title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"What would happen if two people were to attach an IV directly to each other?"
] | [
false
] | null | [
"This is essentially what the first human blood transfusions were. The first transfusions were in the 17th century, both human/human (not great), and sheep/human (bad - it didn't help that they used non-sterile sheep vessel for the transfusion). ",
"If you're on death's door and desperately in need of blood volum... | [
"Are white blood cells filtered out of whole blood donations today? "
] | [
"Yes, otherwise the white blood cells may start attacking the person who's had the transfusion."
] |
[
"Is there a correlation between cancer and body mass?"
] | [
false
] | What I mean is that, since cancer is mostly a stochastic process, a bigger number of cells (which most of the time implies larger mass), at equal environments, should show proportionally higher cancer rates. Is that true? What if we only take into account lean body mass? | [
"Look at PubMed and there are a plethora of studies finding various associations between BMI and cancer",
"Meta analysis of 141 articles - \"Increased BMI is associated with increased risk of common and less common malignancies. For some cancer types, associations differ between sexes and populations of different... | [
"I was more interested in just mass rather than BMI. Obesity has its own problems that everybody knows, including increased risk for some cancers. Rather, I'm interested in the fact that large, not necessarily obese individuals, may show increased cancer risk, just because they have more tickets (cells). "
] | [
"No. There is no study that demonstrates what you are saying."
] |
[
"How did Newton derive the Law of Universal Gravitation?"
] | [
false
] | I just learned the Law of Universal Gravitation in my physics class, and I understand well what it means and how to use it to calculate gravity...but how did Newton derive it? I've done some Googling around but I can't find any solid step-by-step proof of it. | [
"Observations demonstrated that the planets in our solar system orbited the Sun in ellipses. Newton discovered through his investigation (IE invention) of Calculus that a body undergoing acceleration proportional to the inverse square of their distance would travel in an ellipse. He then made a mental leap and re... | [
"Exactly how Newton derived gravitation can be found in his Philosophiæ Naturalis Principia Mathematica. ",
"However, from a more approachable standpoint: you can take Kepler's Laws of Planetary Motion, which are based on observation, and derive the Newton's inverse square law. It is a fairly standard homework ... | [
"Newton actually modified Kepler's Laws of planetary motion which had previously assumed that the Sun was immovable.",
"Because for every action there is an equal and opposite reaction, Newton realized that in the planet-Sun system the planet does not orbit around a stationary Sun.",
"Instead, Newton proposed t... |
[
"What do people mean when they say that Special Relativity \"causes\" Magnetism?"
] | [
false
] | I've heard people claim that special relativity is the source of all magnetism. Can someone clarify what this means for me? Is magnetism therefore not its own separate "thing", but only an emergent phenomenon of electrodynamics applied to relativity (in other words, is magnetism not really a separate phenomenon after... | [
"Yes, magnetism is a consequence of the principle of relativity. To see how this works in the case of magnetism, imagine a wire which contains positive charges and negative charges equally, so that the entire wire is electrically neutral. Now suppose that all of the negative charges start moving to the right. In... | [
"So, there are a few ways to approach this. ",
"First, Classical, the existence of magnetism as defined by Maxwell's equations. In this sense, magnetic fields are not a result of any of their own charges. (No magnetic monopoles have ever been measured) (this is unlike E fields, which are directly related to their... | [
"+1",
"Here's a simpler example if it helps.",
"You have 2 electrons \"at rest\" and you \"let them go\". What do they do? They repel each other. They start accelerating away from each other in some manner. Given that we know the rest mass of electrons, we know how much force they apply.",
"Now let's obse... |
[
"Do different species of animals ever interbreed?"
] | [
false
] | If so, which and why? If not, how do these animals know not to mate with one another? Would two different species of apes be more inclined to mate than, say, a cat and a dog? And again, how do they know? | [
"Yes, there are species that ",
"interbreed naturally",
" (PDF). The thing is, discrete species are part of a human construct to quantify biological diversity. In actuality the lines are much more blurred. That's why there's no unified species concept; there are actually ",
"many species concepts",
". They'... | [
"Could you clarify what you mean by \"natural?\""
] | [
"There are species that absolutely ",
"interbreed naturally",
" (PDF). What you're mentioning is one species concept among many, and there's nothing that prevents some species from interbreeding and producing fertile offspring.",
"There are lots of instances of this happening with crocs, like this hybrid betw... |
[
"Does our brain have a equivalent of binary code or pixels?"
] | [
false
] | null | [
"I'm not quite sure I understand your question. Neuronal firing can be thought of as a digital or binary process - they either fire or they do not. However, the relationship between input and output is non-linear. "
] | [
"When a neuron fires an action potential, it is all or nothing black and white and that's what you'll hear often.",
"However, the inputs that determine whether an action potential fires or not are analog meaning there's a gray area. It combines the strong inhibitory, strong exitatory, weak inhibitory, weak excita... | [
"Well, first off you have to understand that you've asked a question that covers a WHOLE LOT OF GROUND.",
"But, to try to answer some of it in straightforward terms:",
"No, I would say that our brain does NOT really have the equivalent of 'binary code.'",
"The brain encodes information in a lot of different w... |
[
"Why can't i move my eyes smoothly?"
] | [
false
] | Why do our eyes jump from spot to spot when we're looking around? I find that i can only move my eyes smoothly when i'm tracking something that is also moving smoothly. | [
"Your eyes move in small \"jerks\" called ",
"saccades",
". Interestingly, you are effectively blind during a saccade, as the brain simply ignores any information sent to it during that time. The reason for this is to avoid sending useless blurry image data to your brain.",
"The exception to not seeing thin... | [
"thanks!"
] | [
"Also as long as you don't move your head you can never see your own eyes move in a mirror."
] |
[
"Do galaxies revolve around the universe?"
] | [
false
] | If the earth revolves around our solar system because of the sun, the sun revolves around our galaxy because of a black hole, do our galaxies revolve around the universe? If they do, because of what? And if there are other universes possibly they revolve around a gravitational force? | [
"No, they move gravitationally through galactic clusters (although that can't really be called orbit), and in terms of large scale structure the clusters gradually get farther from each other because of the expansion of the universe."
] | [
"Your question implies that the universe has a centre around which galaxies would revolve. But the universe has no centre. Think of the expanding universe as the surface of an expanding balloon (a 2-dimensional analogy for our 3-dimensional universe). Just as the surface of the balloon has no centre, the universe d... | [
"But, they will just pass right through each other for the most part, since matter is so spread out in galaxies.",
"Sort of. ",
"This video",
" is a simulation of the Milky Way/Andromeda collision from the University of Toronto. As you can see, relative to the ",
" the disturbance caused by the collision is... |
[
"What determines whether a projectile pushes the object it comes into contact with aside or penetrates it?"
] | [
false
] | For example: If I push my hand towards you - you will move away from my hand. If a bullet is fired towards you - the bullet will go through you. Is there an equation based on the size of the object and the speed? I'm sorry if its a stupid question but I'm really curious. | [
"The simple explanation of this is stress limits. All materials have properties called Young's Modulus, which is a value of stress around which a material begins to permanently deform, and Ultimate Tensile Strength, which the maximum stress the material can experience before weakening/failing. Say your hand had a p... | [
"Very detailed explanation - Thank you!"
] | [
"as two bodies come into contact, they deform",
"As something deforms, it stretches/compacts/shears/torques locally. This creates stress.",
"If/when the local stress exceeds a yield strength limit, there will be permanent deformation- think bending a paperclip",
"If the stress exceeds the ultimate strength l... |
[
"What I'm assuming is a physics question: What is happening with my capri sun?"
] | [
false
] | null | [
"Alright, take two. Wall of text ahead, but I tried to be very thorough:",
"I believe you're increasing the pressure of the air inside of the container, making it more difficult to push the straw - and the air contained within the straw - deeper inside of the Capri Sun.",
"You may recall from high school chemis... | [
"I've been working a lot with fluid mechanics lately, and if I'm understanding the question correctly, you're noting how much more difficult it is to slide the straw by plastic vs. easier to slide by water (or possibly air). In either case, the fluid (water or air) can deform itself to the movement of your straw, w... | [
"I don't think this answers my question but you sound like you know what your talking about. I'll describe my situation with as much detail as possible. My caprisun is empty. My straw is in the top, the hole that the straw is stuck through is tight enough around the straw that when I blow into it the bag expands an... |
[
"simple questions regarding air pressure?"
] | [
false
] | 📷 not sure if i understand air pressure properly can someone correct my statements below if they are wrong... thanks | [
"Air pressure is caused by air molecules bouncing off of surfaces. Water pressure is also bouncing off surfaces but because water has significantly less compressibility it can't be \"pressurized\" the same way air can.",
"Cold air moves slower than warm air which means that it both hits surfaces less frequently a... | [
"I would say 1 and 2 are correct (enough at least, technical specifics don't really matter here to me)",
"If you had a sealed chamber 3 would also act as you describe. But a standard fridge/freezer cannot be sealed (you would never be able to open the door) so as the air inside becomes less energetic outside air... | [
"The other thing going on in #3 is that the air pressure in the balloon is also fighting against the elasticity of the balloon itself.",
"As others have described, ",
" the fridge were sealed ",
" the balloon was just a barrier between the two amounts of gas that did not exert any forces of its own, then yes,... |
[
"Are all phobias explained by past experience or is this a myth?"
] | [
false
] | We've all heard of obscure phobias, but are they all explainable? do they even need an explanation? can people be born with them etc etc | [
"It also has to be towards an object that the brain has the potential to develop a phobia to.",
"I do not think that is true, and I'm not really sure it makes sense.",
"Using your gun example, the only thing we can conclude from that statement is that no ",
"fear conditioning",
" occurred. This can be defin... | [
"I wouldn't know, but I'm pretty sure all of them are due to experience. People are inherently born with a fear of heights though (see the visual cliff experiment), but this isn't a phobia in my opinion...humans are ground dwellers, and should be afraid of being high up, evolutionarily. We need to be taught to no... | [
"A phobia is defined as \"an ",
", intense and persistent fear of certain situations, activities, things, animals, or people\".",
"The brain does not come hard wired with such things. Phobias are a form of fear association learning that is necessarily required to occur through learning/experience."
] |
[
"Is it possible to predict matter's chemical properties based solely from the elements that make them and how there of bonded?"
