title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"The Panama canal has locks to raise and lower crossing boats. But why aren't the Atlantic and Pacific oceans at the same height?"
] | [
false
] | I would think that the water would flow around somehow (e.g. under South America) since the oceans are connected, but I guess there's some phenomenon I'm not understanding. | [
"Sea Level is sea level, the canal rises over a mountain range and traverses a high land lake ",
".The lake is Panama's largest source of fresh water, without locks on the canal the lake would drain into the ocean and the canal would of had to of been a much deeper cut making it so much more expensive to build."
... | [
"I would think that the water would flow around somehow (e.g. under South America)",
"Around, but not under. The land masses are not floating on a bed of water. Rather, the oceans are pools of water collected in depressions in the rock.",
"(EDIT: I realised just after posting that you probably meant \"south o... | [
"The Panama Canal is a man made construct. Check out ",
"this wiki",
" about probably the most physically challenging aspect of building the canal bringing the continental divide of Panama from ~210 ft above sea level down to ~85 ft above sea level. The sets of locks on both sides of the canal vertically trav... |
[
"It would take 8 minutes for us to see that the sun exploded. But if it just vanished when would the gravitational pull be affected?"
] | [
false
] | Basically... is there a speed to gravity? | [
"Yes. Current theory suggests it should be the same as the speed of light and observations are consistent with that value. So, 8 minutes (a bit over for both actually)."
] | [
"But how do we know the black hole didn't already disappear?",
"What makes you think that we ",
" know that?"
] | [
"So hypothetically if the black hole at the centre of our galaxy were to just disappear, we would stay in our spiral path for anoth 27 thousand years due the the gravitational force already given off by it? "
] |
[
"If you flash a strobe light much faster than the frame rate capability of human eye (for example 2000Hz) would the light look identical to a light which is always on?"
] | [
false
] | this isnt HW its just a thought experiment | [
"You only need about 60Hz to achieve the effect. Most electrical grids cycle at 60Hz and old CRT monitors / TVs commonly refreshed (at a minimum) at that rate. Some people however are sensitive enough to be bothered by the flicker, also if you where to look away or via the corner of your eye it might be easier to... | [
"Your old lights were probably incandescent and the new ones LED. Incandescent lights have a filament which is heated to a high temperature by the electric current flowing through it. This causes it to radiate visible light. It will continue to glow as long as it is hot enough, so as the current changes polarity at... | [
"Your old lights were probably incandescent and the new ones LED. Incandescent lights have a filament which is heated to a high temperature by the electric current flowing through it. This causes it to radiate visible light. It will continue to glow as long as it is hot enough, so as the current changes polarity at... |
[
"Is it possible that there is a star (or planet or whatever space stuff) we cannot discover because it is behind another star?"
] | [
false
] | null | [
"There are objects that are behind other objects (galaxies, typically) that we can still see because of gravitational lensing. ",
"Here",
" is an extreme example, the blue galaxy is behind the yellow galaxy but we can see it because the light from the far galaxy gets wrapped around by the closer one.",
"Stars... | [
"Wow, I had no idea there were actual images displaying gravitational lensing of that magnitude!"
] | [
"What if the behind-star is near enough to the star in front that even with parallax it cannot be seen?",
"Stars that close would orbit each other, thus they could be observed after a time. Even if you had two stars by coincidence being behind each other, that state wouldn't last long, because they either move t... |
[
"Do bones contain blood? Does anything come out of them if they are broken?"
] | [
false
] | In a self defense class, the instructor was discussing reasons for shooting someone in the pelvis. Besides immobilizing them, he said that "the pelvis contains a lot of blood" because it is such a large bone. That got me wondering. Did he mean marrow? I know that marrow produces blood, but I have no idea how that actually works. So, do large bones contain lots of blood? What, if anything, comes out if a bone like the pelvis if it is badly broken (say by a gunshot)? | [
"Bones do contain blood, which runs through ",
"Haversian canals",
" in compact bone. Cancellous bone is also highly vascularized, and as you stated contains bone marrow for hematopoiesis. "
] | [
"Bones do contain blood but it's more the number of important vessels in your pelvic region as well as the potential body cavity spaces (retroperitoneal space, or the space between your visceral organs) that makes the pelvic region such a devastating area for blood loss. Whether from a pelvic fracture or a gunshot ... | [
"Your instructor is probably saying hta tyou should shoot them in the pelvis, not because the bone itself has alot of blood but because that region of our anatomy has alot of blood in it. Also, there's a good chance that if a bullet did hit your pelvis the bullet would shatter and the ricochet's would shred your i... |
[
"Does the effect of time dilation make space travel somewhat more feasible?"
] | [
false
] | If I traveled 100 lightyears at close to the speed of light (say 250 million m/s), would the trip be short enough from my point of view that I could still live a full life after landing? Also, do other relativistic effects (such as increasing mass) make traveling this fast fundamentally implausible? | [
"Yes, and for the time being, yes.",
"To reach a destination 100 light years from here in, say, 5 years, you would need to travel faster than 99% light speed. If you are only travelling 250,000,000 m/s, as you suggest, your Lorentz factor is only about 1.51, and so your trip would still take a bit over 66 years ... | [
"Also keep in mind that, while this travel would be feasible for you, it would not change the fact that your ship time and Earth time are dramatically different. If you reach the destination in 5 years, you may well be able to lead a full life there, but everyone you knew on Earth would be dead by the time you arri... | [
"There is some hope that the fuel requirements could be made more sane by collecting fuel as you go with something like a ",
"Bussard ramjet",
"."
] |
[
"With new media such as easily accessible video, do we have proof that reading something is still the best way to learn it? In other words, should kids be going home and watching videos for their classes rather than reading text books?"
] | [
false
] | I always wondered if I would learn more if instead of text books, we had videos that would explain the same things with audio voiceovers, but also include pictures, maps, and animations. So instead of professors writing text books, they would be creating video scripts. Have any studies been done that might hint that this is not a good option? | [
"Don't know of any studies in the field of explicit and pure video learning.",
"However, an important part of learning is the exposure to different stimuli by the teacher through different media, like pictures, videos or audiofiles.\nPictures especially have certain functions for the learner. Such as a mnemotic f... | [
"I think the idea is that books will theoretically be around forever and can be passed from one class to the next. They don't discriminate against families who may not be able to afford high speed internet access (or any internet access or even a computer for that matter)."
] | [
"The problem with video is that it is generally very detail light. Video is great for showcasing broad-stroked explanation. You can show pretty pictures and animations. You can have interesting voice overs.",
"The fact remains that it is a poor format for covering technical detail. The important thing with a boo... |
[
"In QFT, why is the field operator at point x acting on the vacuum supposed to create a particle at position x?"
] | [
false
] | To my knowledge, applying the field operator O(x) to the vacuum |0> creates a particle at position x, with some spread in position and in momentum which depends on the field. But why is it not centered around 0? For example, if I have a real gaussian centered around 0, I can write it as the anti-Fourier transform of its Fourier transform, that is as an integral over the momenta of some amplitude times the annihilation operator times exp{ikx} plus its complex conjugate. This is a gaussian pulse centered around x=0. If we put x=a we will simply get a smaller value. So why is creating a particle at position y considered to be O(y)|0> instead of O(x-y)|0>? Also, where does the position dependence go if the first is correct? | [
"First of all, in a generic interacting QFT, the state O(x)|0> is actually some complicated sum over \"multiparticle\" states. I used scare quotes because you can argue whether a given interacting field theory has particles, or even if we understand the structure of the Hilbert space at all. ",
"Turning to free f... | [
"Do you agree that O(x)|0> ~ ∫dk exp(-ikx)a_k+ |0>?",
"No, for the free scalar field in relativistic QFT there are extra factors such as 1/sqrt(p",
"+m",
") in the integrand. If you do not insert these factors, you don't correctly diagonalize the Hamiltonian, so there's no way around this. Given that OP is re... | [
"I guess we should be explicit about what O(x) is. If O(x) is a free scalar field with a Gaussian action, then your description",
"is as an integral over the momenta of some amplitude times the annihilation operator times exp{ikx} plus its complex conjugate",
"makes sense, so I assumed you were thinking of this... |
[
"How do astrophysicists map space? How are objects in space properly tracked?"
] | [
false
] | null | [
"Forgive me if I misunderstood the question but the asteroid that was hit was a small one in orbit around a larger asteroid to help mimic the effect of a gravitational field on its altered trajectory. Therefore the measure of whether the mission was a success is how it’s orbit was altered in terms of duration whic... | [
"So for solar system bodies, they are observed via telescopes, or Radar (though, especially with the loss of aricebo, telescopes are by far the most common observation technique).",
"By knowing which stars we're looking at in a given image, we can very precisely determine how the telescope is oriented. Then by f... | [
"It’s observation and complicated math. For solar system objects they can image them over time, and note their position each time, then trace out the path and use math to predict the position over time. It’s amazing how accurate we can be; after all we just launched a satellite, navigated it over the solar system... |
[
"What trait shows the greatest genetic variation among humans?"
] | [
false
] | null | [
"I was under the impression that this was not a system that was particularly variable genetically. Variation in the immune system is primarily a result of (almost) random recombination of fairly highly-conserved genetic material, isn't it?",
"Autoimmune disorders, if I understand this correctly, are primarily a r... | [
"I was under the impression that this was not a system that was particularly variable genetically. Variation in the immune system is primarily a result of (almost) random recombination of fairly highly-conserved genetic material, isn't it?",
"Autoimmune disorders, if I understand this correctly, are primarily a r... | [
"There is a mechanism in place to prevent this- during development of T- and B-Cells, dendritic cells bring portions of the human body cell genome and any cells that recognize these antigens are destroyed, so when they mature they will not attack their own cells (as in autoimmune disorders).",
"So basically, OP i... |
[
"How come the water in the toilet bowl moves when it's windy outside?"
] | [
false
] | null | [
"The S-bend, plus the p-trap underneath prevent this from happening, as you'll get poisonous sewer gas in your home. The water acts as a \"gas-plug\" essentially. ",
"Source : plumber. "
] | [
"If it blows just right it can slowly start drawing the water through the S bend, lowering the water level in the bowl. I've neither seen or heard of it emptying one entirely, though."
] | [
"If it blows just right it can slowly start drawing the water through the S bend, lowering the water level in the bowl. I've neither seen or heard of it emptying one entirely, though."
] |
[
"What's in the middle of a benzene ring?"
] | [
false
] | In the middle of the ring, within all the bonds, what could there be? I mean, it can't be air - so what could it be? | [
"Electron density. If you look at an electrostatic potential map, there is significant activity along the entire molecule, with no \"hole\" in the middle. In fact, negative charge accumulates there so in some respects there is even \"more\" there than along the bonding areas."
] | [
"Nothing.",
"Seriously, nothing.",
"Vacuum. Residual electron density from the single bonds (sigma bonds) between the carbon atoms if you want to get picky.",
"But mostly nothing."
] | [
"Ahh okay. Yeah I figured it'd be a vacuum because there's not much that can reside there. Thanks for the answer!"
] |
[
"If you take an even number of fermions with 1/2 spin and bind them then the spin is now an integer and now a boson. Bosons do not follow Pauli's exclusion principle but fermions do, but now that the 2 fermions behave like a boson would they follow the principle or not?"
] | [
false
] | null | [
"Composite bosons behave like bosons, unless you get them close enough to each other that their substructure starts to become important.",
"If you have composite bosons made of an even number of fermions, as long as you don't force them to come within a length scale small enough that the fermion wavefunctions sta... | [
"An example for this is Bose-Einstein condensate of 4He, which consists of 6 fermions (2 protons, 2 neutrons and 2 electrons)."
] | [
"Also how do you think I've done asking this question and the complexity of the question based on my age (high school freshman)?",
"It's great that you're thinking about these things and asking good questions at that age."
