title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Why do some people see this dress as Black and Blue, while other people see it as Gold and white?"
] | [
false
] | null | [
"This is the only question about the dress that will be on askscience today! All other dress questions will be removed! ",
"Please do not make top-level posts in this thread unless you have relevant expertise.",
"Do not speculate, or post about what colour you see it as.",
"If the thread becomes out of contro... | [
"Hi! me and some other grad students have been discussing this for the last half hour. It's likely due to some kind of ",
" illusion, where some people are perceiving the context to be something like \"lit by blueish daylight\" and others are perceiving it to be something like \"under yellow department store ligh... | [
"Hey, so this post turned into about 50 anecdotes and your comment. We've opted to make a ",
"post using our moderator account",
" so we can moderate it more easily/sticky it/paste the expert explanations into the body of the post. I'm letting you know in case you want to repost your comment in that other threa... |
[
"For every pound of excess fat, how much vascularization and innervation needs to be created to support that this adipose tissue?"
] | [
false
] | I am really curious about the capillaries and nerves that are undoubtedly created when excess fat is stored in the thighs, butt and abdominal region. If one is fat enough and the blood has to circulate through so many more meters of blood vessels, does that put an extra strain on the heart? | [
"does that put an extra strain on the heart?",
"Precisely. The more vascularization there is, the more the heart has to work to pump blood. That is precisely one if the major concerns regarding obesity - the weight puts an enormous strain on the heart, which can damage the organ if it its stressed for a sufficien... | [
"This is also why excess fat ends up having areas of necrosis (dead cells and debris): angiogenesis can't keep up with fat deposition in the obese setting, and so once cells get outside the range of diffusable oxygen, they die. Because vascular and lymphatic networks also deliver circulating cells responsible for c... | [
"I see. Is this why obese people who also happen to be diabetics run the risk of peripheral vascular disease (and eventually an amputation if an infection persists)? Why does the diabetes make the circulation so much worse? "
] |
[
"Do we know whether Covid is actually seasonal?"
] | [
false
] | It seems we are told by some to brace for an epically bad fall. However, this thing slammed the Northeast in spring and ravaged the “hot states” in the middle of summer. It just seems that politics and vested interests are so intertwined here now that it is hard to work out what is going on. I thought I would ask some actual experts if they can spare a few minutes. Thank you. | [
"Emergency Physician here: It’s not because we expect ",
" to be worse, it’s because of all the other Acute Febrile Respiratory Illnesses (AFRI) that ARE seasonal will also occur. Flu pushes US hospitals to brink of capacity most years without any additional new pandemic. And because the symptoms of most are ove... | [
"It's not seasonal because the disease is obviously still ravaging us in peak summer like you say. ",
"However fall and winter are still of particular concern because of a few things: ",
"1) even though the virus does survive in the heat and it should be even more stable (and thus more infectious) in the cold "... | [
"Shouldn't there be less seasonal infections than in previous years due to people wearing masks/washing hands?"
] |
[
"My friend found what He thinks is a meteorite from space in his neighbor's yard. Anyone who can chime in on identifying the mystery object?"
] | [
false
] | null | [
"It's a big marble",
"http://www.rainbowturtle.com/meteor-50mm-marble-p-434.html",
"\n",
"http://www.rainbowturtle.com/chrome-steel-marbles-p-5584.html",
" ",
"This has got to be the most unusual website I've cited for AskScience since LOTRwiki"
] | [
"Or someone dropped it. It may have been there for a while."
] | [
"Which would mean either he's lying or someone is firing marbles out of a cannon somewhere. thanks for input."
] |
[
"Could a satellite gather molecular gases from orbit to maintain its orbit?"
] | [
false
] | [deleted] | [
"It's an active area of R&D. The European Space Agency test fired such an engine in a vacuum chamber earlier this year.",
"https://en.m.wikipedia.org/wiki/Air-breathing_electric_propulsion",
"Conservation of energy is not broken because the engine would take in gas and then use solar (or nuclear) power to expel... | [
"Xenon easy to ionize compared to other noble gases. Atomic oxygen and nitrogen are pretty close. And it gets more complicated when considering molecular gases. The lower molar mass shifts thing toward a higher Isp and lower thrust to power ratio but it's not necessarily a deal breaker. ",
"My point is that it's ... | [
"The ESA study is essentially an ion thruster that uses ambiant gas as propellant. The issue with xenon is that it's a pain to store. You need to get it to 150 to 200 bar to get in the supercritical range and that results in bad mass fraction. Some people believe that the inlet/collection device can be lighter than... |
[
"During a solar eclipse if you followed the path of totality how fast would you need to be moving to stay in darkness?"
] | [
false
] | null | [
"It comes out to basically the speed of the Moon's orbit, which is about 1 km/s or 3600 km/h.",
"As the Moon orbits the Earth, it moves relative to the Sun, and that makes its shadow move relative to Earth. If the Moon moves 1° relative to the Earth-Sun line, then its shadow moves 1° from that line. So the angula... | [
"On the 30th June 1973 Concorde did this, experiencing totality for 74 minutes. This was already quite a 'long' eclipse with totality from the ground of just over 7 minutes, which makes the aircraft tracking an easier task. Concorde was capable of flying at 600 m/s or Mach 2."
] | [
"Right - this is the speed relative to the centre-of-mass of the Earth. If you're actually, you get some speed for \"free\" because you're already rotating with the Earth. The Moon is orbiting in the same way the Earth rotates - west-to-east - so in practice its relative speed is a bit lower than that.",
"At the ... |
[
"Could the principles behind the dyson bladeless fan be applied to airplane wings?"
] | [
false
] | This isn't just layman's speculation, I'm genuinely curious about this phenomenon and would greatly appreciate it if anyone knows more about it. I always thought it was interesting how the dyson bladless fan works. By using an impeller at the base, drawing air in and forcing it out through narrow slits along wing shaped disc, it creates a flow of moving air from an otherwise motionless surface. But this got me thinking, could airplane wings use the same feature? I'm under the impression that lift is created by air moving at different velocities as it passes under and over a wing. I imagine that an aircraft might be able to direct some of its thrust specifically over the wing, even by narrow slits all across the leading surface such as in the dyson fan. The design implications could be profound, such as an ability to maintain very slow flight. Despite a low airspeed that would normally cause a stall, the actual speed of the air moving over the wing would be much higher. I imagine it would operate something like the custer channel wing, (link: ) but much more compact. I swear I once saw a wikipedia page about a Navy aircraft that operated on a similar principle, but I can't seem to find it. EDIT: I am aware that many airplanes use the Coandă effect by the placement of their engines, but I'm more interested in knowing whether this application has been taken to the extreme I also wonder what the potential drawbacks to such a design would be, as it clearly isn't a popularly implemented feature of modern day aircraft...but then again maybe most designers haven't put much thought into it. | [
"I actually worked as a research assistant on something very similar to this for a summer during college. ",
"Here's a paper",
" that describes some of the basic ideas behind the research. I specifically worked on testing different configurations of jet geometries for a standard NACA airfoil (forget which one... | [
"Taking this to the extreme would mean that the engine exhausts in a thin slit over the entire wing, and the wing directs this jet downward for additional thrust. Routing exhaust this way would be very lossy (inefficient) and would be worse than useless at high speeds, where efficiency, rather than lift, is the pri... | [
"There is a fan with blades in the base of the Dyson unit."
] |
[
"If one's optic nerve were severed, but the occipital lobe wasn't damaged, what function would neuroplasticity give this useless heap of tissue?"
] | [
false
] | I was wondering what happens here with blind people. I hear their other senses are heightened and some can even echo-locate. Is this a result of neuro-plasticity? | [
"First, its important to mention that there are other destinations for visual information in the brain, not just the occipital lobe. I'll trace out the pathway below, hopefully making it easier to understand.",
"When light enters the eye, it is transduced by the rods and cones in the outer layer of the neural re... | [
"it is a rare phenomenon in which visual information from the lateral geniculate nucleus is cut off",
"Blindsight is broadly any disorder where visual perception is disrupted, but some low-level visual processing still occurs. For example, a stroke that takes out the visual cortex renders someone perceptually bli... | [
"You may find ",
"this article",
" of interest. It talks about what happens in the brain after damage to a lot of different parts of the visual system. Figure 1 is pretty good, it shows you what happens to someone's visual field if you damage different parts of the visual pathway.",
"One thing that may occur ... |
[
"Why do some parts of the eyes not need blood vessels?"
] | [
false
] | null | [
"The cornea and lens both lack blood vessels, since they need to be clear for good vision.",
"The cornea (front window of your eye) is only about 0.5 mm thick, enabling it to get the oxygen it needs via diffusion (the front half gets oxygen from the outside air, and dissolved O2 in the tear film. The back half ge... | [
"Nuclear Caddy pretty much nailed it.",
"The fact that your cornea does not need or have blood vessels in it, also means the body's immune system also has much more limited access to the cornea. This explains why a corneal transplant from person to person in 1905 was (more or less) the first successful transplan... | [
"Yep!",
"That said, it can last a lot longer on a little bit of oxygen.",
"The scary one is Contact Lenses. This is part of the reason why you have to change your contacts, since wearing them too long can damage the cornea easily."
] |
[
"Tap water looks a bit grey on 11th floor. One roommate says its the chemicals, the other says its the building pipes pressure that makes small bubbles. Who is right? (We are in Santiago, Chile)"
] | [
false
] | null | [
"That high up, the water is pressurized by auxiliary pumps. It may very well be small bubbles, or it could be sediments in the pipes being disturbed by the higher pressure."
] | [
"most likely from the booster pumps used to push it that high. "
] | [
"Fill a glass and let it sit for a bit. If it clears up, BUBBLES! If it doesn't TIME TO MOVE!"
] |
[
"If we just connected Europe and America with a wire, would electric current flow through it?"
] | [
false
] | By connecting continents with a wire I mean just plugging it into the ground. I read somewhere that electric potential in the ground is not the same everywhere on Earth - in fact, it varies greatly. Is this true? If so, why don't we harvest energy this way? | [
"The OP is talking about static charge in the crust of the earth and not electricity grids."
] | [
"Depends on the wire. Here's a handy table to look up the resistance of various gauges and lengths of copper wire.",
"http://www.cirris.com/testing/resistance/wire.html"
] | [
"There are already optical fiber wires across oceans. Sounds like it's doable. Why doesn't it make sense? If the current is very strong, perhaps it is cost effective. I'm really curious."
] |
[
"In snowy mountain areas, avalanches occur, we all know this, but does the same happen in the desert on high dunes?"
] | [
false
] | null | [
"Yes, avalanches ",
"are common and are a fundamental part of how dunes behave/evolve",
". Basically, grains roll and bounce along the windward, more gentle side of a dune and are deposited at the top of the leeward, steeper side of the dune (i.e. the slip face). These grains build up until they destabilize the... | [
"Its misleading to think of those avalanches in the same way snow avalanches occur however. Sand \"avalanches\" are never* large enough to be dangerous. Snow can form different layers with different densities and cohesions that can build up to a dangerous instability, whereas sand will slide almost immediately afte... | [
"Yes, they do. They move pretty quickly (at least compared to other geologic processes), so we can actually measure their migration, ",
"e.g. this paper",
". "
] |
[
"How much man-made space debris is there?"
