title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"How can a super massive black hole have a average density below that of water?"
] | [
false
] | Is says , that: It goes on to explain why that is, but I fail to understand the explanation given. Could some of you wiser guys explain it to me...maybe not like I'm five, but kinda... Thx. | [
"Because it is very dense in a tiny area, but its effective size is gigantic. So a really small bit of it is extremely dense and the rest of it consists of nothing at all.",
"EDIT: the rest of that paragraph goes on to say that a small increase in mass causes a large increase in the black hole's effective volume.... | [
"The size of a black hole isn't super well defined, but a classical way to look at it is like a uniformly dense sphere whose radius is the Schwartzschild radius. Supermassive black holes have hundreds of million times the mass of the sun and a radius on the order of light-hours. Doing the math does indeed yield a d... | [
"The Schwarzschild radius is proportional to the mass m of the black hole. If one black hole is twice as massive as another, it's Schwarzschild radius will be twice as large.",
"However, when we calculate density, we divide the mass by the total ",
". Volume is proportional to r",
" . So, m is proportional to... |
[
"How have the nutritional value of crops such a wheat changed over the last 1000 years and why?"
] | [
false
] | null | [
"This is nearly impossible to determine considering the chemical makeup of our foods hasn't been studied with modern peculiarity for very long. The history of enrichment and GMO sourcing would be a good start and you can almost rest assured that fortified foods are fortified for a reason. Unless there is a reposi... | [
"We're still deep in the gluten scare sadly. I remember this but am not able to source it right now, care to do the leg work for me?"
] | [
"No one really knows. Plants haven't been bred for nutrition until very recently. You have to remember that nutrition as we know it is a very modern concept. Vitamins have only been ",
"discovered in the past one hundred years or so",
". ",
"People did figure out that eating certain things could help with cer... |
[
"Has anyone tested to see if Protons, Neutrons or Electrons (or whatever else) is responsible for gravity?"
] | [
false
] | null | [
"Take a google at \"gravitons\""
] | [
"So. First, if there is such a thing as gravitons, wouldn't it be valuable to find out if it's part of the neutron or proton?",
"Second, I don't buy the gravity is a \"force\" like the other four forces. The other forces decay over time, gravity does not. It remains the same regardless of the age of the particle ... | [
"A graviton is a theoretical fundamental particle -- just like a photon isn't part of a proton, neither is a graviton. Take another look at the wiki. I also recommend taking a look at the FAQ here and searching ",
"/r/askscience",
" for gravity - there are many of descriptions that you can find that may be info... |
[
"Any hope for commercial nuclear fusion of heavier elements?"
] | [
false
] | So most efforts are focused on hydrogen fusion (deuterium+tritium) if I understand correctly. What makes us not even consider Carbon+Carbon fusion for example? Is there any chance we might better control that process ? | [
"Carbon nuclei have a +6 positive charge.",
"Pushing two +6s together is much harder than pushing two +1s together. The +1s are even easier if they're a bit chonky, so D-T or D-D (deuterium and tritium). These +1s are still right at the very edge of our technology, though.",
"This difficulty is known as the Cou... | [
"Muon-catalyzed fusion isn't currently viable because you have to put more energy into creating the muons than you get from the fusion reactions that occur before the muons decay. And even if you're using muons, the coulomb barrier is lower for lower-Z elements."
] | [
"The reactions rate for fusion of two isotopes is proportional to the reaction's cross section.",
"You can see common fusion reactions cross sections plotted ",
"here",
".",
"Essentially, anything not on this plot is not considered viable as the reaction rates (cross section) is simply too low. And even mor... |
[
"Why do so many prescription meds have a side effect of \"suicidal thoughts\"?"
] | [
false
] | null | [
"It's becoming more common knowledge among psychiatric circles that dopamine's role in depression may have less to do with mood regulation, and more to do with motivation, as discussed ",
"here",
". ",
"Studies with rats",
" indicate that varying levels of dopaminergic action affect reward motivated behavi... | [
"It's becoming more common knowledge among psychiatric circles that dopamine's role in depression may have less to do with mood regulation, and more to do with motivation, as discussed ",
"here",
". ",
"Studies with rats",
" indicate that varying levels of dopaminergic action affect reward motivated behavi... | [
"It's becoming more common knowledge among psychiatric circles that dopamine's role in depression may have less to do with mood regulation, and more to do with motivation, as discussed ",
"here",
". ",
"Studies with rats",
" indicate that varying levels of dopaminergic action affect reward motivated behavi... |
[
"Once land has become a desert (e.g. Sahara Desert or Gobi Desert) is there a way to revert it back to usable land?"
] | [
false
] | So I know due to climate change and other factors our deserts are growing. When I googled this subject I could only find information on stoping the spread of deserts. I could not find any information on if land that was previously desert could be fully reformed and use for something like farming or even if a forest could thrive in that area. | [
"My understanding is that the ability to un-desert an area is dependent on why it’s a desert to begin with. ",
"The Great Plains of North America were called “The Dust Bowl” in the 1930’s because it had become a desert. Changes in agriculture practices have reversed the desertification and the area is now the b... | [
"Ecologically/geographically, deserts are ",
" by precipitation. Less than 250mm in a year, it's a desert. More, and it isn't. Plant life tends to follow precipitation very closely. If there's more rain, you get more grasses and shrubs growing. When you hear talk about desertification and reversing it, peopl... | [
"Hypothetically yes.",
"Realistically not with our current technology.",
"Deserts exist in places where water doesn't reach (commonly).",
"There are a lot of ways this can happen, rain shadows, cold (and thus not able to host moisture) air moving from high altitudes towards the poles, areas where the warm moi... |
[
"Does a magnet stuck to a fridge become less powerful over time? What if I keep taking it off and putting it on the fridge?"
] | [
false
] | Do magnets ever degrade? Edit: If they do degrade then what is happening to make them degrade (at an atomic level). | [
"In short, yes, they'll slowly degrade over time. Very slowly, and for multiple reasons. There are quite a few factors that would control the loss rate of magnetic strength, but essentially the ",
"magnetic domains",
" will slowly become unaligned at an extremely slow rate. Today's \"hard\" permanent magnets lo... | [
"Wait, what?"
] | [
"Wait, what?"
] |
[
"Can a gun put a bullet into orbit on the moon?"
] | [
false
] | I'm just curious, if I shot a gun on the moon could the bullet go into orbit around the moon? Also, if it could, is it possible for the orbit to be so low that there would be cause for concern that the bullet could travel around the moon and hit the person that shot it? (if they dont move) Science needs to answer this so we will be prepared for the future moon war. | [
"Better use a railgun"
] | [
"\"Yes\" to the first question, and \"kind of\" to the second. A bullet will only maintain a circular orbit around the moon if the velocity of the bullet and your height above the center of the moon obey a certain relationship. In reality, the precision with which you would need to know the velocity and height woul... | [
"That's a common misconception. True, there's no oxygen, but what's truly necessary is an oxidizer, not necessarily oxygen. Gunpowder comes with its own oxidizer (Potassium Nitrate, or saltpeter), and therefore a gun could be fired in space..."
] |
[
"How does elevation affect the pressure inside a soccer ball?"
] | [
false
] | A football referee here, needing help understanding a rule concerning a football's pressure. The text states the ball (is) of a pressure equal to 0.6 - 1.1 atmosphere (600 - 1,100g/cm2) at sea level (8.5lbs/sq in - 15.6 lbs/sq in) Basically looking for someone to break down the aforementioned rule into "Lehman terms." Also how does this rule change, - if at all - for someone living at an elevation of 645m? | [
"Do you mean layman's terms?",
"The figure that matters is ",
" air pressure - how much higher is the air pressure inside the football than the air pressure outside, and the gauges used to measure ball pressure should already be measuring that. You should just be able to pump up the ball, and then test it wit... | [
"Yes, layman's terms, thank you. ",
"Just so I really understand, would a completely deflated ball have a atmosphere or PSI of 0? That is, the pressure inside the ball is equal to the pressure outside the ball? "
] | [
"We need to distinguish between absolute pressure (which is the difference relative to vacuum) and relative pressure (the difference relative to the outside of the ball).",
"At 0 PSI relative pressure, the pressure inside and outside the ball are the same. That should happen with a 'flat ball', even one that isn... |
[
"Is it actually possible to reconstruct what a person sees by reading their brain waves?"
] | [
false
] | This sounds really cool, but I am somewhat skeptical. How do brain waves carry enough information as to allow reconstruction of entire images? Do these scientists work in ultra controlled environments where they basically already know certain wave patterns correspond to certain images? Or do they actually manage to this calibre of information from brain waves? I thought a big problem with interfacing our biological brains with digital technology was the fact that information is not necessarily stored in each person's brain in an objective manner, i.e. there is no universal brain pattern for "cat" or "dog". I'm a little confused, anyone care to shed some light on this awesome but skeptical technology? Thanks! | [
"NO!",
"It's hugely misleading. There have done two separate experiments, and are presenting them side-by-side in a very misleading manner.",
"Experiment 1:",
"Show a bunch of people some different videos, 5 different categories and analzye their brain activity. Create a classifier that can predict which vid... | [
"I agree the paper itself is not misleading. Just the video on its own gives the impression that it's converting the brain activity into images, which is not true and is misleading.",
"Science is great, and comes with many caveats, which is described in the papers. But when videos like these are released, and see... | [
"They are describing the principle of operation in the paper:",
"“The 20-dimensional EEG feature vector obtained after dimension reduction stage (see “Feature extraction and classification” section above) is mapped into the latent space of a pre-trained image autoencoder, which is capable of reconstructing natura... |
[
"Getting struck by lightning numerous times."
] | [
false
] | I've heard that when a person (or thing) gets struck by lightning, their chances of getting struck numerous times thereafter increase. Is this true? If so, why? | [
"It is possible that rather than increasing someone's chance of being hit by lightning, the first strike identifies people who are more likely to be in situations where one would be struck by lightning. That is, if we didn't know anything about someone, our expectation that they will be struck by lightning would b... | [
"As far as physics is concerned, there is no reason for their chances to increase of getting struck multiple times. If anything it would decrease because they would take cover during a thunderstorm. One assumes that they would want to avoid getting hit by lightning a second time, as it is quite painful."
] | [
"Super-zap is referring to only the few milliseconds following the first strike. After that, the air would have mixed enough to return to its previous conductivity."
] |
[
"How exactly is memory stored in our brain?"
] | [
false
] | I mean like I know it is stored in specific areas of the brain but at the molecular level,how does it "stay"? | [
"Memories, as far as we know, are not stored on a molecular level. They are stored as patterns in neuron arrangements. Human memory is actually incredibly different from what you're probably used to - computer memory."
] | [
"To put it succinctly, the latest and most supported theory is that your brain stories memories in the connections (called synapses) between your neurons. There's a principle developed by neuroscientist Donald Hebb that goes \"what fires together wires together.\" This means that if two neurons that are connected t... | [
"Thanks to visual representations (we are not aware of), it is stored as individual \"images\", but not what we actually see.",
"\nIt is an overall form of an object, which is very simplified. The weight of a single memory (object/s) is clasified by its value it represents. Values are building rocks of memory, fr... |
[
"Should I still get the COVID vaccine if I’ve already had COVID?"
