title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Is a \"global compass\" a marketing gimmick or is it true that most compasses are \"balanced\" for the portion of the earth they're used in?"
] | [
false
] | A friend of mine (in the US) is buying his daughter a special "global compass" for her trip to Australia. He says that the earth's magnetic field varies so much that a compass needle that's balanced for the US will get stuck in Australia. Is this true? EDIT: I'm not referring to declination i.e. the difference betwee... | [
"http://en.wikipedia.org/wiki/Compass#Compass_balancing",
"You're right in your explanation of how compasses work, but wrong about compass design. Simple compasses don't read well off the horizontal plane, so balancing must be done to make sure they don't get stuck when held flat."
] | [
"http://en.wikipedia.org/wiki/Compass#Compass_balancing",
"You're right in your explanation of how compasses work, but wrong about compass design. Simple compasses don't read well off the horizontal plane, so balancing must be done to make sure they don't get stuck when held flat."
] | [
"No, but they also used very inaccurate compasses and knew that they were using very inaccurate compasses. This is why they mostly used celestial navigation. Compasses were for rough direction finding while walking around between taking more accurate measurements.",
"EDIT: This was in response to someone claimi... |
[
"Does the body produce Vitamin D in the presence of moonlight similar to sunlight?"
] | [
false
] | null | [
"No, Vitamin D requires UV radiation to produce, and moonlight has negligible amounts of this. See:",
"http://legacy.adsabs.harvard.edu/full/1974Moon....9..295C"
] | [
"It‘s the ultraviolet portion of the Sun’s spectrum that causes vitamin D production in skin cells. Moonlight is merely reflected sunlight, so if the Moon reflects ultraviolet it will also cause vitamin D production in the skin, though to a far smaller degree since the Moon is much much dimmer than direct sunlight.... | [
"It‘s the ultraviolet portion of the Sun’s spectrum that causes vitamin D production in skin cells. Moonlight is merely reflected sunlight, so if the Moon reflects ultraviolet it will also cause vitamin D production in the skin, though to a far smaller degree since the Moon is much much dimmer than direct sunlight.... |
[
"Is holding your breath as an infant a learned reaction or one you are born with?"
] | [
false
] | Got into a heated argument with my biology teacher whether or not it's one you are born with. She says that it is learned because when a baby gets water in it's lungs it "learns" to not do so again. | [
"The Mammalian Dive Reflex is what causes babies to hold their breath in water. The sensation of cold and pressure on the face, among other things, triggers an involuntary breath hitch, which passively leads into breath holding. Keep in mind, babies develop in a liquid medium without breathing, since they get all t... | [
"Most newborn infants instinctively hold their breath underwater. But this instinct drops out by around 6 months and they have to relearn it.",
"So depending what age you are talking about, you could both be right.",
"Pedroso, F. S., Riesgo, R. S., Gatiboni, T., & Rotta, N. T. (2012). The diving reflex in healt... | [
"Babies don’t develop without breathing, they “breathe” the amniotic fluid to develop their diaphragm. They also hiccup a bunch for the same reason. When they are born and first breathe in air all the liquid that was in their lungs gets absorbed into the blood stream.",
"You are right that they get all their oxyg... |
[
"How does a photon provide a physical force to objects like solar sails when it has no mass?"
] | [
false
] | [deleted] | [
"The momentum."
] | [
"what is p?"
] | [
"what is p?"
] |
[
"According to a recent study at Oxford, only 8.2% of DNA is functional. In theory, could we remove all the 'junk' and create a more efficient genome?"
] | [
false
] | null | [
"Would you mind posting the article? I'd like to read it. ",
"In the meanwhile, look up \"junk\" or \"non-coding\", it's actually believed to be more useful than one might initially think. And also, just because we don't know the biological function, doesn't mean it doesn't have one. :-)",
"http://www.scient... | [
"Efficient in terms of cell division, yes probably. DNA replication goes incredibly fast for how many bases need to be duplocated, but it does still take hours to finish. Bacteria given lots of extra plasmids to copy divide slower than thise that just have their own chromosomes to copy.",
"Efficient in terms of... | [
"No, not all. That seemingly junk DNA is what allows variation and epigenetic regulation. Worms have ~ 20,000 genes and humans have ~23,000 genes. Humans and worms have a lot of the same genes. We also have a lot of repeats of the same genes. One role the repeats have is to be able to mess up or experiment wit... |
[
"How much is known about Oarfish?"
] | [
false
] | It seems, to the casual observer, that there has been a recent rash of Oarfish washing up on beaches. How unusual is this? Any indication of this being something more, like perhaps a result of the deep oceans warming? How much do we know about these strange creatures? | [
"Not a terrible amount. We know for a fact that oarfish are pretty well distributed around the oceans of the world because they've been historically washing up everywhere for hundreds of years. The sea serpent is a good example of sailors mistaking the oarfish for a monster.",
"Oarfish, however, like other deep... | [
"This happens all the time in the fisheries realm. Fish are weird animals and they come in all kinds of shapes and forms. An animal that's about 40 feet long and is not a whale, a shark, or a jellyfish is just too cool to pass up. It's also this kind of exposure that helps us expose these animals to the public s... | [
"On slow news days, the media LOVES reporting stuff like this. \"Big dead fish washes up on the beach\" becomes \"Mysterious deep-sea monster discovered off the coast!\"."
] |
[
"Question per Richards Dawkins book: Is glass a liquid with very high viscosity or a solid?"
] | [
false
] | Per Richards Dawkins book "The magic of reality" on page 78 or so, he states that glass is a liquid with a very high viscosity. I have read studies previously that this was a myth due to cites sources being incorrect. (Medieval church windows being thicker at the bottom, however, there were indeed designed this way.) ... | [
"Yay! Something right up my specialty! This never happens!",
"So here is the deal: The problem with the terms Gas/Liquid/Solid is that these are forms of matter, they are not ",
" of matter. The distinction that I am making seems trivial, but the difference I am drawing is whether or not you're in equilibrium. ... | [
"Thanks for the awesome response. I immediately thought about the famous ",
"\"Pitch Drop Experiment\"",
", which is actually still ongoing (there used to be a webcam set up to view it, but I don't have the time now to look for the link). Essentially, to prove that certain \"solids\" are indeed just supercooled... | [
"I'm going to allow this, because its awesome."
] |
[
"If a pregnant woman is given a vaccine does the unborn child also gain immunity?"
] | [
false
] | Just kind of popped into my head. | [
"For some, yes. Flu shot and whooping cough vaccines provide some protection to the unborn baby for a period of time after birth (e.g. 6 months). That is part of the reason that pregnant women are encouraged to get those two vaccines while pregnant. Not sure about others."
] | [
"Live vaccines such as the MMR (measles, mumps, and rubella) vaccine and the varicella (chickenpox) vaccine are contraindicated in pregnant women due to the theoretical risk of transmission to the fetus."
] | [
"To be a little more specific, the vaccine doesn't pass directly to the baby, like through the placental barrier. The mom gets the vaccine, and the antibodies she develops from having had the vaccine will then pass through the blood supply to the baby, giving the baby some natural defenses. Babies don't have signif... |
[
"Why does RNA have Uracil instead of Thymine?"
] | [
false
] | null | [
"Unfortunately, you've got it backwards and it's a common misconception since we make RNA off our DNA. However, a better question would be Why does DNA have Thymine instead of Uracil?",
"RNA is considered the evolutionary precursor molecule to DNA. RNA is simpler in structure than DNA (single helix vs double) and... | [
"Just to add on something, you said \"RNA is simpler in structure than DNA,\" but the complete reverse is true. Infact, there are a large variety of RNAs in the cell which involve themselves in essentially every biological process known, and adopt complex secondary and tertiary structures which can give them functi... | [
"It may be a simple matter of difference of opinion, but I feel that the 6 foot long strand of double helix DNA, wrapped around histones, rolled up into nucelosomes, further coiled into a chromatin, and then supercoiled into chromosomes to fit inside the nucleus of the cell is a more complex structure than the on-a... |
[
"Why don't we shield exposed reservoirs?"
] | [
false
] | Whenever we have droughts I always see news articles with shocking pictures of reservoirs at their lowest levels yet. But they are always fully exposed to the blistering sun. Why don't we cover them with reflective material when there is no rain? Wouldn't this significantly reduce evaporation? | [
"i think with questions like these its best to think of a simple cost vs benefit system.",
"so the costs are:",
"-it will cost a lot of money to cover the lake.",
"-it will cost a lot of money to maintain the cover, be it either a dome or some form of fabric laid on the top.",
"the benefits:",
"by taking ... | [
"Some places do, but in most cases the added cost and maintenance of the balls seem to be considered more than is reasonable to put the cover into place.",
"I have heard of municipal drinking reservoirs doing that, but can't find a link back to that article, so here is a ski resort, and a manufacturers websites f... | [
"Yes. Water quality would diminish greatly, requiring additional effort to purify for drinking. Maintaining the reservoir as a fresh water habitat is essential to keep the water from turning into a cesspool.",
"The real issue with the reservoir being at their lowest levels is usage, without resupply. We are using... |
[
"Why do the prongs on an electric plug normally stay cool even after heavy use?"
] | [
false
] | [deleted] | [
"The prongs are made of a pretty non-resistive metal (copper perhaps). Resistance would generate heat and waste energy, both of which would be terrible qualities in a plug. The metals and wires chosen are designed to cause as little resistance as possible, for safety and to maximize the power usable by the device (... | [
"The prongs are generally made of brass, which is an alloy of copper and zinc."
] | [
"Not only that, but they have considerable more mass in them than the wires that they connect. If your fuses/CBs didn't function, you would melt the wires before you would see any damage/heat on the (relatively speaking) massive prongs of the plug."
] |
[
"Is there a certain pitch that humans interpret as \"loudest\"? If so, why?"
] | [
false
] | For example, a drum has a certain pitch, and when you play that pitch, it vibrates a little more than usual. Does the eardrum do the same thing? I thought of this because I was listening to the radio and during one note the song seemed abnormally loud. | [
"Yes, it's around 3 kHz. The Wikipedia page on ",
"Equal-loudness contours",
" has a nice figure showing this; for a 20 Hz (barely audible on the lower end) sound to be \"as loud as\" a 3 kHz sound, it needs to be 60 dB higher, which is 1,000 times more energy.",
"The \"why\" is harder to answer... It may hav... | [
"Our ears are more sensitive to certain frequencies than others. For an explanation refer to the Wikipedia entry on ",
"equal loudness contours",
" or dave_casa's answer.",
"I have not seen evidence that drums in general transmit through the body in any significant way. There would need to be a lot of energy ... | [
"Our ears are more sensitive to certain frequencies than others. For an explanation refer to the Wikipedia entry on ",
"equal loudness contours",
" or dave_casa's answer.",
"I have not seen evidence that drums in general transmit through the body in any significant way. There would need to be a lot of energy ... |
[
"Is it more efficient to have multiple grocery lines and people choose which to wait in, or to have one long \"feeder\" line and have a person wait until the next cash teller is available?"
