title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"How does Quantum Tunneling not violate the Law of Conservation of Energy?"
] | [
false
] | How can a particle escape a potential well without "creating energy out of nothing"? | [
"If the system before and after tunneling has the same energy, the law is not violated. That's the whole point of tunneling - it doesn't need to acquire more energy and climb that potential well to escape."
] | [
"This is what tunnelling of an electron through a potential barrier looks like in terms of the electron's wavefunction:",
"https://en.wikipedia.org/wiki/File:Quantum_Tunnelling_animation.gif",
"If you add up all the probability (i.e. add up the area of the curve over all the space) it will always add up to 100%... | [
"In the so called \"classically forbidden region\" you point to, the kinetic energy is indeed negative as the momentum is an imaginary number. This is because the wave is not propagating in that area but rather exponentially dying out. However, total energy is still conserved in that area. Perhaps the conceptual... |
[
"Why does the Trinity site still have high background radiation, but Hiroshima and Nagasaki do not?"
] | [
false
] | So I was reading a Wikipedia article about the Trinity site where they tested the first atomic bomb ( ) and it says "More than seventy years after the test, residual radiation at the site is about ten times higher than normal background radiation in the area. The amount of radioactive exposure received during a one-hour visit to the site is about half of the total radiation exposure which a U.S. adult receives on an average day from natural and medical sources." Meanwhile, Hiroshima and Nagasaki are considered to have normal levels of background radiation. Some articles I read attribute the lack of background radiation levels in these places to the bombs being detonated in the air versus ground level. So why would they be different? I'm guessing perhaps the Trinity bomb was detonated closer to the ground? And why does ground versus air detonation affect the background radiation? Thanks in advance! | [
"had parachutes attached",
"This is a pedantic point, but they did not have parachutes of any sort. They had metal tails that stabilized them, but nothing that retarded their speed of dropping to any degree. ",
"The Trinity tests where ground bursts and therefore irradiated the surrounding area and particularly... | [
"had parachutes attached",
"This is a pedantic point, but they did not have parachutes of any sort. They had metal tails that stabilized them, but nothing that retarded their speed of dropping to any degree. ",
"The Trinity tests where ground bursts and therefore irradiated the surrounding area and particularly... | [
"There are really two factors here:",
"1) How long does it take the radiological risk to human health to go away?",
"2) When will people willingly move back given the risk that is present?",
"Take Pripyat for example, since you bring it up. The actual radiation levels in most places in Pripyat are not very si... |
[
"Can hallucinations occur in a normal situation without outside influence such as drugs or mental illness?"
] | [
false
] | More specifically, can a normal person for example,who has no history of mental illness and who is not on drugs just taking a walk and have extremely vivid hallucinations while on that walk for no apparent reason? | [
"Nearly everyone hallucinates at some point in their life. It's quite common and most cases are not associated with drug intake or mental illness. And a variety of physical or mental stimuli and practices can reliably induce hallucinatory states in most individuals. Some kinds of hallucinations in very young childr... | [
"I'd like to add, extended sleep deprivation will invariably produce hallucinations unless you are taking antipsychotics.",
"Some perceptual anomalies will usually crop up after as little as 24h awake, and full blown hallucinations are pretty common by 72h."
] | [
"Sensory deprivation chamber. It's completely dark, zero light, and also insulated from all outside sound. After a while, around an hour or so, your brain will be so starved of stimuli that it makes it up. Usually auditory, but stay in there long enough and the visual will start."
] |
[
"How do welding magnets with switches work?"
] | [
false
] | They aren't noticeably powered, as in they aren't electromagnets as they have very long lives without any noticeable batteries. They are seemingly just permanent magnets with a switch on them. Are there other magnets that cancel each other's fields? That's the only possibility I have come up with. Hope you can all help. Here is a link for people who don't know what I'm talking about, here's a link to some. their see how it works page was useless | [
"I've disassembled one of these before, but this isn't my field. Somebody else may be able to describe it better, but here is how you could make one:",
"Take a couple of pieces of iron and sandwich something non-magnetic in between. Drill a hole through the edges of the pieces and insert a permanent magnet. If th... | [
"So a related question - Turning the \"switch\" in these magnets is effortless (not literally but very easy to turn) but the magnetic force generated when the switch is \"on\" is huge. How come the magnetic field doesn't resist your trying to turn the switch when rotating the internal magnet?"
] | [
"Ohh, that's a neat trick! Reminds me of how when you take the buckyball magnets and make a cube or other solid shape with them, their magnetism towards other objects is almost nill, but the bond inside the structure is really strong. "
] |
[
"Why don't/can't astronomers use a method similar of that used to discover exo-planets to determine if there is or is not a ninth planet lurking around our solar system?"
] | [
false
] | After reading on the Washington Post about some theory of the existence of a ninth planet (planet x, nibiru) I have to wonder if it is still all a hoax or if there is enough credence to the theory to actually search for planet x. I know astronomers are able to determine the number of exo-planets around a distant star based upon the "jiggle" the see the star do - is a similar method not able to be performed on our own sun to determine the true number of orbiting bodies, or does it require a perspective that we are not presently capable of achieving? | [
"The acceleration of the star is inversely proportional to the square of the distance to the planet. If you have a large planet right next to the sun, it works great. If you have a tiny planet way out, it's not going to be very helpful."
] | [
"Correct me if I'm wrong, but I believe that it is because the \"Jiggle\" is the light being blocked, reflected etc by the planet with that light then hitting earth. Since the supposed 9th planet is not between the sun and the earth the jiggle method wouldn't work. Take this with a grain of salt."
] | [
"Also it's orbital period is believed to be on the order of 10,000-20,000 years. So even if we could detect the doppler jiggle in the sun, the frequency is so low that we'd need hundreds if not thousands of years of observations to even detect a change."
] |
[
"[Astronomy] Science in fantasy, Game of Thrones to be precise"
] | [
false
] | So some of you may or may not have read the fantastic series by George R. R. Martin. If you enjoy fantasy I definitely recommend it. One of the important characteristics of this fantasy world is that seasons last years (e.g a character asks another character who is a grown man "How many winters have you seen?" and the response is 4) and they're not always the same length. At the point in time which the books cover, the world is experiencing one of the longest summers it has ever known ( 9 years if I remember correctly ) and the "wise men" constantly say "a long summer means a long winter". Now, I recently learned that seasons are not based on the distance of the earth from the sun but the way the earth tilts. Our tilt seems to be in sync with our revolution around the sun. So my question is, are there planets whose axial tilt is not in sync with their rotation? Is Earth the exception in this case? Second, are there planets that have irregular "periods" of tilt? Is it actually possible to have seasons of vastly different lengths? | [
"Anything caused by orbital mechanics such as distance, axial tilt, or procession would be very regular and predictable.",
"The seasonal variations you describe would probably be better explained by a long period semi-regular or irregular variable star, that actually gets brighter and dimmer over time."
] | [
"I assumed that the presence of \"winter\" had nothing to do with normal seasons or the planet tilt, but was more like ice ages. I'd figured the climate of the planet was natural unstable, and frequently oscillated between two extremes called \"summer\" and \"winter\". ",
"I guess we'll have to keep reading and s... | [
"As a fan of science and Martin's series, kudos to you for asking a very cool question! I've given a ",
"heads up to /r/gameofthrones",
", I'm sure they'll find this as fascinating as I do. Thumbs up for using fantasy to encourage interest in science!"
] |
[
"Does listening to audio books have the same beneficial effects akin to reading an actual book? Does it stimulate the brain the same way reading does?"
] | [
false
] | null | [
"First of all, you should stop thinking about things in terms of how they are 'stimulating the brain', because that is a vague and pseudosciencey qualifying criterion. It doesn't mean anything. If you're asking whether the two mediums, mainly listening vs reading, are equally effective for comprehension and recal... | [
"I take some objection against the latter statement: \" All language comprehension (regardless of modality) is processed within Wernicke's area of the brain.\" There are many, many other areas involved in language processing. To mention just a few: the left and right IFG, the basal ganglia, and the right STS.",
"... | [
"It is definitely not correct to say that Wernicke's area is ",
" for language comprehension, as many other regions are involved in sensing and processing language (although Wernicke's area is ",
" for speech comprehension, see ",
"Wernicke's Aphasia",
"). Sorry if that was misleading. My point here was t... |
[
"Discharging Capacitors as a weapon"
] | [
false
] | null | [
"Not sure what you mean, but if the idea is to charge in parallel and then discharge in series, that is pretty easy to do with spark gaps. It is called 'Marx generator'",
"http://en.wikipedia.org/wiki/Marx_generator",
"You can also look for it on youtube. "
] | [
"Just a note here. This is pretty fucking dangerous. Don't hurt yourself.\nEdit: I don't necessarily discourage this though, I think Marx Generators are pretty cool. Just be aware of how dangerous it is. I think this was posted on reddit a while back (",
"http://lucidscience.com/gal-rock%20disaggregator-1.asp... | [
"you can pretty much do this by attaching wires to the solder points for the flash on a disposable camera. It is a pretty nasty shock that could potentially kill someone. So i would advise against doing it."
] |
[
"How do archaeologists ensure that they do not damage any surrounding fossils when digging?"
] | [
false
] | I have always wondered what sort of preparation and processes archaeologists perform to ensure that the fossil they had initially discovered and intended to excavate did not damage any fossils that are potentially surrounding it. Does anyone have any experience in that area? | [
"When you mention fossils, you are actually talking about Paleontology, however I think the method is probably the same. I am not an official archaeologist, but when I was in high school I volunteered for The Archaeological Society in Oklahoma. My Mom was a cartographer for The Archaeological Survey, so I was alway... | [
"Archaeology is the study of humanity via remains. Excavating fossils can still be considered archaeology. Just a little nit-pick..."
] | [
"It's very, very tricky sometimes. The reality is that unless the site has some remarkable preservation or some sort of intact structure, most ceramics won't be intact. The weight of the soil over hundreds or thousands of years pretty much crushes them. That's when you get your ceramics experts to piece them back t... |
[
"[Mathematics]Can anyone explain the Riemann Hypothesis in the simplest way possible?"
] | [
false
] | null | [
"At what points does the function y= x",
" - 9 equal zero? The answer is x=+3 and x=-3. What about y=x",
" + 9? There is no real answer, but the imaginary numbers 3i and -3i solve this, where i",
" =-1.",
"The Riemann zeta function is a much more complicated function, where Zeta(x)=1/1",
" + 1/2",
" + 1... | [
"It's not a simple theorem to properly interpret. If you know about complex numbers, you can understand the statement, but it will be meaningless. Understanding of the ideas behind it and why it is important is a little more subtle.",
"I don't have the time to write up something at the moment, but check out ",
... | [
"The statement of the Riemann Hypothesis is useless without discussing [...].",
"I disagree, it is interesting and satisfying to gain an initial concept of the statement, even without delving deeper into the context. "
] |
[
"How small would a planetary body need to be in order for the curvature to be drastically obvious to a human on the surface?"
] | [
false
] | I realize an exact answer cannot be given since everyone will have a different definition for "drastically obvious", but I'm just looking for a general range. For instance, we can see evidence of Earth's curvature when ships sail far out to sea and disappear below the horizon. Did humans on the moon (or perhaps Mars) notice that the body on which they were standing was significantly smaller than Earth from where they stood, or was the moon so big that to the naked eye on the surface, the difference was negligible? | [
"Your question has a slight problem: what is \"drastically obvious\"? This very subjective.",
"To answer your question: it depends. The curvature of a planetary body will be discernible when the angle where you see the horizon exceeds a certain angle. When you are very near to the surface (near to the surface in ... | [
", vs . depending where you live and what language is used by the software is a constant source of annoyance. I should just go with spaces...."
] | [
"Let me rephrase it for you: Only bodies larger than approx. 400km tend to automatically become spherical."
] |
[
"When my candle is lit, why does dust caught in the wax gather around the base of the wick?"