] | [
false
] | If the purpose of a vaccine is to stimulate antibodies as if you were exposed to the disease that you’re being vaccinated for, then why should people who have already had COVID still get the vaccine? | [
"The CDC has ",
"Frequently Asked Questions about COVID-19 Vaccination",
". They say:",
"Yes, you should be vaccinated regardless of whether you already had COVID-19. That’s because experts do not yet know how long you are protected from getting sick again after recovering from COVID-19. ",
"There's also a ... | [
"Please explain this to me because I don’t understand. Your body doesn’t constantly produce every type of antibody it’s ever made. So why would this vaccine be any different than say a polio vaccine? It’s not like your body has been consistently making polio antibodies since your vaccine, yet we don’t worry about h... | [
"Because you're being lied to. Vaccines produce a response in your body that mimics fighting the real virus. When you have a real virus your body has the same response."
] |
[
"Is it possible that dark matter and dark energy are just misconceptions?"
] | [
false
] | I only have a layman's understanding of cosmology, but this is something I've been wondering about. I've heard that maybe WE THINK that the universe's expansion is accelerating because our local cluster is flowing like a river(dark flow) to some point in space, therefore skews our perceptions of the speed of expansion. As for dark matter, is it possible that our models of gravity just need to be modified? Maybe we don't understand some of our fundamental laws as well as we think? I've been trying to get a primer with wikipedia, but there seems to be glaring holes in our understanding of the universe. EDIT: Stumbled on this very relevant article today: | [
"Dark energy and dark matter are ",
" results. They're called dark because we can't see them directly, we only see hints of them. There is no theory that explains either of these results, so it's clear that we don't understand some of our fundamental laws as well as we think we do. ",
" modification to ",
" p... | [
"As with most really deep questions, the answer is both yes and no. Yes, there could be another theory that isn't Einsteinian general relativity (i.e. that evolves differently on large scales, or something) that doesn't require the dark matter / dark energy tweaks on the cosmological scale. But that theory would ... | [
"Yes, it is possible that our understanding of gravity is wrong. ",
"However, \"maybe there are more neutrino-like particles we haven't discovered, yet\" is a much more reasonable claim than \"I have disproved Relativity\"."
] |
[
"Why does holding something close to my eye put things into focus around its edges?"
] | [
false
] | Sorry, this is hard to explain but if I'm looking at something closely so that it's blurry (particularly under 6" or so) and then put my thumb right in front of my eye, the thing I'm looking at comes into focus around the edges of my thumb. One interest effect is that light appears to "bend" towards my thumb. I'm thinking this might be like the effect that you get when a camera appears to zoom in and out when focusing. For example, if I look at a vertical line on my computer monitor very closely so that it goes out of focus, then put my thumb in front of my eye so that it almost blocks the line, it actually appears to bend the line toward my thumb as it comes into focus. I drew this lame diagram to help explain: | [
"I don't want to answer in reply to brolix, but I am not 100% sure what is happening since I am unable to reproduce the issue you are discussing. I am guessing it might have something to do with something like the ",
"knife-edge effect",
". Optical properties change around edges of things, especially things tha... | [
"You are seeing the effect of ",
"stopping down",
" the biological camera that is your eye. ",
"The eye works by focusing light that enters your iris onto your retina. That is to say, light that leaves a particular place on the object you're observing should all land on the same place on your retina, regard... | [
"This is not true. Gravity is not strong enough on such a small scale to have any such effect."
] |
[
"How can I demonstrate the relationship between the work done on a spring and the change in potential energy stored by the spring?"
] | [
false
] | null | [
"Hi Theuniversal82 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 ... | [
"Physics"
] | [
"Physics"
] |
[
"Physics thought experiment question re: gravity"
] | [
false
] | I have a thought experiment I first made up when I was a teenager, and occasionally returned to, but I realized recently there are one or two things I don't know how to answer for myself. The thought experiment is this: If you imagine a perfectly spherical solid planet, let's assume earth like density, and you remove an arbitrary small "slice" off of one spot on the sphere, let's say 1/100 of the diameter of the sphere in and discard that slice, so you have a sphere with a "perfectly flat" surface in one area, what would you perceive it's gemoetry to be like while standing at the center of that flat surface? Elsewhere on the sphere I think it's clear you'd perceive the landscape to be "flat" all around you as the gravitatonal attraction at all other points would be equal, but at the center of that slice, where it's "actually flat" you'd be closer to the center of the sphere and gravity would be stronger, and the entire slice would be gravitationally attracted to that spot closest to the center right? But what shape would it "feel" like it had, gravitationally? My initial assumption was you'd feel you were at the bottom of a bowl, but on rethinking it recently, I realized it might appear to be the bottom point of a cone, or perhaps a parabola? I've used this to explain to people that it's not poetic language when we say mass warps space, but an actual, possible to experience reality, but I'm uncertain which situation is correct. Also, a friend of mine who's a photographer brought up a related question, how dense would the planet have to be to have a noticeable effect on the path that light takes, and would that slice being removed substantially effect light's curvature near the slice? | [
"Do you mean something like ",
"this?",
"The gravitational potential on the x-axis V(x) = -GM/sqrt(h",
" + x",
" ), where G is the gravitational constant, M the sphere's mass and h the height from the center of mass. If the maximum value of x is 2R/100, h ≈ R. We can then plot the ",
"gravitational potent... | [
"It's worth noting that this is just an approximation, since you're treating the planet as a point mass and just looking at the distance from that point."
] | [
"That is assuming the slice is small compared to the sphere, right?"
] |
[
"What is happening to the air in a Lamina Flow Engine that makes it work?"
] | [
false
] | null | [
"I took thermo in college (shortly after the earth cooled), so I should be able to wrap my head around it."
] | [
"I took thermo in college (shortly after the earth cooled), so I should be able to wrap my head around it."
] | [
"Lamina seems to be a popular mistake for what should be laminar flow. Thanks."
] |
[
"A laser of a few watts can reach the ISS, how many watts are needed to reach the moon?"
] | [
false
] | Also, what kind of math would I need to calculate this? | [
"There was a really nice ",
"thread",
" about this many years ago that answers it better than I could. The answer it seems for a laser is a few megawatts.",
"Note that for radar (so radio waves), the Arecibo Observatory has a peak power output of about 2 megawatts (depends on the frequency band). Radar studie... | [
"How dependent is it upon the capability of the receiver? I ask because IIRC Project Starshot wants to send a signal back to Earth from Alpha Centauri ~4 LY with a 1 W signal (crazy small payload on the order of a few grams). But it was going to have some crazy array back on Earth (the same one that accelerates it ... | [
"I assume you're talking about receiving on the radar side of things since I was mostly talking about transmission? I don't quite understand how they are going to want to do that at the moment. My understanding was that Starshot is not going to do the experiment but rather be the technical feasibility study for see... |
[
"Is electrical reactance strictly an AC power concept?"
] | [
false
] | Is it applicable to a DC power circuit with a step, or sine input? I am interested in a RLC series circuit with DC power, being applied a ramp input specifically. It is on a breadboard. The ramp is varied from 2-3 msec. Do I need to do these type of calcuations: ? | [
"Thanks for the link! Example 2 is basically what I need to do. I am familiar with basic derivative/integral type stuff (16 years old), but have never used fourier series. It seems like I can just replace the interval [-1,1] with my interval t = [0,2.4msec] or use the data points from my DAQ as n = [0, 130]. Wha... | [
"Without worrying about the details of your setup, any periodic function (like your ramp input) can be expressed as a sum of sines and cosines via the fourier series. Just find the fourier coefficients, treat each term as if it was a separate AC input and find the resulting output, and sum the output of each frequ... | [
"How can I express the input in terms of fourier series specifically? I have 2 vectors, time and voltage. It makes a roughly linear ramp from 0-5V, and takes approx 2 msec to reach the full 5V. ",
"Is there someplace online I can read more about what you have mentioned here above?"
] |
[
"Question on how separation of a bound quark generates new quarks, rather than an isolated quark?"
] | [
false
] | It is believed that if one quark was somehow pulled out away from a particle such as a proton, color confinement says the energy of the binding would become so great that it generates a new quark/anti-quark pair -- one to replace the removed one, and one to be bound to the removed quark, thus preventing an isolated quark. My question is this: with all the energy building up as the quark's separation distance increases, how does that energy "know" to produce just the right pair of new particles to allow the removed quark to separate out into a new quark pair? Why doesn't that increasing energy produce other particles along the way, throwing out a lepton pair here, a neutrino there, and so on. Why does it "wait" until the energy is just right, and then produce the exact right colored quark/anti-quark pair to make a new meson or what have you, which can fly off, happily ever after? It seems like in particle accelerator collisions, it's just a randomish spray of particles from the high energy gloop. How does confinement get it exactly right on the first try? | [
"Why doesn't that increasing energy produce other particles along the way, throwing out a lepton pair here, a neutrino there, and so on",
"There is not enough energy to create leptons or neutrinos without also balancing out the quarks. If you want to use the system's potential energy to create particles, you have... | [
"The strong force (color/gluons) only interacts with other quarks. So when two quarks are separated, the \"strong/color\" force is increasing--it is that force/energy the creates the quark/anti-quark pair. Because only quarks carry color charge, only quarks will be produced by the increase in color force.",
"Co... | [
"It's not that the energy ",
" to be spend to bind the isolated quarks, it's just that ",
". You might be thinking that when you pull two quarks apart there's this big pile of energy that you can just use, but that's not how it works. The energy when you pull quarks apart is ",
" energy, so it only makes sens... |
[
"What happens to the space where groundwater is removed?"
] | [
false
] | Does it become an empty void in the earth? If civilization is built on top of the groundwater well, could it collapse as a sinkhole? | [
"Air takes its place when ground water is removed. the supporting earth around the well must be more than strong enough to withstand the weight of anything on top of it. "
] | [
"I think you might be thinking of huge underground caverns where ground water is stored. This does occur sometimes, but most of the ground water you'll come across exists in the porous earth - in between the tightly compacted sand, dirt, and rocks. When it's brought out of the ground, either by wells, geological ph... | [
"Sinkhole"
] |
[
"Does energy cause motion?"
] | [
false
] | null | [
"To cause a motion, you must supply a force to it. Energy, in it's most basic dimensions, is a force x distance. "
] | [
"Momentum is the generator of translation. ",
"changes in momentum are due to force, which can be due to some potential or force mediating particle."
] | [
"The ",
" of energy from one thing to another ",
" cause motion. For example, when two bodies collide, one will transfer kinetic energy to the other, which can cause it to move. But transfer of energy does not ",
" to result in motion. For example, if you run an electric current through a wire, some of the en... |
[
"Do all fundamental quantum field theories have to be gauge theories?"
