title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"If every human and manmade creation disappeared from the earth, would one sole survivor be able to fashion basic iron tools in their lifetime given ample shelter/food/water?"
] | [
false
] | How long would it take for someone to go from banging rocks together to using iron tools? Could it be done in a lifetime? What process would the person follow to get there? | [
"with solid knowledge of basic materials, yes. while i ",
" have to look up the details to confirm my shady memories, this is a process i could have easily conceived and completed in one dedicated lifetime. i live within walking distance of a beach that is quite rich with magnetite sand. ",
"http://en.wikipedia... | [
"This is why in my panic bag I have a kindle(S) with text books loaded, and maybe the anarchists book as well, low power, lots of storage... oh and an solar recharger"
] | [
"Anecdote bashing aside, even the lithium ion battery in your kindle has limited service life. Same goes for the solar panels. Long term, you would be better off with paper books. "
] |
[
"When a woman dies giving birth, what exactly happens?"
] | [
false
] | null | [
"The most common is hemorrhaging. There are fairly big blood vessels connecting the placenta to the uterus. During birth the placenta detaches from the uterus, so if anything goes wrong there, she can lose a lot of blood quickly. ",
"Also possible are heart attacks or strokes induced by the exertion of childbirth... | [
"When you consider how many woman give birth globally on any given day, that is still a concerning and surprisingly large number."
] | [
"When you consider how many woman give birth globally on any given day, that is still a concerning and surprisingly large number."
] |
[
"What is the origin of the 'alu pv92' gene sequence?"
] | [
false
] | My AP Biology class is currently doing a lab where we sequence our own DNA to see if we have the alu pv92 gene. My teacher told us that the gene is originally from an "affluent, royal Mongolian ancestor." Is this the same gene that I've heard that Genghis Khan passed along? | [
"Well your teacher is either joking or misinformed. pv92 is an alu insertion site. This is a non-coding segment on DNA. Specifically it is a jumping gene. Sort of like a virus that can insert itself in various places in our genome. We have many, many copies already. This particular instance is on chromosome 16, whi... | [
"pv92 is an Alu element. These elements are retrotransposons and they make up a significant part of the genome. Alu elements are thought to have their evolutionary roots in 7SL RNA which is the RNA component of a very important biological complex called SRP (signal recognition particle). Some Alu's like pv92 are... | [
"Yes that's true, it only exists in certain populations. Though, not as far as I know, any populations associated with Genghis Khan."
] |
[
"When black holes 'emit' radiation/particles, what material is this exactly?"
] | [
false
] | Need some clarification on the behaviour of black holes. It was my understanding that we dont know what occurs at the centre of black holes, but evidence for streams of particles from supermassive black holes at the centre of galaxies means they do something physical other than pull stuff in. When material comes near t... | [
"Black holes do not directly emit anything other than Hawking radiation. Nothing gets spewed out. The \"streams\" you are probably talking about are the result of the ",
"accretion",
". Basically as matter falls into the black hole (before actually crossing the horizon) it becomes so hot that it emits vast amou... | [
"Electromagnetic radiation."
] | [
"Aaaaahhhh thanks"
] |
[
"Does relativity effect radio waves?"
] | [
false
] | if that radio burst from this week in science originated in a much more gravity dense environment would relativity cause it to be much more dense? several (hours, months, years) worth of radio chatter condensed the same way time is? | [
"Yes, but it manifests itself as a Doppler shift. If the source is moving towards us the radio waves will seem higher frequency, and the opposite if the source is moving away from us."
] | [
"If the radio burst came from a region in a deeper gravitational well than earth, then there would be two effects. ",
"1) We would observe the total duration of the signal to be longer than it was at the source. (Gravitational time dilation)",
"2) We would observe the wavelength of the emission to be longer th... | [
"It's not incorrect, it's just a different type of doppler shift.",
"Electromagnetic waves lose energy when escaping gravitational fields and become shifted towards the red end of the spectrum.",
"They also become red-shifted when the source of the electromagnetic wave is moving away from the observer."
] |
[
"When a train starts accelerating, do the air molecules rush to the back?"
] | [
false
] | [deleted] | [
"They don't all rush to the back, but a pressure gradient is created. A force due to acceleration is analogous to the force of gravity.",
"Consider this: let's say you are holding a helium balloon in the train when it starts accelerating. From your perspective, which way does the balloon move?"
] | [
"I just wanted to point out that this pressure gradient is also very, very small compared to the pressure."
] | [
"You can do the balloon trick in a normal car, it's a fun one for the youngin's."
] |
[
"Does colder ice make a better insulator?"
] | [
false
] | Edit: Does the colder the ice gets make for a better insulator. Ex. 30 degrees F vs. 0 degrees | [
"No, in fact, the opposite is true. ",
"The thermal conductivity of pure water ice is inversely proportional to the temperature",
". In other words, colder ice conducts heat better.",
"Edit: Interestingly, ",
"the inverse is true for metals",
"."
] | [
"I don't think the answer is not misleading at all. I answered the question that was asked, exactly how it was asked. I actually assumed that the OP was asking about using snow caves for keeping warm. If that was the case he should know that the air pockets are what do most of the insulating, and the thermal conduc... | [
"While your answer is correct I also find it slightly misleading as the ice cannot conduct heat without being warmed up itself.",
"First of all, water ice is a crappy insulator.",
"Secondly, if you want to keep something cool (I assume this would be the goal, because why else use ice), the cooler your ice is th... |
[
"Why does the sky feel bigger in parts of the western US?"
] | [
false
] | [deleted] | [
"This seems extremely subjective and not something one could really prove...",
"I remember in 5th grade reading an account of Lewis and Clark where they were moving west, and noted that the plains were 'so vast, empty, and flat, that on a cloudless day the sky was just a bowl cupped over us' or something to that ... | [
"No expert, but I'd say mostly flat terrain, clear air, and lack of tree cover to the horizon."
] | [
"You get the same feeling in the Serengetti. Mostly plain, if any, only very gentle hills and few trees."
] |
[
"Can you help my friend with his aphasia?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"medical or safety advice",
"guidelines",
"If you disagree with this decision, please send a ",
"message to the moderators."
] | [
"All I’m asking for is a suggestion for an app that helps people with aphasia communicate. \nAre there any people using common sense involved here, or is this strictly moderated by bots?"
] | [
"We can't help here, sorry."
] |
[
"Would putting a big bag of ice in my freezer use more energy or less?"
] | [
false
] | Half my freezer is now filled with a big bag of ice. I'm wondering if my freezer will have to use more energy to keep it frozen or less because temperature don't drop as much? | [
"Your freezer will use less energy, but only because when you open the freezer door, there is less cold air to exchange with the warm air outside the freezer. Otherwise the energy expenditure won't change, assuming the ice enters the freezer at the same temperature as the freezer. You may have an intuition that bec... | [
"Assuming your door is closed, I don't think it matters.",
"The power used by your freezer depends on how much heat is lost through the walls of the freezer. I don't see how the contents of the freezer makes any difference to that. All that really matters is the temperature inside, the temperature outside, and th... | [
"It's very hard to say without knowing more about how you use the freezer. Initially it would use more energy as the ice is probably at about 0 degrees where as a freezer has a thermostat set much lower. So initially the freezer will have to work to reduce the temperate to -18 degrees. In the longer term the freeze... |
[
"What is the value of Monte Carlo method? Doesn't it just return the expected set of results and variance?"
] | [
false
] | What is the value of Monte Carlo method? Using a simple example of a coin toss: I can expect 1/2 chance of landing on either side, with a Gaussian distribution. Running a Monte Carlo simulation with say, 10 coin tosses won't get me valuable results. It'll return my initial setup. Why is Monte Carlo exempt from "garbage... | [
"The point is using it to calculate something you don't know. ",
"Say you throw an dart at a random point within a square. Inside the square you've inscribed a circle. 'Hits' are counted within the circle, misses outside it. Geometrically, the ratio of hits to throws will approach π. ",
"So you can determine pi... | [
"It's useful for simulating more complex scenarios. For example, I've been working on a muon telescope recently. The muon flux is a fairly well known quantity, as is the angular distribution or muons. However, since the telescope was built using rectangular scintillator paddles, and calculating a solid angle made u... | [
"I think the other answers are fairly complete descriptions, but I just wanted to directly address the question in the headline.",
"Yes, Monte Carlo pretty much just returns the Expectation and Variance/stdev, and other statistical quantities. The value of Monte Carlo is, sometimes it's the easiest way of obtaini... |
[
"Assume we detect a star [that was at one time] about to go supernova; can we point telescopes at the object to watch it exploding in \"real time\", despite the time it takes for the light to reach us?"
] | [
false
] | [deleted] | [
"True, with a caveat. The moment a core collapse occurs, a burst of neutrinos is released, most of which don't interact with the star at all and head out at nearly the speed of light. The pressure waves and photons, however, interact strongly with the material of the star and take hours to reach the surfacem. The... | [
"The event would be observable and we would see light produced by the explosion with the time delay you describe. In fact, scientists are eager to witness a supernova and are actively monitoring the star Betelgeuse which is expected to explode relatively soon (potentially may have happened and we don't know it yet... | [
"For anyone interested, ",
"here",
" is an example of a \"light echo\" of the light from a 16th century supernova reflecting off a more distant nebula so that it was observed in 2008. Ridiculous stuff!"
] |
[
"Is osmosis unique to water?"
] | [
false
] | I was thinking about how seawater dehydrates you if you drink it and I realised I'd never heard of osmosis in substances other than water. I was just wondering if the definition I've been taught ('osmosis is the movement of water across a partially permeable membrane from a high water potential to a low water potential... | [
"No it's not unique to water. It has to do with equilibrium and entropy. Usually things unique to water have to do with the fact that it's a (semi-)polar solvent. If the dissolved substance isn't in relatively equal concentration throughout the solvent, it is in a higher energy state and will move towards a lowe... | [
"from: ",
"https://en.wikipedia.org/wiki/Osmosis",
"Osmosis (/ɒzˈmoʊsɪs/, US also /ɒs-/)[1] is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of low water potential (... | [
"Oh I see, I might have remembered it wrong. Thanks"
] |
[
"Are there any examples of animals that have 'reverted' an evolutionary adaptation?"
