title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"What caused the big bang?"
] | [
false
] | I have heard tons of conflicting theories on this and don't have enough mathematical skill to perform meaningful research on my own yet. So what was the prime mover or ignition, or what was the most probable cause? Edit: Thanks everyone! Extremely clarifying. | [
"We don't know.",
"Our models of physics begin with the big bang - they describe the bang and its consequences but not anything prior to - or outside of that bang.",
"To the extent that such things are unobservable by us there is no constraint on what can be hypothesised. "
] | [
"Causality isn't a rigorous part of physics. Many, nearly all, processes follow causal rules, and that's why we assume it generally describes reality. But not everything does. Nuclear decay is thought to be acausal (without cause) and other quantum precesses as well. The big bang itself could very well be acausal a... | [
"pretty much because our present rules of physics do not have any \"cause\" to the decay. They are simply ",
" to happen, and because they increase entropy, they ",
" happen. I wrote more about it here:",
"http://www.reddit.com/r/askscience/comments/iallj/15_questions_evolutionists_cant_answer/c229j74"
] |
[
"What would happen if the two plates that are used to produce the Casimir effect were charged?"
] | [
false
] | null | [
"Then there'd be a much greater force between the plates, and it would be hard or impossible to measure the contribution from the Casimir effect."
] | [
"Oh wow now that you say that I can see why because the electrons would be attractive as well. I was wondering if people have tried different geometries instead of a simple plane? Like for example what if a person blocked 3 sides of the 2 planes and scaled it such that certain selected wavelengths were allowed betw... | [
"Light is definitely a 3D phenomenon, but the Casimir effect is easy to derive in the case of infinite, flat planes, in which case the problem is effectively one-dimensional. And people want to measure that situation so that it can be compared to the prediction that's easy to derive analytically. I'm sure people ha... |
[
"Why do people and their houses all have different somewhat distinct smell?"
] | [
false
] | You know when you walk into someone's house and it just...smells like them? What is that? | [
"Ah, finally something I can answer with science, sort of. I mean the best science one can afford on his own in such a case as a 15 year old at the time I did this. ",
"I actually wondered about this as a child. I was split between two houses, my mother's and father's, pretty much every week, each t... | [
"Upvote for having the passion as a 15-year-old to conduct an experiment in your own free time knowing there was not due-date or grade involved. "
] | [
"I was a strange child. Me and my brother both... When we were younger than that we spent hours and days, completely determining the password structure from the original metal gear NES game. We knew exactly when every aspect of the password did, could start a game in any location, with any chosen number of am... |
[
"Does glycogen require insulin to be used?"
] | [
false
] | [deleted] | [
"In short, no; you're right in that the breakdown of glycogen happens inside the cell, so you don't need insulin to facilitate glucose uptake from blood.",
"If you want more:",
"glycogen only requires glucagon to be used. Insulin is not necessary, because the particular muscle uses its own glycogen to produce u... | [
"Muscles glycogen doesn't contribute to blood glucose directly, it does indirectly cause when glycogen is broken down inside the muscle into glucose it prevents glucose uptake from blood thus raising blood glucose but this isn't an important determinant of blood glucose levels. Muscles use their stores of glycogen ... | [
"Glycogen is converted to glucose in the liver and then released into the bloodstream. Cells outside of the liver cannot convert glycogen into glucose, they can only convert glycogen into glucose-6-phosphate (a glycolysis intermediate) and then send it through the rest of the glycolysis pathway, generating some ATP... |
[
"How, mechanistically, does water pressure increase at greater depths?"
] | [
false
] | Most people know that water pressure increases with your depth below the surface. In fact, the pressure reaches ~6 atmospheres at only 50 m of depth. I understand from a force-balance point of view why this must be the case- the water below must support the weight of the water above. However, I do not understand this increase in pressure from a molecular point of view. My understanding is that water is largely incompressible, so the density is effectively constant. Lets also assume, for the sake of argument, that the temperature of the water column is constant. Pressure is effectively just the consequence of water molecules striking the walls of a container. However, since temperature (which reflects the kinetic energy of the particles) is constant with depth, and so is density, you have the same number of particles moving at the same average speed at both the shallow and deep depths. So how does the deeper water have a greater pressure? | [
"You seem to be thinking of liquid water on the molecular level as if it were an ideal gas, where the molecules are free to shoot around ballistically with some kinetic energy and only interact when they collide with each other. This picture is wrong. As a liquid, the water molecules are packed in against each othe... | [
"On a molecular level each molecule has a downward force equal to it's mass times gravity which is what causes pressure at depth. In a gas you have a density change based on pressure and temperature."
] | [
"The density of water increases with pressure at fixed temperature. The statement that water is incompressible is an approximation. Often it is a good approximation, but it is still an approximation. The fact that water is nearly incompressible implies that a finite change in pressure will lead to a small change in... |
[
"How come we can move in space at varying speeds, but we can only move in one direction at a constant pace in time?"
] | [
false
] | Sorry if this question is too metaphysical for . But what is time? Why is speeding up, slowing down or going backwards in time not the same thing as speeding up, slowing down or going backwards in space? | [
"This may not be an exact answer to your question, but according to the theory of relativity, everything in the universe is moving at constant velocity ",
" (the speed of light) through 4-dimensional spacetime. This means that an object that is stationary in space (relative to an observer) is moving at ",
" thr... | [
"We do move at different speeds in time. If you are moving at some speed with respect to me, I perceive your time as passing slower with respect to mine.",
"But I feel the essence of your question is, \"Why is time different from spatial dimensions?\" As discussed above, you CAN change your speed in time, but n... | [
"No, the \"rotation taboo\" (the fact that Lorentz transformations can't reverse a timelike dimension) holds just as well inside a black hole.",
"The difference is that, within the event horizon, the timelike dimension is not time. (Remember that \"timelike\" just means it has a negative coefficient in the metric... |
[
"Why can vaccinated people no longer donate convalescent plasma that can be used to treat Covid patients?"
] | [
false
] | null | [
"Can you include links to the Red Cross policy?"
] | [
"https://www.redcrossblood.org/local-homepage/news/article/covid-19-vaccination-guide-blood-donation.html",
"third heading down.",
"The news report in question",
"I recognize that the person posting the news report is anti-vax, and I'm not at all advocating for it. I'm just referring to the report itself (whi... | [
"Seems like a bureaucratic rather than a scientific question."
] |
[
"I’ve read somewhere that candles can burn hotter than lava, is this true? and if it is, why?"
] | [
false
] | null | [
"It is true, but it shouldn't be all that surprising: compared to combustion reactions (which are actively producing a ton of energy due to chemical reactions) lava is relatively sedate, and is only hot because it was recently in contact with a whole bunch of other hot stuff (Earth's interior). ",
"Lava can be di... | [
"As very usefully quantified by the ",
"view factor",
"."
] | [
"As very usefully quantified by the ",
"view factor",
"."
] |
[
"What is the distinction between \"particles spontaneously pick their state when observed\" and \"we don't know what state a particle is in until we observe it?\""
] | [
false
] | Why do we say that particles "pick their state?" How do we know they weren't like that before we looked? | [
"I am sorry, I should have started with: \"You are being nit-picky about OP's phrasing, when it's functionally equivalent to other phrases describing the phenomenon he is referring to\".",
"Can you answer any of his questions?"
] | [
"How do we know they weren't like that before we looked?",
"Well what you're describing falls under something called \"hidden variable theory\" But let's talk about some general things first.",
"1) you only know what happens ",
" observations. Anything between observations is pretty much outside the realm of ... | [
"Basically, observation in this context means forcing the system into a single state."
] |
[
"If the length of vocal chords determines how deep a person's voice is, how big would a giant have to be before his voice would be too low to hear?"
] | [
false
] | Let's assume average, modern human proportions hold up as the giant increases in size and the normal stresses applied by physics wouldn't cause his bones to be crushed under his own weight or something. Human beings can hear down to about 20 Hz. So how big would a giant have to be before the length of his vocal chords caused his voice to be so low that we couldn't hear it anymore. | [
"The average adult male vocal chords are somewhere between 17 and 25 mm in length. However it's not just the size of the vocal folds that influence the range in frequency, the thickness of the folds, as well as genetic factors which can change the actual layered makeup of the folds themselves play a part as well. A... | [
"It doesn't scale this way, for a variety of reasons:\nFirst, just like on a guitar, the length of vocal chords is not the only factor at play. Tension plays a big role too. You have to reduce the tension to emit lower notes, and when the tension is weak, the emitted energy is reduced. Because of physiological con... | [
"60 Hz is quite low. That's lower than C two octaves below middle C. I can say with certainty that the average man is not a basso profundo. 100-120 Hz is much more reasonable.",
"Edit: Your math is very interesting though! Also, I pulled up a chart. 60 hz is between a very low Bb and and B. Definitely outside of ... |
[
"Why are some people more susceptible to mosquito bites?"
] | [
false
] | null | [
"I have been convinced my entire life that they 'like' my dad more than me. However, I am forced to admit that this is purely anecdotal, and I suspect is mainly just me falling victim to personal biases. I suspect a bunch of ",
"Selective Perception",
", mixed with a healthy does of ",
"Confirmation bias",
... | [
"I'm not sure. I would like to see a more thorough answer to this question before I'm satisfied. When I go camping with my family, my parents and brothers all get devoured, but I'll only find one, maybe two, bites. Perhaps you're right, but I can't even find any red dots from bites. Meanwhile, the others are practi... | [
"I'm not sure. I would like to see a more thorough answer to this question before I'm satisfied. When I go camping with my family, my parents and brothers all get devoured, but I'll only find one, maybe two, bites. Perhaps you're right, but I can't even find any red dots from bites. Meanwhile, the others are practi... |
[
"What does it mean that quantum information cannot be destroyed?"
] | [
false
] | This as the top of seems to suggest that according to quantum theory, information cannot be destroyed. What does that mean? Is the universe rewindable in some way? Didn't I learn in physics class that a wavefunction 'collapses'? That sounds like the sort of process where information would be lost. I am guessing there is more going on here, and it has something to do with entanglement, but I am not really sure what. | [
"Quantum mechanics has a property called ",
". Unitarity says that as a quantum system evolves in time, it does so in a reversible way. Thanks to unitarity, two different initial states cannot evolve into the same final state.",
"When a measurement is made in quantum mechanics, we assert that something non-re... | [
"Many Worlds has unitary measurement, because measurement is just entanglement of the measuring device with the system."
] | [
"Yes, this was one of the motivations behind Everett's Relative-State formulation of quantum mechanics (which is the original version of what's typically called Many Worlds)."
] |
[
"If the gravity of the moon is strong enough to create tidal waves, why doesn't it lift up things like tree leaves or small animals?"
] | [
false
] | null | [
"Surprisingly no one has gotten the right answer to this yet! Mass plays a role in tidal forces but what's really important is more often size, not mass. The reason you have a tide at all is the difference in the pull of the tidal body from one side to another. We get a tide on the earth because the side of the ear... | [
"This is right. When I teach it, I draw a diagram that looks something like this...",
"W E W - - - - - M",
"Water = W\nEarth = E\nMoon = M",
"The moon pulls hardest on the close water since it is closest The moon pulls the close W off the E and it pulls the E off the far W. On my whiteboard, of course, the ... | [
"It does lift those things up! The surface of the Earth will vary in distance from the center by about a meter every twelve hours due to tidal forces acting on it. Trees and small animals ",
" lifted up, but so is the ground beneath them.",
"You can maybe (depending on how much unnecessary technical language yo... |
[
"What's the difference between a regular quad core PC and a workstation with two dual cores?"
