title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Can somebody explain gravitational slingshots to me?"
] | [
false
] | [deleted] | [
"Gravitational slingshots allow spacecraft to 'steal' some momentum from planets and increase their speed (relative to the Sun) while using very little fuel.",
"Consider Jupiter, a frequent tool for gravitational slingshots. Relative to Jupiter, a spacecraft comes in with some speed v, then Jupiter's gravity defl... | [
"Imagine there's a truck driving towards you and you throw a bouncy ball at it. How fast does it bounce back? Ideally, it's the speed you threw it plus twice the speed of the truck. From the truck's reference frame, the ball (and everything else) was moving very quickly in the direction of the back of the truck. No... | [
"Another way to think of it is this. When you fall towards a planet, let's say it takes 10 hours to reach the lowest point. If you then burn fuel or position yourself so that the planet follows it's orbit away from you, then it may take only 9 hours to ecape the sphere of influence. Because you spent less time l... |
[
"Does light undergo \"acceleration due to gravity\"?"
] | [
false
] | If you drop/horizontally launch an object near the surface of the earth, its y axis velocity changes at a rate of about 9.8 m/s If I "launched" a beam of light at the surface of the earth, would its y axis velocity also change at a rate of 9.8 m/s | [
"Actually, the beam of light will bend exactly ",
" as you would calculate using the classical acceleration, due to relativistic effects. That's still immeasurably small, however. We do observe that sort of bending for starlight around the sun, and for gravitational lenses, for instance. "
] | [
"\"Classical\" can also be taken to mean nonrelativistic, though \"Newtonian\" is probably the more common (or at least less ambiguous) word."
] | [
"What number do I use for the mass of the light?",
"There's no need to use anything for the mass of light, since all bodies fall at the same rate ;) Just use the Newtonian value of the acceleration due to gravity, apply it to your light ray, and find the angle by which the Earth's gravity bends it. The result wil... |
[
"Can we utilise metal pathways and boots to simulate gravity in space?"
] | [
false
] | [deleted] | [
"Not easily, or not well. We can use magnets to adhere to surfaces, so you could walk around on the metal with fairly small magnets. However, the magnetic force works over a much shorter distance than gravity, meaning that if you were to jump, you would either just fly off or need unreasonably powerful magnets to p... | [
"Adding to that, even if you found the way to make it work so that astronauts can walk comfortably, it still wouldn't prevent the health problems related to microgravity (bone mass loss, muscle mass loss and compromise of the immune system)."
] | [
"thanks for the clear insight✨"
] |
[
"What causes flexibility in humans?"
] | [
false
] | I've heard the muscles/tendons/ligaments/etc. physically get longer when people are able to stretch further, but I feel like there must be more going on. Like what's happening at a cellular or biochemical level when you stretch that leads to you having more flexiblity? | [
"Your body has a stretch reflex. Proprioceptors reside in the parallel with the muscle tissue. These receptors sense the muscle length and tension. When the muscle gets to a certain \"stretch\", then the \"stretch reflex\" is activated, causing the agonist muscle (i.e. the one being stretched) to contract/resist... | [
"Thanks! So from what you've said, is it at least theoretically possible to \"trick\" your muscles into being really flexible? Like say you were so inflexible you couldn't get your hands past your knees, but there's nothing fundamental about your muscles that's preventing you from doing splits? If the proprioceptor... | [
"Patients under general anesthesia are much more flexible than they are normally, due to the inhibition of receptors mentioned above. So it's possible. "
] |
[
"What do hospitals do with cancer tissue after it is removed?"
] | [
false
] | I assume it probably goes to research treatment, but how does that actually work in practice? | [
"At least ",
"one famous cancer",
" was made immortal and is used for research in thousands of labs around the world."
] | [
"they put it with all the other biological waste and incinerate it.\nAlthough if they think it is usable like say for med school use they will keep it. I cant say specifically if this happens with cancer tissue.\nThere are other things like umbilical cords which are filled with a high level of stem cells, you can a... | [
"It is sent to a cellular pathology laboratory for examination by a pathologist who will issue a report that will confirm the diagnosis, determine the prognosis and help guide if further treatment (and what treatment) is required. Some of the material (processed paraffin blocks and microscope slides) will be stored... |
[
"Is the ability to make the decision to not reproduce unique among humans?"
] | [
false
] | null | [
"Armchair zoologist here, but aren't panda's notorious for being too lazy to reproduce?"
] | [
"the end result is that they're deciding not to reproduce in zoos.",
"I think that's too strong a conclusion - they're simply deciding not to have sex."
] | [
"Mate selection isn't just common, it is practically existent in almost all animal species (and I say almost because I will acknowledge that there ",
" be exceptions).",
"Sexual selection is incredibly important to evolution."
] |
[
"Are organs sensitive to touch?"
] | [
false
] | If I could somehow touch one of my organs, would I feel it? I can push on any muscle or organ and I only feel it on my skin. But at the same time, liver shots exist which seems to me that you they do feel pain. I’m guessing organs only cause you pain during acute trauma and not regular activities but I’m curious what t... | [
"Touch sensors (discrete for pressure, vibration, temperature etc) are different from the proprioceptors like stretch or pressure sensors in internal organs, they inform different parts of your brain. So a real \"touch sense\" only applies to skin and mucosa (think mouth, nose, rectum etc).",
"Nerve endings sensi... | [
"I just learned that syphilis infects the brain. I thought it just made your balls rot or something."
] | [
"That explains Krendler's lack of response to the intracranial probing of Hannibal Lecter."
] |
[
"Why are black holes thought to be singularities with infinite?"
] | [
false
] | If a supernova that doesn't have infinite density collapses into a black hole then how can a black hole form that has an infinite density? Could black holes be points or areas that just have enough mass and therefore enough gravitational pull to not let light out, but not an infinite amount of mass? I feel like this co... | [
"First, the term \"black hole\" refers to the region bounded by the event horizon. Thus, black holes have finite density.",
"The singularity itself could possibly be described as having infinite density, but (1) that's just a natural consequence of squeezing a finite amount of stuff into a point of zero dimension... | [
"It's usually just called the singularity."
] | [
"Edit: Also, supermassive black holes aren't necessarily \"bigger\" than other ones. They just have a bigger event horizon.",
"A black hole is a region of space bounded by an event horizon. Since a supermassive black hole is more massive and has a larger (event horizon) surface area than a stellar mass black hole... |
[
"Absolute zero"
] | [
false
] | So i was just in chemistry class today (senior year high school) and we were talking about absolute zero. Can someone explain the concept to me; the teacher was saying that things such as processors would be able to function easier because it would essentially have a straight path. But at like -50° F don't things start... | [
"Resistance doesn't become zero at absolute zero - many metals (including copper) have residual resistance that is constant and nonzero at low temperatures, not decreasing (discussed ",
"here",
"). And for materials that do reach zero resistance at sufficiently low temperatures (superconductors), they typicall... | [
"The temperature of an object is (essentially; more in a bit) the average kinetic energy of its particles. Kinetic energy is 1/2",
"velocity",
" and is strictly non-negative, as mass and velocity",
" are positive. So, when you have no kinetic energy, you cannot get colder, and we call this absolute zero. Temp... | [
"Funny enough, while resistivity in metals decreases with temperature, and in some cases goes to zero resistance well before 0K, semiconductors in computer processors would not function at too low of temperature. The dopants used to change the conductivity of a semiconductor would no longer have enough thermal ener... |
[
"Did the Hunga-Tonga explosion produce a significant overpressure at the spot on the other side of the earth where the shockwave converged?"
] | [
false
] | I'm wondering if locations on the exact opposite side of the Earth from major volcanic eruptions are at some kind of risk for e.g. having their windows blown out. The thought was triggered by . | [
"[Edit - this response is to the idea that there is an ideal antipode and windows getting blown out - see response below to the more general question] No - the idea behind your question is spot on though. In a perfectly uniform spherical system this is what you would expect.",
"However, the Earth is not a sphere,... | [
"To the title question: yes, three times. ",
"Here's an amazing video:",
" the top panel shows a computer simulation of the propagating air pressure wave from the Hunga-Tonga explosion. The bottom panels show actual air pressure measurements at several locations (Hawaii, California, the Carribean, and southern... | [
"The oblateness of Earth is ~20 km difference in radius, far larger than mountains, and it's everywhere not just in a few mountain ranges."
] |
[
"Is it better to accelerate or decelerate through a turn than to maintain constant speed? (Why?)"
] | [
false
] | I distinctly recall my high school physics teacher telling us this would be more important when we were older. I certainly forgot the specifics of this as soon as we left class, but the idea has stuck with me and pops into my head regularly when going around long turns... | [
"Neither. For a maximum non-slipping turn you would not apply any power to the wheels, and only use them for turning. Any additional power reduces the amount of force that the tires can use to turn the car.",
"However this is the case only in a non-slipping turn, with only the static friction of the tires vs th... | [
"But turning ",
" acceleration, and hitting the gas pedal is a bad thing if it causes your tires to skid. The real question is whether OP should be pressing on the gas pedal, the brake, or neither in order to get a better minimum turning radius at a given speed without losing traction.",
"I think the answer is... | [
"Fastest way through a curve is late apex - brake as late as possible turn sharp shortly after the apex and hit the gas. Less time braking, more time on the gas. This is taught at nearly all motorcycle road racing courses, and if you watch racing, you can see it in action. On a side note, this is a good techniqu... |
[
"If I blended everything I ate, would it make a difference?"
] | [
false
] | null | [
"Actually, it's not the juice that's coming out. The juice is just stimulating your bowels to \"clear room\" since you have food incoming. Some foods do this better than others due to their nutrients, but it's a general response to new food in the stomach/upper small intestine. When you make a bowel movement it's n... | [
"A difference? yes - saliva contains amylase which is necessary to breakdown starch (which is high in modern carbohydrate laden diets). The grinding action of the molars and the manual manipulation of a bolus of food around the mouth facilitate a) salivation b) coating of the food bolus with saliva allowing amylase... | [
"What? Complain about non-science and then go on to make a statement based on a guess? The whole purpose of the digestive process is to break down the food, blending is just like chewing - only way better. The enzymes released by blending in no way detract from the quality of the food, in fact it could only aid di... |
[
"Is there a map of the known universe as it \"is\" vs what it \"was\"?"
