title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"What is happening with this chemical reaction?"
] | [
false
] | Thunderf00t is a smart guy and he doesn't know | [
"Product should be one K2SO4, no? "
] | [
"\" the hot H2 would burn. In an truly inert atmosphere, it wouldn't, but if that clown used CO2 the carbon would be reduced\"",
"Maybe you should stick to what you do know rather than calling people names. The inert gas used in this case was argon.",
"The tenuous string of reactions you propose is also very u... | [
"The reaction is certainly NOT 2K + H2SO4 = K2SO4 + H2.",
"What is probably happening is potassium is 'burning' the oxygen n the sulfate. For certain there is residual elemental sulfur left at the end of this reaction and you can see it precipitating as clouds during the reaction.",
"The wired thing is this is... |
[
"How realistic were TV show Babylon 5's Omega-class destroyer's rotating middle sections in simulating gravity? Would the rotating section be able to provide gravity for the entire ship or just the rotating part?"
] | [
false
] | One of my favorite shows of my younger days was Babylon 5. Someone in posted from a sourcebook a few days ago, and it got me thinking about the Omega-class destroyers and how they rotated just about one-third of the vessel to provide gravity, and it got me wondering if they provided gravity throughout the vessel. The bridge definitely had gravity, as they showed multiple vessels' bridges with gravity. The image in that post isn't the clearest, and I can't tell whether it is in the rotating section or right next to it. This is the best YouTube clip I could find to give you an idea of what the Omega-class destroyers looked like. So, how realistic were TV show Babylon 5's Omega-class destroyer's rotating middle sections in simulating gravity? Would the rotating section be able to provide gravity for the entire ship or just the rotating part? | [
"It is definitely possible to mimic the effect of gravity inside a rotating object. You can try this for yourself by partially filling a bucket with water, lifting it up by the handle and spinning around. The water will be pushed against the bottom of the bucket. The same principle can be applied to spaceships and ... | [
"This difference in \"gravity\" depending on the distance from the axis of rotation is a plot point in ",
"Schlock Mercenary",
"."
] | [
"I thought it was fairly comical in the movie. There was a point in the trip where a warning would sound and then they would seem to instantly shift from normal gravity to null gravity, and then moments later another instant shift to normal gravity in the other direction."
] |
[
"Why wasn't the SpaceX Dragon capsule full?"
] | [
false
] | As you can see in , there's plenty of room in the capsule on delivery? Why isn't it full of equipment and supplies? Is volume not the limiting factor? | [
"I think that when it comes to sending ships into space weight is the limiting factor, not volume."
] | [
"I think the cargo was limited since this was the first flight."
] | [
"The Dragon Capsule is rated for a certain amount of cargo by weight, not volume. Think of it the same way as a truck trailer, they're allowed to carry a certain weight so they're rarely, if ever, completely filled (in some cases, hardly at all)."
] |
[
"Does having a small head make you less intelligent?"
] | [
false
] | Do people with a small head (like myself) have a lower amount of intelligence? | [
"There's a very weak, spurious correlation. This correlation is probably due to the effect of childhood malnutrition on both intelligence and general body (including head) size. Based on this, I'd say the answer to OP's question is \"no\", but this really is just quibbling about language usage. "
] | [
"Statistically speaking, yes. Head size does correlate with intelligence. The effect, however, is on the order of a few percent of one standard deviation, so don't think it carries that much predictive value.",
"\nEdit: See refs below for more accurate assessment of the magnitude of the effect. "
] | [
"No, that is not true on either count. ",
"Count 1). It is a spurious correlation. ",
"Truth: The correlation explains 16% of the variance when MRI measures of brain volume are compared to IQ. It is substantial. ",
"Count 2) It is correctable by body size",
"Truth: Only a small portion of the correlation ... |
[
"How does transformation occur in eukaryotic cells?"
] | [
false
] | If I were to insert a DNA molecule into a eukaryotic cell via microinjection, for example, what is the mechanism by which the cell incorporates the foreign DNA into its own genome? Maybe I'm not googling correctly but I haven't found an answer, this question has been bugging me for days. | [
"Hi. As far as i know, P-elements which are a type of transposable elements have been used to insert fragments of DNA. This type of insertion is non specific and the mechanism is somewhat like the P-element from your insert (flanked to your gene of interest) finds transposable elements in the genome of the host and... | [
"It's complicated. You are basically asking how to make a DNA-based retrovirus. You need to accomplish the following:",
"Have a piece of DNA on hand. It can be single-stranded template strand DNA, single-stranded coding strand DNA, or double-stranded DNA. How this works depends on what type of DNA you have.",
"... | [
"Thank you. I completely forgot about viral vectors. Don't the P-elements code for similar proteins like transposase? \nI do not the exact mechanism of insertion using P-elements or retroviruses so your explaination was very helpful."
] |
[
"Is this a meteorite ?"
] | [
false
] | i have found a strange stone. it is very heavy (680grams approx 18.3cubic inch) and on one side is a strange material, which seems to be glass. the brownish aeras are magnetic. | [
"I do not think it is. You can look around this internet for more \"Identifying meteorite\" but ",
"this one",
" is fairly helpful with a step by step guide.",
"Edit- the reason I don't think it is a meteorite is because of the white colored minerals on it, and the bubbles. However you may want a second opini... | [
"the crust can be washed away, but one of the ko arguments are the bubbles. "
] | [
"I'm not a geologist, but 680g/18.3in",
" is not very dense -- only about 2.25 g/cc. How did you estimate the volume? ",
"The brownish areas look like some kind of oxide; since you mentioned they are magnetic, it probably contains iron in some form or another. All of the cavities present suggest to me that it w... |
[
"Is there a limit to the size of the wavelength of an electromagnetic wave, both large and small?"
] | [
false
] | And if so, what creates this limit? | [
"At very long wavelengths, the interstellar medium ends up damping electromagnetic waves, effectively making them die out pretty quickly. There is, however, some theoretical evidence which suggests that you could get wavelengths of light which are so long that they would be able to bypass this damping effect. Thi... | [
"Although there's no theoretical limit, if you have an EM wave with a short enough wavelength, general relativity suggests that a single photon of that radiation would collapse into a black hole. If I remember correctly, the critical wavelength is the Planck length (about 10",
" m). Of course, we don't know how w... | [
"Photons produced at the LHC can have energies in the GeV range, corresponding to wavelengths around 1 fm (roughly the size of a proton)."
] |
[
"Is there any possibility or any suggestion, at all, that life could have been seeded on a fertile, but lifeless Earth?"
] | [
false
] | null | [
"Is this what you were looking for? ",
"Panspermia"
] | [
"Actually, I feel that if we are made of the same KIND of genetic material (DNA, RNA and protein in water-based lipid enclosed cellular systems), such life would resemble quite closely to what we have in our planet. Definitely not in the macroscopic anatomical level, but at least in the cellular level. The problems... | [
"Possible, but highly unlikely. Unless they underwent the same forms of selective pressure in the same sequence, they wouldn't resemble each other."
] |
[
"How does light exist? (please correct me)"
] | [
false
] | Relativity says that for something to travel at the speed of light, either it has to have no mass or, if it has mass, it must have infinite energy to reach the speed of light. However, E=mc says that for something to have energy, it must have mass. Doesn't this mean that light has infinitely small mass (because it must have some mass, since 0 times anything is 0), but it must also have infinitely large energy for this mass to reach the speed of light? I get confused when I apply both relativity and e=mc please unconfuse me! | [
"E=mc",
" is for stationary mass. For things moving relative to an observer you need E",
" = p",
" c",
" + m",
" c",
" With p, as the momentum.",
"If momentum is 0, this reduces to E=mc",
" However, if mass is 0 this reduces to E=pc. So photons get their energy not from mass but from their mome... | [
"Momentum is actually not equal simply to mv, as you learn in a first newtonian physics class. This turns out to be an approximation that is valid for small v. When v is large, you have to use the full form; This gives the result that EtherCJ mentioned. You can also write his relation as E = gmc",
" where g is ca... | [
"However, E=mc",
" says that for something to have energy, it must have mass.",
"No, that is not what this equation means. This equation relates mass to energy, but it doesn't say that all kinds of energy have an equivalent rest mass.",
"Photons possess momentum, but only because of their energy, not because ... |
[
"What happens in the body after a polymer like HDPE is consumed?"
] | [
false
] | null | [
"HDPE does not break down in HCl",
", nor does it react much (if at all) to salts. The temperature/mechanical action along the way isn't enough to break it down either. ",
"Basically, if it is small enough, it'll pass right through you. However, since it doesn't break down, eating large pieces can become stuck ... | [
"You really should not ask for medical advice on ",
"r/askscience",
". Not only for your own sake, but also because you open up the community and individuals in the community (particularly if they are in the medical profession) to lawsuits and all kinds of nastiness."
] | [
"You really should not ask for medical advice on ",
"r/askscience",
". Not only for your own sake, but also because you open up the community and individuals in the community (particularly if they are in the medical profession) to lawsuits and all kinds of nastiness."
] |
[
"How does dark energy result in the expansion of the universe?"
] | [
false
] | [deleted] | [
"Let's consider an analogy from classical mechanics. We can modify Newtonian mechanics by giving everything an additional acceleration of c r where r is the position vector in some coordinate system. It doesn't matter where we put the origin of this coordinate system - every pair of objects will see a relative acce... | [
"To confirm my understanding of your response, even if we express the cosmological constant as a function of energy and pressure, the pressure component's need to be negative is phenomenological since that's what we observe and that's what GR allows.",
"Right.",
"Secondary question, do we know how a material co... | [
"To confirm my understanding of your response, even if we express the cosmological constant as a function of energy and pressure, the pressure component's need to be negative is phenomenological since that's what we observe and that's what GR allows.",
"Right.",
"Secondary question, do we know how a material co... |
[
"What are the stages in brain development of a newborn until its brain can be considered fully-developed, save for later major changes like puberty? Or can a newborn's brain be considered developed but without experience?"
] | [
false
] | null | [
"http://en.wikipedia.org/wiki/Infant_vision",
" -- a strong example of neural development after birth.",
"What you're looking for... a solid theoretical transition from 'developing' to 'developed' doesn't really exist. It's gradual and works for different systems at different rates at different times. You cou... | [
"A good way of looking at it is with Jean Piaget's cognitive development framework. There are 4 stages (hence the name 'stage theory'):"
] | [
"A neonate's brain lacks an awful lot of myelination. This is why, for instance, tonic-clonic seizures don't really occur in newborns--epileptic discharges can't spread throughout both hemispheres very easily.",
"The frontal lobes aren't even completely myelinated until the early 20s. So it is a gradual process. ... |
[
"Why do racecars have wide tires?"
] | [
false
] | I recently learned that surface area does not influence the friction so why are the tires so wide? | [
"Two things:",
"First, the claim that surface area doesn't affect friction is a good approximation, but it isn't exact. It comes from. The fact that the force per surface area of contact is roughly linearly proportional to the pressure, while pressure is inversely proportional to area. These two terms cancel out... | [
"The tires are also \"sticky\" and increase ground friction via some adhesive forces. More contact area for adhesion certainly does increase the grip in that case. "
] | [
"In open wheel racing (not sure about NASCAR), the downforces produced by the aerodynamic surfaces of the vehicle also play a role here, increasing the size of the contact patch, and/or also increasing the force applied on that contact patch. IIRC, a Formula 1 race car generates enough down-force at around 80kph th... |
[
"What would happen if a scientist received a huge grant and just decided to keep the money?"