] | [
false
] | I was thinking about the possibility of humans evolving to breathe underwater then remembered that pretty much all life originated underwater (if I'm not mistaken), which got me wondering if there have been any cases of animals sort of 'going back' to a previous evolutionary form or at least changing one adaptation to ... | [
"The peppered moth is a great example of this! The ancestral peppered moth was typically white, with the evolutionary advantage of camouflage among white tree bark in forests around London. During the industrial revolution, moths with genetic mutations that caused darker coloring (darker grey/black color) were bett... | [
"I think it may be tough to distinguish between 'reverting' to an earlier form, and evolving to a from that, coincidentally, resembles an earlier ancestor. Are dormant genes recurring, or are new mutations simply leading to a familiar solution?",
"Take cetaceans: they're marine mammals which evolved from terrestr... | [
"Whales and other cetaceans are a good example. They had land-dwelling ancestors closely related to the hippo, with regular legs and everything. They changed their limbs into fins, similar to fish (so going way back).",
"Also penguins and other flightless birds. While the origin of flight isn't exactly known, it ... |
[
"How do psychedelic substances like lsd cause perceptual distortion?"
] | [
false
] | What is the explanation for the perceptual phenomena such as 'breathing rocks' and shifting colors? (and for example why is that area affected specifically... I know other psychedelics cause purely auditory hallucinations) Do we know which layer of the visual cortex is involved? What other areas are activated / deactiv... | [
"This is a hard question to answer, but I will try to give you an overview of some key ideas. ",
"The main receptor involved in the effects of LSD is the ",
"serotonin 2A",
" receptor, though others are also involved. These receptors are found in many regions of the brain. In ",
"this picture",
", the hot... | [
"The brain is a bunch of cells.",
"The cells have long spindly tentecley things coming off them.",
"Some tentacles called axons exit the cell, carrying impulses on to the next cell. Others called dendrons enter the cell. Cells communicate by passing signals from Cell 1's axon to Cell 2's dendron.",
"You might... | [
"> The study of psychs was outlawed for so long",
"Nothing frightens that establishment more than a drug that gives it's users a boost of empathy. Can't have that now...."
] |
[
"Nature Mag says SARS-CoV-2 is 60-140 nm, but 3M says standard N95 pores are 300 nm. Cant it fit thru an N95 mask?"
] | [
false
] | I realize if the virus is on a moisture droplet, those droplets are bigger and stickier to micro surfaces in any type of mask. But now we are hearing that this virus appears to be spreading in aerosol form (which seems predictable). Water would presumably evaporate from microdroplets, especially in low humidity. So co... | [
"Yeah there are lots of other materials. There are N99 masks and others with smaller pore size like you mentioned. But nothing you do is gonna block viruses 100% of the time."
] | [
"It can definitely fit through an N95 mask, but the chances are are lower than other masks. At the nano/microscale, things don't easily slide through pores. Van der Waals and other electrostatic forces make everything sticky, so a virus traveling through a small pore would tend to cling to the sides."
] | [
"Are there any other filter materials that could be used, that might have smaller pore size, and still be breathable? For example, I see that Gore Tex claims a .2 micron pore size, although I have no idea how much surface area would be needed to provide adequate airflow"
] |
[
"Considering how annoying babies on long distance flights can be, are there any untoward effects of giving them mild sedatives to knock them out?"
] | [
false
] | [deleted] | [
"Babies usually have reasons for crying. Some of them can't deal with the pressure change and is painful for them."
] | [
"Used to be common, before airplanes - ",
"http://en.wikipedia.org/wiki/Laudanum",
" -",
"See \"Hazards\" and \"Side effects\" for that particular sedative. "
] | [
"again, wouldn't a sedative ease their pain and reduce crying at the same time?"
] |
[
"How can certain types of bacteria (some life-threatening) simply 'live' on or in people - and where do they originate from?"
] | [
false
] | I've been reading up on the (rather alarming) number of people in Georgia currently being treated for a rare flesh-eating disease (necrotizing fasciitis) caused by the bacterium Streptococcus Group A (GAS). At first, I assumed the bacteria had been contracted from an external source (as is the case with E.coli, for eg.... | [
"GAS is indeed a normal part of many people's microbiota (all the microbes in and on a person). For many people, this isn't an issue. The the strain of GAS they have might not even be anything worth \"worrying\" over. But some people do indeed carry more pathogenic strains of GAS. Get it in the wrong spot (an o... | [
"To add to what gfp wrote already you should understand that there is more bacteria on and in your body then there are your own cells. There are many of them that will make you very sick indeed if they go from where they are non-harmful or even helpful, to somewhere they don't belong. You should not be uncomforta... | [
"Thank you for your insightful reply; it has given me much to think about... I've always assumed that the body only accepts 'good' bacteria and fights off all signs of 'baddies'. It just doesn't really make sense to me why the body would allow potentially harmful entities to enter it, hang around & take advantage o... |
[
"Would it be possible to selectively breed for a giant house cat over many generations?"
] | [
false
] | Say you have an infinite amount of cats, time, and money. Could you selectively breed over generations for a gigantic cat? Edit: spelling, capitalization. | [
"they're called Maine Coon cats"
] | [
"I love my 12 pound cat. He",
"s gentle, affectionate and cuddly. I also think if he was 90 pounds larger and was in a pissy mood he",
"d try to take me down."
] | [
"Ha! Ours is thin at 15 pounds, admittedly the steroids for his asthma have plumped him up, but he can reach above my waist on his hind legs. \nYou breed big cats to big cats, and you'll get huge cats."
] |
[
"I have never read a satisfactory layman's explanation as to how quantum computing is supposedly capable of such ridiculous feats of computing. Can someone here shed a little light on the subject?"
] | [
false
] | [deleted] | [
"Grover's search algorithm",
" is a nice example of the kind of thing you can do better with a quantum computer than a real computer. The problem it solves is as follows. Suppose you have an unsorted list of things, and you want to find the position of a specific thing in that list. With a classical computer, ... | [
"There are no commercial quantum computers capable of carrying out Grover's Algorithm (or Shor's Algorithm, or any other algorithm we traditionally think of as a \"quantum algorithm\"). D-Wave's computers are neat but they have no resemblance to what's traditionally been called \"quantum computing\" in the literatu... | [
"I really wish people wouldn't give this explanation, even when acknowledging it's a simplification. OP, I'm going to strongly recommend you read ",
"this",
", an excellent overview of how quantum computers work and what they can (and, perhaps, more importantly) can't do from one of the leaders in the field. ",... |
[
"Why is it widely believed that information is conserved?"
] | [
false
] | Context: I was reading this article: Ok, like most things having to do with quantum physics this article is mostly gibberish to me, but it says the idea that information is not conserved as a resolution to the "black hole information paradox" is a "Non-starter". It doesn't go into much detail as to why that is a non-s... | [
"Mostly because of time-reversal symmetry. If you lose information, it means you cannot \"rewind\" the movie of the universe while still following the laws of physics - else you allow information to come out of black holes. And as far as we know, the universe is time-reversal invariant (well, CPT invariant but what... | [
"Okay, you have a very good point about the quantum mechanical thing. But there is a quantum mechanical variant of the information-conservation theorem (which is called Liouvilles theorem - maybe spelt wrong). I have not studied this so I cannot be sure of what it means but I guess that what it must be about is tha... | [
"The quantum version of information conservation is called unitarity (specifically unitarity of time evolution). There is a time evolution operator U that acts on a current state to give a future state. Unitarity means that the hermitian conjugate of the U operator is also its inverse. This ensures that if two isol... |
[
"How did early humans' sleeping habits change during the winter months?"
] | [
false
] | How did the shorter days of winter affect the sleeping habits of humans before indoor lighting existed? Generally speaking, diurnal animals are active during daylight and settle down for sleep when the sun goes down, but if the average sleep cycle for a human is 6-9 hours, wouldn't strictly following the daylight sched... | [
"Dammit I have to find it. It was a research based on people still living in tribal groups in the wild. They monitored the sleep if all the tribe and found that nobody had the exact same pattern. On any night there was never more than 20 minutes total with everyone sleeping because not everyone went to sleep at the... | [
"It has been discovered that earlier humans had multiple sleep patterns in the same group, meaning there was almost never someone sleeping. This is a trait that helped people get enough hours of sleep while having a natural sentinel rotation trough the night. You would juste be awake in bed listening to strange thi... | [
"It has been discovered that earlier humans had multiple sleep patterns in the same group,",
"Interesting.",
"Source?"
] |
[
"Will a wood splinter dissolve if you leave it in your hand?"
] | [
false
] | I recently got a number of wood splinters on my palm, and picked all of them except this really small one I can't see, but can feel. Will my body's immune system eventually "dissolve" (for lack of a better word) the splinter if I leave it in there? | [
"I have the point of a pencil lead in the palm of my hand. It's been there about 35 years. I can still see it clearly.",
"(Wow, now that I look for it as I type this, it seems a little less apparent than I remember; I don't examine it very often after all this time now. It had looked the same for 30+ years. It mu... | [
"I have the point of a pencil lead in the palm of my hand. It's been there about 35 years. I can still see it clearly.",
"(Wow, now that I look for it as I type this, it seems a little less apparent than I remember; I don't examine it very often after all this time now. It had looked the same for 30+ years. It mu... | [
"What if the splinter penetrates the layers below the epidermis such as the dermis or even deeper than that?"
] |
[
"Is it biologically possible for differing bird species to produce offspring?"
] | [
false
] | I'm not talking about different parrots or finches, I mean like robins and cardinals, geese and ducks, hell even geese and finches. | [
"What you're asking about are very distantly related birds. In that case, the answer is no. Birds are incredibly diverse, with over 10,000 living species. Distantly related birds not able to hybridize any more than a tiger and a giraffe can hybridize.",
"However, within families you can definitely get some weird ... | [
"The hybrids I listed are fertile. I'm sure there are some phaseanid hybrids on the list I linked to that aren't, but many are. Most of the hybrids I listed occur in the wild. I'd say they're naturally occurring, but some are hybridizing at increasing rates due to human-related things like habitat loss. We don't ne... | [
"The hybrids I listed are fertile. I'm sure there are some phaseanid hybrids on the list I linked to that aren't, but many are. Most of the hybrids I listed occur in the wild. I'd say they're naturally occurring, but some are hybridizing at increasing rates due to human-related things like habitat loss. We don't ne... |
[
"How common are blood clots as vaccine side effects?"