] | [
false
] | I have a candle that has three wicks in it and is seated in a circular tin. I've used the candle enough such that all of the wax is liquid when it's lit. I lost the lid for the candle so it just sits on my desk collecting dust. I try to wipe off the dust before I light it but obviously I can't get everything. Anyways, last night after I had been using the candle for an hour (and all the wax was liquid) I noticed that the remaining dust still caught in the wax had accumulated beneath each of the three wicks. Why is that? *EDIT TO ADD ANSWER: When the candle is burning, the capillary forces in the wick are drawing in the molten wax. So the dust gets carried there by the flow. (Thanks Platypuskeeper and everybody else who answered) | [
"When the candle is burning, the capillary forces in the wick are drawing in the molten wax. So the dust gets carried there by the flow. That's my guess at least, I haven't researched it."
] | [
"The wick is pulling up wax, the dust is caught in the flow"
] | [
"This is exactly what happens. In fact, under the right conditions, you can actually see a toroidal convection current around the wick, circulating pretty fast (several times a second). I don't know exactly what's required to make it visible but I've seen it happen with soot particles."
] |
[
"Rehabilitated forests that see an increase in wildlife. Where do they come from?"
] | [
false
] | Just read an article about a forest planting project and after 20 years various mammals, reptiles and land based creatures returned. Where did they come from? How did they get there again after they were driven out previously? | [
"When a man deer and a mommy deer love each other very much...",
"Tongue in cheek, but true. The vast majority of repopulating takes place at the, erm, extremely local level. It takes a bit of time. ",
"Very rarely are populations completely destroyed in any one area. If that occurs - like, say, with beavers in... | [
"The answer to this would be pretty context specific. The range, dispersal, and habitat requirements could all impact what animals could reestablish in a restored forest. The first step, however, is making sure that these animals have what they need (ie. creating a suitable ecosystem through ecological restoration)... | [
"Thanx!"
] |
[
"Why is NASA's James Webb telescope built out of hexagonal panels for its mirror? Why is the mirror not a curved surface, and why were hexagons chosen over triangles or octagons etc.? Why does the Hubble telescope (seem to) not require this geometry?"
] | [
false
] | null | [
"The mirrors are much larger than the hubbles and we didn't have the manufacturing technology to make them in one piece. The hexagons were chosen as they are the simplest shape you can make, requiring the least amount of precise cuts that will not create a continuous line while retaining symmetry in two axises.",
... | [
"Sometimes it's a working title and it gets its cool official name when it comes out. Sometimes it's just a big international collaboration and it's good to choose an obvious and simple name rather than dealing with the politics of naming it after someone or something. It's also nice to have a somewhat descriptive ... | [
"We also use this for large Earth-based telescopes as well. You can check out the list of biggest optical telescopes ",
"here",
" - the top five are all \"segmented\", which means they're made of a number of mirrors tiled together like this. Wikipedia has an illustration of these big segmented mirrors ",
"her... |
[
"Is there a second complex plane?"
] | [
false
] | Does there exist another "complex" plane? Two analogies to explain what I mean: If the real numbers can be seen as the "x" axis, then imaginary numbers can be seen as the "y". Does there exist a number system which also introduces a "z" axis? The question "what is the square root of -1?" is a question about a real number that can only be answered by use of complex numbers. Does there exist a question about complex numbers that can only be answered by the use of a second complex plane? | [
"If the real numbers can be seen as the \"x\" axis, then the complex plane can be seen as the \"y\". Does there exist a \"z\"?",
"The complex plane is not the \"y\", the complex plane is all the x+iy, for x,y real. The \"y\" is the imaginary axis, the complex numbers that are purely imaginary, no x in them. We al... | [
"I think what you're getting at is Quaternions. The bane of computer graphics artists and video game developers everywhere:",
"https://en.wikipedia.org/wiki/Quaternion"
] | [
"Worth noting quaternions are 4-D. There's no 3-D system in between complex and quaternions either."
] |
[
"Can a non-defective calculator randomly make an isolated mistake?"
] | [
false
] | As a kid, I used to do large calculations on handheld calculators repeatedly, hoping to catch them making a mistake. Now, as a college student, I feel a compulsion to do every calculation on my exams twice in case the calculator just messes up. Is there any rational basis to the idea that a non-defective calculator can make one-off, non-replicable calculation mistakes by chance? What about supercomputers running trillions of calculations? And if so, what is the expected frequency of such mistakes? | [
"These are called ",
"soft errors / soft faults",
" and they absolutely do happen. For a single calculator the chances of actually seeing one are astronomically low, they only really crop up in large systems like supercomputers and large network deployments. There's a ",
"great Defcon talk",
" about explo... | [
"One of the most interesting bits of info in that wikipedia article, in my opinion, is that cosmic rays are a main source of soft errors."
] | [
"At least in aerospace, these are called ",
"single event upsets",
" and need to be accounted for when you are determining the reliability of your design.",
"You are to assume that during every flight your CPU (or FPGA/CPLD) will be bombarded by one highly energetic particle that will flip a bit, and you have... |
[
"Is such a thing as \"the smallest particle\" possible?"
] | [
false
] | null | [
"Leptions are just a name for the family of electrons and neutrinos and their relatives (muons, mu neutrinos, tau, and their antiparticles) - things that interact by the weak force, but not the strong force. As far as we know, electrons are as small as anything can be: they have zero \"volume\". What that means fun... | [
"Here is a great answer :",
"http://www.quora.com/Will-physics-ever-find-anything-smaller-than-the-quark",
"?"
] | [
"M theory (modern string theory) posits that everything is made of tiny vibrating strings of energy far far smaller than the smallest particle. ",
"Note that string theory is not yet proven",
"http://en.wikipedia.org/wiki/M-theory"
] |
[
"If the top of every man made structure on Earth were painted white, would this effectively raise the Earth's albedo enough to impact weather or climate?"
] | [
false
] | topic Also consider shiny or mirrored surfaces as potential alternatives to white paint please. | [
"If 80 percent of the roofs in urban areas in the tropical and temperate climate zones were painted white (or some other \"cool\" color, which reflects non-visible light), it would offset 24 billion metric tons worth of carbon dioxide missions. This is the equivalent of our 300 million cars, or of 500 medium-sized ... | [
"Very relevant, thank you. It doesn't quite provide me enough information from which to calculate the answer to my question (including 100% of all building tops in all zones) but it does help me roughly estimate a guess. Nice sourcing, too.",
"Also, I don't know how to convert billions of metric tons of CO2 int... | [
"Except OP was asking about albedo, and that article only talks about reduced cooling bills.",
"I suspect the answer to OPs question is, \"no, there's far too little surface area covered by buildings, and Earth's albedo already varies quite a bit based on cloud cover and snow cover alone,\" but I'd also guess the... |
[
"How would they triangulate the pinger on the black boxes of the Malasian flight?"
] | [
false
] | [deleted] | [
"Okay, I probably have some real insight in this because I had a conversation over lunch with one of the researchers trying to use acoustics to triangulate the sound. We were discussing methods for this exact problem.",
"Here's the essential idea, if I have one sensor by itself, I can try to figure out the distan... | [
"Here's the thing, they aren't looking for MH370 using the sound of the crash. They are using the sound from the blackbox to locate it, which is a completely different problem.",
"The K-129 event is a loud explosion, which is very impulsive and has a really good signal-to-noise ratio and distinct arrival time. MH... | [
"The use of hydrophones is a tried and true technique. The start of ",
"Project Azorian",
" was largely based on sound data taken from 5 hydrophone stations.",
"This figure",
" shows how the data from 3 stations could be used to pinpoint the location.",
"The difference between the K-129 events and MH370 a... |
[
"Space expands more far from large masses than close to it, so how was there expansion during the early period of the universe?"
] | [
false
] | During the early inflationary period, space was pretty dense, but it was expanding incredibly fast compared to today. How could that happen, given the density at that time? It seems like if mass slows expansion, that period should have had enormously slowed expansion. Was the pressure of the contents of the universe high enough to override the effect gravity had? | [
"I provided a source. You could click on the link and then follow their sources."
] | [
"I'm not sure if that's true. Anyway, the expansion of space is so small that the expansion within a galaxy is much too tiny to see.",
"Why doesn't the Solar System expand if the whole Universe is expanding?\nThis question is best answered in the coordinate system where the galaxies change their positions. The g... | [
"There is one thing I'm still not clear on regarding the issue of expansion, and perhaps it's because I've either been misinformed or simply not been informed enough. So, if any of this incorrect, please let me know...",
"Objects moving away faster than the speed of light do not violate relativity because the int... |
[
"What is a phase 3 clinical trial when we talk about vaccines?"
] | [
false
] | My understanding of the phases of clinical trials goes like this; Phase 1: test safety in small number of healthy people. Phase 2: test safety in small number of sick people and obtain early data whether it works. Phase 3: test efficacy in large number of sick people. Phase 4: use new treatment in the clinic and study it. My question is this. Vaccines are given to healthy people to prevent the sickness. So who gets studied in Phase 3? Do you just wait to see how many of those people end up sick after they get the vaccine? | [
"Ooh, I love this question. That is a great summary that you have there.",
"Just for clarity and completeness, the goals of a phase 3 clinical trial are the following:",
"Source: ",
"https://www.cdc.gov/vaccines/parents/infographics/journey-of-child-vaccine.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fvacci... | [
"Thanks for the answer!"
] | [
"As a research biologist finishing up his PhD in the drug discovery field, particularly looking at potential medical utility of snake venom proteins I isolate from extractions, I feel like there are some important things to be said about clinical trials that makes them so tricky and time consuming (whether for vacc... |
[
"How did different neurons evolve?"
] | [
false
] | I understand the basic properties of sensory, motor and interneurons. But how did their different shapes/complexity/function evolve and in what order? I've found a lot of info on the general evolution of the brain (reptilian>limbic>neocortex) but not much on the neurons themselves. | [
"i don't know about other types of neurons, but photoreceptors are very well studied in terms of their phylogeny - e.g. look at ",
"this illustration",
". (let me know if that's behind a paywall, I don't think it should be).",
"photoreceptor phylogeny is studied (generally) by looking at the genes that are us... | [
"How is not really the right question because we can't observe the pressures or chance events that brought them into play. We may be able to infer relatedness of groups of cells based on the tissue they develop from though, and the relatedness of groups of organisms (which are what evolve). Let me posit your quest... | [
"the function of the neurons themselves usually determine the shape and complexity, muscles in jellyfish were likely the origin of complex nerve nets, but it is likely that other sensory cells developed concurrently as stimuli for the muscle cells"
] |
[
"Why doesn't the distribution of elements in the universe follow the progression of the periodic table?"
] | [
false
] | Hydrogen and helium are the two most common elements in the universe, followed by... oxygen? I expected the next element to be lithium, followed by beryllium, boron, and so on. Lithium doesn't even make the top ten list. Why? If stars are fusing nuclei in their cores to form new elements, why isn't it a simple linear distribution by number of protons added? | [
"Let's start at (or near) the beginning. Shortly after the Big Bang, the universe was a quark-gluon plasma which then condensed into protons and neutrons (both of which are composed of 3 quarks). For a short time, the universe was still hot and dense enough for some fusion to occur, so about 24% of the mass got tur... | [
"Great answer. Thank you."
] | [
"I can't explain this in incredible detail, but to give you a preliminary answer:",
"Most of the matter in the universe is either heavy elements created in supernovas, or light elements that have yet to be turned into heavy elements. Hydrogen is #1 because pure energy eventually \"solidifies\" into it, more than ... |
[
"Why is it that gravity slingshots work? Don't the violate conservation of energy?"
] | [
false
] | [deleted] | [
"No scientist here, but I'm pretty sure that the conservation of energy is true with planets as well. The amount Neptune slowed down is probably like 0.0000000000000000001% but that was enough to propel voyager further. "
] | [
"Close - the energy comes from the ",
" of the planet - the planet slows down in its orbit around the sun.",
"It's useful to look at this problem from a couple of different perspectives. First, our camera is following along with the planet. Here, the planet is stationary. The probe falls towards the planet, sli... | [
"Slingshots only work with planets that are in motion. For example, it would not work with a stationary planet (assume all the planets were stationary for simplicity). But if a planet is moving quickly, we can gain some of that energy with a slingshot maneuver.",
"http://en.wikipedia.org/wiki/Gravity_assist",
"... |
[
"Is a 'randomly' generated real number practically guaranteed to be transcendental?"
