title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"If we colonized a new planet, what is the minimum number of men and women we'd need to avoid eventual problems with inbreeding?"
] | [
false
] | [deleted] | [
"Asked recently on ",
"/r/askscience",
" here: ",
"How many people would you need to self-sufficiently populate a planet without inbreeding being a problem?",
"Pitciarn islands makes a nice case study in humans. Pitcairn Islands were ",
"settled by 6 men and 11 women",
"; and the majority of inhabitant... | [
"Here",
" was ",
"/r/maths",
" take a couple of days ago."
] | [
"Apologies then. I did a search and didn't see it, but I'm not sure why I didn't see it. "
] |
[
"Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology"
] | [
false
] | Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! ... | [
"Yes, water molecules definitely form on earth! For example, combustion reactions of carbohydrates produce water."
] | [
"Innate and non-innate (developmental) traits in humans are constantly debated. In many cases, behavior is a mixture of nativist and developmental effects."
] | [
"Innate and non-innate (developmental) traits in humans are constantly debated. In many cases, behavior is a mixture of nativist and developmental effects."
] |
[
"Top-bottom or Bottom-up, best way to present a complex model (simulation) to non-scientist?"
] | [
false
] | So, I have the task to present a complex model to a group of individuals who do not have previous knowledge in simulation and modelling. The model is a social-sciences model which is composed of a collection of components all interlinked. My question is, what would you think is better: Why would you choose any one or t... | [
"Definitely top-down. People need to know the big picture before you explain the components otherwise they will have no motivation for understanding the components."
] | [
"Yes, I was getting more inclined to top-down approach. Basically first to show an overview of the system and then explain \"what\" happens and then if necessary detail \"how\" it happens. ",
"But as the model focuses in a specific individual (a role), I thought starting from the role and then showing a story (in... | [
"One technique that is often used in my field is the idea of a toy model. Basically, you examine and explain the simplest model that exhibits whatever behavior or phenomenon you want to show. Then, when you ramp up to the full, complex model, you make analogies with what your audience has already seen from the to... |
[
"From a medical/scientific standpoint: why are rates of cases of depression and addiction higher in people with above average intelligence?"
] | [
false
] | null | [
"Since no-one has objectively answered this question yet, I'll just add my thoughts on the subject as someone who paid attention while getting an undergraduate degree in Psychology. ",
"I don't know if we'll ever be able to say that there is a direct relationship between being intelligent and succumbing to depres... | [
"Not an answer, but do we in fact know that those rates are indeed higher among the people with above average intelligence? ",
"Wikipedia",
" seems to say no, at least for the case of depression.",
"If you have any references to the literature suggesting otherwise, please share."
] | [
"Not really... OP didn't ask why intelligence ",
" depression, just why they co-occur. Correlations can still be explained (third variable, for example)."
] |
[
"What ties facial expression to emotion and why?"
] | [
false
] | I'm guessing some part of it is neurons firing in the brain. But why do we frown when we are sad? Or make any of the many other facial expressions tied to an emotion/feeling? | [
"Not necessarily. Autism is a disability primarily linked to genetic factors. Someone born without legs doesn't disprove the hypothesis that humans evolved to walk upright."
] | [
"Here are some thoughts from:",
"https://en.wikipedia.org/wiki/Facial_expression",
"Facial expressions are a form of nonverbal communication. They are a primary means of conveying social information between humans, but they also occur in most other mammals and some other animal species. ",
"Humans can adopt a... | [
"More to the why: Humans are social creatures with big brains that seem to be wired up in large part as calculators for guessing at what other humans want, need, know, believe, and feel. Our compulsion to exercise this mental machinery is so great that we invent characters to tell stories about. It stands to reason... |
[
"Let's be honest: Is interstellar/intergallactic space travel possible at all?"
] | [
false
] | , radiation, , overwhelming distances (with the current technology, the shortest trip to Alpha Centauri would take 50,000 years) and inefficient fuel-based transportation... We're nowhere near the speed of light, and even if we were, space is still a place full of dangers. The distances are truly mind-bending: 29,3 lig... | [
"Perhaps in the future we could send an artificial womb aboard a spacecraft. At arrival a machine will assemble DNA and sex cells from raw organic material and grow a number of humans inside artificial wombs. At first the babies will be cared for by robots and later they will be educated and work together with thei... | [
"robots",
"educated...by...computer \"parent\"",
"i can't think of any way at all that this could end badly for us. "
] | [
"You are pretty much correct in your analysis.",
"Long-term generation ships using nuclear pulse propulsion (or similar) could perhaps reach another star, but that technology is too far away to even say how far away it is."
] |
[
"Why do smaller animals have faster heartbeats?"
] | [
false
] | It seems to me that for small animals their blood doesn't need to travel as far between heartbeats so it would be able to maintain its velocity enough to circulate with a slower heartbeat. However, their heartbeats are actually faster. | [
"It's related to the square-cube law and their higher metabolic rate. Their hearts do not pump an equally proportionate stroke volume compared to a larger heart, so their hearts pump more often. "
] | [
"The problem is that surface area grows much, much faster than volume",
"I think you have that backwards. Everything else looks good. ",
"However in my opinion the simplest explanation is that for surface area, you have a radius",
" term and for volume you have a radius",
" term. So the volume grows exponen... | [
"This is actually closely related to another problem, which is why can't cells grow infinitely large? The problem is that surface area grows much, much faster than volume, so any substantial change in size affects the two in drastically different ways. We can see this if we look at an idealized example: let's prete... |
[
"One light, many energies?"
] | [
false
] | Askscience, please help. I'm having the hardest time trying to synthesize a bunch of things I've heard about light and the excitation/emission of molecules. I just learned about various spectroscopy techniques in my chemistry class (Nuclear Magnetic Resonance, Infrared and UV spectroscopy), and I was told that IR excit... | [
"Firstly, why does light of one frequency excite one aspect of a molecule (eg KE), and light of another frequency excite another part of the molecule ",
"The optical-molecular or optical-atomic interaction depends on the energy match between the photon and the energy state it will interact with. Molecular vibrat... | [
"Thank you for your response! This is helpful, thinking about it in terms of springs and resonance. Does the analogy extend to that of thermal motion as well? Translationally/vibrationally (are these the same?), would it be wrong to imagine a line of molecules all knocking back and forth against each other, like wh... | [
"To address your first question, yes kinetic energy can be exchanged between atoms and molecules via collisions. In fact, collisions are one means of de-exciting atoms/molecules that does not produce light/radiation. This type of thing is important in the construction of some lasers where you prefer having light ... |
[
"If the sun were to suddenly vanish, what would we feel first? The effects of no light, or the lack of gravitational effects from the sun?"
] | [
false
] | null | [
"Both light and gravity propagate at 'c', if that's what you're asking. Until ~8:20 after the sun disappeared, you would notice nor be able to measure any difference.",
"However, I would recommend against thinking of impossible hypothetical situations - the sun ",
" just disappear, and for reasons that are very... | [
"Any consequence of gravitational affects likely would not be attributed to the Sun's disappearance in under eight minutes",
"Nor could they possibly be. Information can't travel faster than light, and that includes gravity."
] | [
"Is there proof of this? I wasn't aware that we knew the speed of propagation for gravitational effects."
] |
[
"Why does being sick sometimes kill your appetite?"
] | [
false
] | null | [
"Only thing I can think of is the immune system works better when energy doesn't have to be directed towards processing food and drink.\nIt is well known that the body heals deeper when fasting.\nNot sure what actually happens inside the body when you're ill and something tells your brain it does'nt want food."
] | [
"When you are sick you release cytokines like TNF-alpha that as one of their functions act as an anorexigen (reduces appetite)."
] | [
"These cytokines are what activate your immune system, cause fever, and overall get your body prepared to fight infection or whatever is the cause. I am not sure if there is a definitive answer for why they suppress the appetite, but I believe it is accepted that it is beneficial as a short term process, but in chr... |
[
"How much of an issue to sattlelites/ISS/rockets is man-made space junk? Is there anything really we can do to \"clean up\" orbiting trash?"
] | [
false
] | null | [
"It's a serious issue. Satellites and spacecraft need shielding to resist impacts from small fragments the size of a grain of sand.",
"This page",
" explains at a high level how MMOD (micrometeoroid and orbital debris) shields work, but in short: let the incident object hit a first layer and penetrate it, so th... | [
"A theory was coined in 1978 called the Kessler syndrome, which seeks to explain the phenomena of collisional cascading. This cascading effect has the potential to wipe out almost every object in low Earth orbit."
] | [
"BEAM is a very experimental thing and, so far, it's not being inhabited. Astronauts will merely visit this module four times a year to collect data.",
"http://www.nasa.gov/mission_pages/station/research/experiments/1804.html",
"It does have a robust MMOD shield and the company got a patent for it 2007. However... |
[
"Please help me understand dB gain and power outputs...please?"
] | [
false
] | Hi. I'm trying to understand gain and output for signal strengths. For example: I have a -35dBm output and it's amplified by 30dB. I think the output is -5 dBm but I feel like there should be more to it than that. Any help or confirmation would be greatly appreciated. Thank you. | [
"Unless I'm seriously misunderstanding what you're trying to say, it really is as easy as adding them together. -35dB signal with 30dB of gain would leave you with a -5dB output.",
"The purpose of decibels is to allow simple addition and subtraction of quantities instead of what would otherwise be annoying multi... | [
"Your method is correct. dBm units already express a dB ratio and dB ratios can be added and subtracted from each other to represent gain and attenuation. The only difference is that dB is context free on the reference unit, whereas dBm specifies a reference unit. (0dBm = 1mW)"
] | [
"Thank you! It just seemed a bit too easy with all the math that actually goes behind the dB stuff."
] |
[
"If nothing can travel faster than light, what exactly is preventing it from escaping when traveling beyond the event horizon of a black hole?"
] | [
false
] | The event horizon of a black hole is known to be the point of no return, as light will not be able to escape it's immense gravitational pull. Does this mean that whatever is pulling it inward is traveling faster than light at this point? | [
"Light is not being pulled in by something that is moving. Light is following certain paths in a curved space-time geometry, and all of those paths are constrained to stay within the event horizon."
] | [
"I wonder what's your opinion on this explanation? ",
"\"The river model of black holes\""
] | [
"The popular \"escape velocity\" explanation is in fact wrong because in Newtonian mechanics a slow moving object can escape anything provided it has enough propulsion.",
"But no matter how much propulsion you have, you cannot escape from within an event horizon. This is the power of time. Within event horizon, t... |
[
"Multiverse has more than one meaning?"