] | [
false
] | ...I'm not even in the science field so that's not why I'm asking. For example, Bill Gates has apparently given out grants before. What if a scientist just decided to retire and keep the money? Do they even give the money to the researchers? Or do the researchers have to fill out paperwork to have stuff paid for? Would that be the same as keeping money from a place like the NSF (National Science Foundation)? What would happen? Has anything like this happened before, and what happened? | [
"Grants are not paid into researchers bank accounts. They are usually administered by the university or other research institution and they will pay invoices that are submitted to them by the researcher.\nFraud can still occur of course.",
"(I'm a grant holder on a 3 million dollar grant. I don't get to see the m... | [
"Embezzlement is embezzlement. I don't know why you'd think it'd work any differently with scientific grants. "
] | [
"Well, I'm just getting into graduate study, so I'm not exactly an expert, but they'd go to jail for fraud. A \"grant\" isn't just a check for a huge amount of money written in their name. It's a contractual agreement to provide such-and-such budget for such-and-such amount of time performing research with such-a... |
[
"How Fast Would Something Need to Move in Order for it to Visibly Blueshift?"
] | [
false
] | Pretty much as it says. How fast would something need to move before it would Blueshift to the naked eye? | [
"The relativistic Doppler shift equation for when the source (s) is moving straight toward the observer (o) is:",
"(λo/λs)",
" = (1+v/c)/(1-v/c)",
"Solving this equation for the velocity v gives:",
"v = c (1-(λo/λs)",
" )/(1+(λo/λs)",
" )",
"Let's assume that a clearly visible blueshift would be if a ... | [
"That is correct. A group in MIT actually made a game on this premise that way you can see what the world would look like if you could travel at a significant fraction of the speed of light. ",
"Check it out."
] | [
"About what I expected. Thanks for the quick answer!"
] |
[
"Why does the angle of incidence change when light refracts?"
] | [
false
] | null | [
"When considering refraction keep in mind that the speed of light in the two materials is different. ",
"The easiest explanation comes from the idea that light travels in such a way as to minimize the travel time between two points. In free space it's a straight line. (Near a massive object like a black hole, it ... | [
"When light waves pass into a denser material, they slow down. No new waves are created, so now the wave crests are closer together.",
"At one point (optical axis), the waves strike perpendicularly and must continue on a straight line into the new medium. Everywhere else the wavefront strikes obliquely, which mea... | [
"I wish i could contribute to this discussion more that just saying that you are correct and i'm also a 'fan' of this lifeguard example when it comes to explaining things with refraction."
] |
[
"Slugs. Where are they?"
] | [
false
] | I can find slugs around my house in the shade (when there is shade) and they are in great numbers. they don't seem to bother me and I don't seem to bother them. Here's my question: Where do slugs go when we don't see them? Is there some sort of million-slug orgy going on somewhere that I don't see? related: where do butterflies go when it rains? | [
"I went on a butterfly walk with an entomologist, and that's exactly what she said the butterflies did - hide under leaves.",
"By the way, if you ever hear of an opportunity to go on a hike or walk with an entomologist, take the opportunity. They'll show you all kinds of fascinating little things you'd never ord... | [
"They are probably outside dispersed under rocks and things. Check places that are damp. And there's always a bunch in the hosta :(",
"Butterflies shelter from rain under leaves and in other little nooks and crannies I believe."
] | [
"I'm an avid gardener. I've learned a lot about slugs as I live in on a very damp island in the Pacific South West of Canada.",
"You can find slugs at any time under dense foliage, debris (Plastic sheeting, leaves from last fall, weeded plants, lumber/plywood boards, and anything else that will retain moisture th... |
[
"what does testing negative to COVID-19 mean after being positive? Does it mean the virus has completely left the body or the body's immunity has improved enough to keep a check on the virus? Can an infected person once cured can still infect others?"
] | [
false
] | I'm asking this because a well-known celebrity in my country has tested negative only after sixth time. And she has been discharged from the hospital. Can she still infect others? | [
"s tested negative only after sixth time. And she has been discharged",
"EEEEHHH. The test has a really high false negative rate. You're supposed to get two negative tests in a row at least 24 hours apart before leaving isolation.",
"According to the CDC",
" you can safely leave isolation and not be contagiou... | [
"Here's the first article I could find on it",
". It looks like you have about a 15-25% chance of getting a false negative when tested.",
"If you get 6 tests in a row there's a pretty high chance you'll get a false negative on one of them just by random chance."
] | [
"There's a handful of studies on it. ",
"Here's an early one",
" that shows a pretty dire sensitivity. Some others find the sensitivity to be 60 or 70%. The point is a lot of clinicians are using CT instead of the swab test for initial diagnosis."
] |
[
"Do species with a shorter lifespan evolve faster than those with a longer lifespan?"
] | [
false
] | [deleted] | [
"The answer to your main question is that yes, shorter generation times (lifespan itself doesn't really matter) allow faster evolution, more or less by definition since evolution is a change in allele frequencies from one generation to the next.",
"But the underlying premise is mistaken:",
"insects and the othe... | [
"Organisms with shorter lifespans will have more generations in the same period of time, so more mutations will occur in the population in the same period of time, meaning evolution will happen faster. We often use insects in labs when we want to study the evolution of traits partially for this reason; they also te... | [
"Sure, you always hear the example of the peppered moth, where the dominant color of moths changed between white and black of a couple decades because of industrial pollution levels. The only way a human population could change so dramatically in the same time is for nearly everyone but those of a single race faili... |
[
"Is Electron Exchange a Physical Effect or a Mathematical Trick?"
] | [
false
] | I have been studying DFT (Density Functional Theory) recently, and it is pretty common to see electron exchange referred to as an independent term of the Hamiltonian. I have seen some authors simply refer to the Kohn-Sham hamiltonian (including the exchange term) as "the hamiltonian." However, my understanding is that the exchange effect only appears because DFT uses an approximation to the Coulomb potential that includes electron self-interaction, which must be cancelled out using the exchange functional. From this perspective it looks like the electron-exchange effect is just a mathematical "trick" to correct for approximation errors. To what extent is electron exchange understood as a real, physical phenomenon as opposed to a mathematical convenience? | [
"Exchange effects are not an approximation, and they are very real. They are caused by the fact that electrons are fundamentally identical to each other, and thus indistinguishable from each other. There is no experiment you can possibly perform to tell the difference between \"Electron 1\" at position 1 interactin... | [
"Thanks for your explanations.",
"Unless you have an example of such a formalism, I'm not aware of any.",
"I think this is where I get tripped up. Some texts call formalisms like Slater determinant approximations (at least, when you use a finite set of Slater determinants) which makes it sound like the expressi... | [
"Well, the Pauli principle and spin-statistics theorem are real things, and just generally the difference between how Fermions vs Bosons work. On the macro scale you have ",
"Electron degeneracy pressure",
" as a another way of looking at it. (Feel free to compare the derivation of the degeneracy pressure to th... |
[
"a couple questions about food chemistry"
] | [
false
] | null | [
"Texture is partially a function of the molecules present, but mainly a function of how they're arranged. Layers, fibers, random granules, etc, have a much stronger effect on how a food feels to your mouth than what those structures are made from. We can use this to our advantage when designing food substitutes; mi... | [
"Ok, emulsions:",
"Emulsions are any two fluid substances that do not normally mix, forced into intimate mingling through massive shear forces. Basically, little tiny drops of one substance (discontinuous phase) surrounded by a thin layer of the other (continuous phase). We describe emulsions based on the two pha... | [
"Mayonnaise. seriously, how the ...?",
"Can you elaborate?"
] |
[
"Why do the colors dark purple and deep red \"feel\" visually very related, but they are on opposite ends of the visual spectrum?"
] | [
false
] | [deleted] | [
"This article has many factual errors and is very misleading. Only a very small subset of the colors you perceive have a wavelength. That is, if you split up white light using a prism, only a small subset of colors would be part of the resulting rainbow. Like most colors, magenta does not have a wavelength. ",
"T... | [
"This article has many factual errors and is very misleading. Only a very small subset of the colors you perceive have a wavelength. That is, if you split up white light using a prism, only a small subset of colors would be part of the resulting rainbow. Like most colors, magenta does not have a wavelength. ",
"T... | [
"So anyway, no light source can produce and nothing interacting with light can interact with only one wavelength selectively. You can't even only produce/interact with light that's strictly in between two wavelengths - there's always a smeared out continuous range of wavelengths. This is actually kinda deep and con... |
[
"Why are images displayed in inverse colors when you've looked at an image for a long time, then look away?"
] | [
false
] | null | [
"Because your eye and brain adapt to sensory input. This is a feature to reduce noise in the visual signal.",
"Here's an example. Your retina has ",
"many blood vessels",
". They sit in front of the photoreceptors in your eye. So why don't you see big red blood vessels all the time? Your eye and brain co... | [
"Thank you very much, I had no idea how to google this question so I really appreciate the answer; makes a lot of sense."
] | [
"Psychologists call this ",
"the afterimage effect",
"."
] |
[
"I tried to make double slit experiment but it didnt work. Where did I make a mistake?"
] | [
false
] | So I wanted to make my own double slit experiment and see light as a wave but I ended up seeing it as a particle I guess :( I carved two slits on a thick non translucent paper and used my phone LED light behind that paper ij order to make interference pattern occur on the wall in the dark room but that did not happen. All I got was the two bars illuminated on my wall. Basically tue light just went through rectangular slits and made two rectangular light bars on the wall and there was no interference pattern. I really want to see that pattern for myself. Please help me. Where did I go wrong? Is LED bad light source? Thank you everyone who shares their opinion on this | [
"In order to see diffraction, the slits should be on the order of the wavelength of the light used. For visible light, that means the slits should be on the order of less than 1 micrometer which is like 1/20 of human hair."
] | [
"For the 6 years I was a TA in 1st year physics lab, I'll have you know that not once was a student struck with PERMANENT blindness..."
] | [
"Just take a laser pointer and shine it on a CD/DVD. Should give you a nice diffraction grating demonstrating interference. You can even look at the pattern and try and calculate the relative data density of CDs vs. DVDs given the diffraction pattern you get."
] |
[
"What's in the space between the electron orbitals and the nucleus?"
] | [
false
] | Is it simply a vacuum? Or does the 1s orbital occupy that space? | [
"The most probable spot for the 1S state is called the Bohr radius ",
"Nope. (Although I don't blame you, this is probably the most misunderstood plot in all of chemistry) The most probable ",
" (1 dimension) is the Bohr radius, which isn't the same thing as the most probable ",
" (3 dimensions). ",
"The ",... | [
"The orbitals ",
" like little planet orbits or hallow spheres in which the electrons buzz around wildly.",
"The electron's behavior is governed by what is called the wave-function or the Greek letter Psi. ",
"Here",
" is an example of the first few probability distributions of the Hydrogen atom at the firs... | [
"I'm aware of these 3D representations, which is why I asked whether the 1s orbital wholly occupies that space. That electrons have no known volume is a fair point; I was initially picturing a point mass whizzing around a larger central mass, but it would perhaps be fairer to say that there's a point charge exhibit... |
[
"Why are pigs and humans so alike?"
] | [
false
] | I know that pigs are close enough to humans that we can transplant organs from pigs. My question isn't about the big picture of evolution, but rather why are pigs so close to us compared to other mammals? Do we have a common ancestor with pigs that is closer than whales or dogs? Do we know anything about that common ancestor? | [
"I believe they're not any closer to us than other non-primate animals like whales or dogs, but I'm not an evolutionary biologist, so I could be wrong. People who receive grafts from foreign species (xenographs) are on heavy immunosuppressives. ",
"Pigs are, however, close to our size, and have similar cardiac an... | [
"Humans and pigs are not even closely related. In fact, phylogenetically, humans are more closely related to rabbits and rats than they are to pigs. The last common ancestor to both pigs and humans existed around 90 million years ago, towards the end of the Cretaceous.",
"I was trying to find one grand article th... | [
"Partially true. Their stomach is relatively similar as are the small intestines. Their colon is actually very different, though, as it is arranged in a spiral. Our colon looks more like that of a dog."
