title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Has anybody thought of using a several barrel system, like a revolver, could make rail-gun use much more practical?"
] | [
false
] | Just a thought in relation to this article, but the other sources I've found on railgun research have been pretty vague. | [
"Well, another problem with rail-guns is the need to secure them strongly. When building a rail-gun capable of firing a 20 megajoule shot, physics tells us that when that shot is fired, 20 megajoules will go back into the firing apparatus. If that is so, then the apparatus should be stronger than the force exerted.... | [
"It's an interesting development. However, as far as I know the major problem with rail guns is that the current used through the barrel is so high as to melt and distort it. Hence many working rail guns have unusable barrels after just a few shots. Until material science fixes this issue, rail guns are just nor a ... | [
"With a revolving barrel system, even if each barrel is only good for 3 shots you could up the number of shots of a weapon system to 18 (assuming you had 6 \"chambers\")."
] |
[
"Is there a way to make bubbles glow in the dark? If so, could it be done at home? Would it be safe?"
] | [
false
] | null | [
"Mix in some flourescein or rhodamine - two very fluorescent molecules - with the bubble solution and shine a UV lamp on them in a dark room. "
] | [
"Also, ",
"r/trees",
" has discovered that mixing the liquid inside glow-sticks with the soapy bubble blowing liquid does not work. . . OK sorry that is kind of a joke but why won't that work? Maybe I'm just an idiot but that seemed plausible to me. "
] | [
"OK. Thanks! Two questions. 1. Where do I acquire this flourescein / rhodamine? 2. Will I die or be in any lasting pain if I do this?"
] |
[
"How was soap discovered to be effective?"
] | [
false
] | It is bewildering to me that soap has been around for so long (a quick google says earliest recorded use was in Babylon ~2800 BC - 2200 BC.) Has it always been effective for killing germs? Seeing how far back it has existed in history it seems like it was used a few millennia ahead of its time. I know ancient civilizat... | [
"Soap works because one end of the soap molecule wants to dissolve in water while the other doesn’t, this naturally allows it to surround things in water with the end that doesn’t want to dissolve facing inwards. For this reason it is good at washing things away. It can also kill some germs by disrupting their memb... | [
"They had a lot of free time and decided to boil rotten fat with ashes. They got a fun rock that made bubbles when wet and while playing with it they found the grime got out of their hands, so they started trying it in other parts of their bodies and perfecting the formula. At least that’s how I imagine it went. An... | [
"They didn’t know of the existence of microbes so they would have used soap for its ability to remove dirt from things. ",
"If I'm understanding correctly: ",
"Before germ theory, soap was only used to remove visible (macro) soilage, such as a muddy shirt (cosmetic). ",
"Without getting theory, we're dining d... |
[
"Could you engineer a 100% efficient diet? I.E. one that produces no waste products, feces?"
] | [
false
] | null | [
"That's basically what intravenous feeding is...",
"But if you mean food you actually have to eat... Even if you somehow managed to produce food that contains only nutrients the body is capable of processing in the right quantities, it would still not be possible for your digestive system to absorb it all. The wa... | [
"Dead bacteria makes up some considerable percentage of feces. "
] | [
"Indeed, but bacteria lives in our digestive system only because we eat stuff they feed on. Which is not always the same stuff we absorb. But that's one of the reasons I said \"minimal\"."
] |
[
"What causes the \"rainbow effect\" on fast moving objects in satellite pictures?(Image inside)"
] | [
false
] | I was browsing Google maps and found a plane that was blurred with an interesting "rainbow effect". or Does anyone know why the colors seem to be separated out in the order of red, then green, then blue? My best guess was that the satellite took pictures in a similar process that the Mars rovers followed: taking a se... | [
"I'm fairly certain that most commercial imagery satellites are pushbroom scanners. I know for certain IKONOS is of that type, and I would assume others are (it is a cheap way to do it). This means the detector is a linear array of pixels in the cross-track direction (perpendicular to the ground track of the satell... | [
"Its the same idea, except not with filters, just different colours being registered by the digital camera at slightly different times. The different colour channels are matched together after they're taken to account for the movement of the aircraft, but obviously this falls apart if other stuff is moving.",
"Th... | [
"My best guess was that the satellite took pictures in a similar process that the Mars rovers followed: taking a series of black and white photos with various color filters over the lens and then combining the photos in post-production.",
"Yes, that's probably it. Newer satellites don't always do this, so it's no... |
[
"Physics noob: What happens to the suns heat after it hits the earth?"
] | [
false
] | Here is my very noobish and probably wrong understanding of the physics of heat on Earth. Sun sends rays, rays warm up planet, get stored in plants, animals eat plants, energy becomes kinetic as animals and people move, that energy then becomes heat, then becomes radiation. Is that correct? If it is (which I'm probably... | [
"The first part of your post is essentially correct, the radiation from the sun heats up various things, gets absorbed through photosynthesis in plants and the energy is then transfered to animals who use it to move. And heat is produced along the way. The energy balance on Earth is, as you can imagine, fiendishly ... | [
"Radiation is an incredibly broad concept, which might be confusing. What is most commonly meant by radiation is electromagnetic radiation. This comes in many forms, depending on the wavelength (or frequency, which is a correlated quantity). Visible light is a form of electromagnetic radiation, but so is infrared. ... | [
"Also CO2 is not the largest contributor to the greenhouse effect, water vapor is.",
"Right, but the amount of water vapor in the air at a given temperature is fairly constant. By increasing the amount of CO2 in the atmosphere, you're increasing the temperature, which is increasing the amount of water vapor that... |
[
"Why are serotonin agonists used to stop acute migraine, while serotonin antagonists are used for its prevention?"
] | [
false
] | Could somebody explain why triptans which are 5-HT agonists are used in the management of acute migraine, while pizotifen - a 5-HT antagonist is used for their prevention. I know the pathophysiology isn't perfectly understood but I'm struggling to wrap my head around this | [
"Probably cause serotonin deficiency causes migraine. So to solve this you would use serotonin agonist in an acute case to stop it and you would use an antagonist so in the long run you get a net increase in serotonin via upregulation of serotonin secretion because serotonin receptors can't be activated, so the bod... | [
"That would also explain why taking a lot of triptans over time can increase the frequency of migraines."
] | [
"This isn’t the case at all. The underlying mechanisms of migraines aren’t well understood. There are essentially 3 proposed mechanisms and none of them include a lack of serotonin. One of the mechanisms is a vasogenic cause where increased cerebral blood flow causes increased pressure and therefore pain. Triptans ... |
[
"Will melt-water originating from the Greenland glaciers cause the Thermohaline circulation to stop and cause an ice age in Europe??"
] | [
false
] | Al Gore claims that meltwater from the greenland glaciers could stop the , which in turn could cause an Ice Age in Europe. Does reddit have any experts in Global Climate Change that could test the validity of his prediction? Questions that might help answering the big question: | [
"Philosopher William Calvin used to be one of the big names in this area.",
"I haven't looked at his site for several years, but -",
"- ",
"http://williamcalvin.com/atlantic/",
" -"
] | [
"The short answer is \"no\" -- however, if the Gulf Current were to stop for some reason, Europe would become significantly colder / dryer -- similar to interior countries at the same latitude.",
"Furthermore, the thermohaline circulation could not stop immediately -- it takes thousands of years for a cycle to co... | [
"How exactly will the melt water cause the thermohaline circulation to stop? ",
"Deep water formation can only occur if the density of the surface water exceeds that of water at depth. Both cooling and greater salinity can create increased density. If the water is too fresh, it doesn't matter how much it is coo... |
[
"If they put additional fuel and a LEM in the Space Shuttle's cargo hold, could it land men on the moon?"
] | [
false
] | [deleted] | [
"No, the space shuttle was designed for low earth orbit. It was simply too heavy and couldn't carry enough fuel for a lunar orbit. By adding additional fuel, it would be too heavy for launch in current configuration. Would have to add additional engines/boosters to go to the moon. "
] | [
"To add to this, the S-IVb booster used for the translunar injection of the Apollo program had a mass of 119,900kg , not including the Apollo spacecraft itself. This stage provided approximately an extra 3km/sec needed to change the spacecrafts orbit is that it intersected the moon. ",
"Now, that's a big stage, a... | [
"It's been a very long time since I did these kind of calculations (actually, I am a rocket scientist, but I focus on air breathing propulsion today) but if you'd be able to get enough fuel and a way to attach the shuttle to the tank in LEO, maybe. Just gotta reach escape velocity. It would be a huge engineering ch... |
[
"Do whales or other ocean dwelling mammals get colds or flus?"
] | [
false
] | null | [
"Absolutely. ",
"Influenza is well-documented in whales and seals",
", and at least in whales has been associated with ",
"some mass-strandings",
". Analysis of serum samples show that it's pretty common for marine mammals to get some form of influenza, ",
"usually passed to them from wild birds",
".",
... | [
"Oh wow! I couldn’t think of how an illness could transmit from one marine animal to the next. I never considered birds as a method!",
"Thanks for all the links. Lots of reading material."
] | [
"Wow fascinating thank you for posting this I never would have known!"
] |
[
"Why Does Radiometric Carbon Dating Reflect the Age of an Object Being Dated if the Carbon is Older than the Object?"
] | [
false
] | So, let's say we are dating a animal bone from the bronze era. Carbon dating will reflect it's age. However, the carbon the animal had to consume to make that bone would be older than the animal and was likely a part of some other animal or plant, right? So, how are the isotopes "Reset" to reflect the age of the bone? | [
"The carbon isn't (much) older than the animal, in fact. ",
"Carbon-14 is formed in the upper atmosphere from nitrogen-14 and the products of cosmic rays. That carbon becomes carbon dioxide, which gets mixed in with regular ol' carbon-12 and carbon-13 containing CO_2 and taken up by plants. While the plant is ... | [
"This does explain one of the caveats of carbon-dating though, which is that there are some organisms in some environments which regularly use carbon that hasn't been atmospheric recently. Organisms dwelling in the bottom of the ocean are a classic example, since they could be uptaking carbon that has been out of ... | [
"When animals are alive, they generally contain a set proportion of the isotopes and elements that are relevant for radiometric dating. These proportions only start to change after the death of the animal. So we know the starting proportions, the decay rate, and the current proportions, and can thus calculate the... |
[
"Where do germs go when they’re killed?"
] | [
false
] | If there’s a table covered with germs, and you spray some disinfectant on it, are the germs still there, but dead? Or does the cleaner make them evaporate? I guess I’m just asking what happens to germs and other microscopic organisms when they die? | [
"Depending on the type of cleaner. Some will dissolve the outer layer of the bacteria, causing it to explode and the cell contents will then be destroyed by UV light and chemicals, leaving the basic amino acids behind, this is probably most common. Others could kill the cell but leave it intact, so it would remain ... | [
"Thanks! I’m not worried, I was just curious"
] | [
"They just desintegrate or Vaporize, depending on the Sterilisation Method.",
"If they die Naturally they stay there a little to then eithe desintegrate Naturally, be Eaten by the next Generation or ooze and Vaporize."
