title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Could you use thermochromic ink for tattooing?"
] | [
false
] | I saw this and it made me wonder about putting it into the dermal layer of skin: I've heard that early (pre-1800's) Japanese body suits used to have color changing properties. | [
"Why wouldn't the same approach with pmma work here?"
] | [
"No - you can't. Thinks get a little tricky when the ink has special properties. Remember UV reactive ink? The first to come out turned brown. They finally found a solution - but it was to encase the ink in pmma - this allowed the ink to not come in contact with skin / body fluid.",
"Anyway, look at the chemical ... | [
"Because the mix of chemicals - the lab that makes the pmma inks here in the US said it would require significant advancements in encapsulation technology. ",
"Believe me they want the money - if they could deliver even a marginal, body safe product, they would."
] |
[
"Is it possible using software to determine the hardware circuits of a computer system?"
] | [
false
] | [deleted] | [
"Unfortunately no - and it's the same problem we have with our own reality. :) ",
"With any instruction you execute, the response returned may only be what the emulator you didn't/ couldn't know was running wants you to know. "
] | [
"No, not even what you said. A computer can quite easily lie about quite a few things, and often does for backwards compatibility reasons.",
"There's nothing that says that a computer must allow software to interrogate it about its capabilities, either. It's perfectly possible to have a computer that has no strai... | [
"The software wouldn't know that it was indeed controlling a robot, rather then just being run on an emulator that emulates results from the \"robots\" investigation."
] |
[
"Youngest person to achieve atomic fusion: what has he actually done?"
] | [
false
] | If you haven't seen it in the news here is a link: I understand the basic principles of fusion, but how is this different to what governments are spending billions on? If it's so easy why aren't more people doing it? | [
"Fusion is easy, trivial even. But that's because it's easy to \"cheat\". Particles are small, by putting enough energy into small particles you can initiate fusion. One simple way to do this is to accelerate deuterium nuclei into deuterium or tritium nuclei. You can do this in a handheld device that runs off of wa... | [
"I would first point out that the article says atomic fusion. Bad word choice, it should be nuclear fusion.",
"People have been doing nuclear fusion since the 1930s. It is actually is pretty easy to do. In the most basic definition, I can take a source of Am-241 and aluminum and create nuclear fusion since the... | [
"Actually, making a fusion reactor is ",
"surprisingly easy",
", as ",
"Taylor Wilsen",
" will attest. The thing is, these reactors require loads more power than they put out, meaning you can't use them to generate energy. The ultimate goal of programmes like ITER is to change this, as once you have a viabl... |
[
"How accurate is radiometric dating? and other questions. Details inside."
] | [
false
] | I was reading through an article about the theory of young earth . (Someone linked it in an ) In the 15th citation they mention that radiometric dating is very unreliable. They reference a scientist, Claus Rolfs, and his paper . I tried searching around and I couldn't find much discussion about this actual paper or what he actually proved in his research. I do not want to start a discussion bashing the afformentioned young earth website (even if it is lunacy). If you want that I'm sure would be happy to have you. I'm just curious on how they twist science to meet their ideas and preconceived notions. Can someone explain radiometric dating and give insight into Rolfs' work on the subject? Maybe expand on how it could be misconstrued to fit the young earth believers theories. | [
"A quick note first is that New Scientist is not a peer-reviewed article. So I will disregard this article. The research by Rolfs et al. was published here ",
"http://iopscience.iop.org/0954-3899/32/4/007",
" . Looking at this in isolation it looks interesting. The problem is however that other groups have look... | [
"There is going to be a lot of terminology involved so bare with me regarding definitions.",
"Radiometric dating is defined (by Wikipedia) \"is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay ... | [
"Good response. I would only point out that U",
" has a half life of 700 million years, but U",
" has a half life of about four billion years."
] |
[
"Basics of Speaker Design"
] | [
false
] | So far, I modeled the diaphragm of a speaker as a 2nd order spring damping mass system - and to maintain constant SPL (flat response in the human audible frequency range),the ideal diaphragm should have small mass & spring constant. What are some other factors to consider, and what makes a good speaker? What's the difference in approach between say like Sennheiser and Bose? Are there standard principles they follow? What exactly do audiophiles consider before buying audio equipment? Thanks | [
"Well, you were right to start with the barebones physics. Thiele and Small's research will give you more information on that should you wish to find it. They created equivalent circuit designs to model the mechanical and electrical behavior of speakers, like how the suspension of a speaker acts like a capacitor an... | [
"Lord knows I'm not going to get into the actual physics, but I will say this: Sennheiser don't make \"speakers\" - not room speakers, anyway :). ",
"Bose use a special engineering technique called \"Spending a ton of money on marketing\". Really, I would not be looking to Bose for speaker design tips. Their sate... | [
"Here's a model of speaker impedance I've seen used in several places:",
"---(R1)---(L1)---(R2,L2)---(R3,L3,C1)---\n",
"where objects within parentheses are in parallel with each other, and groups connected by --- are in series.",
"R1 is the voice coil DC resistance, typically about 80% of the quoted speaker ... |
[
"Is Felix Baumgartner actually going to go supersonic, or is he just going to break the speed of sound at sea level?"
] | [
false
] | null | [
"Take a look at ",
"this graph",
". The speed of sound is significantly lower in the regions he'll be falling through."
] | [
"Good ",
"article",
" about the whole setup.",
"Says he will reach 690 mph after forty seconds but will not experience a sonic boom because the air is so thin."
] | [
"Thanks, that's exactly what I was looking for. Also, to clarify, the article states he WILL experience one, but the air is thin enough that it will be insignificant in damage and won't be a problem (...hopefully)."
] |
[
"Would I weigh the same if there was no atmosphere above me?"
] | [
false
] | [deleted] | [
"Any object immersed in a fluid experiences an upward (bouyant) force equal in magnitude to the weight of the fluid displaced by the object.",
"The atmosphere will provide a small upward force and make you weigh slightly less than you otherwise would. In a more dense fluid you'd weigh even less.",
"Say a human ... | [
"This is wrong. Pressure is force applied equally over all sides. Gauss's theorem can be used to show that this exerts no net force on a body."
] | [
"Gauss's Theorem only applies for infinitely small bodies though, the left/right front/back components of pressure on a body would be equal magnitude but the up/down would differ. This is what provides the buoyancy force skeesicks has described above."
] |
[
"If the coronavirus (or any virus for that matter) is so contagious and can be found on surfaces or in the air for long periods of time, then why do you need to swab so deep in your nasal cavity?"
] | [
false
] | I have not personally had a test for COVID-19 but I have seen the procedure. The swab seems to go much deeper than that of a standard flu test. If the virus can be found in most of our mucus membranes why do they need to swab so deep? | [
"You only need to inhale a handful of virus particles to catch the disease. Since the virus reproduces inside you, after a few days that handful becomes trillions. ",
"However, the test isn't sensitive enough to pick up tiny quantities of virus, and the virus does not reproduce in the test, so they swab where the... | [
"To continue this, our current PCR based tests tend to detect SARS-CoV-2 at around 250 genetic copies per mL. The earlier tests needed upwards of 2-3000. The LabCorp test that everybody was sending away for that took a week to come back is actually abysmal. So now they're looking at how well nares or oropharyngeal ... | [
"We use real-time PCR, rather than waiting for the PCR to run a set number of cycles (using fluorescent probes or PAGE and Southern blot to detect the product). We use fluorescent tags during the PCR and count the number of cycles before seeing a threshold. So the whole process goes way faster. We also use engineer... |
[
"How would I find the amplitude of the membrane of my kazoo?"
] | [
false
] | I have a cheap plastic I was messing around with when the question came upon me. I'll explain how it works briefly. The kazoo is a pipe you hum into. This causes a membrane (wax paper in my case, I think) to vibrate sympathetically and produce the unique sound. Let's say that I'm humming at 440 Hz and the wax paper has a diameter of .01m. How far up or down will the middle of the wax paper go? (Bonus: does this distance change based on the frequency?) I'm not sure how to approach this problem. | [
"Attach a tiny mirror to the membrane, perhaps use a fleck of aluminum from a shattered CD. Bounce laser off buzzing mirror. Measure peak-to-peak excursion angle, calculate amplitude."
] | [
"440 Hz is the A above middle C"
] | [
"440 Hz is the A above middle C"
] |
[
"What's the difference between Cocaine and Crack Cocaine, and what's a freebase?"
] | [
false
] | [deleted] | [
"The Cocaine white powder you are familiar with exists in the salt form of Cocaine Hydrochloride (Coc-H+Cl-).",
"Crack Cocaine is a free base, or conjugate base (deprotonated) form of Cocaine. It can be synthesised from Cocaine as such: Coc-H+Cl− + NaHCO3 → Coc + H2O + CO2 + NaCl",
"Furthermore, Crack vaporizes... | [
"Crack is not a concentrated source of cocaine. You can't get any more out of what you start with, so if anything it's less. This rumor might exist because smoking crack is likely going to give someone a much more intense high than smoking cocaine, but only because free based crack won't burn the active molecule be... | [
"A lot of sources say that crack is a concentrated form of cocaine. \nCan you explain how combining cocaine with sodium bicarbonate (baking soda) causes the cocaine to be concentrated?"
] |
[
"Is there any scientific facts that back up this \"Superbrain Yoga\" phenomenon, or is all placebo effect?"
] | [
false
] | Here is a web page on it with a video: Of course, I'm already skeptical given that it is on a homeopathy site, but the video is of a local Bay Area newscast, which lends at least a bit of credence to the claims. Basically, you grab your earlobes and do squats. They interviewed doctors, teachers, etc. that say the people they work with "get smarter". Thanks. | [
"It seems safe to say, there is no scientific research to back it up. Searching pubmed finds no articles for \"superbrain/super brain yoga\" or variations. It seems relatively accepted that exercise has a causal link with overall brain function (personally not an expert) and some ",
"meta-studies",
" seem to ... | [
"You may want to try ",
"r/skeptic",
" for this; however, I would venture that there is little evidence that supports 'superbrain yoga' outside of any benefits usually associated with exercise. "
] | [
"If you cannot clarify your answer in excruciating technical detail, don't answer at all. This is to reduce layman speculation, which is generally not helpful."
] |
[
"If I plant two genetically identical acorns will the trees look the same or is the shape of the trees random?"
] | [
false
] | [deleted] | [
"Phenotype is a combination of genes and environment. If they had ",
" the same environmental conditions and genes (also factoring in random mutations through replication), they would look the same, but even a tiny difference can add up to a lot."
] | [
"It's even harder. Even with identical conditions, the genetically identical acorns themselves will still harbor internal differences -- as will the details of their planting sites. Since these lead to differences in the first weeks of life, they can still profoundly change the resulting tree."