] |
[
"Is there a difference between claws, talons, and nails?"
] | [
false
] | Or are they synonyms of one another? | [
"Claws are the curved pointy bits on the end of digits on mammals, birds, and reptiles (at least some reptiles, not sure about 'all')",
"\nTalons are what you call them on birds.",
"\nNails are the flat non-pointy bits on primates. ",
"Both talons and nails are types of claws. "
] | [
"For mammalian claws and avian talons, there is a pointy sheath, made of keratin, that covers over the last phalanx (the last bone) and the phalanx is curved and pointy like the keratin sheath. Primates have nails rather than claws on most digits (Some primitive primates retain a single claw on their big toes). P... | [
"Why do we have nails rather claws? I know evolution doesn’t follow any “purpose” but I guess I’m asking what benefits/disadvantages does having nails versus claws confer? Or is it just simply a matter of what we descended from and we just never were selected in favor of developing claws? Am I making sense here"
] |
[
"What stops an electron from binding with the nucleus?"
] | [
false
] | It must be obvious but i can't for the life of me think why! The nucleus has an overall positive charge and the electron a negative charge so why don't they attract to the point where the electron become part of the nucleus? | [
"The formal answer is that such a state is not stable in quantum mechanics. But it's worth unpacking that a little.",
"First, you need to understand the notion of a state in quantum mechanics. Part of the weirdness of QM is that a state may not have a well-defined position, or a well-defined momentum, or even a w... | [
"This thing happens in neutron stars (electrons are squashed into protons and form neutrons). But conditions there are bizarre.\nWhy it doesnt happen in ordinary matter ? \nYou have to think 'waves' (de Broglie waves of matter).\nYeah, those waves overlap, but they doesnt mix or merge into one big wave in normal co... | [
"Why it doesnt happen in ordinary matter ?",
"It does happen in ordinary matter. The process is called electron capture. Electron capture is not very probable unless the condition of the nucleus is just right. The rest of your answer is good."
] |
[
"If the Hubble Telescope was in orbit around Alpha Centauri, pointing at our solar system, how many of the planets and other orbiting bodies could it see?"
] | [
false
] | Not necessarily the Hubble telescope, but a civilisation with our current level of astronomical technology is looking at us from approximately 4.4 lightyears away. Can they see Earth? The moon? The rings of Saturn? My back yard? | [
"If we were lined up just right then they could probably see a transit of Venus and Earth. Essentially a mini-eclipse as the planets crossed the disk of the sun. The problem with Jupiter and Saturn is their years are so long they would take a long time to be confirmed. Jupiter takes 12 years to go around the sun, ... | [
"If we were lined up just right",
"In fact, in the context of OP's question, that's not granted. Alpha Centauri is located to the South of the Solar system, so you won't be able to observe any transits from there."
] | [
"Not through direct imaging. The evidence for planets most often comes from (a) transits across a star, reducing the star's luminosity at regular intervals; and (b) Doppler shifts in the light from the star, as the star wobbles to and fro as the planet undergoes its orbit."
] |
[
"My friend is buying a house next to a Superfund site and wants to plant a vegetable garden. Should she?"
] | [
false
] | is the site in question, and is the most current site assessment. Her future house is less than a mile north of the site, with a stream running downhill from the landfill on her property. Her house is on the bottom edge of a valley. I think it's a bad idea, but I'm not entirely familiar with the way groundwater flows or the ins and outs of Superfund cleanup. Is she safe to plant right in the yard? Thanks for your help! | [
"I can't answer your question but one solution might be to build some big planter boxes, buy some topsoil from a store, and avoid the issue altogether."
] | [
"I would be slightly uneasy about that, but it's probably fine. I think the biggest danger is contamination of groundwater if your friend has a well. If your friend has a municipal water supply I don't expect it would be a problem.",
"I live about a quarter mile from a Superfund site which has polluted the ground... | [
"Do this. Measure, measure, and measure again."
] |
[
"How do you conduct vaccine trials for lesser known but dangerous diseases like Rabies?"
] | [
false
] | [deleted] | [
"For vaccines against rare diseases or diseases that are rare because of pre-existing vaccines, typically antobody responses are simply monitored for a particular length of time and are compared to what is known to protect against the disease and how the pre-existing vaccines are known to behave in vaccinated popul... | [
"Comparator groups are not strictly required in all clinical trials. If the disease is well known to be as fatal as rabies is and the treatment is as effective as some vaccines can be, administering placebo is not ethical. Please note that I am refering to post-exposure use of rabies vaccine.",
"Now, there are al... | [
"Well, not quite. Immunogenicity studies would be conducted first on healthy volunteers to see if antibody levels are sufficiently high to warrant further studies and select appropriate dose. It is possible, but unlikely that a new vaccine would elicict neutralising antibody production without being effective. It s... |
[
"How can scientists figure out which parts of our brain do what?"
] | [
false
] | [deleted] | [
"There are many way by which we can narrow down the function of different brain regions. In humans, we are limited primarily to imaging techniques, whereby a person is given a certain stimulus, or asked to perform a certain task, and researchers use indicators of neuronal activity (such as blood flow in an fMRI) t... | [
"Good answer overall, but you seem to be giving short shrift to lesion studies, which were pretty much the sole source of human knowledge about brain functioning prior to modern imaging technologies and other innovations (and a remarkably detailed source at that). There's really no better way of figuring out how a ... | [
"Yes of course. I actually meant to include more on that, including the case of ",
"Phineas Gage",
"."
] |
[
"How did the ancients discover the value/concept of Pi? In what ways was it useful to their lives?"
] | [
false
] | null | [
"One of the earliest calculations was in ancient Egypt. It was used for things like calculating the areas of fields or the volumes of cylindrical granaries.",
"One papyrus says \"Example of finding the area of a round field with a diameter of 9 khet. What is its area?\nTake away 1/9 of its diameter, namely 1. The... | [
"Example of finding the area of a round field with a diameter of 9 khet. What is its area? Take away 1/9 of its diameter, namely 1. The remainder is 8. Multiply 8 times, making 64. Therefore the area is 64 setjat.",
"Also just so everyone is also aware:",
"Math done by words is a very common way of doing math i... | [
"If you work this out, they approximate pi as 256/81 or roughly 3.16.",
"How this works out: they are saying ",
"A = (D - (1/9)D)",
" or ",
"A = (8/9 * D)",
"A = 64/81 D",
" ",
"Compare this to the correct formula, A = π * r",
"A = π * (D/2)",
"A = π/4 * D",
"So we have π/4 ≅ 64/81, which is equ... |
[
"What would happen if you placed a hydrogen atom rather then protons in a super collider?"
] | [
false
] | What would be the end result of replacing protons with hydrogen in a super collider like the LHC? | [
"There would be a huge protest by scientists and funding agencies as the LHC mysteriously shuts down and stops producing results. ",
"Particle accelerators accelerate particles using a changing magnetic field or electric field. Since hydrogen is neutral, it can not be accelerated using the equipment at the LHC. "... | [
"what about a something like iron? It is magnetic, so would there be much more energetic reactions or just more of the same fundamental particles. "
] | [
"The LHC has done runs smashing protons into Lead ions. I don't know whether smashing two beams of lead ions together is possible.",
"http://home.web.cern.ch/about/updates/2013/01/protons-smash-lead-ions-first-lhc-collisions-2013",
"Edit: lead-lead collisions have been done. ",
"http://iopscience.iop.org/1... |
[
"Looking at the Andromeda galaxy with the naked eye shows us what it looked like 300 million years ago. When I use a telescope that is 300x am I seeing what it looked like 1 million years ago? If not, why?"
] | [
false
] | null | [
"No, because no matter what kind of telescope you use, it's collecting light that left at the same time."
] | [
"So that is the question are you looking at light 300 times away or is it magnifying the light that is 300 million years old?"
] | [
"The magnification of the telescope plays no role in the flight time of the light."
] |
[
"Does anyone know why it took so long to invent \"talkies\" when records, gramophones, and phonographs had existed for quite some time? It seems to me that they could have synced the two up."
] | [
false
] | [deleted] | [
"The problem was in syncing audio with video. The original films used large reels of cellophane which would move over a projector to produce an image. Audio was recorded by having a needle scratch either a wax cylinder or vinyl discs, which could then be used as molds to manufacture copies. ",
"Early recordings w... | [
"Just picking at the details: the 'modern' sound-on-film technique you describe is actually the oldest and lowest quality of the four (!) different ways sound is encoded on modern projection film. It may sometimes be fallen back to if whatever digital format the theatre is using becomes corrupted (the loss of qua... | [
"And here's a picture of the four modern sound formats on a single piece of film.",
"The blue pixels on the edge is the SDDS soundtrack. The gray pixels between the sprocket holes is the Dolby Digital soundtrack. The two squiggly lines are the Stereo Variable Area soundtrack, typically encoded as Dolby SR. And... |
[
"What physically happens to someone inside when they fall in love?"
] | [
false
] | null | [
"A variety of hormones play different roles depending upon the stage of love. ",
"This page does a good job a giving you an overview",
" of what is happening."
] | [
"Here's a ",
"graphic",
" of some of the various neurotransmitters active in a brain that is in love. "
] | [
"If you follow this, then the phrase \"addicted to Love\" makes a lot of sense and it's not just a slogan. That explains a lot. Thanks!"
] |
[
"There are thousands of pigeons in central London. They don't seem to be eaten by birds of prey. What's preventing predation?"
] | [
false
] | null | [
"The volume of pigeons far outweighs the predatory ability of birds of prey.",
"That said, there are plenty of good examples of predatory birds making a living off of pigeons. ",
"From wikipedia",
" ",
"One example: Pale Male in NYC"
] | [
"I noticed that Pale Male has, to date, outlived seven mates. Is there any speculation if his mates have just had unusually bad luck (poison, cars, etc.), or has he had unusually good luck for surviving as long as he has?"
] | [
"The shape of a bell curve tells us it's far more likely for seven birds to live to breeding age and then die than for one bird to survive seven times longer than usual.",
"I don't have the exact curve for the longevity of red-tailed hawks to hand at the moment, but it would be a reasonable expectation to think t... |
[
"Have the locations and movements of black holes ever been tracked or mapped?"
] | [
false
] | I am curious if known locations and movements of black holes have ever been mapped or graphed to see if there are any interesting finds about their whereabouts. | [
"Black holes are all over the place doing all sorts of things. The main categories are of course stellar massed and supermassive black holes. Stellar mass black holes are the remains of supernova and neutron star mergers, and have masses between a few and a hundred solar masses. Supermassive black holes have been f... | [
"A wizard that gravitates like a 4 million suns. ",
"But seriously, I can't think of a single alternate explanation that's even remotely plausible. "
] | [
"Here's a gif of stars orbiting",
" the supermassive black hole in center of the Milky Way.",
"\n",
"Main Article",
"\nIt's not a simulation or \"artist's impression\", it's astrophotographs over a period of a few years. The stars are moving hella fast, too."
] |
[
"What is currently being done to clean up the plastics in our oceans?"
] | [
false
] | I have heard that there are bacteria and fungi that are able to breakdown plastics but apparently it takes a lot of time. What other options are out there? Does this issue need to be attacked in a mechanical way or a biological way? Other redditors have commented on the issue of separating microplastics from microorganisms. How would someone go about this undertaking without harming the microorganisms on a large scale operation? | [
"Well, the short answer is, there aren't really any good options. The scale of the problem is mind-blowingly huge, and there are a lot of complicating factors that make any sort of aggressive large-scale cleanup unlikely or impossible. This article does a good job introducing some of those problems: ",
"http://in... | [
"Nothing, and nothing should be done. Other than people disposing of wastes more responsibly too avoid adding to the problem.",
"This is an example of a problem blown hugely out of proportion, the great garbage patch is an aesthetic problem more than a real environmental problem. No one likes the idea of plastic ... | [
"Right now, there is only one solution to the problem-- use less plastic, and get people around you to do the same.",
"Also, make sure your plastic ends up in a proper dump. Plastic is quite inert for the most part, and will do pretty much zero harm buried under some piece of land. "
] |
[
"Is it possible to suspend an incredibly long stretch of rope with one end in space and one end dangling near the Earth's surface using only gravity?"
