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[
"How do giraffes breathe?"
] |
[
false
] |
Basically, the text. The giraffe neck is around 6 feet long, so how do they generate enough pressure for air to travel six feet and also relatively fast? How do they remove air and prevent too much physiological dead space?
|
[
"Long neck, but narrow; massive lungs, 8x the size of a human's; a strong heart that gives it blood pressure twice that of a human's; and a respiration rate 1/3 as slow as a human's.",
"Essentially: their throat will fill with dead air; it's too big not to. But, their lungs are huge, and they have a respiration rate 1/3 the speed of a human's, sucking as much oxygen out of their air as possible. Their cavernous lungs and ability to sip oxygen out of them, plus their hard-beating heart's ability to efficiently spread that O2 all over their bodies, mitigates the threat of dead air build-up in their throat."
] |
[
"I would imagine the main reason for their higher blood pressure is so blood is able to reach their heads, you need roughly 23mmHg per foot in height."
] |
[
"yup, iirc, their skin is super tight around their legs to help get that blood to easily shoot up the neck."
] |
[
"Does the brain go through any physiological changes when the person is in coma? And are there any differences between medically induced coma?"
] |
[
false
] | null |
[
"That's an interesting question, and the answer will depend on several factors. ",
"One way to look at it is comas are altered states of consciousness, brought about by various onsets. The cause of the coma will often contribute to observable brain changes. For example, if someone has an infection in the brain, it could shut down cortical functions and only allow for subcortical activity. Or, you could give someone a general anesthetic dose and increase overall brain activity to the point of overload, which results in a coma-like alerted state of consciousness. Both examples induce a coma-like altered state of consciousness, but the onset and subsequent brain activity profiles are different. ",
"Another factor to consider is time. If someone is in a coma caused by traumatic brain injury, and exists in an altered state of consciousness for an extended period of time, lack of brain activity can lead to atrophy of neural structures and altered brain functionality. In some patients, brain activity looks quite normal.",
"Edit: Strange; I've gotten trolls, replies, and question notifications via email on this comment, but can't see or reply to anything on the Reddit app. Never had that problem before. What gives?"
] |
[
"This is a difficult question to answer without knowing more specifics about exactly what you're trying to ask. ",
"But overall, there are, of course, physiological processes happening during a coma. This is a really complicated topic, but in simpler terms, a coma is the worst condition of what are known as \"disorders of consciousness.\" There can be different degrees of consciousness, and coma simply refers to the state in which there is none. This usually occurs as a result of injury to either the thalamocortical circuitry (believed to underlie what we call \"consciousness,\" which is a whole other neuroscientific and philosophic discussion in itself), or parts of the brainstem (usually the reticular activating system) that is basically a \"switch\" to turn on and off higher cognitive functions (in a normal brain, this is part of the system that helps regulate degrees of mental arousal). ",
"In one of the other comments here, it seems to be suggested that the brain somehow imposes a comatose state on itself to help with healing. This is not the case. A comatose state is a result of the injured brain itself and does not necessarily help or harm the healing process (though in brain injury medicine, we do use medications to try to wake people up). So what is happening in this state? It somewhat depends on the nature and extent of the injury but the body will do what it does and try to clean up the mess; it will resorb blood if there is hemorrhage, clean up any necrotic tissue, salvage what it can etc. Otherwise, the parts of the brain that are still alive will chug along trying to maintain/reform connections. Exactly what is happening here is not super well known yet, and what is known is extremely complicated so I won't go into it here. ",
"Now, you do specifically mention a medically induced coma, and yes, this is a different scenario. There are a few different medications that are/can be used under specific circumstances, but overall, they depress the activity of the brain (usually affecting the same areas I previously mentioned) so that they are not working anymore (almost as if they're injured or hibernating); this is basically what anesthesia does (and indeed same/similar meds are typically used). This does actually have a protective effect because you are decreasing the metabolic demand of the tissue by decreasing its activity. Naturally, this can be beneficial in certain scenarios where there is a supply-demand mismatch to the brain (e.g. overwhelming demand in the case of prolonged seizures, or diminished supply in pts with cerebral vasospasms)."
] |
[
"A coma allows the body/brain to heal more effectively because the brain has shut down many functions.",
"The difference between a coma and a medically-induced coma just comes down to how the coma is introduced to the body/brain. If you get a head injury and your brain shuts down by itself there is no way to know if and when you will come out of the coma. Usually a medically-induced coma is the result of some kind of general anaesthetic and once that is removed you can be woken."
] |
[
"Mass of the universe right after the Big Bang - why all this condensed mass not create a black hole?"
] |
[
false
] |
Assuming the mass of the universe right after the Big Bang was equal to today's mass.... so much mass in such a small area, why was there no immediate black hole formation?
|
[
"The universe was still infinitely big immediately after the big bang, just much much more dense. The universe was also ",
" uniform and ",
" hot. Because it was uniform, the gravitational acceleration on any point is basically zero. There were tiny fluctuations in density, but the universe was so hot that its pressure would just bounce these back before they collapsed. It was also so thick and opaque that it couldn't really radiate the temperature away from any point. It's only later that the universe cooled down enough to allow things to collapse into galaxies and stars and so on."
] |
[
"Hot in the normal sense of very very high temperature :)",
"As the universe expanded, the energy just spread out more."
] |
[
"Hot in the normal sense of very very high temperature :)",
"As the universe expanded, the energy just spread out more."
] |
[
"Why do planetary rings form in a plane instead of a shell?"
] |
[
false
] | null |
[
"Orbital dynamicist here. You're essentially correct. It's the same reason why solid particles in the nebula settled into a plane. I don't think it has to be collisional to work, repeated gravitational interactions would work too. Note that the origin of the rings is still an open question. Them coming from a ripped apart moon is ",
" correct, but the devil is in the details (timing is the biggest issue I believe).",
"I'll go ahead and re-explain what you've said and add details.",
"Say you start of with a jumble of material that has some net angular momentum, i.e. some net rotaiton. Collisions/interactions among the particles will exchange angular momentum between them, with total angular momentum being conserved. With repeated collisions the total angular momentum will get distributed so that each particle basically has the average angular momentum (i.e. total angular momentum / number of particles (note: not quite true in reality, but I believe it should be a distribution that's strongly peaked about the average angular momentum)). Here we need to remember that angular momentum is a vector. So every particle having the about the same angular momentum means that every particle orbits in about the same plane and hence a ring. I think the flattening timescale for rings would be rather shorter than millions of years, but I can't back that up with math.",
"So, why is the angular momentum vector of the rings the same as for the planet? iorgfeflkd mentioned that rotating bodies have a bulge at their equator. The gravitational field is thus not spherically symmetric and the orbit plane of a ring particle will oscillate about the equatorial plane. The orbital planes of the ring particles won't oscillate in phase which will cause the ring to spread out (increased vertical extent). However, as discussed above, collisions among the particles tend to flatten the ring. The end result is that the inclination relative to the equatorial plane is damped, eventually leading to a ring plane that's in the equatorial plane."
] |
[
"I'm certainly not an expert but I'm not sure this is correct. I believe It's true that rings are usually cause by the gravity of the planet ripping apart the moon along it's orbital plane and so the debris spreads apart in the up direction (relative to the planet) instead of the north south direction. However that doesn't explain why the originally chaotic debris settles into a single orbital plane. As in why does the north and south pole end up in the same orbital plane as the equator.",
"I believe that this is cause by the fact that off-planar(the original north and south poles) or highly eccentric (the equatorial surface) particles will cross the debris field twice per period. In doing so it will cause collisions and inevitably over millions of years all off-plane particles will either impact the planet, be ejected, or settle into the ring plane. Everything that is left in a stable ring are those particles with infrequent and low momentum collisions. This also explains why rings are mostly dust and not mostly rocks. All the repeated collisions during formation has ground the moon into dust. ",
"Disclaimer: not an expert, please correct if wrong. (Although I did study orbital mechanics in school while studying to be an aerospace engineer, but that was a long time ago)"
] |
[
"It's because the whole system is rotating, and rotating things tend to bulge at the equator. That's why the Earth is thicker at the equator than pole-to-pole, and why all the planets orbit in more-or-less the same plane.",
"See below for a better explanation"
] |
[
"Walking barefoot in the library at my college, I was just told by a janitor that I shouldn't do that because of all the chemicals they spray on the floor (to remove stains, etc.). In truth, how susceptible are my bare feet?"
] |
[
false
] |
This is a from . Thank you very much. Edit: for those arguing about athlete's foot and other fungus... I actually do have athlete's foot toe fungus on all of my toe nails. It seems to be going away now that I've been going bare foot much more. I've been barefoot most of the time since May.
|
[
"Janitor here so I can tell you that it depends on the chemical being used. If he told you not to do it though he's probably right. Most janitors are trained in at least some basic hazardous materials handling because we tend to have at least one or two chemicals we have to use on occasion that can fuck you up. ",
"For example I've had to use a concentrated floor sanitation chemical that will give you chemical burns if you get it on your skin. Some of the serious sanitation chemicals require you to wear a mask or even a full respirator because of what they can do.",
"If this was in a library chances are it was nothing like those, he was probably warning you because the stuff he was using could irritate your skin (like walking on freshly fertilized grass)."
] |
[
"Come on, this is a SCIENCE reddit. People who walk around barefoot in the library simply do not ever get fungal infections. The problems arise when you go someplace where a bunch of people who normally wear shoes all take off their shoes and walk around on wet floors. The real key is people who wear occlusive shoes with sweaty feet going barefoot on wet floors. Then you have a recipe for athlete's foot.",
"http://onlinelibrary.wiley.com/doi/10.1046/j.1468-3083.2002.00400.x/full",
"\"Several factors influence the prevalence of tinea pedis[athlete's foot], including: (i) the use of public facilities, such as communal showers and cloakrooms, swimming pools, ...; (ii) the presence of minor foot trauma; and (iii) the use of occlusive shoes.\"",
"Your feet are coated with skin - one of the most brilliant protective layers ever invented. They will be no more susceptible to problems from touching the cleaners on floor than, say, your hands would be. And all the cleaners used on floors are evaluted for toxicity from light contact. I say - be a rebel, and go barefoot if you want to. "
] |
[
"No, you didn't."
] |
[
"Why does water seem colder after you chew mint gum?"
] |
[
false
] |
Edit: first kind of popular post! Thanks for knowledge!!
|
[
"Your \"cold\" sensation is reported via an ion channel called ",
"TRPM8",
". Lower temperatures trigger that channel, which reports to your brain that something is cold. However, menthol ",
" triggers that channel, giving you a sensation of coldness.",
"When you take a sip of water after chewing the gum, your TRPM8 receptors are still activated, so you feel cold along with the other sensations of having water in your mouth. That makes your brain assume that the water itself is cold.",
"(Source: ",
"SciShow",
")"
] |
[
"Capsaicin (the chemical in spicy food) activates the TRPV1 channel, which also senses heat. Both TRPV1 and TRPM8 belong to a larger family of ion channels called TRP (transient receptor potential) channels."
] |
[
"Do you know of any other substances that \"short-circuit\" our senses in a similar way? "
] |
[
"What stops hair getting stuck in healing wounds?"
] |
[
false
] |
I recently found myself with reason to worry about this, but it turned out not to be a problem... how come? It certainly makes getting the scab off a pain, though.
|
[
"More of origin. If you were worried about contamination from external sources that'd be different than worrying about hair on your body. ",
"As for leg hair, I don't know. Piloerector muscles around the hair follicles may play a role to pull it loose, or the wound could just shove things out of it as it heals and the fibroblasts begin to pull the wound shut with collagen, or the hair is broken down within the wound itself. "
] |
[
"What kind of hair? Arm hair? "
] |
[
"Well in this case, leg hair. What's the difference?"
] |
[
"What is heat?"
] |
[
false
] |
[deleted]
|
[
"Temperature is, in macro world, the manifestation of particles' mean velocity.",
"Heat makes things (particles) move faster because, either by mixing or by heating up from a plate, we introduce higher-velocity particles into the mixture. When it's mixing, the particles from two different substances mutually exchange energy in random \"bumps\", when it comes to heating from a plate of a surface - then it's just by our mixture coming in contact with the \"moving\" (actually it's rapid oscillation) surface.",
"So, generally speaking, heat is something with higher mean velocity than the substance we apply it to.",
"EDIT: corrected according to the reply to my answer, as I mixed up temperature and heat a little bit."
] |
[
"Heat is energy transfer as a result of a temperature difference. ",
" is the manifestation of particles' mean velocity. "
] |
[
"A good rule of thumb is that it's the energy of ",
" motion. A whole mess of particles traveling in the same direction don't have \"heat\" per se. But when particles are all travelling in random directions, their average motions balance out to zero."
] |
[
"What happens to your muscle when you sprain it?"
] |
[
false
] | null |
[
"A sprain actually doesn't involve any damage within the muscle tissue. A sprain affects the ligaments that connect bones to joints and can vary from a snapped ligament down to just a ligament that has a twist. What I believe you're thinking of is a strain and the easiest way to understand that is to look at a picture of striated muscle tissue and imagine all those little lines as rubber bands, when you strain the muscle some of the rubber bands snap.",
"[edit] I'm an EMT by the way and we basically treat sprains, strains, and closed non angulated fractures all the same way. The treatment is basically the same, immobilize it, ice it, and go easy on it. If you have concerns go get an X-ray cause that's the only way to be 100% sure if it's fractured "
] |
[
"Ligaments are connective tissue connecting bones to bone, and tendons connect muscle to bone. You sprain a ligament, strain a muscle. Straining a muscle involves tearing the elastic fibers, similar to what's written above. Just specifying a little! "
] |
[
"Also a strain. The words are different so that it gives medical providers a much quicker understanding of what structures are actually injured. "
] |
[
"How noisy is it on the surface of the sun?"
] |
[
false
] |
Is it the loudest place in our system?
|
[
"The surface of the sun is considered to be the tau=1 line of 5000A. In easy to explain terms, it is what you see if you look at the Sun in visible light.",
"It is basically where the convective zone ends. Above that is considered to be the Solar Atmosphere."
] |
[
"In fact we can, and we do!",
"Sound waves propagate through all phases of mater: solids, liquids, gases, and plasmas. The energy contained in these waves is a measure of \"how noisy\" it is. ",
"Solar scientist use the propagation of sound waves in the sun to study its interior (helioseismology), just like geologists use sounds to study the interior of the earth (seismology)."
] |
[
"So going of off ",
"u/Jellyman87",
" numbers (150dB on earth, sun 149,600,000km from earth) I did some quick searches and whatnot.",
"Using this formula; ",
"Lp2 = 20 log (R2 / R1) + Lp1",
" with this input; 20log((1/149,600,000,000))+150, I got that the surface of the sun would experience ",
".. Which is ridiculously insane. ",
"As a quick check, I put 373 as noise input level and the immission point at 149,600,000,000 meters ",
"here",
".html) and got that the listener on earth would experience 150dB",
"Anyone who actually has some form of formal education in physics and or math, please check and correct me here if you got the time.\nI don't even know what the \"log\" part in the formula really means (logarithm or something?), and there's a good chance I oversaw something vital and obvious."
] |
[
"Do astronauts come back from space with weak immune systems?"
] |
[
false
] |
Being encapsulated in an artificial place for so long and not being exposed to the amount of bacteria and viruses that exist on earth can weaken one's immune system over time, correct?
|
[
"Believe it or not, ",
"Auerbach's textbook of wilderness medicine",
" has an entire chapter on space medicine. ",
"Here are the bullet points on the effects of microgravity on the immune system"
] |
[
"On a similar note, how about seamen on a submarine that is basically encapsulated for months on end beneath the water?"
] |
[
"While the following is speculation, I offer this article geared towards the layman as compensation.",
"http://www.navy.mil/navydata/cno/n87/usw/issue_31/idc.html",
"The air on a submarine has to be scrubbed of CO2 while underwater, and I presume a certain amount of purification is performed. That said a submarine is by no means sterile so the pathogens common to indoor environments (not to mention a high population density) would be there. The article seems to indicate that the difficulty on a submarine is not any inherently different immune function, but that fact that there is limmited space, supplies, and trained medical personnel when a sub is on a mission. ",
"The difference between the submarine and space is that microgravity is a novel environment and a sub is a highly scarce environment as far as treatment is concerned."
] |
[
"If a nuclear apocalypse were to happen, and every single nuclear weapon in the world was used, how long would it take for the accumulating fallout to decay and make the surface habitable?"
] |
[
false
] | null |
[
"It all depends on what one means by \"habitable.\" You can, for example, still go live near Chernobyl (some people do, and many people work on the site still). It just will expose you to a chronic, low amount of radioactivity, and that will increase the chances of cancer or birth defects in whatever population is exposed, affecting children and pregnant women in particular. Is that \"habitable\"? I mean, if you have an option ",
" make that increase, of course you'd prefer not to. But if you don't have an option, that just becomes your \"new normal,\" in the way that an average ~20% lifetime fatal cancer probability is today for Americans. If your lifetime cancer risk was raised to, say, 30% or 40%, would that be \"uninhabitable\"? This is not a question that can be answered just by numbers alone, as it is about values as much as anything else.",
"In an actual nuclear war, nuclear fallout would ",
" be distributed equally around the planet. You'd get a high concentration of \"local\" fallout downwind of any place where a surface or low-altitude detonation took place. This would be contaminating for a long time in such an area. You would also have a light increase of global radioactivity from the \"global fallout\" of weapons that were detonated as airbursts and any residual products that did not get deposited as local fallout. The latter is going to a slight but measurable up-tick of radioactivity, probably mostly in the Northern Hemisphere, that is likely to raise cancer rates slightly.",
"For local fallout — the stuff downwind of the blast — it will depend on the size and number of the weapons. In the first few hours after the attack there will be downwind areas with acutely fatal levels of radioactivity. But the intensity of the local fallout reduces by ~100-fold every 48 hours. So even in the worst Cold War style situations, where you have multi-megaton bombs going off in close proximity, you are still going to basically not have to worry about fallout as an acute hazard after a few weeks. But if the experience of the Marshall Islands is anything to go by, it will remain an ecological hazard — again, as a chronic cancer and defect risk, not so much because it is sitting on the soil but because it has been taken up into plant and animal matter — for several decades. ",
"Your big problem globally, though, is not fallout, but the likely climatic effects that would come from the amount of burning and smoke. Nuclear winter scenarios in such a scenario are pretty plausible and would cause decades of radically reduced sunlight in such a situation, creating a very difficult situation for recovery — many decades before it returns to \"normal,\" according to many of the models on this."