] | [
false
] | This is a thought experiment I've had for some time. Consider two situations of identical grocery stores, with five cash registers available each. In Store A, each cash register has its own line of customers in queue. An individual who wants to buy their items walks up and waits in a specific line for a specific cash r... | [
"Ignoring lading of groceries, the layout of supermarkets and the difficulties calling people to a register for a moment (which all complicate the problem):",
"This is called an M/M/c queue.",
"https://en.wikipedia.org/wiki/M/M/c_queue",
"In ",
"queueing theory",
" (again, remember I'm ignoring the proble... | [
"I strongly believe you're speculating here, the dynamics of queues aren't always the way your intuition tells you."
] | [
"If I remember correctly, the motivation behind the shared queue is that while total time for all customers is about the same, average time goes down because quick customers go through more quickly.... something along those lines anyway. People, however, psychologically feel like it's slower."
] |
[
"What are the benefits of having an AI learn through human interaction; rather than teaching it beforehand?"
] | [
false
] | [deleted] | [
"There was a big project a couple of decades ago (the name, unfortunately, eludes me right now) to do just that. The goal was to create (or at least enable) AI by instantiating a set of rules to enable parsing and \"understanding\" of natural language. I believe that after many years of effort, the attempt was ei... | [
"By \"hard wire\" do you mean e.g. personally program how cleverbot should react and what cleverbot should say? This is an exceptionally difficult task due to the extremely complicated nature of language.",
"Or do you mean give a bunch of data sets of conversations rather than requiring actual humans to provide t... | [
"No, that was developed by IBM (and I referenced it above). It predated Watson. It was government funded, or maybe a consortium. I just can't remember. (I need machine augmentation for my memory, obviously.)"
] |
[
"Does something like codon degeneracy also exist for RNA genes?"
] | [
false
] | Codon degeneracy exists because there are multiple ways to code for a given amino acid. This means that a sequence with different DNA could in principal produce the same protein. RNA genes are non-coding genes. They are transcribed from the DNA strand but never translated into a string of amino acids in order to produc... | [
"RNA is a transcript of DNA. Transcription of DNA to RNA is based on base pairing rules (A <--> T/U, G <--> C). There is no degeneracy there. ",
"When it comes to functional redundancy, the answer is a firm and decisive \"well that depends.\" Are you talking about comparing non-coding RNAs from different species?... | [
"Calling RNA genes non-coding is going to upset a lot of Biochemists. RNA genes code for ribosomal RNA, tRNA, and numerous small, medium, and long RNAs that are all functional in the cell, (RNA decay, survalance, regulatory mechaisms). ",
"But I know what you mean, these are not translatedi into protein. ",
"Th... | [
"To add to some of the answers here, the fundamental basis of codon degeneracy is that RNA transcribed from DNA must be translated, and the dictionary that is used to translate has many words that mean the same thing. RNA genes are fundamentally different because they are not translated at all. They simply are tran... |
[
"When people have a high pain tolerance, are experiencing less pain, or are they just better at \"sucking it up?\""
] | [
false
] | Basically, is people's pain tolerance all psychological? | [
"No, it is not all psychological.",
"Pain may be mediated by a number of factors, including:",
"\n* Sleep deprivation",
"1",
"\n* Sex",
"2",
"3",
"\n* Humour",
"4",
"\n* Depression and/or Anxiety",
"5",
"6",
"\n* And very likely countless others. ",
"Is there likely a significant psycholo... | [
"First it is important to understand the difference between tolerance and threshold, and I think the answer is there are 2 kinds of people you are asking about. One with high tolerance and one with high threshold.",
"A high pain threshold means that you can sustain a (relatively) high amount of damage to your pe... | [
"Cultural",
"1",
" influences are becoming prevalent. A difficulty in finding reliable reporting tools is that there are cultures that prize emotive responses to give validity to a situation as well as those that value minimal expressiveness."
] |
[
"How do cosmologists equate relativistic mass of galaxies moving away from us (the observer)?"
] | [
false
] | I recently asked/proposed the question/idea about the expansion of the universe as noticed by galaxies moving away from us (the observer) and how it might be true that these galaxies are actually shrinking, causing them to look like they are moving away because the edges closest to us are actually moving away from us (... | [
"A few things going on here. One is that the concept of relativistic mass doesn't translate into an actual mass. It's something that was used to explain the concept of relativistic momentum, but isn't a physical quantity. The only relevant mass is the rest mass. Another is that when we're considering the internal d... | [
"It was my understanding that the physical and real effects of relativistic mass is a key to understanding why objects cannot accelerate to and subsequently exceed the speed of light.",
"Not really; it just shifts the question around a bit, which sometimes satisfies lay-persons.",
"In relativity, accelerating a... | [
"Relativistic mass is an outdated concept. Massive objects can't reach ",
" because their momentum goes to infinity as their velocity goes to ",
".",
"iorgfeflkd is right that galaxies don't go near the speed of light ",
". An observer in any given galaxy will see the CMB as being shifted by only a few to s... |
[
"Which is more efficient? Insect flight or avian flight?"
] | [
false
] | I'm an undergrad biology student and I've been learning about the evolutionary advantages of being bipedal, so I was wondering... Weight for weight, in general, which is more efficient? | [
"Dynamic soaring, as first observed in ",
"Nature",
" is a method of flying employed by some sea birds to fly huge distances with virtually no flapping needed. However some ",
"moths",
" use the jetstream to migrate. To really say which of these is more efficient, you would need to clarify what you mean my ... | [
"i'm assuming its energy output to distance flown w/ respect to its weight"
] | [
"Efficient in what sense? Energy/distance? Energy/height? Energy/speed? Cargo transportation?",
"The first one is easy - eagles, vultures and other gliders will outperform any insect in that sense. ",
"Second...can be tricky. Fleas are fuckn efficient when it comes to gaining height. ",
"As for speed, speed/w... |
[
"Are there any multicellular organisms which are not symmetrical?"
] | [
false
] | I can't think of any. Every animal, every plant, every living thing on this planet is symmetrical in some sense, except apparently for sponges. Is there a reason for this, or is this just a mystery? Is it reasonable to assume that a planet in another solar system with life would also be symmetrical? | [
"Many plants are not symmetrical, nor are the main mass of most fungi (mushrooms are just small fruiting bits).",
"EDIT: As for why things are symmetrical, I can think of two main underlying reasons. First, if you are going to move around, it helps to be symmetrical, because otherwise one side tends to move mor... | [
"Sponges have no symmetry. "
] | [
"I can think of some crabs which have one huge claw and another smaller one on the opposite side. They'd be asymmetrical right? "
] |
[
"Why do whales and dolphins die on shore?"
] | [
false
] | Couldn't they get air like regular mammals? | [
"They can still technically breathe, but the weight of their bodies is what kills them, by crushing their organs and even limiting how much air their lungs can breathe in. Their bodies are designed to be in the water all the time and as such the distribution of weight/organs with their bodies relies on the water to... | [
"This, and they also can't properly thermoregulate on land. They quickly overheat."
] | [
"depending on the species, thermoregulation failure is the biggest killer. keep them wet!"
] |
[
"Question about Special Relativity, time dilation and length contraction"
] | [
false
] | Using the Wikipedia as a reference. Assume John is stationary and is observing Bill traveling at 0.9c This means that Bill travels at 269,813,212.2 m/s. So he covers X=269,813,212.2 m in T=1 s. Now I want to work out the time (t) that John sees has passed for Bill, and the distance (x) that John sees Bill has traveled:... | [
"Your mistake is applying the time dilation equation the wrong way.",
"First let's work in units where c=1 light-sec/sec, and I'll use gamma = 1/sqrt(1-v",
" ~ 2.3 for simplicity.",
"Remember, proper time (the clock of someone who views themselves at rest) can only get dilated (its time dilation if you view s... | [
"Let's just ignore numbers because they make things more confusing.",
"In reference frame A, Bill travels a distance d from x to y in a time t, with velocity d/t.",
"In Bill's inertial frame B, point y moves toward him until it passes him in what he experiences as time t' which is equal to g",
"g. He calculat... | [
"Doesn't length contraction mean the length would be shorter?",
"This is where the numbers help.",
"With my numbers above:",
"γ = 1 / √ (1-v",
" = 1 / 0.4359 = 2.294157339",
"So if d' = γd, then the length would be longer. This doesn't appear contracted, but elongated.",
"I thought it was t'=γt and d'=d... |
[
"How large a colony must be in order to be genetically diverse?"
] | [
false
] | Operating on a example - how many people would be required for a colony to avoid inbreeding? Or to rephrase - how many generations must pass so offspring from the same n-grandfather could mate without consequences? | [
"The homo-sapien population is theorized to have dropped from around 21,000 to around 618 breeding individuals around 195,000 years ago. Due to the Long glacial stage known as Marine Isotope Stage 6 (MIS6) that lasted until roughly 123,000 years ago. This explains the lack of genetic diversity in modern humans. ",
... | [
"How did they get the number 618? That seems pretty specific. "
] | [
"There's no hard and fast rule, and no one can get you an exact number. It depends on a lot of factors, including the exact genetic makeup of the founding population - how many harmful recessive alleles are floating around, etc; how much and what kinds of environmental pressures are acting; mutation rates; and so ... |
[
"What is the purpose, if any, of the second and third generations of matter?"
] | [
false
] | It seems to me that if a top quark, for example, only exists at very high energies and is too unstable to really do anything other than (and for a very brief time at that) that the particular event that created it might as well have just generated a cascade of lower generation particles. Do the second and third generat... | [
"there's not a \"purpose\" to any particle's existence. They just are."
] | [
"No it doesn't really predict 3 generations of matter exactly. Maybe in the future we'll have an argument for why there \"must\" be only 3, but at the moment it seems to just be the case."
] | [
"What I mean to say is, does the standard model predict multiple generations of matter or was it just made to accommodate them because we know they exist? I know the strange quarks were known (sorta) before the standard model was formulated, but what about the rest of the second and third generation particles?"
] |
[
"What would happen if you carved grooves into a fresh vinyl record at random? Is it possible to replicate music simply by carving out the right kind of grooves?"
] | [
false
] | null | [
"In the same way that it's theoretically possible that a room full of monkeys on typewriters could write out Hamlet."
] | [
"Okay, but I'm not fundamentally wrong in thinking it's possible? Like, there isn't anything that would physically prevent a person from creating Abbey Road from scratch, even if they'd never heard it or seen it etc?",
"I get that it's practically impossible, but is it physically impossible? "
] | [
"Right. A phonograph record just has grooves of different depths in the material. You could in theory do that by hand."
] |
[
"Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology"
] | [
false
] | Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! ... | [
"The monolith in Utah, how is that formed?"