] |
[
"If the Hubble or Webb telescopes were focused on a region of space and exposed for a very long time, is it likely that the resulting image would be so dense with galaxies that they could not be differentiated."
] | [
false
] | The Hubble Deep Field image was an exposure of 10 days. The length was required in order to capture enough photons from the dimmer distant galaxies to be detected by the telescope's CCD. If you arranged for an exposure which is on order of magnitudes longer in duration, would so many photons eventually interact with the CCD to create an image that would essentially just be a bright rectangle with every pixel illuminated? IE instead of having black background with a few pixels illuminated by distant galaxies, have the entire field of view illuminated by the billions of galaxies which would fill in the gaps between other brighter galaxies? | [
"The problem is that you can't really expose for longer than one hour with the hubble, as after that it disappears behind the earth for a while. You could make a bunch of pictures of that timeframe and overlap them, but this would not give you an infinite integration effect if you would have infinitely many so to s... | [
"Hubble turns off much more frequently than that due to passages through the South Atlantic Anomaly. All Hubble images are made by coadding a series of shorter exposures."
] | [
"So I suppose in those shorter exposures, the CCD would never reach the critical threshold where it does become activated by the faintest and farthest away galaxies."
] |
[
"Earth has been through several mass extinction events. How quickly did these occur? Did most life die out in months and years or centuries, etc?"
] | [
false
] | null | [
"Earth has gone through 5 mass extinction events throughout its 4.7 billion years of existence. While the exact duration of a mass extinction event is always disputed by scientists we have a general idea of their longevity. To give you an idea, the Permian-Triassic extinction event (also called the Great Dying) la... | [
"The rate of the disappearance of species is as big as the last mass extinctions.",
"Biodiversity is rapidly decreasing everywhere in the world due to us, humans."
] | [
"It's really not that bold at all considering the impact humanity has on the biosphere, see ",
"https://en.wikipedia.org/wiki/Holocene_extinction",
"You could argue that it's not a 'true' extinction event because...no wait, you can't really.",
"Take a look at the makeup of mammalian biomass that's near the to... |
[
"Can somebody please help me understand, at least on some fundamental level, the expansion of the universe?"
] | [
false
] | I want to understand this subject to some degree, but any research I do is either above my head, or very inconclusive (I realize that there is no definitive answer yet). I'm trying to wrap my head around the whole 'what is it expanding into?' thing. From what I understand (or don't understand, not sure), expansion means that distances between objects in the universe are growing? Or is there a defined end to the universe that is actually growing larger and filling another void? I'm sorry if I sound like a complete dumbass here. I just want to understand this better. | [
"Yes, distances between galaxies are increasing even though they aren't moving through space - the space itself is expanding.",
"Imagine a raisin cake rising in the oven. The cake represents the Universe and the raisins are galaxies. As the cake rises the raisins all spread apart, even though they aren't moving t... | [
"But the raisins in the cake are moving. The cake moves them by expanding. Is this where the analogy fails?",
"Jimmycorpse got it spot on, but just to re-iterate:",
"The raisins are moving with respect to one another, but they are not moving through the cake. With respect to the cake mix they are stationary. If... | [
"I probably don't belong in this subreddit, because I was a philosophy major and not a physicist. That being said, what is the difference between the emptiness that exists between objects in our universe and the emptiness that lies beyond. Further, what is to say that in the non-space void outside our universe tha... |
[
"Does the Higgs boson itself have mass?"
] | [
false
] | null | [
"It comes from Higgs bosons interacting with the Higgs field that fills space.",
"Things that get mass get their mass from interacting with the Higgs field that fills space, NOT from interacting with Higgs bosons."
] | [
"No, the Higgs fields are not made of Higgs bosons.",
"Rather, there is a Higgs field. It manifests in various ways. It has a non-zero value that fills space. That is what produces mass for various particles.",
"The Higgs boson is a different entity that the Higgs field can form.",
"In fact, the Higgs boso... | [
"Yes. It has a mass of around 125 GeV/"
] |
[
"How are amino acid residues on proteins numbered?"
] | [
false
] | Being of limited formal education in molecular biology, this has me stumped. For example, bovine serum albumin has 35 cysteine residues. Cys-34 is free. Why is it numbered 34? From the , the free residue resides in position 58 of the ~ 582 amino acids, and is the cysteine in the sequence. I'll accept Cys-1 or Cys-35, but 34? | [
"You're right about general numbering schemes.",
"In the case of bovine serum albumin, residues 1-18 make up a signal peptide that is cleaved off, and 19-22 are also apparently only present in the propeptide, not the final version (not clear where 23-24 go). The functional protein, then, consists of resides 25-6... | [
"This may be influenced by the fully processed or pre-processed variations of the same protein. Many proteins were discovered in certain states and numbered without knowledge of other primary structures. For example, in structure A this residue is cysteine in the 34th position, but the protein only takes on structu... | [
"Generally, they're numbered exactly as you would expect, from the first amino acid starting with \"1\" to the last in the sequence. However, there can be quite a lot of modification in the sequence, such as when introns are excised during ",
"splicing",
". This can throw off the numbering, and there's no abs... |
[
"If the universe's rate of expansion is increasing can we assume this will happen infinitely? If so, what would happen when it is expanding near the speed of light?"
] | [
false
] | null | [
"Yes. The speed of light is not a limit on the expansion of the universe, since the speed of light, c, is, to quote wikipedia :'the upper limit of for the speeds of objects with positive rest mass'. In other words, it is the maximum rate at which information (and energy) can be propagated. This speed does not apply... | [
"According to Kraus's \"A Universe From Nothing\" lecture, once the universe's expansion rate exceeds the speed of light, we will no longer be able to see other galaxies because as fast as their information (light) is moving towards us, the space between us and the information source is moving away faster. ",
"I... | [
"To answer the first part of your question, the jury is still out. That, despite the Nobel prize in physics this year concerning the universe's accelerated expansion. What these scientists observed was an unexpected acceleration of the expansion as of many billions of years ago. It remains to be seen if that exp... |
[
"Do we know how far earth is from the \"location\" of the big bang, or how far the farthest objects have traveled since the big bang?"
] | [
false
] | null | [
"I know that the concept of \"distance from the location of the big bang\" is tricky...",
"It's not just tricky. It's not meaningful. See the FAQ:",
"http://www.reddit.com/r/askscience/wiki/astronomy#wiki_big_bang"
] | [
"I'm not sure what you're referring to with the link.",
"There's a post that states there isn't a center to the universe: ",
"http://www.reddit.com/r/askscience/wiki/astronomy/shapeoftheuniverse",
"Maybe I'm overlooking something, but I also don't see any references to distances traveled since the big bang. O... | [
"First link under the subsection on the Big Bang:",
"Did the universe start as a single point?",
"It doesn't make sense to speak of distance from some \"location\" of the big bang, because it didn't occur at one single point."
] |
[
"If water is at a certain salinity, could you drink an unlimited amount free of consequence?"
] | [
false
] | (I'm excluding dry drowning/ water going into the lungs.) So, if you drink purified water, the water goes into you cells via osmosis, popping them. If you drink seawater, water leaves the cell, causing the cell to die. Is there a value of salinity where neither of these would happen? | [
"If you drink water that is isotonic (~9 g NaCl per Litre of water) then you can drink an awful lot of it without any acute adverse consequences.",
"You can still drink too much of this solution but it just pushes the problem down the line, so to speak. I'm not sure what medical problem would manifest most acutel... | [
"Isotonic saline is used widely in hospitals for fluid replacement. As it has been correctly stated, 9g of NaCl per liter is isotonic to normal plasma. The major fluid compartments of the body are the intracellular and extracellular spaces. The extracellular space is further broken down into the vascular space and ... | [
"I wanted to add a bit about the homeostasis resisting the change, particularly against hypotonic solutions, but couldn't eloquently sum it up. So thanks for adding a lot of detail!",
"To those reading on, this effect is the entire reason we have advanced life: Cell walls and transport mechanisms that allow effec... |
[
"Are optimally aerodynamic and hydrodynamic shapes the same?"
] | [
false
] | I understand that air and water are different fluids, with different reynolds numbers and the like, but given that the goals are usually the same - reducing turbulent flow, dynamic pressure, etc., are the differences we see in these types of shapes due to their different applications, or the different properties of the fluids? i.e. propulsion and materials aside, would an air- submarine and an underwater airplane look like their real world counterparts? | [
"In short, yes and no. You are correct that both air and water are fluids with different properties. The most important property is that both are governed by the physics of Newtonian fluids. That is, the viscosities of air and water increase linearly with added shear stress. Since both are Newtonian fluids, the dim... | [
"The dimensional analysis using the Reynolds number is correct up to some limit, and in the case you mention (air-submarine and underwater airplane) it can be valid for a big range of parameters. One big difference is that the Mach number is very different between air and water. More than that in the case of a norm... | [
"No. Wings are designed to efficiently generate lift and since planes are heavy, you need big wings. Submarines don't need to generate lift, so they don't need wings. The ideal aircraft shape is a wing with no fuselage (e.g. the B-2), while for a submarine, it's all fuselage (which it is). Don't be surprised if... |
[
"Thumb vs Toe Prints"
] | [
false
] | Today I had quite a large piece of skin come off of my foot which looked eerily exactly like a thumbprint(bball in vans. bad idea). Which gave me the idea that you could use pieces of skin off of your feet(because they resemble thumbprints so much) glue them onto your thumbs/other fingers and go about committing crimes and getting away with them. However, i compared my toe print(actually the pad below it not the toe itself) to my thumb and they seemed identical. Q:Is your thumb print them same as your foot/toe print or am I a shitty forensics expert? if they are not, what would prevent people from getting away with crimes by faking their finger prints in this manner? if they are indeed the same, has anyone ever been arrested by toeprinting instead of fingerprinting? | [
"Your finger and toe prints won't always be identical. Fingerprints are formed during foetal development due to differential pressure experienced by the growing skin (known as the volar pad), and is not entirely due to genetics - that's how identical twins end up with different prints.",
"You ",
" glue your toe... | [
"is there any way to make your fingerprint indiscernable?",
"Well, you can sandpaper your fingerprints off if you want, but then you'll be leaving other bodily fluids (blood, etc.) instead. Even if you let it heal a little, most forensic identification experts will tell you that a scar or injury makes it ",
" f... | [
"The two gloves is something people often don't think of, then when they, say, get the victim's blood on the gloves, and their fingerprints are on the inside of the glove, that's one piece of evidence connecting you to the victim.",
"One of the resident physicists will help you a lot more - I know next to nothing... |
[
"Do different kinds of dairy affect lactose intolerant people differently?"
] | [
false
] | null | [
"ie. Will some yogurt make me poop more than milk? ",
"Real yogurt is lactose free."
] | [
"... All my life.... All my life i have been avoiding yogurt. Whyyyyy"
] | [
"I've honestly never understood why people don't like yogurt. I've always loved it. Kefir is really good too.",
"Note that I mentioned \"real\" yogurt. That would be yogurt cultured by bacteria. They process the lactose in the culturing process leaving you with a lot of healthy stuff. There are some \"yogurts\" o... |
[
"Can anyone tell me the name of this rock?"
