title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
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[
"What is stopping video games from using dynamic motion synthesis instead of canned animations for simple actions?"
] | [
false
] | I'm fascinated every time I see real-time demos of dynamic motion synthesis, where characters have a simulated bone/muscle structure and intelligently maintain balance and perform actions without predefined animations. A few examples: Games industry has had physics-based ragdolls for quite some time and recently some triple-A games have used the Euphoria engine to simulate bits of movement like regaining balance, but I haven't seen any attempts to ditch animations for the most part in favor of synthesized, physics-based actions. Why is this? I'm assuming it's a mix of limited processing power, very complicated algorithms and fear of unpredictable results, but I'd love to hear from someone who has worked with or researched technology like this. I was also looking for DMS solutions for experimenting in the Unity engine, but to my surprise I couldn't really find any open-source efforts for character simulation. It seems like NaturalMotion is the only source for such technology and their prices are through the roof. | [
"Caveat: I don't work in this directly, but I develop physical simulations and have some knowledge on control theory and recently went to a research talk on analyzing animal biomechanic reactions.",
"First, the equations of motion of the models you see are basically N coupled differential equations, where N is th... | [
"Yes, ",
" and other animals can do that, and you're incredibly good at it compared to any robot/automated system in existence. Humans walk, sprint, crawl, climb mountains, climb ladders, play sports, lift heavy objects, perform delicate surgery, pick their noses, use tools, and adapt to wildly different tasks wi... | [
"Combine ",
"/u/Overunderrated",
"'s reply with two facts",
"1) A lot of the in-game physics you enjoy in games are so complex that they're already being processed by your GPU (using something liks PhysX) just like the entire environment is being rendered by your GPU. ",
"2) Now consider that in gaming, 60f... |
[
"Why is the light coming from my laptop screen polarised?"
] | [
false
] | null | [
"And here's a video with your answer.",
"Basically, the monitor works because the light is polarized."
] | [
"Yessir. And those of us who like polarized lenses while driving to reduce glare get screwed by cars with LCD displays, such as the one for my gas tank, in-car clock, stereo system display, Nav, etc etc. -_- "
] | [
"To be fair to LCDs, this is a lack of will on the part of manufacturers rather than an inherent limitation in LCD technology. Not only can normal LCDs be manufactured in such a way that they are visible from all normal driving positions, but ",
"wave plates",
" can be incorporated in the design to make LCDs th... |
[
"With planets like Jupiter that have multiple moons, do the moons ever collide? Or is there something in the way they orbit that keeps this from happening?"
] | [
false
] | null | [
"When you have multiple moons, this is the notorious n-body problem (more generalized than the 3-body problem). You can't solve these problems exactly, so you can never truly rule out a collision in the distant future. There is even a possibility that Mercury or Venus might crash into Earth. (That is billions of ye... | [
"The orbital distance (how far away they orbit) is different, but there is nothing specifically to prevent moons from crashing into each other. The history of the cosmos is filled with celestial bodies colliding (or own moon, for example is thought to have been formed when a very large object collided with earth)."... | [
"Thanks! Was just a thought I had and I appreciate your taking the time to answer. :) Interesting stuff."
] |
[
"Why is it that a vaccine like J&J can reduce severity of Covid-19 even in cases where it doesn’t provide full immunity?"
] | [
false
] | The trials indicated that full immunity varied by country, probably due to the different strains. But it was effective at reducing severity across the board at similar rates, regardless of strain. Why does that happen? | [
"Vaccines elicit more than just antibodies. They can also stimulate the differentiation of T cells that recognize the antigens (the proteins of the virus) and these help coordinate the immune response as well as destroy infected cells.",
"For the virus SARS-CoV-2, how quickly the T cell reaction can respond is cr... | [
"We don’t know why. Two possible, not mutually exclusive reasons: reducing viral load, and protection focused on the lungs and organs rather than the nose and throat. ",
"Reducing viral load is pretty obvious. If you have enough immunity to handle x amount of virus, and you’re infected with 2x, then you’re still ... | [
"https://en.m.wikipedia.org/wiki/Polyclonal_antibodies#:~:text=Polyclonal%20antibodies%20(pAbs)%20are%20antibodies,each%20identifying%20a%20different%20epitope",
".",
"Heres a simplified example:",
"Pretend the protein on the outside of the spiky coronavirus is a square shape and is able to connect to the cel... |
[
"What generates the recoil in a railgun?"
] | [
false
] | [deleted] | [
"This is covered by Newton's Third Law of Motion.\n",
"https://en.wikipedia.org/wiki/Newton's_laws_of_motion",
"For the projectile to travel forward, the \"gun\" must experience the same force in reverse. No matter the mechanism - bullet in barrel, linear accelerator, or rail gun."
] | [
"Another difference is that for conventional artillery, it just isn't the projectile that gets accelerated but also the propellant gases."
] | [
"Another difference is that for conventional artillery, it just isn't the projectile that gets accelerated but also the propellant gases."
] |
[
"What could this object seen close to the sun on nasa telescopes be (5th May 2012)"
] | [
false
] | Display: slideshow for the movie * Telescope: Behind COR1 Start Date: 20120502 End Date 20120505 search button. ''''''''''''''''''''''''' Appears on 2nd may 2012 at 19.15 image becomes pixelated on 4th may 2012 at 00.05 but object still visible. up until this point each image is 5mins separated, but from 00.05 the next image is 02.05 then hourly after that until 6th may 10.05 that is the last image available at the moment from the nasa site,and the object is still there. ....................................... perhaps someone could explain what sort of telescope creates these images. Is it a satelite or space station or ground based. the sun does not appear to be rotating , so is the object orbiting the sun along with the telescope. I found this video which seems to explain these kinds of shapes but I am not sure. | [
"How can we tell that it's an object close to the sun if the picture is 2d and there are no other angles?"
] | [
"Reminds me of \"dust doughnuts\", an artifact caused by small particles on the CCD or whatever device is used in the coronograph in question. Typically you would take an exposure with the aperture covered then subtract this so called \"flat field\" from the image to eliminate artifacts like this. Here are some exa... | [
"This is exactly what I was going to say - glad someone else thinks so, too (and bonus points for using ds9).",
"If there's dust inside the optics, it's going to scatter sunlight. Normally this would appear as a bright point, but because the optics are focused at infinity, it ends up imaging the primary objective... |
[
"Could it be that babies cry when they are born because the oxygen in the air is oxidating them and it hurts?"
] | [
false
] | null | [
"Hi mantis6660 thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the foll... | [
"Human body"
] | [
"Human Body"
] |
[
"What causes the magnet/iron files experiment to have well-defined lines?"
] | [
false
] | [deleted] | [
"The rotational ordering arises because the filings are polarized by the magnetic field and align themselves with the magnetic field lines. The positional ordering likely arises from interactions between filings -the N of a given filing is attracted to the S of the next filing, etc, so the lowest energy state is fo... | [
"Iron has a high ",
"magnetic permeability",
". It gets magnetized and you end up with a locally-stronger fields around the filings. ",
"So an evenly-distributed dust of filings will attract and lump together until the the point where the closest filings are too far away for its field to pull them over."
] | [
"I'll preface this by saying that I am a senior in Electrical Engineering studying electric motors currently. So if I am off on anything in my explanation, I'd appreciate someone helping me to deepen my understanding.",
"There is a thing called magnetic flux, that by definition is leaving the north end of the ma... |
[
"Why do coffee beans in a bag with a one way degassing valve appear to shrink wrap themselves in the freezer?"
] | [
false
] | This is a really simple question that I'm perhaps making complicated. Fresh roasted coffee is often stored in laminated, moisture proof, sealed bags with a one way degassing valve. As I understand it this is to protect the coffee from oxygen, while allowing the CO2 that fresh coffee beans give off to escape. I've noticed that when these bags get placed in the freezer and cool, they end up appearing to be shrink wrapped as if in a vacuum around the coffee beans. I understand that the volume of gas in the bag dramatically decreases, and hence I'd expect it to have far less volume in accordance with Charles law, just like a balloon would appear deflated in the freezer. What I don't understand is why this relatively inelastic bag in the freezer to have such a strong vacuum in it, such that the contour of each of the coffee beans contained within is obvious, and the surface becomes irregular as the beans are tightly hugged by the shrunken bag. The frozen bag has the feel of a solid brick, rather than loose beans, even though when the bag is opened, the beans are not frozen to one another. Other sealed bags with no valve in the freezer do not seem to exhibit this tendency, and there is a decent amount of headroom in these bags. That said, I can't say I've put a lot of room temperature, sealed stuff directly into the freezer, so perhaps this is incorrect, and the valve is a red herring. So, does the valve have anything whatsoever to do with this? | [
"Yes, I believe so.",
"I'm a biologist, but I'm not uncertain if the one-way valve can selective between oxygen and carbon dioxide. Most likely it's suppose to keep off the moisture while allowing gas to escape (like a Gore-Tex jacket).",
"With that assumption of the one-way valve (gas can go out, but not in), ... | [
"Your explanation might be correct (if the pressure of a room-temperature gas and a freezing gas is sufficiently different), but the one way valve is indeed to keep oxygen out but allow CO2 to escape. This is because when coffee is roasted, CO2 is generated but trapped in the bean's structure. This CO2 seeps out fo... | [
"I guess my point is that the valve is actually not selective to the types of gases, but only allows gas to escape but not enter."
] |
[
"Have there ever been any undiscovered elements in a meteorite or other object that has landed on earth?"
] | [
false
] | What I mean is, has there ever been an undiscovered material from space that has landed on earth. Does the earth's atmosphere burn the majority of elements before the material lands? | [
" elements, no. All known elements have either been found naturally on earth or synthesized here.",
"There are, however, some very rare elements, like iridium, gold, platinum, and other heavy metals that are found in much higher concentrations in asteroids than in the crust, due to the fact that the majority of t... | [
"It seemed to me like the point of the question was have we ever found an element that only exists extra terrestrially, and since all stable elements are found on earth or have been synthesized then no there aren't any alien elements. "
] | [
"The problem is that stuff constantly falls from space to earth, so pretty much anything you find in asteroids is already all over earth, in the residual spattery bits of previous asteroids.",
"EDIT: I can think of a historical example though. The earliest use of iron was removing pure metallic iron from fallen... |
[
"We have found Moon rocks on Earth, and even Martian rocks on Earth, what are the chances we will find Earth rocks on the Moon or Mars?"
] | [
false
] | null | [
"In a way, ",
"that's already happened."
] | [
"A ",
"recent paper",
" by Hara et al. has shown that there should be scads of rocks from the Earth on the Moon and Mars and many other solar system bodies, and even rocks that have likely made it to other star systems.",
"In their paper, Hara et al. modeled the number of rocks that would have been ejected fr... | [
"Thank you for the informative post. "
] |
[
"Are all stables isotopes naturally occurring?"
] | [
false
] | I was wondering if there are any entirely synthetic stable(i.e. non-radioactive isotopes). For instance, a stable isotope of iron that does not occur naturally but has been synthetically produced? Edit: just noticed the title has a typo. "Stables"🤦 | [
"From the fact that actinides like uranium are naturally-occurring, we can deduce that natural nucleosynthetic processes can reach at least that high in mass (~240). The heaviest stable nuclide is lead-208.",
"So any stable nuclide can be produced somehow in nature. I'm not aware of any stable nuclides which don'... | [
"There is always the odd process here and there that produces them.",
"As an example, if you only consider the main fusion processes then you won't see any stable beryllium and boron appearing in them. They are produced when high energy particles hit larger nuclei and split them. They are very rare in the univers... | [
"While theoretical elements in the island of stability may not be stable in the sense that they will decay, it's likely that they're half-life is long enough (if we were able to synthesize them) that they would be effectively stable, right?"
