title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Bones crushed and used for mortar. Can the DNA be found?"
] | [
false
] | null | [
"Hi tizzlenomics thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the fo... | [
"Archaeology biology"
] | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"/r/AskScience",
"/r/HomeworkHelp",
"guidelines.",
"/r/AskMath",
"/r/AskPhysics",
... |
[
"What is the biological advantage of blushing?"
] | [
false
] | When some people get embarrassed they turn red, causing them to blush more. Body, how are you helping me? | [
"I think ",
"this article",
" might have what you need. He explores various reasons for why we blush in different situations."
] | [
"Now I only have a couple semesters of bio under my belt but it may be linked to getting a mate. Back when we first separated from our ape ancestor, the best male and females would mate. Now if you notice that when you are sick you lose color. So maybe if you blushed, then you would be perceived as being more he... | [
"I don't see any advantage mentioned."
] |
[
"How does propulsion work in space?"
] | [
false
] | [deleted] | [
"Imagine two ice skaters on an ice rink (imagine the ice is frictionless for simplicity's sake). When one pushes the other, they both move away from each other. If they have equal mass, they move away from each other at the same speed. This is conservation of momentum at work.",
"Now imagine one ice skater thr... | [
"Imagine two ice skaters on an ice rink (imagine the ice is frictionless for simplicity's sake). When one pushes the other, they both move away from each other. If they have equal mass, they move away from each other at the same speed. This is conservation of momentum at work.",
"Now imagine one ice skater thr... | [
"Conservation of momentum.\nBasically, a rocket (or ion engine) will shoot small particles at one end, at a high speed. This causes the body of the rocket to move a bit forward.\nDid you ever shoot a gun? It's pretty much like the recoil of the gun."
] |
[
"Why do flashing images cause seizures?"
] | [
false
] | [deleted] | [
"I'm hoping someone with better knowledge comes along, but here's my rough understanding:",
"First, if you haven't already, have a read of ",
"this",
", it explains what particular stimuli can trigger seizures in people with photo-sensitive epilepsy (PSE).\nThen have a read about ",
"epilepsy",
" in gener... | [
"So you are saying that it is similar \nto a operating systems failure due to a \nrelatively unrestricted processing of a function or a \nmemory leak— i.e., how unrelated programs can crash \ndue to a single program heavily using available \nresources? "
] | [
"No - what he is saying is that it is like ",
"soldiers marching in step over a bridge",
" making the bridge resonate in time with their steps."
] |
[
"What is the status on our ability to teleport objects/living organisms?"
] | [
false
] | Has it ever been done? Will it ever be possible? | [
"No it has never been done and no it will never be possible. I really wish that it weren't such a common thing in sci-fi, because it simply does not have any basis in scientific fact."
] | [
"Can you expand on why it's not possible?"
] | [
"Point teleportation is impossible because it breaks relativity. Even if it's constrained to be slower than the speed of light, the math of relativity just is destroyed on a fundamental level if worldlines are allowed to have step discontinuities.",
"Decomposition teleportation (where you get broken down and reas... |
[
"Does the 13.7 billion year age of our universe only apply in our frame of reference?"
] | [
false
] | I have often heard the age of our universe given as 13.7 billion years. However if time is relative to velocity and gravitational fields does this mean different parts of the universe have experienced different amounts of time since the big bang? Also if the earth is only 4.5 billion years old then what frame of refere... | [
"However if time is relative to velocity and gravitational fields does this mean different parts of the universe have experienced different amounts of time since the big bang?",
"Not different parts, but different observers, yes. The number of 13.7 billion years holds for so called comoving observers, observers w... | [
"It should be possible to put a number on that... let me see... ignoring the expansion of the Universe it's like .999998 times 13.7 billion years, so it's not significant."
] | [
"I cannot answer this in full I believe you will want to read into the ",
"Hubble Constant",
" as it was a major breakthrough in being able to age the universe.",
"EDIT: Removed irrelevant information."
] |
[
"Why isnt geothermal energy not widely used?"
] | [
false
] | Since it can do the same thing nuclear reactors do and its basically free and has more energy potential why is it so under utilized? | [
"To start, my answer is going to focus on ",
"geothermal power",
", i.e., using geothermal energy to generate electricity, and ignore other uses of geothermal energy, like ",
"geothermal heating",
", since OP seems to mainly be interested in electricity generation (at least based on the relationship drawn t... | [
"Only thing I’ll add to is existing bore holes rarely can be leveraged for anything other than data. Oil and Gas rely heavily on formation pressures or induced pressures to lift gas and liquids to surface. To pump fluid for purpose of geothermal a pump needs to be run down hole which usually means a much wider bore... | [
"In addition to the other comments, it should be noted that geothermal sources can be quite toxic. ",
"The Hawaii one",
" has had continuous issues with hydrogen sulfide gas releases. It's a great source of energy, but not without its own dangers."
] |
[
"Are solar systems and galaxies fractal iterations of the atomic structure?"
] | [
false
] | [deleted] | [
"There are not really any similarities in how matter on small and large scales form structures.",
"As for some kind of golden ratio, even just for astronomical objects, there is such a large spread in planet, star, solar system and galaxy size that I don't believe any relationship exists."
] | [
"Just a side note: the golden ratio isn't as important in Nature as you've heard. The spiral shapes of galaxies, hurricanes and mollusk shells are completely unrelated to the golden ratio and the golden spiral.",
"There are several types of spirals (archimedean, logarithmic, etc.), and different spirals of the sa... | [
"There are similarities, sure, but when you really get down to it, electrons aren't just little spheres rotating around a nucleus. They're more accurately described as wave functions, meaning their position isn't as well defined as a planet's. Also, the solar system (on a large scale) is pretty much held together e... |
[
"How many fundamental physical fields are there?"
] | [
false
] | This question might be the result of my own misconceptions, but I know that there exists the Higgs field, and the electro-magnetic field (is this better phrased as the electroweak-magnetic field)? I'm wondering what other fields are there? Is there a gravity field? A strong field? Also, are all fields in physics Hilber... | [
"It's easy to forget one here or there, and to some extent it is arguable what is \"fundamental\" (I'm grouping fields that transform as a doublet as a single field but with multiple field components related by a symmetry, but some might describe them as two separate fields, same goes for left and right handed fiel... | [
"Although you could look at these fields as just particular instances of the first four fields at the top.",
"No that's just wrong. The gauge fields do not describe the fermions. "
] | [
"Oh and about the \"sort of\", this paper is very readable:",
"http://philsci-archive.pitt.edu/2673/",
"Even just the introduction may answer your question better than I can."
] |
[
"Since pi is irrational, is there a point in pi's decimals where there are 1 billion subsequent threes?"
] | [
false
] | null | [
"Probably, but not just because it's irrational. For example, the ",
"Liouville constant",
" is irrational but has only 0's and 1's in its decimal expansion.",
"However, pi is strongly conjectured to be a ",
"normal number",
". If this is the case, you certainly can find a billion 3's in a row in its deci... | [
"The Borwein-Bailey-Plouff formula. But it doesn't work backwards."
] | [
"If pi is a normal number, then yes. ",
"As existentialhero pointed out, that conjecture is not yet proven. If it's true, you'd still have to go really, really deep into pi to find that particular combination of numbers with any non-negligible probability."
] |
[
"How does fat move around the body? How does the body choose where the fat goes?"
] | [
false
] | [deleted] | [
"Fat is not very soluble in the mostly-water solution that is your blood, so it gets transported in soluble particles called lipoproteins. There isn't enough battery left on my laptop to type up an answer regarding the body's choice of where the fat goes, but this is mostly a cop-out because I'm much less well vers... | [
"When you absorb fat from your digestive system, it gets transported across the intestinal barrier first with the help of bile acids and some transporter proteins. Then it gets packaged into what are called Chylomicrons: these are just large \"Lipoprotein\" particles, with a large droplets of lipids surrounded by s... | [
"Obligatory \"I didn't downvote you but...\"",
"We (the people who browse askscience, not we as in 'scientists') may not have a good idea of why fat is distributed the way it is, but we can surmise that your guess seems pretty unlikely. In the post-physeal-fusion human body, not much seems to be dependent on grav... |
[
"Why is Dyslexia being removed as a diagnosis?"
] | [
false
] | The latest version of DSM5 is changing dyslexia to specific learning difficulties, being dyslexic will still be mentioned within your diagnoses but it won't be your diagnosis. As quoted from there website Learning Disorder has been changed to Specific Learning Disorder and the previous types of Learning Disorder (Dysle... | [
"\"Learning Disorder has been changed to Specific Learning Disorder\"",
"it's being absorbed by something else that is more descriptive. all dyslexia is not the same."
] | [
"As someone who had a moderately unusual form of dyslexia as a child and had to deal with constant misunderstandings from teachers about how it might affect me, I just want to say that this change to the DSMS seems like a very good thing."
] | [
"As someone who had a moderately unusual form of dyslexia as a child and had to deal with constant misunderstandings from teachers about how it might affect me, I just want to say that this change to the DSMS seems like a very good thing."
] |
[
"Why can't we make a camera that captures images that look the same as how we see them?"
] | [
false
] | [deleted] | [
"What you should be asking is, \"why can't we make a camera that captures images exactly how we see them and reproduce them in a medium which is visually indistinguishable from the original scene?\"",
"Designing a camera that captures information identical to the photoreceptor layer of your retina is simply a mat... | [
"The main reason why most cameras do not have the ability to capture images that look the same as what we see is that ",
"the human eye has a roughly logarithmic response function",
". This means that something that is 10 times brighter than a reference object might only ",
" ~ 2 times brighter to our eyes. ... | [
"Any change away from RGB will have to introduce more primary colors, and in basically all display technologies that has a huge tradeoff in spatial resolution. It's only been in the past few years that any consumer products have included spatial resolution that's good enough to stop worrying about; adding another s... |
[
"How does polarized light work?"
] | [
false
] | [deleted] | [
"It's early in the morning, but I'll try. So, we have these abstract ideas that we call electric and magnetic fields. What do they do, and what causes them, you ask.",
"Magnetic fields cause moving charges particles to change direction. ",
"Electric fields are caused by charges (just sitting there) and by c... | [
"It's early in the morning, but I'll try. So, we have these abstract ideas that we call electric and magnetic fields. What do they do, and what causes them, you ask.",
"Magnetic fields cause moving charges particles to change direction. ",
"Electric fields are caused by charges (just sitting there) and by c... | [
"Well, seems nobody's taken on optically active enantiomers directly, so I'll give it a shot. Instead of dealing with the somewhat-difficult math involved, I'm just going to go with an physical analogy here. But it does have some 'depth' to it:",
"Imagine you're drilling a hole in a flat wall made out of some ord... |
[
"If Mars’ atmosphere is primarily Carbon Dioxide, why isn’t it succumbing to the green house effect that we’re trying to avoid on our planet (by limiting CO2)?"
