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In movies/tv they say there are always a percentage of people who are naturally immune to new diseases, is this true and are there people naturally immune to COVID-19 specifically?
I'm watching The Last Ship right now (lol), and i realized while they're discussing the Immune, we've not really heard anything about any people being naturally immune to COVID-19. why? is that not a real thing?
Very few people are going to be spontaneously immune, in the formal sense of "immunity", to a novel pathogen. What can happen is that people can be genetically resistant to infection or disease caused by a new pathogen, due to random or not-so-random mutations and variations. The classic example is CCR5 deletion -- CCR5 is a receptor for HIV, and people with a particular mutation in CCR5 are highly resistant to HIV ( Genetics of resistance to HIV infection: Role of co-receptors and co-receptor ligands ). (Someone is about to jump in and claim this was a mutation in response to the Black Plague. Nope; that was never more than a wild idea with no evidence that someone threw out in the Discussion section, and there are multiple lines of evidence against it.) Does such a thing occur with COVID? We don't know. One of the ways such genes are identified is through genome-wide association studies (GWAS), and several of those have been conducted with COVID, but so far as I know no slam-dunk powerful resistance loci have been identified. A number of loci have been linked to relative resistance to severe COVID, but none of them are very clear or convincing links. (This is typical of GWAS -- I think the early hopes that GWAS would quickly identify genes very important for infection, or other disease associations, have pretty much faded, and it's generally accepted that most loci identified this way tend to be relatively weak and more important as cumulative contributors.) Someone lacking the ACE2 receptor for SARS-CoV-2 would probably be very resistant to COVID, but ACE2 is an important receptor for many important functions, and people lacking ACE2 would probably be severely affected. There may well be other genes that are important for SARS-CoV-2 infection or replication, and there may be people who have variants in such genes and are therefore resistant, but we don't know of them yet. Further reading: Why Do Some People Develop Serious COVID-19 Disease After Infection, While Others Only Exhibit Mild Symptoms? |
Why is it possible to ground an electrical device by connecting it to the Éarth?
Where does the electrical energy and charge go? Is it possible for the Earth to become saturated at some point in the future?
Remember that net charge is always conserved so to charge the earth you would have to either remove a lot of its electrons and shoot them off into space, or get a whole bunch from space and shoot them into the ground. In addition to this, even if you did manage to change the net charge of the Earth, there is a constant supply of charged particles in solar wind that would return it to neutral. (e.g. if the Earth had a net positive charge, it would attract negative particles and even out). |
What would the proposed DC-AC-DC converters do for the U.S. national power grid?
If they're there to regulate flow from one side of the country to the other, why use these converters and not something else? Thanks!
They aren't there so much to regulate power flow as they are to allow for different chunks of the grid to run asynchronously. Each colored block you see there is a proposed region with a constant phase and frequency. Technically, this means that if you plot a voltage somewhere in one section the transmission system of a colored portion of the grid, and plot the voltage somewhere else in the transmission system of the same colored portion of the grid, they should be more or less the same wave (neglecting small power factor differences and magnitudes). In practice, this means a whole lot of communication must take place between transmission companies, generation companies, distributors, and a whole lot else. If you make the "interface" point between the grids a DC connection, you have no frequency or phase to worry about. The disadvantage is costs and efficiency losses. |
Are film clips still "moving pictures" when recorded and stored digitally, or does the recording of a digital video work differently from analogue recording?
I put computing as flair, but I'm honestly not sure in which category this belongs. Feel free to mark it with more appropriate flair, admins.
The basis of digital video formats is still a sequence of still images, just like analogue film. However, for efficiency purposes, various optimizations are made, because storing a full resolution still image for every single frame would require a large amount of storage space (and a large amount of bandwidth to transfer). The main way that digital video optimizes storage requirements is by not storing each frame as a full still image. Instead, a frame will only contain the differences between that frame and the previous. For most video clips large parts of the scene remain unchanged between two consecutive frames, which allows the next frame to be constructed using a relatively small amount of data. In order to facilitate actions like forwarding and rewinding through a video, a "key frame" is inserted at regular intervals. Key frames contain the full image rather than only the differences between two frames. That way it's possible to start playback at a different point than the start of the video without having to first reconstruct the entire set of frames leading up to the selected starting point. There are various techniques that further optimize the tradeoff between storage, quality and processing power needed, but the basic idea remains the same: Just like with analogue video, digital video still consists of individual frames that are recorded, stored and played sequentially. |
Do plants ever feel "full" if they absorb enough sunlight?
For humans, we have hormones that tell us we feel full when we eat enough food. Do plants have a similar system that tells them when they absorb enough sunlight? What do they do with the excess energy they absorb?
Roughly speaking, photosynthesis turns carbon dioxide + water + light into sugar + oxygen. The sugar production is not evenly distributed through the plant, so the plant must transport sugar from where it is produced to where it is consumed. It has things called phloems (like blood vessels) to do this. There does not seem to evidence of a satiety mechanism like humans have, which (probably) means the entire process in the plant is mediated by availability of inputs and products from a long chain of chemical reactions. So, simply put, if the plant does not have enough tissue to consume produced sugars, it will eventually get "backed up", and prevent the formation of further sugar (for example, the concentration of sugar may be too high for it to be moved from the phloem to the tissues, leading to the concentration being too high in the phloem to move it into the phloem, and excess sugar at the site of production will prevent the chemical reaction from producing more). As an analogy, it's like how you never feel "full" or "hungry" for vitamin B12. If you can't produce it for some reason you'll have problems, but your body will not make you hungry for it, or stop you from eating when you already have enough. There is some separate process within the plant that does long-term storage of the sugar by converting it into starch. It seems the details of that process are not entirely understood yet, despite how it is what fundamentally supports human agriculture. Sources: [1] https://askabiologist.asu.edu/moving-sugars-plants [2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4919380/ [3] https://en.wikipedia.org/wiki/Photosynthesis |
How do computers know which wireless signals are meant for them?
Additionally, how do they know which signals the individual signal fragments belong to? With all the information being sent wirelessly across the globe, it seems like it'd be extremely difficult to know what constitutes any individual signal as opposed to fragments of other messages. How on earth do our computers manage to know exactly what messages are meant for them and the exact content of those messages with all the "noise" they're surrounded by?
Messages which are carried through networks contain meta data as well as payload. The payload might be part of a web page or image. The meta data would be addressing information (sending and receiving IP addresses), and sequence numbers which identify that message (or packet) as a part of a stream. The reieving node looks at the IP address (and MAC address, which is used on ethernet networks) to check that the recipient is correct. It then reassembles the complete message and passes it to the application layer. |
What is the relation between photons and electromagnetic fields?
Photons are the of the electromagnetic field. This means that electromagnetic fields come in discrete 'chunks' called photons. But this is a quantum-mechanical description, not a classical one, so you shouldn't think of photons as particles with definite properties--the photons act like waves, too, just as the EM field did, it's only that they come in discrete chunks of energy instead of continuously variable energies. |
Does water have a limit to how much soluble matter it can dissolve? If so, how is this measured?
Fellow coffee lover here! But definitely not sophisticated enough to be a snob- I just consume large quantities of it. :3 This is actually a very complex question because coffee is not a uniform substance. It contains thousands of different chemical compounds, each with its own unique properties and varying solubilities. Different compounds will be saturated before others, some compounds are more soluble than others, some are present in greater concentration to begin with, some are desirable and others are not. For example, some less desirable compounds dissolve more readily than more desirable ones. This is the main reason that brewing method and time can make such a difference in flavor, and why it usually tastes worse when you make a tiny amount rather than a decent sized batch (higher proportion of "yucky" compounds than "yummy" ones due to variable solubility). Some of the compounds important for flavor are actually non-polar (don't dissolve well in water but instead in fat), which is why coffee strains with higher fat content are linked with better flavor. And the proportions of different compounds present differ depending on which variety of coffee you're drinking and how it was prepared/roasted. What it all comes down to is that unfortunately there is no set way to determine X amount of coffee will saturate Y amount of water. I think the best you can do under the circumstances is to experiment! Maintain the same amount of water, temperature, grind, brew method and time that you normally use, but vary the amount of coffee. Start with a smaller amount than usual and gradually increase the amount of coffee. At a certain point, it will not be stronger/taste better than the one before. That's when you'll know the one you made before is the right/maximum amount you want to use. By the way if you'd like to learn more about the science of coffee you might find this interesting. |
Apart from AIDS, is there any other syndrome/disease the HIV causes? Or is it only AIDS?
A short time after initial infection, many people experience a brief flu-like illness. After this subsides the virus becomes latent for a period of up to a number of years before causing immune deficiency. The virus also can cause neurocognitive changes independently of opportunistic infection, ranging from mild thinking and memory problems to dementia. |
If i let a bottle of let's say vodka sit for a while, will the alcohol rise to the top of the bottle?
Since alcohol has a lower density than water? Additionally, if i freeze the liquid, could i then cut a piece of the top, which would then contain more alcohol than the average of the overall bottle at a specific abs.vol (40%)?
Ethanol has a lower density than water, so if the two didn't mix, you'd have ethanol on the top. Ethanol and water are fully miscible however, so you don't get a concentration of ethanol on the top. The two liquids act as one and don't retain the density properties of the original liquids. Vodka also doesn't typically freeze in a standard freezer. For alcoholic beverages that do, like wine and beer, the part that starts freezing will indeed have a lower alcohol content. Fun facts from my freezer: freezing wine tends to precipitate the tartaric acid. Freezing vodka makes for good cocktails and requires no defrosting. ETA: The idea that two liquids mix into something with new properties is also why volumes aren't additive (100 mL of water + 100 mL of EtOH does not equal 200 mL of mixture) and why the freezing point depresses but not to the point that only water freezes, leaving pure alcohol behind. |
So our brains release dopamine when we listen to moving music, but why?
What's the point of that? how did it come about?
The first step in answering the "why" questions is to look at any evolutionary benefits it might have had - if any activity is evolutionarily beneficial, the body will want to promote it, and one way to do so is to have it be pleasurable so that the individual and eventually the species at large engages in said activity more. There are different takes on the role of music in evolution, Steven Pinker famously claims it's just "auditory cheesecake" and any pleasure we derive from it is a side effect of the development of language. Others have suggested various potential benefits that could have resulted in music being promoted by pleasure circuits in the brain, such as promoting mother-infant bonding, courtship and/or group bonding and synchronization (Daniel Levitin's book "The World in Six Songs" may be a good read if you're interested in that). I'm on mobile right now and can't provide a huge array of sources, but this is a decent in-depth take on different accounts on music, mind and evolution - http://www.mus.cam.ac.uk/~ic108/MMS/ . |
How much is too much coffee?
TIL I'd have to drink about 174 cups of coffee in short succession to die. Thank goodness my 5ish cups a day comes no where near that number! |
How are you supposed to picture complex wave functions?
intro quantum mechanics.