] | [
"artists"
] | [
"Whatever happened to the vaccine against tooth decay I read about in the late 1980s.?"
] |
[
"What exactly is vacuum energy?"
] | [
false
] | I have read bits and pieces here and there but i really don’t understand it still. From what I understand its an insanely high density energy found in the vacuum of space and Its still a theoretical quantum physics theory. Thats about it (wikipedia only goes so far) My main questions are Where did the energy originate ... | [
"Zero-point energy is just the minimum energy that some given quantum system can have, and it's not necessarily zero. Vacuum energy is the zero-point energy of the vacuum state (the state with zero particles) of a quantum field theory.",
"We are certain of its existence because it has measurable consequences, lik... | [
"A useful analogy is to think of the fields in nature (every particle is associated to a field) as a pond, and the particles are (specific types of) ripples on the pond. ",
"You shouldn't imagine the pond as perfectly still when there are no ripples in this case though, it is always fluctuating up and down.",
"... | [
"Oh. For some reason i thought i remembered reading something that said it had a crazy high density energy. Have i mistaken this for something else?"
] |
[
"What algorithms exist to find a set of *n* points within a cube that are at maximally displaced from one another?"
] | [
false
] | A colleague of mine has brought in the dodecahedral equivalent of the Rubik's cube today. The faces are coloured red, orange, yellow, lime green, medium green, dark green, light blue, dark blue, mauve, white, grey, and pink. This led me to wonder how they chose the colours, and whether there is an algorithm for finding... | [
"We do this in our simulations to make clean initial conditions. It's what's called a \"glass\". You set up a bunch of particles, and run a simulation where every particle has a repulsive force on every other particle. You slowly remove kinetic energy from the system (\"anneal\" it), until everything settles down.... | [
"It should be added that algorithms like these sometimes find local minima that aren't the globally best answer...just pretty good answers."
] | [
"True true true... but when you have a million particles, the landscape is so bumpy that the absolute minimum isn't necessarily the most important thing..."
] |
[
"Can underwater currents be remotely sensed from the surface or just under the surface of the water?"
] | [
false
] | null | [
"There is (sort of) another technique for looking at currents throughout the water column, namely seismic oceanography (e.g. see ",
"this review",
"). Whilst this does not allow you to solve for water velocity, it does allow you to remotely infer the density structure of the water column, potentially giving ins... | [
"This is a big problem in oceanography: there's basically no way to measure subsurface currents from the air or from space. There are some indirect methods, like measuring the shape and temperature of the sea surface and using a computer simulation to predict what's below, but there's a lot of ways that can go wro... | [
"Underwater ocean currents are typically measured directly by \"deep water drifters\" or other types of probes. It's also possible to remotely measure the speed of water relative to a device known as an \"Acoustic Doppler current profiler\". These have a range of up to one kilometer, depending on model and conditio... |
[
"How do Jet Engines Work?"
] | [
false
] | null | [
"The basic concept was described by my university Aerospace Propulsion professor as Suck, Squeeze, Bang, Blow. ",
"The first stage of a modern jet engine pulls the air into the engine with a large fan (Suck). Behind the fan, this high velocity air is compressed by a series of compressors (Squeeze). Next, the h... | [
"A lot of fighter jets have an additional step called after burner, where more fuel is pumped into the exiting high velocity, high pressure, high temperature air which can be toggled on and off and is used for short bursts of speed.\n",
"http://www.youtube.com/watch?v=qZKKeg7lOr8",
"\n@2:30"
] | [
"Not true, I'm afraid. Yes, when the plane is static on the ground, the engine does suck air in. When it's at operational speed, the air is pushed into the engine. In either case, most or all of the thrust comes from the pressure of the exhaust pushing on the turbine blades at the back of the engine (or on the back... |
[
"Is there a compound that can be found naturally but cannot be made artificially?"
] | [
false
] | [deleted] | [
"Insulin absolutely can be synthesised, and in fact it was one of the first peptides to be produced by solid-phase peptide synthesis. It's just not a practical route for the vast majority of proteins due to their sizes and post-translational modifications, since it is very time consuming, yields would be very low, ... | [
"Depends in what way you mean by 'made artificially'. Proteins and enzymes are very complex structures that can't really be made by standard chemical reactions, and require a living organism such as bacteria to be produced in a lab. ",
"A good example is insulin, a hormone used to treat diabetics. It was original... | [
"From a theoretical standpoint, no. Potentially anything that is possible in nature (on earth) we could theoretically produce artificially.",
"From a practical standpoint, absolutely. There are countless natural compounds we do not know how to produce, and papers get published all the time by some organic chemist... |
[
"What stops an aircraft from reaching specific altitudes?"
] | [
false
] | So I was reading a bit about an aircraft (MiG 21 or otherwise known as the Fulcrum) and found that the maximum altitude it can reach is specificly 18013m. My question is what stops the MiG from going an extra, say 1000m? Or even better, why exactly 18013 and not 18015 or just 18000? | [
"An aircraft flies at a constant altitude when the sum of the forces acting on that aircraft in the up direction is zero. There's two forces acting in the up direction on aircraft: gravity and lift. From ground level to the altitude airplanes can fly, gravity is basically a constant (it decreases a little bit with ... | [
"They're not floating around. They are constantly freefalling towards the Earth, but travelling sideways fast enough that the rate of which they fall equals the curvature of the earth."
] | [
"Astronauts are weightless while in orbit not because there is no gravity there (if there was no gravity, nothing would hold them in orbit) but because orbits are free-falls. So, the astronauts and the space station (of shuttle or whatever) are all falling together, so it appears as if they are \"floating\""
] |
[
"How empty of a vacuum can we make? How are the more \"pure\" vacuums made?"
] | [
false
] | I imagine it is either impossible or very difficult to remove every last molecule from a given space, so how empty are we capable of making something? Say for example we wanted a 1 m cube with no air or anything inside of it. How would we go about doing so? How much of the air could be pumped out/what other methods wou... | [
"First you have to take into account that perfect vacuums do not exist. Even in outer space, there are a few atoms per cubic meter. A perfect vacuum - with a gas pressure of exactly zero - can not be artificially obtained.",
"There are designations for \"qualities\" of vacuum. What's called \"ultra high vacuum\" ... | [
"Of course, there are certain areas which happen to contain no atoms at a given time. But atoms not being stationary, that area will have some atoms later. Since this perfectly atom-free area isn't at all isolated from everything else around it, it makes little sense to talk about it separately in physical terms."
... | [
"You could never get the piston to touch all of the walls and top so perfectly that there is no existing volume in the cylinder, and that volume will contain some atoms."
] |
[
"Using freezing point depression how does adding salt to ice (0 C) reduce the temp (to <0 C)? or does it?"
] | [
false
] | I understand how freezing point depression works with the salt ions disrupting ice crystal lattice formation. However, when I'm looking at pages for homemade ice cream they say that adding salt allows for the mixture to be below the freezing point of water. While I can see that adding salt to the ice will melt some of... | [
"When you add salt and lower the freezing temperature of the solution, ice will begin to melt because it's then above the freezing temperature. However, ice requires a lot of energy when it melts, which it will take from it's surroundings and therefor decrease the overall temperature."
] | [
"The ice cools it. It takes quite a bit of energy to melt ice. ",
"But if you have a mixture of pure water and ice at 0 C, then it'll stay that way, the proportion of ice/water won't change - some water will freeze and some ice will melt, but it's at the same rate. ",
"If you mix water above 0 C with ice, then ... | [
"Melting is an endothermic process, which means it takes energy from the environment to melt.",
"When you add salt to ice, the ice melts, and the temperature of the system lowers. This is how ice baths - down to about -20 C - can be prepared in the laboratory with ice, water and salt alone."
] |
[
"What will scientist and doctors use once we run out of helium?"
] | [
false
] | I know helium is very important for medicine and science. What will we do when helium runs out? Make more? Replace it with something else? It's just a scary thought. Do I have any reason to be scared or worried about this? | [
"Hydrogen, Neon, Nitrogen.. They'll figure it out. Also, to the people saying Helium isn't used in medicine and science; Helium is used in GC/MS.",
"Edit: Before anyone comments, I'm linking forensics to medicine. Yes, it's a stretch, but the link is there."
] | [
"For many applications, a high temperature superconductor would significantly reduce the need for helium. For example, the LHC uses tonnes of liquid helium to cool the superconducting magnets."
] | [
"It's used in MRI magnets."
] |
[
"Are there any currently existing species that evolved or diverged from any other currently living species?"
] | [
false
] | Creationists love to ask 'If we evolved from apes, why are there still apes?' Of course the answer is that we did not evolve from apes, that we and apes share a common ancestor. My question is if there any current species who at some point diverged biologically from a species that stayed relatively static and still exi... | [
"First off, I'd say that \"still exists\" is sort of a difficult thing to tease apart. If you mean that these two species have been living and interacting within any particular environment, then I would say no, there are probably no species that have remained as static as you would probably consider sufficient.",
... | [
"http://www.talkorigins.org/faqs/faq-speciation.html",
"http://www.talkorigins.org/faqs/speciation.html",
"describes several recent speciation events",
"the wikipedia page on speciation gives examples of each type - some of those may be relevant."
] | [
"Yeah, after thinking more about this, for a situation like what I've described to occur, you'd need some members of a species to stay static for a long period of time while others evolved. The problem with that isn't really the divergence, it's the idea of a species staying so static as to be considered 'still the... |
[
"Why do ladybugs follow a drawn line?"
] | [
false
] | null | [
"Hi zeetotheex thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the foll... | [
"Biology"
] | [
"Biology"
] |
[
"Most galaxies have a black hole at their centre, does this mean that galaxies form around black holes?"
] | [
false
] | Given enough time, will enough matter and stars accrete around a black hole to form a galaxy? | [
"More likely the opposite: Given enough time, a galaxy will form a supermassive black hole in its center.",
"Galaxy formation can be simulated well from the dynamics of dark matter alone. Visible matter and black holes just follow the dark matter clumps."
] | [
"In terms of dynamics this is true, because even supermassive black holes make negligible contributions to the total gravitational potential of galaxies.",
"But we do believe black holes play important roles in regulating the cool gas content of galaxies, and hence the rate at which they can form stars. This happ... | [
"All sufficiently massive galaxies are expected to have a central SMBH. But where that mass threshold lies, and what the origin of the material the BH initially forms from is, are both still somewhat uncertain."
] |
[
"If your visual cortex is damaged, can you see in your dreams?"
] | [
false
] | Particularly, can a patient in a coma dream if the auditory or visual cortex is damaged? | [
"I don't have any direct evidence but I would assume no, based on the following reasoning: losing the part of the visual cortex that allow you to see colour (eventually) makes you unable to imagine colour. More generally, mental imagery activates the same parts of the cortex that are activated through corresponding... | [
"by definition, if you're in a coma you are unconscious i.e. not dreaming.",
"as for dreams with visual cortex damage: there's been no systematic study of this, possibly because every patient is different and would report different things. but also because, i guess, the right people haven't gotten together to col... | [
"by definition, if you're in a coma you are unconscious i.e. not dreaming ",
"So are the dreams people who have been in a coma experience all the result from brain activity during waking up from the coma?"
