title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Is the below-water part of a cruise ship really less dense than water?"
] | [
false
] | Trying to wrap my mind around a cruise ship being less dense than water to float. To get the density of the cruise ship, I'd have to do d = m / v, but wouldn't the 'm' be the mass of the ENTIRE cruise ship, while the 'v' would be the volume of just the ship under the water? If so, that would mean that I have to concept... | [
"No, the volume of the water displaced is equivalent to the mass of the entire ship. ",
"The entire ship, on average, is less dense than water. Mainly because of the enclosed air. ",
"It sinks until enough water is displaced to match the weight of the ship, which is less than the volume of the ship. Thus, some ... | [
"It's \"less dense\" than water because the ship's hull below the waterline is still mostly air. Modern fishing boats will often fill their hulls with foam, which is essentially just \"solid air\", as well (think how small a foam life jacket is. It weighs only a few ounces, yet it can float an entire grown adult). ... | [
"No. The average density of the cruise ship would be its total mass divided by its total volume. The ship will float because this density is less than that of water."
] |
[
"Can some one please explain why time effectively 'slows down' as you travel closer and closer to C?"
] | [
false
] | I just can't get my head around it. You all helped me greatly on my last question. Many thanks. | [
"The thing is, Traveling through time and space is virtually the same thing. Lets call it space-time. space-time doesn't just have a maximum speed, it has a fixed speed. everything goes the same speed. ",
"Now you might think, i'm currently barely moving at all, i'm not moving very fast. But you are, you are movi... | [
"The example usually given is imagine two mirrors on opposing sides inside a box, and you bounce a particle of light between them. It takes said particle a fixed amount of time to ping between the two mirrors because the speed of light is fixed(See EEP). If you were to run with the box, the particle would have a gr... | [
"This is the best explanation I have ever heard to solving this conceptual problem. It had never occurred to me to think of traveling through space / time as a trade off given a fixed rate."
] |
[
"How can we reliably establish the \"now\", irrespective of Earth and whatever else?"
] | [
false
] | Is there an objective way to establish the "now"? For example, I thought maybe current age of the universe would be one method, once we have the instruments to accurately detect that sort of thing. Another idea I had, albeit far more crackpot, was using sports scores, as they're randomly generated numbers that rarely r... | [
"It's not even possible to agree on the ",
" of events for different relativistic reference points. ",
"You could maybe do something like \"UTC plus relativistic frame\" - that is, apparent time/date on earth plus location and velocity relative to some agreed-upon reference (also earth?)."
] | [
"This is correct, but just so no one gets the wrong impression, \"different relativistic reference points\" means events separated by space.",
"Relativity is weird, but for something like a car crash, all observers are going to agree that the cars reached the impact point at the same time. In other words, no obse... | [
"Only if points A and B are at rest with respect to each other."
] |
[
"Are Brain Damaged people cognizant of how much smarter/functional they used to be?"
] | [
false
] | There are several ads about "Not texting while driving" currently going around online and tv. One features a young guy who shows he sent a text saying "yea" before flipping his car over and causing permanent brain damage to himself. He goes on to speak about how much harder everything is now. And I wonder. Just how cog... | [
"I am doctor of physical therapy who is a certified brain injury specialist and works in a brain injury rehabilitation facility. ",
"The answer to your question is that some brain damaged people are very cognizant of how much more functional they used to be (I avoid using the word \"smart\" in most contexts, as ... | [
"Sorry I can't answer this, but how related is it to trying to remember what it is like to feel sober when you're drunk? Maybe I'm the only person who has ever done this, but when I'm drunk I remember logically that my thinking is clearer when I am sober, but even if I try I can't get that feeling of clear thinking... | [
"It would hinge upon the part of the brain that is damaged. Brain damage doesn't always occur universally to the entire brain, you can have one part damaged and the rest relatively unharmed. The disability would then hinge upon the part of the brain that is damaged. ",
"However, It is not particularly hard to rec... |
[
"How does adrenaline make your muscles stronger?"
] | [
false
] | null | [
"13 or 14 years ago I was unloading a truck at work and a rolling pallet with about 1200 lbs. of frozen french fries came off the back of the truck and onto me. I didn't have time to get out of the way, but did have time to get jacked on adrenaline. I caught the pallet and heaved it sideways back onto the truck. wh... | [
"Adrenaline (or epinephrine as it is more commonly called in a scientific context) is a hormone (it is also a neurotransmitter but that isn't relevant) that binds to proteins on the membrane of muscle cells. This activates a cascade of chemical reactions that ultimately increases the production of ATP, which is the... | [
"Tearing of muscles, tendons, and ligaments. Not pleasant, but better than death. "
] |
[
"When a person observes light at the limits of the visible spectrum, what does the transition to UV or IR look like?"
] | [
false
] | Does it gradually fade away or is there a point where it suddenly goes black? | [
"When you look at a rainbow what you see answers your question. A rainbow also contains IR (outer side) and UV light (inner side), you just dont see it. Its the same with a prism, it kinda just fades out.",
"See this photo",
" (note the camera may contain some uv/ir filters) best example is to look a rainbow yo... | [
"Actually the IR part is quite accurate on the photo. On the UV side you would see more somehow unsharp violettish (surprise 😁) parts, as with black light.\nIn addition the lens in our eyes offers high chromatic abberations, hence IR/UV light do not only fade out by the seen intensity but by the ability to focus t... | [
"A rainbow is a good way to judge this, but it does depend on light intensity. You won't see the IR or UV levels when their relative intensity is less than the blue scatter background. If you are unlucky enough to get a near IR laser in your eye you will see a red dot, but you would not see that frequency in the... |
[
"What is the “spin” of an electron?"
] | [
false
] | First of all, I have absolutely no education in quantum physics whatsoever. I imagine the spin of an electron like a planet rotating on its axis, if the orbital is complete, one electron clockwise and the other anti clockwise. The problem with this reasoning is that it only work with a 2 dimensional orbit, if we think ... | [
"Electrons are not rotating balls, and electron spin does not describe electrons as rotating balls. Electron spin is an intrinsic angular momentum that it carries. It's called spin because mathematically it ",
" how we can describe a physical spinning ball."
] | [
"Spin is just an intrinsic angular momentum that particles can carry. An electron will always have spin 1/2; you can never get rid of it."
] | [
"One thing that has always bothered me is that if spin corresponds to a physical, measurable angular momentum, what \"direction\" is it?",
"But I'm guessing the answer is that it has no well defined direction (uncertainty principle and all). If you measured the angular momentum of an electron you would basically ... |
[
"Whats the lowest watt bulb that can be made to run on mains voltage? (alt: what's the point of low voltage lighting?)"
] | [
false
] | [deleted] | [
"A couple of reasons. For very low watt bulbs the filament must be very very thin and long to allow for a high enough resistance to operate at main voltage. If the voltage is lowered, the filament can be much more robust.",
"The next is safety. With some building codes it is easier to run low voltage line in a... | [
"Low-power halogen bulbs are more efficient at low voltage, enough to offset the transformer losses. The filament is much thicker and can run at a higher temperature producing more light for the same electrical input."
] | [
"As ",
"/u/haplo_and_dogs",
" mentions, there can be (when designed and installed properly) increased electrical safety and efficiency. The other big benefit is that you can run them off of 12V batteries or power supplies (like you'd find in an RV or trailer) and not have to waste energy running an inverter. ... |
[
"Why and how did we evolve to a mostly right handed species?"
] | [
false
] | and why are there exceptions? | [
"There's actually an embryological reason why most people are right handed. Initially as infants, we receive more blood flow to the right side of our brain...which generally is the more creative, abstract area. Yet as we reach around age 2-3, the cerebral blood flow shifts asymmetrically to left side (which of co... | [
"The left/right logic/creativity stuff is bunk.",
"See: ",
"http://donaldhtaylor.wordpress.com/writing/modern-myths-of-learning-the-creative-right-brain/",
"Also: ",
"http://theconversation.edu.au/mondays-medical-myth-the-right-side-of-your-brain-controls-creativity-3951"
] | [
"I studied Primate evolution in college and came across this wonderful summation in Primate Diversity by Dean Falk: ...most studies indicated that populations of nonhuman primates fail to show the dramatic preference for general use of one hand that characterizes Homo sapiens. On closer inspection, however, it beca... |
[
"If looking further into space means looking back into time, can you theoretically see the formation of our galaxy, or even earth?"
] | [
false
] | I mean, if we can see the big bang as background radiation, isn't it basically seeing ourselves in the past in a way? I don't know, sorry if it's a stupid question. | [
"The stuff that we're seeing in the distant past is also really far away. To see something, say, a billion years ago, it has to be far enough away that its light traveled toward us for a billion years. So we're not seeing our own past, we're seeing the past of other stuff.",
"We can't see our own past this way ... | [
"So theoretically, if we could instantaneously teleport or pop through a wormhole to some point 4.5 billion light-years away, and had the tech to view our solar system from that distance, then we could actually observe a newly formed Earth (i.e. look into our own past)"
] | [
"Yep"
] |
[
"Biotech/Pharma/Drug researchers, how do we educate the general public on how medicine is made?"
] | [
false
] | The general public seems to have this idea where cures are being held back by "Big Pharma", or that they are right around the corner. The drug industry has somehow joined the oil and finance companies in the axis of evil. How do this happen? What factors contribute to this sentiment? Secondly, how do we spread awaren... | [
"How do this happen?",
"It happens when health care costs rise to the point that many can't afford treatment while some pharmaceutical companies enjoy record profits.",
"It happens when some pharmaceutical companies try to hide adverse effects of medications (Avandia, Vioxx).",
"It happens when most pharmaceu... | [
"I'm wondering more about the ideas of \"quick cures\" and the difficulty of developing medicine, is it possible...or even necessary to relay this kind of information to the general public?",
"I feel as is this negative stigma around big pharma has alot of unintended negative effects. Just look at all the natura... | [
"http://www.youtube.com/watch?v=HVTaJn1dMrs&feature=related",
"thats how"
] |
[
"How truly accurate could this be monitoring my sleep?"
] | [
false
] | I bought a handband that I wear while I sleep. It pairs with my phone via bluetooth and when I put it on, it monitors my sleep. I am curious, from a scientific standpoint, how accurate this could be or is representing my sleep cycles at night. For what it's worth, the app recognizes when I have the headband on, and whe... | [
"Without investigating this specific product in any depth, the idea of monitoring brainwaves is based in science, and one's brainwaves do change during sleep. So in principle, one could create a record of the different phases of sleep by recording the brainwaves that are known to accompany the different phases.",
... | [
"Fair enough. I used it, worked really well to wake me up. I felt great despite it being a short amount of sleep. I also remember waking up when it said I did. It interests me that this could truly be working, especially that well."
] | [
"It's relatively easy to measure brain activity through electrical fields and then compare this to sleep/wake.",
"The real question is if this tells you anything other than what you could figure out on your own. Without access to the thing it would be difficult to tell."
] |
[
"Is there no scientific study on the correlation between the fatality rate and speed of impact in in car crashes?"
] | [
false
] | [deleted] | [
"The scientist in me sees a problem with that.",
"Anecdote.",
"Sample size of 1."
] | [
"The scientist in me sees a problem with that.",
"Anecdote.",
"Sample size of 1."
