title
list | over_18
list | post_content
stringlengths 0
9.37k
⌀ | C1
list | C2
list | C3
list |
|---|---|---|---|---|---|
[
"Are there any animals whose blood is not red?"
] |
[
false
] |
When I googled this all I could find was sci-fi stuff
|
[
"Yes, but it's not particularly common. A common example is the ",
"horseshoe crab",
", which has hemocyanin in place of hemoglobin. Vertebrate blood's red color comes largely from hemoglobin, which is bright red when oxygenated and a darker red when deoxygenated. Hemocyanin is blue when oxygenated and colorless when deoxygenated, so horseshoe crab blood is generally described as blue. Hemocyanin is also used by molluscs (like some snails) and other arthropods (like some spiders)."
] |
[
"I did some reading about the difference between hemoglobin and hemocyanin, mainly highlighting why hemoglobin is more common and the reason that oceanic mollusks and arthopods such as squid and octopus have hemocyanin. That left me with one unanswered question that I'd like to ask. Why do land dwelling slugs/snails and spiders/scorpions have hemocyanin when they aren't subject to the same cold, low oxygen environments that their oceanic brethren live in?"
] |
[
"Hemocyanin is an ancestral trait for those groups. The transition to land likely happened after it evolved."
] |
[
"Isn't Einsteins gravitational field the same thing as the aether that was disproved by the Michelson–Morley experiment?"
] |
[
false
] |
Because when two black holes orbit each other, they create waves in the gravitational field that ripples outward and this slows their spin down enough that they begin to get closer and closer till they merge. So it seems like all of "matter" is on top of this "pool" that does affect our inertia.. just have to be large enough to be affected?
|
[
"The \"gravitational field\" you're referring to is spacetime. Orbiting black holes create gravity waves which move through spacetime. And you're right, all matter is embedded in spacetime. ",
"The postulated luminiferous aether was a medium through which light traveled which permeated all of spacetime. ",
"Spacetime itself is not a medium, so I don't see how they could be the same thing."
] |
[
"Isn't Einsteins gravitational field the same thing as the aether that was disproved by the Michelson–Morley experiment?",
"No -- the luminiferous aether from the Michelson-Morley experiment would have been the hypothetical medium in which light exists, outside of which it might not, or may take a different form. Similar to how sound exists in a solid but not in space, or how water waves exist in a pool but not in concrete. The idea was that light was a wave in some medium that pervades all of space.",
"But, it was found that this isn't the case, and that light is actually just a self-propagating wave; it doesn't need a medium to travel through, it can exist anywhere in space and retain its characteristic nature.",
"Gravity, according to Einstein's general relativity, is the same as the curvature of spacetime. Like light, gravity can exist anywhere in space, and there is no medium through which gravity propagates, there is only the changing curvature of spacetime. There is nowhere we have found that gravity might not exist or might be different from what is described by our current models (insofar as they are able to describe them; things like black holes are exceptional).",
"You can't really call spacetime an \"aether\" because it isn't a tangible medium made of something, rather it is like a mathematical substrate on which media are defined.",
"So it seems like all of \"matter\" is on top of this \"pool\" that does affect our inertia.. just have to be large enough to be affected?",
"You can think of it this way, but it isn't exactly like a pool. Pools have an end, and pools can be filled with things other than water, they can be heated, and even pressured like the bottom of the ocean. A medium like a body of water is made of some kind of material substructure; the atoms which make it up. Water waves, then, are just a disturbance in those atoms, and whatever affects those atoms will change how the water waves work, at least slightly. Light and gravity, however, do not appear to have some material substructure; we can't point to a place and say \"oh and this piece of matter is the electromagnetic field;\" the EM field is not made of anything material, it just ",
", all throughout space, and only detectable by disturbing it and measuring the disturbances (light). Likewise spacetime curvature (the \"gravitational field\") also just ",
", and is only detectable by disturbing its curvature and measuring the amount of disturbance (gravitatonal waves). Neither spacetime nor the EM field appear to have a tangible, material existance.",
"It was thought that the EM field might actually have such an existance, because of the finiteness of the speed of light. However, it turns out that is a more fundamental property of the universe, affecting not only light, but gravity, and the strong force as well."
] |
[
"This is exactly what the Michelson-Morley experiment disproved. If there were a medium, then moving with respect to it would change the properties of light. Michelson-Morley showed this did not occur."
] |
[
"Are there any computer animations of what a supernova would actually look like in real life? What would it look like?"
] |
[
false
] |
Most animations, movies, etc depict supernova as just really big explosions that happen quickly. If you were close to the supernova, but have it still be in your field of view (and let's pretend you can't die, and that your eyes can handle it), wouldn't it appear to expand very slowly (due to speed of light limitations)? Would there be any red/blue shifting effects from the explosion on one side going away from you and on the other side coming towards you? What would an accurate animation actually look like?
|
[
"Yes, many of them look at the fluid dynamics during the collapse so might not look like the massive explosion you want, but here are a few:",
"https://www.youtube.com/watch?v=2RxIwtxdEnQ&t=22s",
"https://www.youtube.com/watch?v=x0jh26fr8Xg",
"There is also the long term telescope images of the 1987 supernova: ",
"https://media2.giphy.com/media/121h7Y3dTIhBGE/giphy.gif"
] |
[
"It depends on how close you are. If you are very close, you see nothing and then suddenly you are in the supernova (because the light doesn't travel much faster than the matter behind it).",
"If you are more distant and don't get directly hit by fast matter, you see the expelled matter expanding very quickly. If you are even more distant, it looks slower. Whatever goes in your direction is blueshifted, but for human eyes it would look white anyway unless you are so far away that it appears as point source."
] |
[
"This is amazing,thanks for sharing this."
] |
[
"Does a magnet ever lose its power?"
] |
[
false
] | null |
[
"Magnets do get weaker over time, very slowly. It's a chemical process rather than anything fundamental to magnetics- magnets lose strength at a similar (like, rough within two orders of magnitude) rate as their structure changes.",
"Neodymium magnets are one of the most stable magnets, for the same reason they're one of the strongest. The neodymium in these magnets is formed into ",
"very long needles (blue) embedded in a supporting honeycomb",
". This ensures that the magnets are lined up with atomic precision and very rigidly. They're very resistant to change and lose <1% strength per decade, which AFAIK is mostly due to oxidization. Oxygen content is the #1 factor in quality in these magnets. ",
"The rate of strength loss tends to drop off after a long time, but it depends heavily on the type and quality of magnet. For instance, steel magnets will tend to drop off very quickly at first and then more slowly. In steel magnets, magnetization causes crystal grains to extend and shrink in certain directions, which causes very large internal stresses. Machinists will know that cold-rolled steel (which has similar large internal stresses) should never be used for precision work, as any cuts will release some of this strain and cause distortions that take hours or days to take full effect. The same thing happens with steel magnets- these stresses will release over time, which will negatively impact the magnetic field. After the largest strains equalize there will still be lots of tiny stresses that will take decades or centuries to decrease (me irl). Over longer timescales, the steel will oxidize, which will eventually fully destroy the magnetism. Wet, salty steel will crumble in a hundred years, while normal water will take millennia, and dry steel will last for tens or hundreds of thousands of years."
] |
[
"No, as long as it's above absolute zero than random thermal motion will eventually mess up the structure."
] |
[
"So if that neodymium magnet was kept in a vacuum or in a chamber with some noble gas (basically, in a place where nothing could react with it), would it theoretically last indefinitely? "
] |
[
"Can single-atom black holes exist?"
] |
[
false
] | null |
[
"A black hole that small would have a radius much smaller than a Planck length. As such, this is the domain of quantum physics. But it also has a black hole, so it's general relativity. Basically, we need a theory of quantum gravity to figure out what would happen.",
"The minimum size to keep the radius above a Planck length is a Planck mass, which is about 2.18*10",
" kg, or about the mass of a flea egg, though a black hole that small would still evaporate extremely quickly."
] |
[
"The minimum size to keep the radius above a Planck length is a Planck mass, which is about 2.18*10-8 kg, or about the mass of a flea egg, though a black hole that small would still evaporate extremely quickly.",
"This isn't quite right; there's a factor of two when you calculate the Schwarzchild radius of a Planck mass. The Planck mass is",
"m_p = sqrt(h_bar c / G)\n",
"Which is something close to 10",
" kg like you said, which is comparable to the mass of an eyelash. ",
"The Schwarzchild radius of a Planck mass is",
"R = 2 G m_p / c^2\n\nR = 2 G sqrt(h_bar c / G) / c^2\n\nR = 2 sqrt(h_bar G / c^3 )\n\nR = 2 R_p \n",
"So the Schwarzchild radius of a Planck mass is two Planck radii. ",
"I want to be pedantic about this point because many people seem to have conjured a mythos around the Planck units as if they have some kind of fundamental significance, when really they're just a convenient set of units. They're useful because you don't have to carry around fundamental constants in your units, and there are some neat coincidences when you plug them into a handful of other equations. In fact, the Planck mass is often defined with an extra factor of 1/sqrt(8 pi) because that's 8pi shows up a lot in general relativity and including it the units helps make the math less cumbersome. The Planck length has attracted the most attention though - claims that it's a 'smallest possible distance' are abundant. In fairness they're not entirely basless; there are some predictions that quantum gravity effects become important at approximately this length scale. "
] |
[
"Uh... let me wave my hands and whisper ",
" ",
"At that scale, it's hard to say. We're mixing incongruous theories. "
] |
[
"WHY do waves propagate?"
] |
[
false
] |
I'm ashamed to say that after studying physics as an undergrad, I never once thought to ask "why?" I understand that as far as, let's say, sound waves go, basically the energy is vibrating through the atoms. The energy travels through air until it hits an atom, then the atom absorbs and then releases energy, and the process continues. I suppose my confusion is really arising when I think about transverse waves. I understand what is happening. I just don't get the why behind it. If we break down a transverse wave and take a look at it particle-by-particle we see the particles moving up and down while the energy is travelling perpendicular. That's my question - why is the energy moving perpendicular? I'm sorry if this is a really stupid and basic question, and I'm a bit ashamed for not knowing the answer already. I'm sure the answer is simple enough, I just never thought to question it.
|
[
"This is a fairly subtle question, actually. The idea of a wave is very challenging to define as it incorporates a huge variety of phenomena. One characteristics of a wave is a transfer of energy from one point to the next without transporting any mass or substance. How can this be achieved? Well, the medium that hosts the wave must have a couple properties:",
"The medium must be near a stable equilibrium.",
"The motion of the components of the medium must be coupled to one another. ",
"It might be easiest to think of a line of particles sitting side by side as our medium. In order to be in stable equilibrium, whenever a particle is pulled a small distance out of its resting position, it would experience a force attempting to return it to its resting position. Then, if we consider that neighboring particles have something like a Morse potential acting between one another (basically a potential that creates a force that attracts the particles to one another if they get too far apart, and repels them if they get too close), when the first particle is pulled out of equilibrium in a direction perpendicular to the string it will pull the second particle out of equilibrium perpendicularly as well. The second particle then pulls the third particle out of equilibrium, and so on. Eventually, the restoring force returns the particles back to equilibrium starting with the first.",
"In terms of energy, all the particle start out in their ground state. When we displace the first particle from equilibrium, we are adding energy to that particle, we can call the amount of energy E. E is initially split between the potential energy of the restoring force and the potential energy of the Morse potential from the second particle. The morse potential then creates a force that pulls the second particle out of equilibrium (does work on that particle) thus increasing the second particle's energy, but due to conservation of energy, whatever energy the second particle gains must be lost by the first particle. At the same time the second particle is being pulled up, the first particle is being pulled down, decreasing its energy. The second particle pulls up the third, transferring some of its energy, and so on down the chain. Eventually, all of the energy, E will reach the final particle on the other end of the chain without causing any displacement of particles along the chain.",
"Hope that helps clarify things!"
] |
[
"In transverse stress waves, the particles do move up and down."
] |
[
"the particles moving up and down while the energy is travelling perpendicular",
"So, its not the particles themselves that move up/down. The up/down represents pressure variation. Think of a compression wave travelling along a slinky, if you periodically squeeze one end of the slinky and let go, you'll have a wave moving from one end to the other. High pressure is like compressed portions of the slinky and low pressure is like stretched portions.",
"Energy is moving the way it is because there is something that is causing it to. In the case of sound waves in air, it is the vibration of the diaphragm of a speaker.",
"When an electromagnetic wave propagates from point A to point B, the wiggly wave that you draw on paper does not represent the actual motion of some sort of particle, it is just the oscillation of the electric and magnetic fields. ",
"EM is fundamentally different from sound in that there does not have to be a medium of propagation or some vibrating object causing the oscillations. An EM wave (light) travels in the direction that it does because you switched a torch on and used a mirror to direct all the light in that direction."
] |
[
"What would the 50 Mt Tsar Bomba blast look like if seen from ISS or the moon?"
] |
[
false
] |
Wikipedia says that it was visible up to 620 miles away. It had a fireball 5 miles in diameter. The blast was still measurable on its third pass around the earth. Surely something of this magnitude could be seen from ISS, but what about the moon? Say ISS was passing over at the time of the blast. What effects could have been measured?
|
[
"As ",
"This picture here",
" shows pretty well, details even 5 miles in diameter would be nearly impossible to see from the moon (at least with the naked eye). I can't say for sure whether or not the flash itself would be visible, but it certainly doesn't seem impossible, if the bomb detonated facing the Moon, with no cloud cover, etc."
] |
[
"The light wouldn't travel in a column, it would radiate (nearly) isotropically. The diameter of the fireball doesn't matter, what matters is the energy released as light, and if its intensity at the moon is such that it is detectable by the human eye.",
"The eye can detect on the order of 10 photons. 50 megatons=200 x 10",
" Joules. Making a wild stab in the dark because I don't know, assume 1% of the energy of the blast was released as visible light, so 2 x 10",
" Joules. Assume it was all red, or ~600 nm wavelength light, then the energy of each photon E=hc/lambda=19.1 x 10",
" J. So total number of photons ~ 10",
" . Given isotropic radiation the photons per unit area at the distance of the moon (R=4 x 10",
" m) is 10",
" / (4 pi 16 x 10",
" )~=10",
" photons/m",
" . Radius of a pupil is about 3mm, or a surface area of pi*(3 x 10",
" )",
" ~30 x 10",
" m",
" . So photons reaching a persons retina on the moon ~ 3 x 10",
" .",
"I think you would see a flash. The energy incident on the pupil would be ~ 6 x 10",
" J. If the flash lasted about a second that's about a microwatt of power. Given the eye can detect a few tens of photons in ideal conditions, and as low as a few thousand in typical conditions, you would see a flash. It wouldn't be very bright, but it would be perceptible, especially if it was night time on Earth where the blast occurred.",
"These are all just rough calculations but I think it demonstrates you would probably see something. Someone with more knowledge about how much of the energy is actually emitted as visible light might be able to elaborate, and I may have made a mistake somewhere in calculation, but I think they're right down to about an order of magnitude."
] |
[
"Wow, very cool. Thanks for taking the time to do (and share) the calculations. This leads me to wonder the smallest a blast could be and still be seen. Could, perhaps, all of our nuclear detonations be visible from the moon?"
] |
[
"Why does newly laid pavement have less water on the surface than older roads?"
] |
[
false
] |
Whenever I drive and it's raining, I noticed that roads that have recently been paved seem to have a lot less or close to no water on the surface than older roads. Mostly because there's a lot less aquaplaning on these roads. Does asphalt lose it's tendency to absorb water over time? Is this true, or is it just an illusion? Or just a coincidence that these new roads have a good slope that avoids water from staying on them? Offtopic: Does this go in Physics or Planetary Sciences?
|
[
"Modern asphalts are actually designed to be porous to allow drainage. Over time, dust clogs the pores and their ability to drain is affected."
] |
[
"Also, ruts can form and puddle water in old roads that see heavy truck traffic"
] |
[
"How is this done? Does it drain all the way through, or does it just have more surface area to evaporate? "
] |
[
"At what altitude above Earth do the effects of Special and General relativity cancel each other out?"
] |
[
false
] |
First, if this question doesn't make sense, please tell me, because I am going under some very rocky understandings of special and general relativity. So as I understand it, in special relativity, the faster someone moves, the slower time is for them, relative to someone who is stationary. In general relativity, the further away you are from a massive object, let's use the Earth, the faster time will move for you, relative to someone on Earth. So astronauts on the ISS age slower relative to us because they are moving extremely fast, but aren't at a high enough altitude for the effects of general relativity to overcome the effects of special relativity. However, for GPS satellites which are in a higher orbit, the opposite is true. So at what orbital altitude do the effects of special relativity and general relativity cancel each other out so that no time dilation occurs relative to a man on Earth, assuming that the orbit is perfect, with the apogees and perigees being equal? Or do I not understand something here? Edit: Thanks for the gold, but I think agate deserved it more.
|
[
"Wow, this is an interesting problem!",
"The time dilation factor for an ",
"object at rest near a spherical planet is",
":",
"t_e = t_f sqrt(1-r_s / r_e) ",
"where t_e is the proper time elapsed at radius r_e, t_f is the coordinate time elapsed very far from the object, and r_s is the \"Schwarzchild radius\", which depends on the mass of the planet. Typically r_e is much bigger than r_s, so t_e is slightly smaller than t_f, so clocks in a gravity well tick slower.",
"The time dilation factor for an ",
"object in circular orbit near a spherical planet is",
":",
"t_o = t_f sqrt(1-(3/2) r_s / r_o) ",
"where t_o is the time elapsed in orbit of radius r_o, compared to t_f the time elapsed very far from the planet. Clocks ",
" also tick slower than they would at infinite distance, but by a different factor than a clock at rest. Your question is, given r_e = the radius at the Earth's surface, for what r_o does t_o equal t_e?",
"It's a pretty easy algebra problem, and interestingly, all the dimensional factors cancel out and the final answer is just:",
"r_o = (3/2) r_e",
"For an orbiting clock to tick at the same rate as a clock at rest on the Earth's surface, the radius of the orbit should be 1.5 times the radius of the Earth, or about 3200 km altitude. (ISS orbits at 400 km; GPS satellites orbit at 20,000 km, so you're right, this is somewhere in between.)"
] |
[
"Fantastic response! Thank you very much for this answer! Funny how some seemingly complex questions can have surprisingly simple solutions."
] |
[
"That was an excellent question! Thanks for sharing!"
] |
[
"Magnet pushed into an open circuit solenoid"
] |
[
false
] |
By Faraday's law of electrostatic, there will be an induced emf. But since there isn't a complete circuit, so no current will flow through it (ignoring that little current). Since there is no current then there won't be a induced pole forming, so no repulsive force when I try to push a magnet into the solenoid?
|
[
"That's right. An open circuit has practically infinite resistance, so the finite emf (which comes from -d(BA)/dt) will result in zero current and therefore zero induced magnetic field."
] |
[
"This is correct, however there will still be eddy currents in the metal which create a drag on the magnet. There is a neat demonstration showing this where you take a copper tube and drop a magnet through it. The magnet will fall very slowly because of the currents induced in the copper tube. This effect will be much smaller for a solenoid, though."
] |
[
"Oh thanks, I read about that Eddy current which is sort of an induced movement of charges in the solenoid. But I'm in GCE O levels so I don't really bother so much about it. Thanks for the help."
] |
[
"Do wasps have an important place in our ecosystem or could they be removed without any really noticeable effects?"
