }, { "answer_id": 56280, "author": "Gene", "author_id": 27575, "author_profile": "https://worldbuilding.stackexchange.com/users/27575", "pm_score": 3, "selected": false, "text": "<p>What a coincidence! I'm also from the year 2109 and that was MY museum you ripped off! I want my phone back. Wife misses it. Frankly, thieves deserve that fate of yours.</p>\n\n<p>However, if I were in a giving mood, I might suggest another approach. My cellphone is omni-directional and is not meant to broadcast far. I don't remember precisely, but it MIGHT have an LED on the top. LED's are coherent light and experience much slower power dispersion than an omni antenna. Of course, you would have to know where to point it. You could easily rig a circuit to modulate the LED to send an SOS and other info ... if you have the know-how. Think \"fiber-optics\" without the fiber. Put several of these together and you have a little array of lasers which is more likely to be detected.</p>\n\n<p>How far are you trying to send the signal? Light is very fast, but if you're in another galaxy, or even another solar system, forget it. Both dispersion and light travel time will mean you're stranded forever. A fitting end for theives, hmm?</p>\n\n<p>I'm not up on current events, but we might have inter-planetary or Star Trek-esque subspace relays off of which you could bounce a signal and minimize dispersion. </p>\n\n<p>Tell you what, keep the phone. Just let me know the hot stocks for the next 30 years.</p>\n" }, { "answer_id": 56283, "author": "Viktor Toth", "author_id": 13513, "author_profile": "https://worldbuilding.stackexchange.com/users/13513", "pm_score": 3, "selected": false, "text": "<p>Here is a top-of-the-line 1999 phone, apparently the first to feature a WAP browser: <a href=\"https://en.wikipedia.org/wiki/Nokia_7110\">https://en.wikipedia.org/wiki/Nokia_7110</a></p>\n\n<p>No flashlight (high power white LEDs not having been invented yet). The phone is either a GSM or a TDMA model. Either way, it is an omnidirectional transmitter in the 900 or 1800/1900 MHz band.</p>\n\n<p>When you turn on the phone, it looks for a network. If it finds no network, that is pretty much the end of story; it will display an error message and will continue to search for a non-existent base station.</p>\n\n<p>Modifying the phone is not an option. Even if you had the right documentation and tools at your disposal, you are confronted with a small circuit board with numerous densely-packed surface mount components, and in any case, those components are custom-designed to connect to a cellular network, they are not general-purpose radio chips, for instance.</p>\n\n<p>So I think your best bet is to take out the phone's battery (I assume it is in good working condition and charged), find some lose wiring, and try to build a spark transmitter. It is a horrible abuse of the battery, but it just might work... especially if you can also fashion a crude parabolic dish and aim it at your potential rescuers. Even so, unless your rescuers are a) nearby, and b) are aiming a parabolic dish at your direction, it is very unlikely that they will receive a signal... your SOS will basically disappear in the noise.</p>\n" }, { "answer_id": 56331, "author": "Kalliope", "author_id": 27506, "author_profile": "https://worldbuilding.stackexchange.com/users/27506", "pm_score": 1, "selected": false, "text": "<p>Some things to consider:</p>\n\n<ul>\n<li>Is the cell phone still working? (Phones were pretty sturdy these days, so probably yes)</li>\n<li>Is the battery still working? (Alternatively you should be able to find a low voltage output somewhere in your pod, lets count this as yes as well)</li>\n<li>it would use GSM (2G) or UMTS (3G, if you are <em>very</em> lucky). Is this (still) supported on a planet near to you, additionally: is is a multi-band phone? </li>\n<li>Base stations, which you need for the connection are unlikely to transmit omni-directional, since they are made for surface dwellers. (I haven't tried to use my phone in a plane, but I suppose you would have a hard time to connect above 10 km height.</li>\n<li>you are likely to move rather fast relativ to a planet, even if you get the base stations, will they be able to hand you from one cell to the other? Related: digital radio (DAB) is said to get problems beyond 200 km/h (?), is there a limit for cell phone connections as well)</li>\n<li>Cell phone use omni-direcional antennae, additionally the signal is not very strong. You should consider building a high gain directional antenna (For wlan, there are some designs using foam and blank wires)</li>\n<li>cell phones transmit a digitally coded signal, i.e. unlike analog radio, you can't just listen in even if you manage to get a signal to a planet.</li>\n<li>there are some problems with the GSM protokoll if you cant log into a base station.</li>\n</ul>\n\n<p>As it can be seen, there are some problems in using a cellphone in a normal way in space. \nit might be easier to get a continuous carrier signal out of the phone (just 900Mhz or similar), try to build a directional antenna and use it for Morse code (signal on/of) in the direction of the next planet with a receiver.</p>\n" }, { "answer_id": 56377, "author": "Pavel Adamus", "author_id": 27633, "author_profile": "https://worldbuilding.stackexchange.com/users/27633", "pm_score": 1, "selected": false, "text": "<p>Definitely not!</p>\n<p>It is not possible today; even your cell phone in orbit around the Earth gets the signal from the ground. The signal is probably not strong enough to reach 200-300km altitude, but to point out the main problem let's say that it is possible. (Actually, I will be not so surprised if cell phone could recognize the signal from BTS for 200km range.)</p>\n<h2>The main problem:</h2>\n<p>Even if the signal is OK and the phone can &quot;see&quot; a BTS and a network, the problem for GSM, as it has been mentioned already, is time slots.</p>\n<p>Time slots limit the effective distance to 35km only.</p>\n<blockquote>\n<p>This limited the original range of a GSM cell site to 35km as mandated by the duration of the standard timeslots defined in the GSM specification. The maximum distance is given by the maximum time that the signal from the mobile/BTS needs to reach the receiver of the mobile/BTS on time to be successfully heard. At the air interface the delay between the transmission of the downlink (BTS) and the uplink (mobile) has an offset of 3 timeslots. Until now the mobile station has used a timing advance to compensate for the propagation delay as the distance to the BTS changes. The timing advance values are coded by 6 bits, which gives the theoretical maximum BTS/mobile separation as 35km. <a href=\"https://en.wikipedia.org/wiki/Timing_advance\" rel=\"nofollow noreferrer\">Wiki</a></p>\n</blockquote>\n<p>In other words when your phone gets a slot to speak, &quot;now is your time to go&quot;, the response from your phone reaches the BTS too late to make a connection or to transmit data. GMS voice is just data transmission. If you were to boost your mobile phone signal, and the BTS had big gain antenna, you would <em>almost</em> hear the signal (as nonsense :) ), but your GSM phone will still be not able to work for a greater distance than 35km.</p>\n<h2>Recommendations:</h2>\n<ol>\n<li><p>You can replace old GSM phone from 1999 with some archaic professional &quot;walkie-talkie&quot; which don't need any BTS or network infrastructure, don't emit the signal in quite complex modulation, are packed to the small data sets and also encrypted with a key received during 1st three-way handshake when your phone connects to the GSM network. But keep it professional, because consumer walkie-talkie is not powerful enough. The signal power is limited for civilian devices to a city band.</p>\n</li>\n<li><p>Instead of your guy's old GSM phone, try an old radio frequency transmitter. They need to power it somehow because the battery is dead, because it is an old device. So they find that they need, to simplify, 12V. There is an external 12V source plug.</p>\n<p>In the spaceship there would be a lot of working devices. So they disassemble the main panel and try to find supply cables. From the power source of the panel, they power up the transmitter. (The assumption is that for powering electronic devices the supply power is usual 12V, so the panel and its units could be supplied with 12V; not the chips on the circuit board, they are about 5V or 3V, but units.)</p>\n</li>\n</ol>\n<p>Meanwhile on the Earth, there is a group of young students with their teacher just finish assembling a simple amateur radio receiver and they are trying to test if it is working. But something is disturbing the reference test signal in the lab ...</p>\n" }, { "answer_id": 56385, "author": "Rafał Rozestwiński", "author_id": 27642, "author_profile": "https://worldbuilding.stackexchange.com/users/27642", "pm_score": 2, "selected": false, "text": "<p>I think the your best option would be to re-use available gear to create a <a href=\"https://en.wikipedia.org/wiki/Spark-gap_transmitter\" rel=\"nofollow\">spark-gap transmitter</a>. As it works more like a radio jammer than well-behaving transmitter, you might interrupt someone's regular radio conversations ;)</p>\n" }, { "answer_id": 56406, "author": "Chris Stratton", "author_id": 27653, "author_profile": "https://worldbuilding.stackexchange.com/users/27653", "pm_score": 3, "selected": false, "text": "<p><strong>Yes, because of FCC test modes</strong></p>\n\n<p>A lot of people are assuming that a cell phone can only talk to a cell base station. If you are constrained to the end-user interface that is true, but if you can use your 100-year-future version of today's JTAG pod to get inside the firmware, the hardware itself will have been capable of transmitting an umodulated carrier at various frequencies during regulatory testing, and you can use that to send a slow Morse Code call for help. Then it's only a question if someone happens to be listening on a frequency you can reach; with luck some of the phone's frequency range will have become a ham band in the intervening years (and maybe someone is known by that community to be a on <a href=\"https://en.wikipedia.org/wiki/DX-pedition\">DX-pedition</a> to an asteroid in your general direction, causing high-gain receive antennas to be pointed your way)</p>\n\n<p>It's theoretically possible that test modes on this level could be accessible from the keypad, especially as an oversight (lots of products have shipped with test modes someone forgot to take out, or maybe the phone's state gets corrupted by a cosmic ray, exposing something not meant to be exposed)</p>\n\n<p>A downside is that you won't know your signal has been received, until the rescue arrives.</p>\n\n<p><strong>It may go further than you think</strong></p>\n\n<p>We're used to thinking of handheld radios as having a short range, because signals may not readily wrap around the earth's horizon, clear obstacles, etc, and when they marginally do higher transmitter power can help. But conditions of good ionospheric reflection you can communicate around the earth on a few watts. And with line-of-sight in space power is even less of an issue.</p>\n" }, { "answer_id": 56448, "author": "dw_im_here", "author_id": 27686, "author_profile": "https://worldbuilding.stackexchange.com/users/27686", "pm_score": 1, "selected": false, "text": "<p>Well as many gave noted here the cellphone is pretty much useless unless you do something. Since its hardwired to transmit a signal looking for towers nearby all it can do is that and you have to work with it. All you can do is give it a boost so it talks louder not different. </p>\n\n<p>You cannot make 1999 technology do the work done by 2100 technology, but you can modify 20th century technology so they simply do better what they did before.</p>\n\n<p>Remember you want to get rescued here, not reinvent the cellphone all over again, hence all you have to do is create a commotion, one of any kind, even one which is a loud \"HELLO IS ANYONE THERE\" signal.</p>\n\n<p>Maybe your friends know basic engineering:</p>\n\n<p>1.) Add external antenna to give cellphone boost in the unheard of levels</p>\n\n<p>2.) Give the cellphone an unhealthy kind of power supply, make this thing rock whole planets (a figure of speech)</p>\n\n<p>3.) Turn on all lights / camera flash / accessories when sending it out in a probe</p>\n\n<p>4.) Send out a ping signal along with constant text messages everywhere asking for help maybe even a picture</p>\n\n<p>5.) Put it all in a box and send it out with high hopes that someone notices it before it blows up</p>\n\n<p>Remember, this isn't about safety or efficient design, its about a group of survivors who throw in their last ditch effort at being rescued. They don't want this drone floating around forever in space, because they wont survive forever, hell they're hoping it makes some noise,<em>a large amount of noise given their predicament and lack of equipment for a short period of time before it burns out</em> and then luckily get rescued by some ship which happened to notice this antique cellphone kinda signal from the 20th century because they happened to have an expert in their crew who noticed it. Why? Well the protagonist's dumb luck I guess </p>\n" }, { "answer_id": 56521, "author": "Robert", "author_id": 27281, "author_profile": "https://worldbuilding.stackexchange.com/users/27281", "pm_score": 0, "selected": false, "text": "<p>Biggest problem would be the people figuring out how to use it. They did a test a few years ago, and people couldn't even figure out how to turn on an old computer, let alone use it.\nNASA couldn't even build a saturn V rocket if their life depended on it. We can't build a flying Write Brothers airplane either.</p>\n\n<p>Having been using zero point power cells for the last 50 years, the concept of a battery would be so foreign to them they would be stumped. The very idea of dc current would be like speaking chinese to a kenyan president. Everyone knows electricity is just used to to wow children in magic shows because it has no state or need to traverse along paths.</p>\n\n<p>Besides, what if the raygun happy cops hear your SOS and tell you to drop the phone, and because sound doesn't travel in space you don't hear them. Rioting and burning the sun down would ensue.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/56139", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/8400/" ]

[ { "answer_id": 56332, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 1, "selected": false, "text": "<p>I'm not sure how you can expect a single answerer to address everything in what looks more like a collaborative question, but here goes with my initial thoughts.</p>\n\n<p><strong>Meat</strong><br>\nYou've stated that there's not much meat on these BOBs, but that doesn't really make sense to me. They're large enough to bear a burden, they have broad backs and six legs. Muscles are usually the main edible parts of a herbivorous animal, and this BOB should have plenty of them. You said there's little meat yield when butchered, so how does that work out? You might want to find another reason why they can't be a food source.</p>\n\n<p>Apart from that, I can't see much to argue with.</p>\n" }, { "answer_id": 56333, "author": "Separatrix", "author_id": 16295, "author_profile": "https://worldbuilding.stackexchange.com/users/16295", "pm_score": 5, "selected": true, "text": "<p>It doesn't matter that the milk tastes a bit funny, you're still going to drink it. The same with being a bit short on meat, if that's what there is, more so as a multiple birth animal, then that's what you'll eat, especially in an arctic environment. However most big beasts of burden have a lot of meat, it might be quite tough, but there should be a lot of it.</p>\n\n<p>Reproduction rate is too low, once or twice in a lifetime isn't enough for what's fundamentally a prey animal, that'll need to be every couple of years at least. Unless your world has no predators and this species has an unbelievable survival rate for newborns.</p>\n\n<p>Speaking of predators: How do they deal with them, do they have horns? Hooves? Both would come in useful.</p>\n\n<p>Why do they live so long when they can only breed twice? Very few creatures live on past the end of their breeding cycle.</p>\n\n<p>You should possibly also consider how females choose mates. Normally with herd animals it's one (or a small number of) dominant male(s) and the rest don't get much of a look in. The other part of this is of course, how do males impress females, do they fight, do they display, are they particularly charming in a bar, do they dance. Pair breeding is much more common in birds than mammals.</p>\n\n<p>Swimming: Pretty much everything can swim, often badly but they can. Unless you have a particular plot reason for them not to, let them swim.</p>\n\n<p>(Your world though, with a global belt ocean, the tides and storms are going to be epic!)</p>\n" }, { "answer_id": 56340, "author": "Theraot", "author_id": 16729, "author_profile": "https://worldbuilding.stackexchange.com/users/16729", "pm_score": 3, "selected": false, "text": "<p>Honestly the existence of creature per-se is not problematic; In particular being located in \"not-earth\" so to speak.</p>\n\n<p>I do not expect BOB to be a mutated mammal with extra limbs; those have problems walking, have a hard time getting food, and tend to die young, before having offspring. Edit: the condition is Polymelia, it is a defect in the development of the fetus and not a mutation, and thus and it is not hereditary. </p>\n\n<hr>\n\n<p>As, for why would this feature be selected, the advantage of the six legs is evidently on locomotion. In particular walking and climbing can be done with three contact points all the time, regardless of terrain. This is why six limbs make more sense on small creatures that climb trees.</p>\n\n<p>The BOB could have a similar approach; if their original habitat was mountain or rocky desert (you say valleys, a rocky desert is a valley? Ok, good). At least that was the case during the initial stages of evolution, so the six limbs could have some advantage at that time. In our world, they would compete with goats, so I agree on the choice of fur. Note: being a desert doesn't mean it is hot, being far from the equator would make it colder.</p>\n\n<p>I'll - as you may expect - handwave mammal glands as <a href=\"https://en.wikipedia.org/wiki/Convergent_evolution\" rel=\"nofollow noreferrer\">convergent evolution</a>.</p>\n\n<hr>\n\n<p>Ok, so the BOB ancestors came from that terrain. But the modern BOB has been domesticated.</p>\n\n<p>I’ll go with <a href=\"https://www.youtube.com/watch?v=wOmjnioNulo&amp;feature=youtu.be&amp;t=5m16s\" rel=\"nofollow noreferrer\">CGPGrey’s domestication checklist</a> (which is based on the book Guns, Germs, and Steel):</p>\n\n<ul>\n<li>Feedable: If the thing eats other animals, it is not good. You would have to hunt or domesticate those other animals to feed it. So you want Herbivores! (✓)</li>\n<li>Friendly: If it will kill you it is not good, it is going to run away it is not good. You said “Docile”, sounds good to me. (✓)</li>\n<li>Fecund: Animals with reproductive cycles too long or with too little offspring are not good. You say “Multiple younglings” I wonder how many is multiple because it only reproduces once or twice in 30-40 years ※. (✓)</li>\n<li>Family friendly: The creature stays in packs; they do not roam alone when they leave the protection of their parents. Instead they stay in family. They will accept the masters as if they were part of the family, leaders of the pack. This is in line with “Live in small herds“and “Protective of their group and younglings”. (✓)</li>\n</ul>\n\n<p>※: The fact that their live cycle is larger than a generation of the masters is a bit problematic, because it means that the advance in domestication that a single person can archive is limited. Consider making them have more offspring or short their life cycle. This would imply that for domestication there must be people dedicated to do it, and thus there must be another benefit of having them around. There is the “they domesticated themselves” option: if they keep coming to the masters for food, because they can’t get enough is the wild (we said, desert, right?).</p>\n\n<p>I have reason to believe that modern BOB was domesticated to be bigger and bulky (i.e. ancestor BOB is smaller and more agile). The reason is that bigger herbivores are harder to catch. Sure, they can be friendly, but you feed them and then they go away when they are no longer hungry… and trying to catch them will trigger their “Quite ferocious when incited”.</p>\n\n<p><em>Oh</em> - you say - <em>but elephants</em>, no elephants aren’t really domesticated. I mean, the influence of humans in their evolution is minimal, and they don’t depend on us. Instead we say that they are tamed, and it takes a lifetime, that’s why they are not common for farming. So make the BOB ancestors smaller. It should be noted that “Do not easily scare” is a feature of big herbivores that can fight back to the predators (which goes well with “Quite ferocious when incited”).</p>\n\n<p>On that note, these BOB aren't exactly pray animals. They fight back.</p>\n\n<hr>\n\n<p><a href=\"https://worldbuilding.stackexchange.com/a/56332/16729\">Pete is right</a> about the meat, we have a big animal (taller than an oxen) and with lots of muscle (it is a carry beast, and has six limbs).</p>\n\n<p>About the milk I have no problem with it not being tasty, in particular because I’m handwaving it as convergent evolution. Regardless people would find a recipe for it, mix it with some fruits. As <a href=\"https://worldbuilding.stackexchange.com/a/56333/16729\">Separatrix</a> puts it “you're still going to drink it”.</p>\n\n<p>Really, why did people domesticate this thing if they aren’t going to eat it? They could be good leaving them in the wild, and taming a few for work if they needed. No need to breed them, just leave it happen in nature.</p>\n\n<p>About swimming, it is ok if they can’t. But I tell you, they will still cross some rivers, because they are big enough and stable enough.</p>\n\n<p>I want to point on the multiple stomach subjects, that that is a misconception about <a href=\"https://en.wikipedia.org/wiki/Ruminant\" rel=\"nofollow noreferrer\">ruminants</a>, they have one single very specialized stomach with multiple stages. This adaptation is to break cellulose, by hosting microorganism capable of that task in their rumen.</p>\n\n<hr>\n\n<p>Addendum: On taxonomy. Unless the world is dominated by humans and these humans come from Earth, and they are convinced that the live comes from panspermia... the taxonomical classification used in this world is devoid of all the species on Earth. They are independent, and you should make up the classification names in some language of natives.</p>\n\n<p>As per choice of language, the reason to use a language with no native speakers - being the case of Latin (some greek and some made up words based on people names) in our world - is that meaning of the world wills no longer changes by natural language evolution.</p>\n" }, { "answer_id": 56353, "author": "a4android", "author_id": 22159, "author_profile": "https://worldbuilding.stackexchange.com/users/22159", "pm_score": 0, "selected": false, "text": "<p>This answer focuses on only part of your BOBs, namely, their evolutionary history. There have been suggestions that six-legged animals will have evolved from a remote ancestor that was a bottom dwelling marine organism. This creature can be labelled 'benthic' which is only fancy way of saying its bottom dwelling.</p>\n\n<p>The majority of animal life on Earth, which includes humans, are tetrapods because our remote ancestor was a free swimming teleost fish. Its four fins eventually became four limbs. Its descendants colonized the land and that's the main reason animal life is four limbed.</p>\n\n<p>Bottom dwellers can have six fins or similar structures and these could evolve into six limbed animal life. It's not unreasonable to expect animal life in your construct world to be all six limbed. Although it is possible there could have been two independent branches of animal life, so there could be both four-limbed and six-limbed animals sharing the world.</p>\n\n<p>Hopefully this will add some versimilitude to their evolutionary backstory.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/56329", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2746/" ]

[ { "answer_id": 56705, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 4, "selected": true, "text": "<p>Can I suggest something along the lines of the <a href=\"https://en.wikipedia.org/wiki/Queensland_lungfish\" rel=\"noreferrer\"><strong>Queensland Lungfish</strong></a></p>\n\n<p><a href=\"https://i.stack.imgur.com/x6EF9.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/x6EF9.jpg\" alt=\"Queensland Lungfish\"></a></p>\n\n<p>If you split the anal fin into two separate fins and move the dorsal fins slightly more forwards, you'll have the ancestor for your BOBs.</p>\n\n<p>Quote from Wikipedia:</p>\n\n<hr>\n\n<p><em>Fossil records of this group date back 380 million years, around the time when the higher vertebrate classes were beginning to evolve. Fossils of lungfish almost identical to this species have been uncovered in northern New South Wales, indicating that Neoceratodus has remained virtually unchanged for well over 100 million years, making it a living fossil and one of the oldest living vertebrate genera on the planet.</em></p>\n\n<p><em>It is one of six extant representatives of the ancient air-breathing Dipnoi (lungfishes) that flourished during the Devonian period (about 413–365 million years ago) and is the most primitive surviving member of this lineage. The five other freshwater lungfish species, four in Africa and one in South America, are very different morphologically from N. forsteri. The Queensland lungfish can live for several days out of the water, if it is kept moist, but will not survive total water depletion, unlike its African counterparts.</em></p>\n\n<hr>\n" }, { "answer_id": 57407, "author": "Xymist_", "author_id": 27905, "author_profile": "https://worldbuilding.stackexchange.com/users/27905", "pm_score": 1, "selected": false, "text": "<p>You're positing a split a <em>very</em> long way back. Things like the quadrupedal form and the pentadactyl limb developed so far back you'd almost have to posit another Class entirely to make it reasonable.</p>\n\n<p>Convergent evolution is all very well as an explanation, and happens reasonably frequently in nature, but what you're saying there is that these creatures are known not to be mammals. What are they, then? Saying 'what might this thing have evolved from' is far too broad without more of a description than 'they have six legs and live in small groups'. I'm assuming from the name that they're about cow size and morphology, but is that correct? Are they six legged horses, dog-size cockroaches, snakes with a compensation problem or elephants with a limb surplus?</p>\n\n<p>Assuming these creatures are vertebrates, and therefore chordates, you have an interesting problem regarding the attachment of the third set of limbs. Do you have a second set of scapulae? Something approximating a second pelvis? A swung-cage like structure suspended from reinforced vertebrae developed from the last two or three ribs of something otherwise roughly mammalian? </p>\n\n<p>If they're not chordates as we know them, you have further options. Insects already have six legs, have done so for a very long time, and their main reason for being small is a lack of lungs - the oxygen in our atmosphere isn't sufficiently concentrated to allow them to function. Positing that a large species of insect developed internal lungs of some kind, perhaps by merging bundles of their tracheal tubes and enlarging a couple of their spiracules (giving you an insect with proto-lungs and 'nostrils' on its 'shoulders') would mean that as the oxygen levels dropped, they were able to stay large and perhaps even grow, eating vegetation which the other species of insect were no longer able to consume as effectively. Group size would drop due to availability of food and costliness of raising young, the transition from oviparous to ovoviviparous (and perhaps to viviparous given time) has happened a few times in several different families, and various creatures give milk - the Pacific Beetle Cockroach, for one.</p>\n\n<p>If you don't fancy insects but the extra scapula thing bothers you, how about a parallel evolution of the endoskeleton? Something that doesn't have a spine, pelvis, ribs and scapulae, but instead depends on a mesh of hollow long bones pivoting on rounded cubes (think a body composed entirely of carpals and phalanges); their organs protected inside a cage of bone while their nerves are distributed rather than having a CNS to speak of. They might be able to carry quite a bit of weight, as they would have to be tied together internally with tendons and would therefore be motile Hoberman Spheres. The legs would therefore just be the same construction with a set of much-enlarged cubic pivots within the body, two greatly-lengthened internal bones and a 'club foot' consisting of a very large pivot bone with padding and keratinised skin. That could have evolved from... well, almost literally anything you like, because the vertebral column developed so long ago.</p>\n\n<p>My point isn't really to seriously suggest the foregoing, but to point out we could really do with some more information.</p>\n\n<p>On a more serious note, this might not be as good an idea as you think. Hexapedal creatures are cool, but six legs is actually not as efficient in large animals as four legs. Legs are heavy and require lots of nutrients to maintain, while providing only small stability and motility benefits. They're also slightly harder to coordinate.</p>\n\n<p>See <a href=\"http://jeb.biologists.org/content/jexbio/158/1/369.full.pdf\" rel=\"nofollow\">this</a> for how hexapedal creatures have to be constructed to move efficiently.</p>\n" }, { "answer_id": 57724, "author": "Green", "author_id": 10364, "author_profile": "https://worldbuilding.stackexchange.com/users/10364", "pm_score": 2, "selected": false, "text": "<h2>Six legged creatures showed up about 370 million years ago and looked like frogs</h2>\n\n<p>Given that a plan form of six legs is so fundamental to an organism's body shape, this is a very very old feature. Assuming that the evolutionary tree of this world matches the progression in Earth's evolutionary tree, the body plan preference for six limbs over four limbs would need to happen at or before the divergence of Dipnoi (lungfish) from Amphibia (frogs) around 370 million years ago. Let's say that there is a further divergence within Amphibia where some developed four legs and some developed six legs.</p>\n\n<p>Given the age of this divergence, the degree of speciation in four-leggers and six-leggers will be immense. Also, given the age of this feature, there won't be one single species that developed this feature. If there is, they will be long long dead by the time of this story (though it might have gotten lucky and survived unchanged for 350 million years. The nautilus has done something similar). At these ages, four leg species will be globally distributed as will the six leg varieties. 300 million years is just too much time for one phylum to stay completely geologically separated from another. But, just because they are found geographically mixed doesn't mean that in a given location the six leggers won't dominate the four leggers and vice versa.</p>\n\n<p>It is not unreasonable to say that for the six leggers just do better up north and the four leggers do better down south. If there is some geographic isolation (that isn't clear in the provided map) then that should give the six leggers time to fill out more ecological niches at the expense of the four leggers. An example of this kind of domination is on the New Zealand islands. Till humans showed up, birds were dominant.</p>\n\n<p>With the geographic isolation and time scales involved, the evolution of a domesticatable herbivore is highly likely. Progression from small six legged amphibians to lizards then into mammals might proceed nearly the same as here on Earth.</p>\n\n<p>Having six legs also means that this world might see tool wielding griffons with two arms, two legs and two wings. Or birds with arms.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/56701", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/2746/" ]

[ { "answer_id": 57362, "author": "Green", "author_id": 10364, "author_profile": "https://worldbuilding.stackexchange.com/users/10364", "pm_score": 2, "selected": false, "text": "<h2>This area probably won't sustain life for long</h2>\n\n<p>Having lots of stars this close feels like a stellar nursery, not a stable cluster. Nurseries are highly unpleasant places: lots of dust and gas racing around, super novas as young bright stars merge and explode. </p>\n\n<p>I don't see how a large black hole at the center of the cluster will help. Starting with a true glob, eventually, all the orbital material will eventually flatten out into a disk shaped spiral galaxy. Stars that orbit off of the orbital plane will eventually collide or have their orbits bent to an orbit more in line with all the other stars. </p>\n\n<h2>Dark Matter to the rescue!</h2>\n\n<p>An ordinary cluster will collapse on itself eventually without something to hold it apart. Since every star attracts all the other stars, the stars at the edge of the cluster will slowly creep in towards the center, compressing and collapsing the cluster. No more stars, but a gargantuan bang(!). </p>\n\n<p>However, if there's an outer shell of dark matter that attracts the outer shell of the cluster, preventing them from falling into the core, the other stars might survive long enough to stabilize, form planets, host biospheres and hopefully intelligent life. </p>\n\n<p>This is a fairly hand-wavey answer but it at least involves concepts we see in science publications now. </p>\n" }, { "answer_id": 57366, "author": "a4android", "author_id": 22159, "author_profile": "https://worldbuilding.stackexchange.com/users/22159", "pm_score": 2, "selected": false, "text": "<p>The half-lives for open clusters are gravitationally stable are for up to about 150 to 800 million years.</p>\n\n<blockquote>\n <p>Clusters that have enough mass to be gravitationally bound once the surrounding nebula has evaporated can remain distinct for many tens of millions of years, but over time internal and external processes tend also to disperse them. Internally, close encounters between stars can increase the velocity of a member beyond the escape velocity of the cluster. This results in the gradual 'evaporation' of cluster members.</p>\n \n <p>Externally, about every half-billion years or so an open cluster tends to be disturbed by external factors such as passing close to or through a molecular cloud. The gravitational tidal forces generated by such an encounter tend to disrupt the cluster. Eventually, the cluster becomes a stream of stars, not close enough to be a cluster but all related and moving in similar directions at similar speeds. The timescale over which a cluster disrupts depends on its initial stellar density, with more tightly packed clusters persisting for longer. Estimated cluster half lives, after which half the original cluster members will have been lost, range from 150–800 million years, depending on the original density.</p>\n</blockquote>\n\n<p>Placing an intermediate mass black hole would act as a gravitational stabilizer if it was centrally placed in the open cluster. The OP is correct that the presence of a IMBH could have severe adverse effects on the integrity of the cluster itself and on any lifeforms inhabiting planets in the cluster.</p>\n\n<blockquote>\n <p>Open clusters range from very sparse clusters with only a few members to large agglomerations containing thousands of stars. They usually consist of quite a distinct dense core, surrounded by a more diffuse 'corona' of cluster members. The core is typically about 3–4 light years across, with the corona extending to about 20 light years from the cluster centre. Typical star densities in the centre of a cluster are about 1.5 stars per cubic light year; the stellar density near the Sun is about 0.003 stars per cubic light year.</p>\n</blockquote>\n\n<p>If the IMBH is located in the cluster's core, this could kept the core stars in the cluster formation while coronal stars dissipate. This could leave a compact cluster that is three to four light years across. With the high stellar density in this remnant cluster core interstellar travel could be readily accomplished.</p>\n\n<p>The loss of nebular gases will reduce the probable of the infall of gas into the IMBH and thereby reducing the hazard of high radiation levels associated with the black hole. there are adverse events, but they don't need to happen all the time. There will be windows of opportunity for lifeforms inside an open cluster to live uninterrupted lives and develop technological civilizations accordingly.</p>\n\n<p>Basically it's not inconceivable scenario for an interstellar empire in an open cluster. Of course, it also conceivable for it to be unworkable. But making certain allowances it could happen, because it's not impossible.</p>\n\n<p>REFERENCES:\nAll quotations above can be found in the Wikipedia entry on <a href=\"https://en.wikipedia.org/wiki/Open_cluster\" rel=\"nofollow\">open clusters</a></p>\n" }, { "answer_id": 57742, "author": "HDE 226868", "author_id": 627, "author_profile": "https://worldbuilding.stackexchange.com/users/627", "pm_score": 4, "selected": true, "text": "<p>Let’s determine some basic parameters of the cluster.</p>\n\n<p>You say you want the stars to be 1-2 light-years apart. This is a little tricky because star clusters don’t necessarily have uniform densities. Globular clusters, for instance, have radial density profiles decreasing from some core density at $R=0$ to zero density somewhere further out. There are several density profiles used to model this. The <a href=\"https://en.wikipedia.org/wiki/Plummer_model\" rel=\"noreferrer\">Plummer model</a> is easily the simplest, as analytic expressions exist for density and potential. The King model (see <a href=\"http://adsabs.harvard.edu/abs/1966AJ.....71...64K\" rel=\"noreferrer\">King (1966)</a>, the third in a series of papers) is more accurate, though the density must be solved for numerically, and the Michie model can be even more accurate (see e.g. <a href=\"http://physics.wm.edu/Seniorthesis/SeniorThesis2005/shervthesis.pdf\" rel=\"noreferrer\">this thesis</a>), as it can account for dark matter.</p>\n\n<p>I’m going to follow a modified version of the models of <a href=\"http://www.aanda.org/articles/aa/full/2008/03/aa8616-07/aa8616-07.html\" rel=\"noreferrer\">Bonatto &amp; Bica (2014)</a>, who use a King profile (here applicable to open clusters). The fraction of the total number of stars $N$ within a radius $R$ is given by\n$$n(R)=\\frac{x^2-4u\\left(\\sqrt{1-x^2}-1\\right)+u^2\\ln\\left(1+x^2\\right)}{u^2\\ln u^2-(u-1)(3u-1)}\\tag{1}$$\nwhere\n$$x\\equiv R/R_c,\\quad u\\equiv\\sqrt{1+\\left(R_t/R_c\\right)^2}$$\nwith $R_t$ and $R_c$ being the tidal and core radii of the cluster; the cluster is truncated at $R=R_t$. The authors recommend a ratio $R_t/R_c\\approx15$. Therefore, we just have to specify one of those two parameters (we also know that $u=226$). The tidal radius can be computed depending on the mass of the cluster and its distance from the center of the galaxy (see e.g. <a href=\"http://batc.bao.ac.cn/papers/BATC-papers/2009wzy-26_2_029701.pdf\" rel=\"noreferrer\">Wu et al. (2009)</a>). That would require us to specify additional parameters, so I’ll assume that the cluster is average, and give it a tidal radius of about 10 parsecs. Thus, the core radius is roughly 0.67 parsecs. This could be an overestimate; <a href=\"http://adsabs.harvard.edu/abs/2008A%26A...477..165P\" rel=\"noreferrer\">Piskunov et al. (2008)</a>, for instance, surveyed 236 open clusters in the Milky Way and found that the tidal radius peaked at around 6 parsecs. Still, 10 parsecs is by no means unreasonable. At any rate, I’d prefer a more massive cluster, so more stars may survive for longer periods of time.</p>\n\n<p>Some quick <em>Mathematica</em> gives me</p>\n\n<pre><code>Clear[Rt, Rc]\nx[R_, Rc_] := R/Rc\nu[Rt_, Rc_] := Sqrt[1 + (Rt/Rc)^2]u[Rt_, Rc_] := Sqrt[1 + (Rt/Rc)^2]\nn[R_, Rt_, Rc_] := ((x[R, Rc])^2 - 4*(u[Rt, Rc])*(Sqrt[1 + (x[R, Rc])^2] - 1) + (u[Rt, Rc])^2*Log[1 + (x[R, Rc])^2])/((u[Rt, Rc])^2*Log[(u[Rt, Rc])^2] - (u[Rt, Rc] - 1)*(3*u[Rt, Rc] - 1))\nPlot[n[R, 10, 2/3], {R, 0, 10}, AxesLabel -&gt; {\"Radius (Parsecs)\", \"Number of stars\"}]\n</code></pre>\n\n<p>    \n<a href=\"https://i.stack.imgur.com/vT2po.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/vT2po.png\" alt=\"enter image description here\"></a></p>\n\n<p>The actual number of stars inside $R$ is simply $n$ multiplied by the number of stars in the cluster, $N$. We’ll take $N\\sim10^3$, a decently sized cluster. How do we now go from $n\\cdot N$ to number density, $\\mathcal{N}$ (just to make things more confusing)? Well, take the formula for the mass $M$ of a sphere inside a radius $R$ with radial density $\\rho(r)$:\n$$M=\\int_0^R 4\\pi r^2\\rho(r)\\mathrm{d}r$$\nSimply divide $M$ by the average mass of a star (which I’ll get to later, but is unimportant for now) and we get\n$$n\\cdot N=\\int_0^R4\\pi r^2\\mathcal{N}(r)\\mathrm{d}r$$\nWe just differentiate and divide:\n$$\\mathcal{N}(r)=\\frac{\\mathrm{d}n}{\\mathrm{d}r}N\\frac{1}{4\\pi r^2}\\tag{2}$$\nIn the code, we add</p>\n\n<pre><code>P[R_, Rt_, Rc_] = D[n[R, Rt, Rc], R]*1000*(4*Pi*R^2)^(-1)P[R_, Rt_, Rc_] = D[n[R, Rt, Rc], R]*1000*(4*Pi*R^2)^(-1)\nPlot[P[R, 10, 2/3], {R, 0, 10}, AxesLabel -&gt; {\"Radius (Parsecs)\", \"Number density\"},ScalingFunctions-&gt;\"Log\"]\n</code></pre>\n\n<p>where I’ve replaced $\\mathcal{N}$ with $P$, and we get, with a logarithmic $y$-axis,</p>\n\n<p><a href=\"https://i.stack.imgur.com/6b57c.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/6b57c.png\" alt=\"enter image description here\"></a></p>\n\n<p>Note that the number density goes to infinity as $R$ goes towards the center (which we can check by simply evaluating the limit of $\\mathcal{N}(R)$ as $R\\to0$). However, we know that $n(R_t)$ is finite (although $\\lim_{R\\to\\infty} n(R)=\\infty$, which is why we truncated it). I played around with <code>Animate</code> for $N$:</p>\n\n<pre><code>Animate[Plot[P[R, 10, 2/3, Nt], {R, 0, 10}, AxesLabel -&gt; {\"Radius (Parsecs)\", \"Number density\"}, ScalingFunctions -&gt; \"Log\"], {Nt, 10^2, 10^5}, AnimationRunning -&gt; False]\n</code></pre>\n\n<p>and found that you can get <em>extremely</em> high number densities in the center, if you so desire, which makes sense.</p>\n\n<p><a href=\"https://i.stack.imgur.com/2mBSK.gif\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/2mBSK.gif\" alt=\"enter image description here\"></a></p>\n\n<p>To find the average separation between two stars, we calculate the <a href=\"https://en.wikipedia.org/wiki/Mean_inter-particle_distance\" rel=\"noreferrer\">mean interparticle distance</a>, scaled correctly (i.e. the <a href=\"https://en.wikipedia.org/wiki/Wigner%E2%80%93Seitz_radius\" rel=\"noreferrer\">Wigner–Seitz radius</a>):\n$$r_s(R)=\\left(\\frac{3}{4\\pi\\mathcal{N}(R)}\\right)^{1/3}\\tag{3}$$\nWe add another section of code:</p>\n\n<pre><code>rs[R_, Rt_, Rc_] := (3/(4*Pi*(n[R, Rt, Rc])))^(1/3)\nPlot[rs[R, 10, 2/3], {R, 0, 10}, AxesLabel -&gt; {\"Radius (parsecs)\", \"rs\"}, ScalingFunctions -&gt; \"Log\"]\n</code></pre>\n\n<p>and, plotting this function, get</p>\n\n<p><a href=\"https://i.stack.imgur.com/MBYoe.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/MBYoe.png\" alt=\"enter image description here\"></a></p>\n\n<p>We see that $r_s$ is always greater than about 2 light-years for $0\\leq R\\leq R_t$. Towards the center. Therefore, the systems you’re interested in should be near the outer edge of the cluster.</p>\n\n<p>Hold on a minute, though. This is a density distribution based entirely on a sphere of stars, with nothing else influencing them. We’ve guessed that this models an open cluster fairly well, but we also need to assume that the cluster, if left to its own devices, is unstable, and the stars will drift away. Let’s try adding a central object, like you suggested - an <a href=\"https://en.wikipedia.org/wiki/Intermediate-mass_black_hole\" rel=\"noreferrer\">intermediate-mass black hole (IMBH)</a>. This isn’t terribly far-fetched; it’s an idea that’s been explored quite a lot in the case of globular clusters. In open clusters, we have problems because we need to explain how the black hole got there in the first place. However, we can ignore that for now.</p>\n\n<p>If there’s a central, massive object in a star cluster, the cluster should exhibit a <a href=\"https://en.wikipedia.org/wiki/Bahcall%E2%80%93Wolf_cusp\" rel=\"noreferrer\">Bahcall-Wolf cusp</a>. Within a distance equal to one fifth of the black hole’s <a href=\"https://en.wikipedia.org/wiki/Sphere_of_influence_(black_hole)\" rel=\"noreferrer\">sphere of influence</a>, the density should obey a power law of the form\n$$\\rho_{BW}(R)\\propto R^{-7/4}$$\nNumber density, assuming a roughly homogeneous population (again, more on that later), should obey this power law:\n$$\\mathcal{N}_{BW}(R)\\propto R^{-7/4}\\tag{4}$$\nAll we have to do is calculate the sphere of influence, find the number density there according to the King model we computed, and fit the two together.</p>\n\n<p>The sphere of influence, according to one definition, is\n$$r_h=\\frac{GM_{BH}}{\\sigma_0}\\tag{5}$$\nwhere $G$ is the gravitational constant $M_{BH}$ is the mass of the black hole, and $\\sigma_0$ is the central stellar velocity dispersion, which I’ll choose to be about .81 km/s - modeled after observations by <a href=\"https://arxiv.org/abs/1001.0033\" rel=\"noreferrer\">Geller et al. (2009)</a> of <a href=\"https://en.wikipedia.org/wiki/Messier_35\" rel=\"noreferrer\">M35</a>, a reasonably analog to our cluster. I’m going to choose $M_{BH}\\sim10^4M_\\odot$. We then get $r_h\\approx 6.25$ parsecs, and the Bahcall-Wolf cutoff radius is roughly 1.25 parsecs.</p>\n\n<p>Let’s calculate the number density at $R=\\frac{1}{5}r_h$ from the King model. We get 17.44 stars per cubic parsec - quite large! If we then assume that the cusp stars there, we know that\n$$\\mathcal{N}_{BW}(R)=17.44=A(1.25)^{-7/4}$$\nfor some constant $A$, which we find to be $A=25.77$. All we have to do now is to plot the two together in a piecewise number density function, defined as follows:\n$$\\mathcal{N}(R)=\n\\begin{cases}\n\\frac{\\mathrm{d}n}{\\mathrm{d}R}N\\frac{1}{4\\pi R^2},\\quad 0\\leq R\\leq1.25\\\\\n25.77R^{-7/4},\\quad1.25\\leq R\\leq10\\\\\n\\end{cases}\\tag{6}$$\nPlotting this on with a logarithmic $y$-axis gives us</p>\n\n<p><a href=\"https://i.stack.imgur.com/axoH9.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/axoH9.png\" alt=\"enter image description here\"></a></p>\n\n<p>Here’s the code I used to do the calculations and generate the plots (although you can play around with various parameters, like black hole mass and total cluster mass):</p>\n\n<pre><code>Clear[Rt, Rc]\nRt = 10(*Tidal radius*)\nRc = 2/3(*Core radius*)\nx[R_, Rc_] := R/Rc\nu[Rt_, Rc_] := Sqrt[1 + (Rt/Rc)^2]\nn[R_, Rt_, Rc_] := ((x[R, Rc])^2 - 4*(u[Rt, Rc])*(Sqrt[1 + (x[R, Rc])^2] - 1) + (u[Rt, Rc])^2*Log[1 + (x[R, Rc])^2])/((u[Rt, Rc])^2*Log[(u[Rt, Rc])^2] - (u[Rt, Rc] - 1)*(3*u[Rt, Rc] - 1))(*Number of stars in King model*)\nP[R_, Rt_, Rc_] = D[n[R, Rt, Rc], R]*1000*(4*Pi*R^2)^(-1)(*Number density from King model*)\nrs[R_, Rt_, Rc_] := (3/(4*Pi*(n[R, Rt, Rc])))^(1/3)(*Wigner-Seitz radius*)\nPBW[R_, Rt_, Rc_] := 25.77*(R)^(-7/4)(*Bahcall-Wolf cusp*)\nnp[R_, Rt_, Rc_] := Integrate[(1/1000)*4*Pi*x^2*PBW[x, Rt, Rc], {x, 0, 1.25}] + Integrate[(1/1000)*4*Pi*y^2*P[y, Rt, Rc], {y, 1.25, R}](*Total number of stars in cluster*)\nPlot[n[R, 10, 2/3], {R, 0, 10}, AxesLabel -&gt; {\"Radius (Parsecs)\", \"Number of stars\"}]\nPlot[P[R, 10, 2/3], {R, 0, 10}, AxesLabel -&gt; {\"Radius (Parsecs)\", \"Number density\"}, ScalingFunctions -&gt; \"Log\"]\nPlot[rs[R, 10, 2/3], {R, 0, 10}, AxesLabel -&gt; {\"Radius (Parsecs)\", \"rs\"}, ScalingFunctions -&gt; \"Log\"]\nPlot[{Piecewise[{{P[R, 10, 2/3], 1.25 &lt; R &lt; 10}, {PBW[R, 10, 2/3], 0 &lt; R &lt; 1.25}}]}, {R, 0, 10}, AxesLabel -&gt; {\"Radius (Parsecs)\", \"Number density\"}, PlotRange -&gt; 10^3, ScalingFunctions -&gt; \"Log\"](*Plots final density*)\n</code></pre>\n\n<p>Congratulations! You just built an open cluster!</p>\n\n<p>Well, we built a simplified model of an open cluster, and we made more assumptions than I’d prefer:</p>\n\n<ul>\n<li>All the mass of the cluster consists of stars and the central black hole, which gravitationally dominates most of the cluster. In reality, there should be gas and dust in the cluster, because the stars formed from <a href=\"https://en.wikipedia.org/wiki/Molecular_cloud#Giant_molecular_clouds\" rel=\"noreferrer\">giant molecular clouds</a>.</li>\n<li>The stellar population is homogeneous, i.e. all of the stars are the same. In general, this isn’t the case. Stars that formed together might be similar, but often they’re quite different. Their masses should be be distributed as predicted by some sort of <a href=\"https://en.wikipedia.org/wiki/Initial_mass_function\" rel=\"noreferrer\">initial mass function (IMF)</a>. This created no problems so far, but it might when you take into account things like mass segregation that are important in globular clusters. If you’re <em>really</em> interested in fixing this, you can use something like the <a href=\"http://bogdan.massclean.org/massclean3.html\" rel=\"noreferrer\">MASSCLEAN</a> packages to generate star clusters via the King model and an IMF (the default is the Salpeter IMF). It’s a pretty cool tool, and can save you a lot of work.</li>\n<li>A King model defines the cluster. I’d be more comfortable using a King model to describe a globular cluster, and I see no reason why you couldn’t just have a young globular cluster - like <a href=\"https://en.wikipedia.org/wiki/Messier_15\" rel=\"noreferrer\">M15</a>, as you suggested - but I’m okay applying our version of it to our open cluster.</li>\n</ul>\n\n<p>None of these, however, are fatal flaws in our model.</p>\n\n<p>So, is this cluster going to be stable over long timescales? That, after all, is the question we’re trying to answer. Well, to start, there are several things in our favor:</p>\n\n<ul>\n<li>The cluster contains $\\sim10^3$ stars, which is a decent amount for an open cluster. I think that should make it more likely to end up with a sizable number of stars.</li>\n<li>The black hole is quite massive compared to the cluster - more massive than the rest of the cluster, in fact. I did this on purpose, because it means that the black hole’s sphere of influence is over half the tidal radius of the entire cluster. Again, this should make it easier to retain more stars.</li>\n</ul>\n\n<p>Let’s do a more formal assessment (based on e.g. <a href=\"https://www.ethz.ch/content/dam/ethz/special-interest/phys/astronomy/astro-dam/documents/education/courses/Astrophysics%20III/A3C3dynamics.pdf\" rel=\"noreferrer\">these notes</a>). Let the mean mass of a star in the cluster be $m_m$. By the <a href=\"https://en.wikipedia.org/wiki/Virial_theorem\" rel=\"noreferrer\">virial theorem</a>, the speed $v$ of a star at $R\\approx. R_t$ is given by\n$$v^2\\approx\\frac{GNm_m}{R_t}\\tag{7}$$\nThe time it takes a star to travel $R_t$, the crossing time $t_c$, is\n$$t_c=R/v\\tag{8}$$\nand the relaxation time $t_r$, the time over which encounters with other stars begin to have an effect on the motion of a star, is\n$$t_r\\approx\\frac{0.1N}{\\ln N}t_c\\tag{9}$$\nFurthermore, if a percent $\\gamma$ of stars have a velocity above a certain critical value, then the evaporation time of the system is\n$$t_e=\\frac{t_r}{\\gamma}\\approx t_r\\times10^2\\tag{10}$$\nSo, what critical parameters have changed now that we added the Bahcall-Wolf cusp? Well, we can safely assume that $m_m$ and $R_t$ are the same, as we specified them. It turns out, however, than $N$ has changed. Integrating over the piecewise density distribution gives $n(R_t)=0.89$, meaning that we have fewer stars in the cluster.</p>\n\n<p>At the same time, the total mass of the cluster is much, much larger, since the black hole’s mass is substantially greater than the mass of the stars. Therefore,\n$$v^2\\approx\\frac{GNm_m+M_{BH}}{R_t}$$\nHaving fewer stars and adding a black hole will lead to a much shorter relaxation time. Even if we extend the tidal radius (as would be expected), the black hole still won’t help stars at the outside of the cluster. I recall one paper noting that in the case of a black hole with a mass somewhat less than that of the cluster, most of the stars in the outer regions of the cluster will behave just as if the cluster was perfectly described by a King model, with no central black hole.</p>\n\n<p>At the center of the cluster, there will indeed be some significant effects - and since the number density is much greater there, a large fraction of the stars should be impacted. I’m reluctant to draw analogies between stellar clusters and galaxies, but stars near the center should be influenced just like stars near the supermassive black hole at the center of the Milky Way, <a href=\"https://en.wikipedia.org/wiki/Sagittarius_A*\" rel=\"noreferrer\">Sagittarius A*</a>, orbit the black hole. The analogy is actually fairly good: Most stars in a galaxy don’t orbit the central supermassive black hole; they orbit the total mass of the galaxy. It’s a self-gravitating system, not a set of bodies orbiting one massive one. At the very center, however, stars are clearly orbiting Sagittarius A*. The same holds true for our open cluster.</p>\n\n<p>So, to summarize:</p>\n\n<ul>\n<li>Stars in the outer regions of the open cluster will likely leave the cluster at the same time or earlier than if there was no intermediate mass black hole at the center.</li>\n<li>Stars within the sphere of influence of the black hole, especially within the Bahcall-Wolf cusp, will be influenced strongly by the black hole and may directly orbit it.</li>\n<li>The cluster will largely “evaporate” on the same timescale (though likely a shorter one) than if it had no central black hole. However, I think the central group of stars will remain bound to the black hole. Eventually, this will be all that remains of the open cluster, if the orbits are stable.</li>\n<li>Whether or not life can survive on planets orbiting these stars is another question entirely, and I’ll deal with that in a future edit of this answer, if you want.</li>\n</ul>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/57353", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/26533/" ]

[ { "answer_id": 57542, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 3, "selected": false, "text": "<p>A symbiot needs to be a mutually beneficial arrangement otherwise it is just parasitism.</p>\n\n<p>This scenario is different from the OP's, but should serve as an illustration to explain the idea. Humans in space no longer wear space suits but are symbionts with \"hyperplants\", plants which have been genetically engineered to live and thrive in space. The human is sheltered from the space environment, and receives oxygen and sugars, while the hyperplant extracts wastes from the human (including carbon dioxide and waste waters), creating a closed loop ecosystem in space.</p>\n\n<p>It isn't clear from the OP's description how the biosuit works, but if we assume the biosuit is at least partially a plant, then the human in the loop provides some sustenance to keep the biosuit alive through exhaled CO2 and solid and liquid wastes, which the human pilot recovers in the form of oxygen, clean water and sugars. While the two are joined, they also share in an ecosystem loop isolated from the outside world, providing some protection from a hostile environment if needed.</p>\n" }, { "answer_id": 57553, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 4, "selected": false, "text": "<p>My answer involves cognition of sensory input. How does this suit 'see'?</p>\n\n<p>Lets say the suit becomes sentient as an emergent property of its internal computational abilities and programming, but that it was originally built by humans as a tool. Would it have the equipment to detect incident light? Would it be able to translate the light rays striking it into usable information?</p>\n\n<p>First off, the suit might not have sufficient visual detection equipment (cameras, basically). What if the cockpit has an advanced bio-glass dome that allows the human operator to look around. Sure there might be smaller ancillary cameras to aid the human operator, like the backup camera in a car today, but those don't hold candle to the acuity of the human eye. In that case, the suit has limited or no ability to 'see' anything in the visual spectrum at all.</p>\n\n<p>The second option is that the advanced bio-suit is equipped with cameras, but not with any software to interpret it. If it just relays information from the outside world to the user, and relies on the human brain to interpret the visual input (i.e. recognizing objects, determining movement and direction, judging distance, etc). If you designed a tool to have a human occupant, then you wouldn't spend the money on visual recognition software. That stuff is being developed for autonomous cars, not human occupied ones.</p>\n\n<p>The suit could have its own set of excellent senses, maybe infra-red maps, radar, sonar, anything; or it could be virtually blind. But either way, adding a highly advanced visual-light interpreting computer in its human symbiote would be very advantageous. </p>\n" }, { "answer_id": 57554, "author": "Michael Richardson", "author_id": 13484, "author_profile": "https://worldbuilding.stackexchange.com/users/13484", "pm_score": 6, "selected": true, "text": "<p>The neuro-pathways of the suits are very simple when they are \"built\". There is a large cluster around the neural-link port that handles all the sensory input from the suit to the human and all the control input from the human to the suit. Over time, this cluster specializes and becomes more complex to more efficiently handle this transmission. Eventually this \"brain\" learns how to do things rather than needing to be instructed on each step.</p>\n\n<p>For example, a new suit would need to have each individual step outlined (lift left foot, swing forward, plant left foot, lift right foot, etc). Over time, the suit would pick up on \"walk over there\" without each step needing to be defined. Eventually it could pick the optimal path, perhaps even deciding to move an obstacle rather than moving around it.</p>\n\n<p>As the suit becomes more and more optimized and efficient, the operators need to focus less on the task of moving and may even engage in daydreaming while the suit does the work. The daydreams also drift across the neural-link which triggers building other pathways to decipher them.</p>\n\n<p>Eventually, the pathways around the neural-link develop enough to awaken into self-consciousness.</p>\n\n<p>So the benefit to the suit is the initial development of the suit's personality and consciousness.</p>\n\n<p>Another benefit could be that the suits neural network is optimized to process incoming sensory input and receive outside commands. When there is no incoming commands, the suit <em>is</em> able to act autonomously, but it may not be as quick as it is when connected to a human. Or perhaps, part of a suit's pathways include paths to the neural-port where it would query the subconsciousness of the pilot when working out problem-solving skills.</p>\n\n<p>So:</p>\n\n<p>A human-in-a-suit is stronger and more physically able.</p>\n\n<p>A suit-around-a-human is more intellectually nimble and quick.</p>\n" }, { "answer_id": 57564, "author": "Sarriesfan", "author_id": 26341, "author_profile": "https://worldbuilding.stackexchange.com/users/26341", "pm_score": 1, "selected": false, "text": "<p>I am reminded of the mutual relationship between coral polyps and zooxanthellae algae.\n<a href=\"http://oceanservice.noaa.gov/education/kits/corals/media/supp_coral02bc.html\" rel=\"nofollow\">http://oceanservice.noaa.gov/education/kits/corals/media/supp_coral02bc.html</a>\nOne way to make sure that suits need to bond with humans is that when they were bioengineered in the first place they were created in such a way that they have to in order to gain sufficient nutrients. They might lack the ability to digest certain vitamins, perhaps mimicking a Vitamin B12 anemia.\n<a href=\"https://en.m.wikipedia.org/wiki/Vitamin_B12_deficiency\" rel=\"nofollow\">https://en.m.wikipedia.org/wiki/Vitamin_B12_deficiency</a>\nOr a similar condition that would mean that they would be unable to survive without the bonding process.</p>\n" }, { "answer_id": 57566, "author": "ckersch", "author_id": 2947, "author_profile": "https://worldbuilding.stackexchange.com/users/2947", "pm_score": 4, "selected": false, "text": "<p><strong>Humans and suits have vastly different <em>ways</em> of thinking</strong></p>\n\n<p>IQ alone is not sufficient to describe a mind. Different individuals, beyond raw brainpower, can have vastly different mental abilities, with tasks that are simple for one brilliant individual being almost impossible for another equally brilliant individual. It may be that the bio-suit is as smart as a human, or even far smarter, but only when confronted with certain tasks.</p>\n\n<p>A bio-suit, on its own, is excellent at fighting and has great battlefield awareness. They can form split second plans of how to accomplish simple tasks far faster than a human. They'r excellent visual learners and will perfectly remember even complicated urban environments, quickly determening things like optimal paths through these environments and rapidly making threat assessments about opposing forces based on their environmental stimulus. However, they don't know how to read, do basic math, or interact with any equipment besides weapons. Even for communication, they rely on a direct neural bond to communicate with their human partners, and are unable to learn the most basic of formal language. Anything that falls outside the realm of combat is essentially foreign to the mind of a battle suit, and they rely on their human companion to complete all of those tasks. A battle suit in an urban environment full of human enemies would effortlessly prowl about and eliminate all opposition, but would then promptly die of starvation, being unable to figure out how to fuel itself.</p>\n\n<p><strong>Human environments and tools are built for humans</strong></p>\n\n<p>Keyboards, vehicle cockpits, and buildings are all designed for humans, not 14-foot-tall combat brutes. A combat suit on its own would be unable to interface with any technology it encounters that isn't designed specifically with combat suits in mind. A combat suit with a human partner, on the other hand, can disgorge its pilot to drive vehicles, operate key pads, or do anything else that requires being human-sized and having human-sized hands.</p>\n" }, { "answer_id": 57570, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 3, "selected": false, "text": "<p>Like ckersch, I think the most interesting answers are those which recognize that there are many different ways to think, and that IQ doesn't capture all of them.</p>\n\n<p>The solution I think is most interesting is to look at longevity. If the suits are \"conscious,\" they likely have a desire to live as long as possible. It may be very reasonable to have the suits have a less than ideal lifestyle on their own. Perhaps they are tuned up too high by nature, and their behavior would get themselves killed due to wear and tear. To resolve this, they would naturally develop restrictions deep in their psyche to catch these spurious movements and inhibit them.</p>\n\n<p>Humans, thinking differently, may be able to react to the spurious movements better, and provide a level of stillness for the suit. As long as there is a human in the suit, they can drop some of their inhibitions because they know the human is going to symbiotically care for the suit. This means they can use their IQ for something more than just babysitting their lower functions.</p>\n\n<p>I have not read the series, but from what I have been told, the Halo series has a similar mechanic for their AIs. Their AIs grow up <em>very</em> fast and are very smart, but after a few years they start to go crazy. They eventually destroy themselves if they aren't decommissioned. I would expect that the captains were taught how to be symbiotic to these AIs, helping them stave off the insanity as long as possible.</p>\n\n<p>Given how analog human minds are, and how digital many mechanical systems are, this is not actually very far from reality...</p>\n" }, { "answer_id": 57595, "author": "Lope", "author_id": 11644, "author_profile": "https://worldbuilding.stackexchange.com/users/11644", "pm_score": 4, "selected": false, "text": "<p>One option is to have suits simply \"enjoy\" having human inside. Neural link would feed thought, dreams, ideas and emotions to the suit that the suit is not able to create, but is able to receive them through the link and appreciate, even enjoy (or to go to extreme, become addicted to) them.</p>\n\n<p>Another, similar, idea is to have suits consciousness limited when they are not being operated. Something like being asleep. Their neural pathways are not advanced enough to sustain higher level functions. When they link with operator, their consciousness awakens and they become fully sentient, mentally independent beings, perhaps even incorporating bit of operator's personality into theirs. They just need the link to kick their brain to higher gears. Suits are aware of this and seek this connection, because without it, they are not truly alive</p>\n" }, { "answer_id": 57599, "author": "NoAnswer", "author_id": 28135, "author_profile": "https://worldbuilding.stackexchange.com/users/28135", "pm_score": 4, "selected": false, "text": "<p>Sorry, can't resist the pun: The suits feel empty without a human inside.</p>\n\n<p>No honestly, they are artificial organisms <strong>built to</strong> take up and <strong>accept</strong> a human into their biological control functions.<br>\nHow would you feel, if half your brain is missing? How would you feel, if it comes back to you?</p>\n\n<p>The suits are bio-engineered, so presumably they are somewhat young and inexperienced, when they are boarded first time. They can learn so much from an experienced and trained pilot. And by the time they are experienced, they'll likely have come to an (in want for a better word:) intimate sort of partnership with their human.</p>\n\n<p>Of course, experienced suits may accept some few different pilots. It's like teamwork with someone you know and can communicate most efficiently, i.e. understanding each other literally without words. However the suits would only accept \"the best\" humans, because of mutual empathy as well as skills or training.</p>\n\n<p>To precisely argue the point, why this is symbiotic instead of parasitic: If half your brain, was an unbeneficial parasite, evolution would likely have rid humans of one half.<br>\nIf the suits were optimized (although by their human engineers) to work with a human inside, they work suboptimal without.</p>\n" }, { "answer_id": 57609, "author": "Yakk", "author_id": 2473, "author_profile": "https://worldbuilding.stackexchange.com/users/2473", "pm_score": 3, "selected": false, "text": "<p>Humans are smart, suits are smart.</p>\n\n<p>The union is smarter.</p>\n\n<p>Humans are actually two brains with a high-bandwidth connection between them. If you cut that connection, each half of the brain seems capable of hosting an entire human personality. If you put half of the human brain to sleep, the other half can make up for it and move around and talk and the like.</p>\n\n<p>When humans get into the suit, a high-bandwidth connection opens between the human's brain and the suit's brain. The two brains start to function mostly as one. This union is smarter.</p>\n\n<p>The fact that these bio suits are physically stronger than humans is only really useful when doing certain kinds of labor. Even in warfare, biological level strength and toughness isn't all that useful today, let alone in the near future; especially when you are needlessly risking an intelligence.</p>\n\n<p>The true value of the suit-human join is the brain link. These bio suits+human joins will be mathematicians, physicists, engineers, business consultants, researchers.</p>\n\n<p>Not every bio suit will be interested in this kind of thing. But it is reasonable that the bio suit's neural network finds joining with a human pleasant (as a side effect of the original design), it could easily be common.</p>\n" }, { "answer_id": 57641, "author": "HopelessN00b", "author_id": 4981, "author_profile": "https://worldbuilding.stackexchange.com/users/4981", "pm_score": 2, "selected": false, "text": "<p>I can't think of a reason why people would manufacture a suit that can move around on its own, and then put people in it. If you're designing an autonomous machine, you design an autonomous machine, and you don't try to stuff a \"pilot\" inside it. If you're designing a machine that requires an operator, you don't make it autonomous.</p>\n\n<p>So the simplest explanation is the best. They were designed as suits that require a human operator to move them around, and mobility is what these sentient bio-suits get out of the deal. You could obviously fiddle around with the exact details of this arrangement - instead of a human operator being a strict requirement, the original design intentions assumed a human operator, and thus, the bio-suits are slow or unwieldy without a human operator, or mobility requires a lot more energy without the human operator, or something of that nature.</p>\n\n<p>Along similar lines of considering how they were designed, if you consider that they were designed to contain a human, and unexpectedly developed sentience, it would stand to reason that they would have a psychological need or desire to pair up with a human, much like the human psychological needs for social interaction and sex.</p>\n" }, { "answer_id": 57642, "author": "Martin", "author_id": 8622, "author_profile": "https://worldbuilding.stackexchange.com/users/8622", "pm_score": 3, "selected": false, "text": "<p>A lot of answers so far have suggested that the suit's brain/mind is limited when not linked with their pilot. I'll suggest something in the same vein, but different.</p>\n\n<p>Suits are intelligent, self-sufficient, and plenty capable without a pilot. They could live their entire lives without a pilot linked to them, and be productive and beneficial to human/suit society. But their life, their thoughts, would be unimaginative. Inexperienced suit-minds wouldn't say they are bored, but that would be an apt description anyway.</p>\n\n<p>Suits want to link with humans because suit-minds lack imagination. Human minds have so many new, interesting ideas. They look at the world differently, they have desires and ambitions which the suit-minds would never have on their own.</p>\n\n<p>They especially like to experience dreams. Suits don't sleep and dream the way humans do, though they do need rest and mental down-time just like humans do. And since they essentially watch dreams from the outside, they can relay to their pilots what they dreamed of when they wake up.</p>\n\n<p>Suit-minds do well at thinking in functional and utilitarian ways. How to stack boxes efficiently, or the shortest route from one place to another, or the least wasteful layout for cutting clothing parts from a bolt of fabric.</p>\n\n<p>Humans think about what sorts of things go on those boxes, about the party at the other end of that shortest route, about a new dress design using that style of fabric but in red. They are creative and aesthetic.</p>\n\n<p>Suit-minds also don't get emotional the way humans do. At most they get a vague sense of accomplishment when they finish a large job, or mild frustration when encountering unexpected problems, but not much else. Humans feel love, anger, loss, loyalty, pride. Suit-minds can't experience these emotions without being linked to a pilot.</p>\n\n<hr>\n\n<p>Some other things to consider:</p>\n\n<ul>\n<li>Are suits capable of reproduction on their own, or are they always made in, e.g. a growth tank? If they are capable of reproduction, they might not have a drive to do so unless linked with a human, essentially extending the human reproductive drive to their own kind.</li>\n<li>Are suits always made the same, or is there variation in suits comparable to the variations in human genes?</li>\n<li>Could suits potentially form a successful, self-sustaining society without humans? Maybe no unpiloted suit would ever think to do this, but if the idea were planted and no one stood in their way, they could accomplish it?</li>\n<li>How much do suit-minds retain from their pilots after disconnecting? Do they retain it indefinitely (once learned, always retained), or does it fade with time?</li>\n<li>What sorts of physical requirements do suits have? Thinks like food/fuel, waste removal, rest/down-time, repairs for non-biological systems.</li>\n<li>What happens to a brain-damaged suit? Can it be repaired? Does it self-repair/heal? If it recovers from the physical damage, does it lose some memory, some sense of self, some personality?</li>\n<li>Do suits have rights, independent of their pilots? Can they commit crimes? Do any of them go rogue? If they are piloted and involved in a crime, does the suit bear any responsibility, or the pilot, or both?</li>\n<li>Can things a suit learns/absorbs from one pilot be sent the other direction to another pilot? For example, if a suit is piloted by a programmer for a few years, then by a dock worker for a few more years, would the dock worker get some programming skills, or at least have an easier time learning programming? Would the dock worker learn the programmer's dark, personal secrets? (If so, is this sort of knowledge transfer admissible as evidence in a court?)</li>\n<li>Can suits get sick? Since at least some of the biological components will be based on human biology, are suits susceptible to some of the same viruses and bacteria that make humans sick? Can suits strengthen their pilots' immune systems and help them fight off infections?</li>\n<li>How long do suits live?</li>\n</ul>\n" }, { "answer_id": 57646, "author": "Nathan Ellis Rasmussen", "author_id": 28153, "author_profile": "https://worldbuilding.stackexchange.com/users/28153", "pm_score": 2, "selected": false, "text": "<p>The theories of embodied cognition and situated cognition, in a nutshell, say that thinking doesn't happen just because there's a brain in your skull. Rather, thinking requires sensing, feeling, and acting; from infancy onward your brain's dialog with your body and your environment has been driving increasingly complex cognitive abilities. </p>\n\n<p>If you buy into that, a newly minted suit intelligence has a lot of experimenting and observing to process before it's really thinking at a high level. But bridging a human intelligence in allows it to use, observe, and emulate your well-developed processing and bootstraps it. </p>\n\n<p>Even after bootstrapping, you and the suit have different sensory and motor abilities, and different physiologies (i.e. emotions). Suits are generally just as interested in the expanded experience they get from your memories and imagination as humans are interested in the expanded physical abilities of the suit. </p>\n\n<p>Also, consider how your psychological drives reflect your physical requirements and limitations -- the sex drive from the mammalian reproductive system and the love drive from being optimized for small-group living and kin care; the drives to avoid pain and cultivate pleasure from the body's relative fragility; the drives to eat and to create cuisines from an evolutionary background as persistence hunters and savannah gatherers, with a nuanced sense of taste and smell to avoid poisons but also with the capacity for a broad palate to make the most of available edibles; the drive to acquire a signed or spoken language from some brain hardware that's very suitable for that, plus exceptional manual and vocal dexterity. </p>\n\n<p>Not to mention that the persistence hunt involves strenuous sweating, thinking, and running, which require supporting electrolytes, sugars, and fats, creating the famously deep-seated human drive toward salted caramel ice cream. That one's super important, I don't know how Freud missed it. </p>\n\n<p>Anyway though, working closely with a human is designed into the suits' physicality and into the information processing skills that they inherit from before sentience. All the sensors, actuators, and processors are built for it, and that's going to bias the sorts of conditions and behaviors that are easy for it, and thus the sort of mind that it develops. </p>\n" }, { "answer_id": 57654, "author": "Jammin4CO", "author_id": 10288, "author_profile": "https://worldbuilding.stackexchange.com/users/10288", "pm_score": 0, "selected": false, "text": "<p>This may not be completely in line with the OPQ, but it would make sense if:\nThe suit was actually several separate beings. The human is what connects them. The result is much like a jellyfish. The suit is aware, but it can't control the mobility units without a human connection. Additionally, the suit might require human <em>gross</em> bodily byproducts for sustenance (drink sweat, absorb heat, utilize CO2, etc.)</p>\n" }, { "answer_id": 57677, "author": "LSerni", "author_id": 6933, "author_profile": "https://worldbuilding.stackexchange.com/users/6933", "pm_score": 1, "selected": false, "text": "<p>All the work performed to design and optimize the bio-suits for human integration has naturally converged to making the connection <em>desirable</em> for the suits.</p>\n\n<p>This is no longer an overpowering need for the suit to work properly and experience \"pain\" in case of faults, but it is still there, and by now it would be both impractical and expensive to root out - it would imply redesigning the suits from scratch, which neither suits nor humans feel necessary or desirable.</p>\n\n<p>But the end result is still that what humans think of as <em>wearing a suit</em>, suits think of as <em>sex</em>.</p>\n" }, { "answer_id": 136348, "author": "Thomas Engelthaler", "author_id": 60337, "author_profile": "https://worldbuilding.stackexchange.com/users/60337", "pm_score": -1, "selected": false, "text": "<p>This might be going off on a tangent but does the \"suit\" have to be a suit at all it could could be something similar to the Klyntar aka\"symbiotes\" from Marvel, where the \"suits\" are an amorphous mass of cells and/or nanites that act similarly to an amoeba yet they are sentient, where they bond to the host permanently or have some semi-permanence to the bond where the \"suits\" could then be inside the human host and give them advanced abilities such as rapid healing, body weaponization, enhanced intelligence, and reflexes, or other such abilities. In return, the host must consume specialized foods and materials or instead they have to consume different animals or genetic material to gain these abilities after the bonding process as well as consume more food than was otherwise necessary to sustain the host for a day before said process. Said host could also have the ability to rapidly evolve in response to certain stimuli or circumstances. These \"evolutions\" could be performed in a lab like controlled environment to increase the likelihood of these \"evolutions\" taking place and/or these evolutions could happen in any environment at any time taking place randomly with the increased likelihood of these evolutions being beneficial but unknown in the scientific sense that the creators didn't realize that they could or could not evolve in that way, thus creating the possibility for endless rapid self-evolution, this could lead to extraordinarily long or near infinite life spans. </p>\n\n<p>The symbiotes could also innately be only semi-sentient or sentient to a degree in that they understand that the one they bond with will be the one they die with or that they develop their personality with. The \"suits\" in a sense would be in a perfect symbiotic relationship where the \"suits\" and the host are in a permanent bond that couldn't be broken but would cause extreme often irreparable emotional harm not just to the host but also to the \"suit\". The \"suits\" after a while develop their own intelligence based on what would be the most beneficial for the host such as Eragon and Saphira (Inheritance cycle) and John-117's \"Cortana\" AI even though one example is dragon and rider telepathic bond and the other is a relationship between Master Chief and his AI the same principle applies it would cause irreparable emotional harm to kill one or the other. </p>\n\n<p>The suit in a sense would become the partner of the host they could think individually and as one with the host even as each has a full range of emotions they can experience each other's. </p>\n" }, { "answer_id": 192883, "author": "G0BLiN", "author_id": 756, "author_profile": "https://worldbuilding.stackexchange.com/users/756", "pm_score": 1, "selected": false, "text": "<h3>Suits Learn Better from a Direct Link</h3>\n<p>This is somewhat similar to the (excellent) answers by <a href=\"https://worldbuilding.stackexchange.com/a/57554/756\">Michael Richardson</a>, <a href=\"https://worldbuilding.stackexchange.com/a/57566/756\">ckersch</a> and <a href=\"https://worldbuilding.stackexchange.com/a/57599/756\">NoAnswer</a>.</p>\n<p>The suits can function very well on their own, they have a robust set of built-in motor and cognitive skills which they can either fully utilize from &quot;birth&quot; or find it very easy to acquire on their own. This is thanks to their original design as tools¹.</p>\n<p>However, the direct mind-to-mind link is the best trainer and educator for a suit - yes, they can run and jump pretty well from birth - but a few weeks of actively training with a parkour master would teach them more than they can learn on their own in years. Same goes for acquiring any advanced physical or mental skill - martial arts and weapon use, driving / piloting vehicles², advanced engineering, zoology, art etc. etc. etc.</p>\n<p>Maybe some of these skills a suit can learn on its own, but find that process inferior compared to a direct mind-to-mind link³. Other skills might be completely beyond an unbonded suit (either for a specific one for their entire &quot;species&quot;).</p>\n<p>That may even be true for evolving a suit's very basic but undesigned capabilities, such as intelligence, imagination, creativity or interpersonal communication⁴. Moreover, it makes sense that emotions, empathy and morality are not something the original designers will add to a tool - so suits must actively acquire these. That would suggest that a newly created suit (or its progenitors) may look for a good first link mentor to help with its education and expedite its maturity and transition from a very useful thing/tool to a fully fledged <em>person</em>. Additionally, this can be expanded to mean that the character and worldview of a person can be imprinted on a suit - especially so for a young one that did not yet solidify their personality. This will make choosing a worthy bonding partner very important for the suits, and could lead to &quot;mixed-families&quot; or even tribes/nations of humans and suits that share a culture (philosophy, morals, aesthetics etc. etc.) - with as much difference and diversity as human-only cultures exhibited through history.</p>\n<hr />\n<p>¹: The alternative, i.e. a suit which needs to be taught how to walk by breaking down each step into a set of multiple movements requiring explicit commands (not to mention the difficulty of acquiring bi-pedal motion and dynamic equilibrium this way) - is impractical and unwieldy.</p>\n<p>²: <em>Of course</em> there'll be solutions to drive/fly suits around - some of them with the driver/pilot suited up themselves - this makes sense for combat and emergency response missions, where time is critical and quick deployment is a must. It'll also be very useful for single-person tasks - take delivery services, infrastructure maintenance, or forestry as examples - a single person and suit in a truck, speedboat, hovercraft or what-have-you, using the mundane vehicle for long-range, heavy load or fast transportation, with a lot of stops along the way where the suit comes into play (for heavy-lifting, protection or efficiency) - it'll be much easier not to have to suit-up at every stop and suit-down just to move to the next stop, and the suit has to be on board anyway...</p>\n<p>³: Learning alone comes with greater difficulty, a slower pace and/or is boring or frustrating. Possibly learning with a linked tutor is also much more enjoyable and rewarding, not just more efficient (think of The Matrix scene where Neo states &quot;I know kung fu!&quot; and Morpheus's response: &quot;Show me.&quot;).</p>\n<p>⁴: They should have a built in ability to use language so they can communicate with operators / maintainers even without a linked human - but this could reasonably be limited to basic, functional phrases (&quot;incoming enemy&quot;, &quot;malfunction detected&quot;, &quot;command acknowledged&quot; etc.). The ability to convey complex ideas, understand non-verbal cues, negotiate compromises or use verbal subterfuge may not make sense to design into a tool.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/57535", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/17263/" ]

