title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Is there any chance of getting an electric shock if you wear ear phones/buds in the rain? And if so, could said shock be damaging in any way?"
] | [
false
] | null | [
"The shocking answer is yes!",
"...sadly, in one case it has nothing to do with the rain, and in the other it has nothing to do with the earbuds.",
"Case 1: You're wearing your earphones out in the rain, and are doing any activity that builds static electricity. ",
"That static electricity could be delivered ... | [
"Earphones usually operate in mV ranges. That's far lower than most other power sources we usually handle, like batteries.",
"You can take a 9V block battery and touch the poles simultaneously with your tongue and won't get more than a tingling sensation and a weird taste. If you get water into your earphones, th... | [
"Awesome thanks. As you guessed I was mainly thinking about the ear phone/your ear getting water in it and somehow conducting, hadn't considered these other scenarios. Really interesting.",
"It would have to be a perfect storm (damp skin that reduces resistance from the normal 100K to 200K Ohms to around 1K Ohms,... |
[
"If you hold in poop does your intestine still absorb nutrients or does it just kind of sit there at the end of the line?"
] | [
false
] | null | [
"Its called ",
"encopresis",
". By the time you have conscious control, its more water being absorbed than anything else. If you refuse to poo, it gets harder and bigger so the next time you poo it hurts. Then, if you are a three year old, you repeat the process ad infinitum and drive me crazy. Don't do thi... | [
"From ",
"Wikipedia",
"Food is no longer broken down at this stage of digestion. The colon absorbs vitamins which are created by the colonic bacteria - such as vitamin K (especially important as the daily ingestion of vitamin K is not normally enough to maintain adequate blood coagulation), vitamin B12, thiamin... | [
"impaction caused by constipation is really common and if it gets so bad you cannot remove it yourself, nurses can do it ",
"it's pretty common in obese and older people"
] |
[
"How can I weigh myself, at home, if I'm not able to stand on a scale?"
] | [
false
] | I am a wheelchair user, and unable to stand. Some hospitals have large scales, with a chair I can sit on, but that isn't an option at home, and I'd like to weigh myself regularly and accurately, which kneeling on the scale doesn't accomplish. | [
"can you pull yourself up by your arms? maybe get a hanging fish scale with a trapeze bar, and use that. ",
"Something like this"
] | [
"I think this is the solution. Thanks!! "
] | [
"Have two scales side by side that you can roll onto, and then add their displays."
] |
[
"What are some examples of different evolutionary adaptions among different populations of humans?"
] | [
false
] | Aside from Alcohol Dehydrogenase, Lactase never 'turning off', and melanin loss after the agricultural revolution I don't know of any changes in humanity that have been caused by environmental factors. Are there others? | [
"Melanin loss predated the agricultural revolution and is due to reduced solar intensity in temperate regions. Malaria resistance is a great example of an adaptation to a biotic factor; altitude adaptation (Tibet, Andes, etc) is a great example of adaptation to an abiotic factor."
] | [
"Body size and stature.\nCentral African people living in the harsh heat of the tropics tend to be tall with long legs, with most of their body fat distributed in just a few places so they can radiate as much heat as possible. The native people of arctic Canada tend to be short and have body fat more evenly distrib... | [
"HIV immunity in some European populations ",
"as a consequence of negative selection by the black plaque",
".",
"Tay-Sachs desease",
" that either increases average intelligence in the population, or ",
"increases resistance to tuberculosis",
", or both. Implied selection in Ashkenazi Jews.",
"The ",... |
[
"Assuming there is a part of the brain that creates the visuals we see when we think (and especially dream) is it within the realms of possibility that other people could, one day, see our thoughts?"
] | [
false
] | I'm not sure how well I phrased the question here but what I mean is, when I think (and obviously, more so when I dream), images are created. What I want to know is if, one day, it would be possible to somehow 'plug in' to this part of the brain and effectively stream thoughts for other people to see. I imagine this wo... | [
"Apparently we already can (sort of). Not long ago this ",
"video",
" came out.",
"Here",
" is a related paper."
] | [
"So you're unhelpful AND sarcastic? I bet you're a real hit with the ladies."
] | [
"any source/elaboration you can give me on that?"
] |
[
"Why does riding a bike last so long in muscle memory?"
] | [
false
] | It's the archetypal phrase when it comes to long-term muscle memory: "It's like learning to ride a bike" What is it about bike riding that once it is learnt it is never completely unlearned? Is bicycling unique in this way or do all dextrous skills "stick" with us for life once we've become competent at them? | [
"Balance and praxis (learned sequences) are largely moderated in the cerebellum as they are learned, not in the muscles.",
"Like almost anything that you learn and rely on daily, the neural circuits for them are reinforced, strengthening them, so that even if you don't use them for a while, they remain accessible... | [
"This would be interesting to experiment with and see if someone with amnesia and doesn't remember learning how to ride a bike, could still ride it."
] | [
"This would be interesting to experiment with and see if someone with amnesia and doesn't remember learning how to ride a bike, could still ride it."
] |
[
"Are vitamins in cereal \"Sprayed On\"? Do you miss some of them if you don't drink the left-over milk?"
] | [
false
] | I grew up being told this, especially about sugar cereals - all the nutrients were "sprayed on" and would wash off into the milk, so unless you finished your milk you would get zero nutrition content. As an adult, I realize that there are some nutrients, such as fiber, where this is obviously not the case. I'm talking... | [
"It depends on the cereal, really. Whole-grain cereals (including puffed grains such as Corn Pops) do in fact have any fortifying nutrients mixed into their coatings. Extruded cereals (Cheerios and the like, anything where the grains are reduced to dough before being shaped) usually have fortifications mixed into t... | [
"I worked briefly in a kelloggs factory and i can confirm all the lines i worked on sprayed on their vitamins. A relatively small bottle, about 500ml, would cover several thousand boxes of cereal. It was sprayed on just after the cooking process. Don't really know much more than that (like if the vitamins come off ... | [
"It depends on the cereal. Many of the \"kids\" cereals are ~49% sugar by weight - 49% so that they slip under the 50% threshold for the definition of \"candy\". Those cereals have few redeeming qualities because of the excess sugar.",
"But for whole grain cereals and those like Cheerios with relatively little ... |
[
"Why is a grossly over expanded nozzle more efficient than a slight over expansion?"
] | [
false
] | So I came across this when I was doing some gas dynamics research, and I am trying to remember back to my high speed aerodynamics class. A grossly overexpanded nozzle moves the oblique shocks at the exit into a normal shock that slowly moves into the nozzle, while a slight overexpansion has oblique shocks outside the n... | [
"An overexpanded flow isn't optimal since it tends to be very unstable. It's generally more efficient at high altitudes where flow separation becomes less problematic. Unfortunately, ideal full expansion for a non-variable nozzle only occurs at a design point (vs a full altitude range), so engineers tend to \"pick ... | [
"Why do they say that a grossly overexpanded flow is more efficient then a slightly overexpanded flow though? That's what I don't get because you'd think it would be the opposite. "
] | [
"This reminds me of the main engines on the (now retired) Space Shuttles. They are often touted as the ",
"most efficient rocket engines ever made",
". It's interesting to note that this is not the case at take-off, but only much later at a much higher altitude, when they reach their design point.",
"Edit: Gr... |
[
"Is there any discernible structure in the cosmic microwave background noise?"
] | [
false
] | null | [
"It would appear the CMB appears sufficiently random that it can be effectively used as a random number generator. That would suggest there's no discernable structure.",
"However, the CMB may not be entirely random, particularly with respect to anomalies like the ",
"CMB cold spot",
", though it's entirely p... | [
"There are some people who are trying to employ new techniques to find hidden structures in the CMB, see e.g. [1], where they use something called `Topological Data Analysis' (TDA).",
"[1]\n",
"https://arxiv.org/abs/1712.08159"
] | [
"not sure I fully understand your question. could you clarify?",
"We do not see the CMB \"now\", we see it 3.8e5 years after the Big Bang (~1.4e10 years ago).",
" structures close by like a galaxy will cause gravitational lensing on it same as any other light wavelength but that's just a local effect (that I'm ... |
[
"Are there solid Planets as big or bigger than Jupiter?"
] | [
false
] | ..or are all the really big planets gas giants? | [
"No rocky planets that large have ever been discovered.",
"Since exoplanet discovery is a relatively new phenomenon, it was previously assumed that exoplanets would follow the same general trends seen in the solar system, but the discovery of Kepler 10c in 2011 disproved that hypothesis. Kepler 10c, the largest r... | [
"is there any scientific reason that solid planets cant get that large?"
] | [
"No, but just to clear something up: there's no precise definition for a gas giant vs. a terrestrial planet. It was thought that around 10-15 times the mass of Earth, a planet would accrete more atmosphere than what is considered \"rocky\" and be more of a Neptune-like planet- a gas giant with a rocky core. (You ca... |
[
"How does toothpaste affect the microbial flora of the mouth?"
] | [
false
] | Hi! I'm a microbial ecology M.Sc. candidate that works predominantly in soil. In soils, there is quite a bit of evidence that anthropogenic changes to the soil affect the microbial community and it seems (at least from what I read and work on) that this can sometimes severely limit the diversity of microbes to species ... | [
"Brushing just disrupts biofilms on your teeth basically. Streptococcus mutans and some other strains of strep live in your mouth and eat sucrose in your mouth to make glycan, which is a sticky extra cellular polymer that is water insoluble. This builds up, and sticks to your enamel. Normally this wouldn't be a big... | [
"Thanks! That's super informative! I'm always amazed at learning about the parallels between microbial ecology and the human microbiome. I guess it's really no different from any other environment when you get right down to it.",
"I wonder whether there are any microbe-related ways to stimulate the growth of orga... | [
"A simplified explanation: Enamel is made up of, among other things, the mineral hydroxyapatite. Acids from bacteria leech the OH (aka hydroxy) group from the enamel, which weakens the structure and makes it prone to cavitations.",
"Fluoride replaces the OH (aka hydroxy) group in hydroxyapatite to form fluoroapat... |
[
"Is there a reason why people \"look\" like their name?"
] | [
false
] | null | [
"It sounds like the question you are trying to ask is \"is there a correlation between names and physical appearance\" that's a different question from the title of your post. Please make a new post."
] | [
"I don't think that's really what I'm asking because I don't think that's really true. Why would there be? Perhaps my description wasn't clear, what I mean to ask is whether science recognises this phenomenon of people believing that the physical appearance of others correlates with their name.",
"So not \"is t... | [
"So the last question you posted makes the most sense to me \"do people believe that there is a relationship between name and physical appearance\". Unfortunately, that phrasing isn't great because it sounds like you're polling the readers of this sub, and that's not what you mean. Maybe something like \"is there a... |
[
"When someone gets a transplant of an organ that they have two of, like a kidney, does the new organ have to come from the same side of the donor's body as the one it's replacing?"
