title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"As you get nearer to the center of the Earth, does gravity get stronger or weaker?"
] | [
false
] | This has bugged me for a while now. The reason that I can't figure it out is because on one hand, there is physically less mass below you to pull you down, but on the other, you are nearer to the central focus of the force. I've asked a few physics teachers, but they just shrugged. | [
"It most definitely gets weaker and if your physics teachers don't know this shame on them. Your comment \"central focus of the force\" is very incorrect and why you are having trouble figuring this out on your own. Gravity originates individually from every piece of matter in the planet. Pro figure out the force o... | [
"Yes and no. The shortcut calculation of using the center point does need a certain amount of uniform distribution. ",
"However no matter what once you are inside the sphere of the planet you have some matter \"behind\" you pulling you in the opposite direction. As you get closer to the center you will have more... | [
"Wouldn't the answer depend on the density difference of the matter at the core, the surface, and in-between?"
] |
[
"Just a quick physics problem"
] | [
false
] | I'm trying to get to grips with some basic mechanics and I encountered the following problem in a textbook. Sorry if it seems so trivial. A stone is thrown horizontally from a vertical cliff at a speed of 20 metres per second. The cliff is 30 metres above sea level and the stone hits the sea after 2.5 seconds. How far from the base of the cliff is the stone when it hits the sea? Take g as 10 m/s I understand that it is best to treat horizontal (x) and vertical (y) motion separately. Since it is distance I want to find, I'm looking to calculate the area under the velocity-time graph of x, which should be a simple line with negative gradient, v=20 at t=0 and u=0 at t=2.5. 20*2.5 = 50, 50/2 = 25m. I'm not sure what I've done wrong: the book produces an answer of 50m. | [
"50 metres.",
"20m/s thrown speed, it takes 2.5 seconds to fall. 20*2.5=50",
"The other information is irrelevant."
] | [
"In typical projectile motion questions, you make an assumption that air resistance is negligible. This reasoning is why you assume the horizontal acceleration is 0 whereas the vertical is the familiar g.",
"You are correct in understanding that the motion along the x is independent of motion along the y. They ... | [
"s = ut +1/2at",
"I take it you are using the equation above with a=0, reducing it to s=ut. Why is a=0? Won't air resistance will cause deceleration in the horizontal direction?"
] |
[
"Can an object that is on fire set another object on fire if the second object has a higher combustion point than the first?"
] | [
false
] | If this is a dumb question or doesn't belong here please excuse my ignorance. As I understand it wood has a ignition point of around 150 degrees. Does that mean the fire itself is burning at 150 and therefore could only light something with a similar ignition point? | [
"The ignition point is how hot it gets before it catches fire. The energy density tells you how much energy it produces, which you could use to figure out how hot it would burn. If objects could only set fire to things with lower ignition points, then you'd only burn the part of the wood that has a lower ignition p... | [
"Thank you scientist!"
] | [
"A common method of lighting thermite involves lighting a magnesium ribbon with a butane lighter. The thermite then begins to burn from the magnesium ribbon, although you cannot light thermite using a butane torch directly."
] |
[
"I've always been told not to stand in front of a microwave when its on..."
] | [
false
] | I assumed it was because it emitted microwave radiation being spewed out of the microwave while it was being used, which would cause cancer or other mutations. I know DNA's absorption spectrum peaks in the UV range (260nm), so it is most prone to mutations then. However, I looked at the electromagnetic spectrum and noticed that microwave radiation has a larger wavelength (less energy) than UV radiation AND visible light. So my question to you, , is why should I not stand in front of a microwave if visible light has more energy than microwave radiation? Wouldn't visible light be more efficient at causing mutations than microwave radiation? EDIT: Thanks for your answers guys, can we focus on why microwaves seem to be more dangerous than visible light? (microwaves have less energy so shouldn't they be less dangerous?) | [
"There's no reason not to stand in front of the microwave. You'll notice a piece of metal with small holes in it in the window of your microwave, that's there to form a faraday cage around the microwave so that only a negligible amount of radiation leaks out."
] | [
"They key is understanding how light interacts with molecules so here is a rough scale.",
"Radio/MW (sub 1THz ish)- Primarily causes molecular rotations, interaction with nuclei with spins or electron spins, phonon modes and low energy vibrational modes of large molecules",
"IR(micron range light)- Molecular ... | [
"High power microwaves are indeed dangerous, and modified or faulty microwave ovens can cause serious injury. Microwave burns are pretty horrible, and (I am not a medical expert) I believe that microwave exposure can lead to cataracts.",
"Microwave ovens are carefully shielded for a good reason. At very least the... |
[
"How does time pass in a gravitational field."
] | [
false
] | null | [
"Inside a shell of mass, there is no gravity. You would have to be outside the sphere for these effects to occur."
] | [
"The combined effects of all that pulling when inside a uniform spherical shell would be no net force."
] | [
"The combined effects of all that pulling when inside a uniform spherical shell would be no net force."
] |
[
"Gamma function as a reliable (?) interpolation of the factorial (in relation to fractional calculus)"
] | [
false
] | Hello, I apologize in advance if I mess up some mathematical terms, English isn't my native language. I tried my best to look up the English equivalents of terms I'm about to use, but please do correct me if I made some mistakes. I'm not a mathematician by trade but I've always had a penchant for math and calculus (I had the more or less "standard" course of it in the university). I've recently stumbled onto an article about and it really interested me. While reading about it and calculating simple derivatives I came up with an interesting observation. Unfortunately there's no way to simply ask this question without showing how I came to it, so please bear with me for the next few paragraphs. Suppose we want to test that the 0.5th derivative of the 0.5th derivative of a function will give us the same result as the 1st derivative of the same function (that is, f0.5(f0.5(x)) = f1(x)). This statement makes sense since the powers of derivatives add up when we perform them one after another. For example, 2nd der. of the 3rd der. is the 5th der., etc. Using the fairly obvious idea from , we attempt to calculate the 0.5th derivative of . See image below: If we don't know anything about the , we have a problem here: this result has a factor of , which is not, to the best of our knowledge, a meaningful number. But we can decide to continue with our calculation. We can simply leave this factor in this original form ( of sorts) and see where it gets us. And so, we continue by calculating the 0.5th derivative of this result. See image below: The original idea that the property of the powers of the derivatives to add up is preserved with fractional derivatives stands true. Indeed, we got the result (= 1) which is the same as the result of the direct calculation of the 1st derivative. But what's more important is that the "bad", "unknown" number (the factorial of 0.5) and we got ourselves a result which is a number. I've tried to do the same thing with other fractional powers of the derivatives (calculating the 1/3rd der. 3 times in a row, calculating the 1/4th der. 4 times in a row) and it works successfully every time. I'm sure there is a simple enough proof that it works for all such cases but honestly I haven't bothered. The problem that is left is to find out the "real" value of the factorial of 0.5. Here one might argue that , since it "disappears" in the process of calculating the 0.5th der. two times. What I mean here is that we can imagine the factorial of 0.5 to be 432, 100500, 0.234 or any other arbitrary number - . Two 0.5th derivatives in a row would still give the correct result. But since we want to know the numerical value of the first calculation ("square root of x times ?"), we have found a way of calculating the factorial of 0.5 by introducing the . It "extends" the factorial function onto a set of real numbers; in particular, we can look up the value of Γ(0.5+1) ( ) and see that it's half of the square root of π. As a result, the 0.5th derivative of f(x) = x is approximately 1.129*sqrt(x). (which, unfortunately, I haven't found a way to express without showing you my thought process above). As shown above, - be it 1.772, 250 or -28 - the fundamental property of the derivative powers to add up would still hold true. If (hypothetically!) the process of calculating the 0.5th derivative two times in a row would give us something like this as a result (just as an example): ... then we would have something to work on. We would know that 0.5!/1.5! equals 1 (the real numerical value of the 1st der. of x), and from this proportion, we would derive some equations to find the numerical value of . But since all such "questionable" numbers disappear from the equations as soon as we get to an integer power of the derivative, . So, once again, this is the question that confuses me: why have we chosen to use Gamma function to calculate factorials of non-integers? Even the Wiki article on the factorial states ( ) that there are other ways to interpolate integer factorial values. And is there a way to know "for sure" which of these numerical results would be the actual correct one? The whole thing with "bad" numbers disappearing from the equations during the final act reminds me of cubic equations and how complex numbers can pop up and go away when you use the . Even if we know nothing about the numerical values of complex numbers, we can simply treat them as some constants and then they will simply go away in the end. However, we do have a way of calculating the numerical values of complex numbers from other mathematical fields. Here, however, it seems that , because . Is it true? We seemingly have no way of "testing" the values of the Gamma function for being proper representations of the factorials of non-integers, yet we use these values in fractional calculus. Why do we use Gamma function and not some other arbitrary function that happens to be equal to N! for integer N's? | [
"I don't 100% know the answer to your question, but I thought this huge post deserves an answer after 12 hours, so I will type one.",
"Speaking as a mathematician, the gamma function is essentially ",
" canonical generalization of the factorial function to reals. As you say, it's not unique, nor can it be (inte... | [
"The gamma function is the unique function that extends factorial that have this property for non-integers.",
"This isn't true. You can choose the values of ",
"(",
") arbitrarily for 0 < ",
" < 1 (of course, ",
"(",
") = 1), and the functional equation ",
"(",
"+1) = ",
"(",
") should determine... | [
"Wow, this is an incredibly elegant demonstration (and I suppose it's easy to generalize it for the 1st derivative of x to the power of anything, not just 0.5). Thank you!"
] |
[
"If a single radioactive Uranium atom was to pass through my digestive system, would any real damage be done?"
] | [
false
] | null | [
"One atom just isn't enough to do anything. A single banana is much more radioactive. In terms of toxicity allowances, they are on the order of micrograms per cubic meter in the air, which is much much much more than a single atom."
] | [
"By the way, your body actually has quite a few uranium atoms in it, naturally.",
"From ",
"http://hps.org/publicinformation/ate/q3414.html",
":",
"\"The average person ingests about 2 µg (around 1/15,000 of an ounce) of uranium in food and water every day, but only a very small fraction—on the order of one... | [
"I'd like to have a little more then just \"No.\" if all possible "
] |
[
"If quantum entanglement can't be used to transmit information, then how is this experiment (see description for link) possible?"
] | [
false
] | Been catching up on some reading, came across here. I've been told over and over again that entanglement can't be used to transmit information. So how the heck does this work? Aren't they extracting or inferring information about one photon's path from its entangled twin's behavior -- the exact sort of thing I've been told isn't possible? | [
"if you have an entangled pair, you cannot transmit information from one to the other without either having them interact again, or by sending a bit of classical information along.",
"In this case, the red light that passes through the image does interact with the yellow readout light through its interactions in ... | [
"Quantum entanglement can't be used to transmit information faster ",
", but you can still do all sorts of things with it.\nThere isn't anything in the article implying that they transmitted information faster."
] | [
"the two modes",
"The two modes, in this case, meaning the two entangled photons? Okay... so you're saying it's not just spooky interaction at a distance. The two photons interact with one another both before and after one half of the pair hits the object being imaged. Somehow, this results in information about t... |
[
"Is it possible to add enough salt (or other solute) to water such that it is still an aqueous solution, but dense enough for a man to walk on?"
] | [
false
] | Pretty much the title. If you added too much solute, you'd be walking on a wet, mucky solid I would think. Is it possible to add so much solute that the aqueous solution is still liquid but dense enough to support a grown man (say 150 pounds over a surface area of 1ft | [
"Corn starch is suspended in water, it does not dissolve and would not be a solution. "
] | [
"Corn starch, but only if you run. A supersaturated solution will become solid under sudden stress, but remain liquid otherwise."
] | [
"Ah, cool. That would be so much fun to do. Is that an example of a non-newtonian fluid??"
] |
[
"Could electromagnetic radiation of a certain frequency be viewed as some base frequency photon being time dialated proportionally to its energy?"
