title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"[Engineering] How do aerodynamics effect cars other than air resistance?"
] | [
false
] | null | [
"Aerodynamics also give cars lift or downforce. Racing cars typically want a large amount of downforce such that they can go around corners faster without slipping sideways due to the increased friction force from the downforce. You obviously want as little lift as possible in a car otherwise you risk turning the c... | [
"When you go testing in a wind tunnel you look for various things besides the more well talked about coefficient of lift or drag.\nPersonally I have done a lot of testing in wind tunnels involving: \nTesting for air intake tracts to test for ram charging - to make sure that the combined intake charge of the vehicle... | [
"Friction plays a role too. The coefficient of friction doesn't change, but the frictional force is equal to the coefficient of friction multiplied by the force normal to the frictional interaction plane. Increased downward force results in greater friction force and thus less sliding. Increased contact surface are... |
[
"Why can't we use medications built like rhogam to combat autoimmune diseases like Diabetes/Lupus?"
] | [
false
] | [deleted] | [
"When rhogam is used, the antigens that the mother is being exposed to are only going to be in the mother's blood very temporarily. The rhogam is used to block the antigen until it is cleared from the body, so the mother's immune system never sees the antigen and develops a response to it. In the other autoimmune d... | [
"In the case of Juvenile diabetes, they have to give themselves injections for the rest of their lives anyways. I also thought that rhogam was given IM and not IV? ",
"Also, I do understand that typically the immune therapies are towards the immune cell or product, like the anti-TNF monoclonals, I was wondering w... | [
"The monoclonal antibodies have there share of side effects. They're pretty safe, but they're aren't really a comparison to the insulin diabetics inject. ",
"Maybe this is a route researchers will try to exploit, but I think there's a lot of hurdles in the way. First is the question of whether it would work. With... |
[
"Why are the lanthanides and actinides removed from the rest of the periodic table?"
] | [
false
] | Does it allow the table to have more descriptive power based on periods/rows? | [
"We don't have to remove them; they could be written on the same line as the rest of the elements in their row. That would make the table 14 boxes wider, which would be hard to fit on a normal sheet of paper or a poster without being hard to read. Instead, the are written as their own block beneath the table. Th... | [
"Exactly the way it was explained to me by my Chem111 professor in college. It's a space issue, similar to the way a lot of maps of the USA put Alaska and Hawaii in boxes near the bottom of the page."
] | [
"We don't have to remove them; they could be written on the same line as the rest of the elements in their row. That would make the table 14 boxes wider, which would be hard to fit on a normal sheet of paper or a poster without being hard to read. ",
"Here's an example of that: ",
"http://www.sciencegeek.net/ta... |
[
"Do our brain cells get replaced?"
] | [
false
] | Today I learned that on average, the atoms in your entire body are all replaced in five years. This was followed by a statement that we can't define ourselves as our physical body, but more as our memories. So do the atoms in our brain get replaced as well? How about our spinal cord? Nerves? If not, why? If so, how do ... | [
"I can't speak on a chemical or physical level -- i.e., whether or not the atoms in you brain are the same atoms they were a year ago, or something like that. ",
"But as far as answering the question \"Do new brain cells ever get made?\" the answer is yes. ",
"There are two regions of the brain that make new ne... | [
"Thanks for your help!"
] | [
"I would ask about this in a philosophy subreddit, possibly ",
"/r/philosophyofscience",
", as this is kind of a textbook philosophical question. An extension is the popular \"brain transplant\" question: if your brain was transplanted into somebody else, would you become that person? This tends to devolve into... |
[
"Why did the ISS crew wear breathing masks when entering the SpaceX module?"
] | [
false
] | One of the astronauts wore a simple face mask, while the other one wore a proper respirator. | [
"A precautionary measure in case there was any dust, dirt, or other detritus floating in the air inside Dragon. No matter how clean you try to keep the interior of a spacecraft, the activity associated with loading it with a bunch of assorted cargo inevitably leads to some foreign matter coming along for a ride. ... | [
"Smells like new car."
] | [
"For those downvoting this comment, the carbon dioxide concentration aboard Mir became so high that it caused serious headaches among the crew. To keep carbon dioxide levels low, one crew member had to be limited in the amount of time he was allowed to exercise. Ethylene glycol in both the air and water was also a ... |
[
"Is human hearing analog, digital, or a mix of both?"
] | [
false
] | I'm trying to settle an argument which has led to an interesting discussion. Arguments for analog: Arguments for digital: Arguments that it's both: Can someone answer the question if human hearing is analog or digital? | [
"Analog. Although you are correct there are a finite number of cochlear neurons, they do not simply signal on/off. The hair cells/neurons at the base of the cochlea are sensitive to very high frequencies (about 20khz), the cells at the apex of the cochlea are sensitive to low frequencies (20hz). There are thousands... | [
"We absolutely know enough about the auditory system to say that it is an analog transmission. The basilar membrane certainly vibrates in an anaolg fashion. Your point about a finite number of nerves would be accurate if, and only if, one hair cell were activated at intervals of frequency. That, however is not t... | [
"We absolutely know enough about the auditory system to say that it is an analog transmission. The basilar membrane certainly vibrates in an anaolg fashion. Your point about a finite number of nerves would be accurate if, and only if, one hair cell were activated at intervals of frequency. That, however is not t... |
[
"Can you render fat from eggs?"
] | [
false
] | My Dad always said that you could live off of just eggs and Potatoes. The only nutrient they lack is Vit D which you can make yourself by going outside. The one limitation is cooking nice potato dishes without fat. But if you could render a good high flashpoint oil from eggs, you'd be set to live off the land easily. | [
"Last time I checked, egg yolks actually ",
" contain ",
"vitamin D",
". The egg albumen is mostly protein, and the majority of the nutrients are in the yolk. An egg has around ",
"10 g",
" of fat. Though yolks are pretty ",
", rendering has the nice upside of drying while it isolates lipids.",
"TL;DR... | [
"Normally to render fat from a piece of meat you would heat it up and collect what drips out then separate the water layer from the fat layer. This isn't really possible with an egg because unlike meat eggs contain a huge amount of emulsifiers. What these molecules do is stabilize the interaction between fat and ... | [
"That is actually the site I grabbed my data from. I've heard that the science is undecided whether the cholesterol from eggs is good or bad. I've also heard that there are genetic markers that may determine whether egg cholesterol will hurt you or not.",
"Is there any simple process that you can perform to de-... |
[
"Has anyone been able to confirm or debunk Boyd Bushman's \"anti-gravity\" experiments?"
] | [
false
] | Boyd Bushman created an experiment where he took two objects of identical size, mass, and aerodynamic surface, and dropped them from a height. One was inert, the other had two powerful magnets oriented with identical poles pushing against one another. The claim is that, when both were released simultaneously, the objec... | [
"The one with magnets can in principle fall slower if there's a conductive material nearby, because the magnetic field induces a current in the conductor, which in turn pushes back on the falling magnetic object.",
"That's the only way there could be a difference. If this guy is claiming that magnetic fields dire... | [
"Considering that there are nearly 500 years of continuous data to support the idea that magnet's ",
" cause a decrease in the acceleration of an object (unless said object was in a particularly shaped magnetic field, or there were conductive objects nearby), I would suggest that it takes extraordinary evidence t... | [
"As always, there is a relevant xkcd. ",
"http://xkcd.com/808/",
"If magnets fell slower, people would use it! Don't you think aircraft, rockets, space shuttles, would all want to fall slower for free if they could? You think the people who make aircraft, rockets and space shuttles have never used magnets?",
... |
[
"If traveling near the speed of light causes time to slow down, then from the point of view of the light, a trip anywhere would be instantaneous, would it not?"
] | [
false
] | Supposing I could ride along with light, could I travel any distance instantaneously? Time stands still at the speed of light, right? | [
"The simple answer is yes, but it's disconnected from anything we can achieve. ",
"Light's frame of reference is only definable as a limit. You cannot actually go at the speed of light, nothing with mass can. "
] | [
"Also, it's fascinating how close massive particles can get to the limit. A relatively ordinary 1 GeV electron-neutrino could be time dilated by as much as a factor of a billion. So over the course of the age of the Universe the neutrino would only have experienced a few years time in its own frame of reference."
] | [
"There was a particle, typically called the oh-my-god particle, that was probably a high energy proton detected at the Fly's Eye detector in 1991. It was traveling at 0.9999999999999999999999951 times the speed of light relative to Earth.",
"From the perspective of this proton, it would fly across the galaxy in l... |
[
"When should scientists not use excel?"
] | [
false
] | This is sort of a meta askscience question, so sorry if this is in the wrong subreddit. My school pushes excel for dealing with data, and sometimes I question if that is the best choice. I'm not very familiar with excel so I know I can't judge it accurately. However, I have a bit of a computer science background and it... | [
"Spreadsheets are great for simple finance related stuff, such as keeping a budget. But most people use them for all of the wrong reasons:",
"MATLAB or SciLab (free version) is useful if you've got lots of numerical data, and need to plot/write functions/manipulate/regression analysis or do numerical approximatio... | [
"For actual science, most scientists don't use Excel for anything, as far as I've seen. Except, perhaps, to throw together a crappy-looking spreadsheet or deal with class grades or something.",
"But most people tend to know how to use the basics of Excel, so for an intro science course, your school would probabl... | [
"a lot of branches use excel, even if it's not yours. My fiance is in analytical chemistry, and all the data is recorded and analyzed on excel spreadsheets."
] |
[
"If a hot electrical wire dangled into a flooded basement, ala video games and movies, would you get shocked from jumping in?"
] | [
false
] | [deleted] | [
"The only difference is the water in his situation would have fewer salts, decreasing the conductivity, and therefore the area of danger. If there are very few dissolved salts, then the danger level would be fairly low. If in your hypothetical situation salt or tap water was used their would be more ions in the wat... | [
"Keep in mind, urban power lines have a much higher voltage (1000-30000 Volts) than a household socket (240 V)."
] | [
"The other day there was a thread about lightning striking the ocean. (Sorry, phone means no link.) If I recall correctly, the danger zone was estimated to extend about 14 feet from the point of contact.",
"In a practical sense, there is no safe area in your example. The only safe thing to do is stay out of the w... |
[
"Would a magnet travelling at 0.9 C follow Lenz's Law when colliding with a body of copper?"
] | [
false
] | null | [
"Maxwell's equations are Lorentz-covariant, so they hold no matter how fast something is moving."