] | [
false
] | null | [
"There ",
" a greenhouse on Mars caused by the predominantly CO2 atmosphere, but it's relatively small because the atmosphere is so thin. ",
"For the three planets that experience a significant greenhouse effect, the amount of warming is strongly a function of how thick the atmosphere is:",
"The expected glob... | [
"Excellent question!",
"While Venus is about 30% closer to the Sun - and should therefore receive about twice as much sunlight - it's also more than twice as reflective as Earth. It turns out our oceans are pretty dark and absorb most of the sunlight that hits them, while Venus' cloud tops reflect the majority of... | [
"Why is the expected temperature for Venus from sunlight alone so much colder than the Earth? Is it the albedo difference? Is the value for the Earth taking into account the Earth's oceans?"
] |
[
"Do tall people have larger internal organs? If not, how do their bodies fill the extra space?"
] | [
false
] | null | [
"General surgeon here.",
"Larger people have larger organs in general for the reasons listed above, I’ve never read any studies on it, it’s just what I see at work. The cavities in your bodies adjust to the need for the organs IN MOST SITUATIONS.",
"Symptomatic Pectus excavatum is a good example of what happen... | [
"Just because somebody is strictly tall doesn't necessarily mean they're volumetrically larger. I mean, you obviously have tall and lanky vs. short and stout.",
", there are physical factors that may directly affect organ size. The most obvious is the heart. In taller people, the hearts have to work harder to pum... | [
"I know essentially nothing about congenital heart defects. They’re incredibly complex and only pediatric doctors deal with them, and only a small subset of them ",
"Edit: thought more about it. If she was part grinch, then her heart could have been up to 3x too small. Studies on this were done by the esteemed... |
[
"How do chemists assemble molecules in specific shapes?"
] | [
false
] | I was reading a Joe Schwartz book where he mentions the development of a molecule with 60 carbon atoms in the shape of a soccer ball. How do they do that? | [
"It's kind of like making snowflakes, they just self-assemble under the right conditions. For C60, you make soot, and the soot contains C60 along with other molecules. Then all you have to do ",
"is separate out the C60",
".",
"Here's a ",
"video of how to make buckyballs in your garage",
"."
] | [
"In chemical synthesis, there are certain reactions that are known as sterioselective - that is, the reaction happens in a way that is selective to one specific shape over another. A lot of this has to do with the reagents you are selecting and how they interact in three dimentions. By selecting reactions and reage... | [
"Naw, we're not actually good enough at synthesis to produce them chemically. (although there's probably a lot of money in it if you can find a good way). By and large we just vaporize carbon with an electrical arc discharge, resulting in a plasma of free carbon atoms and molecular fragments, where a tiny amount wi... |
[
"How positive charges distribute on the surface of a sphere?"
] | [
false
] | I've been thinking about it and can't find a reasonable explanation. I can understand why it happens to negatively charged sphere, because the electrons CAN move. But if you remove the electrons from the sphere, how do electrons rearrange in the interior of the object? | [
"Empty valance electron spots are called \"holes\". They holes have an effective positive charge since they are the places where, with an electron, would have neutral charge. ",
"These holes can \"move\" in the sense that electrons can jump between valance band holes. When an electron moves from a full valance ba... | [
"Yes, it's perfectly fine to model holes as positive particles that moves for most cases. ",
"Just like electrons they are trying to distribute themselves to minimize the electrostatic potential of the system, which happens to be done by placing them all on the surface with uniform spacing for a sphere."
] | [
"But why is the arrangement - negative inside and positive outside? Can I conclude that the \"holes\" act just like a free \"positive electron\" and want to stack in the outer shell?"
] |
[
"Why does my microwave heat up the cup of coffee but not the air around it?"
] | [
false
] | I set the timer to five minutes and when I reach into the microwave, my coffee and cup are hot. But the inside of the microwave itself isn't overly warm. Why is that? Is it how electromagnetic waves travel through different mediums? | [
"The microwaves are tuned at a specific frequency to interact with water and other polar molecules. So all the energy is absorbed by the food, and a negligible amount is absorbed by the different components of air.",
"http://en.wikipedia.org/wiki/Dielectric_heating"
] | [
"You linked to the right article, but your description is incorrect; ",
"there's nothing particularly special about 2.4 gigahertz",
":",
"It's a common misconception that the microwaves in a microwave oven excite a natural resonance in water. The frequency of a microwave oven is well below any natural resonan... | [
"None that would taste good!",
"But in general, there are \"microwave safe\" containers that you can put in the microwave that won't get hot. I think you would need to have an absence (or at least a very low concentration) of polar molecules."
] |
[
"Why hasn't 'ugly' been bred out?"
] | [
false
] | Surely if more attractive people are more likely to produce offspring there should be a trend towards more attractive people. | [
"Genetics is complicated. The shape of your face (for instance) is determined by a rather complicated interplay between a lot of different genes, so the effect a particular gene has depends on all the other genes in your genome. ",
"Perhaps the same gene which gives your father a perfectly-shaped nose will, when ... | [
"To look at it socially, marriage for a long time wasn't based on attractiveness, but it was based on someone being a good provider/hunter for a future family, or possibly the marriage was arranged by family to help solidify business or social connections. ",
"Like Jorgesum said about the genetic factors, there's... | [
"You're right, sexiness and beauty are all about sexual selection, which plays a big role in evolutionary processes. But:",
"Purifying selection",
" exerts weaker effects on the genes controlling phenotypes that are a result of recessive and complex traits as opposed to simple dominant traits. Beauty is undou... |
[
"The Double Slit Experiment."
] | [
false
] | Hi everyone, I've recently been introduced to the double slit experiment, and I am really bothered by it's results. To me, it's perfectly acceptable that matter can exist in both wave and/or partical form. What I dislike, is the idea that it "chooses" to exist in partical form when it's being observed. It's impossible ... | [
"A good way to think of this is that it's not ",
" that behaves weirdly. Nature is not the one with the problem, ",
" are. We are so used to dealing with objects like waves and particles that we can not wrap our heads around things that behave as oddly as quantum objects. Remember, particles and waves are si... | [
"At first I had the same reaction to this result, however a college professor of mine helped to explain it a little better. First of all this is considered to be a quantum physics experiment, and as such it obeys very different rules than most other experiments. Most things in quantum physics are not determined thr... | [
"We are capable of observing which slit it goes through without influencing the interference pattern, at least according to this recent paper: ",
"http://arstechnica.com/science/2012/05/disentangling-the-wave-particle-duality-in-the-double-slit-experiment/",
"I would love it if someone could explain the implica... |
[
"Could the moon be \"bumped\" out of orbit by a meteor strike and be sucked in by the Earth's gravity?"
] | [
false
] | I've always been intrigued by the fact that the moon orbits the Earth and doesn't get "sucked in" by the Earth's gravity despite the bombardment it receives from meteor strikes. I understand its centripetal force keeps it in a stable orbit, but could a sufficiently large meteor strike slow it down enough that it would ... | [
"This isn't quite right. It's not just some coincidence that the moon has exactly the correct velocity and radius of orbit to make the centrifugal force balance gravity. A better way of thinking about is to say that using fact that the moon is in a circular orbit, we can use the handy equation F=mv",
" /r to work... | [
"Because the moon is actually orbiting the sun. Well, obviously it orbits the earth as well, but if you calculate the gravitational force on the moon due to the earth and the sun, you'll find that the moon orbits the sun much more than it orbits the earth.",
"Whoa. What? That doesn't sound right. And Googling sug... | [
"Yes. There exists a quantity, centrifugal force (or is it centripetal?), that is equal to the velocity an object is moving squared divided by the radius at which it is orbiting. If this quantity equals the acceleration due to gravity, the satellite will have a stable orbit. A collision with a meteor could alter ei... |
[
"Do high flying birds need less oxygen?"
] | [
false
] | Do high flying birds need less oxygen in their breaths, or do they take breaths when they are lower altitudes (like whales surfacing for air)? | [
"Birds have efficient lungs, they have air sacs connected to the lungs and oesophagus, when they breath their lungs and sacs get filled with oxygen and when they breath out the spent air in the lungs leaves and the sac air goes into the lungs giving them a double dose of oxygen."
] | [
"Birds that fly at extreme altitudes (such as those that migrate over the Himalayas, have special adaptations that allow them to deal with the lower oxygen content at altitude. ",
"The ",
"bar-headed goose",
" has several mutations/adaptations that allow it to fly at altitudes in excess of 20,000’."
] | [
"I just kept thinking about my vertebrates anatomy course in college. It was interesting learning that many dinosaurs like the T-Rex and other raptors had similar bone structure to modern birds, that their bones were hollow and had the same tubes in them that modern birds have."
] |
[
"Why is absorption of nutrients through the intestines safer than direct injection into the bloodstream?"
] | [
false
] | null | [
"Injection site = risk of blood infection, especially with nutrient-rich fluids as opposed to something like normal saline. Our intestines have natural ways to fight bacteria, like stomach acid. Also, the cells on the inside of the intestinal tract need nutrients too, often getting them directly from the food insid... | [
"When nutrients are absorbed into the blood stream in the intestines, that blood is then sent straight to the liver via the hepatic portal vein. This means that everything has a chance to get filtered by the liver before passing to the rest of the body. As a result, a significant amount of any toxins mixed in wit... | [
"Could be because the intenstine can prevent an over absorbtion of nutrients and it also filters out anything we don't want. Or it keeps a steady rate of absorption so that our body acclimate to the introduction of nutrients. Don't quote me by the way. It's just a thought."
] |
[
"Are the biological children of gay people more likely to be gay than the biological children of straight people?"
] | [
false
] | When I try searching for an answer, I get a bunch of results about whether gay couples can be good adoptive parents, or the affect of fraternal birth order on sexual orientation. This isn't what I'm looking for. Surely in societies where being gay is taboo, a significant number of gay men end up having biological child... | [
"There does seem to be a heritable component to homosexuality, but it is extremely elusive. Twin and family studies",
"[1]",
" have found that homosexuality runs in families. Genomic studies",
"[2]",
" suggest that homosexuality is a complex trait caused by many different genes, and the genes that cause mal... | [
"Not exactly what you're looking for but it is still related to inheritability of sexual orientation. Fecundity in the maternal lineage is positively correlated to the increased likelihood of male offspring who are homosexual.",
"Basically, researchers found that in the families of homosexual men, the maternal au... | [
"Not necessarily. \"Environmental factors\" when referring to genetic studies just means anything that isn't strictly genetic. This could be anything from what your mother ate while pregnant to the air quality where you grew up to whether or not you were bullied in elementary school. Not saying that any of those th... |
[
"If all humans died tomorrow, what traces of our civilization would be left in 10,000 years? 50,000? 100,000?"