] | [
false
] | If this is the case, does this perspective offer any interesting insights? If not, why so? Where in the mathematics does this idea break down? | [
"Time dilation is a really specific effect which requires either relative motion of emitters and observers or gravitational effects. Considering that photons are massless, there's not really a place to naturally decide on a \"base frequency,\" i.e you can always redshift or blueshift a photon more. You can decide o... | [
"This doesn't offer a very useful perspective, because the frequency of electromagnetic radiation is frame-dependent (special theory of relativity) and so we can't point to a photon and say that it has an objective energy/frequency; it only has an energy/frequency relative to a given reference frame. In other words... | [
"No, because photons do not have a rest frame; they travel at the speed of light. If you plug in the speed of light to the time dilation formula, you will see that you get an infinity. For this reason sometimes people say (somewhat sloppily) that photons are \"frozen in time.\""
] |
[
"I can't believe I'm asking this...but, why do men have nipples."
] | [
false
] | Just so you know, I honestly complemented making a throwaway for this question. So me and my friends have been smashing our brains together for an answer. It is just a vestigial structure? Does it even have a purpose? And if we evolved from a common ancestor did the male half of speices have nipples? WHY did they have them if they didn't need them anyways? So... | [
"The Queen's English is no more correct than American English. Your previous spelling was perfectly acceptable."
] | [
"Because women have them.",
"All foetuses start off female. "
] | [
"Basic answer would be that there is no evolutionary advantage to lose them. I'll leave it to the biologists to give a more in depth answer."
] |
[
"Why is the weather hot?"
] | [
false
] | What's the driving force behind heat waves? How can there be sustained hot air that isn't driven away by cooler air? Why am I sweating so much? | [
"During the local summer, whatever hemisphere you're in is tilted toward the sun, so the sun is in the sky longer, and the sun's light strikes the Earth at closer to a perpendicular angle. So the land and air around you get hotter than they do in the local winter."
] | [
"That's just weather. You can think of the atmosphere as being like cotton balls being pushed around on a tabletop. Some of the cotton balls represent masses of relatively warmer air, while others represent masses of relatively cooler air. When a mass of relatively warmer air moves over where you are, the average t... | [
"Heat waves are local phenomena caused by unusual weather conditions. There is differential heating of the ground even at the same latitude because of various things like topography, vegetation (or the lack of it), urban centers, presence or absence of bodies of water, etc. Differential heating simply means that so... |
[
"Does covering up the toilet seat with paper reduce contact with diseases/bacteria?"
] | [
false
] | Or have I been wasting 20 years of toilet paper? What about wiping the seat? Or should you just squat over it? So many questions | [
"In terms of disease, the pathogenic microbiota of a toilet seat, unless you are immunocompromised, is of no significant health risk--barring something foreign/sharp. Your skin is an excellent barrier to microorganisms. The reason we wash our hands is because we end up touching a lot of places that are not excellen... | [
"To add onto this post, the toilet seats themselves are relatively clean in respect to most other items in a bathroom. Provided that the toilet passes the sight test (no ones sprayed the seat with their feces and/or the toilet appears to be cleaned regularly). ",
"As ",
"/u/svenser",
" mentioned, flushing wi... | [
"One spends time washing and cleaning hands only for it all to be for naught because of people who don't clean their hands leave behind their bacteria on the handles for others to pick up.",
"Those people also touch other doorknobs, elevator buttons, the coffee maker, railings, and other people's hands. It seems ... |
[
"Why does failing to fully drain a laptop battery \"condition\" it to having a smaller lifespan?"
] | [
false
] | null | [
"Are you sure you're not confusing lithium ion (laptop) batteries with nickel metal hydride or nickel-cadmium batteries? Voltage depression (sometimes erroneously called a memory effect) from partial depletion is not really a concern with lithium ion batteries, though it was with NiMH and ",
" NiCd batteries. Dra... | [
"What? No, full discharge and charge cycles cause a smaller lifespan. ",
"A shorter lifespan is due to the volume change of the cathode material during charge and discharge cycles causing microstructure fracture. A standard laptop battery can only do about 300 cycles. The more complete cycles you perform, the fas... | [
"The batteries don't benefit, but Apple does when you need to buy a new battery earlier than you otherwise would've. The user gets slightly more battery life per charge due to more accurate sensor reading, but the long term lifetime of the battery is less."
] |
[
"Why doesn't a device work if the batteries are inserted in reverse?"
] | [
false
] | I have with a battery that doesn't indicate polarity. I accidentally put it back in backwards after taking it out to remove the circuit-breaking plastic tab inserted between the contacts that it shipped with. Perhaps unsurprisingly, it didn't work properly. So, what is it about batteries (or, perhaps, electronic devices) that requires current to run in a particular direction? Why isn't the simple fact that electrons are moving through the circuit enough? | [
"This is not really a chemistry question, it is an electronics question. I'll answer for modern semiconductor electronics, but similar comments apply to older stuff as well.",
"Semiconductors come in various types but the easiest to explain are bipolar devices. The most basic bipolar device is a diode, and the na... | [
"If it's a simple device like a single resistor (incandescent light bulb), the circuit will work properly whether \"pointing\" forwards or backwards. But most devices have components like diodes which only work properly if the current is flowing a certain way. A diode is like a one-way valve for current, so if you... | [
"All makes sense, but I guess then it's a deeper question about why it's important that current flows in a particular direction. In the case of a semiconductor/processor I could see that it might be important for one logical operation to occur ahead of another, so that the second operation can react to the output o... |
[
"Is it possible to do blood tests using FTIR spectrometer?"
] | [
false
] | Hey guys, Im kind of lost and confused so i recently acquired a FTIR spectroscope and UV vis spectrometer as well. Basically im testing the water in my area daily. I was wondering what tests i could run on blood samples with these devices? | [
"I don’t think you could get much (if any) usable data from FTIR. The huge water peak at ~3500 would obscure a big part of the spectrum. Also, if there were anything besides water that the FT could pick up they would probably overlap and make the spectrum really hard to interpret. ",
"FTIR is definitely not a goo... | [
"Not really, at least id imagine raw blood wouldnt work. someone else mentioned how the water peak would be massive but even then theres enough junk in the blood that itneoild be kinda hard to differentiate. Even just small metabolites youll find over 100 of them in the blood and unless youre filtering things youll... | [
"You can get some useful info- I believe Bruker makes a specialized FTIR for aqueous protein analysis. There are some other methods available utilizing other FTIR techniques such as ATR-FTIR.",
"There are all sorts of methods for analyzing blood for specific proteins."
] |
[
"How does the Genetic Maternal Effect differ from Cytoplasmic Inheritance?"
] | [
false
] | And how do they differ from Genomic Imprinting? Edit: Thanks for clearing that up for me guys! Great responses! | [
"The Maternal Effect is when a zygote recieves mRNA, proteins and other molecules from the mother's eggs. These are gene products but not actual genes. Nevertheless, since this occurs right at the start of development it can have long lasting consequences.",
"Cytoplamic inheritance refers to the offspring recievi... | [
"To build on this, these maternally-sourced gene products (mRNA etc.) can enact an effect on the phenotype of the offspring, through epigenetic modification, and thus produce a phenotype that might seem to ignore the underlying genotype (as described below)"
] | [
"The genetic maternal effect refers to a case where an offspring inherits the maternal trait regardless of its own genes. So say you have a pink father (p) and a white mother (w). The offspring can inherit either the p gene from their father or w gene from their mother, but offspring with either the p gene or the ... |
[
"What is the most basic form of life that still displays sleep-like behavior?"
] | [
false
] | null | [
"It seems to be the tiny roundworm C. elegans, not coincidentally one of the most intensely studied basic forms of life. It does something sleep-like called lethargus before each time it molts. This tends to suggest that sleep goes way back in our evolutionary history, for whatever reason."
] | [
"Animals are basically all evolutionary traits. You'd be hard pressed to find something that wasn't."
] | [
"Wow never even occurred to me (maybe most people for the matter) that sleep was an evolutionary trait. Makes me wonder if there are animals that never need sleep."
] |
[
"Why does our taste for different foods change as we age, and is there any evolutionary reason why this happens?"
] | [
false
] | null | [
"For the specific case of children tending to become more picky as they grow from a baby to a toddler, I've seen the argument made that this may be an evolutionary response to a child's new increased mobility. You wouldn't want a child starting to walk around eating anything and everything he can find. (I'm dubio... | [
"Well, underneath the post title (with 'comments', 'share', etc.) there is a 'save' option.",
"Click this.",
"When you want to view it later, go to the 'saved' tab on the Reddit main page (next to 'what's hot' and 'top')."
] | [
"Toddlers do put stuff in their mouths, but they just spit it out if they don't like it."
] |
[
"Is there evidence for historic droughts affecting the Mesopotamian area/Euphrates-Tigris Rivers?"
] | [
false
] | Hello all! I read a paper in Nature about the 4.2 kya event in the Mesopotamian region and how scientists think a possible mega-drought contributed to the crises among several empires . I was wondering if there is other scientific evidence for droughts in the Euphrates-Tigris Rivers over the last 3000 years. I know there is a drought currently in the area, but have drought events occurred before? Any peer-review articles or evidence you all know of? Thank you! | [
"This factsheet",
" cites some geological papers that support a drought in that period. Also, some theories point to a drought contributing to the late bronze age collapse (around 1200 BC), which also hit in that region. ",
"Here's a paper",
" addressing it, and I am sure there will be more on that period."
] | [
"There is a pretty extensive literature (which is not exactly hard to find) of climatic variability, drought, and influences of these on various societies in the Middle East / SW Asia at both long (e.g., ",
"Kaniewski et al., 2012",
", ",
"Xoplaki et al., 2016",
", ",
"Flohr et al., 2017",
", ",
"Jone... | [
"Historically,\nWhen the roman empire and the Sasanian Empire went to war against eachother, they would always try to battle during periods of drought, in other to out manoeuvre eachother. The rivers stood as official boundaries between both empires, so anytine there was extended droughts one or the other usually t... |
[
"Why don't I get a shock if I touch a railway track?"
] | [
false
] | I wanted to know how an electric locomotive runs since the pantograph only touches one wire. After some googling I found out that the return current is carried by the tracks themselves. So shouldn't I die of a 250kV shock if I touch the track? | [
"If the rail is Earth grounded, you are at the same potential as the rail. The potential difference between the wire and the rail may be 250 kV but the rail is at 0 V."
] | [
"As ",
"/u/scratchx",
" wrote, the rails are grounded, so the potential between you and the rail should be very close to 0 volts.",
"Also, no rail road in the world uses 250 kV, 25 kV is the highest standardized voltage. "
] | [
"There are a few rails on the line. ",
"Usually you have 2 guide rails and the 3rd one that carries the electricity (on the London Underground anyways) is called the ",
"Third Rail.",
"If you touch this you will be dead in microseconds."
] |
[
"Do all human beings share a common ancestor?"
] | [
false
] | null | [
"All living things on Earth share a common ancestor.",
"The last common ancestor to all life on Earth (",
"LUCA",
") lived ~3.5 billion years ago.",
"It's unknown when the most recent common ancestor of all humans today lived. Estimates are in the thousands of years. ",
"Wikipedia has an overview of studi... | [
"All humans on this earth share a common ancestor not only with every other form of life on earth, with our closest living relatives, and also with each another more recently in time. The last common ancestor (LCA) between modern humans and chimpanzees is thought to be a species existing prior to the emergence of "... | [
"Thank you for your reply. I meant whether all humans alive today share a single human as an ancestor, though."
] |
[
"If we found a mirror in space, pointed at Earth and 100 lightyears away, could we see what happened on Earth 100 years ago?"
] | [
false
] | Since it would take the light time to reach us, wouldn't a very reflective surface (like a mirror) that was facing Earth and was far away actually show us Earth's past? Also, would one that was 100 lightyears away show us 100 years ago, or 200 years ago (since the light has to first get to the mirror, then back to us)? | [
"It would be 200 years ago since the light has to travel twice the distance."
] | [
"AsaChemicalEngineer is correct, 200 years, but its worth noting that since the earth is only reflecting light, not radiating it (visibly), we aren't very bright, so even if such a mirror was miraculously in place, we wouldn't be able to see much."