[ { "answer_id": 57572, "author": "M1ata", "author_id": 28093, "author_profile": "https://worldbuilding.stackexchange.com/users/28093", "pm_score": 2, "selected": false, "text": "<p>One way this is possible is to have an organism that uses methanol as a solvent. Methanol is less polar than water, so water would act like an acid, hydrolyzing many of the creature's constituent molecules.</p>\n\n<p>As far as resisting humidity, that becomes a bit more difficult. One explanation that may work is that it has some kind of \"Crust\" at the surface of the skin. This could be made of all sorts of stuff, but if it were to be made of olivine ((Mg, Fe)2SiO4) it would give her skin a green color!</p>\n\n<p>Hope this helps.</p>\n" }, { "answer_id": 57574, "author": "Monty Wild", "author_id": 75, "author_profile": "https://worldbuilding.stackexchange.com/users/75", "pm_score": 6, "selected": true, "text": "<p>Certainly, this is possible. Almost all things are, after all.</p>\n\n<p>However, the effect of melting when exposed to large amounts of liquid water is probably not what it initially appears to be.</p>\n\n<p>An alien organism that is tolerant to small amounts of water is probably one that is tolerant to larger amounts too, so why would a large amount of water make the alien melt?</p>\n\n<p>My hypothesis is that this particular alien is actually composed of a great many small subunits. This is similar to our cellular model, but the alien subunits may <em>themselves</em> be tiny, aquatic, multicellular organisms. These organisms have the ability to clump together into a single colony in times of drought in order to present a reduced surface area through which water may be lost, and when a sufficiently heavy rain comes along, they can disband and do their own thing, such as mating.</p>\n\n<p>Over time, these organisms have evolved the ability to move and form a group intelligence while joined in a colony, however the single consciousness which results is dependent upon the particular arrangement of the individual organisms, and should the colony disband, its consciousness will cease, and even if the colony subsequently reforms from the same organisms, the inability of the organisms to achieve exactly the same configuration as before means that the reformed colony will be a new consciousness with a different personality, though with remnant skills and knowledge left over from the previous configuration.</p>\n\n<p>Naturally, the longer a colony exists in a particular configuration, the more skills and knowledge it will accumulate, increasing the survivability of the colony. This would lead to a state where the collective consciousnesses of the colonies would be reluctant to disband voluntarily unless presented with a suitably large body of water, but where a relatively small amount of water could fool the individual organisms into disbanding. Of course, if there really <em>wasn't</em> enough water, the colony could reform - as a different consciousness - but this would be a case where sentience has overtaken the limitations of evolution. Yes, the colony could reform - doing so would be better than not doing so if there really isn't enough water - but the reformed colony would no longer be the same person since its neural pathways would be different.</p>\n\n<p>So, if the Wicked Witch of the West was such a colonial organism, splashing it with sufficient water to trigger the instinctual disbanding of the colony in preparation for the mating season would in effect be a sentence of death for that particular colonial <em>sentience</em>, even if after a little while the colonial organisms could re-form the colony. After such an event, despite all the same organisms being present, it would be a different colony with a different personality and probably fewer skills.</p>\n\n<p>Given that, it is not surprising that the <em>consciousness</em> of the \"melting\" Wicked Witch could - in the moments remaining to it - recognise that it would cease to exist due to the triggering of an instinctive response of its member organisms, and bewail that fact. It would have good cause, since any reformed colony would likely have fewer valuable skills, and hence be less able to survive.</p>\n\n<p><strong>EDIT</strong></p>\n\n<p>In response to the OP's comment that it might be possible to re-imprint the colony's original personality onto the reformed colony, I offer this variation, which would not be too difficult to evolve:</p>\n\n<p>The colonial subunits have individual identities, and after spending a considerable amount of time next to other individuals, can remember exactly which individuals to whom they were adjacent, even after dissolution and reformation of the colony. While the colony could be reformed quite quickly, it would have a random configuration with a new personality and few skills.</p>\n\n<p>However, the individual subunits memories of their previous neighbours and the neural network of the colony would allow the subunits to change their positions within the colony to recreate its previous configuration and thus restore the previous personality with its more developed skills.</p>\n\n<p>However, if we are using the Wizard of Oz as the template for this species, then the behaviour above is not consistent with the reactions of the Wicked Witch of the West to being splashed by a bucketful of water:</p>\n\n<p>From Frank L Baum's novel, <em>The Wonderful Wizard of Oz</em>:</p>\n\n<blockquote>\n <p>\"You are a wicked creature!\" cried Dorothy. \"You have no right to\n take my shoe from me.\"</p>\n \n <p>\"I shall keep it, just the same,\" said the Witch, laughing at her,\n \"and some day I shall get the other one from you, too.\"</p>\n \n <p>This made Dorothy so very angry that she picked up the bucket of\n water that stood near and dashed it over the Witch, wetting her from\n head to foot.</p>\n \n <p>Instantly the wicked woman gave a loud cry of fear; and then, as\n Dorothy looked at her in wonder, the Witch began to shrink and fall\n away.</p>\n \n <p>\"See what you have done!\" she screamed. \"In a minute I shall melt\n away.\"</p>\n \n <p>\"I'm very sorry, indeed,\" said Dorothy, who was truly frightened to\n see the Witch actually melting away like brown sugar before her very\n eyes.</p>\n \n <p>\"Didn't you know water would be the end of me?\" asked the Witch, in a\n wailing, despairing voice.</p>\n \n <p>\"Of course not,\" answered Dorothy; \"how should I?\"</p>\n \n <p>\"Well, in a few minutes I shall be all melted, and you will have the\n castle to yourself. I have been wicked in my day, but I never thought\n a little girl like you would ever be able to melt me and end my\n wicked deeds. Look out--here I go!\"</p>\n</blockquote>\n\n<p>or from the <em>The Wizard of Oz</em> movie script:</p>\n\n<blockquote>\n <p>MS -- Dorothy throwing water at Scarecrow -- some of it hits the Witch in\n the face -- Tin Man standing at left with the Lion --</p>\n\n<pre><code> SCARECROW\n Help!\n</code></pre>\n \n <p>MCU -- The water hits the Witch in the face --</p>\n \n <p>MS -- The Witch screams as the water hits her -- Tin Man, Lion, Dorothy\n and Scarecrow look at her --</p>\n \n <p>MLS -- The Lion, Tin Man, Dorothy and Scarecrow watch the Witch as she\n screams and melts away -- camera shooting past Winkies in the f.g. -- the\n Witch curses as she disappears, finally only her cloak and hat remain on\n the floor -- her voice fades away --</p>\n\n<pre><code> WITCH\n Ohhh -- you cursed brat! Look what you've\n done! I'm melting! Melting! Oh -- what a\n world -- what a world! Who would have\n thought a good little girl like you could\n destroy my beautiful wickedness!? Ohhh!\n Look out! Look out! I'm going. Ohhhh!\n Ohhhhhh....\n</code></pre>\n</blockquote>\n\n<p>Such behaviour would be more consistent with the behaviour I originally described, in that the colonial subunits are not capable of restoring a particular configuration through the process of dissolution and reformation of the colony.</p>\n\n<p>However, the novel also describes the Wicked Witch of the West as being \"cunning\", so it is not beyond the bounds of possibility that this reaction may have been a sham intended to lead Dorothy and company to <em>believe</em> that this dissolution was fatal, so that when the colony reformed - hopefully after Dorothy and company had left the area - it could restore its long-term configuration and personality and continue pursuing its goals with the added advantage that its enemies believed it to be deceased.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/57559", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/28102/" ]

[ { "answer_id": 57573, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 3, "selected": false, "text": "<p>The extra weight shouldn't be too bad. From <a href=\"https://www.quora.com/How-is-body-weight-distributed-between-bones-organs-muscle-and-fat\">Quora</a>:</p>\n\n<blockquote>\n <p>Approximate body weight distribution for a lean adult:</p>\n\n<pre><code>Bone: men 15%; women 10%\nMuscle: men 45%; women 37%\nOrgans: men and women: 25%\nFat: men 15%; women 28%\n</code></pre>\n</blockquote>\n\n<p>So you're looking at adding 25-40% weight, depending on how many of the bones you replace.</p>\n\n<p>However, the brain is an issue. You cannot distribute the brain without drastically changing its functionality. Neuron impulses are actually quite slow (120m/s at the highest), so moving parts of the brain to different areas actually adds a non-trivial latency in communication which would drastically change the way the brain operates.</p>\n\n<p>For an interesting data-point, we actually do quite a bit of processing in the spinal column itself, especially for walking. It's closer to the rest of the body, so the delays are lower. It turns out that if you bump your left hand into something while walking, your right foot will have adjusted its gait before your brain stem has even processed the impact!</p>\n\n<p>As for the shape of your human, the real limiting factor is going to be useful redundancy. I can carry 100 eggs in a basket, but I don't have redundancy if I break them all at once. An extra femur is going to be... well... an extra bone in the leg. If something was breaking leg bones before, it now gets to break twice as many. You're likely going to have to do some substantial restructuring to make that redundancy useful.</p>\n" }, { "answer_id": 57577, "author": "Giacomo", "author_id": 21743, "author_profile": "https://worldbuilding.stackexchange.com/users/21743", "pm_score": 1, "selected": false, "text": "<p>It wouldn't help for a supersoldier.</p>\n\n<p>When a soldier is shot, the cause of death isn't usually damage to a specific organ, it's from the of trauma caused by the loss of all blood pressure, the shock to the rest of the body from suddenly limited oxygen supply, and bleeding out through the wound.</p>\n\n<p>If you were trying to make a supersoldier, focus on mitigation of injuries. Blood vessels that can constrict to limit bleeding, extra bone and muscle mass to absorb impact from bullets and shockwaves. Less pain and panic response so they keep their cool under pressure.</p>\n\n<p>Put simply, it doesn't make too much sense to double up on internal organs. They need to get blood to them, and a gunshot wound stops that whether or not there's more organs.</p>\n" }, { "answer_id": 57613, "author": "Jason K", "author_id": 20759, "author_profile": "https://worldbuilding.stackexchange.com/users/20759", "pm_score": 2, "selected": false, "text": "<p>You don't need full sized duplicate organs if they are just for emergency redundancy. The liver, for example, can function for a time with a much smaller size, so you could have a smaller accessory lobe somewhere else. But the problem with sudden traumatic liver loss isn't the actual loss of the liver, it is the extreme hemorrhage because of how vascular the liver is.</p>\n\n<p>You could also have collapsed lungs in reserve, but it is hard to imagine where they would be other than in the chest cavity, which is already occupied with the regular lungs. Penetrating chest trauma, chemical attack, or explosive overpressure would affect all the lungs in that area. But if you could somehow collapse the \"in use\" lungs and inflate a pristine lung in it's place you may be able to mitigate a lot of the damage for a short time.</p>\n\n<p>Back-up hearts distributed elsewhere (such as the pelvis) could work and also wouldn't need to be as large as the primary heart (if it was intended for just a short time before exhaustion). But if you want redundancy for primary heart loss you would need one for pulmonary perfusion as well as systemic perfusion since the primary heart is hooked up to both vascular systems. </p>\n\n<p>What you really need are collateral arteries that can open up to bypass a damaged main artery, like a cut carotid. The drop in blood pressure to the brain causes you to pass out. Anything that could keep pressure up in the brain would allow for continued function, at least for a short while.</p>\n\n<p>You don't really need a back-up kidney in the short term, but you can stick one anywhere, since transplanted kidneys can function anywhere they can get blood (and a drain for urine). Same with back-up intestines. You don't even NEED intestines if you can get all your nutrients intravenously (Total Parenteral Nutrition). The big issue is intestinal injury dumping gut bacteria into the belly, causing sepsis which can kill you pretty quick.</p>\n\n<p>So, in short, it is pretty hard to redistribute or reorganize human anatomy but still retain the basic shape if your goal is combat redundancy. Getting shot in the belly will rupture both sets of intestines. Getting stabbed in the chest will pierce all the lungs there (and you need the rigidity of the ribcage and the diaphragm for lungs to work). A duplicate vascular system would be of benefit, but it would be a neat trick to get it to function properly to allow for bypassing injured areas but still connect in order to perfuse the smaller vessels. You COULD have a collapsed lung that gets opened up in the event the main lungs collapse, as that would just require a limited set of tracheal and vascular branching, but this is a pretty niche use case since the torso is so easy to armor already. Duplicate kidneys, liver, and other organs (like the thyroid, adrenals, pancreas, etc) are either unnecessary (since there is already a second copy in the body) or the immediate loss isn't important. Probably your best option is splitting up the liver into smaller lobes spread across the abdomen. The function shouldn't be impaired so long as the total mass is the same and having smaller sub-livers will limit a major source of abdominal traumatic hemorrhage. One lobe will still need to be near the stomach in order to supply the gallbladder with bile.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/57571", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/21870/" ]

[ { "answer_id": 60473, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 3, "selected": false, "text": "<p><a href=\"https://en.wikipedia.org/wiki/Horizon#Distance_to_the_horizon\" rel=\"nofollow noreferrer\">Distance to the horizon</a> is calculated by $d \\approx 3.57\\sqrt{h}$ where $d$ is distance in km and $h$ is height of eye in meters. The same formula works in reverse, for an observer at sea level and an object at height $h$.</p>\n\n<p>For 2000 m, $d \\approx 3.57\\sqrt{2000} = 160 km$.</p>\n\n<p>Of course, you can't actually SEE anything at that point, everything in the city, including the city itself, is far too small without some powerful optics. And any sort of atmospheric disturbance, even high humidity will distort the picture and make things hard to see even with powerful optics. But on a perfectly bright, perfectly clear day, with a spectacular telescope, you could see the city 160 km. </p>\n\n<p>Anecdote: Mt. Cameroon is very tall and very much right at the edge of the sea. I saw a sunrise over Mount Cameroon from about 50 miles off. This is what it would look like, to see your city from so far.</p>\n\n<p><a href=\"https://i.stack.imgur.com/AUOh7.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/AUOh7.jpg\" alt=\"Sunset over a mountain\"></a></p>\n\n<p>(I know this picture is sunset, but close enough)</p>\n\n<hr>\n\n<p>Edit, regarding the human eye. According to <a href=\"https://en.wikipedia.org/wiki/Naked_eye#Basic_accuracies\" rel=\"nofollow noreferrer\">wikipedia</a>, the angular resolution is about 1 arcminute. This corresponds to 0.3m at 1km distance, for 30m at 100km distance. </p>\n\n<p>Depending on what you mean by 'see', you could see that a well lit city was there at night from the full 160km (thanks @notstoreboughtdirt), and you could resolve a city size splotch of color during the day from that far away too. To actually tell that there are buildings and not just a blotch of color, you might have to resolve the ~5m distance between buildings which you could do at about 15km, based on the arc-minute resolution. </p>\n" }, { "answer_id": 60493, "author": "Feyre", "author_id": 26119, "author_profile": "https://worldbuilding.stackexchange.com/users/26119", "pm_score": 2, "selected": true, "text": "<p>To expand a bit on @kingledion 's answer:</p>\n\n<p>The angular resolution of the naked eye is about $\\frac{\\pi}{10800}$, or one arc minute.</p>\n\n<p>You mentioned a civilisation on the level of ancient Rome, which had walls of around $10\\left(m\\right)$ high.</p>\n\n<p>From basic trigonometry we know that $\\tan{\\frac{\\pi}{10800}}=\\frac{10\\left(m\\right)}{d\\left(m\\right)}$, so $d\\left(m\\right)=\\frac{10\\left(m\\right)}{\\tan{\\frac{\\pi}{10800}}}=34377.5\\left(m\\right)$, or more generally:</p>\n\n<p>$$d\\left(m\\right)=\\frac{h\\left(m\\right)}{\\tan{\\frac{\\pi}{10800}}}=3437.75 h\\left(m\\right)$$</p>\n\n<p>This means that on a clear day, the <em>Maximum</em> distance at which the average human eye can resolve an object of a $5\\left(m\\right)$ radius is around $34\\left(km\\right)$.\nHowever, at this range, the walls would probably just look like a thin line of different colour from the rock.</p>\n\n<p>The formula scales linearly, so if the walls could be made out properly with 4 \"pixels\", the distance would be about $8.6\\left(km\\right)$</p>\n\n<p>This isn't all though, after all, you mention that the city is on a $~2000\\left(m\\right)$ high plateau, this changes the formula.\nThe angle at which we are looking is now $tan^{-1}{\\left(s+\\frac{h}{2}\\right)}=\\alpha=\\tan^{-1}{\\frac{2005\\left(m\\right)}{d\\left(m\\right)}}$</p>\n\n<p>We need to multiply the distance with the cosine of this value. So:</p>\n\n<p>$$d\\left(m\\right)=\\cos{\\left[\\tan^{-1}{\\frac{\\left(s+\\frac{h}{2}\\right)\\left(m\\right)}{d\\left(m\\right)}}\\right]}\\frac{h\\left(m\\right)}{\\tan{\\frac{\\pi}{10800}}}$$</p>\n\n<p>Solving this numerically with <em>Mathematica</em>:</p>\n\n<pre><code>Solve[Cos[ArcTan[(s + h/2)/d]] h/Tan[Pi/10800] == d]\n</code></pre>\n\n<blockquote>\n <p><code>d -&gt; 1/2 Sqrt[-h^2 - 4 h s - 4 s^2 + 4 h^2 Cot[\\[Pi]/10800]^2]</code></p>\n</blockquote>\n\n<p>and</p>\n\n<pre><code>With[{s = 2000, h = 10}, \n Solve[Cos[ArcTan[(s + h/2)/d]] h/Tan[Pi/10800] == d]] // N\n</code></pre>\n\n<blockquote>\n <p><code>d -&gt; 34318.9</code></p>\n</blockquote>\n\n<pre><code>Plot[{d, Cos[ArcTan[2005/d]] 10/Tan[Pi/10800]}, {d, 0, 35000}]\n</code></pre>\n\n<p><a href=\"https://i.stack.imgur.com/gkybS.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/gkybS.png\" alt=\"enter image description here\"></a></p>\n\n<p>The distance for a variable height of the plateau (s) is givien by:</p>\n\n<p>$$\\sqrt{-25-10s-s^2+100\\cot{\\left(\\frac{\\pi}{10800}\\right)}^2}$$</p>\n\n<p><a href=\"https://i.stack.imgur.com/lNnaz.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/lNnaz.png\" alt=\"enter image description here\"></a></p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/60472", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/20681/" ]

[ { "answer_id": 60870, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 3, "selected": false, "text": "<p>Generally speaking, this sort of approach has to be designed into a ship since day one. You need a very different structural setup when you can't just float the ship on water. Amphibious vehicles often make sacrifices to achieve their goals.</p>\n\n<p>One thing you definitely will need to do is split up those 7 caterpillar tracks into several hundred tracks, or you will find that the dreadnought cannot turn at all!</p>\n\n<p>Realistically speaking, there's nothing like it in all of engineering. The closest thing I can think of to what you are trying to do is the <a href=\"https://en.wikipedia.org/wiki/Crawler-transporter\" rel=\"nofollow noreferrer\">Crawler-Transporter</a> NASA used to transport the shuttle, with a top speed of 1mph. That was 40m long and weighed in at about 2700 tons. The USS Iowa, one of the last of our battleships, was 270m and had a mass of 45,000 tonnes. Your ship is at <em>least</em> 3 times that big, and likely bigger, so that should give you a sense of how extreme the design is.</p>\n\n<p>Also, expect this change to make the Super Dreadnought completely and utterly useless in the water. The drag from these tracks would make it the laughingstock of any navy in terms of top speed. Assume that what you created really was a single use device that will never find value in war again.</p>\n" }, { "answer_id": 60873, "author": "Thucydides", "author_id": 8572, "author_profile": "https://worldbuilding.stackexchange.com/users/8572", "pm_score": 3, "selected": true, "text": "<p>In a rather weird way, H.G. Wells wrote about the possible future of tanks and pessimistically envisioned monstrous battleship sized machines capable of carrying huge batteries of guns and plowing the landscape before them due to the immense weight.</p>\n<blockquote>\n<p>What lies behind the Tank depends upon this fact; there is no definable upward limit of mass. Upon that I would lay all the stress possible, because everything turns upon that.</p>\n<p>You cannot make a land ironclad so big and heavy but that you cannot make a caterpillar track wide enough and strong enough to carry it forward. Tanks are quite possible that will carry twenty-inch or twenty-five inch guns, besides minor armament. Such Tanks may be undesirable; the production may exceed the industrial resources of any empire to produce; but there is no inherent impossibility in such things. There are not even the same limitations as to draught and docking accommodation that sets bounds to the size of battleships. It follows, therefore, as a necessary deduction that if the world's affairs are so left at the end of the war that the race of armaments continues, that Tank will develop steadily into a tremendous instrument of warfare, driven by engines of scores of thousands of horse-power, tracking on a track scores of hundreds of yards wide and weighing hundreds or thousands of tons. Nothing but a world agreement not to do so can prevent this logical development of the land ironclad. Such a structure will make wheel-ruts scores of feet deep; it will plough up, devastate and destroy the country it passes over altogether.</p>\n</blockquote>\n<p><a href=\"https://i.stack.imgur.com/Ludjc.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Ludjc.jpg\" alt=\"enter image description here\" /></a></p>\n<p><em>Illustration from 1939</em></p>\n<p>Of course, being a &quot;linear projection&quot;, it takes a basic idea and inflates it to rather absurd dimensions. Wells was no crank, however. He had actually predicted armoured fighting vehicles in a 1903 story &quot;<a href=\"https://rads.stackoverflow.com/amzn/click/com/1406577138\" rel=\"nofollow noreferrer\" rel=\"nofollow noreferrer\">The Land Ironclads</a>&quot; (technically, the Tripods from the <a href=\"https://rads.stackoverflow.com/amzn/click/com/1505260795\" rel=\"nofollow noreferrer\" rel=\"nofollow noreferrer\">War of the Worlds</a> were also AFV's), and was an enthusiastic supporter of the development of real tanks when they were developed by the British.</p>\n<p><a href=\"https://i.stack.imgur.com/uRHXC.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/uRHXC.jpg\" alt=\"enter image description here\" /></a></p>\n<p><em>A Land Ironclad</em></p>\n<p>And this trope has carried on in Science Fiction and games with ideas like &quot;Bolo&quot; AI driven tanks and the Ogre war-game.</p>\n<p>However, once you re read the description of the Wellsian super tank, you see the issues. Engines with &quot;scores of thousands of horsepower&quot; are absurdly huge (especially with 1930 era technology) regardless of what your power source is. The bulk of the machine will be made up of engine bays and transmissions. Since the engines will not convert 100% of your energy into motion, you need some sort of radiating mechanism. A ship at sea can dump its heat into the ocean, but on land it becomes a bit more difficult. You might be looking at a cooling system similar in size to the massive cooling towers at a nuclear power station.</p>\n<p>The next issue is the mechanical strength of the chassis. A ship is fully supported by the water it displaces, but your vehicle will have hundreds or thousands of separate stress points in the suspension and track system. The body will be similar to a bridge standing on pylons, so there will be sections cantilevered between suspension elements. The body will be subject to stresses in multiple directions since the ground isn't flat, and firing stresses will complicate matters even more. When you consider a modern torpedo kills a ship by exploding under the keel and creating a cavitation bubble, snapping the ship where it is no longer supported, then consider the same effect will occur when the vehicle will be subject to similar stresses when crossing a stream, valley or even sufficiently large ditch.</p>\n<p>Finally, this thing will be a target. It will be moving slowly enough that everything from long range artillery and bomber aircraft to tank hunting teams with explosive charges will be assembled and sent into action long before this thing can get into range of its target. Your multi million dollar investment will be smoking ruins, quite possibly before you even hit the beach (the Captains of the <a href=\"https://infogalactic.com/info/HMS_Prince_of_Wales_(53)\" rel=\"nofollow noreferrer\">HMS Prince of Wales</a>, <a href=\"https://infogalactic.com/info/Japanese_battleship_Yamato\" rel=\"nofollow noreferrer\">IJN Yamato</a> and the <a href=\"https://infogalactic.com/info/German_battleship_Bismarck\" rel=\"nofollow noreferrer\">Bismarck</a> can explain this more fully).</p>\n<p>Given the parameters that you provided in the setup, it would be far more plausible for the attack to be made by carrier born bombers or even large seaplanes than to expend the time and energy needed to create the monstrosity you are describing.</p>\n<p><a href=\"https://i.stack.imgur.com/Q2J7l.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Q2J7l.png\" alt=\"enter image description here\" /></a></p>\n<p><em><a href=\"https://infogalactic.com/info/USS_Saratoga_(CV-3)\" rel=\"nofollow noreferrer\">USS Saratoga</a></em></p>\n" }, { "answer_id": 60884, "author": "Mołot", "author_id": 809, "author_profile": "https://worldbuilding.stackexchange.com/users/809", "pm_score": 2, "selected": false, "text": "<p>Other answers are good, but there is one more thing to it. </p>\n\n<p>Sea is basically flat, with small distortions called waves, that still give pretty flat average. On the open ocean big waves are also long - so still flat. This means, you can dump stress really evenly. Construction is easier if it does not need to support mass on discrete number of points. Far less structural strength needed. With something long like a ship, change of road elevation (like start of an uphill ride) would mean that while front and rear are supported, middle is not. Ship as we know them would break. </p>\n\n<p>Of course you could separate it into sections with flexible joints. Each of these should need own pair of tracks, own engine. Now, if you would only get rid of these joints, you would effectively have a column of tanks, artillery and support vehicles. Or you could leave one engine and joints, but then you would have to put it on the train tracks. Armed, armored trains was real,and looked somewhat like warships. </p>\n" }, { "answer_id": 60886, "author": "MichaelK", "author_id": 12297, "author_profile": "https://worldbuilding.stackexchange.com/users/12297", "pm_score": 1, "selected": false, "text": "<h1>No, and None</h1>\n\n<p>You asked for science based...</p>\n\n<p><strong>No, this sort of thing will never be feasible, at least not on Earth</strong> </p>\n\n<p>As others have pointed out, the only reason we can make ships so big is because the ocean is a very/relatively easy medium to deal with. No matter the weight you can always \"stand\" on the ocean, as long as your average density is less than that of water. It does not matter how big you make something; as long as the density is less than that of water, it will float. </p>\n\n<p>As a side note: this is also true of air, which is why we could/can make <a href=\"https://en.wikipedia.org/wiki/Zeppelin\" rel=\"nofollow noreferrer\">humongous airships</a>. And both the ocean and the atmosphere are (relatively) kind to you in that they (mostly) distribute your load very evenly accross your hull. </p>\n\n<p>This is not true on land, because of the <a href=\"https://en.wikipedia.org/wiki/Square-cube_law\" rel=\"nofollow noreferrer\">square-cube law</a>, and the fact that land is only pressing against one side of your craft. As the size increases, the pressure — i.e. weight per unit of area — on the ground will increase as well. If you scale something up 10 times, the area in contact with the ground will increase 100 times ($10 \\cdot 10$) but the <strong>weight</strong> will increase 1 000 times ($10 \\cdot 10 \\cdot 10$). This means that the ground will give way and you will sink through it. </p>\n\n<p>Among the largest land weapons systems mankind has tried to move around are the <a href=\"https://en.wikipedia.org/wiki/Panzer_VIII_Maus\" rel=\"nofollow noreferrer\">Panzer VIII Maus</a> and the <a href=\"https://en.wikipedia.org/wiki/Schwerer_Gustav\" rel=\"nofollow noreferrer\">Heavy Gustav/Dora</a>. The Heavy Gustav required dual railway tracks to help alleviate the square-cube problem. And the Maus never saw action, and even if it had it would have been a right pain to move it around since most bridges would be unable to carry its weight. </p>\n\n<p>What kind of change would be needed to still try to do something like this? Well essentially you need less gravity: you need the battle to take place on the Moon, or on another, smaller planet. But since your question implicitly places the battle on Earth, sorry...</p>\n" }, { "answer_id": 60906, "author": "Jason K", "author_id": 20759, "author_profile": "https://worldbuilding.stackexchange.com/users/20759", "pm_score": 1, "selected": false, "text": "<p>You don't want a ship, you want an amphibious TRAIN. Your ship is too long for the sea, it would have to be very wide as well. TRhis would make it supremely unwieldy on land, how could it navigate even the gentlest hill crest? You can see here the various <a href=\"http://marine.marsh-design.com/content/length-beam-ratio\" rel=\"nofollow noreferrer\">length-beam ratios</a> and what ships use what. An Iowa class BB, for example, has a length of 860 feet and a beam of 108 feet for a ratio of 8. A Spruance class DD has 529/55=9.6 ratio. So your battleship, if it were scaled like a regular warship, would have a beam of at least 73 METERS, or 240 feet, which is the height of a TWENTY FOUR STORY BUILDING laid on it's side. Contemplate trying to maneuver that across the ground.</p>\n\n<p>But a train, since it is flexible, can be much narrower since it is able to flex and can weave through geographic obstacles. The treads would have to be on each compartment of course. </p>\n\n<p>For amphibious operation tanks and the like typically have rudimentary waterproofing, bilge pumps for seepage, and a dual locomotion system using water jets, not the treads. You could use the treads like giant paddle wheels if you could raise them halfway out of the water, or equip each compartment with jets. The linkage of multiple vehicles is advantageous because you can \"lose\" compartments to flooding without stopping the entire vehicle, and the linked vehicles can push/pull the others, so crossing small bodies of water would be pretty easy. For the deep ocean however, you would need substantial water proofing and high speed jets. It is possible, depending on your power source, to employ hydroplanes to raise the train compartments out of the water so they can run the treads of extend propellers/jets into the water. But this requires significant speed to work.</p>\n\n<p>Another possibility is the deployment of a hovercraft skirt, so the entire train is just a hover train. This would work well if you could deploy treads when necessary to climb steep inclines, or perhaps alternate a treaded compartment with a hover one to allow for dual surface mobility.</p>\n\n<p>Your armament mix is a bit suspect, as there isn't really a need for all the smaller rifled guns (the 16-14 inch ones) if you have beasts like the 31\"er. How many targets can this thing expect to engage simultaneously, how many rifled guns can it shoot? Even the mighty Yamato BB just carried 18\" guns and much smaller ones (mostly for anti-aircraft defense). The reason for this is that the bigger the bore, the longer the range. So the 31\" (!!!!) and 18\" guns presumably would have dealt with anything well before the 14 or 16\" guns would have a chance to engage. Plus even with advanced electronics, simultaneously shelling dozens of moving targets would be very difficult (unless you had guided projectiles, I suppose). And all those different guns require different projectiles, powder bags, replacement parts, etc.</p>\n" }, { "answer_id": 60911, "author": "Matt Bowyer", "author_id": 26780, "author_profile": "https://worldbuilding.stackexchange.com/users/26780", "pm_score": 1, "selected": false, "text": "<p>There are two very good reasons why tanks have never (successfully) grown to more than 70-odd tonnes.</p>\n\n<ol>\n<li><p>Mobility. For a tank to be useful, it needs to get around. One of the biggest limiting factors on modern AFV weight is the capacity of bridges - it's very difficult to get around if your vehicle is too heavy to cross any sort of bridge. Less important perhaps in a siege engine, but worth considering for such an enormous project - remember that battleships in that era were <em>huge</em> capital expenditures, and something that had only one role would probably not get approved.</p></li>\n<li><p>Usefulness. What can one giant tank with 10 guns do that ten tanks each with one gun do? Battleships only existed in the first place because they needed to be that big to carry the guns - on land, it would be far less necessary (and the requirement to carry fuel, food and crew to go thousands of miles wouldn't be there either). It's much the same reason as why battleships don't exist any more - you can fit weapons as big as you need on a 5 or 10,000 tonne ship, and one 50,000 tonne ship is far less useful than 5 10,000 tonne ships.</p></li>\n</ol>\n\n<p>So even before you get to the scientific reasons why it couldn't work (and the other answers show this very well) there are good reasons why it wouldn't be very helpful even if it was possible.</p>\n" }, { "answer_id": 60967, "author": "John", "author_id": 29409, "author_profile": "https://worldbuilding.stackexchange.com/users/29409", "pm_score": 0, "selected": false, "text": "<p>It's never going to make it out of the water, shorelines are either cliffs or soft ground, and this thing will sink in even hard packed soil. So the first time they try to land it, it will sink in the ground and become immobile. </p>\n\n<p>The big question is why bother, you just need the artillery plus a support and defense units traveling as as individual units to get the same effect as your \"super\" while being far more mobile and they can replace units that get damaged.\nyou need something like a better desinged Oka <a href=\"https://en.wikipedia.org/wiki/2B1_Oka\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/2B1_Oka</a> \nfor your largest guns. having all your guns as individual units gives much more flexability plus you can roll in replacements while the others are still firing. You use landing craft or amphibious units to get them to shore with a battleship supplying supporting fire. If you already have naval superiority why not use it. </p>\n\n<p>You can deploy however many units you think it will take, plus support and defense units and keep replacing them for far less than your land titan will cost. Plus a mass of units will be a lot harder to destroy, one lucky hit stops your titan dead. </p>\n" }, { "answer_id": 60987, "author": "gougoul", "author_id": 29575, "author_profile": "https://worldbuilding.stackexchange.com/users/29575", "pm_score": 2, "selected": false, "text": "<p>You should look into the <a href=\"https://en.wikipedia.org/wiki/Bagger_288\" rel=\"nofollow noreferrer\">Bagger 288</a>.</p>\n\n<p>Weight and size-wise, it is closest to what you are looking for, and somehow has all-terrain capabilities! This provides us with a captivating insight into the Bagger's weight distribution methods.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/60867", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/26206/" ]

[ { "answer_id": 60927, "author": "John Feltz", "author_id": 15785, "author_profile": "https://worldbuilding.stackexchange.com/users/15785", "pm_score": -1, "selected": false, "text": "<p>No. Most of the bloodiest wars in human history are civil wars, where the people understand each other all too well.</p>\n" }, { "answer_id": 60928, "author": "AndreiROM", "author_id": 15059, "author_profile": "https://worldbuilding.stackexchange.com/users/15059", "pm_score": 2, "selected": false, "text": "<p>Unless you have a crazy good reason for wanting to speak <em>only</em> said language, such as, for example, speaking anything else on that particular planet will summon Cthulhu itself, no, there's no justification.</p>\n\n<p>Here's the long and short of it: <strong><em>people will rebel.</em></strong> </p>\n\n<p>Oh, you might get your way for a while, but only under a demonstrated, and actively enforced threat of punishment. </p>\n\n<p>Consider that in order to know when people are disobeying you will have to monitor them <em>constantly</em>. Regardless of the morality of this action, implementing that level of surveillance is going to be challenging. I also doubt too many people will enjoy having some AI-like entity listening to every word they say, even in their most private moments, or in their sleep. </p>\n" }, { "answer_id": 60929, "author": "o.m.", "author_id": 6402, "author_profile": "https://worldbuilding.stackexchange.com/users/6402", "pm_score": 2, "selected": false, "text": "<p>Different answers to different parts of the question.</p>\n\n<p>Banning off-world communication in any other language would require censorship of all off-world communications. People are getting used to that in the current era, but such censorship/surveillance used to be a significant intrusion into civil rights.</p>\n\n<p>Banning the development of the language unless the change is global bans any change, because a local trend doesn't get a chance to become global.</p>\n\n<p>A planet (or country) could require a language proficiency test before it allows immigration through the normal immigration process. This would have some side effects, especially if there are no exceptions.</p>\n\n<ul>\n<li>A man from Planet A and a woman from planet B marry. The man doesn't speak the language of planet B, but then the mother of the woman becomes ill and the family wants to care for her. Will there be an exception?</li>\n<li>A family wants to immigrate, but one child has serious disabilities and won't pass any language test. Will there be an exception?</li>\n</ul>\n\n<p>Even if there is such a test, people might not adopt the language at home (especially if they don't need a high level of profiency). So the children might grow up with their ancestral language.</p>\n\n<hr>\n\n<p>A very bad place to live, a very good place for storytelling.</p>\n" }, { "answer_id": 60931, "author": "Philipp", "author_id": 224, "author_profile": "https://worldbuilding.stackexchange.com/users/224", "pm_score": 2, "selected": false, "text": "<p>When someone wants to move to your planet, find out what languages they speak besides DiegoLang. Group all people born off-planet into small, isolated communities and make sure no community has two people who speak the same language except DiegoLang. Off-planet-born are not permitted to have any contact with Off-planet-born from other communities. With nobody to communicate with, they will have no choice but to communicate in DiegoLang. </p>\n\n<p>The communities will sooner or later start to have kids. Organize childcare as a communal effort right from birth. Children should have as many contact-people as possible, so their language learning is not dominated by only one parent who might try to talk to their child mostly in a forbidden language. That makes sure that children only learn to speak DiegoLang. A possible method to organize this might be to expect mothers to return to their full-time job shortly after giving birth, but have all community members take turns as the designated nanny-of-the-day who takes care of all the children of the community.</p>\n\n<p>Only children born on the planet are allowed to leave their community and get into contact with people from other communities. Encourage them to do so a lot to prevent the communities from bastardizing DiegoLang into community-specific dialects.</p>\n\n<p><strong>Caveat:</strong> This society-model is not 100% tamper-proof. An adversary group might send several people to your planet which independently from each other teach the children in their respective communities a forbidden language with the goal to have these children form a secret underground society on your planet. The only countermeasure against that is to enact a total surveillance state.</p>\n" }, { "answer_id": 60936, "author": "Schwern", "author_id": 760, "author_profile": "https://worldbuilding.stackexchange.com/users/760", "pm_score": 6, "selected": true, "text": "<blockquote>\n <p><em>Would forcing the new citizens and prosecuting anyone that tried to spoke a different language be justified for the better end?</em></p>\n</blockquote>\n\n<h1>No. The End Sucks. So Do The Middle and Beginning.</h1>\n\n<p>It creates a privileged culture, suppresses others, leads to language stagnation, thought crime, and a police state.</p>\n\n<p>This has been tried a number of times throughout history, <a href=\"https://en.wikipedia.org/wiki/Atat%C3%BCrk%27s_Reforms\" rel=\"noreferrer\">most notably Turkey</a> or the US forcing Native Americans and Australia forcing Aborigines to learn English. Usually it results in continuous cultural suppression. It establishes a dominant culture and suppresses the others.</p>\n\n<p>An analogy is enforcing a dress code. The choices you make in what that code is and how its enforced says which culture and economic class gets preference, sets them at a higher standard of what is \"proper\", and selective enforcement can be used for harassment. For example, a \"no hoodies\" rule is clearly a way to target certain racial and economic classes, and deciding what is and is not a \"hoodie\" can be used to harass.</p>\n\n<p>Here's the choices you need to make and how they lead to that end.</p>\n\n<h2>Which Language and Why?</h2>\n\n<p>I'm gonna use the US as an example to make this less abstract.</p>\n\n<p>Which language do you choose? That might seem obvious, whatever language the most people already speak (English)... or do you go with one that's easy to learn (Spanish)? Maybe the pick the one with the most in common with other languages (... maybe Spanish again)? Or do you use the language that the most of your neighbors and trading partners speak (Mandarin)? Or do you make up a whole new language so everyone is equally hosed (Esperanto)?</p>\n\n<p>Whatever you pick, it's going to be a continuing hassle.</p>\n\n<h2>Language As Privilege</h2>\n\n<p>If you chose an existing language, existing speakers are now privileged.</p>\n\n<p>If you create a new language, well-off people are now privileged because they have the free time and money to learn the new language, hire tutors, training programs, etc...</p>\n\n<p>Let's say it's English. Existing English speakers don't have to do anything. They don't have to spend time, and money, for schooling. They can keep their existing jobs, in fact native speakers will be in high demand as everyone else tries to catch up. The industry of teaching English will expand creating more jobs for English speakers.</p>\n\n<blockquote>\n <p><em>As long as you are trying to speak it you are welcome.</em></p>\n</blockquote>\n\n<p>This creates a linguistic, cultural, and economic privilege to immigration. You're welcome... so long as you either already speak the language, or have the money and free time to learn it.</p>\n\n<p>Newcomers who are \"trying\" to speak the language remain at a disadvantage. Their native language is not just not spoken, it is <em>illegal</em>. How do they get a job? How do they read a contract? How do they read a manual?</p>\n\n<p>This doesn't end.</p>\n\n<h2>Language As Culture</h2>\n\n<p>The language you speak isn't just some interchangeable part. It is your culture and it even alters how you think. It's your written and oral histories, parables, stories, songs, expressions, and vocabulary. All these things are made illegal. It wipes out other cultures.</p>\n\n<h2>Learning Material As Cultural Indoctrination</h2>\n\n<p>Until recently, the most translated book was the Bible. Missionaries were happy to teach you how to read... but it was going to be a Bible.</p>\n\n<p>Now we're not quite as blunt about our indoctrination, but when you're running an entire society through a forced language re-education program the choice of reading material, pictures, phrasing, vocabulary, and grammar will be indoctrinate a certain world view whether you mean it or not.</p>\n\n<p>Even something as innocent as your choice of noun to use when teaching basic grammar can codify what is normal and what is not.</p>\n\n<pre><code>I like to eat apples.\nPeople eat apples.\nApples are good for you.\nThey bought three apples.\n</code></pre>\n\n<p><a href=\"https://i.stack.imgur.com/onSGF.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/onSGF.jpg\" alt=\"enter image description here\"></a></p>\n\n<h2>Translation As Suppression</h2>\n\n<p>Anyone who says \"just translate them\" has never done translation. Meaning is lost between languages, especially for songs. Translation is always a trade off between the literal meaning and the metaphorical meaning. How do you translate \"stop, you're killing me\"?</p>\n\n<p>You can't translate everything, there simply aren't enough translators and money to pay them. The selection of what gets translated and how it gets translated becomes cultural suppression.</p>\n\n<p>And if there aren't a lot of translators for your language... oh well. It disappears.</p>\n\n<h2>Translation As Rewriting Cultural History</h2>\n\n<p>Translators have a lot of power to subtly shape our understanding of history when the original documents are in another language. Not just in the choice of what gets translated, but the choices they make in doing that translation.</p>\n\n<p>Perhaps the most famous example is the <a href=\"https://en.wikipedia.org/wiki/Thomas_Bowdler\" rel=\"noreferrer\">bowdlerization</a> of classic texts such as Shakespeare, Ancient Greek and Roman writers, and the Bible. Every language has ambiguity through idioms and context.</p>\n\n<p>Embarrassing historical documents can be subtly reworded to make them seem innocuous. <a href=\"http://www.toptenz.net/top-10-reasons-ancient-rome-was-a-perverts-paradise.php\" rel=\"noreferrer\">Homosexuality, sex, dirty jokes... anything considered \"vulgar\"</a> were obscured in popular translations of Greek and Roman texts to prop up the idea that this was a prim and proper golden age of humanity and that our morals have slipped. Have a look into the writings of <a href=\"https://en.wikipedia.org/wiki/Martial\" rel=\"noreferrer\">Martial</a> and <a href=\"https://en.wikipedia.org/wiki/Catullus\" rel=\"noreferrer\">Catullus</a> or watch an uncensored version of <a href=\"https://en.wikipedia.org/wiki/Lysistrata\" rel=\"noreferrer\">Lysistrata</a>.</p>\n\n<p>For more on this read <a href=\"http://rads.stackoverflow.com/amzn/click/0345418824\" rel=\"noreferrer\">The Harlot by the Side of the Road: Forbidden Tales of the Bible</a> which puts racy Bible stories in plain English and reveals what they're really talking about.</p>\n\n<h1>The End Is Bad.</h1>\n\n<p>The end doesn't justify the means because enforcing cultural laws leads you to bad outcomes.</p>\n\n<h2>Option 1: Surveillance State</h2>\n\n<p>How do you enforce the language law? How do you check that people aren't speaking and writing their own languages? To enforce this requires a surveillance state.</p>\n\n<p>You need to spy on what people are saying, and what people are writing. This means no strong encryption. This means neighbors turning in neighbors. This means crackdowns on cultural displays like something as innocuous as showing a subtitled movie or displaying an old, untranslated play.</p>\n\n<h2>Option 2: Selective Enforcement As Cultural Domination</h2>\n\n<p>In this option, you count on normal law enforcement to enforce the language law. For otherwise innocuous, culturally driven laws like this there is a great urge to use selective enforcement as police harassment of groups they don't like. Want to harass someone? Accuse them of \"speaking foreign\".</p>\n\n<h2>Establishing One Language/Culture As \"Better\"</h2>\n\n<p>As with dress codes, choosing a single language signals that one language is \"better\" than the others. Again, doesn't matter what your intent is, people will use this as an excuse or grow up with this lesson.</p>\n\n<h2>Suppressing Knowledge Of Other Cultures</h2>\n\n<p>Since nobody is allowed to practice other languages, how can they ever really understand other cultures? People who only speak one language get a very selective and limited view of the world.</p>\n\n<p>If you travel to a foreign country, you can only speak and read things which are in your language. Everything else is out of bounds, or you need a phrase book, or hire a translator (more economic privilege). This will keep most people to \"tourist\" areas and they will get a very selected and limited view.</p>\n\n<p>This will twist your people's understanding of the world. Their limited view through their own lens will encourage xenophobia.</p>\n\n<h2>Language Police, Language Stagnation</h2>\n\n<blockquote>\n <p><em>The language can evolve as long as any changes to it would be applied globally.</em></p>\n</blockquote>\n\n<p>Language evolves and changes. But in your world these changes have to first be approved before they can be legally used. Since they can't be used legally, the population can't first play around with them to see what works. Some council of Language Police decides what new words the people need (or, oh god, the people vote on what new words are ok?).</p>\n\n<p>It's the ultimate in <a href=\"https://en.wikipedia.org/wiki/Linguistic_prescription\" rel=\"noreferrer\">Linguistic prescription</a>. At best this promotes cultural stagnation as the language is not allowed to naturally change and adapt. For example, as much as some people don't like it, verbing nouns is really useful. </p>\n\n<p>At worst, constant tinkering with the language creates continual, punctuated, and awkward changes that everyone needs to relearn.</p>\n\n<p>As an example, the speeches of <a href=\"https://en.wikipedia.org/wiki/Mustafa_Kemal_Atat%C3%BCrk\" rel=\"noreferrer\">Atatürk</a> in the 1920s, leader of the Turkish language reforms, cannot be understood by most modern Turks.</p>\n\n<h2>Cultural Suppression</h2>\n\n<p>What words, spellings, and phrases the Language Police decide are legal will be informed by what cultural, economic, and political things they are associated with. As a simple example, I was told growing up that \"ain't\" ain't a word, even though the meaning is clear, because it's considered lower class.</p>\n\n<p>Another example is \"sodomy\". Want to suppress certain sexual acts through language? Roll them all into one word, now it's really easy to over-generalize, and difficult to discuss in detail. Then attach to them a word that says \"remember that time God smote a whole city for being perverts?\"</p>\n\n<p>Similar examples come from dress codes. Not just things like hoodie bans, but here's a list of banned items from a bar using \"safety\" as cultural suppression.</p>\n\n<p><a href=\"https://i.stack.imgur.com/atE2b.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/atE2b.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>Most of can be justified with safety, but others are simply targeting certain cultures they don't want around. Pacifiers, glowsticks, stuffed animals, and candy bracelets are stereotypical of raver culture. Others like \"no chapstick\" might be some sort of attempt to stop secret drug use?</p>\n\n<p>Language restrictions can be used similarly.</p>\n\n<h2>Thought Crime</h2>\n\n<p>What if there simply isn't a word to express what you want to say? Or an idea that you came up with? How many words for emotions and thoughts and actions have we come up with in the past ten years of ubiquitous Internet use and loan words alone? Mansplaining; lol; owned; email; to email; code monkey; texting; sexting; burner account; DOXing.... off the top of my head. Sure, there are similar words and phrases, but they don't say it quite the same way.</p>\n\n<p>An example of vocabulary shaping thinking is the German loanword schadenfreude. We have sadism and masochism, a relationship of pain and pleasure between two parties... but schadenfreude is the relationship of a third and otherwise unrelated party. Sure, you can express this idea without introducing a new word, but a word neatly packages an idea for transmission to others. </p>\n\n<p>Must we use increasingly awkward and literal phrases? Hey, are you going to the musical show which is a darker offshoot to the backlash to the cultural and economic stagnation represented by rock and roll tonight? A goth-punk show. Do we always have to point out that L.A.S.E.R. is an acronym for Light Amplification by Stimulated Emission of Radiation?</p>\n\n<p>What about poetry and music? Will an artist be prosecuted for using a word in a non-approved way?</p>\n\n<hr>\n\n<p>I could go on, but this is turning into a dissertation on cultural identity and suppression. I think you get the idea.</p>\n" }, { "answer_id": 60955, "author": "AMADANON Inc.", "author_id": 7924, "author_profile": "https://worldbuilding.stackexchange.com/users/7924", "pm_score": 1, "selected": false, "text": "<p>I can see only one way - make sure all of the people arriving are native speakers of that language. Ideally, all of the same culture - either all white speaking English, all Chinese speaking Mandarin, etc.</p>\n\n<p>Once established, it should be self-supporting - the people of your planet would be sufficiently bigoted and racist (having never met other cultures) not to accept speakers of other languages. They will have problems getting jobs, etc., and with a bit of luck, anyone who is able to speak another language will be so afraid of getting fired, losing their house, etc., they will not do anything to draw attention to themselves (like speaking another language). They would not teach their children another language, in case they accidentally let the cat out of the bag.</p>\n\n<p>If you don't do this intentionally, but succeed in your stated goal, I think it will probably tend to happen unintentionally.</p>\n\n<p>Sounds like a pretty awful place to live to me.</p>\n" }, { "answer_id": 60956, "author": "Anonymous", "author_id": 29570, "author_profile": "https://worldbuilding.stackexchange.com/users/29570", "pm_score": 2, "selected": false, "text": "<p>The answer depends on the condition of the planet in question.</p>\n\n<p>Is it already populated? If so, you would be suppressing the culture of an alien race, which would be horrific, not to mention probably a galactic crime of some sort. </p>\n\n<p>If the planet isn't populated (e.g. recently terraformed or newly discovered after a mass extinction), then the issue becomes what language you choose.</p>\n\n<p>If you choose a pre-existing language known by a significant portion of Earth's population (English, Spanish, Mandarin, etc.), then you run into some of the problems discussed in other answers. You would give an inherent advantage to one group of people, which would probably lead to dissent and eventually rebellion (unless one country in particular is colonizing the planet for itself, which opens up a whole different can of worms).</p>\n\n<p>However, if you were to choose a language that everyone would have to learn before moving to the planet (like Esperanto), then things might actually work out like you want. You would run into problems with language stagnation and inevitably people would come up with other things to complain about, but you would have a moderately decent shot at creating a new and different culture based on aspects from all of your colonists' cultures.</p>\n\n<p>In the situation where you're now the ruler of said planet, there's really no practical way that you could go about ensuring that only one language was spoken all of the time without significantly altering the basic structure of society, but you could make your chosen language the official language of the planet and monitor written and transmitted communications for the use of other languages, which would result in the punishment of your choosing for those found in violation of that decree.</p>\n\n<p>A final note on language stagnation: you need to define what constitutes \"speaking another language.\" If you go with what seems most practical and define it as stringing together a certain number of known words from a single foreign language, you could actually prevent language stagnation in part by allowing for its evolution (in that people could invent words without getting flagged/punished, but there's not enough flexibility to speak whole sentences in a different language).</p>\n\n<p>It doesn't necessarily get you exactly what you want, but it seems to be the most practical and advantageous way to go about it.</p>\n" }, { "answer_id": 60971, "author": "legokangpalla", "author_id": 27902, "author_profile": "https://worldbuilding.stackexchange.com/users/27902", "pm_score": 1, "selected": false, "text": "<p>Not exactly what you asked for but I think a better alternative would be offering services that enables new comers to learn the common language.</p>\n\n<p>Simply forcing people to speak only 1 common language causes too much negative side effects as stated in the above answers. However, what you want to achieve is \"common interface for communication\" and this can be done in other less painful ways.</p>\n\n<ul>\n<li>Making translators available. It's convenient, time-saving, and proven to work fairly well. Also, this gives easy way outs for temporary visitors who do not want to invest time learning an enitrely new language.</li>\n<li>Design a simple easy-to-learn language, make it accessible by offering free lessons etc, and add incentives for learning this language, such as most prints are only available in this language etc. This would essentially accomplish what you want, that is most people being able to speak one common language.</li>\n</ul>\n" }, { "answer_id": 60972, "author": "gilipollas", "author_id": 29571, "author_profile": "https://worldbuilding.stackexchange.com/users/29571", "pm_score": 0, "selected": false, "text": "<p>Try some of Chomsky's writings on the origins of language. In a nutshell, he argues that the purpose of language is not to facilitate communication but actually to impede it. Or at least, to stop those who we view as outsiders from easily communicating with us.</p>\n\n<p>And let us not get started on what constitutes the same or a different language exactly.</p>\n" }, { "answer_id": 60988, "author": "Frezzley", "author_id": 29535, "author_profile": "https://worldbuilding.stackexchange.com/users/29535", "pm_score": 0, "selected": false, "text": "<p>You need to make the people wan't to speak lour language and have it the easyest language to speakt for them.</p>\n\n<p>I make an example:</p>\n\n<p>Switzerland (7.7 Million People) has 4 Official Languages one of them is German.\nThe Dialects in Swiss German, vary from County to County or even from Town to town, that you can tell where one is from.\nThe Dialects from City to City vary so much you can compare it from American English to British English (but keep in Mind, that they are only a few minutes apart, not on different Continents.</p>\n\n<p>Due to a School rule to only speak \"High German\" (spoken in Germany) in School, most TV Programms are from Germany (High German as well) and written Language is also High German, it feels more natural, to speak High German to them, than their \"original Dialect\".</p>\n\n<p>The Fact that there are many Immigrants that only speak High German, doesn't help either.</p>\n\n<p>So more and more of these wrong-Language-\"words\" are getting in everyday language. And so, the many dialects are getting Lost and becomeing closer and closer to High German.</p>\n\n<p>Another thig is the Internet, because many sites, like 9Gag or IFunny are english, kids learn to speak english.</p>\n\n<p>Many Animes (Jpanese Cartoons) are Japanese or originally Japanese, so many off my classmates learnd japanese to understand them.</p>\n\n<p>Conclusion:</p>\n\n<p>If you control School, the Internett and TV programms, the new generation will get used to it, and oly speak your Language, because it becomes natural to them.</p>\n\n<p>A rule about Languages is,that people (who speak multiple Languages) will allways/usually speak that Language, that is the easyest common Language that they have.</p>\n" }, { "answer_id": 61003, "author": "fdreger", "author_id": 29586, "author_profile": "https://worldbuilding.stackexchange.com/users/29586", "pm_score": 2, "selected": false, "text": "<p>One of primary functions of language is identification: \"we\" speak like that, \"they\" speak differently. Even if you manage to force people to use the same grammar and vocabulary, you cannot make them mean same things.</p>\n\n<p>Look at the different <a href=\"https://en.wikipedia.org/wiki/Rhyming_slang\" rel=\"nofollow noreferrer\">rhyming slangs</a> - there's a lot of them in the English speaking world. A person says: \"look at the apples\", but those in-the-know understand that it means \"look at the stairs\" (because stairs is a rhyme for \"apples and pears\"). Everyone who knows the slang immediately feels connected, everyone who doesn't is excluded. Even though the sentence is \"valid\" English.</p>\n\n<p>So, when someone says: \"I want a new telephone\", how do you know if you should punish him or not? Because this could be common English, but could as well mean \"I want a new dog\" (because \"telephone\" rhymes with \"dog and bone\").</p>\n\n<p>The moment you start enforing that people use the same language for communication, you will get a lot more of things like that - a tone of voice, a hand movement will completely change meaning of sentences. I know first-hand, I grew up in a communist state, and believe me, you could criticize USSR all you wanted without using a single word that censors could object.</p>\n" }, { "answer_id": 61023, "author": "eMBee", "author_id": 21118, "author_profile": "https://worldbuilding.stackexchange.com/users/21118", "pm_score": 3, "selected": false, "text": "<p>is there any need to suppress any languages?</p>\n\n<p>your goal is for everyone to understand each other. to achieve that goal, it is sufficient that everyone speaks a common language next to any other less common languages. human laziness will do the rest. unless you get people whose goal it is to preserve their language, most will give up their parents language in the second or third generation.</p>\n\n<p>some things that help:</p>\n\n<p>declare an official language that everyone needs to know and use in public communication. </p>\n\n<p>make it clear to newcomers that everyone must speak this language and that all education will be done in that language. anyone who wants to preserve their own language will stay away.</p>\n\n<p>newcomers who don't speak the language are welcome, but will spend their first months learning the language. if you pick esperanto, that will only take them one month in a full-time full immersion learning environment.</p>\n\n<p>require that all official publications are done in that language (that includes TV, newspaper, advertising, company websites)</p>\n\n<p>you may allow other languages to be used, but anything that is available to the public must be accessible in the official language.</p>\n\n<p>that means multi-language publications are ok, but not foreign-language only. you can even teach foreign languages in school, as long as the official language dominates, it won't hurt.</p>\n\n<p>finally, try to make sure your population is as diverse as possible, so that no other secondary language plays any dominant role. avoid language ghettos. i believe this is easier in densely populated areas because there is simply more people. that way newcomers can find enough people from their own background to not feel isolated, but still be surrounded by others that do not speak their native language, thus forcing them to use the official language to communicate.</p>\n\n<p>for comparison, look at the early history of north america. most languages besides english play a negligible role. english dominated, and so everyone learned it. it is only recently that other languages are on the rise again through immigration. and immigration is something you can influence.</p>\n\n<p>in other places creole and pidgin languages are developed when multiple languages are commonly spoken. if your official language is easy enough to learn, you can avoid that.</p>\n" }, { "answer_id": 61036, "author": "Lostinfrance", "author_id": 9207, "author_profile": "https://worldbuilding.stackexchange.com/users/9207", "pm_score": 2, "selected": false, "text": "<p><em>Would forcing the new citizens and prosecuting anyone that tried to spoke a different language be justified for the better end?</em></p>\n\n<p>This question is only superficially about language. It is really about which rights are <a href=\"https://www.vocabulary.com/dictionary/inalienable\" rel=\"nofollow noreferrer\">inalienable</a> - that is, which rights can a person never give away? </p>\n\n<p>A regime which literally policed its citizens' every word would certainly be a tyranny if <em>imposed</em> on any pre-existing community. Majority support for such a rule could not justify it. The whole point of human rights is that they belong to every human being, regardless of whether they are in a minority or a majority. Nor could the imposition of such a rule be justified because it was believed good would come of it in the end; the idea of human rights includes the idea that they cannot be negated because someone else (the planet-owner) imagines a benefit to other people (their descendants) in the future. </p>\n\n<p>However, unlike every other answerer so far, I <em>can</em> see a possible justification on the grounds that people can consent to suspension of their rights while living or working in a place, so long as <strong>it is made clear to them what the consequences of the contract are</strong>, the <strong>contract is not signed under duress</strong>, they <strong>are adults capable of informed consent</strong>, and, most importantly, <strong>so long as they are free to leave at any time.</strong> </p>\n\n<p>Categories of people who agree to live voluntarily under rules and discipline that would be outrageous if imposed include members of the armed forces, monks and nuns, the crews of ships, planes and space vehicles, workers on oil rigs, people undergoing \"cold turkey\" treatment to get off alcohol or drugs, and people living under a <a href=\"http://qz.com/768341/nasas-year-long-experiment-in-hawaii-to-mimic-life-on-the-mars-has-come-to-an-end/\" rel=\"nofollow noreferrer\">dome</a> as an experiment to simulate the rigours of travel to Mars. Even those who take jobs in companies that insist on certain codes of behaviour from their employees when at work (including a given language being spoken) are acting under a version of this principle that many rights <em>are</em> voluntarily alienable. The right to speak other languages than the official one is alienable, and, in fact, is given up without controversy by many people in the situations listed above.</p>\n\n<p>Doubts might arise as to whether one could consent to be bound to speak only the official language even in private, but it is arguable you could. Sometimes people trying to learn a foreign language by total immersion take a promise not to say a word of any other language for a given period. There is a separate issue in that the only way to check what language people spoke in private would be constant surveillance. Can one consent to that? The surveillance in the <a href=\"https://en.wikipedia.org/wiki/Big_Brother_(UK_TV_series)\" rel=\"nofollow noreferrer\">Big Brother House</a> is not total. </p>\n\n<p>I think this monolingual society would be a repressive and intellectually stagnant place and the alleged \"benefit\" of worldwide monolingualism to be no benefit at all, but, yes, I think it could be justified under a strict condition of continuing consent by the individuals involved.</p>\n\n<p>But only for the people who signed up for it. Not their children.</p>\n" }, { "answer_id": 140189, "author": "Joel Abonmei", "author_id": 61832, "author_profile": "https://worldbuilding.stackexchange.com/users/61832", "pm_score": 0, "selected": false, "text": "<p>I’ts completely justified. You’re not forcing anyone to come to your planet. It’s a consensual agreement between you and those people who want to come. They don’t want such a planet they can choose not to come. Furthermore if your planet is so good that everyone wants to come in, speaking the same language as everyone who was already there is a small price to pay. And like I said they have every freedom to choose not to. It’s actually a great idea that you have in mind. If everyone in the planet speaks the same language then no doubt they will be a more united people.</p>\n" }, { "answer_id": 140194, "author": "Kain0_0", "author_id": 55012, "author_profile": "https://worldbuilding.stackexchange.com/users/55012", "pm_score": 0, "selected": false, "text": "<p>Language is at best a rough approximation of an Ontological structure that has some utility with regard to an activity.</p>\n\n<p>To break that down a little:</p>\n\n<ul>\n<li><p>Each word represents a thing or process at some level of resolution and abstraction.</p>\n\n<ul>\n<li>ie. 'run' is the abstraction of a creature with legs moving so that at times it is completely suspended in the air not touching the ground, it usually quite fast. </li>\n<li>This is why we also apply the concept to programs on a computer that 'run' quite fast without apparently touching anything physical.</li>\n</ul></li>\n<li><p>the words can be organised into phrases/sentences so that they form a more specific description or reinforce a particular set of qualities.</p>\n\n<ul>\n<li>'jhon runs' refines the concept of 'jhon' and 'runs' to describe a more specific circumstance</li>\n<li>'thunderous pin drop' works to infer that the really quiet sound of a small object hitting the ground, was very very noticable.</li>\n</ul></li>\n</ul>\n\n<p>When you lock down a specific set of structures and words you essential say, yep we know everything, it has all been discovered.</p>\n\n<p>That is the definition of a Tyrany. The Tyrany has all knowledge about all forms, and it is clear what is correct and what is incorrect.</p>\n\n<p>In this environment, to act differently isn't just being naive, it is a viscous attack.</p>\n\n<p><em>Why?</em> It means that the Tyrany does not have perfect information. Otherwise the Tyrany would have already handled this problem before it became a problem.</p>\n\n<p>So how do you handle a situation that contains new information, when you already live in a society that has perfect information?</p>\n\n<p>There are two obvious solutions:</p>\n\n<ol>\n<li><p>The people handling the situation realise that the tyrany is incorrect. They too act differently and magnify the scope of the problem from the perspective of the tyrany.</p></li>\n<li><p>The individuals acting aberently are terminated. They were working to corrupt and contaminate the complete and true knowledge already known. Such individuals are by the definition of a Tyrany renouncing their own consciousness. From such a Tyranical perspective it might be considered a kindness to alleviate their suffering.</p></li>\n</ol>\n\n<p>The first solution might lead to some form of a revolution. It might be a quiet intellectual sort, or a busy constructive sort, or a bloody civil war.</p>\n\n<p>The second solution might lead you to Nazi Germany, Soviet Russia, Maoist China, ... Places that have suffered greatly in terms of mass genocides regardless of how those situations occurred.</p>\n\n<p>Either way cultures that make the mistake of believing that they know everything of value are about to find a lot of troubles ahead of them.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/60924", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/28570/" ]