] |
[
false
] | null |
[
"Wasps eat flies and other insects. Think of it this way; one female house fly with fertilized eggs, if all her offspring survive and their offspring also survive, etc... in less than a year there would be enough flies to cover the entire earth with flies. So predators on insects are important, although flies are also eaten by birds and spiders and so on, so it's not just up to the wasps. But yes, they do perform an important ecological function by predating on insects and keeping the balance intact. ",
"It's the same with pests (I would object to your definition of \"other pests\" as including wasps because I don't consider wasps to be pests; they don't do any harm). The reason to why humans get problems with pests is that we provide an envirorment where they benefit from an unnaturally high food resource or unnatural protection from predators. We kill all the snakes who eat mice and then provide warm housing for them in the winter, and then we act surprised when the mice invade our crops or whatever. So then we combat mice with poison and traps, instead of having a natural balance.",
"TLDR; Humans are really good at disturbing the balance in nature; hence we have pests. All animals in their natural habitat have a role to fill; a purpose with their lives."
] |
[
"I know that wasps and fig trees coexist. The figs give the wasps a home to reproduce & what-not, meanwhile the wasp helps spread the fig trees sperm (or whatever it is fig trees have).",
"Source: ",
"Common knowledge"
] |
[
"This is a blanket response. True, no species on Earth could be removed without consequence, but my question is whether or not there would be a large noticeable consequence. Species have gone extinct, even some recently, and yet not all of them have a truly noticeable impact on our ecosystem as a whole. Bees, while still around, already have proven their place since their drop in numbers has had a resounding impact."
] |
[
"Can someone explain how this picture of an Atom might be a bad representation of what it's like to be an atom?"
] |
[
false
] |
[deleted]
|
[
"Scale misrepresentations aside, the orbiting electrons are one of the biggest flaws of the Bohr Model, and the point-particle diagrams are inaccurate as well.",
"Firstly, As ",
"Maxwell's Equations",
" state: \"all changing electric field (i.e. moving electric charges) must produce a magnetic field (and the reverse is true, evidenced by the partial differential),\" therefore the orbiting electrons must emit electromagnetic waves continuously and their orbit must decay, eventually crash into the nucleus.Since no natural occurring atoms decay as such, this primitive diagram cannot be an accurate representation.",
"Secondly, with the the formulation of The Uncertainty Principle, and wherein stems ",
"Wave-Paticle duality",
", the electrons, while in orbit, cannot be determined to behave like a wave or particle with 100% certainty. Therefore a particulate representation is also flawed."
] |
[
"Electrons exist in orbitals. Think of a \"shell\" around the nucleus, and the probability for finding the electron exists throughout that shell. As they occupy different states of orbital angular momentum, these shells can take different shapes. ",
"This image is more realistic",
", again keeping in mind that they are probability distributions and do not correspond to the electron's actual motion, which it doesn't have as explained by NonlinearHamilton. "
] |
[
"i have been taught energy levels as S P D F how does l and m relate to this?"
] |
[
"Wheel movement problem!"
] |
[
false
] |
So my physics teacher poses this question that I thought was very interesting, and while I have my own answer for it, I feel like it's not correct. Assume you have a wheel on a ground where friction is too high for ANY skidding to occur. The pedal on the wheel is pointed down wards. The wheel turns right if the pedal turns clock wise, and vice versa. If a rope is attached to the end of the pedal, and the rope is pulled straight to the left, what does the wheel do?
|
[
"Ooh, this is very clever. Assuming the pedal is shorter than the radius of the wheel, the contraption doesn't move.",
"Let the radius of the wheel be 1 meter. Let P the length of the pedal shaft, anything less than 1. Let θ be some angle in radians that the wheel rotates around its axle, less than π/4 radians-- that is, some acute angle.",
"Rotate the wheel without the rope attached. The whole contraption will move θ meters to the right. (This is the definition of radians!)",
"The rotation will also move the pedal leftward, by P*sin(θ) meters. Note that because sin(θ)<θ for all θ>0, and we defined P<=1, that means P*sin(θ) is strictly less than θ. ",
"Observe that the pedal's net rightward movement is the axle's right movement minus the pedal's own left movment: that is, θ-(P*sin(θ)). We just showed that P*sin(θ) is less than θ. Therefore, when the wheel rotates through any acute angle, the value is positive-- meaning the pedal has a net rightward movement.",
"In other words, with no skidding allowed, there's no way to pull the pedal left and have the contraption move right. Your scenario is static and the pull of a nonelastic rope has no result.",
"[Edited to add this part]",
"\n",
" Never mind, I'm sticking with my original answer."
] |
[
"The wheel will rotate on its vertical axis towards the direction the rope is being pulled."
] |
[
"I like this answer! I plan on actually testing this out today, and I'll come back and post if you were right! "
] |
[
"Why are some languages (Kanji and Traditional Chinese, for example) written as \"pictures\", so to speak, and western languages are based more on syllable structures? Is there a historical reason for it?"
] |
[
false
] |
Why have some languages evolved to be picture languages, whereas western languages are usually based on syllables? It can't be random. There's got to be a certain historical reason for it. I'm sorry if the term "picture" language is incorrect, I tried to think of a better way to describe Kanji/Trad. Chinese and this is the best I came up with. :/
|
[
"Writing was independently invented in only a handful of places on earth, and all modern writing systems are descended from the ones invented in Mesopotamia and China. They actually seem to have begun similarly, using pictographs to represent first whole words, then evolving these into more abstract forms (logograms) that could be combined to create a more flexible system capable of representing abstract concepts. They then started to develop phonetic components that represented sounds rather than entire words or concepts. This is where they split. ",
"Mesopotamian-derived systems continued to develop more and more phonetic components and eventually dropped the logographic aspects entirely. Such systems, which have been adapted to nearly every language on earth, now use entirely phonetic components to represent only sounds and not concepts.",
"Chinese did not: instead more and more logograms developed, and they began to reduce some logograms to very simple abstract shapes that were then combined to build up new logograms. Sometimes phonetic components were (are) included, but each individual character is an abstract logogram representing a concept rather than a syllable or phoneme. There are some advantages to such a system, but it didn't spread as widely as the phonetic systems, partly due to cultural isolationism and partly due to geographical reasons, but mostly because it's much harder to learn than a phonetic system."
] |
[
"One advantage is that a single written language can more easily be used by people with different spoken languages and dialects. (Monolingual) Cantonese speakers won't understand Mandarin, indeed speakers of one dialect of Mandarin might not understand another, but all will understand written Chinese (if they can read at all). And there are ",
" of spoken Chinese dialects."
] |
[
"What are the advantages of logogram systems? At first I thought it would be a lack of words that mean multiple thing but in Chinese there are many words that mean multiple things."
] |
[
"When and where would I have to stand on the earth to be traveling the fastest through the universe?"
] |
[
false
] |
So, I'm assuming that it would have to be somewhere on the equator to be moving the fastest on earth. Then there would be a point durring the day that I would be most inline with earths orbit around the sun. And then I would assume that there is one time a year that the earth is moving forward the fastest. But I have no idea how to figure that out.
|
[
"Right now, at this very moment, you are moving at very, very close to the speed of light. You are also at rest.",
"\"Speed through the universe\" isn't a well defined concept. There is only \"speed relative to [thing]\". You can ask where on Earth you should stand to be traveling the fastest relative to the sun. You can ask where on Earth you should stand to be traveling the fastest relative to the Earth's center. You can ask where you should stand to be traveling fastest relative to the moon. But \"through the universe\"? That's just not something that can be given meaning."
] |
[
"I remember talking to some professor about a science fiction book about the wealthy building their houses in the sky to live longer. You might also find this interesting: ",
"http://www.independent.co.uk/news/science/einsteins-theory-is-proved--and-it-is-bad-news-if-you-own-a-penthouse-2088195.html"
] |
[
"The earth is at perihelion (closest to the sun) on January 4 (note this changes slowly over time). When the earth is closest to the sun is when it will be moving the fastest in its orbit.",
"So, on the equator at night (not sure of exact time) on January 4.",
"NOTE: I am not sure where we are in our orbit around the galactic center and how that motion would apply here. I certainly have no clue how to assess our movement relative to the other galaxies in our local group."
] |
[
"Is there any evidence that Dark Matter is comprised of individual Dark Elements? Is there a Dark Periodic Table of Elements? [x-post from /r/AskReddit]"
] |
[
false
] |
Credit to for original question
|
[
"There has been a proposal along these lines by Kaplan et al. You can read a journalistic account of their ideas ",
"here",
" or see their paper ",
"here",
". While this proposal is certainly speculative (we do not have the evidence to rule it in or rule it out), the authors do identify features that would distinguish such a scenario."
] |
[
"There's very little indication about what dark matter is, other than that it ",
" interact (very much) through the electromagnetic force. That's why it's dark!",
"So that means there could indeed be more than one dark particle, even dark forces that dark matter feels but other matter doesn't. That could mean that you might indeed have dark chemistry, if the interactions are complex enough.",
"But that's all speculative. There's no evidence (yet!) for or against any of this, and most fundamental theories don't predict such complex interactions in the dark world."
] |
[
"I have what is probably a silly question, but from what I read there is way more dark matter (85%) than ordinary matter (15%) in the universe. Why isn't there any here? Or is it here right around us and we just can't detect it?"
] |
[
"How does our brain determine which musical tones sound correct or incorrect?"
] |
[
false
] |
The more I learn about music, the more it seems like a sixth sense. What makes a musical tone sound "in key" or "out of key?" How do we detect notes that are sharp or flat?
|
[
"It is worth adding that the notions of \"in key\" and \"out of key\" are learned concepts. As Skull_flower says, the ear works by registering the different frequencies in a sound. But whether that pitch sounds right or not has to do with our cultural conventions of what tones we think are acceptable."
] |
[
"It has to do with how our brain processes sounds from the ",
"cochlea.",
" A certain region of the cochlea is excited for every musical pitch (frequency) and your brain can remember which region that is with practice."
] |
[
"So someone that has never been exposed to music could have a really different idea of what sound musical?"
] |
[
"Can a sun have a ring?"
] |
[
false
] | null |
[
"Yes, and our own sun has two! The ",
"asteroid belt",
" and the ",
"Kuiper belt",
". They happen to be pretty far our from the sun, and may not look like \"classical\" ring systems like Saturn, but consider:",
"Asteroid Belt:",
"a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars, that is occupied by a great many solid, irregularly shaped [rock and/or metal] bodies, of many sizes but much smaller than planets...",
"Kuiper Belt:",
"a circumstellar disc... Analysis indicates that most Kuiper belt objects are composed largely of frozen volatiles (termed \"ices\"), such as methane, ammonia and water.",
"Other stars with rings are known. The first seems to have been discovered in the late '90 by You-Hua Chu (University of Illinois). In ",
", Craig Wheeler wrote (in 2007):",
"You-Hua Chu scored another coup a decade later, at a meeting in Chile to celebrate the tenth anniversary of the discovery of the supernova, when she reported that she had discovered the first star to have rings around it, like the progenitor of SN 1987A.",
"SN 1987A was a supernovae that exploded in 1987. The progenitor (the star that actually exploded), Sk-69 20, was a blue supergiant. ",
"Pictures taken from Hubble",
" showed three rings."
] |
[
"There are other homologies between Saturn's rings and the Main Asteroid / Kuiper Belts, too.",
"Saturn's ring system is particularly detailed in its ",
"gaps",
", which in turn are caused by ",
"resonances with nearby moons",
". If I'm a particle orbiting in the rings and keep getting a nearby pass of a moon in the same place every X orbits, that's eventually going to perturb my path (though there are also resonances that are stabilizing).",
"Although the Main Asteroid Belt likely once had neater circular orbits than present, that was thrown into disarray early in the history of our Solar System when Jupiter migrated inward. That stirred up the asteroids into more eccentric orbits that better resemble ",
"a flat cloud",
" rather than perfect circles. ",
"Nonetheless, Jupiter has a very similar influence on the Main Asteroid Belt to Saturn's moons acting on its rings. Since most asteroids are on eccentric, oblong orbits, if you just plot their average distance to the Sun you still get ",
"a surprising order",
" that shows the resonance gaps with Jupiter.",
"Similarly, Neptune induces ",
"resonances in the Kuiper Belt",
". Pluto orbits twice for every three times that Neptune orbits, making its orbit particularly stable, while \"two-tinos\" orbit once every two orbits of Neptune."
] |
[
"Protoplanetary disks",
" are basically rings. Just like the rings of the planets have gaps from moons these disks develop gaps from planets."
] |
[
"What causes people to act different when drinking than when sober?"
] |
[
false
] | null |
[
"From a medical perspective, alcohol affects different parts of the brain in different concentrations. The most sensitive area of the brain to alcohol is the prefrontal cortex. This is the area of the brain responsible for urge inhibition, planning, and executive thought. With alcohols intoxication, these processes are impaired leading to changes in behavior and poor impulse control.",
"As you continue drinking and blood alcohol levels rise, more parts of the brain are impaired. The frontal cortex is next, leading to problems with speech, coordination, and certain reflexes (like visual tracking). After that, the hippocampus is affected leading to the inability to form memories (blacking out). If you continue to drink, the brainstem can be affected leading to depression of the reticular activating system and several centers critical to the support of vital functions. This will make you pass out and possibly stop breathing."
] |
[
"From a legal perspective, it's a matter of proximate cause. You may not have been acting intentionally once drunk, but you intentionally ",
" drunk. "
] |
[
"While the medically relevant effects show up after drinking a lot, most of the behavior we associate with people who have had a couple of drinks is due to social conditioning. ",
"There is a study that took four groups:\nthe first was given a couple drinks and were told they contained alcohol",
"the second received nonalcoholic drinks and was told there was no alcohol",
"The third was given drinks with vodka smeared on the rim and were told there was alcohol in them",
"The fourth was told they weren't receiving alcohol in their drinks but there was alcohol in them",
"Groups 1 and 3, and 2 and 4 behaved the same, people who thought they were drinking were louder and more gregarious, while those who believed they weren't drinking tended towards staying in small quiet groups "
] |
[
"Why do cans of soda sitting at room temperature always feel slightly cooler than the air itself?"
] |
[
false
] | null |
[
"Metal conducts heat very well. Both the air and metal can are at \"room temperature\" and your body is much warmer. Metal pulls heat from your body more quickly than the surrounding air does, which makes it feel colder."
] |
[
"What kind of biochemical mechanism would there be for detecting heat transfer? Not meant to be a rhetorical question, as I really would like to know. I was under the impression that we do feel temperature, but it is the temperature of our own skin and not of the thing we're touching."
] |
[
"Just adding onto this - you don't feel temperature, you feel heat transfer. This is why 80 degree water feels cooler than 80 degree air (the water transfers heat away from you better). ",
"If you could build an object that was 300 degrees but somehow took heat away from you, it would feel cold to the touch. "
] |
[
"What exactly happens in the breakdown of ingested materials?"
] |
[
false
] |
When we ingest anything, it ends up in our stomach, where there's a very low pH of ~1. This breaks down food, right? My question is, I keep hearing how our bodies take in Amino Acids, Proteins, Drugs, everything through the digestion system. Does the HCl present in the stomach not break down this compounds further? From what I gather, these compounds enter the Intestines, where there's a pH of ~7 and are absorbed into the blood stream. Basically, I understand everything except the stomach. Does the very strong acid not breakdown amino acids, proteins and drugs that we take? Do these just get passed through to the intestines?
|
[
"There is a special enzyme released in the stomach at the same time that the HCl is. It is called pepsinogen and at very low pHs it is cleaved into pepsin. The pepsin enzyme then breaks down the proteins. Once they are broken down into their basic units, they can be absorbed by the blood stream. ",
"The most amazing thing for me about the stomach is that it does not degrade itself. There is a thick layer of mucus to protect the surface from being broken down by the enzymes or damaged by the acid. ",
"An important part of drug discovery is finding compounds that will not be immediately degraded by the harsh environment of the stomach. "
] |
[
"Your teeth are your first step in breaking down the food to a level that's digestable. Your stomach continues this. The pH in the stomach is debatable, because foods will buffer it, so food may only be exposed to pH of 3-5. Regardless, the stomach does not break down glucose or proteins into atoms, so most of the nutrients are bioavailable.",
"Take something like bread. The starch in the bread must be converted to glucose, which is then absorbed into the small intestines. But the glucose is in the very long starch molecules, which are entrapped by the wheat protein, which is entrapped by the bread matrix. So your teeth break up the bread, the saliva contains an enzyme that starts converting breaking down the starch into sugar, the stomach acid breaks down the bread into even smaller particles which is easier for the other enzymes from the pancreas to break down the starch into glucose in the intestines and absorb it. Also, the bread protein needs to be broken down; it has 4 orders of structure. The stomach acid helps break down this structure so the protein enzymes can break it down to amino acids.\nWhile wheat proteins are 98% digestable, corn proteins are much less digestable, so even your stomach acid won't break through a lot of it. A lot of the protein from corn will not turn into amino acids, so after they leave your small intestines, they will end up fermenting in your large intestines, being used for energy instead of building blocks.\nI hope that clarifies a few things."
] |
[
"MD/PhD student here, hoping I can help:",
"The stomach actually relies on more than just acid to break down food. It secretes additional factors that help, including two worth a brief mention: pepsin and intrinsic factor. Pepsin plays a role in breaking down proteins into short chains of amino acids, while intrinsic factor binds vitamin b12 (allowing it to be absorbed later in the GI tract). The stomach also has fairly muscular walls, and is able to churn the food into small pieces via muscle contractions. Things like amino acids, drugs, small carbohydrates, etc. are largely resistant to acidic pH as well as these other methods, and are not degraded in the stomach. As far as how these things are chemically able to survive the acid, I can at best speculate; a chemist might have a better answer on that front.",
"So, what happens after the stomach? Well, food enters the small intestine, which is primarily an absorptive organ. When the food enters, however, it stimulates the pancreas (a truly underappreciated organ) to secrete trypsin (digests proteins), amylase (digests carbs), and lipase (digests fat) into the intestine. Generally, it is these pancreatic enzymes that break down everything into simple enough components (ie amino acids) for the intestines to readily absorb them (they finish the job the stomach started, if that makes sense). Obviously, there's a lot more to the process than this, but I tried to give you a basic idea here. I hope this helps, and if there's anything else you want to know, I'll be happy to try to answer again!"
] |
[
"Is there enough genetic material left in a loaf of bread to trace it back to the wheat plants used to make it?"
] |
[
false
] | null |
[
"Hmm. Interesting question. The first thing to ask is did we destroy the genetic material during the milling process? It turns out that DNA is pretty sturdy, and in labs we’ll often subject cells to some pretty tough conditions (blasting glass beads against them at a high speed, or sonication, for instance) just to ",
" to the DNA, and that generally leaves plenty of intact genetic material for us to work with. Being that the proteins in wheat are still intact (we rely on the glutens, a protein, to “stick” the dough together), it’s likely that the DNA is too. ",
"So the second question is, does the DNA get destroyed during the baking process? A quick google search tells me that the internal temperature of bread rises to 190 degrees Fahrenheit, or about 88 degrees Celsius. Well, in the lab we will raise the temperature of DNA up to almost 100 degrees Celsius during a PCR reaction to denature (that is, separate the two helical strands from one another) without destroying the DNA (when you cool the DNA down, it’ll re-anneal back to the other strand, or to whatever strand you’re trying to make it anneal to). However, this is done inside buffers made to stabilise the DNA. ",
"A quick google search",
" suggests that DNA degradation starts at around 130 degrees c in dry heat. Now, whenever I bake bread, I generally introduce some steam when I first place it in the oven, so it’s likely not terribly dry, nor will it be inside of a wet dough. However, that same paper suggests temperatures above 90 c in moist air will start degradation of DNA. And we said the internal temperature of the bread should be 88c when the bread is done. ",
"In conclusion, I do believe we could isolate intact DNA from a loaf of bread, and that we could recover enough intact DNA to determine its origin. ",
"Source; I’m finishing my PhD in molecular genetics and biochemistry this year (yay!)"