It's not easy when you have a wavefunction that depends on three spatial coordinates and time, and it's complex-valued. But there are little tricks you can use. For example you can often decouple the radial and angular parts of the energy eigenstates. The angular parts are usually just given by the spherical harmonics, which give you those probability density diagrams you often see in chemistry textbooks. Then the radial part just becomes a function of one variable. You can often choose a convention that the radial wavefunctions are all real-valued as well. So now you just have a real-valued function of a single variable. You can plot this very easily. Another way to avoid all of this is to simply plot probability densities. Probability densities are just the squared moduli of wavefunctions, and these are always real-valued. You still have the problem that they depend on three coordinates, but you can plot projections onto 2D planes, or surfaces of constant probability density, something like that. |
Is it possible to have red lightning?
if so how or why does this work?
Might be a camera artifact, color-balance issues. Perhaps it shows up in a photo, but nobody saw any red color during the lightning strike. Odd colors are associated with lightning inside ash clouds. |
Would you still be able to donate your organs if you've gone though chemo therapy?
In practice, the answer is no - but it's not because of the chemo, it's because of the cancer you presumably had which the chemo was treating. If you for some reason received chemotherapy but did not have cancer, I'm not sure if the chemo on its own would preclude organ donation. |
A time travel/astronomy question: could I look at the stars and tell the date at any time in the past?
Let's say my time machine has malfunctioned and I know where I am, but not when. What can I do to determine my location within time?
With careful measurements of the positions of the stars and moons you could work out a range of time in which you found yourself. You could narrow it down further by quizzing locals about comet sightings (assuming after building a time machine you also built a cochlear implant to translate language to understand extinct languages and dialects.) You might be able to get the same estimate of temporal location by observing the species that are alive (or not yet evolved). |
Does lightning make a sound when it strikes small bodies of water?
such as lakes, or Tampa Bay?
Yes. Pretty much all of the sound comes from the air the lightning goes through, not from the target itself. By far most lightning goes only through the storm cloud itself and we can hear these aswell. Only reason they do not seem as loud is because they are further away than if lightning strikes near you. |
Why is it when i dry clothes in a dryer they're soft and fluffy, but air dried in a heated bathroom they come out crispy?
My dryer is broken so I've been hanging up some clothes and it's been bugging me.
The answer for this is simpler than you'd expect. When you dry them on a rack inside your house, they stay in virtually the same position for the entire drying period. The clothes kind of 'set' in the position that they're in. When using a dryer, clothes are tumbled around throughout the cycle and don't have a chance to 'set' as in the above scenario. Thus they lack stiffness. You should notice that when putting them on a line say outside, the stiffness will depend heavily on the amount of wind. They'll be stiffer if there's no wind, and a bit softer if it's windy out! You can always make sure to use a bit of fabric softener in your laundry to make them softer, although keep in mind some materials and clothes strongly discourage the use of softener. |
Has an industrial accident ever caused volcanic lightning?
If not, what would it require? Would it be possible?
Volcanic eruptions typically involve quantities of energy and matter that are very large by human standards. (It would have to be a of an industrial accident to be in the same ballpark.) But something that might be of interest are pyrocumulonimbus (pyroCb) clouds that can result from forest fires, and can produce lightning. -
http://news.nationalgeographic.com/news/2010/08/100816-fires-thunderstorms-thunder-clouds-volcanoes-science-weather-russia/ - https://en.wikipedia.org/wiki/Pyrocumulonimbus_cloud Human activity can cause forest fires, so under the right conditions human-produced clouds can cause lightning. |
How to classify and differentiate of sub-species and breeds.
Hi simple question How do we classify and differentiate if its a sub-species or a breed of something? There are times when a subspecies look alot like the other, but breeds can appear to look very different. (e.g Borneo Pygmy Elephant to Asiatic Elephants = subspecies, Toy poodle to Huskies = Dog Breed) Please provide academic link, google is only giving me forum links. Thanks
A major distinction is that the term "breed" is really only used in animal husbandry and not in taxonomy (classification of species) or in biology. The problem with breeds is that they are often based on shifting sets of physical characteristics both in time and in space. One kennel club may describe a breed a certain way, and another in a different way. Moreover these descriptions often change over time. Describing domestic animals using breeds does not clearly reflect what is actually going on from a natural selection (or artificial selection) perspective. A breed is a specific group of domestic animals or plants having homogeneous appearance, homogeneous behavior, and other characteristics that distinguish it from other animals or plants of the same species and that were arrived at through selective breeding. Despite the centrality of the idea of "breeds" to animal husbandry, no scientifically accepted definition of the term exists. A breed is therefore not an objective or biologically verifiable classification but is instead a term of art amongst groups of breeders who share a consensus around what qualities make some members of a given species members of a nameable subset." Whereas subspecies are typically a more valid classification scheme which take into consideration many different factors. Factors such as: genetics, time since divergence, morphological and behavioural differences, degree of gene flow between populations etc. But before I get into how we classify subspecies it would be best to consider the species classification first. The most popular definition for a species is the "the biological species concept" -- basically a "species" is defined as a population of organisms that are able to reproduce with each other. If two populations can't interbreed, they are two different species. This is typically used for sexually breeding animals, and is not usually applied to other lifeforms, like bacteria, which reproduce asexually. So for the purposes of your question I will simplify my response and concentrate on animals and how we classify one species from another. When a single population of organisms diverges into two separate populations to the point that they can no longer interbreed, then you would say that you have the emergence of a new species. At this point, the two populations are forever separated, and they may follow very different evolutionary paths. As long as two populations can interbreed, there will be some amount of "gene flow" between the populations, and they will never be able to adapt to very different ecological niches. There are many ways for populations to speciate : allopatric, peripatric, parapatric, and sympatric (see the article for details). Usually there is some starting mechanism that begins to pull two populations apart. We can look a many barriers to gene flow external and internal (I can go over these in more detail if you like). Of course populations may be in the process of speciating, it does not happen over night and it can even take a few million years...if it happens at all. This complicates trying to classify populations into one species or another. Some times it is very obvious, like a leatherback turtle and a crow. Other times it is more subtle like humans and Neanderthals, or amur tigers and south-china tigers. Often when we try and classify populations that are speciating we may call them "subspecies". Some factors which may be considered for classifying populations into the "subspecies" catergory: They are in the process of speciation but have not fully speciated yet. Two populations of a species living in two different areas where gene flow between them is very very low, or becoming non-exsistant. It is obvious that sexual and behavioural barriers to reproduction are being produced. That hybrids between the two populations are have less-vigour, not suited to their environment and/or are dying. Genetics will be done on the populations to determine the amount of gene-flow, time since divergence etc. We may also consider human disturbance, in that the population may have been continuous at one point in the not so distant past, but due to hunting or habitat destruction isolated populations have been created. Limited gene flow between these newly isolated populations may lead to speciation. There may also be a human a goal involved in classifying subspecies. From a conservation perspective it is better to split a species up into subspecies because subspecies populations tend to be smaller and more threatened than if all the populations were considered together. When population numbers are low and isolated it is easier to get funding, or to get support to save some track of land. This is not just some "scheme" in the malevolent sense of the word, it makes a lot of sense biologically. Some populations of species are indeed very isolated from other populations to such a degree that they can no longer interbreed. If these isolated populations were not protected they would go extinct, and while the species would remain alive a key component of its genetic diversity would be lost forever. In order to do this, subspecies classification can make all the difference in terms of funding. To give a real example with hypothetical numbers we can consider the tiger. On the whole there may be many tigers in the wild (say 100,000). But these tigers do not all live in the same place, moreover these places are quite isolated from one another. So that a tiger in Russia is not likely to every interbreed with a tiger from India. So by classifying subspecies based on gene flow (i.e. population lines are drawn where gene flow stops) we get a better sense for how tigers really are doing - in that the population in India has 10,000 tigers but the population in Russia has 80. When we consider this, the Russian subspecies is much more threatened then the Indian subspecies. Thus the Russian subspecies likely to receive more funding when it is considered separately from the whole population (i.e. 100,000 tigers) "Breed" is used in animal husbandry, "Subspecies" is used in taxonomy and biology - they are applied differently and the criteria used to distinguish breeds and subspecies are very different. |
Is photosynthesis more efficient than combustion of oil?
Hey askscience, could you guys help me determine if plant photosynthesis is more efficient at energy production than other forms we are using for energy (combusting oil, moving water, decaying radioactive elements)? What does photosynthesis do, that we can't mimic or utilize the process? Thanks! Edit: grammar
I'll let somebody else tackle the comparison to petroleum-- but compared to currently-available photovoltaics (6-40% efficiency, with common panels around 15%), photosynthesis is not very efficient at all. (0.1%-8%, with most plants around 0.1% and most crops around 1.5%). Put another way, generic off-the-shelf consumer solar panels are about 10 times as efficient as crops, which are themselves about 10x as efficient as normal plants. |
Do black holes really have infinite density? (And other questions about black holes)
: I've heard black holes described as having infinite density a bunch of times. Density=Mass/Volume, and black holes definitely have a non-infinite mass (otherwise its gravity would be infinitely attractive). If density is infinite and mass is not, the volume of the black hole would have to be infinitely small, right? : Now, to my understanding, black holes can be formed when a big enough star runs out of fuel. (Are there any other ways to form black holes?). Stars need to have some sort of fusion reaction going on in its center in order to counteract the massive force of gravity, and when fuel for this reaction runs out, the force of gravity overcomes the (pauli exclusion forces? is there some kind of name for this force?). The star then collapses in on itself. But how does this make for a black hole with infinite density? Wouldn't all the matter in the star occupy the space of a single neutron? How can the black hole get smaller than that? Thanks :D
neutron degeneracy pressure is actually only minimally responsible in supporting a neutron star from collapse. At densities greater than the nuclear saturation density (~ density of an atomic nucleus), the strong force actually becomes trying to restore the nucleons back to a nuclear equilibrium. In fact, if you model a neutron star without considering strong force interactions, you'd come up with a maximum possible mass of just ~0.7 solar masses, while most neutron stars are at least twice as massive. If you want lots more detail on this subject, check out , Norman Glendenning, 2nd Ed., 2000. Ch.4 has a good overview to nuclear field theory, for someone with a background in undergrad physics. but of course, i'm just a lowly first year grad student, maybe you have some more insight on this subject? |
Did the early universe have an event horizon and behave as a black hole?
I was watching a lecture about calculating the Schwarzschild radius/event horizon for a black hole, and I wondered what the Schwarzschild radius of something with the mass of the observable universe would be so I ran the numbers on it using an estimate for the mass of the universe from . Where r = 2GM/c r = [(2)(6.67E-11)(3E+52)]/8.99E+16 r = 4.45E+25m = 4.7 billion light years If all of the observable matter in the universe existed within a radius of less than 4.7 billion light years, which it must have during the inflation of space-time, would that not mean that it would have qualified as a black hole? Would it only have appeared as one to an outside observer, but because the density inside the radius would have been so much lower, would it not have appeared as one to a contained observer? And what would have happened after inflation drove the matter outside of its own Schwarzschild radius? Or have I just gone horribly wrong in my math somewhere?
