title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Could we create a computer program with all the known laws of the universe to reverse engineer what we don't already know?"
] | [
false
] | Could we create what is basically a 3D CAD program that had all the known laws of the universe and then ran experiments on it - such as accelerating particles close to the speed of light a la a mass hadron collider - and observing the difference between what happens in the program and what happens IRL? Would this be plausible at all, even if using the bleeding edge of computing hardware? | [
"What you asked is exactly what is done in almost all of physics. ",
"If any scientist tells you that some problem is \"an active area of research.\" It generally means that a new phenomenon is happening, a phenomenon where the theory (which is now calculated using computer simulations) breaks down and didn't pre... | [
"To some extent this already happening. In a lot of branches of science where it is not practical to perform direct experiments we design virtual ones (i.e. computer models). ",
"For instance, I work with geological models which reproduce the behaviour of rivers and coasts in response to climate and sea level flu... | [
"If any scientist tells you that some problem is \"an active area of research.\" It generally means that a new phenomenon is happening, a phenomenon where the theory (which is now calculated using computer simulations) breaks down and didn't predict what actually happened accurately.",
"I wouldn't entirely agree ... |
[
"What happens to pharmaceutical medicine when they are past their expiration date?"
] | [
false
] | Does the chemical composition change to make it less effective? Or maybe toxic? Are these not stable compounds? Do environmental factors have an effect? How is the expiration date calculated? | [
"For completeness sake, light can also break down some compounds. This is why hydrogen peroxide usually is sold in a brown bottle, for example. "
] | [
"Most pharmaceuticals are organic compounds so they tend to react with atmospheric oxygen and water over time. The chemical degradation is accelerated at higher temperatures and upon exposure to air and humidity (breaking the seal). For example, acetylsalicylic acid (aspirin) can break down to salicylic acid and ... | [
"Expiration date is calculated by doing stability testing. At certain intervals and storage conditions, the drugs are tested to see if 95% or so of the active compound is still detectable in the sample. This stability testing also helps determine if the label claim for the expiration date is valid for all samples g... |
[
"Is it true that small animals cannot be hurt in a fall from any height?"
] | [
false
] | [deleted] | [
"In principle, yes. (In vacuum, no. But the animal would have other problems in vacuum anyway...)",
"The key here is the concept of terminal velocity - the falling velocity at which wind resistance and gravity cancel out. It seems the larger you are, the more wind you need to balance gravity*, resulting in a high... | [
"I figure if a mouse can survive a 2.3 meter fall, which is what? 100x it's height or so, then it can survive a higher fall too.",
"~science~"
] | [
"Coming from personal experience when I was 5 years old. It is not true for hamsters."
] |
[
"Why do women, on average, live longer than men?"
] | [
false
] | For example: Of the 69 supercentenarians on that list, only 5 are men. What are the reasons for women living longer? | [
"Part of is is lifestyle. Men traditionally participate in warfare/engage in non-state violence for frequently than women. Men are also more likely to hold a physical labor intensive or dangerous job that results in greater wear and tear or source of accidents. I'm sure some nutritional and genetic factors play a r... | [
"FYI looking at outliers like that doesn't really give you a representation of the average. There's good census data like ",
"this",
" (pdf) that shows that the average life expectancy for for American women is about 5 years longer than that of men. ",
"The reasons are varied - behavior may be a part of it,... | [
"Men have shorter average lifespans due almost entirely to the effects of stress. When you control for stress factors, men and women have the same life expectancy. "
] |
[
"How does Fredkin gates bring computational energy cost to a zero?"
] | [
false
] | Also, Here in this video, what does Phil means when he says that it requires energy to raise information? Around 6 minute mark. | [
"The idea is that a reversible logic interaction won't in theory require energy input, because of conservation-of-energy. In a billiard-ball conservative logic gate, for example, the balls start off with their initial velocities and, under perfect conditions, carry those velocities to the output. If they collide th... | [
"Thank you for taking time to write this reply."
] | [
"I think that \"raise\" is a mishearing of \"erase\". The fundamental cost of computation is that of erasure. Nature did a piece on what was the fastest computer possible, which resulted in a roughly 1 kg red hot sphere, heated by the energy cost of erasure, a small sphere due to the time required to communicate. T... |
[
"How do oil based lubes break condoms down?"
] | [
false
] | Title | [
"If you don't mind, could you go into more detail on the non polar interaction? I find these kinds of things really interesting"
] | [
"If you don't mind, could you go into more detail on the non polar interaction? I find these kinds of things really interesting"
] | [
"A good picture of non-polar interactions is to think about instantaneous dipoles attracting one another (",
"https://en.wikipedia.org/wiki/Van_der_Waals_force",
") and the competition between the forces. ",
"The picture of dissolution is solvent-solute (oil-latex) interactions overcoming the solute-solute (l... |
[
"If someone were to replace their bed with a hammock, would they be at risk for any health problems?"
] | [
false
] | [deleted] | [
"There are studies done on researching how hammocks affect sleep. Without researching the details of it, it seems to be a positive effect. You would have to read or ask about the individual studies to check the integrity.",
"Here's an article based on one such study",
".",
"As far as health effects, I'm not a... | [
"I also thought of sailors, and then it occurred to me that this topic would be a great example of how to manipulate data to imply causation that isn't there: \"Hammock users ten times more likely to get scurvy, study shows.\""
] | [
"Every sailor on every naval vessel prior to the 20th century slept in a hammock. It was not at all unusual for the largest class of three masted warship to have as many as 800 men aboard, all sleeping in hammocks. Even in port between voyages they slept aboard the anchored ship rather than sleeping in barracks on ... |
[
"Our moon orbits around the Earth, the Earth around the Sun, and our Sun orbits the Milky Way. Is there a central object that our galaxy orbits around? If so, does that object orbit around anything else?"
] | [
false
] | null | [
"The Milky Way is part of the Local Group of galaxies. Andromeda (aka M31) and the Milky Way are the two biggest galaxies in it and the center of mass lies in between them. We are not orbiting it per se, but are more on a collision course with Andromeda and will collide in 300,000,000 years or so. ",
"source",
... | [
"The probability of stuff like stars, planets, etc actually colliding in this galaxy-galaxy collision is probably really low, right? I'm thinking this because I imagine that empty space makes up the overwhelming majority of the volume of a galaxy."
] | [
"The chance of a direct collision is very low. However, there will be significant effects due to gravity. The various stars and black holes in the two galaxies will disrupt things as they pass by each other. ",
"More info here",
". Overly dramatic ",
"simulated video",
" of what crash might look like. "
] |
[
"How does methanol damage the optic nerve and cause blindness?"
] | [
false
] | null | [
"Methanol is metabolized by alcohol dehydrogenase to formaldehyde and formate, the latter of which causes optic neuritis and, subsequently, blindness. Formate is toxic to mitochondria via its inhibition of cytochrome oxidase, as described ",
"here",
". This is the same mechanism as with cyanide and carbon monox... | [
"Do non-lethal doses of cyanide and carbon monoxide also cause blindness?"
] | [
"Yes, in both cases. I've included some resources below.",
"Quattrocolo G, Leotta D, Appendino L, Tarenzi L, Duca S. A case of cortical blindness due to carbon monoxide poisoning. Ital J Neurol Sci 1987;8:57–8.",
"Katafuchi Y, Nishimi T, Matsuishi T, Kimura Y, Otaki E, Yamashita Y. Cortical blindness in acute c... |
[
"How do we know which strain of influenza to make the annual flu vaccine for?"
] | [
false
] | Viruses constantly change genetically so how do we know that the flu vaccine for 2015-2016 will protect us from the flu virus that will be circulating during flu season? | [
"We use a variety of heuristics, including information about strains circulating previous year in the same hemisphere, strains circulating six months prior in the opposite hemisphere and notable emergent strains."
] | [
"This answer requires some context. Most flu vaccines now target two proteins that are on the viral capsid of the flu virons; Hemagglutinin and neuraminidase. When you see a flu named H[x]N[y], it's catagorized by the form of these two antigens. Hemagglutinin aids in the entry of a virus into a cell, and neuramini... | [
"Interesting! Thanks for responding."
] |
[
"How do we MEASURE sidereal rotation period of planets¿?"
] | [
false
] | The period of the rotation in its axis. How do we know the period of jupiter, Saturn.... Is it via observation or simple physics? I haven't found anything related about HOW do we measure it. So I would really appreciate a detailed answer. Thanks. | [
"For all planets, we measure them through observation. Take a telescope, and you will see the rotation of Jupiter ",
"quite easily",
". You need a better telescope for further planets, or probes. From the observed rotation, it is trivial math to relate the observed movement and the observer movement to measure... | [
"So, actually there's not a \"formula\" or \"ecuation\" to calculate the rate of ration?",
"Because I'm a (soon to be) physicist and I have found a ecuation that describes with high acurracy the rotation of all planets (with rocky planets it's perfect but with gas giants deviates a little).",
"So, my question i... | [
", actually there's not a \"formula\" or \"ecuation\" to calculate the rate of ration?",
"Because I'm a (soon to be) physicist and I have found a ecuation that describes with high acurracy the rotation of all planets (with rocky planets it's perfect but with gas giants deviates a little).",
"So, my question is.... |
[
"Why do we freeze for a split second when something startles us or makes us jump?"
] | [
false
] | I notice when I'm absorbed in something or not expecting anything unusual something to happen and a loud noise or visual stimulus comes, I jump or "freeze" for a split second. Is there any neurological reason why this happens, I can't see any advantage from the evolutionary standpoint. | [
"The freezing response is mediated by a circuit involving the amygdala and a part of the brainstem, the periaqueductal gray. This circuit can coordinate the typical motor output: freezing, jumping, yelping, etc.",
"Anyone can come up with plausible-sounding evolutionary \"explanations,\" but this can easily spira... | [
"Without going too deeply into it, the mammalian freezing response is mediated by a downregulation of the activity of the vagus nerve and the feedback loop associated with its sensory function (80% of the vagal function is afferent) via the vagal nerve centers in the brainstem. Normally the nucleus ambiguus (NA) fu... | [
"There are times you can figure things out in more detail. I mean, it's pretty simple to show that a population of bacteria in a plate evolves the trait that provides resistance to antibiotics because they were exposed to low levels of that antibiotic. You can perform replicated experiments to show that the antib... |
[
"Why do illnesses, diseases, germs, bacteria, etc... harm their hosts to death, in turn, killing themselves?"
] | [
false
] | I tried to make it as short and simple as possible, otherwise Id ramble forever and sound like an idiot... | [
"There are millions and millions of bacteria that don't kill their hosts or cause any pathogenic effects. ",
"Some of them do, and we obviously tend to notice them more because they'e make us ill and kill family members and what not. These are said to have 'virulence factors'. Usually, death doesn't give any adva... | [
"Well, if you think about it, organisms who reproduce are the ones who pass on their genes, so any offspring will have the genes of someone who had qualities that helped them survive in time to reproduce.",
"If it produces a toxin that makes people cough a lot, it's going to pass itself around and have multiple r... | [
"The Earth isn't a host. We're using stuff we find on it. Are sheep living out of a host by eating grass from a field? Are birds living out of a host by eating worms from the ground and building nests in trees? If you classify the Earth as a living thing, every single form of life is like a vius living out of a hos... |
[
"Are there any poisons/toxins which, if taken separately, are fatal, but if taken simultaneously, are not?"