] |
[
"The next step is finding the plant of origin. Is there enough diversity in domesticated wheat to do so?"
] |
[
"So, I’ll say up front, I deal entirely with prokaryotes, which wheat is not. However, when we want to identify a bacteria, we will examine the 16s rRNA gene, the gene that encodes for the RNA that makes up the ribosome. It’s particularly useful in that it’s conserved enough (or similar enough) in all bacterial species that we can create a single set of primers (short single stranded DNA) that can bind to that gene in every bacteria. But it’s also different enough that, when we sequence it, we can then run it through a database (called BLAST, or Basic Local Alignment and Search Tool) that will compare it to every known DNA sequence we know of, and if we have pure enough, well sequenced enough DNA, we can identify precisely which organism it came from. ",
"Now as I said, I’m not an expert with eukaryotes like I am prokaryotes, but I do believe that the 18s rRNA gene in eukaryotes (and therefore wheat) works the same way."
] |
[
"(Psychology/neurology) Can anyone help me explain some childhood mental/somewhat hallucinatory experience?"
] |
[
false
] | null |
[
"Hi bigbluesanta 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 following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"'Neuroscience'"
] |
[
"Neuroscience"
] |
[
"How does NASA figure out how to rendezvous with a meteor?"
] |
[
false
] | null |
[
"Hi novalavaly 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 following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"Your posting guidelines doesn't mention anything about flair"
] |
[
"'Astronomy'"
] |
[
"Do we know if there is some evolutionary benefit to 'cringing' at things?"
] |
[
false
] | null |
[
"I always thought of it as something useful surviving as part of evolution, not developing due to it."
] |
[
"I understand that, but people think that many social actions are an evolved response. For many things I.e. laughter, disgust you can see the benefit to them. However I cannot see what is a benefit of cringing."
] |
[
"I agree with this. It could be that we've developed empathy through evolution, and a side-effect is cringing at others' pain."
] |
[
"Why don't we just shoot nuclear waste of our atmosphere and into the Sun?"
] |
[
false
] |
A lot of the criticism regarding Nuclear energy that I hear is regarding the decaying materials afterwards and how to dispose of it. We have the technology to contain it, so why don't we just earmark a few launches a year into shooting the stuff out of our atmosphere and into the Sun (or somewhere else)?
|
[
" Because it's stupid expensive and it's stupid dangerous if a rocket blows up on the launchpad. Please don't do this. ",
" ",
"This question gets asked surprisingly frequently.",
" So frequently, in fact, that I'm surprised there is no FAQ answer for it. Anyway.",
"At the moment, the current cost of launching stuff into orbit is about $20,000 per kilogram of your payload. That's just to get into orbit, that's not counting the additional fuel kick needed to get your vessel going to the sun. Also, that's not counting the fact we can't really recycle these craft that are getting sent to the sun.",
"Now consider that there are approximately ",
"270,000 tonnes of fuel waste in storage",
" (not counting medical waste, or radioactive components from old reactors). ",
"Now consider that even one accident trying to launch one of these rockets means you've just splattered a ton of radioactive waste all over the launch facility (or worse, the upper atmosphere). Basically, you've just caused another Chernobyl, irradiating an entire region or country, depending on the altitude of the explosion, local wind speeds, nuclear payload, etc. ",
"But can we design these rockets to be safe? Well sure, they're all safe until they blow up. Spaceflight hasn't had all the bugs worked out yet, ",
"and there are still have incidents on a yearly to monthly basis.",
" Fortunately, these generally ",
"only destroy an unmanned rocket, with a payload of a few satellites, in a big fire ball.",
" That story was from a little over a month ago. Now consider that if even one of our \"waste-to-sun\" shuttles pop, we have just fucked up the environment for years. ",
"And before you say space elevators, they won't help.",
" Rail guns or cannons? ",
"Please no.",
" Space, as empty as it is, is a terrible junkyard. ",
"All in all, we're better off shooting them into the ",
" Of course, by that, I mean burying it. It's closer, and it's less dangerous. If we're lucky, sometime in the future, someone will work out a way to transmute certain wastes into usable fuel really cheaply, or accelerate the decay of the really nasty stuff so that it won't be radioactive for millions or billions of years. ",
"Please, if you have a rocket capable launching from the ground and escaping low earth orbit and large amount of radioactive waste to discard, don't do it. Call up your local division of the Department of Energy or Environmental Protection Agency and they'll get you in touch with appropriate waste disposal agents. Don't tell them about the rocket though, I can handle that- just PM me when and where I can pick it up. I can find something to do with it. "
] |
[
"People thought about putting the waste into subduction zones. However, the fear was that those regions are typically active with volcanoes too and then you have the possibility of it coming out. Radioactive volcanoes would not be fun to deal with."
] |
[
"Russia proposed a plan for a ",
"\"Hot Drop\"",
" where hot, dense radioactive waste would be concentrated inside a tungsten ball, dropped in a borehole, and simply allowed to melt and sink into the Earth indefinitely.",
"The melting process would be very slow, but the heat generated simply would have nowhere to go and buildup of high temps is inevitable if the radiation is intense enough. Drilling the original bore can only proceed so far before the temps get too high for any drill bit made, far below the water table. But the Hot Drop has conceivable limits. As you get deeper, ambient temp increases and the surrounding rock melts easier, and at some point the rock will already be melted into magma and it just needs to sink. ",
"Eventually the temps will become high enough to melt the container. The material may get spread out and the resulting dilution of its energy generation would be unacceptable at lesser depths, but if it's hot enough to melt a tungsten case then it no longer needs the heat of its decay, the surrounding geology is already liquid magma.",
"The Earth's core IS supposed to be pretty radioactive anyhow (we know surprisingly little about what's under the crust). ",
"The concept would only work with concentrated, highly radioactive, high-density waste. "
] |
[
"What would be the result if we disproved the Equivalence Principle?"
] |
[
false
] |
I just read and while it has a stupid/flashy title, the real message is pretty amazing: it claims that results show that the electromagnetic coupling constant varies across the observable universe. What does it mean for us if the universal constants weren't, well, constant? (In other words, what does it mean if we falsified the Equivalence Principle?) What would it mean for creation of new elements and unimaginably exotic life on the other side of the universe? If we traveled to a place with different constants would we be wrenched apart?
|
[
"From the article:",
"which negates Einstein's equivalence principle, which states that the laws of physics are the same everywhere.",
"This is actually the ",
" principle",
", not the equivalence principle."
] |
[
"Ah, you're right. But the question still stands, just swap the words."
] |
[
"Actually, I think the cosmological principle states that there is no preferred position or direction in space; this leads to the isotropic+homogenous symmetry reductions that give us an FRW form of the metric on large scales.",
"There are several different 'equivalence principles': weak, Einstein, and strong. Saying that the laws of physics are the same everywhere goes under the Einstein and strong equivalence principles, because it's saying that the outcome of any non-gravitational experiment in a freely-falling frame is independent of velocity and location of the experiment."
] |
[
"Would a multivitamin be more effective at preventing illness taken before or after being exposed to a virus? Or would it be negligible?"
] |
[
false
] |
[deleted]
|
[
"There is actually no evidence to suggest taking supplementary multivitamins help with immune function (assuming you eat a balanced diet and don't have any metabolic disorders). ",
"",
"Interesting note: The whole vitamin C immune thing was started by Linus Pauling, a Nobel Prize winning chemist. Later in his life he became obsessed (went off his rockers) with the idea that Vitamin C in high doses helps immune function. With the nobel prize in hand, people believed him. But physiology and immunology were not where his expertise was. Consequently, no study has really shown this to be true."
] |
[
"Generally the answer is going to be negligible because, for the most part, whether you take it before or after, a multivitamin won't do much to help prevent illness caused by a virus infection.",
"One vitamin that is critical to immune function and which many people are deficient in is vitamin D so it's certainly possible that you could benefit, though.",
"In any case, if a person did have a deficiency that effected their immune system, then the answer would always be before. There's never going to be a benefit to delaying treatment."
] |
[
"Didn’t he get cancer and die?"
] |
[
"What do magnetic field lines actually represent?"
] |
[
false
] |
I used to think they just graphically represented the direction of the field at a given point, but Wikipedia's article on ferrofluids states that they are regions of higher field strength (hence the spikes on ferrofluid near a magnet).
|
[
"They do represent the direction of the magnetic field at a point. The strength of the field is typically indicated by the density of field lines, i.e., a high density of field lines represents a high intensity field."
] |
[
"But then what causes the ",
"spikes",
" in ferrofluid? Surely there must be a larger magnetic field at those points?"
] |
[
"Hmm, so it's like dunes in the sand — minor asymmetries build up to make big ones?"
] |
[
"Could an induced coma cure someone of an addiction?"
] |
[
false
] |
This was mentioned in a thread on when someone claimed that they went into a coma due to a motorcycle accident and through it lost their addiction to cigarettes. If this is possible, then would it be possible, in very drastic cases, to induce a coma in a person to cure them of an addiction?
|
[
"If a person is unconscious through the duration of their withdrawal symptoms, they could possibly be over the physical addiction when they wake up."
] |
[
"When using Naltrexone to \"fast-detox\", a person is put under general anaesthetic so that they do not get the physical withdrawal "
] |
[
"It exists ",
"UROD",
" but I dont know much about it , and I cant get access to any of the pubmed papers ( all of which are about 20 years old anyway ) so i cant comment on how effective it is"
] |
[
"AskScience AMA Series: We are Tabitha Lipkin and Liv Williamson a Naui Dive Master and NBCLX host and a marine biologist respectively. Ask us anything!"
] |
[
false
] |
We partnered to teach you all about how to restore coral reefs and save our oceans. Liv is a Ph.D. candidate and scientific SCUBA diver at the University of Miami with a passion for coral reef conservation. She loves baby corals, and runs a sort of "fertility clinic" to help corals reproduce and raise their offspring to be fit to survive under environmental stress. Tabitha has been scuba diving for more than 10 years on reefs all over the world. In 2014 she won "Miss Scuba International", and with the title and platform, she's continued to share her passion for ocean conservation and activism around the world. We'll be here at 1pm ET (17 UT), ask us anything! Username:
|
[
"What are some suggestions for how to stop the reduction of coral reefs around the world?",
"Also do you have any internships for a junior in environmental science with a focus on marine conservation?"
] |
[
"Thanks so much for your question! There are many ways that citizens can contribute to coral reef conservation. ",
"Vote! Coral reefs are under threat from many environmental stressors, so voting for politicians that advocate for protecting the environment and oceans is a great way to contribute to positive change on a large scale. ",
"Get involved in a citizen science project to help plant corals on degraded reefs. If you are a snorkeler or SCUBA diver, you can join organizations like Rescue a Reef and Coral Restoration Foundation on coral restoration expeditions and get hands-on experience planting corals! ",
"Reduce, reuse, recycle! Coral reefs and other ocean ecosystems are plagued by plastic pollution, so reducing your consumption of single-use plastics is a great way to help reduce pollution that makes its way to the ocean.",
"Donate to organizations that help conserve and restore coral reefs. ",
"Talk to your friends and family about how they can make more sustainable choices. ",
"- Liv"
] |
[
"I think artificial objects can be a wonderful way to start. Many life-forms in the ocean actually cling to and build off metals and concrete. Tires are made of rubber and not all artificial reefs are the same. marine life doesn't seem to cling-to the rubber the same way, plus they can be corrosive and toxic. Check out this article from Sport Diver: ",
"https://www.sportdiver.com/scuba-diving-rubber-tire-artificial-reefs-france-florida",
"-Tabitha",
"Tabitha is right! Most marine life likes to attach to substances that are made of certain things and give off certain chemical cues, and rubber is not one of those things! They tend to like structures like concrete that resemble a rock-like texture. Many marine organisms really like objects that have crevices and grooves for them to hide in as well, so a textured surface can help. In general, objects that are toxic would not be allowed and would not receive a permit to be able to be placed in the ocean.",
"- Liv"
] |
[
"Do metals/alloys resonate electrically like quartz and other crystals do?"
] |
[
false
] |
I know that quartz crystals can be made to oscillate electrically, and for this reason are used as high-Q filters for the feedback paths of electrical oscillators. Is there a similar resonant property for metals (obviously not piezoelectric)? I know that the quartz resonant frequency is influenced by its dimensions, so I'd be looking for something more intrinsic to the metallic structure itself (independent of overall geometry). For instance, if I am presented with a sample claimed to be 70% gold, with the remainder being copper, is there any way to test that electrically? Something like "The impedance of such an alloy would have a peak/trough at 770MHz. The actual peak was measured at 760MHz, indicating only 60% gold."
|
[
"The reason quartz works is because it's a piezoelectric. This is determined by the crystal structure, which has to have some sort of charge ordering that's distorted when pressure is applied. It also (as far as I know) has to be insulating or else you don't get the localized charges you need. This makes metals inherently bad for this application."
] |
[
"The reason quartz works is because it's a piezoelectric. This is determined by the crystal structure, which has to have some sort of charge ordering that's distorted when pressure is applied. It also (as far as I know) has to be insulating or else you don't get the localized charges you need. This makes metals inherently bad for this application.",
"He wants to test the mixture of the alloy, not create a metal oscillator (unless he had hidden intentions), so your answer seems off target. I can't answer him though, but perhaps you can after reconsidering?",
"As far as I know the low impedance of metals will make the delay ",
" short for changes in the electric field, and factors such as how the alloy is crystallized (wrong word perhaps, I am not native in English) and how well it is mixed could well make it very difficult to make an accurate measurement."
] |
[
"Well, from my perspective the issue is that you won't get any sort of resonant frequency aside from the phonon spectrum, which probably would be a really complicated way to figure out purity."
] |
[
"Why does antimatter have opposite electric charge instead of opposite strong force color (or something)?"
] |
[
false
] |
[deleted]
|
[
"It has opposite charges for ",
" - this includes the color charge."
] |
[
"Mass is different from charges in many aspects."
] |
[
"The answer is that they do, but particles we can actually \"see\" are always white, and the actual color of each quark is always changing anyways.",
"Anyways, the color charges are red, green, blue, anti-red, anti-green, and anti-blue. Particles group up to form white total color charge. So that can be combinations like Red/Green/Blue, or Anti-Red/Anti-Green/Anti-Blue, or something like Red/Anti-Red"
] |
[
"Is it remotely possible for us, in 2029, to send a satellite probe to check out Apophis as it passes so close to the earth?"
] |
[
false
] | null |
[
"It is very possible. We've already launched ",
"a bunch of missions to asteroids",
" and ",
"comets",
"."
] |
[
"Well, I suppose this shuts me up. It's amazing what these guys can do."
] |
[
"Wouldn't it make for an awfully small target?"
] |
[
"Can the gravitational pull of a black hole be measured in terms of speed? If even light can't escape it's pull, does it mean its faster than light?"
] |
[
false
] | null |
[
"Gravitational pull doesn't have a speed. At most, you can measure it as an acceleration. "
] |
[
"If you want to compare it to speed, then think of a black hole's ",
". The escape velocity of a large body is that speed required by any spacecraft (or other small body) to completely escape from the large body's gravitational influence.",
"Note this is higher than orbital velocity, which is what is achieved by the space shuttle, satellites, and early American space missions from the Mercury, Gemini, and Apollo programs (before Apollo 8).",
"In any case, from a simple Newtonian mechanics standpoint, the gravity of a black hole is so strong that the escape velocity is greater than ",
", the speed 299,792,458 m/s (exactly defined), which is also the speed of light in a vacuum.",
"From a relativistic standpoint, which is more accurate, the space around a black hole has a great deal of curvature. So much so that that so-called ",
" and ",
" of motion, which is a different way of saying any motion allowed by relativity for massive objects or for light, is tilted always toward the black hole. There is no allowable path that leads outside the event horizon once it has been crossed."
] |
[
"Great explanation thanks."
] |
[
"Ask Anything Wednesday - Economics, Political Science, Linguistics, Anthropology"
] |
[
false
] |
Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away!
|
[
"Are we actively excavating sites like Gobekli Tepe or is it all shut down due to COVID and other geopolitical reasons?"
] |
[
"I have observed as a citizen in the United States that of my fellow citizens usually vote for the person they dislike the least. Has this been measured and if so is my observation accurate?",
"The term for this is \"Negative partisanship\". Here's a 538 article on the topic.",
"https://fivethirtyeight.com/features/how-hatred-negative-partisanship-came-to-dominate-american-politics/",
"There's some decent evidence that your impression is correct",
"Are alternative voting systems like ranked choice voting possibly yield better results?",
"Perhaps, although it can't be the only thing going on since the US has had its current voting system for a long time but negative partisanship is fairly recent.",
"What can voters with a finite amount of time and lack of expert knowledge and resources do to inform, reinforce and effectively apply our political resources?",
"Interestingly, I've read that the rise in partisanship (not just negative partisanship, but partisanship in general) means that the public today is a lot better informed about the political opinions of politicians and is more effectively able to apply their vote to a politician that represents their political goals. In the old days (eg, the mid 20th century) the parties were not very partisan. There were lots of conservative democrats and liberal republicans. As a result, people at the time were relatively unclear about what policies the parties in general, and politicians in specific, would support. With the rise in partisanship, however, even uninformed voters usually have a pretty clear idea what different parties support, and they can generally expect that a politician in that party will stick pretty close to the party line."
] |
[
"This isn't exactly a scientific question...it's not like we have lots of examples of big collapses in modern societies that we can study and do statistics on to discover the answer.",
"But in a broader sense, I'd say that working at jobs and paying bills are the means by which our society's structures and networks handle the production and distribution of goods. If those networks break down, then people who survive have to find alternate means to meet those needs. So, for example, if you can't go to the office and work because the economic network that supports your job has broken, and you can't take the money and go pay for food at the supermarket because the food distribution networks have broken, in a sense you aren't \"expected\" to work and pay bills, but you are still going to have to go out hunting or scrounging or try to grow crops on a patch of land to survive. You are still going to have to build and repair your own shelter. It's still work, and you are still forced to do it if you want to eat and live. It's just not a wage job and instead of specializing in one thing and then paying other people to fill your other needs, you have to take care of more basic needs yourself.",
"I'd probably argue that in general the collapse of a society will force more people to work, because the efficiency of social networks provides a fair amount of support for a lot of people in society. Not everyone, even in wealthy modern society, has a roof over their head and food to eat. But quite a lot of people ",
" have those things without having to work. If those social networks that provide big food surpluses and other things break down, pretty much everyone is going to have to either work or starve. ",
"There's another possible take on this question too, which is that societies usually transition into another form rather than simply collapse...when one social order breaks down, ",
" other order is going to supplant it. So the answer to the question would also depend heavily on that new social order."
] |
[
"What's making these ice pieces slowly move onto land like this? So bizarre I can't explain it...VIDEO inside."
] |
[
false
] |
I found this video being shared on Facebook and it blows my mind. It shows pieces of ice moving onto the land, encroaching on someone's home. What's causing this? Will it stop? How much force is here? Can this cause serious damage to the house?
|
[
"This is a lake shore property. The ice is coming off the lake, moved by the wind. Imagine a ",
" sheet of ice, several square kilometers, and blow a strong, steady wind across it. The force from all the wind adds up and can be enough to push the entire ice sheet slowly, but steadily onto land. This results in what you see in the video here."
