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mryqop | What makes a hard drive 'hard'? | Why would it be described like that? It's not like SSDs or optical media are particularly soft. | Technology | explainlikeimfive | {
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"Cause before you had floppy disks. Which, as the name inplies were floppy disks encased in a hard plastic box. Then came harddrives which are, you guessed it, harder disks.",
"What others have said it's basically right about floppy disks, however there is another factor... The actual recording media for \"floppy\" disks (12\" flexible all the way down to 3 1/4 hard shelled disks) was a thin plastic sheet. Hard disks use multiple metal disks. So, the actual physical disks inside were either flexible or solid.",
"Hard disk drives are hard when compared to floppy drives. Of course the floppy drives most people remember will be the 3 and 1⁄2-inch floppy disk which were encased in hard plastic. However the older 5 and 1⁄4 inch discs and even older 8 inch ones were indeed floppy and able to bend flex. In general it has little to do with the drives as you handle them but the disks insides. Floppys and similar had flexible disks while HDDs have hard platters inside them. If you ever opened up an old HDD you will have ended up with a broken drive and a cool magnet to play around with, but also some hard silvery looking disk that were stacked one over the other other inside the drive. These platters are what is meant when they say 'hard' compared to the floppy disc that you get when opening up the protective sleeve of a floppy disc."
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mrzpu7 | In the context of programming, what does Return do? | I'm trying to pick up computer programming yet again, and I'm not really understanding the use of Return. What is it? How would you use it? | Technology | explainlikeimfive | {
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"It tells the thing that's interpreting or compiling your code that you want to exit the current function. If you just write 'return' that's all that will happen, but typically you can also follow this up with some values that you want the function to spit out, i.e. the output of the function. For instance, I could define this function (in python code): def PlusTwo(x): x+=2 return x And then if in a command terminal (or some other script/function) I say: \\ > y = PlusTwo(3) The resulting value of y will be 5. You'll often find return statements at the end of a function, but not necessarily. You can have different conditions under which you want the function to exit, with different outputs, and these might be found at different places in the function. However you nearly always find a return statement on the very last line of the function, because anything below that would be ignored. For instance, if I define a function like this: def PlusTwo(x): x+=2 return x x+=7 the last line will never actually be executed, and so this function still just adds 2 to the value of x. Some languages don't require return statements - you just have to specify in the function definition what variables are your output variables. And then whatever the values of those variables are when the function exits will be your output. MATLAB for instance works this way. But others, like C or python, do use return."
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ms0c41 | Why do bigger camera censors have more natural blur? | Technology | explainlikeimfive | {
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"It's more that there is a wider variety of lenses available on cameras that have large sensors, in particular lenses with large holes (apertures). Lenses with a large hole give the rays of light more opportunity to stray off course before they are focussed back onto the sensor. The stuff that isn't focussed is what causes the blur, ie they've got jumbled up with all the other rays of light. A small hole means all the rays of light go straight through and hit the sensor without much opportunity to mix and cause blur."
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ms1ez3 | What is the impact of browsers no longer accepting 3rd party cookies and Apple’s Intelligent Tracking Prevention? | I know it impacts advertisers ability to target, but would love a clearer explanation of how it works and the impact. | Technology | explainlikeimfive | {
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"An analogy: Every time you go anywhere in public, the shops you use, the buildings you enter, and the people you interact with put a coloured sticker with a number on you. It's just a sticker, it contains only a number, it's not \"private\". Say the baker always uses a green sticker, and he numbers based on the order you walked into his shop. And the butcher uses a purple sticker and he numbers based on a random number that he makes up. And the grocer uses a green sticker and he numbers based on how much you buy from him. Whatever. It doesn't matter. The butcher, the baker and grocer don't know what the other people's numbers mean, it's just a number. And when you get home, your arm is full of coloured stickers with numbers on. But it means that when you go out tomorrow, the butcher knows that you're #27, that you buy beef from him regularly and that yesterday you were interested in how to best cook steak. Not a problem. The grocer knows nothing about what the butcher's number means or what the butcher knows about you. The problem comes when the butcher, the baker and the grocer all employ a company to put those stickers on you, because they don't want to do it themselves. The company does it \"for free\" to them, and labels you with a pink sticker with a unique number. When the butcher asks and says that you have a pink number #35 on you, the company can tell him everything he'd normally store about you (because the company have recorded it for him). When you go to the grocer, he can also talk to the same company and ask them for everything he wanted to remember about pink #35. Still not a problem. But now that one company runs all the data collection for lots of people. So they can tell the butcher that you went to a rival butcher's last week because your pink #35 was spotted there. The butcher can ask for other information about pink #35, so he knows that you bought turkey gravy yesterday and maybe he can try to sell you a turkey today. And the company then sells that data about pink #35 to completely unrelated companies that you've never dealt with, say a clothing store, so they can suggest that if you're eating that much meat, maybe you should try a bigger size of jeans, and so on. The stickers are cookies. The company are data aggregators like Google ads, many tracking cookie and analytics firms, and the average website has something like 35 companies that put stickers on you where those stickers are shared with EVERYWHERE you go which uses that same company. Apple's (not new, unique or innovative) idea is to keep your arms covered so you only show the stickers you want to the companies that need them and when you go to the butchers they have to give you a new sticker from the company because you refuse to show them your previous ones, so they have no idea who you are. So they can't tie in that information about you from across the net, sell it, and use it in potentially nefarious ways. And occasionally, they'll take the stickers off you entirely because you haven't needed them in a while.",
"Here's a slightly deeper and wider explanation (ELI8): Let's talk apps first. Your Apple phone is given a unique ID in the factory. This number is unique to your phone like a license plate number or a Social Security or National ID number. If you open the Facebook App, the Facebook app reads your unique ID number and everything you do in Facebook App is reported back to Facebook with your unique ID. So, if your ID is 2399, Facebook App will tell Facebook say that 2399 is looking at puppy pictures. Now, if you click on an ad for a Puppy Game the app store will load the Puppy Game, and you install the Puppy Game. When you buy something in the Puppy Game, the Puppy Game tells Facebook: Hey, 2399 just spent money on the Puppy Game! Facebook now knows that 2399 really likes Puppies from information across multiple apps. Now, Apple doesn't like apps sharing info. So, instead of telling Facebook your ID is 2399 and telling Puppy Game your ID is 2399, it tells Facebook your ID is 5522 and it tells Puppy Game your ID is 999. Apple knows that 5522 is just an alias for 2399 and that 999 is just an alias for 2399. But to Puppy Game and Facebook apps, 5522 and 999 are different people! Now your data is more \"private\" in that two apps can't share info anymore. Of course, if you log into your Facebook account on both Facebook and Puppy Game, Facebook can now figure out that 5522 and 999 are the same person because you use the same email address and password on both apps and both apps tell Facebook. In browsers, the idea is similar except instead of Apple providing the ID for your browser, 3rd party sites leave a cookie (basically just a blob of data) on your browser, which acts as the 3rd party's ID for you. Every website that wants to can look at the cookie and send that cookie back to the website. If two cookies match, then the websites can tell you are the same person. Apple's tech will do the same thing as for the apps, which is that you can leave a cookie for your website, but Apple will choose the cookie, and you can only get the cookie for your website, and that cookie will be different for other websites so various websites can't tell you are the same person. Or the user can disallow cookies altogether. Of course, if you login to a different websites using your email address or Facebook Login, the different websites can tell you are the same person! So, Apple's move basically prevents websites from stealthily knowing you are the same person. There are many ways you can explicitly tell the site who you are without really know it.",
"The explanation by u/ledow is mostly correct. There are two things I’d like to add: - Privacy through aggregation - Consequences of eliminating cookies Google, Facebook, etc. are not in the business of selling your data. They’re in the business of selling ads. That might sound weird at first, but consider the fact that their defensible moat of technology and IP is contingent upon having *that* data. Why would you sell your resources instead of leveraging them towards selling your product? They offer targeted advertising, which might give information about those targeted through completed purchases and account creation, but that’s only once a user has made a decision to buy the product advertised. Eliminating cookies has led to a weird spot. Google’s Chrome is so incredibly popular that they can make changes without much repercussion, and the ones they’re going forward with are “pseudo-privacy” enhancements. They’re more so adjustments to make Google seem like good guys along with Apple, rather than exposing more of you to the internet than before. Before, you’d get unique identifiers attached to you at a website level, which Google would collect to track you across sites. Because it would take lots of collaboration across many, many sites to discern these identifiers, most people would default to just using Google’s in-house ad offering. This was good for your privacy in that, as mentioned above, Google sells ads *from* data rather than the data itself. The change coming is that instead of you having a *unique* identifier, you’re getting a *cohort* identifier. Chrome will have machine learning models built in which map your behaviors to pre-determined cohorts (the models are exported from supercomputer computations of data they already had on everyone, so there is no ML computation going on in chrome; it’s just matching your history to cohorts). For example, if you buy pet food and leather belts, you might be put in the pink35 group. To be clear, these cohorts are **tremendously** complex, are based off of thousands of features, and they’re too abstract for any human to discern. This might seem good for privacy since if you go around with pink35 on you, you’re going around with a tag shared by thousands of people. How could that not help privacy? The reason it doesn’t is that by having cohorts, it becomes quite reasonable to collaborate across sites to discern what these cohorts signify to some extent. You’ve reduced the quantity of identifiers significantly, especially when businesses inside an industry likely share cohort customers. It becomes even worse when there are now thousands of other people who act like you helping to fill in the gaps of what you likely do. Suppose I’m marked with pink35. Everyone else in pink35 is willing to buy without coupon codes or sales, so sellers adjust their sites to hide them from pink35 or to even increase prices. This is price discrimination and often occurs using geography or device screen size. However, with these cohorts, you can do it easier and more robustly. Google is saying “look how helpful I am” while causing a large mess. This analysis of cohorts came from Ben Thompson of Stratechery.",
"First u/ledow's analogy is spot on. It effectively prevents a lot of that creepy behavior when you browse an item at one site and suddenly the Internet is pushing ads for that class of thing on every web site you visit. Buy a lightning cable on Amazon, suddenly the sidebar in Reddit is filled with ads for lightning cables and iPhone accessories. For the most part, this is a good thing. So far, the only thing I've found is that it breaks some banking sites that use a third party for their online banking systems. My personal bank doesn't work with this turned on in Safari and I have to turn off the feature when using the bank.",
"Follow-on question: if cross-site and cross-app tracking becomes less viable, then advertisers don’t make as much money. How does that affect the economy of the web and the availability of “free” websites that make their money selling your data?",
"I do work in the field, and as of now the impact is not that noticeable. Sure, there are less people to target, but there are still enough people using chrome (not yet blocking 3rd party cookies), consenting to cookies or not updating their browsers. Those who know enough about tech to block 3rd party cookies probably also know enough to install adblockers anyway. But it is a huge topic for new business, as there are a lot of cookieless solutions, for example contextual targeting or geo-targeting which yield similar results. So yea, for users it is way better (as the top comment explains) and for advertisers there are just other ways. In my book it's a win-win or at least a win-slightlyinconvenienced."
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ms6h6q | Desalination by RO creates concentrated brine, which is then released into sea back. This causes environment problems. Why cant we use this brine for other process like salt harvesting etc, which requires brine? | Recently I watched these videos which explains the negative impact of releasing concentrated Brine produced from RO Desalination plants back into Ocean. 1. [ URL_2 ]( URL_3 ) 2. [ URL_0 ]( URL_1 ) This got me thinking why can't we use this brine in an commercial beneficial way, given that there are several industrial process that uses Brine as raw material. On top of my head I could think of Salt production, Caustic Soda production etc., Why is brine not used commercially? And what are the challenges and is there a solution? | Technology | explainlikeimfive | {
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"The challenge here is mostly that salt is ubiquitous and fairly worthless - $58/ton It takes a lot of energy to drive off *all* the water and produce rock salt, so the costs are higher than what can be recovered by selling the salt. The brine may have a few uses, but a large DeSal plant is producing brine at a much greater rate than you could realistically consume the salt locally."
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ms75wf | How do gaming headsets allow us to differentiate distance and location of noises, such as if footsteps are on the floor above or below you, or where and how far gunshots are coming from in a BR type game based on where you are standing and which way your camera is facing? | Technology | explainlikeimfive | {
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"It's basically the same as how you do it normally. We can work out where sounds are coming from based on tiny differences in timing and level of sounds arriving at the two ears. There's also some filtering of sounds based on the shape of your ears and the position of the sound. The underlying idea for virtual audio is that you reproduce those tiny differences in the ears using a bunch of computer calculations. Really, it's not all that different from how VR headsets let you see in 3D. You see in 3D because of the differences that your two eyes see. In VR, the headset sends a slightly different picture to each eye to let you perceive depth etc. It doesn't matter how the signals get to your eyes or ears, whether they are arriving naturally or via a screen/earphone. The important thing is what the light/sound is like when it's *in* your eyes/ears. Source: hearing scientist with a PhD in sound localisation :) If you want to know more about how we work out where sounds are, I'll find a link to another thread :)",
"Technically it's not just the headsets that allowes this but also how the game is programmed. In games you have sound files or sound clips that are played based on a trigger, for example a footstep or a gunshot. Based on that sound clip and the location of you and the source of the sound different algorithms can change and affect the sound so you perceive it as being further away. Some games with tighter development budgets or with limited development teams might not have the resources to implement this type of sound design. This leads to some games having worse sound and making it really difficult to tell how close a sound source is or which direction it's coming from. In most games this doesn't really matter too much, but in first person shooters this can be really frustrating when it sounds like an enemy is just around the corner when he actually is on the other side of the building or 30-40m away."
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ms83qg | PoW (Proof of Work) vs. PoS (Proof of Stake) | Im just trying to understand if theres one that is superior and the details of how each works and the pros and cons of each within the crypto space | Technology | explainlikeimfive | {
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"I can explain this. Bitcoin was the first practical system where a bunch of computers can agree on What's What, agree on the state of the data mutually rather than being told it by a leader. It does this by asking each computer on the network for its version of the data. But that raises a problem: someone could insert biased data favourable to themselves, spin up a million virtual machines, and have them all claim that's the state of the data. So Satoshi's solution was to add proof-of-work, computationally difficult puzzles that must be solved to have input regarding the state of the ledger: [Bitcoin: A Peer-to-Peer Electronic Cash System]( URL_1 ) said \"If the majority were based on one-IP-address-one-vote, it could be subverted by anyone able to allocate many IPs. Proof-of-work is essentially one-CPU-one-vote.\" Proof-of-work and proof-of-stake are two slow-down mechanisms designed to add friction to input on the state of the blockchain. You couldn't shout your own data over the other voices, because doing so requires more computers, more electricity, and that's expensive. There are problems with this slow-down mechanism, notably [Bitcoin's enormous energy consumption]( URL_0 ). So proof-of-stake aims to achieve the same thing, but instead of having to buy computers and electricity, you have to buy the cryptocurrency of the blockchain itself. It achieves the same ends, i.e. making it expensive to have input into the state of the ledger, and therefore prohibitively expensive to input malicious scurrilous data, but without the need to burn so much energy."
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msgkkr | What is dynamic range in music? | Technology | explainlikeimfive | {
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"It's the difference between how loud and how soft a song gets. Does it stay just loud, does it just stay soft, or does it have changes in how loud or soft it is?"
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msgmfz | How can choosing pictures of certain objects (stop signs, cross walks, cars, etc.) prove that you are not a robot on websites? | It seems weird that to prove that I’m human I have to look for certain objects or check a box. Why is that? | Technology | explainlikeimfive | {
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"The choosing pictures isn't really to check if you're a robot, it instead helps with gathering masses of data for self driving vehicles. Whether you are a human was already decided in the background, depending on a lot of different factors that google doesn't wanna give out because otherwise botters could use that. Remember when it was words? Similar thing, one word was the check, the other for Google's digitalizing of books. Word and a house number? For google maps. Edit: some additional bits Captcha, the system that is used for checking whether you're human or not, stands for \"Completely Automated Public Turing test to tell Computers & Humans Apart\". And there are several ways to get around these, there are programs out there who are able to solve these tests successfully and seem human, but there have also been instances where humans have been paid to solve Captchas all day long.",
"Because how bots select images on those questions can be detected as automated by the website. People tend to wander with their mouse, and can pretty easily tell the difference between a traffic light and a street light at first glance. Bots tend to be predictably mechanical in the choices they make.",
"It less proves it so much as makes it highly likely. Humans have many millions of years of evolution behind highly advanced object recognition. Our brains being able to tell the difference between a tiger and a vaguely tiger-shaped rock is the difference between life and death. Computers can distinguish between objects too, but in order to do it with a high degree of accuracy (especially when you're not trying to compare apples to battleships) it requires a fairly high degree of training and computing power. Can computers choose the 3 images out of 9 that have a fire hydrant in them? Absolutely. Is it a deterrent to people trying to brute force websites when you're effectively multiplying the amount of time and/or computing power required by 100x or more? Yes."
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mshkr9 | How do hackers find holes? | When I see black hats exploiting gaps in security, I have to wonder, how the hell did someone find this? Is there an algorithm? I would think the white hats would have the algorithms too? Even in video games, how do they find such obscure holes in professional programming? | Technology | explainlikeimfive | {
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"\"Professional programmers\" make mistakes all the time, because there is far more need for people who can code even fairly badly than there are people who are good at it. Companies will sometimes spend tens of thousands of dollars in sourcing costs to find one mediocre software engineer. There are certainly common approaches. For example, it's a very bad idea to store users' passwords in a database, but tons of shoddily-written websites do. Many websites also have much more information exposed than you probably think, and hackers will poke at that information to try to find places where it exposes something it shouldn't. For programs on one's own computer, one can use a program that lets them just look at the computer's actual memory and watch when certain values change. If you pick up a health potion and the value at memory address 0x4a89b92d changes, well, that's probably where the game is storing your number of health potions. So you change the value at 0x4a89b92d to 99999999 and see if you get a bunch of potions. This is just a very basic summary. Finding weaknesses like this is a whole subfield of programming and engineering that tends to attract extremely smart and extremely technical people. There's a ton of security talks on YouTube that are relatively accessible and pretty interesting, if you want to know more!",
"Every time someone closes a security hole, a new one is found. Even at companies, who do security well and try to seal every known exploit, new vulnerabilities are constantly being found. Sometimes the company will find them before shipping the software. Some even have dedicated penetration teams. But sometimes they are found in the wild. You cannot underestimate the tenacity of those who want to exploit your software and the creative ways they think to do so. In many cases, companies don’t have dedicated security resources. Most programmers don’t learn much about security in school. Their job experiences won’t always teach them the right ways to do things. They may have never been in a high-risk environment and needed to think about security. All that adds up to plenty of attack vectors."