] | [
false
] | I’ve seen that both the AstraZeneca and J&J COVID vaccines have blood clots as a side effect ( ). I know that these two vaccines are using more traditional technologies (reengineered viral plasmids if I recall) and I haven’t heard about any blood clots with the mRNA vaccines from Moderna and Pfeizer. It got me thinki... | [
"Not commonly. The prevalence is also the same as the general prevalence for blood clots in the population so it is actually really, really hard to call it a side effect and draw meaningful numbers or studies because of the low numbers. ",
"We are also seeing a higher risk of blood clots and stroke (and other neu... | [
"As I mentioned in a comment above, it's not only the observation of bloodclots as a potential side-effect, which indeed would be extremely hard to differentiate from baseline occurrence in general. It's the observation of an unusual combination of bloodclots and low blood platelets following a strong immune respon... | [
"I agree on the comment relating to prevalence. In EMA's assessment of risk relatwd to the AstraZeneca vaccine, they investigated 62 cases of sinusvenusthrombosis over a total of 9.2 million administered vaccines.",
"However it bears mentioning that it's not a matter of regular bloodclots per se, it's the unusual... |
[
"/r/AskScience, I need some fun experiments for kids aged 9-12!"
] | [
false
] | Hello ! Long story short, I am currently volunteering on a science camp for kids aged 9-12, called NØRDcamp (It's a danish camp - translates to NERDcamp). I am the head of an activity area, where kids shall be able to walk between areas of a lot of scientific FUN experiments, and mainly just have fun with science! My b... | [
"We've got loads and loads of liquid nitrogen, so we'll definitely be making fun with that! :) "
] | [
"This",
" is a pretty interesting demonstration that is easy to do. The idea is that termites will follow the ink trail of certain pens due to it being similar to their chemical cues."
] | [
"On our outreach trips we make slime with borax. The instructions I could find on the web are with ",
"Elmer's glue",
", but polyvinyl alcohol works better.",
"PS, WAUV?"
] |
[
"Are short people less likely to get cancer?"
] | [
false
] | They have less cells that could be corrupted right? | [
"The answer generally seems to be yes, according to the studies I found--although these are correlational studies, and they don't prove that being taller is the primary factor increasing the risk. There could be other factors (such as hormones) that affect both height and cancer risk. ",
"Here are a few studies:\... | [
"Interesting to note that although it may appear that larger humans get more cancer, animals that are larger than humans don't always have increased cancer rates. Elephants have similar cancer rates as humans although they are many times our size. Understanding why this is could be critical in cancer prevention."... | [
"I was aware of p53, but it's not known if it's exclusively why cancer rates are lower.",
"\"Mel Greaves, a cancer biologist at the Institute for Cancer Research in London, agrees that TP53 cannot be the only explanation.\""
] |
[
"[Astrophysics] Do gravity waves propagate at the speed of light, or, if they are ripples in the fabric of Space-time, do they propagate instantaneously?"
] | [
false
] | null | [
"Both light and gravity waves want to travel at \"instantaneous\" speed.",
"The problem is that the maximum speed allowed in the fabric is the ",
"speed of causality",
"). Causality is the relation of a cause and effect. And the speed of casuality is the maximum speed the effect can travel away from the sourc... | [
"Please note that\"",
"Gravity waves",
"\" are a completely different phenomenon than \"",
"Gravitational waves",
"\"."
] | [
"I did not know that!"
] |
[
"What strain/s of yeast produce the most co2?"
] | [
false
] | I was wondering what strains of yeast produce the most co2 per unit of sucrose. I've heard that out of brewing yeast, champagne yeast produces the most, and brewing yeast makes more than baking yeasts. | [
"The amount of CO2 that can be formed from yeast digesting sugars is essentially fixed due to stoichiometry, but different yeasts will have different attenuation levels. A yeast with high attenuation will digest more sugar than a low-attenuation yeast in the same sugar solution.",
"In the brewing world, a high-g... | [
"I guess it surprises me that there aren't strains bred for just raw co2 production. I was reading somewhere that alcohol tolerance is more important to total co2 production than attenuation."
] | [
"It depends on the circumstances. If you have a high-gravity fermentable sugar solution to start with (above about 1.080), then many yeast strains will stop producing CO2 when they reach their alcohol limit. If the solution is lower in sugar concentration, then attenuation will be the limiting factor in how much ... |
[
"Will inland rivers rise along with sea levels?"
] | [
false
] | I was watching a news report about flooding in Venice and the rising sea levels associated with global warming. I was wondering if the rising oceans would affect the level of rivers and if so how far inland would would the river levels be affected? Specifically would the Mississippi River rise around New Orleans? | [
"Rivers will change, but the specifics of how they change will vary from river to river. As already mentioned some may rise in level and some may fall. Others that are currently tributaries of other rivers may eventually flow to the sea themselves. For example, the Thames was once a tributary of the Rhine when Brit... | [
"Both of my points are a tiny bit pedantic so forgive me for that, but just a bit to clarify",
"New Orleans is close to the ocean so I would expect rising sea levels to increase the level of the Mississippi River in that area.",
"Perhaps a better way of thinking about it is that the shoreline of the ocean will ... | [
"Thanks for the answers y'all. I was really just getting at the fact that the Mississippi sits at about sea level down river from Baton Rouge till it gets out into the gulf around Buras, La. I figured since the water would be flowing out to a higher sea it would sort of back up the river, at the parts that run arou... |
[
"To what extent do the bacteria that reside in your bowels control your actions?"
] | [
false
] | I've already seen some vaguely worded articles saying things like "Bacteria have profound effects on adult behavior" bu never elaborating. I have been unable to find journals speaking of the matter. Help is greatly appreciated! | [
"Its hard to address this without knowing what exactly the claim is. Can you provide a link to one such article?",
"Generally speaking, I have not seen any evidence at all of commensal flora affecting behavior directly. I am very familiar with the field from an immunological point of view, and gut flora can have ... | [
"Well, okay. If you consider running to the shitter every five minutes a 'behavior' then yeah, that's controlled by bacteria. But other than that, no not really. "
] | [
"really? From my research, it was recently found that mice w/ the gut bacteria removed were more brave in trials such as mazes and such. My question might not have been worded properly. I meant HOW does bacteria affect us AND to what extent."
] |
[
"Why is bradycardia the same in endurance and non endurance athletes?"
] | [
false
] | [deleted] | [
"Bradycardia just means you have a slow heart rate (<60bpm). In a non-athlete this usually causes dizziness and other symptoms that arise from lack of proper oxygen delivery to your body. If it's because of being in very good cardiovascular shape, it's still bradycardia by definition, but there's no cause for conce... | [
"Regardless of whatever the person is doing to increase their cardiovascular performance, it's still called bradycardia. In either case of the low heart rate being exercise-induced, the doctor would be unlikely to raise any concern if there are no symptoms other than slower heart rate.",
"So yeah, if you have a s... | [
"Regardless of whatever the person is doing to increase their cardiovascular performance, it's still called bradycardia. In either case of the low heart rate being exercise-induced, the doctor would be unlikely to raise any concern if there are no symptoms other than slower heart rate.",
"So yeah, if you have a s... |
[
"In relation to time dilation; if time runs slower during space travel than on earth, does aging of the astronaut slow as well?"
] | [
false
] | [deleted] | [
"The astronaut, their aging, and their perception of time runs at the dilated rate. For example, if the dilation is at a factor of ten, then if ten years pass on Earth then the astronaut will only perceive the passing of one year and will only age one biological year. "
] | [
"Definitely. The effects of relativity affect not only our perception, it's a physical phenomenon that fundamentally affects the whole flow of spacetime."
] | [
"Definitely. The effects of relativity affect not only our perception, it's a physical phenomenon that fundamentally affects the whole flow of spacetime."
] |
[
"What exactly is going on during a nuclear explosion on the atomic level?"
] | [
false
] | How can such small objects contain massive energy? For example, when a nuclear warhead goes off, what is going on when it triggers? | [
"The nucleus of the atom has to primary forces which are fighting each other. The Coulomb force is trying to push all of the positively charged protons apart. The strong force is trying to hold all the protons and neutrons together. ",
"During fission, an extra neutron is added that causes an oscillation of the a... | [
"There is an excellent, but internet-ancient resource on nuclear weapons: ",
"http://nuclearweaponarchive.org",
". In particular, ",
"section 5.3",
" describes what occurs inside the weapon during and after the detonation.",
"As a TL;DR: There are many different types of nuclear weapons, however all of th... | [
"Except the bombs used on Hiroshima and Nagasaki were fission bombs that use heavy material (Uranium 235 in Hiroshima, Plutonium 239 in Nagasaki).\nYou can't really explode a hydrogen atom, as it only consists of one proton and one electron. But you can, as in a fusion bomb, smash hydrogen atoms together to form he... |
[
"Are anti-photons a thing?"
] | [
false
] | If so could you have a flash light that emits darkness? | [
"This is a very common question here,",
"https://www.reddit.com/r/askscience/search?q=anti+photons&restrict_sr=on&sort=relevance&t=all",
"But in short: No. Or more specifically the rules which tells us what a particle's antiparticle is tells us the photon's antiparticle is just the photon. Since they're not dif... | [
"Photons do not directly interact with each other and only do so via higher order (read: rare) processes. As these interactions are higher order they are suppressed at low energies.",
"The process is so rare that it has first been observed in ... 2016.",
"https://cerncourier.com/atlas-spots-light-by-light-scatt... | [
" I didn't realize it was that recent!"
] |
[
"How do computers and machines turn electronic signals into mechanical processes?"
] | [
false
] | [deleted] | [
"To turn an electric signal into mechanic motion you need an electromagnet, or an electric motor (which also contains electromagnets). Actuator is a motor. What does an actuator physically do? It turning like every motor. This turnning motion can be converted to pushing motion too."
] | [
"This is the right answer. Also worth noting that the electrical signal from your \"computer\" won't be the thing that actually powers the motor. Typically you'll have some significant source of power, like a car battery, and your button press provides a voltage which will open a \"switch\", connecting the power to... | [
"This question is what got me into electronics, and took me many years to understand (a little). Don't let that dissuade you though! Electronics is awesome fun!\nTo brutally summarize: ",
"Computers understand everything in binary or on/off, kinda like a light switch. These binary states are grouped together to r... |
[
"Why does spatial multiplexing increase wifi speeds?"