] | [
"Where would all that energy go though? ",
"Also, wouldn’t that mean that instantaneous braking from 0.99 C is possible if we piggyback a vehicle on top of a sufficiently large magnet?",
"Edit: Sorry if my logic is somewhat flawed! I’m asking for my science fiction writing, so I’m not backed by real knowledge. ... | [
"Are you envisioning a situation like ",
"this",
"?",
"You would need an extremely strong magnetic field to stop an object moving at 0.99c relative to the thing you're trying to stop it with.",
"It certainly wouldn't happen instantaneously. And all of that energy has to go somewhere. It could be dissipated ... |
[
"Can we positively charge an object so much that it loses all its electrons and all we have left is positrons and neutrons?"
] | [
false
] | [deleted] | [
"I think you mean ",
" and neutrons. Positrons do not exist naturally in any reasonable quantity.",
"And, yes, this can be done. For example, at the Relativistic Heavy Ion Collider (RHIC) in Brookhaven, gold atoms that have had all their electrons removed leaving ions that are pure gold nuclei (nothing but pr... | [
"Positrons are the anti-matter counterpart to electrons. They have the same mass as electrons, but the opposite charge."
] | [
"For individual atoms, yes.",
"For larger objects the loss of electrons also means a loss of chemical bonding and extreme electromagnetic repulsion between unshielded nuclei, leaving you with ionized plasma."
] |
[
"Is there an acceleration limit?"
] | [
false
] | There is a speed limit (speed of light) but is there a limit of acceleration? | [
"Here is my go at a top level comment because there is an awful lot of unscientific noise in here.",
"There is no current compelling evidence (or consensus) to suggest that space-time is quantised. Current generally accepted theories such as GR, SR and QFT do not have any limit on acceleration.",
"All other an... | [
"It's a good question. Massless particles like photons can ",
" travel at c according to relativity. So they can't undergo acceleration, they come into the world fully formed and travel at c until they are destroyed in an interaction."
] | [
"Does a photon accelerate to C, or does it come into existence at C? (Or is this just a nonsense question because I am an idiot?)"
] |
[
"As a black hole slowly evaporates and the event horizon vanishes, what is left behind?"
] | [
false
] | I've been watching which talks about entropy and the far distant future when all stars have died and black holes eventually evaporate. The show mentions the theoretical "Black Dwarf" as the eventual fate of a white dwarf. I was just wondering if a black hole might also become something similar after they evaporate past... | [
"Black holes evaporate by means of Hawking radiation, and the smaller they become, the more rapidly they evaporate. In the final stage they explode into pure Hawking radiation, leaving nothing behind where they used to be; all of their mass is now radiation that is radiating in an expanding sphere through space. ... | [
"Hawking radiation is ",
" electromagnetic. It arises from virtual particles, therefore it actually can be any particle, although some particles are more probable than others. Here is a brief snippet which I am quoting from a physicist named John Baez:",
"In 1975 Hawking published a shocking result: if one ta... | [
"Naturally, conservation laws apply. If a black hole has a net charge, then the Hawking radiation that it emits will include charged particles whose charges will equal that of the black hole."
] |
[
"What is the scientific process behind using cooking oil to keep food from sticking to the pan?"
] | [
false
] | In terms of the chemistry. | [
"Weak boundary layer. You're forming a thin layer of oil that has poor adhesion properties. You could get the same results with water, it's just water has such a low boiling point, a thin film would completely evaporated before the food cooked. To make up that, we use an excess of water and ",
" the food."
] | [
"Magnetic molecules? I think you meant ",
" molecules."
] | [
"Matter is (generally) electrically neutral, but the charge is not always even in the molecule. Water for example, the electrons spend a bit more time near the O atom than they do around the H atoms, giving it a slight negative charge near the O and a slight positive charge near the H's. Magnetic molecules stick ... |
[
"What happens to photons when they get absorbed by particles? What do they transform into? And do the particles ever get saturated?"
] | [
false
] | null | [
"Photons carry energy. When an atom absorbs a photon, the photon's energy is converted into potential energy in the atom as an excited electronic state, and the photon ceases to exist. These excited states typically decay very quickly back to the ground state, releasing a new photon that is identical to the origina... | [
"Because it has been found that things don't have to have mass to be affected by gravity, and they don't have to have mass to generate their own gravity. Just energy."
] | [
"A photon has no mass. But anyway, when it’s destroyed, it just ceases to exist."
] |
[
"If you could perfectly model a weather system, could you predict it with 100% accuracy?"
] | [
false
] | In other words, is weather truly random? Given a scenario where you could replay the same weather scenario multiple times, with the EXACT same starting conditions, would everything unfold in the exact same way? If there is randomness, what causes it? | [
"It may be true that we live in a perfectly deterministic world, so there is no true randomness at all. But, typically, when we talk about random effects in science, we're not trying to be philosophical, but rather we mean that there is something happening that is far to complicated or complex for us to model dete... | [
"There are quantum effects on weather",
"Uh, no. You do not need to invoke quantum mechanics to discuss turbulence. The latter is arguably more complex and wholly unrelated (recall the apocryphal quote attributed to Heisenberg, \"When I meet God, I am going to ask him two questions: Why relativity? And why turbul... | [
"The atmosohere is highly nonlinear (i.e. you cannot predict a from b exactly). There are higher order terms in the equations within numerical weather prediction models that cannot be resolved due to computational power and cost, and these are the terms responsible for the \"chaos\" at greater time steps in the fut... |
[
"How does your body actually build up tolerances eg to alcohol?"
] | [
false
] | Just realised as a non drinker that if i was to start drinking a light shandy would get me tipsy, however with regular drinking it would take pints. I then realised I had no idea why that was? Whats going on in our oh so clever bodies? | [
"For alcohol specifically, your body has a class of enzymes called \"alcohol dehydrogenases\" which are responsible for oxidizing alcohol into acetaldehyde (this compound is more toxic than alcohol, and is the reason for a hangover). ",
" EDIT: [Alcohol tolerance is dependent on (primarily) the GABA neurotransm... | [
"I stand corrected. It appears that the cause and effect is the other way: there is a correlation between higher levels of ADH and alcoholism.",
"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1682953/",
"Furthermore, the mechanism for tolerance and addiction appears to more closely involve the neuroadaptation of... | [
"False... ",
"http://jpet.aspetjournals.org/content/199/1/158.short",
"\n",
"http://www.nature.com/nature/journal/v263/n5576/abs/263418a0.html",
"\n",
"http://www.sciencedirect.com/science/article/pii/0091305795020551"
] |
[
"How are rotating black holes any different than non-rotating black holes?"
] | [
false
] | Also, if a black hole is a singularity, which is point-like, how can it possibly rotate? | [
"Rotating masses drag spacetime around them in a process called frame dragging. This causes rotating black holes with higher angular momenta to have a region called the ergosphere where spacetime is rotating faster than light. "
] | [
"Isn't that analogous to spacetime getting dragged faster than light?"
] | [
"That's not true, it's just a region where one cannot remain stationary and must rotate. To not rotate, you'd have to go faster than light, but you can't."
] |
[
"Will we ever be able to view a single atom?"
] | [
false
] | I know light is out of the picture because of the wavelength, and electron microscopes cannot see single atoms either, but is there any other method too allow for this to happen? | [
"IBM has been doing single-atom stuff with ",
"tunneling electron microscopes",
" for a while (they were invented at IBM Zürich in 1981). They did ",
"this",
" back in 1989, and ",
"this",
" this year.",
"Even earlier, it's been possible to put a single atom in a Penning trap and observe it— you can't... | [
"We already can :)",
"Here",
" is a single Hydrogen atom.",
"My Masters research back in 2007 was doing computer simulations based on some tunneling electron microscope experiments that had been done. These experiments regularly observe structure down to individual atoms. The first image that came up for me o... | [
"I've always wondered how exactly they aim the laser at the atom. Or do they just know where it will be because they precisely measure the electromagnetic field it's being held in?"
] |
[
"Has there ever been evidence of spatial dimensions beyond the three we can perceive?"
] | [
false
] | Lately I've become extremely interested in spatial dimensions beyond length, width, and height, reading Flatland, etc. I was thinking about something recently. If we have a universe of 2D space that us as three-dimensional beings can look at, we can interact with that universe but only in a distorted kind of sense. A 3... | [
"Thanks for taking the time to write this!"
] | [
"Thanks for taking the time to write this!"
] | [
"I enjoyed doing so. Thanks for taking time to let me teach you something."
] |
[
"What happens when people train themselves to hold their breath longer?"
] | [
false
] | Untrained people can typically hold their breath for around 1 minute, amateur divers for 3 minutes, professional divers for 4-5 minutes, and experienced freedivers for 7 minutes and more. What does this "training" actually do to the body? I'm guessing it's not simply adapting to do the same functions with 7x less oxyge... | [
"Everyone's body becomes more efficient when their face is submerged. It's the mammalian dive reflex. Heart slows, less blood to the extremities, etc. The more you do it, the more efficient your body becomes at it (even lower heart rate = lower oxygen consumption).",
"There is research that suggests the strength ... | [
"While not arguing with all the training points you bring up, I'm pretty sure mammalian dive reflect requires cold water submersion, not just \"face submerged\". I'll try to find a source but I'm pretty sure it requires water temps below 55F-60F to take effect. ",
"Wikipedia page",
" cites \"chilling\" but does... | [
"I'm guessing it's not simply adapting to do the same functions with 7x less oxygen, because if that were possible, the body would be laughably inefficient to begin with.",
"Haha yes it is, but why would be body need to be efficient with oxygen? Oxygen is everywhere! Keep in mind tho, the oxygen consumption of th... |
[
"Are bacteria able to build resistance to hand wash soap as they’re able to against antibiotics?"
] | [
false
] | null | [
"Unless it's that antibacterial hand wash soap, which is kind of pointless because it doesn't work any better than regular soap, ",
" it probably increases antibiotic resistance in bacteria. ",
"https://www.fda.gov/ForConsumers/ConsumerUpdates/ucm378393.htm",
"Theoretically it might be possible for bacteria t... | [
"Hands wash soap doesn't kill bacteria. It simply lowers the surface tension of water enough to allow all the dirt and bacteria to be trapped in the water and be whisked away when you rinse. Nothing to build a resistance to!"
] | [
"Unless it is antibacterial soap they won't form any noticeable resistance.",
"They are physically removed and killed through physical means.",
"The same way that bacteria can't develop a resistance to being set on fire.",
"They will be able to build resistances against low levels of the soaps, same way that ... |
[
"Particles at Cern travel at close to the speed of light when they collide. So given nothing can travel faster than the speed of light relative to anything else what speed do the particles collide at? Or am I just totally way off base?"