] | [
false
] | I have heard the term numerous times, and normally it seems to be explained as multiple universes existing at different points on a dimension outside the three we usually experience. This is the interpretation I take from Brane theory as the Branes are described as multi-dimensional and their intersections at "higher" ... | [
"You've come head to head with one of the most common sources for mis-interpretation and mis-communication between scientists and the public in cosmology.",
"There are multiple meanings for \"multiverse\". These are commonly distinguished as \"Level # Multiverse\" (although there are theories that don't fall into... | [
"I think Popular Science did a piece on multiverses that covered the basics well. The reason you probably don't hear about this classification is that direct science from scientists usually avoids it, and science shows and articles tend to skip past it and just talk about the \"juicy\" stuff.",
"I have a pretty b... | [
"Do they assume everyone already understands what a Level I Multiverse is? Is it just me that didn't?!",
"Nope : ). They just assume that viewers won't care that they don't understand the basics behind the science they talk about. As long as they get cool graphics and can make some profound statement, they don't ... |
[
"What scientific metrics determine how much sound a speaker produces?"
] | [
false
] | What scientific metrics (for example, watts, db, etc.) are relevant to the amount of sound that a speaker produces, and why? | [
"Loudness of a speaker is a fairly complicated thing when you get into the frequency dependence of your ear's sensitivity and the room that you're in. The basics, though, is all in watts. In an open field, intensity is power in watts divided by area in square meters. The area is that of a sphere centered on the ... | [
"So ceterus parabus a speaker with higher watts will be louder than a speaker with lower watts? Is there a catch 22 to the importance of watts? "
] | [
"The sound of a speaker ultimately comes down to the mechanical movement of volume, and with typical speakers thus the amount of energy transferred from a coil, an amount of resistance, a certain degree movement. ",
"The coil is powered via a DC current, and this coil when conducting an amount of current thus gai... |
[
"How does the Higgs Field maintain constant density in an expanding universe?"
] | [
false
] | I tried to ask this question before and I'd be thankful if at least I was told that I'm completely off track - it's bugging me, and I apologize for bugging you with it. To my understanding, the Higgs field permeates the entire universe with a constant density - can I call it uniform? Also, space itself is expanding. Ho... | [
"For the Higgs field, it costs no energy for it to acquire an expectation value on the vacuum. Actually it costs energy for it not to occupy the whole space, so even if you stretch it, nothing is going to happen, since the field occupying the whole space is already the vacuum of the theory. ",
"There are many way... | [
"You answer the question in your own comment even if you don't notice.",
"The law of the conservation of energy does not apply in an expanding universe. We have to be ok with allowing the energy content of the universe to change on cosmological scales.",
"There are obvious examples. The matter in our universe d... | [
"Nowhere. Energy is not conserved globally in an expanding Universe."
] |
[
"Since human and unmanned spaceflight missions compete for resources, and the science from unmanned missions far outpaces the efforts of manned missions, what benefit is there to sending humans into space?"
] | [
false
] | Is the science aboard the ISS really so important that we had to cancel the original or have funding issues with the next generation of space telescopes? | [
"It's mostly to inspire the people on the Earth and keep them interested. The science done by astronauts is trivial compared to what could be done by machines. Sometimes there is a purpose, for instance, when Hubble had to be repaired."
] | [
"Part of Freeman Dyson's talk on \"Living Through Four Revolutions\" is relevant: ",
"http://youtu.be/zq4p2qbE684?t=2m54s",
" "
] | [
"Why send humans to space?",
"Because it's there, and we can!"
] |
[
"Can auditory hallucinations be evoked in individuals who have been deaf since birth?"
] | [
false
] | In a person with reduced hearing loss, there is a chance that he/she can develop auditory hallucinations. For someone who has never experienced sound, could their mind still be manipulated in a way that they would "hear" audio? I've found articles on people who are deaf or developed deafness, but none on people who hav... | [
"The only reason why people experience auditory hallucinations in the first place is because they've experienced sounds before. These hallucinations (especially with Schizophrenic patients) usually take place because of a random activation of the auditory cortex and language areas of the brain. ",
"This is why yo... | [
"This is why you only hear of partially deaf people, or newly deaf people experiencing these hallucinations. It's simply because they've received these stimuli before.",
"When you say \"newly deaf,\" do you mean that as time goes on, they'll lose the ability to have auditory hallucinations?"
] | [
"I'm honestly not sure. I'm not sure if as time goes on, the auditory cortex slowly starts acquiring the ability to process sense of touch, or if that's just a process that takes place with people that have been deaf their whole lives. ",
"Maybe if they're able to remember what sounds are like, then it's a possib... |
[
"What causes the level of liquid inside of the straw to be higher than in the container?"
] | [
false
] | null | [
"To complete the explanation of height difference as a function of straw diameter: ",
"As the other user said, this is a matter of adhesion. There is an energy density associated with adhesion between water and the straw walls. This energy density is negative because water likes to \"wet\" the straw (this means ... | [
"Water molecules move up the straw by adhesion on to the walls, and then other water molecules move up with them through cohesion. Cohesion and adhesion are due to the properties of the water molecules (they are small, polar, and capable of hydrogen bonding), which make them strongly held together, and allows them... | [
"Good stuff. Thank you for the example. That always helps."
] |
[
"How far could someone hit a golf ball on the moon?"
] | [
false
] | null | [
" If that someone is Ryan Winther, current world record holder for fastest launch speed of a golf ball, his lunar range would be 6.3 km, or 3.9 miles. ",
" As above, the current world record for launch speed is Ryan Winther, with a launch speed of 226 mph, or 101 m/s. ",
"Source",
". I should mention this is ... | [
"Not much. Radius of the moon is 1700 km. Our ball is only going 3 km. The correction should be less than 1%. "
] | [
"Will the curvature of the moon have much of an effect on the distance it could travel?"
] |
[
"Why does waking up in the middle of a sleep cycle cause someone to be tired?"
] | [
false
] | What makes it different from waking up in another cycle? | [
"Sleep Inertia",
"."
] | [
"\"One theory is that sleep inertia is caused by the build-up of adenosine in the brain during NREM sleep. Adenosine then binds to receptors, and feelings of tiredness result.\"",
"Thank you! Something like that is exactly what I was looking for. "
] | [
"You should be more clear with your question. Are you asking about waking up in different cycles or waking up in different parts of a sleep cycle (each 90 minutes)? Or both?"
] |
[
"Can electromagnetic waves cool and object?"
] | [
false
] | I havent done any math, figured I would ask first (google turn up laser cooling, seems relevant). From my understanding if an object reflects electromagnetic waves (lets keep it super general for now) via ideal elastic collisions. Then the electromagnetic waves reflected would bounce off so to speak and have twice thei... | [
"Yes, laser cooling, which you appear to have started looking into, can be used to cool an object, the object being a cloud of atoms. It basically works by taking advantage of the doppler shift to allow only atoms which are moving towards the laser source to absorb a photon, decreasing their momentum in that direct... | [
"Excellent, thanks, this is exactly the kind on answer i was hoping for.. Could you elaborate \" As for what you seem to be envisioning, it will not work in a general sense \"?"
] | [
"I am going to use classical electromagnetism to answer your question. I hope this paradigm is enough to answer it. If there's an expert on quantum physics who recognizes that the classical model is not enough, please correct accordingly.",
"We begin by modelling the boundary surface separating the two materials.... |
[
"Dr. Seuss question can a pool be elevated in the air?"
] | [
false
] | So I was reading "Oh, the thinks you can think" to my daughter tonight and one Page has a girl in a pool high above her house. My question is how much helium (or other, better element) would it actually take to float a pool of water to swim in? Sorry if this is a dumb question but I thought it would be interesting | [
"You would need a really big balloon. The lifting force of helium is about 1 kg/m",
" which means you can lift a liter of water per cubic meter of helium (ignoring the material holding both, and at sea level). That comes out to 1000 times the volume of helium needed to lift a volume of water.",
"I'm going to ... | [
"pffft, you could take 8% off that with hydrogen. And it makes for a nice ",
" if it bursts. "
] | [
"Wow... thanks for the answer. That's a LOT more helium than he drew in his book haha... appreciate it!"
] |
[
"When will humans become hairless and why did we lose our need for hair?"
] | [
false
] | [deleted] | [
"It is doubtful we will lose it any time soon, we currently like how it looks and select for those that have nice hair.",
"One theory for why we lost our body hair is that losing it greatly helped us keep cool and also may have reduced parasites that reside in fur.",
"http://www.nytimes.com/2003/08/19/science/w... | [
"having hair does not hinder one's ability to leave offspring, so we will probably never be hairless, unless our environment somehow changes to give the hairless a marked advantage over those with hair"
] | [
"Did the hairless have an advantage over the hairy in the past?"
] |
[
"Why do dreams contain a sense of motion even though our bodies/minds/inner ear aren't moving?"
] | [
false
] | Last night i had a dream i was on a jet with a crazy pilot who kept doing loops and flips and all kinds of manuevers. I could my stomach bottoming out, my body being tossed side to side with the G-forces of the turns and such. I distinctly remember focusing on the horizon and trying to orient myself with what I knew i... | [
"We know very little about dreams, to be honest. But let me address your question in a different way. What if you wrote: \"Why do dreams contain a sense of vision even though our retinas aren't receiving any visual input?\" The inner ear and vestibular system is a sensory system, like the visual system. So, it seem... | [
"Have you felt weightlessness in a pool? Or experienced G-forces in an accelerating car that abruptly braked or turned? Your brain can extrapolate that in combination with things you’ve seen to create the illusion that you have experienced the real thing while you dream. ",
"I used to have dreams about driving be... | [
"It’s a simulation based on your previous experiences. Your brain remembers what those sensations feel like, which is why it is able to convincingly recreate them in your dreams. It’s the same reason dream you was aware enough to try to orient yourself."
] |
[
"Every cell has the same DNA. But not every cell is the same. Why?"
] | [
false
] | [deleted] | [
"I've used this analogy before, so I'll just restate it. Think of DNA as the detailed blueprint of a house. It contains all the information that a builder needs to build the house. However the house is not built all at once, and is built by different specialists working on different parts such as the mason working ... | [
"During development special genes known as Hox genes instruct the differentiation of cells. Differentiation genes can also be triggered by biochemical signals through carious cell signalling methods. I'm not sure of the full details.",
"Another aspect of how cell signalling affects stem cell differentiation which... | [
"Yes, it's due to epigenetics. Beta-cells (cells in the islets in the pancreas) contain the gene for hemoglobin. Strange, right? This doesn't mean the cell synthesizes hemoglobin. It simply means it has the genetic code stored in its nucleus.",
"The genes the cell doesn't need are silenced. This could be done in ... |
[
"What happens when photons hit each other?"