] |
[
"Faster than light communication, and particle physics"
] | [
false
] | Let's say you have a very long pole, actually, the length is arbitrary, but anyways... You have a pole, and a laser parallel to it, at the end of the pole you have a light sensor and a touch sensor. When you push the pole, the laser is turned on at the exact same moment. Could the touch sensor be activated before the light reaches the end of the pole, and the light sensor on the other side? The pole does not move faster than the speed of light, but could the chain reaction of the atoms pushing off of one another reach the end faster than the light? My question is, (besides say, quantum entanglement) can you transmit information faster than the speed of light, by not physically moving matter faster than the speed of light? After thinking about this, I can see one major problem. The EM force carrier particles that let the matter within the field know that there is an electromagnetic force acting on it would have to travel faster than the speed of light for this to work. Photons are EM force carriers, so they obviously cannot travel faster than the speed of light (photons == light particles). I have an extremely basic understanding of physics and general quantum physics concepts, so my logic may have fallen apart much earlier. I guess this leads me to my last question (Though it seems I have been answering them by myself already): what prevents a massless particle from traveling faster than the speed of light? And then, how can it have any energy without mass? (e=mc I am a high school student, so please don't mock me if I am making blatant errors. Instead, let me know where I am wrong so I can learn. That also entails using terms that I will understand, hopefully. Thanks. | [
"Your \"major problem\" is the answer. The force that is transmitted in an object travels at the speed of sound in the object. The fastest that speed of sound can ",
" be is the speed of light. (usually it's much much slower) ",
"what prevents a massless particle from traveling faster than the speed of light? "... | [
"Entangled particles only remain so if no forces break the entanglement. My changing the spin of one, you break the entanglement, and the other one does not change."
] | [
"Entangled particles only remain so if no forces break the entanglement. My changing the spin of one, you break the entanglement, and the other one does not change."
] |
[
"If having blond hair and blue eyes is determined by recessive genes, why do so many Scandinavians have blond hair and blue eyes?"
] | [
false
] | I live in France and blond hair and blue eyes are less common here. However, I've been to Copenhagen and Oslo multiple times and there are . Why? | [
"I think some people conflate \"recessive\" with \"rare\", when those are really separate concepts when talking about genes. "
] | [
"Because they have a high frequency of the blue eye alleles. It is a misconception that the recessive trait would decrease in frequency through time and eventually go extinct. This would appear to be the case at first glance, because if a blue eyed person were to have offspring with a brown eyed person they are mor... | [
"It's probably a ",
"founder effect",
" coupled with a sexual selection. My guess would be that Scandinavians are descended from a relatively small number of founders, one or several of which contained genes for blonde hair and blue eyes. Over time, if blonde hair provided a fertility advantage it would have ... |
[
"What are the rings that form around a mushroom cloud in a nuclear explosion?"
] | [
false
] | There are some really good ones starting at 1:23 in this video: What causes these? | [
"The rings are clouds of condensation. Large explosions or any kind cause areas of high and low pressure in the air. In areas of lowering pressure, the air can cool below it's dew point and water vapor condenses into a cloud. As the air returns to it's normal temperature do to an increase in pressure, convection or... | [
"Cool. Thanks!"
] | [
"Is this basically the same phenomena that causes contrails behind airplanes?"
] |
[
"Generally, if you were to take the latitude of a location in the northern hemisphere, and the equivalent absolute value distance from the equator in the southern hemisphere, are these temperatures the roughly the same in their respective summers and winters?"
] | [
false
] | null | [
"Generally, no. The Southern Hemisphere has much more ocean than the Northern. The proximity of a point on land to a large body of water is usually a good indicator of its temperature extremes (excluding factors like mountain ranges and strong currents). This is because water is very slow to warm up/cool down c... | [
"It is actually quite the opposite. Warm waters tend to move away from the equator towards the poles and warm the more extreme points on earth. The gulf stream is a great example of this."
] | [
"Absolutely. The Gulfsteam current carries warm water to Europe which gives it abnormally warm weather for the latitude it's at. Similarly, the Humboldt current in the Eastern Pacific carries cold water up the West Coast which is why places like San Francisco can be so chilly. If you've never seen it, check out ... |
[
"In movies, people smash their head on someone else's head unfazed. Can anyone do that? Doesn't it cause fairly equal damage?"
] | [
false
] | Just wondering... | [
"It largely depends on impact area. Two people who whack their heads by accident usually both recoil in equal amounts of pain.",
"Someone who is actively attacking with a headbutt will try to strike with the forehead, and aim for specific target areas. The nose, for instance. It breaking, and the victim's head sn... | [
"Big motherfucker came at me, bro. I said \"Get out of my grill, bro.\" He was all aggro, bro, grabbin my lapel and slobberin', bro. \"What're you gonna do, about it?\" So, I looked at the stars. Said, \"This.\" Then I looked at my shoes. And somewhere between, his nose turned to lasagna. Bro."
] | [
"Big motherfucker came at me, bro. I said \"Get out of my grill, bro.\" He was all aggro, bro, grabbin my lapel and slobberin', bro. \"What're you gonna do, about it?\" So, I looked at the stars. Said, \"This.\" Then I looked at my shoes. And somewhere between, his nose turned to lasagna. Bro."
] |
[
"What is the medium between synapses? And what force if there is any, pushing neurotransmitters into receptors?"
] | [
false
] | null | [
"The synaptic cleft, which is the space between the pre- and post-synaptic structures, contain extracellular fluid which in many ways resemble the fluid surrounding the rest of the neurons. It is roughly 20-40 nm in width, which is just shy of the size of the vesicles that release neurotransmitters (50-250 nm) ",
... | [
"From what little I know of this: The synaptic cleft is really really small, no broader than the width of the vesicles that bring the neurotransmitter to presynaptic membrane. The vesicle attaches to the membrane and then it gets stretched out ('exocytosis'), pushing its contents into the cleft. Given the small di... | [
"What about drugs? I’d assume they find their way into the synapse through diffusion too but wouldn’t this require really high concentrations? "
] |
[
"Why does Earth have the highest density in the solar system?"
] | [
false
] | By this list, Earth doesn't just have just have high density, but actually has the highest in the entire solar system. Is that just coincidence, or is there some deep reason, anthropic or otherwise? | [
"No, the Moon is only a bit less dense than the Earth, and it is so much less massive (about 1% the mass of Earth) that adding it back into the Earth wouldn't reduce the density significantly. More massive objects are simply more efficient at compacting themselves."
] | [
"No, the Moon is only a bit less dense than the Earth, and it is so much less massive (about 1% the mass of Earth) that adding it back into the Earth wouldn't reduce the density significantly. More massive objects are simply more efficient at compacting themselves."
] | [
"The inner planets are more dense than the outer planets, because during formation of the Solar System, more volatile elements could not condense closer to the Sun, hence rocky inner planets and gas giants farther from the Sun.",
"As far as why Earth is more dense than Mercury, Venus, or Mars: Earth has more iron... |
[
"Why are the blue lights of police cars so visible?"
] | [
false
] | [deleted] | [
"What do you mean? Those lights are incredibly bright, and are built within reflective lenses designed to be as visible as possible. They are bright because they are built that way. Plus, they are flashing, or moving, and the eye tends to lock onto moving objects."
] | [
"The new lights are often LED lights, and I've found in purchasing LEDs that the blue and white have higher mCd (milli-Candela: brightness) rating than reds and yellows of the same variety. My guess is either the material used to make the blue LEDs produces brighter light than the reds, or it has something to do wi... | [
"I think in my case when comparing two different colour options for the same LED this isnt true.",
"I think it has more to do with the ",
"band gap",
", possibly meaning that blue has the largest (or smallest) band gap meaning for the same current more photons are released making them brighter"
] |
[
"If neutrons are electrically neutral why isn't the universe filled with free neutrons?"
] | [
false
] | My assumption is that free electrons have a tendency to bind with protons as atoms so that is why we don't see free protons as much. | [
"Free neutrons are unstable. A free neutron decays with a half-life of about 10 minutes, generally into a proton, an electron, and an electron antineutrino."
] | [
"There are already a lot of protons and it costs some energy to add more, which is what will happen if a neutron decays into a proton. The energy cost keeps it stable."
] | [
"Sorry, I meant to ask you this...",
"What is it about being bound in a nucleus that stabilizes the neutron so that it won't ever decay (at least not for billions of years)?"
] |
[
"If a black hole is infinitely small and dense, how could there be bigger black holes?"
] | [
false
] | null | [
"The \"size\" of a black hole can be specified by its mass, or the size of the event horizon (a sphere whose size is such that anything that passes within this sphere is trapped by the hole).",
"There can be microscopic black holes all the way up to those whose mass is millions of suns."
] | [
"It depends on what you define as the density of the black hole.",
"Since, in theory, a black hole is a ",
", a mass occupying an infinitely small amount of space, you could say that the density is infinite and that would be true for every black hole.",
"You could also say that a black hole of mass M has a no... | [
"For example, the list of every whole number must have twice as many items in it as the list of every odd number.",
"You are right that there are different sizes of infinity in some mathematical systems, but you are totally wrong about the rest. The size of the set of all whole numbers is identical to the size of... |
[
"What is the mechanism by which a virus dies outside a host cell--and what happens to the RNA inside?"
] | [
false
] | I've read lots on what soap does to viruses (so cool!), but I can't seem to find anything about how simply being outside a host cell long enough renders a virus inert, and I'm especially curious what happens to the genetic material inside once that happens. Does something else grab it up, or does it just wither to nothing? E.T.A.: The subject line should read "RNA/DNA inside." | [
"If a virus is ripped apart by soap, the genome will be exposed to extracellular nucleases that will chop it up really quickly. ",
"Radiation inactivation, like with gamma or UV, will cause major genomic damage that may allow the virus to enter a cell, but never replicate to produce new viruses.",
"Fixing chemi... | [
"Thank you so much! This is super helpful.",
"One more question: if a virion just sits on a surface like cardboard (I saw SARS-CoV-2 takes about a day to go inert on cardboard), what causes it to go inert if it's not directly in the path of, say, sunlight (for the UV)?"
] | [
"That's a great question. In the absence of obvious factors like UV, direct heat, or chemicals, I'm not too sure. Some brief reading suggests that humidity can affect the proteins on the surface of viruses in a way that basically renders them dysfunctional. All viruses contain a little bit of cell juice, so dessic... |
[
"What exactly is chloroform and why does it make you pass out?"
] | [
false
] | [deleted] | [
"The first question is easy. The second question is hard.",
"Chloroform is a chemical with the formula CHCl3 (one hydrogen atom and three chlorine atoms bonded to central carbon atom in a tetrahedral shape). In the classic \"bad guy drugging someone\" scene during movies/TV shows, you usually see a rag filled w... | [
"Nothing about this is correct. This reaction does not happen, and phosgene is a chemical weapon, not an anesthetic, and chloroform can ",
" make someone pass out."
] | [
"Nothing about this is correct. This reaction does not happen, and phosgene is a chemical weapon, not an anesthetic, and chloroform can ",
" make someone pass out."
] |
[
"How come mothers can host babies of a different blood type yet have issues receiving blood from others?"
] | [
false
] | [deleted] | [
"Maternal and fetal blood do not normally mix. Maternal blood is pumped through the ",
"maternal blood vessels in the placenta",
", where nutrients and oxygen are allowed to diffuse into the fetal bloodstream due to the close proximity of fetal vessels. There are a number of ",
"fetal anatomic features",
... | [
"I think it's a matter of semantics. The fetus is inside the woman's body, but there is no strict medical definition of \"part of the body\", per se. The fetus is indeed simultaneously separate from and intimately related to the mother."