] | [
false
] | 2 cars travelling at 100kph collide at a speed of 200kph. 2 particles travelling near the speed of light collide at what speed? | [
"It depends on the frame of reference. In the lab frame the relative velocity of the particles is almost twice the speed of light. This is perfectly fine, because neither of the particles is traveling at or faster than the speed of light, it's only their relative velocity. ",
"In the frame of one of the particles... | [
"See the ",
"physics FAQ",
":",
"If you add two things going near the speed of light, why don't they add up to be faster than the speed of light?"
] | [
"2 cars traveling at 100 kph don't really see each other approach at 200 kph, but rather a little less. This is a surprise but true. The formula for this is (v1 + v2)/(1+v1*v2) where these v's are written as fractions of the speed of light. So in the case of CERN, try this formula when v is 0.99996."
] |
[
"Is it possible to build a hologram projector at home?"
] | [
false
] | null | [
"Not the right sub for home projects. Maybe try a diy sub or ",
"/r/askengineers"
] | [
"*u"
] | [
"*u"
] |
[
"How far away is a roadside \"potalizer\" test, and how might it work?"
] | [
false
] | First, a bit of non-science background. I'm in favor of the legalization of cannabis with the fine folks over in (known as C:LEAR), but I realize that there are a LOT of obstacles that need to be overcome before legalization is a feasible option. The hurdle I'm researching now is THC testing from a law enforcement st... | [
"Since almost all laws against reckless driving include sleepiness and impairment for other non-drug related reasons, probably yes."
] | [
"If it's hard to distinguish between someone who is baked and someone who is extremely tired, shouldn't we be testing for ",
" instead of substances? If someone is impaired I want them off the road, I don't care if they are impaired because of alcohol, weed, lack of sleep, distraction, or anything else. Likewis... | [
"Trust me, I don't want a potalizer that can be beat. I want it cheap, readily available, and with <1% chance of a false result. From what I see, a beatable test can only hinder the legalization process. Besides, driving is dangerous enough when everyone's sober, people dumb enough to drive while impaired deserv... |
[
"How do Pharmaceutical Companies test their drug on humans before knowing what it might do?"
] | [
false
] | Are there lots of unspoken pharmaceutical deaths that aren't mentioned? Additionally - how do they know that some random active ingredient might be used for depression or restless leg syndrome? | [
"They have a very good idea on what it's ",
" to do. This data is available from early research ",
".",
"In terms of side effects, this is gleamed in toxicological studies and ",
"clinical trials",
" - specifically Phase I, where the drug is administered to healthy volunteers. To move onto later phases of... | [
"Not to mention that by the time a drug has reached human trials, it has been tested pretty thoroughly on human analogs (i.e. research animals)."
] | [
"Starting a new comment because I'm directly answering your question but that is not to take away from some valid points made by Rupert and botanist. ",
"I have experience in early R&D at the UKs largest pharma (devilishly difficult clue there). ",
"For a new drug to have even the slimmest chance of getting to ... |
[
"Gold is often found as pure gold nuggets. What other elements can be mined in non-compound, pure elemental form?"
] | [
false
] | As I understand it, most gold that is mined is found as pure gold (e.g. often mixed up with gold-bearing quartz), while an element like aluminum must be extracted from bauxite ore, an aluminum compound. Iron, meanwhile, rarely occurs as a raw element in banded iron formations, and coal is pretty close to pure carbon. W... | [
"Metals found in their pure state are referred to as Native Metals and the ",
"wiki page",
" lists the different elements which can be discovered in native form. In addition to gold, it appears that copper, silver and platinum are the other elements which have been commercially mined in native form. In the cas... | [
"on top of that, Detroit sit on a huge deposit of salt, which existed well before the Detroit Lions"
] | [
"Michigander here, iron and copper were found in large pure deposits. Iron mountain Michigan is named after a giant pure chunk of iron that was on the surface. They also took out sheets of copper from the keweenaw that weighed tons and were pure copper."
] |
[
"How are new viruses created? How does the first person contract it?"
] | [
false
] | null | [
"Good question! And sorry for the wall of text, but dammit I love viruses and I hate sleeping.",
"The spread of a new virus to humans is usually through zoonotic transmission (ie. an animal to a human). Every virus is subject to natural selection and is capable of evolving with alacrity due to how fast they're ab... | [
"Virologist here! Presumably, they all share a common ancestor. Viruses evolve quickly, and there are undeniably many viruses that simply haven't been discovered yet. However, it is possible to construct phylogenetic diagrams of related viruses, and it's been shown that there are relationships between viruses that ... | [
"Viruses evolve just like all other life on the planet. However, viruses also Interact with and depend on their hosts. So, one way you can get \"new\" viruses is by mutation. Existing viruses gain mutations in their DNA or RNA (depending on their genome type), and these mutations allow them to survive better in ... |
[
"Why are all the gas planets further from the sun as opposed to closer to it?"
] | [
false
] | Bonus question: do planets orbit around the sun at different angles? From illustrations it seems like they orbit on one plane. | [
"The main reason is simply heat. During the early formation of the planets, the area within around 4 AU of the sun was too warm for gases such as oxygen and ethane to condense into solids. Only heavier compounds were able to group together to form planets. The reason for their small size was due to the relative rar... | [
"It is far easier for us to discover these exoplanets than any other type of planet."
] | [
"Gas escapes easily and requires a lot of gravity to keep it together. Helium for example will escape the Earth's atmosphere when released. Originally they would have been composed of mainly methane and ammonia and grew to between 3-4 Earth masses, which was enough to begin capturing the highly abundant helium. "
] |
[
"Could matter/light escape the event horizon of a relatively tiny black hole under influence of another?"
] | [
false
] | Say point A in space is just beyond the event horizon of a small to medium black hole, but also further beyond the event horizon of a second super-massive black hole. This second one will, if I recall correctly, have an event horizon many many times bigger. If for some theorectical reason these black holes do not merge... | [
"When black holes get close to each other, generally what happens is that they form a bigger black hole that encompasses both, called an apparent horizon, like ",
"this extremely technical drawing",
".",
"See for example figure 6 of ",
"this paper",
"."
] | [
"I thought for outsiders it would be like that, as there would be a gravitational middle point, however what I am wondering about is whether or not inside this apparent horizon, energy/particles can escape 1 of the individiual event horizons?"
] | [
"That's actually an interesting question. I would expect the answer to be no, but two black holes merging ",
" a very complicated scenario so I guess I can't say for sure. Maybe someone with more directly relevant expertise can say."
] |
[
"Is there a physiological explanation for the feeling of \"weight\" that sometimes accompanies depression?"
] | [
false
] | Many people with depression describe a feeling of heaviness or weight, usually in the chest but sometimes in other areas of the body. Is there an actual physical reason for this, or is it just a mental reaction to distress? | [
"It's thought to be part of the stress response (aka General Adaptive Syndrome) which involves 3 (sometimes 4 depending on who you ask) stages. ",
"Here's a handy visual aid.",
" is the first phase is where the stimulus is first encountered, and the body initiates something similar to a fight-or-flight response... | [
"I can try to find the original journal article, but this was first described by a Canadian scientist ~1940, but, yes, endocrinology is very important when studying physiology. Specifically, what I study is the interaction between hormones and behavior.",
"EDIT: found it and posted it in another reply."
] | [
"This is really informative and concise, thanks a lot. Do you have a specific source where you found the info, or just a solid background in endocrinology? "
] |
[
"A large fan is in my window to blow cooler air in. When it's off, the wind sometimes rotates its blades. What happens to the resultant power that's generated?"
] | [
false
] | null | [
"Most household fans are single phase induction machines. Induction motors operate by inducing currents in a cage around rotor which in turn induces a magnetic field which opposes the field which induced the current, creating torque (turns the fan). When the voltage supply (electric outlet) to the stator is turned ... | [
"The fan blades rotate the shaft which causes friction inside the motor. The friction dissipates as heat. So, not much."
] | [
"Depending on the type of electric motor that is being used, it may or may not generate any electricity.",
"I believe ",
"household box fans",
" (what OP is likely describing) are always made with induction motors as ",
"/u/rystesh",
" points out in another answer ITT. So the answer is really that there ... |
[
"Ask Anything Wednesday - Engineering, Mathematics, Computer Science"
] | [
false
] | Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! ... | [
"Because the whole configuration is a series of compressors and turbines, the turbines power the compressors and keep the gasses flowing in the right direction. It's not exactly an 'open' path, the openings are small compared to the cross sectional area of the engine. ",
"Helpful diagram",
" and a ",
"good e... | [
"The number of pixels ",
" the number of samples. By Nyquist's theorem, it should be twice the maximum \"spatial frequency\" of the image you're trying to capture. Imagine a scanner that scans one line at a time. If we could have up to 300 white/black transitions per inch (spatial frequency) along a line in the o... | [
"That's a full semester-long course summarized in a one line question.",
"Quick answer : ",
"Example : 12 system hours. 8 + 12 = 8. 5 + 10 = 3.",
"Here we had (Z) and we took away any 12-multiples. (0=12=24, 1=13=25, ...) So Z is the group and the quotient group is {x | x= 12a where a in Z}. and the resulted... |
[
"would a drop of Anti-matter destroy a whole planet, or would it only destroy something equal to the size of the drop?"
] | [
false
] | lets just use blocks instead of the drop scenario. Assume I have 1 block of anti matter and 5 blocks of matter... would the one block of Anti-matter destroy all 5 blocks of matter, if they came into contact, or would the 1 block of Anti-matter destroy just 1 block of matter since that is equal to its size? | [
"\"Destroy\", here, is a vague term. A drop of antimatter would annihilate an equal mass of the planet (cause that matter to cease to exist)(size is irrelevant, mass is what's important), but the resulting release of energy, if the drop was large enough, could conceivably break apart the planet \"destroying\" it. ... | [
"The annihilation of one kilogram of antimatter would release about as much energy as the most powerful nuclear bomb. That is enough to destroy a large city but not nearly enough to destroy a planet."
] | [
"Also, the energy released would be defined by e = mc",
" Therefore, I gram of matter and 1 gram of anti-matter would produce about 180 trillion joules of energy - about 10-12 times the Hiroshima bomb (if I did the math correctly)."
] |
[
"Is the mantle of the Earth solid or liquid?"