] | [
"Lots and lots of the 'individual' plants you see day to day are clones of one another -- that is they share the same dna. And they grow at different angles and rates and with different branching patterns. So, neither, really. Which makes them unlike animals. They do this because plants are modular, with differ... |
[
"Does the holographic principle imply that the maximum information (in bits) contained within a spherical region of space must be less than or equal to its surface area in Planck length squares?"
] | [
false
] | I recall reading something to that effect somewhere, but the doesn't explicitly say that's the case, just that the maximum information is proportional to the surface area. | [
"Yes it does imply exactly that (or if not exactly that, then it's certainly proportional to the surface area, not the volume) and here's why.",
"Thermodynamics' second law says that entropy in a closed system must always increase. But what of black holes? Is it possible that they somehow could be used to violate... | [
"Just going by what I read in the Wikipedia article, doesn't it mention it as at least 4 times the area, given Hawkings constant of proportionality ?"
] | [
"Thanks for not deleting it, although I know nothing about physics I enjoyed reading this."
] |
[
"How can light travel in a vacuum?"
] | [
false
] | null | [
"The electromagnetic field exists everywhere, including in the vacuum of space (or any other vacuum). If there's no light, or EM radiation, at a particular location then the field has no energy there, and basically sits still. If there is light, this manifests itself as waves through the field. Since the field exis... | [
"It depends on the wave. Waves need a medium to travel through. With light, that medium is the EM field. Since the EM field is present even in a vacuum, yes, the waves can travel through a vacuum. ",
"Something like sound waves travel through air though. Since, pretty much by definition, there's no air in a vacuu... | [
"It depends on the wave. Waves need a medium to travel through. With light, that medium is the EM field. Since the EM field is present even in a vacuum, yes, the waves can travel through a vacuum. ",
"Something like sound waves travel through air though. Since, pretty much by definition, there's no air in a vacuu... |
[
"Could any plants grow anywhere on Mars?"
] | [
false
] | [deleted] | [
"It would be difficult for plants that reproduce sexually to spread, but simple plants like algae, and even some colony organisms like lichens might find suitable conditions in isolated locations.",
"As for flowers and trees, the conditions on Mars are extremely dehydrating. They would quickly freeze and lose th... | [
"The main problem would probably be atmospheric pressure. The place on Mars with the densest atmosphere has about 1.2% the pressure of Earth's surface. I'm not sure what that would do to a plant but given that surface water isn't stable at that pressure, and multicellular plants need to do a certain amount of eva... | [
"It is believed some extremophiles could adapt to Mars and live comfortably. They've been tested in simulated conditions in labs. It's something being considered by terraformers. As far as we know it would be essential for setting up a carbon cycle. The problem we run into is what would happen to any native life we... |
[
"Why is mad cow/CJD transmissible to humans, but deer chronic wasting disease and scrapie is not?"
] | [
false
] | null | [
"The protein responsible for mad cow disease is, due to its structure, able to bind to some forms of the natural human prion protein and catalyse its conversion to the pathogenic form. Proteins responsible for other prion diseases in animals don't have the same affinity for human prion proteins. Answering in terms ... | [
"Most “why” questions are actually “how” questions in disguise. The difference is in adopting the intentional stance instead of the design or physical stances when thinking about the problem."
] | [
"It’s likely cows eating scrapie infected meat led to prion disease in the cattle. So scrapie —> bovine spongiform encephalopathy —> vCJD in people. So almost like an indirect affinity?"
] |
[
"What is the difference between low-end and high-end vodka, chemically speaking?"
] | [
false
] | [deleted] | [
"Ethanol is ethanol. The source won't change the taste of the ethanol itself, just the impurities."
] | [
"Here",
" is something that sums it up a little better than I can, but there are basically two parts to what makes a \"high end\" vodka. Part one being the recipe/method in which it is brewed, part 2 being the manner/number of times in which it is distilled. The more times it is distilled the closer it becomes ... | [
"So when I mixed lab grade ethanol with lab grade water it was the best vodka ever created?"
] |
[
"Why is pre-fission uranium relatively harmless to humans but spent nuclear fuel must be locked away for hundreds of years?"
] | [
false
] | [deleted] | [
"Think about how nuclear fission works. You take heavy atoms and split them. The original uranium (U-235/U-238) used in a typical water reactor is a relatively weak alpha emitter overall. ",
"When you split uranium, you get two or three smaller fission products. There is a distribution of products that you can ge... | [
"To add a bit more to this, it's not just that the smaller atoms are less stable and more radioactive, it's that their modes of radioactive decay involve the release of much more beta and gamma rays than uranium gives off. Those beta and gamma rays require FAR more shielding than alpha rays require.",
"The stora... | [
"Once the uranium nuclei have undergone fission, they are no longer uranium nuclei. Fission reactions produce many lighter nuclides, many of which will be unstable.",
"Spent nuclear fuel contains some of these radioactive fission products. They need to be stored for a long time so that these radioactive fission p... |
[
"System Neuroscientists: What are your thoughts on people with magnetic implants who claim to \"sense\" magnetic fields?"
] | [
false
] | Related to this AMA: Maybe I'm missing something, but I cannot conceptualize on a physiological level what it is about a subdural magnet that generates transduction in the mechanoreceptors. Any peripheral nervous system neurophysiologists want to chime in here? | [
"I am not an electrical engineer or a physicist, so take what I say with a grain of salt.",
"We know that mechanoreceptors respond to pressure and vibration. This means that if you have a magnet in your fingertip (subdermal, so underneath the mechanoreceptors in your skin) and you approach another magnet, it make... | [
"So then it is the vibration of the magnet that compresses/extends the cellular membrane of the mechanoreceptors in order for transduction to occur. I suppose that makes sense...except that the percept generated from, say, shifting magnetic fields generated from an AC current would do nothing but vibrate the magne... | [
"I think they are maybe using overly generous language when they are discussing the perception provided by these magnets. I don't think there is any neuroplasticity or cortical re-wiring going on, I think its just that they are capable of sensing these vibrations in their fingertips. It makes sense to me that you c... |
[
"Why is Xenon used to power ion thrusters instead of other noble gases?"
] | [
false
] | null | [
" It's the heaviest noble gas. It is also the easiest to ionize. ",
"The fact that it is the easiest to ionize is pretty easy to understand. You have to spend less energy turning the gas into plasma which is good for the efficiency.",
"So now the question is why would you want a heavier particle? People who are... | [
"I might have missed it as I’m reading on a phone, but another huge reason the heavier mass of Xenon relative to other noble gasses is that the larger atomic mass makes it easier to store a larger mass of propellant.",
"The pressure exerted by an ideal gas is P=nRT/V - so a mole of helium stored in any given volu... | [
"You are totally right. As far as I know xenon is stored as a supercritical fluid around 150bars. So the ideal gas law doesn't quite work. I just checked on wolframalpah and it gives you about 2 kg/l for xenon. In the same conditions krypton is around 0.73 kg/l, argon 0.27 kg/l and helium 0.023 kg/l."
] |
[
"Why do muscles fatigue in a static pose if no work is being done?"
] | [
false
] | I've got ideas about why this might be the case, but I wondered if anybody could explain this to me. If I take a plank of wood, shove it in a wall such that it acts as a cantilever, and hang a weight off the end, I can be pretty sure that it will stay there indefinitely. Nothing is moving, hence no work is being done (beyond the initial deflection). If I take a bag of heavy stuff and hold it out to one side, I'll be able to hold it for a while, but eventually my arm will give up. What, biologically, is it about muscles that doesn't allow them to hold a stress for large periods if nothing is moving. Why is my body getting exhausted when there is no physical work being done? Am I misunderstanding something fundamental about the situation? | [
"The plank of wood is in a stable configuration. Although while acting as a cantilever there is tension and therefore stress on the bonds between lignin fibers and other structural aspects of the wood, there is no net input of energy to keep it rigid.",
"Your muscles require a net input of energy to maintain even... | [
"great answer. Just to add on as a side note, one of the notable differences between skeletal muscle and smooth muscle, such as that of the gastrointestinal tract and blood vessels, is that it is capable of \"locking\" into place and not require any more energy input. This is one of the aspects which makes smooth m... | [
"Hm, I thought that in the contraction of the actin-myosin filaments, the binding of ATP caused the detachment of the filaments and that the depletion of ATP would then result in the inability to detach, such as what we observe in rigor mortis.",
"Would i be wrong to say that this is related to the fact that when... |
[
"Why isn't garbage utilized more as a source of power?"
] | [
false
] | null | [
"Sweden is doing this, but was so efficient at reducing trash production, that they have had to import garbage, as reported ",
"here",
". Oslo has had ",
"this problem",
" as well, as have other places in northern Europe."
] | [
"Because fossil fuel corporations control decisions involving the energy industry"
] | [
"In short, economics. Trash is not free. There is a processing cost and collection costs. As a result you have to look at whether your cost per therm of energy is higher or lower than a different fuel source. As a simple comparison, natural gas (by my rough number crunching) has an energy density nearly 4,000 t... |
[
"Is lava flow laminar?"
] | [
false
] | I came across this video, and the question popped in my mind, like a giant, red, burning and deadly pimple: | [
"In theory, it can be either, but what we see in Nature on Earth today is ",
" very often laminar due to a relatively high viscosity (e.g., >1 Pa-s), low speed (e.g., 1 m/s) and small lateral scale (e.g., 1 m). These combine to give a ",
"Reynolds number",
" on the order of a thousand and often far less; the ... | [
"This is counter to what is discussed in literature on the fluid dynamics of lava flows, e.g., the rather comprehensive review by ",
"Griffiths, 2000",
" which discusses that lava flows can be both laminar or turbulent (and both are observed) and the state depends critically on the both the composition of the l... | [
"Turbulence is dependant on the Reynolds number (Re = rho * V * L / mu ) which is the ratio of inertial and viscous forces.",
"The higher the Re, the more turbulent the flow is, so velocity definitely plays it's part."
] |
[
"How can we determine what dinosaurs looked like based just on the bones?"
] | [
false
] | I got into an argument with my friend who claimed that it was just guessing, and i don't know nearly enough about the process to make a valid argument against him. So basically the question is, how can we determine the skin type, organs, etc just from the bone structure? What process is used to determine these things? | [
"Well, \"just\" from bones we have gotten a lot of stuff wrong. If you go look through some of your \"old\" (like 90s) textbooks on dinos, you can see that how they look over time has definitely evolved. People probably have even put bones of dead dinos found near each other together, giving some really interesting... | [
"Thank you for the reply, that clears up my confusion.",
"Unfortunately, you very much supported my friends argument that it is forever changing, so we don't really know for sure."
] | [
"While a large deal of these reconstructions is quite speculative, some basic assumptions can be made based off of studying the correlation between morphology and bone structure in living organisms, and extrapolating from that. "
] |
[
"Do some materials cause precipitation of water at a higher rate than others (such as steel over glass)?"