] | [
false
] | I mean in a lung transplant I can understand why it would matter because a right lung in the left side of the body would be in the way of the heart, but what about kidneys? | [
"Doesn't matter. They don't even put a transplanted kidney anyplace near the original location, anyway, and usually don't remove the old kidneys either. See ",
"this image for a good example",
". ",
"Which side they transplant a kidney to depends really on the surgeon's preference or the recipient's anatomy, ... | [
"I've mentioned this in ",
"another transplant related thread",
" but something else to know is that when the transplant recipient receives a new kidney the original kidneys are usually left in place. It's often the case the ",
"kidney is not functioning in terms of filtering blood",
", but the tissue is ot... | [
"I can only claim blindness. Somehow I missed the rest of the sentence after \"anyway.\" Sorry, didn't mean to repeat what you had already said."
] |
[
"How is heat transferred through the glass??"
] | [
false
] | [deleted] | [
"Some photons pass through glass and heat up what's on the other side.",
"Atoms with higher temperature hit the glass atoms and make them vibrate. The vibration spreads through the glass and then the atoms on the other side of the glass bounce off of the glass atoms and take some of the vibration energy away (hea... | [
"It's both. Just like in the optical, the 'heat radiation' can pass through the glass. I had a quick Google and looked at a transmission diagram for silica and it is mostly transparent in the near-infrared (I think it's reasonable to consider the near-IR, I took a quick look at the sun's irradiance curve). Some of ... | [
"So it's conduction not radiation?"
] |
[
"How come microwaving cooked chicken causes it to become rubbery?"
] | [
false
] | null | [
"Dehydration. You don't need a microwave for this. You can take almost any piece of chicken and put it in a pan on low for 40 minutes. Provided that you don't burn too much of it, try taking a bite and you'll find the same thing. The microwave tends to 'supercharge' the dehydration process causing even more moistur... | [
"Please delete this comment, as it is offensive and adds nothing to the conversation. Thank you."
] | [
"Please delete this comment, as it is offensive and adds nothing to the conversation. Thank you."
] |
[
"Is it true that tasks requiring coordination of both hands ( driving, juggling, playing the piano ) can help with / train one's concentration?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"We do not debunk or vet theories or offer peer review on ",
"/r/AskScience",
". For more information regarding this and similar issues, please see our ",
"guidelines",
"You can find the basic a... | [
"Oh, I thought you guys could at least say what's the current state of scientific community. Controversial / mostly agree / disagree"
] | [
"Sorry, but in general we cannot do bibliographic reviews. It's rare when a panelist has the time to do so or the question is very specific."
] |
[
"If you use a power tool in a vacuum, where does the extra energy that would usually be expelled as sound go?"
] | [
false
] | [deleted] | [
"Heat, mostly. Although even loud noises don't usually correspond to a lot of thermal energy. ",
"Power tools also tend to have fan bits to cool them, plus ordinary conduction/natural convection to the air. In a vacuum, where they can only lose heat through radiation, they'd be likely to overheat. (Which is an is... | [
"I would think the tool would vibrate just a little bit more. The vibrating tool transfers a little bit of that energy into vibrating the air, which has a dampening effect on the vibrations of the tool."
] | [
"The amount of thermal energy lost to radiation per unit of surface area is given by ",
"Stefan-Boltzmann's law",
", which simply states that it's proportional to the absolute temperature to the fourth power, with the proportionality constant depending on the material. ",
"Obviously increasing T would defeat ... |
[
"Why doesn't Windows' 'estimated time remaining' ever work?"
] | [
false
] | null | [
"I believe it's more of a problem of the algorithm they used for calculating the remaining time. I also think they've re-done it for windows 8, it seems better. But anyways, from what I've experienced after years of watching the stupid/crazy file transfer bar, it probably goes something like:",
"start a running t... | [
"Windows (and all GUI's that I am aware) enumerates the file structure before the copy process: it knows the sizes and number of files and folders before it begins."
] | [
"To give a specific example of this: way back in the IE4/5 days the algorithm that estimated the download rate and remaining time didn't start until several seconds ",
" the download started. This gave the algorithm the illusion that a lot of data had been downloaded in a very short period of time. Subsequent run... |
[
"How do apps like Soundhound and Shazam work? Is there a database that matches songs or does it recognise far more than that?"
] | [
false
] | null | [
"They sort of explain it on their ",
"website",
".\nThey have a large database of audio-samples that is labeled (title, author, etc.). But you cant just directly compare your humming and singing with that database, you wouldnt find anything, because for that to happen your humming would already have to be in th... | [
"Shazam is explained in ",
"this paper",
" (see also ",
"here",
")",
"From the sample you send them, Shazam builds a list of numbers using an algorithm they developed, and compares it to the results of the same algorithm\napplied to a big database of songs. This representation is much more compact than t... | [
"Not a direct answer to your question, but as I guess the other answers will talk about complex and highly technical audio fingerprinting algorithms I thought I'd share one I thought was both ingenious and very easy to visualize.",
"Start the song and take the pitch of each note as it's being played. If it is the... |
[
"How did birds evolve wings?"
] | [
false
] | A summary of my understanding of evolution is that random mutations occur which lead to one animal being more likely to survive than the other, therefore passing on the mutated gene while the inferior gene dies out. So how did birds get wings? If I understand correctly it would have to be a very gradual change, lump ->... | [
"Ornithologist/herpetologist here, typing over breakfast, so please forgive typos etc.",
"Dinosaur scales, just like modern-day reptile scales, bird feathers, and bird and crocodile scutes (those tough scaley bits on bird legs, those big smooth bits on crocodile backs) are made from beta-keratin. Scientists have ... | [
"Not a scientist, but there are animals that are gliders. They can't fly, but take advantage of increased skin spread to extend their leaping distance between trees.",
"http://en.wikipedia.org/wiki/Flying_squirrel",
"http://animals.nationalgeographic.com/animals/reptiles/flying-snake/"
] | [
"You couldn't have explained it any better, thanks! "
] |
[
"What causes cell signal to seemingly go in and out, when both I and the tower are stationary?"
] | [
false
] | As I typed the title alone, I went from service, to no service, and back. What factors contribute to this behavior? To help narrow it down, I am indoors, in a public space. | [
"The dominant signal path between you and the cell tower is unlikely to be a direct line-of-sight one; there'll be multiple refractions around and reflections off of intervening objects. That path might be momentarily obstructed, for example by passing people in that public space (6' bags of salty water are great r... | [
"Actually, my professor tried this experiment at a conference where they set up a wifi receiver and transmitter system in a lecture hall and then analyze the channel (all the reflections of all the people). They wanted to see if they could see the difference between a certain person being in the room or not (and ha... | [
"The detail is not there yet but medical applications are invented such as monitoring heart beat of patients in a room etc."
] |
[
"In the split second before someone is about to collide with another moving vehicle, would it be more beneficial for them to tighten their muscles, or relax them?"
] | [
false
] | Hypothetically, if someone is driving through an intersection in their vehicle and is wearing their seatbelt, and they are going anywhere from 30-60 MPH, and they see another vehicle run a red light, and it is going the same speed as they are, assuming there is no chance to stop or avoid the collision, would they have ... | [
"Drunk ",
" trauma victims have a higher rate of survival than their sober counterparts",
". It's possible that the alcohol-induced relaxation may help survivorship during that trauma, though as far as I'm aware, that idea is still speculative. ",
"In general, any structure with some \"breathing room\" can ab... | [
"That sounds like some pretty heavy speculation on the part of the doctors. The relaxation theory makes sense, but it would seem that being ejected from the vehicle (regardless of muscle tension) would greatly increase your chances of harm from extraneous variables. Like having your body collide with a tree, wall... | [
"That sounds like some pretty heavy speculation on the part of the doctors. The relaxation theory makes sense, but it would seem that being ejected from the vehicle (regardless of muscle tension) would greatly increase your chances of harm from extraneous variables. Like having your body collide with a tree, wall... |
[
"What evidence do we have that there wasn't any advanced civilization, like humans are currently, here on Earth some hundreds of millions of years ago?"
] | [
false
] | null | [
"There hasn't been any evidence found in support of it. And while absence of evidence is not evidence of absence, we have no reason to entertain any random claim since there are an infinite number of them. For example, if I say \"what evidence is there that unicorns don't exist and live at the bottom of active volc... | [
"This is not a claim, it's a valid question. And it's not random, it's based on the evolution of species."
] | [
"My answer was from a philosophy of science perspective: When we have a statement, or a hypothesis, or a theory, how do we test it to know that it is true? We either have some confirmatory evidence in support of it and then we might say that it is true as far as we know (something akin to inductive inference), or, ... |
[
"How fast does air get sucked into space?"
] | [
false
] | You see in movies when there is a hull breach or whatnot, air/object get sucked out of the hole extremely fast? How fast is it? | [
"Air molecules move QUICKLY. At 20°C, an average air molecule will probably move around 500 meters per second. When they bounce off something, they push off that thing, they impart some momentum. The force experienced by an area with a lot of air molecules bouncing off it is air-pressure. Normally, you'd have air m... | [
"Air flowing through a hole like this will always be choked, and limited to precisely the speed of sound through the hole, regardless of the pressure difference.",
"The link you provided is very wrong, because ignoring compressibility effects when you have density+pressure variations of this magnitude is wildly i... | [
"This is the correct response. Air flowing through an orifice will max out at Mach 1. At that point, the flow rate is dependent only on the pressure within the chamber. The downstream pressure (vacuum) doesn't matter. The actual amount of time will depend on the size of the chamber, the pressure of the chamber and ... |
[
"Is there a genetic code or mechanism that makes sure that our body grows uniformly?"
] | [
false
] | Like is there something that prevents our hands from growing significantly larger that the other or our bones from growing through our skin? | [
"Short answer: Yes.",
"Answering with a bit less factious cheek: the on/off switches for your genes are controlled by transcription factors. These are activated or inactivated by compounds they bind to. Binding is all about how well things fit against each other combined with how much of each is around. So if the... | [
"Yes, I was trying to cram a lot of information into a short answer.",
"Basically, cells are able to communicate to each other through signaling networks. These work at different levels of cell interaction. \"Cell-cell\" signaling is the term for two cells that are physically touching each other. \"Paracrine\" si... | [
"Thanks for your answer\nIt's a bit difficult to understand but after a few readings i could get, so there's something like a benchmark where the binding partners are present and the cells or the body as a whole grows until the cell's transcription factor reaches it and binds with it, right?",
"Does the binding p... |
[
"A question about how the velocity/acceleration of an object is affected by curvature in spacetime..."
] | [
false
] | [deleted] | [
"Best way to think of it is that general relativity dictates an equation of motion for the object, and from that equation of motion you can determine a potential that is similar to that of Newtonian gravity but with some corrections. The potential still goes primarily as 1/r, which yields stable elliptical orbits w... | [
"you always move through spacetime (with speed of light, actually). if your speed doesn't have any spatial components, you just move in direction of time. you cannot do anything to stop this. you can tilt the direction of your four-velocity vector in some of the spatial directions, so that the time component is sma... | [
"The curvature of spacetime is observed as a force on the object. A force is the same as an acceleration with a scaling factor of mass, therefore the curvature of spacetime accelerates the object.",
"In the case of your orbiting object, it is moving fastest when nearest the focus because this force is acceleratin... |
[
"How did the transition from egg-laying to live birth happen?"