] | [
false
] | Pictures I see on the internet show space debris covering most of the surface. Obviously, the actual debris isn't that large or we'd be seeing it in the sky everyday. So, how much is actually there? What happens to it? How do we avoid the debris hitting spacecraft? | [
"Yes, there is that much stuff and most of it isn't that large. Space is huge compared to space debris. I'm not sure how much debris and obsolete spacecraft there are, but it's a lot, and it's mostly by chance that spacecraft aren't converted into space debris constantly. Save for the International Space Station an... | [
"I think the other way to visualise the danger of debris is to consider the damage that ten grams of metal flying at a kilometre a second does to a person. (Hint: I'm talking about bullets).",
"Objects in orbit are traveling at around nine times that speed. Getting hit by one fucks anything up."
] | [
"A paragraph I got off of someone a while back, don't have time to crop it but it's about a space elevator + debris.",
"\"If I were at FAA or NTSB I would be vocally worrying about the implications of the SoaceX plan to launch 4000 internet satellites in the 1200 to 1500 mile orbit range, possbly to be expanded t... |
[
"Why are most of the world's oldest trees found in North America?"
] | [
false
] | After looking at this on wikipedia, I realized that nearly all of the world's oldest trees come from North America. It is so definitive that there must be a reason backing this up. Could anyone give an explanation? | [
"Last continent colonised? "
] | [
"Probably this. We humans have changed the environment around us so much that anything living on a huge timescale is likely to be negatively effected. Look at the California redwoods, now mostly gone in a single century.",
"Also, you may have noticed many of the oldest trees are pines and grow in high, dry area... | [
"This would be my first thought as well."
] |
[
"Will chewing gum make your stomach secrete acid and enzymes?"
] | [
false
] | I was reading something from a natural foods book about when you chew gum that you'll release stomach acid and enzymes. Apparently when you actually eat you may be low on stomach acid and enzymes which will lead to gas and bloating. Is any of this true? | [
"When the acidic content from the stomach enters the first part of the small intestine, feedback mechanisms are activated that reduce the further excretion of stomach acid, and that neutralize the acidity of the partially digested food as it travels further down. Imagine it as if the small intestine tells the stoma... | [
"Yes. Gastric secretion, that is secretion of acid and enzymes (pepsinogen) in the stomach, occurs or is regulated in three phases: the cephalic, gastric and intestinal phases. In the cephalic phase (cephalic comes from the Greek word for brain, ",
") which is stimulated by factors in the head and pharynx, thinki... | [
"And the secretion isn't really inhibited by anything other than the small intestine.",
"Thanks for the answer! Glad to see this sub-reddit has great comments (first time here). ",
"The only thing I didn't understand is when you said... \" And the secretion isn't really inhibited by anything other than the smal... |
[
"Our Sun and Andromeda"
] | [
false
] | [deleted] | [
"First, our sun isn't going to undergo a supernova event. It's too small for that.",
"Second, while the sun's orbit about the galactic core could certainly be affected, it's unlikely that the orbits of the planets about the sun would be altered much, if at all. "
] | [
"There will, if I remember correctly, be about 6 (six) collisions between stars when the galaxies meet. I don't think we need to be too worried."
] | [
"Heh i'm not worried. What happens is gonna happen."
] |
[
"Do we know of some species with more than two sexes?"
] | [
false
] | Wouldn't having more than two sexes some evolutionary advantage like two sexes reproduction has over one? (in terms of variations,etc.) Even if that is not true why aren't species with three (or more) sexes not common? | [
"There are sparrows with 4 sexes",
"Fungi: Well... ",
"it is complicated",
". ",
"Really complicated"
] | [
"Thanks for the links about the sparrows. It was a really interesting read."
] | [
"“This bird acts like it has four sexes,” says Christopher Balakrishnan, an evolutionary biologist at East Carolina University in Greenville, North Carolina. ",
"Acts like. There are still two distinct sexes, but a chance mutation led a further differentiation due to a problem with chromosome two, leading to com... |
[
"Does pasta have to be boiled in order to cook properly?"
] | [
false
] | null | [
"Boiling increases diffusion, so it can speed up the process.",
"\nAlthough it's not essential, you can try by pouring boiling water over pasta and leave it, it'll get soft as well."
] | [
"Water diffusion into the pasta.",
"\nAlso - heat diffusion - water is 100 C but pasta is not."
] | [
"Diffusion of what? Heat? The water can't gain any more heat, that's why it's boiling."
] |
[
"How would an earth size planet following our exact orbital path and speed on the other side of the sun affect us?"
] | [
false
] | Would there even be any noticeable difference on Earth? Would it have any affect on tides, the lunar orbit, how seasons changed, or what the pull of gravity is on earth? How would it affect other planets in the solar system? | [
"This plot would be symmetrical if there were an Earth opposite in the L3 position. "
] | [
"Planetary orbits are known with precision, and a body that size would perturb the orbits of other bodies.",
"Earth Two would have shown up in photos taken of Earth from the deep solar system.",
"If the Earth's orbit was more eccentric it would surely be visible from here, because of the properties of an ellipt... | [
"I think it couldn't be in the same orbit instead it would have to be in the earth sun L3 point. ",
"http://en.m.wikipedia.org/wiki/Lagrangian_point"
] |
[
"Are \"zero calorie\" sodas really zero calories?"
] | [
false
] | I find it hard to believe that the ingredients in soda will not release any heat when the body breaks it down. And if this is so, then if calories are just a measure of heat/energy, wouldn't the soda have calories? Or maybe I am just completely wrong and the ingredients don't release heat/energy when the body breaks it down. Could anyone explain it please? | [
"According to the ",
"FDA",
", foods with between 0 and 5 Calories are considered \"Zero Calorie.\" Keep in mind that your body is not capable of breaking down every molecule you consume. Regular pop contains a lot of sugar which you can metabolize and is thus a source of Calories. Diet pop contains artificial ... | [
"The only significant contributor of calories in sodas is the sugar. Diet sodas use sweeteners that trigger sweet sensations, but do not yield any meaningful usable energy when broken down.",
"Source"
] | [
"Yup. I acutally never thought of it like this before and my original answer was \"HELL NO!\" But then I did the math (below) and can't seem to find a reason why you would be wrong. Heck it has been a while since I have been in undergrad (for heaven's sake I was a double major bio and chem major but am not in denta... |
[
"In the human body, does being in (great) pain = damage?"
] | [
false
] | [deleted] | [
"No. Your sensory system can be mistaken. (e.g. ",
"allodynia",
")"
] | [
"Yes it does. Living in chronic pain causes physiological changes to the body. This article describes the effects of pain that are experienced from all of the body's systems: ",
"http://www.nursingtimes.net/nursing-practice-clinical-research/understanding-the-physiological-effects-of-unrelieved-pain/205262.articl... | [
"A more interesting question is: does ",
" horrible pain alter any pathways in the brain. Any alteration of brain chemistry due to the experience itself could be called \"damage.\""
] |
[
"If lightning was fired into a vacuum, would it appear straight?"
] | [
false
] | Wondering why lightning is always a jagged shape | [
"You could not fire lightning into a vacuum. Lightning isn't a physical thing, it is the process of an electric current discharging through the air. When the sky and earth build up a difference in charge to a sufficient degree, the electrical resistance of the atmosphere is overcome and electrons flow between the e... | [
"I think this is 90% right, but it might be even more clear if you mention that as the lightning propagates, the air is being ionized (electrons being stripped from the molecules), forming a plasma.",
"In a vacuum, there's no molecules that can be ionized to form plasma, therefore, no lightning."
] | [
"Thank you, yes."
] |
[
"Carbon dating method requiring \"best guess\" before measurement?"
] | [
false
] | This question just came up in my Facebook feed and is most likely some sort of creationist pablum, but I checked talkorigins.org and did my best to sift thru a couple other sites but could not find info on this. Here is the original post: I work with a young Earth creationist contractor who swears carbon dating is nothing but a hoax. He mentioned that if you request an item to be carbon dated the application requires you to estimate the age of the object. It surprised me so I went to verify and he was correct that it asked, but I did not see anything saying it was required at least for the 3 sites I searched. I am awaiting a response back from the sites as to why they ask for this but was curious if anybody else had heard that. I've asked OP for clarity since it's definitely lacking, but has anyone heard of this? Is this a thing? Edit: Here's the site he's talking about: | [
"My guess is that an older sample will require more precise instrumentation to get an accurate measurement. If the sample is getting close to the limits of what radiocarbon dating can be used for, there will be very little C-14 left, which means that great precision will be necessary to establish the correct age, b... | [
"Well, I haven't done anything with radiocarbon dating yet, but I have a few thoughts. You do have to be able to account for the atmospheric concentration of Nitrogen-14 (I think it's N-14, it may be C-14), I believe, during deposition. Since N-14 varies, it can skew results. But we have pretty good estimates for h... | [
"It's almost certainly to do with trying to fit to the correct place on the C14 curve. The amount of C14 int he atmosphere varies with time. Without this information, you'll get a ballpark figure with a larger error on it than you would with an estimated age, which would allow more precise calibration to the curve.... |
[
"With the recent discovery of at least one planet around Alpha Centauri, do we have the technology to directly observe the planet to any significant degree? If not, what would it take?"
] | [
false
] | Say a planet just like Earth is orbiting Alpha Centauri, would we be able to observe it well enough to distinguish continents and oceans? Even more? If not, how likely are we to develop the technology within this lifetime? | [
"Directly observing with visible light is limited by two things:",
"The angular resolution of your telescope",
"Capturing enough light.",
"These are both improved by building a bigger telescope. I don't know the size of this planet, but let's say it's Earth-sized, and 4.37 light years away. I'll call \"observ... | [
"Aren't there arrays of radio telescopes all across the earth that do this same thing? So if they all pointed to Alpha Centauri, they could theoretically observe the planet?"
] | [
"I think if you combined these you would have enough angular resolution to study the planet, but I'm not sure if radio telescopes can be configured to produce images (or if radio images are even useful)."
] |
[
"If the human eye could record video, how much space would one minute take up? (x-post from /r/AskReddit)"
] | [
false
] | Assuming it was being recorded at "full quality" and the highest "framerate" (for lack of better words) | [
"The human eye does not have a frame rate. The amount of data would be very dependent on how you sampled the signal. "
] | [
"The eye itself uses pre-processing and compression strategies before sending the image to the brain. ",
"This article",
" estimated the bandwidth of the optic nerve to be about 8.75 megabits per second, which is around 1 megabyte per second.",
"So a minute would put you right around 60 MB. Note that the 60... | [
"I was thinking more along the lines of a raw video feed, but this was really helpful"
] |
[
"How does obesity physiologically increase one’s cancer risk?"