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mskiqa | How do reflections work in last gen games? I know it’s not ray tracing but how do they work? | For example in last of us 2, there are times you can be in front of a mirror and all your movements are reflected perfectly, no matter what you do. And the scenery in the background moves the same way the scenery in the mirror does. While I know this isn’t ray tracing, what is it? How does it work? How is it different than raytracing? | Technology | explainlikeimfive | {
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"You can render what the camera would see if it where behind the mirror, in another pass. This is one way things were done in older games, often times at a much lower resolution.",
"In older games they literally just put a duplicate player character model there inside a copy of the room the mirror is in. Mirrors really are 'a portal to the mirror world' where a copy of everything exists. When you move yourself then it just moves the character in the mirror too.",
"The quickest dirtiest way to do is to have all the objects duplicated and placed on each side of the mirror, then always apply the same transformations (except mirrored) on both copies."
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mslt5a | How do commercial fishers know what they are going to catch? | They will seek out huge loads of one species and throw out the rest... but how do they hunt and track specific species? | Technology | explainlikeimfive | {
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"Location, depth, bait, tools. Certain fish are only in certain locations, so to fish a specific fish you must be in a specific location, this isn't necessarily the difference of Alaska vs Florida, but can be location where a certain environment or phenomenon is observed IE: where currents come together, or where certain food can be found said fish like. Certain fish swim at certain depths, you fish as deep where the fish will be. Certain fish are attracted by certain kinds of bait. To catch specific fish you might use different methods or tools, something that is most effective for that kind of fish, it's not always just massive nets.",
"By taking everything out then keeping what they want and throwing back dead or alive what they don’t."
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mss9dc | Why does audio sound acute when it's sped up and deep when it's slowed down? | Technology | explainlikeimfive | {
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"What makes a tone sound high pitched or low pitched is its frequency; the space between each sound wave. When you play back some audio at a higher rate, it winds up making the sound outputted have less space between each wave, thereby making it sound higher pitch.",
"Longer waves sound deeper \\ / \\ / \\ / \\ / is lower than WW When you speed things up, the waves get smushed smaller"
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mt1dkq | What causes a bug in software? | Technology | explainlikeimfive | {
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"Writing a computer program requires a high level of precision, basically to the point of perfection. A bug is an error in the programming code. Think of it like a pothole or crack in the road. The bigger it is, the sooner you will notice it and the more damage/disruption it can cause. And some are so small, perhaps in a section of the program that is hardly ever used, that you don't notice it for a while. It's called a bug because back in the Grace Hopper days (I don't remember what decade that was, sorry, but 60s or before for sure) a computer failed because an insect type of bug had gotten into the computer - back then, they were a huge box 4 ft * 4 ft * 8 ft or bigger - and managed to short something out."
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mt2yn6 | Why does rubbing alcohol not damage electronics but water does? | Technology | explainlikeimfive | {
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"Rubbing alcohol (isopropyl) doesn't conduct electricity. It doesn't complete an electrical circuit and it doesn't cause iron to oxidize (rust). Water does. Edit: Pure water doesn't conduct electricity - as I've been informed 1000 times.",
"You can wash electronics with soap and water without damaging them, so long as there is no current running in the device. Capacitors that still have a charge can cause shorts, so this is also a potential hazard when cleaning electronics. Alcohol is used because it evaporates faster and it's a better solvent.",
"The most risky liquid for electronics is salt water. It causes galvanic corrosion and can act to short circuit power components. If you ever drop unprotected battery powered electronics into salt water, you have *seconds* to remove the battery; you have *minutes to hours* to rinse out the salt water and you have *days* to let the clean water dry off. You can make a galvanic cell (battery) by taking any two different metals and dipping them in an ionic solution (eg: acid, salt water etc.) When you drop your phone into salt water, the frame (aluminum or steel) and the circuit traces (copper) form a battery. The very fine copper traces oxidize (rust) rapidly. You can make this happen even faster by applying a voltage to drive the reaction. Clean water on unpowered electronics is pretty harmless. Many electronic manufacturing processes flush or rinse with distilled water. If you leave it for a long time, the damp metal will react with air to rust and it will tend to pick up salts and contaminants that may make it act like weak salt water. Alcohol evaporates very fast and is usually applied very sparingly. The risk with alcohol is not the electronics but the structure. Many adhesives are alcohol-soluble including hot melt (used to tack down wires and physically stressed components) tapes and, most importantly, some of the glues used to build up touchscreens. Generally the amount of mass (for glues and tapes) or the amount of exposed surface (tapes and screens) means that you need a long exposure to do much damage. Soaking a screen in alcohol overnight will almost certainly destroy it while doing the same with clean water probably wouldn't.",
"Rubbing alcohol evaporates quickly. You might still have moisture from water in your electronics for days after, but rubbing alcohol is likely to be gone within minutes.",
"Water (H2O) has the ability to auto ionize. Meaning that molecules of water can react with one another to split themselves into two different ions. Hydroxide: [OH]- and Hydron: [H]+. Ions are very good at carrying charge, and if an electrical component is exposed to an ion containing solution it can short circuit meaning that the charge from the circuit is free to flow anywhere exposed to the solution without much resistance. Isopropyl Alcohol (CH3)2CHOH will not ionize because molecules of rubbing alcohol will not react with one another. No auto ionization means that charge won’t run through the solution and the circuit is more or less safe",
"Water doesn't damage electronics. It shorts their connections. If there is no power to the circuit(s) before it completely dries there is no damage. (Perhaps corrosion later). Rubbing alcohol evaporates rapidly so it dries before any damage can occur. It's that simple."
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mt45af | How come we still have so many cables above ground? | When I travel around my city and regional areas, I’m struck by how, in our high tech age, we still have so many old fashioned-seeming wires and cables, many in the air and suspended up wooden poles (I get that wooden is probably safer than metal!). Can they not all go underground? Is it a cost or knowledge thing? Will we always need them? Will future cityscapes look wireless? | Technology | explainlikeimfive | {
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"some places have unstable ground, places with earth quakes for example. Its is easier to find and fix broken cables if you can see them. Another part is money, why bury them if they are doing just fine where they are"
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mt6gqv | - What is the difference between a HDD and SDD (in terms of computers) | Technology | explainlikeimfive | {
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"HDD's are like merry go rounds. You have to wait until an empty spot for you to put data in. And once data is in, you need to wait for the circle to come all the way around again to take it out. SSD's are like boxes. You put you data in and then put it on a shelf. When you need the data, you take it off the shelf and take it out. No need to wait for the circle to come around again."
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mtdttx | Why has RAM storage not paced with long term storage? | Long term storage capacities, at least for consumers, are easily accessible at 2T with phones routinely coming with 256G base. However, RAM is only seen in 1/2/4G configs. Yes some phones are offering 8 and 16 but that's abnormal. Anyway, why do we not see 256G RAM cards? Is it a manufacturing thing? Obviously, it's not practical to have 256G RAM but my question is more as to why they aren't similar. | Technology | explainlikeimfive | {
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"Ram has increased at a similar rate, but it has always been below storage. Ram is more expensive because it needs to be faster.",
"You seem to be talking phones in particular. On the desktop market you can get 256GB sticks of RAM. That's *huge* compared to 20 years ago. But RAM is expensive because it has to be very fast, and phones just don't do enough things at once or enough huge things to warrant needing all kinds of RAM. Meanwhile, storage increases because people find themselves with the ability to take HD video, which takes up space quick. A phone able to hold all these apps and photos and videos is a selling point. Plus, RAM needs to be continually supplied electricity to keep its data. More RAM means more battery used.",
"RAM is meant for short term storage with quick erasure and replacement. The storage in RAM is designed with that in mind, with longer term writes being pushed into the less volatile HDD or SSD drives. Most programs don't need more than 8 GB of RAM, even on a full PC, pulling information from HDD a little at a time based on the needs at the time. And on a phone, most of that 8 GB is there to allow multiple programs to run at once. They have no need to burn through the storage in the phone with the constant rewriting just to enable 256 GB or 2 TB of RAM."
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mtf94z | How come my phone has 5 bars but no service? What are the bars actually measuring if not service strength? | Technology | explainlikeimfive | {
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"You're probably outside range of your own phone provider's towers and are connected to a different provider's towers. The signal strength is good, but you don't get phone service from them. The reason this works is even if you don't have service with this carrier, you can still call 911 from them, so your phone still tries to stay connected to something, even if it's not a tower it can use for normal service.",
"The bars represent the strength of the connection to the cell tower / Wifi router. If that tower or the wifi router themselves are not connected you won't get internet no matter how strong the connection to your phone is.",
"5 bars just means the phone is connected to the nearest tower, but if the tower doesn't have any internet to give the phone won't get it"
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mth3p1 | How do forehead thermometers measure your internal temperature? Wouldn't it just give the temperature of the surface of your skin? | We have forehead thermometers at work now, and I'm curious how the thermometer measures your internal temp? If I have a fever, but it's 10° outside and my face is frozen, wouldn't that affect the reading? | Technology | explainlikeimfive | {
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"Your forehead is a spot where the flesh on top of the bone is very thin. Lots of little blood vessels(capillaries) in that area as well, so generally your skin temp on your forehead is really close to your overall blood temp.",
"Well. This is a problem that occupied medicine science for a while. And then they discovered that temperature difference between different parts of your body are, at a certain temperature range, somewhat linear. As in, the temperature on your forehead is not the same as your internal body temperature. But in some given circumstances, it is pretty close. And the difference in those circumstances is well known and easy to calculate."
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mth8g3 | How are things like google earth and google maps etc even possible? | It must be a crazy amount of data, how does google earth even work? | Technology | explainlikeimfive | {
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"Google maps actually uses mobile 360 degree cameras mounted on cars driving around for most of its streetviews, with satellite overviews. Google has massive server farms:data centers that process images as they are received.",
"A lot of satellites take those pictures and put them together so you can virtually \"travel\" the world. Since that takes a long time and some places are more populated or popular than others, some of those pictures are new and others are several years old."
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mtj6by | How are DOGE coins made? And at which rate? | I see a lot of conflicting opinions about the 'infinite' number of DOGE coins. If I understand correctly, there are currently around 130 billion DOGE coins and there are 10.000 coins created with every 'block'. But what is a block? And are there more blocks being created if more people buy and sell the coins? If there are people out there who really know and understand the technicalities of the used blockchain, please ELI5: How are DOGE coins made? And at which rate? Thank you! | Technology | explainlikeimfive | {
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"Coins such as DOGE alter the mining difficulty in order to target a set average interval between new blocks (groups of transactions being added to the history of transactions). For this coin specifically, new blocks are added approximately one a minute on average.",
"> But what is a block? Basically its just a grouping of transactions. > And are there more blocks being created if more people buy and sell the coins? No. Blocks are done over a set timeframe. If there are more buy/seller s than the network can handle then they get delayed and the transactions with the highest fees get the highest priority. > How are DOGE coins made? basically everytime there is a transaction the network creates doge and give it to the miners who confirm transactions on a peer-to-peer basis."
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mtsjpw | Windows XP Japanese is faster than the English version of Windows XP | Technology | explainlikeimfive | {
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"> My friend reformatted his old laptop It is far more likely to do with the reformatted laptop than the switch of language.",
"Because of VTEC! JK looks like it’s because he reformatted the laptop removing clutter and gives him a blank slate to work with."
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mtvvau | What does it mean, exactly, when people say ‘once you put something on the internet it’s there forever’? | I’m 21 and know quite a bit about technology. However i’ve always been curious as to what people exactly mean when they say ‘once you put something on the internet it’s there forever’ My first thought is that billions of people are able to screenshot and save your post, even if you delete it. But I’m sure there’s more to it and i’m curious. | Technology | explainlikeimfive | {
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"You pretty much hit the nail on the head. If you put something online, even if you delete it later, there is no way of knowing who saved it and when it might resurface.",
"Besides the other answers referring to screenshotting, there is also the possibility of getting your words or media archived. Police have used archives from instagram and facebook and other popular sites to find deleted posts and use them as evidence in serious criminal cases."
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mu2y5n | why are weapons such as rifles and machine guns still used in war given how overpowering modern tanks, aircraft and artillery are (referring specifically to conventional war not guerrilla war)? | Technology | explainlikeimfive | {
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"Boots on the ground win the war. A tank can't clear a building, an aircraft can't run positive PR with civilians, and both are a hell of a lot more expensive to buy and maintain than a SAW. This equipment all also needs infantry support and cover, a rifleman can bring their weapon to bear on someone more quickly than a tank and can protect the zone immediately around them."
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mu91gq | How is it possible to control machines from Earth on other planets? | Technology | explainlikeimfive | {
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"Radio. Just like you can control a remote car with a radio antenna, so you can control a satellite in orbit, or a rover on Mars. The distance will determine the lag (even radio waves have a speed limit, that of light).",
"It is 99% pre-programmed content, with a little bit of sending goals for that pre-programmed content to accomplish. For instance, while you might normally start a helicopter with a large checklist manually, you can just program that entire process into a drone on Mars. While you could figure out a flight path and then send it, you could instead give it software that can figure out a flight path if you just give it a relative destination. Because of the distance between the planets, you obviously can't do anything real time, so you just need to give your drone a goal and let the software you pre-loaded on it accomplish that goal."
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muav0o | Why were old battles fought with soldiers lined up across from one another? | Technology | explainlikeimfive | {
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"It's going to depend not the era, but many ancient armies were built to fight in one direction. This could be the Greek phalanxes with their long spears and pikes all pointing in a direction, or the Romans with their shields interlocked for protection, but basically having the army pointing in one direction and focusing their strength in that direction was considered a good idea. The wider your line is the more of your soldiers can attack all at the same time, and the more likely you are to be able to flank (move around and attack the undefended sides) the enemy. But if you don't have enough depth then your line is susceptible to breaking, because if there is a hole (because of death or injury, or lack of cohesion) and there isn't someone to plug it, then the enemy can break through your lines and start to attack the unit from the back. So most armies tried to keep a certain depth that they generally trained for (such as 16 deep in Alexander's phalanxes) and as wide as you have forces to deploy. This was often accompanies with less strictly shaped forces such as cavalry or skirmishers on the flanks or forward of the main line. Since both sides tend to deploy the same way, they would generally want to line up so that their strong sides both face each other (you don't want your enemy's strong side pointing to your side or rear), and you end up with the two large lines facing off.",
"Because it was the most efficient way to fight with the technology of the time. Battle throughout history are almost never won by killing the enemies, but by breaking their morale. If the enemy break you can run him over with cavalry, break through his line with tank to encircle him, or you can take an important objective, etc. Tight formation are easier to maintain. You have a friendly face to your right and left, and one behind you. The enemy can only be in face of you and that keep the formation as a whole less likely to break away and flee. The first one to break the enemy formation in ancient or medieval time was usually the one that win the battle and the era of musket wasn't different. Musket and Artillery at the time was highly inaccurate. Battlefield was quickly filled with so much smoke that you were even more lucky to hit anything. So a lose formation of soldier would simply never be able to shoot down a Calvary charge. The cavalry would hunt them down until you had so soldier left. But group your infantry together and you could shoot enough bullet at the enemy that by statistical chance alone you would hit enough of them to make them stop their attack on you. Add a bayonet and your musketeer could act like a field of pike to stop a cavalry charge that would reach them. Massing your infantry on a line also maximize your concentration of firepower. If you have 10 guys spread out over 50 meters, well over that 50 meters you will be able to shoot 10 bullets. But if the guy in front of your line up 100 guys side by side in that 50 meters, then he can shoot back at you 100 bullets. 10 bullets vs 100 bullets, you can see who would win. So the tactic was to spread your men to maximize your firepower over your enemy. Of course the line have some weakness, and good general were able to use the line in the right moment at the right place on the battlefield. This remain true until the invention of the minié ball and better artillery. Both had much higher accuracy, making it far more dangerous to line up your guys. Too dangerous to compensate for the higher firepower you had by doing so. Now machine gun and artillery was what provided you with your firepower, while your infantry was better off spread-out and behind cover.",
"I'm assuming you're referring to the era when muskets were used. The rifles at the time weren't rifled, that is, there were no spiral grooves cut into the inside of the barrel to make the bullet spin. Without spin stabilization, the ball (bullet) was relatively inaccurate; basically, it wouldn't shoot exactly where you pointed it... it might go a little left for one shot and a little right for the next shot. If you line up all your soldiers and have them all fire at once, called a volley, even if some of the balls fired didn't aim true, you still had a \"wall\" of bullets heading for the enemy and the chances of making several hits is improved."
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mug73j | How is autonomous driving programmed to handle unexpected road hazards? | I drive full time for a living, and I've observed a wide variety of hazards and inclement conditions that lead me to wonder how self driving resolves such hazards. Just half an hour ago (I'm pulled over now in a safe place writing this post) I was on a narrow 2-lane road, 50 mph speed limit, with no sidewalk and nowhere to walk safely except the ditch. There were two pedestrians walking right on the road surface, in the dark, with no lights and dark clothing. I had just enough space to avoid them with incoming traffic. I get that radar can already recognize and avoid them (I'm frankly surprised my brand new car didn't even beep at me or have the ability to move itself over), but how does self driving differentiate between hazards? For example, whether it's possible to safely move out of the lane to avoid a hazard, if there's time to stop for it, or if it cannot at all be avoided while maintaining control. Or if it's a small object or small dead animal that can be driven over, between the tires. Can autonomous driving measure that accurately at speed? Also, is it possible for the AI to know that a flashlight or reflective clothing means a person or cyclist is on the shoulder? Is it able to tell between inanimate objects, pedestrians, and animals? This is morbid, but might it be programmed to avoid people at all costs and mow down animals, even if there's ample time and space to avoid them safely? Next, what about ice and snow? Can current self driving tech correct a slide properly, and in the future, may it become more capable at extreme driving than a human rally driver? How does it "see" water and tell between a minor puddle and deep flooding that's to be avoided? In an emergency, can it have an override to go through deep water? What about off-road driving and dirt roads with ruts and bumps, can autonomous driving handle that use without getting high centered or stuck in mud? Lastly, can it recognize a flat tire or vehicle issues and pull over safely? Thanks! | Technology | explainlikeimfive | {
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"Frankly, they can't do most of these things, and fully autonomous driving with no human input is still in the unforeseeable future.",
"I thought of a few more questions. Regarding hazards, can the AI system tell what's safe to hit and what is not? IE, clothing or plywood on the road vs a tire or moving dolly. How does AI handle inaccurate mapping? I frequently take passengers to the airport, which is under construction. There are detours to temporary pickup and dropoff zones, a ton of merging traffic and pedestrians everywhere, and cones and construction barricades to weave through. On busy days an officer directs cars where to park. How does current self driving handle a location like that? In the event of a power outage, does it know which intersections have stoplights so it can stop at them? Trailers, is there any foreseeable way to program the exact dimensions, height, and kind of cargo so it can be driven and backed accordingly?"