] | [
false
] | null | [
"Atropine and physostigmine, in the right combination.",
"Physostigmine causes dangerously high levels of the neurotransmitter acetylcholine. Atropine prevents cells from sensing acetylcholine.",
"Atropine is actually used as an antidote for acetylcholinesterase inhibitors (like physostigmine and sarin), but it... | [
"Yes for example if you are dying from an opiate overdose (coedine, heroin, etc) you are given Narcan. In simple terms it goes to every receptor that has bonded with the opiate and kicks it out. It's an incredibly painful sensation apparently. "
] | [
"It essentially throws you into full blown opiate withdrawal which is very painful by itself."
] |
[
"Who was the first person who discovered that moon has reflected light?"
] | [
false
] | I already searched on google but couldn't find any source. Some say that it was leonardo da vinci, and some say that it was Anaxagoras. | [
"Anaxagoras of Clazomenae is probably the first ",
" person to suggest this, and Anaxagoras actually understood some aspects of the sun/moon/Earth relationship ",
" than Leonardo did almost 2,000 years later.",
"Anaxagoras proposed that the sun's glow came from its intense heat, like a red-hot stone (which is... | [
"Super interesting read. I guess a hot stone is a decent guess when you consider the fact they have no idea what the fuck plasma even is."
] | [
"If you don't get an answer here, you can also try ",
"/r/askhistorians",
", ",
"/r/historyofideas",
", ",
"/r/historyofscience",
", or ",
"/r/philosophyofscience"
] |
[
"Question regarding light and lasers"
] | [
false
] | I've obtained a recent extreme interest in physics lately. I've been learning a lot of random concepts online, and doing small experiments of my own. I decided to pull out my old 532 nm 35 mW green laser pointer today and toned down its intensity in order to more safely study some effects of optics. I found a pair of 3D glasses, and noticed that the red lens seemed to attenuate something like 99% of the beam; I could only make out a very faint beam on the other side when turning out the lights, even though the original beam was very strong. Much of it appears to be reflected, and then what's left is a yellowish-orange diffusion at the spot of incidence on the surface of the lens. If the wavelength of the laser beam is highly concentrated around 532 nm, how could the diffuse scattering seem to redshift a good 40-60 nm? My best guess is that green photons are being absorbed and then remitted at a slightly larger wavelength, with the extra energy being maintained as thermal motions. Thoughts? : My first guess was that there is an appreciable distribution to the left and right of 532 nm, which isn't easily perceived in tandem with the full brunt of the beam. But I disregarded that because I assumed that the distribution may be too small. Now that I think about it, it seems like it may very well be the case! Because if red light is able to go through easily, then almost red light would have more success than the green, but not quite enough to manage itself all the way though and therefore randomly bouncing around a bit. I could be completeley wrong, but it's fun to think about! : Never mind, the distribution seems to be, indeed, too small. | [
"Yup, that's probably correct. "
] | [
"Yes, dyed plastic usually fluoresces quite well. Green -> red (longer wavelength, lower energy). There shouldn't be any blue you can see with a naked eye. There are processes that can do this, but they are very weak, nonlinear effects."
] | [
"Your fist guess was correct there too; The linewidth of a diode laser beam is larger than for many other kinds of lasers, but it's still only on the order of a few nm, AFAIK. It wouldn't be enough to appreciably change the color."
] |
[
"How hot does something have to be before touching it becomes painful?"
] | [
false
] | null | [
"This will depend on the object you are touching. Some materials conduct heat much better than others. Also, some have a higher ",
"heat capacity",
", that is the amount of heat it takes (in units of energy, joules for example) to heat a specific amount of the object a certain amount (measured in kelvin). So yo... | [
"At a the Ontario Science Center I saw a display that was basically a table with a surface which was a parallel series of thin closely spaced alternating warm and cold bars(about 4mm diameter, perhaps 3mm apart). When you touched this surface it felt burning hot. The lesson being that pain and our ability to sense ... | [
"This depends on several variables such as duration, where contact is made on the body, etc. This threshold will also vary from person to person."
] |
[
"How does one clean something that dissolves in water?"
] | [
false
] | [deleted] | [
"You clean them in something other than water.",
"For example, if you want to clean special lenses that are made of pure sodium chloride, you can wipe them down with something like hexane."
] | [
"It's probably not a good idea to use organic solvents on something you intend to ingest. Just wipe it off with a dry cloth."
] | [
"It's probably not a good idea to use organic solvents on something you intend to ingest. Just wipe it off with a dry cloth."
] |
[
"How do you measure air pollution?"
] | [
false
] | null | [
"It depends on which pollutants you're interested in, and whether you need active near real-time assessment, or only weekly/monthly averages. ",
"The most comprehensive case of course, is when you need to know everything, right away. Many urban centers around the world have networks of automated air quality mon... | [
"Nitrogen Dioxide and Carbon Monxide and perhaps CO2, to a degree. The easiest way to measure it is likely by taking a sample, testing that sample via some indicators or a reaction which can tell us the exact number of molecules present in a reactant. Once we have this number, we can actually calculate the averag... | [
"The \"acceptable\" limits vary from jurisdiction to jurisdiction, and usually have different values across different averaged periods (1 hour, 1 day, 1 year). The simplified figures below are set by the United States Environmental Protection Agency:",
"SO₂ - < 75 ppb, 1 hour average",
"NO₂ - < 53 ppb, annua... |
[
"Why is there so much attraction going on at the subatomic level? Strong force, weak force, electromagnetic force. Quarks forming protons, protons and neutrons forming a nucleus, electrons orbiting the nucleus. Why should it be that all this attraction happens at all?"
] | [
false
] | Gravity is explained as spacetime being warped by mass. I've heard it compared to a heavy ball sitting on a rubber sheet, stretching it down and causing nearby objects to roll toward it in this depression. I get this. Kind of. But what about at the subatomic level? Is there a single phenomenon that explains attraction in general? I mean, why should attraction occur at all? | [
"The rubber sheet analogy isn't a great one. It still relies on the notion of things rolling downhill, and thus requires some kind of gravity in the first place. I prefer this more correct, and still simple explanation.",
"If you complete a closed loop in a flat space, you end up facing the same direction you sta... | [
"I presume you mean \"how\", and not \"why\". As for why, I can't point to anything other than the anthropic principle -- if it was any other way, we wouldn't alive to observe it.",
"For \"how\", the Standard Model speaks of messenger particles and virtual particles. Virtual particles are exchanged between char... | [
"The strong, weak, and electromagnetic forces are not universally attractive. You probably know enough about electromagnetism to know this already- electrons are attracted to protons, but electrons repel from electrons. The same sort of phenomenon occurs with the strong and weak forces, to.",
"The reason it seems... |
[
"How can people increase their cardiovascular output capacity by training, even though lung volume essentially remains the same?"
] | [
false
] | During intense aerobic exercise, I believe that the supply of oxygen to the lugs is the 'rate limiting step', which results in the body spending as much energy as possible, given the amount of oxygen provided by the lungs. That being said, how can people dramatically increase their aerobic output power with training, even though the volume of their lungs essentially remains the same? | [
"It’s not the size of the lungs, but the ability of the body to deliver the oxygen throughout the body, and to then expel the carbon dioxide waste. That’s why endurance athletes focus on improving aerobic and anaerobic capacity as a measure of cardiovascular potential/fitness, not lung size."
] | [
"Great question! The body works as a system, and even though you might have huge lungs, the other cooperating systems might not be able to use all that oxygen effectively. \nTo increase your long-term endurance (running or exercising for long intervals), it takes time to train you body to use that oxygen more effic... | [
"Thanks for the reply. Then why does an unfit person (like myself) go out of breath while exercising, even though my lung capacity is more than enough?"
] |
[
"How fast will atmospheric moisture adsorb to dry glass?"
] | [
false
] | I've got an argument brewing with another scientist I work with about this. Let's say I pull some glass at room temperature out of a drybox. How fast does moisture from the air start adsorbing onto it, and how long would it take to equilibrate? My thought is that significant levels of moisture will adsorb within seconds. | [
"I would say that it is heavily dependent on the humidity of the air outside the box. I work with air sensitive materials pretty often and we coat glass slides with novel films for various purposes. If you pull the glass out of the drybox, or better yet an oven with desiccant inside it, you can transfer the slide t... | [
"This paper is really in depth and will help answer your question. I'm sure there other other relevant literature sources if you go through the citations or do your own search that might give you a more specific answer in terms of time scale. I think it depends on what you call significant. It looks like the majori... | [
"Pretty fast I think although it (obviously) depends on the moisture content of the air.",
"I've always learnt that to keep glass dry it needs to be either above ~130 C or stored in a dry environment. I would only trust glass to be completely dry if heated above 130 C in a vacuum and subsequently stored in a dry ... |
[
"Why isn't flooding considered to be a good explanation for the mounds of the Mississippian culture?"
] | [
false
] | Some wiki hopping brought me to a page on who apparently built quite big mounds with structures on top and at least partly lived near rivers and on floodplains. I'm no archaeologist, I actually study hydrology, and the first thought that occurred to me was that these mounds could serve an obvious purpose as a safe haven for when the river flooded. However the wiki doesn't seem to mention them serving this purpose. Wiki states the mounds were used as ceremonial and burial places, however this is also logical in the context of flood protection, because I can imagine you don't want your sacred sites to be flooded and covered in river sediments periodically. Also chiefs often lived on them and they probably also didn't want their homes to be flooded either. Look at this picture of the , they are right next to the river. In the Netherlands and other parts of Europe for floods and were already built in 500BC. Other in America didn't live in the flood plains, but maybe they just took the mound building culture developed on the floodplains to other regions. So my question then is why didn't archeologists start from the assumption that mounds were used against floods and that the other purposes for them logically follows from the fact that they survive floods. | [
"I can give you an anthropologist's perspective on why this theory is not prevalent. The mound builders in Mississippian culture probably did not start erecting these structures earlier than 800 CE. There simply wasn't a large civilization there earlier on. The Hopewell culture in Ohio did build smaller mounds, how... | [
"I really appreciate your input, however I'm still not totally convinced. You mention that some mound sites are currently buried under river sediments. Couldn't it be likely that earlier small mounds for small villages before 800CE have just been washed away? Or the older mounds might have been used to fertilize th... | [
"I just found ",
"this old paper",
" which confirms that they lived and farmed mostly on loamy flood deposited soils due to their fertility and easy tillage. No mention of the mounds though."
] |
[
"can your body get \"used\" to adrenaline?"
] | [
false
] | i know adrenaline can do all sorts of awesome stuff like send more blood to your lungs and heart, and cause your senses to heighten and all sorts of stuff. but if you get into situations that causes the release of adrenaline a lot will your body eventually get "used" to it and make it harder for it to do all those stuff effectively? also if it doesn't, can you just endlessly pump yourself with adrenaline to just make everything better? i assume it probably makes certain stuff harder | [
"Approve of this suggestion. TL;DL, stress in short bursts is good, chronic stress (which is what constant adrenaline amounts to) is the reason we have such high levels of hypertension and heart disease etc etc.",
"Chronic stress can also adversely affect childhood development ",
"http://developingchild.harvard... | [
"Approve of this suggestion. TL;DL, stress in short bursts is good, chronic stress (which is what constant adrenaline amounts to) is the reason we have such high levels of hypertension and heart disease etc etc.",
"Chronic stress can also adversely affect childhood development ",
"http://developingchild.harvard... | [
"A ",
"pheochromocytoma",
" is an adrenaline secreting tumor. I think it provides a good model for the situation you are describing. Pheochromocytomas are classically associated with a triad of symptoms: headache, sweating, and tachycardia. They are also a cause of persistent hypertension. ",
"Interestingly... |
[
"We are putting in two wells in remote villages in Malawi. The salt content is high in these regions. How can we make the water more drinkable?"