] |
[
"Thanks for the answer! If the wind is so strong it's blowing ice like that, how are those people standing up, let alone holding a camera steady?"
] |
[
"The wind speed is not necessarily very high, it is just enough in the same direction over the surface of the ice that the vectors can add up to push the ice. There may even be no wind at all where the people are standing, the wind could just be out on the lake over the ice; then, the ice you see coming onto shore could be pushed by the ice behind it."
] |
[
"The cosmological constant is sometimes regarded as the worst prediction is physics... what could possibly account for the difference of 120 orders of magnitude between the predicted value and the actually observed value?"
] |
[
false
] | null |
[
"Unfortunately, you won't get a nice single \"correct\" answer with this question; this is one of the bigger unsolved problems in physics, and there isn't a consensus yet, although a ",
"number of solutions have been proposed",
"."
] |
[
"The cosmological constant can be calculated two ways: from cosmology and from particle physics, and it's the difference between these two calculations that is this gigantic 120 orders of magnitude.",
"The value from cosmology is fairly robust, since it can be calculated from the extensively studied statistical properties of the cosmic microwave background. Hence it is almost certainly the value from particle physics that is incorrect.",
"Were it the other way around, the universe would have to either be absurdly old (approaching heat death territory) or impossibly young (less than a single Planck time); obviously neither of these are the case."
] |
[
"At what point does the vacuum of space rip a gas environment from a planet?",
"It doesn't. If you have a small planet in an empty vacuum in isolation and you add an atmosphere, the atmosphere will stay surrounding the planet indefinitely, although the density will depend on the mass of the planet. (If you add a LOT of atmosphere, you end up forming a star!) ",
"Solar winds",
" are largely responsible for stripping small planets of their atmosphere, not the vacuum of space.",
"So a planet is just a very very weak blackhole.....It hasn't gotten enough mass to create enough gravity....",
"If you add enough mass to a planet while keeping the size of the planet constant you will eventually create a black hole, but planets are many orders of magnitude less dense than the Schwarzchild limit, and there are important conceptual distinctions (such as the existence of an event horizon and a singularity in the associated spacetime metric) which separate a black hole from an almost-as-dense object that isn't quite a black hole, such as a neutron star."
] |
[
"What would happen if you made the hull of a ship superhydrophobic?"
] |
[
false
] |
I've been thinking about this question for a few days now. I saw this video a while back: And I was wondering if you made the hull of a ship superhydrophobic if it would sink, or move faster, or whatever. If anything at all would change. Also curious what would happen to a submarine.
|
[
"There would be less friction between the ship and the water. Much less. This would result in less drag while the ship is moving."
] |
[
"only if the cost of making it superhydrophobic was less than the savings"
] |
[
"Could this save money on fuel?"
] |
[
"If everyone with HIV/AIDS on earth were quarantined or suddenly died, would HIV/AIDS cease to exist?"
] |
[
false
] | null |
[
"Actually, we do know exactly where the virus came from. It is not a mystery and there is a good deal of scientific consensus on this. In this way there IS a animal reservoir of HIV known as SIV. SIV is still found in non-human primates so as long as we keep consuming non-human primates or coming into contact with their blood we will be exposed to the virus transferring. What is debated is how exactly it became so widespread, we know it came from non-human primates but we don't know exactly when or why (e.g. bushmeat, unsafe medical practices?). Humans are now the vectors for change - the virus is mutating within us creating new strands. In this way we have two sources for new viruses, the non-human primates and humans.",
"\"Both HIV-1 and HIV-2 are believed to have originated in non-human primates in West-central Africa and were transferred to humans (a process known as zoonosis) in the early 20th century. HIV-1 appears to have originated in southern Cameroon through the evolution of SIV(cpz), a simian immunodeficiency virus (SIV) that infects wild chimpanzees (HIV-1 descends from the SIVcpz endemic in the chimpanzee subspecies Pan troglodytes troglodytes). The closest relative of HIV-2 is SIV(smm), a virus of the sooty mangabey (Cercocebus atys atys), an Old World monkey living in litoral West Africa (from southern Senegal to western Côte d'Ivoire). HIV-1 is thought to have jumped the species barrier on at least three separate occasions, giving rise to the three groups of the virus, M, N, and O.\" It is worth noting that \"However, SIV is a weak virus, and it is typically suppressed by the human immune system within weeks of infection. It is thought that several transmissions of the virus from individual to individual in quick succession are necessary to allow it enough time to mutate into HIV\".",
"We got HIV and AIDS from consuming contaminated non-human primates which had SIV for bushmeat, for sport and under unhygienic conditions - where body fluid transfer risk (e.g. blood to blood) is very high.",
"EDIT: It may be worth noting that non-human primates have been living with SIV for a very very long time and have adapted to the virus. They do not get simian AIDS. It is not impossible to think that we too will adapt to the virus, some people already have been reported to have a natural resistance to it - their cells block the virus from entering.",
"This is not unusual, there are many diseases/viruses which go ",
"back and forth between species",
". "
] |
[
"We got HIV and AIDS from consuming contaminated non-human primates which had SIV for bushmeat, for sport and under unhygienic conditions - where body fluid transfer risk (e.g. blood to blood) is very high.",
"Just to elaborate on this a bit.",
"HIV made the \"jump\" from non-human primate to humans this way. It was largely contained in African nations for decades (based on historical samples and genetic typing of HIV-1, HIV-2 and the SIVs) until it spread elsewhere. The origin of this spread out of Africa to Europe is unknown. However, for the US, the rapid spread of HIV in the 80s is tied largely to a single individual with an \"active\" sex life. His name was Gaetan Dugas and he was a flight attendant. He is often called \"Patient Zero\" for HIV in the US. It is believed that he contracted HIV while in Africa and was key to it's spread on both the East Coast and West Coast of the US.",
"edit - of note, there is an \"opposing\" theory which suggests that the main \"source\" of HIV dissemination in the US came from Haiti"
] |
[
"If you could somehow quarantine or killed every single thing on the planet that carried the HIV virus, including any reservoir animals, then yes. "
] |
[
"Is it hypothetically possible to 'capture' light?"
] |
[
false
] |
Let's say you were able to produce a "perfect" mirror (lets no light pass through it and reflects every photon that comes into contact with it without any loss of energy) and you made it into a hollow sphere, with the reflective side on the inside. Inside that mirrored sphere, you created a total vacuum. If you were to turn a light on in there and release photons of light into it, then turn the light off, would the photons released by the bulb be 'captured' and continuously reflected around the mirrored inside of the sphere? Or is there some sort of degradation that would naturally cause the light to disappear?
|
[
"Yes. If you had a hollow, evacuated sphere with perfect reflection on all the surfaces inside it, there would be nothing there to absorb the light and it would bounce around in there forever.",
"In a more realistic situation, of course, your sphere would not be perfectly evacuated and your mirror would not be perfectly reflective."
] |
[
"Sort of related to your question, is ",
"the experiment where",
" ",
"physicists 'froze' light",
" by storing the information of a light pulse in an ultra-cold cloud of sodium atoms."
] |
[
"To the excellent replies I can only add that, if you could construct a box of perfect mirrors and trap some light inside it, the box would have additional mass equal to E/c",
"That way, even though you couldn't see the trapped light, you could detect it indirectly -- on a super-sensitive scale."
] |
[
"Since we can heat metal to the point where it turns into liquid.. can we theoretically heat it to a temperature thats high enough to boil / evaporate it off?"
] |
[
false
] |
I'm just wondering. I know metal doesn't have the same properties as water, but since we can get water to boil and evaporate off.. can we do the same to metal?
|
[
"The name \"freeze drying\" comes from the fact that we first freeze the food so the water turns to a solid (ice), then put it under a vacuum (very low pressure) so that the ice sublimates off, hence removing the water (drying)."
] |
[
"Yes and it is ",
"used",
" all the time to deposit thin films of metal in many fields of science such as microelectronics and nanotechnology. The most common methods are resistive heating evaporators and electron beam evaporators. "
] |
[
"This is called Sublimation. Which, funny enough is also how we Freeze dry foods."
] |
[
"How do blood vessels get nourished?"
] |
[
false
] |
Other parts of body gets nourished because blood is supplied to it through blood vessels. What supplies blood to blood vessels (their different layers) ?
|
[
"Interestingly, there are actually tiny vessels that innervate the external walls of larger vessels called “vasa vasorum” (vessels within the vessels). These help regulate construction and dilation of large vessels. The inner walls of large vessels obtain nutrients directly from the blood that travels inside them. Hope that helps!"
] |
[
"Thank you but what i meant to ask was how does blood vessel get nourished?"
] |
[
"THANK YOU! That helps a lot"
] |
[
"Do any of the Gallilean moons of Jupiter or the large moons of any other gas giant have stable geostationary orbits?"
] |
[
false
] |
Writing a novella and I had the idea for space elevators at these moons, but I wanted to check the hard science first, and I can find very little to no research on this online.
|
[
"Assuming you mean geostationary orbit around the moons themselves, not the gas giants:",
"All the large moons in the solar system are tidally locked to the planet they orbit. That means their rotational period is the same as their orbital period. In this case, it is only possible for a satellite to stay stationary with respect to the moon's surface if it is located at one of the Lagrange points of that moon. ",
"For any of these moons, a space elevator could be built from the moon's surface and passing through the moon-planet L1 or L2 point. This would be much easier to build than a space elevator around Earth for example, because of the lower forces involved, although it would be longer in terms of distance. In fact, there are semi-serious proposals to build a space elevator from the Earth's Moon to the Earth-Moon L1 point."
] |
[
"In fact, there are semi-serious proposals to build a space elevator from the Earth's Moon to the Earth-Moon L1 point.",
"I'll be damned. I thought that space elevator on the Moon was impossible. I forgot about Lagrange points."
] |
[
"It's surprisingly easy. The cable for such an elevator could be built with current technology, and launched to space in a single launch. Just needs some dedicated R&D for all the details and some funding."
] |
[
"Why was the jet engine on the plane I took yesterday not round?"
] |
[
false
] |
It was a 737-800, and the engine looked like . Why this shape and not a circle? Thank you! EDIT - I realise my title suggests the wasn't round, of course I meant the intake.
|
[
"The answer is \"minimum ground clearance\". The flat bottom of that cowling will be parallel with the ground when the wing tanks are fully loaded. There are FAA regulations requiring a particular minimum ground clearance between the engine and the ground, and that cowling shape is necessary to comply with them.",
"e: The reason this was necessary is that the newer 737s are fitted with physically larger engines than they were originally designed to accommodate.",
"e2: I just looked up the ground clearance for the engine cowling on the 737-800 and the minimum clearance (i.e. the clearance at max takeoff weight) between the engine and the ground is only ",
", with a tolerance of +- 3 inches to account for loading variations, oleo and tire pressures, center of gravity, etc."
] |
[
"Its worth noting that inlets don't have to be round. As long as the engine is getting enough air at the right pressure, it doesn't care what shape the air entered in. Ex. F-4s and F35s have rectangular inlets, F-16s have ovals, A10s have circles. Pretty much any shape works."
] |
[
"Because it gives the room for the needed components, while keeping the engine above the minimum clearance requirement. If you're asking why it is specifically oval in shape, it's the best shape to reduce drag, given the situation.",
"Basically, the customer (in this case Boeing) asked ",
" CFM (GE) for an engine that needed to perform at a certain level, and a size requirement, based on how high above the ground the wings are. The engineers that designed this engine realized the only way that they could make an engine of those specs was to make it bigger than they were allowed, so they had to compensate with this shape, which isn't as efficient as the circular shape, but they were able to get the thrust requirements they needed.",
"Edit: Got the manufacturer wrong, thank you ",
"u/mikeincolumbus",
"."
] |
[
"At what point is the body officially hungry or full?"
] |
[
false
] |
Let's say I have a bag of chips, and I am hungry. After I finish them, I am full. At a certain chip does my body tell me that I am full through use of hormones, or is it after a period of time that my body responds with the message of "you are full"?
|
[
"Actually, it's much more complex than that. You are assuming that the physical feeling of fullness is the only signal processed by the brain to maintain a feeling of hunger or \"fullness\". ",
"The first part is a ",
"biological response",
"#Biological_mechanisms). As you eat, your blood glucose slowly increases triggering fat cells to release a hormone called ",
"leptin",
", which decreases the hunger. Since there's a delay in raising the blood sugar, you might become physically full (no further space in the stomach), before the brain thinks you have received enough food. I guess if you ate just ¼ of that bag of chips, and give enough time for leptin levels increase, then you'd probably have no interest in eating the remainder of the bag. ",
"There is also a behavioral component to hunger. Humans eating behavior evolved in response to the fluctuation of food resources. It may be that you eat the bag of chips, because, at a basic behavioral level, your brain assumes that food may not be available for three days, so stock up now. But of course, it's substantially more complicated. Maybe it's also a strategy to give the body more energy to find food.",
"Of course, this behavior is maladaptive in an environment where food is just a short drive away."
] |
[
"The neurology of the digestive system is INCREDIBLY RIDICULOUSLY complex. SkepticalRaptor's answer is good, but it's my understanding there are entire generations of PHD dissertations about this.",
"I hope some of the medical heavy-hitters find this thread."
] |
[
"There is a complex cocktail of hormones involved in the feelings of fullness in response to a meal, both in the short term and the long term. The physical distention of the stomach and duodenum from food stimulates the release of cholecystokinin which acts to stimulate contractions of the gall bladder as well as trigger satiety signaling in the brain (interesting studies done where CCK was injected into the brain of rats confirmed the \"stop-eating\" signal of the hormone). Other intestinal tract derived factors that drive satiety are glucagon like peptide-1 and gastric inhibitory peptide which serve to promote greater insulin secretion. The rise in blood glucose after a meal promotes insulin secretion from pancreatic beta cells. The increased insulin secretion primarily serves to decrease blood glucose but a small portion is delivered to the brain where it can aid in the amplification of satiety signaling. I'm not certain the secretion of leptin after a meal has been fully elucidated and I doubt it is regulated by the rise in blood glucose directly. However circulating levels correlate very well will total fat mass, an indication of overall energy stores in the body. Leptin can cross the blood brain barrier where it inhibits POMC/AgRP neurons in the arcuate nucleus that normally produce hunger inducing hormones PYY and AgRP. Additionally leptin promotes the production of alpha-melanocortin, which can stimulate the production of serotonin suppressing hunger. Insulin can also work through the melanocortin pathway, driving the satiety signal after a meal. On the other side, Ghrelin is high during periods of no food intake, and drives hunger. \nTL;DR Satiety is driven by the integration of hormones derived from the gut and adipose that act on hunger stimulating and suppressing pathways in the brain.\nEdit: Sorry for the wall o' text"
] |
[
"Why doesn't this work?"
] |
[
false
] | null |
[
"Because the ball entering the water on the left must displace a quantity of water equal to its volume upward under the pressure that exists at that depth, the energy required to do so being exactly equal to the energy required to push the ball down on the right side from the surface to the same depth, neglecting friction. (Why? It is easy to push the ball in at the top and displace the water as the pressure there is low. As you push further down you are only overcoming buoyancy as you have already displaced the water. On the left the initial water displacement is much harder.)",
"Which is harder, slipping a book under the top book in a pile of books, or under the bottom book in a pile of books?",
"The deception is on the left, where you think pushing the ball down is as easy as it would be on the right. It is not. On the right, the water has already been displaced and the weight of the water is helping you to push the ball down. On the left, there is no water above to help you push the ball down."
] |
[
"http://www.hp-gramatke.net/pmm_physics/english/page0550.htm"
] |
[
"You can't ever beat the laws of thermodynamics. You will lose every-time."
] |
[
"How does regenerative braking recharge the battery in an electric car or motorcycle?"
] |
[
false
] | null |
[
"A generator and an electric motor are identical. A motor takes electricity and turns it into motion. A generator takes motion and turns it into electricity. When it comes time to stop your vehicle you can switch the function of the motors to harvest the kinetic energy of your vehicle and rapidly slow you down at the same time."
] |
[
"In regards to discharge, the colder the battery the higher the internal resistance becomes. At very cold temperatures (10°C and less) this leads to a lower capacity.",
"In regards to charging the battery, the same resistance issue applies (less held charge and longer charging time), but additionally if temperatures are below freezing youll get degradation of the electrolytes which will permanently lower the capacity or, worst case, lithium plating on the anode, which may disable (parts of) the battery immediatly.",
"At about -25°C the electrolytes themselves freeze (there are some batteries that use different electrolytes with lower freezing temperatures but those arent used in consumer cars).",
"Due to the above reasons there are dedicated battery heaters and limits on the charge/ discharge rate at low temperatures."
] |
[
"The important thing to remember about batteries is that they're ",
" storage systems. Resistance is, in a way, the reluctance of something to let its electrons move. Batteries undergo chemical reactions to free up or absorb electrons. ",
"When it's cold, the chemical reactions slow down, since there's less thermal energy available to catalyze the reaction. A battery with lower temperature will thus have a harder time pumping out electrons and appear more \"resistant.\"",
"Superconductors are an entirely different physical phenomenon."
] |
[
"Is there a limit to how much hair a human can grow?"
] |
[
false
] |
Not just on your head, but everywhere
|
[
"Theoretically, no. Hair follicles can be implanted everywhere, and theoretically grow to infinite length.",
"Hair is fairly easy for your body to generate. It's made of protein, specifically keratin. By the time you reached a severe enough protein deficiency to affect hair growth, you'd have bigger health problems to worry about.",
"Realistically; yes. A lot of areas are naturally void of hair follicles (soles of your feet, inside creases for elbows etc.), meaning you'd need to transplant them there with surgery, and it's may not \"take\" in thicker skin very well.",
"Hair also rarely maintains it's strength as it grows. While a \"perfect\" system should be able to generate an infinite perfect hair strand, external factors (shampoos, environmental wear and tear, radiation, androgen imbalance, all kinds of things) usually degrade hair quality. It ",
" possible to grow Rapunzel-length hair with some determination, but the majority of humans aren't going to achieve it. The longest hair on record was about 18 feet long."
] |
[
"You're right: eyelashes and eyebrows are an interesting one. Unlike regular head/body hair, it has a very specific biological function; to protect your eyes. Eyebrows help divert fluid from entering your eye area, and eyelashes trap dust and debris from getting into your eyes.",
"Your body will attempt to restrict eyelash length to a certain length that it feels is genetically appropriate - people whose genetic background is in sandy/dusty countries tend to have lusher, thicker, longer eyelashes because their ancestors had more of a need to filter out dust from their eyes.",
"Interestingly, if you apply a certain protein receptor to your eyelids (Prostaglandin F), you can override this \"genetic length\" and grow super-long eyelashes that follow the same \"fall out when degraded\" rule that other body hair does. This is the chemical used in Latisse eyelash extender."
] |
[
"Isn’t another factor that certain hairs will just fall out before reaching a certain length? Which is why eyebrows and eyelashes don’t grow to insanely long lengths? "
] |
[
"If we don't burn fossil fuels is the accumulated carbon lost forever?"
] |
[
false
] |
Without humans extracting oil, would Earth run out of carbon as more and more fossil fuels are naturally made from dead organisms over millions of years?
|
[
"No, it would reenter the long term carbon cycle (e.g., ",
"Berner, 2003",
"). Buried carbon in the form of fossil fuels has a few potential fates. If it was subducted, it would end up back in the mantle (a long-term, and large reservoir for carbon) and can return to the surface through volcanic outgassing. If it was buried further and metamorphosed, it would largely break down and release its carbon as CO2 to the atmosphere (but over a much longer timescale than our mining and burning exercise). If it was uplifted and exposed / leaked out, it would similarly break down and end up as CO2 in the atmosphere, but again, on a much slower time scale."