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muguya | Why is not charging a laptop to it's full capacity if you run it on power often better for it's battery than charging to 100%? | I have these [battery settings in MSI Dragon Center]( URL_0 ). I mainly want to know why this is the case. Followup, is this true for phones? Yes, I'm a programmer. Yes I see the irony in the fact that I do not know this already. The laughter is assumed and understandable. | Technology | explainlikeimfive | {
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"Lithium batteries don't like to be charged to 100%. What's happening is the positive and negative sides of the battery are separated by a thin insulator to keep it from short-circuiting. But the higher the voltage, the more electrons want to jump across the insulator -- there is leakage. The higher the voltage, the worse the leakage is, and this damages the battery over time. Anecdotal evidence: I got a Samsung Galaxy S9 and it was my first phone to support wireless charging. So, I got some charging stands and left it on them all day at work and all night when I was sleeping. Result: My S9 has *terrible* battery life now, because it's spent so much of its life at 100%. :( BTW, lithium batteries also don't like to be over-discharged, it causes the chemicals to degrade. So if you run your device down below 20% frequently, you're destroying the lifetime of the battery. It varies by chemistry (Li-ion, LiPo, LiFePO, etc) but generally they're happiest at 20 to 80%."
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mun8we | How do video game cheat codes work, and why are games made with the possibility to use them? | Technology | explainlikeimfive | {
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"Sometimes they are created so testers can test out the games to check how they run without having to go back to the beginning each time etc. At other times they are created by games so they can be sold to players making the company more money for the game.",
"A lot of cheats used to be old developer code they used to test different game mechanics. Companies used to actively discourage cheating, but some devs make it openly accessible, like the open console for Skyrim on the PC.",
"To add to what others said, very old video games could not store the player's progress, so whenever the player finished a level the game would display a password, and when someone came back the next day and wanted to continue where they left off they could just enter the last password they saw and the game would skip to the last level they reached. It's possible that when this limitation went away some developers still wanted to add a few shortcuts locked behind input sequences or codes. Sometimes just for fun, like with the cheat in the original SW Battlefront that made every soldier as small as an ewok. Doesn't help the player, but also doesn't hurt anyone else in singleplayer games, and some people enjoy messing with the game itself just as much as playing it as intended.",
"Imagine you're testing a game. Do you really want to have to go through the ENTIRE game to make sure that end game weapon works? Just type in this code and spawn one instantly for testing purposes. Testing animations but you don't want to reload in the case of accidental death? God mode sounds awesome for you. Essentially, cheats were originally a way of bypassing in game mechanics for testing purposes by the developers. As others pointed out, some games also used codes as a way of saving progress like in Chip's Challenge.",
"Often the cheat codes are for developers. Need to test the story mechanics or clipping issues as the avatar navigated terrain? Encounters: Off. Damage/weapon balancing? Infinite ammo: On. How they work? Good programming comes from breaking monolithic code down to functions, methods, mappings, variables, etc. Discrete blocks of code that can be troubleshot easily, or down right given an “Off” in the variable. For example, make a variable called “track_ammo_on: on/off“. Your game sees function “fire_gun” called with a yes passed to it. “fire_gun” runs logic “if track_ammo_on = off, fire_gun (who cares if you have ammo!), else if ammo_clip != 0 (does not equal zero ammo), fire_gun shoots a bullet. Ammo_clip = ammo_clip - 1 (subtract a bullet)",
"I worked in video games for 23 years. Cheat codes come from two sources. 1) designers and programmers need short-cuts to test parts of the game. Cheat codes that make you immune to damage, let you skip levels, or similar useful things are almost always created for this purpose. Then it can get left in the game for fun. 2) near the end of a project, sometimes the artists don't have as much to do as the designers & programmers. They aren't actually slacking off, but they can take a few extra hours to create interesting new units or textures or effects. Then all they have to do is convince a designer or programmer to put it into the game, which is usually just a couple of minutes of the coder's time. This is where cheat codes such as the bobbleheads in Turok or the storm dog in Age of Empires come from. Artists with spare time.",
"The very first cheat code was programmed in by the developer because the game was too hard for him to play through in order to test. The original Contra gave you 3 lives but if you plugged in the \"contra code\" it set it to 99. The developer forgot to remove it for release and that became the origin. The very first easter egg was where a developer who was upset because he wasn't going to receive credit for his work, built a secret room to say \"Created By < his name > \". Since then there are two main paths that cheat codes and easter eggs have developed. The first is \"developer tools\" or \"dev tools\" which are tools to help the developer build and test the game. Imagine you're trying to build a maze. You would need a saw, hammer, nails, wood etc. But imagine if when you finished you accidentally left the hammer lying around. Now a creative maze runner could do things like start pulling nails from boards to create new unintended routes. The second path is \"for the fans\". Some games, like Goldeneye 64 or Halo, actually use cheat codes as rewards where you can unlock the ability to play the game in new ways. These are treats for the fans and give them ways to experience the game in different ways. Modern games have mostly done away with cheat codes per se and instead have modding communities that rip into the code itself and dig out ways to fundamentally change the game by altering the programming itself. These are \"mod menus\" that you might hear about, or cheaters or trainers. Coincidentally that is how the old Game Genies worked, by actually altering the flow of data between the game cartridge and the console so you could have things like infinite health or unlimited items etc.",
"Originally some cheat codes were never meant to be found by users and just there to allow developers and testers to test a game more efficiently. Stuff like creating a level select screen activated by a button press combination in an old video game without saves and batteries, that allows people to play test the later levels without having to go though the entire game first. Sometimes these were found by players and it added to the appeal of the game, so developers started to leave something like that in deliberately. Since there was already a market for strategy guides that showed all sorts of secret tips and tricks for games, deliberately adding cheat codes as Easter eggs to be found and revealed was just one more part of a game that would get people to buy them."
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muxzui | How do animators match a character's mouth animation to a voice actor's speech? | Technology | explainlikeimfive | {
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"They mostly don't, it's been basically figured out that there is some pretty simple tricks to animating mouths. Like they match a small list of sounds so those match then people basically will ignore anything else. So you just make a round mouth on like \"ooh\" sounds then a few others then the rest is basically random lip flapping and no one really cares or notices."
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muz9pb | How does youtube know exactly what you want, even if you type in something that's not even close to the title, but merely describing the video? | Technology | explainlikeimfive | {
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"Content uploaders can mark their videos with meta tags so I am sure those combined with algorithms get the job done.",
"Basically, the youtube ai can watch videos and detect certain things in it, it doesn't just look at the title. Then when it finds these things in the video, it tags it as having that. When you search something, it sees if your words either match the title of video or the tags it gave. If a video is popular or trending, youtube knows this and therefore has more information on it, more tags, which makes it more easier and accurate to search for it."
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mv25cb | How do people browse websites on TV and in movies? | Hi, When people on TV shows and in movies do fake Google searches or go to phony websites, how does the actual browsing happen? Thanks for your help! | Technology | explainlikeimfive | {
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"TV shows and movies often have \"mocked\" software: it's usually a real phone/PC, but they hire an app developer to write a custom app that pretends to do whatever is called for in the script. The app is just displaying pre-created images, not actually browsing."
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mv6r1y | Why does SSD storage load much faster than HDD storage? | Technology | explainlikeimfive | {
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"Solid state drives have no moving parts. It's pure voltage through circuits instantaneously. Hard disk drives have moving parts, data is stored in different places, and the action of the moving arm to read each individual part of the drive slows the reaction time. Kind of like trying to talk with hic-cups vs talking without hic-cups.",
"SSD is like having a filing cabinet right next to you. You open the drawer and there's the file. A hard drive is like having files all over your house. When you want a certain file you have to run to each room look at the file see that's not it then run to another room until you find the file you want.",
"Simplest answer: An SSD has no moving parts, and stores information On microchips, like a more complicated larger USB memory stick. Because of this, it can close to instantly access information and start moving it. And HDD has moving parts, it has a moving arm which must move across a spinning disk to read information off of it. This means an HDD is limited by how fast that arm can move and that disk can spin."
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mv9uql | Why do photographs when emailed from a iPhone to a computer come out sideways many times? | Technology | explainlikeimfive | {
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"The answer is metadata. As with all tech, companies doesnt agree on a single thing to store data. Sometimes the photos metadata arent compatible to software in a computer used to display it.",
"phones have a little thing inside that tells the phone if it’s upright, sideways, or upside down. when you take a picture with your phone, the information from that little thing gets written down inside the photo to tell other computers how to rotate the photo. sometimes, the other computers don’t read this little note and just show the photo however they want to."
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mv9uqn | What megapixel were analog cameras and how is it different to digital? | Technology | explainlikeimfive | {
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"Traditional film cameras don't have pixels, they have film grain. The film is coated in a chemical mixture which is sensitive to light such that it will change when exposed to light passing through the camera lens, and then can be further chemically processed to form an image. While a digital camera has pixels as the smallest unit of image data, a film camera is limited by the size of the grains of chemical compound on the film. Those grains can be very small, smaller even than modern digital pixels.",
"The answer is none. However an exposed film can have the image printed in higher resolution today or tomorrow without loss of quality. That is because unlike cameras with digital sensor(which ia limited by the tech it was made), a film has all the information stored in it. This is why old movies filmed can be in remastered to a higher resolution than scenes filmed with digital."
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mve38u | why do some apps give you gift cards just for scanning receipts? | I know there are different apps or websites that give you “points” for just scanning your receipts from other stores, and you can redeem points for different rewards like gift cards. What is the website gaining from this? It always seems too good to be true because I don’t know how they’re making a profit. | Technology | explainlikeimfive | {
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"A good rule of thumb is that if a company is giving you a free product, you are the product. They're getting information on what someone of your profile (age, gender, income, background, location) tends to purchase. Compiled with everyone else doing it, they can sell that kind of information to companies interested in creating more targeted ads to the demographic they're interested in.",
"They Gain lots of knowledge about your habits. What you shop, where you shop, when you shop. With that info they can build a profile about you. They can deduce if you have a family, likely ages of kids etc etc. They can then sell that data so that “appropriate” ads can be directed your way.",
"Besides, gift cards are not very expensive - especially when you have so much and detailed information about your customer that you can share Basically, they go see the vendors offering gift cards and say: \"What kind of new customers are looking for? I can select them based on if they purchasing habits and send them your gift cards\"."
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mve4gd | How do phones keep track off time while off and without internet connection? | Technology | explainlikeimfive | {
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"Even when your phone is off, there is still a very small circuit that is powered. This circuit, among other critical things, is keeping track of the current time. It consumes very little power, so it doesn't drain the battery. Even when the battery says it's dead, there's enough charge left to maintain these low power critical functions. Every computer device that keeps time will have a battery somewhere to help it keep time when its main power is gone. Even a desktop computer will have a watch-style battery on the motherboard to keep the circuit going. One extra advantage that cell phones have is that, if they ever happen to go completely dead, they can set their time back via GPS. The way GPS works, satellites in known positions are broadcasting a signal that contains their time. If you get 3 pings and know the current time, you can figure out your relationship to those 3 satellites and it narrows it down to one point. If you can get pings from 4 satellites though, you can actually narrow down your position *and* the time from them. This is why phones have such accurate timekeeping.",
"There is a type of chip called a Real Time Clock which is specifically designed to use as little power as possible to keep track of time. It is usually connected to a tiny battery or even just a capacitor so that it can keep track of time even when the device is powered off and the main battery is out of power or disconnected. It can also be programmed to send a signal to the device to power on or at least wake up from deep sleep at certain times."
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mw0v98 | why/how did coaxial cable become the standard for radio to antenna interface? | Just wondering how and why it became such a ubiquitously good choice. I'm assuming because the copper cable offers the least resistance and reduces signal loss. There seems, at least to me, to be no have real improvements to this and am curious to know why. Or if there are indeed newer and better performing interfaces. | Technology | explainlikeimfive | {
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"You know how an antenna (or \"aerial\", in case your British) is just a metal rod or even just a piece of wire? Now, any antenna can not only receive radio waves but can also send them: if you feed a pass a radio signal as electric current through a wire, the wire will produce radio waves, which radiate out perpendicularly from the wire. Now, if you receive a radio signal from an antenna and want to transmit it to your radio or TV set, you wouldn't want the connecting wire to send most of it back out just into the air, because this way, the signal would leak out, and hardly anything would arrive at the other end of the wire. The point of the coaxial shape is to prevent the cable from acting as a sending antenna, as an ordinary wire would. In a way, the electromagnetic wave is trapped between the central wire and the surrounding shield and moved along through the cable. This works if the radius of the cable is well matched to the frequency you want to transmit",
"Coaxial cable has an outer cylindrical sheath with a second conductor at the core. Because the sheath completely surrounds the core, electric and magnetic fields are only created inside the cable, and don’t “leak” into the outside world. This is bad: it means your cable becomes an antenna radiating electromagnetic waves, and at high frequencies you can lose a lot of signal this way. But just as important is that antennas work as both senders and receivers. The outer conductor oof a coaxial cable also acts as a shield to stop electromagnetic waves from outside from causing interference.",
"The main reason is that coaxial cable is so good at containing the signal and rejecting interference, because the outer conductor acts as a shield. You can run a whole bunch of coax cables together with minimal transfer of signals between them, or from nearby electrical noise. Coax is more expensive, and it's \"unbalanced\", i.e., the two wires are different, so you need a \"balun\" (BALanced/UNbalanced converter) at the end, but today the benefits of coax outweigh the cost. There is still some use of simple twin-lead because it's cheap. It used to be quite common for TVs when it was all VHF, but it was often inadequate once UHF channels came into use because it needs more care in installation to deal with higher frequencies. For very high frequency work, microwaves and above, waveguides win over coax. These can be just a hollow copper pipe of a fixed diameter, and they have lower losses than coax."
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mw6ykm | Why can't a browser just stop and resume downloads later, like a torrent can? | Technology | explainlikeimfive | {
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"Most websites send you files by pointing your internet browser to their warehouse address and say \"Come pick up your package whenever you want it\" but your computer still has to do the work and go \"pick it up\" itself. You can't compartmentalize it (generally, but this is ELI5). With torrents, instead of being told to come pick up your whole package they basically have a whole bunch of different warehouses all around the world (One for screws, one for the wood frame, one for the couch cushions etc). Instead of being told \"Here's where your package is so come get it\" a torrent will first send your computer a file that's basically \"Here is an itemized list of every single box that you're going to need shipped to you one by one\" and the file is also a \"Here is how you let every single warehouse know whenever it's time for you to ask for their box/part.\" tl;dr Most websites just tell you to pick up the couch from their house but torrents will break it down and mail it to you one screw at a time Source: Am Network Engineer Edit: I know this is more like ELI12 but I don't think 5 year olds understand that we've taught rocks to do math. Also thank you for the award, anon.",
"Sometimes they can but it's up to the server that the file is being downloaded from to support the accept-ranges header which most of them don't: URL_0",
"A direct download is like a fully assembled piece of furniture. A torrent is like a flat pack ikea piece of furniture. If you deliver half of the single piece, it is now broken, and you have to deliver a full replacement later. If you deliver half of the flat pack components, then deliver the other half later, you can finish assembling it once you get them."
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mw7h3k | () Why do some photos under a microscope rotate back and forth and why are some still shots? | Technology | explainlikeimfive | {
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"Hey, I am a scientist and microscopy expert. I'm not sure what you are referring to, do you have an example?"
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mw8m07 | How did they code the first computer without a computer? | Technology | explainlikeimfive | {
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"By hand, with switches and wires. You literally use switches to specify binary codes in machine code (the binary commands that the processor understands) and load those directly into memory, one memory position at a time, by manually specifying memory addresses (with other switches). It suuuuuuucks. Hence the relatively rapid invention of assembly code (human \"readable\" machine code), punch cards (ways to quickly set switches), and then compilers and programming languages.",
"The first computers weren't general purpose, their programs were hard wired into the CPU. Software and hardware can be interchangable. ENIAC was the first general purpose, programmable computer, in 1945. It was programmed through a card reader. You had a typewriter like device that would punch holes in cards. The card was printed with numbered rows and columns, and the placement of the holes indicated values in binary. This could be data, it could be CPU instructions...",
"As a person who used to do this for a living I can give you a direct explanation. * You would write the code by hand on a piece of graph paper. The language you used was a form of Assembly language that was one step less complicated than actual binary. * Then having checked this, you would translate, by hand, the Assembler into binary - 0s and 1s. This was also written on graph paper with one line for each bit pattern that needed to be set into each register of the computer. The result was a long table of 0s and 1s. Now you would have to set up the machine with the correct binary code for each register in core memory [See this picture]( URL_1 ). This was the control panel for machine I used to work on - the F1600B. The rest of it was a mass of electronics and hand-wired core memory in big boxes in a severeley air conditioned room. * The red switches on the right allowed you to move up or down by one register in the machines core memory * The long line of grey & green switches corresponds to bits in the core at the register you have selected. Flicking a switch down would set that bit to 1. * As you can see, the line is divided into a bank of nine on the left and three banks of five. The three 5 banks corresponded to three bytes. (only 5 bits per byte on this particular machine) Using the switches you can set each of those bytes to a specific binary value. * The nine on the left are used to set a binary instruction code that tells the machine what to do with the values set in those bytes. So for example you could set a code on the left that said \"add the contents of byte A to byte B and put the result in byte C.\" * After setting all the switches for a particular register you would then use the red switches to move to the next register and set the bits for that. Eventually you would have input a whole program. Eventually, this slow manual process of inputting binary values was replaced with punching holes in paper. In the commercial / IBM world they tended to use cards. In the case of real-time computers (military, air traffic control, process control, space etc) we would use a long rolls of paper tape. These were edited by physically punching holes in the tape which was 8 holes (one byte) across and read in by a paper tape reader. If you made a mistake you would edit your program by [covering holes up with editing tape and punching new ones]( URL_0 ). People got very good at reading binary. I could read through a tape and find a misplaced hole pretty quickly in those days."
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mwfb4u | How does an SSL certificate work | Technology | explainlikeimfive | {
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"Encryption is a pretty deep topic, but here’s the rough shape: An SSL certificate has two halves. A private key kept private, and a public key that is shared. If something is “locked” with the public key, it can only be unlocked with the private key, and vice versa. So you know if a message from a website can be unlocked with the public key, it really came from that site, and you know if you lock something with the public key and send it back, only the server can open it with the private key. It’s a way for two halves of a conversation to verify that their messages can only be read by the intended recipient."