The equation r = 2GM/c is really only valid for a system that can be reasonably approximated by a point mass at the center of the coordinate system and very little mass outside. When you have such a setup of a large concentrated mass one can solve the Einstein Field Equations to get the Schwarzschild metric which explains the curvature of spacetime and hence gravitational influence of the large mass at the center. The observable universe is better approximated as a roughly homogenous concentration of mass everywhere in space - even near the beginning when there was far less space!. This setup leads to a different solution of the Einstein Equations called the Friedmann–Lemaître–Robertson–Walker metric . This solution is often referred to as the "Standard Model" of cosmology and from it one can look at the curvature and expansion of the Universe as a whole. |
How do you calculate the limits of functions using the exponential one?
Something has been bugging me for a while. Let's say there's a function such as . How would you get the limits when x reaches infinity? It sounds impossible to me. Moreover, how did we find out about the way to solve this problem (if we ever did)?
You can use L'Hopital's Rule . If you write g(x)=x and h(x)=e , then f(x)=g(x)/h(x) and the limit of g(x) at infinity is infinity, and the limit of h(x) at infinity is also infinity. It then looks like the limit of f(x) at infinity should be infinity/infinity, but since this is undefined, we can't break up the limit like that. L'Hopital's rule says that the limit of f(x) will equal the limit of g'(x)/h'(x)=1/e and the limit will be 0. |
I think randomness doesn't actually exist, but is only used to fill in gaps of understanding. My colleagues think I'm being ridiculous. What are your thoughts?
Let me explain what I mean first. I am a scientist and always come across statistics used to explain phenomena as best we can, but are ultimately deemed "random" usually because they have far too many nonlinear factors involved in any possible explanation. An example would be quantum physics where we cannot determine where an electron might be at any one time. However, I find randomness to be a stopgap only. While events may "randomly" occur in the view of current scientific understanding, this does not mean the system follows laws of randomness, whatever those might be. Instead, there are laws governing why that electron might be in one location versus another, but we lack the necessary tools to prove that scientifically. Overall, I believe that there is only a "perceived randomness" that we use as a tool to approximate the behavior of the system, no different than when we use finite difference methods to solve numerical simulations. We know that the output of a simulation is only approximate, but we can gain insight from using the output. I feel we should use the same approach towards "randomness" where it is only a tool of understanding and not necessarily a final classification of the behavior of a system since statistics is only a tool we use to gain insight into complex systems, and not a definitive solution. Does any one else think along these same lines? If not, please feel free to explain why. I'm always open to learning new things that I have not considered when it comes to what I believe. Edit: Thanks everyone for responding. I'm glad there are still places on Reddit to have logical, serious discussions, instead of just mindless bashing. I'm learning a lot from each of you! Thank you!
The first thing that came to my mind to address your question was something that I learned from some of the physics panelists' posts: Bell's theorem , which seems to refute what you've suggested. |
When marine mammals have open cuts or wounds does the salt water sting for them?
I asked this in last night and got no answers so I decided to put it up here; I don't think I broke any rules...
Yes, almost certainly. But they are to a degree desensitised to it after a life of living and getting injured in salt water. It’s difficult to measure long term discomfort from a wound in marine mammals because, as with most animals, they ignore the pain and just get on with things. But yes, there is no reason why open wounds wouldn’t sting in the salt water for a while. |
How does the stomach let through food and water, but not the acid?
The stomach doesn’t hold the acid back. First, the stomach makes a small amount of acid when you aren’t eating. When you do eat the acid production increases. However, it gets diluted buy the food/liquids you ingest along with your saliva and mucus. Second, your body neutralizes the acid as fast as possible once it hits the small intestine by secretions from the pancreas and liver. This is partially necessary because the enzymes that you use to digest food are destroyed or don’t work in an acid environment. Third, despite all these mechanisms the acid environment is still quite high in the first part of the small intestine (duodenal bulb) and this is a common place to get ulcers. The intestinal tract is actually very complex and amazing. The diseases of the intestinal tracts are also very diverse and complex. This is why I love being a gastroenterologist so much. |
Is it possible to not "see" a tangible object?
Hallucinations are defined as "an experience involving the perception of something not present", so I was wondering if it were possible for a human to not "register" something that is physically present?
It is absolutely possible. Attention gates our consciousness of visual phenomena - if our attention is directed elsewhere, our conscious mind often misses things. For demonstrations, check out this selective attention experiment and this change blindness experiment . |
What does string theory does differently that current theories do not when dealing with singularities?
From what I gather, in string theory we naturally unify QFT and GR, so does it solve the problems that we encounter at a singularity? If so, what explanation does it offer when particles are broken down to their fundamental bits inside a black hole. Please shed light on how our understanding of black holes, and singularities would further if string theory is indeed true?
In string theory, black holes are actually p-branes. Normal particles are instead strings. When the strings are very close to the brane, it becomes possible for them to interact in a way that leads to no infinities. The interaction is the result of the contribution of all possible histories (as it's normal in a quantum mechanical theory) which can involve strings splitting or joining, string endpoints getting attached to the brane or detaching, some other things and all combination of this building blocks. The outcome is always finite because outcomes in string theory always are. To give an intuition, the "regulator" that prevents the singularity from being truly singular is the finite size of strings which cuts the divergences short - intuitively the string cannot see things smaller than the string length. Instead a particle theory (such as local quantum field theories like the standard model) has point particles and will lead to infinities when placed near a singularity. |
When I'm scuba-diving, I'm breathing pressurized air. Why don't breaths last longer when I'm deeper ? Don't they contain more oxygen ?
The urge to breathe is controlled by rising levels of carbon dioxide, not falling levels of oxygen. This is why you can pass out if you hyperventilate - you're lowering the CO2 levels to such a low level that you can run out of oxygen before you feel the need to breathe. So while it's true that more oxygen molecules are entering your lungs, you are still producing and needing to get rid of carbon dioxide. I am not a doctor, but I do know quite a bit about diving physiology. |
Why doesn’t diesel have different grade levels at gas stations like gasoline?
Gasoline engines compress a mixture of vaporized gasoline and air, and ignite that mixture with a spark plug in an explosion that pushes the piston back down. Now, compressing a gas heats it. That can lead to the mixture detonating prematurely, before the piston has reached the top, in which case explosion will try to push the piston back down in the wrong direction. That's called engine 'knocking'. Obviously that's not helping you move forward, at best, and can destroy the engine at worst. What the octane number measures, is how much compression the gasoline can handle before it causes knocking. (relative a kind of fictional mixture of octane, hence the name. It's a weird unit) Higher compression ratios means a more efficient engine, but not all engines can handle it. (so you can use high-octane fuel in a "low-octane" engine but not vice-versa) Diesel engines don't work the same way. As many know, diesel fuel is much less volatile. It doesn't need to be volatile, because the fuel is not vaporized before going into a diesel engine cylinder. A diesel compresses the air and then injects an aerosol of tiny fuel droplets, which then combust from the compression heat (no spark plug needed), so you don't have the issue of knocking in the same way. Diesel engines can knock, but then it is caused by the fuel igniting too long after injection. |
Why is ADD and ADHD so common now?
I have read it affects somewhere from 5-9% of the population. I myself have ADHD, and have been prescribed Ritalin. However, my diagnosis wasn't based on cognitive ability/other factors, but rather on questions such as "Do you feel so and so when you do so and so?". Is it just overdiagnosed, it is because of television and the internet, or what? Also, is there any way to cure AD(H)D? Edit: Wow, this question got more attention than I thought it would O__O. Don't bother answering the second question if you're going to contribute. Also, could anyone explain the causes behind ADD/ADHD?
[Master's in Clinical Psychology, working towards Doctorate] Go, go, EBSCOHost! QUESTION 1 Sciutto, M. J., & Eisenberg, M. (2007). Evaluating the evidence for and against the overdiagnosis of ADHD. Journal of Attention Disorders, 11(2), 106-113. doi:10.1177/1087054707300094 LeFever, G. B., Arcona, A. P., & Antonuccio, D. O. (2003). ADHD among American Schoolchildren: Evidence of Overdiagnosis and Overuse of Medication. The Scientific Review of Mental Health Practice: Objective Investigations of Controversial and Unorthodox Claims in Clinical Psychology, Psychiatry, and Social Work, 2(1), 49-60. Retrieved from EBSCOhost. Chilakamarri, J. K., Filkowski, M. M., & Ghaemi, S. (2011). Misdiagnosis of bipolar disorder in children and adolescents: A comparison with ADHD and major depressive disorder. Annals of Clinical Psychiatry, 23(1), 25-29. Retrieved from EBSCOhost. QUESTION 2 No, there is no cure. Symptoms can be most effectively managed with a combination of psychotherapy and psychiatric medication. |
Why aren't quadricopters more common in full-scale?
As common as quadricopters seem to be for drones, why haven't we seen a larger adoption of that format in full-scale? The advantages of the platform (easy to fly, stable, maneuverability) would seem to be applicable to some roles that helicopters or airplanes serve now. Is there an inherit disadvantage to the 4 rotor setup in large scale, or do the advantages just not outweigh the drawbacks for most usage?
Quadcopters are great in the hobby scale since they are incredibly maneuverable and can be relatively inexpensive. The maneuverability does not scale up. Just as the surface area to volume ratio of a cube will drop as the cube gets bigger, the ratio of rolling/pitching/yawing power to moment of inertia goes down as well. Also, the weight tends to scale up with length , while lift tends to scale with length . This makes larger quad copters less maneuverable than their tiny counterparts, and explains why a lot of the leading work on quad copters is done with very tiny ones—they have the best maneuverability. As for cost, a lot of that comes from the fact that you can use brushless DC motors directly driving rigid propellers, then vary the speed of the motors for maneuverability. By contrast, a conventional helicopter has to change the pitch of its blades as they sweep out each arc of rotation. The latter configuration is fairly expensive to create for a hobby craft (although there are certainly RC conventional helicopters with that kind of mechanism; I should note that the cheap tiny RC helicopters are using something similar, but it's passively controlled by a weighted bar instead of by pilot input). When you scale up to full-sized aircraft you're going to be spending a lot on the rotors anyway, so it can be cheaper to use one complicated rotor instead of four rigid ones. |
What are physicists' best ideas for solving the proton radius puzzle?
When you measure the proton radius by firing electrons at it, you get a different value than if by firing muons. Currently, this is unexplained by the standard model and there is no widely accepted explanation as to why this should happen. Despite this, what believable interpretations have physicists postulated since?
Yes, I beleive its about 5%, but the quoted ucertainties from the relevant measurements are ~1%, perhaps less. In otherwards the discrepancy of about 5% is significantly larger than the variation one would normally expect to see given the stated precision of the measurements. |
Why do sockeye salmon rot, while still alive, during their trip upriver to spawn?