] | [
false
] | A follow up question: is precipitation solely dependent on temperature differences? Thank you! | [
"Precipitation is basically rain, that happens because of water condensation in the atmosphere. There is hardly any glass or steel floating in the atmosphere so I am guessing you meant condensation. Which is the change of phase from gas to liquid. Some materials do promote condensation, and the brief following expl... | [
"This is a great answer for describing the dynamics of two phase systems. However, I think it's missing an important part. In general metals are much better thermal conductors than any other class of materials. Metal vessels also tend to have thinner walls due to their ductility as compared to most ceramics and gla... | [
"Your last remark made me remember the phenomenom of supercooling, where the gas/liquid is placed below its condensation/solidification temperature but the phase change does not occur because there is not a favorable place for the first nucleus to appear. So for OP's follow up question, phase change is definitely n... |
[
"If the Kuiper Belt and Oort Cloud contains billions of cosmic rocks, how do we know that probes such as the Voyager won't hit anything?"
] | [
false
] | I know the density of the Oort Cloud probably isn't that much, but isn't there still a pretty substantial probability that Voyager I will hit an asteroid or something? | [
"We don't know that the probes will be safe! This is a lesser problem than it might appear, however, because space is really, ",
" big. The popular image of a maze of enormous, moving rocks is pure movie fiction; while the density of objects is much higher than average, space is very empty so the average is extre... | [
"No. There wasn't even much chance going through the asteroid belt.",
"\nIf you were on an asteroid in the asteroid belt, it would be hard to see any other asteroids without at least binoculars. In the kuiper belt and especially the Oort cloud, things are even much, much farther apart."
] | [
"... object, much less hit I .",
"You didn't get to finish your sentence. It would be funny if you typed that from a spaceship that was hit by an asteroid."
] |
[
"What's your favorite unexplained natural phenomena?"
] | [
false
] | null | [
"Is there a way I can transfer the post there from mobile?"
] | [
"Damn. Thanks anyways, kind redditor. :)"
] | [
"Will do!"
] |
[
"Why does atomic radius decrease across the period?"
] | [
false
] | [deleted] | [
"I think the mistake you're making is that you're considering \"stronger attraction\" to be determined by the number of protons, when you should be thinking about charge ",
". Protons are held together by nuclear forces, which are much stronger than electromagnetic forces, so more protons means greater charge den... | [
"It's not about if the numbers of protons and electrons are equal.",
"It's about how attracted a given electron is to the nucleus. ",
"So for the outer electrons (which will determind the atomic radius) they are attracted to the nucleus by it's protons but repelled by the other electrons which partially cancle ... | [
"to piggyback on this comment, You can get more information if you Google: \"why is osmium the densest element?\""
] |
[
"Extra Dimensions in String Theory"
] | [
false
] | So, there are a couple extra dimensions according to string theory that are just too "small" to see. I've seen pictures of the projections into 3-space of Calabi-Yau manifolds all over the place and just assumed that these little manifolds are peppered across our universe. Then I got to wondering what would happen if you were in a space between these little manifolds and realized that what I had envisioned was a bunch of separate dimensions contained within our 3-space, which I realized is total bull. So my question is: are these extra dimensions simply periodic spaces orthogonal to our regular 3 dimensions whose period is an extremely short distance? Like if you were to move through one of these dimensions you would travel however far that dimension's period is and end up back at the place you began while remaining at the same point in 3-space the whole time? Don't be afraid to get somewhat technical, I'm a third year physics undergrad. | [
"You should read about ",
"fiber bundles",
". The total 10-dimensional space is a fiber bundle, where the base space is 4-dimensional space-time, and the fiber is a 6-dimensional Calabi-Yau manifold. ",
"Just think of a torus: That is the total space of an S",
" bundle over S",
" Imagine the circle go... | [
"hmm interesting. I don't have much of a topology background; do you know of any resources that could give me an introductory background?"
] | [
"Well, the short answer is to ask your adviser or some other professor who knows your background. It will probably be hard to read any proper introduction to fiber bundles, because a fair bit of background will be assumed (even if it's not strictly necessary).",
"To just get a basic sense of what's going on, you... |
[
"How does pyroelectricity work? In what real world applications can it be found?"
] | [
false
] | I've briefly read about pyro and piezoelectricity - I had trouble finding understandable applications. I gather it can be used to induce nuclear fusion. Moreover, at what temperature do pyroelectric crystals generate voltage? How feasible is their use in more common applications? Thanks in advance! | [
"I don't know much about pyroelectrics, but if you're interested in the general concept (thermal to electrical energy conversion), I'd suggest thermoelectrics as a much more robust field to explore -- there are already many applications of this effect in use today, and quite a bit of ongoing research into finding n... | [
"For power generation, thermoelectric materials are limited by both the carnot efficiency ( (T_hot - T_cold) / (T_hot) ) and the material properties, which are quantified in terms of the \"figure of merit\" ZT. The material properties are generally the biggest limiting factor in the overall efficiency -- optimized ... | [
"Ah, this is fascinating stuff. One of the motivations for asking this particular question was an interest in its potential use for energy recycling. I saw from the Wiki that power plants use thermoelectric generators for this purpose. I noticed \"low efficiency\" thrown around quite a bit - is this because of a la... |
[
"Why do depleted batteries bounce more than fully charged batteries?"
] | [
false
] | As seen in a recent gif on depleted batteries will bounce higher, but why? | [
"The chemicals inside the battery change state and different states react different to forces.",
"It's similar to raw/cooked eggs. The rotate VERY different. You can try it out. Rotate a raw egg (or try it) and then cook it and rotate it again. "
] | [
"I asked this same question too! Check out ",
"this",
" comment. He or she linked a youtube video that explains it and is worth watching. They also linked the 2 half cells redox reactions and a diagram of the inner cylinder. Anyways a battery contains two half cells. Water is the product of the first half react... | [
"To add on to this: interestingly the less fresh an egg is, ",
"the more boyount it is in water."
] |
[
"If your main utility company were to temporarily shut down, how much time would you have between shut down and blackout at your home?"
] | [
false
] | I'm wondering if there's any "residual electricity" in the wires that could be used in this time and how substantial it is | [
"A few milliseconds. For a sole generator supplying you. There would be 1/2 to 1 cycle of energy (5-20ms) left as inductive or capacitive storage in the lines. This is actually a problem with opening a switch on the main line of a utility. That residual energy can cause voltage surges. But typically any particular ... | [
"Ah okay, I knew electricity travels quickly and that there wasn't much storage along the line.. but I was wondering if the lines were sooo long that you might still be able to draw for a whole second or two before you were \"caught up\""
] | [
"This is the answer I was looking for, thanks!!\nI thought about the \"delay\" like the concept of Light years; where the electricity has already left the source and the user gets to experience that electricity for a couple milliseconds before it ends"
] |
[
"Heisenberg Uncertainty Question"
] | [
false
] | [deleted] | [
"Begin with the uncertainty principle",
"Δ(x) Δ(p) > h/2π",
"So let's divide both sides by Δ(x) for reasons which will be soon obvious",
"Δ(p) > h/(2πΔ(x))",
"So let's just say Δ(x) is just equal to aλ where a is however close to 1 you want to be and say it's on the order of the DeBroglie wavelength. Becaus... | [
"Okay so I'll try and teach the math: ",
"Δ(x) is the uncertainty in x. One way to think of it is a change in x. \nLike how average velocity is Δ(x)/Δ(t). Which is your change in position over your change in time.",
"Defining some variables: x is just position of a particle. p is just the momentum of a particle... | [
"That's the craziest looking math I've seen so far on AskScience. I must learn what it means."
] |
[
"Over time, does a satellite naturally attain synchronous rotation? Pics in question to explain what I mean."
] | [
false
] | There are two scenarios shown . Does the satellite, with no initial rotation, naturally start to rotate as in image 2? Or does it maintain attitude as in 1, until otherwise acted on? | [
"In terms of natural satellites, yes. The moon and earth share this relationship. It's called 'tidal locking'."
] | [
"Artificial satellites would do it too, given sufficient time."
] | [
"AskScience: Why do we only see one side of the moon?"
] |
[
"Does the Milky Way Galaxy orbit something?"
] | [
false
] | Earth orbits the Sun, the Sun orbits the supermassive black hole at the center of the galaxy. Does the galaxy orbit anything? I realize that since the Universe is infinite and expanding then everything is technically at the 'center', but do all galaxies orbit some common center of gravity? | [
"Our galaxy does interact with other galaxies in our ",
"local group",
" to a certain extent. For the most part, it appears that the galaxies in the local group simply orbit a center mass for the entire cluster, but even the local group itself orbits a center mass for our local supercluster."
] | [
"Again you are confused as to the definition of infinity. Infinity is not a limit. \"Infinity\" is a concept designed by mathematicians to explain something that would go on literally for the rest of eternity. ",
"No matter what number you count to, there is always one higher, so it goes on for as long as you can... | [
"Well, it might not be. But it is at least 250 times the Hubble volume..."
] |
[
"In a magnetic hard disk, how are the servos that position the read/write head so accurate?"
] | [
false
] | With the data tracks as narrow as they are (on the order of a hundred nanometers or so wide), these servos must be incredibly precise. How do they achieve that level of precision? | [
"The tracks themselves have embedded information called servo codes that act like a map. The heads are moved by a voice coil motor and can read these codes and see how far they are from where they need to be and then adjust accordingly.\nCheck ",
"this",
" out."
] | [
"It is a mixture of a few things.",
"Direct position feedback. As others have said, before you ever saw the hard drive there are servo wedges written to the disc. There is a big written in signal marking that it is the start of a servo wedge, then a physical position reference (This is Track Position X) as well... | [
"And then on top of that equalization and error correction are applied to the electrical signal coming from the read/right head."
] |
[
"Can you make an image ONLY a colorblind person can see?"