] | [
"Sorry, I'm clearly a moron. ",
"http://www.nist.gov/index.html"
] |
[
"The process of tanning, sunblock and skin cancer."
] | [
false
] | I could not get a definitive answer searching on Google. If sunblock blocks UV light then what makes you tan? Then if UV lights are used in sunbeds why do you still wear sunblock to block them? Does skin cancer develop on areas of your skin that were exposed to sun or can it start let's say on your bum that never sees ... | [
"This actually brought up an interesting question in my mind. Exposure to UV light stimulates melanin production and melanin is able to absorb UV light and essentially render it harmless.",
"So wouldn't it make sense that there would be some sort of equilibrium at which tanning actually has positive, cancer preve... | [
"If 15 minutes of sun/day gives you an adequate amount of Vitamin D, then why are so many people in the US vitamin D deficient? Do people really stay inside that much?"
] | [
"Getting your dose of UV for vitamin D is similar to braving through traffic to get to work though you could in theory get killed doing so. ",
"As far as I know the wearing of sunblock has something to do with UVA and UVB differences. UVA IIRC is much more harmful. Perhaps you could get more out from here ",
"h... |
[
"Why is 1/0 undefined, rather than infinity?"
] | [
false
] | null | [
"I'm going to copy my responses to another, similar question here.",
"The main idea here is that you ",
" define 1/0 = infinity, but then you would ",
". That is, there is no way to consistently define algebra (addition and multiplication) over the extended real numbers (the regular numbers with infinity).",
... | [
"You ",
" define 1/0, if you really want to.",
"It's usually undefined because no value for 1/0 is consistent with some of the most fundamental properties of algebra.",
"Say 1/0 exists. I'm gonna call it Michael. Let's also assume that basic algebra rules apply. By definition of division, if 1/0 = Michael, th... | [
"Why is 1/0 undefined, rather than infinity?",
"It is not possible to define 1/0 because infinity is not a number. That is to say, it does not exist as an element in the set of real numbers ",
". Accordingly, infinity cannot be the result of any operation. In standard analysis, infinity only appears as a sym... |
[
"Do electromagnetic fields distort spacetime like gravitational fields?"
] | [
false
] | [deleted] | [
"Yes, everything with energy acts as a source for the curvature of spacetime.",
"PS The phrasing of your title is a bit off. The distortion of spacetime ",
" gravity."
] | [
"In Einstein's equation, the \"source\" term (which can be thought of as causing the curvature) is the entire ",
"stress-energy tensor",
", so ",
" that has a nonzero energy density will gravitate. (Note that even strains and pressures appear in this tensor and can alter the curvature of space)."
] | [
"But you ",
" define a tensor that corresponds to the electromagnetic field that's also Lorentz covariant, so there will always be a nontrivial contribution to the stress-energy tensor from this. The question was about electromagnetic fields, not point sources."
] |
[
"How valid are the claims in favor of alternative sleep cycles such as Uberman or Dymaxion?"
] | [
false
] | I've been reading about polyphasic sleep cycles like the Uberman cycle in which you sleep for 20-30 minutes once every 4 hours, or the Dymaxion, in which you sleep for 30 minutes once every 6 hours. These sleep cycles drastically reduce the amount you're sleeping, but (supposedly) maintain, or even increase, the amount... | [
"There is no scientific basis for these schedules. They are simply forms of chronic sleep restriction, which lead to the accumulation of cognitive deficits. I discussed chronic sleep restriction and its effects in detail ",
"previously",
". ",
"Chronic sleep restriction -- whether achieved by polyphasic sleep... | [
"These types of alarm devices and apps haven't been scientifically validated. I actually ",
"answered a similar question recently",
". In brief, the idea that sleep is more restorative if there are an exact integer number of NREM/REM sleep cycles is not empirically supported."
] | [
"Hm, this is a bit of bad news, but thank you very much for the response. I watched a few videos online. What do you think of this: ",
"http://www.youtube.com/watch?v=Iq_VKY0L_BA",
" ?",
"Is a lot of it just a placebo effect? He seems very in favor of the cycle he tried.",
"Would it be incredibly detrimenta... |
[
"Is there less gravity the higher up you go?"
] | [
false
] | conversely the closer I go to the core of the earth would there be more gravity? How would I calculate this? I'm asking because I think the closer I get to the center of the earth there is less mass to pull me, as I'm leaving a lot of it behind me. EDIT: I think I should clarify that by "higher" I meant going to a moun... | [
"As you move closer to the center of mass of an object, the apparent force of gravity feels higher. I've been wondering the same. Here is my reasoning, would somebody please correct me if it's wrong:",
"As you go closer to the center, there's less mass below you, so that decreases the force of gravity. However, y... | [
"I was going to correct you, but then I looked it the fuck up, and you're right. Hats off. You are at your heaviest at almost half way to the center, about 2000 miles down.",
"Follow the blue line"
] | [
"The attractive force of gravity acting on any two objects (e.g. you and the Earth) can be calculated using the equation ",
"F=(G x M x m)/r",
"where",
"\nG = the gravitational constant, 6.67 x 10",
"\nM = the mass of the first object; Earth's mass is 6 x 10",
" kg",
"\nm = the mass of the second object... |
[
"Would the gravity on the moon closest to the earth be greater than the gravity on the opposite side?"
] | [
false
] | Was just thinking about this when i was looking at the moon and thinking about the gravity present on it | [
"It's the other way around. When you're on the part of the Moon that is closest to the Earth, the gravity of the Earth pulls you in the opposite direction as the gravity of the Moon, so it partially cancels out the gravity of the Moon. When you're on the other side of the Moon, far away from Earth, both sources of ... | [
"You could measure the difference with a reasonably accurate scale, but you won't notice it otherwise.",
"You actually ",
" measure it with a scale.",
"Earth's gravity does exert force differently on opposite sides of the Moon, but your weight on the Moon wouldn't be any different because of it. The Moon (and... | [
"As you descend into the earth, the pull of gravity would start getting stronger due to how much denser the inner layers of the earth are compared to the surface, but would eventually start getting weaker again due to gravity cancelling out the closer you get to the center of a sphere."
] |
[
"My dad is an old farmer, and he says that wherever a snow drift is during the winter, in the summer that spot will have a lot more nitrogen in it. How would this work chemically? And would snow capture bioavailable nitrogen?"
] | [
false
] | null | [
"Quick quotes from 3 sources.",
"An inch of snow contains ~ 7 milligrams of Nitrogen per square foot. ",
"An inch of snow deposits 0.3 kg of Nitrogen per acre.",
"It is estimated that 2 to 12 pounds of Nitrogen are deposited per acre (annually) as a result of snow and rain.",
"All of these source go on to s... | [
"Excellent, thank you."
] | [
"Excellent, thank you."
] |
[
"If the speed of light isn't constant between mediums does that mean that time isn't constant between those mediums either?"
] | [
false
] | Preface: I am no expert so my question could be undermined by any one of the following false premises. But here is what I is true? So then, my high-school physics education would lead me to assume that the perceived passing of time is then a product of your velocity AND your *relative SOL (ie, your current mediums rel... | [
"No. The speed of light doesn't really change inside of mediums, like glass.",
"What is actually happening is that the photon travels at c until it hits a molecule of glass, get's absorbed, remains absorbed for some small period of time, and then get's re-emitted.",
"The speed of the light (the speed of a photo... | [
"Gracias. That makes sense; consider my assumption thus retarded :)",
"ps: on a side note, this (askScience) is pretty much the coolest thing ever for those of us out of school but still in love with learning :)"
] | [
"From your link: ",
"Denser media, such as water,[58] glass,[59] and diamond,[60] have refractive indexes of around 1.3, 1.5 and 2.4, respectively, for visible light. In exotic materials like Bose-Einstein condensates near absolute zero, the effective speed of light may be only a few meters per second. However,",... |
[
"How much do volcanoes contribute to global warming?"
] | [
false
] | I always hear global warming skeptics say that volcanoes release more carbon dioxide than our burning of fossil fuels ever can. I would like to know how much of an effect they really have on climate change? | [
"Global estimates of the annual present-day CO2 output of the Earth’s degas- sing subaerial and submarine volcanoes range from 0.13 to 0.44 Gigatonnes per year.\nSee Eos, Vol. 92, No. 24, 14 June 2011",
"Carbon dioxide emissions from energy production are about 33 Gigatonnes per year.\nSee ",
"http://www.eia.go... | [
"As others have said, the anthropogenic annual loading is about 100 times that of the total global volcanic production of CO2 annually.",
"As far as climate change is concerned - their effect is negligible - not only because of the amount relative to human, but also that their contribution can be considered to be... | [
"many will argue they have no effect, yet they did manage to raise earths temp by as much as 20 degrees and brought an end to snowball earth 650 million years ago.",
"short 5 min video on snowball earth and the role volcanos played to end it",
"longer documentary on snow ball earth"
] |
[
"How did pre-clothes era humans survive temperature changes? Were they capable to survive winter naked?"
] | [
false
] | The idea that nature made us manufacture clothes to survive seems strange, because as far as I know,other species don't need to manufacture anything artificial that allows them to go on living, everything is taken care of by instincts (knowing how to drink mother's milk) or surroundings (existence of food). Have humans... | [
"We didn't survive in cold temperatures without clothes, actually! It's important to note, also, that our ancestors had a lot more body hair than modern humans do. Even now, people who have historically lived in colder climates tend to be more hairy than people in warmer climates.",
"But that's pretty much why we... | [
"/u/m0rgaine",
" does well to indicate that early Homo Sapiens had more body hair potentially allowing greater thermoregulation. But as R.W. Dennel (2003) illustrates, the record for Eurasia habitation prior to 1 mya indicates repeated, short-lived dispersal events up to 40 degrees north. Representing multiple wa... | [
"Humans used to live exclusively in warmer climates.",
"Instead of evolving fur to survive in colder areas, we evolved higher brain capacity, then took a short cut and invented clothes before we dispersed into different climate zones."
] |
[
"How fast or big would a meteorite have to be to puncture through the Earth?"
] | [
false
] | I was looking at this , and it just made me think - Is this even possible? Could a man made craft or meteorite go fast enough to literally puncture a planet such as the Earth? | [
"If you change \"big\" to \"dense\" then your question works better. Matter would have to be very dense and be moving very fast to be able to punch through the earth.",
"It has been proposed that super dense balls of quarks, far denser than the normal 3-quark combinations of baryonic matter we know and love (a.k... | [
"Has anyone ever been killed by one of these 1-ton quarks?"
] | [
"I study impact craters.",
"Velocity: First of all, the velocity of anything impacting the earth will be an absolute minimum if it hypothetically is at a full stop and gets drawn in by earth's gravity. The speed it would gain by falling is equivalent to the escape velocity of earth, 11 km/sec. The maximum speed... |
[
"Does everything emit radiation?"