] | [
false
] | Explain it like I'm five. ... Wait. Can photons hit each other? I think I knew the answer once, back in school. | [
"Sorry but you're off on all accounts.",
"EarthExplodes was correct - photons ",
" their own antiparticles. An antiparticle is found by conjugating a particle state which, for a photon, is just a photon.",
"Also saying that gauge bosons don't have antiparticles is false. They certainly do, just like other par... | [
"Photons are their own antiparticle, so when they collide, they annihilate. The thing is, they annihilate... into photons!"
] | [
"That is correct. When the center-of-mass energy of the two photons is greater than the mass of two electrons, there is a probability for the two photons to interact, annihilating and producing an electron-positron pair. There is also a much smaller probability for two photons to interact and scatter off each other... |
[
"It always seems that when in periods of drought, no matter how much you water your lawn, it will remain somewhat brown and dead, but as soon as a little rain comes in, it greens right up. Is there any reasoning behind this or am I just overthinking it?"
] | [
false
] | [deleted] | [
"It depends on where you are, what kind of grass it is, and what time of year it is. ",
"In the north temperate zone, lawns composed of Kentucky bluegrass normally go dormant beginning in June, and may look brown and dead all summer, drought or no. If you then water it while it's dormant, nothing happens, becaus... | [
"So what you're saying is, don't water your grass in a drought."
] | [
"Mix some light-acid/base/nutrients in it, Depends on your geographical location."
] |
[
"Why is it that identical light bulbs placed in the same light fixture at the same time burn out at different times?"
] | [
false
] | Just changed a light bulb in the overhead fixture in my room and it got me wondering. | [
"Its a mixture of things.",
"The bulbs components aren't all exactly the same and the flow of electricity to the bulb isn't at a steady rate (its either turned off or on at different times or the electricity surges at different times)",
"Basically in production you are never getting the same exact device/produc... | [
"Well, that depends on what you mean by \"identical\"\nassuming you meaning that they came from the same box then the most likely reason is, they're not quite identical.",
"An incandescent light bulb works by running current through a small wire, called a filament, which then gets very hot and glows. When it bur... | [
"You can't manufacture identical things, also I recommend this movie \n",
"http://www.imdb.com/title/tt1825163/"
] |
[
"How exactly was the evolutionary jump made from single-celled to multi-cellular life? I've always wondered..."
] | [
false
] | null | [
"It is not completely clear, and ",
"a number of hypotheses exist.",
"Evolutionarily, multicellular forms began showing up in great numbers in the fossil record shortly before the Cambrian explosion, but the earliest presence of multicellularity is somewhat controversial.",
"For a great, somewhat-related popu... | [
"The middle step could likely be colony-forming single-celled organisms. Symbiosis which eventually led to specialisation within the colony. \nThink of a mass of cells that each live together (for protection or other beneficial reasons) forming a colony. Let's say that they photosynthesise (for example Cyanobacteri... | [
"This is another relevant recent article",
". It describes how multicellularity can be selected for in only a few hundred generations in yeast. ",
"To clarify, slime molds and fungus are not closely related, so these are independent examples of facultative multicellularity."
] |
[
"Why does stirring a pot of boiling water seem to interrupt the boiling?"
] | [
false
] | null | [
"Unless the pot of water is very hot, there will be a temperature gradient throughout it. That is, the water at the bottom of the pot in contact with the heating element will be hotter than the water at the top in contact with the air. When you stir the pot, you disrupt the thermal gradient and distribute the heat ... | [
"It also disrupts convection briefly"
] | [
"It prevents thermal equilibrium from being achieved."
] |
[
"Why do rockets still explode even if it runs out of propellants?"
] | [
false
] | null | [
"Do you have a specific example in mind?",
"In general even empty tanks have quite a bit of vapors left in them."
] | [
"In that particular case the liquid oxygen ran out. There was still enough RP1 liquid kerosene and vapors to make a nice fireball. But it was quite a bit smaller than when ",
"a full rocket blow up",
"."
] | [
"In June 2016, SpaceX's falcon 9 failed to land because of it \"ran out of propellant.\" "
] |
[
"How many people have lived and died in the last 10 000 years?"
] | [
false
] | null | [
"The estimates vary a little, but the most common figures I've seen are 107 to 108 billion. ",
"Here",
" is one source for that."
] | [
"The source considers 108 billion since 50,000 B.C., but given the population was about 4 million people in 10,000 B.C. and supposing about half that number of people were born every ~20 years, we would get:",
"40,000 years / 20 years * 2 million = about 4 billion people lived pre-agriculture (something on that ... | [
"What's crazy is that there are about 100 trillion microbes living inside just one of those humans. ",
"When I think about how many humans there are relative to, say, tigers, it seems sad to tigers. But when you consider how many bacteria outnumber us all (tigers included) well, I wonder if bacteria are working t... |
[
"Michio Kaku: Physics of the Impossible anyone read it?"
] | [
false
] | I've seen Michio Kaku on multiple History Channel specials and he always fascinated me. I see that he has written multiple books, Physics of the Impossible being the newest. I'm no physics expert, I have a decent amount of knowledge of general theories and such but nothing to in depth. My question to askscience is will... | [
"While he writes really well, I found 'Physics of the Impossible' to be lackluster. ",
"It's been a while since I read it, so I can't think of any specific criticism, it just remember being vaguely disappointed.",
"I thoroughly enjoyed Phil Plait's \"Death from the Skies\" however, it is a bit more 'dumbed dow... | [
"the book is more complicated then you would think, but it's written for the laymen, yes. Not dumbed down, just lots of real life examples. It's literally sitting beside my laptop as we speak. It's a small paperback, but worth the read. Makes you really angry you might not be alive when this stuff comes to pass tho... | [
"Sounds good that it is not dumbed down..(havent read any of his stuff) Rather annoyed(to say the least) by how badly he often simplifies it on tv.."
] |
[
"Does relativistic length contraction happen in all 3 dimensions?"
] | [
false
] | I get that as my velocity approaches c, my time dilates and my length contracts for somebody observing from an inertial reference frame. But I can only travel in a single direction. What happens to my other dimensions? If my x-velocity approaches c, what happens to my y- and z-dimensions? Do they contract too? My y- an... | [
"Only the length in the direction of motion contracts. So, if your x-direction speed approached c, then your x length is contracted while y and z remain unchanged.",
"As for atoms, they will continue to vibrate in 3 dimensions. But, for a \"stationary\" observer watching a vibrating atom moving near the speed of ... | [
"So the vibration of my atoms (and, I suppose, my whole self) would essentially flatten into a plane? ",
"What about if I reached ",
"? Wouldn't all my four-velocity be allocated to me traveling through the x-dimension, with no more left for any movement in y or z?"
] | [
"You wouldn't feel any different because you always experience your own rest frame. But yes, you would look all squished to someone moving relative to you at close to the speed of light."
] |
[
"Does the \"randomness\" of quantum mechanics translate to macroscopic events?"
] | [
false
] | I am not super familiar with the details of quantum mechanics, but I know that you cannot predict where certain particles will be, only the probability of them being in a certain spot. In all macroscopic situations, it seems like any event that has a probability of occurring in one of multiple ways can really be predi... | [
"The statement is not true in quantum mechanics. Einstein, Podolsky and Rosen published a famous paper on this now referred to as the ",
"EPR Paradox",
". It essentially says that quantum mechanics as it's understood is an \"incomplete theory\". This doesn't mean that it's wrong, because all evidence says tha... | [
"In practice no, even at zero kelvin particles will be moving and have a momentum. You could put it in the equation though and get an infinite wavelength. This is what you expect with the uncertainty principle which says you cannot know both the exact momentum and the exact position. If you know the momentum is exa... | [
"Conceptually, you can think of it as a general property of waves. ",
"Consider a standing wave on a string, like one of ",
"these",
", and say these waves extended on in both directions forever. Each wave has a very well defined wavelength, but, on the other hand, where would you say the position of the wa... |
[
"Why is the ocean so salty?"
] | [
false
] | null | [
"You are ",
" mostly right. Salt exists in large deposits all across the globe. As water travels across the land, it picks up salt and other minerals and deposits them in the ocean. When the water evaporates from the ocean, it leaves the salt and minerals behind. Over billions of years, the oceans became salty. G... | [
"No, because eventually these minerals are going to be deposited on the ocean floor and then through plate tectonics they will eventually end up back in landmasses and the whole process starts over again. This is over geological timescales (many thousands of years) mind you. The residence time of the different mine... | [
"Many of them do! Don't even get me started on Diatoms... They are single celled algae that require silicon in order to grow, which they then incorporate into their cell walls. They actually control the cycling of Silicon in the surface oceans. They are also incredibly important to the export of carbon from the sur... |
[
"Can time run backward?"
] | [
false
] | Can time run backward? In his web site , renowned anesthesiologist and researcher Stuart Hameroff describes experiments that suggest that the human brain refers information backward in time. Hameroff has worked with Nobel prize winning Roger Penrose on the problem of consciousness. I am an EE trying to understand qua... | [
"That website looks like total pseudoscience. Also, Roger Penrose never won a Nobel prize (maybe he wins it in the future for inventing time travel).",
"Anyway, as far as we know time just goes forward. Mathematically, antiparticles can be considered as going back in time in the opposite direction (if you're at 5... | [
"I put my skeptical hat on when I saw the name of the website!"
] | [
"There is nothing in the math that says time can't go both directions. The math works no matter what the sign (+ for forward in time, - for backwards). ",
"However, in the real world, things are bit different. Time running backwards breaks causality. (Events could happen 'before' their cause.) Everything get... |
[
"What is happening when I get the \"shivers\" and my skin tingles while listening to a really, really great song?"
] | [
false
] | null | [
"It can be caused by a dopamine response, and ",
"here's a paper",
" describing it being caused by, or at least being contributed to by, the constant denial/payoff expectation reaction in every human being, which can cause \"chills\" in a variety of situations (just like being scared, or being touched in a sens... | [
"This phenomenon is usually known as Frisson. Unfortunately, there isn't a whole lot of research on Frisson or ASMR (similiar feeling with different, non music related, triggers). Some more information can be found ",
"here",
" or you can head over to ",
"/r/Frisson",
" to delve a little deeper into it."
] | [
"I'm glad you mentioned that minor key != sad, too many people make this assumption. I usually just point out that Stayin' Alive is in a minor key and Everybody Hurts is in a major key.",
"As a followup question, why do you think minor key progressions are harder to predict? "
] |
[
"Breaking everything down to an atomic / sub atomic level, aren't we all just one big soup of chemicals reacting with each other? Like a big giant stirring pot of slurp?"