] | [
"Not to mention the fact that a telescope would have to have a truly insane spatial resolution to show us anything useful or interesting."
] |
[
"What would happen to a nuclear power plant if it were to be hit by an EMP?"
] | [
false
] | null | [
"The first thing is the variances in electrical power would cause an rps (reactor protection system) actuation. The system is a fail safe system, and loss or interruption of electrical power causes the scram to happen. You would lose all offsite power. The steam driven cooling pumps would start. The electrical disr... | [
"Existing plants have EDGs with governors which can operate either through a control system or just a mechanical component. Some EDGs only have mechanical governors. Additionally all plants have a steam driven cooling system which can run in blackout conditions if necessary.",
"In new designs, it is required to h... | [
"The ECCS pumps and the DGs are disconnected from the grid and have no electricity in them when they are offline. They are dumb systems which have no controllers and are either on or off. It would unlikely that an emp affect any of those things. ",
"Additionally see: ",
"http://www.reddit.com/r/askscience/comme... |
[
"Why does canned air get really cold when I hold it upside down and spray it?"
] | [
false
] | I mean the type used to clean dust out of electronics. If you hold it upside and spray it it gets very cold. Also, most contents under pressure such as hairspray, cleaners, air fresheners and the like seem to feel colder after I pick them up and shake them. I assume the reasons are the same. PS don't actually test this indoors. The irritant they add to the stuff is strong and lingers for a half hour. | [
"Canned air isn't actually ",
". It's a mixture of nitrogen and other gases. When compressed into the can this mixture takes fluid form. Since some of the gases are heavier than air, when turned upside down the can will spray out the liquid mixture before it has had time to mix with the lighter gases. *When breat... | [
"When liquids evaporate, they ",
" heat."
] | [
"PV=nRT (P=pressure, V=volume, n=number of moles of stuff, R=gas constant, T=temp in Kelvin)",
"When you spray stuff out of an aerosol can the pressure on the gas is dropping VERY drastically as it escapes form the highly pressured can into the atmosphere. In order for the gas law listed above to work, the tempe... |
[
"How do animals with eyes on either side of their head see?"
] | [
false
] | Do they have the ability to alternate which eye they use at a certain time? Or instead, is the image that their brain receives a combination of visual input of both eyes? | [
"Hunters = forward facing eyes = stereo vision = depth perception = prey in tummy ",
"Prey = eyes on side of head = panoramic 2D vision = see hunters = stay out of tummies "
] | [
"Put the palm of your hand on the bridge of your nose, blocking out your central field of view. You now are viewing the world in a similar manner to an animal with a low binocular overlap. What is it like? You have no problem imaging the world as continuous, and you do not see the world as two completely separate ... | [
"Although your eyes are pointing forward, you get a very very wide viewing angle, almost 90 degrees either way. Animals with there eyes on the side have this ability too and therefore likely get a much more panoramic view of their full surrounding. "
] |
[
"Is there any correlation between LTR and RTL languages and the dominate handedness of that language's creator or culture?"
] | [
false
] | [deleted] | [
"Asian countries have the lowest percentage of left handedness of any developed country (2 to 5%, compared to on average 12% in western civilizations.) This would appear to belie reading preference and handedness. The negative corollary would appear to be significant, except the general consensus seems to be that... | [
"Asian writing (i.e. Japanese, Chinese, and Korean) isn't truly RTL in the same way as Arabic or Hebrew though. It's top-to-bottom right-to-left in the traditional format - single lines written RTL can be thought of as multiple one-character columns of vertical writing.",
"http://www.jstor.org/pss/620771",
"The... | [
"Korean isn't RTL at all. Even in vertical writing each syllable is read left to right, and top to bottom. 닭 is an interesting example to use. It's the word for chicken, pronounced 'dalk' with a silent 'l'. \nㄷ - d, \nㅏ - a, \nㄹ - r/l, \nㄱ - g/k"
] |
[
"If motion is all relative to perspective, why would a rotating spacecraft (in space) simulate gravity."
] | [
false
] | I have a basic grasp of physics and understand centripetal force, but at some point all motion would be identical. Why would continued movement along a set path "simulate" gravity? | [
"Uniform motion and freefall are all equivalent. Acceleration and rotation are not."
] | [
"If you (the OP) would like to know more about this, read about ",
"Fictitious Forces",
". I learned them as apparent forces, but as the first sentence in the link above points out there are many synonyms to the term.",
"Since the definitions of ",
"inertial",
" and ",
"non-inertial",
" reference fra... | [
"What's actually occurring in the rotating spacecraft question is a great example of Newton's first law of motion! Any object in motion wants to remain in motion unless acted on by an outside force. In this case, a mass wants to move in a straight line, however the wheel is the outside force acting on the object. "... |
[
"Would glass from the Manhattan Project still be radioactive?"
] | [
false
] | So I recently visited a rock shop that had all sorts of glass, rocks, and minerals from various places. The prize possession of the owner was a chunk of thick yellow glass, maybe a foot tall and at least 6 inches thick. He said that this was glass that was used to view the testing of the bombs for the Manhattan Project, he had gotten a hold of it when someone was trying to dispose of it. If this guy is actually telling the truth, how much danger of radiation would someone be in if they visited the shop or the shop owner himself? | [
"Everything is radioactive naturally. A few thousand atoms decay in your body every second - mainly from potassium which is naturally a bit radioactive. A nuclear explosion nearby can increase the activity, but based on your description it is impossible to estimate by how much, apart from \"probably not relevant\".... | [
"The wikipedia on Trinitite (",
"https://en.wikipedia.org/wiki/Trinitite",
") mentions that it is slightly radioactive, but safe to handle. Would it be too radioactive to wear as jewelry (or something else that is in constant contact with your skin)? It doesn't specify how radioactive or how much handling. "
] | [
"If I get the conversion right, wearing ",
"these pieces",
" 24/7 would give you a radiation dose of about 10% the natural radiation dose for body tissue directly next to it, and negligible dose elsewhere. Compare this to living in Denver with much more than twice the sea-level radiation dose due to more cosmic... |
[
"Do animals abuse drugs?"
] | [
false
] | It is known that animals get drunk from over-ripe fruit. What about other natural high makers like shrooms, opium or coffee? | [
"Rats locked in small boring cages will self-medicate their depression with opiates if you offer it to them.",
"In a nice environment (enough space, privacy, companionship, good food, toys) they apparently won't.",
"Not sure if that counts as abusing drugs, or using them correctly.",
"http://sciencethatmatter... | [
"Catnip",
" is what first came to mind."
] | [
"we could think of abuse as of \"use without the purpose of nutrition but to get high\"",
"Does my consumption of McDonald's constitute food abuse because I eat it for the taste and not the nutrition, or does the presence of any nutritional value whatsoever invalidate the idea of \"food abuse\"?"
] |
[
"I am interviewing a cosmonaut next week. I need your help coming up with some questions."
] | [
false
] | Next week I will be interviewing and I want to ask him some of the top voted questions. Aleksandr Lazutkin is a Russian cosmonaut who was awarded the Hero of the Russian Federation for bravery and heroism after he was on Mir when a supply ship collided with the station and as the on-board engineer help fixed an air leak and saved the lives of his crew. Currently he is the assistant director to Russian Cosmonaut Museum. Ask away, I have some of my own questions but I need Reddit's help. I will conduct the interview in Russian so I will post the translated transcripts next weekend. *Please note that is serious and I had to delete this post from AskReddit because people were posting really stupid questions | [
"I'd be curious to hear his opinion on the risks associated with space travel and exploration, especially in the context of recent discussions of having astronauts volunteer for one-way trips to Mars."
] | [
"Questions:",
"It's hard to imagine working at a museum compares with space flight and the preparation for space flight, how did you adjust to not having these huge goals and responsibilities? I can imagine that shifting into the \"regular\" world was quite a transition.",
"Did the excitement of being in space... | [
"How long did it take to become acclimated to microgravity? What was most difficult when adjusting to this difference?"
] |
[
"Could someone explain this hawking radiation problem to me?"
] | [
false
] | Ok so as far as I understand, hawking radiation occurs thanks to the fact that in a vacuum, there are virtual particles and antiparticles constantly popping into existence and annihilating one another. Sometimes these particles appear just in the border of a black hole's event horizon, and, as I get it, one particle is absorbed by the black hole, so the other one must borrow mass from the black hole to cease being "virtual" and to become "real". My question is, given the fact that the black hole has absorbed one of the particles, hasn't it gained mass? and isn't that mass the only thing the other particle needs to borrow to exist? if this is so, why does a black hole lose mass in this process? or do I simply not understand it? | [
"The virtual particle picture is a description of the calculation Hawking used, but is a very poor way to think about what is going on physically. (One way to see it's a poor way to think about it physically is what you describe here.) ",
"What is going on is that an initial state (the black hole) evolves into a... | [
"virtual particles appear in the vacuum of space and normally annihilate each other. at or very near the surface of a black hole one of the virtual particles can \"fall in\" the other particle cant annihilate thus the fallen particle, necessarily has a negative energy/mass, makes the black hole smaller, and the oth... | [
"why is it necessary that the fallen particle has a negative energy/mass? (thanks for the answer!)"
] |
[
"Feeding People Like Pets"
] | [
false
] | We seem to know a lot about what to feed pets because they get fed nearly the same meal every day for life and do quite well. So if vets can figure this out for animals, has anyone applied similar research for people? Is there a healthy set of meals that one can eat for their entire adult life? I've seen lots of reasons why optimal can't be done but surely we can come up something reasonably good, especially if we focus on the non-picky eaters. After all pets are good evidence that it can be done for many mammals, and birds. | [
"http://www.zupreem.com/our-food/primates/primate-diet-dry",
"They discourage people from buying this for personal use, though."
] | [
"This guy tried living off monkey chow for a week, there's a video a day of his progress:",
"http://www.angryman.ca/monkey.html"
] | [
"The answer is that yes, this is technically possible, but nobody wants to be the one to propose sucking all the joy out of life as a research project or health initiative."
] |
[
"What is the highest altitude we have ever found living organisms?"
] | [
false
] | [deleted] | [
"238 900 miles or 384 400 kilometers is the highest altitude we have ever found living organisms at. Its the distance to the Moon... Yes, I'm taking about humans.",
"All jokes aside, it depends on what exactly you want to know. Highest altitude non-human organism to be ",
" is the GRIFFON VULTURE who reached 37... | [
"Apollo 12 found bacteria living on Surveyor 3 on the moon a few years after the probe had landed."
] | [
"It was a dormant colony, and it is still controversial if it actually survived on the moon or was introduced during transit or during analysis back on earth."
] |
[
"How do worker bees evolve if they aren't the ones reproducing?"
] | [
false
] | Just curious--how do worker bees develop positive adaptations for their survival when the drones are the ones that reproduce, and have a significantly different environment and life than a worker bee? | [
"This is interesting...",
"Since the reproducing bees don'thave the life the worker bees do, the evolutionary pressue is a different one.",
"Well I guess if the workers get a beneficial trait just by chance, the whole colony would prosper. The other way around, if the worker bees get a worse trait for their evo... | [
"It's no more or less indirect than any other mutation on non-germ line cells in other organisms. A mutation that leads to the production of melanin in skin, for example, doesn't affect any of the reproductive cells - but we still treat it as fairly normal. That mutation affects the ",
", not the individual cells... | [
"The most important thing to remember is that in any living system, it isn't ",
" the individual which is under selection pressure, it is the genes themselves. It's therefore useful to think of how genes are passed along in bees.",
"Whilst not literally true, it might be a helpful analogy to think of the entire... |
[
"When We Feel Pain Why Do We \"Hold\" The Area Inflicted?"
] | [
false
] | Didn't know how to word the question so I'll try to elaborate here. If you stub your toe our reaction is to grab and hold our toe. If someone punches your arm the reaction is to grab your arm. If someone kicks a man in the balls he automatically puts his hands there and holds them. Is this some sort of instinctual act? Does doing that physically relieve pain? What are the reasons for doing this, whether instinctual, biological, physical, etc? | [
"http://bodyinmind.org/reducing-pain-through-touch/",
" -with references"
] | [
"Right, that's what I'm saying. It's what I do almost automatically but I can't feel a tangible difference in pain that I feel. There has to be an explanation for why we do it."