] |
[
"Why can't we communicate faster than light using entanglement?"
] | [
false
] | null | [
"See the ",
"physics FAQ",
":",
"Special Relativity - Can quantum entanglement be used to communicate information faster than the speed of light?"
] | [
"Hi! thanks for your answer. I did read those threads and it makes a lot of sense. I still don't understand how it actually plays out in this circumstance I'm proposing. I don't really understand the implications of entanglement, and that's what I'm trying to understand. ",
"What I'm asking is, if there is a cont... | [
"But if one side changes the spin of the incoming particles into meaningful pattern, can't the other side see the pattern as well, albeit with noise?",
"From the very first link in the FAQs:",
"Because you're measuring a fundamental aspect of a particle (let's say spin in this case), and you then know that its ... |
[
"Melting Ice"
] | [
false
] | Every day I freeze a bottle of water and let it melt all day the next day so that I have cold water to drink. I keep the bottle in an insulated carrier so that the ice doesn't melt too fast. I have noticed that the ice melts faster from the bottom up. By the time I leave work, the ice is in a cone shape with the ape... | [
"It could also be that more heat is transferred by conduction from the ground/surface it is resting on than conduction with the air. So the bottom is melting quicker as it has more heat transferred to it."
] | [
"I would make the educated guess that as the ice melts, the water travels to the bottom. This water located near the bottom is a worse insulator than the air above which causes the bottom of the ice to melt quicker. As more and more water builds up it travels up the ice block melting as it goes giving it the cone s... | [
"Thank you. I always thought the heated air in the room was warmer than the surface of the desk."
] |
[
"Do racing games improve your driving abilities?"
] | [
false
] | Do games that include a closed racing circuit that rely on reflexes and braking, such as F1 2013, Forza Motorsport, etc.. improve your real life driving abilities? | [
"Are you asking whether it can in general, or whether it does for you specifically if you play driving games?",
"It's been shown to make a difference for people already, where those with extensive game time in Forza or GT can drive a track for the first time in RL and put up a significantly better time and displa... | [
"It's been shown to make a difference for people already",
"Reference?"
] | [
"Short answer, ",
"yes",
". Long answer, it's arguable that such people were bound to be good drivers naturally, but just as pilots train in simulators, a sufficiently realistic game should test/build up your reactions/reflexes that can translate to actual driving. In more realistic games like the Gran Turismo ... |
[
"How Exactly Does Light and the Ionization of Hydrogen Cause Emission Nebulae?"
] | [
false
] | null | [
"where a star is sending out light energy that ionizes the hydrogen atom, is it really losing or gaining an electron? If H loses an electron, does it emit light in the process?",
"In an H II region the hydrogen is ionised into H",
" it loses an election. When astronomers says something is ionised they usually m... | [
"Yes. Recapturing can release photons but these aren't the ones that dominate the light of H II regions. "
] | [
"Yes. Recapturing can release photons but these aren't the ones that dominate the light of H II regions. "
] |
[
"How come my green laser pointer changes color when pointed at this specific book?"
] | [
false
] | null | [
"I'm not sure what the natural color of the book is, but green laser pointers typically double the frequency of a near infrared light source. I believe in the US, a filter is required to reduce the IR emissions for safety (as the battery dies, you may get only/mostly IR. The eye does not adjust to reduce its intens... | [
"I also want to add, 5mW, maybe 10 is what you'd find in a \"safe\" pointer. If it is any more than that, exercise extreme caution not to shine it on reflective surfaces, and if you can, even get safety goggles to filter the specific frequency out. Depending on strength, some lasers can cause permanent blind spots ... | [
"Interesting - I was thinking this couldn't be right - because the frequencies are usually 1064 nm, frequency doubled to get to the 532 nm green light; The light at 1064 nm shouldn't be visible to the eye at all. However, a web search found ",
"this report",
" which suggests the near IR laser is actual driven b... |
[
"When you have a solution, how come the [OH-] x [H3O+] value always has to equal 1x10^-14? Specifically, why is there always some H+ or OH- left in very basic/acidic solutions?"
] | [
false
] | Sorry if this question is too simple... I've just been wondering since I'm learning about it in chem (well, to clarify, learning about it for the 3rd time, but he first two times I wasn't intuitive enough to care)... EDIT: I guess another example is why Water has to have OH/H+ in it (although I'd assume that's because ... | [
"Any molecule of water is identical and indistinguishable at chemical level from any other molecule of the same compound. One volume of pure water is identical to the same volume of water. Under equal conditions (temperature, pressure...) their chemical and physical behavior will be the same. So if a volume of wate... | [
"That whole thing chages if you have deuterated water, it's really quite cool how such a tiny change can affect so much."
] | [
"Thanks for such an in depth answer. If I understand correctly, there will always be OH-/H3O+ present because there is a real chance that H2O will ionized into those parts [due to its high amount of molecules], and even if OH- and H3O+ come back together then other H2O's will ionize. This holds true at no matter wh... |
[
"A couple of questions on evolution by selective breeding"
] | [
false
] | [deleted] | [
"It is possible, but it is probably fairly unlikely, or at least, very difficult. In part it depends on how reproductive isolation occurs. If it is a result of incompatibility between the dirty bits then you might be able to breed individuals with more compatible naughty parts. If it results from some sort of in... | [
"I'm a little curious what is driving these three questions. Are you trying to selectively breed a giraffe from a palm tree grove?",
"http://en.wikipedia.org/wiki/Reproductive_isolation",
"Recombine also has a technical definition in biology, so I assumed you meant \"two resultant populations [can] reproduce\"?... | [
"Thanks for the answer. Your answers for 1 and 2 are pretty much in line with what I thought the case would be. The third one I had no idea about at all!"
] |
[
"What's the point of grand unifying theory?"
] | [
false
] | [deleted] | [
"So then, there is no difference between the gravitational interaction and the other three? "
] | [
"So the gravitational interaction isn't mediated by any gauge bosons, but the other three are, how does one fit this into a framework of some theory of everything? So far in my exposure to the quantum world, physics is mediated by the bosons."
] | [
"You're at a party and everyone is expected to wear green hats, Gravity shows up with a boat on his head.",
"People just like uniformity and patterns, gravity breaks away from the mold known as the standard model entirely. The question whether gravity does conform to this mold is one worthy of study and pursuit. ... |
[
"Can anything have wave and particle properties? Just like light."
] | [
false
] | null | [
"Yes, as long as by 'anything' we're talking about matter. Matter exhibits wave-like properties according to the de Brogile wavelength (wavelength = h/p, ",
"http://en.wikipedia.org/wiki/Matter_wave",
"). This applies to the fundamental particles just as much as anything else. The wavelength of a person or a pl... | [
"All matter (even ordinary matter composing everyday items) have wave and particle propertied when described from a quantum point of view. This quantum description is necessary if one wants to obtain its macroscopic properties from its microscopic description.",
"For instance, it would be impossible to compute th... | [
"The largest molecule thus far that has been successfully diffracted in a double-slit type experiment had 810 atoms:",
"http://pubs.rsc.org/en/Content/ArticleLanding/2013/CP/c3cp51500a#!divAbstract",
"So yes. Quantum mechanics is a WAVE theory and all matter is described in this language. However, as many diff... |
[
"How do Led Lights/semi conductors function?"
] | [
false
] | Hi, I 'm trying to learn how led/semiconductors work. What I understand so far is that there are 2 sides of the led. one contains negatively charged particles and the other positive. there are gaps in the atoms in the negative side, so the electrons from the positive side go to the other. By changing energy levels, ene... | [
"Why doesnt the P side eventually turn neutral? Should the electroms eventually fill up all the empty spaces and make both sides neutral?"
] | [
"Keep in mind the LED is connected to a circuit. The electrons are pulled from one end and added at the other."
] | [
"I know this is pretty old, but I want to stress that both sides of the pn junction ARE neutral."
] |
[
"Does soda maintain carbonation better in warm or cold temperatures?"
] | [
false
] | What would be the optimal temperature for storage, and why? | [
"Colder, by far. Around its freezing point, water has the highest affinity to dissolve carbon dioxide. That's why warm soda seems to always taste flatter and has more bubbles; the carbon dioxide is bubbling out of solution very fast."
] | [
"It will hold carbonation worse in warm temperatures. When the bottle is warm, the solubility of CO2 in the liquid goes down, and the gas pressure increases. This causes it to diffuse faster."
] | [
"Storage doesn't matter. When you open it though, colder is better. "
] |
[
"Why are all particles bosons or fermions?"
] | [
false
] | Why is it not possible for a particle to be neither symmetric nor antisymetric on exchange? If a particle can have 1/2 integer spin why can't it have 1/3 , 1/4 etc. | [
"Excellent questions - the answers are very subtle.",
"First of all, let's look at your first question, why exchange has to be symmetric or antisymmetric. You may be surprised to know that It's actually a peculiarity of having 3 (actually, just of having more than 2) spatial dimensions.",
"To see why this is, l... | [
"Your second question, of why a particle can't have other spins. It's a result of putting special relativity and quantum mechanics together, actually, in 3 spatial dimensions. For the mathematically inclined, it has to do with the fact that 1/2-integer and integer spins are the only allowed representations of the L... | [
"It follows from the fact that identical particles can't be distinguished. Consider a system of two particles, with wavefunctions Ψ(x1) and Ψ(x2). The wavefunction of the system is:",
"Ψ(x1,x2)",
"The square modulus of the wavefunction is the probability density function, relating to the probability of finding ... |
[
"Please explain it like I'm five. What is the gist of the Pauli Exclusion Principle?"
] | [
false
] | I'm in a Chem 105 class and everywhere I look online explains it to me like I'm in a majors level Physics class. Help me please! | [
"Two electrons can't occupy the same orbital (energy state) and have the same spin. That's all."
] | [
"If you're in Chem 105 then you're probably 18 and not 5. This isn't explainlikeimfive, we treat each other like adults here.",
"Basically it says that two fermions can't occupy the same energy state. An analogy is if you imagine dropping marbles down into a narrow cylinder, their energy is the gravitational ener... | [
"I like this. Succinct."
] |
[
"How is the calorie content of food determined?"
] | [
false
] | How can we found the amount of energy that a human body can obtain from a given food? Can this slightly change from person to person? | [
"A calorie is a unit of energy, specifically how much energy is needed to heat one gram of water 1 degree celsius. I should note that if you're American, when talking about food, what's measured is actually a different unit, kCals, which measures the energy required to heat one kilogram of water by 1C (so one calor... | [
"Thanks, good answer. This is what I was suspecting. ",
"How much variability are we talking about? ",
"How can then we trust nutritional charts?",
"(sorry, but the access article is only through a license). "
] | [
"Out of interest, how accurate is this with materials the body can't really digest (like fibre)? I can imagine that certain things might burn quite well but give very little energy to a human."
