title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Is there any merit to the arguments presented at this link \"Why the Big Bang is Wrong\"?"
] | [
false
] | null | [
"No, there is no merit to this whatsoever. The author uses old controversies which were solved back in the 60s and 70s, and combines them with a general misunderstanding of astrophysics in general. (Not wanting to pull out the argument from authority or whatever, but it does say at the bottom \"John Kierein has a B... | [
"The comparison with refraction and gravitation bending light without blurring is just stupid. Neither works via the Compton effect. Even colored glass isn't colored because of Compton scattering, it is because some light is absorbed.",
"The 'proof by picture' argument isn't that convincing either. Those stars ar... | [
"What he's really arguing is that red shift should not be used as evidence for the big bang. When we came up with these ideas red shift was the primary evidence for the Big Bang. You'll notice that the paper ",
"he cites",
" is from 1968 and the other work he cites doesn't reference much past the late 70's. Cur... |
[
"Design method for analog filter with maximally flat group delay of a chosen value with design pass band?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
"/r/HomeworkHelp",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] | [
"Hi,",
"thanks for looking at my comment. This is not a homework question.... As I stated I'm looking at a possible equivalence between filter design and a research problem I am working on. I had hoped someone with experience in filter design would be available to discuss optimization strategies and equivalence. ... | [
"I did look at the text of your post so please do not presume I have not. The guideline also covers general project assistance. In any case, your question is rather broad and open-ended and so should go to ",
"/r/AskScienceDiscussion",
". If you can narrow the question appropriately then feel free to resubmit t... |
[
"How big would a building have to be to cause a change in the Earth's momentum?"
] | [
false
] | Here's my thought: we keep building bigger skyscrapers. How big would one have to be to alter Earth's orbit? And what might happen if it did? | [
"rmhism is correct, you can't change the Earth's orbit with terrestrial things.",
"However, a tall and massive enough skyscraper could change the Earth's ",
" (not orbit) by changing its moment of inertia because of the redistribution of weight. This could give something like a wobbliness to our rotation. Howev... | [
"It will never alter the earths orbit (the orbit of the center of mass, that is) since there is no external torque. To change angular momentum, the only way possible is to apply an external torque. All the forces that will be needed to build a skyscraper are internal to the system. "
] | [
"No, it affected rotation. Not orbit."
] |
[
"What do you think will be the first major vindication/discovery of the LHC in CERN?"
] | [
false
] | Creation of a mini black hole? Uncover a Higgs particle? Who decides what experiments are going to be done using the facility? Is it a for profit entity where you can pay to use the collider or what? | [
"There are four detectors, and two types of collisions. "
] | [
"Creation of a mini black hole? ",
"No.",
"Uncover a Higgs particle?",
"Maybe.",
"Who decides what experiments are going to be done using the facility?",
"There are two experiments that they do proton-proton collisions and gold-gold collisions. When you say that two different scientists are doing two dif... | [
"Isn't it a bit more than two experiments? Atlas, Alice, CMS, LHCb?"
] |
[
"What are the physics of an explosion in space?"
] | [
false
] | I remembered an episode of mythbusters that disproved the movie notion of explosions forcefully pushing people off their feet and away from the blast. Would the same be true for an explosion in space (e.g., a star going supernova)? Would the explosion be enough to push something (e.g., ship, planet, etc.) away, or is a... | [
"\"Explosions\" are not a class of one single type of phenomenon. Explosions in the atmosphere tend to have a vaguely similar effect since one of the primary ways they propagate their energy is via shockwaves in air. And since they're highly energetic and generally dangerous to humans we lump them into one category... | [
"That makes sense. I'm a complete novice/layman with this, so I appreciate the explanation "
] | [
"When you say \"space\", do you mean outside of Earth's gravity well, just outside the atmosphere, or maybe something else? \"Space\" is kind of a vague term.",
"A force acting on matter can propel it, even ever so slightly. Enough force can move anything. Gravity is the dominant force for celestial movement, ... |
[
"Do dogs have the capacity to understand that if I step on their paw that it was an accident?"
] | [
false
] | Or, from their point of view, do I just hurt them and am immediately after really nice to them with petting and talking to them for an unrelated reason? | [
"Folks, we don't allow speculation here. Answers need to be based on scientific information."
] | [
"There is no evidence that dogs are capable of that type of reasoning. Dogs fail the mirror test for self awareness. Dogs fart and it surprises them, and they chase and bite their tail, which also surprises them. It is known that dogs don't associate punishment with prior behavior. ",
"http://www.dogtraining.... | [
"Oh man, that isn't he answer I was hoping for, but I'd rather have the truth than be ignorant with this kind of thing. Thanks for the response! "
] |
[
"If you quantum entanglement two atoms, and one is sent into a black hole, is there observable changes in the atom outside of the black hole?"
] | [
false
] | null | [
"No. Entanglement doesn't work like that. You can observe a correlation between 2 entangled particles by comparing results of experiments on each of them, but observer A doing something to particle A does not cause particle B to behave in a way that is observably different to observer B alone. It is only after they... | [
"Ok so since u could no longer get any data from the one in the black hole you would have no way of knowing?"
] | [
"Right."
] |
[
"Would a typical modern adult human who'd never seen or heard of a snake before instinctively know it was dangerous and which end to be worried about?"
] | [
false
] | I think that's the whole question, but please ask any questions for clarification. | [
"Monkeys are instinctively afraid of snakes, even captive-born monkeys that have never seen one (",
"http://www.pnas.org/content/110/47/19000",
") but I can't find a source for apes. However, the part of the brain in the macaques that responded so strongly to the snake images is conserved across primate species... | [
"I don't remember where I read it, so take that for what it's worth, but I read about a study that was done that showed snakes were the number one predator humans could spot. Even out of periphery, we can spot them better than anything else. "
] | [
"I saw the same thing, but it included spiders. They did a test where they put a collage of all kinds of animals together and asked the person to find animal x. They consistently found the spiders and snakes quicker than everything else."
] |
[
"If you have an orgasm in your dream, do the same brain areas get activated as though you were having the orgasm while completely awake?"
] | [
false
] | null | [
"If science was driven by what we deemed useful, we wouldn't have the x-ray, data transmission over wires, or hell, the microchip. "
] | [
"If science was driven by what we deemed useful, we wouldn't have the x-ray, data transmission over wires, or hell, the microchip. "
] | [
"If science was driven by what we deemed useful, we wouldn't have the x-ray, data transmission over wires, or hell, the microchip. "
] |
[
"What exactly happens when you get executed by hanging? Technically speaking."
] | [
false
] | null | [
"It depends. There are four different kinds of hanging: suspending, short, standard, and long. Suspending is putting a noose around someone and then lifting them up which strangles them. \nA short drop is when you are on and object and that object is removed, leaving you dangling there.. The drop isn't enough to br... | [
"Sorry for the wall of text. I'm on my phone and I tried to space them out but it seems that that had failed"
] | [
"It depends. There are four different kinds of hanging: suspending, short, standard, and long. Suspending is putting a noose around someone and then lifting them up which strangles them. ",
"A short drop is when you are on and object and that object is removed, leaving you dangling there.. The drop isn't enough t... |
[
"Are there any known objects in our galaxy that are moving near the speed of light?"
] | [
false
] | [deleted] | [
"Not even close. The fastest thing I can find is ",
"S2",
" moving at 5,000 km/s or near %2 lightspeed."
] | [
"That's pretty fast, and it's a large mass. I can imagine an asteroid size mass being gravitationally slingshotted by that to much higher speeds."
] | [
"Pulsars rotate at decent fractions of it. "
] |
[
"How are 25nm transistors made."
] | [
false
] | I'm aware of the process of photo-lithography whereby the surface of a substrate is etched using ultraviolet rays. However 25nm is smaller then the wavelength of ultraviolet light, wouldn't this cause issues and if so how are 25nm transistors made. | [
"The wavelength of UV lasers used in the current 22 nm process is 193, (DUV or \"deep\" UV). The inability to create a spot smaller than the wavelength is called the diffraction limit, and roughly speaking the formula is D = .61 lambda / n sin theta. D is the spot diameter, lambda is the wavelength, n is the inde... | [
"nanoelectronics PhD student here\n25nm or smaller features can be accomplished via a combination of tricks, one of which is the reduction of features AFTER lithography. photolitho will give you a minimum linewidth of, say, 60 or more nm, but you reduce it by etching isotropically underneath a hardmask. You don't g... | [
"Coherent Extreme Deep Ultraviolet (EUV) lllumination, Calcium Floride optics and Interference Lithography are all used to create 25nm aerial images in very expensive photoresist. The exposed resist undergoes photolytic changes that allows it to dissolve in a 'developer' solution. This pattern in the remaining pho... |
[
"Say you took our universe and cleared out all matter except for two electrons, placed 1 light-year apart. They would repel, right? Can someone give some details as to the mechanism?"
] | [
false
] | null | [
"The quantized field is ",
" using virtual photons. They don't 'just appear'; they don't really exist. It behaves ",
" they existed. (but that's only one way of describing the quantized field) Electrons are ",
" constantly emitting photons in all directions. If they were emitting real, detectable, photons, th... | [
"Well, for starters the most well-known QED effects, the Lamb Shift and Casimir Effect (ironically, both are often cited as 'proof' of virtual particles) were both predicted and calculated well before that whole formalism was developed. Then there's the whole starting point of S-matrix theory, and much development ... | [
"Well, for starters the most well-known QED effects, the Lamb Shift and Casimir Effect (ironically, both are often cited as 'proof' of virtual particles) were both predicted and calculated well before that whole formalism was developed. Then there's the whole starting point of S-matrix theory, and much development ... |
[
"If I had a vine and split it into 5 strips and wove those strips into a rope, would the rope be stronger, weaker, or the same strength?"
] | [
false
] | Say there you had a vine and you were able to break it up into 5 even strips that run the original length. If you then took those 5 strips and wove them together, would the new rope be stronger because of the interweaving, weaker because the size of the strips, or the same strength because it is essentially the same as... | [
"Stronger, but shorter due to the weaving, regardless of weave pattern."
] | [
"Weave pattern will also increase the cross sectional diameter, increasing strength."
] | [
"yep, that's why it's shorter."
] |
[
"Why does rocket exhaust sometimes look like this."
] | [
false
] | [deleted] | [
"Those are Shock Diamonds, which are a complex phenomenon resulting from supersonic flow in air:",
"http://en.wikipedia.org/wiki/Shock_diamond",
"You don't always see them because they need specific conditions to form, or at least to be visible, including excess fuel in the exhaust stream. "
] | [
"It's called ",
"Nozzle Overexpansion",
", and it can even happen with high speed aircraft. Rockets and high speed aircraft are typically designed to travel at very high altitudes. ",
"Since it is taking taking off at a hight it's not designed for, there is a bit of inefficiency. This inefficiency causes the ... | [
"The expansion of the gases out of the nozzle are designed to have a relatively perfect expansion at x back pressure. That back pressure varies based on altitude, so at points in the flight path the C-D nozzle is working at lowered efficiencies. This causes the flow to either over or underexpanded, and once outside... |
[
"Why does evolution produce such complex creatures?"