] | [
"Right, that's what I'm saying. It's what I do almost automatically but I can't feel a tangible difference in pain that I feel. There has to be an explanation for why we do it."
] |
[
"How is the success chance of Surgery calculated?"
] | [
false
] | null | [
"Its based on past experience, the success rate of any medical procedure is all about averages. \nPeople do studies and retrospective analyses on surgeries and break down things like survival rates, success rates post operatively and at different time points, and complications that may develop. \nFurther statistics... | [
"More specifically, studies measure technical success (did the procedure work? i.e. did we get the appendix out), morbidity (complications), mortality (deaths), as well as various survival data. Survival data can be short term (30 days, etc), long term (5 years, etc). Survival data in cancer can also be measured in... | [
"There is quite a lot of debate at the moment, at least in the UK, regarding how performance data should be presented.",
"There is a call for more data to be made available and surgeons are now expected to give success/failure rates that are specific to them where possible rather than just quoting general data fr... |
[
"Considering a lot of deep space images are 'coloured in' what are the actual colours of the images released by NASA etc.?"
] | [
false
] | null | [
"It's not so much that they're just colored in as it is that different frequencies of non-visible light are given corresponding frequencies of visible light so that the image can be displayed visually. The pictures themselves are technically accurate, they're just from a viewpoint that humans don't typically have.... | [
"Not necessarily. Have you heard of the Hubble pallet? Essentially, for many Hubble images, certain wavelengths are assigned to be different colors, separately from how they appear to our eyes. For example, helium and hydrogen both primarily emit red light when excited in the way that they are in most nebula. Becau... | [
"Well, that depends entirely upon the colour of the galaxy in question. But, by and large, you wouldn't see galaxies as much more than a pale smudge, as human eyes aren't very sensitive. There are many galaxies that have the same size in the the night sky as the full moon; however, we generally can't see them, as o... |
[
"What is it about metal that prevents it from getting \"soggy\" like fabric or sand, when in contact with water."
] | [
false
] | Just curious why, even a porous metal, won't get heavier, or retain ANY of the water when soaked. | [
"Metals form into crystals, or usually many crystalline ",
"grains",
". The atoms are tightly packed and there usually isn't any space for something as big as a water molecule to penetrate it. (The same is true of sand particles....they are impervious to water.) And metals don't generally form into a porous ma... | [
"Think of the 3d shape of a quantity of sand or fabric, lots of space available for the water to get into and be attracted to as it is a polar molecule. In the sand's case I would guess that the attractions between fellow water molecules and the sand itself keep it together. ",
"Now atoms in a metal are ordered i... | [
"Metal as porous as fabric or sand - it would have to be actual metal fabric, or metal \"sand\" (metal filings). Try with something like that first.",
"If it merely seems porous, but it's an actual chunk of metal, it's nowhere near as porous as the materials mentioned above."
] |
[
"What role does the Fat Content of food have in gaining or losing weight?"
] | [
false
] | I understand that eating High Calorie foods will cause you to gain weight if you don't burn off those consumed Calories, but I keep hearing ads for "Low Fat" or "No Fat" foods. Is this simply a marketing ploy, or does the Fat Content of food actually have an effect on Body Fat? | [
"It's not a marketing ploy in that the foods do actually have less/no fat in them, but you are correct in that Calories are the primary culprit. There is ongoing research to determine how what we eat effects our basal metabolic rate but but from what I know these effects are reasonably small."
] | [
"Fat is one of three macronutrients in food (ie. the nutrients your body requires in significant quantities) - the other two being protein and carbohydrates.",
"The widely accepted and promoted notion that fat in food equals fat on your body is one you should be very careful about accepting on face value. Most nu... | [
"It has some effect, but not too important. You will gain more fat eating 50 grams of sugars and not burning them than eating 20 grams of fat doing nothing. "
] |
[
"Is it possible to die of hypothermia in relatively warm water?"
] | [
false
] | Assuming you were to stay still in relatively warm water (lets say 80 degrese) could you die of hypothermia, since your body's heat would be dissapating into the cooler water? Or would your body not loose heat quicker than it could generate the same amount of heat? | [
"Damn, so given enough time, u could die of hypothermia in 90 degree water"
] | [
"Yes. It will take longer than if the water is near freezing, but it can happen. ",
"Fatal hypothermia occurs when your core temperature drops below ",
"95 degrees F"
] | [
"I think your body has enough internal friction to maintain a high enough temperature for survival in 90 degree water. I'm interested to know what the maximum temperature hypothermia could occur is, though. "
] |
[
"Facial expressions - surprise, fear, anger - nature or nurture?"
] | [
false
] | Is there something wired in our DNA that controls these facial expressions, or do we learn them by watching people as we develop? | [
"Dr. Paul Ekman",
" has published many articles regarding universal expressions and emotions.",
"The universality of the 6 basic emotions",
" suggest that there are some emotions that are expressed irregardless of environmental stimuli.",
"His writings suggest ",
"there are approx. 10,000 different possib... | [
"True, but context is critical. Ekman's research is based on showing pictures of actors assuming various facial expressions and asking the participants to describe the emotion exhibited in picture. This leads to quite a bit of wiggle as to the expression in question. ",
"For instance, it is more common to endo... | [
"Ekman controlled for this in his study with the Fore people. You can read his book. "
] |
[
"Would a attempt to land people on mars using today’s technology be more dangerous then the first moon landing ?"
] | [
false
] | [deleted] | [
"Today's technology, in terms of propulsion, offers little more than it did in the '1960s. Most of the \"advanced\" propulsion technologies, such as ion thrusters or plasma thrusters, would be useless for landing since they are low thrust. In order to land a big mass on high gravity (okay, higher than the Moon) wou... | [
"In fact, it's probably too much involved to use a single-vehicle lander like they did for Apollo, because that would have to be absolutely humongous. What I think would be much more sensible would be something like the mission profile in the ",
" novel, and no doubt also similar real life plans exist/existed. Yo... | [
"The propulsion concept is still similar, but we learned so much in all aspects of rocketry. In 1970 it was completely normal that 10% of the launches failed - crewed launches had a better ratio, but generally failures were very common. Safety standards have improved a lot everywhere. Today most launch failures are... |
[
"Can anybody explain the phenomena of a \"night rainbow\" to me? I just observed my first one. (details in text)"
] | [
false
] | is the weather report at the time of observation (includes moon phases, precipitation). The event occurred at about 11.30pm, Wednesday. I observed the rainbow for about three minutes before it disappeared. I'm calling it a rainbow, because it took on the same shape as the refracted light of a rainbow, the only difference being that what I observed was uniformly white and occurred just before midnight. I tried to take a photo, but I lack the photography skills and equipment to capture such a thing, so all I have is some black squares to show. I'm very curious to know what this is, as I'm usually very aware of the meteorological events that occur in my area, but I've never seen anything like this before. | [
"With the right conditions, a rainbow can occur at night as a result of refraction of moonlight. It seems monochrome, I guess because of the low light level. If the moon was out, and the bow was opposite of the moon, my guess would be that. I think it is called a moonbow."
] | [
"Neat article that discusses this a bit:\n",
"http://www.space.com/12319-moonbows-yosemite-full-moon-lunar-rainbows.html",
"Happening in that article from waterfall spray, but could certainly happen from rain. "
] | [
"Rainbows are formed by light refracting through and reflecting in rain droplets of the correct size and position with respect to the light source. The light enters the rain droplet and begins to spread out ",
"like shown here",
".",
"The light from the moon is similar to light directly from the sun. There ... |
[
"Is dopamine uptake lessened during higher temperatures/higher humidity?"
] | [
false
] | I'm a smoker and I've noticed that when it starts warming up for the summer I start smoking more cigarettes. I'd say I want to smoke about two or three times as much, and I'm wondering if this is a thing or I'm busy being an outlyer. | [
"To start with, you are not an outlier. People tend to smoke the least in February (in the Northern hemisphere) and the most in the summer. The current hypothesis is that people tend to smoke outside and that people hate going outside when it is cold. This trend has become more pronounced due to indoor smoking ban ... | [
"Don't think about it in terms of dopamine. ",
"It is true that there is a particular network of circuits in the brain that has something to do with seeking rewards, and that one specific part of that network of circuits involves dopamine.",
"However, dopamine is used for a dozen other things in the brain that ... | [
"Hey, sorry about replying almost a whole month later. ",
"In the diagram you sent there are four colors representing neurotransmitters, what does each color represent?",
"\nIs the entire reward system affected by heat? The other answer on this post indicated that dopamine uptake is more effective as temperatu... |
[
"When we tag animals so they can be tracked and counted, do the tags affect the way their peers relate to them? Does it affect their mating chances?"
] | [
false
] | We often hear about how birds will select mates based on their plumage and I can imagine other animals noticing differences in fur color, quality, etc. Don't large colorful tags and bands get noticed too? | [
"It really depends on the species. Those species that depend more heavily on smaller color features are more likely to be affected by bands. It's an important consideration in the design of bird tracking studies! Here's an interesting study on zebra finches that found a preference in female individuals for males wi... | [
"Right. If we change their behaviour in any way, then the data we get from the tagged animals might not be representative of the rest of the population, so it might tell us incorrect things."
] | [
"Ideally, though, scientists try to avoid influencing their mating chance, right?"
] |
[
"Physics/Static question: How can you tell which trig function to use when finding the coordinates of A here?"
] | [
false
] | I know that position A is (-10cos70sin30, 10cos70cos30, 10sin70) from looking at someone else's sheet. How do you figure out which trig function to use though? | [
"I think about projecting the line between the origin and A onto relevant planes/axes. If I project into the angle, use cosine. If I project away from the angle, use sine.",
"For example, to get the x-coordinate of A, I need to project into 70 and then away from 30. (It's negative, since it's pointing away from t... | [
"I think my issue is I have trouble visualizing the three dimensions. Is the 30 degree angle representing how far away from the Y axis A is and the 70 degree angle its incline into Z?"
] | [
"Yes."
] |
[
"So how do programming languages work?"
] | [
false
] | How do programming languages work? We type text and then that text is interpreted into making something happen. But how? | [
"Modern programming languages are built on layers and layers of previous progress and the complexity behind them is truly incredible. There are many many millions of person-hours worth of work that have gone into the state of the art today.",
"Start from the bottom.",
"Processors execute \"machine code\", seque... | [
"That’s one of the best explanations I’ve ever heard. I wish that had been in my “Intro to programming using C++” class."
] | [
"Great answer overall, and this is really good advice:",
"Start from the bottom.",
"I'd like to add to this answer by going even further down to the bottom.",
"Processors execute \"machine code\", sequences of instructions and arguments that are encoded in binary and tell the processor what to do. ",
"What ... |
[
"Are there genetic adaptations/mutations that humans underwent tens of thousands of years ago that were necessary for survival then, but not now? If so, what are they?"
] | [
false
] | [deleted] | [
"Wisdom teeth might have been useful if you'd already lost a bunch of teeth-- but if you've still got all your teeth when the wisdom teeth come in, they can cause all sorts of havoc."
] | [
"Lactase persistence",
" is a recent one. It was necessary for survival in cattle herding peoples, but probably isn't under strong selective pressure today.",
"There are also a number of autosomal recessive IQ-boosting genes that are no longer helpful for survival. Some are under slight negative selection bec... | [
"Good eyesight?"
] |
[
"Does an alcohol swab on a public toilet seat improve anything aside from piece of mind?"
] | [
false
] | [deleted] | [
"Assuming you apply sufficient sterilizing solution AND let it sit for the amount of time necessary for it to sufficiently sterilize the surface, you can feasibly end up with a pretty close to sterile surface. This is in fact how we sterilize surfaces in the lab. 70% ethanol is one of the standards for this. Now... | [
"I remember reading somewhere that 70% alcohol is used in place of something more pure because you need the remaining water content to help absorb the alcohol through cell walls. Do you know anything more about this?"