] | [
false
] | Every time I see that cool 3D map of the universe, it is prefaced with, "we are looking into the past". While that's cool and all, we do know the location, approximate distance, and approximate direction of travel and speed. Has anyone ever "advanced" the map to where everything is (or should be) positioned today? | [
"Except in a few special cases, we can't even confidently predict the motion of three objects or celestial bodies, let alone billions of them -",
"we can write down equations which describe the motion of the sun, the planets and any spacecraft flying about between them. ",
"If we simplify the solar system and ... | [
"The simple answer is that it's not so simple. We do have the approximate location and velocity of many things in the universe at the time we see them at, but not even close to the entire universe, and the fact that it is only approximate would make any simulations we create very inaccurate."
] | [
"Wow. I had no idea it was that complex. Thanks for the information:)"
] |
[
"What purpose does inflammation serve in immune response"
] | [
false
] | null | [
"Inflammation does many different things. On the one hand, it directly drives anti-pathogen measures. On the other, it is the connector between innate immunity and adaptive. Both aspects are about equally important. ",
"Inflammation happens when there’s tissue damage, or when cells detect common features associat... | [
"There's a fun new video by Kurzgesagt on the subject of the immune system that mentions this, at around 3:45.",
"https://youtu.be/lXfEK8G8CUI",
"Keep in mind that the video speaks very confidently on subjects that are still debated by science, but they do explain a good interpretation pretty well.",
"The exp... | [
"well itch is a completely different system which basically is present to hide the pain of swelling (in this case at least)"
] |
[
"Why does metal fuse without oxide layers?"
] | [
false
] | I recently found out that metals will fuse together just by touch if they are lacking an oxide layer. I have searched around about this but what I am really wanting to know is why this occurs. I mean what causes this to happen with this type of solid specifically? | [
"Metals fuse without oxide layers because the surface of both the metals before fusing had undergone surface reconstruction. Surface reconstruction is the rearranging of atoms in a different orientation than that of the bulk crystalline periodic structure. It takes energy to create a surface of any material. By pla... | [
"It's because the metals have no way of knowing what the \"edge\" of the substance is. We know that if we put, say, copper atoms in the same place, they'll combine together; this doesn't stop happening if you have two groups of copper atoms that have already aggregated. The only reason it doesn't normally occur i... | [
"I think yours is the only response that beings to address the heart of the question: why does the metallic material bond together but not the oxide?",
"Extending your line of thought, is it because metallic bonds allow for freer movement of atoms and electrons, in contrast to the stiffer ionic bonds of the oxide... |
[
"Does the inverse square law for waves (EMF, Acoustic) hold true at the microscopic level? Is the energy at a picometer away from the source really the square of the energy at 2 picometers?"
] | [
false
] | null | [
"The inverse square law is only true for a point-sized source. If you have a thin but infinitely long glowing line, the light intensity goes like 1/r over the distance to the line. If you have an infinite large glowing plane, the light intensity is constant no matter the distance (moving away from it decreases the ... | [
"In a given solid angle cone you get a larger area of the source as you move away."
] | [
"moving away from it decreases the light intensity from each spot but brings more spots into view",
"Can you elaborate on what this means? Every point on a plane can draw a straight line to any point above that plane without self-intersection, which means that all points on the plane are \"visible\" from any poin... |
[
"Why don’t we have vaccines for all Herpes Viruses?"
] | [
false
] | Ok so I hope I don’t sound like a complete idiot, keep in mind I have very little medical knowledge. So we have vaccines for shingles and chicken pox, which are herpes viruses. However we don’t have a vaccine for Cold sores, Genital Herpes, or Mononucleosis (also a herpes virus). Why is this? I know they are obviously ... | [
"Vaccines work by training your immune system to respond to the pathogen. Herpes simplex virus 1 and 2 (the kinds that cause cold sores and genital sores) are immunoevasive, which means that they have a mechanism to avoid destruction by your immune system. As your immune system begins to respond to the virus, herpe... | [
"It’s not for lack of trying. These vaccines have been in the works for about 100 years but they keep failing the clinical trials. Sometimes the vaccine itself has too many side effects - I remember there was some neurotoxicity - and other times the resulting antibodies weren’t robust enough to eliminate the virus,... | [
"One main factor is cortisol. The \"stress hormone\". It actively supresses your immune system to conserve energy."
] |
[
"I just bought a new microwave oven and it came with a metal rack. You can't use most types of metal in a microwave, so why is the rack okay? Maybe the shape or the composition?"
] | [
false
] | Has microwave technology changed? | [
"Metal objects with points will cause electrical arcing. The rack that came with your oven will not. It's the same technology, it's just the shape of the metal makes it safe for use inside the oven. "
] | [
"Does that mean that metal spoons are microwave safe because they don't have points?"
] | [
"yes, and forks will arc."
] |
[
"I have a question about Schrödinger's cat."
] | [
false
] | Wikipedia states this as an example of quantum entanglement. Now I Understand why it is quantum supposition. After a certain about of time the probability that the nucleus has decayed is high enough that it both has and hasn't and only collapses to one state on observation. But why is this quantum entanglement? I tho... | [
"The classic Schrödinger's cat experiment doesn't really demonstrate entanglement. Entanglement usually refers to a situation where a single system---described mathematically by a single wavefunction---is separated somehow into (what we normally think of as) two systems. The math, however, demands that the two syst... | [
"Keep in mind that \"Schrödinger's cat\" is not a serious interpretation of quantum mechanics, it is an attempt to concoct a thought experiment to discredit (or at least expose the limits of) several of the leading interpretations of quantum mechanics at the time."
] | [
"I think you accidentally a word in your cat analogy at the bottom there."
] |
[
"Are spiral galaxies accretion discs for supermassive black holes?"
] | [
false
] | [deleted] | [
"No. The supermassive black hole at the center of a galaxy has virtually no interaction with the rest of the galaxy not near the centre."
] | [
"Depends on the galaxy, but for the Milky way, the amount of mass in baryonic matter is roughly 10",
" solar mass, and the black hole is roughly 10",
" solar mass, so about 0.001%. And then there is about 10 times as much dark matter as regular matter, so about 0.0001% of the total mass."
] | [
"Speaking as an astronomer, I would informally characterize about 99% of astronomers in being ",
" in the existence of dark matter, as there is a ton of other evidence for it as well. "
] |
[
"Is there a limit to how large marine life could become?"
] | [
false
] | Besides the obvious factors such as finding enough food. I know that land animals can only get so big (though I don't know any exact range) because of both gravity and oxygen levels, but are there similar limitations for aquatic life? And if so, can I get a ballpark estimate for how big some kind of ocean leviathan cou... | [
"Since you didn't mention any sort of phylogeny, no, there is not limit to how large marine \"life\" could become. This is including superorganisms of fungi and plants though. There is theoretically no limit to the size of a single fungus, or say a massive algal bloom caused by a single organism could be. (I'm n... | [
"Considering the fact that the OP was mentioning gravity and oxygen levels as limitations for terrestrial animals, I think that he meant his question to be a little more specific than \"life\". My interpretation would be that he wants to know about vertebrates.",
"Aside from finding enough food, I would guess tha... | [
"One other thing to consider is density. Bony fishes and mammals can only get to a certain size before the amount of bone in their skeleton causes them to sink. This is particularly problematic for air-breathing mammals. This is why whale skeletons are so diminished. Also, looking to larger bony fishes (such as the... |
[
"What's the difference between d^2 x(t)/dt^2 = -x(t), and idx/dt=-x(t)?"
] | [
false
] | In this specific case, it's only true when d x(t)/dt =idx/dt, but is there a more general connection? The two equations give the same solution set. | [
"The two equations give the same solution set.",
"Not quite. The general solution to the first is x=c*e",
"+d*e",
", or equivalently x=a*cos(t)+b*sin(t). The general solution to the second equation is just x=c*e",
". This is not surprising, since second order (homogeneous) differential equations will genera... | [
"It's the same difference between the two equations x",
" +1 = 0 and x-i = 0",
"While i is a solution of both equations, they are not the same equations. More specifically, the first equation has two solutions (i and -i) while the second one has only one solution."
] | [
"Suppose idx/dt = -x(t), or you could write it as dx/dt = ix(t). Then d",
"x/dt",
" = idx/dt = i",
"x(t) = -x(t). So the second equation implies the first. But the first does not imply the second. d",
" sin(t)/dt",
" = d cos(t)/dt = -sin(t), so it fits the first equation, but not the second."
] |
[
"How do plants die? Is there an exact moment when they simply die?"
] | [
false
] | Do they die simmilar to animals, or in a completly different way. | [
"Plants die cell by cell as opposed to animals that ",
" go from a state of being alive to death like when the heart stops. For example with plants if almost the entire plant is dead but you still have a bit of healthy root it would be possible to replant that root and it could grow into an entirely new plant. Th... | [
"To ",
"define death",
" in a multicellular organism is not as simple as you make it seem. A heart stop doesn't equate to immediate death in most meanings of the term.",
"Alongside that difficult question, animals like some starfish can also regrow complete bodies from a single arm, for example.",
"So, yes,... | [
"Agreed.",
"I think the true cause of the perceived difference is mostly because animal cells tend to rely more heavily on a more complicated support mechanism. Plant cells need water and minerals but not much of either, and they are capable of making their own sugars using light. Cut off the \"tap\" -- the con... |
[
"Can all matter be ionized (become plasma)?"
] | [
false
] | null | [
"Roughly speaking, it will dissociate into atoms, then the atoms will be ionized, as you increase the temperature."
] | [
"Yes."
] | [
"How would that work with things that a a mixture of multiple things. Let's say a chocolate bar?"
] |
[
"Is it theoretically possible to control radioactive decay?"
] | [
false
] | Could one speed up the rate of decay by stimulating an unstable nucleus without causing a chain reaction? For example, if an element decays by electron capture, could one bombard the nucleus with electrons to have a stimulated decay instead of a spontaneous decay? Also, I used electron capture as an example but my ques... | [
"I was wondering if theoretically there were safer and faster methods of processing radioactive waste instead of waiting for them to decay to stable elements on their own, preferably without starting a chain nuclear reaction or generating too much gamma radiation."
] | [
"I was wondering if theoretically there were safer and faster methods of processing radioactive waste instead of waiting for them to decay to stable elements on their own, preferably without starting a chain nuclear reaction or generating too much gamma radiation."
] | [
"Rate of decay is constant for elements, however it is possible to cause nuclei to emit particles or otherwise partially disintegrate. For example, in some neutron experiments, neutrons are produced through proton bombardment of tungsten, which emits neutrons during the process."
] |
[
"Can someone be colorblind in one eye?"
] | [
false
] | [deleted] | [
"In the visual pathway, colour is interpreted early on in the visual cortex (V1 specifically) using inputs from both eyes. In this sense, colour is encoded once information from both eyes has been combined. However, if only one eye lacks colour-sensitive photoreceptors (cones) for whatever reason, then the brain wi... | [
"Great response, thank you! I have a better understanding of this now!"