] | [
false
] | I remember the colorblind tests where the number would appear to a person with "normal" vision but not to a person who is colorblind. Can this test be reversed to create an image using the same principles, so that only a person who is color-blind could see it? | [
"Have you ever heard of the color-blind army men, chosen simply for their ability to spot camouflage? There are several articles about studies that have analyzed a possible evolutionary benefit to colorblindness. Why? For some reason, the color-blind seem to be much better at spotting camouflage. ",
"Here",
... | [
"It's possible, but there are some caveats.",
"First, the key is adding distracting color information which obscures patterns in shading, but even differences in shading are visible to people with normal vision so it's just a matter of making something harder to see, not impossible to see.",
"Second, there are ... | [
"That is not correct. Colorblind people are more sensitive to differences in contrast than \"normal\" people. As a result, colorblind people are less often fooled by camouflage. Here are some examples:",
"Those with normal color vision or total color blindness should be unable to trace the line. Most people with ... |
[
"Mount Agung Volcano Eruption Megathread"
] | [
false
] | Hi all, Mount Agung on the island of Bali, Indonesia, has currently been undergoing eruptions. If you have questions about the specific eruption, volcanic eruptions in general, or related topics, feel free to post your questions below! Some relevant links: | [
"This is something that comes up a lot - there's actually some decent stuff in the FAQ.",
"However, to pracie;",
"Yellowstone has erupted hundreds if not thousands of times over the last 2 million years or so. Three of those eruoptions have been 'supereruption', where in excess of 1000 cubic kilometers of magma... | [
"Volcanic plumbing systems are complex beasts; there can be a multitude of interconnected magma reservoirs. As you depressurise one system there is potential to destabilise other parts of the system, which can trigger new pulses of activity We know of 3 or 4 eruptions from Agung in the last 200 years or so; 2 of th... | [
"Every once in a while someone brings up Yellowstone's chance to erupt, but it's all people speculating at gatherings. This is why it's great to have experts in this field to ask questions to!",
"When can we expect a Yellowstone eruption as I am sure it's not an if but a when situation, how bad will it be and wil... |
[
"Can one light wave cancel out another light wave?"
] | [
false
] | In my Physics class last night, my teacher talked about destructive interference and how it is possible for waves to cancel each other out. Is this true for all waves including light waves? If so, how come I (to my knowledge) have never come across or experienced a way to have one light source cancel out another light source. | [
"I'm sure you have come across it many times, you just haven't realised that's what you're seeing. See ",
"thin-film interference",
" for examples, and the ",
"iridescence",
" page has more. These include things like the colours in soap bubbles or puddles with oil spilled on them. A thin film causes the lig... | [
"Polarisation is not necessary for interference. Coherence is. This is why in the double slit experiment we insert a single slit before the double when using a thermal source like a light bulb. the light from such a source is coherent over a small area only, the single slit selects such a region. When using a c... | [
"What happens with thin films is that you are seeing the superposition of 2 reflections. Light reflects of the top the film and light reflects of the surface below the film. If that film is exactly 1/4 the wave length then the light reflecting off the surface has traveled 1/2 wavelength further which makes out of p... |
[
"Is this derivation of F = dp/dt flawed for cases with variable mass?"
] | [
false
] | null | [
"You're wrong in the assumption that F=dp/dt was found using constant mass. That's why you are confused. But even then, does it really matter? Momentum is simply the product of mass and velocity. Whether one or the other, both, or neither is constant doesn't change that. It doesn't change F = dp/dt because dp/dt = ... | [
"ahh that makes more sense thanks"
] | [
"Constant mass is a common simplifying assumption made that allows us to write F=ma. If the mass has some time dependence then properly applying the chain rule when you take the time derivative of momentum will give you the correct form of the force with a non-constant mass. For an example see the rocket equation."... |
[
"Where did all the stars go?"
] | [
false
] | null | [
"The stars didn't go anywhere. They are hard to see when there is light pollution."
] | [
"Light pollution? What’s a example"
] | [
"https://en.m.wikipedia.org/wiki/Light_pollution",
"It just means that there are other bright lights around. You can't see very dim light when there is another bright source around. That's why you see few stars at night in a big city and can see lots of stars if you go into the countryside."
] |
[
"How would you fix something like the Guatemala sinkhole?"
] | [
false
] | Pic for reference: Do they just pour in a lot of dirt? Wouldn't that just become unstable again? If a sinkhole that size was there, wouldn't that mean that the whole city area would be in danger of falling into sinkholes? Is there anything they can do to prevent them from happening? | [
"I was mostly convinced that was photoshopped, then googled it. Blimey. From the article I read on it: ",
"Typically, officials fill in sinkholes with large rocks and other debris. But the 2010 Guatemala sinkhole \"is so huge that it's going to take a lot of fill material to fill it,\" Currens said. \"I don't kno... | [
"Before the sinkhole can be filled other problems need to be addressed. The city sits on unconsolidated soil that can easily be washed away, which, in addition to the tropical storms and heavy rainfall, likely added to the formation of this hole. The underground water system needs to be thoroughly inspected to dete... | [
"Try ",
"/r/askengineers",
" "
] |
[
"If microwaves work by vibrating water molecules, why is it that my bowl is hot while my food is still cold?"
] | [
false
] | null | [
"Microwaves work by exciting rotational modes in polar molecules. Your bowl may be made of some other polar substance."
] | [
"The bowl I was heating at the time was ceramic so that does contain polar molecules (typically). Is that why Styrofoam does not heat up in the microwave? Because it is nonpolar? "
] | [
"That makes sense to me."
] |
[
"If you were standing on Mars, how bright would it’s two moons look in comparison to our Moon on Earth?"
] | [
false
] | null | [
"Phobos has ",
"40% the apparent diameter",
" if you are directly underneath, Deimos has ",
"just 6% of the diameter",
".",
"Their albedo is lower compared to the Moon by a factor ~2, and sunlight only has half of the intensity. Combined you have much smaller moons which also have a dimmer surface. Both m... | [
"Thanks for the reply. This was exactly what I was hoping to figure out. My little guy and I were talking about it being a disadvantage of living on Mars, but then he started wondering how much smaller and dimmer they would be. He feel asleep before you all replied, so excited to share this with him tomorrow. C... | [
"Yes (",
"here is a picture with Earth and the Moon",
"), but Mars' moons are even darker."
] |
[
"What do storm clouds do that make them darker compared to regular, lighter clouds?"
] | [
false
] | null | [
"Simple answer... They're thicker. The dark grey you see in storm clouds is a result of the shadow of more cloud between it and the sun. Storm clouds usually have a large amount of cloud above them that you can't see from underneath, or close to the cloud. You do see it's shadow though, at the base of the cloud, ob... | [
"For an illustrative example, ",
"http://www.snopes.com/photos/natural/graphics/storm2.jpg",
"Notice how the surrounding clouds are might lighter than the bottom of that very thick, central storm cloud."
] | [
"Oh boy that's a fantastic image. I wish they had that in 4k as to utilize it as my wallpaper."
] |
[
"What causes X shaped lines on the stream when I pour milk?"
] | [
false
] | I've noticed that when I pour milk (I think it's any liquid but its most obvious when I'm pouring milk out of the gallon container) that there are X shapes that form likes indented ridges on the stream that is pouring out of the mouth of the container. Why does this happen? You can see the lines that I'm talking about in this picture. Edit: Thank you guys for all the helpful answers! This has been something I've wondered about for ages, and I just used to go "eh, physics" but last night I spent a while looking up stuff about Rayleigh jet instability and waves instead of studying AP Chem, so that was pretty awesome. | [
"In general, fluid dynamic models are very difficult to describe using natural language. The mathematical interactions are so complex to model that fluid simulation is one of the major applications of supercomputers.",
"This case might be more simple, I honestly don't know, but it also might be extremely complica... | [
"Let's look at the cross section of the milk as it falls into the bowl. Take the section right at the mouth of the carton and you have a triangle of milk, 2 edges from the walls of the carton and the third being the top surface of the milk. This is the best shape for the milk to be in because it minimizes surface a... | [
"This is the closest thing to the correct answer here.",
"We, fluid physicists, refer to this as Rayleigh jet instability. You can read about it in plain terms on Wikipedia here: ",
"http://en.m.wikipedia.org/wiki/Plateau–Rayleigh_instability",
"In the particular case of milk, which is a colloid, you get some... |
[
"Did all of the birds of today, flightless and those that can fly, evolve from a single Mesozoic dinosaur ancestor? Or are modern birds the ancestors of several different Mesozoic dinosaurs?"
] | [
false
] | null | [
"Yeah. Flight has been lost multiple times among birds. Penguins are a separate evolutionary branch from ostriches/emus that also lost flight."
] | [
"It's possible that flight, or at least ",
"gliding",
" evolved in therapod dinosaurs a few times. Many of the small therapods were probably highly feathered little critters that flapped their arms about to help maintain balance and scramble up surfaces, and it's ",
" that several lineages independently got ... | [
"This is not true, Archaeopteryx is not thought to be a direct predecessor of birds",
"https://en.wikipedia.org/wiki/Archaeopteryx#Phylogenetic_position"
] |
[
"I read so many science papers that conclude with \"correlation does not equal causation\". Why are such experiments conducted?"
] | [
false
] | This seems to be mostly happening in science dealing with human health. Is there a point in doing such experiments and the take away is just correlation? Isn't it similar to picking two random trends on Google Trends and showing correlation? | [
"The thing is, correlation ",
" imply causation, as long as the study is done correctly. If A and B are correlated, one of four things could be occurring:",
"Properly applied experimental techniques and statistical analysis may be used to determine that #1 is unlikely.* In that case, you're left with #2-4, whic... | [
"It's not an experiment unless some kind of intervention is conducted. Correlation is usually from observational studies. It is hard to change people's health, but relatively easy to observe what is happening with people's health. Correlation was used to discover that smoking was associated with lung cancer. Later ... | [
"Correlation is usually a good hint to bring further study into an area that was ignored before. Linking two phenomenon that previously had no sign of being correlated opens the doors to important questions.",
"Also, statistical correlation is something slightly different from colloquial correlation."
] |
[
"It's a bit crude, but... Why does taking a dump feel so damn good?"
] | [
false
] | null | [
"Try a better title for ",
"/r/askscience",
" such as but not limited to: \"Why is my brain's reward center excited when I excrete?\" or \"Why does it feel good when I excrete?\""
] | [
"Follow up question. Since males have a prostate, does the evacuation of matter from the posterior regions feel more pleasurable to them in comparison to females?"
] | [
"With that it makes an easy enough way to answer,",
"Your body rewards you for pooping because it's essential to survival. Just as eating is rewarding.",
"As far as the allure for Anal sex, there is much more than the sensation of something moving around in the anus. As pain is exciting for some, and with this ... |
[
"Why is it that some molecules can have two opposite effects?"
] | [
false
] | How is it that a molecule, such as prostagladin, can have two opposite affects on one type of tissue, i.e. it can cause both contraction or dilation of smooth muscle. Does it depend on the certain receptors expressed in the tissue or is it something to do with the different signaling pathways that might be active? | [
"One of the biggest reasons is definitely going to be different receptors. For any given signaling molecule, the effect of the signal is entirely determined by the receptor and what the receptor is coupled to. For example, there are both excitatory and inhibitory receptors for many neurotransmitters.",
"I'm not... | [
"The prostaglandins are a complex group of structures that share the basic shape. Side groups change their structure and action. Often two variants oppose each other.\nMore:\n",
"https://en.wikipedia.org/wiki/Prostaglandin"
] | [
"To add to what others have said, while I do not know much about prostagladin, it is not uncommon for cells to express feedback loops, that limit the time of a response. While this is not directly what you asked, many drugs will feed into these cell switches. For instance, you may have one receptor that activates c... |
[
"How are cannabinoids metabolized?"
