title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Why do our pupils dilate/constrict when under the influence of CNS depressors and stimulants?"
] | [
false
] | null | [
"Stimulants typically cause a release in norepinephrine, a crucial neurotransmitter that is normally involves in the sympathetic nervous system that mediates the fight or flight response. As part of that response, the pupils dilate to allow more light to hit the retina, hopefully providing a clearer image of whatev... | [
"It isn't all depressants and stimulants. ",
"Pupil dilation is regulated by the nervous system, not the eyes. So it makes sense that some psychoactive drugs will affect pupil size. ",
"The drugs that most powerfully impact pupil size are those that increase activation of the 5-HT2A receptor in the brain. 5-HT2... | [
"Eye is mostly under the influence of parasympathetic nervous system,so if you take a ganglion stimulants this increases the parasympathtic influence(that causes conctriction),if you take a ganglion inhibitors that depresses the already in charge parasympathetic system(that causes dilatation)",
"Sorry for my engl... |
[
"Why is poor ecosystem peat moss used in potting soil?"
] | [
false
] | I've always thought it odd that peat moss harvested from some of the slowest growing ecosystems (bogs, or ancient bogs), is used in potting soils, sometimes at greater then 50% of a mix. Why? | [
"Peat moss is used not because of its nutrient content, but rather for its ability to absorb and retain water. Also because it allows roots to expand into the soil stratum more easily due to the low large pore size/low density of peat."
] | [
"Peat moss adds acidity to soil. Based on species, the plant will thrive or suffer, but most plants love acidity in soil."
] | [
"Thanks. I was under the impression it was mostly due to water retention. "
] |
[
"Backwards galaxy NGC 4622"
] | [
false
] | null | [
"Correct, from the point of view of the image of that galaxy, it would normally rotate counter-clockwise, however it is rotating clockwise. As to how they measure the rotation, unfortunately I'm unsure of that, hopefully a physicist will be able to explain that :) "
] | [
"Correct, from the point of view of the image of that galaxy, it would normally rotate counter-clockwise, however it is rotating clockwise. As to how they measure the rotation, unfortunately I'm unsure of that, hopefully a physicist will be able to explain that :) "
] | [
"if the galaxy not not at a 90° angle with us, we can see with redshift that one half is moving away and the other half moving towards us."
] |
[
"How do we take pictures of our galaxy if we are in our galaxy?"
] | [
false
] | So we have pictures of the Milky way but we are in the Milky Way? Edit:Rip my inbox Thanks for the replies everyone!!! | [
"Assuming you mean plan view, we don't.",
"All images like that described as showing our galaxy are either digitally (or manually) produced images, or images of other galaxies similar to ours.",
"We can see the milky way in our sky, and being on the outer limb of one of the arms we see it as a broad band of sta... | [
"It's more like taking a photo of a landscape, using trigonometry to work out how far away the trees are, then drawing a map to show where the trees are relative to each other. You never need to go and touch the trees; it's all just angles and distances."
] | [
"Oh i get it. It's like taking a selfie of parts of your face and putting them together and photoshopping them and smoothing them out."
] |
[
"Is 95% confidence in a result the same as \"the result is 95% likely to be true\"? Or are confidence and probability different in this aspect?"
] | [
false
] | null | [
"In statistics, there is a very precise notion of a \"confidence interval\". This notion is as counterintuitive as it is unhelpful when it comes to communicating statistics to the lay public.",
"As a result, language involving confidence intervals and % confidence often gets repeated without understanding, and di... | [
"Just to add an example that illustrates the difference between a 95% confidence interval and being 95% certain the something is true, suppose that we want to estimate the average resting heart rate of an athlete. I can construct a 95% confidence interval as follows:",
"Suppose that we flip a coin and get tails -... | [
"There are two viewpoints on this, but neither of them is that the result is 95% likely.",
"In frequentist statistics, the true value of something you are estimating is fixed (albeit unknown) so it doesn't make sense to assign a probability for it to be in a certain range. The 95% means that 95% of the time you m... |
[
"Why does a dog cock its head to the side when confused?"
] | [
false
] | null | [
"I believe it is because it is easier for an animal with ears on each side of its head to localize sounds in a horizontal plane. If there is some mysterious sound they are trying to learn more about, it's hard for them to know how high/low it is without changing the orientation of their head."
] | [
"If you've had a dog for a long time and have regular verbal commands, try speaking those in distorted pronunciations to the dog, it'll cock its head at you."
] | [
"If you've had a dog for a long time and have regular verbal commands, try speaking those in distorted pronunciations to the dog, it'll cock its head at you."
] |
[
"Is there a limit to how fast a black hole can spin?"
] | [
false
] | [deleted] | [
"Yes, there is a limit. The limit of how large its spin can b depends on the mass of the black hole. Its angular momentum J needs to be ≤ M² in suitable units (where M is the mass). If that condition is broken, you get an overextreme Kerr solution (Kerr black holes are rotating ones) which has a naked singularity, ... | [
"Thank you for leading me to discover the “Deep Astronomy” podcast. I have been looking for astronomy and physics based podcasts with content intended for an audience with greater than average knowledge of the topic. I’m no academic but it gets old to constantly hear the sentence “black holes are objects SO MASSIVE... | [
"Thank you. After going down that rabbit hole I've only gained more questions haha. I should have expected this."
] |
[
"Why do fizzy drinks served on planes not fizz everywhere when opened? (Or explode when they get up there?)"
] | [
false
] | null | [
"Cabins are pressurized to prevent health problems that arise from being in high altitudes (many commercial planes fly at 40,000ft). They are pressurized by siphoning some of the air that is compressed in the engine (before ignition). The cabins are pressurized such that the maximum altitude you feel is at most 8,0... | [
"While flying at such a high altitude, it is difficult to make the cabin pressure so high. Also, most people don't experience health problems until 8000 ft or more.",
"Here is the procedure: The plane starts out at the pressure of the airport it takes off from (say, sea level), then it decreases the cabin pressur... | [
"The ",
"SyberJet SJ30",
" can provide sea-level pressure at cruising altitude. It also costs $7.5 million.",
"Planes must be stronger to resist larger pressure gradients. "
] |
[
"How does our circulatory system handle losing a limb?"
] | [
false
] | Edit: thanks everyone for their comments. And someone in the comments pointed out my view of a circulatory system is pretty bad and probably comes from horrible drawings of it in textbooks. Also I now know more about our body so thanks! | [
"Forgive me if I'm wrong but I suspect you are asking this because of a simplified understanding of our circulatory system, thinking that arteries carry blood all the way to the end of our limbs, then the blood is carried all the way back to our heart by veins, and severing this flow means arteries are no longer co... | [
"Follow up question(totally ignorant on the subject). We typically have like 5L of blood in an adult. if you lose a limb(and survive obviously) do you produce less total blood? Makes sense that we would but nice to "
] | [
"The mechanism simplified is all about meeting aerobic metabolic needs. In other words, \"Is enough oxygen being delivered to the cells of your tissues to allow them to function appropriately?\" If not enough oxygen is being delivered to the kidneys they release a hormone called Erythropoietin that starts the pro... |
[
"Why is the symmetry of fundamental forces temperature dependent?"
] | [
false
] | If i understand this right, above a certain temperature there is a symmetry between the electromagnetic and weak nuclear forces, meaning they operate identically and are for all intents and purposes a single force. Now, really this is just a specific example of a larger concept so i guess trying to understand why temperature is even a factor in any symmetry, or "why do symmetries in general break based on temperature?". I'm not sure if specificity is my friend here. I'm just trying to form some sort of intuition so hopefully this doesn't require getting too technical. If i could get some explanation for how these temperature sensitive symmetries relate to Noether's theorem that'd be the cherry on top. I know in a general sense that physical symmetries correlate to specific conservation laws (or the conservation is the expression of the symmetry? I'm not sure what's the correct way to parse this). so does that mean that above the electroweak symmetry temperature there was some property that was conserved that is no longer a conserved property in our colder reality? if so, I'd love to know what it is if it's articulable. on a more general note, any resource that has a concise listing of symmetries and their corresponding conserved properties would be very much appreciated. preferably something neater than some dense dissertation where I'll get lost in the weeds XD | [
"In the vaguest sense, it goes something like this. Consider a potential V(x) = x",
" - x",
". Go ahead and pull up your favourite graphing calculator and plot it. You'll see that it is symmetric with respect to flipping along the y axis, but if you put a marble at zero, it will decay to one of the two wells on... | [
"Maybe this can help motivate it a little bit. The energy for a field has terms which are conventionally called kinetic and potential terms. These terms are called that because the equations look a lot like linear elastic waves in media, and in those continuum mechanics theories, the terms literally represent kinet... | [
"my background is materials science, so i can understand the intuition of overcoming an energetic barrier.but let me take you a step back.why does this logic apply to symmetries in the first place?",
"i can understand a phase breaking down into two different phases when the temperature drops, but this seems a LIT... |
[
"How big would the Sahara desert have been 1000 years ago?"
] | [
false
] | I know Sahara desert had a wet period a few thousand years BCE but didn't manage to find any information about the rate of desertification in recent (so to say) years. | [
"I have been taking a class on Africa and its early peoples. I don't have much to tell you but you should look into the Inter Tropical Convergence Zone (ITCZ). We learned that this line, delineated by the meeting of SW and NE winds across the continent, determines how much and where rain falls. As you can see ",
... | [
"It was smaller. Herodotus records many of the areas as being fertile. Yes, I know Herodotus also described flying snakes and ants that could chase down camels, but it is one of the few sources we have to go off of.",
"It is generally believed that the Sahara was expanded by continuous goat farming in the area.... | [
"A thousand years isn't even halfway to Herodotus' time."
] |
[
"Is it possible for an Asteroid to be composed of Gold or other Precious Metals?"
] | [
false
] | To my understanding, Asteroids are usually iron/nickel, but is it possible for asteroids to be composed of less heavy metals? | [
"statistically, yes. there is so many asteroids that one of them is bound to be made of gold",
"That's not how statistics work. ",
"Do you have a source or anything to back up your claim?"
] | [
"If you mean only gold or nickel, no. Iron asteroids, which probably represent the cores of small parent bodies will have enhanced amounts of elements that follow iron into the core as it forms (",
"siderophile elements",
"). These include Ni, Co, the ",
"PGEs",
", and Au. Gold in iron meteorites (samples f... | [
"if you take a regular quarter, and flip it a million times, it is bound to to land on tails once",
"No. That's not how statistics work. There is a non-zero chance of flipping only heads. ",
"Also, even if statistics did work that way, it wouldn't be relevant: the analogy is completely inaccurate. The compositi... |
[
"Question about dark matter, dark energy and unseen dimensions for reddit physicists and cosmologists"
] | [
false
] | Background: Roughly 5% of our universe is directly observable, another 23% is made of dark matter and a whopping 72% is composed of dark energy (percentages are approximate). We can indirectly measure the effects of dark matter - the gravity it exerts bends light and we measure the resulting distortion. We can't measure dark energy but infer its existence by the accelerating expansion of our universe. Also extra (unseen) dimensions are required for String Theory to work. The most promising version of String Theory (M Theory) requires 11 dimensions total, of which only 4 we can observe. Some would argue whether String Theory and M Theory are really theories since they haven't predicted anything and are not testable yet. However since M Theory appears to be the best candidate to explain quantum behavior and gravity in a unified theory, let's assume for the moment M Theory is correct. Question: If these theories are correct, we have 95% of the universe that we can't directly measure and 7 dimensions that we can't observe. Is there a connection here? Is some or all of this unobservable matter and energy possibly tied up in the unseen dimensions of M Theory? I could be way off base here but curious nonetheless. | [
"Observational cosmologist/astrophysicist here. ",
"There is no mathematical reason that dark energy and the extra dimensions of string theory would be connected. The dimensions of string theory are confined to the smallest scales, whereas dark energy only exerts its influence on the largest scales.",
"There is... | [
"Thank you for that explanation. Another response from an expert - two for two today.",
"Follow up question to your statement that we can measure dark energy. How is that done? Is the estimate based on the acceleration of the universe's expansion or some other method? "
] | [
"First of all we should separate the idea of extra dimensions and string theory. Certainly string theory popularized the idea, but if we find extra dimensions it in no way means that string theory has been validated. ",
"The most popular theory for dark energy in extra dimensions was put forth by ",
"Greene and... |
[
"Light speed and time travel."