] | [
"It's been too long since I learned about the specific mode of action, that I don't even feel comfortable making an educated guess. Perhaps someone with a better memory for that stuff than I will chime in."
] |
[
"Why do Special Relativity and General Relativity time dilations take the same form when put in terms of energy? Is there a deeper reason for this?"
] | [
false
] | Special Relativity Time Dilation T = T_0/(1- v / c ) Replacing E = 1/2 mv T = T_0/(1 - 2E/mc ) General Relativity Time Dilation T = T_0/(1 - 2GM/Rc ) Replacing E = -U = GMm/R T = T_0/(1 - 2E/mc ) Which is of the exact same form. Is this some freaky coincidence or is there a deeper reason for this connection? | [
"Coincidence. K = mv",
"/2 is not valid in relativity."
] | [
"No, because dimensionless factors don't necessarily have to be constants. For example, relativistic equations abound with the Lorentz factor (1 / (1 - v",
"/c",
"))."
] | [
"Gravity is caused by a gradient in time dilation. If you change the metric to change the time dilation factor, you'll also change the kinetic energy",
"This entire comment is nonsense."
] |
[
"Given thalidomide's useful applications, if the only side-effect is found in pregnant women why is it not still prescribed for men or women not having children?"
] | [
false
] | There are studies showing thalidomide reducing angiogenesis in cancer and other applications. It has been used in treating leprosy in India, Africa and recently in Brazil but resulting in the associated birth defects in newborns. But why can't it be prescribed just for men and then used more widely? | [
"Thalidomide is indeed still prescribable in the US, with several indications. Prescribers have to be part of a special program, counsel women of childbearing age (WGA) on contraception and emergency contraception, and help monitor them for signs of pregnancy.",
"There are a number of drugs problematic enough tha... | [
"Also many others.",
"Please post, this is interesting."
] | [
"If I remember correctly, there was an issue with it switching isomer whilst in the body. I have no source for this though. Any one else?"
] |
[
"Is the coefficient of friction we use in the equation F=μN just a heuristic device of lower-level physics? There seems to be no practical way to predict the fricative force that will act on an object without already KNOWING it's μ. Can it be determined by its physical/chemical traits?"
] | [
false
] | So say you've got a simple situation with a block on an inclined plain. Is there a way to determine the force of friction that will be opposing the gravitational force both without measuring it and without knowing μ beforehand? | [
"You can derive the coefficient of friction by simulating the interactions of many individual atoms, like they've done in this paper: ",
"http://physics.aalto.fi/~asf/publications/10.1007_s40544-013-0021-3.pdf"
] | [
"The coefficient of friction is dependent on area of contact and material properties like surface roughness and elastic modulus [and many others]. While you in theory could use the sum of all relevant properties to calculate the friction coefficient, it's much easier/simpler/faster to just measure it. There are a... | [
"this is exactly what it is, but its on an even more complex level. Think about the interface of the components, on the nano scale these textural gradients are as mountains in proportion to the relative size of the molecules. We are able to approximate it much like trigonometry, functions at increasingly, arbitra... |
[
"Is our sun orbiting something?"
] | [
false
] | As a follow up question I was wondering about G-Force. How come we don't experience it the same way if we are hurdling thru space at astronomical speed? | [
"Yes, we orbit the center of the Milky Way Galaxy. ",
"As for G-forces, these are caused by ",
" not by speed. For a test you can do at home, accelerate in your car really fast. You'll feel yourself be \"pushed\" into your seat. Then stay at whatever speed you are at. No matter how fast you are going you won't ... | [
"It's worth noting the sun (and almost all other stars in the galaxy) does not orbit the supermassive black hole. We orbit around the center of mass of the 500-700 million stars within our radius around the Milky Way, not the 1 million solar mass black hole which makes up a tiny percent of the total mass. ",
"Onl... | [
"Hey thank you."
] |
[
"What do tumors and cancers actually do thats so deadly?"
] | [
false
] | What is different from like a cyst growing in the same place? | [
"A cyst is like a little sac of fluid. If it gets very large it might push on the tissues near it, but that's unlikely. In any case it's just a single, well-contained thing. If necessary it can be drained or surgically removed. ",
"Some cancers are benign, and act similarly. They stay in one spot. At worst they c... | [
"Your cells die a while after they are created, this is a deliberate process that goes on constantly at different rates throughout your body. Cells have a sort of lifespan in which they are useful and will basically replace themselves and shut down, then be removed.\nCancer occurs when a cell stops functioning prop... | [
"Cancer cells do not have longer telomeres. They do not follow the normal processes of self-regulation, and that's what makes them cancerous in the first place. In many cases they have shorter telomeres than healthy cells, but even that is not always true."
] |
[
"[Human Body] What caused the sores on Mark Watney's body at the end of The Martian?"
] | [
false
] | null | [
"Hi CatatonicTaterTot thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of t... | [
"Human Body "
] | [
"'Human Body'"
] |
[
"What is the science behind CDC reducing quarantine to 5 days for covid?"
] | [
false
] | The CDC recently reduced quarantine guidelines stating: “The change is motivated by science demonstrating that the majority of SARS-CoV-2 transmission occurs early in the course of illness, generally in the 1-2 days prior to onset of symptoms and the 2-3 days after. “. Sounds good but they don’t provide references. What is the actual evidence? | [
"Here is the science behind the decision:",
"\n",
"https://www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/scientific-brief-options-to-reduce-quarantine.html",
"In particular -",
"\n\"Wells et al (6) (preprint pending peer review) estimated the post-quarantine transmission risk (PQTR) for persons w... | [
"The key is symptom free.",
"Much like when they said vaccinated could take off masks and the unvaccinated said they said no more masks.",
"Sadly they won't read the actual point of this...at least the people who don't want to anyway."
] | [
"The key word ",
" is so vital but is being left off all the news article titles. It seems disingenuous and dangerous to me."
] |
[
"Why does fashion change?"
] | [
false
] | Why is it that certain fashions from the 70's and 80's are no longer in style today? Why do people stop seeing bell bottoms as the "cool thing" and now see them as tacky and quaint? Why is it when I look at pictures from the past I go what the hell where people thinking when it came to clothes? | [
"The (really famous) french sociologist ",
"Pierre Bourdie",
"u has a really interesting theory which applies on this subject but also far beyond.",
"His main idea is that every choice that we make as an individual is driven by our social environment. He drew this ",
"diagram",
" that exemplifies well thi... | [
"To be sure, the earliest punks in London (1975, before the term 'punk' was even known there) were seen as nothing but a bunch of bohemian weirdos. Rotten and his gang of street kids looked like recently released mental patients to most people. Nobody wanted to mimic them, not even the bourgeoisie that normally l... | [
"Fashion usually is the way to look different and better than the average. When the average becomes like you, you have to move forward, as in different animal species."
] |
[
"How can lighting safely hit an airplane?"
] | [
false
] | There are many YouTube videos of airplanes being struck by lightning. I was wondering how that is possible without causing serious damage to the plane or the people on it? | [
"Lightening \"tries\" to find the easiest path to the ground. It is much easier for electricity to flow through metal than through air, so, when the lightening hits the plane, the current travels through the outer casing of the fuselage not through the air inside."
] | [
"As you can see in ",
"this video",
", the lightning doesn't actually end at the plane, so the energy of the lightning doesn't dissipate into the plane. The electrical charge just moves trough the plane, in it's search for the route of least resistance. ",
"The amount of energy that is dissipated in an object... | [
"According to Gauss' Law of electromagnetism, an electric field cannot penetrate a completely enclosing (perfect) conductor. And although the aluminum skin of an airplane is not an ideal conductor, it is pretty good. ",
"Any charge which might remain on the airplane (which doesn't continue to travel on with the ... |
[
"What happens at the exact middle point between two black holes that are of equal strength?"
] | [
false
] | Is there a theory that explains this question? I was watching a video about black holes that orbit each other and started to wonder what would happen at the middle point of two equal mass/strength black holes? | [
"That depends on how close you are to either black hole, and how massive they are.",
"Tidal forces close to a black hole (and any particularly massive body) would cause an object near it to stretch because the gravitational field strength at the bottom of the object would be noticeably stronger than the strength ... | [
"A second grader asked Neil DeGrasse Tyson this question.",
"Video Here"
] | [
"That doesn't answer my exact question but that was interesting to listen to."
] |
[
"Can Someone Explain 'Efficient' Burning to Me?"
] | [
false
] | I was talking to a friend of my brothers who works with polymers and to simplify the discussion completely, I asked what we should do with excess plastic and he said to efficiently burn it. He sort of explained that it means supplying more oxygen to bound with carbon but I'm still confused. What is left over after efficient burning? Since the carbon is taken out of a compound what is the ash? He also said that if you efficiently burn it, you can burn anything without producing harmful gases othe than co2. Why is this? | [
"The basic end product of combustion of organic material is nearly always carbon dioxide, but this relies on there being enough oxygen available. Gases like CO can form after incomplete combustion, or some kind of solid residue can be left behind. These compounds are often toxic, which is why burning plastic can be... | [
"The ",
" PVC contains only carbon, hydrogen and chlorine. Complete combustion with oxygen will form carbon dioxide, water and hydrogen chloride (HCl gas)."
] | [
"With efficient burning we mean that all the material is burned sp that one does not end up with unwanted chemicals.",
"For example if one was to burn Hydrogen gas(H2) EFFECTIVELY what happens is that the hydrogen reacts with the oxygen molecules(O2) in the air and forms water(HO2). Simply water, nothing else.\nT... |
[
"Scientists: Do you have shaky hands? What do you do about it?"
] | [
false
] | This has been an issue for me for the past few years. I feel like my hands are much shakier than your average person. This is very scary, since my career is to basically work with very small components. I don't want to hit 35 years old and be unable to continue hands on research because of my hands. Does anyone else suffer from this problem. Am I just overreacting? Should I exercise my hands more? Is the problem just exaggerated since I work with tiny objects and tweezers all day? I would really like to know others experiences with shaky hands. edit: my grandmother, and great aunt both have an essential tremor. | [
"Where I'm from, P.I. in an academic setting means \"primary investigator\". We generally talk about P.I.s in the context of government grants, as in \"she is the P.I./primary on that grant\". "
] | [
"Where I'm from, P.I. in an academic setting means \"primary investigator\". We generally talk about P.I.s in the context of government grants, as in \"she is the P.I./primary on that grant\". "
] | [
"Yes, it's actually been a problem in my field of work. Nanotechnology does not go well with shaky gorilla hands.",
"You just have to move slowly and deliberately and be very, very careful. If it's really bad, maybe some occupational therapy."
] |
[
"Prosthetics: Can someone born without a limb (rather than losing it after birth) use advanced prosthetics controlled by nerves and neural pathways?"
] | [
false
] | I understand (or at least, I think I do to some degree) that if someone loses an arm, for example, cutting-edge prosthetics can utilize nerves and existing neural pathways to control the prosthetics. Let's say instead, however, that someone is born with an arm that stops short of the elbow due to a birth defect/genetic condition. At no point have they had an elbow, or forearm, hand... If he are she is born this way I presume that there is no neural pathways/nerves to dock onto. I am sure that technology will continue to advance so I guess I am not asking if it likely will ever be possible but rather if it is possible with existing tech and approaches. The inspiration for this question is the video that has made more than a few circulations around the internet: a video where a little boy (maybe a few years old) with arms that stopped just short of the elbow who was interacting with his newborn sibling. He utilizes his arms and mouth to pick up his sibling's pacifier and put it in her mouth. A very heart warming video. Many of the responses commented how jealous they were that he would grow up to have awesome android arms. But one comment asked whether it would be possible to have these and cited concerns that there might not be neural pathways to use them. Any thoughts? Thanks so much for the response everybody! This is my very first post to reddit after years of lurking... First, let me say that I was totally overselling my confidence when it comes to how much I understood about this subject at a base level. To clarify the question, I believe what I was picturing in my question was what is referred to as a myoelectric prosthetic. That seems to be the system of prosthesis that is most commonly featured in videos and articles. I will briefly read up on the basics of myoelectric systems before trying to read any more responses. While I am definitely interested in the use of neurons with prosthetics, the question is probably more appropriately: Can someone born without a limb as opposed to losing a limb later in life use myoelectric prosthetics? Why or Why not? | [
"This is a amazing question and one I cannot fully anwer. The sheer complexity of the nervous system is mind boggling. From my understanding you phrasing however is somewhat flawed. Prosthetics don't 'interface', for lack of a better word, with nerves. They instead use the output of said systems. You're nerves send... | [
"The only point I would make in this, is that I think it partially depends on why they don’t have a limb, which could effect how the nerves form. That being said, I would guess there is a good chance the nerves would get pruned if they don’t have one at all, or even if born with a limb, but lose it very quickly "
] | [
"The original answer is not correct. Modern prosthesis don't connect the nerves which are lost to the robotic mechanism. What is typically used is targeted muscle re-innervation which remaps a different area or nerve to control the robot. For instance, it can remap squeeze a muscle on your back to close fist. Most ... |
[
"Does pregnancy affect lifespan in any mammalian species?"
