title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Is there a biological reason humans evolved to see the range we call visible light?"
] | [
false
] | Or in another way, is there anything special about the 400–790 THz band that makes it especially useful to see? Along the same lines, are there any organisms out there that perceive a different band? | [
"The majority of the energy put out by the sun per wavelength is in the visible spectrum. ",
"Spectrum Image"
] | [
"It's high enough in energy to not be drowned out by thermal radiation, which is the case for a lot of the infrared (at least in daytime). And it's largely transparent to small molecules, so it penetrates air and water nicely, but it does interact with solid objects, making it pretty useful for what we use sight fo... | [
"There's also a nice dip in the ",
"opacity of the atmosphere",
" around visual wavelengths and near infrared to mid infrared. The next big dip is at radio wavelengths."
] |
[
"The phrase 'dimensions' is used in science fiction all the time as another plane of existence; what does theoretical physics say about dimensions and whether they exist or in what terms the word 'dimension' is used for in science?"
] | [
false
] | Hopefully apart from length, width, and height. | [
"I'll try to provide an intuitive explanation of the concept of a dimension. A dimension is an independent coordinate that you can use to describe the location of a point in some kind of mathematical space. When we talk about an n-dimensional space, that means that we need n dimensions to specify a unique point in ... | [
"If everything you said is accurate to the topic (and I'm assuming it is since I have no reason to disbelieve you) this is the best simple explanation of extra dimensions I have ever read. Thank you. "
] | [
"There are other arrangements which dimensions could theoretically take on, and those \"macroscopic\" ones are usually the sort to which sci-fi refers.",
"I.e., if our universe, in all four of its dimensions, could be metaphorically represented as a single page, some \"other dimension\" could be another page (usu... |
[
"How exactly does air traffic control radars work? (Civilian systems only if there’s a difference between civilian and government)"
] | [
false
] | Do planes need to be at a certain altitude to be tracked in the “blip”. Do they need certain FAA requirements to be seen on radar, do they need specific speed, or mass? All of the above? | [
"Do planes need to be at a certain altitude to be tracked in the “blip”",
"They need to be at a specific angle above the horizon with respect to the point-of-view of the tranceiver. otherwise the signal is lost amid noise from closer and larger objects on the ground like buildings and hills. Therefore planes fly... | [
"First time replying on ",
"/r/askscience",
" so apologies for any unintended protocol oopsies...",
"/u/Diligent_Nature",
" provides a good summary response and I'd just like to expand on that a bit.",
"There are several different operational environments and associated radar/surveillance systems with the... | [
"Air traffic control almost always uses ",
". Secondary radar works by the aeroplane having a radio transmitter and receiver known as a ",
". The radar sends out a \"who are you\" signal and the transponder replies with information such as aircraft callsign, altitude, and so on. Transponders are a legal require... |
[
"What would an AM and FM radio signal look like if broadcast in the visual spectrum?"
] | [
false
] | Radio signals are just light, correct? If we rigged up a radio broadcast system such that it emitted a signal in the visible spectrum with brightness such that a human could easily see it, what would that signal look like? Would we see lots of blinking? Would we see rapid shifts in brightness and color? How would AM and FM signals differ? Would the entire antenna glow, or only certain points? Moreover, how would you do this? How hard would this be to accomplish if I wanted to see for myself? | [
"Radio signals are electromagnetic waves. What we refer to as light, or visible light, also consists of electromagnetic waves, but of a different frequency than radio signals.",
"If for some reason, we would use visible light to broadcast radio transmissions, what you'd see depends on whether you use AM or FM. Ei... | [
"if you reproduced e.g. the FM broadcast radio (i.e. audible signals) spectrum (from 88 to 108 MHz) in visible light by scaling all the frequencies by a factor of about ten million, it would fit ",
" the visible spectrum; the ratio of the longest to the shortest FM radio wavelengths is about 1.22, while the ratio... | [
"First, even though it is all electromagnetic radiation light and radio, there are key differences between them.\nUsually the wavelength of the wave is similar to the size of the object emitting it. The electrical currents oscillate at frequencies and scales similar to the one of the emitted wave.\nWhen you get to ... |
[
"How does the candle relighting trick work? the one where you light the smoke trail?"