] | [
false
] | null | [
"I can explain for some cancers.",
"Body fat which contains cholesterol can provide ground substance for producing steroid hormones one of which is oestrogen. Excess fat - > excess oestogen. In females, oestrogen has stimulator effect on breast and uterine lining-endometrium. Stimulation - > increased multiplicat... | [
"Yes they can but obese people are more likely to have larger amounts of visceral fat. ",
"Your points were sweeping generalisations which I felt mislead the person who asked the question so I thought I’d put a counter point. If you still think what you said was more accurate then it’s up to them to do their own ... | [
"Yes they can but obese people are more likely to have larger amounts of visceral fat. ",
"Your points were sweeping generalisations which I felt mislead the person who asked the question so I thought I’d put a counter point. If you still think what you said was more accurate then it’s up to them to do their own ... |
[
"Can someone explain Faraday's Law and Lenz's Law to me please?"
] | [
false
] | Any explanation would be awesome, I just need a better understanding of it. Examples/Diagrams would be helpful. | [
"What kind of understanding of calculus do you have?"
] | [
"A pretty good one I'd say.\nI've taken up to calculus 3 at my university and now I'm in linear algebra and differential equations"
] | [
"What is your current level of understanding of Faraday's law? What is it that you're having trouble understanding? Did you look at some YouTube videos and Wikipedia?"
] |
[
"How can the Higgs boson be everywhere? How come we don't see it if so?"
] | [
false
] | I know we feel its effect, but if it's everywhere surely we should be able to see it - and anyways, how is there enough energy to make higgs bosons for the whole of the observable universe? | [
"Nah, the Higgs boson isn't everywhere. Higgs bosons are pretty rare.",
"The Higgs' vacuum expectation value (VEV) is everywhere and it's pretty big. We don't see it because it doesn't couple to photons, which is why photons are massless. It gives mass to the other fermions and bosons, and that's all it does at l... | [
"sort of, it's the value that the Higgs field has in the ground state. For most fields, that's zero, not so for the Higgs field."
] | [
"Sorry, what's a Vacuum expectation value? Is it like the default state of the Higgs field?"
] |
[
"How does a magnifying lens concentrate heat from sunlight along with the light, and do so without getting hot itself?"
] | [
false
] | i've been playing around with this fresnel lens i took from an old projection tv and i started wondering how the heat from sunlight could be condensed. | [
"Lenses don't concentrate heat, they only concentrate light. The effect you're noticing is that the light gets converted to heat when it strikes a material. "
] | [
"It's easier to talk about a round glass lens than a fresnel lens, so I will. But first some theory.",
"Light heats a material because the electron cloud of a material will absorb some particles of light and the energy they carry (I mean they're moving pretty fast, there's a lot of energy to dissipate). Materials... | [
"As gammalbjorn alluded to, some of the energy in the sunlight is actually absorbed and converted to thermal energy in most lenses. Not all the visible light is transmitted - maybe 15% is absorbed. Also, depending on the type of glass or plastic, much of the infrared and UV wavelengths are absorbed in the lens. (He... |
[
"If warm water has energy that can be used, does frozen water also have energy?"
] | [
false
] | null | [
"A heat engine requires two reservoirs at two different temperatures to extract work. A heat pump is a heat engine in reverse. You are expending work, not extracting any."
] | [
"A heat engine requires two reservoirs at two different temperatures to extract work. A heat pump is a heat engine in reverse. You are expending work, not extracting any."
] | [
"Warm water doesn't have energy that can be used unless you have something colder as well. You can only get energy out of a temperature ",
". Transferring heat from a hot thing to a cold thing gives you usable energy. But a system where everything is at the same temperature has no usable thermal energy regardless... |
[
"Why does time have a direction?"
] | [
false
] | really, I'm just curious about time in general. Please don't refer me to a particular book for information, I don't really have time to research in depth. Condensed answers are good enough | [
"Because not all processes are invariant under time reversal. On human scales entropy increase is the most noticeable example, but there are others too.",
"Or do you mean some kind of philosophical why? We can't really help you there."
] | [
"Further to your comment, the 2nd law of thermodynamics is an axiom. We have no way to prove that entropy is an intrinsic law of nature other than it is a feature we continue to see over and over again. ",
"Philosophy of science seems like an interesting thing to argue, but at the end of the day it usually gets y... | [
"Well considering that all systems increase entropy, it is no suprise that we perceive the arrow of time in the direction we do. Human beings need to increase entropy to function, therefore the more chatoic path is the \"down stream\" side of time for us. If there was a being that ran off a decrease in entropy then... |
[
"What's past the cosmological horizon?"
] | [
false
] | Do we know what's past the cosmological horizon in the un observable areas of the universe? | [
"By definition, no; the observable universe encompasses all that we can have any information about. But there's no particular reason to imagine it would be much different from the local area--it's just impossible to confirm."
] | [
"As the universe is the same everywhere we can look it should be the same in places a bit farther out as well. But this is purely inference, we can't observe it by definition."
] | [
"The definition of the cosmological horizon has it that it is the furthest we can have information from; there's no way of knowing about anything further. The ",
" is that it's just more space, the same of here, nothing of interest. From there you can speculate on things such as the ",
"shape of the universe",... |
[
"Is string theory relativistic?"
] | [
false
] | Is string theory Lorentz invariant or is someone going to have to reconcile that later after they better understand what it is? | [
"String Theory obeys relativity and concepts like Lorentz invariance."
] | [
"String theory is meant combine quantum field theory and general relativity. Both require Lorentz invariance, so string theory would naturally have it as well.",
"I can't imagine any unified theory not incorporating it as well."
] | [
"The reason I wonder is that I have read that string theory is not background free and remains a purturbative theory. Not understanding that very well I wondered if it implied that string theory, as currently formulated, is not Lorentz invariant.",
"OTOH, as you say, if it successfully becomes a theory of gravit... |
[
"When turtles pull their heads into their shells, do their spines buckle or contract?"
] | [
false
] | I was reading Cat's Cradle and I stumbled upon this fascinating question. Unfortunately, it was left unanswered. If they neither buckle nor contract, then how do they get it all to fit? | [
"Good question. There are actually two answers to it. Two main suborders of turtles exist - Cryptodira...most turtles and tortoises that you encounter including freshwater turtles, snapping turtles, tortoises, soft shell turtles, and sea turtles actually lower their head and contracting their vertebrae to allow the... | [
"Nice answer - just to add a clarification, in cryptodires the vertebrae don't \"contract\" exactly; the neck just deepens its bend in the vertical plane (as opposed to side-necks in which the neck bends in the horizontal plane). When a cryptodire pulls its head in, the neck basically goes from ",
"this position"... | [
"All vertebrates have spines. In turtles its ",
" the shell, but it's still there."
] |
[
"I do not understand the nature of light... I do not know what I do not understand about it either..."
] | [
false
] | So, I'm looking at a star -- say the North Star. Now, I understand that there is a stream of particles (waves?) flowing from the surface of the North Star straight into my eyeball... Also, the light emanating from Polaris is moving out in all directions from the surface of the star. ( I imagine a sort of shell of light [composed of trillions of photons] pulsating from the star, the thickness of a photon, over and over again.) How is it that I can look in the sky and see the North Star as a of light... I assume it has to do with the surface area of the star (how many photons are being emitted) and the size of a photon and in relation to the size of my eye -- But, I really don't get it... | [
"Imagine that the surface of the North Star is spherical. Now, pick any point on the surface of that sphere, and draw a line from the very center of the sphere, through that point on the surface, and continuing outward. Now, imagine that there are lines like that coming out of every possible point on the surface of... | [
"How is it that I can look in the sky and see the North Star as a point of light…",
"Because your eyes have lenses in them that focus the light that intersects them, forming an image.",
"It's the same basic idea as exposing a piece of photographic film to light, versus putting it behind a lens. In the first cas... | [
"That still doesn't make sense to me... I think it has something to do with the <refresh rate> or whatever you would call it biologically... For instance, if you do a long-exposure you get light trails... Those light trails seem to be a more reasonable depiction of reality than what we actually perceive. ",
"Ther... |
[
"Why do I feel better after vomiting even when what caused the nausea has long since been digested?"
] | [
false
] | I meant to ask this question this morning, but decided to go back to bed instead. | [
"I know we aren't supposed to make off topic comments but it makes me smile that your title includes complex fluid engineering and you're commenting on vomiting. I'm also easily amused and it's been a long day."
] | [
"When you vomit, ",
"endorphins",
" flood your bloodstream, making you feel much better. It's a weird kind of natural high, I suppose you could say.",
"As for citations, ",
"wikipedia",
" mentions this, as does that endorphins article I linked, but I can't find much material more scientific than that. T... | [
"Anecdotally, about twice a year I will get severe migraines that last for >6 hours. The only relief comes when I eventually vomit. ",
"And when it happens, I feel GREAT afterward from a combo of pain relief and apparently the endorphins that are released. I also develop a raging appetite and elevated mood. ",
... |
[
"Do paper toilet seat covers really work?"
] | [
false
] | You know, the ones you find in the better public bathrooms. They're made basically out of toilet paper and they're shaped like a toilet seat, and you put it over there. How effective are they for shielding you from bacteria and the like? Or is it just there to make me feel good? | [
"Interesting fact for you but the typical toilet seat is cleaner than the typical computer keyboard or the typical paper bill, or really anything else you handle with your hands alot. Hands are one of the big ways that we pick up and transmit bacteria. Toilet seats just don't get touched alot not to mention the mat... | [
"[citation needed]"
] | [
"[citation needed]"
] |
[
"What is the aluminum-foil-looking material on spaceships, and what does it do?"
] | [
false
] | [deleted] | [
"I think you are referring to Multi-layer insulation (MLI).",
"\nIt consists of several layers of thin opaque foils which are kept separate by layers of webbing or by letting the outer layers crinkle, thereby reducing the thermal conduction significantly.",
"\nTherefore the only way of heat transportation left ... | [
"I don't know that brand of bottles, but normally for everyday applications other types of insulation is used, e.g. just a foam material to hinder conduction and a reflective surface to reduce absorption. Expensive and sometimes sensitive materials like MLI are not needed there.",
"\nMLI has the advantage of bein... | [
"So my CamelBak insulated water bottles have space technology in them?"
] |
[
"What is multiplication ?"
] | [
false
] | null | [
"From a purely computational standpoint, this in a sense boils down to how one explains multiplication by fractions, such as 0.7 * 2. Clearly that is 0.7 + 0.7, but it is also 7 * 0.2 = 0.2 + 0.2 + 0.2 + 0.2 + 0.2 + 0.2 + 0.2, where all we're really doing is playing around with powers of ten. Once you understand ho... | [
"Sounds like you want to take a class in real analysis. The really quick answer is that your definition works for rational numbers, and we extend that to irrational numbers by defining them as limits of sequences of rationals.",
"Here's a bit longer answer, but you'd likely need at least the first few chapters of... | [
"It is easy to understand a multiplication as the area created by the factors of the multiplications. For example, e x π would be like the area of a rectangle that has a side e and a side π",
"....e.....",
"| e x π | π",
"|..........|",
"There are a lot of super nice videos in ",
"this you... |
[
"Was I smallpox vaccinated in eastern europe in the late 90s? If not, what are these scars?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed.",
"We do not offer ",
"medical advice",
" on ",
"/r/AskScience",
". Please see our ",
"guidelines.",
" If you have concerns about your or someone else's health, you need to speak to a medical professional.\nWe also cannot... | [
"Probably BCG"
] | [
"confirmed, asked fellow eastern european who did not get it due to allergy"
] |
[
"Is the sleep you get after being really drunk (i.e. passing out) the same as a regular night’s sleep?"