] |
[
"How Is Light Slowed Down?"
] | [
false
] | A few years ago research results were released which showed the ability to slow and even stop light. What exactly is happening when this happens? I've browsed Wikipedia but I still have a few questions, mainly: Thanks! | [
"The slowing down of light can be undestood by assuming that matter is composed of small dipoles, like positive and negative charge on a string which act like an oscillator. Almost like a mass on a string.\nWhen light enters the medium, it drives the oscillators. And the driving frequency is different than resonant... | [
"Wow, So I got them completely inverted. The waveguide is more like things bouncing around and the refractive index is more like waves being phase shifted. In any case It doesn't sound like my scenario in 3 would happen."
] | [
"In the wave picture of light passing through a refractive medium there is the front velocity which is the Propagation of the first non-zero disturbance of the wave. This is always c just as massless particles travel at c. Nothing can slow a photon down and no valid reference frame can be constructed for particles ... |
[
"With today's technology, how fast can a human-made object go in space?"
] | [
false
] | null | [
"Sounding rockets can get to space (100 km+) in just over a minute while carrying a several hundred pound payload. The one example I can get while not at work hit 100 km in 75 seconds: ",
"https://www.youtube.com/watch?v=GLhaNd_H5bM",
". There are probably some that went a bit faster but I don't have access t... | [
"In the old racing mantra, \"Speed costs money. How fast do you want to go?\". ",
"NASA's Solar Probe mission will go just over 0.1% of the speed of light -- most of that speed comes from falling all the way down the Sun's gravity well. Helios was a probe that was launched in the 1970s and achieved 250 km/sec ... | [
"Your question had me thinking. While fastest speeds will almost always come from taking advantage of the Sun's gravity accelerating a craft, how much speed can we get \"departing Earth\" out of just the rocket engines we currently (or used to) possess?",
"Here's an exploration of a possible merged launch vehicl... |
[
"Why was it much harder to develop blue LEDs than red and green LEDs?"
] | [
false
] | null | [
"Gallium nitride (GaN), which is the material used to create blue LEDs, is hard to grow. In order to make an LED you need to make a P-N junction, meaning a layer of p-type material (positively doped) on top of n-type material (negatively-doped). \"Doping\" a material is the process of changing the carrier concentra... | [
"The light given off by a solid state device is individual photons that correspond to an energy gap. The energy gap is the 'height' that the electron falls into a hole in the emmissive layer of an LED. ",
"Blue photons have a higher energy than red or green photons. This means that you have to have a large hole ... | [
"Nah you can run blue LEDs at whatever brightness you like, everyone just started using ultrabright blue LEDs because apparently blinding blue light = \"future\" :|"
] |
[
"How come there are two planets able to support life in our solar system (counting Mars too, as it theoretically was in the past), when our star is just like any other of its class and this kind of planets are seemingly hard to find alone as far as our spectrometers can measure?"
] | [
false
] | null | [
"These kinds of planets are ",
", but they probably should be common. There has been an explosion of exoplanet observations over the last couple of decades, and we've found that there are planets of all sorts of sizes in all sorts of environments. However, it's typically easiest to detect really massive planets, ... | [
"Well, rocky planets with roughly similar gravity, and the right temperature to have liquid water may be fairly common. But the Earth's atmosphere is the result of billions of years of biological influence, so we're not likely to find a planet with a similar atmosphere unless it already has similar life on it, and ... | [
"We have no idea how likely life evolves on these planets. Anything from \"almost guaranteed\" to \"less than 1 in 10",
" is possible."
] |
[
"How long does it take to digest food? What are the major factors that affect this and how do they affect it(e.g. water, protein, fiber, carbohydrate, fat content, etc.)? Also what does the literature say about buildup of bad stuff in the intestines due to the average westerner's diet?"
] | [
false
] | I am very short on money for the coming fortnight, and haven't eaten in about 24 hours. I've been passing solid waste consistently for the past month, but today it felt like those little pelets you get sometimes, but looked like brown salsa. I'm not asking for medical advice, I'm just curious about the mechanics of why... | [
"I'll address the second part. There is no intestinal build up from food in normal, healthy individuals. Your entire GI tract is coated in very slick mucous which makes it very difficult for things to stick. Peristalsis throughout the intestines is occuring constantly, squeezing things along. "
] | [
"Two thoughts to add to what mobeilehypo gave you. Normally, about 30% dry weight of your feces is bacteria. Even if you are fasting, they are still there, and you'd still need to defecate some of them out. ",
"You also defecate out dead red blood cells. So again, even if you are fasting, they still need to b... | [
"So the new age hippy types that claim there's toxins built up in your intestine from eating meat are wrong?",
"What are your thoughts on the whole fasting for a long time and shitting out the toxins thing? I think it's internal bleeding from an iron defficiency, but I'm not expert."
] |
[
"How does deep sea life maintain the pressure to not be crushed and how does it effect their life cycle."
] | [
false
] | Man needs heavily reinforced steel to dive to the bottom, yet whales do it casually to hunt squid, while there are entire ecosystems at the bottom of the mariana trench. Excluding whales, how do these animals maintain the pressure to not be crushed, while still being able to (i assume) lay eggs. As a side question; If ... | [
"The biggest issue for us is that we need sea-level type air pressures for our respiratory system to work. ",
"Deep sea animals don't have that limitation (they rely on gases dissolved in fluid, which is in equilibrium with their ambient pressure)",
"As far as your last question - nothing is stopping us, but it... | [
"No rover is targetted at mapping that kind of area though. Opportunity has covered 30 km in 8 years, and only really observed a narrow strip of that length. ",
"James Cameron has been famously quiet about how much his little sojourn to the bottom of the Marianas Trench cost, but simply chartering the support shi... | [
"The pressure inside the deep-sea organisms is the same as the pressure outside, as long as they do not descend or ascend rapidly. Thus, they do not have to withstand pressure in the same sense that a human diver with hollow lung-space would. There is an equilibrium between their bodies and their surroundings. If y... |
[
"How can a 100 solar mass black hole be \"too big\"?"
] | [
false
] | Reading the recent news just causes me confusion, I thought the black holes at the center of galaxies have billions of solar masses? How can there be a limit? Won't stuff just keep falling in and increasing the mass? | [
"Basically they have very different formation scenarios and exist in very different places. Black hole binaries observed by LIGO are a completely different population than supermassive black holes."
] | [
"Lone blackholes that keep moving around (stellar mass and intermediate mass\n black holes) are usually small compared to the supermassive blackhole we have at center of the milky way \"sagittarius A*\"",
"The difference is supermassive blackholes like sagittarius A* are not that massive from start , their main s... | [
"Stars in the range of 100 black holes are thought to completely destroy themselves in ",
"massive explosions ",
" , before achieving the critical density. So astronomers seem to be missing a link in the sequence of stellar collapse."
] |
[
"Does drafting take energy from the car in front of you, or is it just using energy that would otherwise be wasted?"
] | [
false
] | null | [
"While this is correct, it doesn't explain why BOTH cars go faster. In addition to the effect you describe the second car creates bubble of air pressure that literally pushes the lead car forward.",
"Interestingly, NASCAR teams have recently taken to actually touching the car in front of them and pushing them, ef... | [
"Neither. You are using less energy to drive in the partial vacuum created by the passage of the lead vehicle through the atmosphere."
] | [
"I see. But would a more aerodynamic would have a smaller vacuum? Doesn't creating that vacuum slow the vehicle down?"
] |
[
"How do you measure the effectiveness of vaccines without a controlled experiment?"
] | [
false
] | Working on these of data on flu vaccine effectiveness, I had some questions about how these estimates are made. First, whats the difference between vaccine effectiveness, and vaccine efficacy? Second, this data come from studies using the described below: Under the test-negative design for influenza VE, study subjects ... | [
"The only way you could test the number of people it definitely worked on would be to purposely expose people to the virus. Hardly ethical.",
"I mean that's been done and it's considered perfectly ethical, with informed consent. ",
"But of course it's not the only way to test vaccine efficacy. You don't have to... | [
"Efficacy is basically how well it works under perfect conditions while effectiveness is how well it works in practice. A medicine can have high efficacy but if people have trouble using it, the effectiveness might be low. e.g. A drug might have a 100% chance of killing a particular virus (which makes it very effic... | [
"I don’t think you understand the system. They absolutely know if they’re vaccinated and they absolutely know what strain they’re infected with. That’s the “test” part of the “test negative design”. ",
"Edit to explain: they’re testing people with flu-like symptoms, but since there are many viruses that cause flu... |
[
"Why do some types of bread grow mould, while others become hard?"
] | [
false
] | I was chewing on some rock-hard french bread when this thought occurred to me the other day | [
"Bread going hard is due to staling. It was originally thought to be due to loss if moisture from evaporation, but staling is now understood to be a manifestation of starch retrogradation, the recrystallization, water migration out of the granules, and hardening that take place when cooked starch is then cooled. In... | [
"So if I store my bread on a refrigerator it will go stale quicker, but I would avoid mould from growing on it?"
] | [
"Yep, that's about right. Other than freezing bread, one of the best ways is to keep it in an unglazed clay pot with a lid on. It is counterintuitive but what is happening when bread goes stale is that the starch molecules in the bread are crystallizing, which requires moisture as does any mould spores. The clay w... |
[
"Why is DNA made up of adenine, thymine, cytosine, and guanine?"
] | [
false
] | It is common knowledge that DNA is what "codes" many biological functions. But why is it made up of the famous ATCG nucleobases? Is there some chemical property behind them that made them "ideal" for playing an important role in life? Was it something that occured when life was just being formed on the earth that led t... | [
"The nucleotide bases are particularly good for storing infomation. They have 3 bonding positions, 2 are used to create the main chain, the last to form a weak bond with a matching base. This makes them particularly good at storing information, being read and being copied. Other chains have some of these properties... | [
"RNA came before DNA, but since RNA is less stable than DNA (RNA has an extra oxygen which makes it prone to strand breakage) DNA became the long-term store for genetic information, while RNA is used (mainly) as a transient message in the cell. I'm not sure what you mean by \"why didn't the change from RNA to DNA b... | [
"RNA is easier to make proteins from, but a lot less stable. DNA can be coded into RNA though.",
"It's akin to a computer with RAM and a HDD. The RAM (RNA) is fast but unstable, the HDD (DNA) is better for long term storage and can be dumped to RAM for use."
] |
[
"Why do some people suffer mentally, when spending extended periods of time with other people?"