] | [
false
] | I have referred to many sources, including teachers, and the view seems to differ wherever I look so, is the mantle solid or liquid? | [
"The ",
"mantle",
" is either a solid or a fluid (not liquid), depending on P-T (",
"pressure - temperature",
") conditions, with upwards of ~3% melt fraction. Fluids can undergo shear stress, while liquids (such as water) cannot. Earth's outer-core is a liquid, hence why secondary / shear (",
"S",
") w... | [
"It's solid. However the mantle does undergo a very, very slow creeping flow (think cms/year). This is connected to mantle convection a process that brings up heat from the interior to the surface, and in the case of down-welling plates cold material from the surface back into the interior."
] | [
"That is what I thought, but because of it being able to flow (however slowly) led to confusion due to the contrasting views."
] |
[
"From an engineering standpoint, how feasible are \"clean\" energy and energy independence in the US?"
] | [
false
] | Are politicians lying when they say we can be energy-independent? This country is a HUGE consumer of oil. Can we possibly produce all of our energy domestically without importing oil? Is a full transition to wind/solar/other clean energy possible? | [
"U.S. energy consumption can largely be broken down into two main types: stationary and portable. The electrical power grid would be the main use of stationary power, while cars, trucks and the like would be the majority of the portable demand. Depending on how you break down industrial and commercial use, the rati... | [
"That is mostly buzzwords for the uninformed voter. Oil importation is important for us in financial terms as our enormous refining capability would be wasted without oil imports. However our local industry wouldn't grind to a halt if imports stopped."
] | [
" You are overlooking the recent invention at MIT in 2009 of the industrial-scale ",
"cheap liquid metal battery",
". We no longer 'have to' \"go all-nuclear\" to meet our electricity demand; rapid large-scale deployment of this American-developed battery technology will solve the renewable energy availabilit... |
[
"Do all links in a chain experience the same force when carrying a load?"
] | [
false
] | Hey lovelies! Imagine a steel chain, suspended with a weight attached on the end. Would the links further up have greater force acting on them as they would be holding up more links or would the 'equal and opposite' thing balance everything out. And now imagine a chain drawn horizontally with a force applied to both en... | [
"If the chain was dangling vertically, links near the top would be experiencing higher stress because it is supporting both the load at the end of the chain and the weight of the chain itself.",
"If the chain was holding two things in tension horizontally (two ships pulling against each other), the stress would b... | [
"There may be a dip depending on the tension applied to the chain and the weight of the chain, in which case there would be a higher load on the ends, which now have a vertical component to their force, similar to if the chain was dangling free. If the chain is pulled taut, however, the load would be the same every... | [
"There could still be more tension in some links than others, it just has to be symmetrically distributed. The link at the bottom of the dip would have less stress on it than the ones right next to the dip."
] |
[
"Why does wood skip the liquid stage of matter?"
] | [
false
] | Every time wood burns, it always appears to skip the liquid stage of matter. Is this true? If so why does this happen? If it's not true then what is actually happening when wood burns? | [
"Wood doesn't even enter the gas phase when it gets hot. When you heat a solid up, all the bonds holding the material together start jiggling, including those bonding interactions that keep different molecules stuck together. If you keep on heating, one of those interactions can jiggle fast enough to break apart.... | [
"\"wood\" is a very complicated mixture of thousands of different compounds, each with different melting points (in fact, some organic compounds don't have melting points at all; they decompose into different molecules if you try to heat/pressurize them too much), so \"wood\" doesn't have a melting point in the sam... | [
"Wood's not a pure substance - it's a very complex mixture of biomolecules and others (lignins, carbohydrates, water, terpenes). So it's not going to do clean phase transitions. And burning isn't an example of evaporation, either, since the smoke coming off isn't just wood molecules flying off into the gas phase."
... |
[
"Which would return to room temperature first?"
] | [
false
] | null | [
"The vodka, since a change of state takes extra energy and the difference in specific heat of alcohol and water isn't enough (or even a difference in the right direction in this case) to counteract this."
] | [
"The water has a higher specific heat than ethanol. It takes more energy to raise its temperature. So the vodka should warm up first. "
] | [
"Thank you, was a random thought "
] |
[
"What is the physical difference between a memory I have from yesterday and the memory of the dream I had last night?"
] | [
false
] | [deleted] | [
"This is a pretty difficult question, for me at least, and as someone who doesn't work on dreams I can only speculate with my current knowledge. ",
"As other posters have already stated, one of the best theories for dreams is that they are used to help organize and store information and memories in the brain that... | [
"And why is it that if I have my heart broken in a dream I am actually heart broken all day, even though I know it's fake I still have that sinking feeling. Same thing with falling in love in a dream, but that's worse because she's not even real... it seriously happens though and stays with me for longer than I wou... | [
"Well, theories are backed by evidence. There have been some mice maze studies where they're able to find out that the mice actually dream about the mazes in their sleep. I think they do it by seeing that the same neural connections are activated when they sleep as to when they were learning the maze, im not sure e... |
[
"Does light have inertia?"
] | [
false
] | [deleted] | [
"It has impulse, and exerts pressure when absorbed (double that when reflected): ",
"http://en.wikipedia.org/wiki/Light_pressure"
] | [
"Intertia is defined as the linearity constant between force and accelration in Newton's 2nd law, this is often equated with gravitational mass which appears to be correct to within experimental errors for all matter, however this is not a given and should not be done without caution.",
"We know that light exerts... | [
"No it is not, intertia has units force/accelration."
] |
[
"Does sleep hypnosis actually work? Is it possible for our brains to retain enough information while sleeping to change behavior?"
] | [
false
] | examples: quit smoking, weight loss/diet change hypnosis, etc. Also, do our subconscious' "pick up" anything when falling asleep during a movie or while listening to music? | [
"It's important to note that traditional hypnotherapy does not actually place the person into a \"sleep\" state. I assume, however, that you aren't talking about traditional hypnotherapy, which does have a certain amount of scientific support (despite a limited understanding of the associated neurobiological mecha... | [
"I routinely leave the tv on and have dreams that combine with the shows/movies I'm watching, and at times are conscious of this fact during sleep and can usually tell which state of sleep I'm in. So you're saying that I'm not able to learn from this but it's merely just an interaction with the environment? Why am ... | [
"Would you mind elaborating on the effectiveness of traditional hypnotherapy? Can a willing patient actually be put under hypnosis, and can hypnotic suggestion yield effective results?"
] |
[
"What attributes change the index of refraction of a medium?"
] | [
false
] | [deleted] | [
"In short, the electric and magnetic properties of a material affect how fast an EM wave (light) will propagate through that material. Specifically the permittivity (epsilon) and permeability (mu) of the material",
"To use the wave model, let's go back to the derivation of the wave equation from Maxwell's equati... | [
"Permittivity is usually noted as epsilon and permeability by mu, right? I come from engineering but I ",
" physics uses the same convention there. It doesn't help that they picked words that are so similar for the two phenomena...",
"While I'm not so intimately familiar with optical frequency stuff (I'm an RF ... | [
"To add a bit to it, you can think of epsilon and mu as describing how much the material resists changes in the EM field - it's in a way the 'stiffness' of the material in an electromagnetic sense"
] |
[
"What is the highest frequency laser, and what challenges exist for making a higher frequency laser?"
] | [
false
] | null | [
"X-ray lasers",
" exist, and ",
"gamma ray lasers",
" are not forbidden by any fundamental law of physics, just an enormous engineering challenge. However, they are not of the same design of more conventional lasers like that used in your CD/DVD/Blu-ray player.",
"To make a laser you basically need to cycl... | [
"In addition to the 3 ways you mention, a common technique used in ultrafast physics labs is ",
"High Harmonic Generation",
". This is a nonlinear strong field physics technique resulting in lasers with photon energies over 100 eV. I believe the highest energy to date is over 250 eV (granted the average power o... | [
"While high harmonics get pretty fancy, the technique is similar to a very common laser, 1064 nm Nd:YAG with a frequency doubler to 532 nm, aka the green laser pointer. Not quite as sci-fi as it initially sounds! "
] |
[
"Falling from a high altitude into water"
] | [
false
] | I'm having a debate with a co-worker regarding what causes the most damage when falling from high altitudes; we can't decide if the surface tension of the water or the viscosity of the water causes more damage. I understand that it takes a greater force to break the surface tension of the water than it does to travel t... | [
"You are both wrong.",
"The liquid has three basic properties relevant to this problem. Surface tension, viscosity, and density. The density of water is doing the damage.",
"The ",
"drag equation",
", appropriate at high Reynolds numbers, says that the force goes like the density of the fluid times veloci... | [
"Mechanical Engineer chiming in. You are partially correct. I remember from my first physics class in high school is that \"pain/damage\" is a result of either impulse (change in momentum) and/or pressure (force/area). In this case, it is impulse that makes it hurt. And you are right to say that the force of dr... | [
"It is all a question of the Reynolds number. If it is much less than 1, the viscous forces dominate. If it is much greater than 1, the inertial forces (density of the fluid) dominates.",
"I get a Reynolds number of about 10",
"If you don't believe me, try jumping into a vat of superfluid liquid helium at ter... |
[
"If one downloaded a YouTube video using a tool like, say, youtube-dl, does that download count as a view in YouTube's eyes?"
] | [
false
] | null | [
"That depends on what methods YouTube uses to track download counts. Every time you open a video on YouTube, your browser makes a number of requests to different files from YouTube's servers. For example, you will download the HTML, CSS, JavaScript, configuration data, and the actual movie content files. ",
"If t... | [
"Its likely that YouTube tracks the number of times that clients request the video manifest file which would include downloader scripts, but I couldn't say for sure without actually seeing the source code.",
"We'd have to get some input from a person that works with YouTube to be certain, but if your statement ",... | [
"There are some good technical reasons to say it does.",
"YouTube does not allow you to download videos. If you try to do so by accessing the same HTTP resource via a direct download (e.g. via web browser), it will be blocked. It only works if some HTTP query string options are sent so that the server knows the v... |
[
"How frequently is brain failure a primary cause of death?"
] | [
false
] | We often hear about liver/kidney/heart failure as causes of death, and the possibility of synthetic organs replacing failing organs in the body doesn't seem all that out of reach due to recent advances in 3D printing/stem cell research. However, it seems like the brain would be much trickier to replace without losing a... | [
"The interesting thing about this question is that “death” has multiple definitions, and modern medicine can do amazing things to keep people “alive.”",
"Some people think that death means ",
", as in the cessation of cardiac activity which leads to death of all other organs. In medicine, we define death as ",
... | [
"It depends on a lot of things (genetics, environmental factors, alcohol consumption etc.) but the truth is that you would be hard pressed to find people over the 90 age limit that don't have some degree of dementia or cognitive deterioration. The risk of this developing likely increases with age, though I can't fi... | [
"Brain failure is a weird word that is not used as a diagnosis. But there are options for your brain to \"fail\" you:",
"trauma. Get hid on the head hard enough, and you could die from the trauma (bleeding and swelling -> cell death > brain fails you)",
"CVA. Cerebrovascular accident, either bleeding or infarct... |
[
"Would i be able to stave off dehydration by immersing my body in water?"