] | [
false
] | I understand evolution is a very slow process. I can imagine a small node or protrusion slowly becoming a fin and a fin slowly becoming a limb, etc. But visually I have a hard time imagining what the "in-between" stages looked like between egg-laying animals and mammals that have live births. Did egg-laying animals slo... | [
"There are a lot of animals now that are basically the intermediate stage. They're live bearers like guppies, Platies, several types of snakes, sharks, flies... They're basically egg laying species that delay the egg laying step until after the eggs have hatched and then lay live young. This differs from true li... | [
"From the species alive today, we can guess how mammals transitioned from laying eggs to having a live birth. As you may know, echidnas and platypuses both lay eggs. The shell is more like a leather skin than a hard eggshell that you see when making your breakfast. The young will hatch early as there are not a lot ... | [
"Evolution doesn’t necessarily HAVE to happen with gradual changes, there is a model called punctuated equilibrium that describes periods of not much change interspersed with periods of rapid change. ",
"https://en.m.wikipedia.org/wiki/Punctuated_equilibrium",
" ",
"I don’t know about egg laying/live birth at... |
[
"What is the lowest possible orbit a satellite have on earth?"
] | [
false
] | If a satellite moves fast enough, would it be possible to orbit at 100 feet? 10 feet? 1 foot? | [
"Ignoring the presence of the atmosphere, a satellite can orbit at any height above the surface (ignoring the presence of mountains, etc.). Including the atmosphere, orbiting close to the ground would result in you no longer having a satellite pretty damn quickly. "
] | [
"Assuming atmosphere, the lowest a satellite can orbit without beginning to experience significant decay is 160 km. Atmospheric drag is high enough to cause break up around 80 km, so technically a satellite with an engine to counter decay could dip below 160 km. ",
"https://en.m.wikipedia.org/wiki/Low_Earth_orbit... | [
"Theoretically yes, as the difference in gravitational pull is minimal. If you assumed the earth were a smooth sphere then almost any any distance is feasible if you go fast enough, although how close you could get before you'd have to go past the speed of light I don't know"
] |
[
"Why do I only seem to hear about “upper” respiratory infections but never “lower” ones? Is there such a thing?"
] | [
false
] | Also, if they are a thing, what would a “lower” respiratory infection be in relation to an “upper” respiratory infection | [
"Its more a matter of language than that there aren’t lower respiratory tract infections - you just know them as pneumonia, acute bronchitis and tuberculosis for instance. Upper respiratory tract infections are generally more common, so you hear about them more often, and more diverse (anything from colds, sinusiti... | [
"Upper respiratory infections are very common. Colds and Flu's are common upper respiratory infections. They happen primarily in your mouth, nose, throat area.",
"Bronchitis is when the infection reaches the bronchial tubes. Pneumonia is when it reaches the lungs. They just don't call it a lower respiratory infec... | [
"While upper respiratory infection are most common... one can not get one while traveling through the south. one can still get an upper respiratory infection in the north. ",
"With out treatment, an upper or lower respiratory infection could spread to become a sideways infection. Most cases are self limiting but ... |
[
"If you placed a combination of molten metal inside a centrifuge that is inside a furnace, would the metals separate in the same way as it does when placing blood in a centrifuge. Heavier metals going to the bottom and lighter to the top?"
] | [
false
] | null | [
"Metals are atom sized. Gravity has nearly no effect atoms because they are so small. The only force moving the atoms is going to be heat.",
"This is not a good explanation. Take oil and water- the oil floating on top of the water is due to gravity. Oil and water may be molecules, but I know there are metal atoms... | [
"Phase diagrams are almost universally simplifications, and typically don't account for non-hydrostatic/anisotropic stress states. Just wait for Thermo 102 ;-)!",
"Edit: More to the point, liquid (or solid) solutions don't rule out chemical concentration gradients, especially at non-equilibrium conditions. "
] | [
"I'll defer to someone with more specific expertise, but here's my take:",
"In the case of blood separation, you're dealing with relatively large solid particles suspended (not dissolved) in a fluid. In the case of different liquid metals mixed together, it would depend on whether the metals are miscible (soluble... |
[
"Would it be better to neutralize an acid spill with a weak base or a strong base?"
] | [
false
] | null | [
"How you neutralize depends on the acid. If you spilled concentrated sulfuric acid, you're best off avoiding water and using something like solid calcium carbonate. If it's hydrochloric acid, you should dilute before attempting neutralization because HCl produces vapors when it heats up. If you spill something l... | [
"What makes HCl a weaker acid than HF?",
"HF is the weaker acid. (pKa 3.2 vs -6.5 for HCl) ",
"But HF is toxic. The F",
" combines with Ca",
" to nearly insoluble CaF2 but the body needs its calcium. ",
"Additionally the lower acidity means that more hydrofloric acid exists as non-dissociated hydrogen flu... | [
"The acidity is determinded by the equilibrium.",
"HF <-> H",
" + F",
"and",
"HCl <-> H",
" + Cl",
" respectively.",
"H",
" has always the same energy. But when I say F",
" is less stable (with respect to HF) than Cl",
" (with respect to HCl) then the first equilibrium is more on the left side a... |
[
"AskScience AMA Series: I was NASA's first \"Mars Czar\" and I consulted on the sci-fi adventure film THE SPACE BETWEEN US. Let's talk about interplanetary space travel and Mars colonization... AMA!"
] | [
false
] | Hi, I'm Scott Hubbard and I'm an adjunct professor at Stanford University in the department of aeronautics and astronautics and was at NASA for 20 years, where I was the Director of the Ames Research Center and was appointed NASA's first "Mars Czar." I was brought on board to consult on the film , to help advise on the... | [
"Do you think there are compelling reasons to eventually build large scale settlements on Mars, or will human presence there be limited, like on Antarctica?",
"If you think colonization is realistic what do you think will motivate a large number of people to move to Mars?"
] | [
"Some people say that this desire to live on Mars is to ensure the survival of the human race, if and when a large scale extinction event occurs here on Earth. That's a valid reason. We've evolved, with the rest of the world, to pine for the maintenance of our own genetic line. Putting human beings on the face of a... | [
"Some people say that this desire to live on Mars is to ensure the survival of the human race, if and when a large scale extinction event occurs here on Earth. That's a valid reason. We've evolved, with the rest of the world, to pine for the maintenance of our own genetic line. Putting human beings on the face of a... |
[
"General relativity question"
] | [
false
] | From my understanding, planets are imbedded in time space as it expands, so the planet is moving with space time as well as through space time. But what about the point where space time and the planet actually meet, does space time continue through the planet, or stop at the surface of the planet? I thought perhaps spa... | [
"http://en.wikipedia.org/wiki/Spacetime",
"\n\"In physics, spacetime (or space-time, space time, space-time continuum) is any mathematical model that combines space and time into a single continuum. [...] By combining space and time into a single manifold, physicists have significantly simplified a large number o... | [
"So you're saying that the fabric of space time is not a literal thing and is used to help understand theories "
] | [
"That's my understanding, but I'm no physicist. Light slows and even changes direction when it passes large celestial systems, creating a gravitational lense. ",
"http://en.wikipedia.org/wiki/Gravitational_lens"
] |
[
"Why does a clock gain time?"
] | [
false
] | null | [
"Clocks tend to work by having some sort of oscillating natural phenomenon. The clock counts the oscillations and thus makes the time. However, the oscillations are not exactly in sync with real time as they don't tend to be that fast and so the clock loses time."
] | [
"Thank you for your response!\nBut in this day and age, isn't there a better way to keep time?\nOr is it just not cost effective? "
] | [
"There is, and it's called an internet connection."
] |
[
"How much lava is there on earth?"
] | [
false
] | My son’s actual question (the relevance of which we may ignore for now) was if there was more water or more lava on earth. I have read estimates on the amount of water, but it seems to be an interesting, uncommon question how much lava there is on (in) our planet. (I guess this would be a question for Randall Munroe..)... | [
"In terms an actual number on the total amount of magma (liquid rock not erupted) and lava (liquid rock erupted) that exists at a particular time, it's going to be very hard to quantify with any accuracy. ",
" To go beyond that general statement, let's do some estimations. For the sake of these comparison, let's... | [
"The earth's mantle is mostly soft hot rock, so let's go with the earth's outer core. That's liquid.",
"170,391,230,000 cubic kilometers.",
"Estimated water on earth is 1,400,000,000 cubic km So, there's about 121 times as much magma in the earth as water."
] | [
"The Earth’s core isn’t what we would call magma though. It does not solidify into rock, it is never erupted and it has no material interaction with the mantle."
] |
[
"Is there such a thing as a perfect hermetic seal and/or a material which is completely impermeable? If not, is such a thing even theoretically possible?"
] | [
false
] | Basically, what I am asking is if there is anything which can perfectly contain fluids, in particular hydrogen and helium, without any leakage. As I understand it, even metal flasks have trouble with this, due to the hydrogen seaping through. Moreover, this seems to especially be a problem with helium since it is monoa... | [
"\"Perfect\" is a tricky word. No container is going to give you zero losses over an indefinite period of time (if nothing else your container will eventually evaporate). As a practical matter, you have to define acceptable losses per unit time."
] | [
"What is the best one could do? What material has the lowest reported permeability to hydrogen/helium?"
] | [
"I'm sorry, I don't know."
] |
[
"Quick question about the ionosphere and radio waves."
] | [
false
] | So, I live in Northwestern Ohio, and I was working today at my delivery job. So obviously, for entertainment, I'm listening to my radio. I have it turned to 88.7, which is an alternative rock station based in Detroit. And as I'm listening, it starts to fade out, and I hear, clear as day, a completely different station ... | [
"I've never heard of it in the FM frequencies (but neither have I looked). But I know for sure that plenty of people use this for AM and Shortwave radio communication. Radio waves do bounce off of the nighttime ionosphere and can travel vast distances from this reflection."
] | [
"This is certainly possible. Searching for long-distance propagated TV and FM signals is a common pastime in the amateur radio community, which wikipedia refers to as ",
"TV DX",
". The mechanism's of propagation over long distances are generally more complex than just 'bounced of the ionosphere', though.",
"... | [
"Somebody could have been streaming internet radio on a smartphone and using a small FM transmitter to listen to it on their car stereo."
] |
[
"Are the martian landscapes we see in photographs uncharacteristically flat and smooth for Mars in order to make it easier for the rovers? Are there typical, dramatically steeper/rockier landscapes that we haven't seen yet from the ground because the rovers can't go there?"