] | [
false
] | Excluding mortality due to birth complications, does pregnancy itself affect lifespan? Have such effects been noted in mice or other mammals? | [
"Don't have any information on mammals, but if you remove the ovaries from anoles they survive much better. This may be due to the resources which would have gone to reproduction being available to maintain the lizards in higher condition.",
"EDIT: Source, a paper I read last week. The anoles were brown anoles... | [
"I came across ",
"this",
" which addresses your question with humans (skip to the \"UPDATE\" about 1 screen in), though the answer seems to be: \"it depends\". ",
"If you have access to the American Journal of Human Biology, you can read more ",
"here",
".",
"In human females allocation of resources t... | [
"interesting question...but can be logically reasoned out. The longer the pregnancy, the greater the amount of energy the parent must spend on the offspring in embryonic development. Longer pregnancy also means the size of the offspring will be larger, leading of course to a larger adult organism. Larger organisms ... |
[
"Why does blowing at a candle/wind extinguish the flame?"
] | [
false
] | Shouldn't blowing increase the volume of oxygen that passes through the flame allowing it to burn brighter? | [
"You are removing the fuel. A candle flame consists of a pocket of vaporized fuel (wax) whose surface burns, fed by oxygen. When you blow out a candle you are blowing away that pocket of vaporized fuel before it has a chance to be replenished. You have blown out the candle. The candle remains hot enough for a while... | [
"Depends on how hot, depends on how much, depends on how fast. If the air was as hot as the average temperature in the area surrounding the flame and slow enough that weird hydrodynamic effects don't become important, it would continue to burn. But at this point you're probably melting the candle itself with your m... | [
"So what if you blew hot sir onto it?"
] |
[
"I have electrical outlets in my tiny bathroom, how does the steam from every shower I take not create an \"electric mist\" and electrocute me?"
] | [
false
] | null | [
"Water vapor is pure water, which is actually an insulator. Water itself is not a conductor at all, but when it has impurities inside of it the impurities are what conducts the electricity.",
"Even if the water vapor did somehow have conductive properties it would take the path of least resistance, which is direc... | [
"You missed the point that water vapor/mist exists in the air as small 'droplets' that are separated by air. There is no unbroken path of water vapor from the socket through the air."
] | [
"If I am not completely mistaken, the \"measuring\" in this case is not so much a fancy electronic device, as it is a coil wrapped around the live and neutral wires. Because the current is AC, this would induce a current in the coil unless the current in the two wires is precisely equal in magnitude (thus inducing ... |
[
"Can black holes be accelerated by a gravitational field?"
] | [
false
] | I'm wondering if the mass inside a black hole can be attracted to another body, and so by extension if we theoretically have two black holes somewhat close to each other, is it possible for them to orbit each other? | [
"While not observed yet, this idea of binary black holes is definitely possible! There's nothing special about black holes disallowing them from being able to orbit one another. They're just large masses like other celestial objects that happen to have their mass contained in an infinitely small space. Binary black... | [
"Yes on all counts - it's even possible for two black holes to merge.",
"At this point, I'd usually quote some examples of known objects, but hopefully you'll appreciate that it's actually quite difficult to find a black hole binary system! However, a similar class of objects are x-ray binaries, where we can see ... | [
"That's actually so cool! I realized that the answer to my other question was really obvious because if a black hole cannot be accelerated then it'd break Newton's Third Law, but it turns out that my additional question was more interesting. Thanks!"
] |
[
"Would it be possible to create an aerogel like substance out of caesin?"
] | [
false
] | You could follow to make the protein fluff. Then take the protein fluff and put it under a vacuum in a freezer to sublimate out the water. | [
"It would not have the structural properties of a aerogel, it would likely crumble."
] | [
"No answer to your question, but I'm curious why you would want to. Any uses in mind for a substance like that?"
] | [
"Low(ish) calorie protein bars."
] |
[
"Does the color of light affect plant growth?"
] | [
false
] | My wife and I were hiking and chatting the other day and both of us noticed how a weeping willow we'd passed appeared entirely yellow because of the yellow reflecting from the new spring buds. The branches, the trunk, and of course the buds all appeared to be in almost sepia tones. Chatting led to pondering, and now I'm wondering if the color of the light hitting a plant will have an effect on the plant's growth and, if so, whether variations in the color of flowers, buds, and leaves may in part be a method through which a plant can regulate the colors of light reflected and absorbed. I'm a lawyer, not a biologist, so I apologize if this question is idiotic. I have almost zero science background. | [
"Yes it does. Plants contain a chlorophyll which absorb all colors but mostly red and blue. Green is reflected thus we perceive the plant as green. This means that plants will not grow as much in green light but will in all other colors. That's about the extent of my knowledge of plant physiology though. I'm not su... | [
"There are different types of stars in the universe. Our star gives off lots of red light. Plants evolved on this planet, so naturally, they evolved to take advantage of the most numerous types of photons of light available to them. (You can think of a photon as a packet of light energy.) But blue photons are hi... | [
"what? the spectrum of the sun peaks at a greenish wavelength."
] |
[
"Is light pure energy? Is there even any meaning to the phrase \"pure energy\"? Can energy ever exist by itself?"
] | [
false
] | I've heard people talk about photons as being little packets of "pure energy." I was under the impression that energy was simply a quantification of something's ability to do work. If this is the case, how could "the ability" to do something ever exist all by itself? Is it more accurate to say that energy can only ever be a property of something, and never a separate entity in and of itself? | [
" ",
" Light does have the advantage of being energy that is only in the form of momentum. E",
" - p",
" c",
" = m",
" c",
" . When you have no mass, then E=pc. But for everything else, its energy is both the energy of its motion (momentum) and the energy of its mass.",
"edit: Strikethrough, new text ... | [
"Everything that exists is energy, in one sense or another."
] | [
"Energy is not a physical construction of any kind. So it doesn't make sense to 'be' energy. Objects in the universe have a property that we call energy. Much like an apple can have the property of being red. "
] |
[
"How long would it take a closed, undisturbed Nalgene bottle with tap water to be 'in stasis' for eternity?"
] | [
false
] | I've started drinking water from an old-school nalgene bottle (original white and blue, not the fancy ones) lately and started wondering about how long it would take (cap screwed on) for the tap water to turn into something undrinkable and what that would turn into over a longer period of time. We started thinking of variables, such as the tap water source, the size of the bottle mouth, whether it was completely sealed, etc. and realized that AskScience might be better at thinking about the factors involved. I'm curious to see how long it would take for all of the organisms contained in the bottle to run out of a food source, die, be broken down by RNases and DNases, and for those -ases to stop working also. Will the bottle ever reach a state of stasis where it will stay that way (if still closed and undisturbed) for eternity? Will it take 50 years? 1000 years? What will the water be like then, in stasis? Will it become consumable again? | [
"I can't comment on the biological aspects of this, but as far as I know Nalgene bottles are made of polyethylene, which degrades over time. I would expect that on geological timescales your bottle will unseal, releasing all the water, and eventually become a puddle of smaller hydrocarbons."
] | [
"That's not something I even considered. Thanks!"
] | [
"That's not something I even considered. Thanks!"
] |
[
"Does magnitude of smell have a unit? Would the quantity be a vector, or would it be scalar?"
] | [
false
] | [deleted] | [
"The number of particles would affect potency, so maybe parts per billion or parts per trillion. However, concentration only helps compare identical compounds. A low cocentration of sulfur has a \"more powerful\" smell than a high concentration of nitrogen."
] | [
"Sensitivity would also be extremely varied among species, even among individuals. Parts Per X seems to be the only objective form of measurement."
] | [
"This is completely inappropriate for ",
"/r/AskScience",
"."
] |
[
"If a \"spaceship\" like one found in sci-fi movies were to actually be blown up in outer space, would it resemble anything at all like we see in movies?"
] | [
false
] | Often in movies, we see fireballs or flame and smoke. I'm pretty sure there would be no sound, as that is simple science. But the explosions... are they possible because of the oxygen that escapes at demolition? How would it look? | [
"Not for long!"
] | [
"Not for long!"
] | [
"We're a long way from militarized spaceships, so any discussion of this in detail is going to be tentative.",
"That said, if there are human crews on a ship and the ship gets exposed to vacuum (whether from rail gun fire or some more prosaic form of chemically powered artillery), the air will rush out and that w... |
[
"Since the Earth is not a perfect sphere is gravity different on different places? If so, would that mean time passes differently in those places as well?"
] | [
false
] | null | [
"Yes, on both counts. The effect has been measured, but it is tiny; see this ",
"newspaper article",
"."
] | [
"Also, to be clear, the article is slightly misleading when it implies that you'd notice time passing at a different speed (if it wasn't different by trillionths of a second of course). Even if you spent a year somewhere where time passed half as fast (like on an extremely-fast-moving spaceship) it would still feel... | [
"The speed of the beam is necessarily measured from all inertial reference frames to be c, the same. If there seems like there'd be a difference in the speed of light to reconcile with this fact, what you'd find is the wavelength of the light contracts or expands. It propagates at c, though."
] |
[
"Why do our planets orbit without drifting closer to the sun?"
] | [
false
] | Did we just get really lucky with the way they lined up when caught in the sun’s orbit? | [
"There's a couple things at play here. ",
"First, planets weren't really captured by our Sun. The Sun and the planets all came from the same rotating disk of particles called a ",
"protoplanetary disk",
". Random, small clumps which happened to stick together, and over millions of years, those small clumps gr... | [
"The distance from the sun for all the planets does vary by a few million miles. But for the average distance to decrease the velocity of the planet would need to be decreased. And there's not a lot out in space to slow down a giant planet."
] | [
"With only gravity and constant masses the orbits stay the same.",
"Satellites in low Earth orbit decrease their height over time because Earth's atmosphere provides a little bit of drag, but that doesn't apply to planets orbiting the Sun (the solar wind is completely negligible).",
"The Sun is losing mass, whi... |
[
"How much pollution did nuclear weapon testing cause?"
] | [
false
] | There has been 2482 nuclear test bombs detonated, how much pollution has this caused, and how much of an impact has it had on the climate and atmosphere? | [
"Nuclear testing above ground spread radioactive fallout all over the world.",
"For the average individual, whether that individual is a plant or an animal or a person, the effects have been negligible.",
"At the population level however, ",
"it has become apparent that the radioactive fallout from nuclear te... | [
"The 50s and 60s have been posited as a potential start to the potential Anthropocene epoch, partly due to the fact there is now a sedimental record of when nuclear testing began. 1952 is approximately the time this record became global rather han concentrated around test sites "
] | [
"Wow, so if humans become extinct and in the distant future visiting aliens were to do earth samples they could see that someone developed nukes?"
] |
[
"Has there been any known examples of non-valence electrons being used in a chemical bond?"