] | [
false
] | Hello All! We have a well company putting in two bore holes in a remote village in Malawi. These regions are known to have salty water. To the point where it is sometimes not okay for drinking. Does anyone have any solutions to this problem? How can we make the water drinkable? What equipment can we get here that is economical and easy to train how to use it? Is there any organic way of removing the salt? Anything we can add to the pump? Didn't know where to put this. This area has really high cholera cases, we need a solution asap! Edit: Issues: No firewood or charcoal. There is a near by water source but is VERY polluted. It is a heavily populated area. 200+ people will be using the water source so it needs to be able to produce enough water. If each person gets 10 liters a day it needs an output of AT LEAST 2000 liters daily. No electricity. Theft of equipment. Maintenance: cost/training. There is a lot of sun. There is down time in the rainy season where it is very cloudy but that only lasts about 2 months. I am not an engineer, so I need you guys that understand the above limitations and knowledge about this to upvote what will work best, if any, and then explain to me like I'm 5 how it will work. Edit: . There is lots of wind here. I didn't think about this because I have never seen it utilized for anything. Just to clarify to those that think I own a well company and have no idea what I'm doing: I do NOT own the well company. I came across this village that is in desperate need. Well companies here seem to not care so much about salt content issues and just drill the holes and go. I wanted to know more about what can be done with salt content. Please stop insulting me for it. Also: If there are any Hydrogeology experts/students that want some field experience I'd be happy to organize a trip out here and see what we can do? | [
"I am a water/wastewater engineer. If I understand correctly:",
"Sources: brackish groundwater, polluted (with what? assume human waste?) stream.",
"Restrictions: no electricity, fire, or charcoal.",
"Producing: 2 m",
" per day of potable water.",
"I am not a politician so I won't mince words, you are pre... | [
"This will not scale to the required volumes at all. You would need hundreds/thousands of small stills, or a large still that would have capital, construction, and maintenance requirements that are completely insane.",
"Best approach is a hydrogeological survey and better well design/drilling.",
"Source: I am a... | [
"Hydrogeologist here, as a general rule of thumb, water gets more saline as you go deeper. There are some exceptions to this, near mountain fronts where permeable layers outcrop, then dip steeply under the overlying rock, which may contain a separate permeable unit with salty water from a distant recharge area for ... |
[
"Why is the human sense of smell so weak?"
] | [
false
] | What sort of evolutionary benefit can a weak sense of smell be? Is it just that we rely on eyes so much that it doesn't really matter how the sense of smell changes. It would seem to me that weakening it would be a bad thing in terms of evolution. | [
"Evolution is not free. Bodily structures cost energy, complexity, and space. Weak smell is a benefit in the sense those biological resources are better spent somewhere else.",
"It is like putting a towing hitch on a Prius. There is nothing ",
" with a towing hitch, but it is weight and space spent on someth... | [
"I can expound on the \"cost energy, complexity and space\" bit. Compare the relative size of our ",
"olfactory tract",
" to a mouse's ",
"olfactory bulb",
". The olfactory tract in humans is the two flat structures at the base of the brain ending in a bulbous connection, whereas in mice, the olfactory ce... | [
"In what way is it weak? I mean, compared to a dog it isn't that great, but humans have been shown to be able to ",
"scent track",
" and we are able to detect scents with a concentration of less than ",
"1ppb.",
"That 2nd link goes on to tell us how some smells aren't odours at all, but are triggering tempe... |
[
"Is it possible to calculate how fast we're moving through time?"
] | [
false
] | [deleted] | [
"One second per second. Which also happens to be the speed of light."
] | [
"You're always at rest relative to yourself, remember."
] | [
"Correct. My mistake."
] |
[
"Who is more likely to get struck or hurt by lightening first? A man under a tree, the man in the swimming pool or the one on the golf fairway holding a 5 iron?"
] | [
false
] | null | [
"The tree is the most dangerous since it is likely much higher in the air than the pool or the golfer. While the tree may conduct much of the electricity through it's trunk, there will no doubt be transient forks that may hit anyone standing under the tree and kill them. "
] | [
"The \"path of least resistance\" is a clever metaphor for lay-persons but it is not an entirely accurate portrayal of how electricity works. Electricity will generally follow all viable paths, but the current is inversely proportional to resistance. Lighting going through air works a little differently but you are... | [
"I've always thought that the main danger of someone standing under a tree is shrapnel when water inside a tree boils after it was struck."
] |
[
"Is there a \"due north\" for determining x,y,z coordinates in space?"
] | [
false
] | This had me puzzled when reading about distances of objects from the sun, earth, etc... | [
"Celestial Coordinate systems is how you would orient yourself with one other object in space. With the use of Right Ascension and Declination.",
"Be careful here - there are actually many different coordinate systems used in space. Right ascension and declination are only useful if you're talking about where you... | [
"In short, no. Everything in space is based on a relative coordinate system (called the Celestial Coordinate System). Basically, if you want to know where you are, you use other objects (planets, stars, other spacecraft, etc.) as a reference point, and determine where you are based on that. ",
"Very similar to ho... | [
"Here is a long but thorough read on the development and implementation of the International Celestial Reference System, which is the current standard reference system as designated by the IAU (International Astronomical Union). Its origin is the solar system barycenter and its axes are determined with very accurat... |
[
"Why does food get cold much faster after heating it in a microwave as opposed to on the stove etc.?"
] | [
false
] | null | [
"As long as you heat both to the same temperature and then treat them the same after heating then they will behave exactly the same. There should be no chemical or physical changes upon heating, so all that matters is how hot it gets and the conditions around it during cooling.",
"The only difference between the... | [
"It could come from a variety of factors. Once you stop the active heating there is a lot more latent heat in the stovetop, so if you let the food sit for a little after cooking there will be a noticeable difference. Microwave heating can also be deceptively uneven (ever try to microwave a hot pocket, especially ... | [
"Thank you for your answer!",
"I heard this so many times though that it makes me wonder: did this myth come to be because people tend to heat their food less in a microwave so that it is significantly warmer when prepared normally? It's just their impression that it cools faster after microwave but in reality it... |
[
"How \"efficient\" is a supernova?"
] | [
false
] | [deleted] | [
"You are on track but your terminology is a bit off. Roughly 0.1% of the mass is converted to energy. The rest remains as mass - these are the two fission products that are created. So the \"potential energy\" - the difference in binding energy between the uranium nucleus and the two daughter products, is entire... | [
"You are on track but your terminology is a bit off. Roughly 0.1% of the mass is converted to energy. The rest remains as mass - these are the two fission products that are created. So the \"potential energy\" - the difference in binding energy between the uranium nucleus and the two daughter products, is entire... | [
"Your typical type II supernova sends out 99% of its energy via neutrinos. About 0.01% comes out as light.\nFun fact: The star's atmosphere is ejected at around 10,000 km/s"
] |
[
"Will we be beaming information through the earth (as opposed to around) in the future?"
] | [
false
] | null | [
"Since most of the Earth is not transparent, the fastest data transfers would occur at the speed of sound through the Earth which is approximately 10km/s ",
"(order of magnitude estimate)",
". Satellites communicate at the speed of light, which is about 300,000km/s (30,000 times as fast as the speed of sound th... | [
"Thanks for the reply! I am a little unclear on what \"transparent\" means in this context. ",
"Why would the speed of sound through the earth be the deciding factor? Is there no speed of light through earth? I mean radio waves penetrate concrete and other stuff (and they are at least EM radiation if not actual l... | [
"Sure, radio waves could penetrate a couple feet of concrete. But the earth? No way. 12000 miles of rock stops just about anything. MAYBE not neutrinos. But if a neutrino doesn't interact with 12000 miles of rock, how would it interact with anything we build? There's really no other way to catch a neutrino th... |
[
"How can you permanently flatten a PTFE sheet?"
] | [
false
] | null | [
"Not the right sub. Maybe try ",
"/r/askengineers"
] | [
"Thank you. Should I delete the post? "
] | [
"Already removed"
] |
[
"Why don't we see any main sequence Red Giants or Blue Dwarfs?"
] | [
false
] | Pretty simple question, probably with a pretty simple answer. Blue Dwarfs are a theoretical stage of life for Red Dwarfs, that much I know, but why don't we see any small main sequence Blue stars? Is it just not possible to get that hot and that small? And the same goes for Red Giants - all the big stars seem to be Blue. Why are none of them Red? Why is that only the dying stage of a larger star? | [
"A star's evolution is mostly driven by just two numbers: its initial mass, and its age. Almost all stars of the same mass will go through the same evolutionary stages at the same ages. We see a diversity of stars because stars were formed at different times and with different masses. There are other effects, but t... | [
"we do see blue dwarfs",
"Yeah, but the term \"blue dwarf\" isn't used in astronomy that much, typically because it causes confusion. Usually when I've heard it used, someone asks for clarification whether they meant an O- or B-type main sequence star, a blue dwarf galaxy, or even a ",
"hypothetical star that d... | [
"The red giant is one of the last stages of stellar evolution. This means that the star does not have enough fuel to continue resisting gravitational collapse, after the star begins to swell to prevent collapse (this is an attempt to balance the forces of gravitational collapse and internal pressure), so the star b... |
[
"What makes molecules stable?"
] | [
false
] | I'm in Biology, and I'm having some trouble grasping these concepts. I was wondering if anyone could help. Is a molecule most stable when it has an equal number of protons and electrons? (no charge) | [
"The presence or absence of a charge does not necessarily make any difference. ",
"Stability is actually really relative - there is no absolute measurement for stability. A molecule can only be more stable than another molecule. A more accurate word is \"persistent.\"",
"The short answer is: A molecule is sta... | [
"In molecules, there are several kinds of bonding that may occur, each of them having differing strengths. Van der Waals forces inside a molecule (it also works on intra-molecular and larger levels) which is the weakest, and then covalent (which is deemed the strongest by bonding energy, but in reality there are no... | [
" has it down, but I just wanted to add my $0.02.",
"It's true that the entire field of chemistry is devoted to understanding the reactivity of molecules, and (in the 20th century) the underlying quantum mechanics that really describes why. Still, there are a few basic trends that apply maybe 95% of the time that... |
[
"What are carbon nanotubes?"
] | [
false
] | Can anyone please explain what carbon nanotubes are in the most non-scientifical way possible please? I understand that they are sheets of graphene and there are SWNT, DWNT, and MWNT. BUT i dont understand why they are soooo much better than normal graphene and the difference between the types of nanotubes. as in electrical properties and why (for example the electron flows or mechanism when funtionalized.) thank you soo much | [
"Just pretend it's just like chicken wire rolled up into a tube -- except the wires are made of very stable carbon-carbon chemical bonds. They are so tiny that around one billion of them will fit onto a meter stick. ",
"However, you don't have to roll up the wire lengthwise. You can do it at an angle. You can mak... | [
"are there any ways to explain its electronic properties without being VERY technical?"
] | [
"Like what coniform said, the rolling plays a very important part in determining the electronic properties. So, depending on how you roll it, you can have one of three electronic behaviours:",
"1) Metallic conduction:\nThe nanotube acts like a metal and conducts electricity very well. In fact, it exhibits \"balli... |
[
"How do the Starlink satellites in very low orbit overcome drag?"