] | [
false
] | I learnt in class a while back that if one were to generate a number by picking each digit of its decimal expansion randomly then there is effectively a 0% chance of that number being rational. So my question is 'will that number be transcendental or a serd?' | [
"When we talk about probability distributions on the real numbers, we are really ultimately talking about a ",
". A measure is a rather technical way of assigning a length to an interval or a volume to a region. We can actually define many measures on the real numbers, but we typically stick to so-called ",
". ... | [
"It is 0. This may seem counter-intuitive, but after all, they are an element of the set from which we pick, so any single number can be picked. This is unlike a dice roll, were a roll of 7 on a standard die is impossible.",
"The probability, however, is infinitesimal, so incredbly low, that any number greater th... | [
"Stepping back from the mathematics angle and looking at it computationally: the algorithm you specify - picking each digit of a number at random to build your random number - is guaranteed to be ",
" because you have to stop at some point to return the number. Your algorithm would require an infinite number of s... |
[
"How thick in atoms does carbon need to be to absorb light?"
] | [
false
] | When a atom absorbs, and transmissions light, I have been told that single atoms are transparent, whatever the element. So how many atoms thick in carbon does it take to completely absorb all wavelength, and frequency of light. Is it basically as you increase the amount of atoms in a crystalline, or non crystalline structure, there is just too many electron absorbing the amount of photons hitting, and getting absorbed by the electrons, and light just cannot get through. The light just gets absorbed weather the material is amorphous, or not. So its only the energy of electron that will let light pass, and transmission through like in glass, and carbon diamond Is this correct. Thank you for your help, anything helps, even a few words. | [
"1.",
"Graphene absorbs about 1% of incident light.",
"http://www.cz2dcarbon.com/en/uploadfile/201352315521996.jpg"
] | [
"So how many atoms thick in carbon does it take to completely absorb all wavelength, and frequency of light.",
"The first layer of graphene absorbs 1% of the light, the second absorbs 1% of what's left over, etc. After n layers about 0.99",
" of the light remains. If you want to absorb all light, ten you have 0... | [
"I'm guessing you are being facetious, but the result of this is rather interesting if you simply look at a practical limit (i.e. when does only 1% of incident light pass through the graphene layer?). It would take about 460 layers of graphene which is about 1500A, only a tenth of a micron. "
] |
[
"If a great dane and a chihuahua can't breed, how can they be considered part of the same species?"
] | [
false
] | Forgive me if I'm making any false assumptions here, but it is my understanding that: - a) fertile members of the same species are able to breed with one another, b) great danes and chihuahuas are both part of the species Dog (specifically, subspecies ), and c) great danes and chihuahuas are too far removed from each other to be able to breed. Which of these assumptions is false, and if none, what does it all mean? | [
"What makes you believe that Great Danes and Chihuahuas cannot breed? That is a false assumption. Just because you haven't seen any puppies of that mixed breed doesn't mean they ",
" exist. Although it may be geometrically difficult, it is possible."
] | [
"\"Species\" is an artificial concept which is very useful in some subfields of biology, while not so with others. I think almost every question about evolution and ",
" puts the latter into the \"not useful\" bucket.",
"What if two breeds of dog can't or don't want to breed? It's not an effect of their belongi... | [
"Not true. Dogs have 78 chromosomes (same as wolves) and foxes have 34, there's no way they can possibly produce fertile offspring because they lack homologous sets of chromosomes. You may be confusing this with Sibfoxes (",
"http://www.sibfox.com/",
"), which are actually foxes bred to be more docile, which ... |
[
"Is there an easy to remember formula for calculating the cooling time of a given amount of liquid?"
] | [
false
] | A couple of months ago, I tried to google a formula for calculating how long it would take to cool a can of beer to about 3 degrees Celcius (I'm Swedish, hence the non-Fahrenheit units). Based on a thread I found in some random forum, I gathered the following: 4,18 (some kind of constant?) x [Amount of liquid in liter] x [The temperature difference between the beer's current temperature and the compartment used for cooling] You would then take the result of that equation and divide it by the temperature in the compartment used for cooling. This is the weird part, because it didn't say anything about negative degrees. So, is this formula at all right, or just something that seemed to produce a somewhat correct answer? Does it even exist an easy to remember formula for this? (The follow-up question to this would be if there's an easy way to calculate how long it would take for a steak to reach 59 degrees Celcius in a 200 degree owen. Feel free to educate me if there is.) | [
"To answer your question about negative degrees, Heating and Cooling (in fact, every equation that uses temperature) in science require use of the Kelvin scale of temperature.",
"T(in K) := T(in C) + 273",
"So 0C is actually 273K. The reason Kelvin are used is because it extrapolates all the way down to where 0... | [
"In principle, yes. It's Newton's law of cooling. But in practice, no. On the scale found in a kitchen, the approximations necessary to use the formula are significant. For instance, Newton's law requires that the temperature of the object's interior be the same as its surface. This is clearly not the case when coo... | [
"Thanks for the clarification! So I suppose the 4.18 is the thermal conductivity of aluminium (at least that was what the guy at the other forum pinned it at). But if that guy also used Kelvin, I must've read his other numbers wrong. "
] |
[
"What would happen physically to Earth if it was hit with a Gamma Ray Burst?"
] | [
false
] | What would happen physically to Earth if it was hit with a Gamma Ray Burst such as the 1997 ones on ? | [
"Here's the Gamma ray burst section of a show called ",
"Last Days on Earth",
". The consensus is that we're pretty much screwed. Also, Neil DeGrasse Tyson FTW!"
] | [
"I hereby summon the Bad Astronomer to answer this question! Let's hope he's still redditing actively."
] | [
"I thought it would be interesting to work out how close a GRB would have to be to give humans radiation sickness.",
"So let's say the GRB is composed of ",
"150 keV photons",
". From wikipedia, the density thickness of the atmosphere can be worked out to be about 1 kg/cm",
" , so using the energy absorpti... |
[
"[META] F-O-O-D Food Food!"
] | [
false
] | Dear AskScience, Starting this week we are introducing a new regular META series: theme weeks. They won't happen every week, just once in a while, but we think having themes every so often would be a lot of fun. As a brief intro to our first ever theme, there are 2 aspects to how the theme weeks will work: Theme week will kick off with a mass AMA. That is, panelists and experts leave top-level responses to this submission describing how their expertise is related to the topic and We'll have special flair, when appropriate. : panelists and experts leave a top level comment to this thread, and conduct an AMA from there. Don't ask questions on the top-level because I have no idea! This week we begin with an important topic: FOOD! This week we hope to spur questions ( ) on the following topics (and more!): Taste perception Chemistry of gastronomy Biophysics of consumption Physics of cooking Food disorders & addiction Economic factors of food production/consumption Historical and prospective aspects of food production/consumption Nutrition Why the moon is made of so much damn cheese? ( ) Growing food in space Expiration, food safety, pathogens, oh my! What are the genomic & genetic differences between meat and milk cows that make them so tasty and ice creamy, respectively? Or, anything else you wanted to know about food , such as physics, neuroscience, or anthropology! Submissions/Questions on anything food related can be tagged with special flair (like you see here!). As for the AMA, here are the basics: The AMA will operate in a similar way to . Panelists and experts make top level comments about their specialties in this thread, and then indicate how they use their domain knowledge to understand food, eating, etc... above and beyond most others Even though this is a bit different, we're going to stick to our normal routine of "ain't no speculatin' in these parts". All questions and responses should be scientifically sound and accurate, just like any other submission and discussion in . Finally, this theme is also a cross-subreddit excursion. We've recruited some experts from (and beyond!). The experts from (and beyond!) will be tagged with special flair, too. This makes it easy to find them, and bother them with all sorts of questions! Cheers! PS: If you have any feedback or suggestions about theme weeks, feel free to share them with the moderators via . | [
"Expertise: Chief Creative Officer at Serious Eats and author of ",
"The Food Lab",
", a weekly column that explores the science of home cooking. My education is in science and engineering (biology and architecture), my work experience is in restaurants. Prior to Serious Eats, I was Senior Editor and in-house s... | [
"Expertise: PhD in Microbiology - Infectious disease, with a research focus on foodborne pathogens.",
"I'm at work right now but promise to get back to you at some point today. "
] | [
"My rule of thumb for dealing with raw meat (and trust me, this is always on my mind since my research was on ",
" O157:H7 and shiga-like toxins) is this:",
"Handle the meat as you need to, but any time you touch it, the next thing you touch should be the sink with warm water and soap- not the salt and pepper, ... |
[
"Assuming you could create a hole in the middle of the earth without it collapsing, if you threw an object down would it just float in the middle?"
] | [
false
] | I've always heard that gravity is caused because somehow matter distorts the surrounding space-time. If that's the case, wouldn't that mean that if a hole existed in the middle of the earth, then objects thrown into it would just be pulled towards the hole's wall rather than just floating in the middle? | [
"This depends on what you ask. Since you speak of throwing an object in, one would assume you mean a tunnel through the Earth's core, out the other end. Let's take a look at what would happen. There's a ",
"youtube video",
" and an ",
"article on howstuffworks.com",
".",
"First off all, the Coriolis effec... | [
"There is a ",
"FAQ",
" on this topic."
] | [
"Nice summary! Just two things: one, even without air resistance, an object will oscillate around the center of the tunnel, assuming it coincides with the earth's center of mass--it will just never come to rest, but will keep bouncing back and forth between the poles like a ball on the end of a slinky.",
"Regardi... |
[
"Can domestic and/or wild animals recognize reflections of themselves in mirrors?"
] | [
false
] | I realize that they do stop freaking out (for lack of a better term) over it after a while, but is this due to them "getting used to it" or actually recognizing it as them? And, to extend the question, is it possible for an average dog to do this? | [
"Dolphins and some apes can, the vast majority cannot."
] | [
"Magpies can, too.",
" Knowing the intelligence of crows and ravens--especially compared to magpies and \"less intelligent\" corvids--they should be able to, as well."
] | [
"Do you have any citation for this? I appreciate the answer, but I'd like to have a starting point for any further inquiry I have into the matter."
] |
[
"Do radiologists (doctors) have higher incidences of cancer or dangerous radiation exposure?"
] | [
false
] | I was wondering of medical students take this into account when deciding on their futures (provided they have the scores to compete). | [
"Before 1950 or so, the risks of radiation were not very well known. In fact, it was early increases in skin cancer among radiologists that helped link radiation to cancer. ",
"Anyone that works with radiation in their day-to-day job is classified as a \"radiation worker\" - they wear badges that measure their ... | [
"Rewording it, I think he meant to say that \"the idea that for any increase in radiation dose there will automatically be a higher incidence of cancer is still up for debate\"",
"While we know pretty well what the effects of large exposure to radiation are, we're not really certain what the effects of much small... | [
"There's some interesting discussion of the effects of increased daily radiation exposure in this article on Wikipedia: ",
"http://en.wikipedia.org/wiki/Ramsar,_Mazandaran",
"In short, the thought that any increase in radiation dose will lead to higher incidences of cancer is an open question."
] |
[
"How does scientists create higher nr of isotopes of uranium and why haven't we gotten any further already?"
] | [
false
] | I read the askscience thread about the island of stability and it got me curious. We're able to create new isotopes of uranium for example, but how do we do this? Do we insert neutrons or something? If so, how does one come about carrying neutrons? Since we know how to create higher isotope numbers of this element, how come we haven't been able to come any further than we already are? can't we just continue with the same method as the previous ones that's been created? | [
"I'm not exactly an expert, but to answer your direct questions, neutron bombardment is one way to create heavier nuclei. However it has inherent rate limitations. If the new nuclei decay faster than you can create them, you can no longer continue building up larger nuclei with the same method."