] | [
false
] | Do you go through the same stages? Do you stay in a certain stage longer? | [
"No, it isn't. Alcohol causes problems with the placement and duration of REM stages, causes disruptions in sleep maintenance, as well as problems with SWS stages. It isn't the same for everyone, and it actually depends on how much alcohol a person has had.",
"EDIT:",
"For those asking about ",
"cannabis an... | [
"The point isn't whether you pass out or whether you fall asleep intentionally; alcohol, regardless of the quantity, changes sleep architecture. The problem is that there is a lot of disagreement about what the effects are and at what dosing. Having one drink, and then going to bed 3 hours later should have very ... | [
"Guess I'll put on the \"Mod Hat\" as well. ",
"This is ",
"/r/askscience",
". ",
" Thanks!"
] |
[
"What would the perspective an observer going near-light speed look like?"
] | [
false
] | I understand that, according to Einstein's Relativity, the closer one gets to the speed of light, the slower time moves for them (relative to our perspective here on Earth, for example). If we were to theoretically look at them, we would see them move extremely slowly because they experience time at a much different rate than us. But let's say we were the travelers. What would we see if we were theoretically able to stably observe the world moving past us? If we were able to observe Earth? Would it look like Earth, and everything on it, was moving in fast motion? | [
"They would play \"catch up\" and see a bunch of photons they had almost been outrunning catch up to them and light coming from Earth would go in fast-forward (well, at least compared to the way it looked on the way out) until they got back to Earth, resolving the paradox.",
"That's not what resolves the paradox ... | [
"You're thinking of the two clocks as ticking like this:",
"|---|---|---|---|---|\n|----|----|----|----|\n",
"Both in the same \"direction\", with one ticking slow, and, therefore, necessarily, one ticking fast.",
"But relatively-moving clocks in special relativity don't tick like that. They tick along differ... | [
"Paradoxically the traveller would also see Earth going in slow-mo. It breaks intuition, but that's what GR says would happen. Both frames of reference perceive the other as being slow.",
"Now if the traveller were to stop and turn around and come towards Earth, then it gets interesting. They would play \"catc... |
[
"Are two individual carbon atoms identical in every way or are they each unique?"
] | [
false
] | null | [
"Adding to what others have been saying here, assuming you are talking about two atoms of the same isotope with the same charge, they have to be indistinguishable to resolve the ",
"Gibbs Paradox",
". If they were different, you could come up with a system that violates the Second Law of Thermodynamics."
] | [
"There are different isotopes of carbon, but I don't think that's your question. Two C atoms of the same isotope are going to behave like each other chemically, and if you take carbon-14 atoms, each is just as likely to decay as the next, in a given amount of time.",
"Does it really matter if they're unique, if t... | [
"From my understanding, yes.",
"All atoms of the same type are completely identical in terms of structure. There is only one real way that atoms could ever be 'classified' and that is by their probability to radioactively decay. But the beautiful thing about radioactive decay is - it's like flipping a coin. It d... |
[
"Is it likely that a monocyclic HCN-pentamer could form adenine in interstellar space?"
] | [
false
] | My textbook describes Aminoimidazolecarbonitrile as a precursor to adenine. I see here there was a study done by Glaser,R in a 2007 article called "astrobiology 7:455-470" Is there anyway I can look up this mechanism? Ive tried google and nothing is showing. | [
"So in grad school we actually looked into this. Its really a bitch of a problem. ",
"Linked here is a paper we wrote.",
"The problem with complex molecules is they have to survive a lot of improbable situations. This makes predicting the chemistry extremely difficult. Even the best calculations for the dynam... | [
"Strange, because I found ",
"a pdf",
" of that article very quickly with google.",
"It's a theoretical study (of the kind I do, really). To answer your question, I don't think it's very likely with the mechanism given. It involves very energetic intermediates to the extent that it'd simply never ever happen ... | [
"To expand on your high energy comment. The general rule of thumb is that any reaction that happens in space is going to have to have barrier of around 0 or <0 kcal. The reaction pathway in the paper has one barrier at 75kcal which is way way way way below the available thermal energy .",
"The annoying thing is... |
[
"If light is red-shifted due to the expansion of the universe, does that mean that its energy is not conserved?"
] | [
false
] | As space expands, photons travelling through it increase in wavelength. But isn't an increase in the wavelength of light the same as a decrease in its energy? Does that mean the universe is losing energy as it gets bigger? And if not, where does that energy go? | [
"Energy is not conserved in expanding universe models. It's my understanding that the energy lost from redshift is just lost. The reason is that Noether's theorem tells us that conservation of energy is derived from a time translation symmetry. ",
"The standard model of cosmology",
" is not invariant under time... | [
"simplistically it's an issue of energy v. energy density... but it's actually complicated to the point of unasking the question. very zen actually.",
"http://preposterousuniverse.com/writings/cosmologyprimer/faq.html#energy",
"http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html"
] | [
"First answer: From a Newtonian perspective energy is conserved. Photons lose energy, but since they have a pressure, they do PdV work in expanding the universe. These two factors exactly cancel out.",
"Second answer: From a GR perspective, there is no such thing as a conserved quantity called energy, because th... |
[
"Why does an electric toothbrush need to operate in such high RPM?"
] | [
false
] | What is the reason that electric toothbrush operate at so high rpm? What is the science behind it? | [
"The reason for a fast rate is simple inertia. If it was slow, the bristles would not \"flick\" the food particles off as well."
] | [
"I don't think the toothbrush head itself is actually spinning, it's only going back and forth extremely quickly without actually completing a whole turn.",
"Although there is a motor inside of the toothbrush and it's the ",
"cam and gear unit",
" that converts the high-speed spinning motion of the brush's e... | [
"If you're talking about ultrasonic toothbrushes, this higher speed increases the frequency of vibrations needed for breaking up biofilms made by plaque bacteria and the calcified deposits of tartar they leave behind."
] |
[
"How much \"gravity\" is there around the Earth's core?"
] | [
false
] | Ok, so I got this idea from watching "The Core" - not one of the most scientifically accurate films, I'm well aware - during a scene in which our heroes are trying to handle some very heavy equipment inside a ship that's floating in the Earth's outer core. The ship bucks, and the equipment falls and breaks someone's leg. And that got me thinking - how heavy would the equipment actually be at those depths? Let's assume that you managed to get an airtight capsule that was strong enough to withstand the crushing pressure at that depth, and pressurized so that the air inside wouldn't kill whoever was in it, and place that capsule somewhere inside the Earth's liquid outer core, and placed, say, a 1kg weight on a measuring scale inside it. How different would 1kg weigh at the Earth's outer core compared to the Earth's surface? In a sealed environment that allows anything inside to ignore the force of the pressure around it, does gravity get stronger as you get closer to the core (since it gets weaker the farther you get from the Earth), or does it get weaker because you're only being drawn towards the core, which, while hugely dense, is still a smaller amount of the mass that accounts for the gravitational pull of the Earth? Again, I know "The Core" isn't really the film to be pitching any type of serious physics question at, but it struck me as an interesting thought experiment. Has already tackled this issue before? | [
"As mentioned in a different answer, inside a hollow uniform spherical shell you feel no net force from the shell, no matter where inside it you are. It perfectly balances.",
"Outside a uniform hollow spherical shell, it behaves exactly like a point mass at its own centre with the same mass.",
"Therefore, as yo... | [
"Oddly enough due to the high density of the Earth's core, if you could walk around the Earth's outer core you'd experience an actual maximum in your acceleration due to gravity of ~10.7 m/s",
" . ",
"(Dziewonski & Anderson, 1981)",
" This is known as the Preliminary Reference Earth Model (PREM).",
"calcula... | [
"does it get weaker because you're only being drawn towards the core, which, while hugely dense, is still a smaller amount of the mass that accounts for the gravitational pull of the Earth?",
"Pretty much. Check out the ",
"shell theorem",
": A solid, spherically symmetric body can be modelled as an infinite ... |
[
"Why do these biotite crystals have blurred edges in thin section?"
] | [
false
] | [deleted] | [
"You would probably get more traction over at ",
"/r/geology",
" (where you can post images). Without knowing exactly what you're describing, my guess would be it's simply a product of the orientation of the biotite grain with respect to how the thin section was cut and/or an effect of \"seeing through\" a less... | [
"By blurry do you mean rounded? Like if the crystal habit looked like a “rounded rectangle” instead of perfect sharp corners? That could actually just fall out of the Wulff construction for crystal habits but I’m not sure what it actually means for the conditions in which the crystals were grown except the surface ... | [
"Thank you for your reply, really helpful! The biotite does overlap quartz, so could it possibly just be the way the section is cut, that it’s just slightly see through around the edges, and not actually anything characteristic of the Crystal itself? Thanks again!"
] |
[
"Whats going on in your body when you get the irrational \"I feel like something is behind me\" feeling?"
] | [
false
] | I'm sure everyone has gotten this at some point. Its the uncomfortable feeling you get maybe if its late at night, where it feels like someone is behind you. Its an urge that can only be satisfied by turning around and checking. What is going on internally when this happens and what causes it? | [
"Humans evolved in the wild. We were not always so completely safe from other predators. People who developed a good response to the possible threat of a predator typically survived long enough to reproduce and pass on those traits. What you consider as irrational now may have been a perfectly justified response wh... | [
"There are two main functions for goosebumps. By making your hair stand on end, you trap a layer of air between the individual hairs (if you were a hairy ape) and so it acts as additional insulation. That's why we get them when we're cold. The other reason is to make yourself bigger and more threatening. This behav... | [
"It's an involuntary response that's associated with the activation of your sympathetic nervous system. Deriving pleasure from music, activates the reward pathway in the brain and in turn leads to activation of the system. But this is just something I covered briefly in one of my modules at Uni so I'm probably not ... |
[
"How accurate are the fuel pump meters at gas stations?"
] | [
false
] | null | [
"Most states in the US require the fuel dispensing pumps (and any scales used for commerce, under generally the same regulations) to be inspected annually or so. You'll usually see a rather prominent inspection sticker. ",
"Here's a Car & Driver article on it: ",
"http://www.caranddriver.com/features/the-pump... | [
"Every pump I've ever seen has had a sticker on it labeling when it was last inspected. I'm pretty sure that if even one was to be found significantly off, a politician's opponent would lambast him in the next election.",
"Therefore, logically, I predict they are at least somewhat accurate. It isn't like it's d... | [
"I think this question is better suited to ",
"/r/askengineers",
" or even just ",
"/r/answers",
" "
] |
[
"Hey, Reddit! If an explosion happens in a cloud, how is the cloud effected?"
] | [
false
] | Title about sums it up. Does the explosion propel the matter of the cloud outwards, therefore dispersing the entire cloud, or what? | [
"Does the explosion propel the matter of the cloud outwards, therefore dispersing the entire cloud, or what?",
"The explosion creates a pressure wave through the cloud. It does get pushed outward a bit, but generally there isn't enough gas released to really cause the vapor to be significantly displaced. Dependin... | [
"I lose all of my photos and most of my music"
] | [
"The cloud will just ripple like water."