] | [
false
] | [deleted] | [
"http://www.history.com/shows/life-after-people"
] | [
"Read 'The World Without Us' by Alan Weisman.",
"Brief summary:",
"In The World Without Us, Alan Weisman offers an utterly original approach to questions of humanity's impact on the planet: he asks us to envision our Earth, without us.",
"In this far-reaching narrative, Weisman explains how our massive infras... | [
"The World Without Us has an excellent mouseover chart"
] |
[
"Does melatonin cause others to wake up at odd hours and have vivid dreams?"
] | [
false
] | I sometimes wake up on a strange schedule when I take melatonin to sleep and I also experience some of the strangest dreams I've had when I take melatonin. I am wondering if this is common and why it happens. | [
"I wake up at odd hours whether I take melatonin or not.",
"The main difference is that with melatonin, I can get back to sleep.",
"The vivid dreams are just a bonus."
] | [
"I'm not sure, but I took 5 mg melatonin and a vitamin b6 supplement last night to catch up on sleep and I suddenly woke up after a long, intense, vivid dream thinking it was probably 5 o-clock in the morning, but it was only 11:30 pm. I couldn't even imagine what the rest of the night would be like after that."
] | [
"It happens to me some nights I take it and then others I sleep like it's not a problem. Weird stuff man."
] |
[
"Why do dogs prefer to pee on vertical objects?"
] | [
false
] | null | [
"Animals navigate in much the same way that we do and use significant landmarks as waypoints and aids; like like boulders and tall trees. And in a modern context, lampposts and fire hydrants. ",
"Urination is used as a navigational aid, a literal breadcrumb trail when exploring new places, as well as for marking ... | [
"To add to this, the reason it's on vertical surfaces is because that's nose height for other dogs, plus it's high enough that the wind catches it and spreads the scent even further.",
"Cats do this too, and there's also feces marking although that's done less often."
] | [
"Other answers are true, but heres another take. The higher your pee is the higher your status. Even some female dogs will gcontort themselves or stand up so that theire pee gets deposited high up on a fencepost or tree or other object. If peeing high isn't possible, lots of dogs will pee on the ground and then ... |
[
"Why is Carbon and Water so fundamentally necessary for life? Couldn't an extraterrestrial lifeform be based on, let's say, silicium?"
] | [
false
] | [deleted] | [
"Water is important because it is a potent solvent and is liquid in a temperature range that is conducive to organic chemical reactions.",
"Carbon is important because it is fairly inert once in molecules so you can form many long complex molecules off the same more or less inert back bone. this has to do with th... | [
"Silicon doesn't form homopolymers anywhere near as readily as carbon, which is another problem for complex life."
] | [
"We KNOW for sure that life like ours exists and therefore CAN exist. There are zillions of other theoretical possibilities, but they're all just pure speculation. For now, it makes sense to stick with what we know is possible."
] |
[
"In Quantum Mechanics, how does the bound state of a negative delta potential relate to the first bound state of an infinite potential well?"
] | [
false
] | Hey guys, I'm getting a bit confused when it comes to delta potentials. I was wondering if someone could shed some light on why the bound state centres above a negative delta potential the same way that it centres within an infinite square well. Also perhaps, what would happen to the bound state when there are two clos... | [
"What do you mean by \"centers the same way\"?"
] | [
"Does the potential really go to zero at a finite distance from the well in the second case? I'd think it would decay asymptotically to zero at infinity. The reason the wavefunction is 'centered' around the well is that the potential is symmetric on both sides of the well. The system in the first case is symmetric ... | [
"If you had mutiple negative delta function potentials, I imagine the wavefunction would have more peaks, like this.",
"Just gonna jump in here really quickly.",
"If you had multiple negative delta function potentials arranged ",
", then you would use Bloch's theorem for solving Schrodinger's equation for a c... |
[
"Is there a universally used symbol to denote hours, days, weeks, months and years?"
] | [
false
] | For example, the way that "kilometre" is denoted as "km" I'm in university, and over the course of the last few years, I'm getting really frustrated by the (very small) inconvenience of writing these words in full. Some people use 500mg/52 to denote 500mg per week (as there are 52 weeks in a year), but I feel like usin... | [
"ISO 8601",
" is an international standard for dates, times, durations and time intervals."
] | [
"I suppose that the \"standard\" way would be h, d, w, and y (months is particularly problematic). In context, it's probably clear what you mean by this."
] | [
"The only \"defined\" unit of time is the second, and you probably won't catch anyone using a decimal time system.",
"Ask others have stated, short units are pretty common and self-explanatory. When in doubt, you can always follow good practice in documentation and write it first in full, followed by the abbrevia... |
[
"If I look someone in the eyes in a mirror (or glass, foil, etc.), is he also looking me in the eyes back?"
] | [
false
] | null | [
"Yes"
] | [
"Even if the foil is crinkled, or the glass is dirtied in a specific way? Basically, is there anyway for it to be untrue?"
] | [
"Maybe I don't understand your example. If the person isn't looking at you (in the mirror), then no. "
] |
[
"Do photons and other massless particles interact with the higgs field? And if so why don't they gain mass?"
] | [
false
] | null | [
"No, they don't.",
"Nothing without mass interacts with the higgs field, which is why they can go up to the speed of light. If you do interact with the higgs field, you have mass, and are limited to speeds below the speed of light."
] | [
"Nothing with mass interacts with the higgs field,",
"Just to clarify, this is a typo. It should be \"Nothing with",
" mass...\"."
] | [
"Ah, yes it is... Thanks for pointing that out :P"
] |
[
"Does the Hoover Dam need the water from Lake Mead to stay structurally sound?"
] | [
false
] | I’ve been reading articles about how low the water level is in Lake Mead and it got me thinking about two things. Does the concrete that was used to build the dam rely at all on being continuously wet (i.e. is the concrete prone to crumbling prematurely when it’s dry for extended periods of time)? Since the dam was bui... | [
"A few items of note. First, the concrete does not rely on being continuously wet. Once cured, water has little effect on concrete itself. Water, and especially repeated wet-dry cycles, can affect the reinforcement within concrete, but concrete itself is largely unaffected by water. However, Hoover Dam is largely b... | [
"Dam good answer. Thanks"
] | [
"One interesting thing about Hoover Dam is that they had to install refrigeration equipment and actively cool the concrete. ",
"Without cooling, the interior of the dam would have reached about 140 degrees Fahrenheit (60 degrees Celsius) and taken 150 years to cool to ambient, during which time considerable therm... |
[
"Why are some fungal skin infections like tinea versicolor incurable/chronic?"
] | [
false
] | What causes the source of the infection to remain so that the condition can flare up again after treatment and remission? Why can’t we nuke the little fungi out of existence? Aren’t some fungal skin infections like tinea pedis (“athletes foot”) completely curable? | [
"Not a dermatologist but a vet tech and animals can also have chronic or one time fungal diseases that are highly analogous to ours in many cases, so although previous posters are correct that systemic anti fungal treatments can come with some hard core side effects, I don’t actually think that’s the reason for the... | [
"Fungi have been around long before us, and will be around long after haha.",
"Fungi are eukaryotic organisms just like we are, so things that kill fungi also tend to kill us (e.g. cycloheximide), making a chemical treatment rout somewhat challenging, and spore forming reproduction is exceptionally resilient."
] | [
"There is a certain point as with chemo treatments for cancer, where you are pretty much poisoning the host along with the foreign infection/tumor you are trying to get rid of, pretty much just hoping you kill off the problem before the person. Some fungi are just that resilient. It's possible that you could essent... |
[
"In biology, what is Hierarchical Assembly?"
] | [
false
] | I can't find a well versed explanation of this. Am I on the right track if I say... 1) The fewest building blocks in producing molecules is ideal 2) It provides quality control. Various noncovalent bonds that bind macro-molecules together prevent the wrong building blocks from attaching or prevent misfolding | [
"I'm also new to this idea, but after a little reading, this is what I got. Basically, if you want a complex structure to be self assembling from a mixed pool of the building blocks, you want smaller simpler self-assembly steps to be energetically preferable, and you work your way up, to prevent the complex structu... | [
"Thanks! I appreciate it!"
] | [
"Do you mind explaining differential binding too? Is it just the various noncovalent bounds that holds macromolecules together, such as proteins"
] |
[
"What exactly makes inbreeding so bad?"
] | [
false
] | [deleted] | [
"Inbreeding itself is not such a bad thing. It's when inbreeding occurs in large populations where it becomes bad. You see, large populations have a lot of defective/bad alleles (forms of genes) that are mostly masked by good, dominant ones. When you start inbreeding, you end up having a higher chance of getting tw... | [
"On a small scale and timeframe, this is not that much of a problem. However, inheritable disorders become more apparant. Most notable, autosomal recessive disorders become more dominant in the blood line. Autosomal recessive disorders in short are disorders requiring two \"carriers\" of the disorder to mate. If on... | [
"Relatives share too many of the same chromosones so the off spring often comes out with disabilities including things like cleft pallet cleft lip downs syndrome type mental disabilities and other problems.",
"Oh and its just straight freaky."
] |
[
"Can someone explain why this doesn't violate conservation of energy?"
] | [
false
] | [deleted] | [
"Key point: Quantum efficiency is not the same as energy efficiency.",
"Quantum efficiency=number of electrons you get out ÷ number of photons absorbed",
"Energy efficiency=amount of energy you get out ÷ amount of energy absorbed",
"In theory, this type of process means the solar cell absorbs one photon with ... | [
"well stated"
] | [
"It isn't an energy efficiency. It is more of a mobile charge production efficiency. This efficiency being over 100% means that, on average, more than 1 electron is freed from it's parent atom per 1 photon entering the material. The actual energy efficiency is most likely a bit less than 100%. "
] |
[
"Where does uranium come from?"
] | [
false
] | I made a post in askreddit trying to get an answer to this question but this seems like a better place, but I am trying to figure out where the naturally occurring elements with the higher atomic numbers like uranium come from. None of the processes I was reading about in wikipedia like proton capture or neutron captur... | [
"Same place all the other heavy elements — everything heavier than iron — come from: supernovas.",
"Sometime in the distant past, before the Earth existed, there was a star. That star formed out of the primordial hydrogen (mostly) that precipitated out of the Big Bang. It burned for a while, and in the process fu... | [
"A little more detail... all elements heavier than Fe are formed by neutron capture and subsequent beta decay in stellar environments. In the s-process (",
"http://en.wikipedia.org/wiki/S-process",
"), beta decay rates exceed neutron capture rates; in the r-process (",
"http://en.wikipedia.org/wiki/R-process"... | [
"I do apologize. When I wrote that, I'd not long before come out of a solid hour of people telling me, over and over in different words, \"Wow, you're like totally blowing my mind, man, like woah.\" Idiot cannabis-headed kids get on my nerves like you wouldn't believe, and I brought some of that baggage with me whe... |
[
"Concerning Mitochondrial Eve and Adam..."