] | [
false
] | I'm not sure if I'm phrasing this right. What I want to know is why there aren't just bacteria, instead of complex multi cellular organisms like mammals and reptiles. Aren't bacteria a lot better at reproducing than large organisms? What advantage do larger, more complex organisms have compared to small bacteria? | [
"How complex are organisms supposed to be ? You could equally ask why aren't organisms way more complex than humans and dolphins ? We don't know, but it seems that it's the level of complexity associated with the amount of energy the earth receives. Maybe if the sun were brighter everything would get more complex."... | [
"that's actually what happend early in evolution! for like 3 billion years there was only colonies of bacteria on earth but for some reason it wasnt sustainable for bacteria to just keep multiplying. there was a phase change - the internal structure of modern cells suggests that there have since been numourous symb... | [
"efficiency through outsourcing is one thing, e.g. each of our\ncells contains mitochondria which are little cells with their\nown DNA, they make ATP which powers\nour cells. The reason it's more efficient that way is that each kind of cell has its neiche and is specialized. when a cell has to do many different thi... |
[
"How stable are the Lagrange points?"
] | [
false
] | We know that L1, L2, and L3 are inherently unstable, whereas L4 and L5 are stable. But how much does it take to actually affect the equilibrium of an object in an unstable Lagrange point? Let's say we have a ship parked at L1 between the Sun and the Earth. Now if this ship was to move a little closer to the Sun, its gr... | [
"This image is great for this",
". The height of the striped surface indicates the energy due to the gravitational force + centrifugal force, as seen in the rotating system where we consider the earth and sun to be stationary. The force is the gradient of this surface, a steeper slope indicates a stronger force (... | [
"L1, L2, L3 are unstable because any object that starts near them will quickly fall in or out",
"That is a great diagram, but I don't think this is the right way to think about it. Objects in orbit don't \"fall down the hole\": because of the Coriolis effect which you mentioned, they move along the curved purple... | [
"At an inherently unstable point, any displacement will affect the equilibrium. The only difference is how rapidly displacement increases, which depends on the mass of the orbiting object as well as the magnitude of the initial displacement. "
] |
[
"Is there or has there ever been an important role in our body for hiccups?"
] | [
false
] | null | [
"The first air-breathing fish and amphibians extracted oxygen using gills when in the water and primitive lungs when on land—and to do so, they had to be able to close the glottis, or entryway to the lungs, when underwater. Importantly, the entryway (or glottis) to the lungs could be closed. When underwater, the an... | [
"Oh my god - this is the most bullshit thing I think I've read on Reddit (and I occasionally frequent ",
"r/brickporn",
"). This theory was proposed a while back by some sleep researchers - not a fuck was given!",
"The more accepted (read: medical) explanation is that hiccups are diaphragmatic spasms, and th... | [
"Here's the journal article that I believe you are referring to",
". As far as I can tell it appears valid. As a note, this is a hypothesis, not a fact. ",
"EDIT: According to recapitulation theory the hiccup is evolutionarily antecedent to modern lung respiration. Additionally, they point out that hiccups a... |
[
"Is it theoretically possible to create a human from DNA alone?"
] | [
false
] | [deleted] | [
"No, not really. Human DNA is just the carrier of the bulk of the information. There are numerous other ingredients needed to make a human being - epigenetic information inherent in the uterine environment and the sequence of steps undergone by a fertilized egg; additional DNA carried in mitochondria; additional ... | [
"To add onto what was said, the other thing many people fail to understand is that \"environment\" can be on a very very small scale as well, not just the general surroundings of an organism that we tend to think of. For instance, maternal mRNAs and proteins are directly provided by the mother for the developing oo... | [
"I'm sure they could. But there's a lot hidden in the \"sufficiently advanced\" part of that sentence. "
] |
[
"Why are atoms preferentially made up of electrons instead of another charged lepton?"
] | [
false
] | null | [
"Because the other charged leptons are unstable. ",
"Higher-generation leptons can decay into lower-generation leptons through the weak force. For example, the μ decays into electron + ν_μ + anti ν_e. You can tell it's a weak interaction because neutrinos show up. The muon neutrino is there to carry away the \"mu... | [
"For anyone who doesn't know the numbers, I just wanted to add that \"relatively long-lived\" means that muons live an average of two microseconds. From a particle physics perspective that's pretty long."
] | [
"The reason electrons and protons (and neutrons in nuclei) dominate the amount of matter has to do with the ",
"totalitarian principle",
": any process which can occur (is not forbidden by some conservation law) eventually will occur.",
"There's nothing preventing the higher-mass leptons from decaying into el... |
[
"I asked once already, but no one answered. If my kid is vaccinated, I have nothing to worry about. Right?"
] | [
false
] | null | [
"Vaccines are not 100% effective, though some have really high protection rates of 90%+. Various vaccines have different rates of protection (you'd have to look up the rates for each one), and there are also biological factors that come into play such as weakened immune systems. Vaccines are to a large degree a tea... | [
"For the most part, yes.",
"Your kid is most likely one of the lucky 98% who properly develop immunity after vaccination, so he/she should be protected.",
"For some, the immunity doesn't build up properly, which places them at risk if they come in contact with infected people, this is why the \"herd immunity\" ... | [
"I can't find the specifics, but some people have 'low blood titers' meaning that their body does not develop very many antibodies when they are vaccinated.\n",
"https://answers.yahoo.com/question/index?qid=20080909135601AAo0c3o",
"\n",
"http://www.motherjones.com/environment/2015/02/open-letter-parent-unvacc... |
[
"How much water does our skin absorb during a 5 minute shower. I'm sure there are a few different variables, but my sister-in-law was trying to convince me that it could be up to 8 cups which seems ridiculous to me."
] | [
false
] | null | [
"Your skin does not absorb water, and is in fact very resistant to water movement in both directions. The wrinkling effect is an internal mechanism which increases your grip in wet environments, caused by the contraction of blood vessels and regulated by the sympathetic nervous system."
] | [
"It is my understanding that human skin is waterproof and therefore NO water is absorbed during a shower. Otherwise, how can we swim without getting waterlogged and sinking until we drown? And wouldn't waterborne diseases just enter our bodies through our skin? I am pretty sure that skin is resistant to water. "
... | [
"Totally blew my mind when I found out that wrinkling is a nervous system response. Some paralyzed people lose that ability!"
] |
[
"Why are the primary colors for paint different from the primary colors for computers?"
] | [
false
] | In art class in elementary school I learned that the primary colors were Red, Yellow, and Blue. Later, I learned that computer colors are made of Red, Green, and Blue. Furthermore, we used the RGB color wheel in Chemistry in high school, which is apparently the standard ( ). I'm guessing the difference has to do with t... | [
"Because the difference between ",
" and ",
" light. Also, your eye sees in RGB, but CYMK (Cyan, yellow, magenta, black) is whats used for printing.",
"When mixing dyes, you can create any color using RYB. These is because dyes mix in a way that one color is indistinguishable from the other. Dyes are made w... | [
"Best way to explain this is...",
"Paint and objects in the world remove colors. This means that they absorb all colors except the one that they reflect. A plant isn't really green, for example, because it absorbs all colors except green which it reflects. Paints work the same way by \"sucking up\" all colors exc... | [
"Hi, not an expert, but if you look up ",
"additive color",
" and ",
"subtractive color",
" on Wikipedia, you'll get a good explanation. ",
"Short summary is that when you shine a red torch and a blue torch at a white wall, you are adding the frequencies to produce purple.",
"When you paint a white wal... |
[
"How does center of mass/gravity work and how can you manipulate it?"
] | [
false
] | [deleted] | [
"That's a vague question, what exactly do you mean?"
] | [
"Like the definition of the center of gravity, how it works(properties), how you could manipulate the center of gravity (as in the location with forces and such). It is rather vague, but I kind of want a big answer, if that isn't too much of a hassle."
] | [
"Like the definition of the center of gravity",
"The proper term of it is actually \"center of mass\".",
"It's the location in an object where its mass is evenly distributed in all directions. If you could put your finger ",
" an object to its center of mass, it would balance perfectly on your fingertip in a... |
[
"Micro-fusion for spacecraft propulsion, is it possible? "
] | [
false
] | null | [
"Great question! Unfortunately I did not work on this project directly, but close friends of mine did conceptual work on something very similar.",
"The basic idea was to use muon-catalyzed fusion. I'm not a particle physicist so I don't know the details, but essentially muons can serve to make fusion much \"simpl... | [
"I wonder if recently developed tabletop laser driven accelerators could help create muons for use in this case? (see ",
"http://www.nanowerk.com/news/newsid=22491.php",
")"
] | [
"Hmmmm....I don't know. I know my colleagues did extensive research on technology for muon production, but I don't know if they came across this or if this serves their needs. If I remember, I will ask my friend the next time I see him. "
] |
[
"How does our body know when we need to drink water?"
] | [
false
] | null | [
"A previous comment is correct that thirst regulated by osmolarity sensors associated with the hypothalamus, but I want to provide some more detail about that mechanism because it is really cool. ",
"You actually have an osmolarity sensing organ in your brain called the organum vasculosum of the lamina terminalis... | [
"Resuming it, our hypothalamus has a group of neurons that work as an 'osmolarity sensor. Mainly focusing on sodium levels, the more concentrated the blood, the thirstier you are, since it assumes you are lacking water to make your blood go up in concentration.\nIf I recall correctly, there's also ADH (antidiuretix... | [
"Actually no, it's not. This is a structure inside the brain, and the brain itself doesn't actually have any pain sensors. However, the membrane which attaches your brain to the inside of the skull (the meninges) does. When you're dehydrated, your brain shrinks in volume and puts tension on this membrane, which giv... |
[
"Evolution of Galaxies that have no Super Massive Black Holes in their centers?"
] | [
false
] | It's still fascinating to me that such a HUGE galaxy like the , which is 10 times wider than our galaxy, does not have a Super Massive Black Hole (SMBH) in its center. Will it form a new SMBH under gravity or will it eventually "dissolve"? | [
"Ooch, this is a tough topic. We don't actually know exactly how SMBHs form. While we know that galaxies tend to have mass concentrations in the centre, so it seems likely that having all that mass in a small space will give you an SMBH, the exact process is unknown, and why some galaxies have SMBHs and others don'... | [
"As a counter-example - ",
"M33",
" is a nice spiral galaxy that doesn't have a black hole either.",
"Elliptical galaxies may actually be ",
" likely",
" to have bigger SMBHs than disc galaxies."