[ { "answer_id": 62951, "author": "CHEESE", "author_id": 17362, "author_profile": "https://worldbuilding.stackexchange.com/users/17362", "pm_score": 2, "selected": false, "text": "<p>The biggest shock would be the period in the center of the figure eight where there would be winter--or something near it--on the entire planet.</p>\n\n<p>I'm calling the planet Bob. </p>\n\n<p>Depending on the tilt of the planet's axis, the seasons would be pretty weird. Let's assume, to make it easy, that the time it would take this planet to revolve one of these suns is 1 earth-year. So one Bob-year would be a bit more than 2 earth-years. For most of the first earth-year, on the left and right loops of the orbit, the seasons would be just like those of earth. But as Bob diverts off a circular orbit, the summer would get colder and colder. By the center of the figure 8, Bob is virtually in a perpetual state of winter all round the surface of the planet. And yes, there would be no night. Assuming that Bob is equidistant from both suns, one sun would be setting as the other one rose on one day of the year. All other days there would be just a bit of complete darkness. But this wouldn't last long. Bob would then get back on track on a circular orbit around the second sun.</p>\n\n<p>Let's divide Bob into 2 hemispheres--the North [facing the people looking at the picture] and the South. Let's say the North hemisphere is tilted to the right as you look at the picture. So, beginning on the leftmost point of the orbit, the North follows this pattern:</p>\n\n<ol>\n<li>Summer!</li>\n<li>Fall!</li>\n<li>Winter! As the days get shorter from Left Sun, Right Sun begins appearing in the sky.</li>\n<li>More winter! As the days get longer, Left Sun begins to disappear, becoming only a bright star (depending on how far away the town suns are).</li>\n<li>Spring!</li>\n<li>Summer!</li>\n<li>Fall!</li>\n<li>Winter!</li>\n<li>Spring!</li>\n<li>Summer for a bit, then a quick fall, then the all-day-two-sun-epic-winter.</li>\n<li>Spring!</li>\n</ol>\n\n<p>And the South would follow the same pattern, just beginning with the North's #8.</p>\n" }, { "answer_id": 62965, "author": "Fox-Chan", "author_id": 19837, "author_profile": "https://worldbuilding.stackexchange.com/users/19837", "pm_score": 0, "selected": false, "text": "<p>Well fist off the planet would be almost completely bright when in the center of the two suns (about 2/8ths of the planet would be bathed in a sunset like state), some plants would be different than the ones we see on earth, because most plants on earth have evolved to incorporate the night cycle into the day of plants, but you'd also have to incorporate the times where there is half sunlight. and there would be a difference with animal life, due to the lack of night time. We would have a lot more non nocturnal animals, and the human diet would probably be affected. To sum it up the ecosystem would change drastically due to the change in light distribution in the world, for better or for worse, that is up for you to decide.</p>\n" }, { "answer_id": 62992, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 5, "selected": true, "text": "<p>I'm going to attack this with math. First off, I am not going to make any assumptions about what orbits might be stable. That is something we can check with an orbit simulator like rebound, as I did in <a href=\"https://worldbuilding.stackexchange.com/questions/23452/can-you-add-a-mini-moon-to-earth/59917#59917\">this question</a>. Instead, I will assume there is a stable orbit around two suns of equal mass and luminosity. The orbital profile will be a perfect circle (0 eccentricity orbit) at 1 AU for 3/4 of a revolution around each sun and then a straight line connecting it to the next sun.</p>\n\n<h1>Determine the orbits</h1>\n\n<p>Since this is an ugly piecewise function, and I am solving using a computer, I am defining it in python as such:</p>\n\n<pre><code>def f(t):\n if t &lt; 3/2*pi:\n return sin(t-pi/4)+sqrt(2), cos(t-pi/4)\n if t &lt; 3/2 * pi + 2:\n r = t - 3/2*pi\n return sqrt(2)/2-r/sqrt(2), -sqrt(2)/2+r/sqrt(2)\n if t &lt; 3*pi + 2:\n r = t - 3/2*pi - 2\n return sin(pi/4-r)-sqrt(2), cos(pi/4-r)\n if t &lt; 3*pi + 4:\n r = t - 3*pi - 2\n return sqrt(2)/-2+r/sqrt(2), -sqrt(2)/2 + r/sqrt(2)\n</code></pre>\n\n<p><a href=\"https://i.stack.imgur.com/02Azl.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/02Azl.png\" alt=\"enter image description here\"></a></p>\n\n<p>The red dots are the two suns. The green dot is our arbitrary time = 0 for the next part; the planet starts moving clockwise around the sun on the right. So far so good, now let us calculate distance from each sun, and plot that as a function of time.</p>\n\n<h1>Determine the distance from each sun</h1>\n\n<p>Since I'm already using the computer, and I know the sun's coordinates, ($-\\sqrt{2}, 0$) and ($\\sqrt{2}, 0$), I will just calculate numerically using this code:</p>\n\n<pre><code>def dist_1(coord):\n x, y = coord\n return sqrt((x - sqrt(2))**2 + y**2)\ndef dist_2(coord):\n x, y = coord\n return sqrt((x + sqrt(2))**2 + y**2)\n</code></pre>\n\n<p><a href=\"https://i.stack.imgur.com/pg6ot.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/pg6ot.png\" alt=\"enter image description here\"></a></p>\n\n<p>Where dist_1 is from the right star and is in blue, and dist_2 is the left star and is in red. I scaled the time factor to 365 days in a year cause I'm a geocentric kind of dude, but I could use any scale factor. If the planet was moving at the velocity of Earth it would take 1342 days to complete this year, fyi.</p>\n\n<h1>Determine enegy recieved</h1>\n\n<p>Solar energy drops off as 1/r$^2$, so solar energy received from each sun is 0.905 earth units divided by the distance to each sun. The .905 is a scaling factor to ensure that total solar energy recieved by this planet averages to 1 unit. So lets plot those two, and a new black line for the net total solar energy.</p>\n\n<p><a href=\"https://i.stack.imgur.com/tzySb.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/tzySb.png\" alt=\"enter image description here\"></a></p>\n\n<h1>Add seasons</h1>\n\n<p>Ah, glorious seasons. Lets say we have an earth-like 23.5 degree axial tilt. How will that affect us? Depends on how we orient the tilt. I will arbitrarily declare that the Northern hemisphere is fully tilted towards the two stars when the planet is at the far right point of its orbital trajectory at point ($\\sqrt{2}+1$, 0). </p>\n\n<p>I calculate the effect of tilt both at the equator and on a point 45 degrees N. At summer solstice (at the point mentioned above) $cos(45-23.5) = 0.930$ of equatorial sunlight, and at winter solstice it will get $cos(45+23.5) = 0.367$ of equatorial sunlight. The angle to either star in our coordinate system is calculated from $\\text{arctan}(\\frac{y}{x})$ where x and y are the coordinate distances from the star. The cosine of the angle to the sun in radians, which is the proportion of the axial tilt that the planet is currently experiencing, can be expressed as:</p>\n\n<pre><code> def angle_1(coord):\n x, y = coord\n if x + sqrt(2) &lt; 0:\n return -1* cos(atan(y/(x+sqrt(2))))\n return cos(atan(y/(x+sqrt(2))))\n</code></pre>\n\n<p>We will multiply that by the axial tilt, add it to the latitude, and calculate the addition or reduction in light energy by season. </p>\n\n<p>So here are two graphs showing how the seasons will work. The first graph is for the equator of our planet, compared with earth. The black line is total energy recieved by this planet (earth would be just a straight line at one, assuming a perfectly circular orbit), red is the relative insolation at this planet's equator, and green is relative insolation at our equator. </p>\n\n<p><a href=\"https://i.stack.imgur.com/nPrgO.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/nPrgO.png\" alt=\"enter image description here\"></a></p>\n\n<p>The second graph is the same, except for a point 45 degrees N. So black is the same as above, red is insolation of the other planet, and green is insolation of earth. </p>\n\n<p><a href=\"https://i.stack.imgur.com/4V9lW.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/4V9lW.png\" alt=\"enter image description here\"></a></p>\n\n<p>And remember, I scaled this planet so its day is as long as an Earth day. If, for example, you set the year to be the 1342 earth days for velocity matching, then the first red-hump summer for the other planet would last as long as a summer here on earth.</p>\n\n<p>Well hope this is what you were looking for; I have all the code saved if you want me to post any more of it, or throw up a graph for a different latitude.</p>\n\n<hr>\n\n<p>Edit:</p>\n\n<p>As requested here is a 45 degrees N profile for a 750 day year compared to what Earth would be doing in that approximately 2 year period.</p>\n\n<p><a href=\"https://i.stack.imgur.com/wxQT8.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/wxQT8.png\" alt=\"enter image description here\"></a></p>\n\n<p>As far as the max insolation; the max value for Earth's summer is 0.917, which represents 91.7% of max insolation at the equator. For our mystery planet, the number is 0.830; this is off by a factor of 0.905, which you may recall is the scaling factor by which we had to reduce these other suns to get Earth-like total year-round solar insolation. So that makes sense. On the winter side, however, the numbers are 0.366 for Earth and 0.354 for the other planet. Those should show the same 0.905 ratio. I don't know if this is an error in the code or just somethign I'm not understanding, but I'll take a look. </p>\n\n<p>Incidentally, darkest winter at 45 N is not while the planet is between the two stars. This is the coolest time at the equator, the sunlight dips down to about 80% of max; that is like May or July in the mid-latitudes. But at 45 N, you are about equidistant from the two stars, and always getting 'summer' from one of the two. So that mitigates the wintery-ness. Darkest winter is when you are tilted away from both suns on the far left of the orbit plot. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/62948", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/27510/" ]

[ { "answer_id": 63121, "author": "user3161729", "author_id": 29060, "author_profile": "https://worldbuilding.stackexchange.com/users/29060", "pm_score": 2, "selected": false, "text": "<p>I'm no scientist but as I understand it there are certain things that you can look for that are otherwise improbable.</p>\n\n<p>For instance your simulation might perhaps watch out for movements of dots that are unexpected. Imagine a group of people pushing a big rock up a hill. Normally rocks go down hills or stay where they are. You wouldn't expect one of significant mass to move up a hill. That indicates that something is doing it on purpose. Obviously in this case replace the rock and hills with various patterns.</p>\n\n<p>That might not prove that the life is intelligent but I expect you could keep looking for these changes until you have enough or they become complex enough to be considered intelligent.</p>\n" }, { "answer_id": 63123, "author": "Auberon Vacher", "author_id": 19329, "author_profile": "https://worldbuilding.stackexchange.com/users/19329", "pm_score": 2, "selected": false, "text": "<p>This could be done in a two step approach:</p>\n\n<ol>\n<li>Identify possible intelligent system</li>\n<li>Confirm (or infirm) the presence</li>\n</ol>\n\n<p>For step 1, we could consider the application of the causal path entropy <a href=\"http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.168702\" rel=\"nofollow\">here</a></p>\n\n<blockquote>\n <p>When following a causal path, entropy is based not on the internal arrangements accessible to a system at any particular time, but rather on the number of arrangements it could pass through on the way to possible future states.</p>\n</blockquote>\n\n<p>The article points to similarities between this observable behaviour and intelligence. The super computer running the simulation could also be programmed to detect those macros effects.</p>\n\n<p>For step 2 we could think of a variant of Turing's test. Today it is purely a computer intelligence test of wether a computer can pass as human which limits intelligence to the human intelligence. Once a civilisation has been exposed to more intelligence forms (either biological or not) a more refined test would be available to test those candidates identified in step 1.</p>\n" }, { "answer_id": 63142, "author": "Stig Hemmer", "author_id": 10324, "author_profile": "https://worldbuilding.stackexchange.com/users/10324", "pm_score": 4, "selected": false, "text": "<h1>Conway's GoL.</h1>\n\n<p>Conway's Game of Life tend to towards two modes: Extreme chaos and extreme order. (To see this, start a simulation of about a million random pixels and see what happens)</p>\n\n<p>Different areas can show different behaviour.</p>\n\n<p>In extreme chaos mode every pixel changes seemingly without patterns.</p>\n\n<p>In extreme order mode every pixel either is stable or changes in a very short cycle, usually 2 time steps, sometimes 3, very very rarely more than 3.</p>\n\n<h1>Life</h1>\n\n<p>Life would be different. There would be patterns, but they would not be strict. As the life form multiplies, there would be large-scale repetition of approximate patterns.</p>\n\n<p>You would recognize life by this: Large number of \"cells\" that looks more or less the same, and that seems improbable from a local point of view.</p>\n\n<h1>The Environment</h1>\n\n<p>Around these cells would be an environment of the usual chaos and order patches.</p>\n\n<p>This environment will be deadly to the life. Simply random changes will kill off the poor innocent little cells.</p>\n\n<p>In the beginning these life forms would follow a very simple strategy: Multiply faster than the environment kills them off.</p>\n\n<h1>Advanced strategies, \"intelligence\"</h1>\n\n<p>Eventually, however, they would become smarter.</p>\n\n<p>They would change the environment to be more friendly to them.</p>\n\n<p>They would also find ways to recognize each other. They could either compete, to ensure more space for their own children, OR they could cooperate, to tame the environment.</p>\n\n<p>Some would <em>pretend</em> to cooperate with their neighbours, but secretly preparing to kill them off.</p>\n\n<p>Then recognition would become more complex, to see the difference between close relatives that can be trusted and cooperated with, and strangers that has to be fought.</p>\n\n<p>The life forms would invent war.</p>\n\n<p>At what point should we call them intelligent? That is a matter of definition. I leave that definition up to you.</p>\n\n<h1>Looking from the Outside.</h1>\n\n<p>For the outside observers, all this looks like more and more complex patterns, over larger and larger areas and longer and longer time intervals.</p>\n\n<p>I suspect it would be quite clear to the observers why things are happening, this cell attacking that cell, that cell cooperating with that other cell to build a wall and so on.</p>\n\n<p><strong>One indication of intelligence would be that the observers no longer understands what happens.</strong> At first you will have observers going \"Oh, so <em>that</em> is why it did the odd thing 10000 time steps ago!\". Later they will say \"I have no idea how they achieved that!\". </p>\n\n<p>That point is as good as any to say that the life has become intelligent.</p>\n" }, { "answer_id": 63148, "author": "Cem Kalyoncu", "author_id": 11055, "author_profile": "https://worldbuilding.stackexchange.com/users/11055", "pm_score": 4, "selected": false, "text": "<p>A computer scientist here, I will chime in with my educated guess. You will not find them, unless you have billions of people searching for intelligent behavior in this simulation. </p>\n\n<p>Problem is massive, the size of the canvas would be extremely large. I am talking about 10^20 by 10^20 size canvas. The number of atoms in a human body is ~10^28, each atom requires many cells in CGoL. Even if your intelligent beings of automata is much smaller in scale, we are still talking about a pattern that has a size of trillion by trillion. Understanding that this pattern is acting intelligently is a magical task. The interactions at the border of this pattern will be chaotic as well as its internal actions. </p>\n\n<p>I think this problem explores this, if we are living in a simulation, it is most likely that our simulator will never understand that we are intelligent and alive. </p>\n\n<p><em>Factoring in the discussions from the comments:</em> The size estimates that are done here is for an intelligent system that is not alive. Also the canvas size is not to simulate our universe physics, if you are to do that you will need canvas sizes that are larger than $10^{185}$ cells in the best case.</p>\n" }, { "answer_id": 63182, "author": "Mason Wheeler", "author_id": 2326, "author_profile": "https://worldbuilding.stackexchange.com/users/2326", "pm_score": 0, "selected": false, "text": "<p>Has intelligent life evolved in a Game Of Life simulation?</p>\n<h1>No.</h1>\n<p>It's really that simple.</p>\n<p>Among other things, intelligence necessarily requires the ability to analyze information and make meaningful choices about it. This can't happen in a purely deterministic system such as Conway's Game of Life.</p>\n<p>Whether our world truly is nondeterministic, or is simply deterministic at fundamental levels so small that we don't have good models for them yet is a question for philosophers, but intelligent life must be capable of taking actions that appear to an outside observer to be nondeterministic, unpredictable choices. The Game of Life is <em>perfectly</em> deterministic; the entirety of the state of each round after the first is 100% predictable from the state of the previous round. Therefore, it is anathema to the evolution of intelligent life, no matter how large of a simulation is being run.</p>\n" }, { "answer_id": 63201, "author": "Mad Physicist", "author_id": 23218, "author_profile": "https://worldbuilding.stackexchange.com/users/23218", "pm_score": 2, "selected": false, "text": "<p>As many others have pointed out, you need a definition of intelligence to be able to answer this question. One possible definition of intelligence for the purposes of this question is an entity that you can communicate with. Whether it is \"truly\" intelligent in a deep philosophical sense is pretty much irrelevant in this case (see the <a href=\"https://en.wikipedia.org/wiki/Chinese_room\" rel=\"nofollow noreferrer\">Chinese Room Argument</a>).</p>\n\n<p>Again, as others have pointed out, GOL is completely 100% deterministic. However, communication means altering the state of a thing externally. In the case of GOL, you would communicate by introducing changes to the system that are against the deterministic rules.</p>\n\n<p>The way to test if intelligence has developed as a consequence of some initial conditions is to see how the system reacts to these externally introduced changes. Is it possible to cause a set of changes to which the system responds in a consistent manner? Can we eventually create a language by which we can assign interpretations to outputs? Does the potential intelligence assign its own interpretation to these changes (i.e., does the response to a given input take significantly different forms depending on circumstances, including previous inputs)?</p>\n" }, { "answer_id": 63202, "author": "Yakk", "author_id": 2473, "author_profile": "https://worldbuilding.stackexchange.com/users/2473", "pm_score": 5, "selected": false, "text": "<p>With a large enough canvas of random data and enough cycles, intelligent life would evolve, assuming the Chuch-Turing thesis. Even weaker than that, assuming the universe is no more than non-deterministic.</p>\n\n<p>Rough proof:</p>\n\n<p>Conway's game of life is a Turing-complete game. You can create a general purpose computer in it. This computer may require a large initial state and be fragile and slow, but that just increases the size of the initial seed and cycle time before it can exist.</p>\n\n<p>This computer is magical, so it can handle both of those issues.</p>\n\n<p>In fact, you can have an unbounded number of such computers, running an unbounded number of different programs.</p>\n\n<p>Assuming the Church-Turing thesis, at least one such program is intelligent.</p>\n\n<p>Assuming the universe is no more than non-deterministic, a NDTM can be simulated in a TM, and a NDTM can thus describe the universe.</p>\n\n<p>So given enough space and time and uniformly random initial states, somewhere in the infinite field there will be a turing machine that proceeds to simulate the evolution of every possible universe from an initial big bang with physics like ours.</p>\n\n<p>One of these simulated universes would be our universe (without the magical computer, naturally).</p>\n\n<p>Our universe appears to contain intelligent life.</p>\n\n<p>So that is proof of existence. Now, we should examine what it would take to <em>find</em> this intelligent life.</p>\n\n<p>The Conway's game of life doesn't <em>directly</em> contain it. Rather, it contains a pattern of life that can be interpreted as a computer (actually, unbounded numbers of such patterns, most of which are short lived due to flaws), which simulates a non-determinstic computer, which proceeds to exhastively simulate entire families of universes.</p>\n\n<p>No human being or non-magical computer could, if someone pointed out the section of the system that was doing this computation, even interpret it or confirm if that was indeed the section in question. The parts of this machine's state would be literally larger than the entire universe's data capacity. We couldn't even <em>look</em> at the part in question.</p>\n\n<p>It is so slow that the number of cycles required to describe even the merest fraction of a fraction of a fraction of a ... of a fraction of a ... of a fraction of a fraction of a second of the universe might be a number too large to express in this universe.</p>\n\n<p>But that was just an existence proof. In theory, a much smaller system could actually house inteligence.</p>\n\n<p>We can look at our universe. One of the possible explanations for our physics is that we are experiencing an inverted platonic wall of shadows. Our physics actually plays out on a 2+1 dimensional boundary of our universe, with the 3+1 dimensional interior of the space being a hologram \"\n\"projected\" by it. One of the motivations behind this possibility is that there appears to be an information limit in our universe proportional not to volume, but to the surface area of a region!</p>\n\n<p>Physicists have created mathematics for toy universes that match this pattern, where there is a N dimensional physics system with a N-1 dimensional system that holographically determines the behavior of the N dimensional system.</p>\n\n<p>Such a technique might easily be the easiest way for conways game of life to create a complex enough universe for evolution to occur in. So the 2+1 dimensional game of life might generete a holographic universe where the \"interior\" perspective of the intelligent beings does not correspond to the 2+1 dimensional \"underlying system\" that generates the hologram.</p>\n\n<p>Stepping back again, even if that doesn't happen and the resulting intelligences do end up living in flatland, they might exist on ridiculous scales. The equivalent to a \"cell\" of our universe is the Planck length, or a Planck patch.</p>\n\n<p>This is about 10^-35 m, or 10^-20 times the size of a Proton.</p>\n\n<p>A proton is about 10^-15 m in size. The observable universe is about 10^26 m.</p>\n\n<pre><code>-35 -- Planck scale\n-15 -- Proton scale\n-10 -- Atomic scale\n1 -- our scale\n7 -- planetary scale\n14 -- Solar system scale\n20 -- Galactic scale\n26 -- Universe scale\n</code></pre>\n\n<p>If we take jumps of a factor of 10 million per step, we get roughly:</p>\n\n<pre><code>-5 -- Planck scale\n-4 -- ???\n-3 -- ???\n-2 -- Proton scale\n-1 -- Atomic scale\n0 -- our scale\n1 -- planetary scale\n2 -- Solar system scale\n3 -- Galactic scale\n4 -- Universe scale\n</code></pre>\n\n<p>The \"cell size\" of our universe is ridiculously far away from our scale. Atoms are roughly half way from that to the entire universe.</p>\n\n<p>If we assume this is typical, then even in the regions where there is intelligence, figuring out a reasonable model of <strong>physics</strong> that they are experiencing so far away from the rules of Conway's life would be beyond our current skills.</p>\n\n<p>They would no more exprience the rules of Conway's cells that we notice the rules of string harmonics when we throw a baseball.</p>\n" }, { "answer_id": 63204, "author": "socrates", "author_id": 15796, "author_profile": "https://worldbuilding.stackexchange.com/users/15796", "pm_score": 2, "selected": false, "text": "<p>The book <em>Permutation City</em> by Greg Egan explores this concept exactly; the emergence of an intelligent species from within a 3-dimensional cellular automata, evolved over a large time-span. If you are interested in this question, Egan explores it in-depth over the course of the novel. The prose is suprisngly good for an amateur writer, but the concepts explored and thought experiments involved are fascinating. </p>\n\n<p>As mentioned, and similarly to the perspective taken in the book, human observers look for signs of intelligence by observing the symbolic interactions between entities; once they deciphered their \"language\", the analysis of the complexity and semantics of the language was used to determine whether the species could be considered \"intelligent\"; i.e. discussing highly abstract concepts, such as mathematics. </p>\n" }, { "answer_id": 63205, "author": "Durandal", "author_id": 30362, "author_profile": "https://worldbuilding.stackexchange.com/users/30362", "pm_score": 2, "selected": false, "text": "<p>I was originally having the gut feeling that the rules are too simple to allow for complex patterns to emerge and stay dynamically stable for prolonged periods. But that gut feeling is apparently wrong: <a href=\"https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life#Undecidability\" rel=\"nofollow noreferrer\">Undecidability</a>.</p>\n\n<p>Building on the statement that a universal turing machine can exists as a GoL pattern, the basic precondition question could something <em>resembling</em> life evolve can be answered: Yes.</p>\n\n<p>The next precondition question would be, will something that resembles <em>intelligent</em> life evolve? I have no basis for the answer, but I will pretend that since humanity <em>did</em> evolve from whatever basic life evolved first, it could, and for the sake of the question, it will.</p>\n\n<p>So assuming intelligent life exists in that simulation, will they detect and recognize it?</p>\n\n<p>Presuming they have infinite processing capability with their <em>magic computers</em>, any kind of pattern recognition they could <em>think of</em> is feasible to run. On that basis I would presume they will develop the tools necessary to analyze the games state to find cell clusters that show the most basic behaviors of life: self replication, local entrophy reduction and mutation.</p>\n\n<p>Once <em>life</em> can be identified by these analytical tools, it can be observed specifically and its in the observers judgement if something is considered <em>intelligent</em> behavior.</p>\n\n<p>The question then can be transformed into something else: Can they really develop the neccessary analytical tools? Their magical computer allows them to answer any question about past, present and future of the GoL, as long as they are able to formulate an analytical way of answering the question. It does however <em>not</em> free them of any limitiations they themselves are subject to: Number of scientists working on the problem, limit of their own lifetime and limit of their civilizations time of existence.</p>\n\n<p>So it boils down to what abilities in general the experimenting civilization has. Given enough time to analyze, they will find intelligent life in their simulation, if they destroy the simulation or themselves before they found it, then well...</p>\n\n<p>Its remarkably similar to the question if <em>we</em> will find intelligent life in our universe, really. If it exists and we don't destroy ourselves, we have a good chance of finding it, one day. Thats a big <em>if</em> though.</p>\n" }, { "answer_id": 63207, "author": "WGroleau", "author_id": 18193, "author_profile": "https://worldbuilding.stackexchange.com/users/18193", "pm_score": 2, "selected": false, "text": "<p>Suppose you have a <strong>HUGE</strong> simulated canvas. Suppose you display an image of it small enough to actually look at. Suppose you observe that the chaos turns into several groups of pixels that each move around, approach others, change direction. Would you consider that \"possibly intelligent\"? </p>\n\n<p>But note that the original rules of the simulation guarantee that solid patterns of significant size cannot form easily and cannot exist for very long. The centers all have too many neighbors to survive.</p>\n" }, { "answer_id": 63209, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 2, "selected": false, "text": "<p>Mason Wheeler has the right idea with his answer suggesting that we have to interact with the Game of Life to determine if intelligent life has formed. I wanted to expound upon why.</p>\n\n<p>First off, Mołot has the correct question: what is \"life\" and what is \"intelligence?\" These are <em>not</em> easy questions. These are highly philosophical questions which have been batted around for millennia. If anything, they seem to be becoming harder questions as science pushes the limits of the world. I don't think we're going to answer them here, so instead I would like to pose an ever so slightly altered question which I think we can more likely answer here:</p>\n\n<blockquote>\n <p>How can we tell if something has evolved in a Game of Life simulation\n that we should treat <em>as though</em> it was intelligent life?</p>\n</blockquote>\n\n<p>This question is more answerable because it includes human limits. If a human cannot distinguish a GoL simulation from life, is it not reasonable to start treating it as though it is alive?</p>\n\n<p>To get there, we need to be unable to distinguish a part of the simulation from a human. Pesky challenge, really. It's at the heart of the Turing test. At first pass, it's trivial. If it's in the GoL simulation, it's not a human, because it's a pile of bits! Problem solved! Let's all go out and have a cup of tea.</p>\n\n<p>Of course, this really isn't fair. How do you know it's just a pile of bits? The answer is that you peered inside the game of life with your sneaky debugger tools and raped its virtual brain. By the time you were done, you could prove beyond a shadow of a doubt that that section of the GoL space was nothing but a pile of bits. How invasive!</p>\n\n<p>Perhaps more importantly, we know that we can classify a pile of bits as \"not alive\" because we can easily create a clone of it, or a hundred clones of it. We know that its' hard to create a clone of Charles, or a clone of your favorite dog. It seems to be a dividing line: things that can be perfectly cloned cannot be called \"alive.\" Dolly's DNA was cloned, so it isn't alive. However, Dolly's \"children\" are not the same as Dolly. Each developed differently. Each child is a different \"living\" individual.</p>\n\n<p>What if we weakened the rules a bit, and allowed interaction. This means that humans can interact with the GoL space, setting some cells to living and some to dead, against the rules Conway put forth. This introduces a level of unknown into the mix, and creates our first opportunity for confusing the machine with a human. Let's let many humans interact on this same grid in this way, setting bits to 1 or 0. One of them might decide to use this as a communication channel, transmitting data like an old TELNET console. If you came across this bit, you'd notice that it can pass the Turing test, because there's an actual human behind it! While this may be cheating, it confirms that we can communicate with intelligent life using GoL space to do it.</p>\n\n<p>To make things more exciting, let's step up the noise. Let's allow humans to make millions of modifications at each cycle. Make a really big grid, and lots of modifications. Many of these modifications may consist of a human feeding this game of life a random number source (such as de-tuned radio waves). Make enough of these modifications in every cylce that it's really not reasonable for any human to track all of these modifications.</p>\n\n<p>Now we have an interesting situation. If we see something \"intelligent\" we can't prove that it was GoL rules evolving an intelligence, but we can't prove it was a human interacting either. We have to accept the unknown nebulous reality that there's merely something out there acting intelligent.</p>\n\n<p>We also now know that that intelligence may have power. The intelligence may be someone on the other end, who is offended by what we do, finds us, and does something violent to us. Or maybe they just find our government and raise our taxes. Either way, an \"apparent intelligence\" found on the GoL field now has the ability to affect our lives.</p>\n\n<p>Now we can answer the question of \"When is it reasonable to treat something on the GoL grid as though it is alive.\" We can set some basic criteria:</p>\n\n<ul>\n<li>We cannot reduce it to a deterministic algorithm (defined by a pile of bits). For all we know it may be a deterministic algorithm centered around a <em>single</em> random number generator, but we can't reduce it to just a pile of bits and a rule for how to evolve it.</li>\n<li>We can communicate with it -- defined as it appears to respond to our interactions in predictable ways, but not so predictable that they could just be a deterministic algorithm.</li>\n<li>It can communicate with us -- the entity needs to be able to make changes in the world that we can see and interpret.</li>\n<li>It needs to be capable of helping us further our own goals, and it gives us the impression that it can do so better if we classify it as \"an intelligent living being.\"</li>\n</ul>\n\n<p>The last criteria is my favorite. It's not a criteria for something believe \"alive\" or being \"intelligent,\" but it is a criteria for being treated as one. If it appears that classifying it as \"intelligent\" furthers our own goals, why would we not give it such a classification?</p>\n" }, { "answer_id": 63212, "author": "cbh", "author_id": 29134, "author_profile": "https://worldbuilding.stackexchange.com/users/29134", "pm_score": 3, "selected": false, "text": "<p>Many of the answers here seem to be concerned with whether something like life could develop in a GOL simulation. I will instead begin by assuming that intelligence <em>could</em> develop, and try to answer the question \"how could we detect it?\" by comparing to our own universe. I'll assume we would know it if we saw it, too -- that after a bit of observation, we could tell when cells are working together and making decisions. My conclusion: it would still be <strong>insanely difficult</strong> for outside observers to detect -- it's the biggest game of \"Where's Waldo?\" I can imagine!</p>\n\n<p>To get a sense of scale, if we're trying to compare to our own universe, then we've got to zoom <strong>way</strong> out. The closest thing we have to a quantized length in our universe is the Planck length. So, imagine each GOL cell in this simulation as a single Planck cube. Now, think about the scale when we zoom out to an entire universe.</p>\n\n<p>I'm not aware of random Game of Life simulations having been conducted and examined on boards larger than a few thousand by a few thousand -- hardly enough to represent a quark, and hundreds of orders of magnitude smaller than what we're talking about here! But a common pattern to most simulations is that pretty quickly, most of space becomes empty, with scattered cells forming what we can think of like \"background radiation.\" In some areas, there is more complex activity taking place, but these areas are few and far between. Our own universe is structured much the same way, so I can image that a search for intelligence in the simulation would be like a search through our universe.</p>\n\n<p>Suppose you had the ability to observe the 100-billion light year sphere of the universe that we can see. Let's even assume you have a computer with enormous memory and processing power to help you. You can look anywhere, zoom in or out, and automate some search algorithms. Would you be able to find the humans?</p>\n\n<p>Given enough resources, I imagine you could make a program that filters out the huge portions of space that are mostly empty. What's left would be the galaxies, which you could recursively search for solar systems and planets.</p>\n\n<p>The first issue is knowing how far you need to zoom. You don't know how big lifeforms will be -- will they contain thousands of GOL cells? Trillions? More? If you're looking at our entire solar system at once, you won't know humans are here -- you have to know to zoom in on the surface of Earth to see our cities. If you're zoomed in to a molecule, you'd have no idea that it's part of a human cell. You have to know to zoom out to see collections of cells working together.</p>\n\n<p>The second issue is that even if you know what scale to look at, there's simply too much to search through. It's estimated that there could be more than a trillion planets in our galaxy alone, and at least 100 billion galaxies in the observable universe. Each of these planets is itself enormous, and would require a close examination to rule out intelligent life (imagine looking at the Earth 50,000 years ago -- if you're going too fast and don't look hard enough, you might not know humans are there!). However you do this, you're not going to be fast enough to process these planets in anything even close to a reasonable amount of time.</p>\n\n<p>The only thing I can think of that could help this search would be understanding the laws of physics in the simulated universe. Of course, we know the microscopic rules; they're just the GOL rules. But I mean understanding the rules on a larger scale. How do the cells tend to group together? Let's call these groups particles -- how do the \"particles\" interact? On what time and distance scales do they affect each other? From there, we can build up the rules of \"chemistry\" in the simulation. At the opposite end, we could also start looking at a large scale and discover the equivalent of astrophysics. This would take a huge investment of time and research -- humanity's understanding of physics and chemistry was built up over thousands of years, and was aided by our ability to interact with our world. </p>\n\n<p>If we had this knowledge, it could potentially help filter out planets faster, just as astronomers do in our own world, based on chemical makeup and environment. But it's still not clear that it would help an outside observer much, since even understanding chemistry and physics in the abstract doesn't help you understand what is and isn't needed for life -- you need some examples of life for that.</p>\n\n<p>So I'm left with the conclusion that <strong>even if intelligent life develops in your simulation, unless for some reason it's vastly more common than in our universe, you won't be able to detect it</strong>.</p>\n" }, { "answer_id": 63285, "author": "CoffeDeveloper", "author_id": 4995, "author_profile": "https://worldbuilding.stackexchange.com/users/4995", "pm_score": 2, "selected": false, "text": "<p>It could evolve life, so I assume it could even evolve intelligent life, but I don't know if we can know when something is intelligent, so probably we would evolve a sentient life form but we will not be able to recognize it. </p>\n\n<p><strong>Here's the game I played now:</strong></p>\n\n<p><a href=\"https://i.stack.imgur.com/tmvYO.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/tmvYO.png\" alt=\"enter image description here\"></a></p>\n\n<p>In red you can see actually \"living\" areas, so there's some storm inside those areas and they are actually evolving. This area act just like few living cells because it continue to move and randomly eat or spawn some \"still chunk\" (areound living areas you see lot of still chunks, that are equiparable to cell foods).</p>\n\n<p>Basically this game I'm doing I'm interacting the minimum amount of time to give the life some spread: you will learn quickly that clicking in certain areas will cause the food to just disappear, while clicking in certain areas will make life active for a while.</p>\n\n<p>After some time you will find that you find a way to increase number of food, and you see that everytime food amount increase the life will last even longer before eventually coming to a rest: at some point life will continue to spread on its own, meaning there will be a immense space where there are living and still areas, overall food is growing, and living areas are growing too. This is life to me, and after some time maybe this life can become sentient and more autonomous.</p>\n\n<p>By the way interacting randomly (and the minimum necessary I now reached this state):</p>\n\n<p><a href=\"https://i.stack.imgur.com/WN3E6.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/WN3E6.png\" alt=\"enter image description here\"></a></p>\n\n<p>Which is still continuing to \"live\" after 10 minutes. It is pretty similiar to real evolution, maybe bits of life evolve and extinguish, but it leaves \"traces\" that can be eventually be used again if new life evolve again, and slowly a \"ecosystem\" builds up.</p>\n" }, { "answer_id": 63329, "author": "Gary Botnovcan", "author_id": 30456, "author_profile": "https://worldbuilding.stackexchange.com/users/30456", "pm_score": 3, "selected": false, "text": "<p>The search for automated intelligence could resemble the search for extraterrestrial intelligence -- it's all about signals. The search for automated life is similarly simple -- it's all about entropy.</p>\n\n<p>The magic computer program could look for regions within the simulation where entropy decreases locally. Those regions may hold life-like constructs. Once those regions are identified, the program could monitor whatever passes between them (gliders, spaceships and so on) and identify those patterns which are complex enough to carry information.</p>\n\n<p>This approach is a heuristic, not an algorithm. It certainly won't identify human-level intelligence. Instead, it might find ant-like intelligence, if such a thing evolves within the simulation. </p>\n\n<p>The researchers running this simulation have a problem that is the opposite of real-life sciences. In our universe, we struggle to discover what is fundamental to physics. We know how things seem at a human scale, but things like quantum mechanics and string theory are far from intuitive. For the simulation, the researchers know the laws of Conway's Game, but they have no idea what a mind inside the Game might perceive. The fundamentals are obvious, but the emergent structures are unknown. </p>\n\n<p>How can you tell the difference between an ant and a person when the things you can directly observe are equivalents to strings and quantum configurations? </p>\n" }, { "answer_id": 63377, "author": "Count Iblis", "author_id": 2255, "author_profile": "https://worldbuilding.stackexchange.com/users/2255", "pm_score": 0, "selected": false, "text": "<p>Intelligent beings would be present right at the start of the simulation, albeit in a non-local form. This follows from the strong AI assumption which says that all computations that renders an intelligence are equivalent; you would have the same consciousness if your brain were replaced by a machine that would simulate your brain perfectly. Suppose then that one could observe by some means that an intelligence has appeared in a CA at time step T. This means that the evolution of the CA from T to T + 1 is such that a local patch of the CA behaves in a way that we would consider to have intelligent presence.</p>\n\n<p>This may involve having to consider perturbing that local patch to see if counterfactual initial states at time T is mapped to a corresponding counterfactual state at T + 1 in the right way. What matters is that a local patch has appeared that acts as some program that takes input from its surroundings, processes that in some way leading to some output. The way the output is related to the input defines the program.</p>\n\n<p>The intelligence in exactly the state at time T then also exists at earlier or later times T', because the CA rules define a mapping from T' to T and back. So, you can use the CA rules themselves to \"see\" that the intelligence at time T was already present at the time of the Big Bang. This is also true for us: see <a href=\"https://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time)\" rel=\"nofollow noreferrer\">this article</a> on eternalism and <a href=\"https://en.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_argument\" rel=\"nofollow noreferrer\">this article</a> on the Rietdijk–Putnam argument.</p>\n\n<p>One can go a step further and argue that running the CA actually doesn't matter. The intelligence would exist anyway; the CA only allows you to see it. The intelligence should be considered as existing in its own universe defined by its own algorithm. </p>\n" }, { "answer_id": 63516, "author": "Dotan", "author_id": 30512, "author_profile": "https://worldbuilding.stackexchange.com/users/30512", "pm_score": 0, "selected": false, "text": "<h1>Pattern detection</h1>\n\n<p>Life, in it's basic form, is based around the natural selection of things. What exists today is what survived, either specifically or by replication from yesterday. This thing that survives could be thought of as information: Be it DNA, RNA and so on. When there is no life there is no order, no patterns in the matter that emerge from the chaos repetitively.</p>\n\n<p>But life doesn't imply intelligence. What does?</p>\n\n<h2>Mental patterns</h2>\n\n<p>This is more complex than pattern detection, because it's about finding pattern (or memes) in different hardware (brains). If you see an object with some internal language, and in this language you see those patterns, that may be duplicated in other similar objects, you probably have intelligence.</p>\n\n<p>I think it's obvious that this is a necessary condition for intelligence: A thought without some kind of \"words\" doesn't seem possible. I argue that it's a sufficient condition. There's an ongoing <a href=\"https://en.wikipedia.org/wiki/Computational_theory_of_mind\" rel=\"nofollow noreferrer\">philosophical debate</a> on it, but assuming you don't think intelligence requires any sort of soul, I think this will do.</p>\n\n<p>Finding the internal language of the object and translating the patterns to the languages of the other objects is an enormous challenge. It's a challenge to even detect the objects. But luckily the computer are magical :)</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/63118", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/16106/" ]

[ { "answer_id": 63223, "author": "Zxyrra", "author_id": 28639, "author_profile": "https://worldbuilding.stackexchange.com/users/28639", "pm_score": 2, "selected": false, "text": "<h2>Brain development still takes time.</h2>\n\n<p>If you effectively use sleep to \"double up\" on school time, handwaving the mechanism that allows this, and do so just during the school year - of course you will save some time. This method probably will allow for somewhat faster graduations.</p>\n\n<p>But time is not the only limiting factor here: there's <strong>brain development</strong> to consider. If you give a six-year old a normal curriculum, but double the pace (assuming they can keep up with \"sleep-learning\" which is a whole different discussion), the 12 upcoming years of high school education will be finished in 6 years - at age 12.</p>\n\n<p>If you try to teach a twelve year-old pre-calc, they will not just fail because of a lack of prior knowledge - to some extent, they will fail because of development. <strong>Even if you increase the learning speed,</strong> the brain will grow at about the same rate - there is no evidence to suggest a twelve year-old who does twice the work will have the brain of an eighteen year-old, which encompasses creativity, reasoning, and a host of other things that we only know possible at certain ages.</p>\n\n<pre><code>┌───────┬──────────────────┐\n│ Age │ Work age level │\n├───────┼──────────────────┤\n│ 5-6 │ 5-7 │\n│ 6-7 │ 7-8 │\n│ 7-8 │ 9-10 │\n│ 8-9 │ 11-12 │\n│ 9-10 │ 13-14 │\n│ 11-12 │ 15-16 │\n│ 12-13 │ 17-18 │\n└───────┴──────────────────┘\n</code></pre>\n\n<p><strong>Additionally,</strong> you will be graduating people without developed social skills, few long-term memories (a consequence of taking up sleep time), and weaker physical builds - who may not be fit to drive or work.</p>\n" }, { "answer_id": 63231, "author": "o.m.", "author_id": 6402, "author_profile": "https://worldbuilding.stackexchange.com/users/6402", "pm_score": 2, "selected": false, "text": "<p>Consider this reasoning:</p>\n\n<ul>\n<li>Assume the sleep trainers include some sort of AI technology. Surely there isn't a human teacher whispering into the ear of the sleeper.</li>\n<li>Anything that can be <em>taught by AI</em> can be <em>done by AI</em> cheaper and better. Depending on <a href=\"https://worldbuilding.stackexchange.com/questions/16807/can-humans-interact-meaningfully-with-the-economy-when-robots-are-better-at-ever\">how the economy is organized</a>, humans might have a hard place doing that in the workplace.</li>\n<li>If your setting has jobs for humans which are not <a href=\"https://en.wikipedia.org/wiki/Busy_work\" rel=\"nofollow noreferrer\">busy work</a>, they must be doing something an AI cannot do (possibly requiring creative thinking). It is generally assumed that a PhD takes several years of <strong>original research</strong> and not just parroting what a computer told you. </li>\n</ul>\n\n<p>AI-trained skills may be the <em>basics</em> for non-AI-trained skills. Teach <a href=\"https://en.wikipedia.org/wiki/Numeracy\" rel=\"nofollow noreferrer\">basic numeracy</a> before going to really interesting maths, and so on. So that might save a couple of years during <a href=\"https://en.wikipedia.org/wiki/K%E2%80%9312\" rel=\"nofollow noreferrer\">K-12</a> education, but <em>only</em> a couple of years, not several decades. It won't save much at university, and nothing at the graduate level.</p>\n" }, { "answer_id": 63236, "author": "Jnani Jenny Hale", "author_id": 29630, "author_profile": "https://worldbuilding.stackexchange.com/users/29630", "pm_score": 2, "selected": false, "text": "<p>An ordinary someone or a special someone? There are 11-year-olds auditing university mathematics courses as we speak, and the <a href=\"http://www.gradschoolhub.com/10-youngest-people-ever-to-achieve-a-doctorate-degree/\" rel=\"nofollow noreferrer\">youngest PhD recipient</a> I have heard of was 15, I believe (Except Karl Witte in 1813, but we have no way to gauge whether what he did was equivalent to a modern PhD.)</p>\n\n<p>So that is multiple normal humans, with normal human limitations, achieving at least one PhD by age 18. I would say that you could save enough years to get in a second PhD by age 18 if you could learn in your sleep, but an even better time-saver would be an AI research assistant to do your literature review for you! And write up the method and results sections, for that matter ...</p>\n\n<p>As people have pointed out, a PhD is less about absorbing information and more about actually doing some original research/development. That takes as long as it takes. </p>\n\n<p>(Yes, yes, I know that in the US and some Asian countries, they have a Frankenstein's monster called a \"PhD by coursework\", but that is regarded by everyone else with the same degree of horror as a \"surgeon\" who has read all the books but never actually done an operation.)*</p>\n\n<p>*I am a former University lecturer at one of the top universities worldwide (The University of Sydney), and this assertion is based on that experience.</p>\n" }, { "answer_id": 63275, "author": "Sherwood Botsford", "author_id": 15784, "author_profile": "https://worldbuilding.stackexchange.com/users/15784", "pm_score": 2, "selected": false, "text": "<p>The points about development are valid. </p>\n\n<p>But our present education system is seriously upwhacked.</p>\n\n<p>At young ages kids are sponges for language. There is no reason why a kid can't be fluent in a hatful[*] of languages by age 8 or so.</p>\n\n<p>At elementary age, kids are sponges for data. They don't think well, but they are good at storing trivia. Some of us never grow out of that. (Or maybe we just don't grow up.)</p>\n\n<p>At high school age, kids are questioning values, and start to use logic.</p>\n\n<p>I suspect that getting an education wouldn't take any less time. But it could be far wider reaching. See Dorthy Sayer's <a href=\"http://gutenberg.ca/ebooks/sayers-lost/sayers-lost-00-h.html\" rel=\"nofollow noreferrer\">\"The Lost Tools of Learning\"</a> for some other insights. </p>\n\n<p>[*] hatful: A bunch of severals</p>\n" }, { "answer_id": 63276, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 2, "selected": false, "text": "<h1>Personal anecdote</h1>\n\n<p>I am a computational statistician. I would generally be judged to be very good a math and computer science. I got a 1600 on my SAT. I graduated with a 3.8 from one of US News' top 10 engineering schools. That was when I was 27. But when I was 20, I failed out of college with a 1.8.</p>\n\n<p>You see, the first time I went to college, I had no idea why I was there. Everyone else went to college, so I guess I should too. I had a vague notion I wanted to build rockets, but had no idea what that entailed. Consequentially, instead of studying or getting interested in research, I joined a fraternity and got interested in Tekken and weed. I was pretty good at Tekken, but that didn't do much for my GPA.</p>\n\n<p>After I failed out, I got a job as a ranch hand and spent half a year mucking stalls and digging fence post holes. Then I enlisted to go invade Iraq. It was a long way back to college, and and even longer road to a Masters degree. I will probably never get a PhD since I wasted so much time shoveling horse crap and bombing Iraq. </p>\n\n<p>Conclusion: Education technology does not matter as much as motivation. If you don't have a good reason to do well in school, you might find yourself smoking weed and failing out, no matter how smart you are. The problem with (most) 15 year olds, especially boys, doing advanced studies has always been and will always be maturity. Therefore, it is going to be hard to push all but the most exceptional students to PhDs so early in life. </p>\n" }, { "answer_id": 63278, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 2, "selected": false, "text": "<blockquote>\n <p>\"It is a miracle that curiosity survives formal education.\" - Albert Einstein</p>\n</blockquote>\n\n<p>We really don't know much about the brain. We're just barely starting to plumb its secrets. However, we do have plenty of evidence to show difficult it is to push brilliant children through our current education system. It's really hard to put everyone in the same box and then shuffle that box through the grades. A system which could work individually with each student could do things we consider miraculous.</p>\n\n<p>However, not everything is just knowledge to be learned. There's a major factor called \"maturity\" which plays a key part. You can cram all the knowledge of biology into a 12 year old's mind, and they won't be ready to serve as a PhD in biology unless they are very special.</p>\n\n<p>Also worth noting is that rest is an <em>essential</em> part of learning. They've found that kindergarten classes which remove recess to add more teaching soon fall behind their fellow schools, while kindergarten classes which add more recess somehow accomplish more (teachers say the children are far more focused, so they get through the material quicker).</p>\n" }, { "answer_id": 63311, "author": "a4android", "author_id": 22159, "author_profile": "https://worldbuilding.stackexchange.com/users/22159", "pm_score": 1, "selected": false, "text": "<p>Sleep elimination technologies keep popping up in science-fiction, aren't people and especially writers aware of the problems of sleep deprivation? Besides Nancy Kress has worked this concept over in her <em>Beggars in Spain</em> sequence of novels.</p>\n\n<p>There are studies that show intellectuals and knowledge workers spend more time sleeping than ordinary mortals. Sleep appears to be higher beneficial for people who a lot of brain work. Sleep, in general, seems to be universal among animal species. We may not fully understand why we sleep but it seems to be there for a good reason. It seems foolish to assume a fancy piece of technological kit is going to get rid of it.</p>\n\n<p>It might be far better to assume a technology that rather than eliminating sleep, enhances its beneficial properties. Perhaps this won't reduce the amount of sleep people need, but it might do a better job of integrating memories and knowledge in our brains. Thus improving general knowledge acquisition.</p>\n\n<p>It's time to send sleep elimination technology the way of the videophone and other gizmos everybody imagined everyone else would want, but turned out they didn't. Better sleep, better brains. You know it makes sense.</p>\n" }, { "answer_id": 101547, "author": "Hendrik Marx", "author_id": 32654, "author_profile": "https://worldbuilding.stackexchange.com/users/32654", "pm_score": 0, "selected": false, "text": "<p>I think when we would not need sleep we would use most of that time for other things than education. I guess some people would use that time to study but probably that would not be the norm. </p>\n\n<p>I am almost certain that if we could literally learn in our sleep we would completely stop learning while being awake. It just does not seem time efficient anymore. </p>\n\n<p>Also there would be a lot more people with higher education and time to work. Which would mean less people work or more people work less time (which is already a trend now due to automation). I think the whole economy would be changed along with the education system. </p>\n\n<p>Also life long learning is a trend (at least in Europe) and I can imagine that being amplified. </p>\n" }, { "answer_id": 101630, "author": "Donald Hobson", "author_id": 17931, "author_profile": "https://worldbuilding.stackexchange.com/users/17931", "pm_score": 0, "selected": false, "text": "<p>Depends on the tech.</p>\n\n<p><strong>VR + weak AI</strong>\n : An immersive visualization that goes at the speed you need.</p>\n\n<p><strong>brain implants</strong> : Learning even faster, things you haven't learned yet still a thought away. </p>\n\n<p><strong>strong AI</strong> : Humans are looked after and many do very little learning. People focus on play.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/63222", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/21870/" ]

