title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Is there a theoretical solution to the acceleration problem of getting a human from earth to Andromeda in an hour (traveler time)?"
] | [
false
] | In theory if you accelerate fast enough towards the speed of light, you could travel any distance in a short amount of time from the traveler's perspective. The problem is that if you're accelerating at 1G, the trip to our closest galaxy will take around 50 years. Are there any theoretical solutions to this problem? | [
"Really soft chairs?",
"No, seriously, the best examples of very high accelerations for humans is being hit by a train or a drop from a plane on to concrete. Imagine the effect of being hit by a high speed train many, many times a second. Figure out what you can do to a human body to make it survive that and you ... | [
"Note that any kind of protection is cheating.",
"Not necessarily, protection is exactly what we are looking for in this case. Assuming we had a craft capable of arbitrary acceleration there are many things we could do to enable humans to survive extreme acceleration.",
"For example a prolonged 3g acceleration ... | [
"I meant physical protection on the body (like amour or something). What that does is increase the impact time from the train and thereby decreases the number of g's you experience. This clearly wouldn't work in a spacecraft where the g's are constant.",
"But yeah, there's certainly things you can do to help the ... |
[
"Is there a Universal Center?"
] | [
false
] | For the most part, star systems, star clusters, galaxies, and galactic groups are bound by some super dense place at the center of said systems. I guess this isn't always the case, but as a general rule in the cosmos, things collapse spherically. Obviously the universe is doing just the opposite of collapsing but anywa... | [
"No, ",
"on a large scale, the universe looks same everywhere",
". ",
"If you are referring to the expansion of universe, the expansion isn't from any central point. It is the metric itself which is expanding, i.e. the \"scale\" of things. All distances increase at the same rate."
] | [
"But if there is an edge, where there is no matter beyond that point, surely there must be a point halfway between there and the opposite \"edge\" which is the middle?",
"Well, yes. But there is no evidence of any edge. In our current models the universe is infinite. "
] | [
"As I understand it there are 3 remaining possibilities for the shape of our universe, but none of the remaining possibilities has an edge (\"boundary\").",
"The possibility that is most consistent with observation is that our universe is perfectly flat and infinite in all directions. You could travel as far as ... |
[
"Biochemically, how do anabolic steroids assist muscle growth, and what are the differences between different types of steroids"
] | [
false
] | [deleted] | [
"This information is wrong. hGH is a peptide hormone (a protein) not a steroid. Steroids are lipids (basically fat molecules). Also hGH act on cell surface receptors. Steroids act on intracellular DNA transcription factors. "
] | [
"The difference lies in their chemical structure and how they interact with receptors, I don't know the specific differences though. For example human growth hormone (hGH) binds to certain receptors found on the surface of cells which then induces growth in that cell. Steroids all do this by promoting proliferation... | [
"My fault, of course hGH is a peptide, and sorry about the misinformation. All steroids are lipids meaning they can enter the cell (hGH can't) and thereafter bind to different nucleus receptors which when activated changes transcription in the cell, meaning changing the protein setup in the cell."
] |
[
"What is happening physiologically when you have a “knot” in a muscle?"
] | [
false
] | What is happening physiologically when you have a “knot” in a muscle? By knot I am referring to a tight or particularly sore area in a muscle belly. When palpated it can feel like a small lump or tense area. They tend to go away with stretching, and or some pressure to the area. | [
"Nobody knows, actually. There have been numerous studies where a single patient or small set of patients with knots are blind-tested or otherwise examined by various professionals who claim to be able to diagnose them and basically none of them agree. Similarly there is not a good theoretical basis for guesses as ... | [
"\"We aren't sure.\" Is certainly the most accurate answer.",
"The mechanism that I get the most mileage out of with my patients (Physical Therapist), is that the act of sarcomere contraction (the smallest unit of muscle fiber) requires actin and myosin to attach to active sites on each other and \"power stroke\"... | [
"Ya, this is the most reasonable answer. Whether “knots” even exist depends a lot on definitions. What they are biologically is certainly not known, and a LOT of people basing treatments off of knots are BS. ",
"A longer read, but as a bonus it keeps things in layman’s terms so thought it would be worth a post: ... |
[
"Why do warm-blooded animals have different internal body temperatures?"
] | [
false
] | It seems like most (I'm scared to say all) proteins found in almost all life work best at higher temperatures (Ex. The optimal temperature for ATP hydrolysis is 60°C (140°F) ). I'm sure anyone able to answer the first question would probably be able to answer the question, Just for kicks, some interesting numbers on i... | [
"Of all the organisms on the planet, only mammals and birds display this phenomenon.",
"Well... kind of. The dichotomy between endothermy and ectothermy is mostly artificial and perhaps even an artifact of inadequate information. Insects, for example various species of honeybee, will use their wing muscles to rai... | [
"ATP hydrolysis isn't the only reaction that takes place. Each chemical reaction has its own set of enzymes and substrates; these enzymes may be more or less thermostable than others. The DNA polymerase from ",
", used in PCR, is functional at 72°C, even after being heated to 95°C. Many proteins or cellular st... | [
"Yeah, I agree with those points. I guess I was thinking of dimorphic fungi that tend to infect their animal hosts as a yeast and live a filamentous lifestyle in the soil. There are many other fungi which are opportunist pathogens and primarily cause problems for immune compromised individuals.",
"Fungi grow be... |
[
"Does the expansion of spacetime happen at every scale of the universe?"
] | [
false
] | Does the same type of expansion happen at an atomic scale as it does in space? As far as I understand it right now, gravity counteracts that expansion. Is that true? If so, does that mean that in the early life of our universe, there was no gravity? | [
"In the presence of matter, no. Einstein's field equations are non-linear. They include contributions from both matter/energy and dark energy. So at small scales (matter dominated) there is no expansion; at large scales (dark energy dominated) there is expansion. This may seem contradictory, but in GR superposi... | [
"If by early you mean mere moments after the Big Bang, then yes. The four fundamental forces we know of today arose out of a single, all encompassing force. Furthermore, gravity - when compared to the other forces at least - is extraordinarily weak, and our laws of gravity tend to break down at the atomic scale. A ... | [
"Two very minor clarifications concerning the above. It's important to note that the statement,",
"The four fundamental forces we know of today arose out of a single, all encompassing force",
"is speculative. There are theoretical and aesthetic reasons supporting unification of all the fundamental forces but th... |
[
"Does aluminum foil help things bake?"
] | [
false
] | I've always used aluminum foil when baking things (particularly when making pizza bagels, which I'm enjoying right now), and I've always lined the bottom with foil. While I've always assumed it was just to get any mess on the foil, and not the pan, so that it's an easy clean up, I was thinking about an article I read a... | [
"Excellent question (I love these cooking questions). Aluminum is good for cooking because it has really good heat conductivity (transfer) and a low specific heat (doesn't 'hold' much energy). So, if you heat up one part of the foil the rest of the foil will heat up pretty quickly, too. Alternatively, if you tak... | [
"There is also a group of people that say the shiny surface of the aluminum foil reflects heat better than the rough side of aluminum foil (there is a shiny and rough side due to the processing of the foil, they roll two aluminum foil sheets at once that are pressed together and that gives a rough surface at the in... | [
"The engineer in me would tell your friend to punch a long nail through the center of the potato to cook it faster and forget about the foil ;D"
] |
[
"How do stars with a CNO cycle run out of fuel?"
] | [
false
] | I used to think fusion cycles simply evolved from basic hydrogen mergers up until iron, at which point a star begins to collapse. Now that I know about the I want to know how any star that fuels in this manner actually runs out of fuel. Is it just a matter of proton-proton fusion slowly whittling the fuel supply down... | [
"Question: why would they not run out of fuel by this method?",
"Edit: that is to say, what about the CNO process would make the star not run out of fuel, opposed to any other process? The star still radiates energy, and that energy must come from somewhere. "
] | [
"The effective net result is the same for both the p-p and CNO cycles. 4 protons react and form 1 helium + energy. In the p-p chain, the protons fuse with one another. In the CNO cycle, the protons fuse with C, N, or O, and at various stages the energy, helium, and other products are given off. So in both cases... | [
"Ah, now I see it more clearly. I should have skipped the equations and gone straight for the diagram. I see now the input of hydrogen at the various stages (which would naturally deplete the supply). Sorry for the foolish question."
] |
[
"Is there a significant correlation between how well you chew your food and how much of the nutrients are absorbed by your body?"
] | [
false
] | I assume there is difference, but how significant is it? It makes sense that the things that (certain seeds, corn, etc) are obviously better broken up more by your teeth, but for everything else, is it simply a matter of the rest of your digestive system having to do the work that your mouth did not? | [
"I assume there is some small difference too, but it is probably much smaller than you would assume. Your body is quite good at taking it's time and carefully extracting the maximum nutritional value from food that it can.",
"It might vary with the type of food you are eating - for example, we all know how corn... | [
"\"Nature shall castigate those who don't masticate.\" ",
"-",
"Horace Fletcher",
", The Great Masticator",
"But yes, on a more serious note: ",
"More Mastication Cuts Calorie Intake by 12 Percent",
"."
] | [
"Like AnatomyGuy said, if there is any difference it's insignificant. The main purpose of mastication is just to get your food into a bolus to pass easily through the esophagus- extra chewing is not going to chemically alter nutrients, and the GI system physically churns the food anyways via peristalsis."
] |
[
"How do artificial neural networks work?"
] | [
false
] | I've looked up a bunch of things about how ANN work but can't seem to get it so if someone could explain it for me, I would appreciate it. | [
"Here is a mathless intuition: ",
"Fundamentally, a neural network is a way of relating an input to an output. You can think of it as a function or a mapping.",
"Here is an example of a very simple network: a smoke detector: there is one sensor (input node) that detects smoke. If there is smoke (there is input ... | [
"Artificial neural networks are a type of general purpose function approximator. You know through algebra (I assume you've got at least an algebra-level experience in math for this answer) that if you have a function y = f(x), given any x, you can map that to y by putting the value of x into the equation. You can a... | [
"Yes absolutely. That would correspond to something like a grayscale image in the picture example or to any continuous or graded feature more generally. ",
"In the case of binary inputs, you can think of it as representing whether a feature is present or absent. Other than for black and white images, this can be ... |
[
"Why do people wake up when someone gets in close proximity?"
] | [
false
] | null | [
"Your sensory systems are still functioning and processing input, including the breathing of someone else, their body heat, changes in amount of light falling on the body, etc."
] | [
"We're most sensitive to sudden changes (even when awake). So if there is continuous loud music playing, for example, you might be able to fall asleep / sleep through it. The evolutionary story is that things that change in the environment are exactly the sort of things we should be detecting: if something is diffe... | [
"These are the same people that will sleep through a riot but wake if I'm 2 inches from their face. I understand that events affect people differently. I jump awake at any change in light while it's very difficult to wake me with noise. I have found this to be pretty much universal (also, I lean in extremely silent... |
[
"What type of tree is this"
] | [
false
] | null | [
"That is the leaf of the ",
"Gingko biloba",
", which is actually the only existing species in the entire genus Gingko! The modern Gingko tree has fossil relatives going back all the way to the Permian era, ~270 million years ago."