] | [
"You are right. You are essentially describing the r and s process that occurs in stars. Neutrons either slowly or rapidly making isotopes. "
] | [
"To add to the previous answer, not only can we make new isotopes by neutron bombardment. We also do fragmentation reactions where we smash large isotopes apart and measure the fragments. If you do this with something like uranium, the fragments are really neutron rich. We can also do knockout reactions where we... |
[
"What is the highest altitude at which a mosquito can sustain flight? Why? What about other insects?"
] | [
false
] | null | [
"fully laden?"
] | [
"I don't know the exact answer to your question.",
"I am, however in East Africa and am on Malaria pills. The info sheet I have for Tanzania says that Malaria risk exists at altitudes below 1,800m (5,906 ft). So take that for whatever it's worth."
] | [
"If it's any consolation, the number of downvotes will probably be the minimum number of people who got the reference.",
"In the case that you were not attempting humor, however, you bring up an interesting consideration. How different would the absolute ceilings be of empty and blood/nectar/juice-full mosquitoes... |
[
"How does the eye actually turn photons into signals in our brain? What's the physical process that allows that to happen?"
] | [
false
] | null | [
"Chromophores capture light photons and are located in the visual pigments of the retina. Known as retinol, which is derived from vitamin A (precursor is beta-carotene, eat your carrots!).",
"When we receive light from our favorite star, photons are absorbed by rhodopsin (visual pigment in rods) and transfer ener... | [
"u/Ha2ha3ha4",
" did a good job of answering it, but I like simpler answers, so I'll try. Pigments (rhodopsin) change shape when a photon hits them. Photons = energy and energy => shape change. The pigment is bound into a protein so that when it changes shape, the protein does too. The shape change closes ch... | [
"what you want is ",
"Phototransduction",
"I'll give you a quick summary: You know how light is an electromagnetic wave? Bonds in molecules are also electromagnetic, so light affects those bonds. In your Retina you have molecules which change their structure when hit by light waves. This change in structure is ... |
[
"What is the purpose of interpreted languages?"
] | [
false
] | Maybe I'm just not understanding virtual machines like JVM or CLR correctly, but I just don't understand what the purpose of interpreted languages are. I'm thinking of it like this (a horribly generalized analogy, but please catch my drift). Say I wanted to translate French (high level programming language) to Chinese, Japanese, and Korean (machine code for different processor families), wouldn't I just write 3 dictionaries? But instead, what I'm understanding is people want to translate French to Latin (e.g. Java bytecode or CIL), then translate that into Chinese, Japanese, and Korean. I'd have to write 4 dictionaries, which is one more dictionary than I would like to write! I'm just imagining a poor sod at Microsoft (more like a team I suppose, or several, or a whole department) developing a version of .NET for each instruction set they can think of. Why not, like C++, just write the same number of compilers to achieve the same thing? But then again, I guess C++ is very old and has compilers for everything. You can get technical in your answer, but I'm less interested in the nitty-gritty and more interested in the path that lead us here. Is it because of technological constraints of which we are now free? Is it because development teams have become so large that how we view workflow has changed (I'm not sure how an interpreted language would help that, but I'm thinking something-something portability)? What is the human factor in all this? Please Reddit, I'm here instead of Stack Overflow because Redditors are nice and don't try to be intentionally esoteric. P.S. Understanding compiled vs. interpreted just as a general public consumer of software is enlightening, but it only explains . How did I end up having a million versions of the .NET framework installed on my computer? How does Java have the balls to bug me every week about updating it? But it doesn't answer ? | [
"Say I wanted to translate French (high level programming language) to Chinese, Japanese, and Korean (machine code for different processor families), wouldn't I just write 3 dictionaries? But instead, what I'm understanding is people want to translate French to Latin (e.g. Java bytecode or CIL), then translate that... | [
"An additional advantage of the bytecode virtual machine model is that you can separate the steps of the traditional compiler chain, in either space or time.",
"For a traditional compiled language, there are a number of stages to the process of converting program text to machine code. This basically involves:\n1.... | [
"As for your post script, there are different versions of .NET and Java on your machine because people are still working on them. Bugs are constantly found and fixed. New features are added and existing ones are changed. Version X might break a program people use, so it's easier to keep version W around than than i... |
[
"Does a fish's mouth heal after it's released from being caught on a hook?"
] | [
false
] | The "skin" there near the mouth sort of resembles cartilage. Does this sort of tissue, whatever it is, heal properly after a fish is hooked? | [
"It does heal. I've seen though with experience that larger holes caused by large barbs or a hook in a particularly thin tissue (think mouth of a crappie), that it may take some time for those.",
"I don't have a source off hand but I've been an avid fisherman most of my life."
] | [
"You can often see scar tissue in larger fish that have been caught before. If the hook was removed the right way it leaves a relatively small hole which is very difficult to spot, but if the hook was torn it often leaves holes that look like old piercings."
] | [
"How can you tell it heals?"
] |
[
"What is happening to the Gulf Stream and the Great Conveyor now and what is predicted if temperatures continue rise and the Arctic ice melts?"
] | [
false
] | null | [
"There's an excellent section on thermohaline circulation in the most recent ",
"IPCC report",
" (Chapters 11 and 12). Basically, climate models all pretty much project the thermohaline circulation in the North Atlantic (AMOC) to become weaker over the next hundred years in response to greenhouse warming. How m... | [
"Thank you. Just what I was looking for."
] | [
"The salty water that's being moved by the gulf stream warms up and moves north. When it gets up around the arctic circle, the water cools down, sinks and returns. \nAs the ice caps melt, they introduce more fresh (not salty) water to the ocean which can interfere with its current. As far as I'm concerned (and I ma... |
[
"Cetaceans evolved to live in the sea, most of them lost the need to sleep. Why sleep is uncommon and even not needed in a lot of sea animals?"
] | [
false
] | null | [
"Cetaceans do in fact sleep, they just do so in a strange alternating way to avoid drowning. They can sort of turn off parts of the brain and swim slowly to rest while still having the motor function necessary for sleep. Many fish also sleep as well, and since they have gills breathing is largely not a problem for ... | [
"Amazing"
] | [
"As for other sea creatures such as jellyfish and anemones, they are very simple and one of the most important parts of sleep is resting the brain, something these creatures lack and many other simple sea creatures have minimal nervous systems. ",
"But even such simple creatures still exhibit signs of sleep. It a... |
[
"General Science Blog Suggestions?"
] | [
false
] | [deleted] | [
"I've entertained the idea of writing a weekly or monthly recap of the recent articles that don't make the news, whether they be important but not sexy, or just silly or weird."
] | [
"I thought about that as well, mostly because it doesn't seem like the actual \"news\" can ever get it right. I have seen the most absurd assumptions made of research projects made in the news."
] | [
"Then we would need a ",
" for posting content or links to these articles. assuming there's other panelists who'd be interested..."
] |
[
"Can sleeping on a part of your body (i.e. your arm) actually cause tissue damage by cutting off circulation?"
] | [
false
] | Holding a limb in an odd position or sleeping on it often causes pins and needles. If maintained long enough, would gravity/your own weight be enough to cut off circulation and cause local hypoxia/necrosis/any damage besides pain when circulation is restored? And if so, how long would it take? | [
"The pins and needles feeling is actually not caused by cutting off blood supply, but by compressing the nerves. You can damage your nerves to some degree this way, I know two people who had their arm go numb for an entire day or two from sleeping strangely, but it should heal and return to normal. Constant, excess... | [
"Over time if you don’t move around enough when in bed, you could wind up with bed sores. That’s damage to your skin, but eventually can become non-healing wounds that go all the way to bone, and actually become fatal (not to mention quite painful)."
] | [
"Former ER RN here. This is a big issue with alcoholics and drug abusers. You can cut off circulation, feel paresthesias (pins and needles sensation), and will consciously it unconsciously move. People who are under the influence may not. It's called \"compartment syndrome\" when they cut off circulation to a part ... |
[
"I've never seen a adequate explanation about the speed of light vs. the speed of electricity. Is light only faster because of the medium it moves through? How fast does electricity travel in optimal conditions?"
] | [
false
] | Title says it all. | [
"There's a vast difference between the speed of an electric ",
" through a conductor, and the speed of ",
" through a conductor.",
"The first one is relativistically fast. Generally between 0.6c and 0.99c for various modern cable designs. This is a measure of how fast ",
", in the form of an electromagnetic... | [
"My old electronics teacher taught us, \"imagine you have a mile long pvc pipe filled with ping pong balls. This is your copper wire. Now when you connect this copper wire to a power source, it's like adding a new ping pong ball to one end. You see immediate effects at the other end of the pipe, but each ball only ... | [
"Another way to look at the problem is water flowing through a hose. If you turn on the tap with the hose full of water, the information that the tap is open travels at the speed of sound in the water, meaning that the water starts flowing out of the end quite quickly. However, it takes much longer for water from t... |
[
"Is there a nutritional difference between fruit ripened on the plant and fruit that ripens on the shelf at the grocer?"
] | [
false
] | A lot of fruit is picked from the plant in a "raw" state, such as bananas, tomatoes and avocado's. Does the fruit receive a lot of nutritional value if it ripens while still attached to the plant? Would an unripe fruit that ripens on the shelf in your local grocer have just as much nutrients as one that ripens while still attached to it's plant? | [
"For most fruits, the ripening process is controlled by the ",
"plant hormone ethylene",
". This is a gas that is produced in the fruit to induce ripening, but is also a diffusible signal that can act over distances. For instance in some species, if you put ripe fruit in with unripe fruit, the ripe fruit will... | [
"*I would like to apologize for any misinformation that I may have given. I wanted to retract my post until I have some time to write a thorough, concise answer that explains my previous posts' links and statements. I encourage you to read some of the other posts below that all have relevant information but I don't... | [
"Using tomatoes, fruit ripened on the plant accumulates nearly all the sugars and many of the flavonoids in the last 3 days on the vine. So when someone asks if the nutrition is there, I ask if the flavor is there because when the flavor is present, the nutrition will be optimal.",
"Caveat that a lot more goes in... |
[
"How does NASA detect what chemical elements/substances are on the surface (or in the composition) of certain planets?"
] | [
false
] | This is in regard to he recent discovery of water at the poles of Mercury but not necessarily specific. I'm not exactly interested in the apparatus that does that but HOW it does that? How do we know it's water and not something else? | [
"They use ",
"spectrographs",
", a device which measures the light that comes off that planet. This works because most substances have their own spectral fingerprint, which is very recognizable. ",
"For example, if you hold salt in a candleflame and look at the spectrum, it will have a bright orange emission ... | [
"The answers so far, while they give ways of identifying materials, do not actually cover the way ice was determined to be on Mercury. That process is described ",
"here",
" and, in more detail with some excellent images, ",
"here",
".",
"The work was multiple-step. First, a while ago, radar from the Ea... | [
"Think of the electrons in an atom like a set of bookshelves. All of the lower shelves (energy levels) are filled with electrons, but there are also additional higher shelves which are unfilled. If an electron gets just the right amount of energy (in the form of a photon) it can pop up to a energy level (shelf), an... |
[
"There is a bird inside a large cargo plane. Does the plane weigh less if the bird flies inside the plane?"
] | [
false
] | This question was asked and the popular answer is that the downward pressure from the bird's wing would push against the floor of the plane and have the same effect as if the bird were standing on the floor. I argue that this pressure would mostly dissipate before reaching the floor and have minimal effect, and that the lift created by the bird's wing would nullify any effect it had on the weight of the plane. Any thoughts on this? Edit: I believe could test this problem, unfortunately I don't have the resources to do this myself. You can build the enclosure out of a lightweight but airtight material with one transparent face. Pilot the drone as high as possible within the enclosure to try to eliminate any ground effect. I'm almost 100% certain that the counterweight will drop as soon as the drone is near the top, if not before. | [
"The original answer to this question is of course correct.",
"You are wrong to assume that the \"downward pressure\" (or better said downward momentum of air) ",
" before reaching the floor. In fact it ",
". That means the momentum transferred by the wings onto few air molecules is then spread by molecular c... | [
"It would have to be exactly the same as the gravitational force on the birds weight to keep it in the air, any more and the bird would climb and hit the roof, any less and it would hit the floor."