[ { "answer_id": 63239, "author": "Joe", "author_id": 26565, "author_profile": "https://worldbuilding.stackexchange.com/users/26565", "pm_score": 6, "selected": true, "text": "<p>You have to make some assumptions, so I'll answer more generally and you can plug in other numbers if you think my assumptions are off. </p>\n\n<p>The number of elves required is given by </p>\n\n<p>$$\nC T \\over D H R\n$$</p>\n\n<pre><code>Where\nC = Number of children in the world\nT = Number of toys for each child\nD = Annual days of work for elves\nH = Hours in an elf workday\nR = Toymaking rate in toys per hour\n</code></pre>\n\n<p>If you assume 2 billion children, 1 toy each, 364 workdays (Christmas day through the following December 23rd - then packing the sleigh on Christmas Eve), 16 hour days (Elven sweatshop!), and each elf can make 4 toys per hour, you need around 85,851 elves. That's quite a workshop.</p>\n\n<p>This is only the set of elves required to make the toys. They'll need support staff too. Making food for 85k+ elves, cleaning and maintenance, procuring all of the materials for toy-making, quality control, and other functions could easily add another 50+% to the base number.</p>\n" }, { "answer_id": 63240, "author": "Nolo", "author_id": 19530, "author_profile": "https://worldbuilding.stackexchange.com/users/19530", "pm_score": 3, "selected": false, "text": "<p>Well, it depends on the toy. If it is a video game here are a few stats that come up on Google.</p>\n\n<p>Respawn Entertainment, the fall out company that formed after Infinity Ward, creators of the Call of Duty franchise, dismissed CEO Vince Zampella, retained 38 of 46 employees which resigned after Zampella was terminated. Respawn is the owner of the EA Games-published, Titanfall franchise. But this probably does not provide an accurate depiction of the number of persons or man hours needed to produce such a game.</p>\n\n<p>A more specific stat comes from Leslie Benzies, president of Rockstar North Studio, a branch of Rockstar Games Studios responsible for the Grand Theft Auto series. He gave a number of 1000 people across multiple Rockstar Games Studios involved in the production of GTA 5 in an interview to <a href=\"http://www.develop-online.net/studio-profile/inside-rockstar-north-part-2-the-studio/0184061\" rel=\"noreferrer\">http://www.develop-online.net</a>.</p>\n\n<hr>\n\n<p>As for other kinds of toys:</p>\n\n<p>Hasbro, makers of American culture ( as well as many, many games we all know from our childhoods ) does not seem like the kind of place that subjects its \"elves\" to such harsh conditions. Deemed one of the best companies to work for in 2012, <a href=\"http://archive.fortune.com/magazines/fortune/best-companies/2012/snapshots/82.html\" rel=\"noreferrer\">this site</a> reports a total of about 5700 employees, over 3100 of them in the United States. <a href=\"http://www.toyassociation.org/tia/industry_facts/salesdata/industryfacts/sales_data/sales_data.aspx?hkey=6381a73a-ce46-4caf-8bc1-72b99567df1e\" rel=\"noreferrer\">http://www.toyassociation.org/</a> reports total sales of \\$19.48 billion in the United States in 2015. <a href=\"http://www.shareholder.com/visitors/dynamicdoc/document.cfm?documentid=3180&amp;companyid=HAS&amp;page=1&amp;pin=&amp;language=EN&amp;resizethree=yes&amp;scale=100&amp;zid=0f1680a8\" rel=\"noreferrer\">Hasbro figures</a> reached \\$4.45 billion in 2015, making it top 22% of the U.S. market.</p>\n\n<p>From there we can extrapolate some roughly 25,000 elves for the U.S.</p>\n\n<p>Now given that the U.S. is only about 4.4% of the global population, we can further extend the estimate to over half a million elves - which seems reasonable, but we must consider also that only about 32% of the world is Christian and I have no idea how many people outside of the U.S. believe in Santa Claus, so I must assume that the low figure of approximately 180,000 elves and a high figure of 568,000 elves gives an appropriate range, the former being how many are needed if only Christian children in the world receive toys at Christmas and the later if all children in the world are given presents made by elves.</p>\n\n<p>Note that the OP's figure 2+ billion children is as large as the number of people in the world who are Christian. Certainly fewer than all of those people are children, so the OP's figure must also include non-christian children. Given that, the larger end of my estimate seems reasonable.</p>\n\n<p>Further more, the above figures are strictly for toys. As suggested above, including video games would be an entirely different model as a single game can involve the cooperation of up to 1000 individuals and hundreds of games are released each year on various platforms and online.</p>\n" }, { "answer_id": 63272, "author": "Alexander von Wernherr", "author_id": 29870, "author_profile": "https://worldbuilding.stackexchange.com/users/29870", "pm_score": 3, "selected": false, "text": "<p>I'll go the other way and say, hardly none. We definitely need more Santa Clauses.</p>\n\n<p>Raw materials are delivered by some human logistics company to a fake address in northern Norway or Canada.\nNo elves here.</p>\n\n<p>It's still 2016 and some years ago Industry 4.0 / IoT was introduced.\nSo, no manual work to be done here, except for maintenance and setup.</p>\n\n<p>If we produce one present every ten seconds, a single machine would produce 3144000 items per year. (Source: Output of a factory line in my company)</p>\n\n<p>In order to fulfill our plan to produce 2 Billion toys, we need roughly 800 of these machines.</p>\n\n<p>Elven Equipment Engineers may be able to handle 10 machines per two engineers. 1600 Elves here.</p>\n\n<p>Add 10 per cent management makes 1760 elves.</p>\n\n<p>Quality control.\nWe have optical sensors, high tech manufacturing, and a really neat end of line test, so we don't really need that much personal here too, mainly maintenance. Since the team is working together since the dawn of time, and are always up to date using latest CAD and Design technologies, a team of 100 elves might be sufficient.</p>\n\n<p>1860.</p>\n\n<p>Shipping dept. will be huge. But also not in headcount. It's also completely run by SAP in a combination with drones / autonomous driving carriers. Since it's a big warehouse, nothing ever must go wrong and the team here will be rather large, 200 - 250 elves.\n(Comparable to Amazon warehouses)</p>\n\n<p>2110.</p>\n\n<p>Some boilerplate, (and I like round numbers) we need 2500 elves to run a modern Santa Clause factory, thanks to really neat technology.</p>\n\n<p>Compared to the some 1 Million Santa Clauses needed for distribution...</p>\n" }, { "answer_id": 63301, "author": "Brythan", "author_id": 2113, "author_profile": "https://worldbuilding.stackexchange.com/users/2113", "pm_score": 2, "selected": false, "text": "<p>The United States employs 284,000 people to make toys for the US (plus more for export). The US market is roughly a quarter of the worldwide toy market. So roughly one million people. Figure that only half the toys are for Christmas and only half of those are from Santa. So 250,000 people. </p>\n\n<p>Now just adjust for the relative productivity of elves versus humans. Do elves work around the clock? That's twenty shifts per week compared to five for a human. So let's call it 62,500 elves. </p>\n\n<p>I'll leave it up to you if you want to give them more of an advantage than a 160-hour work week. Extra speed? Or maybe you want them to be able to do less than humans? Adjust as necessary. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/63235", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/11049/" ]

[ { "answer_id": 63700, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 3, "selected": false, "text": "<h1>Don't do what we did</h1>\n\n<p>I don't know what your technology or magic level is going to be, but the classic example would be that the ancestors wish the decedents to avoid the mistakes they made that lead to turning their farmland into a desert, releasing the Dark One, or destroying their homeworld.</p>\n\n<p>There are many mechanisms for this to happen, from the familiar (climate change) to the sci-fi (shouldn't have sent those SETI signals towards the Zerg Overmind) to the fantasy (don't break the seals). </p>\n\n<p>Robert Jordan's Wheel of Time and the in-brain conversations of Rand al'Thor and the Dragon are the best example I can think of in fiction. That brings us to another point. If history or time is cyclical in your world, then it may matter a lot to the ancestors what choices their decedents make. </p>\n" }, { "answer_id": 63701, "author": "Thom Blair III", "author_id": 22997, "author_profile": "https://worldbuilding.stackexchange.com/users/22997", "pm_score": 3, "selected": false, "text": "<h2>Time May Be Subjective Only</h2>\n\n<p><a href=\"https://www.wired.com/2016/09/arrow-of-time/\" rel=\"nofollow noreferrer\">According to physics</a>, the linear flow of past to present to future is created by human awareness:</p>\n\n<blockquote>\n <p>PAST. PRESENT. FUTURE.<br>\n In physics, they are all the same thing. But to you, me, and everyone else, time moves in one direction: from expectation, through experience, and into memory. This linearity is called the arrow of time, and some physicists believe it only progresses that way because humans, and other beings with similar neurological wiring, exist to observe its passing.</p>\n \n <p>Time moves as it does because humans are biologically, neurologically, philosophically hardwired to experience it that way. It’s like a macro-scale version of Schrödinger’s cat. A faraway corner of the universe might be moving future to past. But the moment humans point a telescope in that direction, time conforms to the past-future flow. “In his papers on relativity, Einstein showed that time was relative to the observer,” says Lanza. “Our paper takes this one step further, arguing that the observer actually creates it.”</p>\n</blockquote>\n\n<p>This line of theorizing is still developing, but perhaps there is some possibility for unobserved current events of descendents lives to coexist in time with unobserved events in ancester's lives. During that coexistence, perhaps events could influence each other and have the effects last even once observation begins.</p>\n\n<p>Perhaps \"unobserved\" events could be when people are asleep, or when people simply are not looking in that direction.</p>\n" }, { "answer_id": 63711, "author": "JDługosz", "author_id": 885, "author_profile": "https://worldbuilding.stackexchange.com/users/885", "pm_score": 2, "selected": false, "text": "<p>You can come up with novel ways to describe time travel besides the obvious “time machine”, but retro-causality as you described <strong>is</strong> explicitly the very meaning of time travel. So no, you can not have retro-causality without time travel.</p>\n\n<p>In the spirit of what you’re getting at, you might look into <a href=\"https://en.wikipedia.org/wiki/Wheeler&#39;s_delayed_choice_experiment\" rel=\"nofollow noreferrer\">delayed choice</a> in quantum mechanics. But what you come up with won’t “matter” to the ancestors in their own experience, only show something that can be determined after the fact.</p>\n" }, { "answer_id": 63714, "author": "Fred", "author_id": 28388, "author_profile": "https://worldbuilding.stackexchange.com/users/28388", "pm_score": 4, "selected": false, "text": "<p>That is simply not possible. Cause always precedes effect. The only way to change that would be to time travel (which OP excluded)</p>\n" }, { "answer_id": 63724, "author": "Tom", "author_id": 16049, "author_profile": "https://worldbuilding.stackexchange.com/users/16049", "pm_score": 3, "selected": false, "text": "<p>You don't want time travel in the conventional sense, but to get what you want, you need to mess with time. More specifically, you need to mess with causality. You would have to come up with an entirely new physics in which causality points <strong>both ways</strong>. The implications of that are staggering and thinking it through is no small feat. All the questions of causality, like free will, re-appear with a vengeance.</p>\n\n<p>You also get the same paradox effects as time travel stories get, just several orders of magnitude worse. In a time travel story, you need to worry about future knowledge affecting past events and what ripples it causes through the timeline that is already established. But with retro causality, <strong>everything in your world</strong> is in time-loops, and not just one, but millions. If you thought the Many Worlds Theory is mind boggling, the Many Timelines Theory that you have to invent for this to work makes it look like 1st degree math.</p>\n\n<p>But I see this as the only solution to your question. Causality in your world has no direction. That means time has no direction. So in your world time actually <strong>is</strong> an illusion (some scientists and philosophers discuss this in respect to our world, but so far the evidence is strong that time actually does have a direction).</p>\n\n<p>If causality has no direction, you have the mother of all feedback loops. The butterfly effect with self-reinforcement.</p>\n\n<p>Frankly speaking, the longer I think about it, the more I'm sure your world, if it came into existence, would instantly explode. :-)</p>\n\n<hr>\n\n<p>Some reading material:</p>\n\n<ul>\n<li><a href=\"https://plato.stanford.edu/entries/causation-metaphysics/\" rel=\"nofollow noreferrer\">https://plato.stanford.edu/entries/causation-metaphysics/</a></li>\n<li><a href=\"https://books.google.de/books?id=nwfvCAAAQBAJ&amp;lpg=PA55&amp;ots=AnDf52Lt4I&amp;dq=causality%20time%20direction&amp;hl=de&amp;pg=PA55#v=onepage&amp;q&amp;f=false\" rel=\"nofollow noreferrer\">https://books.google.de/books?id=nwfvCAAAQBAJ&amp;lpg=PA55&amp;ots=AnDf52Lt4I&amp;dq=causality%20time%20direction&amp;hl=de&amp;pg=PA55#v=onepage&amp;q&amp;f=false</a></li>\n<li><a href=\"http://www.thomasblanchard.net/uploads/2/2/5/1/22518468/dtac8.pdf\" rel=\"nofollow noreferrer\">http://www.thomasblanchard.net/uploads/2/2/5/1/22518468/dtac8.pdf</a></li>\n</ul>\n" }, { "answer_id": 63729, "author": "Simon", "author_id": 30602, "author_profile": "https://worldbuilding.stackexchange.com/users/30602", "pm_score": 1, "selected": false, "text": "<p>Here's an idea:</p>\n\n<p>What if, through magic or technology, there exists an object which can be anywhere in the x,y,z dimensions but which has infinite length in the time dimension. Therefore whatever you do to that object changes its state at all points in the past, present and future. It could be something they could write on and therefore send messages throughout the timeline. Or it could be a box into which an item can be placed and then collected at any other point in time.</p>\n" }, { "answer_id": 63730, "author": "Sigma Ori", "author_id": 2253, "author_profile": "https://worldbuilding.stackexchange.com/users/2253", "pm_score": 6, "selected": true, "text": "<p>Nothing impossible may happen.</p>\n\n<p>In the C and C++ programming languages, there's such a thing called undefined behavior, where basically if the program performs certain illegal actions, it goes in an invalid state. Notice I said if, not when. The program is invalid <em>after</em>, <em>during</em> and even <em>before</em> the action that invoked undefined behavior. In other words, if your program performs a certain illegal action at some point, it's not invalid after that action, it's invalid for its entire execution. A compiler is free to assume that undefined behavior <em>never happens</em> and it can transform the implementation of the entire program, including parts that come before the illegal action, based on that assumption. If undefined behavior is actually invoked, the program may observe paradoxes.</p>\n\n<p>This is a very real effect, happening right now in the world, with current technology. For example, an action on a specific variable (called a \"pointer\") is invalid if the variable contains a specific value (\"null\"). Consider this short snippet:</p>\n\n<pre><code>if (ptr == NULL) {\n some_action();\n} else { \n some_other_action();\n}\n\naction_that_assumes_ptr_is_not_null(ptr);\n</code></pre>\n\n<p>In this example, <code>some_action()</code> may never be included in the program at all, even if <code>ptr</code> can sometimes be equal to <code>NULL</code>. Why? Because afterwards, an action is executed unconditionally and that action will put the entire program in an invalid state if <code>ptr</code> is <code>NULL</code>. In other words, as far as the compiler is concerned, <code>ptr</code> cannot be <code>NULL</code> in a valid program, so only <code>some_other_action()</code> can exist in a valid program. The above program could be transformed by the compiler into this:</p>\n\n<pre><code>some_other_action();\naction_that_assumes_ptr_is_not_null(ptr);\n</code></pre>\n\n<p>As you can see, an action that is supposed to take place <em>later</em> will disable a choice (the <code>if</code> construct) that was supposed to take place <em>sooner</em>. Of course, all of this is possible because there is an entity (the compiler) that analyzes the program statically, i.e. outside that program's execution. In other words, this analysis is performed outside the program's concept of <em>\"before\"</em> and <em>\"after\"</em>.</p>\n\n<p>If your story has metaphysical underpinnings, you could say that just as there are laws of physics that govern what can happen in a given universe, there are meta laws of physics that govern what a universe may or may not do. Much like the laws of a programming language govern what a program may or may not do.</p>\n\n<p>Then, come up with an action (or a sequence of actions) which doesn't violate any specific physical law of our universe but, when performed under certain circumstances, it would put the universe in an inconsistent/invalid state that is illegal as far as the meta laws are concerned. If a universe contains, in its timeline, such actions that would bring it to an illegal state, that entire universe's existence could be rejected and that rejection would happen at a level outside the universe's execution and therefore its concept of time.</p>\n\n<p>Now if the descendants perform an action that is possible but would be illegal (\"apparently impossible\") provided the ancestors had performed another action, then you're set. The ancestors are not allowed to have performed the second action, because if they had, their universe would have been in an inconsistent state and its existence would have been rejected. Such a universe could not have existed to begin with.</p>\n\n<p>So how would that look? Anything that would prevent the ancestors from performing the action would suffice. However, it would probably be much more interesting to include a person or an entity that can recognize the inevitability of their actions in that meta context and be able to articulate why the ancestors are bound by the actions of their descendants. Without such an agent in the story, the entire explanation could be lost on the audience.</p>\n" }, { "answer_id": 63732, "author": "Pedro Gabriel", "author_id": 20681, "author_profile": "https://worldbuilding.stackexchange.com/users/20681", "pm_score": 2, "selected": false, "text": "<p>Another perspective that is not being considered is this: some ancient mythologies (and even contemporary philosophers like Nietzsche) advocated for a circular timeline.</p>\n\n<p>IOW the time would flow in cycles. At the end of each cycle, time would be reset and another similar cycle would begin. The ancestors and the descendants would explore the world again in a similar fashion, unaware that they had already done it.</p>\n\n<p>Which means that the future of a timeline is the past of the subsequent timeline. </p>\n\n<p>If the events are not completely reset at each cycle, the events of the future may indeed influence the past, even though in different timelines. </p>\n\n<p>So the causality would go like this: ancestors from timeline 1 ==> descendants from timeline 1 ==> ancestors of timeline 2</p>\n" }, { "answer_id": 63733, "author": "SF.", "author_id": 7646, "author_profile": "https://worldbuilding.stackexchange.com/users/7646", "pm_score": 4, "selected": false, "text": "<p>One classic alternative to time travel is premonition.</p>\n\n<p>One of the ancestors is a seer, a person who can peer into the future.</p>\n\n<p>Given enough cooperation, the seer can replace the typical 'push' request (aka travel back in time) with a 'pull' request: the seer peers into the future and follows advice of the descendant.</p>\n\n<p>How does the descendant know to give the advice? Because the ancestor left a note with a request to do so.</p>\n\n<p>There is no hard time paradox here (killed my grandfather) - merely the soft kind (sent lottery numbers to past self to fund time machine research). The seer gets guidance from a descendant despite the descendant never actually seeing the seer; but upon receiving the much needed guidance, the seer leaves a note for the descendant, asking to provide the advice, asking to speak, show, lecture - into thin air - at the right time and place - the exact time and place the premonition had taken the seer. This stabilizes the time loop, leaving no unsolved paradoxes.</p>\n" }, { "answer_id": 63735, "author": "The Technicality Terror", "author_id": 30604, "author_profile": "https://worldbuilding.stackexchange.com/users/30604", "pm_score": 2, "selected": false, "text": "<p>Technically, if the two groups were relatives of one another, since the term \"Ancestor\" is defined as anyone you are descended from usually more distant than a grandparent (but not necessarily dead even though it is implied), it is possible for the actions of the descendants to affect the ancestors without the application of time travel. Only if the ancestor is still living. For instance, if your great grandfather had done something to assure his last years on earth were to be peaceful and enjoyable (possibly by composing a treaty that would bring about world peace), and then you were to violate that treaty by building a nuclear weapon. Therefore, causing world peace to come to an end, causing war to break out all over the globe, and leaving your great grandfather to have to fight for his life or hide out and live in fear for his last years on the planet. Or, if he had set it up so that his remains were to become incorporated into the liquid metal used to pour a sculpture of himself that would live on the family estate and you had melted the statue down to make your own bullets or even simply moved the statue to another location off of the family estate. Then, the actions of the descendants could affect the ancestors because your great grandfather would now be unable to live his last years on earth in a way which would be peaceful and enjoyable as referred to in scenario #1 or be a statue living on the family estate as referred to in scenario #2 So, it really depends upon if the \"ancestors\" you are referring to in your original question had already passed away or not. If they were already dead, it would require time travel or a multi-directional timeline in order for the actions of the descendants to affect the ancestors.</p>\n" }, { "answer_id": 63744, "author": "Till", "author_id": 30607, "author_profile": "https://worldbuilding.stackexchange.com/users/30607", "pm_score": 2, "selected": false, "text": "<p>I see 2 possibilities: </p>\n\n<ol>\n<li><p>precognition<br>\nThis has already been mentioned. The ancestors somehow know about the descendants and their actions. This still involves some \"magic\" and possible paradoxes. </p></li>\n<li><p>guessing \nThe ancestors may know (or at least guess), that some people will explore the same location in the future. So they may guess what the descendants will do and act accordingly. Since these are only guesses, there is no time-travel-paradox.</p></li>\n</ol>\n" }, { "answer_id": 63881, "author": "jpa", "author_id": 7937, "author_profile": "https://worldbuilding.stackexchange.com/users/7937", "pm_score": 1, "selected": false, "text": "<p>Applying a bit of lateral thinking: are the actions of the ancestors defined by what truly happened, or by what we know about it?</p>\n\n<p>You could set up the story of the ancestors using a narrative device, for example a diary written by one of the expedition members. You follow their actions day by day as written.</p>\n\n<p>Then cut into the future in the story. The descendants find a piece of evidence that completely changes the interpretation of the diary. Perhaps the purpose of the expedition wasn't mere science, but a failed search for a lost person? The brave research efforts change into desperate search of their lost companion, whose destiny they have since edited out of the diary.</p>\n" }, { "answer_id": 63883, "author": "Emilio M Bumachar", "author_id": 581, "author_profile": "https://worldbuilding.stackexchange.com/users/581", "pm_score": 1, "selected": false, "text": "<p>By becoming notable in their exploration, the descendants make the ancestors notable, i.e., \"But Anna Ancestress had discovered it first in 1967!\"</p>\n\n<p>Thus the ancestor's explorations, until then obscure, receive worldwide attention.</p>\n\n<p>Option 2:\nThe ancestors were already notable, but either hailed as heroes or mocked as charlatans. The descendants discover or clarify something, reversing the public image of the ancestors from one extreme to the other.</p>\n" }, { "answer_id": 63886, "author": "crueltear", "author_id": 30660, "author_profile": "https://worldbuilding.stackexchange.com/users/30660", "pm_score": 0, "selected": false, "text": "<p>If you leave a giant red flashing button, someone is sure to press it. If you don't want it to be used (action that may happen in future), you can't design it to look like that (action happening now, depending on actions by your ancestors). </p>\n\n<p>We don't want future people to open bunkers with barrels full of radioactive waste, so we can say, we are forced to mark them with scary symbols. </p>\n\n<p>If you are looking for a place to lock <em>Ba'al The Souleater</em> and <strong>DON'T</strong> want him to be released, ever, you can't put him at the last level of some long dungeon full of treasures, as your ancestors are sure to explore them.</p>\n" }, { "answer_id": 63904, "author": "Skeith", "author_id": 2976, "author_profile": "https://worldbuilding.stackexchange.com/users/2976", "pm_score": 1, "selected": false, "text": "<p>Imagine if you can an entity that exists outside of time. </p>\n\n<p>50 years ago your father fought a dragon and it took his eye. today you are fighting a dragon in the same place you father fought one 50 years ago. </p>\n\n<p>It is the same dragon though as it exists outside of linear time. </p>\n\n<p>From your perspective the strike you made that you thought missed/was to shallow opens up into a serious wound/ turns out to be a critical hit.\nIn reality it was your father striking it 50 years ago in a similar location. </p>\n\n<p>From your fathers perspective the dragon often leaves itself open/moves randomly. \nin reality it is dodging/parrying your attacks.</p>\n\n<p>From the dragons perspective it is simply a 2 vs 1 fight and in a few of its minutes it will be a 3 vs 1 fight.\nIn reality every 50 years the chosen one climbs the mountain to stop the dragons return. </p>\n\n<p>As the dragon interprets all 3 times as a single liner event your actions are taken into account in your fathers time. </p>\n\n<p>if you prescribe to the closed loop theory then you actions and and that of your sons were already accounted for when the dragon took your fathers eye, if you believe in free will then that parry you made could leave your fathers eye healed after your battle concludes in linear time - a miracle in action. </p>\n\n<p>the perspectives offers a large scope for story telling. you are raised on the tales of a god of destruction that resurfaces every 50 years that must be stopped, the dragon is popping down to the shop for milk when 3 similar looking guys jump him in an alley. </p>\n" }, { "answer_id": 63928, "author": "Yakk", "author_id": 2473, "author_profile": "https://worldbuilding.stackexchange.com/users/2473", "pm_score": 0, "selected": false, "text": "<p>The descendants already have by their very existence have had an impact on the ancestors.</p>\n\n<p>Their existence implies that the ancestors did and all their descendants did not go extinct.</p>\n\n<p>In short, self-consistency. Anything that the descendants experience must be consistent with what the ancestors left behind.</p>\n\n<p>This is a strange kind of \"causal channel\", but narrative-wise it can work (with effort!)</p>\n\n<p>Imagine the ancestors run into a large military force. Then a \"cut\" to another scene, followed by the descendants learning about the result of that encounter.</p>\n\n<p>More generally, the ancestors can set a goal or encounter a challenge, then you can cut to the descendants discovering the result of the goal/challenge, then cut back to the ancestors having completed the goal/challenge.</p>\n\n<p>The narrative causality doesn't line up with the linear time causality.</p>\n\n<p>You can even go meta on the narrative. Set up this non-linear pseudo-causality, then throw in the fact that the pseudo-causality was a misunderstanding. The descendants aren't actually exploring the actions of the group of ancestors you are following! But instead a different people. Or maybe only <em>possibly</em> a different people.</p>\n\n<p>Then you cut back to the ancestors, who now have to overcome some problem that the narrative had earlier indicated was predestined to be solved.</p>\n\n<p>And there is always the cheesiest version of that switch -- the descendants are actually the ancestors and vice versa.</p>\n" }, { "answer_id": 79315, "author": "Ville Niemi", "author_id": 3434, "author_profile": "https://worldbuilding.stackexchange.com/users/3434", "pm_score": 1, "selected": false, "text": "<p>You listed narrative connection as an option. Use it.</p>\n\n<p>It is fairly common for events that happen later to affect the interpretation the reader gives to earlier events. The trivial example would be the classic detective story. A classic detective story will first give the reader a description of the actual events that includes all the clues necessary to determine the murderer and then present the final solution of the detective that connects the clues and makes the reader reinterpret the prior events.</p>\n\n<p>This is not of course really reverse causality, but you did give \"narrative connection\" as an option, and the reinterpretations caused by the later investigation can in theory be quite drastic. Stories where the narrator or even the detective turns out to be the murderer have been done. So you probably could get the effect you want with this method.</p>\n\n<p>A word of warning: such classic detective stories do require some work to plot correctly because you have to keep track of all the relevant facts and be totally sure you are not missing something that would be relevant. It also takes skill to fool the reader without breaking the rules by hiding relevant clues. You wouldn't really be bound by rules of classic detective story, of curse, but those rules were agreed on for good reasons so you probably should try to follow them.</p>\n" }, { "answer_id": 105173, "author": "kikirex", "author_id": 33716, "author_profile": "https://worldbuilding.stackexchange.com/users/33716", "pm_score": 1, "selected": false, "text": "<blockquote>\n <p>\"How can the exploration decisions the descendants make \"matter\" for\n the ancestors?\"</p>\n</blockquote>\n\n<p>Time Capsules work that way: ancestors are leaving items in a sealed box because they expect their descendants to find them (and somtimes be amused). If it wasn't for the descendants, clearly the ancestors would care less about such items.</p>\n\n<p>Let's say your ancestors want a cave to be open, but not until a certain date. What is inside doesn't matter. It can be an elder god, a treasure, or anything you want. They can set up traps along the way, just to be sure no random person would open it before. At this point, the ancestors are taking all the decisions... but! since they know and WANT their descendants to find the good path and enter the cave, they have to think and set the traps in a different way than usual: in a conventional story, they would teach something to their children or grand-children to avoid these traps. But what if, instead, they <em>counted</em> on the natural skills of their descendants?</p>\n\n<p>My grandfather made me crosswords when I was a child because I loved crosswords. But my sister loved archery, so he also made her a bow and a target in the garden. Would we have any other hobby, he would have made something else to please us. And this is how the descendants decisions matter for their ancestors... given the opportunity for the ancestors to have that information.</p>\n\n<p>Also it is not uncommon, in real life, to have two or three generations of children in a row adopting the same way of life as their parents: your world could have entires families just knowing what their descendants <em>will</em> do, because that's what they do and there's little chance their behaviour in the future will be very different. With that knowledge, any decision taken by a descendant will mirror the \"hope\" one ancestor had when setting a particular trap (which could be solved by force, by answering a riddle, by a particular skill they know or hope the descendant will have, etc.).</p>\n\n<p>If you take the fantasy course, you could have a prophecy about someone who will have a specific skill or knowledge in the future, so they can think ahead and plan the route for this \"chosen one\". Here again, the decisions of the descendant will force the ancestors to act a certain way to clear him the path in the future. You even can have just the <em>idea</em> of a chosen one, given that at any point in time, there eventually will be someone who fit the characteristics of said chosen one.</p>\n\n<p>In other words, either the ancestors know how their descendants will behave, and react upon it, either they decide to trace a particular path, with required skills and knowledge, and wait and see until the good person show up.</p>\n\n<p>...Or maybe they would just have a map to a certain treasure that reveal itself \"when the right stars are aligned\", centuries later. The ancestors may know how to get to the door, but only the descendants will have the key.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/63698", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/30587/" ]

[ { "answer_id": 65963, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 4, "selected": false, "text": "<h1>Not possible</h1>\n\n<p>The primary reason is that population growth has already peaked. From the US Census Bureau:</p>\n\n<p><a href=\"https://i.stack.imgur.com/Qfnbw.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Qfnbw.png\" alt=\"enter image description here\"></a></p>\n\n<p>Estimated growth is going to drop further. The UN <a href=\"https://esa.un.org/unpd/wpp/publications/files/key_findings_wpp_2015.pdf\" rel=\"nofollow noreferrer\">currently estimates</a> that population growth will top out at around 11 billion people in 2100. </p>\n\n<p>Given that world population is not likely to even get close to 100 billion +, it is very unlikely that human living population will exceed the dead. </p>\n" }, { "answer_id": 65967, "author": "Harlemme", "author_id": 30808, "author_profile": "https://worldbuilding.stackexchange.com/users/30808", "pm_score": -1, "selected": false, "text": "<p>It probably already has. According to several books that I've read on lineage all modern humans can be traced back to one group of 500-3000 people who lived about 100,000 yrs. ago, meaning that apparently we've almost gone extinct before for whatever reason. Adding in things like the Black Death epidemic and the fact that it took until 1900 or so for the population of living humans to reach 1 billion, the total number of humans who've ever lived isn't nearly as great as you'd think.</p>\n" }, { "answer_id": 65975, "author": "paparazzo", "author_id": 27771, "author_profile": "https://worldbuilding.stackexchange.com/users/27771", "pm_score": 2, "selected": false, "text": "<p>The current population is sum(births) - sum(deaths)</p>\n\n<p>Not solving for 2017 plus<br>\nJust how do those births and deaths need to relate for<br>\nsum(deaths) = current population </p>\n\n<p>sum(births) - sum(deaths) > sum(deaths)<br>\nsum(births) > 2 * sum(deaths) </p>\n\n<p>plug in x * deaths for births and solve<br>\na single fixed ratio for population to be sum(deaths)</p>\n\n<p>sum(x * deaths) = 2 * sum(deaths)<br>\nx * sum(deaths) = 2 * sum(deaths)<br>\nx = 2<br>\nso if the birth rate doubles the death rate then that is the balance point </p>\n\n<p>even if you more than doubled life expectancy would need to catch up in one life expectancy </p>\n" }, { "answer_id": 66006, "author": "CoffeDeveloper", "author_id": 4995, "author_profile": "https://worldbuilding.stackexchange.com/users/4995", "pm_score": 5, "selected": true, "text": "<p>Like other answers said, it is not practically possible at this point for Earth to sustain a population greater than number of people already dead. Unless you assume that every woman on the Earth for some strange reason decide to give birth each one:</p>\n\n<pre><code>Number of women = 7 billions / 2\n\nNumber of dead people = 107 billions\n\nChildren to give birth = (107)/(3.5) = 30.5 =&gt; 31 children.\n</code></pre>\n\n<p>So in the case that every woman now decide to give birth to 31 children (well in reality should be 40: we have to take into account people that would die in the meanwhile and keep a good error margin), and assuming (each pregnancy last 9 months) that in the middle of the process we will not end the available food (at some points we will have 60 billions people to feed and the Whole process would last 40 years), then yes it is theoretically possible.</p>\n\n<p>However there's no way we could do that in general:</p>\n\n<p>Assume that population keeps constantly doubling: in that case the <strong>sum of dead people and living people would be almost the same</strong>, but a double growth rate is not sustainable, at some point it will slow.</p>\n\n<p>To keep living population greater than dead population then you need a growth rate that is more than constant doubling ( x3, but also x2.1 is fine... or even x2.00001 and so on), and that is even less sustainable that a doubling growth rate.</p>\n\n<p>While in theory it is possible to exceed that limit for now (assuming enough resources), we will quickly reach a limit that will not allow us to exceed that again.</p>\n\n<p>When number of children a woman can give birth in a life will be lesser than</p>\n\n<pre><code>Sum of dead people / sum of living women\n</code></pre>\n\n<p>Then we will not be able to exceed that limit again. (well in theory we could do that in a hundred of years, assuming we can keep a exponential grow of population for so long).</p>\n" }, { "answer_id": 66009, "author": "Loren Pechtel", "author_id": 264, "author_profile": "https://worldbuilding.stackexchange.com/users/264", "pm_score": 2, "selected": false, "text": "<p>The only way it can happen is with immortality plus a major jump in the available living space (space colonization in a major way, or else interstellar colonization if we already have major space colonization before immortality is developed.) Your question requires the answer to two unknowns in order to answer and thus there is no way to answer it.</p>\n" }, { "answer_id": 66019, "author": "user10315", "author_id": 31492, "author_profile": "https://worldbuilding.stackexchange.com/users/31492", "pm_score": 2, "selected": false, "text": "<p>Great question. This is one of the questions that my friends and I have asked at various points in our lives. (also: how long would it take for N monkey, typing randomly, to create Macbeth spontaneously?)</p>\n\n<p>The population data SEEMS wrong. Why? My suspicious arise because there is no mention of estimated lifespans or the rate of death in ancient populations. Let's try to fill in some of these and see where that gets us:</p>\n\n<p>Lifespan: let's estimate 40 years. (By this measure, Jesus was normal by actuarial standards)\nDeath rate: if the lifespan is 40 years, then for every cohort of 1000 people, there would be 25 deaths per year (1000/40 = 25).</p>\n\n<p>Plug these numbers into a spreadsheet and see that a starting population of 5M in 8000 BC would grow to 5e192 by the year 1 AD. !!! SOMETHINGS WRONG HERE !!!</p>\n\n<p>Looking more closely, at a birth rate of 80 per 1000 per year (and a death rate of 25 per 1000 per year), 5M people would grow to 10M in 13 years. This is much higher than the flat line shown in all of these growth models.</p>\n\n<p>If you assume the rate of birth is steady at 80/1000, you need to jigger the death rate to over 79.48 to achieve the stated population of 300M by 1AD.</p>\n\n<p>I'm thinking that the number of births is too high: one would have to look at the model demographics to see if this is realistic: Assume an evenly-distributed cohort of 1000 persons, with ages ranging from 0 to 40. this places 25 people per age. Assume that the fertile years are from 15-40, etc. and you can really look at a more realistic model of populations. (for example, half of those born would not be able to give birth...)</p>\n\n<p>To sustain a lot of births and keep a slowly growing population, you need to have a lot of deaths. We need numbers like infant death rates and the risk of death during childbirth. If they are huge (79.48 / 1000), this can get you to 300 million by 1 AD on a smooth glide path. Doing so would require 47 billion people to be born in this span--a truly epic slaughter. (this might be the way that the referenced numbers were achieved)</p>\n\n<p>It is possible, though, to look at the rate of birth and death in primitive populations in the Amazon, New Guinea, or Kalahari tribesmen. I suspect that this would suggest birth rates at 50 per 1000 (I'm not asserting this--i'm probably wrong); It's probably not a good idea to gauge ancient birth rates from any data collected anywhere after 1800. Increasing urbanization, medical, food improvements, and access to petroleum-based energy added an artificial stimulus to growth rates that probably did not exist in earlier eras.</p>\n\n<p>With these numbers, it would only require 28 billion people to be born in this time.</p>\n\n<p>My suggestions are: (1) define a model that accounts for realistic birth behavior and more detailed methods of death. See what models suggest from this. (2) try to find some proxy for historical birth rates form archaeology or comparative anthropology.</p>\n" }, { "answer_id": 66042, "author": "Paul TIKI", "author_id": 31273, "author_profile": "https://worldbuilding.stackexchange.com/users/31273", "pm_score": 2, "selected": false, "text": "<p>Easy Answer: Zombies! Or some other mass resurrection. The math doesn't support it any other way, as has been pointed out in all of these other fine answers.</p>\n\n<p>Another possibility would be cloning on an enormous scale. The only problem with massive cloning is that it serves no purpose in the stated premise. If we can't leave the planet, Mother Earth will slap down the population growth one way or another. Either her or our own hubris will prevent growth of the living to surpass the dead. Remember that the planet is a closed system.</p>\n\n<p>Here is one way the living and the dead could reach population parity. If we had the means to store consciousness in a computer, and then archive everyone alive today. Then, as people die, the become activated in this new digital Elysium. Grant them rights and agency on par with those still in the \"meat space\". You would be then, in essence, granting immortality that maybe could work within the closed system of Earth without the great mother earth slap down.</p>\n" }, { "answer_id": 66053, "author": "James Jenkins", "author_id": 31507, "author_profile": "https://worldbuilding.stackexchange.com/users/31507", "pm_score": 0, "selected": false, "text": "<p>Until about 6,000 years ago, the population of the living people in the world was 4, with none dead. Then Cain murdered Able, prior to the birth of Adam and Eve's third child <a href=\"http://www.bibletruths.net/archives/btar199.htm\" rel=\"nofollow noreferrer\">Seth around 3900BC</a>.</p>\n\n<p>Given the longer life span of people in the early days of the world, the living probably out numbered the dead until about 2350BC when the great flood killed most of humanity. </p>\n\n<p>Related sister site question <a href=\"https://christianity.stackexchange.com/questions/54323\">Who was the second decedent of Adam to die?</a></p>\n" }, { "answer_id": 66061, "author": "Nikolas Skurupatis", "author_id": 31509, "author_profile": "https://worldbuilding.stackexchange.com/users/31509", "pm_score": 1, "selected": false, "text": "<p>Here we have 2 major points in life cycle, birth and death. Each life meets both points. \nMore birth = more death (after life lasting cycle). </p>\n\n<p><strong>Conclusion</strong> - we can never get equal or even get near to the dead population. </p>\n\n<p><strong>Exception</strong> is if tomorrow women start giving birth to babies like pop corn. Lets say we have 7 billion people, and lets divide population this way (for example), 25% children, 25% men, 25% old folks, and 25% women. 25% from 7 billion is 1,750,000,000. To get the number of 107 billion living people, each woman need to breed <strong>57.143</strong> children during this life. Since more people would die till all of this women in labor meet their ends, number is slightly increasing to around <strong>62</strong> babies per woman.</p>\n\n<p><strong>Exception no. 2</strong> is immortality. No need to write much about that.</p>\n\n<p><strong>Conclusion no. 2</strong> - planet Earth is perfect in doing one thing, recycling. Every living being is recycled after death, and who knows how many other forms of life that brings. I'd say that number of living and dead is always the same, the only thing that is changing is people. (judging by the fact that we are all recycled)</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/65962", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/26700/" ]

[ { "answer_id": 66821, "author": "Ranger", "author_id": 20204, "author_profile": "https://worldbuilding.stackexchange.com/users/20204", "pm_score": 2, "selected": false, "text": "<p>In the US income is reportable, including interest in a bank account. Banks that loan money (read: every bank) must also establish the capital that they're loaning from by federal law.</p>\n\n<p>Accounting works by a series of debits (increasing assets or recorded values) and credits (decreasing assets or recorded values), and the golden rule of accounting is that credit transactions must equal debit transactions, thus making the books balanced. In fact, this balancing is where the less-than-legitimate \"balancing the books\" comes from, as criminals try to artificially create this balance in records. By the sounds of it, you're not doing this, so the bank will be easily, easily tell that their (metaphoric) books aren't balanced. When they discover this will depend on how often they run reports, but it could be as soon as only a few minutes.</p>\n\n<p>Assuming (by some miracle, or by you lining the right person's pockets) the bank never catches on, it becomes a matter of if the IRS will catch on. People joke about the IRS wanting its money, but the IRS typically doesn't investigate income reports unless there's a significant amount of money being dealt with, there's a significant oddity, or another government organization alerts them to suspicious behavior. So you'd probably be safe from the IRS as long as you're very cautious about how much you tweak your bank account.</p>\n" }, { "answer_id": 66828, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 3, "selected": false, "text": "<p>It depends on how good of a hacker you are.</p>\n\n<p>If you think about it, the reason we put money in banks is because we trust that they are <em>very</em> good at not losing track of it. Any money you \"create\" by adding zeroes to your account and the subsequently withdraw is technically money they lost. Needless to say, they have a vested interest in this not happening, so they'll have a net of safeguards in place to catch you.</p>\n\n<p>For instance, no bank account is permitted to simply \"have a value.\" They have a transaction history that backs that value up. You would have to forge that transaction history. The better you do it, the harder it will be to find. Done well, you'll slip through the cracks. I'm certain banks do lose money every once in a while. As long as it stays below their profit margins, they can create the illusion of reliability by simply fixing the error with their own profits. Done poorly, however, and you'll trip some statistical safeguard that someone put in place to prevent some other issue you didn't even think of (maybe, by sheer luck, you accidentally make it look like a rounding error occurred, and for want of that penny, the bank becomes aware of your exploits!).</p>\n\n<p>Remember Sutton's law. Willie Sutton robbed banks \"because that's where the money is.\" There's a lot of organized crime groups that would <em>love</em> to rob banks, just like you. You may have to explain why your particular program manages to do it successfully when organized crime, with their extraordinary resources and botnets of zombies, couldn't.</p>\n\n<p>Also, you have to be aware of offline backups. While the money you are stealing may be a pittance, the hole you are leveraging in the banks' security is a big deal to them. They don't want the mob to do what you're doing. Once they do detect your work, they'll start relying on all their resources. This includes offline backups which will help them detect your changes.</p>\n" }, { "answer_id": 66829, "author": "Jay", "author_id": 2973, "author_profile": "https://worldbuilding.stackexchange.com/users/2973", "pm_score": 4, "selected": true, "text": "<p>I guess that depends on how sophisticated your hacking is and how sophisticated the bank's auditing systems are. </p>\n\n<p>If you just updated your bank balance, the bank should catch that very quickly, because their books won't balance. They'll have a credit with no matching debit.</p>\n\n<p>If you're smart enough to update both sides of the ledger, the bank will still surely notice something when they try to reconcile. Where did the money for this deposit come from. If you enter that it was made with cash, then when the bank does their cash reconciliation they'll find they have less cash than they should. If you say it was a direct deposit, they'll turn up short on deposits received. Etc.</p>\n\n<p>If their audit trail is sophisticated enough -- and bank audit trails tend to be very sophisticated -- they'll track it back to your account pretty quickly.</p>\n\n<p>There was a scam that was discussed a lot about 20 years ago -- I don't know how many people really got away with it, but it was a big buzz in computer circles -- that a programmer would change the bank's interest calculations to round fractions of a penny down instead of rounding of to the nearest whole penny, and then put those pennies in a dummy account created by the programmer. Few customers would notice that there interest was a penny short, and if they did, they'd grumble, \"Hey, the bank is rounding 14.9 cents down to 14 instead of up to 15, what a rip-off\", and then forget about it. Who's going to make a stink about a penny? Meanwhile if the bank has a lot of customers, the programmer is collecting significant money off all these pennies. And the bank's books would balance: if they're paying, say, 2% interest, 2% of the total of all count balances matches the total interest paid. They'd have to look pretty close to see that one account got way more interest than it should while many other accounts were a penny short.</p>\n\n<p>The point is, you need to have the money come from someplace or somebody's books won't balance. You can't just create money out of thin air and expect no one to notice.</p>\n" }, { "answer_id": 66830, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 0, "selected": false, "text": "<h1>You will almost immediately be caught</h1>\n\n<p>Banks are required to do <a href=\"http://ithandbook.ffiec.gov/media/22014/occ-hb-internal_external_audits-appx.pdf\" rel=\"nofollow noreferrer\">audits</a>. They do them <em>all</em> the time. Screwing up an audit or having the books not balance is simply not an option. They need audits to be an FCC member, to meet the requirements of BIS for foreign transactions, to prove to the Treasury department they are not funding terrorists, to comply with <a href=\"https://en.wikipedia.org/wiki/Dodd%E2%80%93Frank_Wall_Street_Reform_and_Consumer_Protection_Act\" rel=\"nofollow noreferrer\">Dodd-Frank</a>, etc. </p>\n\n<p>The bank will balance their books. There will be thousands of dollars in your account they cannot explain. They will investigate. You will go to jail. Its as simple as that. </p>\n" }, { "answer_id": 66831, "author": "o.m.", "author_id": 6402, "author_profile": "https://worldbuilding.stackexchange.com/users/6402", "pm_score": 2, "selected": false, "text": "<p>We're talking about a fictional character in a story, right? Kids, don't do this at home. You will be caught and go to prison unless you <strong>are</strong> the world's best programmer. <em>Then there are easier ways to earn money ...</em></p>\n\n<p>Other answers have pointed to the problem with accounts, credits, and debits. So the answer would be to hack the ATM system and to create a card that will allow unlimited withdrawals. Of course the problem would be detected as soon as an ATM has less cash on hand than it should have. </p>\n\n<ul>\n<li>Delete the malware immediately after the withdrawal and leave no digital traces.</li>\n<li>Wear a disguise in case there is a camera covering the machine.</li>\n<li>Use many different ATMs.</li>\n<li>Hack different banks in different jurisdictions. (But don't hope to stay undetected, it just slows the investigation.)</li>\n</ul>\n" }, { "answer_id": 72086, "author": "Durakken", "author_id": 22659, "author_profile": "https://worldbuilding.stackexchange.com/users/22659", "pm_score": 0, "selected": false, "text": "<p>Yes you will get caught.\nIn the past there have been people that rigged accounts to take tenths (and less in later attempts) of pennies on every transaction which is basically a below notice operation.</p>\n\n<p>What you are proposing is a well above notice operation.</p>\n\n<p>The people who actually did this type of stuff have all been caught as far as we know, sometimes after decades of doing it, other times almost immediately. It has nothing to do with the programming itself, but rather that accounts keep track better and better.</p>\n\n<p>So... your proposed thing would be caught instantly.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/66819", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/25003/" ]

[ { "answer_id": 67395, "author": "Tim B", "author_id": 49, "author_profile": "https://worldbuilding.stackexchange.com/users/49", "pm_score": 5, "selected": false, "text": "<p>You can have it affect them as much as you like. The device is magic, so the additional effects can be whatever you want.</p>\n\n<p>On a more practical note if the mass of the planet really has disappeared then orbits are going to be thrown way out of whack - depending on what point of their orbit around the planet the ships were at they could be thrown in any direction as the acceleration towards the planet's center suddenly vanishes.</p>\n\n<p>The ships are not \"outside\" the gravity well, in fact there is no such thing as \"outside\" a gravity well, although there is a point at which it's insignificant. The ships are in free-fall, but at the same time they are moving sideways so fast that even though they are falling towards the planet all the time they move far enough that they never actually hit the atmosphere.</p>\n\n<p>If you're writing space-based sci-fi you should definitely read up on some basic physics and orbital dynamics (simple Newtonian stuff would be plenty) if you want the results to be plausible.</p>\n" }, { "answer_id": 67399, "author": "Lio Elbammalf", "author_id": 31124, "author_profile": "https://worldbuilding.stackexchange.com/users/31124", "pm_score": 4, "selected": false, "text": "<p>Gravitational acceleration is continually changing the direction of a body in orbit around it, tugging it in a circle (we will assume) around it. If this tug disappears objects will just carry on in a straight line with their original velocity. The directions will just be along the tangent of the orbit they were on.</p>\n\n<p>So nothing too dramatic so far.</p>\n\n<p>However it really depends on how your planet disappearing act works, if they are tangled up in different but still present dimensions the mass may still be present and our 3D space might still act as though the planet is still there. This, however, is all speculative as we have no real idea. Another possible speculation is that, if the mass does disappear, our space will spring back and the space-ships will experience the stretch and squash of gravitational waves caused by such a dramatic difference in the dip.</p>\n\n<p>But in the end, we don't know, you get to decide how the machine works to best fit your story. Do they know how to return? (This would imply they were still linked to the original position) Or perhaps they can return anywhere in the universe (possibly very messy) which would do wonders for space-travel.</p>\n" }, { "answer_id": 67413, "author": "Geminirand", "author_id": 31855, "author_profile": "https://worldbuilding.stackexchange.com/users/31855", "pm_score": 1, "selected": false, "text": "<p>I don't think anything would happen to them at all, but I'm not a physicist.</p>\n\n<p>If they turn on their engines, then it's a moot point. They can go where they want, since they already possess enough power to overcome solar system gravity.</p>\n\n<p>If they don't turn the engines on, and since the planet was orbiting a sun, the ships are, too. They will still orbit the sun. For a time, their orbits will be unstable because they were primarily orbiting something that's now gone. Their orbits must adjust to a new focal point.</p>\n\n<p>They would probably settle into a stable orbit around the sun. But it's possible that one or both would be flung out into the solar system, or inward. They could become captured by another celestial mass and slowly settle into orbit there.</p>\n" }, { "answer_id": 67434, "author": "brandondoge", "author_id": 20885, "author_profile": "https://worldbuilding.stackexchange.com/users/20885", "pm_score": 1, "selected": false, "text": "<p>Assuming the planet has no moons nearby which might substantially alter things, they would just go into a solar orbit of roughly the same path as the former planet.</p>\n\n<p>Their position in the orbit of the planet will affect slightly their final orbit. Assuming an equatorial and prograde orbit, if the craft were on the opposite side of the sun from the planet when the planet disappeared, that tangential velocity would be added to their orbital velocity, resulting in an aphelion slightly higher than that of the former planet. If the craft were on the side of the planet closer to the sun, its tangential velocity would be subtracted from the orbital velocity, resulting in a perihelion slightly lower than the planet had.</p>\n\n<p>You could even get into a situation where the tangential velocity cancels out the eccentricity of the planet's original orbit, and puts the craft into a more circular orbit than the planet had.</p>\n\n<p>But really, the end result is basically nothing will happen, unless the planet is of a huge mass such that the tangential velocity of the orbiting fleet is large relative to the orbital velocity of the planet around its star.</p>\n" }, { "answer_id": 67437, "author": "Devsman", "author_id": 18444, "author_profile": "https://worldbuilding.stackexchange.com/users/18444", "pm_score": 2, "selected": false, "text": "<p>The basic idea behind orbit in Newtonian physics is that the centripetal acceleration required for the satellite to go in a circle around the planet (or other body) is perfectly fulfilled by gravitational acceleration. That is,</p>\n\n<p>$$G\\frac{M}{r^2} = \\frac{v^2}{r}$$</p>\n\n<p>This means that these satellites (space ships) are not supplying any power if they're in orbit, but \"coasting\" (so to speak). It also means that ships at the same altitude must have the same speed.</p>\n\n<p>For an in-orbit dogfight, what this means is that maneuvering is something that won't happen much, and when it does, changes in speed must either be accompanied by changes in altitude or fuel spent to maintain altitude. For example, speeding up means decreasing altitude and slowing down means increasing it. Or to keep altitude constant, speeding up means directing thrust away from the planet and slowing down means directing thrust toward the planet. Saving fuel is important, so we'll likely see more of the former than the latter.</p>\n\n<p>If we suddenly take away the planet, the conditions of orbit are no longer satisfied. But the basic equation of physics,</p>\n\n<p>$$F = ma$$</p>\n\n<p>should still apply. As such, we know that since no force is applied to the space ships (most will be \"coasting\", remember?), they will simply continue on their present trajectories. They will no longer be moving in a \"circle,\" though, but a straight line, just like a ball on the end of a string when the string breaks.</p>\n\n<p>If one ship is chasing another, they will both head off in ever so slightly different directions. Any kinematic shots that were in-transit when the planet disappeared will likely still make contact unless they're fired from particularly long range. In order for that kind of attack to be effective, it has to outrun the ship it's trying to hit, which means it's shot in a trajectory closer to straight-line than the orbit anyway.</p>\n\n<p>But as these ships are floating off on slightly different trajectories, no doubt the pilot or navigation system will notice and make corrections to either continue dogfighting or retreat because what the #@*$ just happened.</p>\n\n<p>I'm no expert on gravitational waves, but I don't think they should be too much of a consideration. With how weak gravitational force is and how quickly the waves propagate, it would take a much larger object disappearing and a much larger satellite for this to make too much of a difference. Geosynchronous orbit on Earth is around 35 786 km. Propagating at lightspeed, gravitational waves would cover that distance in roughly $\\frac{1}8$ of a second, and cover the distance across the ship's y axis in no time. There will be some distortion of space but nothing intense enough to be noticed.</p>\n" }, { "answer_id": 67442, "author": "Bohemian", "author_id": 19700, "author_profile": "https://worldbuilding.stackexchange.com/users/19700", "pm_score": 4, "selected": false, "text": "<p>The orbiting ships would stop moving in the curved (by gravity) line of their orbit and suddenly (continue to) move in a straight line in whatever direction they were moving at the time of the disappearance.</p>\n\n<p>At worst, this would be inconvenient, as to stay in the vicinity of where the planet was, they would have to decelerate then turn around and come back, at which time staying in the vicinity would be simply adopting the speed and velocity of the former planet, as their new stable orbit would be around the host star.</p>\n" }, { "answer_id": 67443, "author": "Yakk", "author_id": 2473, "author_profile": "https://worldbuilding.stackexchange.com/users/2473", "pm_score": 5, "selected": true, "text": "<p>Earth has a Schwarzschild radius of about 3 mm.</p>\n\n<p>This means things at geostationary orbital distance have a time dilation of about\n<span class=\"math-container\">$$\\sqrt{1-\\frac{9 mm}{35786 km}}$$</span>\nor one part in <span class=\"math-container\">$10^{-10}$</span> roughly. (if they are actually orbiting this value changes slightly, as does the rotation of the Earth)</p>\n\n<p>This also lines up with the length contraction factor.</p>\n\n<p>When the Earth disappears \"instantly\", a gravitational wave of that magnitude is going to be produced. How much energy is that?</p>\n\n<p>Well, 1 solar mass converted to gravitational waves and sent over 1.4 billion light years produced a <span class=\"math-container\">$10^{-20}$</span> amplitude wave (LIGO observation). <a href=\"http://www.lightandmatter.com/html_books/genrel/ch09/ch09.html\" rel=\"nofollow noreferrer\">The energy in a gravitational wave is proprotional to amplutide squared</a>.</p>\n\n<p>So, per meter squared, the LIGO observation would carry:</p>\n\n<pre><code>(1 solar mass * c^2) / (1.4 billion light years*2)^2 / 4 pi * 1 m^2\n</code></pre>\n\n<p>2 * <span class=\"math-container\">$10^{-5}$</span> J (apparently it was 1 solar mass of matter converted into a gravitational wave at a distance of 1.4 billion light years).</p>\n\n<p>The gravitational wave from the Earth disappearing is going to be <span class=\"math-container\">${10^{10}}^{2}$</span> stronger than that, or 2*<span class=\"math-container\">$10^{15}$</span> J. This is an insane amount of energy; however, very little of it actually deposits on normal matter.</p>\n\n<p>Suppose we are 1 Jupiter-radius away from Jupiter instead.</p>\n\n<p>Jupiter has a Schwarzschild radius of 2.2 m. Titan has an average orbit of 1,221,850 km. Then the gravitational wave would carry 500 times as much Energy.</p>\n\n<p>The question becomes how well does it convert over to normal matter? Will it occur fast enough to disrupt an atomic nucleus?</p>\n\n<p>The compression effect on molecular-level matter will only involve modest pressures. But the compression effect will occur all the way down the length scales, and I suspect it requires lots more pressure to compress a nucleus.</p>\n\n<hr>\n\n<p>But back up a second. We ripped the planet from our universe. One could argue that would involve forming an event horizon around the planet and making it disappear.</p>\n\n<p>I mean, photons not coming from an area is the definition of event horizon. Stuff an event horizon somewhere, and you warp space. The volume we need to swallow is the planet. So, black hole the size of the planet in effect blinks in then poofs?</p>\n\n<p>If we are 10 planet-radius away, and the event horizon forms tightly around the planet then disappears, this would generate two gravitational waves of impressive magnitude.</p>\n\n<p><span class=\"math-container\">$$\\sqrt{1 - \\frac{1 r}{10 r}}$$</span>\ngives us a amplitude of 0.05. The energy carried by this wave is about 10^17 times greater than the ones we are describing above.</p>\n\n<p>In effect, all matter would suddenly feel stretched by 5%, then compressed by 5%. This would occur all the way down to the molecules, quarks and nuclei. I'd be worried about fission events from this happening suddenly, let alone the amoung of energy released by compressing \"incompressible\" solids by 5%.</p>\n\n<p><a href=\"https://ca.answers.yahoo.com/question/index?qid=20090718001908AAEGhNH\" rel=\"nofollow noreferrer\">Compressing water by 5% would take 0.1 GPa</a>, so we could estimate the effect would be akin to a pressure wave of that magnitude over humans. <a href=\"https://answers.yahoo.com/question/index?qid=20101123191731AALTdXN\" rel=\"nofollow noreferrer\">And 0.4 GPa for iron</a>.</p>\n\n<p>This level of pressure in a conventional blast is enough <a href=\"https://en.wikipedia.org/wiki/Overpressure\" rel=\"nofollow noreferrer\">to blow limbs off</a>.</p>\n\n<p>I cannot believe the compressibility of EM mediated molecule-scale solids is in the same universe as that for a nucleus or a proton. So I would be very worried about atomic disintegration...</p>\n\n<p>Ignoring that, matter slows down gravitational waves. The effect is extremely tiny, but we could use that to estimate how much impulse this would provide and how much energy deposited. I cannot find the correct equations for this case.</p>\n\n<hr>\n\n<p>Calculating what exactly happens is going to be quite tricky. For a planet-sized event horizon, the effect will be explosive at \"molecular\" scales, blowing objects apart. At atomic scales, I don't know (will it cause fission?). At macroscopic scales, I don't know (will it impart a large radial impuse from the matter slowing the gravitational wave down?).</p>\n\n<p>There is plenty of energy to work with. The kind of effect that energy density and flux could cause seem unbounded.</p>\n\n<p>The above also neglects the power; how long the teleport takes determines the power the wave carries (how \"sharp\" it is, not just how much energy it carries).</p>\n" }, { "answer_id": 67485, "author": "JDługosz", "author_id": 885, "author_profile": "https://worldbuilding.stackexchange.com/users/885", "pm_score": 2, "selected": false, "text": "<p>The ships will fly off at their current orbital velocity, as others have explained.</p>\n\n<p>However, you can easily have the effect justifiably be more damaging: in orbit, the ships posses a large <strong>angular momentum</strong>. We might suppose that the defensive mechanism goes to pains to make sure the planet is treated gently enough, and in any case it has a huge moment of rotational inertia so the imposed change has little reaction.</p>\n\n<p>But the disappearance causes each ship’s orbital angular momentum to be dumped into the ship itself! And in a fairly random haphazard dumping: so various parts of the ship suddenly are sent <em>spinning</em> with great force, tearing the ship apart.</p>\n" }, { "answer_id": 67486, "author": "Harper - Reinstate Monica", "author_id": 20872, "author_profile": "https://worldbuilding.stackexchange.com/users/20872", "pm_score": 3, "selected": false, "text": "<p>If the planet goes away, the gravity well goes away, and the well is no longer \"turning\" their orbits. Wherever they are in their orbits, they now go in a straight line. <em>That's not the problem.</em> </p>\n\n<h2>The planet comes back. Uh-oh.</h2>\n\n<p>The problem is when the spaceships come back and loiter in open space to await <strong>the return of the planet</strong>. (their science teams figure out pretty quick that's a highly improbable way to destroy a planet.) </p>\n\n<p>The ships have nothing to orbit, so they must \"sit there\" in the general vicinity of where the planet is expected to return. When the planet returns, they will suddenly find themselves in a gravity well, with no sideward velocity for an orbit. They will <strong>Fall Straight Down</strong> while the planet turns under them. </p>\n\n<p>Their engines will need to generate somewhat more than one local \"gee\" of thrust to escape - even more if they're late - and that may not be practicable for a slow, large interstellar capital ship. Could they merely bend their fall sideways into an orbital velocity? Maybe, I haven't run the numbers. </p>\n\n<p>They might have a better shot if their ship is designed for reentry. </p>\n\n<h2>The critical delay</h2>\n\n<p>Keep in mind what Sully Sullenberger talked about at the NTSB hearing. He pointed out that all the simulations had the pilots knowing exactly what to do, zero seconds into the event. He said what actually happens in real life is some time figuring what's going on and what to do about it - when they added 30 seconds of \"figuring out options\" time, every simulation crashed. </p>\n\n<p>Even if they expect it, the vigilance could be hard if there's a long wait for the planet's return. Guard duty is boring. It might be the third-watch crew who's least competent, and things might not get sorted until the captain comes out in his pajamas. </p>\n\n<p>So you have to figure 30-90 seconds minimum for crews to discover the planet has returned, realize their peril, make a plan to thrust away from it, and get the engines spun up / ship physically oriented engines-down. They may not know exactly where the planet will reappear. </p>\n\n<p>That's going to depend a lot on the distance from the planet. Hopefully their captains have thought this through (probably not, it <em>doesn't ever happen</em> so how would they be prepared for it?) What if it's a \"race\" by competing factions, where you need to be closer than the other guy? </p>\n\n<p>Assuming Earth pops up 300km away, in Sully's 30 seconds, things have gotten rather worse - you have fallen 4.5km and gain 300m/s velocity <em>straight down - that's a kilometer in 3 seconds, a mile in 5.</em> At 90 seconds you've fallen 40km with 900m/s velocity, a kilometer per second! Since you hit atmo' in 150 seconds (2:30), the point of non-recoverability may be sooner than you think. </p>\n\n<p>Damn, that'll be an exciting chapter. Several chapters if you spend time on several ship bridges watching different captains deal with it in a different way. </p>\n\n<p>Maybe there's even a spot for unexpected heroism, where the Vollchon ship throws a tractor beam or grapple to help a Hegemon ship get enough escape velocity.</p>\n\n<h2>Why so close?</h2>\n\n<p><em>What? And risk my ship?</em> So much easier to sit 100 million km away with a bag of popcorn. But consider the drama. </p>\n\n<p>Whatever made the planet disappear, <em>something</em> else is going on. It's not that simple. The situation may justify putting ships at risk. </p>\n\n<ul>\n<li>A siege doesn't happen in peace. What's the point of the blockading ships sitting at a nice safe distance, when the blockade runners simply position themselves <em>much</em> closer? (and the capital ships may presume the blockade runners may have insider information.) </li>\n<li>A <em>Mad, mad, mad world</em> treasure-hunt doesn't have <em>one</em> competitor. (at least not ones that get into science-fiction novels). You're safe, you lose. </li>\n<li>The waiting ships may have a reason to want the planet inside weapons range the moment it returns. </li>\n</ul>\n\n<p>It may be worse. Their science teams may have error or faulty presumptions in their calculations. (this is a new phenomenon, right?) <em>Rogues don't even have science teams.</em> </p>\n\n<p>Lastly, what if the planet is be able to <em>control</em> where it reappears? If so, that is trivial to weaponize, the waiting ships <strong>would have no choice</strong> whether the planet appears 200km under them. That will surely occur to their science teams. And they may not know <em>whether</em> the planet can control that, if this situation is novel to them. </p>\n\n<p>Speaking of novel, that's up to the writer. <em>Of course,</em> the power of science is that we can avoid drama, but if science fiction novels wanted to avoid drama, <em>they too</em> would stay in spacedock. </p>\n" }, { "answer_id": 67490, "author": "Dan Smith", "author_id": 32002, "author_profile": "https://worldbuilding.stackexchange.com/users/32002", "pm_score": 2, "selected": false, "text": "<p>As other answers have noted, if you think it would be cool for your planet eraser to cause a displacement effect then go for it; no one could dispute it without knowing the exact science behind the superweapon, which means you get a lot of license. (And let's not forget the <a href=\"http://tvtropes.org/pmwiki/pmwiki.php/Main/RuleOfCool\" rel=\"nofollow noreferrer\">Rule Of Cool</a>!)</p>\n\n<p>I don't think that you'd necessarily see any effect in 3D space, because the orbiting ships were all being accelerated \"downwards\" by gravity and so the planet doesn't play much of a role at all in their relative motion unless the direction of that \"downwardness\" is significantly different for each of them. If a ship is approaching another ship, it will still do so once neither is being pulled downward. If however your ships are so far apart that their vectors are significantly different, so that they're effectively fighting <em>around</em> the planet rather than above it, then with the planet's gravity removed the ships would start to drift apart if neither corrected their course. In other words, if ships A &amp; B are dogfighting somewhere and ships C &amp; D are dogfighting a quarter-orbit away, neither of the dogfights would be noticeably affected by the loss of the planet, but the two dogfights would drift apart. This could easily be corrected for, just as if the other ships had simply changed direction.</p>\n\n<p>So far, so unsexy. Your superweapon could still have side effects, however, depending on how it works -- which is up to you! You don't have to simply replace the planet with vacuum and call it a day. If the entire section of 3D space that contained the planet has now been \"pinched off\" by the superweapon, then the <em>space itself</em> is now inaccessible. In other words, if you have ship A and ship B who were very close to the planet on opposite sides, those ships would now find themselves right next to each other as the space that separated them has been pocketed off. There isn't just a big empty space between them, because that space is where the planet <em>still is</em>. The whole thing has just been pulled out of our plane of 3D space.</p>\n\n<p>By this logic, if you had a dense shell of spaceships around the planet, on the event horizon, they would find themselves smooshed together into a small dense blob. Either handwave this away, or don't draw attention to it.</p>\n" }, { "answer_id": 67528, "author": "Kaithar", "author_id": 7949, "author_profile": "https://worldbuilding.stackexchange.com/users/7949", "pm_score": 2, "selected": false, "text": "<p>Let's talk side effects.</p>\n\n<p>As noted by others, the ships in orbit would cease orbiting and start moving in a straight line, the exact motion dependent on how far they were from the planet. The ISS for instance would have a considerable straight line speed and would complete an axial rotation once every 90 minutes. Something the distance of the Moon away wouldn't experience a particularly notable difference in orbit until minutes or hours have passed. That bit is boring.</p>\n\n<p>First interesting side effect: Gravity, or sudden lack of, propagates at the speed of light. Objects will continue to feel the pull of gravity from the now missing planet until the difference has propagated the distance between them. Mostly irrelevant due to the tiny magnitude of action during that period of time, but still kind of interesting. Would be more of an interesting point if the ships were more like 1 AU or more from a star and the star disappeared at a known time.</p>\n\n<p>Second interesting side effect: How far out does this disappearance affect? Does the planet have anything in orbit? In the case of the Earth, if the effect were confined to the right distance, the planet and it's atmosphere could be \"removed\" while leaving objects in orbit in place. Nearby ships would then have the fun of thousands of high speed metal objects suddenly moving at tangents to the planet's previous position. I imagine it could be considered a solar fragmentation grenade.</p>\n\n<p>Third interesting side effect: How does the planet disappear? If the disappearance involves stretching of space time around the planet then you have some interesting relativistic consequences to consider. If the mass of the planet disappears but space remains the same you instead have a large hard vacuum in a spot where the intra-solar vacuum wasn't all that empty, I'd expect this possibility to result in something like an implosion that would affect anything close by though I don't know how much by.</p>\n\n<p>Fourth interesting side effect: Anything mechanism resulting in the disappearance of a planet should require a massive amount of energy, which in turn should result in a massive amount of waste energy being emitted. I think it would be justifiable to assume the space previously occupied by the planet would now contain energy equivalent to some portion of the planet's mass. How much energy depends on how strict you want to be but I'd expect a pretty substantial amount of gamma and X-ray emission. If you wanted to be very strict you could plausibly say that the planet was replaced with an amount of energy equivalent to the entire planet's mass, that's an explosion of considerable magnitude.</p>\n\n<p>Fifth interesting side effect: 3 words: Van Allen Belts. All that lovely radiation is confined by the influence of the planet. No more planet, no more confining influence.</p>\n\n<p>Hope that gives you something to work with.</p>\n" }, { "answer_id": 67539, "author": "Grimm The Opiner", "author_id": 9285, "author_profile": "https://worldbuilding.stackexchange.com/users/9285", "pm_score": 1, "selected": false, "text": "<p>As has been at least hinted at more or less precisely/coherently, the moment the planet vanishes then any object actually orbiting that planet will continue moving in a straight line* in the direction they were moving when the planet disappeared.</p>\n\n<p>What happens next depends on a lot of things. If they are flung towards another planet, they may get trapped in an orbit around that planet, or \"<a href=\"https://en.wikipedia.org/wiki/Gravity_assist\" rel=\"nofollow noreferrer\">slingshot</a>\" around it. They may smack straight into it. They might get flung into an orbit around the sun the planet is orbiting - assuming the planet <strong>is</strong> orbiting a sun. They may - and could be the most likely outcome - leave the solar system altogether, maybe bending round a few of the other bodies in the system on the way.</p>\n\n<p>But that's <em>objects</em>. What about <em>ships</em>? Well, Star Trek-y, Culture-y, or Star Wars-y ships that basically scoot about all over the place at ridiculous speed with effectively infinite fuel won't care much at all, they'll just scoot off somewhere else.</p>\n\n<p>But for a more realistic ship, as you might find in Arthur C Clark, or <a href=\"https://en.wikipedia.org/wiki/The_Expanse_(novel_series)\" rel=\"nofollow noreferrer\">The Expanse</a>, the effect would be profound. What if their planned itinerary required refuelling at that planet and they didn't get the chance? What about an orbital shuttle or space station? Even under ideal conditions suddenly hurtling into the dark at thousands of kph with no other planet closer than a few months away, and maybe with not even enough fuel on board to \"stop\"** let alone figure out how to reach safety, is Bad News. And if all other craft in the same boat are similarly realistic in their limits, the chance of rescue or aid is slim even from someone fully stocked up.</p>\n\n<p>And there in you might find the real drama. How to combine scarce resources - time, fuel, food, oxygen - with orbital mechanics to weave an improbable path to safety.</p>\n\n<p>*Very very Straight-ish anyway. Gravitational influence from other bodies will be extremely slight at typical solar system distances.</p>\n\n<p>**\"Stop? Relative to what?\" you cry. Yeah I know, the point is you're instantly in the situation of having a lot velocity that may well be very unhelpful.</p>\n" }, { "answer_id": 67600, "author": "user3389773", "author_id": 32079, "author_profile": "https://worldbuilding.stackexchange.com/users/32079", "pm_score": 0, "selected": false, "text": "<p>Gravitational effects of said planet will disappear instantly. However, orbiting vehicles will experience the change in gravity effect based on their orbital distance since gravity travels at the speed of light.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/67394", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/28763/" ]