] | [
false
] | A example would be water which is H2O and hydrogen peroxide which is H2O2 but have completely different chemical properties. Would i be able to make a guess to the chemical properties of H3O6? | [
"yep, the differences between HOH and HOOH are pretty evident. The O-O bond is quite weak, with a low bond dissociation energy (~140 kJ/mol), while HOH is quite strong, with a high bond dissociation energy (~460 kJ/mol). The bond dissociation energy is simply the amount of energy it would take to degrade (break apa... | [
"What he said. Chemical reactivity can be \"intuited\" from identifying the molecular (bonding) geometry and presence of functional groups. Additionally the spectra across the EM field can be predicted if the geometry is known -or- the geometry can be deduced by analyzing the spectrum in a specific spectral region ... | [
"Almost entirely, yes. That is one of the important achievements of Chemistry. However, when dealing with large numbers of atoms instead of individual ones, additional information is sometimes required such as external pressure, temperature and volume of the system and it's surroundings."
] |
[
"How did people wash themselves and clean their clothes and utensils before the invention of Soap?"
] | [
false
] | null | [
"Soap was invented in prehistory. For the most part, in the event that someone wanted to feel cleaner, they washed themselves and their stuff in the river. Rainwater going through wood ash produced lye, which when mixed with fat that had cooked over the fire made soap. People were often near rivers, and often cooke... | [
"Soap is real old, actually. It predates the Babylonians. But some people would also use oil (or oil mixed with sand or ash, so it was exfoliating) to wash. We know for sure ancient Greeks and Romans did this, because they had dedicated tools called strigils, but it's likely the practice is a lot older. The idea is... | [
"you never washed or saw someone wash a pot with river sand (like when camping or something)? Also, water is a pretty good solvent by itself especially warm/hot water. So water and grit would be enough for most things."
] |
[
"Do birth control pills delay the onset of menopause in women?"
] | [
false
] | null | [
"Med student here skimming through old notes.",
"Overall, age of menopause is an average of 51 years.",
"It looks like the the clear determinants of menopause are:",
"All of the other supposed determinants are iffy - age of menarche, race, stress levels, diet, environment, etc.",
"Overall, menopause is NOT ... | [
"Of interest, a woman has approximately 50,000 eggs at first ovulation, and roughly 10,000 at menopause. The ~40,000 eggs are lost through both ovulation as well as ",
", or simple loss that doesn't produce eggs (e.g. ovarian cysts and others).",
"Related to what harharharbinger said: the early onset of menses ... | [
"Short answer: no.",
"Long answer: As harharharbinger has stated, even when you're taking the pill, your follicles are still dying. You just aren't releasing the egg cell in that follicle. Birth control pills are not designed to hasten or delay menopause (the former is possible, the latter is most likely not). Th... |
[
"What makes an allele dominant?"
] | [
false
] | Do all dominant alleles have something in common with each other that recessives lack? | [
"There are a couple mechanisms:\n1) Dose dependence.\n2) Neomorphs- they do something the other alleles don't.\n3) Poison subunits- they damage large complexes by binging to the."
] | [
"This previous post should help.",
"There are difference reasons for alleles to be dominant or recessive, so, no, there is no one thing they have in common. As described in the post to which I linked, we do have an idea of some of the fairly common reasons why some are dominant or recessive, but the reason is no... | [
"If i recall, there are dominant negatives that are neomorphs and poisoned subunits that are not dominant negatives as well. But yeah, you're right."
] |
[
"How does lightning \"know\" which direction is the path of least resistance?"
] | [
false
] | : Is lightning looking for a general minimum resistance, or only a local least resistance in the area of the next molecule? That is, does lightning for the least resistance path, or is it "moving" from one molecule to the next, looking only for which of the adjacent molecules has less resistance? Over how wide of an a... | [
"You have a large boulder. The surface is pretty irregular.",
"You pour a bottle of water onto the top, and you notice that water flows down specific paths - sometimes along existing channels, other times almost at random, like slowly pouring water down a pane of glass.",
"How does water \"know\" where the chan... | [
"I didn't really get a great glimpse of the leaders in the video MonkeyNin posted but I found one here ",
"http://www.youtube.com/watch?v=8waV48897o4",
" at around 14 secs in."
] | [
"Damn that's cool looking. The more I learn, the more I find out nature already beat us to the hard stuff.",
"Thank you!"
] |
[
"What's an example where a monosaccharide forms into a disaccharide and how would this further progress to a polysaccharide?"
] | [
false
] | Simply, I want to know the overall process on how these saccharides function together. I know that they can bond but how does the water molecule get eliminated to form the disaccharide. How do the monosaccharides form a large chain to create a polysaccharide? | [
"It's biosynthesis, usually, so enzymes catalyze reactions powered by phosphate groups being split. Sucrose, for instance, is made by the enzyme sucrose-6-phosphate synthase, which takes activated (phosphates attached) forms of glucose and fructose and sticks them together. Starch, the classic polysaccharide, is ma... | [
"Would like to add the benefit isn't just of starch not moving out of the cell and losing energy from to he cell, but that starch is osmotically inactive compared to glucose. Storing glucose would draw so much water into cells."
] | [
"Thanks for your reply! Clears up a lot of the confusion I had regarding the biosynthesis of saccharides. "
] |
[
"Can mass be relative?"
] | [
false
] | [deleted] | [
"There is a relativistic mass. It's γm. If you use it, then F=γma...",
"That's not true though and only one of the ",
" reasons why relativistic mass is a useless concept. The force ",
" is ",
" parallel to the acceleration ",
"."
] | [
"Actually, energy and mass are not exchangeable. In a manner of speaking, mass is one type of energy, but not all energy is mass. (It gets complicated, but that's the basic idea.)",
"Mass is invariant, meaning that it doesn't depend on your reference frame."
] | [
"To suggest that there is a relativistic mass is to suggest that the internal structure of our object changes depending on our reference frame. It doesn't make sense to say that the amount of matter present has changed, hence why we've ",
" mass to be a Lorentz scalar, as ",
"/u/RobusEtCeleritas",
" mentione... |
[
"How is the process of splitting H2O with electricity reversed?"
] | [
false
] | null | [
"You burn it. Hydrogen and oxygen with a heat source make fire which releases a lot of energy and makes water as the only product. Alternatively you can use a hydrogen fuel cell which does essentially the same thing, just extracting the energy through an external electrical circuit rather than through heat."
] | [
"So a candle at my house doesn't make water... it requires H and O to happen and I would imagine there isn't enough H?"
] | [
"The only way it would not make water is if there were no hydrogen, and that is extremely unlikely for any material that would behave like a normal candle. Is this a specific claim of the candle, and if so does it say what it is made from?"
] |
[
"What is the limit to how fast air can enter an aircraft engine?"
] | [
false
] | I am going to specify what I mean with my question. At cruise conditions, the mass flow through an engine can be approximated using the airspeed and the frontal area of the inlet. However, on take-off, the air has to be sucked from the surrounding environment, so what is the limit, if there is any, to how much air can ... | [
"Well the absolute limit of mass flow per unit area is when the inlet is ",
"choked",
" i.e. air is entering at the speed of sound, however the inlet itself would never be choked on a subsonic engine like a high bypass turbofan. Instead the compressor, and possibly the fan depending on the design, would be chok... | [
"You could make air hit the fan blades at higher speed, yes, though it would require some kind of converging-diverging intake which would be a poor design choice for numerous reasons. But the absolute limit to the mass flow rate of fluid you can suck in is reached at this choking condition. For air with a ratio of ... | [
"The hard limit is 14.7psi when airspeed is zero. That's the hardest you can suck air into the engine if you had a fan which created a perfect vacuum. If you have some airspeed, then you are essentially ramming air into the engine and then your hard limit is 14.7psi plus the ",
"stagnation pressure",
" at tha... |
[
"iss stil orbits inside the atmosphere?"
] | [
false
] | this information could be wrong but the iss orbits at circa 400 Km while the earths atomosphere continues to 480 km, does the iss compensate for the atmospheric drag in some way or is there just so little air up there that it doesnt really matter? sources: | [
"The atmosphere is very thin up there, and it would definitely feel like a (lethal) vacuum to a human. However, it is enough to produce a little bit of drag that slows it down. So every now and again, they need to give it a bit of a boost.",
"There's a nice plot ",
"here",
" of the ISS's height over time. You... | [
"i would assume little debris getting some drag, too. So the orbit clears itself, am i wrong?"
] | [
"But the cost of boosting it every now and again is way cheaper than having to fly up twice as high (or more) every time a mission goes up there.",
"Higher up would also mean higher radiation doses for the humans (and the electronics) - this is independent of the atmosphere, the shielding due to Earth's magnetic ... |
[
"How much do all the living organisms living on planet Earth's crust contribute to the force of gravity of Earth?"
] | [
false
] | null | [
"It's pretty much a wash- all of the mass of living creatures came from the earth itself and, to a small extent, the atmosphere. There is essentially no difference between the gravitational effect of the mass of living organisms and what the gravity would have been before the atoms were organized into living beings... | [
"To answer the additional question, according to the wiki ",
"the biomass of all plant and animal life on earth",
" is around is around 560 billion tonnes. That number possibly doubles if you include bacteria.",
"The force of gravity and size of said sphere that much mass exerts at its surface depends on the ... | [
"Interesting, hadn't thought of that. Thanks for the quick response, sir."
] |
[
"Why do airplanes tilt when turning? Why can't they turn without tilting?"
] | [
false
] | Essentially what i'm asking is why can't a plane turn from facing north to facing east without tilting vertically at all? why cant you just increase thrust on the engines on the left side of the plane so that it is moving faster that the right, thus turning the plane without tilting or banking it. | [
"They can. There is a ",
"famous incident",
" where the pilots were forced to fly this way when the controls gave out.",
"The reason they don't normally fly this way is for efficiency and comfort. When a plane turns, the ailerons are tilted on the wings at the same time the rudder is turned. This banks the... | [
"This banks the plane as it turns so the passengers don't feel the g-forces and get airsick.",
"To clarify, they still feel the increased g-force, it's just directed downward rather than at an angle to one side."
] | [
"The other posts here have covered passenger comfort, and the desire to keep the airflow over the wings coming from directly in front and not from the side. I'd like to add one further thing: airliners and most aircraft (modern fighter jets being a notable exception) are designed for stability in yaw, pitch and rol... |
[
"How do we have such accurate maps of the Milky Way if we are inside it?"
] | [
false
] | It makes sense for galaxies like andromeda that we can see but how are our maps of our own so precise if we are on one of the spiral arms? | [
"We really don’t. Most of it is still unmapped and what we have mapped is mainly what’s right around us and what’s so big off in the distance that you can see it clearly from earth with our telescope technology like nebulas and very large stars."