I'm watching an episode of Monster Fish, and they briefly touched on it, but didn't really give any explanation for it. Just that the salmon "undergo a dramatic change" during their trip upriver, and the flesh literally rots off of them by the time they're done. Why does this happen? And does it provide some kind of an evolutionary advantage?
Pacific Salmon go on a one way trip to spawn. Once they start upstream they stop eating, but still need large amounts of energy to get up those turbulent cataracts. That energy has to come from somewhere, so their bodies strip off the body fat and starts to eat itself from within to supply the body with nutrients to complete the swim and spawning. Then, body spent, they die and add nutrients to the stream ecosystem, and bears. The advantage is that it gives them enough energy to get to the safe spawning zones so they can spawn wee baby salmon, once theyve done that they have no further use. |
How can we experience such seemingly long dream sequences if REM Sleep cycles only last 10-15 minutes?
I may be wrong, but it's my understanding that there is REM sleep during which dreaming occurs which lasts about 10-15 minutes, then we go through Stages 1-4 then 4-1 of the sleep cycle before we get back to REM sleep. Furthermore, we very rarely can recall our dreams unless we are woken up during REM sleep. I'm perhaps incorrectly presupposing that dream sequences are not continuous and related from one period of REM sleep to another because of the long period of time separating them. So, my question then is how can we experience "events" during dreams that we perceive to elapse over a significantly longer period of time than actually passes in the real world? Thanks in advance for anyone who takes the time to read and respond.
There seem to be a few potential misconceptions here, so let me add some thoughts. 1) As has been pointed out, REM sleep bouts are short early in the night but become longer towards the end of the night. 2) It is not usually true that "we go through Stages 1-4 then 4-1 of the sleep cycle before we get back to REM sleep". Early in the night, we will usually get to stage 3 (note that there is no such thing as stage 4 anymore, as it had been combined with stage 3 now), but after the first couple of cycles, almost all of NREM sleep is spent in stage 2, with some time spent in stage 1. 3) Subjects report dreaming about 90% time of the time when woken from REM sleep. But it is not true that people only dream in REM sleep. Dreaming can also occur in NREM sleep (e.g., http://psycnet.apa.org/psycinfo/1993-20351-001 ). In general, the more vivid and detailed dreams are associated with REM sleep, but it is definitely not the only stage in which dreaming can occur. 4) People tend to only remember dreams upon awakening, not because those dreams are necessarily special, but because short term memory does not function normally during sleep. People will only tend to remember a dream if they are awake for a while after it. Most people wake up briefly 10+ times per night, but tend not to remember these brief awakenings. People also often report not remembering things that happened just prior to falling asleep or during the night (e.g., getting up to answer the phone) for the same reasons. |
Just read about denaturation. Question about fevers
So I'm taking Biol 190 and just read about how proteins can undergo denaturation. As I have understood it, this is basically the proteins losing their shape and becoming useless. the book then mentions that high fevers are fatal because the proteins in the blood become denatured at the high temperatures. I know that ice packs are usually put on a person's body to help cool them off. I was wondering if injecting a cooled saline solution into the blood stream would also work or work quicker? Or if that would cause more damage?
Perfusion would be the act of pumping blood into the organs. Vasoconstriction can lead to multitudes of issues - by definition, it would mean the "tightening" or "narrowing" of blood vessels. You have it right - if we vasoconstrict someone's vessels by using vasopressors, we pharmacologically increase someone's overall blood pressure. The reason why decreased perfusion is bad is because it means that blood is not reaching the organ well, and with that comes decreased organ function. |
Does turning a box of icecream on its side with the top off make it melt faster?
I have been pondering this with my grandpa. He usually does this to make it melt faster. It does seem logical; given that cold air is heavier than warm air, it would presumably "spill" out, or the air that has been cooled in the heat exchange will fall down and allow new warm air to exchange heat. But maybe the thermodynamics are more complicated than that.
It's more likely just about contact area. Ice cream cartons sit on a ridge so the only contact between the cold ice cream and the countertop is a thin ridge of material and so heat is not transmitted into the ice cream very quickly. . When your grandpa turns it on its side then the cold carton is touching the countertop directly and so heat can be transmitted more quickly into the ice cream. |
[Earth sciences] I have some trinitite. How would I check if it's legit?
Use a geiger counter. Or put it in a very dark room with no light and look at it with your cell phone camera. If you see little distinct white dots in the picture it is emitting beta/gamma radiation that can be picked up by the camera's CCD. |
Why isn't CO2 visible?
I happened across a of CO2 which included the very end of the visible spectrum. It seems to show CO2 absorbs light in the 630-700 nm wavelength, at least somewhat. I'm curious why, if CO2 seems to absorb some visible light, high concentrations of it are not visible as bluish/cyan gas (white light removing the deep reds). Is there something I am missing here? What led me to this was an interest in replicating the sort of things shown or . These all seem to use mid wave IR and a narrow bandpass filter. I would imagine that if a narrow bandpass filter around 650 nm on a regular camera would let you see CO2, they would have done that instead. But I don't see why it wouldn't work. : As Shookfoot notes below, the units on the graph are wavenumber, not nanometers wavelength. As such, the absorption isn't in the visible spectrum at all.
Hi there! The answer to this question is about the units of the absorbance spectrum you have shown us. The units are in wavenumbers, not nanometers. 600 wavenumbers is approximately 17,000 nm. Hope that clears things up! Source: aspiring chemist. |
In double-blind studies measuring effectiveness of birth control, does the control group receiving the placebo have affected pregnancy rates?
Depends what you mean by placebo affect. Medically it means all the non-specific effects of a trial. For example participants might be having regular check ups with doctors as part of trial, or be told not to drink during a trial, which would all be part of the 'placebo effect'. A lot of people use the term to just mean the effect that taking a placebo actually has on a person. However it appears this generally only has an effect on subjective reported outcomes. For example if you ask people whether they have fewer wrinkles after taking a placebo they will say yes, but if you record the number of wrinkles before and after there generally won't be a difference. I certainly know of no studies that show a 'placebo effect' on something as objective as getting pregnant. |
Why are old buildings so good at blocking phone signals?
This is labeled a physics question, but I think it's just as much a structural engineering question. Ignoring ancient Roman buildings, modern concrete construction really began in the late nineteenth and early twentieth centuries. However, construction isn't a fixed thing. Like every kind of technology, it improves over time. Some things that have improved: Stronger concrete: we've learned a lot about designing higher-strength concretes. A modern high strength concrete commonly used in large buildings will have a strength three times that of concrete used in the early twentieth century. Today, we can use less concrete to carry the same amount of load. Concrete construction today is significantly more slender than that of a century ago. Stronger steel: steel has also increased in strength. Our metallurgical and manufacturing technologies have greatly improved, at least doubling the strength of steel reinforcement compared to the early twentieth century. Since the reinforcing bars are stronger, we don't need as many of them. As a conductor, steel will do a lot to block radio signals, so less rebar means less radio signal blockage. More advanced design: when concrete construction was in its infancy, engineers didn't know as much about how concrete buildings perform and age as we do today. They also lacked modern computers to perform complex structural analysis calculations. They had to use large factors of safety to make up for this imprecision in design. There's an old civil engineering adage, "when in doubt, make it stout!" Those old designers took this quite literally. All of these together mean that old concrete buildings are substantially heavier and have substantially more steel in them than current buildings of the same size. Thicker walls and floor slabs between your cell phone and the tower means lower quality cell service. |
How do we know that Polio has been eradicated from North Korea? From uncontacted groups in the Amazon?
, Polio was eradicated from Brazil around 1990 and North Korea in the mid-1990s. But how do we know this? Does North Korea allow disease surveillance by international organizations? And what about in the Amazon? How do we know that they don't harbor Polio?
You can find a high-level overview of what is involved in polio-free certification for a region (it's region-based, not country-based) on this WHO page . The short answer is that, yes, North Korea does cooperate with the WHO, and the extent of that cooperation is documented in cooperation briefs also available from the WHO . (I don't have an answer about the Amazon off the top of my head.) |
Did inflation of the early universe stop or did it just slow down?
Is the current expansion of the universe a remnant of initial inflation phase or is dark energy a different mechanism? If they are the same mechanism does that mean that the rate of inflation is decreasing? If inflation stopped ... why?
In the most accepted models, Inflation was caused by an excited exponential scalar field , and stopped when it rolled down to its ground state. |
Why Can't the brain interpret the image it sees to make things clear to people who need glasses?
Yes the brain makes us ignore blind spots, this is not the same as filling in the missing visual information. With blind spots we just don't notice that nothing is there and if we do it is usually just a white or black spot or a kind of smear of the images around it. Maybe you multiple images idea would work if we had compound eyes but it side steps the problem of the brain processing a 'low resolution' image into a 'high resolution' one. In other words, no matter what software (brain) you have it will be limited by the hardware (eyes). |
How do we have images of the Milky Way Galaxy?
We don't. We have pictures of other galaxies. We know that the milky way is a spiral galaxy. So pictures of spiral galaxies stand in for the milky way. |
How many unique selves are implied by the major histocompatibility genes?
From my understanding, there are about 6 major genes that are considered during transplant matching, and at least two of these - HLA-A and HLA-B both have thousands of variants leading to millions of permutations. So if we considered all of the major histocompatibility genes and the # of known variants, how many unique immune signatures would we get? If the immune system sort of defines "self", does this then give us an upper bound of the number of unique "selves"? Here's a quote from The Song of the Cell talking about the variants: Humans have multiple “classical” major histocompatibility genes, and potentially many others, of which at least three, and possibly more, are strongly related to graft compatibility versus rejection. One gene, called HLA-A, has more than a thousand variants, some common and some very rare. You inherit one such variant from your mother and one from your father. A second such gene, HLA-B, also has thousands of variants. You might have guessed already that the number of permutations between just two such highly variable genes is mind-boggling. The chances that you’d share such a barcode with a random stranger you met in a bar are vanishingly small (and all the more reason not to fuse with him or her).”
There may be thousands of individual genes per locus (ie 7712 for A locus currently), but only about 100 of them are common. Many are caused by synonymous mutations or are found in the non-coding regions (introns). Also there is strong linkage disequilibrium between B-C as well as DRB1-DQB1 as those genes are ver close together on the chromosomes. There are still a lot of possible combinations. Thirty percent of the population will have a matching sibling and most others can find a non related match.
The only thing that might reach the level of permutations that you seek would be in VDJ recombination seen in the repertoire of antibodies/B cell and T cell receptors. |
Are fish and other aquatic animals able to see regularly underwater or do they have the same blurring in their vision that humans have?
If they can’t see regularly underwater do they have other senses to make up for it?
When the prehistoric creatures moved out of the water, their eyes adjusted over time to the air. The way that fish and other aquatic animals see underwater is equivalent to what we see on land. Over time our eyes have adapted to our surroundings. |
Why doesn't the Earth build up a positive charge from cosmic rays?
We are continually bombarded with lots of cosmic rays, which are mostly bare protons. Shouldn't this mean that the Earth accumulates an excess positive charge over time?