] |
[
"I don't think it would necessarily be that cut and dry if per OP's inquiry every currently functional nuclear weapon in the world were to detonate in a nuclear exchange. Consider for example the scenario where a nuclear detonation coincided with a severe weather system such as a tropical cyclone (as we're headed into this years Atlantic hurricane season). You wouldn't necessarily experience fallout simply settling back to Earth locally \"downwind\". As the number of warheads known to be possessed by declared nuclear states still number in the several thousands, would there realistically be any where on Earth that isn't downwind?",
"Local fallout — the stuff that is the most contaminating — settles within several hours. So yes, that's what we mean by downwind. ",
"If it doesn't settle for several hours, that means that the nastiest stuff tends to decay (the short-lived fission products), and the rest of it gets diffused over a very large area. ",
"I don't know where hurricanes are coming into this (they were ",
" in OP's question) but storms can cause \"rainout\" which does act as a way of getting more local fallout in the short term. Whether that would be better or worse is going to depend exactly when and where things deposit and where the hypothetical \"you\" is in this situation. But if you are asking if there anywhere that isn't \"downwind\" — yes, such a thing would still be \"local\" if it was producing rainout, or it would be \"global\" (the slight uptick in background radioactivity that I mentioned before). ",
"Can we see them please? Even if you have crunched the numbers, there is nothing \"normal\" about the scenario OP posited. A realistic nuclear exchange that fits your description involves at most a few dozen or so successful attacks. ",
"One cannot easily \"crunch the numbers\" on hypothetical situations with regards to fallout, but there were ",
" studies of the use of nuclear exchanges ",
" than what exist today during the Cold War. (The total world stockpile megatonnage, which is what is going to tell you how much fallout there is or isn't — in terms of fission products produced — was ",
"between 10,000 and 20,000 megatons",
" ",
" in the 1950s through 1960s. Today it is more like 2,000 megatons.) Even in the worst case scenarios you have the local/global distinction, and my account is based on such discussions. If you want to look up numbers, look up Project Sunshine (a US study of global fallout from 1953 which, while not perfect, gives a sense of the dimension of the issue) and Glasstone and Dolan, Effects of Nuclear Weapons, 1977 edn., chapter 9 (the 1957 edition also has a chapter on global fallout, chapter 10). ",
"Ultimately what matters for a contamination hazard is the concentration of radioactive materials and the level of radioactivity. For anything that is not local fallout, the concentration is relatively diffuse. And as noted the level of radioactivity for fission products ",
"follows a predictable curve",
" — within a few weeks even the worst stuff will be a chronic and not an acute risk.",
"Which is to say, it would more or less (as much as one can generalize for a global phenomena) follow the description that I have outlined: an acute threat downwind from local fallout (groundbursts or rainout) that would over time turn into a chronic contamination issue, and a broader but weaker contamination issue for people globally, but mostly concentrated in the northern hemisphere. ",
"It is disingenuous for you to imply that current experience with something like Chernobyl or even all the weapons testing conducted in the past can be used benchmark the unimaginable. \"...and every single nuclear weapon in the world was used,\"",
"You may not be aware, but the number of nuclear weapons in the world ",
"is roughly 20%",
" of what it was several decades back. And that the question of nuclear exchanges was studied very closely in the Cold War. So this is not unimaginable in the slightest: it has been imagined and studied and calculated and recalculated and simulated again and again and again. There are books one can read on such topics. And any of those projections from the Cold War are going to be significantly worse than the situation today, simply because the quantity and size (in terms of yield) of modern weapons is significantly less than what they used to be. If you are truly interested in looking into the details, the SCOPE 28 report (\"Environmental consequences of nuclear war\") from 1985 covers many angles of this (again, for a much larger stockpile). ",
"That doesn't mean things would be great at all. But it puts bounds on the problem. Nuclear weapons are not magical — fallout radiation decay is extremely well characterized (as a result of said weapons tests). "
] |
[
"significantly revised some of the original data that were presumably used to carry out those calculations and simulations?",
"It's not that significant a revision from a damage perspective. They are saying, \"oh, this thing we had judged to be 100 kilotons was really 110 kilotons.\" That sort of thing. From a war planning perspective, that is a difference without distinction (damage doesn't scale linearly, it scales as a cubic root, so small changes like that don't change much). It is only useful if you are very interested in making sure your ability to simulate the ",
" of nuclear weapons is very well calibrated (because you no longer test them).",
"That isn't a margin of error one can simply sweep under the rug.",
"For the question of \"what would happen to a city if the weapons went off,\" it is though. ",
"Let me demonstrate: ",
"100 kilotons",
" vs. ",
"120 kilotons",
". Not a huge difference, even on a city like NYC, where the density of people is high enough that you get some difference with small changes. (Change it to Washington DC to be even more underwhelmed by the difference: ",
"100 kt",
" vs ",
"120 kt",
".) Not enough of one to make any big difference in planning, anyway. Again, the relationship of damage to energy is not linear; you need to increase the yield of a weapon by a factor of eight to get twice the damage on the ground.",
"The differences Spriggs talks about are important from a stockpile stewardship (making sure you know how your weapons are going to behave in a world in which you can't test them anymore) and maybe a nuclear forensics (being able to after-the-fact correlate an appearance or radiological signature with a yield, which would be useful in the case of nuclear terrorism in particular) context. Not a \"do we have an idea of what would happen if there was a full nuclear exchange sort of thing,\" and the kinds of differences they are talking about bear very little on the broader questions we're talking about here (they do not up-end the understanding of how fallout work).",
"There are, to be sure, many unknowns about large-scale scenarios, including differences between the present day and the simulations of yore. Cities, for example, are not made of the same materials as they used to be (much more glass, much more plastic), and that changes how fire and smoke effects would behave. But if one is looking at big, bulk questions — how would fallout behave?, for example — the answers are essentially the same, or at least, are within the same levels of uncertainty that existed at the time. ",
"If everything you think you know is based on such skewed data, no amount of documentation/citation you present would validate the authoritativeness of your position.",
"I just want to note that this dramatically overestimates the \"skewedness\" of this data (Spriggs doesn't indicate, for example, which types of yields were off, or what the average error was, or anything like that, or ",
" — he indicates, in a loose way, what the most extreme errors might be, and again, it is ",
" about fireball-based yield estimations, which is but one of many things they look at), and, dangerously, you've taken a study that is about refining some data and used it to create an epistemic position that makes you willing to throw ",
" evidence-based reasoning out the window. I am not claiming you are doing this nefariously or on purpose, but beware! This is the common technique used by denialists of all sorts, and it is certainly ",
" a good way of reasoning about this. Even if some of these numbers were WAY off (which they aren't), that does not actually change the overall conclusions very much — and getting yourself into a position where you reject all documentation/citation is a bad epistemic space to end up in. There have ",
" a range of uncertainty in estimates on things like the effects of radioactivity on the environment and even the human body (there are still fundamental debates about these things going on). Nonetheless, there are a range of realistic outcomes. Don't let uncertainty become the balm that lets you ignore all actual data, it's a dumb way to be! :-)"
] |
[
"Surnames appear to be \"lost\" with each generation of humans (typically through marriage or lack of procreation). Is the pool of last names slowly shrinking over time? Are we converging to a small subset of last names?"
] |
[
false
] |
It seems to me that the number of unique last names, over time, will eventually dwindle down to a smaller set of what exists today. When I list the things that "create" surnames vs. things that "eliminate" surnames, the former list seems much smaller than the latter. Things that "create" last names: Things that "eliminate" last names: Could this be a real phenomenon? Is this only a problem in Western culture - are other cultures generating new surnames with their customs?
|
[
"Yep, it's a known and studied process with it's own name--the Galton-Watson process.",
"The best documented example is from China, where family names have been used for a long time. 12000 names are known from the historical record, but only 3100 are in use today. ",
"http://en.wikipedia.org/wiki/Extinction_of_family_names"
] |
[
"Wow, I had no idea this phenomenon has a name, much less so studied. Thank you very much!"
] |
[
"All together, the top hundred surnames account for 84.77% of China's population. By way of comparison, in the United States the top 100 surnames account for only 16.4% of the population, and reaching 89.8% of the US population required more than 150,000 surnames. ",
"https://en.wikipedia.org/wiki/List_of_common_Chinese_surnames"
] |
[
"Why can't we just \"bleed out\" lead poisoning victims who can't afford the full treatment?"
] |
[
false
] |
I'm sure I must be missing something really obvious here, but I keep hearing about kids in underdeveloped countries who are dying from lead poisoning because they couldn't afford treatment. but since lead poisoning is just dangerous concentrations of Pb in blood, couldn't a cheap form of treatment be to bleed out the patient a little bit every ~2 months or so, just enough to keep them healthy? Wouldn't the volume of blood eventually be restored between each procedure, thus increasing the ratio of "pure" blood to contaminated blood and decreasing lead concentrations? Or is the lead not actually in the blood, but absorbed by organic tissue?
|
[
"Its toxicity comes from being absorbed by normal tissue, not just the amount that's free in the blood. Most of how they treat it is chelation therapy, where you give people chemicals that bind to lead, and then they excrete it. Also, bleeding people is a bad idea when one of the main symptoms of lead poisoning is anemia. "
] |
[
"Lead does bind to soft-tissues and bone, in addition to circulating in the blood. Also, lead that remains in the blood already has a half-life measured in weeks, which means that blood-letting could not safely accelerate this process in a meaningful way. "
] |
[
"This is more a complicated question than what others have tried to answer.",
"For example, \"bleeding out\" chronic iron poisoning patients works. And is in fact used in some situations as opposed to just using chelation. This works despite the fact that the problems with iron toxicity relate to it being absorbed by tissue other than blood.",
"Why it works though is that the iron in your tissue is easily reabsorbable into your blood stream, so by removing blood every so often over a period of time, you'll eventually lower total body stores.",
"Now, the question is would this work with lead. And to be completely honest, I don't know the answer to that off the top of my head. I don't know if anyone has ever looked at it, but the two things to take into consideration would be:",
"1) Does regularly removing small amounts of blood lead to a gradual removal of lead from your body? IOW, how much of an equilibrium is there between lead in your blood and lead in your other tissues?",
"2) Is is any more effective/cheaper/safer than available chelation therapies?",
"And I don't know if anyone knows the answer to either of these questions, or whether the risks of regular bloodletting would outweight the benefit of having a cheaper and more readily available treatment for lead poisioning."
] |
[
"Why is the EM drive \"impossible\"?"
] |
[
false
] | null |
[
"In what way does it violate the law of conservation of momentum? I'm a chemist not a physicist so it's a bit hard for me to understand. "
] |
[
"In what way does it violate the law of conservation of momentum? I'm a chemist not a physicist so it's a bit hard for me to understand. "
] |
[
"So it doesn't matter that the energy of momentum is cancelled by the energy lost from the EM wave if it's not pushing against anything (according to current laws of physics)?"
] |
[
"If I walked out of a spaceship naked, into the near vacuum of space, would I be hot or cold?"
] |
[
false
] |
The breathing on Mars question made me curious. The vacuum of space is an insulator. Is it enough of an insulator to cause me to overheat? Or would I freeze?
|
[
"It would depend on if there was another heat source besides your body. Tests with animals have shown that when exposed to vacuum their fluids immediately evaporate and form thin layers of frost (water freezes at about -70C in near vacuum). A person being thrust into a vacuum situation would have this thin layer of frost all over their body immediately from whatever fluids were on the outside of their body, as well as any open orifices (of which humans have several), making them initially feel very cold. The person would not immediately freeze solid or anything because their skin would protect the rest of their fluids from evaporating. If the person was in direct sunlight they would quickly experience uneven heat distribution on their body. Parts of them would start to cook and others would feel very cold.",
"There is a famous account of an astronaut who was accidentally exposed to near vacuum during a training exercise. He passed out and when he recovered he said the last thing he remembered was the liquid boiling out of his mouth (counter to what you would think this means his mouth was freezing, not getting very hot)."
] |
[
"NASA used to have a very good FAQ page about this stuff but it is gone. Here is one of their ",
"pages",
" referencing the astronaut incident. ",
"This",
" is a second hand reference to animals' fluids freezing. The studies they have done on animals don't seem too easy to find online but they are referenced all over in other places. As for the concepts of cooling and evaporation that I am explaining, that is all from my extensive schooling, so I don't have any sources that aren't available via wiki or wolfram."
] |
[
"Are you exposed to sunlight or shielded from it by a shadow? In a vacuum the temperature difference between lit and shaded sides can get very extreme."
] |
[
"As far as we know, is matter continuous or discrete?"
] |
[
false
] |
[deleted]
|
[
"There is a theorised smallest length, called the \"planck length\". In short, it's the absolute minimum length that it is theoretically possible to measure, regardless of how good our measuring technology becomes. I've heard it referred to as the \"pixel size of the universe\", which seems fitting if it truly is the smallest possible length. ",
"Here's the Wikipedia link for further reading"
] |
[
"The Planck length is the hypothesized length scale of quantum gravity. This is very different from being the smallest length possible. For example, the length scale of an electron in an orbital about an atom is around an angstrom, but that doesn't mean it's the smallest length possible, merely that nothing very interesting happens at smaller scales."
] |
[
"Thus I believe my assertion that this is the smallest length is justified?",
"No it isn't, it's the equivalent of you saying \"I can't see beyond the horizon, so nothing beyond the horizon is physically meaningful.\""
] |
[
"Is it possible there are dinosaur bone fragments on the moon due to the Chicxulub impact?"
] |
[
false
] |
We have rock here in the form of meteorites so I thought that it might be possible for something go have made it into space from the impact here on earth.
|
[
"Dinosaur vapor maybe.",
"Throwing something out of the atmosphere at escape velocity is hard. ",
"You totally can",
" and it is faintly possible Earth's microbes might even have made it to other places in the solar system inside a rock. ",
"Flaming dinosaur chunks could follow a similar trajectory, but organic material doesn't cope well with either hypersonic in-atmosphere flight on the way out or smashing into the surface of the moon at several kilometers per second. Optimistically you are looking for a diffuse carbon smear."
] |
[
"Indeed. It would however still have to contend with the intense metamorphism and shock due to the initial and terminal impacts implicit in the process. Even the original mineralogy does not necessarily survive that. Fossils would'nt fare much better."
] |
[
"Indeed. It would however still have to contend with the intense metamorphism and shock due to the initial and terminal impacts implicit in the process. Even the original mineralogy does not necessarily survive that. Fossils would'nt fare much better."
] |
[
"Can someone explain why there are so many variants of allergies to cats?"
] |
[
false
] |
I seem to be allergic to every cat, but invariably, people tell me "Oh, but this is a long-haired cat. My brother is allergic to most cats, but not long haired." Or, "Try to get a Siamese cat, no one is allergic to Siamese cats." Do people have different triggers for different cats, or are all my friends full of shit? I seem to be uniformly allergic to all cats. Thanks, Reddit!
|
[
"Since the most common allergens are produced in cat's saliva, cats who groom more should theoretically have more of the allergen in their dander.",
"I know from personal experience that I have a much worse reaction to my female cat who is a constant groomer (and also sheds quite a lot). My male cat grooms himself far less and I have almost no allergic reaction to him."
] |
[
"The main allergen of cats is called secretoglobin. It's a protein found in cat skin and saliva. The amount of the protein in different breeds varies, but still all cats have it. It really depends on the person how sensitive he/she is to the allergen and their combinations. Cats have total of 5 different allergens. We have three cats and people with cat allergy seem to tolerate our ",
"Selkirk Rex",
" the most. She has a very thick woolly hair, which might prevent her dandruff from spreading all over, but this is just my speculation."
] |
[
"They're full of shit, as most people are."
] |
[
"Would the Superconducting Super Collider, that was cancelled have been a huge science gain over the LHC?"
] |
[
false
] |
I was wondering because of this post that brought up how it looks today: For those curious:
|
[
"It would have had about three times the energy: 40 TeV total vs 14. That means that it would have gotten the same results faster (look at how fast the LHC found what the Tevatron spent years looking for) and would have had a better chance at finding new physics like supersymmetry."
] |
[
"With the issues the LHC has had so far, would those and others have only been magnified if we went forward with this beast?"
] |
[
"Likely yes. The SSC would have been capable of a much more thorough test of the existence of the Higgs boson (among other things) than the LHC."
] |
[
"In stem cell therapies, how do doctors get stem cells to the tissue or organ they are attempting to repair? Are stems cells too large to be delivered through an injection?"
] |
[
false
] | null |
[
"Stem cells can be delivered via injection; however, that does not guarantee they’ll stay where you put them. For example, a relatively recently study in horses showed that the majority of stem cells they injected intra-articularly (into joints) ended up migrating to the lungs. "
] |
[
"I'm not sure if technology has progressed to where we are actually growing new organs for people but it's extremely close. This is almost like a 3D printer but the blueprint is stem cells. ",
"If you're getting a stem cell transplant (also bone marrow transplant) for cancer basically first they kill your existing bone marrow. Then you'll get your new stem cells IV kind of like a blood transfusion. Then it takes a few months for your body to become \"engrafted\" where it accepts the new stem cells and begins to make new blood without cancer. ",
"Your blood type can change with this process fyi."
] |
[
"Very interesting, thanks for the response. Do you have a link to that study? I'd be interested to check it out "
] |
[
"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!
|
[
"Well for example changing eye colour is possible in the current day, but not through DNA altercations... Most of those examples humans do through different means then what you're talking about (Self tanner, Hair dye, etc) Because the risks out weigh the costs of affecting those through DNA in adults... For excample:\nTheres a way to change your eye colour from brown to blue, as everyones eye colour is blue deep down, just brown eyes have more layers to them, so if you shave off those extra layers then boom blue eyes! But it's not easy as it's usually only done in third world countries and will most likely make you completely blind."
] |
[
"Is there a way to use CRISPR/RNA editing on adults? and as someone who want's to go into gene editing/biotech area are there any online resources or communities you can recommend to further my studies right now?"
] |
[
"CRISPR has actually started being used on adults with severe diseases in the US"
] |
[
"Why does ethanol evaporate out of my cleaning solutions or off the glass im cleaning but not out of my gin and tonic?"
] |
[
false
] | null |
[
"Well, it does in both cases. It's just a question of rate. ",
"Assuming ideal behaviour, ",
"Raoult's Law",
" says that the vapour pressure of substances in a mixed solvent system reflect their relative composition in the solvent. So the component that makes up more of the solvent will end up being more of the vapour, leading to faster evaporation. ",
"Ethanol has a higher vapour pressure than water, so at high or middling concentrations it will dominate. However at lower concentrations, it will be less volatile than the water it is mixed with.",
"Cleaning solutions have a higher concentration of ethanol, so have a higher vapour pressure of ethanol, which leads to a faster rate of evaporation. A mixed drink has an ethanol concentration of 10-20%, so its vapour is dominated by water, which means the ethanol will evaporate comparatively slowly. ",
"In both cases they will eventually completely evaporate, but if you start with high ethanol, it will decline faster than the water, while if it starts low, it will not evaporate noticeably faster than the water it is with.",
": As pointed out below, Raoult's law doesn't hold well in this case. The answer by ",
"/u/AugustusFink-nottle",
" has a better explanation of this phenomenon."
] |
[
"In addition to what ",
"/u/superhelical",
" has said, there's one more thing to consider: surface area. When you wipe your window with cleaning solution, you're spreading a small volume of liquid over a large surface. There is now a much larger surface area to evaporate from, compared to the liquid surface in your glass."
] |
[
"Ethanol-water deviates from Raoult's law because it is a ",
"positive azeotropic mixture",
". For an ethanol-water mixture, the vapor pressure of the mixture can be higher than either component alone. ",
"Water and alcohol make a positive azeotrope because they don't stick to each other as well as each one sticks to itself in solution. Therefore each liquid tries to \"push\" the other out of the mixture and into the air as vapor. If you have more than 95% ethanol, the water evaporates at a higher proportion, so evaporation makes the drink even more alcoholic. Anything under 190 proof, and the ethanol evaporates faster than the water.",
"So, your alcoholic cleaning solution evaporates faster because the total mixture has a higher vapor pressure (because it is closer to the azeotrope (i.e. maximum) at 95% ethanol). It also helps that it has less surface tension, so it can maximize the surface area when wiped on glass. A cup of cleaning solution would also evaporate faster than a cup of gin and tonic, but both solutions are becoming more watery with time. ",
"Oh, and the ice in your gin and tonic helps slow the rate of evaporation."
] |
[
"For any given probability density function, is there an upper limit on the difference between median and mean in relation to the standard deviation?"
] |
[
false
] |
[deleted]
|
[
"Are you asking is there a bound on (mean-median)/sd ? That's bounded between -1 and 1.",
"See, for example,",
"O’Cinneide C.A. (1990),",
"\n\"The mean is within one standard deviation of any median.\"",
"\n",
" ",
", 292–293",
"(the basic result is considerably older)",
"With some additional information about the distribution you can bound it further.",
"but it is hard to find anything in google.",
"Weird. If I type in only keywords from your post: ",
"then I get this as the first hit:",
"https://math.stackexchange.com/questions/503710/distance-between-mean-and-median",
"which has answers containing a demonstration of the result you're asking about, such as ",
"this one",
".",
"If you know more terms its easier to locate the information but just terms in your question is sufficient."
] |
[
"This requires the existence of a mean and standard deviation. PDFs needn't have them"
] |
[
"and the standard deviation. Those are huge restrictions. Stable distributions can't violate both those requirements."
] |
[
"Please help with a thermocouple problem."
] |
[
false
] |
[deleted]
|
[
"If no one can help you here try ",
"/r/askscitech",
" or ",
"/r/beakers",
"."
] |
[
"Type R or S might do the trick. That's just eyeballing off of these ",
"voltage-temperature curves",
".",
"Edit: And B might be worth looking into, though it isn't on that curve. It's also got a not-so-steep slope."
] |
[
"Here is my suggestion: Find a user manual for the hot press. Find out what thermocouple its supposed to have. Then ",
"just buy a damn thermocouple.",
" They're cheap, a hell of a lot cheaper than buying a new piece of equipment because the temperature controller didn't work properly because it was connected to the wrong thermocouple type."
] |
[
"What would be the consequences of a global, significant and sustained population decrease on the economy?"
] |
[
false
] |
Would it necessarily imply economic collapse? Deflation? Can economic growth be possible in such conditions; if so how?
|
[
"The problems arise when the population has more older people than younger people, as it poses significant challenges to social programs and other societal institutions that depend upon a relatively large workforce to be sustainable. There are already countries facing this issue right now, like Japan, which sells more adult diapers than baby diapers. The good news is that populations aren't projected to start decreasing until around 2050, and technology will either make this a nonissue, or we'll all be dead due to an AI apocalypse"
] |
[
"The key issue would be a decrease in the percentage of the population capable of (efficiently) performing labour.",
"It varies from person to person, but between 50 and 80 a large majority of people become unable to perform physical labour and an increasing number become less capable of performing other work.",
"Additionally, countries would need to reshape training. Today's 60 year olds never encountered computers at school. Considerable retraining would be needed."
] |
[
"That's a very likely possibility. A significant decrease in Earth's population would affect a variety of factors for both businesses and consumers. Less people means less need for supply and demand, fewer people would start businesses, reducing competition in the marketplace, less drive to innovate...the effects would change the nature of the world economy as a whole. Also, you would have to take into account who's left over following the aforementioned decrease; individual survivability would be rather difficult one way or another considering that recent generations' education/lifestyles are more contingent/dependent upon technology than skill. Its more likely that we'd see a return to emphasis on more local economy versus global, more of a scaling down than a collapse, provided that things happen ideally."
] |
[
"Living and traveling all around the US, I've heard lots of stories about invasive species of plants, fish, insects, etc. wreaking havoc on the local enviornment. Are the examples of American flora/fauna invading other countries?"
] |
[
false
] | null |
[
"Yes.",
"UK. Grey Squirrels are an invasive species that have largely driven out our smaller, but much, much cuter, red squirrels.",
"Others from the US are: the American Bullfrog, American Mink, Floating Pennywort, American Skunk Cabbage, Raccoon, Pitcher Plant, and Signal Crayfish.",
"And those are just the ones causing problems.",
"https://www.discoverwildlife.com/animal-facts/facts-about-uk-invasive-species/"
] |
[
"They dont grow particularly aggressively where I live in New England",
"That's the thing. They've been there so long everything else has adapted and eats or competes with it, or has learnt to avoid it... Point is, they adapted along side it. ",
"But bring it somewhere else and nothing knows what to do with it. It can have a massive advantage, or fill an unmet niche in the new environment and flourish."
] |
[
"Oh, absolutely. There are several invasive American insects, for example.",
"The Colorado potato beetle is particularly notable for having being a destructive pest in America first. It originally fed on buffalo bur, a native American ",
" species (this is a large plant genus that also includes potatoes, tomatoes and eggplants). Potato plantations gave it a new food source, and starting in the mid-1800s it began to spread across the entire continent, and shortly afterwards it showed up in Europe. It is now found all the way across to China. There's some interesting research on its evolution during this time; for example, you can see ",
"adaptations to European winter conditions",
" in some of the northern populations.",
"Another example is the fall webworm, which is perhaps best known for being mentioned by a Metal Gear Solid character ",
"during a deranged rant",
". But it's a real insect! It's a moth, well known as a garden pest in China and Japan; it defoliates trees, including popular ornamental trees like cherry. This is another species where we have good data on its evolution during recent decades, including adjustments to its life cycle that make it survive better in the Japanese climate."