] | [
false
] | Would Earth's gravity eventually just pull it back down no matter what? Could the moon's gravity (or that of another body) be used to help balance Earth's, therefore keeping the rope suspended forever? What would happen if you tried to climb the rope? | [
"Cf. ",
"space elevator",
"."
] | [
"In theory, yes. It would simply take a balance of the centripetal force and gravitational force. Seeing as a rope is generally of uniform linear mass, it may require a weight at the opposite end of the rope (in space), but if we ignore possibility of destruction of the rope and a few other inconsequential things... | [
"This design is sometimes called a skyhook. The cable would actually need to be just as strong. the main load the cable has to bear is the rest of the cable."
] |
[
"Chicken or egg? (But with time and space)"
] | [
false
] | [deleted] | [
"We say the Universe is 13.7 billion years old (give or take a bit) because we understand its expansion history and can trace that back to when it had zero size (as a limit). See ",
"this Wiki page",
" for a decent explanation."
] | [
"Furthermore, the radius of the observable universe is much larger than 13.7 billion light years do to expansion."
] | [
"Once you get well out beyond everyday experience, the things that are the closest to what we normally think of are often the ",
" useful concepts."
] |
[
"If there is an ocean below the ice surface of Europa, is the ice shell buoyant? Geologically supported? Or is it kept in place by the distribution of gravity?"
] | [
false
] | In other words, how does the solid surface exist with a liquid layer beneath it? Forgive my ignorance if I'm missing any obvious answers to this :D | [
"It is buoyant. The shell is no different than the ice shell of a massive frozen lake on Earth, just curved slightly more. So you can extend it to a complete sphere without any issue. All of the water still will be denser and support the ice the same way a lake does."
] | [
"Yup, as long as the water is water, it is effectively incompressible and more dense than the ice no matter how thick the ice is.",
"If you drop more ice on top or cool the moon further, it may cause some of the water to turn into ice, but it will be at the top or float to the top, keeping all the ice at the shel... | [
"and more dense than the ice no matter how thick the ice is.",
"That's not strictly true. ",
"As you add more and more ice on top, pressure increases at the bottom. Eventually somewhere around 2 GPa (about 10,000x atmospheric pressure at sea level), the bottom layers will form either ",
"Ice VII",
" or ",
... |
[
"a spaceship travels at 99% lightspeed for 5 years and comes back to earth, time passed on earth will be 36 years. what if the reference point is the spaceship instead of earth, will the time pass on the spaceship be 36 years instead?"
] | [
false
] | [deleted] | [
"No it won't, the space ship won't be the reference point because for it to come back to earth it will need to steer at some angle which in turn gives it some centripetal velocity which gives it acceleration, and it cannot be taken for a reference point. \nSource: my physics high school teacher answered the same qu... | [
"The ship won't have been stationary in a single inertial frame of reference during this journey, thus the scenario isn't completely symmetrical. The ship accelerated and Earth did not. Acceleration isn't relative like velocity. Acceleration can be measured within a closed system without external reference, unlike ... | [
"Nope. You in the vehicle experience acceleration, which is not relative. You know it's you moving away, not the earth moving away from you."
] |
[
"How much of the adverse health effects commonly attributed to heroin are actually caused by various contaminants present in street heroin?"
] | [
false
] | What would be the effects of heroin addiction if it was legally produced and sold in controlled conditions? What would be the production costs given mass production? | [
"Statement of experience: i am a drug counselor with significent education and training in neuropsych, psychopharmocology of drugs of abuse, anatomy and physiology and addiction. I am an expert in Methadone Maintenance Treatment and work exclusively with opiate addicts.",
"Heroin, like all opiates, do very little... | [
"Probably the longest post I've read in full for a while. That was really interesting and exactly what askscience should have more of, thank you."
] | [
"He never mentioned withdrawals. When he does you'll consider not doing heroin. "
] |
[
"If a population's average age was kept very low by environmental factors for millennia and those factors were removed, would that population's lifespan have been permanently shortened? (Highly theoretical and nerdy)"
] | [
false
] | Sorry for the long title, and let me try to explain. I run a campaign in a fictional setting of my own design. Within the setting is an isolated nation of people that have been completely cut off from most of humanity by natural features that arose after a great cataclysm about 2000 years prior. They are a coastal people and due to the nature of the cataclysm the seas and earth around them are full of toxic metals such as mercury, lead and gold. Their birthrate is low and their lifespan has been cut very short. Few live above 25 years old and 30 is almost unheard of due to the creeping heavy metal poisoning that is the inheritance of every new child. Getting closer to the question: Suppose that these people were relocated to an area with good soil and water. Many have already absorbed enough metal to ensure an early death, but the next generation won't have that curse hanging over them except in possible genetic damage caused by the toxins (I think). So now the question: Since the primary factor deciding longevity for these people was resistance to the damage caused by heavy metal poisoning, would they now find that their lifespans are much shorter because it has not paid off in terms of natural selection to be long-lived? Would they find themselves dying almost as early due to reduced resistance to ageing and diseases? The fate of an entire fictional people (the Celegeri) rests upon the answer. | [
"Possibly, but in more indirect ways than you may be thinking.",
"Evolution doesn't care a lot what happens to you after you are done having kids. And living much past the age of fertility is a new trick we've only picked up recently. A lot of the problems we experience in old age aren't really selected for or ... | [
"Yeah, if short lifespan is an important plot element, making a specific killer is the way to go.",
"\"You know that +2 to Con and Fort saves you get? Enjoy it while you can, because the Wasting is going to kill you off by 30.\""
] | [
"There is an interesting article on Tasmanian devils that discusses this. Basically, the problem is a facial cancer that is spread through contact. This effectively shortens the lives of the devils. This is effectively the scenario you are talking about. The results? Earlier age at first breeding, more offspri... |
[
"Why is sodium chloride the dominant salt in seawater?"
] | [
false
] | Why sodium instead of lithium, potassium, etc? Why chloride instead of sulphate, phosphate, etc? | [
"So when considering this question, we have to consider two things. First, what are the concentrations of each element on earth? Second, what chemical form(s) is each element found in? To be found in seawater in large quantities, an element needs to preferentially form stable, water-soluble species. ",
"This page... | [
"Interesting. I see that Na and K have very similar abundances, and they are similar chemically, so why isn't there more potassium? Is it due to NaCl's almost flat temperature v. solubility curve? Most salts crystallize out when their aqueous solutions are cooled, but NaCl practically doesn't."
] | [
"It's due the varying residence times of those elements. Sodium and chlorine have long residence times, while potassium precipitates rather quickly. ",
"https://en.wikipedia.org/wiki/Residence_time_(fluid_dynamics)"
] |
[
"Why can't we send an astronaut to just orbit Mars and send them back?"
] | [
false
] | null | [
"Landing on Mars is not necessarily a one-way trip because of fuel constraints. It's every other part of the trip that is also extremely difficult.",
"Getting to Mars and back would take about 2 years. This means launching a ship with 2 years worth of food, water, air, radiation shielding, and other supplies, eve... | [
"Mostly because there is very little reason to do so. We can do everything via a remotely controlled orbiter for the most part that a human could do by orbiting, so there is no reason to risk someone's life and limb. The only reason for doing what you say that I can think of would be for testing systems needed fo... | [
"Please post ",
"in the official thread",
" in order to consolidate information."
] |
[
"When does velocity in lagrangian approach equals velocity in eulerian approach (fluid mechanics)?"
] | [
false
] | null | [
"The Eulerian description of some quantity Q (pressure, temperature, velocity, etc) is dQ/dt. The Lagrangian viewpoint this is DQ/Dt = dQ/dt + u dot grad Q. The trivial case is when the fluid is at rest since u = 0 in both frames. The second case is when grad Q = 0. This is that spatial derivatives of the quantity ... | [
"My question wasn't intended like this, we haven't even taken that formula at university. Can I pm you? I have some questions about my post."
] | [
"Physically there are two scenarios. The fluid is at rest (not moving). The other is that the fluid velocity is the same everywhere. So if you imagine a fluid flowing where the velocity is 5meters per second everywhere then both frames will result in 5meters per second. If there is any variation at all in space the... |
[
"How do equations like general relativity, which models the effects of gravity, have solutions such as the evolution of the universe?"
] | [
false
] | [deleted] | [
"The Friedman equation describes the scale of the universe as a function of time given various geometric parameters, assuming it is homogeneous and isotropic. It can be linked to general relativity through the Robertson-Walker metric, where the solution to the Friedman equation scale factor, a(t), is the coefficien... | [
"On large scales, the only force that matters is gravity, and so if you want to study the overall behavior of the universe, general relativity is what you need.",
"The other forces are either short range (the strong and weak forces are negligible at sizes bigger than that of an atomic nucleus) or effectively rend... | [
"General relativity isn't just a theory of gravity, it's a theory of ",
". That's all the expanding Universe is, really. It's a particular model of spacetime. It's a model in which spacetime looks the same everywhere at any one moment, but is allowed to change with time. So it's a natural thing to look for in gen... |
[
"Why don't ants drown when it rains a lot?"
] | [
false
] | Are their tunnels built to be safe in high-moisture conditions? What about in areas with flooding? Do they simply retreat to higher ground? | [
"Quick google search: ",
"Usually the construction of the anthill itself allows water to drain very rapidly. Most anthills are filled with tunnels that drain the water from the hill. There are even ants, like fire ants, that have a central hill that is covered with a hard covering of soil and their entrances and ... | [
"Oh, cool question! Atruen has answered in part - his response is about drainage through ant hills. But I've got another cool piece of information for you. Many ants are able to grapple together to form ",
"living rafts",
" by increasing their surface area overall compared to their volume and overall mass. I've... | [
"Your link to a source is a non-existant page on discover banks website? Not sure if that was some sort of typo."
] |
[
"What could replace oxygen as a metabolic agent for extraterrestrial life?"
] | [
false
] | I've seen a lot of topics about how carbon could be replaced (by silicon, usually) as a biological building block. What elements could replace oxygen or CO2s (and let's even include water) roles in the metabolic process for, say, life on a planet with no oxygen? | [
"Great question! Among other purposes, a major role of oxygen is to serve as a final electron acceptor during aerobic respiration. In short, because it is a pretty electronegative element, organisms are able to generate energy by shuffling electrons to oxygen gas.",
"Many organisms on Earth have found ways of u... | [
"Poul Anderson proposed one using hydrogen instead of oxygen and using ammonia instead of water. Technically the animals would be reducing and the plants oxidizing, but it seemed to work out on paper.",
"I've seem fluorine, chlorine, and sulfur in one story or another, and all seem reasonable. I've also seen meth... | [
"Chemoautotrophy or chemosynthesis. But I think you're conflating two different ideas (which happens a lot with these two things so don't feel bad). There are organisms that use various non-oxygen molecules for the purpose of respiration (which are the kind of critters that OP is asking about) and there are organ... |
[
"How are Chromosomes separated?"
] | [
false
] | I know that chromosomes come in pairs, and that crossing over and changing of alleles during meiosis is how sperm / egg cells end up genetically different. What I don't quite understand is how chromosomes split into discrete objects and then into pairs. From what I gather, genetic information is stored as a single long strand of DNA, so are chromosomes all attached and could be viewed as "knots" within the single long DNA strand, or is my understanding flawed, and each one is a discrete bundle of DNA that somehow finds it's partner within the nucleus for cell division, meaning that DNA is in fact several smaller pieces all working together? | [
"From what I gather, genetic information is stored as a single long strand of DNA",
"This is incorrect. While bacteria have one long chromosome that is the sum of their DNA (aside from plastids), more complex creatures have several DNA molecules, and each chromosome is its own separate molecule; they aren't all a... | [
"Ahh, right. I was under the impression that genetic information was stored as a single, continuous DNA strand. This makes things a lot clearer and also makes chromosomal abnormalities like Downs make more sense to me. Thanks for clearing that up."