] |
[
"Why do LCD readouts, such as digital clocks, appear to \"bounce\" when you view them and chew at the same time?"
] | [
false
] | I hope that others have also experienced this phenomenon. I could understand that the force of our jaw is enough to cause our eyes to vibrate somehow, but why is it so pronounced in these circumstances? | [
"Here's the key; only one segment of the display is on at a time. This is because only a fixed amount of power is available to the display, so the number 8 (made up of 7 segments) would otherwise be dimmer than a number 1 (made up of 2).",
"They cycle through so fast that they appear to be continuous... but when ... | [
"Oh okay good. I thought you were sitting on the couch watching the evening news with a vibrator on your head."
] | [
"CRTs work in a similar way, and you can recreate the above example of the display moving in a straight line very fast with an oscilloscope. This actually messes with me often at work when I think I see erratic movements on my scope, but it was just me clearing my throat."
] |
[
"Question about determining the expected activity and dose rate from a sample of fissile material (U-235 or Pu-239 in this case) exposed to a flux of thermal neutrons?"
] | [
false
] | null | [
"I figure that the best way to do this would be to sum through the entire list of fission products, weighted by their fission yields, using the standard neutron activation equation to determine the activity at EOI.",
"As far as I know, this is the only way to do it.",
"But you should try a more specialized nucl... | [
"Ah, I figured. Do you have any recommendations of subs that might be able to help? I've tried ",
"r/nuclear",
" as well so far."
] | [
"/r/nuclear",
", ",
"/r/AskEngineers",
", maybe ",
"/r/AskPhysics",
"."
] |
[
"What technology will cell phones of the future undoubtedly possess, but currently cannot due to size (or other) constraints?"
] | [
false
] | null | [
"Such hypothetical / speculative / open-ended questions are better suited for our new-ish sister sub ",
"/r/asksciencediscussion",
". Please consider reposting there instead."
] | [
"While there may be some speculation, I definitely think my question is grounded in reality and may warrant some great answers by people who work for telecommunications companies or technology companies that are developing future mobile technologies. If you insist, I'll repost, but for these reasons, I ask you reco... | [
"All people who have flair here have flair there as well."
] |
[
"What did Earth look like from Space at the dawn of life?"
] | [
false
] | It must have looked very different. For one, the atmosphere had a completely different composition. Also, the geography must have been very different as well. What can we infer from the geologic record about the appearance of the Earth so many billions of years ago? | [
"Single cell life came about ~3.8 billion years ago or so, but our grasp of geography during those time is a bit shaky. This is \"just before\" the formation of the first (theoretical) ",
"super continent, Vaalbara",
", which started forming around 3.6 billion years ago (completed at around 3.1 billion, and br... | [
"I am curious about the atmosphere. What colour would the sky have been? What about cloud cover?"
] | [
"I am not an expert but I do take interest in these topics. Considering Earth had a reducing atmosphere at the time, it would've been filled with volatile chemicals, mostly methane, CO2, and nitrogen, possibly ammonia, with some other trace compounds so the sky was possibly an orange color like a permanent sunset. ... |
[
"Considering the winter storm in the Midwestern U.S. currently, at what temperature would wildlife start dying?"
] | [
false
] | How cold does it need to be for the region's wildlife - foxes, deer, owls, coyotes, wild cats - to just not outlast it? Also, could it ever get so cold that trees or other plants are killed? | [
"Conservation Biologist here. Cold spells are like any abiotic factor which will cause changes to survival rates. Think about it like other natural disasters - e.g. hurricanes, floods, fires, etc. etc. etc. Most of the creatures that live in these regions have already evolved over thousands of years to be somewh... | [
"Conservation Biologist",
"Interesting field of work. What's your typical day at work like?"
] | [
"The temperature that an animal dies at depends on how desperate the animal is. ",
"A well fed animal with available natural shelter will probably survive the coldest weather in a century. But most of the animals might die.",
"Wild animals are rarely well fed. They are often at the edge of starvation especial... |
[
"If there is a stationary source of sound, and I am moving away from it, will I experience a Doppler shift?"
] | [
false
] | If so, will it be different from the Doppler shift that would be experienced if the source was moving and I was stationary? | [
"Yes. There may be differences based on the relative speed of the source, the air and you. Otherwise no, it will be the same."
] | [
"I can understand why you can downshift all the way to 0 Hz when moving away from the source (when you begin to travel faster than the waves propagate through the medium), but why is there a theoretical limit to how far the signal can be downshifted when the source is moving? It would seem that as the source moves... | [
"I was a derp. No theoretical maximum, but the magnitude of the shift is different. If you're moving away from the source at the speed of sound, the sound is shifted to 0 Hz. You can imagine this as just riding next to a pressure wave, without the wave causing any vibration of your eardrum.",
"If the source is mo... |
[
"Does fog form over the deep ocean?"
] | [
false
] | I've had a brainworm on the ocean and I've not been able to find an answer. I've asked a military subreddit and then also Navy servicemembers and they weren't able to say one way or the other. On the deep ocean, hundreds of miles from land, does fog form? If so, is it known if it is a common event? Lastly, and assuming it is within the purview of AskScience, if it is common, how do ships deal with it? Thank you! | [
"Yes it does. However, you won't get it forming in the lowest meter or two over the water, due to the curvature effect (water vapour will condense onto the ocean surface rather than into droplets). Also, there are fewer nucleation particles for fog to condense onto. Finally you won't have as much radiation fog beca... | [
"Thank you so much for finding this post and answering it! ",
"I'm writing a story that at one point focuses on a fishing boat deep in the Pacific at a point when Earth is suddenly covered in fog. I wanted to depict the crew's reaction as realistically as possible. ",
"So to be clear, fog does form, but it woul... | [
"Yup, so the main takeaway is that fog can form, but less commonly than over/around land. It won't form at the lowest metre or so close to the water, which is lower than most deep ocean boats, I want to say?",
"I can't say exactly how common it is, except that it does happen but is less common than in coastal/lan... |
[
"Splenda and other artificial sweeteners are \"hundreds\" or \"thousands\" of times sweeter. How do they measure this? They taste the same to me."
] | [
false
] | Artificial sweeteners like Splenda are said to be hundreds or thousands of times sweeter than real sugar. How do they measure this? And why is it that a teaspoon of splenda in one of those little packets tastes exactly as sweet as a teaspoon of sugar? Shouldn't my mind be absolutely blown by how sweet it is? | [
"Because it's also diluted thousands of times so that in the packet it's about a 1:1 analog of sugar. ",
"That way when you are used to putting one packet of sugar in your coffee, you use one packet of Splenda. Otherwise your mind would be blown. Plus, it's hard to put only a couple of grains of Splenda in your ... | [
"You can purchase pure Neotame on eBay (also called newtame), which is 8,000 times sweeter than sugar and actually tastes pretty good. I purchased some years ago and like to dip a toothpick in the powder and then tap off the excess and have people lick it. Your mouth is overcome with sweetness from the smallest a... | [
"That's not how it works. Pure sucralose is 300-1000 times sweeter than sucrose. 1:1 volume substitutes with sucralose is included with a lot of filler.\nJust because something is \"derived\" from something else does not necessarily give them similar properties."
] |
[
"Are SpaceX rockets susceptible to inclement weather on landing? What means do they have for delaying landing in such cases?"
] | [
false
] | null | [
"First stage never achieves orbit, it's on a more or less ballistic trajectory and can't really wait for the conditions to improve.",
"\nSomething they ",
"did recently",
" was move the droneship on which it lands to a different position due to storms."
] | [
"They have precisely 1 means of delaying the landing in case of unacceptable weather at the landing site: Postponing the launch. What goes up but doesn't reach orbit, must come down rather immediately.",
"The Space Shuttle had similar requirements at launch for weather conditions at its abort landing sites in A... | [
"There's landing weather criteria, ",
"here's a pic",
" showing wave and wind conditions required. Not sure if it has been revised since.",
"\nThey have delayed a launch at least ",
"once",
" due to unfavorable landing conditions."
] |
[
"Why do COVID-19 deaths go up and down on a weekly cycle?"
] | [
false
] | [deleted] | [
"Reporting differences on weekends are quoted as a reason, but would deaths really go unreported for days?",
"It can take a couple of days for a death to be formally reported and logged.",
"The paperwork is likely done pretty quickly but it will take some time for the paperwork to be processed. This is why it... | [
"For example, in several countries, like the UK, if you've ever had Covid -even if you have completely recovered- and die for any reason, for example run down by a car, then your death is recorded as a Covid death.",
"I've heard this conspiracy nonsense since the early days of Covid, but I have yet to see even a ... | [
"It is what was stated in the press briefings by the authorities in the UK."
] |
[
"If we could anchor an object into space itself, how would it appear to us on Earth?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"If you disagree with this decision, please send a ",
"message to the moderators."
] | [
"I'm super confused. I can't ask a question about something I don't understand because I don't understand. What's the point of this sub? "
] | [
"I am sorry but that question just doesn't make sense. You cannot \"anchor a object to space\". There is no absolute reference frame so you can't define a fixed point in space. To make it simple everything moves relative to everything else so you can't define something as immobile."
] |
[
"If you're under a mountain, would the slight increase in gravity from being closer to the core be negated by the mass of the mountain above you?"
] | [
false
] | Had a student ask be this today. | [
"At the most general level (and not specific to the particular scenario), if we consider a simplified version of the density structure of the Earth (e.g., ",
"PREM",
"), because generally density increases with depth (with some large step-changes across specific transitions) we would expect gravitational accele... | [
"I'm a geophysicist, and your explanation of the nature of the bouguer anomaly is one of the clearest ones I ever saw."
] | [
"If this was the short clear version, I’d hate to see what an in-depth analysis and explanation would be. (⚆_⚆)"
] |
[
"Can dark energy tear apart black holes?"
] | [
false
] | null | [
"Hi Sp1hund thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the followi... | [
"'Astronomy'"
] | [
"'Astronomy'"
] |
[
"What kind(s) of motion does an air bubble trapped in an acoustic standing wave (propagating through water) have?"
] | [
false
] | I'm working on a project involving sonoluminescence and need some help with the hydrodynamics. We've trapped air bubbles in an acoustic wave traveling in water and saw a pattern in our readings which I don't think can be explained by the pulsating of the bubble's radius. Our measurements are made from a piezo-electric crystal at the bottom of a water tank which will read the pressure fluctuations over time from the movement of the trapped bubble and display these readings on an oscilloscope. We get what looks like a sinusoidal function in a saw-tooth waveform envelope. This saw-tooth envelope is in phase with the acoustic frequency in the water. Could this be explained by the bubble's radius collapsing and expanding over time or is there some other form of motion that we're not considering? | [
"What is the radius of the bubble and what is the frequency of the wave? For an air bubble in water, the resonance frequency and radius multiply to about 3 m/s (e.g. a 3 mm radius bubble would have a resonance frequency of 1 kHz). You could try ramping the frequency and seeing if there's a resonance peak around thi... | [
"If you could put up an image of the signal you are seing that would help quite a bit in trying to decipher the behavior. "
] | [
"well as far as a sonoluminescing bubble goes, there actually tends to be more light at colder water temperatures"
] |
[
"Does pushing on an object propagate through the object at its speed of sound?"