] | [
false
] | The more closely orbiting satellites have an altitude of 340km/210mi. Does atmospheric drag play a major role there? I know satellites often have a small engine to maintain orbit, but wouldn't it burn through the fuel relatively quickly? How long of a lifespan can be expected? | [
"The Starlink sats are only below 400 km for a few weeks immediately after launch. They are gradually raised to their mission orbits of about 550 km (where atmospheric drag is considerably less) using Krypton ion thrusters. These electricly powered thrusters are also used for station keeping and the eventual deor... | [
"It's temporary for the current satellites (they raise their orbit to 550 km), but later they'll deploy satellites that will stay at ~350 km. They will need to use their ion thrusters a lot, otherwise their orbit decays within months.",
"Wikipedia has a table",
"."
] | [
"TBF, 550 km is still a very low orbit (as it relates to atmospheric drag), so the question is still valid, and answered, IMO, very concisely."
] |
[
"I noticed that a strong disc magnet will refuse to flip over in my hand, always landing the same side up. Can anyone explain this behavior? Video inside."
] | [
false
] | Thanks! *Edit I'm disappointed that I'm being downvoted here. I have a real mystery on my hands and I've documented it as best I can. I would have expected people to be much more curious about this phenomenon, but everyone seems to be dismissing my evidence. I've even made an additional video here on request: | [
"Have you tried asking someone else to do this without telling them the purpose of the experiment (a blind test)? You may be inadvertently influencing the way you're tossing the magnet because of your expected outcome, though it's also possible that it's being influenced by magnetic fields that are keeping it orien... | [
"Pretty sure it's just how you're throwing it. Notice in the slo-mo of your video that you're throwing it straight up so it doesn't really flip. There is a point in the video when it gets a good flip and does land on the other side. Try actually flipping it so it spins several times in the air. My guess is the resu... | [
"There is no way this would happen outside of a magnetic field (the earth's field just isn't strong enough to cause this). It must be the way you are flipping it. "
] |
[
"How exactly do non-Newtonian fluids work, and what determines the force at which they 'activate'?"
] | [
false
] | So I've been trawling the internet for a while, and I'm struggling to find a high quality and reliable explanation for why the fluids posses their unique properties. A friend suggested that I try my luck with the good people of Reddit's AskScience, so I'm hoping you can help me on this one. What I'm somewhat more interested in though, is what exactly determines the necessary conditions for different non-Newtonian fluids to solidify. For example, I doubt that a cornstarch and water mix could stop a bullet, but I understand that it's very much possible for polyethylene in a glycol gel to do just that. What makes the two so different? Many thanks in advance. | [
"I am gonna restrict my answer to shear thickening fluids, as that is what your question seems aimed at.",
"These fluids usually suspensions of a solid particles in a liquid, such as corn starch in water. At rest the corn starch particles are completely surrounded by water molecules, which is their preferred stat... | [
"Thank you for the answer! As a bit of a follow up, is there any chance you could tell me why that is the preferred state of the molecules? Some specific intermolecular force, or something else entirely maybe?"
] | [
"In addition to what yoenit said, I'll point out for yourself or anyone else who is reading and curious that a fluid is not the same as a liquid. A fluid is merely a substance that when under shear force will deform to a depth of 0."
] |
[
"At what point, specifically referencing Earth, does Euclidean geometry turn into non-Euclidean geometry?"
] | [
false
] | I'm thinking about how, for example, pilots can make three 90degree turns and end up at the same spot they started. However, if I'm rowing a boat in the ocean and row 50ft, make three 90degree turns and go 50ft each way, I would not end up in the same point as where I started; I would need to make four 90degree turns. What are the parameters that need to be in place so that three 90degree turns end up in the same start and end points? | [
"The answer to the title question is \"always\". The Earth is spherical. Period. Whether the spherical shape of Earth matters to you is dependent on the what you're measuring and your threshold for error.",
"As to your more specific question...",
"On a sphere, the area of a triangle formed by three geodesics (a... | [
"A good way to visualize this is to cut the earth into 8ths. Cut it in half at the equator, then cut the northern and southern hemispheres in half, then cut each quarter in half again. The surface area of each of those 8 pieces will be 1/8 the surface area of earth, and each one will have three 90* angles on th... | [
"Okay this is a baller example for anyone who was having trouble visualizing it, hadn’t even though about a physical object having three corners that explain it so easily"
] |
[
"On a cellular level, what causes a sore throat?"
] | [
false
] | I am very curious as so what is happening to yor cells when you have a cold and a resulting sore throat. Responses are much appreciated. | [
"First read about ",
"pharyngitis",
".",
"Then read about this ",
"inflammation",
".",
"Then ask any questions you have.",
"I don't mean to sound condescending but watching the episode of The Magic School Bus where they go inside Ralphie when he is sick will really help visualize everything. ",
"li... | [
"I agree with luckypenne, but to briefly write something here: sore throats as either viral/bacterial pharyngitis/laryngitis/tonsilitis are manifestations of pathogens colonizing and destroying actual cells that they are using to replicate. Both the destruction of cells and the presence of pathogens stimulate che... | [
"I have to agree with the Magic School Bus episode. I watched it with my kids, and I really don't think I could do a better job of explaining it simply. "
] |
[
"If the environmental conditions were favourable, would it make a positive difference to launch rockets from areas with high elevation such as Colorado?"
] | [
false
] | [deleted] | [
"Would it be beneficial to launch at high elevation?\nYes. You start off closer to space, which means you need a little less fuel or can carry a bit bigger payload.",
"But Colorado? No. The best places to launch rockets into space are locations near the equator. This is because the rockets more or less piggy-back... | [
"For low Earth orbit, most of your energy is spent accelerating sideways rather than lifting the rocket up. Consider that the ISS orbits the Earth every 90 minutes, so it is moving very fast. Because of this, being close to the equator is more helpful than being high up.",
"Not that being high up doesn't have som... | [
"Theoretically, yes. The higher you start, the easier it will be. ",
"However, there are quite a lot of variables in play besides elevation. First, the closer to the equator the better, as you get a boost from the rotation of the earth.",
"Second, you need the infrastructure available to support a space progra... |
[
"Do things that have similar scents/smells have similar chemical makeup? Or can two distinctly different things with distinctly different chemical makeups smell the same?"
] | [
false
] | null | [
"Actually, they just have similar ",
" but may have completely different compositions. Certain molecular bits (functional groups as they are called) have shapes that cause certain molecules to fit in certain receptors, but molecular bits that are similar in shape and size can also fit in those receptors.",
"The... | [
"A bit of trivia:\nStereoisomers can also have different smells.\nAn example is R-carvone (spearmint) and S-carvone (caraway seeds)."
] | [
"\"An alternative to the widely accepted theory of shape olfaction\"",
"Eh, the shape theory is more testable and makes more sense."
] |
[
"How do we know which river merges into which and continues being that river?"
] | [
false
] | I.E. How do we know the Missouri River flows into the Mississippi instead of the other way around? | [
"The bigger river is the main one. Look at the convergence between the Mississippi and Missouri rivers ",
"here",
". The Mississippi river is the bigger one.",
"It's worth noting that you are sort of working backwards here. The Misssissippi was named downstream, at the mouth, and then mapped backward to th... | [
"Just wanted to add, sometimes things are named and then we just go with it even though it should change when more is discovered. Where the Ohio meets the Mississippi, the Ohio is the larger, so it should be the Ohio to the gulf. "
] | [
"Also true"
] |
[
"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! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away! | [
"You still produce respiratory droplets just through normal breathing, you just don't produce as many of them. And most people cough or sneeze occasionally for reasons unrelated to having a virus (like dust, or stepping out into the sun, etc). Asymptomatic spreading is probably much less effective than symptomatic ... | [
"How does asymptomatic viral shedding cause new infection, if a virus is typically spread by respiratory droplets?"
] | [
"What’s the process of making a vaccine? Can you elaborate on vaccines with dead or alive viruses?"
] |
[
"Why does the hair on the average human head continue to grow while all other primates have hair that stops naturally at a relatively short length?"
] | [
false
] | null | [
"It's theorized that long human hair came about much in the same way.",
"Citation?",
"If this was a Fisherian runaway process, then that would mean that many individuals should have a strong ",
" predisposition to be attracted to individuals with long hair. I'm rather skeptical of that. I did a really brief s... | [
"It wouldn't, since by the time most men go bald, historically they already would have passed on their genes. Aka Doesn't Matter, Had Kids."
] | [
"Think Peacocks.",
"Peacock feathers likely evolved because Peahens saw brilliant plumage as a sign of health. So, Peahens who liked brilliant plumage mated with Peacocks who had brilliant plumage.",
"The male children of these Peacocks and Peahens likely had more brilliant plumage, while the female children l... |
[
"Does the salinity of ocean water increase as depth increases?"
] | [
false
] | Or do currents/other factors make the difference negligible at best? | [
"As the name suggests this circulation is driven almost entirely by changes in temperature and salinity",
"This is one of these 'facts' that are often repeated, but are actually false, and it's simple to explain why. Aside from mixing within the ocean interior, all processes that affect the density of water (e.g.... | [
"As the name suggests this circulation is driven almost entirely by changes in temperature and salinity",
"This is one of these 'facts' that are often repeated, but are actually false, and it's simple to explain why. Aside from mixing within the ocean interior, all processes that affect the density of water (e.g.... | [
"Cooled water from the poles sinks as a result of both its salinity and temperature profile. Cooler water is denser than warmer water. Cooler water with high amounts of salt is even more dense. So it sinks and is replaced by less dense and less saline (fresher) water. So yes, the salinity of water increases with de... |
[
"Alcubierre metric and T^00 energy density: how is the \"total energy\" calculated and what does this \"mean\" on a practical level?"
] | [
false
] | I realize that people have asked about , but reading the various warp drive papers and trying to understand the physics behind them motivated this question; the question itself is only tangentially related to Alcubierre. The specific question stems from (warning: PDF) and the third equation in that paper: T = -(c /(8 G))(v ρ /(4r c ))(df/dr) Where: If I am not mistaken (and I probably am!), this equation's units come out to be Newtons (kg m/s ) rather than anything I understand as "energy density" (e.g. Joules / m ). That aside, it's often said that a warp drive using these principles would require tremendous amounts of energy (negative energy at that, but let's table that particular aspect for this conversation) -- What's the next mathematical step? Further, , such that the warped spacetime is established and then remains, or is it something that must be expended continuously (representing, perhaps, the per-second energy expenditure)? Appreciate any insight into understanding the math here anyone can offer! | [
"The stress energy tensor represents a lot of things together. T",
" represents something ",
" how the P",
" value changes with respect to the X",
" direction (where P and X are 4-momentum and 4-space vectors respectively). {specifically, it's the P",
" flux through a surface of constant X",
" } ",
"T... | [
"I'm having a hard time understanding how units of Force can be used to describe energy density (or even energy content).",
"Recall our first definition of energy in physics. We define work to be Force (dot) displacement. A force applied along some displacement is work. Work is energy. ",
"I was really confused... | [
"The final quantity is the squared derivative of a dimensionless function, so will also be dimensionless.",
"This is your mistake! The derivative of a dimensionless function with respect to a dimension-full parameter is ",
" dimensionless. All of the rest of your dimensional analysis is correct, but you should ... |
[
"The moon is able to redirect the sun's illumination onto the earth. Does the earth also illuminate the moon the same way? With less, or more intensity?"