] |
[
"Why do humans have to brush their teeth in order to keep it healthy while most (all?) animal naturally have good teeth?"
] |
[
false
] | null |
[
"Animals do not have any better dental health than us. Most animals die before they get old enough to have serious dental disease, or the dental disease it self kills them. ",
"80% of cats and dogs will have some form of dental disease by 5 years of age (stat from my professor in vet school). They don't get cavities like people, but other forms of dental disease, mostly periodontal disease where the ligament and bone holding the tooth in place are destroyed leading to loss of teeth, pain and infection. I pull plenty of teeth in animals on a regular basis. It's recommended that all cats and dogs have their teeth brushed daily (with special pet tooth paste and brush), but that is very rarely the case.",
"Many herbivores and rodents have open rooted teeth that continue to grow. They are worn down through grinding their food. In horses, it can lead to sharp edges on their teeth that can lacerate the inside of their mouth. The sharp edges need to be ground down by a vet, which is called \"floating.\" Rodents and rabbits need to have good chewing surfaces to grind down their teeth and make sure the teeth have good occlusion (line up so they grind on each other). If not, it can cause their teeth to grow so long that they can't eat and will starve. Occasionally, the teeth will even grow into the animals skull and kill it.",
"Elephants, and the related mantee and hyrax, have a different way of replacing teeth. As the aged, the cheek teeth slowly migrate forward to the front of the mouth and are replaced by new teeth erupting from the back of their jaws. By the time they fall out, they are too worn to use any way.",
"As zoo populations age, due to increased life span, dental care is becoming more and more important in their overall health. That goes for many species."
] |
[
"I'm quite sure that I would die of bleeding if I were to try to brush my cats teeth every night.",
"Is there something you can do instead? Chewing toys or special kinds of food or stuff like that?"
] |
[
"From a human end, we don't have a lot of antibacterial components to our saliva. Also, we eat a lot of processed foods with simple carbohydrates (read sucrose) in them. These case acidogenic bacteria to produce acid and demineralize tooth structure. This demineralization over time causes cavities (a disease called caries). There are different ways to stop this process. Fluoride is the main way. It has a topical effect from drinking water constantly and prevents certain bacterial enzymes from working thus slowing down the acidogenic bacteria. Also, it is incorporated into the hydroxy apetite crystals forming fluoro apetite crystals which are mush less soluble in acid.",
"Pets benefit from the fluoride in the water as well since they drink primarily tap water and no sodas like a lot of people."
] |
[
"Do cell organelles float freely in the cytoplasm? Or are they attached to the cell membrane/some other structure through microtubules?"
] |
[
false
] | null |
[
"For the most part, they're anchored directly or indirectly to intermediate filaments (IFs), which are part of a eukaryotic cell's cytoskeleton. This tethering may involve microtubules. As far as your question on free-floating organelles is concerned, there is a scaffold-mediated internal architecture to the cell. The cytoskeletal scaffold can even mediate signaling events within the cell that help support organelle function.",
"A lot of research is being done on this, much of which is relevant to cancer biology in the phenomenon known as the epithelial mesenchymal transition (EMT). EMT allows cancer cells to change shape and leave their environment for metastasis.",
"Here's some further reading on IFs:\n",
"http://www.molbiolcell.org/cgi/content/abstract/22/13/2282",
"\n",
"http://jcs.biologists.org/content/114/24/4345.long",
"\n",
"http://www.jci.org/articles/view/38214/version/1",
"\n",
"http://jcs.biologists.org/content/61/1/87.short"
] |
[
"just as a visual aid, here is a picture of an endothelial cell with the keratin (just one type of IFs) stained:",
"http://www.microscopyu.com/articles/fluorescence/filtercubes/yfp/yfphyq/stains/images/yfpcy2keratinptk2cells.jpg"
] |
[
"This is correct. Cells are actually highly structured and organized spaces. Most movement of organelles within the cell, for example, occurs on microtubule highways driven by ",
"motor proteins",
". "
] |
[
"Why did the atom in the video \"vanish\" instead of being gradually engulfed?"
] |
[
false
] | null |
[
"These are not two individual atoms of gold but nanoparticles with a diameter of about 25 nm from the looks of the larger one. The graniness of the bodies is actually the individual atoms. I have experience identifying latice plains in transmission electron microscopy.\nAs for your question. These particles seem to be fairly slowly migrating and the time in between capturing images is greater than you might think. This doesn't look like real time. The two bodies probably did have some sort of deformation and agglomeration before becoming one, but that could have happened between captures on a very tiny time scale."
] |
[
"To add to this, the sample appears to be heated, which is why the gold nanoparticles are moving. Once the two particles make contact, the surface energy of the 'almost two particle' system is much higher than a single particle, and therefore the two quickly merge to form a lower energy shape"
] |
[
"Hard to tell what's going on here. I can think of a couple possible explanations. One is that for whatever reason that atom or collection of atoms popped out of the focal plane. But since the other agglomeration appears to get bigger after the smaller one disappears, I think what's more likely is that the two groups of gold atoms got close enough to bond and therefore the small clump disappears as it becomes part of the other clump.",
"As for why that would happen: gold doesn't oxidize at STP and for metals in general it's pretty strongly favorable to bond. So once the clumps of atoms get close enough, the electrostatic forces rapidly suck them together."
] |
[
"E of a photon is proportionnal to frequency. As energy can't be infinite, does that mean frequency have a maximum value ?"
] |
[
false
] | null |
[
"There is no maximum energy or frequency for a photon."
] |
[
"Why ? Does'nt infinite energy break physics laws ?"
] |
[
"The energy is always finite, but there is no maximum."
] |
[
"What's going on with the Novel Langya Henipavirus that's in the news currently? I have a few questions."
] |
[
false
] |
I have a few questions about this virus because these news articles don't make it too clear:
|
[
"Can’t really help you with the first 2 questions, about Number 3, there is a possibility that this virus get airbourne transmisión. If not, there may be, for different reasons, a higher number of infected animals (in this case, bats, or a number of other possible natural reservoirs ) that may transmit the virus to humans. In China, the living conditons of the rural population are of high risk for zoonotic infections. People in rural areas live in close relation with animals, which they raise to get food. Some of this animals could get infected with the virus and then transmit the virus to people, acting as an intermediate reservoir.",
"About question number 4, as I know, known henipavirus family members are not really highly transmissable among humans . This reason is why there are outbreaks every certain time, but do not really spread too much. If this virus get to be transmissible between people in an airbourne way, it might become a serious issue. That is what scientists are studying right now.",
"About question 5. Other henipavirus family members are indeeed classified as biosafety level 4, with mortality rates as high as 70%. This does not seem the case for this new virus, as reported cases havent died after infección. Non the less more studies are needed to evaluate if there have been people killed by the virus, and the virus have not been tracked to them. (As this is a new virus, médical staff have not yet tools to look out for infection)",
"Hope i have helped. Sorry for my english, im a little rusty, and im writting from a spanish keybord with auto correction."
] |
[
"Do not apologise, that's lovely information. Thank you."
] |
[
"Articles say human to human transmission hasn't been identified. How did 35 people presumably get the same virus?",
"This isn’t at all surprising, for a couple of different reasons. Firstly, it is really hard to prove human-to-human transmission - you might recall the very early stages of the COVID-19 pandemic, particularly Jan 2020, this was still contentious - and that was a very infectious disease.",
"Secondly, it’s common for infectious diseases to not be spread person to person. The infectious disease responsible for the second most deaths worldwide (single agent) is malaria, which is not spread person to person. Tetanus, Legionnaires’ disease, and Lyme disease are also examples. Even something like cholera isn’t spread ",
" from person to person - you can kiss someone with cholera and be fine. Exactly what constitutes “person to person” is up for debate and depends on context. I would describe cholera as person to person because there can be a very short time between it leaving one person and infecting another (like airborne respiratory infections), but others might not because you get it from drinking infected water rather than direct contact."
] |
[
"Would it be possible to induce the feeling of hunger in someone who had a full stomach simply by putting certain hormones, etc into their bloodstream?"
] |
[
false
] | null |
[
"While it's always a bit more complicated than simply putting certain hormones into their bloodstream, yes, it's very possible. Your body uses several hormones to regulate food intake and satiety:\nLeptin: Produced by fat (adipose) tissue, increase satiety by binding to Neuropeptide Y neurons in the hypothalamus\nNeuropeptide Y: Increases food intake, its release is decreased by leptin\nGhrelin: Increases food intake also, released from the stomach."
] |
[
"using marijuana simply ",
" the munchies counteracts nausea."
] |
[
"nausea makes you not want to eat. marijuana makes you want to eat. what do you think?"
] |
[
"Why are earth years used when referring to the age of things that existed before planet earth existed?"
] |
[
false
] | null |
[
"It's just a unit of time. It's easier for humans to understand what \"one year\" means. One year is defined exactly as 31,557,600 and that definition is valid regardless of whether humans or Earth exist."
] |
[
"Because years are a unit of time that humans understand and these numbers are used by humans to communicate to other humans."
] |
[
"It seems strange to me that it's used when referring to the existence of other things that are much older than the earth itself."
] |
[
"What is water tension? And do other liquids have the same property?"
] |
[
false
] |
I may have already been taught this way back when, when I used to do Chemistry, but have completely forgotten. Is it something to do with the molecular structure of water or is this a property found in every/many liquids? Thanks x
|
[
"All molecules have surface tension. Basically it's a result of the fact that molecules in a liquid attract more strongly than molecules in a gas. So at the surface of the liquid, where the two meet, there's more attraction from the liquid side than from the gas side. "
] |
[
"I'd like to add that water experiences a much more noticeable surface tension due to increased intermolecular forces, namely dipole-dipole and hydrogen bonding. Due to water's rare ability to hydrogen bond with itself, it has one of the highest cohesion forces of any non-metallic liquid."
] |
[
"Water tension, and other surface tensions are created by ",
"Intermolecular Forces",
". These forces, are basically a small amount of attraction between the molecules that brings them closer and resist separation. These happen between molecules, and the bonds' strength depends on the structure and atoms within the molecule.",
"Source: AP Chemistry textbook >_<"
] |
[
"What causes that squeaky noise when you rub a wet finger over a mirror or other smooth surface?"
] |
[
false
] |
why doesn't it work with a dry finger?
|
[
"There's two scenarios at play here: one where your finger is touching the surface, and the other where it's touching water. The surface has a higher coefficient of static friction, meaning it will do a decent job of keeping the finger in place despite other forces (it's sticky). The water, on the other hand, has a quite low coefficient of kinetic friction, meaning it's not good at slowing down objects that it's contacting (slippery). ",
"Let's look at a finger moving along the mirror at a constant-ish speed. Your skin is kind of springy, it stays in a certain place and the further you pull it away the more it wants to go back. To start, the skin is in contact with the mirror (pushing aside the water). When the finger moves far enough to the side, there's enough force to pull the skin off the mirror. The skin then glides over the water until it's past where it would be if it were sitting still. As it gets to the point where it's not moving past the mirror, it sinks into the water and grabs the mirror again. Then the process repeats.",
"This repeating process of sticking and slipping always takes about the same amount of time to repeat (with the same mirror, water thickness, finger force) and it happens pretty fast. Anything that repeats like this is going to vibrate the air around it and cause a squeaking noise. It's really the same thing as a violin, but instead of vibrating a string with a bow you're vibrating your finger with the wet mirror.",
"The pitch of the squeak is how many times your skin slips back and forth per second. It doesn't work with as well with dry surfaces because there isn't as much difference between static and kinetic friction, so your finger is dragged along constantly instead of skipping."
] |
[
"BlazeOrange gave a good response, but there's a name for what this phenomenon is called. ",
"Schallamach waves",
" occur when an elastomer (or springy substance like the skin on your finger) is rubbed across a smooth surface with high ",
"surface energy",
". Waves of contact and separation occur across the elastic material. They actually move in the direction opposite of motion (ie. push your finger forward, little waves of separation on your finger move backward). The tribological properties of the two interacting surfaces and the relative velocity between them determine if the phenomenon occurs or not, and the stiffness of the elastomer determines the frequency of the 'squeek'. This question was one of my PhD prelim exam questions, except for the example of basketball shoes squeeking on a freshly waxed court. I have a ~1 hour powerpoint answering the question if you want :)"
] |
[
"I really would like the know a complete answer for this but i have some input that i think might be a reason.",
"possibly something to do with the glass being to smooth? and the water rubbing up against such a smooth surface?",
"im not sure man! but id love to find out!"
] |
[
"AskScience AMA Series: I’m Stephan Lewandowsky, here with Klaus Oberauer, we will be responding to your questions about the conflict between our brains and our globe: How will we meet the challenges of the 21st century despite our cognitive limitations? AMA!"
] |
[
false
] |
Hi, I am Stephan Lewandowsky. I am a Professor of Cognitive Psychology at the University of Bristol. I am also affiliated with the Cabot Institute at the University of Bristol, which is an inter-disciplinary research center dedicated to exploring the challenges of living with environmental uncertainty. I received my undergraduate degree from Washington College (Chestertown, MD), and a Masters and PhD from the University of Toronto. I served on the Faculty at the University of Oklahoma from 1990 to 1995 before moving to Australia, where I was a Professor at the University of Western Australia until two years ago. I’ve published more than 150 peer-reviewed journal articles, chapters, and books. I have been fascinated by several questions during my career, but most recently I have been working on issues arising out of the apparent conflict between two complex systems, namely the limitations of our human cognitive apparatus and the structure of the Earth’s climate system. I have been particularly interested in two aspects of this apparent conflict: One that arises from the opposition of some people to the findings of climate science, which has led to the dissemination of much disinformation, and one that arises from people’s inability to understand the consequences of scientific uncertainty surrounding climate change. I have applied my research to both issues, which has resulted in various scholarly publications and two public “handbooks”. The first handbook summarized the literature on how to debunk misinformation and was written by John Cook and myself and can be found here: . The second handbook on “communicating and dealing with uncertainty” was written by Adam Corner, with me and two other colleagues as co-authors, and it appeared earlier this month. It can be found here: . I have also recently published 4 papers that show that denial of climate science is often associated with an element of conspiratorial thinking or discourse (three of those were with Klaus Oberauer as co-author). U.S. Senator Inhofe has been seeking confirmation for my findings by writing a book entitled “The Greatest Hoax: How the global warming conspiracy threatens your future.” I am Klaus Oberauer. I am Professor of Cognitive Psychology at University of Zurich. I am interested in how human intelligence works, and why it is limited: To what degree is our reasoning and behavior rational, and what are the limits to our rationality? I am also interested in the Philosophy of Mind (e.g., what is consciousness, what does it mean to have a mental representation?) I studied psychology at the Free University Berlin and received my PhD from University of Heidelberg. I’ve worked at Universities of Mannheim, Potsdam, and Bristol before moving to Zurich in 2009. With my team in Zurich I run experiments testing the limits of people’s cognitive abilities, and I run computer simulations trying to make the algorithms behave as smart, and as dumb, as real people. We look forward to answering your question about psychology, cognition, uncertainty in climate science, and the politics surrounding all that. Ask us almost anything! : We spent another hour this morning responding to some comments, but we now have to wind things down and resume our day jobs. Fortunately, SL's day job includes being Digital Content Editor for the Psychonomic Society which means he blogs on matters relating to cognition and how the mind works here: . Feel free to continue the discussion there.
|
[
"I don't think so, because progress in science usually involves simplification. For instance, astronomer's knowledge about the movement of celestial bodies before Kopernikus was much more complicated than after that. By simplifying our knowledge we can teach it more efficiently, freeing our capacity to work on the new frontiers of science. "
] |
[
"Just posted this in the Stephen Hawking AMA, but then saw the title of yours and said: Hey. I should post that there. So here it is: ",
"This was a question proposed by one of my students: ",
"Then follow-ups to that:",
"if not, why not?",
"if we do, how far in the future do you think that might be, and why?",
"if we do, would we resort to machines/computers solving problems for us? We would program it with information, constraints, and limits. The press the \"go\" button. My son or grandson then comes back some years later, and out pops an answer. We would know the answer, computed by some form of intelligent \"thinking\" computer, but without any knowledge of how the answer was derived. How might this impact humans, for better or worse?"
] |
[
"That's a very hard question - essentially it is about how to distinguish reliable information from propaganda, given that the propagandists (for various causes, from ideologies and religions to corporate profit) are often very skilled at pretending to have all the features that characterize reliable information. On factual questions, I think by and large it is a good idea to trust scientists more than non-scientists, and among the scientists, to trust the predominant consensus (if there is one) more than the maverick position. That is because a broad consensus among scientists is most likely the result of converging opinions of very clever people who come from very different backgrounds (different personal interests, different biases and prejudices, different knowledge). It is extremely unlikely that the majority of scientists in a field could be biased or corrupted in the same direction. "
] |
[
"Can you please explain the approach orbit for Rosetta to the comet it is landing on on Jan 20? (Link, Video inside)"
] |
[
false
] |
Seen here: and directly on YouTube here The spacecraft approaches in this weird triangular orbit with almost-straight lines. I assume there's a burn at each of these points but that is a lot of changing direction for I'm not sure what purpose. Do you think it's needed for 3D imaging the comet as much as possible?
|
[
"The video you posted is a stylized representation of Rosetta's approach of the comet. That type of video is meant to provide a sense of the mission without providing real numbers or sense of time or scale. Some annotation would have been nice.\nSimilarly, this video shows the craft's journey from earth to the comet (note the gravity assists off Earth and Mars): ",
"http://www.youtube.com/watch?v=Taz4m1a4NCg",
"There is a full mission profile here; it is an outline which is being filled in as each portion of the mission is accomplished: ",
"http://starbrite.jpl.nasa.gov/pds/viewMissionProfile.jsp?MISSION_NAME=INTERNATIONAL%20ROSETTA%20MISSION",
"Excerpt:\n\"The spacecraft reaches the comet on 22-May-14 at a distance of 4.0 AU from the Sun. A sequence of four rendezvous manoeuvres within 30 days reduce the relative velocity with respect to the comet from 780 m/s to 50 m/s. The spacecraft is in active cruise mode. During this phase Rosetta approaches the comet without observing the comet with the navigation camera (NAVCAM). The comet orbit is determined by a dedicated ground-based astrometric observation campaign. The errors in the estimated position of the comet can still be several tens of\nthousand km. The final point of the NCD phase is the Comet acquisition point (CAP) at 100000 km distance from the comet. The selection of this position depends on two factors: avoiding cometary debris (assuming there is any), and achieving good comet illumination conditions.\"",
"All this happens before the craft turns on its cameras. The final ~100000km to the comet will be done with camera assistance."
] |
[
"Based on the ",
"mission profile",
" it appears that you're right that it is for imaging the comet. Primarily for the purposes of finding a safe way to approach the comet through the debris and then to find a suitable landing site."
] |
[
"One other thing to keep in mind, this is not like orbiting a planet. The gravitational pull is minuscule in comparison. Instead, think of this as drifting back and forth along the line of advance of the comet. The directional changes are not going to require a lot of energy."
] |
[
"Are there any society-wide (epidemiological) consequences to the widespread use of flu vaccines?"
] |
[
false
] |
I was curious if there was any mechanism with vaccines similar to the "antibiotics -> super-bug" issue. I found but I was curious if there were any other issues that epidemiologist-types watch out for. I've read a handful of studies and articles enough to have a decent understanding of vaccines on a local/individual level, but couldn't find anything [reputable] that really addressed my question. I was specifically looking at flu vaccines since their target changes so rapidly, but I would imagine any vaccine going after a "moving target" would be the same. As a related follow-up, is it possible for a society (not an individual) to overuse a vaccine? Or is it basically a (pardon the over-simplification) "magic-bullet"?
|
[
"The epidemiological consequence of widespread use of flu vaccines would be a widespread drop in flu infection rates =) There is no (reputable) evidence that widespread use of vaccines have any significant downside (standard caveats about exceptional or rare side cases apply). As the thread you linked pointed out, vaccines won't produce \"super-viruses\" in the same way that antibiotics produce \"super-bacteria\" because they work in a fundamentally different fashion.",
"You are right that vaccines going after a \"moving target\" make it difficult for the vaccine to result in disease eradication (like what happened for smallpox, and what has nearly happened for polio). Not surprisingly, lots of viruses (as well as other types of pathogens) use the strategy of \"I'm going to rapidly mutate/shift my surface proteins to evade an immune response\" because, well, it's a damned effective way of evading an immune response!",
"There are tricks that we can use, however. The flu is a useful example. In most cases, vaccines are very good at eliciting CD4 T cell-driven antibody responses. Antibodies do a wonderful job at gumming up (literally) viral particles and preventing them from infecting cells, but they rely on having physical access to the specific viral bits that they recognize. Thus, viruses that can rapidly change their exposed bits can evade antibody responses.",
"There is another kind of immune response, though, driven by CD8 T cells that targets the cells that have been infected by a virus. When cells make proteins, they chop some of those proteins up, and stick the bits of protein on their surface. Your immune cells know what proteins are supposed to be there, and don't bother a healthy cell. If a virus infects a cell, though, the cell starts putting bits of the virus on its surface. CD8 T cells can recognize these bits, and when they do, they tell the cell to commit suicide, thus preventing more viruses from being made.",
"The key point in this process is that when a cell puts the viral bits on its surface, it doesn't distinguish between the variable surface proteins or the more conserved core proteins of a virus. Thus, if you can generate a CD8 T cell response against a part of the virus that can't vary (ie. a part that plays a key functional role for the virus), then you can target a wide variety of viral strains. Unfortunately, vaccines tend to elicit poor CD8 T cell responses. There is research being done right now to create a flu vaccine that specifically causes a CD8 T cell response, and would thus function as a universal flu vaccine. If/when we are successful doing this, the fact that the flu is a \"moving target\" wont hamper us nearly as much, and hopefully we'll be able to make flu infections much more rare/infrequent. Presuming there is a widespread use of the new vaccine =)"
] |
[
"Usually, when a vaccine works, the pathogen is eliminated, and doesn't have a chance to survive, therefore it doesn't have a chance to adapt and evolve new mechanisms of survival.\nSo, that's why you don't see things like \"Super Polio\" popping up, because some vaccines pretty much work very effectively, in some cases, at eradicating a pathogen. \nAnd as far as flu viruses go, it's not like a moving target. Once you are treated with an H1N1 vaccine, your immune system will have the instructions on how to handle the H1N1 strain if it should ever get in you. \nThe reason for the variations in the strain of flu virus is from the way they came about: most are from other organisms, such as pigs or birds. And so if you get infected with a different strain, but still have the H1N1 vaccine, you will get infected, get sick, and become a host of the new strain, then develop immunity.\nI don't personally think a vaccine can be overused in any cases, since their design usually calls for eradication.\nAlso, there has been a trend to say that vaccines are terrible, etc. Since the anti-vaccine trend started, the number of cases of whooping cough and other treatable diseases have increased because their pathogens are surviving in patients who didn't get vaccinated."