Cosmic rays are not the majority of particles striking Earth. In quantity they are greatly outnumbered by the particles of the solar wind, which are both positively and negatively charged. If the Earth does happen to acquire a slight positive charge, it will tend to repel positively charged particles and more strongly attract negative ones. If Earth acquires a negative charge then the opposite will happen. This means that over time, the charge of a large object will tend toward neutral. |
Can you have two colds at once?
You definitely can be infected with two viruses which cause the common cold at once, although it's probable that one will dominate over the other before long, with only one surviving and continuing the symptoms. The epidemiology of the wintertime respiratory viruses (the viruses which cause the common cold) is one of the most fascinating, complex, and least understood topics in medical science, and there are a lot of unanswered questions. One of the things that is known is that knocking out one pathogen can sometimes open up an "ecological niche" for another one to proliferate. An interesting phenomenon which has been observed for decades is that when a new strain of influenza emerges, one of the old strains just sort of magically disappears. This is likely due to the new strain "out-competing" one of the old strains within a population as a group of people, but the core battle happens within individual hosts, one person at a time, where someone is co-infected with both viruses, but only one dominates and survives in the end (until your immune system figures out how to get rid of it, at which point you get well). But co-infection with two cold viruses at once for at least a little while is pretty common. Here's a study looking at the incidence: https://link.springer.com/article/10.1007/s10096-012-1653-3 The Health Protection Agency Public Health Laboratory (HPA PHL) Birmingham, UK, routinely uses polymerase chain reaction (PCR) to detect common respiratory viruses. . A total of 4,821 specimen results were analysed. Of these, 323 ( , 22 ( . Reciprocal patterns of positive or negative associations between different virus pairs were found. Statistical analysis confirmed the significance of negative associations between influenza A and human metapneumovirus (HMPV), and influenza A and rhinovirus. Positive associations between parainfluenza with rhinovirus, rhinovirus with respiratory syncytial virus (RSV) and adenovirus with rhinovirus, parainfluenza and RSV were also significant. Age and temporal distributions of the different viruses were typical. This study found that the co-detection of different respiratory viruses is not random and most associations are reciprocal, either positively or negatively. The pandemic strain of influenza A(H1N1) was notable in that it was the least likely to be co-detected with another respiratory virus. So if you've had at least 10 colds in the past over the course of your life, you've probably had two at the same time at least once. |
A2 Physics coursework unexpected result? (LASER + Diffraction Grating)
Whilst trying to get data for my A2 physics coursework (measuring the wavelength of light by the bending through a diffraction grating- not the best, but the alternative was literally paint-drying), I've been having some troubles with the diffraction grating; I should expect to see the brightest spot being straight ahead of the laser hitting the diffraction grating, a lá Phasor theory- however instead I'm getting the brightest dot offset to one side (dependant on the rotation of the grating, but not which side it's going though). Even more strangely, the offset between the brightest and the straight ahead is slightly more than between either and the next dot out. That is, between '0' (middle/straight on) and l1 (brightest dot) there's 1.6cm, whilst between l1-l2 and 0-r1 the gap is 1.5. (l2-l3 and r1-r2's 1.7 cm). I could take pictures if my wording isn't sufficient, but it'll have to be later as I'm about to go out. Please help me to explain this counterintuitive result! My teachers couldn't explain it either, putting it down to diffraction within the grating until I realised that it would always bend the same way, independant of the normal. They then were puzzled again. (The diffraction gratting is 300lines/mm, the laser is 532nm, but also happened with a 650nm. The behaviour was witnessed with several gratings of the same type, but a 15000line/inch (different make) and an unknown spacing grating I got for free from a uni visit don't have the behaviour).
I'm doing my Ph.D in laser spectroscopy, so I think I can help you. Sadly I'm not sure I fully understand your premise. Maybe a cartoon would help ? |
I remember reading somewhere that major cities that experienced catastrophic fires (ones that burned down the majority of the city) converted to gridded road systems, whereas those that had no major fires didn't. Is there any truth to this statement?
Not really any truth to this statement. London is the perfect example to demonstrate this. London burned completely to the ground in 1666, but yet the road layout in the center of the city is over a thousand years old. In the days after the fire there were lots of plans to completely redo the road system, and the entire layout of the city. The plans still exist in a museum in the city. All these plans were dropped. Why? For two main reasons: Firstly, to redraw the entire map was going to cause a legal nightmare. Buildings may have been burned down, but people still owned all the land, and it was not possible to simply build a new road through someones land. Even in London centuries ago, the state didn't have the power to arbitrarily redraw maps Secondly: the city needed to get back to business and life as normal, and the quickest way of doing so was to simply rebuild all the houses/businesses in the same places as before. Bakers etc. simply had their shop rebuilt and opened selling bread again a few weeks later. In the case of London, all that the officials achieved was a slight change to the building codes stating how wide roads had to be. The roads were made a little wider. |
How does oxygen go from lungs into blood? Could you explain in details and simply?
Thank you in advance
Think of it as a wall with 1-way valves in the shape of oxygen (into the bloodstream) and CO2 (out of the bloodstream) There's no directed "valve". Diffusion there is just a matter of the different concentrations on both sides. |
Is there adequate evidence, beyond the anecdotal, to suggest that the internet has lowered attention spans, memory and/or patience?
You may be thinking of this Science article , which reports: This is preliminary evidence that when people expect information to remain continuously available (such as we expect with Internet access), they are more likely to remember where to find it than to remember the details of the item. One could argue that this is an adaptive use of memory—to include the computer and online search engines as an external memory system that can be accessed at will. |
What happens when a particle loses all energy? Can you drop below the ground state? [physics]
The ground state is, by definition, the lowest energy state a particle can be in. If it was possible to drop lower then that lower state would the ground state. Depending on the situation, the ground state may be zero energy, or some small finite nonzero energy. |
What can we use bronze for today and why?
I was wondering what we use bronze for today and the reason for it. I cant seem to find a reason for using bronze in industrial and non-industrial purposes.
Bronze type alloys are often used in places where you want low friction with steel parts. The most common example are oil infused bronze bushings for rotating parts. They are cheaper and take less space than roller bearings. |
Does Earth tilt/seasons affect the amount of moonlight we get like it does with the sun?
Like… do we get more hours of moonlight per day in the summer vs the winter? Or maybe it's the other way around? Or does it not matter and we always get the same amount?
No. Seasons exist because the axis of rotation of the earth isn't "vertical" to the earth's orbit around the sun, and the axis doesn't really change. So for large parts of the orbit, the northern hemisphere points slightly away from the sun, and gets less sunlight. Half a year later, the sun has moved "around" the earth (relatively speaking), and the southern hemisphere now points away. The moon, however, moves "around" the earth (also relatively speaking) once a month, so earth's lunar "seasons" are about a week long. |
Is absolute motionlessness impossible in the universe?
Let's say I get in a spacecraft and travel to the area between our galaxy and Andromeda, then just stop. As I understand it the galaxies would still be moving away from me due to the expansion of space, and relatively speaking I'm also moving away from the galaxies due to the expansion of space. Does mean that it's impossible to be perfectly motionless since everything is moving relative to each other?
You are motionless in your rest frame. You are moving in another equally valid frame of reference. There is no absolute frame of rest. Consider two objects that are not at rest relative to another. You can either be in a reference frame in which one is moving, the other is moving, or both are moving. |
How do accents form?
I was talking to my dad about this today. How does an accent come about, and why do they exist? I was thinking specifically about somewhere like Australia or America, where it was colonised by British settlers. Thanks in advance!
I would like to add a follow up question: Are accents just precursors to new languages? If Donald Trump built a wall around the former Confederate States, would the southern accent eventually become another language in a few centuries? |
Psychologists and/or psychiatrists, what is the difference between dissociative identity disorder and alter ego?
An alter ego has no psychological definition, and as a result refers to many things. Many of those things are engaged in willingly by the person, such as: A second family A pseudonym Superhero civilian personas Dissociative identity disorder involves an individual possessing an alter ego, but it is one that the person cannot control. |
Why does a spine have protrusions on it? What causes this and how are they evolutionarily useful?
The that protrude from each vertebra in the spine have two main purposes. The longer ones are attachment points for ligaments and muscles, giving muscles more area to attach, and also acting like long levers to help the muscles bend, straighten, and rotate the spine. There are also smaller protrusions, called , that help each vertebra fit together with the vertebrae above and below it. |
Why can I hear a snapping/popping sound when scuba diving or snorkeling near coral reefs? What makes that noise?
My best guess is that it is small organisms popping in and out of coral. I am curious what the real answer is. Can anyone help me?
Underwater organisms are loud! There are lots of crustaceans and fish making various noises down there cracking shells with their claws, crunching hard shelled organisms with their teeth and communicating to each other via all manner of sound producing organs... |
Question on Time Dilation
So I finally read up on special relativity and I'm a bit confused right now. Using the analogy of two spaceships, if one space ship moves at 0.9c relative to the other, the moving one would have its time slowed down from the reference of the second. However, because velocity is relative, the second spaceship would also be observed to have a slower time relative to the first. Here's where my confusion comes in. So when both spaceships suddenly travelled at equal velocity such that both are of zero relative velocity to one another and thus of equal reference, which one would have the slowed time?
You've discovered the twin paradox . The answer is that you can't have the spaceships "suddenly" be at rest with each other. Either one or both must undergo acceleration. In the case of one spaceship accelerating and becoming at rest with the other, the accelerating spaceship has its time dilated. If they both accelerate at the same rate to reach the same frame of reference, then neither's time is dilated - symmetry is conserved. In the case that the spaceships never attempt to reach the same frame of reference, views are valid. |
Theoretically, how small can a nuclear warhead be made?
It's called the Special Atomic Demolition Munition . But the W54 warhead is possibly the smallest nuclear device capable of being fired from a weapon with a yield dial-able between 10 tons and 1 kiloton. |
If terrestrial plants get the majority of their mass from the carbon dioxide in the air, where do aquatic plants get their mass from?
Carbon dioxide in the water. Water can have gasses dissolved in it, so pretty much the same processes happen in water as in air. Plants suck dissolved CO2 out of the water, break it apart and react it with water, then spit out excess O2. Fish and plankton absorb this oxygen, then expel CO2. |
Do 'normal' cats have the same wrinkles that sphinx cats have under their fur?
Does this apply to other mammals with fur? Also, is there an evolutionary advantage to the large amount of wrinkles sphinx cats have?
Yes, sphinx cats are just hairless cats and I don't think there's a real advantage to it.
They get cold very quickly so owning one they must always have clothing, they also have no hair to groom so they get stinky pretty easy and needs baths every 2-3 days.
Source: I'm a vet nurse trainee, just had one come in the other day |
How did Houston communicate with the astronauts on the moon?
USB . But not the adapter type. Radio waves - the general method of communication in space for basically everything (laser links are a very recent development). By changing the amplitude or (better) the frequency of the radio waves you emit many times per second you can transmit information. |
In a theorized multiverse, how are "universes" separated from one other and can they influence each other?