] | [
false
] | Are we only seeing photos of the martian "great plains" because our rovers couldn't handle the martian "Rocky Mountains". | [
"We see where the rovers can go. Mars is a very tricky planet to land on: it has a very dusty atmosphere where particles impact heat shields, but it also doesn't have enough atmosphere to decelerate a probe to a safe landing. Since parachutes are not enough, the last part of the descent is usually performed on retr... | [
"Mars mission planning is always a conflict between the scientists, who want to go to \"cool\" places, and the engineers, who want a nice safe flat spot to land on. (That's not fair, the engineers want to go cool places too, but they know the risks.)",
"Over the years, as we've gotten better at recon and landing... | [
"Thanks. I'm just starting to really appreciate that landing once or twice on a planet isn't close to exploring all it has to offer. I look forward to future missions and seeing many as-yet unseen wonders of Mars. PS: Your second photo is now my desktop"
] |
[
"Is dark energy/matter created by the expansion of the universe? Does this violate conservation of energy if it does?"
] | [
false
] | null | [
"Dark energy has a constant energy density. If the volume of a region gets larger by expansion, the total dark energy inside obviously increases. This clearly violates conservation of energy, but energy is not conserved in cosmology, so no problem.",
"Dark matter is actually much more down to earth and acts like ... | [
"A better way to phrase it is that general relativity does not have a well defined, global \"total energy\" so conservation of energy doesn't really apply to a cosmological scale. ",
"General relativity does require ",
" conservation of energy, so any reaction happening at any point will obey energy conservatio... | [
"The first law of thermodynamics ",
" conservation of energy. This is a tragically common misconception. In cosmology, the law of thermodynamics are true, energy conservation is not."
] |
[
"Phd about fungal alpha carbonic anhydrase!"
] | [
false
] | [deleted] | [
"The function of carbonic acid anhydrase is pretty simple, as the reaction barely needs catalyzing to begin with (just H2CO3 <--> H2O+CO2 has a barrier of ~20 kcal/mol in water). In this case, it's likely little more than the zinc ion acting as a Lewis acid. ",
"If you want to see a change, I suppose the obvious ... | [
"I'm not familiar with fungi, specifically, but I've flanked it with bacteria and mice. In both of those, the first question would be \"Did we really get it?\"",
"1) It sounds stupid but....are you sure you got the gene? Run a Southern, not just PCR, to see if the gene is ",
" gone.",
"2) Is the transcript ",... | [
"You are absolutely correct. A friend of mine was given a transgenic ",
", which was supposed to have only one gene of an operon knocked out...it tuned out that the entire operon was gone, as well as any chance of publishing during her master's program. ",
"I would certainly determine the status of the \"knoc... |
[
"Why do human beings have such distinguishable facial features?"
] | [
false
] | We could identify each other just by examining our faces from 7 billion other people in the world, why doesn't this apply to any (most) other species? | [
"It's not that our features are inherently recognizable, it's that our brains have evolved to recognize our features."
] | [
"We are 'wired' to specifically recognize and differentiate human facial features and expressions. If you were a Baboon, you would be able to recognize specific features of other Baboons very well, but not humans. Basically, most animals are tuned to be able to recognize specific features of their species (sounds, ... | [
"Also, you are very capable of training yourself to recognize the minor differences in animals. Cattle and sheep herders can often recognize every individual in their flock, while to the untrained eye they all look the same. Those who do long term studies on social animals (primates, elephants, dolphins, whales...)... |
[
"What does \"structure of lowest energy\" mean?"
] | [
false
] | How come: low surface area => low energy? see 10 seconds of the video linked below | [
"Imagine molecules being bonded as people holding hands and trying to make a shape. If you cover a lot of surface, people will have to stretch and this is very tiring. On the opposite, if you squish everyone together people will be crushed and this is very tiring as well.",
"There is a shape that all those people... | [
"Surfaces can always be considered as defects. The specific reasons for this vary whether you are looking at a solid, like a metal or crystal; a liquid; or more complex matter, as the bubbles in your example.",
"In solids, atoms at the surface have a higher energy because they have a non-ideal bonding configurati... | [
"How come: low surface area => low energy?",
"You mentioned that with certain constraints they make weird shapes, so does that mean that this isn't always true?"
] |
[
"Does fitness (or lack thereof) affect immune function? (IOW, do out-of-shape people get sick more?)"
] | [
false
] | Having a debate with someone on the matter and I didn't recall seeing any evidence one way or the other on the matter. | [
"There are several lines of evidence to suggest that physically fitter people have stronger immune systems compared to people lacking fitness; however, as with all immunology, nothing is straightforward!",
"This study found that people with a high level of self-reported fitness experienced fewer colds (46% fewer)... | [
"Sorry, the increased infection rate is for upper respiratory tract infections (URTI, colds and the like), which rather rules out foot injury. I should have mentioned! ",
"These studies are far from conclusive, due to inherent errors in self-reporting both URTI frequency and perceived fitness. Non-fit/strong im... | [
"I saw a cool seminar on this about 5 years ago by Monika Fleshner (UC Boulder). She studies aerobic exercise in rats. The running (on the running wheel) releases endorphins. The endorphins impact neural activity in the hypothalamus that causes the release of noradrenaline in the spleen (sympathetic effect). The re... |
[
"Do human females produce pheromones during ovulation to attract males?"
] | [
false
] | null | [
"The most fascinating thing is, women have evolved to attract males from a distance as well (ie. when they're not close enough for them to be able to smell naturally released pheromones).",
"For example, at a bar or night club, more women are likely to be wearing perfume, but there are hints men can pick up subco... | [
"This looks like an interesting starting point:",
"http://pss.sagepub.com/content/21/2/276"
] | [
"Nope:",
"http://www.slate.com/articles/double_x/doublex/2011/08/the_scent_of_a_woman.html"
] |
[
"If there are 10x as many micro-organisms on you as there are cells in your body, do they make up most of your weight?"
] | [
false
] | null | [
"They make up about 1-2 kg of your weight. Don't forget that the most abundant type microorganism of your body, the bacteria, are only a fraction of a size of a single eukaryotic cell (they're about as large as mitochondria), and only weigh a tiny fraction of an eukaryotic cell as well. Even though the number of ba... | [
"It's also worth noting that a portion of a human's mass stems from non-living matter. Bones, teeth, etc all contribute to our mass, though they aren't included in the 'self cells' vs 'non-self cells' question."
] | [
"You mean the mineral component of bones and teeth in the extracellular matrix though, right? Because bones and teeth are absolutely built from and incorporate living tissue with an active metabolism that is capable of proliferation + differentiation, apoptosis and regeneration."
] |
[
"If we could dig a hole deep enough that the heat was enough to convert water to steam, could we produce an endless supply of power by harnessing that steam?"
] | [
false
] | I'm making a couple of assumptions in my question - namely that we can move water to the hole in a steady consistent fashion and that we can build a steam turbine at the hole or close enough to the production of steam to be useful. I don't know if the water would eventually cool down the heat source. I just think about... | [
"Yes, you're describing ",
"geothermal power",
", which has been around for over 100 years, though didn't start to be used on industrial scales until around 1960. The main issue with geothermal is the cost of getting a plant up and running as it requires drilling (which is always expensive). These in many ways ... | [
"As long as the earths core produces heat, there will be a supply of energy. You pouring water there is neglible to the temperature.",
"Earths core is powered mainly by radioactive isotopes with half lifes ranging from 1billion to 14 billion years. So very slowly the energy supply is dimishing, but remember that ... | [
"Geothermal energy is limited in the same way as solar energy. It's not literally infinite, but it comes out at the same rate whether or not we use it (the amount of Earth's interior heat that's lost through the surface is much more than human energy usage, but it absolutely pales in comparison to the amount of sol... |
[
"Is GP120 found anywhere besides the exterior of an HIV molecule? If yes, where? If no, what traits of the HIV molecule prevent the development of an effective GP120 inhibitor?"
] | [
false
] | null | [
"gp120 can also be found in SIV (simian immunodeficiency virus), and it can also be shed from the HIV surface. I do not know the difference/similarity between gp120 of different viruses.",
"gp120 is hard to inhibit because it contains multiple variable regions. Constant regions that are required for binding are c... | [
"My basic understanding is that the nature of the protein makes it difficult for immunoglobulins to attach/bind to. There has been moderate amount of research into producing such antibodies that are able to accomplish this, with mixed results. As far as why its particular structure or electrostatic properties keep ... | [
"Thanks for the link and the answer; it was a better description than my teacher could give "
] |
[
"How dense does air get in the compressor of a jet engine?"
] | [
false
] | How dense does air get in the compression and propulsion stage of a jet engine? Is there a way to conceptualize how incredibly dense this is in simple terms? | [
"For an isentropic (idealized) compressor, the density change is equal to the pressure change raised to the power of 1/gamma (1/1.4 for air). So a (high end) compressor ratio of 40:1 will give a density ratio of 14:1.",
"At sea level, you're looking at 1.2 kg/m",
" ambient density, so it'd be compressed to ~17 ... | [
"The density of air at 1 atm is 1.204 kg/m3. So the max pressure of air in the GE90 should be 50.568 kg/m3. This is about 1/20th as dense as water.",
"kg/m",
" has units of density, not pressure. Compressor ratios of 42:1 doesn't mean the density of air increases 42 times, it means the pressure has increased 42... | [
"viscosity?"
] |
[
"Determining the path c(t) of a particles using it's starting position+velocity?"
] | [
false
] | This has been bothering me for some time now: Say you have a particle in a (static-)field (e.g. an electron in an electric field, or a small asteroid near the sun) If you know it's starting position and it's velocity wouldn't that be enough to analytically determine the path c(t) of the vector as the classical laws/ma... | [
"You're asking if differential equations have solutions? They do, as long as the function E is not too pathological. See ",
"the Picard–Lindelöf theorem",
".",
"You're asking if we can write those solutions as \"nice\" expressions? That can't even be done for integrals. See ",
"Liouville's theorem",
"... | [
"Yes and no.",
"The acceleration of the particle depends on its position and the position of the other particles around it. This results in the formula for position usually being expressed as a differential equation. We can approximate it with varying degrees of success, but an explicit solution for position is... | [
"The 3-body problem is sort of similar to what I'm trying to determine but not exactly. For the 3-body problem you have 3 particles and they all interact, but in my situation there is 1 particle and the field in which it moves is independent of the particle itself.",
"\nI saw on the wiki page for the 3-body-probl... |
[
"Is it possible that matter and antimatter were produced in equal quantities and that our abundance of matter where we are is just due to a slightly uneven distribution of matter/antimatter production during the Big Bang?"
] | [
false
] | Apparently the cosmic microwave background has slight density variations, which have been attributed to quantum fluctuations way back nearly 14 billion years ago. Could our abundance of matter be due to similar circumstances? I'm imagining it something like this: When the universe was undergoing the Big Bang, many regi... | [
"Could our abundance of matter be due to similar circumstances? I'm imagining it something like this: When the universe was undergoing the Big Bang, many regions produced matter and antimatter, most of which annihilates. However, some areas had slightly more matter, such as our region, and perhaps other regions hav... | [
"It's not an abundance of matter, it's only a small fraction of matter over anti-matter"
] | [
"Why did this get down-voted. The imbalance is around like 1%... seems pretty small.",
"http://science.slashdot.org/story/10/05/18/0034227/matter-antimatter-bias-seen-in-fermilab-collisions",
"Love me some Reddit where people get negative karma for being right... "
] |
[
"Question about instantaneous transfer of forces."