] | [
false
] | null | [
"It depends so much on the architecture of the chips being used that it's hard to make any firm statements.",
"In a ",
" general sense, the memory hierarchy is going to work differently. The memory hierarchy goes from the lowest level of data storage, the registers, which hold the data that the processor can wo... | [
"Economics. Render farms proves that they can do it. There is nothing physically preventing Nvida, Intel and game designers from making a game just for millionaires that would require 100 titan X's. ",
"I mean, they do a limited run sometimes of 1500 or 3000 dollar graphics cards that are just 2 top of the lin... | [
"Most of the things millionaires would want to do (watch a real-time render, 1000K videos, super high resolution video games, etc...) are actually quite hard to parallelize. A video game, for instance, can split its load between four processors easily (two for render, one for physics and one for gameplay/audio for ... |
[
"What is the most advanced artificial intelligence that we have created so far?"
] | [
false
] | null | [
"Netflix, Google, and the like—",
"Or, for something more research-y and interesting take a look at ",
"LDA",
", ",
"Kalman filters",
", or hybrid processes.",
"More specifically, AI doesn't exist in the way scifi makes it out to. Not today, and not yet foreseeably. Though we believe theoretically that ... | [
"IBM's jeopardy computer ",
"that's being tuned to help in healthcare",
" ranks pretty high for some definitions of 'intelligence'. It's probably the most hyped AI computer these days.",
"Some interesting discussion about ",
"chat bots aproaching the ability to pass the Turing test appeared on /r/programm... | [
"It's certainly the most publicised. ",
"A couple of genuine questions here, I'm not having a go:",
"What other AI projects are you aware of?",
"Would you consider pose estimation on the kinect (working out where your arms and legs are; which is which; and who they belong to) to be AI?"
] |
[
"What exactly happens to blood as gas exchange happens in the lungs, what organic chemistry is happening - does the pH change?"
] | [
false
] | null | [
"You’re blood transports CO2 mostly as carbonic acid (H2CO3) since it’s more soluble than CO2. In high CO2 conditions (like the muscles) the blood will get slightly more acidic as CO2 waste is converted to carbonic acid, that acid then ends up in the lungs where equilibrium shifts (since there is less CO2) and carb... | [
"Cool. I was reading about the bicarbonate exchange today",
"I’m just interested in hypoxia and hyperoxia ",
"How do lung tissues respond to these situations?"
] | [
"The lungs shouldn’t really experience hypoxia in a healthy individual unless they are traveling to high altitude, because of course they have the most readily available access to it. Do you mean how the rest of the body reacts to hypoxia?",
"Our bodies can rapidly tell how much CO2 is present based on the pH. Mo... |
[
"Why is CMB in every direction?"
] | [
false
] | The cosmic microwave background radiation (CMB) is observable in every direction. It is the radiation emitted by the opaque plasma that existed after the big bang that is now reaching us 13 billion years later. if we are still moving away from the origin of the big bang, surely after 13 billion years we would have exited the bounds of the plasma cloud that sources the CMB. Is this true? If so, why is the CMB in every direction? Wouldn't it be like looking at the earth from above the surface, filling a little or a lot less than half the sky? | [
"if we are still moving away from the origin of the big bang",
"That's your problem. We aren't moving away and there wasn't an origin point. All of the universe expanded in all directions at the same time and there is no no center of the universe. It's counter intuitive I know but this guy explains it pretty well... | [
"Try not to think of the big bang as an explosion that threw everything out. It's an expansion of space. Think of a galaxy as a raisin in a piece of raisin bread that is rising. As time goes on, you see the other raisins moving away, but you're all inside the bread.",
"All matter in the universe used to be comp... | [
"So, the matter in the observable universe is not an arc of the surface of a sphere, like the pressure wave of an explosion?",
"It is not.",
"So, is it uniform roughly in every direction?",
"Right.",
"And when people talk about us being on the surface of an expanding balloon, they are only referencing the s... |
[
"Reddit, what's the science behind speeding up the \"fizz down\" of soda by sticking your finger in it?"
] | [
false
] | null | [
"the oil from your skin lowers the surface tension of of the bubbles, causing them to fizz down"
] | [
"The way I have been told, oils on your skin reduce the surface tension of the liquid, causing the bubbles to burst. While ",
"this does have scientific grounding",
", I am unable to find a reliable source specifically addressing the soda- or beer-bubble case."
] | [
"Sticking your finger in a soda increases the surface area onto which bubbles can form. In a soda, bubbles cant spontaneously form, they must begin at some type of surface nucleation point, typically the side of the glass or a scratch on the glass. Your finger provides many of these, and fizzing occurs. This is als... |
[
"Are there similarities between native Alaskan languages and languages native to northeastern Asia?"
] | [
false
] | null | [
"Maybe. The ",
"Dene-Yeniseian Hypothesis",
" proposes a relationship between the Na-Dene language family of North America and the Yeniseian language family of Siberia. The Na-Dene family is very large and diverse, extending from Alaska to the southwest United States, and includes such languages as Navajo and K... | [
"Eskimo-Aleut is almost entirely located in North America, but a few Yupik languages (a subfamily) are spoken in Siberia.",
"The Dene-Yeniseian link is a hypothesized language family that is gaining acceptance among linguists, though is not considered \"proven\" as of yet. The Dene branch (called Na-Dene) is a fa... | [
"Yes, in fact Yupik live in both Siberia and Alaska--and they all speak similar languages. "
] |
[
"How do dyes that excite at the same wavelength emit different intensities?"
] | [
false
] | I feel like I am missing something obvious but just can’t wrap my head around it right now. I am using Alexa-546 for Cysteines and Alexa-546 for Lysines, yet when I excite them, Cysteines is giving me an intensity of about 4000 AU and Lysines is 12000 AU | [
"I'm assuming that you're labelling amino acids in a protein, and that the final concentration of fluorophore in each case is identical (i.e. same amount of protein and same number of labelled residues in each case).",
"Fluorescence quantum yield depends on the environment the fluorophore is in. Anything that cau... | [
"The two dyes have the same fluorophore but differ in the reactive group attached to the linker. ",
"This is Alexa 546 NHS ester",
", used to label amines. ",
"This is Alexa 546 maleimide",
", used to label cysteines. I'm not sure where you got yours from but ThermoFisher sells the NHS ester as the triethyl... | [
"I did both labeled to a protein (with same amount of prot and labels) and just free dye in solution",
"Thank you for all the information though! "
] |
[
"Why is hydrogen bonding only possible with hydrogen?"
] | [
false
] | I know this may seem like quite a self-explanatory question, but why not an atom that is even less electronegative than hydrogen, such as boron? Is it due to its size? Shielding effect of inner shell electrons? Charge density? Any answer would be greatly appreciated. Thanks! | [
"Because hydrogen is the only element that normally bonds with the 1s valence shell. On can thing of hydrogen bonding as being due to polarization of the electron cloud by proximity of a more \"electron loving,\" or electronegative in the jargon, element. This leaves an electron deficiency on the part of that shel... | [
"The shielding effect of electrons was the right answer. ",
"Or rather the entire lack of. If hydrogen is covalently bound, then - that bond requires hybridization of the orbitals of that hydrogen with the atom it belongs to. \nThat means it’s density function is mostly between the hydrogen and the other atom. ",... | [
"It is possible to have other atom to participate in \"hydrogen-like\" bonding. Halogen atoms do this quite often. There are electostatic interactions between an electronegative atom (usually N or O) and a halogen atom covalently bonded to another electronegative atom. Those types of bonds are called halogen bonds"... |
[
"In what ways/methods did humans change bananas from their natural form and why?"
] | [
false
] | I've seen it mentioned multiple times that the current image of a banana is vastly different from what their natural state is. While I understand the basic mechanics of how this can happen, I don't understand why it was necessary. Basically I'm looking for a rundown on the domestication and cultivation of bananas... | [
"Wikipedia's page on Banana's",
" is pretty detailed about the development of modern cultivars. ",
"Probably the biggest difference between the Cavendish banana's you're familiar with and their wild ancestors is that the Cavendish has tiny seeds. You can't actually plant a cavendish and grow another tree. Th... | [
"thanks for the thorough reply! That last paragraph is really interesting. So if a disease wipes out the Cavendish plant, would we have to basically restart the process?"
] | [
"The Gros Michel is still out there, but just very rare. Some who have tasted it say it's ",
"better than the Cavendish",
", which does kind of make sense. Banana growers didn't want to grow the Cavendish while the Gros Michel was still viable. If the Cavendish is wiped out by something, we'll likely be stuc... |
[
"What's happening at the molecular level when a metal is heat treated?"
] | [
false
] | What exactly changes in the metal's molecules or structure that stops it from going back to the way it was when it cools off? | [
"There are a few different kinds of heat treating that can be done to either soften or harden different metals. In each case you are looking to alter the crystal structure of the final cooled metal. The solubility of different chemicals in the bulk metal will also change at different temperatures.",
"At differe... | [
"Thanks for the explanation. Also, I'm curious what did the pan end up looking like?"
] | [
"Probably one of the most common problems with warped cookware is the bottom will no longer be flat. This means concave portion will all the grease/oil will coalesce. There are some ",
"methods for flattening a warped pan",
" but if I remember we just bought a new one. "
] |
[
"What force(s) keeps magnets from sliding down a tilted/vertical surface if it's not friction?"
] | [
false
] | null | [
"If the objects in your diagrams are meant to have 0 net force, then clearly ",
" cannot be normal to the surface."
] | [
"If ",
" is normal to the surface, there is a net non-zero force along the surface. So as I said, if the net force on the object is ",
", then ",
" clearly cannot be normal to the surface. "
] | [
"If ",
" is normal to the surface, there is a net non-zero force along the surface. So as I said, if the net force on the object is ",
", then ",
" clearly cannot be normal to the surface. "
] |
[
"Can quantum teleportation allow for faster than light communication?"
] | [
false
] | For example, suppose particles A and B are entangled. Leave A on Earth and send B to a point light years away. Couldn't both sides manipulate their particle to communicate instantly with the other? Obviously there would have to be a communications protocol, but in this simple example, something like Morse Code would do. If it's not possible, what factors would be prohibitive? | [
"No. You can't manipulate the state of the entangled particle like that; doing anything to the particle breaks entanglement."
] | [
"No, this effect cannot be used for FTL communication. The big thing is that if either Alice (or Bob) does something reversible to her qubit, it doesn't effect Bob's qubit. Taking for example the usual entangled pair, |00> + |11>, in which both Alice and Bob measure the same bit, if Alice does a bit flip, the sta... | [
"Flipping your particle does nothing to affect the particle on Alpha Centauri, other than break the entangled state."
] |
[
"Hey AskScience, how come electrons never seem to crash into protons if they attract each other? What would happen if they did?"