] | [
"The energy could be converted into heat, but conservation of momentum says the plane ",
" become heavier due to the flapping. A force is keeping the bird up; an equal and opposite force is pushing the plane down."
] |
[
"How does Molecular Beam Epitaxy work?"
] | [
false
] | Also why is the electron gun necessary? Thanks for your attention. | [
"What electron gun? The RHEED (Reflection High-Energy Electron Diffraction)? It has nothing to do with the growth. It's just a way of measuring the current thickness of the film as you grow it. ",
"As for how it works I don't think it's conceptually that different from any other growth technique. A very dilut... | [
"Thank you. Our teacher said electron gun instead of RHEED and it confused me."
] | [
"Well the \"molecular-beams\" are really effusors that \"shoot\" a stream of gas particles (just look up effusion,). Now in terms of HOW one produces these gas particles, I believe, though I'm not too knowledgeable on this stuff, one strategy involves using an electron gun to sublimate particles off. A more conve... |
[
"Does the ozone layer affect the color of the sky?"
] | [
false
] | I know that the color of the sky is due to Rayleigh scattering so would the color change if the ozone layer were depleted? If so, what color would it be? | [
"You are right that the different atomic structure of oxygen (O2) and ozone (O3) affect their absorption properties.",
"What if the ozone layer was composed of a different molecule than O3?",
"What would happen if there was no ozone in the ozone layer? It would be called something else and there would be no ozo... | [
"The ozone layer doesn't greatly influence the color of the day sky. However, you can see the ozone layer at two incidents, both of which taking place at sunrise and -set: ",
"Earth's shadow",
"blue hour",
"In both cases, the blue hue comes from Chappuis absorption, not from Rayleigh scattering. "
] | [
"That makes sense. So as oxygen levels in the ozone go down, the color of the sky would become lighter and lighter blue until white?",
"So what if there was an abundance of oxygen? Would it become bluer?",
"What if the ozone layer was composed of a different molecule than O3? I imagine a different atomic struct... |
[
"How is a mirror both silver AND able to reflect everything at the same time?"
] | [
false
] | [deleted] | [
"I believe your question is asking how can a mirror be colored silver, and at the same time show a reflection.",
"The way vision works is that light hits an object, bounces off, and then hits our eyes. When this happens some of the colors of light get absorbed, and what is left gets reflected. A green leaf will a... | [
"Mirrors are colorless in the visible spectrum. Or you could say they're whatever color they're reflecting at the time. However, mirrors are definitely not \"the color silver.\" In fact, you could say that the metal called silver isn't even \"the color silver\" as in meaning \"shiny grey.\" Silver reflects basicall... | [
"Not in the same way that an apple has a color. Those silver bars ",
" gray, but they're not gray in the same way that a gray Lego block is gray. If you read my whole post, you'll understand what I'm saying.",
"Another way to put this is that \"silver\" is not a color, it is a description of specular reflection... |
[
"What would happen if you melted 2 pieces of uranium that are in different times of their half life together? Would it still decay at their original times?"
] | [
false
] | null | [
"The total activity would just be the sum of the activities of the two individual pieces."
] | [
"So even though they are mixed they would still decay at their original times?"
] | [
"Yes. Each atom has no \"memory\" of how long it has existed. It still has a probability of decaying in any instant of time which decays exponentially on a timescale set by the half-life."
] |
[
"Is our technological progress accidental?"
] | [
false
] | Just wondered if we went back in time and randomly removed from history many of great inventors ( marconi' edison, bill gates, tesla, etc), would we have world going in same direction? Would someone eventually invent all these (maybe a bit later) things or we were just lucky that had these people born? | [
"Well with those examples it's pretty easy. Bill Gates is an entrepreneur, not an inventor. As for the others, I don't think we'd have been set back much at all without them. They all had their most important inventions independently invented at the same time or very nearly the same time by other people. They were ... | [
"There is a chapter in Jared Diamond's ",
" that deals with this. His argument is that all of the great inventors we think of generally built their inventions on the backs of the progress made by those before. So he claims that, had an inventor such as Edison never been born, the discovery would have been made ... | [
"Here",
" is an interesting discussion on just this.",
"Also note that it is common for separate groups or individuals to simultaneously discover the same thing, which seems to favor a social view of discoveries."
] |
[
"Were \"cavemen\" \"white\"?"
] | [
false
] | I know that the Homo genus is thought to have emerged in Africa, and that Homo erectus left Africa and developed in Asia and Europe while Homo sapiens were still developing in Africa. When I see depictions of Neanderthals in the media, they often seem to have more Caucasian than African features, with lighter skin and hair. Do we know anything about the skin color of early hominids, or is it all just speculation? | [
"TIL Northern Canadian and Siberian populations didn't become light skinned, even though there was less sun, because they were mainly fishing cultures, and so gained enough vitamin D from their diet."
] | [
"Neanderthals did evolve light skin. ",
"Some of them even had the gene for red hair.",
" (Edit: ",
"better link for that",
" now I'm not on my phone.)",
"The earliest Homo sapiens sapiens were dark-skinned, though, and ",
"didn't evolve white skin till much later",
" . We didn't inherit from the Nean... | [
"Yes, the region of where Neanderthals have been living has a large impact on the color of their skin for all the reason you listed. Also, you'd be surprised how much information DNA these days reveals, even though many exterior features can only be speculated. I'm not sure if this is exactly answering your questio... |
[
"What is the difference between shock- and soundwave?"
] | [
false
] | As the title says, what is the difference? Isn't it basically the same thing, soundwave being a weaker version of shockwave? Like an explosion - you hear the pop due to pressure "front" reaching your ears, be you close enough - you'll get hit, far away - just a soundwave with no real damage potential. Or am I mixing something? | [
"I'm a PhD candidate writing a dissertation about this topic now (applied to volcanic explosions).",
"Sound and shock waves are both pressure waves. You can hear a shock, though it may blow your eardrums out if it's strong.",
"Sound waves are infinitesimal in amplitude, meaning that the pressure change of a sou... | [
"Great info! I think I get it know!",
"Still a little confused about one thing - does the shock wave traveling faster than the speed of sound mean that the sound will ultimately travel faster as well or you will feel a punch first and hear a sound later? (If so, how can there be no sound from shockwave pressure?)... | [
"It's not really accurate to say that a shock is sound. By definition, sound cannot propagate faster than sound. You could say that they are both pressure waves. ",
"Sound is really a special case of pressure waves where the wave pressure is small enough that the physics become easy."
] |
[
"AskScience AMA Series: I'm Marina Picciotto, the Editor in Chief for the Journal of Neuroscience. Ask Me Anything!"
] | [
false
] | I'm the Professor of Psychiatry and Deputy Chair for Basic Science at Yale. I am also Professor in the departments of Neuroscience, Pharmacology and the Child Study Center. My research focuses on defining molecular mechanisms underlying behaviors related to psychiatric illness, with a particular focus on the function of acetylcholine and its receptors in the brain. I am also Editor in Chief of the Journal of Neuroscience, a fellow of the American Association for the Advancement of Science, and a member of the National Academy of Medicine. I'll be here to answer questions around 2 PM EST (18 UT). Ask me anything! | [
"Hi! My fist ever AMA answer. I think systems neuroscience is exploding right now because of a lot of new tools. If you have been following the BRAIN initiative news coming out of the White House, the goal has been to develop new ways to study the nervous system, and many of them have enabled us to study neurons as... | [
"As a student looking to specialise into neuroscience, what in your opinion are the most exciting new areas?"
] | [
"How comes accessing one Journal of Neuroscience article for one day from one computer costs US$30.00? Neither the authors nor the reviewers receive any of that money, and taxpayers fund most of the research. Universities waste ",
"millions of USD every year in journal subscription fees",
" (e.g., Harvard's exp... |
[
"Is anorexia naturally occuring, or has it been \"created\" by modern society?"
] | [
false
] | What I mean is, has western culture and the ideas of having to be thin to be beautiful created this disorder, or are there cases and accounts of anorexia pre-popular culture (early 20th century) Any ideas, thoughts or anything relating to bulimia and other eating disorders would be interesting too. Thanks. | [
"Anorexia was first recorded in 1684 and has appeared across cultures since. This suggests that there is an underlying cause other than just societal impact in the form of a genetic predisposition, such as people who have a lessened pleasure response or even a painful response to the consumption of food, this can c... | [
"To be clear, you're probably thinking of the eating disorder ",
"anorexia nervosa",
". Anorexia is simply the symptom of lack of appetite, which may be caused by any number of non-psychiatric conditions."
] | [
"Anthropology student here.",
"There are a number of culture-specific 'disorders', meaning certain 'abnormal' behavioural traits have much higher instances of occurrence in some cultures rather than others. Anorexia appears to be one of them, though it's not limited to only Western cultures. It seems to be a res... |
[
"Why does a lit candle make a sound when you blow on it a little?"
] | [
false
] | [deleted] | [
"Sound is practically (just like wind) is a difference in air pressure. You are making sound using your flute/sax because of this (",
"http://www.thefluteplayer.net/basics-flute-harmonics-explained.html",
" or, if you want to be scared: ",
"http://en.wikipedia.org/wiki/Bernoulli%27s_principle",
" ). Blowin... | [
"A hot object can behave as a sound amplifier. This effect drives the oscillation in the ",
"Rijke tube",
" physics demo: varying the velocity of air adjacent to a heated wire will vary the air's thermal expansion rate, which produces pressure changes in the air (sound waves.) Probably this also causes the l... | [
"Wait. So you're saying that blowing on a candle will create more noise than blowing on a homogenous air space? (I mean, I know this is true... I've been alive for a few decades). Is this essentially the same principle behind what happens when we hear thunder vs. wind? Is blowing on the candle creating a mini weath... |
[
"Why is water in oceans/seas salty?"
] | [
false
] | null | [
"All natural water has some salt content, but in fresh water it's just too little to notice. Lakes have rivers/streams that take water out to keep salt from building up. In the ocean, there's no flow of water out, just evaporation, so the any salt dumped in there from the rivers stays there and doesn't go it. It ju... | [
"To expound on this, the salt originally comes from the ground that rivers carve through."
] | [
"It is a matter of accumulation. Inland water bodies are constantly \"flushed\" with freshwater from precipitation and all geogenic salinity is transported into the oceans. The latter are always the final receiving waters, thus salt accumulates as it will not evaporate (to form clouds, and rain aso.).\nFor inland s... |
[
"How would splitting an atom in a nuclear bomb affect the universe - using our understanding of string theory?"
] | [
false
] | null | [
"What reason do you have to think that this might occur?"
] | [
"What reason do you have to think that this might occur?"
] | [
"Got to thinking about the dangers of nuclear weapons and their effects in the macro sense. You can't just be messing with particles like that without considering quantum entanglement. ",
"Now the rest of my thought process for this one unravels into science-fiction (as we see it now). ie UFO's, aliens, blah blah... |
[
"Are there any Earth sized object in space that behave like comets?"
] | [
false
] | Are there any really huge objects out there that are just flying around through space the way comets do? | [
"What do you mean flying around through space the way comets do?",
"Earth does fly through space the way comets do, with the exception that comets are more highly elliptical and sometimes off the plane of elliptic. ",
"But there are no Earth-sized comets in our solar system, at least not that we've discovered. ... | [
"I mean are there any planets that don't have their own star? Flying through interstellar space.",
"Yes, there are. But those don't inherently behave like comets - they're not similar really. They're called ",
"Rogue Planets",
".",
"Are all object in our solar system from only our solar system? Do they ev... | [
"I mean are there any planets that don't have their own star? Flying through interstellar space.",
"Are all object in our solar system from only our solar system? Do they ever come in from outside it?"
] |
[
"What is observation?"