] | [
"Gingko biloba is not only the only species of the genus, but the only species of an entire order, Ginkgoales---\n",
"http://www.ucmp.berkeley.edu/seedplants/ginkgoales/ginkgo.html"
] | [
"Ginkgo",
"http://en.wikipedia.org/wiki/Ginkgo_biloba"
] |
[
"What exactly is this property that things have called 'momentum'?"
] | [
false
] | When I started studying classical mechanics, momentum was . Later I learned that Newton's second law was actually expressed as force being proportional to the the rate of change of momentum, which mathematically I'm happy with if you accept as momentum = . This is especially true when I also learned that term impulse i... | [
"Momentum is the quantity that is conserved in systems that are invariant under spatial translations.",
"For a nonrelativistic, massive particle, this comes out to approximately equal m",
"."
] | [
"As trite as this definition sounds, this is the most fundamental definition there is for momentum. To expand on this a bit, ",
"Noether's theorem",
" is a very deep theorem in mathematical physics which states that every symmetry in a system has an associated conservation law. ",
"More simply, if you do an e... | [
"It’s true in general relativity as well. There is a Killing vector corresponding to each direction of spacetime that the system has translational invariance in."
] |
[
"[Chemistry] how does a medicine, like Mucinex DM, have a cough suppressant and an expectorant not cancel each other out?"
] | [
false
] | Taking it right now (few days) and not coughing so how is the expectorant supposed to work. How do they not cancel each other out as they are opposites? | [
"They aren't opposites. A cough suppressant inhibits your cough reflex, whereas an expectorant loosens up the secretions in your respiratory system. ",
"The first one makes you less prone to coughing, and the second one makes the stuff that's stuff in your airways easier to cough up.",
"In other words, you coug... | [
"It's been a long time since my respiratory pharm class in med school but if I'm not mistaken it's because those two properties are due to two different active ingredients, thus they compliment each other instead of canceling each other out. One is guaifenesin that helps loosen mucus and dextromethorphan (related t... | [
"Adding on, ",
"dextramorphan",
" was developed to replace codeine as a cough suppressant. Codeine and opioids can act as a cough suppressant due to their CNS activity, however due to serious side effects, like dependence, toxicity, and respiratory depression, they usually are not prescribed for this purpose, ... |
[
"Does the Human Brain have a Limit on the Amount of Information that can be Learned and Stored?"
] | [
false
] | null | [
"Oh, thank you. I didn't know that sub-reddit existed. Is there a difference between the two?"
] | [
"A good home for this question would be ",
"/r/AskScienceDiscussion",
"."
] | [
"The other is a sister subreddit of AskScience that we run. It's good for more open ended questions like this memory one."
] |
[
"Could you anchor a big cable to the moon and let it dangle into Earth's atmosphere?"
] | [
false
] | [deleted] | [
"There is no material strong enough for a cable going from the Moon all the way to Earth. Space elevators to geostationary orbit (and a bit beyond) might work in the future.",
"If we ignore material strength then xkcd covered it: ",
"https://what-if.xkcd.com/157/"
] | [
"You wouldn't have to go to the moon. GEO space elevators have been in the books for a while now",
"You mentioned the weight of the cable, it is one of the main hurdles in the design. We don't have a material that is quite right for this application. We need low weight/high tensile strength material",
"I have a... | [
"This is the answer, a cable hanging from geostationary orbit would just hover over the ground, 0 lateral speed. But mind you need an equivalent weight beyond geostationary to balance the hanging line.",
"The one hanging from the moon is a whip of destruction cutting the atmosphere at nearly 1400 kmh, does not so... |
[
"Can Musou black / Vanta Black paint defeat police laser and radar speed guns?"
] | [
false
] | I recently watched a YouTube video where they painted a car in Musou black paint. These paints are known as the blackest paint in existence since they can they only reflect ~0.0005% of incoming radiation (including light, microwaves and radio waves). Considering this, it got me wondering if a vehicle painted these colo... | [
"For the sake of argument, I'll assume that the speed guns in question emit a single pulse and look for a reflection. I would expect actual operation to involve multiple pulses and some behind-the-scenes algorithms to detect a vehicle's speed. Let's establish some parameters to start.",
"Musou Black published s... | [
"Yes maybe effective against lasers but definitely not microwave radar.",
"BTW radar speed guns generally use CW (continuous wave, not pulsed) waveforms, just a triangle wave, mixed straight back down to DC using the tx signal, with the frequency difference being the range rate (then use the cosine of the radar u... | [
"You could, but anybody could detect your car emitting tons of RF signals which, if it is strong enough (which should be if you want to drown out the signal from the radar) would be illegal as hell and you would be caught in a day or two (or earlier, depending on how strong your jammer is and how much you annoy the... |
[
"(Biochemistry) Most naturally occurring fatty acids have even numbered carbon chains. Why is that?"
] | [
false
] | null | [
"http://en.wikipedia.org/wiki/Acetyl-CoA",
"http://en.wikipedia.org/wiki/File:Saturated_Fatty_Acid_Synthesis.png",
"Most fatty acid synthesis is done using this coenzyme.",
"You can see on the end there is a two carbon chain. This two carbon chain is the building block used to make fatty acids. Since every mu... | [
"Thank you (:"
] | [
"The oxidation of even numbered fatty acids requires less ATP than the oxidation of odd numbered fatty acids.",
"Example:",
"Starting with a 16 carbon fatty acid. Each cycle reduces it by 2 carbons. Eventually you get to 4 carbons, which is cleaved again producing all cleaved products as acetyl CoA.",
"For od... |
[
"at what speed would you have to travel west at, in order for the sun to appear to stand still in the sky?"
] | [
false
] | [deleted] | [
"lets see:\ncircumference at the equator is about 25000 miles, you'd have to run that in 24 hrs, so about 1,041 mph."
] | [
"In order to solve this, we can think of the Sun as a stationary point with the Earth rotating such that you are in sunlight if you are on the half of Earth facing the sun. So, if the Sun is going to appear stationary, you must be moving at the speed of the Earth's rotation for where you are, in the opposite direct... | [
"This speed would be reduced the further north or south you go. Once you are beyond the arctic circle in summer, or antarctic circle in winter, you would not need to be moving at all for the sun to always be in the sky. "
] |
[
"When we see electricity arc or a lightning strike are we really seeing the \"color\" of those flowing electrons?"
] | [
false
] | Electrons are too small to be observed directly using light microscopes (or electron microscopes), so are we seeing electron density itself or is a reaction with air producing the visual? | [
"If my past chemistry knowledge serves me correctly, I believe that the light you see from lightning is caused by the electricity exciting electrons in atoms in the air. These excited electrons move up to a higher orbital than usual, and when they fall back down, they release a photon, which is what you see. This i... | [
"You are seing the color that air makes when the electrons drop from an excited state. The color is dependent on the gas composition not the electrons. If lighting where to happen in a neon gas then the lightning bolt would be orange. "
] | [
"In addition to the light coming from excited gas, as other commenters have pointed out, in hot plasmas a lot of the light also comes from blackbody radiation; it's just so hot that it glows bright white. If you looked at the spectrum of a lightning bolt, you'd see a smooth curve corresponding to the temperature of... |
[
"Does your brain \"compute\" physics or does it \"go from experience\"?"
] | [
false
] | Let's say i'm trying to throw a ball at a target. When I take aim, does my brain try to calculate the physics "behind the scenes" or is it more like "the last few times I threw a ball this heavy this hard with this wind, it'll land about there"? | [
"This is a current hot topic in psychology. For some recent reviews, see ",
"Ullman et al. (2017)",
" (<- pdf!) and ",
"Kubricht et al. (2017)",
" (<- pdf!) which separately argue that we do physics-engine-like simulations that instantiate physical laws. These groups argue that we \"compute\" physics as you... | [
"“Physics” in general is complicated, and taken altogether is probably a little bit of both. The element I learned about a little while back was depth perception. Even the first time babies are put on a part clear / part not clear platform called a “visual cliff,” babies are resistant to crawl over it. These resear... | [
"Catching and throwing things is a learned skill, so experience is needed. It is a “muscle memory”, meaning that the thinking brain has little to do with it. Professional athletes often make a mental image of the result they want to achieve, rather than the mechanics of how they will achieve it. Thinking too hard w... |
[
"As the earth orbits the sun, does it speed up and slow down? Is there a \"slingshot effect\"?"
] | [
false
] | Also, does "rounding" the "peak" (perihelion?) affect the rotation of the earth in any way? | [
"Yes, it speeds up and slows down. Planets follow the second law of Kepler (A line joining a planet and the Sun sweeps out equal areas during equal intervals of time) so that means they have to move faster in the perihelion. I don't know what you mean with \"slingshot effect\", that term is used for gravity assists... | [
"I think by \"slingshot\" OP is referring to Earth's closest approach to the Sun as opposed to it's most distant. But, as you point out, Earth doesn't escape the effect of the Sun's gravity so the term \"slingshot\" doesn't apply.",
"What is the percentage in speed change and during which times of year does this ... | [
"Earth's orbit is almost circular, so the speed change is very small. Taking this numbers (",
"http://curious.astro.cornell.edu/question.php?number=614",
") the Earth is 4% slower in the aphelion than in the perihelion.",
"Right now we get to the perihelion at January 3rd and to the aphelion at July 3rd. Even... |
[
"If time is affected by gravity then how can we measure light years accurately?"
] | [
false
] | I'm not very knowledgable of and haven't studied physics or astronomy, so this is something I can't get my head around. Time is affected by gravity, right? So something with a strong gravitation pull (a planet?) is going to have slightly faster "time" than the "time" that is further away from the gravitational pull. An... | [
"Oh I see now, you mean that the distance error is 20 orders of magnitude higher than time dilation error, I thought that you meant something entirely different."
] | [
"Oh I see now, you mean that the distance error is 20 orders of magnitude higher than time dilation error, I thought that you meant something entirely different."
] | [
"20 orders of magnitude? If we are that imprecise how do estimates even mean anything? "
] |
[
"What is the mechanism that causes particle decay?"
] | [
false
] | As the title. | [
"Particles decays because there exists a state of the energy of this particular system which is lower, hence more stable. It is the reason why particle decays, because they want to reach this minimum energy state. This decay can take many forms afterwards depending on the kind of particle which is decaying. We say ... | [
"Please don't use words like \"want\" or \"like\" when talking about elemental particles. There's no difference in transition probability between a decay and a capture reaction, it's just that it's much less likely to have the (usually) multiple products at the same place. A proton can turn into a neutron through e... | [
"Particles want to be in their lowest energy state. Think about a ball on a slope. The ball will roll until it reaches a flat surface. The ball will always roll downward spontaneously and never upward spontaneously. This is the same concept as particle decay. The particle wants to be at the bottom of the hill. In t... |
[
"Flight from Australia to South America?"
] | [
false
] | null | [
"Hello,",
"We don't allow this kind of question here, but you could try ",
"/r/answers",
"."
] | [
"Maybe I wasn't explicit enough. I'm trying to find out what kind of tools are needed to measure a plane moving around the globe. Thought that might fall into science?"