] | [
false
] | I understand the concept that the faster you travel the slower your personal time travels relative to someone who is stationary. However take the following scenario. I get into a rocket ship and travel to Alpha Centauri and back (8.6 light years round trip). If i complete the trip traveling at 99.99% the speed of light does it still feel like it took 8.6 years to me and 600 or so years for earth or does it feel like a couple of minutes to me and 8.6 years for earth? | [
"from the Earth's reference frame, your trip takes 8 years and 7 months. From the reference frame of the ship, it takes just over 44 days to complete your trip."
] | [
"How do you calculate this?"
] | [
"To figure out the time as measured on Earth, take the distance as measured by Earth and divide it by the speed as measured on Earth. Since the ship is going at 99.99% the speed of light for an 8.6 light-year trip, it should take just about 8.6 years.",
"To figure out the time on the ship, multiply that number by... |
[
"What would happen to the Earth if the sun suddenly went out?"
] | [
false
] | null | [
"That really depends what you mean by \"went out\". Do you mean completely disappear or fusion stopped?",
"Either way, we wouldn't notice anything until a little over 8 minutes after it happened. ",
"If fusion stopped and the solar mass still exists, all the radiation expended by the fusion would cease. Sunligh... | [
"As far as the temperature, I could only speculate. ",
"Here",
" is an article that seems to be backed by research that might help answer that. ",
"As for what could cause fusion to stop? Once a thermonuclear fusion reaction starts, the only way to really stop it is to cool it enough to prevent further fusion... | [
"Thank you! What would we expect the temperatures to drop to on Earth, without a Sun? Also, what kind of things could cause the fusion to stop?"
] |
[
"If the universe is expanding, why do the stars look like fixed objects in the sky?"
] | [
false
] | Are we just not capable of seeing their movement relative to each other? It just seems to follow that if something is expanding, its visible dimensions have to be changing. Yet the night sky looks completely and utterly static apart from planets and meteoroids. Similarly, if the solar system was created earlier/closer to the origin of the Big Bang, would the expansion be apparent to the naked eye? | [
"Their movement relative to one another (due to intragalactic dynamics, not cosmological expansion) occurs over thousands of years, so people can't notice it in their lifetimes. If you look in a telescope at multiple-star systems, then you can see them moving."
] | [
"As iorgfeflkd said, that motion is \"due to intragalactic dynamics, not cosmological expansion\". Cosmological expansion is an effect that occurs only between very, very distant objects. It simply isn't the case that expansion is causing the stars in our galaxy to move away from us."
] | [
"Lots of things in this.",
"Human eyes can't see movement of the stars on human timescales because they're too far away. Telescopes can see movement. For example, ",
"this",
" is a list of stars that have high proper motions (or motion in the plane of the sky, as in, not coming towards us or away from us). ... |
[
"How do two interfering EM waves conserve energy in all cases?"
] | [
false
] | Intro below, question in bold at the bottom. Hey guys! I'm a molecular electronics PhD student at Leiden university, and before that did a nanoscience MSc at Groningen university. I've asked this question to my fellow students and also some postdocs and professors. We have not yet found a satisfactory answer. The problem is a gedankenexperiment where two laser beams or more specifically: two electromagnetic waves meet each other and interfere perfectly destructively or constructively. So we have two (for example) laser beams that cross paths. Now, each laser sends out an oscillating electromagnetic field with a certain power (say 100 watts). We set up the system in such a way that they interfere constructively completely. When the two beams cross and in, we can add the beams vectorially and end up with an EM-field with twice the amplitude. Since the energy density of an EM-field goes with the amplitude squared, we suddenly have four times the output power. Now, I know that this cannot be. We could simply use quantum mechanics and say: well, we just have twice the amount of photons now, and photons do not interfere with each-other, only with themselves. Therefore, you just have twice the power, not four times. However, this answer sounds unsatisfactory to me. I think that the answer should be simpler and should not require quantum mechanics, or anything other than the laws of Maxwell. Furthermore, I'm not interested in answers along the lines of: "Well, you can never make a laser like that, since the laser linewidth is never infinitely sharp". I think that the solution should not be practical one, but a principle one. I have looked at thread. However, the answers here are among the lines of: well, the intensity goes somewhere else. So that means that whatever interferes destructively somewhere, should interfere constructively somewhere else. This sounds like the most valid answer, but I don't see how this is a fundamental and not a practical issue. For example: we could take a laser beam with a width of half the wavelength (I now this is not practical, but I don't see why we cannot do this fundamentally), and at 90 degrees cross another identical laser beam, so that they interfere constructively. Twice the field amplitude, four times the power. We could also interfere destructively and end up with no power. | [
"You have the answer on your hand, you're just dismissing it on no basis. The answer is actually really on point because the issues you claim are purely \"practical\" are actually consequences of Maxwell's equations, the equations of motion for the EM field, which are absolutely fundamental. In fact, conservation o... | [
"Below is an answer I've previously posted on the subject to provide a bit of background for others who might come across this thread. The answer to your question, OP, is closer to the bottom of this post, but you may find some insight in what's below as well",
"When doing anything related to interferometry, you... | [
"You certainly can. But you can't cause just ",
" interference pattern with laser beams-- i.e., ones that don't conserve energy. EM waves are governed by Maxwell's equations, and those equations are ",
" intimately linked to fundamental principles."
] |
[
"What makes fish smell like fish?"
] | [
false
] | Also why do fish that smell like fish smell different than shellfish who also smell like fish? | [
"The smell of fish is caused by ",
"amines",
" produced by decay. Fresh fish has no odor, the natural revulsion to fish smell is due to its indication of decay. The majority of the odor comes from cadaverine, which produces a general odor of death and rot, while trimethylamine provides the extra \"edge\" of the... | [
"Exactly correct. This is why it is common to squeeze lemon juice onto fish. The citric acid in lemon juice protonates the amines to produce ammonium salts. Ammonium salts aren't volatile and thus the fish will have a less \"fishy smell\" after the lemon juice is added. And as a bonus, lemon juice is tasty. "
] | [
"Damn...I've been studying chemistry for 3 years and never realized that, I always assumed it was just for flavour"
] |
[
"Can something be in a superposition between existing and not existing?"
] | [
false
] | [deleted] | [
"That can surely happen, but the correct way to phrase it is that there is a bigger system which has states where your object does not exist and states where it does, and this bigger system is in a superposition of two states from these classes.",
"For example, the (quantum) electromagnetic field can be in a supe... | [
"It wouldn't. If you measured it you'd observe EITHER state 1 or state 2, NOT a still-excited atom and an emitted photon. The two states have the same total energy; there is zero probability of finding the system in the atom-still-excited-and-photon-emitted-state."
] | [
"Observing the system.",
"Some might tell you that it entails some kind of 'wave function collapse', but it would be more accurate to say that the two quantum systems - the observed system and the observer or measurement apparatus him-/her-/itself - become coupled. This coupling of a quantum system with its envir... |
[
"Can a planet sustain life without a hot core? What would happen if the earth's core suddenly produced no heat?"
] | [
false
] | null | [
"Howdy! I've removed your post for its open-ended and speculative nature. I can redirect you towards ",
"/r/AskScienceDiscussion",
" which better suits such posts."
] | [
"How would you recommend I rephrase it, to be acceptable? Or is such a question not suited to this sub?"
] | [
"The first question is alright on its own, but it'd be better to rephrase it more like, \"What ecological roles does the Earth's core play?\"",
"The second question can't be helped. The only way would be to rephrase it more along the lines of asking what happened to Mars when it's core cooled--to which I suggest ... |
[
"Since the honeybee is an foreign species in North America, would it really be that bad for NA if all honeybees died out?"
] | [
false
] | Since honeybees are technically an invasive species, would it have much impact? How did pollination work before bees in the Americas? | [
"Bees aren't the only pollinators; before european bees were introduced in 1600, other pollinators played a central role.",
"But you can't feed the US of today with the technology of 1600s. Crops that depend on pollination by bees today include apples, avocados, onions, oranges, pears, and pumpkins.",
"Eliminat... | [
"The problem is that WE are an invasive species, too. And, we have a bunch of crops that we use to survive that need pollinating. And, the native bees are just not as good at it as the invasive honey bees we use.",
"Essentially, native bees would not pick up the slack if all our honeybees died off."
] | [
"I might add....",
"The crops that Native Americans used for most of their food were corn (wind pollinated) and squash (self pollinated) and various berries that are good for native bees to pollinate. "
] |
[
"Andromeda is the closest galaxy to the Milky Way but is the Milky Way the closest galaxy to Andromeda?"
] | [
false
] | null | [
"The Local Group basically consists of two large galaxies - the Milky Way and Andromeda - each with their own systems of dwarf galaxies orbiting around them. There are also a few other small galaxies floating around. Then there's quite a lot of open space around the Local Group with very few \"field\" galaxies, unt... | [
"M33/Triangulum is \"another small galaxy floating around\" :P",
"It's closer in mass to the Large Magellanic Cloud (M33 is ~5x bigger) than to the Milky Way or Andromeda (M33 is ~20x smaller than either)."
] | [
"Why no love for Triangulum?",
"I know it's smaller than the Milky Way and Andromeda, but it's definitely a full-on spiral galaxy player when it comes to the Local Group."
] |
[
"Why is my current cold \"a cold in the nose\", whilst others are \"in the head/chest/throat\"? Is the infection localised there, or is it that different cold viruses exhibit different symptoms?"
] | [
false
] | null | [
"There are certainly countless different viral strains, whose infectivity may range from asymptomatic to severe. Especially with the common cold. It also mutates all the time so new \"mixes\" of different phenotypes are always transpiring around you.",
"The infection might very well be more localized, but most li... | [
"Rhinoviruses aren't the only virus that causes colds. Coronaviruses, adenoviruses, and among children sometimes respiratory syncytial virus and parainfluenza look like colds. Heck, Epstein-Barr (which causes mononucleosis) looks like a cold among younger children. Most of the cold symptoms aren't actually viral sy... | [
"Excellent response. Thank you."
] |
[
"How can a virus cause a person to Vomit?"