] | [
false
] | No this is not a pick up line. | [
"I would not say we're nothing - that is just wrong. Just because most of the ",
" in an atom is empty space, it is still very, very different from actual \"nothingness.\" Just like most of the solar system is empty space, that doesn't mean you can equate an equal volume of ",
" empty space to the solar system.... | [
"Basically, yes. But there is no big benefit to interpreting things that way - at least I don't see one. The true complexity of the system is lost when you reduce it to one word - \"chemicals.\"",
"It's like saying \"Isn't Usain Bolt just doing what almost everyone can do - running - but just faster?\""
] | [
"Well at a basic level if you really want to be specific we are actually nothing.",
"We are made up of atoms and atoms are mostly empty space. That being said we are just nothing that is interacting with more nothing."
] |
[
"How can our Sun, with it's mass, keep Neptune and Uranus in orbit yet not consume a much smaller and closer Mercury?"
] | [
false
] | null | [
"Planetary orbit relies on a force balance:",
"(mv",
" )/r = (G m m2)/r",
"m = smaller orbiting mass",
"v = velocity of smaller orbiting mass",
"r = distance between centers of small mass and large mass",
"m2 = mas of larger mass (Sun)",
"G = gravitational constant",
"On the left is the centripetal ... | [
"Mercury is moving at a very fast rate around the sun compared to say Neptune.\nLets define 1 year as the amount of time it takes (in Earth days so we have an easy point of reference) for a planet to completely orbit the sun 1 time.",
"The length of a year on Mercury is only about 88 Earth days. It has a mean orb... | [
"Because the stable orbital velocity depends only on the distance from the Sun, not at all on the mass of the orbiting object."
] |
[
"Do people's internal voice change when they learn a language?"
] | [
false
] | Do people's internal voices change when they learn a second language? Or is there always translating going on via the native language at some level? | [
"When I was learning in French, it obviously took a lot of translating. But there came a point when I was so comfortable with it that I could think in French and no longer had to create the sentence in English ",
" before expressing it in French ",
". I could dive right into French. So, at least for me, ther... | [
"I had a Norwegian roommate that spoke better English than most of my American friends (fellow grad student). She experienced this phenomenon while she was on the phone with her mom (speaking Norwegian) I asked a question, and she replied to it in Norwegian because she was currently thinking Norwegian, she was so c... | [
"I can't answer you scientifically, but as a trilingual person, it does for me.\nPortuguese is my native language and I learned English when I was really young, 3 maybe. I don't need to translate much between those. I started learning Korean 2 years ago, by myself, with no money, and I speak it ok. I still don't ne... |
[
"Is there a theoretical maximum size of a rocky planet?"
] | [
false
] | null | [
"Sorta. For a \"normal\" planet forming a \"normal\" way, roughly 1.5-2 earth radii, and roughly 10 earth masses. Beyond that, a planet tends to be far too good at holding on to lots of hydrogen/helium, and will be more like a gas giant. see eg: ",
"figure 3 in Chen & Kipping (2016) for typical mass-radius relat... | [
"Not necessarily. If your big piece of rock consists only of iron, it will never be a star, as nuclear fusion of iron absorbs energy instead of releasing. It won't shine, it will directly collapse into a black hole if you keep adding mass.",
"Of course, this would never happen naturally."
] | [
"Thanks so much for the link to the article. I have never seen this article."
] |
[
"Have we ever monitored the brain of a dying individual and if so were there any interesting phenomenon observed?"
] | [
false
] | null | [
"If you're interested in ",
", ",
"This PNAS study",
" (on mice, not humans) may explain the phenomenon.",
"In summary: There are 4 stages of dying. CAS stands for Cardiac Arrest Stage. ",
" ",
"\nWhat's interesting is that in CAS 3, there was an increase in synchronized gamma waves, indicating ",
"... | [
"I am a clinical neurophysiologist and I have personally examined the continuous EEG (cEEG) records of about a dozen patients who have died during monitoring. These are generally patients who are critically ill before dying.",
"My observation is that there is steady deterioration of EEG prior to actual arrest, pr... | [
"So passing out from oxygen deficiency could result in the same expirience?"
] |
[
"Do hands-free devices really impact inattentional blindness while driving? If so, why is there such a big difference between using a hands-free device and holding the phone with one's hand?"
] | [
false
] | null | [
"Yes, they really do. ",
"It has been shown time and time again",
". (a quick find:)",
"We suggest that (a) there are significant costs to driver reactions to external hazards or events associated with cell phone use, (b) hands-free cell phones do not eliminate or substantially reduce these costs, and (c) dif... | [
"I suppose I should rephrase my question, then, to get what I'm really looking for. Is there a consensus on the effectiveness of hands-free devices? (with regard to attention-span and reaction time)",
"Also, if: ",
"(b) hands-free cell phones do not eliminate or substantially reduce these costs",
"is generall... | [
"According to the US Dept of Transportation, talking on a cell phone, whether hand-held or hands free, is not associated with decreased driver performance. ",
"http://www.distraction.gov/download/811757.pdf",
"The attention issues come from manipulating the phone. "
] |
[
"How is the mass of a black hole determined?"
] | [
false
] | null | [
"If you are talking philosophically, a black hole is considered to have the same mass as an object that can create the same gravitational field at a distant point",
"If you are talking practically, there are a number of methods. If the black hole is a part of a binary system, we can use information from the Doppl... | [
"It doesn’t have any impact outside of what a star or other object of the same mass would have."
] | [
"What effect does the mass of black holes have on binary systems and accretion disk?"
] |
[
"With NASA's Kepler telescope nearing the end of its life cycle, what are some of its notable contributions?"
] | [
false
] | null | [
"Since nobody has answered I'll give it a go. ",
"Kepler has confirmed the existence of over 2000 exo planets with as many again suspected but not confirmed. ",
" The planets discovered are also very different in nature to the ones previously discovered due to the methods used. ",
"Previously most planets fou... | [
"Keplar has confirmed the existence of over 2000 exo planets",
"2600 out of 3800 known planets. About 2/3 of all known exoplanets were discovered by Kepler (a few of the 2600 were known before, not many enough to matter).",
"PS: Kepl",
"r."
] | [
"There were 500 exoplanets discovered before Kepler, I would not call that not enough to matter."
] |
[
"Are there any placebo effects that aren't psychological?"
] | [
false
] | I know they have been shown to treat depression, pain, anxiety etc., but I am wondering if there is any evidence that they can treat things like healing time, length of an illness, etc. The closest thing I've found is that they can treat Parkinson's disease, by stopping the firing bursts of neurons; still arguably psyc... | [
"I'd say no, there are none.",
"\"A 2001 meta-analysis of clinical trials with placebo groups and no-treatment groups found no evidence for a placebo effect on objectively measured outcomes and possible small benefits in studies with continuous subjective outcomes (particularly pain).[10] A 2004 follow-up analysi... | [
"It's well-known that if you give a patient a placebo in place of morphine, pain can be reduced. If, however, you give naloxone (a drug that blocks the effect of morphine) to patients after they receive morphine, the pain comes back.",
"What happens if you give a patient naloxone after giving them a placebo to r... | [
"Psychological cause of physical effect?"
] |
[
"If sound waves travel farther and faster in denser media, such as water, than it does through air, then why do walls and other solids block sound from passing through?"
] | [
false
] | null | [
"It bounces off those objects because the waves don't have enough energy to vibrate something so massive. The materials are too dissimilar and impedance (Pa·s/m",
" is too high. Sound waves already lose a lot of energy just going through the air so almost all of them will be reflected back."
] | [
"This is exactly right. ",
"But put more simply, it's exactly the same effect as light bouncing off the surface of water. Ever notice how, when you're underwater, the surface is reflective, preventing you from seeing out? When waves change speed, they bend. And in the case of the water interface, they bend a lot ... | [
"If you think about how loud music has to be before you can actually feel the air moving around your hands (if you even experienced it), then you get an idea of how little force the sound waves actually carry. When you apply that small a force to a solid object which is very likely at least several thousand times h... |
[
"What mechanism causes this lobe/torus pattern?"
] | [
false
] | The star's matter is clearly ejected primarily in the directions of two poles (which I'm guessing are its magnetic poles) and in every direction in the perpendicular plane. What causes this formation? | [
"Oh, downvote me will you? Have the original source, NASA's Goddard image site on flickr. I quote: \"The onion-like layered structure of the more diffuse cloud surrounding the central cocoon is caused by periodic bursts of material being ejected from the dying star. The bursts typically occur every few hundred year... | [
"Thankses."
] | [
"That's one of the coolest astronomical images I've seen. Does anyone have a link to the source? Tineye didn't help. "
] |
[
"How long would the second hand on a clock need to be, for the tip to be going the speed of light?"
] | [
false
] | And what would happen if you could actually try it..? | [
"Naively:",
"The second hand travels at 360/60 = 6 degrees per second.",
"Speed of light is 299,792,458 meters per second.",
"The length of a 6 degree arc with radius ",
" is 6*(pi/180)*",
". We want the length of the arc to be 299,792,458 meters, so plugging that in and solving for the radius we have ",... | [
"It's length would be about ten times the distance to the moon from here (2.86 million kilometers.)",
"If you actually constructed it, and found a motor to turn it, it would quickly deform, then break."
] | [
"How did you know to use one light-minute and two pi? Explain using only arithmetic."
] |
[
"Why does the tip of your finger hurt after you cut the nail too short?"
] | [
false
] | null | [
"The skin under your nail has lots of nerve endings in it, just like the rest of your hands. These nerve endings are not used to being touched because normally they have a nail covering them up, so they are pretty sensitive. When you cut the nail too short you reveal the sensitive skin and it hurts. "
] | [
"Nociceptors-- the cells that send pain signals-- don't adapt to stimulus over time like thermoreceptors do. So regardless of the length of stimulus they will always send the pain signal",
"For more reading:",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2852643/"
] | [
"You cut into the 'quick', the layer of living skin that generates the nail. If you enter the lower layer (",
"), you will encounter blood vessels and pain sensing nerve fibers. The wound will bleed and hurt."
] |
[
"Why do we sometimes jump suddenly as we fall asleep?"
] | [
false
] | Hey guys So I was thinking about this last night. I'm talking about when you're starting to fall asleep and you're starting to dream but you trip and straighten your legs waking you up, or something similar. I really can't think of any evolutionary advantage for this so please enlighten me! Thanks | [
"It's called a ",
"Hypnic Jerk",
"As to why...No idea."
] | [
"This page",
" has some additional info. My understanding has always been that as your body is relaxing for sleep sometimes your muscles relax too quickly and your proprioceptors detect it as \"falling\" so your reflexes startle for a split second, trying to get you upright. "
] | [
"Yes, I believe that this explanation is the most current one. It is said to have an evolutionary advantage because our ancestors would spend time in trees. If the body sensed that it was beginning to fall, the organism would undergo such a jerking movement and would hopefully wake up to save itself before it fell ... |
[
"Do the planets aligning actually do anything?"