Which 'multiverse' are you talking about? One view of the multiverse is that the big bang was a point origin of our universe, but there may be other point origins far removed from ours. This is the multiverse. These universes are separated from each other by immense distances. They can never influence each other. In the multiverse theory, the universe branches off every time a quantum effect settles on a random number. (Or possible only certain quantum effects.) This is where you find your parallel universes where anything that could have happened somewhere did happen. They are not really separated from each other; in this theory, all possibilities exist somewhere, but we humans are only able to follow and understand one of time's infinite threads. There may be faint interactions between these universes, and we can speculate that may lead to one possible universe being able to influence another. The theory leads to a multiverse separated by distance in one of the ten dimensions of space-time, as described by certain quantum string theories. They do influence each other, sharing some gravitational wells and possibly other phenomena -- recently it's been speculated that dark matter is a brane interaction. But these other universes are alien and probably without the same physical laws, so it's not as if you'll see people living there. And then there are theories where all these possibilities (as well as other multiverses, such as the holographic universe) are all true . When the theory gets that complicated it's impossible to say what can and cannot interact. tldr; We don't know whether there is a multiverse, or which of several theoretical multiverses may actually exist. Some allow interaction between universes and some don't. |
Using two video cameras, getting two different angles of a flying object what could you prove?
Given a flying object, of unknown size, speed and distance, being filmed by two stationary cameras, with a known distance between the cameras and hopefully known angles that the camera are set at what could you prove regarding the flying object? I dont really want to talk specifically about the case below, but more in a general fashion. Lets say I was out in Nevada at Area 51 (its just convenient for the description). Me and my buddy TinFoil have the exact same cameras (Red One) and we have set up on two different points of the same height etc and we have measured the angles of where our cameras are pointed. Out of nowhere something appears, we film, and it goes away. THen we sit down with our footage, we sync it up 100% good, and we start doing the math. What could we for sure prove about the object? Since the distance to the object, the objects size, and the objects speed are all unknown variables, and since the object is in the sky, during day time, making it more difficult to find an anchor point to fix it too. How much more could we prove with more cameras at different focal points. This question was fully inspired by this reddit post I read today [ ]
With the angle and knowledge of the camera lenses and FoV we can determine the precise location of the object with triangulation. We can also determine the cross-section from both angles, and given some maneuvering of the craft, an accurate measure of its shape. Since we can determine its location we can also determine speed while it is in view of both cameras, but once we have its size we can calculate range and position (and thus speed) from a single camera if we assume it is of a fixed size. |
Does tire pressure change when they are in motion (rotational)?
I know that there is only one point of the tire that touches the ground at once and it applies a static force to the ground forcing the vehicle forward, but does this force cause a compression (significant or insignificant) to the tire itself. If it does, how much? Thank you!
The weight of the car will cause a miniscule pressure change in the tire (as compared with an unmounted tire), but typical acceleration and velocity will not cause any further changes. The force that moves the car forward is a result of torque at the axles. This torque is transmitted through the wheel and tire to the contact patch. Tires are extremely stiff in the rotational direction, so there won't be much deformation as torque is applied, and what deflection does occur will be a very slight "twisting" of the sidewalls such that the wheel will be slightly "ahead" of the outer surface of the tire. This deflection, however, won't have any significant change on the volume of the tire. Edit: I assumed OP was not asking about effects as a result of the tires heating from rolling friction. This is obviously the dominant factor causing changes in tire pressures while driving. |
Is there any evidence linking the period of heavy nuclear testing (1940s to 1970s?) to increased rates of cancer, either locally, nationally, or globally?
Yup, Castle Bravo. Was supposed to be about 6 megatons, instead it was 15. The problem was that Lithium-7 (which makes up most natural Lithium) is basically inert at low to medium neutron energy levels, the sorts of neutron energies which come out of fission reactors, for example, and were used for studying the properties of isotopes at the time. But at high neutron energy levels, the sorts that come out of fusion reactions, Li-7 breeds Tritium quite readily. That means that instead of just the 40% of Lithium-6 in the enriched Lithium fusion fuel, almost 100% of the Lithium could participate in fusion reactions via Tritium production. This is only half the story though, because it boosted the fusion yield of the bomb from about 3 MT to 7.5 MT, but the bomb was surrounded by a U-238 jacket. U-238 can't be used to make bombs or reactors on its own because, just as with Li-7, it doesn't react much with neutrons that are in the energy range of fission reactions, so it can't participate in a fission chain reaction (the neutrons it produces aren't energetic enough to fission further U-238 atoms). But when bombarded with an external source of neutrons, especially high energy ones, it'll fission quite easily, which is an easy way to double the yield of thermonuclear weapons. So an additional 7.5 MT of fission reactions occurred, and an additional 7.5 MT of fission fallout spread across the contamination area. In comparison, when the 100 MT Tsar Bomba was tested they used an inert jacket instead of U-238, so it had a yield of 50 MT, avoiding contaminating the Soviet countryside with 50 MT of fallout. |
How come Nuclear Pasta is the strongest material on the universe?
Yeah, they'd explode. They only exist because of the enormous pressure inside the star. Take them out and they decompress and produce regular nuclei like you find on earth. |
Why do microwaves damage circuitry?
Microwaves, or any light for that matter, are oscillating EM fields. In the case of MW its on the same size order of most of these objects so the fields couple very well. These fields then induce a current which then proceeds to short or melt various parts of circuits. |
Do females and males have different amounts of rods and cones in their eyes?
Do females and males have different amounts of rods and cones in their eyes? I have heard it as a back up to a theory that women and men see colour differently, but I don't remember there being any differences in anatomy from biology class.
There is an important gender effect on cones - the L/M wavelength cones use a photopigment that relies on genes located on the X chromosome. when that gene is defective, you generally have red-green colorblindness. since women have two X chromosome, they are far less likely to be r-g colorblind, since they'd need to have inherited 2 defective copies of the gene (only ~2% of X chromosomes in human circulation carry the defect). a further thing on this phenomenon - the L/M pigment genes can be defective in several different ways. usually the defect results in undifferentiated pigments in the L/M cones (colorblindness), but sometimes it results in a that is sensitive to wavelengths a little different from the normal L/M sensitivities. when this happens in a man, he is merely 'color anomalous', meaning he has trichromatic (Red-Green-Blue) color vision, but just a little different from normal. but in a woman, it's possible to get color vision, meaning there is effectively a fourth type of cone in some human female retinas. this phenomenon was only discovered very recently and I don't think it's thought to really have very significant perceptual consequences, but it's not inconsequential. summing up: most men and women probably have similar forms of trichromatic color vision. ~1-2% of men are r-g colorblind, and far fewer women (.01%) are, because of the sex-linked L/M pigment. some women might be tetrachromats, but it's not clear how this really affects how they see colors. So, we mostly see colors the same way, but there's lots of room and reason for differences on a gender basis. |
Since space isn't a complete vacuum does light ever actually travel at the speed of light?
No, but it travels close. Due to free electrons in the interstellar medium, light waves undergo dispersion . Dispersion is the same optical effect that you see when white light goes through a prism and splits into different colors of the rainbow. In practice, dispersion only affects radio waves measurably but it does affect all light. The time delay is proportional to the density of electrons along the entire path the waves travel, given by the (DM) quantity, and inversely proportional to the frequency of light squared. So, the higher the frequency is, the less of a delay, which is why this doesn't practically impact frequencies above radio light. So, if there was a vacuum, then DM = 0 and so you'd get some extra delay = 0, that is, the light is just moving at c. But, since space is not a perfect vacuum, then there is some extra delay and it moves at a speed slightly less than c. This is a bit backwards though since the dispersive delay is from the fact that the group velocity of the waves is less than the speed of light given a frequency-dependent index of refraction. |
Would a biological radio be possible?
I thought about the amazing senses we have and wondered if it would be possible for a sufficiently advanced race to communicate telepathically via radio waves, also i'm going to split this into two parts for ease of understanding. Is it possible to have a biological radio transmitter/reciever I.E a radio organ at all? If possible would a average size mammal be able to produce enough power to transmit over meaningful distances, say 10-100 meters. In essence, if both of these are true, telepathic communication would be possible right?
Well, it surely wouldn't be impossible. There are animals featuring electric organs . Also, it seems that some of them can already communicate modulating weak electric fields ( see here for example), which is probably the closes thing we have to radiocommunicating animals. To do that long-distance and well modulated like radio would probably require a lot of evolutive jumps that I can't honestly fathom now, however. If someone with experience on radio technology can tell us what are the essential requirements for a radio, we can begin to wildy speculate :) |
Are there any residential scale carbon capture technologies available?
I’m considering adding an non-grid tie solar system to my home. As solar is somewhat variable in energy production the system would need to be sized for poor production times of year/days. Are there any electrically based carbon capture technologies that could be run with excess electricity production? I’ve seen some diy solutions but by the time I’ve purchased and had shipped the needed chemicals then disposed of them I’ll have spent all the carbon I would have captured.
If you want to personally remove some carbon from the air, grow corn, sorghum, or some other C4 crop, make charcoal from the inedible parts, and bury the charcoal in your garden. Charcoal degrades very slowly in the soil, so the carbon it contains will stay out of the air for a long time, and the internal surface area of charcoal particles in soil is good for plants. If you want a use for your electricity that benefits the world, run your air conditioner or heater extra hard when you have extra electricity so that you don't have to spend grid energy on climate control at night, or run a computer and donate the computing power to folding@home. |
Could a brown dwarf sustain a life-bearing planet/moon and if so what would be the goldilocks zone?
I'm curious about Arthur C. Clarke's idea of Jupiter becoming a brown dwarf and it's Galilean moons becoming habitable (I think this was from the novel 2010?). I wondered how realistic that was, or if they would be too close. Also for bonus points: what do we call a body that orbits a brown dwarf - is it a planet or a moon?
The problem with brown dwarfs is that, unlike stars, they don't provide a constant source of light, but rather one that diminishes greatly over time. When first formed, a brown dwarf is pretty hot and easily rivals the brightness of a small star. However, it quickly burns through its deuterium reserves (and potentially lithium), but isn't massive enough to fuse regular hydrogen...at which point it begins cooling for the rest of its life. So, for the first ten million years a brown dwarf might have a temperature close to 3000 K, and a reasonable habitable zone to go with that. However, by the time it reaches 1 billion years old, that temperature has dropped to somewhere around 1500 K, pulling the habitable zone inwards by a factor of 4x. Planets that were once reasonable candidates to harbor liquid water and maybe even life will become frozen, permanently icy worlds. Bear in mind that we think life took a few hundred million years to get started here on Earth, so you might be able to get a few microbes before they get encased in ice. At the opposite extreme, planets just entering the habitable zone around this time will have been baked for most of their early life; by the time they're finally reaching a temperature that liquid water could exist, most of it would have already evaporated away into space. Depending on the mass of the brown dwarf, by the time it reaches the age of our Sun, it might not even have a habitable zone. For example, WISE 0855−0714 (which is also one of the closest objects in our stellar neighborhood, less than twice the distance to Alpha Centauri) has a temperature colder than Earth - it's literally incapable of maintaining a habitable zone. : Brown dwarfs spend most of their lives cooling, meaning the habitable zone around them is constantly shrinking until it just disappears entirely. That's not a good candidate in the search for life. |
Can we pull a reflected image off a "nonreflective" surface?