] | [
false
] | null | [
"Well, for example ",
"norovirus",
" attacks the lining of the stomach and small intestine, causing an immune response (inflammation). Vomiting is a natural defense mechanism when the stomach lining is irritated, as it indicates a problem and getting the substance that's causing the problem out of the body is ... | [
"This is the correct answer. In most cases vomiting and diarrhea are caused by our own body trying to get rid of a pathogen, although some viruses like Polio will hijack this response in order to spread."
] | [
"Also it's not so much the virus that is causing you to throw up but rather those are symptoms your body has in response to trying to get rid of it. In the same manner of having a cough or stuffed nose your body is causing these to occur in order to rid of the virus."
] |
[
"Why aren't there \"snow thunderstorms?\""
] | [
false
] | We all know about rain thunderstorms, but I don't ever remember experiencing a snow thunderstorm. Do they not exist? If so, why? | [
"They exist, they're just rare. Thunderstorms are typically driven by a temperature differential between two bodies of air. The cold air in winter typically doesn't produce the right conditions for a thunderstorm, but it can happen occasionally. ",
"https://en.m.wikipedia.org/wiki/Thundersnow#Formation"
] | [
"It's a once in a lifetime thing, we had a thunder snow storm in Vermont a few years ago and it was kind of a big deal"
] | [
"Drove through one last week near Cleveland. It was really cool except for the blinding lake effect snow"
] |
[
"Is is possible to tan through a (glass) window?"
] | [
false
] | I've been debating with my father whether it is possible to get a sunburn, or tan in general through a window or if direct sunlight is required? Similar with a car window? | [
"\"Ultraviolet light, which causes both erythema (sunburn) and tanning, ranges in wavelength from 4,000 angstrom units (A) down to about 100 A. (Light with wavelength greater than 4,000 A lies in the visible spectrum.) The most potent rays for burning and tanning lie in the 2,900-3,050-A range, with radiation of 2,... | [
"Ordinary window glass, however, is pretty much opaque to wavelengths below 3,000 A.",
"Then why do printed materials in a video rental store fade especially near the window? Are there just enough UV rays to fade the inks, but not enough to tan? ",
"I work for a printer and we add an anti-UV coating to material... | [
"No, you can just end up looking like ",
"this guy",
"."
] |
[
"How is it possible that the strong coupling constant is greater than 1?"
] | [
false
] | I can't wrap my mind around this at all. Basically for strong interactions, the more complex the interaction, the more likely it is to happen. But you can always make an interaction more complex by adding more propagators which make it more likely to happen. Doesn't this make an average strong interaction an infinite order interaction? Does is max out eventually and the probability starts to decrease? | [
"Doesn't this make an average strong interaction an infinite order interaction?",
"When the strong coupling constant is large, the assumption that you can treat interactions perturbatively breaks down. That's why when you expand in a power series in the coupling constant, you reach this conclusion.",
"Using the... | [
"Generally when you are doing perturbation theory you assume higher order terms are smaller than lower order terms. If coupling is strong this is not the case and perturbation theory is typically no longer useful. "
] | [
"While the coupling constant of a quantum field theory is smaller than one, it means you're in the semiclassical (or perturbative) regime. Sure, the theory ",
" quantum, and the quantum effects ",
" matter, but you can still describe the system as \"basic classical system plus quantum corrections.\" How many co... |
[
"What causes sleep paralysis? And why do some people see demons when they experience sleep paralysis?"
] | [
false
] | I spoke to someone this happens to frequently, not the demons, but sleep paralysis. I just curious to how it works. | [
"I have it frequently. The brain \"shuts of\" certain muscles when you sleep so you wont move around when youre dreaming and the brain sometimes shut them of too late. "
] | [
"Freaky!"
] | [
"I have it as well, and I really don't care for it at all. Not because it scares me, because I can instantly tell what it is, but because I could imagine it happening during an emergency (fire, robbery) and not being able to respond. I wonder if there has ever been a study linking sleep paralysis with sleep apnea/o... |
[
"Hey askscience, r/trees needs your help."
] | [
false
] | null | [
"Heating aluminum and inhaling isn't harmful to your lungs in and of itself. A lighter doesn't get aluminum hot enough to vaporize or oxidize which would be necessary in order for it to be inhaled. Your oven, for instance, gets hotter than your smoking device would, and there's no harm in using an aluminum baking p... | [
"Your oven, for instance, gets hotter than your smoking device would",
"I'm not sure I've understood you correctly here. A candle flame is around ~1200C and the melting point of Al is ~650C. No domestic oven I know can reach 650C let alone 1200C"
] | [
"It's found in many ",
", but nowadays most deodorants contain antiperspirants so the distinction doesn't really matter.",
"http://en.wikipedia.org/wiki/Aluminum_zirconium_tetrachlorohydrex_gly"
] |
[
"Can someone explain Maxwell's Equations?"
] | [
false
] | Reference Image: I am interested in the Integral form specifically. Can someone explain what each equation means, and how it can be used/applied? Bonus Question: I can't for the life of me figure out what ds represents | [
"The first equation is an expression of Gauss' Law and states that the integral of the electric field over a closed surface (specifically the component of the field normal to the surface) is proportional to the charge enclosed by that surface. This law can be used to, among other things, derive the inverse-square-l... | [
"That's the final two, yes. The first two state the essential nature of electricity and magnetism, respectively. The first states that closed systems with an electrical charge have a field that is related to that charge. Conversely, magnetic fields in a closed system always balance (think north and south poles), wi... | [
"And..in super simple terms..",
"A changing magnetic field makes an electric field",
"A changing electric field makes a magnetic field",
"This can be self-sustaining, resulting in electromagnetic waves like light"
] |
[
"When there is a momentum transfer between two charged particles (via a virtual particle) is that transfer instantaneous?"
] | [
false
] | So if particle A emits a virtual photon that interacts with particle B, is the transfer of momentum from A to B instant, or does it take time for the information about the interaction to reach particle A? | [
"It doesn't make sense to talk about \"emitting\" and \"receiving\" virtual particles. ",
"The process is not instantaneous, the particles interact for some finite time just like in classical mechanics."
] | [
"The other thread is quite correct, but I get the feeling OP might still be a little confused.",
"Here is a slightly broader picture.",
"When you begin talking about virtual particles being able to carry momentum by themselves and transfer it from one particle to another, there tends to be quite a lot of confus... | [
"That doesn't make any statement about the time.",
"And you could equally say the other particle emitted it, gaining momentum p, while the first one absorbed it, losing momentum p. It is literally the same process. It is meaningless which direction you use in English, in the equations there is no such direction."... |
[
"If people sweat to cool down during physical activity, then is it best to leave the sweat alone when you're working out instead of drying off with a towel periodically?"
] | [
false
] | When I'm running I sometimes use a towel to dry off my arms, neck, etc. Does this raise my body temperature? Should I just leave the sweat alone? | [
"Well first and foremost, it matters where you are running. If you're on a treadmill with no wind, your sweat -once it has been perspired - won't be doing a great deal help in terms of thermoregulation. Get rid of it.",
"You should know, however, that sweat cools in two ways. The most well known and noticeable is... | [
"The towel does absorb most of the sweat, but also distributes a fine layer or moisture across your skin and hairs. Combined, this causes more evaporation close to the skin, and the loss of heat due to evaporation is not lost on cooling down sweat drops."
] | [
"In theory, yes, leaving the sweat will help maintain lower body temps. However, I have no idea how significant (i.e., what temperature difference) the effect would be."
] |
[
"When I cut something, what is happening to it at a small scale? Atomic/molocule level?"
] | [
false
] | When i was cutting up chicken today I got thinking about what was actually happening between my knife and the chicken at the smallest scale? | [
"Molecular physics/engineering PhD here. Most of the comments here have unfortunately been, I believe, a little misleading. ",
"When you cut something, in general, you are ",
" melting it. A scientist will describe you as \"applying stress\" to the material. Imagine breaking a twig with your fingers. You're not... | [
"You're right, it's basically all about introducing enough strain (by applying stress) to force the bonds to break. ",
"Certain cutting techniques may actually result in enough local heat transfer to melt a very small volume of material around the cut. In general though, you're not melting paper when you cut it w... | [
"Technically, scissors shear; they don't cut.",
"Edit: from below",
"There is a difference. Cutting is applying pressure along a thin line, shearing is applying pressure from two sides along adjacent thin lines.",
"The resultant separations look different."
] |
[
"Is dark matter just an invention by scientists to support existing \"knowledge\" of physics? Are there more mysteries that support the idea that scientists have done some false adoption earlier and now we accept it as a law of physics resulting in such terms as \"dark materia\" and \"dark energy?"
] | [
false
] | The whole concept of dark matter sounds really strange to me. I mean, it sounds like we make up a name for things we cannot find or even for sure know exists. Could it that there is some major error hidden behind all of our laws we follow in physics? Also interested in hearing about unsolved mysteries in physics like the 'Pioneer anomaly'. Ironically, this whole dark matter issue, seem similar to explaining the unexplainable by believing in God, making up stuff. Also want to thank all of the people answering the questions to the less informed here on , easily my fav subreddit! | [
"Whenever your observations of the Universe disagree with your predictions, there are two possibilities: either your equations are wrong, or the stuff you've put into the equations are wrong. Dark matter postulates the latter, that we got incorrect answers for things like galactic rotation rates because we assumed ... | [
"The wikipedia article",
" on dark matter should give you some idea of the evidence supporting dark matter. All of these issues can be explained by there being mass which we simply cannot see. 'Dark Matter' fits all of the available evidence, even if we haven't detected it directly yet. It's not really 'making up... | [
"To put it simply (and I'm probably repeating what adamsolomon has already said), when the rotation of galaxies doesn't match the predictions of orbital mechanics, either the orbital mechanics theories are wrong, or our knowledge of what galaxies are made of is wrong. Orbital mechanics can be tested very accurately... |
[
"Is there a way of diagnozing Schizophrenia without ever talking to the patient?"
] | [
false
] | Neuro connectivity is affected but is there a specific part of the brain activity that can be measured to show symptoms of schizophrenia or is it strictly diagnozed after talking to a patient. | [
"It's still a clinical diagnosis. That is to say, other tests are useful for ruling out other causes, but talking to the patient (plus other sources of practical information, especially family and close contacts) is at the core. Remember that schizophrenia is a chronic condition by definition, and evaluating someon... | [
"To expand on the use of medical imaging:",
"MRI scans of the brain are generally unable to diagnose mental illnesses, be they psychological like schizophrenia or depression, or more clearly degenerative like Parkinson's or dementia. Physicians will order a head MRI mostly to rule out other things that might pre... | [
"a clear neural signature of schizophrenia would be kind of like a holy grail of schizophrenia research, because it would mean that we have the beginnings of a clear neurophysiological explanation for the disorder. and to put it simply, we do not have that. not at all."
] |
[
"Does the lagging Strand of DNA code for something else?"
] | [
false
] | So in DNA A=T C=G. So a strand running 5'-3' that is AATGACTG would be attached to a 3'-5' strand going TTACTGAC. ATTGACTG would could for a different protein pattern than its opposite strand (flipped to 5'-3') of CAGTCATT. Some my question is does the opposite strand even code for the same information as the other side? Is the entire DNA strand a palindrome so that as long as you read 5'-3' the results will always be the same? Is there some other mechanism involved? | [
"Genes are encoded on both strands of DNA - there are both sense and antisense transcripts. We wouldn't usually call it the lagging strand - that is a term referring to the mechanism of DNA replication.",
"Some areas of the genome have sense and antisense transcripts right on top of each other; so the same sequen... | [
"So if i am understanding correctly the opposite side varies. Sometimes it codes for nothing, sometimes a whole other protein, and sometimes its structural shape just influences gene expression of the first side.",
"Would it be wrong to think that introns connect to this in any way?"