] |
[
"Not surprisingly, lots of viruses (as well as other types of pathogens) use the strategy of \"I'm going to rapidly mutate/shift my surface proteins to evade an immune response\" because, well, it's a damned effective way of evading an immune response!",
" comes to mind as far as antigen shedding/shifting pathogens are concerned. By the time the host's immune system has mounted an immune response to the antigens this parasite sheds them and dons a new pair and the host must begin again and use more energy. The disease state is sleeping sickness and the method of host evasion is rather brilliant."
] |
[
"What is the mathematical proof of the lift equation used to determine the lift produced by an aerofoil?"
] |
[
false
] |
The lift equation is L=Cl A 1/2 ρ v I understand why lift is produced by an aerofoil, I was wondering the proof behind it. I originally thought that Bernoulli's equation 1/2 ρ v = K-P However the closest I have got to is A 1/2 ρ v =K-P Is there a way to derive the lift equation without calculus? Or if there isn't, how would you prove the equation?
|
[
"The 'Cl' is determined experimentally, and encapsulates a lot of physics regarding, for example, the shape of the wing; it's not possible to derive the specific lift equation that includes the 'Cl' without more information. On the other hand we can easily argue that the form of the lift equation is correct. It is obvious that the lift is proportional to the area of the airfoil. So that just leaves the rho v",
" term. To gain some intuition here, consider conservation of momentum, and imagine a single particle deflected downward by the wing. The lift is a force, and force is the momentum change per unit time. For each particle deflected downward, the force (by Newton's 3rd law, or equivalently, conservation of momentum), is equal to the momentum transferred to the wing per unit time. The momentum transferred is mv (if the particle is mass m and v is the change in velocity due to the deflection), and the number of particles per unit time that transfer that momentum is proportional to the velocity. So you know that the force must be proportional to mv*v, ie proportional to rho v",
" (since m is proportional to the mass density rho). "
] |
[
"Well since Cl is a constant (depending on AoA) couldn't you assume that K=Cl and derive the equation from there?"
] |
[
"What is K? In any case, if you assume a constant AoA, and absorb any constants in Cl, then the argument above works fine."
] |
[
"In humans, what happens to the majority of platelets after absorption by the spleen?"
] |
[
false
] |
I know that the spleen stores some platelets for release during a need, but surely they can't just build up in there forever? Are they broken down? If so, how? I haven't found any clear information on this.
|
[
"Platelets are phagocytosed (basically, \"eaten\") by macrophages in the spleen. I'm not sure what happens to those macrophages at the end of their life cycle. I'll look into it and post here if I find a good answer. "
] |
[
"No, macrophages are white blood cells that act as scavengers, consuming and destroying bacteria and cellular debris through phagocytosis. Macrophages are several times bigger than red blood cells, whose sole purpose is to carry oxygen from the lungs to the tissues and CO2 back from the tissues to the lungs.",
"Platelets are not long lived, they only live about 9 days. Once they're phagocytized (\"eaten\") by macrophages in the spleen, they are destroyed by enzymes that the macrophages make and secrete into the compartments (phagolysosomes) where they are storing the dead/dying platelets. You can think of this as somewhat analagous to your stomach acid and digestive enzymes digesting your food, though AFAIK macrophages do not gain energy from this the way you do eating something.",
"I'm sure parts of the platelets are recycled in a sense just like anything else in the body, but they cease to be platelets which I think answers your question."
] |
[
"Macrophages also do the same, or similar, to erythrocytes, correct?",
"Thanks for the answer!"
] |
[
"If a planet is tidally locked around its parent star, then is it impossible for it to have moons?"
] |
[
false
] | null |
[
"Depends on the Lagrange point :)",
"L1, L2 & L3 are unstable, even though they are equilibrium points. So if a small planet was placed interior to our orbit at the L1 point, it'd eventually float away. You don't find natural astronomical objects at unstable points.",
"However, L4 & L5 are stable. These are the points that at the same distance from the sun as us, but 60° in front and behind us in our orbit. While we don't have a \"moon\" there, we find lots of asteroids there. Jupiter has even more - the \"Trojan\" asteroids."
] |
[
"Related question: How plausible would it be to have a moon that just sits at a Lagrange point?"
] |
[
"I have heard you can increase the L1, L2 & L3 points stability by having an object orbit around the point as opposed to sitting in the point. I am not sure about the dynamics of it. Is there an upper limit as to how large an object you can do that with? Or, does it require some amount of energy to maintain the orbit around the point?"
] |
[
"Are \"core memories\" a real thing?"
] |
[
false
] |
Hey guys! I was recently thinking about the movie Inside Out, and more specifically "core memories". If you don't know, in the movie core memories are basically super important memories that help define your sense of self. So if you really like basketball, your first game may be a "core memory". You also only have a very small handful of them (<10). Now I'm not expecting a Pixar movie to have 100% accurate neurology, but are there any general concepts that are analogous to "core memories" in Inside Out? Are core memories, in any real sense, an actual thing?
|
[
"No, not a thing. As you describe them, these \"core\" memories would be part of autobiographical memory (memory about oneself). But there is no limited number of particularly special autobiographical memories that define people typically. A possible exception is a highly traumatic event.",
"Another slightly similar concept is a \"flashbulb\" memory, where people remember a particular event very clearly (although not always accurately). Classic examples would be the moon landings, Challenger disaster, or 9/11/2001. There are often not autobiographical though, but they might be highly emotional."
] |
[
"It's more analogous to something you cherish than any real concept.",
"In real life, you may remember your first game of basketball, or you may not remember something of the sort until you win a big championship game. But there's no biological or emotional guarantee that you'll remember it any better than any other thing you do, even if you really like basketball.",
"In addition, you'll notice in real life that we're more likely to remember ",
" events, rather than good. While you might not remember the championship game or the resulting celebration quite as well, you will almost definitely remember the exact position you recall being in when the ball broke your nose during one game. Despite Inside Out's attempt to show \"core memories\" as a good thing, it's more likely that if they were to have a real life counterpart, it would be ",
" rather than anything good, as things which are traumatic for the brain tend to induce more recollection of it.",
"So long story short: No, core memories aren't really a thing, although you could easily relate it to the way high emotion/trauma tends to induce greater recollections of events. It's one of the many ways movies like this tend to simplify concepts we don't fully understand yet to make a feel good story out of it."
] |
[
"Thank you for the response!"
] |
[
"r/askscience, how feasible is it to \"do\" math research independently (no mentor, all by myself) and be able to publish in a journal, etc?"
] |
[
false
] |
Hi all, I"ll start with some background info. I've been working in a lab throughout college where the research focus is on brain cancer (Glioblastoma multiforme, to be precise). Our lab has a heavy molecular biology bent, so there's essentially no physicial or formal mathematical work done. The eventual plan is medical school but I'm planning on practicing Academic Medicine, so research is always something I'm planning on staying involved in. However, mathematics is a field that has always interested me and I'm motivated to learn/understand it better (particularly Topology). Moreover, I'd like to eventually try my hand at tackling some research problems (at least to the best of my ability). I'm wary of going to a mentor because of my pre-existing lab commitments, and along with everything else, I was intending on making my math studies an weekday evening/weekend type of venture. I feel like it'd be unreasonable of me to expect a mentor to take me on with those inconvenient hours. My question to all of you is, can I do research independently? And in the very very slight chance that I come up with something publication worthy.....do I stand a chance and submitting to a journal without a mentor? I'd welcome everyones thoughts/advice on this. Thank you :) P.S my mathematical qualifications (calc, diffeq, linear algebra). Obviously, before I undertake this task, I'd be spending a good number of months self-studying everything.
|
[
"I have tried and failed."
] |
[
"To be honest, it'll be extremely extremely difficult, and self-studying and working probably won't work. If your math level is similar to mine (lower division undergrad calc/dif eq/linear algebra), than I would imagine it would take years before you could understand enough math to even realize what research problems are out there and how they are being approached.",
"If you are serious and very interested, you should just take math classes, and change labs. Especially in biology, there is TONS of mathematics work to be found, with modelling and the such. It might not be the same as topology or some other pure math field, but it could bridge the gap. ",
"Working by yourself is possible, but would be extremely different. The issue won't be really journals not letting you submit, but rather you most likely will not have publication-worthy material if you don't have a mentor. You work in a lab- you should have some sense of how difficult it is to publish and how valuable having mentors are.",
"If you are interested, by all means try to learn more, take classes, talk to professors, etc. Just realize that taking it a step further to actually be part of thee academic math field and doing research will be an enormous step."
] |
[
"Mathematics at the university level is very collaborative. Researchers in a university department will talk to their colleagues in their department and at other universities. They will attend conferences and talks and read the latest journals, all in an effort to stay up to date.",
"A research student working towards their PhD will study with a mentor who is a world expert in their subject, and will guide them with a research topic that will eventually culminate in their thesis (which will hopefully be an outstanding piece of work that pushes the boundary of our collective knowledge). Once they have their PhD they could quite rightly be called an expert in their tiny little subfield, but they will still need to interact with other researchers if they are to have any hope of staying up to date with the forefront of research.",
"So, yes, you could if you study hard and diligently gain a level of understanding that would allow you to tackle research level projects. But without interaction with other people with a deep knowledge you will be at a significant disadvantage. Even just casual discussions over coffee in a university department may lead to breakthroughs in understanding that might take months of study individually."
] |
[
"Would a human born on mars be stronger on mars than an earthling is on earth?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"/r/AskScienceDiscussion",
"Please see our ",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"Earth actually has a stronger gravitational force, so someone born on Mars and accustomed to Martian gravity would be ",
" than someone born on Earth and accustomed to our gravity. ",
"So your muscles have to work harder on Earth than on Mars, meaning they become stronger on Earth"
] |
[
"Yes, I know earthlings would be able to exert a greater force than martians, but could they lift the same mass in an environment with 3 times as much gravity as the martian has to lift in?"
] |
[
"Does water count as boson, since it has even number of baryons and electrons?"
] |
[
false
] |
I've read somewhere that a boson is any particle with integer spin. And alpha particle is a boson too because it consists of an even number of fermions (in this case, proton and neutron). So if any composite particle consists of even number of fermions, shouldn't water molecule count as boson too? Normal water has one 16-Oxygen and two 1-Hydrogens, so the baryons (which are fermions) are even, and the electrons (fermions too) are even too. But there's nowhere said that water is a boson, so I must be wrong somewhere…
|
[
"Yes, a water molecule is a boson. It can have nuclear spin 0 or 1 (integers, you note). Ortho-water is water with spin 1 and para-water is water with spin 0. It's only quite recently we've been able to separate the two and find they have different chemical reactivity.",
"https://cosmosmagazine.com/science/chemistry/a-choice-of-waters-still-sparkling-para-or-ortho/?amp=1"
] |
[
"An H",
"O molecule composed of hydrogen-1 and oxygen-16, with all of its electrons, is a boson."
] |
[
"But there's nowhere said that water is a boson, so I must be wrong somewhere…",
"You'll have a hard time finding a situation where it would matter. Generally you need very cold temperatures for molecules, but water at cold temperatures forms ice where the crystal structure is more important."
] |
[
"Can I carbonate a beverage with helium?"
] |
[
false
] |
[deleted]
|
[
"You cannot \"carbonate\" a beverage with helium; ",
"carbonation",
" specifically refers to dissolving CO2 in a liquid. ",
"However you can ",
" gases other than CO2 in beverages to make them fizzy. One (fine) example is ",
"Guinness",
" beer, which contains mainly nitrogen gas (N2):",
"Draught Guinness and its canned counterpart contain nitrogen (N2) as well as carbon dioxide. Nitrogen is less soluble than carbon dioxide, which allows the beer to be put under high pressure without making it fizzy. The high pressure of dissolved gas is required to enable very small bubbles to be formed by forcing the draught beer through fine holes in a plate in the tap, which causes the characteristic \"surge\" (the widget in cans and bottles achieves the same effect). This \"widget\" is a small plastic ball containing the nitrogen with also just a little beer itself. The perceived smoothness of draught Guinness is due to its low level of carbon dioxide and the creaminess of the head caused by the very fine bubbles that arise from the use of nitrogen and the dispensing method described above. \"Original Extra Stout\" contains only carbon dioxide,[31] causing a more acidic taste.",
"For nitrogen-pressurized beer, it's often important to include a \"",
"widget",
"\" which holds some of the nitrogen and beer, and which ",
"nucleates",
" bubble formation (",
"example",
"):",
"Some canned beers are pressurized by adding liquid nitrogen, which vaporises and expands in volume after the can is sealed, forcing gas and beer into the widget's hollow interior through a tiny hole—the less beer the better for subsequent head quality. In addition, some nitrogen dissolves in the beer which also contains dissolved carbon dioxide...",
"When the can is opened, the pressure in the can quickly drops, causing the pressurised gas and beer inside the widget to jet out from the hole. This agitation on the surrounding beer causes a chain reaction of bubble formation throughout the beer. The result, when the can is then poured out, is a surging mixture in the glass of very small gas bubbles and liquid.",
"As for other gases, there are two particular ones which will change the taste. Using CO2 tends to result in a more acidic taste, due to the equilibria:",
"CO2 + H2O ⇌ H2CO3\nH2CO3 + H2O ⇌ H3O+ + HCO3-\n",
"Dissolved nitrogen does not change the pH of solution, and itself has not discernible taste. Were helium to be used instead, it would likewise have no discernible flavour. ",
"It should be noted that CO2 works much better because of how it reacts with water; this results in a ",
"significantly higher solubility in water",
", compared to other common gases. CO2 is about 190x more soluble (mol/mol or ~vol/vol) than He and about 70x more soluble than N2 in water. However high pressure can be used to shift the equilibrium in order to increase the amount of dissolved gas (i.e. ",
"Le Chatelier's principle",
"). ",
"A second gas which can greatly affect taste is oxygen gas (O2), as it tends to oxidise the beer, causing it to turn and develop a sour flavour. Beer producers take great lengths to ensure that oxygen is absent during the bottling process.",
"As for helium, one additional concern would be that the application would be particularly wasteful, given the Earth's limited supply of He, typically extracted from natural gas reservoirs. "
] |
[
"Wow that was really interesting! And a really well written answer! I had no idea Guiness was like that cause of Nitrogen. ",
"But to answer one of OPs other questions: no you wouldnt talk funny after drinking a drink with dissolved helium. You only talk funny because you inhale helium. Drinking it would mean its in your stomach and not your lungs. You might burp different though. "
] |
[
"While CO2 is indeed a natural product of fermentation, that does not mean that it is used to carbonate beverages. For fermented drinks (beer, wine) it depends on how the fermentation process was carried out and whether the bottling was done under pressure. For most beers sold, carbonation is achieved by directly adding CO2 during the bottling / canning process. For some beers, along with some sparkling wines and champagne, in-bottle fermentation is used to effect carbonation. This typically requires addition of sugar and yeast prior to sealing, which then produces additional CO2. It may not be cheaper, as the storage temperature must be carefully controlled, which has associated costs. A simple guide for beer is whether any sediment (dead yeast cells) can be observed. For large-scale production, carbon dioxide is injected into the bottle rather than produced via fermentation, which can result in a more consistent process.",
"Sources: local brewer, ",
"posts",
", ",
"Wikipedia",
"."
] |
[
"If I was standing on the surface of Europa, how bright would the day be, comparatively to earth? Would Jupiter's vastness in it's Horizon compensate in reflective lighting for the large distance away from the sun?"
] |
[
false
] |
[deleted]
|
[
"One thing that should be added to the pure astronomical calculation (1/5.2² = 3.6% of earth's illumination):",
"If only about 4% of the light hits your retina... it won't seem to you as if it is that dim. Our eyes perceive on a ",
" (minor quibbles possible). Our indoor lighting for example is ",
" dim compared to sunlight; yet we don't perceive it as ",
" much less light.",
"Typical values given for illumination on earth:",
"bright sunlight (noon): 100'000+ lux",
"overcast day (midday): 1000-2000 lux",
"moonlight: less than 1 lux (!) (clear full moon about 0.2)",
"So 3.6% illumination (~4000 lux) would imply that unobstructed sunlight on Europa would be brighter (!) than Earth at noon with (total) cloud cover. Also brighter than your typical indoor lighting (100-1000 lux).",
" ",
"Added because this is now the highest voted comment: I've run the numbers on ",
" on Europa in ",
"another comment",
" in this thread: It is small. Only about 0.02 lux (ballpark, not accurate), meaning that ",
" just as it does on Earth with moonlight (if slightly less so). You'd probably be able to adjust (with night vision) to jupiterlight even if it is an order of magnitude dimmer than moonlight, but it doesn't contribute much light for Europa compared to solar illumination."
] |
[
"I suppose this explains why, during a recent solar eclipse I experienced in southern California, where the sun was basically down to a sliver, it was sort of disappointingly bright outside! I was hoping it would get really dark, but it didn't. "
] |
[
"It did, but your pupils expanded to allow more light in. ",
"Imagine you were taking pictures with an SLR camera and manually adjusted the settings to be adequate for daylight before the eclipse. During the eclipse, you didn't adjust the aperture or exposure time at all and kept shooting. Your pictures during the eclipse would be extremely dark."
] |
[
"I understand how evolution selects for traits in a life-and-death sense, but what about for traits that have no bearing on whether the species lives or dies?"
] |
[
false
] |
[deleted]
|
[
"However, it seems like there are tons of traits that somehow are selected for and carry on, but have absolutely no bearing on whether a creature was more likely to survive, or more likely to reproduce.",
"One explanation of this phenomenon would be genetic pleiotropy, a mechanism in which one gene has a distinct effect on multiple phenotypic traits. If we take your butterfly example, for instance, it's quite possible that the gene involved in producing the eyespot is also responsible for less important, seemingly neutral characteristics. However, since the production of the eyespot is beneficial, it gets propagated along with the other traits it is attached to genetically."
] |
[
"However, it seems like there are tons of traits that somehow are selected for and carry on, but have absolutely no bearing on whether a creature was more likely to survive, or more likely to reproduce.\nThere seem to be plenty of purely aesthetic traits that humans have",
"Don't confuse the fact that humans have a trait with the idea that that trait was selected for. Traits can exist randomly even if not selected for. The classic example of this in biology is called spandrels.",
"http://en.wikipedia.org/wiki/Spandrel_%28biology%29"
] |
[
"Here's an example of how non-selected traits may still be passed from generation to generation:",
"Let's take your example of butterfly eye patterns, where the patterns are under strong selection for some phenotype that we'll assume is produced by genotype. Now, being very clever molecular biologists, say we have identified that these patterns are produced by some number of genes on one chromosome. And let's say the eye-pattern producing allele is very important and always transmitted, i.e. those without it die. Traits that are favored by selection have a higher probability of transmission from generation to generation. However, since the genes are located on one chromosome, they are not transmitted independently, but are transmitted jointly unless ",
"recombination",
" occurs by introducing ",
"linkage disequilibrium",
". This means there is a greater probability that genes near a strongly selected trait will also be transmitted in what is called a ",
"selective sweep",
"."
] |
[
"We know when the big bang happened; do we know where?"
] |
[
false
] | null |
[
" Hubble"
] |
[
"the centre of the universe, where the big bang happened, is "
] |
[
"If we do as you suggest, we would find that the centre of the universe is right here. The galaxies seem to be spreading away from us, and the further away galaxies are from us the faster they seem to be spreading away.",
"But, this isn't some special property of here, this is also true for every point in the universe. It doesn't matter which galaxy you were on, every other galaxy would seem to be spreading away from you, at a velocity proportional to its distance from you.",
"This is actually a discovery of Edward Hubble, known as Hubble's law.",
"His discovery suggests either that the universe doesn't really have a centre, or if you want a slightly more romantic view, everywhere is the centre of the universe."
] |
[
"What effects would someone without mental health issues feel from prolonged use of antipsychotic medication aimed towards the treatment of schizophrenia?"