] | [
false
] | [deleted] | [
"There was probably a major bottleneck due to a supervolcano eruption around 70 000 years ago. Look up the Lake Toba supervolcano. And yup, it could happen again. There are several of those around the world, including under Yellowstone Park :)",
"However, there's no need for a bottleneck to explain this at a... | [
"It doesn't mean they failed to. It only means that none of them are likely around today. It's hard to make mathematical arguments on reddit, but ",
"here's a link",
" that explains the idea."
] | [
"But even with such a terrible volcanic event I can't imagine how every other woman of her generation failed to produce their own family lines. To think all of humanity was essentially \"ground-down\" to one family at various points in history... "
] |
[
"Is there a type of star that emits only UVA light?"
] | [
false
] | Wondering if there is such a thing as a star that would essentially be a giant black light. From what I can find on Wikipedia, it would have to be a very hot star, meaning near the beginning or end of its lifecycle. Assuming such a star exists, could you reasonably expect an orbiting life-bearing planet be filled with ... | [
"Stars emit ",
"black-body radiation",
" corresponding with their temperature, which is essentially a distribution of frequencies (and colors) centered around a mean which is determined by their temperature. No matter how hot the star is, there is still going to be some portion of their spectrum emitting in th... | [
"https://en.wikipedia.org/wiki/O-type_main_sequence_star",
"Not only UV, but mostly"
] | [
"Yeah, that part was definitely more of a thought exercise than anything. I'm just trying to visualize what life on a planet orbiting a giant black light would look like... if it were to exist. ",
"Ultimately I'm just interested in knowing if there is a \"black light\" star. "
] |
[
"How fast could you theoretically travel in the vacuum of space with gravity being the accelerant. What if the gravitational force was everything in the universe clumped together?"
] | [
false
] | [deleted] | [
"your speed could get close to c. That's about as much as can be said."
] | [
"I figured this would be the answer. I'm disappoint :*("
] | [
"Correct me if Im wrong (which I often am) but isnt it possible for space to expand past c? This is my understanding of what would happen if space continues to expand at an accelerating rate. ",
"Wouldnt a gravitational force stretch space to a point to or past c? "
] |
[
"Does headphone use have an adverse affect on one's ability to hear?"
] | [
false
] | [deleted] | [
"Hearing damage comes from exposure to loud sounds; the louder the sound, the less exposure is needed to cause damage. But that's not the whole story.",
"The problem with headphones is that they don't give you the 'bodily experience' that live music or even full-range loudspeakers provide: only your ears get the ... | [
"Why we like music? We like it because we make the music, and we make what we like to hear.",
"Music by itself does not destroy your hearing... listening to music loudly all day long will.",
"And 'loudly' depends of 'for how long'. Plenty of information is available on the web about sound exposure limits."
] | [
"if our auditory is not designed for constant exposal music, why do we like it so much? To me, it seems dumb to make us love music when it basically destroys our hearing. or is this just one of those things where \"we developed faster than evolution could keep up\"?"
] |
[
"I don't understand \"Nuclear Radiation\". How does it work and what separates it from other forms of matter/elements in our world that seem to make it so much more dangerous?"
] | [
false
] | I understand that it's 'bad', is most closely related nuclear power plant meltdowns and atomic bombs. But I don't understand HOW it works. Are there different types of radiation? Is the radiation our phones give off the same exact thing, except at a much lower level? What is happening to our body when radiation give... | [
"Regular matter is made of atoms. And every atom has a nucleus, made of protons and neutrons. Some nuclei are ",
", meaning that they decay. When a nucleus decays, it emits radiation.",
"There are different kinds of nuclear radiation. Some examples are alpha particles, beta particles, gamma rays, protons, neutr... | [
"a good way of explaining is by thinking of money. Say you have a dollar and it is unstable and randomly 25 cents breaks off and flies across the room. The dollar is now 75 cents and the 25 cents shot across the room and broke a window.",
"Same idea. If you have Uranium 238, 2 protons and 2 neutrons (exactly the ... | [
"Energy, momentum, angular momentum, etc. are all conserved during decays. If you add up these quantities for all the particles in the final state, they are the same as what they were before the decay."
] |
[
"Is the shape and general make-up of sperm identical, or at least similar, amongst all sperm producing animals?"
] | [
false
] | While watching a program on television documenting creepy sea creatures, they filmed a sea cucumber producing sperm in hopes of it finding eggs. I know the shape and make up of individual human sperm, I would assume it would be similar in chimpanzees (but maybe not?), but what about in animals such as sea cucumbers? | [
"Oh man, not even! For example, some species of fruit fly have sperm tat are multiple times longer than the fly itself. Some species have heterogeneous populations, some being incapable of fertilization but serving as 'blockers', some even being hunter killer sperm!",
"Check out Sperm Wars. It's a rad book. "
] | [
"Not to mention all the crazy sex proteins that go ",
" with those sperm which can impart all kinds of behavioral effects!",
"I just found this great quote that puts the large sperm you mentioned into perspective:",
"Much of the research focused on the sperm of ",
"; an impressive six centimeters. The resea... | [
"Huge differences between mammalian species. Many kinds look different when you compare them via microscope. The craziest one I know off the top of my head is the echidna - individual sperm join together into a massive bundle of mega sperm\n",
"http://ichthyologist.tumblr.com/post/55037909532/echidna-sperm-bundle... |
[
"How can you determine the interference path of sound?"
] | [
false
] | [deleted] | [
"The interference pattern should be exactly the same as that for any wave phenomenon.",
"If you have two sources with spacing d with equal wavelength l, then sin (theta)= n.l/d for the angle theta of the nth minimum.",
"If you want to extrapolate this to 2 dimensions then you would have to take account of the a... | [
"The mechanics of determining the interference condition is the same as for light. the only real difference is the wavelength and type of wave."
] | [
"Are the formula the same as for the double-slit?"
] |
[
"When a meteor strikes the earth, are the pressures created upon impact great enough to compress any carbon present into diamonds?"
] | [
false
] | [deleted] | [
"Sure, there are examples from ",
"Finland",
". When there is an impact of a meteorite, there isn't just the impact pressure itself, but it creates a massive amount of heat. "
] | [
"To add to this, any diamonds formed by an impact such as a meteor strike will be very small and of poor quality. A perfect diamond has a single crystal lattice structure through it's entirety - part of what makes it so beautiful is that it is literally a perfect arrangement of atoms which repeats indefinitely, an... | [
"Nanodiamonds are commonly observed in impacts and can be used to document impact events even in the absence of a known crater. For example, ",
"Nanodiamonds in the Younger Dryas Boundary Sediment Layer",
"."
] |
[
"Are they any examples of 2-way predation in biology?"
] | [
false
] | What I mean is two species who both eat each other as part of their diet. I know there are examples where the prey can be a physical threat to the predator depending on the circumstance, but I've never heard of two species being both predator and prey to each other. | [
"Ooh, sure!",
"Intraguild predation",
" describes how predators sometimes kill and feed upon each other, usually when competing for shared prey items. The dynamic is often asymmetric, especially among adult animals, with one 'dominant' predator positioned at a higher trophic level, and another 'intermediate' pr... | [
"and there are no examples, as far as I'm aware, where two mature predator species ",
" prey on one another",
"It's not that regular even there, but there is ",
"the curious case",
" of Malgas Island, where lobsters eat sea snails (the normal order), and nearby Marcus Island, where sea snails eat lobsters. ... | [
"Oooh! That's really cool. Density-dependent inter-predator predation (oof, words) is a first for me, and kinda' seems the best example for what OP was looking for. Thanks for sharing!"
] |
[
"How is entanglement able to move faster than light?"
] | [
false
] | null | [
"Entanglement is just a fancy way of saying that two particles are correlated. To use a simple analogy, you take two coins, and you put them in two boxes in a way that one has to be heads, and one has to be tails. You move the boxes arbitrarily far apart, then you open one. It's tails, so you ",
" know that th... | [
"I don't think it demonstrates existence of higher dimensions, particularly since no-one has yet shown how it works or understood it. All we can do is show it occurs, not how."
] | [
"It doesn't.",
"This is a very common misconception arising from the application of classical logic to quantum-mechanical systems. The logic goes like this: \"",
" and ",
" can each be either ",
" or ",
" but whenever ",
" is ",
" then ",
" must be ",
" and vice versa. Therefore, if I measure ",
... |
[
"Why do airplanes fly at 30,000+ feet and not lower?"
] | [
false
] | [deleted] | [
"The air is less dense at altitude, allowing the aircraft to fly faster, and more efficiently.",
"You mention buildings, but I would suggest mountains too, although this is not the real answer."
] | [
"When it comes to commercial aviation jet engines function better at higher altitudes where the air is colder and less dense. That allows companies to save in fuel $$. Also we live in the troposphere above that in the tropopause is the where the jet stream is with winds usually well about 50 knots and that saves ti... | [
"Less resistance "
] |
[
"Can cells fuse togther, like mitosis in reverse?"
] | [
false
] | null | [
"For a \"typical\" cell, I would say no, they do not undergo fusion such that you have two cells in one(or any type of \"reverse mitosis\"). They can, however, transfer material by packaging material in vesicles and these vesicles can move into adjacent cells, which is kind of related to what you're asking."
] | [
"Yes. There are many cells in our bodies that are known to \"fuse together\". This is described as ",
"syncitial",
". However, keep in mind two points:\n1) This is NOT equivalent to \"mitosis in reverse\". Many examples of fused cells retain the multiple nuclei of their uni-nucleate fore-bearers.\n2) The inciti... | [
"Wow thats really interesting. Thanks for the info man!"
] |
[
"Why is the clitoris on the outside of the vagina?"
] | [
false
] | If the only purpose of the clitoris is for pleasure, why has it evolved outside the vagina? | [
"You are thinking of this the wrong way. Evolution does not create traits with 'goals' in mind. The male and female genitourinary structures are embryologically ",
"derived from the same structures",
" and contain ",
"homologous anatomy",
". The clitoris is embryologically homologous to the glans of the ... | [
"Don't they urinate out the vagina too?",
"EDIT: I guess it sounded like a joke but it is true, technically. In pigs the vagina and urethra share a ",
"common urogenital passage",
" \nI remember this from A&P",
"EDIT 2: Wow, still getting downvotes? I hope you all never take an A&P class with fetal pig diss... | [
"It's worth mentioning that some animals (pigs for instance) have the clitoris inside their vagina."
] |
[
"What keeps two solid objects composed of the same element from 'sticking together'?"