] | [
false
] | So obviously with all the Higgs discussion going on surrounding CERN's exciting announcement today, I've been reading (and re-reading) a lot about quantum physics in general. Very fascinating stuff, even for an uninitiated layman such as myself. I feel like I can grasp some of the major concepts and discoveries involving this branch of science, but it so nuances, and in some cases rocks, the very fundamental assumptions we make about the physical universe that some of these topics are endlessly elucidated by continuous and repeated explanation. One such topic, for me at least, is the role of observation in quantum science. I've been lucky enough to have some very intelligent people, including quantum physicists, explain in straightforward but rigorous terms certain implications of concepts like quantum entanglement, the double-slit experiment, superpositions, etc. One of the revelations, as I understand (please brutally correct me if I'm wrong), is that the observation of a system is endogenous to that system; i.e., in some cases the act of observing an experiment affects the outcome. So is this simply the result of the methods of quantum physics? Is it possible to observe these phenomena adding energy to or interacting with the systems in which they occur? And if so, what would we see? If not, what exactly is observation, and why is it that way? Does quantum science affect the philosophy of science and how? I know this kind of question could quickly devolve into mystical sorts of speculation very easily. I have to be clear that's not the kind of discussion I'm looking for. I'm hoping can (as usual) smack down my misunderstanding and give me some solid grounding on the fundamentals of science from experts who know what they're talking about. | [
"Searched",
"Relevant ",
"discussion",
"Original comment by ",
"Burdybot",
"My friend and I are currently arguing over this concept. He says that an observer requires consciousness to determine the state of a system according to quantum superposition. I say that an observer does not have to be a living, c... | [
"I understand that \"sentience\" and \"consciousness\" have nothing to do with this topic, but I'm still wondering what observation actually is. ",
"The top comment of this thread",
" begins to get at what I'm asking, I think. But is it theoretically possible to observe quantum particles without interacting wit... | [
"The act of observation collapses the wavefunction, because it destroys the superposition of states. In fact, ",
". \"Observing\" them without interacting with them is giving the trivial solution - that is, in the case of the double slit experiment - the particle goes through both slits.",
"Imagine you're playi... |
[
"Why can we use microwaves to heat our food, when microwaves have less energy than visible light?"
] | [
false
] | [deleted] | [
"The general idea is correct here, in that we use microwaves to excite water molecules, which then relax from that excited state by dumping energy into translational energy, which is heat. But one clarification to make is that microwaves don't excite water into vibrationally excited states, but rather rotationally ... | [
"It's not really so accurate to say microwaves have less energy than visible light. You can have any amount of energy in microwave radiation, just like you can have any amount in visible light. It just comes in smaller increments (i.e. photons) when you use microwaves.",
"In a nutshell, visible light doesn't work... | [
"Basically its like microwaves are pingpong balls (lower energy) and light would be basket balls (high energy). If I hit you with one ping pong ball, nothing. If I hit you with a basketball, you notice it. If I pelt you with 10million ping pong balls you will really notice it. Kinda the same thing. It is not the am... |
[
"Is burning gasoline carbon-neutral?"
] | [
false
] | Presumably, (this is where a potential correction fits) most of the carbon dioxide released from the burning of crude oil and its derivatives was at one point stolen from the atmosphere and used by living organisms that became fossil fuels. Wouldn't this mean that burning gasoline is, in fact, a carbon neutral activity? (I am not considering the toxins and other compounds it would release and obviously have an ill effect on the air. It's very obvious that gasoline is a proven pollutant, I'm asking whether it's carbon-neutral.) | [
"Gasoline comes from petroleum, which is taken from the ground. On a human timescale it's not carbon-neutral at all, but on a ",
"timescale of 100-200 million years",
", then yes, carbon does recycle. But that's not the intent of the term \"carbon neutral\", it's intended to refer to the human habitat."
] | [
"Others have answered well regarding the timescale.",
"The big semantic issue is the term \"carbon neutral\" - the term is generally used in the very-short timescale. On the order of \"less than a year.\" Such that the amount of CO2 in the atmosphere is the same \"immediately before that quantity of fuel enters... | [
"I don't mean the atmosphere as a sentient being. Sorry it sounded that way. I mean it, and the ocean, as a thermoregulator. But you're right, that was poorly phrased on my part. ",
"And of course all life isn't going extinct. It will just displace billions of humans, especially poorer ones, and kill off many mor... |
[
"Why are there no freshwater octopuses or squid?"
] | [
false
] | There are freshwater crustaceans, gastropods, and bivalves. Why are there no freshwater cephalopods? | [
"Living in freshwater requires that you have the ability to excrete fluid from your cells efficiently, because osmotic pressure causes water to constantly move into the cells. Why they haven't evolved to deal with this.....honestly I have no idea. It really doesn't make sense does it?",
"I will note that this i... | [
"Interesting observation.",
"You might try soliciting opinions from ",
"r/biology"
] | [
"The majority of groups of animals are limited to marine environments.",
"That really makes sense when you think about it. Freshwater is innately familiar to us, since we drink it and live near it, but it's easy to forget how niche of an environment it is.",
"Follow-up question: I wonder if the general rareness... |
[
"If an object is approaching you at a speed close to the speed of light will the color frequency of the reflected light change due to the Doppler effect?"
] | [
false
] | null | [
"Yes. It's called relativistic blueshift, or in general relativistic Doppler shifting. "
] | [
"Sorry, my wording was confusing. I meant that in the example about measuring relative velocities of stars we were concerned with radiated light rather than reflected light.",
"Reflected light is shifted, too. This is how radar guns (like the police use to catch speeders) work. That would have been a better examp... | [
"EDIT: We learn the relative velocities of stars using this phenomenon, although in the case of measuring relative velocities of stars, we are concerned with radiated light rather than reflected light.",
"We can look at a spectrograph of a star and by the relative positions of the peaks, we know what each peak co... |
[
"If you stack layers of graphene does it turn into graphite?"
] | [
false
] | I've heard things like, "graphene as thin as saran wrap could hold an elephant balancing on a pencil". But if graphene is just a single layer of graphite how could you stack it and still have graphene (if that's even possible). | [
"Correct. Graphene layers only weakly bond to each other via ",
"Van der Waals",
" forces and once you have several layers you really cannot call it graphene anymore. The properties of multilayer graphene are drastically different from single layer. Stacking enough layers to make saran wrap would result in a gr... | [
"One word answer: yep. "
] | [
"Thanks for clearing that up. It would have been embarrassing telling people how tough graphene is if you stacked it up."
] |
[
"Can a vacuum cleaner interfere with the broadband connection?"
] | [
false
] | Whenever I'm in my girlfriends house and she vacuums, her broadband connection goes down. It happens every time and I find it a bit strange. Can anyone explain this? | [
"Suppression. Capacitor across motor supply. "
] | [
"Electromagnetic interference. The vacuum cleaner generates electromagnetic emissions (radio signals) that interfere with the broadband device(s) by inducing currents that aren't supposed to be there.",
"What kind of broadband? Fiber-optic to the house? 3G? ADSL?"
] | [
"Fiber-optic broadband to the house. Its very annoying because it keeps going regularly afterwards."
] |
[
"Is it possible that previous human civilizations used technologies made from organic materials, leaving no trace, therefore were more advanced than we are currently aware of?"
] | [
false
] | null | [
"I've asked my self that question many times as well. A new question rised for me as well. We now use technology to store our knowledge such as servers, hard-drives, memory chips/cards. Say civilization sort of collapses in on itself, and thousands of years later new advanced civilizations sprawl. Will they hav... | [
"Yes. At least from a cultural perspective. ",
"Look at cultures like the ",
"Mound Builders",
". If they hadn't decided to move earth around, we would probably have no idea they existed. ",
"Just like we don't know much about who built ",
"Gobekli Tepe",
" becuase it was the only stone thing they seeme... | [
"OP is asking a different question than the one in the link. Although taken literally this question is unanswerable, the closely related question:",
"'Is it possible that previous human civilizations used technologies made from organic materials, leaving no trace ",
", therefore were more advanced than we are c... |
[
"GPS requires microsecond clock accuracy in the satellites but the terrestrial receiver accuracy doesn't matter at all. Why is this?"
] | [
false
] | null | [
"Think of it like a math problem where you are trying to solve for your coordinates (X,Y,Z) ",
"If you know the current time, you can solve this by comparing the signals from 3 satellites, which have a known position and broadcast their current time.",
"It takes longer for the signal to reach you from satellite... | [
"The GPS satellites transmit their clock signals. Anyone can pick them up and have a super-accurate stable clock.",
"I used to work in a radio-frequency lab. An RF lab that needed a stable frequency reference, typically 10MHz, which was carried on coax cables to all the instruments in the lab. Each instrument ... | [
"To add to this, because each satellite transmits the time it is possible to compare the arrival times of signals from different satellites. If you can see more than 4 satellites, you can work out the actual time at the receiver without needing a super-accurate clock at the receiver.",
"By comparing the delays (d... |
[
"Are there any reactions more exothermic than nuclear fusion of hydrogen to helium?"
] | [
false
] | is hydrogen the only element that can be tempted to fuse? | [
"I suppose it depends how you're defining 'exothermic.' Do you want the most energy/fuel mass? Or most energy/reaction? ",
"To the extent of my knowledge, hydrogen fusion is the most exothermic nuclear reaction ",
". It's pretty easy to see from the ",
"binding energy per nucleon.",
" Since the sun fuses by... | [
"In a sense, yes, there is exactly one of me."
] | [
"To fuse, nuclei have to collide. I'm not saying it's impossible, but how often do you think 26 nuclei collide at once?"
] |
[
"Is it feasible to grow plantlife on mars in an attempt to oxygenate the planet?"
] | [
false
] | If not, is there any other idea as how to Increase martian oxygen levels to 20% or higher? Some sort of "Total Recall" scenario? | [
"We would have to increase the atmospheric pressure first. As is, there is not enough atmosphere to support any earth-based plant life."
] | [
"Most organisms that can ",
" in space cannot actually ",
" in space. They go into some sort of hibernation or other method for surviving extremely harsh conditions. Even if they can function to some degree, it would be only for a limited amount of time.",
"And a cyanobacteria/tardigrade hybrid doesn't really... | [
"There are a number of exceedingly challenging things about mars that are often glossed over in the popular science/scifi presentation. There's no magnetic field, so little protection from the charged cosmic rays. The planet's small and the combination of small planet and no magnetic field seems to mean that the at... |
[
"Could there be any subterranean oil or gas reserves deep enough to come in contact with mantle? If so is there any evidence of an underground explosion occurring?"
] | [
false
] | Just a random thought I had. Couldn't find anything about it online. | [
"No. Oil and gas form within a rather restrictive temperature range, commonly referred to as the ",
"\"oil window\" of between ~60-160 degrees Celsius",
". A normal ",
"geothermal gradient",
" in the earth is ~25 degrees C per kilometer, so the oil window in most places occurs at depths of ~2.5 - 6.5 km. By... | [
"One thing to keep in mind, heat + oil does not equal an explosion. You still need some form of oxidizer to create combustion and an explosion, like Oxygen."
] | [
"What would happen if a Volcano formed through a deposit of natural gas or oil? "
] |
[
"What causes you to feel terrible during a hangover?"
] | [
false
] | I know a big part is dehydration, but what exactly makes you feel like sh*t? | [
"Besides dehydration, it's also the highly toxic and carcinogenic chemical ",
"acetaldehyde",
", which enzymes in your liver turn alcohol into. Normally this is turned by your liver into acetic acid, the primary ingredient (besides water) of vinegar, but not all of it is properly converted, which contributes to... | [
"Alcohol is turned to acetaldehyde by alcohol dehydrogenase, and then acetaldehyde is turned into acetic acid by acetaldehyde dehydrogenase. The production of alcohol dehydrogenase is usually sufficient, but the production of alcohol dehydrogenase is limited, so acetaldehyde accumulates in human body and causes neg... | [
"This cannot be a good answer because I (like many people) have been *much* more dehydrated for non-alcohol related reasons than I ever got drinking alcohol, but the hangover symptoms are very distinct."
] |
[
"Could you feel the gravity from a teaspoon of Neutron Star matter on Earth?"