] | [
"Well what do you mean by \"measure the plane moving\"?"
] |
[
"Can you get radiation poisoning by having contact with or being near someone who's been irradiated?"
] | [
false
] | null | [
"Not ",
"\"poisoning\"",
", which requires a massive acute dose, but under a few specific circumstances people could get a small dose which has a tiny chance of causing cancer.",
"The key is to distinguish ",
", which in this context is fast particles which do their damage almost instantaneously and then ar... | [
"But that is putting a radionuclide into their body. It is not "
] | [
"Low-energy won't, but above several MeV it can cause photonuclear reactions and activate material.",
"This is a negligible amount for this discussion though."
] |
[
"Does basic rain exist?"
] | [
false
] | Like acid rain, but with a pH higher than 7? | [
"Not on this planet. Due to the presence of carbon dioxide, and occasionally sulphur dioxide and nitrogen oxides as well, in the atmosphere, rain has the pH of about 5.8 on the Earth.",
"In other planets and satellites, it is a possibility due to the presence of ammonia. However, from here on, our working definit... | [
"I had a read of the full text, and I better make some minor corrections. In the article the highest recording for rain pH was 7.6, although the vast majority were still below 7.0. (The paper's definition of \"alkaline\" is anything above pH 5.5.) High pH rain is usually recorded in areas with high quarry mining ac... | [
"There's ",
"this article",
" from a 2000 edition of the journal Science of the Total Environment which reports identifying alkaline rain in Turkey. They don't include the pH in the abstract (and the article is behind a paywall), but they say that 58% of their samples were alkaline. Do they just mean \"more alk... |
[
"Magnetic Gas"
] | [
false
] | Can gasses be magnetic? If so, where in any given cloud of the substance would the north and south poles be? How would it react to other ferrous objects interacting with it? | [
"It's because magnetism in materials comes from the alignment and ordering of adjacent atoms. When the atoms are all moving about randomly they can't be ordered."
] | [
"MIT has observed magnetic properties in Cyrogenic Lithium Gas. ",
"http://www.popsci.com/scitech/article/2009-09/scientists-create-first-ever-magnetic-gas",
"This would be the only known magnetic gas. ",
"Someone can explain why gases don't make for good magnets, id assume there is too much chaos and motion... | [
"They can in the presence of an external field, can't they?",
"A gas can never be ferromagnetic, paramagnetism is possible (and common) though."
] |
[
"At the challenger deep, would my body gets crushed to a thin film?"
] | [
false
] | I understand that the pressure at those depths is immense. But I'm not sure if it'll just crush my air cavities like lungs or if it'd completely crush meat and bones to a thin paste/film. | [
"Undersea pressure is uniform in all directions. Its not like being crushed under a weight on land. The result is that things are compressed, not squashed. Pressure difference across a boundary is what causes deformation, like the air in your lungs.",
"Water is ",
" incompressible, but at 1100 times atmosphe... | [
"In a gas (which styro",
" is full of), pressure and volume are inversely proportional (all else equal), so doubling the pressure cuts the volume in half. So if you're normal at 15 psi, v=.5 at 30 psi, .25@60 psi, .125@120psi, etc. etc.",
"That first 15 psi gets you a .5 reduction, while the next 90 psi only g... | [
"I have one that only went down 1000ft or so and it's about the size of a shot glass. It doesn't take much depth for the compression to begin."
] |
[
"How are neutron beams guided?"
] | [
false
] | Charged particle beams (protons, electrons) are guided with an electric and/or magnetic field, but neutrons are uncharged. | [
"Apart from extremely low-energy neutron beams which can be guided just with gravity and/or their magnetic dipole moments, they're simply not guided at all.",
"You start with some source of neutrons, and you just collimate down to the beam direction and size you want. ",
"Here's",
" an example from a spallati... | [
"Neutrons can be described by their de Broglie wavelength and their behavior can be predicted using neutron optics theory. This is similar to light optics with scattering and reflection, so materials have characteristic neutron refractive indexes, which can be derived from the atom number density and the coherent s... | [
"Cold neutrons can be reflected using \"mirrors\" under certain angles and can be steered. Ultracold neutrons reflect under all angles on some materials (e.g. nickel) and fill a volume made of such a material like an ideal gas."
] |
[
"Can you make a magnetic liquid by dissolving iron shavings in water?"
] | [
false
] | [deleted] | [
"Well, for one, iron fillings wont dissolve. They're much too large."
] | [
"NaCl behaves differently when solvated by water than would elemental Iron. Primarily, you wouldn't see the same ionic solvation, that is the Iron atoms would not break apart. Same thing as trying to dissolve an iron nail in water, the nail won't dissolve. The best you could achieve is a suspension."
] | [
"There are substances called ",
"ferrofluids",
" that are mixtures of extremely fine magnetic solids interspersed in some kind of fluid (which is sometimes water).",
"However, iron shavings will not dissolve. Also, the iron (if it is just iron) would likely rust in the water, seeing as how finely dispersed it... |
[
"Why can bats still navigate with echolocation when in a large swarm?"
] | [
false
] | Bats use echolocation but when there are ~1 000 000 Bats in the cave, there must be an enormous interference right? How can the bats still orientate? | [
"There are two things going on here, orthogonal signals and contextual processing. ",
"In signal processing theory there is something called a matched filter which actively looks for a pattern that was transmitted to reduce noise, radar and sonar both do this. Orthogonal signals are signals that can be distingu... | [
"Is it not possible that bats use simple \"swarm\" behavior (like birds) when in large groups, allowing the bats at the front (who have less going on, sonically) to guide the entire group?"
] | [
"Bats have no method of vision beyond the sonar so they still need to use fancy signal processing to triangulate the position of other organisms. And regardless of their position in the swarm they will still be experiencing noise from all the other organisms in the area. Individual bats would likely need to eithe... |
[
"Why do some flowers, mushrooms, and plants prefer areas with less light to grow? Shouldn't all plants want more energy from the sun?"
] | [
false
] | null | [
"Firstly, mushrooms are parts of fungi and do NOT photosynthise. The mushroom is a fruiting body used for reproduction. ",
"As for plants, sunlight is a double edged sword. It provides the energy to do photosynthesis, but sunlight is bad for plants the same way it can give us sunburn-- the high energy photons dam... | [
"Biology PhD student here. ",
"In general there are 2 types of leaves (regarding to sunlight) shadow leaves and sun leaves. Shadow leaves being thinner and having less palisade mesophyll. Palisade mesophyll is a layer of columnar cells lined up to each other and it's found on the upper side of the leaf.",
"Sun ... | [
"evolution removes traits that hurt the species through natural selection. plants that evolved to inhabit typically dark areas like forest floors did so by losing the trait of needing lots of sunlight for energy. along the way they become intolerant of too much sun. the fern is an example. ferns that needed a lot o... |
[
"Can someone really get knocked out by having a pressure point hit?"
] | [
false
] | Like the points shown in this video. | [
"He's not asking if it's safe for his friend to knock his pressure points to cure his insomnia. Medical advice is not the same thing as asking a question of physiology. "
] | [
"Ignore tag, not highly relevant.",
"I am suspicious. Obviously, anything that blocks the cartoid artery has the potential to knock someone out. (Using a simple sleeper hold where you put your arm around the front of the neck and grip on an arm to the side of the head, then put pressure. This technique will produ... | [
"That's ridiculous for its own reasons, however I see no reason to censor askscience because somebody somewhere might hurt someone with the knowledge they learn here. Where do you even draw the line? "
] |
[
"If you get all your daily nutritional value in one meal and don't consume anything for the rest of the day, is it bad for you? If so, why?"
] | [
false
] | Can your body not sufficiently use all of that in one sitting? Will it store most of it instead? What exactly happens? | [
"Some of the good stuff can't be stored by your body, and it's more about having a constant adequate supply over time than it is about getting your daily/weekly/annual amounts.",
"Imagine taking all your vitamins for the year on the 1st January then not consuming any more for the rest of the year. You're not goin... | [
"Your body can only absorb so much of certain nutrients in one sitting, so if you are eating all you need at once, much of that is just going to travel through your GI tract and right out of you."
] | [
"How would it physically affect your body though? Would you gain/lose weight with either method as oppose to the other?"
] |
[
"How do hospitals go about using radioactive isotopes for medical testing if the isotopes have a short half-life?"
] | [
false
] | [deleted] | [
"While not an expert by far I have had some exposure to radioactive isotope imaging basics.",
"Isotopes are chosen for their particular half-lifes. And most do get delivered made directly from fission sources, from memory isotopes like iodine-123.",
"However I know of at least one instance of an isotope being u... | [
"Most are produced either on sight or rapidly delivered from medical particle accelerators, mostly cyclotrons. ",
"Canadian hospital Youtube video!",
" These devices were originally developed for nuclear science, but these devices are mostly industrialized now. "
] | [
"Your last sentence essentially answers the question. What I think you fail to grasp is that the radioactivity is their useful property. The EM radiation from the decay is measured and sometimes imaged, to provide the desired information. Depending on the delivery mechanism (I.E. What type of substrate it is combin... |
[
"Have we ever found \"Indiana Jones\" like traps while exploring sites?"
] | [
false
] | null | [
"Sort of. There's records indicating the first Emporer Qin of China had elaborate traps. The only traps encountered are high levels of mercury, supposedly from artificial rivers of mercury meant to ensure immortality for the late emperor. ",
"Here's an article on it.",
"I recommend asking in ",
"/r/AskHistori... | [
"http://www.reddit.com/r/AskHistorians/comments/spezo/did_ancient_temples_and_tombs_and_such_ever_have/",
"I asked the same thing a while back. "
] | [
"But surely for that to be considered a trap it has to be designed with the intention of stopping intruders? The mercury is dangerous but that's not why it's there. "
] |
[
"2 questions for the geneticists"
] | [
false
] | Could FISH be considered optical mapping and could whole genome shotgun be considered massively parallel sequencing? | [
"I think FISH ",
" be considered optical mapping, though in general optical mapping is just done with a chromosomal stain and smashed chromosomes. I wouldn't consider old-school shotgun sequencing to be massively parallel sequencing though. I think the term is used more for the current Illumina, 454, and SOLID sy... | [
"So everyone else knows what's going on here:",
"I'm not qualified to talk about shotgun sequencing and massively parallel sequencing, maybe someone else can chime in. ",
"additional info- ",
"-",
" basically means \"in the situation,\" and it's considered an intermediate between ",
" (a living sample) an... | [
"Ok thanks, it was more of a 'where is the cut off point for these terms' as in, when does something become 'massively' parallel and is optical specific or and optical method, but from what you say it is more of a technique than a family of techniques. Thanks :P"
] |
[
"Relative Spin"
] | [
false
] | Is spin relative to a frame of reference as is normal motion? Example: I'm in a spinning spaceship and I experience something that mimics gravity. This implies that the ship is not only spinning but that I can compute how fast it is spinning by the G forces I'm experiencing. What am I spinning in relation to? How come ... | [
"Einsteins Theory of General relativity states that acceleration is the same as Gravity. That means that if you are indeed spinning in the spaceship and cannot see outside, you would not be able to do any experiment that says you are not being pulled down by gravity.\nSo, you are in a non-inertial reference frame (... | [
"Actually what you are saying is not what happens but is exactly what I'm asking about in relation to why there \"seems\" to be a preferred state of rest which should not be the case according to relativity. In your example, regardless if I have windows that can see out, I can tell that my spaceship is spinning by ... | [
"You are incorrect.",
"What you are refering to is described in this ",
"page",
". But what OP is describing would be if the elevetor was spinning along one of its axes.",
"The ",
"coriolis_effect",
" is one of the things you can observe in an experiment.",
"And there are other properties, you can obs... |
[
"Is there an \"uncanny valley\" for sound like there is for sight? Does the sound of very nearly replicated voices, or oddly filtered voices, elicit the same sense of revulsion as does the sight of very nearly-human robots?"