] | [
false
] | [deleted] | [
"I'll try to answer as best as I can.",
"Different streams of information is ideally send in a different channel. A channel implies a certain frequency range that is available. Frequency is directly related to wave length and therefore, in a static situation (no objects moving) different channels will have have a... | [
"Some sources are saying it sends the same info in parallel, which increases speed because the chances of a strong signal reaching the receiver is higher. So the same packet is getting sent from each antennae?",
"Other sources are saying that \"Every path will then carry unique data,\" so packets are split, and e... | [
"Overview of the capacity of the MIMO channel.",
"In the end the answer is plainly simple, more antennas means more observations of the same data. That is where the true power of MIMO lies, the path to antenna 1 and the path to antenna 2 have different channels, more channels = more data can be sent."
] |
[
"Where does all of the snot come from when you have a cold?"
] | [
false
] | Does your body just start producing it like crazy, or do you have like a secret mucus receptical that just decides to empty into your sinuses? | [
"or do you have like a secret mucus receptical that just decides to empty into your sinuses?",
"Mucus is a compound built from a small amount of specific proteins (mucins) and a lot of water.",
"So \"all the snot\" mostly comes from the water in your body, the gelling agent can be produced in pretty small quant... | [
"Never ceases to amaze how someone always knows this niche information and can produce a great link to explain exactly like they mean as you did with the Richard Hammond video. On top of that, make it super easy to understand and enjoyable too!",
"Great reply, thank you."
] | [
"Many answerers don't know a lot about the subject at the time of reading the question, but get intrigued and just start reading about it. It's pretty fun actually, you get to learn it yourself first and then hone your writing skills by distilling the information into an easy to read comment.",
"I read of a study... |
[
"Screen Rotation Outer Space"
] | [
false
] | How would an IPad screen rotation work in 0 gravity, for example in the ISS? | [
"It does not work at all. It misinterprets acceleration in any direction as a change in orientation and flips inappropriately. This is why iPads used on the ISS have rotation lock enabled by default."
] | [
"Yes.",
"http://www.cultofmac.com/218804/international-space-station-engineer-uses-ipad-to-record-video-transmissions-to-earth/"
] | [
"This is why iPads used on the ISS",
"Are there really ipads on the iss?"
] |
[
"Answer me one thing about beta radiation"
] | [
false
] | [deleted] | [
"It's not an actual electron coming from the shell of the atom - it's a neutron that decays into a proton, an electron, and an antineutrino. This is where the proton comes from. "
] | [
"a quark which makes up the neutron changes flavour.",
"from Down Up Down to Down Up Up",
"Certain properties are always conserved - charge being one of them.",
"So as a proton is produced at +1 you need -1 to take it back down to 0 - thats where the electron comes in.",
"Remember also lepton number is also... | [
"Oh..okay...and how does the neutron become a proton?"
] |
[
"This has probably been done before but I couldn’t find it so here goes. How do earbuds get so tangled in our pockets?"
] | [
false
] | null | [
"Spontaneous knotting has been studied. The behaviour is similar to a ",
" - parts of the string moving about randomly (within the constraint that the string can't stretch or break) will result in knots forming. There are lots of ways it can be knotted and only one non-knotted configuration, so when the string is... | [
"I suppose I should be clear. It depends on the precise definition of 'configuration'. If you just take the geometry there are a vast number of ways the string can be wrapped and twisted without being knotted. If you take a topological definition based on knot theory then there can indeed be only one \"unknot\"."
] | [
"There are lots of ways it can be knotted and only ",
" non-knotted configuration",
"I know this is often repeated, but isn’t it quite obviously wrong?"
] |
[
"Why did my apple juice only freeze after I poured it in a cup? (see pic inside)"
] | [
false
] | So I accidentally left a bottle of fizzy apple juice ("Apfelsaftschorle") in the freezer for a day. When I took it out, it was still liquid. Then I poured some into the cup and it started freezing. you can see the cup. At first everything was liquid (like the bottom) but the rapidly froze in a bottom-up manner. Why? Ha... | [
"This happens when you supercool a solution beow it's freezing point. I answered a similar question ",
"recently",
" and I'll copy from that answer: ",
"If there's no point at which ice crystals can start to form (this can be a point on the edge of a container, speck of dust, or other impurity), you can cool... | [
"Apple juice has an osmolality (a measure of how concentrated the sugars and other dissolved contents are) of approximately ",
"730 mOsmol/kg",
". Due to ",
"colligative freezing point depression",
", the ",
" freezing temperature of the juice is ",
"=-1.4",
" C. The temperature referred to as the "... | [
"Great response! I'd like to know a bit more about your statement \"[freezing] is very slow until the supercooling approaches 43 K\". This number is new to me and I'm interested to hear the background behind it.",
"As a side note: be careful about switching between Kelvin and Celsius is your responses. Their equi... |
[
"Which 6 of the 16 Einstein field equations are duplicates, and why?"
] | [
false
] | around 12 minutes in explains that the Einstein field equation contains two indices, each of which can take one of four values (0,1,2,3 for t,x,y,z), which means one equation is really 16. Six of these equations are purportedly "duplicates." Which are they, and why? | [
"The field equations can be written as",
"G",
" = 8πT",
"where T",
" is the stress tensor and and G",
" is the Einstein tensor",
"G",
" = R",
"-g",
"R/2",
"where R",
" is the Ricci tensor, ",
" is the scalar curvature, and g",
" is the metric. You can also include a cosmological constant t... | [
"Each of the 10 equations is a scalar* equation.... 10 coupled nonlinear second-order partial differential equations to be exact. The entire system is a mix of hyperbolic and elliptic equations.",
"Technically, there are actually only 6 independent equations. There are symmetries that the Einstein tensor satisfie... | [
"I wrote the equations in geometrized units (G = c = 1), and the cosmological constant term is also symmetric since it is proportional to the metric. For many solutions, we just leave the cosmological term out, for a variety of reasons. Mathematically, we can always group the cosmological term with the stress tenso... |
[
"Relativistic Computing"
] | [
false
] | I was thinking last night about how speed affects time, and I was curious as to if we could harness that ability on earth. Assuming the following: Solid state super computer (so centrifugal force wouldn't effect the spinning plates or heads of the hard drives) Put it in a giant centrifuge (like a silo) with a counterwe... | [
"It would actually experience less time and run slower."
] | [
"Simple fix*. We put the Earth in the centrifuge and leave the computer relatively motionless.",
"*This is why I was a physicist and not an engineer."
] | [
"Damn. I was hoping I didn't have that backwards :/"
] |
[
"Does the human genome contain all the information required to make a human?"
] | [
false
] | Hypothetically, if our species became extinct could sufficiently advanced extraterrestrials "make" new humans with nothing more than a copy of the genomes of individual humans? My understanding of "genome" is that it consists of all of the DNA in our 46 chromosomes. Inside a cell DNA is transcribed by RNA. Would the ... | [
"The egg contains a lot of maternal-effect genes that keep the zygote going until it can start making its own proteins.\nAnd the major thing that would be missing by making a human from DNA would be the mitochondria, which are maternally inherited as well. "
] | [
"We and all life form are dependent on the continuity: Though the DNA encodes everything, we still need machinery for reading it at least in the first place. Imagine you have a DVD with an operating system and all the files required to run a computer, and on top of that you also have absolute complete instructions ... | [
"Well, if the alien species knew absolutely nothing about our biology, then no.",
"The next part they would get stuck is synthesizing proteins. Ribosome are required to synthesize proteins and while they are mostly made of RNA, they still have some essential protein components, so it's sort of a chicken and egg ... |
[
"What are the SI units of psi in schroedinger's quantum mechanics equations in various numbers of dimensions?"
] | [
false
] | I cannot find this in my text book. I cannot find it anywhere on google either. I remember it being 1/(m) for 1d and 1/m for 6d. Could you also explain why? | [
"If you are working with normalized wavefunctions in position space, the integral of Psi",
"Psi over some interval in space is a probability, and therefore dimensionless. So if you have a normalized one-particle wavefunction in ",
" dimensions, Psi has units of 1/length",
". For a normalized multiparticle wav... | [
"Wow, people like you make Reddit great. Thank you so much for taking the time to answer my question. "
] | [
"My pleasure."
] |
[
"(Cross-post from Military) Is this physically possible from a materials science or physics POV?"
] | [
false
] | Here is the animated GIF: Please discuss! :) | [
"Ow.",
"Assuming the average car tire PSI is 35-40 (probably even more for a larger utility vehicle, like this truck), along with heat from the sun/pavement expanding the air in the tires for even greater pressure, this tire was likely to be extremely pressurized. The person slashing the tires received roughly th... | [
"Agreed. Where I work (trash/recycling company) the larger dump trucks call for 100 PSI normally. I would imagine that there are vehicles that call for even more than that, but if it is inflated to 100, then driven hard on a hot day, it could become quite dangerous..."
] | [
"IIRC, some tires for large vehicles like mining equipment are very very highly pressurized - so much so that they have to be kept in steel cages when they're being changed, and a burst can easily kill someone. I can't seem to find a source right now, though.",
"EDIT: It seems like I may have been wrong, and tir... |
[
"Why are thunderstorms so rare on the west coast of the US?"
] | [
false
] | I used to live in Florida and there it seemed like there was thunder and lightning almost every time it rained. Now I live in California and while it rains quite a bit here in the winter, we only get thunder maybe once a year. | [
"Some of these answers have touched on likely reasons, but certainly Florida has a lot of warm, moist air which leads to strong convection and therefore thunderstorms.",
"California (or parts of it) may have moist air, but not as warm. There are more hills, valleys, and mountains which may interfere with low pres... | [
"Alternatively: why are thunder storms so common in Florida?"
] | [
"It's where the lows come down from Canada. That causes storm fronts at the pressure difference. This difference is usually around central usa and pushes east. Also storms form over warmer water. The Gulf is warm. The Pacific is not. "
] |
[
"If mercury wasn't so dangerous, what real world applications could it have?"
] | [
false
] | null | [
"It has real world applications like in thermometers..."
] | [
"Well I know that. I know it has some applications currently, but I'm asking if it weren't dangerous, what else could it be used for"
] | [
"Ah. Such open-ended questions are better suited for our new-ish sister sub ",
"/r/asksciencediscussion",
". Please consider reposting there instead."
] |
[
"How is it that our bodies have digestive acids are strong enough to dissolve zinc, bones that are 4 times as strong as concrete, and can filter harmful waste products, but not have developed a way to naturally guard itself from plaque?"