] | [
false
] | This makes it seem like everything thar isnt at absolute zero emits radiation, and we can measure the temperature of an object by measuring the wavelength of the light it emits Can I put a person in some kind of faraday cage and take their surface temperature by measuring the amount/quality of EM energy they emit? Can ... | [
"Yes, everything emits radiation. This is called \"thermal radiation\" and both the spectrum and the intensity of the radiation depends on the temperature of the object.",
"So in theory, you could determine the temperature by measuring an object's thermal radiation. But in reality, there are some complications. P... | [
"You wouldn’t need a faraday cage. You just need to see how much infrared (IR) light they emit. Infrared is a non visible wavelength of light, and light is sometimes referred to as EM (electromagnetic) radiation. There are sensors that can detect IR, which are used in IR imaging (sometimes referred to as heat visio... | [
"An outside measurement of the radiation coming from the light bulb will contain the thermal radiation from the filament, but with dips that correspond to the absorption spectra of the gas and glass, combined with the thermal radiation of the gas and the glass.",
"and of the air in between the glass and your sens... |
[
"Instead of covering and entire ceiling in expensive solar panels why dont we use a smaller more efficient panel and a magnifying glass to focus light on it?"
] | [
false
] | You can use a relatively cheap glass lense to focus the energy over the entire roof to a more compact point and save a ton of money on panels, right? Or would the focused light be too high in energy and the panels to inefficient to metabolize it? (for lack of better word) | [
"We do! They're called concentrator cells, and they are used sometimes when the photovoltaic material is expensive (like gallium arsenide), or when the conversion process is more efficient under greater solar flux. This does add cost to production, though, and at the moment it's cheaper to pump out lots of less e... | [
"Well not only that but efficiency drops with temperature so there is a point where more surface area is more useful than more concentration."
] | [
"In the UK (with limited solar input), medium-temperature thermal power is gaining popularity for domestic heating (rather than the high-temperature systems than can drive a steam turbine).",
"Thermal panels can get water up to 70-80 degrees, which saves burning gas or using electricity to heat the water for radi... |
[
"Why is a full circle 360 degrees? Why not just a round number like 100 or any other number?"
] | [
false
] | null | [
"It should be made clear that 360 is completely made up, it has nothing to do with circles, only how people have used them in the past. For that matter 100 is not a special number in any way either, so having it be 360 degrees or 100 degrees are both equally arbitrary.",
"We use 360, because it has a lot of divis... | [
"Yes! Occasionally, people use ",
"gradians",
" insteads of degrees, which break the circle into 400 grads. This means that right angles are 100 grads which has an appeal. This is also what the deg/grad/rad button on a calculator would use. Apparently it's mostly used in surveying."
] | [
"It comes from Mesopotamian mathematics along with sundials and many astronomical units. The sun takes roughly 360 days to complete a full circle in the sky and it's based on that. They used a base 12 system (duodecimal), as opposed to our base 10 system. ",
"Bonus fact: You get to 10 by counting fingers and 12 b... |
[
"What happens to a group of entangled particles when you measure one of them?"
] | [
false
] | null | [
"Multiparticle entanglement is complicated, for N=3, there's two main kinds, ",
"https://en.wikipedia.org/wiki/Greenberger%E2%80%93Horne%E2%80%93Zeilinger_state",
" ",
"https://en.wikipedia.org/wiki/W_state",
" ",
"What happens when you measure a single member depends on which we're dealing with. For t... | [
"You can prepare the same state a million times and do experiments on the three particles in turn, verifying that the state you keep creating has the desired entanglement.",
"Actually, for this specific example, there's a game you can play (I'm taking this from John McGreevy's notes, which cite Boccio). Consider ... | [
"If you measure 1 particle and the other two become unentagled, how do you know they were ever entangled originally?"
] |
[
"Can a black hole lose enough mass to be visible?"
] | [
false
] | Considering the effects of Hawking radiation, it is known that black holes slowly lose mass as they take in negative energy from nearby virtual particles and it is possible that they will eventually evaporate completely given enough time. Would it be possible, at least in principle, for a black hole to lose enough mass... | [
"/u/Rantonels",
" has already explained the circumstances that cause black holes to radiate Hawking Radiation. But in fact there are many black holes of larger size that are observable because they are accreting matter, a process that produces radiation up to 50x as efficiently as fusion. The most luminous transi... | [
"Black holes in classical and semiclassical gravity always have horizons shrouding the interior. The interior is ",
" exposed. When the black hole evaporates, the horizon just gets smaller. But nothing that is inside can ever get out.",
"With that out of the way:",
"At a certain point the horizon will have le... | [
"True, but that's actually because the matter near the black hole's event horizon is being superheated by friction to the point of becoming extremely luminous, since it's forced to orbit it at significant fractions of the speed of light. The black hole itself would appear as a black disc against the surrounding mat... |
[
"Leaving the army on 30 aug, need some direction."
] | [
false
] | null | [
"Alright \n1) if you have not already applied for VA benefits do so NOW you have up to 1 year for a number of 'presumptive' conditions so go to the doctor and get that all documented thoroughly. I recommend you do this through a veteran's service organization such a Veteran's of Foreign wars. in addition to GI bene... | [
"Thanks for the info, I got started with the VA over a year ago, so all of that is out of the way. You don't wait until you are out anymore. Sustainable energy sounds like an awesome field that I have always really been interested, I guess my big question is how does one get into that? What do you pick? And no i do... | [
"ya, chemical engineering. i'm in the sustainable, alternative energy field."
] |
[
"What would be the result of a human who was given sufficient hormones so that their testosterone and estrogen were in equal, natural (for the respective genders) levels - long term?"
] | [
false
] | null | [
"I don't believe anyone has ever tried that experiment, so I can't say for sure. But you might be interested in some genetic conditions that result in hormonal imbalances:",
"Klinefelter's = XXY",
"de la Chapelle syndrome = XX but male",
"XYY, which affects .01% of men and is pretty much harmless.",
"XXYY, ... | [
"There's also XXX and XO as well. Uhh, what are they - Turner's Syndrome for the XO, and the XXX is simply known as \"Triple X Syndrome\"",
"XO/Turner's - This can have a whole host of effects on the female body. Most of these tend to focus toward reproductive health, but there are a large cascade of other differ... | [
"I think the most important distinction to make is whether this is occuring during development. We have both internal and external genitalia. If you were to do this to a someone who is fully matured, you may develop ambiguous secondary external sexual characteristics (gynaecomastia, facial hair, cliteromegaly, deep... |
[
"Is the shape of an atomic nucleus actually a lumpy clump like in science textbooks?"
] | [
false
] | null | [
"I think this question is related to the one \" do electrons actually orbit the nucleus?\" that people ask because they see the classical pictures. In reality, it is hard to visualize. This realm is dominated by quantum mechanics so classically picturing it would be difficult.",
"Best explanation is you have a ... | [
"\"Shape\" is a very macroscopic concept. It doesn't carry over well to atomic phenomena. There are a number of ways to answer your question but keep in mind that all of them involve some assumption as to how to define \"shape\" that the responder has made that you may or may not be comfortable making yourself.",... | [
"It's called the colour force, the strong force, the strong nuclear force, or the nuclear strong force. All those names are correct. The residual strong force is analogous to atomic/molecular bonding in chemistry. In both cases, the underlying mechanisms are quantum systems, and cannot be fully explained classic... |
[
"If you get sick with a common cold virus, are you less likely to contract a cold again that season?"
] | [
false
] | [deleted] | [
"Yea, that's why it is difficult to make a vaccine against the common cold. There are about 100 different serotypes of rhinoviruses and apparently your antibodies to one type aren't very cross-reactive with the other type. So if you get infected with a certain type of virus you will probably be able to fight off ... | [
"I was referring to the flu, not the common cold. Sorry if that caused a bit of confusion.",
"There are many, many forms of both common cold virus and the flu virus (numbering in the thousands).",
"I wasn't saying there are only 2-3 common types, I was referring to the 2-3 MOST common types for that particular ... | [
"What we call a \"common cold\" is basically a viral respiratory tract infection, and the symptoms can be very similar between different types of infection. This can be caused by a variety of viruses, so it is not just a question of serotypes.",
"Rhinoviruses are probably to most popular, but other viruses such a... |
[
"How do humans, unable to digest cellulose, get the nutrients from within the cell wall of, say, spinach?"
] | [
false
] | Most nutrients in all vegetables and greens are inside the cells, which are bounded by a cellulose membrane. You eat a spinach salad, hoping and expecting to get many nutrients from it. But is it not the case that the only nutrients available are the ones your digestive system can extract from the surface of the actual... | [
"The cellulose cannot be degraded by human enzymes, but that does not mean that we can't punch open a bag of cellulose with mechanical and chemical action."
] | [
"To the best of my knowledge, true cellulose degraders are incredibly rare in the human gastrointestinal tract. It is generally accepted that humans as a species (microbes included) can't digest cellulose. That said, they have found some Japanese people who can digest certain parts of seaweed that it was thought ... | [
"Only a small number of organisms can actively digest cellulose, and they are all either bacteria or single celled eukaryotes. Anything that eats a cellulose intensive diet proactively harbors these organisms in it's digestive tract, and they are not at all compatible with a human gut. So, humans can't access what'... |
[
"Is a toroidal star possible?"
] | [
false
] | Would it be possible for a star to be toroidal? I am imagining a donut shaped star, spinning like a Stanford torus. Could a star be massive enough to ignite fusion without collapsing the torus? Could a star form this way naturally? | [
"No. Gravity pulls the mass of the star together in all directions equally coalescing into a spheroid. Fusion causes it to expand to equilibrium.",
"To conjure up a universe where torodial bodies were the norm or even possible would require weaker gravity and cotradictions that are boggling my mind. Hypotheticall... | [
"There are binaries called W auras Majora stars (named after W Ursa Majoris) whee two stars are so close, their atmospheres overflow each other. They're roughly peanut shaped."
] | [
"A very rapidly spinning star could have a dumbbell shape, but I don't think toroids are stable."
] |
[
"Why does tannish/greyish beach sand heated to 1950 degrees F turn orange?"
] | [
false
] | I put some sand from the Washington coast and some from the Massachusetts coast in a kiln and heated it. Both turned orangish brown. What would have caused this? Did it oxidize? Why did it happen with heat, when it doesn't at the beach? | [
"Many dark colored minerals contain iron in the 2+ oxidation state. When they are heated strongly in air, the iron can be oxidized to the 3+ oxidation state. Many iron 3+ compounds are orange, red, yellow, or brown in color, including rust.",
"As for why the reaction only happens in the kiln, there is some activa... | [
"You are seeing the emission of light by the sand. If you look at room temperature sand in a dark room it will appear black (no photons emitted). The color of room-temperature sand with the room lights on is just the color of reflected light (the sand absorbs some of the colors of the light, and reflects other colo... | [
"The room temperature sand is a different color (more orange/brown) than the same sand before it was heated. Sand samples from other locations didn't noticeably change color before/after heating. My first thought was oxidation, but wasn't sure why it would happen to beach sand at high heat, and why you don't natu... |
[
"If I look up at night, I can see stars. Why do many pictures of stuff on the ISS, the moon, etc., are relatively \"starless?\""
] | [
false
] | null | [
"Because the object in the picture, like the ISS or the moon's surface, is very bright compared to the stars. The sun is shining on the object in the picture, so it's as bright as any object you see in daylight. If the photos were exposed long enough to pick up the stars, the ISS or lunar surface would be overexpos... | [
"If the space station is lit up by light from the sun, it would be quite bright. The cameras have to expose for this bright light leaving the rest of the image (the space where we should see stars) underexposed. The light from stars is not nearly as bright as the sunlight reflected off the space station."