] |
[
"How big can a planet get??"
] | [
false
] | I feel like most planets fall within a certain size but I don’t know why size would have anything to do with a clump is mass. What would prevent a planet from becoming the size of our solar system or something? Would it turn into black hole? | [
"What a body accretes past a certain size gravity will trigger fusion, and the result is a star.",
"Jupiter is big, but it is estimated it would need to be about 75 times bigger to initiate hydrogen fusion."
] | [
"Based on modelling and observation of exoplanets, Jupiter is near the largest size a planet can get under normal circumstances. More massive worlds are just more compressed, so as you increase mass there actually appears to be a ",
"slight downward trend",
" in radius. Once you pass 13 Jupiter masses the inter... | [
"Yes, actually."
] |
[
"Can wearing reading glasses damage your vision if your vision is perfect?"
] | [
false
] | I sometimes wear reading glasses just for the magnification I get from them, but sometimes I worry that I may be stressing my eyes by forcing them to adjust to the magnification when it's not absolutely necessary. Are my worries valid? | [
"When your eyes are working hard for a long period of time, they become tired, much as any muscle would. The strain may result in a number of physical effects including sore or itching eyeballs, headaches, back and neck aches and blurred vision. Because you often don't blink enough when focusing on a single object,... | [
"The big thing with reading glasses isn't the magnification (which is usually negligible and won't do anything to you even if it was large other than perceptual adjustments that would be required), but the ability to relax your muscles responsible for accommodation. This is actually needed around age 40-45 because... | [
"I don't think so. This question came up at my last eye doctor visit. Wearing glasses that are the wrong prescription for your eye does not have any long term damaging effects on your eyes. Thus in your case, wearing reading glasses should not weaken your eyes. ",
"Relevant Link"
] |
[
"How can certain species interbreed while others can not?"
] | [
false
] | For example, how can a horse and donkey breed to make a mule, but a dog and cat cannot breed to make a hybrid offspring? Does it have to do with the order or genus that they are in? | [
"It has to do with a great many factors, but as Pravusmentis points out, the term \"species\" is arbitrary, and any one definition hardly works well across all of life as we know it (much less as we don't know it). But, to simplify the problem, if we have two species they must be insufficiently diverged from each ... | [
"THe problem is is that there are multiple definitions of the word species, these are called concepts, the most familiar to most people is the 'biological species concept', I hope this helps you",
"http://en.wikipedia.org/wiki/Species"
] | [
"I am familiar with this concept. To clarify, i would like more elaboration on how some animals with different binomial nomenclature can breed while others cannot"
] |
[
"What is the natural of neutrino interaction with matter ?"
] | [
false
] | Neutrinos rarely interact with regular matter, but they do eventually and that's how we can detect it. But what is the nature of this interaction ? Is it ionization for example ? Or other kind of interactions with the subatomic particles ? Ultimately, will an ultra dense high energy neutrino burst be lethal with sempto... | [
"Ultimately, will an ultra dense high energy neutrino burst be lethal with semptoms similar to radiation poisoning/sickness ?",
"Yes. You have to be ",
" a supernova to make it lethal, however - and if you are inside an exploding star you probably have other things to worry about before.",
"https://what-if.xk... | [
"It's almost exclusively via the weak force (gravity is negligibly small). Many kinds of interactions can occur, like elastic scattering off of a nucleus, or a reaction called \"inverse beta decay\", where a neutrino interacts with a nucleus, changing its species, and causing an electron/positron to be emitted. "
] | [
"most people believe they don't interact at all.",
"Well I hope most people don’t believe this, because we know it’s certainly not true at all.",
"Neutrino interactions with matter are improbable, but well-understood.",
"Maybe that's because these are similar to Neutrons being chargeless, but without a size, ... |
[
"Is there an IC that will give me a high/low value for a specific input bits?"
] | [
false
] | I'm trying to find a relatively cheap IC that will give me a high or low depending on a signal it gets. I have 6 input bits. For now, I have a "digital comparator" in mind, where the 6 input bits will be compared to the 6 bits that I wanted... so the problem here is that I have to individually wire each bit (14 lines p... | [
"Do you mean a programmable comparator? 74526, 74527 and 74528 are fuse programmable comparators."
] | [
"leave it to a physicist to add in additional complication by reducing everything to the most fundamental elements."
] | [
"That's funny! As an electronics geek I was thinking all those additional resistors."
] |
[
"Can someone explain Planck Length? Is it really the minimum distance a particle can travel?"
] | [
false
] | null | [
"No, it's not. Where did you read that?",
"It's a distance constructed from physical constants, so if we ever meet an alien civilization we can share a common ground in our units by explaining them in relation to the Planck units. Not all Planck units are necessarily small: the Planck momentum is typical of a thr... | [
"It's a collection of physical constants that isn't even unique. Planck put it together in 1899, which explains why he used Newton's gravitation constant ",
", for example, rather than the ",
" that appears in Einstein's equations, and it was never updated.",
"The ",
" would have made the Planck length abou... | [
"The second paragraph isn't even universal to all quantum gravity theories. Planck units make a lot of algebraic constants zero, simplifying the math if we do specific problems in Planck units. Due to this simplification, some theorists pick it as a convenient choice of scale for new physics."
] |
[
"Where do mosquitos hang out/spend their time?"
] | [
false
] | How are they able to so quickly be on you every time you step outside? | [
"Adult mosquitoes dislike heat and will stay in shady areas during the day, only coming out to feed if they sense your CO2. That shady area might be under a deck, for example, though they mostly like the underside of leaves, especially dark glossy leaves. Ivy ground cover and rhododendron are two notorious hotspots... | [
"Thank you! Makes sense as I live in Florida where there is plenty of vegetation so they’re always nearby!"
] | [
"Males and females both first get food from flowers. Then, after mating, the females become vampires for egg nutrients.",
"Males don’t really need to be around animals (only by relation because they need to be near females which need to be near animals), so we tend not to see them as often. But usually, they’re m... |
[
"Do free floating planets inevitably become orbiting planets eventually?"
] | [
false
] | This article on the front page is what got me wondering: Do these free floating planets eventually sort of drift in the vicinity of a star and begin orbiting? It seems like if it were just drifting in space it would eventually enter the gravitational field of a star -- or is there something that prevents this? | [
"It gets captured by a star if its speed is roughly below the star's escape velocity, the square root of 2GM/r, where M is the star's mass and r is the distance between the planet and the star.",
"The planet needs to be below the escape velocity ",
", not when it's in interstellar space. And since it approaches... | [
"It gets captured by a star if its speed is roughly below the star's escape velocity",
"No it doesn't. There's no such thing as two-body gravitational capture. Two-body orbits are conic sections (circles, ellipses, parabolas, or hyperbolas) and nothing else. A rogue planet entering the vicinity of a star would be... | [
"You also have to note that without the presence of a third body or large tidal forces, a free planet can not get captured into an orbit. "
] |
[
"Why are young kids able to learn new languages so much faster and easier than adults?"
] | [
false
] | [deleted] | [
"You are, quite simply, wrong, and not just a little wrong. The studies of language and critical periods are really well developed. Especially with respect to people who are first native in a second tongue and then move to the USA, these things are well studied. The ability to learn language begins to go downhill... | [
"Oh, jeez. You've opened up a huge bag of worms within the language science community. I'm trained as a linguist, so my preferred idea comes from ",
"generative linguistics",
", a school of thought pioneered by Noam Chomsky. According to Chomsky, kids are able to learn language so quickly (and use language i... | [
"There is a controversy within linguistics and cognitive scientists about the term 'innate'. There are two main ideas floating around:",
"The language structures in the brain are innate (determined by genetics) and develop over time. This is the common view of many linguists including Steven Pinker. So basically:... |
[
"What does the little plastic thing on masks do?"
] | [
false
] | Here's an image | [
"It's a breather. So instead of air just filling up the mask when you exhale the breather allows a path for the air to leave the mask while still keeping a barrier between the outside air and your nose and mouth."
] | [
"Many have pointed out that this is a valve.",
"Given the current Covid19 issues it's probably worth pointing out. This will work well if you have to wear a mask around sick people, and will help prevent you breathing in the infection, while being a little more comfortable.",
"In the main people are being asked... | [
"It's a ventilation port that helps limit any dizzying or discomfort from wearing your mask. A valve that allows the release of CO2 from your breathing area. As you inhale oxygen the valve closes and when you exhale, it opens letting you breathe better."
] |
[
"My daughter asked me a simple question that I haven't the foggiest answer to. \"Why do batteries get hot?\""
] | [
false
] | We've all experienced it. The laptop battery getting hot on our lap. Our cell phone batteries. Various electronic appliances. What's going on that generates that heat? And is the amount of energy lost due to that excess heat a significant inefficiency, or is it really just a tiny amount of the energy actually provided ... | [
"Like the others already explained, the heat generated is an inefficiency in the transformation of the stored energy to usable energy in your electronic device. This is the same reason lightbulbs get hot. Additionally, it might not just be heat from ohmic resistance, but also exothermic heat from chemical reactions... | [
"On battery charging: NiMH batteries actually have a very specific temperature profile while charging that you can use as the most accurate way to determine when they are fully charged. "
] | [
"This is called \"internal resistance\" and it's present because the chemical reaction that powers the battery only proceeds when the battery voltage drops. The lower the voltage, the more reaction occurs, and the more electrons/current that gets produced. This relationship between voltage and current is identical ... |
[
"Why do hybrid cars have poor acceleration and 0-60 times if electric motors have their maximum torque from a standstill?"
] | [
false
] | I read that electric motors are at 100% of their potential torque when accelerating from 0. Is this correct? And if it is true, then why don't all hybrid car makers design their cars to accelerate using their electric motors, since the lack of power is one of the major downsides of hybrids? | [
"Most hybrids use a very small electric motor. The electric motors in the Prius add about 35hp-- so even though they may make all the torque they can make at low RPM, they don't make a lot of torque. They're just not very big.",
"No reason you can't make a neckbreakingly-fast hybrid or electric car-- but most o... | [
"Gasoline powered cars also have their maximum torque at standstill. The engine certainly doesn't, but the engine ",
" at a standstill, and they're in first gear, and the clutch/torque converter is making up the difference.",
"Saying that electric motors have their maximum torque at a standstill is also kind o... | [
"Actually unless they're at the peak torque curve, they are not completely at peak torque, only approaching it because they're in the highest torque applying gear.",
"The torque converter allows slip but generally it is not going to slip all the way to peak torque. This is why performance automatics have increase... |
[
"How much current do my glasses produce when I'm accelerating on Earth?"
] | [
false
] | My metal frames should produce a current, no? How much if, say, I accelerate from 0mph to 60mph on a highway ramp on 6 seconds? | [
"I think you're asking about moving a conducting loop through a magnetic field, right?",
"In that case, the answer is \"not much\", meaning ideally zero: the induced emf (voltage) around a loop is equal in magnitude to how fast the magnetic flux through the loop is changing. (emf = -d(flux)/dt). If you travel in ... | [
"I vote no. I mean both the nuclei and electrons are being accelerated with you as you move forward. I could be wrong, but that's my thought. In any case it would probably more appear as a voltage different rather than a current as it doesn't complete a circuit."