] | [
false
] | If I hit one end of a long rod for instance, the sound wave travels down the rod at its speed of sound, caused by the electromagnetic force affecting successive molecules pushing against one another. If I instead slide to the rod forward, the pressure applied to one end of the rod sends a wave through the material via those same forces. So does the far end of the stick respond to a push at the speed of sound? | [
"Yes, it does. Any disturbance at one end of a body will not be instantly noticeable at the other end, but travel through it at the speed of sound. It is important that the speed of sound can be pretty fast in solids, up to 12'000 m/s in diamonds. ",
"Here is a useful list"
] | [
"I'm not 100% sure because this isn't my field, but isn't the speed of sound synonymous with the velocity factor for a mechanical signal?"
] | [
"Nope, it depends on the \"speed of signal propagation\" in the material. The speed of sound also depends on the material.",
"EDIT: apparently I was wrong, as explained in other comments :)"
] |
[
"Is it highly probable that aliens would evolve sexes, or are our male/female sexes a freak of nature and the norm is no sexes or gender?"
] | [
false
] | null | [
"http://www.sciencemag.org/content/333/6039/216",
"\nGood evidence it's strongly selected for hence likely."
] | [
"Thanks very much!"
] | [
"Since by aliens, you likely mean aliens with a comparable intelligence to humans, I would agree that a male-female gender pattern would likely emerge. However, this does not hold true for all potential alien species.",
"On our planet, most if not all mushrooms have evolved to not use a male-female gender pattern... |
[
"Why does my AM clock radio depend on it's orientation while my car receives clearly in all directions?"
] | [
false
] | null | [
"Directional antennas are less likely to pick up erroneous side-band noise and harmonics from other signals, but require to be aimed in the direction of the transmitting signal. Omni-directional antennas require no aiming, but need a stronger signal for clear audio. The manufacturer of the clock radio assumed you... | [
"Don't forget the obvious. One antenna is huge and open to the air, the other is tiny and inside 4 walls and a roof."
] | [
"The size of the antenna has less to do with the result than the gain of the antenna. But the walls and roof will affect the signal. Not as much as higher frequencies (FM, TV, ect.), but it will affect it. That being said, even outdoors you're likely receiving an AM signal after it has reflected off walls or the... |
[
"What would happen if gravity was \"turned off\"?"
] | [
false
] | null | [
"It's impossible, but if it did happen, the Earth and its atmosphere would fly apart from the massive pressure that exists at the core."
] | [
"Wow! I didnt even think of that! So the entire earth, from crust to mantle and core would seemingly explode? That's awesome."
] | [
"You should read Larry Niven's \"The Integral Trees\". Like a lot of Niven's stuff, it's a really brilliant concept, artfully imagined then rendered into a pretty puerile teenage novel with stilted dialogue and lots of sex (most of which happens by allusion only). But it's worth wading through the schlock for the... |
[
"How did the first RNA/DNA strains not break down from hydrolysis?"
] | [
false
] | Correct me if I am wrong, but don't the amino acids that build RNA, which is thought to be the start of life on our planet, break down when introduced to water? (hydrolysis) How did it avoid this? | [
"The RNA world hypothesis (",
"Wiki",
") is what I think you are referencing. It is thought that RNA came together with help of random chemical processes. RNA is somewhat special in that it can take on many conformations in a single strand (or even double strand state), these RNAs are able to actually catalyz... | [
"under neutral conditions, the phosphodiester bond in RNA and DNA is very stable. also, amino acids make up ",
", not DNA/RNA. what makes up DNA/RNA are ribonucleotides."
] | [
"I am not a scientist but I do read lots of science magazines, etc.",
"The conditions at the start of life on earth were VERY different than they are now and there is always exotic places where life could have started such as geothermal vents. I recall these two life origin theories I read about somewhere along ... |
[
"Questions about Metatharians..."
] | [
false
] | Are there any extant species of Metatharians that are not marsupials? I'm aware of extinct marsupial ancestors that were Metatherian, but not of any living ones. Are Prototherians (i.e. monotremes) the ancestors to Eutherians and Metatherians? Further, are Metatherians the ancestors of Eutheria? Am I correct in my assumption that all Eutherians are more closely related to one another than any of us are to Metatherians? That is, humans, wolves, whales, elephants, armadillos and bats are all more closely related to one another than any of them are to kangaroos and bandicoots? | [
"Well, a thorough read-through of ",
"this",
" would probably get you most of what you want to know (and far far more). However, I'll do my best to give condensed answers to your specific questions.",
" As far as I can tell, no. I'm by no means a specialist on taxonomic stuff like this, but the ",
"section ... | [
"The following link should answer your second and third questions. Basically, these three groups aren't monophyletic, there are extinct groups of mammals that existed alongside the extant groups. ",
"http://tolweb.org/Mammalia/15040"
] | [
"In the same way that modern reptiles are not the ancestors of humans, but our common ancestor would have been classified as a Reptile",
"This is incorrect. The common ancestor we share with reptiles would have been more \"reptile-like\", but it would not formally be classified as a reptile. I should also note th... |
[
"How much longer will Venus be visible in the night sky?"
] | [
false
] | Venus and Jupiter were visible throughout March. Jupiter seems to have disappeared at this point, but Venus still shines brightly every night. Will it last for a few more weeks? (I hope that bright point of light I see IS in fact still Venus, otherwise I've just made a fool of myself.) | [
"Yes, that's Venus up there.",
"One good way to answer this would be for you to download some planetarium software and see for yourself :) I really enjoy ",
"this one",
". Set it to your location and set the time and date to tonight, then skip forwards days and hours until it pops behind the sun."
] | [
"As a rule of thumb, it's visible a few months at sunset in the west, then disappears, then it's visible a few months at sunrise in the east, then disappears, repeat."
] | [
"As others have mentioned, yes its Venus.",
"It should stick around until the end of may at which point it will be too close to the sun to really observe well.",
"mars and saturn are also up right now not too long after dark.",
"and yes, stellarium is an awesome free planetarium program."
] |
[
"When we measure an object's mass using scales, are we actually measuring the *mass* of the object, or just inferring it (more inside)?"
] | [
false
] | Hello, science people, My question is quite simple, really. When we use scales (say, for instance, the electrically powered ones you stand on) to measure an object's mass (in our example, a human's mass) in KG, aren't we actually measuring the object's weight, and converting the result from Neutons into KG, using the assumption that we're working in an environment of 1G? If so, then would these devices need to be calibrated when used in environments of lower or higher natural gravity? Could they even be calibrated without a reference mass object, like the ACPO's Silicone sphere? | [
"It depends on the scale. If it uses force (like your bathroom scale) the result would indeed be different depending on you location in space (even differs on earth quite a bit). However, if you were to use a balance, it wouldn't change, since it compares the weight of both sides (even though the actual weight in y... | [
"the result would indeed be different depending on you location in space (even differs on earth quite a bit)",
"For anyone curious, cool science folk have mapped this pretty well; it's called the ",
"geoid",
". It's a lookup table of how much gravity you'll experience at any given point on earth.",
"It look... | [
"No, the balance idea is genius. If you have a reference object that you know has a mass of 1kg, and the object on the other side of the scale balances it perfectly, than it doesn't matter what gravity is, you know they are the same weight and therefore the same mass."
] |
[
"Why are the mods ignoring their own rules to accumulate karma?"
] | [
false
] | null | [
"It isn't about accumulating karma. The mods are actively discussing whether it was appropriate to include that joke in a distinguished post. We understand that a lot of people in the community are upset by the decision and are certainly taking that under advisement. Thank you."
] | [
"I'll be honest. It bothered me because I am literally, as I discovered this question, studying for my physiology test in which that is a major point of discussion. My answer is correct, but now nobody will see it because they're all pissed I tried to call out a mod. If this truly is not a scientific community, ... | [
"right now your answer is sitting at 5 up and 1 down. I don't think people are rejecting your ",
" in addition to your \"calling out\" of a moderator. Granted even if they did, that's still something that I would ",
" with, but have no power to stop. That's kind of one of the problems of the reddit voting syste... |
[
"During fertilization the sperm mitochondria are marked with ubiquitin and destroyed and the human embryo only receives the mother's mitochondria. Why?"
] | [
false
] | Wouldn't it be better to receive two copies of mitochondria in case the mother's version was faulty? Also wouldn't it help natural selection to have mitochondrial DNA and genes participate in sexual reproduction as well instead of the asexual cloning process that our mitochondria experience? | [
"Last time I've heard this topic come up, I believe it was still being debated, so there isn't a clear answer yet.",
"First off, yes, there is evidence that sperm mitochondria are targeted for degradation. It is not a simple matter of sperm mitochondria dilution. The sperm tail is not excluded from the embryo upo... | [
"The amount of mitochondria in a sperm cell is so little (50-100 mitochondria) compared to the one in an egg (100.000-200.000) so mtDNA is inherited through the female. ",
"That probably happens to prevent lethal cytoplasmic gene competition and to prevent the inheritance of sperm mitochondrial DNA which is degra... | [
"The reason we only have maternal mitochondrial DNA is because only the head of the sperm (which contains the parental DNA) enters the egg and combines with the maternal DNA to create an embryo. All the paternal mitochondria is in the tail of the sperm which propels the sperm (its the only part of the sperm that n... |
[
"What makes stainless steel resistant to corrosion?"
] | [
false
] | I know its a passivating layer of chromium oxide that protects from corrosion, but why does a layer of chromium oxide not allow for further oxidation while iron oxide fails to do the same thing | [
"Most metals when they oxidize produce a relatively strong layer that protects metal underneath form further oxidation, however iron is a little different because iron oxide reacts with water, increases it’s volume and just falls off exposing more metal",
"If you have a metal that creates a protective oxide layer... | [
"Stainless is about 3 times as expensive as regular steel, it also has different mechanical priorities, and it’s harder to work with weld and form, so it’s not quite that simple ",
"Most of the time it’s not worth it for structural stuff, iron really doesn’t corrode all that fast in regular conditions anyways"
] | [
"OK thanks again :-)"
] |
[
"Does the Universe have a center of gravity?"
] | [
false
] | null | [
"No.",
"There are two possibilities:",
"Space is flat and simply connected. This implies that it is in fact Euclidean space, and is infinite. Then you cannot average the position of masses in the Universe because the sum diverges. The mass distribution is uniform on very large scales, and this goes on forever."... | [
"there isn't a concept of centre of gravity or centre of mass in GR."
] | [
"nah, that's a pretty local feature in the grand scheme of things. It's just a large clump of mass some 50-70 Mpc away. Over much larger distances the distribution becomes uniform."
] |
[
"How is energy going to be harvested from nuclear fusion reactors?"