] | [
"From what I read from NASA this galaxy might already be a result of 2 merged smaller galaxies and their SMBHs got slingshot away hence the absence of central SMBH. The diffuse core makes me think that the bulge's stars are expanding due to lack of gravity. Yes I also think that SMBHs exist in the early stage which... |
[
"Do planets fall out of orbit just as our satellite fall out of orbit?"
] | [
false
] | I know that satellites we put in space eventually fall out of orbit over time. As well as debris. Does this go the same for planets? Obviously the star in a system may probably collapse before a planet ever were able to be swallowed into it but I just saw an article on Facebook about the satellites falling out of orbit... | [
"Satellites in LEO (low earth orbit) are still in a very thin atmosphere and thus experience drag and eventually slow down enough to start descending, hitting thicker atmosphere and then burning up. The planets generally aren’t considered to be in the suns atmosphere, although the planets do experience ‘solar winds... | [
"Thanks! That’s what I thought but I still read somewhere that even though space is a vacuum there’s still particles in the deepest parts of space. At least within our solar system. I knew satellites decayed cuz of the thin atmosphere. But I figured maybe the same was with the planets and sun"
] | [
"It is so thin that it doesn't matter over the lifetime of our solar system. Mercury, Venus and probably Earth will eventually fall into the Sun as it expands and the drag gets significantly larger.",
"The orbits also lead to the emission of gravitational waves. While this is an even smaller effect, it is one tha... |
[
"Why are carbohydrates considered bad by some?"
] | [
false
] | The underlying philosophy of some diets, like the keto- paleo- and to a lesser extent the 'slow carb diet', is all based on the assumption that carbs are bad. What, scientifically speaking, makes carbs bad? Is there a distinction between good carbs and bad carbs? | [
"The references in this section on Wikipedia: ",
"http://en.wikipedia.org/wiki/Insulin_resistance#Management",
"provide some good peer reviewed sources on both the effects of and treatment of insulin resistance."
] | [
"The references in this section on Wikipedia: ",
"http://en.wikipedia.org/wiki/Insulin_resistance#Management",
"provide some good peer reviewed sources on both the effects of and treatment of insulin resistance."
] | [
"Sugars from fruits are also carbohydrates. But compared to simpler sugars like glucose, fructose (the sugar in most fruit) takes longer to break down in the liver and therefore doesn't go all into your blood at once. This is compounded by the fact that fruit also contains a lot of fiber, which means even slower di... |
[
"When trying to build muscle, people often recommend eating lots of protein. Proteins are made of amino acids, so is it possible to get the same effect by just ingesting amino acid suppliments? Are there any advantages/disadvantages?"
] | [
false
] | null | [
"1) Practicality. The cost of getting aminos through supplements vs whole proteins would be astronomically higher.",
"2) From a scientific standpoint the breakdown of proteins in whole food to aminos is facilitated by metabolic trickery that allows amino acids to enter the cell with relative ease. On their own, q... | [
"This is kind of silly. Do you realize how many different amino acids are in protein? It would be WAY more expensive to get them individually than to get either cheap meat or protein powder.",
"You may be thinking of BCAAs, which are pretty common and not too expensive. ",
"Even still, my ON 100% Whey was $5... | [
"More simply put, how are you going to initiate protein synthesis without a pool of excess aminos in the first place? Leucine's mechanism of action parallels insulin, but again, all totally worthless if you don't have the substrate in the first place."
] |
[
"Is there such a thing as a mathematical discontinuity in nature?"
] | [
false
] | I know that due to the existence of vacuums or near vacuums, material discontinuities can exist, but can a mathematical discontinuity exist as an observable, physical manifestation? One potential example I can imagine would be the singularity of a black hole, which is a 4-dimensional asymptote as gravitational pull ap... | [
"One example where discontinuities pop up in nature is phase transitions. Depending on the specific phase transition you're studying, you might find that things like the entropy, density, heat capacity, etc. are discontinuous across the transition."
] | [
"Except, if you remember your stat mech, real phase transitions don't exist in nature. Only infinite systems have true transitions."
] | [
"A shock wave from a supersonic aircraft or projectile is close... typically it is modeled as a discontinuity, but in reality there is a finite transition (a similar sort of issue relating to the phase transitions discussed above)."
] |
[
"Does an organism with a \"fast metabolism\" have any benefits over an organism with a \"slow metabolism\"? Or vice versa."
] | [
false
] | [deleted] | [
"For your basic question, it would depend on the situation. If it's winter, or somewhere that being eaten is not something very imminent, then having a slow metabolism would be helpful. But if you are, let's say, in the savannas of Africa, with mild seasons and sufficient grass, water, etc, then having a high metab... | [
"It depends what the body is doing with that energy. On a cellular level, that increased metabolic rate might mean that bacteria 1 can produce new cells faster than bacteria 2. Or it just might mean bacteria 1 is less efficient, perhaps because it is using nitrate as an electron acceptor instead of oxygen.",
"Wit... | [
"Basal Metabolic Rate is not just some number you are gifted with, it changes based on your muscle mass and how much you use your muscles (exercise / fitness level). Somebody with 10% higher BMR than another is likely stronger and in better shape. The muscles that he has that burn the extra energy will certainly ... |
[
"Suppose for a second you had a 2 light year long rod, if you pushed one end, would the other end move at the same time?"
] | [
false
] | null | [
"For your rod to be infinitely stiff then by that you are already surmising that all motion exerted on one end of the rod is immediately communicated to the other end through the bonds between their atoms; ie faster than light. ",
"In effect what you're saying is \"If I have something that travels faster than the... | [
"In a universe where special relativity is correct, you cannot have any material that is infinitely stiff."
] | [
"If i remember correctly, if you pushed it from one end, the force of the push you make would propagate through the material (any material) at the speed of sound.. therefore the other end wouldn't move until the movement got there"
] |
[
"Carbon dating (and presumably other isotope techniques) rely upon a constant background ratio in the atmosphere. Was this background ratio always the same?"
] | [
false
] | I don't know much about isotope aging techniques, but this in response to comment thread. As I understand it, to date items via isotope dating, we compare the current isotope ratio to what the background/atmospheric level is. My issue is, how to do know that the background level was the same 20,000 years ago, 100,000 y... | [
"For Carbon dating, the background ratio of C-14 (the radiogenic one which decays) has not stayed the same. This is because of the way C-14 is produced, namely an interaction between a nitrogen atom and a cosmic ray. The flux of cosmic rays reaching the earth's surface fluctuates over time, and thus the production ... | [
"Awesome! Thanks!"
] | [
"The best geochronological method is U-Pb in zircon crystals. It's efficacity is unaffected by atmospheric composition, as neither Pb nor U are even trace components of the atmosphere and the magmatic systems which produce dateable zircon crystals are sequestered from the atmosphere."
] |
[
"Is West Nile Virus still an issue?"
] | [
false
] | null | [
"West Nile Virus first appeared in North America in 1999. In 2015 it is endemic across most of North America. While it doesn't make the news very often, the CDC still monitors it. ",
"HERE",
" is the 2015 Surveillance data from CDC. ",
"HERE",
" is a map of lab verified human disease in 2014. As an example... | [
"In some parts of the world, mosquitoes could give you or your child malaria, dengue virus and other quite serious diseases. In North America, the diseases (like West Nile Virus) are less likely to cause serious disease in an otherwise healthy person. However, the risk is not zero. People can reduce the risk by us... | [
"In some parts of the world, mosquitoes could give you or your child malaria, dengue virus and other quite serious diseases. In North America, the diseases (like West Nile Virus) are less likely to cause serious disease in an otherwise healthy person. However, the risk is not zero. People can reduce the risk by us... |
[
"Plasma: how can the same phase of matter seem so eclectic in its behaviour?"
] | [
false
] | Are different types of plasma as uniquely behaved as they seem, or is their apparent broad categorization justified? I don't know if this question is naïve, and I am a layman. Lightning, stellar surfaces, fire, aurora, etc. are all categorized as types of plasma, or at least partially so, but behave and appear quite di... | [
"The definition of plasma is straight-forward: it is a gas of charged particles, typically free electrons and positively charged ions. In principle, you can get exotic plasmas (I've heard about electron-positron plasma, and you can also get 'cold' plasma), but I will not discuss those further here.",
"Plasma can ... | [
"The term 'plasma' refers to an ionized gas where the kinetic energy of the particles far exceeds their Coulomb potential energy. This seemingly innocuous property leads to a lot of complexity in behavior, as ",
" processes, involving large numbers of particles acting in concert and interacting with the self-cons... | [
"The definition of plasma is straight-forward",
"Your definition is incomplete, unfortunately. It's also required that the plasma coupling parameter (the ratio of potential to kinetic energy) is small. Otherwise, you're dealing with what's called strongly coupled plasma, which, despite its name, isn't really plas... |
[
"Why does silly putty behave differently when placed under pressure?"
] | [
false
] | For example, it shatters when or when . What happens on the molecular level that causes an otherwise soft, highly malleable material to become hard and shatter? As an aside question, from what I can tell, a combination of water and corn starch produces a similar effect, hardening when under sudden pressure, . Is this t... | [
"Silly putty is a fun type of fluid because it's viscosity isn't constant. ",
"Viscosity",
" is a property of a fluid that determines how it responds to a stress, basically, how much it will flow if you push on it a bit. ",
"Newtonian fluids",
" have a viscosity that is constant relative to the applied st... | [
"Good question!",
"There are three different parts to your question that I would like to address separately. First is how pressure matters here. Pressing on a fluid, or on a wad of silly putty is one way to stress it. The force you are applying to the volume by pressing is perpendicular (also called 'normal') ... | [
"You're exactly correct. Both are Non-Newtonian fluids, or a fluid without a constant coeffeciant of viscosity. As pressure is applied, the viscosity changes.",
"\nCheck it out!\n",
"http://youtu.be/3zoTKXXNQIU",
" "
] |
[
"Why is there so many variations of f1 cars/planes/rockets? Wouldn't a 'perfectly' aerodynamic shape exist?"
] | [
false
] | In the sense that out of all the permutations you could design something, surely there is just one particular way which would have the perfect shapes to create the right lift/drag/aerodynamics where it is needed? | [
"There's an old credence used by engineers to describe these questions. Think of finding the \"perfect\" design for anything as finding the perfect spouse. Science would dictate, with a given amount of variables, that one could find the theoretical perfect spouse. A man/woman that perfectly satisfies every one o... | [
"To build on this metaphor, for aircraft, its even more complicated. Now instead of trying to find your perfect spouse, you're trying to find one person who will be the perfect spouse for say... five very different people.",
"Since we demand very different things from our different type of aircraft (their general... | [
"Oh boy! My specialty is aerodynamic design optimization! Incoming rant.",
"surely there is just one particular way which would have the perfect shapes to create the right lift/drag/aerodynamics where it is needed?",
"Problem number 1 in optimization: define what \"optimum\" actually means. What do you mean by ... |
[
"Do sunsets look like sunrises?"