] | [
false
] | Some people can spend time with others indefinitely, whilst others need to take time away, alone, to recharge or cool off. Why is this a problem for some people and not for others? | [
"As is the case with most things in psychology, there is no defined answer that seems to totally fit as an explanation. There are two explanations I can think of for this and one is related to personality and the other is a neurological function. In short you're asking a question on what causes the social aspect of... | [
"When talking about extraversion-introversion, Eysenck's theory is one of the most popular ones.",
"\nWhat Eysenck basically said is that introverted people get aroused ",
" easily by stimuli, while extraverted people get aroused ",
" easily by stimuli.",
"\nThe effect of this is that an introvert will get ... | [
"I liked the neurological explanation, I never considered it that way. I always thought in terms of personality. ",
"So you're saying that neurologically, some people have more \"energy/stamina\" for executive functioning than others? (I say energy/stamina for want of a better word)."
] |
[
"Could the lithification process expand/shrink the original fossil size?"
] | [
false
] | Meant petrification*, the process by which fossils are formed. | [
"Fossils can be deformed, but that doesn't have anything to do with the actual process of fossilization. It's typically due to tectonic activity that flattens or shears fossils. ",
"The page you linked to is a gross oversimplification of the process by which fossilization occurs, which may be leading to your conf... | [
"Both diagenesis and lithification tend to involve dewatering and compaction. So if anything any changes in size might be expected to be reductions. Getting bigger is basically out of the question."
] | [
"Lithification is the process by which fossils are formed.",
"Ahhhh. I think you might be mistaken, and are actually asking about taphonomy?",
"Lithification is certainly one process that is very important. And there are unquestionably biases imparted to the fossil record due to taphonomy. But the reduction in ... |
[
"I read the story on the front page about Mount Fuji's imminent eruption, what global implications does this have if the eruption is as big as the say it potentially will be?"
] | [
false
] | null | [
"A quick point on reading articles about volcanoes.",
"If they use the word 'overdue', start treating it as an overhyped piece of garbage.",
"To deal with it point by point:\nWe know Fuji is active - an eruption at some point in the future is almost inevitable. We cannot at any point use the word overdue, and a... | [
"Not sure what article you're looking at. Link would be appreciated.",
"But all that has been reported is that there is a higher pressure regime under there than there has been for some time.",
"That does not mean an eruption is imminent. It also gives no information on potential eruption volume. Fuji tends to ... | [
"http://www.wired.co.uk/news/archive/2012-09/06/mount-fuji",
"This was posted in ",
"r/worldnews",
"."
] |
[
"When I cook food in the oven, what does hotter temperatures versus a longer cooking time do to the physical structure of my food?"
] | [
false
] | This is something I wonder about whenever I fire up my toaster oven. How does turning the heat up versus leaving it in for longer affect my food? Do they have discrete properties that affect the food? Or is it just a mathematical function? heat x time = heat energy radiated into my food. Could I halve the cooking tempe... | [
"Although you can sometimes tweak the temperature and time ratios in a recipe to get the same result, cooking is a ",
" process -- this means that there are some specific, critical temperatures above/below which certain processes will/won't happen. ",
"For example, meat/fish items usually have to be cooked in s... | [
"For example, meat/fish items usually have to be cooked in such a way that the entire object reaches some minimum temperature (160F, or so) in order to ensure that dangerous bacteria and the like have been destroyed. ",
"This isn't totally accurate. At 160F, bacteria die instantly. That is from what I understan... | [
"Go find and watch Good Eats with Alton Brown. He goes into the specifics of the affects of certain cooking techniques on the foods featured.",
"For instance, if you are cooking meat that has a lot of fat and connective tissue (like ribs and pork shoulder) you want to cook it for a long time at a lower temperatur... |
[
"I just read a research paper about \"downregulation of cannabinoid receptors in daily cannabis smokers\". Does that mean that cannabis actually does have a mechanism for physical addiction?"
] | [
false
] | Full disclosure, I am a cannabis smoker myself. We've always liked to tell ourselves that weed isn't addictive like caffeine or heroin that have direct chemical effects on your brain, it's just psychologically addictive like anything else you enjoy, like TV or shopping. But I recently found this study, and I'm wonderi... | [
"So there's a few things we should clear up first. The terms \"physically addictive\" and \"psychologically addictive\" are not great. They lead to people misunderstanding how addiction and dependence works. What you are calling \"physically addictive\" is the idea that when people use certain drugs for some period... | [
"To add, downregulation or desensitization of a receptor when exposed to high levels/prolonged levels of an agonist (or partial agonist as with THC) is nothing extraordinary, rather is something to be expected in the pharmacology world. The decrease in receptor number and a decrease in signaling efficacy certainly ... | [
"Why do you say nicotine doesn't cause dependence? Or are you just speaking relatively to stronger drug related dependencies? I certainly notice I become irritable and often get headaches (similar to caffeine withdrawals, but worse) if I haven't had nicotine in a while (usually about a day). I don't have a strong ... |
[
"If we could travel and c+1, what would happen if I outpaced the expansion of the Universe."
] | [
false
] | What would be in the zone that would eventually be filled later by the expansion of the universe. I realize this might be a stupid question. | [
"First, everything we know about the universe tells us that nothing can change position faster than the speed of light. If your question requires us to assume that you ",
" change position faster than the speed of light, then your question cannot be answered.",
"Second, the rate at which an object is receding f... | [
"You seem to have asked several questions at once, but I am not really sure what you are asking. What does c+1 mean?"
] | [
"This question is ",
" somewhat related to ",
"\"What is the universe expanding into?\""
] |
[
"How can quadriplegics breathe?"
] | [
false
] | I've always heard the phrase "paralyzed from the neck down". Is this really the case? If so, then how does the heart beat? And how does digestion work? I'm assuming this isn't the case, so why is it only the arms and legs that are affected? | [
"It depends on the level of paralysis. The diaphragm is innervated by the ventral roots of the cervical roots from C3/C4/C5, so lesions at or above those levels may indeed result in loss of diaphragm function, and thus require mechanical ventilators to breathe. ",
"The heart functions fairly autonomously (since... | [
"CN 3, 4, 5 keeps you alive."
] | [
"Many quadriplegics ",
"require breathing equipment",
" to force air in and out. (Injuries to C1-C2 necessitate this)",
"A large percentage of patients die due to pneumonia as they are unable to evacuate fluid from their lungs. ",
"Digestion and heartbeat are entirely separate functions, governed by brainst... |
[
"If the Milky Way collided with another galaxy, would our solar system be affected? Would Earth change?"
] | [
false
] | I've heard about galaxies colliding but due to the massive size, would anything likely happen? | [
"Generally speaking, two galaxies colliding wouldn't be a collision that you would fit in the every day sense of the word. Despite the immense amount of material in a galaxy, the density of that material is still reasonably small since it's spread out in structures with diameters on the scale of hundreds of thousan... | [
"We might get hurled out of the soon-to-be singular galaxy, or we might get hurled into the center. At worst I could imagine the gravity of a passing star disturbing orbits, I doubt direct collisions are likely, though."
] | [
"I remember seeing something about this somewhere. It was a TV show. ",
"You have to remember the distances between stars are immense. The closest star (other than the sun) to us is Proxima Centauri, at 4.24 light years away. That's 2.49248392 × 10",
" miles away (24,924,839,200,000 miles).",
"So the chance ... |
[
"How would one explain Slowing of a mechanical clock as satisfactorily as the photon clock?"
] | [
false
] | I understand how a photon clock, placed perpendicular to motion, slows down and also the fact that since one clock is slowing down all others must as time, a physical phenomenon, must behave the same. But how would one explain exactly HOW a mechanical clock would slow in relativistic conditions? | [
"You would have to know ",
" specifically how the clock works. Which is why it's much easier to just point out, hey, all clocks in a single reference frame should agree."
] | [
"The thing is, it feels like you're assuming the slowing of a photon clock is the explanation for time dilation, when it's actually the converse - time dilation is an explanation for why a photon clock will slow down.",
"The photon clock example, while relatively easy to understand, is still highly counter-intuit... | [
"This is an excellent excellent answer. I understand that dilation isn't BECAUSE of the clock slowing down, rather it's the dilation slowing the clock down. But there appears to be a very definite way in which the photon clock is slowing down however I fail to find such a mechanism behind more conventional clocks. ... |
[
"Does the removal of leaves from suburban land very year cause damage to soil quality?"
] | [
false
] | I was watching the town trucks pick up leaf piles curbside and it got me wondering. non-science person here, sorry if im misunderstanding some basic concept. Every year* | [
"Generally leaf litter is a positive contributor to soil health in a number of ways, including but not limited to:",
"Recycling elements such as carbon dioxide and nitrogen to be absorbed again by plants, and playing a part in the nitrogen cycle.",
"Providing important food to microflora and fauna, which in tur... | [
"Most likely you would be able to detect very minute changes over long spans of time (say decades) but if you look at what percentage of a tree actually comes from the soil and not the air then you would have a much better perspective. Over 90% of the tree comes from the air not the soil, this is in the carbon that... | [
"Removing leaf litter is also a recommended practice for managing plant pathogens; they tend to overwinter in this stuff."
] |
[
"Why is it so satisfying to rub our eyes for long periods of time? And why do we see all the pretty \"shapes and colors?\""
] | [
false
] | null | [
"I don't know why it's so satisfying, but the pretty 'shapes and colors' are called an 'endoptic phenomenon'. It's caused by applying pressure to the eyeball, which raises the intraocular pressure, or the pressure inside the eye which in turn affects blood flow to the capillaries that feed the retina, causing stran... | [
"That satisfying, calming feeling that occurs when you rub your eyes is due to the oculocardiac reflex. Pressure being applied to the eyeballs or the extraocular muscles can decrease an individual's heart rate. In turn, this results in a calming, relaxing sensation."
] | [
"To further elaborate on the strange shapes and colors, increasing the intra-ocular pressure stimulates the rods and cones in your eyes (the photoreceptors responsible for seeing color and brightness). As it stimulates them, it causes them to send signals to your brain perceiving the sensation of colors or shapes. ... |
[
"Why are lions and tigers considered separate species if they can produce fertile offspring?"
] | [
false
] | Isn't the ability to produce fertile offspring the defining characteristic of a species? This is why all dogs are the same species, while horses and donkeys are separate, right? | [
"No, ",
", for example, can produce fertile offspring but are different species. Same with domestic cats and several species of jungle cats. ",
"Some of the ways speciation can happen is through geographic separation (eg, migration to island) or behavioural separation (eg, one group mates in winter, other in su... | [
"Dogs and wolves are the same species, but different subspecies (Canis lupus familiarus vs. Canis lupus lupus, respectively). ",
"So speciation happens due to myriad causes, which all eventually lead to reproductive isolation. As virkon points out, this doesn't have to be inability to produce fertile offspring. I... | [
"Isn't the ability to produce fertile offspring the defining characteristic of a species?",
"It depends on your definition of a species. What you're describing is the popular biological species concept. However, that is simply one of about ",
"26 or so definitions."