] | [
false
] | null | [
"Yes it does. If you can find a place with low enough light pollution, (mostly places away from cities) look at the moon when it is in the crescent phase. You will see the bright crescent illuminated by the sun and you will see the rest of the moon's disc illuminated by reflected earth light. It's faint but unm... | [
"Yes. Think of when the moon is a thin crescent. It is often possible to see the entire moon, because the part not illuminated directly by the sun is receiving reflected illumination from the earth.",
"Also, as bright as a full moon appears, the moon's surface has an albedo of .12, which means that only 12% of ... | [
"Sun->Earth->Moon->your eyes on Earth"
] |
[
"Is there hard data on the number of potentially catastrophic issues fixed before Y2K?"
] | [
false
] | Most of what I've seen in the 18 years since has been along the lines of "nothing really happened, so the panic was silly." But do we have any data on the number of fixes that prevented disasters the scramble to prepare for it? I guess it might be hard to count the number of times somebody said "well could have been disastrous, I'm glad we caught it", but has anyone put together that type of estimate? | [
"As Y2K passed with a low number of computer failures due to the Y2K bug, post-analysis is less of a Computer Science issue, and more something better discussed in terms of business and governance, as your question is less about the science of computing, and more about the human response to the bug. But I'll try t... | [
"This makes me think of movies like Deep Impact or Armageddon. In Deep Impact, an asteroid threatens to wipe out humanity, but the government initially keeps it quiet to avoid panic. This story makes me think that’s a very plausible scenario IRL. Before, I would have thought, “how could so many people stay quiet... | [
"Thank you. That definitely helps. Without more precise numbers, would it be irresponsible to say Y2K could be labeled one of these two options?",
"-A crisis averted because of widespread preparation.",
"-A less serious situation that didn't call for the degree of concern it received."
] |
[
"Why is it that cutting an artery often leads to immediate blood loss and death, but amputating an entire limb carries a high survival rate?"
] | [
false
] | Or at least that's the way it's often portrayed in the media. | [
"Please don't do this-you're better off putting pressure on the wound and getting immediate emergency help"
] | [
"Please don't do this-you're better off putting pressure on the wound and getting immediate emergency help"
] | [
"When a limb is completely amputated, and an artery is completed transected, this allows the artery to spasm, close up, and retract back into the wound. This is why even complete traumatic amputations may not bleed as much as one would expect from such a severe injury."
] |
[
"Which one of the two isomers formed by connecting a benzene ring with the isostructural borazine would be more stable, the one with a carbon-boron bond or the one with a carbon-nitrogen one?"
] | [
false
] | If one of the benzene rings in biphenyl was substituted by a borazine one which of the two isomers would prove more stable? Does the fact that the carbon-boron bond is stronger than the carbon-nitrogen one tell the whole story? | [
"It doesn't tell the whole story, because you also have to consider the relative strengths of the B-H and N-H bonds. I believe that the N-H bond is stronger, so that should help the case of the rings being connected through the boron.",
"I wish I had time to run a calculation on this molecule so I could say some... | [
"No, if you make the bridge between the boron and carbon, that's one less B-H bond that can be in the molecule. Same deal for nitrogen. You have to consider it all for an accurate estimate of relative energies."
] | [
"A quick search on wolframalpha indicates that the B-H bond is slightly stronger than the N-H one, 389 kJ/mol vs 386 kJ/mol."
] |
[
"Is there a way to generate, and subsequently visualize, a tagged protein in vivo?"
] | [
false
] | The question is a bit vague. Is there a way to give an animal something (food, injection, etc.) such that it begins to produce the tagged version of a protein? Has this been done? For example, lets say you want to visualize dopamine production in the brain. Can you change the production of the protein such that they begin to incorporate some sort of reporter that can be visualized in vivo? Or maybe...is it possible to transfect a cell with some vector with DNA for the tagged protein (in an in vivo model) such that it starts producing the tagged protein? Or will this be detrimental to the organism? The purpose of asking this question is because I'm just thinking that it might be a way to visualize processes as they happen in a living organism, so we wouldn't have to sacrifice and do histology or something. | [
"Not my branch of biology, but this sort of thing definitely does happen. However I don't think it's very practical in adult animals. In cell/microbiology you can generally transfect or transform the cell with either an altered version of that same protein fused with a ",
"GFP",
" reporter or simply GFP with th... | [
"I don't know about production, but you can do ",
" imaging using transfection in a variety of models. One example is ",
" tadpoles, which are transparent enough to visualize while still alive; you can transfect a marker for whatever you're interested and visualize it many times in a living organism."
] | [
"Absolutely! We do this a lot in my line of work, often by transfection (as you suggest) which causes the cell to express the a fluorescent version of a protein, or introducing some kind of fluorescent molecular probe that selectively binds to the protein in question.",
"Generally, these sorts of probes emit in t... |
[
"How long can a virus’s incubation period truly be?"
] | [
false
] | [deleted] | [
"HIV can take years to manifest symptoms, or even show up in tests. It's part of why they recommend testing regularly, even if you haven't been sexually active in a while, or your last test came back clean and you've been monogamous since then."
] | [
"I know that ",
"rabies",
" is known to have a possible incubation period of up to 7 years. If I recall correctly, HIV and one of the herpes viruses can have incubation periods on the scale of decades as well. ",
"Again, if I recall correctly (and there is no guarantee that I do), it has something to do with ... | [
"Just a quick correction, the median and mean incubation period for Covid-19 is about 5 days. 14 days represent the upper end of the incubation period and is the exception, not the rule.",
"Sources: ",
"https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Steckbrief.html#doc13776792bodyText4",
" (in g... |
[
"If there used to be a lot of water on Mars, what happened to it? Did it leave the planet and atmosphere?"
] | [
false
] | ^ | [
"Mars almost certainly had an ocean worth of water early in the life of the Solar System. However, the planet's low mass means it also has a relatively low escape velocity, and all sorts of escape processes can cause atmosphere to leak out to space. ",
"Water vapor on its own is just a bit too heavy to easily esc... | [
"That's actually an incredibly cool tidbit about why mars is red. Is this the only/biggest reason for the colour?"
] | [
"If we look far enough back at the history of mars would there be an explanation as to how it built up an ocean in the first place, before it all started disappearing? When I see water on mars being explained it always starts half way through the story where mars already has a ton of water and it all starts disappe... |
[
"How do the antibodies in mother's milk get into baby's blood stream?"
] | [
false
] | Don't they get destroyed in the baby's stomach? | [
"Great question. I didn't know either, so I looked it up a little and found this: ",
"The capacity of the digestive tract to absorb intact proteins must not last beyond one or two weeks, since once foods other than milk are ingested the proteins and other antigens in them would also be absorbed intact and could a... | [
"Antibodies are not tiny! They are ~150 kDa! Just as a clue, the average molecular weight of an amino acid is 110 Da. Hence, a 150kDa protein would have around 1360 amino acids! ",
"Tiny structure doesn't really have relevance as far as enzymatic processes go either. "
] | [
"My knowledge is in non-human domestic animals, but we are all mammals, so I hope you will still find it relevant.",
"No, they do not get destroyed in the stomach. During the first day, the PH is quite a bit higher due to residual amniotic fluid in the GI, and the epithelial cells lining the digestive tract have... |
[
"Electrolysis of water yields proportionally small amount of gaseous Oxygen. Where does the Oxygen go?"
] | [
false
] | null | [
"Some of it might turn into carbon dioxide, but then you should just be collecting carbon dioxide instead.",
"You have nothing listed that can form a solid precipitate and didn't report one. Did the electrode have a metal core? Is it possible that there was a leak on the oxygen side?",
"You probably want to use... | [
"Something like this is more suited for ",
"/r/chemhelp",
" or ",
"/r/homeworkhelp",
"."
] | [
"Perhaps, I will try. Thank you :)"
] |
[
"Can you use a regular compass on Mars?"
] | [
false
] | null | [
"Thank you so much for the thorough answer!"
] | [
"Thank you so much for the thorough answer!"
] | [
"I've seen some more recent studies that point towards Earth having a large moon that is in a relatively stable orbit being the reason that our planet still has a molten spinning core after billions of years. It's an alternative theory to the old \"radioactive materials are the reason Earth still has a molten crus... |
[
"Could you carbon date something from the future?"
] | [
false
] | I was watching Terminator guys! And I started wondering whether you'd be able to date something from the future | [
"In principle yes, but it won't be of much use.",
"Carbon dating doesn't determine the age of an object, but rather how long it (or the organic materials it was made of) has been dead.",
"Carbon comes in multiple forms (isotopes). The most common one, carbon-12 is stable. However, a heavier form, carbon-14 is r... | [
"Holy shit. I didn't know how bad I wanted to know this until finding this post! Thank you for your comprehensive answer. "
] | [
"You hinted at a possible answer without striking it. The so called 'bomb pulse' ",
"https://en.m.wikipedia.org/wiki/Bomb_pulse",
"Basically because of the atomic bomb tests the ratio of C14 is elevated as compared to C12. The rate that this ratio falls has been tracked and it is not unreasonable to think it co... |
[
"Is it possible for a large moon have a satellite of its own?"
] | [
false
] | I was watching and it mentioned that the Galilean moons were the size of planets. | [
"Due to the tidal effects from the host planet, orbits around a moon would not be stable in the long-term. In the short term, you can orbit a moon just like any other body, but we don't expect to find natural satellites of moons due to how brief the arrangement would be."
] | [
"I don't think they left anything in orbit. There are currently two craft that I know of in orbit around the Moon, the ",
"Lunar Reconnaissance Orbiter",
" which has been orbiting for nearly 5 years, and the ",
"Lunar Atmosphere and Dust Environment Explorer",
" which has been orbiting for about six months.... | [
"Hi, did the Apollo projects leave something in orbit around the moon? Is\nit still there?"
] |
[
"Chemically, what differentiates a good shampoo from a bad one?"
] | [
false
] | Like chemically what ingredients should I be looking for and which ones should I avoid? I've been having a hard time finding correct information about this since sites are terrible. So which ones SHOULD I look for/get? What are the good ingredients? I've been googling and I can't find credible sites for this. It's bothering me. In before someone recommends drbronner, what's so special about them? Seems like reddit really likes their marketing. | [
"As an expert, I'm going to disagree with everyone except ",
"thisaccountisbs",
". My background: I worked for one of the world's largest producers of shampoo in R&D.",
"Shampoos are not slightly acidic, their pH isn't that important.",
"The surfactant is really important in making the stuff work.",
"Ther... | [
"This is going to sound glib, but you should use whatever shampoo makes you happy. They all more or less work the same, but shampoo companies are really good at manipulating human psychology. Even knowing all this, when I go to buy my next bottle of shampoo I can't help but think about how dumb I am for springing f... | [
"I seem to recall it was at least a decade old. ",
"As for organic and green...trust me, the marketers manipulate those too. For example: Ever notice how recycled paper products are usually brown? This is to make you think, \"Oh, they didn't want to waste money/resources dying/bleaching this paper and so they jus... |
[
"Why don't cats and dogs get brain whiplash when they shake their head?"
] | [
false
] | You know those shakes dogs do when they try to get rid of water? Seems quite high speed. Cats do it just to straighten their hair. Yet they are fine with it. Is it because their brains are small compare to humans? | [
"This research on ",
"wet dog shaking",
" suggests that they shake at a frequency of 4Hz. The high speed video on the site seem to show that the dogs actually only shake their head by a fairly small amount, maybe only 40 degrees of arc in total.",
"I just tried to shake my head at the same speed and arc, it's... | [
"But if you look at ",
"this plot",
" it clearly shows that all the dogs they have data for (circles) are shaking at less than 10 Hz, with larger breeds shaking slower.",
"I will concede about the video however, I only watched the first 2 or 3 shakes. The amplitude does get bigger with time."