] | [
false
] | null | [
"I would strongly recommend against this experiment as I am a little overly attached to this planet. A few things first.",
"The instant this mass was removed from the star it would expand violently, very violently, so violently that I cannot even begin to explain it in real life terms, if this helps here is the m... | [
"A teaspoon of material from a neutron star will be terribly unstable outside a neutron star. However, if it were stable, than the force on a 50 kg man from 1E12 kg 1 meter away would be 7E-11 * 50 * 1E12 / 1",
" = 4000 N (all calculations done with 1 significant digit). The force of attraction will be equal to... | [
"Having trouble understanding your result.",
"Are you saying someone would feel as if they were being pulled with the force of 400 kilograms? Or that the attraction is equivalent to standing near a large motorcycle? ",
"Or is it something else because both of those results make no sense.",
"A teaspoon full ... |
[
"Do chickens or other birds have unique “voices”?"
] | [
false
] | [deleted] | [
"Yes! I can easly tell apart some of my chickens by the way they cluck. Its a change in pitch in some. In others they may draw out their cluck longer or just cluck in a certain definable pattern. Somechickens sound very similar however.",
"Edit: cant to can"
] | [
"Yes, my parrots most definitely did. It was most noticeable when they would talk. I could tell who was speaking very easily, even if I couldn’t see them. Their calls were also quite different, even if they were the same breed. As for chickens, I can’t speak to their differences.",
"Edit: also, flicks in the wild... | [
"Interesting, I wasn’t aware about the dialects either"
] |
[
"Is there a limit to how strong materials can theoretically be?"
] | [
false
] | People have managed to create extraordinarily strong materials such as carbon nanotubes and graphene, as well as other materials such as carbyne. But, in the future, it is possible that we could create future materials that are even stronger? Is there a limit to how strong a material can be, and of scientists were to create the strongest substance that is physically possible, how strong would it be? | [
"Yes, if you're talking about regular molecular matter that we can create and manipulate. You're limited by the strength of molecular bonds, which have well-defined and known values.",
"It turns out that carbon-carbon bonds tend to give you the best strength to weight ratio due to their high intrinsic strength a... | [
"The highest possible strength-to-weight ratio is c",
" = 9*10",
" kYuri. The highest known is the colossal carbon tube at 59,483 kYuri. So the theoretical limit is about 1.5 trillion times stronger. ",
"Source"
] | [
"How is that ratio calculated?"
] |
[
"[Mathematics] What is the problem with a dictator in the Arrow's Paradox in ranked voting? Wouldn't the dictator change each election, so that it isn't just one person forever in charge?"
] | [
false
] | null | [
"I am not sure what you are asking. \"Dictator\" in this sense means that the overall rank-order, which is ostensibly a function f(x",
", x",
", ...., x",
") where x",
"'s are the individual rank-orders of the voters, is really just a function of one particular voter's rank-order. That is, f = f(x",
"). T... | [
"Ok, so in a system with the two conditions needed to ensure a dictator, even if everyone else voted E>D>C>B>A, in this case if x put A first, then A would still win?"
] | [
"Yes that's what it means for X to be a dictator. "
] |
[
"If a blackhole has the same gravitational pull of a star with the same mass, how come light can excape the star but not the blackhole?"
] | [
false
] | null | [
"The gravitational pull depends on the mass that is pulling and the distance to the pulled object.",
"A black hole is much more concentrated than a star.",
"In the case of a star if you get close to its surface most of the star is still far from you.",
"In the case of a black hole, since its so concentrated, ... | [
"While the comments here are fine, it is important to note one thing that makes black holes very different from stars. In general relativity, gravity is the geometry of space time. A star will form a gravity well, but not a singularity. The singularity is what makes a black hole so different. Since all its mass... | [
"When you move inside a spherical shell of uniform mass, the gravitational pull cancels out. If you were able to push an infinitely insulating and strong tube through the center of the sun, you could hang out in the center with zero gravitational pull from it. In a black hole, all the mass from the star is concentr... |
[
"How long it takes for crude oil to form?"
] | [
false
] | I'm just fighting with this god believer guy As far as I know it takes millions of years for it to form but why does it take that long? How do scientists tell that it takes that long? | [
"The amount of time it takes to form crude oil is variable because it depends on how quickly you can bury organic material, how deeply it becomes buried and heated, and the pressure that the organic material experiences. These processes are controlled by tectonic activity, which occurs on millions-of-year timescale... | [
"It takes that long because it is such a complicated and complex process. You need the perfect tectonic environment which has formed over millions of years to create a basin structure capable of trapping carbon-rich material. You then need the perfect climate to cause this material to decay without being eaten by b... | [
"The correct answer is ",
" - people who have strongly held (wrong) beliefs don't change their mind when presented with evidence. It's like arguing that night is day. There is a link to another reddit discussion on the subject of belief vs reality:\n",
"http://www.reddit.com/comments/262n45"
] |
[
"Is storing energy mechanically (like winding a watch) less efficient or expensive than batteries?"
] | [
false
] | I was wondering if it would be practical to store solar energy using a mechanism that is analogous to a wind-up watch. Would a mechanism like this have to be enormous? Would it have to be made of incredibly expensive components? Would it break down easily? | [
"Springs can be very reliable and efficient over a small travel range when unimpeded. However, they're not very dense – particularly if you're trying to use them over their more-efficient range or in an open, unimpeded arrangement.",
"Watch springs are fine if you're only trying to store a couple joules. You only... | [
"When you say turbine I've got no clue what you mean. Do you mean an object with mass that is set to spin on a spindle? ",
"Like if I had a big cylinder of granite on a spindle? ",
"If that is what you are talking about, having low friction bearings and a vacuum on the inside ends up being a very efficient f... | [
"From the description that would be one type of turbine. Stores energy as mechanical energy traveling in a circle.",
"It is good for short term, long term that bearing is a bad vampire load, and no vacuum is ever perfect and creates new loads.",
"Very efficient for short periods of time but your energy leaks aw... |
[
"How close could two planets get before they would start to pull each other apart?"
] | [
false
] | I know hypothetically they would just crash into one another but if they were somehow held at a distance would their gravity wells pull things off the surface of the other planet? Would there be some sort of gravitational limbo in between where they mixed? | [
"it's called the Roche Limit and it depends on the masses",
"http://en.wikipedia.org/wiki/Roche_limit"
] | [
"http://en.wikipedia.org/wiki/Roche_limit"
] | [
"very cool thank you sir!"
] |
[
"How does the human body separate waste into solids and liquids and why?"
] | [
false
] | null | [
"Urinary 'waste' and gastrointestinal 'waste' are two fairly distinct entities.",
"Stool is mostly just the undigested portions of whatever you ate, with some added biliary secretions and gut bacteria added in. Think of it as 'waste' in the sense that some of what you're eating is 'wasted', rather than getting di... | [
"So basically if the GI tract was more efficient we'd need to poop less often?"
] | [
"It does not have much to do with efficiency- the majority of the nutrients that you eat are absorbed (unless you have some kind of inflammatory bowel disease or other problem). They've calculated the efficiency, and it was mentioned in a lecture back in med school. I can't remember the number but it was over 90% f... |
[
"What is gained from having different blood types? [Biology]"
] | [
false
] | null | [
"There may not be any advantage at all. (Not everything that is around today has evolved because it is advantageous.) ",
" (Edit: we have a good idea of why they exist, which I wasn't going to get into, but short version is that different people in different parts of the world were exposed to different kinds of d... | [
"That list of \"The ten worse evolutionary designs\" is simplistic to the point of almost being wrong. To be sure, each of those things is likely not an ideal design, but it is a trade-off of a larger advantageous adaptation. To deconstruct a few of their examples:",
"[1]. It basically says that \"sea mammals sho... | [
"That said, one idea that comes to mind for how it might be advantageous is that having diverse blood types might make life a bit harder for blood-borne pathogens. If everybody's blood cells are flagged with different antigens it becomes more complicated trying to disguise itself from the immune system when hopping... |
[
"What would be different if Homo Sapiens had gone extinct instead of Neanderthals?"
] | [
false
] | [deleted] | [
"This is really an impossible question to answer without wholesale speculation. We do not actually know enough about Neanderthal intelligence or culture to make many conclusions."
] | [
"Since this is purely speculation, I strongly recommend ",
"The Neanderthal Parallax",
" trilogy by Robert J. Sawyer. ",
"This deals with your question in detail. An alternate Earth where Neanderthal man survived into a technological age, and a rift opens between that world and ours. It's a bit utopian, but g... | [
"why?"
] |
[
"Do animals seek a variety in their diet?"
] | [
false
] | For animals, why are feeding chains organised into food webs, rather than chains, is it because having more than one source of nutrition provides a security in the case of an extinction occurring to a species you're feeding on, or do they simply enjoy having a variety in their diet, much like the way we humans do? | [
"This largely depends on the animal! Some animals, like the leatherback turtle, whose diet consists solely of jellyfish, are specialists that lack variety in diet. Animals that DO eat several food sources generally do so because of two main reasons. ",
"First off, many food sources are only seasonally available. ... | [
"Suppose an animal has access to two types of food: A and B. Will it always choose its favorite one, or will it ever think: \"I've had a lot of A recently, I'll have B today for a change\"?"
] | [
"Animals catagorically do eat for pleasure. If you offer a pet a treat as opposed to their normal fare they'll scarf the treat eagerly. Pleasure from good tasting stuff is not human exclusive."
] |
[
"Why does copper form a nice coating on iron, but not silver during electrolysis?"
] | [
false
] | Okay that was a retarded title, but I did a chemistry experiment at school which involves the electrolysis of substances in solutions. One we did was the electrolysis of an iron nail in a CuSO4 solution, and we observed copper forming on the surface of the iron nail, which can be filed off. We also tried doing the same experiment without the battery, and we got the same result. This is purely my speculation, but would iron ions not go into solution in the experiment involving the battery, and would go into solution in the one without a battery? Because of the battery constantly supplying electrons to the iron nail preventing Fe losing electrons and becoming Fe2+? Secondly, we did another experiment, but this time with AgNO3 instead of CuSO4. I observed silver forming on the surface of the nail, however unlike copper, this can be wiped off very easily, and flecks of it would fall off the nail even while the circuit is connected. Why does copper adhere better than silver? Furthermore, we also did an electrolysis of copper in CuSO4. In this case, copper was formed much more significantly at the edges of the cathode, not the flat surfaces, and unlike the formation of copper on the iron nail, the excess copper falls off quite easily too. Why? I've read that this reaction is referred to as the purification of copper. Why? We also tried using graphite electrodes, instead of metallic electrons, and throughout the experiment carbon kept falling out. Shouldn't the graphite be non-reactive? Also, copper and silver forming on the graphite appears to be in a flatter, smoother structure, as opposed to the crystal-like structure observed elsewhere. However, it wasn't too hard to remove... How is graphite different from other substances? Thanks for the science. | [
"It's a crapshoot whether an electroplated metal will stick or flake off the electrode surface. Metal atoms pack in a regular pattern called a crystal lattice. Not all atoms adopt crystal structures that mesh well together. It just happens that silver and copper don't fit well together, but iron and copper do. ... | [
"The rougher parts of the surface tend to be the places where the number of surface defects is higher. These spots also tend to have higher reactivity."
] | [
"I read that in graphite the carbon is bonded with three other carbons and has an electron that is delocalised. Could it be that during the electrolysis process that the electron is removed?"
] |
[
"Why don't elements consistently increase in stability as more neutrons are added?"
] | [
false
] | From what I understand, neutrons and the strong nuclear force are what allow elements other than hydrogen to exist. However, as an example: U238 has a half-life of about 4.4 billion years, but U240 has a half-life of about 14 hours. I am aware of the existence of neutron and proton shells, but that's about the limit of my knowledge. | [
"Neutrons are fermions. If you keep adding them to an atom, they will go to higher and higher energy states as the lower states are already filled with neutrons and the Pauli principle exclude those states from being occupied by multiple neutrons. Their binding energy is therefore much lower and they can escape eas... | [
"I believe you are; the strong force actually gets stronger or is constant with distance.",
"The nuclear force (which is to a certain extent, as van der Waals is to the electromagnetic force) does however decay with distance, Yukawa style."
] | [
"Naw, the similarities don't go that far."
] |
[
"The Indian subcontinent was an isolated landmass for millions of years. Did unique dinosaurs or wildlife evolve during that time?"