] | [
"As ",
"/u/rastolo",
" mentioned, the leading and lagging strand simply refer to the directionality of replication. However, during translation, either strand may contain the template sequence for synthesizing the various RNAs (this is the template strand). The opposite side of the strand (the coding strand) wi... |
[
"Is it possible to have one eye color blind and the other one not?"
] | [
false
] | null | [
"For most common (i.e. genetic) forms of colorblindness, no. However, if you have some degenerative disorder that specifically affects one eye or optic nerve, then you can selectively impair color processing in that eye. ",
"Also, you could be colorblind in one hemifield (left or right visual field) if colorblind... | [
"I just wanted to add that genetic conditions such as mosaicism and chimerism should also be able to result in colorblindness in one eye only.",
"I also want to add, as ",
"/u/albasri",
" alluded to, that it's not as straightforward as 'left eye sees the left and right eye sees the right'. Each eye has a left... | [
"The body isn't symmetrical, and while certain portions of the body are created at different times, some parts are actually created in unison. Both eyes are formed at the same time, now in the situation we have damaged genetic material governing the growth of a fetus's eyes (or one eye) in the womb, said Fetus coul... |
[
"Could we tell a message is maximily encrypted from random?"
] | [
false
] | null | [
"No, and a simple thought experiment can show why. But first, a bit of explanation on how we're going to treat the concept of \"maximally encrypted\".",
"The most secure encryption method available is known as a One Time Pad (OTP). In an OTP, you have two parts -- a message you want to convey, and a one-time, p... | [
"To be clear, otp is the \"best\" algorithm that exists for our weakest notion of symmetric encryption security, IND-EAV. In the real world we want better security such as AEAD, which OTP cannot achieve on its own."
] | [
"Thanks for this detailed answer. I had the intuition only."
] |
[
"What is the density of the Carina Nebula?"
] | [
false
] | In a James Webb photo thread, someone posted that the Carina Nebula has a density of a few atoms per cubic meter. This seems off to me, as this is close to the average density of the intergalactic medium of one atom per cubic meter, which is much less than the interstellar medium average density of one atom per cubic centimeter, which is much less than the average density of a planetary nebular (100-10,000 atoms per cubic centimeter). But I can't find any information on the web to help me understand this better. | [
"Variable, but I think in line with or higher than your planetary nebula figure:",
"I did a search for NGC 3324 column densities, and this was an early hit: ",
"https://academic.oup.com/mnras/article/456/3/2406/1089538?login=false",
"The gas column density has values in the range from 6.3 × 10",
" to 1.4 × ... | [
"Glad it helped. You can \"just\" divide them by a reasonable depth to get from number per square cm to number per cubic cm. But barring something like this situation where 1 or 2 sig figs is fine, figuring out the depth is rather hard. And, like, I'm ignoring that it'll vary depending on where in the cloud."
] | [
"Ah, thanks for that. I saw those gas column density numbers but could not begin to make sense of how those numbers convert to a cubic density volume."
] |
[
"Do cross-eyed people see the world in double and learn to operate that way? Or does their brain learn to process the image correctly?"
] | [
false
] | I assume it's the latter because I doubt anyone's eyes are 100% straight/aligned, but in that case - when a baby is born cross-eyed, do they already know how to correctly interpret images, or do their neurons have to learn? | [
"The first several years of a childs life is when the neurons are learning how to work properly. If it is severe enough, the child will essentially block out the image from one eye. They will see single, but it will be monocular. If it isn't fixed early enough in development, the eye that is ignored will never be a... | [
"The above is correct (see link at bottom of post). To expand a bit, crossed eyes (or more accurately, any mis-alignment of the eyes) is called strabismus. Strabismus not discovered early enough in a child's life can lead to amblyopia, where one of the eye's signals to the brain will not be processed properly, es... | [
"Yes the brain is amazing that way. If a child has crossed eyes, they will see double in the beginning but the brain will try to correct this in several ways. Usually, one eye's signals to the brain will get suppressed, so that they only see from a single eye. They also move their head and body in certain ways to g... |
[
"If the symptoms of flu(fever, coughing) are from the immune response, rather than the virus. Why don't we get flu like symptoms after a flu vaccine?"
] | [
false
] | null | [
"Those that are applied by injection are inactivated flu viruses, so they don't have the ability to actually infect cells. They serve as a \"sample\" for the immune system to develop defenses against the pathogen. So, symptoms-wise, you may develop fever, headaches, fatigue, etc ",
" but nothing specifically in t... | [
"That's why I HATE it when someone says they won't get the vaccine because last time they got the flu shot they got the flu. No you didn't. Well, you might have gotten a different strain than what you got vaccinated for, but the actual vaccine didn't give you the flu!"
] | [
"They may have also just actually been unlucky and contracted influenza during the latency period (usually a couple of weeks) between when they got the vaccine and when it actually became effective. ",
"In any case, I agree - still not a reason to not get the flu shot!"
] |
[
"What IS a flame?"
] | [
false
] | I understand that fire/flame is a relese of chemical energy through an exothermic reaction, but what IS the flame itself? WHAT is it made from? In researching it, all I can find is explanations of how they occur and what causes a flame, but not its actual make up. Can anyone help? | [
"what is fire?"
] | [
"Have a look at previous discussions ",
"here",
"."
] | [
"thank you very much!"
] |
[
"Does surgery leave any air bubbles inside the body?"
] | [
false
] | I was wondering, when they open the body and sew it back together, how do they get rid of the air that would be introduced inside the body? If they can't remove it, does that pose any risk to the health of the person? | [
"Yes surgery regularly leave air bubbles, and that is perfectly safe. ",
"Regular room air usually takes about a week to dissolve back into the blood, while gas from laparoscopic procedures which is CO2 dissolves a lot faster usually disappearing after 48 hours or so.",
"That is why people who have abdominal su... | [
"Yup. It is a referred pain from the phrenic nerve crossing over at the cervical plexus to supraclavicular nerve to the shoulder. It's more commonly termed as the Kehr's sign."
] | [
"Is that referred pain?"
] |
[
"How does an egg (reptile, chicken, etc.) embryo develop?"
] | [
false
] | I understand that during pregnancy in humans, the fetus receives nutrients through the umbilical cord and this helps sustain them. In an egg, how does this work? Is the embryo strong enough to 'eat' parts of the yolk and gain nutrients from that? Or does it absorb them some other way? | [
"The yolk of the egg is essentially the embryo, the albumen (white bit) contains the sustenance the embryo needs during development up until hatching. As far as the method of \"eating\" the albumen i would assume it gains sustenance from it via absorbing the proteins present until it has developed a mouth and dige... | [
"You might enjoy this ",
"video",
". Basically, it all comes down to ",
"blood vessels",
". A network of blood vessels branches out through the yolk, circling around the ",
"germinal disk",
". The nutrients within the yolk and albumen travel to the rest of the body via the blood vessels. "
] | [
"This answered my question perfectly, thank you so much!"
] |
[
"Can a password be complex enough to be future-proof?"
] | [
false
] | If I wanted to choose a password that nobody could ever break, how big must my haystack (search space) be? Is this at all possible? I would assume that there must be some kind of physical limit related to the amount of computation the universe itself can perform in its life, but is there a smaller limit? For example, the search space size of one of my passwords is approximately 2×10 and, according to it would take "6.29 billion trillion centuries" for a massive cracking array to crack it. But that assumes current technology. If I can't make my password future-proof, when would this password become easily crackable (e.g., in one day), given current trends? | [
"while one may disagree with Schneier on a principle, I guess, he made a point in one of his books:",
"https://www.schneier.com/blog/archives/2009/09/the_doghouse_cr.html",
"One of the consequences of the second law of thermodynamics is that a certain amount of energy is necessary to represent information. To r... | [
"Couple points:",
"First, your password is likely stored hashed. That is instead of recording ",
"P@$$W0Rd!",
" in the database they store in the db ",
"ef890b$f919b1dabb6d3c196b1e631dad4b209ad15c85a7d0824fcfedc91ce7762d3136",
" (where ",
"ef890b$",
" is a random salt). That is they store ",
"salt... | [
"You should note all the exponentiation was lost above quote.",
"One of the consequences of the second law of thermodynamics is that a certain amount of energy is necessary to represent information. To record a single bit by changing the state of a system requires an amount of energy no less than kT, where T is t... |
[
"Is tooth erosion an irreversible process?"
] | [
false
] | null | [
"I actually got so happy when I saw this post haha. So I am currently doing research that involves answering your question. In short, no, tooth erosion is not necessarily irreversible. What I am currently working on is exploring how our own DNA can template hydroxyapatite mineralization. A few years ago, my team ca... | [
"Nothing active and available as far as I know, but according to the article, it may be coming soon. Basically filling the decayed area with an alzheimer's drug seems to regrow teeth. ",
"http://www.dailymail.co.uk/health/article-4101996/Could-end-fillings-Scientists-create-method-regrow-teeth-using-Alzheimer-s-d... | [
"First of all, erosion is very different than caries or abrasion.",
"By erosion we're referencing the damage tissue suffers after being repeatedly exposed to chemical substances. In terms of enamel; The remineralization process somewhat handles erosion within specific parameters, that is to say, the combination o... |
[
"In Japan, it is common for people with cold infections to wear surgical masks in public. Does this affect the rate of infection in Japan? If so, why does no government elsewhere promote them?"
] | [
false
] | null | [
"A 2008 study published in the International Journal of Infectious Disease concluded that when used correctly, masks are highly effective in preventing the spread of infections. Family members of children with flu-like illnesses who used the masks properly were 80 percent less likely to be diagnosed with the illnes... | [
"Actually, many of the masks in Europe and Asia now have antimicrobial coating on them that release toxic O3 when exposed to light. The O3 only travels a few micro meters from the surface to kill germs and not you. It's very effective, even against tough germs such as MRSA. It's currently being evaluated by the FDA... | [
"It's hard to say because it doesn't just stop with the masks. Japanese are taught to gargle and wash their hands EVERY time they come in from outside, in addition to wearing masks when they get sick or want to prevent illness when a flu or going around.\nIt's said that this behavior accounts for the low rate of SA... |
[
"If an airplane acts as a Faraday Cage, why can we still use 4G and GPS reasonably well inside (at low altitudes)?"
] | [
false
] | null | [
"An airplane has windows which are large enough the 4G radio wave energy can pass through without being attenuated 'much'.",
"",
"Two things.",
"",
"Radio's can work 'fine' with extremely attenuated signals. In the big scheme of things being inside an airplane with windows doesn't effect the signal very m... | [
"In order to act as a Faraday cage, any openings in the conductive material must be no larger than a fraction of the wavelength of interest (I think it's 1/2). GPS and cell phones operate at frequencies that have a wavelength on the order of 12cm or less, so they easily penetrate the windows."
] | [
"Cell phone repeaters were introduced in 2004. When you make a call from your phone on board an aircraft you're connecting to the on-board repeater. Prior to 2004 calls from aircraft above 10k feet was impossible."