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mwlkxa | How does auto focus in digital cameras and mobile cameras work? How does the program know what it is focusing on and how far the object is and whether it is focusing correctly? | Technology | explainlikeimfive | {
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"Kind of like a trial and error. If the image is too blurry, it will auto-adjust to focus at a further or closer distance, if the image sharpens, and the pixel data from the image becomes more complex (sharpens) than a blurr, it's a good sign that it's adjusting in the right direction. After overcorrecting in one direction and it becomes blurry again, the sensor can determine that it has adjusted too far, and will go back to the sharper image. At least that's how I would design autofocus software on a camera. This may be computationally expensive. I've also heard of range detection like ultrasound in some cameras to determine the objects distance from the lens to determine the proper focus. Then a motor rotates the focus dial on the lens.",
"Followup question. What diabolical bastard made phone cameras like mine, that auto focus to perfect clarity every time, then pop out of focus?",
"You've asked two separate questions here. The first is how does the camera focus. The second is how does the camera know what to (try to) focus on. Let's take them in that order. First, how does autofocus work? There are basically two different types of autofocus technology. One is called **contrast detection** and the other is **phase detection**. **Contrast detection** starts from the observation that, if the object in the picture is in focus, you'd expect to see some sharp edges. So the camera basically looks at the picture, and measures how much contrast there is in the small areas where it's trying to get the focus right. The assumption is that more contrast = sharper edges = better focus. So the camera just focuses the lens in and out, on a sort of trial and error basis, until it gets the highest contrast reading. If it moves the lens and the contrast reduces, it knows it needs to move the lens the other way. If it moves the lens and the contrast increases, it knows to keep moving the lens in that direction until the contrast stops increasing. A couple of interesting observations fall out of this. Firstly, note that contrast detection relies on being able to process and do calculations on the image, so it's strictly for digital cameras only. Old-style film cameras simply can't do this. Secondly, contrast detection requires contrast: it can't focus on smooth uniformly coloured objects. **Phase detection** works differently. It starts from the observation that, if the object in the picture is in focus, then all the different rays of light from the object, which have travelled through different parts of the lens, must all end up in the same place on the sensor. So the autofocus sensor effectively looks at the light that's coming through the top of the lens, and compares it with the light that's coming through the bottom of the lens. If they show the same picture, the subject is in focus. If they don't, then by comparing the two pictures the camera can work out whether the focus is too far forward or too far back, and by how much, so it can tell the lens to go to the correct place directly. Phase detection doesn't have to work directly on the image sensor. It can, but it's only relatively recently that manufacturers have been able to do that. It was more common for cameras to have a separate autofocus sensor. For example SLRs would reflect some of the light down to a sensor in the bottom of the camera, and that would work fine as long as the light path to the AF sensor was the same length as the light path to the imaging sensor. Note also that phase detection works on the light coming through the lens, not on the digital image, so phase detection AF is quite workable in film cameras (and in fact it was invented before contrast detection AF). So that's how the AF works. Now **how does the camera know what to focus on?** With some cameras, you tell it to focus on whatever's in a particular area of the sensor. That's particularly common in 'pro' cameras. These cameras will often also be able to look at the areas surrounding the one you've specified, so that if the subject moves from one area to another, the camera can track it automatically. Most digital cameras also have a set of 'rules' that they use to look at the picture and work out what's likely to be the most interesting or important part. If there's a big area of blue at the top, that's likely to be sky and you don't want to focus on it. If there's a big area of green at the bottom, that's likely to be grass and you probably don't want to focus on it. If there's an oval area of pink in the middle, it might be a face so you might want to focus on it. Obviously this is hugely simplified but you get the idea. These days they can also work out which bits of the picture are eyes, and that's really important because getting somebody's eyes in focus is more important (if you have to choose) than other parts of the face. Does that all make sense?",
"Some cameras use contrast to determine if they're in focus. They look at what's coming in to the camera and does some comparison to see how sharp the image is. If an image is blurry, the contrast (difference in brightness) between two adjacent points will be low, but as the image becomes clearer, the difference in contrast between two adjacent points becomes greater. Side note, there's basically two types of autofocus: Passive and Active. Passive would rely on the camera looking at the incoming light and seeing what the contrast is like (as above). Active sends out a beam of energy (e.g. ultrasonic waves) to determine how far away things are / if anything is nearby to assist with focusing. Some cameras use an autofocus assist beam (i.e. an infrared beam of light to light up the scene) to aid with focusing."
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mwpcnb | Why is uninstalling so much faster than installing something? | The same amount of data is getting added or removed from your system each time I think, so why is removing it so much faster? | Technology | explainlikeimfive | {
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"Because you don't actually delete anything. Data bits aren't overwritten, only the section is declared empty to be overwritten when a new files is saved",
"Data isn't physically deleted, it's just marked to say it can be written over. If you imagine the hard disk as being a blackboard. Installing the program is drawing a complicated image on the blackboard, all different coloured chalks, and all the rest of it. Uninstalling the program is just hanging a sign on the blackboard to say \"Feel free to use this board if you need it.\"",
"All file systems are different but most work a bit like this. When writing data to a device the computer adds the name and length of the file as well as the first place it will write the data into a file allocation table which is basically a list of all the files in your device. Then it copies data it is receiving onto many sectors one the device. Sectors are like sheets of paper that the data is written on. If it gets too the end of the sector and still has more data to write, it writes the address of the next sector it is going to write on. This continues until all the data is written. Uninstalling (deleting) a file is much simpler. It just erases the entry in the file allocation table."
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mwpcuy | Why is it so hard for a camera lens to capture the depth and the quality as seen with a naked eye? | Technology | explainlikeimfive | {
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"The simple answer is that it is just as hard for the eye. Our eyes also have depth of field issues, but we constantly shift the point of focus. Rather than thinking if the eye as taking a photo think of it more like a video camera that can refocus almost instantly. As soon as we look at a blurry part of the picture it immediately snaps into focus. Our brain then stitches it all together so we perceive it as a sharply in focus world.",
"Although good cameras are better than the human eye to capture something, the difficulties to make a good picture are as it follows: * Your eye got a resolution of a few millions of pixels (total amount of \"photoreceptor cells\" in your retina). To get such a good resolution, you either need a giant artificial \"retina\" or a retina with very tiny photoreceptors, both of which are hard to create. * Your brain analyses the picture. Your camera barely do it (and only the digital ones). This makes what you see clearer than what you detect, while the camera usually don't turn the raw measured data into a vectorial picture. * You need to make quite a lot of parameters setting with your camera that are automated in your eye. Like focusing or the time of exposure (well, your eyes don't have any time of exposure IIRC, so that's a thing a camera will have to deal with that an eye don't) EDIT: * and the focal is very different, causing a picture to seems so unlike what you see (think of taking a moon picture with your smartphone camera and how bad it looks? Well it's because there is a such higher focal than your eye, making everything far seems little)",
"I'll answer for the depth part with hopefully easy to understand solution, that doesn't take the physics/biology too literally and only explain the basic concept. Camera only uses one lens and seeing depth requires two points of views (2 eyes). The brain perceives depth from the difference between the two pictures seen by 2 eyes. If you try to perceive distance with only 1 eye open you will notice that it is a lot harder. 2 points of view (or eyes) is required because then the brain can analyze the small differences in light traveling different distance/direction from the same object into your different eyes. There are these virtual reality/3D movies/glasses and the depth in these is created from the different images projected into each eye.",
"If you look at the optical properties of our eyes, they are terrible. But as many here said our eyes are in constant movement and 'scan' our field of vision. Also and most importantly out brain does the main work in our perception. So rather than compare our eye to a single picture you would have to compare it to a series of images that are processed by a computer afterward."
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mwspa8 | How does the weighing scale measure body fat? | Technology | explainlikeimfive | {
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"text": [
"By sending a small electric current trough your body. Manufacturer will pretend it will encounter a difference resistance whether it encounter fat, bones or muscles, which is true, but not accurate at all. Truth is, it simply doesn't work and is just marketing"
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mwtvfc | How does Nvidia DLSS work? | I understand its some sort of AI/network but I don't get how just turning that on for a supported video game give me extra frames. | Technology | explainlikeimfive | {
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"It renders the game at a low resolution and then upscales it to a higher one, in a way that is much less demanding than rendering the game at a high resolution to begin with. The trick is that they upscale it now using a standard image-scaling algorithm, like we've been using since digital images existed, but a special system 'trained' on scaling that specific game. Here's the much-simplified gist of how that works: You have a program whose job is to look at a low-res image and guess what it should look like in a higher-resolution, then output the result. It keeps track of a vast collection of image statistics to help it make that guess. At Nvidia HQ, they run the game and render it twice simultaneously, once at a low resolution and once at a high resolution. A computer looks at each frame of the low-res image, makes its best guess as to what the upscaled version should look like, then makes a few alternative guesses by using slightly different versions of its stored stats. Then it looks at the real higher-resolution image it's provided, checks which guess was closest to that, and adjusts its stored stats to better align with that guess. Next time you feed it that same low-res frame, its guess will be closer to the ideal. Do this over and over and over and over again, and eventually you've got a program that's pretty damn good at turning low-res images into high-res ones. Nvidia then ships the code to users and it can be run on graphics cards that has the special hardware optimized for this. Doing it per-game helps a lot because what works for one game's graphics won't necessarily work for another game's (imagine scaling The Last of Us when the system trained on Minecraft). Now it won't ever be as good as actually rendering the game in the higher resolution to begin with, but if it's done well it can look a ton better than taking a low-res image and upscaling it the traditional way, and it's still a lot cheaper (in terms of performance cost) than rendering it in the target resolution. (This ignores the aspects that are special to rendering videogame assets and not just plain video feeds, but it's Explain Like I'm Five, not Explain Like I'm a Computer Science Student, and hopefully gets the general idea across.)"
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mwuj76 | why are some programming languages faster than others? | For instance python is slow and c++ is fast. Why is that? | Technology | explainlikeimfive | {
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"In the specific instance you cited, python is a \"scripting language\" which means that it gets read and executed (interpreted into machine language) line-by-line each time it runs. C is a compiled language, which means it gets converted into an executable file (machine language) before you run it. So basically the line-by-line reading part gets done in advance.",
"This won't be true in all cases, but I'm the case you mentioned it's because Python is an interpreted language and C++ is a compiled language. When the computer executes a Python script it has to translate into another language the computer understands. C++ translates itself to another language when you compile it, and thats what your computer reads. Its like being handed one book in a language you understand (compiled C++ code), and another book with a different language and a pocket dictionary (Python code). You're going to be able to read both in the end, but you'll read the first book way faster",
"People do mention compiled languages vs scripting interpreted languages which certainly is probably the biggest factor but there are smaller significant factors worth discussing. C++ has \"harsher rules\" than Python for instance, at least to the newbie programmer. IMO I prefer to call the C++ rules \"unapologetically simpler\" instead of harsher, but these harsher rules means that the C++ compiler can make a lot of useful assumptions that the Python interpreter cannot. For instance C++ is \"strictly typed,\" while Python is \"weakly typed.\" In Python you can try to assign for instance numbers to strings, mix and match strings and numbers in lists, etc. Python will only catch these errors at runtime. C++ doesn't let you do that, the C++ rules require each variable to have the type it is declared before it is used and then enforces these types for everything from assignments to addition to make sure you aren't adding weird things like strings together. But once the compiler checks all these things, the program it compiles to does not have to check this all at runtime. When C++ is told to add two number variables, it just adds them, Python instead has to check whether the variables you are adding in the first place are numbers and then add them together. This takes a lot more time than the just adding. This is just one example but there are many like it. Another example is that C++ gives the programmer full control over memory and it is up to the programmer to make sure that memory is freed once unused, Python instead has a complicated scheme to make sure memory is freed once unused. To do nearly anything Python often has to do all sorts of checks for all sorts of edge cases prior to doing the actual operation listed on the line. C++ doesn't, its more annoying with its rules sometimes but this is what I mean by C++ being \"simpler,\" Python's rules let you do more but Python's rules also come with a lot of exceptions (pun intended) and Python has to check that its not violating these. Every check adds more time it takes to run. IIRC there is no reason Python can't be a compiled language beside the fact that no one has yet made a compiler for it. But all of this stuff would certainly get in the way of performance compared to C++, so no one bothers to make one.",
"As a general rule the \"closer to the metal\" a language is the faster it is. C++ is compiled down to something the processor can understand on its own and run with very little overhead. The compiler isn't perfect so some inefficiencies sneak in, but it's very minor. Python however is interpreted. What happens is that a different program (the interpreter) reads your python code and on the fly tells the processor what to do and when. This intermediate step of the interpreting the code you wrote and translating it to something the computer understands will slow down the overall program compared to c++ which runs directly on the processor."
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mx82ve | How computer really work? because for me, its like a magic! please | Technology | explainlikeimfive | {
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"This isn't really an ELI5 questions. This is more like the subject material of two college courses.",
"You know how when you want to store the number 13, you write the digits 1 and 3 next to each other on a piece of paper? Well the computer does the same, but sadly it does not have 10 digits to work with like we do. It is based on electricity, so it only has two states: on and off. Well, we made the computer quite smart because it takes those two states and translates them into two separate digits: off becomes 0 and on becomes 1. Now we just gotta come up with a number system that uses only those two digits. Lucky us, there is one, it's called base two or binary. So our number 13 written in binary is 1101. The number only and uniquely written with 1s and 0s. So now since we based our system on the on and off system, we simply have two cables turned on, one turned off, and then another one turned on. 1101. That's how the computer has short-term memory of stuff like numbers. For long-term stuff, it needs something more permanent than electricity. Magnets! The computer has a bunch of magnetic disks and instead of having power off for a 0 and on for a 1, it instead leaves a tiny mark on the magnetic disks if a 1 is supposed to be there and nothing if a 0 is supposed to be there. Then, later, it has a tiny arm that goes to different spaces on different disks and can detect the presence and absence of these tiny marks and boom, you read binary from the magnetic disk. This was trying to cover your specific questions, as the topic itself is very broad. If you have any further questions feel free to ask in a response to this."
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mxcupf | Why does slowing down audio sometimes deepen voices, but sometimes not? | Technology | explainlikeimfive | {
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"Sound being deep or high pitched is based on the frequency of the sound. When you slow down a recording it basically also slows down the frequency of the waves that make the sound and so it gets deeper. I have never experienced a situation where slowing down a recording didn't deepen the sound so I can't speak to what is going on there."
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mxgzrw | how do devices that use batteries, like phones, know the percentage of the charge remaining? | Technology | explainlikeimfive | {
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"Hi :-) TL;DR: A full battery has more volts than an empty one. So for example, 4.2v=100%, 3v=0%. But it's not linear. & nbsp; Voltage of a battery drops when discharged over time. Some phone apps (or programs for your laptop) will even let you see the voltage. You probably have seen the 1.5 volt label on regular AA/Mignon alkaline batteries. It's actually a little higher initially. Then it will gradually go to 1.4...1.2v. Once it reaches 1 volt or less (drop off happens more suddenly), many devices stop working. Battery testers or battery circuits measure this voltage (or any $3 multimeter can to some extend if you add a load). Same with lithium batteries. Some may be labled 3.6V, but when full, they're over 4v. Under 3v they would get damaged, so devices (or a circuit on the battery pack) will cut off. This is the reason why old phone or laptop batteries will sometimes cause the device to just shut off at, say, 20%, as the old battery's voltage will drop unexpectedly fast compared to a new one (EDIT2: And when the load is high). So the percentage is just a \"guesstimate\" using the common discharge properties of a battery. Some smart programs will recognize old battery behavior though and compensate. EDIT: [Example discharge curve of an alkaline battery]( URL_0 )",
"the less charge a battery holds, the less voltage it outputs. the device just checks the voltage and determines the percent.",
"The battery pack or the android main board has a \"battery fuel gauge\" IC which keeps track of the charge state of battery. You cannot achieve that level of precision by only measuring voltage. Basically, it uses fuel gauge. There are several algorithms for Li-Ion chemistry, and the gauge might use one or more of them.",
"To be a little more more ELI5 than some of the other comments, a battery is like a water balloon. When the battery is fully charged, it's like having a water balloon that is full to bursting. When you let the water out, it comes out harder and faster when the balloon is full than when the balloon is almost empty. The phone looks at how hard and fast the water is coming out to figure out how full the balloon is."
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mxk3vz | In a F-14 Tomcat, what does "Goose" do? | In the movie *Top Gun* we see pilot Maverick with his offsider Goose. The F-14 clearly needs a second man; but the A-4 does not, nor does the ~~Mig-28~~ *F-5E.* The F-15 and F-18 comes in both one and two man variants, but I don't think I've seen a two man F-16. Modern MiG's and Sukhoi's seem to be one man fighters. | Technology | explainlikeimfive | {
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"The aft seat in a Tomcat is for the Radar Intercept Officer. They're responsible for communications such as satellite linkage etc., and jamming enemy radar as well as operating their own radar. They may also handle the weapons systems. Offloading some of these duties to a second person allows the pilot to put more focus into what they're doing. It is also helpful to have a second pair of eyes to establish and maintain visual on an enemy craft. A lot of modern craft that have tandem seats also have multi-function displays that allow cockpit customization, and each crew member can optimize what displays they have to play to their individual strengths.",
"Goose was the weapons systems officer ( URL_0 ). Some aircraft don't require an additional officer to manage the weapons either because they are not intended for the same high-intensity dogfighting that requires all of the pilot's attention or because the avionics are more advanced and support the single pilot better. And more importantly, Goose was a damn good man.",
"In Jets that usually have 2 officers, the 2nd officer does things so that the pilot can focus on piloting: keep track of targets, adjust weapon loadouts, operate the radio, etc. Remember that the number one cause of plane crashes is pilot error. We no longer see many fighter jets with 2 officers because we now have more capable computers that can do all that. When a jet does come in a 2 officer variant it is most likely a trainer.",
"\"Goose\" is a Radar Intercept Officer, RIO. the thing about the Tomcat, and older aircraft like the F-4, was that the radar was so complex that a second crewmember was needed so that the pilot could concentrate on flying the aircraft. so basically, a RIO was for operating the radar and other systems the Tomcat used to detect enemy aircraft and give the pilot the information he needed. there´s much more behind that, but this covers the basics. nowadays, many of the stuff that needed to be handled manually is now done automatically which is why you see two-seat fighter aircraft only when they do challenging stuff like air-to-ground operations (F-15E) or something like that. otherwise, trainer versions of said fighters like an F-16B or F/A-18B are also twin seat"
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mxrq37 | Are the high-quality streams of a live sports broadcast recorded and stored somewhere? | I was watching a soccer match and this struck me: is the live high-quality broadcast stored anywhere or is it just streamed? I suppose it needs to be stored somewhere to make highlight reels, but wouldn't this storage take up TBs of space and therefore not be economical? | Technology | explainlikeimfive | {
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"Most broadcast networks save everything. Yes, it's TBs of space but compared to the budget required to make the broadcast in the first place a stack of TB storage drives, especially at scale, is peanuts. It would be certainly be less than 1% of the overall budget. YouTube is storing far more than all the sporting events that have ever happened and they can pay for that just off ad revenue.",
"Most OTT (over the top) video broadcasters hold on to the raw recordings. There’s a lot of value in these recordings beyond just the original sports broadcast. Say a famous sports player passed on. There’s a lot of value in replays of their past games. The revenue stream goes beyond just the broadcast itself. It extends to include syndication, royalties, etc. The videos are stored offline, yes cost is a big issue, but there’s usually a method to the madness. Hot storage for most recent videos, warm storage for older ones and Cold Storage for archives. There are those that store everything on cloud and some that store everything on site and there are those in between. It depends on their production workflow and their demands for the footage in those workflows and businesses. Modern broadcasters will balance the type of storage they have with the cost to own and operate them. Overall they make more money than they spend. Their profitability allows them to spend what they need on the right type and amount of storage they need. It grows constantly, but usually the tech develops fast enough that the cost of storage per TB reduces over time with higher storage densities, better workflows, better tech etc."