] | [
false
] | [deleted] | [
"Our bodies are pretty good at fighting inanimate objects. Our stomach acids can dissolve some impressive things, and our bodies are great at what they do. Bacteria and viruses however, have been evolving alongside humans for millions of years and they developed ways of circumventing our bodies defenses. You may wa... | [
"From an evolutionary standpoint, our bodies have an excellent mechanism for guarding against plaque: replacing our first teeth with a second set which subsequently would last us through the typical breeding age of a human.",
"Of course, this also helps with changes in jaw size as we grow. ",
"From an evolution... | [
"Super cool. I've never given any thought before to the evolution of baby teeth!"
] |
[
"Why is it that some plastics, when bent, turn white at the break point?"
] | [
false
] | null | [
"This is pretty cool, actually! It's the same deal with plastic bags turning white if you stretch them gently. It's a phenomenon known as strain-induced crystallization.",
"Ordinarily, the plastics that you're talking about (HDPE, PETE, etc.) are not very crystalline. They're polymers, so they have a bunch of ... | [
"I think it depends more on the type of polymer - the visible effect is more likely to be crazing in something more brittle, like PC or PMMA. But in something like LDPE, you're going to see strain-induced crystallization.",
"Nice catch, though; I should've mentioned crazing too."
] | [
"Just to add on here, while crystalization is an important effect that causes the white, the more predominant effect is ",
"Crazing",
"."
] |
[
"Hiw do our bodies produce heat?"
] | [
false
] | I assume that it has something to do with our blood because that's the thing that circulates throughout our body and regulates our heat (presumably it mostly warms us while our sweat cools us). I really don't know and would love it if someone could help me. | [
"It's a result of all the chemical reactions that occur via our resperation and all the other general bodily functions.",
"With all chemical reactions an amount of heat is always generated. In the body this ranges from converting glucose into lactic acid for muscle contractions, to the nerochemical signals in our... | [
"Metabolism itself generates some heat and quite a bit of heat is generated by muscle contractions. That’s why you start to shiver when cold; your muscles are contracting, albeit not at full force, at rapid intervals. The bloodstream distributes the heat since water has a very high capacity to absorb it without act... | [
"Heat is ultimately generated from breaking down sugars, fatty acids, and amino acids. These are the things that provide the calories that you need to stay alive and do extra work like walk around, digest things, or regulate your body temperature. All your energy comes from those three groups of molecules and all y... |
[
"Does the volume of ingested bacteria or virus affect how sick you get?"
] | [
false
] | [deleted] | [
"The number of live bacteria or virus you put into your body will matter. ",
"Example is C. perfringens: if you eat food with only 100,000 per gram of these bacteria, you likely will not get sick (body stomach acid will kill most of it). However if you eat food with one or ten MILLION per gram of these bacteria i... | [
"But is it sick to varying degrees depending on how much you ingest, or is it just \"sick\" and \"not sick?\""
] | [
"It's both. You've got a range of possible illness that goes from: Not sick -> may get sick -> will definitely get sick -> will shit your guts out. The more bacteria you get into you in your initial dose, the more will be present when your immune system finally wakes up and tries to get rid of them. If you start... |
[
"What would happen if all the world's carnivores and omnivores disappeared overnight?"
] | [
false
] | I know there would be huge herbivore die-offs due to overpopulation and starvation, but would the world's herbivorous population eventually stabilize itself, or would the animal kingdom be permanently and irrevocably wiped out? | [
"So, in ",
"/r/askscience",
" we often remove questions of the form \"What would happen if...[insert thing that could not possibly happen]\", but I want to note (especially for other mods who may move to remove this question) that, phrased another way, there are some interesting community ecology questions here... | [
"I think we would have a strong selection for self-preservation (which I think we already have in a lot of species), after all it's more beneficial for a species to have fewer but strong individuals than it is to have many half-starved to death and weak individuals.",
"The second thing that would happen, is that ... | [
"I think this belongs better in ",
"/r/fantasyworld"
] |
[
"Is acquiring a taste for something like black coffee a physical change, a psychological change, or a combination of both?"
] | [
false
] | null | [
"The psychological and physical (i.e. biological) aspects are interdependent: it's a combination of both. However, as in most psychological changes, they are a consequence of changes in the underlying neurobiology (this also implies that a behavioral change will effect changes on neurobiological function, leading t... | [
"Follow up question: is there any reason to believe that people, like myself, who drinks coffee black is more prone to eating spoiled food without noticing?"
] | [
"Caffeine is the most widely consumed psychoactive substance worldwide. As such, it might generate a certain dependency. Fortunately for many of us the effects of caffeine are more of an alertness thing than anything else—yet some of us will be very, very cranky without the usual dose of caffeine, especially in the... |
[
"Why is the C squared?"
] | [
false
] | With my limited understanding, the amount of energy an object has (in movement) is related to its mass. As it gets faster, it gains mass. So nothing can move faster than the speed of light since it would take an infinite amount of energy. So why is the C squared in Einstein's equation? Wouldn't that be a speed way beyo... | [
"This is not a complete answer by any means, but look at the units used here:",
"[energy] = [mass]*[speed]",
"And remember that speed = [length]/[time], which will be important for below.",
"Energy units, such as Joules in SI, when described by the more \"basic\" units of time/length/mass, look like:",
"[ma... | [
"It sounds like you have a more basic misunderstanding about what the equation is than the answers you've been given suppose.",
"This equation stems from an idea that there's a more intrinsic relationship between mass and energy than you might intuitively think. As in, the one can be converted into the other. "... | [
"Also, we do not really think about an object as gaining mass when it has a relative velocity, we consider the mass as being the same regardless of the speed. The extra energy that in movement is a kinetic energy, which changes the total energy (rest mass + kinetic) to be E = mc",
" /sqrt(1- v",
" /c",
" )... |
[
"Do atoms orbit objects?"
] | [
false
] | [deleted] | [
"Gravity is really weak. The gravitational \"escape velocity\" of a person is less than a millimeter per second, and do to their thermal motion an atom might be going hundreds of meters per second, fast enough such that the gravitational field is entirely negligible.",
"In addition, residual electrostatic forces ... | [
"No.Orbit is a balance between in downward force of gravity and an objects inertia, or tendency to move forward. A few things prevent atoms from orbiting objects on the Earth's surface. The first is the gravity at sea level is much stronger than the gravity at the altitude satellites orbit at, due to this when you ... | [
"While many people here correctly state that this does not happen on the small (ie, human) scale, on the level of solar systems and above, this absolutely does happen. Atoms and molecules can orbit other objects, though they are easily perturbed by pressure due to light and the solar winds. ",
"In the absence of ... |
[
"Do people who have been sexually reassigned have a lower rate of STD transference?"
] | [
false
] | It might just be the time of night, but I got to thinking... The transference of STD's has to do with certain types of tissues and/or blood transference, right? Or else you would have all types of STD's spreading into other systems rampantly (which granted, some do, but you never hear of, say, Genital Herpes spreading ... | [
"It might not offend you, but some transwomen would be offended by your use of the term \"normal women.\" Maybe cis women instead?"
] | [
"The whole time I kept thinking \"neopus, hm. I wonder...\" and then right at the end I was vindicated. Kudos for picking one badass username."
] | [
"The whole time I kept thinking \"neopus, hm. I wonder...\" and then right at the end I was vindicated. Kudos for picking one badass username."
] |
[
"Can we ever \"see\" anti-matter?"
] | [
true
] | [deleted] | [
"From my understanding, antimatter would emit photons just the same as ordinary matter. If you had a brick made of anticlay that was not in contact with any \"ordinary\" matter, it would just look like a plain old brick. Until it touches something and everything explodes."
] | [
"I just tried to think of what an anti-photon would even be like and it hurt my head a little. I suppose you'd need anti-electric and anti-magnetic fields. More importantly, I suspect that you'd have to request anti-funding to study it. And nobody wants to request anti-funding."
] | [
"Antiphotons ",
" photons, so there's no problem here. The only problem with visually observing antimatter is that we don't know where to get enough of the stuff to see."
] |
[
"What is the physiological difference between doing 50 sit ups one after the other versus doing 1 sit up every 10 minutes 50 times?"
] | [
false
] | So besides time management, 50 sit ups where each one is 10 minutes apart seems much easier than just doing 50 at once. So what's going on different in terms of our bodies? | [
"The difference is on the hormones response to lactic acid: doing 50 sit ups in one go would tire your muscles quicker and increase too much lactic acid in a short period of time, leading to increased release of stress hormones such as cortisol and growth hormone."
] | [
"I don't know. Increased growth hormone would stimulate muscle growth, but increased cortisol would cause muscle breakdown via gluconeogenesis, but maybe the muscles that cortisol would somewhat destroy would be less active muscles -- I believe in use and disuse theory, which I think is from Lamarckism."
] | [
"OK, but do we get beefier faster by doing one or the other?"
] |
[
"Is the maximum electricity a generator can output equal to the mechanical energy input?"
] | [
false
] | Human powered electrical generators are somewhat impractical as a viable source of electricity due to the relatively low ability of the human body to produce energy (~75-100 Watts). But, even with this low number, can you push up the electrical output by simple attaching it to a larger generator with more magnets and c... | [
"can you push up the electrical output by simple attaching it to a larger generator with more magnets and copper coils?",
"No, this would be creating free energy out of nowhere.",
"If this were the case, why even have the human at all, just wire up an electrical motor putting out 100 watts and then use your mag... | [
"Bigger generators/motors can handle more power. They do not ",
" more power. In the same way that you need a bigger wire to conduct more electricity, you need more motory bits to generate more power. If you want to actually produce more power, you need to turn the shaft harder and/or faster."
] | [
"Power dissipated by Joule heating is R I",
". IR has units of electric potential (energy per charge, like volts). So both quantities are not really comparable."
] |
[
"Are there known solar systems with planets NOT all orbiting in the same plane?"
] | [
false
] | I could find that the planets in our own solar system all orbit in the same plane due to how the solar system was formed. Is this the only possibility or would it be possible for the planets to orbit in let's say, 2 planes? | [
"All planets form out of the same protoplanetary disc so all planets form more or less within the same plane around a star. There is the possibility of capturing a rogue planet through gravitational capture though. ",
"Considering how unlikely a gravitational capture is and how sparsely the stars are spread out i... | [
"Pluto doesn't orbit the same plane, it has a 17 degree tilt and its orbit occasionally puts it closer to the sun than Neptune. This was one of the reasons as to why Pluto got declassified as a planet (it doesn't \"clear the neighborhood\" around its orbit). Nevertheless it does has numerous planet-like features an... | [
"It would be extremely unlikely to find a solar system with planets orbiting in random planes. Conservation of angular momentum will tend to force all planets into the same plane over time.",
"The only way that I can think of that a solar system might have planets in different planes would be if it were a very yo... |
[
"Why is there a UTC+14:00? Does that mean there are 26 hours in an Earth rotation, or is that the same as saying UTC-10:00?"