] |
[
false
] | null |
[
"We know this pretty well, since antipsychotics are used for some patient groups who don’t have schizophrenia. They’re prescribed for depression, bipolar disorder, and others. Yes, these represent mental disorders. But really, the physiology of antipsychotic adverse effects is the same in almost everyone. ",
"Antipsychotics block dopamine receptors. Dopamine overactivity in a structure called the mesolimbic tract is believed to be one of the causes of schizophrenia. But we can’t precisely target this circuit only. The effect of dopamine antagonism in other circuits leads to side effects. ",
"The worst ones occur by dopamine blockade in the nigrostriatal pathway. This regulates voluntary muscle movement. What happens is dopamine blockade leads the brain to over-produce dopamine in an effort to compensate. This in turn causes the neurons that receive the signals to desensitize. ",
"This desensitization can lead to extrapyramidal symptoms and tardive dyskinesia. These cause involuntary, repetitive muscle movements, especially in the face and mouth. They also cause a restless pressure to move, e.g. pacing around, accompanied by anxiety. These can be permanent. ",
"Another problem is hyperprolactinemia. Dopamine regulates the secretion of prolactin. Antipsychotics lead to too much prolactin. In men, this can cause breast development and discharge. "
] |
[
"I’m a psychiatrist.",
"While the issues related to movement disorders (tardive syndromes) mentioned by other responses are right, these are fairly benign side effects. By that I mean they are not life-threatening, but they are obviously not ideal since they can be quite pronounced and bothersome (interestingly, more so to others than the patients, usually).",
"Medically, there are much more serious side effects of antipsychotics. In epidemiological studies, some antipsychotics are associated with an increased risk of death over the long-term compared to those who do not take them. The mechanism of why this occurs is unknown, but population-based studies repeatedly show this for some antipsychotics. This is associated with an increased risk of death due to cardiovascular causes, so it’s possible antipsychotics have some kind of effect on that system. This may also be a secondary effect of developing metabolic syndrome as mentioned below. ",
"For several newer antipsychotics - typically called atypical or second-generation antipsychotics - there is a clear association with metabolic syndrome, which consists of the triad of weight gain, dyslipidemia (i.e., dysfunction in cholesterol/triglyceride regulation), and insulin resistance (resulting in the development, over time, of type 2 diabetes). This is much more significant medically as all of these things reduce lifespan if poorly managed.",
"Specific antipsychotics have other specific side effects (for example, thiothixene can cause issues with the retina that may lead to blindness), but these are fairly rare and generally associated with antipsychotics that are not in common use these days",
"There was - or still is - some degree of concern that antipsychotics may cause neuronal death. This was particularly a concern for haloperidol, one of the older first-generation antipsychotics. Most evidence suggests that this doesn’t occur to a meaningful degree, but it’s nevertheless a concern that is sometimes mentioned in the literature. ",
"We also know that those with schizophrenia have a reduced lifespan irrespective of whether they take antipsychotics or not. And the reduction is significant - about 20 years. The mechanism is unknown, but it might be a combination of biological effects - in other words, perhaps the same process that results in the syndrome we call schizophrenia also causes other subtle medical problems we’re not aware of - and effects from the disease itself (for example, lacking the insight or motivation to properly manage medical conditions as often occurs in those with psychotic disorders).",
"In general, these effects are only a problem when antipsychotics are taken over the long-term (years). Sometimes antipsychotics are used over the short term - for example, a few months as augmentation when treating depression - and this doesn’t seem to confer the same degree of risk for these issues, though we really don’t know for sure since this is a difficult effect to study. It’s for this reason that antipsychotics are typically used at the lowest dose possible and for the shortest amount of time possible to reduce exposure unless necessary. Unfortunately, there are some psychiatric conditions for which antipsychotic treatment is unavoidable: the psychotic syndromes are one category, but antipsychotics are also commonly used in bipolar disorder. In those cases, the argument is that all of these risks are worth the potential benefit of improving someone’s functioning such that they’re able to live a fairly normal life, or at least achieve a higher degree of functioning compared to not receiving any kind of medication treatment.",
"All of these issues occur even if antipsychotics are given to those that are not psychotic. They are independent actions of the drug themselves, not the disease process. "
] |
[
"increased risk of death due to cardiovascular causes",
"Non-medical person here, but am very curious about this. In regards to increased risk of cardiovascular outcomes, if that's the case, then are these patients then also prescribed things like statins to counter the effects of the increased cardiovascular risk? "
] |
[
"How do calculators/computers figure out how to display e or pi or the square root of 2? When you push the pi button on your calculator, what is it doing?"
] |
[
false
] | null |
[
"For pi and e, in all likelihood the calculator is simply recalling a constant it has stored which still leaves the question of sqrt(2) open. ",
"An important consideration is that digital devices cannot perform infinite precision arithmetic so when is comes to calculating the value of something like sqrt(2) what the calculator actually does is compute the value to some amount of places sufficient for what is displayed on the screen. This means that what the calculator has to do is simply calculate a good enough approximation. ",
"There are various approaches to calculating square roots, in fact ",
"Wikipedia has a page on it",
". I personally don't know which approach handheld calculators use if I'm to be honest, but Wikipedia suggests they use the method it has listed as the Exponential Identity.",
"For other functions such as sine and cosine they can be expressed as ",
"a series",
" which converge to good approximations within a handful of iterations."
] |
[
"I personally don't know which approach handheld calculators use if I'm to be honest, ",
"Early HP calculators, including the first handheld \"scientific\" calculator the HP-35, used CORDIC (which also computes trig functions).\nI'll leave out the gritty details, but it turns out that some basic arithmetic operations are easy with binary numbers (like addition, or multiplication and division by powers of 2. So the CORDIC approach takes advantage of this and works roughly as follows.",
"\nYou want to find the square root of L (which we'll call Y)\nSet Y to zero",
"\nSet X to the smallest value X such that (2",
" )",
" > L (i.e. count the number of binary digits in 'X', and divide by two rounding up).",
"\nSubtract 1 from X",
"\nIf (Y + 2",
" ",
" < L then Y = Y + 2",
"\nDecide if you have enough precision in 'Y', if not go back to the \"Subtract 1 from X\" step. ",
"There are a lot of addition and squaring steps, but because all the multiplication involves straight powers of two it's VERY quick to do via bit shifts. ",
"I do not know if this technique is still used for More modern pocket calculators almost certainly have things like more general hardware multiplication in them that would allow one to move away from shift-and-add style solutions."
] |
[
"General-purpose computers tend to use a lookup table and/or bit-fiddling tricks to get an initial approximation, followed by a few steps of Newton-Raphson or something similar to refine it to full precision. (I think this is just because the memory for the lookup table, and the circuitry for fast multiplies, is available now when it wasn't on early calculators.)"
] |
[
"Do Black Holes Precess as They Spin?"
] |
[
false
] |
Do black holes precess as they spin? Can the direction of their rotational axis change over time? I assume their angular momentum is the sum of the angular momentum of everything they have consumed, so if a black hole eats something new, its axis will change directions accordingly. But for a black hole with no external forces on it, is it possible to precess? If it is possible, does this mean that we could potentially see pulsing quasars?
|
[
"Hm, that's a very good question. ",
"I'd say no, they do not precess because they don't spin in the usual sense of the word. They do have angular momentum, but strictly speaking, there is nothing what actually can spin because that part of spacetime we call black holes is mostly vacuum.",
"Spacetime geometry of such black holes has clear signature of the angular momentum, but I wouldn't say that spacetime is spinning."
] |
[
"It's really an interesting question. I mean, on the other hand, I'm a NMR guy, and we can sure model proton spin in an external field as precession, even though that is a classical approach that doesn't cover it fully. Wondering if something like it could go on here,"
] |
[
"There's two types of precession. One is inherent to the object; this kind of precession a black hole cannot possess, because they are symmetric around the axis of rotation. However, precession caused by gravity (the same precession that the earth and the moon mostly experience) can happen for black holes."
] |
[
"In the double-slit experiment, wouldn't the act of observing the photographic plate, even after the fact, collapse the wave function?"
] |
[
false
] | null |
[
"I would reason that even the act of using a photographic plate would count as \"observation\"",
"You reason correctly. Yet this observation does not carry the information about which slit the photon travels through, so there is no conflict."
] |
[
"Observation doesn't collapse the wavefunction, INTERACTION does. Despite what the pop-sci Youtube videos say, quantum mechanics has absolutely nothing to do with conscious observation."
] |
[
"The photon hits the detector and the detector registers a \"hit.\" It gives you a position where a photon was detected. It has no information about which slit the photon came through."
] |
[
"What makes light reflecting off of a surface, change its color to that of the surface?"
] |
[
false
] |
As a photographer I often wonder why this is. I can bounce a strobe off of a colored surface, and the light will change to that color. Obviously not as strong or vibrant as the original surface color, but noticeably close. Additionally, what is happening when I shoot a strobe (flash) through an orange gel? The light becomes orange, is that due to certain light being filtered out, or does the gel act differently?
|
[
"Additionally, what is happening when I shoot a strobe (flash) through an orange gel? Is that due to certain light being filtered out?",
"Exactly, the material absorbs all colours except orange. The same goes for reflections - a red bowl absorbs all colours except red, which it reflects. Of course, nothing absorbs/reflects perfectly, so your orange gel will let some blue light through, and my red bowl reflects some green light."
] |
[
"Thanks! I'm gonna get a prism and do that, sounds like a cool experiment. "
] |
[
"Thanks! "
] |
[
"I need help finding out what this animal is."
] |
[
false
] |
I live in NW Pennsylvania and I found this leaf shaped, slug-like creature on a leaf in my back yard today. I really want to know what it is. I have took pictures of its back, underside, and *mouth. Please look at the pictures and tell me if you know what it is. * This picture is took under a microscope
|
[
"Can't offer advice, but I happened to see one in SE PA yesterday. Shape of it looks akin to a stink bug."
] |
[
"It's not a stink bug because it doesn't have legs."
] |
[
"No image. Bad link?"
] |
[
"Is it possible for a body of water (lake, pond, etc) to be naturally carbonated?"
] |
[
false
] | null |
[
"In fact, many bodies of water are naturally carbonated - they're called soda lakes. When you dissolve CO2 in water, you get carbonic acid which has a pKa of around 6.3. So when your body of water is sufficiently basic (pH>pKa1), carbonic acid will act as an acid and deprotonated to exist as bicarb. If your lake is even more basic than that (pH>pKa2), bicarb will act as an acid again and deprotonate to exist as carbonate. "
] |
[
"Speaking of taste buds, ",
"San Pellegrino",
" mineral water is bottled with naturally carbonated water."
] |
[
"Lake Nyos",
" is an example of such a lake. It's an example of an \"exploding lake\" that can under some circumstances, degas rapidly as it did in 1986 which resulted in the asphixiation of almost 2,000 people."
] |
[
"Why don't antibiotics kill the good bacteria in our system?"
] |
[
false
] |
So, I know antibiotics are taken to kill bacterial infections, but how do they target only the bad, infecting bacteria and not kill the natural bacteria in our stomachs, intestines, etc.
|
[
"Actually, antibiotics ",
" kill the bacteria naturally found in your body. Antibiotic therapy is associated with overgrowth of ",
" gut flora in your bowels leading to intractable diarrhea.",
"When this occurs, it is recommended to ",
"change antibiotic therapy",
".",
"This is not a common occurrence, but when it does happen steps need to be taken to treat the side-effects of the antibiotic therapy that caused this type of diarrhea."
] |
[
"They do actually, which is why abdominal pain, diarrhea, and things like that are listed under the side effects of just about every antibiotic on the market. But theres just a lot more of the good bacteria than any infectious bacteria so unless youre septic and on something really powerful like IV cipro for a longer time period, theyre not completely eliminated before the infectious bacteria is. Antibiotics can upset the bacterial balance in places other than your GI tract as well, its not uncommon for people on antibiotics to develop thrush and vaginal yeast infections. ",
"If youre ever on strong antibiotics, its a good idea to eat a pack of that activia yogurt after you finish the course to replenish some of your gut fauna. "
] |
[
"Sometimes pathogenic bacteria and normal bacterial flora are the same thing. These are known as opportunistic pathogens.",
"\nYou should know that there are different classes of antibioticsc (",
") used to attack particular structures in bacteria that some have and some don't have (",
")",
"In short, antibiotics don't differentiate between pathogenic bacteria and normal flora because often they are the same. But your doctor can choose what class of antibiotic you take to possibly minimise killing off normal flora while maximising effect of the drug.",
"Antibiotics can kill normal flora, in your gut for example, which allows another normal bacteria to grow out of control and cause infection. "
] |
[
"Would we be able to tell if a planet millions of light years away actually had life?"
] |
[
false
] |
[deleted]
|
[
"Spectrometry can help us learn about the chemical composition of the atmosphere.",
"There are patterns we could see that would be a good hint that life exists. For instance, oxygen tends to combine with things, so free oxygen could be a sign that life recently created it.",
"Here are some ",
"slides",
" on the topic."
] |
[
"Doesn't matter too much how far away it is.",
"Yes, it does.",
"In order to see a spectrum of a planet's atmosphere passing in front of its parent star, you have to have a very good signal-to-noise ratio. In other words, you have to be sensitive to very subtle variations in the amount of light your telescope receives from the parent star...and that can really only be done with stars that are relatively bright from our perspective, otherwise you're just not receiving enough photons to detect subtle differences in light.",
"It's pretty much impossible with our current technology to have that kind of sensitivity for a star that is millions of light years away - that places it well outside our Milky Way Galaxy."
] |
[
"The most distant exoplanet we've detected is about 20,000 ly away, and that was discovered through the gravitational lensing of its host star's light (meaning that we have no information about the planet itself unrelated to its gravity). With current technology we are very far from being able to detect planets millions of light years away, far less glean enough information about them to detect life. "
] |
[
"Given limited resources, what sort of experiment could someone do to demonstrate relativistic time dilation?"
] |
[
false
] |
[deleted]
|
[
"Are you near a mountain? Or have a balloon? You could measure the effect of time dilation on the decay of cosmic ray muons ",
"http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html"
] |
[
"I don't think it would work. Theoretically, time passes more slowly for the moving mirror, but how are you planning to measure that with a laser? The only thing I can think of is if it is going fast enough and the mirrors are perfectly straight the beams would diverge slightly. And even that is not really time dilation, just a consequence of light having a finite speed.",
"If you want time dilation from relativity you either need to move very fast, have very accurate clock, or run the the experiment for a very long time. Preferably all 3. I can't think of a way to do this in a classroom but maybe someone else can."
] |
[
"That's the first thing I thought of, but it would only be really compelling if you also had clear proof that muon's aren't supposed to live that long."
] |
[
"Is it possible that there are galaxies that we will never see because they are moving away too fast?"
] |
[
false
] |
My colleague said this could be if space itself expands. Not sure what this even means and didn't find a lot on the subject so far. Layman here. My understanding is that relativity dictates that no two things can move away from each other faster than the speed of light, so light should always be able to reach the other object... Can someone shed some light here?
|
[
"Your colleague is in fact right. The current limit radius of the observable universe is 47 billions of light years, every object beyond that limit is invisible to us. This doesn't conflict with relativity: it's the space itself that is expanding, not any single object that is moving beyond the speed of light. As I assume this short explanations may leave you more confused than before, feel free to ask more specific questions ;)"
] |
[
"I'm still confused. But I was just linked to \"Metric_expansion_of_space\" on Wikipedia, so I'm reading up on that."
] |
[
"Summarizing, I guess my confusion stems from my lack of understanding the difference between special and general relativity. Since I won't understand that in the near future I'm giving up on the topic. Thanks for trying to help though :)"
] |
[
"How to distinguish between an unstable atom and an element with a very short half-life?"
] |
[
false
] |
Oganesson, the current last element of the periodic table, has a half-life of merely 0.89 milliseconds. Are there other standards that deem it to be a genuine element instead of a bunch of stuff forcibly bound together?
|
[
"The IUPAC has decided that the ",
"criterion for discovering a new element",
" is the following:",
"‘Discovery of a chemical element is the experimental demonstration, beyond reasonable doubt, of the existence of a nuclide with an atomic number Z not identified before, existing for at least 10",
" s.",
"And the physical explanation for 10",
" seconds is:",
"Note 1. This lifetime is chosen as a reasonable estimate of the time it takes for a nucleus to acquire its outer electrons. It is not considered self-evident that talking about an ‘element’ makes sense if no outer electrons, bearers of the chemical properties, are present.",
"It represents the minimal timescale over which the electron cloud can form, and therefore the absolute minimum timescale that it has to exist in order to participate in chemistry. If there are no isotopes which have half-lives greater than 10",
" seconds, then chemists don't consider it an element.",
"There's more about this in our physics and chemistry ",
"FAQs",
"."
] |
[
"You are absolutely right. A nucleus having a very small lifetime is called a resonance. Despite not living much, you can detect them by searching for an increase of the production probability of that given nucleus at the energy of the resonance.",
"As to why this is important I will give you just a simple example. Stars usually burn hydrogen to produce helium. So how do you produce the carbon we are made of? Two resonances! First two of this helium nucleus form a beryllium-8 nucleus, that exists only as a resonance. If, by chance another helium nucleus interacts with the beryllium, there is a very important resonance called the Hoyle state that allows to produce an excited carbon nucleus with a very small lifetime. Nonetheless there is a small chance this carbon doesn't explode back to helium and stabilises himself by emitting gamma rays. Notice that if it wasn't for that resonance to be at just the right energy, we wouldn't be here writing this post."
] |
[
"Wouldn't a physicist still be interested in shorter lived elements to some degree? It might not be relevent to chemists but I would think even short lived stability would have some impact on more fundamental physics if for no other reason than to understand the nature of such instability?"
] |
[
"May be a dumb question, but why do some things (like bouncy balls) bounce, while others (like watermelons) explode on impact?"
] |
[
false
] |
Was just thinking about this, and realized I don't actually know the answer. I mean, if I were asked, I'd probably guess something like a watermelon is more brittle, but at the same time I also feel like if you filled one of those huge hollow rubber balls with liquid, it would probably explode too, so there must be more to it than just that, right? I'm also not super science-literate, so ELI15-ish where possible? And thanks in advance!
|
[
"Elastic vs. plastic deformation, tensile/compressive strength, and brittleness vs. ductility/malleability.",
"Elastic vs. plastic",
" is like the difference between dropping a gummi bear and a chocolate bar, one bends but reverts to the original shape, one bends and stays bent (dented).",
"Strength (in this context) is how much the material wants to hold together when a force tries to move adjacent molecules apart. That could be by pulling, crushing, sheering, etc. But the root failure is always two adjacent particles, molecules or even internal atoms in a molecule, being moved in different directions.",
"In a brittle material the bonds holding two particles next to each other fail in the elastic deformation stage. Think of the watermelon rind. It can bend, but it's not going to hold a bend like a piece of metal. So it's not brittle like glass, but it doesn't undergo plastic deformation before it cracks. That would classify it as a brittle material. ",
"The rubber has so much range for elastic deformation it doesn't even get into the plastic range. Part of that is because of long molecules twisted and knotted around each other, spreading the force across a lot of bonds = high tensile strength.",
"This is a layman's understanding, I'd love a proper explanation from a materials scientist."
] |
[
"It is actually a couple factors at play. First though, it is important to understand that many materials can be thought of as springs, even though they do not seem as such in real life. ",
"These springs are actually the atoms of the material. When a material is not under stress, atoms in it are all spaced apart such that there are no net forces acting on them. Now, say you squeeze a rubber eraser: the atoms in the eraser move closer together, and they exert an opposing force. that tries to make the eraser jump back to its original shape. And as soon as you stop squeezing, the eraser does just that (so long as you didnt squeeze it to hard and break it). This countless number of atoms pushing against each other when under pressure can be thought of as a spring.",
"A bouncing ball acts on the same concept.",
"The first and most important factor is elasticity. If something is more elastic, then when it hits the ground it squeezes itself under its own weight (colloquially speaking). It sores most of the energy that it got from gravity inside itself, just like when you compress a spring. Once the \"spring\" (actually the total of all the atoms inside the ball) has all the energy from the fall stored itself, it releases it and the ball bounces back up! All this happens in the blink of an eye - in the few milliseconds the ball is in contact with the ground.",
"Now why do things break? This has do do with the strength of the material. Every material can only take a certain amount of pressure before it cracks. If the ball got more energy from its fall that its atoms can hold, the material will splatter. This is what happens to a watermellon when it falls - its skin is not strong enough to take the stretching of its mollecules and it shatters.",
"The last thing I want to mention is that there is something between shattering and a perfect bounce, and that is the object being dropped could just deform. Take the example of putty. WHen you drop it, it just changes shape when it hits the ground, but never really cracks or explodes. This is sort of an intermediary state between perfectly bouncing back, and cracking.",
"In the example of a big bouncy ball filled with water: Remember the energy of the bounce (that needs to be stored in the ball's mollecules) originally comes from gravity, and the more massive the ball the more energy it needs to store. Since water makes the ball heavier AND it decreases the number of molecules (ie fewer tiny springs), it could cause the ball to rupture when dropped. Also, water is virtually incompressible, so it can not act as a spring in the way a solid material does.",
"So depending on the material, it can do any of these three things: bounce back perfectly, deform itself, or crack. It can also do a combination of these three things."
] |
[
"Wow, thanks for such an in-depth reply. I think I get it. One question, though. You said a ball filled with water will be heavier (which I get) and have a decreased number of molecules, but with all the water molecules inside the ball, wouldn't there actually be an increased number of molecules? Or am I misunderstanding?",
"And thinking of the atomic compression as relative to a spring really helped, thank you, but what is it that makes something like a kickball work like a spring, but not a watermelon? It seems both their atoms would \"bounce back\" similarly, though I know that isn't the case. Is there something different about the structure or composition of the atoms that makes some things less able to withstand the pressure from the atoms compressing?"
] |
[
"Is there a physical difference between “true” yellow light and a red/green mix?"