] | [
false
] | You always hear how the planets aligning causes things like changing tides, changing the tilt of the Earth, or others more fantastical things, but do planets aligning have any effects even if they're minor? | [
"Scientifically speaking, the only way they could affect us is via gravity. But they are so small and so far away, that the net effect is zero no matter what.",
"They actually do something when they are aligned: they provide a beautiful view in the evening."
] | [
"What a timely question! A very rare such event, called the transit of Venus, will occur this year (2012) in June. If you miss it, catch the next one in 100 years.",
"http://www.transitofvenus.org/"
] | [
"the only way they could affect us is via gravity.",
"Yes, but specifically, by way of tidal forces., and those forces decline as the cube of distance. This is why the moon is a greater influence on earth's tides than the sun is, in spite of the sun's much greater mass."
] |
[
"If you have a machine or program that randomly selects five numbers between 1-100, what are the odds that it will pull a series of numbers in sequence (e.g. 24, 25, 26, 27, 28)?"
] | [
false
] | This started with a conversation I had with a friend about if you played the lottery, would you have the same statistical advantage by playing random numbers or selecting a sequence of numbers on your lottery ticket. Also, if this program did the same thing for 1-1000 does the mathematical odds remain the same (as the ... | [
"There are a couple of ways to interpret your question. It looks like ",
"/u/all_the_mercuries",
" has attempted to address the probability of getting the string of numbers ",
". So that the 25 is drawn first, then the 26, and so on. If that's what you're wanting, then that answer is almost correct, except th... | [
"For the 1-100 case, it seems that the first number could be any number from 1-96, so that's a 96/100 chance. Then once that number is chosen, the next one has to be the next higher number, so that's a 1/100 chance (assuming you're looking for the odds of an ascending sequence just like the example you gave, and n... | [
"This is the correct answer to the question if the computer random generator can repeat numbers and both it and you care about the order of numbers. In a lottery, the order of numbers does not matter, and there is no replacement (ie it can't draw 26-26-26-26-26)."
] |
[
"How do fish not get lost in the ocean?"
] | [
false
] | I understand the concept of sonar and migration patterns, but without any clear landmarks to look towards, how do fish/dolphins/sharks/whales not become lost? | [
"One example is through smell. After their birth salmon learn the smells associated with their seaward migration and follow them back years later. ",
"Source: Homing in Pacific Salmon: Mechanics and Ecological Basis. Published 1996 in the Journal of Experimental Biology. ",
"Edit: I should also add fish do get ... | [
"Hammerhead sharks have pores on their skin which are sensitive to electromagnetic waves, and can navigate using the earth's magnetic field, although I'm not sure if other sharks do this.",
"In addition, there most certainly are landmarks in the ocean; sharks have been known to follow undersea trenches or ridges ... | [
"As other people have mentioned, it has to do with magnetoreception. Most research I've read has to do with birds, but I'm sure marine animals have similar capabilities. Generally there's a deposit of magnetite (or something like such) in the nasal cavity to provide orientation along with magnetosensitive pigments ... |
[
"How did \"dis-\" and \"dys-\" both survive as prefixes?"
] | [
false
] | For such a short, simple prefix, how did both permutations survive? Why isn't it "disphoria" or "dysarray"? | [
"Compare the wiktionary pages for ",
"dys",
" and ",
"dis",
". They're from different root languages, and while many words adopted into English are indeed anglicised in various ways, it's actually quite common for many phrases and words to be adopted verbatim into common vernacular. Both survived simply bec... | [
"That's because they have different origins, and, to some extent, different meanings.",
" is from ancient Greek, meaning \"bad\", while ",
" is from Latin, meaning \"apart\" or making the word negative."
] | [
"Why isn't the word ",
" \"dystress\", then? Positive stress is eustress and negative stress is distress? Doesn't that not make sense, one being a Greek prefix and the other Latin?"
] |
[
"What is the precision of the human ear for pitch?"
] | [
false
] | Is the human ear able to disambiguate between 440Hz and 440.01Hz for example? | [
"I found this website a little while back for individual ear training. This test gives you two tones (a base tone followed by one that changes) and you have to determine if the second tone is higher or lower than the first. It's easy at first but the intervals between pitches get smaller and smaller until they soun... | [
"Found this on wikipedia:",
"Frequency resolution of the ear is 3.6 Hz within the octave of 1000 – 2000 Hz. That is, changes in pitch larger than 3.6 Hz can be perceived in a clinical setting.[5] However, even smaller pitch differences can be perceived through other means. For example, the interference of two pit... | [
"When I was in middle school jazz band, the director's ear training exercise consisted of playing two random notes from the chromatic scale on a piano, and then having us write down the interval between them. You can accomplish this either by getting acclimated to each interval's dissonance and consonance and \"fee... |
[
"why do galaxies that are hundreds of thousands of light years across or more appear to be symmetrical (or do they not?) even though they're moving?"
] | [
false
] | shouldn't they appear to be distorted because the light reaching us from the farther side is hundreds of thousands or millions of years older? or is it just that galaxies are moving at speeds proportional to their size that this distortion doesn't happen? | [
"If I understand your question correctly, you're wondering if because of the distance between us and the front/end of a galaxy, that we might see distortions because of the time it takes light to propagate that extra distance, and in that time the farther side of the galaxy might have changed shape? If that's the c... | [
"Your question is a good one. ",
"When we take an image of a galaxy ten million light years away, the photons from the near side of the galaxy left their respective stars ten million years ago; while the photons from the far side left their stars ten million + the radius of the galaxy years ago. OP asks why, if... | [
"thanks for the reply"
] |
[
"What would happen if a Comet destroyed, or significantly damaged the moon?"
] | [
false
] | I was reading this " " and I was wondering what would happen if a comet this size struck the moon? What changes would occur on Earth? Would there be a nexceptional change to our climate? How would it effect ocean currents? How much debris would we have to deal with? I'm assuming animals would be affected; how badly? Wo... | [
"It's hard to grasp just how ",
" it would be to ",
" an astronomical body. We imagine blowing things up with explosives and having those things shatter into little bits that fly away, but when you're talking about an object that's bound together by its own gravitation, that's a ",
" harder. You'd have to acc... | [
"It depends on how you define \"much of the debris.\" Astronomical bodies are ",
" Larger than you think, if grew up watching too many science fiction movies.",
"There's a basin near the south pole of the moon that's thought to have been created by a single huge impact event of unusual character. It's barely no... | [
"and many fewer love songs",
"I lol'd",
"Would I be right in thinking that because the moon has no atmosphere and gravity on its surface isn't as strong as on the Earth's surface; if there was an impact with a large comet that much of the debris would escape into the depths of space?",
"Also, just how big of ... |
[
"What percentage of all hydrogen has never been a part of a star?"
] | [
false
] | After the big bang a large amount of hydrogen was formed (as an aside, was hydrogen formed? Is hydrogen ever created from... i don't know... breaking apart a helium atom?). Some of that original hydrogen went on to form stars. Did any hydrogen simply float off by itself, or in clumps that were not large enough to form ... | [
"Is hydrogen ever created from... i don't know... breaking apart a helium atom?).",
"Helium is much more stable than hydrogen, so it is very unlikely to directly break apart.",
"However, there are many fusion and fission reactions that release protons, or that release neutrons that then decay into protons, so i... | [
"This is highly speculative and there is no research done on this subject that I've heard of. (working on PHD specializing in early universe) "
] | [
"Is there any way to tell the difference between hydrogen that was at one point a part of a star and hydrogen that has never been a part of a star?",
"No, unless the hydrogen in question is currently part of a planetary nebula or something.",
"Can hydrogen even escape a star?",
"Yes. In a star like the Sun, f... |
[
"Why does drag on one dimension depend on the speed of the other dimension?"
] | [
false
] | Imagine an object moving in a 2d plane at velocity v at an angle a with the horizontal axis (x) The drag acting on the object should have the magnitude k v *cos(a) however if we only look at the problem in terms of the x axis, the object should be moving at v (v*cos(a)) if i am right in my calculations... this means... | [
"The force of drag does not mix components. The x-component of drag only cares about the x-component of velocity, and the same for the others.",
"Quadratic drag does mix components. Generally speaking, ",
" = -c|",
"|*",
", which results in a coupling of terms if the motion is along more than one axis (brea... | [
"The force of drag does not mix components. The x-component of drag only cares about the x-component of velocity, and the same for the others.",
"Quadratic drag does mix components. Generally speaking, ",
" = -c|",
"|*",
", which results in a coupling of terms if the motion is along more than one axis (brea... | [
"Just choose the x-axis to be parallel to the velocity vector, then there is no angle involved and the drag is kv",
" in one direction. If you do it your way you also have to take into account the y-component that comes in with a sin",
" and you can use sin",
" + cos",
" = 1 to get a drag of magnitude kv",
... |
[
"Are advancements in medicine the only major factor contributing to our life spans being longer than our ancestors?"
] | [
false
] | When people talk about how much longer we're living and how much longer we'll live in the future the conversation always seems to center on medicine. I'm mostly curious as to whether our lives are naturally growing longer aside from medicine, though I know that our lifestyles being safer in general contributes to that... | [
"No, not really. If you look into the research you can see that better sanitation has more of an impact on our average life span than advancements in medicine."
] | [
"Don't have to be so derisive, if he thought of those he wouldn't have asked on this forum. Besides, as far as I know, there isn't research to success that physical labor and comfort are really associated with longevity. If the lack of comfort or excessive physical labor contributed to higher mental stresses, then ... | [
"Don't have to be so derisive, if he thought of those he wouldn't have asked on this forum. Besides, as far as I know, there isn't research to success that physical labor and comfort are really associated with longevity. If the lack of comfort or excessive physical labor contributed to higher mental stresses, then ... |
[
"What color would the sky have been during the Carboniferous period?"
] | [
false
] | I was watching Ancient Earth, and during their episode on Carboniferous giant insects there was a throwaway line that mentioned the sky would look sepia due to the high oxygen levels (32% vs. the 21% of today). Is this true? If not, what color would the sky have been? | [
"The oxygen-rich late Carboniferous was plagued by wildfires, regularly burning through even the wettest rain forests. There were so many fires that the air was likely continuously smoky year-round. ",
"It was this omnipresent smoke that made the late Carboniferous sky yellow-beige",
", not the extra oxygen.",
... | [
"Assuming the total atmospheric pressure remained about the same, the clear-air sky would likely look about as blue as it does now. The blue colour is due to Rayleigh scattering of sunlight by particles much smaller than the wavelengths of the light, and nitrogen and oxygen molecules aren't significantly different... | [
"Thanks! We do have abundant evidence proving that wildfires were as rampant as predicted with such high oxygen (Carboniferous aged coal can be up to 30% charcoal by volume). The show definitely said the sepia color was due to the oxygen, but perhaps they meant the fires fueled by the oxygen."