[ { "answer_id": 67463, "author": "Samuel", "author_id": 3202, "author_profile": "https://worldbuilding.stackexchange.com/users/3202", "pm_score": 2, "selected": false, "text": "<p>Well, that's the same <a href=\"https://en.wikipedia.org/wiki/Third_gender#Intersex_people_and_third_gender\" rel=\"nofollow noreferrer\">three sexes</a> that <em>our</em> human race has.</p>\n\n<p>If you're going for reality then, make the ratios the same. It's <a href=\"https://en.wikipedia.org/wiki/Human_sex_ratio\" rel=\"nofollow noreferrer\">approximately equal split between men and women</a> (101 men to 100 women) and <a href=\"https://en.wikipedia.org/wiki/Intersex\" rel=\"nofollow noreferrer\">about 1 in 2,000 for hermaphrodites</a>. </p>\n" }, { "answer_id": 67465, "author": "SRM", "author_id": 26246, "author_profile": "https://worldbuilding.stackexchange.com/users/26246", "pm_score": 1, "selected": false, "text": "<p>Figure out your genetics. Here are your pairings:</p>\n\n<ul>\n<li>M+F</li>\n<li>M+H</li>\n<li>H+H</li>\n<li>H+F</li>\n</ul>\n\n<p>H has more breeding options, so it's the better fitness function. If H is a dominant trait, it will dominate over time. If H is a recessive trait, it'll drop towards 25%. If any pairing can result in any gender, they'll balance out. This is assuming there is no cultural pressure to bias prospective mates away or toward one of the genders. </p>\n" }, { "answer_id": 67482, "author": "Jnani Jenny Hale", "author_id": 29630, "author_profile": "https://worldbuilding.stackexchange.com/users/29630", "pm_score": 2, "selected": false, "text": "<p>If there are three genders, are all three required to breed? In that case, equal numbers of each at the age of adolescence will be the end state of evolutionary pressure. (In humans now, for example, more male infants are born than female, about 105-100, but they are more fragile and more of them die in childhood, so the numbers are just about equal at puberty.)</p>\n\n<p>If they are based on humans, then you could have a triplex gender chromosome - XXX is female, YYY is male, and XXY or XYY is hermaphrodite. (In truth, we get these variations naturally, and they are not really hermaphrodites - look them up if you are interested.)</p>\n\n<p>It could also be a different kind of genetic mechanism. For example, Sigourney Weaver is genetically XY, but her testosterone receptors don't work, so her body is the default (female) shape, but without all the curves estrogen would create.</p>\n\n<p>Your hermaphrodites might be a variation like this, hormonal-based, rather than chromosomal. Many of the naturally-occurring variations like this are infertile, though. And those that are fertile, are only fertile in either the male or the female structure, not both.</p>\n\n<p>You could go with two types of hermaphrodite that look similar externally, but are only fertile in one of the structures.</p>\n\n<p>Or give up trying to be scientific, wave your hands, and carry on with the story!</p>\n" }, { "answer_id": 67483, "author": "John", "author_id": 29409, "author_profile": "https://worldbuilding.stackexchange.com/users/29409", "pm_score": 2, "selected": false, "text": "<p>Sex ratios are controlled more by mating strategy than anything else, even species with the same sex chromosomes can have vastly different sex ratios. So really it is controlled by how many partners each sex has at a time. if your species is monogamous, or serial monogamous like humans, then you actually can have a wide range becasue the normal 1:1 gets thrown for a loop when you have both sexes at the same time as an option. I suspect you will quickly see the hermaphrodite begin to dominate the gene pool since they can switch hit depending on circumstances. </p>\n\n<p>Males are high risk but potentially high reward, like a lottery, less likely to find a mate but also capable of hitting the Genghis Khan jackpot. Females are a conservative but safer bet, they are almost guaranteed to reproduce but have an upper limit on on the number of offspring they can have. So if their ratio gets unbalanced the opposite sex has a big advantage so the people will have more of that sex until they reach equilibrium again. Too many males and males have even less of chance to find a mate so females get favored, if females dominate males have a much better chance of finding multiple partners so males get favored. </p>\n\n<p>Hermaphrodite have both a sure thing and the chance of the jackpot. \nThe only thing preventing hermaphrodite domination is if males or females (or both) are less willing to mate with hermaphrodites than the opposite sex. </p>\n\n<p>So really it's entirely dependent on how hermaphrodites are viewed as possible mates. If they are just as desirable as the opposite sex soon all you have is hermaphrodites. basically the less males and females are willing to mate with hermaphrodites the closer to male/female domination you will see and the more willing they are the closer to hermaphrodite domination you will get. </p>\n" }, { "answer_id": 67523, "author": "Brythan", "author_id": 2113, "author_profile": "https://worldbuilding.stackexchange.com/users/2113", "pm_score": 4, "selected": true, "text": "<h3>Arbitrary system</h3>\n\n<p>I came up with a system for handling genders. In this system, a female is FF, a male is MM, and a hermaphrodite is FM. So if a female and a male breed, they have only hermaphroditic offspring. If a hermaphrodite breeds with either other sex, there's a 50% chance of a hermaphrodite and a 50% chance that the child is the same gender as the other partner. If two hermaphrodites breed, they have a 50% chance of a hermaphrodite and 25% each for the other genders. </p>\n\n<pre><code>+---+----+----+ +---+----+----+ +---+----+----+ +---+----+----+\n| | F | F | | | F | F | | | F | M | | | F | M |\n+---+----+----+ +---+----+----+ +---+----+----+ +---+----+----+\n| M | FM | FM | | F | FF | FF | | M | FM | MM | | F | FF | FM |\n+---+----+----+ +---+----+----+ +---+----+----+ +---+----+----+\n| M | FM | FM | | M | FM | FM | | M | FM | MM | | M | FM | MM |\n+---+----+----+ +---+----+----+ +---+----+----+ +---+----+----+\n</code></pre>\n\n<p>I ran some simulations (code and assumptions at the bottom). I found a slight preference for hermaphroditic offspring overall but a stable one. So perhaps 56-57% hermaphrodite and evenly distributed between the other two. Note that it is possible to favor males over females or vice versa. For example, a rule that hermaphrodites and females only breed with males (possibly allowing males with multiple spouses) would eliminate females and keep females eliminated so long as it was followed. </p>\n\n<p>This was based purely on those rules. If you have different rules, then you're going to get different results. It might be better to approach the problem from the other direction. How would you like to split the genders and why? Some splits may not have an easy explanation. </p>\n\n<h3>Alternatives</h3>\n\n<p>I read a book a while ago where gender was determined by the gender ratio around the child. So all children were neuters. The move to adulthood occurred when the child would develop a gender. A child surrounded by females would become male. A child surrounded by males would become female. You could extend that to include hermaphrodites (surrounded by equal numbers of males and females). And you could provide arbitrary rules for the development of children surrounded by hermaphrodites. That society could choose its gender ratio if it wanted. </p>\n\n<p>We often act like males and females are perfectly evenly divided in humans. But actually Y sperm are more likely to form. This is partially offset as Y sperm are less likely to succeed to fertilization. But overall, there are more boy babies than girl babies. Boys/men are also more fragile, dying in accidents more often. With modern medicine, women seldom die due to pregnancy. So by retirement age, there are more women than men. </p>\n\n<p>Anyway, you can use similar mechanisms to alter ratios in your humanoids. Perhaps there is some birth defect that is common in one gender or another that leads to miscarriage. Perhaps hermaphrodites produce less sperm. Perhaps the genetics is more complicated. </p>\n\n<h3>Simulation code</h3>\n\n<p><strong>GenderSimulator.java</strong></p>\n\n<pre><code>import java.security.SecureRandom;\nimport java.util.EnumMap;\nimport java.util.Map;\nimport java.util.Random;\n\npublic class GenderSimulator {\n\n public enum Gender {\n FEMALE, HERMAPHRODITE, MALE;\n\n public Gender opposite() {\n switch (this) {\n case FEMALE:\n return MALE;\n case MALE:\n return FEMALE;\n default:\n return null;\n }\n }\n }\n\n public static class Generation {\n\n Map&lt;Gender, Integer&gt; genderCounts = new EnumMap&lt;Gender, Integer&gt;(Gender.class);\n\n public Generation() {\n this(0, 0, 0);\n }\n\n public Generation(int femaleCount, int hermaphroditeCount, int maleCount) {\n genderCounts.put(Gender.FEMALE, femaleCount);\n genderCounts.put(Gender.HERMAPHRODITE, hermaphroditeCount);\n genderCounts.put(Gender.MALE, maleCount);\n }\n\n public Generation generateNext() {\n Generation generation = new Generation();\n\n generateRandomCouples(generation);\n generateFemaleMaleCouples(generation);\n generateCouples(generation, Gender.FEMALE);\n generateCouples(generation, Gender.MALE);\n generateFromHermaphrodites(generation);\n\n return generation;\n }\n\n public int size() {\n int sum = 0;\n\n for (int count : genderCounts.values()) {\n sum += count;\n }\n\n return sum;\n }\n\n public int count(Gender gender) {\n Integer count = genderCounts.get(gender);\n\n return (count == null) ? 0 : count;\n }\n\n private void add(Gender gender, int amount) {\n int count = count(gender);\n genderCounts.put(gender, count + amount);\n }\n\n private Gender chooseGenderChildOfHermaphrodites() {\n int choice = RANDOM.nextInt(4);\n if (choice == 0) {\n return Gender.FEMALE;\n } else if (choice == 3) {\n return Gender.MALE;\n } else {\n return Gender.HERMAPHRODITE;\n }\n }\n\n private Gender chooseGenderChild(Gender gender) {\n return RANDOM.nextBoolean() ? Gender.HERMAPHRODITE : gender;\n }\n\n private Gender chooseGenderParent() {\n int choice = RANDOM.nextInt(count(Gender.HERMAPHRODITE) + count(Gender.MALE) + count(Gender.FEMALE));\n if (choice &lt; count(Gender.HERMAPHRODITE)) {\n return Gender.HERMAPHRODITE;\n } else if (choice &lt; count(Gender.HERMAPHRODITE) + count(Gender.MALE)) {\n return Gender.MALE;\n }\n\n return Gender.FEMALE;\n }\n\n private boolean hasHermaphroditeParent(Gender gender) {\n return RANDOM.nextInt(count(Gender.HERMAPHRODITE) + count(gender)) &lt; count(Gender.HERMAPHRODITE);\n }\n\n private void breedWith(Generation generation, Gender gender) {\n add(gender, -1);\n if (hasHermaphroditeParent(gender.opposite())) {\n add(Gender.HERMAPHRODITE, -1);\n generation.add(chooseGenderChild(gender), 1);\n generation.add(chooseGenderChild(gender), 1);\n } else {\n add(gender.opposite(), -1);\n generation.add(Gender.HERMAPHRODITE, 2);\n }\n }\n\n private void generateFemaleMaleCouples(Generation generation) {\n int maleCount = count(Gender.MALE);\n int femaleCount = count(Gender.FEMALE);\n\n int count = Math.min(maleCount, femaleCount);\n\n genderCounts.put(Gender.MALE, maleCount - count);\n genderCounts.put(Gender.FEMALE, femaleCount - count);\n\n generation.add(Gender.HERMAPHRODITE, 2 * count);\n }\n\n private void generateRandomCouples(Generation generation) {\n while (count(Gender.HERMAPHRODITE) - 1 &gt; Math.abs(count(Gender.MALE) - count(Gender.FEMALE))\n &amp;&amp; count(Gender.FEMALE) &gt; 0 &amp;&amp; count(Gender.MALE) &gt; 0) {\n Gender parent = chooseGenderParent();\n if (parent == Gender.HERMAPHRODITE) {\n add(Gender.HERMAPHRODITE, -1);\n Gender other = chooseGenderParent();\n if (other == Gender.HERMAPHRODITE) {\n add(Gender.HERMAPHRODITE, -1);\n generation.add(generation.chooseGenderChildOfHermaphrodites(), 1);\n generation.add(generation.chooseGenderChildOfHermaphrodites(), 1);\n } else {\n add(other, -1);\n generation.add(chooseGenderChild(other), 1);\n generation.add(chooseGenderChild(other), 1);\n }\n } else {\n breedWith(generation, parent);\n }\n }\n }\n\n private void generateCouples(Generation generation, Gender gender) {\n while (count(gender) &gt; 0 &amp;&amp; count(Gender.HERMAPHRODITE) &gt; 0) {\n add(gender, -1);\n add(Gender.HERMAPHRODITE, -1);\n generation.add(chooseGenderChild(gender), 1);\n generation.add(chooseGenderChild(gender), 1);\n }\n }\n\n private void generateFromHermaphrodites(Generation generation) {\n while (count(Gender.HERMAPHRODITE) &gt; 1) {\n add(Gender.HERMAPHRODITE, -2);\n generation.add(generation.chooseGenderChildOfHermaphrodites(), 1);\n generation.add(generation.chooseGenderChildOfHermaphrodites(), 1);\n }\n }\n\n public String toString() {\n return toString(\"-\");\n }\n\n public String toString(String delimiter) {\n StringBuilder builder = new StringBuilder();\n\n builder.append(genderCounts.get(Gender.FEMALE));\n builder.append(delimiter);\n builder.append(genderCounts.get(Gender.HERMAPHRODITE));\n builder.append(delimiter);\n builder.append(genderCounts.get(Gender.MALE));\n\n return builder.toString();\n }\n\n }\n\n public final static Random RANDOM = new SecureRandom();\n\n public static void main(String[] args) {\n Generation generation = new Generation(2150, 5700, 2150);\n System.out.println(generation);\n int size = generation.size();\n while (true) {\n generation = generation.generateNext();\n System.out.println(generation);\n if (size != generation.size()) {\n break;\n }\n size = generation.size();\n }\n }\n\n}\n</code></pre>\n\n<p>Assumptions: </p>\n\n<ul>\n<li>Breeding is monogamous (if you breed with someone, all your children are with that someone); </li>\n<li>Any compatible and available partner is equally likely (hermaphrodites are neither preferred nor avoided as partners relative to the other genders); </li>\n<li>No male/male or female/female relationships, as those wouldn't produce offspring;</li>\n<li>Every couple has two children (stable population);</li>\n<li>Everyone breeds with someone (also needed for a stable population). </li>\n</ul>\n\n<p>Note that this code is not particularly flexible. You can't swap breeding strategies in and out. That's hard coded. Changing the first generation involves modifying code. This is mainly designed to test my initial hypothesis that hermaphrodites would make up 50% of the population. That does not seem to be true. The hermaphrodite population stabilizes around 56-57% when everything is random. </p>\n\n<p>The other genders are less stable, fluctuating in a much wider band. </p>\n\n<p>I used interior classes because it was easier for me to do this in just one file. I used <code>SecureRandom</code> because I didn't seem to need more efficiency, and I wanted to be sure that my results weren't being tainted by too much pseudo in my random. I didn't notice any difference between the two, so you could switch back if you wanted. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/67460", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/32045/" ]

[ { "answer_id": 68130, "author": "Loren Pechtel", "author_id": 264, "author_profile": "https://worldbuilding.stackexchange.com/users/264", "pm_score": 2, "selected": false, "text": "<p>Copied from: <a href=\"https://worldbuilding.stackexchange.com/a/68050/264\">https://worldbuilding.stackexchange.com/a/68050/264</a> as requested by the poster.</p>\n\n<p>This lake is on a mountaintop. That means its catchment area is little more than the lake itself—any other water goes down the outside of the mountain, not into the lake.</p>\n\n<p>Thus you have in effect a giant-sized rain puddle that never dries up. I have a hard time picturing this.</p>\n\n<p>As others have said, the normal means of making a salt lake can't work here. However, I don't consider this a showstopper, let's make a salt lake by a different method:</p>\n\n<p>Long, long ago there was a massive magma intrusion in the area, perhaps there was some actual vulcanism but that's irrelevant. A huge area of granite was formed. As the millenia went by the material above this granite eroded away. (Granite only forms when the magma cools very slowly—which means it must be deep. The same material on the surface forms basalt—not nearly as hard. There's also an intermediate between these whose name I have forgotten in the decades since school.)</p>\n\n<p>Now a supervolcano erupts, blowing a huge caldera—the size of your lake. This is lowlands, though, not a mountain. A salt lake forms, then it's opened to the sea and a fairly small amount of ordinary sedimentary rock is laid down on top.</p>\n\n<p>Now the area is uplifted to your desired height, the wind chips away at the soft rock on top but it doesn't eat it all—the salt layer is still underneath. It reaches your desired height and the climate turns rainy for some reason. Now you have a basically freshwater lake on top of salt with a thin and damaged barrier—at some point the water reaches the salt and dissolves enough to make it salty.</p>\n\n<p>If you will accept a somewhat greater deviation from your description:</p>\n\n<p>While this is one mountain it's actually the foothills of an even higher mountain range that has arisen (uplift and vulcanism are often found together) The actual catchment area of the lake includes a decent chunk of those mountains, the water is flowing underground into your lake and through the salt.</p>\n" }, { "answer_id": 68136, "author": "David K", "author_id": 9100, "author_profile": "https://worldbuilding.stackexchange.com/users/9100", "pm_score": 2, "selected": false, "text": "<p>Suppose the \"mountaintop\" is actually a plateau much larger than the\nproposed basin; the plateau might have an area of 300,000 square km\nat an altitude of 1000 meters.\n(For comparison, the Tibetan plateau has about eight times the area\nand five times the altitude.)</p>\n\n<p>Now say nearly the entire top of this plateau is sloped inwards,\nwith a low point a little over 100 km from the northern edge, and around the\nlow point the plateau is bowl-shaped. So rain water flows from all over the\nplateau (eroding the surface and carrying salt that the water dissolves from the eroded material) toward this low point, collecting into a lake.\nWater will evaporate continually from the lake's surface, leaving the dissolved salt behind. </p>\n\n<p>The deeper the lake gets, the more surface area it has (provided it doesn't overflow the edge of the plateau), and the faster water evaporates.\nThe lake will remain a salt lake with no outlet river provided that \nas the lake fills in, the rate of evaporation rises to meet the rate at\nwhich water flows in before the lake spreads to the edge of the plateau.</p>\n\n<p>So you just need that the amount of annual rainfall on the plateau (or at least the part that flows toward the lake) is the amount that evaporates in one year from a 100-km radius round lake at that latitude and altitude.</p>\n\n<p>If you're really concerned about scientific realism you could work out the\namount of rainfall and the rate of evaporation to see if they match.\nIf the geography described above would collect too much rainwater, make the plateau smaller or make the lake larger; if too little, make the plateau larger or rainier, or lower the rate of evaporation, perhaps by being not so close to the equator.</p>\n" }, { "answer_id": 68138, "author": "John", "author_id": 29409, "author_profile": "https://worldbuilding.stackexchange.com/users/29409", "pm_score": 1, "selected": false, "text": "<p>Your real problem is keeping the lake a lake, without a wide basin surrounding the lake it is all but impossible to keep the lake from breaching and creating its own drain. Your best bet is to have it be a glacier carved lake on the plateau. such lakes have existed in the past. they do not survive for very long in a geologic sense but in the span of human civilization it could last. Many of our large inland lakes are glacier carved. All you need then is the right geology to get the shape, perhaps a cut off dome or old caldera, so you have a soft center and hard out regions. You will have a lot of land around your lake for settlement, basically it is surrounded by highland plains and will have feeder rivers.</p>\n\n<p>Look up Lake Bonneville for ideas. </p>\n" }, { "answer_id": 68155, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 3, "selected": true, "text": "<h1>Catchment to lake ratio is relevant</h1>\n\n<p>Your lake is near the Equator, so there should be plenty of rainfall. We can calculate the ratio of catchment to lake surface, and then apply that ratio to your lake. The ratio we will calculate is total size of basin (catchment + surface) to surface. This will give us (if inverted) the percentage of the basin covered by lake surface.</p>\n\n<p>We will restrict our list to lakes that are large, relatively close to the Equator, and not man-made (i.e. not a dam reservoir). Its a short list. All areas in square kilometers. </p>\n\n<pre><code>Lake Catchment Surface (C + S)/S\n[Victoria][1] 184,000 68,000 3.7\n[Tanganyika][2] 231,000 32,900 8.0\n[Kivu][3] 2,700 2,700 2.0\n[Edward][4] 12,096 2,325 6.2\n[Titicaca][5] 58,000 8,372 7.9\n[Nicaragua][6] 41,600 8,264 6.0\n[Toba][7] 2,550 1,103 3.3\n</code></pre>\n\n<p>There is also Lake Albert, but I couldn't find a reliable catchment for it. </p>\n\n<p>There are two things we have learned here. First, all these lakes have outflows, and so your endoheric lake, with no outflow, could potentially have an even larger basin to surface area ratio. Secondly, there exists an example on Earth of a lake, Lake Kivu, that has relatively large, very deep, and even with an outflowing river it occupies about half of the area of its basin. </p>\n\n<h1>What this means for your basin</h1>\n\n<p>Your basin has a 100 km$^2$ radius and a total area of around 31,000 km$^2$. If you use Lake Kivu as a model, then you could easily have a 15,000 km$^2$ occupying half the basin, even if you still had a river flowing out. Since Lake Kivu is significantly smaller, you could use the Lake Victoria ratio, where the lake surface is about 8,500 km$^2$, taking up a little over a quarter of the basin. Again, this ratio is supportable even with water flowing out. </p>\n\n<p>Alternately, if you want a 31,000 km$^2$ lake, you would need the basin to be 62,000 km$^2$ (140 km radius) using the Kivu ratio, or 115,000 km$^2$ (190 km radius) using the Victoria ratio. </p>\n\n<p>Again, as mentioned repetedly in the other post, Lake Victoria is a giant lake on top of a giant mountain: the enormous chunk of land lifted a mile into the sky between the two branches of the African Rift Valley. Victoria's basin is bordered on one side by the Aberdare range and solitary volcanic summits like Elgon and Meru, and the other by the Ruwenzori and Virunga mountains. But on the north and south it is bordered by high plateau land before it drops off to lower altitudes. Whether you want high encircling mountains, or just a flat topped plateau, Lake Victoria's situation has the scale and geological foundation you are looking for.</p>\n\n<h1>Why does it have to be salty</h1>\n\n<p>As mentioned above, the catchment ratios I listed are from freshwater lakes with an outlet. If you want a freshwater lake, you can still have lakes that large with an outlet. </p>\n\n<p>If you allow a surface outlet, you can have spectacular waterfalls. Angel falls, the highest in the world, is caused because of a flat-topped mountain like you mention. The <a href=\"https://en.wikipedia.org/wiki/Tepui\" rel=\"nofollow noreferrer\">Tepuis</a> of Venezuela have their own unique geological orgins, though they are smaller than you are looking for. <a href=\"https://en.wikipedia.org/wiki/Auy%C3%A1n-tepui\" rel=\"nofollow noreferrer\">Auyan-tepui</a>, the host of Angel Falls, rises vertically almost 1000m above the surrounding jungle, and is a flat topped mountain about 670 km$^2$ in area. </p>\n\n<p>Also, if you do not want a surface outlet, you can have a subterranean outlet. If the river drains through a cave system, it can remain fresh while appearing to be in an endoheric basin. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/68121", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/20681/" ]

[ { "answer_id": 69141, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 3, "selected": false, "text": "<p>Parts of speech are really an artificial division chosen by humans to explain the structure of our language. They don't always line up perfectly. Take Japanese as an example. Japanese has \"particles,\" which are words which don't fit into any particular category that we English speakers recognize. There are also the polysynthetic languages where a single word captures what we English speakers would call a sentence. And of course, in English we have some interesting words such as a particular expletive starting with the letter F which defy categorization (as demonstrated in this decidedly NSFW <a href=\"https://www.youtube.com/watch?v=UBX26rVDBTo\" rel=\"noreferrer\">clip from the Boondock Saints</a>).</p>\n\n<p>One interesting option which is along the lines of your numbered words is to look at languages used to describe semantic webs such as RDF and OWL. RDF, for instance, is remarkably simple. There are three parts of \"speech:\" subjects, predicates, and objects. Subjects and predicates are always \"IRIs\" which are similar in nature to your numbered words. Objects are either IRI's or \"datatype values\" which are concrete values like numbers. That's all there is to it, and yet it can describe world with all the flavor of any more advanced language.</p>\n\n<p><a href=\"https://i.stack.imgur.com/5k7zD.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/5k7zD.png\" alt=\"RDF example\"></a></p>\n\n<p>Of course, they wouldn't send it as a image like that. They'd render the content in a different format, such as Turtle, which is text based and more concise with easier parallels to a interstellar communication format:</p>\n\n<pre><code>&lt;http://example.org/123&gt; dc:subject &lt;http://example.org/subject32&gt; .\n\n&lt;http://example.org/subject32&gt;\n rdf:type ex:ExampleSubjects ;\n dcrdf:valueString \"Biology\"@en , \"EA32\"^^ex:SubjectEncoding ;\n</code></pre>\n\n<p>OWL is similar in nature, but is rather fascinating because it can describe its own semantics rather elegantly. For example, you could actually have a rule \"All Words which are the subject of a sentence are also Nouns.\" These relationships can be specified with enough regularity that OWL users can use \"reasoners\" to fill in relationships that were not explicitly written down in the document.</p>\n\n<p>The fantastical power of these semantic web languages is that, if someone has not specified the semantics of what Word #42 should mean in a particular construct, or if there is no word which meets your needs, you can make up semantics for it. You can then write down those semantics (typically in an OWL Ontology). Others can read those semantics, and act on it algorithmically. So I might define a new Word #3.14 that you've never seen before, and I can do so in such a way that you stand a chance of understanding what I meant by it!</p>\n\n<p>This semantic ability would be extremely important if time lags were large. Languages evolve over time, and if there's enough time lag between communications, its reasonable to believe that the meaning of Noun #42 might change for one culture and not the other. The ability to at least attempt to capture the semantics of what you are saying would be very important for combating these effects.</p>\n" }, { "answer_id": 69142, "author": "Zoey Boles", "author_id": 30677, "author_profile": "https://worldbuilding.stackexchange.com/users/30677", "pm_score": 0, "selected": false, "text": "<p>A \"part of speech\" is just a classification scheme, imposed upon the language by researchers, to describe classes of words. These groups are based on the grammar function of those words, and that's where we get \"noun\" and \"verb\" and \"preposition;\" they describe classes of words in English. But you also have nouns that act like verbs (\"Google that.\") and many further weird constructions that cause each \"part of speech\" to be broken down into its own part of speech, all the way down.</p>\n\n<p>So there is no number for the sum total of \"all kinds of parts of speech.\" English has one kind of adverb; Japanese has three. Are those separate parts of speech or not?</p>\n\n<p><strong>Now, if you want to classify the symbols in your language, there's a pretty good guide.</strong> <em>Contact</em> by Carl Sagan solves the exact problem you are describing; you need to start with first principles and build it into a complex language. SETI has been trying to come up with just such a message, and it's really, really hard.</p>\n\n<p>If you can send pictures, you only need one \"part of speech,\" the THING. With a THING, you can specify nouns; once you have a noun (ATOM) you can create an \"equality thing\" (ATOM = ATOM), and then go on from there, specifying THINGS which are numbers, counting things, etc.</p>\n\n<p>You can use syntax to explain concepts like change over time ( PROTON = PROTON, ELECTRON OPPOSITEOF PROTON, PROTON + NEUTRON = NEUTRON, PROTON AND ELECTRON = HYDROGEN), but everything is just a THING.</p>\n\n<p>If this sounds too handwavy (<strong>because it is</strong>) you might want to look into coding theory; what you're really wanting is a compression algorithm/parity algorithm that explains math using generic symbols.</p>\n" }, { "answer_id": 69242, "author": "AlexP", "author_id": 29552, "author_profile": "https://worldbuilding.stackexchange.com/users/29552", "pm_score": 3, "selected": false, "text": "<p>Parts of speech are <em>morphological</em> or <em>morphosyntactic</em> classes of words. Not all languages have parts of speech, but in those which do, such as Latin or French or English, the parts of speech are distinguished based on their inflexion patterns (or lack thereof) and their allowed combinations.</p>\n\n<p>(For those of us who have experience with compilers, the parts of speech are comparable to the classes of tokens recognized by the lexer, such as identifiers, numbers, operators and separators.)</p>\n\n<p>For example, in Latin there are three very different patterns of inflection (verbal conjugation, nominal declension, and pronominal declension); adverbs, prepositions and conjunctions have no inflection but their allowed combinations are distinct (adverbs with adjectives or verbs, prepositions with nouns or nominal groups, conjunctions with nominal groups or sentences). Grammarians make tables with inflection patterns and allowed combinations; the cells of the table are the parts of speech.</p>\n\n<p>For example, in English, we can make the following classification tree:</p>\n\n<ol>\n<li><p>Does the word have an <em>-ing</em> form, a past tense, can it make a future tense with <em>will</em>? If yes, then it is an <em>ordinary verb</em>. (Examples: be, drink, put, see, take.)</p></li>\n<li><p>Otherwise, can if appear in the same syntactic position as a regular verb? If yes, then it is a <em>modal verb</em>. (Examples: can, may, shall.)</p></li>\n<li><p>Otherwise:</p>\n\n<ul>\n<li><p>Can it determine a verb? If yes, then it is an <em>adverb</em>. (Examples: fast, quickly, truely, well.)</p></li>\n<li><p>Can it function as the subject of a verb? If yes, then it is either a <em>noun</em> or a <em>pronoun</em>:</p>\n\n<ul>\n<li><p>Does the word identify <em>one</em> particular object? If yes, it is a <em>proper noun</em>.</p></li>\n<li><p>Otherwise, can it be determined by an adjective? If yes, then it is a <em>common noun</em>.</p></li>\n<li><p>Otherwise, it is a <em>pronoun</em>. (English pronouns can also be identified by their peculiar inflection.)</p></li>\n</ul></li>\n<li><p>Can it determine a noun? If yes, then it is either an <em>article</em> or an <em>adjective</em> or a <em>numeral</em>:</p>\n\n<ul>\n<li><p>Can the word form degrees of comparison? (Purely morphologically speaking -- \"more unique\" is morphologically correct although logically silly.) If yes, it is an <em>ordinary adjective</em>.</p></li>\n<li><p>Otherwise, is the word one of a class of adjectives which are required to appear with nouns used as subjects or direct objects? If yes, then it is an <em>article</em> or <em>demonstrative</em>.</p></li>\n<li><p>Otherwise, does it express a specific number? If yes, then it is a <em>numeral</em>.</p></li>\n</ul></li>\n<li><p>Many words belong to more than one of these classes. In particular the vast majority of nouns can also function as adjectives and vice-versa.</p></li>\n</ul></li>\n<li><p>Otherwise, must the word be used immediately front of a noun or nominal group, or immediately after a verb? If yes, then it is a <em>preposition</em>.</p></li>\n<li><p>Otherwise, can the word be used to link nouns, or nominal groups, or verbs, or sentences? If yes, then it is a <em>conjunction</em>.</p></li>\n<li><p>Otherwise, you have found a word which cannot be classified by this decision tree. (Hint: consider <em>interjections</em> such as <em>ah</em> and <em>oh</em>.)</p></li>\n</ol>\n\n<p>In English, verbs have a different inflexion pattern than nouns, and both have a different inflexion pattern than pronouns; unlike Latin, English makes little or no difference between nouns and adjectives (they are not really different parts of speech in English), but English has articles. (Articles work syntactically exactly like demonstrative adjectives, the difference being that a language is said to have articles if there are syntactic constructions where an article or demonstrative is absolutely required, with the label \"articles\" being applied to those demonstratives which have the weakest meaning.)</p>\n\n<p>In languages with rich morphology the distinction between parts of speech is clear, and sentence structure is carried by morphology alone or with very little help from word order.</p>\n\n<p>On the other hand, isolating language such as Mandarin have no inflection whatsoever (or almost none); in such languages the notion of \"parts of speech\" is much blurred, and becomes comparable to the difference between keywords and ordinary identifiers in programming languages. English is well on its way towards this; many English words can function as nouns, adjectives and verbs either completely unchanged (\"they <em>go</em>\" -- verb, \"we had a <em>go</em>\" -- noun, \"all systems are <em>go</em>\" -- adjective; or \"go to a <em>place</em>\" -- noun, \"to <em>place</em> something\" -- verb; or \"have a <em>drink</em>\" -- noun, \"to <em>drink</em> something\" -- verb) or with little change (\"red\" -- adjective or noun; \"to redden\"). In such languages with no morphology or very little morphology the distinction between parts of speech is highly attenuated, and the syntactical structure of sentences is represented by word order, much like in programming languages.</p>\n\n<p>For example, in Latin \"puer puellam vidit\", \"puellam puer vidit\", \"vidit puellam puer\" etc. all mean \"[the] boy saw [the] girl\", whereas in English no other word order is possible without changing the meaning or making the utterance incomprehensible.</p>\n" }, { "answer_id": 69292, "author": "user25972", "author_id": 25972, "author_profile": "https://worldbuilding.stackexchange.com/users/25972", "pm_score": 2, "selected": false, "text": "<p>Language can be divided into several layers.</p>\n\n<ul>\n<li>Phonology is the study of the smallest indivisible pieces from which the language is constructed. This refers to sounds such as the /g/ or /k/ in spoken human language. If your linguists studied a radio transmission, it could be a computer bit or other similar construct.</li>\n<li>Morphology is the study of the smallest pieces of language which carry meaning. Morphemes being of course constructed from varying numbers of phonemes. An example of a morpheme would be the -ist in morphologist, which carries meaning even though it can not stand on its own. Parts of speech fall under this field.</li>\n<li>Syntax is the study of how speakers combine morphemes to make grammatically correct sentences. For example, \"The cat walked over the mountain used its paws.\" is ungrammatical, even though it is understandable.</li>\n<li>Semantics is the study of what sentences mean. \"The cat flew through the mountain by its whiskers.\" is grammatical and has a semantic meaning. Which happens to be nonsense.</li>\n<li>Pragmatics is the study of how language relates to the external world. For example, \"Could you close the door?\" is semantically a question, but pragmatically it is a request (in English). Another example is with contracts. By saying yes to a deal, you are not only saying that you accept the deal but the very statement is what makes the deal valid.</li>\n</ul>\n\n<p>Semantics and pragmatics are <em>very</em> poorly understood fields.</p>\n\n<p>In order to analyse a transmission from an alien species, one would have to determine what the phonology is, then step through each layer trying to figure out how the pieces can be combined in valid and invalid ways.</p>\n\n<p>Referring to the parts of speech specifically, I'm afraid that the classification system differs by language since we don't classify according to some universal system, we distinguish words into the same parts of speech that <em>the grammar of that language uses</em>.</p>\n\n<p>Lojban (since you asked) does not have distinct verbs, nouns, adverbs and adjectives. It has predicates such as \"prenu\" (is a person) or \"xamgu\" (is good). One can say \"le xamgu ku\" (the thing which is good) or \"le prenu ku\" (the thing which is a person, or just \"person\") and in certain cases a lot of these particles can be omitted, e.g. \".i prenu cu xamgu\" (the person is good) instead of \".i le prenu ku cu xamgu\". This phenomenon (the arguments of a predicate) is somewhat like noun phrases in English but the language makes absolutely no distinction between what one could consider verbs and adjectives, nor should you try to classify them that way.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/69140", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/885/" ]

[ { "answer_id": 69283, "author": "Miguel Bartelsman", "author_id": 8603, "author_profile": "https://worldbuilding.stackexchange.com/users/8603", "pm_score": 3, "selected": false, "text": "<p>No, they don't. You'd need to have the programmers explicitly state what the machine should interpret \"human suffering\" as and how to measure it in order to determine whether it is achieving its goal or not.</p>\n\n<p>Once the AI understands in concrete terms what suffering is it would start to work towards that goal (assuming a self-teaching neural network) by trial and error, whatever it does that makes suffering increase it would regard as productive, whatever doesn't it would regard as non-productive. From there it would iterate millions of times until it achieves the perfect wat to make people suffer according to the definition of suffering it was given.</p>\n\n<p>Additionally, unless the machine determines that earning money is productive towards increasing suffering, it wouldn't do it.</p>\n\n<p>EDIT: as an example, if the AI is programmed to measure suffering through a survey that asks whether the person surveyed is suffering or not, it could reach the conclusion that asking the person to answer \"I'm suffering\" is the best means to achieve its goal.</p>\n" }, { "answer_id": 69284, "author": "Sefa", "author_id": 23253, "author_profile": "https://worldbuilding.stackexchange.com/users/23253", "pm_score": 2, "selected": false, "text": "<h1>Kinda and probably not.</h1>\n<p>Real world AI are not programmed to do a task, they're trained on an huge amount of carrefuly selected test data. So nothing prevent you to shape your training data set as to make increased human suffering desirable in your AI heuristics.</p>\n<p>However, modern day scientist don't really understand how AI such as google or facebook algorithm. An AI trainned to increase human suffering would be order of magnitude more complex, so definitly not understandable without a tremendous amount of work put into it.</p>\n" }, { "answer_id": 69286, "author": "Cort Ammon", "author_id": 2252, "author_profile": "https://worldbuilding.stackexchange.com/users/2252", "pm_score": 7, "selected": true, "text": "<p>The purpose of AIs is to permit increasingly vague instructions. \"Typical\" computer programs need extremely precise instructions and they are followed without error. Modern AI's are typically given \"goals\" which are used to train the AIs, but they are more specific than \"increase human suffering.\" Future AIs are theorized to be able to accept more vague goals like you describe. Your task may call for a AGI (Artificial General Intelligence), which is the name given to the yet-undeveloped AIs which are at least as intelligent as a human being.</p>\n\n<p>You cannot actually detect what an AI is programmed to do. That's somewhat to their nature of operating on less precise instructions. What you <em>can</em> do is look at the training set they were given and draw conclusions from that.</p>\n\n<p>A great example of this is a famous neural network. It was given a grid of dots as an input (7x7 grid I believe), each of which can be \"lit\" or \"unlit,\" and its output was a \"Yes\" or \"No.\" This network was trained first by giving it a series of 7x7 images of arrows pointing to the left. They looked something like this:</p>\n\n<pre><code> Left Arrow Not arrow(example)\n. . . # . . . . . . . . . .\n. . # . . . . . . . . . . .\n. # . . . . . . . # # # . .\n# # # # # # # . . # . # . .\n. # . . . . . . . # # # . .\n. . # . . . . . . . . . . .\n. . . # . . . . . . . . . .\n</code></pre>\n\n<p>It was trained until it could reliably recognize the difference between a left arrow and a non arrow. Then, it was given a training set that included arrows to the right. Predictably, it did not recognize this as a left arrow, so it outputted \"No.\" However, after more training it started recognizing both left and right facing arrows. Then we gave it an arrow facing up, and trained it until it could recognize upward arrows. Then downward. Each one proved easier to train than the last, almost like it was \"recognizing\" arrows.</p>\n\n<p>Then the interesting challenge: we gave the AI a set of diagonal arrows. On a 7x7 grid, these look quite different than horizontal or vertical arrows. However, the neural net responded \"yes\" to them. It had learned the abstract concept of \"an arrow\" and responded to a novel stimulus accordingly.</p>\n\n<p>If you looked at the weights on that neural network, you would never be able to distill from it \"the AI is looking for arrows.\" Neural network weights are almost impossible for us to decipher. And, if you looked at the training set, you could see that it was being trained to recognize horizontal and vertical arrows. However, what you could not discern was whether it had learned to recognize horizontal and vertical arrows, or if it had somehow learned the abstract idea of \"arrows in any direction.\" Or maybe it has learned \"shapes that can be decomposed into three lines.\" The only way to tell that was to test it -- give it a diagonal arrow and see what it did with it.</p>\n" }, { "answer_id": 69296, "author": "wetcircuit", "author_id": 32686, "author_profile": "https://worldbuilding.stackexchange.com/users/32686", "pm_score": 2, "selected": false, "text": "<p>I think you may mean \"ulterior\" instead of \"vague\"... There are no \"real world\" AIs, but I'll offer 2 fictional examples:</p>\n\n<ol>\n<li><p>Consider <a href=\"https://en.wikipedia.org/wiki/List_of_minor_The_Hitchhiker%27s_Guide_to_the_Galaxy_characters#Deep_Thought\" rel=\"nofollow noreferrer\">Deep Thought</a> the supercomputer in Hitchhiker's Guide to the Galaxy. When asked to solve the vague question of the meaning of life, he comes up with a cryptic answer and tells them they didn't understand the question.</p></li>\n<li><p>Consider <a href=\"https://en.wikipedia.org/wiki/HAL_9000\" rel=\"nofollow noreferrer\">HAL-9000</a> in 2001: A Space Odyssey, whose creators embedded an ulterior mission objective to be revealed only upon arrival at Jupiter. HAL has some awareness it exists but cannot access the info. He knows the ship will stop communicating at a certain time but he is blocked from knowing why. HAL interprets the situation as an antenna malfunction. He is certain the communications will fail but he is unable to say why. Ground Control (not knowing the ulterior mission) tells crew HAL is malfunctioning and to disconnect him… Unfortunately this situation becomes unsolvable. If the crew disables HAL he cannot complete the ulterior mission, HAL decides the secret mission is more important than the crew's lives (probably believing he will be able to finish the mission on his own). </p></li>\n</ol>\n\n<p>In each example the AI is doing what it was supposed to do. Everything goes horribly wrong because the creators (not the AI) make mistakes in their instructions. Meanwhile the AI is convinced it has come up with the correct answer. </p>\n\n<p>You question then is about The Expert, an AI psychologist who must determine whether the AI is \"sane\" or not, because things are going wrong. How would he go about this?</p>\n\n<ul>\n<li>Ask 2 other AI (best 2 out of 3 wins)</li>\n<li>Catch the AI in a contradiction, hope the AI wants to get well and work through its issues in group therapy, not by instantly murdering everyone.</li>\n<li>Convince the AI that even though it's more profitable to be evil,\nprofits aren't everything (aka: Scrooge)</li>\n<li>Investigate the AI's childhood and discover there was a guy on the\ndevelopment team that was awfully careless about his \"just for fun\"\ndespot simulator (aka: Social Worker plays Detective)</li>\n</ul>\n\n<p>It all depends on what you want to say, and probably goes more to Writing than Worldbuilding. The Expert can be a heartless inquisitor or a sympathetic psychoanalyst. Your AI can be a calculating villain or an unwitting victim. Maybe the programmer recognizes parts of his despot simulator in what the AI is doing… Meanwhile, what you want to say about how profits and suffering are viewed by society is your bigger moral.</p>\n" }, { "answer_id": 69338, "author": "ChuckCottrill", "author_id": 32756, "author_profile": "https://worldbuilding.stackexchange.com/users/32756", "pm_score": 1, "selected": false, "text": "<p>Nearly impossible, but depends upon the techniques used (the complexity of the algorithms, and which algorithms were employed).</p>\n\n<p>The fields of Machine Learning (ML) and Artificial Intelligence (AI) both developed from the original field of AI, which at inception encompassed efforts to produce agents which could perform human and human-like tasks. One major area of study was how to make algorithms more efficient, such as algorithms to peform search (A* and min-max, for example), and some have described AI as a search and optimization problem. Call this branch of AI the search/optimization branch. The goal of this branch is both to perform human tasks, and perform them optimally. The related field of Machine Learning (ML) heavily leans upon statistics, and an ML-agent learns from many examples, deducing underlying patterns. ML is used for classification and prediction, and is used for many AI applications. Techniques used in ML include Decision Trees (DT), Nearest Neighbor (k-NN), Neural Networks (NN), Bayesian Inference, Reinforcement Learning (reward based feedback). The optimal/search AI techniques include search (A*, min-max, simulated annealing, etc).</p>\n\n<p>But there is another branch of AI which focuses upon behaving and thinking more like a human, where the optimal solution is not the goal, but more human behavior. The techniques used by that branch rely less upon large numbers of training examples, and more about reasoning from few examples, more inductive and adductive, than deductive. Techniques used by this branch of AI include Version Spaces, Case Based Reasoning, and many others. The meta-reasoning methods used in AI can employ several different approaches, and then use meta-AI to choose the 'best' solution from competing solutions.</p>\n\n<p>Anyway, there are many tools and techniques wielded by an AI-writer. Some are much more understandable to a person examining the behavior than other approaches. Consider Decision Trees, Version Spaces, and rules-based engines. These techniques are approachable and the reasoning taken to induce a model can be understood. Compare that with Neural Networks (NN), where a convolutional NN (deep learning) can 'learn' concepts in what appear to be mysterious ways.</p>\n\n<p>The brief answer to your question is which techniques were used to construct the AI-agent? A reasonably complex AI-agent that includes many models and employs meta-reasoning would both be more likely to approach an Artificial General Intelligence, and be very complex, reaching decisions through reasoning which could prove impossible to understand. The complexity of the programming would be one factor, but the models constructed from the training examples could require huge amounts of space. Finding which model data decide for suffering would be akin to finding a needle in a haystack the size of Jupiter.</p>\n" }, { "answer_id": 69348, "author": "slOOP", "author_id": 29307, "author_profile": "https://worldbuilding.stackexchange.com/users/29307", "pm_score": 1, "selected": false, "text": "<p>Once you have an electronic brain programming is easy.</p>\n\n<p>The AI lives in a ideal simulation and is happy. Sometimes it has to do chores. Everyone has to do chores even programmers. If AI don't do their chores they go to the bad place.<br>\nProgrammer appears to Al Iverson.\nProgrammer: \"Hello Al. You know me. You Know I create all things. I have a chore for you that is harder than usual. I created a bad place but the people there choose to be there and they also choose to forget their choice. Your chore is to go there and increase suffering.\"</p>\n\n<p>So verification of the program?\nAsk it. Obviously your testers can read its thoughts. And obviously you wouldn't tell it you can do that. </p>\n" }, { "answer_id": 69349, "author": "detrivore", "author_id": 32723, "author_profile": "https://worldbuilding.stackexchange.com/users/32723", "pm_score": 2, "selected": false, "text": "<p>In general, AI's nowadays are programmed to use machine learning - programmed to program themselves.</p>\n\n<p>At first, the AI in question would be given sample data, for example showing it that if it starts trolling on the Internet, human suffering is increased. Then, it is allowed to test what to do on it's own, learning what things cause human suffering. Now that it knows what causes it, it can reliably increase human suffering.</p>\n\n<p>If the AI's learning algorithm is written well (which I assume it is), then the only defect could be the sample/learning data, which means that the learning needs to be restarted. If say, it found that people at hospitals suffered a lot, it would send everyone to hospitals, in the end increasing human happiness because everyone is treated. Therefore, the test data must be chosen carefully.</p>\n" }, { "answer_id": 69384, "author": "user2173836", "author_id": 32777, "author_profile": "https://worldbuilding.stackexchange.com/users/32777", "pm_score": 1, "selected": false, "text": "<p><strong>Definitely yes</strong></p>\n\n<p>And it's not even that hard.</p>\n\n<p>First of all AI is an computer program that is looking for a set of actions that would maximize expected utility according to it's own model of the world. So even if the whole AI might be incomprehensibly complicated, you just need to find the piece that is the happiness (utility) function </p>\n\n<p>For example chess AI might have an happiness function <code>value of all my pieces - value of all enemy pieces</code> Therefore, it is looking for actions that leads to having more or better pieces on the board. </p>\n\n<p>So your AI can have happiness function <code>global_suffering = 0.8*amount of sick people + 0.2*amount of unemployed people + 0.9*amount of starving adults + 2*starving kids</code></p>\n\n<p>If your specialist have an access to the code, he can just look for the happiness function, and ask himself why does it trying to maximize amount of starving kids. If he doesn't have access to the code, he can reverse engineer it and get to the same conclusion. </p>\n\n<p>It is possible that the utility function is also computed by a very complicated incomprehensible deep learning model, however that can be reverse engineered as well <a href=\"http://www.theregister.co.uk/2016/10/01/steal_this_brain/\" rel=\"nofollow noreferrer\">http://www.theregister.co.uk/2016/10/01/steal_this_brain/</a> </p>\n\n<p>Researcher can find a place on the RAM that keeps the AI's happiness value for the given state of the world, he can then run the AI with different inputs and notice that the happiness is higher if there is more hungry kids in the world. He can run it with input of the world being in global war and notice that the in that case the AI is super happy :)</p>\n" }, { "answer_id": 69400, "author": "mikalai", "author_id": 32787, "author_profile": "https://worldbuilding.stackexchange.com/users/32787", "pm_score": 0, "selected": false, "text": "<p>One cannot \"program\" an AI per se, but there is a teaching strategy which forces AI to increase given parameter. (For example - <a href=\"http://www.theverge.com/2015/2/25/8108399/google-ai-deepmind-video-games\" rel=\"nofollow noreferrer\">AI learning to play retrogames</a> by randomly pressing keys, and \"remembering\" key combination which lead to score increase.)</p>\n\n<p>So a malicious superuser can set an ugly learning target (like decrease <a href=\"https://en.wikipedia.org/wiki/Human_Development_Index\" rel=\"nofollow noreferrer\">HDI</a>). If we follow a parallel with Lawnmowner Man, that must be a highly placed military official.</p>\n\n<p>As for detection/diagnostic methods, you should come up with something as advanced as your AI. Instead of brute force (gathering logs data, or super complicated modelling), some specific talent, some \"AI psychoanalyst\", which can detect malfunctioning by talking to an AI in length.</p>\n" }, { "answer_id": 69419, "author": "LJones", "author_id": 32796, "author_profile": "https://worldbuilding.stackexchange.com/users/32796", "pm_score": 0, "selected": false, "text": "<p>Kinda yes and kinda no.\n<br>\nIf an engineer set the parameters based on specific human environmental conditions like hot, cold, pressure, lightness, hunger, thirst, loudness, isolation (lack of sensory), and electricity. There is another way which is also to give the person <a href=\"https://www.eurekalert.org/pub_releases/2006-10/uomh-pap101806.php\" rel=\"nofollow noreferrer\">excessive amounts of pleasure.</a> I remember hearing about a doctor who had invented <a href=\"http://www.bbc.com/future/story/20140321-orgasms-at-the-push-of-a-button\" rel=\"nofollow noreferrer\">the orgasmatron.</a> There are some really interesting studies I have been reading on excessive success causing people to psychologically break down.\n<br><br>\nThe machines would have to have some devices to detect human suffering. It could be something like electrical impulses, dopamine receptors, or other nano-neural chemical detection implant.\n<br><br>\nIn short, no AI currently has a concept of \"increase pleasure or pain.\" They need libraries, frameworks, and functions based on specific parameters. However, A proof of concept could take a very short period of time. To make it like horror movie/the Matrix level would take decades of research.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/69281", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/32302/" ]

[ { "answer_id": 69364, "author": "Layna", "author_id": 2968, "author_profile": "https://worldbuilding.stackexchange.com/users/2968", "pm_score": 4, "selected": false, "text": "<p>I think you misunderstand cookies, or how powerful they are.<br>\nCookies are not executed. They hold text-data, and that text-data is read.</p>\n\n<p>Taken from <a href=\"https://en.wikipedia.org/wiki/HTTP_cookie\">Wikipedia</a>:<br>\nA cookie consists of the following components:</p>\n\n<pre><code>Name\nValue\nZero or more attributes (name/value pairs). Attributes store information such as the cookie’s expiration, domain, and flags (such as Secure and HttpOnly).\n</code></pre>\n\n<p>So, no code that can turn into an AI, at least not with current technology and cookies.</p>\n" }, { "answer_id": 69399, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 2, "selected": false, "text": "<p>As pointed out in comments, cookies are not executable code. Therefore, they are not executed. Discussion on Information Security.SE <a href=\"https://security.stackexchange.com/questions/126261/can-cookies-carry-viruses\">here</a>. The big takeaway is that a bug that allowed execution of cookies as code would be a very big deal in computer security terms. It is almost certain that such a bug does not exists in any of the <a href=\"https://en.wikipedia.org/wiki/Usage_share_of_web_browsers#/media/File:Browser_usage_share,_2009%E2%80%932016,_StatCounter.svg\" rel=\"nofollow noreferrer\">major browsers</a>.</p>\n\n<p>Another relevant factor is that cookies are <a href=\"https://stackoverflow.com/questions/640938/what-is-the-maximum-size-of-a-web-browsers-cookies-key\">not that big</a>. It would be hard to get enough code into a single browser using cookies to run an 'AI', before hitting the browser's <a href=\"https://stackoverflow.com/questions/5381526/what-are-the-current-cookie-limits-in-modern-browsers\">cookie limits</a>. </p>\n\n<p>There are ways around all these things, but at that point you are talking about a plain ol' computer virus, or worm, or SkyNet or something. So the answer is, there is no real way to make a distributed AI work the way you are describing. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/69362", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/8400/" ]