] | [
"Anti-Kell in the maternal blood? So Kell antigen on fetal red cells?"
] |
[
"Mars is red because of the iron oxide present in its soil. What is preventing us from separating the Fe from the O, using the O for breathable air, and the Fe to build habitats for us to live?"
] | [
false
] | Chemistry class was 12 years ago. I have no idea how difficult the process is to separate the two. | [
"IMHO one of biggest problems to run a Mars colony would be the shortage of energy. There are no hydrocarbons to burn and no oxygen to burn them with. Solar power is between one half and one third of that on Earth (depending on the Martian season), and a hypothetical colony would use most of its energy for heating ... | [
"These challenges make me wonder why the fixation with Mars. The cost vs rewards and risks don't seem favorable.",
"Why not very large space stations. Then the moon. If we can do that well then venture out further. "
] | [
"Just a side note from someone unexperienced in the field, Mars does have some winds particularly near sundown and sunrise as the heat from the sun and the cold soil. Could possibly lead to wind turbines.",
"\"There are no seas on Mars, but there are areas where the thermal inertia of the soil changes, leading to... |
[
"In-depth AC Current questions"
] | [
false
] | I have a hard time understanding AC current. I would like an indepth explanation as to: The more detail the better! I read the wiki and it wasn't exactly what i was looking for. Edit: I forgot one question :) Thank you, | [
"How it works",
"Fundamentally, it's not so different from DC. Current tries to flow around a circuit, from positive to negative. In AC, the positive and negative change places periodically (hence \"alternate\").",
"We usually generate AC via an alternator, which is very similar to a motor, only opposite ;) It ... | [
"How it works",
"The source generates an electromotive force(EMF) which changes polarity at some frequency. This causes the electric field in the conductor to change direction. I am not sure if this is the kind of answer you're looking for, but have a look at what nalc wrote :)",
"How do the electrons themselve... | [
"Roughly, current is caused by an electric field. The valence electrons, or \"outer\" electrons of the atoms that make up the conductor are the least strongly bound to their position, and (in metals) can move through the lattice fairly easily. Electrons, being charged particles, move due to the field. They bump ... |
[
"Is it possible to have very vivid false memories?"
] | [
false
] | So a good while ago, I had a traumatic experience where I was blackmailed during a conversation with 3 people/strangers that I met somewhere. Ever since, I have been medicated for severe anxiety and depression and it ruined my life. After 3 years of digging, I still can’t find a trace of these individuals. Nothing, zelch. I was on both adderall and diazepam at the time and i was a bit exhausted/sleep deprived. I am starting to question if the conversation even happened. I recall the memory with extreme clarity. Is it possible to have full on vivid and traumatic false memories? | [
"What you are describing would be a hallucination rather than a false memory. A memory of a hallucination would be as vivid and traumatic as the hallucination was itself, because you are remembering something that you felt actually happened to you. "
] | [
"also this is sometimes an issue in marriages / relationships where a spouse may feel like \"x did such and such\" when it never happened. ",
"many men will probably attest to angry wives that wake up after a bad dream where they think their spouse did something to them, but I think that is the lighter of the cas... | [
"Yes - check out things like the \"lost in the mall\" study where a false memory is implanted into people.",
"https://en.wikipedia.org/wiki/Lost_in_the_mall_technique",
"Some suggest that vivd false memories could come from dreams where we mix the dream events into real life.",
""
] |
[
"Why can i see light even though my eyes are closed?"
] | [
false
] | null | [
"Yes it is passing through your eyelids. "
] | [
"Does it still affect your eyes well being? "
] | [
"Yes -- staring into the sun is bad, even with your eyes closed, even with sunglasses."
] |
[
"Why is the Sun composed solely of all the elements with a 1:1 proton/neutron ratio? Discarding the lightest and heaviest."
] | [
false
] | Also, what makes Fe so special? Do all stars share this composition? | [
"Well, when you throw out 75% of the sun's composition you're already being a bit picky-choosy.",
"The sun tends to made out of elements with low atomic number, because elements with high atomic number are made by dying stars, and the sun is alive. Small nuclei tend to have the same number of neutrons and protons... | [
"Aluminum is the first element (13) where the most common and stable isotope has more neutrons than protons.",
"Lithium-7 and beryllium-9 would both like a word with you... And the lithium, at least, is pretty significant for stellar fusion paths.",
"Edit: Boron-11 is also the most common isotope."
] | [
"Nickel 62 is the most stable isotope in terms of binding energy per nucleon.",
"Iron 56 is lighter on a per nucleon basis because it has a higher proton/neutron ratio."
] |
[
"Planck's quantum hypothesis proves that a body can't emit radiation beyond a certain frequency, but this still means that it will emit waves in ALL THE POSSIBLE FREQUENCIES below this limit. So wouldn't the body still be losing energy at an infinite rate?"
] | [
false
] | Or am I misunderstanding something? | [
"Your first sentence is simply not true. A blackbody emits at all frequencies. Where did you get that there is an upper limit?",
"As per your last question, just because it emits at all frequencies it doesn't mean the energy is infinite. The total intensity is the integral of the spectral insensity per unit wavel... | [
"You are simplifying the ",
"ultraviolet catastrophe",
" a little, but I think I understand why you are confused. For any finite volume of space, there are only a finite number of frequencies below the \"limit\" (even if that finite number can get really big when we think about large volumes), so that is why th... | [
"Here's a concrete example of your question. Take a 1 kg lump of iron and treat it as a blackbody. The specific heat of iron is 0.45 J/(g K) so at room temperature, this lump of iron has 0.45",
"293 J ~ 60,000 J = 4e23 eV of heat energy. If this lump of iron dumped ",
" of its heat energy into one massive photo... |
[
"What resolution is real life in?"
] | [
false
] | null | [
"Do you mean something like temporal or spatial resolution of the eye?"
] | [
"I mean a tv has a set pixel resolution regardless of how well your eyes are. If you if you took a real life image how many pixels can you say it has in comparison?"
] | [
"The terms you are using are still a bit too unclear for someone to be able to answer your question.",
"By \"real life\" you seem to mean observer independent, so I guess you just mean the universe? ",
"A pixel is a \"picture element\" so maybe you mean what are the elementary units of the universe? ",
"I gue... |
[
"How much does viral load contribute to the severity of symptoms for COVID-19?"
] | [
false
] | Have there been studies on this yet? For those that have said they had mild symptoms, was this mainly because they were infected with a small amount of virus vs. Someone who say inhaled a lot of virions? Or are severity of symptoms independent of viral load and strictly based upon immune system? | [
"Your question has two questions within it: 1. does viral load contribute to severity, and 2. does the dose of virus from the initial infection contribute to severity. These are two separate questions.\nQuestion 1: as far as we’ve seen, patients with worse symptoms typically present with higher viral loads in sever... | [
"Nothing to cite although I believe the data is available and could probably be found with a Google search, but I have read that a) more severe symptoms correlate with a higher viral load and b) lower viral loads and difficulty detecting via PCR correspond with milder clinical symptoms.",
"However - whatever is f... | [
"Of course. Viral load is basically a determination of how much virus is in a given sample at a given time of reading. For example, I test how much virus you have right now in a sample from up in your nose - that will tell us your viral load. The viral dose on the other hand would be the amount of virus that you ar... |
[
"If an increase in green house gases causes an increase in temperature due to more heat being radiated back to earth why doesn't the increase cause more heat to be radiated back into space from the sun?"
] | [
false
] | null | [
"Greenhouse gases reflect infra-red radiation mostly. The light form the sun is ",
" effected by this. So when light from the sun hits the earth it warms it up, as the earth warms it emits infra-red radiation, it is this infra-red radiation that is reflected back to the earth by the greenhouse gases. For more inf... | [
"Cheers mate that clears it all up"
] | [
"Yeah. Think of your car. Light goes in the window, heats up the black dashboard, which heats the air in the car, then the heat builds in the car because hot air cant go through the window."
] |
[
"Why do people pace back and forth when they're thinking really hard about something?"
] | [
false
] | I know I do this, and I start doing it without even thinking about it. Does it help you concentrate somehow? | [
"I don't know if there is any literature on the subject out there, but one possible reason may be less about thinking and more of a physiological response to the stress or anxiety that comes along with it. We tend to use rocking or rhythmic patterns when trying to regulate. (You can look into research on stress reg... | [
"Walking stimulates the hippocampus, which generates new neurons - likely because your ancestors often needed new brain-space to cope with new environs reached by walking."
] | [
"Having trouble finding any scholarly articles (mostly because \"pacing\" is a broadly-used word), but I'm pretty sure that pacing is a type of stress coping mechanism, such as nail biting, foot-tapping, and self-touching. I'll see what citations I can come up with."
] |
[
"Why must you wait 28 days after testing positive for covid before getting the vaccinne?"
] | [
false
] | The current guidance in the UK is that you must wait 28 days to get ur vaccinne if you have tested positive and I'm just wondering whether there is a scientific reason for this? Also, would there be negative affects if an asymptomatic (but covid positive) person gets vaccinated? | [
"It’s nothing to do with “immune system resets” or anything like that. It’s just to make sure you don’t infect people when you go to get vaccinated. ",
"Here’s CDC guidance:",
"Vaccination of people with known current SARS-CoV-2 infection should be deferred ",
". This recommendation applies to people who expe... | [
"I just graduated from medical residency from a large Chicago hospital. When the vaccines came out earlier this year, we were encouraged by hospital administration to get the vaccine regardless of if/when we contracted COVID.",
"I would also like to add that even before COVID, in medical practice, there are very ... | [
"Mainly to allow time for the immune system to reset*. 28 days is enough time for the infection to be completely over and all virus expelled from the body. It means the immune system can focus fully on the vaccine so your immune response will be better. It also makes it beneficial as the vaccine dose will act like ... |
[
"Why is there more steam from boiling water *after* I turn off the burner?"
] | [
false
] | Gas burner, if that makes a difference. Just something I've always found curious. | [
"You're on the right track! It doesn't have anything to do with the type of burner you're using, just that it's on and then gets turned off. Since steam is actually invisible, what you can see is when the vapor cools enough to form small droplets in the air. When you've got heat being pumped into the water, that st... | [
"My ",
" is that the Gas burner increases the condensation point (?) in the air by heating it up. When I turn off the burner the water vapor is emitted at about the same rate, but the air is cooler allowing me too see it. ",
"Would be interested to know if this is a well-understood phenomena with a more robust ... | [
"I was just wondering this the other day while making some mac n cheese. Thanks for the great answer, wish my timing was always this good."
] |
[
"Why can we treat AIDS but not cure it?"
] | [
false
] | [deleted] | [
"HIV, the causative agent of AIDS, is a retrovirus. Part of the retroviral life cycle is the synthesis of DNA from its viral genome and subsequent incorporation into your own genome. From here, it can go two ways depending on the activation state of the cell: it can either just lay dormant (or quiescent), or its ge... | [
"It's certainly possible! Though I can't think of one off the top of my head, I believe that a strain of human papillomavirus has been shown to be vertically transmitted in germline DNA (but don't quote me on that). As you said, there would need to be no observable effect, and when viruses establish latency, such a... | [
"Even though this has nothing to do with the OP, since you're a virologist, I'm going to ask anyway. Are there any examples of viruses which can infect the germ-line cells and show up in future generations of people without any observable effect on the person initially infected in the first place?"
] |
[
"Is E85 sustainable even in the short term?"