] | [
false
] | Could one tell if a picture displays sunset or sunrise without knowing when and where it was taken? Also for a video played backwards or forwards? | [
"To some extent, ",
" so - sunsets tend to be more colourful, owing to slight changes in atmospheric condition in the evening compared to the morning. The sun itself, of course, is emitting exactly the same light, and the amount of air that sunlight needs to pass through likewise remains the same. However, increa... | [
"So, you're saying as a side benefit of pollution we'll get prettier sunsets until we start heading down the other side of the curve and blocking out the sun with smog."
] | [
"Even those probably won't compete with the amount of particulate matter thrown into the atmosphere by e.g. ",
"volcanoes"
] |
[
"If people can eat frozen fecal pills to transplant healthy microorganisms to the intestine. Could kissing someone with a healthy mouth flora replenish your own?"
] | [
false
] | I have heard of doctors giving fecal transplants. Im wondering if the same idea could be applied with saliva and for the mouth. So can kissing someone healthy benefit your own health? | [
"In short, we don't know enough yet to know. But as someone who actually does this type of research, I've asked very similar questions. What you're talking about is essentially a probiotic, but for other parts of the body, instead of the gut which we generally associate with probiotics. We know the mouth is coated ... | [
"Oral flora is less likely to be involved in illness, so replacing it is a lot less important.",
"As someone working in this field, I strongly disagree with your last sentence. We know that changes in oral and respiratory bacterial communities (The word flora should die a fiery death! We aren't talking about plan... | [
"Oral flora is less likely to be involved in illness, so replacing it is a lot less important.",
"As someone working in this field, I strongly disagree with your last sentence. We know that changes in oral and respiratory bacterial communities (The word flora should die a fiery death! We aren't talking about plan... |
[
"Would putting a polymer composite into an ultrasonic cleaner damage the materials the piece is made of?"
] | [
false
] | For example, if part of the piece was a rubber below its glass-transition temperature, and the other piece was a hard piece of plastic. You know, like the rubber ring around a coffee mug cap that helps seal the liquid inside. Yes, I'm going to gently clean my coffee mug cap inside an ultrasonic cleaner with soapy water... | [
"I know that anecdotes are frowned upon in this subreddit, but there isn't much literature on cleaning coffee mugs with lab equipment. So without further ado, I present a list of things that I have successfully cleaned in an ultrasonic cleaner:",
"Hard rubber stoppers",
"Soft rubber septums",
"Borosilicate gl... | [
"I think anecdotal evidence for a question like this is quite alright. My question both has both a silly side and a serious side.",
"Polyethylene glassware",
"Poly (polymer) and glass are contradicting to me, initially! Is the polymer considered glassware because the polymer is amorphous instead of a crystallin... | [
"I clean my polycarbonate lensed, metal framed glasses in my ultrasonic clean with no ill effects to them."
] |
[
"Will all the Lithium-ion batteries we keep in our attics ignite eventually?"
] | [
false
] | Won't each one of them ignite as soon as their protective layer fails to keep the oxygen out? Or do they somehow "disarm" themselves over the years? | [
"Why in the world would you store lithium batteries in a place that has such extreme temperature swings? The short answer is that they won't do a thing if you store them in the discharged state. If they're being stored fully charged, there is the possibility of rupture and fire, especially when they get very hot.... | [
"They can still catch fire in the fully discharged state. If the seal gets compromised and air gets in, it can cause the lithium to react, heat up, and then catch fire.",
"In addition there are many different ",
"lithium chemistries",
". The ",
"lithium thionyl chloride primary cell",
" is more dangerous ... | [
"That's true, but OP asked about lithium ion batteries, which generally refers to a battery with lithium cobalt oxide/graphite electrodes, or something similar. At no time does lithium enter the metallic state, unlike lithium anode batteries."
] |
[
"If dark matter generates a gravitational field, and dark matter can 'clump' like ordinary matter, can dark matter collapse under its own weight like regular matter to make a dark-black hole?"
] | [
false
] | [deleted] | [
"dark matter can 'clump' like ordinary matter",
"No, it cannot.",
"Regular matter - there's gravitational attraction, and then there's friction (collisions) between particles. Gravity pulls everything together, and then friction slows particles down (relative speed decreases) so that they can \"clump\" together... | [
"Dark matter is different from normal matter than in that it doesn't interact with itself using all of the other forces (only gravity and weak interaction).",
"Normal matter can properly form planets and stars because it can bind together using the other forces. Dark matter doesn't have this property. It is attra... | [
"You have it backwards. Everything not evident by ",
" significant interactions is simply ",
" dark matter."
] |
[
"Is it possible to dive so fast you can turn upwards and exit the water?"
] | [
false
] | I dove from small heights in the past, about ten feet or so, and as soon as I hit the water I bent my body upwards, did a vertical U-turn, and exited the water before stopping halfway out. Well, I guess it was more of a J turn... Is it physically possible to dive from a high enough place that you can use that speed, tu... | [
"Terminal velocity for a skydiver is about 195 km/h. Most of that energy would be absorbed by the water upon impact, not giving enough time to turn your angle back upward to exit. Mythbusters did an episode of shooting bullets into water. Most of them stopped moving in the water after a couple feet (especially when... | [
"To clarify, it is completely possible to have enough downward momentum to turn it back upward while moving through a fluid; this is how gliders work. However, due to the limits of terminal velocity and the high surface tension and viscosity of water, most of the momentum would be absorbed on impact and in the ens... | [
"That is the weirdest most interesting explanation of lift I've ever heard. But your premise is false. This is essentially an energy problem that you could theoretically work out by KE + PE + losses = const. Lift and flight in general is much more complex than that. ",
"In reply to the OP: ",
"The limiting fact... |
[
"If we were hit today by an asteroid similar to the one that killed the dinosaurs, would the human race survive?"
] | [
false
] | null | [
"Here is a ",
"good discussion",
" of the effects caused by the Chicxulub impact. The effects are complex and do not depend solely on the size of the impactor. Factors like the target (rock vs. water), type of rock (sulfur-rich, for example), and location on the globe also play important roles. It is the second... | [
"I don't think its the kinetic energy that will kill us, but the ensuing ice age."
] | [
"The human race could not be very easily assumed to be doomed by a single shot of one asteroid; however if the single asteroid is accompanied from debris it collected from other collisions previously accumulated through smashing into smaller but still significant asteroids in a larger swarm that would strike around... |
[
"Why do arm hair and leg hair stop growing at a certain length?"
] | [
true
] | [deleted] | [
"What is the speed of dark?"
] | [
"Hair Follicle Cycle",
"And jeez, this has to be the most common question here, besides the speed of light ones."
] | [
"7"
] |
[
"Have we hit a sort-of dead end in cosmology?"
] | [
false
] | We know a lot about how/when the universe started, but we still don't know it started. Time itself started with the universe so what came makes no sense, but obviously something caused it to happen! According to my understanding, we didn't know earth wasn't flat for atleast about 2000 years, when finally by the 15-1700... | [
"First, many ancient societies and most educated people in the age of exploration (ie prior to and contemporary with Columbus) knew the earth wasn't flat. You can show it isn't without needing to circumnavigate the thing. The Greek's size estimate is actually fairly close even. ",
"To be honest, cosmology is a fi... | [
"but obviously something caused it to happen",
"why?",
"According to my understanding, we didn't know earth wasn't flat for atleast about 2000 years",
"Your understanding is wrong; Eratosthenes accurately calculated its radius in Hellenistic era."
] | [
"So, as a cosmologist, I can say for certain that we haven't hit a dead end. There are lots of efforts ongoing to probe the inflationary epoch, which occurred in the first 10",
" seconds of the universe. That probably won't answer why the universe started, but it might shed some light on theories that try to do ... |
[
"Is the normal force \"real\"?"
] | [
false
] | That is to say, is it a force that is distinguishable from the force "pushing" something against another, or is it something that isn't real but makes our model work. | [
"The normal force is real. At root, it's one way the electromagnetic force can manifest."
] | [
"You need to be very careful discussing normal forces and third law pairs as there are a lot of misconceptions in this area, for instance people thinking the normal force and the force due to gravity are a third law pair (equal and opposite) which is very much not the case as can be shown by looking at what happens... | [
"it seemingly (from my limited knowledge of physics) only results from the application of another force.",
"Well that's also true. If you weren't being pushed into the table it would exert no force back on you; you'd be just hovering over it slightly without putting any pressure on it. Normal forces are 'contextu... |
[
"If you put a large number of charged particles (say, electrons) into a star, what would happen?"
] | [
false
] | From what I understand, the electromagnetic force is much stronger than gravity. The only reason we don't see its effects on a cosmic scale are because protons tend to find electrons so the charges all balance out. However, if you were to manipulate a star so that its electromagnetic field was as strong or stronger t... | [
"This occurs in neutron stars. Neutron stars have huge magnetic fields (10",
" G compared to 0.5 G for Earth). As these magnetic fields sweep through space they induce huge electric fields parallel to the surface of the star. For an electron this electric force is about 10",
" times greater than the gravitation... | [
"That's not the ",
" reason why electromagnetism sort of \"self-regulates.\" Apart from the fact that most matter is electrically neutral, energy-dense electric fields will tend to radiate away their charge via spontaneous pair production.",
"Once you cram enough energy into an electric field, it becomes favora... | [
"I'm disappointed that no one has ever told me how awesome neutron stars are. Thanks.",
"How is it that neutron stars have such a strong charge? Does the total charge of the star plus the magnetosphere cancel out? If not, what happened to the extra charge?"
] |
[
"How much does the centrifugal force of the earth’s rotation counteract gravity at the surface? If the earth wasn’t rotating, how heavy would a kilogram be at sea level?"
] | [
false
] | I was reading about how the Gault asteroid is spinning so fast the surface material overcomes gravity and escapes. This made me wonder about the earth’s rotation and how much centrifugal force is acting against the earth’s own gravity. Would it make any measurable difference if there was no rotation? Would it be so muc... | [
"At the equator, where the centrifugal force is maximal in magnitude and directed straight upwards, the magnitude of the centrifugal acceleration is 0.3% of the magnitude of the gravitational acceleration at the surface of the Earth.",
"So an object in this situation is 0.3% \"lighter\" than it would be if there ... | [
"The centrifugal acceleration (in m/s",
") of a rotating object is w",
"r where w is the angular speed (in radians per second) and r is the radius of its rotation (in meters). Earth does a full rotation in one day, which is 2pi radians in 86,400 seconds or an angular speed of 7.27x10",
" rad/s. The radius of ... | [
"If you want to measure the mass of something with an accuracy better than 0.3% you have to calibrate your scale to the place where you use it."