] | [
false
] | I guess it's all in the title. When we see things that look human but are ever so slightly off, like some bad robots or zombies etc, there is a characteristic revulsion that people seem to feel, attributed to a variety of neurological and psychological responses which I don't fully understand. Does the same effect exis... | [
"This paper",
" offers some speculation about the \"audio uncanny valley.\" The author gives the following recommendations about how to design uncanny sound:",
"Certain amplitude envelopes applied to sound affect perceptions of urgency.",
"Frequency might have an effect on the unpleasantness of sound and thi... | [
"Possibly not related to this but you might want to check out the coconut effect. Which is where early media used false sounds as recording the real effect was to difficult but now recording has got better people have become conditioned to associate certain false sounds and find it hard to accept the correct audio.... | [
"Desynchronization is a big one - even just a could hundred milliseconds of desync will make someone speaking seem off."
] |
[
"Do Black holes and anti-matter Black holes have different characteristics, and if so what are those characteristics?"
] | [
false
] | I know they both consist of having an Event horizon and a singularity, but other then that, what makes them different? | [
"No, there is no distinction between a black hole formed from matter or from anti-matter. General relativity tells us that the properties of a black hole are determined by its mass, electric charge, and angular momentum. How those properties arise is irrelevant."
] | [
"They're saying that it doesn't matter (heh) what type of matter went into the black hole. If you must draw the distinction, the collision you're talking about would look the same as if two \"regular\" black holes merged (because it ",
" the same). LIGO observed one of those last year."
] | [
"Ok thanks for the info, I apologise for asking and I know what I'm about to describe has never been observed but would would happen if a matter and anti-matter black hole where to collide?",
"Would we get what is supposed to happen with matter Black holes I.E huge tides of gravitational waves and they form as 1?... |
[
"What state of matter is fire?"
] | [
false
] | null | [
" is most accurately described as a ",
" - an event - and therefore is not a state of matter. While there are components involved that are in the solid, liquid, gaseous, or plasma states, fire is more than just the sum of the components. It is also a chemical reaction - that is, these components are undergoing co... | [
"Would it be correct to call fire just, light? An EM wave."
] | [
"But not any light source is a fire.",
"Edit: Come on guys, don't downvote for asking questions!"
] |
[
"Why is time squared in D=1/2gt^2?"
] | [
false
] | Why is time squared in D=1/2gt^2? I think I can sort of understand why it's 1/2 cuz the trajectory path is one half of a parabola (though that's just what I thought of, I could be totally wrong there lol) but I don't really understand why t^2. | [
"In general, the equation is:",
"d = v0*t + 1/2*a*t",
"and if you're starting from rest and falling under the force of only gravity, yet it does simplify to ",
"d = 1/2*g*t",
"So, why the (1/2) and why the t",
"?",
"First, let's look at the t",
" term. The ",
"g",
" is an acceleration due to gravi... | [
"Not really different than what was said in the other post, but simpler:",
"The distanced traveled by an object is the object's average velocity times the time it is in motion.",
"For an object that started from rest and is accelerating at a constant rate, such as a dropped object, the average velocity is half ... | [
"g is acceleration, so to get the speed you need to multiply g and time.",
"To get the distance D you need to multiply the speed and time.",
"As you can see, you need to multiply g and time twice to go from acceleration to distance. The reason there's a 1/2 factor is because the speed is changing at a steady ra... |
[
"How come, when we rub our eyes hard enough we see those weird colors and patterns?"
] | [
false
] | null | [
"Last time someone asked this one of the answers said it had to do with physical stimulus to the optical nerves, and the nerves sending the information the only way they know how. I'll see if I can find it hold on",
"Edit: ",
"/u/kgluds",
" with the answer, link to comment: ",
"https://www.reddit.com/r/asks... | [
"Those are vitreous floaters. They are actually inside your eye. They are basically pieces of collagen. "
] | [
"What about when you get a head rush, you know stand up too fast or feel odd and you get like pixels n fractal weirdness going on for a moment whether you close you eyes or don't- is that basically the same thing?"
] |
[
"What does it mean when a series converges? Laymans terms."
] | [
false
] | I know that if you use it in the context of area under a curve that when it is convergent, it has a finite area. When it is divergent then it has an infinite area. Thanks guys. | [
"Consider 1/2+1/4+1/8+1/16... each term is smaller than the last and each additional term brings the series closer to 2. This is a convergent series, each additional term brings it closer to converging on a finite value.",
"Consider 1/2+1/3+1/4+1/5+1/6+1/7... this series does not converge. It reaches infinity wit... | [
"Yes it is hard to conceptualize but there is a very simple proof that the sum of 1/n will grow without bounds as n gets large. Look at this series:",
"A = 1/2 + 1/4 + 1/4 + 1/8 + 1/8 + 1/8 + 1/8 + ...",
"Which is just a laborious way of writing ",
"1/2 + 1/2 + 1/2 + ...",
"It is obviously divergent. Now co... | [
"Your first impression may be that if you add up an infinite number of anything, that their sum must be infinite. However, this isn't necessarily the case. ",
"The most common example is the series 1/n",
", where n is integers. Writing out the first couple of terms you get 1/1 + 1/2 + 1/4 + 1/16 +... You can tr... |
[
"Is Montessori's \"Sensitive Phases/Periods\" an accepted concept? Alternatively: Is it possible children never catch up something they didn't learn at the right time?"
] | [
false
] | This came up in a conversation with a coworker about the Corona lockdowns. She claimed that children would have life long deficits in speaking, mimicking, etc. because when they don't learn such things at the correct time, it's almost impossible to catch up to the usual path. I doubted that because I thought those skil... | [
"A starting point might be Piaget's theory of cognitive development and the various studies which find that past a certain age, the brain is not capable of forming some structures (i.e. grammar).",
"However, and saying this as a parent of children who went to a Montessori kindergarten/school (and were taken away ... | [
"Are there scientific studies/theories/experiments that support or deny that claim?",
"In linguistics and speech pathology we definitely have the concept of 'critical periods'. That should provide you with a good springboard to go do further research. The 'critical period hypothesis'",
"And yes, it's widely acc... | [
"As others have pointed out, humans do have sensitive periods during which neurological and sensory growth is tied to increased receptivity to environmental information and skill development.",
"Some areas that you can research are:",
"Of course, these are general sensitive periods, and they may be able to be s... |
[
"How does Narcolepsy work, and how is it diagnosed?"
] | [
false
] | I just want to know is it really the uncontrollable urge to fall asleep (out of their control and must fall asleep). Plus how do they diagnose it? | [
"Narcolepsy is a disease associated with a defect for a neurotransmitter called orexin (synonym hypocretin). Orexin, secreted from neurons of the hypothalamus (interbrain), plays a small role in appetite regulation (stimulates the feeling of hunger)... but its main purpose is its modulating effect on the sleep cent... | [
"Wow, thank you for that explanation. It makes a little more sense."
] | [
"We do not allow medical advice or anecdotes on ",
"/r/AskScience",
". Do not ask users to post personal medical information here."
] |
[
"Has there or can there ever be an animal that is allergic to itself?"
] | [
false
] | [deleted] | [
"There are a wide range of what are known as '",
"autoimmune diseases",
"' . These are cases in which the immune system attacks a tissue or substance that is a normal part of the body."
] | [
"Quite right. I assumed that the OP intended 'allergic' in the colloquial sense."
] | [
"Quite right. I assumed that the OP intended 'allergic' in the colloquial sense."
] |
[
"Can other animals be allergic to us?"
] | [
false
] | We all know that people can be allergic to cats and dogs but is the opposite true? Can our pets be allergic us? If so, is this just in mammals or across all/most species? | [
"Yes! You can get your pet tested for human dander and even get them allergy immunotherapy shots for it. ",
"Info here: ",
"https://wagwalking.com/condition/human-dander-allergies",
"Here is the veterinary catalog for Greer which makes allergen extracts. Human dander is on page 20 (item E18): ",
"https://ww... | [
"Yes. Cats and Dogs can be allergic to humans. For the same reasons humans can be allergic to them ",
"\"Dander\" or dry shed skin.",
" Dogs and Cats can also be allergic to one another. ",
"To my knowledge most if not all animals can have allergies and against most if not all shed skin it should be theoretic... | [
"Allergic dogs' most basic symptom is being itchy.",
"In lay terms - their skin barrier doesn't function correctly, leaving gaps for opportunistic bacterial infections, exacerbated by the act of scratching. Their body overreacts to normal elements of their environment with an out-of-control inflammatory response.... |
[
"Why does a single gas molecule which is hot rise above another one which is cool?"
] | [
false
] | I know that they say an area of hot air becomes less dense, and so it rises above colder areas of air. However, this seems to be treating areas of gas molecules as though they are a coherent aggregation, like a solid. To explain my question, let me refer to an example: a plank of wood floats because the molecules const... | [
"Metrics such as temperature describe the behavior of a system that is made up of components. These types of properties are termed emergent properties because they are derived from the behavior of the system as a whole and are not observable if you were to look only at the components.",
"So, for your specific qu... | [
"an area of hot air becomes less dense, and so it rises above colder areas of air. ",
"First, you need to look at it the other way around - hot air doesn't rise, cold air sinks. As it sinks, it forces the hotter air upwards.",
"Now, think of a mess (and I do mean 'mess' for the imagery, not 'mass') of cold air... | [
"But what if there was a single constituent molecule from that wood existing in the water? Would it float? It is neither densely nor sparsely aggregated, existing all by itself.",
"My reaction to this is no not really - a single molecule would have dynamical behavior that isn't familiar like the bouyant force exa... |
[
"What limits the speed of healing?"
] | [
false
] | I was thinking about this earlier... it seems reasonable to assume that a living thing that was able to heal faster than its competition would have a definite Darwinian advantage, but it seems as though most animals have sort of plateaued at about the same place. For example if I get a small cut it will probably take a... | [
"In a way it does happen fast! The most important part of fixing an injury would be to make sure you don't get any infections from it, and we do mount responses to that end in minutes (or maybe an hour or two) by clotting the wound, recruiting LOTS of immune cells and making sure that infectious agents don't enter ... | [
"growth factors are released locally when you are wounded and are highly regulated. you need them for healing, but they are released in tiny bursts. every time they are released, they almost immediately stop being released. the reason for this is that releasing growth factors without \"rest\" (bad term, eh..) is on... | [
"How does hyperbaric treatment accelerate healing? or is this just a gimmick professional athletes fall victim to?"