] | [
false
] | null | [
"Here are a number of AskHistorians threads that you will find interesting:",
"How long have people known about time zones and how were they first discovered?",
"Did ancient people use time zones?",
"When did time differences start to become an issue?",
"When was it realised that time differences (zones) ex... | [
"Yes. ",
"Here is a clock in Kiribati",
" and ",
"here is a clock in Hawaii",
". ",
"Here is a time zone converter",
" to compare them side by side."
] | [
"The Line Islands in Kiribati ",
"should be UTC+14",
" (and that site showed that when I linked them).",
"I really don't know what to tell you. A time zone means clocks are set to a certain time, and in the UTC+14 time zone they're set 14 hours ahead of UTC. "
] |
[
"How Does the Equipment in Hospitals/Labs Produce Gamma Rays in the MeV range?"
] | [
false
] | Do they just use radioactive material decays or do they have machines that concentrate/focus them in a way? I know that Cobalt 60 can produce up to 1.3~ MeV during its decay into nickel. I have also seen alpha bombardment of boron using polonium but that only gets up to 3~ MeV. I could not find any information on how h... | [
"There are some common laboratory gamma ray sources (cobalt-60, potassium-40, sodium-22, cesium-137, etc.), but this will generally produce gamma rays of a few hundred keV to a few MeV.",
"To produce ",
" high energy gamma rays (up to ~ 100 MeV), you can use inverse Compton scattering in a free electron laser. ... | [
"Plain Bremsstrahlung will do. You need an electron beam of energy greater than 6.8 MeV, 7.5 MeV sounds like it might be worth a try.\nStop it in a radiator target (warning - you'll deposit a lot of energy there if you use any kind of current, so make sure it is water cooled). and place your Hg sample behind it. Su... | [
"This is my time to shine! I am a medical physics master student working at a hospital. Here in our hospital we have medical linear accelerators, they work in the 2.5 - 16 MeV. Here we mostly use the 6 MV energy for most treatments but for any electron therapy we have machines commissioned for up to 12 MeV (16 MeV ... |
[
"Is it possible to replace human limbs with robotic ones?"
] | [
false
] | I've been playing Deus Ex Human Revolution and I was curious as to whether it would be possible. I figure a super strong robotic arm or leg would come in handy someday. | [
"http://en.wikipedia.org/wiki/Prosthesis#Robotic_limbs",
"We are already marching towards this technology with the production of robotic prosthetics.",
"In principle it is definitely possible to replace human limbs with robotic ones. In practice, there are two engineering hurdles to be overcome. The first is th... | [
"Thats pretty cool. Thanks."
] | [
"In theory, yes. In practice, not yet. But we are indeed working on brain/computer interfaces that would allow for robotic prosthetic limbs. I just wouldn't start cutting my arms and legs off quite yet, we're still quite a ways away from being turned into the 6-million dollar man from an operating table."
] |
[
"Why ocean acidity is rising, what happened to carbonate-bicarbonate buffer?"
] | [
false
] | Back in school (it was a few decades ago) I was taught that ocean acidity remains constant due to so called carbonate-bicarbonate buffer. Free H+ ions interact with some of the dissolved carbonate ion to make bicarbonate ions (or vice versa). This way adding extra H+ just changes the ratio of carbonate:bicarbonate, whi... | [
"Quick and dirty answer: the ocean pH is kept constant mostly through the CaCO3 compensation process where CO3",
" from carbonic acid is combined with Ca",
" from weathering rocks on land. So long as this process can keep up with the formation of carbonic acid, the pH should stay constant.",
"Carbonic acid is... | [
"Good reply. I'll just add a complementary tidbit about historical variations in oceanic pH, which has fluctuated a lot through time. One notable example is the Permo-Triassic crisis (AKA \"The great dying\", about 250 MY ago), where oceanic pH went all the way down to 2. The mechanism for that is unclear, seems se... | [
"I don't know off the top of my head of a bicarbonate buffer system in the earth's oceans. ",
"He could be thinking of fresh water. "
] |
[
"If normal human body temperature is 98.6 F, why does that external temperature feel very hot to us?"
] | [
false
] | My only guess is that the body generates excess heat that it must get rid of, but I honestly don't know the exact physiological answer to this question. | [
"You should really check out ",
"this /r/sciencefaqs thread",
". Look there first next time."
] | [
"So no exaggeration then? Just your feelings? Thanks for the clarification of your post."
] | [
"We sense temperature changes, aka heat flowing in/out of our bodies, not temperature.",
"When the air temp is 98.6 (ignoring air flow, etc) our body doesn't lose much if any heat, so we sense it."
] |
[
"How do satellites that calculate carbon emissions work?"
] | [
false
] | null | [
"Hi cvielma thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the followi... | [
"Environment"
] | [
"Earth Sciences"
] |
[
"Can one's eyes go bad if they use bad glasses?"
] | [
false
] | [deleted] | [
"By \"bad,\" do you mean that they are the wrong prescription? In that case, they'll probably give you headaches, but it has no long term effects. Otherwise, I really doubt that anything bad will happen."
] | [
"Thats odd, all my life my parents would tell me if someone wore glasses that didn't fit their eyes would start to get worse and worse. What causes these headaches?"
] | [
"Headaches are caused by strain in the muscles that control focus, as they are constantly flexing trying to compensate and they never get to rest."
] |
[
"How is it possible for a medical examiner to find COVID-19 cases for people who passed away weeks / months before community spread was known about?"
] | [
false
] | I ask because California’s Governor has just asked medical examiners to reevaluate deaths from as far back as December. How long does a medical examiner have access to a body? Shouldn’t these people be long buried / cremated by now? | [
"The medical examiners may still have preserved blood samples available even if the bodies are long gone. I seem to recall reading that the California reevaluation included a few instances of reviewing blood or tissues samples previously collected which allowed them to detect the virus that way."
] | [
"I would imagine that ICU notes and records in particular are very detailed."
] | [
"I would imagine that ICU notes and records in particular are very detailed."
] |
[
"Hi r/askscience. What exactly is \"modern\" damascus steel made of and follow up question is it at all like THE damascus steel of myth and legend? Thank you for your kind consideration."
] | [
false
] | null | [
"I am a materials engineering student and this is a topic we covered in particular in class.",
"The origins of Damascus steel is a bit foggy, the exact properties of what would qualify as \"Damascus steel\" is equally foggy.",
"Modern Damascus steel is made by taking a certain kind of steel called \"Wootz\" (pr... | [
"As a smith I can tell you that this is the lazy cheap way to make a blade look pretty without any effort, the correct modern technique is to layer high and low carbon steel and draw it out, then cut and fold then forge weld, and repeat this until the desired number of layers are achieved. This provides the best re... | [
"What is the difference between Damascus steel and Crucible steel? I watched a documentary on the Viking sword and it focused on a specific blade called the Uthbert. It was a high carbon blade that was very popular at one time, to the point that people were counterfeiting them. It was one of the only blades that ... |
[
"\"Warning: This contains materials known to the state of California to cause cancer\"... what's the truth behind these labels?"
] | [
false
] | I've seen this label on a few things. One is some barbell weights, another is some metal wire used to hang paintings. Can handling this stuff really cause cancer? If so how is it even legal to sell? I would love an explanation behind these labels. | [
"Often this label is associated with products which contain lead, and the laws in California are such that manufacturers have to err on the side of (sometimes extreme) caution or face risks of huge liability even when the real risk is very small.",
"Don't eat products like this or use them in the preparation of f... | [
"It's a Prop 65 warning. It was passed as the Safe Drinking Water and Toxic Enforcement act of 1986. Basically, this law requires a list to be compiled of substances that can cause cancer or reproductive toxicity. You can read the full list here: ",
"CA OEHHA Page",
"Take a few minutes and skim that list. There... | [
"Yet another well-intentioned law that actually makes things less safe."
] |
[
"Can one biome turn into another naturally? If so, what specific things can turn one into another?"
] | [
false
] | [deleted] | [
"Just change biome settings.",
"Ahem. Yes, they can. Things like new river pathways, new mountains, or new valleys, as well as volcanos can change the climate of the region to a certain degree. Of course, it takes many thousands of years..."
] | [
"Sure the Sahara had a very different climate in it's fairly recent past.",
"https://www.livescience.com/4180-sahara-desert-lush-populated.html",
"A similar thing happened with the Southwest USA. There were rapid swings between wet and dry periods.",
"https://uanews.arizona.edu/story/cave-reveals-southwest-s... | [
"Sure the Sahara had a very different climate in it's fairly recent past.",
"https://www.livescience.com/4180-sahara-desert-lush-populated.html",
"A similar thing happened with the Southwest USA. There were rapid swings between wet and dry periods.",
"https://uanews.arizona.edu/story/cave-reveals-southwest-s... |
[
"Has volcanic activity ever been observed on Jupiter's moon Io?"
] | [
false
] | I learned that volcanoes are on Io, I just want to know if the volcanoes have ever been observed while erupting. | [
"Yes!",
"See also: ",
"Io, Volcanism (Wikipedia)"
] | [
"It's the easiest way to transmit photos over vast distances. More colourful pictures use more data, and therefor need more power to transmit. They also have a greater chance of degradation over vast distances."
] | [
"Yes - furthurmore, Io appears to be the most volcanically active body in the solar system; it is way more active than Earth."
] |
[
"What is preventing cold air from reaching Europe?"
] | [
false
] | I've been looking at the 850 mb/hPa temperatures for a while now (for instance on (I'm assuming the 6h forecast is pretty close to the actual temperatures) ), and the cold air seems to avoid Europe like the plague. Why does the cold air never plunge into Europe? | [
"Right, if you notice, Rome and Chicago are at exactly the same latitude, yet Rome is very clearly quite a bit warmer on average.",
"There are 3 main categories of explanation for this:",
"1) Common wisdom: the Gulf Stream. Warm water in the Gulf of Mexico exits the gulf and heads northeast across the Atlantic,... | [
"Wind belts and Hadley cell's, Earth's atmosphere is a complex system of high/low pressure systems, and hot and cold fronts caused by differential heating from the sun because of Earth's tilt of 23.5",
" ",
"Due to this you can typically expect the East coasts of continents to be colder in the Northern hemisphe... | [
"Wind belts and Hadley cell's, Earth's atmosphere is a complex system of high/low pressure systems",
"Wind belts and Hadley cells are axisymmetric, though, so they don't explain why east coasts and west coasts should be different.",
"and hot and cold fronts caused by differential heating from the sun because of... |
[
"Why isn't every month the same length?"