] | [
"Dynamic range",
". Cameras have less dynamic range than your eyes."
] |
[
"Is there any truth in the old saying, \"Red sky at night, shepherds delight; Red sky in morning, shepherds warning\"?"
] | [
false
] | Any time I see a red sky this little rhyme always goes off in my head and I'm just wondering if there is anything scientific that puts any truth into those words? | [
"i've heard this same expression with \"sailors'\" substituted for \"shepherds\".",
"anyhow, yes this is a valid saying, at least on the East Coast of the US where I grew up. if there were clouds in the morning eastern skies making the sunrise turn red - and the wind was coming from that direction - you'd know w... | [
"anyhow, yes this is a valid saying, at least on the East Coast of the US where I grew up. weather typically moves from the east into the west",
"It's the opposite in the U.S. weather typically moves from west to east."
] | [
"here's a link that does a better job explaining than i did: ",
"http://www.loc.gov/rr/scitech/mysteries/weather-sailor.html"
] |
[
"Do batteries in a device which remains idle degrade faster than batteries not in a device?"
] | [
false
] | If so, why? | [
"This depends on like... a thousand factors. But generally speaking, power leaves the battery when there is a load on the circuit. And a LOT of devices(I dare say far too many) have a draw when there is no activity at all, a Standby power of sorts. Your car for instance is probably absolutely ripping with it. And e... | [
"All semiconductors have a leakage current, even when they are supposed to be off. So the battery will be loaded by that. Unless there is a hard switch which disconnects it (which these days there isn’t, even my torch has a “soft power button” rather than “a switch”)"
] | [
"It depends on what type of battery it is, but all batteries lose charge over time, regardless of how they're stored, Just like data rot for optical media. Most alkaline batteries will corrode due to oxidization, oxygen leaking into the sealed cylinder and causing the battery to leak or corrode around the terminals... |
[
"How does a region being open or closed affect the calculation or value of an integral over that region?"
] | [
false
] | [deleted] | [
"It typically doesn't, although it depends on the measure and the set you're integrating over. For the Lebesgue measure, most well-behaved sets have measure zero boundaries, so integrals over them are zero, but that's not always the case.",
"Usually when derivatives are involved in the integrand, you'd like to re... | [
"The ",
"Smith-Volterra-Cantor set",
" for example. It has empty interior, so since it is closed it must be its own boundary. And since it has positive measure, that boundary also has positive measure.",
"Note that if ",
" is not open, it may contain parts of its boundary, which makes your question of ",
... | [
"I'll assume you mean one variable integration, on the real numbers. (But this actually makes sense for many other types of integrals.)",
"Think of the integral as being the area under the curve. What's the difference between the area corresponding to [a,b] compared to (a,b]?",
"It's the exact same shape, excep... |
[
"\"If you travel through space in a straight line, you will wind up back where you started\" - Is this statement true?"
] | [
false
] | null | [
"No. Regardless of whether the universe is \"flat\" or not (even if it's not flat, it's pretty damn close), you could never get further than any point that is currently about 14 billion light years away, because the space in between is stretching out as we speak. Because of this expansion, points that are currently... | [
"No. Even if you modify the universe (for the sake of the hypothetical) so that it is no longer expanding (and thus there is no cosmic horizon), your statement refers to a closed universe, which evidence actively suggests against. So it ",
" be true, but saying it ",
" true is wild speculation and contrary to o... | [
"I could try to explain it in my own words, but I really don't understand the theory enough. This video will kinda explain what you're talking about.\n",
"http://www.youtube.com/watch?v=0w9R_foNLrg"
] |
[
"Can a nuclear reactor with a fixed amount of fuel \"conserve\" energy at times when demand is low, or does it always output the same amount of energy?"
] | [
false
] | null | [
"Yes. Though typically commercial reactors become more difficult to control at low power levels (<10%). This has to do with fine control of the feed water system, usually.",
"In a commercial Pressurized Water Reactor (the type I'm most familiar with), reactor power basically follows the demand on the generator. I... | [
"Nuclear engineer here.",
"Your answer was answered pretty well by others, but some added info.",
"Whenever a reactor core is reloaded, one of the critical parameters is the number of \"Effective Full Power Days\" (EFPD) worth of fuel the new core will have. 1 Effective full power day means that the reactor ran... | [
"Short answer: Yes, it works the same way.",
"Long answer: I started typing out a long answer, but just read up on ",
"MOX fuel.",
" That should answer your question."
] |
[
"If you plug a submerged straw with your finger and then lift it from the liquid, a volume of liquid remains in the straw; is there a maximum diameter of cylinder (straw) where this is still possible?"
] | [
false
] | What other limiting factors come into play? | [
"The surface tension of the inverted meniscus at the bottom of the straw limits it. For a bubble of air to move up and a drop of water to move down, extra surface has to be created against the tendency of the surface tension to minimize the area (*). At some point the energy required to create that extra surface i... | [
"Yes this is correct, you also hear this cohesion referred to a London forces (or other names). This of course applies to a classic physics test question where you assume everything is under ideal conditions and there is no temperature, friction or air currents (wind) interfering. Also, I’m a biologist and not a p... | [
"I am curious about maximum diameter specifically"
] |
[
"How are innate desires encoded in genes?"
] | [
false
] | Firstly, I have been operating with the assumption that the brain can be treated as a general purpose, goal directed, adaptive controller. Through evolution, we have come to innately desire some things, like sex, food, water, warmth, and possibly even social acceptance. If these are innate, they must be encoded in our ... | [
"Emotions, instincts and desires are mediated through neural networks and hormonal (chemical) signals.",
"Gene expression creates the initial framework of neural networks. That initial framework includes innate desires.",
"A given cell in the body is at a particular chemical balance (hormones released elsewhere... | [
"These genes are there because this desire of sex, food, water, etc. increases your chances of survival and/or reproduction. I know it sounds strange, but complex behaviour can be coded by simple genetic instructions, and this has been proven with, for example, bees.",
"If you are familiar with the laws of Mendel... | [
"That question is impossible to answer under the knowledge our species has of the human body. Also the answer may contain to many variable to ever definitely say."
] |
[
"Can you guys weigh in on the apparent new cure for AIDS"
] | [
false
] | null | [
"It's ",
"in",
" ",
"mice",
". Google \"HIV cure mice\" and you'll see a lot of high-impact legitimate research.",
"Don't hold your breath. It's great and all but..... it's mice. I personally have cured asthma twice and helped cure COPD once. I know a guy that cured CF two years ago, a lady that cured dia... | [
"Why is it so much easier to find cures in mice?",
"There are inherent reasons and artifactual reasons. As far as inherent reasons...I would say they breed like rats, but rats breed slowly compared to mice. This allows for you to rapidly expand a project. They are easy to house; mice like being crowded together (... | [
"Considering one leads to another i don't think it makes much of a difference to a lay person.",
"If you can cure AIDS and live safely with HIV everybody would be content, and if you can cure HIV then AIDS becomes a non issue, so again everyone is content.",
"As such i don't think its a major issue for any lay ... |
[
"What are the implications of The Banach–Tarski Paradox for real world physics?"
] | [
false
] | [deleted] | [
"The Banach-Tarski theorem is a mathematical theorem; it has no consequences on physical objects. For one, real objects do not occupy all of nicely defined sets and real objects cannot be subdivided arbitrarily. The theorem does not say anything like \"we can divide a cupcake into two equal cupcakes\", however awes... | [
"It relies on a trick to do with infinity. You can, for example, take an infinite set of numbers and partition them into two other sets. Just go along the set and put the items in alternating buckets.",
"At the end of it, you have two infinite sets.",
"It's similar (although obviously much more involved) with B... | [
"You have to be careful about questions like this when thinking about how mathematics is related to physics. Math is not some immutable collection of facts that describes reality - it is a method of rigorous reasoning that allows you to deduce conclusions from assumptions (or tells you what sort of assumptions give... |
[
"How do you model a gas when P, V, and T can all vary simultaneously?"
] | [
false
] | For example, if you take the Ideal Gas Law PV = nRT and adjust everything with a scaler to describe a percentage change in each variable, (P * a)(V * b) = nR(T * c) you aren’t able to get an insight into how each variable is changing with respect to each other. (As V is decreased by a factor of b, what is happening to ... | [
"The ideal gas law is always true for an ideal gas, no matter what quantities, if any, are held constant.",
"This is not an issue of the ideal gas law, it’s just math. You have one equation and more than one unknown, so the system is not determined uniquely."
] | [
". As the gas is compressed, V decreases and P,T increase. How do we model this relationship? ",
"That's an adiabatic compression (and also implicitly, the number of particles is constant). Assuming you know all initial quantities (temperature, pressure, and volume), and the final volume, you have two equations a... | [
"You are right, the idea gas law alone is not enough. ",
"Depending on the specifics of the system you are looking at, different calculations apply. See the \"Applications to thermodynamic processes\" section on Wikipedia:",
"https://en.wikipedia.org/wiki/Ideal_gas_law",
"One common situation is the \"Isentro... |
[
"Is water in the bladder recoverable?"
] | [
false
] | If I have a full bladder (meaning I need to urinate), then don't drink anything, can my body reabsorb some of the fluid held in my bladder to hydrate me? | [
"If you become thirsty, your body begins creating Antidieuretic hormone (ADH), which is made in your hypothalamus. ADH is what regulates water retention in the kidneys. High levels of ADH cause the kidneys to conserve water, creating more concentrated uring. ",
"This reabsorption of water occurs in the kidneys. A... | [
"This is correct. That said, the colon is capable of reabsorbing water, so as much as that wasn't a portion of your question, in a way, it relates to the answer."
] | [
"It's an osmotic reabsorption. This means a number of factors relate to how much water the colon absorbs, but it typically reabsorbs over 95% of what enters it.",
"Further reading here: ",
"http://www.anaesthesiamcq.com/FluidBook/fl3_5.php"
] |
[
"What can be practically simulated or generated with a 50-qbit quantum computer today?"
] | [
false
] | In one lecture Prof. Leonard Susskind mentioned the number of states 400-qbits have is more than number of Plancks (1.62×10 m) in entire universe. So what can be practically simulated or generated on a 50-qbit quantum computer that can actually be used for business today? References to available tools: | [
"First off, I think it's worth pointing out that quantum computers can only do things normal computers can already do (they're still \"merely\" Turing-complete). Quantum computers are purely a speed-up for certain very specific tasks. A regular computer can simulate anything a quantum computer can do, but large eno... | [
"As previously mentioned, IBM has an online Quantum computer. There's information on the IBM Q experience here: ",
"https://quantumexperience.ng.bluemix.net/qx/experience",
"I believe I read that there are 70,000 registered users to the online Quantum computer. There's a discussion forum off the link above. It ... | [
"Thanks this is a great answer.",
"So, I understand why practical \"quantum\" cryptography would be little hard to implement on current devices.",
"However, here's a device from IBM:\n ibmqx5 (16 Qubits)",
"You can send this machine OpenQASM code and it runs it on real quantum computer (there's also 20 Qu... |
[
"What is the purpose of finding alternative sources for hydrocarbon fuel, when we are currently focusing on reducing our hydrocarbon consumption?"