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my6zzk | The whole Pentagon selling dormant IP addresses thing | Technology | explainlikeimfive | {
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"A LOT of info is still missing about this incident but you can think of it this way: Yesterday it *appeared* that the DoD gave a MASSIVE (like 5% of all IP addresses) amount of digital real estate to a “company” that basically has no known employees, income, or even a street address. A lot of people are curious *why* this happened.",
"Let's say the DoD owned 600 thousand square miles of property (about 5% of all arable land on Earth, larger than Texas, California, and Montana combined) and then one day somebody suddenly announced that all mail addressed to this property should go through him. This was odd because previously, nobody could send mail to the property. Nothing changed as far as who owns the property, or who can access it or anything but now a new person is responsible for delivering mail to it. We don't know what that means. When we tried to contact the new person, it looks a lot like he's actually somebody's imaginary friend. Which makes everyone nervous because imaginary friends are often created to take the blame for getting in trouble. All this happened just minutes before the old president left office and after he fired the person in charge of the DoD.",
"When the Internet was created it was intended as a smaller research network. A stop gap between ARPANET and the future OSI network still under development. So they handed out big chunks of the IP address space quite liberally. The Department of Defense who have their headquarters in the Pentagon building did get assigned a lot of different address blocks for their research. After all the Internet was designed from their requirements for a self healing and redundant global network so there were a lot of different research groups within the DoD working on developing the Internet. Now fast forward to about a decade ago. The small research network called the Internet is now not so small any more. And despite all our efforts and workarounds we are running out of IP addresses. But most of the addresses assigned to the DoD is still unannounced. That means that the DoD have legal ownership over the addresses but have yet to tell the rest of the Internet where these addresses might be reached. That puts a bit of pressure on them to release some of these address assignments to the public, or at least sell them off at a profit. However the DoD refused most of this. It is possible that these addresses are used internally with some systems and that it is hard to assign the addresses to others as this would require changing the addresses of these internal systems which can be a huge job. Some companies have even started using these addresses internally in their own systems assuming that the DoD will never announce them. And in this context internal may involve networks with tens of millions of users and devices. Fast forward to the 20. of January a company called Global Resource Systems LLC announces that a number of these addresses can be reached through their systems. Little is known about this company, in fact the only think we know is their name and address, and the address is likely just a mail forwarder. The date is however a bit curious because this was the day of the presidential inauguration. Washington Post released an article about this and their efforts to find out why this was happening. But they were unable to find out any information. There was not even anything proving that GRS had any rights to announcing these addresses or even if they did it on purpose or if they had just misconfigured their systems. However a group called Defense Digital Service within the DoD did come back to Washington Post and confirmed that they were behind the announcement and cited it as \"security research\" without going into much detail. We still have no idea what any of this means."
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my84es | Internet of Things Security Weakness | So I recently read that a thermometer in a fish tank caused a network security vulnerability because it was connected to the IoT. Why? How can it be that something like a smart appliance is a gateway back to more sensitive areas of the network? | Technology | explainlikeimfive | {
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"Your device connects to your network, and in the process receives its own address on that network – a private IP which is only accessible to other devices on your network only. So your computer can send things to your IoT device if they're on the same network. However it cannot be used to communicate to it from outside the network. But, once in a while your device might also need to receive communications from outside the network, lets say from the servers of the vendor of the device. So, often a common way to do that is to map its address to the public IP address of your network, which makes it so that communications can be received by your IoT device by dialling up that public IP address. This is called port forwarding - if your network's public IP is 0.0.0.1, your IoT device could say that if you try to connect to port number 4321 of that IP, it will send that traffic to the IoT device (so 0.0.0.1:4321 directs the request to the IoT device). Unfortunately, it seems a lot of vendors of smart appliances or other IoT devices don't always focus on security. Which means that once an exploit is discovered and since typically the port number used during port forwarding will usually be the same (so my smart thermostat might use port 4321 and yours probably will too by default), it's easy enough for someone who knows your home network's IP to use a commonly known exploit to that smart thermostat and direct it to 0.0.0.1:4321. Also once you're able to access the one device it might be possible to use it to connect to other, non-port forwarded devices on that same network, since the smart appliance could be your gate into the network. But here we're talking about an extremely bad security vulnerability. I am grossly over-simplifying this but that's kind of the gist of it.",
"Things with internet access are running software. Software often has bugs which, if severe enough, will allow an attacker able to communicate with this thing to run their own software on it. If this thing is inside your home, the attacker basically has their own agent inside your home. Now it's able to do anything inside your home can... get access to your file shares on your PC, try to login to your router and change settings on it, trying to impersonate the router itself, all sorts of nasty stuff that can lead to a worse situation. If you're a business and you've let one of these things in, the potential for financial damage could be WAY worse. The problem with \"IoT\" devices is they usually need to be cheap because, well, that's how people choose what things to buy. Given the choice between something with internet access and one without, that price difference really needs to be as small as possible if you want it to sell. This means the software budget is probably pretty low, so a security audit, extensive testing, etc probably doesn't happen or is low effort. Then you buy it and you're giving one of these things your wifi password. (there are safety precautions you can take, which basically amounts to treating these devices as untrusted and segregating them. But this requires more expensive network and wifi equipment, or maybe buying two different wifi access points, which the typical user doesn't do, and even some businesses don't)"
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my9i28 | Why do movie theaters still use projectors? | They aren't shooting movies on reels, movies are edited digitally, so wouldn't a cable display to a large screen provide a better resolution? | Technology | explainlikeimfive | {
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"No, Projectors can be just as high resolution as Screens. Also, sitting from far away the resolution doesnt matter as much as you would think. Making a screen that large is also incredibly difficult, there is a reason you cant buy a 600 inch screen yet.",
"A projector can provide the same resolution as a screen, well beyond the extent that it matters in this setting. However, making a seamless screen that's fifty feet wide is far more expensive than making a projector that can project an image like that.",
"Even if it does. Think about how even your home TV can have a burnt out led. Imagine all those pixels being on the screen and and if even a few start to go out. It'll cost so much to replace and make a horrible watching experience. A projector is mostly just replacing the bulb and a smaller unit to repair.",
"There are some issues with building large screens. It would be a pain to transport to the movie theater and get into the building for a start. And the way signals travel over the much larger distances in a larger screen is a huge problem. You can get screens built up of multiple panels but there is usually a bezel around them for structure and cables and these creates visible gaps. This type of screen is sometimes used in large public spaces where a projector would be hard to do. But in a movie theater which is already set up for projection it is much cheaper and better to use a movie projector.",
"Viewing angle. Projection screens have sort of a reflective/diffracting coating which reflect the projected media widely, making the viewing angle nearly infinite. Unless you want ten seats all right in the center of the pavilion layout.",
"I would also like to add, continuing to use a projector retains some of that \"classic feeling\" of theater. Plus the technology evolved to fit the need. A theater already has a projector room and a big screen out in the front, so they invented newer digital projectors where you fit a hard drive provided by the studio to show a film. It was much cheaper for theaters to replace their reel projector (and get rid of a lot of the moving parts and maintenance associated with that) with a digital one, than to buy an absolutely enormous LCD screen to put out front. Not every theater has that kind of money. Plus, this technology was hitting theaters a good time before we had the giant displays we can make now. There may also be a case to make about restricting access to the floor the projectors are on (and thus keeping the hard drives more secure) rather than putting them right by where there's usually an emergency exit.",
"It's not practical to build such a big screen; you would need to tile several smaller screens, and the seems between them would be visible.",
"Sime display manufacturers, like Samsung, are working on it. However, building a 4K or even 8K display in theater size is not exactly easy. You cannot really use the same techniques you use to build display panels for home use, since those are pretty much limited to the practical size for a glass pane, plus the failure rate would go up quite quickly along with the area. You cannot make them out of multiple TV screen modules either, since that would leave visible seams. The alternative is LED matrix displays. Not the stuff you see in a standard \"LED TV\", that is just an LED-backlit LCD that faces the above issues, but the stuff you see in billboards and stadium screens and stuff like that. To build those screens to the size where you can show a movie in full resolution however, they need to be huge - though display manufacturers are trying to develop smaller LED pixels to bring that technology both to cinema screens and even to the television. However, we need to ask ourselves, where is the advantage? Projectors are a proven technology, they are reliable, they are... well, not cheap, but much more affordable than LED walls. The reason billboards and stadiums use LED matrices is simple: They are outside in bright sunlight, they need the brightness. A projector has a lamp that needs to illuminate the entire screen, so the light from the screen tends to be fairly dim - to get good contrast out of that, the room needs to be much dimmer than that. But cinema rooms are designed to work under that limitation - no windows outside, subdued lighting that is dimmed and then shut off to only leave emergency illumination before the movie begins, dark carpets, dark seats, all walls except the screen also dark. If there is one thing a cinema screen does not need, it is to be bright. And that darkness is part of the cinema experience as well, it helps you tune out all the other viewers and directs your focus to the movie that is playing. So there is absolutely no incentive for a cinema complex to retrofit one of its theaters for this new unproven technology."
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mya3vi | How does Bluetooth work? | Technology | explainlikeimfive | {
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"At the very basic level, Bluetooth is using high frequency radio waves. Perhaps surprisingly, it's using much the same frequency of radio waves as the typical microwave oven uses. But Bluetooth uses so little power, it can't heat anything up really. Your car and your phone both have a radio transmitter and radio receiver, and they use those transmitters and receivers to send information to each other in a sort of conversation that follows what amounts to a very specific set of rules. For instance, when you paired your phone to your car, they had a conversation like this: > Car: Hey! Is there anyone out there? > > Phone: Hi! I'm here! I'm a mobile phone. Here's my ID#, and I'm called \"Haerveu's Phone\". > > Car: I understand. Here's my ID, and I'm called \"Haerveu's Car\". If you'd like to pair with me, send me a special code I've given to my driver. > > Phone: I understand. My user told me the secret code is \"1234\". > > Car: That's the code! We're paired now. You can send me music or use my antenna or speakers if you like. > > Phone: Great! Yes, I agree we're paired now. I'll let you see my user's contacts if you like. > > Car: Great! We're done now? > > Phone: Yes, we're done now. Later, if you say you want to play some music, they have a conversation like this: > Car: Hey phone? > > Phone: Yeah? > > Car: Our user wants to play some music. What do you have? > > Phone: Well, here's a list of all the music I have. > > Car: Could you send me the track called \"XYZZY.MP3\"? > > Phone: OK, I'll send it to you in chunks. Here's the first chunk.... {bunch of stuff}... got it? > > Car: Got it. > > Phone: OK. Here's the next chunk... {bunch of stuff}... got it? > > Car: Got it. > > {and so on...} > > Phone: OK. That's all. > > Car: Got it. Thanks!",
"It's the exact same thing as wifi, but with slightly different software to make it use way less power for devices with small batteries like wireless headphones.",
"Bluetooth is wireless communication that has a set of very specifically defined commands. In order to say your device is Bluetooth compatible it must be able to support that set of specifically defined commands."
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myfozi | Why can't we make a storage that can perform all the tasks RAM does while being used as a disk drive as well? | Technology | explainlikeimfive | {
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"We can. You can buy several terabytes of RAM and there are (server and workstation) CPUs and motherboards that can use them. Just make sure it never has a power interruption. It also costs several thousand dollars for the same drive space as a 30$ HDD or 100$ SSD so...",
"We can, the issue is actually cost, it's more money than it's worth in terms of selling to the general public.",
"> Why can't we make a storage that can perform all the tasks RAM does while being used as a disk drive as well? Where does this assumption come from? Your system already uses part of your hard drive as emergency-RAM in the the form of virtual RAM (a swap file). The other way around is called a RAM-disk where RAM is used as a volatile storage drive. Prohibitively expensive and pointless with the advent of NVME SSDs.",
"RAM loses its contents when the power goes off, so imagine losing everything if you unplug or the battery dies. If you have lots of RAM you can set aside a portion to use as a temporary disk drive.",
"You can use system RAM (DRAM) as a disk, it will just lose all its data after it powers down (volatile) unless you have some kind of battery backup. There are niche products that do this, but I'm sure that's not what you mean. You can also use storage as system memory, most operating systems in fact already do this, it's called Swap or Page file. But they reserve this only for situations where the memory required is too large for RAM or not needed right now, because storage is so much slower than RAM. That DRAM behaves this way is not really a deliberate decision. If we could make a storage technology that was as fast as DRAM, but non-volatile (doesn't lose data without power), we would probably use it. But all the technologies we've used so far for memory and storage, it just seems to be the case from a physics perspective and the way these circuits are designed, that in order for it to be as fast as DRAM it has to sacrifice volatility. Generally speaking, the longer you need to store the charge in a specific place (which is what you're doing with long-term storage) the longer and more energy it takes to change the charge state (which determines read/write speed). In terms of bandwidth, an NVME drive is not far off DDR4 RAM - 4GB/s compared to about 25GB/s. But in terms of latency, even NVME is several orders of magnitude behind, measured in milli or micro seconds, compared to nanoseconds for RAM, which in turn is about 100 times slower than L1 CPU cache."
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myhwg1 | - The new flip phones | So the new phones that literally fold the screen in half. Doesn’t look like they have a clear line to separate the two sides - how does it work? | Technology | explainlikeimfive | {
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"text": [
"Plastic screens instead of glass, and flexible P-OLED displays that can be bent during use (and also happen to be really expensive)"
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mywhsb | How exactly were cave paintings made and how have they stayed in relatively good condition for tens of thousands of years until our time? | Technology | explainlikeimfive | {
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"For starters, we wouldn't know of cave paintings that *didn't* make it to modern times. If a cave sweats enough to wash away the paint or some other phenomenon happens that erases the paintings we would never know a specific cave ever had any cave paintings. For the paintings that *did* last to modern day, caves are surprisingly well protected from weather patterns. Unless a painting was close to an opening, there's next to no moving water to wash it away, there's very few plants, if any, that can grow (to break apart the pigments), short of a cave collapsing on itself or animals rubbing against it, there isn't that much that will get rid of the paint...so it tends to stick around for a long time.",
"Cave paintings were typically made using paint made out of dirt or charcoal mixed with spit or animal fat. The reason they endure for so long is because the pigment of the paint was partially absorbed into the porous walls and because the binding agent (the spit or fat) dried and stuck to the wall.",
"Can't answer the first part but for the latter surviving paintings to tend to be found inside dry caves where the absence sunlight and damp helps preserve them."
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myzvxg | How does GoogleTranslate turn random gibberish into anything? different? | Most people have tried this, I would think, but if you go into Google Translate and select Detect Language, then type in some random stuff like “aiaiaiaiaisiaiaiaiaiai” most of the time it’ll come up with something. That doesn’t make that much sense to me, seeing as I would expect it to just be reading from a table of known words and translating directly for each of them. | Technology | explainlikeimfive | {
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"> I would expect it to just be reading from a table of known words and translating directly for each of them Most languages do not translate perfectly into another language. It isn't a matter of \"word a\" translates into \"word b\". This is why you can pass a sentence through multiple language translations and end up with completely non-sensible sentences. This is also why you can watch shows translated from one language to another *by different sources* and end up with different words/slightly different meanings. It isn't a table of of what each word means in each language, but rather it's a mix of certain usages of words, grammar, inflection, and other factors. As a result, translations aren't perfect, and something that's complete nonsense in one language may actually form something in another language.",
"Old translation software used to do that but no modern translation software does that. It's all probability based now and looking for patterns because it also assumes you made a typo on the word. Also the old way of doing it just worked really badly and was pretty much always wrong. It's the same reason why you have to hire actual translators fluent in both languages rather than just relying on a dictionary when you try and do serious translation work. For example: URL_0 To put it another way, translation software rarely actually comprehends what it is that you're trying to communicate. It just looks for the closest matching set of words that typically belong together. In this case it's doing something similar, it's looking for a language with a sequence of words that match the gibberish as closely as it can."
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mz21sk | How does long exposure photography works? | Technology | explainlikeimfive | {
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"The shutter inside the camera is simply held open for a longer time than normal, which is around one 60th of a second. The long the shutter is open, the more light that is allowed in, especially good for taking pictures in dark areas, or of the night sky. The downside is that if the camera is moved (bumped, or natural movement when hold a camera), even a little bit, you get blurry photos, so a camera stand or mount is usually required. According to [Nikon USA]( URL_0 ), a 20sec exposure is good for taking pictures of stars. Any longer and you'll get blurry images because of the movement of the Earth."
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mz35jq | Why do coin batteries seemingly die, then after a days rest return with renewed vigour? | Technology | explainlikeimfive | {
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"Battery voltage depends on how much load is being placed on the battery. One that's 3.0V at rest will fall to, say, 2.9V with a light load. Under a heavy load, it might fall to 1.5V. The reason is there is a rate limit to how fast the chemical energy can be converted to electrical energy. If a battery is placed under a heavy load, the reaction goes as far as it can before it \"falls behind\" demand. You're basically stripping off the \"surface charge\" and have to wait for the \"deeper\" charge to replenish the \"surface\". If you then let the battery rest for a while, the chemical reactions can \"catch up\" and restore voltage. The voltage drop is also influenced by the battery's own internal resistance (which is always more than zero), so if you put a battery under load the voltage will instantly drop some (due to resistance) and then slowly fall more as you deplete the surface charge."
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mz72yn | Ive looked it up but i still don’t get it, what exactly is an NFT? Why do people pay so much for some? What does it have to do with crypto? | Technology | explainlikeimfive | {
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"It’s a non fungible token. Fungibility is when things are exchangeable and nothing is different. For example my one dollar bill is the same as all other dollar bills. Non fungible means this token is not the same as another token. People pay so much for some because either they are super rare or the buyers are stupid. Cryptography is used to make non fungible tokens exist."
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mzb6vs | How/why do magnets mess up electronics? | Technology | explainlikeimfive | {
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"Electrical currents produce magnetic fields and magnetic fields can produce electrical currents. Electronics depend depend on precise states of electrical components to operate correctly. Strong enough magnetic fields can interfere with that.",
"For the most part, they actually don't. Most electronics these days are very small and go mostly unaffected by even larger magnets. However, some components (like large inductors) may pick up a relatively large voltage from a powerful nearby magnet moving past. Additionally, some components use magnetism to their benefit (like hard drives) and a nearby magnet may falsely trigger whatever effect the magnet is being used for.",
"Old style (CRT) monitors (and TVs) used electrostatic or magnetic fields to direct an electron beam to the individual \"pixels\" on the screen. A magnet held near to a CRT would deflect the beam, causing at a minimum color shifting, and worst case an unviewable display. If part of the CRT was left magnetized, it'd have to be degaussed (de-magnetized) to fix it. Floppy disks, and to a lesser extent hard disk drives, store data by recording a signal in a thin magnetic film (very like cassette tapes). A magnet held too close could change or blank the data. Additionally, some hard drives used pre-recorded \"servo\" tracks to locate the data. If any of the servo data got damaged the disk, or at least part of it, became unusable. Other than those parts, I'm not aware of electronic parts that can be affected by ordinary magnetic fields."
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mzcov8 | why aren’t all online video games cross play? | Technology | explainlikeimfive | {
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"text": [
"Because the console manufacturers don't want it. Thats really about it. Sony has been particularly oppositional to any sort of cross play for the most part."