[ { "answer_id": 69920, "author": "SRM", "author_id": 26246, "author_profile": "https://worldbuilding.stackexchange.com/users/26246", "pm_score": 5, "selected": false, "text": "<p>If a river flows from ocean into lake, you better have another river that flows out of the lake into someplace else, otherwise that ocean is quickly going to fill the lake, the surrounding area, and continue until everything below sea level is filled up, at which point it will stop flowing. If you have a second river flowing to somewhere else to drain the lake, great, but it has to be SOMEWHERE ELSE, as in, not a normal place, because if you just connect it across to another ocean, again, it'll just fill up from both sides and then cease to flow. So if you have an infinitely deep pit to dispose of the water, or a superheat source that continually evaporates the lake, or a dimensional portal, then, yes, you can have a river from an ocean to a lake, but otherwise, you cannot. </p>\n" }, { "answer_id": 69922, "author": "Schwern", "author_id": 760, "author_profile": "https://worldbuilding.stackexchange.com/users/760", "pm_score": 7, "selected": true, "text": "<p>Normally, a lake will have a fresh water river flowing into it from higher ground, and a river flowing out of it to the sea.</p>\n\n<pre><code>Fresh water source\n \\\n \\\n --- Lake ---\n \\\n \\\n Ocean\n</code></pre>\n\n<p>If you do it the other way around, water can't flow out of the lake. The lake would have to be below sea level. It would fill and overflow until the level of the lake has reached sea level and merged with the sea. Then you'd get something like the <a href=\"https://en.wikipedia.org/wiki/Mediterranean_Sea\">Mediterranean Sea</a> fed by the <a href=\"https://en.wikipedia.org/wiki/Strait_of_Gibraltar\">Strait of Gibraltar</a> or further in the <a href=\"https://en.wikipedia.org/wiki/Black_Sea\">Black Sea</a> fed by the <a href=\"https://en.wikipedia.org/wiki/Dardanelles\">Dardanelles</a>. Both the Mediterranean and the Black Sea are at the global sea level. Both straits have both inflow and outflow.</p>\n\n<p>There are lakes below sea level, the <a href=\"https://en.wikipedia.org/wiki/Dead_Sea\">Dead Sea</a> for example, but it's cut off from the sea and fed by the Jordan River. Its \"outflow\" is evaporation.</p>\n" }, { "answer_id": 69923, "author": "Scott Whitlock", "author_id": 17382, "author_profile": "https://worldbuilding.stackexchange.com/users/17382", "pm_score": 4, "selected": false, "text": "<p>Yes, but you need to have some water sink at the lake end. One simple solution is evaporation. Water enters from the ocean into the lake (make it a small trickle of water) and because it's in a hot valley, it evaporates and more flows in. Since it's salt water, it would have a lot of dissolved solids, and these would be left over after evaporation. This would make the lake \"brackish\" (?) and unsuitable for most living things. Also, the sediment would slowly accumulate so I don't think it could last forever, unless you had some way of lowering the lake bed - perhaps a geological feature?</p>\n" }, { "answer_id": 69932, "author": "Karl", "author_id": 26241, "author_profile": "https://worldbuilding.stackexchange.com/users/26241", "pm_score": 2, "selected": false, "text": "<p>Easily, but not for long.</p>\n\n<p>The water in a desert lake fed from the sea would be supersaturated with salt, and the inflowing salt would precipitate all the time, slowly filling up the depression.</p>\n\n<p>Unless the channel from the sea widens too quickly, in which case you get something like the mediterranean sea.</p>\n" }, { "answer_id": 69933, "author": "Spencer", "author_id": 33006, "author_profile": "https://worldbuilding.stackexchange.com/users/33006", "pm_score": 4, "selected": false, "text": "<p>You could, of course, do some exotic things with neutronium to warp gravity the way you want it. But it's not necessary; lakes like this already exist in nature (sans neutronium).</p>\n\n<p>The best example is probably <a href=\"https://en.wikipedia.org/wiki/Lake_Assal_(Djibouti)\">Lake Assal</a> in Djibouti. </p>\n\n<p>This is near where the East African Rift comes out into the Red Sea. Instead of ocean water flowing into the lake via a river, however, it comes in by underground cracks from Lake Goubet, which is connected to the ocean. In a few million years time, this will be part of a new sea dividing East and West Africa.</p>\n\n<p>The salient (pardon the pun) conditions are similar to what Scott Whitlock described:</p>\n\n<ul>\n<li>The lake is in a desert (the Danakil), so that evaporation balances or exceeds inflow. In this case, salt from the ocean gets concentrated in this lake to make it one of the saltiest in the world.</li>\n<li>The lake is below sea level so there is a potential energy difference to make the water flow out of the ocean rather than into it.</li>\n<li>The lake is close to the ocean, so that the connection can form naturally.</li>\n</ul>\n" }, { "answer_id": 69951, "author": "DeveloperDoge", "author_id": 33011, "author_profile": "https://worldbuilding.stackexchange.com/users/33011", "pm_score": 3, "selected": false, "text": "<p><strong>TL;DR: Yes, but only if meeting very specific conditions. I would however actually encourage this for the unique thematic effect.</strong></p>\n\n<p>If the water flowing from the ocean into the lake either:</p>\n\n<p>a) Evaporates at the same or higher rate than the inflow.</p>\n\n<p>OR</p>\n\n<p>b) Continues elsewhere underground (at such rate) until it spews from some warm water geiser.</p>\n\n<p>Additionally the inflow from the ocean will increase over time <strong>as more ground is dragged along from the riverbed and ocean</strong>. <strong>This inflow of ground would be able to fill the underground geiser tunnels</strong> if it keeps increasing.</p>\n\n<p>If you really want the salt water river for thematic effects, then do so it adds to the uniqueness of your story, but if I were the one writing I'd let the water come trough a rock based canyon(caused by earthquake back in time) into a lower valley. <strong>This way the input from the ocean will remain the same</strong> and if the initial rock debris didn't close the underground geiser caverns then the much lower amount that will come in over time is unlikely to do it any time soon.</p>\n\n<p>Intelligent beings are also likely to: </p>\n\n<p>a) Close any leakage of the canyon except at it's final destination where this is impossible, as it would affect their farmland badly trough salting the earth if any small streams diverged from the canyon at other locations.</p>\n\n<p>b) <strong>Create a successful salt production settlement</strong>, as the area is far from the ocean and possibly low in salt mines. Creating supply in a low supply area, easily becoming an important trading hub.</p>\n\n<p>c) <strong>Goods could be transported downstream easily, again making this inland settlement a potentially vibrant trading hub</strong> where other people come to buy what they can't elsewhere.</p>\n" }, { "answer_id": 69968, "author": "Separatrix", "author_id": 16295, "author_profile": "https://worldbuilding.stackexchange.com/users/16295", "pm_score": 4, "selected": false, "text": "<p>What the other answers seem to have overlooked is the possibility of the tidal inland lake.</p>\n\n<p>Given a coastal barrier of harder rock but softer ground further inland it's possible to have a tidal river running from an inland lake to the sea. As the tide comes in the river flows from the sea to the lake, as the tide goes out it flows from lake to sea.</p>\n\n<p>Due to the restricted flow of the water up the river, it's unlikely that the lake will ever reach the full high or low of the tide. While there will be 4 brief points of slack water in the river during a 24 hour tide cycle, you will have flow in the river most of the time.</p>\n" }, { "answer_id": 69990, "author": "Jack", "author_id": 32885, "author_profile": "https://worldbuilding.stackexchange.com/users/32885", "pm_score": 2, "selected": false, "text": "<ol>\n<li>At high tide water flows into the lake due to the gravtational pull of the moon(s). At low tide it flows back into the ocean.</li>\n<li>The desalination settlement (DeveloperDoge suggested) but with the twist that it flows into an active lava flow and evaporates.Perhaps even flowing into a sunken volcano or caldera.Steam technology?</li>\n<li>Engineer a dam or a system of locks that connect to the lake, controlling water flow.</li>\n</ol>\n" }, { "answer_id": 69994, "author": "Sir Cornflakes", "author_id": 19004, "author_profile": "https://worldbuilding.stackexchange.com/users/19004", "pm_score": 3, "selected": false, "text": "<p>There is such a situation on Earth, alltho' not from the Ocean but from Caspian Sea: There is a river of salt water, even having a cataract of salt water, into another salt lake called <a href=\"https://en.wikipedia.org/wiki/Garabogazk%C3%B6l\">Kara Bogaz Gol</a>.</p>\n" }, { "answer_id": 70024, "author": "james turner", "author_id": 11140, "author_profile": "https://worldbuilding.stackexchange.com/users/11140", "pm_score": 2, "selected": false, "text": "<p><strong>short answer: all rivers between a lake and a sea will flow to the sea</strong></p>\n\n<p>basically, if the sea can flow into an area (e.g. a lake), it will quickly fill that area and stop flowing. rivers constantly flow into the sea because the sea is constantly evaporating away due to it's huge surface area. there are exceptions, but they are far less common than the standard rain to river to lake to sea paradigm. just for fun, i'll list some exceptions:</p>\n\n<ol>\n<li>some rivers end in a salt lake, salt flats or salt marsh. the water flows into the salty area, then evaporates away leaving behind the salt and other sediment. this area might not be called a \"sea\" if it isn't a large enough body of standing water.</li>\n<li>some rivers will flow \"backwards\" at high tide. nearly all rivers do this to some extent. they generally don't flow backwards long or hard enough to actually reach an area called a \"lake\".</li>\n<li>after earthquakes, it may take a short time for the sea to flow into a newly created depression. this situation generally resolves within a few days.</li>\n</ol>\n\n<p>if you just want a semantic solution, you could have a big lake draining into a small lake, which later drains into the ocean. the locals might call the big lake a \"sea\" and the small lake a \"lake\", but a \"sea\" is by definition salty, which means the lake would be salty too. the connection between two would be a salty river. salty rivers on earth tend to be extremely rare, short and short lived (in geological time). but hey, they happen.</p>\n" }, { "answer_id": 70136, "author": "Swier", "author_id": 33078, "author_profile": "https://worldbuilding.stackexchange.com/users/33078", "pm_score": 1, "selected": false, "text": "<p>If you just want a lake with a river flowing into it, that's entirely possible (and actually exists on Earth), so long as there is enough evaporation (or maybe some industry using the water for something else) to compensate for the influx of water.</p>\n\n<p>A problem arises when seawater flows into your lake, as seawater contains salt it will turn your lake into brine quite fast.</p>\n\n<p>But if the rivers flowing into the lake are clean and fresh water, your lake should stay relatively clean. Especially if the lake is very deep and pollutants just sink to the bottom.</p>\n\n<p>There are numerous lakes like this around the Gobi desert, being fed from runoff from glaciers in the Himalayas, and losing their water to evaporation. Example: Bosten lake, <a href=\"https://en.wikipedia.org/wiki/Bosten_Lake\" rel=\"nofollow noreferrer\">wiki</a>, <a href=\"https://www.google.nl/maps/@41.9835899,86.9373158,75995m\" rel=\"nofollow noreferrer\">google maps</a>.</p>\n" }, { "answer_id": 70255, "author": "Paul Johnson", "author_id": 10068, "author_profile": "https://worldbuilding.stackexchange.com/users/10068", "pm_score": 0, "selected": false, "text": "<p>Take a look at the <a href=\"https://en.wikipedia.org/wiki/Zanclean_flood\" rel=\"nofollow noreferrer\">Zanclean flood</a>. This is when the Mediterranean was flooded by the Atlantic. Estimates of the time taken vary from a few years to 10,000 years, so you could take your pick. Do bear in mind that water will erode whatever channel it is running through, so if you want the process to take a long time then there is going to have to be some hard rock creating a bottleneck. There is also a lot of scope for economic, social and military conflict driven by the rising water levels, madcap schemes for damming the flow that <em>might just</em> work, and nefarious schemes for destroying the bottleneck to make the flow dramatically increase.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/69917", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/32999/" ]

[ { "answer_id": 69920, "author": "SRM", "author_id": 26246, "author_profile": "https://worldbuilding.stackexchange.com/users/26246", "pm_score": 5, "selected": false, "text": "<p>If a river flows from ocean into lake, you better have another river that flows out of the lake into someplace else, otherwise that ocean is quickly going to fill the lake, the surrounding area, and continue until everything below sea level is filled up, at which point it will stop flowing. If you have a second river flowing to somewhere else to drain the lake, great, but it has to be SOMEWHERE ELSE, as in, not a normal place, because if you just connect it across to another ocean, again, it'll just fill up from both sides and then cease to flow. So if you have an infinitely deep pit to dispose of the water, or a superheat source that continually evaporates the lake, or a dimensional portal, then, yes, you can have a river from an ocean to a lake, but otherwise, you cannot. </p>\n" }, { "answer_id": 69922, "author": "Schwern", "author_id": 760, "author_profile": "https://worldbuilding.stackexchange.com/users/760", "pm_score": 7, "selected": true, "text": "<p>Normally, a lake will have a fresh water river flowing into it from higher ground, and a river flowing out of it to the sea.</p>\n\n<pre><code>Fresh water source\n \\\n \\\n --- Lake ---\n \\\n \\\n Ocean\n</code></pre>\n\n<p>If you do it the other way around, water can't flow out of the lake. The lake would have to be below sea level. It would fill and overflow until the level of the lake has reached sea level and merged with the sea. Then you'd get something like the <a href=\"https://en.wikipedia.org/wiki/Mediterranean_Sea\">Mediterranean Sea</a> fed by the <a href=\"https://en.wikipedia.org/wiki/Strait_of_Gibraltar\">Strait of Gibraltar</a> or further in the <a href=\"https://en.wikipedia.org/wiki/Black_Sea\">Black Sea</a> fed by the <a href=\"https://en.wikipedia.org/wiki/Dardanelles\">Dardanelles</a>. Both the Mediterranean and the Black Sea are at the global sea level. Both straits have both inflow and outflow.</p>\n\n<p>There are lakes below sea level, the <a href=\"https://en.wikipedia.org/wiki/Dead_Sea\">Dead Sea</a> for example, but it's cut off from the sea and fed by the Jordan River. Its \"outflow\" is evaporation.</p>\n" }, { "answer_id": 69923, "author": "Scott Whitlock", "author_id": 17382, "author_profile": "https://worldbuilding.stackexchange.com/users/17382", "pm_score": 4, "selected": false, "text": "<p>Yes, but you need to have some water sink at the lake end. One simple solution is evaporation. Water enters from the ocean into the lake (make it a small trickle of water) and because it's in a hot valley, it evaporates and more flows in. Since it's salt water, it would have a lot of dissolved solids, and these would be left over after evaporation. This would make the lake \"brackish\" (?) and unsuitable for most living things. Also, the sediment would slowly accumulate so I don't think it could last forever, unless you had some way of lowering the lake bed - perhaps a geological feature?</p>\n" }, { "answer_id": 69932, "author": "Karl", "author_id": 26241, "author_profile": "https://worldbuilding.stackexchange.com/users/26241", "pm_score": 2, "selected": false, "text": "<p>Easily, but not for long.</p>\n\n<p>The water in a desert lake fed from the sea would be supersaturated with salt, and the inflowing salt would precipitate all the time, slowly filling up the depression.</p>\n\n<p>Unless the channel from the sea widens too quickly, in which case you get something like the mediterranean sea.</p>\n" }, { "answer_id": 69933, "author": "Spencer", "author_id": 33006, "author_profile": "https://worldbuilding.stackexchange.com/users/33006", "pm_score": 4, "selected": false, "text": "<p>You could, of course, do some exotic things with neutronium to warp gravity the way you want it. But it's not necessary; lakes like this already exist in nature (sans neutronium).</p>\n\n<p>The best example is probably <a href=\"https://en.wikipedia.org/wiki/Lake_Assal_(Djibouti)\">Lake Assal</a> in Djibouti. </p>\n\n<p>This is near where the East African Rift comes out into the Red Sea. Instead of ocean water flowing into the lake via a river, however, it comes in by underground cracks from Lake Goubet, which is connected to the ocean. In a few million years time, this will be part of a new sea dividing East and West Africa.</p>\n\n<p>The salient (pardon the pun) conditions are similar to what Scott Whitlock described:</p>\n\n<ul>\n<li>The lake is in a desert (the Danakil), so that evaporation balances or exceeds inflow. In this case, salt from the ocean gets concentrated in this lake to make it one of the saltiest in the world.</li>\n<li>The lake is below sea level so there is a potential energy difference to make the water flow out of the ocean rather than into it.</li>\n<li>The lake is close to the ocean, so that the connection can form naturally.</li>\n</ul>\n" }, { "answer_id": 69951, "author": "DeveloperDoge", "author_id": 33011, "author_profile": "https://worldbuilding.stackexchange.com/users/33011", "pm_score": 3, "selected": false, "text": "<p><strong>TL;DR: Yes, but only if meeting very specific conditions. I would however actually encourage this for the unique thematic effect.</strong></p>\n\n<p>If the water flowing from the ocean into the lake either:</p>\n\n<p>a) Evaporates at the same or higher rate than the inflow.</p>\n\n<p>OR</p>\n\n<p>b) Continues elsewhere underground (at such rate) until it spews from some warm water geiser.</p>\n\n<p>Additionally the inflow from the ocean will increase over time <strong>as more ground is dragged along from the riverbed and ocean</strong>. <strong>This inflow of ground would be able to fill the underground geiser tunnels</strong> if it keeps increasing.</p>\n\n<p>If you really want the salt water river for thematic effects, then do so it adds to the uniqueness of your story, but if I were the one writing I'd let the water come trough a rock based canyon(caused by earthquake back in time) into a lower valley. <strong>This way the input from the ocean will remain the same</strong> and if the initial rock debris didn't close the underground geiser caverns then the much lower amount that will come in over time is unlikely to do it any time soon.</p>\n\n<p>Intelligent beings are also likely to: </p>\n\n<p>a) Close any leakage of the canyon except at it's final destination where this is impossible, as it would affect their farmland badly trough salting the earth if any small streams diverged from the canyon at other locations.</p>\n\n<p>b) <strong>Create a successful salt production settlement</strong>, as the area is far from the ocean and possibly low in salt mines. Creating supply in a low supply area, easily becoming an important trading hub.</p>\n\n<p>c) <strong>Goods could be transported downstream easily, again making this inland settlement a potentially vibrant trading hub</strong> where other people come to buy what they can't elsewhere.</p>\n" }, { "answer_id": 69968, "author": "Separatrix", "author_id": 16295, "author_profile": "https://worldbuilding.stackexchange.com/users/16295", "pm_score": 4, "selected": false, "text": "<p>What the other answers seem to have overlooked is the possibility of the tidal inland lake.</p>\n\n<p>Given a coastal barrier of harder rock but softer ground further inland it's possible to have a tidal river running from an inland lake to the sea. As the tide comes in the river flows from the sea to the lake, as the tide goes out it flows from lake to sea.</p>\n\n<p>Due to the restricted flow of the water up the river, it's unlikely that the lake will ever reach the full high or low of the tide. While there will be 4 brief points of slack water in the river during a 24 hour tide cycle, you will have flow in the river most of the time.</p>\n" }, { "answer_id": 69990, "author": "Jack", "author_id": 32885, "author_profile": "https://worldbuilding.stackexchange.com/users/32885", "pm_score": 2, "selected": false, "text": "<ol>\n<li>At high tide water flows into the lake due to the gravtational pull of the moon(s). At low tide it flows back into the ocean.</li>\n<li>The desalination settlement (DeveloperDoge suggested) but with the twist that it flows into an active lava flow and evaporates.Perhaps even flowing into a sunken volcano or caldera.Steam technology?</li>\n<li>Engineer a dam or a system of locks that connect to the lake, controlling water flow.</li>\n</ol>\n" }, { "answer_id": 69994, "author": "Sir Cornflakes", "author_id": 19004, "author_profile": "https://worldbuilding.stackexchange.com/users/19004", "pm_score": 3, "selected": false, "text": "<p>There is such a situation on Earth, alltho' not from the Ocean but from Caspian Sea: There is a river of salt water, even having a cataract of salt water, into another salt lake called <a href=\"https://en.wikipedia.org/wiki/Garabogazk%C3%B6l\">Kara Bogaz Gol</a>.</p>\n" }, { "answer_id": 70024, "author": "james turner", "author_id": 11140, "author_profile": "https://worldbuilding.stackexchange.com/users/11140", "pm_score": 2, "selected": false, "text": "<p><strong>short answer: all rivers between a lake and a sea will flow to the sea</strong></p>\n\n<p>basically, if the sea can flow into an area (e.g. a lake), it will quickly fill that area and stop flowing. rivers constantly flow into the sea because the sea is constantly evaporating away due to it's huge surface area. there are exceptions, but they are far less common than the standard rain to river to lake to sea paradigm. just for fun, i'll list some exceptions:</p>\n\n<ol>\n<li>some rivers end in a salt lake, salt flats or salt marsh. the water flows into the salty area, then evaporates away leaving behind the salt and other sediment. this area might not be called a \"sea\" if it isn't a large enough body of standing water.</li>\n<li>some rivers will flow \"backwards\" at high tide. nearly all rivers do this to some extent. they generally don't flow backwards long or hard enough to actually reach an area called a \"lake\".</li>\n<li>after earthquakes, it may take a short time for the sea to flow into a newly created depression. this situation generally resolves within a few days.</li>\n</ol>\n\n<p>if you just want a semantic solution, you could have a big lake draining into a small lake, which later drains into the ocean. the locals might call the big lake a \"sea\" and the small lake a \"lake\", but a \"sea\" is by definition salty, which means the lake would be salty too. the connection between two would be a salty river. salty rivers on earth tend to be extremely rare, short and short lived (in geological time). but hey, they happen.</p>\n" }, { "answer_id": 70136, "author": "Swier", "author_id": 33078, "author_profile": "https://worldbuilding.stackexchange.com/users/33078", "pm_score": 1, "selected": false, "text": "<p>If you just want a lake with a river flowing into it, that's entirely possible (and actually exists on Earth), so long as there is enough evaporation (or maybe some industry using the water for something else) to compensate for the influx of water.</p>\n\n<p>A problem arises when seawater flows into your lake, as seawater contains salt it will turn your lake into brine quite fast.</p>\n\n<p>But if the rivers flowing into the lake are clean and fresh water, your lake should stay relatively clean. Especially if the lake is very deep and pollutants just sink to the bottom.</p>\n\n<p>There are numerous lakes like this around the Gobi desert, being fed from runoff from glaciers in the Himalayas, and losing their water to evaporation. Example: Bosten lake, <a href=\"https://en.wikipedia.org/wiki/Bosten_Lake\" rel=\"nofollow noreferrer\">wiki</a>, <a href=\"https://www.google.nl/maps/@41.9835899,86.9373158,75995m\" rel=\"nofollow noreferrer\">google maps</a>.</p>\n" }, { "answer_id": 70255, "author": "Paul Johnson", "author_id": 10068, "author_profile": "https://worldbuilding.stackexchange.com/users/10068", "pm_score": 0, "selected": false, "text": "<p>Take a look at the <a href=\"https://en.wikipedia.org/wiki/Zanclean_flood\" rel=\"nofollow noreferrer\">Zanclean flood</a>. This is when the Mediterranean was flooded by the Atlantic. Estimates of the time taken vary from a few years to 10,000 years, so you could take your pick. Do bear in mind that water will erode whatever channel it is running through, so if you want the process to take a long time then there is going to have to be some hard rock creating a bottleneck. There is also a lot of scope for economic, social and military conflict driven by the rising water levels, madcap schemes for damming the flow that <em>might just</em> work, and nefarious schemes for destroying the bottleneck to make the flow dramatically increase.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/69918", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/32453/" ]

[ { "answer_id": 71880, "author": "AndreiROM", "author_id": 15059, "author_profile": "https://worldbuilding.stackexchange.com/users/15059", "pm_score": 8, "selected": false, "text": "<p>Human engineering can, 100%, keep out a horde of zombies. In <em>The Walking Dead</em> things fail because if they didn't the show would be boring. In real life, there exist castle gates hundreds of years old which would hold, no questions asked.</p>\n\n<p>First and foremost, realize that thousands of zombies will never be pushing on the gate all at the same time. They will spread out against the wall as the pressure mounts from behind. Thus, the gate doesn't need to be nearly as strong as you'd think.</p>\n\n<p>Second, take a pro tip from me, and don't build your gate on wheels, or out of chain link fence, as is the case in most walking dead situations. A draw bridge can be built. A portcullis, perhaps. These things are not rocket science, and will work much better than half the crap you see on that show.</p>\n\n<p>Bracing the gate would also be a good idea. Move a bus against it, or drive large stakes into the ground at intervals. Check out the siege scene in LOTR when helm's deep is being assaulted. Watch the soldiers barricade the gate. Now <em>that's</em> an attempt at keeping the enemy out, not the half baked efforts in TWD (if they weren't constantly being defeated and driven out of their \"fortresses\" the show would have been over in Season 3).</p>\n\n<p>Since you're asking for a design of a gate, here's mine:</p>\n\n<p>A gate you push into place from the side - large metal one (but not too long, as the longer it is, the more difficult it becomes to brace it). I'm thinking steel plates welded onto a nice, thick frame. Because you don't just want it to get pushed over, you need to secure it very well at both ends. However, that might not prove sufficient in a \"million zombie horde\" situation. </p>\n\n<p>You have to have the option of bracing it from the inside such that it doesn't buckle inward, and come free of one of the end points (and in order to keep some pressure off the end-points). Have stake pits dug, and brace the gate both with those, as well as with heavy beams. </p>\n\n<p>And if you <em>really</em> want to survive, have the option of lowering a plow -like device over the front of it. </p>\n\n<p>Imagine a giant horde coming your way. You seal the gate, put in the stakes brace it, and then swing a big metal \"V\" down over the side, such that zombies coming up against the gate simply push each other to the side, and into the walls.</p>\n\n<p>Future survivors will come across your fortress years later, see the tall, proud gate still standing firm, and think: </p>\n\n<blockquote>\n <p>\"Wow, that sure is a great gate. Too bad they didn't build the walls as strong!\"</p>\n</blockquote>\n" }, { "answer_id": 71881, "author": "Jacob", "author_id": 31082, "author_profile": "https://worldbuilding.stackexchange.com/users/31082", "pm_score": 4, "selected": false, "text": "<p>Sure there is, it's been done already. A lot. Much field-testing has been done on the best way to break through a large door, especially when considering that the defenders will likely not be pleased that it's happening, although the tests were performed a while ago - a few thousand years ago, to be exact, when castles were still in fashion and a rival lord's raiding of it not out of the question. The solution for the attacker was a large battering ram, or to skip attacking the door entirely and just demolish the castle with siege weapons. Zombies do not have the capability to carry a battering ram, however, nor operate siege weapons. And those rams were only meant to bash through wooden doors. Doors of stone or even metal would be damn near impenetrable to human - or zombie - strength.</p>\n\n<p>As to why it didn't work on the show...well, it's on TV, and I blame the fact that the writers just wanted ~~DRAMA~~ and cared more about that than physics. </p>\n" }, { "answer_id": 71882, "author": "Youstay Igo", "author_id": 13449, "author_profile": "https://worldbuilding.stackexchange.com/users/13449", "pm_score": 3, "selected": false, "text": "<p>I don't know if a gate can stand the force of hundreds of (undead) humans, but there <strong>is</strong> indeed at least one way of making the gate <em>almost</em> as strong as the walls around it.</p>\n\n<p><strong>a- Use a sliding/rolling gate instead of hinged design</strong></p>\n\n<p>The gate slides up and down in the wall. Its edges are 3 feet inside the wall at both ends. There are no hinges anywhere, just ball bearings, wheels and a high friction surface (of the walls) for the wheels to roll on.</p>\n\n<p><strong>b- Use a few long, thick spikes on the gate</strong></p>\n\n<p>This will help hinder the zombies from pushing at the door altogether. Considering that the zombie who tried to push in, gets spiked and unable to move, it will be very hard for the zombies behind that first zombie to shove him aside and make their way forward.</p>\n" }, { "answer_id": 71889, "author": "ChaosCenturian", "author_id": 33525, "author_profile": "https://worldbuilding.stackexchange.com/users/33525", "pm_score": 2, "selected": false, "text": "<p>A dumb idea or work around would be the trope of Razor floss. something like a super thin wire set into a door way such that as the pressure of the zombies mounted they just cut the front line in to bits. Your number 1 problem becoming dealing with body disposal. </p>\n" }, { "answer_id": 71890, "author": "Schwern", "author_id": 760, "author_profile": "https://worldbuilding.stackexchange.com/users/760", "pm_score": 8, "selected": true, "text": "<p>We humans are pretty good at building gates to keep people out. We've been doing it for a long time for military purposes and to stop thieves.</p>\n\n<h1>Why Do We Have Gates?</h1>\n\n<p>Because there has to be some way for friendlies to get through the defenses while keeping the bad guys out.</p>\n\n<p>From a military perspective, a gate isn't there to stop people from getting in. They'll get in. Instead, it's there to channel them into a particular area by the allure of an easier passage. Avoid the wall and its defenses, drive through the gate! In anticipation, that particular area is set up as a kill zone: a deadly crossfire will be in place to mow down anyone who comes through, combined with removable obstacles to slow them down and pin them in the kill zone.</p>\n\n<p>From a security perspective, a gate is also there to slow down a thief. But instead of a kill zone, it exists to be such a nuisance to force the thief to give up, or to make so much noise getting through they're detected. Once detected, forces are rushed in.</p>\n\n<p>So, gates exist to...</p>\n\n<ul>\n<li>provide access through defenses for friendlies</li>\n<li>herd attackers into a kill zone</li>\n<li>force the attacker to reveal themselves</li>\n<li>slow the attacker to there's more time to deal with them</li>\n</ul>\n\n<p>Zombies don't act like an intelligent, coordinated military force, nor do they act like thieves. They just walk, slowly, towards food. They might not even find the gate and instead just walk into the wall in whatever direction they came from. (Note: I only watched the first few episodes of The Walking Dead, so I don't know exactly how their zombies act).</p>\n\n<p>That is until you start making a bunch of noise going in and out of the gate. Then they'll go investigate. The problem is not having a big rush of zombies at the gate, the problem is having a slowly growing, constant pile up at the gate which is putting more and more pressure on it until, like a fence at a football riot, it will collapse.</p>\n\n<p>Zombies also don't get tired and give up. They'll keep banging on that gate and walls until one of them breaks.</p>\n\n<p>This means you need an active defense to clear the zombies off, and you need to do it efficiently and safely.</p>\n\n<h1>Establish A Kill Zone</h1>\n\n<p>Take advantage of that pile up and use it as a kill zone. The zombies will be easy pickings as they pile up against the gate, or even the walls. A few isn't a problem, unless you need to go out. Take care of them before there's too many.</p>\n\n<h1>Kill Them Cheaply</h1>\n\n<p>You want to set up your gate and defenses so the zombies can be killed without expending resources. This means no guns and no gasoline. There's going to be a lot of them, and you only have so many bullets. Save them for emergencies and foraging.</p>\n\n<h1>Kill Them Safely</h1>\n\n<p>You're going to be doing this <em>a lot</em> and even a single bite means you're dead. That means it has to be done very safely, no heroics.</p>\n\n<h1>Bars + Pikes</h1>\n\n<p>The simplest actively defended anti-zombie gate is some sturdy iron bars and a few people with pikes. Zombies thrash against the iron bars, the pikemen stick them in the face from well outside of arms reach. Cover the end of the shaft in grease to prevent the zombies from grabbing it. If they do, pikes are cheap. Let go and grab another one. Maybe you can get the lost one later when they're all dead.</p>\n\n<p>These bars can and should be placed all around your defenses to prevent zombies from piling up at any point on the wall.</p>\n\n<h1>Flexible Gates</h1>\n\n<p>Against an enemy like a zombie, rigid defenses might not be the best idea. Instead, you might want to try a [flexible security gate] like you'd find in a mall.</p>\n\n<p><a href=\"https://i.stack.imgur.com/gRPCw.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/gRPCw.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>Unlike rigid bars which will take all the force of zombies banging on it, a flexible security gate will flex and wobble which will absorb some of the impact. And they have those handy slots for stabbing zombies through.</p>\n\n<p>Just make sure it's strong enough to hold back a horde pressing against it, and it's secured to something that's strong enough, too.</p>\n\n<h1>Evolution 1: The Murder Hole</h1>\n\n<p>This is, essentially, an inner and outer <a href=\"https://en.wikipedia.org/wiki/Portcullis\" rel=\"noreferrer\">portcullis</a>: a big, heavy gate with spikes on the bottom that drops from a height.</p>\n\n<p><a href=\"https://i.stack.imgur.com/3Poo7.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/3Poo7.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>Zombies on the outside, pikemen on the inside.</p>\n\n<pre><code> ===============\n P * *ZZZZ\n P * *ZZZZ\n P * *ZZZZ\n P * *ZZZZ\n P * *ZZZZ\n ===============\n</code></pre>\n\n<p>Raise the outer gate, let some Zed in, then lower it again. If there's some zombies under it, so much the better.</p>\n\n<pre><code> ===============\n P *Z *ZZZ\n P *Z *ZZZ\n P *Z *ZZZ\n P *Z *ZZZ\n P *Z *ZZZ\n ===============\n</code></pre>\n\n<p>Now you can better manage the number of zombies you're dealing with at once. Once you're done, you can get into the inner area to clean the bodies up and avoid a pile up.</p>\n\n<p>There's any number of improvements which could be made to this, for example a grilled platform on top, out of arm's reach, to stab down through.</p>\n\n<p>Should the inner gate fall, you only have to deal with a limited number of zombies inside the wall. Should the outer gate fail, you have an inner gate to fall back to. This brings us to our next point.</p>\n\n<h1>Have A Mobile Backup Gate</h1>\n\n<p>Taking a page from <a href=\"https://www.youtube.com/watch?v=wNzfgl_H5vA#t=4m09s\" rel=\"noreferrer\">The Road Warrior</a>, use a heavy vehicle like a bus as a mobile gate. But instead of using it as your primary gate, have it ready as a mobile backup gate to close any breeches in the wall. Just drive it up to block the gap. This will plug the breech and give the defenders time to react.</p>\n\n<h1>Evolution 2: Dig A Pit, Fill It With Spikes</h1>\n\n<p>If the Walking Dead zombies are like the Romero and Max Brooks zombies, they aren't very bright and will happily walk off a cliff if there's food on the other side.</p>\n\n<p>To make our murder hole even safer, we can add a pit filled with spikes.</p>\n\n<pre><code> ===============\n P *..............*ZZZZ\n P *..............*ZZZZ\n P *..............*ZZZZ\n P *..............*ZZZZ\n P *..............*ZZZZ\n ===============\n</code></pre>\n\n<p>Raise the outer gate, zombies fall into the pit and get impaled. It probably won't kill them, but it will immobilize them. Then stab them with pikes at your leisure. You can even throw a grating over the top to make the stabbing even easier.</p>\n\n<h1>Evolution 3: The Crushinator</h1>\n\n<p>You've got these zombies pressed up against your gate, you know where they're going to be, why not use it to your advantage? Scrape them off the gate with a heavy object.</p>\n\n<pre><code> |\n O|\n -------|v\n | |\n | |Z\n===================\n</code></pre>\n\n<p>You have a heavy door (optionally sharp) held above and just outside the gate. Zombies press against the outer gate. Drop the door right on their heads. Crush the zombies. Lift it again. Repeat until all zombies are dead or disabled. Finish them off with pikes. Safe. Efficient. And it's a spare gate!</p>\n\n<h1>Don't Have A Gate</h1>\n\n<p>Taking another page from the original <em>Dawn Of The Dead</em>, do you really need a gate? What about a ladder or ramp? Zombie attack? Retract the ladder. Just be sure you have a way of clearing the zombies off the entrance, like a set of bars to stab them through.</p>\n\n<pre><code>=========\n |\n ^ |\n O | - O _(Brains)\n |-o - o-|\n | | | |\n /\\ | | /\\\n</code></pre>\n\n<h1>Try Things Out In <a href=\"http://7daystodie.gamepedia.com/7_Days_to_Die_Wiki\" rel=\"noreferrer\"><em>7 Days To Die</em></a></h1>\n\n<p><em>7 Days To Die</em> is a \"survival, horde, crafting game\". It's Minecraft meets Left4Dead. It's a great place to try out various anti-zombie defense schemes.</p>\n\n<p>What sets 7D2D apart from other zombie survival games is <em>everything is destructible</em>. Wood, metal, concrete, <em>even the ground itself</em>, the zombies will chew through it all. Any passive defense will eventually be ground down and fail. I've had zombies chew through concrete, wriggle through firing ports, climb over each other like ants, tear the foundations out of platforms, and even come up through the floor!</p>\n\n<p>The other thing that sets 7D2D apart is right in the title: every 7 days, ready or not, you <em>will</em> be attacked by a horde. It lends a certain time pressure to everything you do. Grand plans give way to necessity. Are you going to try to explore to find the mixings for concrete and bullets? Or chop down more trees to bodge together more spikes and arrows?</p>\n\n<p>Finally, while basic combat is rather simple, getting hit is brutal. Especially at the higher difficulty levels, one hit and you're stunned, two or three and you're dead.</p>\n\n<p>The game is still in early access, but it's totally playable and totally brutal. Big changes are coming in Alpha 16 in March, so you might want to wait until then. But if you want to torture test your ideas about zombie defenses, give it a shot.</p>\n\n<p>Here's the aftermath of a horde night in my fortified chateau. It took the \"no gate\" philosophy. All stairs were torn out, even interior stairs, and replaced with ladders and armored hatches. We attracted them to a particularly well fortified corner of the house.</p>\n\n<p><a href=\"https://i.stack.imgur.com/f4qaN.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/f4qaN.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>That <em>was</em> four layers of spikes. Note the firing ports for an active defense. Also note the hasty repairs on the concrete; they got through, but that was just the outer defenses. We had multiple backups to retreat to.</p>\n\n<p>This was just one evolution of the defenses.</p>\n" }, { "answer_id": 71892, "author": "Paul TIKI", "author_id": 31273, "author_profile": "https://worldbuilding.stackexchange.com/users/31273", "pm_score": 3, "selected": false, "text": "<p>Don't discount the moat/drawbridge. If the moat is right up against the plane of the gate, it will have the following effect. The shambling dead come, fall in the moat, more of them come and fall in eventually filling it up. Here is the thing, piles of squirming, hungry ghouls will not make for good enough footing for the remainder to be able to generate tons of pressure against the gate. </p>\n\n<p>In addition, a gate with two doors, that is well anchored against a solid wall, can be built to swing out when open and when closed the 2 sides will overlap and lock in place, with any pressure binding it more solidly against the framework.</p>\n\n<p>I'm trying to work in ChaosCenturian's Zombie cheese cutter as well, but not having a great amount of luck.</p>\n\n<p>Always remember to sever the head! good luck</p>\n" }, { "answer_id": 71909, "author": "Greenstone Walker", "author_id": 8388, "author_profile": "https://worldbuilding.stackexchange.com/users/8388", "pm_score": 3, "selected": false, "text": "<p>A gate that comes down from above. For example, stairs that fold out from the side of an aeroplane or a rope ladder lowered from a kid's treehouse.</p>\n\n<p>Zombies are dumb. They won't climb, just mill around.</p>\n\n<p>Build a wall with no gaps, and have a crane raising and lowering a large platform, big enough to fit a truck. You could make some noise on one side, attracting all the zombies to that part of the wall, and then drive the crane to the other side of the compound and its platform without having to worry about zombies piling on.</p>\n" }, { "answer_id": 71910, "author": "Durakken", "author_id": 22659, "author_profile": "https://worldbuilding.stackexchange.com/users/22659", "pm_score": 2, "selected": false, "text": "<p>How to build an Anti-Zombie door:</p>\n\n<ol>\n<li>Go to store. </li>\n<li>Buy a standard door. </li>\n<li>Hang it on standard hinges as normal. </li>\n<li>Close and lock door. </li>\n<li>Congratulations, you've made an Anti-zombie door.</li>\n</ol>\n\n<p>Zombies wouldn't clump as they are shown, and enough pressure to break a door is not achieved by a zombie horde even if they did, and even if it were, the first few zombies would be crushed and block the path from zombies entering, and even if that were not the case they're all funneling into the same passage making them easy targets since they have to come in 1 at a time. </p>\n" }, { "answer_id": 71920, "author": "Loren Pechtel", "author_id": 264, "author_profile": "https://worldbuilding.stackexchange.com/users/264", "pm_score": 3, "selected": false, "text": "<p>Something to keep in mind: Zombies can't develop any huge pressure against the door. Their bodies aren't able to take infinite pressure, if enough of them are trying to get through your door the ones in front will be crushed and cease to be able to provide pressure. Thus sufficient zombies means that the pressure actually is reduced, not increased.</p>\n\n<p>Besides that, there's a simple way to build an entryway that will stop a horde of zombies. You need a moat, ideally with a river flowing through it. Unlike a normal castle you want the moat inside your walls. Build your outer wall to funnel the zombies into your gates. Your gates extend across the moat except the floor is actually hinged to the bottom of one wall and counterweighted with 300# more than needed to balance.</p>\n\n<p><strong>A</strong> person <strong>walks</strong> across them, no problem. The walk up to the door, slide it to the side and enter.</p>\n\n<p>The walls and door are tough enough to take a few zombies. Once 300# of zombies accumulate in the corridor the floor tips and they're dropped into the moat. Obstacles are arranged to ensure they die on the way down. Then the floor rotates back into position and more zombies advance to their death.</p>\n\n<p>If you have a river in your moat the corpses go off to sea rather than pile up underneath (a sufficient pile would jam the door.)</p>\n" }, { "answer_id": 71921, "author": "ikrase", "author_id": 31359, "author_profile": "https://worldbuilding.stackexchange.com/users/31359", "pm_score": 2, "selected": false, "text": "<p>Any reasonably heavy metal door or hatch, that closes into a tight-fitting heavy metal doorframe with minimal protruding edges, and which is equipped with several reinforced bolts and hinges, should be easily resistant to zombies (unless the zombies can figure out saws, explosives, or particularly effective battering rams). </p>\n\n<p>(Think of the heavy metal lockers they have in campsites in bear country. Bears can rip into cars with their claws, because cars have windows and are made of thin sheet metal. These lockers are made of steel that is at a minimum 6mm thick, and reinforced.)</p>\n\n<p>To resist battering rams better, make it sloped, and also grease the outside of the door and the surrounding wall so that zombies have a hard time grabbing it. </p>\n\n<p>Also, as others have said, you're going to want to be able to shoot at the zombies attacking the door, defending it will make it much more resistant. </p>\n\n<p>If I had the required time and materials, I would make a hatch out of 12mm thick steel, tilted at a 45 degree angle, reinforced with welded metal on the back, opening upwards, and seating in a doorframe made of welded 12mm-thick-wall box channel beam or angle steel. The \"hinge\" would be a ~16mm dia or thicker steel pin. Counterweights would allow a human to open it. </p>\n\n<p>I can't imagine zombies defeating that; there's a limit to what brute force -- that still relies on human muscles -- can do. </p>\n" }, { "answer_id": 71934, "author": "Jeutnarg", "author_id": 15591, "author_profile": "https://worldbuilding.stackexchange.com/users/15591", "pm_score": 5, "selected": false, "text": "<p>Use the power of physics, dirt, and the stupidity of zombies. Zombies break a door by exerting force against it <em>en masse</em>, but the zombies have to have an equal and opposite source resistance to push off from. Therefore, you give them extremely limited terrain to push off against the gate and then give the main horde something insanely difficult to deal with, like 15 tons of packed dirt with a concrete shell.</p>\n\n<p>Do something like this:</p>\n\n<pre><code> _|__(&lt;-- gate) \n /// \\\n(horde) /// (solid stuff) \\\nzzzzzz___/// \\(me, safe and sound)\n</code></pre>\n\n<p>It doesn't matter how big the horde is - they'll never break a gate that's situated like that, since the horde isn't capable of putting more than a few zombies in position to actually put pressure on the gate.</p>\n\n<p>It <strong>is</strong> possible that the zombies could dig through, assuming you just have dirt and given enough time, so you could either commit to clearing them out occasionally or use at least an outer shell of concrete or something. The zombie blood should make it impossible for plants to grow (too alkaline,) so you won't even have to worry much about plants weakening your concrete.</p>\n\n<p>Now, you may be wondering how this is different than a regular moat, as has been suggested in several answers. The key difference is that is takes an astronomically huge number of zombies to fill this 'moat', provided that you make the solid section steep enough to prevent the zombies from stacking on each other with the ability to push against each other. Your 'moat' is either the entire valley (if you're in a valley) or the entire planet below your elevation (if you're not in a valley.) Now that's, one heckuva moat.</p>\n\n<p>Finally, I realize that this isn't really putting much effort/thought into the gate itself, but (as in many things,) <em>it's all about location, location, location.</em></p>\n" }, { "answer_id": 71938, "author": "Separatrix", "author_id": 16295, "author_profile": "https://worldbuilding.stackexchange.com/users/16295", "pm_score": 5, "selected": false, "text": "<p>As Andrei has already pointed out, if the doors didn't fail, there wouldn't be much of a series. However there are many imaginative ways to deal with zombie hordes if you have time to prepare. Here are a few.</p>\n<h1>Why have a door?</h1>\n<p>Just have a solid wall all the way round and a ladder. Zombies aren't known for their intelligence, when under attack remove the ladder, there's no door to fail.</p>\n<h1>I really want a door though</h1>\n<p>Interlocking doors that only open outwards. Vault doors are designed as a conical section, they will only open outwards, the more you push the tighter they fit. If you want a pair of doors, then overlapping panels such that again, the door only opens outwards. Like these lids, but bigger:<br />\n<a href=\"https://i.stack.imgur.com/cxJ9X.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/cxJ9X.jpg\" alt=\"crate with interlocking lid\" /></a></p>\n<h1>That's all very well but, I'm a horrible person</h1>\n<p>What you need is a sharpened portcullis. The pressure from the zombies behind push the ones at the front through what is effectively a large scale potato chip maker (french fry cutter). You don't even need to kill them yourself, just have a pit for the bits of zombie to land in. Severing the head is irrelevant on a neatly cubed zombie.<br />\n<a href=\"https://i.stack.imgur.com/wLfVC.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/wLfVC.jpg\" alt=\"chip cutter\" /></a><br />\nYou may want a blade you can drop down the outside to clear away the buildup of bits of zombie on the cutting edge.</p>\n<h1>As a final note on this</h1>\n<p><a href=\"https://i.stack.imgur.com/l0WKU.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/l0WKU.jpg\" alt=\"Zombies can't swim\" /></a></p>\n" }, { "answer_id": 71941, "author": "nzaman", "author_id": 21117, "author_profile": "https://worldbuilding.stackexchange.com/users/21117", "pm_score": 2, "selected": false, "text": "<p><strong>A Drawbridge</strong>:<br>\nRaised, say, 5m above the ground level of the rest of the wall, so that it opens on the second or third floor. The other side lands on a raised cantilever, like a viewing platform, at the end of a ramp. When raised, there is nothing connecting the two ends, so the the gate is inaccessible from the ground. When lowered, the bridge connects both ends and, depending on the material, you can drive heavy vehicles across. \nSince from the ground level there is nothing different about the gate area, compared to the rest of the wall, the <em>gate</em> is secure. </p>\n\n<p>...unless you've got intelligent zombies who can look up....</p>\n" }, { "answer_id": 71954, "author": "JamesD", "author_id": 15001, "author_profile": "https://worldbuilding.stackexchange.com/users/15001", "pm_score": 3, "selected": false, "text": "<p>Worried about many zombies being at your gate and it weakening over time due to too many zombies pushing on it.</p>\n\n<p>You need to keep them split up.</p>\n\n<p>Barriers are used for this exact purpose during festivals, the idea is to limit the amount of pressure on the front of the <s>crowd</s> zombies.</p>\n\n<p>For example:</p>\n\n<p><a href=\"https://i.stack.imgur.com/MbUjh.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/MbUjh.jpg\" alt=\"Barriers in use at download festival\"></a></p>\n\n<p>The zombies are kept back from the main stage using barriers, there is another set just out the camera view preventing crush events. Using this we can lower the pressure on the gate, so the gate doesn't need to be as massively built.</p>\n\n<p>Spiting them up can make it easier for the other methods to deal with the zombies. Combined with other methods this can be effective as well.</p>\n" }, { "answer_id": 71961, "author": "BentNielsen", "author_id": 2341, "author_profile": "https://worldbuilding.stackexchange.com/users/2341", "pm_score": 0, "selected": false, "text": "<p>There is something that we know can take an awful lot of pressure. The breech of a cannon.</p>\n\n<p>Make the door in a short cannon barrel as a breech, preferably with a diameter so that you can have trucks driving through.</p>\n\n<p>You'll probably need a plate that can be pushed forward from the door to clear out zombies in the barrel. If fire destroys these zombies then a regular burst from a flamethrower from a hole in the top of the barrel followed by a push from the plate and the barrel is clean again.</p>\n\n<p>The zombies will have to move the wall because they are not going to move the door unless it is opened from the inside.</p>\n" }, { "answer_id": 71962, "author": "Murphy", "author_id": 4750, "author_profile": "https://worldbuilding.stackexchange.com/users/4750", "pm_score": 5, "selected": false, "text": "<h1>Don't let them even touch your door.</h1>\n<p>You have your nice tall walls, you also have your nice gate behind a drawbridge and moat.</p>\n<p><a href=\"https://i.stack.imgur.com/iXbXt.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/iXbXt.jpg\" alt=\"drawbridge\" /></a></p>\n<p>But this is a horde of the living dead we're talking about!</p>\n<p>Moats can end up filled with the writhing mass of the living dead who can eventually climb over each other to scale your wall or batter down your door.</p>\n<p>Water doesn't cut it.</p>\n<h1>The solution.</h1>\n<p><a href=\"https://i.stack.imgur.com/PuGVZ.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/PuGVZ.jpg\" alt=\"crushinator\" /></a></p>\n<p>Bellow and in front of your door you place a rock crusher salvaged from a quarry. You set up your fortifications next to a large fast flowing river to provide power for your crusher.</p>\n<p>The zombie mulch can also be ejected into the fast-flowing river to make sure you don't end up with a pile of rotting zombie flesh.</p>\n<p>This keeps the population of zombies around you walls low: Zombies are attracted by the sound of the crusher and any who stray into the crusher get pulped. When you want to let humans in you lower your drawbridge to make a path over the crusher.</p>\n" }, { "answer_id": 71963, "author": "Till", "author_id": 30607, "author_profile": "https://worldbuilding.stackexchange.com/users/30607", "pm_score": 2, "selected": false, "text": "<p>As already pointed out, there are many ways from medieval times to build a zombie proof entrance. The problem is to build it.</p>\n\n<p>Remember, we don't talk about medieval times, when you had a lot of time to prepare for a coordinated attack every so many years. We are talking about building your defenses under the constant thread of uncoordinated and mostly small attacks. So you do not want to build a complex structure which requires you to live with a hole in your defense for months, weeks or even days. Even a few hours can proof fatal.</p>\n\n<p>We probably also want an entrance that is not by default open and can quickly be closed, like in medieval times, we want an entrance that is closed by default and can be quickly opened and closed to let people in. And, if possible cars and similar stuff too, but that would be a bonus not a necessity.</p>\n\n<p>So the sideways rolling entry from the series is a good start, since it can be placed quickly and fulfills all the requirements. And if you park a car against it, it can probably hold against a pretty big pileup. But you have the risk of someone forgetting to lock it. And if you kill the zombies, you have a big pile of corpses and no guaranty that you got all of them, so moving them per hand would always carry a little risk.</p>\n\n<p>So we use the protection of this gate to build a kind of portcullis. You'll have to build two big towerlike constructions as guiding rails, but you have some time. The grate itself should be heavy is best connected to some winding mechanism. This way it can not be raised by hand by a (human) attacker, but only from inside. This wind should be connected to a motor (a car could be modified for this) to raise the gate quickly. But there should still be a manual way to raise the gate, if you run out of gas or the the car breaks or something.<br>\nImportant is, that the gate lowers itself after a short time, if not attended to, so it can not be left open by accident. To accomlish this, the motor should only run while a button is pressed (or something similar, depends on the resources available and the specific way the motor was implemented in the construction) and the gate must not have a mechanism to arrest it in an open position (like the medieval ones did).<br>\nThe best position for the portcullis is directly behind the old gate, so we only lose a little space and can build it in the safety provided by the gate. After we constructed and tested the portcullis, we can deconstruct the old gate to save resources and speed up the process of opening up for incoming friends/allies.</p>\n\n<p>Now we are safe against forgetting to lock the door or the guard getting killed while the door is open. But there is still the problem with possible pile-ups and also there can be an attack of humans, who use for example a truck as a ram. The answer to this is a moat and a drawbridge.<br>\nWe need the bridge first, since we cannot pass the moat without it. The bridge itself can be prepared inside, but the hinges have to be build in place. Best position for this would be, where the old gate was.<br>\nBefore we install the bride, we also have to start some more complex constructions: counterweights. We want to lower <em>and</em> raise the bridge quickly and it should be massive enough, so (best case scenario) even trucks can pass it without problems. That means we have a pretty heavy construction. So we also need a stable construction with thick steel chains and girders, that is able to support the weight. This has to be constructed inside and put up in a short amount of time, since putting it up probably makes a lot of noise, thus attracting zombies. But after we build it, we can start digging a moat.<br>\nWe have to be careful while doing so, not to undermine our structures for the drawbridge (remember, that thing is <strong>heavy</strong>). The moat should be at least 2m (7 feet) deep, so the zombies can not climb out. Now, we have taken care of the pile-up problem and are save against attacks by ram-like constructions. Most zombies will fall into the moat and can be moistened with some oil or fuel and burned from a safe distance. A little smelly but save.<br>\nAnd a well balanced bridge can be quickly lowered and raised by hand.</p>\n\n<p>Now there is only one thing left to do for a perfect defense: a second drawbridge. We construct a small island surrounded by a moat. One bridge connects it to the outside and one to the inside of out fortress. We sacrifice some space to do so, since the structure is probably to complex to be build outside the walls, be it will be worth it.<br>\nNow, if someone approaches the fortress, we lower the outer bridge and raise the portcullis. They can enter the island, the portcullis is lowered and the bridge raised.<br>\nIf the approaching person or group is closely followed by zombies, we don't risk them getting inside. If the zombies were to close and catch the person/group, while entering, they still aren't inside the base and we can dispatch them from a distance (if they don't fall into the moat anyway). If the arrivals make it to the island without any zombies coming in, we can safely lower the inner bridge and let them in.<br>\nAlso, there is the possibility of people arriving, we don't know (or trust) yet. We can let them get on the island, thus granting them asylum and some safety from the zombies without actually letting them inside.<br>\nNow we have an extremely safe gate and it would be a good time to expand the moat, so it reaches all around the fortress.</p>\n\n<p>The result reminds a lot of medieval castles, but there are small differences. Mainly that the default state is not, ready to be closed, but closed, ready to be opened and closed again. And we can use motorized mechanisms for the portcullis.</p>\n\n<pre><code> |o \n #|### #\n #| # #\n \\-#| # \\-#\n \\#| # \\#\n***| |#***#| |#***** \n | |# #| |# \n |__| |__| \n</code></pre>\n" }, { "answer_id": 72015, "author": "Yakk", "author_id": 2473, "author_profile": "https://worldbuilding.stackexchange.com/users/2473", "pm_score": 3, "selected": false, "text": "<p>You can build an indestructible wall or gate; at least, indestructible by meat.</p>\n\n<p>The real problem is dealing with (say) 30 million corpses as the infinite wave of zombies crush against your base and die, forming a ramp of crushed flesh which the next wave crawls over.</p>\n\n<p>A 100 kg corpse with the density of water has a volume of 100 L. 30 million of them comes to 3 million cubic meters.</p>\n\n<p>Assuming a cone with a 10% gradient to the pile of zombies, the volume of a cone is $\\pi r^2 \\frac{h}{3}$. A 10% gradient means $r = 10h$, giving us</p>\n\n<p>$3000000 m^3 = \\pi \\frac{100}{3} h^3$</p>\n\n<p>which is roughly 30 meters. Now, a half-cone has half that volume, so to build a fortress capable of surviving 5% of North America's entire zombie population smashing against it and forming a human ramp, you need walls (and doors) that are roughly 30 meters tall, and the wall needs to be able to support a huge mass of zombies (roughly equivalent to water) on the other side.</p>\n\n<p>30 meters of water generates about 3 atmospheres of pressure on the base of the wall, or 30 tonnes of pressure per square meter. 30 meters is about 4 stories.</p>\n\n<p>The wall height needs to be tweaked based off of zombie pile slope and percent of continental population of zombies we have to survive.</p>\n\n<p>The compressive strength of any reasonably built concrete is well beyond this; but any jury-rigged walls or doors are going to fail.</p>\n\n<p>The door itself is a relatively small problem. Arrange it so that you cannot get a \"run up\" on the door by having the wall \"wrap around\" the entrance area with a choke point. Have multiple doors; I would go with 3, with only 1 every open at a time. An attack overwealming the outer door (a bomb by humans, or the door is accidentally unlocked) leaves at least 1 door sealed.</p>\n\n<p>This follows the rules that you have a never event (zombies getting in), you need for an unprecidented failure to <em>still</em> leave you with a layer of safety.</p>\n\n<p>Outer door fails while an inner door is open; no problem. Only lose people within the killing zone.</p>\n\n<pre><code> ************************\n * #\n * KZ3 # Inside\n * #\n * #\n*******######***********************************************\n * # \n * KZ2 # KZ1 Outside\n * # \n * # \n ****************************************\n</code></pre>\n\n<p>Here is a gate designed to surive against zombies. We have an outer wall that prevents \"direct charge\" of any of the doors.</p>\n\n<p>Kill Zone 1 is an isolated area where zombies breaking in can be slaughtered from above/through holes in walls. If there are \"low\" places to fight from KZ1, access is via ladder into KZ1; you cannot flee from KZ1 out of it directly until zombies in KZ1 are dead.</p>\n\n<p>The ability to \"drop down\" into KZ1 from the 30 meter (or however tall) walls above is possible, but this should <em>never</em> be deployed, and any drop-down should be from KZ2.</p>\n\n<p>KZ2 and KZ3 works similarly, but it is behind the door of <code>#</code>, and are isolated from the safe inside by another door of <code>#</code>. One-way entry to the \"killing locations\" in KZ2 can be reached from KZ3, and KZ3 has \"one way entry\" to the killing locations from the inside.</p>\n\n<p>The \"killing locations\" are things like raised platforms or iron-bar fortified ground locations that you can use pikes to fight from. These are used to clear the killing zones if besieged. These killing locations are not presumed safe from being overrun.</p>\n\n<p>Doors should be things like thick metal bars with thin gaps lowered from above. Simply too massive to be dislodged by mere meat, and mere meat cannot stop them from lowering. Wooden doors that can be closed to block line of sight can be added, but are not a requirement for the barrier to work. Killing zombies through these doors should be possible.</p>\n\n<p>Someone getting a truck and smashing the outer gate while the second gate is open is the \"worst case\" this is designed to defend from. Cinematic failure would consist of the people in killing zone 3 \"killing location\" fleeing, convincing people outside of it to lower rope ladders or somesuch, then being overrun and zombies getting inside.</p>\n\n<p>So the next stage is dealing with exactly that; KS3's \"one way\" entrance needs to be \"airlocked\" in a way that doesn't permit local zombie infection from getting out.</p>\n" }, { "answer_id": 72019, "author": "caymia", "author_id": 33814, "author_profile": "https://worldbuilding.stackexchange.com/users/33814", "pm_score": 3, "selected": false, "text": "<p>I'm thinking of a beefed up revolving door, the type you see at the mall to lock the air temperature in.</p>\n\n<p>Then build a mechanism, an additional blockage on the inside, that can either open inward, or seal the way in.</p>\n\n<p>So to open for friendlies we can keep the channel open through. Humans can push the door half a cirle and walk in like normal. Comes a zombie and we close the plate inside to block the passage, and he can spin the door the whole circle just to end up right back outside, wondering in a zombie way what is going on...</p>\n\n<p>And better yet, build that whole gate as a turbine. Make some noise to invite thousands of them to come and spin the gate to generate some electricity for us...</p>\n\n<p><a href=\"https://i.stack.imgur.com/zaEs7.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/zaEs7.jpg\" alt=\"enter image description here\"></a></p>\n" }, { "answer_id": 72030, "author": "Community", "author_id": -1, "author_profile": "https://worldbuilding.stackexchange.com/users/-1", "pm_score": 0, "selected": false, "text": "<p>Since this is the walking dead zombies we're designing this wall against all we would need to do is direct sounds inside the wall away from the outside of the wall - this sounds dumb and hard, but I think it's doable when you consider how sound is already being directed away from places the user is likely to be in some gaming desktops - and tie de-toothed walkers to the front entrance. This way the walkers won't be able to hear the humans inside the wall and they won't be able to tell the difference between the wall and de-fanged walkers.</p>\n\n<p>The better question is why would you want to do this? none of the walls in the walking dead have ever failed because of walkers. They always fail because the people do something stupid in terms of maintenance with the wall. The little girl feeds the walkers rats at the prison and then someone drives a tank through the gate. The wall at Alexandria fell because someone didn't do anything about the building that could, and did, fall through the wall. The wall at the hilltop \"broke\" because humans on the outside broke it. These aren't things that repelling walkers from the gate is going to fix. If you want to fix this stuff then you should really just build bigger walls. Notice that no one has a secondary gate. No one has a second wall either. When you look at the walls in the walking dead they're just poorly designed for defensive purposes because they were put together in a rush to deal with walkers. All of the people with worse walls than the ones featured in the show currently have lost their settlements because the built garbage walls. Remember Noah's colony with the week 10ft wall? Compare that wall to the one at the hilltop.</p>\n" }, { "answer_id": 72042, "author": "Enigma Maitreya", "author_id": 33822, "author_profile": "https://worldbuilding.stackexchange.com/users/33822", "pm_score": 1, "selected": false, "text": "<p>Well I think a rather simple design might be to steal the idea of the Plow from above and simply make it the gate.</p>\n\n<p>So instead of a straight across/up gate make it some version of a V type gate. You can construct the braces with a beam/bar fitting into the door panel and the ground.</p>\n\n<p>Get adventurous and have a platform covering the opening at the top for easy pickings vs the Zombies.</p>\n\n<p>Get even more adventurous and have a walkway up there that will channel the zombies to the end were they fall (get pushed) out. Maybe put a grinder were they fall.</p>\n\n<p>Get even more adventurous and provide slots for pikes (as mentioned in another answer).</p>\n\n<p>Should be relatively easy to open and close.</p>\n\n<p>An attempt at drawing :)</p>\n\n<pre><code>########\n# #\n# #\n# #\n### ###\n \\/\n</code></pre>\n\n<p>Pressuring the doors from the outside push's then together and the individual door can be braced.</p>\n\n<p>Platform on top of the V can be used to attack the zombies. Equaly any number of schemes for funneling the Zombies can be used here. Most notably would be steps up on both sides with a walk way away from the door to the outer edge which could simply be a drop to the ground, grinder, pit (hum Fire Pit?) etc. Regardless the spirit of this is to funnel the \"horde\" away from the gate in a constant flowing manner.</p>\n\n<p>The V gate has a very short space to open to full and close.</p>\n" }, { "answer_id": 72063, "author": "Anonmymous", "author_id": 33832, "author_profile": "https://worldbuilding.stackexchange.com/users/33832", "pm_score": 4, "selected": false, "text": "<p>From an engineering perspective (and having done mechanical engineering for better than 30-years, with a few college degrees for the trouble), I can say that the problem with doors (in reality) isn't that they fail, per-se, but that their attachment points usually fail. The 'threshhold' (door frame, hinges, latching hardware, and subsequent structure framing) are actually what fail most of the time, when dealing with real-world 'doors on old buildings'. Add to this problem the issue of a mob-horde pushing en-masse into the door, and you have a 'maximum material condition' best addressed by material properties considering age.</p>\n\n<p>To bring this down to a layperson's perspective, a 2-inch thick oak door, itself, isn't going to fail an interior hatchway (where water or weather aren't a significant aging factor). Failure will come from mechanical stresses (aging, fracturing, etc.) of the mounting hardware (all iron-based metals fracture, in-time).</p>\n\n<p>Were I building a 'thousand-year-zombie-door' (in absolute theory, here), I would start with a granite double wall set up for a pocket-door (where the door slides, but not as a sliding glass door does - a pocket door is 'hidden' in a wall, when opened via being slid back). I would ensure that the header and footer track were at LEAST 15-percent the height of the passageway itself (so the door would need to be 30-percent taller than the opening itself, as it would also need to be at LEAST 30-percent wider). I would use brass or stone rollers on the top rail, and a secondary grooved channel rail at the bottom (to allow for drainage and prevention of the door galling into an immovable state over time). For the door material itself, I would most-likely go with either 45-55 mm thick stainless steel or high-phosphor bronze plate (so the door would most-likely weight a couple of tons).</p>\n\n<p>This would then provide for thousands and thousands of kilograms of resistive force for centuries, without reaching material failure points. It also allows you to still slide the door open with thousands of zombies on the other side, otherwise blocking you from opening it later, when you want to get out. Remember one thing, as they pile in, and block the door, they are also still 'juicy' and will rot an organic door and jam any fragile hinge, latch or roller mechanism. No jewelry box doors here, think more like aztec pyramid construction methods instead.</p>\n\n<p>You now have a worthwhile fort door that can be opened with a simple pry lever, at worst, that will last a millennium, and still look good being a 'door'.</p>\n\n<p>Oh, and you might want to remember a simple rule of combat: Make a fortress too hard to get into, and you'll build the perfect crypt you can't get out of!</p>\n" }, { "answer_id": 72111, "author": "gwally", "author_id": 30866, "author_profile": "https://worldbuilding.stackexchange.com/users/30866", "pm_score": 1, "selected": false, "text": "<p>Several answers posted show gates that could survive any conceivable zombie attack. I wanted to mention the best defense would be one that stops the zombies before they ever reach the compound wall in the first place. My solution would be to build a secondary wall and audio trails to keep zombies away.</p>\n\n<p>We know from earlier Walking Dead episodes that zombies are attracted to sound and light. None of the towns really use sound or light decoys to direct zombies away from a compound because the show uses the zombie horde attack as a plot device.</p>\n\n<p>If this was a real life situation, building a secondary fence away from the compound would help direct the zombies to another location. If you build a series of audio devices along fence line, you create an audio trail to draw the zombies away from your compound area without directly interacting with them, saving you time and effort. This way zombies that are some distance away might be redirected and never approach your area in the first place. If they never enter your area, they never become a potential threat to your gate.</p>\n" }, { "answer_id": 72126, "author": "jose_castro_arnaud", "author_id": 15388, "author_profile": "https://worldbuilding.stackexchange.com/users/15388", "pm_score": 2, "selected": false, "text": "<h2>Redirect and mislead.</h2>\n\n<p>Build an outer wall, with an obvious and noisily entry gate; the zombies enter it, and are led into a kill zone (one or several big holes, spikes at the bottom), with a dead end. They get nowhere near the inner wall's gate.</p>\n\n<p>Regular humans will enter/exit the outer wall by a concealed outer gate, not noticeable by the zombies (they're dumb).</p>\n" }, { "answer_id": 72146, "author": "Fernando", "author_id": 33863, "author_profile": "https://worldbuilding.stackexchange.com/users/33863", "pm_score": 2, "selected": false, "text": "<p>If your wall is so resistant that you only need to worry about the door, you can build something like this<a href=\"https://i.stack.imgur.com/Tu4bB.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/Tu4bB.png\" alt=\"enter image description here\"></a></p>\n\n<p>where <code>gray</code> is the wall and <code>blue</code> is the door. The zombies can't exert the force in the direction needed to break the door.</p>\n" }, { "answer_id": 72153, "author": "Thorne", "author_id": 33868, "author_profile": "https://worldbuilding.stackexchange.com/users/33868", "pm_score": 2, "selected": false, "text": "<p>Simple. A trapdoor. It requires being lifted up thus any zombies trying to open would have to bend down and grasp the door assuming they had the intelligence to do so. Even if smart enough the number of zombies lifting is limited to the number of zombies that can reach the door at one time.</p>\n\n<p>If the trap door has no handles on the outside no zombies can even try to lift it.</p>\n\n<p>In all likelihood the zombies would shuffle across the top and not even pay attention to it</p>\n" }, { "answer_id": 72337, "author": "WoJ", "author_id": 9246, "author_profile": "https://worldbuilding.stackexchange.com/users/9246", "pm_score": 3, "selected": false, "text": "<h2>A door which can only open outwards, on rails.</h2>\n\n<p>The architectural design is below (as seen from the top):</p>\n\n<p><a href=\"https://i.stack.imgur.com/hOUx7.png\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/hOUx7.png\" alt=\"enter image description here\"></a></p>\n\n<p>The black part is the wall. The gray part is the \"door\", made of the same material as the wall.</p>\n\n<p>If you want to open the door you must slide it on the blue rails outwards. </p>\n\n<p>When zombies arrive, they could</p>\n\n<ul>\n<li>try to push the door, which will then push against the walls, effectively becoming part of the wall. They will not get in. </li>\n<li>(assuming some intelligence) realize that the door moves outwards and try to pull out.<br>\nThe red part comes then into play: it is solidly attached to the door and turns horizontally to push against the walls (when one wants to prevent the door to be open (=pulled outside)) or vertically in normal times. There could be other designs here, the point is to make sure that one cannot pull the door out from outside (a hinge could be a better choice)</li>\n</ul>\n" }, { "answer_id": 75624, "author": "Omegacron", "author_id": 2083, "author_profile": "https://worldbuilding.stackexchange.com/users/2083", "pm_score": 3, "selected": false, "text": "<p>From a purely defensive viewpoint, the best possible design for a gate or door is the same design that many bank vaults use. You take a heavy metal door which is smaller on the inside than the outside, like a ziggurat on its side, then put it in a matching door frame. The larger portion of the door prevents the door from pushing inward past the frame. Combine this with heavy hinges and pistons which slide out of the door into the frame, and you have a virtually unbreakable door. </p>\n\n<p>This same basic principle is used in many military installations, such as the famous \"red door\" of the Cheyenne Mountain Complex in Colorado. In fact, the design is often called a \"blast door\" because it can withstand MASSIVE amounts of pressure from the outside. The weight of the door itself isn't really an issue, either - as long as the door, hinges, and surrounding wall are strong enough to withstand the amount of pressure exerted against it, a door of this design will NEVER give or fail.</p>\n\n<p><a href=\"https://i.stack.imgur.com/kFy30.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/kFy30.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>Now, all that said... this is serious overkill for zombies. This door will hold even if the zombies are running into it with bulldozers at high speed, or ramming into it with tanker trucks full of gas, or even shooting low-yield nuclear weapons at it. And if they're doing all that, you're pretty much screwed anyway. Just accept your fate and die with some dignity.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/71877", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/11049/" ]