] | [
false
] | What do they bind to in the blood stream and what is the detectable metabolite in urine? | [
"http://www.health.gov.au/internet/main/publishing.nsf/Content/health-pubs-drug-cannab2-ch47.htm",
"After smoking, the initial metabolism of THC takes place in the lungs, followed by more extensive metabolism by liver enzymes which transform THC to a number of metabolites. The most rapidly produced metabolite is ... | [
"As far as I know cannabinoid receptors are some of the most common binding sites in your body with virtually every cell sporting them. So really it binds everywhere."
] | [
"Not sure where your source is, but I found ",
"this",
". Your reply seems to be generally correct, but I was trying to find if red blood cells had those receptors too (seems that they don't).\nStill, cannabinoid receptors should clearly be widespread as they ",
"do cool signalling stuffs",
"."
] |
[
"How do Civil Engineers go about factoring in the curvature of the Earth when dealing with extremely long bridges?"
] | [
false
] | Engineering | [
"The Earth's curvature is fairly predictable so during the planning stages you can make pretty reasonable approximations of what the differences in height will be. Then, when it comes to actual construction, the areas are surveyed so you'll know the exact difference in height. In most cases, I'd bet that local vari... | [
"Is the 1.5 inches something that's planned for? That's 0.02% flatness across the side of the tower, right? (They're 693 feet tall)"
] | [
"I'm a civil engineering major and I have never come across this in any of my classes. You could try asking ",
"/r/civilengineering"
] |
[
"Are all muscles contracting? As in there are no \"push\" type muscles?"
] | [
false
] | What about other species besides humans? And what are non-contracting (I'm assuming stationary) muscles generally used for? | [
"Yes, muscles can only ever contract themselves. Muscles can only be stretched with another muscle, a \"stretcher\". You will always have muscles working either way on most of the body's joints. The fingers are a bit different."
] | [
"sphincter muscles (the round ones that control most digestive processes, the irises of your eyes) are a little different, in that sphincters “open and close” vs push and pull, so they don’t need a counterpart like a bicep has in a tricep in your upper arm or quadriceps and and hamstrings in your leg."
] | [
"As for the second part of your question, there are not really non-contracting muscles, except those that are atrophied and thus not working or muscles that are not needed. Ligaments, tendons, and fascia, for example, provide the extra support without contracting."
] |
[
"[physics] - Where would I have to go on land (not water) to find earth's weakest point of gravity?"
] | [
false
] | I got conflicting answers. I was told any land point on the equator would be the place where gravity is weakest. However, I was told that there are some "hot spots" where gravity is even weaker. I would like to ad that even on other "physics" websites there is disagreement with conflicting citations: | [
"Based on the GOCE satellite, gravity appears weakest in Southern India.",
"http://news.bbc.co.uk/nol/shared/spl/hi/world/10/goce_gravity_field/img/goce_gravity_field_786map.gif",
"That axis is mislabeled though, the units should be milligal (1 gal=1 cm/s/s)."
] | [
"Not as a human, no. Maybe with sensitive equipment."
] | [
"If I could somehow travel instantly from Iceland, where it appears to be strongest, to Southern India, where it appears to be weakest, would I notice a difference?"
] |
[
"Is digital, lossless audio amplification possible?"
] | [
false
] | If so, is anyone working on it? If not, why not? | [
"It should be noted that you can't just \"raise\" the amplitude value without first looking at the entire file. If you do so, you risk hitting the upper bound and causing clipping. You first have to inspect the entire file to see how much the highest peak can be raised before hitting the maximum, then raise all sa... | [
"If by \"amplification\" you mean either compression or normalization then yes, there is nothing degrading about either of these processes, although they would be difficult to reverse. if you have a 48bit wav file and you want it to be \"louder\" you just \"raise\" the value for the wave at each time an amount pro... | [
"I typed that way too late at night. You are right, if it is just an applied gain then you could reverse it (with roundoff errors) easily, but if it is something dynamic, like compression or normalization with a finite sample time, then it would be more difficult to determine what was applied where, and at what fr... |
[
"Why are vaccines traditionally given via injection vs a pill or other method?"
] | [
false
] | Has there been research into other delivery methods' efficacy? What would possible limiting factors be for pills or other ingestible versions? | [
"The oral route does not tend to be very good at delivering antigens to the immune system. You don't generally ",
" your immune system to respond to oral molecules: think about the general awfulness of wheat or peanut allergies. Your body not only tends to break down molecules for sustanence, but also has some ... | [
"Your immune system will not react differently to an antigen on the basis of its point of entry.",
"Actually, that's not accurate. There's a whole subset of research on mucosal immunology because the immune system has so many unique properties at mucosal surfaces. Within that area are labs that solely focus on on... | [
"Your immune system will not react differently to an antigen on the basis of its point of entry. ",
"You don't generally want your immune system to respond to oral molecules.",
"If these virus[es] normally infect via an oral route, then that can be a good way to inoculate.",
"This suggests your immune system ... |
[
"Can God fuck a piece of cake and eat it afterward and have it NOT taste like cum?"
] | [
false
] | null | [
"Ah on second thought, per the 3rd bullet point could a mod please move this to AskScienceDiscussion?"
] | [
"Ah on second thought, per the 3rd bullet point could a mod please move this to AskScienceDiscussion?"
] | [
"Ah on second thought, per the 3rd bullet point could a mod please move this to AskScienceDiscussion?"
] |
[
"Does the size of an adult of a species affect the size of the gametes? For example, do elephants have bigger ova than humans? Do mice have smaller sperm?"
] | [
false
] | I'm also curious to know if smaller animals have smaller (ie: thinner) neurons compared to humans. | [
"I don't know about general trends, but fruit flies rather famously have the longest sperm in the world.",
"wikipedia"
] | [
"Yes and no. There's a general trend that smaller animals have smaller parts, but this is not universal. Evolutionary pressures have a lot to do with it, and most of the time, we're not sure why an organism deviates.",
"For example: Squid have ",
"giant nerve axons",
".",
"This trend is less true for indivi... | [
"Couldn't find a comparison to humans, but for small mammals, body size and neuron size are coupled",
"source"
] |
[
"Why does it snow less near the coast?"
] | [
false
] | I've always been told it's because of salt coming off the sea into the air, which causes the snow to thaw, but this sounds more like an urban myth than actual science. | [
"It has nothing to do with the salt but it certainly does snow less in coastal areas. This is due to the ",
"Maritime Effect",
" which in a nutshell gives coastal areas more mild seasons. It snows less near the coast because it is in fact generally a few degrees warmer on the coast during the winter."
] | [
"The Lake Effect",
" is actually the result of the colder inland air passing over the relatively warmer water then back over the colder land. The same thing can happen from the ocean.",
"This effect occurs on bodies of water of every size, it is just some bodies of water are not large enough for a noticeable i... | [
"And cooler in the summer. This is because it takes more energy to heat up/cool down water than other similar substances. It's polarity means that it forms hydrogen bonds, which require more energy to break."
] |
[
"What's happening when my eye gets red?"
] | [
false
] | [deleted] | [
"The red lines you see are the blood vessels in the conjunctiva, a translucent tissue that covers all but the cornea in front of your eye. The conjunctiva prevents anything from going behind your eyeball, including contacts. When your eye gets irritated, dry, or detects a foreign body or substance, it becomes inf... | [
"The irritation of your cornea causes a histamine response in response to a possible foreign object in the eye. This causes the blood vessels in the sclera (the white part) of your eye to dilate some and get more blood to the area, mostly in order to supply your tear glands with more raw material to make tears with... | [
"Thanks!"
] |
[
"Is PTHrP parathyroid hormone-related peptide or protein?"
] | [
false
] | Searching around I've found both used in academic literature, is one more correct than the other or are they completely interchangeable? | [
"Peptides are shorter than proteins. Peptides usually range from 2 to 50 amino acids while proteins range in the hundreds or thousands of amino acids. PTH is 85 amino acids long therefore is more accurately classified as a polypeptide."
] | [
"Apologies, read your question correctly and halfway through typing the answer my brain switched to parathyroid hormone and only realised you were asking for parathyroid hormone related peptide. ",
"According to ",
"this",
" review article it has a variable amino acid length of 139 to 173 amino acid. I guess ... | [
"Would the same be true of PTHrP?"
] |
[
"For how long will a bug survive if I swallow it whole?"
] | [
false
] | I just swallowed a fruit fly which had invaded my beer and I can't waste a single drop of it. I'm sure it's long gone by now, but how long did it survive? What if we upped the ante and considered a cockroach instead? Are there any non-parasitic multicellular animals which could survive the whole process and come out alive? | [
"It's quite unlikely that the fruit fly lasted very long once it hit your stomach. The sheer acidity of the digestive fluids would have dissolved most of the chitinous tissue within a minute or so. Even if you were to indadvertedly swallow an entire cockroach within damaging it, the chances of survival are quite lo... | [
"Hint, there's a reason we have teeth. Chew your food! Things aren't supposed to be alive by the time they hit the esophagus."
] | [
"Thanks for the hint! Henceforth I will chew my cockroaches well and good."
] |
[
"If men typically have more muscle mass than women doesn't that mean that they need more sleep than women to rest/repair/ and build muscle from daily activities?"
] | [
false
] | null | [
"No for a few reasons, recovering from exercise isn't the determining factor in how long we need to sleep. 8-9 hours of sleep is appropriate but substantially less than that is needed to recover from most exercise. Also, the differences in muscle mass and daily exercise load are more varied within men and within wo... | [
"Just to be clear- sleep is a requirement for for brain functioning, for reasons that aren't completely understood. Muscle repair requires resting the muscle, or at least not high exertion, not necessarily sleep. "
] | [
"I'd argue sleep is required for complete recovery for hormonal reasons. Insulin and hGH are important factors in recovery and their levels are affected in important ways by sleep. "
] |
[
"Is there a reason the \"gravity map\" lines up somewhat with the fault lines of earth tectonic plates."
] | [
false
] | gravity map, . | [
"This is exactly backwards. Mountains in either Free-Air or Bouguer gravity maps are lows, and the extensional basins are gravity highs due to the decompression and upwelling of hotter, more dense asthenosphere. This is seen in the Basin and Range in the Western United states as a wide rift example, the Llanos basi... | [
"I'm sorry, but I have to be adamant about this. It is not correct what you are saying. ",
"You will notice that all of the mountains that are showing up as a positive have either magmatic intrusions, or they have basaltic cores. Himalayans have a basaltic core called the Abor mafics. The Pontides in Turkey are a... | [
"Of course of course. Gravity is sensitive to only one thing, and that is density variations. Whether those come from mafic intrusions or mass deficits at the bottom of the crust, this is exactly what gravity is sensing. And yes, Bouguer maps are more useful for certain types of detections. Unfortunately, the G... |
[
"Why do larger stars burn out faster than smaller stars?"