] | [
false
] | Like if i was a "castaway" after the ship sunk, would i survive longer by floating in the water instead of sitting in the life-boat? | [
"Hi, this question was asked not too long ago, I recommend you check out this link: ",
"http://www.reddit.com/r/askscience/comments/nhb8o/if_placed_up_to_our_chin_in_water_could_we_still/",
"That should answer your question. In short, I believe you would nut suffer from dehydration in the traditional sense, but... | [
"Only dead skin cells absorb any significant amount of water, the rest of your skin is almost waterproof. The amount of water your body needs to stay hydrated couldn't be absorbed through your skin before your skin began to die."
] | [
"I'm terrible with science, but wouldn't the salt water actually work against you in this case? I'm actually kind of interested myself."
] |
[
"How do we know neutrinos have mass?"
] | [
false
] | My own answer is: since the Super Kamiokande and SNOLAB we know that neutrinos can change flavours. My reasoning is: solar neutrinos are all electron neutrinos originally. To change flavour an infinitesimal (but non-zero) amount of time needs to pass (simply to have the 'room' to switch). Particles moving at c don't ex... | [
"Your understanding is more or less correct. ",
"The key piece is that neutrino oscillation implies that the flavor states are not the same as the mass states. This means that flavor states are mixtures of the mass states, and vice versa. ",
"The existence of flavor oscillations (observed as a deficit of solar ... | [
"You can make it less hand wavy by saying they can only change in proper time and the proper time for any null path is (hence the name) 0.",
"The argument that neutrinos must be massive for flavor oscillations to be possible because no oscillations could occur if the proper time of a neutrino's world line is alwa... | [
"You can make it less hand wavy by saying they can only change in proper time and the proper time for any null path is (hence the name) 0. ",
"In other words just because you can't construct a reference frame doesn't mean you can't talk about the proper time of a wordline.",
"Also the problem with the differenc... |
[
"How do radio waves contain information?"
] | [
false
] | [deleted] | [
"There are several ways to encode information on an EM wave. There are 5 parameters that uniquely define an EM wave, each of which can be used to carry information. The 5 parameters are:",
"Suppose you wanted to vary the amplitude of the light to carry a signal in binary. You could very easily turn the signal ... | [
"The article you linked to doesn't really answer the fundamental question of \"how do radio waves carry information?\", which you answered nicely. The article answers the question, \"how do we send many different signals on the same radio wave?\", which is a more complicated question and is called multiplexing.",
... | [
"Their dependence is based on the speed of light, which isn't the same in all mediums.",
"So, it's better to consider all 5 parameters to define the wave, even if there aren't 5 degrees of freedom."
] |
[
"How do short takeoff/landing planes work?"
] | [
false
] | I'm really curious about the science behind planes that can take off and land with literally 6 feet of runway? Why do other planes need hundreds of yards/meters to take off where these planes can do it in like 6 feet/ 2 meters? | [
"The short answer is STOL fixed wing aircraft work by brute force. They all depend on the power plant and use more fuel. Brute force costs more than a more efficient solution.",
"Technical answer: it's the wings.",
"Let's compare and contrast a few things.",
"Gliders have long, skinny wings. These are the mos... | [
"The question is about STOL but your examples are all VTOL, which is a different beast entirely.",
"STOL planes are not inherently less efficient than conventional planes within their design envelope. They just have features that allow them to accelerate quickly and generate a lot of lift and drag at low air spee... | [
"The question is about STOL but your examples are all VTOL, which is a different beast entirely",
"STOL to me is things like the Twin Otter, Beaver, and similar bush planes. The Twin Otter has twin PT6 turboprops, generating about 1500 combined horsepower. I've personally witnessed one take off across a landing s... |
[
"Why won't fuses protect electronics from an EMP?"
] | [
false
] | My understanding is that an EMP fries circuits by inducing a very large current in the circuit. Aren't fuses supposed to break the circuit in case of a very large current? | [
"First of all, EMPs are so quick that a fuse would not be able to help, however, an EMP creates current everywhere in the circuit, so even if your fuse could react fast enough it wouldn't do anything."
] | [
"A \"complete\" circuit is just a way of saying that the size of the circuit elements are small compared to the wavelength at the operating frequency. An EMP produces very high frequency waves which are tiny in comparison to the circuit elements. In other words, you get currents that flow in very small loops right ... | [
"The electrons are pushed by the E-M pulse, it doesn't matter that it's not a \"complete circuit\", all a circuit needs is electric potential and that's what an EMP provides. If you were to hold just a piece of wire and run a magnet by it, you would be creating a current in it, that works the same way an EMP would ... |
[
"When dolphins open their eyes above water, are things blurry like when humans open their eyes below water?"
] | [
false
] | What adaptations do dolphins and other marine mammals have to see clearly under water and how does that affect their vision above water? | [
"I know I'm late, but I'm in the unique position where I actually study corneas for a living and I've been consulted before regarding dolphin eyes. The real answer to this question is that dolphins rely on their echolocation almost exclusively. They have eyes, and they can see, but they are practically vestigial at... | [
"The refractive index of the lens in your eye as well as the fluid inside and on the surface of your eye all interact to give you a focused image. Air has a refractive index of 1, and water is higher at 1.333. This means that light passes through air differently than water. Human eyes are best adapted to see in air... | [
"Can they echolocate through air, or just water?"
] |
[
"How are space telescopes shielded against cosmic rays?"
] | [
false
] | Space telescopes usually record photons as counts by converting their energy into an electric signal. But seeing as how cosmic rays may register as counts as well, I'm assuming they somehow need to be kept out of the equation. But how is this usually achieved? | [
"You can't avoid it, it is a background. It doesn't make single bright spots, so it is usually easy to take into account. You look for objects brighter than the general background noise (which comes from other sources as well, e.g. thermal noise)."
] | [
"It doesn't make single bright spots, so it is usually easy to take into account.",
"The more energetic cosmic ray hits on CCD detectors often ",
" look like bright spots or streaks - they're quite noticeable and appear even in ground based data. One might lose any useful data in the area of a hit, but that's l... | [
"If you make a very brief observation, yes. But by increasing the observation time, the noise begins to cancel out, and weak targets become visible."
] |
[
"Is \"Clean Coal\" purely a marketing ploy?"
] | [
false
] | I know there is a lobby group designed to promote the idea that so-called "clean" coal can be used to generate electricity with little or no pollution. I don't know if their science is reputable or not. What does Reddit Science say? | [
"The term \"clean coal\" is just a marketing phrase, but the underlying technologies do have some merit.",
"It is difficult to make an honest assessment because there is a lot of disinformation on both sides. Environmentalists may say there's no such thing as clean coal, and lobbyists will have you think that it... | [
"I've only ever heard of one successful demonstration of carbon sequestration with a coal plant, and it was both small scale and very expensive. The coal industry has no plans to implement the technology but it is still spending millions of dollars on advertising with the \"Clean Coal\" brand while simultaneously ... | [
"The amount of terms thrown around 'clean coal', 'green coal', 'geosequestration', 'carbon sequestration', 'carbon capture and storage', 'CCS' often times makes it confusing. As others have addressed sometimes these terms are describing all emissions, sometimes it is simply about carbon dioxide. The reality is that... |
[
"On some bottles of vitamin pills it says: \"take in before or after a meal.\" Is that actually necessary?"
] | [
false
] | null | [
"All of the vitamins that you and all of your ancestors ever ingested before the invention of pills were assimilated in the presence of and in the matrix of food. You can figure out the rest. A chunk of ascorbic acid flowing through your gut is not something that the gut and the rest of the body is exactly ready ... | [
"Some have to be taken on an empty stomach, and some can't.",
"This is just to make sure you know it is not one of those situations.",
"if you had no such notice, you would not know when to take it, or under what conditions it'd be ineffective, or dangerous."
] | [
"Some nutritional supplements are best taken before a meal for best absorption, while some are best taken AFTER as some nutrients are fat soluble and should be taken with a bit of food. ",
"Taking them at the wrong time won't harm you. It just means you won't get the most out of them. ",
"NOTE: There are except... |
[
"Is Dark Matter expected to interact with a black hole in any way other than the way that boring baryonic matter does?"
] | [
false
] | I'm guessing that a black hole will trap Dark Matter just like it does everything else, but I have nothing to back this up other than some hand waving, which probably wouldn't convince anyone. | [
"Imagine a heavy thing in an otherwise empty universe. It can be a star, a planet, a black hole or a bowling ball; doesn't matter.",
"Now imagine a much smaller thing orbiting the heavy thing at some reasonable distance.",
"What happens? Nothing happens. Literally. The smaller thing continues to orbit the heavy... | [
"All of its time, actually. Black holes are just things, not fundamentally different in the way they gravitate from any other things, really.",
"Okay, there is one difference that's rather interesting. A rotating black hole — and it's expected that all black holes rotate to a greater or lesser extent; conservatio... | [
"Actually it's an excellent assumption. If dark matter ",
" interact promiscuously with other dark matter, the way ordinary matter does with ordinary matter, then we would not find dark matter in the places and configurations that we've found it. Instead of existing in vast, sparse halos around galaxies, it would... |
[
"Could two large black holes create tidal stresses strong enough to tear a small black hole apart?"
] | [
false
] | [deleted] | [
"Tidal forces around large black holes are very weak compared to those around small black holes."
] | [
"With our current understanding black holes, the singularity is a point object, having no volume. Therefore it has infinite gravity, and cannot be pulled apart."
] | [
"I don't think anyone would say the singularity can be described as a point object or any other type. It can't be described with current physical theories."
] |
[
"Since accelerating is equivalent to being in a gravitation field, would a clock at the edge of a rotating disk experience gravitational time dilation?"
] | [
false
] | That is, time dilation in relation to a non-rotating inertial observer, not someone else on the disk. If so, what would be the formula to calculate this figure given the diameter of the disk and rotation speed? Also how much does special relativity account for the clock being time dilated? | [
"Yes. A good example is; the outer rim of a phonograph record or CD is younger than the center.",
"An experiment conducted at MIT (I think) placed an atomic clock (measuring the decay of Cesium 131) at the base of the physics tower and another on the 6th floor. The clocks had been precisely synced prior to thei... | [
"In that case the effect of the differing gravity field is bigger than the effect of different speeds of rotation. "
] | [
"Thanks but I still don't have the answer to my question about the rotating disk."