] |
[
"I think you're ignoring or at least minimizing other long term fates.",
"I'm confused generally, as you essentially describe transfer between the same reservoirs in my answer and as discussed in detail in the Berner paper.",
"Carbon captured as carbonates and buried into sediments becomes limestone and can be metamorphized into marble",
"Since the question was specifically about what happens to carbon stored as petroleum / coal, the fate of carbonates is a somewhat tangential issue, though certainly another important aspect of the long-term carbon cycle, and by mass, more significant than fossil fuels in terms of near surface carbon reservoirs.",
"If it is subducted into the mantle, yes it can be transformed into CO2 and outgassed from volcanoes, but otherwise it is unlikely to return to the carbon cycle without man's intervention.",
"I'm not sure the point here. The rates of outgassing, especially at mid-ocean ridges, while hard to quantify directly, are certainly significant in terms of the long-term balance of CO2 in the atmosphere (e.g., ",
"Coltice et al., 2004",
", ",
"Dasgupta & Hirschmann, 2010",
"). I'm not sure what carbon in the mantle would return to the atmosphere with the help of humans, or maybe I'm misunderstanding that last bit of your sentence.",
"Not every bit of continental or oceanic crust ends of being subducted, at least not on sub-billion year time scales.",
"Sure, for continental crust and this is relevant for fossil fuel deposits hosted on continental crust, but given the maximum age of the sea floor is ~200 Ma (and the vast majority, much younger), I would push back strongly on that characterization for oceanic crust."
] |
[
"Not \"enhanced\" for any of the life on Earth from the past few million years. Ordovician life might like it though."
] |
[
"Why do plants absorb visible light wavelengths and others not?"
] |
[
false
] |
I mean, why do plants absorb the same spectrum of colors that the humans see (the visible spectrum) and not UV nor IR rays (and others)? Is this something related with an evolutionary process? Thank you all!
|
[
"That's a very good question. I will try to explain to the best of my abilities, but keep in mind that English is my second language.\n Firstly, you are correct in saying that the sun emits all kinds of wavelengths, but it doesn't emit them in equal quantities. Most of the energy is emitted in the visible sector. And it would make most sense to focus on it. \n Secondly, it should be noted that plants use a couple of proteins to be able to use some parts of the visible sector (not all of it). If they wanted to use a weider rage of wavelengths they would need a lot more proteins and it most cases the investment would not be worth it.\n Lastly don't forget that some wavelengths may have harmful effects on the organism. For example UV light can directly damage DNA or create Reactive oxygen species, which can further damage cell structures. That doesn't mean they can't be used, but it poses a fair share of problems and in most cases it happens not to be wort it."
] |
[
"That's an awesome explanation! Thank you so much! :D"
] |
[
"The other answer is a great start but I have a few corrections. ",
"1) a minor point for the purpose of this answer but photoreceptors are not proteins but pigment molecules (chlorophyll, carotenoids, xanthonoids). ",
"2) The graph at the link below overlays the emission spectrum of sunlight with the absorption spectrum of plant pigments. As you can see, plant photoreceptors focus on certain areas of the spectrum with maximal sunlight. By focusing on a specific wavelength, they can extract the maximal possible energy from the light source.\n",
"http://environ.andrew.cmu.edu/m3/s2/graphics/embedded/fig6-2.gif",
"3) We have so far only talked about pigments that absorb energy for photosynthesis but plants do absorb UV light through another class of pigments called anthocyanins (purple pigments). The main purpose of these pigments (besides making pretty colors for attracting pollinators etc) is to soak up excess UV radiation so it cannot pose a threat to plant cells. This is similar to how people near the equators have evolved darker skin pigmentation to absorb excess UV present there."
] |
[
"What do you think about 23andme genetics test?"
] |
[
false
] |
I just received my kit today as they are on sale for a limited time. I always wanted to do this, but only now I can afford it. From a scientific perspective what do you guys think about the reliability and usefulness of such a genetic test?
|
[
"Most people will misinterpret the results, but it's still a lot of fun. Just don't go thinking that if you're \"less susceptible\" to a particular disease, that you can go ahead and eat whatever you want because you won't get it. Absolute risk is not calculated. Even if you're 100 more likely to get a disease, 100*0.0001 is still a small number."
] |
[
"For diseases they just give you probabilities of elevated, typical, or lowered risk. It does not say anything about future risk, so I'm assuming it's simply genetic risk based on current research. There is a section where they tell you whether or not you're a carrier of variants of certain genetic disorders. There's a confidence rating, which essentially tells you how confident they are in their numbers depending on how much genetic research has been done on the disease. But even then, sometimes even this is not completely accurate. For example, here's a snapshot of the \"Traits\" section of my profile: ",
"http://i.imgur.com/RnsIt.jpg",
"For all the traits with the highest confidence ratings they're pretty much spot on, except for the \"Hair Curl.\" It says \"slightly curlier on average\" but my hair is completely straight. However, when I click on it to read more info, it says that I carry a gene, which in Europeans, gives them curly hair. I'm not of European descent."
] |
[
"They're not currently worth the money if you're looking for medical advice (unless you have a known risk of a rare genetic disorder). We don't have enough information on which risk factors are important to make the tests useful yet. We also don't know how to translate that knowledge about risk factors into treatments or preventative actions.",
"So companies like 23andMe can tell you \"This SNP means that you have slightly higher risk of diabetes\". So what does that information do for you? Well, pretty much nothing. The genetic counselors can tell you to eat a healthy diet and get plenty of exercise, but you should be doing that anyway - you don't need a 1000 dollar test to tell you that.",
"The big payoff is going to be 5-10 years down the road, when these mutations begin to be better understood. Then we'll know which mutations are really important, and even better, many of them will be druggable targets. ",
"Until then, the only reason that you should get a test is if you have spare cash laying around and want to satisfy your curiosity."
] |
[
"Can there be oxygen and nitrogen chains?"
] |
[
false
] |
Basic carbon chains (alkanes) have carbon atoms bonded to each other in a chain, with three hydrogens bonded to each end of the chain and two bonded to the other ones. Could you do the same thing with nitrogen (two hydrogens at each end and one for the rest) or oxygen (one hydrogen at each end and then just oxygen), and then add all sorts of functional groups?
|
[
"A peroxide is a pair of oxygens bound to one another with groups hanging off either end",
".",
"An ozonide is similar",
".",
"An azo compound would be closest to a peroxide with nitrogen instead of oxygen",
".",
"As for extended polymers, I can't think of any stable ones. All of the compounds here aren't particularly stable themselves.",
"As for extended "
] |
[
"However, you can sometimes string a ",
"shockingly large number of nitrogens together",
"."
] |
[
"Hell yeah. That's one bitchin' molecule.",
"From the experimental, via the comments:",
"The use of suitable protective clothing,in particular a face shield, ear protectors, a ",
", arm protectors,and kevlar gloves,as well as appropriate shoes for protection from electrostatic charge,is mandatory. Ignoring these safety precautions can result in serious injury!",
"Emphasis mine."
] |
[
"Are electric cars actually better for the environment? Wouldn't the increased electricity generation be just as bad or even worse than gasoline?"
] |
[
false
] |
Probably not the most scientific question, feel free to interpret it however.
|
[
"Electric cars are a net win no matter what the fuel the power plant consumes. On the broadest level, the larger the heat engine, the more efficient it can run. GE manufactures a combined-cycle gas turbine that generates electricity at 60% efficiency. ",
"For comparison, a modern, typical gasoline engine in a car is only 20-25% efficient. ",
"And keep in mind, that gasoline had to be refined and transported, at great secondary cost. It's much cheaper and cleaner to pipe more current down a high tension line."
] |
[
"not only this, but electric cars also separate the source of energy from the vehicle itself. This allows future grid improvements such as solar or nuclear to take place without having to replace the vehicle",
"also, when an electric vehicle is stationary it is hardly using any energy at all (save for what it takes to power the low voltage and control systems). this is not true for ICE's as they idle and waste fuel. On a side note, micro-hybrids with start-stop technology can greatly increase fuel economy because of this reason."
] |
[
"What thegreatgazoo said:",
"http://cleantechnica.com/2012/05/18/txu-is-first-to-offer-free-night-time-electricity-rate-plan/",
"Wind power tends to be greatest in the wee hours. Texas wind power sometimes has to be curtailed or wasted because there’s no one to use it at night.",
"If you charge your electric car at night in Texas, you'll be using wind power."
] |
[
"How do the beam splitters in a Michelson interferometer split the light initially and then only allow 1 returning beam to reflect and the other returning beam to travel through?"
] |
[
false
] |
Im not sure how the beam splitter can act as something transparent and reflective(im not talking about the initial splitting but when the light splits and it returns somehow the 2 split beams paths are altered or not altered through the beam splitter into the detector). On another note: no light is reflected back towards the laser right? The setup im looking at is found here: Edit: I guess the original question is moot because it was based on an incorrect assumption about how the interferometer works.
|
[
"I think it is reflected back to the laser as well. The description says that \"50% of the intensity of each reflected beam is transmitted/reflected towards the screen for observation\", so the other half would be transmitted back towards the laser. It's just not shown in the figure, since it's not the thing that you want to observe.",
"Apparently it's a bit more subtle than this though. \n In ",
"this description",
", they note that \"the beams recombine back at the beam splitter, so some of the light is directed toward the detector while some is reflected back toward the source\", but then they say that by adjusting the distances carefully, you can set up constructive/destructive interference, so that all the light ends up on the screen. I guess that's where the interference pattern comes from? Like, there would be one set of bands on the screen, and if you look at the area near the laser that should be a complementary set of bands which add up to the original light intensity?"
] |
[
"If the beams travel exactly the same distance, their light waves will be perfectly aligned so that they result in total destructive interference (LIGO is deliberately designed to make this happen if no gravitational waves are passing). But if for some reason the lasers don't travel the same distances, their light waves are no longer in sync as they merge, which means no light, a little light, or a light as bright as the original laser beam reaches the photodetector. And if the arms are changing length over time, a flicker appears as the beams experience a range of interference depending on how they are meeting up in any given moment.",
"https://www.ligo.caltech.edu/page/what-is-interferometer",
"The detector is measuring basically a single “point” of light that has come along two different paths. But the measured intensity with vary depending on the lengths of those paths because of how the two beams (split from the same original beam in phase with itself) interfere."
] |
[
"You will see a change in intensity as the path length is varied between the two beams. The detector is an intensity counting machine. ",
"If you think of the double slit experiment, you have a spatial pattern in intensity (bright and dark areas). This is because the path length difference between the two slits is different at each point along the screen, so you get interference between the two as they go in and out of phase. The michelson interferometer is like looking at only one spot on the double-slit screen, but then you vary the distance between the slits (relative path length difference, equivalently phase)."
] |
[
"Just how effective is the 12 step program as a treatment for Alcoholism on a purely scientific basis?"
] |
[
false
] | null |
[
"Generally it has a high drop out rate after the initial program has been completed, the system has many critics, some look at it as just another way for religions to recruit new vulnerable members with the treatment program taking a backseat. ",
"http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.476.5193&rep=rep1&type=pdf"
] |
[
"Tricky to quantify. Ethically, you can’t run an RCT on a group of alcoholics because death is a real possibility. Also, the fellowships are founded on anonymity, making longitudinal studies notoriously difficult. See: Orford, J. (2008), Asking the right questions in the right way: the need for a shift in research on psychological treatments for addiction. Addiction, 103: 875-885. doi:10.1111/j.1360-0443.2007.02092.x"
] |
[
"https://www.theatlantic.com/magazine/archive/2015/04/the-irrationality-of-alcoholics-anonymous/386255/?fbclid=IwAR257gOG5X_gS4aGcg0BP-JCzsWPScDYseDvVBzxww3-j_WG3MZE--bFgBs",
"An interesting article on this issue."
] |
[
"Do we know how large dinosaur populations were?"
] |
[
false
] |
When we’re shown concept imagery of dinosaurs, we often see that dino’s were plentiful. Is this accurate to the actual population sizes?
|
[
"There are 2 easy ways to infer significant population sizes:",
"Fossilization is a very rare event. Therefore the rich fossil record requires a large potential number of dinosaurs to be fossilized ",
"Species do not persist and evolve with small numbers. Disease, bad weather, natural disasters can and frequently do wreak havoc on populations. Small population sizes simply aren’t robust enough to survive in the long term"
] |
[
"Oh, so the populations must have been large enough for natural selection to occur at all. \nAre we able to estimate population sizes by the density of fossils in a certain area?"
] |
[
"You might find this interesting, it discussed some of the ways",
"http://tetzoo.com/blog/2020/5/1/stop-saying-that-there-are-too-many-sauropod-dinosaurs-part-5",
"Basically, one thing you can do is try to calculate how much the environment could support based on some assumptions about plant productivity and grazer metabolism. You can also make some comparisons with modern situations. It's not an exact science.",
"However, one important thing to note is that dinosaurs population structure was weird. You had a few large adults and a ton of small juveniles, quite different from modern mammals, because dinosaurs laid a lot of eggs and grew more slowly than mammals."
] |
[
"Why is it that some celestial objects (such as planets) spin clockwise and others spin counter-clockwise?"
] |
[
false
] |
[deleted]
|
[
"The solar system didn't come into existence until about 9 billion years after the Big Bang. There is no way that the planetary spins observed can be related to it in any way. Most planets in the solar system spin in the same direction as the result of accretional processes in the original protosolar nebular disk. (See the Wiki article on the ",
"formation of the solar system",
" for more information. The planets that spin in other directions, or along tilted axes, are hypothesized to be the result of large collisions late in the formation of the solar system. "
] |
[
"No, the big bang caused the expansion (or the expansion is what tells us there was a big bang, depending on how you look at it).",
"The point is that the spin of our solar system has nothing to do with the spin of the spin of the universe at the time of the big bang. It's more like the big bang produced a lot of swirls and eddies of gas. As a gas cloud gets pulled in by its own gravity it spins faster (like a skater pulling her arms in) and forms a disk. This disk is what becomes a star at the center and planets around it.",
"Our sun is probably a 3rd generation star so our solar system was formed from part of the gas cloud left over from an earlier exploding star, so the rotation of our solar system has even less to do with what happened in the big bang."
] |
[
"So, then, the expansion of the universe is not related to the big bang?"
] |
[
"If two observers are traveling in opposite directions at half the speed of light, are they traveling light speed relative to each other? If they use a laser to communicate, what would happen?"
] |
[
false
] | null |
[
"Their relative speed is found by the formula for relativistic velocity addition. Whenever classically you'd have u+v, relativity tells you that the relative velocity is actually",
"(u+v)/[1+uv/c",
"]",
"Here, where u=v=.5c, we get a relative velocity of .8c, or 80% the speed of light.",
"If they use a laser to communicate, that laser light will travel at speed c relative to both ships. There will be a Doppler shift in the frequency of the light between the frames of reference of the two observers, using the relative speed .8c."
] |
[
"Is it possible for objects to exceed light speed, relative to each other? What happens to the laser signal in such a case?"
] |
[
"Is it possible for objects to exceed light speed, relative to each other? ",
"No, the relative speed is always capped by the speed of light.",
"The laser signal itself travels at the speed of light according to all observers; this is one of the fundamental principles of Special Relativity."
] |
[
"What's stopping us from creating smaller than ~5nm transistors and also makes it difficcult to even reach there?"
] |
[
false
] |
[deleted]
|
[
"TL;DR: uv lithography uses wavelengths way larger than the transistors it draws and extreme uv is not viable yet.\nNot an expert but I just watched a video on this I think it was from gamers nexus but Idk.\nFirst understand how insanely small and precise 10nm is: a human hair is 181μm according to Wikipedia so a cpu transistor is 18100 times smaller at 10nm. We currently use ultraviolet lithography to draw circuits. Essentally we make something that reacts to uv light and then use a laser to draw the circuit. The thing is the uv spectrum only goes down to 10nm in wavelength and current lithography machines use 193nm argon or 248nm Kempton fluoride lasers. This makes it very hard to make small patterns and so they have to do multiple exposures. Think of it like painting the Mona lisa with a paint roller. Extreme uv lithography is supposed to be the next step up (13.5nm wavelength) and would allow for much more precision, however it can only be generated by a Tin plasma laser currently as the plasma absorbs 13.5nm light. So its way harder to make a high intensity source, tin constantly accumulates on the mirrors so they need cleaned, more power is required. The machine has more downtime. (Like a full 24hr period every week). The tech for extreme uv is just not usable in a production line. Also if we get a whole lot smaller we have to deal with things like shot noise, where an electron quantum tunnels into an adjacent wire. Generally as wires get smaller, resistance goes up and resistance turns electrical potential energy to heat. That's why you need a deiticated cooler for your CPU. So. . . various reasons I guess"
] |
[
"I've also heard that at a certain point quantum tunneling can begin to be an issue. With such small gates (~5nm) it is possible that the electrons that you are trying to observe and run through the gates will just \"blink\" around the gate. The likelihood of this happening increases as your gates get smaller. This compounds with the difficulty of manufacturing silicone to such precise values. So, from what I have read, the problem not only lies with the manufacturing, but the viability/reliability of sub 5nm transistors. After that point we may be looking for a successor to the traditional transistor architecture."
] |
[
"Extreme uv lithography is supposed to be the next step up (13.5nm wavelength) and would allow for much more precision, however it can only be generated by a Tin plasma laser currently as the plasma absorbs 13.5nm light. So its way harder to make a high intensity source, tin constantly accumulates on the mirrors so they need cleaned, more power is required.",
"EUV is ridiculous. You have droplets of molten tin falling tens of thousands of times a second, and you blast them with a CO2 laser pulse, again at tens of thousands of times a second, just to get that little bit of 13.5nm light. Oh, and you can't miss the droplet with the laser, or bad things happen."
] |
[
"Magnetism and the conservation of energy."
] |
[
false
] |
Suppose I had a giant cloud of hydrogen that I then separated into two stars. A little fusion later and I've got two giant lumps of ferrous metal that are magnetic. Suppose I then put the two lumps close to one another, perhaps on the surface of a planet in between the two stars. Magnetic attraction draws them toward each other, ultimately smashing together and transferring some kinetic energy to surrounding objects in the process. I know this whole sequence of events must comply with basic laws about conservation, but it seems like there would be some net gain from the magnetic attraction. What am I missing?
|
[
"To simplify the thought experiment, imagine two containers of iron in plasma form, separated by some distance. The plasma cools, leaving us with two magnets some distance apart. Suddenly we have potential energy in the system, equal to energy it would take to pull the magnets apart. Did we just get free energy?",
"I think the energy it takes to align the magnetic moments is being missed. As each container cools, the iron atoms begin to align with themselves. If there is another magnetic field present -- such as a field coming from the other container -- then the process of aligning ",
" against that field. If we sum all the work done by aligning the atoms, it would equal the potential energy stored in the magnetic field between the two containers."
] |
[
"Thanks for the response. Wouldn't the potential energy fluctuate based on the distance between the two magnets? If so, would the energy required to align the iron atoms also be proportional to the distance between the two masses?"