] |
[
"How does the light during \"daytime\" on other bodies in our solar system compare with the light on Earth?"
] | [
false
] | So if I were to take a space ship right now to the surfaces of the following: I'm ignoring things like atmosphere and just wondering how much sunlight makes it to those distances. How would it compare to times of day here? I was wondering whether we would be able to see if we were on the surface of places like this. ... | [
"Light from the sun travels away from it in a sphere, which means that the intensity of the light at a certain distance changes with the inverse of the square of that distance. For example, an observer at twice the distance from the sun as the earth is would experience 1/4 the intensity of light we experience on ea... | [
"Although Sunlight intensity decreases quite rapidly with distance (1/r",
" so twice as far away from the Sun, the sunlight is a quarter as bright), the Sun is so incredibly bright that even as far out as Pluto day time will be noticably much brighter than night time. (Phil Plait did the maths for Pluto and the S... | [
"I'm ignoring things like atmosphere and just wondering how much sunlight makes it to those distances. ",
"This isn't a good idea, and I'll tell you why in just a moment.",
"How would it compare to times of day here? ",
"And that's the point, there is no such thing as a universal daylight brightness here on... |
[
"How can trauma to the spinal cord cause quadriplegia while leaving all other bodily processes requisite for continued life unaffected?"
] | [
false
] | null | [
"without getting too technical zebra-stampede has the right idea. Now allow me to get a little bit technical. ",
"Your heart basically beats on its own. The brain modulates the rate and force of that beating via sensory afferents which are integrated in a part of the brain called the ",
"nucleus solitary tract"... | [
"In my anatomy lab we used a rhyme \"C3-5 keep the diaphragm alive\" to remind us of what levels make up the phrenic nerve"
] | [
"Without doing too much research, based on my physiology and anatomy classes I'd say because your spinal cord houses your peripheral nerves, but the brain and brain stem are controlling everything else. So presuming those parts aren't damaged you can continue with your other processes. You might not be able to move... |
[
"Why was Aristotle wrong?"
] | [
false
] | He argued that objects fall to the ground in proportion to their weight. Is the force of gravity not dependent on the mass between 2 objects? Wouldn't two objects of varying mass accelerate at different speeds on a micro scale? Is gravity (in this case) just negligible because of the mass difference between 2 rocks and... | [
"Force = mass x acceleration",
"acceleration = Force / mass",
"Since, as you alluded to, the force of gravity on an object depends on it's mass, as the mass scales up, so does the force (in a linear relationship). This means that for objects held at the same height, they will accelerate towards the Earth's cent... | [
"The force of gravity does increase with a rocks mass but so does the rocks inertia increase with mass, these two effects cancel out and result in acceleration that only depends on the planets mass.",
"You can see this by equating newtons 2nd law and his gravitational law",
"ma = GmM/r",
"where little m is th... | [
"Well there's a difference when you talk about an objects gravitational acceleration and the amount of gravitaional force between two objects. Gravitational acceleration on earth is the same for all objects because it only depends on the mass and radius of the earth which don't really change. The mass of the objec... |
[
"Can someone explain in depth the Receptor docking process?"
] | [
false
] | [deleted] | [
"Wow, something I know!",
"I am a PhD student working with LGICs and ligand binding specifically (trying to show a novel acetylcholine binding orientation in a set of genes that are different from standard nAChRs). ",
"Anyway, if you don't mind I will refer to the 5HT3 receptor as it is a ligand gated ion chann... | [
"I will read it later, I am doing revision at the moment, but you misinterpreted my first question (poor wording on my behalf).",
"What I meant is of the entire chemical makeup of a single neurotransmitter, how many of the atoms will actually interact with the receptor. ",
"Take Serotonin: Does the Amine, Indol... | [
"Much of the 5HT3 stuff has been generated from homology modelling with specific experimental analysis (SCAM, standard amino acid mutagenesis, etc).",
"But for starters the binding pocket (as mentioned by XIllusions) is fairly well studied. I would suspect a majority of the core of serotonin doesn't directly inte... |
[
"What is the minimum number of mating pairs to sustain a human population?"
] | [
false
] | null | [
"Technically the only thing you need to create a new population of any sexual species is one male and one female, or a female which is pregnant with a male fetus.",
"Inbreeding is only detrimental if you have deleterious alleles. Not everybody processes such alleles, or \"bad genes\" (to a certain extent). Of cou... | [
"Why pairs?"
] | [
"That figure is known as the ",
"minimum viable population",
". ",
"If you believe in the population bottleneck caused by the ",
"Toba supervolcano eruption",
", the human population survived with 1,000-10,000 breeding pairs. ",
"The number I see most often is about 5,000 adults. I wish i had more time... |
[
"Any Evidence regarding the pyramids in Egypt?"
] | [
false
] | null | [
"What are you asking exactly?"
] | [
"Do you know any documentaries about the pyramids that don't involve woo"
] | [
"Not the right sub for such questions. Perhaps try a history sub"
] |
[
"Why are there no three-legged animals?"
] | [
false
] | As we all know, there are two-legged animals, and four-legged animals. I was wondering why there aren't any three-legged animals. And yet there are five-legged animals, like sea stars. I understand that bilateral symmetry is important. But then why would a subset of animals develop five legs, and not three legs. Why ar... | [
"I don't know that we can say that three legs are less efficient than four or two. A three legged dog isn't a dog that evolved to run with three legs, it is a dog that evolved to run with four legs and through a developmental or physical accident, it has lost one. To put this another way, consider three wheel vehic... | [
"Trilobozoa had tri-radial symmetry. But they did not use it for movement. So, I doubt inefficieny was the reason behind their extinction. I just used it as an example to state taht trilateral/tri-radial symmetry exists in nature.",
"But you are right, when it comes to animals, movement is extremely critical for ... | [
"Odd numbered legs: good for sitting level on many surfaces, bad for locomotion."
] |
[
"Do animals with high body fat, like seals or bears, suffer higher rates of heart disease than other animals?"
] | [
false
] | null | [
"They have large amounts of subcutaneous fat to help insulate them from the cold. That does not mean they have more fat around their organs which is what adds to heart disease in humans."
] | [
"And if they did I have a feeling it would be one of those things where it doesn't make a difference in their mortality as they would likely be killed by other causes before it becomes an issue."
] | [
"This is pretty much the answer to a huge amount of species comparison questions that ask 'why does x species get y disease when humans do?'.",
"There are exceptions, elephants having multiple P53 gene copies is suspected to provide cancer resistance for example, but often the case is that wild animals normally d... |
[
"Why does multiple pregnancy cause pre-eclampsia?"
] | [
false
] | Also, a related condition, what exactly is the vanishing twin syndrome? | [
"According to UpToDate: \"The pathophysiology of preeclampsia likely involves both maternal and fetal/placental factors. Abnormalities in the development of the placental vasculature early in pregnancy, weeks to months before development of clinical manifestations of the disease, are well-documented. These abnormal... | [
"Because it has an immune component. It has been hypothesized that it is actually an autoimmune disease. ",
"You don't have immune reactions the first time you are exposed.",
"Preeclampsia is associated with antibodies to a certain receptor that helps regulate blood pressure (angiotensin II type 1 receptor. Cal... | [
"Thank you for this explanation! However, I was under the impression that preeclampsia/eclampsia can occur on the first pregnancy, not just the second one? One of the risk factors we learned for eclampsia was nulliparity.",
"In med school, we were only given a lecture about the clinical aspect of preeclampsia/e... |
[
"Why is Water Most Dense at 4° C?"
] | [
false
] | [deleted] | [
"Hydrogen bonding. As water freezes, the strong bonds between hydrogens and oxygens of neighboring molecules cause water to \"spring back\" into a crystal lattice upon solidification.",
"Edit: spelling"
] | [
"As water decreases in temperature, the speed of the molecules decreases. Below 4 degrees C, the molecular movement is slow enough for the formation of the lattice structure due to Van der Waal forces (hydrogen bonding, basically)."
] | [
"What do you mean by most dense? I remember Brain Cox saying water on the surface of Titan would be as dense as steel. Is this question too vague or am I over analyzing this?"
] |
[
"Why are so many people allergic to peanuts?"
] | [
false
] | Peanut allergies seem to be incredibly prevalent. Why are so many people allergic to peanuts and not other foods? | [
"So parents are withholding allergens because they think their children could be allergic, but withholding them for so long is exactly what makes them allergic?"
] | [
"It could also be an issue of ",
"exposure",
". In Israel the popular peanut-flavored snack, Bamba, is consumed from very young ages. Because of this, scientists have seen extremely low rates of peanut allergies throughout the Israeli population. "
] | [
"Edit: As others have pointed out, parents choosing to withhold common allergens has been due to infant feeding consensus guidelines and advice provided by trusted medical professionals, such as their family GP. ",
"The Conversation makes a great point in their article",
":",
"The problem is, there have been ... |
[
"Are capsaicin analogues like olvanil, arvanil or phenylacetylrinvanil also spicy in taste?"
] | [
false
] | These compounds are much stronger TRPV1 agonists than capsaicin, but according to various sources "lack pungency". If they indeed aren't spicy, how does it work? Paper about phenylacetylrinvanil: | [
"Nociception is the process whereby the nervous system makes the brain/mind aware of physiological pain.",
"A TRPV1 (pronounced TRIP-vee one) is one of the links in the nociception network. More specifically, a TRPV1 is an ion receptor channel located at the tip of the sensory neurons which relay pain signals to ... | [
"That doesn't really answer the question, I might do some experiments myself."
] | [
"So olvanil is still potent enough (64 times less than RTX) to kill the neuron before any pain is felt? That's why it's referred to as not pungent? Frankly this article doesn't seem to be of good quality."
] |
[
"Some of the pyramids in Egypt are over four thousand years old. If America was abandoned for a similar amount of time, what would be left standing?"
] | [
false
] | null | [
"While an avid reader myself, you might want to check out the television show \"Life After People\" ",
"http://www.history.com/shows/life-after-people",
"Each episode starts with the premise that every human on Earth instantly disappears without warning or leaving a body. It then follows what would happen to it... | [
"to add to that, this show depicts that the longest lasting structure in the united states would be ",
"Hoover Dam",
" and that it would out last all other structures in america.",
"edit:\nhere is the clip from the actual show he is referring to. Life After People claims that the hoover dam would last for 10,... | [
"Some years ago there was a ",
"US government project",
" to solve exactly this problem, specifically to warn future generations away from nuclear waste deposit sites:",
"Full PDF.",
" 19.5 MB"
] |
[
"Do mice and birds have different colour vision?"