] | [
"It says dog shakes up to 30Hz.",
"This video, from your link",
" show the dog shaking his head almost 180 degrees from side to side.",
"I am sorry, you are obviously wrong."
] |
[
"Could you trap light in a fibre optical cable, if you sent a short beam through and spliced the ends together before it reached the other end?"
] | [
false
] | And if yes, how long would it continue to travel, assuming the cable is a couple of light seconds in length? Edit: Thanks for you answers. | [
"No need for such an elaborate procedure. ",
"Getting light to travel in a circular path isn't anything super exciting and is done routinely. These structures are called ",
"optical ring resonators",
" and they have widespread applications in fiber optics, especially telecommunication.",
"Here's what they ... | [
"You can trap light in a small glass sphere such that it ",
"races around the inside edge of the sphere",
" many times before leaking out."
] | [
"Even if you could splice it quickly enough there is still attenuation in the fibre that gradually reduces the energy of the propagating light. In the best optical fibre the attention is about 0.2 dB/km at 1550nm, which is actually very close to the theoretical minimum for silica. Even if we assume the splice is pe... |
[
"Where do lichen get their phosphorus?"
] | [
false
] | All life on Earth has DNA, and DNA is made of Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus. Therefore, all life needs access to these 5 atoms in order to grow. Lichen seem to be able to grow almost anywhere. I understand that they get their carbon from CO2 in the air (via photosynthesis), and hydrogen/oxygen are present in water. Wikipedia says some lichen have cyanobacteria, which is capable of nitrogen fixation (i.e. extracting nitrogen from the air into usable form). This explains nitrogen. But there is no phosphorus in the atmosphere. Where do lichen get their phosphorus? | [
"It is thought that they derive most of their phosphorus directly from the rocks they grow on with* some likely minor contributions of P in rain water. ",
"This paper suggests that they enhance weathering of rocks to increase P availability",
"edit: with instead of without"
] | [
"As far as I know all rocks have some amount of phosphorus, but the concentration can vary ",
"by a factor of 30",
". Lichen productively would certainly be limited on very low P rocks but I don't know the threshold at which it would become more limiting than other factors. "
] | [
"Interesting! So does that mean lichen cannot grow on rocks that have no phosphorus? If my roof tiles had no phosphorus, would that prevent lichen from growing on my roof? (Or can they use phosphorus from dust/pollen when in an urban environment?)"
] |
[
"Is there an online resource where one would be able to find info on the relative safety of certain substances to humans?"
] | [
false
] | This is regarding a number of substances/chemicals. I've tried using google scholar, but the papers that come up are rarely relavent. Any help for a layman here? | [
"MSDS"
] | [
"You can search for the MSDS for the particular product and get all the necessary information, though I will warn that things will often sound much more dangerous than they are (even water can be deadly, when misused!). If you want strictly toxicological information, the MSDS is probably sufficient. If you're won... | [
"erowid.org"
] |
[
"E-Coli in your body."
] | [
false
] | Okay, so I understand that there is E-Coli in the body naturally. So why does the body respond so badly to E-Coli from an outside source? Also, Does anyone know how much E-Coli it takes to actually cause the body to respond adversely? | [
"What you are talking about is the difference between colonisation and infection. Colonisation is basically the 'natural' populations of bacteria in and on your skin, mucus membranes, and gastrointestinal system. Infection occurs when the virulence factors of colony of bacteria outcompete the host immune system. Th... | [
"different strains",
"http://www.cdc.gov/ecoli/general/"
] | [
"I'm pretty sure the most common pathogenic strain of E. coli is the 0157:H7 strain that produces a shiga like toxin that causes diarrhea."
] |
[
"When sending things to other planets, why do we choose not to use the moon as a mini gravity-assist? Surely it would just reduce fuel (even slightly) and thus reduce the mass of spacecraft?"
] | [
false
] | null | [
"We can and do! The STEREO probes used the Moon for instance.",
"One thing that makes it tricky is that the Moon moves so fast in ",
". The Moon is orbiting the Earth at 1 km/s, compared with other planets that are moving at 10s of km/s, but the Moon is much closer, so its angular speed is much higher. The Moon... | [
"Lightning around the time of launch is a big no-no. Also wind shear can affect stability/control of a vehicle during launch. Flying into clouds with ice particles (e.g. hail) could be bad for the structural integrity of the vehicle. Remember that a breakaway piece of foam ended up dooming the shuttle Columbia.",
... | [
"Lightning around the time of launch is a big no-no. Also wind shear can affect stability/control of a vehicle during launch. Flying into clouds with ice particles (e.g. hail) could be bad for the structural integrity of the vehicle. Remember that a breakaway piece of foam ended up dooming the shuttle Columbia.",
... |
[
"Why is Neoprene more resistant against ozone?"
] | [
false
] | Why is Neoprene more resistant against ozone than regular rubber (latex)? Regularly, I think that the dubble bonds in the rubber polymers burst when they react with ozone, so that the whole rubber eventually ruptures. This doesn't occur to the same extent with Neoprene (polychloroprene). Why? Does it have something to do with the chlorine in the rubber, that the chlorine reacts with the ozone instead of the dubble bonds? Please explain! | [
"Thank you!!!"
] | [
"Is it so that the more crosslinks there are in rubber - the more oil resistant the rubber is?"
] | [
"Yes, ozone deteriorates rubber by reacting with the double bonds to cause breaks in the rubber polymer. ",
"Ozonolysis is an electrophilic reaction",
", meaning the ozone attacks electron rich double bonds. Natural latex rubber has ",
"methyl group substituents on the double bonds",
" remaining after pol... |
[
"Why don’t wild animals get ill from drinking dirty outside water whilst we do?"
] | [
false
] | Dirty water (found outside) is portrayed as having all sorts of bacteria, viruses and fungi etc meaning that we can’t drink it without getting very sick. How is it we’ve evolved to have very little tolerance for this meanwhile other animals can drink almost any water found outside and be fine? | [
"Well, we haven't, really. For the vast majority of our existence on this planet we drank the same water as other animals. Over a billion people make do without a source of clean water even today. You rarely get \"very sick\" from drinking water from a river or a lake, unless it's obviously contaminated in which ca... | [
"Most wild animals have parasites precisely becaue they drink dirty water and eat raw food. The thing is most parasites don't outright kill their hosts so there is a certain managable parasitic load.",
"Heres a pretty great and easy to read article",
" from the University of California about how mammals general... | [
"People have been drinking outside water since water has existed. Unless it has been exposed to pollutants (especially human fecal matter) it isnt dangerous. If water is infected animals as well as humans can get sick but often have partial immunity to common local bacteria. So would feral humans living in the... |
[
"Do lucid dreamers have a better chance of waking up from a coma?"
] | [
false
] | null | [
"Sleeping and Coma are two completely different things. In a full coma there is no sleep-wake cycle. The brain is turned off just enough so that the body doesn't respond to anything, but not so much that the heart stops. Sleep, on the other hand, is a very active brain process full of signals and semi-random ner... | [
"He is talking about a tv episode coma i.e. The patient is 'fine' but just in a 'coma' yeah it is kind of hard to understand but i get it"
] | [
"Being physically completely fine and being in a coma are mutually exclusive states, I'm sure."
] |
[
"How close to a perfect sphere is a black hole?"
] | [
false
] | Is there much variation in the surface of a black hole? I'd imagine because of its relatively small size and huge mass black holes would be very close to a perfect sphere. | [
"A black hole with zero angular momentum has perfect spherical symmetry. But any realistic black hole will likely have ",
" angular momentum. In that case, it's not longer spherically symmetric but rather axially symmetric about the axis of rotation."
] | [
"A better visualization of that, for me at least, is if you blow up a billiards ball to the size of the earth, it would have higher mountains and deeper valleys"
] | [
"I don't think anyone takes the time to identify and name mountains on billiard balls. "
] |
[
"Does muscle repair faster when asleep, rather than lying completely motionless?"
] | [
false
] | Let's say you go to the gym and do some lifting, for example bench press. Will your pectorals repair faster if you're sleeping or will it repair at the same rate as if you were lying still? Thanks | [
"Your answer is a combination of pseudoscience and myth. Lactic acid isn't the boogeyman it is purported to be, and stretching has had scant support in scientific studies for reducing injury or soreness, see: ",
"http://www.ncbi.nlm.nih.gov/pmc/articles/pmc1250267/"
] | [
"Your answer is a combination of pseudoscience and myth. Lactic acid isn't the boogeyman it is purported to be, and stretching has had scant support in scientific studies for reducing injury or soreness, see: ",
"http://www.ncbi.nlm.nih.gov/pmc/articles/pmc1250267/"
] | [
"Sleep involves increased secretion of growth hormone, which does stimulate increased protein synthesis in skeletal muscle.",
"http://science.education.nih.gov/supplements/nih3/sleep/guide/info-sleep.htm"
] |
[
"If time is relative, and we traveled in space a distance that is light years away at light speed, would we age, or would there be a time delay?"
] | [
false
] | I'm curious as to whether or not traveling at higher speed towards distances light years away would affect the aging process? I know that we cannot achieve actual light speed, but can come close. To what extent is time dialated if we could, in fact, travel at such great distance at such high speed? How far of a distance would it take for a human to biologically age, if at all? I apologize in advance for any holes in my question. Answers explained in common tongue would be greatly appreciated, as I'm not as science savvy as some. I could post this in /rELI5 but I'd like to get some deep insight from you fine folks here. Please let me know if this post belongs elsewhere. | [
"It depends on the speed you're moving. If you were to move at slightly more than .7c (square root of 1/2, to be exact), then your subjective time would pass half as quickly as time \"outside\". That is to say, a second in your ship would take 2 seconds to pass. If you were in that ship for 50 subjective years, a c... | [
"\"Outside\" means \"relative to a stationary observer.\" Which is complicated to explain in depth because, relative to you, the observer is the one moving at close to the speed of light, and so you'll see time moving more slowly for him. And even more complicated because time dilation by relative velocities isn't ... | [
"Well, regardless of the speed, the pilot will age. This is the realm of relativity, so the ",
" is what is important.",
"Let's say you are on the ship, and I am sitting there with you. We're traveling pretty quickly, how fast exactly isn't totally relevant for the thought experiment. If we travel for 30 years,... |
[
"Red/blue shift in a contracting universe."
] | [
false
] | [deleted] | [
"That would be true only for galaxies on your own side of the center of the universe. Galaxies on the other side of that center would be blue-shifted no matter the acceleration factor. And if you're at the center of this universe, everything would be blueshifted.",
"Also, you're assuming that such a universe woul... | [
"The short answer to your first question is yes.\nThe question of the expanding universe actually belongs to the domain of general relativity. Within this theory you can construct solutions where the scale of space varies at different times, however, you can convert this to a point of view where the scale is not ch... | [
"Since there is lorentz contraction as you approach c",
"This is not true with respect to space expanding. The rules about masses approaching the speed of light do not apply to space.",
"I guess the question is what is more fundamental, distance, or c?",
"Definitely ",
". But remember that the speed with wh... |
[
"What are some factors that determined the size of Earth's dominant species?"