] | [
false
] | Where I live in Temple, TX an HEB opened a gas station this week and they're selling E85 @ around $2.60 a gallon. People were lined up 10 cars deep at . Now I'm sure a good portion of these people where there for regular gas which they were selling @ $2.99 (gas has been about $3.25 here). Regardless, My question is that if the demand for E85 raises significantly, is it even possible for the demand to be met in the short term? The research I've done on E85 says that it is an inefficient bio-fuel that is only being produced because of corn subsidies keeping the price of corn artificially low, and that we don't have enough farmland in the entire country to support a total e85-based fuel economy. | [
"•Bio fuels (when burnt in an engine) may produce less carbon emissions than regular gas/petrol but they still produce a fair amount",
"It depends on the biofuel, but if you allow me to use Brazillian ethanol made with sugar from extant brazilain farmalnd and fertilized with inorganic nitrogen reduced with electr... | [
"I don't know about E85 specifically, but as far as \"bio\" fuels are concerned they must surely rank as one of the worst ideas in human history:",
"There is nothing \"bio\" or \"green\" or ethical about biofuels. The only motivation for these fuels is that currently they cost slightly less than regular fuels. Bu... | [
"Even given the transportation costs. I've actually never heard of any industrial process that did not suffer diminishing returns on the top end of the economies of scale and increasing returns on the bottom end, so yes, biofuels will see this but then again, fossil fuels do too. Most of the models I've seen do p... |
[
"What's the difference between ultrasound and echocardiogram?"
] | [
false
] | [deleted] | [
"Here’s a good article that describes the different types of echocardiograms. The quick answer is that an echocardiogram is a specialized ultrasound. There are several types of echocardiograms however including some that are done by feeding equipment down the patient’s throat. Why more expensive? Because cardiology... | [
"Echocardiogram is just an US of the heart. Originally used the same machines, but now the echocardiogram machines are more advanced in terms of software designed to measure blood flow, etc. ",
"Echo is more expensive compared to a gall bladder US for example because it’s a longer test where the operator have to ... | [
"The idea is the same. Why is the echocardiogram more expensive? It's about the same as a difference between a spectrometer and a spectroscope.",
"You can get a nice ",
" if the spectrum with very inexpensive equipment. But when you require data to analyse the spectrum, determine exact intensity of each wavelen... |
[
"What is it about being suddenly woken that often prevents you from clearly remembering the next few moments?"
] | [
false
] | [deleted] | [
"Firstly: does this actually happen? I don't think it does in my subjective experience.",
"If it does happen to many, I would ",
" that it's related to the complexity that is human consciousness. We have 'awake' and 'asleep' but within and between those there can be many differences in what the brain is doing a... | [
"ive always had quite a degree of difficulty in remembering anything from most woke-me-up phone calls. the feeling is strange, its like a tip-of-the-tongue moment, i ",
" things were said but can't actually remember what it was. this effect occurs regardless of whether or not i go back to sleep or hop in the show... | [
"It happens to me ",
". My alarm will go off, I'll get up, cross the room, shut it off, and go back to sleep shortly thereafter. Sometimes I'll be woken by a phone call and not recall the conversation or associated time whatsoever. According to people that interact with me during these times, I'm alert & ratio... |
[
"[Biology/Medicine] Shouldn't Toxoplasma Gondii be a Bigger Deal than it is?"
] | [
false
] | [deleted] | [
"my lab works on T gondii infections, particularly in reactivation.",
"T gondii infects (mice, cats, humans) and usually goes quite for a really really long time. in a very few people, either due to severe infection or immune suppression, it reactivates, and can cause brain inflammation, but by the time that happ... | [
"Unless you're immune compromised, very young, or very old, toxoplasma isn't really harmful to humans. In addition, there are already available treatments.",
"It is being researched quite a bit though, you should check out Sapolsky's recent work."
] | [
"there are a number of treatments for toxoplasmosis; pyrimethamine, sulfadiazine, sulfamethoxazole, and sulfisoxazole are the ones specifically labeled for that indication by the FDA.",
"\"nobody cares about it\" because generally speaking if you're not immunocompromised your body will fend off this infection fai... |
[
"How do we know how it will take around 5 billion years for our sun to turn into a red giant?"
] | [
false
] | We've been looking at stars for such a small amount of time how do we know the length of time between changes, or is 5 billion just a very rough estimate? | [
"Even though we've been observing stars for a small amount of time, we've been observing a lot of them. Think of an alien observing all humans for a few days. Not long enough to observe an entire life cycle, but long enough to determine what the average lifespan is. (Grossly simplified since human life spans hav... | [
"So how do we know the ages of the stars we see?"
] | [
"If we just observe some given star which is in the ",
"main sequence",
" phase of its lifetime, we actually don't know its age very well at all, unless we can get some pretty robust measurements. Once a star leaves the main sequence, it goes through a very interesting path on the Hertzsprung-Russell diagram, m... |
[
"How do the drills used for oil mining deal with torque?"
] | [
true
] | [deleted] | [
"Watch \"Oil Drill Animation\" on YouTube\n",
"https://youtu.be/fl8L4qSqSqE",
"Generally speaking, the teeth of the drill bit are driven by forced liquid called \"mud\" (which also acts as a preventative to keep the reservoir pressure from shooting out of the ground - higher pressures require more dense mud).... | [
"Glad to. There's so much more involved. Another \"real life\" rig in action can be seen here : ",
"https://youtu.be/HtLOXyoB9Ko",
" ",
"It's very dangerous, hard, and yet exciting work. ",
"A good crew \"tripping\" pipe (going in and coming out of the hole with the pipe) is exciting, but hard and dang... | [
"Glad to. There's so much more involved. Another \"real life\" rig in action can be seen here : ",
"https://youtu.be/HtLOXyoB9Ko",
" ",
"It's very dangerous, hard, and yet exciting work. ",
"A good crew \"tripping\" pipe (going in and coming out of the hole with the pipe) is exciting, but hard and dang... |
[
"Do all medical experiments still use a control group?"
] | [
false
] | It seems like we would already know what happens to a person with untreated pancreatic cancer. It seems like not giving someone with a terminal illness in a drug trial a possible life saving treatment would be unethical if we already know without any treatment what will happen. | [
"Drug development follows a more-or-less defined progression of phases. Not all phases are set up to see if a drug is effective though, initially you want to find out how the drug is metabolized and what kind of doses can be tolerated. For this you don't need a control group. ",
"As far as large randomized contr... | [
"No, neither has it ever been the case that all medical experiments always use a control group (there are different study designs). In the case of your example, however: the effectiveness of a treatment is often researched using a control group. The reason this is done is that you want to investigate the difference... | [
"Does that mean that someone who has participated in a research trial for New Treatment A and had no benefit would be unable to later test out New Treatment B, even though it could potentially save them? Would they be required to wait for NTB to be tested and made available first, or does the rule against using the... |
[
"How can scientists know that the intergalactic space has a density of one molecule per cubic meter?"
] | [
false
] | [deleted] | [
"Well you can look at the non-absorbed parts of the spectrum. Like each atom only absorbs specific small bands, \"lines\" usually, of the overall spectrum. So just look where the lines aren't and you can see how bright it \"should\" be. ",
"We can even do more advanced stuff, like for very very distant sources...... | [
"Enlighten us, please?"
] | [
"B is us right? So how do we know the original intensity of the light as it left A if all we can see is its intensity after passing, or not passing through the amounts of matter we are trying to estimate?"
] |
[
"Would a dinosaur be able to survive in Earth's current atmosphere?"
] | [
false
] | Let's pretend that we can clone a dinosaur (or snag one with a time machine, or whatever); would the dinosaur be able survive in our atmosphere, or would it suffocate? | [
"oxygen levels then were at 26% compared to 21% today. I would assume 5% would not be significant enough to suffocate a dinosaur considering life today exist at different altitudes with lower amount of oxygen the higher you are. ",
"Source"
] | [
"lower pressure means less air to breathe. The percentage levels remain the same but the physical amount of oxygen is less at higher altitudes."
] | [
"This is probably a dumb question, but is there a significant difference between oxygen levels at sea level and a mountaintop? I was under the impression that the most significant change was the pressure. A 5% change seems (to me, a layman) like a substantial change. "
] |
[
"Knowing that hackers can use radio waves to hack phones, is it possible that humanity will be attacked by advanced AI in different star system?"
] | [
false
] | null | [
"Such hypothetical questions are better suited for our new-ish sister sub ",
"/r/asksciencediscussion",
". Please consider reposting there instead."
] | [
"Thank you for your reply. I assumed there would be clear answer telling me that electromagnetic waves can't hack military grade equipment as it's shielded or something else wild but specific.",
"\nI did re-post this question to ",
"/r/asksciencediscussion",
" and will delete my post here.",
"\nI hope you s... | [
"Got the message! Cheers!"
] |
[
"If all of the mass in the universe was to be inside of one black hole right now would the event horizon be larger, smaller or the same size as the universe is right now?"
] | [
false
] | also if this was possible would this effect the rate at which the universe expands (especially if the event horizon of this black hole is larger than what the universe is right now) | [
"That black hole cannot form. In fact, that mass is already inside its own Schwarzschild radius: if you do the calculation that radius is about equal to the radius of the observable Universe, so you can tell already something doesn't add up.",
"An intuitive understanding for this is perhaps as such: the uniform d... | [
"How would an observer distinguish between a bog-standard universe and the interior of a very large and diffuse black hole?",
"Latter has a singularity in the future of any observer in finite proper time, former doesn't. The latter also isn't isotropic.",
"As i understand it, once you've crossed the event horiz... | [
"Static gravitational fields (the ones that give Newton's law) don't travel. They are instantaneous. "
] |
[
"Stem Cells and regeneration"
] | [
false
] | I am curious about stem cells and regeneration from damage. For the sake of discussion lets imagine a hatchet wound to a quadriceps muscle, right in the muscle belly so there is no need to worry about nerves, ligaments, or tendons. Could stem cells be injected via syringe or some other method into the wound to accelerate the muscle/skin repair? How much faster would it heal? If this is impossible, is it due to inherent limitations in how stem cells work or just limited by where we have the technology today? | [
"I'm not a stem cell researcher, but I noticed no one has given you an answer so I can give you a little information.",
"Stem cells and regenerative medicine is a huge field as you might imagine. There is nothing that would prevent stem cells from being used in this capacity in principle, but it's tricky. It's a ... | [
"Thank you for the clarification, I was envisioning stem cells as a raw biological material that could be used as a sort of wound spackle in the this case, which would dramatically improve healing time. "
] | [
"I work with stem cell niches, so I can briefly elaborate on XIllusions' answer. ",
"Adult stem cells in the body are essential to the generation of short-lived cells, and are held in tightly controlled environments called \"niches\". For instance, the adult stem cells that produce reproductive cells, called germ... |
[
"Is it possible for binary planets (2 planets orbiting each other) to exist ? Why haven´t we found one ?"
] | [
false
] | Hello ! Binary stars and asteroids exist. Is it possible for a planet the size/mass of the earth to exist in a binary state, having another planet of roughly the same size orbiting it. Like a moon, but both are roughly the same mass. | [
"Pluto and Charon are in this configuration."
] | [
"(",
" Pluto's not a planet. ",
")"
] | [
"We haven't found any binary planets because a 'binary planet' would by definition not be a planet: they haven't cleared their orbit."
] |
[
"If I took a picture of a sunrise over the ocean and a sunset over the ocean, is there anyway for someone else to tell which picture is which?"
] | [
false
] | null | [
"You are technically correct, the best kind of correct.\nYou're still a dick though."