] | [
false
] | We recently took in a female ginger Manx cat (quite unusual). She’s a great mouser but doesn’t catch many birds, which is ideal. I’ve seen on Reddit a simulation of how tiger’s prey are typically colourblind to its stripes, allowing the orange to blend in with green grass and leaves. Is it possible that birds can easil... | [
"There's a huge difference in bird and mouse vision. Mice have two cones, and are basically red-green colorblind. They are also naturally nearsighted. ",
"Birds on the other hand have ",
" cones, which is actually more than humans have (we have 3). Furthermore their \"red\" and \"green\" cones are spaced fu... | [
"The spectral response functions (i.e. how sensitive is each cone to each wavelength) for some animals' eyes can be seen in ",
"this figure.",
"Source: ",
"https://doi.org/10.3389/fpls.2020.618203",
" (Fig 7)"
] | [
"Compared to those animals, humans seem unusually bad at ultraviolet. The large overlap between the red and green receptors also seems pretty suboptimal.",
"I guess ultraviolet sensitivity is extra beneficial for small animals, since diffraction limits an eye's resolution (in radians) to the ratio of the waveleng... |
[
"Because every cell division can lead to mutation, I suppose some mutations happen as a fetus grows. How many different genomes does a new-born baby have?"
] | [
false
] | [deleted] | [
"The machinery that replicates your DNA, DNA Polymerase, makes one mistake out of every billion base pairs that it creates. This is after a variety of proofreading proteins have done their job. You have 6 billion base pairs, so expect 6 mistakes every time a cell divides. ",
"Are the cells of my left arm more clo... | [
"The somatic cells in your body have the same exact DNA sequence (almost), but not gamete cells (which are reproductive cells - sperm or egg).",
"As mentioned by skyskimmer12, DNA replication is prone to errors, but cells have mechanisms for DNA repair to ensure faithful replication. So even when mistakes occur (... | [
"The rate of mutation depends on species and even genome region. Also, some mutations lead to cell death and are not propagated. I think this would be a difficult question to answer correctly, but information on rates of mutation can be found ",
"here",
"."
] |
[
"Can any carbon-based molecule undergo combustion?"
] | [
false
] | null | [
"Carbon dioxide can't."
] | [
"Normally we think of combustion as a reaction involving some molecule and oxygen.",
"Since the carbon atom in CO2 is fully oxidized, it's an example of a carbon based molecule that won't be able to undergo combustion."
] | [
"Ah, yes, I suppose that would be the obvious exception. CO can though?"
] |
[
"What causes electrons to move (and also eventually slow) in a current?"
] | [
false
] | I know that they interact with electric fields of conductors, but what gives them the initial push? And how do they eventually stop? | [
"At a finite temperature, free electrons are always moving due to pure thermal motion. This doesn't give rise to any current because the electrons are moving in random directions, and their net motion cancels to zero.",
"When an electric field exists across the material, it creates regions of high and low electri... | [
"This is a simple model but fails to explain why some crystals are insulators and others conductors or semi-conductors. Why do the electrons only move in some crystal structures? A more sophisticated model revolves around the \"band structure\" of a crystal.",
"Electrons in a crystal can be treated as plane-waves... | [
"There's a nice paper on this ",
"by the authors of M&I undergrad physics text.",
"Electric currents within circuits are driven by \"static electricity,\" by surface charges and electrostatic fields.",
"When a switch is closed, the imbalance of surface charges will redistribute across the metal wires at about... |
[
"Why isn't Ireland more forested?"
] | [
false
] | The pictures I see of Ireland are mostly vast expanses of flat greenery. Why isn't it more forested? Or, are the pictures just playing to our expectations? If the answer is that there are conditions that favor flat greenery, are there other places in the world with the same conditions and same results? | [
"This article",
" discusses the history of forests in Ireland, and their decline (and the current efforts to increase the amount of forest). Much like other areas of Western Europe, Ireland previously had much more forest cover, much of which was removed by human activity. This was firstly to increase the amount ... | [
"While that article is correct and that human activity has had massive impact in destroying much in the way of forest everywhere, it also doesn't cover an important aspect. ",
"What it doesn't cover is the fact that a large quantity of photos people take of rural Ireland tend to be in the west where the Burren is... | [
"Whilst that may make Ireland look disproportionately ",
", I don't think Clare and Galway are too unrepresentative of the amount of ",
". Ireland has the second smallest amount of forested area in Europe.",
"With the exception, perhaps, of County Wicklow, a photo of a random piece of Irish countyside wouldn'... |
[
"Why is aluminum (with internal inert coating) a greater material preference than copper for a reusable water container?"
] | [
false
] | I'm wondering why copper is not very common in reusable water containers- like the ones that SIGG makes... is it just due to cost? Would purchasing a copper water container (and only using it with water) be less desirable? Wouldn't the "antibacterial" characteristics in copper make it a good choice? | [
"Copper is over 3 times more dense than aluminum, much softer and does not stand up to the elements as well. The aluminum oxide layer that forms on any exposed aluminum is unnoticeable and almost completely inert while copper oxide is dark brown and only form more slowly. Copper can also form verdigris (copper ca... | [
"http://en.wikipedia.org/wiki/Aluminium#Etymology",
"The British discoverer of this element initially referred to it as alumia, but eventually settled on aluminum. Others thought aluminium sounded better, and for most of the English speaking world, this spelling stuck. However, one of the American pioneers of pro... | [
"http://en.wikipedia.org/wiki/Aluminium#Etymology",
"The British discoverer of this element initially referred to it as alumia, but eventually settled on aluminum. Others thought aluminium sounded better, and for most of the English speaking world, this spelling stuck. However, one of the American pioneers of pro... |
[
"Does Mars get Meteor Showers?"
] | [
false
] | Knowing that meteor showers are debris of comets/asteroids compressing atmospheric gasses to high densities/temperatures that appear as bright lights in the sky, and also that Mars has ~1% of the Earths atmosphere, would you see meteor showers from Mars? Or would they just plummet through to the surface relatively unsc... | [
"I disagree with your conclusions. The small meteors in Earth's meteor showers, typically smaller than your average grain of sand, begin to glow at ",
"about 100 km altitude",
", where the atmospheric pressure is far less than 1 Pa (",
"around 33 mPa",
"). Mars' surface pressure ranges from 100-1000 Pa, dep... | [
"Atmospheric pressure is 101,000 Pa. No one made a typo but you.",
"EDIT: Why is your field of view smaller?"
] | [
"Probably not. Mars has an effective surface pressure ",
" 1/80 of that on Earth. So if you consider that the average barometric pressure on Earth's surface is 1000 millibars, then Mars' atmospheric pressure would be ",
" 6 millibars. Furthermore, this means the atmospheric friction would also be significantly ... |
[
"Why do we make calculations regarding radioactive decay in base e instead of base 1/2?"
] | [
false
] | The equations in base 0.5 seems so much more straightforward: N0 = Nt (0.5) Instead of in the base e where lambda have to be introduced as L = ln2/h And then plugged into the equation: N0 = Nt (e) | [
"You can do either. Most of us that do these kinds of calculations regularly can fluently switch between the two, so it doesn’t matter.",
"If you look at databases for nuclear and particle physics information, nuclear physicists tend to work in terms of half-lives (favoring base 1/2), while particle physicists te... | [
"The half-life is ln(2) times the mean lifetime."
] | [
"Thank you so much for the clarification, it was very clear. Just one point i could use some clearing up: what is the difference, or correlation, between half-life and mean lifetime?"
] |
[
"Where does the residue from deodorants go, and what effects does it have on our bodies?"
] | [
false
] | null | [
"\"This is about 2.5% of the aluminium typically absorbed by the gut from food over the same time period.\"",
"I'm going to continue on w/o sweaty pits."
] | [
"\"This is about 2.5% of the aluminium typically absorbed by the gut from food over the same time period.\"",
"I'm going to continue on w/o sweaty pits."
] | [
"The aluminium in deodorant is not aluminium oxide. Aluminium oxide is an insoluble ceramic, whereas the aluminium in deodorant is dissociated. Safety information for aluminium oxide is not relevant, as it is incredibly inert and biocompatible. Dissolved aluminium is not."
] |
[
"How does a computer know when one second has passed?"
] | [
false
] | Correct me if this is the wrong subreddit. Apologies if so. | [
"Three mechanisms.",
"First, every CPU has a thing called \"clock signal\", which is basically just a rapidly oscillating electrical signal. On the one hand, the rate at which the clock oscillates is known, so it can be used for timing; on the other hand, it can be off by several percent even in normal operation ... | [
"For the interested:",
"A real time clock circuit works in a very similar way to counting CPU clock oscillations. The main differences are that RTCs will use a more accurate oscillator (usually quarts based running at a constant clock rate) and they will sometimes compensate for the variables which change clock r... | [
"Without a peripheral, it doesn't. Not really. It can assume that a given number of CPU cycles is roughly a second, but this isn't really accurate, as the clock speed of a CPU can vary quite a bit, intentionally or unintentionally. For some purposes this is acceptable, so simply couldn't ting the appropriate num... |
[
"Siphonophores like the Portuguese Man o War are actually colonies of organisms. How do these colonies reproduce?"
] | [
false
] | If I understand my biology correctly—and please correct me if I don't—creatures like the Portuguese Man o War are not actually single organisms; rather, they are colonies of many smaller and highly specialized organisms. Here's my question(s): how do they reproduce, if they are a bunch of organisms? And how do the orga... | [
"That's really informative, but now I'm even more confused. What makes these collective \"organisms\" different from our various organs and systems if they all come from an egg and can't survive separately?"
] | [
"That's really informative, but now I'm even more confused. What makes these collective \"organisms\" different from our various organs and systems if they all come from an egg and can't survive separately?"
] | [
"They share the same DNA, differentiate, and perform functions for the communal health, exactly like what our cells do. ",
"Why would they be classified as a community? I have no idea and am just as confused as you are. "
] |
[
"What happens if you put a spring in a centrifuge?"
] | [
false
] | This might be a stupid question, but what happens if you put a spring in a centrifuge? When I compress a spring with my hand, for example, the spring compresses uniformly as I increase the force. Would a spring in a centrifuge compress uniformly? I'm asking because I have an intuition that the centrifugal force is weak... | [
"Your intuition is correct, the centrifugal force is proportional to the distance from the axis of rotation.",
"This sounds like an interesting mechanics problem. If you have a spring (constant k) with one end fixed, and the other rotating with some constant angular velocity ω, and a mass m on the other end, ther... | [
"There's no need to think about the equivalence principle or even different reference frames to see that the stability of the equilibrium can switch depending on the parameters.",
"It may be helpful to point out that the centrifugal term in the effective potential is actually just part of the kinetic energy (the ... | [
"Does it make sense that the equilibrium would be stable or unstable depending on certain parameters? There should be no difference between an accelerated reference frame and a gravitational one. This would imply that a regular old spring with a mass compressing it from above would have stable and unstable equilibr... |
[
"Our bodies, our cells. Or: How much difference is there between the human body and a colony of ants?"