] | [
false
] | null | [
"This doesn't really answer OP's question. In no case are carbon's inner shell electrons (those two in the 1s orbital) used in hybridisation or bonding. All four in the 2s and 2p orbitals (hybridise as appropriate) are the valence electrons.",
"OP: None that I'm aware of. The energy difference between valence an... | [
"To be a little pedantic, any electron involved in a chemical bond is by definition a valence electron, so in that sense your question doesn't really make sense - you can't have a non-valence electron in a bond. However, I think you're really asking whether there are examples of bonds formed using electrons not fro... | [
"I believe sulfur and phosphorus can form bonds using their d orbital electrons, this allows them to form five bonds simultaneously. I believe some halogens can also form 5 coordinate systems which implies that they're using their d orbitals as well. Thats it i think for organic atoms.\nAs for inorganic materials i... |
[
"Do people with advanced HIV have no allergies?"
] | [
false
] | [deleted] | [
"I would made an initial conjecture that by the time they lack sufficient CD4+ T cells to generate new IgE producing B cells that they are probably not long for this world anyway.",
"They'd have the same allergies that they've had prior to that point of course. Losing CD4+ T cells doesn't make your memory B cells... | [
"I don't understand what you are saying... I'm not a doctor"
] | [
"I don't understand what you are saying... I'm not a doctor"
] |
[
"[Astrophysics] Can a black hole be ripped apart by going between two other black holes?"
] | [
false
] | Consider 3 black holes, or a black hole and 2 sufficiently massive bodies. Imagine two of the black holes are in some form of paired orbit, perhaps they were paired as a double star during their earlier lifetimes. The third black hole passes through what you might consider L1(Lagrangian 1). Half our wandering black hole will be closer to one of the paired black holes, and the other half of our wanderer will be closer to the other. If the pair of massive bodies has a sufficiently small distance between them, could the third wandering black hole be ripped apart when passing through the exact center. If it does get ripped apart, would gravitational forces distort space sufficiently for the contained matter to spill out? Or would the singularity become two black holes which each move toward their respective closer massive body? Or perhaps some other action would occur? Bonus points if you show your math. Thanks! | [
"Half our wandering black hole will be closer to one of the paired black holes, and the other half of our wanderer will be closer to the other. If the pair of massive bodies has a sufficiently small distance between them, could the third wandering black hole be ripped apart when passing through the exact center. If... | [
"Our current understanding of black holes forbids them breaking apart again once they have formed. Imagine that you could, and a singularity has just split apart into two singularities that are currently a very short distance from each other. Both singularities are almost certainly well within each others' event ho... | [
"Yeah, the point mass problem is a major issue. Thanks for the solid analysis. I suppose this does set up a potential experiment to see if a black hole truly acts as a point mass. Thanks for the solid analysis. "
] |
[
"What determined the size and shape of the tectonic plates?"
] | [
false
] | [deleted] | [
"Our current best theory for the mechanics of plate tectonics is that it's driven by convection cells within the mantle: Hot rock and magma rises up through the mantle to the boundary of the crust, where some of it breaks through to form new oceanic crust in mid-ocean rifts, but much also moves along the bottom of ... | [
"If I understand you correctly, the boundaries between different continental plates are formed due to many different variables (temperature, fluid dynamics, heat and pressure resistance of the rock and magma, preexisting motion, etc), and that's why they are unpredictable and inexplainable?",
"Follow up questions... | [
"Plates change all the time (by geological standards) but the modern-day continents have pretty long histories. The continents are formed around cratons, billions-years old sections of tough crust. North America is formed around a particular large one so has existed in a more-or-less recognizable form for at least ... |
[
"How can NaALO2 (Sodium Aluminate) possibly exist?"
] | [
false
] | Metals have a tendency to always loose electrons, right? they have less electrons in their outermost shells than there are needed to fill it's outermost shell completely. How the hell is Aluminum borrowing electrons from Sodium? It's a metal. It makes it highly unstable. And if not, then what is going on? Please explain in detail. It even seems to be forming a covalent bond but metals don't form covalent bonds. P.S.: I am a 10th grade student and am struggling to learn about science. Please don't shout at me. | [
"The aluminum is in a positive oxidation state (+3) here as well. As a simplification, think of the compound as a salt of the positive sodium ion (Na+) and the negative aluminate ion (AlO2-), in which there are basically covalent bonds between Al and the two Os. (In practice, the chemistry of Al is super-complicate... | [
"so Al is forming a covalent bond? Is this possible? and if it is, then whom is Na bonded with?"
] | [
"It doesn't really answer your question, but bonding is more of a spectrum with ionic at one end and covalent at the other. Aluminium is a strange element as it kind of lies in the middle, it's bonding could be classed as covalent (in AlCl3 for example) or ionic (like in alumina)."
] |
[
"Has light always been present in the universe? If not, when did the first light emitting object form?"
] | [
false
] | null | [
"Light has been present since at least a small fraction of a second after the Big Bang. However, for the first 380,000 years thereafter, light would bounce around from atom to atom, never travelling very far before hitting the next one, so it wasn't for 380,000 years that the Universe became transparent and light c... | [
"Jesus. That's the second dumb mistake I made in that post. Yes, I meant transparent (and have edited it). Thanks. I posted that literally right after waking up, which I guess is telling me I should have a cup of coffee before posting here :)"
] | [
"Yep. Typo corrected. Thanks."
] |
[
"At what percentage of alcohol, would the hydrating effects of water and the dehydrating effects of alcohol cancel each other out?"
] | [
false
] | Say I have a drink that is ethanol and water, like a watered down vodka. Presumably, the water in the drink would hydrate me, and the alcohol from the drink would dehydrate me. At which ratio would the hydrating/dehydrating effects cancel each other out? Was the wine/beer of the past weak enough so that people didn't need to supplement it with water when wine/beer was the standard drink? | [
"This is going to be a pretty difficult question to out and out answer, as many things beyond just what % alcohol the H2O/EtOH mixture you are drinking happens to be. Your kidneys are dealing with a lot of filtration of various electrolytes and metabolic byproducts, and the whole process is affected by a complex ne... | [
"People have died from drinking as little as 1-1.5 gallons in ~1 hour. It's actually not too difficult to die from upsetting the electrolyte balance in your brain."
] | [
"So how much water is too much, on average?"
] |
[
"If observing a quantum particle causes its wave function collapse, how is it possible for us to know what the wave function is?"
] | [
false
] | So my last question asked about how the function f(x) changes before and after observing a quantum particle, but that brought me to wonder how we even formulate the equation for what the initial wave function of a given particle looks like if we can never observe it in its natural state. I'm guessing it's some sort of derivation/integration of the resulting dirac delta function? | [
"If you just have a single copy of the system in question, then in general it is impossible to reconstruct the wavefunction that it is currently in. ",
"If you have several copies, then you can make several measurements. In quantum mechanics a measurement corresponds to a projection in the sense that the expecta... | [
"take a look at this for instance ",
"http://physicsworld.com/cws/article/news/2013/may/23/quantum-microscope-peers-into-the-hydrogen-atom",
" "
] | [
"You're right that we can't really know the initial state before measurement, except if we had many copies of the same state. But you do know the resulting state once you've measured it, and then you can plug that state into the Schrödinger equation to see how it will change over time to predict subsequent measurem... |
[
"Is there an upper bound to the EM spectrum?"
] | [
true
] | [deleted] | [
"Current theories normally allow for photons with arbitariliy high energies. Issues such as pair production of massive particles as mentioned in other responces will limit the energy of photons we ever see. Since very high energy photons will very likely produce massive particles. However as far as current theories... | [
"Essentially no. Photons can have arbitarilly small energies. At least with current theories. This actually causes lots of calculational difficulties for certain problems.",
"There may be some argument that if the universe has a finite size, then the lowest possible energy a photon could have would be one with wa... | [
"No, this isn't correct. Pair production can occur, but only in the presence of an electric field. Photons are perfectly capable of existing at energies greater than 2 x electron mass (the threshold for pair production) if there is nothing to interact with. And pair production itself is a stochastic interaction,... |
[
"How can Burning wood (carbon) generate UV radiation?"
] | [
false
] | null | [
"Note that your blackbody radiation plot is log scale and therefore has to be cut off at some place on the y-axis. ",
" temperature blackbody will emit ",
" UV radiation. "
] | [
"Do you expect a lot of UV for some reason?",
"The thermal emission will contain tiny amounts of UV. In principle chemical reactions can directly lead to UV emissions as well but I'm not aware of specific reactions that would occur in a wood fire."
] | [
"The hydrogen part of the burning wood emits UV. Some ",
"fire sensors",
" specifically detect this UV.",
"Edit for the neg rater:",
"http://www2.emersonprocess.com/siteadmincenter/PM%20Rosemount%20Analytical%20Documents/FGD_MAN_UVS-H2_Hydrogen_Flame_Detector.pdf",
"The UVS-H2 is a smart, stand alone fire... |
[
"Who is moving compared to who based on inertial frames and time dilation?"
] | [
false
] | null | [
"Each twin observes the other twin to be aging slower, because each twin is at rest in their own rest frame and it's the other twin that is moving - hence the \"paradox\" part of the twin paradox. If you change the speed of one twin or the other, you're introducing acceleration which breaks the symmetry in order to... | [
"Thanks for the response. According to what I have read in literature, the accelerated twin will age slower, and upon return and slow down to his siblings frame he will still stay physically younger as time did tick past slower in the accelerated frame. \nThe difference being is that if we accelerate the twin at re... | [
"The difference being is that if we accelerate the twin at rest to the frame of the already accelerated twin, he would start aging slower as opposed to if we slow down the accelerated twin, who will age faster compared to how he was while travelling at high speed.",
"No no. As I said before, movement is relative.... |
[
"AskScience AMA Series: We study neutrinos made on earth and in space, hoping to discover brand-new particles and learn more about the mysteries of dark matter, dark radiation, and the evolution of the universe. Ask us anything!"
] | [
false
] | Neutrinos are one of the most exciting topics in particle physics—but also among the least understood. They are the most abundant particle of matter in the universe, but have vanishingly small masses and rarely cause a change in anything they pass through. They spontaneously change from one type to another as they travel, a phenomenon whose discovery was awarded the 2015 Nobel Prize for Physics. Their properties could hold the key to solving some of the greatest mysteries in physics, and scientists around the world are racing to pin them down. During a , scientists will discuss the hunt for a “sterile” neutrino beyond the three types that are known. The hunt is on using neutrinos from nuclear reactors, neutrinos from cosmic accelerators, and neutrinos from man-made particle accelerators such as the Fermilab complex in Batavia, Ill. Finding this long-theorized particle could shed light on the existence of mysterious dark matter and dark radiation and how they affect the formation of the cosmos, and show us where gaps exist in our current understanding of the particles and forces that compose our world. This AMA is facilitated by the American Association for the Advancement of Science ( ) as part of their , IFIC/CSIC and University of Valencia, Paterna, Spain , scientist at Fermilab, Batavia, Ill. , scientist at Lawrence Berkeley National Laboratory, professor of physics at the University of California, Berkeley, and co-spokesperson for the Daya Bay neutrino experiment in China , Communications Director, Fermilab | [
"How exactly can neutrinos shed light on the nature of dark matter? Is there any hypothesis that scientists want to test regarding the connection between the two, or is the research more exploratory at this stage? "
] | [
"Olga Mena Requejo (OMR) and Katie Yurkewicz (KY): Thanks for your question! It turns out that all neutrinos are a form of dark matter. The three neutrinos we know exist and have been already discovered are hot dark matter particles. We call it hot dark matter because they have tiny masses. On the other hand, ster... | [
"KY: Great question, and one that we are all asked whenever we venture outside the scientific world. I like to answer this in three parts.",
"1) We are making these measurements, and hopefully these breakthroughs, nor for ourselves but for our grandchildren's grandchildren. We have no idea right now what we could... |
[
"Just found out there is an ongoing lawsuit in my town because of Benzene pollution. Many people attributing it to their illnesses/cancer. What is the radius and exposure time to be seriously affected by this? (Links enclosed)"
] | [
false
] | Here is a link to the map showing the pollution (Zip code 14150): Here is a link to the article about the pollution: I don't really want to reveal where exactly I live on the internet, but if anyone can shed some light on what areas are unsafe to live in and for how long a period of time. My girlfriend and I have lived in Tonawanda for the past year and plan to for one more year at least for financial reasons...but our lease is up in February and we will move if we are in danger of experiencing negative affects of this pollution. Thanks for the help | [
"Benzene toxicity usually occurs through inhalation. You would need to know the levels of benzene are in your local area to make any estimate of toxic effects. Just as a general rule, you would be better off higher up (upper levels of a multi-story building, or living on a hill) than lower. Since benzene is heavi... | [
"Very helpful, thank you. Who would I contact to find out Benzene levels in my particular neighborhood? Or I might look into that bucket test the people in that article conducted."