] | [
false
] | So I finally got around to watching the new Cosmos (which is pretty great by the way) and I got a little confused about the interactions of atoms and molecules. The show explains that atoms have this 'electron cloud' that keeps solid objects from really 'touching' each other. The example they used was a human finger go... | [
"Great question! The first thing to note is that there are ",
" of substances and materials, and molecules in each of these stick to each other in different ways.",
"For instance, you have metals like gold and iron where atoms are bonded because their outer, most energetic electrons have become ",
"delocalize... | [
"Typically, metals have a thin layer of oxide on them that prevents them from bonding with other metals. For example, a bar of pure iron will develop a thin coat of rust pretty quickly. If you prepare to metals in a vacuum without an oxide layer, you can touch them and have ",
"cold welding",
"."
] | [
"To add to this. In a vacuum deposition chamber, such as is used to apply thin coats of metals and construct semiconductor electronics, you don't have to do anything special to get the atoms you are spraying to stick to the substrate and become part of it. The bonding just happens naturally because the vacuum condi... |
[
"Why is radioactivity associated with glowing neon green? Does anything radioactive actually glow?"
] | [
false
] | Saw a post on the front page of regarding some green water "looking radioactive." What is the basis for that association? | [
"One of the first widespread applications of radium was luminescence - self-powered lighting. For instance, ",
"Radium Dials",
" or clock faces were popular, as they glowed in the dark. These materials convert the kinetic energy of radioactive decay (and subsequent ionization) into visible light. If you comb... | [
"My preceptor had me read this about the \"radium girls\" when I was on a nuclear pharmacy rotation. ",
"http://www.damninteresting.com/undark-and-the-radium-girls/",
"Very interesting. "
] | [
"Yeah, the Radium Girls is one of the first things you learn about whenever you study radiation protection. It was a real tragedy, but it lead to the creation of lots of good reforms. Their subsequent lawsuit established the right of a worker to sue for damages from corporations due to labor abuse. It helped kic... |
[
"How thick of a mattress would a person need to survive a fall at terminal velocity?"
] | [
false
] | What material would such a mattress be made of? Also what positional orientation would be best to land? Clarification: By surviving, I mean land reasonably comfortably. | [
"This is not quite enough to answer the question. The mistake is assuming constant deceleration. Initially, after hitting the mattress, you would have a deceleration of 0 (assuming a few things that I will get into shortly). The reaction of the mattress onto your body would increase linearly with its deformation (H... | [
"Let's say that the decceleration when hitting the mattress is a. Terminal velocity is 200 km/h. The time to deccelerate is then t=200km/h / a. Distance travelled is x=1/2 * a * t",
" = 1/2 * a * (200km/h / a)",
" = 1/2 * 200 km/h / a . From wikipedia, a brief 40 g acceleration seems to be just about survivable... | [
"Very thorough, thank you both."
] |
[
"How much of the earths surface can we see from the moon?"
] | [
false
] | null | [
"From the side of the moon that is facing us, one would see about half of the earth at any single point in time, or all of the earth over a period of time.",
"From the side of the moon that is not facing us, one would see none of the earth ever.",
"Asking \"How much of the earths surface can we see from the moo... | [
"How would being an oblate sheroid make it possible to see more than 50%? You cant see more than 50% of a flat disc either.",
"Also I would assume that everything you said would be dwarfed by the fact thay Earth has an angular size of 2 degrees seen from a moon. Using basic geometry, this would mean we could see ... | [
"The southern hemisphere of the earth is larger than the northern one (I will admit, that is not true of all oblate spheroids, but the one we are talking about is), which precludes there being an axis of symmetry other than through the poles.",
"You are modeling the earth as a perfect sphere, with a perfectly smo... |
[
"When whole cities flood, does this mean the sewers are backing up into the streets or is there some sort of containment mechanism?"
] | [
false
] | My knowledge of sewers stems entirely from AHH Real Monsters, TMNT, and the fact that there are open drainage areas in the streets for rain overflow. I don't know how they've designed to differentiate between run off and waste once everything goes below street level, and in my brain if I can see the open run off holes ... | [
"Modern sewer systems have 2 totally different systems, 1 for storms that empties into a lake or whatever and one for waste that goes to the shit plant. If something's going to overflow it's almost guaranteed to be storm. Old cities built combined systems years ago because street runoff was essentially sewage and t... | [
"There's no containment. Sometimes sewer water comes ",
"gushing out of manholes",
". "
] | [
"Oh man. That is really good to know. Thank you for the answer! "
] |
[
"Smoke different from smell?"
] | [
false
] | The other day I heard that the smoke coming off of something (say a cigarette) is separate from the smell of the smoke. Meaning that the smoke molecules you see in the air are separate from the molecules that activate your smell. Is this true? I always thought the smell of the smoke the smoke itself. EDIT: Meant to ask... | [
"Chances are that there are still smoke particles in the air, but they are too dispersed to be visible. Smoke detectors can be very sensitive so this could potentially still set off the alarm",
"EDIT: see ",
"this",
" for details"
] | [
"The reason you smell smoke is because it contains various molecules that activate specific receptors in your nose. Our noses do not contain receptors for every molecule and if you do not have a receptor for a particular molecule, you will not be able to smell it. As a result, only a fraction of the molecules in sm... | [
"That makes senes, thanks for the response. But what about if you ",
" see the smoke in the air but you do smell it? Does that mean there are smoke particles that could trigger the alarm?"
] |
[
"How do we know that dark matter isn't just ordinary matter our instruments can't detect?"
] | [
false
] | Most of the pop-sci explanations for dark matter that I've seen compare the light we detect from a galaxy with some observation of its mass: gravitational lensing, velocity, etc. There isn't enough light to explain the mass. But how do we know that this isn't just a limitation of our instruments? Is it possible that th... | [
"For example, we cannot rule out that the dark matter might be asteroid-mass black holes (e.g. figure 10 of ",
"this article",
"). Why couldn't it just be asteroids?",
"The main lines of evidence against such a possibility are related to the early universe. This is a time when the the universe was very hot. A... | [
"I think to restate this simply (with the caveat that simple == less correct) is that we do know it’s not things we can detect easily, like elements (hydrogen, helium, iron, etc). These things tend to clump together and do things like fall into stars where we can detect them by their emission lines. Which how we kn... | [
"These things tend to clump together and do things like fall into stars where we can detect them by their emission lines.",
"I think that requires some additional assumptions. Dark matter indeed couldn't be gas, because we can detect gas on its own, and also gas would lose energy and fall into things (whereas dar... |
[
"What could I expect to find at the bottom of a sinkhole?"
] | [
false
] | null | [
"Depends on your location.",
"If you have a water-filled sinkhole in the countryside, then dove to the bottom of the debris cone, you'd find branches and trees, leaves, various small animals that fell in and limestone rocks. ",
"I've had the chance to get into a bell cavern formation where the locals had used i... | [
"Here is a story about the original image. It is NOT a sinkhole. Rather, it is a \"piping feature\" which is very different, and far more dangerous. These sort of features are caused by the settling of lots and lots of volcanic rock or lava, over time. It turns out they are incredibly unstable to build on.",
"htt... | [
"Another question based on the picture in the original post. How come that the hole in the picture is circle shaped? I doubt it's a perfect circle, but it sure looks like one, it almost looks hand made."
] |
[
"Why do some songs sound \"sad\" or \"happy\" when we listen to them?"
] | [
false
] | null | [
"Happy and sad (and more) comes from the Amygdala. However, I don't know why major sounds happy or neutral and minor sounds sad.",
"I expect it has something to do with the tone when we speak or cry. And this is mimicked by the chords."
] | [
"A major chord can be heard and processed through the brain smoothly because there is minimal tension between the notes. ",
"In a minor chord, the lowered fifth doesn't fit as perfectly. (This has something to do with differences in frequency and wavelength but that's a whole other story) That tension as a res... | [
"This is not true. First of all, a minor triad consists of the first, third, and fifth scale degrees, it does not have a lowered fifth. are you referring to making a major chord minor? If thats the case then you would lower the third by a semitone to make it minor. A major or minor triad by itself will have no exte... |
[
"Black holes can expel jets of charged matter at relativistic speeds; do these jets provide thrust to the black hole?"
] | [
false
] | These 'astrophysical jets' are understood to be ionized matter. Should the incredibly powerful expulsion of this matter (thrown across thousands of parsecs at speeds up to .80c) not propel the expelling body in the opposite direction? Could not the supermassive black hole at the center of every galaxy be accelerating a... | [
"Well, first of all: yes. Black holes are still subject to conservation of momentum, so expelling something in one direction would accelerate it in the opposite direction. However, the jets are in opposite directions and so would cancel each other out. Also, the black hole could not drag the galaxy with it - the ga... | [
"On the other hand, that would require the black hole to be asymmetrical in some way and I don't know if that's even possible.",
"Jets are always at least slightly asymmetrical, and it's been my key area of work for 3 years now. In the Fanaroff-Riley classifications, hybrid sources (one jet is type FRI and the ot... | [
"On the other hand, that would require the black hole to be asymmetrical in some way and I don't know if that's even possible.",
"Jets are always at least slightly asymmetrical, and it's been my key area of work for 3 years now. In the Fanaroff-Riley classifications, hybrid sources (one jet is type FRI and the ot... |
[
"What happens if VY Canis Majoris explodes?"
] | [
false
] | Since we are a tiny molecule in front of it. What will happen to us if it goes super nova? | [
"Short answer? Essentially nothing, it's too far away.",
"VY Canis Majoris is a huge star, no doubt about it - it's more than a thousand times larger than the sun. But it's also ",
" far away - almost 4000 light years. (",
"http://arxiv.org/abs/1109.3036",
") A type II supernova has a visual magnitude of ar... | [
"But wont the radiation or other stuff reach us in 4000 light years?"
] | [
"If it exploded 4000 years ago, we could see it explode today. We can only tell what it did 4000 years ago. If it exploded 3000 years ago, we won't know about it for another 1000 years."
] |
[
"Is going in a circle at the same pace turning at the same rate, still considered an inertial frame of reference?"
] | [
false
] | I had been given an experiment in which I held a ball tied to a string and walked in a circle at a constant pace. There was no acceleration. I was supposed to drop the ball after walking on the circle for 5 revolutions, then I would observe what happens to the ball and someone else who was stationary observes what happ... | [
"Is the person moving in a circle at a constant speed in an inertial frame of reference or not?",
"A rotating reference frame is not inertial, even if the angular speed of the rotation is constant.",
"We had to identify if the 2 frames of reference were 'Inertial' or 'Non-inertial'.1 being the person moving in ... | [
"Technically, velocity is a vector quantity, meaning it is comprised of magnitude (speed) and direction. Even though you’re moving in a circle at a constant SPEED, your direction is continuously changing. So say you’re circling in the XY plane. If you look only at the x-axis component of your motion, it oscill... | [
"Yes. The definition of inertial reference requires that the object be stationary or at a constant velocity along a linear path. Person 1 does not fit that description because his velocity (remember this includes direction) is always changing. "
] |
[
"Can someone explain what happens to the mind & body when it is suffering from anxiety ?"