] | [
"I actually have very, very mild color blindness. I can't tell the difference between very dark blues and black with either eye. I also see colors more vibrantly with my right eye. With my left, they are all a little bit more dull. I would assume that this is due to some problem with the cones in my left eye."
] |
[
"At noon on Dec. 21 a beam of sun shines through a window. It lights up spot X on the center of an adjacent wall. We know the Lat-Lon and elevation of the window and wall. Can we predict where on the wall the sunlight would strike for any given time and day of the year? With what degree of precision?"
] | [
false
] | Let's assume that: The window frame and walls are insignificantly thick. In other words, the window frame, sill and thickness of that wall will not interfere. The beam on the wall will take the shape of the window, albeit distorted. Consider one corner of that shape to be the spot X which we're tracking. (This should b... | [
"In fact you can. When you were done, you'd have constructed an Analemmatic sundial. ",
"http://en.wikipedia.org/wiki/Analemmatic_sundial"
] | [
"Here",
" a handy demonstration of the motion of the sun throughout the year. Put your latitude to whatever you want, the time is set to noon by default but you can change that too if you want. Then you can drag the arrow on the calendar to change the date and see where the sun will be on that date at the chosen ... | [
"Thank you; that's very interesting. I'll need to spend some more time playing with it. Hopefully I'll be able to form a general conceptual understanding of the relationships of the sun, window and point X. "
] |
[
"When it is cold enough outside to see my breath, why can I not blow smoke rings?"
] | [
false
] | null | [
"This is anecdotal but I've definitely blown steam rings in the cold, was just doing it yesterday. Its harder and fainter but doable."
] | [
"When it's cold outside, the air in the atmosphere condenses into water vapor - thus we have \"smoke\". More accurate would be vapor.",
"When you smoke, the chemicals leaving your breath isn't only air/water. It consists of many more elements that make it denser. Because the smoke actually has density IN RELAT... | [
"I know you can blow rings with water vapor. While I was unable to find any photographic or video evidence of people doing it with only their breath in cold weather, I found a few instances suggesting it was possible but that it requires very stable air. So try it in a small enclosed space like a car. "
] |
[
"What happens if I shoot one single photon to a semi-transparent mirror?"
] | [
false
] | We can create single-photon laser emitter [1], and half-transparent mirrors can be created with very good accuracy. My question is: If I (multiple times) send a single photon to a 50% semi-transparent mirror, will I always get the same result (like the photon will always either pass through the mirror or be reflected)?... | [
"Any one of the photons will either pass through (transmit) or reflect; there is no partial transmission or partial reflection when talking about individual quanta.",
"Of the multiple photons, 50% of them will transmit and 50% will reflect, so you won't get the same result each time."
] | [
"It's a little more complex than this. The photon's wavefunction will split into two pieces, one transmitted and one reflected. So the photon, as a wavefunction, will both reflect and transmit at the same time. You are not really splitting a photon in half though, because both the reflected and transmitted parts ar... | [
"The photon's wavefunction will split into two pieces",
"I've not heard a photon as having a wave function. could you clarify what you mean by this? I've only ever heard of wave functions as being associated with quanta of matter, not energy."
] |
[
"Question regarding the big bang, quantum field theory, virtual particles, matter dominance, and the end of the universe."
] | [
false
] | A brief background of my limited understanding: As I've learned from Steven Hawking and Lawrence Krauss, our current understanding is that random quantum fluctuations happened to cause the big bang; that these same random fluctuations in the quantum field are also what is responsible for spontaneous virtual particle/an... | [
"Virtual particles are due to the uncertainty principle. Because of that they can exist for a short time. What happens with hawking radiation is that due to the uncertainty principle the virtual pair can exist, and quantum mechanically they event horizon is not perfectly defined. This lets one particle \"escape\" ... | [
"If both the universe and virtual particles spring into existence from nothingness via the same mechanism, do their similarities end there?",
"The similarities continue. A virtual particle pair can remain in existence as long as it doesn't violate the mass-energy bookkeeping of the universe. For a virtual particl... | [
"I am not an inflationary cosmologist, so I can't talk sensibly about the universe at extremely early times, but I do think that the analogy of virtual particles is generally taken too far.",
"Virtual particles are simply a bookkeeping device in quantum field theory. They are not, in a strict sense, really partic... |
[
"Why are we not photosynthetic?"
] | [
false
] | I'm assuming, based on the fact that we never incorporated chloroplasts (we being humans), that it is unfavorable evolutionarily, if that is a fair assumption, why is that? | [
"I can think of two evolutionary reasons.",
"First, it just doesn't produce enough energy for a mobile organism with a high metabolism.",
"Second, photosynthesis has two functions, the production of ATP for energy, and the conversion of CO2 to sugar and eventually other hydrocarbons. Since we get our sugars fr... | [
"We are to a limited extent, as our skin will produce Vitamin D when exposed to UV light. ",
"Source"
] | [
"You're making the common mistake of assuming evolution has a goal and that its goal is to make us more and more advanced or adopt a wider array of biologic tools. This isn't so. Our ancestors never incorporated, end of story. It might be favorable for us, today, to have done so, but it's not what happened. We ... |
[
"What prevents whales from getting the bends?"
] | [
false
] | How can aquatic mammals rapidly and deeply dive safely? | [
"There are a couple things going on here: First, risk of decompression illness is much greater when you breathe compressed air. When you just hold your breath, there's not a high risk.",
"Second, there's recent evidence suggesting ",
"that whales do in fact have decompression damage",
"."
] | [
"I'm not sure how you meant that statement but I want to stress to ",
" hold your breath while SCUBA diving."
] | [
"Your lungs can explode.",
"Air is a gas and is compressible; at a certain depth underwater the air will be at a certain volume. If you breathe in compressed air at a certain depth, hold your breath, then ascend, the air expands because there's less pressure at shallower depths. ",
"I'm probably mangling that a... |
[
"In the future will it be possible to implant a working third eye?"
] | [
false
] | [deleted] | [
"The eye and vision work very specifically through specific neural connections in the brain. Think of the brain as a jumble of wires connected very specifically to allow specific function. The brain is \"wired\" in a very specific way and changing just one thing could affect many different things.",
"To add an ey... | [
"there is a similar story about a",
" man who lived after having a pole go through his skull and through is frontal lobe",
". The brain retains neural plasticity which is it's ability to change and create new neural connections, however it has it's limits. These stories are more evidence for our brains to be ab... | [
"there is a similar story about a",
" man who lived after having a pole go through his skull and through is frontal lobe",
". The brain retains neural plasticity which is it's ability to change and create new neural connections, however it has it's limits. These stories are more evidence for our brains to be ab... |
[
"Do Organelles Just Float Around in the Cytoplasm of Cells?"
] | [
false
] | I know the Mitochondria in Plant and Animal cells floats around in the Cytoplasm, but do other organelles do, like the Nucleus, Vacuoles, ER, etc? I would guess so, but isn't cytoplasm jelly like? How exactly do the manage to move around? | [
"Actually, organelles, including mitochondria, don't simply float around the cell randomly... Cells have a highly structured cytoskeleton, which provides spatial and mechanical functions. Microtubules, for example, one of the three cytoskeleton constituents, determine the positions of membrane-enclosed organelles a... | [
"There is a fantasic animation made ",
" for Harvard students by some company about this:\n",
"http://www.studiodaily.com/2006/07/cellular-visions-the-inner-life-of-a-cell/",
"Someone edited out the parts with motor protein walking along the microtuble, in the background you can see how there is a network of ... | [
"A bit off topic but I would like to add that these animations only depict the cytoskeleton, motor proteins, the cellular membrane and vesicles during transport.",
"Videos like that are great if you want to study intracellular transport mechanisms, but it leads many people to imagine cells as mainly empty water b... |
[
"How does bioluminescence work on a biological level?"
] | [
false
] | Is it mostly found in deep water marine life? | [
"Luminescent organisms produce a pigment (called ",
"luciferin",
") that can undergo a chemical reaction with oxygen that gives off light. During the chemical reaction, an electron drops from an excited state to a lower energy state, causing a photon to be emitted.",
"This reaction is slow unless catalysed by... | [
"Also, many organisms bioluminesce because they have special organs that basically \"farm\" bioluminescent bacteria. The organism themselves cannot fluoresce but they harbor bacteria that do. Its a pretty neat symbiosis. "
] | [
" (a G- bacterium) uses ",
"quorum sensing",
" to activate its oxygen-dependent light-emitting ",
"luciferase",
" proteins, which allows clusters of the organism to act as on-off switches to each other. It does this by secreting small chemical messengers, to let nearby bacteria know that they have neighbour... |
[
"Is it really possible to build up a tolerance to toxic chemicals like cyanide/arsenic?"
] | [
false
] | This might just be a Hollywood legend, but it is really possible to build a tolerance to extremely toxic compounds despite the fact that less than a gram could kill the average person? | [
"In theory yes ",
"The body produces proteins called Metallothioneins which bond to dangerous chemicals and substances in order to protect your organs from damage.",
"They aren't produced in large amounts normally which is why you can die from taking large doses of hazardous chemicals. In theory you could condi... | [
"I've read stories on people who live in areas with unusually high arsenic deposits. Places like some parts of Mongolia and especially Bangladesh. Some of these people deliberately ingest it by sucking on and eating stones found around the area that are high in arsenic. They build up a tolerance. I did see some pic... | [
"Honey badgers can be bitten by cobras and survive"
] |
[
"Why are some viruses only transmitted by blood/sex and some only by saliva"
] | [
false
] | Reading about HIV I got wondering it's not transmitted by spit? What's special about blood and sex fluids that saliva lacks? And then I realised that the cold & flu are transmitted by coughing/sneezing (presumably saliva) and I've never heard anyone get the flu from sex. Why do some viruses get transferred by some meth... | [
"Viruses rely on receptors on the outside of cells to recognize cells (and gain entry into them). Different cells have different receptors, and so different viruses recognize different types of cells. ",
"The same way that a lock pick will not get you into a door with a digital keypad, and a circuit analyzer will... | [
"It's going to vary virus by virus, but let's start by offering an alternative to the hypothesis that you've offered (what does saliva lack to allow infection) to think about \"does saliva contain anything that might inhibit viral replication?\".",
"At least for HIV-1 it seems saliva contains certain properties t... | [
"Viruses come in all different shapes and sizes. Some are wrapped up nicely in a protein coating, some have different shapes of different protein shells, some are made of DNA while others are made of RNA. Because of all this variability, different types of viruses can only survive in different conditions. Some viru... |
[
"Are there populations of people that exhibit better mental health than others, and have they been studied?"