] | [
"Perhaps you are thinking about motion through a magnetic field?"
] |
[
"Does laughter serve an evolutionary purpose?"
] | [
false
] | Does laughter improve survival chances or is it some weird side effect of carrying around supercomputers in our heads? It's clearly some form of human communication...but what exactly is being communicated? From introspection, I've thought that maybe laughter is a response to a perceived danger where the response, "N... | [
"Yes! ",
"This radiolab episode",
" gives a great summary of why we laugh.",
"From what I remember, one theory is that it has to do with play. For example, if two young chimps are chasing after each other, \"wrestling,\" grabbing each other, etc., they would make a laughing sort of sound to indicate they ar... | [
"Man I love radiolab! This episode in particular was great, as well. "
] | [
"I've been wondering this for a while, interesting stuff."
] |
[
"Is it easy to count in tens because we have ten fingers? So if we instead had eight fingers, would we count in eights?"
] | [
false
] | null | [
"Yes it is believed that if we had eight fingers we would have a so called ",
" counting system. In fact some computing functions use base 8 and call it ",
"octal",
". 10 is arbitrary from a mathematical perspective and is not optimal for manual use as 10 has so few divisors. Some ancient civilizations even... | [
"I have read that the Babylonians' base-sixty system arose because of their way of counting on their fingers. To wit:",
"Does anyone know if this is just speculation, or is there textual or anthropological evidence of people actually counting this way?",
"Either way, it's a pretty nifty way to count to surpris... | [
"Sure, just like programmers get really good at base 2 math. It's all about exposure."
] |
[
"Is it cheaper to turn your hot tub down or leave it at your ideal soaking temperature?"
] | [
false
] | A friend and I have a disagreement on this issue, I think he is wasting money turning his hot tub down to 87 every night and that he would save money by leaving it at 102, he dismisses the idea outright. I tried to do the math myself, here is what I came up with: Assumptions: First we calculate the heat transfer rate a... | [
"What you've done is calculate the length of time the hot tub would have to sit at 87F before turning it up to 102F would cost the same as always having it at 102F. But in the latter case you would have already had to get the water from 87F to 102F. In other words, assuming that in both scenarios the water starts a... | [
"given an assumption that the energy to heat the pool is greater than the losses to the environment. ",
"This is the critical bit. This assumption is incorrect-- you can only lose as much energy to the environment as you've put into it. Never more. ",
"He's right-- the primary difference is that keeping it h... | [
"Yep. It's always going to use less energy to heat the house if you turn it down or off when away when compared to keeping it at the same temperature while you're gone. There's practical limits, of course-- you don't want it so cold the pipes freeze, and you need to keep in mind how long it will take to warm back... |
[
"If a p value of p=.01 was obtained does that mean that the likelihood of my results being due to sampling error would be 1% or 99%?"
] | [
false
] | I am finding it hard to get my head around so if someone could explain to me I would be very greatful! | [
"The p value is the probability of observing the result you did given the assumption of the null hypothesis. If you get an extreme p value, the implication is that the original assumption is false. However, there may be many reasons your p value is extreme - unrepresentative sample, poor randomisation, other variab... | [
"If you have some hypothesis, and you get a p-value of 0.01, it means that ",
", there is a 1% chance of observing a result at least as extreme as what you observed.",
"This indicates that what you observed is not very compatible with your hypothesis."
] | [
"The p value is the probability of observing the result you did given the assumption of the null hypothesis.",
"Almost: it's the probability of observing a result ",
" as you did, given the null hypothesis. Your p-value includes not only the result you saw, but also any results that were even further from what ... |
[
"How does the cosmic microwave background persist? Why hasn't it been distorted and destroyed by new sources of energy pumping into space?"
] | [
false
] | null | [
"This is just nonsense.",
"There is no \"distance to the CMB\"; the CMB is an omnipresent background radiation left over from when photons were no longer in thermal equilibrium with matter. This event took place at a redshift of about z = 1100, or about 370,000 years after the big bang.",
"It is not true that t... | [
"This is just nonsense.",
"There is no \"distance to the CMB\"; the CMB is an omnipresent background radiation left over from when photons were no longer in thermal equilibrium with matter. This event took place at a redshift of about z = 1100, or about 370,000 years after the big bang.",
"It is not true that t... | [
"The universe is largely transparent. Sure, some parts of the radiation have been absorbed, and there is a bit of new emission at this wavelength range, but overall it is not a large effect and it can be taken into account."
] |
[
"What evolutionary adaptations would occur in animals (and plants) in an environment bathed in constant low-level sunlight?"
] | [
false
] | null | [
"Well it's pretty difficult to speculate even what types of life would evolve, and by no means is it limited to animals and plants. It's also incredibly hard to say for sure what features evolution will come up with, since it is random which mutations happen first (despite some being preferable). I imagine this is ... | [
"This isn't something we can predict.",
"There are too many possibilities and variables. Any answer would be purely speculation."
] | [
"I think it fairly unlikely that anything related to the circadian rhythm would've evolved, but this is HIGHLY speculative."
] |
[
"Is there a consensus on how cannabis impacts the brain in the long term?"
] | [
false
] | I always read the research on acute effects, which while useful, I find to be less personally important than long-term effects. This is because I use it usually in contexts where I'm okay to have some deficits in memory etc. However, is there good research on the long-term effects? I'm looking to the literature now but... | [
"There are very few studies into the long term effects of THC on the brain, specifically on developed adult brains, for a few reasons. It's been very difficult to study THC because of its restrictions in the past, although now it has become less restricted there hasn't been enough time for long term trials. Most o... | [
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4104335/",
" ",
"It limits your ability to form memory, specifically when consumed young. Its why even when de-criminalized, its still a criminal offence to give to teenagers.",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4880314/",
"As much as people would lo... | [
"I have come across this thread. The research paper in it and the short discussion below the post might help out.",
"I can not really tell if it is a \"good\" or \"bad\" article but at least it is a quite large meta analysis.",
"\n",
"https://www.reddit.com/r/science/comments/s9s0hb/meta_analysis_finds_cannab... |
[
"Why are patients with concussions told not to sleep, or not to sleep for long periods?"
] | [
false
] | null | [
"Patients are ",
"no longer advised",
" not to sleep after concussions."
] | [
"When a person gets a concussion, they always have to be monitored for a few hours because after a concussion the inside of the head might be filling up with fluid. The fluid might cause the person to pass out and when someone is asleep this cant be noticed."
] | [
"This was the thinking, but current recommendations and guidelines no longer suggest waking them. It still says dont let them go to sleep immediately, but a couple hours of being awake is usually seen as good enough."
] |
[
"Do insects sweat or show any other type of physical signs to excessive heat?"
] | [
false
] | null | [
"Death?",
"Okay, seriously now. Insects are generally better at handling cold than heat. Honey bees actually exploit this for protection/defense. The Asian Giant Hornet can devastate a bee hive that is unable to defend itself during an attack on the hive. Native Japanese bees, however, have evolved a defensiv... | [
"Huh. I knew about the \"hug of death\" phenomenon, but I'd always thought that insects handled heat better than cold simply due to the seasonal and geographic distribution of insect diversity as it relates to heat - all over the bloody tropics and huge population booms in the summer, and barely present in winter o... | [
"Ya I’m with you. There are many pest insects that rise in numbers with mild winters. And the one thing guaranteed to knock back the population is a cold winter. The pine beetle devastating Canadian pine forests is only held in check by bitter cold snaps in the winter, mild winter and the populations explode. I"
] |
[
"How does a muscle attach to a tendon and how does a tendon attach to a bone?"
] | [
false
] | Is it physical structures like microscopic hooks/anchors? Some kind of biological "adhesive"? Edit: Question answered. Several very knowledgeable people have done a great job of explaining that there is no "attachment" rather there is no end between bone/tendon and muscle, they all just merge into each other. Which is ... | [
"Tendons are something in between pure fibrous tissue and bone tissue. So they kinda stick to the respective bone as a very adhesive tissue that is interwoven with the bone cortex. As you follow the tendon to the where it connects with muscle, it is more fibrous is origin and resembles muscle itself in structure. F... | [
"At entheses, the tendon or attaches either directly to the bone or indirectly to it via the periosteum, i.e. the outermost layer of the bone. If you look at a histological section of it, there is no point of clear differentiation between where the bone ends and the tendon begins, but rather there is fibrocartilagi... | [
"There is a process called ",
"Osseointegration",
" where bone will envelop artificial structures attached to them (say, pins or joint replacements). This happens with organic tissue as well, as is referred to in ",
"articles such as this one",
"."
] |
[
"How does \"anti-odor\" clothing work?"
] | [
false
] | For example, Uniqlo HEATTECH and AIRism is marketed with anti-odor properties. Is it a characteristic of the fabric they use, or is it a chemical? I believe many other brands like Under Armor do similar things. | [
"Copper is an antibacterial, which is one of the two components in brass, the other being zinc."
] | [
"While I have not researched the brands you mentioned, as I understand it, the reason they are able to be anti-odor is because they are anti-bacterial. I'm told there are two metals that have this property innately - brass (which is actually an alloy, so I'm not certain which metal, or the combination, may supply t... | [
"I have a couple UnderArmor undershirts that have silver woven into the fabric at major sweat points like the back and armpits. While it isn't perfect, it does make a noticeable difference on oder levels post-workout."
] |
[
"How exactly do big, heavy snakes like boa constrictors and anacondas catch prey that is so much faster and heavier than they are?"
] | [
false
] | I always see documentaries where big constrictors have caught antelopes and are trying to swallow them, but how on earth do they catch them in the first place? EDIT: Maybe it's just because I usually frequent less popular subs, but lol my inbox is overflowing. Thanks for all the info! | [
"Same way crocodiles do it. Ambush. They stealthily get close and wait for the prey to come to it. Don't underestimate the power and speed of a big snake. Think of it this way, a big snake means it's good at being a snake. He's about that snake life. "
] | [
"In addition to the \"ambush predator\" responses, snakes are cold blooded, which drastically cuts calorie requirements. It means snakes can go a month+ without a meal. They don't need to catch something every day, so they can afford to be patient. "
] | [
"What does it do while not hunting? Travel? Take the fam to Disney?"
] |
[
"Do black holes continue to grow in mass indefinitely?"
] | [
false
] | Will they continue to consume anything that crosses the event horizon or do they eventually reach equilibrium by ejecting radiation? Or is there another option I haven't been exposed to yet? | [
"If you keep feeding them, they'll keep growing. However, you are right that due to Hawking radiation, it's possible for a black hole to consume matter at (on the average) such a slow rate that they lose more than they take in, and so lose mass on the whole. But in normal black holes Hawking radiation is such a tin... | [
"Hawking radiation is extremely low for normal size black holes. It's less than the cosmic background radiation. This means that the black hole absorbs more energy from the background radiation than it radiates as Hawking radiation. Thus its mass will increase. This will continue to happen until the universe has co... | [
"And yes, if the temperature of the Hawking radiation matches the temperature of the space outside a black hole, it will reach an equilibrium.)",
"I would think the equilibrium would be only momentary, as the decline in the temperature of the cosmic background radiation would lead to continual black hole shrinkag... |
[
"How deep could you dig to still be able to mine gold, silver and gems?"