] | [
false
] | To clarify: Why are we researching methods such as biomass to hydrocarbons and combining electrolysis of water and atmospheric carbon to produce hydrocarbons, when we are currently trying to reduce the production of green house gases? | [
"Creating fuel from atmospheric carbon dioxide is an economically impractical endeavor (requiring lots of refrigerators, pumps, electricity, and stuff like that). When included with all the other phony \"carbon capture\" schemes, I find the projects all tend to be aimed at getting heaps of money for large construc... | [
"Consideration of green ammonia as a fuel is sufficiently foreign that I should probably provide a few basics regarding ammonia as a transportation fuel: A nominal spark ignition compression ratio for green ammonia is around 18:1. An extra strong spark is needed to initiate combustion at compression ratios below th... | [
"To answer a question I don't think you're asking, we are researching alternative sources of hydrocarbons because hydrocarbons are a convenient storage mechanism. We have a massive infrastructure in place for purifying, distributing and using them, and they are several times more energy dense than anything else we... |
[
"Why do electrons move? What is fueling them to go around the atom at such high speeds?"
] | [
false
] | null | [
"The most easily understood answer is based on the uncertainty principle. If they were still, their position would be perfectly defined and thus the uncertainty in their momentum would be infinite meaning they could not stay where they were. It also should be stated that electrons are not particles flying around th... | [
"Your explanation is pretty good, but you said that moving charges produce radiation, when in fact it's only accelerating charges that radiate. If the electrons are going around in classical uniform circular motion, then they'd be accelerating and radiating, which would result in energy loss and a decaying orbit. T... | [
"You're correct, it's ",
" that's significant, not merely motion. "
] |
[
"Why do negative experiences \"stick out\" more than positive ones in the short term, but the positive ones are more commonly remembered years down the line?"
] | [
false
] | There's this weird dichotomy with what we tend to focus on, and I'm curious as to how it would be explained in psychological, neurological, or perhaps even evolutionary terms. Negative responses or experiences seem to completely overwhelm positive ones in the short term (getting in a fender-bender right after seeing an... | [
"Non-scientific answer: negative experiences are usually exceptional, possibly dangerous. It behooves you to recognize if your mental model of the world has been violated or is incorrect. Negative experiences are usually a short term shock to the model of \"everything is usually fine and non-threatening\".",
"Pos... | [
"there was some paper that talked about how we ignore discouraging obstacles, but remember positive outcomes; in relation to goal seeking. But I don't think they had figured out why any of that happened.",
"we just don't know enough about the brain an answer your question"
] | [
"At the risk of doing that speculating thing that we're not supposed to do, I'm going to chime in that this seems to my [very uninformed] mind to be related to the fact that you can often clearly recall pleasurable feelings much more readily than pain.",
"You can probably recall very clearly the delicious taste o... |
[
"Are there any groups of researchers out there trying to calculate the effective speed of evolution?"
] | [
false
] | I perused the wikipedia article on this, but it was mostly riddled with jargon that was beyond my knowledge. Basically, I'm wondering if there are any people out there working to try to figure out if there's a means by which to calculate how quickly a given population will evolve based on the size of the population, re... | [
"I was an evolutionary dynamics session at a large physics conference recently, and there were several researchers talking about how cooperation and competition between different strains of yeast and E. coli affects the rate at which both population and evolutionary dynamics occur. Here's a link to one of the abstr... | [
"I wonder if there would be a way to try and understand how variables like these interact and effect the overall evolution of a given population. Although I suppose it would be arrogant to think we have the ability to actively account for all of the variables present in the real world."
] | [
"Well, all these people are studying evolution from a physics point of view, which involves reducing the complexity of the system as much as possible while still keeping the interesting behaviour present. This gives you more control over and insight into the system that remains, but it's important to know the limit... |
[
"[Physics] Could electromagnetic radiation, with a precisely calculated waveform, affect chemical reactions in the vicinity of its source?"
] | [
false
] | As I understand it, a chemical reaction occurs when atoms and molecules collide with sufficient force to break electric bonds between their constituent particles. Would it be possible to, say, find a gamma wave with all the right properties that vibrates molecules of hydrogen and oxygen and prevents them from colliding... | [
"Consider ",
"photosynthesis",
": electromagnetic radiation (light) provides energy to a reaction that produces ATP.",
"Or chemical photography: Light causes a reaction in the film. Later when the film is processed, the unexposed areas (with the original chemistry) become clear (in a black-and-white negative ... | [
"My question, really, is whether a specific set of frequency, wavelength, etc. can induce or prevent a reaction that would otherwise have occurred. I got this question when a friend suggested that a device implementing this could prevent plastic explosives from exploding when deployed in an airplane, or could be us... | [
"In theory, if you could target molecules with horrific accuracy with photons of outstandingly perfectly tubed frequency and what not you could likely control what reactions do or don't occur IF you know the exact spatial arrangement and movement of all the molecules in question. As I recall this was used in the ga... |
[
"Is light speed relative to the source it started from or relative to any viewer?"
] | [
false
] | For instance if I'm on earth and a space ship were traveling away from earth at an extremely high speed—lets say 99% the speed of light, and a second ship was at rest relative to Earth as the moving ship passes the resting one they both shine a laser at a target on earth. Will both lasers hit at the same time? | [
"To a person on earth it would appear to be moving at the speed of light, so 1% faster than the spaceship. However, for the person on the spaceship it would appear to be moving away from them at 100% the speed of light. Unlike in classical physics, relative velocities are not the same in different reference frames.... | [
"Depends on the level you're looking for. If you've taken any math or physics at university level you could probably just look up a first-year textbook section on special relativity, or and open-course like ",
"this",
". If you're looking for a more layperson intro I'm not too familiar with really good sources ... | [
"I've got a math degree, but during college I unfortunately did the minimum to get good grades and wasn't curious. I never ended up getting into relativity in any of my courses. I'm just now getting interested and learning so much more on my own now that I'm interested than I did in school. Thanks—I'll check out th... |
[
"Why are we so concerned about Colony Collapse Disorder if bees aren't even native to the Americas?"
] | [
false
] | How did we get by in the past without them? Is it just that we have more people, more crops now and we rely on the bees to pollinate the increased amount? Were there other native pollinators that the imported honeybees replaced, so now we've become dependent on them? | [
"There are most certainly ",
"bees native to North America",
". In fact, there are ",
"more than 4,000 species of native North American bees",
", which adds up to about 20% of known bee species. ",
"Many of these have been in decline over long periods of time. For example, four species of North American b... | [
"Honeybees are widely used to pollinate crops. They are shipped around on trucks from location to location as needed, and are really a commercial agricultural species as much as the plants they pollinate (many of which are also old-world). Anyway, one of the main concerns about colony collapse is the economic eff... | [
"More to the point on CCD, there are a lot of different problems affecting honeybees right now. Some of them affect other bee species too, but CCD is something that is unique to, or has only been documented in honeybees. It has recently been shown that some of the mites that some studies have linked to CCD affect b... |
[
"Artificial Neural Networks essentially follow a linear path from input to output, how does a brain compare to this when information travels?"
] | [
false
] | This simplified diagram shows the architecture of an artificial neural network: In normal brains do the neurons also have cyclic communications and cross over between layers or jump over layers etc. I am interested in what are the deficiencies of ANNs compared to the human brain. | [
"So to address the first part, ANNs are typically not linear, that is, the activation functions used are not linear. While it is possible to use a linear activation function in an ANN, you essentially end up doing a linear regression and your results are not very good. Instead, non-linear activation functions such ... | [
"Indeed, did my PhD on functional MRI and currently work at an AI company"
] | [
"As far as i know, AI 'neurons' do not behave exactly like our own neurons",
"AI neurons operate with floating data whose value has a meaning, e.g it would be well suited to output it's 60% sure the picture has a dog in it",
"Our own neurons operate more with 'spikes' whose 'amplitude' is less relevant than exi... |
[
"If you have a high alcohol tolerance, does that mean that you metabolize alcohol more quickly or that you are less affected by an equivalent BAC?"
] | [
false
] | In other words, if a person has high tolerance, does that mean that they handle their alcohol level better or that their alcohol level is lower? Along the same lines, does drinking alcohol more often increase the efficiency with which you metabolize alcohol, or does it just make you less prone to its effects? | [
"They have ",
" i.e. they have upregulated the enzymes that metabolize alcohol. ",
"They also have ",
" i.e. they have downregulated GABA receptors and upregulated NMDA receptors to produce less of an effect at a given BAC."
] | [
"A third factor is body size. A larger person simply has more blood and therefore it takes more alcohol to reach the same BAL"
] | [
"I am honestly not sure"
] |
[
"Please explain temperature where there is no air."
] | [
false
] | From what I understand, "air" holds a temperature. "It is 80 degrees outside" translates to "the air outside has a temperature of 80 degrees". In space, where there is no "air" and/or "oxygen", what is holding the temperature? I understand that near Pluto "it" is cold and closer to the sun, "it" is hotter, but what is ... | [
"As an astronomer (and this explanation applies far beyond that) you end up having to break down the \"temperature\" into many subsets of measurements of energy. For example, a molecule can be extremely translationally hot but vibrationally and rotationally near absolute 0.",
"Now you may say, \"By ghast that ma... | [
"As an astronomer (and this explanation applies far beyond that) you end up having to break down the \"temperature\" into many subsets of measurements of energy. For example, a molecule can be extremely translationally hot but vibrationally and rotationally near absolute 0.",
"Now you may say, \"By ghast that ma... | [
"Temperature is generally related to the average kinetic energy not average velocity, but otherwise great explanation."
] |
[
"How large would a rotating space station have to be in order for its occupants to not feel the coriolis effect?"
] | [
false
] | null | [
"This question comes up about once a week, and is usually answered badly, just read this . . . .\n",
"http://en.wikipedia.org/wiki/Artificial_gravity"
] | [
"Ever tried walking across one of those rotating discs in a fun house?"
] | [
"This is perfect, thanks! Solid Science!"
] |
[
"What's happening when you \"get the breath knocked out of you\"?"
] | [
false
] | I always wondered if this was literal or just a way of explaining what it feels like. And does it have anything to do with a collapsed lung? | [
"After a blow to the chest your diaphram (a muscle which contracts causing a vaccuum in your chest [pleural space] which causes your lungs to expand creating another vaccum within the lungs which then sucks in air) seizes and you can't breath for a few moments. It's the same muscle that twitches to cause hiccups."... | [
"Anecdote, so I won't make it top-level, but I don't want to repeat what's already written. ",
"Having had it happen (I caught an elbow or something in the solar plexus while wrestling) it literally feels like having it knocked out; it's gone and you can't breath. One of the scariest moments of my life."
] | [
"It's essentially your diaphragm (which was described below) rapidly vibrating so it doesn't allow your lungs to open and close as they normally do. The vibrations quickly stop and your diaphragm begins acting as it usually does."
] |
[
"How does the brain store temporal order information for various memories?"