] | [
"Not for certain, but you can often make a good guess.",
"Over the course of the day, the sun heats the air and evaporates water, creating clouds and fine suspended water droplets. The humidity, and droplets scatter blue light, making the sunlight that reaches your eyes redder. At night, the water condenses and ... | [
"With a long exposure time, it might be possible to infer which direction the sun is moving.",
"The colour of the sky is caused by Rayleigh scattering. When the sun is near the horizon, the light is traveling through denser atmosphere and for longer, which filters out the higher-frequency colours. Depending on wh... |
[
"Zoologists: How do animals keep their teeth clean?"
] | [
false
] | I imagine there'd be great evolutionary benefit to dental hygiene. So what methods, if any, have animals developed to keep their teeth clean? | [
"Gnawing on hard materials can help break off tartar. This doesn't ",
" persay, but it does help. So carnivores will gnaw on bones for various reasons and an added side effect is this mild tartar removal. It can lead to tooth fractures though (so be careful giving bones to your pups)",
"Rodents require constant... | [
"Very well said, the only think I'd like to add is that most animals don't live nearly as long as humans, so most mammals die before before their teeth totally disintegrate due to cavities."
] | [
"Yeah! That is also a very important fact. Also good to note that a lot of carnivores don't chew as much as swallow so issues with their teeth may be less noticable"
] |
[
"Where did the mass that set off the Big Bang come from?"
] | [
false
] | [deleted] | [
"To ask what happened \"before\" the big bang is ill-defined. The big bang was, for all intensive purposes, the (chronological) start of the universe. There is no \"before\", there is no \"from what\". The best we can hope to do is craft theories (which are independently validated) that might give us a theoretical ... | [
"You're right, forgive my poor choice of words. In essence, yes, the Big Bang was, as it were, the beginning of time. However, for such an event to be possible there had to be mass in the first place, correct? I'm not trying to make a point or go on some sort of ill-advised and nonsensical crusade. Just curious if ... | [
"However, for such an event to be possible there had to be mass in the first place, correct?",
"What do you mean, ",
"? The big bang ",
" the beginning. There is no \"before\". The mass/energy that existed after the big bang have always existed ",
"."
] |
[
"Is there physical differences between blood types?"
] | [
false
] | If I put a drop of blood under a microscope could experts be able to say what type it is? Is there a visible difference? What does A,B, O etc actually mean? And what does the positives and negative’s mean? Thanks | [
"There are 4 main types of blood: A, B, AB, and O. Any one of these 4 types can be + or -.",
"On the surface of the blood cell there are proteins called antigens. The important antigens for this explanation are: A antigen, B antigen, and Rh antigen.",
"Someone who has A antigens on their blood cells would be ty... | [
"Very tiny. A blood cell is around 7-8um across (there are 1000 um, micrometers or microns, in every millimeter). A surface protein is probably around the 10s of nm (nanometers, there are 1000 nm in every um) large. So roughly a thousand times smaller. ",
"It is relatively easy to see cells with a micr... | [
"Depending on how you dye/stain the cell, yes. The surface proteins are distributed all across the surface. So if you use a dye which only sticks to those proteins it would color the whole surface of the cell. ",
"There are ways of binding dyes to targeting moeties, like antibodies, that only stick to one ty... |
[
"Could the setting of Venus visibly affect the brightness of the whole sky?"
] | [
false
] | Let me give a bit of context. I'm a fan of historical novels of Patrick O'Brian, set in the early 19th century. O'Brian is generally known for his careful attention to historical and scientific detail. In the third book of the Aubrey/Maturin series, , there's a scene set on a ship that's sailing in the South Atlantic, south of the equator. There's a bet on whether one of the characters can read at night just by starlight and phosphorescence from the waves. The crucial detail is that they're waiting for Venus to set because then, it is claimed, the starlight is diminished. Allow me a brief quote: ‘We are waiting for the agreed moment, sir,’ said the chaplain. ‘Perhaps you would be so good as to keep time and see all’s fair: a whole bottle of pale ale depends upon this. The moment Venus sets, Dr Maturin is to read from the first page he opens, by the phosphorescence alone.’ ‘Not footnotes,’ said Stephen. [...] At this speed the frigate’s bow-wave rose high, washing the lee head-rails with an unearthly blue-green light and sending phosphorescent drops over them, even more brilliant than the wake that tore out straight behind them, a ruled line three miles long gleaming like a flow of metal. For a moment Jack fixed the glowing spray as it was whirled inboard and then across the face of the foresail by the currents from the jibs and staysail, and then he turned his eyes westwards, where the planet was as low on the horizon as she could be. (the emphasis is mine) Some friends of mine who're astronomical amateurs, but certainly more knowledgeable about astronomy than me, claim that this is definitely impossible; Venus's setting cannot have such a huge effect as to make it so "the starlight distinctly lost in power". Since Venus is the evening star, they say, its setting could indicate the coming darkness, but it can't have the immediate effect as described in the book. Are they right? Is O'Brian here completely wrong? Could you give me an explanation and maybe some data? | [
"Venus is in fact bright enough that someone with good night vision can read by it.",
"However, the story is unlikely. As an object gets lower on the horizon, you are looking through more of the atmosphere and the object gets dimmer. This is called atmospheric extinction.",
"At 5",
" , Venus loses about 3 m... | [
"Just to be clear, the question is \"Does Venus significantly brighten the night sky?\""
] | [
"That depends a lot on the phase of the moon, doesn't it?"
] |
[
"If big cats don't purr, then what's going on in this video? (Link in text)"
] | [
false
] | See, I've always been told that the thing that separates big cats from small cats is that small cats can purr while big cats can't (with the exception of the cheetah). So what's going on That sounds like purring to me. He's clearly happy. Cats purr when they're happy. | [
"Well as most science information tends to be spread around, what you've been told is ",
" true. ",
" big cats can purr, like ",
"cheetahs, lynxes, pumas and more",
". But others, notably in Pantherinae, make purr-like sounds which aren't actually purrs and these include lions, leopards, tigers, and jaguars... | [
"No, all the cats you mentioned belong in separate genuses, none of which are in Felis. Lynx is its own genus and Puma is its own genus."
] | [
"Lynxes and pumas are Felis. They're small cats. "
] |
[
"What are the biggest scientific discoveries of the past 30 years?"
] | [
false
] | When I think of major scientific discoveries since 1900, most that come to mind are from before I was born: relativity, quantum mechanics, transistors, the double helix, the big bang, etc. There are probably some ideas that haven't been around long enough to be recognized for their true importance, but what ideas or discoveries in the past 30 years will future generations regard with the same respect as the ones I listed above? | [
"Hard to say one discovery is bigger than another. Here are some off the top of my head; obviously this list is biased towards my interests; e.g., advances in biology/chemistry aren't listed.",
"The universe is expanding at an accelerating rate.",
"The universe is 13.7 +/- 1% years old, made of 4% baryons, 23%... | [
"They're inventions, not discoveries."
] | [
"I'll add a couple:",
"figuring out how to amplify/sequence/clone DNA on the cheap",
"genetically modified and transgenic organisms"
] |
[
"How is it that both SSRIs and SSREs are both effective antidepressants, despite having the exact opposite mechanism of action?"
] | [
false
] | Selective Serotonin Reuptake Inhibitors (SSRIs) supposedly increase the extracellular level of serotonin, while Selective Serotonin Reuptake Enhancers (SSREs) supposedly do the exact opposite. Yet both classes of drugs have been effectively used as antidepressants. What's going on here? This seemingly paradoxical effect makes me wonder if perhaps we're getting this entire mechanism of action wrong. It's commonly believed that SSRIs treat depression and anxiety by increasing serotonin levels, which makes us feel better. In other words, more serotonin = better. But it's also known that SSRIs can often make things worse before they slowly get better. What if the real cause of eventual relief is of serotonin receptors after being inundated with extra serotonin? What if serotonin is actually causing the problem? This theory would explain why SSREs (or more specifically Tianeptine, the only SSRE currently on the market) have a much faster onset of action... they're addressing the problem by reducing serotonin levels. In other words, too much serotonin = bad, and SSREs attack this issue directly. Of course, this is all a wild conspiracy theory on my part, and I'd love for someone to prove me wrong and explain how all this really works. What say you, AskScience? | [
"Theyre not necessarily opposite function. Ssri's increase the amount of serotonin in the synapse, which allows more serotonin to saturate receptors. Ssre's however, despite their name, do not increase serotonin to be removed from the synapse, they increase the sensitivity of serotonin receptors, meaning more serot... | [
"This review will answer where we're at with depression theories and how we think tianeptine (SSRE) works... ",
"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2902200/",
"The real fact of the matter is the science of most mental/neurological disorders goes way beyond neurotransmitter issues. However, our current... | [
"From what I've read, and this is by no means my field but I have studied some of these mechanisms, simply put, we have no idea. Some antidepressants work, some don't, some do very different things in different people, and many people often become attenuated and need dosages need to be increased medications switch... |
[
"electromagnetic shock waves"
] | [
false
] | if an object surpasses the speed of sound, the shockwaves produced (accumulation of wave fronts) create a sonic boom. how is the equivalent of electromagnetic shock waves handled? because aren't electromagnetic waves governed by c? | [
"Nothing can ever go faster than c, since it is the speed of light ",
". ",
"However, in materials, the speed of light is actually reduced by the material's index of refraction, and is given by v=c/n. If an extremely energetic particle moves faster than the speed of light for that material, the particle can p... | [
"your welcome. I'm going to use the wave model to explain the slowing of light in a material. ",
"The speed of light in vacuum can be written as c=(wavelength)x(frequency). The frequency of light stays the same when going between media (since the wave has to be continuous across a boundary). This means that wa... | [
"ok right, ive read about cherenkov radiation and its really cool, but is this because the (whatever medium) atoms absorb the light as energy then re-emit the light when returning to the lower energy state?",
"how are EMP's relevant in this discussion?"
] |
[
"How does a CPU physically work?"
] | [
false
] | [deleted] | [
"Hi, Intel engineer here,\nI just tried to type out a very simplistic example....and ended up getting longer and longer. But to try and sum it up: We have hardware (rtl - register-transfer level logic) and software in combination to tell the cpu what to do. on a very simple scale, if a pin is logic high (1 or vc... | [
"Hi, another computer engineer here. I have some free time so let me expand on OP's explanation.",
"Let's start from the ",
"MOSFET",
". A MOSFET is an electronic switch; you can think of it as an open or closed switch for our purposes and ignore its use as an amplifier for now. There are two types of MOSFET... | [
"Well to answer the last part of this question, it's all based on the logical circuits that are in the CPU itself (see ",
"Logic Gates",
"). These are circuits that take certain inputs (a set/combination of 0's and 1's) and produce certain outputs. These outputs are determined based on \"truth tables\" - tables... |
[
"Why does the reaction H2 + O2 produce H2O rather than H2O2?"
] | [
false
] | null | [
"Oxygen has 6 of 8 electrons in its outer electron shell. Having 8 electrons in the outer electron shell is a favorable (i.e. stable) configuration. ",
"H2O looks like this with \":\" representing shared electrons:",
"H:O:H",
"In this configuration, O shares two of its 6 electrons with the H atoms and the H a... | [
"It's the way the shells, or how the electron orbitals are shaped. One form is more stable than the other, which in this case H2O is more stable than H2O2. It's why the lable on the H2O2 sign says \"keep out of sun\". The energy from the sun is enough to break the H2O2 into H2O and O2"
] | [
"What's already been said, especially the bit about the low amount of energy required to decompose hydrogen peroxide. The synthesis of water from hydrogen and oxygen gas gives off a lot of energy (look up hydrogen balloon explosion) and that energy would be enough to decompose any hydrogen peroxide formed, giving o... |
[
"Why does drinking coffee make me pee faster than if I drank the same volume of water in the same time period?"