] | [
"Those pictures are a mixture of data and guesswork. They're created from careful data collection over the past hundred years to identify and map tens of thousands of stars, followed by clever design and construction of automated mapping satellites to identify another ",
" stars in the past ten years, plus a who... | [
"If you're inside a building, you can tell what shape it is by seeing where the walls go. Equivalently, we can trace the spiral arms and other structures of the Milky Way by looking at where the stars are.",
"It's not fundamentally that hard, it's just time-consuming because there are such a large number of stars... |
[
"Do field lines compress on a quickly moving magnet like air waves on a jet?"
] | [
false
] | Can a magnet break the ‘magnet’ barrier like a plane breaking the sound barrier? | [
"In a vacuum, no. The propagation speed of electromagnetic fields is the speed of light. As the magnet moves faster, time dilation causes the waves to always move away from it at the speed of light from its frame of reference. It can never \"catch up,\" just like any other physical object with mass. ",
"Howev... | [
"Absolutely, but the effect of relativistic doppler is only on the wavelength of the light. Not the speed at which it propagates. The magnet in this example would still perceive the electromagnetic waves zooping out away from it at the speed of light. It's just that the light would get more and more blue-shifted... | [
"It is possible to compress magnetic field lines and increase magnetic flux:",
"https://en.m.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator",
"If a magnet or other source of magnetic field ( electrons/charge carriers moving in a loop) would be moved through some substance then yes magnetic fie... |
[
"So I sliced my Ring Finger washing dishes... Why does my Middle Finger feel like it's sliced too?"
] | [
false
] | null | [
"The median nerve innervates the thumb, index, middle, and half of the ring finger along with their nail beds. I suspect that your body is experiencing some difficulty distinguishing pain in that last split of the nerve between the fingers. You might have some nerve damage, it is probably worth seeing a doctor if y... | [
"I did not slice my middle finger... :P"
] | [
"The ring finger and the middle finger are served by the same nerve, as Phage0070 pointed out to you. You've caused enough damage to the surrounding tissue to swamp the ends of the nerve with information."
] |
[
"What exactly is the barycenter of a pair of binary stars?"
] | [
false
] | I understand that the barycenter is the fixed point two stars rotate around, but I have no idea what causes it. Like, how is it chosen? Can the barycenter change during the lifetime of the binary stars? Any insight would be welcome. | [
"Well, if you ignore the pull of the galaxy, there are no outside forces on the pair of stars. No outside forces means the center of mass will never change velocity. No matter how the stars orbit, the center of mass has to remain at the same velocity.",
"It can't change unless there is some kind of outside forc... | [
"I'm not sure what you're asking. After formation, they are in orbit in whatever orientation/speed/position they happen to be in."
] | [
"Any time two things orbit around each other (like the moon around the earth), they orbit around a central point. The moon is much smaller than the earth, so it's not an equal pull. The point that they orbit around is under earth's surface. If the moon were larger, you'd see the center of mass move away from the mi... |
[
"Why does fission release a lot of energy but the weak nuclear force doesnt?"
] | [
false
] | null | [
"What weak processes are you thinking of?"
] | [
"The weak nuclear force causes decay and when an atom decays it ejects a smaller atom, if im not mistaken right? What makes this different than fission that fuels things"
] | [
"The weak force causes ",
" kinds of decays (beta decay and electron capture), but not others. Fission is something which can happen as a decay or as a reaction, and they both tend to release similar amounts of energy for nuclides of similar masses."
] |
[
"Is there a formal way of deciding what fraction of a game is chance?"
] | [
false
] | The card game of "war", in which players flip cards and compare their values without ever making any decisions is clearly entirely probabilistic, (each player will win half the time, as long as the deck is perfectly shuffled before each game.) The game of chess has no probability involved because the game state is enti... | [
"I'm not sure how developed the concept of ",
" is. There is a paper by Jakob Erdmann from the Friedrich-Schiller-Universitat that deals with the concept. ",
"Here is the pdf link.",
"Their goal is to create an algorithm for automatically determining the extent of chance and skill in a game."
] | [
"I feel the problem intrinsically lies in the somewhat ambiguous terminology.",
"To distill this issue, one can look at the game of connect 4. There are strategies and general concepts, but a perfect game has the first player win every time. Does this mean, assuming who goes first is set randomly, the game is c... | [
"While it is believed that ",
"chess is solvable",
" it is not yet known how it would be solved. We don't know if white could always force a win, if black could always force a win, or if either player could always force a draw. Without that information, we can't say if the randomness of the starting color mak... |
[
"How powerful a magnet would you need to effect the iron in a persons blood?"
] | [
false
] | Follow up, could someone be kill this way? | [
"Wiki on Human Iron Metabolism:",
"Most well-nourished people in industrialized countries have 4 to 5 grams of iron in their bodies. Of this, about 2.5 g is contained in the hemoglobin needed to carry oxygen through the blood, and most of the rest (approximately 2 grams in adult men, and somewhat less in women of... | [
"The magnetic field of a magnetar is strong enough to kill you via the diamagnetism of ",
". I'd say that's more significant than iron."
] | [
"At a distance halfway to the moon, a magnetar could strip information from all credit cards on Earth.",
"Wait a minute...",
"TylerDurden1976 (talk) 21:00, 21 August 2010 (UTC)",
"I knew it!"
] |
[
"Would an object travelling close to the speed of light experience friction due to the hydrogen in space?"
] | [
false
] | null | [
"Absolutely. However the intergalactic medium is so thin that the main obstacle is actually the cosmic microwave background, which dominates collisions with protons. In this recent paper ",
"here",
" the interaction of a relativistic spacecraft with the redshifted CMBR is studied and it is found that a gigantic... | [
"Per that article, the CMB effects start to play a role only at speeds ",
" close to speed of light (",
", which is 99.99999999999999999% of the speed of light). "
] | [
"No friction. But there are two interactions you should consider. One would be with matter. Atoms may absorb or scatter a photon. Next is gravity (or really the distorted space-time). Energy warps space time according to Einstein's field equations in General Relativity. Light will follow the path of minimizin... |
[
"How do space agencies prevent germs and bacteria on their rovers (Mars Rover) from contaminating the planet they visit?"
] | [
false
] | Or do they even try and prevent it? Am I correct in thinking that the scientists have something in place to stop living organisms/bacteria contaminating Mars when objects come in contact with the planet? If so how is it done? | [
"They clean and sterilize the object before it's launched. This eliminates any food for bacteria or microbes. ",
"Also, space is incredibly hostile to life. Several months of cosmic rays, unfiltered UV radiation, and freezing cold will kill all but the hardiest of microbes. "
] | [
"All that, and we ",
" found evidence that some of the rovers had life on them at some point. Life is incredibly stubborn. Lol"
] | [
"There are pre-flight bakeouts at over 100 C as well as cleaning everything down with alcohol. Lots of work is done to keep human contamination (skin, hair, etc) off, because it leads to being a tasty food for bacteria. ",
"There are also limits for how close the rovers can get to potentially life-bearing areas d... |
[
"We know many species of animals are now extinct. Are there any extinct plants in the world? How did they reach extinction?"
] | [
false
] | null | [
"Plants go extinct for the same reasons animals go extinct - they can't survive in their ecological niche anymore. Maybe a new species of plant crowds them out, like in rainforests where plants are in an arms race to grow taller faster. Maybe a new parasite or disease kills them off, like Dutch Elm disease. Maybe c... | [
"Man-made reforestations of burned areas is a serious one. For example in Greece, from 1900-today, for reforestation of burned areas like hills and mountains, they use pine trees ( easy to propagate, grow well in the dry conditions of Greece, etc.). The pine needles (leaves), once they fall on the ground and start ... | [
"Here is a list of endangered or extinct plants: ",
"Endangered and Extinct Plants",
"This lists 5,773 plants that we know to be endangered or extinct. There however will be more plants that we have yet to find in fossils or will simply never know about. Chances are there are more extinct plants than there are ... |
[
"Why is the radiation from Chernobyl and Fukushima so intense, when Uranium has a half life of billions of years? Shouldn't it be minimal?"
] | [
false
] | null | [
"Nuclear power plants make energy by splitting uranium nuclei in two: \"nuclear fission\". The two new nuclei made, \"fission products\", are almost always radioactive and under go beta decay. ",
"A wide variety of fission products are made",
" with a wide span of half-lives, down to sub-second and up to many... | [
"It's not the Uranium that releases most of the radiation. Once the Uranium is washed away or evaporates into the air it's no longer at critical mass and reacting. The half life of U235 is long enough that it doesn't release much radiation, but it is toxic as a heavy metal metal poison.",
"The dangerous radiation... | [
"Once the Uranium is washed away or evaporates into the air it's no longer at critical mass and reacting.",
"Actually when there is not a careful geometrical arrangement of Uranium and a neutron moderator it will stop reacting. The Uranium generally does not leave the disaster area. If it easily washed away or ev... |
[
"Why do laser pointers look \"grainy\" or look like they are a bunch of dots when you look at the laser point on a surface?"
] | [
false
] | [deleted] | [
"As Sycosys said, the grainy pattern is called a \"speckle pattern\".",
"Basically, the lenses that are in front of the laser are far from perfect, and there are random fluctuations in the air as the laser light travels through it (turbulence, etc.). This causes distortions on the wave front as the light propaga... | [
"There's also the fact that because of the coherent emission, microscopic imperfections in the surface it is reflecting off of causes the interference patterns. ",
"If I'm not mistaken, that's actually the dominant source, and the sub-speckles are the other factors. The fact that the speckles appear to shift and ... | [
"The speckle pattern would exist even if the laser lenses were perfect and the beam were traveling through vacuum.",
"The optics of our eyes are just as important in perceiving laser speckle."
] |
[
"Is it possible/practical to build a \"filter-feeding\" ship that is powered by Uranium from seawater?"
] | [
false
] | [deleted] | [
"That's sounds like a Brussard Ramjet, except a boat instead of a spaceship.",
"Anyway, I don't think so. The amount of uranium you'd get is tiny compared to the massive amounts of power to run a ship. Also consider that given its density uranium is more likely to be found at the bottom of the ocean."
] | [
"As I understand it, there's two big downsides.",
"First, it's really slow. The process is basically submerging huge sponge-like objects into the sea, waiting for water to filter through them so they can collect the uranium, hauling them back up, and processing them.",
"Second, the net energy return is barely p... | [
"So in a sense, it'd be about 500,000 times more practical to build the same sort of contraption that "
] |
[
"Have human beings ever created a new species?"
] | [
false
] | We're in AP Biology discussing speciation and the argument desperately needs some hard supporting facts. Microevolution is most definitely observable, but have we ever truly accomplished speciation? Pardon the awkward wording; I'm trying to pay attention. Currently we're discussing pigeonesque chickens. | [
"Bananas, broccoli, cauliflower, lettuce, maize, dogs, etc, etc. Humans have artificially selected for any number of desirable characteristics in indigenous species--some to the point where interbreeding is no longer possible."