] | [
false
] | null | [
"I answered this a while ago but here's my comment:",
"If you want to go with the neuroanatomy, then we shall start with the ",
"amygdala",
". This area is a group of nuclei that respond strongly to emotional / stress challenges. This area of the brain sends signals to the Lateral Hypothalamus and Paraventric... | [
"I'm not so sure about the system turning completely off, but the stress response will definitely decrease over time. There are a couple of mechanisms that do this: ",
"1) They hypothalamus is composed of several subnuclei that can monitor what it is in the blood. Normally, the brain is \"blood exempt\" by the bl... | [
"Personally, I try and stay away from the word \"wrong\" in neuroscience. The brain is extremely plastic (meaning it adapts very quickly to new situations). I truly believe that in things like anxiety disorders, it is the brain becoming hypersensitive because it was useful in the past (not evolutionary terms, talki... |
[
"If dark matter can bend light does it mean that stars further away may appear to be in the wrong position?"
] | [
false
] | I've recently read an article where it explained that large clusters would bend light from stars and even galaxies. It did not get into specifics. I just assume that if light would get bent by large gravitational forces it would change direction, thus appearing to be in a different position in the universe than it actu... | [
"Yes but only by a tiny amount."
] | [
"Exactly, and that's one way we know that some type of dark matter exists. We know how deflected galaxies should be based on the mass we can see, but we measure a deflection much greater. Thus, there must be some mass that we can't see, some kind of \"dark matter\"."
] | [
"Thank you. That is pretty much the answer I was looking for. "
] |
[
"Why do old helium balloons half-float"
] | [
false
] | I get that the amount of helium reduces but what is the actual reason that a healium balloon will float at say 1 foot off the ground after a certain amount of time. Is it something to do with air pressure/gravity vs the amount of helium left | [
"Look closely. Most balloons have a string attached. Initially it can easily support its weight and the weight of the string. As it looses helium it will reach the point where it can no longer support the entire string and it will drop until it is only lifting the amount of string it can bear. Thus as it contin... | [
"Tiny differences in temperature and pressure can cause a difference in density. \nThe balloon floats at a height where the air underneath it is more dense than the balloon and the air above it is less dense. "
] | [
"Think about putting something at the bottom of a pool. Things don't float only a little bit and then stay there unless something funny is going on with the density of the water."
] |
[
"Why doesn't the phase velocity of light carry useful information?"
] | [
false
] | I've been looking around the internet and can't find a satisfactory answer. I was thinking about how dielectrics slow down the group velocity of light, but not the phase velocity, and then wondering if that would violate causality in some way. Apparently, the reason why it doesn't violate causality is because a pure si... | [
"Imagine you have a light source (currently off) at one end of a medium and a detector at the other end. The medium is one light-second long. The group velocity of the frequency you're sending in this medium is 0.5 c, while the phase velocity is 2 c. After you turn on the source, the detector will start receiving l... | [
"Yes but the information is that the source is sending waves with that frequency to the detector. That information travels at the group velocity."
] | [
"Photons are made up of a continuum of frequencies contained within an envelope, like ",
"this",
". The group velocity describes how fast the envelope propagates, and the phase velocity describes how fast the peaks within the envelope travels. In a dispersive medium, each frequency has a different phase velocit... |
[
"Are we able to observer and directly quantify any forms of magnetism outside of our galaxy?"
] | [
false
] | [deleted] | [
"Yes, magnetism is not unique to our galaxy. In fact all the light which we receive from other galaxies have a magnetic component to them. So if you ever see another galaxy in the sky the light hitting your retina has a magnetic field which initiated in another galaxy and your eye is quantifying it by its wavelengt... | [
"Absolutely, black holes have some of the strongest magnetic fields in the universe. Large black holes have so much ionised material orbiting them so rapidly that it creates an enormous magnetic field. As far as forces go there are forces acting on everything everywhere all the time. Gravity is the major force that... | [
"Absolutely, black holes have some of the strongest magnetic fields in the universe. Large black holes have so much ionised material orbiting them so rapidly that it creates an enormous magnetic field. As far as forces go there are forces acting on everything everywhere all the time. Gravity is the major force that... |
[
"How are protons and neutrons arranged within the nucleus?"
] | [
false
] | Are there different lattices as with atoms? Is there only a single stable configuration? How do additional neutrons (isotopes) affect the arrangement? | [
"Nucleons in a nucleus have a shell structure similar to that of electrons in an atom. For a given nuclide, there is at most one stable state, which is the ground state. Any excited state can decay to the ground state, and often the ground state can decay to a different nuclide."
] | [
"The nucleon orbitals are probability distributions, just like the electronic ones."
] | [
"Is that, again, a matter of probability, like the position of electrons? Is the mental model of sticky, little balls working when it comes to geometrical distribution?"
] |
[
"What is TV static and how does it come to be?"
] | [
false
] | null | [
"Most of it is ",
"noise",
" generated in the TV's tuner. TV's have automatic gain control circuits to be able to bring in weak stations or strong stations. In the absence of a signal, gain is at maximum, and so is amplifier noise. If an antenna is connected, terrestrial sources, the Sun, or Cosmic Background R... | [
"I'd say that covers the basics. Without a TV station pumping a signal at a certain frequency, the radio signal is just a white noise mixture from all the faint earth sources as well as extra terrestrial sources. I've heard that some of the wave energy is actually the cosmic radiation background leftover from the b... | [
"I am pretty sure that tv (and radio) static is all the extraneous signals that are being picked up by your antenna. Lots of things make electromagnetic waves, which is what the antenna is designed to pick up, but they have no information, it is the em version of noise. This is where we get the term noise to signal... |
[
"How does a tempered glass screen for your smart phone pass the sense of touch to the sensors below?"
] | [
false
] | The title pretty much sums it up. I can guess that it would be through heat or possibly shadow but I can't say for sure. It probably isn't from pressure because the tempered glass seems very hard and therefore wouldn't flex much. | [
"I am currently working on a capacitive touch design right now, so I can take a stab at this.",
".",
"First you basically need a way to measure capacitance. There are several ways to do this, and every touch manufacturer has a variance on it. Essentially you apply a stimulus to the \"sense\" pad and then look... | [
"Touch screens work on the electrical conductance of your finger. That's why if you use it with a wet finger and leave water on the screen, you will get strange behavior. You can use it with a cold piece of metal as well, as long as the surface area is big enough.",
"IIRC, there are many small areas of a clear, e... | [
"In capacitive touchscreens the electrically conductive layer is actually on the ",
" surface of the glass. When a conductive object, like a finger, is pressed against the outer surface of the glass the whole system - two conductors separated by an insulator - forms a capacitor (thus capacitive touchscreen). This... |
[
"What is exactly meant by \"cementitious products\" formed in concrete?"
] | [
false
] | [deleted] | [
"\"Cement\", in the context of architecture and engineering, refers to Calcium oxide.",
"A bit more generally, cementitious particles could refer to calcium hydroxide, any one of multiple phases of calcium-silicate-hydrate (CSH) gel, or other phases. The chemical nature of cement is complicated. In this context, ... | [
"Cementitious Products are those products which contain cement. \"Cement\", in the context of architecture and engineering, refers to Calcium oxide. Examples of cementitious products include concrete, mortar, and terrazzo flooring."
] | [
"Thank you!"
] |
[
"Please tell me major things that old physics books have misinformed me on."
] | [
false
] | I recently started reading , and a few years ago I read . They're both absolutely classic science texts from which I can/have learned a ton, but I also know there are some caveats in learning out-of-date information. Some of them I can catch from my own knowledge (Feynman said that we don't know the intermediate betwee... | [
"The Feynman lectures took place in the early 1960s, and a lot of little things have been learned since then, but not too many big things.",
"The structure of protons and neutrons was just being discovered in this decade, which lead to quantum chromodynamics, the theory of quarks (partons according to Feynman) an... | [
"There is no such thing as relativistic mass. Things don't get more massive the faster they move relative to you. Applying the Lorentz transform to mass gives you back a number which looks like a mass and acts like a mass in your equations but which actually means absolutely nothing whatsoever.",
"That's not so m... | [
"There are three yes."
] |
[
"Why do heavier elements (e.g. Lead) produce more secondaries when bombarded with radiation than lighter molecules (e.g. polyethylene)?"
] | [
false
] | null | [
"Secondary what? And bombarded with what kind of radiation? At what energy?"
] | [
"Deep space radiation of heavy elements like lead is said to produce more \"secondary radiation\" than lighter shielding. The article I read wasn't overly technical and used a lot of analogies rather than direct explanation of mechanics."
] | [
"They probably mean bremsstrahlung from charged particle radiation and possibly electromagnetic showers from high energy photons. Basically both of these processes become stronger with increasing atomic number of the target. That's what makes lead a good shield against certain types of radiation, but it also makes ... |
[
"magnets have the ability to do work, and energy cannot be created or destroyed, so how are they able to do SO MUCH work (w=fxd) over their life?"
] | [
false
] | My guess is that its potential energy is tied to its electrons, NOT joules? | [
"Magnets create a magnetic field. Magnetic objects in this field have ",
" energy. The situation is similar to masses on earth. They gain potential energy when you lift them up. However, the earth itself (or the magnet) does not create the energy. No, its ",
" who does the work, by lifting them up."
] | [
"When you \"make it into a magnet\" you certainly have to put a lot of energy in it. "
] | [
"Ah ok, after you have done the work to separate them, and created the potential energy, this energy can be used to \"close the gap\" again. The total energy is always conserved. In principle, you could repeat such a process forever."
] |
[
"Can we just send prefabbed pieces for a Mars \"exiter\" ahead of a manned mission, assemble it once on Mars then return on it?"
] | [
false
] | I guess Im asking can we send easy to put together parts for some sort of launcher and supplies to Mars ahead of our manned mission. Send a rover to make sure its all intact and operational. Then a manned mission with something thats not designed to land and take off but just land safely (possibly bumpy). Assemble the ... | [
"You might want to consider the scales involved here. Lets look at MSL/Curiosity: The rover (ie final payload) weighted 900kg, and the rocket needed to get it to Mars weighted 334000kg. Based on that you'd need to use over 350 rockets to deliver the mass of one rocket to Mars. And that doesn't include any equipment... | [
"Thats a good point. Well could we use the ion propulsion systems for the larger pieces to slowly get there to help with the weight and then send a separate payload of just fuel using the same thing. I dont know just spitballing here. Then once its there send the rover to give it a look over to make sure nothing br... | [
"The ",
"Mars One mission",
" intends to do this to send over their materials, rather than as an \"exit\" strategy - but they include the rover!",
"(I have heard it mooted as an \"exit\" strategy before, though I don't know if that was mission-specific)"
] |
[
"Does fiber simply speed up our digestive system, or do our bodies want to expel fiber quickly?"