] | [
"While bacteria have one long chromosome that is the sum of their DNA (aside from plastids)",
"I think you're referring to ",
" which are shorts strands of deoxyribonucleotides (DNA) that code for a gene that gives the organism some advantage (such as heat resistance, cold resistance, antibiotic resistance, etc... |
[
"Can too much capsaicin actually hurt you?"
] | [
false
] | I mean, obviously it hurts like a bitch. But is the pain you're feeling directly related to any actual damage, perhaps at a much higher level of concentration of the chemical? Edit: Just to clarify. I'm wondering specifically if the feeling of pain and burning is because you are actually being hurt in some way. It is absolutely fascinating to hear all these stories, though. Godspeed, super-hot pepper eaters. I could never be so brave. | [
"Well, it's go an LD50 of 47.2 mg/kg, and if ingested it large quantities can cause abdominal pain and vomiting. Because its action upon neurones simulates a response to burning, the tissue at contact often becomes inflamed which can cause permanent damage, just like any inflammatory.",
"Dietary consumption is us... | [
"That's what pepper spray is.",
"It's possible to choke on your own mucus because of it."
] | [
"I've eaten wings at about 4 times that unit count, and it made me vomit a few hours later.",
"A drop of that vomit splashed into my eye. Worst night ever. :("
] |
[
"Why am I able to drink unfiltered well water in the rural US but not able to drink unfiltered well water in rural Ecuador?"
] | [
false
] | Growing up in rural America I have childhood memories of drinking unfiltered spring water from my grandparents' well. It didn't make me sick and it wasn't filtered at all. A couple of years ago I went on a trip to Ecuador and drank unfiltered spring water in a remote mountainous village and it made me sick. Why did the spring water in Ecuador make me sick when the spring water in the US didn't affect me at all? | [
"Here's some info from the ",
"US Geological Service",
"It's more than just human pollution. Based on the geology of the groundwater aquifers, even natural sources of water \"unaltered\" by humans can be dangerous to drink. There are natural organisms that could have infiltrated into groundwater systems that wo... | [
"Wastewater treatment facilities. In many places around the world untreated sewage is allowed to seep into groundwater, contaminating it with bacterial diseases, like cholera. In the US, groundwater is mostly protected, unless you live in places like Wyoming or Pennsylvania where their water is being polluted by ... | [
"In Canada, and presumably in the US, wells are required to be tested before they are deemed safe. There is an extensive chemical analysis done of the water to ensure contaminants are below acceptable levels. In addition a bacterial analysis is done. If there are any issues, the town will not certify the well. No c... |
[
"Why can't you refuel while the engine is running?"
] | [
false
] | I know this 'rule' in the context of cars, but I assume also true for airplanes and boats. Why is this the case? Its not like refuelling opens the combustion chamber... And if fumes are the ones in danger to ignite, couldn't that happen from the petrol in the tank anyway? Excuse my poor knowledge of internal combustion engines ! Edit: Thanks for all the answers. To simplify, I will make a clarification before going to sleep; for a car in a gas station, what would cause ignition? The electrical wiring? The buildup of static charge? The heat in the engine components? Or the engine's combusting? ... For a brand new car what would be the main danger, and how has this changed over the years i.e. by using different materials / engine design? | [
"Generally there is no issue with refueling on modern cars while it is running. The only issue is the EVAP system can test while you are refueling. The EVAP system monitors and controls the capture and burning of fuel vapors in the tank. Gasoline is always creating vapors and those vapors are stored and burned when... | [
"You can. In fact, it's a standard military technique. ",
"https://en.wikipedia.org/wiki/Aerial_refueling",
"However, it creates risk that is simply unnecessary in ordinary life and likely wastes gas in the case of a car or boat. Why would you want to leave an unattended vehicle running to stand next to the ... | [
"Yes, filling past the point of shut off. Basically filling past that point has the potential to put liquid fuel into the valving/hoses and canister for fuel vapors. The likely hood to cause damage doing one or a couple of times is very low but has happened. The more it is done the higher likely hood of damage."
] |
[
"What do emission spectra reveal about stars?"
] | [
false
] | I've heard they can reveal composition, and velocity amongst other things, but what can we fully know just from the emission spectra of stars? | [
"As you've already recognised, we can deduce the composition of a star from the spectra, assuming we know enough about the placement and surroundings to compensate for various shifts. From this we can classify the star, and with just a bit more information about their luminosity, we can more or less pin down what t... | [
"You hinted at this but you should also be able to determine the composition of an orbiting planet's atmosphere as well."
] | [
"I also thought I read a similar piece. In fact, it was most likely just what was PLANNED and the fact is we know it works from study of our solar system.",
"edit: it will work if/when we get the resolution"
] |
[
"Is it possible for two distinct intelligent species to evolve on the same planet?"
] | [
false
] | Using the development of humans as a species on planet earth as a benchmark for intelligence and technology, is it possible for two distinct species to evolve to such a state on the same planet? | [
"Yup. It happened here on Earth. Multiple species of hominids evolved, then our ancestors wiped out/interbred with their contemporaries. Also, dogs, birds, apes, and dolphins are pretty smart."
] | [
"Genocide?"
] | [
"Yeah, what foolproof mechanism is there to stop it? "
] |
[
"Is it safe to store food in open cans?"
] | [
false
] | My mom taught me to always transfer the contents of canned food to a different container once opened. She thought it wasn't healthy to leave it in the can. Was she right to do this? | [
"It depends on how you open the can. If your can opener is the sort that tears through the metal on the center of the lid (the older kind) then you run a very high risk of contaminating the inside of the can - transfer the food to a clean vessel.",
"If you have a can opener that cuts through the double-fold seal ... | [
"Doesn't leaving the food in the can make it taste metallic?"
] | [
"No, it has already been in the can for ages, and has not taken any taste. This is due to the coating of cans, made of plastic (often containing bisphenol A). "
] |
[
"How does the female human body use both XX chromosomes?"
] | [
false
] | Both X chromosomes carry the same genes (with obvious variances) yet humans with only one copy of the chromosome suffer from Turner Syndrome which comes with a catalogue of symptoms; webbed necks, short stature, no periods, no breasts, heart defects etc. How/why does having two copies of the genes on the two X chromosomes permeate females? | [
"One of the two copies of the X chromosome is mostly inactive, a phenomenon creatively called ",
"X-inactivation",
". This means that any human carrying two X chromosomes is, for the most part, only getting gene products from one of them. ",
"So your question is good, but the logic that led you to it is bad. ... | [
"No, it's random. That's how you get things like calico cats (see the wiki article I linked above), where each X chromosome affects a different fur color. So whichever patch of fur has inactivated whichever chromosome gets a different color."
] | [
"I've never heard of something like that but if you've got a reference I'd be happy to learn about it."
] |
[
"I can switch between breathing from my mouth, my nose, or both, even with both of my mouth and nose open. Anatomically and physiologically, how does this happen? Also, how does the body switch between the right and left nostrils?"
] | [
false
] | Edit: Thank you for those who made helpful, scientific replies! There are too many of you for me to thank individually, so, thanks to all of you! | [
"There's a flap of tissue near the end of the nasal passage that at least some people can voluntarily close. This helps, among other things, to prevent the water and food you swallow from ending up in your nasal passage. You can actually see it in a mirror with your mouth open: it's at the back and top of your thro... | [
"I've actually never asked, but I've generally assumed the people who close their nose with their fingers in the presence of a bad smell can't easily. There are a few structures where only some people can voluntarily operate them. For example I can regulate the pressure in my inner ear by voluntarily opening the eu... | [
"Not everyone can do it voluntarily?"
] |
[
"If pi goes on forever, does that mean its possible for 3141592..... to appear again i.e. pi within pi?"
] | [
false
] | Can all the digits in pi repeat themselves in their previous order infinitely if you eventually go through all the numbers in pi? I've been thinking of this because infinite is huge, so it only makes sense to me that if given enough numbers it will copy itself. | [
"If you're asking whether any finite subsequence of the digits of pi can occur more than once, then yes (and in fact they almost definitely do, infinitely many times).",
"If you're asking whether pi could appear 'within itself', so e.g. pi = 3.14.......(lots of other junk)[another copy of pi] then no, because tha... | [
"I'd never thought about whether another irrational could be nested inside an irrational number. Fascinating."
] | [
"No. Pi has been proven to be irrational. If it eventually repeats, then pi would be a rational number. "
] |
[
"Can you numerically analyze non-linear differential equations?"
] | [
false
] | The answer I have gotten from my professor is that if you want to numerically analyze a non-linear differential equation, you mostly can't. I can understand why some won't have answers in terms of elementary functions, or even at all, but surely there must be a method to evaluate those you can? | [
"I am a bit confused by your question, particular this part:",
"if you want to numerically analyze a non-linear differential equation, you mostly can't.",
"Actually, the non-linearity of the equation makes analysis so generally difficult, that numerical methods are often the only way to solve the equations. The... | [
"There are however weaknesses of numerical methods which are complemented by the strengths of analytic techniques. Where by analytic techniques I mean stuff like applying perturbation theory, or studying the long term behaviour or stability of solutions, not looking for a closed form expression. ",
"Numerical met... | [
"No, it's almost impossible. Only very few differential equations have closed form solutions. If you closed your eyes and wrote down a random differential equation you will write one down that does not have a closed form solution pretty much every time. I want to say with probability 1 (I'm assuming it is) but I do... |
[
"How does hand-eye coordination work?"
] | [
false
] | How is it that my brain can calculate the trajectory of a thing flying through the air and move my hand into the proper space to catch it ahead of time? | [
"From these videos I gather that the answer is largely unknown. This one comes foremost to me:",
"http://www.ted.com/talks/daniel_wolpert_the_real_reason_for_brains.html",
"And here's something on Grid Cells.",
"http://www.ted.com/talks/neil_burgess_how_your_brain_tells_you_where_you_are.html"
] | [
"I would also add that we have an additional \"sense\" in addition to sight, hearing, etc, that is often unmentioned. ",
" is our body's ability to sense where it is relative to itself. This is how we can touch our nose even with our eyes closed. The neurons involved in this system monitor the degree of stretc... | [
"The first few years of your life are spent learning how to control your body. It's a trial-and-error learning process. Eventually your brain learns how to effectively control your limbs. As for learning how to catch, that is just pattern recognition. After seeing enough ballistic trajectories, your brain learns ho... |
[
"What happens to water as its subjected to greater and greater compressive(pressure) force? Does its physical or chemical properties change?"
] | [
false
] | null | [
"If you know how to interpret a phase diagram, this might help you... ",
"http://startswithabang.com/wp-content/uploads/2008/08/water-phase-diagram.jpg",
"X axis is temperature while Y axis is pressure, so as you increase the pressure at a constant temperature you can change the phase, but if you're starting at... | [
"if you're starting at liquid, you will only continue to stay liquid when increasing pressure",
"Not according to ",
"the full diagram",
"."
] | [
"I stand corrected."
] |
[
"Why does the moon look bigger than usual on some nights?"