] | [
false
] | [deleted] | [
"The sun and the earth also attract each other, but they don't appear to crash into each other either. Same thing with protons and electrons.",
"Also because of quantum mechanics the electron is actually spread out, so even if it doesn't have any angular momentum, it's charge cloud surrounds the proton. But there... | [
"Wish I could answer it myself, but ",
"this",
" seemed to adress just about all of your question! "
] | [
"It can happen in certain unstable atoms. It's called electron capture and it results in the proton turning into a neutron and the electron turning into a neutrino."
] |
[
"What's the property of mass that affects its acceleration?"
] | [
false
] | null | [
"I can think of no better answer than \"because that's what mass is.\" Mass is what makes this hard to accelerate."
] | [
"I think his point was that why is gravitational mass = inertial mass.",
"To which there is no good explanation, except that it is observed."
] | [
"Einstein was among many who have been stumped by this one. At this point, we just chalk it up to being part of an observed, if unexplained part of relativity, called ",
"The Weak Equivalence Principle",
" "
] |
[
"does this phenomenon have a name? briefly before sunrise in southern Australia the sky will act like a UV light and cause things to glow"
] | [
false
] | [deleted] | [
"Are you sure that it doesn't happen in america? According to wikipedia, due to the longer path length the effect of rayleigh scattering will remove short wavelengths more noticeably, so this would likely lessen the flouresence that is being exhibited rather than increase it.",
"Based on this, I would think that... | [
"At any rate, the phenomenon you described would fall under fluorescence, or biofluorescence: ",
"https://en.wikipedia.org/wiki/Fluorescence#Aquatic",
"Also, you might want to look into bioluminescence, however these organisms do not require UV to stimulate light emission. In addition to deep sea fish, there ar... | [
"At any rate, the phenomenon you described would fall under fluorescence, or biofluorescence: ",
"https://en.wikipedia.org/wiki/Fluorescence#Aquatic",
"Also, you might want to look into bioluminescence, however these organisms do not require UV to stimulate light emission. In addition to deep sea fish, there ar... |
[
"Is it possible to create a laser (laser-like phenomenon) with something other than light (photons)?"
] | [
false
] | For instance, could one make an 'electron laser', where you 'stack' a bunch of electrons' wave functions atop one another? I vaguely feel like 'exclusion' means it could only works for bosons rather than fermions (assuming I remember my physics correctly), but I am curious about laser-like machines that 'shoot' things other than light (both in theory and in practice). I tried to search for similar questions, but the nearest thing I could find was: | [
"There is something sort of equivalent in Bose-Einstein condensates called an atom laser: ",
"http://en.wikipedia.org/wiki/Atom_laser",
"There's something called an electron laser but it's not what you're describing. It's a way of using electrons to create a \"laser beam\" of x-rays."
] | [
"SASERs (Sound amplification by stimulated emission of radiation)",
" are the \"acoustic analog' of a laser. ",
"In a SASER device, a source (e.g. an electric field as a pump) produces sound waves (lattice vibrations, phonons) which travel through an active medium. In this active medium, a stimulated emission o... | [
"All the particles in a laser beam are in the same quantum state. The exclusion principle makes this impossible to do with electrons (or any other fermion). As ",
"/u/iorgfeflkd",
" points out atom \"lasers\" have been made from Bose-Einstrin condensates."
] |
[
"[Earth and Planetary Sciences] - Are there Hadley/Ferrel/Polar-like cells ABOVE the Tropopause?"
] | [
false
] | As far as I can deduce, Hadley, Ferrel and Polar cells are all located below the Tropopause - the Trop being their upper limit. Want I want to know is whether cells exist above the Tropopause. I'm assuming that there must be because there always seems to be some sort of "gear" action going on in the atmosphere - where a circular motion of air is balanced out by an opposing circular motion. High pressure systems are balanced out by low pressure systems, and Hadley's are balanced out by the adjoining Hadley and a Ferrel. So is there a balance above the Troposphere? I mean, if there is a wind blowing below the Trop, then surely there would be a wind blowing the same direction above the Trop? | [
"As far as I understand, there are no such organised large-scale circulation cells above the tropopause.",
"To understand why, think of the three cells we have. If the Earth is not rotating, we would have one giant cell, rising at the tropics (due to intense solar heating) and sinking at the poles. But because th... | [
"There is air above the stratosphere, but I've not heard of any organised circulation cells like those in the troposphere. That is to say, there are no regular patterns of motions that exist in the stratosphere (as far as I know).",
"This of course does not mean that there is no motion. There will be winds that f... | [
"Oh I get you. I didn't think of starting with that model.",
"Though to be honest, if there is air above the Trop then there must be some airflows above it as well? Surely there is a wind there. Which way does it flow? Why does it flow in that direction?"
] |
[
"Why don't humans have a mating season, or do we?"
] | [
false
] | [deleted] | [
"Do you have a source for this? Agriculture is quite recent, from an evolutionary perspective."
] | [
"Most of Africa has very mild seasonal changes so it was better to just reproduce whenever we can. ",
"Women have periodic (heh) fertility/infertility but don't go in and out of estrous. Pheromones don't reveal fertility very strongly either, men don't respond much to pheromone changes that still exist. This is p... | [
"Could you give an example of the mild remnant? Everyone seems to be more easily sexually excited during Spring. Or is that the result of a Social process, rather than a biological one?"
] |
[
"Would the global spread of solar panels lower temperatures globally since heat is being converted to electricity instead of being reflected?"
] | [
false
] | null | [
"Averaged over the entire earth, not really. The energy that was converted to electricity doesn't disappear; it'll eventually be released, and almost all of it will end up as thermal energy again. For instance, maybe it turns into chemical potential energy in an electric car's battery, then into kinetic energy when... | [
"it'll eventually be released, and almost all of it will end up as thermal energy again",
"Yup, someone asked a professor at my college almost this same question. We got the roof, and parking lots covered by panels. Professor said the majority of that energy went to the air conditioning."
] | [
"So.. oil spills are good for the environment? I'm on it. Wish me luck."
] |
[
"Habituation and sensitization: how are their causes different?"
] | [
false
] | They seem to be opposites, but from what I can tell have the exact same cause which is "repeated administrations of a stimulus". How are their causes different? | [
"I apologize for the late reply! The processes yielding these results on a macroscopic level are really beyond my realm of knowledge, and I really don't want to confuse you with any speculation. Best of luck!"
] | [
"If you mean biochemically then ",
" is due to phosphorylation of potassium channels, in response to serotonin from a neighbour ",
", which yields longer depolarisation and a greater influx of calcium which in turn yields a greater neurotransmittor release ==> greater signal. ",
" if I recall is due to the sy... | [
"Do you know, what is the difference in what the organism actually has to experience for either process to occur? From what I can gather, both occur due to exposure to stimuli. Is there anything that makes them different in this sense?"
] |
[
"What differentiates the \"start\" end of a DNA strand from the \"end\"? Is information ever encoded in both directions on a strand of DNA?"
] | [
false
] | null | [
"DNA is double stranded. If you read along both strands one is running 5'->3' and the other is running 3'->5' (also referred to as Watson and Crick strands (at least in yeast)). Both strands can have DNA encoding for proteins. So you can have:",
"5'---start....end-------3'",
"3'----------------------5'",
"or"... | [
"I was just trying to diagram this out to explain. So yes, genes can be encoded in both directions. You can also add another layer with non-coding RNA transcripts, as these can overlap genes but in an opposite direction."
] | [
"It is still in the 5' to 3' direction as the strands of DNA are antiparallel:",
"5'-ATGTCACCCGGGAAATTTTGACAT-3'",
"3'-TAGAGTGGGCCCTTTAAAACTGTA-5'",
"See how there is a start codon (ATG), some random codons, and then a stop codon (TGA) reading the top strand forward and the bottom strand backwards leading to ... |
[
"Does the “attention” (as in point of focus) lag behind when you move your eyeballs?"
] | [
false
] | null | [
"not very much. it depends on what exactly you're doing.",
"there's a good theory of \"attention remapping\" described here: ",
"https://www.sciencedirect.com/science/article/pii/S1364661310000288",
"it seems that from the moment you begin (unconsciously) planning an eye movement, the visual system begins the... | [
"Our eyes can only see when they're not moving. When you move your eyes, the brain receives a very blurry image, which you don't actually see. Instead, when the eyes arrive, the brain fills the period when they were moving with the new image.",
"See here for a more detailed explanation: ",
"https://en.wikipedia... | [
"i don't think this is true, especially the 'filling in' part. illusory filling-in is a very specific kind of process that is not a normal part of vision.",
"'saccadic suppression' is a concept many still believe in, the idea that during a saccade (eye movement) visual perception is completely suppressed. but I t... |
[
"How does reproducibility happen in very expensive experiments?"
] | [
false
] | [deleted] | [
"Similar to cheap experiments. A few examples:",
"The ",
"LHC",
" has four big experiments. Two of them are large general-purpose experiments, ATLAS and CMS. They have the same physics goals, but a different design and they are run by independent collaborations. If one of them finds something new the other on... | [
"and RHIC in the US",
"\"Relativistic Heavy Ion Collider\" just to satisfy my curiosity. What speed qualifies as relativistic?"
] | [
"They reach up to gamma=100, or 99.995% the speed of light. That is clearly relativistic."
] |
[
"How close are we to being able to directly interface with computers?"
] | [
false
] | I remember an where everyone had a computer implant installed at birth that allowed them to directly access their version of the internet. I'm wondering if it's at all likely that I will see anything similar to this in my lifetime. | [
"I will be a 4th year undergrad studying Molecular Biology and following that up with Graduate school in Biomedical Engineering. I'm extremely interested in Brain-computer interfaces or Brain-machine interfaces (it's why I'm studying what I am).",
"The short answer is far away.\nThe longer answer is there are man... | [
"I use a keyboard. It works well."
] | [
"I even use a mouse sometimes. It's pretty reliable."
] |
[
"How does a heating coil work? Why does it not electrocute you when you touch it?"
] | [
false
] | Okay, so I know that a heating coil (like on a stove) works by sending electricity to the coil. The coil itself is a resistor of some type... electrons collide instead of conduct and heat is released. So why do you not get a shock when you touch a heating coil? And then why do you get a shock if say dropped in water (like a hair dryer). | [
"It's deceiving because a typical heating coil on, say, a stove top typically has three layers - the inner metal coil (to conduct electricity and generate heat), a layer of ceramic insulation around that (electrical insulation), and then a metal sheath around the insulation. So even though what you see is a metal c... | [
"PLEASE don't go touching exposed coils either directly or with conductive tools while they are powered. Saying that the electricity prefers to go through the coil is misleading. If you touch the coil close to the end connected to the active you are still going to have most of the voltage across your body. This is ... | [
"I want to reiterate again what has been said by a few. According to Ohm's law, the amount of current that will pass through your body in a household shock is dependent on TWO and ONLY TWO things. Your impedance presented to the circuit and the voltage across your body. Sticking a fork in an electrical socket is... |
[
"r/AskScience, how far from having a functional energy shield are we?"