] |
[
"What is the temperature of the vacuum?"
] | [
false
] | If the temperature is just a representation of average kinetic energy of the moving particles, then it would be 0 in the container perfectly empty. But somehow we do not measure nor observe any such phenomenon in vacuumed containers. Why? | [
"I'd rather say it would be \"undefined\" for a completely empty temperature - what's the average value of no objects? You would have to divide zero energy by zero particles, which is rather difficult to get a sensible answer from. Temperature doesn't really work until you have large numbers of particles to generat... | [
"In the case you describe there would be heat transfer - the body would radiate electromagnetic waves in the vacuum because of the vibrations in the molecules and atoms of the body. If you had space devoid of any particles or electromagnetic radiation, your body would continue radiating until it reached the tempera... | [
"But how would heated body behave in such (vacuumed) enviroment? Would there be any heat transfer at all? I'd say no, because the vacuum would be a perfect heat isolator. Now, if there is no heat transfer, from the simple convection law of cooling we can deduce that temperature of the vacuum is the same as the temp... |
[
"Looking for sources for Raw Technology Material, Please Advise"
] | [
false
] | I know this isn't the usual question, but I think this subreddit is well suited for it. I work for a science museum and I'm trying to put together a visitor program about the engineering that goes into electronics technology. Essentially, we're dissecting things like cell phones, computer monitors, computers, etc. and ... | [
"http://www.memc.com/index.php",
"http://www.memc.com/index.php?view=Contact",
"I know about them b/c their headquarters in MO is close to my undergrad. Had a few friends work there. They moved wafer production away from MO though...",
"Try asking them.",
"EDIT: Oh and they have to cut off the top and bott... | [
"Thanks! I shot them a quick message. Hard to tell from their site, do you know if they handle just the crystal growth or if they do the circuit etching also?"
] | [
"I think they just do crystal growth. An actual wafer is going to cost them money so you can always say put a little thing on it saying 'donated my MEMC' or whatever. ",
"As for an etched one somebody at MEMC may have a contact. Otherwise i'd ask a company that makes something cheap like 5$ flash drives, heh. ... |
[
"How does sublimation turn water from a solid to a gas without it being a liquid in between?"
] | [
false
] | If turning ice to steam or air vapor is just a matter of adding heat (aka energy), wouldn't water *have* to go through a liquid phase-even if for just an instant? | [
"Chemical potential, μ , tells us how favorable a phase is. Systems tend toward lower chemical potential e.g. above the melting point of a solid the liquid phase has a lower chemical potential than the solid phase. The relationship between the μ and pressure (or temperature) for a solid or liquid is well approxima... | [
"Correct me if I'm wrong; your rational is on an atomic length scale and short time periods (kinetics). A part of that is to think of it in terms of the distances between the atoms. So the thought is that as you sublime a solid to a gas, the atoms must at some point be separated by a distance that conforms to a liq... | [
"In sublimation, atoms/molecules simply depart the solid to fly off into the adjacent gas. There's no problem with each particle individually gaining enough energy to enter the gas phase. ",
"In contrast, formation of a liquid phase would require some (but not all) bonds to be broken in concert to nucleate this p... |
[
"Why do people bite their nails?"
] | [
false
] | null | [
"It is classified as an impulse control disorder. Specifically it is considered within the obsessive compulsive spectrum.",
"Nail biting isn't an advantageous trait and can actually lead to infections of both the mouth and fingers. There are actually quite a few habits like this that aren't helpful. Things like i... | [
"Here is a BBC article discussing this very subject. \n",
"http://www.bbc.com/future/story/20140710-why-do-we-bite-our-nails",
"There seems to be no real consensus, but through history many [unscientific] theories have been pitched to explain the causes."
] | [
"You can't force another person to change their behavior. At best you can adjust their environment so it's more favorable to change a behavior than maintain it, but at the end of the day, they're in charge of what they do to their own bodies.",
"If they don't have any desire to stop nail biting, your first step w... |
[
"Why can't I see close up with my glasses on after getting my pupils dilated?"
] | [
false
] | null | [
"There is a lens within your eye that is both connected to and controlled by what is know as the ciliary muscle. This lens contributes to your eyes \"power\" and ultimately allows you to focus on objects at different distances by increasing or decreasing its \"power\". When you look at something near to you, the ci... | [
"Thank you!"
] | [
"Dilating your pupils increases the ",
"aperture size",
" of your eyes. In a camera, for a given focal length, increasing aperture size results in a narrower field of focus (e.g. Photographers love to use a very narrow field of focus to have objects at a very specific distance in sharp focus with everything ne... |
[
"How can 8oz of Diet Mountain Dew have 0 calories, but the 20oz bottle have 10?"
] | [
false
] | is it related to how they measure, variances, etc.? | [
"Crazy Food Laws",
"There are specific rules and regulations in how a company must list the Caloric information on their products. Calories must be listed in 5 calorie increments up to a total of 50, anything beyond that must be in 10 calorie increments. Weirdly, anything below 5 calories can be listed as 0.",
... | [
"That's not ",
" a crazy food law. It could just be the error bars of the product. eg, they can only measure to a precision of +/- 2.5 Calories, or perhaps variations among the product can only be controlled within that range, etc."
] | [
"So instead they decide to increase the error range by 5 and 10? "
] |
[
"If a Rubik Cube can be scrambled in x amount of moves, is it then possible to, without having seen the scrambling process, solve it in x amount of moves?"
] | [
false
] | [deleted] | [
"I don't know the exact answer to your question, but a related problem was actually recently solved. It is now believed that every configuration can be solved in 20 moves or less, though I'm not sure if an algorithm exists to compute the required sequence of moves. ",
"Here's an article",
" about it, and ",
"... | [
"It sounds a bit like you're asking whether every Rubik's Cube scramble has a unique path to get there. If that were true, then the unscrambling route would ",
" to be the reverse of the scrambling route.",
"This is not the case. In general, there are multiple ways to get any particular pattern, so you can't ... | [
"What you said is true; but on a side note: It would make sense to see half a turn clockwise and counterclockwise as the same operation. The direction of the turning is irrelevant and should, thus, be abstracted."
] |
[
"Is it possible to increase the rate of evaporation of water when drying clothes?"
] | [
false
] | Is there something that can be added to the water in a washing machine, or another process that would cause the water to evaporate quicker, without leaving some sort of residue or damaging the clothes? Drying clothes just takes so much longer than washing them. | [
"Do you mean in terms of a clothes dryer or air drying them?",
"For a clothes dryer - have the ducts cleaned, clean the lint trap regularly, reduce the size of the loads (this one especially!).",
"For air drying - put them in an area with lots of air flow, like in front of a fan or outside, and don't bundle the... | [
"I meant with a clothes dryer. I know about keeping the ducts clean etc it just annoys me how much longer it takes to dry clothes than wash them. My washer is done in around 20 minutes, but then drying the same load takes almost an hour."
] | [
"Soaking them in water is easy. Evaporating that water is harder."
] |
[
"If I take a 100 ft rope and fold it in half does the tensile strength double?"
] | [
false
] | Does it change if it's twisted together down the length of the rope? | [
"To a first order approximation yes, you double the strength.",
"In practice, though, you could see ",
" different results. A single strand will have a variation of tensile strength along its length due to manufacturing inconsistencies. When you pull the rope until failure it will fail at the weakest point. ... | [
"It's important to distinguish that the tensile strength of the rope itself doesn't change. What's happened is that the stress in the rope has been halved, since the area over which the force is exerted has doubled."
] | [
"True. But the tensile strength is a material property of the rope that is unchanged."
] |
[
"What programming language are programming languages written in, and what are they written in?"
] | [
false
] | For instance Minecraft is written in Java, but what is Java written in? | [
"Short answer: another language, initially. Many programming languages were created by developing their first compilers in another language. Initially, one would create a compiler that can compile the smallest possible subset of the new language being developed. The new compiler would then be used to develop ano... | [
"I only have one word to say to that:",
"NOOP\n",
"(Technically a program in assembly, although it explicitly does nothing)"
] | [
"No, the JVM is written in C++, but has a good part of the classes implemented in Java.",
"This is the usual for all languages that compile down to machine code. Java produces Java bytecode, and CPUs don't run that directly, so a Java program needs something that would interpret that bytecode.",
"You could tech... |
[
"Does a material exist that becomes more malleable the colder it becomes?"
] | [
false
] | null | [
"Not what you're looking for, exactly, but for what it's worth gases under \"ideal\" behavior (low pressure, reasonable or high temperatures) become ",
" viscous at high temperature. This isn't totally out of the question. I imagine there's probably some alloy that undergoes a phase change such that over some lim... | [
"My gut feeling is that this would be possible in polymer blends that display an Upper Critical Sollution Temperature. In such a system the two polymers mix below the UCST but when you heat them up they demix. If the mixed blend is more malleable than the demixed composite you'll see a sharp decrease of the malleab... | [
"I don't think that gases technically count as 'malleable' so there's those, which will become solid and malleable as you cool them, then less so as you cool them more. "
] |
[
"We don't feel the earth spinning because it is constant. Yet it is fastest at the equator and gets slower as you move away from it. My question is how come no one ever notices the increase or decrease when traveling towards the equator or away from the equator?"
] | [
false
] | null | [
"No you're not. You're asking questions because you want to learn. That's a clever thing to do. ",
"It is tough to understand the physical explanation without having some sort of knowledge of classical mechanics. Things with fictitious forces are hard for undergrads as well"
] | [
"Haha thanks! But could you maybe explain it in more simple terms im not the smartest science guy lol "
] | [
"Haha thanks! But could you maybe explain it in more simple terms im not the smartest science guy lol "
] |
[
"800yr old human footprints in England. How did they date them? and How did they wash away?"
] | [
false
] | This article: is amazing. However I don’t understand. It says that they had to race against the incoming tide to record them. With so little time how might they have dated the footprints. It also it says the footprints washed away, is it that they are buried in sand again? How could the footprints have lasted that lon... | [
"I've got some more sources!",
"So apparently Happisburgh, this small town in Britain, has received a fair amount of press for a similar incident that occurred a few years ago. Basically, the cliffs are washing away very quickly, because they're only made of clay and sand and the tides are getting higher. When th... | [
"I found it, the BBC article doesn't really give enough information. Wikipedia does.",
"The footprints were discovered in May 2013 by Nicholas Ashton, curator at the British Museum, and Martin Bates from Trinity St David's University, who were carrying out research as part of the Pathways to Ancient Britain (PAB)... | [
"and the tides are getting higher.",
"Is there a known reason for this? Is it an astrophysical reason? Is it anthropogenic? ",
"Edit:\nwoah what's with the downvotes, is this a dumb question? I'm not asking why the tides get higher on a monthly basis, but rather decades/centuries/..., mind you!"