] |
[
"Certainly the potential energy increases as you pull the magnets apart.",
"There is also the energy involved in aligning an atom even in the presence of a single magnetic field. When the containers are far apart, the influence the fields exert on each other is negligible, of course.",
"Potential energy can be confusing because it is always relative to something; it's not an absolute quantity. It's a shorthand concept. Pick any two planets in the solar system; they have a potential energy between them, measured by the work would take to pull them apart. Whether they happen to be closer or farther apart doesn't affect any absolute measure of energy in the system.",
"Another way to think about your magnet problem is from the entropy perspective. You are spending energy to create more order -- that is, aligning atoms. We mislead ourselves by thinking the final cooled state is similar to some non-magnetic material, when in fact the magnetic material absorbed a bit more energy during its formation."
] |
[
"How exactly does nuclear radiation interact with water?"
] |
[
false
] | null |
[
"Being exposed to radiation doesn’t necessarily mean it will become radioactive. Only in particular cases does that occur. The water itself may become slightly activated, but it’s nothing compared to the radiation coming directly from the core or the spent fuel.",
"“Contain a fatal dose of radiation” isn’t really a meaningful thing to say in that situation. You don’t want to drink that water, but it wouldn’t necessarily be activated at a dangerous level.",
"Yes, the water would get a dose that would kill a human if the human had absorbed the dose. If a human stands next to the spent fuel, they will die."
] |
[
"1) If you stirred the water to create a current, would the radiation spread outside of the safe zone because of the movement of the water, or would the nature of water (being dense) still block the radiation from going too far?",
"If there is radioactiv",
" in the water, it will diffuse and advect around within the water (assuming a water-soluble substance).",
"However radiation itself doesn't really diffuse. Imagine radiation as bullets flying through the air, and radioactivity is the guns firing the bullets. The guns can move around with the water if they're inside it, but the bullets don't care much about how the water's moving.",
"2) The XKCD says it would be \"a hell of an energy drink,\" but also says we wouldn't want to drink it. If we drank some of the water that we pulled up from next to the fuel rods, would it have similar effects to just swimming next to the rods? What else would/could happen?",
"You don't want to drink it because it's not just water. There's other stuff in it, like boron for example, which is used as a neutron absorber. The activation of the water itself probably doesn't cause a radiological concern, but there's plenty of other reasons not to want to drink on swim in the water."
] |
[
"1) If you stirred the water to create a current, would the radiation spread outside of the safe zone because of the movement of the water, or would the nature of water (being dense) still block the radiation from going too far?",
"If there is radioactiv",
" in the water, it will diffuse and advect around within the water (assuming a water-soluble substance).",
"However radiation itself doesn't really diffuse. Imagine radiation as bullets flying through the air, and radioactivity is the guns firing the bullets. The guns can move around with the water if they're inside it, but the bullets don't care much about how the water's moving.",
"2) The XKCD says it would be \"a hell of an energy drink,\" but also says we wouldn't want to drink it. If we drank some of the water that we pulled up from next to the fuel rods, would it have similar effects to just swimming next to the rods? What else would/could happen?",
"You don't want to drink it because it's not just water. There's other stuff in it, like boron for example, which is used as a neutron absorber. The activation of the water itself probably doesn't cause a radiological concern, but there's plenty of other reasons not to want to drink on swim in the water."
] |
[
"Is there any validity to the idea that light slows down in medium due to being absorbed and reemited by atoms in the medium?"
] |
[
false
] |
So I've been told several times that this common explanation of why light slows down in a medium is wrong because it implies that light should exit the medium in random directions which doesn't match observation. That's always made sense to me, but a few months ago I came across that uses a similar explanation but specifically makes the point that of course any model of light at a quantum level needs to reproduce classic effects when we'd expect to see them and claims that this version of the explanation does that. The main difference between his explanation and the common but erroneous one is that he makes the point that we should think of each photo taking every possible path through the medium (I think that's the Feinman path integral formulation, but please correct me if I'm mistaken) and atom absorbing and reemitting each photon, but he then says that ever individual atom has only a very small chance of doing this, but we'd expect it to happen at least some of the time because there are just so many atoms. But he just said that we should think of ALL the atoms doing it, so which is it? Do they all do it, or is it random and it somehow works out the that paths still cancel out properly so we get the observed path? Or is this explanation simply incorrect?
|
[
"If you want to get a group of physicists to fight, get them in a room and ask them why light travels slower and refracts when passing through matter. The fact that there isn't an agreement on the matter might make you say \"oh, so they don't know.\" But I would answer \"we do know, there's just multiple ways of thinking about it\" and which one you prefer is likely based on what type of physics you're currently doing. Part of the reason it's hard to give a \"definitive answer\" is because photons are ",
"identical particles",
". ",
"Identical particles in physics is perhaps a stronger statement than what most people might think \"identical\" means. Identical means asking \"is this particle the same particle as we observed before\" is impossible to answer. If a photon is absorbed and then re-emitted, you can't answer \"is it the same photon or a new photon\" since all photons are identical. They are impossible to label. If a charged particle gains an electron, you can't answer \"the electron which was gained went into a certain shell\" or if it loses and electron saying \"the electron which it lost came from this shell.\" You cannot label them, even in principle. ",
"So, this leads to the fact that you can't even answer \"are the same photons which entered a material the same ones that exited.\" You can't track them. ",
"So, where does this leave us. Well, we do know the simplistic view, thinking of photons as \"point particles\" which get absorbed if they happen to hit an atom, and then re-emitted in any which way, cannot explain ",
"Snell's law",
". But Snell's Law can be derived a number of ways. Maxwell's Equations, thinking of light as a wave, can perfectly explain the behavior. Huygen's Principle (the method used in your linked article) does it via constructive and destructive interference. You can also directly calculate it from conservation of momentum and energy. ",
"So, in field theory (which if you see my flair, you know might be my preference), a massless particle must always travel at 'c' so we distinguish between the speed of light (c) and the speed that a light wave propagates (less than c in a medium). A condensed matter physicists would say, of course a photon can't travel at less than c, but when it's in matter it is a ",
"polariton",
", which is a quasi-particle, caused by a photon strongly interacting in matter. Physicists more interested in electromagnetism will probably use the Maxwell method. I would say they are all valid. They don't necessarily contradict each other, rather it is multiple ways of describing the same phenomenon. ",
"Sorry if that isn't the answer you're looking for, and you'll likely get someone who will give you a \"definitive answer\" that is the definitive way of thinking about it in their field, but at the end of the day, we have a collection of models, and our models describe the universe (some better than others)."
] |
[
"If you want to get a group of physicists to fight, get them in a room and ask them why light travels slower and refracts when passing through matter.",
"This is accurate and I have literally seen this happen. Not a physical fight, but a pretty heated discussion at lunch."
] |
[
"Yes."
] |
[
"Are there any known moons that have moons orbiting them?"
] |
[
false
] |
If not then is there any theory to this?
|
[
"No, there are not any known moons with natural satellites.",
"It is certainly possible however. I mean, we have been to the moon, and we have had many orbiters around the moon. The theory behind this is simply gravity.",
"Naturally however, depending on the mass of the planet, a moon's moon would probably be a short lived phenomenon. Tidal interactions between the planet-moon-moon system would likely destabilize the orbit over a short (in universe time scales) time period. In this case, the moon's moon would just become another ordinary moon."
] |
[
"Typically no, although I suppose it depends on a bunch of factors. For one, multiple star systems tend to orbit a common center of mass, instead of one orbiting another, which then orbits another, etc., since they are typically of similar masses.",
"The mass distribution of the stars matters. In a planet-moon-moon system, it is assumed that the moon is significantly less massive then the planet (else the planet would orbit the moon), and the moon's moon is significantly less massive than the moon. This gives the planet the most gravitational influence and its strong pull on the moon's moon (much stronger than the moon's). This is what causes the stability issues. The planet constantly tugs on the moon's moon and eventually pumps enough energy into the orbit to yank it away from the moon.",
"Sure, a multiple star system could be in the same type of configuration (unstable), but it is probably unlikely since there would have to be a huge mass difference of the stars. Observationally however, stars of similar masses seem to form and stick together."
] |
[
"Sorry but I don't quite understand what you're asking here. Are you asking why there aren't any planets whose moons have moons?"
] |
[
"How do forest fires start 'naturally'?"
] |
[
false
] |
I know that forest fires are a natural part of the lifecycle of an arboreal environment, but how do they start? Most lightening occurs during a rainstorm which would reduce the chance of starting a large fire. Are there other causes?
|
[
"Lava flows/volcanic sources, spontaneous combustion from organic material overheating (think compost piles or certain types of coal), and rockfalls producing sparks are all potential other sources but lighting is by far the most common.",
"Rainstorms are often isolated sporadic events. For example it can rain on one side of a stream and not the other and lighting doesn't have to strike under the rain, it can hit a tree on the other side of the stream so the rain will not effect any fire produced. \nThere is also a lot of energy in lighting a good strike on a tree can set the whole tree ablaze even in a rainstorm. While the rain may put out the exposed fire, sheltered embers in the core of the tree can continue to smolder until well after the rain passes and then flare up. There are many areas where organic material is very deep and a fire may smolder underground. Fire can burn on the bottom of a log or under the shelter of a larger tree's limbs protected from direct rain."
] |
[
"Lightning can occur with little rain, or the lightning can occur on the edges of the rainstorm. ",
"See this cartoon.",
"Forest fires can travel in root systems underground, over large areas. Organic matter in the soil and wood underneath the forest canopy (partly shielded from rain) can smoulder for long periods of time. Fires are of course more common during periods of drought, when there is more, drier, material to burn.",
"Fire suppression policies (e.g., putting out the fires) can lead to larger, more dangerous fires as dead wood builds up in forests, and the available dry wood to burn can lead to larger, more destructive fires. ",
"Interesting fact: ",
"Jack pine needs fire to open its cones",
" and proliferate. "
] |
[
"lightning or lava"
] |
[
"Why aren't animals living in the Mariana Trench translucent like those discovered in that lightless cave in Romania?"
] |
[
false
] | null |
[
"Some are, and some are colorless, like that amphipod.",
"From my answer to a similar question",
".",
"There are some in both habitats that are translucent, or pale reddish, or dark red.",
"The basic reason behind it is that pigmentation is an energy sink in those habitats. The other is that other pigments were selected against because those were colors that made them conspicuous. Red light is very low energy and is absorbed/reflected/scattered at a relatively very shallow depth. This will also carry true for caves if the light source is at an opening and the light is absorbed with the horizontal distance (you can treat this as analogous to depth in terms of light).",
"Blue/violet light penetrates the deepest, so anything that is a \"color\" at the opposite end of the spectrum is essentially black at that depth since they don't reflect any of the blue/violet light. That's why I put color in quotations, because they only appear red closer to the surface, or if you have a light to shine on them. Sort of the same principle if they are translucent, you'll only see the background.",
"In addition to that, their eyes or light sensitive organs (if they have any) are tuned for blue/violet light at depths, since that's the only light they have, so any organisms that are towards blue in color are easy to see.",
"The Photosensitive Pigments In\nthe Retinae of Deep-Sea Fish",
"To give you an idea, according to that paper, the human eye would be able to detect daylight down to about 950m, and beyond that our eyes aren't sensitive enough. In contrast, deep-sea fishes can absorb 90% of the blue-green light (while we can only do 30%), essentially giving them 3x better vision at depths. Granted this paper is from 1957, so these may be different now."
] |
[
"At 6 to 10 km down, aside from bioluminescence, is there any \"light\", therefore colour, at all? Maybe infrared from lava vents?",
"I don't understand what an animal could \"see\" down there."
] |
[
"At even less than 6km it's the aphotic zone, which is devoid of sunlight. There may be bioluminescence, or light from thermal vents, but animals living at that depth don't rely on vision, since you're right there's not much to see at all. If their eyes aren't reduced, the can certainly see bioluminescence. They must rely on the other senses though, some have a much more developed lateral line, or specially adapted hairs called neuromasts, and a well developed sense of smell.",
"Some fish do have the ability to see UV or infrared light, but that's more in those which live in the mespelagic zone, which can have very large eyes like the lanternfish.",
"The eyes of deep-sea fish I: Lens pigmentation, tapeta and visual pigments"
] |
[
"Why is in the Alveolar gas equation the pressure of water subtracted from the atmospheric pressure?"
] |
[
false
] |
I would have guessed that it would be added on top of the atm-pressure. Any help is much appreciated!
|
[
"What is subtracted from atmospheric pressure is the saturation vapor pressure of water. This is the total vapor pressure of water at a given temperature and pressure. By subtracting this off from atmospheric pressure you get the pressure that is available to be filled with oxygen. If the total pressure is 100 kPa and the vapor pressure of water is 6 kPa, the remaining gases in the breath account for 94 kPa. This is the first step to finding the vapor pressure of oxygen."
] |
[
"But why exactly is the vapor pressure not further increasing the total pressure. And why is it space that could potentially be filled by oxygen when it is a volume in and of itself? It just doesn't click"
] |
[
"Ah, so your confusion is with what a ",
" is. The partial pressure is the fraction of the total pressure taken up by a component gas in a gas mixture. Basically, if you sum up all the partial pressures in a gas you will get the total pressure of the gas. ",
"One of the assumptions of the equation is that the alveolar gas is saturated with water vapor. Which means the partial pressure of water is equal to the saturation pressure. So we are subtracting off the portion of the alveolar gas that is made up by water vapor, and then using the percentage of the inspired gas that is oxygen to find the partial pressure of oxygen available in the gas. Because CO2 displaces oxygen, we then subtract off the partial arterial pressure of CO2 (modified by the exchange ratio) which reduces the ability of the alveoli to uptake oxygen. This gives you the final calculated value for the partial pressure of oxygen. ",
"You’ll notice that there are some assumptions there, which is why this equation is an estimate. "
] |
[
"When does a comet stop moving?"
] |
[
false
] |
Where does it derive its velocity from and how long will it travel through space? Would gravity from stars and planets it passes through somehow slow it down? EDIT: I need to re-phrase. 'Would gravity from stars and planets it passes somehow slow it down?'
|
[
"You can think of a comet entering our solar system as a ball rolling down a hill. As it gets closer and closer to the sun, it'll speed up more and more. When it heads away from the sun, it'll be slowing down, like a ball going uphill. This is because of the effect of the sun's gravity. It won't otherwise come to a stop, per se. It'll be in some sort of orbit.",
"It is, however, possible for something else to change that orbit. For example, Jupiter has redirected comets into new orbits when comets have passed too close to it."
] |
[
"There definitely is a force present, namely the force of gravitation. And it changes the momentum of the comet all the time. What doesn't change is the mechanical energy, that is the sum of potential energy and kinetic energy.",
"Or if you look at the whole system which includes the comet and all other relevant celestial bodies, then the total momentum of all those combined doesn't change due to conservation of momentum. "
] |
[
"I can't answer all of this without doing more research, but the velocity is derived from its momentum - there is no new force or thrust being applied, the zero-resistance conditions in space simply allow it to go for a very, very long time on momentum. Where that momentum comes from isn't clear; science isn't sure of the origins of comets.",
"If it literally passes ",
" a star or planet, the complete destruction will slow it down much more than the planet's gravitational field."
] |
[
"Do atoms have colours?"
] |
[
false
] |
I know they're more likely to reflect certain colours (blue and hydrogen, for instance), but as I understand it, this is a result of electrons moving rather than any property of the particles themselves. Do atomic particles have colours in and of themselves? Is it possible for them to have it?
|
[
"No. ",
"Color is a property our brain assigns to electromagnetic rays within the visible spectrum. An atom, however, can never be \"seen\" in visible light.\nThe reason for this is, that the wavelength of visible light is ~400-700 nm = 4 x 10",
" - 7 x 10",
" m.\nAtoms have roughly the size of ~1Å = 1 x 10",
" m.",
"As you can clearly see, the shortest wavelength of visible light is still more than 3 orders of magnitudes bigger than an atom. Thus, visible light will never be able to represent Atoms.",
"What we can do, and what we are already doing, is using particles of shorter wavelength than visible light, like electrons.",
"This will result in an representation of Atoms in visible light, but the colors assigned to atoms on the computer display are essentially random."
] |
[
"What? Try and read this sentence one more time. Maybe read it out loudly. Sometimes this helps people who have a hard time understanding written content. "
] |
[
"These are color charges of quantum chromodynamics. They have nothing to do with visible colors. It's just a convenient way of keeping track of an abstract system which has three possible charge types."
] |
[
"Why are the Galapagos Islands specifically so important to study?"
] |
[
false
] |
I always see the Galapagos Islands as the big place that people are studying. I realize there are major historical discoveries that have happened there, but aren't there likely to be many archipelagos that are near a mainland that display the same amounts of natural selection and adaptive radiation? Are they just the "famous" archipelago? Is there a really unique situation there? Or are people building upon 100+ years of research in that specific place?
|
[
"It's for a number of reasons. Largely because of the fact that the Galápagos is a volcanic landmass that was never connected to any continent. This means that all the species there had to migrate there, and there are no natural large predatory mammals, so they're able to survive there. Because of this, and because of how different the Galápagos landscape is compared to anywhere else, species were able to adapt in ways that we haven't seen before. There are many species there that can't be found anywhere else in the world. For instance, there's a native species of Iguana there that's adapted to aquatic life, which is something we've never seen from Iguanas. "
] |
[
"Hawaii has almost 1.5 million people on it is heavily tainted by long and significant occupation and the introduction of feral species."
] |
[
"It's a combination of being far from the mainland, and the actual islands being relatively far from eachother. This is important for two main reasons:",
"",
"1: Because they're far from the mainland, and were never attached to a land mass, all animals on it migrated to the islands from one place or another. This is important because such migrations are generally rare events, so any population of seed-animals was likely small and not refreshed by further immigrants from the mainland. Because of this, we can assume that all of the similar varieties of sparrow there, for instance, came from the same root population.",
"",
"Because there's a pretty good distance between the islands, this means that populations on one island -could- move to another, but it'd be relatively uncommon. This helps to boost speciation since populations could move to all the islands over time, but a population on one island are relatively unlikely to mate with members of the original species they descended from. This allowed distinctive species to evolve on each island as they interacted with that particular island's geography and population of flora and fauna."
] |
[
"When you roll a snowball across a snowy surface, why does it grow rather than shrink? Why is the transfer of snow always from the surface to the snowball?"
] |
[
false
] | null |
[
"I most agree with your answer.\nThe wikipedia page for sintering cites the compaction of a snowball as an example. I believe that is the technical term that encapsulates what you have described. ",
"https://en.wikipedia.org/wiki/Sintering"
] |
[
"I most agree with your answer.\nThe wikipedia page for sintering cites the compaction of a snowball as an example. I believe that is the technical term that encapsulates what you have described. ",
"https://en.wikipedia.org/wiki/Sintering"
] |
[
"The density of a snowball is higher then the density of freshly fallen snow. This results in a greater force from the ssnowball to the freshly fallen snow, than within in the freshly fallen snow. So this force causes a compression in the contact zone between snowball and freshly fallen snow, similar the process of forming a snowball. The greater force leads to a stronger bond between snowball and freshly fallen snow than within the freshly fallen snow which leads to growth of the snowball. Still the growth is limited, as the compression achieved does decrease by size of the snowball as the new layer will never be as dense as the initially layer.",
"Edit for clarification:\nDifferent types of snow should be considered, whereas the cristal structure is the most distinctive quality measurement, besides the temperature of the snow. Both result in higher or lower bondary force. You should always consider that the crystal structure is directly related to the temperature. First crystal structure is influenced by temperatur while snowing second when already on the ground. "
] |
[
"How do the power tester strips on the side of batteries work?"