] | [
false
] | As an enthusiastic sci-fi fan, my superior knowledge clearly states its theoretically possible :P Seriously now, regarding real-world experiments have there been any developments in this particular subject? : energy shield, force field, deflector shield, etc... think Dune, Independence Day, Stargate, Star Trek, ... | [
"Actual Star Trek force fields aside, there are already uses of 'energy shields' today. Many modern tanks include one of many forms of ",
"reactive armour",
". This type of armour reacts to incoming projectiles in a way that reduces their impact on the tank.",
"The closest to a force field is electrical react... | [
"I think he's talking about something immaterial but can block projectiles and energy from penetrating."
] | [
"I'm sorry, I assumed the concept of a force field would be universal given its popularity. To be honest, having to explain the concept - especially in this subreddit - is somewhat puzzling.",
"As Beemecks said, some kind of energy field that effectively blocks projectile and energy from penetrating it's interior... |
[
"Does cyanide *actually* smell like almonds, or is that just an artifact of cyanide classically being extracted from almonds?"
] | [
false
] | I always thought that cyanide smelled like almonds (and vice versa!), but it turns out almonds contain amygdalin, which breaks down into benzaldehyde and cyanide (and sugars) -- and of course culinary almond extract isn't cyanide. Clearly the cyanide isn't the only thing responsible for the smell, and maybe it doesn't itself smell of almonds at all! In that case, I guess my question is really about the history of cyanide preparations. Why would they leave in the benzaldehyde? I suppose it could be for safety (like odorants added to natural gas), but if it's being made for legit organic chemistry uses I could see impurity being an issue, and if it's being made for poisoning people then safety probably isn't the primary consideration. So where does cyanide get the reputation for smelling like almonds? | [
"Cyanide smells like ",
", which is not at all the same thing as a normal almond. This is because bitter almonds actually contain some cyanide. All commercially available almonds are sweet almonds, so the vast majority of people wouldn't know what bitter almonds smell like."
] | [
"Oh, interesting! Any idea if the smell is at all similar?",
"Someone else pointed out that there are cyanide-producing millipedes that smell like (sweet) almonds -- are they producing both benzaldehyde and cyanide? If they produce amygdalin, this would make sense..."
] | [
"the following chemicals all smell very similar:"
] |
[
"Are brain games effective?"
] | [
false
] | In this doucumentary ., A guy sets on a journey to change imporve is brain with help of couple of scientist,first he goes by imrpoving his attention span by juggilng then he goes to next exercise called double decision . The scientist helping with him, claims this would help a tons imrpoving certain aspect of brain. how true is it? | [
"The brain works just like a muscle. You can train by exercising. Once you stop exercising the effect goes away. ",
"I’ve done it myself. Did a programme and after a while I could reproduce/remember 16 numbers after a few seconds of exposure. Once i stopped with the programme I very quickly couldn’t do it anymor... | [
"Building off of ",
"/u/Nunc27",
"'s post.",
"The more you do something, the better you get at it. Your brain is a series (or web) of connections. The more the connections are used, the stronger the links become. This is called ",
"Hebb's Rule",
", which is basically the leading theory as to why the brain... | [
"I don't know about modern games, but in the 90s, the Tetris effect has been studied extensively. The short conclusion is that after some practise in playing Tetris, some brain areas become less active, some more, indicating brain efficiency, which is related to intelligence (since Tetris involves planning, visuo-s... |
[
"How do supercomputers run so much hardware in parallel?"
] | [
false
] | [deleted] | [
"There are two main ways it's done.",
"The first is something similar to what you're describing. A bunch of processors linked together with custom hardware, basically creating one giant motherboard (though it does a lot more work than a standard motherboard.)",
"The second is by taking separate server racks of ... | [
"The formal dividing line between these two classes of systems is how memory is arranged. (This is sometimes referred to as the \"size of the coherence domain\".) When a processor modifies a location in memory, can a different processor directly read the new value? These are referred to as \"single-image systems\" ... | [
"You can think of a supercomputer as a bunch of small computers on a network working together. Supercomputers are typically composed of a bunch of identical systems. A simple example is a Beowulf cluster. (",
"http://en.wikipedia.org/wiki/Beowulf_cluster",
")",
"Programming supercomputers so that all the ... |
[
"Stars related question"
] | [
false
] | I've never posted here before, but since I work night shift, I've been wondering this for a while. (And this may be terribly worded, if any of you need clarity, feel free to ask.) Since the universe is expanding and whatnot, and even though it takes many years for us to see the light of the stars (unless we use telescopes and the like), why doesn't it look like the space between stars (or constellations) is also expanding? We've had the same constellations for centuries. | [
"Are the constellations permanent?",
"Ancient astronomers often spoke of the \"fixed stars,\" which maintained permanent positions in the sky. And, indeed, the stars do seem almost fixed in place; the patterns they form look much the same today as they did when the constellations were first named nearly 3000 year... | [
"The universe is expanding, but this expansion is only important on a very large scale. If we look at galaxies billions of light years away from us the effects are obvious (they're all moving away from us, at a speed proportional to their distance), but the motion of nearby galaxies (within a few million light year... | [
"http://cseligman.com/text/sky/bigdipperchange.jpg",
"->",
"The address you entered is not a valid page name.\nUse one of the links above to reach your destination.",
"But when I paste the URL into the address bar, I get a picture. Midnight blue background, white drawing."
] |
[
"Are there any combustion-like reactions that don't involve oxygen?"
] | [
false
] | There's the "fire triangle", and how combustion is defined as a reaction between oxygen and another substance. So would combining any other set of substances/compounds elements produce a similar result? By that I mean light, heat ect. Everything you might think of when you hear "fire". | [
"Absolutely. Fluorine is another powerfully electronegative element that starts extremely vigorous fires with a wide variety of substances. Plenty of light, plenty of heat, and plenty of terribly poisonous and corrosive by-products, just as a bonus."
] | [
"Yes, halogens are a good example, specifically fluorine and chlorine. An example being a reaction between sodium metal and chlorine gas. The sodium, acts like a \"fuel\" and the chlorine acts like an oxidizer, because technically, it is. An oxidizer, which gets its namesake from oxygen, is very electronegative a... | [
"Is chlorine trifluoride what you meant? I wasn't able to find anything on difluoride.",
"But I did find ",
"this",
". It's in French and rather old, but they show what happens when chlorine trifluoride contacts (in order) Plexiglas, a rubber glove, clean leather, not-so-clean leather, a gas mask, a piece of ... |
[
"Are there any foods we eat today that are genetically unaltered from our ancient ancestors?"
] | [
false
] | I have a friend who used to say, "Strawberries are proof god loves us and wants us to be happy." I countered that strawberries have been genetically engineered for hundreds of years to produce the fruit we enjoy today, but that got me thinking, are there any foods in our modern diet that we haven't changed to make them better/tastier/more nutritious? The only thing I could think of was honey and wild game, but was interested in a more concrete list. Edit: Not sure if this should be flaired for biology or anthropology, sorry. | [
"Even honeybees are probably different that their wild ancestors. IIRC domesticated bees are calmer than their wild cousins. Your guess at wild game rings true of course. I'm sure many of our garden crops, mint and some onions come to mind, are not altered much and can grow wild. Rhubarb grows wild where I live, th... | [
"What humans have done to plants and animals, until very recently, has artificial been selective breeding. This affects the plant's or animal's genetics over time, just as selective breeding in captive wolves created the cocker spaniel, but it isn't really the same thing as \"genetically engineered.\" It's a hit-o... | [
"A lot of berries grow wild, ie wild strawberries, raspberries and blackberries. So if you ever collect or eat wild berries then that would be an example of a food that hasn't changed. In terms of what you can buy from the supermarket, I think most foods have changed at least somewhat from domestication. Strawberri... |
[
"Why/how do benzodiazepines and Z drugs/sleeping pills cause damage when used long term?"
] | [
false
] | null | [
"Both drug families target the same binding site of GABA(A) receptors and potentiate GABA responses. This causes an enhancement of inhibitory signals in the neural circuits. As a consequence, there are less action potentials and thus we get relaxed and less responsive at sensible doses. ",
"In a healthy individua... | [
"They disrupt stages of sleep, decreasing REM sleep. ",
"Also chronic Benzodiazepine use increases risk of Dementia, 50% in 1 study. ",
"https://www.huffpost.com/entry/this-is-your-brain-on-dru_b_439577/amp",
"https://www.bmj.com/content/345/bmj.e6231#:~:text=Results%20of%20a%20complementary%20nested,1.95)%20... | [
"How long after cessation would it take for the brain to recover from this (specifically high doses of z class for several years)?"
] |
[
"How does this work?"
] | [
false
] | If magma is lava that is under ground, does a volcano spew out magma or lava? When does magma become lava? | [
"By definition, melted rock beneath the surface is called magma. Once it erupts, it is called lava. The distinction is largely semantic and done for convenience (i.e. by describing it correctly as either magma or lava, you are conveying extra information in terms of its location), though there are some true differe... | [
"Once it's at the surface, it's lava. It doesn't specifically refer to contact with air (i.e. if it's erupted under water, still lava)."
] | [
"Thank you!"
] |
[
"Specific question about electromagnetic attraction and Coulomb's law."
] | [
false
] | Imagine I have two positively charged point masses (mass A, mass B, each with a charge of 1 C, mass of 1 kg) at rest on a surface. The masses are separated by a distance of 1 m. The surface is frictionless. According to Coulomb's Law, the Force of A on B should be the opposite of B on A, and should have a magnitude of ( )/ Assuming qA = qB = 1 and r = 1, |F|= . So this is all neat and dandy if we look from the inertial frame of reference of A, as B experiences a force of , and if it has a mass of 1 kg, B moves with an instantaneous acceleration of m/s away from A. Similarly, from the reference of B, A has an acceleration of m/s But what if we use the table as a stationary frame of reference, a frame that does not move with A or B? In this case, A and B both repel each other and move away equally from a central point defined as the midpoint between the two masses (0.5 meters from each mass's starting position). EDIT: Forgot to make this clear, lol. Sorry, my bad! Anyway, what I meant to ask: So which is right? The frame of reference of the table, where each charge speeds away with an acceleration of k m/s , and if we convert this to one of the charge's frame of reference, the other charge speeds away at 2k m/s ? Or, do we start initially from the frame of reference of one of the charges, calculate the other charge to be moving away at k m/s and leave it at that? The conflict is with one method (originally using the table's frame then converting to the charge's frame) you end up with one charge stationary and the other accelerating at 2k m/s With the other method (initially using the charge's stationary frame) you end up with one charge stationary and the other accelerating at only k m/s | [
"Thanks. The stationary frame is ALWAYS right because it is an inertial frame. In the moving frame, you have to add a ficticious force, which will give you the correct 2k result.",
"(This is related to Einstein's postulate that an accelerating reference frame is indistinguishable from a gravitational field.)"
] | [
"What's the question, exactly?",
"The table frame is definitely correct, since it's an inertial frame. When you go to an accelerating frame, you have to add ficticious forces to make things work correctly.",
"EDIT: Oh, also in a moving frame, electric and magnetic fields partially change into each other, depend... | [
"Sorry about that, question fixed!"
] |
[
"How is the analog signal from a HDD read head processed before it is digitized?"