] | [
false
] | null | [
"Actually, you are thinking of alcohol. ",
"Caffeine, on the other hand, can act as a mild diuretic by triggering ",
"dilation of the afferent arteriole",
" and increasing the amount of filtrate produced... It is also possible caffeine may decrease some Na+ reabsorption. Either way, more filtrate could mean... | [
"My mistake. It has been a while since I dusted out the old cobwebs. Thank you for the correction."
] | [
"The caffeine acts as an inhibitor for antidiuretic hormone which causes your kidneys to absorb water. Since it is not taking water in for your body, it is expelled.",
"Bonus: The dehydration caused by caffeine can actually make your hangovers worse, so drink water not coffee."
] |
[
"why does bleach feel \"slimy\" on your skin, particularly when you try to wash it off with water?"
] | [
false
] | [deleted] | [
"The bleach breaks apart the lipids of your skin cells and turns them into fatty acid salts. In a nutshell, the top layer of your skin is turning to soap."
] | [
"That's not quite what he said. He was saying the bleach was turning the top layer of your skin into 'soap', but soap does not do the same thing to the top layer of your skin. Soap is a surfactant, which means that it helps to lower or break the surface tension of water. Basically, it lets water pickup stuff off yo... | [
"That's not quite what he said. He was saying the bleach was turning the top layer of your skin into 'soap', but soap does not do the same thing to the top layer of your skin. Soap is a surfactant, which means that it helps to lower or break the surface tension of water. Basically, it lets water pickup stuff off yo... |
[
"Why do lots of low clouds have flat bottoms?"
] | [
false
] | I see this all the time. Giant crazy clouds that spread in every direction, but flat on the bottom. | [
"Clouds that form very low to the surface tend to have flat bottoms for two reasons: firstly, clouds normally form above what's called the \"boundary layer\", which is the level at which turbulent surface winds give way to even and horizontal atmospheric winds. This lends to a flattening out of the second factor: t... | [
"AcerRubrum got it mostly right. The \"boundary layer\" comment isn't really relevant to this question, but the LCL (lifting/lifted condensation level), is the level at which a parcel of moist air begins to condense. The atmosphere generally cools with height, and a parcel of moist air lifted to a certain heigh... | [
"I mostly wanted to illustrate that the winds above the boundary layer run mostly horizontal to the surface, rather than turbulently when mixed by the land surface. And you're right about different cloud types. Low clouds tend to be denser with higher moisture contents due to higher pressure if I remember my meteor... |
[
"Is the brain sexually dimorphic?"
] | [
false
] | I recently got into a discussion with a family member about wether or not the brain was sexually dimorphic or not, and they sent me that claim to demonstrate that the brain isn't sexually dimorphic at all. Are the articles accurate in their claims? | [
"People often make a rather annoying error of thinking that if there is some difference between men and women that means all men are something and all women are something else. And on the other hand people dismiss gender sex differences because “not all women/men”. Both of those ideas are fallacious. ",
"I like t... | [
"The articles are peer-reviewed, collaborations between respected scientific institutions, they present their data with conclusions...",
"Were you asking because these articles are counter to biases you may already hold? If so, consider why you may have these biases."
] | [
"While I agree with you on the first part, I find the second a bit harsh. A lot of earlier studies came to the conclusion that the brain structures of the genders differed significantly from eachother, so I understand why that belief is still ingrained.\nAlso all these studies agree that there are brain forms that ... |
[
"How can electrons move through a superconductor without any Joule effect ?"
] | [
false
] | Last time in class we started talking with the teacher about superconductors and he just said that one of the current challenge was to find a material that has superconduction proprieties , because we would be able to transport electrical energy without loosing it. When I asked him if it was near 0 or actually 0 joule effect he stated that there was NONE joule effect , when I asked him how could this even be possible he told me that he was not a specialist of this field and so that he wouldnt say something wrong. So now i'm asking it to you! How is this possible? | [
"Short answer: We're not completely sure.",
"Longer answer: The BCS theory of superconductivity attempts to explain a number of effects by postulating that if we take a crystal lattice of some form and have electrons moving within it, under sufficiently bizzare conditions, they start becoming correlated. An ele... | [
"To give a little more background on what is and isn't known: once you have electron pairing, all aspects of superconductivity are very well-understood. In fact, the Russian Landau-school physicists were basically only missing this key ingredient in the early 50s, but had otherwise developed a completely correct pi... | [
"What you're referring to in your second sentence is ballistic transport and it's not the same as superconductivity. There are very small silicon transistors today whose size (several or tens of nanometers) is smaller than the mean free path of electrons, but they are not superconductive. ",
"Even without scatter... |
[
"Is there a limit to the resolution of images a spy satellite could capture?"
] | [
false
] | I'm interested to know the answer to this. I work with spatial data, and the big satellite provider, Digital Globe, can provide imagery with pixels of around 0.5 m. This is a US government imposed limit, I think. What is the theoretical limit of the resolution of an image captured from space, either from a spy satellite or that . I'm guessing it is limited by atmospheric distortion, but this can be modelled and solved for in post processing, right? | [
"The diffraction limit of an optical system is: theta = 1.22*lambda/D, where lambda is a wavelength, like 500 nm, and D is the diameter of the objective. So if something had a 2.5 meter objective, and was at 350 km altitude, it would be able to see features 8.5 cm across.",
"edit: And then there's ",
"the Membr... | [
"... it would be able to see features 8.5 cm across.",
"This is inaccurate. You would be able to distinguished two points which are more than 8.5 cm apart. It is not like you would be able to see a CD because it is 10 cm across.",
"Each point (on earth) would give rise to a ",
"Airy pattern",
" on the image... | [
"This is interesting question. ",
"I'm assuming that you talk about resolution that can be achieved with single image. Oversampling (taking multiple pictures over time) together with signal processing could increase the resolution from what is theoretically possible with single image. There is also all kinds of w... |
[
"According to Einstein, time, length, and mass are relative. Is there any unit of measurement that is not relative to the observer?"
] | [
false
] | I'm just wondering it there is a non-relative unit of measurement, since time, mass, length, and the speed of light are all relative to the observer. Or do we measure all things "relative to point (X,Y,Z) at the surface/center of the earth/solar system/galaxy/local group? | [
"The old way of doing relativity made mass a variant quantity, with m = gamma * m_0, with m_0 being the \"rest mass\". Then momentum was given by p = m * v like normal. There is a relativistic invariant here too, which would be m / gamma. That quantity doesn't have a special name afaik. ",
"The more modern way ta... | [
"Care to clarify the mass part? In OP's question, he states mass as a Lorentz-variant property. I'm curious as to which it is. ",
"Although he/she also says the speed of light is dependent upon the observer, which is not true"
] | [
"Care to clarify the mass part? In OP's question, he states mass as a Lorentz-variant property. I'm curious as to which it is. ",
"Although he/she also says the speed of light is dependent upon the observer, which is not true"
] |
[
"Why does most of the attention for alternative fueled cars center around electric batteries, and not hydrogen?"
] | [
false
] | I know that several years ago I was seeing a lot of news surrounding hydrogen fuel-cell cars, but recently it seems like cars running off of electric batteries have gotten all of the attention and research. I know that hydrogen can be dangerous, but is that the reason that they aren't being developed? It seems like all of the complaints against electric (short range, long recharge time, poor responsiveness) would be solved by using hydrogen. | [
"Hydrogen fuel cell technology is still advancing but there are some definite drawbacks that are hard to escape.",
"Firstly, hydrogen isn't a very good fuel for transportation energy. It has a terrible ",
"energy density",
" compared to batteries or liquid fuels, even when massively compressed. If we did us... | [
"The hydrocarbon sources, still produce CO2 emissions though correct? So the main reason we're looking at switching to alternative fuels is still applicable to these."
] | [
"There could (not a chemical engineer, here) be reactions that turn hydrocarbon sources into other carbon compounds, and release hydrogen gas. Ie, the carbon would be stored away (sequestered) in some form, like a solid compound, and so not go into the air."
] |
[
"Human powered energy?"
] | [
false
] | This is a serious question and if it is not possible I would love to know why. Why couldn't you take a large amount of people, preferably overweight individuals (the US has plenty), stick them on an excercise bike, and pay them a stipend for the amount of wattage they produce? Seems like to me you are denting the job/energy market, curing plenty of diseases (reducing healthcare costs) by getting people in shape, and producing clean energy. I noticed on the excercise bike this morning, while watching tv and playing on my phone mind you, I was producing 70 watts. What's wrong with this idea? | [
"Been asked a few times. Essentially, there are gyms that run this gimmick. But at the end of the day you don't produce enough for it to be worthwhile."
] | [
"From an energy perspective, this is a very inefficient way to produce electricity. Humans get their energy from food and we are very inefficiently turning this energy into mechanical energy. You would get more energy by just burning the food directly and converting it in electricity. On top of that it cost a lot o... | [
"Let's say you're Lance Armstrong and you hammer out 500 watts for an hour. The total energy output is 0.5kW-hr, which costs about 5 cents when you plug something into the wall.",
"So the best cyclists in the world can produce about 5 cents/hr in energy output.",
"In the process he's burning over 1500 calories... |
[
"Is there a energy limit for a single photon?"
] | [
false
] | Is there a limit for how much we can supercharge a single photon? If so, what is it, and how does it compare with the amount of energy we use to, for example, throw a ball? How short would the wavelength be? | [
"As the amount of energy in a photon depends on the observer, there can be no such limit. Imagine that there was such a limit that an observer would measure the maximum energy of a photon. And then imagine that this observer accelerated towards the photon. What would happen? Unless the photon increases in frequency... | [
"But what happens when the wavelength of the wave reaches the planck length, does it continue to shorten if an observer accelerates toward it and sees is blue shifted?"
] | [
"Yes. The planck length is not anything like the resolution of the universe."
] |
[
"How does salt kill a slug?"
] | [
false
] | null | [
"Hello! This is a very straight forward answer. When you dump salt on a slug it draws the water out of its body and the slug dies from dehydration. This is due to osmosis, as you probably remember from grade school science courses. Slugs really need to maintain high levels of water content in their bodies in order ... | [
"I recommend deterrents like copper tape or metal slug fences around your plants. You can also use sheep wool pellets in your garden as a repellent (replace when wet, they stop working). You could also plant plants in the area you don't mind sacrificing to the slugs, like yellow mustard, lettuce, cucumber, zuccini ... | [
"Oh I see, so that's why. What would you recommend then?"
] |
[
"Can animals enjoy music?"
] | [
false
] | [deleted] | [
"I know a lot of birds enjoy dancing to music and some sing a long. ",
"https://www.youtube.com/watch?v=5DYFHHjSxAA"
] | [
"I'm not a biologist, so take everything I say with a healthy pile of sodium chloride, but I've heard that music has significant connections to human speech and its patterns. So \"human\" music wouldn't make sense to animals."
] | [
"Another interesting question, thought the answer is probably very complicated, why do we enjoy music? Its just a bunch of sounds, but it can evoke a pretty strong response in our brains.",
"First of all, cool reddit. Music has such a strong and deep resonance with humans because it was through music that it is b... |
[
"What would it take to make a telescope that could see details on a hypothetical planet orbiting the closest stars?"