] | [
false
] | null | [
"If a population that small were to have the same suicide rate as in the US they would only have one suicide every 10-15 years. Since they are a small, homogenous community that have been infrequently observed I don't know if we can really extrapolate a lot from this fact. "
] | [
"If a population that small were to have the same suicide rate as in the US they would only have one suicide every 10-15 years. Since they are a small, homogenous community that have been infrequently observed I don't know if we can really extrapolate a lot from this fact. "
] | [
"Some extracts from the Wikipedia page on the Pirahã:",
"The Pirahã people are an indigenous hunter-gatherer tribe of Amazon natives, a subgroup of the Mura, who mainly live on the banks of the Maici River in Brazil's Amazonas state, in the territory on Humaitá and Manicoré municipality. As of 2010, they number 4... |
[
"For Practical Purposes, do Black Holes Remove Energy from the Universe?"
] | [
false
] | From a practical standpoint, is something within a black hole still part of the universe? To my knowledge, the only way the contents of a black hole interact with the rest of the universe is through gravity. Any thermal or light energy within a black hole does not interact with the rest of the universe (Unless energy p... | [
"Things that fall into a black hole won't themselves re-enter the rest of the universe. But, the black hole itself can still release energy either through quantum-mechanical Hawking radiation, or by interacting gravitationally with other objects (including other black holes). As a concrete example, the recent gravi... | [
"So, if there's gravitational energy, where does it come from? Does matter lose mass in the form of gravitational energy? Eventually, will all matter deteriorate into gravitational energy?",
"Also, if heat energy turns into gravitational energy by enterring a black hole, does that reduce entropy?"
] | [
"That's basically right. It's hard to define a total energy in general relativity, especially for a black hole, but by at least one good definition the black hole is ",
" gravitational energy. Things that fall in just become gravitational energy instead of whatever they were before. Some of that energy is stored ... |
[
"Why do I have a specific taste in my mouth when I'm taking a small nap on my table/couch and awaken suddenly?"
] | [
false
] | null | [
"No, I don't mean that.",
"That's a very specific taste when I'm feeling very exhausted, take a mini-nap for 3-4 min during work and being awaken suddenly.",
"That doesn't happen when I'm exhausted and just go comfortably to bed.\nI thought it was something chemically that \"puts me to sleep\""
] | [
"I know what you mean, to me it only happens while actualy naping, this doesnt occur when sleeping normally at night. "
] | [
"'It's as if a cat urinated in your mouth while you were napping'",
"Mystery solved."
] |
[
"When scientists talk about consciousness, are they referring to the subjective experience of perceiving the world, or the ability to be self aware?"
] | [
false
] | [deleted] | [
"A self driving car is aware of its physical location with respect to everything else. I am self aware because I am aware of my thoughts in addition to external stimuli. I don't think we have any evidence to suggest that cars have this. Calling them self aware, and saying they have a subjective self because they h... | [
"Well this is a very complex question. Actually there's a semantic and philosophical discussion about what consciousness is. \nIn general lines, consciousness is the ability to experience or know an external or internal object. However, as Velmans said, the disagreement on the definition of the term might mean that... | [
"Christopher Koch and Giulio Tononi (who are generally considered serious and rigorously scientific scholars of consciousness) I think generally ask more about the first thing. That is, the subjective \"phenomenal\" self (which is a dirty philosophy word that's poorly defined but most people have an intuition of wh... |
[
"Would it be possible to synthesize a functional blood cell with little/no iron? Or would iron be required to have functioning hemoglobin from the start?"
] | [
false
] | For people with disorders such as sickle cell anemia / thalassemia (major), frequent blood transfusions ultimately cause toxic build-up of iron. While chelation is possible to some extent, it's a restrictive, physically taxing and expensive process. Rather than pay for these treatments, I was wondering if a blood cell... | [
"In principle one could design a cell with hemocyanin (using copper) instead of hemoglobin(using iron) oxygen carrier. I suspect that this would require immunosupprssion, however as this protein is not endogenous to humans. Hemocyanin is hemoglobin surrogate in arhtropods and the reason their blood is blue (from ox... | [
"Iron is the ‘active ingredient’ of red blood cells. Red blood cells are little sacks of haemoglobin, and the body places a single iron atom at the centre of each molecule of haem",
" (heme) which makes it able to carry oxygen molecules and get rid of carbon dioxide (and makes red blood cells red). So you’d have ... | [
"Quite right! I wrote “molecule of haem” when visualising it in my mind but thought it looked wrong and changed it to ‘haemoglobin’ without checking. Have made the correction above. Thanks for that."
] |
[
"Can some infinities be larger than others?"
] | [
false
] | “There are infinite numbers between 0 and 1. There's .1 and .12 and .112 and an infinite collection of others. Of course, there is a bigger infinite set of numbers between 0 and 2, or between 0 and a million. Some infinities are bigger than other infinities.” -John Green, | [
"Yes. For instance, the set of real numbers is larger than the set of integers.",
"However, that quote is still wrong. The set of numbers between 0 and 1 is the same size as the set of numbers between 0 and 2. We know this because the function y = 2x matches every number in one set to exactly one number in the ot... | [
"When talking about infinite sets, we say they're \"the same size\" if there is a bijection between them. That is, there is a rule that associates each number from one set to a specific number from the other set in such a way that if you pick a number from one set then it's associated with ",
" one number from th... | [
"I've always like this explanation, it seems to help get the concept:",
"\n",
"Look at this picture",
". The inside circle is smaller than the outside one. Yet they both have the same amount of points on them. For every point on the inside circle there is a corresponding point on the outside one and vice vers... |
[
"Do black holes interact with the electromagnetic field? If so, what kind of interaction?"
] | [
false
] | [deleted] | [
"Black holes can have net electric charge (say, if it had been constructed entirely out of protons and no electrons), in which case they interact with the electromagnetic field just as a charged particle would. It's important to note that while a (classical) black hole has no memory of what fell into it (e.g. proto... | [
"Whar exactly do you mean that the EM fields interact gravitationally? Is it that they change that energy tensor thing?"
] | [
"Exactly: the EM fields contribute to the stress-energy tensor (a measure of the mass and energy density), which is responsible for curving spacetime in GR."
] |
[
"When a diabetic hypo's, why do they not switch to burning ketone-bodies, like a runner who 'hit the wall'"
] | [
false
] | null | [
"In short, they do in fact switch to ketosis, but, as the other posts explain, its not as easy as just getting ketotic and switching back out again. In such an insulin low state, a diabetcs body cannot get glucose into their cells, which triggers ketosis. However, whereas a runner can just drink some glucose and ge... | [
"Diabetic ketoacidosis is a common complication of diabetes, and as many of the posters here state it is associated with an absolute insulin deficiency and a ",
" blood sugar level. My impression is that the OP is asking why do ketone bodies not form when a diabetic becomes hypoglycaemiac.\nThe answer here is tha... | [
"In a brief nutshell, it is my understanding that they have a high insulin resistance. The Insulin essentially \"ties up\" the fat cells that would normally be used for energy; ketosis. Unfortunately the body can sometimes resort to eating muscle and organs because the energy rich fats cells are not accessible du... |
[
"How to remove glycol based contaminant from metal substrate without damaging substrate?"
] | [
false
] | working as a temp for a semi-conductor company... boss told me to figure this out. how to remove glycol based contaminant from metal substrate without damaging substrate. the substrate would primarily be either stainless steel or aluminum. also if there is a test to determine if all the glycol based contaminants are re... | [
"What kind of glycol?",
"If its short chain the ethylene glycol or propylene glycol Why not just boil it off. If it's longer chain use ethylene glycol to dissolve it then boil off the residue.",
"Also, do your own work"
] | [
"hey entropy.. thanks for the help\ni only ask because i've been instructed to post on scientific community forums for the help, but thought that it'd be quicker to get a response from here... seeing as how there are some very intelligent people here"
] | [
"lol just giving you a hard time. You may wish to phrase your problem more precisely if you want quality answers. Glycol doesn't refer to any specific chemical compound I can find but a class of compounds, maybe even you mean PEG? Also by contaminant do you mean like a thick buildup or more like a monolayer and ... |
[
"How does the energy compare with fusion of larger atomic nuclei to the fusion of hydrogen atoms?"
] | [
false
] | I think that the potential energy would have to be higher for large nuclei to fuse, but would this also mean the energy released would also be higher? Thank you for any responses! | [
"You can calculate the Q-value for any nuclear reaction ",
"here",
"."
] | [
"The Q-value of a nuclear reaction is the energy released during the reaction due to a change in the rest mass of the particles. During a nuclear reaction, mass is converted to another form of energy (generally kinetic energy of the products). This is given by the famous E=mc^2.",
"",
"The Q-value is then the ... | [
"Can you explain this with a bit more detail?"
] |
[
"Could zero point energy theoretically be applied to humans?"
] | [
false
] | null | [
"Zero point energy is not \"theoretical\" in the sense I think you mean it. We know for sure the it exists; it's a very straightforward consequence of quantum mechanics.",
"Zero point energy can never be a \"limitless supply of energy\", because by definition, it's the minimum energy that a given quantum system c... | [
"I think what I meant to say is the theoretical application of the energy. I do know that indeed exists, but the usage and harnessing of said energy is what I'm deeming as theoretical"
] | [
"\"Harnessing\" zero-point energy is impossible."
] |
[
"Why can't you have fusion products with an atomic mass greater than that of iron?"
] | [
false
] | null | [
"You ",
" have fusion reactions which create arbitrarily heavy known nuclides, however the Q-values can be negative.",
"Can you give a specific example of a reaction you’re talking about?"
] | [
"But surely, if this is the case, there are fusion reactions with positive Q-values which produce nuclides heavier than those of iron (simply by considering the change in binding energy per nucleus) and should therefore occur in the cores of main-sequence stars."
] | [
"Any reactions that ",
" happen in stars ",
" happen to some extent. It's an oversimplified picture to just consider a few fusion reactions happening in stars. In reality there are ",
" reactions that can and do happen in stellar burning."
] |
[
"Can metals evaporate? If so, can the gas be condensed back into solid metal?"
] | [
false
] | [deleted] | [
"Yes they can. In fact, ",
"this is a common technique used to deposit thin films of metals."
] | [
"This is one way that mirrors are made, yes. Aluminium is evaporated and deposited on the back of a piece of glass, and then covered with a protective layer. "
] | [
"Like mirrors in the back of glass? "
] |
[
"Why does my AC Power Adapter make clicking and humming noises?"