] | [
false
] | I understand that the larger stars have to to maintain higher temperatures to balance their additional gravity, and this consumes fuel much faster. I must be missing something, but I would think that the larger star as it burned through it's fuel would lose mass and require less temperature over the course of it's lifetime. Is it simply not burning off enough of it's mass? | [
"Indeed, [isolated] stars stay at roughly the same mass for their entire lifetimes before they stop burning hydrogen and they leave the main sequence. Let's estimate the mass lost by the sun in its main sequence lifetime.",
"Main sequence Lifetime = 10",
" yr",
"Luminosity = 4 * 10",
" erg/s",
"So mass ch... | [
"Thanks for the mathematical explanation. I think I sort of brought myself to this conclusion as I was writing, it but still wanted to hear a panel member's precise answer. "
] | [
"Stars do not \"burn stuff off\" in the way that a burning piece of wood or paper does.",
"What is happening in a star is that smaller atoms like hydrogen and helium are undergoing a process called fusion which essentially merges the nuclei together to form a heavier element.",
"Some of the mass from the smalle... |
[
"What is the Pauli Exclusion Principle and how does it manifest itself?"
] | [
false
] | [deleted] | [
"It says that two identicle particles whose angular momenta are odd multiples of half of Planck's reduced constant (fermions) cannot occupy the same quantum state. In practice, this means that electrons and protons can't overlap the same space, and electrons cannot all be in the same energy level of an atom."
] | [
"I would say no. The Pauli Exclusion Principle is mainly a \"bookkeeping\" procedure of labeling electrons. Electrons don't interact because of this law but instead this law is in place to track where areas of high electron density (molecular orbitals) are located. Furthermore, solids are solids through atomic bond... | [
"Correct, the Pauli exclusion principle does not apply to particles belonging to different atoms - the upshot of which is that 2 electrons in neighbouring oxygen atoms can be in the same quantum state."
] |
[
"Are there any characteristics of people physical or psychological based on blood type."
] | [
false
] | I recently had an operation and I found out my blood group is AB +. Does blood type affect us as individuals. | [
"Lucky for you to be the \"universal receiver.\" But there aren't really any physical impacts of blood type. In fact, it's pretty much the go-to example of a neutral trait, meaning it has no impact (positive or negative) on fitness.",
"Edit: I missed the psychological aspect of your question. The evidence is m... | [
"Your first paper ",
" of pseudoscience. The paper almost exclusively self-references, and non-self-references are to books, unpublished articles, and 'overview' articles, with little relation to the topic at hand."
] | [
"True life. I thought it was worth directing the reader to, for interest. I tend to put less weight on research that's so old because I feel like it wasn't reviewed as thoroughly. Which is what I was trying to imply by saying \"here is a much more recent study\" and linking to the more legit one. I just figured... |
[
"How many particles in the universe?"
] | [
false
] | [deleted] | [
"So people always say there's like 10",
" particles in the universe or something like that.",
"For clarity, I believe that figure is the upper limit on an estimate for the number of ",
" in the ",
" universe.",
"But how many particles are estimated to be in the actual universe?",
"In order to estimate t... | [
"Additionally, the number of particles changes depending on whether you are accelerating or not (Unruh radiation). There is no observer independent particle number."
] | [
"Additionally, the number of particles changes depending on whether you are accelerating or not (Unruh radiation). There is no observer independent particle number."
] |
[
"Why does alcohol prevent my cola from foaming when poured over ice?"
] | [
false
] | When poured over ice, cola foams a ridiculous amount. As in, I pour a quarter of the glass and the rest is full of foam that takes almost a minute to disperse. Much more than if I pour cola in the same glass with no ice. Now I understand the reason for the foam is because the ice forms a surface for the bubbles to form, causing the quick release of carbon dioxide from the mixture (see: Diet Coke and Mentos). My question is why does adding an ounce of hard alcohol (say vodka or rum) before I pour the cola prevent the foam from building up? I thought maybe it was partially melting the ice cubes, smoothing the surface, but an ounce of room temperature water did not cause the same results. (Interesting note from my service industry days: fountain drinks don't foam nearly as much when poured over ice, I assume because they're much more watered down) | [
"Alcohol has low surface tension, so the bubbles end up popping much more rapidly, preventing much head from forming."
] | [
"You can also see alcohol surface tension effects in drinks in other ways. When a drink is said to have \"good legs\" i.e. large rivulets around the glass when you swirl the drink, generally wine, around the glass, The size of the legs is governed by the alcohol content. This means the ever classy \"this wine has ... | [
"Yes, it turns out surface tension is the basis of bubbles. It turns out that the bubbles in soda are caused by the dissolution of carbon dioxide into water forming carbonic acid. When held at high pressure carboic acid is stable but when you open up the can you reduce the pressure the carbon dioxide is no longer s... |
[
"How do some people walk away from being struck by lightning while others die?"
] | [
false
] | null | [
"The immediate-death effect of being struck by lightning is cardiovascular. The bolt essentially acts like a defibrillator. If a person's heart is still beating after being struck, they will likely be fine. The route the bolt takes through the body (ie, through the chest, or not) will determine if the person's hear... | [
"I was told recently that If you somehow know you are about to get struck, say by noticing a static buildup around you, you should quickly lay flat on the ground. They justified this saying it would provide the shortest route through you to the ground and this would help save your life. ",
"Are there any facts or... | [
"I've heard this advice as well, and though I've never seen any evidence to support it, it does make logical sense. Giving the bolt a 'target' in the form of your gluteals may help prevent the bolt from running through your chest. "
] |
[
"Exactly how many stars are contained in a 100 light year radius around Earth? Or, is there a tool to easily calculate/observe this kind of thing?"
] | [
false
] | null | [
"We don't know exactly, because we don't have a complete count of the most common type of star (red dwarfs) beyond 10-20 light years, because they are so dim. But we can count the sample of stars closest to us where we probably aren't missing any, and use that number to extrapolate the number of stars in the larger... | [
"very cool i didn't realize red dwarves are so dang common. Thanks"
] | [
"About 512 G-type stars ",
"according to this site",
". This is arrived at by direct observation. You'll have to look at the other types individually (see list at the bottom under Other Information), as it doesn't give a total for all types together. "
] |
[
"Why do nuclear reactors not explode after starting fission?"
] | [
false
] | null | [
"Because they are not prompt critical, it's delayed neutrons that maintain a fission reaction in a nuclear reactor. See ",
"here",
" and ",
"here"
] | [
"Sorry but this isn't true. Control rods would be useless in the event of prompt criticality, which is essentially what happens with a nuclear weapon. Control rods do control the reaction rate by absorbing thermal neutrons (ergo leaving fewer available to cause further fissions), but in current designs (with the ex... | [
"In a bomb, the products from fission (such as free neutrons) meet other nuclei and trigger fission in them. In a reactor, there are things (control rods) in place that absorb many of these products before they can trigger another reaction. This leads to a controlled but sustaining reaction."
] |
[
"Altitude Sickness? How sudden can it take effect, what can happen?"
] | [
false
] | Hello again scientists! So, my latest question is pretty simple. Altitude sickness, how long does it take to have an effect? I'm finding online that it usually takes between 12-24 hours for somebody to feel ill due to a raise of over 8000 feet. Well, what if somebody were suddenly exposed to such an altitude!? What if, for instance, some massive giant were to scoop you up from the ground and raise you, miles above the surface and right up to his own face? Any info, random tangents, strange possibilities etc are more than welcome, thanks for takin' a look! | [
"The cabin altitude of most airliners when in the cruise is about 8000ft. For most healthy people being suddenly raised to 8000ft pressure altitude and spending many hours there is a complete non-issue. There are plenty of long haul flights over twelve hours and 17 hours is the longest scheduled service I’m aware o... | [
"You should look up hypoxic hypoxia. It's a lack of oxygen from air surrounding you, and is regulated for in air law for altitudes of 12.000 feet and up. It can cause euphoria followed by death, a very dangerous combination."
] | [
"Jet airliners do have their cabin pressure controlled. They typically cruise at about 40000ft and the cabin pressure is equivalent to about 8000ft (ie not cruising level and not sea level but in between).",
"Long term periods at up to 10000ft pressure altitude basically have no effect on healthy people - in fact... |
[
"Joseph Postma: The Greatest Scientific Fraud of All Time?"
] | [
false
] | null | [
"We don't vet videos or blogs on this sub"
] | [
"Would it be more appropriate to link to his book on the same topic? I can't type out his full physics argument in one post, what would be most appropriate to link to?"
] | [
"Such posts are better suited for our sister-sub ",
"/r/asksciencediscussion",
". Please post there instead."
] |
[
"If the sun is white but appears yellow because of atmospheric scattering, why doesn't the moon also appear yellow?"
] | [
false
] | null | [
"The moon ",
" appear yellow or even red when it's low in the sky (or there are a lot of particulates). You think of the moon as white or pale yellow because usually when you see it it's high in the sky and therefore tending towards white. If you looked at the sun at solar noon (don't), it would look a lot whit... | [
"Another reason the moon may look less yellow is that ",
"color vision is worse in low light conditions and blue light is seen more easily",
". "
] | [
"Is it possible the contrast to the night sky makes it appear \"more white\"? "
] |
[
"Why isn't the deep sea frozen?"
] | [
false
] | I've heard somewhere that deep sea temperatures can be well below zero degrees Celsius. So, why isn't their a layer of ice in the depths of the ocean? | [
"You heard wrong: Deep-ocean water can be quite cold, but when we say \"quite cold\" we mean typically between ",
"0 and 3 C (32-37F)",
".",
"The deep ocean can be ",
" below 0C however, and there are ",
" three reasons why it does not freeze:",
"The ocean has a lot of dissolved salt and other materials... | [
"Salt + pressure."
] | [
"Also, water is most dense at 277.15K, so water of this Temperature will sink."
] |
[
"Why did herbivorous dinosaurs get so large?"
] | [
false
] | null | [
"Why is almost always not a good question to ask of evolutionary biology as you will always get a hefty amount of speculation. Perhaps being large deterred carnivores the same way it does today, perhaps selective pressures just happened to lead to increases in size. "
] | [
"The easy answer is that it was probably as a defense against predators.",
"But there is a concept under debate in evolutionary biology called \"Cope's Rule\", which describes the tendency for a lineage of animals to gain a larger body size over time. It's not clear if this is because there's an innate advantage ... | [
"The point that is might have evolved as a defense against predators is a valid idea. However, let me offer another point that is from the stance of trophic ecology. This can work in conjunction with the points brought up by ",
"/u/dblmjr_loser",
" and ",
"/u/loki130",
". ",
"In trophic ecology, you have ... |
[
"Can we know anything about the older star that created our sun?"