] | [
false
] | Doing a simple estimation, a hard drive might be able to read 128 MB/s. Maybe it has 4 platters, giving each read head a reading speed of 32 MB/s, or 256 Mbit/sec. So this would be a 256 MHz signal coming from the read head, but of course it's not a clean digital signal. Some of the magnetic domains might have lost some of their alignment making their signal weaker, and in any case everything would bleed together a bit, right? What does the signal from the read head look like, and how is it processed to become digitized? Furthermore, how does the HDD even know where the read head is in terms of the circumference of the platter? | [
"Hard drives use some form of ",
"Forward Error Correction",
" with ",
"Soft Decision",
"; in some cases, ",
"Reed-Solomon",
", with ",
"Viterbi decoding",
" is used. Reed Solomon may be popular, but there are other forward error correction schemes in use such as ",
"Turbo coding",
" or ",
"Lo... | [
"Q: What does the signal from the read head look like? \n A: An analog signal, or more simply, something like a sound wave. :)",
"Q: How is it processed to be digital?\n A: First, understand the data flow: Head(s) > Preamp > Controller Read Channel > HDD Controller Interface > Host Interconnect. ",
"When it'... | [
"Thank you, finally a detailed answer that doesn't gloss over the fact that there's a great deal of math that goes into deciding which bits are ones and which are zeroes. It's not just a bit-at-a-time threshold decision. "
] |
[
"My understanding is that light waves extend forever. If so, are the periods constant, or does it increase infinitely?"
] | [
false
] | [deleted] | [
"I'm not sure I completely understand your question, but I think this will mostly answer it. The closer you are to a source that radiates photons, the more photons you'll get hit by. That's why a light source seems more intense the closer you are to it -- it's not because the individual photons lose energy on the w... | [
"For an object of set size, the closer you are to a light source the more light you receive. Think about how object appear smaller as they become more distant; given a set energy output per exposed area, more distant objects would have less energy distributed over their surface."
] | [
"Light is conserved, it just gets spread out (like butter scraped over too much bread!) over a larger area the farther you get from the light source.",
"Consider a light source, be it a campfire or a star. It's putting out a constant amount of energy per time. Now imagine a sphere that just encloses the light sou... |
[
"Linguists: How do you think the internet will effect the evolution of language?"
] | [
false
] | null | [
"I haven't finished my degree in Linguistics yet, so take what I say with a grain of salt, but I think I can give you an idea.",
"First, the most immediate thing the internet is doing is expanding our vocabulary. In English, for example, our propensity for making verbs out of nouns has put \"to unfriend\", along ... | [
"I came here to say what the above two posts have already said, but I'm going to take it a step further.",
"I focus on Asian languages, and I lived in South Korea for a while. South Korea is an example of an extremely closed society that's been opened via internet connection. Despite their own private sector of t... | [
"It's a system for identifying a subject, object, or verb within a sentence, or declaring association between numbers.",
"In English, sentence structure is mostly SVO (Subject, verb, object.). But it gets complex fast.",
"Consider the following sentence:",
"Sally went to the store.",
"Sally (Subject) went (... |
[
"Why can we NOT drink seawater to survive?"
] | [
false
] | I know we can drink small amounts of seawater but why is it we cannot drink it to survive. We require trace metals, minerals, ions etc. that can be readily found in seawater and yet when we drink it we instinctively spit it out and feel a stomachache afterwards. We also cannot survive solely on DI water, since it has none of the trace metals, minerals, ions we require and instead we must eat food to obtain these micronutrients. Yes, seawater will dehydrate you but can you not simply drink more? | [
"The problem with seawater is not trace minerals and metals, but rather the >3% salt content. Your body needs to maintain a certain percentage of electrolytes, and doesn't have a good way to absorb only the water and not the salts from sea water. The result is that you'll need more and more water to offset the incr... | [
"No, drinking more saltwater won't eventually help because that water isn't going to make it into the cells due to osmotic pressure.",
"Imagine a fish tank, and in the middle of the fish tank is a wall that divides it. One side is filled with salt-water and the other side has freshwater. The dividing wall is \"... | [
"On a side note, the reason that sea gulls can drink sea water is because they have nasal \"salt\" glands that assist their kidneys by concentrating salt into a 5% salt solution and secreting it."
] |
[
"What is the largest feasible size of space station that could currently be put into orbit and maintained?"
] | [
false
] | [deleted] | [
"Define feasible. You're pretty much only limited by the amount of money and resources you want to spend building and maintaining it, but the ISS already represents an absolutely staggering investment, at an estimated cost of somewhere well north of ",
"$100 billion dollars",
".",
"Edit: Apparently $100 bil... | [
"So I don't know exactly how to answer op's question, but I do know that answer to this: yes, I have seen our moon.",
"OK, jokes aside, the reason the moon isn't ripped apart is, in layman's terms, because it's much further away from the earth than a station in LEO. I believe the prevailing theory behind Saturn's... | [
"So I don't know exactly how to answer op's question, but I do know that answer to this: yes, I have seen our moon.",
"OK, jokes aside, the reason the moon isn't ripped apart is, in layman's terms, because it's much further away from the earth than a station in LEO. I believe the prevailing theory behind Saturn's... |
[
"How accurate are our methods for dating life/rocks?"
] | [
false
] | i.e., Carbon-14 dating, Potassium-Argon Dating, Argon/Argon dating, other methods of dating. | [
"Very accurate, although the level of accuracy will vary with the preservation quality of the sample, the sensitivity of the machine being used, the concentration of the necessary isotopes int eh sample, the size of the sample, and whether the material being dated has undergone any form of chemical or physical alte... | [
"Thanks for the reply-- do you have any recommended reading? I've found it surprisingly difficult to find some articles on the subject. Google has been failing me. ;;"
] | [
"Depends what it is you want to know really. The reference list from the wiki page on radiometric dating is probably as good a place to start as any. ",
"http://en.wikipedia.org/wiki/Radiometric_dating",
"It's a technical process though, so it basically only really gets properly discussed in the scientific lite... |
[
"If all movement is relative, is there a cosmic constant zero angular velocity?"
] | [
false
] | I'm a layperson when it comes to physics, so bear with me. One of the things hammered into my head in physics class is that all motion is relative to whatever reference frame you happen to be using. But why, then, do we feel centrifugal force if we're spinning around an object, but not if that object is spinning and we're remaining still? For example, if a spaceship tried to orbit the Earth at a high velocity, it would be flung away from the Earth. But if the ship stood still above the Earth and the Earth began to spin very quickly, the ship would simply fall toward the Earth. Seen from the ship's reference frame, both of these events look the same, but have different outcomes. What causes this difference? Thanks! | [
"Velocity is relative, and there is no way to tell how fast you are moving. We cannot feel the motion of the planet even though we are flying through space at a very high speed.",
"Acceleration, however, is not frame independent. That is to say, you will be able to tell if you are accelerating because you will fe... | [
"(Not a physicist) Because one thing is inertial motion, and another thing is ",
" motion. Inertial motion is completely reative to the frame of reference. Acceleration is ",
" relative in the same way."
] | [
"two observers in inertial reference frames will measure the same acceleration of an object. being in different inertial reference frames is like being off by a constant and measuring acceleration is taking the derivative so the constant goes away"
] |
[
"Why don't Cats need haircuts?"
] | [
false
] | [deleted] | [
"I don't know exactly how I would source this, but hair and fur work the same way - they both go through periods of 'growth' and 'rest', called the anagen and telogen period respectively. After a while the hair falls out and then the process begins again. The only real difference between humans and short haired ani... | [
"Could it be because we were covered in hair at one point and now most of it is centralized in one location on the body? ",
"No because we have pubic hair still and this grows to a rather short lenght compared to the head. And human males grow beards too.",
"The best answer really is \"we don't know.\""
] | [
"Short answer: We have no idea.",
"There's no real determined reason to confirmed idea as to why humans have long hair other than perhaps, it looks nice. ",
"Sexual selection, cultural influence, we don't really know."
] |
[
"Is there more oxygen in water or air?"
] | [
false
] | Is assume there is more O2 in air but if you took the oxygen from H2O, does it add up to more oxygen than total oxygen in all the molecules in air? Also, would be possible to make a device to harness the oxygen in H2O to breathe it? ( I'm imagining some fancy little device you put in your mouth and then you can breathe water. ) | [
"I am not sure of the question, but if you mean whether an equivalent volume of air or water holds more oxygen, the answer is (under typical conditions assuming the dissolved oxygen is at equilibrium with the air) the air. Oxygen only dissolves to the extent of a few milligrams per liter of water (around 8mg/L at 2... | [
"Do you mean like...if you somehow split the H2O and got all the oxygen out of it, would there be more from that than there is in the air?",
"Yes. Much more. Pure water has a molarity of roughly 55, so if you somehow split that all up you would end up with roughly 55 moles of O per liter. Oxygen is about 16 g/mol... | [
"In addition to this, the total amount of oxygen in the air vs. in the water on Earth (roughly):",
"Water:",
"880g/l --> 8.8x10",
" kg/km",
"\nTotal Volume of Water on Earth: 1,386,000,000 km",
"\nTotal Mass of Oxygen in Water: 1.22x10",
" kg",
"Air:\n276mg/l -->2.76x10",
" kg/km",
"\nTotal Volume... |
[
"If quartz oscillates at an exact frequency, how can an atomic clock be any more accurate?"
] | [
false
] | null | [
"All clocks have sources noise at some fundamental level and we have a variety of ways of measuring the stability. For crystals, there are a ",
"number of effects",
" which alter the frequency on both short timescales and long timescales. A good way to think of short timescales is with the precision of a tick o... | [
"One month is enough to see a difference between quartz and atomic clocks. ",
"\"a typical quartz clock or wristwatch will gain or lose 15 seconds per 30 days (within a normal temperature range of 5 °C/41 °F to 35 °C/95 °F) or less than a half second clock drift per day when worn near the body.\" ",
"\"The mo... | [
"Quartz's oscillation frequency is exact to a certain number of decimal points. After that, not. ",
"Atomic clocks are accurate to more decimal points. ",
"After a thousand or a million years, those decimal points start to matter. "
] |
[
"If we copy a brain into a computer, will it still forget things?"
] | [
false
] | null | [
"Neuroscience"
] | [
"Neuroscience"
] | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"guidelines.",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"Why do herbs taste good to us, in spite of having no nutritional value?"
] | [
false
] | null | [
"Well it's not particularly that they do not have a high nutritional content, it's that the standard consumption amount is less than 5 grams. If you take almost anything and reduce the sample size to 5 grams you end up with a bunch of zeros on the fact sheet.",
"Most herbs have your standard leafy green goodies -... | [
"A 3g serving of raw chives has:",
"Vitamin A 131IU 3%",
"Vitamin C 1.7mg 3%",
"Vitamin K 6.4mcg 8%",
"Folate 3.2mcg 1%"
] | [
"Where did you find this? I wan't to know the nutrition facts of cannabis."
] |
[
"Why do different molecules diffuse evenly across a vacuum?"
] | [
false
] | For example: You put in nitrogen and oxygen on separate sides of a container. Why is the density of oxygen and nitrogen relatively equal everywhere? | [
"They're not necessarily evenly spaced, just randomly distributed."