] |
[
"Why is it beneficial to remove pus from a wound instead of letting it settle naturally?"
] | [
false
] | null | [
"Pus is a sign of infection. It is your body's immune cells that have died fighting the bacteria and no longer serve any purpose and is actually getting in the way. If it can be removed without damaging surrounding tissue, spreading the bacteria, or is required as there is so much of it, then it should be as it g... | [
"To remove the bacteria and other foreign material contained within the pus. Many bacteria commonly found in wounds produce cytotoxic substances which slow healing/the formation of granualtion tissue, so you will removing those as well. Foreign bodies will produce a foreign body response, which similarly is pus and... | [
"Sometimes, too, the tissues around the abscess serve not only to keep the pus in, but also to keep further WBCs out of the site of infection. Lancing an abscess can thus (when done properly) grant your immune system better access to whatever is causing the infection."
] |
[
"Do photons have a wave function that collapses like fermions?"
] | [
false
] | I'm given to understand that when we say that fermions such as electrons behave like waves, it's just their wave function - a description of how they are probably behaving - that acts like a wave. Is this also true for photons; that their wavelike nature describes where they will probably be? | [
"Wavefunction \"collapse\" is not unique to fermions. In fact it doesn't really have anything to do with bosons versus fermions, it's just one way to interpret what happens when you make a measurement of some property of a quantum-mechanical system.",
"That being said, a photon can't really be described using you... | [
"Attempting a simpler answer than already given:",
"In quantum mechanics, ",
" has a wave function and those wave functions all collapse in much the same way. ",
"Young's double-slit experiment",
" is perhaps the most famous experiment credited for this discovery--and the experiment works just as well wheth... | [
"There are tons of good books out there, Peskin and Schroeder, Schwartz, Zee, there are some lecture notes by Tong as well."
] |
[
"What is the relative speed of two photons traveling in opposite directions?"
] | [
false
] | Two cars going 60 mph in the same direction have a relative velocity of 0, and two cars going 60 mph in opposite directions have a relative velocity of 120 mph. So if two photons are travelling in opposite directions, is their relative velocity still C? Or is it 2C? If it is 2C then what is to stop anything from going ... | [
"If you apply the velocity addition formula, you'll find that (c+c)/(1+c",
" /c",
" ) is still c. However, it's a bit moot because you can't really consider the rest frame of a photon.",
"Two cars going 60 mph in opposite directions are actually going 119.9999999999995 mph relative to one another. "
] | [
"In any inertial reference frame moving along the direction of photons' travel, the rate of change of the distance between the two photons traveling oppositely from one another in vacuum is 2c. As ",
"/u/iorgfeflkd",
" notes, it's not appropriate to consider the rest frame of a photon traveling in vacuum so one... | [
"Would the two particles (if we use something other than photons and at v slightly less than c), when view from my inertial frame, be closing the gap between their two origin points at 2*~c or only ~c?",
"And I think I realized that they will (E: close the gap at 2*~c) and how that does not affect their perceived... |
[
"How do we judge height on planets and moons without a Sea Level, where do we start measuring from?"
] | [
false
] | null | [
"Sea level is only relevant on a planet with an atmosphere and ocean because it tells you the likely atmospheric pressure at your location. Water has the tendency to fill in all the lowest points which makes this measurement work.",
"Mars has an atmosphere and no ocean, this means that there is really only an ave... | [
"This is actually a complicated question. ",
"Here is a quote from Ken Crowswell's book \"A Magnificent Mars\",",
"The new topographic maps, derived from Mars Global Surveyor's laser altimeter, are as informative as they are colorful. Purples depict the planet's depths, blues the lowlands, greens and yellows so... | [
"So would scientists have to scan the entire surface of a planet before they could say how high a mountain was, for example?"
] |
[
"What's the deepest point through the planet that we believe life to exist?"
] | [
false
] | null | [
"As far as I know we haven't found a place with water without life on Earth. ",
"Don Juan Pond",
" needs more studies.",
"There is certainly (even complex) life at the bottom of the ",
"Mariana Trench",
", at nearly 11 km below sea level.",
"Desulforudis audaxviator",
" has been found in rock 3 kilome... | [
"See the part about \"found\" and about water.",
"High temperatures (>150 C) seem to be quite effective in stopping life."
] | [
"It's pure speculation and imagination but I wouldn't be surprised if there's microbial life up until where the rock gets molten."
] |
[
"We have cat/dog/etc. food that seems to give a complete and nutritious diet. What is stopping science from coming up with human versions of the same thing?"
] | [
false
] | null | [
"We have",
". It's called Nutraloaf, and they serve it to prisoners when they're being punished. That should tell you something about how good it tastes.",
"I'm not sure of how many efforts there have been to produce a good tasting version, but I'd imagine it would be met with a lot of uncertainty, which I wo... | [
"Funny thing is that I have had some nutraloaf (my sister works in a prison) and i found it to be ok, so I wouldn't have an issue eating it for most of my meals if it gave me all of the nutrition that I needed. ",
"The only issue/worry that I have is with this part of the wiki article. What is needed to make it c... | [
"Thank you, that's something I didn't know. "
] |
[
"How do roots know to grow down, and sprouts to grow up?"
] | [
false
] | null | [
"The apex (top) of a root has receptors for light. through measuring the ambient light the root knows from where the light is coming and points itself away from the light source. Therefore it will grow downwards, away from the sun. The sprouts also detect light and will grow towards the light.",
"If you want more... | [
"This is a really fun question! This is due to receptors and hormones that stimulate the growth of plant cells. Sunlight stimulates plant cells in the apex of the plant to become oblong in the direction of the light. Roots cells are oblongated downward due to the stimulus of gravity. ",
"The process is a bit more... | [
"I would have expected a mechanism linked to gravity or such!",
"This means, if I shine a powerful enough LED just on the base of the stem of a plant, it would bend the roots of it to the opposite side?"
] |
[
"If the age of the Universe is measured to be 13.798 billion light years, how the observable universe can be 93 billion light years in diameter?"
] | [
false
] | null | [
"Astronomy FAQ",
":",
"http://www.reddit.com/r/askscience/wiki/astronomy/theobservableuniverse"
] | [
"I read this. But does it mean that Universe is expanding spatially with speed faster than speed of light?",
"\n(14 + 14) * 2 < 93",
"\n14 because of because of universe age",
"\n+ 14 because with speed of light only that distance can be reached",
"\n*2 because size of observable universe is given as diamet... | [
"It's also answered in the astronomy FAQ."
] |
[
"Is the CMB at the edge of the universe or is it spread throughout the vacuum somehow?"
] | [
false
] | null | [
"The CMB fills all space and every day we see CMB light from a bit father away."
] | [
"The CMB comes from everywhere in the young Universe, and it exists everywhere as well.",
"Imagine a enormous field filled with people who are all spaced 10 meters apart from one another (stretching for kilometers). All of whom have their watches synchronized, and at the exact same moment they all shout incredibl... | [
"The universe doesn't have an edge.",
"The universe used to be smaller and more densely packed. As a result for the first 380,000 years it was opaque. It was constantly emitting and reabsorbing light. Once it became transparent, it stopped doing that, and the light that was emitted just kept going. The light that... |
[
"Is there a science behind Origami, or do different shapes get discovered simply by trial and error?"
] | [
false
] | null | [
"The ",
"Huzita-Hatori axioms",
" (sometimes called the paper folding axioms) is the origami equivalent of ",
"Euclid's axioms",
" for Euclidean geometry. From these axioms we can rigorously explore the mathematics of paper folding and we can construct folding patterns by design.",
"You will be happy to k... | [
"Also, if you want a good explanation of the math behind TreeMaker and a generally readable and excellent intro to the mathematical theory of origami, Robert Lang's ",
" can't be beat. He wrote TreeMaker and developed a lot of the math behind it."
] | [
"Thank you!!!"
] |
[
"Can we say that the efficiency of an heating device (in term of energy converted) is 100% ?"
] | [
false
] | Usually when converting energy from one 'kind' to another (electrical to mechanical, thermal to electrical, etc.) there are always losses and most of the time, it is thermal loss (friction, Joule effect, ...) But if the purpose of the conversion is to heat stuff up, then it is not really 'loss', is it ? And then the ra... | [
"Yes, most conventional heaters (and most common appliances) have a heating efficiency that is effectively 100%. However, if we try we can actually do even better. ",
"Heating is one of my favorite examples of highlighting the subtleties involved in talking about thermodynamic efficiency. While in most cases the... | [
"That's absolutely right, the electromagnetic (EM) radiation emitted this way is called ",
"thermal radiation",
". In fact, any object above 0K will emit (but also absorb) such radiation. This radiation is one of the main mechanisms for how say a space heater transfers heat to warm up a room. Put simply the spa... | [
"Correct me if I am wrong, but when material is heated up to certain degree, it starts glowing, thus emiting photons and loosing energy that is not really thermal energy, until it interacts with electrons in another material"
] |
[
"Question about vaccines"
] | [
false
] | Many of you have probably already seen the post about an that the FDA has approved human trials of an HIV vaccine. My question is, can you vaccinate someone who is already infected with HIV? I would assume that perhaps the virus will mutate once an individual is infected, but if the entire point of a vaccine is that ... | [
"This vaccine is used to prevent infection with HIV by teaching your immune system to recognize the virus. HIV is a virus that uses the machinery of specific cells of the immune system; this seems like an immunization would just encourage infection if you were exposed, as it would trigger a stronger immune respons... | [
"Vaccination is used to prevent entry into cells. Vaccinating a patient who is already infected, may have efficacy, but once the virus starts replicating inside your cells it undergoes a high amount of mutation and antigenic shift, just as you suspected.",
"If you take a look at a sample of the HIV virus in a pa... | [
"thank you both, very informative"
] |
[
"How do space crafts like New Horizons communicate back to earth?"
] | [
false
] | null | [
"With radio and a directional dish antenna as large as possible subject to mass and dimension constraints. On Earth, huge and powerful antennae are used, positioned around the world (see ",
"NASA Deep Space Network",
"). It is indeed almost preposterous to think that we can receive the transmissions of the New ... | [
"That's probably already factored to the bandwidth figure. They're transmitting at such speed and with such amount of error correction that data loss or corruption is improbable - the latency would make frequent ACKs or retransmit requests completely infeasible."