] | [
false
] | I understand that electricity causes vibration, etc... and thus certain noises. But what specifically is going on inside that box between the plug and my laptop that causes audible clicks and humming noises? | [
"As a former electrician and current electronics geek, your power supply should not be making clicking sounds or humming. Typically these problems have to do with the power supply capacitor (the power is rectified, filtered through a large filter capacitor and then buck converted to a lower DC voltage at high frequ... | [
"Thanks. It is an iGo, which has been reviewed pretty well, but now I'm nervous. Could it \"fry\" my laptop?",
"I should probably stop holding it up to my ear, too."
] | [
"I'd have to hook it up to my oscilloscope and look at what's going on at the voltage output to answer that question."
] |
[
"Silly magnets, why is this not possible?"
] | [
false
] | [deleted] | [
"So if you take two magnets oriented so they attract each other, they'll accelerate and snap together. The amount of force they exert to attract each other is the same amount of force it will take to then pull them back apart. You're car scenario may approach a stationary magnet and accelerate towards it, the iner... | [
"That's more or less the concept of a mag-lev.",
"\n ",
"http://en.wikipedia.org/wiki/Maglev_(transport)"
] | [
"Maglev works similar to this, but it uses electromagnets, and as the stationary magnet on the train gets closer, the electromagnet will turn off, then possibly reverse polarity so that the stationary magnetic doesn't cause a loss of forward momentum by attracting in the opposite direction, and in the case of rever... |
[
"Why do we \"Weigh\" things in kg,g,and mg, if grams are units of mass? If I've got some powder on a scale and it reads 40mg, is it actually calculating the weight and then dividing it by 9.8 to tell me the total mass of the powder on the scale?"
] | [
false
] | null | [
"Why do we \"Weigh\" things in kg,g,and mg, if grams are units of mass?",
"We measure mass by exploiting Newton's 2nd law: F=ma. The acceleration due to earth's gravity at its surface is about 9.8 m/s",
", so we can measure an object's mass by measuring the force gravity exerts on it and then dividing by 9.8 m/... | [
"The mass of something has two effects: it resists acceleration, and it attracts other things by gravity. To measure mass, you have to measure one of these two effects. An ordinary scale measures the force of gravitational attraction of the object to Earth. If you used your Earth-calibrated scale on another pla... | [
"Congratulations, you've just repeated what I said but less intelligibly. "
] |
[
"Is it possible to \"carbonate\" liquids with other gasses?"
] | [
false
] | What is special about carbon dioxide? can we use other gasses to "carbonate" a liquid instead? If so why c02. If not why can't we. | [
"Many gases (like N2 and O2) dissolve in water. But carbon dioxide is special because it doesn't just dissolve, it ",
" with water to form carbonate and bicarbonate ions:",
"CO2 + H2O --> 2 H",
" + CO3",
"CO2 + H2O --> H",
" + HCO3",
"This releases hydrogen ions into the water, making it acidic, which ... | [
"You can aerate water with tons of stuff. We just don't see it in faily life because a CO2 is readily available, tries to \"leave\" water under normal atmospheric pressure (giving it that nice bubbly), and not going to harm you when ingested. ",
"I constantly aerate water at home, with my aquarium. A pump agitate... | [
"Absolutely. In many places they are making ",
"beer",
" with a nitrogen/CO2 mix to decrease the size of the carbonation bubbles.",
"Carbon dioxide is unique though as it chemically reacts with the water, forming carbonic acid. This allows for much greater quantities to be dissolved in the liquid, as well as... |
[
"If a person eats junk food with a stuffy nose, will their brain receive the same chemical reward as it would when they can taste normally?"
] | [
false
] | I was eating chips with a cold and was wondering this. | [
"Oral Doctor here! [That sounds wrong]\nTo give you a short answer: The brain receives the same impulses as it would without a stuffed nose. However, your brain interprets it as being tasteless. Smell is 70-80% of the taste.\nThe impulse is the same but the feedback is different because of the lack of information.\... | [
"So this would mean that you receive less of a \"reward\"?"
] | [
"I don't really know what you mean by reward?\nIf reward means how strong a taste is, then yes. Because you can't smell it it has 70% less taste."
] |
[
"Evolution by randomness or necessity?"
] | [
false
] | [deleted] | [
"\"It doesn't makes sense for me Evolution by randomness. Maybe a combination of both? I don't know.\"",
"It's this. Evolution via natural selection itself is ",
" random. Like, not at all. This is a common misconception. Instead of a lottery, it's a game played where the ",
" players tend to 'win'.",
"Howe... | [
"Also, most of the time that single card that got swapped out doesn't make any difference at all. It was a minor change that wasn't ever part of your play strategy. Many rule changes later it may become an advantage or disadvantage, or it might forever remain some unimportant variant between your deck and the pla... | [
"So... evolution is basically a game of War but with Mao rulings?"
] |
[
"Why are sunburns warm to the touch?"
] | [
false
] | My forearms were sunburned today. When I press my cheek against the burn, it feels warmer than if I touch it to a non-burned area. What are the physiological reasons behind this? | [
"Your body sends an increased amount of blood to area of the burn in order to heal it. The blood is warm, so the skin above it feels warmer. "
] | [
"No, you break out in shrubs."
] | [
"There are 5 'cardinal signs' of inflammation: heath, pain, redness, swelling, and loss of function. The first are the classical signs, described by Celsus, while the loss of function was later added."
] |
[
"Is there a limit to how big planets can potentially be?"
] | [
false
] | Is there by any chance a planet as big as our sun or even bigger? What's the largest planet known to man at this present time? | [
"Yes there is. At about 13 times the mass of Jupiter a planet will be reclassified as a brown dwarf. These can fuse deuterium at their core for a brief time. At about 8% the mass of the Sun that brown dwarf will become a red dwarf star."
] | [
"The limit would still be the Chandrasekhar limit. Your big ball of iron would collapse into a Neutron star or a black hole under it's own gravity. "
] | [
"'Planet' and 'star' is a human classification. If there is a super rare event that someone artificially put thousands of giant ball of iron together then sure, it will collapse into some object similar to a neutron star due to gravity. But the newly form object could not be considered a 'star' because historically... |
[
"If golf balls have dimples on them to make them more aerodynamic then why don't cars or planes have them too?"
] | [
false
] | null | [
"Because golf balls are so short compared to a car or plane, drag is dominated by sperating flow behind the ball. By using dimples to trigger a turbulent boundary layer, speration can be postponed thus reducing drag. ",
"Cars and planes are longer more narrow bodies and drag tend to be dominated by skin friction... | [
"A few reasons come to mind:\n1. Different Reynolds number regimes. Golf balls are a different size and shape than cars or planes, so the turbulence transition enhancement from dimples would be different. \n2. There have been some studies on on this (and related hump back whale fin ridges), and some showed that the... | [
"And to expand, while cars and planes may not (commonly) have dimples on them, they often use other devices to induce a turbulent boundary layer to inhibit boundary layer separation. ",
"Vortex genertors",
" which acheive a similar results as dole ball dimples are seen in both planes and race cars."
] |
[
"Why are we so interested in Europa and Titan, but have heard so little of Ganymede?"
] | [
false
] | From a layman perspective anyways. I was just reading about it, and it looks like an even candidate for life with Europa, but I haven't seen any mission planned to it or anything... Edited for clarity. Edit2: there is a mission planned! | [
"I'm not sure why you say that it seems like a better candidate than Europa. Europa is the stronger candidate for having a subsurface ocean, and its outer layer is entirely ice rather than being a rock/ice mixture like Ganymede and so many other bodies. Titan is interesting for a variety of reasons, partly because ... | [
"I haven't seen any mission planned to it or anything...",
"So by interest you mean exploration? Actually ESA is planning a mission to Ganymede: ",
"http://www.esa.int/Our_Activities/Space_Science/JUICE_is_Europe_s_next_large_science_mission",
"The same mission is planned to perform two Europa fly-bys before ... | [
"Well, the history here is an odd one...",
"Originally there was going to be a joint NASA/ESA flagship mission to Jupiter's moons, the ",
"Europa Jupiter System Mission (EJSM)",
". Flagship missions are the largest, most expensive class of spacecraft (Cassini was the last flagship). This thing was planned to ... |
[
"Are carbon-based lifeforms the only plausible type of lifeforms?"
] | [
false
] | Given different environments, could life develop to use something besides carbon as their primary element for their organic chemistry? (presumably one as versatile as carbon, with 4 valence electrons) | [
"It's been asked quite a few times if you search for it. To repeat what I've said then: Not really. ",
"Carbon-carbon bonds are simply more stable than (say) silicon-silicon ones, and while the environment does affect the overall stability, the relative stability is more or less the same. Carbon's always better. ... | [
"Yes, \"Life, but not as ",
" know it\" is a sci-fi trope. As I said, non-carbon based life is stretching it as far as I'm concerned, so non-",
" life is just an idea that's just far too vague and speculative for my tastes. It's best left as science-fiction without trying to give it some scientific rationale, a... | [
"I'm sorry, but this has been debunked in two recent studies",
"here : ",
"http://www.sciencemag.org/content/337/6093/467.abstract",
"\nand here : ",
"http://www.sciencemag.org/content/337/6093/470.abstract",
"and noone believed the original NASA paper anyway, DNA incorporating arsenic would have severe s... |
[
"Hot objects in space."
] | [
false
] | Heat travels through converction. If I were to take a brick of lead, and stick it in the over to let it heat up, then remove it. It is going to cool off to room temperature over some time period as it radiates it's heat energy into the air surrounding it, and the surface it is resting on. What if I did the same expe... | [
"Heat travels through converction. ",
"Convection, radiation, diffusion are the main ones.",
"If I were to take a brick of lead, and stick it in the over to let it heat up, then remove it. It is going to cool off to room temperature over some time period as it radiates it's heat energy into the air surrounding ... | [
"You're mixing up convection and radiation. Convection is when the heated body comes in contact with a medium (such as air) and give energy off to it.",
"Radiation (infrared, if we're talking about heat, or Black body radiation in the more general case) happens independent of any medium - and that would be the do... | [
"Would it remain hot for a longer period of time as there is little, if any medium for it to radiate heat into?",
"You only mentioned one of three kinds of heat transmission:",
"Convection, by way of gas molecules",
"Conduction, by way of solid vibrations, i.e. \"phonons\".",
"Radiation, by way of the elect... |
[
"Why is more than half the world's oil located in the Middle East, geologically?"