] |
[
"Why we can't use supercaps as a battery alternative?"
] | [
false
] | I know that caps can provide a huge power within a short period of time, while common batteries can provide power over a long range of time. But why we can't just put a into the circuit with the supercap to make the discharge time longer and to use it then as a battery alternative? | [
"You can delay the discharge of any capacitor (or supercap) by increasing the resistance of the circuit. However, there are two things that need to be considered: "
] | [
"Batteries also have a much flatter discharge curve (their voltage stays relatively flat from 100 to 0 percent). A cap has a much steeper curve. Nothing a simple power control circuit can't rectify (hehe), but that just adds cost and complexity. "
] | [
"I think its not just about the discharge time, but also charge duration, as in amp-hours. You would need lots of capacitors to provide the same total amount of watt hours, which ends up costing lots of money.",
"This is currently done in applications where cost isn't a big factor, like the SAE's Formula Hybrid ... |
[
"Radiocarbon Dating seems the most popular form of dating objects. What are it's flaws and what other options of dating are available?"
] | [
false
] | [deleted] | [
"ACtually, carbon-14 is only used for dating relatively young things. For other methods used in archaeology ",
"this wiki article",
" is probably a good place to start. The ",
"wiki article on radiometric dating",
" covers a huge array of methods used in geology and cosmochemistry for dating older mateiral... | [
"Thanks for responding. I've read this article on radio metric dating and the flaws aren't easily detectable. Can scientists explain the flaws with the scientific methods of dating objects? Where are the objective scientists who challenge scientific methods?"
] | [
"Radiometric dating is so well tested that it is accepted in the scientific community."
] |
[
"Question about DNA phosphodiester bond?"
] | [
false
] | Hi, I'm in a microbio course right now in college, just started. I feel like my question is just an issue in wording, but here's the reading: "Nucleotides have a 5’ phosphate group at one end and a 3’ hydroxyl group at the other end. When nucleotides are polymerized, the 3’ hydroxyl group of the first nucleotide is ... | [
"Hydrogen bonding is what happens between the two complimentary stands of DNA. The phosphodiester bond in the DNA backbone is at the phosphate group. What is circled ",
"here"
] | [
"To add to the post by ",
"/u/NeuroBill",
", the 3' and 5' refer to standard numbering of the ",
" of each nucleotide. In DNA, the phosphate group connects the 3' carbon on one deoxyribose unit to the 5' carbon on the next deoxyribose unit. ",
"This is all about the covalent connectivity of a single strand ... | [
"take a look at nucleotide structure - a phosphate group attached at the 5-position of (deoxy)ribose, with the nucleobase attached to the 1-position of the ribose.\nso the monomeric nucleotide has the ribose 3' position vacant.",
"the 'diester' part indicates that two carbon chains attach to the phosphorous, one ... |
[
"I have a science presentation for inter-city middle schoolers coming up, looking for some cool ideas."
] | [
false
] | I'm a PhD student and volunteer at a Boys and Girls club. I've been asked to put on an hour-long presentation for some 10-15 year-olds, and I'm hoping to blow their socks Bill Nye style. I have a large, well-funded lab at my disposal. Initial ideas include an invisible ink station (pH dependent), some kind of liquid... | [
"When we did these science demonstrations in college we bubbled propane through soapy water in a bucket to make propane bubbles, then scooped them up in our hands and set them on fire. You get a neat little fireball mushroom up from your hand and it has that 'wow factor'.",
"If you do this, remember to soak your... | [
"Check out ",
"http://www.unitednuclear.com/experindex.htm",
" for some cool chemistry experiments (they sell the chemicals, but explain the entire procedure with no purchase necessary). I've personally done ",
"http://www.unitednuclear.com/negx.htm",
" with great results. You mix a few dry, powder reagents... | [
"Get a water cooler bottle (the giant ones) and make a 10 ft or more rail with four PVC pipes at the corners so the bottle can slide easily along the rails but wont deviate from the path of the rails. Build plywood bulkheads at either end one with a hole drilled out of the middle so the bottom end of the bottle pok... |
[
"The way, when witnessing an object fall into a black hole, it seems to slow to a halt. Does this mean that if you were to fall into a black hole, by the time you got beyond the event horizon you would have outlasted the universe?"
] | [
false
] | null | [
"The infalling observer reaches the singularity in finite proper time."
] | [
"I did answer your question. Someone hovering outside the black hole never sees the object fall past the horizon. The infalling object reaches the singularity in finite proper time. It does not see all of the universe's future."
] | [
"Ohh okay I didn't realise I would be wrong. So the time that appears to go by on the outside from the infalling observer point of view, it speeds up but not infinitely? ",
"Edit: I read up on proper time. It is the time measured by the clock held by the infalling observer. And yes, the proper time to fall in the... |
[
"Why are the boosters on the Atlas V arrayed asymmetrically?"
] | [
false
] | . Is it to help with gravity turning? | [
"Its because originally the Atlas V rockets weren't designed to accommodate solid boosters. They were added later upon request. However, the main engine section on the Atlas V has important features running down its side in fixed places (oxygen supply and electrical stuff IIRC). Therefore the boosters cannot sim... | [
"Do they adjust thrust levels, or thrust vector via gimbals to keep the center of thrust through the center of gravity?"
] | [
"So that they could attach additional boosters incrementally depending on the desired thrust. The attachments are in the same location whether there is one or five being added. These boosters control vertical thrust only, there would have been other thrusters to control the direction laterally. "
] |
[
"What exactly gives certain materials the ability to better cope with different kinds of stress?"
] | [
false
] | For example, concrete is great at handling compressive stress, but awful at handling tensile stress. Why? | [
"This is a complex, interesting question in general, but concrete specifically is very simple. Concrete is a mixture: solid aggregate bonded together with cement. Cement is weaker than concrete and the bond between the aggregate and the cement is even weaker. When you pull on concrete it breaks that bond and the ... | [
"It mostly comes down to the molecular structure of the individual material. For, example with a lot of metals, they are fairly ductile and can stretch elastically and plastically under a tensile load before they finally break. That is because the electron sharing in ",
"metals allows the atoms to slide across on... | [
"For homogeneous materials, it mostly comes down to the bonds between atoms in a material. Ceramics, which are typically good in compression and very bad in tension, are predominantly formed with ionic bonds, which are the transfer of valence electrons between two oppositely charged ions. This makes the bond very v... |
[
"How do the proteins that manage RNA and DNA know exactly what to do without having their own DNA?"
] | [
false
] | They make RNA, replicate, etc... but how can a simple protein be able to know and do all those complex cells without having any organelles or anything? | [
"This is a great question!",
"The simple answer is that there are many many many proteins involved in these processes. Thousands and thousands. ",
"Each performs a very specific function. For example, in DNA replication, you have initiator proteins, primases, RNases, DNA helicases, DNA polymerases, each of whic... | [
"Hey! It's nice to see my comment reached someone!",
"I know there's a bit of confusion in the responses to your comment so I'll try to put things straight a bit. Like ",
"/u/arrein",
" says, there are about 20,000 coding genes (give or take). But ",
"/u/happytime1711",
" isn't wrong! ",
"It's not at al... | [
"While there are some other good answers already here, I thought I'd try to stay as much on topic of your question as possible. ",
"without their own DNA?",
"Every protein is encoded by DNA, transcribed to RNA, and then translated into a long chain of amino acids that eventually adopts a three-dimensional shap... |
[
"How long would it take to upload/download 1 gig of data to/from a mars rover?"
] | [
false
] | Basically I'm wondering what kinda bandwidth NASA is working with when sending and receiving transmissions to satellite probes and such. | [
"http://www.msnbc.msn.com/id/4269545/ns/technology_and_science-space/t/mars-rovers-get-bandwidth-boost/#.Tr6V2VaGWvk",
"Post-February: 256,000 bits per second; (1 gigabyte) / (256 000 bits) = 33 554.432; 33 554.432 seconds = 9.32067556 hours = 0.388361481 days",
"Pre-February: 128,000 bits per second; (1 gigaby... | [
"You forgot propagation delay. The first bit takes:",
"(225 million kilometers) / the speed of light = 12.5086536 minutes",
"to reach earth (according to google calculator). ",
"Where 225 million km is the average distance between Earth and Mars according to this: ",
"http://www.universetoday.com/14824/dist... | [
"but it will significantly lengthen the time taken to transmit the data.",
"This is highly doubtful, unless you have sources to back it up. NASA engineers are not idiots, and most likely will know better than to use standard TCP on an interplanetary connection.",
"Reasons why acknowledgements might not signific... |
[
"Does it take more energy to open a door when applying force close to the hinge?"
] | [
false
] | An interesting question which caused a on Stackexchange. Assuming an ordinary hinged door (M=3Kg, L=1m), would it take more to open it when applying force in the middle of the door (point b: r=50cm), rather than at the end of the door (point a: r=100cm), where the door knob is? What about the situation where you forcef... | [
"It requires the same amount of energy to move the door, but it's 'harder' for a person to apply the force required when you get closer to the hinge. It takes more energy for a person to create a large force over a short distance than it does for a person to create a small force over a long distance. This is specif... | [
"Energy consumed is the same assuming the distance opened is the same. The force required to open at different points of the lever are different and decreases as you move away from the hinge. Remember that energy in this scenario is work applied over a distance. Closer to the hinge the amount of force required i... | [
"Ignoring friction. The only thing that happens when you put more energy in the door is that it will move faster. It doesn't matter where you insert the energy.",
"\nIf you push closer to the hinge you apply more force over a short distance. But when you push farther from the hinge you apply less force over a lar... |
[
"What exactly is Anti-Matter?"
] | [
false
] | I have seen some YouTube videos but really couldn't grasp what exactly antimatter was. Any explanation would be awesome. | [
"Both neutrons and antineutrons have charge 0.",
"The opposite charge thing is just ONE of the differences between matter and antimatter. It's usually given as the only difference in ELI5 explanations. ",
"There are some other, more complicated differences between matter and antimatter.",
"For example, a neut... | [
"Both neutrons and antineutrons have charge 0.",
"The opposite charge thing is just ONE of the differences between matter and antimatter. It's usually given as the only difference in ELI5 explanations. ",
"There are some other, more complicated differences between matter and antimatter.",
"For example, a neut... | [
"Matter that has the opposite charge on its particles. So it would contain a positive electron. (A positron) *along with all the atom's other subatomic particles"
] |
[
"If electrons had a spin of 3/2 instead of 1/2, why would there be 4 Pauli-slots for different spin orientations instead of 2 for a given set of n,l,m numbers? Intuitively I would still think there are 2, +3/2 and -3/2."
] | [
false
] | null | [
"A spin of 3/2 can have a projection along any given axis of +3/2, +1/2, -1/2, and -3/2."