] | [
false
] | The Tau Tona Mine is 3.9 km deep and they are mining gold. How deep could you dig but you won't find any solid minerals, gold/silver because the pressure would be to high or gold would have already melt? | [
"No, the drillbit doesn't \"stop working\". The drilling process is a lot more complicated than that. Drilling in what's known as hot hole conditions is done daily all over the world. I've done lots of it.",
"The true limitation of drilling deep like that is controlling the direction of the well bore and torqu... | [
"http://discovermagazine.com/2006/sep/innerfortknox#.UOqhqXevO-0",
"You could go to the solid core, where there's much more gold."
] | [
"The question becomes, how deep can we dig before certain metals/alloys start to melt? The thickness of the crust varies where you go (it's actually thinnest in the oceans, but we're not ready for experimentally deep holes at the bottom of the ocean). The deepest humanity has ever dug is the ",
"Kola Borehole in ... |
[
"Is \"the speed of light\" really a misnomer?"
] | [
false
] | [deleted] | [
"One of my friends in college once said this",
"Do you know why I believe in God? Water freezes at exactly 0 Celsius and boils at exactly 100 Celsius"
] | [
"well that's the speed of propagation of light ",
". The photons themselves still travel at c. They just get absorbed by charged particles and held for some time and then re-emitted, slowing the bulk travel through the material."
] | [
"a photon can be slowed down to the speed of sound",
"No it can't. The photon always moves at ",
". ",
"The photons are absorbed and retransmitted a moment later that gives the illusion of slowing down.",
"Source",
"This is something that popular science articles like the one you've linked always fail to ... |
[
"What exactly does the inverse-square law apply to?"
] | [
false
] | I know it applies to heat radiating from something, but what else? Light? Other methods of transferring heat? Sound? If it applies to some things and not others, how are they different? | [
"From just the other week: ",
"Why do so many phenomena follow the inverse square law?",
"."
] | [
"Anything that radiates out forever in all directions from a central point ought to work in the same way. It's related to the surface area of a sphere. A=4*pi*r",
" , where r is the radius of the sphere. Given a certain amount of some flow through a smaller sphere (like light passing through the sphere around the... | [
"The inverse square law is justa rleation between things that are proportional.",
"Basically the intensity of the property is directly proportional to the square of the sepearation between the elements."
] |
[
"Does anesthesia have a purpose other than preventing pain?"
] | [
false
] | If you couldn't feel pain, would you still undergo anesthesia? | [
"Hi, I just want to make a shameless plug for my specialty.",
"I think the term “anesthesiologist” is somewhat of a misnomer. Sure, part of our job is to make patients unconscious to allow surgeons to perform their operations. But what isn’t readily apparent is that our job only begins once the patient is asleep.... | [
"First year med student here. I never thought of anesthesiology as a potential career until now, wow thank you for that insight, and well put."
] | [
"I agree with what ",
"/u/lallen",
" says about the BIS monitor, which gives you a processed EEG that sort of tells us how aware a patient is. It's not infallible, though.",
"Rest assured that awareness under anesthesia is not very common in general. There is a study that looks into awareness ",
"here",
"... |
[
"How far are we from a treatment that safely cleans blockages and plaque from our arteries?"
] | [
false
] | null | [
"This may not fully answer your question but it will be a fundamental part of the understanding.",
"\nThe currently most widely used treatment protocols for \"cleaning blockages and plaque from our arteries\" is PCI.",
"\nPCI is percutaneous coronary intervention. It usually consists of placing a stent in the ... | [
"Thanks for the helpful reply! Do you think a system wide treatment for atherosclerosis is possible?"
] | [
"What do you mean by system wide? Like a pill that dissolves established plaque and reduces atherosclerosis body wide? Currently there are ",
"a bunch of different medical devices that can roto-root out most plaques (atherectomy is the correct term)",
"."
] |
[
"Which part of the body lasts longest after death?"
] | [
false
] | [deleted] | [
"Bones and teeth. That's why bones and teeth are left when we unearth thousands of years old bodies."
] | [
"Teeth last longer than bones. They are much harder and do not readily decompose if moving through a digestive system."
] | [
"But is it bones OR teeth?"
] |
[
"Are new vs old tires (treadwear difference) enough to affect speedometer calibrarion?"
] | [
false
] | null | [
"Yes, a quick calculation shows the calibration could change by about 1.5 mph (~2.5 kph) at highway speeds.",
"Tire tread depth generally starts around 11/32\", while old tires can have about 3/32\" of tread so we lose about 8/32\"=1/4\" of radius over the life of the tire. Tires are generally about 10\" in radiu... | [
"That's an oddly specific question. Are you trying to fight a ticket?"
] | [
"No, it's 10% below the needle; just something I noticed a few weeks after buying the car and confirmed via GPS. So if I want to do 70 I need to have the needle near about 76-78.",
"In fact it's keeping me from speeding because, well, if I don't think about it I think I am going 5mph over when in fact I'm 2-3 bel... |
[
"Question about orbital physics: How hard is it to disrupt the orbit of an object?"
] | [
false
] | I'm relaxing and contemplating the growing collection of space junk that is surrounding the planet. Due to the incredible range of speeds and altitudes of the various debris, it seems next to impossible to ever sweep it all up. But perhaps a repurposed SDI concept would work, something that could detect and then remote... | [
"A small nudge will only (very) slightly alter the orbit and not cause the object to spiral to the atmosphere. Say you have something at a similar altitude as the ISS (400 km). Then you want to deorbit it to 50 km altitude where the atmosphere will do the rest. You need to change the velocity of the object by about... | [
"To add to this, one solution proposed to manage 'space junk' is to aim a ground-based laser at the junk. The force of the photons hitting the junk would, over time, be enough to slowly de-orbit the junk."
] | [
"A space based laser would be much more effective - less atmospheric absorption and much better targeting angles (ie along the horizon as the object rounds the planet)."
] |
[
"Mass Effect question: How fast would a lead projectile the size of a grain of sand have to be moving to have the same energy as a regular bullet?"
] | [
false
] | In Mass Effect, "to generate ammunition a weapon shaves a projectile the size of a sand grain from a dense block of metal contained within the weapon's body. The projectile is launched at supersonic velocities by decreasing its mass in a mass effect field." Ignoring the bit about the mass effect field, I tried to figur... | [
"You want to solve the equation (mass of sand) x (velocity of sand)",
" = (mass of bullet) x (velocity of bullet) ",
" "
] | [
"Kinetic energy (in SI units) = 1/2 * (mass) * (speed)",
"Therefore:",
"1/2 * 1,3 * 10",
" * 10",
" kg * (speed)",
" = 1,796 J",
"(speed) = 1,662,251 m/s"
] | [
"The math was provided in another post, but from a practical standpoint, I would like to add that the speed of such a projectile would be such that traveling through an atmosphere would disintegrate it."
] |
[
"If telephone companies see value in from using negative voltage, why don't power companies do so as well?"
] | [
false
] | The recent AskScience question regarding got me wondering about why phone lines are typically delivered in negative 48 volts. I consulted the and learned about the cathodic protection provided to the copper wires by the use of the negative voltage. Assuming that this is correct - why wouldn't electrical companies also... | [
"i'm a bit confused on the phone thing and not an expert, we us AC in the home which means both positive/negative voltage. you also normally have 3 lines in with one neutral and the other two in opposite phase from each other -120/120 so when you use them together you get 240 volts. Being AC they oscillate but stay... | [
"Two-phase was actually 90 degrees out of phase, which you can't directly double, and it largely doesn't exist anymore. Most homes are wired \"double\" single phase (240V/120V/Neutral), and the 240V is most commonly sourced from a nearby pole-mounted step-up transformer.",
"Large apartment complexes are another m... | [
"Where are you getting your information from? Power line voltage(and current) is alternating(both negative and positive). Also things such as positive and negative are relative, flip the wires around and there you go(in terms of DC but this isn't applicable in this situation). All circuits have current(electrons) r... |
[
"[Physics] Why do black holes affect light?"
] | [
false
] | null | [
"My understanding is that gravity is the force of attraction between mass",
"This understanding is wrong. Mass acts as a ",
" for gravity, but mass is not necessary to be ",
" by gravity. Maybe to gain some intuition, note that if we ignore air resistance, if you were to drop a feather and a bowling ball, the... | [
"But surely something with no mass would just pass right through like a neutral charge in an electric/magnetic field"
] | [
"Nope, due to the equivalence principle. The inertial mass (the m in F=ma) and the \"gravitationa charge\" m, are the the same, so the \"m\" cancels out in both sides of the equation GMm/r",
" = ma, and an object will accelerate in a gravitational field totally independent of its mass. Another way of thinking abo... |
[
"Is it possible to lose weight by going on a cold-water diet?"
] | [
false
] | Can one possibly lose weight by drinking cold water? Burning calories with cold water seems really far fetched, but somewhat possible since your body would heat cold water up and thus use energy to do so. Just how much cold water, say 2°C, would you have to drink to burn the same calories as a small bag of Doritos (abo... | [
"This question has been asked ",
"here",
" and touched on ",
"here",
" as well as some other threads I can't find at the moment.",
"The effect of drinking cold water would have a minimal/negligible effect on daily calorie intake.",
"AFAIK brain freeze is the ",
"soft palate",
" in the rear of your m... | [
"250 kcal / 30 degrees = 250 liters of cold water. Doesn't seem particularly practical."
] | [
"I think you may have missed the divide by 30. I got 250kcal / (35K x 1cal/mL.K) = 7.15L water at 2",
" C."
] |
[
"I was wondering if someone was to open a door on a plane while it was average height and speed if people would be sucked out or if the plane would drop because of change in pressure."
] | [
false
] | [deleted] | [
"Well, first of all, it would take superhuman strength to open up a cabin door at cruising altitude since they are designed to open inward and the pressure difference between the cabin and the surrounding air applies considerable force to it, keeping it firmly sealed against the fuselage (can someone here do the ma... | [
"Lower cabin pressure would actually help the airplane stay up, though it's not a big effect. I'll let someone else address the \"sucked out\" bit in detail if they want, but the short answer is \"not really\".",
"\n",
"http://en.wikipedia.org/wiki/Uncontrolled_decompression#A_small_hole_will_blow_people_out_o... | [
"The greater dangers are impaired brain function from lack of oxygen and the airframe losing physical integrity (tearing apart). ",
"http://en.wikipedia.org/wiki/Uncontrolled_decompression#Notable_decompression_accidents_and_incidents",
"Hypoxia is serious business: ",
"http://www.youtube.com/watch?v=WTNX6mr7... |
[
"Serious Question - Why can't we remove stomach fat in an easier fashion?"