] |
[
"Does Earth appear as a bright light to other planets in space, like Jupiter and Saturn do in our night sky?"
] | [
false
] | [deleted] | [
"have you never heard of the pale blue dot. that's a picture of earth from the satellite \"Voyager 1\" (I'll have to double check that) orbiting Saturn.\nits a barely visible dot from orbit so no interference ",
"Edit: ",
"Link to picture",
"\nalso it is from voyager 1"
] | [
"We may look bright in the Mars and Venus skies, but I'm not so sure about how bright we are to Jupiter and Saturn. Look at how big they are compared to us and only appear as dots in our sky."
] | [
"The brightness of a planet as viewed from another planet depends on a few factors. The first is phase angle. This is the angle between the light source and the observer, with the planet of observation at the vertex. The body will be brightest at a phase angle of zero degrees (think full moon), and dimmest at 180° ... |
[
"Do lines of latitude and longitude move?"
] | [
false
] | Systems like GPS and Google Maps can give you lat-lon coordinates of features on the Earth down to several decimal places. I'm assuming they're using some kind of reference geoid. But do the actual lines of latitude and longitude move around with the earth's precession and nutation? Do the north and south pole, where t... | [
"Do the north and south pole, where the axis of rotation intersects the surface, move around?",
"Yes, they certainly do.",
"Polar motion is observed routinely by very long baseline interferometry, lunar laser ranging and satellite laser ranging. Current and historic polar motion data is available from the Inte... | [
"Continental drift is on the order of centimeters per year, which is enough to require compensating for now and then. But this isn't really lines of latitude and longitude moving, just the position of objects on the planet moving.",
"It's also possible for the rotational axis to shift relative to the surface, som... | [
"The Earth's axis of rotation relative to an inertial reference frame (e.g. stars far away) changes with a 26,000 year cycle, but its rotation relative to the landmasses is more stable: ",
"https://en.wikipedia.org/wiki/Axial_precession"
] |
[
"If the y chromosome is human specific what causes the differentiation of male and female apes?"
] | [
false
] | I guess I just want my confusion cleared up on this article about the y chromosome Adam... Was the y chromosome due to the fusion of apes 24 chromosomes into our 23? Here's the article: | [
"The Y chromosome originally evolved from an autosome which acquired sex-determining characteristics. Apes also have X and Y chromosomes; in fact, many vertebrates do - mice have XY (male) and XX (female), birds have ZZ (male) and ZW (female). ",
"Some vertebrates don't have their sex determined in this way. Ofte... | [
"They didn't ",
" to be, but evidence suggests (according to Wikipedia) that they lived within a few ten thousands of years of each other."
] | [
"So by y chromosome adam do they mean the point at which sex was not determined by environmental factors and instead the y chromosome was the deciding factor? Thank you for the link by the way!"
] |
[
"Why is it that after staying up all night and feeling tired, you become more energetic, passing a certain interval of time."
] | [
false
] | Additional quesiton: Why is there a sweet spot of sleep deprivation where one is more likely to be creatively inspired. | [
"The reason one begins to feel better towards the end of the night is due to the circadian rhythm in alertness. The body contains a circadian clock that promotes sleep during the night and wakefulness during the day. As the next day begins, that circadian wake promoting signal also begins, which partially counterac... | [
"To add onto OP's question. Why is it when morning comes around again often headaches will set in"
] | [
"I can't give a simple answer to that anecdotal observation. The relationship between sleep and headaches is complex. Headaches have been associated with both reduced and extended sleep. The physiological mechanism by which sleep deprivation induces headaches is still not known. We do know that sleep has effects on... |
[
"I wear glasses. Why did the optometrist not give me super vision?"
] | [
false
] | The other day I was sitting at the traffic department to have my drivers license renewed. Part of the renewal process requires me to have an eye test. I wear glasses and was tested both with, and without, my glasses on. Without my glasses I failed the test, but with my glasses on I tested as having 6/6 (or 20/20) visio... | [
"The best your optometrist can do is to make sure the image on your retina is perfect. That's why they correct the geometrical defects of your eye. But there can remain some imperfections: shape of the cornea, size of the eye, shape of the retina, etc. And it doesn't change the \"resolution\" of your retina (how ma... | [
"They're called multifocal inraocular lenses. If you win the \"I got cataracts lottery\" and have good insurance or have a fair amount of cash you can get back to the vision you had when you were young. ",
"Now go away. I'm not telling you any more of our rich people secrets"
] | [
"Optometrist here. LASIK works by reshaping the cornea so that light rays will focus on the retina. \"Age related degeneration\" also known as presbyopia is due to the lens losing its flexibility because of free radical damage (aging). There is nothing wrong with the muscle (ciliary body). It is still doing its... |
[
"A lot of things in this new video by minutephysics don't seem logical to me, can anyone explain some things for me?"
] | [
false
] | So in made by minutephysics in combination with Vsauce, there were a couple of things that, although I am a layman, didn't seem very logical at all. A) 1:28 - 1:52 I have the smallest problem with this bit, but he says "you could float freely around with no sense of up or down". 1, once you reached terminal velocity in... | [
"A) For starters, they've assumed no air resistance, and therefore no terminal velocity. I agree with your second point - it's a minor nitpick - and they're really just trying to point out the lack of a net force acting on the person. \"Freely\" in this sense doesn't mean \"at will.\" It just means with no resistan... | [
"With the first one I just got a bit annoyed that they showed the stick figure almost swimming about. I feel sort of dumb for having missed that it was supposed to weigh the same. It took me a minute to understand what you were saying for C, but I get it now, and it's sort of interesting. Wouldn't you sort of drift... | [
"For the case of being inside a hollow sphere?"
] |
[
"When something is heated by induction, is it only metal that is heated?"
] | [
false
] | Because induction heating is so efficient and precise I am curious if there is a place for it in industrial fields, specifically quickly heating (cooking) a large amount of something | [
"only effects ferromagnetic metals, and in so far as they are below the curie point for said metal. This makes melting metals basically impossible",
"I'm not an expert, but I don't think this is correct. See ",
"this",
":",
"... eddy currents (also called Foucault currents) are generated within the metal a... | [
"only effects ferromagnetic metals, and in so far as they are below the curie point for said metal. This makes melting metals basically impossible",
"I'm not an expert, but I don't think this is correct. See ",
"this",
":",
"... eddy currents (also called Foucault currents) are generated within the metal a... | [
"Sure, ",
"induction furnaces",
" aren't uncommon in foundries these days.",
"A pretty cool (although not that common) application is ",
"levitation heating",
", which uses the same high frequency magnetic field to induce a current and levitate the object being heated.",
"You could use induction heating... |
[
"What medical uses does the decay of radioisotopes have besides treating certain forms of cancer?"
] | [
false
] | null | [
"The entire field of ",
"nuclear medicine",
" is involved with radioisotopes in medical applications - not just in treatment, but in imaging as well."
] | [
"While not treating a disease, ",
"PET scanning",
" uses a variety of radioisotopes for diagnosis, research, and medical imaging."
] | [
"Radiation is used extensively in imaging. Apart from that, there are several non-cancer diseases we can treat with radiation. Most of them are similar to cancer, in that they involve excessive cell growth. Radiation can be used to prevent ",
"keloid scarring",
". It is often given after traumatic pelvis/fe... |
[
"If an Astronaut would take his iPhone into Space, how would the different sensors react?"
] | [
false
] | How would the accelerometer, magnetometer and especially the gyroscopic sensor work or not work and why? | [
"There is a difference between how the gyroscope works on Earth and in space. On Earth the gyroscope will record one turn every 24 hours (of the casing about the gyroscope). In orbit the iPhone will maintain the same orientation, and this turn wouldn't get recorded. This is all assuming that neither device is handl... | [
"The gyroscope would work as it doesn't depend on gravity. The accelerometer would work unless it's to determine which way is up or down as it doesn't experience proper acceleration in free fall. ",
"I'm not too sure of the magnetometer. "
] | [
"Oh yes thanks for that. I forgot to consider the rotation itself. "
] |
[
"How long does it take for cellular damage to result from total hypoxia"
] | [
false
] | I see a lot of people talking about choking fetishes that some couples enjoy, wherein pressure is used to restrict the breath until the other becomes either light-headed or completely loses consciousness. They had standard warnings involved that you should be careful with 'breath play', but nothing other than that. Tha... | [
"I know that in the event of a stroke it usually takes 2-4 minutes for ischemia to do permanent damage to the cells (Glucose, however, again in the case of a stroke, takes only seconds to deplete and cause damage). If it takes a few minutes for oxygen depletion to actually kill brain cells getting NO perfusion, I w... | [
"The answer depends on the cell type. To the best of my knowledge, neurons (the cells that make up much of the brain and the activity of which results in conscious experience) are some of the most susceptible in the body to short term hypoxia. 5-8 seconds is enough to induce unconsciousness, hence the effects of th... | [
"Great response, thanks!"
] |
[
"How can sensitivity (d') increase and bias (C) increase in a memory paradigm?"
] | [
false
] | null | [
"Increase over the course of what? Like if you do two sessions of a memory experiment and find that people are better the second time around?"
] | [
"I'm measuring an independent variable. Let's say it is height: as people get taller, they increase in both sensitivity and bias to remembering a certain type of apple (also made up). ",
"Conceptually, how can people both be biased to saying yes to red apples, but also more sensitive to red apples? Also, how do I... | [
"That's the whole point of signal detection theory - sensitivity and bias are separable. In your example, maybe people encounter lots of red apples during their lifetime so they become expert apple detectors and can recognize them much more easily. They also become biased to \"see apples everywhere\" so even when t... |
[
"Reading the post about Uranus and it’s 90 degree axis - Why do planets rotate to start with?"
] | [
false
] | null | [
"Planets rotate because of the Conservation of Angular Momentum. The gas and dust that forms planetary systems has some net rotation to it before it starts contracting. There are a lot of reasons for this, but basically it's very hard to not have angular momentum. If any particle moves in a way that's not directly ... | [
"its like dropping a ball and expecting it not to roll some distance from where it lands. possible but almost never happens."
] | [
"Perhaps an explanation of 'angular momentum' is in order?",
"Consider two small objects in stable orbits of different radii, about a central body. \nThe object with the smaller radius orbit will be moving faster about the center than the one with the wider orbit.\nAs the two approach each other, and gravity draw... |
[
"Do people in the International Space Station experience day and night? Or is it continuously one or the other?"