] | [
"This ",
"picture",
" was a favourite of one of my genetics professors. The difference between species is phenotypically observable to say the least."
] | [
"Yes. That's correct."
] |
[
"Can we consistently define a set of all possible ways a function can asymptotically grow with total ordering on it?"
] | [
false
] | [deleted] | [
"to your first point, there are many functions that grow faster than exponentials...consider, for instance, the ackerman function.",
"Or how about, consider f(n,k) to be n followed by k \"up arrows\" followed by n. This would grow faster than any exponential in either n or k. ",
"Going even higher, the busy bea... | [
"What you are asking for is a description of the ",
"order type",
" of the order you've constructed. (BTW: this is only a partial order).",
"I'm pretty sure this is wickedly complicated. For a start I suggest you read ",
"this",
" concerning such classes of functions where the domain and range are the nat... | [
"great link, thanks"
] |
[
"If I had an aquarium filled with distilled, deionized water, how long would it be before fish could live in there?"
] | [
false
] | This is a question about how gases dissolve in liquids. Assume STP and the water is not being agitated. The volume of the aquarium is obviously important, so let's just say it's 20 L. Let's assume there is absolutely no oxygen (or any other gases) in the water at the onset. What is the concentration of oxygen required ... | [
"Tricky. Some fish, like the goldfish and carp, are very good at handling anoxic conditions. The crucian carp, a very close relative, ",
"can remain active under these conditions",
" , and goldfish are very tolerant too. Furthermore, any goldfish placed in anoxic water will gulp at the surface...it doesn't h... | [
"I work in a lab too, and use various degassing techniques for HPLC purposes.",
"There are various ways to degass solvents including vacuum, sonication, helium sparging, boiling, and most HPLC systems now have inline degassing systems.",
"Your vacuum degassed solutions will \"regass\" very quickly. Probably le... | [
"On what part?"
] |
[
"Is hydrofluoric acid strong enough to destroy dna?"
] | [
false
] | I know certain acids like hydrofluoric acid can be used to chemically dissolve organic matter, but is it strong enough to destroy the DNA of that organic matter beyond the ability to use it for identification purposes? This question came to me while watching season one of Breaking Bad, when Walter and Jesse are looking... | [
"Hydrofluoric acid isn't a strong acid- it's pKa is 3.17. The tissue damage primarily comes from the fluoride. So no, it isn't a strong enough ",
" to destroy DNA... But fluoride does not discriminate. Given enough time and fluoride, it can damage DNA beyond identification. "
] | [
"The concentration in drinking water is very low (0.5 to 1.0 mg/L according to wikipedia) and so would not have harmful effects. A small amount is beneficial for oral health but there isn't enough fluoride in floridated water to start causing damage elsewhere in your body."
] | [
"Based on my assumption? Absolutely not. That's the equivalent to saying \"a fall from 2,000 meters onto concrete is almost certainly fatal to humans. So, based on this assumption... it is not unreasonable to think that a fall from 2 mm would also be almost certainly fatal.\"",
"I'm only addressing the falacy of ... |
[
"When astronomers discover a planet..how do they know if its in the goldilocks zone of the star,the temeprature on the planets surface,the orbital period of the planet,what class it is,whats the diameter,mass?"
] | [
false
] | null | [
"A read through the wikipedia page on ",
"exoplanets",
" would answer all of those questions and provide interesting details. "
] | [
"Thank you sir."
] | [
"They can tell visually the properties of the star (mass, size, intensity).",
"Based on the frequency of the dimming coupled with orbital mechanics tells them distance from the star.",
"Based on the magnitude of the dimming they can get the approximate diameter since they know the orbital distance."
] |
[
"How do giraffes (and other leaf-eating animals) get enough protein?"
] | [
false
] | null | [
"A lot of people here are talking about the scientific definition of protein, which I think is missing the spirit of the question (despite being technically correct).",
"When push comes to shove living organisms really just need the chemical building blocks for their proteins/lipids/nucleic acids. In addition to ... | [
"Even leaves have protein in them. Rubisco is the name of the protein that grabs carbon dioxide out of the air and sticks it into sugars during photosynthesis and it is the most abundant protein on earth. There are lots of other proteins in plant tissue. To get enough the herbivores just need to eat a little more l... | [
"Some plant structures like cell walls contain a great theoretical source of proteins but are impossible for our bodies to digest because of the difficulty of breaking the bonds between structural polymers plants produce, like cellulose. ",
"Herbivores have a variety of strategies for getting enough nutrients fro... |
[
"How long would a human survive, if their bone marrow was completely removed?"
] | [
false
] | [deleted] | [
"Bone marrow makes your red blood cells and a red blood cell lives about ",
"120 days",
".",
"One would assume they are all equally spread out over that time so some are brand new and some are about to die and everything in between.",
"The question then remains is how much of your red blood cells can you lo... | [
"As a followup to Zerowantuthri's comment, ",
"here's some information on anemia",
". Combined with ",
"an article on hemoglobin",
", and we find that the hemoglobin concentration for the average adult male is 13.8 to 18.0 g/dL (grams of hemoglobin per deciliter of blood). Let's go for the best case scena... | [
"Once the bone marrow is destroyed, the number of blood cells starts dropping, but death won't be from a lack of red cells but rather from the inability to produce new white cells. As time goes on they will be increasingly vulnerable to infection and will die from that. So it wouldn't be immediate, but certainly wi... |
[
"Do both magnets and gravity behave differently at hot and cold temperatures?"
] | [
false
] | Relating to electronic components with heat and lack of heat, does a magnetic bond strengthen or weaken depending on what the temperature is? Same question regarding gravitational force. | [
"Magnets: The bond doesn't generally weaken or strengthen with temperature, but permanent magnets will undergo a phase transition at some point causing the spins that add up to create a coherent magnetic field to randomize. This will cause two \"bonded\" magnets to no longer attract each other.",
"Gravity: Wherea... | [
"While technically true, this effect is entirely negligible until you reach temperatures such that kT is comparable to mc",
", where m is the mass of a particle in the system. For something as simple as hydrogen, this is on the order of ",
"10",
" K",
"."
] | [
"Gravity: Whereas a permanent magnet is a collection of dipoles oriented in the same direction, all matter attracts all other matter gravitationally, so there's no way any analogous phase transition can occur.",
"There is a correlation between temperature and gravity though. If I increase the temperature of a sys... |
[
"When we hold an image too close to our face, we see it as blurry. Is it possible to intentionally print a blurry image so that when held at the same distance, it becomes in focus?"
] | [
false
] | [deleted] | [
"If we print something that is blurry, then holding it close will only make it blurrier! Our eye has a lens behind the pupil that focuses the image into a smaller image, which can cause out of focus images.",
"You may want to take a look at this: ",
"http://en.wikipedia.org/wiki/Focal_length",
"Anyway, what d... | [
"Nah, if you print it blurry then you miss details which could otherwise be seen when focused properly. The brain can do a lot, but it can't add details on its own. "
] | [
"That's not how it works. Glasses improve focus: how you perceive the image, not the image itself. The image is what it is, you can try to focus as much as you like but you won't create detail that isn't there. Otherwise, we could store an 1080p film on a floppy disk.",
"There are plenty of ways to create opti... |
[
"How exactly does quantum tunneling work?"
] | [
false
] | Spurred by (hover over red button), I realized I never fully understood how quantum tunneling works from P-Chem. How exactly does a particle without enough energy pass through a mountain of potential energy? | [
"Because the mountain is not infinitely high. Let's think about 1-dimensional solutions to the Schrodinger equation. The solution to the equation is completely determined by the choice of the potential. In quantum mechanics, if a potential is not infinitely high, then the wavefunction is nonzero on the other sid... | [
"Using Tex the world",
"If we have a barrier on the right with a particle/wave coming in from the left",
"~~__",
"_",
"Where the barrier has some height V(x)=V solutions to the Schroedinger equation will look like",
"[;\\psi (x)\\sim e ",
" k x};]",
"to the left, and right, of the barrier, ",
"[;k=\... | [
"Mathematically, it's because when you solve Schrodinger's equation for non infinite potentials you get an exponentially decaying wavefunction instead of a classical region of non existence.",
"Physically? I have thought about it a little for particles. When they are incident on a barrier they do not instantly lo... |
[
"Is there a limit to the amount of available randomness in the universe?"
] | [
false
] | I'm not sure if this should be categorized as physics or mathematics. | [
"I don't understand the question. Define \"available randomness\"."
] | [
"If you are referring to entropy and thermodynamics, then yes, the limit would be heat death of the universe. This will occur when everything is the same temperature, so no more work can be done, basically meaning that the world is at maximum disorder."
] | [
"It's maximum disorder, though it may not seem like it.",
"\nThe disorderness of something can be defined as its likelihood to occur randomly.",
"\nIf you were going to randomly distribute all energy across the universe, the chance to get an even distribution is absurdly high.",
"\nMeanwhile, the chance to ge... |
[
"Why do you lose consciousness in a rapid depressurization of a plane in seconds, if you can hold your breath for longer?"
] | [
false
] | I've often heard that in a rapid depressurization of an aircraft cabin, you will lose consciousness within a couple of seconds due to the lack of oxygen, and that's why you need to put your oxygen mask on first and immediately before helping others. But if I can hold my breath for a minute, would I still pass out with... | [
"Because when the air pressure drops, the partial pressure of oxygen in the air drops lower than the partial pressure of oxygen in your blood - and as your lungs aren't strong enough to hold pressure in, the pressure in your lungs drops to be about the same as the outside.",
"So the oxygen diffuses out of your bl... | [
"This is the correct answer you're looking for OP. Low atmospheric pressure hypoxia is fundamentally different from garden variety respiratory depression because the partial pressure of oxygen is so incredibly low at those altitudes, oxygen reverses flow from the body into the air because normal flow of oxygen from... | [
"Keep in mind that pressure and volume are inversely related. So if he holds his breath during depressurization, his lungs would expand due to the pressure decreasing. He may eventually be unable to hold his breath due to the volume of air in his lungs expanding. This is why when you get trained for SCUBA diving, t... |
[
"Could a solar sail spacecraft carry its own laser emitter to provide propulsion or does a laser push its own emitter backwards?"
] | [
false
] | There’s a classic physics problem that asks why we don’t put fans on our sailboats to power our boats when there’s no wind? The obvious answer is that the fan will always provide equal or more impulse in the opposite direction than it provides to the sail. Does this same principle apply to solar sails? If you had laser... | [
"The obvious answer is that the fan will always provide equal or more impulse in the opposite direction than it provides to the sail.",
"This isn't why we don't do that. Not that Mythbusters is scientifically rigorous, but they did make some cool experiments and in this case, they got it right. ",
"You certainl... | [
"This isn't the answer I expected and I love it more because of that. Thanks for the knowledge internet stranger!"