] | [
false
] | So there will be glowing hot ball of plasma 10x hotter than the core of a star inside of an enormous magnetic field. How is energy going to be harvested from the reactor? | [
"Each fusion of deuterium and tritium nuclei yields neutrons of kinetic energy 14 MeV (about 22 millionths of an erg). These fast neutrons are electrically neutral and can easily escape the plasma and its confining magnetic field. Their kinetic energy could then be converted to heat--for instance, by depositing the... | [
"Very interesting. Concerning the neutrons of kinetic energy, however, is there any chance that these could damage the reactor as they leave the core? It seems like a lot of energy moving out of the core."
] | [
"Indeed, fast neutrons can do all kinds of bad things to reactor materials by introducing dislocations, defects, and the introduction of nuclear reactions in the nuclei, which can lead to alpha decay and pockets of helium within the matter. All this tends to make metals and other matter brittle. ",
"Developing ma... |
[
"When you solve quadratic or cubic equations one or two results may make no physical sense to us. Do they play an important role in some other area of physics/math?"
] | [
false
] | As the title says, if I'm solving for Volume, and my equation ends up having two answers that satisfy the equation. one result being 5 and the other being -5, by our understanding a negative volume does not make sense. Does that -5 value play a role in some other type of physics that can be applied in our understanding? | [
"This is sort of how the idea for the positron was conceived. Dirac realized that his equations could be solved with either a negatively or a positively charged electron."
] | [
"The Schroedinger equation is built on the total energy equation from Newtonian mechanics:",
"H = p",
"/2m + V",
"Which is known as the Hamiltonian. The Schroedinger equation comes from the substitution p->-iћ(d/dx), E->iћ(d/dt), which can be derived from the de Broglie and Planck relations.",
"The relativi... | [
"Positron emission tomography"
] |
[
"If infrared is just another \"place\" on the spectrum that includes visible light, can something be painted infrared? Or is the \"visible light spectrum\" different in some way apart from the fact that we can only see that?"
] | [
false
] | Also, if something had the "color" infrared, or ultraviolet, would it be invisible to us? | [
"Yes. Although when you say \"painted\" you're defining the spectrum as what you can see. A blue object reflects blue light and absorbs light from all other colors in the visible spectrum. But a what you call a blue object may also reflect infrared light. So to an animal that has the ability to see some of the infr... | [
"Also, I think I may have reversed lead/bone colors. Someone can correct me.",
"Yes, you have. Things look black if they absorb of all visible wavelengths or white if they reflect all of them. Hence lead would look black to this hypothetical creature, and our bones would look white (or \"X-ray colour\", for want ... | [
"You can certainly paint something infrared. ",
"This",
" youtube video shows a special type of coating that is opaque in the visible but reflective in the infrared. You can think of it as a type of infrared paint.",
"Similarly, it's possible for a material to be opaque in most frequencies but reflective in... |
[
"How much fructose do we need to consume before our liver starts to produce triglycerides?"
] | [
false
] | null | [
"The general answer you're looking for, if you're talking about the synthesis of triglycerides, is immediately - insulin production brought on by the consumption of sugars activates FA synthase. Like all biochemical processes in our bodies, it works by feedback - how much insulin there is present affects how much F... | [
"sorry I am not sure I understand. I was under the impression that fructose which unlike glucose is processed by the liver and it can only handle a certain amount. Once we hit this limit instead of turning it into glycogen it turns it straight into a fatty acid ah la triglycerides? "
] | [
"Wikipedia seems to agree with you \"High fructose consumption can lead to excess pyruvate production, causing a buildup of Krebs cycle intermediates.[34]Accumulated citrate can be transported from the mitochondria into the cytosol of hepatocytes, converted to acetyl CoA by citrate lyase and directed toward fatty a... |
[
"Why do some vaccines leave scars?"
] | [
false
] | I recently got my BCG vaccine as I work in a lab but when they informed me of the blistering and scaring phase I was a little perplexed. What makes the site blister and scar only after several weeks/months? I know it’s to do with your immune system reacting but what is specifically involved / what’s the processes involved and why does sometimes it cause such a prolonged severe reaction at the site of injection? ( How come its only with live vaccines too?) | [
"For the smallpox vaccination, \"leaving a mark\" is the sign that the vaccine worked. The vaccine requires multiple punctures giving multiple infection start sites, so it becomes very inflammatory - leaving behind the scar tissue. The TB vaccine is different, in that it is a single injection, but BCG is extremely ... | [
"Thanks. I never knew that was the reason why. I haven’t really thought about it in the 23 (or so) years since I had my BCG, but I just checked for the scar...yep, still there."
] | [
"It appears to genuinely be a carryover from Jenner’s initial testing back at the end of the 1700s. This is an interesting study (albeit with a minuscule sample size) suggesting the inner arm might actually be a better location: ",
"https://academic.oup.com/cid/article/42/4/e16/385953"
] |
[
"If an object falls into a still body of water, can the water that is thrown into the air exceed the initial height of the object?"
] | [
false
] | [deleted] | [
"Yes. Can we agree that a turd at the moment of release is lower than your balloon knot? I say yes. The fact that the water can still make a brown bullseye proves that it achieved a height higher than the turd. The object would probably have to be big enough to displace some water so the water claps back into place... | [
"It only applies if the exit velocity is equivalent to free fall. Otherwise assume a slow pinch off on a suspended turd."
] | [
"I believe it's caused by the water being lifted up as it's forced out of the path of the turd, while at the same time the turd creates a depression in the water. As the water falls back into the depression, all the force is compressed into the epicenter where the turd fell. The water cannot be forced down and so... |
[
"What would it be like to swim in a pool on the moon?"
] | [
false
] | Assuming it was inside a pressurized, breathable environment. In terms of the lower gravity, how would the viscosity and buoyancy of the water play a role? Would it be like swimming through syrup? Would we be able to swim more efficiently? | [
"Actually, and surprisingly, there wouldn't really be any difference at all. First, water is (nearly) incompressible, meaning it would be at the same density on the Earth or on the Moon, and buoyancy is not a function of gravity so you would have to swim just as hard to stay afloat in both locations. The only real ... | [
"buoyancy is not a function of gravity so you would have to swim just as hard to stay afloat in both locations.",
"I'm not sure this is accurate. You would float at the same level, but the effort required to keep you upright with your head above water should be less. If you push down with your hands at the wate... | [
"Wait, wait, so if we go swimming on the moon we can swim upwards and out of the water while doing crazy aerobatics like dolphins?"
] |
[
"What is the smallest sized objet we would be able to see on Mars from Earth using current technology?"
] | [
false
] | This question came about when I was reading The Martian. Is there any chance that we could use land or space-based telescopes to see a human on Mars? | [
"For Earth based telescopes, the largest aperture belongs to Gran Telescopio Canarias (GTC) at 10.4m. Assuming (incorrectly) that this telescope is ",
"diffraction limited",
", and that Earth was at aphelion, Mars at perihelion and opposition (closest possible approach), GTC would theoretically be able to resol... | [
"Did you read the words that immediately followed that statement, or did you just stop there?"
] | [
"The HiRISE camera (",
"official site",
", ",
"Wikipedia page",
") on the ",
"Mars Reconnaissance Orbiter",
" has a resolution of ~0.3 m/pixel (~1 foot/pixel). An average human standing on Mars would be just over one pixel wide if viewed from straight overhead."
] |
[
"What is the practical significance of ENTHALPY? (Both in chemistry and physics)"
] | [
false
] | For e.g, 1. When we say Internal Energy, we mean the sum total of the energy of a system (U) which is the function of temperature. When we say Gibbs free energy (G), we mean the amount of energy in a system which can be converted into useful work. When we say Entropy (S), we mean the energy which cannot be converted into useful work anymore because it has been used to increase the entropy of the system. When we say Heat(Q), we talk about heat exchanged b/w the system and the surrounding So what do we mean when we talk about enthalpy? Why did scientists feel that there was a need to introduce the term enthalpy ? And why was Internal Energy not enough? | [
"Enthalpy is an incredibly useful quantity in thermodynamics. It is given by",
"H = U + PV ",
"Where U is internal energy, P is pressure, and V is volume. Since U, P, and V are state functions, H is also a state function. Enthalpy takes into account the energy used for expansion.",
"One of the more useful pro... | [
"So while talking about U, we are talking bout a system at constant volume? Without any exceptions?",
"And about entropy... Most of the books define it as \"randomness of a system\". I know it's beyond the scope of a Reddit thread so can you suggest any text which talks about entropy?",
"And one last ques, do a... | [
"Spontaneous processes will have a negative Gibbs energy vs the previous state (assuming constant T, P, etc).",
"I generally think of enthalpy in solids. A way to then frame it is the energy of the bonds. Attractive bonds have a large negative enthalpy and repulsive bonds are positive (through convention). So, if... |
[
"Why don't the edges of gas giant planets appear as a gradient? What defines the limits of their spheres?"
] | [
false
] | null | [
"I know more about Earth's atmosphere than gas giants, but I assume it would be similar. On Earth, the atmosphere is very much a gradient... the air gets thinner and thinner and some of it just keeps escaping into space. In fact, a lot of satellites (and the ISS) have to contend with atmospheric drag, which is why ... | [
"Light scattering gasses add up quickly too. Think of seeing a little smoke from a smoke machine and it not obstructing view much - now add just several more feet and it looks like a dense fog that is solid. The gas on those planets is very dense and after looking through a fractional amount of thickness the gas ... | [
"There is a gradient. But the diameter of the star is usually much, much bigger, so the fading edge appears razor-sharp by comparison.",
"E.g., here are images of the Sun I've captured during the transit of Venus in 2012.",
"http://florin.myip.org/pictures/index.php/2012-06-06-transit-of-Venus",
"The diameter... |
[
"Excluding the Sun, if all of the remaining mass that exists in our solar system were combined, would it be enough to collapse into another star?"
] | [
false
] | I'm sure my question is worded poorly. I am also sure that I e heard that the Sun has more mass than all other objects in the system combined. I'm wondering if even a small star could form, given the above scenario. Thanks! | [
"No. ",
"The graphs here",
" show why pretty nicely.",
"Also, brown dwarfs, the least massive stars, are ~100 Jupiter masses."
] | [
"Yup! Almost all the mass in the solar system is in the sun, but almost all the angular momentum is in the planets. That was totally unrelated, but I just think it's a cool fact."
] | [
"Very illustrative. When I was thinking about this, I thought how all the planets combined would only be such a small fraction compared to the sun. However, I (intuitively) didn't think it was such a landslide. Dito for the fact that Jupiter basically has 70% of the mass of all planets. A true giant. Even though Sa... |
[
"If you stimulate your brain during a heavy workout session, will you brain adapt to become more efficient in the future due to less oxygen in the brain?"
] | [
false
] | My reasoning is that the central nervous system adapts to chemical imbalances, making things like physical addiction to substances and withdrawal symptoms possible. Would reduced oxygen in the brain force the CNS to burn oxygen more efficiently, and when the brain is regularly and consistently stimulated during periods of reduced oxygen, does the brain/CNS adapt to this imbalance? | [
"I'm not sure what you mean by burning oxygen \"more efficiently.\" Burning oxygen is only done one way and that is through cellular respiration. Your body can't make the consumption of oxygen more efficient.",
"The other thing is the fact that the brain, in general, is very very bad at adapting to lower oxygen l... | [
"Thank you for the insight. I didn't realize that oxygen is prioritized to the brain anyway. Does more oxygen even mean more cognitive function? That was just an assumption I made as well."