] | [
false
] | the solar system (along with other stars) were created by a cloud of gas and dust formed by the nova of a previous star. is there anything we can learn or find out about what that "parent" star system was like? like.. theres gotta be some kind of evidence. Can we find clues as to what kind of planets were around it when this old star existed? what kind of star it was? | [
"There was no such thing.",
"Many former stars contributed material to what formed the Sun later, although most of the mass is hydrogen and helium that was never part of a star."
] | [
"Interesting question. Best answers would probably be in the form of asteroid study - as these chunks of rock have undergone the least \"reflow\". Planets and moons have been heated, squeezed, whacked, and often subjected to billions of years of chemical reactions, so there's very little there. But asteroids are... | [
"hmm, is there at least a way to study star systems from our galaxy that don't exist anymore? i know theres some evidence leftover."
] |
[
"What are the dangers of using AAA batteries in place of AA?"
] | [
false
] | null | [
"This isn't a safety issue, but there's a battery lifetime difference. Duracell's spec sheets say that a AA Coppertop battery's output will drop below 1 V after 20 hours of use when connected to a 10-ohm resistor, whereas a AAA Coppertop battery will drop below 1V after just 6 or 7 hours. See Duracell's ",
"websi... | [
"The problem is the uncertainty of the wad of aluminum foil, not the batteries themselves. ",
"Your \"Standard\" sizes of batteries do all share the same voltage (1.5v for AAA, AA, C, D, etc.). In fact, you can buy adapters that will allow you to use smaller batteries for larger applications on most any website... | [
"What would cause the heat transfer to increase when using AAA? Less surface area?"
] |
[
"What did they think would happen before they set off the first Atomic Bomb?"
] | [
false
] | Did they know how big the explosion would be when you would try and split an atom? How is that calculated? Thanks Guys! (P.S. Big upvote to the mod team here. I love the constant moderation that keeps this community pure!) | [
"As was already mentioned, they had a descent idea on the yield for the first explosion (trinity). Keep in mind that trinity was a test explosion; it was not an attack of any sort. Data was collected from that and the formula to estimate an explosion was developed. (See wikipedia for the equation, its formatting is... | [
"There were two initial types of atomic bombs made, both for use as war-time weapons.",
"The ",
"Little Boy",
" uranium gun-type weapon worked by firing a subcritical mass of uranium at a stationary subcritical mass of uranium at the other end of the bomb. When the two parts collided they formed a supercritic... | [
"Was it formulated to be an attack weapon from the start? Or was the idea to pursue the advancement of science? ",
"Along the same idea, any suggestions for good documentaries on the subject?"
] |
[
"When you donate blood or let's say an organ to someone, what happens to your DNA in those cells?"
] | [
false
] | null | [
"Red blood cells don't have a nucleus and therefore no DNA, so no issue there. Normally for blood donations, the white blood cells (which do have DNA) are removed. In the case of organs, the host cell DNA remains intact, which is why it is necessary to get a match between donor and host, and why immunosuppressive d... | [
"So in theory would it be possible for the organ donors DNA to affect or cause a mutation to the hosts DNA? "
] | [
"I don’t think DNA does that?"
] |
[
"Why do they say not to put a car battery on a concrete floor?"
] | [
false
] | The old wive's tale has been proven anecdotally that putting a car battery on a concrete floor kills the charge. Is there any science behind this or is it coincidental? | [
"Leaving a car battery on a concrete floor won't do anything abnormal to affect the charge.",
"The belief stems from an outdated set of circumstances that no longer exist. Once upon a time, battery casings were made from more porous materials - tarred wood, ",
"rubber",
", etc. - which were susceptible to de... | [
"This is the correct answer. However you would be \nSHOCKED how strong this myth is. I have been a Mechanic for 20 years now, and while I work for myself now, I spent 15 years working in all manner of shops. No matter how many times I explained this to my bosses, they ALL forced me to put a piece of wood under batt... | [
"Mechanically, newer cars don't require this at all. Manufacturers actually recommend not idling your car, as it wears out the engine. ",
"In reality, the when it's -25 or below out, I'm running my car for a good 20 minutes, just so my ass doesn't freeze to death. However, your car will heat up faster in motion, ... |
[
"Methylcellulose question"
] | [
false
] | If methylcellulose (citrucel) capsules are crushed, does this ruin the methylcellulose? The company says not to do it but wont tell me why, other than "it hasnt been tested." | [
"It doesn't chemically ruin the methylcellulose. Methylcellulose passes through your digestive system pretty much unabsorbed and attracts water in your colon. Crushing it won't change how your body processes it chemically, but it might make it work less effectively if it causes it to be more dilute in concentrati... | [
"Thank you so much!!! My 5-year-old daughter has to take a fuck-ton of this stuff because of a colon condition, and it's very hard for her. I'm always looking for ways to make it more palatable."
] | [
"We aren't allowed to give out medical advice, so knowing you are asking because your daughter has a colon condition causes me to be conflicted. ",
"That being said, I will say this: There are many 'drugs' that you shouldn't crush, for many reasons. Some drugs for example have an enteric coating on them so they c... |
[
"Underground ocean 3 times bigger than our own?"
] | [
false
] | null | [
"I'm not sure if there's been a more recent set of splashy articles, but when ",
"Pearson et al., 2014",
" and shortly thereafter ",
"Schmandt et al., 2014",
" were published in 2014, there were endless \"multiple oceans worth of water found in the mantle!\" pop-sci articles published, like ",
"this one",... | [
"That was such an interesting response. Thank you."
] | [
"Thank you! Fun read"
] |
[
"Why don’t we explore different directions of space?"
] | [
false
] | null | [
"There are no planets in those directions"
] | [
"But how do we know if we have not deeply explored that direction."
] | [
"We can look in that direction without having to send a probe"
] |
[
"To what extent does the Pauli Exclusion Principle hold true regarding splitting of energy bands? No two energy levels are allowed \"in the same place\", but what if the sample was a single crystal the size of a basketball or larger?"
] | [
false
] | 1 mg of iron has about 10 atoms, and the Pauli principle therefore requires that each separate energy level in the free atom split into some 10 levels in a 1 mg crystal. This means each of those electrons need to be in a different energy state, with the range of states so close to each other they're considered a band. I get this. Both sides of this crystal are considered "the same place". But it's pretty easy to grow single crystal samples that are extremely large (maybe not of iron, but of other materials like silicon). So if you had a chunk of silicon the size of a basketball or even larger, are of the electrons truly unique in energy? Does the electron on one end of the sample really know not to share the same energy level as the electron on the opposite side of the sample? Or is this just a mathematical construction that is truly an estimation, and we use it to make the maths work out better? The reason why I ask is because I've heard a professor say something similar regarding quantum mechanic equations we use for magnetism- they're all just really approximations, and to call them is incorrect. The way I initially argued with myself and told myself that this has to be true is the neutron star or white dwarf example. In a white dwarf, the electron degeneracy pressure is what supposedly helps the star maintain its shape without further collapsing. Meaning all of those neutrons must have a different amount of energy. But then I realized that even neutron stars can collapse into black holes, and not only that, but to me this doesn't prove that every single fermion in that star is in a different state, it just tells me that no near-neighbors can be in the same quantum state (energy and location). | [
"If you want to deal with continuous bands, it's easier to forget about split levels and instead start with an 'electron gas' model. (See e.g. ",
"these lecture notes",
") You'll find that the expression for the 'exchange energy' (the change in energy by taking the Pauli principle into account) is strikingly si... | [
"Keep in mind that the actual Hamiltonian of this thing is really really really complicated. When you do the \"band\" approximation, you're actually doing a mean field limit that averages out some of the interactions. At the end, Pauli only cares about antisymmetry of the wave-function when you interchange coordina... | [
"So as long as they're connected by atoms, no matter what, it's 100% true without a doubt and can be proven experimentally that they hold different amounts of energy? You answer isn't convincing at all."
] |
[
"How do you measure the Earth's core temperature?"
] | [
false
] | I was just wondering how we estimate the Earth's interior temperatures. Obviously we can't get that far, how'd we come up with exact numbers? | [
"One piece of evidence comes from seismic waves. The speed those waves travel depends on the properties of the matter that they are traveling through, including temperature. Also some kinds of waves cannot travel through liquids, which we can use to tell that the core is partially liquid. So it must be hot enough t... | [
"Earth has a magnetic field, which probably means a liquid iron core.",
"Is not necessary. It is an unfortunate coincidence that the core is thought to be iron and iron is magnetic at room temperature. It confuses a lot of people. No material can be magnetic at those temperatures, because they are beyond the ",
... | [
"We know it is made of iron predominantly, thanks to studies on the propagation of seismic waves. Iron is the only element that is abundant enough in the universe and closely matches the seismic properties of the earth's core: We know its density, we know the pressure, we know also that there is a liquid and a soli... |
[
"What does \"cross tolerance\" mean in immunology?"
] | [
false
] | Myeloid-Derived Suppressor Cells Promote Cross-Tolerance in B-Cell Lymphoma by Expanding Regulatory T Cells I was skimming through the article but didn't quite get the gist of the paper. Do they mean that in the presence of MDSC, Treg has less of an immunosupressive effect on B-cells? | [
"I don't think it really \"means\" anything. I think what they're trying to say is that it promotes tolerance in more than one way: MDSC directly inhibit CD8 cells -- we've known this for a long time. Now it seems they ",
" directly activate and increase Treg cells, which is a tolerizing kind of cell, adding anot... | [
"It's a tricky subject. Yes, we absolutely need to address suppressor cells (of all kinds) while also avoiding massive autoimmunity. (Shock isn't really the word you're going for here.)",
"I've seen papers recently for MDSC conditional knockouts that have just as much autoimmunity as scurfy mice, so we can't just... | [
"I saw the Viagra part too and I was like huh? ",
"Well, btw -- thanks for the explanations. Do you think it is a good idea to deplete MDSC/Treg for cancer/injury treatment? Though, patients can go into shock due to increased level of inflammation.",
"Edit: Also another question, does MDSC have any direct metho... |
[
"Are other animals born with disabilities like down syndrome etc ?"
] | [
false
] | null | [
"Animals can have genetic diseases, too. This happens all the time in pure-bred animals due to ",
"inbreeding depression",
". You'll see dogs with the equivalent of cerebral palsy because of this."
] | [
"I know that askscience isn't the place for this kind of thing, but this is one of the ",
"funniest things I have read on the internet.",
" It's a great read if you've had a stupid dog."
] | [
"Like what Tekmo said because of inbreeding some purebred dogs have what is very similar to an obsessive compulsive disorder in humans. Commonly they will chase their tails until they pass out from exhaustion.",
"http://www.petwave.com/Dogs/Dog-Health-Center/Mental-Disorders/Obsessive-Compulsive-Disorder.aspx"
] |
[
"What was the difference between splitting the atom and nuclear fission?"