] | [
"Black doesn't really make light disappear, it just converts it to heat and re-radiates it as infrared.",
"This infrared produces thrust.",
"For a thin black sail, both sides of the sail are hot and both are producing thrust. Not much motion happens.",
"For a thick (insulating) black sail, a dark-colored blan... |
[
"What happens inside the body to make someone \"Wake up\" from a coma?"
] | [
false
] | null | [
"First, there needs to be an understanding that a coma is most likely the result of a traumatic brain injury and therefore, the outcome for coma and vegetative state depends on the cause, location, severity and extent of neurological damage. ",
"Following this, if people are to actually wake up from a coma, there... | [
"Clearly it will depend a great deal on the cause of the coma and there are many causes, which we can think of as either primarily neurological, or not.\nThe non neurological causes are the easiest - these are when a process that causes usually some sort of general metabolic upset effects global brain functioning. ... | [
"Tack on question: What leads up to this? During the coma is the body preparing for waking up or is it something sudden?"
] |
[
"How does glow in the dark work?"
] | [
false
] | null | [
"The main thing behind is called phosphorescence. Googling can produce lots of info with that term.",
"For info, here is a quick summary:",
"Basically, an electron goes trapped in a meta-stable high energy state. It will eventually decay. How long that takes depends on several things, but the point is that it w... | [
"Which type? Glow in the dark paint, glow in the dark frisbees, watches with nightlight, fireflies or glow sticks?",
"Chemiluminescence is typically mixing an oxidizer with a phenol in presence of fluorescent dyes (fluorophores). The oxidation/chemical reaction releases energy that is absorbed by the dye which i... | [
"Good answer, I'd like to add however:",
"Another mechanism is simple fluorescence where the electron simply drops to the stable state really quickly without having any meta-stable state available to it.",
"This is how certain glow in the dark compounds work. However you need to shine some sort of light on it. ... |
[
"Do black holes really appear 'black'?"
] | [
false
] | I know we presume black holes to be black because their gravity is too immense for even light to escape. What about the light that passes just along the event horizon? Doesn't it bend around the black hole as an orbiting satellite would do? My question is that if light was heading towards the black hole from all direct... | [
"black holes that are actively consuming matter are actually quite bright, The accretion disc heats up to incredible temperatures as matter accelerates into the gravity well. ",
"Black holes that are dormant are just pure darkness. Any light that ends up in an orbiting pattern is forever lost to us, and the only ... | [
"Yes, you are correct that given the right configuration of a background light source and a black hole between it and the observer, the black hole could act as a ",
"gravitational lens",
", just as any massive body would. The light still isn't being emitted from the black hole, just being bent around it in such... | [
"Even if the accretion disc is bright, isn't the hole itself and everything inside the event horizon black?"
] |
[
"Why is gyroscopic precision 90 degrees out of phase?"
] | [
false
] | I used to know this, but have forgotten.. | [
"thats a cool explanation, but why is it 90 degrees out of phase, and not 47, or 123?"
] | [
"If I hit the ball very hard and it was rotating slowly, wouldn't it reach its peck deflection before 90 degrees, and likewise if I hit it very softly and it was rotating very fast, could it not complete multiple revolutions before it reached peak deflection?"
] | [
"Imagine a ball on a string anchored to some sort of floating point that violates physics. There is no gravity, and the ball is horizontal and moving counterclockwise. When the ball is on the east, you hit it down. Now instead of going north, it's going north and down a little. But it still moves in a circle, so in... |
[
"Do bigger cat species also land on their feet?"
] | [
false
] | When a cat, falls, it always lands on its feet. Do bigger cat species also do this? Presumably cat-sized wildcats do, but what about bigger cats like bobcats, lynxes and cougars? I think it would be hilarious if lions and tigers could do this, but I doubt it. | [
"The Soviet shot put team doesn't have much to do in between the Olympics."
] | [
"Larger animals are less maneuverable than smaller, just because of more mass, so all other things being equal, larger cats are at some penalty here.",
"Not sure just how important this is in practice. ",
"My hunch is that anything up to the size of a cougar/leopard/jaguar should be pretty good at this. (And no... | [
"I pity the poor grad student doing this experiment."
] |
[
"Why does choked flow happen and why it is related to the speed of sound ?"
] | [
false
] | I'm diving into the venturi effect (example: rocket nozzles and chocked flow happening in the admission valve of a ICE) and it seems that when the gas approaches the speed of sound, the flow starts to choke. Why does this happen ? | [
"To preface this answer: information about a medium travels at the speed of sound in the medium. So if you change the conditions of a flow at one point, the effect on the medium travels at the speed of sound upstream in the medium.",
"If you imagine a venturi nozzle and a flow condition where the speed of sound i... | [
"Oh wow, that's very helpful.",
"I always felt it was very unintuitive. I knew that it had something to do with the speed of sound and propagation; but I've never seen it so laid out. I knew about flow upstream being affected by the downstream, but I never quite connected the dots that it would break down at the... | [
"If you already have the necessary background, only the last two paragraphs need to be read.",
"Choked flow is the condition where a decrease in pressure downstream of nozzle does not cause an increase in mass flow through the nozzle. ",
"In a rocket nozzle, the pressure gradient between the combustion chamber ... |
[
"How does sound volume add up?"
] | [
false
] | So, imagine I have one jet engine running, which produces 130 dB. What would happen, if i place 10 jet engines right next to each other? What would happen to the volume? Would it be 10 times louder, thus resulting in a 140dB volume? And on a more physics level, do soundwaves add up, cancel eachother out, or what? | [
"Here's the basic rule, if the sound sources are not intimately connected to eachother, the sound ",
" adds. This would cover your situation with the jet engines. If the sound sources are intimately connected, then things get more complicated.",
"I'll first talk about the unconnected sound sources, like your je... | [
"Thanks for the detailled explanation! The last part was a bit confusing though. Thanks!"
] | [
"I was worried that it might be. Here's a second try.",
"Suppose I had a series of numbers that went:",
"+1, 0, -1, 0, +1, 0, -1",
"Now, suppose that I had two of those sets that I was adding together, but I can't be certain if either series starts with a +1, 0, or -1.",
"If they both start with +1, then th... |
[
"Is it theoretically possible to melt pure carbon?"
] | [
false
] | null | [
"Here is a phase diagram for carbon",
"You can see it requires gigapascals of pressure (thousands of atmospheres) in addition to very high temperatures. The way to achieve this would be to massively compress carbon with some sort of explosion or rapid compression wave, similar to how the National Ignition Facilit... | [
"Yes, but since it has the highest melting point of any element how would we be able to hold it while melting it?"
] | [
"It would probably be only temporary, or you could just have thick walls in which the inner part gets ablated. Probably any realization of this would use a very small sample, which could be held in the middle of a larger vacuum chamber. The main tool for holding things at really high pressure is the diamond anvil, ... |
[
"Chances of survival in a tsunami?"
] | [
false
] | I've been wondering what exactly makes a tsunami as deadly as it is. I guess from the outside, it's pretty easy to underestimate the sheer force of the water and the suspended debris but I can't help but think that some of it must be survivable provided I'm a good enough swimmer. What would be my best bet if I can't ... | [
"I got dumped out of a raft on a rafting trip. I have no idea how fast the current was but it was August so, relatively speaking, current wasn't too fast and the water was the warmest it was going to get. We had been given directions on what to do if we ended up in the water: assume a sitting/reclining position wit... | [
"I'm not sure that swimming skills would help much. Someone looking at tsunami videos ",
"estimated",
" the velocity of the recent tsunami in Japan over land near the Sendai airport at 5-6 m/s. World-caliber swimmers go about 2 m/s during a race -- but that's in nearly-perfect conditions. In a tsunami, you'd b... | [
"That's like saying that someone who's skilled with a shovel would have a reasonable chance of surviving a meteorite impact."
] |
[
"Why do some mushrooms grow in rings?"
] | [
false
] | I know they are referred to as circles (or fairy circles), but the mushrooms only appear on the edges of the circle which is why I use the term "ring". To be more specific, why do the mushrooms appear on the edge of the circle and not in the center? My guess is that the ring is the product of outward expansion and depl... | [
"I don't know if we know for sure exactly why fungi that produce fairy rings only produce fruiting bodies on the outer most edges of the mycelium. I think that the #1 \"just-so\" story right now is what you've already mentioned, that is, as the mycelium grows outward there is a depletion of resources in the center... | [
"Not exactly. What we typically think that a fungus is, i.e. a mushroom, is actually only the fruiting body of a much larger organism. Much of the fungus actually exists as an underground network of hyphal tubes, known as a mycelium. These networks typically grow as an outwardly expanding circle, and so what we ... | [
"Maybe better asked in ",
"/r/mycology",
"."
] |
[
"How does circumcision affect HIV infection rates?"
] | [
false
] | I keep hearing everyone talk about how effective circumcision is in preventing HIV infection, but how could that possibly be true? All you're doing is removing skin! I should say that I'm very much against child circumcision, but in the interest of being intellectually honest, I would love to know what askscience has t... | [
"Removing the penis entirely has 100% reduction in transmission."
] | [
"The proposed mechanism is of keratinization of the glans penis. The skin of the glans penis is nonkeratinized stratified squamous before circumcision. Afterwards, it keratinizes. This is thought to reduce the adhesion and penetration of HIV to the man. Hence the reduction in female -> male transmission."
] | [
"Seconded. "
] |
[
"Why hasn’t a cooling equivalent of the microwave been invented for mass production?"
] | [
false
] | I shouldn’t have to wait a whole hour when my beer isn’t cold enough goddamit | [
"It is easy to add heat: Just blast it with radiation. Microwaves are practical but any type of radiation would work. What is the opposite? Make the object emit a lot of radiation. Well, you can't. Objects naturally emit thermal radiation, you can avoid external radiation hitting the object and then wait for the ob... | [
"... they have, in effect. ",
"Blast chillers are real, but super-cooling a carbonated beverage in a can or bottle is probably not the best idea. ",
"https://www.hotelrestaurantsupply.com/BEV-CF031AG.html?gclid=Cj0KCQiA2ITuBRDkARIsAMK9Q7MAPubsdHjCEi6rgrTiClLbpAcpnmlRk778jUDQg1a8S7jcAhHBIqUaAsVREALw_wcB"
] | [
"That thing doesn't seem very effective. It notes that it chills from 194F to 37F in 90 minutes. That's about 1.6F per minute assuming a linear cooling curve. That means it would take 25 minutes to cool beer from 77 to 37. An ice water bath would work faster than that. See comment below."