] | [
false
] | null | [
"This typically has to do with where in the sky the moon is. We typically experience this phenomenon when the moon is low in the sky near the horizon. Our brain compares the angular sizes of objects to determine distance and size. The idea is that your brain sees that the moon subtends the same angle as that pal... | [
"There's a kind of cool way to trick your brain into realizing the actual size too. When it's near the horizon and looks big, turn your head upside down. The image flip takes away the familiarity of the horizon and makes the moon appear normal size again. "
] | [
"Another thing you can do is get out your digital camera and point it at the moon. For some reason it looks normal in the camera viewer. This can hurt your brain a little because you can look back and forth at the moon and at the moon in your camera and it's hard to understand why they look so different, yet lin... |
[
"Could radium girls be saved with today's medicine?"
] | [
false
] | Hey, I've read about radium girls. I know that a lot of them survived, but some of them, with more radium burden had onj and radium-induced bone cancers which killed them. However, I wonder, is it possible that at least some of them could have survived(or lived longer, like, several years longer) with today's medicine? I am not really good at medicine's history, but I guess that maybe we can controll osteonecrosis of the jaw a little better(infections and stuff) and we have something like jaw transplants too. Also, I suspect that we have better tools to deal with cancer today. We have better radiation therapies, chemotherapy and stuff, and I've read that some osteosarcoma-s have a >50% prognosis. However, I guess that the problem would be that even if we can cure them from cancers, they'll get them again because we can't remove the radium? | [
"I'm a nuclear physicist working in medical imaging and not a physician, so I can tell you very little about the medical part of the question.",
"I've been googling a bit (not too much) about the radium girls and... I haven't found specific data. I can't seem to find ",
" data about what's the estimated dose th... | [
"Interesting links, thanks. But I cannot study them in depth.",
"From a quick view I've found In the first link that they state that the lowest dose associated with cancer was a total of 60 uCi (total over worklife). ",
"The second link reports an interesting estimate of radium intake over the years, as regulat... | [
"I've read some of those resources: ",
"TOXICOLOGICAL PROFILE FOR\nRADIUM",
" and ",
"Radium: a review of us studies",
"\nYou can find a lot of data and tables with Initial System Intake and sceletal dose at death in chapter 4 of the second link(especially after page 98)\nIn the 5th chapter there are some r... |
[
"Why did it take civilization so long to arrive at the bicycle?"
] | [
false
] | Gears were around since Aristotle, chain drives were first described by Philon of Byzantium in the 3rd Century BC, the forged welding of metals was around since the middle ages and wheels have been around since the cavemen. So why did it take mankind until the 19th Century to arrive at a functional bicycle? (Excluding theoretical sketches from earlier.) | [
"Bicycles are actually very complex and sophisticated machines, really only able to be produced until the late 19th century. It's noteworthy that many of the early auto manufacturers began as bicycle makers. Indeed, the Wright brothers were bike mechanics, as it was on the forefront of advanced technology at the ti... | [
"Inner tubes and vulcanized rubber. I think that could be it. I was thinking back to the wooden-spoked wheels of Marie Antionette's coach and the pharoah chariots and wondering why Ben Franklin wasn't visiting Jefferson on his wooden wheeled bicycle. But the comfort of an inner tube on a seated bicycle probably was... | [
"Inner tubes and vulcanized rubber. I think that could be it. I was thinking back to the wooden-spoked wheels of Marie Antionette's coach and the pharoah chariots and wondering why Ben Franklin wasn't visiting Jefferson on his wooden wheeled bicycle. But the comfort of an inner tube on a seated bicycle probably was... |
[
"As something necessary to confirm the CERN discovery is replication, does that mean we would need to have another LHC, or how could be results be reproduced by scientists around the world?"
] | [
false
] | without having to use the original equipment to get the results and therefore reducing the chance that it may be something intrinsecal to the LHC itself? | [
"Which CERN discovery? If you mean the faster-than-light neutrinos, then the LHC wasn't involved. They used protons from CERN's SPS booster (that feeds the LHC) to crash into a target and create a beam of neutrinos.",
"Fermilab actually has a nearly-identical setup. It's called ",
"MINOS",
". Fermilab produce... | [
"Sure, it should be capable of a similar measurement. In fact, it's probably interesting since they use a different beam geometry, which would be subject to different systematic errors. I'm not sure if they've got their timing good enough, or if they collected enough data to say anything yet. They're still recoveri... | [
"Could they aim the beam at other neutrino detectors around the earth, like the Super Kamiokande in Japan?"
] |
[
"Can you clone an insect?"
] | [
false
] | Recently I thought about bee's and there declining population, and then wondered why don't we just "make" more. Sure I realize that getting them to work as a hive, amongst other things would be hard to do, and it's not like your cloning a sheep or pet. But what I'm curious is can we clone an insect, or has this been tried before? | [
"I suppose so, given that some species clone themselves at the larval stage. Paedogenetic species such as ",
" gall midges come to mind; so the mechanisms can work.",
"However, even if it could be artificially induced in honey bees, you'd still be cloning bees with the same vulnerability to whatever is decimati... | [
"True that, that outcome would be no bueno, but I mean if someone were to do some crossbreeding before hand, and make a hardier breed of bee, that would be interesting. Anyway I thought it was an intriguing idea."
] | [
"With enough time and investment, anything is able to be cloned I'd suspect. The problem is that for insects cloning is probably the route that is an absolute last resort. No one that I know of has cloned insects, mainly because they do a damn good job on their own as any sticky summer's day will show.",
"It is m... |
[
"Do any other species show right or left hand preferences?"
] | [
false
] | Or 'limb' side preference? | [
"Radiolab did a bit about this recently.",
"According to the show, most animals have a roughly 50-50 split in handedness. Both parrots and humans have a split in favor of one or the other, humans being right-favored and parrots ",
"left-favored",
". They suggest that speech processing in the brain is involved... | [
"Some do.",
"Crayfish have been studied for 'handedness'. ",
"Here's a recent study on it",
".",
"It's a little shaky. But there's some evidence that there is some preference for a particular \"side\" of the crayfish."
] | [
"Cockroach wings overlap a little bit and it's almost always the case that the left wing is on top of the right wing. This seems to be true for most cockroach species and I don't know why. I don't know about other insects but I would be interested to find out."
] |
[
"Could a solar (photovoltaic) cell \"beat\" entropy?"
] | [
false
] | I presume the answer is no, but I'm having a hard time explaining myself out of the following example / thought experiment: Consider a closed system containing a gas and photovoltaic cell that are both at an equilibrium temperature T - low enough for the cell to work. Certainly, the radiation spectrum (based on T) of the gas would occasionally produce photons which cause a voltage difference / current in the cell, which can be used to perform work (right?). Even if the energetic enough photons would be extremely rare at the temperature T, they would occur sometimes, perform useful work, and then obviously reheat the system (conservation of energy not violated). My best guess is that at least as often as a photon is absorbed and turned into current, current is lost and turned into a photon by the photovoltaic cell, thus requiring a significantly "hotter" photon source. Other than that, perhaps some temperature property of photovoltaics I missed (remember I am considering a system where the temperature is low enough for the cell to work). Relatedly, reading the , the second point saying: "...the electrons are only allowed to move in a single direction," sounds vaguely like Maxwell's Demon - and probably the cause of my misunderstanding. I also think "nantenna"s may be relevant to this discussion but the wikipedia article on the topic seems lacking / poorly written: So, why can't a photovoltaic cell (very slowly) extract useful work in a system that's in thermal equilibrium? | [
"There has to be a temperature difference. Remember that if the cell is at equilibrium temperature of the environment it will also emit black-body radiation.",
"Shockley used a thermodynamics approach like this to find an upper limit to photovoltaic efficiency:",
"http://en.wikipedia.org/wiki/Shockley–Queisser_... | [
"Note that normally, a solar cell is receiving it's energy from the sun, which is an extremely hot source. On the other hand, the solar cell is discharging at ambient temperature. The net result of this is that the efficiency limit due to temperature difference alone is somewhere above 90%, well beyond the Shockley... | [
"Yeah, I was thinking about how the temperature difference would come into play, just couldn't find the info on it. Thanks"
] |
[
"Why do fires caused by electricity arc off in those crazy flame waves?"
] | [
false
] | Like in this gif, , whyzit doin that? | [
"Electrical arcs are a plasma - that is, a collection of ionized molecules/atoms and free electrons. Because plasmas essentially just comprise a collection of charged particles, they're excellent conductors of electricity.",
"In the gif you posted we can see that one of the electrical lines has arced to the tree,... | [
"Dude that's incredibly concise and interesting. Thank you very much for the response."
] | [
"Ok so I'm reading this again- where does the plasma..come from? Is it wrought by the energy in the powerlines, which in essence forges its own conductor out of the air?"
] |
[
"Do mammals all have the same musculature but different shapes?"
] | [
false
] | For example, does a cat have the same biceps brachii as humans, but they're toned differently so that they stand on all fours? If I learnt the muscles of a human, would they all be similar to other mammals? | [
"Not identical (humans don’t have tails or retractable claws! Cats don’t have collarbones! And our teeth are extremely different…) but all the major bones, muscles, organs, and nerves in humans are generally present in approximately the same locations in companion mammal species. Evolution is very conservative! It’... | [
"A fun add-on to this: If you compare the bones in a horse's front leg with those in a human arm, you'll see that all the major stuff corresponds pretty neatly but with wildly different geometry. For example, what we might call the horse's lower leg actually corresponds to the bones of one human finger. There are s... | [
"careful, the ungulate navicular is not equal to human navicular. in ungulates it's part of the digit, not the wrist"
] |
[
"Why does the hot water from my kitchen tap come out cloudy?"
] | [
false
] | [deleted] | [
"Little of column A, little of column B....mostly A.\nBut it's really 'air', more so than specifically oxygen."
] | [
"There is less oxygen in hot water than cold water..."
] | [
"It's air bubbles. "
] |
[
"Is there some body part or organ (or brain part) that you think hinders us?"
] | [
false
] | I was recently reading about the first frontal lobotomies, and how they were considered effective until people realized that the anxiety that disappeared when the frontal lobe was tampered with was a result of a loss of all foresight in the patients. intriguing. so obviously that didn't go as well as initially thought. this got me thinking, is there any part of the body, maybe some obscure gland that produces a chemical that affects are brain in x a way, that ya'll think hinder us In some way? more of an opinion related question, and I know you guys like facts here. but there's nothin wrong with using facts to back your opinions :) | [
"The appendix really enjoys blowing up while at the same time not showing an appreciable use."
] | [
"My favourite anomaly in the body is the recurrent laryngeal nerve, which supplies the motor and sensory aspects of the larynx (voicebox). It goes from the base of the brain, into the chest, loops round the aorta and back into the neck. This makes it more suspect able to damage, especially when performing thyroid s... | [
"The thought is that the appendix serves as a reservoir of \"healthy\" normal flora bacteria, in addition to serving as a lymphatic (i.e. immune system) part of the intestines.",
"Fair arguement that it is sometimes harmful, but in only roughly 10% of people. Same argument can be made for/against the palatine to... |
[
"Do the expenses fuel cylinders from rockets crumple upon falling back down to earth?"
] | [
false
] | You know those fuel cylinders that detach from the rocket as it goes up into space? Why do they fall back to earth as regular cylinders in every video I see? Aren’t they thin metal sheet cylinders? I would expect them to deform like a water bottle submerged in cold/hot water with respect to the temperature of the bottle (both cases lead to deformation right?). Can someone explain to me what’s going on? | [
"Well if you’re referring to spacex 1st stage boosters they are designed to return to earth in tact. As for other tanks, you don’t see them on their entire journey down, just the initial few seconds as they detach, by the time they hit the ground they’re not in tact."
] | [
"SpaceX Falcon 9 boosters are designed to land, first off they use a considerable amount of fuel performing a reentry burn to slow down before reentry, so they don't burn up or get shreeded by aerodynamic forces, after that, get get precisly controlled by nitrogen thrusters and grid fins so they stay in a position ... | [
"In space there is nothing that would make them deform. If they enter the atmosphere in an uncontrolled way they get destroyed. That's the fate of nearly every rocket booster.",
"SpaceX makes them enter with the engine section first and uses some fuel to slow them down and to protect them against the atmosphere, ... |
[
"If supernovas are massive enough to become black holes, why do the stars themselves not become black holes prior to going nova?"