] | [
false
] | [deleted] | [
"Can you provide any more information? Where did you find it, how heavy is it, etc? More pictures might also help.",
"That being said it reminds me of a rock I once found which appeared to be porous obsidian. That had a similar structure but was more of medium-dark gray rather than the deep black the stone in ... | [
"I'm stumped. Obsidian that formed foamy rather than dense is still my best guess (gas bubbling through it as it cooled perhaps). Hopefully someone my knowlegable than I can help you out. This ",
"rock identification guide",
" may help though it seems some of the questions are tough to answer... "
] | [
"As entropy2057 said, we need some more info.",
"I have seen graphite look like that, so if it doesnt mark paper I can't help you without maybe some more angles, where its from, etc. "
] |
[
"Why prescribe different antibiotics for different illnesses?"
] | [
false
] | [deleted] | [
"Broad spectrum antibiotics work against many types of bacteria including both gram positive and gram negative. But different bacteria have different strengths and vulnerabilities, so if they can identify the specific bacteria it can be targeted by a narrow (specific) spectrum antibiotic.",
"The main reason for w... | [
"The effectiveness of individual antibiotics varies with the location of the infection, the ability of the antibiotic to reach the site of infection, and the ability of the bacteria to resist or inactivate the antibiotic. ",
"Antibiotic susceptibility testing (AST) is an in vitro (laboratory) measure to assess ... | [
"Not all antibiotics work on all types of bacteria. There are broad spectrum antibiotics, narrow spectrum antibiotics, etc. Certain infections are more likely to contain certain types of bacteria and therefore are more likely to respond to certain antibiotics. When possible testing is done to see which type of bact... |
[
"Does light make a sound (in a medium)?"
] | [
false
] | In my very surface level understanding of the physics of photons, I know that photons have no mass but still have momentum that can be transferred to other particles. If enough photons interact with a medium, could it generate compression waves and be registered as sound? To be specific, I don't mean signal transformations like radio waves where signals are coded and decoded. And would there be any correlation between the frequency of the light and the frequency of the sound? (If any part of this post sounds weird, it could be because the question came to me as I was trying to go to sleep. But, it could also be that I have no idea what the hell I'm talking about.) Anyway, thank you and I'm looking forward to the responses! :D | [
"Sonoluminescence",
" is the production of light from acoustically excited bubbles in a liquid. The time-reversed equivalent of this process would be light producing sound, so it’s certainly possible in theory. ",
"A more straightforward approach to produce sound from light is to focus a laser beam to a small w... | [
"Well, within a solid (and actually in liquids and gases too), the \"quantum\" of sound is called a phonon, and photons can absolutely be absorbed by a material to create said phonons. So on the face of it, that's your question answered. However, if we think sound, like from a speaker, there's actually more going ... | [
"Optical phonons are gapped, acoustic phonons are not and can have arbitrarily long wavelengths, that's the main distinction. ",
"Regardless, if we're willing to get a little hand-wavy, look at a typical optical phonon gap, take for example that in our favorite material silicon; the energy cost to excite an optic... |
[
"What causes that we sometimes \"feel\" a presence whenever we are afraid?"
] | [
false
] | I am intrigued by what kind of brain signal is involved on this: For example, we watch a horror movie. Later we go to the kitchen to have a glass of water, and when coming back to the bedroom through the dark corridor, we falsely feel the presence of someone. Has science documented this kind of reaction? Thank you very much and sorry for any mistakes when writing. I am not native english. | [
"We're scared so our brain is in panic mode. We perceive the slightest movements to be a crazy axe murderer, because hey, better safe than sorry."
] | [
"Sound, vibrations from walking, seeing them, etc. It's just that it is very subtle so you don't really notice it."
] | [
"Sound, vibrations from walking, seeing them, etc. It's just that it is very subtle so you don't really notice it."
] |
[
"The instructions say \"microwave for 60 seconds at 800w\", but my oven only goes up to 750w. How do I calculate the appropriate time for my oven?"
] | [
false
] | null | [
"60 * 800 / 750"
] | [
"Can plain inverse proportion really be applied here though? I feel like cooking 64 seconds at 750w wouldn't be the same as cooking 60 at 800.."
] | [
"In terms of pure energy delivered by the microwave oven: Yes. The unit \"Watt\" is defined as Joule/second, so if you multiply the amount of Watt by the number of seconds, you get the total energy.",
"Since microwave ovens don't deliver the energy in the same way to all areas of the interior (which is why the bo... |
[
"What is fire?"
] | [
false
] | What is fire itself made from? and what causes it to form the shape it does? I hope this question doesn't seem stupid or anything... | [
"The visible flame is composed of hot gases (carbon dioxide, water etc.) and particles of soot (unburnt carbon and other particulates). Its shape is mainly formed because the hot gas is rising while being cooled down by the surrounding air. The gas nearest the edge cools fastest and so stops glowing sooner whereas ... | [
"Fire is essentially a chemical reaction of some object with another, usually oxygen. In typical combustion, a hydrocarbon, like methane CH4 reacts with 2 O2 moleclues to form CO2 and H2O. Because the potential energy of CH4 and 2 O2 is higher than CO2 and H2O heat is released, the CO2 and the H2O leave the react... | [
"Link"
] |
[
"Boil, Microwave, or Wait for Tap? Which way is more efficient to get a cup of hot tea?"
] | [
false
] | [deleted] | [
"This depends solely on the efficiency of your microwave/water kettle.",
"And what do you consider efficient? The water from the tap has to be heated, too. It's not like it's naturally hot. From your description it seems that you have a serious amout of time before hot water comes out of your tap. In my house i g... | [
"I know the water from the tap has to be heated. So does the water in the pipe. There are losses from the pipe filling with hot water, which is never used as hot. That's one area of waste. ",
"So...my question is, which method takes less energy to get a 250 ml cup of 100 C water? Included in that calculation, i... | [
"You should not ever cook with or consume hot tap water, it leeches undesirable things from the walls of your water heater and piping."
] |
[
"How can atoms that are bosons occupy the same state in a Bose-Einstein condensate if they are made of fermions which can't be in the same states as each other?"
] | [
false
] | null | [
"If you have a Bose-Einstein condensate of Cooper-paired fermions (I'll just call this a superconductor), and write the wave function in terms of the underlying fermions, you'll find the the Pauli exclusion principle still holds for all of them.",
"I'll come up with an example of how this works using the simplest... | [
"Since you seem to be an expert on this topic (especially given your tag), follow up question, if you don't mind. ",
"We're often taught in physic classes than ",
"He will act as a boson because it can have a zero or integer spin nucleus, which is why it behaves as a superfluid at cold, but not extremely cold t... | [
"Tangential topic but what condensed matter textbook do you recommend? "
] |
[
"[META] April Fool's Day is Over: The Demise of Sponsored Content"
] | [
false
] | Many of you saw the new plans on AskScience. We introduced it at about 6:30 AM in the timezone of New Zealand, and have kept it going through sometime this afternoon (though it got more and more ridiculous as time went on!). We progressed from shilling oil to shilling homeopathy and quantum healing. We broke our own rules (non-scientific content on AskScience). We also broke with the time-honored convention of assuming every redditor is in an American time zone. Many of you were not amused by our clear abandonment of the preferred time zones and unsubscribed in protest (though bizarrely we have more subscribers now than when we started). Those of you who fell for it shouldn't feel too bad: some of our own panelists who missed the memo were even angrier than you. We can all be somewhat proud that some of them resigned in protest, at least until we pointed out the date. Our modmail and PM volume was much higher than normal - both people who were extremely amused, and people who were extremely angry. Over the day, the mods got called every name in the book, and got called on to resign (more than once). And while we don't like getting angry mail, we like seeing how much everyone cares about this corner of the web, and rest assured that we care about it too. Everyone pulled together to make sure the crappy sellouts who mod this place didn't get their way, and we thought it was awesome that so many people were so defensive of AskScience's integrity. But rest assured: no one is going to be putting any Sponsored Content in, we haven't hired an , and the guidelines of the subreddit are firmly in place. There was no Grand Design or pedantic lesson behind this joke (we just thought it would be fun!), but two things should be made clear: Scientists aren't humorless robots And industrial science isn't inherently bad (many of our panelists work in industry, and are great scientists). The intent wasn't to mock industry, it was to mock transparent PR, and to have fun pretending like we were blatant sellouts. So, it's back to business as normal on AskScience. Sound off below if you have something you want to say about the April Fool's prank, or if you have to say about AskScience. To further the joke, we had been removing everything that mentioned April Fool's. We're going back and undeleting those, so you can see how many of those posts there were. | [
"I can't believe people actually got angry over this. It was obvious that it was an April Fool's joke and I for one thought it was hilarious. "
] | [
"I can't believe this was all a joke. I was patiently waiting for my money to arrive and now I found out that there wasn't any. This is completely unacceptable."
] | [
"Sure, why not."
] |
[
"Why did the big bang not result in the creation of a black hole?"
] | [
false
] | So, if moments after the big bang, the universe existed in an immensely hot and dense state, and given that E=mc (mass and energy are equivalent), why didn't the immense density result in a gravitational collapse, and the creation of a black hole? | [
"This question has already been answered here.",
"http://www.reddit.com/r/askscience/comments/qxyne/why_didnt_the_big_bang_turn_into_a_black_hole/",
"http://www.reddit.com/r/askscience/comments/ovxel/mass_of_the_universe_right_after_the_big_bang_why/",
"http://www.reddit.com/r/askscience/comments/i3vyg/why_di... | [
"regions of space that the Universe have yet to have expanded into",
"There are no such regions; the universe is ",
" of space, and (as far as we can tell) there are galaxies throughout all of it."
] | [
"E=mc2 is an incomplete formula, describing only stationary objects. It's truly written with an additional + mv for mass x velocity aka momentum.",
"You're right E=mc",
" is somewhat incomplete if m is the rest mass but adding mv does not fix the problem. That does not even have the same dimension. The complete... |
[
"How did researchers avoid triggering a severe immune reaction with mRNA vaccines?"
] | [
false
] | Just read this great article ( ) detailing the development of the COVID vaccine, had my mind blown by how crazy/smart the development of this vaccine was. It mentioned one of the big obstacles in animal trials was avoiding a dangerous immune response, but the solution was glossed over. The article mentioned the vaccines developed just coded for the spikes, so was the solution to use just a tiny amount of mRNA so it would fly under the radar and avoid triggering an allergic reaction? | [
"Freely floating mRNA causes immune reactions but also blood clotting and other dangerous stuff.\nAs far as I understand the vaccines use specific coatings for the mRNA, which liberate the mRNA when it enters muscle cells and thus prevent it to float freely."
] | [
"The mRNA is encapsulated in a lipid ‘shell’ kinda like the sugar coat on an ",
"m@m",
"... this shell does two things-",
"1) hides the mRNA from the host immune system so it doesn’t trigger a response and",
"2) the shell fuses with the membranes of muscle cells and releases the now naked mRNA into the cell... | [
"A liposome, liberal definition would be a ball of fat that houses the mRNA in its center.",
"Also, the general idea would be for dendritic cells to take up the mRNA."
] |
[
"How are we able to tell how animals sees things? e.g. a snake seeing in infrared or a mantis shrimp seeing more colors than a human can"
] | [
false
] | null | [
"Researchers do this by analyzing the pigments contained in the light sensing organs of animals. Specific pigments react to certain wavelengths of light, so presence or lack of those pigments determine the light wavelengths that are detectable by an animal."
] | [
"There's two basic lines of approach here. First is looking at the structures that do the seeing and determining what kinds of light they respond to. You can look at the light absorbing chemicals in the eye and see what wavelengths they respond to. You can also measure the electrical response of the nerves conne... | [
"Nobody really knows, but rats and new world monkeys have been successfully taken from 2 to 3 color sensing pigments and developed the ability to see more colors as a result, so I suspect it would work. ",
"Medical regulators frown on doing experiments on people because it's really awesome instead of because it ... |
[
"Does light exhert a backward force to propel itself forward?"