] |
[
"Why do some earthquakes cause major tsunamis but others only minor tsunamis? What factors are at play?"
] | [
false
] | There was just another major earthquake in Japan ( ) that affected the region that had previously been affected by the Fukushima-related earthquake. There were reports of a 20cm high tsunami reaching the shore. This new earthquake is reported to have a magnitude of 7.3, which is more powerful than the Fukushima-quake w... | [
"Great question. Although there is a serious misconception here to deal with first. Earthquakes of the same magnitude can indeed have completely different tsunami generating potential. However, the big Honshu Earthquake in March 2011 was a Magnitude 9, not a 7.1, so was 1000 times more powerful.",
"But back to ... | [
"Yes, to some extent. The reason the Boxing Day 2004 Tsunami in East Easia was so terrible in its effect was that it occurred in relatively shallow water. In a deep body of water there is more accomodation space, so the displacement can be mitigated somewhat."
] | [
"That makes perfect sense. ",
"Does that mean it has to do with the amount of displacement relative to the amount of water above it?",
"e.g. 1m of displacement at 10m depth would be worse than 1.5m's displacement at 20m's depth?"
] |
[
"Why does the Up quark have so much more mass compared to the other quarks?"
] | [
false
] | null | [
"You mean \"top quark\", right?"
] | [
"The short answer is \"we don't know.\"",
"One of the goals of the experiments at the Large Hadron Collider (LHC), is to search for the Higgs Boson. This is a so-far hypothetical particle that could be used to explain the nature of mass. The theory (called the Higgs Mechanism) is that a Higgs Field permeates all ... | [
"My bad -- yes. Thank you."
] |
[
"If human cloning were legal, would a scientist be able to clone a human from HeLa cells or would the numerous generations of cells grown in the laboratory, intentionally or unintentionally, have had too many mutations to be of any use for human cloning?"
] | [
false
] | I've heard of these cancer cells taken from a lady named Hela Lacks (I don't remember how to spell her name). According to what I've heard scientists not only were able to keep the cells alive outside of their human host, they were able to reproduce them in the lab. In fact, according to the places I've read, they have... | [
"(It's Henrietta Lacks - check out the book about her life and the story of these cells: ",
"http://rebeccaskloot.com/the-immortal-life/",
")",
"HeLa cells are so far removed from anything that resembles human cells there's no chance you could do much with them beyond culturing them in a dish. They've accumul... | [
"That already exists"
] | [
"The point was it would never work. All you'd get are tumours. "
] |
[
"Where does all the heat go?"
] | [
false
] | Ok, here's a simple problem that's been bothering me and which i haven't been able to find an answer for: Things in the world generate heat. Our bodies, most living things, our computers, factories, cars, etc. So where does all this go? Immediately the answer is "dissipated into the air": but then where? The logical as... | [
"Everything gives off light at a frequency distribution and power proportional to their temperature. This is called ",
" So a room-temperature cricket ball in the intergalactic void would radiate light, mostly in the infrared. Each time the cricket ball emits a photon, its temperature will drop slightly, changing... | [
"Because when one object emits blackbody radiation, it's not raising the temperature of another object by exactly the same number of degrees. It's raising the temperature of a hundred billion trillion objects by an immeasurably tiny fraction of a degree."
] | [
"That'll do it. Thanks."
] |
[
"[Mathematics] Is there a faster way to multiply (large) numbers?"
] | [
false
] | [deleted] | [
"F(n) = O(n",
")",
"That should be O(n",
") or about O(n",
")- otherwise you would be better than O(n).",
"https://en.wikipedia.org/wiki/Karatsuba_algorithm"
] | [
"F(n) = O(n",
")",
"That should be O(n",
") or about O(n",
")- otherwise you would be better than O(n).",
"https://en.wikipedia.org/wiki/Karatsuba_algorithm"
] | [
"What is faster to do in your head is highly subjective. Computers usually use pretty much the algorithm you describe because when done in binary you only need to do multiplication with 2",
" which can be done easily by shifting bits. ",
"The algorithm actually becomes trivially easy to do even by hand in binar... |
[
"For \"breakthrough\" Covid cases in fully vaccinated people that are deemed to be \"mild\" (presumably in terms of symptoms), is there still danger of other hidden internal damage (i.e. heart, lungs, etc)?"
] | [
false
] | null | [
"It isn't completely understood yet, but most likely no. ",
"The damage is caused by a positive feedback loop leading to either immune cells killing infected cells or the cells killing themselves.",
"Antibody responses actually inhibit this process, greatly reducing the overall inflammatory response. The antibo... | [
"Most of the damage caused by the SARS-COV-2 virus is due to an inflammatory reaction by your immune system. When you develop this condition it is called covid-19. This is called a cytokine storm, and it is an overreaction by the immune system that causes massive inflammation; usually as a result of the immune sy... | [
"The cytokine storm and it's inflammatory results are not the only symptoms that cause long term damage. There are neurological issues, not fully understood, but unrelated to the above, that cause long term brain fog, dizziness, and olfactory nervous problems. There are also other symptoms that can cause harm outs... |
[
"Why do some males grow so little facial hair?"
] | [
false
] | null | [
"That doesn't explain places like India or the Middle East."
] | [
"Very good point. I looked up Afghanistan's climate, and it said temperatures can get as low as 15 degrees F in the winter. India has a much warmer climate in the winter at around 65 degrees F."
] | [
"Genetics governs how much facial hair is grown, and evolution is what would have influenced perceived differences in the quantity of facial hair in different \"ethnicities\""
] |
[
"What is the scale of the largest structures that are expected to hold together despite the metric expansion of space?"
] | [
false
] | null | [
"Clusters and superclusters of galaxies are something like 1 million light-years and are not expanding.\nBut there is also what we call the \"cosmic web\" which is a network of filaments joining these clusters. The typical size would be 10 or 100 millions light-years. Matter is accreting to the clusters via these f... | [
"Metric expansion only increases the distance between things that aren't ",
" in any way.",
"You don't start seeing the effects of metric expansion until you get out to scales where the gravitation of ",
" is negligible. For comparison, our galaxy masses about ",
" the mass of our ",
" So to start seeing ... | [
"How do we know they're not expanding? "
] |
[
"What causes gravity?"
] | [
false
] | Just a quick question. Are there any recent theories or information regarding the origin of the force of gravity? I understand that the more mass an object has, the greater its gravitational influence, but I'm asking where does the force of gravity reside inside of that mass? My current hypotheses are either that it's... | [
"Well it actually isn't really a force. It only looks like a force due to some really interesting properties of our universe. That's the current consensus. ",
"Let's start with a basic principle. We know that all observers must agree that light travels at c, the speed of light (in a vacuum). The resolution is to ... | [
"\"Recent?\" No, not recent. The theory explaining gravity is called general relativity, and it's going to be a hundred years old in five years. In short, gravity is an optical illusion that results from the relationship between stress-energy and geometry.",
"I hope you take this in the most polite, constructive ... | [
"Care to elaborate if you wouldn't mind, how does it cause two stationary bodies to move toward one another?",
"It doesn't. The presence of stress-energy changes the geometry of spacetime such that the future of a nearby small object points toward the source of gravitation.",
"Where does the acceleration of gra... |
[
"How does bleach change the colour of clothing?"
] | [
false
] | null | [
"The other two answers are correct, but I wanted to answer a question that you ",
" asked. Your question was how does bleach remove color? A similar question, with a really cool answer is how does bleach make my white clothes look brighter?",
"Bleach contains molecules called optical brighteners. These molecule... | [
"Dyes produce the phenomenon of colour because they contain chromophores - molecules or parts of molecules that absorb electromagnetic radiation in the visible region. This then leaves only certain colours of light to be reflected from the material. Bleaches are strong oxidising agents and they are capable of break... | [
"Bleaches tend to be either oxidizers (like to take away electrons) or reducers (like to give away electrons).",
"by reacting with the pigment molecules and either (a)removing an electron, thus breaking chemical bonds to break apart the pigment molecule, or (b)adding electrons, thus altering the chemical bonds (e... |
[
"Do protein shakes actually help you build muscle?"
] | [
false
] | I'm assuming that you are eating an average American diet in addition to the protein shakes. A lot of my friends swear by their protein shakes, but I was under the impression that the average American already consumes way more protein than they need. Furthermore, I have never been told by any athletic coach to suppleme... | [
"There seems to be a lot of disparity in the 1.0-1.5 grams of protein as to whether that is per pound or kilogram of bodyweight. In Arnie's bodybuilding encyclopedia I believe it says per kilogram, although I have seen both used extensively on the internet and other books. It only takes a quick Google to check that... | [
"There seems to be a lot of disparity in the 1.0-1.5 grams of protein as to whether that is per pound or kilogram of bodyweight. In Arnie's bodybuilding encyclopedia I believe it says per kilogram, although I have seen both used extensively on the internet and other books. It only takes a quick Google to check that... | [
"as an extra question that bothered me for a while: what if I just eat meat for dinner everyday? can that be enough/better than those protein shakes?"
] |
[
"We've reached > 500 panelists!"
] | [
false
] | *Welcome, new panelists! * I had a 22-day backlog in processing panelist applications, but that's behind us now. If there's a typo, wrong color, or just plain wrong tag text, please let me know! Also, if you think you've been skipped, now's the time to tell! It was quite a list, so I'm sure there are mistakes here and ... | [
"As a lurker in this subreddit I genuinely thank all the awesome contributions people have done, I've learned a lot, it's like a turn based discovery channel."
] | [
"Who wants old cookies?"
] | [
"I've learned a lot, it's like a turn based discovery channel.",
"Does that mean we'll have ice trucker, logger, and crab fisherman contributors? "
] |
[
"Since energy cannot be created nor destroyed, where did it come from?"
] | [
false
] | null | [
"There are two schools of thought on this. Neither one is unambiguously correct; both are basically valid.",
"One school of thought says that the universe has some total energy, and that that total remains constant. If you were God, and thus you were omniscient, you could add up all the energy in the universe at ... | [
"The universe was opaque to light until about 380,000 years after the Big Bang.",
"This line really piqued my curiosity.",
"I found a bit of reading material on this idea",
" in case anybody else finds it interesting. I'd be fascinated to hear/read a bit more about it too if anyone wants to provide.",
"It m... | [
"Of course, the third school of thought on this, which I advocate, is that energy can't be defined for the universe as a whole, since the FRW metric doesn't have a timelike Killing vector, and so it is meaningless to talk about the global energy of the universe."
] |
[
"What actually makes us be warm blooded? What is the actual mechanism?"