] | [
false
] | Possibly a stupid question. Encountered something that said that . This confused me, because I thought . Am I missing something here? What specifically was discovered in 1938 -- just that splitting an atom could release a large amount of energy? If so, why was that not apparent when they first split the atom six years earlier? | [
"\"Splitting an atom\" is a non-technical phrase that doesn't really have any specific meaning, while \"fission\" is a technical term for certain kinds of nuclear reactions.",
"The reaction performed by Cockroft and Walton was",
"p + ",
"Li -> ",
"He + ",
"He",
"which could be considered ",
"Li(p,α), ... | [
"Thomson believed that atoms were complicated vortices of many, many negatively-charged, low-mass \"corpuscles,\" which he believed were the Proutean \"fundamental particle\" of atoms. So he believed that he had discovered subatomic particles, but that there was only one subatomic particle. He believed these partic... | [
"I would just add, as an historical note, that physicists were interested but not ",
" that if you accelerated protons to fairly high energies and shot them at other atoms, you could get interesting nuclear reactions. Going from p + Li-7 to He-4 + He-4 is interesting but didn't contradict how they thought about a... |
[
"How much better is the James Webb Space Telescope going to be than Hubble?"
] | [
false
] | Is it possible to take a Hubble photo, draw a rectangle on it, and say "JWST will have the same resolution on this little square"? Any other advances beyond resolving power? | [
"In terms of pure resolution it is difficult to compare. Angular resolution is a function of wavelength and the two telescopes observe at different wavelengths (JWST is primarily infraread, Hubble is mainly optical/UV). The angular resolution of the JWST is about 0.1 arcseconds at 2 micrometres, this ~ the same as ... | [
"Handy visual aid",
" courtesy jwst.nasa.gov"
] | [
"The wavelength that these cryogenically cooled telescopes (Herschel 60-700 microns, AKARI was 2-180 microns) is even longer than the JWST. The longer wavelength the more influence temperature has on noise. This is why these telescopes had detectors that were as cool as 1K or so.",
"A big reason why JWST can stay... |
[
"The coefficient of static friction is greater than that of kinetic friction. Why?"
] | [
false
] | I shelved this question back in intro to physics but it just came up again. What's the deal? | [
"This is how my physics teacher explained it to me:\nThere is no such thing as a completely smooth surface, they all have small bumps and cracks. So whenever you have one surface lying on top of another, their bumps and cracks slide into eachother, causing the static friction.\nWhen your object is already moving, n... | [
"Well, let's say the coefficient of static friction were less than that of kinetic friction. Then start applying more and more force to a body at rest. You'd reach the point where the force was great enough to overcome static friction, but it since the force wouldn't yet be enough to overcome kinetic friction it st... | [
"I'm no expert at these things, but I would guess that the timescale that the forces you describe act on is very small, far too small to cause the substantial difference between static and dynamic friction.",
"Could it not be macroscopic effects? At small spatial scales, those rough teeth, once moving over a bump... |
[
"Is there any way that the sandworms from Dune could actually travel through the sand like it is described in the books or would the sand be too dense a medium to move through?"
] | [
false
] | null | [
"Viscosity?"
] | [
"http://cronodon.com/BioTech/Earthworm_locomotion.html",
"It should be fine. The real issue is how fast they go."
] | [
"They sift sand plankton for nourishment. Little tiny plants and such."
] |
[
"AskScience AMA Series: We are paleontologists here to talk about Dakota the Dinosaur Mummy, AUA!"
] | [
false
] | Hello ! Dinosaur mummies preserve skin and other soft tissues, but how they fossilize has always been a bit of a quandry. It's generally thought that very rapid burial is required to protect remains from predators, scavengers, and other agents of decomposition. However, they often also appear desiccated, which usually takes long-term exposure on the landscape. Recent preparation on the Edmontosaurus mummy "Dakota" revealed the first evidence of predator activity on dinosaurian soft tissues and provided an alternate explanation for how these rare fossils form. You can read in PLOS One. Joining us today are: ( ) is a paleontologist at the University of Tennessee whose research focuses on the processes of fossilization, evolution, and biology, of crocodiles and their relatives, including identifying bite marks on fossils. Find her on Twitter @UglyFossils. ( ) is paleontologist and Lab Manager of the Johnsrud Paleontology Lab, with the ND Geological Survey. She worked on preparing part of the tail, foot, and body block of Dakota the Dinomummy. ( ) is the Senior Paleontologist at the North Dakota Geological Survey and Curator of the North Dakota State Fossil Collection. His research focus in on ornithischian dinosaurs, including specimens of Edmontosaurus like Dakota the Dinomummy. ( ) is a fossil preparator with the State Historical Society of North Dakota. She prepared the right arm, portions of the left foot, helped with parts of the tail, and is currently preparing the body block of Dakota the Dinomummy. We will be joining you to answer questions at noon ET (1600 UT), AUA! | [
"Without time traveling it's really hard to say for sure! The more specimens we get, and the more with soft tissue, the better our depictions get. Looking at historical paleo art is quite the trip - lumbering, kangaroo, skinny, bland, wattles, etc.. I agree though - there were a lot of dinosaurs that were shrink... | [
"How accurate are artists renderings for the true shape of these creatures? It always looks to me like they drew the body shape too close to the bones. I know the temperatures were such that they likely wouldn’t have needed fur or much fat, but do these fossils show us a more true shape?"
] | [
"Brendan Fraser needs no warning. He is obviously immune to all possible dinomummy curses.",
"\nI wish we had had Brendan Fraser on our side the week the dinomummy went on display here, because we were NOT immune to the curse. Flights delayed and canceled, 6\" of water in the gallery, the electrical failed in t... |
[
"Falling speed is independent of mass. Why is a heavy sled faster than a light one?"
] | [
false
] | [deleted] | [
"Because a heavier sled carries greater momentum, and is subsequently less affected by friction."
] | [
"By Newton's second law f=ma",
"Gravitational force on the surface of Earth is given by f=m(9.81), ",
"so net acceleration is given by a=f/m=[m(9.81)]/m=9.81",
"Now then consider friction (whether due to air resistance or runners on snow).",
"a=(fg-ff)/m",
"As ff gets bigger acceleration gets smaller.",
... | [
"Static friction (i.e. the friction between two non-moving objects) is dependent on the pressure between the objects (in this example the weight of the sled) whereas kinetic friction (i.e. the friction between two objects sliding against each other) is less dependent on the pressure between the objects, meaning tha... |
[
"Theoretically, can you gain energy through nuclear fusion then gain energy through fission of the same material?"
] | [
false
] | null | [
"Unfortunately, no. The energy we're gaining (to use to heat steam in a reactor, say) comes from the change in binding energy per nucleon in the nuclei we're working with. Here's a ",
"nice plot",
" of that quantity, with atomic number (number of protons) on the x axis.",
"Looking at that plot, what you ca... | [
"Iirc those are usually formed in supernovae when fusion isn't sustainable in a star."
] | [
"There's an emerging set of data that strongly suggests that another very large contributor might actually be neutron star merging. Would still follow the r-process, just a different manner of getting there.",
"https://en.wikipedia.org/wiki/R-process#Astrophysical_sites"
] |
[
"What kind of steel makes magnets stronger?"
] | [
false
] | [deleted] | [
"Electrical steel is what is used in transformers and motors. It has high permeability and small hysteresis. You can also look up magnetic circuit to see how your fixture could be used to generate the highest field for the flux generated by the magnet."
] | [
"Laminated steel is often used in those applications to reduce hysteresis, but those involve changing electric currents and magnetic fields. As I understand OP’s question there will be no electrical current (AC or DC) involved, only a permanent magnet. So I believe hysteresis is not a consideration. Please correct... | [
"Non electric, permanent neodymium magnet ( a magnet in a blok of steel with a rope attached, to trow in the ocean an pull the rope back to retreave sweet treasure)"
] |
[
"What would Earth be like if it rotated on the ecliptic?"
] | [
false
] | null | [
"You mean if the orbit of the Earth lay in the ecliptic plane? It does in any situation where the Earth orbits the Sun (Edit: like in real life).",
"You mean if the rotation of the Earth had it's axis in the ecliptic plane? The seasons would be dramatic - like the entire planet was in the arctic circle. The equat... | [
"Diagram",
"I hope this makes sense. I've only described how the sun would look for the seasons on the poles and equator. There would be a sinusoidal gradient that gives the description in between. I've also mostly only shown the behaviour at the peak of each season - again the gradient in between follows a sinus... | [
"Diagram",
"I hope this makes sense. I've only described how the sun would look for the seasons on the poles and equator. There would be a sinusoidal gradient that gives the description in between. I've also mostly only shown the behaviour at the peak of each season - again the gradient in between follows a sinus... |
[
"Traveling through the universe. [Big Bang] [Time Travel]"
] | [
false
] | Assuming that the phenomena of the Big Bang did occur. If there truly was a singularity that our universe existed in. Then, according to the theory, if you were to travel in the direction where this singularity once existed; would you be technically traveling back in time? Also how difficult would it be to determine where this singularity once existed, based off of the movement of surrounding galaxies? EDIT: Of course, to truly head back in time, you would need to travel faster than the speed at which the universe is expanding. | [
"No?",
"I really dislike the balloon analogy, but this is one case where it may be helpful. Imagine that you have this perfectly spherical balloon. The 2-dimensional surface of that balloon is all of space (we're dropping a spatial dimension so that you can picture it). The only directions in which a person livin... | [
"the direction where this singularity once existed",
"That's not a real direction (unless you consider \"straight into the past\" a direction). The so-called \"Big Bang\" was not an explosion into an empty void, away from which all matter is now moving. Rather, it was the rapid expansion of all of space in such a... | [
"That's what the analogy says, but it's not quite right (the balloon analogy is really only good for one or two things, but it can often mislead which is why I don't like it).",
"There are two main places where the balloon analogy fails here:",
"1) In the analogy, the two-dimensional surface is curved in a thre... |
[
"What is Time ?"
] | [
false
] | What is time, and why does it occur. What would happen if there was no time ? How does it occur and is it something like a wave or something physical or none of these. | [
"So let's start with space-like dimensions, since they're more intuitive. What are they? Well they're measurements one can make with a ruler, right? I can point in a direction and say the tv is 3 meters over there, and point in another direction and say the light is 2 meters up there, and so forth. It turns out tha... | [
"Time is directly related to change. If there was no time there would be no change, the universe would be in some constant state, and the only possible way to move in space (given there is space) would be at c. ",
"The best description that I've ever read (and I do believe it was here on ",
"r/askscience",
"... | [
"That's an amazing answer.. So is there time on the very edge of our universe. Do scientist believe that once you get to the edge of our ever expanding universe is there time on the other side (I'm bad at phrasing this) "
] |
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