Can we pull a reflected image off a "nonreflective" surface? Reflectiveness is relative. A dirty mirror could be called reflective. A cracked or distorted mirror too. But how about white sheet of paper? Or a rock? It may not be an image that our eye or mind can appreciate, but maybe we could run the reflected light through a noise filtering algorithm. So I guess the real question is, how good are our reflected light image extraction algorithms? What's the limit on extractability?
Yes, if you're willing to use a specialized time of flight camera and pulsed light source. Here's a cute short video that explains and demonstrates . You can see the latest work from those researchers on their webpage . |
How small can a radio receiver get?
In addition, does the size of the receiver have any bearing on the number of frequencies it can distinguish?
In terms of the antenna that must be within 1/4-1/2 of the wavelength of light in order to efficiently receive/emit. That being said there are fractal antennas that fold upon themselves to create a long length in a short space, as well as short lengths for multi frequency reception. |
What actually is the dial up internet noise?
What actually is the dial up internet noise that’s instantly recognisable? There’s a couple of noises that sound like key presses but there are a number of others that have no comparatives. What is it? Edit: thanks so much for the gold.
Everything you need to know about the acoustic modem handshake can be found here on this map: https://oona.windytan.com/posters/dialup-final.png Then you can listen to the actual handshake and follow along:
https://www.youtube.com/watch?v=abapFJN6glo Yes, this is what network engineers still do with packet sniffers and other protocol analyzers on various types of layer 2 networks like ethernet, PPP, MPLS.. etc. |
Do larger animals have a bigger chance to get cancer?
Larger animals have more cells, and since cancer is a defect cell, more cells should mean a higher chance at cancer, right?
In general, larger animals are not more prone to getting cancer, and this is known as Peto's Paradox , after Richard Peto: These may be nicely illustrated by a comparison of mice and men: A man has 1000 times as many cells as a mouse (although the ratio of our epithelial stem-cell numbers is not known), and we usually live at least 30 times as long as mice. Exposure of two similar organisms to risk of carcinoma, one for 30 times as long as the other, would give perhaps 30 or 30 (i.e., a million or a billion) times the risk of carcinoma induction per epithelial cell. However, it seems that, in the wild, the probabilities of carcinoma induction in mice and in men are not vastly different. Are our stem cells really, then, a billion or a trillion times more "cancerproof" than murine stem cells? This is biologically pretty implausible; if human DNA is no more resistant to mutagenesis in vitro than mouse DNA, why don't we all die of multiple carcinomas at an early age? Presumably some concomitant of our evolved ability to grow big and to live for threescore years and ten is involved. -- Richard Peto. Epidemiology, multistage models, and short-term mutagenicity tests Peto's Paradox has been discussed widely . One summary of the various arguments is Peto’s Paradox: how has evolution solved the problem of cancer prevention? . There are likely many solutions to Peto’s Paradox in nature, because large body size has evolved independently so many times across the history of life. We know that whales did not evolve the extra copies of TP53 like elephants [8, 9]. In fact, there is no evidence that whales evolved extra copies of any tumor suppressor gene—even the gigantic bowhead whale (Balaena mysticetus), which has a lifespan of over 200 years [9]. ... Since many lineages faced the trade-off between large body size and cancer risk during their evolution, there have likely been many different pathways in which cancer suppression has evolved. |
Knowing that we are all stardust is there a way to find out from how many is, approximately, each person made?
I think on average, each human is made from roughly 75 kg of stardust. Depends on the weight of the person. No, honestly, how do you define stardust? We do probably consist entirely out of stardust (depending on your definition). You could say that stardust is everything that once was in a star. That means that every element except hydrogen is surely stardust. The fraction of hydrogen that has not yet been in a star is probably also very low. A very rough estimate then says that you consist to at least 80% out of stardust (probably much closer to 100%, but I am no astronomer). |
Why at airports can they complete the detection for drugs quickly and accurately, and yet medical results and such can take weeks for results?
For scanners that you walk through, they search for an isotope of nitrogen (for example) because many explosives contain a lot of it, and if the particular isotope is out of balance with what should be present, it's a good bet a follow up is warranted. Certain nuclides can be detected easily because even tiny amounts will produce gamma radiation with certain energies that can be simply tested (Assuming decay of the nuclide produces gamma radiation, obviously) If you get randomly selected to get your hands wiped, that is a form of mass spectrometry. MS is not a long process, but it is destructive and can't be done in the body. Also as mentioned in prior responses, airport tests are usually concerned with binary existence and not with concentrations. Concentrations are hugely important in health determinations. |
What is the trade-off that requires astronauts to be able to withstand several Gs during launch?
I know about escape velocity, but in my mind it doesn't help much in knowing about the acceleration during launch, especially why the acceleration couldn't be made less. As a side question, how much as far as Gs during launch does it matter if we are headed to LEO or headed to the moon or beyond?
It's a matter of efficiency. Consider the following thought experiment: What if you have a rocket that can just barely accelerate under gravity (it provides enough thrust to fight gravity, and just a little more)? After 10 seconds, it has only picked up a few m/s of velocity, but it has spent 10 seconds worth of fuel fighting gravity. By the time you reach orbital velocity (or escape velocity, or whatever velocity you want), you will have to have spent a great deal of fuel just resisting gravity. Now consider a high-g acceleration rocket. If it accelerates at 4G, then 1G goes to countering gravity and 3G goes to increasing velocity. It needs less time to reach the desired velocity, so it doesn't have to fight gravity for as long (once you are in orbit, you don't need to fight gravity any more). A high acceleration rocket is much more efficient for liftoff. Once you're in orbit, it doesn't matter as much (for reasons I'll skip for the time being), so there are other factors that determine efficiency in orbit. But for liftoff, higher accelerations are more efficient (until you reach the point where atmospheric friction becomes significant, but that's another problem), regardless of final destination. |
What happens when an object enters Earth's atmosphere traveling faster than its terminal velocity?
As a side question, what would happen if something enters another planets atmosphere, say, Jupiter, faster than it's relative terminal velocity?
What happens when an object enters Earth's atmosphere traveling faster than its terminal velocity? Drag slows it down toward its terminal velocity. As a side question, what would happen if something enters another planets atmosphere, say, Jupiter, faster than it's relative terminal velocity? Same thing, just with its terminal velocity on Jupiter. |
Does putting on sound-canceling headphones decrease the amount of noise my ears, or add it it?
If I put in sound-canceling headphones, is it adding noise to my ears, like if I had 110 units of sound (forgive my lack of knowledge on the subject) and I put on sound cancelled, and I still taking in 110 units, just quieter? Interpreted quieter? Or is the music I then put on making it 170 or so? (again, it's just for understanding)
The noise cancelling headphones detect the ambient sound and then emit the exact opposite of that waveform causing destructive interference #Mechanism). This reduces the movement of the air in your ear and so decreases the noise, I hope that's the right question I've answered, it was a little confusing. |
How do we know that dark matter interacts weakly with other matter. Isn't it possible that it doesn't interact at all?
Isn't it possible that it only interacts gravitationally?
Yes, it's absolutely possible. That's a terrifying prospect that people obviously avoid talking about, but it's there. In most reasonable scenarios for dark matter and grand unification though, there's hardly any way of avoiding some very weak interaction with SM particles. A completely non-interacting DM is pretty hard to fit in most theories beyond the SM, so we stay hopeful. |
There are several "health products" becoming increasingly popular such as the ionic foot detoxer, water ionizer, nanosilver water, and ozone generators. Could these "health products" actually be harmful?
The pamphlets that I have read for these products describe how they can make you healthy. For example, read the very scientific-sounding explanation of how the ionic foot detoxer works, I am obviously skeptical of the validity of their claims but I do not know enough (Chemistry, Biology, ect.) to understand why these products wouldn’t have the stated health benefits. Can anyone ELI5? Even more important, can these products be harmful to a person’s health?
Yep for sure they have the potential to be harmful! There is tons of research that is going into this currently! Though right now I think they're working on the physiological effects of fish gills (and therefore certain ion pumps that are critical to our respiratory and circulatory functions similar in humans). If you want to look up some articles, I know that Dr. Greg Goss (from the University of Alberta) does a lot of collaborative work with other professors in the States to research toxicology of silver nanoparticles on physiology (i.e. zoology, cause at this stage they can really only test on model animals). |
Can therapy really cure mental illnesses or is it an outdated method?
As I've understood, a lot of mental illnesses can be connected to an unbalanced production of neurotransmitters, e.g too much dopamine and too little serotonin leading to OCD. Can all mental illnesses be cured simply through drugs, either existing or potential? Are mental illnesses simply due to a chemical imbalance? Or is therapy a modern, effective and recognized approach to these disorders?
Many mental illnesses are indeed caused by physical differences in the brains of the sufferers from the baseline population. However, at the moment, our knowledge of the mechanics of the brain is not so great that we can simply fix that; the many interlocking systems mean that adjusting one part will quite often lead to other parts becoming unstable. In these cases, what therapy does is allow people to work around their illness and develop routines and techniques that allow them to function close to normal. It is unlikely to fix many more severe mental illnesses on its own in the sense that most people would understand as curing the illness, but often that is less important than allowing people to simply act normally. There are also illnesses that are much less due to unusual brain chemistry or structure, such as phobias. Therapy is generally much better at treating these than medication, because they are part of a normal and healthy human mental function (in this case, fear) simply taken to an extreme in one case. Rather than just knocking out the entire system with medication, it is easier to use therapy to just target the problem areas. If I am allowed to guess, I would say that this question arises from a misunderstanding of what therapy is in modern psychology. One of the most common forms of therapy (Cognitive behavioral therapy) is focused less on understanding the root causes of the illness, as the stereotypical 'tell me about your mother...' therapy is, but about simply learning to control the aberrant thought patterns. CBT is used for (and I'm going to take the liberty of quoting wikipedia because this passage makes a nice point): CBT has been applied in both clinical and non-clinical environments to treat disorders such as personality conditions and behavioral problems. A systematic review of CBT in depression and anxiety disorders concluded that "CBT delivered in primary care, especially including computer- or Internet-based self-help programs, is potentially more effective than usual care and could be delivered effectively by primary care therapists." In adults, CBT has been shown to have a role in the treatment plans for anxiety disorders; depression; eating disorders; chronic low back pain; personality disorders; psychosis; schizophrenia; substance use disorders; in the adjustment, depression, and anxiety associated with fibromyalgia; and with post-spinal cord injuries. There is some evidence that CBT is superior in the long-term to benzodiazepines and the nonbenzodiazepines in the treatment and management of insomnia. In children or adolescents, CBT is an effective part of treatment plans for anxiety disorders; body dysmorphic disorder; depression and suicidality; eating disorders and obesity; obsessive–compulsive disorder; and posttraumatic stress disorder; as well as tic disorders, trichotillomania, and other repetitive behavior disorders. - Wikipedia.org |
Do planets in pictures of gaseous looking galaxies actually have gas in the space around them?