] | [
false
] | As shown in this gif | [
"In order for something to burn, you need to vaporize the fuel. So when you light a candle, it takes a second or two to melt and vaporize the wax before it can ignite and become self-sustaining.",
"When you blow out the candle, the residue heat from the wick keeps vaporizing wax. The \"smoke trail\" you see isn't... | [
"This picture",
" that hit the front page yesterday shows the wax that continues to come up after the candle is blown out."
] | [
"You shouldn't pour gasoline on a fire at all, though, surely?"
] |
[
"How much uranium does a Russian made VVER-1000, 1000MW nuclear power plant use?"
] | [
false
] | Also follow up, does a nuclear power plant needs to be continually refueled everyday, or every few weeks/months/years? | [
"A typical Large nuclear reactor will have something like 160-200 tons of uranium in it. Typically 1/3 of the fuel is replaced every 18-24 months (depending on design). ",
"One notable exception is the candu reactor type, which loads small fuel segments in the front and drops them out the back into a pool of wate... | [
"1 GW(e) reactor outputs around 3 GW(t) power. That equates to around 10",
" fissions per second. So 10",
" uranium isotopes used per second means around .04 grams of uranium used per second. That is around 1200 kg of U-235 used up per year. "
] | [
"I got curious, although didn't find out the amount specifically in that reactor type but did find out quite a bit about fuel rod assembly from a promotional brochure from a company that supplies them. Pretty interesting PDF entitled \"Nuclear fuel for VVer reactors\" : ",
"http://www.tvel.ru/wps/wcm/connect/tvel... |
[
"What happens to Helium?"
] | [
false
] | From my understanding there is a finite amount of He on our planet, and we extract it from where it is trapped in rocks... Then we fill up party balloons with it. What happens to the He once the balloon pops? Does it just go into space? Does it collect anywhere? What happens to it? | [
"Normally, the ballon shrinks and appears to gain wrinkles because the He atoms have leached out of the balloons skin. The size of the small particles can easily fit through the lattice-like structure of the balloon, and become smaller and more dense; and sinks down from the roof where you cousin let it go.",
"On... | [
"25%",
" of the mass of the Milky Way galaxy is helium.",
"There are \"pockets\" of He floating around, however, they are intermixed with hydrogen and form gas clouds and populate the interstellar medium.",
"The He atoms don't really accumulate since there is no force acting on them to do so. They are lighter... | [
"So the He way up in the atmosphere. Does it accumulate at all, or does the solar wind just 'blow' it away? Does it when it does get blown away get attracted to deeper gravity wells? Basically I am wondering if there are cosmic pockets of He just floating around."
] |
[
"How are old buildings built with asbestos demolished safely?"
] | [
false
] | null | [
"no need for \"moon suits\" or wrapping the entire building. You work section by section, room by room. You will seal off each room and pull negative pressure through a HEPA filter to catch all the fibers. And you wear a tyvec suit or another material that is fiber resistant, with a respirator to protect the lun... | [
"This is how it ideally works but I worked in a demolitions crew for a bit and we specialized in removing asbestos (in reality we were always the lowest bidder) and we used absolutely no protection save for gloves and long pants. We’d just rip it up, shove it in a trash bag, pour water on top of it, tie and tape th... | [
"asbestos was the wonder material of the last century, this century, not so wonderful. When toll booth operators were getting asbestosis just from car braking at toll booths, I knew we had a problem"
] |
[
"Can earthquake equipment detect underground tunneling ?"
] | [
false
] | [deleted] | [
"It won't necessarily be the best detector of active tunneling, since seismic equipment is picking up tiny movements all the time. But if it's used in a more ",
"targeted way",
", it may be able to detect anomalies underground, spotting already-made tunnels that way. This method, and others, have been used to f... | [
"Thank you"
] | [
"Thank you"
] |
[
"Was Einstein's contribution to physics necessary for building the atomic bomb?"