] |
[
"AskScience AMA Series: We're Rob Dagle, Bob Wegeng, and Richard Zheng - experts in extracting low carbon hydrogen from natural gas from the Pacific Northwest National Laboratory and STARS, LLC. We're here to answer your questions. AUA!"
] | [
false
] | Hi Reddit, tomorrow is National Hydrogen and Fuel Cell Day, and we hope you'll have a gas! Hydrogen and fuel cells are the perfect partners for clean, fuel-efficient transportation and a secure energy future. Here at Pacific Northwest National Laboratory (PNNL), we have expertise in creating low carbon hydrogen from natural gas, and we have two projects we want to discuss with you. The first is Solar Thermochemical Advanced Reactor System-or STARS, a technology that converts a record-setting 70 percent of solar energy into chemical energy, such as hydrogen. STARS uses thermal energy from the sun to break down natural gas and water into hydrogen and carbon dioxide in a steam methane reforming process. PNNL licensed STARS to a spin-off company, STARS, LLC, who is working with Southern California Gas Company to implement the technology. Read about STARS here: . The second project uses a low-emission process to convert natural gas to hydrogen, carbon fiber, and carbon nanotubes. The process creates hydrogen that can be used in fuel cell vehicles and industrial processes, as well as carbon fiber that can be used in applications from medical devices and aerospace structures to building products. The goal of the project is to make hydrogen-fueled cars and trucks cost-competitive with conventional gasoline and diesel vehicles. In addition, this technology would virtually eliminate CO2 emissions from the methane-to-hydrogen process. The technology development and commercialization team includes PNNL; West Virginia University; Southern California Gas Company; and C4-MCP, a Santa Monica-based start-up company. Read more about project here: . We invite you to look over the information in these links, and we will be back at 11-1 PDT (2-4 ET, UT) to answer your questions. | [
"On STARS, ",
"How is the 70% efficiency noted in the article defined, and what's the overall energy balance? If we think of the solar input as \"free\" and the methane as the input energy, what is the efficiency in producing hydrogen, and how does that change if we also consider the chemical energy stored in th... | [
"Why is STARS creating hydrogen and carbon dioxide from water and natural gas rather than just hydrogen and oxygen from water ? I would assume that when you want to create a clean energy source you would want to avoid carbon dioxide completely ?"
] | [
"On the carbon fiber process,",
"CO2 emissions are said to be virtually eliminated. I'm excited to have them significantly reduced at all, so virtually eliminated sounds great, but it is also vague. I appreciate that there's likely some uncertainty, and so I don't expect you can give me an exact number, but can... |
[
"How do scientists know what elements distant planets are comprised of, without actually going/sending probes there?"
] | [
false
] | I always see reports describing the chemical composition of distant planets and their atmospheres, but I've never discovered how we know. Help? Thanks! | [
"Spectroscopic analysis (mentioned by Zito773) can currently only be used on planets that are a) transiting, b) not too distant from Earth, and c) close to their host star, otherwise we just don't get enough light to make any meaningful measurement.",
"The first-cut way to guess at a planet's composition is to me... | [
"Woooosh."
] | [
"Thank you! "
] |
[
"How does an eraser on a pencil work? And why can you erase pencil but not pen?"
] | [
false
] | null | [
"The eraser works in a way that when you rub it, it removes the graphite from the papers surface. The rubber is more \"sticky\" then the paper and thus the graphite preferes the eraser over the paper. Another way some erasers works is the eraser damges the top layer of the paper effectively removing the graphite t... | [
"The ink in most erasable pens is also not absorbed into the paper as well as regular liquid inks."
] | [
"What about pens with erasers? How do they work? "
] |
[
"If birds have hollow bones, and bone marrow produces red blood cells, how do birds make red blood cells?"
] | [
false
] | I'm sure there's a simple answer to this but I've been wondering it for years. | [
"This",
" is what I found from searching for \"cross-section of a bird bone\""
] | [
"Birds have different types of bones, Pneumatic are those which are \"hollow\", ",
" like a straw but composed of a matrix of criss-crossing bone-fibres, these are the bones connected to the air sacs. \nCancellous bone is at the epiphysis and makes some red blood cells. \nBut that doesn't make all the marrow bird... | [
"Do you have any good images or diagrams of this? I'm having a hard time visualizing this, thank you! "
] |
[
"Who would die first of starvation? Fat people or thin people?"
] | [
false
] | null | [
"I'd have to go with the skinny person dying. The body stores glucose (fuel needed to get electrons to power mitochondria) in a few forms. There's glycogen which acts as a quick reserve, and then there's fat. The body actually converts glucose to a fatty acid through several steps and stores it in adipose tissue. W... | [
"But he got vitamin supplements. How long could an obese person survive with a vitamin deficiency? "
] | [
"But he got vitamin supplements. How long could an obese person survive with a vitamin deficiency? "
] |
[
"What element is the best at generating plasma?"
] | [
false
] | null | [
"\"Best\" in what way? The easiest element to achieve full ionization is hydrogen. But that's not the only way one might qualify an element as being \"best\" for it."
] | [
"In what other ways could an element qualify as \"Best\"?"
] | [
"Well what did you have in mind for the original question?"
] |
[
"What factors affect mosquito bite size and duration?"
] | [
false
] | null | [
"Mosquitoes release a protein that helps keep your blood from clotting. This protein causes swelling and itching. The more protein the more significant the reaction, so the longer the mosquito is attached, or the larger it is, may indirectly factor into the bite's total size. As far as how long it lasts, the more p... | [
"If I ignore a bite it seems to go away almost instantly. If I itch one it seems to stay for days. ",
"Is this just a placebo effect?"
] | [
"I don't think it's placebo, when I was tested for allergies with a skin prick test they told me not to touch the welts that formed because if I did they would get bigger and much worse."
] |
[
"If the moon is tidally locked to Earth, how are there craters on the side facing Earth?"
] | [
false
] | null | [
"For reference"
] | [
"I assume your question is essentially how do things hit the near side of moon if the Earth is in the way. The Earth is far enough away from the moon that there is definitely room for an object to slip past. In fact the gravity of the Earth can bend the trajectory of objects into the moon."
] | [
"You can ",
"fit every other planet in the solar system in between the Earth and Moon",
" with a little wiggle room to spare!"
] |
[
"Why does a lacrosse ball skip forward on the second bounce?"
] | [
false
] | When a lacrosse ball is thrown (out of a stick or out of someone's hand), it's first bounce is normal. Following that its second bounce will skip forward and with a much lower trajectory than expected? Lacrosse balls are solid rubber so I'm not sure why it would have the abnormal second bounce unlike any other ball that I am aware of. | [
"Are you imparting any backspin on the ball as you release it? If so, one would naturally expect the first and second bounces to behave differently. In a way, it is the first bounce that ",
" normal, as you have a ball with backspin that fights the forward motion that it has."
] | [
"Probably because of spin. When you throw it, there is little spin, but on the first bounce, it picks up lots of spin. The second bounce shows the effects of the spin.",
"The effect is explained well here ",
"http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/the-spin-of-a-bouncing-ball/",
"... | [
"The ball gains topspin on the first bounce causing it to jump forward on the second bounce. The same thing will happen, but slightly less noticeable on the 4th bounce. It is also much more noticeable on blacktop."
] |
[
"Why is it that generally people lose their high frequency hearing as apposed to their low frequency hearing when they're going deaf?"
] | [
false
] | I don't really know how true this statement even is. I would just like a little enlightenment on it. | [
"I didn't answer OP's question. I just said that the source that you cited did not seem credible."
] | [
"4th year med student here. The most common reason for this is due to aging called Presbycusis. ",
"It has to do with how the cochlea turns sound into something our brains can understand. Put simply the cells that are sensitive to high frequency sounds get damaged more than those that are sensitive to low freque... | [
"Thanks a lot. That's very helpful."
] |
[
"Is there dielectric breakdown in a liquid? What are the effects of the breakdown on it?"
] | [
false
] | If a solid undergoes dielectric breakdown, I’ve read it permanently damages the solid usually, and for a gas, it ionizes the gas but doesn’t “damage it”. What about for a liquid? | [
"Yes! (Depending on the liquid)\nSpecifically, the insulating mineral oil used in transformers is subject to very high voltages. This oil has a resistance in the range of 10kV per centimeter seperation. When the dielectric breakdown limit is surpassed occasional arks happen. The fluid serves to cool and quench the ... | [
"If the voltage exceeds the dielectric breakdown strength of the liquid, it will \"cut\" through and form a momentary ark. \nFor a sustained ark, there would need to be alot of current present to fight the cooling and collapsing bubble that is formed. Enough that whatever conductor/contacts the ark is originating f... | [
"Interesting, thanks! Also, with enough voltage, can an arc be sustained through the liquid? And/or could the arc “cut” through the liquid and sustain itself?"
] |
[
"Are certain insects evolving (or evolved) to have the idea of not banging mindlessly onto windows wired into their heads?"
] | [
false
] | Glass is a brand new invention and getting stuck behind a window and possibly sprayed with raid is not nearly as much of a factor as soot covered tree trunks but it certainly is a factor nevertheless. I guess I just feel bad for them, I imagine them going "WORLD! Y U NO MOVE? I'm flying ffs!" I know they still can't tell lightbulbs from the sun so I assume changes in bevior take longer than changes in appearance but, well, who knows, that's why I'm wasting your time asking: are there any glass-smart bugs? | [
"Interesting side note on this. I'm pretty sure the deer in my neighborhood have learned to be cautious around roads and vehicles.",
"When I was young, I remember deer would often panic and jump into a vehicle's path. Deer carcasses would line the street at different times of the year. Some time ago I witnesse... | [
"I think your observation about the deer might be closer to evolution than flies and glass widows: Cars actually can put selective pressure on a population of wild animals, whereas a glass window really doesn't put much pressure on a population of insects - they can't leave the room for a while, but thats only rare... | [
"... they can't leave the room for a while, but thats only rarely lethal.",
"Tell that to the wasps who come down my bathroom vent, then die as they cannot escape.",
"Another matter with my case is that selection in hive insects are different. The death of one individual basically has zero impact on the hive - ... |
[
"Why are there so many children allergic to peanuts these days?"
] | [
false
] | When I was a kid growing up in the 80s, peanut allergies were non-existant! I new nobody who was allergic to peanuts. I know a primary school teacher and she said that this year there are 6 in her grade, and more than 30 kids school wide who are allergic to peanuts. Why is this so? | [
"The prevailing theory (and I stress theory.. nobody really knows) is that today parents and people in general keep their bodies/living spaces as clean as possible (anti-bacterial such and such), avoiding contact with kids until they wash their hands, etc. Babies, and everyone really, need to be exposed to as many ... | [
"Media sensationalism has given rise to an over-reaction on the part of concerned parents. ",
"The public seems to have an exaggerated perception of the risks of food allergy, probably spurred on by the media. Recent headlines in national newspapers in the United Kingdom include: “One bite and he dies,” ",
"B... | [
"One reason I see besides the ",
", is that the last 200-400 years, people have started to get exposed to a lot more foreign foodstuff. Northern Scandinavians are not used to peanuts and citrus fruits. Australian Aborigines did not eat bread or any grain at all, this is why they get health problems keeping a Euro... |
[
"Ok scientists, I am working on bringing science to students with special needs. I would love to know 1) what is the \"essential questions\" of your field and 2) who are the scientists that people should know about from your field and why?"