] | [
false
] | null | [
"Fiber acts as a bulking agent, and as mentioned by HonorAmongSteves, it carries water, creating a rather substantial mass that moves through one's digestive tract. Peristaltic movements by the colon and eventually defecation are stimulated by stretch receptors present in the wall of the colon. Due to the increased... | [
"Let me translate it into layman language:",
"Fibers are bulky.",
"Without the fibers, your guts think there's nothing there, and they get lazy. With the fibers, all that bulk tells your guts \"hey, there's stuff in here, get busy\" - and they do."
] | [
"Your body can't break down fiber, and it holds water as it moves through your bowels, making it easy to eliminate compared to denser or drier stuff. "
] |
[
"How would Superman's cape actually behave if he was flying in space?"
] | [
false
] | null | [
"If Superman is \"flying\" in space, we can remove two of the effects that usually act on a cape: gravity and aerodynamic effects. We're left with the forces on the part of the cape attached to Superman's neck, which will generally follow his flight, and internal friction forces in the material which will eventuall... | [
"Outstanding. Many thanks. "
] | [
"It would wave more than it would in an atmosphere as the only resistive force would be from the spring effect in the individual fibers of the cape."
] |
[
"Any tips/protocols on making your own recombinant ligase?"
] | [
false
] | I'd like to clone the T4 DNA Ligase gene. Then I'd like to purify T4 DNA Ligase. Has anyone attempted this on their own before? | [
"Amplify the mRNA using PCR. Insert that into a vector apt for protein expression. Transform some E.coli and select your single colony cultures. Sequence the vector for confirmation of insert. Check a lysate for protein expression using a western or something. Let those bad boys grow like there's no tomorrow. Lyse ... | [
"I've got access to T4 DNA, so I plan on just PCRing it up with His-tags and then cloning it. Antibodies kinda defeats the purpose. His-tagging seems like the easiest way to do it.",
"I was hoping I might be able to find a protocol, though. I've all I got so far is some papers from the 80s."
] | [
"Are you allowed to use kits? Check Qiagen if so. ",
"Google has never failed me for some protocols. "
] |
[
"Why do canaries show symptoms of poisonous gas before humans do, in the context of canaries in coal mines?"
] | [
false
] | In elementary school, I was told by the teacher that canaries have smaller lungs than humans, making them more susceptible to poisonous gas but that answer never sat well with me because smaller lungs should take in less total poison dose. Also birds are smaller than humans so the poison concentration should be fairly ... | [
"Canaries, like other birds, are good early detectors of carbon monoxide because they’re vulnerable to airborne poisons, Inglis-Arkell writes. Because they need such immense quantities of oxygen to enable them to fly and fly to heights that would make people altitude sick, their anatomy allows them to get a dose of... | [
"Bird have respiratory systems that are way more efficient than ours. They need tons of oxygen to power flight so they have a unidirectional flow of air, while we have bidirectional. We inhale fresh air, gas exchange takes place, and then we breathe out, repeat. Birds have lungs and air sacs. The air comes in, and ... | [
"Slightly off topic, but if like me you used to feel sorry for the canaries, a lot of them were kept in resuscitator cages like the one shown at ",
"this link,",
" (sorry i don't know how to embed the picture)"
] |
[
"Do stimulants (like Adderall and Ritalin) really have a different effect on \"ADHD brains\" as opposed to \"normal\" brains?"
] | [
false
] | [deleted] | [
"Everyone's brain is structurally different - this is the reason that we are all unique. ",
"Stimulants like amphetamine and methylphenidate work by increasing the levels of the neurotransmitters dopamine and norepinepherine (although the mechanisms in which they do so vary slightly).",
"ADHD disorders are asso... | [
"Aderrall at least, once in the bloodstream, stimulates the production of norepinephrine and dopamine, both of which are associated with attention. It also stops these hormones from being absorbed quickly, so that the effects of increased focus last longer. The reason it would affect a non-ADHD person so well is ... | [
"Although it hasn't been 100% scientifically proven, those with ADD and ADHD typically have lower functioning prefrontal cortexes. Stimulants, such as Ritalin, increase the functioning in this area. Video games have also been shown to stimulate this area which is why people with ADD and ADHD can typically focus ver... |
[
"What are the major disasters we'd see if bees really disappeared?"
] | [
false
] | I've heard all this: "Oh no, bees are disappearing!!!! Help them everyone but I haven't yet heard a good reason for why it's such a big deal. I have a feeling it has something to do with pollination but I'm not very informed. | [
"Yes, you're correct, it's all about pollination. Without bees to pollinate plants, we'll lose a lot of food products that have been staples of human life for millennia. Take a look at this ",
"list of plants that bees pollinate",
" and imagine the ones listed as 3 or 4 on the pollination impact scale no long... | [
"Yes, but it would require incredible amounts of time and money. The production would be significantly reduced, and the cost of food that had to be hand pollinated would skyrocket to the point of being unaffordable to most people. The cost of hand pollinating, for example, apples to keep current production levels... | [
"Radiolab did an episode where they discussed this exact thing and according to the farm in China, hand pollination actually resulted in greater yields considering you got near 100% pollination as opposed to a mismatched 75% or so that bees tend to have. Write up on it by Robert -> ",
"http://www.radiolab.org/sto... |
[
"If wealth was distributed evenly amongst all of Earth's population, how well-off would each person be?"
] | [
false
] | Assuming productivity remained the same. | [
"Total global wealth is ",
"currently pegged at $231 trillion (pdf)",
", so that's $33,000 per person. Global GDP is around $70 trillion, which makes for $10,000 annual income per person.",
"According to the Credit Suisse report, global wealth is expected to increase to $345 trillion in four years, which will... | [
"True. I wasn't figuring property, but yeah it would be worse if people didn't get to keep the stuff they already had. It would become a free for all if all things were equal. "
] | [
"Is that 345 trillion nominal dollars, or real dollars?"
] |
[
"Do humans have the ability to \"sense\" when someone is behind them or staring at them or is it usually just a lucky guess?"
] | [
false
] | I've always wondered... You'll be sitting somewhere like the library, then suddenly you look up and turn around and catch someone looking at you, or simply standing behind you. Can we naturally sense when someone's behind us or next to us or does it just depend on the situation? EDIT: I suck... "I've always wondered," ... | [
"Obviously you can't tell what someone else's eyes are doing (the difference between them looking at you and not looking at you). This is a great opportunity to consider bias! When you look around and no one is looking at you, that doesn't stand out in your brain. But when you \"feel watched\", look around, and ... | [
"Try it yourself, ask someone to stand behind you and see if you can tell when he looks at you and when he looks away."
] | [
"I like this kind of answer because it encourages testing the world around us to find out, rather than asking someone else."
] |
[
"Do Animals have Blood Groups like humans?"
] | [
false
] | null | [
"human blood types (ABO) are present in other primates. The other great Apes have very similar blood to ours. not much research has been done on this for a lot of reasons (for one human blood is much easier to get than gorilla blood). It is probably possible to transfuse ape blood to an acceptable donor (accounting... | [
"Blood groups in humans typically describe features of the cell surface antigens on our red blood cells. These antigens can be sugars or proteins or a mixture of proteins with sugars bonded to them. The ABO designation is controlled by which version of an n-glycan sugar is sticking out of your red blood cells. But ... | [
"The blood of the marine lugworm ",
" contains a type of hemoglobin that is a more efficient O2 carrier than the human hemoglobin, and there has been a lot of research on the potential of this hemoglobin as a therapeutic agent. This would not be a blood transfusion, though, just hemoglobin. ",
"Here is a refere... |
[
"What happens to neutron stars, pulsars, and other super dense objects after they've spent their energy? Can their material be reabsorbed into new stars, solar systems, or galaxies?"
] | [
false
] | Considering how dense objects like neutron stars are, what happens to them after they die? Are they broken apart, exploded, absorbed into new objects, or something else? | [
"What do you mean by \"spent their energy\"? Neutron stars are already fragments of stars that have spent their fuel (for nuclear fusion) and then exploded in supernovas. As such, neutron stars are just really tightly packed blobs of neutrons (and other matter). These bodies don't need an input of energy in order n... | [
"/u/totitiganiisuntgunoi",
" described what we know (and don't know) about neutron stars pretty well.",
"We also have a pretty good idea of what will happen to White Dwarfs over time; like neutron stars they don't require fuel to resist collapse. Electron degeneracy pressure holds them up against gravity (where... | [
"Thank you for the answer.",
"Always!",
"Does the mass and gravity of these super-dense objects slow them down relative to other objects in the galaxy they are a part of?",
"Yes, time passes measurably more slowly on these stars compared to almost anywhere else in the galaxy. ",
"Would the galaxy they were ... |
[
"How close do atoms in a given space have to be in order for sound to be able to travel across them?"
] | [
false
] | I've learned that there's no sound in space, because there are none (or very few) atoms, whereas sound moves just fine through our atmosphere. So where's the line drawn? How many atoms are needed for sound to travel and how close must they be? | [
"The is no distinct line. The average distance between atoms in a gas (ideal gas really, but it's the same at the low-pressure limit) is inversely proportional to the pressure. ",
"So what you're asking is the same thing as what the lowest pressure is, at which you can have sound. But sound is a propagating ",
... | [
"Well, no, not really. But atoms/molecules are moving about, the Cosmic background temperature is about 3 K. And there is a point at which the forces will be negligible compared to the average velocities. That is, they're moving much faster than the required 'escape velocity'. For a pair of non-charged, ordinary si... | [
"Is there a certain point at which the pressure is sow low, and thus the distance between particles large enough so that they don't interact witch each other any more?"
] |
[
"On a molecular level, is there a gradual transition between phases of matter, or is more like a lightswitch? For instance, are the molecules in melting ice switching from solid configuration directly to liquid configuration, or is more of a gradual transition process?"