] | [
false
] | Like, I know warm blooded animals maintain their temp internally and cold blooded animals don't, but does that happen is my question. Also, could a human get an operation that would convert them to being cold blooded, like a lizard? If so, would you need a lot less food? I know this seems like a stupid joke question, b... | [
"An area of you brain called The hypothalamus regulates temperature. Certain conditions can muck up with this - e.g. when you are fighting a bacterial infection your body makes itself warmer, or when you take certain drugs, e.g. alcohol can make you hypothermic - but without the hypothalamus you would die (it has o... | [
"In addition to the items discussed on other comments, there are also some tissues specifically meant for generating heat. Brown adipose burns through a relatively large amount of energy keeping babies necks the right temperature. (probably mostly for the spinal cord?) Adults have brown adipose too, but it’s less c... | [
"A human, or an endotherm for that matter, would not be able to undergo an operation to become an ectotherm (cold-blooded). The term \"cold-blooded\" actually misconveys the idea of ectothermy. It's not that a lizards blood is cold, but rather they have to use outside sources to gain body heat (sunbathing for examp... |
[
"What causes logs to turn white while burning, and why do moving black patches appear?"
] | [
false
] | I was camping this weekend, and I noticed that the burning logs that were already white had black patches moving up and down the log. What causes this phenomenon? | [
"The ash that is produced is composed of several products. Some of of it is incompletely combusted carbon which tends to be black. Other components are due to other elements in the wood such as magnesium which forms white magnesium oxide when burned. The colour fluctuations you see while it is burning is due to ... | [
"This is speculation, but the dark patches may be emitting light as well, just not as much so they appear dark. Sunspots, for example, are very bright but appear dark since they are less bright than the surrounding solar material."
] | [
"The white product of wood combustion is ash.",
"I'm not certain about the moving black patches though. Another reaction? Heat disturbing the layer of ash? I have wondered about that myself."
] |
[
"[Physics] I have a couple of questions about gravitational waves?"
] | [
false
] | Idk if this is the right sub for this and I'd previously posted on the megathread a week or so ago but here goes: I was reading an article on the NY Times app, and at the end of it it says "only three days before the black hole chirp...antenna readings were plagued by radio interference." and earlier was mentioned how... | [
"In reverse order:",
"Unfortunately, there were no other gravitational wave interferometers running that could have detected the signal that day. This would have not only provided more data, but also allowed better spatial localization of the source.",
"Could this be radio interference? Very, very unlikely. ... | [
"Thank you for your answer. Much appreciated."
] | [
"The fact is, gravitational waves could help us learn about dark matter! G-waves are a new way to see the Universe, since before their detection we could only use electromagnetic radiation (light) to observe cosmological phenomena, and light is pretty useless when dealing with dark objects such as black holes and d... |
[
"Cleaning and Seasoning Cast Iron: What's Going On?"
] | [
false
] | Two-part question, that arises from reading through a good deal of advice on the web that's sometimes contradictory, usually anecdotal, and often lacking hard information to justify why a given method is superior: First, what's an ideal way of cleaning cast iron cookware (regular iron, no chrome coating or enamel) that... | [
"I just picked up a cast-iron skillet from a second hand store and had some of the same questions. I came across a site that uses some science based techniques and goes into a little further detail as to why seasoning is important and how it works. The site can be found ",
"here.",
" The lady seems pretty knowl... | [
"Thanks for the link - yes, I'd seen that post, but then read elsewhere that the oven method of seasoning can damage a pan - so I wanted to get some other folks to weigh in. (I think the oven is safe, but I know nothing about polymerization of oil onto iron etc.)",
"Yeah, I just got an old (1890s I think) skille... | [
"Soaking in a lye-water solution",
"That'd work. Seems kind of over-kill though. Why not just use a metal brush (at worst)?",
"Using electrolysis",
"I don't see how that'd work, really. And it wouldn't be the most practical method even if it did. Electrolysis is used for removing patina from silver, but that'... |
[
"Election diffraction confusion."
] | [
false
] | I was curious to know whether or not the two angles produced when electrons are accelerated towards a crystal (of unknown material) are due to two separate planes (with 'n=1' substituted to the Bragg equation nλ=2dsin(θ)) so there are two separate plane separations 'd'. Or alternatively, it would be due to n=1 and n=2 ... | [
"What do you mean by \"the two angles?\" Electrons will be diffracted by a crystalline material at a number of angles, each corresponding to a certain crystallographic plane with a reflection allowed by the structure factor. So each diffracted beam is due to a different d-spacing. the different n values in the Brag... | [
"Yes, sorry about being vague in my question. I was discussing a problem with one of my peers after a lecture on the topic. The two angles are the angles produced when electrons were fired at a crystal film to produce a cone shape of diffracted electrons that hit a screen to produce two rings (from the two cones). ... | [
"Okay, so in this case you had a polycrystalline sample. This gives diffraction rings rather than spots because the electron beam hits enough randomly oriented crystallites to cover all azimuthal angles. ",
"For the material and 2theta range you measured, the sample gave two diffraction rings. These originated fr... |
[
"Can you fill a black hole?"
] | [
false
] | No matter can escape the gravity if a black hole, but what happens to the matter in the hole and could you "fill it up"? | [
"That becomes a very complicated topic very quickly. The simple answer is: probably.",
"The reason we \"need\" dark matter is because of supermassive black holes. These are black holes at the center of almost all, if not all, galaxies. They have masses ranging between 10",
" - 10",
" (maybe 10",
" solar mas... | [
"The event horizon of a black hole scales with the mass of the black hole. r_h=2GM/c",
" for a Schwarzschild black hole, where M is the mass. What we really mean by the mass of the black hole is the energy content of the black hole (since E=mc",
" So any energy that crosses the event horizon is added to that to... | [
"Do we 'need' dark matter to make our expectations of black holes' sizes match observations?"
] |
[
"How can ants lift up so much weight if they are so tiny? What are their muscles like?"
] | [
false
] | null | [
"It's nothing special, just a side effect of them being tiny. An ant-scale piece of your muscle could probably lift about the same amount. A human scale bit of ant muscle could lift about the same amount as you could."
] | [
"It's not necessarily that their muscles are different in any fundamental way (although I'm sure there are difference between your muscles and ant muscles, these differences do not account for the apparent difference in strength). It's simply a result of ",
"allometric scaling",
". The strength of a muscle is p... | [
"Could you please elaborate?"
] |
[
"Can rocks really move through soil? Is the ground not as stagnant as it seems? repost from /r/askreddit"
] | [
false
] | first round: I was talking with a farmer and he told me a story about a giant boulder appearing in a field his family has worked for decades. We live in a very sandy area in West Michigan. Does this really happen? Is it limited to sandy soil or does it happen in clay and other soils too? Thanks! Also, in my research I'... | [
"This certainly happens in places where the ground freezes. Many New England farmers complained about fields that every season there would be a new crop of rocks at the surface, which they would carry to the edge of the field and add to the stone fences.",
"Depending on where you live, there is an ",
"expected... | [
"Happens all the time. The process is called \"frost heaving\", and it is realy easy to grasp: When water freezes and expands, it pushes againt everything above it. Large rigid objects such as rocks have enough surface area for that force to find a purchase and are pushed upward. When the ice melts, the mud and sed... | [
"Seems plausible. If you have a container with several sizes of objects when shaken the largest objects will be more likely to be near the top and smaller objects on the bottom. This is called ",
"granular convection",
". The wikipedia article even mentions stones working their way up as an example."
] |
[
"Why do we have fingerprints?"
] | [
false
] | Follow up: What kind of evolutionary process led them to exist. | [
"Tactile friction. They help us grip things."
] | [
"Are they a function of evolution? Mutation?"
] | [
"Everything was once a 'mutation', but the useful ones tend to stick around. Things that are useless now were once useful and we haven't 'evolved out of them' yet, i.e. the appendix doesn't have a major use anymore. Fingerprinted mammals must have performed better in their environment than their non-fingerprinted c... |
[
"CERN is trying to reach an arbitrary level of certainty to accept the higgs boson. What is that arbitrary level?"
] | [
false
] | This relates to an earlier post I made. | [
"That arbitrary level is called 5 sigma. This places the chance that the data is a statistical anomaly at 1 in 1.7 million. The Higgs is currently measured to a significance of about 3 sigma, which means there about a 1 in 300 chance that the bump they see is a statistical fluke. ",
"I in 300 seems pretty like p... | [
"Another interesting aspect of the Higgs search (at least, I'm not sure about other particle physics experiments) is the look-elsewhere effect. Since the scientists are looking at a wide range of masses, it's to be expected that unlikely events will happen.",
"By analogy, take a look at ",
"this xkcd",
".",
... | [
"In medicine or psychology or whatever maybe, but in particle physics you need to be 99.9999% certain."
] |
[
"Why does thunder rumble so long?"
] | [
false
] | Lightning flashes in much less than a second. Sound travels at about 340 m/s or so. Suppose a lightning stroke is 1000 meters long, and you're standing so that it points directly away from you. Then I'd expect the thunder to last about 1000/340 ~= 3 seconds. That's a pretty short rumble, considering the generous assu... | [
"I'm no expert, but I'm pretty sure that most of the rumble you hear is a combination of the lightning bolt being really long, as you said, and the sound echoing off the ground and trees and houses and everything else around you. Thunder is crazy loud, so it is able to echo pretty easily even over long distances, c... | [
"Good you calculated that, i thought it might be nonlinearity of the medium; different frequencies of sounds going at different speeds, but i don't remember hearing that much of a different pitch over time, and doubt that sound in air is that nonlinear..(Unless at extreme amplitudes, but the lightning will only pro... | [
"It's rumble time is likely also a function of the length of the bolt. If you assume the bolt is perpendicular to the ground and 2000 feet long, and strikes 4 times during 0.3 seconds (from wikipedia article on lightning), considering it a right triangle with you at the far point, you can see that it's going to ta... |
[
"As Earth’s land masses shift due to tectonic movements how does it impact global weather patterns? Is it measurable?"
] | [
false
] | null | [
"On geologic timescales (i.e., millions of years), the motion of plates and consequences thereof definitely impact climate. Some important processes (but not an exhaustive list) are 1) opening and closing oceanic gateways and resulting changes in ocean currents, 2) latitudinal distribution of landmasses, e.g., whet... | [
"It can possibly be measurable in the time scale human have existed. ",
"That being said, you can clearly deduce that tectonics have a climate impact over long time periods. For example the creation of the Himalayas by the Indian subcontinent moving north has no doubt transformed the climate over time. Both the ... | [
"Wow. Thank you!"
] |
[
"Did some animals develop \"smell camouflage\" ?"