] | [
false
] | To what extent is gauge symmetry a requirement? Related Question: Do any known ways exist that describe the same physics in QED using some other mathematical apparatus which doesn't have the U(1) gauge group in it? | [
"This is going to get technical, but to add to the other good answers: there is no way to imbed a massless spin-1 particle into a four-vector field without including gauge redundancy. I use the word redundancy rather than symmetry here (see also ",
"/u/squarlox",
"'s response) because it's really forced on you ... | [
"No, but gauge theories are more predictive, and therefore more useful scientifically. U(1) gauge symmetry ",
" electromagnetism. But of course we could have QED without knowing anything about gauge theory. QED happens to possess U(1) symmetry; there is no way around that. "
] | [
"For simplicity let me just work at the classical level.",
"Classically, a symmetry is a mapping that takes one solution of the equations of motion into a new solution. By a solution of the equations of motion, I mean a complete prediction for all the observable quantities at all times.",
"Gauge symmetries are ... |
[
"If electrons act as both particles and waves, what properties in the wave form is oscillating?"
] | [
false
] | Is it the energy, velocity, position, mass, existence? | [
"The waveforms correspond to probability amplitudes. Electrons behave in such a way that, in most situations, their observable properties like position, momentum, and energy are spread out over many possible values. The exception is that immediately after we make a measurement we know exactly what value the elect... | [
"I would say that the waveforms are \"field strength\". The reason why this appears to be related to probability is that an interaction is a probabilistic event, which has higher probability for larger field strengths.",
"The electron is an \"electron field\", which is to say that it is a field that displays cert... | [
"I understand your point, but I'm not so quick to concede ontological primacy to the second quantized (field theoretic) description of quantum phenomena. The electron field is an operator-valued distribution. The terms appearing in the Dirac Lagrangian are creation and annihilation operators, and I would debate t... |
[
"How badly have CFC's destroyed the ozone layer? Is it getting better or worse? What will the effects be?"
] | [
false
] | null | [
"Since the Montreal Protocol, CFCs are no longer in production though it may still be used in limited amounts in old appliances in developing countries. However, it will take time for CFC to disappear from the atmosphere, and it is not certain when the ozone will start recovering.",
"This website",
" has a few ... | [
"This",
" is the key graph I think, and it agrees with what I've seen when environmental physicists give colloquiums. It ",
" the ozone layer is recovering, but it's going pretty slowly."
] | [
"the international reaction to the cfc/ozone problem has been showcased as a success story which gives hope that humanity is able to tackle global environmental problems. ",
"http://www.universetoday.com/27561/ozone-success-story-nasa-video-of-enviro-action-that-worked/"
] |
[
"Is there a meteorite at the bottom of every lunar crater?"
] | [
false
] | null | [
"There may be shards of the original impactor found in and around some craters, but a monolithic çhunk of rock is unlikely.",
"The average lunar impact occurs at approximately 15.5 km/s (vs about 18 km at the top of the atmosphere on Earth). With no atmosphere to decelerate, heat, or shock the object, the object... | [
"To compare energy scales a little: At 15.5 km/s, the specific kinetic energy is ~120 MJ/kg, while vaporising initially cold iron should take somewhere around 10 MJ/kg."
] | [
"Not necessarily. ",
"Meteors are classified into three categories: stony, metal, and stony-metal. Metal being the most sturdy and likely to survive an impact.",
"Besides composition the other large factor is speed, no matter what it’s made out of if it’s going fast enough it WILL blast itself into dust.",
"S... |
[
"Why can't they make pregnancy tests like a blood glucose meter?"
] | [
false
] | Why don't they make pregnancy test that are similar to a blood glucose meter? Doesn't the same hormone exist in the blood. Is it just because ppl don't want to prick themselves? I just thought this would be easier then the pee on a stick. | [
"The hormone indeed is in the blood but a lot of people have a fear of needles, which would make it more difficult for them to obtain a sample, plus there is the process itself which involves a sterilizing swab, some pain, and another swab to stop the bleeding, none of which are required to pee on a stick, so yes t... | [
"Thanks, I was just thinking back to when my wife and I were trying to get pregnant. The difficulty she had with the pee on stick method (the first few times she used it) and the cost of buying it multiple times. "
] | [
"If she doesn't mind sharing, what was the nature of her difficulty? Was it in getting the pee onto the stick, or reading the test?"
] |
[
"Why is a group of clouds often on an equal altitude instead of varying in altitude?"
] | [
false
] | null | [
"This is not a hard fast rule of course, but it is true that in most weather regimes, clouds all seem to \"hang\" around the same height. The key to understanding this is realizing that clouds are not \"objects\" like lakes or mountains or lego bricks; they are just \"blobs\" of air that have cooled to the point wh... | [
"I would say it's unlikely. The heights of the bases of clouds depend primarily on the difference between the dew point and temperature of the initial lifted bubble of air. While there will be increases in average temperature in most places, the moisture will likely also increase, and I would expect these effects w... | [
"Typically, the air temperature is a gradient, falling off with altitude. The base of the clouds begins at an altitude which is a function of the dew point. That's the temperature at which water droplets condense out of the air. That's why the bases are ",
" flat and just about level with each other, minus some c... |
[
"Why does ethanol have a health hazard of 2, while isopropyl has only 1?"
] | [
false
] | I am referring to the NFPA 704 health hazard rating which is a 2 for ethyl alcohol, but for isopropyl alcohol it is a 1 Isopropyl is significantly more toxic than Ethanol upon ingestion, so why is it considered a lower health hazard? Does it have to do with some other exposure, besides ingestion? | [
"The NFPA diamond is generally a quick guide for firefighters to assess the hazards of a substance or area at a glance. It's not the be-all, end-all of toxicological standards. You're right, that the LD50 values of isopropanol make it more toxic than ethanol, even though they're really pretty close. 20-30% diffe... | [
"I'll try to answer, but my English on this matter is not that good, so I'll try my best to make it comprehensible. I'm speaking as a pharmacist.",
"What uberhobo said is correct, but there's a little more. ",
"A fact we need to remember: the ketone generated by the alcohol methabolism/biotranformation will alw... | [
"I can't really make that call. LADH has a high affinity for ethanol over methanol (and most likely isopropanol, too), so it can knock out acetaldehyde at a somewhat faster rate than acetone, which might have some effect. However, I have no idea what other fates the alcohols and their metabolites have in the body... |
[
"Why does infrared radiation make things hotter than visible light?"
] | [
false
] | Basically the title. Also why does this occur despite the fact that visible light caries more energy per photon? | [
"You're absolutely right in that visible photons can heat things up too - the two questions here are (a) how much energy is there in photons of which wavelength (visible or infrared), and (b) how well does the surface getting hit absorb photons of different wavelengths.",
"So let's start with part (a), which for ... | [
"thank you so much"
] | [
"If both are absorbed equally well by the surface, they will heat the surface about the same. But our eyes are very good at picking up visible light-- enough visible light to \"feel warm\" would be very, very bright. On the other hand, we have no good way to tell how \"bright\" infrared radiation is, so we don't ... |
[
"When did we know that birds are descended from dinosaurs?"
] | [
false
] | I remember back in school, some 25 years ago, that I was taught that birds and dinosaurs were related but that there was no real evidence. Did paleontologists (or whoever knows these things) not know back then, or was my teacher's information just outdated? | [
"Almost as soon as the first ",
" was formally described by Richard Owen, other scientists noticed the many similarities between this \"first bird\" and certain dinosaurs. Within 5 years—so, 1868—you had Thomas Huxley loudly banging the \"birds and dinosaurs are related\" drum, as well as Cope and a few others. W... | [
"Continental drift theory was accepted ",
" fast, and surprisingly recently. A number of lines of evidence came together in the mid-1960s...the Alaskan Good Friday earthquake (which my parents both experienced firsthand) providing direct evidence of continental subduction, the ship ",
" taking deep-sea core sam... | [
"The idea was proposed back in the 1860s. It was the 1970s however before it started to become accepted in the scientific community and the evidence from fossils was available to really prove it. It would be the mid 80s before the deal was sealed by cladistics: Gauthier, Jacques. (1986). \"Saurischian monophyly an... |
[
"Does the electronegativity of an element in an acid (fluorine in HF) share any relation to how strong the acid is?"
] | [
false
] | I know that acids basically just have a bunch of naked protons which “steal” the electrons from other substances, but does the electronegativity have anything to do with how strong this reaction is? If not, what does? | [
"Electronegativity is the measure of how strongly an element will pull the electron density off of another atom in a covalent bond. This is not a 1:1 measure of the acidity. ",
"The acidity of a substance doesn't depend on the species with a proton. Chemicals do not give up protons because they want to get rid... | [
"It can etch glass and is very corrosive but it is considered a weak acid. It does not completely disassociate, there is still some HF molecules in aqueous solution, while something like HCl will basically be all H+ and Cl- with no HCl left."
] | [
"Isn't HF an extremely powerful acid?"
] |
[
"What are the consequences of Baby Dynamic Yoga?(Re-Post from /r/videos)"
] | [
false
] | Saw this this morning and thought there has to be some other long term effects that go beyond We've all heard about Shaken Baby Syndrome. What about the strain on their limbs and joints? OP: | [
"i would be surprised to find out that this didn't harm the babies..."
] | [
"i know the removal policy for ask science....but does it apply when something is clearly not science, not medicine, and obviously child abuse",
"on the plus side there's no way baby dynamic yoga can cause brain damage, because there is no chance those children inherited any intellect from their parents"
] | [
"It's strange, yes, but not obviously child abuse. It may do damage; we don't know but clearly the babies are not being harmed outright or on purpose. I do know that they used to say weight training was harmful to children but now we know that it's not. Best to let science come out...Also it would be interesting to... |
[
"Inspired by Interstellar: What happens to the rotation of a large planet orbiting a black hole?"
] | [
false
] | Imagine a roughly spherical planet orbiting a black hole. This planet also rotates around its own axis. What happens if the planet is big enough that the passage of time is significantly different on the near side than the far side? I understand the passage of time on the near side would be relatively slower than on the far side. What happens to the velocity of the planet's sides in the rotation? Are they different? Does the physical shape of the planet warp over time to "correct" for the relativity difference? | [
"The reason for the time dilation that happens isn't directly due to the black hole itself, it is more to do with how fast the planet needs to orbit the black hole to maintain a stable orbit. If the planet is moving too slow it would just get sucked into the black hole. So for a stable orbit near a black hole that... | [
"Doing a quick, back-of-the-envelope estimation with WolframAlpha, I got 0.999999999867c for the planet's effective velocity without gravitational effects using only special relativity, though I feel that general relativity is required in this situation. "
] | [
"Time dilation also happens due to large bodies of mass, does it not?"
] |
[
"Does the expansion of the universe affect the value of the Planck length? How do we know? How can we even know?"