] | [
false
] | If a lunar cycle is a constant length of time, why isn't every month one exact lunar cycle, and not 31 days here, 30 days there, and 28 days sprinkled in? Edit: Wow, thanks for all the responses! You learn something new every day, I suppose | [
"Our current calendar originated with the Romans. They were a little lax about keeping time, so they had 10 months (hence ",
") that they cared about, and then an intercalary period of indeterminate length.",
"Then the second king of Rome, Numa, said \"Dude!\" And he added two extra months, and changed the numb... | [
"Thank you for actually answering the question. It is pretty funny how months 9 through 12 are prefixed \"sept, oct, non, dec\". Clearly they were meant to be 7 through 10."
] | [
"A solar year is about 365 days, twelve lunar cycles is about 354 days. If you make the months synch up with the lunar cycle, like in the Hebrew calendar, the year won't synch up with a solar year. If you ensure that the year synchs up with the sun, like the Gregorian calendar, it won't match the lunar cycle."
] |
[
"What makes an atomic bomb/explosion stop expanding? Why don't atoms continue to split more atoms etc?"
] | [
false
] | After countless hours of searching google I couldn't come up with a definite answer. Sorry if this is a dumb question. | [
"The short answer is they blow up. Which is to say the stuff needed for the reaction is violently pushed apart. As a result there is only a very narrow time window for the reaction to occur.",
"There are two types of nuclear weapons:",
"It is worth noting that a hydrogen bomb has a fission bomb wrapped around... | [
"Theres 2 basic types of atom bombs. Fission, and fusion.",
"Fission works by splitting already unstable atoms (specifically the nucleus is unstable) so I'll go there. Basically only certain atoms are unstable and prone to breaking apart. Imagine an unstable atom like uranium-235 is a mouse trap thats been set ju... | [
"Basically, the sheer amount of empty space in atoms means that the conditions for fission or fusion are very, very specific. Atoms are not packed tightly. The necessary domino effect of the chain reaction is like mousetraps loaded with ping-pong balls. The chain reaction only happens if you have an assload of trap... |
[
"If two unnaturally powerful fans were aimed directly opposite of each other with their intake facing each other, would it create a black hole or some kind of rip in time?"
] | [
false
] | null | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"It is hypothetical or speculative in nature. We do not allow hypothetical questions because questions that cannot be confidently answered with any available data often invite non-scientific speculation.... | [
"It’s a question, is that not the point of this sub?"
] | [
"Sorry, we don't allow questions that require speculation here. This would be suited for our sister subreddit ",
"/r/AskScienceDiscussion",
" however - feel free to post there."
] |
[
"Why is Plutonium-239 fissile but Plutonium-238 isn't?"
] | [
false
] | null | [
"For a nuclide to be \"fissile\" means that it can undergo neutron-induced fission with neutrons of arbitrarily low energy. If for some nuclide there exists some threshold energy (typically on the order of MeV) for neutron-induced fission, then that nuclide is not fissile.",
"We quantify the probability of a nucl... | [
"Pairing is what makes binding energies oscillate between odd and even isotopes, yes. And that’s what makes it easier or more difficult to excite the compound nucleus above the fission barrier."
] | [
"Yes, but it’s only true for a given type of nucleon. Neutrons want to pair with neutrons, and protons with protons. They pair into states where their angular moments cancel each other out."
] |
[
"Can chewing gum be created to mimic and make obsolete the need to brush your teeth?"
] | [
false
] | null | [
"Unfortunately, it is very unlikely that a chewing gum could be created to mimic a toothbrush. In fact, such a gum would be far more difficult to use then our current tooth-cleaning methods.",
"The very nature of chewing gum is a crushing force transmitted mainly by the occlusal surfaces of the teeth, with very ... | [
"In the past, she was absolutely correct. Chewing gums containing sugars are very bad for the teeth; chewing such gums is giving the number one enemy of your teeth, your oral bacteria, an extended feeding session as sugars are slowly released over the duration of your chewing. The long-term sugar release defeats an... | [
"No, when you chew gum, it pretty much only touches the occlusal surfaces of the teeth (the parts that meet when you close your mouth)",
"Brushing is needed to clean the sides of the teeth especially near the gum line."
] |
[
"Will too much close-work *really* worsen my myopia if I'm no longer a child?"
] | [
false
] | null | [
"This is absolute nonsense.",
"Axial myopia is due to one's eyes being too long. Accommodation is a separate issue. Some have suggested that extended periods of close work would cause myopia by stretching the eye, but it hasn't been shown yet in humans.",
"Further, presbyopia, which is the inability of older ... | [
"This Wikipedia article",
", and I'm sure it's sources too, talk about a range of research on the topic. As far as I can tell, and this is not my field, the question is still open. "
] | [
"This is absolute nonsense.",
"Citation?"
] |
[
"Does photon duality mean we can record light like we would sound?"
] | [
false
] | null | [
"For low frequencies, yes. This is just an antenna. ",
"The problem with visible light is that the wavelengths are so small and frequencies are so high. The problem is that a super high frequencies the normal assumptions we have about electric circuits break down. "
] | [
"Things like ohms law are no longer true. Materials don't have linear resistances at super high frequencies. You need to know much more about the medium things are propagating in, especially when the frequencies correspond to wavelengths around the size of molecules or the spacing of atoms."
] | [
"Can you expand on the bit about the normal assumptions breaking down? ",
"I understand the bit about the wavelengths being tiny in size would make the electronics themselves be ungodly small, but how would that cause our electronic laws to break down? "
] |
[
"Why doesn't ice become more malleable as it approaches it's melting point?"
] | [
false
] | Just like plastic, metal, wax etc... | [
"It has to do with how the solids are staying together, in a sense. Metals have a crystalline structure, which has natural faults (known as dislocations) in it, which makes them more malleable. Think about how you can bend a metal ruler, but if you had a piece of ice in the same shape and tried to bend it, it would... | [
"However, cold ice is a lot more brittle than just-below-melting-temperature ice."
] | [
"For Ice Ih, yes, sort of. It's not the cause though so much as a related phenomenon. The expansion of water as it freezes into Ice Ih is a result of hydrogen bonding causing water molecules to align in an ordered hexagonal pattern that, in simple terms, takes up more space than the random distribution of water m... |
[
"In what ways could one forge a radiocarbon age?"
] | [
false
] | As I understand it, radiocarbon dating determines the approximate age of an organic object by determining how much time has elapsed since it extracted carbon-14 from the atmosphere (with a lot of caveats). One way someone might fool carbon dating for, say, a document, would be to write on genuinely old paper. What othe... | [
"Make paper using pulp from old dead trees?",
"This could work, assuming you mean trees that have been dead for a long time; pulping antique furniture for the purpose, for example, maybe, if the varnish didn't become a problem? ",
"You'd need to be careful with this, though, since you'll want to use antique pa... | [
"Doesn't much matter which part you use, since it all dies at roughly the same time.",
"But isn't all of a tree except the outer layer dead? So the core of a 400-year old tree would carbon date 400 years older than the outermost ring?"
] | [
"Hmm, apparently so for species that form heartwood (we could argue over whether xylem is technically dead too, I suppose; for these purposes it might well count). In that case, I don't see why it wouldn't work."
] |
[
"Why does the Milky Way appear arch-shaped when photographed from Earth?"
] | [
false
] | null | [
"Actually it does not. It should be a line across the sky. But it might seem like an arch:\nThe if you draw a straight line across a half sphere, this is indeed an arch, but you are always looking from inside the plane. If this is photographed with a wide angle lens, the distortions might make it look like an arch ... | [
"Any physically straigth line will always appear arc shaped if it covers long enough area of your vision.",
"Its just our brains can make us realise they are really straigth if there is enough context. For the case of milkiway center there isnt. Cameras can cause further confusion.",
"Its like inverse version o... | [
"I think this is because we tend to think of the sky as a cylinder rather than a hemisphere. If we imagine reaching straight up from the horizon, we tend to think it just keeps going up forever, up the sides of the cylinder (and an angled line would spiral up forever).",
"We also have trouble with imaging very wi... |
[
"How can plant varieties be 'resistant' to things without antibodies?"
] | [
false
] | To the best of my knowledge, plants don't have an immune system in the same way animals do. How can it be that they can be more or less vulnerable to disease? Obviously mechanical threats like being eaten by insects or animals can be mitigated by being unpalatable or containing pesticides. | [
"Plant biology is not my field, but I am a fan of all types of immune systems. If any botanist wants to jump in and bitchslap me with more knowledge, please do so.",
"Plants do have an immune system, and parts of it are kind of like ours.",
"They have specific compounds and proteins in their tissues that can in... | [
"Plant pathologist reporting! Both plants and animals can detect specific molecules that signify the presence of unwanted microbes. These are molecules that are shared within entire groups of microbes, and some of the same molecules are used in detecting microbes in both plants and animals. When a plant detects ... | [
"Plants can even emit chemical messengers that signal parasitic wasps to come and eat when the plant is being eaten by insects. There are some fabulous examples of co evolution of plants aphids and wasps. This somewhat relates to your question"
] |
[
"What frequencies are used for radio transmitting over very long distances?"
] | [
false
] | null | [
"Engineering"
] | [
"Engineering"
] | [
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
"To check for previous similar posts, please use the subreddit search on the right, or Google site:reddit.com",
"/r/askscience",
" ",
"Also consider looking at ",
"our FAQ",
... |
[
"How is accurate dating of sedimentary rock achieved?"
] | [
false
] | I am not a creationist, I am just an interested nerd working his way through The Greatest Show On Earth for the second time, and I didn't find Dawkin's explanation satisfactory. Ok look, from my layman's perspective, I understand how we can date igneous rock using half-lives of elements. The "atomic clock" is zeroed wh... | [
"I believe that ",
"superposition",
" and ",
"stratigraphy",
" is used in tandem with potassium argon dating. I have also read a bit about xenotime dating, though I believe it is not yet widely used. However, h",
"ere is an article",
" about its uses in dating sedimentary deposits."