] | [
false
] | null | [
"Quote from my answer to this question: ",
"http://www.reddit.com/r/askscience/comments/n3mx1/could_an_astronomer_tell_me_if_kepler_22b_would/",
"So, if you mean see features of the planet itself, then the answer is we would not be able to see any direct features. (Hubble telescope cannot even really resolve fe... | [
"Yes it was, but the formulas and such still hold, just now instead of the \"2200 km\" it becomes 16 km in diameter for the telescope. (Compared to Hubble which is 2.4 m, and James Webb's 6.5 m diameters. )"
] | [
"if I understand correctly, that last link is if it were 600 light years away?"
] |
[
"Exactly how does an influx of sodium ions create saltatory conduction in a myelinated axon?"
] | [
false
] | The lecturer in my neuroscience class today said that electrons associated with the Na ions make a circuit that goes from one Node of Ranvier to the next. The Na ions are not diffusing down the axon themselves. He also said it was a physical chemistry question that he wasn't qualified to answer. I am hoping someone can explain it fairly simply to me or else provide links to a good explanation. Thanks! | [
"I assume, from context, that you understand how the action potential travels down an unmyelinated axon. The individual sodium ions do not diffuse down the axon, but their concentrated positive charge pushes other positive ions away and pulls negative ions towards them. This creates a wave of positive charge tha... | [
"By thickening the cell membrane with myelin, the ions on the inside and outside of cell are further away and influence each other less. This means less charge is stored across the myelinated membrane, and more charge can immediately travel down the axon. In physics terms, the myelin decreases the capacitance of th... | [
"The dispolarization of that segment at the membrane causes an electric field that reaches the next ranvier node, provided the influx is big enough to cause that, and this is the stimuli for this next node to start the influx of sodium."
] |
[
"Are there ocean dead zones where there is little or no life activity? If so why do they exist?"
] | [
false
] | [deleted] | [
"Absolutely. ",
"Consider a typical oceanic water column of about 3.5 km. The overwhelming majority of living critters are found within the photic zone, which ends at an average depth of about 200 m. Within this zone, all of the necessities of life are present: an energy source and nutriments. However, light from... | [
"While ",
"/u/Gargatua13013",
" focused more on the ecologic zones of the ocean, I think OP was asking more about dead zones in the sense of anoxic/hypoxic dead zones, so I'll try to clarify.",
"Basically, when nitrogen or phosphorus levels in a region of the ocean get too high, usually from fertilizer runoff... | [
"For basic everyday use these two words are synonyms although historically I believe one was an adjective and the other a noun. Today they both can be used interchangeably as nouns; at least in American English. "
] |
[
"Why are fathers around the world referred to as some variation of 'papa' or 'baba' in a lot of different countries?"
] | [
false
] | When was it collectively decided that that was what we referred to fathers as? | [
"archydarky's comment about the history of languages is correct but there is a more fundamental and interesting (but also more speculative) theory:",
"The word for father is some variation of papa or baba for the same reason that the word for mother is commonly some variation of mama or baba; those are some of t... | [
"The Mama/Baba phenomenon is NOT an Indo-European phenomenon!",
"Versions of 'Mama' for mother and are found all over the world.",
"In Semitic languages (Arabic ",
"), Basque isolate (ama -mother), Dravidian languages (Teluga ",
"), indo-Aryan languages (Bengali ",
"), East Asian languages (Korean informa... | [
"The Mama/Baba phenomenon is NOT an Indo-European phenomenon!",
"Versions of 'Mama' for mother and are found all over the world.",
"In Semitic languages (Arabic ",
"), Basque isolate (ama -mother), Dravidian languages (Teluga ",
"), indo-Aryan languages (Bengali ",
"), East Asian languages (Korean informa... |
[
"Our eyesight is almost always stable. Do we have something close to 'Optic Image Stabilisation'?"
] | [
false
] | null | [
"Yes we do - we have the ",
"vestibulo-ocular reflex",
". It's an extremely efficient piece of hard-wiring in our brains and ears and eyes that moves your eyes almost instantly in response to changes in head position. If I remember correctly, as few as three neurons are involved in keeping your eyes stable. The... | [
"Here's an experiment you can try at home: close one of your eyes. Now, gently wiggle the open eye by softly pressing down on your eyelid. Your vision should wobble. So here's the question: why doesn't our vision wobble when we move our eyes to look at something? Shouldn't this happen? How is our eyesight stable?",... | [
"Just saw ",
"this Steve Mould video",
" on the subject. He starts by teaching you how to move one eye without moving the other, but the majority is pretty good science. He talks about the things you mention as well as ",
"smooth pursuit",
" which is what enables you to follow a moving object smoothly. "
] |
[
"Does molecular geometry have any significance?"
] | [
false
] | So I was looking at the wikipedia article about molecular and atomic geometry and was wondering what role they play. For example what can we know about molecules and atoms simply from their geometry? Can we know what bonds will form? Do they literally fit together like legos based on their shape (in any dimension)? | [
"Absolutely! There are tons!",
"One big influence is on the polarity of the molecule. Essentially, more asymmetrical molecules (like water) have areas that are more positively charged and areas that are more negatively charged. This means that the molecules will attract each other more when in a group compared to... | [
"There is an entire branch of chemistry completely dedicated to symmetry applications of molecules. By understanding symmetry of molecules you can predict how that molecule will behave in spectroscopy (IR and Raman). As well as how that molecule will react.",
"We can also use symmetry to know ligand field diagram... | [
"The shape of a molecule helps to determine its properties.\nFor example, carbon dioxide is a linear molecule. This means that co2 molecules are non-polar and will not be very soluble in water (a polar solvent).\nOther molecules have different shapes. Water molecules have a bent structure. This is one reason why wa... |
[
"AskScience AMA Series: I'm Dr. Paul Knoepfler, stem cell and CRISPR researcher, here to talk about how you might build a real, fire-breathing dragon. AMA!"
] | [
false
] | Hello! I'm , stem cell and CRISPR researcher. My 17 year old daughter Julie and I have written a new book about how you might try to make a real, fire-breathing, flying dragon or other cool creatures like unicorns using tech like CRISPR and stem cells. We also satirically poke fun at science hype. We're here to answer your questions about our book, the science behind it, and the idea of making new organisms. AMA! We're planning to come online at noon Eastern (16 UT), AUA! EDIT: Here's a post where I discuss a review of our book by Nature and also include an excerpt from the book: | [
"Overly simply stated, I understand that CRISPR can selectivly find/replace bits in a given genome, right? So wouldn't creating a \"New\" property like breathing fire require an existing and perfect model of both the original host ánd the property to be added?",
"I can imagine that changing bits here n there woul... | [
"It's much more efficient to make genetic changes in sperm/eggs and then let those be carried naturally into all or nearly all the cells of the adult vs. trying to engineer a trait into cells in an adult. However, it might be possible to make traits in adults via something like CRISPR if you can deliver it into eno... | [
"You don't need an existing model, but that would be really helpful. For instance, since we have thousands of models of flight, it'd be much easier to engineer flight in a new creature. Or we could even start with a creature like a bird that already flies. Engineering fire, an entirely new trait, by contrast would ... |
[
"Can you survive on the surface of Mars wearing a Scuba suit/gear? (minus the fins)"
] | [
false
] | null | [
"If anything, a lack of pressure is the problem. Humans can't survive anything less than 1/3 atmosphere (height of Mt Everest I believe). Space suits are pressurised (why they look puffy). ",
"Some info about this in this show ",
"http://www.reddit.com/r/Documentaries/comments/24eu9p/pbs_nova_can_we_make_it... | [
"If you were wearing a wet suit that offered enough compression I bet it would be possible."
] | [
"Could a human survive with an airtight facemask (with air supply), googles, (earplugs?) and warm clothing?"
] |
[
"Why do we have to cry when we are sad or hurt?"
] | [
false
] | Is there any biological use or psychically use to it or why would the body use water for crying? | [
"First of all, I guess we should specify that two things usually go on when we cry: there are tears, and there is noise, and that noise can be seen a lot more liberally in children, who have no social reason to inhibit or retard their cries. Anyway, with that in mind we should probably consider the reasons a person... | [
"Thanks for the long and great explanation! :) ImI find psychology also very interesting!",
"BTW, do you know / is there a simple explanation why men usually cry less than women? Is there a use or - just why? "
] | [
"I have no training or experience in biology/psychology what so ever, just read it somewhere, that men tend to cry less, because of the way they are raised. They must be the MAN, the strong one, to protect themselves and the loved ones. They cannot show weakness. That is the reason why if a man experiences somethin... |
[
"How do we know that humans interbred with neanderthals rather than just got the genes from a common ancestor?"
] | [
false
] | How do we know that humans interbred with neanderthals rather than just got the genes from a common ancestor? | [
"The evidence comes from looking at different populations of modern humans. The neanderthal alleles are found only in those populations that left Africa and were in contact in Europe with neanderthals. The African populations that did not come into contact with neanderthals lack the alleles. So it's the geographic ... | [
"Also we have neanderthal nuclear and mitochondrial sequences from fossils to compare. It's worth pointing out that all of our genes were inherited from our common ancestors with neanderthals. The sequences diverged over time (as all sequences eventually do) and therefore we can infer neanderthal ancestry to those ... | [
"All non-Africans are supposed to have ~1-3% neanderthal alleles. This happened 40-80 thousand years ago.",
"Sources ",
"here",
" and ",
"here"
] |
[
"Why is laughter contagious?"
] | [
false
] | null | [
"Because it's largely a social reflex"
] | [
"Is it a matter of mirror neurons then?"
] | [
"Not sure if it's been traced to them specifically, but they almost certainly play a role."
] |
[
"Do Lithium ion batteries gain weight when they are charged?"
] | [
false
] | null | [
"If you're thinking of some excess of electrons or such, then the answer is no. Batteries don't charge by grabbing a hold of electrons - they do so by transporting electrons from one compartment to another. For more about how a battery operates the ",
"Wikipedia article",
" is a good place to start.",
"Now, f... | [
"What do you mean? I don't understand the context of your question."
] | [
"Yes. Anything which gains potential energy (in this case chemical potential) gains an equivalent mass coming from the famous mass energy equation.",
"However ... let's take the Hiroshima nuclear bombing. That whole explosion took on the order of 1 gram of mass. 1 gram was equivalent to all that energy.",
"N... |
[
"If sound is the vibration of the air, and the state of matter is determided by how much it's molecules vibrate, can sound melt something?"
] | [
false
] | Even if you'd need a impossibly high pitch, is it theoretically possible? I feel like I'm forgetting something very important about how heat works. | [
"Yes, ultrasonic welding is a method of solid state welding where the material such as plastic between two parts are melted together. The sound vibrates at a high frequency, at the low kHz, to heat up the plastic where it is pressed together in a vice or a press. No glue or soldering needed to meld them."
] | [
"Yes! I work in product design with a focus on injection molded plastic parts and ultrasonic welding is a robust and reliable permanent assembly method. In designing parts for USW there are actually very specific geometries that are utilized in order to focus the vibratory energy directly into the weld area, as to ... | [
"Yeah, any sound over time can potentially damage your ears. It's just the way life is. It's like looking at too many bright objects, coloring your hair, scratching your skin. Stimulus over time wears out the receiving subject. ",
"That being said, it's not like you put your ear directly in front of the horn. It'... |
[
"Are trinary star systems possible?"
] | [
false
] | [deleted] | [
"Yes, there are triple star systems, and also quadruple, quintuple, etc. However, they tend to arrange in subgroups. Say you have a triple system with components A, B and C. Probably you'll have A and B orbiting together closely one to the other and the C component orbiting both A and B from far away, as if A and B... | [
"You don't even have to go too far to find an example of this - Alpha Centauri is the closest star system to the Sun, and has exactly what SantiagusDelSerif just described. Alpha Centauri A and B orbit their shared center of gravity every 80 years or so, while Proxima Centauri orbits that same center of gravity eve... | [
"For the most part, you can take a stable binary pair and replace one of the stars with a much more closely orbiting pair. Basically a small binary system orbitted by a more distant cousin. This first somewhat unintersting kind of trinary system is relatively common. There is believed to be a more interesting trina... |
[
"What came first, dogs or cats?"