] | [
false
] | The brain stores memories, as strengths of connections (synapses) between neurons. How does it know which memory was created earlier? It seems that there has to be a directory system that tags each memory with a "timestamp" of sorts, and this has to be stored somewhere else. Messing this directory would make us lose t... | [
"Oh great question!!! I do not have a great answer but I can point you to some resources. There is a scientist named Howard Eichenbaum who has studied a lot about memory, and here are some things he has found about time and the brain:",
"Recent models of hippocampal function emphasize the potential role of this b... | [
"Your memory doesn't have a timestamp on it. Instead your brain reassociates it with other memories in real time while recalling it. I have a memory of giving a presentation at work. I remember what topic it was on and what stage of the project I was in. I associate this with my other memories of that project and a... | [
"This is actually an ongoing area of research, but the hippocampus and the medial prefrontal cortex are crucial for temporal memory. Many studies have modeled temporal memory by exposing rats or mice to sequences of odors and then administering a \"probe test\", in which the animal is exposed to two odors from the ... |
[
"How are particles identified in accelerator collisions?"
] | [
false
] | [deleted] | [
"Particle identification in collider experiments is a complicated process. You have to distinguish between particles that are directly observed and those whose presence is deduced from the observation of other particles.",
"Direct observation is the most straightforward of course. But still, to catch as much as p... | [
"/u/Rannasha",
" gave a great answer. I just want to give a more compact answer in bullet point form:",
": an energy deposit in the electromagnetic calorimeter with a track leading to it",
": an energy deposit in the electromagnetic calorimeter without a track leading to it",
": an energy deposit in the ele... | [
"Is a particle really more like an eddy formed in water? There's nothing solid there, but it's an energetic pattern temporarily self-sustained by countering energetic forces.",
"I would say yes, though every solid object you've ever encountered is obviously made of these ripples in quantum fields. The solidity of... |
[
"Why do countries like India not have the annual flu vaccine that seems to be so common in the USA?"
] | [
false
] | Indian here and I have never taken or heard about the flu vaccine being given in india. We have a really huge vaccination programme otherwise. Is this because the virus is only prevalent in some countries? | [
"It's not just countries like India that don't do flu vaccinations. I live in Sweden and I'd never even heard of the concept of getting an annual flu vaccine until I saw a picture on Reddit a few years ago of an American flu vaccination campaign. I looked it up and apparently the official recommendation here is to ... | [
"I like to add this on, that many western countries recommends and follows the same guidelines, only people in danger of serious illness and death is recommended the vaccine"
] | [
"1.35 billion/135 crore vaccines each year for 70 years is definitely a greater investment in both time and resources than the same number of once in a lifetime vaccines."
] |
[
"Are there any differences between a hurricane and a typhoon?"
] | [
false
] | null | [
"The difference is primarily just the name. The collective name for the phenomenon is \"tropical cyclone\", where the \"tropical\" part refers to the part of the world where these cyclones originate (the tropics).",
"In the Atlantic Ocean and north-eastern Pacific Ocean (i.e. close to North America), tropical cyc... | [
"Tropical Revolving Storm",
"This name is not commonly used. As far as I'm aware it only appears in maritime textbooks. Maybe it's more common in other languages, I dunno."
] | [
"As far as i know, the common name is \"Tropical Revolving Storm\" - this can be a hurricane, typhoon, cyclone or other local names."
] |
[
"Does it become easier to form stars as the strength a gravitational field increases?"
] | [
false
] | Hypothetical situation / thought experiment: find some massive yet energetically inert object and set up some sort of container that can withstand / contain thermonuclear fusion nearby. Inject the inside of the container with a bunch of hydrogen and/or whatever stars are made from. Will a star have an easier time formi... | [
"It's not really gravity per se that causes the cores of stars to undergo fusion. The real critical factors are density and temperature, and it's just that the gravitational collapse of a cloud of hydrogen raises the temperature and density to a point at which self-sustaining fusion can take place.",
"Star forma... | [
"If the container is in orbit, no, as the star would experience no gravity from the massive object. If the star was suspended above the massive object, it would be helpful, but you would need to exert force on the star container exactly equal to the force you're applying across it. You might as well devote your sup... | [
"Stars are formed when you cram a bunch of hydrogen together really, really hard, creating a fusion reaction.",
"Gravity just happens to be the easiest way to do that in a self sustaining manner...the emerging energy counterbalances the force of gravity, leading to a reaction that will last a billion years. ",
... |
[
"Can Neutrinos be measured as waves, like Photons?"
] | [
false
] | I've been having trouble working out the whole particle/wave duality thing in my head recently. So the entire EM spectrum is emitted as photon particles (or waves), right? Are Neutrinos and other radiation like alpha, beta, gamma, neutron, etc separate from that spectrum? Can neutrinos also be measures as waves in the ... | [
"Can Neutrinos be measured as waves, like Photons?",
"Yes. Neutrino flavor oscillation is evidence that neutrinos have wave-like properties as it is a result of interference, which is a wave effect. I don't know exactly what you mean by \"measured as waves\"? If you mean getting an interference pattern on a grid ... | [
"All particles, in principle, are also waves. However, to my knowledge, the wave nature of neutrinos has not been ",
" observed in the form of diffraction, interference, etc, essentially because the neutrinos that we detect have very high energies and act more like particles than waves. This is analogous to gamma... | [
"The only radiation that lives on the EM spectrum is gamma radiation (high-energy photons).",
"I have always assumed that all of the EM spectrum could be considered \"radiation\", but only X-Ray and Gamma is considered \"ionizing\" and therefore harmful radiation. Is this not the case?",
"Also, yes, since neutr... |
[
"How many intelligent civilizations would have to exist in our galaxy for one of them to have picked up our radio transmissions by now, assuming they are evenly distributed?"
] | [
false
] | Or, assuming another intelligent civilization somewhere else in the galaxy developed radio technology at the exact same time and the exact same rate we have, what's the closest they could be for us to pick up their transmissions in the next, say, 50 years. | [
"what's the closest they could be ",
"You want the farthest, not the closest.",
"Making many simplifying assumptions and assuming they began transmitting in 1927 (when we began commercial radio broadcasting), the farthest they could be would be (2012 - 1927) 85 light-years away. Any farther and we would have to... | [
"It is a very difficult question to answer. Picking up radio transmission is not just an issue of being in range. It is also a question of having the right equipment directed in the right direction at the right time. And even if you pick up the signal it is not obvious that you will correctly understand the origin... | [
"radio waves only travel at the speed of light, even the first radio waves broadcasted by humanity have not travelled that far out"
] |
[
"Why are painkillers so huge while it only contains a couple milligrams of the active substance?"
] | [
false
] | null | [
"Since over-the-counter medicine is sold directly to the consumer, certain safeguards must be put in place to avoid/deter any tampering that could lead to over-doses or abuse. Using a large amount of binder in a pill is one way to avoid someone accidentally taking too much."
] | [
"Also kind of a placebo effect. Give someone a good sized pill and they unconsciously think that because it is bigger it will work better than a smaller one."
] | [
"Damn, my eyes have been opened. Hard thing to swallow those pills, just for safety."
] |
[
"If the higgs boson is not found, what does it mean for the standard model? Does it mean it is flawed?"
] | [
false
] | null | [
"It means that the Higgs hypothesis for electroweak symmetry breaking is incorrect, and other avenues (like Technicolor) must be examined. Those searches are being done in parallel at the LHC but haven't come up with anything yet.",
"We know the standard model isn't complete. It doesn't describe gravity, or expla... | [
"Technically, physicists have been searching for a while, and still haven't given up hypotheses from the standard model. When they can't find one using the technology available, they create a bigger and badder one utilizing even more energy to locate it. If the LHC can't find it conclusively, they would have to sit... | [
"Not at all - in fact, the Higgs boson (assuming it doesn't have any funny properties, which it appears not to) is the very ",
" component of the Standard Model yet to be detected. If the LHC finds a Standard Model Higgs (which, again, seems likely) and doesn't find anything new (which, unfortunately, is a distin... |
[
"Have humans as a species made enough of an impact on Earth, that if gone tomorrow, in 65 million years \"they\" would know an \"advanced\" species existed?"
] | [
false
] | Thinking about how long of a time scale 65 million years(~extinction of dinosaurs) is got me thinking. Humans have made a massive impact on Earth from cities, agriculture, pollution, etc. You can see our impact from space and we continue to change the Earth more and more each day. These things, in the context of one hu... | [
"If some GMOs species manage to survive until then, their modified DNA sequences wouldn't fit in a philogenic tree and would be evidence for intelligent design."
] | [
"There are a number of rare but long lived isotopes from the uranium-235 decay chain, such as plutonium-244, which has a half life about 80 million years.",
"The relative abundance of these isotopes would be a pretty clear indication an advanced, fission using society existed 65 million years ago."
] | [
"we have fossils hundreds of millions of years old of squishy creatures made of snot, so I think we will leave a trace."
] |
[
"Is water pressure the same above and below sea level?"
] | [
false
] | [deleted] | [
"what tezznet said is that the pressure at 10 meters below water level would essentially be the same. Air pressure does change with altitude, but not much. Sea level pressure is ~ 100 kpa, at 1 mile elevation the pressure is about 80 kpa. Water pressure increases about 10 kpa per meter you go down. If a submari... | [
"ah ok. thank you for the swift response"
] | [
"ah ok. thank you for the swift response"
] |
[
"[physics gedanken] Reconciling accelerating charge and equivalence principle"
] | [
false
] | The Larmor power formula tells us that an accelerated charge radiates. The equivalence principle tells us that a uniform gravitational field can be equated with a constant acceleration reference frame. A charge in a uniform gravitational field obviously does not radiate. Where is the disconnect? | [
"John Wheeler once asked a group of relativity theorists to vote on whether the falling charge radiates or not; their responses were split almost precisely down the middle.",
"The correct answer is now understood thanks to Dewitt & Brehme (1960): The charge does radiate, precisely reproducing the non-relativistic... | [
"If you're measuring a charge on Earth, you're accelerating in pace with the charge. My gut tells me that this means no measurable effects.",
"Though I would think that we would see the Earth releasing radiation into space, which I don't think happens, either.",
"I guess it's because the charges don't actually ... | [
"I think that last question is the reason they came up with quantum mechanics."
] |
[
"Why does moist dirt absorb new water better than dry dirt does?"
] | [
false
] | I think everyone with a house plant has probably experienced this when they let a pot dry out too much. Here's a about possible flooding due to the reduced capacity of dry soil to absorb water: Due to the drought conditions over these regions, the soil has a reduced capacity to absorb water. Heavy rainfall thus increas... | [
"It's because of the high surface tension of water. Water in soil forms microscopic channels around/between the soil particles. The initial formation of these microscopic channels in dry soil must overcome the surface tension forces. Once the initial formation occurs, (wet soil) it is relatively easier to expand... | [
"This is the correct explanation. Have you ever seen a bead of water sit on dry clothing? If the clothing were already wet, then the water would just soak in. Since the clothing is dry the water has to overcome its surface tension (break the bead) to wet the surface of the fibers the first time. Same principle with... | [
"This is such a great analogy that if this question ever comes up in my personal life, I'm going to pass it off as my own and not give you credit.",
"Seriously though, thanks."
] |
[
"How are memories stored at a cellular level?"