] |
[
"If you could theoretically survive on Venus, would you be floating in mid-air?"
] | [
false
] | From the wiki: "The atmospheric mass is 93 times that of Earth's atmosphere while the pressure at the planet's surface is about 92 times that at Earth's surface—a pressure equivalent to that at a depth of nearly 1 kilometer under Earth's oceans." Would something like airships be possible there? | [
"The density of air at the surface of Venus is 6.5% that of water, it's not the same deal.",
"Buoyancy pretty much only depends on volume displacement alone, and not pressure. You look at the volume displaced, calculate the force of buoyancy, and then subtract the affects of gravity (the mass, and therefore densi... | [
"Density, not pressure is the key point for buoyancy. According to wiki,",
"The density of the air at the surface is 67 kg/m3, which is 6.5% that of liquid water on Earth.",
"So while the air is 50 times denser than Earth's air, it's still like 15-20 times less dense than the human body, so you won't float."
] | [
"I don't think so, if my calculations are correct you'd need approximately an entire cubic meter of air in your suit for a 68 kg person to begin floating on Venus. Quite a fat suit. (and a typical human being is less than 0.1 cubic meters in volume, for perspective)."
] |
[
"Diffraction of Light Waves"
] | [
false
] | If light waves could be diffracted, what would we see when we are walking around a corner? Would we see some of the objects around the corner? EDIT: I should have said diffracted as much as sound waves. | [
"Light waves CAN be ",
"diffracted",
". ",
"Scientists have made a ",
"Laser camera [that] takes photos around corners",
" by reflecting light",
"We can't see around corners with our eyes because the light is scattered too much to make use of it. If there was a mirror on the corner...."
] | [
"Okay, so they can be diffracted, but when I said corner, I meant like on a street corner, or the corner of a single square. Sorry, I'm having trouble explaining myself."
] | [
"Well if light didn't travel in straight lines, but in curves instead then yes you could see around corners. Mirrors do this nicely. In terms of diffraction, the less direct the light (bouncing off multiple objects before you see it) reconstructing the image becomes extremely difficult. If you can model quickly eno... |
[
"Is there a finite limit to how large/massive a star can be?"
] | [
false
] | We know of stars that exist such as VY Canis Majoris, NML Cygni, RW Cephei, and UY Scuti. They are all upwards of 2,000,000,000KM (roughly 1,250,000,000 miles) in diameter. So just how large can a star get? | [
"Size can have different meanings when it comes to celestial bodies. ",
"As far as diameter, Eta Carinae is so large it's actually difficult to determine how large it really is. Eta Carinae throws off so much coronal mass that its solar wind obscures measurements of its radius.",
"As far as mass, R136a1 is es... | [
"If the star becomes to massive, it falls within its own Schwartzschild radius (2",
"G/c",
") and therefore becomes a black hole. ",
"Now you should take in account, that the density of stars can vary a lot, our sun is at 1408 kg/m",
" while a neutron star can reach about 5*10",
" kg/m",
" (that is dens... | [
"So R136a1 is bigger than the limit? That doesn't make sense."
] |
[
"How do we know that bitcoins are made by Satoshi instead of others?"
] | [
false
] | null | [
"Hi,",
"Unfortunately, this is a bit of a misunderstanding.",
"The Bitcoin protocol does not attempt to link identities (private keys) to individuals. What it does is establish a distributed protocol for agreeing on an arbitrary amount of work done. Participants in the protocol sign their proof-of-work using th... | [
"Thanks a lot!"
] | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):"
] |
[
"Why aren't there more Icelands?"
] | [
false
] | The mid-Atlantic ridge continually creates new seabed, however at Iceland it has broken the surface and piled up into a volcanic island - why has this only happened here, rather than all along the faultine? Why has it happened at all, rather than just being open ocean? | [
"The most common (and generally accepted) idea is that there is a ",
"'hotspot'",
" beneath Iceland, ",
"specifically the Iceland Plume",
". The exact relationship between the Iceland plume and the northern Mid-Atlantic Ridge is still a bit contentious (at least as far as I know), the northern Mid-Atlantic ... | [
"Huh? I mean what's the date you're going to set for the start of 'normal'? All land formed at some point, Iceland is just younger than many other terrestrial crusts. "
] | [
"Huh? I mean what's the date you're going to set for the start of 'normal'? All land formed at some point, Iceland is just younger than many other terrestrial crusts. "
] |
[
"Do alzheimer's patients lose \"muscle memory\" as well?"
] | [
false
] | null | [
"in response to other post, no they dont have brains but what the OP is possibly referring to is the kind of skills that we develop that have to do with coordination: gross motor skills such as walking, fine motor such as needle point. These skills can be developed and learned. ",
"I have worked with a couple of ... | [
"Does dopamine play a role in the development of motor skills?"
] | [
"There does appear to be dopaminergic innervation",
" (dopamine does play a role) in the cerebellum, the part of the brain strongly tied with motor learning (muscle memory)."
] |
[
"If dark matter is spread like a halo around entire galaxies causing the stars on the outer arms to rotate faster around than center of the galaxy, why don't our planets experience the same effect?"
] | [
false
] | I just watched a video about the rotation speed of stars in Andromeda being one of the first clues about the existence of dark matter. So why doesn't dark matter affect our planets the same way as outlying stars in a galaxy? | [
"Our solar system and the galaxy it's part of are shaped completely differently.",
"Let's start by talking about the sun, and how big it is. We will say, for sake of approximation, that the sun is five light-seconds across. Don't worry about how big or small a light-second is compared to the distance from your ho... | [
"No, that was a typo. Some extra zeroes slipped in there when they shouldn't have. The management regrets the error."
] | [
"Thanks for taking the time to explain this!",
"Wow, is the galactic halo of dark matter really 400 times wider than our galaxy? (1200 trillion / 3 trillion light seconds)",
"Doesn't that make it 40 million lightyears across? (assuming baryonic diameter of Milky Way is 100,000ly)",
"According to my wall poste... |
[
"Do your cells stop dividing the second you die? If not, how long do they divide after you are dead?"
] | [
false
] | null | [
"Well that will vary for each cell. Most will die once they no longer have enough oxygen for aerobic respiration and thus can't power their necessary functions. If your someone like Henrietta Lacks scientists have kept your cells growing long after death."
] | [
"As stated, it really depends on cell type. Neural tissue will die quick. Deep connective tissue may survive much longer. Ultimately, cells that can survive with low oxygen demand have low metabolism and don’t really divide, however those close to dividing may be able to complete mitotic division but I doubt any su... | [
"There are groups that are actively researching what happens to cells of an organism after the organism dies. It looks like there are specific genetic programs that cells can activate after the organism they belong to dies. Apparently they are now referring to this collection of genes as the \"thanatotranscriptome\... |
[
"Why don't women taking anti-estrogens masculinize the way men taking anti-androgens feminize?"
] | [
false
] | As I understand it, both men and women naturally produce sex hormones "belonging" to the other sex, just less of it. Consequentially, a man taking a testosterone-blocking anti-cancer medication like cyproterone may lose sex drive and get gynecomastia because his natural estrogen is now the only thing floating around hi... | [
"the most basic way to explain this is that the presence of a males hormones leads to masculine traits, while the absence leads to feminine traits. Men have a Y chromosome which is responsible for triggering these masculine traits, women do not. During gestation the cells which will grow into a person and the surro... | [
"There are xx males though, yes? "
] | [
"No, but there are xxy and even xxxy males. You must have a y chromosome to be male."
] |
[
"How long before a robot can ride a motorcycle like an expert?"
] | [
false
] | How long do you think it will be before a robot can ride like this: . I mean - a human sized and human shaped robot that can ride a motorcycle designed for people - not a robotic motorcycle or some such. I got the idea for this post after seeing the video in this submission: . . Edit Hapax_Legoman, obnoxious as he is -... | [
"\"anything that sounds real cool.\"",
"But that's not what I thought.",
"Here's a question for you - if you went to a science museum would you complain to a curator about an exhibit that featured a robot riding a motorcycle?",
"r/asktechnology",
" doesn't exist.",
"You're the kind of person that feels to... | [
"I'm guessing someone could engineer something like that today, we have the technology to balance robots quickly and even have the technology to build robots that can drive down a complex path without gps. But it wouldn't be trivial and would require a decent amount of funding. ",
"Anyway, any answers here will b... | [
"From what I can tell it's mostly a balancing problem, and I don't see that as being overly complex. Engineers like Dean Kamen have mastered building stable robots/vehicles that can balance really well; I am speculating that this could be extended to something like a motorcycle. "
] |
[
"What will be the flash point of two flammable liquid mixture?"
] | [
false
] | null | [
"Not quite. The flash point of the mixture absolutely depends on the mixing ratio and the type of fluids, but is nowhere near linear. There are a number of models developed to describe it, for more information see ",
"here",
". ",
"This",
" is an open access paper that focuses on mixtures that exhibit a min... | [
"Pretty close. The vapour pressure of a mixture often deviates from a purely linear one based on the mixing ratios, but to a first approximation the flash point will go linearly from -10 to 35 as a function of the amounts of each."
] | [
"Huh, I'd have guessed it would essentially be the lower flash point rather than a sliding scale.",
"Since that one might flash at it's temp (still the same chemical after all) then trigger the other one.",
"But perhaps that's the \"non-linear\" part."
] |
[
"I often hear 'Northern California is Overdue for an Earthquake'. Is this true? How do we know?"
] | [
false
] | To clarify - how can we say earthquakes are 'Overdue'? How far back do our records go? Does 'Overdue' mean any day now, or a hundred years from now? | [
"I was able to find ",
"this press release (PDF)",
" for a study that measures fault creep (the sliding of each side of the fault against each other), although I couldn't find the study itself. Fault creep is a good thing, it's basically the slow release of energy. When the fault \"locks\" and the sliding is re... | [
"Put your two hands together with oil on them and see how nicely they slide back and forth. Now do it with dry hands and a slight pressure. Notice how your hands somewhat stick to each other and instead of being able to free slide the pads may hold and once enough pressure builds up the hands slide a bit at once? T... | [
"Future technology? Fracking has been causing earthquakes for quite awhile now. This would be a nice spin on it for the oil companies tho."
] |
[
"Do those who sleep for longer intervals live longer lives?"