] | [
false
] | null | [
"Not really, Einsteins contribution to phsyics with regards to building a nuclear bomb was minimal and restricted to Mass–energy equivalence (i.e E=mc",
" It gave nuclear physicists clues to refine their designs for an effective nuclear bomb. ",
"Its very likely that without Einstein the nuclear physicists invo... | [
"But wouldn't they at least have had to have know that matter can be converted into energy, and isn't Einstein the one who theorised this?"
] | [
"Even without focus on E=mc",
" , work on nuclear energy was conducted with experiments on radioactive materials since the early 19th century",
"Einsteins Mass–energy equivalence contribution only provided to be a tool in finishing the atomic bomb more quickly and efficiently like I said in a comment below",
... |
[
"If/When humans make the trip to Mars, will we be able to walk or will we hop like the astronauts on the moon?"
] | [
false
] | null | [
"In between. The gravity there is about 40% as strong as Earth's."
] | [
"Depending on the mass of a spacesuit, the total weight an astronaut would have to move would be comparable to the weight the astronaut has to move on Earth. The Apollo spacesuits weighted 180 pounds on Earth, as ",
"NASA reports",
". An astronaut who weighed 180 pounds on Earth wearing this suit on the Moon ... | [
"The gravitational field on the surface of a planet is primarily a function of its mass and radius. Larger mass, larger gravitational field; larger radius, smaller gravitational field. The gravitational acceleration can be computed to be ",
"G M / R",
"where G is a constant of nature, M is the mass of the plan... |
[
"What is it about Mercury (Hg) that makes it so good for measuring pressure?"
] | [
false
] | I'm an American pilot, and although there is no actual mercury in my instrumentation, things like altimeter setting and manifold pressure are measured in inches of mercury (InHg). Why is this element used, and how does it compare to the accuracy of millibars (no other country has inches)? | [
"Other folks have mentioned the weight. Another benefit of mercury is that it's not prone to phase change at particularly low or high pressures. This is useful when you want to measure a vacuum; water for example would tend to boil or become water vapor when exposed to a vacuum, which would then feed into whatever ... | [
"Before we had electrical pressure transducers, measuring pressure was typically done by filling a U-shaped tube with some kind of liquid. One end of the tube is open to the atmosphere and the other end if attached to the pressure you want to measure. The positive or negative pressure you want to measure causes t... | [
"water for example would tend to boil or become water vapor when exposed to a vacuum.",
"What you mean is, water has a reasonably high vapor pressure at ordinary atmospheric temps. Moreover it varies quite a bit from, 0 C to 35 C."
] |
[
"How can a photon even exist if it travels in no time and is absorbed in 0.0 seconds?"
] | [
false
] | It doesn't really exist for any length of time. Or how could it exist in one time frame and not in another? | [
"What he means is that in the rest frame of a photon, the elapsed time between two events is zero."
] | [
"If you really want to be mathematically technical - and perhaps one needs to be in order to answer your question, a photon does not have a properly defined rest frame. ",
"You can choose any rest frame that you want, and the photon will be traveling at the same speed.",
"In the limiting case, the proper time o... | [
"I should have also mentioned - if you have no mass, then it doesn't make any sense at all to have a rest frame.",
"The energy of a photon is dependent on the frame of reference in which you view it as it will be blueshifted or redshifted.",
"The energy of a photon (E) is related to its momentum (p) by p = E/c ... |
[
"Why can't we relocate endangered species (such as orangutans) to countries that won't kill them?"
] | [
false
] | [deleted] | [
"We (the human race) have a long history of screwing up a habitat by introducing species that are not native to that area. The natural order of any given environment is rather fragile even when it doesn't seem so to us as individuals. ",
"We just don't know enough to do it without bad side-effects. We do know ... | [
"We often do",
". However, there are rampant discussions on the effects some practices have, and I am not aware of any cases where an entire species was moved to captivity. However, there is a particular conservation status, ",
"extinct in the wild",
" which denotes an animal which, after being endangered, ha... | [
"While biologically inaccurate, \"human race\" is an everyday English expression used to refer to the human species. Nothing wrong with using everyday English."