] | [
"Entropy. If you look at the number of ways to arrange all the molecules, and consider the number of ways you can rearrange the molecules so that they are partitioned to the number of ways you can rearrange them so that they're mixed, the number of mixed ways is much, much, much greater. If all the molecules are mo... | [
"I think you're asking why diffusion occurs along each molecule's partial pressure. i.e. if you have oxygen and nitrogen at equal pressures on separate sides of a container, why do they move? ",
"/u/iorgfeflkd",
" was saying that molecules disperse randomly in a space. Consider each molecule independently. Oxy... |
[
"What happens when magma meets an oil reservoir?"
] | [
false
] | I've always wondered why we've never experienced the crisis of losing an oil reservoir due to magma finding its way in. I've accepted that there would be no catastrophic explosion due to lack of oxygen, but what does happen? Does the heat 'cauterize' some of the oil, blocking the magma off? Does the magma slowly eat its way through the reservior, boiling it into a useless sludge? | [
"First, I need to clarify what an oil reservoir is. It is ",
" a big underground cavity filled with oil - that's a common misconception. Oil is stored in tiny pore spaces between sediment grains, and in order to be extracted, there must be connective spaces between those grains. Thus, an oil reservoir is a ",
"... | [
"Also, for magma to exist in a sedimentary basin, usually a high geothermal gradient would need to exist. This would mean accumulations of oil could be found at shallower intervals. \nGenerally, you won't find magma in similar locations or depths as oil, which is why it's an uncommon occurrence. "
] | [
"Minerals are (in an over-simplified way) the chemicals that make up crystals that comprise rocks. Oil is found in sedimentary rocks - that is, rocks comprised of grains of sediment, from whatever source, that have bonded together through pressure and heat. There are no specific minerals that accompany oil.",
"Th... |
[
"How to get a standard deviation greater than value for a nonnegative number?"
] | [
false
] | I have seen in multiple presentations the author present a value of something that can't be negative (cost of healthcare, moles of product formed, survival time, etc) that will have a standard deviation that is greater than the value itself. While this isn't an issue for something that can be negative, what does this mean if you can only have a positive value? | [
"When a standard deviation is presented like this, it's usually meant to represent some kind of confidence interval for the value of some estimated parameter.",
"A 90% confidence interval tells you that 90% of identically-constructed intervals would be expected to contain the true value of the parameter, for exam... | [
"Purely from mathematics: {1,1,1,1,6} has a mean of 2 and a standard deviation of sqrt(5) which is larger than 2 even though all values are larger than 0.",
"If you use these numbers to estimate a parameter that cannot be negative then see the other comment."
] | [
"The standard deviation has a mathematical definition: it's the root of the mean of the squares of the distances between samples from the distribution and the mean of the distribution.",
"The normal distribution is characterised by only two variables: the mean and the standard deviation. Because many distribution... |
[
"Why are single-poled magnets physically impossible?"
] | [
false
] | null | [
"As others have said, magnetic monopoles are not physically impossible, just unobserved. What is worth knowing is not only are they physically possible, they are a natural consequence of most grand unified theories that combine the electromagnetic, weak, and strong forces into a single over-arching force. Thus, t... | [
"Great answer!"
] | [
"Not impossible, ",
". If they existed it would make some scientific theories a bit mathematically tidier."
] |
[
"How long did non-avian dinosaurs survive after the asteroid hit?"
] | [
false
] | I’m sorry if this is worded poorly, but I’m wondering how long the non-avian dinosaurs survived after the initial impact. Were they gone within a few days, or were there small populations that stuck around for a few years? Thanks! | [
"The fossil record doesn't have the resolution to say anything about that definitively. There's been a bit of debate lately over the exact timing of the extinction, the impact, and some volcanic events occurring around the same time, all of which are measured with errors or 10s to 100s of thousands of years.",
"B... | [
"There have been some dinosaur fossils found in rocks from the Danian age (64-66 mya) of the Paleogene period. These are mostly thought to have been reworked from underlying (older) sediment from the very end of the Cretaceous 66 mya. That is, natural forces such as erosion removed the fossils from where they forme... | [
"Did someone specifically claim to find something 1 million years after the extinction, or is this just someone rounding to the nearest 5 million year mark?"
] |
[
"Why can't we feel the acceleration of the universe?"
] | [
false
] | If the universe is expanding at an accelerating rate, why can't we sense it speeding up? | [
"The expansion of space is not the same as movement through space."
] | [
"We don't sense gravitational acceleration from the sun, the moon, Jupiter, or local galaxies.",
"For the other question: I can't quote well on my phone so try reading the first paragraph here:\n ",
"http://en.m.wikipedia.org/wiki/Metric_expansion_of_space"
] | [
"It's too tiny. It gets completely overwhelmed by all the other forces when you're looking at anything smaller than a galactic cluster."
] |
[
"Is it possible to use a flow of positive nuclei/protons instead of electrons to form an electric current?"
] | [
false
] | [deleted] | [
"Yes, of course. Some common examples in which the current is a flow of positive charge are:",
"action potential of a neuron: positively charged sodium and potassium ions",
"electrolytic solutions (e.g., salt water): negatively charged chlorine ions (which are not electrons) and positively charged sodium ions",... | [
"I think that your answer, while technically correct in its way, doesn't answer the actual question being asked.",
"On the contrary, I answered exactly what the OP asked. I gave three examples in which electric current is not the flow of electrons. The examples, respectively, were that of (1) the flow of positive... | [
"I am afraid you are completely wrong. ",
"There are many materials that can transport protons. Nafion is widely used in the industry.",
"https://en.wikipedia.org/wiki/Proton_conductor"
] |
[
"Does the Monty Hall Problem apply here?"
] | [
false
] | Does the Monty Hall apply in the following situation? If not, how is it different from the classic Monty Hall problem? Let's say 3 runners of equal ability are going to race. They are called Alvin, Simon, and Theodore. At the beginning of the race, I bet on Alvin. 6 miles into the race, a bear appears on the track and eats Simon. The betting office announces the chance for me to change my bet at this stage. Should I switch my bet to Theodore? | [
"No. But I can re-word it so that it does. ",
"Three runners are running a race. You are the gambler, and I am the race coordinator. While you think the runners are equal, I have given one of the runners springs in their shoes so that I know they'll run faster. After you place your bet, I place a piece of meat in... | [
"After a runner gets eaten, the odds go from 1/3 to 1/2. The randomness in who gets eaten makes it impossible to discern any information, and the randomness in who wins makes it impossible to divide the runners into two groups."
] | [
"i see two main problems with your scenario:",
"1) the information in the Monty Hall problem is set and known in advance (to the show, not to the contestant). the grand prize is behind one of the doors at the beginning. in your race scenario, the winner is not set and not known beforehand.",
"2) the Monty Hall ... |
[
"When I was younger, I placed an ice cube in a pot of very hot oil. At first nothing happened, but when I nudged the pot, the oil exploded violently. What exactly happened?"
] | [
false
] | [deleted] | [
"After reading ",
"https://redd.it/414a29",
" and the respective top comment i think the theory with superboiling water is pretty likely.",
"The only other thing i could imagine is a occurence of the ",
"Leidenfrosteffect",
". The oil would need to be really hot though to make it work with an ice cube. Sh... | [
"Initially the water around the ice melts and becomes cold water. This sinks below the ice to the bottom. Then at some point the water at the bottom will have heated up enough to boil and will do so violently from below the oil. It may be that your pot was so clean that the water had no impurities to boil off of an... | [
"I think there is a bit more to it than just that, water itself and hot oil don't mix well as it is. The temperatures are hot enough that it rapidly heats the water, making it steam. Which needs a significant more amount of space. It's more likely the ice, while melting, was able to form a barrier of lower tempe... |
[
"Why is it hotter in my house at night than during the day?"
] | [
false
] | null | [
"We can't really comment on anecdotes / isolated incidents without resorting to speculation which we try to avoid."
] | [
"Okay. Should I delete this then?"
] | [
"Already removed."
] |
[
"What does it mean when people say we've mapped the entire human genome, and how come we don't know what genes cause what if we have?"
] | [
false
] | null | [
"It means we know the sequence of the genome (to a degree of certainty) but we don't know what sequence means what. A somewhat similar analogy is : Think of it as a computer program code. We have pages and pages of code, module after module, each of which refers to other modules, etc. Imagine you just come across t... | [
"We make meaningful guesses all the time. But that's exactly what they are- guesses, until you can prove them, which in science is by cause-effect relations. i.e. Knock out/in the gene and see what happens. i.e. Disable a module--- see what happens, then re-enable it,(by a third party/accessory module) and see if t... | [
"I am a programmer so this made perfect sense! thanks for your response. How far would you say we are from figuring out what each gene \"does\"? Is it even possible ot make a meaningful guess at this point? "
] |
[
"Why is rabies (nearly) invariably fatal?"
] | [
false
] | [deleted] | [
"You pretty much nailed it - once it's too late for the vaccine to work (around the time symptoms appear, sometimes longer), you're screwed. Rabies has a particularly nasty way of telling the brain to shut the body down. Nobody knows why our immune system can't fight the disease before it reaches the CNS. Perhaps b... | [
"Rabies is the type member of the ",
"Rhabdoviridae",
" family of viruses. It infects skin cells from an animal (usually dog) bite, and from there it infects nerves. It travels through the nervous system until it eventually reaches the brain causing severe encephalitis and eventually death. ",
"Interestingly,... | [
"From an evolutionary standpoint, being 100% deadly is unfavorable as it makes viral transmission more difficult.",
"Take into account that something can be invariably fatal and still very transmissible if it takes a long time to kill someone or is very easily transmitted. Untreated HIV is invariably fatal, but i... |
[
"Is there a limit to the size of a star?"
] | [
false
] | I mean, is it possible for a star the size of a galaxy or bigger to form without collapsing into a black hole? EDIT: Wait, no. What I meant was, is it possible for a star the size of a galaxy to exist? | [
"I believe the limit is around 150 solar masses for stars formed in the last 10 billion years. I know there is one exception to this but that was recently discovered and IMO has a very good chance of being downgraded in mass.",
"I am not really sure exactly what the reason for this limit is. I know a fair portion... | [
"Incorrect, this limit just refers to the max mass for an astral body before gravity overtakes electron degeneracy pressure and collapsing begins.",
"Take a glimpse at this ",
"article",
"."
] | [
"The bigger they are, the shorter they last."
] |
[
"Can single enantiomer medicines spontaneously switch to the other chiral form, making them toxic?"
] | [
false
] | Someone got it in my head that this just happens over time and that this is why old medicines should be thrown away. I think most are mixtures of enantiomers, but with some only one form is beneficial and the other is detrimental. Naproxen is my example for this as one enantiomer is a commonly used NSAID and the other is a liver toxin. So the question is: Do these chemicals spontaneously switch? Would leaving them in a hot car, keeping them beyond expiration, or some other simple storage mistake possibly kill you or make your medicine toxic? | [
"Short answer: Yes, but it depends on the drug in particular. If this process, presents a real hazard the drug in question usually doesn't make it to market. It can happen over time, elevated temperatures, moisture, acidic or basic conditions can make it happen faster. Really depends on the drug though. ",
"Long ... | [
"I am in no way an expert on this, but many years ago I did a small bit of work on ",
"voriconazole",
", which has a mildly toxic enantiomer in which the methyl group and the H across from it swap places.",
"\nAnyway, as far as I can remember, the enantiomer is a product of the final part of the synthesis bei... | [
"Just adding the classic example of chiral conversion in ",
" causing massive issues: Thalidomide. After intake, the conditions of the human body are sufficient to allow thalidomide conversion from one chirality to the other resulting in the birth defect side effects."