] | [
false
] | null | [
"Physics"
] | [
"Physics"
] | [
"Does light exhert a backward force to propel itself forward?",
"Yes. Light carries momentum."
] |
[
"Is there feasible, truly green energy?"
] | [
false
] | Lead by a comment in a below thread, in how dams are heavily impacting the nature in and along the subjected river, I wonder, is there truly green energy that is feasible to produce? Green energy here being energy that doesn't impact nature (in a negative way). So, what am I missing here? Can we, in a scifi mindset, produce truly green (and cheap, or at least economic) energy for the world? Or do we always have to alter (up to) massive parts of nature to satisfy our ever growing hunger for energy, given that we are not willing to pay endless amounts for the power generated? | [
"I think your outlook is far more bleak than is warranted by the technologies which are already available and the rapid ongoing progress in their advancement. At the moment, the key barrier to the transition from an economy mostly reliant on fossil fuels to one primarily powered by renewable energy sources is not a... | [
"I think what you're really asking is, \"is there a way to power a civilization without affecting the natural world in any way\", and the answer is plainly \"no\". There's no free lunch for energy. It has to come from something, and inevitably that means something has to change.",
"One of the biggest failings of... | [
"Why have you chosen such a strict definition of the word 'green?' ",
"All human activities have an environmental impact. It's all just pushing stuff around from point A to point B. ",
"Environmentalism shouldn't necessarily be about 0 impact, but mitigating the impact to the point that we can 'live with it.... |
[
"Are there any natural processes in which something grows in order to contain a toxin?"
] | [
false
] | null | [
"Could you explain a bit more? Do you mean a growth to surround a toxin and prevent it causing harm? I guess you could say antibodies 'grow' around toxins by recognising their structure and binding to them. This creates a shield to prevent the toxin interacting with the body. ",
"http://en.wikipedia.org/wiki/Neut... | [
"There are structures in many cells that contain substances that would be toxic if they weren't contained within the structure. Lysosomes for example contain digestive enzymes in an acidic solution. These structures grow for the sole purpose of isolating otherwise toxic substances from the rest of the cell, keepi... | [
"I can't give you an example of a structure built to contain (I think you're implying sequestration) a toxin, but I can give you evidence of acquiring a way to be resistant to a toxin. Many many bacteria produce toxins to kill other bacteria for environmental competition. These bacteria develop an anti-toxin or imm... |
[
"How do driverless cars detect and deal with ice and snow, especially when it comes to braking?"
] | [
false
] | As a seasoned winter driver, I often have to anticipate stopping distance and turn speed based on the road conditions ahead. You could be on a plowed patch of a main road, and then turn onto a snowy/icy side street. How do driverless cars deal with these conditions? Do they also “see” or is it based on the tire traction? | [
"Snow is a “really interesting problem” for self-driving vehicles, says Carl Wellington, a senior engineer at Uber’s autonomous research centre in Pittsburgh. No company has quite yet claimed their cars have mastered the ability to drive through snowy conditions. ",
"1"
] | [
"I think OP is asking more regarding anticipation based on visual perception rather than real-time adjustments. For instance, living in New England, I drive in snow all the time. One technique is, heading uphill, you notice some snow 2/3rds the way up the hill. In anticipation of getting to the snow I will gather s... | [
"If you would not add some artificially produced effects on the steering wheel, so you can feel the condition, the driving experience would be worse.",
"This was actually a problem they discovered when power steering became popular. They originally made it so there was nearly no resistance, for the optimally smoo... |
[
"How do we know scientific studies are true and not fake?"
] | [
false
] | [deleted] | [
"When publishing a study in a journal, there is a peer-review and editorial-review process.",
"Authors are required to indicate their funding sources. This tells you who paid for the study and why. If you fail to acknowledge sources of funding (or even income) which might indicate any bias — you may have to retra... | [
"There is no guarantee. ",
"However, the beautiful thing about science is that for it to be accurate - it must be replicable by an independent party. So peer review and verification usually helps root out the evildoers :)"
] | [
"There's a more pernicious kind of bias than outright fakery.",
"Let's say you've got 2 scientists. Both of them are honest and set up their experiments. But they each have very slightly different methodology, and honest differences of opinion about what the \"right\" method is, and the arguments are subtle and... |
[
"Am I reading this Pubmed article about accuracy of pregnancy ultrasounds correctly?"
] | [
false
] | (It isn't long) As I understand it, they took 280 pregnancies. They used IVF to determine exactly when conception occurred. In the 1st trimester, CRL was accurate inside of 7 days about 99% of the time. In the 2nd trimester, BPD was accurate within 7 days about 8% of the time. Is that correct? Also, what exactly does this mean: In singletons there was a high correlation in the gestational age at birth assessed from the time of IVF and from CRL, from the time of IVF and from BPD. If I've posted this in the wrong place, please forgive me. | [
"It looks like CRL was accurate within 7 days ~99% of the time (3/208 were off by more than this) and BPD was within 7 days ~87% of the time (27/208 were off by more). I got that info from the results section between Tables 1 and 2. ",
"As for the sentence \"In singletons there was a high correlation in the gesta... | [
"Thanks.",
"I know the percentages go up if you only count the singleton pregnancies, but did the study say anywhere that they weren't counting the twins?"
] | [
"For that first set of accurate within 7 days statistics both singletons and twins are definitely included (\"In three pregnancies there was a difference of more than 7 days between the gestational age estimated from the IVF and from the CRL and in 27 pregnancies between the gestational age estimated from the IVF a... |
[
"How can TSA/Airport security workers stand next to X and T ray machines all day everyday without any ill effects?"
] | [
false
] | I know the people walking through the machines have nothing to worry about, but are there any precautions in place to stop the workers absorbing these rays? Do the machines focus the radiation into one area? Thanks in advance. | [
"Like any radiation worker, they apply ALARA. That means that you should take steps to make your radiation exposure \"As Low As Reasonably Achievable\". The ways to do this are the maximize distance from the source, minimize time near it, and use shielding when possible.",
"If you pay close attention when passing... | [
"You can use anything as long as the mass is sufficient. Lead is used because it's relatively easy to make and use a lead apron, for instance, and since lead has a high atomic number it will block a lot of radiation per unit of volume. ",
"But really in theory you could construct a wall of french toast to protect... | [
"I didn't think I would ever need to know how thick a wall made out of french toast needed to be to protect me from gamma rays, but now I do.",
"How much french toast would I need to protect myself from an xray machine?"
] |
[
"Why does smoke from incense or cigarettes not (usually) set off smoke alarms?"
] | [
false
] | [deleted] | [
"Fire Alarm / Smoke Detector Manufacturer here.",
"Household smoke detectors (excluding Heat and CO) fall into two catagories, Ionisation and Photoelectric.",
"Ionisation smoke detectors (the detectors with the radioactive symbol on their label) are designed to detect sub-micron particals of combustion (differe... | [
"The what and why of smoke detector installation has been debated for many years, to the point where manufacturers are either too vague in their installation guidelines, or cover themselves from litigation (and drive up sales) by suggesting that smoke detectors of different types are installed EVERYWHERE. Both meth... | [
"Would it be beneficial to have both types installed?"
] |
[
"What is the travel time to the Saturn's moon Titan?"
] | [
false
] | null | [
"While there's no definite maximum speed that modern technology can go, it took the ",
"Voyager 1",
" spacecraft about 3 years and 2 months to get to Saturn from Earth, using a ",
"gravity assist",
" maneuver at Jupiter."
] | [
"What speed are you going at?"
] | [
"The maximum speed modern technology can go."
] |
[
"Why do antigen rapid tests not work after 15 minutes?"
] | [
false
] | I've used two different types of antigen rapid tests. Both say that the results aren't valid if more than fifteen minutes have past since testing (dropping the solution onto the test kit.). Why is this so? Do the coloring/colored molecules that do the binding no longer work, or weaken, after 15 minutes? Or does a positive turn into a negative? | [
"These tests work by detecting the virus with manufactured antibodies that recognize some specific feature of the virus, like the infamous spike protein. There are two antibodies that together form a sandwich around the antigen (the feature the antibodies are looking for). The sandwich is formed when all the parts ... | [
"Yes, absolutely. Generally you’re supposed to read it after a specific number of minutes has passed (the exact time differs slightly from brand to brand.) Wait any longer than that and it could show a false positive."
] | [
"Another redditor commented that these types of tests are the same for pregnancy tests. Does that mean that if someone who was not pregnant were to take a test, receive their negative test, and throw that test in the trash. That after some time, that negative test could then show positive?"
] |
[
"Cell tower triangulation - can they track data usage and location with that too?"
] | [
false
] | [deleted] | [
"Data/device 'usage' is accomplished completely separately from tower triangulation--regardless of where/which towers the cell was connected to, if successfully connected to ANY tower, the provider will have a log of the in/out call data for the phone. Voice calls, text messages, and if applicable, cellular data s... | [
"Even without triangulation, there are countless readily available ways to track device data and activity. Triangulation is probably one of the more difficult methods to achieve at this point, and yields limited information about a target. Remote access tools, key loggers, device malware, and software/device securi... | [
"Essentially Cell triangulation is done based on beacon signals sent by the cell phone to nearby towers. This can occur without a call being made or data being used, so long as the cellphone is searching for a tower to talk to. The triangulation is done based on relative signal power between each tower and the cell... |
[
"Can ants understand the chemical signals left by another species of ant?"
] | [
false
] | It seems that it would be evolutionarily advantageous for ants to be able to understand some of the markers left by other types of ant (eg - don't go this way or you will die, FOOD!, etc.). Is there a basic chemical language common to most ants? | [
"I can't speak too far on the premise of your question, but it would appear that there is at least ",
" ability for cross-communication between species:",
"Ants use pheromones for more than just making trails. A crushed ant emits an alarm pheromone that sends nearby ants into an attack frenzy and attracts more ... | [
"So if you want to get rid of ants, killing them with force is actually counter productive?"
] | [
"Squishing them wouldn't be an effective way to get rid of them even without the alarm pheromones since you're only killing a few of the worker ants, and the rest of the colony is still bustling. Ant baits (those little plastic things) usually work well because the worker ants don't ingest the poison, but collect i... |
[
"How much could we tell about our solar system from X light-years away?"
] | [
false
] | With things like and those other "look at how big X is compared to our sun!" charts, it seems like we have a very precise idea of exactly how large planets farfarfar away are and even an idea of how they look. The only photo I've seen of Earth from a distance is , and at the edge of our solar system it's just that. I've never seen a full image of our solar system from beyond it, and now I'm curious. Say an alien civilisation made and analysed images of our solar system from just beyond it, one light-year away, five light-years away, ten light-years away, and 100 light-years away. How much would they be able to tell, from a Hubble-quality telescope, about our solar system's composition, the nature of our sun, and even individual planets? From the edge of the solar system, would you know that Earth is populated? | [
"but acids are still \"water-based.\" Water is almost a necessitating condition for life imo. Reactions in solids take place ",
" too slowly, and gasses are extremely diffuse. So we need a liquid. But we need a liquid that supports all kinds of elements and molecules in solution, so it can't be super hot like mol... | [
"the only candidate in our solar system to possibly have life on it.",
"What about Europa? ",
"http://en.wikipedia.org/wiki/Habitable_zone#Criticism"
] | [
"not much more than a couple of light years actually. It gets so weak it's swamped by the cosmic background."
] |
[
"Are certain types of people more or less influenced by ads?"