] | [
false
] | Many years ago, when I was in high-school biology class, I asked my teacher in several different ways whether or not human cells are sentient. I asked several different ways because at first I thought his inability to come up with an answer was because I was being unclear. Ultimately I realized that he had no idea, and... | [
"We are actually very much like ants when it comes to cellular moving. Your immune cells move around the body based 100% on chemical gradients -- they move towards the source of the chemica signals, called chemokines. Just like ants follow chemical signals their friends leave in order to find the trail to the food.... | [
"This is an interesting question, but perhaps you are approaching it from the wrong angle. Perhaps you should ask: in terms of evolution, why do we have cooperative (everything from bacterial plaques to true multicellularism to colonies and civilization) behaviour? Part of the answer is simply that it works, but th... | [
"Leave the memes in another subreddit. Humor is fine, but make sure it adds to the discussion."
] |
[
"Question about gravity within our solar system"
] | [
false
] | How is the gravity from the sun strong enough to keep the giant planet of Jupiter in orbit, but not suck tiny little Earth right into itself? | [
"Earth moves faster than Jupiter and gravity decreases with distance."
] | [
"Aside from effects of momentum the gravitational force between two objects is dependent on the masses of both objects and the distance between them. The only reason either planet dosn't fall into the sun is because the force applied from the orbit is canceling the gravitational force.",
"F= G x (m1 x m2)/r"
] | [
"Does Jupiters mass make any difference? I didn't think so. If I waved my wand and turned Jupiter into a pea, I imagine the orbit would change due to a shift in the Sun/pea center of mass, but wouldn't it still obit at approximately the same radius if going the same speed? I imagine gravitational \"force\" goes ... |
[
"How long does it take for soil to lithify?"
] | [
false
] | Can it happen within a few thousand years, or does it always take millions? | [
"It really depends on a number of things. It usually takes several thousand to tens of thousands of years. ",
"The main variables are the availability of water, the supply of the dissolved \"cement\" species and whether the rate of chemical activity which allows precipitation of that cement. In some very specific... | [
"Thank you for the reply, the info about the beach rock is fascinating "
] | [
"A pleasure!",
"One last anecdote: there is an outcrop of beachrock in South-Africa (wish I had a link to the reference) next to an old weapons factory, which had hand grenades embedded in it. Truly exciting rocks, from which I would strive very hard to keep away the avid little hammers of first year undergrads..... |
[
"Can breast tissue \"migrate\"?"
] | [
false
] | I have been reading many of the posts in as well as many of the links provided therein. There is repeated mention of "breast tissue migration" described as breast tissue that has moved away from its original place to the sides and even onto one's back. In some of the posts/links, it is said that this "migration" is t... | [
"http://www.venusianglow.com/2009/09/get-rid-of-armpit-rolls-in-5-seconds.html",
"This is the only \"explanation\" I found for it, and I'm... skeptical, to say the least. I'd like to hear some legitimate physiological backing up of this idea if it is indeed true. ",
"edit: Some more googling, and every single... | [
"While AskScience isn't the place for jokes, a cursory observation would indicate that taking that as proof would also indicate that males who don't wear bras can have breast tissue migrate to their backs. "
] | [
"Anatomically, breast tissue can often extend into the axilla (armpit). It is common enough to appear in some anatomy atlases. My guess is that what the women are seeing is the age-dependent accumulation of fat in those places, combined with the sagging as time stretches the ligaments that hold the tissue in place.... |
[
"If we can manufacture mirrors to reflect upside down, can we manufacture them to show a \"reversed reflection\"?"
] | [
false
] | [deleted] | [
"It seems OP was asking about a single mirror system:",
"is it possible for ",
" mirror to be able to flip you over the vertical axis",
"Any ",
" mirror system will not flip an image, it will reflect it. Mathematically, a reflection and flip (rotation) are not equivalent but you can get a flip from two ref... | [
"I'd like to answer this in two steps: First by addressing the 'funhouse mirror' concept, and then secondly by addressing what it means for an image to be 'flipped L/R but not U/D'",
"When you look at certain mirrors (I'm going to use fun house from here on out) you appear upside down in the image you see.",
"... | [
"is it possible for a mirror to be able to flip you over the vertical axis",
"Short answer: yes it is.",
"You did a great job explaining why people might think a mirror flips left and right, but that wasn't the question. If a curved funhouse mirror can make you look upside down, then rotate that mirror 90 degr... |
[
"When things fall into a black hole, why does it not built up enough kinetic energy to come back to the original position?"
] | [
false
] | Classic physics demonstration of pendulum shows that when an object is falling, it will built up enough kinetic energy to come back to its original position. Classical orbital mechanics also confirm this as bodies in elliptical orbit always come back to the original position and velocity (in ideal cases atleast). But, ... | [
"Orbital mechanics work differently in GR than they do in Newtonian gravity. As you noted, it is in fact possible for objects to fall into a body and not be able to escape in GR, whereas this is generally not possible in classical orbital mechanics for point particles (extended objects can of course collide). Suc... | [
"Classic physics demonstration of pendulum shows that when an object is falling, it will built up enough kinetic energy to come back to its original position.",
"Actually, isn't the classic physics demonstration that it ",
" build up enough kinetic energy? That's why physics teachers holding bowling balls up to... | [
"There are a couple of ways to look at it. One way is that the potential well for say, a pendulum has finite depth. A black hole is has a singularity, the potential well has infinite depth so you will never cross it and go back up."
] |
[
"Why do words begin to sound alien when repeated enough times?"
] | [
false
] | null | [
"This is called ",
"Semantic Satiation",
". ",
"The analogy I like is this: just like when you stare into a light you get a blind spot, repeating the same word over and over numbs out the neurons in your cortex that make sense of the word leaving you with that alien sounding feeling. "
] | [
"Non mobile link: ",
"http://en.wikipedia.org/wiki/Semantic_satiation"
] | [
"Words are \"saved\" in the mind in a cluster of information called a lexical entry. The lexical entry consists of the semantic information about the word -- its meaning and related concepts -- and the phonological information -- the sounds in the word and the mouth movements required to pronounce it.",
"When yo... |
[
"Is there any evidence that pricing a product at, say, 9.99, results in a higher volume of sales than pricing the same product at 10.00?"
] | [
false
] | Other than the obvious, "It's a penny cheaper," I was wondering if the received wisdom regarding this aspect of consumer psychology has ever been tested and vindicated. Or is it simply a truism that has stuck around out of tradition? | [
"It's a little hard to believe but it's a thing",
"Lay article: ",
"https://www.livescience.com/33045-why-do-most-prices-end-in-99-cents-.html",
"White paper 1",
" & ",
"paper 2 - PDF warning",
"EDIT – heart-felt and obligatory thanks for the awards!"
] | [
"The theory is called \"Psychological Pricing\", and it yes, it's a real behavioral phenomena, but there are a number of theories that seek to explain it.",
"https://en.m.wikipedia.org/wiki/Psychological_pricing",
"The most commonly cited explanations are not that people are happy to save a penny, but rather th... | [
"It's more than just 99 cents. It works with 97 and 96 cents hanging off the end of numbers as well. ",
"The phenomenon is well studied in behavioral economics."
] |
[
"Clouds (in the sky): a) why are they vapour? It's -45C up there, they should be ice! and b) why do they stick together? What force is making them do that?"
] | [
false
] | null | [
"They aren't vapour. They are actually small water droplets condenced on dust, charged particles, ion's etc.. They condence because of the cold up there. You usually cannot see vapur, and the steam rising from pot is visible for the same reason, condensation as water vapour cools down."
] | [
"Clouds need a few things to be in place to form: water vapor (invisible water gas, from evaporation), a dip in temperature, and something for the water to condense on. As mentioned earlier, clouds are actually tiny drops of water, formed as water condenses onto tiny bits of dust or other particulates. ",
"As for... | [
"If it's cold enough to form ice, there is typically ice present in clouds. Clouds that appear \"wispy\" contain ice."
] |
[
"If new elements are created by fusing old ones together (I'm aware that this is greatly simplified). Are there infinitely many undiscovered elements?"
] | [
false
] | Are there infinitely many undiscovered elements waiting to be created (regardless of the difficulty of creating said element) or is there some sort of invisible wall that we might hit? Thank you. | [
"This gets brought up fairly often in these kinds of threads, but I'm of the opinion that it's not really useful to call a neutron star a \"nucleus\". Yes, it's a bound system of many nucleons. ",
" it's bound by gravity, completely different than the nuclear force, which saturates at a few femtometers (neutron s... | [
"No, probably not. The IUPAC sets the criteria for the discovery of a new element, and one of them is a minimum lifetime of around 10",
" seconds. That's roughly how long a nucleus needs to live for in order to form an electron cloud and be considered a chemical element.",
"You can have nuclei with much shorter... | [
"The ",
" of stability is different than the ",
" of stability. The valley of stability is just all stable-ish nuclides currently on the nuclear chart.",
"The island of stability is the hypothetical \"stable-ish-ish\" grouping of extremely heavy nuclei near shell closures.",
"It's possible that they have li... |
[
"What's the mathematical proof that demonstrates that two parallel lines meet at infinity?"
] | [
false
] | null | [
"You need a setting where the \"Line at Infinity\" is actually a thing. If we use coordinates, then the ordinary plane is the collection of all points (x,y), where x and y can be any real numbers. In this setting, a line is the solution set of an equation of the form Ax+By=C, where A,B and C are real numbers, and a... | [
"\"Two parallel lines meet an infinity\" is a fast and loose sentence that doesn't make much sense in most rigorous mathematical frameworks.",
"There are several such frameworks we can use. Most common are the Euclidean geometry (the one that is normally studied in high school), the projective geometry, the ellip... | [
"I've sometimes wondered what would happen if you do the opposite thing. The projective plane is what happens when you say \"just as any two points have exactly one line connecting them, so any two lines have exactly one point at which they intersect.\" But you could go the other way, and say, \"just as there exist... |
[
"How do ISS astronauts prevent pathogen transfer?"
] | [
false
] | I was watching a .gif of a water balloon being popped on the ISS and the force of the burst sent some of the water flying, yet still suspended in the air. It struck me that a sneeze would work the same way, with the mucous stuck in the air just waiting to spread disease to anyone who's floating between cabins. How does... | [
"NASA uses a ",
"pre-launch quarantine",
" to ensure that no one in space is sick in the first place. In addition all food and water is sanitized before it is stored. "
] | [
"The lesson NASA learned from the flight of Apollo 7 was to isolate the crew from external contact with non-quarantined personnel 10 days before launch. ",
"Wally Schirra's head cold on Apollo 7",
" jeopardized the mission and caused the astronauts to reject safety protocols by riding through re-entry without t... | [
"I'm not a biologist, so perhaps somone can confirm this. I'm not currently aware of any functions in pathogens that require the use of gravity to function. Other than that, standard immunizations are kept up to date for the astronauts. I also do beleive that there is a purifier attatched to the air filtration syst... |
[
"When an anti-electron annihilates does it have to contact an electron or would a neutron (or any non-antimatter particle) also cause the annihilation? This is something I've always wondered."
] | [
false
] | [deleted] | [
"If you shoot antiparticles into a black hole, the black hole will still gain mass. Antiparticles do not have negative mass."
] | [
"If you shoot antiparticles into a black hole, the black hole will still gain mass. Antiparticles do not have negative mass."
] | [
"An antineutron will annihilate with a neutron. But a neutron will not annihilate with a positron."