] | [
false
] | null | [
"Barapasaurus,Indosaurus and a Ichthyosaur species have been found in India. Also not to mention one site that had over a thousand fossilized dinosaur eggs. There’s new evidence suggesting that hoofed mammals of the horse and rhino linage evolved near or on the Indian subcontinent. Also the primates we see in India... | [
"Also here’s a good article on early India biological interchange. ",
"https://www.nature.com/articles/ncomms12132"
] | [
"That first article mentions how India has the highest number of fossilised Dino eggs and nesting sites, from 68 Ma ago “deposited during a time of volcanic activity”. Do they mean the Deccan Traps? I didn’t realise it was already active at that point. Whether they mean that or not, I wonder if nesting continued wh... |
[
"Does the Sun experience \"tides\" due to influence of it's satellites (the planets)?"
] | [
false
] | Water on earth is notably affected by the Moon and the Sun. Does our favorite big ball of plasma experience an equivalent distortion caused by the planets? | [
"There are tidal forces from the planets, yes, because the gravity of the planets affects the sun, but they are very small. The largest tidal acceleration would be from Jupiter, and it's on the order of GM_J / a_J",
" * R_sun / a_J ~ 2x10",
" m/s",
" . I may have left out a factor of 2 in there somewhere, but... | [
"This is the formula for the tidal acceleration on the sun due to jupiter on the axis connecting the two centres of mass. Where M is mass of jupiter and a is the distance between the two centres of mass and R is the radius of the sun and G is the gravitational constant. It could also be written as (2",
"M*R)/a",
... | [
"This is the formula for the tidal acceleration on the sun due to jupiter on the axis connecting the two centres of mass. Where M is mass of jupiter and a is the distance between the two centres of mass and R is the radius of the sun and G is the gravitational constant. It could also be written as (2",
"M*R)/a",
... |
[
"How do self-focusing projectors work?"
] | [
false
] | [deleted] | [
"They have a built-in rangefinder that determines the distance between the lenses and the screen. Using the data that the rangefinder supplies, the little computer inside the projector calculates how it should position its lenses so that the light focuses on the screen. Once the calculation is done, small motors at... | [
"How does the microcontroller calculate the lens position? Is it just an equation based on the distance from the screen? What if I moved the piece of paper I wanted to project closer to the lens, how does it correct for that, since the distance from the lens to the screen wouldn't change?"
] | [
"Yes the lens configuration is probably calculated using a function with the distance as a parameter.",
"Is it an overhead projector we are talking about here? Because when you say simply \"projector\" I imagine you're talking about a device that takes digital signals as input and projects an image onto a screen,... |
[
"Is the maximum velocity of every atom the same (i.e. is the maximum velocity of an iron atom the same as the maximum velocity of a plutonium atom?)?"
] | [
false
] | null | [
"Yes; the maximum velocity of anything, no matter what it is, is the speed of light (nothing massive can ",
" the speed of light, but anything can get arbitrarily close to the speed of light). "
] | [
"No, all atoms behave the same at any velocity, owing to Einstein's (special) relativity; there is no such thing as absolute motion, and no way to tell whether the atom is moving or whether it is you who are moving. It sounds like you might be confusing velocity with acceleration (which is change in velocity, due t... | [
"An interesting example of this is the ",
"\"Oh-My-God-Particle\"",
", which was a particle of cosmic radiation, proton for example, that was found that traveled incredibly close to the speed of light, so close that if this particle traveled in parallel to a photon, it would take 200,000 years for the photon to... |
[
"Question About Global Warming"
] | [
false
] | [deleted] | [
"I hesitate to get into conversations about anthropogenic global warming because of my stance on the subject, namely that global warming is a definite reality but us being the sole cause or the biggest contributor is a little dubious.",
"However this one's an easy answer. The ice melting that they're afraid of is... | [
"As others have mentioned, land locked ice will melt and put water into the oceans, increasing the level.",
"Even if we were only considering floating ice, the water level would still not go down (or up, for that matter). An ice cube floating in water displaces its weight in water (with the rest floating above th... | [
"my geochemistry book disagrees with this notion, but, sure, i'll look at what you have. ",
"According to what I have: basically, the concentration of O-18 decrease toward the inland of continents, and with an increase in latitude due to Rayleigh fractionation. So, as you get to the poles, you have less O-18 than... |
[
"Why do people appear to not be bleeding in images/videos of surgeries in progress?"
] | [
false
] | Pictures/videos of surgeries always have no blood anywhere, and a gaping wound...they might wipe every now and then, but for the most part, there is no blood. Is it all anti-anticoagulants? Do they clamp off all the capillaries? Am I answering my own question? Why do folks need multiple transfusions then? (during/after surgery) | [
"While it depends on the type, surgeries do tend to bleed a lot. Superficially there may not seem to be much bleeding, however a large amount of blood may have been suctioned away or hidden, collecting at the bottom of a cavity (e.g. abdominal surgery). However, unless there is truly significant blood loss, there i... | [
"Hope that answers your question\nSource: I am an orthopaedic surgery resident in the US"
] | [
"Lets also add a major factor, surgeons try very hard to avoid slashing through major blood vessels. Surgeries tend to be planned to avoid them."
] |
[
"[Weekly Discussion Thread] Asking for Suggestions"
] | [
false
] | We have had eight installments of the weekly discussion thread and I think this is a good time to ask for suggestions from the community. So instead of a regular thread this week this is the place to offer your ideas for future topics and I will do my best to use them all in the future. Here is last weeks thread: | [
"This could be fun or it could be a disaster (disaster seems more likely but I'll just throw it out there): \"Scientists, what's a 'fringe hypothesis' that you find really interesting even though it's not well-regarded in the field?\""
] | [
"What is one thing you would change about the way science is done (wherever it is that you are)?",
"What about your science keeps you motivated on a daily basis?",
"What is something really cool about the science in your field that gets you excited when talking about it."
] | [
"Not the best questions, but I figured I'd suggest something:",
"Scientists, what are some of your favorite books & authors from your field?",
"How do you deal with blocks? As in, when you are trying to figure out a problem and you just keep hitting walls/blocks. What are some of your tricks in dealing with thi... |
[
"What are Neil Degrasse Tyson's contributions to the field of physics?"
] | [
false
] | null | [
"NdGT was not a heavy-hitter as a scientist like those other names you mentioned. He has spent almost all his career in outreach. His ",
"PhD thesis",
" was about measuring the number of a certain types of stars in our galaxy. He was also like the nineteenth author on some big astronomy papers in the 90s like "... | [
"So basically he is a personality that people have come to accept as a face for astrophysics. I just dont get the hype. I saw his picture on a shirt with the aforementioned bigger names, and it got me wondering what he actually did to become so famous. Thank you for the info! "
] | [
"Such questions are better suited for our newish sistersub ",
"/r/asksciencediscussion",
". Please post there instead."
] |
[
"What do you think science/humanity's goal should be?"
] | [
false
] | What do you want to see in the world? A planet of super intelligent, super organized people? A planet with no hunger? I have personal goals. I want to graduate from college, make some money, be secure in my life, have fun, etc. But does our collective humanity have a goal? What are we gravitating towards? Asking this in because I envision a generally happy, science fictionized future. | [
"For humanity's goal, I want to see a peaceful society unmarred by endless war, where instead of destroying, people strive to use our greatest gift of intelligence and promote knowledge, education, and enlightenment. There should eventually be a time where everyone is granted certain rights and freedom and people t... | [
"Ubiquitous pantsless monkey butlers."
] | [
"http://singinst.org/upload/CEV.html"
] |
[
"What happens to fields as they approach and reach the speed if light?"
] | [
false
] | I am curious what physically happens to a field as it approaches and then hits the speed of light. Like say a magnetic field, does it change? Or electromagnetic? Or are there any fields that behave strangely as they speed up and hit C? I asked this question once in a FB group and got a smartass remark about “Maxwell’s equation tells you, duh.” Sadly, I am not well versed enough in math or physics to be able to understand his equations and what they mean “in the real world.” I’m not exactly a layperson, but I am by no means well-versed. | [
"So \"fields\" no matter what are everywhere in the universe regardless if it is being interacted with or not. If there is a disturbance of that field, that shows up as a wave or a particle depending on how you look at it. Everything that is a wave is a particle and everything that is a particle is a wave and it on... | [
"Yeah, another post made me aware of the problem with my thinking. I was thinking, basically, take a magnet and accelerate it to C, what happens to the magnetic field, as if the magnetic field is only around the magnet. Thank you for taking the time to throughly explain it."
] | [
"I feel like you are thinking the same thoughts as \"What happens if a car travelling at C, turns on its headlights?\". If so, i would direct you to this article, it explains it extremely well and simple.",
"As even though we can't have a car, or a magnet in this case travelling at C, you can still wonder:",
"h... |
[
"How can images from particle detectors inform scientists about the nature and properties of particles?"
] | [
false
] | null | [
"For example, the size of the ",
"swirls in a bubble chamber",
" depends on the charge-to-mass ratio of the particles, and the direction they swirl depends on whether the charge is positive or negative."
] | [
"It's not merely images which a particle detector produces -- the detector produces a lot of data about those particles, such as their mass, momentum, and charge. The images produced are not actual photo images, they are computer-generated representations of limited parts of the data; there is much more that canno... | [
"Conservation laws are key. For example, if you measure the energy and momentum of some resulting particles, then you know the energy and momentum of the particles that created them. Similarly with charge. So you can work through a process of what you detected, and piece together how they could have been produce... |
[
"Why is digital camouflage preferable to more traditional styles?"
] | [
false
] | I always thought that camouflage is supposed to conceal its wearer by breaking up his/her figure with naturally occurring shapes and forms. Is there any scientific reason why randomly placed squares conceal the wearer better than say, woodland patterns? Also, if digital camouflage is more effective than a traditional one why don't more hunters use it? | [
"Some references ",
"here"
] | [
"I'd just like to point out that camouflage has a variety of use cases with distinct considerations. Camouflaging is different for objects of different size, either still or active, in different environments and against different observers in different ranges.",
"Military camouflage on individual fighters is ofte... | [
"I see! Thanks for the response!"
] |
[
"Were the Supermassive Black Holes at the centre of our Galaxy (and others) Stars at some point?"
] | [
false
] | And if so, how big were they? Do galaxies form around the supermassive star or do they have to collapse into the Black hole in order to form the Galaxy? | [
"This is one explanation, and probably the most likely, but the reality is that we don't know. ",
"Other explanations include primordial black holes (formed immediately after the Big Bang) and black holes formed through large-scale collapse of gas clouds in the early universe."
] | [
"When the universe originally formed, the abundance of hydrogen was much greater than that of today, resulting in massive stars that exhausted their fuel supplies over millions of years; collapsing violently in hyper novae explosions and the first black holes. These black holes eventually accumulated and merged, fo... | [
"It's possible, but unlikely (at least in my view). ",
"There is a limit to how quickly a black hole (or any object) can acquire mass. Disregarding problems with dissipating angular momentum (and this is no easy problem to solve) infalling matter will heat up quickly by friction as it falls down the gravitational... |
[
"What happens when we crack knuckles?"
] | [
false
] | Why do some people's knuckles crack while others' don't? What happens when a crack happens? Are there any proven methods for avoiding the build-up of whatever cracks? Is cracking knuckles safe? | [
"The cracking noise is produced by the collapse of bubbles of synovial fluid vapour caused by the movement of the joint.",
"There is no evidence it causes any problems.",
"\"Habitual knuckle cracking in children has been considered a cause of arthritis. A survey of a geriatric patient population with a history ... | [
"This study",
" suggests that habitual knuckle cracking was associated with manual labour, alcohol and smoking. However, that may not be causative, and I think it means associated with the habit of cracking, rather than the actual bubble formation. ",
"This is a more technical article",
" that might have the ... | [
"From the second link:",
"Repeated performance of articular release may decrease the occurrence of arthritis.",
"Am I reading it correctly that there is some evidence that knuckle cracking may actually be helpful in decreasing the chances of getting arthritis?"
] |
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