] | [
false
] | Some of the discussion on the question about reading and its influence on the brain, made me wonder if some people are more influenced by ads than others. For example is intelligence a factor? education, ethnic background, cultural identity, social ties? Maybe, loners are less influenced than social butterflies? I'm interested in any factor that might make a difference. And, on the same subject, but a different question, how much of the influence are we aware of? Can we feel entirely non affected, yet still be affected? EDIT - Finally saw glaring spelling mistakes. EDIT2 - Thank you for all of the thoughtful answers. You've given me a lot to ponder. | [
"Ooh! This one's right up my alley. Having studied advertising and worked in the advertising industry, I can say that this is a huge point of interest for advertisers as well.",
"As others have said, it has less to do with the ",
" of person you are (educated, versus uneducated, ethnic background, etc.) and way... | [
"As a matter of fact, most people believe everybody else is strongly affected by ads and propaganda, while they also believe they themselves are pretty much immune. It's called the Third Person Effect. Doesn't answer your question, but I thought it'd be interesting to add. I don't have any citations right now, but ... | [
"The antihipster ethos is just regular douchey enough, I take it?"
] |
[
"Why doesn't DNA get tangled inside the nucleus?"
] | [
false
] | We've got about 1.8m of DNA in our nuclei and for most of the time it's not condensed so why isn't it just a single hypercomplex knot like my headphones when I put them into my pocket? | [
"for most of the time it's not condensed",
"Your assumption here is wrong.",
"Most of the DNA in each nucleus is condensed to chromatin, although it is not in the highly discrete chromosome confirmation you see in meiosis/mitosis. Typically only the portions of DNA undergoing active transcription are uncondense... | [
"We actually have enzymes called topoisomerases that prevent our DNA from getting too knotted, by passing strands through each other. Viruses don't have these enzymes, so occasionally when they splort out their DNA, it's knotted."
] | [
"Also, it's not just 1.8m of free-floating strands. The DNA is wound op on proteins called Histones, resulting in 90 micrometers of chromatin."
] |
[
"Why do Lightning strikes on my iPhone 6s appear like drops of water?"
] | [
false
] | null | [
"Hi RyanJT324 thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the follo... | [
"I thought hurricane season was over?"
] | [
"I thought hurricane season was over?"
] |
[
"If I could exert a large force on the entirety of the earth, what direction would cause the earth to fall into the Sun first?"
] | [
false
] | This is ignoring the fact that the Sun is expanding, obviously. My ideas were a force pushing the earth directly towards the sun and a force directly against the direction of its orbit, slowing it. | [
"Actually, if you wanted to push the earth into the sun, you'd want to exert the force against the earth's direction of motion. ",
"Pushing any other direction increases the earth's kinetic energy at its current point in the orbit - the best way to 'lower' the earth into the sun is to remove kinetic energy until ... | [
"The direct approach (integrating the acceleration of the earth due to the sun's gravity) is a pain in the ass. ",
"Fortunately, it's easy to just use Kepler's third law. If the earth comes to a dead stop relative to the sun, then it is now on a highly elliptical orbit. In fact, the eccentricity is 1 so the ellip... | [
"There is already a force pushing towards the sun- gravity. Increasing this force would make our orbital period shorter, and our year quicker. ",
"Pushing in the opposite direction of our orbit is the way to drop us in to the sun- this direction is \"retrograde\". You'd have to push hard in order to drop us into ... |
[
"Has there a type of amnesia that affects semantic memory?"
] | [
false
] | I've always heard of retrograde and anterograde amnesia, but never procedural or semantic. Has amnesia caused people to forget that "the sky is blue?" | [
"While there are many types of aphasia (difficulty with language), what you're talking about is different. In Broca's aphasia, for instance, one \"knows\" what one wants to say, but simply can't say it. A loss of semantic memory would mean the loss of the underlying concept.",
"The answer is yes, and it's called ... | [
"There are acquired language disorders, such as Broca's aphasia (difficulty in fluent sentence production) and Wernicke's aphasia (difficulty in producing sensical language utterances-- with no fluency issues). There is also anomia, difficulty in remembering nouns and agrammatism, difficulty in producing 'functiona... | [
"Amnesia affects episodic memory. Although episodic and semantic memory are both part of declarative memory, only episodic is affected by amnesia. So by definition, no. It cannot cause semantic impairment. ",
"There are disorders that can result in impairments to both episodic (ie personal knowledge and memories)... |
[
"Is there some scientific way to measure smell and attraction as it relates to humans?"
] | [
false
] | null | [
"And every piece of ",
" says that they don't. That one piece of research doesn't prove anything or come close to proving they do."
] | [
"They don't ",
" anything. Until they do, it's safe to assume that pheromones don't exist in mammals."
] | [
"So, let me get this straight. They don't prove anything because TitsKnobs says they don't. And, I should believe you over scientific studies because, well, just because?"
] |
[
"What screen resolution would be equivalent to the resolution of the average person's eyes?"
] | [
false
] | In other words, if we were to say what resolution humans saw in would it be 100000x100000 or something | [
"Human eyes (and probably all other eyes, including eagle) only see detail in a small area focused at the center of vision. So a display the size of a house might have smartphone-density pixels for the central 1m",
" area, gradually becoming less dense as you go further out, until the \"pixels\" in the periphery ... | [
"The resolution of the human eye is measured as angular resolution. ",
"Foveal vision",
" (the subsection of your visual field that is actually high-resolution) is about the central two degrees of the visual field. With a typical angular resolution of 1 arcminute = 1/60 of a degree, that would mean high-resol... | [
"It is less about resolution and more about pixel size and density."
] |
[
"How small a space could the mass of the milkyway be compressed into?"
] | [
false
] | [deleted] | [
"If you were to compress all the mass in the milky way into a black hole it would have a radius of about 0.2 lightyears."
] | [
"I thought the radius of the mass would be 0 or infinitely small but the radius in which light could not escape would be .2 light years. "
] | [
"All that is known about the actual mass distribution inside a black hole is that current physical theory fails to accurately describe it. The conclusion of \"infinitely small\" only occurs if you naively apply both the 'large object' physical theory (general relativity) and the 'low mass' physical theory (the sta... |
[
"Which is larger, the largest known star in the Universe or the largest known black hole in the Universe?"
] | [
false
] | null | [
"In terms of mass, the largest known black hole is like 20 billion times as massive as the sun and the largest stars are a few hundred times the mass of the sun.",
"In terms of radius, it's a bit closer, but the biggest supermassive black holes have a Schwarzschild radius on the order of light-days whereas for th... | [
"Black hole."
] | [
"No"
] |
[
"If a piano, a violin and someone's voice can each reach the same frequency (note), what is it about the sound they make that allows you to differentiate them?"
] | [
false
] | null | [
"The term for that difference is the ",
" of the sound. It is caused by different relative amounts of overtones and harmonics. Say you play a standard A (440Hz). The string is vibrating at 440 cycles per second. This is what is called the ",
". But that string is also vibrating (less intensely) at its ",
"har... | [
"This is a good start to the explanation. It's true that differences in sound are caused by sympathetic resonances and chorus effects not only in the instrument itself, but also the room, and even sometimes inside the human ear itself(!), but there's a little deeper explanation rather than just \"it changes the tim... | [
"Isn't a waveform just the sum of the fundamental frequency and the harmonics and overtones, like Fossafossa said above?"
] |
[
"[Physics] If strong force is strong enough to keep protons together, why do atoms need neutrons to keep the protons from tearing apart?"
] | [
false
] | I was watching Crash Course Chemistry and watched the lateral SciShow video about how quarks are held together with strong force, which keeps protons together and also ties together the whole atom through nuclear force. When I got back to the video on the nucleus, however, Hank stated that neutrons are important because without them the protons would tear each other apart. Wouldn't the strong force be more likely to pull the protons in close? What force would be pushing the protons apart and creating a need for neutrons? | [
"You might be tempted to say that the Coulomb force is what prevents all-proton nuclei from existing (except hydrogen-1 obviously). But that's not the full story.",
"In fact, if you replace all the protons with neutrons, the system is still not bound.",
"So the ",
" simply cannot bind a system of multiple pro... | [
"Why is it that no amount of neutrons can form a bound state?",
"The nuclear force is spin- and isospin-dependent. If you try to form a system of nn or pp (both of which have isospin-1), Pauli exclusion forces you to anti-align their spins. The spin-spin part of the nuclear force is repulsive for spins pointing i... | [
"The short explanation is that two neutrons feel a Pauli repulsion, meaning they both contain udd quarks in the same spin state, so some quarks would need to go to a higher-spin state (which costs energy) to get close to each other. This repulsion is stronger than their residual strong force attraction, so they are... |
[
"Is carbon fiber a heat conductor or a heat insulator?"
] | [
false
] | No matter how much I google, I keep getting constantly contradicting results on the thermal conductivity of carbon fiber. Some say that since it has low thermal conductivity that it's an insulator, but I keep constantly seeing other contradictory remarks about it having a lot of potential for heat conductivity, so if anyone can clarify I'd appreciate that. | [
"Carbon fiber itself, the literal fibers, are fairly thermally conductive (generally less than most metals but far more than conventional insulators). The actual value of conductivity depends on the method of production.",
"Probably part of the problem you're having finding information is that carbon fiber is mos... | [
"Carbon fiber itself has a thermal conductivity around 24.0 W/(m·K) while epoxy often used as the matrix in carbon composites has a thermal conductivity of 0.17 - 0.79 W/(m·K). So if you are asking for the fiber itself, the conductivity is as above. If you are asking about a composite, it depends on the density of ... | [
"The heat-resistant tiles you're thinking of were reinforced carbon-carbon composite and the insulation was provided by the voids inside the carbon matrix, not the carbon itself.",
"Beyond that, the RCC was used for its high temperature tolerance, not its low thermal conductivity. In fact there had to be insulati... |
[
"On a molecular level, why is sugar sticky when wet?"
] | [
false
] | null | [
"It’s kinda a weird mix between the hydrogen bonds in the sugar being broken and made again with water meaning that the sugar will be more likely to H bond with say the sweat on your hand. Why this would happen I would say is due to the sugar molecules being relatively big and each -OH group will be sterically hind... | [
"Stickyness is really bonding? Wow I've never really though about that before"
] | [
"Put a different slant on it. When sugar is very concentrated in solution the solution is viscous (thick) like honey. This means that is acts a little like a fluid as well as a solid (viscoelastic). As a fluid it wets any surface it touches and sticks to it (if it didnt want to stick then it wouldnt wet it) The sol... |
[
"Are modern occurances of appendix ruptures more prevalent than in the past, and if so could it be an evolutionary mechanism to select out a vestigial organ?"
] | [
false
] | null | [
"Regardless of the actual answer, I'm pretty sure it wouldn't be an evolutionary mechanism because most people reproduce regardless of whether their appendix ruptures or not so the genes that cause appendicitis would get passed to the next generation regardless. "
] | [
"You are also \"cheating the system\" by taking any modern medicine for any ailment so to speak. What's considered routinely preventable today were once deadly diseases. This is a wrong way to think about any medical intervention. \nThere need be no grand system to cheat and no grand plan... And it is ok.",
"Also... | [
"It is not really mutation, rather recombination. Though mutations may play a role also. "
] |
[
"Why doesn't deuterium fusion occur in main sequence stars?"