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mzi8z5 | What is NFT ? Why is it buzzing all of a sudden ? | Technology | explainlikeimfive | {
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"NFTs are a digital title that declares you the owner of of a digital asset. The asset can be anything from art, music, nba cards, video game items etc. The reason why it’s getting popular is because it introduces scarcity to digital assets, which has driven prices up for some things greatly. For example, if I’m an artist and I release a song online, people can buy and download the song, but what each person downloads and owns is identical to what everyone else owns. However, if I make an NFT of the song, only one person can buy and have ownership of that NFT, which increases its perceived value. There are other potential use cases for NFTs but for now they are basically exclusive, limited edition, digital collectibles."
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mzic8q | How does using contactless debit cards reduce fraud? {Please read below} | In my ICT class, my teacher said that using contactless debit cards reduces fraud as less money is taken out (less money taken out because contactless cards have a limit, for example: $50, every time you withdraw). She said that, because of that limit, if someone wants to withdraw $150, they have to withdraw 3 times if the limit is $50. But how does this reduce fraud? If the card is stolen, the one who stole it can still make 3 withdrawals and get $150. Plus, I don't understand why there is alimit in the first place, I searched online, and it said that the limit was because there is no way to identify that the user of the card is the owner, but it doesn't make sense, since even if the card is stolen, the one who stole it can still withdraw multiple times, like the owner. Thank you :) | Technology | explainlikeimfive | {
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"It may be different in other countries but in the UK you can't directly get money with contactless. It's only used when purchasing goods. In your example the thief could go buy something that's $50 but they couldn't get something that's $150. If the purchase amount is over the current threshold (£45 in UK right now) then the machine refuses contactless and requires a PIN. The limit then is there just to gate that access. The outcome of there being less fraud is because thieves would want the big ticket items they can resell rather than lots of low value items."
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mzihuu | how does noise cancelling headphones actually work? | Technology | explainlikeimfive | {
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"Sound travels as waves, and those have a shape that dictates what sound you actually hear. Simply put it has properties called *frequency* which controls the pitch and tone, and *amplitude* which controls the volume. If the total wave reaching your ears has 0 *amplitude* you don't hear anything because it's silent. What **proper** noise cancelling headphones do is they measure the sound waves around you and play an \"upside-down\" copy of that wave shape that cancels out the incoming background noise. They essentially subtract the background noise from itself, so all the *amplitudes* cancel out to be 0 across the whole background sound wave.",
"Noise-cancelling headphones listen carefully to the sounds around you and try to figure out the pattern. Once they've got it down, they play the opposite into your ears, cancelling the recurring noise. What I mean by this is that since every sound is a pattern of pressure waves, rippling through the air, the headphones line up a peak for every valley and a valley for every peak. The result is nicely flattened out. This is also why they can't do a damned thing about irregular noises: there's no way for the headphones to predict the sudden crash of someone dropping a bottle, and thus no counter-sound they can work out to play in sync with it."
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mzjguz | How does a Computer know, how long a second lasts? | Technology | explainlikeimfive | {
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"The computer (and every digital watch/clock) has a [crystal oscillator]( URL_0 ), a tiny crystal that vibrates at a constant rate when electricity flows through it. By counting the vibration and dividing by the number of vibrations per second (which is a known, fixed number) you get the number of seconds that passed.",
"The same way your digital watch does. It uses a quartz crystal that will oscillate at a certain frequency which can be used to create an electric signal at that frequency. It is not entirely unlike a clock that uses a pendulum that swings back and forth at a set frequency or how mechanical watches work. The difference (or at least one difference among many) is that a pendulum will swing back and forth at a frequency of once per second or 1 Hz and mechanical watches work at frequencies like 4 Hz, while quartz crystal can be made to oscillate thousands of times per second. The ones use most commonly in computers and devices and watches are set to a frequency of 2^15 Hz, this is very convenient as computers calculate and count in powers of two and two to the 15th power is something very easy to deal with for electronics. One problem that you may already have thought of is that watches and digital clocks use batteries and don't work without electricity. Your desktop computer will keep the time even when turned of and even when unplugged though. How? Because the watch part in your computer has a tiny button sized watch battery to keep it going. If that battery ever runs out and you turn your computer off it will ask you on your next boot what time it is because it doesn't have any idea. Of course computers and devices connected to the internet have the ability to check their watch component against the time they get from other computers on the network and adjust if they are behind or fast by a bit. The official time usually comes from Atomic clocks that are much, much more precise than quartz clocks and that tell everyone else what time it is over the internet or long wave radio."
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mzl4n8 | how do the cameras work that can see through clothing? | I recently found out that these cameras exist and I'm curious how that works. I understand how X Ray imaging works and how MRI works but I don't understand how you could see through clothing with a camera (and do they really show a naked body or just the shape of your body?). If someone could help explain it to me that would be awesome. Disclaimer: I'm not at all interested in buying one or making one. Just confused how it works. | Technology | explainlikeimfive | {
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"The ones I've seen use infrared. The wavelength penetrates your clothes (which are uniformly dense) and hit your skin. Different areas of skin will reflect the wavelength differently so it's possible to get a rough image of what's below the clothing",
"These cameras are sensitive to infrared light. IR light is not visible to humans, but certain cameras can pick it up. Certain clothing is good at blocking visible light (so it looks opaque to a human) but does allow IR light to pass through relatively unhindered, so for an infrared camera, the clothing is slightly transparent."
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mzq366 | why do clocks both tick and tock? | Technology | explainlikeimfive | {
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"The mechanism inside mechanical clocks the regulates their speed (and hence time) is called an “escapement”. There are many designs but they all have a common design of releasing one tooth on a gear (“tick”) and then allowing the gear to turn exactly one tooth then catching it again (“tock”). The sounds are the escapement catching and releasing the teeth. Edit: useful illustration. URL_0",
"Aside from the answer explaining the design of clocks, there's also the grammar rule that explains why its tick then tock but not the other way around. \"Reduplication in linguistics is when you repeat a word, sometimes with an altered consonant (lovey-dovey, fuddy-duddy, nitty-gritty), and sometimes with an altered vowel: bish-bash-bosh, ding-dang-dong. If there are three words then the order has to go I, A, O. If there are two words then the first is I and the second is either A or O. Mish-mash, chit-chat, dilly-dally, shilly-shally, tip top, hip-hop, flip-flop, tic tac, sing song, ding dong, King Kong, ping pong.\" From URL_0",
"I seem to be able to make it go tick- , tick-, tick-, or tock-, tock-, tock-, just by trying to hear it so",
"And why don't they just click and clock?",
"The same reason the sound doesn't keep going up. One movement is building pressure, one is releasing it.",
"There is also a phenomenon by which two ticks with all equal properties are PERCEIVED as tick and tock (or some other entrained rhythm ) URL_0",
"It is amazing to mean how a good mechanical (automatic) wrist watch can run 24/7 for decade without service. Imagine idling your car for decades without ever checking the oil let alone changing it.",
"Is this a riddle? “Sit down, Batman, and take stock. Why do clocks both tick and tock?”"
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mzu7h2 | Can someone explain an Existential Forgery Attack against RSA Digital Signature? | Hi everyone! I am in cryptography class and I'm having a hard time understanding the Existential Forgery Attack and the textbook isn't helping either. Can anyone explain it to me? I appreciate any help or examples you can give me! | Technology | explainlikeimfive | {
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"The attack is just a means of producing something with a technically valid signature. However what that \"something\" is, well, it is essentially garbage most of the time because you're forcibly constructing something with a valid signature out of parts with valid signatures. What you get in the end will be effectively random. In most cases it would be a case of \"Look, he signed this document!\" \"This looks like something produced by an infant who'd never seen a crayon before.\" \"Yes, but he signed it, and I can prove it mathematically!\" The math is fairly simple. RSA signatures are essentially done by raising a number to an exponent. EncryptedText = OriginalMessage^e (modulo N) and the decryption process is OriginalMessage = EncryptedText^(d) (modulo N). For signing you just swap e and d, and replace EncryptedText with SignatureOfMessage. e is the public exponent and d is the private exponent in both situations. Now modulo arithmetic can often be treated as simple integer arithmetic and then apply the modulo at the end rather than at each step in a long calculation. I can do all the math without considering of the modulo and then fix it at the end. So I can really just abuse the usual rules of multiplication and exponents to build a technically valid signature by combining 2 (or more) other known signatures. SignatureOfMessage1 = Message1^(d) and SignatureOfMessage2 = Message2^(d). Not knowing what d is but having the originals and signatures of any old messages, I can still combine these into a valid combination, SignatureOfMessage1 * SignatureOfMessage2 = Message1^d * Message2^d = (Message1 * Message2)^d = A valid signature for message Message1*Message2 (modulo N) In most situations this isn't very useful, but you have technically constructed a new message and its valid signature without breaking the private key."
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mzxqvy | How do 3D printers work? And what are their limitations? | Technology | explainlikeimfive | {
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"3D printers are conceptually relatively simple. First, you have an arm, that using a mix of gears, belts, or pulleys. Is able to be programmed to move forward, backwards, left, right, up, and down. How big you can 3D print something is determined by how large of a frame you put this system on. Then, you run a feed to that arm that carries your medium, usually plastic, these thing strands of plastic are then run through the arm where they are heated to the point of melting just as they get pushed out onto the item being printed. Or alternatively you might here people “3D printing a house” where instead of using plastic they use cement on a much larger scale. That’s the basics of how it physically functions, belts moving around an arm/pointer that deposits plastic. Now integrate that with 3D CAD software that gives the printers instructions on where to deposit plastic and where not to deposit plastic, and you can print out items.",
"Ones you can buy for home use melt plastic and use motors to carefully place the melted plastic on a build plate. It builds the object one layer at a time, stacking the plastic on top of the previous layer. You can almost always see each individually when you look closely at something 3d printed. There's another type of home 3d printer where it uses UV light to solidify a layer of resin on the build plate. It works basically the same as above, but instead of melting plastic it uses a tiny LCD screen to stack the individual layers of solidified resin. You can scale up both of these methods - for example, you can use the first method to make 3d printed chocolate, clay, cement (even things as big as entire houses). You can scale up the second method to create parts in metal - picture a sandbox of metal dust and a laser scans a layer of the part sintering together the metal it hits, then it spreads more metal dust on top and repeats. The limitations is a little more difficult to answer. You are limited in materials - for the first type you need something liquid that can stack without squishing itself apart. Additionally, the strength of the thing you print is also limited and not usually as strong as other manufacturing methods. Most industrial uses of 3d printing use the printer to make a mold which then they use in traditional manufacturing."
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mzyq1o | what is a lumen and are higher numbers good or bad to look for in a flashlight? | Technology | explainlikeimfive | {
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"Lumens is *not* the same as intensity. Lumens measures the total light output. Some flashlights are like floodlights: they spread their light widely and evenly so there is no bright \"hotspot\" right in the middle. This illuminates a wide area. Say this flood flashlight has 100 lumens: if we were to narrow the beam to illuminate a smaller area, that area would be lit even more brightly, even though the flashlight is still 100 lumens. Taking it further, let's focus that light into a narrow beam to illuminate a very small area. Still at 100 lumens, that little spot will be much, *much* brighter than when we were flooding. It gets even more complicated because most flashlights have a center hotspot that is surrounded by a dimmer halo, called \"spill\". So it's really hard to make apples-to-apples comparisons when different 100 lumen lights have larger or smaller hotspots and larger or smaller spill. All this is to say, a 50 lumen flashlight that has a tight beam can illuminate something more brightly than a 150 lumen flood light. So if you want to know how bright a light is, you also need to know the beam width of the hotspot and spill.",
"A lumen is a unit to measure the output of light. More lumens means more powerful/bright beam of light. I've noticed alot of companies like about how many their product puts out.",
"Lumens is a measurement of how much light is coming out of something. The more lumens, the brighter the light, the fewer lumens, the dimmer the light."
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n03d4z | Why is plastic easy to tear at some angles but virtually impossible at others? | Technology | explainlikeimfive | {
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"During the production process the polymer chains can be aligned in certain directions. If you're tearing parallel to the chains it'll be a lot easier than against them. Same reason it's easier to tear paper (and toilet paper) in certain directions, basically."
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n08ckt | Why do fuzzy radio signals become a lot clearer when stand in front of or grab the end of the antenna in you hand? | Technology | explainlikeimfive | {
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"While standing near the radio you are messing with something called multipath fading. Radio signals bounce, they bounce around inside your room, off walls etc. These Various reflections combine at the receiver, and depending on their phase the result can be amplification or dampening. (See answer by captain-carrot for a good explanation of this) It's also worth mentioning that with an FM radio source around 100MHz you as a human are about half a wavelength tall. This means that the human body is very effective at changing the 'multipath'. (The why is probably too complex for Eli5) The result of all this is that a bounce off you will almost always have a notable effect on reception Physically touching the antenna is a different phenomenon, you become an aerial extension Owners of older models of TV with set-top antenna will be familiar with both of these in action",
"Radio signal is a wave. It goes up and down. The signal bounces off all sorts of things, like walls, furniture, people and and so on, so the antenna actually receives multiple versions of the same signal at once, like an echo. If those versions line up - so the peaks and troughs of the waves are hitting at the same time - it boosts the strength of the signal. This has a scientific name: constructive superposition. If those versions don't line up, it messes up the signal making it weaker and can even cause the signal to cancel out. The scientific name is destructive super position. The wavelength - distance between peaks - for FM radio signal is about 3m. Because your body can affect the signal, moving around within this distance of a radio can effect the strength of the signal either boosting it, or blocking it."
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n0ejxo | Why do airtags need to be special Bluetooth tags to track instead of smartphones tracking any Bluetooth device? | With airtags on iPhones and smart tags for Android becoming common now for tracking objects I don't understand why they need to be attached to electronics. Why can't I track my headphones, smart watch and other Bluetooth things through the same tracking apps? | Technology | explainlikeimfive | {
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"Some of the features on the AirTag have been around on different devices for a long time. Things like activating a sound, blinking a light or showing the name and phone number of the owner. They are usually not killer features of things so they are not included unless it just involves a small software update. If AirTag proves to be a success then it might be something that can be integrated into more things quite easily at just a small increase in hardware cost. One of the innovations we have not seen that often before is the way the phone can locate the AirTag. This can not be done with Bluetooth though and requires modified Bluetooth tranceivers that is capable of switching from Bluetooth mode into a wideband locator signal. This is an old technology which have been used for a long time in purpuse build locator devices however they have not been built into a Bluetooth transceiver before. But it is something which might become more common over time as we see new hardware being developed for it."
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n0fqnh | Why is there no video quality setting for the 500-600 range? | So we all know 144p, 240p, 360p, 480p, 720p, and 1080p. But why is there no setting for something like 550p? | Technology | explainlikeimfive | {
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"You will notice that these go up roughly (in most cases exactly) in a 1:1.5 ratio. In other words each jump improves horizontal resolution by 50% So an extra resolution between 480 and 720 would be an anomaly.",
"PAL DVD video is at 576i or 576p and so is PAL digital television that is in SD and not in HD. Generally the vertical resolution will always be something divisible by 96 for digital TV and media standards. Computer resolutions are more varied but usually are in some way derived from old time 640 × 480 or 320 × 200 monitor resolutions. If you trace things back far enough you will find that IBM punch cards came with enough room to leave 80 x 12 holes in them, which ended up leading to text-based interfaces having 80 or 40 characters per line and each character being made up out of 8 by 8 pixels. The common shape of TVs made for the 4 by 3 ratio and those constraints let to early display resolutions and newer once are just those multiplied by a certain number in size and adjusted for the 16 to 9 or similar ratio in modern wide screens."
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n0gid6 | How do bank phishing scams actually work? | A friend of mine recently got scammed by a bank phishing link sent to her phone. She made the mistake of clicking on the link (it was a fake message saying someone had made a transaction and to click the link if it wasn't her) and next thing she knew, $5k was taken from her bank account. She didn't enter any details at any point, she just clicked it. She was luckily able to call her bank and get the money back, but it got me thinking - how are scammers able to take money from you just because you click on something through your text messages? | Technology | explainlikeimfive | {
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"I think it depends if she has connected any electronic fund transfer systems to it, eg. Apple Pay, pay pal and cash app",
"I've seen many that will create a fake \"login\" page, and use any information entered in an attempt to gain control of the victims account long enough to issue a bill payment to a recipient they control."
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n0xjph | How does the phone compass even work? | Technology | explainlikeimfive | {
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"Phones have a small sensor called a \"magnetometer\". When coupled with the phone's accelerometer, the magnetometer can sense the Earth's magnetic field and tell you which way north is, no matter which way the phone is facing. Of course, this isn't enough for scientific applications, but it can tell you which way you're facing in your favourite map app."