] | [
false
] | null | [
"The orbital period of the ISS is about 96 minutes, so they experience multiple sunrises and sunsets per day. I'm not sure what kind of toll that takes on the circadian rhythm and how they combat that, though. I'm an orbits guy, not a bioastro guy!"
] | [
"yes, they experience day and night. Of course, its also orbiting very fast (about 1.5 hrs per orbit), so one \"day\"/\"night\" only lasts a short time",
"edit: ",
"check out the map"
] | [
"You can take a look at ",
"this ISS activity log",
" to get a general idea what a day's work looks like aboard the ISS. As you will note, sleep time is regularly scheduled from 9:30PM to 6:00AM (times are in Greenwich Mean Time), with some padding on either side for \"pre sleep\" and \"post sleep\" activities... |
[
"If time is stopped at the speed of light, than is time existent for light itself?"
] | [
false
] | null | [
"There are no inertial frames where the photon is at rest, so it doesn't make physical sense to ask what happens when you reach light speed or what a photon experiences in its rest frame, because in all rest frames, massless particles including photons move at ",
". Asking \"does time stop at the speed of light?\... | [
"No. Because the photon is a massless particle, it ",
" move with speed ",
". Unfortunately, there's no 'if's' here, massless particles are required to move at speed ",
"."
] | [
"No. Because the photon is a massless particle, it ",
" move with speed ",
". Unfortunately, there's no 'if's' here, massless particles are required to move at speed ",
"."
] |
[
"What is that 'curtain' of gaseous stuff that we usually see falling down the sides of a rocket during launch ?"
] | [
false
] | If you look closely at rocket launches (Saturn V or maybe other rockets too) you will find some kind of a curtain of gaseous stuff falling over its sides. Till this day, I have no idea what that is :( Photo: and I have this nagging question ever since I was a kid (now I am 30 but no answer in sight). I am hoping someon... | [
"ice- most modern rockets are hydrogen based. And are propelled by large amounts of liquid oxygen in hydrogen, making the surfaces of the rocket very cold before launch, enough that ice forms on the surface, which then falls off during launch. "
] | [
"Thanks!!! Now I know :)"
] | [
"If you really want to know more than you've ever known before about the shuttle and its launch then watch the 45 minute long documentary ",
"Ascent - Commemorating Shuttle",
". ",
"It's shuttle footage hand picked by shuttle engineers and narrated by shuttle loving engineers.",
"\nDownload a HD copy, the... |
[
"General questions about Multiverse Theory and related concepts"
] | [
false
] | null | [
"Your 3rd point is your only actual question:",
"CMB Cold Spot - what about this spot shows imprints/evidence of another universe?",
"Simple quantum fluctuations are likely sufficient explanations for the CMB fluctuations, and thus, ultimate formation of galaxies. You should understand the basic idea of quantu... | [
"the number of black holes a universe has indicates how much more down the evolutionary line the universe is.\nNo it doesn't. The universe has many more black holes now than it did 13 billion years ago. So that's probably not making a universal statement about our universe.",
"This was actually something I learne... | [
"You could make the argument that a large number of black holes indicates that the universe is further ",
", meaning optimized for making black holes. But that doesn't reflect the number of universes that came before it. By chance, one line got might have gotten really good really fast."
] |
[
"A question about earth pre- Pangea."
] | [
false
] | I recently read an article( ) and I was confused about this specific part: "It appears that Kenorland broke up around 2.6 billion years ago, creating a massive spike in rainfall. This in turn caused a decrease of greenhouse gases like carbon dioxide" My question is why would the breakup of a supercontinent such as Keno... | [
"Since no one will have an actual answer for this I will try and take a stab at it. PhD in Mechanical Engineering, so not exactly a layman, but feel free to correct me geologists and climatologists.",
"Weather is very dynamic, and geographical features play a major role in the local environment. For example, th... | [
"Well the hotter a liquid is the faster is evaporates. With a smaller body of water the water will evaporate quicker. The more shallow the water the easier it is to heat it up."
] | [
"In addition, the Himalaya only cuts off a relatively \"small\" part of the global landmass, central Asia. But it seems likely that in a \"supercontinent\" much of the inner landmass would be dry deserts of one kind or another. ",
"With the breaking up of such a supercontinent not only would there be direct-effec... |
[
"Are there examples of evolutionary change or adaptation in humans evident from the last few thousand years?"
] | [
false
] | From the peppered moth to the tawny owl, we see examples of rapid evolution. Though I'd expect nothing of the speed of these two creatures evolutionary adaptation, I'm wondering if there have been any examples of evolutionary adaptation that can be seen in humans in the last few thousand years(I'll keep that time frame... | [
"Lactose tolerance in Europeans and North Africans, which apparently developed in both populations independently of each other and obviously after the domestication of cows, so some time in the last 10000 years. The idea is, that being able to use milk as a food source gave you a survival advantage when there food ... | [
"It doesn't even run with \"whatever works.\" It runs with \"can I still reproduce successfully with this mutation.\""
] | [
"Another one is resistance to malaria disease. ",
"https://malariajournal.biomedcentral.com/articles/10.1186/1475-2875-11-349",
"“The first generally recognized evidence for genetic resistance to malaria in humans was in 1954 [7] for sickle-cell haemoglobin heterozygotes AS. Overall, the “malaria hypothesis” of... |
[
"I wear glasses for distance, but if I look through a tiny hole in my fist, I can make things come into focus. What's going on?"
] | [
false
] | [deleted] | [
"optometrist/vision scientist here. this is called the pinhole effect. light coming from 'straight ahead,' or incident to the lens does not get diverged from it's path. if you can eliminate off-axis, or non-incident light, you get a fairly clear image without having to change the optics (i.e. don't need your gla... | [
"To add to hokieod's answer, this is also used as a test as to whether someone has reduced visual acuity due to an uncorrected refractive error (nearsighted, farsighted, astigmatic) or if their reduced visual acuity is due to an organic cause."
] | [
"Yes, and astigmatism. "
] |
[
"In space disasters (ex: Challenger), when they mention remains, what was actually left?"
] | [
false
] | Rather morbid, but I've always been curious as to what was left of the occupants of Challenger, Columbia etc. Tangentially, what actually killed them, was it something like fire or oxygen deprivation? | [
"The publicly released reports state that several of the Challenger crew managed to activate their emergency oxygen supplies after the orbiter breakup, and may therefore have remained conscious until impact, unless the cabin was spinning ast enough to cause a blood-deprivation blackout. They would have been killed... | [
"Depending on the type of spacecraft failure that results in death, not much in the way of remains can be left over. Here below is a link to a NSFL image from the Soviet archives, showing the remains of Cosmonaut Vladimir Komarov, whose Soyuz 1 capsule suffered multiple failures - both while he was on orbit and dur... | [
"Only Challenger. Also, they probably would not have been conscious. They would have lost consciousness due to oxygen deprivation quite quickly.",
"There is no way that the Columbia crew survived the initial breakup of the orbiter given the speeds they were traveling."
] |
[
"Have Noticeable Earthquakes Become More Frequent?"
] | [
false
] | I was tinkering with some data here (for fun): Note that I'm aware that I'm looking at data for 23 years of a planet much much older than that so the sample size isn't even great. Based on the number of global Earthquakes in 3 categories (magnitude 4.0+, 5.0+ and 6.0+), can we say though that there will likely be more ... | [
"To a first order, numbers of earthquakes of different magnitudes are well explained by the ",
"\"Gutenberg-Richter Law\"",
". If you take a look at that page (or look other things about this relationship) you will see there is some slop in that, especially in regards to the \"b value\", which is an empirical c... | [
"You should look into the concept of induced seismicity as it explains the increase in smaller magnitude quakes (~mag 4). The most common cause of these small quakes is fluid injection for industrial wastewater (primarily off of oil/gas operations). The exact cause of the slip is somewhat case dependent but is in... | [
"I appreciate the info!"
] |
[
"Shouldn't a black hole have only as much gravity as the star that formed it did?"
] | [
false
] | A question fueled by Dr. Who. Where does the extra mass come from that makes a black hole so dense if it was only made from a single star? | [
"Black holes have ",
" mass than the star from which they formed. As a general rule of thumb, when a star undergoes the kind of supernova that can create the pressure necessary to make a black hole, about three-fourths of its mass is blown off out into space. A twenty-solar-mass star becomes a five-solar-mass bla... | [
"1) Yes. 2) They have no extra mass, only higher density."
] | [
"Not all stars are capable of forming black holes. They have to be above a certain mass."
] |
[
"My physics teacher reckons the \"heavy and light objects fall at the same rate\" demonstration only works below certain heights. Is there any truth in this?"
] | [
false
] | I'm a trainee teacher, and I was doing a subject knowledge lesson in Physics today. The tutor told us about a demonstration showing that objects of different mass hit the ground at the same speed, using an empty whiteboard marker and one filled with sand. Pretty standard. However, he cautioned us that if we did the dem... | [
"Air resistance will definitely cause things to fall at different rates, and have different terminal velocities - although that has more to do with the shape than the mass.",
"But he is absolutely incorrect in saying that, in the absence of air resistance, heavier things will start falling faster if you drop them... | [
"My physics teacher tried to demonstrate a way to neglect air resistance.",
"He dropped a textbook and a sheet of paper separately. Of course, the textbook hit the floor first as the paper drifted down on light air currents.",
"Then, he put the paper on top of the textbook and dropped them both, so as to situa... | [
"A better demonstration would be crumpling the paper and dropping it independently, because placing it against the book does like you said, the paper is caught against the book because of air pressure as the book falls."
] |
[
"Is there a known gas that burns without creating visible light?"
] | [
false
] | null | [
"Yes, hydrogen glows mostly in the infrared and UV spectrum when it burns, but it emits almost no visible light. Furthermore, water vapor resulting from the combustion also glows in infrared and UV due to thermal radiation, but since it is (almost) transparent in the visible spectrum, ",
"Kirchoff's law",
" det... | [
"Because they are \"single use\" the Delta IV first stage motors have an ablative inner nozzle lining that contains carbon which slowly burns away as the engine runs.",
" The Space Shuttle main engines are intended to be re-used and so do not have coatings that are meant to be burned off during operation."
] | [
"The video you linked is about Apollo 11. That was a Saturn V rocket, which burned RP-1 (very refined kerosene) in its first stage. Certainly a kerosene flame won't have the same properties as a hydrogen flame.",
"For the Delta IV, ",
"/u/Guysmiley777",
"'s answer is correct."
] |
[
"Will opening a door darken a room?"
] | [
false
] | Suppose you are trying to sleep in a small room with several doors and a lamp. It is hard to fall asleep because of the brightness of the lamp. Will opening the doors "darken" the room (the rooms on the other side of the doors are dark)? Will some of the photons now travel to the other room as opposed to bouncing of... | [
"Furthermore, turning your lamp off will eventually darken the room as the photons are absorbed into the materials that they collide with."