] |
[
"Could the milky way have already collided with another galaxy like 6 billion years ago?"
] | [
false
] | Or heck, at any point. What if we, millions or a few billion years ago already merged with another galaxy? Could we tell it happened to our galaxy if our galaxy already fully formed with the other and assumed its new shape? | [
"Actually, it seems likely that ",
"the Milky Way collided with a dwarf galaxy somewhere between 6-10 billion years ago",
". After tracking 7 million stars with data from the Gaia satellite, astronomers found a lot of metal-rich stars near the galactic center with eccentric orbits, a pretty good sign that we sl... | [
"Taken from ",
"FutureTimeline.net",
":\n“Our galaxy is surrounded by dozens of smaller dwarf galaxies. These will occasionally pass through the disk of the Milky Way, disrupting both it and the incoming satellite. One such collision occurred in roughly 100 million BC. This was confirmed by observations of 300,... | [
"Don't stars migrate out as they age?"
] |
[
"Why are prions so hard to destroy?"
] | [
false
] | Most proteins denature below boiling temperature. Prions, as far as I know, are just a type of protein. Is there a specific reason why prions are so hard to destroy? And is it in any way linked to the diseases they cause? Or is it just pure coincidence? | [
"Prions are proteins folded into special configurations that are extra stable. ",
"They’re folded into alternating rows and form sheets—think something quilted into a big square blanket. There’s a high amount of cohesive forces in between each row, so it’s held together quite well and takes an extremely high temp... | [
"my rudimentary understanding is that they are essentially a special case of denatured protein whose shape \"breaks\" other proteins of the same kind, in the same way. Or put another way, prions are proteins that have denatured in a particularly unfortunate way, and this particular structure happens to be stable en... | [
"Well, \"hard\" is relative.",
"They are in a highly energetically stable molecular configuration, and a lot of the things we are used to doing to prevent the spread of disease -- boiling water, cooking food, sterilizing equipment -- doesn't reach the required energy level to overcome that stability. That's why ... |
[
"Is there a 4 dimensional analog to a sphere like a tesseract is for a cube?"
] | [
false
] | null | [
"One of the first things you learn in college is that you didn't learn anything in highschool."
] | [
"Yes, the sphere ",
", which is the ",
" sphere (embedded in Euclidean four-dimensional space), is the set of points (",
", ",
", ",
", ",
") such that",
" + ",
" + ",
" + ",
" = 1",
"Similarly for higher number of dimensions."
] | [
"Sorry, I didn't mean high school geometry. I was thinking of introductory courses in differential geometry."
] |
[
"To eliminate the need for an extra day every four years, why couldn't we just redefine the second?"
] | [
false
] | Since we need (approximately) one extra day every four years to keep our calendar in sync with our orbit, why couldn't we just multiply (four years +1/ four years) 1461 / 1460 = 1.0006849315... to each existing second? After four years' time we'd be enough later to eliminate the need for the leap day, right? Obviously all GPS satellites/world clocks/etc would have to be adjusted but that seems like something that could be done. I know this is missing something but that why I'm here! | [
"This would mean a day is not 24 hours any more. So each day, \"midnight\" would slip a little bit. After 2 years, \"midnight\" would be in the middle of the day!",
"The fundamental issue that can't be solved here is there are not an integer number of days in a year."
] | [
"The ratio of Earth's orbital period to its rotational period is not an integer. That is why we have leap years, not because of units. If you don't do this, the solstices and equinoxes start moving through the calendar, and we try to avoid that."
] | [
"There's not a whole number of days in the year, yet a day will always begin when the sun comes up and end when it goes down. So instead of slipping in the extra time into each day, we save up a day's worth and use it all at once every four years. "
] |
[
"Why, in layman terms, was the black body problem so important in quantum physics?"
] | [
false
] | I am reading about it, but I cannot make sense out of it. Why quantization was so controversial? What was the problem really? I know high school physics, so not so layman. | [
"Black bodies at thermal equilibrium emit radiation. The spectrum of the emission at low frequencies is predicted by the ",
"Rayleigh-Jeans Law",
" and is dependent only on temperature. You can use this law to calculate wavelength (or frequency) of the emission. The black body problem refers to the prediction t... | [
"Yes. Planck thought it was only a mathematical trick, but actually he accidentally invented quantum physics. The photoelectric effect is a great example for the quantisation of light."
] | [
"A bunch of folk around the same time were shooting light at metal.",
"They found that given a certain colour of light, electrons were stripped off of metal.",
"They assumed that increasing the intensity of light will lead to those electrons to leave the metal faster, or for another colour to be able to strip e... |
[
"Has it been proven we live in a deterministic / probabilistic universe?"
] | [
false
] | As I understand it, a lot of processes on the atomic scale seem to be totally random, for instance radioactive decay. This is then used as proof that the universe is probabilistic, i.e. that anything can happen in the future. But has it ever been definitively proven that these processes are indeed random. I could imagine that at the moment we just do not understand why an atom will decay into another at some time, but that a reason does exist. Following, if all molecular / atomic / sub-atomic processes are deterministic, would that imply that the universe is deterministic? And that everything that will happen in the future is already set in stone? | [
"I would say that IFF all molecular/atomic/sub-atomic processes were determined to be deterministic then that would imply that the universe as a whole is deterministic. ",
"What you are talking about is the hidden variable theory of quantum mechanics, which states that while we may be unable to predict with perf... | [
"no. The heisenberg uncertainty principles says that ",
" and in particular the product of their RMS spreads is ~hbar/2. It doesn't have anything to do with measurement."
] | [
"I don't think the Bell theorem excludes the possibility of a deterministic universe for two reasons:"
] |
[
"Are humans the only species that commit suicide?"
] | [
false
] | null | [
"It's not clear what 'commit suicide' means.",
"For example, there are many species where reproduction leads to death - so individuals 'voluntarily' do something that leads to the death of the individual but that propagates the species. Is that 'committing suicide'?",
"Is whales beaching themselves 'committing... | [
"The parasites the other redditor mentioned are certain species of Nematamorph worms, but they aren't the only parasites that cause this kind of \"suicidal\" zombieism.",
"\nA really interesting one makes tiny fish in marine estuaries go to the surface and flash their shiny sides at predatory birds. The birds are... | [
"Here",
" is what wiki has to say on the matter. It is up in the air but there are plenty of well documented instances where animals have harmed or killed themselves, seemingly out of stress or depression. It seems like we don't have enough information at the moment to tell if the animals are acting on the same e... |
[
"Is there a spot where the big bang happened? do we know where it is? Is it the center of the universe? If you go there, is there a net force of zero acting on you in all directions ( gravity)"
] | [
false
] | EDIT: Wow thanks for all of the answers and the support, this is my most popular post yet and first time on trending page of this sub! (i’m new to reddit) | [
"The big bang happened ",
", right where you're sitting now included. The universe doesn't have a center; instead, ",
" is equally the center. When we talk about the universe expanding, what we mean is that ",
" is expanding, not that the universe is expanding into something or away from a center point.",
"... | [
"thank you for this reply, this is very helpful. one question. by “everything expanding” do they mean galaxies are getting farther apart, or so they mean that everything is getting bigger, you, me, all atoms? "
] | [
"You would think that if you took into account the motions of all the galaxies that you'd be able to calculate a \"center.\" Say, for example, you had a small explosive surrounded by glitter. If you set the explosive off and tracked all the glitter, you could calculate where the explosion was. That's NOT how the un... |
[
"If the US one year gave its defense budget of $750 billion to science, what discoveries might we expect in the following 20 years?"
] | [
false
] | null | [
"This isn't an answerable question, I'm afraid. The only possible responses would be pure, pointless speculation."
] | [
"Kurzweil's reputation among scientists is … well, let's not mince words, shall we? He's worse than useless."
] | [
"But if Galileo could have predicted Newton, we wouldn't have needed Newton."
] |
[
"How are wall-to-wall buildings demolished?"
] | [
false
] | null | [
"Explosives are used far less often than TV would lead you to believe. Jackhammers mounted on excavators are far more common and more controlled than explosives. Explosions are cool but the exception not the rule."
] | [
"Usually, the non-load-bearing walls are removed. Then the inner load-bearing. Then the outer shell walls."
] | [
"What do you mean by \"wall-to-wall buildings\"? "
] |
[
"Does quantum physics solve the problem of determinism/free-will?"
] | [
false
] | null | [
"somehow gives the universe a probability/in-determinant quality at the sub-atomic level... and that therefore there's a real chance that we have real freewill.",
"If your actions are determined by random fluctuations of particles, how is that free will? In other words, how does your question differ from \"",
... | [
"The issue of free will comes up when you consider the ramifications of a deterministic or random system.",
"If it is determined, then you could not do otherwise, and are therefore not free. If you are not free then you are not responsible for your actions.",
"If it is random, then it is not by your choice tha... | [
"I think there's also the issue of distinguishing between determinism and mere causality. Determinism means that something has a cause (or network of causes) which can theoretically be determined through measurement. Causality just refers to events having causes, regardless of whether they are deterministic. ",
"... |
[
"Why does touching an electric stove top while it's on burn you instead of electrocute you?"
] | [
false
] | null | [
"No... this is very incorrect. A quick google search says an electric stove coil on high produces somewhere in the range of 2000 watts of heat. If you're running off of 120 volts thats 16.7 amps which by any reasonable household definition is a lot. ",
"It is amperage that kills you, not voltage",
"This is a hu... | [
"Because the thing is ",
".",
"There is a wire through which electricity flows, then a layer of non-conductive material and then an outer metal layer.",
"A properly functioning stove top element will not have electricity going through its outer metal part.",
"If you think about it, if electricity was flowin... | [
"This is definitely the correct answer, I just wanted to say that even if it wasn't insulated, if you touched the element, you would be fine (as far as shock goes). Current has a much better time going through the heating element than it does you.. Your body resistance is pretty wicked high in comparison, you woul... |
[
"How intelligent are spiders?"
] | [
false
] | Can spiders be trained to do tasks like lab rats? Do they possess any qualities that can be attributed to having some form of intelligence? | [
"Greatly varies, and we can say with certainty that most spiders are not intelligent, but there are some remarkably intelligent, even problem-solving spiders: ",
"Check this out",
"."
] | [
"Is what just an assumption? If you're talking about their intelligent hunting behavior, no, it's not assumed, it is observed."
] | [
"If I can add to the question, do we know how spider plans its web? I imagine it must asses the place, decide whether it is good or not, check the distances, corners, eventual obstacles, etc. Is it all just trial and error or there's actual thought process?"
] |
[
"Is it possible to create visible light?"
] | [
false
] | null | [
"A superposition of UV and IR won't result in light which is the difference in frequency between them.",
"However there are nonlinear optical media which ",
" change the frequency of the light you send into it."