] |
[
false
] |
I don't know if they're common or not so these are what I'm talking about . When you press down on the white bits it shows a yellow bar to show it has power left.
|
[
"When you press, a strip of conductive material makes contact with the battery terminals. It has a well-characterized resistance so it heats up to a temperature that varies with the battery state of charge. It's covered with a strip containing ",
"thermochromic crystals",
" which change color. Then there's an insulating plastic so your fingers don't get too hot (and don't affect the reading too much)"
] |
[
"Ok I like that explanation. Please add to it by explaining why the strip fills up like a thermometer going up. Shouldn't the whole strip heat up linearly? Why does a low voltage cause a small fraction of the strip to change? Why does a high voltage cause the whole strip to change? "
] |
[
"It sounds like it would work the same as the ",
"thermometer pictured in the Wikipedia article",
" except instead of 6 discrete cells there's a continuous gradient of temperatures. As you go further up the strip it requires a higher temperature to change the color, so the 100% section only changes color at the temperature the strip hits when the battery has a full charge."
] |
[
"Have any animals ever re-evolved the ability to breath water after evolving to live in water again?"
] |
[
false
] |
I have noticed land animals that have evolved to live in the water, like sea snakes, sea turtles and whales, have just developed the ability to hold there breath for a very long time (or an anaerobic process for help). Has anything re-evolved gills or water breathing ability? If not, is it not really practical/possible?
|
[
"Whales can't breathe underwater, they just hold their breath for a long time.",
"like sea snakes, sea turtles and whales, have just developed the ability to hold there breath for a very long time (or an anaerobic process for help)"
] |
[
"Just to clarify (you're not wrong) animals which \"breathe water\" are breathing the air which is in the water. "
] |
[
"huh! what a great question. i can't think of any, but i would love to know if there were/are. i don't think it would have been \"practical\" (although evolution has no direction so you can't really talk about it as a thought process)... so, if an animal with developed lungs started exploiting aquatic sources for food, it seems to make more sense that individuals that develop the ability to hold their breath longer would be more successful and breed faster than say, a scenario in which a population would develop gills again, which would probably take much more time to develop than breath-holding skills... does that make sense?"
] |
[
"Sometimes night time is not so dark because the sunlight reflecting off of the moon acts as a \"night light\", is this the same for the moon when it is dark? Does the sunlight reflect off of the earth and light up the moon?"
] |
[
false
] | null |
[
"I think some of the Apollo astronauts talked about the illumination from earthlight when they were there.",
"You can also see, when the moon is nearly new, some illumination of the moon's dark side— as I understand it, this is sunlight reflected off the earth (which would be nearly full at that point from the moon's perspective), illuminating the moon, and then back to your eyes on earth."
] |
[
"about the size of a quarter in the sky",
"This isn't a good way to describe size in the sky because you don't know how far away to hold the quarter. If you said a quarter one foot from your eye, you'd have a better description. You can also use the angle of view that it covers which doesn't vary with distance from your eye.",
"There's a famous picture that was taken from lunar orbit (not from the surface of the moon) on Apollo 8 that gives you some perspective called ",
"Earthrise",
". There's probably one from the surface too, but I didn't see in a few minutes of searching."
] |
[
"The Earth/Moon radius ratio is nearly 3.66, so it would appear about 3.66 times as large in diameter or about ten times as large by area. "
] |
[
"What about water puts out a fire?"
] |
[
false
] |
Is it blocking off the fuel from making contact with air? Stealing away the activation energy? Something else? All of the above?
|
[
"Mostly, it steals away the energy from the area. The evaporation of the water requires a lot of energy, and thereby results in reducing the temperature. Hopefully below the ignition point of the fuel, so the fire is contained or even put out. Most everyday things will only burn if the heat is concentrated. Like a single log will not burn on its own, since it radiates too much heat away. You need to build a fire that concentrates the heat at the center to sustain the fire. Robbing it of just a little bit of that heat, and the fire is no longer sustainable.",
"But the steam produced also lower the oxygen density of the air around the fire. And the water no doubt also simply washes some of the combustible gasses out of the air, before it can reach any free oxygen."
] |
[
"It absorbs some heat and vaporizes, which reduces oxygen available to burn (pushed away by water vapor)).",
"It also absorbs/marries with MOST fuels making the fuel more difficult to oxidize and burn for the same reasons.",
"If you wet a porous charcoal, it can't begin the burning process until the water is gone because the carbon compounds need to reach a higher temperature than liquid water can reach. So it has to steam out first. ",
"Obviously there are exceptions of flammables that water doesn't really help with if the fuel can oxidize itself or there is no way for the water to disperse around the flame and extinguish it. Like burning oil which floats on water, flammable gas (some of which can burn in low oxygen environments etc.)",
"Really oversimplified as \"fire\" of each thing is a different chemical reaction and there are oddball minerals that burn in water/with water by chemically converting it on contact"
] |
[
"For a short answer, the water leeches away the activation energy. Water has a very high \"specific heat\" meaning it takes a lot of energy to heat up a cup of water by 1 degree.",
"There are other substances that would do this too but water is readily available and convenient.",
"With enough water, like submerging a flame in a bucket of water, it would technically block the fuel from making contact with air as well and remove the oxygen source but that's typically secondary to the above."
] |
[
"Probability help: 10,000,000 coins, each flipped one time - select 100 at random: What are the odds all 100 will be heads?"
] |
[
false
] |
I'm having trouble remembering how to calculate this. I posted this as an example in comment. Now someone is asking for an explanation, and I don't remember how to do the math. Help?
|
[
"Yeah, ",
" is correct. The probability is (1/2)",
" and it doesn't matter how many coins you originally flip since each coin has a 1/2 chance of being heads. Anyway, what I REALLY came to say is I read your original post, and ouch that hurts. I think what you meant to say is that if you flip 10,000,000 coins, the probability of getting at least 100 heads is higher than flipping 100 and getting all heads. "
] |
[
"The coin flips are independent events, it doesn't matter how many coins you flip, just the number of flips you are counting. Thus, flipping 10000000 or just 1 coin doesn't matter, so long as you get 100 total flips to count. The ",
"Binomial distribution",
" is the correct one for modeling coin flips, and the probability looks to be around ",
"0.00000000000000000000000000000078",
" for the question you are asking (though I don't have a proper table with me to verify). The real issue here for ",
"/r/askscience",
" is why selecting a sample of 100 trials from 10000000 is representative of the greater distribution. (EDIT: if you don't have fair coins, you will need to change the parameters for the distribution, but it will still be a Binomial distribution)"
] |
[
"It doesn't matter how many coins you flip before choosing your 100. Look at it another way. You have 10,000,000 unflipped coins, select 100, and then flip all 10,000,000. You've reversed the order, and its obvious the other coins don't matter in this situation, but this is equivalent (since you aren't choosing the coins based on their outcome)!"
] |
[
"Simple question about the uncertainty principle of quantum mechanics."
] |
[
false
] |
I understand that this principle explains you can not know where the object is and what it is doing at the same time, (If this is wrong please correct me.) Does this hold true for dual/multiple observers? In other words, does the number of observers change the accuracy of the detection? Where I was leading with this is the idea of having three different computers could eliminate the issue. Having one computer observe where the object is, another to observe what it is doing, and the final to combine the data..... Just an idle thought and couldn't think of anyone to ask.
|
[
"I understand that this principle explains you can not know where the object is and what it is doing at the same time, (If this is wrong please correct me.)",
"It's close enough for nontechnical purposes.",
"Does this hold true for dual/multiple observers? In other words, does the number of observers change the accuracy of the detection?",
"It holds true in general. No detection system can determine all properties precisely, even if that detection system is \"several different computers\"."
] |
[
"Alrighty, Thank you for the timely response!"
] |
[
"It's actually even more interesting. If you have multiple copies of the same system, you can't ever measure both the position and momentum in such a way that violates the uncertainty principle, even if you do the measurements on different copies."
] |
[
"I sit for 5 minutes in the hot sun during my hour break every day without sunblock. I don't burn at all but it keeps me from looking pasty. Could this be dramatically increasing my chance of getting cancer?"
] |
[
false
] | null |
[
"I am not a doctor, but I've taken a fair amount of bio classes, and I can tell you two things. First, all sun exposure, no matter how brief, increases your risk for skin cancer. Second, the amount it increases your risk grows with continuous exposure. So, 12 five minute sessions are less risky than a solid and continuous hour. Given that sunlight has a lot of health benefits (like vitamin D production), I'd guess your five minutes in the sun is probably doing more good than harm."
] |
[
"So pretend it isn't personal and just think about the question relating to sunblock and sun exposure.",
"Aren't all questions asked for personal reasons?"
] |
[
"It continually bemuses me that people like you post things in ask science. Go to the wikipedia page on vitamin D and read ",
"."
] |
[
"How does graphene integrate into spider silk?"
] |
[
false
] | null |
[
"Hi dawillus 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 following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"'Biology', 'Chemistry', 'Engineering'"
] |
[
"Chemistry "
] |
[
"Electromagnetic radiation and its alleged negative health effects. A hoax, or legitimate."
] |
[
false
] |
Electric heat blankets to transmission lines. As far as my understanding goes emf is produced from alternating current. That said, dc power sources should have no such effect. Also there are advertisements for anti-radiation pads, yet I was taught nothing could interrupt emf waves.
|
[
"There's no evidence that the fields or radio emissions from alternating current have any negative health effects, attempts to detect things like claimed ",
"electromagnetic sensitivity syndrome",
" (not a recognized medical condition) have all turned up the result that there is no detectable effect on people.",
"Any conductor will stop a radio wave. Some electronics are shielded inside what are known as ",
"Faraday cages",
", which is basically where you surround it with a mesh of conducting wire. This is commonly used near radio telescopes, where the radio waves from electronics might otherwise interfere with the telescope."
] |
[
"Electromagnetic radiation can harm you, it can be harmless. For example: \n-UV radiation in sunlight causes sunburn\n-gamma radiation from space can cause cancer\n-X-rays can cause problems if the dose is too high",
"But visible light, radio waves, and lower energy waves are harmless.",
"Also, electromagnetic fields (emf) are completely harmless.",
"And both DC currents and AC currents produce magnetic fields, the difference is an AC current will have a changing field while a DC current will have an unchanging field",
"Things stop electromagnetic radiation all the time: whenever light hits an opaque object. For blocking high energy radiation that typically passes through objects that visible light cannot, dense materials like lead are used. Lead pads can block x rays and gamma rays.",
"Electric blankets and power lines are harmless.",
"EDIT: Alright, technically you could kill someone with a magnet or burn their face off with visible light. You can also die from drinking too much water. The dosage of visible light and magnetism you find in everyday objects is way too small to harm you."
] |
[
"To clarify: EM radiation of all frequencies can be harmful, because too much of it can still impart a harmful amount of energy."
] |
[
"Would altering the physical characteristics (e.g. pureeing) food affect it’s available calories or nutritional content?"
] |
[
false
] |
Basically I’m think in terms of either eating a carrot or steak as-is, versus throwing them in a blender. You would still be ingesting the same content, it would have just been broken down physically. (Excluding heat or cooking as a factor.) Would this impact our effective calories or nutritional benefit during digestion in any way?
|
[
"In some cases yes. For example, when a chef tenderizes a slab of meat by pounding it with a mallet, what happens is some of the muscle cells are broken apart, and certain enzymes in the cell leak out and begin to digest the tissue. This makes for more tender meat, but also increased content of smaller molecules (mainly small peptides) which can be more easily broken down or absorbed by digestion. Blending a steak is likely going to take this effect to its extreme end.",
"For vegetables however, the dietary concern is often the loss of vitamin content after harvesting, or during cooking. ",
"As an aside, broccoli have compounds called sulfpraphanes which are believed to have anti-cancer properties. However they aren't present (at least not at useful concentrations) in cooked broccoli. turns out, that the enzymes that make the compound in broccoli are destroyed by cooking, but activated by chopping up the broccoli, so its recommended that people who are interested in consuming sulphoraphanes chop up their raw broccoli, wait about a half hour before lightly cooking it. ",
"ref",
"edit* accidentally typed \"have cancer properties\" rather than \"have anti-cancer properties\""
] |
[
"I may be oversimplifying.. But are you saying if I eat cut up raw broccoli, it increases my risk for cancer?\nTried to find the full article, but could only read the abstract "
] |
[
"Gram for gram - No the chemical bonds remain the same and thus the same amount of energy (calories) can be extracted from it. (This is NOT true for heating)",
"However, pureeing food may make it easier to consume a larger (? My own hypothesis) amount and change the practical intake and therefore increase the calories a person consumes in one sitting. ",
"It would also slightly decrease the amount of used in the digestion compared to solid food, leaving more calories remaining"
] |
[
"Is there an equivalent of evaporation for melting?"
] |
[
false
] |
[deleted]
|
[
"This is a question that really bugged me when I was first studying materials science as a PhD student, my undergrad training being in a different field. To put it more generally, if we know that all solids at equilibrium must be surrounded by their own gas, why don't all solids also exhibit a thin layer of liquid on the outside?",
"Well in fact the surfaces of solids can be quite different than the interior, because not all molecular bonds are ideally satisfied. As a result, the surface may be \"reconstructed\"---exhibiting different crystalline bonding than the interior---and atoms may diffuse more easily as a result. ",
"Another consideration is that liquids and solids, unlike gases, exhibit a relatively large surface energy, meaning that they are cohesive---the atoms tend to bond rather than fly off freely. Consequently, there is an energy penalty to forming a large, flat area of liquid, but in at least some cases this is a lower penalty than having an equal area of solid. So a phenomenon called ",
" occurs, which is exactly the thing we were wondering about. It is discussed ",
"here",
", for example, that the liquid phase can appear on the surface of lead up to 100 K below the melting temperature. This satisfied my curiosity at the time, but if I wanted to learn much more, I'd start by searching for \"premelting\" in Google Scholar."
] |
[
"Yes, even below the freezing point, part of the frozen water would dissolve in the ethanol."
] |
[
"Yes, even below the freezing point, part of the frozen water would dissolve in the ethanol."
] |
[
"Why do some drinks drip down the side when poured and others don't?"
] |
[
false
] | null |
[
"Mercury will run out of a glass (without \"dribbling\" down the side) MUCH easier than water. This proves that \"dribbling\" is not caused solely by surface tension. From your post, one would expect that the higher the surface tension, the more \"dribbling.\" This is not the case.",
"Surface tension is causing it to stick to the pitcher.",
"This is not correct, either. Surface tension is mandated largely by ",
" forces, whereas ",
" explains the liquid sticking to something else. Both of these factors are at play here, as well as viscosity, density, and surface tension. You can think of viscosity as a sort of resistance to flow. If you have a more viscous material, it will not flow as well as a less viscous material.",
"You need to consider all of the above phenomena for an accurate description of what is occurring during this \"dribbling.\" Even if mercury had a ridiculously high adhesion to the glass, greatly cohesive properties and high viscosity, it's mass density would keep it from dribbling down the side.",
"You can consider situations of all types, but you will quickly realize that all of these factors are necessary to account."
] |
[
"Sorry if I was unclear. ",
"The OP asked about water sticking to the side of a pitcher when it is slowly poured. The explanation given was that water has some amount of surface tension, and that surface tension causes the water to stick. To overcome that, the water must be poured faster to break the surface tension.",
"Then the explanation talked about how mercury has a higher surface tension than water.",
"You claimed that the explanation was wrong because mercury is actually less likely to stick to a pitcher than water in spite of a higher surface tension.",
"I noted that while mercury has a 6x higher surface tension than water, it is 13x heavier. So it appears, when compared to water, the force that would cause the mercury to stick to the side of the pitcher is in fact weaker than the force that would cause it to not stick (gravity).",
"I'm not sure where adhesion, \"dribbling\", cohesive properties, or viscosity come into play. I understand that you believe the original explanation was incorrect, but I'm still not sure what the correct explanation is. I'd love to hear your explanation for the phenomenon."
] |
[
"The simple answer is surface tension. Say you're pouring water out of a pitcher. Surface tension is causing it to stick to the pitcher. Liquids like to stick to hard surfaces because it's a lower-energy arrangement, so when you have a really full pitcher and tip it slightly so you don't flood the glass immediately, some of the water will pour, while a lot of it will just run down the side of the pitcher.",
"To stop this, you just have to pour at a fast enough rate to break the surface tension, and \"unstick\" the water from the glass.",
"As to why some drinks do, and some drinks don't. I used water as an example, but not every liquid has the same chemical makeup and properties as water. Some liquids will have higher surface tension than others. For example water has a surface tension of 72.8 dynes/cm at 20 °C, whereas mercury has a surface tension of 465 dynes/cm. "
] |
[
"Dear Astronomers / Physicists, could you help me understand tidally locked planets?"
] |
[
false
] |
I'm curious about tidally locked planets orbiting red dwarves, such as GJ 581g, and their potential for sustaining atmospheres or even life. As one side of the planet is faced away at all times from its star, do the freezing temperatures that occur prohibit an atmosphere from forming? Also, in regards to the red dwarves the planets must be orbiting so closely, is radiation due to closer proximity also a problem? As many have taken the time during the epidemic to explore themselves a little more, I've decided to pick up science fiction writing. As a large part of the story is placed on a tidally locked planet, it's important to me to keep things realistic in a sense. Looking forward what you guys can educate me on.
|
[
"While we have no tidally locked planets in our solar system, consider that:",
"Venus rotates so slowly that night lasts about 60 Earth days, but its dense atmosphere transports heat so effectively there is virtually ",
" difference between daytime and nighttime temperature of the surface.",
"Earth's poles experience 6 months of darkness. They're cold, sure, but the atmosphere doesn't freeze out and in the Arctic the sea ice only gets so thick with liquid ocean beneath.",
"On Mars the temperature does drop low enough during the polar night for CO2 frost to form, CO2 being the main component of the Martian atmosphere. But this still hasn't got rid of it all.",
"With that in mind, I'd predict that a tidally locked planet could keep its night side warm enough to prevent a major atmospheric freeze-out, given a thick enough atmosphere."
] |
[
"As far as I know we do not have clear observational evidence for atmospheres around Earth-like exoplanets that are tidally locked. If the atmosphere is dense enough before tidal locking occurs, it could transport some heat to the night side, perhaps enough to keep it from fully collapsing. One thing you might look at is ",
"this paper showing oceans can also help",
" in cases like that. ",
"And yes, red dwarfs tend to be quite active - and that activity means X-ray flares, which aren't expected to be good for atmospheres, as well as really big coronal mass ejections, which can cause pretty aurorae (and fry electronics, and erode the atmosphere of a small planet, too). All in all they may be quite hostile. Of course, as a science fiction writer, you can pick and choose to some extent!"
] |
[
"Thank you so much for the detailed explanation and the paper! Luckily I was betting on the survival on such a planet to be neigh impossible without some fictional intervention, and you gave some excellent boundaries to write a story within."
] |
[
"A shot glass that was sitting on a table for days, untouched, just violently shattered into pieces for seemingly no reason. What the heck just happened?"
] |
[
false
] |
It was directly i front of me about 10 ft away, and there was nothing near it at all. The shot glass was very thick glass, and there was a little residue of liquor in it. I was in direct view of it while watching tv when it happened and it scared the crap out of me.
|
[
"Your shot glass must have been made from ",
"toughened glass",
". It allows internal faults to build up without notice until the glass fails \"spontaneously\". When the outside layer is scratched it fails catastrophically.",
"News story"
] |
[
"Prince Rupert's drops",
" are a pretty specular demonstration of how this can work. (better view of the ",
"shattering here",
")"
] |
[
"Glass dust, don't breathe this"
] |
[
"How does mercury polish silver?"