] | [
"After using the internet for years upon years... I still can't tell if this is a joke, science, or both."
] | [
"One extra note: everything depends on the reflectivity of the door in comparison with the reflectivity of the room behind the door. It the door would have a reflectivity of 0%, and absorb all the light falling on it, then opening the door would lighten up the room.",
"Practical: if the door is made of a pitch bl... |
[
"What's the smallest possible number of fundamental units, and what would they be?"
] | [
false
] | I know the SI system has 7, but I was thinking and realized that distance and time are actually the same, aren't they? And a mole is just a numerical multiplier, right? So, how few units could you end up with? | [
"Mass can be expressed in units of distance (Schwarzschild radius).",
"That's fantastic! I never thought about that!"
] | [
"Mass can be expressed in units of distance (Schwarzschild radius).",
"That's fantastic! I never thought about that!"
] | [
"In principle, you can have only one unit. ",
"The idea is that some fundamental constants are actually just proportionality factors, so you can just set them as 1. These are the speed of light, Planck's constant and Boltzmann constant. So distance and time are the same, which are inverse mass, energy, frequency ... |
[
"If the centre of the Milky Way happened to contain a Quaesar, would it have affected anything here on earth? Would it just be a brighter light in the night sky, or would it perhaps have more affected significantly the evolution of life?"
] | [
false
] | null | [
"It's possible that the centre of the Milky Way ",
" \"active\" at some point - like a low-level quasar. The centre of the galaxy is still obscured by dust, so all the bright visual-light radiation would still be dropped down into infrared and you still wouldn't see much. The effects on the structure of the galax... | [
"A cursory read over the wikipedia page that you linked to seems to imply that the Yarkovsky effect is only important \"in relation to meteoroids or small asteroids.\" I have very little knowledge about astrophysics, so I'm not sure that one can extend that principle to entire galaxies. Do you have any information ... | [
"No, most celestial bodies have a prograde motion, so the force would accelerate these objects outward. However, the Yarkovsky effect is reduced even further on a star, which does not radiate inbound EM waves the same way that solid objects do. Asteroids also expel gases in response to the solar radiation, so tha... |
[
"When you touch something, do you feel it in your brain or your body?"
] | [
false
] | [deleted] | [
"Short answer: It's your brain. You can stimulate the brain's sensory parts directly and create \"fake\" sensations that are felt out in the body. ",
"Longer answer: The brain works together with the body to generate your sensory experience. The specialized neurons in your skin translate various forms of tou... | [
"Thanks for the answers. ",
"So really, our brain is virtually creating sensations in a 3D space. If you close your eyes and someone pokes your hand, your brain produces a sensation that would seem to be in that exact spot. It's kind of like virtual reality..."
] | [
"This is part of your Somatosensory system. Neurons in your body pass feedback to the brain which translates that and lets them know it's feeling something. ",
"Your brain can absolutely mix up feelings. It's actually pretty common. Phantom Limb Syndrome is a phenomenon where amputees will still claim to experien... |
[
"How does the body determine what it is going to be allergic to? And what stage of development does it occur?"
] | [
false
] | [deleted] | [
"To add to the great points above, the body doesn't determine. It's random chance, genetics, and (bad)luck. Some allergies are mediated by what are called innate immune cells, e.g. Mast cells, that produce histamines (which is why you need anti-histamines). Other allergies/autoimmune disorders are mediated by adapt... | [
"It is my understanding that mast cells and T-cells are present in most forms of allergic responses, and they are better classified as IgE vs non-IgE responses. Am I missing something?"
] | [
"Correct me if I'm wrong but I believe it works by your immune system attaching to 'Invaders'. A leaky gut would be the most common place through which we get the stuff in. With about 70% of the immune system around the gut, it is the first place where particles are detected that don't belong in the body. With a b... |
[
"Why are there so many differences (racially, linguistically, etc.) between India and China?"
] | [
false
] | For countries that are so close to each other it seems odd that the racial differences are so pronounced. Does it have to do with the mountains dividing them? | [
"The Himalaya Mountains separate India from China. That mountain range is ",
". It is easier to cross oceans than the Himalayas."
] | [
"We both speak a phonetic language, have similar diets, and they have intertwined history. India and china really have none of those in common not even a war."
] | [
"Melanin/Race falls under Biology",
"Linguistics falls under Soc./Poli-Sci/Econ./Arch./Anthro./etc"
] |
[
"[Physics] What is the highest angle from the horizontal a standard road automobile (IE: Honda Accord or something similar) can drive up without sliding down or flipping?"
] | [
false
] | I'm aware there are a lot of contributing factors (coefficient of friction, tire quality, material of the road being driven on) but if there's a somewhat general answer, I'd love to hear it. | [
"You can do a loop without flipping:",
"http://scienceblogs.com/dotphysics/2009/08/31/5th-gear-loop-the-loop/"
] | [
"This is a good point that displays the complexity of the question."
] | [
"There are a number of factors in play here that I don't see being addressed. A car's traction is based on friction between the tires and road. This, in turn, is based on the vehicle's wheel size, the coefficient of friction between the tires and road, and whether you've already lost traction or not (Wheels spinnin... |
[
"What's new in Fluid Dynamics?"
] | [
false
] | I'm an undergrad applied math major and a professor recently sent me a link the DARPA's 23 Mathematical Challenge questions. Question #4 was looking for a fluid mechanics for the 21st century. The problem description implied the limits of the classic Navier Stokes Equations in dealing with things like foams and liquid ... | [
"I work in a field called nanofluidics where we study the behaviour of fluids in regions under 100 nanometers. The whole field is only about ten to fifteen years old. This is related to microfluidics and the \"lab on a chip\" paradigm.",
"Before that I studied the dynamics of oscillating bubbles, which is also f... | [
"How did you define a bubble? Was any bubble shaped interaction between two fluids fair game? i.e. letting out a breath under water, or maybe olive oil and water. Or were you more concerned with soap type bubbles?"
] | [
"I was keeping them spherical. A spherical cavity of gas inside a liquid. ",
"This does not have to be the case",
". The bubbles I was studying were very small so surface tension forces dominated."
] |
[
"How do bacteria gain immunity on antibiotics?"
] | [
false
] | I read that microbes can and will be able to adapt immunity to antibiotics at a matter of time. Is this also the same at alcohol and soap? | [
"Good explanation but there are a few errors.",
"Bacteria that are already resistant to antibiotics are present everywhere, even on your hands right now. Using antibiotics kills more of the non resistant strain allowing the resistant strain to dominate.",
"Bacteria can evolve to have anto biotics resistance but... | [
"Thanks for explaining!",
"I'm not sure if that's beneficial and I don't know if there is any research about that because the effect of soap/sanitizer works so damn effectively against almost every variety of bacteria. So weakening the concentration/potency of the soap is basically just testing \"how can we mix o... | [
"So bacteria have 2 ways of storing their genetic information: the chromosome, in the nucleoid region and plasmids scattered throughout the cytoplasm.",
"By using antibiotics, we are basically exerting evolutionary pressure on the bacteria in question. Through random chance, some individuals possess mutations tha... |
[
"Are there any substances that can induce a delayed mental illness state when exposed to?"
] | [
false
] | null | [
"What do you mean by \"mental illness state\"? Many recreational drugs including alcohol take some time to \"kick in\" to have metal effects"
] | [
"Akin to exhibiting a schizophrenia or bi-polar where there was none previous to exposure"
] | [
"Not really, no. The closest might be some drugs producing auditory hallucinations perhaps."
] |
[
"Do bigger cars have an advantage over smaller cars when the driver hits a deer?"
] | [
false
] | null | [
"I couldn't find the height of the CR-V grill so based on the picture and height of the tire (215/70R16 is 27\" tall) it looks to be around 40\". White-tail deer shoulder height is 21\" to 47\". The CR-V would hit the body of the tallest deer, and the altima would hit the legs and probably end with the deer through... | [
"You could look at this from a simplified conservation of momentum point of view.",
"Basically, the heavier the car you're in, the less you are going to slow down after hitting the deer. Assuming it's over the same amount of time (Which has a lot to do with how much the hood of the car compresses, and some other ... | [
"head on? who hits deer head on? you smack them in the side."
] |
[
"Why is botulism toxin (botox) able to be injected despite being so incredibly toxic to humans?"
] | [
false
] | Also, what makes it so potent compared to other compounds like Sarin or VX? | [
"Part one of your quesition: It is injected in very very dilute concentrations, into peripheral facial muscles.",
"To answer the second part of your question:",
"Sarin and VX are chemical warfare nerve agents. Botulism is an organic compound [Edit: meant to say toxin]. [edit: Nerve agents are organic as well,... | [
"It's not just the dose, it's also the distribution. Botox is injected locally to exert its desired paralyzing effect. Injecting botox into the bloodstream would result in a much more deleterious outcome. Lidocaine would be another example. Inject it locally, fantastic anesthetic. Administer it systemically, and... | [
"It's the dose that makes the poison. Nicotine, atropine, and scopolomine are nasty poisons at doses that mean you wouldn't want to eat the nightshade family plants they come from. But we use all of those drugs medicinally, albeit at much lower doses."
] |
[
"Why does a sugar-free energy drink actually taste sweeter than a regular energy drink?"
] | [
false
] | null | [
"Sugar-free drinks contain artificial sweeteners (for example aspartame or stevia). If these are present in sufficient quantities, the drink will taste sweeter than its sugar-containing equivalent."
] | [
"No, on the contrary. The sweetness of a drink doesn't determine how (un)healthy it is. In general, sugar has a number of known negative health effects, affecting risk of obesity, diabetes and dental issues.",
"Artificial sweeteners don't have those effects on health. Artificial sweeteners are considered food add... | [
"No, on the contrary. The sweetness of a drink doesn't determine how (un)healthy it is. In general, sugar has a number of known negative health effects, affecting risk of obesity, diabetes and dental issues.",
"Artificial sweeteners don't have those effects on health. Artificial sweeteners are considered food add... |
[
"Does binocular dysfunction also cause loss of 3D thinking, and not just stereopsis?"
] | [
false
] | null | [
"By 3D thinking do you mean something like mental rotation? If so, then the answer is no (",
"Klein, 1977",
"). People can get spatial and depth information from other cues."
] | [
"Always makes my day to see my supervisor get referenced in the wild! I had no idea he had written on this topic. Coincidentally we're currently stewing up a study on depth effects in a Posner-esque cueing task."
] | [
"I mean... what you're basically asking is, \"if someone has no senses that can perceive in three dimensions*, will they lack an ability to ",
" in three dimensions?\"",
"The answer is that we don't perceive in three dimensions. Our eyes perceive in two dimensions, which we then manipulate to give an illusory c... |
[
"If you mix pure Hydrogen and pure Oxygen, do you get Water or Hydrogen Peroxide?"