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n0xt4q | How do conferencing programs like Zoom handle so many different screens so quickly, when sometimes single videos in other apps lag? | Technology | explainlikeimfive | {
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"You're not directly connecting to 9 other people, like 9 different peer-to-peer connections. Everyone has one connection to Zoom's central servers. Zoom puts them all together into one big composite and sends a single stream back to you and everyone else. So from your device's perspective, it's not doing any more work than videoconferencing with a single other person. It's uploading one video stream, and downloading and displaying another. By the way, Zoom got in trouble for advertising that their videoconferencing is \"end-to-end\" encrypted. It's obviously not. They decode all of the video streams on their servers in order to put them together. They could easy spy on you if they wanted to. Edit: well, this blew up! I was basing my information on [articles like this one]( URL_1 ) that talked about how as recently as a year ago, Zoom did not do end-to-end encryption, and in fact they've been [faced with lawsuits]( URL_0 ) over their misleading advertising. However, it looks like I was mostly incorrect about my implication that Zoom processes the video on the server - it sounds like they actually just send you multiple low-quality video streams all packaged together in one connection.",
"The top posts are all incomplete or wrong, so let me try. This is probably more like an ELI10 than an ELI5, but it's the best I can do. First, let's talk about what we want from a good video conferencing system: 1. High resolution (sharp images) 2. Low compression artefacts (clear, undistorted images) 3. Low latency (no lag between you and other participants) 4. Low enough bandwidth (don't use more bandwidth than your internet can support) 5. Low enough CPU cost (don't use more CPU power than your computer has) These parameters are in contention with each other. More resolution takes more bandwidth and CPU. Compression lowers bandwidth, but increases CPU cost and latency. A big part of a good video system is selecting and adjusting these parameters. It's hard because the computer usually doesn't know how fast your CPU is or how much bandwidth you have, so it has to guess and adjust. The main part of your question is about how Zoom can work so well for large group video chats. There are two extra tricks applied here: 1. The video is all sent to a central server 2. The central server can transcode the video (adjust the parameters mentioned above) The reason for the first trick is simple; it's easier for your computer to send the video one place instead of to every participant. The second one is related to setting the appropriate parameters. If someone is looking at 16 participants in a grid view, they likely don't need every video at full resolution since they are so small on screen. The client can ask for a lower resolution video, and save CPU and bandwidth. Similarly the compression can be tailored for each participant. Slower devices and connections can get scaled down video The server has a lot of CPU power and can change the video formats easier than your personal computer could generate all the options. Addressing some mis-information elsewhere: 1. Typically, you won't see all videos encoded into one stream. You can see this easily with Google Meets, where you can use javascript to reposition the videos wherever you like. It's not flexible and the hard boundaries between participants compress poorly. 2. The central server doesn't remove the ability to have end-to-end encryption, but the need to transcode the video does. That's the biggest gain of this strategy, so an end-to-end encrypted video conference would require more resources or have less consistent quality than what zoom can provide.",
"When you have a bad connection or something is going wrong, YouTube (streaming) and Zoom (live streaming) handle it differently: YouTube slows down by buffering, because who cares Zoom slows down by dropping frames and quality randomly degrading so that you can keep up with the stream, because it's \"live\" and generally you don't want to miss what the other person is talking about, or be behind on the stream Not sure I understand your question, but maybe you just don't notice the quality drops in Zoom because they don't *feel* as disruptive as buffering? FWIW even non-live streaming has started to do this. If you watch something with a bad connection on prime, or set a youtube video to \"auto\" quality, it will adjust on the fly to reduce buffering.",
"While not the most technical explanation, it's also worth considering that software's performance is in *a lot* of real-life cases limited by how much optimization goes into making it fast, not actual hardware limitations. So there's a bias which makes all applications just fast enough so they work \"okay\". MS Teams takes over one second to switch from one chat tab, containing twenty lines of static text, to another, also containing twenty lines of static text. Meanwhile, modern computer games draw millions and millions of 3d triangles on the screen in less than 0.02 seconds. There is no technical explanation for this. It's just laziness on the developer side. Computers are insanely fast these days. I think most end-users dont't realize just how fast they actually are, since many applications like to keep a lot of that to themselves, for ease of development.",
"It is much closer to a single video than 100 videos for 100 zoom conference participants. Think of it as a multi-player online video game. All players are connected to one server \"live game\"; and each player is seeing the game and the other players from his/her own point of view as a single video stream. so you are not streaming a video for each conf participant, you are streaming 1 video on what the server has prepared as your point of view of the conference.",
"I think it’s that it’s favoring quantity over quality. Let’s take YouTube, for example. If you open a video and choose 1080p, it’s gonna be 1080p. That means 1920x1080 pixels arive every second, so your connection has to handle that. Now take Zoom call with 10 participants. Every participant is streaming 1080p video, so the same amount of data as YouTube does. Does that mean that Zoom call with 10 1080p users uses 10 times more data? No, because when you see all 10 people, their windows are smaller, right? So Zoom only shows you 192x108 videos of your callmates, which is gonna make the bandwidth the same as one full-screen YouTube video. Once you click on someone and expand his view, Zoom kicks the quality up, showing you higher resolution, let’s simplify this to 1920x1080. But since you see only one person out of 10, the bandwidth is still the same! It’s a bit oversimplified, it might not cut the quality by 9/10 and lot’s of decoding happens too, but I’d say that this is how it works. If I am wrong, feel free to tell me, I will be glad. EDIT: 192x108 is obviously 100 times less than 1920x1080. That’s what 2 years of integrands do to your brain....",
"For starters, conferences aren’t sending you full resolution streams, there’s multiple resolutions available and if you’re not focused on one user then the stream resolution for that user will be substantially lower bitrate and resolution. You can see this with zoom recreations on the news which have a much higher quality video that is actually feasible - in a few films from the last year and in some news videos. Secondly, the bitrate of video streams for conferences are substantially lower overall, than video on sites like YouTube. The same goes for audio. The frame rate is also incredibly low in comparison. It is also potential that the video streams are being muxed (multiplexed) such that the bitrate can be varied for all streams simultaneously. Another method is to combine them into a single feed although that requires an encoder and is not cost effective for large free meetings which these services are hosting a litany of. Lastly it is worth mentioning that webcam video usually has very little interesting information. Most of the video is usually a static background which doesn’t require much information to describe by the encoder. The only thing you really see on the average user webcamera is the face moving very slightly and perhaps a few shifts in position. Even then you’ll probably notice that large movements look jittery because the encoder puts key frames so far apart in time. In addendum to this fact, the colour depth of webcams is usually fairly poor and so the compressor doesn’t have to have such a high bandwidth for colour when throwing out uninteresting information during domain transformations. Conferences are glorified slideshows.",
"Hard to ELI5, i actually worked on a video conferencing system and can tell you a bit more about the setup involved, a few comments covered some things really well, this is a bit more on top (ELI15 maybe): There are multiple encoding algorithms, each with tradeoffs as mentioned, the main issue usually stems from latency: * you have latency transmitting data to the server * latency from encoding the data * latency from sending data from the server to the client. Now, depending on the algorithm, you also get latency depending on how it \"delivers\" the video to your screen: ie: HLS (used widely) creates chunks of a few seconds, and generates a playlist that keeps adding new file chunks to the end. Your player plays those video chunks in order and fetches the playlist occasionally. (this is a bit oversimplified, but essentially correct) Each playlist includes multiple streams with different encoding (resolutions). This is how you switch from 480 - > 1080p on youtube seamlessly: * you click on the toggle to switch resolution * on the next chunk, the player selects the higher bit rate stream * all chunks are exactly the same, so it's perfectly seamless. * this is why it is not instant. There are more advanced techniques, but they are out of the scope of this explanation. So, what does this mean for latency? If you're running 1 seconds chunks, the video will be 1 second + transmission/encoding delays behind. You cannot send the 1 second chunk before it is recorded. So what do we do to decrease latency -- In come newer encoding algorithms that can have very small chunks, 0.2s or less, or just give up chunks altogether. How do these get around encoding? Simple, imagine an image which contains 8 pixels in a square. Imagine those as black blocks, now add another 8 white ones in between. You now have a 4 x 4 pixel array with alternating black and white blocks. You can now have 2 streams, one for the black squares and one for the white. The downside of smaller chunks or no chunks, is variations in speed. Imagine your connection as a water pipe, sometimes the pressure is high, sometimes low. These variations can be buffered by longer chunks, but cannot if chunks are too small/non existent. So, how can we handle these variations? Using the 2 stream example i gave, you request both, if one is more reliable and the other one is dropping data. You play just one, which renders at exactly half the resolution. When both work well, you combine to form a higher resolution image (the pixels are offset, right, so combining both produces the same image with more pixels all in the right place) There are more advanced techniques with how you route the 2 streams, and how you can combine the data. In other words, by doing so, you are unlikely to lose both at the same time, so they can be used to keep a consistent video output, at low latency and when your connection is stable enough, combine both for better quality. This can obviously be extended. This is the main trick for delivering low latency streams with the best video quality and reliability. Hope this helps :). Edit for the curious, without getting into much more complex explanations, there are multiple ways to transmit data over the net, in chunks or as a pipe (websocket), a websocket keeps an open connection to the client and can continuously send data over it. The new algorithms use websockets. Not using websockets also incurs a penalty for handshaking on each chunk etc..",
"Oh you mean like the single video you try to watch on the reddit player? The darned thing takes like 3-4 attempts before its ready to play.",
"Smaller screens mean smaller resolution. Less data to send. Purely hypothetically; 9 1/9th mini-screens is the same amount of data as 1 1th big-screen."
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n0zlqc | How do peers and leechers in pirating on Utorrent work? Do any other site use them? | Technology | explainlikeimfive | {
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"If you've copied someones homework at school, you are now also a point that someone else can copy homework from, as long as everyone who copies the homework copies it identically (this is done by hashing a torrent's content and checking it against the source) it doesn't matter who you copy from, so if there's a 100 people in the hallway u can copy homework from you can essentially copy the first answer of 1 guy then the next answer from a guy 10 feet down the hall later and when you bump into someone who needs one of the questions you have already copied he can copy from you. If many people seed and few people leech then you can quickly find someone to copy from, if many people leech and few people seed then you'll be in a crowd and things will slow down.",
"Imagine there's a book. It's 10,000 pages long. I have a copy, you want a copy. I sit down, start writing the book page by page for you until all 10,000 pages are finished. We both have the book, and my hand is probably *way* cramped. Right when we finish, Jeff shows up. Jeff *also* wants the book, but now you and I both have a copy. We each agree to write 5,000 pages and Jeff gets their copy of the book in half the time. We're *seeding* the book. Now Dave shows up. You and I look at Jeff and say, \"Cool. Each of us only has to write 3,333 pages,\" and Jeff says, \"Actually, I have to get back home and polish my katanas,\" instead of sticking around to help? Shit. We're stuck writing the same number of pages, and the next person doesn't get their book any faster than you did. Jeff is a *leech*. He shows up, gets his copy, and then leaves without helping anyone else. Torrents with lots of seeders make it easier for more people to get the file they want faster, because more people are helping. Torrents with lots of leechers mean the sharing never speeds up."
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n1aypo | How early Morse code telegraphs transmitted eletric pulse to that specific sound? | What is the mechanics behind it? | Technology | explainlikeimfive | {
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"The electrical pulse energizes a solenoid (basically a coil of wire) with a piece of metal inside. This causes the iron to be temporarily magnetized (called an electromagnet). This magnet draws another piece of metal to it (that has a spring attached) and when it strikes, it makes that click sound. When the pulse ends, the electromagnet demagnetizes and the piece of metal is returned by a spring making a return click. That sound is simply pieces of metal striking each other.",
"The telegraph did not transmit any sound waves, it was just on and off. The sound was made by the equipment at the receiving end. Initially it would be just the mechanical noise of the electromechanical receivers being in tune with the receiving signal as it was not initially intended for humans to be able to interpret the signals by listening to them. But later on they would add circuits to intentionally make sounds for the operator. The classical simple sine wave sound associated with Morse code today was not actually used on the first telegraphs but were how radio telegraphs would work. The transmitting stations sent out a simple pure sine wave as it would occupy a single radio frequency and be easy to filter out. But on the receiver they would tune to a slightly different frequency. And it just so happens that when you do this you get an oscillating signal as the received signal would fall inn and out of phase with the receiver. And this produced the clear sine wave tone that we now associate with Morse signaling.",
"The electrical pulse does not make the sound. What it does is powers a coil that becomes a magnet and pulls a small metal tab down. The click is the sound of the metal tab, hitting the metal core of the coil. The tab is mounted to a spring, that returns the tab to the up (or open) position when the electrical pulse ends."
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n1b7hh | How exactly does software decay work? | Technology | explainlikeimfive | {
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"Software doesn't really \"decay\". If you don't touch it, it won't change ever. What can change is the environment in which the software is operating. Say a software for doing tax declarations will slowly become ever more obsolete as laws and regulations change. Left unchanged, the software will also be left behind by it's competitors who keep modernizing their products. The software starts feeling \"old\" in comparison. Software can also become obsolete, when it's written with technologies that nobody is learning anymore. The software keeps working for a while, but when something breaks, there's nobody around to fix it. Another form of \"decay\" happens during (long term) development. Due to budget and time constraints changes are often \"bolted on\" in the quickest way possible. Little regard is paid to how well the change fits into the original architecture of the software. Over the years the source code starts \"loosing\" it's cohesion/organization/architecture and eventually becomes impossible to maintain. It's a human made problem, but because it happens \"unconsciously\" it feels like \"decay\"."
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n1bidl | How do they do "age progression" with photos? What do they base their predictions on? | I'm talking in general, like when you see age progression done to old photos of missing persons. Is it some kind of AI stuff? | Technology | explainlikeimfive | {
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"Faces age in pretty predictable ways. Things like noses and ears grow at certain rates. Fat sits differently with age, stops being in the cheeks for example. Gender differences start to show after puberty, wider jaw for boys and so on. They can take a picture, put markers at key areas of they face and add how the years would change the face. Im sure there's a very fancier way and explanation of the computer programs but that's the simple idea behind how it works"
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n1cfvv | What is ray-tracing and how does it work? | I keep seeing stuff about ray-tracing but when I look it up I don't under what I am reading. | Technology | explainlikeimfive | {
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"In computer-generated graphics, one of the tricky bits is to simulate lighting. To keep rendering fast, early game graphics would make general assumptions like \"light comes from here\" then brighten or darken textures depending on how directly they faced a light source and how far they were from it. As technology improved, more advanced algorithms could be used, but they often still had short-cuts to keep rendering times down. While these algorithms had results that looked good enough for most cases, they still didn't simulate how light really works in real life. In real life, surfaces bounce, absorb, and refract light. Trying to simulate this in computing is called ray-tracing (ie. tracing the path of rays of light as they bounce around an environment) and has traditionally been extremely computationally expensive. If you read about the history of old Pixar films, they would take hours to render each frame of film as they used ray-tracing to illuminate their models. But now we're finally to a point where the technology of hardware and software can perform some degree of ray-tracing in real time, allowing it to be used in games or other real-time modeling simulations."
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n1d6tu | How does ray tracing work? | Technology | explainlikeimfive | {
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"Former game developer here, So you have 3D points, 3 points make a triangle (polygon) in 3D space - the smallest primitive object you can make. Everything can break down into terms of triangles. The surface of that triangle also so happens to describe a 2D plane that goes on to infinity in that 3D space. The surface of the triangle, that plane, faces a direction - we call that a \"normal vector\". You can think of it as an arrow, pointing from the surface of the triangle, and for the sake of argument, just presume it's at a right angle to the surface, it points straight out. (It doesn't always, we can tweak it for different effects.) The points of a triangle can all have their own normals, too, and can have more than one normal if that one point is shared with multiple adjacent triangle. Then you have matrices. These are numbers, very complicated numbers with multiple parts. Remember complex numbers, from high school algebra hell? a + b*i*? Shit like that? That's not an equation you *solve for*, notice there isn't an equal sign anywhere. That mathy thing is a way of representing a kind of number. Matrices are also a kind of number, and they come in different sizes. For 3D games, most matrices have either 9 or 16 terms. We can write them in a handy notation of rows and columns, in tabular form. So you'll see 3x3 or 4x4 grids of numbers, those are matrices. A 3x3 matrix represents, mathematically, 3D space. Literally the whole universe. You can rotate it, scale it, or transform it - maybe your space has a slant to it... A 4x4 matrix has X, Y, Z, and W. W is interesting, it's a translation. What it is, is a 3D matrix with a position. We're talking ONE UNIVERSE relative to ANOTHER UNIVERSE. This is very useful, because if your torso is represented by one matrix, then your arm can be represented by another matrix. Now you can describe how your arm is positioned relative to your torso. And when you rotate your arm matrix, the whole arm universe rotates with it, along with your arm in it. The torso remains unaffected. When you rotate the torso matrix, it moves the arm with it, because the arm is relative to the torso. We build whole hierarchies of matrices, one relative to another, and build up a whole universe. You can draw the relationship like a tree. When a character is standing there and their head is moving around, their head matrix is changing, and then you can multiply the matrix against all the points that make up the triangles of the head, and now you know where in the universe the head polygons go, and their orientation, and everything. And matrices multiply against each other, too. You have one matrix at the top, typically your camera, and that's the center of the universe. And then you start multiplying from the top of the hierarchy down. So all the map geometry, all the model geometry, all the items, you multiply them from the top of the hierarchy down to the bottom, that's how everything gets placed in the universe. Something moves, and everything relative to it moves too, requiring some recomputation. To render your 3D space, the camera is a matrix that skews the universe, things further away are smaller, because the universe is actually geometrically smaller the further away it is! Then the matrix also collapses the Z axis, making this skewed projection flat. Because your screen is flat. So in the end, you have all this 3D geometry being transformed into 2D geometry. So now you have some light source. It typically boils down to a single point of light. It has color and intensity. You need to \"cast a ray\", which is a line with a starting point and a direction, and it goes on forever. You need one for every pixel on your screen. You point it outward into your universe - you cast it, and then do some math to find out what's the first physical thing in your universe it intersects. It's going to be a surface, and that surface is going to have a lot of information, like \"material\" properties, which are just color properties, and textures, which is more color for blending, plus all this normal data we talked about earlier. These days, every pixel of a texture has it's own normal. These normals work into the maths to decide just how that ray, is going to reflect off. There's also some maths behind if or how the ray splits, because the color on that surface you've first encountered is the sum of all the light that shines on it. But the sum of all the light that shines on it includes all the surfaces that are shining their light onto it. The color of my hands as I type this is more than just the sunlight, it's the air, the clouds, even the walls in my room which are illuminated by the sun, the light bouncing off my hands and into my eyes. So you need to trace rays from that first intersection outward to their next intersection, and outward again, and again, until all the rays find themselves back at a light source. You know how pool is a game of geometry and angles? That people bounce billiard balls off the walls and other billiard balls to score pockets? Same thing. The pool que is the initial ray cast, the first billiard ball is the first intersection, the bouncing and scoring in pockets are the last rays finally hitting light sources. Now that you know the paths the light took to get to your pixel, you can sum the colors and intensities and do all the blending to end up with the final color for that pixel. Now, for a 1920x1200 monitor, just do that 2,303,999 more times, 60-120 times a second.",
"Ray tracing uses math to trace linear \"rays\" out from the camera and off the surface of objects back to a light source to determine the color of pixels on a screen. It traces a line out until it hits an object, determines what direction light would be coming from to reflect back toward the camera, and follows that path, repeating until it finds where the light is coming from. This is a method that is a closer approximation of actual physics of light and vision, and can produce much more realistic images. However, this is more computationally complex, and we are only recently achieving the necessary technological advances and optimization techniques to make this practical to do in real time.",
"You have a dark room. In it is a tinted copper mirror 45 degrees to the left. You shine a thin beam of white light at it. You can see on the mirror where it hits, and the point on the left wall where it hits and now has a slightly different color due to having reflected off of the tinted copper. You just traced one ray. It wouldn't be too hard to program this, just one light source, simple angle of reflection, and accounting for the tint of the reflective surface affecting the light when it hits the second surface. It would be done on your computer pretty much instantly. Now make the scene more complex, say a car sitting in the room. And instead of one thin light beam, you have a normal light source, and you track that light source as millions of thin light beams going every direction from the light source, and you track their reflections off the car to the surrounding environment, and you track their reflections from the surrounding environment to the car. You can go further and track more reflections (floor to car to ceiling) and account for what percentage of light gets reflected off of each surface. If you trace your reflections pretty far out and do a high number of rays, this can look quite realistic. This takes intensive CPU work simply because the number of rays and reflections that has to be calculated is insanely high."
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n1mosa | why are certain site domains considered more reputable/credible than others? As in, why is a .gov or .org website safer to trust than a .com? Couldn’t a team of hackers manipulate info on those sites as well? Couldn’t those sites also be taken down? | Technology | explainlikeimfive | {
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"To my understanding, The US government has a large amount of control over the issuance of \".gov\" domains, since they only want those being used by actually governmental entities. .org/.net domains don't have any restrictions on issuance, despite their association with their intended meanings.",
"Because anyone can just buy a .com domain URL and put up whatever they want on the website. There are more specific requirements to get a .org or .gov website, so the average Joe can't just go and buy ' URL_0 ', so if a website ends in .gov, you know it's a government-owned website, not some random idiot named Joe posting whatever random thoughts pop into his head. Yes, hackers can hack government websites, but those websites also tend to have better security than random Joe's antivax website he just threw up in a day, so it's a lot less likely to happen.",
"You don’t need to be a hacker to put whatever you want on a .org. Those domains are not necessarily any more credible than a .com. Really all it means is that the owner of the site payed a bit more and put in more effort because they wanted to look more official. .gov sites are a bit different, but still upload many articles from people without any fact checking or credibility. My college English professor really hates that high school teacher teach that."