] |
[
false
] |
ive seen it , but i want to know!
|
[
"Two processes: Mercury dissolves the outer layer of silver in amalgamation, as another poster stated. Also, mercury directly reacts with silver sulfide (the main component of tarnish) to form cinnabar (HgS) and metallic silver, so it directly attacks the tarnish as well."
] |
[
"This is probably a better answer than mine. I didn't bother explaining the reaction and simplified it."
] |
[
"Anyone who doesn't know what he's talking about, ",
"here's a video",
".",
"It's a process called ",
"amalgamation",
". Basically, the mercury combines readily with the surface silver, which is tarnished. Gently polishing the outside will remove the amalgamated layer, the tarnish, from the pristine inside. ",
"Basically you're just removing the outside of whatever the object is."
] |
[
"Why did the Space Shuttle have main engines? Wouldn't it just be easier to have more powerful boosters and just equip the shuttle with orbital maneuvering thrusters?"
] |
[
false
] | null |
[
"The solid-fuel boosters alone couldn't have carried the shuttle to orbit without being ridiculously large. The shuttle needed the more efficient liquid-fuel engines.",
"Development of the space shuttle was...long and complicated, but I think the general intention is that by keeping the main engines on the orbiter, they could be recovered with the shuttle and reused, reducing cost. Refurbishing ended up being quite expensive, so that didn't end up paying dividends as much as hoped.",
"The Soviet space shuttle, Buran, did place the main lift engines on its launch vehicle and only had small orbital thrusters on the orbiter, and there were plans to make all sections of later launch vehicles--orbiter, launch vehicle, boosters--totally reusable. But funding for the program dried up after the fall of the Soviet Union, and Buran only flew once, unmanned, so we never got much of a chance to see if that was a big improvement."
] |
[
"The boosters were solid fuel rockets. Solid fuel rockets are simple, powerful, and relatively cheap. But that simplicity comes at a cost: you can't really control them. You don't have much in the way of a throttle, and stopping and restarting them is all but impossible. They're great for getting you off the ground, shit for getting you to orbit. ",
"That's why all rockets that take cargo to orbit or the moon are liquid fuel: to get finely controlled thrust. ",
"That's why the space shuttle had that huge tank on its belly: fuel for the main engine. ",
"Getting to orbit isn't just about getting to the right ",
", you must reach that altitude at the right ",
". Too fast or too slow and your orbit will get all wonky, you risk falling back to earth. It's hard to get that precision with solid fuel rockets."
] |
[
"There were plans to give the Shuttle liquid fuelled boosters that would land themselves, like Falcon 9, but the funding was cut."
] |
[
"What will happen when all the coral reefs die?"
] |
[
false
] |
What will happen if all coral reefs die? Recently there more and more news coming in about the death of coral reefs.. eg.
|
[
"Extinction. An ecosystem which has existed for millions of years will be gone forever. Some specimens will continue to be kept in aquaria and laboratories. But if we continue to burn all the oil and natural gas we can find, the oceans won't be a safe habitat for reintroducing them for 10,000s of years.",
"Edit1: To summarize some thoughts from discussions below. The loss of the corals, like the loss of many terrestrial ecosystems, is fundamentally due to the loss of habitat. Unlike on land, the loss of habitat is not necessarily due to a local encroachment. While recent cases of bleaching have been attributed to temperature increases, the long-term demise is due to a global reduction in ocean pH. We have already observed some global reduction of pH and more is already locked-in based on simply accounting of the amount of fossil-fuel burned so far and how much will likely be burnt in the next century. Budgets of the future global carbon cycle all agree that the majority of the fossil fuel carbon burned for energy will end up in the ocean. It hasn't happened yet, current estimates are about 20-25% of the burned carbon is in the ocean. The rate limiting step is the transfer of carbon-dioxide across the air/sea boundary. Given all the carbon we have already burned over the last several decades, the relative inventory has built up in the atmosphere more than the ocean but that will change over time as the system equilibrates. ",
"If the corals were only being threatened by increased temperature, there might be hope. One could try to find suitable new habitats at higher latitude. But with the global reduction of pH - the entire ocean is becoming inhospitable. There will be no places one could transplant colonies to. ",
"Eventually, after this geological bulge of carbon works through the system, the chemical conditions might return to those like today: however, the timescale for that, which requires deposition into the seabed, have been estimated at 30,000-50,000 yrs. Source: ",
"Fate of Fossil Fuel CO2 in Geologic Time",
"."
] |
[
"In terms of ocean biochemistry, I don't think it will be a big impact. There is indeed incredible species ",
" on reefs but in terms of total ",
" in the ocean, corals are a small blip compared to all the krill, copepods, diatoms, dinoflagellates, etc. Locally, the absence of reefs will have effect on the ocean environment, but globally not so much. "
] |
[
"There's potential for there to be an effect on the earth's radiative budget. The extent of this is still pretty unclear though. The idea stems from the ",
"CLAW hypothesis",
". It essentially is an idea that biological sources (in particular, phytoplankton, but coral is also considered) are part of a feedback loop with the oceans, atmosphere and sun.",
"For example, under stress or increased sunlight/heat, the coral will release more of a substance known as dimethyl sulfide. Dimethyl sulfide undergoes processes in which it can become a cloud seed. The more cloud seeds you have, the whiter the clouds that are formed are. The whiter the clouds (higher albedo), the more sunlight reflected back into space. The more sunlight reflected into space, the cooler the earth (thus \"destressing\" the coral). ",
"There are very large uncertainties in the effect a dying coral reef would have though, mainly due to the fact that all of the interactions that occur are quite complex and variable. The CLAW hypothesis and a lot of the research is focused on phytoplankton too, so whether the actual impact of a changing coral reef on the atmosphere is significant or not is still in doubt. On top of this, there is a second process in which cloud seeds are influenced by coral through sea spray formation. This process is said to have an opposite effect to the CLAW hypothesis. The extent of the influence of the sea spray aerosols is still relatively unknown again. ",
"Anyway, what I'm getting at is that IF the coral reefs were to die, there is a chance that something that might be important in regulating the earth's climate will be gone. Which means that the temperature of the earth may increase, eventually. "
] |
[
"Why do movies look more blurred when paused?"
] |
[
false
] |
I noticed that when I pause a movie to get a print screen, the still image is blurrier than the moving image would lead me to believe. Is this an optical illusion: i do not notice blur when it is moving. Or is it the result of a halted interpolation by the media player. Or something else? extra: if it is the second case, what program can i use to grab clean stills
|
[
"Most movies are shot at 24 frames per second (fps). While it is possible to create 24 sharp images of a moving object in one second, the result would look very choppy, since the fps is way too low. You would clearly see each frame and jumps between different positions of the object. By letting each frame get a bit blurred, our eyes will create the illusion something is actually moving (but it isn't, because you are watching still images, just in quick succession)."
] |
[
"Also a lot of films are shot at a 180 degree shutter angle. That means each frame is exposed for half the amount of time as there are frames per second (one 48th of a second for film shot at 24fps). Doesn't sound like much but if you shot all your still photos at 1/50 sec you'd see more blur than you would think. "
] |
[
"Is this an optical illusion: i do not notice blur when it is moving",
"Essentially yes. Your brain is exceptional good at reading these images as real moving things. It builds a model that appears detailed and smooth rather than slightly blurry and going 24 steps ",
"Or is it the result of a halted interpolation by the media player",
"This is really complicated for compressed digital video formats. The short answer is that the majority of the blurriness you're seeing on pause is a function of the shutter angle and the recording frames a second and not really a result of the codec. Compression does reduce detail and introduce a kind of blur but this manifests as compression artifacts rather than something which looks like motion blur."
] |
[
"Why does the Swift-Tuttle debris stay put?"
] |
[
false
] |
I know that the Perseid meteor shower is the Earth passing through the debris left by the tail of the comet Swift-Tuttle. But Swift-Tuttle has a 133 year orbit. Why does the debris stay in place, thus allowing us to pass through it every year? Why doesn't it dissipate or move?
|
[
"It doesn't stay in place. It travels on the same orbit as comet Swift-Tuttle. "
] |
[
"Just like the Earth's orbit itself doesn't change much over the course if a human lifetime, neither does the comet's. The two orbits intersect in one particular place, which is the position the earth happens to be in around August 13. Swift-Tuttle's orbit is filled with debris, all in about that same orbit around the sun. We don't hit the same debris every time. "
] |
[
"so how is it that we travel through it at pretty much the same time every year? Or is the reason it may move a day or two every several years because of this?"
] |
[
"Quantum Entanglement and Black Holes"
] |
[
false
] |
So Quantum Entanglement allows us to know what is happening to one particle when it is entangled with another, so if it were to be entered into a black hole, would we be able to understand the inside of a blackhole?
|
[
"Entanglement doesn't really let you know what is happening to the other particle in general. If you have two entangled particles, A and B, then you can measure B and it will tell you something about A, but what you just learned about A could have come about just because you measured B, not because of something that happened to A directly."
] |
[
"That's an interesting question. I think we do not really know the answer yet. What's clear is that entangled particles do not transmit any information between them, so the particle in the hole wouldn't be able to tell it's former sibling what's going on in there.",
"What's ",
" clear however, is where the information stored in the initial entangled state goes. Two qubits in a pure, maximally entangled state contain exactly 2 bits of information which is stored in the correlations between them. The individual qubits however are in mixed states, containing zero information. Once a particle falls into the black hole, two bits of information hence appear to be lost. Ultimately, however, information has to be conserved in the universe. So where did it go? This question has led to a famous and still ongoing debate in cosmology and quantum mechanics. I'm not going to give you the full story, because it's ",
"much better described",
" on Wikipedia. ",
"To get back to my point: since we do not yet know where the information goes, looking for it on, for example, the horizon of the black hole, might still tell us something about the black hole itself.",
"That last bit is wild speculation though."
] |
[
"On that note, people seem to think that if you change particle A, particle B changes as well. Their idea is that this could let you transmit information instantaneously across the universe. In reality, if you change particle A... you disentangle the particles. They don't let you violate causality."
] |
[
"Would a house with a self contained electric system run more efficiently on DC power? Could higher voltage be used to achieve better efficiency?"
] |
[
false
] |
I feel like in the future, houses may run on self contained solar/ battery systems. Would it be more efficient to run everything at, say, 400 VDC instead of 120/240 VAC? Could most appliances be easily converted/ designed to run on DC power. Would higher voltage be a problem due to insulation?
|
[
"So this, for the most part, is true. However, HVDC (high voltage direct current) is quickly starting to become a good choice for high power long distance lines (Such as the one from the Columbia River ",
" on the Oregon side, down to California). ",
"It's good for long distance bulk power transmission with no intermediary taps and is especially good for undersea cables due to the huge capacitance in some of those lines. "
] |
[
"Never.",
"Well sort of.",
"You have to remember when it comes to products their are three types, consumer, intermediate, and industrial/commercial and have there different grade.",
"Companies are much more adapt to spend more on more efficiency and longer life even if it hurts them short term, they will make up the difference. So highly specialized parts engineered for maximum efficiency and monitored 24/7 by many staff. Aka a solar power plant etc.",
"Any home device while not a bad idea, getting off the grid or taking some stress off it's great. However you as a consumer are buying low level parts, because consumers are cost oriented very highly, and normally underinformed. A contractor could help but then take into account that it's done to work for your home where you are, not a special location picked for wind or sunlight, not the highest end parts or longest lasting, and no one monitoring and adjusting 24/7 for defaults you can begin to see the problem.",
"Now the intermediate user may value longevity and other factors and spend the extra cash, but as a normal probably successful smart individual you still have limits less than that of a power company specialized in this field. You will fair better than an average consumer, but still a specialized plant will still fair much better in efficency and output then you ever will.",
"That is not to say if you were insanely rich and wanted the best of the best, and had an engineer to design the house and solar panel or wind panel grid, in an area of maximum output, and top efficiency for cost, with long long lasting parts. This is nothing I or most likely you or even the intermediate smart individual could afford. I doubt any rich people would be adapt to do it either.",
"To address the second part of your question voltage will require higher quality insultation or a different type, and is depent on country. However higher voltage, and using more than one phase can contribute to higher efficency in a way.",
"Higher voltage allows you to push more power through the same conductor, but the shielding needs to increase.",
"Amperage requires you increase the conductor size.",
"Power is voltage * amperage = wattage/power.",
"So using a transformer which allows you to alter voltage and amperage in a system, up the voltage amperage goes down by same amount and vice versa.",
"So you can use less conductor and save on the costs of metal by using a lower amperage but higher voltage and transfer same amount of power. However voltage can be thought of electrical pressure, thus think of the current jumping or arcing. So it requires better shielding.",
"It's a double edged sword, normally a lower amperage and higher voltage is beneficial but only due to shielding costing less then upping the size of the conductor or wire. There are also other factor but hopefully that helps a lot."
] |
[
"Wikipedia page \"War of Currents\" might be relevant for you to look at:",
"http://en.wikipedia.org/wiki/War_of_Currents",
"Basically, DC is good if you have a small power source close to where the current is being used (e.g. a battery in a flashlight). AC is good if you want to transport current over long distances from one really big generator (e.g. from a nuclear power plant to a city). ",
"If every household put solar panels, wind generators, etc on their houses instead of buying electricity, then it would make sense to use DC instead of AC."
] |
[
"Do greenhouses gases also keep sunlight from entering the atmosphere in the first place?"
] |
[
false
] |
[deleted]
|
[
"And ",
"here's a chart",
" which compares the spectrum of incoming radiation from the sun vs. outgoing thermal radiation from the Earth. As you can see, there's very little overlap."
] |
[
"Most of the sun's energy arrives in the form of visible light. ",
"Chart",
" Relatively little energy is coming in as infrared.",
"Almost all of the energy trying to leave Earth is in the form of infrared. As it happens, CO2 has an absorption band close to the wavelength that corresponds to Earth's black body temperature. Solar energy cannot get out as easily as it came in. The Earth's temperature rises until a new equilibrium is reached.",
"So yes, but the amount of energy being kept out is tiny while the amount of energy being kept in is large."
] |
[
"The gas does block some incoming sunlight, but it blocks the outgoing infrared better. A lot of the sunlight that hits earth warms it, and then the earth \"glows\" in infrared light. In effect, the visible light gets changed into infrared, and the greenhouse gas (or glass in a greenhouse) blocks outgoing infrared better than incoming sunlight. Net result, much of the energy is trapped.",
"This page has a good diagram (2nd one down)",
"http://www.learner.org/courses/envsci/unit/text.php?unit=2&secNum=3"
] |
[
"What are the Primary, Secondary, Tertiary, and Quanternary structures of a protein?"
] |
[
false
] |
I do not understand how Tertiary and Secondary differ, and how Tertiary and Quanternary differ.
|
[
"Primary is the sequence of the amino acids. Secondary is local substructure, typically alpha helices and beta sheets. Tertiary is the overall folded structure of the protein and how all the secondary structures interact. Quaternary structure is how the protein interacts with others into an active holoenzyme, for example."
] |
[
"One way to think of it is that each structure level represents interactions of the preceding one.",
"Primary structure is the single, unbroken chain of amino acids. Secondary structure is the amino acids interacting with one another to form regular structures such as helices, turns, and sheets. Tertiary structure is when these secondary structures interact with one another to form more complex structures. Finally, Quaternary structure describes the interactions of distinct strands of amino acids and their respective primary through tertiary structure.",
"(Note: I'm annoyed by how often I had to use the word \"structure\" in this response. Any biochemists know of acceptable synonyms that I could use to mix up the prose? :p)"
] |
[
"Not exactly a biochemist, but some synonyms I've heard commonly used are primary sequence, secondary and tertiary folding, and quaternary interactions. You could also use shape, or conformation."
] |
[
"Why do I get the conservation of energy when I solve the Euler-Lagrange equation?"
] |
[
false
] | null |
[
"There's a theorem called Noether's Theorem that says that when a Lagrangian (or the action) is invariant under a particular transformation, the system exhibits a symmetry pertaining to that transformation. ",
"In the case of conservation of energy, when we shift the system from q(t) to q(t+dt), you can easily see that the action is invariant. "
] |
[
"If a Lagrangian has no explicit time dependence, then the system exhibits conservation of energy. The energy turns out to be the Hamiltonian H associated to the Lagrangian L (i.e., H is the Legendre transform of L with respect to the velocity variables)."
] |
[
"Strictly speaking, no explicit time dependence in the Lagrangian means that the Hamiltonian, H, is a constant of the motion, which will not necessarily be the total energy of the system. While in many cases of course it is, there are fairly simple systems you can construct where H is conserved, but it does not correspond to the total energy."
] |
[
"Passing on your genetic material without having children?"
] |
[
false
] |
[deleted]
|
[
"There's not much to add to this except that this is basically the topic of much of Richard Dawkins's book ",
". A classic which everyone should read!"
] |
[
"It's not exactly \"passing on your genetic material,\" it's more that genes that are identical to yours can be passed on to the next generation because other people also have that gene. Your siblings are about 50% genetically identical to you. That is, you share about 50% of your alleles with your sibling. So when your sibling has a child, that child is about 25% genetically related to you because your sibling contributes half of the child's genes. "
] |
[
"Seriously?"
] |
[
"What happens to the blood vessels in fat when you lose a lot of weight?"
] |
[
false
] |
So I've heard the "rule" that for What happens to those vessels when you lose that fat?
|
[
"Yep, and sometimes it gets grotesque; patients who've had extensive lipo will get neck fat, etc."
] |
[
"Oh dear. Mother Nature wins again."
] |
[
"Unless you have surgery - you don't loose fat cells they just shrink. SO the blood vessels would still be in place but having to cover a smaller area. Often leading to varicose veins."
] |
[
"What are the criteria for being a primate?"
] |
[
false
] |
[deleted]
|
[
"Oh, humans are primates, there's no dispute there. I prefer genetic demonstration over morphological when it comes to proving it though; retroviral insertions & psudogenes are quite convincing."
] |
[
"That seems like a pretty comprehensive list, what kind of features are you looking for?"
] |
[
"not certain kinds of features. i've seen in museums and online and heard biologists reference a set of defining characteristics that make something a primate so to speak, but i don't remember seeing anywhere what they are. i remember reading something recently that said \"there are 8 [or so, i don't remember the exact number] characteristics that every primate has, and humans have every single one of them\" it was arguing that humans are primates."
] |
[
"Can gravitational waves be affected by gravity?"
] |
[
false
] |
[deleted]
|
[
"Yes."
] |
[
"With suitable definitions, they carry energy-momentum, just like light. Also as small fluctuations from a background shape, they can be proven to be affected by the background shape itself."
] |
[
"How can gravity manipulate it? Aren't they fluctuations in spacetime rather than anything with mass/energy, and thus unable to interact with gravity?"
] |
[
"How many calories does the human brain consume in a day?"
] |
[
false
] | null |
[
"Your brain runs around ",
". 10 Watts = 10 Joules per sec. There are 4.184 Joules in a calorie (little c, not Calorie, which is 1000 calories). That's 2.39 calories per second. There are 86400 seconds in a day. 86400 x 2.39 = 206496 calories, or ",
"EDIT: I was going off of some research that I had done about a week ago, namely ",
"#30 in this list",
". Being lazy as I am, I didn't read into it and just remembered the 10 watts. As several people in the comments are saying, the power is closer to 20 watts. ",
"WolframAlpha",
" is one source of this other wattage. So double my original estimate = 413 Calories.\n"
] |
[
"In other words, if you were a brain living in a jar, you would only need to eat one bowl of Ramen every day to support yourself. With a six pack of Ramen at $1 each, that's an annual food cost of $65.21 including tax if you live in California."
] |
[
"the question is, can your brain handle that much sodium?"
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.