] | [
"Okey, thanks. Whats the theoretical explanation for that?"
] | [
"If the spin is J, the projections are -J, -(J-1), ..., (J-1), J. So (2J + 1) total.",
"For J = 3/2, that’s 4."
] |
[
"Mars has little atmosphere while Venus has a very thick atmosphere yet both planets don't have a magnetosphere. Why?"
] | [
false
] | From my understanding a planet that has no magnetosphere will eventually have their atmosphere stripped away due to solar winds. Both of these planets have no magnetosphere but are complete opposites from one another. Whats going on here? | [
"Due to Venus' lack of magnetosphere, it is currently experiencing significant atmosphere loss. As to why it has more of an atmosphere than Mars in the present day, I would expect it to be a combinations of:"
] | [
"Volcanic activity usually suggests a liquid core, but there are three requirements for a planetary core to act as a dynamo: conducting liquid, rotation, and convection. It's thought that because the first two requirements are satisfied (though the rotation is slow), that there's no convection. We aren't sure of ... | [
"Wouldn't volcanic activity imply an active core, which would generate a magnetic field?"
] |
[
"Is it possible that some virii are created from mutations in the replication of DNA in more complex life forms?"
] | [
false
] | null | [
"I would just go with 'viruses'.",
"What you're describing is the escape hypothesis, which says rather than viruses having developed before complex and truly reproductive capable DNA holding organisms, viruses are the result of the escape of some lower bound threshold of replication capable components that could ... | [
"Virii is what's known as a ",
"hypercorrection",
". The correct plural is viruses."
] | [
"Thank you."
] |
[
"Do changing magnetic fields induce current in the air?"
] | [
false
] | Title says it. Changing magnetic fields can induce current in nearby conductors so there should be a minimal amount of it in the air everytime a magnet moves around. Is that correct or do the currents possibly cancel each other out? | [
"Air is a really bad conductor."
] | [
"Air isn't a conductor. If you took a general physics class, air is modeled accurately when looking at dielectrics in capacitors. Air is a dielectric with permativity of e0. ",
"The most that happens is momentary polarization."
] | [
"Lightning can happen because it ionises the air, enabling the flow of electrons."
] |
[
"Is there a way to tell the charge remaining on individual batteries?"
] | [
false
] | null | [
"Do you mean the state-of-charge remaining in the batteries? I think you may be able to estimate it from the open circuit voltage based on discharge curves."
] | [
"You can measure the potential difference and current between two batteries quite easily given a known resistance. I'm curious as to what you mean by \"",
" remaining on individual batteries\"? Also your definition of \"battery\" if you don't mind."
] | [
"For example, if I have a remote control that stopped working, would there be a way for me to tell which battery lost charge more?"
] |
[
"I've heard that we can't see the atom and will never be able to. Is that true? If so, why?"
] | [
false
] | The exact phrase was "it's not about technology, we just can't see the atom directly and will never be able to, despite all the technology that is available to us now and will be available in the future". | [
"It really depends on what you mean by \"see.\" If you mean see with the unaided eye, then no we cannot. If you mean unambiguously detect and visualize, then we can.",
"https://www.physicsforums.com/insights/can-see-atom/"
] | [
"We can't 'see' atoms with wavelengths our own eyes are sensitive to. We never will because the diffraction limit of visible light is still much larger than a single atom, no matter how powerful your microscope. ",
"We can use other technology to 'see' atoms by having a computer interpret the results from say ele... | [
"Yes, they do interact with atoms in a practical way. X-rays are diffracted by electrons, so you can use them to study the structure of crystals. ",
"X-ray crystallography",
" is an extremely powerful tool for that. But again, you do not directly \"see\" atoms with that method, but rather some ",
"interferenc... |
[
"At what ratio of salt to water does it cease to be hydrating?"
] | [
false
] | [deleted] | [
"Which is about a 3% saline solution (for reference, a 0.9% saline solution is isotonic, which means it's equivalent to the osmolarity of your blood which is important so your cells don't lyse [explode] or crenate [shrivel]), or 3 grams of salt per 100 ml water. "
] | [
"Which is about a 3% saline solution (for reference, a 0.9% saline solution is isotonic, which means it's equivalent to the osmolarity of your blood which is important so your cells don't lyse [explode] or crenate [shrivel]), or 3 grams of salt per 100 ml water. "
] | [
"If you are thirsty, you aren't supposed to drink stuff like salt water and soda because the salt will actually make you more thirsty. OP is probably asking the maximum level of saltiness such that you will be less thirsty."
] |
[
"Where does the heat in our bodies come from ? Are we generating heat intentionally or is it a byproduct of our internal activity ?"
] | [
false
] | [deleted] | [
"to add to prior comments, we also have '",
"futile cycles",
"' with the sole purpose of maintaining a core temperature. these futile cycles are regulated by varying the concentrations of the products or substrates, allowing temperature to be modulated. "
] | [
"ATP (which is the chemical used to provide energy in many cellular reactions) breaks down to provide the energy from its bonds. For many cellular processes, the match up between energy released by the ATP and the energy actually needed leaves a little left over which is 'heat'. Also ATP can be broken down without ... | [
"This is why wrapping yourself in a blanket does not actually \"warm\" you, rather, it merely keeps more of your own body heat closer to you."
] |
[
"Why is it that when you hear yourself on a recording, you sound different than what you thought? Also, which one is what you actually sound like? What you hear when you talk, or what you hear on a recording?"
] | [
false
] | null | [
"When you talk, part of what you are hearing is the vibrations through your facial bones. When you hear others (or a recording of yourself), this component is not present.",
"If you record your voice on a high quality recorder, what you hear from the recorder is what other people hear."
] | [
"Would that mean that it's impossible to just hear it the way other people hear it without it being a recording? Because I hear myself sometimes and it sounds like it does on a recording. Sometimes just randomly while speaking, but I can also specifically listen and hear it the way I assume other people are hearing... | [
"Yes. \"Bone-conducted\" vs. \"air-conducted\" sound. When you hear yourself speak, you are receiving input from both sources, when you hear a recording, you are only receiving the air-conducted source. There is actually a certain type of hearing aid which is sort of a vibrating implant. It can help people who have... |
[
"Do the meals you eat always get expelled in the same order?"
] | [
false
] | This question came up when I was considering people who hide small objects by swallowing them. Can they somehow prolong how much time that object spends inside them? Maybe by eating it with something oily? | [
"I dont entirely agree with this answer and find it too simple. The lumen of the gastrointestinal tract is not completely full nor are its contents entirely solid. Moreover, the different constituents of your food are all digested at different rates depending on voluntary and involuntary mechanical digesting and th... | [
"To answer your title, for the most part things get crapped out in the same order the get consumed. There might be a bit of leeway here and there (say, having a solid breakfast and a liquid lunch and having the liquid slide by the solids), but for the most part more recent food just pushes the food that was ingeste... | [
"Since the gut is a simple long tube, there is no anatomical means for today's lunch to bypass today's breakfast (if that is what you mean)."
] |
[
"If Nitrogen is the most abundant element in our atmosphere, why did organisms adapt to breathe oxygen instead?"
] | [
false
] | If Nitrogen is the most abundant element in our atmosphere, why did organisms adapt to breathe oxygen instead? | [
"First thing is that O2 has a lot of free energy available in the context of O2-->H2O. Life gets energy by very regulated transfers of electrons to terminal electron receptors like oxygen, and electron transfers tend to be in the form of pairs of electrons, usually accompanied by a proton. This works well for oxy... | [
"It's much harder to make a living on N2 than O2, because N2 is so much less reactive because of its strong triple bond. However, there are ",
"nitrogen fixing bacteria",
", which take N2 out of the air and convert it to ammonia, which is then used for other purposes."
] | [
"There are organisms that get by on far less favorable redox couples than that of dioxygen. The main impediment is not the smaller energy gain from the reduction of ammonia, but rather the incredibly high activation energy. ",
"Organisms that utilize dinitrogen don't use it as a terminal oxidant, as you said, a... |
[
"Why is carbon the element that all organisms have in their organic molecular structure?"
] | [
false
] | I want to know why carbon, why not some other element. What makes carbon special? | [
"Well, molecules based with carbon can form ridiculous numbers of variety from the same constiuent species. They chain together in repeating (or nonrepeating) units that can be broken at room temperature. DNA, the code for all known life, (unless you want to be pedantic and count things that soley use RNA) is a h... | [
"Carbon has four valence electrons; ",
"forms chains easily",
"; and makes stable molecules with abundant elements like hydrogen, oxygen, and nitrogen.",
"According to ",
"this article",
", silicon can form chains but they are reactive with water so they wouldn't survive on Earth. Phosphorous can form lon... | [
"It is hypothesised that other forms of life on other planets could be based on silicon and the likes, but it just so happens that where we live the atmospheric conditions favour carbon. There was alot of 'behind the scenes' carbon-chemistry happening early on in the development of our planet though, long before th... |
[
"Does the Heisenberg Uncertainty Principle describe a literal or figurative effect?"
] | [
false
] | At the most basic level, the Heisenberg Uncertainty Principle is usually described as observing something changes it. Is this literal, as in the instrument you use to observe it bumps it and changes its velocity/location etc? Or is this a more woo woo particle physics effect where something resolves or happens by the s... | [
"Your statement of the \"most basic level\" for the uncertainty principle is the heart of your misunderstanding. You cannot take this at the most basic level. You gotta stop thinking about very small objects as particles. They are wave-particles, and the uncertainty principle arises from the wave nature of matter."... | [
"At the most basic level, the Heisenberg Uncertainty Principle is usually described as observing something changes it.",
"That’s not an accurate description, maybe some pop science articles say that but no actual physics lesson would. ",
"The Heisenberg uncertainty principle is a simple truth about how wavefunc... | [
"The neat thing about the HUP is that it goes for ",
" waves, not just quantum mechanical particles. Take a simple sine wave extending forever. It's made up of just one frequency, but is so very spread out that you can't pin down one single location and call it \"the wave's position\". Frequency is well defined, ... |
[
"Every time I put gas in my car, the tank isn't completely empty. Does that mean there is a trace of gas from the very first fueling in it?"
] | [
false
] | Although incredibly diluted, is there any reason that some gas from the very first fueling of the car isn't in the tank? | [
"It doesn't matter whether you're talking classical or quantum physics. The impossibility of telling two identical molecules apart doesn't change the actual probabilities in the calculation he gave above. So the question as asked can be answered very easily: ",
"No, the fact you don't fully empty the tank doesn'... | [
"That is interesting and wanders off into quantum teleportation in fairly short order.",
"I'm reminded of an essay called ",
"'What colour are your bits'",
". This byte here is from a blockbuster movie and is unquestionably the property of the copyright holder. This ",
" byte is from your rather shabby fanf... | [
"Well you could perform a hypothetical experiment with isotopically labelled fuel which would be fairly close to identical."
] |
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