] | [
false
] | Alright, I'm a pretty tall guy, and people would view me as "average" for weight/fatness. When I bend my back and lean forward, the amount of fat on my stomach is ridiculous, it's more than a large handful of fat. However, if I'm just standing, it seems to "spread" out and not look too terrible. I have no clue how star... | [
"Fat serves two purposes: Insulation and food storage. If you did cut your stomach open, underneath the layer of skin would be a layer of fat. Its essentially attached to your skin, though.",
"your epidermis and dermis (skin) are not actually that thick. If you pinch under your arm (opposite of your bicep) and pu... | [
"The patterns of body fat growth are decided by genetics and hormones. ",
"There's no reason blood flow would have anything to do with it. Adipocytes (fat cells) actually have very low metabolic activity and don't require a lot of blood flow. In fact, during surgery you can cut right through fat without it ble... | [
"Six pack is not muscle itself(which is actually flat), but something else(can't really tell you what it is).",
"Yes, it is a muscle. The ",
"rectus abdominis",
" muscle is composed of 6, 8, or 10 muscle segments (the bulging parts of the '6-pack') connected by tendons (the sections between the bulges).",
... |
[
"How is it theoretically possible to \"see\" the big bang?"
] | [
false
] | I keep hearing that with a strong enough telescope it's possible to see back in time, maybe even as far as the big bang. However, my question is this: how can a ray of light, originating from the starting point of the universe and everything in it, travel in a straight line and somehow loop back and hit mass with the s... | [
"Your misunderstanding here comes from what the Big Bang essentially was. The Big Bang occurred EVERYWHERE at the same time. So the Big Bang happened right where you're sitting ~13.75 Gyr ago just as it happened 12 million light years away, ~13.75 Gyr ago.",
"Now, as we know, light travels at a finite speed. So l... | [
" \nAwesome response! Do you happen to know what energy/wavelength of photon was created at the CMB event? Does the term 'microwave' describe the emitted photon or the way red-shifted one we would measure now?"
] | [
"What we're currently measuring is a blackbody peak of around 1.875mm (1875000nm, for reference) wavelength, which is obviously in the microwave region. This corresponds to a temperature of ~2.725K. ",
"The 'decoupling' event as they call it (when the process stopped) occurred for a temperature of ~3000K, which w... |
[
"[Particle/Quantum Physics] What is symmetry in quantum fields, and how and why is weak interaction tied to the Higgs field?"
] | [
false
] | I am currently reading Sean Carroll's "The Particle at the End of the Universe", which talks about the in-depth search as CERN and the LHC for the Higgs Boson which occurred back in 2012. In the second chapter the book mentions quantum fields (which I personally understand at the degree the book requires to convey of t... | [
"A quick point to add on to the other good answers so far. I noticed that a couple of times you described symmetries as being \"between fields\" or \"to other fields.\" That's not always the right way to think of it. Many symmetries in physics aren't between different kinds of fields, but within the description of ... | [
"Thank you for that explanation; I understand the general mechanics of symmetry breaking (mexican hat potential, etc), but this is a great way of analogizing it to broaden the conceptual links."
] | [
"Thank you for that explanation; I understand the general mechanics of symmetry breaking (mexican hat potential, etc), but this is a great way of analogizing it to broaden the conceptual links."
] |
[
"Can you consume vaporized alcohol?"
] | [
false
] | Alcohol has a pretty low boiling point. If you got a still and held it just over alcohol's boiling point, and inhaled the fumes: Would the alcohol be able to enter your bloodstream through the alveoli? If it could, how would the rate of absorption compare to ingesting different types of alcohol? Would it cause any phys... | [
"While it is possible, I would not recommend it. Alcohol is absorbed faster, thus increasing your risk of overdosing. "
] | [
"This once happened to me by accident while I was cleaning the inside of a lead tank that shields a 250 keV Van de Graaf positive ion accelerator. ",
"The interesting thing is that while you get drunk, it's all in your bloodstream, so removing yourself from it lets you sober up very quickly without absorbing more... | [
"Also you wouldn't be able to throw excess of it out."
] |
[
"Do aquatic animals urinate? If so, do they have urine bladders?"
] | [
false
] | null | [
"They do. I'd suggest having a Google of the excretory systems of different animals because how it works varies lots between species (fish vs whales vs squid vs worms...). But they do need some way to get wastes out of the body. Not all animals have a bladder equivalent if there's no need to store waste products (s... | [
"Strictly speaking they ",
" do and it depends on what the animal in question is.",
"Urination is a mechanism used to remove excess nitrogen from the body which would otherwise be toxic. However, the production of urine isn't the only way to remove nitrogen from the body and different animals do it in different... | [
"Thank you"
] |
[
"Questions about steam, water vapor, and humidity"
] | [
false
] | First of all, what is the difference between steam, water vapor, and humidity? there any difference between the terms "steam" and "water vapor"? Is there a difference between the terms "gas" and "vapor" in general? What is the difference? Also, I was under the impression that steam could not exist below 100 C, (at 1 at... | [
"Water vapor is water in the gaseous state. It is transparent.",
"Humidity may be one of several measures of the amount of water vapor in the air.",
"Steam consists of liquid water droplets suspended in the air. Many clouds may be considered masses of steam, others are made of ice. Your breath may form puffs... | [
"(This is also why this doesn't work when you've got your A/C on \"circulate\", because the humidity never leaves the car.)",
"Not true. Humidity condenses on the A/C coils and exits the car via the drip tube. Your home AC also readily removes humidity from the air even though it is recirculating the air. I belie... | [
"No, you did not.",
"The term \"steam\" invariably refers to clouds composed of liquid water droplets. Such clouds form from one's breath, from kettles, smokestacks, etc. Water droplets scatter light and are visible. ",
"\"Water vapor\", as is indicated by the term \"vapor\" is gaseous. It is transparent. ... |
[
"What happens to a ship once it runs aground?"
] | [
false
] | Inspiration for my question here: I was wondering- if an event occurs like this large freighter running aground after a snapped anchor line, what are the salvage options? Someone on that LL thread said that the ship would most likely never sail again because it's parallel to she shore and so close in. What makes this... | [
"\n",
"\n",
"\n ",
"\n",
"\n",
"\n",
"\n ",
"\n",
"\n",
"\n",
"\n",
"\n ",
"\n",
"\n",
"\n",
"\n",
"\n ",
"\n",
"\n",
"\n",
"\n",
"\n ",
"\n",
"\n",
"\n ",
"\n",
"\n",
"\n",
"\n ",
"\n",
"\n",
"\n",
"\n",
"\n ",
"\n",
"\n",
"\n",
"\n"
] | [
"If it's stuck tightly enough in the shore, the effort to pull it free could be too costly and difficult in comparison to the losses from scrapping it. That would depend greatly on what resources are quickly available to pull it out before it settles further.",
"Ships are heavy."
] | [
"Amazing."
] |
[
"Concerning speciation following polyploidization in flowering plants"
] | [
false
] | I heard recently that whole-genome duplication events have been suggested as explanations for many speciation events in flowering plants. I understand how this mechanism could occur for a selfer, but I'm a bit confused about how this would work for an outcrossing plant. If a diploid plant has its whole genome duplicate... | [
"A mechanism for the formation of a tetraploid population in the above scenario would be the triploid bridge. You identified that back crossing to the diploid population would cause the formation of triploid offspring. These offspring usually have lower fitness than their even-ploid parents, but can survive to repr... | [
"i've always wondered this as well. polploidization is always given as the textbook example of sympatric speciation, but is is common enough for reproduction to be feasible with other polyploids? "
] | [
"Thanks a lot for the info!"
] |
[
"What is contained within a volumetric measure of a brain region using structural MRI?"
] | [
false
] | So I've started wondering what can be deciphered with structural MRI regarding more specific neuronal processes in the brain, given that MRI volumetric measure are fairly broad in scope. When you gather an image of a brain structure of interest, what could be accounting for an increase or decrease in it's volume at the... | [
"The nature of gray and white matter changes identified with VBM (voxel-based morphemetry, the most commonly used method for studying brain volume) is still poorly understood. Cell death and neurogenesis is certainly one explanation, but it is also possible that changes in volume also reflect changes in neuron dens... | [
"Below the skull there are three levels of meninges. The first level that you'd see is the duramater- which is a relatively tough membrane. Below that is the arachnoid which, befitting its name, looks sort of like a spiderweb. Finally, after the duramater and arachnoid, is the piamater. In my (limited) experience a... | [
"There are no neurons in the meninges. "
] |
[
"Is it possible to consume too many vitamins/minerals from food alone?"
] | [
false
] | I have recently started eating lots of foods with loads of vitamins and minerals in them: kale, spinach, quinoa, seeds, legumes, beetroot, flaxseed, chia seeds, etc... Is there any vitamin or mineral which might be too redundant in some of these foods, which one should watch out for? I know that it is possible to take ... | [
"Yes, it is absolutely possibly to eat too many vitamins from food alone.",
"Hypervitaminosis A is probably the most famous example. As you've probably guessed, that is when you eat too much vitamin A. And the most \"textbook\" source is, believe it or not, polar beer liver. Polar beer liver (along with the liver... | [
"Yeah, THAT would definitely be hard to do on \"normal\" food without using any kind of supplements/pills. I won't say it's \"impossible\", because i've seen some competitive eaters do some crazy things, but it's definitely not something your average joe needs to worry about."
] | [
"chances are high, that you wont OD on Vitamins trough normal 'common' Diet like local Fruits or Meat etc. you would need to eat such ammounts of that food that you would barf before even getting close to OD"
] |
[
"When we die from natural causes don't we all ultimately die from cardiac arrest?"
] | [
false
] | This may sound like a bad question but I'm looking for a serious answer please. I'm not looking for answers like, "No, if you get decapitated you don't die from cardiac arrest." I am looking for answers like, "Yes, if you get pancreatic cancer and go into respiratory arrest, this ultimately leads to cardiac arrest, so ... | [
"But didn't all these people ultimately die from cardiac arrest (heart failure)?",
"Recording every death the same way is useless. If you are going to record every death as \"failure to pump sufficient O2 to the brain\" you might as well just say the cause of death is \"death\". Recording what caused the body to ... | [
"You could live without a heart if you replaced it with something else to pump your blood, so I'd argue that having your heart stop functioning isn't the moment of death. The closest thing we could have to an unambiguous moment of death would probably be brain failure rather than heart failure"
] | [
"\"Natural causes\" is 100% of the time hypoxia to the brain (along with every other death). For example a heart attack: cardiac muscles are too badly damaged & stop pumping blood which stops transporting O2 everywhere including the brain & when the brain doesn't have oxygen, the body stops. "
] |
[
"What is the science behind gluten allergies and intolerance?"
] | [
false
] | While I support change for those with allergies or Crohns, but I'm skeptical of whether the science behind it is hard fact or very preliminary. Any links to peer reviewed articles would be highly appreciated! | [
"There's no doubt about the existence of Celiac Disease. At a ~1% rate in the general population, it is one of the most common and deadly chronic diseases. It's also extremely under-diagnosed and several studies have suggested that the failure to diagnose is because most ",
" aren't even that well-educated abou... | [
"Novel as in, being distinct from the better-understood allergic reaction. Specific details of the Celiac response are still being figured out, and beyond that, there seems to be pretty strong evidence for even more types of immune response that are not allergy or Celiac:",
"http://www.schres-journal.com/article... | [
"But Celiac isn't an allergy, it's a novel immune response that is still varied from patient to patient. There are other novel, non-Celiac immune responses that have been discovered as well."