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n1sasi | Why can't compressed oxygen be transported to india on planes, only on roads and trains? | Technology | explainlikeimfive | {
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"Containers filled with oxygen are generally not transported on board aircrafts as they are considered combustible and may pose a risk to the planes. Oxygen behaves differently to nitrogen and other inert gases. It is very reactive. Even a small increase in the oxygen level in the air to 24% can create a dangerous situation. It becomes easier to start a fire, which will then burn hotter and more fiercely than in normal air.",
"Compressed oxygen is actually really dangerous as others have mentioned. I'm a nurse and get incredibly frustrated when I find O2 cannisters free standing...they need to be in proper storage racks. God forbid there comes a time one tips and hits the floor the wrong way, we'd be toast.",
"Liquid oxygen is actually quite heavy and airplanes is not able to carry as much weight as trains and boats. Not only is the oxygen quite heavy but it requires thick tanks and cooling equipment in order to transport it which is also quite heavy. And of course if something were to go wrong and the liquid oxygen were to spill out there are few ways of preventing the airplane from crashing.",
"Oxygen is dangerous and a leak of pure oxygen has the ability to light almost anything on fire. On a boat or a train that's alright, you have fire fighting equipment and nearby crews can come help you if it starts getting out of hand. On a plane, a fire is extremely dangerous because you can't stop what you're doing and fight it, you have to deal with it before it takes out control systems and you die, and a cargo full of compressed or liquid oxygen would quickly rupture the other vessels adding more oxygen making the fire bigger and its all out of control very quickly. Most cargo actually moves on passenger planes not dedicated freight planes, and because these tubes are packed full of people there are limits in what you can ship under them. Anything particularly risky (bulk lithium ion batteries or other flammable material) has to go on dedicated freight planes once you get over a certain relatively small amount, and if you want to ship a lot then you'd need to commission lots and lots of planes, or just reroute things from a more local supplier via train. A far far better solution than sending compressed oxygen via planes would be sending *oxygen generators* that can pull oxygen from the air and compress it into the canisters for use. These are bulky but non-flammable and can serve far more people for the same weight.",
"LOX (liquid oxygen) is VERY reactive, not just flammable, but corrosive. There is a reason why rockets using LOX only fuel up moments before launch. It can rapidly corrode many metals in addition to structurally weakening them. Just by way of example, take something ordinary like clothing, paper, charcoal, they will burn. But if liquid oxygen were to get spilled on them, they wouldn't burn, they would EXPLODE For that and many other reasons, you don't want it on a pressurized aircraft that can't safely vent it if there is a failure. But wait don't airliners have oxygen on board for passengers? They do but not in liquid form. They use oxygen concentrators which pull in outside air, compress it, pass it through a kind of filter membrane which pulls out most of the nitrogen (remember 'air' is mostly nitrogen) and what's left is concentrated oxygen gas and trace elements. This is where the oxygen in flight comes from. In case of fire or sudden loss of pressure, there are also chemical oxygen generators which very quickly 'burn' to release large quantities of oxygen to the breathing masks."
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n1u7i6 | after Michael Collins had dropped the others off and was orbiting the moon, how did Buzz and Neil get picked up again into Columbia? | Technology | explainlikeimfive | {
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"This was actually a serious problem and one of the main issues that the Gemini progarm was designed to test out. How can two spacecraft join up in orbit. It was actually such a dificult problem that they considered landing the entire spacecraft on the Moon, command module and everything. This would have required a much bigger rocket to be able to bring all the fuel required to the surface of the Moon and back again. Even the early Gemini program had huge issues with this as the astronauts had a hard time getting close to the target Agena rocket launched a day before their mission. Even the Russians had issues with this although they were able to get a bit closer then the Americans. It was actually Buzz Aldrin who cracked the problem. He was a decorated fighter pilot from the Korean War but had been rejected for the Astronaut corps. So he started studying at MIT and published his Sc.D. in astronauting on *Line-Of-Sight Guidance Techniques For Manned Orbital Rendezvous*. This was a revolutionary paper which translated the complex physical models of two spacecraft in orbit into simple terms that a pilot like himself could understand. This allowed the astronauts to do the quick calcualtions needed to find out where to fire their thrusters to get close to and eventually dock with another spacecraft. Buzz Aldrin was accepted as an astronaut and were able to fly on a Gemini mission himself where he again solved one of the biggest issues they had and performed the first fully successfull EVA thanks to his diving experience. The fact that he was the first man to land on the moon was a coincidence.",
"The Lunar Lander had a small rocket motor to lift it back into lunar orbit. The top part (crew module) of the lander separated from the bottom (lander) section, and flew up to meet the Command Module in orbit.",
"The Lunar Lander was actually two parts, a descent stage and an ascent module. The gold base with the legs on it had fuel tanks in it and several smaller rocket engines on it and was used to get them safely to the surface of the moon. The silvery capsule on top also had fuel tanks and rocket engines on it. The engine on this stage was used to get them off the surface and into orbit of the moon where they could meet up with the Command Module and transfer into it. When it was time to go and the orbiting Command Module was in a good spot for a meet up they'd disconnect from the descent stage and the legs, fire up the engines, and then dock with the Command Module in orbit Leaving the legs behind greatly reduced the mass they were trying to get into orbit, combined with the low gravity of the moon meant that it was possible to get back into orbit with a relatively small engine and limited amount of fuel. The legs of all the Lunar Landers are still on the moon today."
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n1v1t6 | Why are 3D printers not commonly used in large scale manufacturing? | Technology | explainlikeimfive | {
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"3D printers are great for making one of something. If you want to make 1,000 other methods such as injection molding are much faster options.",
"Too expensive. If you're going to mass produce say, happy meal toys, why do you need to use a printer that can print anything? You just need a way to make the toys. Its far cheaper to make something like an injection mold machine instead. Then if you want to make a different toy you just swap the mold plates out and go for it.",
"3D printers are great for prototyping because they're flexible, you can load your design in and have it printed by the morning which is pretty good for prototyping, but only getting one piece every few hours is garbage for large scale manufacturing. 3D printers are also expensive, your plastic prototype might cost you $20 in material which is better than $500 for a new plastic die, but *each* unit will cost you $20 so if you make more than about 25 it would have been better to pay for the die. Injection molding is orders of magnitude faster. A relatively small part that might take your 3D printer 20 minutes to print could instead be injection molded in under a minute in a die that produces 500 pieces all within that same minute. If you need to get 100,000 parts a day then you'd need a huge array of 3D printers or a single injection molder running for half a shift. Injection molders have dies that can be swapped out so you can use the same big honking machine and swap the dies to make other parts. 3D printers are good for high mix/low volume but cannot scale to high volume manufacturing. We already have equipment that is significantly better for low mix/high volume production of plastic and metal",
"Because the materials you can 3D print with are limited. And then cost of replacing existing manufacturing lines isnt worth what you might save using a 3D printer. Most 3D printers essentially work only with polymers (plastics) and cementitious materials (materials that start as a liquid but then set/harden) There are some that can print metal, but again not all metals since there are vastly different properties (melting temp being important) for each kind. 3D printing is helpful for making complex shapes, but we also have another technology that can do that, molding/injection molding. Could 3D printing start entering the manufacturing world moving forward? Yes absolutely I’m sure people will find applicable uses for it. But it isn’t wide spread now because it isn’t economic in most cases to replace existing manufacturing techniques."
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n207i4 | How does a DVD work? | Technology | explainlikeimfive | {
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"Imagine that you were trying to tell someone over the phone how to draw a picture. You'd have to describe what you wanted in detail, in a way that they'd understand. You would make instructions and the person on the other side would follow them. That's roughly how a DVD works. We've learned how to take a movie, a series of images and sounds, and create instructions so that the DVD player can create those images and sounds in the right order. It's like a file on a computer. The DVD is full of the files that the computer in the DVD player can understand and turn into a movie. The disc has tiny tiny little holes in it, and the laser in the DVD player shines over those holes and can tell when there's a hole and when there isn't. It's able to use the pattern of little holes and not holes, to read the instructions. It's like a code that the DVD player can understand."
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n21mu7 | How those anti-counterfeiting stickers work? | Isn't it true that everyone can create those stickers? I mean like these [ URL_0 ]( URL_0 ) | Technology | explainlikeimfive | {
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"These types of stickers is designed so that they are quite hard to make yourself. You can not just print them out on a printer but they need to be printed on a press with a very expensive type of die with specific microgroves in them to make the exact fine texture that gives it these effects when seen in different light conditions. So you either have to develop some sort of new technology or you need to spend hundreds of thousands of dollars on making such a die. However when you have that die you could print them out in the millions. This is why it is cheap for manufacturers to make these stickers but very expensive for forgers who only need to make a handful of them."
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n23fbi | .avi vs .mkv | I noticed recently that if I can just rename an .avi file to be .mkv instead it runs fine... can someone explain to me why this works and what the difference between .avi and .mkv is? Is it a bad idea to rename my .avi files to be .mkv? | Technology | explainlikeimfive | {
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"So... you have to understand that avi and mkv are _container_ files... and avi is a proprietary Microsoft standard while MKV is an open one (and its slightly more flexible). Basically every container file contains a video stream, along with one or more audio streams and sometimes other stuff (subtitles whatever). Each audio and video stream can be compressed using various codecs. You can have an avi that contains mpeg video with mp3 audio for example. You can also have an avi that contains h.256 video and mp4 audio. (its been a while since my A/V days so that may not be entirely accurate, but u get the general idea.) So whatever program you used to playback your not-really-an-mkv avi file probably looked inside the file, saw that it was really an avi and just assumed that's what you _meant_ it to be, saw that the audio and video streams were encoded using codecs it understood and just played it anyway. So you lucked out. Im not sure why - unless you have some form of OCD and all your files have to have matching extensions - you'd want to rename all your avi files as mkv, I'd suggest you just leave them all alone.",
"Since they’re encoded completely differently, you can’t just convert the files just by changing the extension. What is likely happening is that whatever program you’re using to open the files is just ID’ing the file type from its encoding and continuing to opening it as MKV. All changing the file extensions will do is cause other programs to take longer to open them and make other, less robust programs unable to do so.",
"It works for you because your player software is able to tell that your .MKV file is just an incorrectly named .AVI. Some players might not be able to play it. So yeah, it's a bad idea to rename .AVI to .MKV. As for the differences between the two... .AVI is an older format and is pretty limited in what it can do. .MKV supports multiple audio and video streams, supports VBR audio, supports very large filesizes, supports chapters, etc., etc., etc.",
".avi and .mkv is file extensions which indicates two different multimedia container formats. A container format is basically the structure of a file which usually contains multiple media streams and their relations. Usually you will find a video stream and an audio stream but often subtitle streams, chapter or scene markers, metadata or additional video or audio streams in the same file. This is why you need a container format to bind these together. The thing is that the file name extension, the three letter name at the end of the filename, is just part of the name. It does give your operatinsystem some hints on what to do when you open it but it have nothing to do with the content of the file. And most applications know better then to trust this extension when finding out what file format it is. Since most multimedia players can handle both AVI container format and MKV container format it will just look at the content of the file to see which one it is and just play it. This usually works for most files but there are some exceptions. A lot of times when someone creates a file format they reuse existing formats. For example text files, compressed archives, image files, XML files, etc. can often be reused to create new file types. However these can also be opened in other applications, it might not make much sense to them as they do not have the right context but they can open them. So when you for example rename a file from say a .pdf file to a .txt file then the operating system will think that it is a text file and open it in a text editor. The text editor will be able to open it since it is essentially text but it will not know how the typesetting works and will therefore just display the raw code instead of the intended document. But as long as you open the file with the right application and that application ignores the file name it should work just fine."
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n253w0 | why does a movie filmed in 24 fps look totally fine but a game running at 24 fps look awful? | Technology | explainlikeimfive | {
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"Partly it's the fact that you're accustomed to higher framerates in games than in movies, and in a lot of action games, those tiny fractions of a second really do matter. Probably the major reason, though, is motion blur. Video game rendering generally shows you a snapshot of a 3d world at a single, precise moment, whereas motion pictures shot on film, the film is being exposed for a *duration*, not a moment, and moving objects are blurred along the direction of motion. This helps to visually \"bridge the gap\" between one frame and the next. If you ever watch old movies which feature stop-motion animation or 'claymation', you'll see they have the same weird 'jerky' quality that you feel when playing a low-framerate game. It's for the same reason: the lack of motion blur.",
"Movies can be shot as a slower shutter speed, meaning each frame that contains movement has a slightly blurry effect that makes the slower frame rate appear smoother than it is. Video games produce sharper frames and need to be run at a higher frame rate to appear as smooth in movement."
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n2iyoc | how does an engine brake work? | Technology | explainlikeimfive | {
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"A normal diesel engine works by sucking in air, compressing it, adding fuel, which burns and expands - producing power, and then expelling the exhausts gases. If you stop adding fuel, it takes energy to compress the air, but you get 99% of that energy back when it expands again. Instead, after compressing the air, the valves open and release it, making a farting sounds. Now you've wasted all that energy, slowing the truck down.",
"An engine requires a lot of energy to run. There is a lot of resistance as the metal moves through the oil films and all the auxiliary services like water pumps, oil pumps and alternator use some energy. In addition when the engine is running it will move air from the intake, compress it and release it into the exhaust. This too requires a lot of energy not only to move the air but when you compress it the air heats up and gets cooled by the metal in the piston, cylinder and head. So the air pressure drops a tiny bit which means that it does not push the piston down with the same force that the piston used to compress the air. Engine braking works by putting the car in a low gear and release the throttle therefore cutting the fuel supply to the engine. The wheels then have to drive the engine instead of the other way around and the car will slow down due to all the energy required to run the engine. This is usually a preferred way to brake, especially for longer distances. Firstly there is a lot of mass in the engine so it does not change speed as fast. And because the braking force is dependent on the speed of the engine you do not get sudden changes in braking force which can make the car uncontrollable. Another advantage is that normal brakes have a very small area to get rid of its heat so they tend to heat up if you use them too much. However an engine have a huge radiator, fan and water cooling to prevent it from overheating. So it takes much longer for the engine to overheat then the brakes when going down a hill. Engine braking is often used by trucks to help them reduce their dependence on their regular brakes. In these trucks there is often valves in the air intake or exhaust to further convert the energy to heat and noise."
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n2jie0 | Why does 50% volume on video and music players not sound half as loud as 100% volume? | Usually if a video is too loud, 75% sounds almost the same as 100% and only at around 30% there is a noticeable difference in volume. | Technology | explainlikeimfive | {
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"Human hearing is complex. For something to be perceived as twice as loud, it needs to be 10 dB louder, which is 10x power. But to be 4x louder, it's 20 dB louder which is 100 times as much power. So it really depends how the player has implemented it's volume slider. If it does it linearly, i.e if you have it at 50% it just multiplies the audio signal by 0.5, then it's be way to sensitive at one end and not enough at the other. So the volume slider should probably be linear in dB.",
"Human hearing works on a logarithmic scale while usually the player volume bar is on a linear scale. In really simple terms, you have to use multiplication instead of addition. To put it in numerical terms with an example: \\- Start with volume at 10% and move to 20%. The value has been multiplied by 2. To increase the perceived volume further by the same amount, you have to multiply again. So the next step is 40%, then 80%. Working with your numbers, going from 100% to 50% doesn't halve the perceived volume but it reduces it by some amount. If you want to reduce it again by the same amount, you have to go from 50% to 25%, then 12.5% and so on. Since you are on a logarithmic scale and addition has been replaced by multiplication, it's hard to provide a meaningful definition of \"half as loud\". This is highly subjective and difficult to put in numbers."
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n2l5qi | How are video game AIs programmed? Is it a just a long series of "If Then" statements? Why are some AIs good and others terrible? | Technology | explainlikeimfive | {
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"While the other comments are true and most games do operate off shifting \"states\" and such, there's one more advanced technique that some games use called \"Goal-Oriented Action Planning\", or GOAP. In GOAP, AI consists of two things: things it wants to achieve (goals), and things it can do to change itself or the world around it (actions). An AI is given a set of goals (kill the player, stay alive, etc), and long lists of actions that it could do (move, shoot, reload, etc). The AI then decides which goals it should be going after, and calculates what actions it could be doing at any given time to satisfy as many goals as possible. For example, imagine that an AI soldier is hunting the player, who is somewhere on the other end of a warehouse. The AI's goals are (from highest to lowest priority): * Stay above 10% health * Kill the player * Keep the player in view * Avoid the player's line of sight * Keep its weapon loaded The AI's actions are (in no particular order): * Move to a specific spot * Shoot gun (kills the player, but only when gun is loaded and the player is visible) * Reload (keeps the gun loaded) * Jumpkick player (kills the player, but only when the player is visible and right nearby) * Use a medkit (gives health back) At first, the AI can't see the player. None of the actions it has at its disposal let it kill the player at that moment in time and it's not losing health, so it doesn't bother with those goals and instead tries to get the player into view. Once it sees the player, it realizes that the \"shoot gun\" action would let it kill the player, so it stops moving and starts shooting. If it runs out of ammo and the player isn't dead yet, then it can no longer shoot, so it stops trying to kill the player, moves somewhere to avoid the player's line of sight, and reloads. If the player takes the AI's health down to 10%, it remembers its highest priority, stops shooting, and uses a medkit. If the player gets too close while the AI's out of ammo, then it jumpkicks the player instead of reloading. Process repeats until the player is dead. The cool part is that the programmers don't have to code the nitty-gritty of any of this. All they have to do is decide the AI's list of goals, decide what each action requires and satisfies, and which actions each AI has. The AI then decides the rest on its own. What's more, you wouldn't have to change much to create a vastly-different enemy. For the example above, imagine that the \"Avoid line of sight\" goal was second on the list instead of fourth. Suddenly your brutish soldier AI is doing everything it can to lurk out of sight, only stopping to attack the player once the player has lost track of it. Whole new enemy, only one (1) line difference. If you want to read more, I recommend [this guy's website]( URL_0 ) and the papers he's written on it.",
"It is more or less just a string of priorities tied to set objective, yes. And It was in one of the Halo games that the difference in bad / good enemy AI is not based on any command strings, but the amount of time you need to deal with the enemy (i.e. larger health pool makes enemies look smarter).",
"An absolute base AI could be made from if-then-else statements but to have AI people consider good there's many systems layered on top of that to give a little more realism, things like having a \"state\" like relaxed or alert and shifting priorities and decisions by shifting states etc., and can include even things like altering the breadth and depth of vision cones so an actively alert enemy will be paying more attention as well as looking at spots identified as a hiding place instead of just doing a back and forth patrol etc. There's a YouTube channel called AI And Games that does a lot of exploring on AI in regards to videogames specifically as well as mapping out the specific ways specific games do their thing."
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