] | [
false
] | [deleted] | [
"The signal transfers through the balls at roughly the speed of sound in the metal. Because they are so much smaller than the distance sound can travel through metal in a second, it appears instantaneous. If you had a bunch of balloons filled with jello in the same configuration, it wouldn't seem so instantaneous."... | [
"That's pretty good reasoning from balls to a rigid body. The force is going to be transferred from one side to the other by a compression wave, and the speed of that wave is determined by sqrt((bulk modulus)/(density)). So a wave would travel through an infinitely stiff object infinitely fast, and would have an ... | [
"The force would be transferred instantaneously ",
"rigid***. In reality, there is no such thing as a truly rigid object. Matter simply doesn't work that way.",
"When the balls collide they deform. If the forces in the collision are really high (hitting them with a sledgehammer) they will deform inelastically- ... |
[
"Why doesn't the strong force make atomic fusion easier?"
] | [
false
] | If the strong nuclear force is such a strong attractive force that increases with distance between hadrons (to a point at least), why does it take so much energy to combine nuclei instead of them getting close and fusing together by themselves? | [
"The forces between quarks increase with distance (really the potential is approximately linear with distance, so the \"force\" stays constant).",
"But the forces between ",
" do not increase with distance. This is called the \"residual strong force\", or simply \"nuclear force\". The nuclear force is generally... | [
"I see, I didn't realize that the coulomb forces were that strong, but I suppose they do interact over a much larger distance. In that case could we not bombard a nucleus with neutrons that would then beta decay into protons and give off energy? Or am I misunderstanding the neutron decay?"
] | [
"In that case could we not bombard a nucleus with neutrons that would then beta decay into protons and give off energy?",
"Sure, you can do that. This happens in some astrophysical situations; it's how many of the heavier elements are produced in nature."
] |
[
"How do greenhouse gases 'trap' heat?"
] | [
false
] | I read today, "...Some of them can trap more heat than CO2. A molecule of methane produces more than 20 times the warming of molecule of CO2..." It lead me to wonder what's the physical property of such molecules which makes them 'trap' heat. Is there a combustion reaction with CH4 which releases energy? If that was th... | [
"The relevant property of the gas is its absorption spectrum.",
"The Earth continuously radiates heat out into space, keeping it in thermal equilibrium with the incoming energy from the Sun. The amount of energy radiated away and the wavelength of it depend on the temperature of the Earth. This radiation is calle... | [
"And here's a wikipedia page, with the actual math used to compare greenhouse gases, and some practical examples:",
"https://en.wikipedia.org/wiki/Global_warming_potential"
] | [
"molecules are atoms connected by bonds, but these bonds are not rigid but springy. Infrared radiation is absorbed by chemical bonds and the energy is converted into vibrational energy, making these springy bonds vibrate. ",
"Different bonds absorb different wavelengths of infrared, so absorb different amounts of... |
[
"Does the atmosphere have tides?"
] | [
false
] | It’s my understanding that the moon causes sea levels to rise and settle as it’s gravity pulls water towards it. Does it do a similar thing with the air surrounding earth? Does the atmospheric boundary fluctuate as the moon orbits? | [
"Yes - the atmosphere has tides, but they are predominantly thermally driven. Consider if the Earth was stationary, and you suddenly turn on the sun. A portion of the atmosphere would heat up and expand, creating a pressure wave which would propagate around the Earth at a speed proportional to √h, where h is the co... | [
"Good question, the answer is yes. Atmospheric tides have been studied for centuries. There are a lot of papers written about them, google scholar is a great resource for these. Atmospheric boundary layers fluctuations are influenced by the moon but solar forcing via heating, turbulence, and an assortment of w... | [
"the speed of sound is the propagation speed of vibrations of audible frequencies in air, and is actually different for each frequency. If your wavelength is comparable to the height of the medium, different physics (",
"Lamb waves",
") is needed to accurately describe the propagation"
] |
[
"How circular is our moon’s orbit, and do any moons have very stretched orbits or are they all usually circular?"
] | [
false
] | null | [
"It has an ",
"eccentricity",
" of 0.055, the farthest and closest point differ by ~10%. The gas giants have some very eccentric moons, most likely captured from asteroids passing by. ",
"Jupiter LXVII",
" with an eccentricity of 0.5569 is an example, its closest and farthest point differ by a factor of abo... | [
"Short answer: orbiting for a long enough time could make an orbit stable. Same thing happened with the moons rotation, and it became tidal locked, which means only one side faces us. (One rotation every orbit makes it look like its not rotating)"
] | [
"I'm actually surprised there is no answer to this yet...",
"Orbits are not circular. They follow a path called an ellipse which is something like a circle, but it has two centers. In shape is close to what most people call an oval. In any given orbit, the larger object will sit at one of the two foci of the s... |
[
"Straight To The Gut: Why When Some People Put On Weight It Appears To Gravitate To A Certain Body Part IE. <Butt,Gut> Is There A Scientific Answer To This"
] | [
false
] | When we gain weight are some people more prone to gaining weight in specific areas? Shouldn't it spread proportionally throughout everyone? Before someone else says it, an example of this would be a girl gaining an extra few pounds but instead of going to her stomach it appears to show up on her butt, or a guy gainin... | [
"There is a fairly clear association with the distribution of fat and circulating sex hormone levels. Unfortunately, while there are pieces of the puzzle being worked out, I don't think anyone can say for certain why men gain weight in their gut, while women gain it on their arms/thighs/butt. It's related to test... | [
"Thanks!! Though if anyone else has further info, I'd love to hear it."
] | [
"I kinda have a question to add on to it, if anyone answers. ",
"I've heard that stress can promote fat being stored in the abdomen. A woman gains 40 pounds, but was always very stressed and most of the weight went to her abdomen. Say if she were to lose the weight, and gain it again minus the high stress levels,... |
[
"How does GABA(a) presynaptic depolarization lead to inhibition of transmitter release?"
] | [
false
] | [deleted] | [
"Yes, the classic/textbook view of GABAa effects is about anion currents and hyperpolarization (as this review affirms in its introduction).",
"The place you refer to in the review is specifically addressing axo-axonic connections to primary afferents—sensory nerve fibers traveling in the spinal cord toward their... | [
"In case it helps, here's one important thing to understand about ionic currents:",
"A given ion type does not always do the same thing. Opening sodium channels does not always depolarize a cell, opening potassium channels does not always polarize a cell.",
"In actuality, opening channels for a particular ion ... | [
"Thank you so much. I will give it a read. '",
"It may help to suspend your notions of how GABAa receptors classically work and follow the evidence and arguments carefully.",
"Hahah. yeah. That is a skill I really need to work on."
] |
[
"Is it possible that creatures very similar to those currently extint come to exist again in a very distant future? (through evolution)"
] | [
false
] | null | [
"It depends what you mean by \"very similar\", but I believe you will find the answer you seek in the concept of convergent evolution. This is what happens when different unrelated organisms converge upon the same solution to the set of problems which is a given way of life.",
"There are numerous examples, but a ... | [
"Thank you for that great answer"
] | [
"Yes, I agree this is a good answer. Additionally, there is the idea that \"nature abhors a vacuum\". In ecology, the concept is that a vacant ",
"ecological niche",
" will not stay empty for a long time."
] |
[
"If the core of the earth is 5,700K, the earth is constantly bombarded by tons of energy by the sun, and heat doesn't dissipate well in space, why is the surface a moderate 298K after 4.5 billion years?"
] | [
false
] | I was thinking about geothermal energy and hit this question. | [
"I'm on mobile and just woke up so I can't do the energy balance equation for you, but the thermal energy generated within the planet and the energy received are balanced with outgoing energy in the form of e&m radiation. Heat can definitely be dissipated effectively in vacuum, but only through radiation (convectio... | [
"making the equilibrium of this heat flow occur at higher temperatures, when the earth gives off even more infrared radiation.",
"Well, sort of.",
"The Earth is trying to emit exactly as much radiation as it receives from the Sun to maintain planetary energy balance. If it's prevented from emitting this much be... | [
"It sounds like you're saying a warm planet with greenhouse gas is a stable equilibrium, as is a cooler planet with less greenhouse gas.",
"Yes, but my point is that they will both emit the exact same amount of radiation. The warm planet ",
" emit more than the cold planet if both are in equilibrium.",
"Heat ... |
[
"Why is it that all Marine Turtles have flippers, and all freshwater turtles have feet that work on both land and water?"
] | [
false
] | I know that there are exceptions to this rule, like how Fly River and Soft-shell turtles basically have flippers, and Diamond Backed Terrapins lives in brackish areas. However, it does seem to be the general rule. There’s plenty of costal areas where the terrapin body type would work, and plenty of large lakes and rive... | [
"During winter months, the flippers wouldnt allow freshwater turtles to dig proper holes to hibernate. In marine turtles, there able to swim to warmer waters during the winter months and therefore need the flippers to swim long distances."
] | [
"I was just about to start spotlighting the pig-nosed turtle when I saw that you are already aware of it. I think the answer to your question has less to do with whether flippers on a terrapin ",
" benefit them and more to do with ",
" it would benefit them.",
"Sea turtles are specifically adapted to a marin... | [
"But wouldn’t turtles that live in warm areas not need to worry about digging down to brumate, or needing flippers to migrate?"
] |
[
"Why does motion of electrons cause magnetism?"
] | [
false
] | I am familiar with the classical concept, but I am wondering, how does relativity fit into this. What is the reference point for the magnetic field to "know" it is moving in relation-to. Is a magnetic field, merely a cause of a quantum of energy change at the wave-level, like a ripple in a pond? | [
"This is an argument that relies on two principles from special relativity.",
"Let's say we have an infinitely wire with stationary positive charges and moving negative charges from our frame of reference. (Could be protons and electrons if you want.) Also, this wire happens to have a balanced, net-zero charge in... | [
"Electric and magnetic fields are two different manifestations of the same thing.",
"Imagine I'm standing still and you're moving at some velocity, while holding some charged object.",
"You're not moving relative to the charged object, so all you see is an electric field.",
"I ",
" moving relative to the ch... | [
"Suddenly this - charge \"sees\" a whole lot more + charges in the wire",
"Huh? I don't follow. Why does the negative charge suddenly 'see' more + charges?"
] |
[
"How does traveling faster than light violate the principle of causality?"
] | [
false
] | null | [
"Thanks much for this comment. That's a good explanation and helps a great deal. ",
"However, I still don't get how that violates causality. Instead, that seems more like the perceiver (i.e., the one reacting to the cause) being tipped off to the cause before the perceiver can perceive the cause. To put it anothe... | [
"Special relativity tells us that if two non-accelerating observers are moving relative to each other, they will obtain different results for when and where things occur.",
"Now we apply the rules of special relativity to something traveling faster than the speed of light. So suppose there is an object that trav... | [
"Wouldn't the ships frame also crash into the door because the operator didn't open it, regardless of perspective"
] |
[
"Why do mosquitos not spread HIV and other blood-sharing diseases?"