"Gaseous-looking" is kind of both right and wrong. They might look gaseous because galaxies have a LOT of stars. Interstellar space is quite empty, but most of the stars might blend together in the picture and make a bright fog. More clarity means you can see more stars in said fog. On the other hand, interstellar space is not totally empty either. Just very close. So yes, there is gas, but no it doesn't make a huge difference in images. |
Did Antarctica's land wildlife go extinct? Or did it evolve into the marine wildlife that lives there presently?
Given that was temperate and presumably inhabited by land animals, and , where did all the animals go as Antarctica became colder/drier? Did they go entirely extinct, or are some of the pinnipeds/cetaceans/birds that live there now descended from antarctic animals? )
Seals originated in or near the arctic and cetacians originated in Pakistan , so they aren't from Antarctica at all. Penguins did ancestrally live in the southern hemisphere, however they were flightless and aquatic long before Antarctica got it's glaciers. See this early penguin from New Zealand, for example http://en.wikipedia.org/wiki/Waimanu The stuff that used to live on Antarctica went extinct. It's a shame, there was probably an interesting batch of marsupials living there. We don't know much about them though, because of the difficulty of digging for fossils. |
Why do some countries (Japan, Norway, etc.) which have reasonably good economies have such low exchange rates with USD?
Question is fairly self-explanatory. I guess I've always sort of interpreted a currency having a low exchange rate with the US as a sign of the country in question being economically weak, but I'm noticing that countries which seem reasonably prosperous, like Japan and Norway, also have this going on. For example: 1 Norwegian Krone: $0.04 1 Japanese Yen: $0.0098 I know the prices of things in these countries is often similar to the items' price in the US, once you convert (e.g. Japanese vending machine prices vary from 50 to 3000 yen according to Wikipedia, which is between about $0.49 and $29.40). Do some countries prefer to just have a single unit, rather then doing the dollars/cents thing? Is there some historical reason? Am I just horribly misinformed about these countries' economic state? Please enlighten me, this has been bugging me for awhile.
You numbers are wrong. 1 krone is 0.16 US$. Until 1933 i US1$ equaled 1.5 grams gold. Norway had 1 krone equaled 0.4 gram gold until 1931. So at that time the rate was 1 krone was 0,26 US$. Since that time, deflation, inflation, differences in real trade and financial trade and differences in interest rate levels have moved each currency up and down. Norway has been seen as a European safe haven when there is probelms with the Euro, and German investors love to put their money here. It moves the currency up; that hinders export, and the Norwegian central bank try to press it down. And on and on it goes. Currencies never started 1=1, and there are no right level. A currency is hard if it has been moving upward for a long time. But it may still be 0,00XY something. Some countries have no cent. Norway have øre, but there no longer exist any physical coins, so if paying in cash, you will get to closest krone. Do no mix the currency and the price level of some single consumer good. Local prices may be higher or lower than in the US, but that is a completely different discussion. |
Can someone explain Quarks in a simple manner?
I've been curious about the subject, but any time I try to look up the page on Wikipedia, I always get too confused by the terminology. So since I'm such a slow person, I'd like a simpler explanation as to what Quarks are, and what they actually do.
Quarks are (as far as we can tell) fundamental constituents of matter, so they are not themselves made of something else. They possess mass, electric charge (±1/3 or ±2/3) and what we call "color" charge of green, red, blue. Or if they are antiquarks they can have, antigreen, antired, and antiblue. While the forces between the electric charges are mediated by the electromagnetic field (via photons or light), the color force is mediated by the gluon field. The gluons of the gluon field are massless like light, but carry one color and one anticolor. Quarks can form combinations of color which make the overall particle "colorless." This is due to a process called confinement where color forces with distance which prevents free quarks from existing. There are two main types of quark combinations (though others exist): Mesons: Quark—antiquark pairs with a color and anticolor or some superposition of such combinations. Baryons: Three quarks or three antiquarks each with a different color. This is what protons and neutrons are. Adjacent neutrons and protons still feel "residual" color force which allows them to bind together forming atomic nuclei, the process can by approximated by this animation:
https://upload.wikimedia.org/wikipedia/commons/3/35/Nuclear_Force_anim_smaller.gif This is a lot to take in, so if you need some words defined, feel free to ask. More technically we can talk about weak hypercharge which is how the quark's interaction with both electrical forces and weak forces can be united in electroweak theory. We've ignored their spin which is 1/2 making them fermions. Fermions have half-integer spins and Bosons have integer spins. They behave very differently, for instance fermions cannot occupy the same quantum state together. More technically we can talk about how they combine into 8 distinct states that are a superpositon of different combinations of color and anticolors. |
Do photons experience any form of time?
After reading , I began wondering if this is a legitimate understanding of the implications of relativity theory. So is it true that because photons only travel at the speed of light, they experience infinite levels of "time dilation" and "length contraction"? I understand the claim about time slowing down as one approaches the speed of light, but are the claims about photons experiencing zero time merely conjectures? Or are they legitimate implications of relativity theory?
We know of absolutely no tachyonic particles. And we have good reason to suspect that such things cannot exist. (they'd cause logical paradoxes) |
What would happen if a bee/wasp stung me on the eyeball?
Let's assume the person in question has no allergy to bees/wasps/whatever does the stinging. In what ways would the effect differ from being stung on skin? Would blindness result? Would the effect of stings (edit: the effect of the stinger's penetration has been pretty well handled; how about the effects of the toxins?) on the white, iris, or pupil be different from each other in any appreciable way?
Not necessarily. I had a stick go through the pupil of my eye and I don't have a 'scar' on my eye. (It only went through the front of the eye. If it had hit the back then I'd likely be blind. But I don't think a stinger is big enough to hit the back.) I would think the poison would be the real problem. |
What happens to mosquitoes when they suck your blood while you are intoxicated?
I apologize if this has been asked before, my attempts at google and reddit search have not shown any actual studies or questions asked on this. So does the alcohol in your blood have any affect on a smaller mosquito? I'm assuming that either the alcohol is not concentrated enough to affect the mosquito, or the sac that the mosquito stores the blood in does not absorb the alcohol? Maybe a better understanding of how mosquito store blood would render this whole question moot. This could also go for any type of substance in your blood. Like if I drank some sort of human safe DEET. Could I be mosquito's destroyer of worlds?
Scientists routinely puff ethanol vapors at insects and measure their sensitivity with devices called inebriometers. Bugs are no lightweights, often withstanding vapor concentrations of 60 percent alcohol, far more than what’s in our blood after a couple beers. “Someone who’s had 10 drinks might have a blood alcohol content of 0.2 percent,” says entomologist Coby Schal of North Carolina State University. To a mosquito, a blood meal that contains 0.2 percent alcohol is like drinking a beer diluted 25-fold. Source |
How big can a crystal get?
I'm sure many of us have heard about some planets being discovered that could basically be giant diamonds. (And that's a whole other complicated can of worms, but let's not open it here.) I think a lot of people probably hear "diamond" and think that this is the type of thing where you'd be able to see some sort of crystaline structure from space - facets, planes, etc. I assume that that's not possible, because that would require the crystals to form at a massive scale. However, I don't actually know if my assumption is correct, nor why. What prompted this line of thinking was a discussion in another sub where an of the Omega/Swan/Horseshoe nebula was being (needlessly) debunked by Phil Plait. It's clearly fake, but it got me wondering how large a crystal formation can actually get. There are those amazing ones in the , though obviously there's a huge difference between a crystal that's 39ft tall and one that's 15 light-years tall. Is there an upper-boundary for how big a crystal can get? Gravity and mass are probably the biggest factors, of course. And even if you had the material and conditions to form a 15 light-year tall crystal formation, the mass would probably collapse into a black hole. But let's speculate a little. Could a mile-long crystal exist, for example? If we ignored mass and/or gravity (except for what is needed for crystal formation in the first place), and assumed a limitless supply of source material, could a crystal theoretically grow forever? I really don't know anything about crystallography, or even anything beyond the most basic mineralogy. (I'm a web designer.) I apologize if I'm using terms incorrectly. Thanks!
Without knowing the exact answer, at the high end you'll be limited by gravity and general relativity. Crystals by definition are materials with repeating units (the "unit cell"). That can only repeat indefinitely in "flat" space. For example, a crystal is only a crystal if the axes of the unit cells in the crystal remain perfectly parallel to each other. (I'm open to corrections if I've misstated relativity here) If you have enough material that it starts to induce relativistic effects - distortions in space - then the axes will bend inward, won't be parallel any more, and the crystal stops being a perfect array. If you're willing to tolerate some deviation from ideal, you'll still run into gravity, where the force packing your molecules or ions into the crystal is eventually overcome by gravity and collapses. I'm pretty sure you'd end up with gravitational collapse and formation of a neutron star or black hole before you get to the theoretical perfect crystal destroyed by distortions in space-time. Though I'm not certain on that one. In the intermediate size range, you're probably more practically limited by things like purity (impurities can distort the crystal lattice), stress and strain. |
I recently quit using tobacco after 10 years of use. My family is telling me that I need to do a cleanse. Is there any scientific evidence to say that these detoxifying cleanses work or are they BS?
I've heard a lot about body cleanses and detox but I'm wondering if there is any legitimate scientific research done on the subject? For example, members of my family do a cleanse where they drink lemonade/maple sugar/cayanne pepper for a week straight with no food, claiming it detoxes them. When I search for information on the matter all I can find are new age/holistic websites that I do not trust to be unbiased. Thank you for any relative information. EDIT: BTW I was a chewing tobacco user.
The first question I ask about anything like that is whether they can name the specific "toxins" that are supposedly being removed. They generally do not get specific because they're not actually doing anything helpful. |
When we view distant cosmic bodies, do relativistic effects cause us to see their changes at a slower rate since they are moving so fast relative to us?
I was under the impression that galaxies are flying apart from each other at a pretty rapid pace. I was also under the impression that time slows down for fast moving objects. If we can see the light from one of these galaxies as it is soaring away, wouldn't that mean that from our vantage point that they would move/change very slowly? For example- Say we observed a distant galaxy rotating while is is soaring away from us at speeds close to the speed of light. Would the rotation speed we see correspond to the rotation speed measured by an inhabitant of that same galaxy? If this is already a thing, how does it affect our assumptions and observations about distant objects, and how to we compensate for it?
You're using a speed almost 3 orders of magnitude too large. Objects receding at about the speed of light are at a redshift of about 1.5. |
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