] | [
false
] | I guess an analogy would be two different light switches. Where one is the on off type, and the other the dimmable type. The light can be on or off in both cases, but in the latter there is a gradual transition from on to off. I hope this makes sense. : Thanks for all the answers! posted by user in I think best illustr... | [
"Somebody correct me if I'm wrong, but the molecules themselves don't have \"states\" so to speak. They just kinda do their thing. If, say, in ice, enough energy gets into a single molecule that it begin to drift, you wouldn't necessarily consider it liquid, only when they are all moving relative to each other. Bas... | [
"Well, sort of. If we take water for instance, when it freezes, it does crystallize forming a hexagonal geometry. It's not just a jumble of molecules.",
"So yeah, I get what you're saying about them not having \"states\" but solid and liquid water definitely have different arrangements of their molecules"
] | [
"As always, it depends.",
"Phase transitions can be defined in term of some order parameter. It might be something obvious like temperature but can equally be something more obscure. Phase transitions with a discontinuity in energy vs order parameter are called first order transitions and are very much one-or-the... |
[
"Why don't LEDs \"run out\" of electron-hole pairs during recombination?"
] | [
false
] | We learned recently in class about how recombination in LEDs turns an electron-hole pair into light energy, but doesn't this deplete LEDs eventually? | [
"I think this comment is missing the point. Thermal excitation alone is not enough to power an LED. Otherwise, you would have a perpetual-motion / free-energy device on your hands (a magical LED that outputs light using nothing but ambient thermal energy!).",
" ",
" carriers are injected into the p and n region... | [
"I think this comment is missing the point. Thermal excitation alone is not enough to power an LED. Otherwise, you would have a perpetual-motion / free-energy device on your hands (a magical LED that outputs light using nothing but ambient thermal energy!).",
" ",
" carriers are injected into the p and n region... | [
"In a conducting LED holes are created in the p-type material and migrate towards the junction. The electrons freed in creating holes become the current flowing round the circuit which eventually flows into the n-type material where they recombine with holes.",
"Every extra free electron created results in an ext... |
[
"What has more possible building combinations- 50 2x4 lego bricks or 100 2x2 lego bricks?"
] | [
false
] | null | [
"I don't think that's entirely true. Picture three 2x4 bricks connected in a straight line, two below and one on top. This is going to be an elevated piece, supported at each end. Try to do the same with your 2x2 blocks and it would be several separate pieces, you'd have to modify the design. I do think 100 2x2s is... | [
"If \"building combinations\" is defined so that only the overall shape matters (and assuming all the bricks have glue on their sides so they can join horizontally), then this analysis is pretty much correct, but if it depends on the individual bricks as well, then consider the following: a 4×4 square has only one ... | [
"I'm not sure we should assume the blocks can be joined at their side, since the question specifies lego bricks, and they can only be joined top and bottom.",
"So, if we take that view, that we're only interested in structures that can be made by joining bricks together, then we know:\n- There are 3 different way... |
[
"What is the fastest known object with mass?"
] | [
false
] | So as far as I know a massless object must move at the speed of light, but what is the fastest known object that has mass? | [
"If you mean relative to us, we have studies suggesting the existence of high energy cosmic rays, composed mostly of protons, that are slamming towards our atmosphere at approximately 99.9999999999999999999% of the speed of light.",
"It seems they are accelerated to such speeds with the help of a black hole. Some... | [
"at approximately 99.9999999999999999999%",
"Are all those 9's ",
"significant",
" or are they hyperbole?",
": Added link to clarify my use of the word \"significant\" per \\u\\RepostThatShit's comment ",
"here"
] | [
"They're significant. When you're dealing with (special) relativity 'gamma' is the all important quantity. The difference each 9 makes is definitely noticeable. Its like comparing the energies of the tevetron particle collider and the large hadron collider. Its just another decimal point closer to c."
] |
[
"Where does the swelling volume come from when you get injured?"
] | [
false
] | When you get injured, from where does all that extra volume originate? Is there a maximum volume increase that you can get from swelling? | [
"I think what you're talking about is inflammation around an injury, correct? If so, this is due to the inflammation response of your immune system. There are a lot of things going on when you are injured. First, you might notice that the area around the injury becomes reddened; this is due to increased blood flow ... | [
"In simplest terms, the swelling is part of what causes the pain. In order for you to properly use that body part again, aka be able to go through full range of motion, the swelling would have to be reduced or gotten rid of completely."
] | [
"Could you by any chance also explain the reason many efforts immediately after an injury focus on reducing swelling? I was under the impression that the swelling prevents further injury from movement. "
] |
[
"How did ancient people preserve their food?"
] | [
false
] | I buy fruit and vegetables from my local farmer's market, and often find them turning moldy within 3-4 days of my purchase. If I am storing them in the height of preservation technology (the refrigerator) how did ancient people preserve their crops through the winter? I really hope the answer isn't "They weren't picky... | [
"There are lots of ways you can do it. Refrigeration is in the \"Make the food inhospitable for microbes\" department, and this is a reasonable and long-practiced habit. In fact, the Romans were among the cultures to use refrigeration pits long before the mechanical refrigerator came along. Pliny talks about Rom... | [
"how did ancient people preserve their crops through the winter?",
"In one sense, they didn't. Cheese, yogurt, yeast bread, and alcohols (esp wine, beer, mead, or cider) are all basically just controlled spoiling of foods, and the edible \"mold\" (actually bacteria) displaces harmful stuff, so it stays edible ev... | [
"You insulate it with dirt, sawdust, and plant matter. In other words, you bury it. There are still ice pits behind old houses you can fall into if you're not careful.",
"Keep in mind that the Alps are in what's now northern Italy."
] |
[
"Can the kind of DNA lesion that causes melanomas also damage germ line cells (in a way that damaged DNA is passed forward) if similarly exposed to UV radiation?"
] | [
false
] | [deleted] | [
"Sure can! I want to point out though, there's not one kind of lesion that causes melanoma (you can induce melanoma the same way you induce any other cancer); it just so happens that skin is heavily exposed to UV light, so UV lesions are the most common.",
"If you exposed germ cells to UV, they would acquire the ... | [
"Yes and no - There's a lot of speculation that this is the source of many cancers, where dividing cells (they're often referred to as cancer stem cells) undergo damage, which then spread the mutation to other cells. This is somewhat contentious because there are indications that sometimes you can cause mutations... | [
"Ok, try to answer those one at a time:",
"In modern humans, does UV penetrate to the gonads?: not really. Check out this illustration: ",
"http://library.med.utah.edu/kw/derm/pages/meet_2.htm",
"Basically, the skin does a very good job of stopping UV light. By the time you get to the testes, just about all... |
[
"Why do squealing-scraping sounds like nails on a chalkboard and forks across a ceramic plate irritate us/our ears so much, even if they're not that loud?"
] | [
false
] | null | [
"This sounds like a Just-So story to be honest. What evidence is there that nails on a blackboard sounds like a human baby cry? Frequencies are not the only component of sound, and anyway a huge number of natural sounds fall into the human speech frequency range. Yet there are not the same response to these ambi... | [
"By all means, if you find fault with my explanation please feel free to offer an alternative. If you read my response, you'll see at no point do I compare nails on a blackboard to a human baby cry. That would be silly. Ignoring the issue of baby cry/nails on blackboard;",
"The human brain processes sounds of dif... | [
"Our ears are attuned to certain frequencies (more generally, the range of frequencies that human voices cover) meaning we 'hear' those sounds louder than others.\nEvolutionary psychologists suggest especially high pitched noises elicit a greater response because they sound like the noises we make under distress - ... |
[
"What is the biological reasoning behind the frustration that you can feel in the middle of your chest?"
] | [
false
] | Why do we feel it only at the chest? Does some sort of acid build up? | [
"Stress releases epinephrine increasing heart rate and constricting blood vessels, norepinephrine activating the amygdala and increasing heart rate, and cortisol which will increases stomach acid and blood pressure. It is likely you feel it most in the chest because the heart and esophagus are under increased load ... | [
"This is something I've always wondered as well. Strong feelings of things like frustration, shame, embarrassment and regret all seem to make something in my chest feel ignited. Negative emotions can sometimes feel physically painful when they are strong enough. I'd love to learn more about the science behind thing... | [
"Can we suppose this is the origin of the former belief that the heart was the seat of the emotions?"
] |
[
"Light Speed travel and Invisibility?"
] | [
false
] | Could an object traveling at faster than light (I know its impossible but for this question lets assume it isnt) conceivably be invisible to the naked eye? Since the eye requires light to register images would an object traveling faster than light not give off color and hence not be observable? | [
"Imagine a jet fighter. It travels faster than the speed of sound, but that does not make it inaudible. Regardless of the consequences of time travel and infinite energy requirements, an FTL object with mass would encounter normal matter in its path and collide with massive consequences, which would certainly be vi... | [
"I know its impossible ",
"Then there is no need for asking, right? From the guidelines for askscience:",
"Avoid hypothetical questions that require speculation. ",
"Examples of violation: ",
"“What do we see when we go faster than light speed?” ",
"Asking for impossible things can never be answered s... | [
"Cherenkov Radiation",
" is relevant here. It is the light equivalent of a sonic boom.",
"You cannot go faster than the speed of light in a vacuum, but it is possible to go faster than light in a dielectric (where light slows down because of interactions with the atoms and electrons).",
"While I cannot really... |
[
"Antibiotics kill a wide range of bacteria, which is needlessly destructive to the human microbiome. Is there an effective alternative that only kills specified bacteria?"
] | [
false
] | If not, is there any research being conducted to create such a therapy? | [
"Antibiotics do have some selectivity. As shown ",
"here",
", antibiotics have what we call a spectrum of activity (tetracyclines being the broadest one). Having a wide range isn't necessarily a bad thing, because bacteria are very diverse. While we can associate a pathology with a specific bacteria, it can hav... | [
"It is not actually used in healthcare anywhere. As far as I remember, the discovery of antibiotics interfered with the research in phage therapy, because it was seen as useless at that time.\nNowadays, with the increasing problems with antibiotic resistance, it looks like an interesting alternative again, so there... | [
"In the past there has been work with bacteriophages to eliminate unwanted bacteria called ",
"phage therapy",
". Bacteriophages are viruses which infect only a select number of bacteria and could consequently leave the human microbiome unharmed. There is current research into using phage therapy to eliminate s... |
[
"What do we know about Long-Covid (i.e. people who haven't had any measurable damage but feel like something is wrong in their body)?"
] | [
false
] | null | [
"There is a lot of noise out there on what causes long covid and almost no medical consensus, however, there are a lot of theories, and the truth likely lies in one or more of them. ",
"Firstly it's important to note that long covid is not defined aetiologically but symptomatically and circumstantially. It is a d... | [
"This article ",
" discusses how Covid tends to lead to a significant increase in autoantibodies (antibodies that recognize human proteins). That could potentially lead to an autoimmune response over a long period of time that could lead to long Covid."
] | [
"I'm a dysautonomia awareness advocate and participating in research on POTS (a form of dysautonomia). Viruses have long been known to trigger Dysautonomia, and it seems that COVID is triggering POTS at very high right. Pre-print studies show that 5-8 percent of people who have had COVİD still have POTS symptoms ... |
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