] | [
false
] | The only thing that comes to mind is that the outward pressure of fusion somehow counters the gravitational pull from the density of the object, but if a star is dense enough to become a black hole after going supernova, I would think it was dense enough to be a black hole from the start. Can anyone explain this to me? | [
"Something along the lines of the force of nuclear fusion trying to pull the star a part is counter balanced by the force of gravity attempting to crush it to a point. Once the star runs out of fusible material the force of gravity is no longer balanced and the star collapses into a black hole."
] | [
"You are right- the force is called the hydrostatic equilibrium. The outward pressure of released energy keeps the core from collapsing.",
"Each time a star loses a certain kind of fusion-capable material in its core, it will collapse. However, once temperature and pressure reach a certain point it can fuse a new... | [
"When a star is fusing anything lighter than iron in the core, the energy released by the fusion is greater than the amount of energy required to fuse the nuclei and this energy release counteracts the pull of gravity.\nHowever, once the star starts burning iron, its the end of the road because the binding energy o... |
[
"Why aren't GFCI receptacles built into the breaker?"
] | [
false
] | I installed one of yesterday between a set of wall outlets in my kitchen and the source. This way I only needed to buy one $15 GFCI which protects the 8 $2 outlets I installed. Why are these not installed in the breaker box to protect all the outlets in your home? | [
"Some are. ",
"GFCI breakers are more expensive",
"."
] | [
"Most likely, the National Electrical Code just says \"GFCI protection\" under section 210.8(a)(b). But, states and municipalities have their own electrical codes on top of the NEC and although I went through a 5 year IBEW electrical apprenticeship program, I've been out of the trade for 12 years. One should always... | [
"Answer is not so much scientific as practical. When you have to reset one, it's easier to walk over and hit a button at a nearby outlet than it would be to trudge all the way to the breaker panel (often in the garage or basement) and figure out which of a dozen or two breakers needs to be reset!"
] |
[
"If energy cannot be created or destroyed, how much energy is in the universe?"
] | [
false
] | null | [
"Well, first off, the universe may well be (probably is?) infinite in extent, in which case there's the possibility of infinite energy.",
"But more interestingly, ",
"energy is not conserved",
" in general relativity. For example... as the universe expands and creates more space, more \"dark energy\", which ... | [
"Not OP, but just quickly how can something be infinite and expand at the same time?"
] | [
"Simple example, take the function:",
"x(t) = nt",
"where n is some number.",
"Certainly x(t) expands as time goes on: 2x(1) = x(2), for example. It's a function which grows as t grows.",
"We can take",
"lim",
" nt = inf for all t>0",
"But it doesn't change the fact that the function expands with t.",... |
[
"How much radiation is an astronaut exposed to on the moon?"
] | [
false
] | I know it’s meant to be a lot but I need something for comparison. How would it compare to a CT scan? | [
"It depends. Completely unshielded the dose is much higher than e.g. with a space suit, but completely unshielded the lack of air kills you so this is not a realistic scenario anyway. Spacecraft offer better protection than space suits, and habitats will most likely be shielded even better. It also depends on the s... | [
"What is the average of how many times more radiation they get compared to a human in earth ?"
] | [
"Typical natural doses on Earth are 2-3 mSv/year, but some places are notably higher (10-20 mSv/year, e.g. 12 in Denver). In the US people have an average of 3 mSv/year from medical procedures (CT and PET scans mainly) in addition, but that is very non-uniform - many people have 0, some have much more.",
"If the ... |
[
"How was the wave structure of a photon deduced?"
] | [
false
] | How did we first discover the wave structure of a photon? Is observing the motion of electrons or charged particles the only way to observe a photon? | [
"Maxwell realized that is electromagnetic field equations could be used to describe a wave. The speed of this wave depended on the electric and magnetic properties of the medium (or vacuum) that it propagated through. He realized that this speed was very close to the measured speed of light. This lead to the electr... | [
"You've got this a bit backwards, the wave nature of light was supported well before the existence of photons - just set up a diffraction grating and shine a light through it and you've got evidence for the wave structure of light.",
"The photon nature of light - the corpuscular nature - was shown by Einstein, in... | [
"First things first: When we talk about photons we are talking about ",
". ",
"Up until the beginning of the 20th century we thought we had a pretty good handle on light. The work of Maxwell, Faraday, and many others all seemed to show that light was a ",
". The quintessential example of this wave nature is t... |
[
"Sanitation question for you microbiologists here in askscience to help us over in r/homebrewing"
] | [
false
] | Over in we discuss, almost daily, sanitation of equipment we use to make beer/wine/mead/etc. there are a few popular products out there for use, with being one of the most popular. If you click on the link you can hover your mouse over the picture to get a good idea of what StarSan is composed of. Many of us home brewers use this solution in a spray bottle and spray down our equipment. Many people ONLY spray and do not submerge and soak the equipment. Sometimes that’s due to size constraints and sometimes it's just because a spray down is easier. My question is this: Once the StarSan spray makes contact with the surfaces in question, how long must it sit in order to sanitize the surface? We realize that sanitizing a surface is not the same as sterilizing however for most cases this is all we need. So, with your knowledge of microbes, starsan's ingredients, and pertinent application could you give me a "Best estimate" as to what a safe time limit is to assume that the StarSan does its job? | [
"I'm a homebrewer and I have been working in micro for ~6 years now. I know that this is a HOTLY contested issue. It's like RNA work. Your way is ",
" for yearts...right up until your first batch of bottle-grenades, then that old, tried and true practice BLOWS and you are NEVER going to use that crappy method aga... | [
"I know it isn't an answer, I'm just curious.. ",
"Curious why you dont use bleach and a heated dishwasher?",
"I ask because my dad brewed beer for a number of years and he always just added a bit of bleach to the washer (took out the top shelf so he could fit the 5 gallon in there). I honestly can't remember h... | [
"It's not volatile, but it is reactive. It doesn't stay hypochlorite for long in the presence of water, especially with any kind of heat. And the products of its degredation (Cl & O2) are volatile."
] |
[
"How does my brain know where my hands are in 3D space?"
] | [
false
] | [deleted] | [
"Humans have more than the 5 \"classic\" senses. One sense we have that people seem to overlook is ",
"proprioception",
". There are specialized stretch receptors in muscles and ligaments that allow your brain to figure out the positions of joints and the force being applied by muscles.",
"An interesting qu... | [
"Through a sense known as ",
"proprioception",
". Basically your brain keeps a constantly updated map of your posture derived from a combination of many different types of sensory information. ",
"Relevant article on recent research."
] | [
"If you are really interested, you can look into ",
"alien hand syndrome",
". In this case, the sufferer has no control over the arm or hand and it seems to have a mind of it's own at times. I am truly fascinated by what a stroke can do to people and the implications for research of the human brain. "
] |
[
"Will the use of a neutron reflector always cause criticality/supercriticality of a fissile material?"
] | [
false
] | null | [
"No. It will change the requirements for criticality, but it doesn't guarantee that you'll reach it."
] | [
"Do you mean to say that it will be easier to reach criticality? For instance, if a system with a neutron reflector (at low temperature) was compared with a system without a neutron reflector (at higher temperature), the requirements for criticality could otherwise be the same?"
] | [
"A reflector will generally make it easier to reach criticality."
] |
[
"A seemingly simple probability question has got me confusing myself."
] | [
false
] | You're playing a simple game. You have two 6-sided dice, one black, one white. You roll them together. When the black die reads "1", you write down the number shown on the white die. You win the game when you've written down each of the six numbers at least once. So here's the question(s): What is the probability of winning the game in only six rolls? in 7? What are the odds of failing to win in 1,000,000 rolls? I think I can answer the first, but I'm having trouble reasoning out the last. Can someone explain how to think it through? | [
"Probability of black die landing on 1 each time: 1/6",
" . Probability of white dice having a different number each time: 6!/6",
" . Total probability: 6!/6",
" = 3x10"
] | [
"Not sure if you want a full solution or just a hint. In either case I prefer hints over solutions, so here's my pointer as how one might think about this...",
"You can either look at all the \"paths to failure\" and add up their probability mass, or you can use partition of unity, i.e. the chance to fail in 1mil... | [
"Well, that's encouraging. Here I was thinking I was stupid for not being able to work it out in my head.",
"Strange as it sounds, the question arose from a video game. An enemy has a 1/3 chance to drop 1 of 3 items, all of which you need. I was thinking: \"How many times should I 'expect' to have to do this? At ... |
[
"What did the surface of the Earth look like before Pangea?"
] | [
false
] | I often hear geologists discuss how the continents used to be merged into one super continent, and how plate tectonics has caused them to slowly drift apart. This is as far back as I've heard discussed however. Was Pangea the shape the earth was in when it first cooled and water condensed and the oceans formed, or were there other surface structures prior to Pangea? Or is this as far back as we are able to cohesively piece together from the fossil record? | [
"For some reason, Pangea is embedded in the public consciousness, but Pangea is just the most recent supercontinent and occurred relatively late in Earth's history (occurring ~300 million years ago, compared to the ~4600 million year history of the earth). It's a relatively well established idea that the earth's pl... | [
"There is ",
"this animation",
", which is one possible scenario for future plate motion which runs to ~250 million years, until the formation of a new predicted supercontinent, called \"Pangea Ultima\" here. Note that this is highly speculative, but is reasonable in the sense of rates and styles of plate motio... | [
"Oh, please tell me there is a decent model that shows the current plates moving into the next supercontinent configuration.",
"Also, if the separate continents periodically squeeze together to make supercontinents, how high do the highest mountains get?",
"I'll take my answer off the air."
] |
[
"How do we know the specifics of a laboratory molecule?"
] | [
false
] | Hello Reddit! I'm a 3rd yr ChemE student and something that has always bothered me is how do we know specifically if what we are working with in lab is Cis or trans, Z or E, ect ect. I mean on paper when looking at the structure its easy to see, but how do we know in lab? Also I know they have different properties, MP, BP, ect. that you could identify them with, but before we knew what the Bp of a specific cis molecule we had to identify it as cis then find the BP wouldn't we? Sorry if this was really confusing I put it into words as best I could, thanks! | [
"There are a number of ways that you can obtain the structure of a molecule. These techniques include:\n* X-ray diffraction\n* Proton NMR\n* Carbon-13 NMR\n* Mass spectrometry\n* Infrared spectroscopy",
"X-ray diffraction (through X-ray crystallography) is one of the more important techniques here. A crystal of... | [
"In the future you can check out past posts as well:",
"http://www.reddit.com/r/askscience/comments/hpvek/how_did_scientists_determine_the_inner_structure/",
"http://www.reddit.com/r/askscience/comments/1ot5p7/how_do_chemists_figure_out_the_structure_of/",
"In addition, NMR in particular can give spatial inf... | [
"Makes sense, thanks!"