] | [
"Why is it fairly common for brain function to become significantly impaired during a strenuous workout? Is this actually doing any damage?"
] |
[
"Do you save more energy if you dim your house lights to half, rather than having them all up to full?"
] | [
false
] | Granted not all house have dimmer switches, but I was just interested to know if it saves you more money to have your lights dimmed lower. | [
"Old dimmers, used a variable resister to dim the light. Lets look at a simple example.",
"example",
"We can find total resistance (RT), by adding up all the resistance.",
"RT = R1 + R2 = 0 Ohms + 144 Ohms = 144 Ohms",
"Then we can find the total current (IT).",
"IT = ET / RT = 120V / 144 Ohms = .83A",
... | [
"Old dimmers, used a variable resister to dim the light. Lets look at a simple example.",
"I've never seen such a dimmer. Even going back 40 years or so, all I've ever seen are semiconductor dimmers. The variable resistor in your example would be dissipating 24 watts, which would make the whole fixture hot to the... | [
"Yeah, that sounds more like a variable resistor setup than a TRIAC. If it's actually getting hot to the touch rather than just warm, though, it might be worth replacing the dimmer and/or the wiring."
] |
[
"Why do so many animals have yellow eyes? Does the color of an animal's eye indicate anything about the eye's structure?"
] | [
false
] | null | [
"Yes. Eye color is a combination of structural (reflects some colors away, and some directly back) and absorbent (reflects some directly back).",
"In humans the structure of the iris reflects as blue, and melanin absorbs to reflect as brown. All other colors of the iris are on a spectrum between the two. That is,... | [
"This article might give you a good starting point (Negro et al. 2017). The short answer seems to be we don't know. As the authors write: ",
"\"To our knowledge, however, no study has identified all selection factors conducive to light or dark eye coloration\".",
"Most species have invariant eye colours i.e. al... | [
"Can you explain the human brown and blue eyes a little more? Does it actually reflect the ability to reflect and absorb?"
] |
[
"AskScience AMA Series: We invented a better version of CRISPR. Ask us anything!"
] | [
false
] | We are CRISP-HR Therapeutics, Inc., an early stage biotech company which has developed a dramatically improved CRISPR-based genetic engineering platform, Cas9-HR. The improvements include increased editing efficiency enabling previously unfeasible large edits (1000s of base pairs) at a clinically viable level, in addition to lower cellular toxicity. Our Cas9-HR Platform represents an exciting step for gene editing. We plan to use our Cas9-HR Platform to develop therapeutics, specifically treatments for genetic diseases that are caused by a diverse number of mutations. Since existing high-efficiency CRISPR technologies are limited to small edits (1-50 base pairs), we believe this is an area where we can make a significant impact. Answering questions today are the two co-founders: We'll start answering questions at 19:00 UTC (8pm BST, 3pm EDT, 12pm PDT) on Friday, July 30th. We're looking forward to hearing from you! The guests have finished for today. Thanks for all the great questions! | [
"I'm a molecular biologist, I use CRISPR on the daily. What is it you've done that's different, exactly? You haven't really explained. CRISPR combined with homology-directed repair is very well established at this point. I'm literally using it right now to insert a 2000-base pair gene into primary cells. There are ... | [
"Really missed an opportunity to call it “CRISPIER”"
] | [
"Can you please provide links to your papers so we can read more ourselves?"
] |
[
"Could a double orbit between a binary star exist for a planet?"
] | [
false
] | I have been thinking about this a lot. My guess is no but I wanted to see what others think. Could a planet orbit two stars (aka a binary star) in a figure eight style? I would think not, because if the planet would be going very fast, when it comes within the gravitational pull of the second star it wouldn't properly transfer orbits, it would just stretch the current one. Then again if the stars and planet were all very far away from each other to the point where the orbit is very slow then maybe it would be possible. Then again, we would have to take into account Star B having a gravitational pull on the planet the whole time it is orbiting Star A. What do you guys think? | [
"Yes, this is the Arenstorf orbit, discovered in 1963 and used (in part) for the Apollo missions. ",
"This question",
" discusses the orbit and contains some interesting links (unfortunately, the link to the technical paper is broken). Arenstorf orbits are actually a family of solutions to the restricted three-... | [
"The problem with this being possible is that binary stars orbit each other in addition to the planet orbiting the system. It wouldn't be possible (mathematically speaking) for a stable orbit to hold that shape with the stars also in motion. Additionally, binary stars are typically much closer to each other than pl... | [
"It wouldn't be possible (mathematically speaking) for a stable orbit to hold that shape with the stars also in motion.",
"I once wrote a gravitation simulator with a planet going around a binary star system and found it would be stable if the planet were in a RETROGRADE orbit.",
"If the stars rotated clockwise... |
[
"How big of a nuclear bomb would be needed to disrupt or destroy a massive wedge Tornado?"
] | [
false
] | I had a trippy dream about this last night, thus the reason I am asking. In other words, lets say someone wanted to run an experiment to see how big a blast would be needed to destroy a tornado, and prevent that particular supercell from spawning another, how big of a yield would a bomb need? I'd imagine it would be in the megaton range, but could someone here give an estimate as to many megatons? Ignore the small problems like fallout and 3rd degree burns. | [
"Well yes, you could obliterate the storm. Let's look at the energies involved, shall we?",
"In order to disrupt a tornadic storm, let's assume you would need to blast it with roughly the same order of magnitude of energy. Supercells (and all \"convective\" storms) are fueled by latent heat released by the conden... | [
"That is one of the coolest questions I've ever seen."
] | [
"Seems like a good idea to me, radioactive hypertornados."
] |
[
"Can someone explain the current atomic model/orbital theory?"
] | [
false
] | My understanding of physics is probably above average but certainly nowhere near doctorate level. All through school you're taught about the Bohr model (good teachers will say it's not an accurate representation of reality, bad teachers will just hope nobody asks too many questions). I understand why as it's a good way to visualize and study atoms without overwhelming young students. Later on you learn more accurate valence shell atomic representation, which to my understanding means there's different quantum numbers instead of simple energy levels, and there is probability of finding electrons at certain levels but they can be other places. So here comes my questions: I hope none of my questions appear foolish because I am genuinely wondering about these things. As Einstein once said "I have no special talents. I am only passionately curious.". | [
"Is it still correct that electrons travel in orbit around a nucleus? Do they all travel in the same direction?",
"No, electrons are quantum particles and thinking of them as orbiting around the nucleus the way planets orbit around the sun is incorrect.",
"Is it correct to say that electrons are negatively char... | [
"Is it still correct that electrons travel in orbit around a nucleus? Do they all travel in the same direction?",
"No, the entire concept of classical trajectories is invalid in quantum mechanics, because a particle can't have an exact momentum and position at the same time. So both the concept of 'orbit' and 'di... | [
"There does exist a \"shell\" or ",
" for each electron energy in an atom. If you free a core electron, one that is near to the nucleus, and a higher energy electron will drop down to fill that new vacancy. In order to compensate for the energy change, a photon of energy equivalent to the electron energy drop w... |
[
"Why hasn't the double slit experiment been tried with \"non quantum\" objects?"
] | [
false
] | The double slit experiment has been tried with several particles. All of them are very small. Buckeyballs have 60 carbon atoms; "Thomas Juffmann" in Vienna used molecules with 58 and 114 atoms. But has anyone tried with items that are large? (Human proteins, for example.) How are the sizes and distances calculated for double slit experiments? How big would the slits need to be; how far away would the screen need to be for a macro object? For example, the "nano scale" zinc oxide used in modern sun screen. | [
"Here's the simple answer:",
"The double slit experiment for particles is interesting because it demonstrates the wave-like nature of mass. However, that wave like nature is only observable for ",
" small things. If you look at the wave function of an electron, the position distribution is large enough that you... | [
"I believe you. But is that supported by any experiment?",
"The larges objects successfully to see an interference pattern I know of were ",
"fullerenes",
" and specifically C-60 balls from what I remember.",
"Thing is, the math for the interference pattern makes it so that, the heavier the object, the shor... | [
"The double slit experiment only produces an interference pattern if the diffraction from each of the two slits overlaps. The intensity of light in the diffraction pattern from a single slit is ",
"I(theta) = I sin",
" (delta/2) / (delta/2)",
" ",
"where ",
"delta = 2 pi a sin(theta) / (lambda). ",
"... |
[
"What happens to The vibration of a subwoofer when The Volume is increased/decreased?"
] | [
false
] | null | [
"The amplifier controls the power (wattage) of the electrical signal going to the subwoofer. ",
"In the subwoofer itself, an electromagnet (the \"voice coil\") is attached to the speaker cone. The voice coil becomes magnetized depending on the strength of the electric signal- a more powerful signal at any given t... | [
"Yes. The frequency determines the pitch, the distance it goes in and out (amplitude) determines the volume. "
] | [
"So the distance it goes in and out increases when the volume gets louder? But at the same frequency"
] |
[
"Is it possible to describe knots using mathematical functions?"
] | [
false
] | null | [
"There's a whole branch of mathematics called knot theory, part of which involves finding unique ways to describe different knots. Knots are generally described by the number of times they cross over themselves (e.g. the simplest knot crosses over itself three times, ",
"here",
" is a table of all knots with se... | [
"That's a very vague question, can you explain better what you mean?"
] | [
"No formula is known, but there are ",
"exponential lower and upper bounds"
] |
[
"Is there a speed of gravity similar to the speed of light?"
] | [
false
] | For example: If you were measuring the gravitational effect that a single object(A) exerted on a second object(B), and if you were to shift A so as to alter the effect exerted on B; is there a delay between the action and the observation dependent on the distance between A and B? Secondary question: Would the substrate (or lack thereof) through which the force is exerted affect the speed of this transmission? | [
"Yes, it's believed to be the same as the speed of light, but our observations are limited so we can only put this within about 20%."
] | [
"http://www.nrao.edu/pr/2003/gravity/",
"tldr: Measuring the change in electromagnetic waves from a quasar as they passed through Jupiter's gravitational field."
] | [
"Wouldn't that allow you to send information faster than the speed of light using gravity and thus allow you to violate causality?"
] |
[
"What might the surface of the moon look like (were you standing upon it) during a \"blood moon\" like last night? Would the ground have a red glow, or would it be too subtle to notice up close?"
] | [
false
] | null | [
"A blood moon is a result of the Earth's atmosphere filtering out the non red light which hits the moon, then bounces back, gets filtered again, and hits your eyeballs. It would be the same color you see, minus about 50-80% redness. The math would depend on the precise moment that you're talking about, because... a... | [
"The red tinge you see on the Moon happens for the exact same reason you see the sky turn red during a sunset.",
"Light from the Sun will pass through the Earth's atmosphere on its way to the Moon, and certain wavelengths will be scattered. The red is all that remains. ",
"You would certainly be able to see thi... | [
"Right. The moon has virtually no atmosphere. ",
"The refraction of light we're discussing is occurring as the light passes through Earth's atmosphere ",
" hitting the moon."
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.