] | [
false
] | I'm specifically asking about oil formation in terms of geological factors, etc. I am not at all asking about anything to do with politics, economics, etc. | [
"Oil (and coal) get their beginnings in places where life flourishes but frequently gets buried without access to oxygen. Places like swamps and river deltas. The organics that are buried then start moving around due to plate tectonics and make trips, and over millions of years, sometimes to locations that have abs... | [
"The ocean floor is as much subject to plate tectonics as much as any other part of the crust.",
"The organics are buried due to various events, tectonic ones included, and in those anaerobic conditions are broken down into fossil fuels of various sorts depending on the exact conditions. These buried reserves are... | [
"The ocean floor is as much subject to plate tectonics as much as any other part of the crust.",
"The organics are buried due to various events, tectonic ones included, and in those anaerobic conditions are broken down into fossil fuels of various sorts depending on the exact conditions. These buried reserves are... |
[
"Why do we sometimes refer to creatures by their scientific names as \"genus species\" and sometimes \"genus species species\"?"
] | [
false
] | For instance, . The title of the page calls the animal elaphe obsoleta; the picture caption calls it elaphe obsoleta obsoleta. As a secondary question, is my capitalization there correct, or should genus names be proper nouns? | [
"This indicates a subspecies or variety. Genus should be capitalized always."
] | [
"Awesome, thanks very much. I'm glad I know that now."
] | [
"All species and genus names should also be italicized (unless handwritten, then underlined)."
] |
[
"External intelligent entities, mathematics and further communication"
] | [
false
] | null | [
"Hi there! This question would be perfect for ",
"/r/AskScienceDiscussion",
" due to the speculative nature of any answers that would be provided.",
"Cheers!"
] | [
"can you move it? I will I have to repost it?"
] | [
"Repost. We don't have fancy tools to move posts because the admin don't love us. "
] |
[
"Does receiving a blood transfusion give you immunity to viral illnesses that the donor has had (and recovered from)?"
] | [
false
] | I have looked for an answer to this but most information seems to talk about blood type compatibility issues which is not what I am asking. To refine my question, these would be conditions that you had not been previously exposed to. Put another way, do antibodies or the body's knowledge of how to make specific antibod... | [
"It only has to do with the amount of antibodies present in the blood (usually need a larger than normal amount), if you spike the donor with antibodies then yes, but only for a certain amount of time. It's called Passive Immunity."
] | [
"If you receive a large number of antibodies from someone you might get temporary protection from some infections. Up until those antibodies were degraded and lost. ",
"To gain a permenant immunity from a blood donor you would instead likely need a transplant of activated mature B and T lymphocytes from the donor... | [
"It is also worth pointing out that such transplant of mature B and T lymphocytes would be very likely rejected by your immune system. ",
"In most cases the relationship between donor and host immune systems is pretty hostile. E.g. after transplantation of bone marrow the cells of donor are attacked by the host i... |
[
"Would it be possible for two people to grow together if they both were to cut off a hand/finger and then hold the wounds together?"
] | [
false
] | Assuming blood types and so on are identical. | [
"Ignoring practical issues like being able to brace the wounds together for the weeks it'd take to heal, you would have to go beyond just matching blood type--the two people would need matching HLA haplotypes or else each person's immune system would try to reject the other person's tissues. (There may be ways arou... | [
"Somewhat related question: if I cut off both of my hands and held the wounds together, would the same thing happen (get one continuous \"loop arm\")?"
] | [
"Many people with damaged or burned hands have them sewn inside their abdomen. There they heal and new growth takes place."
] |
[
"On average, and not including direct human intervention, how do ant colonies die? Will they continue indefinitely if left undisturbed? Do they continue to grow in size indefinitely? How old is the oldest known ant colony? If some colonies do \"age\" and die naturally, how and why does it happen?"
] | [
false
] | How does "aging" affect the inhabitants of the colony? How does the "aging" differ between ant species? I got ants on the brain! | [
"Ant colonies can die off in a variety of ways. Mites, other forms of parasites, ant wars, death of the queen, lack of food or sugar or water, predators, disease, and so many more. A colony can usually grow proportionate to its amount of resources, and room to roam. I am not sure how old the oldest ant colony is, b... | [
"When ants colonies fight. A lot of ants are highly territorial and will battle over resources and territory."
] | [
"Can you please elaborate on these \"ant wars\"?"
] |
[
"AskScience AMA: We are scientists from the team that recently discovered a malaria protein with the ability to target many different types of cancer. Ask us anything!"
] | [
false
] | Hi Reddit! We are Dr. Mads Daugaard, Dr. Nader Al Nakouzi, Chris Wang, and Gunjan Kumar from the Vancouver Prostate Centre. We are part of the group that recently published a study detailing the use of a malaria protein, VAR2CSA, as a new and novel way of targeting cancers. Cancer and the placenta show many similar cha... | [
"Hello!",
"I'm a newly started Danish student from Aalborg on 1. semester in Medicine with Industrial Specialization. I wish you the best of luck with your project! I have a few questions:",
"What do you think the odds are, that this will end up as a major breakthrough? I'm curious about the odds of it working ... | [
"1) I think the odds are pretty good! The main concern is safety and whether there will be any unforeseen side effects. \n2) I completely agree on your concern here, but I think the critique should be directed towards the media. The problem is that the media wants to sell news papers. We have been very careful in o... | [
"When will we see this tested in real patients?"
] |
[
"Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology"
] | [
false
] | Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! ... | [
"I'd say we don't know enough of the brain to be able to do that, but we ",
" know enough about technology to be able to do that. ",
"If you gather enough data, for example by using electrodes, you can use machine learning to decipher this data, without relying on the actual knowledge of how the brain is proc... | [
"I'd say we don't know enough of the brain to be able to do that, but we ",
" know enough about technology to be able to do that. ",
"If you gather enough data, for example by using electrodes, you can use machine learning to decipher this data, without relying on the actual knowledge of how the brain is proc... | [
"No. I'll give an example from a much simpler animal, the fruit fly. Fruit flies have 51 compartments to their sense of smell, called olfactory glomeruli. Every fly has the same 51 glomeruli, and if you could measure the activity of these brain areas, you would know what they fly is smelling. So far so good.",
"T... |
[
"If you dropped batteries into a glass of water, and put a balloon on top.. would the balloon fill with Oxygen? If not, what would happen?"
] | [
false
] | null | [
"Water certainly does split, I'm not sure where you're getting your information or maybe I don't understand?\n",
"Water splitting",
"In 18 megaohm water you certainly wouldn't see much, but tap water has plenty of ions to keep the resistance low."
] | [
"Water certainly does split, I'm not sure where you're getting your information or maybe I don't understand?\n",
"Water splitting",
"In 18 megaohm water you certainly wouldn't see much, but tap water has plenty of ions to keep the resistance low."
] | [
"You can't just mix hydrogen and oxygen together and make water. It takes additional energy to force the electrons to bond. "
] |
[
"If 100% of the population smoked cigarettes on a daily basis, would evolution cause us to become 'immune' to the carcinogens?"
] | [
false
] | null | [
"I would have to say no. Most of cigarettes lethal affects occur after multiple decades of their use. The cancer caused from smoking occurs after our reproductive years so any benefit one would gain from a mutation that resisted the carcinogens would not alter their reproductive success.\nEvolution only occurs when... | [
"Evolution only occurs when a genetic mutation increases ones ability to have viable offspring.",
"True, but I'd caution that 'viable' doesn't just mean healthy at birth, it also means that the offspring themselves grow up and reproduce. Humans invest a huge amount in rearing both their children and grandchildre... | [
"This sort of thing actually happens. Maybe not with a payload as comprehensive as that of a cigarette. My example is a type of lemur in Madagascar. It eats the root of a bamboo that grows there that actually contains cyanide. This particular species of lemur evolved an ability to metabolize cyanide and this ba... |
[
"What is the difference between a single-cell organism and a cell in our body?"
] | [
false
] | I know there is a large variety of types of cells, but.. Can you say that our bodies are just a large colony of single-cell organisms working together? | [
"Can you say that our bodies are just a large colony of single-cell organisms working together?",
", yes. But that's a bit oversimplified. There are plenty of single-celled organisms that work together and divide labor in a similar fashion, but at the gene expression level it works quite differently.",
"The cel... | [
"Single celled organisms, such as yeast or most bacteria, are capable of surviving and multiplying independently. Each cell can sufficiently gather all the nutrients it need to survive and can divide indefinitely.",
"We are multicellular. Although we are made of many individual cells, a cells from our liver would... | [
"Each single-cell organism has to carry out all of its own life processes in order for that cell to survive. They sometimes live together in colonies, but if their friends (clones of themselves) die, they can carry on without them.",
"In contrast, even the simplest multi-cellular organisms have specialized, diffe... |
[
"I just learned about foreign accent syndrome, when brain damage makes it sound like you have a foreign accent. Do those who suffer from it actually speak with an accent from one they know or is it just the new speech patterns that come with the syndrome making it sound similar to an existing accent?"
] | [
false
] | null | [
"I'll answer this with the caveat that this is a very rare condition ",
"(<20 cases worldwide to date)",
" and with an etiology that is not perfectly understood. ",
"The basic idea is that after a stroke regions of the brain are damaged that result in a changed prosody. Most of the time, the change in speec... | [
"I think the syndrome is far more common than is reported. I've seen 3 cases in 5 years of working with brain injured patients. The patients I've seen are actually using a foreign accent, and when cued to speak with their American accent, being Americans, they will do so for brief periods before they forget and l... | [
"No, it's a change in the way they produce speech which just seems to sound (to some speakers) like another specific accent. The man who gained an Irish accent after a stroke would not have sounded Irish to an Irish person. "
] |
[
"Can someone explain the science behind this video of a water bottle instantly freezing?"
] | [
false
] | null | [
"It's called supercooling."
] | [
"To crystalize into ice water needs a nucleation point. Once you have some ice in there it's easy to make more crystals, but it's hard to form that first crystal due to the entropy loss. Ice is a lot more ordered than water.",
"If you hit the water hard, say by pouring it, you provide a nucleation site for crysta... | [
"I agree, that the water is supercooled, and in beer for example it's the drop in pressure when opening the bottle.",
"I know of pure water not freezing and then when the bottle is slammed on a table, it freezes. As fas as I know this is because of a pressuredrop in the top when the water rushes down in the slam.... |
[
"Can moving water wear down a diamond?"