] |
[
"Mathematics and the \"real\" world"
] | [
false
] | The title is poorly phrased because I'm not sure exactly what I'm asking, but hopefully as I type it will become clear. There will probably be multiple questions buried in here so I'll try to sum up at the end. Whenever I read about topics such as relativity, string theory, higher dimensions, etc, in articles/publications meant for the lay public (or the somewhat educated lay public, i.e. non-specialists), I generally come out pretty confused. It seems that the writer goes through some serious verbal contortions to explain ridiculously complicated topics. for the sake of an example, (scribd link, the actual article is behind a paywall) that talks about the possibility of the universe being a "hologram". I read something like that, and all the words make sense, but I still come out thinking that's a load of gibberish. What I want to know is: is this a consequence of trying to explain a mathematical concept without using the math? Is this concept basically a set of equations describing a model of reality, and if you're versed in the math you look at the page and think "oh, of course, this and that equals that so therefore this other thing does this"? but then when you try to explain in English what that means, you end up having to say all sorts of things that make it sound like you're on drugs? (the universe, maaaaaaaaaan) Do physicists/cosmologists spend a lot of time translating the math into English in the course of their work -- in professional discussions, I mean? I have a biology background and my mathematical education probably ended with a little bit of calculus and a fair amount of statistics, and I've been thinking about teaching myself higher math, for kicks; to better understand the mathematical models of reality we employ. anyway: Apologies for the rambling nature of this post. It's difficult to ask a question when you don't know what you're asking. :) EDIT - Thanks to all for indulging me! | [
"is this a consequence of trying to explain a mathematical concept without using the math?",
"Yes.",
"Physics is the science of relationships. In order to make a science out of the identification and description of fundamental relationships, you have to quantify the things that are related to each other, and ex... | [
"Someone get this guy on a podcast, or a PBS program with Neil Tyson."
] | [
"I wish I could RSS him. LOL.",
"You can."
] |
[
"Why have there been no innovations past normal toothpaste in recent memory?"
] | [
false
] | [deleted] | [
"Hey! i know this is old, but there was a more recent thread that took off.",
"http://www.reddit.com/r/askscience/comments/o951g/are_we_close_to_being_able_to_naturally_regrow_or/c3fek84"
] | [
"Thanks!"
] | [
"\"Innovations\" in toothpaste \"technology\" are frivolous bells and whistles. Baking soda is all it takes (has ever taken,) and many dentists have even done away with traditional tooth-cleaning/polishing methods and have gone to blasting teeth with baking soda to get them clean.",
"Toothpaste creates suds and ... |
[
"Plug a hole in a space ship with your hand?"
] | [
false
] | [deleted] | [
"ATM is 15 pounds per square inch. In a 3mm diameter hole, that's roughly .01 square inches, or .015 pounds.",
"I think your hand would be fine."
] | [
"I would guess your hand would be fine (@shadydentist), but I don't think the frostbite would be as severe as you suggest. To lose heat there has to be contact between matter to transfer the energy - with a vacuum outside I doubt you would get cold quickly, if at all because there is so little matter to xfer energ... | [
"What I came to post."
] |
[
"Resonant Frequency?"
] | [
false
] | [deleted] | [
"The short answer is: constructive interference.",
"The long answer is:\nYou're sitting on a swing (you are a bond), going back and forth (resonating).\nThe amount of time it takes for one full cycle depends on the length of the chain/rope/whatever (bond characteristics, notably length).",
"As you're swinging, ... | [
"Yep, that's what constructive interference describes."
] | [
"That answers part of my question, thank you. ",
"I believe the bridge (as it was explained) collapsed on a windy day due to something like cumulative overcorrection; the wind twisted it, then pushed on the exposed area until the bridge overcorrected, then pushed on that area etc.",
"EDIT: accidentally a word."... |
[
"How and why acceleration of charged particles produce photons?"
] | [
false
] | Hi Sciencefolks, Given that acceleration of charged particles produce photons, and vice versa (how antenna and radios work), there are two parts of my question. How does it happen? Lets say an electron travelling at 1000 eV (initially went through a potential of 1000 V) stops in 10 seconds. How many photons will be emitted due to this deceleration, and of what wavelength? Assuming the electron is stopped by a wall of 1000 Volts. Why do charged particles acceleration produce photons? (This may be a teleological question, and may not have a physical answer, let me know if this is true.) Thanks in advance. | [
"You don't need photons to explain why acceleration of charged particles produces light. When you calculate the electric and magnetic fields of a particle undergoing acceleration, you get radiative terms, which means that there must be light propagating away from the particle. And photons are the quantization of l... | [
"On a very simple level I always justified it like this: An electron at rest has an electric field. If it accelerates, the electric field must change as a function of time. But a time changing electric field produces a spatial change in the magnetic field which produces a change in the electric field which produces... | [
"On a very simple level I always justified it like this: An electron at rest has an electric field. If it accelerates, the electric field must change as a function of time. But a time changing electric field produces a spatial change in the magnetic field which produces a change in the electric field which produces... |
[
"What causes the force that results from the Pauli exclusion principle?"
] | [
false
] | I was reading about white dwarf stars in Stephen Hawking's "Brief History of Time", and he states that the only thing preventing a white dwarf from collapsing into a black hole is the repulsive force provided by the Pauli exclusion principle, but for stars with masses past the Chandrasekhar limit, this force is eventually overcome by gravity. My question is where does this force come from (does it have a force carrier) and can it be explained in terms of the four elementary forces? Also as an aside, how can the exclusion principle be "overcome" by gravity? Does the law simply break down with forces that large? | [
"(does it have a force carrier) and can it be explained in terms of the four elementary forces?",
"No. Pauli exclusion doesn't fall under any of the fundamental forces. It would still exist for identical fermions that don't self-interact at all. It's just a lack of available states where any two identical fermion... | [
"I would not classify it in that way; it's not like any of the fundamental forces. It has no \"force carrier\" particles, it's not something that you include in the action of your theory. Instead, it's a result of the anticommutation properties imposed on the fermion fields.",
"Something that arguably could be co... | [
"So I guess I'm confused a bit, and you seem knowledgeable.",
"Pauli exclusion \"supports\" and object that is being compressed, preventing it from compressing further. So even though matter is being accelerated inwards, that acceleration is being counteracted by ",
". And according to the fundamental laws, s... |
[
"Why is it that water usually puts out fires while the elements in water usually help combustion?"
] | [
false
] | null | [
"Because the elements do not confer the chemical and physical properties into the chemical compounds that they make up. In other words, it's because they are different chemicals.",
"It's the same reason that table salt, sodium chloride, is neither an extremely reactive metal (sodium) nor a poisonous gas (chlorine... | [
"Here's a way to look at it to help you understand; yes, hydrogen is flammable and oxygen is an oxidizer. However, they do not help combustion because they are already reacted. Water is the product of hydrogen being oxidized by oxygen. They can certainly be separated from one another by a more powerful reaction, bu... | [
"The separation of oxygen and hydrogen in water is actually quite easy to do and is a pretty common. A simple 5 volt batter hooked up with a cathode and anode wire can get you good H2 and O2 separation. I'm sure you know this is hydrolysis and is extremely common. "
] |
[
"Why isn't the big bang the center of the universe?"
] | [
false
] | I just recently watched a video which stated the universe has no center. Assuming the big bang created the universe, I thought that would be the center, since this is where it originated from. I posted my question in the comments and was told "no you fool" so I'm hoping that someone here can explain it to me. | [
"Because there's no point called \"the big bang\". The big bang was everywhere."
] | [
"There is no center of the universe because the expansion is the same everywhere. It is not expanding from one point outward, the whole universe is expanding equally at each point."
] | [
"Don't think of stuff exploding into a big empty space: think of space itself exploding, like unfolding a popup tent. An ant crawling on the tent might crawl around looking for \"the place where it was all wadded up originally\", but there isn't any special place like that."
] |
[
"How much petroleum, natural-gas, and coal has been lost due to tectonic subduction."
] | [
false
] | This is something that I have always wondered. Given that tectonic plates move around and are subducted back into the mantle, how much of the fossil fuels created throughout the billions of years has been lost back to the molten core? Furthermore, how many kJ of stored energy is that? Would it potentially be enough energy to have some effect on the internal temperature of the earth? There are A LOT of fossil fuels on the planet currently(even though we can't get to most of it),and assuming that the planet has been making fossil fuels for as long as there has been life, the amount of stored solar energy must be enormous. | [
"Fossil fuel deposits couldn't really form before the carboniferous (~300 million years ago), when organic material became abundant. Also, it is highly speculative that subducted material ever makes it down to the core. And it is likely that light weight organic sediments would be scraped off the subducting plate i... | [
"To add to AFCfans answer: If it was pure oceanic crust that was being subducted, then there wouldn't be any fossil fuels formed or reserved in those pillow basalts. "
] | [
"Exactly what I was going to add. Most fossil fuels have continental host rocks, which will not be subducted. Probably there have been far more substantial losses due to leaking reservoirs, which allow hydrocarbons to escape to the surface.",
"Edit: spelling."
] |
[
"For millions of years we didn't brush our teeth, floss, or use mouthwash. Why is it so important then?"
] | [
false
] | null | [
"Because our modern diet contains acidic and sugary foods that erode enamel and feed bacteria that causes tooth decay. We went from a diet of roots and game meat to bathing our teeth in phosphoric acid and sugar and chomping on a variety of meats dressed in sugary spices. Let that sit in your mouth for a while and ... | [
"I can, I'm a dental student. Sucrose (refined sugar) is needed for plaque. Also, refined sugars contribute to caries (the disease that causes cavities). Without brushing your teeth you likely wouldn't last past the age of 30 with any real dentition."
] | [
"Sugar is a large part of that. There are definitely societies that have long lived people who do not brush their teeth and still have them into old age.",
"Sugar is added to virtually anything processed these days and it is extremely easy to get a snack that has a high amount of sugar or complex carbs which our ... |
[
"How do we shield against Gamma Rays?"
] | [
false
] | According to this website: "γ GAMMA: To reduce typical gamma rays by a factor of a billion, thicknesses of stop-gammashield need to be about 13.8 feet of water, about 6.6 feet of concrete, or about 1.3 feet of lead. Thick, dense shielding is necessary to protect against gamma rays. The higher the energy of the gamma ray, the thicker the shield must be. X-rays pose a similar challenge. This is why x-ray technicians often give patients receiving medical or dental X-rays a lead apron to cover other parts of their body." Source: You would need 1.3 feet of lead to shield against Gamma rays. My question is, are there more practical ways of shielding against Gamma rays? I've read that deep space travel is largely impractical as of now, because we have no means of shielding the prolonged exposure to gamma rays. Besides lead, what are more practical methods of protection from gamma rays? | [
"So is depleted uranium and lead the only options?",
"Anything with high Z works. Lead is probably the most common.",
"Could we make a space ship with depleted uranium coating?",
"In principle, yes. But the problem is that gamma shielding is inherently very heavy, and bringing heavy things into space is costl... | [
"I've read that deep space travel is largely impractical as of now, because we have no means of shielding the prolonged exposure to gamma rays.",
"Actually, there aren't a lot of gamma rays in space. The real problem is ",
", i.e. charged particles coming with a lot of kinetic energy (usually >300 MeV). Also, i... | [
"The best way to shield against gamma rays is to use high-Z material (Z is the atomic number). So things like lead and depleted uranium. There isn't really anything better than that, all of the main processes by which gamma rays interact with matter have probabilities which increase pretty strongly with Z."
] |
[
"Does antimatter produce electromagnetic radiation?"
] | [
false
] | If so, how does it differ from electromagnetic radiation produced by traditional matter? | [
"Yes, both matter and antimatter can produce EM radiation. As for the nature of the EM radiation, it doesn't come in particle/antiparticle pairs. For example, while an electron has an antiparticle- the positron, the photon (the basic unit of EM radiation) is its own antiparticle. In fact, this principle is the key ... | [
"Yes, in the same way that regular matter does."
] | [
"Mass enters all fundamental physics (as far as I know) quadratically so I don't think you can really distinguish positive and negative mass in that sense"
] |
[
"Why can’t humans survive without a pancreas?"