] | [
"Forget the bandwidth for a second-- The latency is atrocious! You can pretty much forget about controlling anything at such a large distance in realtime.",
"Best you can do is plan everything ahead of time that it's going to be dealing with and ",
" nothing goes wrong, because if it does, you're not going to b... |
[
"My car is under an outside carport over night, and the windows do not frost while the cars not under the carport do frost. Why does this happen?"
] | [
false
] | [deleted] | [
"Also when the air cools and the atmospheric water vapour condenses it falls; that's dew. When it's cold enough it freezes; that's frost. When your car is under cover the water vapour falls on the car port, not on the car, so there's no water to freeze into frost."
] | [
"There is, but not enough to form visible condensation."
] | [
"It has to do with radiant cooling. ",
"This article",
" explains it nicely."
] |
[
"Why is PSI used as a measurement of for liquid form fluids?"
] | [
false
] | My understanding of gasses and liquids are this: gasses are inherently compressible. I can take 2 cubic feet of air and stuff it into 1 cubic foot of volume. Liquids are, from what I've gathered and been taught, not compressible, or at least not very compressible. However, in my time in the Navy, we had fireman loops t... | [
"Pressure =/= Volume change. I'm a structural engineer. We put pressure on steel, which is also incompressible. Pressure is just force over an area. The pump puts a force on the water, causing it to accelerate (Newton's second law)."
] | [
"Liquid incompressibility is a myth. They compress much less than ",
" gases (a few % vs 99+%), but they do compress.",
"Check out Figure 4 in page 418 of the following article: ",
"https://link.springer.com/article/10.1007%2FBF00503880",
"You'll see the density (mass per volume) of n-pentane at a range of ... | [
"They compress much less than fluids (a few % vs 99+%)",
"The compress much less than ",
" for the same pressure rise, you (presumably) mean. Both liquids and gases are fluids."
] |
[
"Is there a physical limit to how fast something can travel in water?"
] | [
false
] | null | [
"The physical limit is 225000000m/s. As that is the speed of light in pure H2O.",
"The speed of light in a medium is not the speed limit of objects in that medium."
] | [
"The physical limit is 225000000m/s. As that is the speed of light in pure H2O.",
"The speed of light in a medium is not the speed limit of objects in that medium."
] | [
"Yes, but it depends on a lot of things, primarily including the shape of the object and how much propulsive force it has. For a smooth-shaped object with little propulsive force moving through still water, ",
"Stokes drag",
" applies and can be used to find the terminal velocity of the object. At higher speeds... |
[
"Will monozygotic twins have the same sexual orientation and why?"
] | [
false
] | E.g. If they are both male and one of them is a homosexual, does that mean that the other one is probably a homosexual too? What determines this (genes, the environment they are in, the combination of multiple factors or something else)? What about a monozygotic male-female combination (I know this is VERY rare), how w... | [
"Do gay identical twins (same egg and sperm) prove the existence of the \"gay gene\"? If one is gay, must the other be gay as well?",
"Top comment is...",
"/u/zebbielm12",
"Twin studies are done specifically to separate the effects of genetics and environment. Most twin studies done on this subject suggest a ... | [
"Just because the genetic influence is only 20% doesn't mean that a wild wizard waving his wand at 6 months gestation isn't what results in homosexuality.",
"There is an interesting study on males whose mother as already had a boy more likely to be gay.",
"Could be a result of changes in parental behavior with ... | [
"Wow, only ~20%? I am surprised. ",
"Thanks for the link."
] |
[
"Please help me clear up a few things about the Cosmic Background Radiation."
] | [
false
] | From what I understand, it's uniform (for the most part) and comes from every direction. If you look out 1 light year, you're looking 1 year into the past. If you're looking out 1 billion light years, you're seeing the universe as it was 1 billion years ago. So if you look out ~13.5 billion light years out, you're s... | [
"If you're looking out 1 billion light years, you're seeing the universe as it was 1 billion years ago. So if you look out ~13.5 billion light years out, you're seeing the universe as it was right after the big bang",
"An unfortunate property of cosmology is that there are a large number of ways in which to defin... | [
"Right now the CMB we're seeing was emitted from galaxies sufficiently far away that the light has taken 13.7 billion years to reach us",
"The CMB was not emitted from galaxies.. From your knowledge I suspect you know this and just mis-typed, but it's an important distinction. It was emitted from the cosmic goop ... | [
"It absolutely is an important distinction that I correctly made elsewhere but missed there; thank you for catching it."
] |
[
"Why are there varying winds?"
] | [
false
] | If the earth is constantly rotating, why isn't there a constant breeze, or why doesn't the air keep momentum with the earth and not become wind? I'm sure it is an easily answered question, and anyone who can, thanks! | [
"Wind is caused by the sun heating the atmosphere. The warmed air is less dense and pushes its way above colder air, creating small convection cells that change constantly.",
"The coriolis effect, which is caused by Earth's rotation, ",
"does affect weather patterns",
" but on a large scale - a scale that doe... | [
"Okay, that's easy to understand, thanks!"
] | [
"Coriolis affects things on a far smaller scale than Global. ",
"Synoptic and Mesoscale weather are also quite happy to be affected by Coriolis force",
"for instance a Hurricane is a Mesoscale weather phenomena and it is quite obviously under the influences of coriolis"
] |
[
"Why does sour taste trigger your taste glands to release saliva ?"
] | [
false
] | Why do your taste glands release saliva when you eat something sour but not when you eat something sweet or bitter? I've noticed this everytime I eat something sour but haven't seen it with any other type of flavor. Is it a specific gland that releases saliva ? | [
"There's a handful of glands that release saliva, with the bulk coming from the parotid, submandibular, and sublingual glands. ",
"All of the basic tastes stimulate salivation, but sour is the strongest, followed by salty. Generally, sour receptors respond to acidity. While high concentrations of sugar are harmle... | [
"the pain one sometimes feels slightly below the ears when eating something sour (usually quite intense if you haven't eaten anything in a while) is smooth muscle contracting around the glandula parotis (main saliva gland). the muscle contracts and \"wrenches\" out the saliva. this is sometimes a little painful."
] | [
"Saliva also contains the protein buffer system, which involves IgA (antibody), amylase and perhaps albumin.",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1803027/"
] |
[
"Does the colour at the end of a mirror tunnel depend on the materials the mirrors are made of?"
] | [
false
] | [deleted] | [
"My initial thoughts are yes, using different glass will change the color of the infinite mirror tunnel. As light travels through different medium it refracts with the change of index of refraction. Looking at yourself through one mirror gives you 2 passes through the soda-lime glass. Looking through the mirror tun... | [
"Actually, when I was talking about the mirror tunnel, I was referring to endless reflection of two mirrors facing each other. If you look into the infinity that is thus created, you can see that the reflection gets dimmer and dimmer, and also colours green. I wanted to know whether the green colour at the end of t... | [
"... Will the colour at the end change if we use glass of different colour.",
"Yes. The glass, the reflective material, and the air will affect the color. You can also stick a filter in the path between the mirrors."
] |
[
"Is it possible to compress a liquid?"
] | [
false
] | null | [
"Of course. Water for example is commonly referred to as incompressible, but that is just a shortcut for common conditions. Water ",
" be compressed, it just takes a lot of pressure for not very much change. Other fluids are similarly behaved."
] | [
"Yes. "
] | [
"water phase diagram"
] |
[
"How do I grow a large crystal ~a few cm of NaClO_3?"
] | [
false
] | I have 500g of 99% reagent from Aldrich Chemical. I need something ~ cm in size. The bigger the better. I have not processed a chemical since high school chemistry. Pointing to some helpful resources would suffice, but any help is appreciated. Thank you. | [
"You'll want to create a saturated solution of the Sodium Chlorate in water. This can be done by slowly adding NaClO3 into water until no more will dissolve. I'd start with a small amount of water at first and scale up once you've had some success. If you then allow the water to evaporate slowly then crystal(s)... | [
"Hey, just FYI, thank you. I got some nice ones. :-)",
"Edit: ",
"I like them anyway!"
] | [
"Cool, glad it worked out!"
] |
[
"Do plants absorb water vapor from the air?"
] | [
false
] | I live in a highly humid climate. Naturally we get plenty of precipitation, but I was wondering if plants can absorb any amount of water from the air, or do they get all of their H20 through the roots? If plants can absorb water from the air, why can't they absorb enough to sustain themselves? If they can't, doesn't th... | [
"Some plants, like ",
"epiphytes",
", do absorb water from the atmosphere. They are the exception. ",
"The vast majority of plants need to lose water to the atmosphere, in order to get water from the ground. They do this by opening ",
"stomata",
" on the underside of their leaves. That lets water evaporat... | [
"Worth noting that epiphytes and broyophytes aren't really an exception in the usual sense of the word, as they are ",
" common and diverse in the tropics. I have some awesome photos of trees in the mountains of Ecuador that are covered in more leaves from other plants than their own leaves. (will provide if requ... | [
"http://en.wikipedia.org/wiki/Pleopeltis_polypodioides#Habitat_and_water_absorption",
"TL;DR Yes. Here is an extreme example of that sort of adaptation."
] |
[
"If I have 6 standard C cells, and four are fully charged while two are close to dead, is there an optimal way (for saving charge) to put them in a six-cell battery?"
] | [
false
] | I am a poor musician with a battery-hungry instrument. | [
"The optimal way is to get two more fully charged ones; the close-to-dead ones, no matter how you put them, will put extra internal resistance into the circuit and drain the good ones faster. "
] | [
"If you don't find a satisfactory answer here, try posting to",
" /r/askelectronics",
" as well."
] | [
"I'm assuming here that you don't have access to two more good batteries or you wouldn't be asking the question.",
"Put in the four charged ones, and use bits of wire to short out the other two battery slots. The dead C cells will act as resistors (turning the charge of the good batteries into waste heat) if you... |
[
"Can people with lazy eye choose which eye to use and alternate between them?"
] | [
false
] | [deleted] | [
"Optometrist here. The answer is \"sometimes,\" and \"it depends.\"",
"\"Lazy eye\" means many different things to different people. The clinical definition of lazy eye, or \"amblyopia\" is an eye with reduced vision not due to any organic cause. Basically it is a healthy eye, but due to hindered development, doe... | [
"Latching on to this to give personal experience. I can make a concious effort to \"use\" my lazy eye, but I end up with double vision when I do so as my brain tries to refocus back to the \"good\" eye. "
] | [
"i heard that if a baby has a lazy eye then you can put an eye patch on the good eye for a month or two and the lazy eye gets strong again? true story? or false as farts?"
] |
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