] |
[
"When jumping into a body of water, is there a way to calculate the distance into the water someone will go based on the height they jump from?"
] | [
false
] | I notice that when jumping from say 1 metre, we might go 30cm down above head height into the water. Where as jumping from 5 metres, obviously this increases. But it seems to increase slowly after that, for example a 10 metre jump might not take you much deeper than a 5 metre one. Of course this depends on how you land... | [
"You can get a reasonable approximation if you take a 2 stage approach. First create an equation of motion for the air section of the motion containing gravity and drag:\np= density\nv=velocity\nA = surface area\nC = drag coefficent",
"ma = 0.5pv",
" CA -mg ",
"you can then integrate this with respect to time... | [
"Ill try and clear up some of the answer then. The first section of the answer is about finding out your impact velocity. This can actually be difficult to calculate depending on the fall height as the density of the air changes with height. ",
"Here is a graph",
" that I produced in my degree to demonstrate t... | [
"Thanks! I don't fully understand the answer but some more research and hopefully I'll produce some numbers for this. "
] |
[
"Can chemists (or physicists?) 'predict' what stable elements should or could exist but have yet to be discovered?"
] | [
false
] | Stable elements or even just mostly stable ones. Iron for example has 26 electrons and protons and 30 neutrons while Uranium has has 92 electrons and protons and around 144(ish) neutrons. So could one simply predict elements which could exist based on known laws of physics & what is known about atomic structure? | [
"This already has happened. When Mendelev put together his Periodic Table, he noted \"gaps\" in it. He was able to predict the nature of the missing elements. They have, since then, been discovered and his predictions found to be correct. (Germanium, Gallium, and Scandium)\n",
"http://en.wikipedia.org/wiki/Men... | [
"It's difficult to tell, so we're not really sure. We're almost certain we've discovered every remaining naturally occurring element, but we may be able to produce more synthetic ones.",
"There's something call the ",
"island of stability",
" which is a hypothetical group of radioactive isotopes for very heav... | [
"Yes, but only in approximations. As you try to look at larger and larger nuclei there are more parts so it gets very complicated. Nuculear structure (even among the well known stable elements) is still a very difficult problem and something that theorists and experimentalists are still working on. ",
"The theory... |
[
"What would happen if two faults on opposite sides of a tectonic plate shifted simultaneously?"
] | [
false
] | I was reading and wondered what would happen if the and the had events occur simultaneously? I don't know that these faults are exactly on opposite sides of plates, but hypothetically, if an earthquake happened in both of the areas at the same time. | [
"First, the Cascadia subduction zone is on the western edge of the North American plate, but the New Madrid seismic zone is an intra-continental feature, i.e. it is in the middle of the North American plate. The eastern edge of the North American plate is the ",
"Mid-Atlantic Ridge",
". ",
"Going with the spi... | [
"Thank you for answering! Yes I wondered if (and not knowing the proper terms and details I'll explain best I can) two events happened on opposite sides, would that effect the land in the middle. I imagined the plains becoming squished up against the Rockies in a ripple, you know? ",
"I think things like that are... | [
"Even in the largest earthquake events, the amount of surface deformation perpendicular to the fault drops off pretty quickly to the point where it is zero within 10s (to maybe 100s, but at that scale you're talking about perhaps fractions of a millimeter) of kilometers. So you would not expect any effect in the ce... |
[
"Where did all the lightning bugs go?"
] | [
false
] | The recent controversy about bee population decline being linked to pesticides got me wondering about another insect. I live in North Texas and around 15 years ago when I was really young (6ish), I remember going out during the night and catching lightning bugs. These things were everywhere. Not only do I remember my f... | [
"The two main factors that researchers believe to be responsible are destruction/disruption of their natural habitat, and an increase in light pollution. However, there are additional factors that are most likely more prevalent in other areas, such as pesticide usage, environmental pollution (both air and water), a... | [
"Fireflies are actually beetles (Coleoptera) and not part of any fly Order. I always thought that was neat. Carry on..."
] | [
"http://articles.chicagotribune.com/2007-08-01/features/0707300227_1_photuris-fireflies-light-meal",
"http://www.thaibugs.com/?page_id=707",
"sorry it's not much in terms of links to studies, but they do make references to recent research."
] |
[
"Why do electrochemical cells (batteries) make a specific voltages?"
] | [
false
] | A guess I am asking why does one cell of Zinc-Carbon produce 1.5 volts? This voltage seems the same for both large and small cells. Unless I am wrong a battery cell the size of the earth would still produce 1.5 volts. Why do battery cells not produce more or less voltage? | [
"Understand it by looking at the electrical potential of a ",
" first, which comprises an ",
" and an ",
" and a reaction involving transfer of electrons (an electrochemical cell is two half cells).",
"Any redox reaction (transfer of electrons) will have a ",
". For example ",
"Zn(OH)4",
" + 2 e",
"... | [
"You can achieve different voltages by changing the concentration of the dissolved species; in this case, particularly Zn ions. 1.5 V corresponds to ",
"standard conditions",
" (1 mol/l concentration). Since the concentration (or rather, activity) enters the ",
"Nernst equation",
" in a logarithmic manner, ... | [
"The voltage question has been answered quite well, so I'll cover the other two aspects of batteries, current and capacity. For capacity, let's talk about the standard 1.5v alkaline cells. AA. AAA, C, D, 9V (which actually use 6 AAAA in series). They all use the same chemical reaction to produce voltage, but the bi... |
[
"Could someone please help with the uncertainty principle?"
] | [
false
] | and me and a flatmate were having a discussion and neither of us could answer why, when you can determine with greater accuracy the position, of a photon of light, you increase the uncertainty in the velocity. I understand the equation and that to keep within the limits when one increases, the other must decrease; but ... | [
"I explain it to my students using this analogy:",
"Picture two cameras, with two shutter speeds. Both are used to take a picture of you running through the frame in a circle. The fast camera will tell us exactly where you were when the camera clicked-but no sense of what your speed was.",
"The slow camera tell... | [
"I think it's best to look at how the uncertainty emerges. Any wave can be described as the sum of sine waves of different frequencies. In quantum mechanics the wave itself corresponds to position and the various frequencies of the sine waves that make that wave correspond to momentum. Let's start with a simple cas... | [
"I used a similar analogy a while ago, and the consensus was that it is insufficient to explain the Uncertainty Principle, also that all we do when giving analogies is clarifying the problem - but they do not really relate to the Uncertainty Principle itself.",
"My analogy was: If you want to know the speed of an... |
[
"How is the same species of moose native to both Eurasia and North America?"
] | [
false
] | With the Columbian Exchange, species like horses, pigs, maize, tomatoes, potatoes and others became available on both continents. Moose are native to both continents, but are also the same species, which seems odd to have not diverged in however many millions of years. I would be very surprised if early European explor... | [
"Many animals that range into cold climates were able to disperse between continents when sea levels were lower during ice ages. A great many large mammals in the northern part of the northern hemisphere did this (including humans). although many have since gone extinct in one hemisphere or the other."
] | [
"There was a land bridge between what is now Russia and Alaska called Beringia. It’s how humans migrated to the Americas around 16,000 years ago. Evidence suggests Moose came later, towards the end of the most recent period when the land bridge was exposed, as recently as 11,000 years ago. We have fossil and other... | [
"According the Wikipedia \"moose\" article they migrated from Eurasia to North America in the late Pleistocene, less than a million years ago, in the Bering Sea area. So probably over land when sea levels were lower."
] |
[
"Is it possible to farm electricity using lightning rods or similar techniques?"
] | [
false
] | null | [
"It is pretty impractical. When farming electricity you want a steady constant source as much as possible so you don't need to store it which results in efficiency loss, not a huge violent (and random) blast 75 times a year."
] | [
"In theory, yes. Practically we don't have reliable or safe means of handling and storing the incredible burst of energy contained in a lightning strike."
] | [
"No, it is neither possible nor practical to farm electricity from lightning. ",
"There are electrical issues (converting lightning into usable electricity), location issues (lightning is not frequent enough in any known location), and total output (all lightning only produces 1250 kA at 250 kV).",
"There are m... |
[
"Is it possible to tell the shape of a piece of metal from the sound it makes when stuck?"
] | [
false
] | More wondering if that information is transmitted in the sound, and if with infinite precision, could it be done. Obviously this would be nearly impossible by hand. | [
"You're asking one of the great fun questions from the physics of the 20th century!",
"It turns out that the answer is yes, ",
"at least to a set of related shapes if not a single exact shape",
". The limitation is that there are groups of objects that are ",
" to one another, which is to say that their res... | [
"To an extent. The shape of the metal will determine the frequencies it resonates at (the overtones, in musical terms), which can be heard and recorded.",
"But to go from the spectrum of sound produced back to the shape of the object is an ",
". Inverse problems are generally hard. Without some additional const... | [
"It is indeed possible. Jet engine manufacturers use a principle like this, but in a different way.",
"Called a “ping test” or an “impact test”, this tests whether a pipe installed on an engine (like an oil pipe, air pipe, or fuel pipe) will survive the harsh vibratory environment of multiple flight cycles. ... |
[
"Claim: \"Fourth-generation nuclear power plants will use current nuclear waste products as fuel.\" Is that true?"
] | [
false
] | In this Ted talk Stewart Brand makes the claim that fourth-generation nuclear power plants will use the nuclear waste from our current powerplants as fuel Is there any accuracy to that? is this one of those "in 20 years… XYZ will happen!" And then 20 years later somehow that thing is still 20 years in the future? or is... | [
"Some of them. There are a few different kinds of plants planned as the 4th generation. One of which is a fast spectrum reactor. These plants use the emissions from fuel which the other plants cannot. This means they are able to use fuel that has already been through an different plant. The spent fuel from the... | [
"Safety is nearly a non issue. If you were to ask how many people have been killed by nuclear reactors I would bet they would guess very high. Actual number? 32. Plants are so safe it is laughable the injustice they are done. ",
"Then look at the Gen4 reactors and it becomes an even bigger joke. Pebble bed,... | [
"It depends a bit on the type of IV-gen reactor, but there's nothing wrong with the actual principle. ",
"Fast-neutron reactors",
" can do this, and potentially convert long-lived nuclear waste into much shorter-lived isotopes. (Nuclear reprocessing of fuel, which also exists, can reduce the amount of waste as ... |
[
"How big can black hole get ? Is there a limit ?"
] | [
false
] | null | [
"If by \"big\" you mean spatial extension, there is really no way to answer this question.",
"The black hole itself is a singularity, meaning it has no volume whatsoever. Thus, the size of black holes is mostly measured by the radius of its event horizon (or ",
"). ",
"The size of the Schwarzschild radius is... | [
"Let's start with the trivial answer: a black hole's event horizon cannot be larger than the universe, so there's an upper limit right there. Next, since matter in the universe seems to be clumped in galaxies, and since the universe is expanding, and since the distances between galaxies is so large that in the futu... | [
"It's a weird situation when that is mentioned in that context. The space in between distant galaxies can expand at such a rate that they are moving away from eachother faster than the speed of light ",
", but that is a different thing entirely from the objects themselves having a speed greater than light. There... |
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