] | [
false
] | I have nothing...Maybe a toxin that kills it? | [
"Well, some insects can spread certain specific blood born diseases. ",
"Malaria",
" is spread this way as is ",
"Yellow fever",
". The problem is that if a pathogen hasn't specifically evolved to survive or reproduce in a specific host, survival is highly unlikely. In the case of say HIV, the virus itself ... | [
"Well, we are completely different species. It isn't something particularly special about mosquitoes that makes them immune, they just do not provide the natural habitat that HIV requires. "
] | [
"Mosquitos apparently don't ingest enough HIV particles/virions to cause infection to a host. But this is largely irrelevant because for HIV+ blood to travel from a mosquito's stomach to your bloodstream it would have to somehow get into the mossie's salivary glands first, assuming it can survive the harsh environm... |
[
"How much angular momentum does blood flowing through the aortic arch have?"
] | [
false
] | I am not sure if I am thinking about it right but it seems as though the fact that the blood arcs from front to back changing its flow direction by 180 degrees means there would be a significant amount of angular momentum in the system. I don't well understand how angular momentum works in fluids, but my question arose... | [
"I don't have numbers in front of me, but determing the volume of the aortic arch, determine peak flow, find mass of the blood in the aortic arch at this time, determine velocity, and you should be able to calculate angular momentum and any resulting gyroscopic forces. ",
"i would wager that the pressure differe... | [
"L = r m v. ",
"r = radius of turn\nm = mass\nv = [tangential] velocity",
"I would imagine the mass of blood flowing through the arch to be very low (comparable to the rest of the body), so not a very high angular momentum.",
"[edited: clarification]"
] | [
"to be a bit more precise ",
" is actually the components of the velocity perpendicular to the length ",
"."
] |
[
"Uncertainty principle - why is the ability to measure the location and movement simultaneously a violation of the laws of physics instead of insufficiently advanced measuring tools?"
] | [
false
] | [deleted] | [
"An ELI5 explanation would be that the uncertainty principle is a statement about the structure of waves. Position uncertainty basically corresponds to how spread-out a wave is, and momentum uncertainty corresponds to how spread-out the wave's frequency spectrum is. These two things are inversely related to each ot... | [
"The uncertainty principle (UP) is not a statement about measurement. It is a mathematical consequence of the foundations of QM.",
"Consider a wave function ψ, which is an element of some abstract separable Hilbert space and which contains within it all information needed to describe a particle or system of parti... | [
"The uncertainty principle is not fundamentally a statement about measurement, though that's one of the consequences. It's a statement about the possible physical states of a system in quantum mechanics. For position and momentum, for example, there simply are no states that have both a perfectly well-defined pos... |
[
"About how many water molecules are in an average size water droplet?"
] | [
false
] | [deleted] | [
"As ",
"/r/ahhwell",
" said, one drop of water is about 1/20th of a milliliter. This is called one ",
"metric drop",
".",
"If you look at the bottom of that very page, the number of water molecules would be 1.671*10",
"."
] | [
"Given that a water/rain droplet has a large variance (",
"see here",
"), I'm going to assume ~1 mL. Given that the density of water is 0.99997 g/mL, this corresponds to 0.99997 g of water. Since the molecular weight of ",
"water",
" is 18.01528 g/mol, this corresponds to 0.0555068 mol of water. Now, to con... | [
"I'm going to assume ~1 mL. ",
"Your size for a water drop is a bit off here. As your link says, they can vary a bit, but they don't ever get to this big a size (a cube with sidelenght 10mm would be 1mL, while the largest recorded raindrop had 8,8mm diameter according to ",
"Wikipedia",
"). ",
"A water drop... |
[
"Does this simple experiment cause problems for gravity?"
] | [
false
] | null | [
"Can you elaborate? The same would apply for something like a boomerang. How do they experience gravity? ",
"Is this not the same equation used for the Earth? Only the center of mass is the core because of its shape"
] | [
"Can you elaborate? The same would apply for something like a boomerang. How do they experience gravity? ",
"Is this not the same equation used for the Earth? Only the center of mass is the core because of its shape"
] | [
"I’m confused here. I was taught throughout physics every single item is applying a gravitation force to me, but they are small compared to Earths. Except, if you have a radius of near zero, it would overwhelm every other gravity force. How do these things experience gravity?"
] |
[
"Chimps and Humans have around 98% same DNA. In order to know this we would have to know the 2% difference. Why can't we take the 2% difference from Humans and put it in the Chimps?"
] | [
false
] | Scientists say that we have similar DNA to Chimps. In order to know that we have similarities we would have to know the differences. Since we know the differences, why can't we take them and put the in the Chimps to try to produce a transitional-man made Homosapian. I am simply trying to understand some questions I hav... | [
"You'd have to make millions of little individual changes and we don't have the technology to do that. You can't just take the part that humans have and chimps are missing and stick it on the end of the chimp genome.",
"There are parts that chimps have that humans don't so you'd have to remove stuff as well as a... | [
"Because it's ",
" a coincidence. Humans and chimps sharing a lot of the same DNA is ",
" what you'd expect to see if humans and chimps are related–combined with a lot of other smoking guns of common descent, like fossil lineages linking us."
] | [
"Well in the grand scheme of things our DNA isn't ",
" dissimilar to chimps, but even small changes can have huge effects."
] |
[
"How accurate is this saying and why does it work? \"red sky in the morning, sailer heed warning. Red sky at night sailors delight\""
] | [
false
] | null | [
"It seems to be true within limits but of course very limited compared to modern techniques. to quote from ",
"this website",
"\"When the western sky is especially clear, there is often a red sunset. That's because as the sun sets, its light shines through much more of the lower atmosphere, which contains dust,... | [
"To add to this, the saying would of been more true in the days of wind powered ships where vessels had limited maneuverability in getting out of potential storms that were forming. In today's navies, conventional ships are much faster and able to sail against the wind quicker and more efficiently than tacking woul... | [
"Interesting. The saying in the UK is \"Red sky at night, shepherd's delight, red sky in morning, shepherd's warning\". So not necessarily due to stormy seas. But definitely to do with weather in which to work in. Or not, depending on the sky colour. "
] |
[
"Why don't cats get sick from licking their dirty feet all the time?"
] | [
false
] | If i stopped and licked my feet clean every 2 minutes I am sure I would be experiencing some gastrointestinal troubles. | [
"When humans learned to control fire and cook their food, about 125,000 years ago, they no longer had a need for a highly acidic stomach, since cooking kills most pathogens. Because a highly acidic stomach, when no longer needed, has its disadvantages and its maintenance is a drain on the body’s resources, it was g... | [
"What reason is there that humans lack this? Is it something we had but lost, or that we never had?"
] | [
"A cat's stomach is very acidic. This acid kills most dangerous bacteria; thats why it's OK for a cat to eat a live mouse but you should never even think about it. This high acidity is common among most predatory species and is even stronger among carrion eaters like buzzards and vultures."
] |
[
"Like animals, are there any food plants or fruit trees got extinct over the years or considered as endangered species which might go extinct soon?"
] | [
false
] | null | [
"Famously, most banana's today are all clones, and were bred because they were resistant to a local blight that killed off the last variety. If it adapts to the new variety ",
" it can/will wipe out the rest of them within a couple years."
] | [
"Too late. A version of Panama disease (the disease that ",
"wiped out the Gros Michel",
") called TR4 has already adapted to ",
"attack the current strain",
" of bananas that we eat today (called the cavendish).",
"TR4 has ruined banana crops in Australia and Africa already. While it hasn't reached Latin... | [
"Not an expert in anything really, but your question made me think of corn. The corn we have now is not anything like the corn found hundreds of years ago. We've selectively bred only the most productive strains, so other \"original\" strains are probably greatly diminished or possibly extinct due to cross-pollin... |
[
"My school's chem department threw this out, it was way too cool to trash so I took it. But what is it?"
] | [
false
] | null | [
"It's a roundbottom flask. You use it for certain types of organic chemistry reactions. The ones I've used were like 3\" across, so that one looks awesome.",
"And to my knowledge it's not illegal to own it, you're just not allowed to use it to make meth. SO- DON'T MAKE METH :D"
] | [
"I don't know if anyone has mentioned this, and even if they have it bears repeating",
"You have no idea what might have been in it and residues could make you sick or possibly even kill you.",
"I wouldn't even have it in the kitchen if I were you. "
] | [
"Betting someone's health on the idea that some grad student wouldn't improperly dispose of a piece of lab equipment is insane."
] |
[
"What about deep breathing makes us lightheaded?"
] | [
false
] | As in, how does deep breathing cause lightheadedness? If it's simply "Too much oxygen" what about all that oxygen results in feeling lightheaded? What mechanisms are at play/ what's going on? | [
"Hyperventilation removes more CO2 from the blood than is being released into the blood via cell respiration. This increases the pH of the blood, a condition called alkalosis, which in turn causes blood vessels to constrict, reducing blood flow. Alkalosis also reduces the amount of freely ionized calcium in the blo... | [
"The blood needs to do two things to supply your brain (or any cells) with oxygen. First, the heme group needs to absorb oxygen in the lungs, and secondly, it needs to release oxygen in the cells. This two way equilibrium reaction is affected by the pH of the blood. Too low and your blood won't absorb oxygen (acido... | [
"OK. The real answer. IT DOESN'T. Deep breathing does not cause lightheadedness. The deeper answer.... ",
"The rate at which you breathe controls the clearance of CO2 from your blood. The level of CO2 in your blood controls the drive for breathing. So, while you are breathing heavy, your blood gets plenty of oxy... |
[
"A concussion is the impact of the brain on the skull. Do animals with an exoskeleton experience a similar phenomena when their exoskeleton receives an impact?"
] | [
false
] | null | [
"Animals with exoskeletons in general do not have brains. They have multiple ganglia which are knots of nerve cells that together act like a brain but are nowhere as complex and large in comparison. On the plus side, since they aren't as heavy they do not \"bounce\" around. Concussions are a problem that not many a... | [
"Its a mix of a few things:",
"If we think on natural movements and falling:",
"now if you smash or flick an insect against a hard wall or hit it with a fly swatter that is of course a different thing but then you will mostly also break the exoskeleton and damage the whole body."
] | [
"So is it not possible for them to receive damage to other organs from them moving around, or are they typically so packed in that there is no room for movement?"
] |
[
"How much of a bottleneck is protein folding in the drug development process?"
] | [
false
] | I'm a total layman but I've been really excited to read about the Alphafold breakthrough. Assuming it does what they claim it does how much time and money would this save? From my understanding starting a drug from scratch and releasing it to the general public takes about 15 years (not sure if this is accurate). Ho... | [
"Kind of a null question. Some drugs target proteins whose structure is already known. Overall, start to finish, determining the structure of a protein can take anywhere between a month and a few years, if it can even be done (some are tricky). The longest part of drug development is testing the drug itself in clin... | [
"Basically, it's (maybe) a game changer for determining protein structure (but standard crystallography will never go away). It helps drug development, but not entirely sure I would say its a game changer for drug development."