] |
[
"r/science, Does IQ matter? Is it really indicative of intelligence?"
] | [
false
] | null | [
"It does certainly have merit/credibility in the real world and what it predicts is of value. However, anyone in psychometrics will tell you that it's not the only thing that matters. The general idea behind modern IQ tests is analysing different areas of intelligence (that's why modern tests take so long) and comp... | [
"It has a lot of credibility, correlates quite highly with academic achievement. It is indicative of intelligence to a certain degree and works best for people around the mean. Persons with IQs in the lower or upper 2% are much more difficult to accurately assess.",
"The main problem is defining what \"intelligen... | [
"IQ is considered reliable (not changing too much if you measure it more than once) and valid for diagnosing disorders such as retardation.",
"http://en.wikipedia.org/wiki/Intelligence_quotient#Reliability_and_validity",
"The different tests measure different things, and they change over time, so bear that in m... |
[
"What came before the single cell organism?"
] | [
false
] | What particles or molecules joined to create the single cell organisms which all life evolved from? I was wondering how small we can get before them. | [
"It's one of biology's most broad and fascinating questions: one that addresses the very origins of life, and therefore the beginning of biology. ",
"The first organism was a very simple prokaryote that had hereditary material, substances to catalyze reactions, and a method for absorbing energy, among other thing... | [
"Thanks for the insightful answer! I understood most of those words, but I can tell you were excited about the process as well. "
] | [
"Definitely! It's amazing how much we can piece together about events that occurred billions of years ago using molecular evidence. ",
"If there is anything that I wasn't clear on or didn't explain fully, please feel free to ask away!"
] |
[
"Why do dark-skinned people have white palms?"
] | [
false
] | I've noticed that almost everyone has white palms - regardless of race. But it's more noticeable in people with darker skin. I've also noticed that the heavy creases and lines in the hands of black people tend to be the same darker color as the rest of their skin, but the rest of their palm is white. (Also true for all... | [
"I know the answer to this! (I'm so excited to be able to contribute inside my field of research.)",
"The layers of the skin go (from outer to inner): the stratum corneum, the epidermis, and the dermis. The stratum corneum is the outer most layer of skin and consists of dead skin cells (they've lost their nucleus... | [
"http://www.ncbi.nlm.nih.gov/m/pubmed/15117970/",
"From the abstract:\n\" The melanocyte density in palmoplantar human skin (i.e., skin on the palms and the soles) is five times lower than that found in nonpalmoplantar sites.\" ",
"I have no scientific leads as to why we evolved like this, but this study gives... | [
"Because, while it's the best filtering mechanism, it isn't the most easily achieved. The stratum corneum DOES actually thicken in response to UV radiation the same way that melanocyte production is increased, but it's negligible/unnoticeable.",
"The stratum corneum on the palms needs to be thicker for grip and p... |
[
"In quantum physics, is time quantized as well?"
] | [
false
] | I apologize if this is an oversimplification, as this is not my field. My understanding of quantum physics is that at the most basic level, fundamental particles move in discrete intervals. My questions is: does time also progress in discrete intervals (and thus velocity etc is discrete and not continuous). | [
"Current prevailing theories don't call for quantised time (among other things, quantisation is typically associated with a carrier particle and our models don't call for chronons). Some modern theories predict that time might be quantised (e.g. loop quantum gravity) but these remain far from widespread acceptance.... | [
"Your understanding is a bit off. Particles don't move in discrete intervals, but rather the probability of finding a particle in a certain location is described by a function, and that function can only take on discrete forms based on the conditions imposed by the environment.",
"That being said, time is not dis... | [
"Can you elaborate at all? Or point me to readings that describe these functions?"
] |
[
"How do our brains deciding which words to use when talking aloud?"
] | [
false
] | I don't know about you guys, but when I talk aloud there's not a whole lot of planning going on upstairs. I'm not visualizing any words, yet coherent sentences come flowing out of my mouth. How does this happen? Who is calling the shots up there? This seems completely opposite to how I communicate through text, where I... | [
"Something similar came up in another thread. I would advise you to look at an actual linguistic transcript of everyday conversational speech. We’re not nearly as coherent as we think we are. We often have to reformulate sentences on the go, mess up grammatically, lose our train of thought mid-sentence, use tonnes ... | [
"The brain is complicated, and we understand very little about ",
" it works, though we generally know what different areas of the brain do.",
"It’s known that the frontal lobe does most of the high level functions in the brain, including creating and forming concepts. It’s also known that Broca’s area in the b... | [
"If you want to get super freaky, look up an area of linguistics called “collocation”. Basically, every language has words which tend to be “magnetically” drawn to other specific words. Our brains know instinctively which words should be paired with others and do this automatically. ",
"One example is with coffee... |
[
"Can anyone identify this four-mandibled insect?"
] | [
false
] | When my dad was on his tour of duty in Nui Dat, Vietnam, he and the other Australian soldiers occasionally encountered an insect they called the "RTA bug", as it looked so fierce that they suspected sustaining a bite would result in the soldier being 'Returned To Australia' for medical treatment. The most striking feat... | [
"I suggest reposting this on ",
"/r/whatsthisbug/"
] | [
"http://en.wikipedia.org/wiki/Solifugae",
"Tadaaaa!"
] | [
"Looks like Melanoblossidae is the only family found in Vietnam.",
"http://www.solpugid.com/Melanoblossidae.htm"
] |
[
"How do we measure distances in space?"
] | [
false
] | We say that alpha centuri is 4.3 Light years away. How do measure/calculate that? Is the process the same for more distant objects? | [
"For objects that are relatively close, like alpha centauri, the standard approach is to use triangulation/parallax (i.e., notice how much the star moves against the background as the earth moves around the sun, and use trigonometry to determine how distant it is). For more distant bodies, standard candles are use... | [
"One other technique we use on bodies that are much closer to us like the Moon and Mars is laser ranging. Basically we shoot a laser away from earth, bounce the light off the surface and see how long the entire trip takes. Using this method we can measure the ",
"distance to the moon",
" to within a centimeter.... | [
"Is the process the same for more distant objects?",
"No, for more distant objects (such as distant galaxies) we can use other methods such as measuring their red shifts."
] |
[
"Doppler effect applied to photons"
] | [
false
] | While I can understand the Doppler effect on light considered a wave phenomenon, how does the relative motion of the photon source and receiver effect the perceived energy (color) of a photon? | [
"The change of frequency between reference frames happens for the same reason that the ",
"classical Doppler effect",
" does-- the wavecrests will reach you closer together or farther apart depending on whether the object is traveling toward or away from you."
] | [
"However your last sentence simply states that the frequency/energy varies between reference frames, but does not suggest a mechanism",
"I would say, that this is simply an issue with the particle model. Light is something more complex than either a wave or a particle, thus both models fall short in some situatio... | [
"Dear MCMXCII -",
"Thanks for the rapid response! However your last sentence simply states that the frequency/energy varies between reference frames, but does not suggest a mechanism; but as a friend of mine says, \"anyone who can explain quantum theory without hand-waving doesn't appreciate it\".",
"Norm Palle... |
[
"When a computer game is loading, what’s actually happening?"
] | [
false
] | null | [
"It is loading game logic, textures and models from disk into memory. Often times the models and textures must also be sent to the GPU's memory, since they do not share resources. It also performs initialization routines to prepare the game for the user."
] | [
"Hard drives are not part of the virtual address space.",
"It's kind of a quirk of history that this is true, and it doesn't have to be true on all sorts of systems. Some old mainframes included storage directly in the address space, for example. Early in teh history of such things, you just did the equivalent ... | [
"There is often significant difference between the data as it is stored on the disk vs. the same data as represented in memory. I'm not only talking about trivial matters like compression, but converting the saved data to a format more suitable for run-time usage. This is often called deserialization. ",
"Loading... |
[
"Is it possible that elliptical galaxies gradually go spiral once they have a massive, growing black hole at their core?"
] | [
false
] | There is, after all, a certain familiarity with the appearance of a spiral galaxy. Perhaps things really are going down the drain. | [
"In terms of evolution of galaxies, it actually goes the opposite way. Spirals turn into elliptical galaxies once disrupted by major mergers.",
"An easy way to think of it is like this. Spiral galaxies are highly structured. If you disrupt this, the system will get more chaotic with orbits going everywhere. But g... | [
"This is a good answer. I also want to note that even super massive black holes in the center of spiral galaxies has like near zero net effect on the entire spiral galaxy so there's nothing which is being like \"sucked in\" as in water running out a drain in your bathtub, if that's what OP is thinking about."
] | [
"You are operating under a false assumption.",
"Once a star becomes a black hole it does not start to \"suck\" things more.",
"The change which occurs moves the stars mass in a much smaller volume than it previously occupied, so thing can get much closer to the mass.",
"The closer you are to some mass, the st... |
[
"Why do waves always move towards the shore?"
] | [
false
] | null | [
"A wave is a transfer of energy, the energy is coming from the movement of water from the main body of the sea. There's no force coming FROM the land, so there's no real waves coming from there.",
"The exception is when you see a wave hit a wall and then you see the wave going out, as the force goes out, usually ... | [
"As a wave travels, the part of it closest to land begins to slow down in shallower water. This essentially \"bends\" the wave toward the shore. It is difficult to picture without a visual, but as each part of the wave slows down, it changes the direction of the entire wave. It is the same reason that light changes... | [
"This is the fundamental reason that waves seem to be coming into shore from the perspective of a person on the shore. The waves are bent toward the land as water becomes shallow and the waves slow down from friction with the bottom. ",
"The waves out there in the open ocean are just moving in whatever directio... |
[
"Can anyone tell me what kinds of clouds these are?"
] | [
false
] | My mom thinks they are a part of a government conspiracy and I'd just like to simply explain them to her in a sciencey manner. Thanks | [
"The other response is correct that the prominent streak is a ",
"contrail",
", but the patterned clouds are not cirrus clouds, they are ",
"altocumulus undulatus",
" clouds, and form in the mid-troposphere in under certain conditions that feature horizontal wind shear.",
"As a word of advice though: hard... | [
"Well the streak is a contrail from an airplane. It is the condensed water vapor/exhaust fumes from the turbo fan jet engines of a passenger plane. This is really not too different than seeing your breath on a cold day. ",
"there is no conspiracy. ",
"http://en.wikipedia.org/wiki/Contrail",
"http://en.wikipe... | [
"Thanks! I knew they didn't look like cirrus. Also thanks for the advice... I do what I can."
] |
[
"Why are solid, liquid, and gas phases so common?"