] | [
"Thanks for you answer! May I ask you about these optical media ? What are they ?"
] | [
"There are many different kinds, but ",
"this",
" is a good starting point to read up about them."
] |
[
"What would happen if I started to rotate a 100,000km rod at 1 round per second?"
] | [
false
] | Made out of the strongest lightest material possible. The perimeter is larger than the speed of light per second. | [
"You couldn't make it go at one round per second. No matter how much energy you put into accelerating the rod, the most outer part would still move at some subluminal speed. As you put more and more energy into the system the outer part rotates closer and closer at the speed of light but it never can reach it.",
... | [
"Won't the atoms interact with each other at the speed of ",
"? The movement at one end would translate through the rod at the speed of sound, effectively leading to the motion not having any effect for a long, long time."
] | [
"Won't the atoms interact with each other at the speed of sound?",
"Principally yes, but then again you can come up with weird scenarios where the e.g. ",
"the group velocity of your phonons becomes faster than the speed of light",
". Of course information can still only be transferred at subluminal speed.",
... |
[
"Is it possible to build a truly empty box?"
] | [
false
] | I mean a box that is not just devoid of air or even matter but no photons, neutrinos, nothing. Not even EM fields. One obvious problem would be the inside edges of box would occasionally decay and release photons into the box but could they be somehow prevented from travelling too far inside by a large gravitational or EM field outside of the box? What's the most empty anything could conceivably be? | [
"You can't have no EM field. Electromagnetism exists, you have to deal with it. The only thing you can have is the EM field at the lowest possible value. That's what physicists call \"vacuum\". But even in the vacuum, you still have some energy and some quantum fluctuations. Vacuum is not empty."
] | [
"I don't think so; you would probably have always ",
"virtual particles",
"."
] | [
"Best not to think too hard about \"virtual particles,\" frankly. They don't actually exist. They're just mathematical objects that we use to describe the state of a ",
" The field is the real thing; virtual particles are something we made up to do maths with."
] |
[
"Why are there no green stars?"
] | [
false
] | according to the Hertzsprung-Russel Diagram green is not a part of the stellar spectrum. why? | [
"Because a blackbody that's hot enough to have its peak emission in the green part of the spectrum emits enough orange and blue light relative to green such that it looks sort of like white light. ",
"pic"
] | [
"http://en.wikipedia.org/wiki/File:Solar_Spectrum.png",
"The suns blackbody actually peaks at green(ish).",
"As iorgfeflkd said the visible range is very narrow so any blackbody is going to have is going to have a broad range of emissions that make it appear as white. Its actually neat to note that the eye is ... | [
"Stars emit light over a range of frequencies depending on their temperature.",
"The distribution of the radiation is skewed towards high frequencies (shorter wavelengths), but after a point, drops off suddenly, like ",
"so",
".",
"When the output peaks at lower frequencies, you only see reds and yellows, t... |
[
"Why do flames flicker at a relatively consistent rate?"
] | [
false
] | In the following paper, one can see that different flames flicker at 10-12Hz. However, I cannot understand the paper itself. Could anyone simplify why it's the case that seemingly unrelated types of flames flicker at a really specific frequency? Chen, T., Guo, X., Jia, J. et al. Frequency and Phase Characteristics of Candle Flame Oscillation. Sci Rep 9, 342 (2019). | [
"They're not unrelated types of flames, they're groups of candles. In other words, the buoyancy jets formed by the flames have very similar temperature gradients. Candle flames are driven by buoyancy associated with density differences between the hot flame and combustion products and the surrounding atmosphere. Th... | [
"Figure three in my link gives the flicker frequency as a function of sqrt(g/D) for pool flames. You can see there that observed frequencies range from ~0.2 to 20 Hz, so about two orders of magnitude. The flicker frequency is not super sensitive to flame temperature. However, it's certainly wrong to say as a blank... | [
"Tom Scott recently made a video about wildfires where he referenced the fact that wildfires (his wording was ‘fires’ so maybe all fire) also flicker at about 12 hertz. Maybe it isn’t just the burning medium."
] |
[
"What is meant by DNA Half-Life?"
] | [
false
] | I understand biological half-life (the amount of time it takes for 50% of a given sample of a drug to metabolize) and radioactive half-life (the amount of time it takes for 50% of a given sample of radioactive material to become... not radioactive), but as far as I know DNA is not inherently radioactive, so what doe the half-life mean in this context? | [
"Think of time as very slow metabolism, and you've got the idea. DNA degrades on standing - it's not the most robust molecule in the world, and in living cells it's surrounded by a complex repair and maintenance system. Heat, light, humidity, oxygen and other factors will gradually hydrolyze bonds and cause side re... | [
"Following the death of a cell containing DNA, enzymes such as nucleases begin to cleave the phosphodiester bonds holding the bases in DNA together, creating DNA fragments. In addition, microorganisms will digest the DNA as well.",
"However, once all the cellular material and microorganisms are long gone, intact ... | [
"I'll simply state that the mechanisms of DNA decay in cellular contexts are fairly well-understood and they do not appear to hinge on the decay of any one isotope of any one atom."
] |
[
"What would an object traveling at speed greater than light appear considering doppler effect (and not considering relativistic effects)?"
] | [
false
] | null | [
"So, we're dealing with tachyons here and a few points are important. First, the existence of electrically charged tachyons would almost certainly result in a runaway pair-production process, so we have to assume the object isn't charged. Second, you couldn't use tachyons to convey information faster than the speed... | [
"as we are learning, we are dealing with models and simplifications all the time. For example when dealing with planets and gravity and theit orbits, we ofter tend to simplify planet to mass points even when that means those mass points should have phisically impossible infinite density and this disregarding a few... | [
"Your planet analogy is a completely different thing. It's an approximation. ",
"Saying we can't go faster than the speed of light is not some kind of fudge factor approximation we make. It's a fundamental law of the universe. Your are correct when you say your question doesn't make sense."
] |
[
"Why did a semi-finished bottle of rum freeze solid in my fridge, but an unopened one didn't?"
] | [
false
] | I had two identical and unopened bottles of 40% abv rum in my deep freeze for several days. Both stayed liquid. I opened one and made myself a small cocktail. Removed maybe 1/6 of the entire bottle. Closed it and put it back in the deep freeze. Couple of days later I checked and noticed that the unopened bottle was still liquid, but most of the rum in the opened bottle had frozen solid. Why would it do that? | [
"My guess:",
"According to ",
"here",
" the freezing point of a 40% ethanol solution is -23 C, and 30% is -15C. Depending on your freezer, these temps are quite obtainable. I would guess that two things happened when you opened your rum: ",
"1) humidity from the air very slightly diluted the rum, raising t... | [
"While I think you're right about the possibility that some of the water in the air diluted the rum, I'm inclined to think thats the smaller effect here. How important this is will entirely depend on the temperature of the freezer, though. If, somehow, the freezer temperature was perfectly in the middle of the free... | [
"Maybe the alcohol in the open bottle evaporated?"
] |
[
"Why do some people's bruises readily appear while others hardly show?"
] | [
false
] | [deleted] | [
"Bruising (i.e. bleeding) is regulated by your body's ",
"haemostatic",
" systems, which maintain a fine balance between pro-clotting and pro-bleeding states. ",
"As a general overview, haemostasis can be thought of as being governed by three things: (i) blood vessels, (ii) ",
"platelets",
", and (iii) th... | [
"thanks for the complete response. A true champ here."
] | [
"Vitamin K",
" is an essential co-factor for the synthesis of coagulation factors in the liver and is found primarily in the photosynthetic tissues of plants. As a result, regular dietary intake of vitamin K is important for the maintenance of a proper haemostatic equilibrium. Despite this, dietary vitamin K defi... |
[
"Where do files encrypted with password, like .rar files, store the password?"
] | [
false
] | [deleted] | [
"Right answer should be \"nowhere\".\nEncrypted file is just marked with specific flag. This flag is stored in the header of the file.\nInitial content is being encryped with the given password and written into encrypted file.\nPassword is not stored at all.\nTo decrypt file you have to know password. If it's right... | [
"Your operating doesn't know the password, if it just had a file with the password in it it wouldn't have to ask you for it. ",
"What happens is, in the first few bytes of the password protected file there is a marker that signals that the rest of the file is protected by a password. To read the rest, or at lea... | [
"All the program does is try your password on the encrypted archive file. It's like sticking a key into a keyhole. You can turn it, but if it's the wrong key it will just get stuck. For most encryption systems, if you put the wrong password in, you get gibberish out, or you get an explicit error. ",
"If it's gibb... |
[
"why are the WHO flu vaccine recommended strains different for egg-based and cell/recombinant vaccines?"
] | [
false
] | For both quad- and tetra-valent vaccines, the first strain mentioned differs between egg-based and cell culture- or recombinant-based vaccines. Why is this? Thank you. | [
"When the WHO influenza vaccine group reviews potential viruses for ",
" vaccines, they have to ask ",
"When they look at ",
" vaccines, they ask",
"The second requirement is obviously different, and so they may find different candidates that work better for the different vaccines. ",
"(This is very simpl... | [
"Don’t confuse flu ",
" with flu ",
". Different subtypes (H1N1, H3N2, H2N2) come from new animal sources (birds, pigs). Once those subtypes are in humans, they evolve and mutate in response to population immunity, and form new ",
". ",
"Within those strains, there are of course trillions of individual vi... | [
"I've recently become aware that ",
"there are 12 different strains of HIV, and each might be an independent instance of cross-species spillover",
". Given that this flu strains difference involves the viruses growing better in different \"places\", could this imply that different flu strains involve spillover... |
[
"How does a spider pick where to put its web? Do they have the ability to 'sniff' out whether there's a lot of bugs in a certain location?"
] | [
false
] | null | [
"Air flow. If you see a web in your house, there is air flow in that area. Flying insects use air flow to move. Spiders eat flying insects, so they set up shop where the highway for their food is. "
] | [
"None other than years as a weatherization contractor. When I seal up a house to make it more energy efficient, I always look for webs first. That's normally where I find the biggest leaks to the outside. Just put two and two together. "
] | [
"That makes sense! Do you have a source? "
] |
[
"How are rivers and lakes affected by global warming?"
] | [
false
] | We've all seen the apocalyptic predictions of sea encroachment into areas like the American South and the European Low Countries. My limited understanding is both icecap melt and the change in ocean water volume are to blame. I am wondering what effects the predicted change in temperature has on inland bodies of water, such as streams, rivers, and lakes. Will rainfall be different? Evaporation? | [
"Current ",
"predictions",
" tell us that dry regions will become dryer and wet regions wetter. Summers are also expected to become dryer and winters wetter. Thus, in some areas rivers and lakes will dry out, and in others they will grow. Moreover, a warmer climate will influence the ecology of lakes. Lakes mig... | [
"This turns out to be a remarkably difficult question to answer. For all that there's only so many places water can go, how it gets there depends on a lot of things that vary with climate change, and we don't necessarily know how much they'll vary and when. There are also a lot of human dimensions questions that co... | [
"It sounds like we could see widely varying effects by ecosystem, and even within a system. Thanks for the specifics on Lake Michigan. I was born in Wisconsin, so that's an example I can get my head around. "
] |
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