] | [
false
] | I've noticed that many of my friends either sleep for very few hours a night (5-7) or for very long periods (10-12). Are there any studies that have been done which attempt to gauge levels of happiness, mood, or lifespan on these different sleep patterns? | [
"Statistically, people who sleep longer than 9 hours a night have an increased risk of death. The study did not demonstrate a causal relationship however. For example, people who are already ill tend to sleep longer, and longer sleep could be an indicator of existing ill health.",
"\n",
"http://www.journalsleep... | [
"In agreement with other two posts. To add:\nThere are currently prospective cohort studies that are measuring the relationship between sleep patterns in middle age and death rates of different diseases later in life. But they will take decades to complete. ",
"Can't emphasize enough the reverse causation iss... | [
"Quite the opposite. Sleeping for more than nine hours per day is linked to increased risks of back pain, heart disease (esp. for women), obesity, and diabetes."
] |
[
"In a sealed heated room with only a window and you open the window to the freezing cold outside, is there movement of air or just heat/cold transfer?"
] | [
false
] | I am thinking for air to move, you need two holes in the room. One to draw in air and the other to let air out. HOWEVER, I'm thinking one of two scenario's is happening in my prescribe above mentioned situation. scenario #1 - since cold air is more dense, I'm thinking it would just flow into the room via the lower part... | [
"Yes, that window example answered another thought I had. Thanks!"
] | [
"Yes there will be movement of air by natural convection. Lets assume the pressures between the room and the outside are constant, that way we have no spontaneous movement due to pressure differences. As heat diffuses from the hot air to the cold air near the window, that cooled down hot air will now be more dense ... | [
"Air, at the molecular level, is a lot of different molecules (in our atmosphere mostly N2, with some O2, CO2 and others) all bouncing around in between eachother. The average kinetic energy of all the particles bouncing around correspond to the temperature of the gas.",
"So, you have two regions separated by a w... |
[
"What is stress?"
] | [
false
] | Language in articles/studies seems to suggest that stress is an objective, measurable, condition. Yet individuals discuss stress as a more intangible, metaphorical concept. 1) For example, I see articles/studies that say things like "Reading cuts stress levels by 68%" or "Stress shrinks the brain" -- what is the 'stres... | [
"First, the experience of stress and the definition of stress will be different, and I believe that is where part of your question comes from.",
"Language in articles/studies seems to suggest that stress is an objective, measurable, condition. Yet individuals discuss stress as a more intangible, metaphorical conc... | [
"I might be mistaken, but your question seems to be implying that stress is some kind of unhealthy thing to be done away with. Excessive stress can be debilitating, but so can excessive tranquility, or excessive enthusiasm for that matter. Like any emotional state, stress plays an important role in the life of an... | [
"Unfortunately there isn't a definite answer to this question. There isn't a clear consensus on whether stress is the cause of the mental/physical distress or if it is the response itself. I think this is a question that is probably going to be investigated more in the future so that medical researchers can learn... |
[
"What are some simple but stunning science experiments or demonstrations that you know of? I am teaching Science in a developing country and really want to spark the students' interest."
] | [
false
] | Hello, ! You might remember me from a few months back, when I worked with you to answer questions from 6th graders. I'm back, with another education-related request! I am currently with a volunteer organization teaching in the Marshall Islands. I am in Majuro, the main island, for mid service, so I have the luxury o... | [
"I've always liked seeing a ",
"magnet fall slowly down an aluminum tube",
". ",
"Wonderfully counter-intuitive and opens up a lot of discussion about something that is hard to visualize. "
] | [
"This actually works much better with a copper pipe, and the stronger the magnet the slower it will fall. The magnet will induce an emf field in the pipe and oppose the falling direction of the magnet. I've used this in my classroom and it really has that Wow feeling to the students."
] | [
"Inertia: Pull a cloth from under a plate. Make sure the cloth doesn't have a hem.",
"Centripetal force: fill a cup with water, attach string to the top rim, and swing it around your head. Demonstrate that the water stays in the cup.",
"You can teach tides and moon phases together, having students plant sticks ... |
[
"At what point in time did mental diseases like schizophrenia get introduced into our species and do other animals suffer them as well?"
] | [
false
] | null | [
"Mental illness has likely affected the human species as long as it has existed, although categorizing mental illness into specific groups like schizophrenia is relatively new. (Schizophrenia was not labeled until 1908)",
"It's difficult to determine the effect of mental disorders in non-human animals, since we h... | [
"http://genomebiology.com/2008/9/8/R124",
"There is a theory that the changes in the ways the brain functions that were necessary for our minds develop as they have may have allowed for problems like schizophrenia to develop as well.",
"In this study we find a disproportionately large overlap between processes ... | [
"Please allow me to broaden this question a bit - I think it might fit into this topic - and, yes, I feel a bit stupid, too: \nNon-primates, such as big cats, which are held in non-species-appropriate captivity, tend to develop a certain behaviour as one can see here: ",
"http://www.youtube.com/watch?v=bwX-KGm4uR... |
[
"What non-biological factors contribute to regional soil fertility?"
] | [
false
] | I'm looking to develop a simplified model for estimating soil fertility across arbitrary, random terrains that are generated by a computer program. I'd like to understand what geographical and geological factors are predictive of soil fertility in the real world, in order to make my model reasonably believable-looking.... | [
"The limiting factors in plant growth tend to be access to water and inorganic nutrients like nitrogen, phosphorus, and metal ions. ",
"Water retention ability and porosity are important because access to water limits the amount of photosynthetic tissue that can be maintained. A plant pulls water from root level ... | [
"Type of parent material",
"Soil texture (sand, silt, clay)",
"Bedrock; depth to and structure affect drainage",
"Topography; height and steepness of hills",
"Latitude",
"Altitude",
"Aspect; south-facing gets more sun and is warmer than north-facing",
"Nearby mountains; western side is wetter than eas... | [
"A lot of places that set glaciated are or were extremely fertile.",
"Growing season length-depends on a few things like lattitude, temp, sunshine.",
"Adjacent to large bodies of water-the Fingerlakes region in New York can host plants that only grow south two or three regions.",
"In NE Iowa there are tallus ... |
[
"Why are microphones so much smaller than speakers?"
] | [
false
] | How can microphones still pick up low frequency vibrations if the size of the thing inside that vibrates is smaller than the wavelength? We value larger speakers presumably because they can produce lower frequency vibrations, but we don't see huge microphones. | [
"You don't need the full length of a wave to pick it up. The physics behind it can be complicated, but basically there is a piece of metal between magnets and the flux of the metal as it move in the pressure wave creates a voltage in the magnets. This voltage can be very small, as long as it's measurable. Once it's... | [
"For a loudspeaker you need to move a certain amount of air per stroke in order to produce a given sound pressure.\nThat amount is a function of wavelength, so deep tones need either a large area loudspeaker or very deep stroke.",
"The reason we don't just use very large loudspeakers in the entire audible range i... | [
"You can also use large speakers as microphones. For example you can put a 15\" speaker on a bass drum and record it that way. Microphones are really just the reverse of speakers. You can even play music through microphones. "
] |
[
"Is there such a thing as 'race'? There are species... And cultures... What is a race?"
] | [
false
] | Is there actually a genuine category of 'race'? What is it? edit: How can a person be a 'racist'... is this just a misnomer? | [
"\"Race\" is not a word with a precise meaning. It can entail anything from genetics to culture. There's a meme going around that \"race is a social construct\", which is terribly misleading because while it's technically true for certain academic definitions of race, it sounds to a layman like it might mean someth... | [
"Ethnicity might be a better term. The idea is that groups of people share genetic traits that are common or completely ubiquitous within the group and not seen outside of the group. If you take it a step further you find it isn't separated into clear cut groups but is a continuum with higher concentrations among s... | [
"It's important to note that those trees, and population clusters are using SNPs in non-coding DNA, since non-coding DNA mutates very fast.",
"Fast enough to pin down the",
" longitude and latitude",
" of your origins. ",
"\nBut it's really cool how distinctly the nations of Europe cluster.",
"I'm not sur... |
[
"Do cats and reptiles have similar eyes because of convergent evolution, or could they maybe be using the same genes?"
] | [
false
] | null | [
"You would need to clarify what you mean by \"similar eyes\". If you are referring to the vertically elliptical pupils that cats have (narrow rather than round), then yes, it is probably convergent. If you look at an evolutionary tree of the terrestrial vertebrates, vertically elliptical pupils appear in a handful ... | [
"Convergent evolution. Though they may sometimes look similar, cat and reptile eyes are put together very differently.",
"For one thing, when reptile eyes contract and dialate, they use striated muscle, like you have in your arms, while cats use smooth muscle, like you have to control your blood vessel dialation-... | [
"//edit",
"Excuse me I was wrong.",
"Cats evolved to be nocturnal hunters, and they can see well in very dim light. Because their eyes are so sensitive to light, cats need precise control over the amount of light reaching their eyes.",
"Being able to reduce the pupils to slits rather than tiny circles gives t... |
[
"Hey Reddit! Has anyone taken an Anatomy and Physiology course at college and managed to find some great online learning resources/software to help them with the harder parts of the class?"
] | [
false
] | [deleted] | [
"i can recommend books:\nAnatomy : Grays if you like pictures, Snells if you like words",
"Physiology: Guyton and Hall is, IMO, the best book ever written and should be read by all people regardless of what they study. It is a fascinating and highly detailed explanation of how your body works. ",
"If you dont h... | [
"Many things will cost money. In terms of an atlas, Netter is well known but I prefer Clemente. However, free tends to prevail so I would recommend google body:",
"http://bodybrowser.googlelabs.com/",
" "
] | [
"I've been trying to talk to my students about this all semester, and, for the most part, they just test themselves repeatedly. For instance, I've provided them with pictures of all the models so they can label each structure one by one. Then they skip the ones they got right before in order to focus on the ones th... |
[
"Can you teach yourself to enjoy pain?"
] | [
false
] | There are many people who enjoy or at least don't seem to mind putting themselves under a lot of pain: masochists, body modification lovers, people who enjoy fights and so on. Is there any neurological difference between them and "normal people"? Or can anyone learn to feel less pain or even enjoy it? | [
"Does this matter so much? The context is the same. Any answer will be welcome.",
"Or should I always define my question in a specific field of science?"
] | [
"Does this matter so much? The context is the same. Any answer will be welcome.",
"Or should I always define my question in a specific field of science?"
] | [
"I've actually wondered about the possibility of neural differences between masochists and non-masochists before, so I did a literature review of the area. My finding, unfortunately enough, is that there is virtually no scientific research into masochism; whether that's due to ethics, or social norms, or whatever, ... |
[
"What exactly happens when your ears are ringing, and why does it happen?"