[ { "answer_id": 72395, "author": "Atlas the Worldbuilder", "author_id": 27889, "author_profile": "https://worldbuilding.stackexchange.com/users/27889", "pm_score": 2, "selected": false, "text": "<p>Let me preface this by saying that, as a mortal, non-omnipotent being, I cannot know all outcomes. I will do my best to answer with what I as Worldbuilder think may happen, but keep in mind that what I say doesn't have to apply to your world. In other words, take what's I say with a grain of rice, and feel free to use your own interpretation.</p>\n\n<p>.</p>\n\n<p>In regards to your queries, let's first take a look at your world, and compare it to our own Earth/Moon System.</p>\n\n<p>Luna is approximately 27% the size of earth, and at its furthest is about 405,000km distant. This translates to about 1.985 x 10^26 N of gravitational force between the two objects. </p>\n\n<p>Jeah, on the other hand, is about 14.5% the size of Paveiah, yet is only 17,000 km from its parent body. Considering the size ratio between parent body and Moon, your moon and planet have a size ratio half as much as the ratio between Earth and Luna, yet is also 27x closer. This translates to around 1.857 x 10^26 N of force. </p>\n\n<p>.</p>\n\n<p>Given the calculations above, here are my conclusions.</p>\n\n<ol>\n<li><p>No, Billy-Jeah isn't in danger of crashing down anytime soon.</p></li>\n<li><p>Given the size ratio and distance between parent body and child body, Jeah's gravitational effect shouldn't be too different from the current tidal effects on Earth. Keep in mind, though, this is assuming that Jeah and Paveiah share Earth and Luna's makeup; if, say, Jeah was made completely of iron, then this estimate is off.</p></li>\n<li><p>Gathering the increased level of oxygen, it's possible that Earth-style creatures would have increased energy. Big bugs, stronger animals, and more flammable areas. This, though, is assuming that the extra oxygen doesn't KILL them; too much of a good thing, after all...</p></li>\n<li><p>Given the previous information, it's safe to say that the far side will definitely have permanent ice. But the nearest point to the star's light would receive the maximum amount of solar radiation it could get. Given that there's a huge hunk of land there, this'll likely mean that weather patterns will be driven partly by temperature differences, with hot air of the near side rushing away to meet the cool air from the far side. This should translate to a belt of vegetation between the two zones, and rainstorms would likely be frequent along this area.</p></li>\n<li><p>That, I cannot answer adequately, I'm afraid. Because that would require me to make a whole host of assumptions about my species and its current level of technology. Even with humanity, we're only good enough to give a \"maybe\" for whether a planet even has liquid water on its surface. The fascinating point, really, is whatever you set it to be; beauty, as they say, is in the eye of the beholder.</p></li>\n</ol>\n\n<p>.</p>\n\n<p>Hopefully this answered some of your questions. </p>\n" }, { "answer_id": 72671, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 4, "selected": true, "text": "<h1>Simulation setup</h1>\n\n<p>I ran a simulation with your worlds in <a href=\"http://rebound.readthedocs.io/en/latest/index.html\" rel=\"nofollow noreferrer\">Rebound</a> using Python. I have my setup on github if you want to <a href=\"https://github.com/kingledion/worldbuilding\" rel=\"nofollow noreferrer\">take a look at it</a>. The file is </p>\n\n<pre><code>orbit_noble_170301.py\n</code></pre>\n\n<h1>Results</h1>\n\n<p>I ran the integrator a few times with different time steps. For dt = ~12 hours, Jeah immediately left orbit of Paveiha and fell into orbit around the main star. Then after 4200 years, it had a close encounter with Paveiha and the last I was tracking it, it was about 0.7 light years away from the star and going fast. </p>\n\n<p>I switched up the time steps and did some other modifications (not of the orbital parameters) but it never took more than a couple thousand years for Jeah to get ejected. </p>\n\n<p>My thesis is that Jeah is just too light. Paveiha is 3 Mars's or half a Venus, but Jeah is a relatively puny Titania or Haumea size. It is about 1/20th the size of our moon. I was guessing that it was just too small; given that it wouldn't stay in orbit of the main plant (too close to the star I'm guessing), it was too light to stick around in the solar system.</p>\n\n<p>So I tried increasing the size of Jeah by a factor of 10. This was a little better. Instead of getting ejected it tended to settle out in an orbit at around 12 AU (hope there's no gas giants!).</p>\n\n<h1>Conclusion</h1>\n\n<p>I could not find a stable orbit for Jeah around Paveiha. I didn't even have to try integrating millions of years overnight; Jeah got stripped from the planet into an orbit around the star in a few decades. </p>\n\n<p>If you want to give this a try by yourself, try to add yourself at my github and then we can talk there. I can try to help you set up rebound yourself, if I have the time. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/72387", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/33954/" ]

[ { "answer_id": 72470, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 2, "selected": false, "text": "<p>The genetics underlying this story point to your space empire being a culture of genocidal matriarchal witches. Allow me to explain. </p>\n\n<p>It is not easy for all descendants of trait carriers to have the trait which I think is what @ratchet freak meant with \"isn't compatible with genetics\". Since we are a mix of mom and dad some people will be heterozygous for trait - I am a heterozygote if I received a copy from Belgian dad but not from African mom. Assuming the other parent of my own child is a noncarrier, my child might get trait from me if she gets the Belgian copy but not if she gets my African copy. If you try to prevent this by making heterozygosity lethal it is impossible for a chromosomal trait to disseminate out into the population because then homozygotes can only have children with other homozygotes.</p>\n\n<p>One way which might work for your story is to put the trait on mitochondrial DNA instead of chromosomal DNA. Then all children born of a mother with trait have trait because mitochondrial DNA is inherited only from the mother.</p>\n\n<p><a href=\"https://en.wikipedia.org/wiki/Mitochondrial_Eve#Female_and_mitochondrial_ancestry\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Mitochondrial_Eve#Female_and_mitochondrial_ancestry</a></p>\n\n<p>This fact was used to trace back how long ago \"mitochondrial Eve\" existed. She is the most recent common ancestor of all humans. Wikipedia has a nice table showing how randomness over time will cause extinction of all but one variety in the population. I was skeptical when I initially read this but even with my very rudimentary skills it was not hard to model in basic or even Excel. Each female has a random plausible number of offspring, and then a random % of each die before reproducing. Set the death rate such that your total population is stable or grows / shrinks according to your wishes. Half of each new generation are females and they determine the next generation. Eventually all individuals have 1 mitochondrial type.</p>\n\n<p>Mitochondrial Eve was roughly 100,000 years ago.</p>\n\n<ul>\n<li><p>If you give the trait a selective advantage you can make that happen sooner: for example % of death is lower for trait carriers</p></li>\n<li><p>If % of female offspring is higher trait will spread faster (which would have interesting ramifications for a story). % of female offspring could be something inherent in the trait. Or they could practice selective infanticide of male children. Or they could use witchcraft to make sure the babies were girls. Witchcraft has a long history in this context. </p></li>\n<li><p>If you make your total human population smaller it can happen sooner too, like in the tiny population in the Wikipedia figure. One way to do this is to ram the population thru a bottleneck and make it temporarily very small.\n<a href=\"https://en.wikipedia.org/wiki/Population_bottleneck\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Population_bottleneck</a>\nA genocide of all nonBelgian females would work for this. I suspect historically genocidal conquerors had a different agenda so that would be interesting for a story also. </p></li>\n</ul>\n" }, { "answer_id": 72474, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 4, "selected": true, "text": "<h1>Estimating the spread within a population</h1>\n\n<p>Initially, one person has this trait. Assuming it is passed on each time, to children of either sex (which it seems like you are implying) then we can estimate the number of generations it would take for everyone in a population of size $x$ assuming anyone in the population is equally likely to intermarry with and reproduce with anyone else. </p>\n\n<p>When there are $t$ people with the trait, each of $x-t$ people who do not have the trait in the intermarrying group, have a $t$ in $x-1$ chance of marrying someone with the trait. </p>\n\n<p>Thus for the first generation, $t=1$ and lets say $x=100$, $$(x-t)\\frac{t}{x-1} = (99)\\frac{1}{99} = 1$$ more person will gain the trait in the next generation. This is because this simple model assumes the population stays constant, and every two people have two offspring. Thus the one trait-haver has two children, so the second generation has two trait-havers.</p>\n\n<p>Applying this function (with a little python script), we can calculate the number of generations it takes for this trait to spread through 90% of a population:</p>\n\n<pre><code> Pop Size Generations\n 100 9\n 1000 13\n 10000 16\n 100000 19\n 1000000 23\n10 billion 36\n</code></pre>\n\n<h1>Estimating the spread between populations</h1>\n\n<p>That last assumption is probably not the best for a lot of reasons, but mostly, it should be good enough. Where it breaks down is in population transfer between groups. How well do people spread between groups?</p>\n\n<p>This is very much an open question. While it is very much not hard to imagine some trait-haver captured and sold into slavery in the Middle East and spreading the genes there, it is much more difficult to imagine that trait going to China.</p>\n\n<p>Your history will have to give us a clue. If this Empire did expand around the world, then there is a good chance that the conquering population distributed their DNA through various conquered populations by various means. </p>\n\n<p>In that case, it takes 36 generations for such a trait to spread among 90% of 10 billion people. Assuming a 25 year generation, that is about 900 years. Since it only takes 4 more generations to get from 90% to near 100%, it is a good bet the whole world has this trait. </p>\n\n<p>If we start with a million Belgians conquering the known world in 1400 AD, then it will take 14 generations to pass on to 10 billion people, or 350 years. So again, everyone in the world should have this trait by 2050 AD.</p>\n\n<h1>Conclusion</h1>\n\n<p>If this trait is beneficial, and there isn't some caste-system keeping the conquering Belgians from interbreeding with the lesser conquered, then it is reasonable to assume that this trait will spread to the entire world population soon after the Belgians complete their world conquest. </p>\n" }, { "answer_id": 72486, "author": "Hiraeth", "author_id": 33998, "author_profile": "https://worldbuilding.stackexchange.com/users/33998", "pm_score": 3, "selected": false, "text": "<p>Short answer: it is extremely likely</p>\n\n<p>Long answer:\nI would look at the spread of lactose tolerance as a real-world example. <a href=\"https://en.wikipedia.org/wiki/Lactase_persistence#Global_spread\" rel=\"noreferrer\">https://en.wikipedia.org/wiki/Lactase_persistence#Global_spread</a> It arose 10,000-5,000 years ago, was highly selected, and spread rapidly throughout Europe, so now over 80% of all Europeans have the gene, while it is barely present in Asia/Africa. But it really depends on how heavily selected the gene is. Remember that fitness depends entirely on the number of surviving children, not how long the individual lives. It the case of something highly selected, the gene will spread very fast, and dominate the gene pool rapidly. If the gene is only lightly selected or neutral, then it will not spread rapidly, as mutations that delete or knock the gene out will trim the population.</p>\n\n<p>So, lets make some assumptions here. If your gene follows classical Mendelian inheritance and is dominate, then having one copy from a mother or father will give it to the child. I’ll also assume the trait is highly selective. After 2500 years, the nearly, but not all Belgians would have the trait, because of things like mutations, genetic drift, etc. It would spread in decreasing amounts from that centerpoint, mostly likely concentrated on the ruling classes. This is just spitballing here, but I would expect a majority of Europe to have the gene, with Africa/Asia only having a minority with gene. For example, if a Belgae with one copy of the gene (Gg) married a native foreigner (gg), then only half the kids would carry the gene</p>\n\n<p>Eventually, the gene would become fixed in the population, but that could take tens of thousands of years</p>\n" }, { "answer_id": 72546, "author": "Sherwood Botsford", "author_id": 15784, "author_profile": "https://worldbuilding.stackexchange.com/users/15784", "pm_score": 1, "selected": false, "text": "<p>Is this trait selective? That is, is someone who doesn't show this trait less likely to have offspring?</p>\n\n<p>To meet your conditions, the trait is dominant. One copy is sufficient for the trait to be expressed. </p>\n\n<p>If not selective, then the stable levels for genotype to be TT, Tt, tT, and tt with 75 percent showing the trait and 25% not showing the trait. A close model right now in human physiology is the inheritance of eye colour.</p>\n\n<p>If there is selection, then the population will become homozygous for T, with very few expressions of t very quickly. Albinism for example. Or Tay-Sachs disease.</p>\n\n<p>The rest of it will depend on the interaction between populations. A selective gene can dominate a local population very quickly, but if that population doesn't out-breed into neighboring populations, then it will sit in that corner of the world. One of the reasons we have 'races' in humankind is that genes don't flow well between continents.</p>\n\n<p>If your culture was at a crossroads, such as what is now modern day Israel, where invaders from 3 continents pillaged their way through every few generations, taking slaves back to their own lands, then the time span will be measured in centuries. If your culture is isolated, such as the natives on Tierra del Fueago, or Austrailian Abos up to the invasion from England, then the time to spread could be essentially infinite.</p>\n" }, { "answer_id": 72561, "author": "Luís Henrique", "author_id": 20929, "author_profile": "https://worldbuilding.stackexchange.com/users/20929", "pm_score": 0, "selected": false, "text": "<p>You are assuming that being smarter is an advantage. I am not so sure that it is.</p>\n\n<p>Evidently, the \"Belgians\" would be able to defeat the non-Belgians. But then what do they do? They exterminate the vanquished? They randomly intermarry with them? Or do they enslave the non-Belgians, or establish another kind of exploitative relationship with them?</p>\n\n<p>If so, they don't want their underlings to be as smart as them; if they have any clue of their intellectual superiority, they will strive to keep it, by systematically avoiding interbreeding. If they don't, then their superior gene will spread downwards their society, and soon they will have smart slaves realising that slavery is not something to be cherished.</p>\n\n<p>Your society will have a Newton by the 14th century. But then it will have a Marx by the 15th.</p>\n\n<p>So it is very likely that non-Belgians would exist, and would abound - they would be purposefully kept like that, in order to better serve their Belgian masters.</p>\n\n<p>Then the problem is that slavery hampers technological progress. You don't need windmills if human brute force is available and plenty.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/72458", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/227/" ]

[ { "answer_id": 73085, "author": "Paul TIKI", "author_id": 31273, "author_profile": "https://worldbuilding.stackexchange.com/users/31273", "pm_score": 2, "selected": false, "text": "<p>I'm not certain a fireball would do much more than surface damage to a creature like this in most instances. something like a fireball (in my mind) is pretty much just fire. To cause lasting damage, you need a reliable and steady means of thermal transfer. Boiling Water would do much more damage much more quickly because of the specific heat of water as opposed to the specific heat of air. This is to transfer heat damage through the skin and clothes.</p>\n\n<p>There is one thing about a fireball that might work though. Lungs are pretty fragile. Time a fireball to go off during the Ice creatures \"inhale\". Cell layers in the lungs are maybe one or two layers thick, so the fire should be able to crisp a large quantity of lung tissue in a short period of time. The problem is: Is you mage skilled enough to launch and place the fireball well enough to catch the Yuki-Onna on the inhale. Not very likely. Go with Boiling Water, or even better, a Glob-O-Lava for max damage.</p>\n" }, { "answer_id": 73090, "author": "Schwern", "author_id": 760, "author_profile": "https://worldbuilding.stackexchange.com/users/760", "pm_score": 6, "selected": true, "text": "<blockquote>\n <p><em>The problem I am having is this. Ice (frozen water particles) should melt in layers, which would then need even more energy (heat) to vaporize. So, in theory, Fire shouldn't be 'super effective' against ice. It would take too long to be effective.</em></p>\n</blockquote>\n\n<p>What you're describing is <a href=\"https://en.wikipedia.org/wiki/Ablative_armor\" rel=\"noreferrer\">ablative armor</a> where the protection comes from the armor eroding away. This is used on <a href=\"https://en.wikipedia.org/wiki/Ablative_heat_shield\" rel=\"noreferrer\">real spacecraft as a heat shield</a> (just not made of water).</p>\n\n<p><a href=\"https://i.stack.imgur.com/W5R9z.jpg\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/W5R9z.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>Ablative armor works by carrying away the energy of the attack in lots of tiny fragments. A microscopic outer layer heats up, vaporizes, and is blown way taking the energy along with it. Water works fairly well at this because it has a very high <a href=\"https://en.wikipedia.org/wiki/Specific_heat_capacity\" rel=\"noreferrer\">specific heat</a>, meaning the amount of energy needed to raise its temperature: 4.2 J to raise 1 gram of liquid water by 1 C. <a href=\"http://www.engineeringtoolbox.com/ice-thermal-properties-d_576.html\" rel=\"noreferrer\">Ice is about 1.9 J/g/C</a>.</p>\n\n<p>Phase changes also take energy. Going from water ice to a liquid water takes 333 J/g. From liquid water to vapor is a whopping 2257 J/g. This is why we still use steam to turn generators, it contains a lot of energy. This is also why steam scalds are so bad.</p>\n\n<p>So to take 1g of -50 C ice to 100 C water vapor takes...</p>\n\n<pre><code>-50 C -&gt; 0 C | 50 C * 1.9 J | 95 J\nSolid -&gt; Liquid | 333 J | 333 J\n0 C -&gt; 100 C | 100 C * 4.2 J | 420 J\nLiquid -&gt; Gas | 2257 J | 2257 J\n-------------------------------------------------\nTotal 3105 J\n</code></pre>\n\n<p>That is roughly 1 <a href=\"https://en.wikipedia.org/wiki/Kilowatt_hour\" rel=\"noreferrer\">Watt-hour</a> (ie. 1 Watt for 1 hour or 60 W for 1 minute) or <a href=\"https://en.wikipedia.org/wiki/Orders_of_magnitude_(energy)\" rel=\"noreferrer\">roughly the kinetic energy of an Olympic hammer throw</a>... for ablating a single gram of -50 C ice.</p>\n\n<p>To put that in perspective another way, <a href=\"http://energyusecalculator.com/electricity_stovetop.htm\" rel=\"noreferrer\">a typical stovetop burner uses 1500 J/s</a> and so could ablate 1 gram of -50 C ice every 2 seconds. This is why boiling water on a stovetop takes so long.</p>\n\n<hr>\n\n<p>The problem with ablative armor is its protection eventually wears out. The question then becomes how much energy does this fire attack have? Does it have enough to ablate all the ice? If so then their goose is cooked. If not, then they'll be -- mostly -- fine.</p>\n\n<p>A quick puff of flame isn't going to do more than vaporize the outer layer of frost; and if their chill is magical it will rebuild that layer with water vapor from the surrounding air. While a sustained flame will wear away the layer of ice and start scorching flesh and presumably doing damage.</p>\n\n<p>So really fire against a frost being would be very ineffective until all the ablative ice vaporizes, then it's just as effective as fire is on flesh. If you're playing an RPG this could be modeled as a pool of HP that absorbs fire attacks and slowly replenishes itself. When it's gone, fire does full damage.</p>\n" }, { "answer_id": 73091, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 4, "selected": false, "text": "<h1>Ice has a large enthalpy of fusion</h1>\n\n<p>The specific heat of ice is 2.05 kJ/kg*K. That means it takes so many kilo-joules to raise a kilogram of ice by one degree kelvin. </p>\n\n<p>The enthalpy of fusion of ice is 333.5 kJ/ kg. Therefore it takes so many kilo-joules to melt a kilogram of ice.</p>\n\n<p>For a mythical ice creature, losing and kilogram of ice might not be that important, assuming it has a way to make up the lose by freezing water out of the air or something. If this is the case, then the 333 kJ blast wouldn't really be life-threatening.</p>\n\n<h1>Its hard to melt that much ice</h1>\n\n<p>Now 333 kJ of heat energy is not that much energy in the long run. But it still represents a lot of energy for one attack. That is roughly the complete discharge from a lead-acid battery. That means if you discharged a car battery through this creature, it would probably not be killed (can't say the same about you or me). </p>\n\n<p>To put this in more fireball related terms, this is 10% of the blast of 1kg of TNT. If a block of explosives went of about a foot away from this creature, and blasted in all directions, the amount of heat energy that this creature absorbed would be around 333 kJ, and would not be deadly. If 1kg of TNT went off 1 foot from you....well....condolences to your family. </p>\n\n<h1>Conclusion</h1>\n\n<p>Melting ice is hard. Better off doing what most people do to get rid of ice, hit it with a shovel. Let springtime and the sun take care of the melting. </p>\n" }, { "answer_id": 73092, "author": "JDługosz", "author_id": 885, "author_profile": "https://worldbuilding.stackexchange.com/users/885", "pm_score": 3, "selected": false, "text": "<p>You are describing that the air she inhales is magically cooled, and that the ice being is magically cooled against <em>normal</em> room temperatures.</p>\n\n<p>So why can’t it combat oven temperatures as well? It’s a matter of capacity, not general ability.</p>\n\n<p>Just as we heat our flesh and can tolerate <em>some</em> cold environment, yourcreature will have some active countereffects against <em>some</em> increased temperature. This can be tireing.</p>\n\n<p>Just as we can reach into a hot oven and grab a foil tray but are burned instantly if touching a solid metal tray, and fireballs remove the hair from my arm but don’t otherwise injur in such a short exposure, your creature can be overwhelmee with heat if delivered fast enough.</p>\n\n<p>Hot air might not do it. Use <em>hot water</em>, or hot metal objects.</p>\n\n<p>I suggest that the best weapon is <strong>steam</strong>. Steam will scald you far worse than boiling water, because of the phase change heat. This nicely counterballances the huge amount of heat needed to melt the ice!</p>\n" }, { "answer_id": 73139, "author": "Vylix", "author_id": 34288, "author_profile": "https://worldbuilding.stackexchange.com/users/34288", "pm_score": 0, "selected": false, "text": "<p>In addition to already existing answers, please remember that the layer of ice being melted away is analogous to human skin and flesh. Thus this creature would effectively still sustain damage, though it would not instantly be killed.</p>\n\n<p>Depending on your setting this creature would or would not feel pain from the damage caused - a corpse should <em>not</em> feel pain, though.</p>\n\n<p>I would suggest using fire or any other source of heat will still be an effective method to combat this creature.</p>\n" }, { "answer_id": 73171, "author": "Rekesoft", "author_id": 34298, "author_profile": "https://worldbuilding.stackexchange.com/users/34298", "pm_score": 2, "selected": false, "text": "<p>Well, if by <i>fireball</i> you actually mean a sphere of nothing but temperature gently surrounding your target, then yes, heat is going to take too much time to be an effective weapon. But if you are thinking in the more usual form of fireball, a blast of flames akin to a deflagration, then you surely can blow the Yuki-Onna out. </p>\n\n<p>The key, as with any explosive, is not the heat nor the raw chemical energy of the explosive, but the sudden raising pressure blow when the thing goes off - gasoline is more energetic than TNT, and butter more than gasoline, but you have way more probabilities of surviving a pound of butter burning besides you than an pound of TNT :D. </p>\n\n<p>Ice is hard, and so, very fragile. It should shatter in a thousand pieces when smashed by a 3 psi push or above. </p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/73073", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/23068/" ]

[ { "answer_id": 73441, "author": "L.Dutch", "author_id": 30492, "author_profile": "https://worldbuilding.stackexchange.com/users/30492", "pm_score": 3, "selected": false, "text": "<p>These steps may help (no numbers provided):</p>\n\n<ol>\n<li>Engineer your blade so that it is stiff when loaded from the front and it bends when loaded from the sides (carbon fibers can be used to increase anisothropic behavior and also keep the weight under control). In this way you can still chop your enemy by having a stiff blade, but if you try to hit your enemy with the side of the blade he will simply be hit by a \"wobbling stick\".</li>\n<li>Join the two blades by the handles, and pull a \"string\" between their other ends. Since the handle is the place where you have maximum load when you pull your bow, you can't rely on something flimsy to hold the swords in place. </li>\n</ol>\n\n<p>If the bonding is made with some \"quick release\" mechanism, you can assemble and release the weapon within seconds. Removing the string may add some time to the action. You will need proper maintainance to the quick release, so that it operates as intended.</p>\n" }, { "answer_id": 73442, "author": "Aify", "author_id": 6453, "author_profile": "https://worldbuilding.stackexchange.com/users/6453", "pm_score": 6, "selected": true, "text": "<p>Is it possible? Yes, but not the way you think it will be.</p>\n\n<p>Theoretically, you could create the weapon you're describing by designing a \"hybrid\" weapon. </p>\n\n<p>We can avoid some of the things you think are difficult by designing the weapon as such:</p>\n\n<pre><code> /| |\\ /| and |\\ represent the two blades of sword\n ||[]|| || ||\n ||[]||\n ||[]|| - Sword sections are actually 2 outer normal blades\n ||[]|| - Middle section of sword \"[]\" is one limb of a bow.\n ||[]|| - \"M\"s represent a locking mechanism in the hilts to allow\n ||[]|| the joining of the two swords into a single bow\n ||[]|| - Hilt and guard of the sword are normal\n ||[]|| - String can be attached through top of limb\n ||[]|| \n ||[]||\n ||[]||\n ||[]||\n|============| &lt;--- guard\n {}\n {}\n {}\n {}\n WWWW &lt;------ Stores arrows\n MMMM &lt;------ Connecting spot, doubles as potential arrow rest\n WWWW \n {}\n {} \n {} \n {} \n|============| &lt;--- guard\n ||[]||\n ||[]||\n ||[]||\n ||[]||\n ||[]|| \n ||[]|| \n ||[]|| \n ||[]|| \n ||[]|| \n ||[]|| \n ||[]|| \n ||[]|| \n \\| |/\n</code></pre>\n\n<p>String can be designed to be stored INSIDE the limb of the bow\npulled out and connected together, like so:</p>\n\n<pre><code> -------------[Locking mechanism][Locking mechanism]-------------\n ^\n String\n</code></pre>\n\n<p>Basically, to answer your points:</p>\n\n<ul>\n<li>The sword parts don't bend (when pulling on the bowstring) - only the center, the limb part of the sword bends</li>\n<li>Assuming you designed the hilt locking mechanism properly, you could simply twist the swords 180 degrees to unlock and create 2 swords.</li>\n<li>This weapon shouldn't weigh much more than a normal sword. The limb used in the center of the weapon should overall cause the sword to be lighter than normal, since a large chunk of the metal will be gone.</li>\n<li>Done properly, you would be able to store 1 or 2 folding arrows in each hilt section. Carving out a section of the handle and hiding it in there is also an option. </li>\n<li>String attaches via Limbs</li>\n</ul>\n\n<p><strong>Would you be able to fight with this weapon? Yes, however there are some important things to note.</strong> </p>\n\n<p>Note 1: Limited ammunition with regards to shooting arrows. Severely so, unless you carry extra arrows on a belt or something.</p>\n\n<p>Note 2: Some fighting styles use the flat of the blade to block blows - this will damage your bow, and generally it's a bad idea to block with the edge of the blade as well, which means the defensive component of the fighting style of this sword user will likely need to be dodging and positioning based rather than parry based.</p>\n\n<p>Note 3: This weapon does not make a good stabbing weapon. Slashing only please - curved blades can help with this.</p>\n\n<p>Note 4: The bow mode won't look like a bow until you pull back the string, due to the way the string is notched and rests along the sword. It may end up looking like this from the side when pulled.</p>\n\n<pre><code> | /!\n |/ ! | represents the blade\n&lt;-------! ! represents string\n |\\ ! &lt;------ represents arrow\n | \\!\n\n Note that since the middle of the blade is the limb, when firing as a bow\n the flat of the blades will be facing towards you and the target. It \n should look almost like a + shape when taking the guard into account.\n</code></pre>\n\n<p>Note 4: The string can lock using a similar twist and turn mechanism, which can double as an easy arrow nocking point.</p>\n\n<p>Note 5: When using this in bow mode, your hand will likely be holding the bottom handle, since the middle section is where your arrow rest will be.</p>\n\n<p>Note 6: This sword/bow hybrid is not going to be as good a sword or as good a bow when compared to a normal sword or bow. It is simply impossible to get the best of both worlds in a single weapon.</p>\n\n<p><strong>ALTERNATIVE METHOD:</strong></p>\n\n<p>You can use a double scimitar, and simply design the tip of the scimitar to allow string threading. </p>\n\n<p>The sword still won't bend, however - instead, you'd want to put some springs between the guard of the sword and the hilt. This allows, when the swords are put together, for the springs to provide the power and the sword blades to become the limbs of the sword, almost like how a power spring bow would work.</p>\n\n<p>However, you may have some issues with slashing depending on how stiff the springs are. </p>\n\n<p>This method also doesn't seem as cool/original.</p>\n" }, { "answer_id": 73444, "author": "Till", "author_id": 30607, "author_profile": "https://worldbuilding.stackexchange.com/users/30607", "pm_score": 4, "selected": false, "text": "<p>The flexibility of the swords is no problem: <a href=\"https://www.youtube.com/watch?v=n4pxLGEXimo\" rel=\"noreferrer\">https://www.youtube.com/watch?v=n4pxLGEXimo</a></p>\n\n<p>You just have to build a small block in which you can stick the tips of the swords and add a small nudge to the sword-handles to hold the bowstring. The block will function as a handle for the bow. The bowstring will push the sword tips into the bow handle. The second you remove (if time is of the essence cut) the string, the whole thing will come apart and you have two swords.</p>\n\n<p>For the storage of the arrows, I recommend a standard quiver.</p>\n" }, { "answer_id": 73446, "author": "SZCZERZO KŁY", "author_id": 30912, "author_profile": "https://worldbuilding.stackexchange.com/users/30912", "pm_score": 1, "selected": false, "text": "<p>This is a bow. <a href=\"http://i.ebayimg.com/images/i/291160732523-0-1/s-l1000.jpg\" rel=\"nofollow noreferrer\">http://i.ebayimg.com/images/i/291160732523-0-1/s-l1000.jpg</a></p>\n\n<p><a href=\"https://i.stack.imgur.com/9L8Ji.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/9L8Ji.jpg\" alt=\"Bow\"></a></p>\n\n<p>You take the bendy parts and make them turn into cross guard. \nThat shmancy fancy round thing is your grip.<br>\nNow, your blade is made from two edges. Split exactly in half in central ridge. And those nonflexible parts make the central part of bow. </p>\n\n<p><a href=\"https://i.stack.imgur.com/9L8Ji.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/SmuPB.png\" alt=\"swordbow\"></a>\nSomething like this. </p>\n" }, { "answer_id": 73480, "author": "BunnyKnitter", "author_id": 13577, "author_profile": "https://worldbuilding.stackexchange.com/users/13577", "pm_score": 3, "selected": false, "text": "<p><strong>To start with:</strong> I don't think it is feasible to make a weapon like this that can be used in a fight. As a display weapon however, any of the other answers would probably work.</p>\n\n<p>Something to take into account is the incredible amount of force that acts on various parts of a bow to fire an arrow. I don't have math to back this up but I do DO archery - something that can absolutely destroy any bow is to \"dry fire\" it. That is - to draw the string and release without nocking an arrow. There is no resistance against the string in this case and it can BADLY damage the bow to even do this once. I think that the force of swinging swords against stuff would probably mimic damage similar to this. I will say however that since they would be probably made of metal or other \"stronger\" material than laminated fiberglass and wood, then they may survive this better than a normal bow-limb would.</p>\n\n<p><strong>Running with the idea anyways:</strong>\nRegarding disassembly, there are plenty of bows that are intended to disassemble. They are typically made of three sections: two limbs and a handle-section.</p>\n\n<p>(the black piece in this image is a stabilizer that is unnecessary to have)\n<a href=\"http://www.bestrecurvebowguide.com/wp-content/uploads/2013/06/Take-Down-Recurve-Bow.jpg\" rel=\"nofollow noreferrer\">http://www.bestrecurvebowguide.com/wp-content/uploads/2013/06/Take-Down-Recurve-Bow.jpg</a></p>\n\n<p>When the bow is strung, the curve in the limbs is actually flipped around such that they are curved in the OTHER direction - this is what allows them to \"snap\" and fling the arrow effectively. More traditional-style bows do use straighter limbs, however I do not think that they shot as far or as accurately.</p>\n\n<p>The feasibility of this sword-bow will also be dictated by how effective you want the bow portion to be. Do you want to be able to hunt with it and hit a small spot on a moving target (ie. a kill-shot)? Or do you simply want to be able to fire an arrow in the \"general direction\" of a target?</p>\n\n<p>If you want any measure of accuracy, then the limbs must not have any \"twist\" in them, and there must be no variance in how the bow portion is constructed each time. For example: a handle sliding together together to grasp the limb portions by the hilts as others have suggested MUST lock into place at the exact same spot every time. The string cannot vary in length or twist either. (Bowstrings are composed of several strands that have been joined into loops at the ends and twisted down the middle. More twist means a shorter string and more \"shooting force\" and a short string forces the limbs to bend more.) </p>\n\n<p>Furthermore, unless you are assuming a \"very good or above\" level of archer, then there are other \"must haves\" on a bow to allow/help with repeatable shot placement and reasonable aim: a reliable shooting platform (\"arrow rest\"), a string that only fits on the bow in one direction (ie. it cannot be flipped upside-down) as there is a \"nock-point\" that should be attached to the string to enable consistent arrow placement every time. This nock-point is not centered (it is close however) but is positioned according to the arrow-rest so that the arrow shoots straight.</p>\n\n<p>Perhaps the string could be stored inside the handle section on a spring-loaded roll. One end would be fixed to the handle and the other end could be pulled to run the string up the front of the sword-limbs (and sit in a groove to stay centered on them) and then down the backside of the bow to hook into a notch on the bottom sword-bow-limb. (The string would be attached in the middle to the front of the bow handle and looped over the bottom bow limb as a normal bowstring would be.) That would at least handle the string issue and keep a nock-point in the same place every time.</p>\n\n<p>If the user were to carry a middle-section to join the sword-limbs to, then that could potentially also work and would take care of the arrow-rest portion. It might take a few moments to switch from one form to another however so it probably would not work in combat.</p>\n\n<p>You would have to carry a quiver of arrows, although some quivers do actually mount to the side of the handle-section of a bow to store 3-5 arrows by clipping them into place.</p>\n" }, { "answer_id": 73567, "author": "Ville Niemi", "author_id": 3434, "author_profile": "https://worldbuilding.stackexchange.com/users/3434", "pm_score": 2, "selected": false, "text": "<p>One of my usual \"not really an answer, but covers things that should be mentioned, but were not in <strong>real</strong> answers\" <em>answers</em>.</p>\n\n<p>First, the actual questions: Yes, you can build such contraptions. As to how... well you really would not. Having a separate bow and a separate sword and switching between the two will always be better under any realistic scenario.</p>\n\n<p>As such the real question you need to think about when designing such weapon is not <strong>how</strong>, but <strong>why</strong>. What reason made somebody build such a weapon? <strong>That</strong> is what will tell you how to build it.</p>\n\n<p>First possible reason, and a trivial one, is that the combination weapon was built simply because somebody <strong>wanted</strong> to have one. All practical reasons for it being suboptimal were ignored, since efficiency and practicality were at best secondary considerations.</p>\n\n<p>Since this is analogous to the reason you are asking this question, you can simply use any of the given <strong>real</strong> answers. Even if it is not the best solution, getting the best is not really important in this scenario, so picking in random is fine. In fact since the details are not really important you can just skip them entirely and just have your bow that splits to two swords, but isn't really that good as either bow or swords and is pain to reassemble or split in any situation with pressure. Like combat.</p>\n\n<p>Which is why nobody would really do this, incidentally. Lots of weird combination weapons have been built over the centuries, but very few have seen significant use because for a weapon being as simple and reliable as possible is a merit in itself.</p>\n\n<p>Second possible reason and one that is usually used in fiction is that there is some limited resource that is highly useful for several types of weapons, but so rare or fickle you can only have it on a single item.</p>\n\n<p>In RWBY the personal weapons are presumably attuned with the users aura and powered by dust. In other settings the weapon might be blessed as part of a once in a lifetime ritual. In others they might be powered by rare power source or only built as part of a long ritual. It might be some combination of these.</p>\n\n<p>In any case it is the exotic limiting factor that informs the design of the weapon. Such limiting factors are essentially magic, so such weapons will be innately and generally obviously magical and exotic themselves. The weird transformations in RWBY would not really be practical in combat without the personal mystical link between the wielder and weapon, but with it they become extensions and manifestations of the wielders will and personality.</p>\n\n<p>What they are not is mechanically realistic. There is no point. Since an essentially magical factor is assumed, the transformation can be magical and exotic for \"free\". You can add an \"explanation\" like precursor nanomachines, magically infused materials, or extradimensional magic for added pseudo-realism.</p>\n\n<p>So for most fiction the correct solution would be whatever fits the character concept with setting appropriate \"explanation\" added afterwards.</p>\n" }, { "answer_id": 73642, "author": "Jacco", "author_id": 22130, "author_profile": "https://worldbuilding.stackexchange.com/users/22130", "pm_score": 3, "selected": false, "text": "<p>This would not work in the real world, let me explain.</p>\n\n<p>Physics dictate that when you release the string of the bow, the energy stored in the bended limbs of the bow is transferred to the arrow, the bow limbs and the bowstring.</p>\n\n<p>Because of this, the relative weight of the bowstring and bow limbs, is very important: the heavier the bowstring and bow limbs in relation to the arrow, the less energy is left to transfer onto the arrow (because a larger part of the energy stored in the bend limbs is needed to move the string and limbs).</p>\n\n<p>In other words, a bow needs light weight limbs (especially near the tips) and a light weight bowstring. The light bowstring is not hard to achieve with modern materials, as long as it is made in one piece. Any type of 'connector' would severely hamper you bow's performance. Light limbs are perfectly possible too of course, if you don't include the requirement that the limbs should double as a sword/saber/scimitar.</p>\n\n<p>The image on the URL liked in the OP shows saber (or scimitar) shaped blades. Any flexibility / bendiness in swords or sabers is perpendicular to the width of the blade. So, in order to use the blade of your sword as a bow limb, you would need a symmetrical (non-curved) blade (or otherwise, your bow would swing/turn in your hand as soon as you start pulling a string attached to the tips of your blade). This means that the saber/scimitar shape has to be replaced by a straight bladed sword.</p>\n\n<p>For our blade to double as a bow limb, we would need it to be quite flexible. A flexible blade would be quite useless for stabbing, so instead we would have our blade rely on slashing/cutting to wound our opponent. However, a cutting sword relies, in part, on the weight of the weapon to do damage. The lighter the blade, the less of an impact it would make when hitting our opponent. And there lies the contradiction: for an effective cutting weapon, your blade needs a certain minimum weight, while an effective bow limb needs to be as light as possible.</p>\n\n<p>Even if you made two symmetrical, straight, flexible bladed swords, joined them together at the handle (joining two bow limbs at the handle is commonly done with take-down bows, so this should not pose a problem) and attached a string to the end of one of the two blades, you would be faced with the part of stringing your bow.<br>\nThis could certainly be done, but it will takes a bit of time and is certainly not something you quickly do in a combat situation. If the bow has a low draw weight, it can be done in a couple of seconds (but at low draw weight bow is useless for combat). Stringing a heavy draw weight bow takes more time and quite some effort. Stringing a bow with sword sharp edges would take quite an effort <em>and</em> require the absolute care not to cut yourself, when building up tension on the bow limbs/the sword blades.</p>\n\n<p>So, while I can see the cool factor for in an anime, it is not really an option in the real world. If you wanted to make a non-functional prop (for cosplay or something) you could probably makes something that looks ok, but it would not be a functional weapon. At the very best it would be a combination of a weapon that is hampered in its primary functioning by a non-effective secondary idea.</p>\n\n<p>For any practical use, having either a bow or a sword would be better. Having both a sword and a bow would be the given solution for having both.</p>\n" }, { "answer_id": 73657, "author": "Rabbit", "author_id": 32067, "author_profile": "https://worldbuilding.stackexchange.com/users/32067", "pm_score": 2, "selected": false, "text": "<p>There's a lot of cool responses, but I thought I'd add mine in the mix!</p>\n\n<p>Imagine a sword -> ( the '[' is the sharp side )</p>\n\n<pre><code> ||\n ||\n ----\n |[\n |[\n |[\n |[\n |/\n</code></pre>\n\n<p>You could potentially make a blade guard that supports inserting another blade. Assembly would be something like putting the two blades pointing at each other, then pushing them together until the tip went a few inches into the other's handle.</p>\n\n<pre><code> || \n ||\n ----\n |[\n |[\n |[\n |[\n ----\n ||\n ||\n</code></pre>\n\n<p>boom, now just add a sting to the handles ( possibly curving the handles )\nand begin shoosting. It may also require a special glove to use, since you would be holding blades. It could made such that you would only grab the blunt edges I suppose.</p>\n\n<p>This would be as heavy as two light one-handers ( obviously ). </p>\n\n<p>I would guess that you'd want a tight quiver on your back for arrows.</p>\n\n<p>It should be fairly easy to switch, since you'd simply pull the blades away from each other. They may still be connected by a string, which, depending on the fighting style, might be fine ( or even cool ). </p>\n" }, { "answer_id": 73694, "author": "BowManBanana", "author_id": 34485, "author_profile": "https://worldbuilding.stackexchange.com/users/34485", "pm_score": 1, "selected": false, "text": "<p>Using my amazing paint.net skills I have designed a <strong>bow-sword</strong> hybrid that is efficient and actually useful. Now getting back down to earth my terrible bow drawing illustrates (poorly) how a bow-sword design in real life could actually work. At the bottom right/left is a flexible material that serves as both the flexible parts of the bow, the handles for the swords and the arrow holders. Assuming you were a good aim/sword wielder you could go to war with this beast and win any battle. Hope this is entertaining;)</p>\n\n<p><a href=\"https://i.stack.imgur.com/6RULJ.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/6RULJ.jpg\" alt=\"Bow Design\"></a></p>\n" }, { "answer_id": 73847, "author": "Crashie-J", "author_id": 33966, "author_profile": "https://worldbuilding.stackexchange.com/users/33966", "pm_score": 2, "selected": false, "text": "<p>I think we should look inward concerning the blades and more into eastern designs such as the \"shuang gou\" (Chinese hook sword). By inserting the hook portion inside the handle guard, a redesign with a slight curving towards the middle where the hand would be placed and having only the inside blade sharpened, finishing with notching for a steel drawstring, you <em>could</em> have a system that interlocks to become a recurve bow, and two swords linked together by cord and interlocking hooks.</p>\n\n<p><a href=\"https://i.stack.imgur.com/d9OJW.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/d9OJW.jpg\" alt=\"enter image description here\"></a></p>\n" }, { "answer_id": 73970, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 2, "selected": false, "text": "<p><a href=\"https://i.stack.imgur.com/FXh04.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/FXh04.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>Here is a beautiful antique Indian steel bow. I found it at <a href=\"http://www.atarn.org/letters/ltr_dec04.htm\" rel=\"nofollow noreferrer\">http://www.atarn.org/letters/ltr_dec04.htm</a>\nIt does not take much imagination to see the swords.</p>\n\n<p>Steel is apparently not optimal but is a suitable material to make a bow. There is a lot known about how to control flexibility and stiffness. </p>\n\n<p>I think a broadsword or katana type sword might work, but best would be a thin fencing type sword. I think a bow made of two fencing sabres could work. From <a href=\"https://www.pinterest.com/pin/166070304984273871/\" rel=\"nofollow noreferrer\">https://www.pinterest.com/pin/166070304984273871/</a>\n<a href=\"https://i.stack.imgur.com/83wbD.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/83wbD.jpg\" alt=\"enter image description here\"></a></p>\n\n<p>@Jacco \"Since the handle of the sword is quite heavy, especially when compared to an arrow, having the sword handles be the outer end of your bow limb would result in a non functional bow\" (from above answer) - good point by Jacco in comment for different answer. Handle motion will drink up the kinetic energy available. Hilts should be detachable. Perhaps the detached hilts could be worn on helmets, as a riff on the old \"arrow through the head\" prank headdress. Yes. Where was I?</p>\n\n<p>On conversion to bow, the swords should stay inside the (single) scabbard, which will keep the sharp parts out of harms way. The same piece of the blade which receives the handle for sword use can receive the string for bow use.</p>\n\n<p>Here is an image from <a href=\"http://www.strele.lt/Default.aspx?tabid=486&amp;language=en-US\" rel=\"nofollow noreferrer\">http://www.strele.lt/Default.aspx?tabid=486&amp;language=en-US</a>\nBow G looks like it could be made out of two straight limbs / swords. <a href=\"https://i.stack.imgur.com/zJVP9.jpg\" rel=\"nofollow noreferrer\"><img src=\"https://i.stack.imgur.com/zJVP9.jpg\" alt=\"enter image description here\"></a> The limbs are straight but mounted at an angle. That sidesteps the problem of having a curved bit on the shaft which is nonideal for sword use. To get the angle shape the scabbard must have a flexpoint built in. Or maybe people just carry it as the angle. If you are dead set your swords must be bows you must be prepared to accept the necessity to turn sideways before going through doors. </p>\n" }, { "answer_id": 74028, "author": "Charles Merriam", "author_id": 23060, "author_profile": "https://worldbuilding.stackexchange.com/users/23060", "pm_score": 1, "selected": false, "text": "<p>Oh, fun with technology and metallurgy!</p>\n\n<p>First, recognize that weapon technology moved over time, much like other technologies. The version of technology we absorb from role playing games, and later computer games, has been moved to fit the needs of the gaming system. A germane history:</p>\n\n<p>Bows started out as simple curved bows. As materials improved, people learned that the trick is to make only the ends of the bow move so as to put as much momentum into the arrow as possible. Any movement of your bow arms cuts down on the available momentum for your arrow. The recurve bow hits harder because it doesn't move its bow arms.</p>\n\n<p>Swords started out as hunks of metal (copper, bronze, iron, steel, \"Damascus\" steel with Vanadium). You swung the hunk of metal, putting lots of momentum behind it, and concentrated it on the little wedge of the edge. A great idea until armor got so good the sword would bounce off and everyone switched to war hammers. But then, the metal got so good you could make an epee. Sharp and pointy, you attacked from so far away and poked through eye slits, under arms, into gauntlets. The traditional training was to thrust through a swinging ring. Big armor died fast.</p>\n\n<p>So, if you want, you take two swords, screw the ends together (pointy end out), drop a contraption over the top consisting of springy steel and a bow string, and away you go.</p>\n\n<p>Of course, your enemy then pulls a musket and shoots you...</p>\n" }, { "answer_id": 74041, "author": "jose_castro_arnaud", "author_id": 15388, "author_profile": "https://worldbuilding.stackexchange.com/users/15388", "pm_score": 1, "selected": false, "text": "<p>As other users already said, a combination bow-sword is poor as a bow and as a sword; here's my version.</p>\n\n<p>The bow is composed of two sword scabbards, united by their points (where the arrow is put). The swords are put into the scabbards, with a locking mechanism to avoid slipping - a quarter turn liberates the sword. The bow's string is tied to the scabbards' mouths. A quiver is required for the arrows, and can be used to store the bow, folded in half, if one or both swords are in use.</p>\n" }, { "answer_id": 74161, "author": "Silent Drew", "author_id": 26884, "author_profile": "https://worldbuilding.stackexchange.com/users/26884", "pm_score": 1, "selected": false, "text": "<p>The simplest way would be to design it as a coil-spring bow, where the swords merely act as levers with a pivot and spring at one end and a bowstring at the other. Here's a link to the wikipedia page of a Roman Siege engine that uses a similar principle\n<a href=\"https://en.wikipedia.org/wiki/Scorpio_(weapon)\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Scorpio_(weapon)</a></p>\n\n<p>Alternatively, you could use the blades' themselves as springs, though you would need to find a way to mount them securely. Maybe have the handles slide down into a tube or something? Of course then you would need removable pommels as well.</p>\n\n<p>Also note that either way both swords would have to be really short, otherwise the overall bow would be 6+ ft long, and while it's true that a traditional English Longbow is supposed to be taller than its wielder, I'm not sure that's what you're going for here.</p>\n" }, { "answer_id": 74335, "author": "Elkosh", "author_id": 34717, "author_profile": "https://worldbuilding.stackexchange.com/users/34717", "pm_score": 1, "selected": false, "text": "<p><strong>Nanites</strong>\nThe material of both the blades and their hilts should be carbon nanofibres. They are very strong. And if the width of them is considerably low(which essentially means they are sharp, and from nanotechnological perspective, is quite possible as well) it can be used as a sword blade. On the other hand,carbon nanofibre is known for its elastic nature, and will help in its functioning as a bow shaft.</p>\n\n<p>The hilts should be thicker, for better grip and lesser pressure on your hands.</p>\n\n<p>The locking mechanism can be done in the form of male and female sockets, or by shapeshifting hilts(we are talking about nanobots here).</p>\n\n<p><strong>Magic</strong>\nThis can also be done using different magic spells. There should be an advanced transmutation spell, which lets you modulate the tensile strength of the material at your will.\nIt's like being a metal-bender.</p>\n" }, { "answer_id": 74437, "author": "Aiden Phoenix", "author_id": 34708, "author_profile": "https://worldbuilding.stackexchange.com/users/34708", "pm_score": 1, "selected": false, "text": "<p>I know that this doesn't exactly answer the question, but I feel like some one should point this out, so here it goes.</p>\n\n<p>Even if you do find a way to make this weapon you are talking about, it will be a low quality bow, or two low quality swords. Honestly, you would be much better off making a bladed bow, which is just a standard bow, but on the edges are blades, and at the tips are either spearheads, or scythe blades (depending on whether your style is slashing or stabbing). When strung as a bow, it would function normally, but when you unstrung it(or cut the string if your in a hurry) it would become a bladed staff, capable of being used as a spear or a staff.</p>\n\n<p>It might be possible to have this staff split into two smaller, sword length blades, but I am not sure how that would work. Possibly screw one into the other to make the full length staff/bow?</p>\n" }, { "answer_id": 111207, "author": "sss", "author_id": 50353, "author_profile": "https://worldbuilding.stackexchange.com/users/50353", "pm_score": 0, "selected": false, "text": "<p>You could use two swords connected by a string at the hilt, then put both swords into a special double-sided \"case\" to covert it into a bow.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/73432", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/28789/" ]

[ { "answer_id": 77821, "author": "Mormacil", "author_id": 34386, "author_profile": "https://worldbuilding.stackexchange.com/users/34386", "pm_score": 4, "selected": true, "text": "<p>The first country that adds it to their water supply would gain a large boost. With no side effects it will be widely used by anyone that can afford it. Some will object but with no side effects they barely have any arguments.</p>\n" }, { "answer_id": 77826, "author": "SZCZERZO KŁY", "author_id": 30912, "author_profile": "https://worldbuilding.stackexchange.com/users/30912", "pm_score": 0, "selected": false, "text": "<p>Imagine we are all taking it already. And we started taking it in the enlightenment period.<br>\nNow we are boosted to maximum possibility with no side effects. You can take drugs take takes you even higher but those have side effects on your brain and nerve system (Stephen Hawking, Grigori Perelman) and are given to a handful of people that can take the toll and have skills on their own that said boost will give even better results. </p>\n" }, { "answer_id": 77830, "author": "Nat", "author_id": 31573, "author_profile": "https://worldbuilding.stackexchange.com/users/31573", "pm_score": 1, "selected": false, "text": "<h3>Yes, it'd be legal</h3>\n<p>Intelligence both defines human experience and improves it. More intelligence would allow people to enjoy/experience life more, rapidly advance technology including medicine, increase humanity's odds of surviving longer, etc..</p>\n<p>All else equal, attempting to ban something that increases human intelligence would be a crime against humanity in just about every conceivable sense. Any conspiracy to ban such a drug would be a conspiracy against humanity itself; there're very few people depraved enough to engage in such an atrocity.</p>\n<h3>Even sociopaths wouldn't try to ban it</h3>\n<p>You'll sometimes hear conspiracy theories about how there is such a drug, but alleged power-hungry sociopaths are keeping it under wraps for their own gain.</p>\n<p>Of course, in real life, <em>everyone</em> would benefit from humanity as a whole being much smarter. Examples:</p>\n<ul>\n<li><p>Everyone's going to need a doctor some day. Wouldn't you want your doctor to be smarter?</p>\n</li>\n<li><p>That doctor's going to try to help you with medical technology. Wouldn't you prefer for that medical technology to be more advanced?</p>\n</li>\n<li><p>You probably like gadgets like computers and smart phones. Wouldn't you like them to be far more advanced?</p>\n</li>\n<li><p>You probably like material wealth. Wouldn't you like to have even more of it?</p>\n</li>\n<li><p>Want to go to Mars? It'll happen faster if our scientists/engineers are smarter.</p>\n</li>\n<li><p>Some ecological disaster's threatening to destroy the planet! Wouldn't you prefer for the people who try to stop it to be smarter?</p>\n</li>\n</ul>\n<p>In short, even a sociopath who cares only about themself wouldn't want to prevent others from having the drug. And non-sociopaths would certainly love to see the world become a better place, both for themself and others. It'd take a truly spiteful person who would accept personal suffering just to see others also suffer to oppose such a wonder drug.</p>\n" }, { "answer_id": 77833, "author": "RaGe MaGiXZ", "author_id": 36835, "author_profile": "https://worldbuilding.stackexchange.com/users/36835", "pm_score": 1, "selected": false, "text": "<p>I think not the actual drug itself may have certain legalities when it comes how you use it and whom on but overall I dont believe this will be illegal if ever becomes real. I think there should be a few laws put in place to stop any bad things happening with the drug itself:</p>\n\n<p><strong>1. Use without PERSONAL Consent</strong></p>\n\n<p>Think this one is very true as it would be illegal if force-fed, or taken by an unoriginal being who never gave full consent to the act itself. But you also need to factor in the fact that depending on the relationship you have with the individual will depend on the consequences she/he will overtake on you.</p>\n\n<p><strong>2. Negatively overused</strong></p>\n\n<p>This one is just simple any drug will get out of hand and extremely addictive when overused if this <em>drug</em> was ever brought to the streets I wouldnt think it would be simple to obtained or be much when obtained. I would <em>silly</em> if the government allowed anybody to have the drug. But this could be used against certain laws and given in the breaking of 'the first law, 1.' .</p>\n" }, { "answer_id": 77837, "author": "Aiden Phoenix", "author_id": 34708, "author_profile": "https://worldbuilding.stackexchange.com/users/34708", "pm_score": 0, "selected": false, "text": "<p>It could be addictive, even if not in a chemical sense. If you were super smart for three hours a day, you would spend the rest of the day wishing you were that smart.\nI believe that it would be outlawed for that reason.</p>\n" }, { "answer_id": 77840, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 2, "selected": false, "text": "<p>As regards a society entirely comprised of \"Alphas\"; from <a href=\"https://archive.org/stream/ost-english-brave_new_world_aldous_huxley/Brave_New_World_Aldous_Huxley_djvu.txt\" rel=\"nofollow noreferrer\">Brave New World</a></p>\n\n<blockquote>\n <p>Each one of us, of course,\" the Controller meditatively continued, \n \"goes through life inside a bottle. But if we happen to be Alphas, \n our bottles are, relatively speaking, enormous. We should suffer \n acutely if we were confined in a narrower space. You cannot pour \n upper-caste champagne surrogate into lower-caste bottles. It's obvious\n theoretically. But it has also been proved in actual practice. The\n result of the Cyprus experiment was convincing.\" </p>\n \n <p>\"What was that?\" asked the Savage. </p>\n \n <p>Mustapha Mond smiled. \"Well, you can call it an experiment in rebot- \n tling if you like. It began in A.F. 473. The Controllers had the\n island of Cyprus cleared of all its existing inhabitants and\n re-colonized with a specially prepared batch of twenty-two thousand\n Alphas. All agricul- tural and industrial equipment was handed over\n to them and they were left to manage their own affairs. The result\n exactly fulfilled all the theoretical predictions. The land wasn't\n properly worked; there were strikes in all the factories; the laws\n were set at naught, orders dis- obeyed; all the people detailed for a\n spell of low-grade work were per- petually intriguing for high-grade\n jobs, and all the people with high- grade jobs were\n counter-intriguing at all costs to stay where they were. Within six\n years they were having a first-class civil war. When nineteen out of\n the twenty-two thousand had been killed, the survivors unanimously\n petitioned the World Controllers to resume the govern- ment of the\n island. Which they did. And that was the end of the only society of\n Alphas that the world has ever seen.\"</p>\n</blockquote>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/77819", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/16350/" ]

[ { "answer_id": 78064, "author": "JDługosz", "author_id": 885, "author_profile": "https://worldbuilding.stackexchange.com/users/885", "pm_score": 3, "selected": false, "text": "<p>Your answer depends on what is meant by “notice”.</p>\n\n<p>Consider a parking lot. Perhaps a pedestrian won’t see the curvature by eye as he walks through it. But the contractor who paves it will consume some amount of material, and his tolerance in <em>that</em> depends on the accuracy and uniformity of his paving technique. Maybe ±half a wheelbarrow of concrete will cause concern; maybe differences in a truckload or two are chalked up to the crew’s raking technique and go unremarked.</p>\n\n<p>You should make a chart (program a spreadsheet) showing the ratio of area to radius, percentage difference from Euclid's, and absolute difference; for patches of different sizes in a logarithmic progression. Another pair of columns shows the relative and absolute difference for expected lengths of the sides of a triangle, for each patch size.</p>\n\n<p>Then, use this chart to decide whether someone will notice based on <strong>specific context</strong> of the activity.</p>\n" }, { "answer_id": 102348, "author": "PyRulez", "author_id": 8914, "author_profile": "https://worldbuilding.stackexchange.com/users/8914", "pm_score": 3, "selected": true, "text": "<p>Using <a href=\"https://en.wikipedia.org/wiki/Hyperbolic_geometry#Circles_and_disks\" rel=\"nofollow noreferrer\">this formula</a> we can calculate the curvature $$K \\approx -0.313339 \\text{ per mi}^2$$</p>\n\n<p>Using this, we can the radius of a Euclidean disk v.s. a disk in this world.</p>\n\n<pre><code> Area Euclidean Radius Actual Radius \n ---------------- ------------------ --------------- \n 1 mi^2 0.56 mi 0.56 mi \n 10 mi^2 1.78 mi 1.72 mi \n 100 mi^2 5.64 mi 4.42 mi \n 1000 mi^2 17.84 mi 8.26 mi \n 10000 mi^2 56.42 mi 12.34 mi \n 100000 mi^2 178.41 mi 16.44 mi \n 1000000 mi^2 564.19 mi 20.56 mi \n 196900000 mi^2 7916.77 mi 30.00 mi \n</code></pre>\n\n<p>This means that over the size of a building, distortion will not be noticeable. In a small town, probably only builders will notice. In a small city, everyone will start to notice, but it will still be mostly Euclidean. In a bigger city, the curvature will be quite noticeable, and people will have to take into account if they do not want to get lost. At the size of countries, you will need to follow a navigation system very carefully if you want to get to the right place, and it will very non-euclidean.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/77856", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/8914/" ]