] | [
false
] | null | [
"Thanks for spreading scientific education! ",
"What level of science knowledge are the students at? Many of the \"essential questions\" of specific fields are incredibly difficult to explain without some prior knowledge. ",
"In general, I think the biggest thing you could do for a science (especially physics a... | [
"You might get more responses in ",
"/r/AskScienceDiscussion",
".",
"May I ask what sorts of students we're catering towards here? The needs of your students will affect the concepts we ought to communicate to them and how we should frame them."
] | [
"Historian of science here.",
"Maybe start with a discussion of what science is, then follow with some of the ideas here, by discipline. I don't know the age of the folks you're working with, nor their cognitive abilities, but taking an organized approach with a simple definition of scientific thinking followed... |
[
"How does the excess salt from salting roads affect the environment? Things such as bodies of water or soil quality?"
] | [
false
] | null | [
"Seattle and Portland have actually found that this is a huge problem. Salmon return to the same area every year to make babies, and they guide themselves by the gradient of salt to fresh water as they move upstream. When there is too much salt from the roads, they get lost and spawn in the wrong place so their bab... | [
"I attended a seminar on this. After winter storms, salinity can spike in stream reaches, and temporarily become fatal to the life there. Additionally, after a while the salinity spike dissipates, but each year, the baseline salinity rises.",
"They still didn't know or understand much about the long term effects.... | [
"I don't know what Seattle uses, but on the Olympic peninsula we just use plows and sand. We don't get a lot of snow, or very often so they just try and keep the levels down on the main roads and throw sand for traction. "
] |
[
"How does ISON's speed, currently estimated at > 0.1% the speed of light, compare to the fastest things in our Solar System?"
] | [
false
] | Is ISON currently the fastest object (let's say bigger than a baseball) in our solar system? If not, what is? | [
"Most things in the solar system go at 10s of km/s. Earth goes at about 0.01% of the speed of light, or about 30 km/s. Even Mercury is going at less than 60 km/s. So if ISON was going at 0.1% of the speed of light, it's going at 300 km/s, which is more than 5 times faster than the next fastest thing.",
"This spee... | [
"What's an order of magnitude or two between friends?"
] | [
"Wouldn't that be ~10% of the speed of light?"
] |
[
"How do they polarize glass?"
] | [
false
] | Evert time i google how polarized glass is made i get some non-technical stuff about how they are good for fishing, reduce glare, remove horizontal light waves. One article mentioned something about iodine crystals but didn't elaborate. I just want to know how they treat the glass to get the polarization effect. | [
"There are many different ways, one is simply placing a PVA (poly vinyl acetate) foil on the glass. This material approximately has the consistency and thickness of plastic wrap. The manufacturing process begins by heating and stretching PVA to five times its natural length, making it even thinner. This lengthens P... | [
"You stretch it in a single direction?",
"Yes. The \"Pull Direction\" is the direction which the molecules align with."
] | [
"But how does one choose the direction of polarization like this? You stretch it in a single direction?"
] |
[
"Bear domestication."
] | [
false
] | [deleted] | [
"See ",
"my thread from last year",
" for a discussion."
] | [
"Bears are quite a bit bigger than wolves (60-100lbs compared to 90-370 lbs for black bears-grizzlies are larger). If a tame wolf gets aggressive with you, you stand a chance of fighting it off especially if you have a stout stick. A bear could maim you almost accidentally with a single swipe in a moment of irrit... | [
"You have to understand that there's no absolute division between possible and impossible in things like this. With decades of work, huge expense, and probably a number of human deaths you could breed a bear down to something approaching a domestic animal. It would probably in some ways resemble a cat more in tem... |
[
"How can my brain know that it's being fooled, yet still continue being fooled?"
] | [
false
] | I apologise for the badly worded question, so I'll give an example. The reason I may throw up when dizzy is to empty my stomach because my brain thinks I am being poisoned. How can my brain still make my body throw up when I - the brain - know I have not taken poison and am just dizzy? If I still haven't made myself clear, I'll try to explain some other way :) Thank you in advance. | [
"Well, in this instance your stomach is largely autonomous. The brain is responsible for decision making and processing new information, but it has little control over processes like the beating of your heart, gastrointestinal digestion or the movement of the sphincters along your gastrointestinal system. Thus, dis... | [
"Your brain isn't just one thing. It is a whole constellation of (usually) coordinated processes. What one part of your brain 'knows' is not automatically used by all parts of the brain. This is especially true when we are talking about physiological reactions such as nausea, heart beats, breathing, pupil dilation,... | [
"Thank you very much, this was a great help!"
] |
[
"How is the amount of matter in \"the vacuum of space\" represented? Moles per km^3 ?"
] | [
false
] | I asked this in a thread and got a couple upvotes but no answer so apparently this question is on a couple peoples minds. When you read about a gas cloud I assume that the center can either be the same "pressure" as the majority or it can be 10's of thousands of PSI if it decides to become a star. For example, there is a cloud containing trillions of gallons of ethanol. How many m would you have to condense to get a gallon of ethanol? | [
"Typically in astrophysics we use grams per cm",
" or number of particles per cm",
" If you look at the interstellar medium in our galaxy. A very typical density is one particle per cm"
] | [
"And 1 particle/cm",
" is 1.6E-9 moles/km"
] | [
"For example, there is a cloud containing trillions of gallons of ethanol. How many m3 would you have to condense to get a gallon of ethanol?",
"Are you asking about a specific cloud? Otherwise, the question doesn't make sense. Some clouds are more dense than others.",
"If you were referring to the massive cl... |
[
"How would the life support system on a Mars habitat be different from thr life support systems seen on the moon landings and in the iss?"
] | [
false
] | null | [
"Hi fellxcatking thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the fo... | [
"Mars\nSpace\nISS\nInternational space station\nMoon\nLife support."
] | [
"'Engineering' 'Physics'"
] |
[
"AskScience Panel of Scientists XVII"
] | [
false
] | This post is for new panelist recruitment! The previous one is . The panel is an informal group of redditors who are . All panelists have at least a graduate-level familiarity within their declared field of expertise and answer questions from related areas of study. A panelist's expertise is summarized in a color-coded AskScience flair. Membership in the panel comes with access to a panelist subreddit. It is a place for panelists to interact with each other, voice concerns to the moderators, and where the moderators make announcements to the whole panel. It's a good place to network with people who share your interests! Are studying for at least an MSc. or equivalent degree in the sciences, AND, Are able to communicate your knowledge of your field at a level accessible to various audiences. Choose exactly one general field from the side-bar (Physics, Engineering, Social Sciences, etc.). State your specific field in one word or phrase (Neuropathology, Quantum Chemistry, etc.) Succinctly describe your particular area of research in a few words (carbon nanotube dielectric properties, myelin sheath degradation in Parkinsons patients, etc.) Give us a brief synopsis of your education: are you a research scientist for three decades, or a first-year Ph.D. student? Provide links to comments you've made in AskScience which you feel are indicative of your scholarship. Applications will not be approved without several comments made in itself. Ideally, these comments should clearly indicate your fluency in the fundamentals of your discipline as well as your expertise. We favor comments that contain citations so we can assess its correctness without specific domain knowledge. Here's an example application: Please do not give us personally identifiable information and please follow the template. We're not going to do real-life background checks - we're just asking for reddit's best behavior. However, several moderators are tasked with monitoring panelist activity, and your credentials will be checked against the academic content of your posts on a continuing basis. You can submit your application by replying to this post. | [
"Username: ",
"/u/bencbartlett",
"General field: AMO Physics",
"Specific field: Quantum Physics | Quantum Information ",
"Particular areas of research currently include simulating realistic (error-prone) quantum networks and designing error correction schemes for them. Will likely transition to more experim... | [
"Username: ",
"/u/contact_fusion",
"General Field: Astrophysics",
"Specific Field: Magnetohydrodynamics",
"Particular Areas of Research: Star Formation. Magnetized turbulence, scientific supercomputing, submillimeter polarimetry, fluid mechanics. Also work on impact diversion of asteroids and x-ray interact... | [
"I just want to say I'm really psyched about you becoming a fellow panelist. I've seen your comments in various climate-related threads, and they're always on point."
] |
[
"Is ALS more common today than in the past?"
] | [
false
] | I’m willing to consider the fact that we’re just more aware of it as a society after the ice bucket challenge, but it seems much more common today. | [
"Yes, scientists believe ALS is slightly more common today than in decades past, but they can't explain why. In my opinion, although it may actually be more common today based on statistics, it also appears to be because of things like the ice bucket challenge, and the fact that it's starting to appear in younger p... | [
"I'd be happy to.",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4334292/",
"https://www.alzforum.org/news/research-news/lou-gehrigs-disease-rise"
] | [
"I want to add to the discussion the strange hypothesis that ",
"cyanobacteria can cause ALS",
".",
"Cyanobacteria, or blue-green algae, produce the amino acid BMAA. The idea is that some people have a genetic predisposition for having this amino acid accumulate in their brains. This leads to excitotoxicity a... |
[
"What separates animals that recognize themselves in a mirror from ones that don't?"
] | [
false
] | [deleted] | [
"It's thought that animals that can pass the ",
"mirror test",
" have ",
"theory of mind",
" (ToM). This idea however has many critics who, among their qualms, accuse the test of being overly anthropocentric. "
] | [
"Generally this is associated with higher intelligence. As far as I've heard it has to do with them being able to process the concept of them existing outside their environment as an individual. This is similar to object permanence in children. At a certain point children develop to where they realize things exist ... | [
"My dog can recognize herself in a mirror, I have proven this by placing a treat on her head. She sees the treat in the mirror and in order to get said treat she shook her head till it fell. @xarhtna"
] |
[
"Before antibiotics were bacterial diseases just not curable?"
] | [
false
] | If you got pink eye, chlamydia, strep throat, or any other type of bacterial infection, was there no hope? Is the human immune system not capable of healing itself? | [
"Some things the body will eventually take care of. Maybe. Like strep throat. But without antibiotics, a patient ",
" have a higher likelihood of developing further problems, secondary issues, that come with having that infection.",
"Before antibiotics, there were other things that were used sometimes. Salt... | [
"Strep throat will get better without treating it. Treating only reduces the duration of the illness by less than 1 day, but it prevents some of the bad complications of it such as rheumatic fever, rheumatic heart disease, and post-strep glomerulonephritis."
] | [
"Before antibiotics, you would either live or die. Depending. Often because of associated complications. Now we can avoid many of those complications.",
"I did have a friend though who had strep throat which was misdiagnosed as mono. He ended up getting scarlet fever and had to get part of his throat surgically r... |
[
"How do I, as somebody outside higher education, get access to published journals?"
] | [
false
] | null | [
"This might be better suited for ",
"/r/AskAcademia"
] | [
"Thanks for the tip. I wasn't even aware of that sub"
] | [
"Hi the_dummy thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the follo... |
[
"What is the lowest frequency that can be transmitted in a vacuum?"