] | [
false
] | null | [
"The problem is when do you call a dog a dog if you don't include domestication? For example:",
"\"Although mDNA testing suggests an evolutionary split between dogs and wolves around 100,000 years ago, no specimens prior to 33,000 years ago are clearly morphologically domesticated dog\"\n",
"link",
"As for as... | [
"I accidentally a word in my original question (that I'll go fix now) but I meant to say that I assumed cats would come LATER because of higher scenes. ",
"Also I guess I should clarify that I was wondering about the split between canis and felis. You link looks really interesting and I'll have to check it out wh... | [
"I'm assuming that between 100kya and 33kya 'dogs' were just wolves that had learned to follow humans around but hadn't joined the pack yet, so to speak. Is that on track?"
] |
[
"AskScience AMA Series: I am a leading researcher in the areas of cannabis plant science and plant physiology at Volcani Agriculture Research Center, in Israel. My name is Nirit Bernstein and I am researching cannabis plant sciences, and the best ways to grow medical cannabis, Ask Me Anything!"
] | [
false
] | Medical cannabis is a fast growing field and researchers are delving into the implications of cannabis for medical purposes. Israel hosts one of the world's leading primary research facilities in the area of medical cannabis. I was the first scientist in Israel to study the plant-based science of medical cannabis. I and my team work to advance the academic and applied science of the cannabis plant. Their objective is to develop basic and practical knowledge of secondary metabolism in health-beneficial plants, including cannabis, to contribute to human health and food security, while protecting the environment. Here are some links to some of my research: I will be available at 12 PM PT (3 PM ET, 19 UT), Ask Me Anything! Username: | [
"Is there any scientific evidence that flushing plants (feeding only water or decreasing concentration of hydroponic solution) before harvest does anything useful to the final product?",
"Is there any scientific evidence that leaving plants in total darkness for ~24-72hrs prior to harvest increases cannabinoid co... | [
"What is the biggest science misconception about the cannabis plant?",
"And what has your research told you about the best way to grow it? Is it sustainable to still farm it outdoors as the world gets warmer or will future cannabis farms be in fully controlled environments?"
] | [
"Is the industry headed toward whole-plant cultivation, or cannibinoid isolation and processing for individual benefits? I assume pharma is pushing for the latter outcome, but the former is more scalable and socially equitable. Which is more beneficial from a science perspective?"
] |
[
"Is there anything alive in the soil 100 feet below ground level?"
] | [
false
] | Let's say you're drilling around 100' deep. Is there going to be any bacteria in the dirt/clay thats brought up? Is it completely sterile? | [
"Bacteria have been found ",
" below the surface. And that is not a limit of life - it is a limit of how deep we searched systematically. Some of them live from radioactive decays, as long as there is liquid water once in a while and the temperature range is fine they can survive, no contact to the surface necess... | [
"There are bacteria in the ",
"Yellowstone Grand Prismatic Spring",
" that ",
" to live above the boiling point of water."
] | [
"https://www.newscientist.com/article/dn10336-gold-mine-holds-life-untouched-by-the-sun/",
"https://en.wikipedia.org/wiki/Desulforudis",
"Radioactive decays produce H2 molecules and some sulfur compounds, the microbes found 3 km below the surface use this to live."
] |
[
"Is energy physical?"
] | [
false
] | Can energy be described as a physical "thing" or is it more accurately regarded as a behavior/quality of a physical thing? I am a science buff - even by the standards of casual geeks - and I am under the impression that the smallest physical "things" are little vibrating "strings" of energy (you can already tell that answering my question may involve clearing up misunderstandings I have from too many Science channel shows). Does that mean that energy has a physical form? Is the observation of energy like the observation of a of nature is it an observation of a of nature? Is it more like the gravity involved when an apple falls or is it more like the apple itself? ...maybe I should have done this as an ELI5 v__v | [
"Energy is a number that you can calculate. It's a number that usually if you calculate it ",
" and calculate it ",
", the number stays the same between both of those times. ",
"Moreover, you calculate energy like E=((mc",
" )",
" +(|",
"|c)",
" )",
" , where m is the mass of the thing, and ",
" i... | [
"Can energy be described as a physical \"thing\" or is it more accurately regarded as a behavior/quality of a physical thing?",
"It's more accurately regarded as a property of physical particles or systems; a property that is absolutely conserved in local interactions, and is related to rest mass, momentum, and o... | [
"Thank you for your time, this cleared things up nicely. "
] |
[
"Is it possible to see sound waves?"
] | [
false
] | [deleted] | [
"I'm not sure if this is the kind of thing you were interested in, but you can set things up to allow you to visualize sound waves. Check out ",
"Ruben's tube",
"."
] | [
"I've always wished to do this project:",
"Audible sound is soundwaves between 16 and 16000hz. Any sound you hear is a mixture of one or more of these waves in more or less amplitude.",
"Visible light is radio waves from 400THz (red) to 800 THz (violet). Any color can be represented by a mix of the basic red, b... | [
"That sounds amazing. I would be very interested to see something like this."
] |
[
"Do lions (and other cats) have spikes on their penises?"
] | [
false
] | null | [
"Yes."
] | [
"Google image search does wonders my friend. ",
"NSFW"
] | [
"Lions and other cats also have spikes on their tongues to help separate meat from bone. "
] |
[
"Are household appliances perfectly efficient in winter (because all waste heat just heats the house anyway)?"
] | [
false
] | null | [
"In a lot of places, heating with gas (by furnace) is cheaper than heating electrically, so it might not be perfectly efficient from a cost perspective.",
"Also, a lot of work goes into designing a heating system for a home so that heat is distributed somewhat evenly. Heat coming from appliances probably isn't go... | [
"I think OP was more saying that the appliances are going to be wasting energy via some of the energy they use ending up as heat no matter what you do, so in the winter, they contribute (however slightly) to heating your home, and thus, there is no 'waste' at all, making them 100% efficient because every single bit... | [
"Part of the problem here is that efficiency has a specific meaning in thermodynamics and the OP is not using it in thst context. I think he is simply observing that the heat normally regarded as waste heat is actually useful in heating the room. This has nothing to do with the devices efficiency. It just good use ... |
[
"Is It Possible Our Universe Is Inside A Black Hole?"
] | [
false
] | [deleted] | [
"In short, yes there are theories on this. The holographic principle ",
"holographic principle",
"I can't link the papers i've read as you can usually only get them with subscriptions or through a university library log in etc... but a quick google search will get you things like this:",
"black hole holo arti... | [
"The holographic principle does not actually say the universe is in a black hole - it just says it's sorta analogous.",
"Plus, we don't even know if the universe started from a singularity anyway."
] | [
"Asked previously: ",
"http://www.reddit.com/r/askscience/comments/kbvdv/is_there_any_scientific_evidence_for_the_idea/",
"Our universe really is nothing like a black hole. A black hole has a centre, while our universe does not appear to. Also, there are no stable orbits inside a black hole - ",
" beyond the ... |
[
"Calling all physicists, especially those who are an expert in 2-d circular kinematics"
] | [
false
] | Ok, Reddit, I hate to do this but this is my last resort. I am calling in the big guns to help me answer a friend's physics question homework. I haven't taken kinematics in awhile so I am a bit rusty so I will detail the question out, there is no diagram. I spent literally like 40 minutes on this question and this is as far as I got. See question below. An automobile enters a constant 90 meter radius of curvature turn traveling at 25 m/s north and exits the curve traveling east. The car completes the turn in 5.4 seconds. Assume the speed of the car can be modeled as a quadratic function of time. Ok so here is what I did. I modeled the velocity equation, (the professor told us that the function of speed and velocity can be used interchangably). We are required to figure out initial and final values of arc length, velocity, acceleration, angular velocity, and angular acceleration. v(t) = a(t) + bt + c plugged in initial conditions t(0) and simplified the velocity function to v(t) = a(t) + bt + 25 so for the final value of velocity equation I have v(5.4) = a(5.4) + (5.4)t + 25 I used derivation to figure out the function for acceleration which I got to be: (ac is acceleration since a is already used) ac(t) = 2at+b and using initial conditions I found the initial acceleration equal to: ac(0) = b and final value of acceleration to be ac(5.4) = 10.8+b and finally I used integration of the velocity function to get the function or arc length equal to (I used the equation s = r(x) where x is equal to theta, s = arc length and r = radius, in radians to figure out arc length) 90s(t) = a(t) / 3 + b / 2 +25t. Using initial conditions I simplified initial arc length to 0 and final arc length to be equal to 52.488a + 14.58b = 70.686 after simplifying by figuring out final arc length to be 70.686 by using trigonomtery to figure out that the car did an exact quarter of a circle arc. And that is as far as I got, I have 3 equations with 4 unknowns and no idea how to figure out the rest of the data. Any help would be greatly appreciated, time is a issue here, it is due in about 6 hours. | [
"r/homeworkhelp"
] | [
"Did not know that subreddit existed, just posted the question there too, thanks !!"
] | [
"you're welcome "
] |
[
"Caffeine came from plants. What evolutionary advantage does caffeine provide for plants?"
] | [
false
] | [deleted] | [
"This ",
"interesting article",
" describes a study concluding that caffeine in the ",
" genus can act as an attractant for bees. I haven't read the source study yet.",
"This ",
"2007 paper",
" describes the use of caffeine as an insecticide, and outlines the general view of caffeine as a defensive seco... | [
"The first paper is about caffeine in coffee seedlings. 1) it's more concentrated than it would be in the environment, and 2) your statement was about competeing plants. The second paper is about caffeine occurring in leaves, etc. Which is, at best, a first step to showing that allelopathy is possible. ",
"Ne... | [
"Here you go.",
"EDIT: Oh, and ",
"this",
", but it's behind a paywall. "
] |
[
"What would be the consequences for the neighbouring areas of the Atucha Power Plant in Argentina if it underwent something similar to other known nuclear disasters?"
] | [
false
] | null | [
"'Accident analysis' in design space is broken down into four categories. This doesn't include severe/significant accidents like Fukushima, as they are outside of the plant's design.",
"The four categories are normal operations and transients, anticipated operational transients (things that are expected to happen... | [
"Just some context: the ",
"plant",
" is by a river, some 100 km upstream from Buenos Aires. What would be the risk to the city?"
] | [
"Thanks for the Link, I couldnt find it in English."
] |
[
"If the Sahara desert starts receiving 100 inch of rain per year, would it eventually become a forest?"
] | [
false
] | Assuming no humans goes in there and start messing with things, of course. If it does become a forest, how long would it take? | [
"Absolutely. I don't know who these folks are who are saying no.",
"With available water, pioneer species could move in and a unique community of primary succession could start. You would have a temperate rain forest fairly quickly.",
"Fun Fact:",
"Some climate scientists project that in a warming earth, ch... | [
"I do not agree with this in the slightest.",
"Of course it couldn't happen instantaneously, but there are plenty of plants, fungi, and lichens that can grow in poor soils with enough water. With 100 inches of rain per year, the sahara would be one of the most productive places on earth. I would venture a guess... | [
"It takes more than water. Consider all the worry regarding topsoil runoff. With enough runoff, a forested area can experience desertification.",
"So, with rainfall alone? No. With rainfall and nutrients? Yes. Topsoil is required for plant growth."
] |
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