] | [
false
] | While staring at the ceiling above my bed and thinking about the universe (quite literally), I was wondering about the implications of its expansion as best as a layman could. I was particularly concerned with the question whether the expansion of the universe is the consequence of a general expansion of space-time, or if the universe expands within a given space-time. To my layman understanding, this would have a drastical impact on how we can actually measure the universe's expansion, leading to my question if the Planck length remains static during the expansion or if it's somehow directly tied to it, and if we are even capable to measure it under these circumstances and in the light that is probably quite difficult to experimentally prove the value of the Planck length anyway. tl;dr: Is there a predictable effect of the universe's expansion on the value of the Planck length and can we verify this prediction by measurements? Are we even capable to measure it? | [
"No, the Planck length is just a length constructed from physical constants, which are constant. It is smaller than what can be measured. However, from what you're asking it sounds like you have the idea that the universe is fundamentally made of Planck-sized pixels, which isn't the case."
] | [
"Can I ask how you came to that understanding? I'm curious as to how this gets spread."
] | [
"No - the Planck length is defined by the square root of two constants divided by a third constant. L_p = (hbar*G/c",
" )",
" None of those constants are thought to be affected by expansion so therefore the planck length is not either. To put it another way - given the way the planck length is defined - if it c... |
[
"Why do we feel euphoric after we evacuate our bowels?"
] | [
false
] | null | [
"Haha just found this after browsing comment history. Let me take a stab at this. You can thank pressure on your prostate which forms into the g spot in females. "
] | [
"Hmmm . . . do I feel grateful or stalked?",
"Edit: Regardless, thanks for giving an answer."
] | [
"It's ok to feel both. "
] |
[
"Would it be possible for an antenna to emit light in the visible spectrum?"
] | [
false
] | null | [
"Hi Jack_Mackerel 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 f... | [
"Physics"
] | [
"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",
... |
[
"Future Helium Alternatives?"
] | [
false
] | After seeing this reddit post in energy i became curious in possible futures of this technology. But many of us science types are aware that helium is not a renewable resource and is actually on its way to becoming a (kind of) a rare gas. So the question i submit to you askscience is: are there any gasses that we could use in our foreseeable future that is lighter than "air" completely stable yet abundant enough that we could use in an everyday technology? | [
"One of the main uses of Helium is to cool things down to 4K. Hydrogen has a boiling point of 20K and is thus useless as a Helium replacement."
] | [
"Well, if we ever manage to use fusion as a power source, then we would get helium as a byproduct of hydrogen fusion. Using just fusion power, and assuming I did the maths right, we'd need to fuse ~350 tonnes of hydrogen per year (this seems really low, I might have missed something here) to meet our current (2011)... | [
"Laser cooling is for tiny amounts of gases. Say you want to operate the LHC. Then you need super conductors to reach the necessary magnetic field strengths, which means you need to cool down tons of material to 2K. Not doable without Helium.",
"Helium balloons are for children's birthday parties and completely i... |
[
"If we defined the meter as a static portion of the width of the universe (so as one expanded in size, the other did proportionally), about how much would our meter be expanding in, say, an hour?"
] | [
false
] | By “width of the universe”, I’m not talking about the universe, but rather I’m referencing the rate at which space itself seems to be expanding. (Although I would be interested in using the observable universes growth as our constant as well). Perhaps my question doesn’t have enough constraints to be answerable, or perhaps it’s already a well-observed constant? My apologies if it’s easily calculable. I just wouldn’t even know where to go looking for info on this, or how to rigorously describe my question, for that matter. | [
"You've described exactly what we refer to as the \"Hubble constant\", H_0. Typically instead of your \"one meter reference separation\", we are talking about the distance to a (distant) galaxy. And instead of saying \"how much further per hour\" we ask \"how fast does it appear to move away from us\". That's ju... | [
"This is a beautiful response. Thank you! I wish I could give more than one upvote..."
] | [
"I appreciate the positive feedback even more than the upvote! :) Glad it was helpful."
] |
[
"What is the coldest recorded temp in the Arctic or Atlantic oceans?"
] | [
false
] | The salinity of the water would vary, and effect the temp, but how low can it get in a super dense volume of salt water? | [
"There definitely is an absolute answer to this. You need to use calculus regarding the relationship between temperature, maximum (or a more robust calculus to consider optimized if it is not linear enough) salinity, and change of state temperature point.",
"Unfortunately the change of state temperature is still... | [
"I'll merely remark that I've been taught 4C as the most dense oceanic water can get before freezing which it does at -1.9 or so...",
"This is not true. For pure water, the maximum density occurs at 4C but it is not the case for salt water. Water with typical ocean salinity (3.5%) does not have the inflection p... | [
"Just a related tangent:",
"as others mentioned, the freezing point of typical seawater is about -1.9. It varies with exact salinity, of course. You definitely see temperatures this low in the very surface waters of the high latitude oceans, particularly in the winter seasons. You have cold arctic/antarctic air c... |
[
"Are omozigote twins like clones?"
] | [
false
] | Except of DNA mutations, are omozigote twins comparable to clones looking at their DNA? If no, why? Thanks and I'm sorry for my bad english. | [
"Yes, homozygote twins descend from the same sperm and egg which means they will get the exact same DNA replicated to each embryo when the fertilized cell splits into two parts. Except for mutations later during the fetus stage, their genome is exactly alike"
] | [
"The fathers and the uncles genome is exactly identical. Whether it would've been twin 1 or twin 2 being the father, the kid would with high probability look the same being either twin 1's or twin 2's biological offspring. With mother 1, twin 1 and twin 2 could get the same looking kid (depending on which chromosom... | [
"So, if one of the twins has got a child, the kid is \"genetically son\" of both of them, is that right?"
] |
[
"If the four dimensions of space and time are intertwined, why can we not rotate an object into \"time\" the same way we can rotate an object in 3D space?"
] | [
false
] | Forgive me for being naive, but this seems like an intuitive question. | [
"You can “rotate into time”, just change your speed. Mathematically, changing between different reference frames looks like hyperbolic rotations that mix spatial and time coordinates. Using some identities from complex analysis, you can think of hyperbolic rotations as regular rotations, by imaginary angles."
] | [
"Not really, unless you consider a flip to be a rotation. Certainly no continuous rotations exist."
] | [
"Question",
"Is it possible to rotate something of a single dimension? "
] |
[
"Is there a correlation between the complexity of an organism and the genetic diversity of its species?"
] | [
false
] | What sorts of species have very low genetic diversity? High? How do humans compare relative to the rest of life on Earth? | [
"There is no particular reason that genetic diversity and \"complexity\" (which is fairly difficult to define quantitatively) would be correlated. Genetic diversity is dependent on many factors, including:",
"These and other factors that affect genetic diversity can be highly variable from species to species, an... | [
"Genetic bottlenecks can drastically decrease the genetic diversity of a species regardless of the organism’s complexity. I think genetic diversity is really determined by the environment that species is in, which is why you see an increase in biodiversity as you get nearer to the equator. "
] | [
"Great answer, thank you!"
] |
[
"How do radios work? (and other devices controlled by radio waves) How is the sound information encoded onto the wave, and how does the home radio turn the light information put back in the speakers?"
] | [
false
] | I understand that radios (like what is in your car) need electrical power (from batteries/wall outlet/car) and get radio waves that are from transmitters. Radio waves are a kind of light wave. However, in my daily experience with light, information is not encoded onto the light wave other than color (and maybe amplitude.( This is another thing that is unclear to me. What is the amplitude of a light wave? Is it even meaningful to say "the amplitude of a light wave"?) How is the sound information encoded onto the wave, and how does the home radio turn the light information put back in the speakers? Thanks so much! | [
"There are different methods of encoding, for instance ",
"Amplitude Modulation (AM)",
" encodes the signal in the amplitude, ",
"Frequency Modulation (FM)",
" in the frequency, ",
"Phase Modulation (PM)",
" in the phase, and so on. I am going to dive into a bit more detail, but I want you to know that ... | [
"Thank you! In, say, a phase-modulated wave, how does the information of phase shifts(which is only one variable, f(t) get turned into the sound information (which has many variables—frequency, amplitude, for multiple waves)"
] | [
"Directly, ",
" is what your speakers will reproduce. ",
"What you are calling variables, are better thought of as the terminology used to describe signals. That is they can be used to help describe aspects of the signal ",
" or the transmitted signal ",
", but ",
" is the signal your speakers reproduce a... |
[
"Can I overcharge an electronic?"
] | [
false
] | Is it possible if I leave my phone or something with a rechargeable battery on the charger too long for it to be damaged somehow? | [
"This is the case with cheap electronics using batteries other than lithium. All lithium battery chargers are \"smart\" with circuitry to prevent overcharging, as that could result in a fire. ",
"Some cheap electronics that still use the older style NiCd and Nimh battery technology use trickle charging - electric... | [
"Aye, cellphones and other things with recharging circuits generally have stuff in them to stop the charging process once the battery is sufficiently full."
] | [
"As long as you are using a charger designed for the device you are charging you should be fine in most cases. ",
"One exception would be a battery charger for car batteries. Some will turn off automatically when done charging or after a set period of time. Some will not and will destroy the battery if left on fo... |
[
"Last night I dreamed that a nuke went off in the distance and I went and talked to my father before the blast got to our house, what would be the formula for calculating the amount of time you have between seeing a nuke go off and the explosion actually reaching you?"
] | [
false
] | null | [
"If you are in the vaporization region, the formula is t=0 seconds. Seeing light is being burned by the light.",
"If you are going to be hit by the acoustic shockwave, then it will be slightly higher. The shock wave would be an acoustic event. I don't have the best knowledge of acoustics, so I would put my first ... | [
"Not exactly, the shockwave loses velocity extremely quickly. If you want an exact formula:",
"http://www.saecanet.com/astronomy/515-calculation-of-blast-waveradius-and-expanding-velocity.html",
"If you don't want to do that math, then just know that the speed of that wave is dependent on the air, time, and the... | [
"Thanks for the answer!\nI don't know what the range of the acoustic shockwave is, but assuming a mile is inside that range - If I'm a mile away by your calculation I would have about 5 seconds, right?",
"(1 mile) / (710 mph) = 5.07042254 seconds"
] |
[
"How much data is transferred across the internet in one second?"
] | [
false
] | Hello, I'm curious as to how much data (in bytes) is transferred across the internet in one second. For the purposes of the question, transfer across the internet is assumed to be anything that gets transferred through your ISP from a computer or other such device. So, a local network file transfer doesn't count, nor does the universities local mail server. Thank you very much. | [
"This is old data, but 494 exabytes of data was transferred across the globe on June 15, 2009 according to the Digital Britain Report. ",
"That's 6.6 × 10",
" bytes, or 5 995 terabytes per second (Using binary prefixes rather than SI). Likely it's many times larger today."
] | [
"Note the word \"also\". ;)"
] | [
"What is the law that states computer growth is exponential?",
"Applying that, imagine what the data transfer is today. :D"
] |
[
"What was the daily temperature during the “little ice age”?"