] |
[
false
] |
I've been trying to wrap my brain around the whole light physics stuff lately, and here's one of the (many) things that still eludes me. So the perceived color of visible light is a function of its wavelength, right? But at the other hand, our eyes have only receptors for red, green and blue light, so any color we perceive must be a combination of those. Now, I can sort of understand how yellow light at ~600 nm would trigger both our red and green perceptors, seeing that it sits in the middle of those two in the spectrum. But if I mix pure red and green light, it clearly has the same effect, as witnessed on CRT and LCD displays. But does this process actually somehow yield pure yellow light at just one wavelength, or is it just that our eyes can't tell the difference? In other words, is there a measurable physical difference between single-wavelength light and the RGB mixture that produces the respective color in our eyes? I should probably mention that I have a background in audio, so I tend to intuitively think about it the same way I think about sound waves, even if I know that that'll do me no good :P Great explanations, guys. Thanks a bunch!
|
[
"You can flash red light briefly (~10ms) followed by green light (~10ms) and you'll perceive a single yellow flash. It's called \"cortical yellow\". It's still an open question whether or not this happens at the level of the eye or of the brain, but some neat tricks (for example, you can do it binocularly - red light to one eye green to the other) provide strong evidence that it's the brain. It's also still an open question whether we have access to information like this at some unconscious level.",
"On the other hand, mixed red/green light and yellow light should be indistinguishable to humans if the yellow were the right wavelength. IMPORTANT TO NOTE that this is not \"pure yellow\", though - green cones are more sensitive than red cones so the single wavelength you'd use would be slightly green-yellow if your mix was equal luminance green and red."
] |
[
"See: \n",
"http://de.wikipedia.org/w/index.php?title=Datei:Cone-response.png&filetimestamp=20050707063120",
"there are three types of sensors in your eye, which respond like shown in the graph to a certain frequency (its the red, blue and green curve).\neach frequency creates a unique pattern of the 3 values. ",
"But you can combine three frequencies together to get the same pattern from the sensors, so the brain cannot distinguish. ",
"That means, that a red and a green light looks yellow only to human eyes. an animal, that has sensors with different sensitivities could distinguish the bettween the two. ",
"Since all displays relay on that fact, tv sure looks weird to a dog, i guess."
] |
[
"You could take the light coming out of the TV and split it with a prism, and so be able to distinguish a pure yellow from a red/green mix. That means that there is a real physical difference. If you want to think about it like audio, having red/green/blue receptors is analogous to only being able to perceive sound by watching three bands on an EQ meter. Our eyes neglect a great deal of the information contained in the colour of visible light.",
"In fact, there is no combination of red and green that can exactly match perception of pure yellow (570 nm) light. The reason is that green light excites your \"blue-sensing\" receptors slightly, whereas yellow doesn't do that. No matter how hard you try, green-red will always have a bit of blueness mixed in when true yellow does not.",
"Even more, your computer screen produces a \"red\" which is a distribution of colours near pure red, and likewise for its \"green\" and \"blue\" emitters. As a result, computer monitors cannot exactly match the sensation of ",
" pure colour at all, not even red or green or blue! ",
"This",
" might give you some sense of how many colours are missing."
] |
[
"If someone had every element on the periodic table could they in theory create any compound through a series of reactions?"
] |
[
false
] | null |
[
"There are no known compounds of Helium or Neon, as far as I'm aware, so sadly not.",
"As you may have learned in High School Chemistry, the elements on the far right of the periodic table are called the Noble Gases. They have unusually stability/un reactivity due to their electronic configurations and so don't normally form compounds. Why then, have I singled out Neon and Helium? Well, Xenon and Argon can both be 'convinced' to form compounds by bonding with Fluorine, the party animal of the periodic table. Xenon has also been made into a compound bonding with Oxygen through a Fluoride intermediate. These compounds are highly unstable and only exist under extreme conditions, if I remember rightly, very low temperatures.",
"The other major problem you'd have is that some of the elements are highly unstable and might not exist for long enough to actually form a compound. Some of them exist only in the order of nano-seconds though I guess if you were quick off the mark and got them bonded with something supremely reactive (most likely our old friend Fluorine) you might be able to manage it.",
"TL;DR No, it wouldn't be possible - sorry."
] |
[
"Yes and no. It depends on how you frame the question.",
"Every atom in everything you can see, touch, taste, or feel was either created shortly after the Big Bang, or in a supernova. Every compound in existence ",
" ultimately formed from its constituent elements.",
"It's not feasible for humans to reproduce that process in every case, though. It does make for an interesting thought experiment. Pick a compound... how would you synthesize it from the elements given limitless resources?",
"If you mean \"could we make any arbitrary grouping of atoms,\" ... then absolutely not. Certain things (He2 is a simple example) cannot exist."
] |
[
"Since you can ",
"buy xenon difluoride",
", it can't be that unstable."
] |
[
"Are the surface irregularities on a column of high pressure faucet water due to the aeration of the water exiting the faucet or due to the turbulence in the water?"
] |
[
false
] |
When you turn on the water in your faucet at high pressure, the water looks gray. I know this is because of surface irregularities in the water column that reflect light at various different wavelengths and the fact that our eyes samples the light and average it as a middle gray color (correct me here, if I'm wrong on any part). What I'm wondering is if these surface irregularities are due to the turbulence in the water column or because they have been aerated through a mesh in the faucet leaving them full of air bubbles. I would test this out but I do not have a faucet without an aerator that can be easily removed. I tried capturing these in photo as best as I could to demonstrate what I mean. Please note that I have edited the contrast, sharpness, and clarity in these photos to better display the flow behavior. Water column at mid-pressure (you can see the air bubbles inside): Water column at max-pressure (surface irregularities are clearly visible):
|
[
"Well, the aerator is generating turbulence as well as density irregularities (air bubbles) in the flow. The higher the pressure, the higher velocity, and the more turbulence is created. More turbulence means it takes less time for perturbations to grow large because they're starting somewhat large already. It also means that it takes more time for damped perturbations to shrink (because they start larger), so the bumps you see at higher pressures will appear more irregular as there is more content at the other frequencies in addition to the amplified frequency."
] |
[
"Well the aerator adds turbulence to the flow as well so there's that effect too (google \"grid turbulence\"). Higher velocity will cause more grid turbulence here. ",
"But in general, surface irregularities are going to be caused by a combination of flow irregularity (like turbulence or bubbles in the flow) combined with surface tension. Note that for seemingly perfectly regular flow, tiny perturbations will grow and still cause this breakup. The field looking at growth of perturbations in a flowfield is known as ",
"hydrodynamic stability",
". This particular instability is the ",
"Plateau-Rayleigh Instability",
"."
] |
[
"As for what's responsible - turbulence in velocity or the air bubbles... it's kind of a chicken and egg question. The aerator causes turbulence which causes the air bubbles. But ultimately, they will both contribute. There's gonna be leftover grid turbulence which gets amplified. There's also gonna be density irregularities from bubbles which get amplified."
] |
[
"Is it good or bad to have fluoride in our water supply?"
] |
[
false
] |
I hear people for and against fluoride. People who claim it's good, say it's needed for our teeth. People who are against it say it's slowly killing us, that it's a poison and it sedates the population. Whats the real truth about having fluoride in our drinking water?
|
[
"I'm sure fluoridealert.org is a fair and unbiased source. It refers to a retracted paper."
] |
[
"The study confirmed previous findings of an inverse relation between fluoride concentration in the drinking water and dental caries in children.",
"Community Dentistry and Oral Epidemiology Volume 38, Issue 3"
] |
[
"The thing is, it's beneficial at small concentrations, but as you increase the concentration it starts causing fluorosis and other diseases. The measured levels at most municipalities are far below that threshold, however, meaning that it's doing by far more good than harm. The conspiracy theory idiots are unable to cope with any nuance in their understanding of the issue, and they latch on to the studies that confirm that at high enough doses, yes, there is a problem, and they extrapolate incorrectly from that to \"fluoride is bad for you\" without taking into account the concept that the dose makes the poison, i.e. amounts matter. Add that with the natural tendency to distrust science and/or the government, and you've got a perfect breeding ground for idiots to pronounce that we're being mind controlled by lizard people through fluoridation."
] |
[
"What is it about wax and a wick (candle) that makes the wick not burn to cinders quickly?"
] |
[
false
] | null |
[
"Candle wicks are designed to draw liquid fuel into their own bodies and provide a steadily burning flame. Candle wicks are generally made of braided cotton around a core that gives the cord its rigidity (so that it stands up). The composition and position of the candle wick affects how a candle burns.",
"So, basically, it absorbs the liquid wax and that keeps it from burning, while still being flammable enough that it doesn't go out. "
] |
[
"am I right in thinking that neither the solid or liquid wax burns, but the vapour, which is evaporated from the surface of the wick by the heat of the flame, so the wick is protected by the liquid wax, apart from the very tip of the wick which either evaporates the wax too quickly, or can't draw enough wax up to protect it, so dries out and is able to burn. hence why the wick gets shorter over time."
] |
[
"That is about right. "
] |
[
"Why are the mirrors on the newer telescopes shaped like hexagons?"
] |
[
false
] |
I've seen in the news that there's going to be a big telescope in Chile, or Argentina? Can't remember. Anyways, the mirrors are tons of small hexagons. Why this shape and not squares or triangles?
|
[
"Disclaimer: amateur astronomer. I have a clue, but no guarantee that I'm right!",
"In the past, large telescopes like the 200\" at Mt. Palomar would be just one large circular mirror. When you try to scale up much beyond that, you get problems like the mirror sagging under its own weight, ruining the image. The modern multi-segmented mirrors are a workaround to this problem. I believe that the hexagonal shape of the mirrors is simply for most efficient packing, getting the most surface area within a given overall diameter. The first big multi-mirror scope, the MMT in Arizona, used 6 circular mirrors, and if you look at pictures of it, the wasted space really jumps out at you."
] |
[
"Another comment says they start with circular mirrors and cut away the edges. I think the word \"harder\" is probably incorrect, but you'll have to cut away (and thus waste) more of your circular mirror to get a square than you will to get a hexagon. Perhaps they meant \"more economical\"."
] |
[
"For the same \"diameter\" of the mirrors you need fewer hexagons than squares or triangles, and the hexagon shape avoids sharp edges. It is closer to circles which means you can use existing infrastructure with smaller modifications. It also means you only have to put together three components at the corners, not 4 or 6."
] |
[
"What causes the \"post orgasm blues\"?"
] |
[
false
] |
Is it just that you're going from such a good feeling to nothing in a short period of time? Or is there a different explanation?
|
[
"It's known as ",
"Post-coital tristesse",
" -- sexual intercourse leading to feelings of melancholy."
] |
[
"I have no experience of what you are talking?",
"Is the feeling accompanied with shame? If so, you might can find a new partner."
] |
[
"In French it is called ",
"La petite mort",
"."
] |
[
"How will a potential manned mission to mars transport enough fuel and technology to break grip of martian gravity to come home?"
] |
[
false
] |
When looking at the size and scope of a earth liftoff just to ship something on a one-way trip to mars, I don't see how any trip could possibly bring the boosters and fuel needed to come back. Are there plans for this?
|
[
"Actually, the plan would probably be to launch quite a few Rockets the size of a saturn 5. Some would be met up with in earth orbit, some in mars orbit, and some even in mars orbit on the return flight (or just the same cabin they took the trip in and then left in orbitaround mars while they landed in something that met them there.) Computers would fly those extra rockets. People going on a 2 way trip to mars is a very complicated thing to do, thats for sure"
] |
[
"I know that for the fuel to return there are plans to gather elements in the atmosphere of Mars to make fuel for the return. As for the boosters, it is not nearly as hard to leave Mars's atmosphere. The gravity on Mars is only 38% that of earth's and the atmosphere is less than 1% of earths, so I don't think boosters would be needed to escape Mars's atmosphere."
] |
[
"Assemble it in Earth orbit."
] |
[
"If we are creating super bugs by over using and incorrectly using antibiotics, are we doing the same by cleaning our hands and disinfecting surfaces etc?"
] |
[
false
] |
Out damn spot. Is this an issue at all?
|
[
"I'm not sure why this got downvoted. This is the correct answer.",
"Hand sanitizers use alcohol. Alcohol kills everything. The \"0.1%\" of bacteria that are left are alive because they did not come in contact with the alcohol. It's not that they survived the contact and are evolving.",
"The problem with antibiotics is that they need to be selective to only kill foreign agents and not your own cells. In other words, the drugs that you have to put in your body are the ones creating superbugs, not the topical ones.",
"Not the best source, but a start:\n",
"http://www.gojo.com/en/United-States/About-GOJO/News/Corporate-Statements/Facts-About-Sanitizers-Macinga.aspx"
] |
[
"I'm not sure why this got downvoted. This is the correct answer.",
"Hand sanitizers use alcohol. Alcohol kills everything. The \"0.1%\" of bacteria that are left are alive because they did not come in contact with the alcohol. It's not that they survived the contact and are evolving.",
"The problem with antibiotics is that they need to be selective to only kill foreign agents and not your own cells. In other words, the drugs that you have to put in your body are the ones creating superbugs, not the topical ones.",
"Not the best source, but a start:\n",
"http://www.gojo.com/en/United-States/About-GOJO/News/Corporate-Statements/Facts-About-Sanitizers-Macinga.aspx"
] |
[
"I'm just going to be really anal on a few of your statements:",
"As far as we know, bacteria cannot become resistant to things like isopropanol or iodine.",
"Endospore forming bacteria are resistant to those things. If you are a nurse working with someone with ",
" and you use something like isopropyl alcohol to \"sterilize\" your hands, then you are not really sterilizing them. You need to use a hydrophobic solvent, like most soap, to wash away the endospores, the mechanical action of washing your hands and the spores being carried away by the soap is what \"disinfects\" your hands from endospores, and not sterilants like isopanol.",
"If you heat a surface so it's glowing hot, there's ",
" on it. ",
"I know you didn't mention them, but glowing red hot will ",
" destroy/inactivate prions. They have incinerated cows infected with Mad Cow diseases, and from their ashes found activated prions still there."
] |
[
"Have scientists really discovered a new state of matter?"
] |
[
false
] |
Just saw an article posted in but its supposedly a real discovery. I am very curious to hear actual scientists weigh in on this. This is the Have they really discovered a new state of matter, or that a misnomer? Is this legit? What have detractors said about this, the experiment and the phenomenon?
|
[
"I'm not a physicist, but I'm familiar enough with scientific journalism to tell you that answers to this kind of question (about claims made in science journalism, that is) can usually be found by clicking the link at the bottom to the actual article in question.",
"In this case, ",
"the article can be found here.",
" Neither the words \"new\" or \"matter\" appear anywhere in the abstract.",
"This is hardly surprising, given that no matter how they may behave, photons aren't matter."
] |
[
"Actually, in the last paragraph of the Nature paper, the authors list one of the potential applications as \"the exploration of a novel quantum matter composed from strongly interacting, massive photons.\" I'm not sure if that's just the authors being overexcited about their results though.",
"Matter is a poorly defined concept, but being massive is a good place to start."
] |
[
"Physicists with more background, please, feel free to correct me. So, a few things.",
"Ice, alone, has 15 distinct states.",
"Bose-Einstein condensate",
"The article is written in such lay-language, however, it is really hard to tell what they are getting at. I'm absolutely sure that the scientists in question have discovered a new state of bosonic matter, however, this is not some earth shattering revelation, like confirmation of the ",
"higgs boson's",
" mass or, if it turns out to be accurate, the ",
"amplituhedron",
". ",
"Anyways, someone with post-grad physics should chime in. ",
"But in short answer: this shit happens all the time. "
] |
[
"Is there a physical limit to how fast a human being can run?"
] |
[
false
] | null |
[
"Yes. ",
"Several sources say this, but LiveScience did a great summary",
" ",
"Essentially, 40 mph. At that point, too much force is shocking the muscles, breaking them. And the brain will shut down from too much energy exertion"
] |
[
"In the linked article, it says that Usain Bolt has maxed at 28 mph... and never surpassed"
] |
[
"40 mph is theoretical. It would have taken seriously extraneous amounts of energy to have reached 40 mph in the first place. The acceleration to the point of that velocity is the hardest part"
] |
[
"What is the pressure of blood in our arteries?"
] |
[
false
] |
Blood pressure is measured traditionally in millimeters of mercury, and that conversion is simple enough to pounds per square inch, with 100mmhg being roughly 2 psi. But the pressure being measured is the pressure inflating a cuff sufficiently enough to occlude the veins in the arm. My question is: how does that measurement correlate with the actual gauge pressure of the fluid in our arteries? I'm intuitively willing to accept they're proportional (are they?) but it doesn't make sense to me that they'd be equal. Thanks, science!
|
[
"That's why you also have to listen with a stethoscope as you inflate and deflate the cuff. You first inflate it so that the artery closes off completely and then you back it off, deflating until you hear the beginning of blood flow which has a ",
"distinctive sound",
" and that's when you know that you've equalized the pressure in the cuff with the arterial pressure."
] |
[
"In my line of work, we will frequently cannulate an artery to transduce blood pressure directly. The pressure is essentially equal to that obtained with a blood pressure cuff, although there is a small amount of error with the cuff in both directions from measurement to measurement (perhaps 5% at most, and more so in the diastolic pressure).",
"Also, it's not the air pressure occluding the veins, but the arteries. Minor point."
] |
[
"the pressures are actually the same. think of it like a hose. if the water in the hose is exerting 1 psi on the wall of the hose, and you put a box of sand that exerts .999 psi on the hose, there would still be water flowing, but if you put just a little more sand so that it now exerted 1 psi on the hose, it would be completely blocked. the same with taking your blood pressure, if the pressure exerted by the sphygmomanometer (the thing that you use to take the pressure), is less than the actual pressure in your arteries, then the artery will not be fully closed anymore and you will hear blood start to flow again. this is akin to blocking off the hose by putting in a lot of sand, then slowly taking some sand out until you see the water flow again. the water will flow as soon as the pressure exerted by the box of sand is less than the pressure exerted by the water flowing through the hose. it is not proportional, it is the same number."
] |
[
"Why do some people pass out when seeing blood?"
] |
[
false
] | null |
[
"I don't know about particular theories related to blood or violence in particular, but the \"fainting\" reaction related to all stressful situations is called a \"vaso-vagal reaction.\" To some, a stressful situation is seeing blood or violence. The stress overstimulates the nucleus tractus solitarii in the brainstem. This in turn amplifies the parasympathetic system, in other words your rest and digest nervous system. This causes cardio inhibition and dilation of your blood vessels, which causes blood pressure to bottom out as a result. In turn, you faint. Ask if you have any more questions about the physiology of this process. "
] |
[
"The pain sensor nerve cells that give you the deep throbbing pain have unmyelinated axons (they don't have \"insulation\"), so they actually conduct at slower speeds than the myelinated sharp pain sensory neurons that let you know that you injured yourself."
] |
[
"Is this why often times when you just injured yourself, you feel fine at first, and after a few seconds (seeing blood, perhaps?), the pain kicks in?"
] |
[
"Why do we hiccup?"
] |
[
false
] | null |
[
"It's a left over nerve action from when we were fish millions of years ago. ",
"Your lungs used to be swim bladders in fish and fish had an automatic way of adjusting the swim bladder to be higher or lower on the water.",
"\nFor us this auto system now manifests as hiccups.",
"What triggers hiccups? Actually can't remember, sorry."
] |
[
"There are a few triggers for hiccups but the most common one is swallowing large amounts of air, such as when one is eating too quickly."
] |
[
"I don't think that's even possible.",
"I suspect it's triggered when you breath in but windpipe is closed (epiglottis is closed) so you get a negative pressure or something that irritates a nerve"
] |
[
"Why do certain noises hurt to us? (Nails on a chalkboard, rubbing styrofoam together, etc)"
] |
[
false
] | null |
[
"It's still a mystery, but recent research found that, if you don't know that it's ",
"from styrofoam, or squeaking chalk, then it's not nearly as horrible."
] |
[
"The investigation of sounds with certain frequency ranges modified seems familiar, but I don't remember reading about the effect being dependent on knowing what's making the sound. That's pretty interesting, and might be a problem for the warning call theory: if you hear a warning call, but you don't know it's a warning call, how can it be effective?"
] |
[
"I'm not a biologist, but i actually know the answer to this one! ",
"A proposed reason for this, is that the Human ear canal is shaped to amplify frequencies significantly between the 2000-4000hz range, which is roughly the frequency of the human voice. Because of our reliance on verbal communication, our ears are shaped to amplify the voices, so that they aren't drown out by background noise. So when another sound (like nails on a chalkboard) is within this frequency range, it is amplified instead of becoming white noise, and can be disorienting or even painful.",
"Source",
"This",
" and ",
"This",
" are also some interesting conclusions.",
"Edit: Added hypotheticals"
] |
[
"When a food has sugars on the nutritional value section, what type of sugar is it?"
] |
[
false
] | null |
[
"Here in the US, the type of sugar isn't identified. The sugar in unadulterated dairy is lactose (a complex disaccharide, or double sugar, composed of galactose and and glucose) but not listed as such. Sugars in a simple fruit jelly would be both fructose (fruit sugar) and sucrose (table sugar, from cane,) and possibly other sugars as well. There are a number of sugars used in manufacturing mass marketed foods, each with various rates of absorption/glycemic index. Labels list them all merely as \"sugar.\""
] |
[
"While not identified on the nutrition label, many if not all companies will list the different types in the ingredients. That may be a legal requirement, or they might do it because it allows them to split up the sugars so they make up a smaller percentage, allowing them to appear further down the list of ingredients and make consumers think there's not as much sugar in it. "
] |
[
"Following up on this, where do they draw the nutritional line between \"sugar,\" \"carbohydrate\" and \"fiber?\" My understanding is that chemically speaking, they're ",
" technically carbohydrates, but of varying saccharide chain length."
] |
[
"Can ears become insensitive to certain frequency ranges?"