] | [
false
] | I know Pancreatic cancer is one of the most deadly types, as I’ve been taught that you can’t live without one due to the role it plays in the body by regulating blood glucose levels and producing enzymes for digestion. However with modern medicine, can we not control these things by giving nutrients via IV, or is there another function of the pancreas we cannot recreate? | [
"You can absolutely survive after complete removal of the pancreas, I have done this surgery a couple of times in fellowship, it is difficult but definitely possible. ",
"However you will face two big issues.",
"1) digestion: you will need a completely set of digestive enzyme replacement, which is possible but ... | [
"“Eat when you can and sleep when you can and don’t touch the pancreas “",
"Well somebody got too sometimes"
] | [
"The pancreas does a lot of things. It not only produces insulin, but also glucagon, somatostatin, as well as the pancreatic polypeptide, which all regulate several functions in the body, and digestive enzymes, plus it neutralises the stomach acid.",
"Recreating or replacing ",
" these functions with medication... |
[
"Are any Gram positive bacteria tolerant of EMB agar?"
] | [
false
] | I am characterizing bacterial isolates in an undergraduate microbiology lab. One of my group's isolates was able to grow on an EMB plate, however a gram stain and KOH test indicated that it was Gram positive. Everything I have found on the internet says that EMB is selective of Gran negatives, and no exceptions are mentioned. Is it more likely that we have the Gram status wrong, or that the isolate can in fact tolerate EMB agar? | [
"Thanks very much! I didn't record the results for that test so I don't remember if it looked like growth on top of a very heavy inoculum, but that might have been the case. I'll redo the test next week. "
] | [
"Hey, so I redid the EMB test and there was indeed growth, although it appeared very inhibited. Our sequence data came back and confirmed Gram positive status, so I guess we just have a special a special snowflake! My professor didn't seem too think it was much of a big deal. "
] | [
"almost certainly not able to survive EMB. To test this, ask for a new plate and restreak it, incubate it a day at 37C (or whatever it was incubated at). If it grows, try the Gram stain again.",
"As for why it could have grown, if it is indeed G",
" it may have been that the local concentration of eosin was j... |
[
"Does the imaginary part of the voltage in an RLC circuit really exist, or is it just an artifact of the math we use to derive it that can be discarded? Is there any way to measure it?"
] | [
false
] | So in my physics class that I took last semester we learned about RLC circuits and my teacher sort of handwaved away the imaginary part of the voltage, saying "we only care about the real part." Is this totally true or is there just a deeper rabbit hole he didn't want to get into for the purposes of our class? If we have a capacitor, resistor, and inductor in series and in a closed loop with no external voltage source (for the purposes of this explanation, anyways.) We can use kirchoff's law to derive the fact that the voltage drop over any closed loop is zero, so we get: -L(dI/dt)-IR-(R/C)=0 =-L(d Q/dt )-R(dQ/dt)-(Q/C)=0 =(d Q/dt )+(R/L)(dQ/dt)+(1/LC)Q=0 So now we have a differential equation, whose solution we can guess is something like : Q=Ae Therefore: -ω A +iω(R/L)A -(1/LC)A =0 =-ω +iω(R/L)-(1/LC)=0 Where (1/LC) is some resonant frequency ω squared, so we can solve the quadratic: -ω +iω(R/L)-ω =0 to find ω, which will be: ω=i(R/L)±sqrt(ω -(R /4L )) [edit: i skipped some parts here, i'm just going off what i have in my notebook] so finally Q=Ae which is e to a complex power, which can be re-written using euler's formula, which gives a real and an imaginary part: Q=Ae cos(ωt)+Ae isin(ωt) so now for Q we have a real and imaginary part. So what does the imaginary part mean in reality? If we tried to see it on an oscilliscope, per se, could we? Could we have some sort of device that would measure charge or voltage in the complex plane? Or does none of this matter because the imaginary part is just an artifact of the mathematics that doesn't have any real meaning? thanks for your time, anyone who reads and is able to respond to this. | [
"The imaginary part helps to determine the phase of the oscillatory part. It has a real meaning in the sense that different initial configurations of the capacitor and current will result in different values for the real and imaginary parts."
] | [
"The imaginary part describes how the circuit responds to oscillating waveforms. For DC signals there is no non-zero frequency component and the L/C components have no effect other than being a short/open circuit respectively. ",
"In physical terms, it describes the steady-state equilibrium resulting from constan... | [
"It's real, it's just out of phase. When we push that into a circle to do math, it looks a little like it's jmaginary, but that's a misnomer. ",
"It turns out that the jmaginary parts of complex math work great for analysis of phasing components (LC parts) so we stole them while the Maths people were trying to p... |
[
"Is there any evidence that prolonged computer use is harmful?"
] | [
false
] | I am just wondering what the negative sides of staring at a computer all day are, and if that's simply because you are starting at a monitor half a metre from your face. At what point does it become a long-term problem? dangerous? etc. | [
"not the computer use - more the not doing anything for extended periods of time"
] | [
"Sitting for extended periods is dangerous."
] | [
"It can hurt your eyes if you don't blink or take breaks from the monitor. It can hurt your back if you have bad posture. It can give you carpal tunnel syndrome. In short, yes."
] |
[
"Why is our solar system not considered an oxygen atom?"
] | [
false
] | null | [
"An atom is made of electrons organized in probability clouds around a nucleus of protons and neutrons. Electrons don't orbits the nucleus, they behave in weird and complexe quantum mechanical ways.",
"The fact that there are 8 planets doesn't make the solar system an oxygen atom anymore than having tens fingers ... | [
"Is there any known substance that mimics the quantum mechanics of our solar system then? "
] | [
"Our solar system doesn't behave in a quantum mechanical way. You can pretty much model it with classical physics. You might need to use general relativity if you want to get down to the details.",
"In general quantum mechanics is used to describe how very small objects behave."
] |
[
"If you shot a gun in space, what would happen to the bullets?"
] | [
false
] | null | [
"They would travel with constant velocity until they hit something that stops or slows them."
] | [
"The velocity wont be constant anymore once it starts to seriously interact gravitationally with other objects."
] | [
"\"Objects in motion tend to remain in motion unless acted upon by an outside force.\""
] |
[
"What would happen if we had a supersonic submarine?"
] | [
false
] | Akin to an airplane breaking the sound barrier, is it possible to break the sound barrier underwater? If not, why? Theoretically what would happen? | [
"you'd get a shock wave. you can see this on a small scale in the pistol shrimp. it snaps its claws so quickly that it creates cavitation bubbles that produce shock waves when they collapse. ",
"practically, though, i can't imagine a submarine could ever really exceed the speed of sound in water. current submarin... | [
"An object moving sufficiently fast under water starts to form rapidly expanding and collapsing bubbles of gas in spots where the movement of the object causes rapid changes in pressure. This is known as cavitation. When an object moves very fast through water the wavefront of pressure in front of the object is su... | [
"Cool, I'm familiar with cavitation and how it happens. I just didn't know that this could cause it to happen."
] |
[
"When preserving organisms for dissection, how do companies make sure red latex is ONLY present in arteries and blue latex ONLY in veins?"
] | [
false
] | A&P student here, I've dissected quite a few cats in my time and most have had red/blue latex injected to show off the arteries and veins. How do the companies (i.e. Fischer Scientific) make sure that the red latex is only expressed in the arteries and blue latex only in the veins? | [
"They inject red latex in the aorta in the neck simultaneously with blue latex in the superior vena cava. The latex flows through the artery/vein until it reaches a capillary bed and meets blue/red latex, there is sometimes a little mixing. "
] | [
"There is a valve that prevents blood flow from the aorta (the first and major artery) back to the heart called the aortic valve. If red dye were injected in the aorta, the valve would close and the red would only go into the arteries. Since the blood normally flows to the the heart in the veins, the injection of ... | [
"Aside from the other answers, in my experience that stuff seems to have trouble travelling through small diameter veins and arteries. And remember veins and arteries only contact in the heart (where they are seperated by valves) and the capillaries (often narrow enough that only one red blood cell can pass at a t... |
[
"What are factors which affect our height?"
] | [
false
] | [deleted] | [
"There are three parts to this equation. Genetics, the environment and the response of your genotype to the environment. There are many genes that contribute to height. Environment could be anything from food to exercise to stress (and more). And finally the interaction between these two is the complicated response... | [
"Ah thank you. I can now see how my upbringing could have led to my current height. "
] | [
"genetics really is the major player in height.",
"The only thing that can make you short is malnutrition and I doubt you had to deal with any issues like that. My mother isn't very tall but her brother (my uncle) is over 6 feet.",
"Genetics just sometimes works like that."
] |
[
"[Engineering] Why don't all air planes have the vertical winglets on the wing tips"
] | [
false
] | I was watching an episode of 'Engineering Connections' about the Airbus A380 and in it, they explained that the vertical winglets at the end of the wings made the wings provide extra lift, without being 'wider' if that is the correct term for it So, my question is, why aren't these winglets on all planes? I of course mean planes developed AFTER the effect of these winglets was discovered. But also, in a lesser sense, it seems like a very easy adjustment to an already in-use plane | [
"It's not such an easy adjustment to retrofit winglets to an aircraft due to aerodynamic, structural and bureaucratic principles:",
"More modern aircraft without winglets would typically have the airfoil section near the tip modified to reduce life near the tip in order to reduce tip vortex effects. Adding a wing... | [
"Thank you for the detailed explanation, that was very helpful"
] | [
"Most modern commercial aircraft are sold with winglets. Many many many older aircraft could be retrofitted with winglets, but airlines either can't afford to retro-fit winglets or are unable to due to manufacturers not designing any."
] |
[
"Dark Matter question: Are WIMPs a) particles in the standard model or b) totally new yet unknown particles and the standard model needs an expantion?"
] | [
false
] | null | [
"WIMPs would be an extension of the Standard Model."
] | [
"(a) No. Dark matter particles would have to be part of some extension of the Standard Model",
"(b) They would be new, but they wouldn't be totally unknown, since we know some of the properties they must have. For one they must be electrically neutral (i.e. \"dark\")."
] | [
"c) both",
"Some of the non-luminous non-baryonic (atomic) dark matter is stuff we already know about, such as neutrinos. But neutrinos are generally \"hot\" dark matter, because they more or less always travel at very near c. Various lines of evidence indicates that most of the mass of the Universe is in the for... |
[
"I am curious about mass human collective energy and how it affects Life around us. How does human energy alter other energies?"
] | [
false
] | null | [
"There is no such thing as the \"energies\" that you are asking about. It's pseudoscientific nonsense."
] | [
"Can you provide more specific information about what you mean by human energy and global energy, and perhaps a link/source to the map you mentioned."
] | [
"per: realitysandwich.com",
"The\n most well-known field is the auric field. Many believe that our auric field is\n the same as our electromagnetic field, a continually emerging and fluctuating\n field of energy produced by the electrical currents in our bodies. Every cell\n in our body pulses with electricity. E... |
[
"Is it theoretically possible to detect brain activity from a distance and extract meaningful information from it, or modify that detected brain activity from the same distance?"
] | [
false
] | A common conspiracy theory you hear, particularly in the "targeted individual" community, is that military/intelligence agencies have the technology to secretly detect brain activity from a distance and extract meaningful information from it and even modify said brain activity without any conspicuous or invasive device. Basically remote mind reading and mind control. They often cite patents such as these as proof this technology exists or has been worked on: I was arguing with someone who believes this and it got me wondering about the technical feasibility of this concept. I don't know enough about neuroimaging and EEG to answer the question. | [
"I leave the science to others... But there is a reason your friends refer to parents, not scientific articles.",
"Patent examiners rarely check if one has a working machine when one files a patent. A filed patent is no proof for science or engineering. ",
"Perpetual Motion Machine ",
"https://patents.google... | [
"so I Will take the science if you dont mind 😊. \nmagnetic impulse or topometry are the 2 commons techniques to \"see\" the brain activity. actually, this is more like seeing what area of the brain is active at a specific moment.\nyou can cross thoses techniques with experiments like displaying simple picture or s... | [
"Absolutely incredibly 'no' given current technology.",
"Almost definitely 'no' even with crazy future technology, just because the signals you're dealing with are so small compared to everything else that they will be annihilated by interference over any real distance."
] |
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