] | [
false
] | Moreover, are short term memories stored by a different physiological mechanism than long term memories? Or is all memory and learning achieved by the same fundamental cellular changes to neurons? | [
"Lots of people think that it's CamKII/NMDAR. It sits in between neurons that are connected. As they fire together, the complex strengthens the association between the two neurons. The process involves successive incidents of calcium binding. This is called a \"molecular coincidence detector.\" As the neurons fire ... | [
"Your asking something that isn't really known right now. After MIT figured out that memories in rats could be brought forth by a laser on specific neurons/neuron clusters and that the Npas4 gene is what allows us to even form memories (without it you wouldn't remember anything) the question then became HOW they ar... | [
"The memory is a distributed pattern of neuronal activation. If you remember a rose you smelled in England last year with your girlfriend, the areas of your brain devoted to those sensations and concepts will become electrically active. The electrical activation of a neuron occurs when its membrane voltage rises. T... |
[
"Does the light output/effectiveness of an LED change with respect to the level of heat generated?"
] | [
false
] | I have sensors over some growing plants that measure reflected light, and while it makes sense that over time the amount of reflected green rises, I cannot seem to pinpoint as to exactly why over the course of a given 24 hour day my readings rise and then fall. I wonder if this has something to do with LEDs not working... | [
"I'm a PhD candidate in an LED lighting center and we have a plant lighting specialist who suggests the following: Flip your sensors around and have them measure the light coming directly from the LEDs. If that signal fluctuates then there is your answer. Also, what kind of sensor are you using? Spectrometer, pho... | [
"by saturation current is that the same as the reverse saturation current?",
"Yes. \"Reverse saturation current\" refers to when the diode is in reverse bias, ie V is negative. If V is a very very negative number, e",
" is basically 0, so",
"I = I",
"(e",
" - 1) = -I",
"And hence the term \"reverse satu... | [
"LEDs produce less light as temperature increases, that is true. The power (light) they generate is roughly",
"P = VI",
"(e",
" - 1)",
"where I",
", q, and k are all device or physical constants (saturation current, electron charge, and Boltzmann's constant, respectively), V is the voltage the diode is at... |
[
"How much do we know about how and why cells in a developing fetus assume different forms and have different functions?"
] | [
false
] | Obviously not only mammals, - cells start dividing, then at some point - this one becomes a nerve, that one a scale or a hair, another a heart, blood to go through the heart, and so forth....just held my new grandson a couple of days ago, and was thinking how not long ago he was one, then two, then all of them.... Than... | [
"We know a lot about how, chemical gradients and which ones drive the large processes such as which side is up and which side is down, left vs right. Why is more of a question of evolution, that goes way way back i.e. gills form before lungs a tail comes and goes away, the webbing between joints goes away to form f... | [
"We know quite a lot; we ",
" know far more. Studying embryonic development in all sorts of species is a long-standing way of learning about basic genetics. There are whole textbooks on the subject. To hugely oversimplify, cells at the head make a lot of chemical H, while cells at the tail make a lot of chemica... | [
"Obviously not only mammals, - cells start dividing, then at some point - this one becomes a nerve, that one a scale or a hair, another a heart, blood to go through the heart, and so forth....just held my new grandson a couple of days ago, and was thinking how not long ago he was one, then two, then all of them....... |
[
"How do semiconductors work? Specifically, I have a question about n-type/p-type extrinsic semiconductors."
] | [
false
] | [deleted] | [
"What I didn't understand is why we're not simultaneously bringing in holes from the dopant along with the extra electrons we know the dopant has.",
"Think of doping as not adding but replacing the silicon atoms. So in terms of their intrinsic holes and electrons (caused by thermal fluctuations), the numbers have... | [
"What I didn't understand is why we're not simultaneously bringing in holes from the dopant along with the extra electrons we know the dopant has.",
"Think of doping as not adding but replacing the silicon atoms. So in terms of their intrinsic holes and electrons (caused by thermal fluctuations), the numbers have... | [
"If you look back up a section in the article at the 'Carrier generation and recombination' it explains that because of thermal fluctuations: ",
"In some states, the generation and recombination of electron–hole pairs are in equipoise. The number of electron-hole pairs in the steady state at a given temperature i... |
[
"What is the electrical current actually doing in am antenna?"
] | [
false
] | From what I've read so far, an antenna is just a conductive piece of metal and radio waves induce an electric current in it which can be decoded into sound or images. But a piece of metal can't discriminate and is being bombarded by every radio and TV station and wifi signal and garage remote in the area right? So are ... | [
"AM broadcast antennas are usually ferrite rods with a coil of wire around it. That's because their wavelengths are 200-600 meters. Long wire antennas can also be used. The antenna coil is connected in parallel with a variable capacitor. Together they form a resonant circuit which is very frequency sensitive. ",
... | [
"You ever rock back in forth in a bathtub, getting the water wave higher and higher? It only works if you move a certain speed. The antenna works a bit like that. ",
"Mathematically, the signal of interest is modulated (multiplied) by a sinusoidal carrier wave at the base frequency for the station. You can think ... | [
"From what I've read so far, an antenna is just a conductive piece of metal and radio waves induce an electric current in it which can be decoded into sound or images. But a piece of metal can't discriminate and is being bombarded by every radio and TV station and wifi signal and garage remote in the area right?",
... |
[
"If Newtons's second law of motion is F=ma, then why is the speed of an object falling in an vacuum not dependent on mass?"
] | [
false
] | [deleted] | [
"It depends on the force.",
"For good 'ol gravitation there's a mass term in the Force which get's canceled out:",
"F = GmM/r",
" = ma",
"GM/r",
" = a",
"The big M relates to the mass of the other body. For forces like those defined by say an electric motor and a string, the speed at any given point wil... | [
"You have to consider what the F in F=ma is: the force acting on the body to accelerate the mass.",
"Gravitational force (or weight) is also proportional to mass. An object that has double the mass also has double the weight. Gravitational force can be expressed in terms of gravitational acceleration and mass:",
... | [
"Fundamentally, you can cancel the ",
"'s on both sides because inertial mass is the same as gravitational mass. So the deeper version of the OP's question is, \"Why are gravitational mass and inertial mass the same thing?\" In other words, \"Why is an object's extent to which it resists acceleration the same ext... |
[
"Can you cool an object hotter than fire with fire?"
] | [
false
] | Not sure if I understand the thermodynamics behind the answer to this question. | [
"Yes, you can use fire to cool something that is hotter than fire, but the fire cannot cool it below the temperature of the fire (assuming that the room isn't cooling the object further).",
"When two things are put together that are at different temperatures, heat flows from the hot body to the cold body until th... | [
"What is this? If the thermometer were already at some temperature hotter than 250°C and it came in contact with the \"fire cube\", it would lose heat to the \"fire cube\" until it read 250°C (assuming the thermometer has negligible thermal mass)."
] | [
"But the answer to the question \"Can you cool an object hotter than fire with fire\" is an unambiguous \"YES!\", not \"No\" - I'm not sure what you were saying or trying to prove in your original post."
] |
[
"Why aren't shadows completely opaque?"
] | [
false
] | I'm trying to figure out why a shadow, which is formed from light not being able to pass through an opaque object, isn't itself opaque. I can see whatever object upon which a shadow is being cast. Is this because light is still shining around the initial shadow-casting object? Or am I thinking about this the wrong way ... | [
"If you had a sole light source shining on an object in a vacuum, then anything in the shadow would not be viewable. But light tends to scatter around in air, and there are usually multiple sources of light. So if you stand outside and cast a shadow, light from the sun is bouncing off of the air, or other objects... | [
"Yeah - even on the moon shadows aren't totally black because of the light bouncing off the rocks around you."
] | [
"Diffraction doesn't matter unless you're talking about very small objects. It's more likely that there are just other light sources around that decrease the shadow's intensity.",
"If you think about a play or musical, when there's only the overhead lights shining on the actors, their shadows are pretty dark."
] |
[
"Why are there no really shallow seas?"
] | [
false
] | [deleted] | [
"Shallow bodies of water tend to be short-lived because the moving water will erode a lot of dirt/rock in a short time, geologically speaking. Ironically, though, the same effect will tend to deepen the rivers and shallow the regions of their outflow: sediment is transported from up along the riverbed to where it ... | [
"Almost all the water that used to go into it was diverted by Soviet projects to grow cotton in the desert.",
"e: It's pretty similar to what the US is doing to the Colorado River"
] | [
"To add to what has been said:\nShallow lakes will generally allow for a large amount of vegetation growth. As that vegetation dies, it sinks and decays at the bottom whole new vegetation grows up. This gradually causes the lake to be come shallower and shallower, and if there is no counter acting for forces, the b... |
[
"When integrating real functions, we're basically getting an area under the function. Is there a similar analogy for complex integration?"
] | [
false
] | I'm a student, currently 2nd year of physics. We're doing complex integration and I just can't grasp visually what we're actually doing. Is there a comparison with surfaces under real functions, or is it something completely different where I should just deal with the fact that I need to look for residues and integrate... | [
"It will be hard to visualize in the same way as Real Integrals. Complex Integrals essentially do what real integrals do, but if we have a complex function F(z), we can break it up into the real and imaginary parts F(z)=f(z)+ig(z) where f and g are real valued. The line integral of F(z) along some curve in the comp... | [
"Had to read this a few times but I really feel like I got it now. You cleared up my question with the first part, but thank you for going into details and explaining the poles too. Visualizing this IS kinda hard, but I guess that it's important that I understand what's going on really. Thanks again for the detaile... | [
"note that line integrals follow a one dimensional path through the 2d plane of complex numbers , not a 2d area in the C plane. whereas real integrals are over a 1d subset of the 1d real line. so the integration path is one dimensional in both cases. ",
"(rather useless but for the 4d complex volume under a comp... |
[
"Why does an object become radioactive when in proximity to a radiation source?"
] | [
false
] | My understanding is that when you have a radioactive material, e.g. Uranium, it decays which causes it to emit high energy particles, i.e. ionizing radiation. But say for example you leave a piece of clothing next to said Uranium for some time, the clothing will then become a radiation source itself. So how does this w... | [
"Ignoring contamination since that’s not what you’re asking about, there can also be ",
", where the material itself is made radioactive by radiation.",
"Any type of radiation, at sufficiently high energies, can induce nuclear reactions in matter, and the products of those nuclear reactions are not necessarily ... | [
"The material can capture neutrons emitted by the radioactive material, leading to neutron activation. The resulting isotopes in the nearby material can be radioactive and decay themselves, thus becoming radioactive.",
"https://en.wikipedia.org/wiki/Neutron_activation"
] | [
"Thank you for your answer!"
] |
[
"Is teleportation feasible?"
] | [
false
] | Can one hypothetically be able to make a machine that can transfer people and objects from one place to another by dissolving their matter and reconstructing it? | [
"Just FYI, there are well defined theoretical upper bounds on information bandwidth."
] | [
"Short answer: No.",
"Consider electronically transmitting a human via computer. There are about 10 trillion or so (maybe more) cells in the human body. Storing just their location to the micrometer, in a (1m * 1m * 2m) box, with 1 µm accuracy:",
"1m / 1µm * 1m / 1µm * 2m / µm = 2 * 10",
" possible locations... | [
"You're right. When you put it like that, I can't imagine it's possible to collect that much information that quickly. I still don't want to rule it out completely, that's never a good idea, but the complexity is incredible."