] | [
false
] | What makes the proton-proton chain reaction the preferred method of fusion in main sequence stars if deuterium fusion occurs at lower temperatures? Following that, why does the carbon-nitrogen-oxygen cycle become the preferred method of fusion in stars starting around 1.3 solar masses? | [
"Deuterium fusion is too easy. There's only a small percentage of deuterium to start with, and it (along with lithium isotopes) are fused early on, during the transition from protostar to main-sequence star. Hydrogen fusion is dramatically slower, which is why stars live so long, they ",
" burn their fuel any fas... | [
"Its not that simple. Deuterium fusion has a relatively high reaction rate, so it all burns off pretty much immedately as soon as the star gets above a million degrees or so. Hydrogen fusion then begins, once the small amount of easily fusible isotopes are gone. Which route occurs depends on the mass and compositio... | [
"Thank you. So there isn't that much deuterium to begin with, and once the star becomes hot enough, it simply just starts fusing hydrogen?",
"I'm assuming that once you increase the temperature further, then CNO fusion starts to occur, correct?"
] |
[
"How/Why did the first organism develop its need for a heart/lungs/kidneys/etc?"
] | [
false
] | [deleted] | [
"\"It is believed that the first lungs, simple sacs connected to the gut that allowed the organism to gulp air under oxygen-poor conditions, evolved into the lungs of today's terrestrial vertebrates and some fish (e.g. lungfish, gar, and bichir) and into the swim bladders of the ray-finned fish.[5] \""
] | [
"\"It is believed that the first lungs, simple sacs connected to the gut that allowed the organism to gulp air under oxygen-poor conditions, evolved into the lungs of today's terrestrial vertebrates and some fish (e.g. lungfish, gar, and bichir) and into the swim bladders of the ray-finned fish.[5] \""
] | [
"There really isn't a \"first organism\" to develop each specific organ, because there will be lots of organisms over time with varying pieces and types and sizes of different versions of these and over time minutes changes to those eventually proved to be better for survival. They are intricate in design because t... |
[
"Most types of life I can think of seem to have originated in the ocean but I've never seen an \"ocean mushroom\". Did the fungi kingdom originate there too then move onto land later? What was the world like then?"
] | [
false
] | null | [
"Single-celled fungi, like yeast, can live in water and the ocean. There are even varieties of multi-cellular fungi exist in the ocean but they tend to be rather small.",
"P.S. ",
"http://deepseanews.com/2011/08/marine-fungi-are-totally-badass/"
] | [
"I too have trouble thinking of an 'ocean mushroom'. Let's remember however that mushrooms do not occupy the entire of the fungi kingdom. Fungi can exist as single celled organisms, and there are quite a few of these that live in aquatic environments. ",
"For example, many fungi of the ",
"Chytrid",
" divisio... | [
"I found that article too! It's worth noting that fungi of all types really are apparently less common in marine environments. They didn't state it outright, but it seems like this could be because most fungi live on decaying matter and detritus, and the ocean is lacking in decaying plant matter (and fungi are in... |
[
"Why are some human internal organs asymmetric, or located on one side of the body?"
] | [
false
] | Doesn't nature strive for symmetry? Also, are there any animals that are naturally asymmetric externally? Like they look different on one side compared to another. Thanks! | [
"Evolution is trial and error, symmetry works well for things like eyes (depth perception, field of view, etc.), ears (identifying the directions of sounds), and limbs (motion by legs/feet work well in even pairs). Internally it's a different story for mammals like you pointed out. ",
"It has little to do with wh... | [
"On your assumption on symmetry: Symmetry ",
" not be what is striven for—it's could just be that it's easier to encode for. Just a thought."
] | [
"My favorite theory about this is that at some point the ancestor of chordates basically fell over, with one side eventually becoming the top and the other side becoming the bottom. The external features rearranged to become bilaterally symmetrical again, but the internal organs stayed jumbled up. However, this t... |
[
"People who contract Covid 19 report losing their sense of taste and smell. Is this temporary while the virus runs its course or permanent?"
] | [
false
] | null | [
"Friend and his wife had it, both in their 50s, they lost their sense of taste and smell as one of the last symptoms. Started to come back after about a week also. They still have some lingering issues after 3 weeks but sense of taste and smell has returned."
] | [
"Friend and his wife had it, both in their 50s, they lost their sense of taste and smell as one of the last symptoms. Started to come back after about a week also. They still have some lingering issues after 3 weeks but sense of taste and smell has returned."
] | [
"Did anything happen to your lung capacity?"
] |
[
"burning wood to create energy does not create global warming?"
] | [
false
] | I was watching a Feynman video on youtube where he was talking about fire.. he explains that trees take CO2 and break it into C and O2 with energy provided by the sun (by this point am assuming this is and Endothermic reaction). Then he later states that when you collide O2 with C again with enough energy they will reattach themselve creating CO2, and releasing the "light" (flames) or energy previously provided by the sun to break them appart in the first place. So if trees take the CO2 in the air to grow, and then when they die (burn) they release that CO2 that was originally in the air back to the air again, burning woods to create energy would not create any surplus of CO2 in the atmosphere, thus not creating any global warming (I know am taking big leaps here). Its all a balance of some sort I guess. If we (the planet) are a closed space (theres no CO2 getting in or out of the planet) and everything is balancing out, why do we have global warming? is the CO2 generated by burning oil not initially in the air? Sorry if this sounds stupid!, I know am making a mistake in here, I just wanna know where.. | [
"Our planet has not always been the same as it was now. It took a very long time for photosynthetic life to store all of the carbon currently sequestered. (It's also worth noting that not all carbon in the world is either in plants or the atmosphere.) The problem is that when people burn wood for fuel, we have the ... | [
"So basically we are decreasing the amount of carbon stored in land (oil, wood, etc) and increasing the amount in the atmosphere..",
"thanks!.."
] | [
"We dig up coal, gas, and oil to burn carbon from eons ago, faster than the CO2 is consumed by today's trees. In addition, there are other greenhouse gases that contribute to global warming."
] |
[
"Where did the fish in volcanic crater lakes come from?"
] | [
false
] | I've seen two volcanic crater lakes in Southeast Asia - Lake Toba and Lake Taal. Both have fish, but both are isolated and cut off from other bodies of water. Since they're volcanic crater lakes wouldn't the eruption would have killed all the fish? So where did the fish in the lakes come from? | [
"Mostly from migratory Birds. A duck that goes from Lake to Lake will often carry eggs on its feet. All it takes is a few and with them traveling so much it's about the only way that you can have a species of fish that spans multiple areas. Otherwise every Lake would end up with a unique species due to a lack of ge... | [
"The general answer is that either humans transported the fish there (intentionally or accidentally) or that the fish arrived as eggs clinging to the legs of waterfowl. ",
"That said, although experts generally accept that dispersal by waterfowl is the most likely reason, it hasn't been formally proven - in other... | [
"Thank you! "
] |
[
"The creation and destruction of matter and energy?"
] | [
false
] | Does the law of "matter and energy cannot be created nor destroyed" still hold today? And if it does, has there been any advancement of knowledge and theory on where current matter and energy comes from? Like GOD!!! (j/k, scientific theory/fact only please) | [
"Matter isn't a precisely defined term in science. What we do know is that ",
" is a kind of energy along side energy of motion: E",
" = (pc)",
" +(mc",
" )",
" . And we know that energy is conserved for \"time translation invariant systems\"",
"The law of conservation of energy stems from a fundamental... | [
"Unsure if I understand. So if that's the case, in a mathematical representation of a physical system could you ever do something that doesn't create a bunch of terms that cancel out? Or would any change applied to the \"Lagrangian\" always result in a continuous symmetry?"
] | [
"yeah there certainly can be cases. For instance if we construct a Lagrangian with some potential energy that changes as a function of time, that system won't conserve energy ",
". When we get down to the nitty-gritty levels of reality, the fundamental particles, yes energy and momentum are conserved because the ... |
[
"What is it about water or bismuth that makes it expand when it freezes?"
] | [
false
] | Water expands when it turns into ice, and that's how ice weathering works. But what is it about water and other substances (bismuth, gallium, germanium, etc.) that makes it do that? | [
"Water has a lot of odd properties that mainly stem from it's tendency to form hydrogen bonds with itself. Water can form up to four hydrogen bonds with neighboring water molecules. These bonds are pretty strong compared to most interactions between molecules, but not strong enough to be essentially permanent like ... | [
"Does this hydrogen bonding add to the heat of fusion?"
] | [
"In a way, the hydrogen bonding exhibited by water ",
" the energy of its enthalpy of fusion. The enthalpy of fusion is defined as the change in enthalpy to change its state from solid to liquid (or vice versa). So since water as a solid is held together by hydrogen bonds, the enthalpy of fusion when melting goes... |
[
"Is there a symmetry associated with the conservation of information?"
] | [
false
] | I have a mediocre understanding of Noether's theorem, and I've gathered that conservation of information also appears to be a fundamental property of the universe. Is there a correlated symmetry or does the conservation of information come from a completely different place/idea? | [
"In quantum mechanics conservation of information is phrased as \"unitary evolution\" or you might say the conservation of probability. I think typically you'd consider this a postulate of the theory rather than a consequence of some symmetry, but it can be related to (for example) the \"phase symmetry\" of the wav... | [
"In QM, systems either evolve via unitary evolution (according to the Schroedinger equation) or, when measured, via collapse.",
"If that were true this would be an enormous self-inconsistency in QM. This clear if you consider a situation in which my total quantum system contains elements that make \"measurements\... | [
"In QM, systems either evolve via unitary evolution (according to the Schroedinger equation) or, when measured, via collapse.",
"If that were true this would be an enormous self-inconsistency in QM. This clear if you consider a situation in which my total quantum system contains elements that make \"measurements\... |
[
"What's the difference between organic fruits and vegetables and regular fruits and vegetables?"
] | [
false
] | Isn't everything organic? I don't understand. If I have a banana and an organic banana aren't they the same? I mean if a regular banana has pesticides on it, I'm not eating the peel. Can someone clear this up for me? Thanks ! | [
"The requirements for organic certification vary depending on the country, but usually require that synthetic chemicals including pesticides, fertilisers, antibiotics and additives are not used, and have not been used where the food is grown for a number of years. There are usually other requirements too. You can l... | [
"No anecdotes in ",
"r/AskScience",
" please.",
"Organic food uses pestisides, uses fertilisers, and additives. They are just \"organic\" in the fact they were not synthetically made. In many cases they can be worse for the enviroment. It depends on the crop grown; some organic food production may not use fer... | [
"I specified synthetic. I didn't go into specifics since the exact requirements vary so much between countries and certifications. (The requirements for Soil Association certification in the UK, the one I'm familiar with, are listed ",
"here",
" in excruciating detail. Note, for example, that there are allowanc... |
[
"AskScience AMA Series: I'm Mike Parker Pearson, Archaeologist and Professor of British Later Prehistory at University College London, here to talk about my research around the world and on Stonehenge, AMA!"
] | [
false
] | Hi, Reddit! I've worked on archaeological sites around the world in Denmark, Germany, Greece, Syria, the United States, Madagascar, Easter Island (Rapanui) and the Outer Hebrides. I have been UK Archaeologist of the Year and am a Fellow of the British Academy. My research on Stonehenge over nearly 20 years has helped to transform our understanding of this enigmatic stone circle, including the discovery of a new henge, a settlement where Stonehenge's builders may have lived, and the quarries for Stonehenge's bluestones in the Preseli hills of west Wales. I've published 24 books on a wide variety of archaeological topics, but I really love being out doing fieldwork. You can follow more of my recent work on PBS' , where my team and I painstakingly searched for the evidence that would fill in a 400-year gap in our knowledge of the site's bluestones. The episode reveals the original stones of Europe's most iconic Neolithic monument had a previous life before they were moved almost 155 miles from Wales to Salisbury Plain. I'll be ready to go at 3:00pm EST (20:00/8:00pm GMT), AMA! Username: | [
"What do we know about the social organization of the people who built Stonehenge?"