] | [
"dating advice should be directed to ",
"/r/relationship_advice",
"."
] | [
"Diagenetic minerals such as ",
"http://en.wikipedia.org/wiki/Glauconite",
" can be used;\nFossil records-if we know fossil a died out 165mya then if its in a rock the rock is probably older than 165mya;\nIgneous layers found within sedimentary layers (ash deposits);\nMarker beds from events (the iridium layer ... |
[
"What is some specific evidence that shows that true randomness exists?"
] | [
false
] | Thanks in advance. I have some questions about randomness: I know (or do I? Please correct me if I'm wrong) that the distribution of electrons in an atom is truly random (and if I'm not mistaken, this also relates to the fact that you can't predict exactly when a radioactive atom will decay). I've heard that Heisenberg... | [
"http://www.reddit.com/r/sciencefaqs/comments/gx7p8/randomnesshidden_variables_in_quantum_mechanics/",
"Thar you go."
] | [
"Randomness is fundamentally a statement about the ability of a certain group of actors to predict what is going to happen next.",
"I remember an introductory logic design problem, where we had to get a random number when a human presses a button. There were a lot of over-thinking approaches for this, but a simpl... | [
"You've got me intrigued now, how are mutations not as random as one would expect?"
] |
[
"What caused the different branches of Proto-Indo European (PIE) to have different order in grammar (subject verb object etc.)?"
] | [
false
] | null | [
"The terms you're thinking of are synthetic and analytic. Generally, languages maintain their complexity in some form or another. For example, the language loses one feature but gains another. (English lost many of its inflections but gained strict word order.)",
"In general, even synthetic (e.g., Ancient Greek) ... | [
"I'm not expert, but I believe the PIE was not order based but ending based (I forget the technical term). These endings were lost over time and the identification of the function of words shifted to word order instead."
] | [
"Right, I believe that's why verbs conjugate differently and nouns (even in English at one time) would be different depending on whether they were subject, object, etc. (I believe you're referring to case declension). I'm just curious if it was random or some cause/factor why some turned out to have verbs at the en... |
[
"How hot can something get just from receiving sunlight? Does it have a limit? (Think of something left in the car directly exposed to sunlight) Does it change if something is exposed to the sun in a vacuum where it can’t dissipate heat as easily?"
] | [
false
] | null | [
"The hottest something can get exposed to sunlight is 5778K which is the temperature of the surface. If the objects temperature was higher it would actually cool when exposed to sunlight. You can't get around this limit using a magnifying glass either, light goes both ways and anything hotter than 5778K would radia... | [
"5778 K is the absolute limit (from thermal processes, in equilibrium, and neglecting some technical details). You reach that if you focus sunlight so good that the object \"sees\" the Sun in every direction.",
"Practical considerations will lead to lower limits."
] | [
"I feel like OP probably means how hot can something get ",
" when exposed to sunlight, which probably depends on a wide range of factors."
] |
[
"Can you feel the ISS move?"
] | [
false
] | Not sure if the flair was correct or not. I was thinking about astronauts and space walks this morning when I started wondering about speed. The ISS is essentially hurtling around the earth at breakneck speeds right? When an astronaut goes out into space they tether to the ship and complete their walk. Can the astronau... | [
"You can't feel movement. For all intents and purposes, there's no difference between standing still and uniform motion.",
"You can feel acceleration though, because acceleration and force go together, as per Newtons laws.",
"On Earth, you feel motion because there are ever-present friction and air resistance t... | [
"They're moving at that speed too! Can you feel the earth moving in space? Same principle. When you feel movement in a car for example, what you feel is the speeding up and slowing down of the vehicle but if it stayed at a constant speed with no external forces (friction/wind resistance) you would feel stationary."... | [
"Thanks that's what I was thinking but my mind kept nagging away at me."
] |
[
"If you could conduct any experiment without any moral, legal, financial, or ethical restrictions, what would that experiment be? What questions would you be looking to answer?"
] | [
false
] | If you could conduct any experiment without any moral, legal, financial, or ethical restrictions, what would that experiment be, what questions would you be looking to answer, and what do you hypothesize would be the outcome? In this hypothetical situation, you would not get any backlash for conducting an experiment th... | [
"A friend of mine who is in med school told me that supposedly it's safe for pregnant women to drink alcohol (he said as much as one drink a day), but that no one wants to test it for obvious reasons. I'd love to see the outcome of an experiment seeing how much alcohol a pregnant woman could consume on a daily basi... | [
"If you could conduct any experiment without any ",
", ",
", financial, or ",
" restrictions,"
] | [
"I'd take everyone who's deemed for capital punishment and use them to test medicinal therapies which hold great promise but are not tested ever because they're simply too risky to test on even a single human. 99% likelihood it won't even be painful, it will have an extremely good chance of starting to cure huge nu... |
[
"Why aren't there any other species of humans?"
] | [
false
] | null | [
"By definition \"",
"human",
"\" is the species ",
". Now if the question is rephrased to \"Why aren't there any other species of the ",
" genus?\" The answer is that, except ",
", other species have gone extinct.",
"Based on fossil records, we know the existence of those ",
"extinct species",
".",... | [
"Good question. My Internet connection is acting up, so I will have to rely on my shoddy memory. ",
"In terms of Neanderthals, one hypothesis suggests that Neanderthals are more adapted to the cold ice age climate, which we're not. As the ice age pass, we were more able to compete in those territories. Large scal... | [
"Neanderthals survived alongside (but separate from) humans until quite recently, 30,000 BC or so."
] |
[
"Does evolution occur on a species-wide basis, or is there always an \"Adam and Eve\" of every new species?"
] | [
false
] | Put it this way. When a new species is formed, are there only 2 member of this species, and those members have to build it from the ground up, or does the evolution occur simultaneously? By simultaneously, I mean on a grand time scale, but with each member of the former species evolving at the same rate to create the n... | [
"Evolution is predominantly a species-wide phenomenon, as it involves the spreading of alleles (new traits) throughout a population until it has changed significantly from the source population. ",
"One of the better analogies I've heard is to think of evolution like the transition from one colour to another, s... | [
"It's called the Founder Effect in genetics (you can google that for various examples). It happens when small numbers of individuals are isolated from the main body of an original species. Evolution may happen \"quickly\" as inbreeding magnifies changes from the original population. In particular, it shows up in... | [
"If a species where all but the specific mutation were wiped out in an extremely short time span, it probably has an Adam and Eve.",
"Example: ",
"Silent Crickets in Hawaii",
" - if every chirping cricket disappears in the next couple of years, there would've been an source insect (in this case, two separate ... |
[
"Do girls mature faster than boys?"
] | [
false
] | [deleted] | [
"For clarification, what do you mean by mature?"
] | [
"Here's a few:\n",
"Trajectories of adolescent emotional and cognitive development: effects of sex and risk for drug use",
"Development of Set-Shifting Ability from Late Childhood Through Early Adulthood",
"Potential differences in spelling & writing",
"Boys and Elementary School",
"Gender Achievement Gap... | [
"Let me also qualify that these differences are seen in some studies and not in others, depending upon the measures used. They're also 'on average', not 'all boys' versus 'all girls'. Many boys will outperform girls in language, and girls in math. A lot of the research now looks more at self esteem and self efficac... |
[
"Holographic principle: Since there is a limit to the amount of information that a volume can contain, how does nature prevent me from adding more?"
] | [
false
] | A very big volume has a relatively small surface, therefore I would expect it to reach its maximum amount of content without reaching a high mater/energy density. That density would be too low for the content to form a black hole. Black holes react to more information by expanding; but what would happen to my hypothe... | [
"An object that has this limiting amount of information is a black hole, so if you add anything to it, you will wind up causing the black hole to grow in size."
] | [
"Does that mean that there is no volume so large that it can reach its information limit and still have, say, only one particle per cubic meter?"
] | [
"The mass density of a black hole is inversely proportional to its mass squared; see ",
"here",
".",
"Get a black hole with a trillion solar masses, and its mass density will be quite small."
] |
[
"I've heard that red light is the best for seeing in the dark, is that true? And if so, why?"
] | [
false
] | Also, would that be why red light is a common colour for emergency lighting? | [
"That's not why red lights are used in the dark. Red light doesn't cause night blindness in people like other colors. You can work in red light and then go outside in the dark and be able to see quite well. "
] | [
"Biological night vision\nFor more details on this topic, see Adaptation (eye).",
"In biological night vision, molecules of rhodopsin in the rods of the eye undergo a change in shape as they absorb light. Rhodopsin is the chemical that allows night-vision, and is extremely sensitive to light. Exposed to a spectru... | [
"Now that you've answered the question I thought I'd throw in a bit of fun knowledge. You have special cells in your eyes that sense light and mediate the circadian rhythm, these prg cells only detect light of the blue part of the visible light spectrum (slight shoulder in UVA), so when you see blue light signals g... |
[
"Is there a possible orbit around the Sun with a period of 1,200 years?"
] | [
false
] | Preferably a very eccentric orbit akin to a comet. | [
"Sure. Such an orbit would have a semi-major axis of 112 AU if my math is right. In order to be a very eccentric orbit the aphelion should be a lot higher, but it's ok, the Sun's sphere of gravitational influence extends so far that there's room for much higher orbits than the one you're asking."
] | [
"You should be careful with that. The sun has a very large hill sphere considering its current proximity to other stars, but in the past it has had quite a few close passes that could destabilize orbits."
] | [
"Have we ",
" these stars, specifically, or just deduced that close passes must have happened, based on orbital forensics in the solar system?"
] |
[
"Does a solar eclipse happen everyday somewhere on the planet?"
] | [
false
] | Same with lunar eclipses | [
"No. For a solar eclipse to happen, the moon must be directly between the sun and the earth. For a lunar eclipse to happen, the earth must be directly between the sun and the moon. These alignments are somewhat rare events, happening only a few times a year."
] | [
"I'd just like to clarify: they're very ",
", but not ",
" the same plane."
] | [
"This image should help you understand it\n",
"http://ottawa-rasc.ca/wiki/images/thumb/f/f1/Hamner_Articles_Moon_orbital_mechanics16.jpg/450px-Hamner_Articles_Moon_orbital_mechanics16.jpg",
"The short version is the Moon goes around Earth on a different plane that the Earth goes around the Sun. So it's not very... |
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