] | [
false
] | During the little ice age, the climate was from 0.5 to 2.0 C colder than today. What does that mean in daily high and low temps for summer and winter? This has been surprisingly hard to find. | [
"It might be hard to find because it's too vague a question, as the answer will depend a lot on the location of interest. For one example, there are a few long temperature records from central England, so for this location at least, you question is answerable, e.g. ",
"Parker et al 1992",
". Page 20 of that art... | [
"Earth Sciences"
] | [
"Earth Sciences"
] |
[
"How much of a problem is space debris for the ISS and shuttles?"
] | [
false
] | [deleted] | [
"There are no more space shuttles, but for the ISS and other spacecraft, the answer is space debris is a potential hazard, but fairly easily managed. NASA and the DoD track tens of thousands of pieces of debris to ensure there are no collisions. The orbits of the ISS or any other spacecraft can be adjusted to avoid... | [
"Hi, I'm on the ISS MMOD team.",
"For the ISS orbit, the debris flux is fairly low compared to higher altitude orbits. However the ISS is still costantly bombarded with meteoroids and orbital debris, however most of it is small enough that it does not result it significant damage but it will still cause surface d... | [
"what is the protection against a few millimeter debris strike against an astronaut during a spacewalk? Relatively low risk, or the suit can take the hit, or something else?"
] |
[
"How would one go about visualising an imaginary number?"
] | [
false
] | And do transformations of real numbers apply to imaginary numbers in the same way? | [
"You can picture a two dimensional axis: the x axis represents the real numbers and the y axis represents imaginary numbers. Any point that's not on either axis is a complex number."
] | [
"A two dimensional vector."
] | [
"If you want to go further, look up Quaternions. However, they have to specifically constructed. All operations on real or complex numbers will give you a real or complex number."
] |
[
"What is the difference between animals that are considered white meat and red meat?"
] | [
false
] | I am wondering if there is some biological difference between mammals such as pigs and cows that causes their meat to be classified in this way. | [
"\"Why is pork a \"red\" meat?\nOxygen is delivered to muscles by the red cells in the blood. One of the proteins in meat, myoglobin, holds the oxygen in the muscle. The amount of myoglobin in animal muscles determines the color of meat. Pork is classified a \"red\" meat because it contains more myoglobin than chic... | [
"\"Pigs are lazy animal; they are not as active as cows\" Source?",
"Cows are grazers, while pigs are foragers. Also, anyone who has observed domestic cows and pigs can tell you the pigs move more."
] | [
"\"Pigs are lazy animal; they are not as active as cows\" Source?",
"Cows are grazers, while pigs are foragers. Also, anyone who has observed domestic cows and pigs can tell you the pigs move more."
] |
[
"Black holes; are they really a \"hole\", or are they a solid, spherical mass?"
] | [
false
] | null | [
"They are a solid, spherical mass. Okay so you throw an apple up and it comes back down due to gravity right? But on the moon, there's less gravity because the moon is smaller. You throw an apple up and it goes much higher and comes down much slower.",
"So if instead you landed on a planet twice the mass of earth... | [
"Actually, in any scenario the apple would get back to your hand going the exact same speed as you threw it up with, or even less if you consider air resistance. The gravity will only change the time scale over which this happens e.g. large gravity->apple goes up and down quickly compared to the same initial veloci... | [
"I assure you I understand both your points, but the OP was asking if black holes were literal holes, I tried to use a more simplistic explanation that didn't delve into the mathematic elements of it"
] |
[
"What happens at the atomic level when you cut something into two? Why aren't you able to put them back together?"
] | [
false
] | null | [
"Let's say you cut a piece of stainless steel in half with a magic knife that maintains the structure of all the atoms but just separates them. That would be an ideal cut; just breaking the chemical bonds that hold the material together. Now, what if you tried to put it back together a few minutes later? Somewha... | [
"This is really, really cool."
] | [
"Ok, that makes sense. Let me try and repeat, so I understand:",
"The reason we cannot put two halves of a freshly cut block of material (you used stainless steel, but I'm assuming the principle remains true for ",
" most substances) is that once separated, the atoms on either end react with oxygen, oxidizing t... |
[
"When Baumgartner broke speed of sound in free fall, did he experience complete silence?"
] | [
false
] | null | [
"As far as I'm aware, he would continue to hear air hitting his suit. ",
"Let's say that you rode on the Concorde from New York to Paris. At some point over the atlantic, you would break the sound barrier and start travelling faster than the speed of sound. ",
"However, the cabin would not suddenly go quiet ... | [
"he would hear sounds from in front of him, even from outside his suit."
] | [
"he would hear sounds from in front of him, even from outside his suit."
] |
[
"What makes certain genes more dominate than others?"
] | [
false
] | Just a general question. For example. If a Caucasian person has a child with a Japanese person.. The Japanese genes will be more dominate in the child. Of course it happens with many more ethnicities than those two but just used them as a general example. Can anyone explain this to me? | [
"I'm not a molecular biologist, but there's a problem inherent in your explanation. What happens in homozygous recessives? How do you avoid silencing yourself to the point of having no phenotype at all. Do you have to inherent methylator with the dominant trait? Could it also be possible that gene products may inhi... | [
"I'm almost completely certain your \"example\" is completely fabricated, based on confirmation bias.",
"Dominance (like all parts of genetics) is extremely complex, so simplification may be in order. Dominance is, in short, caused by the fact that when alleles are expressed, multiple proteins or enzymes may atte... | [
"I don't think 'Japanese genes' are necessarily 'dominant' over 'Caucasian genes'. Rather, the dominance of different alleles of a gene is largely determined by the nature of the protein that it encodes. For example, defects in structural proteins generally manifest as dominant traits because being heterozygous r... |
[
"Why are chimeric plants (and some animals such as lobsters), often split straight down the middle?"
] | [
false
] | Examples: | [
"Chimerism results from events like spontaneous mutation, transposon action, or mitotic recombination in only some cells of an organism. If it happens very early on--say, at the two-cell stage--then the result is two cells, one with the genotype of the parent and one with the mutation. If it's a visible mutation,... | [
"Would any differences arise in organisms which undergo spiral cleavage?",
"EDIT: Finally got to a computer, looking at the photos seem to indicate that the same thing happens as with everything else."
] | [
"I really don't know, actually. It's an interesting question, but development's nearly as far from my area of expertise as you can get."
] |
[
"Does a second dose of vaccine restart immunity or does it carry the 80% protection from the first dose through the whole process?"
] | [
false
] | Will you still be 80% protected from the first dose immediately, or a day or two, after receiving the second, or are you back to no immunity until the second dose is fully active? | [
"The immunity generated from the first dose doesn’t magically go away. The second dose is there to build on the work of the first dose and remind your immune system what does the enemy look like. In more technical terms, the first dose generates IgM antibodies that serve as an immediate response to the foreign prot... | [
"The second dose usually has more side effects because you already have an immune system ready to attack what is being injected into your body. It’s a good thing. In fact, I’ve read that one of the reasons that people have reactions during the first dose is because they had COVID and didn’t know about it (asymptoma... | [
"Ok, I just wasn't sure that with the second dose if maybe your immune system was too busy figuring out the new dose to fend off outside infection, since the second dose typically has more side effects",
"Thank you for your response"
] |
[
"Difference in color of Zink/Tin?"
] | [
false
] | (I'm not aware of if I'm in the correct subreddit) Let's get this straight; How do i determinate, by just looking at it, if a chunk of metal is made of zink or tin? Or if i have one bit of tin and one bit of zink next to each other? | [
"Just eyeballing it? I doubt you could do it reliably. You could measure their densities most easily. Beyond that, you'd need the power of qualitative analysis to figure it out."
] | [
"That's very often a thin layer of oxide that you're looking at instead of the metal itself. It might be enough to distinguish the two metals, but I don't think it would work on a pair of freshly polished metal surfaces."
] | [
"eyeballing it from wiki pictures (obviously not accurate) seem to have zinc with a blue-er tinge than tin. ",
"Is there any resource that plots some kind of reflectivity spectrum for various metals/materials? Compare the relative reflectivity of blue to red for zinc and for tin, maybe find tin a \"flatter\" dist... |
[
"How do cities of various sizes change weather patterns?"
] | [
false
] | This may just be a meteorological coincidence, but I noticed the storm line as it was approaching the Dallas metroplex seemed to be in a nice crescent curve as it passed through Texas, until about 30 minutes ago when it started to pass by Fort Worth. Piqued my curiosity, do cities have an impact on weather patterns like this? Or is it just a coincidence? | [
"There was a paper published just a few months ago on this: ",
"Energy consumption and the unexplained winter warming over northern Asia and North America",
". They found waste heat from cities can alter and widen the jet stream, effecting weather up to a 1000 miles downstream."
] | [
"Large cities can definitely affect weather patterns. For one, skyscrapers and other large buildings cause turbulence in the lower layer of air movement (wind), which will increase the buffeting effects of wind. ",
"Second, the air above a city can be significantly warming than if the urban area was not present. ... | [
"A sudden increase in surface roughness is going to force convergence at the surface, which will definitely have an effect when the atmosphere is unstable enough to sustain convective storms. The same thing happens along coastlines, when the wind passes from a smooth sea/lake surface onto the land."
] |
[
"will a nuclear bomb produced 20 or 30 years ago still detonate as it is planned?"
] | [
false
] | i always wondered what would happen if you deploy a nuclear bomb produced long time ago. obviously nobody has ever tried this so it all very theoretical. to get full force all components have to be very precisely calibrated but nuclear materials decay with time. is there a chance that it will go off but just create a lot of pollution without proper detonation? are the active materials supposed to be renewed once in a while? if so is anybody is doing this in reality? | [
"In the US, ",
"stockpile stewardship",
" is one of the big missions of the DOE, and it about exactly this. Making sure that the aging stockpile is still ready to be used at any time, even though since the 1990's we no longer perform \"integrated testing\" of nuclear weapons."
] | [
"you absolutely need to some kind of live testing to be sure...",
"Well the DOE disagrees. We can do very sophisticated calculations, and various kinds of tests of the subsystems without producing a real nuclear yield. This is what the US is currently doing to maintain its stockpile. And I don't think any nation ... | [
"I think the Russians are absolutely doing it too. There is even evidence that they have done some underground testing recently, which the US doesn't do anymore."
] |
[
"Does it matter from which plant pollen comes from when creating a seed?"
] | [
false
] | Will pollen from a rose pollinate a lily just the same as any other plant? | [
"Pollen is what's called a 'gametophyte' and is one of the reproductive cells from a plant and as such holds 1/2 of the genetic material needed to form a viable seed. it forms on the stamen of the flower, the (usually) longer interior stalk nestled in the center of the petals. reproduction in plants is genetically ... | [
"Some are so different that they don't fit before pollination and other are genetically instable after pollination. There is no simple answer. "
] | [
"The pollen must work its way down through the pistil into the ovary for proper fertilization. Fertilization doesn't happen immediately upon contact between pollen and pistil. (I don't know what causes the pistil to accept the pollen, it could be surface receptors and such, maybe someone can clarify my schooling is... |
[
"What type of fundamental force would fire and chemical reactions fall under?"