] | [
false
] | It seems like a lot of animals developped strong camouflage skills to avoid being spotted by the eye. But since a lot of predators use mostly their sense of smell to track down their prey, how come those preys did not evolve to no smell anything? For example, deers have a very strong smell, making it rather easy f... | [
"There are definitely some examples that I think can be comfortably placed into this category. I'm not aware of many examples of this sort of thing with large mammals, but there are quite a few insects that use olfactory camouflage to hide themselves from predators or prey (this might just be bias on my part thoug... | [
"In the case of the deer, deer musk probably developed to become \"muskier\" to attract a mate. Being able to attract a mate also means being able to pass on your genes to offspring. The deer has to hope this musk doesn't attract wolves as well...",
"That is still an excellent question though, since smell can be ... | [
"Or, the musky buck does attract more wolves, but hasn't been eaten yet, so his muskiness is an honest signal of fitness that the female would be wise to select for."
] |
[
"When you recieve a blood donation, what happens to the DNA of the blood you recieved?"
] | [
false
] | null | [
"Normally, red blood cells have no nucleus at all. So no DNA there.",
"If you receive white blood cells, they generally don't reproduce, so the DNA gets digested and recycled with the rest of the cell when it dies.",
"If you receive a bone marrow transplant, it will have stem cells that can keep making more blo... | [
"Correct and it should be noted that people who receive a bone marrow transfusion can have a problem with the donor immune system attacking them. It is called graft vs host disease and it can happen in blood transfusion as well although to a much lesser extent. That is why transfused blood is ideally leukoreduced (... | [
"Theoretically, yeah.",
"Practically, sometimes, we're working on it.",
"Realistically, it's often vastly simpler to make a new person than to alter an adult."
] |
[
"How does losing your sense of taste affect digestion?"
] | [
false
] | I was taught that as soon as your tongue detects certain tastes (e.g. sugar) your body prepares to process that food (e.g. produce insulin), but if your sense of taste is impaired, does digestion proceed optimally? Is it slowed down? | [
"You may delay the initial stages by a bit, but it wouldn’t make much difference overall, as long as the rest of the digestive system is intact. You can consume food without tasting anything (e.g. being fed via a tube down your nose or directly into your stomach) and still digest and absorb that food pretty much no... | [
"There’s 3 main phases of digestion.",
"Cephalic",
"Gastric",
"Intestinal",
"The cephalic phase is what would be impacted by losing your sense of smell. Basically your brain integrates all the different signals coming in before you’ve actually ingested the food (sight, smell, sound, taste) and begins the pr... | [
"You're talking about sense of smell, do you mean taste?"
] |
[
"Why do wind turbines have to be placed so far apart from each other?"
] | [
false
] | [deleted] | [
"The exact distance apart depends on many factors. At my old university, there was a professor who was exactly studying this. For example, if money were no issue, then you want the wind turbines to be as close as possible! Each one would not produce very much but at that density, together they will still be better.... | [
"It makes sense to have them spaced widely behind a turbine due to turbulence and diminishing returns, but i also read they should be about 4 rotor diameters apart from a parallel perspective. Wouldn't they be ok closer without affecting the other turbine's airflow?"
] | [
"Mostly it is because the wind is slowed down when powering the rotors.",
"So the air needs some way to gain kinetic energy again, since you want the most out of your investment of the turbine.",
"Sorry, I didn't fine a source atm, but I had a lecture about it at university last year."
] |
[
"How is quantum mechanics responsible for modern-day technology?"
] | [
false
] | We hear this a lot but I just wanted to know how exactly quantum mechanics discoveries are responsible for the modern day technology revolution. Perhaps as a start-off point, how did it lead to the invention of a computer? Why would a computer be impossible without quantum mechanics. I have a good understanding of un... | [
"Exhibit A : ",
"The transistor",
". The Intel Nehalem processor has 2.6 billion of these little fellas, yes you read that right, 2.6 billion of them. Transistors are in every piece of electronics that you own, millions of them.",
"And we wouldn't know how they worked, or be able to design them without unders... | [
"While I agree with you, I think sarvagnap's original question could be paraphrased as: what modern technologies require an understanding of quantum theory before they can be developed?",
"We can (and did) invent light bulbs prior to discovering quantum theory. Explaining why they work had to wait but they kept u... | [
"You can't even explain how a lightbulb works without quantum mechanics. Seriously, think about it. How does a lightbulb work? It heats up a piece of metal and the metal glows? The the hell does the metal even glow?",
"How about why things are different colors? Nope, can't explain that without quantum mechanics."... |
[
"How would listening to music in surround sound be in Orfield Lab's anechoic chamber?"
] | [
false
] | For reference, the . I'm curious as to how an 'echo-less' room would affect listening, and whether it would be an improvement or a detriment to the experience. | [
"The specialty of that particular room is that it's the (or at least one of) the most effective soundproofed chambers so it's incredibly quiet and it's said to be quite unsettling. The stories about it freaking people out and people being unable to stay in there are all exaggerations though.",
"Good work on that ... | [
"To my untrained and wholly subjective ear, it doesn't actually make a huge amount of difference.",
"Obviously in an anechoic chamber you remove the reverb, but note that acoustic energy decreases precipitously with distance anyway (The Inverse Square law), and your hearing system also suppresses small amounts of... | [
"It looks like standard acoustic dampening material that you can buy online. I suppose they might have a 5-star super-silent aircon system, but I remain extremely skeptical that there is a genuine, measurable difference between this and any other anechoic chamber. And even if there is, it is splitting hairs really,... |
[
"What would happen if an anti matter photon interacted with regular matter?"
] | [
false
] | Or if a beam of the antimatter, say from a flashlight interacted with regular matter. | [
"Photons are considered to be their own anti-particle. That is, anti-photons and photons are the same thing."
] | [
"Two photons can annihilate into e.g. electron-positron pair. So the electron-positron-annihilation is time-reversible."
] | [
"Two photons can annihilate into e.g. electron-positron pair. So the electron-positron-annihilation is time-reversible."
] |
[
"What is the speed of gravity?"
] | [
false
] | null | [
"Light and gravitational waves both move at the speed of massless particles."
] | [
"Gravitational waves move at the speed of light. You can read about this ",
"here",
" or, for the technical article, ",
"here",
"."
] | [
"Photons and gravitational waves both propagate at the same speed (in a vacuum), that speed being the speed of light"
] |
[
"Why do different animal lifespans vary so much?"
] | [
false
] | [deleted] | [
"There are hundreds of contributing factors to the lifespan of any particular species, but generally the biggest include:"
] | [
"I would argue that stem cell retention is most important (many factors contribute to this). For example rats have a lifespan of 2-3 years while squirrels that are extremely similar to rats in size and metabolic rate can live around 15-20 years. I can not find the link now but it has been shown that tissue specific... | [
"But you don`t have to look far for exceptions to this. Lab mice have much longer telomeres than humans, even at the end of their lives, and their lives are shorter than ours by a longshot. They actually usually die of cancer, which is likely caused in part by their long telomeres. ",
"Senescence may play a role ... |
[
"Do tiny-brained creatures feel emotions like humans do?"
] | [
false
] | For example, if I picked up and relocated an insect, would it feel danger while I relocated it? Or fear once placed in an unfamiliar place? Or loneliness without its colony? | [
"There is no proven answer to this question. We infer animals' state of mind from actions reminiscent of our own, but have no way of verifying that reality. Elephants appear to mourn deaths. Crows and octopuses solve problems to obtain rewards. Fungi find the most efficient path through mazes without anything that ... | [
"Exhibiting danger avoidance isn’t enough to prove emotions, and it is usually just instinctual. Trees will change their direction of growth and even “call for help” from other trees when in unsuitable conditions. If you touch a hot pan and quickly pull away you are not exhibiting a fear response, especially since ... | [
"Well, they can clearly feel fear and danger. That is evident from just watching the little critters scurry. See an ant on the counter? Bang your first on the counter near it and it will run away. That is them interpreting the slam as potential danger and exhibiting fear in the attempt to get away. Likely, these fe... |
[
"Why is the sun made of hydrogen, while the planets are mostly made of other stuff. How come matter was not evenly distributed when the solar system formed?"
] | [
false
] | null | [
"To start... while more types of planet are possible, you have three main classes of planet in the Solar System:",
" These are the rocky ones, i.e. Mercury, Venus, Earth, and Mars. Mercury is an odd case, since its iron content is actually high enough (and its silicate rock content low enough) that some sources... | [
"Our planet (as well at the other rocky planets) do not have sufficient gravity to capture hydrogen and helium. Jupiter and the other gas giants did and thus have a lot of both. What was left over was blown away from the Sun's radiation.",
"Oddly enough there ",
" a lot of hydrogen on Earth, but it's mostly tra... | [
"Great answer! Just to expand a bit, though...",
"The ice giant-gas giant boundary (i.e. where surface gravity is high enough to retain a large hydrogen envelope) is expected to occur between 50 and 70 times the mass of the Earth",
"...this is also going to depend a lot on the temperature of the planet's upper ... |
[
"What makes cast iron a good cookware?"
] | [
false
] | [deleted] | [
"Properly seasoned, cast is non-stick. Its greatest attribute is even distribution of heat. Cast (especially the bigger, heavier pans) need to be pre-heated. They can also be used as baking pans, and some have handles on two sides."
] | [
"I'm personally a fan of cast iron, but I don't see any possible way you can claim it provides the 'best surface' to cook on. PTFE (Teflon) and the related newer materials used to coat 'non-stick' pans are simply better at that. To the extent that it was quite a technical challenge to get it to stick to the the pan... | [
"I should have made it more clear, but I meant taste-wise. I’ve heard that food tastes better when cooked in cast iron rather than non-stick."
] |
[
"How does Hubble's Law affect the size of the visible universe?"
] | [
false
] | I'm only a layman in terms of astrophysics, so I'm sure that my understanding of some of the concepts involved are lacking, but I never was quite satisfied with the explanation that I was given in my astronomy class as to the limits of the size of the visible universe. It makes sense to me that being as the Universe is... | [
"There is a part of space called the observable universe. It is ~93 Billion lightyears across. This is all the light that has managed to reach us. This light is 13.8 billion years old but due to the expansion of space these objects would now be 93 Billion lightyears away from us. Anything further away we can't see ... | [
"Hmm. Well, I see now that I was mistaken about the specific size of the observable Universe as it stands, though not the underlying physical causes of the boundary. I will edit the topic to reflect this. I was simply failing to take into account the past expansion of the Universe's effect on the travel time of lig... | [
"Hubbles law IS the expansion of space. There is no difference between the two. \nWell the cosmic microwave background is just normal EM-radiation redshifted. So light from any other source during that period (I am not aware of any other source) will have the same redshift. \nAnd yes there are objects that are furt... |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.