] |
[
false
] |
My father is getting fever (for seemingly unidentified reasons) since more than 20 days, so I bought a thermometer. Now for some very weird reasons, he is not able to hear that 'beep' sound which notifies that thermometer has completed measurement at all? He is 60 but he otherwise can hear all the sounds, in fact even lower volume sounds pretty decently. He could hear very faint voice from his phone far away while measuring fever and mistook it for beep. I told him it was not thermometer. Then, when it was actually beeping, he was literally holding it in hand and asking me me if it is beeping??! I only tried with my mother once, but she also couldn't hear it, however, she hears less on one ear so it didn't surprise me much. That leads me to the question whether this is a known phenomenon? The only plausible explanation I could think of was that beep was of constant frequency (I don't know proper term for it but 's same sound you would get if you would supply a speaker with dc signal) and his eardrums don't vibrate at that frequency perhaps due to aging. PS : I'm new and couldn't decide what would be a better flair, physics or human body.
|
[
"The main issue isn’t the eardrums, but the hairs in the cochlea that sense individual frequencies.",
"Basically, the ear drum transmits vibrations through some other funky looking bones to a wound up bit of cartilage called the Cochlea. Inside the cochlea are strategically placed hairs. Depending on where in the cochlea the hairs are placed, they are sensitive to vibrations at specific frequencies. Each hair bundle is linked to nerves, so when the hair vibrates it stimulates the nerve which sends the signal to your brain. These hairs can be damaged (mostly due to loud noises) and do not regrow. As these hearing hairs are lost, the person will lose hearing at those frequencies.",
"Typically the high-frequency hairs are easier to destroy, and thus high-frequency hearing tends to go first.",
"The way this system works is actually quite a bit more complex than I have written hear, but the Wikipedia page on the Cochlea is pretty decent if you want a place to start."
] |
[
"Yes. It’s very common to have hearing loss in the upper ranges as we age. Our eardrums stop having the flexibility to vibrate at those frequencies as they get older. Totally normal. And might be helped with a hearing evaluation."
] |
[
"You can have dead ranges of the cochlea absolutely. Specific frequencies for which the hair cells don't work.",
"He's also ill at the moment which ",
" cause a middle ear infection, dropping his hearing by a bit. But a conductive loss like that should affect the low pitches more.",
"So this sudden loss for high pitch beeps over just 20 days is very concerning. Go to the GP now and make sure it is just a middle ear issue.",
"The sooner you catch a sudden loss like that, the better the chance we can fix that."
] |
[
"There appears to be a monumental military/science experiment going on in a Chinese desert, visible on Google Earth. Can anyone tell what exactly is happening here?"
] |
[
false
] | null |
[
"\"Exactly\" what is happening, no, but there are a LOT of reasons to do this kind of thing, not all of them requiring tin-foil hats. Monumental is a bit of an overstatement, it's mostly white plastic on the ground. Also of interest is that it doesn't follow topography. It's meant to be viewed orthogonally.",
"Examples - When you have an imaging system (satellite, airplane, blimp) you might need to calibrate/test it with a big target of specific known size and shape. (to be used with computer vision algorithms)",
"Weapons testing (looks like explosions nearby) Let's say you're developing a weapon to take out road intersections, airfields, whatever (cripple infrastructure, logistics) then you need something to shoot at for testing. Explosives are expensive and so is the damage to the target, the plastic just lets you know where you hit.",
"Artillery practice - If you had a regular grid, soldiers wouldn't have to think about their adjustments like they would in combat, so it forces them to do the whole process.",
"The crates and explosions are probably just that. Bomb testing. Explosives aren't simple, there is a lot of engineering that goes into making complex military targeting possible, and the only way to see if it will really work is to try it.",
"So basically I don't have a clue, but there are pretty easy explanations for all of this."
] |
[
"Having watched this area and activity for years when I was in the military. There's several things that you've found out here. Some of it is \"cool\" and some of it is just random.",
"The Gobi area is rife with military activity. The Chinese frequently use it as a military training area. They use it to test new Radars/Weapons Systems/Aircraft etc... Sometimes it's nothing more than just lame artillery training and other times we've been able to catch them testing some pretty advanced weapons systems they've developed to counter our systems. This was the case when I was able to watch them over the course of a few days testing out their \"Dragon Eye\" system before they placed it on their Luyang II DDG's. Which is their equivalent of our \"Aegis or Spy I\" system on our DDG's. ",
"The areas that are random roads are just training areas for artillery as speculated. ",
"There are other neat things to look out for as well out in that area. They frequently test their upcoming aircraft out there all the time. You may catch them testing out their XXJ fighter, which is their answer to the F-22 and the F-35. In addition, they are testing the J-10 out there as well. You may catch things like the Y-8AEW flying around as well monitoring the activity. ",
"Other neat areas in China to watch for military activity...Dinghai Shipyards outside of Shanghai. This is where a lot of their current DDG's that they are creating are housed and tested. If you look closely you can see SA-10 and SA-20 arrays just outside of the shipyards. Dalian Shipyards...they build and test most of their submarines here. Guangzhou and Fuzhou are also neat areas to watch as well. In addition to the Bohai Gulf. ",
"Up and down the Yangtze and Huang rivers you can catch glimpses of them conducting shallow water trials with their DDG's.",
"There ya go...have fun!"
] |
[
"For the record, 'tin foil hats' are actually quite effective at amplifying signals from two specific wavelengths.",
"MIT investigation",
"Among a fringe community of paranoids, aluminum helmets serve as the protective measure of choice against invasive radio signals. We investigate the efficacy of three aluminum helmet designs on a sample group of four individuals. Using a $250,000 network analyser, we find that although on average all helmets attenuate invasive radio frequencies in either directions (either emanating from an outside source, or emanating from the cranium of the subject), certain frequencies are in fact greatly amplified. These amplified frequencies coincide with radio bands reserved for government use according to the Federal Communication Commission (FCC). Statistical evidence suggests the use of helmets may in fact enhance the government's invasive abilities. We speculate that the government may in fact have started the helmet craze for this reason"
] |
[
"What is the scientific response to Shmuley Boteach's assertion on the probability of evolution"
] |
[
false
] |
[deleted]
|
[
"Shuffle a deck of cards.",
"The chance of that deck coming up by chance is 1:10",
".",
"By that logic, shuffling a deck of cards is impossible.",
"Evolution is a scientific fact and anyone arguing against it should pretty quickly be dismissed as lacking scientific expertise. "
] |
[
"He points out that mutations are generally bad, and uses this as an argument for intelligent design. ",
"The problem is, as long as these bad mutations are selected against, they die out. The one-in-a-million beneficial mutations are favored by natural selection, and thus become more common in the population. That's how evolution works."
] |
[
"mutations are generally bad",
"Most mutations are neither bad nor good. "
] |
[
"If clams have nerves but no brain to interpret signals, how can they feel pain?"
] |
[
false
] |
[deleted]
|
[
"Consider a human touching a hot pan. The body reacts by pulling away before the pain is ever 'felt'. Feeling the pain was not a prerequisite to reacting to it."
] |
[
"Its difficult to say how and what other animals feel, especially one as different from us as a clam. In reality, they likely don't \"feel\" anything, merely react to stimuli. That being said, even simple creatures like clams are still treated as if they can feel pain in the lab, and are treated with an anesthetic before cutting them.",
"I'm also not overly familiar with clams but if they have large enough ganglia they may have sensations like pain, but it would be difficult for us to interpret."
] |
[
"This question gets to the heart of what pain is - \"an unpleasant sensory and ",
" experience associated with actual or potential tissue damage, or described in terms of such damage,\" according to the ",
"IASP",
" (emphasis mine). Clams have a nervous system but do not have a brain capable of emotional or affective experience, so they don't feel \"pain\" in the way we humans typically think of it. That said, they are capable of nociception, or the processing of noxious stimuli. In this way, clams have the potential to respond to situations which may endanger them (e.g., escape).",
"The distinction between nociception and pain is frequently lost. Many more organisms are capable of nociception than pain as we conceptualize it."
] |
[
"Do all people of the world have similar bacteria on their bodies and in their homes, or are there distinct breeds of bacteria for every continent?"
] |
[
false
] |
Is there such a thing as New World bacteria and Old World bacteria?
|
[
"I'll add to this that, besides the fact that many human-living microbes and viruses are becoming more cosmopolitan due to the interconnectedness of the modern world, there is some seriously interesting stuff going on in microbiome studies.",
"The human microbiome is the sum total of species living on or inside us, and it differs from person to person in ways that we're only just beginning to understand. For example, there are results suggesting that humans can be divided into three discrete categories ",
"based on their gut bacteria",
" - apparently with ",
". So even if where you are obviously plays some part in determining your body's species assemblage, it may not play a very large part."
] |
[
"Just like how certain animals live in certain places, so do bacteria. Not every bacteria can be found everywhere. That being said, because of the increasing amount of globalization, more \"germs\" can be found in the same places. ",
"Take smallpox for example. Until the Europeans arrived from their respective continent, smallpox had never been encountered in the Americas and so the natives' immune systems did not know how to fight it off.",
"I assume you were looking for a more current answer, but that last example illustrates the early stages of mixing \"germs\". I use that term loosely because it encompasses a wide range of single- and multi-cellular life. ",
"Bird flu is a good example to use in today's world. The virus that causes it is adapted to bird, hence the name. It is usually only found in North America, though there have been cases in Asia as well. ",
"With the ability to fly across continents in less than a day, the spread of pathogens and other microbes has become more apparent than 100 years ago. "
] |
[
"The composition of species comprising the gut microbiome is heavily influenced by diet, which generally speaking is influenced by the environment of the host. Many studies have showcased that the typical Westerner's gut has a very different balance of the two major bacterial phyla found in the gut, compared to say someone from Africa, and a lot of this has to do with diet. Generally speaking, high-fat high-sugar (Western) diets result in a decrease in the presence of cellulolytic bacteria (",
"), while low-fat high-complex-carbohydrate diets (such as African diets) result in a proliferation of cellulolytic bacteria and decrease in bacteria less efficient at digesting plant cell walls (",
"). Recently, we have identified a bacterium in the gut of Japanese hosts that specifically targets unique polysaccharides found in components of seaweed, presumably there as a result of the constant ingestion of nori over thousands of years. ",
"So yes, there are distinctions to be made between the gut microbiomes of people on different continents. However, there is still a large contingent of bacterial species common to human gut microbiomes in general. ",
"Source: I have a PhD in biochemistry with a focus on the gut microbiome and the carbohydrate-digesting abilities of these bacteria"
] |
[
"Why is integration the opposite of differentiation?"
] |
[
false
] |
[deleted]
|
[
"Let f(x) be some function and let F(x) be the area-under-its-curve function (say, the area under f(x) between 0 and x).",
"Think about the derivative of this area function. If you increase x by a little bit, you increase F(x) by adding on approximately a rectangle of height f(x). There's a pretty good ",
"picture",
" of this on the Wikipedia ",
"article",
". From this, you can see that f(x) is the derivative of the area function F(x), so F(x) is an antiderivative of f(x)."
] |
[
"...and FWIW, ",
"here's",
" Herb Gross' wonderful lecture on the Fundamental Theorem. OP may or may not be able to jump into the middle of a lecture series, but it's a pretty swell explanation."
] |
[
"I always find math a little easier to understand when you think about in terms of describing a physical property. And with calc I find distance, velocity and acceleration. ",
"So what are you measuring when you take a derivative? You're measuring the rate of change of the dependent variable to the independent variable. This is the slope. If you plot your position vs time on a graph the slope can be calculated by rise over run or x/t in this case which is velecity. So now you can plot you chang in velocity with respect to time, the slope of that will give you (x/t)/t or x/t",
" which is accelaration. You can do this in reverse order by taking the area under the curves. The area under the curve tells you how much the dependent variable changes of specific range of the independent variable. Say your accelration is constant then the area under your curve is given by a rectangle with height a and length t. The area in the rectangle is given by (a) times (t), or (x/t",
" (t) which gives you units of x/t, or velocity. Note also that as t increase the area increase meaning v will not be constant but increase so it will have a slope not equal to zero, in this case it will be a triangle. Now you can find the area by .5(base)(height) if the base is time and the height is velocity you have .5(t)(x/t) so you get units x, now your back to position. Note here that now as you increase t, v (height on the triangle) also increases by the rate of the slope. This will cause the area to increase exponetially so x(t) will be a quadratic. "
] |
[
"If Earth was located in another orbit, further away from the sun, would the sky have a diferent color?"
] |
[
false
] |
I'm guessing "yes" but if we were really far away.
|
[
"If the atmosphere remained constant, then the only change you would see when pushing the Earth further away from the sun would be that everything would look darker, but the actual color (i.e. spectral color) of the sky would not change. The reason is that the color of the sky is only determined by two things: 1) the spectral profile of the sun and 2) the nature of the scattering centers (i.e. atoms, molecules, or particulates) that direct this light towards you. First of all, think about why you even see anything at all when you look at a spot in the sky far away from where the sun is. The sun's rays are pretty much parallel, so naively you would expect that you would see bright white light when looking directly at the sun and complete darkness (or starlight and such) when looking elsewhere. In fact, this is exactly what it looks like ",
"on the moon",
" or other celestial bodies that lack an atmosphere.",
"On Earth, on the other hand, part of the incident sunlight is scattered by the atoms and particulates in the atmosphere ",
"as shown here",
". On a clear day (and in the absence of pollution), most of the scattering is mediated by small atoms, which have a size far smaller than the wavelength of the incoming light. In this regime, the scattering you get is so-called ",
"Rayleigh scattering",
", which has the important property that its intensity scales as (1/l)",
" where l is the wavelength of the light. This means that the shorter components of sunlight (i.e. the blue components) are scattered more efficiently than the red components. This is why the sky looks blue on a clear day. ",
"On the other hand, on a cloudy day things would be different. The reason is that in contrast to atoms, the water droplets making up the clouds are on the same lengthscale as the wavelength of visible light. In this regime, the dominant scattering mechanism is so-called ",
"Mie scattering",
". Mie scattering has no strong wavelength dependence, so blue and red light are scattered about equally. This why clouds looks white, they simply scatter light that has the same spectral profile as the incoming sunlight, i.e. white! As a sidenote, Mie scattering is also the reason why paper looks white.",
"To sum it all up, the effective color of the sky only depends on the spectral profile of sunlight (or whatever the dominant source of illumination is), and the nature of the scattering centers that redirect this light downwards. Neglecting the changes to the atmosphere that would be caused by pushing the Earth further away from the sun, the color of the sky would not appreciable change. The only major effect would be that the total intensity of the sunlight would be far dimmer, so everything would just look darker. "
] |
[
"Unfortunately there's no simple answer to that. ",
"This has been asked before",
" and there are good answers in that thread. tl;dr: it's a combination of factors:"
] |
[
"The one thing I don't get is why the sky isn't violet seeing as it should be scattered the most efficient "
] |
[
"Are there screens that can display all colours?"
] |
[
false
] |
So it's impossible to make every colour using only three primaries, and what's more, apparently most screens use sRGB which only covers 30% of the CIE colour space. Is there anything that covers 100%?
|
[
"Covering more of the full horseshoe-shaped CIE chromaticity space in the ",
"Wikipedia link",
" comes down to two things:",
"To directly answer the original question, there is nothing that covers 100%.",
"In the future, there may be tech that uses tunable lasers to emit exact spectral color, hitting any point on the horseshoe curve. See ",
"this Q&A",
" for more info. This technology could get very close to perfect color reproduction.",
"On one side of the imaging coin is display technology; on the other is camera technology. Cameras that have more than RGB sensors are called ",
"hyperspectral",
" cameras. The camera equivalent of the tunable laser display would be called an ",
"imaging spectrometer",
"."
] |
[
"Hey, thanks for the answer and info! I had given up hope.",
"\nIf you don't mind, I'll ask a couple more questions.",
"We're a very long way from turning those lasers into a screen, right? It's nice to know there's a possible path though.",
"\nIn the meantime... looking at the wiki page on ",
"sRGB",
", I notice that the sRGB triangle gets brighter towards its edges than you'd expect. And they talk about it being non-linear - I'm guessing that much of the uncovered colour is actually shades ",
" the brightest and dullest colours? So the situation isn't quite as dire as ",
"this image",
" implies?",
"Hyperspectral imaging is pretty astonishing. It really highlights just how much data our eyes miss - there could be all kinds of structure in the light hitting one of our cells, and yet we'd just see it as one colour."
] |
[
"Yes, as far as I'm aware there have been no published successes (or even attempts) of making a display with tunable lasers, although you can buy screens and projectors that use fixed-wavelength lasers.",
"The reason that the sRGB triangle looks brighter at the edges is because that graphic is designed in a confusing way. In the graphic, the CIE horseshoe, which represents all spectral colors, is mapped into sRGB because the graphic itself is an sRGB png. So the spectral colors around the edge of the horseshoe are represented by their closest approximation in sRGB in the graphic. Normally, when such a graphic is made, the primaries of the sRGB triangle aren't represented by their actual values (pure R, G, and B) because those are already representing colors on the rim of the horseshoe, so they are represented by a less-saturated version of themselves. But in ",
" graphic, the sRGB triangle is the actual sRGB triangle, with fully-saturated primaries. So the sRGB space is shown twice--a version that's stretched into a horseshoe shape, and a version that appears in the position it would appear if the horseshoe was a true spectral representation.",
"To answer your question about how dire sRGB's coverage is, I would say it depends. If you're trying to build a display that can fool a hyperspectral camera into thinking it is looking at reality, instead of a display, the situation is indeed dire. If you're trying to fool a human, the situation is far less dire. The key thing to remember is that the CIE horseshoe represents all possible colors in the visible spectrum, which is actually more colors than any human eye can see. Most people are trichromats with RGB photoreceptors, meaning that human-visible color is actually an RGB triangle inside that horseshoe just like sRGB, only larger. Current RGB laser projectors may actually have a triangle that encloses the limit of human vision in the chromaticity diagram. However, the issues limiting the realism of these systems' color reproduction are not actually related to chromaticity range at all, but rather to dynamic range.",
"You mentioned the values in between the brightest and dullest sRGB colors that are uncovered, which is a good place to start this discussion. In digital representations, these uncovered, or skipped colors could only be represented by adding more bits. sRGB uses 24 bits to represent a color--8 bits for each primary, meaning that there are 2",
" (~16 million) possible colors in sRGB. If you used 16 bits per color channel, there would b",
" 248 (281 trillion) possible colors--the equivalent of an entire sRGB color space worth of colors in between every single possible color of the original sRGB color space! Dynamic range is the ratio between the luminosity of brightest possible white and the dimmest non-black representable color in the color model. You mentioned that sRGB is non-linear. What this means is that the apparent dynamic range is increased relative to a linear model, because human perception is more sensitive to differences between really dim pixels than between really bright ones. So ",
"sRGB has the equivalent dynamic range, as far as human perception is concerned, as a linear model using 11 bits instead of 8 per color channel.",
"The contrast ratio of a display is a physical dynamic range (the ratio between the whitest white and the blackest black at a given brightness setting). Since no display has a zero-luminosity black, they use this value instead of the dimmest representible non-black color as is used for the color model's dynamic range because of the issue of dividing by zero.",
"At currently achievable contrast ratios, there's no point in adding additional colors in between the colors of sRGB, because humans can't tell the difference between adjacent colors at 24 bits per color. However, an extremely bright display with very black blacks would result in human-perceptible differences between adjacent sRGB colors.",
"I believe that it is possible to make a display using RGB lasers, and source images that are HDR using more than 24 bits per color, that exceeds the practical limits of human vision--at least in terms of color reproduction for trichromats.",
"There is limited experimental evidence of the existence of functional tetrachromats, which are (extremely rare) humans with a fourth type of light receptor that peaks at a different wavelength than the normal RGB receptors, and who can be experimentally shown to be able to perceive differences between certain colors that trichromats cannot. The existence of non-funcional tetrachromats, who have four types of receptors but whose perception ability does not differ from trichromats, is supported by a much larger body of experimental evidence than the existence of functional tetrachromats. For a true functional tetrachromat, RGB display technology is intrinsically inadequate. The good news is that you only have to add one additional color channel to cover all humans even if functional tetrachromats exist, at least until we become cyborgs with hyperspectral eyes, or the ",
"mantis shrimp",
" achieves human levels of intelligence."
] |
[
"Is there a book that will get me from mechanics to quantum physics (or at least far ahead), that also teaches the math that is included?"
] |
[
false
] | null |
[
"No, there is no one single book which will do all of that.",
"For the math, there is Boas' ",
". She gives some physical examples varying from classical mechanics, electrodynamics, etc."
] |
[
"I am a Ph.D. student in physics."
] |
[
"Yes."
] |
[
"Why doesn't dark matter inexorably collapse into black holes?"
] |
[
false
] |
As I understand it, dark matter interacts with matter primarily of exclusively through gravitation. Given that, it seems that any clump of dark matter would inevitably grow denser as it attracted more dark matter. In the absence of normal repulsion forces (particle interaction-based pressure/quantum mechanical exclusion shenanigans) what prevents this clump from automatically collapsing into a point? In my head the evolution equations look like Euler's equations with a negative pressure/density dependence which sort of looks like a backwards heat equation-the father of singularities. Why isn't that what happens?
|
[
"Short answer: conservation of angular momentum and lack of friction.",
"Long answer: most dark matter lies in and around galactic disks. In this regime, gravity acts mostly Newtonian, and Newtonian gravity conserves angular momentum. This is the reason it's actually rather hard to capture moons, asteroids, etc., in the gravity of a larger body. For a massive body to gravitationally capture a smaller body, that smaller body must first come close enough to the larger body where the larger body is the dominant gravitational attractor. Then, the smaller body has to lose some of its angular momentum. If it doesn't, it will have the momentum to just escape out again.",
"Dark matter, as far as we know, only interacts gravitationally. The way you gravitationally capture a body requires some kind of interaction between the smaller body and either a third entity or itself (e.g. collision, so the smaller body gives its momentum to another body, or separation, where the smaller body breaks into multiple pieces, some of which escape while the rest are captured). The only way for the smaller body to lose the momentum it needs to lose through gravitational interaction is if a third body happened to pass by in the right trajectory to take some of that momentum. The parameters of this are pretty specific, so the probability of this randomly happening in a galactic disk is actually pretty small.",
"The problem with the picture in your head is that the heat equation models a dissipative field. Gravity, on the scale and in the mass ranges of dark matter, is a conservative field.",
"(End-note: because of the event horizon, black holes, too, can only interact gravitationally [except for Hawking radiation, but for large black holes this is extremely tiny]. There's no particular reason to think that there can't be dark matter black holes out in the cosmos. I would estimate they would look almost indistinguishable from regular-matter black holes.)"