] | [
"Mummified and fitted together as composite bodies? What do you mean?"
] | [
"What part of your job is spent kneeling in the dirt, and what part of it is spent using lab tools to analyze what you found in said dirt? I always picture archaeologists in holes or ditches but I figure you guys must use a lot of \"new\" tech as well!"
] |
[
"What are computer architectures and how are they different?"
] | [
false
] | I'm a Computer Science student and I feel like I should know this. I've looked it up and I have a basic understanding but I'd like to get a better understanding of this. What are some common types of computer architecture and how do they differ from one another? How does this impact development of software for these computers? I recently overheard a conversation where someone claimed that Sony's PlayStation 3 had a different architecture than the Xbox 360 or even the Playstation 4 which made it difficult to develop games for the PS3. Why and how does a system's architecture make it difficult to do things on a certain system versus another, and why would companies make the decision to support an architecture that could make development of software for that system difficult? | [
"In the question you asked, computer architecture refers to the logical structure of, and the interoperability between processors and memory. Take XBOX 360 and PS3 as an example. While both have processors derived from the PowerPC ISA (instruction set architecture), they are very different in their computer archite... | [
"I'll try to simplify, as computer architecture is a large area in Computer Science and you might want to find a course on it if you like it. ",
"The basic difference between different architectures that affect development is the assembly instructions set.",
"Intel and AMD have slightly different architectures/... | [
"To answer your direct question about the popular architectures out there and hopefully show the difference. Here's a very simplistic look at the difference between a RISC vs CISC (reduced vs complex set)",
"the x86 arch",
"http://www.azillionmonkeys.com/qed/k7-architecture.gif",
"vs",
"ARM arch",
"https... |
[
"Can stars spit out elements we've yet to discover?"
] | [
false
] | Okay. Well, I am a scifi buff. I play EVE Online. In EVE, we use minerals with scifi origins and and psuedoscience lore to explain their existence. We also use actual elemental stuff like technetium and polonium, to name only a couple. I understand that all of the elements we know of on the periodic table, the ones we encounter here on Earth, originate from our star as a byproduct of the sun's life cycle. Heavy elements created as a byproduct of our sun's fusion, spat out in solar flares, traveling through the void and eventually collecting and making new stuff. Obviously not all of our celestial material came from just our star, but all of the material came from a star at some point. What I want to know is, is there any scientific precedence, theoretical or known, that could explain the existence of elements that may be unique to a star system? Like, for instance, an extremely large, very hot, very old star. It's so old it's spitting out elements heavier than any we've ever encounters naturally or in a laboratory. Kryptonite, because why the hell not? Could these elements exist? Or are the elements we know of here on Earth and in our own galaxy consistent throughout the entire universe? Can modern science explain the existence of unique and strange elements we've yet to discover as a natural occurrence due to star emission? | [
"What sorts of things could stable super heavy elements be used for?"
] | [
"Well atomic matter up to a point can be made in a particle a accelerator. Unless there is a mechanism that we're not understanding or are over looking in the processes creating atomic matter than I don't think stars are doing anything different. Maybe there is some strange quark neutron star which spits up stable ... | [
"Like, for instance, an extremely large, very hot, very old star.",
"In our current understanding of star formation and evolution, very hot (or equivalently, very massive) stars don't live very long (still a couple of million years though). So the oldest stars will have very low masses. But this also implies it w... |
[
"Can someone explain the stress-energy tensor to me and how it plays into general relativity?"
] | [
false
] | I know it has something to do with energy density, but not much more than that. | [
"For any conserved quantity there's a current, which is a vector quantity. When you put the density of that quantity together with its current, you get something called a four-vector, which has four components instead of three, and is essentially a vector in spacetime.",
"But energy and momentum already form a fo... | [
"You can calculate it for a rigid body, in which case it's a fairly straightforward combination of the object's energy and momentum as well as any stresses within it (I don't remember all of the formulas off the top of my head). More often, though, you're interested in the stress energy tensor of either dust (a col... | [
"Well, spacetime curvature is encoded in a 4-by-4 matrix as well, and the two are related by ",
"Einstein's equation",
"."
] |
[
"With all the recent \"super Earth\" discoveries, what is the heaviest gravity world a human could live on?"
] | [
false
] | The heaviest gravity a human could live in for a standard life span while being able to maintain a "normal" life. This means without adverse effects causing early death or deformities. You can also expand on what you think possible through the evolution of humans breeding and propagating on said planet. I would also be interested in things like atmospheric density and pressure, whether a thicker atmosphere might be present due to a stronger gravitational pull or magnetic field, and how that would affect the people living on the planet. I am mainly interested in this for colonization purposes and I believe we need to populate other planets to survive as a species. I know humans can live in places with lesser gravity but not without some health problems. (I looked to see if this question has been asked before but couldn't find anything, if it has please share the link!) | [
"I know you're probably mostly interested in the physiology of humans in high gravity environment. I can't really comment on that but I can tell you that Earth is pretty close to the limit where we are able to get to orbit using rockets. If you increase the surface gravity by about 50%, then we'd be unable to get t... | [
"It's all explained in detail in the article I linked. But the short version is that we're already at the point where about 85 to 90% of a rocket is fuel. With a higher surface gravity this number would have to go up. You get to some point, say 99% of fuel, where you can't construct the needed structure to support ... | [
"Doesn't work like that. Huge rockets have to carry themselves as well, you just end up wasting fuel. The Saturn V is about as big a rocket as you could ever efficiently build, if it can't even get to space, you probably won't ever."
] |
[
"Why do foods that are unhealthy taste better than foods that are healthy?"
] | [
false
] | For example, foods that contain a lot of sugar or fat vs one that doesn't. | [
"The main reason is that our brains have learnt to have a higher pleasure response to energy-dense foods. This makes sense in a primitive environment, the advantage being you have a desire for rich foods with plenty of calories!",
"Since then, however, we do not have to seek out meals in a primitive sense anymore... | [
"why, not what."
] | [
"Primitive humans:",
"What this means is, for them, calorie dense foods like sugar and fats were the healthiest foods they could possibly eat because those were the foods that were best at keeping them alive.",
"Then we invent agriculture and other technologies that let to a surplus of food, but retained our pr... |
[
"Does a star visibly change when it begins using a new fuel? And is the timescale observable?"
] | [
false
] | For example, if a star fusing hydrogen has enough mass to fuse helium when the hydrogen is depleted, will it visibly change? And if so, will it happen quick enough for us to see the change? | [
"Was confused as to why the earth had already been destroyed.",
"This is a good opportunity to use the Future perfect tense: \"The Earth will have already been destroyed several billion years earlier.\" ",
"(In the future I'm talking about, this has happened between now and then)",
"Otherwise, thanks for the ... | [
"Stars like our sun do an hours-long transition to helium burning called a ",
"helium flash.",
"The helium flash is guaranteed to not destroy the Earth because there is almost no immediate outward change, and because Earth was already destroyed several billion years ago much earlier in the ",
"red giant phase... | [
"It changes a lot, but not notably (to the human eye) within a human life span. Supernovae are an exception.",
"https://en.wikipedia.org/wiki/Red-giant_branch",
"Some stars change their brightness a lot frequently while keeping their fuel type. ",
"Mira",
" is an extreme example. It varies by a factor of mo... |
[
"Why is the universe cooling down?"
] | [
false
] | null | [
"The amount of heat in the universe is really really small compared to the amount of space in the universe. The sun is hot, and heats a big piece of out solar system pretty well, but if you divided that heat evenly across our solar system, it'd be too cold for any life. Same principle with the universe. It's really... | [
"The universe is expanding so volume is increasing."
] | [
"I'd guess that the book tried to tell about ",
"http://en.wikipedia.org/wiki/Heat_death_of_the_universe",
" ."
] |
[
"A question about light."
] | [
false
] | My main question is; Can we see a star in the night sky whose light has been bent by gravitational pull? [ ] If that does happen, would it be possible to see the same star twice? [ ] | [
"Yes, but it's not as extreme as your diagrams suggest. A search on \"gravitational lensing\" turns up a bunch of ",
"pictures",
"."
] | [
"That picture is awesome. "
] | [
"See ",
"Gravitational lens",
".",
"I don't think there are cases of light bending as much as your diagram suggests, though."
] |
[
"When you have a cold, why do you feel worse in the mornings and evenings and better during the day?"
] | [
false
] | I've always noticed that when I have a cold, my nose is stuffier for a few hours after I first wake up, and when I'm going to sleep. It's not because I stop paying attention to it during the day, either - it actually clears up a lot more during the day. This happens with other symptoms too, for example, headache and sore throat, but mostly with a stuffy nose. Why does this happen? Thanks! | [
"As the other comment says, position probably has a lot to do with it. You're laying all night, the mucus drains and pools and runs down your throat, causing stuff nose, sore throat, headache from sinus pressures, etc.",
"Another factor is the body's circadian rhythm. Your body goes through daily cycles where a... | [
"You’re actually right: sleeping with a very big pillow under your back and head, half-sitting, is a great way to not feel as bad during the night."
] | [
"Makes sense. Maybe I'll try sleeping sitting up next time haha."
] |
[
"Does the body have a single thermostat, such that if <part> gets cold, you shiver, and if <part> gets hot, you sweat?"
] | [
false
] | I'm just curious whether there's a single spot or set of spots that tell the brain what your body heat is, or whether it is distributed across your whole body? | [
"The hypothalamus, a structure of the lower brain, is responsible for thermoregulation in humans. The hypothalamus directly receives a variety of inputs from the blood, one of which is temperature. When blood temperature rises, the hypothalamus induces sweating and vasodilation, and when blood temperature drops we ... | [
"Thanks for this answer.",
"Could you reconcile this with shut_it's response below regarding the localized sweat response your arm would experience if it alone was put outside on a hot day?"
] | [
"I do not think that there would be a localized response. The arm cannot be thermally isolated from the rest of the body (blood flows through the arm and back to the body) so heating the arm would also cause a bump in core body temperature and should cause a full body response. If we think about thrusting an arm in... |
[
"How would a hydrophobic coating effect the buoyancy of an object?"
] | [
false
] | [deleted] | [
"Not much; the displacement wouldn't really change though skin friction drag (which is only a tiny part of total drag) might decrease a bit.",
"Next time, use the search box on the right. I put in \"hydrophobic ship\" and the top result was this previous question:",
"If one were to coat the outside hull of a sh... | [
"If it's flexed inwards more water will be below the object and displaced, and the object will ride marginally higher. I didn't mention this because it's basically negligible at boat sizes."
] | [
"By that logic the entire interior of the boat, which is air, not water, should lessen the buoyancy and cause it to sink. Think it through a little bit and you'll see what's going on. When you replace what would have been below the water level with something less dense, you get buoyancy. Replacing something above t... |
[
"How do engineers check the structural integrity of a building, particularly after a damaging event like an earthquake?"
] | [
false
] | null | [
"I'm an aerospace engineer not civil but the same basic principles apply. We have to do something similar if we suffer a tail strike. It all boils down to Nondestructive Inspection (",
"NDI",
"). The simplest will be a visual inspection, if anything is cracking or deformed. A quick test people do (for composite... | [
"The short answer is that if you know how the building was built, you know the weak points for an earthquake and you look for cracks. The direction and location of cracks will tell you how connection points may have held together (drywall is quite brittle so cracks easily).",
"A typical seismic assessment guide i... | [
"Every building type is unique in the way that it fails, but when it comes down to it, generally it is just looking for cracks. Damage is primarily caused by displacement of the building, or drift, which varies for different types of buildings.",
"Reinforced concrete, for example, is more stiff than wood, and wil... |
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