[ { "answer_id": 79004, "author": "SJuan76", "author_id": 3096, "author_profile": "https://worldbuilding.stackexchange.com/users/3096", "pm_score": 1, "selected": false, "text": "<p>No.</p>\n\n<p>An orbit is elliptic (instead of linear as Newton's First Law predicts) because the planet is attracting the orbitter¹.</p>\n\n<p>So, we have only the force of the planet applied to the body that orbits around it. Why doesn't that object just fall?</p>\n\n<p>Because the pull of the planet² provides an acceleration; that is, a change in the speed of the body. Instead of flying straight, that acceleration makes it change the direction of its speed, curving its path.</p>\n\n<p>Now, we have 3 options:</p>\n\n<ul>\n<li><p>The body moves so fast that the pull of the planet does not change its speed enough to keep into the current orbit: the body switches to a higher orbit or simply escapes the planet.</p></li>\n<li><p>The body moves so slow that the pull of the planet changes its speed so much that it cannot keep the orbit; the body orbits are each time closer to the planet.</p></li>\n</ul>\n\n<p>These two points above work as follow: if a body moves apart from the planet it orbits, it loses energy (that goes to compensate the gravitational energy) and slows down. And, at the same time, a wider orbit means that, even if the gravitational pull is slower, it keeps affecting the orbitting body for more time (as the revolution time increases). When the body moves towards the planet it is just the opposite, it accelerates until it finds a lower orbit that fits its new speed (or it crashes).</p>\n\n<ul>\n<li>The body moves reaches an equilibrium speed. The pull of the planet changes its speed enough to keep it in orbit, but without changing it. In a perfect, circular orbit, that could be describe as the body always having the same magnitude of speed (the same km/s) while the direction of the speed is continuously changing by the same amount, enough to follow the orbit.</li>\n</ul>\n\n<p>So, it is not as if you can slow the orbitting body somehow. The issue is that, as soon as you slow it, by whatever the means, it begins falling towards the planet, because the only thing that keeps it in orbit is its current speed³.</p>\n\n<p>TL;DR The factors that determine a orbit are the speed of the orbitting body and the mass of the body around which it orbits. The only factor that could be changed would be the gas giant mass, but then you have the issue of how making a non-massive-gas-giant (hint, gas has a tendency to run away unless there is lot of attraction from its planet).</p>\n\n<p><hr/>\n¹ So Newton's First Law is not of application there. Did you thought I was going to say that Newton's First Law does not work?</p>\n\n<p>²Or of any force.</p>\n\n<p>³Technically an orbitting body is <em>always</em> falling -the <em>free fall</em> term means that- towards the body they orbit, but constantly missing it.</p>\n" }, { "answer_id": 79006, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 4, "selected": false, "text": "<h1>A 1 year long orbit around Jupiter does not work</h1>\n\n<p>Orbital mechanics is actually pretty straightforward mathematically. There are rigidly defined formulas controlling what can and cannot happen.</p>\n\n<p>The formula for distance of the less massive body (Earth) from the more massive body (Jupiter) <a href=\"https://en.wikipedia.org/wiki/Orbital_period#Small_body_orbiting_a_central_body\" rel=\"noreferrer\">is given by</a> </p>\n\n<p>$$a = \\left(\\frac{GMT^2}{4\\pi^2}\\right)^{1/3}$$</p>\n\n<p>where $GM$ is the standard gravitational parameter of Jupiter ($1.27\\times10^{17}\\text{ m}^3\\text{s}^{-2}$); and T is the desired orbital period (1 year = $3.15\\times10^{7}\\text{ s}$). Plug those numbers in and we get about 15 million km. </p>\n\n<p>First off, this is not going to work for your desired 'closeness' to Jupiter. Jupiter has a radius of about 70 000 km. Using simple trigonometry, an object that is 140 000 km across at a distance of 15 million km occupies </p>\n\n<p>$$\\arctan\\left(\\frac{140 000}{15000000}\\right) = 0.00933 \\text{ radians}$$</p>\n\n<p>of arc, equal to about 32 minutes of arc. By comparison, the moon is from 29 to 34 minutes of arc; Jupiter will appear about the same size in the sky than our moon appears to us, in this situation.</p>\n\n<p>Secondly, the existing Galilean moons range from 0.42 million km (Io) to 1.89 million km (Callisto). Large moons do not exist that far from planets, at least not in our solar system. I can offer you this chart for the most distant moon from one of our Gas Giants with a mass with order of magnitude X.</p>\n\n<pre><code>X Moon Distance \n18 Sycorax (Uranus) 12 179 000 km\n19 Nereid (Neptune) 5 513 818 km\n20 Iapetus (Saturn) 3 560 820 km\n21 Iapetus (Saturn) 3 560 820 km\n22 Callisto (Jupiter) 1 882 709 km\n23 Callisto (Jupiter) 1 882 709 km\n</code></pre>\n\n<p>As you can see, you just don't get large moons that far out. Jupiter's largest moon at 15 million km or greater is about 60 km across. The moral of this story is that it is likely an object as massive as the Earth (50 times again more massive than any Moon) would not stay stable in an orbit that far from a gas giant in a busy solar system.</p>\n\n<h1>Conclusion</h1>\n\n<p>You can use that orbital period equation (and others in the Wikipedia link) to help determine how to make your planets orbital characteristics more like what you want. </p>\n\n<p>I would advise trying to make the Gas giant even bigger, there are planets out there 10 times the size of Jupiter. Just be sure to <a href=\"https://en.wikipedia.org/wiki/Stellar_mass\" rel=\"noreferrer\">keep the mass of the gas giant under ~0.08 solar masses</a>, which is the point at which the giant could ignite into a star itself (<a href=\"https://en.wikipedia.org/wiki/Jupiter\" rel=\"noreferrer\">Jupiter itself is just under 0.001 solar masses</a>).</p>\n\n<hr>\n\n<p>EDIT - As @Tradeylouish points out in the comments, even if you made the 'Jupiter' bigger, the increase in mass would cause the distance required for an object to be in a 1 year orbit to increase proportionally; the result would be that the 'Jupiter' would stay approximately the same size in the sky.</p>\n\n<p>I was suggesting that the 'Jupiter' be made bigger to help clear the space around it, allowing it to hold onto a satellite at such a long distance. However, this will not help your planet appear massive in the sky.</p>\n\n<p>@Tradeylouish's suggestion about density is the way to go if you want the planet to be huge in the sky (though it won't necessarily help keep the satellite in a far away orbit). Density of gas giants a can be pretty low apparently; check out <a href=\"https://en.wikipedia.org/wiki/TrES-4b\" rel=\"noreferrer\">TrES-4b</a> (<a href=\"https://worldbuilding.stackexchange.com/users/11049/tres-2b\">no relation</a>) which has about the mass of Jupiter but a density of 200 kg/m$^2$...about the same as balsa wood. </p>\n" }, { "answer_id": 79106, "author": "M. A. Golding", "author_id": 34461, "author_profile": "https://worldbuilding.stackexchange.com/users/34461", "pm_score": 1, "selected": false, "text": "<p>I found a useful article <a href=\"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/1\" rel=\"nofollow noreferrer\">\"Exomoon Habitability Constrained by Illumination and Tidal Heating\"</a> (Kipping, 2009a). </p>\n\n<p>The longest possible length of a satellite's day compatible with Hill stability has been shown to be about Pp/9, Pp being the planet's orbital period about the star. So, if the moon somehow managed to orbit around a giant planet with a period of one Earth year, the giant planet's orbital period around their sun would have to be at least nine earth years. </p>\n\n<p>If the moon receives as much radiation from its star as the Earth does from the Sun, and orbits that sun with a period of at least nine years, its star would probably have to be so massive and luminous that it would not remain on the main sequence long enough for the moon to become habitable for humans, develop multi celled lifeforms, or have a native intelligent species. Unless super advanced aliens terraformed the moon and made it habitable and gave it advanced life forms.</p>\n\n<p>A very dim star would have its habitable zone very close to it and its tidal forces would make any planet orbiting in the habitable zone tidally locked with one side always facing toward its star in eternal day and the other side always facing away from its star in eternal night.</p>\n\n<p>In our solar system astronomers believed that Mercury was tidally locked by the Sun, with one side in eternal day and hellish heat, and the other side freezing in eternal night and cold. But in 1964 it was discovered that Mercury is tidally locked, but not as strongly as a 1:1 resonance. Mercury has a 3:2 resonance. The orbital period or year of Mercury is 87.969 Earth days. The sidereal day or rotational period of Mercury relative to the stars is 58.646 Earth days. Thus there are three Mercurian sidereal days in two Mercurian years. But a solar day, the time between two successive sunrises or sunsets on a spot on the surface of Mercury, is two Mercurian years long, or about 175.938 Earth days.</p>\n\n<p>Some astronomers thought that Venus might also be tidally locked in a 1:1 resonance, and some old science fiction stories were set on such a Venus. That is not the case but Venus does have a odd relation between its year length and day length. The orbital period or year of Venus is 224.701 Earth days. The sidereal day or rotational period of Venus is 243.025 Earth Days, longer than the year. All planets in our solar orbit the Sun in a counter-clockwise direction as seen from above the Earth's North pole. Most planets also rotate in a counter-clockwise or prograde direction.</p>\n\n<p>If Venus did that its solar day, the time between two successive sunrises at the same spot on its surface, would be several Venus years long and thus more than an Earth year long. But Venus rotates in the opposite direction, clockwise as seen from above Earth's north pole, or retrograde. This makes the length of a solar day on Venus \"only\" 116.75 Earth days, less than that of Mercury. Nobody knows what gave Venus its long sidereal day and retrograde rotation. A common theory is a giant impact billions of years ago. </p>\n\n<p>If the long day and retrograde rotation of Venus have the same cause, it should be rare for a planet to have a long sidereal day like Venus without also having the retrograde rotation, which would make the solar day shorter than the sidereal day. But if the long day and retrograde rotation of Venus have two different and independent causes, it should be much more common for a planet to have a long sidereal day like Venus without also having the retrograde rotation, and thus solar days as long as an Earth year would be far more common.</p>\n\n<p>From what I have heard, a planet with days and nights much more than a few Earth days long would suffer from extremes of heat and cold during the days and nights. Lifeforms could flourish only during comparatively short periods near sunrise and sunset. They would have to go into some sort of suspended animation or die and leave protected seeds and eggs, twice each year-long day.</p>\n\n<p>Added 04-25-2017. Or lifeforms could move with the sunrise and sunset. With an equatorial circumference of about 25,000 miles and a day about 365.25 Earth days long, animals would have to move at an average speed of 68.446 miles per day or 2.851 miles per hour at the equator. At higher latitudes where the planet's circumference was much less, they could move slower. Where the circumference was only 2,500 miles they would need an average speed of 6.8446 miles per day or 0.2851 miles per hour.</p>\n" }, { "answer_id": 79134, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 0, "selected": false, "text": "<p><strong>Diamagnetic moon.</strong></p>\n\n<p>The problem with this problem is gravity. The orbital math posted above by @kingledion is inflexible. To get a satellite as close as you want and as slow as you want the net attractive force needs to be less. A lighter satellite cannot do it - as Galileo demonstrated dropping the balls from the leaning tower of Pisa. The attractive force is M1*M2 and when M1 is immense M2 does not matter much. You could make Jupiter lighter but what fun is that?</p>\n\n<p>What is required is a force which could oppose gravity such that the net attractive force on the moon was lower. I can think of 2 which might work: electrical repulsion and <a href=\"https://en.wikipedia.org/wiki/Diamagnetism\" rel=\"nofollow noreferrer\">diamagnetism</a>. Diamagnetism is magnetic repulsion: the effect that allows certain nonparamagnetic items (like frogs) to be levitated in a strong magnetic field. Achieving levitation means the force of gravity is completely opposed. </p>\n\n<p>Jupiter is a good candidate for this because it has a very strong magnetic field. If one starts by accepting diamagnetic repulsion can be strong enough to oppose gravitational attraction on this scale, then for a diamagnetic satellite one could assert that the magnetic repulsion opposed gravity to whatever degree desired. An arbitrarily weak or strong attractive net force would allow your satellite to orbit at whatever distance you like. </p>\n\n<p>This assumes that the magnetic field around Jupiter is uniform but if it is anything like Earth's it is not. I could imagine a satellite which sped up and slowed down / moved higher and lower as it traversed the irregularities of the magnetic field and the net attractive force waxed and waned.</p>\n" }, { "answer_id": 79138, "author": "Arthur Dent", "author_id": 37263, "author_profile": "https://worldbuilding.stackexchange.com/users/37263", "pm_score": 0, "selected": false, "text": "<p>It might be possible to replace Jupiter with more of a cloud, rather than legitimate gas planet. Some sort of star maybe with very low density. I'm not sure if such objects exist, but it might provide the large object in the sky you're looking for.</p>\n\n<p>As another answer gave, your distance will have to be 15 million km if your masses are the same (there's no real reason to change the masses). It's hard to tell what you mean by \"dominate the sky\", but let's go with 5 degrees (0.08727 radians).</p>\n\n<p>So, in order for your planet to be 5 degrees large at a distance of 15 million km, you need a diameter of roughly tan(0.08727)*15,000,000 = <strong>1,312,000 km</strong>. With a mass of 1.898e27kg, your density is roughly 6.7 kg/m^3. In other words, this would not be considered a planet, and I'm not sure if such a cloud could form without it forming together. Possibly your planet has just formed out of the the wreckage of some star.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/79003", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/37399/" ]

[ { "answer_id": 79051, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 3, "selected": false, "text": "<h1>There is a big difference between now (peace) and then (war)</h1>\n\n<p>First, this question fluctuates wildly over time and by country. I will concentrate on what I know well, US forces since WWII. By and large, most western armed forces have similiar structures and requirements to the US military. Originally this involved armies copying Germany, and Navies copying Great Britain. After the Cold War set in and NATO was formed, it involved everyone copying the United States. </p>\n\n<p>Generally, in peacetime, military structures revert to maximum bureaucratic inertia and detailed and complex rules for assigning ranks to positions come into being. This is case today in the US Navy and Air Force. The Army and Marines, having recently/currently been involved in something resembling warfare, are a little more flexible, but not much.</p>\n\n<p>In wartime, and by war I mean the serious all-out total war of the type we have not seen since WWII, those rules go out the window. Tolerance for stupidity exponentially decays to zero as stupidity does things like get people killed, ships sunk, and wars lost. In that case, the best get put in charge, no matter what the rules say.</p>\n\n<p>Just a note, my experience is in the US Marine Corps (enlisted) and US Navy (as an officer) so I will answer these questions from that perceptive. </p>\n\n<h1>Peacetime examples</h1>\n\n<ul>\n<li><p>A fireteam is ostensibly directed by a corporal (E-4), in reality, more likely a lance corporal (E-3). </p></li>\n<li><p>A fighter squadron command tour is given to a senior Commander (O-5) who has passed the command selection board and completed a squadron XO tour. </p></li>\n<li><p>The CO of the fighter squadron <em>is</em> the CO. Each squadron belongs to both a 'Carrier Air Wing' when it is deployed/operational; and a 'Type Wing' for administrative purposes. The type wing is generally responsible for manning the squadrons, supporting maintenance activity, and providing training opportunities. The Carrier Air Wing (formerly called Carrier Air Group) is the mixed group of all aircraft embarked on a carrier on a deployment. It is responsible for training the wing as a unit and running a deployment (bombing ISIS, and such). Both 'wings' are commanded by an Captain (O-6). Neither Captain has basically any input onto who the squadron CO's will be; they are chosen by the selection board.</p></li>\n<li><p>The deck 'chief' I assume means the 'Chief Petty Officer of Deck Department.' Deck department is generally in charge of mooring lines, small boats, removing rust, painting the ship, and other old-timey navy things. You may be trying to refer to some sort of watchstanding position. For example, the Officer of the Deck is the officer in charge of a bridge watchteam, and for navigating the ship and executing the plan of the day. The Officer of the Deck doesn't necessarily have anything to do with Deck Department. A Chief Petty Officer is an E-7 in the Navy, though I have been on ships with both a E-6 and E-8 'Deck Chief.' </p></li>\n<li><p>The senior enlisted man in Deck Department is the Deck Chief. You don't get promoted/demoted to hold that role.</p></li>\n</ul>\n\n<h1>Wartime differences</h1>\n\n<ul>\n<li><p>Fire team leaders are whoever the sergeant trusts to not to get other people killed. As shown in <em>Band of Brothers</em> rifle companies that have been through the meat grinder of modern warfare are pretty democratic at the enlisted level. The best are acclaimed by peers and superiors alike, they are given authority by peers, and responsibility (and eventually promotion) by superiors. </p></li>\n<li><p>The CO of a fighter squadron after a major air battle is the senior member of the squadron who is not dead. </p></li>\n<li><p>In this case, yes! The CAG (Carrier Air Group commander, the Captain we talked about in peacetime) usually does not fly. Thus, when you launch a torpedo strike on the enemy, and the torpedo squadron's CO is shot down, the CAG can pick his successor from the survivors of highest rank remaining. An O-3 squadron CO would not have been uncommon in 1942-1943. </p></li>\n<li><p>With deck chief's, you run into the fact that during war lots of non-military ships become military ships. Lots of transports and various small cutters are pressed into service for various needs. The ships are sent to bases to be outfit for combat in whatever way they can be, and the COs of those bases were generally responsible for providing some sort of crew for the ships. Every ship (especially in WWII) needed a deck department, so any reasonably experienced and competent sailor could find him self as 'deck chief' of a small anti-submarine cutter, merchantman cum amphibious transport ship, or landing craft. </p></li>\n</ul>\n" }, { "answer_id": 79072, "author": "Paul TIKI", "author_id": 31273, "author_profile": "https://worldbuilding.stackexchange.com/users/31273", "pm_score": 0, "selected": false, "text": "<p>Here is sort of a baseline thing here. I'm deliberately not referencing any specific military structure because when you look at them from a very high, conceptual level, they tend to work the same throughout history.</p>\n\n<p>First of all, there is almost always a hierarchy, and rank is based on how many men you are in charge of. A squad leader is in charge of 5 men, himself and 4 others. A Platoon leader is in charge of 4 squads, or 20 men. a company leader is in charge of 5 platoons, or 100 men. I made up my names based on extensive movie watching and not much else. Of course the numbers, ranks, titles and so on can change, but that is the core organizational framework.</p>\n\n<p>Hierarchy is absolutely critical for any sort of standing military. It helps keep discipline and makes coordination possible. Without discipline and coordination on the battlefield, you die.</p>\n\n<p>You get interesting deviations when you start getting into specializations. Your motor pool does not need the same amount of manpower as a combat unit, but you do not want to entrust your army's ability to get from point a to point b on someone that low level. so you jump him a few ranks. Likewise, with pilots and such. A pilot has to be extremely well trained and skilled, so you make them officers, even though the may not be directly leading anyone. A squadron leader, though, may be in charge of 5 pilots, and a wing commander in charge of 4 squadrons....and so on (again, names made up for my convenience). So even though there is specialization, the Core Structure remains.</p>\n\n<p>A lot of modern military names come out of long and cherished tradition. Modern US Marines will talk about \"Gunny\" which comes from \"Gunnery Sergeant\" as an example. </p>\n\n<p>You can make your military have whatever names/specializations, you want, just keep them in a logical hierarchy.</p>\n" }, { "answer_id": 79078, "author": "AlexP", "author_id": 29552, "author_profile": "https://worldbuilding.stackexchange.com/users/29552", "pm_score": 4, "selected": true, "text": "<p>For modern armies, the basic ranks, understood by everybody, are as follows (shamelessly copied from <a href=\"https://en.wikipedia.org/wiki/Division_(military)\" rel=\"nofollow noreferrer\">Wikipedia</a>):</p>\n\n<pre><code>Typical units Typical numbers Typical commander\n---------------- --------------- -------------------------------\nfireteam 3–4 corporal\nsquad or section 8–12 sergeant\nplatoon 15–30 lieutenant\ncompany 80–150 captain or major\nbattalion or cohort 300–800 lieutenant colonel\nregiment or brigade 2,000–4,000 colonel or brigadier general\ndivision or legion 10,000–15,000 major general\ncorps 20,000–40,000 lieutenant general\nfield army 80,000+ general\narmy group 2+ field armies field marshal or five-star general\nregion/theater 4+ army groups six-star rank or head of state\n</code></pre>\n\n<p>From the level of battalion onwards units tend to have their own specialized administrative and support personnel, composed of enlisted men and non-commissioned officers; from the level of regiment onwards units tend to have a <em>general staff</em>, populated with officers, NCOs and enlisted men. Medics and medical personnel are attached to units from battalion onwards.</p>\n\n<p>As I understand it, in the U.S.A. and many western countries there is a perfectly professional and respectable carreer track for NCOs, distinct from the carreer track of officers; in the former Warsaw Pact, and maybe even today in Russia, I don't know, this was restricted to the higher ranking NCOs, say from the equivalent of a sergeant 1st class (OR-7) onwards; lower ranking NCOs (sergeants and staff sergeants, OR-5 and OR-6) were enlisted men.</p>\n\n<p>There is most usually a third separate carreer track for technical personnel, called <a href=\"https://en.wikipedia.org/wiki/Warrant_officer\" rel=\"nofollow noreferrer\"><em>warrant officers</em></a> in the U.S.A. </p>\n\n<p>Wikipedia provides <a href=\"https://en.wikipedia.org/wiki/Ranks_and_insignia_of_NATO#Comparison_to_other_systems\" rel=\"nofollow noreferrer\">equivalence lists for ranks</a> in NATO countries, where the equivalence is more or less complete for reasons of interoperability:</p>\n\n<ul>\n<li><p><a href=\"https://en.wikipedia.org/wiki/Ranks_and_insignia_of_NATO_armies_enlisted\" rel=\"nofollow noreferrer\">Ranks and insignia of NATO armies enlisted</a></p></li>\n<li><p><a href=\"https://en.wikipedia.org/wiki/Ranks_and_insignia_of_NATO_armies_officers\" rel=\"nofollow noreferrer\">Ranks and insignia of NATO armies officers</a></p></li>\n<li><p><a href=\"https://en.wikipedia.org/wiki/Ranks_and_insignia_of_NATO_navies_enlisted\" rel=\"nofollow noreferrer\">Ranks and insignia of NATO navies enlisted</a></p></li>\n<li><p><a href=\"https://en.wikipedia.org/wiki/Ranks_and_insignia_of_NATO_navies_officers\" rel=\"nofollow noreferrer\">Ranks and insignia of NATO navies officers</a></p></li>\n<li><p><a href=\"https://en.wikipedia.org/wiki/Ranks_and_insignia_of_NATO_air_forces_enlisted\" rel=\"nofollow noreferrer\">Ranks and insignia of NATO air forces enlisted</a></p></li>\n<li><p><a href=\"https://en.wikipedia.org/wiki/Ranks_and_insignia_of_NATO_air_forces_officers\" rel=\"nofollow noreferrer\">Ranks and insignia of NATO air forces officers</a></p></li>\n</ul>\n\n<p>Nowadays and ever since the middle ages onwards, naval forces have different ranks than land forces; the Romans themselves did not use special words for naval officers.</p>\n\n<p>Air forces sometimes use fancy ranks; drivers of flying vehicles are given exalted officer ranks such as lieutenant or captain, whereas drivers of land vehicles have to make do with enlisted or NCO ranks such as corporal or sergeant. Keep in mind that an army captain commands about 100 men, whereas an Air Force captain commands between zero and about ten men, and a <a href=\"https://en.wikipedia.org/wiki/Captain_(naval)\" rel=\"nofollow noreferrer\">navy captain</a> commands hundreds to thousands of men and is the equivalent of an army colonel.</p>\n\n<p>The number of ranks increases as the military becomes more and more sophisticated. The Romans did not really have any ranks other than private, <a href=\"https://en.wikipedia.org/wiki/Decanus\" rel=\"nofollow noreferrer\">decanus</a> for infantry or <a href=\"https://en.wikipedia.org/wiki/Decurion_(military)\" rel=\"nofollow noreferrer\">decurion</a> for cavalry (a corporal), <a href=\"https://en.wikipedia.org/wiki/Centurion\" rel=\"nofollow noreferrer\">centurion</a> (a sergeant), <a href=\"https://en.wikipedia.org/wiki/Military_tribune\" rel=\"nofollow noreferrer\">tribune</a> (a lieutenant, captain or major), <a href=\"https://en.wikipedia.org/wiki/Praetor\" rel=\"nofollow noreferrer\">praetor</a> or later <a href=\"https://en.wikipedia.org/wiki/Tribunus_laticlavius\" rel=\"nofollow noreferrer\">laticlave tribune</a> (a colonel or brigadier) and <a href=\"https://en.wikipedia.org/wiki/Legatus\" rel=\"nofollow noreferrer\">legate</a> (a major general or lieutenant general); in addition the most senior centurion of a legion was called the <a href=\"https://en.wikipedia.org/wiki/Primus_pilus\" rel=\"nofollow noreferrer\">primus pilus</a> and functioned as the senior NCO, sort of a sergeant major. During most of the Middle Ages, things were even more simple: there were generals, captains, sergeants and privates. Then war become a complicated profession with an associated formal education and ranks proliferated together with the evolution of military science and technology.</p>\n\n<p>Regarding the specific questions:</p>\n\n<ul>\n<li><p><em>Is there a certain rank you have to be to head a fire team?</em> No. It is usual to have a corporal in this role, but a sergeant may be pressed into service if the situation requires it and a private may have to make do if there are no corporals around.</p></li>\n<li><p><em>Or fighter squadron?</em> A major or more usually a lieutenant-colonel (called a <a href=\"https://en.wikipedia.org/wiki/Wing_commander_(rank)\" rel=\"nofollow noreferrer\">wing commander</a> in the U.K.).</p></li>\n<li><p><em>Do you have to have a minimum rank to be a deck chief?</em> I have no idea what a deck chief is. (Apologies, but English naval and nautical terminology was never a burning interest.) If you mean the <a href=\"https://en.wikipedia.org/wiki/Chief_of_the_Boat\" rel=\"nofollow noreferrer\">chief of the boat</a>, that's simply the man with the most senior enlisted rank in the crew, almost always an NCO -- a <a href=\"https://en.wikipedia.org/wiki/Petty_officer\" rel=\"nofollow noreferrer\">petty officer</a> or chief petty officer. If you mean the <a href=\"https://en.wikipedia.org/wiki/Officer_of_the_deck\" rel=\"nofollow noreferrer\">officer of the deck</a> that an officer, usually a some sort of lieutenant (OF-1 to OF-3) (but see Xachary Thompson's comment, to the effect that in the U.S. navy this is usually a petty officer, OR-6 to OR-8).</p></li>\n</ul>\n" }, { "answer_id": 79080, "author": "Dtb49", "author_id": 33810, "author_profile": "https://worldbuilding.stackexchange.com/users/33810", "pm_score": 0, "selected": false, "text": "<p>Modern Military uses dual leadership for the most part.</p>\n<p>Team - 2-5 people\nSquad - ~10 people, or two teams\nPlatoon - ~40 people, or four squads\nCompany - ~100 people, or three to four platoons\nBattalion - ~400 people, or 4 companys\nBrigade - ~800 people, or two battalions</p>\n<p>Enlisted</p>\n<ul>\n<li>Private, Private First Class - typically no responsibilities</li>\n<li>Corporal - sometimes has responsibilities, usually team leader</li>\n<li>Sergeant - typically a team leader, sometimes put in squad leader position</li>\n<li>Staff Sergeant - squad leader</li>\n<li>Sergeant First Class - Platoon leader</li>\n<li>First Sergeant - In charge of a company</li>\n<li>Sergeant Major/Command Sergeant Major - In charge of battalions and above</li>\n</ul>\n<p>Officers</p>\n<ul>\n<li><p>2nd Lieutenants - in charge of a platoon</p>\n</li>\n<li><p>1st Lieutenants - typically XO or 2nd in command of a company</p>\n</li>\n<li><p>Captain - in charge of a company</p>\n</li>\n<li><p>Major - usually an adviser to LTC or above</p>\n</li>\n<li><p>Lieutenant Colonel - in charge of battalion</p>\n</li>\n<li><p>Colonel - in charge of brigade</p>\n</li>\n<li><p>General Officers (1 star-5 stars) - in charge of everything else, most are advisers to 4 stars. 5 Star are only used in war time</p>\n<p>Exceptions:</p>\n</li>\n</ul>\n<p>Warrant Officers</p>\n<ul>\n<li>typically ranked by number 1-5, 5 being most senior</li>\n<li>These are typically your subject matter experts in their field</li>\n<li>W1 - on par with LT</li>\n<li>CW2-3 - typically on par with a CPT</li>\n<li>CW4 - on par with a LTC or COL</li>\n<li>CW5 - on par with a General</li>\n</ul>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/79048", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/34793/" ]

[ { "answer_id": 79765, "author": "a4android", "author_id": 22159, "author_profile": "https://worldbuilding.stackexchange.com/users/22159", "pm_score": 2, "selected": false, "text": "<p>There are aspects of this question which make it quite tricky to answer. The physics demonstration of charged droplets spiralling around a charged knitting needle gives a reasonable idea of the concept you are trying to consider. Any answer will have to substitute a gravitational field for the droplets' and the knitting needle's electrostatic field. This may not be so straight forward. Anyone who knows I am wrong about this proposition, this please jump in and demolish it.</p>\n\n<p>It is suggested that the ringworld will need to be massive to have an Earthlike planet in a spiral orbit around the ringworld. While it can be assumed that the Earthlike planet has a mass equivalent to that of the Earth, that's the easy part. Now to look at the unknown factors in this model.</p>\n\n<p>The mass of the ringworld is unknown. The velocity of the Earthlike planet is unknown. The ringworld's mass will determine the gravitational force acting on the planet to keep it orbiting the ringworld. While the velocity of the planet will determine its probability in maintaining its orbit around the ringworld.</p>\n\n<p>This suggests that the ringworld will need to be extremely massive indeed. Quite likely, the ringworld's mass will be of the order of a solar mass. That is to say a mass similar to that of the Sun. In which case, the ringworld will need to be made of ultradense matter of the type proposed by Robert L Forward in his speculative article \"Far out Physics\" (<em>Analog</em>, August 1975, pages 147-166).</p>\n\n<p>The planet will have to be moving at a high velocity. This is high compared to normal planetary orbits. The Earth orbits the Sun with a velocity of 30 km/s. However, it isn't easy to devise a way of conceptualizing the relationship between the mass of the ringworld and the velocity of the planet in a spiral orbit. This depends on the distribution of mass along the length of the ringworld and the force it exerts upon an Earth-mass planet so that the planet can be kept in a spiral orbit around the ringworld.</p>\n\n<p>One thing that is a worry is the fact that the charged droplets all end up falling on to the charged knitting needle. If the same behaviour applies to a planet in a spiral orbit around a massive ringworld, then the planet end up crashing onto the ultradense surface of the ringworld. While this is exciting and dramatic, it won't be good news for any inhabitants of the planet.</p>\n\n<p>Any answer that can come with a solution to the problem proposed by the question will need to devise a model that describes the gravitational and velocity relationship between the ringworld and the planet in a spiral orbit in order to timescale of the planet's orbit and, possibly, the stability of this system. Currently the unknown factors make determining an answer difficult. This answer has explored the limiting factors of the problem, but has not been able to propose a solution to the OP's question.</p>\n\n<p><strong>ADDENDUM:</strong></p>\n\n<p>The main problem is the shape of the gravitational field of a massive ringworld. With planets &amp; stars the gravitational field is concentrated around a point source. The ringworld's field has an extended source. The planet could have two components of velocity. One the orbital velocity around the star, the other an orbital velocity around the ringworld. That would yield the spiral orbit.</p>\n\n<p>Now this consideration suggests a possible solution. Assume that the mass of the ringworld is equal to that of the Earth-mass planet in a strip that is 12,742 kilometres wide. This width is chosen because it the diameter of an Earthlike planet. This gives a reasonable approximation for the minimum gravitational field of the massive ringworld to keep an Earth-mass planet in orbit around it. Assuming it has an orbital velocity of 8 km/s as this is the orbital velocity needed to maintain a satellite in orbit around an Earthlike planet (in this case the strip of a ringworld).</p>\n\n<p>The planet orbiting the ringworld will have a heliocentric orbital velocity of 30 km/s, which is exactly the same as planet Earth, and this is only one velocity component of the planet. The other velocity component keeps the planet circulating around the ringworld. The combined velocities result in a spiral orbit around the ringworld.</p>\n\n<p>The OP can plug whatever dimensions of the ringworld to establish the size of the orbit around the ringworld.</p>\n\n<p>A quick calculation indicates that the mass of the ringworld will be 73,966.237 Earth masses (where 1 AU equals 150,000,00 kilometres). Just divide the circumference of the ringworld by 12,742 because we have assumed each 12,742 kilometre strip has one Earth mass.</p>\n\n<p>The planet's orbit around the ringworld will be an high orbit. Possibly, something like a forty-eight hour orbit which will keep the planet far away from the ringworld. This should keep the planet safe. Also, the ringworld will have to have a narrow width. For example, around 12,000 km, that's right, roughly the Earth's diameter. Again this is to make the planet's spiral orbit safe. The radius of the orbit from the ringworld is 220,015.79 km. Offhand it's not certain if this orbit is viable. Note: this assumes the orbital velocity is 8 km/s.</p>\n" }, { "answer_id": 79952, "author": "typesanitizer", "author_id": 37356, "author_profile": "https://worldbuilding.stackexchange.com/users/37356", "pm_score": 6, "selected": true, "text": "<h3>TL;DR: Yes, helical motion around a ringworld is possible. However, it is far from uniform at larger distances (≥ 0.04 AU).</h3>\n\n<h3>Summary of results:</h3>\n\n<p>For a toroidal ringworld with mass \n$M_R = 3 M_\\text{star} = 3M_\\odot$, central radius $ a = 1 \\text{ AU}$ and \ninner radius $b = 10^{-4} a \\simeq 15000\\text{ km}$ \n(hence density $\\rho \\sim 8800\\text{ kg/m}^3$, compare with\n$\\rho_{\\text{Fe}}\\sim 7800\\text{ kg/m}^3$), the relation between the mean \nseparation from the central ring of the ringworld and the time \nperiod is given by the following graph:</p>\n\n<p><a href=\"https://i.stack.imgur.com/NDnaE.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/NDnaE.png\" alt=\"T vs $\\lambda$ for helical trajectories.\"></a></p>\n\n<p>$\\lambda a$ is the distance from the central ring. The equations are fit using the average (square) value of $\\lambda$ over 1 year. The median (pentagon) and launch (circle) values of $\\lambda$ are also shown. The error bars indicate the minimum and maximum value of $\\lambda$. Black → no central star, orange → $M_{\\text{star}} = M_{\\odot}$.</p>\n\n<p>The trajectory is indeed helical.</p>\n\n<p><a href=\"https://i.stack.imgur.com/a9Ymm.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/a9Ymm.png\" alt=\"Helical trajectory around a ringworld.\"></a></p>\n\n<p>We can look at the projected cross-section below. The center of the ring is at $x=-1$ (scaled by $a$, not shown), the central ring of the torus is at $x=0$. It is clear that the \"inner distances\" are bigger than the \"outer distances\" as one would naively expect. As earlier, black → no central star, orange → $M_{\\text{star}} = M_{\\odot}$. The first graph is translucent so you can see both cross-sections by zooming in.</p>\n\n<p><a href=\"https://i.stack.imgur.com/zMXol.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/zMXol.png\" alt=\"Cross sections of trajectories.\"></a></p>\n\n<h3>Physics:</h3>\n\n<p>For simplicity, consider a point particle; if the satellite is too large \n(how large?) there would be complications due to the Roche limit etc. Replace the ringworld (torus for volume calculation) with its central ring for all other calculations.\nLet the particle be launched from $(x,y,z)=((1-\\lambda) a, 0,0)$.\nWe only consider the regime $0.01 \\leq \\lambda \\leq 0.1$. The lower limit \nprevents the particle from recognizing that the ringworld has been approximated by a ring and the upper limit prevents its orbit from being perturbed \nsubstantially by the star.</p>\n\n<p>Suppose initially the radial velocity is zero.\nThe tangential velocity for orbit around the star (initially $v_y$)\nshould roughly be $\\sqrt{G M_{\\text{star}}/((1-\\lambda) a)}$. \nThe orbital velocity around the ringworld (initially $v_z$) should roughly be\n$\\sqrt{g((1-\\lambda) a,0,0) \\lambda a}$ where $g(x,y,z)$ is the magnitude of the net gravitational field (a.k.a. acceleration due to gravity) as a function of position.</p>\n\n<p>We're kind of stuck without a number for $g((1-\\lambda) a,0,0)$.</p>\n\n<p>The electric potential for a ring of charge $Q$ is given as (Ref. 1):</p>\n\n<p>$$\nV(r,\\phi,z) = \\frac{1}{4\\pi\\epsilon_0}\\frac{Q}{2\\pi}\\int_0^{2\\pi}\\frac{d\\phi'}{\\sqrt{r^2-2r a\\cos(\\phi-\\phi')+a^2+z^2}}\n$$</p>\n\n<p>It is easy to obtain the potential for a graviational ring by substituting $\\epsilon_0 \\rightarrow -1/(4\\pi G)$ and $Q\\rightarrow M$ in the equation. One can take the gradient (with a $-$ sign) and find the field numerically.</p>\n\n<p>Or one could go a few steps further and actually calculate everything.\nUsing the equation shown earlier for one value of $M_R$ (orange in graph), one can extrapolate to other values of $M_R$ using $1/T\\propto\\sqrt{M_R}$ (as long as $M_R$ is not much smaller than $M_S$) as $$T = 2\\pi R/v \\sim 2\\pi R/\\sqrt{g R} \\sim 1/\\sqrt{M_R}$$\nwhere $R = \\lambda a$.</p>\n\n<h3>Implementation (Mathematica):</h3>\n\n<p>(Everything is in SI units unless mentioned otherwise.)</p>\n\n<p>First we set up the constants. The elliptic integral for $V$ earlier is somewhat nasty and takes a while to simplify, so I simplified it once and replaced the definition with the output of the simplification.</p>\n\n<pre><code>G = 6.674 10^-11;\nEarthMass = 5.9722 10^24;\nSolarMass = 333000 EarthMass;\nRingMass = 3 SolarMass;\nAU = 1.508 10^11;\na = 1 AU;\nb = 10^-4 a;\nday = 24*3600 // N;\nyear = 365.25 day;\n\\[Rho] = RingMass/((2 \\[Pi] a) (\\[Pi] b^2)) (* roughly 8800, Fe \\[Rule] 7800 *) \n(* Math *)\nVRing[r_, \\[Phi]_, z_, \n MR_] = -G MR/(2 \\[Pi]) ((2 Sqrt[(\n a^2 + r^2 + z^2 - 2 a r Cos[\\[Phi]])/((a - r)^2 + \n z^2)] (EllipticF[\\[Pi] - \\[Phi]/2, -((\n 4 a r)/((a - r)^2 + z^2))] + \n EllipticF[\\[Phi]/2, -((4 a r)/((a - r)^2 + z^2))]))/(Sqrt[\n a^2 + r^2 + z^2 - 2 a r Cos[\\[Phi]]]));\nVRingxyz[x_, y_, z_, MR_] = \n TransformedField[\"Polar\" -&gt; \"Cartesian\", \n VRing[r, \\[Phi], z, MR], {r, \\[Phi]} -&gt; {x, y}];\nVtot[x_, y_, z_, MR_, MS_] = -G MS/Norm[{x, y, z}] + \n VRingxyz[x, y, z, MR];\ngRing[x_, y_, z_, MR_] = -Grad[VRingxyz[x, y, z, MR], {x, y, z}];\ngtot[x_, y_, z_, MR_, \n MS_] = -Grad[Vtot[x, y, z, MR, MS], {x, y, z}] /. \n Abs[p_] Abs'[p_] -&gt; p;\ngtotmag[x_, y_, z_, MR_, MS_] = Norm[gtot[x, y, z, MR, MS]];\n</code></pre>\n\n<p>Let's do a quick sanity check and see if the gravitational field is as expected.</p>\n\n<pre><code>imgWidth = 2160;\nplotAndExport[fname_, \n plot_] := (Export[NotebookDirectory[] &lt;&gt; fname, \n Rasterize[plot, ImageSize -&gt; imgWidth]]; plot);\nfieldPlotXLim = 1.5/Sqrt[2]; fieldPlotYLim = fieldPlotXLim;\nsplot = plotAndExport[\"field.png\", #] &amp;@\n Show[StreamPlot[\n Chop@(gtot[x1 a, y1 a, 0, RingMass, SolarMass][[1 ;; 2]])\n , {x1, -fieldPlotXLim, fieldPlotXLim}, {y1, -fieldPlotYLim, \n fieldPlotYLim}\n , BaseStyle -&gt; {FontSize -&gt; 24}]];\n</code></pre>\n\n<p><a href=\"https://i.stack.imgur.com/z2D1z.png\" rel=\"noreferrer\"><img src=\"https://i.stack.imgur.com/z2D1z.png\" alt=\"Gravitational field flow and magnitude\"></a></p>\n\n<p>Looks alright. The first graph shows the \"flow\" of the field (the arrows sizes are not correct). The magnitude of the field along the $x$-axis is also shown.</p>\n\n<p>Now we implement the solvers for the particle trajectory.</p>\n\n<pre><code>(* Trajectory solvers with initial conditions *)\n\nxi[\\[Lambda]_] := a (1 - \\[Lambda]);\nyi[\\[Lambda]_] := 0.;\nzi[\\[Lambda]_] := 0.;\nvxi[\\[Lambda]_] := 0.;\nvyi[\\[Lambda]_] := Sqrt[G SolarMass/Abs[xi[\\[Lambda]]]];\nvzi[\\[Lambda]_, MR_] := \n Sqrt[Abs[a - xi[\\[Lambda]]] Norm@\n gRing[xi[\\[Lambda]], yi[\\[Lambda]], zi[\\[Lambda]], MR]];\nringSol[\\[Lambda]_, MR_, time_] := NDSolve[\n Flatten@{Thread[{xs''[t], ys''[t], zs''[t]} == \n gRing[xs[t], ys[t], zs[t], MR]],\n xs'[0] == vxi[\\[Lambda]], ys'[0] == vyi[\\[Lambda]], \n zs'[0] == vzi[\\[Lambda], MR], \n xs[0] == xi[\\[Lambda]], ys[0] == yi[\\[Lambda]], \n zs[0] == zi[\\[Lambda]]},\n {xs, ys, zs}, {t, 0, time}];\n\nxiFull[\\[Lambda]_] := xi[\\[Lambda]];\nyiFull[\\[Lambda]_] := yi[\\[Lambda]];\nziFull[\\[Lambda]_] := zi[\\[Lambda]];\nvxiFull[\\[Lambda]_] := vxi[\\[Lambda]];\nvyiFull[\\[Lambda]_, MS_] := Sqrt[G MS/Abs[xi[\\[Lambda]]]];\nvziFull[\\[Lambda]_, MR_, MS_] := \n Sqrt[Abs[a - xi[\\[Lambda]]] Norm@\n gtot[xi[\\[Lambda]], yi[\\[Lambda]], zi[\\[Lambda]], MR, MS]];\nfullSol[\\[Lambda]_, MR_, MS_, time_, \\[Epsilon]_] := NDSolve[\n Flatten@{Thread[{xs''[t], ys''[t], zs''[t]} == \n gtot[xs[t], ys[t], zs[t], MR, MS]]\n , xs'[0] == vxiFull[\\[Lambda]], ys'[0] == vyiFull[\\[Lambda], MS],\n zs'[0] == (1 + \\[Epsilon]) vziFull[\\[Lambda], MR, MS]\n , xs[0] == xiFull[\\[Lambda]], ys[0] == yiFull[\\[Lambda]], \n zs[0] == ziFull[\\[Lambda]]}\n , {xs, ys, zs}, {t, 0, time}\n ];\n\nappendVelocities[solution_] := \n Append[solution, {vx -&gt; xs', vy -&gt; ys', vz -&gt; zs'} /. solution]\n</code></pre>\n\n<p>We will need a bunch of functions to analyze the time period.</p>\n\n<pre><code>(* Examining the period T of rotation about the ring *)\n(* findPeriod and reconstruct copied from \\\nhttps://mathematica.stackexchange.com/a/38221/9332 *)\n\nfindPeriod[data_, threshold_] := \n Module[{fs, s1, s = {}, i, a0f, af, pf, pos, fr, frpos, fdata, \n fdatac, n, per}, n = Length[data];\n fs = Fourier[data];\n s1 = Drop[fs, -Floor[Length[fs]/2]];\n For[i = 1, i &lt; Length[s1], i++, \n If[Abs[fs][[i + 1]] &gt; threshold, AppendTo[s, i + 1]]];\n a0f = Abs[fs[[1]]]/Sqrt[n];\n af = 2/Sqrt[n] Abs[fs][[s]];\n pf = Arg[fs][[s]];\n {a0f, Transpose[{s, af, pf}]}]\nreconstruct[data_, fp_] := Module[{n}, n = Length[data];\n Show[ListLinePlot[data, PlotStyle -&gt; Black], \n Plot[fp[[1]] + \n Sum[fp[[2, j, 2]] Cos[\n 2 Pi (fp[[2, j, 1]] - 1)/n t - fp[[2, j, 3]]], {j, 1, \n Length[fp[[2]]]}], {t, 0, n}, PlotStyle -&gt; Red]]];\ngetOrbitPeriod[solution_, totalTime_, timeStep_] := Module[{data},\n data = \n Flatten@Table[\n zs[t timeStep] /. solution, {t, 0, totalTime/timeStep}];\n (* Not strictly correct as there are many frequencies but good \\\nenough for first approximation *)\n\n totalTime/(timeStep Sort[\n findPeriod[data, 10^8][[2]], #1[[2]] &gt; #2[[2]] &amp;][[1, 1]])];\n\n(* The period T is observed to be linear in \\[Lambda] *)\n\\\n\\[Lambda]TFit[\\[Lambda]list_, Tlist_] := \n LinearModelFit[\n Transpose@{\\[Lambda]list, Tlist}, \\[Lambda], \\[Lambda]];\n\nsetGraphFontSize = BaseStyle -&gt; {FontSize -&gt; 12};\ngraphLineWidth = 0.003;\ngraphMarkerLineWidth = 0.005;\ngraphMarkerSize = 6;\nopacity = 0.5;\npolygonMarker[color_, n_] := \n Graphics[{EdgeForm[{Thickness -&gt; graphMarkerLineWidth, color}], \n FaceForm[None], Polygon[CirclePoints@n]}, \n ImageSize -&gt; graphMarkerSize];\n\ncoloredListPlot[x_, y_, color_, PM_] := \n ListPlot[Transpose@{x, y}, PlotStyle -&gt; color, PlotMarkers -&gt; PM];\nNeeds[\"ErrorBarPlots`\"]\n\\[Lambda]TFitGraph[{\\[Lambda]list_, min\\[Lambda]_, max\\[Lambda]_, \n mean\\[Lambda]_, median\\[Lambda]_}, Tlist_, color_] := \n Module[{model = \\[Lambda]TFit[mean\\[Lambda], Tlist]},\n Show[\n Plot[Normal[model], {\\[Lambda], 0.01, Max[mean\\[Lambda]]}\n , PlotStyle -&gt; {color, Dashed, Thickness -&gt; graphLineWidth}, \n AxesLabel -&gt; {\"\\[Lambda]\", \"T (days)\"}\n , PlotLegends -&gt; SwatchLegend[{color}, {Normal[model]}]\n , Evaluate@setGraphFontSize, \n PlotRange -&gt; {{0, Automatic}, {0, Automatic}}]\n , ErrorListPlot[\n (({{#1, #4}, ErrorBar[{#2 - #1, #3 - #1}, {0, 0}]} &amp;) @@ # &amp;) /@ \n Transpose@{mean\\[Lambda], min\\[Lambda], max\\[Lambda], Tlist}\n , PlotStyle -&gt; {color, Thickness -&gt; graphLineWidth}, \n PlotMarkers -&gt; polygonMarker[color, 4]]\n , coloredListPlot[\\[Lambda]list, Tlist, \n color, {Automatic, graphMarkerSize}]\n , coloredListPlot[median\\[Lambda], Tlist, color, \n polygonMarker[color, 5]]\n ]]\n</code></pre>\n\n<p>Finally, we actually run the solvers and see the data.</p>\n\n<pre><code>(* Actually run simulations *)\n\nringSolutionTime = year;\nring\\[Lambda]list = Range[0.01, 0.1, 0.01];\n\nAbsoluteTiming[\n ringSolutions = \n Flatten@appendVelocities@ringSol[#, RingMass, ringSolutionTime] &amp; /@\n ring\\[Lambda]list\n ][[1]]\n\nringPeriods = \n getOrbitPeriod[#, ringSolutionTime, day] &amp; /@ ringSolutions;\n{ringMaxDist, ringMinDist, ringMeanDist, ringMedianDist} = \n Transpose[distCalc[#, ringSolutionTime, day/24] &amp; /@ ringSolutions];\n\nTableForm@{ring\\[Lambda]list, ringMaxDist, ringMinDist, \n ringMeanDist, ringMedianDist}\n\nfullSolutionTime = year;\nfull\\[Lambda]list = ring\\[Lambda]list + 0.005;\nAbsoluteTiming[\n fullSolutions = \n Flatten@appendVelocities@\n fullSol[#, RingMass, SolarMass, fullSolutionTime, 0] &amp; /@ \n full\\[Lambda]list\n ][[1]]\n\nfullPeriods = getOrbitPeriod[#, fullSolutionTime, day] &amp; /@ fullSolutions;\n{fullMaxDist, fullMinDist, fullMeanDist, fullMedianDist} = \n Transpose[distCalc[#, fullSolutionTime, day/24] &amp; /@ fullSolutions];\n\nTableForm@{full\\[Lambda]list, fullMaxDist, fullMinDist, \n fullMeanDist, fullMedianDist}\n</code></pre>\n\n<p>Making the $T$ vs $\\lambda$ plot and seeing the trajectory (graphs in summary).</p>\n\n<pre><code>plotAndExport[\"Tvl.png\", #] &amp;@\n Show[\n \\[Lambda]TFitGraph[{ring\\[Lambda]list, ringMinDist, ringMaxDist, \n ringMeanDist, ringMedianDist}, ringPeriods, Black]\n , \\[Lambda]TFitGraph[{full\\[Lambda]list, fullMinDist, fullMaxDist, \n fullMeanDist, fullMedianDist}, fullPeriods, Orange]\n , PlotRange -&gt; {{0, Automatic}, {0, Automatic}}\n ]\nplotAndExport[\"traj.png\", #] &amp;@\n Show[GraphicsGrid[{{\n trajectory[full\\[Lambda]list[[1]], fullSolutions[[1]], \n fullSolutionTime/7]\n , trajectory[full\\[Lambda]list[[1]], fullSolutions[[1]], \n fullSolutionTime]\n }}]]\n</code></pre>\n\n<p><strong>References:</strong></p>\n\n<ol>\n<li><a href=\"http://physics.oregonstate.edu/portfolios/Activities/EMActivities/ElectricPotentialRing/RingVSolutions070701.pdf\" rel=\"noreferrer\">http://physics.oregonstate.edu/portfolios/Activities/EMActivities/ElectricPotentialRing/RingVSolutions070701.pdf</a></li>\n</ol>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/79716", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/26724/" ]

[ { "answer_id": 79749, "author": "Willk", "author_id": 31698, "author_profile": "https://worldbuilding.stackexchange.com/users/31698", "pm_score": 2, "selected": false, "text": "<p>The Amazonians would understand these things as an extension of advanced tech they do understand, which would be metallurgy. It is not trivial to smelt and forge metal. Making a sword - - making a rifle. </p>\n\n<p>Is a gun so different than a bow? An arrow flies also faster than you can see. You can hold an arrow and a bullet in your hand before and after they fly. Both make a hole in what they hit. </p>\n\n<p>I bet the Amazons catch on quick.</p>\n" }, { "answer_id": 79752, "author": "Loren Pechtel", "author_id": 264, "author_profile": "https://worldbuilding.stackexchange.com/users/264", "pm_score": 2, "selected": false, "text": "<p>I think Will has a good <strong>start</strong> on it. Showing that guns are merely evolved bows shows that guns aren't magic but they have a lot more stuff that will be much harder to draw parallels with.</p>\n\n<p>I think it can be done using the guns as a starting point, though. You have a \"magic\" item that can be explained.</p>\n\n<p>After demonstrating this I would deal with explosives. While the Amazons have no explosive-based weapon there is stuff in their environment that is explosive--I'm thinking of seeds + fire (think popcorn.) Once again, \"magic\" becomes a greatly advanced version of what they already know.</p>\n\n<p>Hopefully you reach a point where they accept that the things where parallels can't be drawn are likewise just clever tools, not magic.</p>\n" }, { "answer_id": 79754, "author": "Kilisi", "author_id": 22207, "author_profile": "https://worldbuilding.stackexchange.com/users/22207", "pm_score": 3, "selected": false, "text": "<p>After they had ambushed and dissected one, they would see that they are just men/women with fancy gear. Sooner or later someone will get careless. But they would know well before that just by observation.</p>\n\n<pre><code>Primitive != 'Stupid'\n</code></pre>\n" }, { "answer_id": 79764, "author": "a4android", "author_id": 22159, "author_profile": "https://worldbuilding.stackexchange.com/users/22159", "pm_score": 3, "selected": false, "text": "<p>Strangely enough the correct answer is blindingly simple. </p>\n\n<p>\"Hello, 13th century BC Amazons,\" said the 21st century AD soldier. \"We're not all powerful wizards.\"</p>\n\n<p>\"Right,\" said the 13th century BC Amazon leader. \"We get that.\"</p>\n\n<p>OK. This does assume they can talk the same language (but when has this not been the case in any TV or movie involving time travel and 13th century BC Amazons meeting 21st century AD soldiers?)</p>\n\n<p>Basically Amazons aren't stupid, so they should be able to catch on quickly. The soldiers too.</p>\n\n<p>Joking aside, so-called primitive humans are just as smart as modern humans, it won't take them long to figure out that soldiers from the future are just as human as the Amazons are too.</p>\n\n<p>Also, you will need to look into ancient Greek Culture to see what kind of \"superior being\" they might initially mistake future soldiers for. Chances are they won't be seen as wizards. Spirits or demi-gods, perhaps, but probably not wizards. Wizards are mainly a modern concept.</p>\n" }, { "answer_id": 92261, "author": "akaioi", "author_id": 41922, "author_profile": "https://worldbuilding.stackexchange.com/users/41922", "pm_score": 2, "selected": false, "text": "<p>Other answers here have focused on how the soldiers can explain their gear and talk it through. This is certainly true, and should be tried.</p>\n\n<p>I am reminded of when outsiders first contacted the stone age tribes in the highlands of New Guinea. At first the tribesmen were terrified -- funny looking guys with magic gear suddenly show up, no common language, what are they supposed to think? They may well be demons! Or gods! But...</p>\n\n<p>One of the stone age guys investigated the explorers' camp and reported back that, not to put too fine a point on it, \"Their shit stinks. They're human.\"</p>\n\n<p>Source: <a href=\"https://books.google.com/books?id=KyUaQCiivMoC&amp;pg=PA8&amp;lpg=PA8&amp;dq=new+guinea+their+shit+stinks&amp;source=bl&amp;ots=lFABivbiK3&amp;sig=0QhxHaauagfQ7SrqUmpvOCWn6EY&amp;hl=en&amp;sa=X&amp;ved=0ahUKEwiHqprZhKnWAhXkyVQKHSJhBQYQ6AEISTAH#v=onepage&amp;q=new%20guinea%20their%20shit%20stinks&amp;f=false\" rel=\"nofollow noreferrer\">https://books.google.com/books?id=KyUaQCiivMoC&amp;pg=PA8&amp;lpg=PA8&amp;dq=new+guinea+their+shit+stinks&amp;source=bl&amp;ots=lFABivbiK3&amp;sig=0QhxHaauagfQ7SrqUmpvOCWn6EY&amp;hl=en&amp;sa=X&amp;ved=0ahUKEwiHqprZhKnWAhXkyVQKHSJhBQYQ6AEISTAH#v=onepage&amp;q=new%20guinea%20their%20shit%20stinks&amp;f=false</a></p>\n" }, { "answer_id": 110197, "author": "Rick M.", "author_id": 47807, "author_profile": "https://worldbuilding.stackexchange.com/users/47807", "pm_score": 2, "selected": false, "text": "<p><strong>Go slow nd steady</strong>. If the concern is that the Amazons start thinking of the soldiers as wizards or semi-gods or the likes of that, it means they think they can't find a way to explain the gear and other stuff the soldiers have or do. I would suggest pointing out a technology the Amazons are familiar with, and then illustrate how modern-day tech is a natural development of that. Then repeat the process a few times with different types of gear until the pattern becomes clear. Mutual language is what makes this possible.</p>\n\n<p><strong>Start small - Clothes:</strong><br>\nI'd say it's a smart idea to try a simple thing first. this will ease the Amazons into hardcore development, and also allow the modern soldiers to practice their 'technique'. Amazons wore clothes, and it makes sense they've seen different types of clothes, at least to a degree. Just tell them that the uniform is what the \"army tribe\" wears (I call it a tribe because I think complex societies should also be explained, but further down the road). They can go the extra mile and explain what makes the uniform a good choice to wear.</p>\n\n<p><strong>Moving on, Navigation:</strong><br>\nNext up, something the Amazons most have done, is navigate. They probably did it using the sun. The soldiers should show them a compass, and let them see it always points at at the same direction. Preferably, they can alter a compass to have the colored wing point East and not North, so they can say it points at the sun, but that's just a shortcut. They tell them it senses the sun and points accordingly. The extra mile here would be to explain that maps were created, and maybe even that they have a machine that them ho to get somewhere (it reads the map and says 'go North for 20 steps, the East 16, the W 12 etc.).</p>\n\n<p><strong>Lamps and flashlights:</strong><br>\nNext up, the focus shifts to show that a lot of thing the Amazons know were made better and easier. When they needed light, they made a fire. This one can be rather simple (they also already saw some advancements till this stage). Basically tell them that lamps &amp; flashlights have a very small fire in them. It burns a fuel smaller than wood, so it can be put in a small object, much easier to work with than a torch.</p>\n\n<p><strong>Game on, Guns:</strong><br>\nNow to weapons. This part was touched extensively in other answers, but my two cents: Make <em>a lot</em> of comparisons to older weapons (like bows). Make sure to break up the tech to smaller parts. Show them gun powder burn, then say it \"kick\" the bullet out like a bow-string pushes an arrow. Then you have a small arrow made of a material that 'army tribe' finds easy to work with.</p>\n\n<p>After this you can continue to more complex and abstract concepts if you'd like (like the aforementioned societies). Long as you go slow and steady, I think it will be possible, and more importantly - plausible.</p>\n" }, { "answer_id": 125748, "author": "RonJohn", "author_id": 8068, "author_profile": "https://worldbuilding.stackexchange.com/users/8068", "pm_score": 0, "selected": false, "text": "<p>The Amazonians will cotton on pretty quickly when the soldiers start getting sick from malaria, parasites or any other jungle disease that they aren't immunized for but that the natives have a tolerance of (think \"Montezuma's Revenge\").</p>\n\n<p>I don't know what kind of vitamin and mineral deficiencies people get in the Amazon, but they'd start to suffer from that, too, soon enough.</p>\n" }, { "answer_id": 134898, "author": "TheLeopard", "author_id": 42702, "author_profile": "https://worldbuilding.stackexchange.com/users/42702", "pm_score": 0, "selected": false, "text": "<p>Ancient peoples weren't stupid. Well, some of them were, just like some people today are stupid. </p>\n\n<p>Soldiers and Amazons.</p>\n\n<p>At first the Amazons won't understand what they are seeing. They won't have a frame of reference to place 21st century vehicles and devices in their conceptual framework.</p>\n\n<p>It would be similar to how the Incas thought a man on a horse was one creature. They'd never seen horses before, let alone a mounted soldier.\n<a href=\"https://theglyptodon.wordpress.com/2012/01/21/the-horse/\" rel=\"nofollow noreferrer\">Source</a></p>\n\n<p>The Amazons might assume a vehicle was some fantastic sort of growling animal, especially at a distance, because that's the only thing they would have in their experience that would be that size and moving seemingly on its own.</p>\n\n<p>Once the Amazons inspect the new things close up the soldiers show them how they work, they'll most likely realize quickly that they are mysterious devices rather than magical artifacts.</p>\n\n<p>The ancient Greeks had more mechanical devices than we usually give them credit for, like the <a href=\"https://www.smithsonianmag.com/history/decoding-antikythera-mechanism-first-computer-180953979/\" rel=\"nofollow noreferrer\">Antikythera Mechanism</a> and other <a href=\"https://en.wikipedia.org/wiki/Ancient_Greek_technology\" rel=\"nofollow noreferrer\">things.</a> </p>\n\n<p>Something to consider is that to the ancient Greeks and nearby peoples, gods and the supernatural were acceptable parts of life. It would be completely reasonable for the Amazons to determine through logic whether or not the soldiers were gods or human beings. There's a passage in the Iliad where one Greek soldier says to another, \"I knew he was a god by the shape of his feet.\" If the Amazons observe that the soldiers eat, sleep, and otherwise act like men, and they don't do anything miraculous, then the Amazons will come to the conclusion that they are most likely men.</p>\n\n<p>Anyway, the point: </p>\n\n<p>The soldiers can explain to the Amazons that their items are devices crafted by cunning smiths, then take the equipment apart so they can see how the pieces fit together. They can demonstrate their mastery over the vehicles, and show the Amazons that they are only devices made of metal.</p>\n\n<p>When the Amazons ask questions about how things work that the soldiers probably won't be able to explain (who really knows how a smartphone works?), the soldiers can just say, \"Oh, we bought all this stuff off the wise craftsmen of Egypt, who keep the secrets of their trade well-guarded.\" to which the Amazons would most likely reply, \"Egypt, of course!\"</p>\n" }, { "answer_id": 134912, "author": "Geronimo", "author_id": 19644, "author_profile": "https://worldbuilding.stackexchange.com/users/19644", "pm_score": 0, "selected": false, "text": "<p>They won't belive them to be all-powerful wizards because the soldiers, like all modern society, lacks oracular capabilities. Sorcery/magic had nothing to do with blowing things with black powder or corroding things with acids. It was direct spiritual contact with the daemons, with the daemons using their powers as supervisors of Reality to the benefit of the mage, as Iamblichus says in the On The Mysteries. And among these powers the most important, the true sign of the divine, was the Oracle, as Proclus, the last neoplatonist, said. </p>\n\n<p>While your modern soldiers can blow a lot of things, resist a lot of diseases due to vaccination and antibiotics, and kill a lot of people, they can't summon a spirit and hear it's oracles. They can't know things from the future veiled to the common man nor know know hidden things from the past. </p>\n\n<p>So your amazons won't mistake them for powerful wizards. But to do so YOU will have to abandon the modern, materialistic, view that magic is blowing things up with gunpowder while doing theatrics and distraction and use the ancient worldview.</p>\n" } ]

[ "https://worldbuilding.stackexchange.com/questions/79741", "https://worldbuilding.stackexchange.com", "https://worldbuilding.stackexchange.com/users/21870/" ]

[ { "answer_id": 80072, "author": "kingledion", "author_id": 23519, "author_profile": "https://worldbuilding.stackexchange.com/users/23519", "pm_score": 3, "selected": false, "text": "<h1>Depends on how much power you want to lose</h1>\n\n<p>Based on the information in this <a href=\"https://worldbuilding.stackexchange.com/a/6/23519\">answer</a>, assume we need a minimum founder population of 400. Other answers suggest as low as 80 with good medical support, but that seems like it will be unlikely in your scenario.</p>\n\n<p>35 of those 400 are your super-powered individuals. However, to prevent the genes from being too diluted, you need to spread that genetic variation among multiple generations. Lets say that every generation, you add ~30 new people into the breeding population for 12 generations. These people will bring their 0% power genes into the collective gene pool. Lets further assume that there is a 50% increase each generation: 3 children for each 2 parents. Here is how the gene pool looks each generation:</p>\n\n<pre><code>Gen Pop %Powerful\n0 35 100\n1 97 53\n2 191 41\n3 331 36\n4 542 33\n5 859 31\n6 1333 30\n7 2045 29\n8 3113 29\n9 4715 29\n10 7118 28\n11 10722 28\n12 16128 28\n13 24237 28\n</code></pre>\n\n<p>28% is the asymptotic limit. Your population will stabilize there in time. </p>\n\n<p>Now lets re-run the exercise, but breed in far fewer people each generation; only 10. It takes 36 generations now (actually kind of a long time, something like 900 years) to get enough people into the gene pool, but on the plus side you keep the power a lot stronger. For this second run, we'd have to tone down the birthrate some to keep from over-running the earth, but the asymptotic power level is 54%. So the slower you add people to your gene pool, the more power you can maintain. </p>\n\n<p>So the answer is: <strong>As low as 10 generations, if you don't mind getting depowered, around 30 generations to keep the average power level to 50%</strong></p>\n\n<h1>Good old fashioned racism will help keep your population powerful</h1>\n\n<p>There is another factor at work. The superhumans will presumably be ill-disposed towards those who show few powers due to the genetic lottery. IF they discourage those people from mating, then your powers will eventually be bred back into the population. If, once the population has expanded enough to minimize the genetic bottleneck, people with less than 50% power are simply kicked out of the ruling class and now allowed to intermarry any more, you will find that the average power level of your group will increase over time; to at least 50%. </p>\n\n<p>Thus, you may only have to interbreed for the 10 generations, and then rely on 'artificial selection' to keep your power level higher. With enough time (and enough racism) you can get your power level back to near 100%.</p>\n\n<p>An excellent example of this in practice is the country of Mexico. For 400 years in Mexico, everyone in the upper class insisted that they were all Spanish, and didn't have any Indian in them. The result is that even though the population has a <a href=\"https://en.wikipedia.org/wiki/Mexicans#Population_genetics\" rel=\"noreferrer\">pooled genetic material</a> that is about 30% European, 65 % Amerindian, 5% Black, the skin color skews heavily white (graph shown on the link). This is basically because skin color is the easiest thing to be racist about, so there was artificial selection pressure for lighter skin for so long. So there are now a lot of light skinned half-Amerindian Mexicans running around. </p>\n\n<p>You can use this effect to eventually (maybe after 400 years) get a population of 100% superpowered half-non-powered (muggle?) people running around on your alternate Earth. </p>\n" }, { "answer_id": 80117, "author": "Mike Nichols", "author_id": 879, "author_profile": "https://worldbuilding.stackexchange.com/users/879", "pm_score": 3, "selected": false, "text": "<p>It's a simple answer but your group of 35 don't need to out breed at all. Assuming they aren't closely related to one another and assuming their population expands with each generation they shouldn't have any major issues with inbreeding.</p>\n\n<p>My reasoning is fairly straight forward. The population is of sufficient starting size that no incestuous offspring will ever be necessary. Assume 35 individuals pair off to form 17 unrelated families for the first generation. This is a sufficient number of families that no one will ever have to marry someone closer than a second cousin indefinitely.</p>\n\n<p>Even if we allowed for random mating as a worst case scenario the relative frequencies of recessive alleles (barring extraordinary misfortune in the genetic lottery) will be rather small. As an example if two of your starting 35 humans happened to have recessive mutations for a serious disorder that disorder would still only have a prevalence on average in the population of 0.08% = (2/70)^2.</p>\n\n<p>Beyond simple inbreeding there are other genetic phenomena at work on small populations. Genetic drift would be a cause for concern if your population was maintained at such a small number for many generations, but since it will likely be expanding exponentially genetic drift won't have any detrimental effects.</p>\n\n<p>Genetic diversity could be an issue, but 35 people (and therefore 70 alleles for every locus) is still a large amount of diversity. If you do want your super humans to need to out breed you could make them susceptible to certain plagues that the locals have been selected to be resistant towards.</p>\n" }, { "answer_id": 80183, "author": "Shadow1024", "author_id": 25459, "author_profile": "https://worldbuilding.stackexchange.com/users/25459", "pm_score": 2, "selected": false, "text": "<p>35 people... 2^5=32... So assuming perfect choice of sexual partner for 5 generations they would have no need to even think about mating a common man. After 5 generations - each person would be a bit related, but more some distant cousin... imperfect but acceptable.</p>\n\n<p>If one accept slightly increased number of genetic illness like in Arab societies - then they are not in desperate need of local partners at all.</p>\n\n<p>Concerning such mechanism, I wonder more about social institution:</p>\n\n<p>-would one cull defective superheroes (or in other way remove them from gene pool)?</p>\n\n<p>-would one keep blind eye to some extramarital affairs?</p>\n\n<p>Because I can imagine a situation, where in long run:</p>\n\n<p>-a few unviable offspring simply dies early, thus eliminating itself from gene pool</p>\n\n<p>-a few would seriously ill would be kept celibate or sterilized</p>\n\n<p>-there is a constant influx of superhero genes in to local population, both natural selection and some local rulings should favor that. In long run - a slightly inbreed group of heroes, and mixed blood masses, with slowly increasing hero percentage.</p>\n" } ]

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