] | [
false
] | I was looking at the , which shows many possible arrangements of atoms. Many substances have at least one phase which is easily described as solid, many likewise have a liquid and gas phase. Why are these phases found in so many materials. Why don't individual materials have a variety of phases, each of which has un... | [
"It's kind of a circular reasoning question. We inhabit the temperature/pressure range where intermolecular interactions are the most diverse and prevalent (that is, electromagnetic bonds between electrons of atoms). As a matter of fact, we exist because of these interactions. Environments outside of this range wou... | [
"One very profound result in physics is that the ",
"ideal gas law",
" is actually universal, that is, it holds for any dilute collection of non-interacting particles. So no matter how big, small or weird your molecules are, as long as they're uncharged and in low concentration, they will always form a gas.",
... | [
"Interesting; thanks! I suppose I was puzzling over why there were not more substances with intermediate states between, say, permanent and transient interactions. I suppose it is circular in the sense that I say, considering only the substances which have these three states, why do they have the three states."
] |
[
"I can grasp and understand the concept of a 4th spacial dimension pretty well. Now can anybody explain to me how a 2nd time dimension would work?"
] | [
false
] | I've watched and read up a bunch on a 4th dimensional cubes and whatnot, and even though I can't imagine one, I can understand the idea behind it. However as hard as I try I can't grasp a 2nd time dimension. Would anybody be willing to explain it to me? | [
"There's a reasonable amount of work that's been done using \"imaginary\" time (i.e. time scales that depend on i - this also comes up with energy in electrical engineering, since the solutions to some of the circuit differentials wind up involving i [\"reactive power,\" for example]). I'm not sure how you'd concei... | [
"Complex numbers pop up all the time in electrical engineering because of their deep connection to exponentials and trigonometric functions, making them incredibly useful for simplifying problems that involve pretty much anything that involves periodic behavior. It's a convenient mathematical tool but not an examp... | [
"I was using it as an analogy for how it comes up in physics - it appears as an artifact of the equations but since there are phenomena that take place in imaginary and/or complex time it behaves similarly to some manner of additional dimension. I'd have a better example if I were a physicist but as it stands the o... |
[
"If you use hormone blockers to stop puberty, would you have to stay on blockers for your entire life?"
] | [
false
] | null | [
"You mentionned puberty blockers for transgender care specifically: no they are not usually taken for life. Puberty blockers are typically only presribed for children until they are over 16 at which point they usually either start hrt (hormone replacement therapy) or just stop taking puberty blockers and puberty re... | [
"Yes. HRT overrides your hormone levels, and you experience puberty based on your replacement hormones."
] | [
"Yes, HRT needs to be taken indefinitely. Everyone produces both estrogen and testosterone naturally but a trans person is never going to get to cis levels by natural production. Procedures like an orchiectomy for trans-feminine people will effectively negate testosterone production, but you’ll still need to take e... |
[
"If we uploaded our consciousness to a computer or put our brains into a robot body, wouldn't the loss of the chemical reactions in our head mean the end of all emotions?"
] | [
false
] | I often read sci-fi writers or transhumanists toying with the idea of scanning one's brain and uploading it to a computer, but never have I heard of anybody address the issue that our bodies heavily influence the way we think and thus removing it might completely change our personalities? When we experience something t... | [
"Well you kind of answered yourself already. Why couldn't we simulate the chemicals or even the rest of the body (or just provide a reasonable input/output to the \"sensors\"). The chemical basis to life and brains isn't anything special. It's just means to an end.",
"Your simulated brain would never directly dep... | [
"Ah, yes. I should've known. It's probably worth pointing out that Kurzweil has an ",
" poor reputation in academic circles, due to his apparently being a crazy person who thinks because he knows something about computers he must also know something about neuroscience."
] | [
"Emotions will probably be convincingly replicated by AI in the very near future…",
"I'd be very interested to hear how you reached that conclusion."
] |
[
"Why do deserts/dried up lakes form polygon patterns of dried ground?"
] | [
false
] | I wanted to know why do dried up lakes form this polygon (4-5) patterns on the ground. What is the reason for this? Example can be seen below. | [
"What you have there are \"desiccation cracks\" or what are commonly referred to as mudcracks. The surface dries out at a faster rate then the sediment beneath it due to the influence of the sun. In science speak, \"desiccating clay soils crack when the tensile stress developed in the soil due to the matric soil... | [
"They don't really form periodically repeating polygons. The shapes are irregular for the most part. You get major cracks propagating through the soil because it is easier for the cracks to grow rather than new cracks to start."
] | [
"I'm a little late to this party, and it looks like some have answered your question, but let me give you a comprehensive answer:",
"Your question specifically addressed the cracks that form in dried up lakes (which consist mostly of mud, clay and silt), and they have their own idiosyncratic properties and proces... |
[
"Do flying insects avoid rain drops or do they take shelter during showers and storms?"
] | [
false
] | It's raining slightly outside and I wonder how flies and other flying insects fare during this weather? They do a good job of avoiding me when I swat at them, but how about when avoiding rain drops? | [
"I seem to recall watching some high speed video slowed down of insects getting hit by rain, and getting deflected a little, but not much more due to the way they're built.",
"Sorry this isn't more helpful, but maybe you can find some videos on youtube, they were pretty intesting. Nature can be beautiful.",
"Q... | [
"Depends on the drop size, wind conditions and the size of the insect. Of course, a small insect will be taken out by rain drops. Insects have more trouble with wind than rain. In most cases, the insect will seek shelter and avoid flight. "
] | [
"Small insects like gnats get pushed out of the way by the air wave in front of the droplets so they can fly how they like and be buffeted around harmlessly. \nHowever since most food sources exposed to heavy rain and wind either shelter or become inhospitable then I assume the insects follow suit. There would be n... |
[
"What makes a solution to an equation \"analytic\"?"
] | [
false
] | I sometimes read about physicists finding or failing to find an analytic solution to a set of equations, and I'm not quite sure what that means. It seems to be contrasted with "numerical" solutions, but what that means isn't all that clear to me either. | [
"What an \"analytic solution\" usually means is that we can write it in terms of elementary functions: arithmetic, exponentiation, logarithms, trig functions, and hyperbolic trig functions. Usually this excludes the situation where we can write down, say, an integral of such functions but cannot evaluate the integr... | [
"That is a great analogy. Except, of course, that you can find roots of some quintics quite easily (such as x",
" -1). But in general, you cannot write down exact roots for quintic polynomials the way that you can use the quadratic or cubic equation to write down the roots for those kinds of polynomials."
] | [
"Well.. there is a more complex mathematical definition of an \"analytic\" function. In real/complex analysis, an analytic function is one that can be represented as a convergent power series at all points inside its radius of convergence. It is infinitely differentiable within that region and in general, behave... |
[
"How are numbers such as Pi and e actually calculated?"
] | [
false
] | I'm not sure how to specifically word or clarify my question but I think it is fairly straightforward? Like where do the numbers come from? | [
"Wikipedia has a great article for the computation of pi.",
" The two easiest formulas are probably Leibniz's ",
"pi/4 = 1 - 1/3 + 1/5 - 1/7 + 1/9 - ...\n",
"or that implied by the ",
"Basel problem",
"pi^2/6 = 1/1^2 +1/2^2 + 1/3^2 + 1/4^2 + ...\n",
"Unfortunately, both of these are horrendously slow, s... | [
"There are different ways, especially for pi. I'll focus on ones that are easy to understand, which may not be the most efficient.",
"Because the tangent of pi/4 radians (45 degrees) is 1, the inverse tangent of 1 is pi/4, and by approximating the inverse tangent function as a polynomial series, we can calculate ... | [
"This",
" is the web site of the guy who is the world record holder for Pi, he explains in detail and you can use his program for your self if you like. "
] |
[
"Why do we always think of regretful stuff before we go to bed? Is there any psychology behind it?"
] | [
false
] | null | [
"Rumination",
" is the term for dwelling on distressing feelings and their causes. I'm not sure why it occurs before we go to bed, perhaps because it is a convenient time to think (no other distractions, tasks to do etc). I'll see if I can find any papers.",
" Okay, so this paper by Tanno and Takano (2010) ",
... | [
"You know exactly what op means. Ease up."
] | [
"Are you interested more in why we ruminate in the first place? Because it happens to everyone, it just may be more common at night time in people with depression. "
] |
[
"How can gravity do work without using up any energy?"
] | [
false
] | I feel silly asking this, but it's one of those things that has never made any sense to me. Planets in orbit must have an enormous amount of momentum that wants to go outward/in a straight line, but they're forced to keep accelerating inward by gravity. How can that not use up energy? If I'm in my spaceship going x spe... | [
"The answer is that if gravity does work, it uses up energy. If I drop an object, I'm converting potential energy stored in the gravitational field into kinetic energy to move the object. ",
"For planets in orbit:\nLet's start with a circular orbit. The pull of gravity is always normal to the direction of moti... | [
"This actually really helped. Very eloquent explanation. The part about changing your reference frame is a perspective I've never considered before.",
"Although, that raises another issue entirely... If you're accelerating a body through empty space, it requires more and more energy to accelerate it further as yo... | [
"I'll answer your questions one by one. As a broad summary, gravity is an attraction force between objects. It causes objects to come together, but as you cannot make or destroy energy it causes an equal and opposite reaction to do so.",
"Planets do go want to go in a straight line, but they fall at a speed suffi... |
[
"Why can't mathematicians calculate (or agree upon) the percentage of hands of \"Klondike by Three\" (Solitaire) that are solvable? (Some estimate the number of solvable games is between 82% and 91.5%, others claim 66.875%.)"
] | [
false
] | The is from Wikipedia, referencing [PDF]. claims the number is 66.875%. I understand that there are "more than 7,000 trillion possible hands" so if that is the difficulty, what sort of computing power would be needed to calculate an accurate answer? | [
"It's a different sort of problem than, say, chess or checkers. In chess, you have one starting state, and calculate every possible game. In Solitaire, you have 52! starting states, all of which would have to be calculated through all possible plays (because you still have choices to make as you play). So it an ... | [
"Yes, it's hard to brute force, but it's not as if mathematics is without ways of finding patterns and simplifying problems."
] | [
"The 66% link doesn't link to a paper. "
] |
[
"Why isn't sunlight just the hydrogen and helium emission lines?"
] | [
false
] | The emission spectrum for hydrogen and helium only include a few lines of visible light. White sunlight seems to include the full continuum of wavelengths minus some absorption lines due to the atmosphere. Why isn't sunlight just a few distinct emission lines? | [
"Emission lines are due to electrons within atoms moving between energy states. This is why the energy of the photons (and therefore colour) are quantised - the energy state must be well defined. There will be a colour for n=2 to n=1 transition, one for 3 -> 2, etc.",
"What occurs in stars is super heated matter ... | [
"Sunlight is a blackbody spectrum, minus emission (absorption) lines of what the sun's atmosphere is made of. This obviously includes hydrogen, but it was actually how helium was discovered in the 1860s."
] | [
"An object doesn't need to be ionized to be a black body.",
"A piece of glowing hot iron is a black body, but all the electrons are still more or less attached. Heat is random motion and shaking of atoms and accelerating charged objects (atoms, induced dipoles) always produces electromagnetic radiation. The kinet... |
[
"Why do scientists not use night-vision cameras when exploring the deep sea?"