] | [
false
] | For example, given a variable oscillator, and an antenna placed in a vacuum. What is the lowest frequency (electromagnetic wave) that can be radiated from the antenna? The antenna can be of any size or shape. I realize most usable frequency transmitted are in 300kHz and above, but what about the lower frequencies < 1kHz, does it have do with amount of energy in the wave? | [
"None. There is no lowest frequency.",
"Just by coincidence, I was working on a problem related to this just a few hours ago. I wanted to have numbers handy, so I was working out the Hawking radiation of Sagittarius A*. That's a black hole that radiates (assuming my maths are correct here) at a peak frequency of ... | [
"There is a technicality that you run into when you start dealing with wavelengths that are close to or longer than the Hubble length. The math stops those modes from being oscillatory; modes with a wavelength longer than the Hubble length are \"frozen\"."
] | [
"Photon. With a fffff."
] |
[
"How does plate tectonics explain continental drift?"
] | [
false
] | This has always confused me. So there are these huge stone plates that can slide on top of liquid mantle. They are very tightly packed and there are forces that cause them to move in relation to each other. Where they collide they either deform (forming mountain chains) or slide on top of each other (usually resulting in trenches). I suppose they can also deform at other places causing the land to either rise or sink, although plate tectonics don't seem to allow for that. But isn't that how Sahara used to be at the bottom of an ocean? What I don't understand is how this explains actual continents moving closer or away from each other. They are not somethings floating on water, they are protrusions on respective plates. Why would South America and Africa fit each other, and why would that make sense in the light of plate tectonics? How could they have been one continent and later drift apart if both plates have underwater sections as wide as half an ocean? And why would super continents form every few hundred million years? Thats one huge bulge on one side of the planet. Kind of strange with all that gravity acting on the plates and the mantle trying to keep the shape of a spheroid. | [
"What I don't understand is how this explains actual continents moving closer or away from each other.",
"The continents are parts of the plates, as the plates grind together or separate, the continents move closer and further apart. The plates move relative to each other.",
"Why would South America and Africa ... | [
"Continental crust is lower density than ocean crust so it doesn't get sucked under usually. "
] | [
"I am too tired to do a full response to this but one correction is needed.",
"The mantle is not liquid. The mantle is solid. Near the surface of the earth, just under the crust (the lithosphere) is fairly runny but still a solid (like plasticine)"
] |
[
"What is the difference between an organism made up of smaller individuals(e.g. sea salp, pyrosome) vs. a multicellular organism?"
] | [
false
] | null | [
"A salp ",
" a multicellular organism. ",
"I think you’re confusing two concepts uni-& multi-cellular organisms vs colonies.",
"Typically a multicellular organism will have specialized cells. This is what differentiates, say, a group of choanoflagellates from a sponge. A choanoflagellate is one cell type -... | [
"Isn't the defining characteristic whether the cells have the same DNA or not?",
"Many cells with different functions but same DNA -> multicellular organism",
"Collection of very similar cells with different DNA -> colony"
] | [
"Most (nearly all) colonial organisms are made of clones and also have identical DNA in all cells."
] |
[
"Since there is evidence of our universe expanding, does that mean that the universe is finite?"
] | [
false
] | If anyone could link articles are other informtion about it I would appreciate it. | [
"Imagine the real number line. Now consider some interval along the line, say from -1 to +1.",
"Now multiply the whole thing by two.",
"The interval you were considering is now twice as large as it was; it goes from -2 to +2. But the line started out infinite, and it was infinite after you doubled it.",
"In o... | [
"It's easier to think of the universe just getting less dense with time."
] | [
"That doesn't follow. Just because the universe is infinite it doesn't mean it will have such and such density. Also, there probably is a star in all and every angle, it's just that we're limited to the observable universe."
] |
[
"Why are angles measured in radians?"
] | [
false
] | Is there a particular reason why in trigonometry, angles are measured in radians? Is it just a standard, or is there some "sense" or "logic" behind it? Wouldn't it be simpler to measure angles in "turns" so as 1 turn =360 degrees = 2 Pi Radians? I mean, we still end up expressing everything in fractions of Pi. | [
"Are you familiar with calculus? Radians make a lot of sense when you start thinking about the derivatives of trigonometric functions.",
"For example, if theta is measured in radians, the derivative of sin(theta) is cos(theta). If theta is measured in \"turns\" (as you propose), the derivative of sin(theta) is ... | [
"A radian is the angle formed by taking an arc whose length is exactly the same as the radius of the circle. This means it's really simple to go back and forth from the angle to the circumference to the radius to the area. ",
"There are alternative ways to measure angles, but none of them are as easy as radians w... | [
"sin(x)=~x",
"Near zero, that is."
] |
[
"What purpose does skin-to-skin contact with the mother and baby after childbirth serve?"
] | [
false
] | I'm learning a lot about childbirth today because my close friend is having her first baby any moment now. Is there a physiological response between the baby and the mother? What happens when the baby or mother does not have skin-to-skin contact? | [
"There are only hypotheses at this point, but there are a lot of observed benefits. ",
"From survival to weight gain and attachment.",
"And it costs very little to accommodate,unless you're in the US when its an extra fee."
] | [
"I was told skin to skin, particularly soon after birth, helps to calm the baby and mother. The baby can hear the same heart beat it was exposed to in utero, and the resonance of mothers voice through her ribs is closer to the in utero experience also. This will calm the baby, and that calming has a positive feedba... | [
"No, babies are exposed to the microbiome naturally as they come out. And it’s been tested pretty extensively in the US, where healthy babies are being born via C section about a third of the time"
] |
[
"why do anti-depressants take time to work?"
] | [
false
] | ie, they usually are advertised as taking 1-2 months to show any real effect. Why is this? | [
"Yeah, of course it isn't. As i fully acknowledged, \"more research is needed before we'll understand it completely.\""
] | [
"Yeah, of course it isn't. As i fully acknowledged, \"more research is needed before we'll understand it completely.\""
] | [
"Did you see ",
"this?",
" It happens to be asking your exact question. ",
"This sort of depends on what you mean by \"work\". If you mean a noticable mood change then it's important to note that moods are controled by many more chemicals and receptors than are affected by antidepressants. Individual chemical... |
[
"If ball bearings are continuously dropped at 1-second intervals from some height above the ground, will they also hit the ground at 1-second intervals?"
] | [
false
] | If not, would would be the formula to calculate what the time intervals between consecutive ground hits would be given a drop height and regular interval between consecutive drops? Edit: I feel kind of silly asking this since I'm almost sure that the answer is "yes". The reason I ask is because in trying to have an intuitive understanding of gravitational time dilation, I came across a diagram that showed an accelerating rocket ship with a photon emitter near the front pointed at the back, and a photon receptor in the rear. The diagram explained that since the rocket was accelerating, if photons were emitted at (locally to the front) 1-second intervals, then the photon receptor in the back would receive photons at intervals longer than 1 second. I then thought if this were true, it would also have to happen with anything, wouldn't it? But I don't think it would happen with ball bearings. | [
"Ah, well given your question I assumed a classical system in an inertial reference frame where nothing was moving besides the ball bearings. That logic can't be simply applied to other situations like the rocket example you give. To take a classical example:",
"Suppose I am in an elevator with an open top and yo... | [
"Interesting that everyone is saying yes.",
"Really, it depends on who is counting the seconds:",
"If the person at the top of some tower is dropping them at one second intervals, the person at the bottom of the tower will definitely measure them as hitting the ground at less than one second apart. This is the ... | [
"The rocket example you are talking about is often used to demonstrate changes in the rate of time in a gravitational field, or equivalently in a non-inertial (accelerating) reference frame. The photons will indeed not arrive at 1 second intervals, despite being sent at 1 second intervals, because the rocket is acc... |
[
"If you have the flu, does every exhale you take contain the flu virus?"
] | [
false
] | I was talking to a friend and they were arguing that if you don't get the virus within 10 minutes being around someone, then you can't get the virus. I didn't think that was true though because 1.). I'm not inhaling every particle that the sick person is exhaling, so it could take longer than 10 minutes. 2.). Not every exhale that the sick person exhales contains the virus particles/amount of virus particles. But I'm not sure if these are actual facts or not, hopefully someone can give me more insight, thank you. | [
"Yes. ",
"... viruses are very efficiently spread through aerosols by the patient’s breathing only. It is not necessary for the patient to cough or sneeze. ... The fact that the spread of different viruses occurs through normal breathing of infected persons has now also been proven by various other working groups... | [
"There's also the matter of how much you get exposed to at once.",
"The body takes time to respond to infection. ",
"If you start out with 1000 infected cells, you'll end up exponentially more sick before your body has the response ready to go.",
"If you start with one infected cell, the body has a lot more t... | [
"I don't know about #2, but #1 is certainly true. ",
"Also, there's an incubation period for every disease. Even if you acquire the disease within minutes, you won't know about it for a little while. For influenza/the flu, the incubation period is normally 1-4 days. During this time the virus replicates until the... |
[
"Quantum erasers: is one single photon capable of interfering with itself?"
] | [
false
] | [deleted] | [
"You may be looking for ",
"this paper",
".",
"The single-photon experiments are just creepy and feel very intuitively wrong; there's no way to interpret it without a particle being in more than one place at once. The worst of them all is probably the ",
"delayed-choice version of this experiment",
" wher... | [
"Yes, you see that interference patterns you see in Young's double-slit experiment or a Michelson interferometer are still there even when you work with individual photons. "
] | [
"I feel the poster made that assumption when writing \"if we don't try to measure which path\". But I guess it bears underlining that a \"measurement\" in QM doesn't neccesarily mean an deliberate attempt to measure in the everyday sense."
] |
[
"What do the x and y stand for when I hear about the new HxNy flu threat?"
] | [
false
] | H1N1, or "Swine flu", was the first time I had seen this systematic naming, but now, apparently, there's an outbreak of H7N9, and I seem to recall a concern over H5N1. What information is conveyed in these names? | [
"Hemagglutinin (HA) and neuraminidase (NA) are the two large glycoproteins on the outside of the viral particles. HA is a lectin that mediates binding of the virus to target cells and entry of the viral genome into the target cell, while NA is involved in the release of progeny virus from infected cells, by cleavin... | [
"To add to this, Birds have a large pool of H and N varients lots more than humans have (as stated). These H antigens are responsible for attaching mainly to your respiratory cells thus inducing the infection. Therefore if a human does not have say H6 then the disease will not be readily transferable. However in cl... | [
"And this is what makes these viruses so annoying to combat. The strains can be mixed and matched in any which way (in theory). The flu vaccine is actually just a big probability game where they decide which strains are most likely to give you the flu this season. Other viruses besides Influenza (which is an orthom... |
[
"How does a breathalyzer test represent your blood alcohol content? How does a test of the breath give accurate information on the alcohol content of the blood?"
] | [
false
] | null | [
"Deep in the lungs are alveoli which have very small capillaries all over them. This is where gas exchange occurs. The oxygen we breathe in crosses over the capillary membrane and into our blood (mostly bound to hemoglobin) and carbon dioxide crosses from the blood and into the lungs to be exhaled. But carbon dioxi... | [
"This answer is correct, but I just wanted to provide some numbers in case OP was interested. About 95% of the ethanol we take in is metabolized enzymatically, whereas the remaining 5% is excreted unchanged in the lungs. Breathalyzers take advantage of this to calculate BAC from the breath sample.\n-An interestin... | [
"A breathalyser is not not accurate enough to charge someone with DUI (in Australia at least)\nIf you test over the limit on a breathalyser you get taken to the station for a blood test, it's just a less invasive initial test."