] | [
"Protein folding is not currently a mjaor step in the drug development process. However, being able to accurately fold proteins- which this program is much better at but still not perfect- is the first step on simulating more complex processes, which eventuality will allow us to speed up effectiveness and toxicolog... |
[
"How does an immune system combat toxins (like snake venom)?"
] | [
false
] | I understand (at least crudely) how our immune system reacts to viruses, bacteria, and mold, but I'm ignorant as to how exactly it fights toxins. The recent TIL about Bill Haast developing a strong resistance to various snake venoms made this thought jump into my head. Does our immune system simply treat a toxin in wha... | [
"It should be noted that these days you rarely make mass quantities of antibody by injecting things into horses - nowadays (actually since the 70s) we make them by fusing cultured B-cells with melanoma cells and making hybridomas, which pump out monoclonal antibodies like nobody's business."
] | [
"Your body can't really tell whether a protein is a toxin or not, it just knows that it shouldn't be there in the first place. The immune system will usually recognize and try to neutralize any proteins that it identifies as foreign. That's why organ transplants are problematic; your body knows that it's foreign ... | [
"Thanks!"
] |
[
"Prolonging laptop battery life"
] | [
false
] | I have already made certain changes to my laptop usage to help prolong my battery life, such as lowering the screen brightness and changing certain other appearance settings. But I remember hearing something about how fully charging the battery, and then using it until it is almost fully drained before recharging someh... | [
"I believe it depends on the construction of the battery. An Apple Store representative told me in 2008 that the \"use it until it's drained\" advice was accurate for older batteries, but newer ones are worn out by any change in their stored charge. That is, the battery is worn through expenditure and charging, so ... | [
"Relevant information: ",
"http://www.apple.com/batteries/",
"The documentation for my MacBook Pro (2010) recommends completing at least one charge cycle per month (as described in the above link). In other words, don't let it sit plugged in, or completely drained, for weeks at a time. ",
"Apple also recomm... | [
"while in theory li-ion battery should work forever, shelf life, cycling and temperature would affect its lifespan. every charge therefore weaken it capacity. that said, partial discharge would prolong it life by reducing stress.",
"How much? let say at 100% discharge, your battery life is about 3 times shorter t... |
[
"What results in me getting more wet, walking or running in the rain? Or would it be the same?"
] | [
false
] | null | [
"It depends on the rate of rainfall, angle of rainfall, your speed, your direction, and the shape of your body. If rain is",
"and you are",
"and",
"then the net rainfall on you consists of",
"and the amount of time it will take you to reach your destination is D/Z, so the total amount of rainfall you will e... | [
"You can split the amount of rain hitting you in two components:",
"So it is best to run as fast as you can to minimize the time spent in the rain.",
"Here's a Minute Physics video explaining this very well: ",
"Is it Better to Walk or Run in the Rain?"
] | [
"You will get more wet walking. The more time you are under the rain the more wet you get. Running doesn't make you get hit by more rain. You are just traveling faster so the impact is harder so it can trick you in to thinking you are getting hit by more rain."
] |
[
"Is there a such thing as a material that does not absorb light? What would happen if you built a room out of it and turned a light on inside the room? Would light just bounce around it forever?"
] | [
false
] | null | [
"Light will either interact by absorption or reflection, a combination, or passing through. No ideal reflective materials exist though there are very good reflecting surfaces or non-interacting materials. What would define these greatly depends on the wavelength of light. Let us consider a microwave. The wavelength... | [
"What if you left the light on in the room? Would the room ever \"Fill up\" with light where no more light can fit into the room? "
] | [
"If light interacts with a medium, there are three possibilities: reflection, absorption and transmission. ",
"If there was a material, that had a 100% reflection rate (which there is not), then, yes, the photons would keep bouncing off the walls forever."
] |
[
"How and why is a RadioCarbon (14C) date calibrated?"
] | [
false
] | I am looking at several AMS 14C dates and cannot for the life of me understand why they are being used uncalibrated in the literature or why calibrating a date is necessary. A date of 8030 ± 160 turns into 6974 ± 233 after calibration (CalPal) What is the process behind calibration? Which is the more correct number? Th... | [
"Just to add on, the uncalibrated date is given in case readers wish to compare to other artifacts using a different calibration method as well as leaving a good record of the process used for data workup."
] | [
"Radiocarbon dating can date material by comparing the quantity of C14 in a sample of previously-living-but-now-nonliving matter to the concentration of C14 in the atmosphere. Though the rate of C14 decay is a constant (",
"though the mechanism requires some advanced physics",
"), the amount of C14 available in... | [
"And, in case you are curious, the principle mechanism for changing ratios of 14C:12C in the atmosphere is fluctuation of the earth's magnetic field. Stronger fields reduce penetration of cosmic rays. weaker fields allow greater penetration. Cosmic rays interact with N to form 14C in the upper atmosphere. Greater... |
[
"Will anything terrible happen if I walk or play on a lawn that's been treated with herbicide, pesticide, or fertilizer?"
] | [
false
] | Can the chemicals cling to your shoes more than three days after spraying? Can you track them into your home, where pets and babies may lick them or absorb them through skin? Should such lawns be avoided forever? I have a close friend who avoids walking on these lawns, everywhere, to the point where we can't enjoy some... | [
"Contact poisons: ",
"http://en.wikipedia.org/wiki/Contact_poison",
"You can only be sure by checking the ~cide used.",
"Meanwhile, organic fertiliser (ie shit) can infect cuts/sores for as long as it remains on the lawn. Artificial fertiliser: check the label."
] | [
"My Yates (r) Glysophate weedspray says, among other things:",
"DO NOT allow children and pets to enter treated areas until spray has dried."
] | [
"Short answer: no. I used to spray this stuff on commercial properties as a summer job. Basically the EPA has very strict laws on what kinds of chemicals can be sprayed on lawns that pets and humans come into contact with. Of course don't lick the grass, but feel free to play."
] |
[
"when a limb gets amputated, how do they stop the flow of blood?"
] | [
false
] | Do they somehow connect the artery to the vein, up the limb past the amputation? | [
"Surgeon here: You wouldn’t want to connect a major artery to a major vein — that would result in high pressure oxygenated blood pouring rapidly into the vein, raising pressure in the venous system and wasting oxygen. For large blood vessels we tie them off with ligatures (surgical thread, basically) or clip them... | [
"Depends on the size of amputation. A pinky toe? No different. Both legs at the hip? Yeah they can run into some cardiac issues which there are theories about why. I've attached a very topical paper on this if you'd like to read.\n",
"https://pubmed.ncbi.nlm.nih.gov/18281705/"
] | [
"Would an amputee (or double, triple, quadruple amputee for eg) have increased blood flow to the rest of the body since there is less \"body\" that the heart needs to pump to? Or does the heart just work less hard?",
"\nAre there positive/negative side effects because of this?"
] |
[
"Is water really tasteless or are we just so used to the taste of water we don't give any thought to it?"
] | [
false
] | null | [
"There is evidence that mineral content in water affects the flavor we perceive. Bottled water manufacturers add in the desired minerals rather than selling distilled water, which some say tastes \"flat.\"",
"Here's a study about the chemometric analysis of bottled and tap waters that had been through blind taste... | [
"You have 'taste buds' in your mouth that are you 'taste', they detect five things. Salty, sour, bitter, sweet and umami(savory). If the thing you are eating or drinking does not have any of these elements in it, it will not have a taste because is not taste to detect.",
"If water has nothing we can taste it is t... | [
"idk, but how would you know if something is tasteless? There's so much stuff in your mouth, if water would really be tasteless, 'tasting water' might actually be 'tasting the stuff in your mouth', and how would you really know?"
] |
[
"Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology"
] | [
false
] | Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! ... | [
"No cephalopods (octopus or squid) have evolved to survive in freshwater, but Gastropods (snails) and bivalves (e.g. mussels), which are in the same phylum, have been able to do so. Why might this be?"
] | [
"???",
"From calendar:",
"9 Aug Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science",
"This is the 2nd time I recall this happening. I had written out multiple astronomy questions already :("
] | [
"Yeah, this is a good question. There have been a number of site-wide reddit issues with AutoModerator for awhile now, which does the scheduling of things like Ask Anything Wednesday. I'm not sure if that's the actual cause though but it seems possible. If you have questions, I'd be happy to attempt to answer them ... |
[
"[Warning: Transfinite numbers] Regarding the cardinality of rational vs real numbers"
] | [
false
] | If the cardinality of the set of rational numbers is aleph null, and is countable, is there a set of numbers that is not countable with a cardinality of aleph null? If the set of real numbers has a cardinality of c, and c is > aleph null, does that mean the cardinality is >= aleph one (or however you say it)? Is there ... | [
"The definition of being countably infinite is to have cardinality aleph null - all sets with cardinality aleph null have the same cardinality, so it makes sense that you shouldn't go from 'countable' to 'uncountable' by staying the same.",
"Is there a cardinal number between aleph null and aleph one?",
"This i... | [
"Aleph 1 is defined as the first cardinal that is different from aleph 0, so by definition,\nthere is no cardinal strictly between aleph0 and aleph1.",
"(The aleph numbers are defined as equivalence classes on the ordinals, two ordinals being equivalent if there exists a bijection between them.)",
"I have to th... | [
"Is there a cardinal number between aleph null and aleph one?",
"This is essentially the ",
"continuum hypothesis",
".",
"Nah, it's just the definition of aleph one. CH says that aleph one = |",
"|, and that's probably model-dependent."
] |
[
"Is a sphere rotationally symmetrical across all 4 axes in 4 dimensions?"
] | [
false
] | null | [
"A sphere in N dimensions is symmetric under rotations in N dimensions."
] | [
"The surface defined by r",
" = Σ",
" x",
" is invariant under SO(N) rotations."
] | [
"I have no idea what that means."
] |
[
"Is it possible for the moon of one planet to have satellite of its own?"
] | [
false
] | null | [
"Gravity does not have rules about what is allowed to orbit what. Also the phrase \"moon \" is just a label for a body that is orbiting something that is also orbiting a star. So yes, it is possible. Bear in mind that orbits are not stable like an eternal clockwork mechanism, so given enough time things will eit... | [
"The Earth is a 'moon' to the Sun and we have a moon of our own. Its certainly possible, as others state, but gravity likes stability and will force all gravitational relationships into a stable state (eventually). This makes it hard for moons of moons of moons to exist, but its possible. In fact.. interesting scif... | [
"It's also worth noting that a few of the Apollo and Luna missions were artificial moons for our moon for some length of time, so we have examples that prove it's possible.",
"To restate the stability thing in another way, the only real issue hindering how many levels you have is that for every level you go down,... |
[
"Why can't we harness the electricity in lightning?"