] | [
false
] | null | [
"Basically all of chemistry is electromagnetic."
] | [
"Thanks man! So 2 follow up questions"
] | [
"It depends on how you heat them up, but basically anything you can do to them while still remaining within the realm of chemistry (as opposed to accelerating them to very high energies and colliding them) will ultimately be the result of electromagnetic forces."
] |
[
"What Is This \"Imaginary\" Mass That Is Created by the Higgs Mechanism? Layman Explanation, If Possible?"
] | [
false
] | null | [
"Can you give some more context for where you saw imaginary mass?"
] | [
"Actually don't remember where I found that part. I just don't see how that mass is created."
] | [
"Well there aren’t any physical particles with imaginary masses. The Higgs field gives mass to particles which interact with it, because it has a nonzero vacuum expectation value. That means that the field is not zero even in an empty space. And anything which interacts with that field has some energy associated wi... |
[
"How does the curved shape of a chopper's blade cause an increase in the speed of air passing above the blade than below it?"
] | [
false
] | About airfoils, it's said that a wing's top is curved and its bottom is flat. . This relates to Bernoulli's Principle. I have never been able to understand this fact about airfoils, or to be more precise, I could never...errr... visualize it? How does an increase in surface area (i.e. curved rotor blades) cause an increase in speed of air passing over it? I understand that this speed increase causes a pressure decrease due to Bernoulli's principle, but why exactly does the speed increase? | [
"Airflow and the way a wing works is actually a complicated and misunderstood topic.",
"https://phys.org/news/2012-01-wings.html",
" ",
"If you needed a curved airfoil, then a flat wing could not create lift. Many model aircraft that fly fine with flat wings would like to prove you wrong. Less efficient, but ... | [
"Agreed. In addition, if curvature of an airfoil were the only factor in creating lift, aircraft couldn't fly inverted (that is, upside down). My answer addresses the OC's question, but @joefarmer13 makes an important point.",
"The primary value of the curvature in an airfoil is two-fold: 1) a curved airfoil will... | [
"This is indeed the standard argument that you hear repeated a lot, but it's worth emphasizing that it's completely wrong! In an actual wing there is sheer, and the sheets don't unite at the same position (the air above the wing is faster than the one below). E.g. ",
"here",
" is a video from a wind tunnel whic... |
[
"Would the backscatter scanners at air ports detect objects concealed under rolls of fat?"
] | [
false
] | null | [
"No, they don't see anything behind or under skin."
] | [
"It cannot pick up anything, of any kind, inside your body. The X-rays bounce off of your skin, which is what draws the image. Anything beneath or behind anything denser than skin won't show.",
"Yes, you could hide things in your rectum and they would not show up.",
"A standard metal detector would be much be... | [
"It cannot pick up anything, of any kind, inside your body. The X-rays bounce off of your skin, which is what draws the image. Anything beneath or behind anything denser than skin won't show.",
"Yes, you could hide things in your rectum and they would not show up.",
"A standard metal detector would be much be... |
[
"Is there a difference in efficiency of solar power in space compared to on Earth?"
] | [
false
] | I was browsing through the astronaut AMA when I thought about the solar panels that they have on space stations. So I wondered if, considering the lack of a huge magnetic field and atmosphere/ozone, more solar power can be gained from the sun when in space rather than on Earth. | [
"Efficiency doesn't necessarily increase for more incident light (less atmospheric absorption) since its in the denominator (i.e. power producer per power of light incident). Power output definitely does however. You can get an idea of how much a difference the atmosphere makes ",
"here",
". Solar panels tend t... | [
"Very nice response. Almost everything is right on and explained well, however the efficiency goes up in general as light intensity increases. This can be found by looking up concentrator PV or light intensity variation efficiency.",
"While a first approximation would say that just by increasing the amount of lig... | [
"You are indeed correct for traditional architectures. I was thinking of the type of PV I used to work with where the opposite is true, and I should have done some more poking around. Regardless, the increase seems to be fairly ",
"small",
" for the amount of light intensity change we are talking about. "
] |
[
"Why do humans and other animals have multiple eye color possibilities?"
] | [
false
] | Is there a reason for this evolutionary or is it just a mutation that never had negative effects so it stayed? | [
"It's a mutation with no real drawbacks in terms of survival, so it has thrived amongst the \"normies\" within each respective species."
] | [
"I am only in first year optometry school:",
"Our eye color depends on the amount of melanin produced by melanocytes in our iris. The more the melanocytes are stimulated to produce melanin the darker our eye color. Thus, people with lighter eye colors have less melanin producing melanocytes than people with darke... | [
"The iris has two layers, the stroma and the epithelium. In a blue-eyed individual, the stroma (the top layer) is weakly pigmented, and the epithelium has very strong pigmentation. Longer wavelengths of light travel through the stroma and are absorbed in the dark epithelium. Shorter wavelengths of light undergo Ral... |
[
"What was the big deal with the Y2K bug?"
] | [
false
] | I remember back in the end of 1999, people were going crazy about the Y2K bug. They said that once the clocks hit midnight on new years eve, all the computer systems worldwide would crash because the year category would go from 99 to 00. My question is why would this cause such a scare? So some date categories on some computer files would be inaccurate. Why was this that big of a deal? | [
"Imagine banks flipping their dates from 1999 to 1900, or going from 1999 to 19100. You'd have interest rate calculations and such operating on wildly inaccurate dates.",
"Any time-critical application could be compromised. Nobody cared about personal files."
] | [
"Well depending on the system, different things could happen.",
"Some would be lucky that the date would just be wrong.",
"\nWhich has its own problems considering how many businesses use computers for record keeping.",
"Others wouldn't be so lucky.",
"\nThe main problem would be a GPF because the system is... | [
"As tempting as it is to say that it was all hype, the truth is that it was a foreseeable problem, and there were many working hours spent working on the solution. There were no worldwide problems because companies did prepare for it. "
] |
[
"What determines the color of the Aurora Borealis?"
] | [
false
] | I normally see green, but I hear that different colours can occur. | [
"I found the answer here: ",
"http://odin.gi.alaska.edu/FAQ/#color",
"It seems the colour's based on height of the aurora (different atmosphere composition), and also the energy of the excitation. It's not as simple as I thought it would be."
] | [
"Green is generated by molecular oxygen, while brownish-red by atomic oxygen and blue+red by molecular nitrogen, apparently."
] | [
"A bunch of the Common gases such as Oxygen, Nitrogen (plus many others) are commonly found as diatomic molescules. Oxygen that we breath in is O2 (i.e. two oxygens bound together)",
"http://en.wikipedia.org/wiki/Diatomic_molecule"
] |
[
"How do remote control cheating dice work?"
] | [
false
] | null | [
"In this particular video, the bottom plate is important. It will most likely contain an electromagnet that is powered by the device standing to the side. The dice have a piece of metal embedded on one side. The remote controls the electromagnet, so when the remote is used the side of the dice with the metal is att... | [
"That would be logical, but the die is clear, and in some close up shots I've seen of the clear variants, there doesn't appear to be any meal or magnets inside. Additionally, most advertise that you can smash them to bits and not find the mechanism"
] | [
"I suppose that the material used to make the markings on the faces of the die could be metallic. The 6-face will have more of it than the other faces, so it'll interact with the magnet the most."
] |
[
"Does mankind now possess the ability to roughly predict what evolutionary traits humans will take on in the future?"
] | [
false
] | null | [
"It's not possible to predict this, since we don't know what environmental factors humans will face in the future.",
"We can say things like, ",
" - but we don't know for sure whether it's going to get colder, warmer, or what.",
"(Repeat for many, many other factors.) "
] | [
"Evolution takes such a long time, technology advances are taking place at the equivalent of a blink of an eye. There is no chance that natural evolution will take place for our reliance on technology unless there is a very very long term stagnation.",
"Secondly the natural selection part of evolution doesn't rea... | [
"Evolution takes such a long time, technology advances are taking place at the equivalent of a blink of an eye. There is no chance that natural evolution will take place for our reliance on technology unless there is a very very long term stagnation.",
"Secondly the natural selection part of evolution doesn't rea... |
[
"Why does a black hole gets less denser when you add mass to it? Shouldn't gravity make it even more dense?"
] | [
false
] | null | [
"We don't really know what happens when mass goes beyond the Swarzschild radius. Mathematically, at the center of a black hole is a singularity, which is a point with infinite density, but that seems to be unphysical. Since we don't know how matter is distributed in a black hole, we can't really make a definitive s... | [
"The density of a black hole isn't the most meaningful parameter, but here we'll define it as the ratio of the mass of the black hole to the volume enclose within the Schwarzschild radius. The radius here is proportional to the mass, but the volume is proportional to the cube of the radius. If the black hole gets t... | [
"If we know that within the schwarzschild radius, is contained everything absorbed by the black hole that hasn't been paid back to hawking radiation, couldn't we start to make assumptions based on speculation and see what might fit the data?",
"There is no data, we have no idea what the mass inside a black hole a... |
[
"Are there any animals besides humans that cook/prepare food in anyway? (x-post from r/AskReddit)"
] | [
false
] | null | [
"There are no other animals that are known to cook food to the same extent or quality as us. Only one captive bonobo, ",
"Kanzi",
" taught himself how to start a fire and cook food. Other then that there are no living examples, besides us who are able to accomplish such a task. However, fire and cooked food pre... | [
"Might not be what you had in mind but a good example would be Spiders and Snakes using venom to aid in the digestive process. "
] | [
"Certain tribes of japanese snow monkeys wash their food in the sea to add a salty taste scientist presume.",
"It started as a habit of a single female but spread over the whole tribe quite quickly. This is seen as a rare occurance of \"cultural\" behaviour in other species than humans."
] |
[
"Why are ungulates classified by toe parity?"
] | [
false
] | I just discovered on Wikipedia that, contrary to my intuition, deer, moose, giraffes, camels, and sheep are all only very distantly related to horses. The former are all Artiodactyla while horses are Perissodactyla. This is rather strange to me because they look very similar and certainly more similar than a moose and an orca do (apparently orcas are also Artiodactyla). How is it possible that orcas and moose are more related than horses and moose? Edit: For clarification, I understand how phylogeny works based on shared ancestry, not morphology. What I am more interested in is any more in-depth background on how the decision was made to classify ungulates based on toe parity, and perhaps anything on how exactly orcas fit into this. | [
"It is because we determine things as more closely related if they share a more recent common ancestor. So orcas and moose shared a common ancestor more recently than orca and horse or moose and horse. \nDNA supports Perissodactyla and Artiodactyla (or Cetartiodactyla) as two separate groups. \nWithin mammals, conv... | [
"The ungulates (hoofed mammals) often share a superficial resemblance to one another because they are all loosely related. Before the genetic era taxonomists attempted to classify them based on morphology alone. There was a fair amount of guesswork involved in deciding which morphological features were taxanomicall... | [
"I can expand on this and answer specifically the question in the title. Organisms are classified based on how closely related they are to one another, not based on a single morphological trait, but a morphological trait can be a convenient way to distinguish between two groups. Even when phylogenies are built from... |
[
"Why was increase in biodiversity so slow during much of earth's history?"