] |
[
"When you \"burn fat\" how exactly do you loose mass?"
] | [
false
] | Do we sweat more, poo more, per more? | [
"the main source of sustainable weight loss is through breathing. You can of course lose mass by sweating and peeing, but that is not sustainable as most of that loss is water which needs to be replaced for proper function of organs. Weight loss (specifically of fat) follows the same formula as burning gasoline:",
... | [
"This is a fun question to ask people, because, as you did, most people guess poop.",
"You lose the weight through breathing and releasing carbon dioxide. That being said, if you're heavy and trying to lose weight, don't just start breathing in and out quickly, you'll just hyperventilate.",
"Similar to the ques... | [
"It's kind of funny that \"burning\" fat isn't even a colloquialism. Cellular respiration is actually a tightly controlled combustion reaction. That fact still blows my mind"
] |
[
"How many mph does something vibrate back and forth, like a tuning fork or a speaker?"
] | [
false
] | Obviously it starts and stops a lot, but what would the range of speed be at its peak? | [
"Peak would be ωA = 2π(440 Hz)*0.002m = 5.53 m/s, assuming it's a simple harmonic oscillator. The harmonics might throw it a bit off that. "
] | [
"If you assume a 2 mm (peak) amplitude, then it is double what you calculated as there will be a total of 8 mm traversed per cycle, not 4 mm. Therefore: 3.52 m/s (7.87 mph).",
"However this is only the average speed. The peak speed will be higher."
] | [
"All of this is going to depend on the pitch of the sound and what instrument is producing it. Just throwing out a ballpark number for tuning forks, though:",
"Supposedly, these days most tuning forks vibrate at 440Hz, that is, 440 cycles per second. Assuming an amplitude for the fork's arm of about 2mm (dependin... |
[
"What is the relation between the mass and radius of a star?"
] | [
false
] | I've been looking on the Internet for some kind of formula without success. I guess that the radius of a star might be influenced by many factors; if you want to describe them that would be great, but I would be happy just by knowing how the gravity of the mass influence the radius, simplifying phenomena like photon pr... | [
"Probably the simplest thing would be to restrict yourself to \"main sequence\" stars, otherwise you have things like red giants and white dwarves and whatnot. The mass-radius relation is usually described as a powerlaw where R is proportional to M",
" for stars smaller than the sun or M",
" for stars bigger th... | [
"If you're not used to fitting data that spans multiple orders of magnitude, make sure you look on logarithmic axes."
] | [
"Thank you! I fitted an exponential grow curve in those data points. That will do for the moment :)"
] |
[
"Are there any species where their gender birthrate isn't 50% male and 50% female?"
] | [
false
] | [deleted] | [
"Off the top of my head, sea turtles!",
"...But that's highly conditional.",
"At a certain temperature, birthrate is ~50/50. However, once a certain average temperature is lowered or raised, birthrate can become skewered to one gender or the other. This is a big problem with Global Warming impending."
] | [
"I believe there are many species. The hymenoptera are a nice example (bees, wasps, ants). ",
"In most of these species, males develop from unfertilized eggs, having only half of the chromosomes of their mother; something called hapolodiploidy.",
"A consequence is that sisters are genetically 3/4 related instea... | [
"Humans. 49% of all humans are female, 51% are male. It has to do with men being born more with physical and mental disabilities due to their Y chromosome. Its natures way of compensating."
] |
[
"Could abiogenesis occur again?"
] | [
false
] | [deleted] | [
"Not likely on this planet, at least not in nature. Existing life has filled every conceivable niche available to it, and will quickly gobble up any free resources in its environment, including any bits of goo that happen to contain a brand new kind of replicator. A brand new life form just isn't going to be able t... | [
"We're still trying, but we don't know all the details.",
"It's folly to try to predict when we'll be able to, just that we will eventually if we don't die out first."
] | [
"There are two things to consider with this; firstly that the chances of abiogenisis occurring is incredibly small and in the timeframe of humanity, a mere speck in Earths timeline, very unlikely. Secondly, the natural conditions that exist today differ greatly from the conditions that existed. For example, the mil... |
[
"In the way we can detect a small change in temperature when running the tap, can we feel the same slight changes with extreme temperatures?"
] | [
false
] | I understand that changing the temperature of water slightly can be felt but what about for example, the difference between my hand touching a 180C oven and a 220C oven? Will they just give that same burning pain or is there a vast difference between them? | [
"The limit might be when your proteins denaturate, losing their functionality and causing tissue necrosis, needless to say that happens at temperatures far lower than 30,000,000c :) "
] | [
"Well the just noticeable difference can't just be linear FOREVER, because AFAIK, there's no limit on temperature, and neurons can't just continue distinguishing information with infinite resolution. I guarantee you can't notice the difference between 30,000,000 degrees and 30,000,040 degrees.",
"I can't find rel... | [
"It depends on whether you are talking about the sensation of pain or the sensation of warmth or heat. The sensation of heat-induced pain appears to scale linearly with temperature. The sensation of warmth, however, is exponential (over a small area of your skin) so that an equivalent change in temperature is going... |
[
"How was it discovered that same metals would stick together in void? (plus a couple of questions in comments)"
] | [
false
] | [deleted] | [
"Metals in space do not act as if they're covered in glue. Vacuum welding is an effect where, theoretically, metals and crystals can form a single object by touching clean surfaces together. This works, because at the atomic level, there is no reason for the structure to \"end\". Take a piece of pure iron, it is a ... | [
"The Soviets actually fired a 23mm canon from the Salyut-3 space station just prior to it reentering the atmosphere. Do yeah, appropriately designed firearms should work fine in vacuum."
] | [
"So the notion that a firearm will vacuum weld itself together after being fired once is a possible-but-very-unlikely scenario?"
] |
[
"Why are siphonophorae considered \"colony organisms\"? What's the difference between a morphologically specialized zooid and an organ?"
] | [
false
] | Why was a distinction needed? The zooids share the same DNA, comes from the same egg, are non-mobile respectively to one another and are incapable of surviving on their own. (and even if some segments of their organisms were able to survive and regrow if cut from the rest of the body, the starfish, which aren't conside... | [
"We consider siphonophores to be a colony organism because of how they develop and are organized compared to other cnidarians.",
"The cnidarians body plan generally falls into one of two categories. The medusa or the polyp. The most common example of a medusa form cnidarian is a jellyfish, and a common example of... | [
"It might actually be easier to think about it from the other direction.",
"Honeybees probably represent the closest equivalent to siphonophores in the animal kingdom. A colony of bees is made up of individuals who function much as a single organism would.",
"The queen bee takes on the reproductive role, and ma... | [
"the distinction is made based on the origin of the zooids",
"in everything from a fruit fly to a human the first fertilized cell divides many times into a mass of cells, aligns itsself along some gradient and develops bands of cells with know fates ",
"siphonophore cells bud off the first fertilized cell with ... |
[
"Is there ANY way to count a second flawlessly?"
] | [
false
] | Thought about this while watching 'The Cube' on TV today, one of the challenges required the contestents to count down from 10 to 0 and press a buzzer to pass (they were allowed 9 - 10 seconds) so it got me thinking is there a method of counting perfect seconds every time? | [
"He's probably referring to mental tricks."
] | [
"It's the most accurate way because that's what a second actually ",
", according to our system of measurement. A second is \"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.\""
] | [
"Atomic clocks are pretty much the most accurate way I think, specifically the Caesium one at NPL, with accuracy of ~ 2.3 × 10-16."
] |
[
"Why does a shock wave distort light?"
] | [
false
] | You can see a shock wave clearly in an example like but why? It is very similar to the way light is distored as it enters a new medium. However, it's still the same medium, does it have something to do with the density of that medium around the wave as it propagates through the air? | [
"It is very similar to the way light is distored as it enters a new medium.",
"does it have something to do with the density of that medium around the wave as it propagates through the air?",
"Your intuition does you credit, this is exactly what is happening. The change in density results in a modified index of... | [
"Correct. In particular, the \"shockwave\" is in effect a severe gradient of density in the medium, which has the effect of bending the light. In other words, the relative density of the air at the point of the shock is so greatly different than the surrounding air that light is refracted by it.",
"EDIT:",
"In... | [
"You've got the right idea. A shock wave is a discontinuity in pressure, so at the shock front the density of air is higher.",
"Light is distorted not just when entering a new medium, as you say, but whenever there is a change in the ",
"refractive index",
" of a material. So, when the density of air changes... |
[
"Is a person exposed to radiation contagious?"
] | [
false
] | If a radiation-exposed person touches something or someone, does it also become irradiated? | [
"If radioactive particles are on or in the body, then yes, the person is radiating anything around them.",
"If a person was exposed only to the radiation in a form of rays, like x-rays or gamma rays, then they will not be radioactive themselves.",
"Imagine fire, instead of radiation. If you hold your hand very ... | [
"Depends on the exposure type. But in general terms, no he is not contagious. ",
"Someone that has been exposed to the radioactivity will not be contagious. This person would basically have received a dose of high energy particles (x-rays, neutrons, gamma rays…. Or many others). This exposure is common when y... | [
"That's actually a good analogy. The biggest contribution to heat transfer from a fire to surrounding objects is via infrared light, which also is a form of radiation. If you sit close to a fireplace, feeling the heat in your face, try holding your hand or even a thin piece of paper in front of you, it will block a... |
[
"How do you get consistently sized dna?"
] | [
false
] | null | [
"Hi usastar3 thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the follow... | [
"Biology"
] | [
"‘Biology’"
] |
[
"How far up will helium travel?"
] | [
false
] | Will helium continue up and disappear into space or will it stay somewhere in the atmosphere? If it stays in the atmosphere, how far up? | [
"Helium will (and does) escape the atmosphere if it reaches high enough altitudes.",
"At low altitudes, collisions between helium and other gas molecules like nitrogen and oxygen keep it within Earth's atmosphere. However, at higher altitudes, it reaches high enough velocity to escape the atmosphere."
] | [
"To add to this there is also the interaction with the solar wind that effects the most extreme parts of the atmosphere. In short it blows away unlucky molecules that get too high up or are just in the wrong spot, ie near the magnetic poles."
] | [
"To add to this there is also the interaction with the solar wind that effects the most extreme parts of the atmosphere. In short it blows away unlucky molecules that get too high up or are just in the wrong spot, ie near the magnetic poles."
] |
[
"Is there a psychological disorder that features the disability to hate something?"
] | [
false
] | null | [
"I'm not sure if there exists a disease in which the intrinsic feeling of hate (or less extremely--if on the same spectrum--dislike) is inhibited or absent. However, Angelman Syndrome may be of interest to you because these patients are often characterized by excessively happy demeanour. That being said, hate is an... | [
"The DSM-IV-TR has a stipulation for every disorder that the patient does not meet the criteria if their symptoms are not causing a disruption to their daily lives or others. While there very well may be a group of the population who lack the ability to feel strong negative emotions, it would likely not be consider... | [
"Ok, that seems like a pretty bad condition. Thinking more about the question I'm more and more convinced that hate probably is way more complex of an emotion and requires some cognitive processes to be perceived (which is why those patients with a lack in development are particularly happy). That being said, it mi... |
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