] | [
false
] | null | [
"I think you are talking about a situation where a natural diamond is on the surface of a riverbed. I don't have any answers for you there, but a study in 1993 investigated rain-like erosion properties of diamond. Here is a link to the publication: ",
"http://www.smf.phy.cam.ac.uk/Publications/Strength%20papers/3... | [
"Rocks in the water would have to be extremely sharp and moving very fast.",
"They don't need to be particularly sharp nor fast.",
"Breaking a diamond into smaller diamonds is relatively easy depending on the angle of impact. Despite their hardness, diamonds have cleavage and are brittle. Every heard of someb... | [
"Rocks in the water would have to be extremely sharp and moving very fast.",
"They don't need to be particularly sharp nor fast.",
"Breaking a diamond into smaller diamonds is relatively easy depending on the angle of impact. Despite their hardness, diamonds have cleavage and are brittle. Every heard of someb... |
[
"Is it possible to keep a cell phone charged longer by using stray electromagnetic energy and a broadband antenna?"
] | [
false
] | null | [
"Yes, there has been some research: ",
"http://www.eetimes.com/electronics-news/4195530/Nokia-working-on-energy-harvesting-handset",
"However, you can't harvest too much energy that way (unless if you are near a big radio transmitter or something).\nSome megawatt radio transmitter can even light up lightbulbs. ... | [
"This is an anecdote, but your answer is correct so I hope I'm not against ettiquete:",
"A family friend of mine used to work with radios, and there's a picture of him standing in front of a transmitter with a florescent tube, which is lit way the fuck up. Radio waves are energy in the air, and that can be trans... | [
"In theory, yes. But in 99.9% of cases the tiny amount of energy you harvested wouldn't make any kind of noticeable difference. Check ",
"this",
" out for an idea of what kind of energies we're talking about here. "
] |
[
"Is it true that women with - RH factor miscarry + RH babies and why or why not."
] | [
false
] | [deleted] | [
"Not quite the same question, but I answered a ",
"similar question in a thread recently",
", along with ",
"another similar one before that",
".",
"Take a look through those two threads"
] | [
"I thought the shot was a vaccine against RH+ antibodies ... Usually, the first baby will be fine, but if this occurs again, the mother will have RH+ antibodies which will destroy the baby's blood cells if I remember correctly. If the shot isn't used, the baby might need to be completely emptied of its blood after ... | [
"I thought the shot was a vaccine against RH+ antibodies ... Usually, the first baby will be fine, but if this occurs again, the mother will have RH+ antibodies which will destroy the baby's blood cells if I remember correctly. If the shot isn't used, the baby might need to be completely emptied of its blood after ... |
[
"If the Earth was condensed to the size of a peanut, and it turned into a black hole, would the black hole be stable?"
] | [
false
] | null | [
"Yes. The Hawking temperature would be some 2 hundredths of a Kelvin, while the CMB is hotter at 2.7 K. The black hole gets more power in that it radiates out."
] | [
"You need to go a tad smaller. Try it yourself, set the Hawking temperature equal to the CMB temperature and find the mass of the black hole."
] | [
"Wow!",
"I thought tiny black holes \"evaporated\" really fast via Hawking Radiation. I assumed one this size was well within the going ",
" range in short order. Guess I am off by a few magnitudes of size.",
"Learned something new today. Thanks!"
] |
[
"How did spacecrafts in 1960s transmitted photos of space and the moon when digital photography had not been invented yet?"
] | [
false
] | What I am missing here? | [
"They used analogue photography, e.g. TV cameras."
] | [
"Whoa, whoa. Define \"digital photography\" because my parents were watching fast moving photography in the 1960s in their living room. We tend to call it television. The technology that powered television powered these cameras. Yes, it was an analog process, but it was 100% electric and sending analog signals is ... | [
"Your claim that they used film is grossly incorrect, for many cameras in use in the late 1960s, there was no film involved. For example:",
"https://en.wikipedia.org/wiki/Apollo_TV_camera",
"http://www.myspacemuseum.com/apollocams.htm#A11%20B&W",
"There was also no film involved in the Venera cameras which w... |
[
"When a dog sniffs around for a place to poo, what is his criteria?"
] | [
false
] | null | [
"It depends on the dog's social status and current mental state. In general, higher-status dogs will use their feces to cut other dogs off from certain areas. Lower-status dogs will try to keep their feces out of the way in order to avoid upsetting a higher-status dog (or in the case of domestic dogs, a human). ... | [
"Essentially, it treats humans like other dogs and then figures out its status based on how those humans treat it. Generally, they will consider themselves lower in the pecking order, but if they are spoiled they may think they are in charge."
] | [
"Essentially, it treats humans like other dogs and then figures out its status based on how those humans treat it. Generally, they will consider themselves lower in the pecking order, but if they are spoiled they may think they are in charge."
] |
[
"Were mental illnesses suchs as depression as common 100 years ago? If not what's the main cause that they are more common today?"
] | [
false
] | null | [
"We can't answer that question, because the modern definitions and characterizations of mental illnesses are ",
" recent--like, the 1980s (when the DSM-III came out). There aren't reliable, large-scale epidemiology studies before that era--at the very earliest, the data goes back to the mid-century.",
"When we ... | [
"Some mental illnesses are caused by environmental factors (lead comes to mind). Others could go undiagnosed or ignored. When you are struggling every day to not die, most people were living short miserable lives. Others still would get you locked in an insane asylum or killed for devil possession. "
] | [
"Is there any source at all for this claim?"
] |
[
"What is oscillating in an electromagnetic wave?"
] | [
false
] | What I'm trying to ask is that if waves formed in the ocean are oscillations/vibrations of the water particles and sound is the oscillation/vibration of air particles. What is actually oscillating to form an electromagnetic wave. I think I'm phrasing the question wrong or I've just misunderstood the concept of electrom... | [
"You are basically asking \"through what medium do photons propagate?\" Waves in the ocean propagate through water, sound waves propagate through air (or anything else really). But it turns out photons don't need a medium to propagate. The confusion stems from the fact that EM waves seem to have all the properti... | [
"The electric and magnetic field vectors are oscillating."
] | [
"An electromagnetic wave is not a stream of particles, it can be considered a stream of photons but I don't think you need to involve wave particle duality to understand the idea behind an em wave. ",
"If we are talking about a wave we are talking about something which oscillates in space/time. In a water wave we... |
[
"How do avalanche beacons work, and why do they follow flux lines?"
] | [
false
] | I feel that I understand the basics of radio beacons, but I don't understand how avalanche transceivers figure out direction. If you had 3 antennas I assume you could do some rough triangulation to get the direction, but avalanche beacons don't give the exact direction, they "compute distance and direction" from "the e... | [
"I thought that radio beacons transmit uniformly in all directions",
"This is not correct. The pattern in your diagram is that of a simple dipole antenna, what you get from electric current oscillating back and forth along a straight wire. See ",
"this",
" for an explanation. ",
"This",
" is a better i... | [
"Could you explain what causes the dipole pattern and how the pattern can be used to find the direction to the transmitter?"
] | [
"Consider what tao observers see when a charged particle accelerates (linear motion).",
"An observer along the motion hardy sees anything happen.",
"An observer perpendicular to the motion sees a change of the direction of the electric field. This change, perpendicular to the line of sight, is the radiation fi... |
[
"Screw Thorium, why are we not using Toroidal Fusion reactors now?"
] | [
false
] | null | [
"Quite simply: they don't work yet.",
"I am a fusion physicist; I work at the JET site, though on a different tokamak (",
"MAST",
").",
"To get deuterium and tritium (the most likely fuels for a commercial plant) to fuse, the plasma has to be at a temperature of about 100 million K. In order to have a self-... | [
"Two Main reasons:\nPhysics and Engineering.",
"Firstly, engineering: These things are super hard to build. We need very carefully made reactors to confine something as hot as 100000000K. We still aren't sure if we can do all the things we need to be able to do to run a working power plant. Things like remotely r... | [
"We need more vespene gas",
"In all seriousness though the fusion problem has gone from always being 30 years away to being 10 years away. ",
"I've been to a few talks on tokamack fusion concepts. The problem seems to be sustaining the reaction while extracting energy. ",
"All of them are good ideas and in f... |
[
"How do cassette adapters transfer the sound output from my phone to a magnetic encoding readable by the play-head?"
] | [
false
] | [deleted] | [
"The trick is that there's no real conversion needed. ",
"You record on a tape by changing a magnetic field near the tape. You play a tape by running it past a magnet to detect the changes. ",
"You get sound from a speaker (or headphones) by changing a magnetic field in the speaker coil. You pick up sound f... | [
"The tape had iron oxide particles which can be magnetized as they pass through a magnetic field, in the same way that you can magnetized a sewing Needle by rubbing it against a magnet. As the current through the head changes in response to the audio signal, some of the oxide particles will be oriented one way, so... | [
"The cassette adapter doesn't have an actual ribbon, it's a spinning head that doesn't store data like the ribbon does. Electrical signal from your device gets runs to the \"write\" head of the cassette adapter. That means the magnetic field output by the write head changes with the signal, and the read head in you... |
[
"Why do wet dogs smell so bad?"
] | [
false
] | It seems odd to me that there is a unique smell that virtually all dogs have when wet that is completely absent when they are dry. What's the scientific account? | [
"First of all, what actually makes something smell?",
"\nMolecules have to leave the smelly objects and get to your nose through the air and that means that these molecules must be very small and volatile. That's to say they must be easily evaporated. The chemicals that make dogs smell are mostly what we call v... | [
"I thought dogs didn't sweat. Have I been living a lie all this time?"
] | [
"Is that saying that the concentration difference between the substance on the skin and the substance in the air is greater when the substance on the dog is dissolved in water than when it is not? Wouldn't dissolving it in water decrease the concentration? How could the difference be any greater than when the subst... |
[
"What domestic or wild animal provides the most efficient kilogram to kilogram, gram to gram, conversion from eating grains/plant based material to meat, or do all herbivores have equal ratios?"
] | [
false
] | null | [
"This is measured as the ",
"feed conversion ratio, or FCR",
", which is calculated as kilograms of feed per kilograms of body weight (or sometimes carcass weight, dressed weight, etc). Exact FCR will depend on what the feed source is - a cow eating corn has a lower FCR than a pasture fed counterpart since the ... | [
"How do we factor in farming practices and conditions? For example, a cow fed corn grown commercially in Indiana almost certainly has a higher net impact than a cow grazed on marginal land in Montana that would otherwise be agriculturally unproductive."
] | [
"This can get really complicated depending on how detailed you want your analysis to be:",
"All things equal, the corn fed animal will produce more meat faster, hence the prevalence in modern food chains, but corn fed production is not sustainable in the long term, especially as global per capita meat consumption... |
[
"What impact, if any, would the growing of hemp have on the medical community?"