] | [
false
] | Many species of dinosaurs were very large. Why did they evolve to be larger than many of our current land animals? I assume the force of gravity played a part in determining the size and strength of humans as well as other forms of life on this planet. If humans evolved on a planet with higher gravity is it likely that we would on average be relatively stronger and larger? If a copy of Earth existed but was scaled up say 10 times in size, would all forms of life be 10 times larger than they are on a normal sized Earth? | [
"Dinosaurs were among the most varied vertebrate family on earth. It is unsurprising then that they had vast differences in size, some being as small as pigeons and some being quite massive: size allowed species to fill a niche and they filled it.",
"As for why large size was abundant, it is hypothesized that a f... | [
"First of all, please define \"dominant\" species, in some ways, we're walking hotels for bacteria ;)",
"Secondly the size of organisms is the result of evolution (no duh), which is a complex interplay of the organism within a food web/chain. Whale that feed on planktons need to be relatively large in order to ef... | [
"Many species of dinosaurs were very large. Why did they evolve to be larger than many of our current land animals?",
"Straight Dope to the rescue.",
"All of your other questions seem to assume that evolution is following a predictable pattern. It is at its very heart random. The path that evolution takes wil... |
[
"What did Cambrian land look like?"
] | [
false
] | [deleted] | [
"Just some algae covered rocks near the oceans edge - the land would have many geological features (mountains, valleys, rivers (it still rained back then), sand (rain and wind erosion) but there would be no soil. No plants, no algae growing far away from a water source.",
"Here is an older picture of what it look... | [
"EDIT - ",
"this is so cool - representation of soil accumulation during denovian",
"Soil is the accumulation of dead plant organic matter it takes a long time to make. Soils would likely have been thin in early Devonian especially as you move away from water. The Devonian saw a flourish in the colonization of ... | [
"Very informative, thank you! Would the land have been that red like mars because there was no soil? I guess I hadn't thought of that part. "
] |
[
"Is there a significant difference in harm done between sleeping 1-2 hours and not sleeping at all? Are they equally bad or not?"
] | [
false
] | Is there a 'healthier' choice between getting 1-2 hours of sleep and not sleeping at all (ie. trying to avoid drowsiness in the morning)? Assuming someone who had to make this choice one time per week, which one is better for his mental/physical health? | [
"In general, naps are beneficial in reducing the effects of sleep deprivation. 1-2 hours of sleep is certainly not healthy, but it is better than nothing (although see the caveat below).",
"For example, ",
"this study",
" kept participants awake for 88 hours. One group had to stay awake the whole time, while ... | [
"This'll serve. Thank you for the dedication to source every statement, I expected much less."
] | [
"A friend had a class at 8:30am, and asked me at 5:00am if he should go to sleep a bit or skip it completely.",
"He finally decided to sleep until 7:00am :)"
] |
[
"Why does music sound so much faster to me when I first wake up?"
] | [
false
] | I know one of my friends has experienced this as well, although I have heard people have this happen late at night as well. | [
"Your mind has a rhythmic expectation that affects how fast or slow it perceives reality. If you play a computer game, try this cool trick to observe a similar effect:",
"Watch a replay in that game at 2x speed for about 20 minutes and then play a game at normal speed. The game will feel like it is in slow-moti... | [
"Watch a replay in that game at 2x speed for about 20 minutes and then play a game at normal speed. The game will feel like it is in slow-motion because your mind's \"clock\" has been set to a higher speed.",
"Exactly. I used this method for a short skill-boost in some online tournaments I've attended. And let me... | [
"Is it the same thing we experience when driving? I always find that driving at 30mph feels unbearably slow after pulling off the motorway."
] |
[
"When is a rock considered to be “born”?"
] | [
false
] | You often hear that a rock is 1 billion years old or 300 million years old or whatever age it may be. What is the starting point for a rock’s age? I assume it might vary based on the type of rock, like maybe volcanic rocks are “born” when they emerge from a volcano, or sedimentary rocks are “born” when they harden from whatever swampy material they were before, but I’m not sure, and Googling mainly tells me that Dwayne Johnson was born in 1972, which is interesting but not helpful. Since just about every rock is made of material that has been around since the Big Bang, it’s confusing to know what science considers the start of a rock’s existence. What defines a rock’s birthday? | [
"Your assumption is largely correct. At the simplest level : 1) For igneous rocks, the age generally reflects when the rock crystallized from a melt (i.e., when it solidified). 2) For sedimentary rocks, the age reflects when the sediment that forms the rock was deposited. And 3) for metamorphic rocks, the age repre... | [
"What an amazing response! Thank you!"
] | [
"This isn't really a direct answer to your question, but as a sidenote:",
"Since just about every rock is made of material that has been around since the Big Bang,",
"The exact opposite is true. The Big Bang only created Hydrogen, Helium, and Lithium, every element heavier than that was created either in fusion... |
[
"I have a weird question about micro-gravity."
] | [
false
] | Testicles use gravity to regulate their temperature by hanging closer or further from the body. So what happens in space? does it cause discomfort to astronauts? Also does micro-gravity increases the risk of testicular torsion? Are 'private' problems caused by space travel documented by space agencies? | [
"I'll attempt to answer part of this question seriously. I wouldn't know anything about the first two questions, but in terms of the third question you may be interested in ",
"this nice Slate piece",
" which has quite a bit of information.",
"In addition, you have several problems with radiation. Cosmic ra... | [
"So what happens in space? does it cause discomfort to astronauts?",
"The testicles may ride higher in microgravity. I don't think that it would cause discomfort. Think of it this way: when lying down, gravity is not pulling the testicles downward. Is it uncomfortable to lie down?",
"Also does micro-gravity ... | [
"Well, that makes sense, it also reduces the payload of the spacecraft.",
"Thanks"
] |
[
"At what temperature does moving water freeze?"
] | [
false
] | I was thinking about this as it get colder out. Small ponds will freeze at 32 but does it need to be even colder to freeze a stream since the water is in motion? If so how cold? | [
"Water always freezes at the same temperature. The stream and the pond just have different ways of distributing the heat and ice that allows the pond to freeze over first. ",
"In a pond, as you get close to freezing, the warmer water sinks to the bottom. This is because the ",
"density of water peaks at about 4... | [
"There are two main types of energy which are thermal and kinetic.",
"I have no idea what you are trying to say here. Thermal energy is a catch all term for many kinds of energy stored internally in a system, including kinetic energy."
] | [
"There are two main types of energy which are thermal and kinetic.",
"I have no idea what you are trying to say here. Thermal energy is a catch all term for many kinds of energy stored internally in a system, including kinetic energy."
] |
[
"Do processors work with radio frequencies?"
] | [
false
] | Is it rf, electron movement or something else? I thought electron movement was slow. | [
"Do you mean a computer processor? It's just simple electricity, which travels very fast (",
"https://en.m.wikipedia.org/wiki/Speed_of_electricity",
"). Remember it is not a single electron that flows, but a propogation of charge (like an ocean wave). "
] | [
"Thanks but I don't think it's so simple. In fact your article does talk about the question.",
"The speed at which energy or signals travel down a cable is actually the speed of the electromagnetic wave, not the movement of electrons.",
"An electromagnetic wave is radio frequency as far as I know.",
"Edit: ... | [
"What you appear to be asking about is the electric field. The drag speed of electrons is very slow (actually it's very fast, but since they move here and there and everywhere, they have a ",
" defined on their average movement, which is very slow). But the electric field propagates along the wire at almost the s... |
[
"Would the Higgs Field reaching true vacuum state be catastrophic for us no matter when/where it occurred, or are there distances at which it could happen and its effects never reach us, due to propagating too slowly to overcome the rate of universal expansion?"
] | [
false
] | [deleted] | [
"It's really a bad time to talk about this. The Lambda-CDM model which is about the expansion of the universe from the big bang and dark energy is arguably the biggest debate in cosmology right now.",
"The Lambda-CDM model includes a Hubble constant which is a parameter of the expansion rate of the universe. Ther... | [
"The distance between two objects grows at a rate proportional to the distance between two objects. Even with a constant Hubble constant, there is a horizon to how far light can travel due to universal expansion. Everything in this horizon is called the “observable universe.”",
"To put this another way, suppose l... | [
"Thank you for such an informative comment! You are awesome. :) "
] |
[
"Can you count algae in a non-pure culture with a hemocytometer?"
] | [
false
] | I would like to get a quantitative count of algae in an IBC tote full of nutrient rich water(used for hydroponics). We've noticed biofilm in the tank and would like to get a baseline algal count before we start treating it. I've used a hemocytometer to count algae before but only in pure cultures. I was just wondering if it would work in a non-pure culture. Thanks! | [
"My advice to you is to stop looking for a perfect solution. What you need is a close enough estimation, as even a modest amount of error will likely not be significant for your results. Here is an arbitrary example for you to get the gist : ",
"Initial Measurement : 5.0e5 cells / mL",
"Post-Treatment Measurem... | [
"That's an interesting idea as well. We have a recirculating system right now and the filters aren't perfect, my worry with the spectrophotometer (as well as the current hand held ATP monitor that were using) would be the non living particles would potentially cause us to get improper results. ",
"I could be tota... | [
"If your tank has a problem with Particulates, then yes, this could change OD readings. And I would agree with you that the field widely accepts this method as inaccurate due to this problem. In this case, OD readings will likely overestimate algae content. In contrast, using a hemocytometer will likely underestima... |
[
"How do cell phone and laptop batteries wear down?"
] | [
false
] | Why do cell phone and laptop batteries lose maximum capacity with substantial use? | [
"Over time a lithium polymer battery develops internal resistance and loss of charge acceptance due to frequent charging and discharging. This is because of cell oxidation, the cells of the battery loosing electrons, that occurs resulting in lower charge acceptance. Cell oxidation also causes the high internal resi... | [
"So I'm not too knowledgeable with computers and laptops. What would be the best method of charging my laptop in order to maintain its health and functionality?",
"At the moment it is on charge the vast majority of time, but if it's not then the battery will drain down really low, sometimes all the way until I pl... | [
"The smaller the depth of discharge the better. So a battery that is frequently discharged only 10% will last a great deal longer than a battery frequently discharged to 50% capacity. Lithium batteries don't have the dreaded \"battery memory\" associated with Nickel batteries, so a full discharge is not necessary f... |
[
"What causes us to feel heartache? Are there any evolutionary advantages to the pain we go through?"
] | [
false
] | null | [
"Was anyone under the impression that \"heartache\" involves the cardiac muscle? Do you have any evidence that emotional distress and/or physical symptoms (such as tightness in the chest) upon the severing of romantic relations is cultural? Certainly the term \"heartache\" is cultural, but again I don't think anyon... | [
"Was anyone under the impression that \"heartache\" involves the cardiac muscle? Do you have any evidence that emotional distress and/or physical symptoms (such as tightness in the chest) upon the severing of romantic relations is cultural? Certainly the term \"heartache\" is cultural, but again I don't think anyon... | [
"I don't really have an answer to OPs question as it is outside my field; however as my comment is slightly off-topic, I'll keep them brief. Hopefully it is interesting, if nothing else.",
"There is a condition called 'Takotsubo cardiomyopathy' which is also known as 'Broken Heart Syndrome'. It is characterised b... |
[
"What is happening when you \"get the wind knocked out of you\"?"
] | [
false
] | null | [
"Getting the wind knocked out of you is often referred to \"being hit in the solar plexus\". That's actually a misnomer, it has nothing to do with the solar plexus, which is also known as the ",
"celiac plexus",
".",
"Blunt trauma to that region can ",
"cause the diaphragm to spasm",
", making it difficul... | [
"Getting \"hit in the solar plexus\" has nothing to do with the solar plexus (",
"source",
"). Motor and most sensory innervation to the diaphragm is via the phrenic nerve at spinal cord levels C3-C5. The celiac plexus is T5-T9 and providing innervation to the viscera of the abdomen, not the diaphragm."