] | [
false
] | Diagrams such as this one: shows how global biodiversity has been increasing very fast during the past 150 million years, despite the K–T extinction event. Biodiversity also exploded until the Ordovician–Silurian extinction. Why does increase in biodiversity between mass extinction events appears so slow between the Silurian and Jurassic period? Is it many smaller extinction events, a badly preserved fossil record, fewer continents..? | [
"Punctuated equilibrium, aka 'everything is calm until an asteroid hits'",
"Punctuated equilibrium (also called punctuated equilibria) is a theory in evolutionary biology which proposes that once species appear in the fossil record they will become stable, showing little evolutionary change for most of their geol... | [
"Good question!",
"The first thing to note about that diagram is that 4 of the 5 largest mass extinctions occurred between the Silurian and the Jurassic, with the largest ever extinction event (end-Permian mass extinction) near the point where the derivative changes from negative back to positive (~250Ma). It's i... | [
"That is necessarily an incomplete explanation. The K-T extinction event was neither the only nor the largest mass extinction event during the phanerozoic, and biodiversity already seems to be trending rapidly upwards by the mid-Cretaceous, so the meteorite is surely no the only cause. "
] |
[
"If the universe is infinite, how are we getting recurring comets? \"This comet last passed us 10,000 years ago\" hold up, why wouldnt it just, keep going? I understand its path would get swayed by planitary objects, but to go exactly full 360 over and over, and repeatedly pass us? Confused"
] | [
false
] | null | [
"Almost all of the non-star things we can see from Earth are gravitationally bound to our Sun. The other planets, the asteroids and comets, moons, etc are all part of our solar system, which means they are bound to the Sun. Most of the planets have nearly circular orbits, so they have very repeatable, normal patter... | [
"This is an amazing answer, thank you 👑"
] | [
"To expand further, the individual stars that we can see are generally gravitationally bound to the Milky Way Galaxy. Our sun and other stars are orbiting the galaxy itself (it gets confusing. Stars individually orbit the galaxy, but they, collectively, ",
" the galaxy.)",
"Entire galaxies aren't necessarily ... |
[
"Are modern day lenses for glasses (the kind you wear) still made of actual glass, or are they plastic now? If they’re made of plastic, how can they correct vision as effectively as actual glass lenses?"
] | [
false
] | null | [
"Are modern day lenses for glasses (the kind you wear) still made of actual glass, or are they plastic now?",
"There's a mixture of glass and plastic lenses around. Many have various coatings too, for tinting or scratch resistance.",
"If they’re made of plastic, how can they correct vision as effectively as act... | [
"To add to the other answer. For a good spectacle lens you want a material with:",
"Various plastics meet these requirements quite well, as does glass.",
"Besides material choice it's just a case of making the lens to a high quality. A good pair of glasses will have lenses made to a precise shape and well polis... | [
"There's another \"high-index\" plastic that is used for very high prescriptions, though I don't remember offhand what it's called.",
"Thiourethanes, according to Wikipedia. (I didn't know either, and I wear them!) I hadn't heard that softness was an issue with them. I'd always been told that it was simply becaus... |
[
"What happens physiologically to a crash victim in an airplane crash on impact?"
] | [
false
] | My girlfriend passed away a while ago in one and last night I had a rather violent dream about it. I'm sure (or hope) that victims don't die that way, but now I'm wondering how they DO meet their demise. In my girlfriends case specifically, the pilot overshot the runway, crashing into a valley because there was no runway left. It wasn't exactly plummeting out of the sky, but investigations say the pilot probably attempted to abort the landing so I'm assuming the plane was at takeoff velocity. Assuming there was no instant fire, what happens physiologically on impact at that speed? (and out of curiosity, will it be the same for an aircraft that "falls out of the sky"?) (EDIT: It's highly unlikely that anyone can answer what exactly happened in this specific case, so I can't really expect to get an explanation in that respect. Just looking to know what happens in general =)) | [
"I think you found the right man for this question. I have a airport right by my hospital and I am trained to deal with aviation emergencies. I just need to know what type of aircraft we are talking about. Also what type(s) of aircraft are you interested in hearing about (private prop plane, private jet, charter je... | [
"The sheer amount of things that can happen in high speed impacts is almost limitless. Cause of death can range from heart trauma, to brain trauma, to loss of blood, to almost anything. If you interested in any specificts please let me know.",
"In the case of commercial aviation accidents there is however a short... | [
"Smoke inhalation is not only variable from person to person but also from situation to situation depending on the type of smoke, the volume of smoke, and amount of ventilation. Essentially, if the cabin were to remain mostly intact, it would probably take around 5 minutes from the first sign of fire and first few ... |
[
"Why are our thoughts linguistic/auditory, and not (for example) visual?"
] | [
false
] | [deleted] | [
"You're talking about some pretty outmoded cognitive psychology. We don't actually have language making up our thoughts (e.g., ",
".) When you start to think about it a bit, you'll find that for our thoughts to be done in language it'd be such a complex garble of information it would not be interpretable. You're ... | [
"Do we really reason predominantly linguistically? How would you know? If what you mean by reasoning is explicit, cconscious manipulation of propositions then that's almost begging the question, isn't it. But if you mean draw inferences from data, obviously that's all our brain does, right down to the most basic no... | [
"you only think in language, never in pictures, pure sounds (that are not language), smells ...? I do ... I also totally agree with Ilikebluepens, I don't think it is possible to express all thoughts in language in our heads while thinking, it is just that when you try to express them, you will most likely choose l... |
[
"Why do spiders have eight legs?"
] | [
false
] | Insects have six legs so that they form a tripod when they take a step - they are too small to have a falling part of their gait as tetrapods do. But why do spiders, fairly closely related to insects and often facing similar locomotory challenges, have eight legs? Is this to do with max speed or efficiency when walking and running? | [
"Spiders and insects are not particularly closely related. ",
"This estimate from timetree.org",
" says that spiders and ants last shared a common ancestor 581 million years ago. At this time, our ancestors looked like this: ",
"http://upload.wikimedia.org/wikipedia/commons/5/54/Pikaia_BW.jpg",
"One major i... | [
"I'm glad you pointed out the distance between arachnids and insects - because in any of the still controversial arthropod phylogenies, the distance between Hexapoda and Chelicerata is quite dramatic.",
"I would like contest the claim:",
"One major innovation in the Arthropods is the evolution of segmentation."... | [
"Fundamentally, the scientific consensus around evolution says that this is random and happened to work.",
"When you start asking \"why\" a biological entity is \"designed\" a certain way, you start running up against philosophical questions well beyond biology.",
"Consider, why ",
" we have eyes in the back ... |
[
"Why don't you get high the first time you smoke marijuana?"
] | [
false
] | null | [
"i was ripped my first time"
] | [
"I didn't get the same results."
] | [
"I didn't get the same results."
] |
[
"Is is true, as this paper cites, that \"All dwellers at high altitudes are persons of impaired physical and mental powers\"?"
] | [
false
] | I was reading this article called , and it cited a 1925 paper by Barcroft with the statement mentioned in the title. That people who live for their entire lives in high-altitude environment suffer some level of damage from the low amount of oxygen despite short-term and evolutionary adaption, and are noticeably less intelligent or physically vigorous as a result. Is there any merit to this? | [
"I don't have any scientific evidence but think of this: that was published in 1925 before we really knew too much about genetics. During a time were eugenetics were practiced and believed. ",
"I would not believe it unless it was proved by multiple papers with the last 15 years. ",
"Here is a website researchi... | [
"Thank you for your research :) The link appears broken though."
] | [
"That's weird. It was definitely there when I linked it. ",
"Well here's another paper, the interesting part about adaptations is near the end ",
"http://anthro.palomar.edu/adapt/adapt_3.htm",
"http://evolution.berkeley.edu/evolibrary/news/101001_altitude",
"I did a casual search for intelligence and low ox... |
[
"Is centripetal force-induced artificial gravity really as simple as we think it is?"
] | [
false
] | Considering a rotating circular spaceship, centripetal force would theoretically work... if you is standing still; but if you are moving in any direction in respect to the rotation of the spaceship, wouldn't it change the downwards force applied on you? For instance, if you were walking in the opposite direction of the rotation of the spaceship at the same speed as it is rotating, would you not just start to float? Or in contrast, if you were walking in the same direction as the rotation, would the downward force applied on you increase? --Sorry, not really well versed in the mathematical-physics realm yet, just wondering... | [
"In theory, yes, it's that simple. And the disadvantages you point out for walking in the same direction as rotation or opposite to it are correct.",
"In practice: you need to keep the angular velocity below 2 rpm to avoid motion sickness. In order to achieve usable gravity while rotating so slowly you'll need a ... | [
"Also, another reason the ring has to be so big is that if it's small, the gravity you feel at your head will be different than the gravity you feel at your feet. Your body doesn't like that... so I've been told."
] | [
"Yes, but I'm expecting the docking ship to be a very small mass when compared to the space station. For instance Mir was 130 tons, the ISS is 450 tons, a Soyuz spacecraft is only 8 tons."
] |
[
"Can I wash my hands with soap and tapwater in areas with contaminated water, or will the final rinse just recontaminate my hands?"
] | [
false
] | null | [
"Did I do it right?"
] | [
"Did I do it right?"
] | [
"Did I do it right?"
] |
[
"Besides a large spinning cylinder, what other options are scientists pursuing as a viable option of creating artificial gravity in space?"
] | [
false
] | null | [
"In a ",
"beam powered interstellar railway",
", a craft could be accelerated at 1g toward and then away from the destination, so that craft inhabitants would experience normal Earth gravitational acceleration. It would be nice to accelerate faster than 1g to get to the destination sooner, but humans would have... | [
"140 million tons",
"Which is the equivalent of 2.72X10",
" MT... or 5.456X10",
" Tsar Bombas. That's a lot of energy. It might honestly be easier to just take the Earth with you."
] | [
"140 million tons",
"Which is the equivalent of 2.72X10",
" MT... or 5.456X10",
" Tsar Bombas. That's a lot of energy. It might honestly be easier to just take the Earth with you."
] |
[
"Why does milk spoil if left out but the FDA says you can leave butter out as long as you need?"
] | [
false
] | null | [
"Butter has a much higher fat content, around 80%. Compared to milk, which has a much higher water content. The high fat content and low water content of butter makes it less susceptible to bacterial growth. ",
"That’s also why if you’re going to leave butter out for an extended period of time, it needs to be sal... | [
"Water. Very few microorganisms can grow in foods with low water content, and butter is down there. At 16-18% water by mass, it has less water than honey and about as much as typical dried fruits. Milk, by comparison, is around 87% water, and a much more hospitable environment for spoilage organisms.",
"A bigger ... | [
"Thank you for your time and detailed response I appreciate the clarity"
] |
[
"Why do mosquitoes transmit some viruses, like West Nile Virus, but not HIV?"