] |
[
"How many genetically diverse people would it take to successfully colonize a new world without the effects of inbreeding?"
] | [
false
] | [deleted] | [
"I recall learning about this in my ecology classes but didn't recall offhand what the numbers were so I did some searching. ",
"It appears",
" that between 50 and 500 individuals would be needed for a successful population. 50 individuals would prevent inbreeding while 500 would ensure genetic variability. ... | [
"I'm not sure what the number would be, but I'd like to point out it would be a far smaller number if you brought along a bunch of sperm and eggs. Each new offspring from the colonists could be genetically distinct. "
] | [
"Here's a ",
"similar post",
" and the response I gave there. The take-away is the number's higher than you might think, dependent not only dependent on the initial diversity of the population, but also the size in general (see the bit about genetic drift)."
] |
[
"would there be muzzle flash if a firearm was fired in a vacuum?"
] | [
false
] | null | [
"The muzzle flash of a firearm is the explosion that is propelling the bullet out of the barrel following the round and exiting behind it. That explosion is produced by the propellant inside the bullet's casing (or the casing itself for caseless ammunition). The explosion would still be present, though it may appea... | [
"Most modern gunpowders contain their own oxydiser. So if you were to fire a gun in space, it would shoot. The flash may look different, but it would still be there."
] | [
"thank you. "
] |
[
"With current electricity production methods that are in use, how much greener is an all-electric car compared to a petroleum car?"
] | [
false
] | Obviously a traditional petroleum car produces CO2 and other nasty gases, but if I plugged in a car, wouldn't some power plant be burning something else producing similar gases somewhere else in order to power the car? In this case, the only difference is where the fuel burns. Because I am primarily concerned with greenhouse gases, I am asking from a chemistry perspective. From what I understand nuclear power only requires cores and cooling usually with water, though waste is a problem, so though not totally true could we assume that power from nuclear plants is pure and without side effects [for this question at least]? In the US nuclear power roughly accounts for 19% of all power production. Also in the US renewable energy accounted for 12.5% of power production in the US in 2012 apparently. All these factors included, who wins the green fight? Whoa, thanks for the massive response. Just got home so I'll be reading through the night | [
"You are certainly right that switching to electric cars doesn't directly eliminate the problem of greenhouse gas emissions if the electricity used to power them was generated through methods that themselves release CO2. The main advantages of electrical power, however, are two-fold. Perhaps the most immediate adva... | [
"Some very rough math to conservatively estimate the carbon intensity of an electric car like the Nissan Leaf, if you were to charge the battery from exclusively coal-fired power stations:",
"Carbon emissions per kWh produced by average U.S. coal power station:",
"~ 1 kg CO2 / kWh",
"Natural gas is ",
"roug... | [
"Missing from this analysis is the fact that gasoline is responsible for significant additional emissions before the fuel even makes it to the car.",
"The refining process in particular requires a boatload of electricity and other fossil fuel energy. The EIA estimates about 6 KWH per gallon refined. ",
"That'... |
[
"Why do human males have nipples? What purpose do they serve?"
] | [
false
] | null | [
"Because in theearly stages of pregnancy the fetus is sexually ambiguous, and the 'stronger chromosome' essentially decides the sex of the baby during later stages of the gestation period "
] | [
"To add to this, it's called a ",
"spandrel",
", borrowing a term from architecture."
] | [
"From conception until 6 weeks, the fetus is asexual. This means physical traits of the body develop the exact same way. Around this time, a genetically male fetus (XY chromosomes) starts producing testosterone & continues as a male (no mammary glands develop), while a genetically female fetus (XX) produces estro... |
[
"Could a massless particle gain mass?"
] | [
false
] | [deleted] | [
"Well, what you're basically describing is the Higgs mechanism (ever heard of the Higgs boson?).",
"The basic idea is that there is a quantum field, which we call the Higgs field, permeating all space. It's similar in concept to other fields you're probably more familiar with, like the electric or magnetic or gra... | [
"I recall reading something about how the Higgs field only accounts for a small portion of the mass in atoms, and that the rest of the mass is binding energy.",
"Yes.",
"If the elementary particles in an atom were to stop interacting with the Higgs field, what would happen to this binding energy? Would it stay,... | [
"But can a particle that doesn't interact with the Higgs field somehow change and begin to do so?"
] |
[
"Can we talk yet to any other species in our world?"
] | [
false
] | null | [
"No non-human species has language as we do, so in that sense no. "
] | [
"We will be able to make it happen? Or no one is interested? I mean that could lead into helping other species to evolve it makes me wonder and dream big."
] | [
"As far as we know, no known species currently have the capacity for language. We can communicate with them, but their methods of communication do not have the hallmarks of language. ",
"Here",
" is a discussion of some of these features. This theory is a bit outdated at this point, but the general ideas are st... |
[
"Questions on the relativity of motion."
] | [
false
] | [deleted] | [
"According to the special theory of relativity, if you are traveling at absolute constant velocity, you can claim that you are stationary and the rest of the universe, and observers can claim they are stationary and you are not, and both claims are right.",
"Yep.",
"But how can they both be right? If the rest o... | [
"Gravitomagnetic",
" effects come to the rescue and are equal and opposite to the increased gravitational field. It's basically the same thing as in electromagnetism, where changing reference frames turns magnetic fields into electric fields and vice-versa. Think of two charged particles in the lab frame, where ... | [
"Gravity is the curvature of spacetime, but Einstein's equivalence principle asserts the equivalence of an accelerating reference frame to one in a uniform gravitational field. The effect of gravity is ",
" like an acceleration.",
"To quote Einstein, \"we shall therefore assume the complete physical equivalence... |
[
"Building Height math.."
] | [
false
] | How tall would a building in Washington DC have to be, to see the skyline of Philadelphia? | [
"Man, I really wish reddit had a decent search function, because a few weeks ago I answered almost this exact comment, except it was with New York and San Francisco.",
"Anyways, the idea is this. The distance between New York and Philadelphia is 129 km as the crow flies. The circumference of Earth is 40,000 km,... | [
"They are 220 km apart. According to an approximation, the height required to see a distance d is (d/3.57 km)",
" , so about 3.8 km high."
] | [
"Nobody has factored in realistic cases of refraction yet. Is the effect significant?"
] |
[
"Would it even be possible to revive the people who have been cryonically preserved?"
] | [
false
] | null | [
"Modern cryo attempts circulate anti-freeze compounds before bringing to liquid nitrogen temperatures to minimize crystal formation. So crystalization isn't that much of an issue. See ",
"here",
" \nThe short answer to OP's question really is that we don't know either way if cryonically preserved individuals wi... | [
"For preserving whole humans there are still a few things to worry about. One is that you have to use a ",
" of the cryoprotectant chemical (since humans are quite large compared to a single organ, or an even tinier cluster of cells, and you have to be certain that it penetrates to every part of the body), and t... | [
"Currently, no. One of the biggest problems with freezing someone is that we are primarily water, and when frozen, water crystallizes. Imagine billions of water crystals forming in your blood vessels, brain, and other organs. These would (and do) tear these tissues to shreds. Thawing someone out just turns them int... |
[
"Why are rockets/ spacecraft corrosion resistant, if there is no oxygen in space?"
] | [
false
] | I was reading about the different types of alloys used in rockets, and many of them are labeled as 'corrosion resistant'; does this actually matter or is it just a useless byproduct of the alloys that rockets use? (btw, sorry if I used the wrong flair.) | [
"There are 3 main aspects that are relevant there on why you would want corrosion resistant materials.",
"First while the goal is to send the thing to space it will spend a significant amount of time on the ground first. Even in a clean room environment you can get corrosion. Moreover contrary to a lot of other v... | [
"Thank you! I can't believe I forgot that rockets aren't always in space lol"
] | [
"Trust me, everyday I whish we could build spacecraft directly in space. It would make a lot of things so much easier."
] |
[
"How does curved spacetime cause acceleration?"
] | [
false
] | If I'm free-falling, I feel no forces. So how would I explain the fact that the earth is accelerating towards me? I understand that I'm on a geodesic that minimizes my action, but how does the fact that spacetime is warped cause me to move in the first place? Edit: Please only reply if you have a working knowledge of general relativity | [
"For simplicity, let's treat a universe with just you and one other person, so we don't have to deal with orbital stuff.",
"You and this person are initially at rest relative to one another. If spacetime were flat and didn't respond to your masses, then your worldlines (essentially, the collection of all spacetim... | [
"coördinate",
"I had never heard of this before.",
"https://en.wiktionary.org/wiki/coördinate",
"Alternative spelling of coordinate"
] | [
"Moreover, the rate at which the distance decreases gets bigger over time, so there's an apparent acceleration.",
"Also, you don't ",
" the acceleration the way you would with, say, a rocket engine. It feels like your moving along a straight line, because in the metric, you technically are. ",
"(Of course sin... |
[
"How quickly does boiling water sterilize a surface?"
] | [
false
] | [deleted] | [
"Disclaimer: Don't take any medical advice from reddit, and yes this kind of counts because you made it relevant to yourself. However I'll explain because it's telling you not to.",
"A common sterilisation technique used in science is autoclaving which involves steam at around 120C for around 20 minutes to steril... | [
"So how is it that chicken need only be cooked to an internal temperature of 165 F to be considered safe? That is significantly less than the 212 of boiling water."
] | [
"This might not be 100% accurate, but I would assume it has to do with the main thing you are getting rid of is salmonella. It is recommended to heat at 167F for 10 minutes to kill salmonella. "
] |
[
"Do we know the general lifespan for dinosaurs?"
] | [
false
] | Of course, it would differ from species to species, but have we been able to date bones? Or are we only able to compare them to modern reptiles/birds... | [
"Most dinosaurs have lines of arrested growth in their bones which most scientists think are laid down annually (think tree rings essentially). This allows us to estimate ages based on the assumption that one LAG = 1 year (this is not necessarily true, but it is not a bad assumption and even if it is wrong, i.e. b... | [
"Amazingly the answer is no. One year has stayed roughly the same length in seconds, but the day has been growing steadily longer due to ",
"tidal friction",
". The Moon is slowing us down. ",
"But this effect wouldn't be huge. ",
"This paper",
" estimates the change at only 2 hours a day over 650 million... | [
"did one year 100-200 millions year ago last around the same amount of time as now? e.g. did the earth have about the same number of days and did each day last about the same duration as the days now?"
] |
[
"Why do people with dementia experience hallucinations? In particular, why do the vast majority experience seeing children?"
] | [
false
] | My grandmother has dementia and whenever I visit her she talks about seeing children in the room with us. I’m particularly interested in this phenomena because she is blind. | [
"There are probably two things going on here; dementia in combination with Charles Bonnet syndrome.",
"\"Charles Bonnet syndrome\" (",
"http://www.rnib.org.uk/eye-health-your-guide-charles-bonnet-syndrome-cbs/understanding-charles-bonnet-syndrome",
") is a relatively common syndrome in people with deep blindn... | [
"Where did you hear it? Explanations for phenomena are only useful if the phenomena is backed up with strong evidence."
] | [
"Thanks for the thorough reply! It makes a lot of sense.",
"You wouldn’t happen to know why dementia patients see children in particular though do you? I’ve heard it is the most common hallucinations attributed to the disease."
] |
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