] | [
false
] | They always say we have only seen a glimpse of the eternal darkness and creatures in it. But they always use submarines with standard lights on. | [
"IR is absorbed by water much more than visible and uv light.",
"I cant promise that this the entire reason, but it is one contributing factor at least."
] | [
"Seawater does a ",
"very good job absorbing infrared light",
". See the table at the bottom of the Optical Properties section.",
"Oceanographers are actually doing a pretty good job, nevertheless, ",
"imaging and even color-correcting benthic environments",
" using optical sleds. Color correction of im... | [
"Photo-multiplier tubes rely on there being photons to multiply. This gives the grainy green images you see in military applications.",
"At the bottom of the ocean there hardly any light whatsoever and therefore the multiplier tubes see mostly complete darkness.",
"You need to bring your own lights with you dow... |
[
"What is the smallest, known or theorized, size/mass necessary to create a black hole?"
] | [
false
] | I know that if a star collapses in on itself it could form a black hole, but, in theory could a dwarf planet? Atoms? Is there a certain size a star must be first before it's possible to become a black hole? If someone were to try and create a black hole in a lab setting, what is, in theory, the absolute smallest amount... | [
"What is the smallest, known or theorized, size/mass necessary to create a black hole?",
"The answer is not known. General relativity does not predict a lower limit -- it just says that you must ",
"cram enough mass into a small enough space",
". The smaller the space, the less mass must be crammed in there... | [
"As QM and Relativity have not been unified, theory breaks down for black holes smaller than the Planck mass, about 21 micrograms. A Planck mass black hole has a radius of a Planck length, and it's not clear how meaningful distances are below that scale. It's difficult to call such an object black, as it would evap... | [
"Noted. I believe we're on the same page. You're just including constructions of alien origin in the definition of \"artificial\" while I am not. :)"
] |
[
"Does moving water freeze at slower rate than stagnant water?"
] | [
false
] | null | [
"Yes! Freezing is a matter of removing energy, which could be either thermal (heat) energy or movement (kinetic) energy in this case. The more energy a water molecule has (warmer or moving), the more energy has to be removed before it will stay in one place (even tho the molecules are still actually vibrating a bit... | [
"Freezing is a matter of removing energy",
"Freezing is the phase transition from liquid into solid form. It normally proceeds through crystal growth starting from a nucleus. Note that lowering temperatures is not the only way to achieve this: You can also solidify liquids through pressure. However, this depends ... | [
"No. Kinetic energy is relative, while temperature is absolute (ish). ",
"To measure kinetic energy, you have to measure it relative to something else. A spaceship collision can be measured from any frame of reference, with either one being stationary or both moving relative to an outside object, and you can math... |
[
"Is Gravity Affected by Newton's Third Law of Motion?"
] | [
false
] | So I'm not entirely versed in the current theories involving gravity. I know enough to know that it is a force, that it can bend space, and that there is a theory that hypothetical particles called gravitons are responsible for gravity. I also understand how the third law of motion works, that any force applied to an o... | [
"Gravity follows the law. If you somehow managed to not follow it, then you would violate several conservation laws. "
] | [
"I think the easiest way to explain it is using Newton's Second Law. Since Force = Mass x Acceleration, then if both forces are equal and opposite, both Mass x Acceleration must be equal. So in the case of the gravitational force between you and an asteroid, your mass is much less than that of the asteroid, so prop... | [
"Yes, but there is a refined and more general version of Newton's third law: it's just conservation of momentum.",
"So, what happens is that a certain amount of momentum is transferred to the field that mediates the interaction between objects. So, Newton's third law is not correct, but momentum is still conserve... |
[
"If I ate this whole bottle of vitamins, what would happen to me?"
] | [
false
] | null | [
"International Units",
" or IUs are biological equivalents for substances like vitamins. There is no standard conversion such as 1 IU always equals 0.5mg. It depends on what vitamin we are talking about. This may seem unnecessary at first, but when you consider that various versions of pre-vitamins result in diff... | [
"Wow, every single potential question answered. Thank you!"
] | [
"IU is International Unit. It's a weighing unit used in pharmaceuticals.",
"First, because of the Vitamin A, you will risk overdose on that vitamin. Vitamin A, and Iron are two nutrients you don't want to overdose on. Zinc is also a bad thing to get too much of. I have to leave it to the nurses and Doctors fo... |
[
"what exactly is a hangover?"
] | [
false
] | null | [
"It's not completely known, but a large part of the effects are probably due to accumulation of the products of alcohol (ethanol) metabolism in the body, as well as the direct effects of ethanol itself.",
"The liver processes ethanol into acetylaldehyde, which is then processed into acetic acid, which is then exc... | [
"No problem! One other interesting fact is that there is a drug (you may already know about it) called Antabuse that is sometimes used in the treatment of alcoholism. Its effect is to block the processing of acetylaldehyde into acetic acid, so the acetylaldehyde just keeps building up. This makes the consumption of... | [
"thank you nice to know"
] |
[
"Is it possible (practically and theoretically) to slow down radioactive decay?"
] | [
false
] | Scientists keep on producing new elements through fusion, but these superheavy atoms only last for nanoseconds. Is there a way to slow down the decay of these atoms (if not actually, then theoretically)? Does cooling to temperatures close to absolute zero help? | [
"Speed them up."
] | [
"To elaborate on Dimpl3s correct point, special relativity makes it so when something travels at say 0.99c (gamma=7) (say you accelerate a muon beam) that time goes slower (from your non-moving perspective). E.g., a muon at rest normally decays in about 2 micro-seconds (mean life-time), would then last for about 1... | [
"There's some speculation that neutrinos can somehow affect the rate of radioactive decay. It's very preliminary at this point though.",
"http://news.stanford.edu/news/2010/august/sun-082310.html"
] |
[
"Does a dead battery act like a short circuit or an open circuit?"
] | [
false
] | [deleted] | [
"Many people have already done the experiment, similar to what I did a few months ago.",
"e.g. A radio that uses 6 of the AAA batteries to run.",
"Now imagine you put in 5 fresh batteries, and leave one dead battery in place. The radio will work as if it had 5 batteries.",
"Certainly not an open circuit, and ... | [
"This is false, otherwise you could force a current through a battery to get a higher voltage - which does not work.",
"A battery is a voltage source with an upper limit on current. Chemical batteries work with acids, cathodes, and anodes. More advanced batteries may function differently, but ",
" to behave t... | [
"That varies by product. It all depends on if the batteries are wired in series or not. A missing battery will definitely make an incomplete circuit in many electronics. "
] |
[
"When you detonate a nuclear explosion, where does all that energy come from? Follow up, if you detonate in space (with no air to push) what is the \"force\" that is hitting you?"
] | [
false
] | null | [
"The energy comes from nuclear reactions. And if you detonate a weapon in vacuum, the material that makes up the weapon itself blows outward. There's also a lot of radiation emitted from the nuclear processes going on."
] | [
"Would it be the material that blows outward from the explosion what pushes you away? Like I would expect getting hit by a nuclear blast in space would be something physical pushing you but I can't imagine what since its space?"
] | [
"Nuclear weapons have been tested in space, and there are videos. Google “Starfish Prime”."
] |
[
"Did the natives of the Americas have their own virues/bacteria/germs that they were immune to but would have caused Europe problems if colonization roles were reversed?"
] | [
false
] | null | [
"So there's an entire video about this by CGP Grey but the short answer is not really. Most plagues that detriment unexposed populations are from other species that we've domesticated like cows or horses. To those species they're minor illnesses that don't usually kill the host, because most viruses don't want to k... | [
"There is some evidence that Syphilis may have originated in the Americas and was transmitted by returning members of Columbus’ expedition to Europe. ",
"The matter is still being debated by scientists and historians, but so far a lot of evidence seems to stack up in favor of a New World origin for Syphilis. ",
... | [
"Native Americans lived in somewhat isolated populations so they weren’t exposed to as wide a range of pathogens as your average European of the time. Also, let’s be honest, Europe was pretty filthy and disgusting in the 15 and 1600s and anyone that survived had a pretty extensive list of natural immunities. "
] |
[
"Would running a faster oil pump cool an air-cooled engine more effectively than running a standard one?"
] | [
false
] | Hi there. I'm part of a community of motorcycle enthusiasts keen on air-cooled Honda C90s. One of the former engine models from the 70s has a problem with seizing, which is probably due to overheating. Some members think a solution is to run more oil through the pump, thinking it will cool the engine more effectively. ... | [
"Some say that this is good in the short term but eventually the engine will run to heat saturation and no amount of oil pumping will cool the engine more.",
"This faction. In eg a car, the radiator is exposed to airflow. It transfers the heat to the passing air, which then leaves the system, removing energy from... | [
"Is this an example of entropy?"
] | [
"Loosely, yes. In this context, an increase in entropy means the system is able to do less mechanical work. So the petrol has most of the potential energy. Combusting the petrol does work on the piston, which gets converted to mechanical work via the drive train and wheels. Combustion also generates heat, which tra... |
[
"If a bullet is shot straight into the air; how fast/dangerous will it be when it comes back down ?"
] | [
false
] | [deleted] | [
"Deadly.",
"According to ",
"Major General Julian Hatch",
" bullets returning to the ground will have a terminal velocity between 200 & 330 feet per second (60-100 m/s).",
"This is enough to penetrate unprotected tissue & the skull.",
"While the ballistics of each bullet will be different, don't do it. "
... | [
"I'll do the math the other guy failed at doing.",
"An M16 fires a 5.7 mm diameter bullet. The weight of the round is about 4 g.",
"The drag coefficient for a bullet is approximately 0.295.",
"The equation for terminal velocity is",
"https://wikimedia.org/api/rest_v1/media/math/render/svg/ee680de6632767977... | [
"True but I'm not going to do a ballistic analysis on every cartridge & projectile. Nobody is.",
"Like all firearms, do not fire them in an unsafe manner unless you plan to kill your target. And always assume worst-case scenario."
] |
[
"How can there still be sand at the bottom of the river next to my home?"
] | [
false
] | ...or any river for that matter. It's a rather shallow river that flows at around 3m3/sec in the summer but blows up to 90m3/sec in the spring. It then becomes a very fast flowing torrent with quickly rising waters, huge trees ripped from shores upstreams floating by etc...But once it's over, there is still the same sa... | [
"Sediment in a river system is very dynamic and is moving all the time. The sediment that was in the river before the storm event you mention had to come from somewhere, it didn't come from parent material that weathered in the channel, it came from somewhere up-slope in the watershed. The same storm that lead to... | [
"There is part of your answer then: the St-Charles watershed crosses a variety of types of glacial deposits which include a goodly sand-sized fraction derived from the Laurentides and the surrounding area. These deposits are what feed the sediment traction-load, so of course there will constantly be a significant s... | [
"Thank you. It all makes sense. It's just so counter-intuitive somehow. The river seems extraordinarily powerful and from the looks of it, you'd believe that the bottom of the river should have reached the bedrock by now! But year after year there isn't much change. I guess some of the sediments must flow away duri... |
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