] | [
false
] | I'm in the DFW area and we had a safety training class at work today and one of the topics was west Nile virus. I asked the "safety Rick" why west Nile virus can be transmitted by mosquitoes but HIV isn't. He muttered something about it's changed by our blood. | [
"HIV doesn't infect the salivary glands of the mosquito",
", which is required for transmission to another person."
] | [
"This was asked before, I cant seem to find it, but the amount of blood that is drawn, if it was from someone who is infected with HIV, there wont be enough of the virus in the sample + the possible trade of blood when the mosquito bites another person, to infect the new person.",
"I wish I could remember more bu... | [
"Several reasons:",
"Virus strains evolve to fit their hosts/mode of transmission, and the HIV viruses simply did not evolve to survive inside an arthropod vector.",
"HIV \"dies\"/is destroyed (depending on whether you consider viruses to be lifeforms or not) through contact with Oxygen in the air.",
"Source:... |
[
"How much slower do people at the equator age compared to someone at the south pole?"
] | [
false
] | Time is affected by velocity. A point on the edge of a spinning sphere is traveling faster than a point at its poles. It stands to reason that these two points should experience time at different rates. My question is, how much of a difference is there? (however minuscule) | [
"If you spent all of your life on the equator (40000 km in circumference, goes around once in 24 hours) the time dilatation you will experience is 1.00000000000238 relative to someone standing on the pole (and thus not spinning very fast). \nWhat does this extra 0.000000000238% means? Well, let's say you live to be... | [
"How would gravity fit in this?",
"\nPlease bare with my as I might be mixing things up. Does the centrifugal force at the equator cause gravity to have less of an effect on a person than as someone at either poles, and thus effect the time experienced? So is gravity lower (by minuscule amounts) at the equator?"
... | [
"Another reason is that the Earth is not a perfect sphere. The poles are 'flatter' than the equator so the distance between the poles and the core is less which leads to slightly higher gravity at the poles."
] |
[
"Geologists/Earth Scientists: Will all the current land on earth eventually be \"refreshed\" via subduction?"
] | [
false
] | [deleted] | [
"A simple steady state mass balance approach that gets to an estimate of the time it takes to recycle the continental crust:",
"The answer is that the crust is recycled, but not really in the way you're thinking of. Continental crust (CC) isn't really subducted much. Because oceanic crust is denser, when an ocean... | [
"Which, considering the life cycle of the sun, is longer than the earth has left to exist."
] | [
"Fantastic, thank you!"
] |
[
"I've been reading on quorum sensing inhibitors, and I'm having a hard time finding an answer to my question. Do they eventually lead to bacteria death? Otherwise, what ultimately happens to the bacteria after their communication is disrupted?"
] | [
false
] | null | [
"In some species of pathogenic bacteria quorum sensing is the method that induces virulence. If there are enough bacteria they produce the toxins or whatever that cause the disease. If these pathways are blocked the bacteria would essentially think its alone, and therefore not become virulent. This is a great medic... | [
"To add, quorum sensing is often used in biofilm production and biofilms can protect bacteria from the immune system "
] | [
"Sorry if this is incorrect, but your question makes it seem like you believe a quorum sensing inhibitor is literally one \"thing\" that's been discovered that disrupts bacterial communication.",
"This is incorrect.",
"Quorum sensing inhibitors are ANY chemical (Hell, it doesn't even have to be a chemical, but ... |
[
"Some ants cultivate fungus for food and use pieces to start new gardens. Do their cultivated fungus have evolutionary differences to their wild counterparts?"
] | [
false
] | I was thinking how different cultivated foods are versus wild ones in the human world. | [
"Ants' domesticated fungi are definitely distinct from their wild kin.",
"Here we document reciprocal shifts in the genomes and transcriptomes of seven fungus-farming ant species and their fungal cultivars. We show that ant subsistence farming probably originated in the early Tertiary (55–60 MYA), followed by fur... | [
"Thank you very much for taking the time to answer this question."
] | [
"Technically it's not speculation to point out that quarantine procedures for animals like ants are not as strict when it comes to things that are not pathogenic to them. So, it makes sense that there would be a lot of gene-flow between wild and \"domesticated\" strains, especially in the immediate surroundings. ",... |
[
"When my T.V is on mute, there is still a high pitched noise. What is that noise?"
] | [
false
] | i always assumed it was the speakers even though they were on mute, but the speakers blew on a tv in my house and i can still hear it | [
"Here's the ",
"device",
" that causes it. ",
"The physical explanation (called ",
"Magnetostriction",
") is that the transformer (which is just coils of wire) is carrying high-frequency alternating current (AC). As the electric field changes due to the AC, the magnetic field around the coil also changes.... | [
"Also, anybody much over 35 or so was far less likely to hear the noise.",
"When I was in high school, the new big thing was the mosquito ring/notification tone that was high-pitched enough that most older folks (like teachers) couldn't hear it. ",
"I'm not sure what causes the change over time in some sets ver... | [
"I used to repair televisions (way back when they had tubes in them, and not just the CRT!)",
"Some that came in would have this whine VERY loudly, others made no sound at all. But the most interesting thing was that 50% or more of the people I ever asked could not hear it at all. There were some sets that would ... |
[
"How much lower would sea level be if all the animals were taken out of it?"
] | [
false
] | Not entirely sure how scienc-y of a question this is, but I can't think of a better place to put it... | [
"Given that the ocean is very, very big and that even the biggest of animals are very, very small in comparison, I will go out on a limb and say there would be absolutely no measurable difference.",
"Now for numbers, Wiki lists the total biomass of the whole planet at about 560 billion tonns (plants and animals i... | [
"You're thinking of the commonly thrown around statistic for the SURFACE of the planet. There's much more mass beneath the oceans. "
] | [
"Thank you for being the first and only person to answer. Really - only 10% in the oceans? I'm completely off then, I was imagining a lot more, considering the planet is about 80% water..."
] |
[
"I boiled an egg with a pinch of baking soda in an aluminum pan and it turned black. What reaction happened in there?"
] | [
false
] | The surface where the water touched the pan and I can't seem to scrub it away. | [
"I'm no chemist (just and engineer), but here's my best guess since there's only one other answer:",
"The baking soda stripped away the protective oxide from the Aluminum, which then reacted with something else in the water. This is where it gets tricky. What order did you add the egg and the baking soda? When di... | [
"eHow suggests it is because of low pH, \"oxidation,\" or high temps in the dishwasher.",
" It also recommends a technique by which it may be removed.",
"I'm a chemist- wish I knew precisely what was going on (I'd like to say it was the sulfur in the egg, but aluminum sulfate isn't black), so I look forward to ... | [
"actually the opposite... the black IS an oxidation layer.",
"Go buy a brand new aluminum pot (restaurant supply houses have them, I bought a 10 gallon stockpot for brewing beer) and boil plain water in it. where the water touched will turn dark grey. add baking soda (or oxyclean, what I use for cleanup, bu... |
[
"[Rocketry] Is the specific impulse of the space shuttle (LOX/LH2) rocket based on the molecular mass of H2 or H2O?"
] | [
false
] | Armchair rocketry fan here so sorry if it is a very basic question. My understanding is that the Specific Impulse (Isp) is inversely proportional to the root of the molecular mass of the reaction mass and proportional to the root of the temperature. Therefore in low thrust/high-efficiency scenarios (e.g. orbital transfers), you want as high an ISP as possible and therefore as light and hot a propellant as possible. Sorry if this is unclear. I guess what I am asking, is if a standard LOX/H2 rocket uses H2O as its reaction mass (flame temperature ~3500K, molar mass 18), than it seems that you can greatly increase efficiency without needing NERVA etc but with conventional methods which heat H2 to a fraction of the temperature (1160K, molar mass 2). | [
"It's based on measurement of the engines, of course. But H2O gives the best specific impulse in an ideal rocket engine. The reason is that self-contained rockets have to carry two kinds of supply: ",
", which is matter that contains energy to be used for propulsion; and ",
", which is matter that can be loa... | [
"If I remember my college propulsion class correctly, it's the average molecular weight of the exhaust gases. I remember hearing somewhere that sometimes in LOX/LH2 engines deliberately run rich, which puts more H2 in the exhaust, and lowers the average molecular weight of the exhaust, improving the specific impul... | [
"One of the big advantages of NTRs is precisely that you can use low-molecular-weight gases as exhaust. However, without having nuclear fission as a heat source where are you going to get the energy to heat up the exhaust in a \"conventional\" thermal rocket? The likely answer is a chemical reaction. But that means... |
[
"What time zone is used in the North and South Poles?"
] | [
false
] | null | [
"At the absolute tip of each pole, Greenwich mean time. But the time zones extend all the way to the poles. For example, Antarctic Research bases operate in several different time zones (usually corresponding to their sponsor nations) even when they're fairly close to each other.",
"But truly, you can operate o... | [
"Because when time zones were invented, GMT was considered the \"start\", and all other time zones radiated out from there."
] | [
"Why does it have to be GMT at the absolute tip? All the time zones converge there so shouldn't it be any time zone, and is there an international convention that has been agreed on the time zone at the absolute tip?"
] |
[
"How much does the earth's mass change over time?"
] | [
false
] | I've heard the earth is gaining mass because particles/dust from space is always adding to it but is the earth losing mass also? How and to what degree? | [
"We lose about 3kg of hydrogen and 50g of helium each second (about 10",
" per year) due to ",
"Jeans escape",
". ",
"http://www.scientificamerican.com/article.cfm?id=how-planets-lose-their-atmospheres",
"We also gain 10",
" to 10",
" kg per year due to meteorites and such.",
"http://www.tulane.edu/... | [
"Net is zero, with a negligible fraction escaping as heat. The reasoning is that the solid mass is turned into various gases and soot, which either remain in the atmosphere or fall back to the ground."
] | [
"Net is zero, with a negligible fraction escaping as heat. The reasoning is that the solid mass is turned into various gases and soot, which either remain in the atmosphere or fall back to the ground."
] |
[
"How did the first sexually reproducing organism come into existence?"
] | [
false
] | [deleted] | [
"We don't know, but we do have some theories"
] | [
"At one point, was there an organism that could reproduce both sexually and asexually?",
"There are many such organisms.",
"Bacteria, for example, can undergo binary fission, but they also exchange DNA with each other directly (conjugation) or through a bacteriophage intermediate (transduction). They can also a... | [
"The last gender split was during reptiles. Mammals use the XY system with males as hetero-gametes, birds use ZW with females as the hetero-gametes, reptiles use temperature (except for snakes), and insects use the haploid-diploid system (males have only half the chromosomes that females do)."
] |
[
"If food contained no water would it heat up in a microwave?"
] | [
false
] | null | [
"Yes, but more slowly. Water is not the only molecule that absorbs microwave radiation. Other molecules have some degree of polarity and get jiggled and heated by microwaves."
] | [
"The molecule would have to be polar though right?"
] | [
"Even if it's non-polar there will be some heating from ionic conduction (ie ions will respond to the E-field, producing alternative current in your food). "
] |
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