] |
[
"I'm not sure what this response has to do with the comment you're responding to.",
"It's true that the black holes out there in the Universe most likely have negligible electric charge and therefore only interact gravitationally (barring any \"fifth forces\" through which they might also interact), but that's a happenstance of Nature, ",
" something which comes about \"because of the event horizon\" as you said in your top-level post. It's just not true that an event horizon requires a black hole to interact only gravitationally."
] |
[
"You could just as well ask why all the planets don't spiral into the Sun - after all, they only interact through gravity, right? Or why the stars in the galaxy don't all collapse into the center. It's the exact same question.",
"Except it isn't quite. Dark matter haloes are actually ",
" likely to collapse into black holes than the solar system or galaxies or galaxy clusters exactly ",
" they don't have electromagnetic interactions. All the systems I've talked about don't collapse, as you know, because they have angular momentum, they're moving too quickly relative to each other for gravity to overcome them. Electromagnetism leads to ",
", and the friction slows down moving particles and hastens that collapse. Because dark matter lacks friction, a cloud of dark matter loses less angular momentum than a cloud of gas and dust. This results in things like the ",
"Bullet Cluster",
", where a dark matter halo extends beyond the region occupied by gas in a cluster for exactly this reason."
] |
[
"Why, in a circuit, does electricity travel both directions in a junction and not just through the path of least resistance?"
] |
[
false
] | null |
[
"As ProblemIsInPants said, going through both resistances is the least resistive path. If you consider two (or more) resistors in parallel, the equivalent resistance is given by the formula",
"Req = (R1*R2)/(R1+R2)",
"So Req is ",
" smaller than R1 or R2 (check yourself if you don't believe me). It's always \"easier\" for the electricity to travel over both paths, rather than only go through one.",
"Another way to look at it, which is the one that I prefer, is that current is a byproduct of voltage and resistance. So, if I have two resistors and a voltage source (battery) wired in parallel, there is an applied voltage across ",
" resistors, and there is therefore current through both of them.",
"Basically, instead of thinking \"the battery makes a current, and the current splits at the junction,\" think \"the battery applies a voltage, and if there's voltage across a resistor, there's current, so there has to be current in both resistors.\""
] |
[
"Here's a metaphor: If you punch a bunch of holes in the bottom of a bucket of water, why doesn't all the water flow out just through the largest one? ",
"People sometimes say \"Electricity follows the path of least resistance.\" People also sometimes say things that are incorrect, and this is one of them. Electrical current follows ",
" available paths, but the ones with less resistance get more current. "
] |
[
"The path of least resistance is the one where both paths are used. Even if the other path has a huge resistance compared to the other one, some goes through there."
] |
[
"How was the speed of light first measured to some degree of accuracy?"
] |
[
false
] | null |
[
"https://en.wikipedia.org/wiki/Speed_of_light#First_measurement_attempts",
"This page has some listings you might find illuminating"
] |
[
"You can also try ",
"/r/askhistorians",
", ",
"/r/philosophyofscience",
", ",
"/r/historyofscience",
", and ",
"/r/historyofideas"
] |
[
"I believe it was by Rømer, who used the moons of Jupiter:",
"https://en.m.wikipedia.org/wiki/Rømer%27s_determination_of_the_speed_of_light"
] |
[
"What makes a gas a greenhouse gas? For example, what are the molecular properties of carbon dioxide (CO2) that allow it to retain heat, that nitrogen (N2) lacks?"
] |
[
false
] | null |
[
"Greenhouse gases absorb and re-emit infrared radiation. This means that instead of passing through the atmosphere and directly into space, some of the infrared radiation is re-emitted back toward the surface of the earth, increasing the net heat on the planet's surface. If it were re-emitted in the same direction that would be no problem, but the absorption and re-emission randomizes the direction of the light, effectively bouncing some of it back to the ground. Like a greenhouse does, hence \"greenhouse effect\". ",
"The molecular property you're looking for is frequencies of vibration. The ability to absorb and re-emit infrared comes from a molecule that has a change in energy of vibration frequencies that corresponds to infrared energies. They absorb the photon, vibrate at a higher frequency, and re-emit that photon as they return to their less energetic state. Vibration frequencies are characteristic to each molecule, and in fact are often used as an analytical tool to identify unknown ones. So, the gases with vibration frequencies that can be perturbed by infrared radiation are greenhouse gases while gases like nitrogen, oxygen, and argon are not. "
] |
[
"Just to tack on to the last sentence - molecules that have vibration frequencies that can be perturbed are polyatomic. This has to do with the vibrational frequency degrees of freedom. Linear molecules (all diatomic, some polyatomic) have 3N-5 degrees of freedom, where N is the number of atoms. So a diatomic molecule has (3x2)-5 = 1 vibration frequency. A polyatomic linear molecule like CO2 has (3x3)-5=4 vibrational frequencies (properly, as some below have noted, modes). Non-linear molecules have 3N-6 degrees of freedom, so a molecule with three atoms (like (edit) H2O) has (3x3)-6 = 3 vibrational frequencies (truly nodes). Therefore the non-linear molecule can be perturbed by radiation to bounce between different vibrational frequencies - absorbing and emitting the radiation - but the diatomic linear molecule (i.e. N2 or O2) only has one vibrational frequency (node), so it can't be perturbed to move a different one. "
] |
[
"So a diatomic molecule has (3x2)-5 = 1 vibration frequency.",
"This is technically right, but it's a bit more complex than that.",
"Saying that a diatomic molecule has one vibrational frequency sort of implies that it can only ever vibrate at a specific frequency. It would be more precise to say that they have one vibrational ",
". That mode has one fundamental frequency, but it can oscillate at multiples of that frequency. Each one of these frequencies has its own energy level.",
"To understand the difference between a frequency and a mode, check out ",
"these",
" animations. There are six different vibrational modes here. Each one of those modes can oscillate at different frequencies (imagine the animation running faster or slower).",
"Molecules can change the frequency of a certain mode by absorbing or emitting a photon. The energy (and frequency) of that photon must match the difference between the molecule's vibrational energy levels (conservation of energy).",
"However, all the energy levels within a certain mode are equally spaced (at low energies), so it takes the same amount of energy to go from the 1st to 2nd level and the 14th to 15th level. Furthermore, the molecule can only move up or down one energy level at a time (this is called a selection rule). Therefore, all transitions involve the same amount of energy, so a single vibrational mode only interacts with a single frequency of light, which brings us to your original conclusion.",
"Basically, saying that a diatomic molecule only has one vibrational frequency is actually a bit misleading from a mechanistic standpoint, but it brings you straight to the correct conclusion (only one frequency of light) without going into too much detail.",
"(In fact, I wouldn't be surprised if you knew all this already but were just trying to keep it simple. But I'm also writing this in case anyone wants to know the details.)"
] |
[
"How difficult is it to \"clean up\" radiation?"
] |
[
false
] |
Is dumping water and concrete on it the most efficient way we have as of now?
|
[
"Cleaning up radioactive waste is an extremely processing-intensive procedure. To dispose of radioactive waste (generally in the form of a thick sludge), it must be vitrified (basically locked away in glass) and sealed in thick metal canisters. Vitrification (and glass science in general) is a very complex science that has many processing challenges.",
"These canisters are then shipped off to Yucca Mtn and stored in a dry location deep underground."
] |
[
"There's no way to just make the radioactive particles stop being radioactive. You have to immerse them in something that prevents the radiation from escaping; concrete is used because it strikes a good balance between ease of transport/use and power to block radioactivity, and water is used because it's easy to remove things from water."
] |
[
"Does the water that is used to cool the fuel rods in a power plant become radioactive? Does it have to be filtered or processed somehow before it is released into the environment?"
] |
[
"Question about relativity and I think what is called the \"twin's paradox\" after reading Hawking's \"A Briefer History of Time.\""
] |
[
false
] |
Okay, so one twin is born at sea level and the other on the top of, say, a mountain 100 million miles high. The twin on the top of the mountain will age slower, let's say twice as slow. If the sea-level twin were to take a telescope that could see faster than the speed of light, in instant-time, would the mountain-twin be moving in slow motion? What if the telescope were limited by the speed of light reflected off the mountain twin's skin? (I believe telescopes can't actually see that far.) *I think I am correct in saying that the person closer to gravity ages faster, not positive. It has been 8 months since I read Hawking's book.
|
[
"Okay, so one twin is born at sea level and the other on the top of, say, a mountain 100 million miles high.",
"We're going to change that to \"100 miles\" in order to at least keep our thought experiment in the realm of the not-entirely-ridiculous. It doesn't affect the maths.",
"The twin on the top of the mountain will age slower, let's say twice as slow.",
"Faster. Not slower. (And not nearly by a factor of two, but again, that's just a scalar value. It doesn't change the maths.)",
"If the sea-level twin were to take a telescope that could see faster than the speed of light, in instant-time, would the mountain-twin be moving in slow motion?",
"Flip the sea-level and mountain twins, and the answer is yes. You don't even need the magic telescope. Though the difference would be ",
" difficult to detect. It's better to imagine that the sea-level twin has a clock that broadcasts a radio signal of a very particularly chosen frequency. The twin at the top of the mountain will observe that the clock at sea level ticks more slowly than he would expect it to if he didn't understand general relativity.",
"I think I am correct in saying that the person closer to gravity ages faster, not positive.",
"It's clearest to think of this in terms of inertial and accelerated reference frames. Gravity is just a particular case of an accelerated reference frame. I'll explain how that works in a minute.",
"If you're moving inertially — that is to say, your accelerometer measures no acceleration — and you're observing a clock that's also moving inertially but at some velocity relative to you, your own clock will tick faster than the distant clock. If we restrict ourselves to inertial motion only, the local clock is always the fastest clock.",
"If you're in an accelerated reference frame, then clocks in a ",
" accelerated reference frame will be observed by you to tick more slowly than your own, while clocks in a ",
" accelerated reference frame (including the unaccelerated reference frame of inertial motion) will tick more quickly than your own.",
"Around the Earth, this equates to radial distance. If I'm on the surface and you're at the top of a 100-mile-tall tower, I will see your clock tick more quickly than mine, because your reference frame is ",
" accelerated than my own, by virtue of your being at a higher altitude.",
"These two effects come into play in the GPS system. GPS satellites are equipped with precise clocks, and its these clocks that GPS receivers on the surface use to triangulate their positions. Because these satellites are high above the Earth's surface, they tick more quickly than ground-based clocks. But because they're moving at orbital speeds, they tick more slowly than ground based clocks. The two effects do not exactly cancel out. If I remember correctly, the slowing-down effect of orbital motion is smaller than the speeding-up effect of high altitude, so the net result is that the clocks run ",
" faster than surface-bound clocks, but not as much faster as would be predicted by taking into account only their altitude.",
"But it's a very slight difference, on the order of a few dozen microseconds per day. We only notice because the positioning accuracy of GPS is a function of how accurate the orbiting clocks are compared to ground-based clocks. Over time it would add up if not compensated for, so the orbiting clocks must be periodically corrected to stay in sync with ground-based clocks."
] |
[
"No question is stupid. All corrections that are applied are applied during the processing of the data. The data you receive from a GPS satellite is, more or less, the range (uncorrected for satellite error) in meters (based off of satellite clock transmission time and ground receipt time multiplied by the speed of light) as well as carrier phase (a measure of differential position to the satellite since tracking began). The satellite clocks do get updated but it's not very often (maybe a couple times a month).",
": All corrections (satellite clock, tropospheric, ionospheric, relativity, clock drift, etc.) are applied during post-processing of the data."
] |
[
"Great response, I'm just here to clarify the relativity portion of the GPS explanation.",
"Relativity and clock drift are two different things. The error due to relativity on the GPS signal is something on the order of 10s of nanoseconds (equates to a couple meters of accuracy) at any given time and arises due to the relative (duh) rotational motion of the GPS spacecraft and the Earth. The clock drift is not due to relativity, but rather due to imperfections in the clock frequency generation. ",
"There are two main types of GPS clocks used, Rubidium and Cesium. Rubidium clocks tend to have very great frequency stability but they also usually show an offset from the desired frequency. Cesium clocks tend to drift slightly around the desired frequency and average to be very close to the required oscillation frequency. GPS NAV messages contain both the clock offset (local to GPS time) of the satellite in question as well as the clock drift rate (on the order of 10",
" seconds per second). These values are required to compensate for satellite clock error in point positioning (satellite clock error can be tens to hundreds of meters), whereas relativity is not required (on the order of single meters)."
] |
[
"Do the different types of genetic mutation occur at equal rates?"
] |
[
false
] |
Specifically talking about transition, transversion, addition, and deletion (or more, if there are other types I haven't read about yet).
|
[
"I imagine substitution is more common than indel, because the latter produces much worse effects (frameshift mutation). So there should be a strong selection pressure against indels. Transition (A-G or C-T) is much more common than transversion (A-C or G-T).",
"Overall, the most common mutation is a ribonucleotide insertion. This occurs during replication of the DNA strand, when a ribose-nucleotide is inserted rather than a deoxyribose-nucleotide. This occurs every 600-1000 basepairs.",
"Spontaneous mutations are also quite common. For example, a guanin can randomly react with an oxygen radical and form an 8-oxoguanine. These mutations are usually quickly repaired.",
"Complex mutations (like CNV, repeat expansions, transposon insertion) are very rare."
] |
[
"I'm designing a simulation for bacterial mutation. I saw the overall mutation rate was on the order of 10",
" per base pair and S. Aureus has 2.8x10",
" base pairs approximately. Thanks for the info, with that I can make the simulation a little more realistic."
] |
[
"I see. Prokaryotes are more complicated. You may need to factor in ",
"GC skew",
" (different strands of dsDNA have different mutation rates) and ",
"mutational codon bias",
" (different codons have different mutation rates). To be completely accurate, you also need to look into repair rates (or maybe your mutation rate includes repairs?). Good luck."
] |
[
"How small can a gas planet be?"
] |
[
false
] | null |
[
"Uranus has the lowest mass",
"Uranus is slightly larger in mass.",
"Which one is it? :S"
] |
[
"This is very temperature dependent, the reason planets lose atoms/molecules of gas is mainly due to thermal loss, atoms which have sufficient energy to get to escape velocity and leave the planet. For small planets the energy required is very low (compared with say, the same thing on the earth) and a high fraction of molecules in the gas have an energy above escape velocity, leading to rapid loss until the \"planet\" would boil off entirely. ",
"If however the planet was in orbit of a dead star (say a brown dwarf) then it could be at a very low temperature (~3 Kelvin) and very small bound states of gas might be possible, but there is no obvious way these could be observed and probably wouldn't be considered planets anyway but \"gas dwarfs\"."
] |
[
"Because of the (currently considered correct) model of planetary formation, called \"core accretion\", it is estimated that a planet must be ~5-10 the mass of earth. While it might be that much larger than mass of earth, it's diameter will be larger, because of an average lower density in gas planets. But, because this model says that planets will accumulate dust and rocks in the solar nebula, the planet must reach that size before the gravitational field will be strong enough to accumulate gases. "
] |
[
"Are poodles really hypoallergenic?"
] |
[
false
] |
I know several people who have poodles because they are supposedly "hypoallergenic." What's the basis of this claim? What gives a poodle this magical quality that other dogs don't have?
|
[
"Relevant wiki link.",
" The gist of it is that poodles are not truly hypoallergenic; all dogs shed and therefore can provoke allergies. However, their fur sheds less frequently, and loose fur and dander tends to be more effectively trapped by their curly fur than that of other dog breeds. In addition, many poodles are cleaned and groomed more often than other breeds due to being more of a \"showpiece\", if you will, and this removes dander and saliva, the other common allergen. Thus, while poodles are not hypoallergenic, they are less likely to provoke an allergic response due to their lower dander output."
] |
[
"As far as I'm aware, hair and fur are both keratin growing out of follicles. I'm not sure what the distinction you're making is."
] |
[
"Thanks for this. However, in regards to your statement that they shed allergenic proteins less frequently-- By following links in the article you referenced, I found a reference to a study that tested levels of allergens in the homes of dog owners: ",
"http://www.ingentaconnect.com/content/ocean/ajra",
"No classification scheme showed that the level of dog allergen in homes with hypoallergenic dogs differed from other homes. "
] |
[
"Please help me help 8-year-olds understand how heat and light affect evaporation!"
] |
[
false
] |
I'm an elementary school teacher preparing a science lesson for my students' upcoming unit on the water cycle. I'm not sure my school administration envisioned the teachers they're trusting to build the school's curriculum going to reddit for answers, but all of the textbooks and websites I usually check to make sure I'm not completely screwing up the way my students understand the universe have slightly different answers on this one. I don't want to synthesize them into my own best guess and, in doing so, risk giving incorrect information to my students. My kids will be doing an experiment which will result in their understanding that water evaporates more quickly when it's left in sunlight. All of my sources are pretty clear about the role of heat, and I anticipate that my students will definitely get that increased heat results in an increased rate of evaporation--I'm going to activate prior knowledge by bringing up boiling water for them to reach this conclusion if they don't get there from the experiment alone. My sources are less clear on the impact of light. Some imply that light has a unique role in making the water evaporate more quickly. None of those explain how. The others don't mention light at all. I need to know if light affects the rate of evaporation and, if so, how. If possible, language that I can translate into 8-year-old-speak would be appreciated! Thank you!
|
[
"1) Light directly heats up the water. Refer back to what they know about hot water.",
"2) Light itself is made of photons which are basically packets of energy where the energy depends on the color of the light. For example, green light is made of photons with about 2.33 eV of energy. For water at room temperature, the enthalpy of evaporation is 44000 Joules/mole which equates to about 0.45 eV/H20 molecule. This is smaller than the photon energy of visible light which suggests that photons can directly vaporize water molecules through a quantized transfer of energy. This may not occur much or at all in nature because you have to consider whether visible photons ever interact with water molecules. Considering water is clear, we would be inclined to think that the visible light passes through but there might be a small probability for this interaction. \nThis may be too advanced for 8 year olds but other than the light heating up the water I do not see what else could be going on. But hey, in my mind, no child is too young to learn about quantum mechanics. Let me know if you need elaboration on anything."
] |
[
"The reason things evaporate is that not all of the water molecules in the glass of water (or whatever) have exactly the same energy. ",
"There is a certain threshold amount of energy that a water molecule needs in order to leave the liquid body of water it is in and become a gaseous molecule. Imagine a gatekeeper that you need to pay some amount of money in order to get past. In this case, the amount of money needed to open the gate is the amount of energy needed to evaporate. ",
"Cool water evaporates even though it has an average temperature well below its boiling point because sometimes a few of its molecules happen to get enough energy to open the gate. These molecules are rare since they need way more than the average amount of money to get to evaporate. But what happens when the sun heats up the water? Now the average temperature (amount of money) of the water is higher. This means that if a water molecule wants to escape it doesn't need to be quite as rich relative to its neighbors. This means that the likelihood that he randomly comes upon enough money to open the gate is higher, so the evaporation rate is faster. "
] |
[
"Thank you for answering. This makes sense to me, and I know I can easily make this example work for my students. ",
"I think that my language in framing and phrasing my question was a little unclear, though--in fact, I think some of my word choices reveal that I need to do some more looking into what I mean by concepts I hadn't really thought I had to think through too much, like \"light\" and \"heat up.\"",
"I think I actually have a pretty good grasp on the process you're describing (although, again, I'm totally going to steal your gatekeeper analogy to head off all of the \"But why hasn't ALL of the water evaporated??\" questions I know I'm going to get). My breakdown is occurring here:",
"But what happens when the sun heats up the water? ",
"Could you explain to me how exactly sunlight heats up the water? I understand the impact (heat), but I'm guess I'm realizing that I don't really have a great understanding of how, um, light...works. Which makes me feel really, really silly to say. ",
"Thank you again!"
] |
[
"Is there a lifeform which does not use DNA/RNA for its genetic code?"
] |
[
false
] |
[deleted]
|
[
"I’ve taken more genetics courses and read more genetics papers than I care to admit to, but I’ve never heard of such a thing. DNA/RNA is one of the basic necessities of life. Are you sure you didn’t read a paper that was extrapolating the idea of DNA-less life?"
] |
[
"It was probably that strain of Halomonadaceae from Mono Lake that was hyped a few years ago, because it was thought it could substitute arsenate for phosphate in its DNA, which turned out to be not so correct."
] |
[
"https://digital.library.unt.edu/ark:/67531/metadc832429/m2/1/high_res_d/1016932.pdf",
"That was the original, but it's largely refuted by now. The strain is arsenic tolerant, but depends on phosphate."
] |
[
"Do oxygen levels drop in areas during night time?"
] |
[
false
] |
[deleted]
|
[
"I'm not an expert, but some plants do produce oxygen at night. Orchids are an example. "
] |
[
"Yes, plants convert oxygen and sugars into energy and carbon dioxide the entire day. But while photosynthesis takes place the amount the plant needs for itself is negligible compared to the amount it releases into its enviroment. ",
"So at night most plants release carbon dioxide and no oxygen and thus the oxygen level is slightly decreased."
] |
[
"Yes they are. But as long as photosynthesis occurs, the amount of oxygen produce is larger than the amount consumed. At night, photosynthesis stops, but plants keep on consuming oxygen. (the total consumption of oxygen is lower than the production of oxygen if you take the average through the year). You learn that in basic biology."
] |
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