] | [
false
] | Since both Hydrogen Peroxide and Water and composed of both H and O, would you end up with one or the other? or would you have both becoming products of the reaction? | [
"In a combustion reaction between hydrogen and oxygen, water is the product, as it is the lower energy product compared to hydrogen peroxide. Even if hydrogen peroxide is formed, it will decompose into water and oxygen."
] | [
"See ",
"the Wikipedia page",
". The method either involves the use of other compounds, or the use of a catalyst to avoid the high energies associated with combustion."
] | [
"Hey thanks bud. So since combustion is the reaction for water, what method would a chemist use for H2O2?"
] |
[
"Could I go far enough underground to survive a wayward gamma ray burst?"
] | [
false
] | If a nearby star went nova and splashed Earth with a wash of gamma rays, could I find a mineshaft and survive? I realize the likelihood of such an event occurring is low and all that jazz. | [
"No. This is because the gamma ray burst wouldn't ever directly affect you even if you were standing outside at the time.",
"The problem is that they would cause a chemical reaction in the upper atmosphere changing molecular nitrogen into nitrogen oxides, depleting the ozone layer and exposing the surface to sola... | [
"I'm not 100% sure that Phage0070 is correct about gamma rays from a ",
" supernova not making it through the upper atmosphere, although he very well could be. I tried to do some rough calculations to check his assertion but I got lazy when the numbers I needed weren't conveniently available. I happen to be stud... | [
"This is the type of thing you can look up in the particle data book. ",
"Dry air has a radiation length",
" of about 300 m at 1 atm. The density will be lower at higher altitudes, so the radiation length will be higher but let's just keep that in mind for now.",
"The mean free path for a high energy gamma ra... |
[
"Did eyes evolve only once on Earth? Is there something about the small band of \"visible\" light that makes it optimal for eyes to evolve to see? Or is it just a coincidence that most animals see in the same spectrum?"
] | [
false
] | I have heard of animals that see infrared & ultraviolet. But they all see (or so I think) the same frequency of light we see. Would an alien eye be more or less likely to see nothing in our "visible" band of light because it sees a higher or lower frequency? If eyes evolved once, it may be that the commonalities are ... | [
"\"eyes\" evolved independently in an enormous number of species.",
"Or more accurately, the basic parts of an eye developed waaay long ago in the species that formed the base of a lot of different genetic trees.",
"Long before the dinosaurs, or before most mammals existed.",
"And this has to do with what the... | [
"Great answer. The Sun gives off most light in the visible spectrum ",
" water (where most early animals lived) is transparent in the visible spectrum."
] | [
"You're a bit confused as to what \"frequency\" means. Frequency is the reciprocal of wavelength, and we use wavelength for light, because frequency is very clumsy when you get into petahertz.",
"Visible light runs from roughly 800 nanometers to 450 nanometers. As light gets shorter wavelength (higher frequency) ... |
[
"How does radiation cause cancer?"
] | [
false
] | I've been reading about Chernobyl and it made me wonder. Also, how does it cure cancer? Are there different kinds of radiations? Thanks | [
"Ionizing radiation damages DNA. When DNA is damaged, 1 of 3 things can happen.",
"1) The DNA damage is repaired, and the cell returns to normal",
"2) The DNA damage is unrepaired, and the cell dies.",
"3) The DNA damage is unrepaired, but the cell survies with altered (mutated) DNA.",
"In normal cells, th... | [
"Thanks so much, and finally one of my askscience questions got answered. That makes sense what you said and it's makin me want to do more reading up on it. Thanks askscience"
] | [
"You can try ",
"a quick search",
" as well to show the many times this question has been asked and the excellent answers those questions received."
] |
[
"Can elephants breath through their mouth ?"
] | [
false
] | null | [
"Yes! Elephants can and do breathe through their mouths, just as most other mammals do.",
"Human newborns (can after a few months but prefer to use nostrils even after, comment below with source), horses (unless there are issues, see comment below), rodents and rabbits cannot, for example. They are referred to as... | [
"Just want to say that it’s awesome that you took your time to search and site your sources. Thank you!"
] | [
"You should never just take someone's word for it, and it's part of the sub-rules. :) ",
"I'm happy to find sources, I ended up reading a lot about elephant anatomy in the process. For example, they do not have a pleural cavity as most mammals do. The pleural cavity allows lung volume to change with the thoracic ... |
[
"It looks as though new SSD technologies will be nearly as fast and durable as DRAM. Can we expect fundamental changes to how operating systems handle storage as a result?"
] | [
false
] | An awful lot of the way we work with data seems to be built around the concept of slow serial IO; read()ing records into buffers a chunk at a time, rewinding file pointers, etc - as it has been since the days of magtape. What happens if and when it's safe to assume that all your data is random-access and equally fast; ... | [
"Hm. Intel are claiming that their new '3D Xpoint' nvram is 1000x more durable than current offerings, and 1000x faster also.",
"The cheeky buggers made a prototype SSD in a DIMM form factor... which is what prompted my question.",
"Thanks for the info on XIP; that's just what I was after."
] | [
"As far as I know SSD durability is going the other way.",
"But it does seem like the move towards SSDs is moving us towards the times before mag tape where everything was in memory. SSD could eventually be regarded as an extension of memory space.",
"It seems as though people are already experimenting on what... | [
"It's been possible for a long time to use normal pointers when writing to files. Using mmap you can map a file to a memory area and write to it using pointers.",
"\n",
"https://en.wikipedia.org/wiki/Mmap",
" ",
"There will most likely be something like a file system in the future also. Sharing files betwe... |
[
"Is there a physical limit on how big a kite could be?"
] | [
false
] | Would the mass of the kite eventually be unable to be supported by the wind? | [
"The biggest kites I have heard of are used for pulling cargo ships. If the ship is sailing with the wind they can release a kite that is attached to the bow and It helps pull the ship along and get better gas mileage. Google \"Kites pulling ships\" or just check out some of thes pictures and Diagrams.",
"http:... | [
"definition of a kite",
"This reminds me of an apocryphal story about a paper-plane competition: the winner balled up their paper and threw it."
] | [
"Would the mass of the kite eventually be unable to be supported by the wind?",
"No, not really. Theoretically floating structures can be built of almost ANY SIZE. For example Buckminster Fuller proposed floating spherical cities. ",
" with thousands of people living in them a mile or two wide which would float... |
[
"Were there any mp2 files, what about an mp5? Where does the 3 and 4 come from?"
] | [
false
] | null | [
"MP2 is MPEG1 Audio Layer 2. The others are:",
"MP1: MPEG1 Audio Layer 1",
"MP3: MPEG1 Audio Layer 3",
"MPEG refers to the Moving Picture Experts Group that developed the various video compression standards in use. Today the most common is probably MPEG4, although there are others in common use as well, like ... | [
"To go one further, mp1 is a simplified version of mp2 (computationally more efficient, lower fidelity), and mp3 shares the core psychoacoustic trick to reduce bitrate as mp2 but with higher precision, followed by a second lossy coding trick based on pure mathematics, and the lossy signal is finally compressed usin... | [
"A ",
"container format",
", most commonly used to store audio, video, and certain sorts of metadata like subtitles, EXIF tags, still images, etc. It's part of the ",
"MPEG-4",
" specifications.",
"An audio coding format for digital audio, which uses a form of lossy compression. It was defined by the MPEG... |
[
"Is there a genetic upper limit for size? For example, can we selectively breed largeness in dogs to get them to the size of bear?"
] | [
false
] | null | [
"An organism's size is determined by its growth rate, the rate at which certain structures like growth plates ossify & fuse, and the ability of its body to handle the biomechanical and nutritional stresses of a larger size. Really large animals need much stronger hearts to deal with the increased circulation requi... | [
"Chickens are bred to be extremely large aren't they? To the point where they can barely even support their own weight."
] | [
"It's not exactly a genetic limit in a hard sense, but dogs can't be bear sized, because their various organs and nits are meant to be a certain size. Above a point, pumping blood becomes difficult without the sort of adaptations and changes you would find in other animals of a comparitive size.",
"You can see ... |
[
"How is autism diagnosed in adults? Is it being overdiagnosed?"
] | [
false
] | null | [
"The two main reasons that an adult may be diagnosed is that they've had difficulties that have not been identified until that point, for example a person might have an intellectual disability diagnosis but then gets hospitalized as an adult and there is a thorough assessment where ASD is diagnosed.",
"OR the per... | [
"Autism is now often diagnosed in childhood but there is greater awareness now than there was decades ago. \nAutism is a spectrum disorder - some kids are diagnosed very young, some are not diagnosed until much later.\nIt is not unusual for a child to be diagnosed and then for a parent to recognise the behaviour tr... | [
"Autism is diagnosed usually at a young age of about 1 year old. Symptoms include unusually antisocial behavior, and fits when one day is dissimilar to another, such as a daily routine being ruined. ASD doesn't usually present itself later in life."
] |
[
"Is infinity possible in the real world?"
] | [
false
] | I know the concept of infinity is useful in calculations, e.g. limits, but is there any sort of physical measurement or "meaningful calculation" that can yield infinity as a result? By meaningful calculation, I mean one that uses real data from real objects/particles , not a hypothetical spaceship. | [
"I know the concept of infinity is useful in calculations, e.g. limits, but is there any sort of physical measurement or \"meaningful calculation\" that can yield infinity as a result?",
"No by definition. Physical measurements can only suggest infinities, they cannot measure them. The reason is that measurements... | [
"If you have a particle at a point, how many paths can it possibly take to move to another specified point ? You'll find an infinite number of paths, but in practice its impossible to differentiate a lot of these paths because of the limitations of whatever measuring apparatus you use. If we had measuring apparati ... | [
"If the universe if finite (and I'm pretty sure that it is), than nothing that has finite size, mass, etc. can occur an infinite number of times or it would be larger than the universe.",
"You can make intangible things infinite (particle paths, etc.), but nothing physical, that I'm aware of, can be infinite."
] |
[
"Are there any colors that remain difficult to produce as dyes in modern times?"
] | [
false
] | In Medieval England, it seems that dark blue, purple, and red dyes were difficult to make because few sources produced the colors. Was that just because these sources didn't exist in England at the time, or are they just naturally difficult colors to produce? | [
"I’ve no clue about dyes, but you might find this interesting. ",
"The range of colours produced by any technology is the “gamut”. As I understand it, every tech we have has a gamut that is smaller than human vision, in that, no matter how much you paid for that monitor, there are colours it can not display. ",
... | [
"Thank you for the info!"
] | [
"Oh, wow. I didn't think anything like that still existed. Thanks for the info!"
] |
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