] | [
false
] | Hypothetical world: Hemp is legalized and being grown across the States. Hemp growers will grow both male and female plants because they need the stalks and leaves, not the bud. Assuming fertilization of the plants happens within the fields regularly: Would this then lead to some sort of evolution to the plant? | [
"I'm not sure what your question is. Evolutionarily growers have been selecting for generations for better quality and more potent plants. In terms of impact on the medical field, there would be less chronic pain management nonsense to deal with and an easier time managing nauseated cancer patients. "
] | [
"As you said, the current selection goes more for quality of the plant, or THC levels. But hemp growers would most likely just be going for things like height and density of the plant assuming they want to grow more plants in the area they have."
] | [
"Sure, maybe if they're just trying to maximize yield per acre. But customers are often driven more by considerations of shall we say refined quality and delicate flavors. I think we'd see more of the vineyard model, with a recognizable high end producing intentionally limited quantities of expensive bottlings for... |
[
"What causes the relativistic contraction of the innermost electron orbitals of heavier elements, given that electrons don't actually \"orbit\" the nucleus with a given velocity?"
] | [
false
] | I've been trying to grasp what's going on with the so-called that cause the contraction of the electron orbitals of heavier elements, and a lot of what I have found online talks about the greater nuclear charge of said elements causes the innermost electrons to travel at relativistic velocities, which in turn causes th... | [
"An orbital represents a standing wave, so you are right that it does not change with time. However, the electron still has angular momentum and kinetic energy in an orbital. This might seem contradictory, but we only need the values for these quantities to be constant with time, they don't need to be zero. The ave... | [
"You can roughly think of an electron in an orbital as obeying the virial theorem",
"In terms of expectation values, it ",
" obey the virial theorem."
] | [
"If my understanding is correct, then presumably the notion that contraction is caused by the electron approaching c is flawed? Is there a more cogent explanation?",
"It's basically correct. You're right that the picture of electrons zipping about in nice well-defined orbits around the nucleus is incorrect, but t... |
[
"What does it mean for a photon to have \"more energy\"?"
] | [
false
] | Gamma ray photons are more energetic than visible light photons which are more energetic than microwave photons. What does "more energetic" actually mean? More what? They all travel at the same speed, and are massless, so there's no additional kinetic energy. I don't think frequency has much meaning when you're referri... | [
"Frequency ",
" have a meaning in this case. Higher energy, higher frequency. A blue photon has more energy than a red photon.",
"Another way to think about it is what happens to a system that absorbs a given photon. If it absorbs a higher energy photon, it will see a greater increase in its energy."
] | [
"Another example: if a photon hits an atom and knocks out an electron, that electron will be moving faster if the photon has higher energy."
] | [
"It is kinetic energy. Without going into too much detail, since i'm late for class, when you get into really small massless particles, they in fact do have kinetic energy, though it is not related to the mass. This is part of quantum physics. The kinetic energy is related to the frequency, which fr gamma ray is mu... |
[
"What made scientists decide to start smashing particles together at high speeds?"
] | [
false
] | Most people (of this sub, at least) know of the LHC and that high-speed collisions of particles can produce particular kinds of particles, but how did it start? What did scientists expect to find by smashing particles together at extremely high speeds, and why did they expect that? Moreover, why did the first scienti... | [
"In 1905 Einstein proposed the concept of photons, particles of light with energy proportional to their frequency (E = h f , where h is Planck's constant). Light waves with a higher frequency will have a shorter wavelength (the more cycles which pass by per second, the smaller that each cycle is in length). For e... | [
"I'm not sure what kind of electromagnetic frequencies we can get up to nowadays, but a simple reason is that you can accelerate protons (or electrons) over and over again. So you can keep adding energy to them. There are limitations to this if you're using a circular accelerator, but for a linear accelerator you c... | [
"I'm not sure what kind of electromagnetic frequencies we can get up to nowadays, but a simple reason is that you can accelerate protons (or electrons) over and over again. So you can keep adding energy to them. There are limitations to this if you're using a circular accelerator, but for a linear accelerator you c... |
[
"Do fish hold their 'breath' when pulled out of water, in the same way we hold ours when we go under?"
] | [
false
] | Do fish right before they're removed or voluntarily remove themselves from water have a big intake of oxygen (in the same way a human takes a breath before submersion) to sustain themselves while out of their natural environment? If yes: comparing to humans (and other species) storing air in their lungs, how do fish do... | [
"Fish can still extract oxygen through gills if water can still run over them. Technically you can run water through a hose over their gills perpetually and they'll still live. This is how fish surgery tends to be done.",
"The key is making sure water is moving across the gills to work their counter-current exc... | [
"Yeah sure!",
"Here you go, a fish surgery at the Vancouver Aquarium!",
" Notice the water is pouring over the gills, not into the stomach. This is so the fish can still gas exchange while under anesthetic.",
"So, there's myriad reasons for fish surgery. It seems funny that we'd be doing surgery on a fish ... | [
"The don't really hold their breath as they don't have lungs to hold it in. For the majority of fish they force oxygenated water across their gills, which have a capillary network that allows for the exchange of oxygen and carbon dioxide. Your lungs have basically this same network, we just suck ours into our lungs... |
[
"If you know how many people are in a store at a set starting time, and you know the rate at which people are entering and leaving the store, can you calculate the average amount of time that a customer spends in the store?"
] | [
false
] | Imagine that a store opens at 9am and closes at 6pm. If you know: (a) the number of customers in the store at noon; (b) the rate at which customers enter the store (e.g. customers/sec); (c) the rate at which customers leave the store (e.g. customers/sec); (d) that the store is empty at 6pm; Can you calculate the averag... | [
"Knowing the rates that people enter and exit the store (whether constant or as functions of time) and the number of customers you start with (initial conditions), you could set up an ODE to describe the amount of people within the store at a given time. ",
"In the simplest case of constant rates, it would be for... | [
"The answer is ",
", without any other assumption on the model, and with closed formulas (no simulation is needed). You need the data (a)-(c).This comes from a inversion of summation.",
"I'll use some LaTeX formulas. To visualize them, you can copy and paste them into an online editor (for instance ",
"here",... | [
"The way it's usually done is by simulation. You give a starting situation and just add the number of people entering/leaving each second.",
"Now, if you want something more advanced (let's say not a fixed rate of people arriving, some costumers spend longer time on the store, etc.), you do need more advanced mat... |
[
"When the last black hole in the universe evaporates and explodes, what happens to that radiated energy?"
] | [
false
] | A model of the future universe predicts that, after trillions upon trillions of years into the future, all the stars have exhausted, all matter has accumulated into black holes, and the black holes themselves evaporate. When the last black hole in the universe radiates away, there are no other structures in the univers... | [
"Just like most other radiation and stable particles (only a very small fraction will fall into black holes) it will just fly through the universe forever. The expansion of the universe will separate all these particles from each other."
] | [
"The expansion of the universe will separate all these particles from each other.",
"It'll also leech off photon and kinetic energy. If proton decay were a thing, the situation would get even 'worse' as with each decay, yet another share of the energy content of the universe would become subject to this cosmologi... | [
"Angular momentum is a good point."
] |
[
"How do new born babies survive starvation for several days under rubble?"
] | [
false
] | [deleted] | [
"I would like to point out that most babies do not survive such conditions - the cases pointed out here are exceptions."
] | [
"The layers of fat provide nutrition. Its their life fat-ket"
] | [
"you only notice something when it hits and not when it misses."
] |
[
"What happens if you eat or drink something without waiting 30 minutes after using fluoride mouthwash?"
] | [
false
] | null | [
"Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light. Total protonic reversal. ",
"No, seriously. It's just because we want to give a generous amount of time for the fluoride to absorb into the enamel of our teeth. Fluoride is safe; it's ... | [
"it is naturally in our drinking water",
"before anyone comes in here and hits you with something stupid"
] | [
"You ingest fluoride which passes the blood brain barrier with ease.",
"Does it matter though? Probably not, since one cup of water contains roughly the same amount of fluoride as a bit of toothpaste or the leftovers of mouthwash and we ingest that all the time everyday (unless you drink bottled or well water).",... |
[
"Can sudden bursts of loud noise (specifically through headphones) cause significant hearing loss?"
] | [
false
] | I am a music producer and I work with studio headphones on. A new piece of equipment that I use has a sensitive volume control and a few times now I have accidentally turned it to 100%. Obviously I knocked my headphones off each time as quick as I could, but could these instances contribute to significant, permanent he... | [
"The external noises you hear come from sounds waves entering the ear canal. These waves are physically transmitted to the inner ear, where they bend tiny, hair-like structures called cilia on \"hair cells.\" As the cilia bend, they transmit signals to the brain, and this information is processed, giving you the ex... | [
"It would be much easier to answer this question if you could approximately tell us the dB level of the sound at 100% volume, or measure it even, since you're a music producer after all. Hearing damage is worse for higher frequencies and higher volumes, so the more you can tell us the better."
] | [
"I don't have the equipment available to measure the output decibel level. This would be hard to do even if I knew the output from my computer because I can't account for the monitor headphones."
] |
[
"Does water get any more slippery as it approaches the freezing point? i.e. Does driving on wet roads that are 33F pose any more risk of sliding than roads that are, say, 40F?"
] | [
false
] | [deleted] | [
"I don't know about water, but as the temperature drops, the road surface and your rubber tires harden up, which reduces the amount of traction they can provide to you.",
"You can see this in action at a drag race. Racers will do a burnout just before their race, to heat up the tires, increasing traction. Cold ti... | [
"When rubber warms up it becomes softer and easier to deform. This allows the rubber to better deform around the small imperfections in the road and this increases traction. So if you have colder tires they deform less on a small scale and consequently have less grip on the road surface."
] | [
"when the rubber ties harden up at lower temperatures, why does that reduce traction? Is it because the surface area of the tires that come in contact with the road is less since the cold condenses things?"
] |
[
"How much more energy does a hairy human expend growing hair than the same body without [much] hair? Is it a metabolically meaningful amount?"
] | [
false
] | For example, in my case, a 6'1" 230 lbs. 46 year old hairy male. Thanks. | [
"Hair grows in stages and at the last stage stops growing, so there is an upper limit to hair growth that varies from person to person. The reason I mention this is that your question seems to mostly be about body hair, which unless you shave or wax is already at it's final stage for the most part and thus wouldn't... | [
"Producing the hair in the living parts of the hair follicle must have a metabolic cost, regardless of whether or not the end product, ie the hair itself is no longer \"living\"."
] | [
"I would actually expect the extra hair growth to result in a net energy surplus for the body. Anorexics and other people who are starving will grow a very fine hair all over their body called lanugo (newborn babies also have this). Lanugo provides a kind of blanket to maintain body temperature in the setting of lo... |
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