] | [
false
] | null | [
"(I'm reposting this from here ",
"from a similar discussion",
") ",
"It's simply not enough energy and very hard to transport. I used to have a fun dream to think about ...move to Florida, mid-peninsula which has one of the highest rates of lightning strikes in the world, and try to earn a living catching l... | [
"I, too, am not an expert but the brevity of lightning is the difficult part. Imagine trying to charge a battery from 0% to 100% in ",
"30 microseconds",
". At this time, there is nothing that can store that kind of energy that quickly."
] | [
"What if you flew a kite high enough that you could grab electricity directly from the clouds before it forms into lightning? Then you wouldn't have to figure out how to store all that fleeting energy, you'd just distribute it right away."
] |
[
"Why hasn't the car industry explored a diesel/electric car instead of hybrid drive with gasoline?"
] | [
false
] | null | [
"Because it's not a function of Diesel/Electric vs Gas/Electric, it's Diesel/Electric vs AtkinsonCycle/Electric vs. OttoCycle/Electric. An Atkinson Cycle engine is as fuel efficient as a Diesel, it just lacks the torque (made up for by the electric) and uses cheaper fuel."
] | [
"Diesel is actually a lot cheaper in some markets btw."
] | [
"The problem with diesel was that until 2007, good clean diesel fuel wasn't widely available and diesel emission control system of passenger cars couldn't satisfy emission standards in all 50 states. However, you will see the diesel revolution soon: GM, Mazda, Chrysler and some others are bringing passenger cars wi... |
[
"If black holes bend space-time, do they bend time too?"
] | [
false
] | [deleted] | [
"Space and time are connected insofar as gravity and the fabric of space-time goes. When a large mass, like a black hole, exists, it bends the space-time around it. This pulls things in to orbits, just like the Earth is in orbit around the Sun, but also \"bends time.\" If you were to watch something fall in to a bl... | [
"Yes. In fact, this is why black holes are inescapable. An observer near any massive object has its future time axis bent towards the object. If the object is massive enough, and the observer is close enough, then the observer's entire future ",
" — the bundle of places they can possibly go to or affect — points ... | [
"You're probably right but I don't get it. What does bending time mean? What are these effects you speak of? What's a ultra-relativistically movement?"
] |
[
"What does \"Earth-analog outgassing rates for surface pressure\" mean?"
] | [
false
] | I'm reading this paper: page 8, 10 lines down. | [
"Gas leaving the rock and going into the atmosphere, probably - here modeled to be at the same rate as for Earth. They explicitly discuss outgassing of CO2 in the following paragraph."
] | [
"I’m not sure if you’re just parsing the sentence strangely in your mind - in addition to what mfb- said, it’s worth mentioning that the sentence as you quoted it is incomplete. ",
"“These two atmospheric models assume Earth-analog outgassing rates for surface pressure... ",
"”",
"The authors are discussing d... | [
"Thanks"
] |
[
"Why does squinting or partially closing one's eyes make vision clearer?"
] | [
false
] | I don't quite have to squint to notice a difference, often I can just close my eyes a little and distant text becomes much more clear. Why does that help, when glasses do something so different to my eyes to make things clear? | [
"The way I understand it, if you squint (or look through a pinhole - try it), you are effectively just using the center of your lens. Very little focussing needs to be performed in this situation; the center of the lens is barely curved and the light mainly goes straight through. ",
"As a result, the image is dim... | [
"There are two different ways this works.",
"The first one involves the way images are formed in the eye. Light rays entering the eye through the lens ideally converge on the retina. However, due to refractive defects, these rays may converge at a point closer or further than this ideal spot.",
"Here's a releva... | [
"This is correct. By squinting you are removing the paraxial rays, which create the most blur on the retina. Myopia derives its name from the proclivity of a myope to squint. A downside if this is you get less light into the eye. This trade-off is apparent in the pinhole eye of the Nautilus. "
] |
[
"Kepler Exoplanet Megathread"
] | [
false
] | Hi everyone! The team just announced 1284 new planets, bringing the total confirmations to well over 3000. A couple hundred are estimated to be rocky planets, with a few of those in the habitable zones of the stars. If you've got any questions, ask away! | [
"Woohoo! Exciting stuff! I understand that this is a very small region of the sky and Kepler can only detect planets in the orbital plane that matches our line of sight. How much of an effect do these new detections have on the estimate of the total number of exoplanets in our galaxy? Do they fall within expected ... | [
"The bigger point is that this is HOW we're constraining that number. Kepler is only looking at a small patch of sky, but much of what Kepler was designed to figure out is the frequencies of various planets, particularly earth-sized planets in earth-like orbits.",
"So these results will be what are used to figure... | [
"I wonder how many of these it will be possible to make ",
"surface maps",
" of, and whether we can get good spectroscopy data with the next generation of telescopes."
] |
[
"Since the speed of light is the faster anything can go, is there a slowest speed something can go?"
] | [
false
] | Since there is a limit to how fast something can go, is there some kind of universal frame of reference? And, as a result, is there an absolute zero speed in the universe? I know that we are moving on a planet, moving in a star system, moving in a galaxy, moving through the universe. So we are not at that zero speed. I... | [
"is there some kind of universal frame of reference?",
"Nope. One of the biggest consequences of the theory of relativity is that there is no preferred frame of reference. All reference frames are equally valid.",
"Combine that with the speed of light being the \"speed limit\", and you get some very weird (or... | [
"Ah, well I should say, anything can move at speed 0, but that's only in one frame of reference. Not all observers will agree on that speed of 0 like they do all agree on the speed of c for light."
] | [
"Sure, 0. "
] |
[
"Why doesn't the glass found within fiber optics break/shatter when the cord is bent?"
] | [
false
] | Glass is rigid and brittle, so how is it that you can bend it without it breaking (at least to some degree)? | [
"It's because the fiber is very thin. Suppose I had a glass rod ",
"=10 mm thick, and I tried to bend it into a circle with a radius of 100 mm. The radius of the curve is smaller on the inside edge, and larger on the outside edge. That means that the glass must stretch on the outside and compress on the inside... | [
"It does break, which is why fiber has minimum bend radius specifications which are very important to follow.",
"Also, fiber cables have layers of cladding and sheathing which prevent you from kinking the fiber inside. Distribution cables have a rigid fiberglass “stick” down the middle of them that makes them qu... | [
"It does break, which is why fiber has minimum bend radius specifications which are very important to follow.",
"Actually the bend radius specifications aren't just about breaking the fiber! The light rays are confined to the fiber by ",
"total internal reflection",
"; bending the fiber causes the rays to en... |
[
"How many internal organs can be removed from a person, and they still lead a normal, un-medicated life?"
] | [
false
] | I recently had my gall bladder removed due to chronic gallstones and have had to make no real changes to my lifestyle or medical requirements post-op. Along with another obvious candidate, the appendix, how many organs from one person could be removed without having to take drugs or cause major, life altering issues af... | [
"You don't need your gallbladder. You can lose 70% of your liver (however it must be 70% loss in one area). You can lose your spleen. You don't need your appendix. Don't need 1 of the kidneys, don't need 1 of your lungs, don't need your stomach, don't need that 2nd eye or genital organ. You could keep going on. The... | [
"So, you can live without your stomach and no medication, if you're willing to make dietary changes, but without the stomach, you're gonna probably have protein deficiencies, and your food won't be churned into chyme. You're also not going to have your secondary chemical digestion from hydrochloric acid. And, becau... | [
"You don't need your stomach?"
] |
[
"Why is varicella more dangerous to get as you grow older?"
] | [
false
] | [deleted] | [
"Sounds to me as though you are attempting to confirm a bias, not learn something. If you already know everything about the answer, why did you ask the question?"
] | [
"Sounds to me as though you are attempting to confirm a bias, not learn something. If you already know everything about the answer, why did you ask the question?"
] | [
"Essentially what we know is that the reason varicella is worse/more harmful as you get older is because you’re more likely to suffer complications. ",
"By this I mean everything else other than blisters/rashes, like flu symptoms, high fever, loss of appetite, these kind of complications. Regardless if you’re imm... |
[
"Why is the nozzle on a rocket engine designed to reduce the gas pressure to the external pressure ? How is it more efficient ?"
] | [
false
] | I've been learning on my own how rocket engines works (well approximately), and I've understood the part about the third law of motion and conservation of momentum. But I don't understand the pressure related aspect of such engines. I've seen that depending on what altitude you mean to use it, you have to elongate the ... | [
"Your intuition of high pressure --> higher exhaust speed is valid, but to get the most out of that pressure you have to let it accelerate to that speed, i.e. expanding back to atmospheric pressure. Whatever pressure above atmospheric is left over at the end of the nozzle continues to accelerate the exhaust without... | [
"To add to what others have said, there's an element of vector analysis involved. When the exit pressure is too high, the escaping gas blows outward from the nozzle, instead of straight back. When the exit pressure is too low, you get shock diamonds, which is the opposite (but similar in terms of lost efficiency)... | [
"What makes you say that?",
"Because the density varies ",
" in a rocket nozzle. The whole thing is built around how compressibility fundamentally alters the behavior of fluid flow. Bernoulli is right out. The most fundamental aspect of ",
"de Laval nozzles",
" is that it exploits the fact that subsonic flo... |
[
"Why do we treat hyperacidemia in cardiac arrest patients, if hemoglobin has a higher tendency to release oxygen at lower pH?"
] | [
false
] | I work as an EMT, and I was pursuing my paramedic certification but got incredibly bored, among other things. In my biochemistry book, it states that "Oxygen affinity of hemoglobin decreases as pH decreases from a value of 7.4. Consequently, as hemoglobin moves into a region of lower pH, its tendency to release oxygen ... | [
"One reason is that acidosis causes hyperkalemia and hyperkalemia causes impaired conduction and v-fib (prevented by amiodarone).",
"The heart is also already the most efficient organ at oxygen uptake from the blood, so the slight benefit is really outweighed by other factors."
] | [
"This might help if you can get access. \n",
"http://www.ncbi.nlm.nih.gov/m/pubmed/2155764/?i=4&from=/2852199/related"
] | [
"A couple of reasons. The heart probably won't pump as well in an acidemic environment, so maybe raising the pH will improve contractility if you bring the heart back. Some people think epinephrine is less likely to help a heart in an acidemic environment because it has poorer contracitilty in that setting, so mayb... |
[
"When firing a bullet out of a gun, at which point does the bullet reach its maximum speed? Is it at the point the bullet leaves the barrel or is it a couple of feet later?"
] | [
false
] | null | [
"Not strictly true, there will still be some pressure from expanding gases exiting the barrel, but since it can now expand radially the force will fall rapidly. "
] | [
"It depends on the length of the barrel and other factors like rifling, twist rate, smooth bore. It's possible the bullet could reach its maximum velocity somewhere in the barrel if it's long enough. Short barrelled guns like pistols will have the bullet reaching maximum velocity at the point where they exit the ba... | [
"All of the accelerating force happens inside the gun - when the bullet is out of the barrel there is nothing to make it go faster than it was going at the moment it left the barrel."
] |
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