] | [
"I spent a little time digging, and am having trouble finding any legitimate concentration values for benzene in your area. But based on restrictions put on coke manufacturers in the past few decades, and an already large dip in monitored benzene levels from even 2007, you should be fine. ",
"If you feel comfor... |
[
"Why do some people get headaches after drinking draught beer?"
] | [
false
] | I work in a restaurant and often people order a bottle over a draught that's on special and claim the reason is that draught beer gives them a headache. I've been surprised by how often I've heard this. Is there any scientific reasoning behind why this would happen? | [
"Cheese has never been demonstrated to cause, trigger, or promote headache:",
"Holzhammer J, Wöber C. Schmerz. Alimentary trigger factors that provoke migraine and tension-type headache. 2006 Apr;20(2):151-9.",
"\"Controlled trials suggest that alcohol and caffeine withdrawal are the most important nutritional ... | [
"Cheese has never been demonstrated to cause, trigger, or promote headache:",
"Holzhammer J, Wöber C. Schmerz. Alimentary trigger factors that provoke migraine and tension-type headache. 2006 Apr;20(2):151-9.",
"\"Controlled trials suggest that alcohol and caffeine withdrawal are the most important nutritional ... | [
"Tyramine indirectly causes a pressor response when it's taken into nerve terminals and causes the release of catecholamines. In most situations, 1) monoamine oxidase can metabolize tyramine relatively quickly before this sympathomimetic action can occur, and 2) the amount of tyramine in food is not nearly enough ... |
[
"What does it mean when science articles say super high-frequency graphene CPU's do not have the \"required on/off ratio\" for discrete calculations? Link to article in post."
] | [
false
] | I was reading when I came across this interesting but jargon-filled article: The part that was very interesting to me was the 7th paragraph, Graphene transistors may be able compute faster than conventional transistors, but are not ideal for PCs yet, Lin said. Because of the lack of energy gap in natural graphene, graphene transistors do not possess the on-off ratio required for digital switching operations, which makes conventional processors better at processing discrete digital signals. And I became very curious as to exactly what that meant and why it was so! I interpreted it to mean the transistors used could not "isolate" charge very well, so for a given cycle the CPU required some kind of majority of transistors to be one charge, and some minority to be the other, and that if not some kind of capacitance would take effect between them and cause malfunctions. I know there must be some physicists, EEs, or material science types in here who can help me better understand the what and why of this! Thanks guys! | [
"I'm sure the guy who made the comment knew what he was trying to say but maybe the journalist 'simplified'. First, IBM developed an experimental transistor which sets a speed record (this is probably a better article ",
"http://physicsworld.com/cws/article/news/2011/apr/07/graphene-transistor-shines-on-diamond-l... | [
"Very interesting, thanks! I've studied some basic computer engineering stuff, but never did I come across an analog transistor before, kind of a weird idea to me because I have no idea how they're used. But you've basically answered my question! Now I have a lot of stuff to google."
] | [
"I did not articulate the concept of signal vs switching transistor well but it is worth noting that the world is, essentially, analog. If I could insert a graph, I'd show that the input/output ramp of a signal transistor tends to be a gentle ramp while the same graph for a switching transistor tends to be a steep ... |
[
"If general relativity, or the physics of the Big, and quantum theory, or the physics of the Small, cannot be reconciled - where's the line between them?"
] | [
false
] | Shouldn't there be some point at which they overlap? Or is there a gap between them? Does general relativity apply, for example, to the cellular level? Or the molecular level? | [
"In answering a question like this, it is crucial to distinguish between the formalism of the theory (the equations and how they are used to make predictions) and the behavior of the universe that we model with the theory. We believe that the universe, at all scales, follows all the laws all the time. We believe gr... | [
"Q: Can GR and QM be reconciled?",
"A: At first glance this question seems to suggest that quantum theory and GR are inconsistent. But they aren't inconsistent.",
"Q: Then what needs to be reconciled?",
"A: In modern theoretical physics you write down a classical Lagrangian. IE an equation that describes the ... | [
"Even when you do QM + GR you still get quantum fluctuations, this is what leads to Hawking Radiation. After all, QM + a specific solution of GR gives you QFT. That solution to GR is a smooth manifold, it gives you SR.",
"The issue becomes \"what does it mean to quantize gravity?\" We do not currently have a sati... |
[
"What would a monomolecular sword (or wire) really do?"
] | [
false
] | The concept is well know from SF (William Gibson, Shadow Run, Warhammer 40k). I guess my question consists of two parts: 1) Is it, theoretically, possible to construct something that consists of a long "string" of single atoms or molecules (I'm naively thinking of a sort atomic pearl necklace, I guess), and 2) assuming we could construct a monomolecular sword/wire, what would it do when it comes into contact with solid matter (I can't quite see how a chain of single atoms could "cut" something in half, as those things do in SF) | [
"Ell975 makes a good point. If you tried to cut something with a monomolecular wire (like an atomically thin cheese-slice I guess?) the Van der Waals forces would cause the two separated surfaces to re-join. ",
"There have been a ",
"number",
" of ",
"syntheses",
" of atomically-thin wires, mostly made of... | [
"That's not wholly accurate. It while van der wals forces would cause the object to rejoin to itself, it would do so with numerous defects.",
"For example, if you cut through a strand of DNA it's going to have a very hard time joining back together without defects.",
"If you cut through a polymer it may well br... | [
"A line of atoms would be useless for cutting. This is because a regular sword splits an object apart and the two pieces are too far away from each other to rejoin. However, by using an atom thick blade, the molecules of the material being cut would still be close enough to attract each other."
] |
[
"My friend told me he thinks microwaved water kills plants. I call on you all to help me convince him that microwaves are perfectly safe."
] | [
false
] | [deleted] | [
"It's complete hogwash. Nothing happens when you microwave (pure) water other than it gets warmer. There's no way of telling, even in theory, whether or not some quantity of water has been microwaved in the past or not. ",
"I'm afraid you won't find any articles in Scientific American, because they don't usually ... | [
"snopes.com/science/microwave/plants.asp",
"Here. Snopes is legit. And they give reasons for their answers. Hope it helps. "
] | [
"Tell your friend that microwaves are machines that use light in the microwave region to induce rotations and vibrations in water molecules that increase the overall kinetic (and thermal) energy of the sample. Microwaves are just slightly higher in energy than radio waves (",
"http://upload.wikimedia.org/wikipedi... |
[
"Is it true that meteorites could have created life on earth ?"
] | [
false
] | [deleted] | [
"All life that we have studied thus far has shared similar genetic strategies, using nucleic acids to store information and pass that information on to subsequent generations. If there were a form of life that originated elsewhere in the galaxy and arrived here we might reasonably expect that it would use a differe... | [
"Lab tests have shown various organic compounds could survive extremely long durations in space, including reentry. If, for example, Mars or Venus or Europa (or any body for that matter) were once teeming with life and a meteorite impact propelled surviving organic compounds to Earth. The primordial cell you're tal... | [
"It sounds like what you're talking about is ",
"panspermia",
". Everything that I'm going to say about it you can find in the wiki article as I am no expert in the subject but anyway, it's the idea that life is able to survive in asteroids or other similar things and when these objects crash into a suitable en... |
[
"[Astronomy] The sun's magnetic poles swap every 11 years. Does this have any effect on the earth?"
] | [
false
] | It says that The solar magnetic field extends well beyond the Sun itself And is more about the "heliospheric current sheet". My question is, is earth effected by these magnetic changes at all? | [
"Firstly, we should note here that the sun's magnetic poles don't swap every 11 years, as the sun does not have magnetic poles like Earth. Instead, it has multiple norths and souths all over it because it's a plasma. This is why that article you cited has a lot about north/south sunspot pairs in it.",
"The 11 y... | [
"The first part is not quite true I don't think. While the magnetic poles and field lines of the Sun aren't like the Earth's, the solar hemispheres do have a reasonably well defined polarity. ",
"This",
" shows it quite nicely. In one cycle, for the northern hemisphere, the south polarized sunspots always occur... | [
"Beyond that, no, the magnetic field of the sun doesn't really affect us on Earth at all",
"Actually, (It's a pretty subtle phenomenon, noticed only by those in the shortwave radio community I'm guessing) but the height of solar activity that occurs every 11 years can actually boost signals and enable longer dist... |
[
"What happens if you break the sound barrier under water?"
] | [
false
] | null | [
"There would be a sonic boom, just like in air. ",
"Cavitation",
" and ",
"sonoluminescence",
" would probably be the main differences you'd notice, and there would be tremendous amounts of heat produced (much more than in air).",
"I think you'd run into a lot of issues trying to do it in reality, though,... | [
"The Glock has a muzzle velocity of ~375m/s. The speed of sound in water is ~1500m/s . The only thing that video is showing is the release of gasses from the round."
] | [
"Interesting! I didn't know that. Maybe they have a video of a supersonic gun firing underwater? I can't imagine it would look too different though.."
] |
[
"If the Earth was flat, would rainbows be straight lines?"
] | [
false
] | null | [
"Rainbows have nothing to do with the shape of the Earth, only to do with the refraction of light through (roughly) spherical raindrops. The refracted light spreads out in a cone and the part-circle we see is a cross-section through that cone. (If you are ever fortunate enough to experience a rainbow while flying i... | [
"No, because the prisms are still more or less randomly oriented.",
"There actually ",
" prisms in the air, in the form of ice crystals. There are several optical phenomena related to refraction with these, namely ",
"parhelia",
", various ",
"arcs",
" or the ",
"22° halo",
". The prism structure de... | [
"If raindrops were prism-shaped, would rainbows be straight lines?"
] |
[
"How large does building has to be so the curvature of the earth has to be considered in its design?"
] | [
false
] | I know that for small things like a house we can just consider the earth flat and it is all good. But how the curvature of the earth influences bigger things like stadiums, roads and so on? | [
"Definitely for the Large Hadron Collider and similar insanely large particle accelerators or that laser-bouncing tunnel for detecting gravity waves. Not just because they are huge but because their operation relies on incredible precision.",
"IIRC the LHC had to account for how the moon's gravitational pull move... | [
"The Humber suspension bridge has a main span a little less then a mile long (4,626 ft). Due to the Earth's curvature the two main supporting towers (510 feet tall) are 1.4 inches further apart at the top than the bottom.",
"https://en.wikipedia.org/wiki/Humber_Bridge"
] | [
"I love this information. I had not considered research facilities. I'm sitting here thinking about enormous warehouses and indoor football fields and crap. ",
"However, I'm not sure they sculpted the building's structure specifically to the curvature of the earth for the precision required. That seems like more... |
[
"Steady eyes"
] | [
false
] | How exactly do we keep our eyes fixed on an object when we move our head around? For example, if I'm looking at a lamp across the room, I can move my head around while my eyes stay locked on the lamp. While still looking at the lamp, I can keep my head still then move my eyes around, obviously using muscles to do this. Why don't I feel the muscles keeping my eyes steady in the first scenario and how is it done? | [
"This thread",
" explains why quite nicely. Basically, you have two sets of eye muscles, one of which is specifically designed for movement tracking."
] | [
"Your vestibular system is in charge of figuring out the position of your head. Your ear has tubes called the semicircular canals, which are oriented along various axes and filled with fluid. They work just like a level tool to sense the angle and position of your head. There are nerves that are constantly sending ... | [
"Thanks for the information, that helps to clear it up a bit :)"
] |
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