] | [
false
] | [deleted] | [
"Oooh oooooh, this is one that I can actually answer (somewhat vaguely because this is mostly from memory)",
"The sensation of ringing in one's ears is known as ",
". Inside your inner ear, there's a whole smorgasbord of little organs, most of which have the function of allowing you to hear sound. I forget the ... | [
"Neuroscientist here. This is not my specialty but I'll try my best. Using mostly layman's terms and trying to be succinct, so sorry if I over-simplify.",
"Pasta's correct that you have lots of little \"hair cells\" in your cochlea that are each tuned to different frequencies. When the stereocilia (little hairlik... | [
"How about the temporary ringing in the ears that come out of nowhere sometimes, and passes within a minute or two?"
] |
[
"How are the fundamental forces related, and how does the weak force fit in? (many questions)"
] | [
false
] | Hi, I hope I'm not breaking any rules or etiquette with this post, but I've got a lot of questions about the fundamental forces. From what I understand, gravity has one property (sorry I don't have a better word for this) and reaches it's lowest energy state when anything displaying this property (mass) is brought clos... | [
"From what I understand, gravity has one property (sorry I don't have a better word for this) and reaches it's lowest energy state when anything displaying this property (mass) is brought close together. Electromagnetism has two properties, positive and negative charge, that reach lower energy states when brought t... | [
"What are the eight different charges of the strong force? I've only heard of red, green and blue, and you said didn't count anti-charges as a charge of its own!"
] | [
"In technical language they are the \"generators of the SU(3) gauge group\". If you want to use colors to describe them, then one description is the color combinations of the ",
"eight gluons",
". But as I tried to describe, the \"colors\" way of thinking about things should be taken with a grain of salt. For e... |
[
"How does spontaneous symmetry breaking explain the Higgs field?"
] | [
false
] | null | [
"I don't really know what you mean by \"explain\" the Higgs field. IF there is a scalar field that has an energy dependence such that it is in some symmetry broken state THEN it can have a non-zero vacuum expectation value. IF a field with a non-zero vacuum expectation value couples to something like the electron f... | [
"Like ",
"/u/cantgetno197",
" I'm not totally sure what you mean by \"explain the Higgs field.\" The Higgs is a field which spontaneously breaks symmetry - the Higgs comes before spontaneous symmetry breaking, in a sense. In case what you're asking is why spontaneous symmetry breaking helps the Higgs give mass ... | [
"Technically yes.",
"The potential (which you differentiate to get the force) is Exp[-r/R]/r, where R is a constant (usually considered to be the range of the force), and where Exp[x]=e",
" but reddit insists on reading r/R as a subreddit and so won't let me use it in a superscript. At distances much shorter th... |
[
"When someone recalls a sensation, what parts of the brain are involved?"
] | [
false
] | [deleted] | [
"Yes -- there is evidence that primary sensory areas are somewhat reactivated (in addition to other areas), but not to the same extent as actually seeing the thing. ",
"I apologize if my answer is a bit short, but questions about \"what part of the brain is active when X happens\" do not always yield informative... | [
"Thank you. I haven't been on this account for a while, but you provided useful information."
] | [
"If you took every bit of known activation imaging and combined it, wouldn't the data reveal suggestive associations? What about combining this data with all biophysical markers associated with given activiation states?",
"If public school was better we'd probably have enough people to make rapid progress on thes... |
[
"How exactly is the \"direction\" of the flow of power measured in a alternating current system?"
] | [
false
] | (Quick info to start with, I'm from Germany, so I may make some mistakes with the technical vocabulary and some best practices may differ) So this is a kinda awkward question for me to ask, considering I'm an electrical engineer planning the electrical systems for all kind of construction projects, and I like to think ... | [
"There's one thing I think most people are forgetting. Let's assume a power factor of 1. ",
" is alternating (it is a sinusoid). ",
" is also alternating (it is also a sinusoid). The ",
" is ",
" alternating. ",
"If power factor is 1, the current and voltage are in phase, which means they positive and neg... | [
"The real power is oscillating as well, it's just that the mean value of the real power is V",
"cos(theta).",
"There is a double frequency component of oscillating real power on top of it."
] | [
"Fundamentally, the power is flowing in the fields rather than the voltage and current. The direction of power flow is determined by the ",
"Poynting vector",
".",
"Edit: misspelled Poynting as pointing"
] |
[
"Why does red plus blue make magenta with additive color mixing?"
] | [
false
] | Blue is a frequency of about 450nm, red is 750nm. When these two are mixed together, we get magenta, which is a kind of bluish-violet. But, violet is 390nm, so we are getting something with a lower wavelength (maybe 425nm or something). I would have thought that we would have gotten something between blue and red (say ... | [
"To understand the answer, it helps to step back and consider how color vision works in humans. Under sufficiently intense lighting when color vision is possible (formally called ",
"photopic vision",
"), it is mediated by specific biological dyes located in ",
"cone cells",
" in the retina of the eye. The... | [
"Wrong answer! The explanation on the wikipedia page links to a page that shows a completely inaccurate graph of the cone responses:\n",
"http://web.atmos.ucla.edu/~fovell/AS3/theory_of_color.html",
"Compare the graph that crnaruka linked to:\n",
"http://upload.wikimedia.org/wikipedia/commons/0/04/Cone-fundam... | [
"Visual Neuroscientist here and our friend ",
"/u/crnaruka",
" knows whats up. one point of clarification, and a minor one at that: It's true that the color distinction through separate channels occurs in the retina (through the different cone pathways) but a lot of \"color perception\" takes place in the visua... |
[
"What would happen if our solar system was separated from our galaxy?"
] | [
false
] | To explain this in a narrative: Our galaxy finally collides with the near by Andromeda. Instead of being sucked into its galactic center Sol is lucky enough to be flung out on one of its tidal tails. In essence our solar system is flung out into space and starts to move through the universe as a "rogue" solar system of... | [
"There's a hypothesis that a ",
"mass extinction ~450 million years ago was caused by a gamma-ray burst",
". If we were flung out into intergalactic space we would have basically zero chance of getting hit by one of those up close."
] | [
"besides the view at night?",
"To be fair, ",
"the view at night",
" would be highly resplendent."
] | [
"Not if we were flung out as part of a tidal tail-- in those circumstances it's a tidal force on a large number of stars, all of which get dragged out into the tail. If the Sun were flung out as part of a 3-body interaction with other masses, then the planetary orbits might well get disturbed (it should be noted th... |
[
"Is friction a point force or distributed force?"
] | [
false
] | null | [
"Can you go into more detail on why you would ask this? In theory friction is the result of tiny defects in surfaces gripping each other, so it is a distribution of point forces. However, it is even enough that we can model it as a point force if we want for statics purposes."
] | [
"It's modeled as a point force perpendicular to the normal force."
] | [
"Friction is a distributed force because it acts over an area rather than at a single point. However, it's not useful to think of friction as a sum of infinitesimal pieces of friction because friction itself is better understood as a macroscopic force -- the actual physics of friction is usually only talked about e... |
[
"How do they stop the water when building a dam?"
] | [
false
] | It doesn't seem possible to build a dam when water continues to flow. How do engineers build around such a difficult situation? | [
"They build another dam! Seriously!",
"Construction teams usually start by building diversion channels, which can be quite a complicated engineering feat itself. These will head around the dam's proposed location. When these are opened up, a temporary dam (called a coffer dam), made of rubble, is put in place t... | [
"Divert water around the site, build the damn, seal the diversion tunnels."
] | [
"Okay. But divert how? Another dam? I feel like your explanation adds nothing that wouldn't be added by \"dams, all the way down.\""
] |
[
"Why are peanut allergies so prominent?"
] | [
false
] | null | [
"As far as I know its not actually more common per birth. Its just that peanut butter is relatively common so before we have a knowledge of this allergy most kids would have dies for an unknown reason leaving no one who was allergic alive. Now we know the allergy exists and we now how to keep people with it alive. ... | [
"Here is one leading theory: ",
"http://en.wikipedia.org/wiki/Hygiene_hypothesis",
"As part of this theory, there is a correlation that populations with higher rates of parasitic worm infections (particularly ",
"http://en.wikipedia.org/wiki/Helminths",
") have lower rates of peanut allergies."
] | [
"There is also a hypothesis that one of the major peanut proteins is similar to a common bacterial protein, so the body is already primed to respond to it as a threat. The problem with this idea is that no one has figured out what bacterial protein this might be."
] |
[
"Has a satellite in a geosynchronous orbit ever been tethered to the earth?"
] | [
false
] | I know there has been talk of space elevators using similar technology. What are the drawbacks/hurdles to stop this from happening? | [
"Find your way onto a sailboat and peek into a few lockers. It'll take you about three seconds to find a length of coiled rope.",
"Pick it up. What's the first thing you notice? It's ",
" And that's just a few dozen feet of the stuff. Imagine what 50,000 miles of the stuff would weigh.",
"Any \"tether\" like ... | [
"you wont find any rope on a sailboat.\nyou'll find a metric boatload of line though."
] | [
"Quarter-inch nylon rope is 1.5 pounds per hundred feet. If my memory is correct, geostationary orbit is about 30,000 km. That means the rope would weigh...74000 tons. The biggest thing we've put in space, the ISS, is under 500 tons."
] |
[
"Could metamaterials be used for radiation shielding?"
] | [
false
] | null | [
"The index of refraction for visible light doesn't really have any bearing on the response of the material to ionizing radiation."
] | [
"The index of refraction of a material depends on the frequency of the light. Every material basically has index of refraction 1 in the gamma part of the EM spectrum, meaning that the gamma rays don’t refract at all."
] | [
"Yes, that's why the index of refraction is always going to be 1 for gamma rays, in any material."
] |
[
"I hear about it all the time and despite researching the topic heavily, I still don't know what quantum computing is or what it does. Anyone care to shed some light?"
] | [
false
] | null | [
"I'm not an expert but I can try to shed a little bit of light on the topic. The idea is that instead of independent bits which can read either 1 or 0, quantum computers have qubits with quantum mechanical wave functions that can interfere with each other and form quantum mechanical superpositions (it's similar in... | [
"quantum medium can have, say, states of -3, -2, -1, 0, 1, 2, and 3.",
"This isn't right. Quantum bits (qbits) are in a ",
" of the states 0 and 1. The value of a qbit is a0 + b1, where a and b are complex numbers and 0 and 1 are states. a and b can be any values such that |a|",
" + |b|",
" = 1. This allows... | [
"quantum medium can have, say, states of -3, -2, -1, 0, 1, 2, and 3.",
"This isn't right. Quantum bits (qbits) are in a ",
" of the states 0 and 1. The value of a qbit is a0 + b1, where a and b are complex numbers and 0 and 1 are states. a and b can be any values such that |a|",
" + |b|",
" = 1. This allows... |
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