] | [
"Getting \"hit in the solar plexus\" has nothing to do with the solar plexus (",
"source",
"). Motor and most sensory innervation to the diaphragm is via the phrenic nerve at spinal cord levels C3-C5. The celiac plexus is T5-T9 and providing innervation to the viscera of the abdomen, not the diaphragm."
] |
[
"Growing fruit trees from seed, what triggers fruiting?"
] | [
false
] | When growing fruit trees from seed (apple, pear, citrus, etc.), there is a wide variation of time when the seedling will mature and grow fruit. Some apple seedlings will produce fruit in a little as 3 years, some 10 years, some many years past 10 years. What causes this difference? Is fruiting genetically determined, size of the tree, size of roots, number of branches, etc? Or is it a combination of many factors? | [
"With respect to apples the biggest influence would be the type of rootstock used. As another poster mentioned, commercial apple trees are propogated from small segments of branches (scions) from the desired cultivar which are then grafted onto the roots of another apple tree cultivar (the rootstock). The rootstock... | [
"Apples are done this way because they are not true to seed, meaning you won't get the same type of apple as the parents were. Doesn't really answer the question, but growing an apple by seed could get you one of something like 40,000 different apples, most of which are not good to eat. If not familiar, look up J... | [
"Hmmm well in practice fruit trees are propagated from cuttings and thus are clones and are not grown from seeds. Propagation ensures the consistency. Keep in mind that fruit trees are highly altered and manipulated from their wild ancestral form. Many tree varietals found in nurseries cannot be grown from seeds at... |
[
"How does antimatter (potentially) improve space travel?"
] | [
false
] | [deleted] | [
"Assuming you have some mechanism to get mass amounts of antimatter and sufficient technical know-how to safely handle it, you could use it to provide thrust for a spacecraft that's orders of magnitude better than anything we can dream of doing today. Speculative designs (sci-fi locked to hard numbers, basically) ... | [
"This is assuming we will never improve the current accelerators and stuff like that."
] | [
"naturally, though 8 orders of magnitude increase in intensity, much less storage, of anti-matter will not be the easiest thing. "
] |
[
"If the type of element is directly correlated with its number or protons/neutrons/electrons, why aren't there infinite elements and why is 'discovering' a new one a big deal?"
] | [
false
] | null | [
"Because you can't put an arbitrary number of protons and neutrons in the nucleus.",
"A proton by itself is stable while a neutron is unstable. Happily, the proton is slightly more stable than the neutron is unstable, so the two together are stable. Thus, you cannot add too many neutrons without adding more proto... | [
"There are not necessarily infinitely many elements that can exist, because eventually there will be a point where the system is so heavy that it won’t be able to sustain bound states if you add anymore nucleons.",
"Discovering a new one is a big deal because we’ve already discovered all the ones that aren’t extr... | [
"Their explanation doesn't rule out the island of stability because they didn't specify ",
" exactly the number of protons becomes too high for the nucleus to remain bound. Nobody knows the answer to this question.",
"\"Superheavy element\" typically refers refers to elements with Z > 100, so we've already disc... |
[
"Why is time measured in with 60 seconds/minutes and not 100?"
] | [
false
] | null | [
"It is based on the Sumerian number system that had a base of sixty instead of 10 and sixty is a superior highly composite number meaning it has many divisors. What this means in practice is that you can divide an 60 minute hour evenly with twelve different factors, many more than a ten based system would allow.\n ... | [
"Because 360 can be divided by : ",
"1,2,3,4,5,6,8,9,10,12,15,18,20,24,30,36,40,45,60,72,90,120,\n180,360",
"100 can only be divided by:",
"1, 2, 4, 5, 10, 20, 25, 50, 100.",
"Or 24 factors against 9. Now it may not matter, but historically easy division was important."
] | [
"Shortly after the French revolution, when they were converting to decimal units (metres, litres, grams etc) they also decimalised time. Each day consisted of 10 hours, each with 100 minutes, each with 100 seconds, giving 100,000 seconds in a day (our system has 86,400 seconds per day). It never caught on though, p... |
[
"How would you determine the molecular identity of the ion that is being transported through a receptor activated channel? Have there been any experiments that were designed to accomplish this?"
] | [
false
] | null | [
"There have been LOTS of experiments designed to accomplish this.",
"It's usually pretty simple. The first step it to make a guess. In order to do this, you need to know the \"reversal potential\" of the current through the ion channel. You do this by the following, you stick a small glass electrode inside a cell... | [
"Thanks a bunch!! Are there other known techniques aside from the one you outlined? Also, are there any notable experiments that you could list that have used that technique? "
] | [
"Those are the main ones.",
"Notable experiments? Well probably the most famous is",
"Currents carried by sodium and potassium ions through the membrane of the giant axon of Loligo",
"A. L. Hodgkin and A. F. Huxley",
"But that might be a bit difficult to understand because it is so old."
] |
[
"When a marathon runner hits a wall, what happens physiologically? And what's happening when they push through it?"
] | [
false
] | null | [
"I can't say. The reason we can say that marathon runners' walls are caused by glycogen depletion is because it's so extreme, and that analytical models (such as the one I linked you) can produce results that more or less match observed results. ",
"On the other hand, given a random person in the gym, or out runn... | [
"Your body has a limited store of carbohydrates (in the form of glycogen). This is usually your body's primary fuel when engaging in exercise. Hitting the wall occurs when you've depleted your store of glycogen. Pushing through it is the processing of forcing your body to start using fat stores, which is a process ... | [
"Very cool, thanks! Would it be fair to say that when someone is working out and doing cardio, after they hit their \"mini-wall\" and keep going, they're starting to burn off fat?"
] |
[
"What would the effects of negative-mass (if real) be in space-time?"
] | [
false
] | effects/properties/uses/etc. | [
"Well, you could stabilize wormholes with negative energy density aswell as create an ",
"Alcubierre drive",
" (Warp drive). But ",
"negative mass",
" would show weird phenomena. For example, it would always repel \"positive\" matter (runaway motion).",
": Also imagine exerting a force on a negative mass.... | [
"No. E",
" is the sum of squares and is always positive. E can still be negative."
] | [
"\"Negative mass\" is a moot concept. The fundamental quantity is not mass, but mass squared (E",
" - p",
" c",
" = m",
" c",
" Since m",
" = (-m)",
" \"negative mass\" is exactly the same thing as positive mass.",
"If mass ",
" would be negative, you would get tachyons. However, tachyons cannot e... |
[
"Animals other than humans can laugh- are there animals that can cry?"
] | [
false
] | If not, what's so special about crying? How is it different from laughter? | [
"are we assuming here that animals laugh for the same reasons humans do? I'd like some references for that for a start. ",
"Crocodile tears? It's a hard life when everyone's afraid of you. "
] | [
"This article is a good start:",
"http://www.nytimes.com/2007/03/13/science/13tier.html?ex=1174536000&en=9e64514e5d308a59&ei=5070&emc=eta1"
] | [
"It's not quite the same though is it? In the examples of animal 'laughter' it's a social tool. Human laughter can be this, but humans also laugh when they're completely alone because they find something funny. Animals playing might be having 'fun' but that's not the same as finding something funny. "
] |
[
"Is it possible to mathematically determine the wavelength of light being reflected off of a particular kind of molecule?"
] | [
false
] | null | [
"Yes, this is done by calculating the energy levels of the electrons in the molecule using quantum mechanics. The light that is absorbed and re-emitted (reflection on a microscopic scale) depends on the difference between these levels."
] | [
"The simplest way to take the following into account: ",
"The nucleus acts on the electrons with a force of 16ke",
" /r",
" where k is Coulomb's constant, e is the fundamental charge, and r is the radius of each electron.",
"The electrons experience a centrifugal force mv",
" /r that is equal and opposite... | [
"Wavelength = speed of light / frequency.",
"Wavelength = color, in normal practice."
] |
[
"How would a bleeding wound react in space?"
] | [
false
] | Hello, I've been wondering this lately. Assuming it's not zero gravity (i read somewhere that the current ISS is under something called instead), and for the sake of it there is a doctor and medical equipment available. If someone gets a deep wound, caused by stabbing, would it be possible to treat it the way we treat them on earth, if at all? how would the body react under micro gravity environment, in terms of bleeding and healing? would it form just a huge blob of blood? would it be any risk for the blood to stay inside the body? (instead of it pouring outside the body). PS: My apologies if something seems unclear to you, English is not my native language so i had a bit of trouble making my questions clear enough. Feel free to point out anything seems unclear. Also, i'm not sure if it should go under Medicine or Physics. | [
"They have actually ",
"done experiments",
" on this, including performing ",
"small surgeries",
" during parabolic flight. The gist seems to be that surface tension of blood does cause it to form a dome above the wound but that normal surgical techniques like suction and sponges are still effective. "
] | [
"Once again, they injured a bunch of rats on Endeavor to answer this question;) ",
"Turns out that",
" wounds are likely to to have a poor healing response in micro-gravity. ",
"They are looking at ways",
" to overcome this, perhaps with stem cells. "
] | [
"If left open, yes, it would be a big blob of blood, and interestingly enough, it would stay a big blob, attached to your body similar to how tears do in space (Chris Hadfield demonstrated this recently, IIRC), until some force moved it away. ",
"Other than that, the wound should be able to be treated as it would... |
[
"Why would a spinning ring in space create artificial gravity?"
] | [
false
] | null | [
"First of all, the centripetal force would throw you ",
", not inward. So you would be standing with your feet on the inside of the outer surface, and your head pointing back toward the center. ",
"Technically, if you were floating in the middle of the ring before it started spinning, then yes it would just spi... | [
"So what your saying is that objects on the inside of the ring would have to be made to rotate around the ring at a rate equal to the ring?"
] | [
"But wouldnt it would only throw you outward if there is something tethering you to the center or to the ring itself. Wouldn't only work if the ring were divided into sections who were at an angle of 90º to the center of the ring? that way the astronauts in each section would feel the constant acceleration of the f... |
[
"Do the FAA, Air Force, or any other flight monitoring/traveling agency go to any kind of special \"alert status\" during events such as tonight meteor shower? Are we at an increased risk of flying tonight?"
] | [
false
] | Bonus question: odds of satellites and planes being taken out by a meteor? | [
"No. Not in the least.",
"It depends heavily on composition, size, and the angle at which it enters the atmosphere, but most of the pretty meteors people are seeing tonight are well above surface of the Earth, probably greater than 60 miles. For reference, a commercial jet typically flies at an altitude of 6 or 7... | [
"Are we at an increased risk of flying tonight?",
"Meteors fall through the atmosphere at all times. It's not like space particles only wait until you're facing away from the sun to hit earth."
] | [
"I've been freezing my ass off looking East since 9. Damn Columbus Ohio for light pollution. I haven't seen any yet."
] |
[
"Why do different vaccines last different amounts of time?"
] | [
false
] | I know different types of vaccine preparations have different effectiveness at stimulating immune cell recognition, but why do some wear off before others? Thanks! | [
"This has to do with the course of illness of a given disease -- slow vs. fast.",
"Vaccines are meant to induce a high antibody response against a given pathogen. Being vaccinated usually results in high antibody counts in an individual that persist for certain amount of time (usually fairly long). These antibodi... | [
"Appropriate reply. It also helps the OP to know that different serum concentrations of antibody are determined to be acceptable \"normal\" levels based on the the type of antigen for which they're specific. Hep B concentrations that are considered effective would be far different than concentrations considered eff... | [
"Thanks a lot for posting, very helpful and 100% answered my question."
] |
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