] |
[
"How does s1=433, s2=333, s3=123 not break cantors diagonal proof?"
] | [
false
] | null | [
"I don't understand your question. Cantor's diagonal proof produces a number not on the list by constructing a number that differs from the ",
"th number in the ",
"th decimal place."
] | [
"But the number constructed by those three is 433, which is equal to s1, a number on the list"
] | [
"Hm? Cantor's proof is a proof that the real numbers are not countable. So it starts with a purported list of all real numbers. That is, an infinite number of numbers, which each have infinitely many decimal places. You've provided three 3-digit numbers. (Also, \"433\" does not differ from the second number \"233\"... |
[
"What is it about the flu virus that makes it seasonal?"
] | [
false
] | null | [
"There are lots of explanations, but it's still not completely clear which of them is most right. (Probably, as with most biology, there are many different reasons adding up.) Some of the reasons put forward are:",
"Some of these are more convincing than others (I'm pretty skeptical about nutrition in particular... | [
"Never mind debunked, it was never bunked. It’s pure nonsense. Human influenza doesn’t work that way. Whoever told you that had confused the source of pandemic influenza (of which there have been four over the past 100 years) with seasonal influenza (which happens every year)."
] | [
"I was taught years ago that it's because of seasonal bird flight patterns, and the flu DNA somehow getting remixed while the birds carry it into one of 128 possible strains..",
"Is that hypothesis debunked now?"
] |
[
"I heard we are running out of helium on Earth. How true is this, and is anyone working on a way to find/create more of it?"
] | [
false
] | null | [
"Helium is produced as a byproduct of natural gas. During the Cold War, the US subsidized helium production and created a massive stockpile. Over the past decade, they have been selling it off, which has made helium very cheap...so cheap, it hasn't been profitable to capture it from natural gas wells, so it gets ... | [
"Scientists would love to find a way to ",
"make helium out of hydrogen",
". Their main goal in this isn't actually to have more helium, though."
] | [
"Where in the world are you seeing highly reactive hydrogen gas just sitting around?"
] |
[
"Why does public transportation typically not have any seatbelts?"
] | [
false
] | [deleted] | [
"When a massive object collides with a small object, most of the damage is to the small object. So, when a car and bus collide, the bus passengers are much less likely to get hurt.",
"I was once in an accident where a car rear ended a city bus. The bus shook a little and barely had any damage. The car was totaled... | [
"Everyone gets thrown around and gets hurt and it makes worldwide news. Luckily you don’t see that news that often. Per mile buses are the only transit safer than an airplane. "
] | [
"But what if the bus collides with a wall?"
] |
[
"Black Hair and Blue eyes"
] | [
false
] | [deleted] | [
"Punnett squares don't work well here because there are multiple genes that affect your eye color (many people have more than one color in their eyes, or the color is not uniform)."
] | [
"Just as an aside, punnet squares are good for really simple types of inheritance, but eye color isn't a simple trait that is readily conducive to looking at punnet squares. And I think that it's pretty obvious that it's possible, because I know people with naturally dark hair and blue eyes. "
] | [
"All right so since she is hardcore Asian (genetically). Let us assume that she would have dominant dark genes in all six loci. There are three identified genes for basic eye colour (not including those that effect yellow rings etc. I am assuming she just wants blue and is not worried about rings.) Each gene has tw... |
[
"This may sound dumb, but why when a human gets shot in the brain its an instantaneous death?"
] | [
false
] | I understand a bullet to the brain would kill u very fast but why is it immediate and why can't surgeons retract the bullet and cauterize the vessels as any other part of the body? I'm not looking for answers like "because it's the control center". I would appreciate a detailed answer. Thank you. | [
"It's not necessarily instantaneous death, but it can very well be. The difference is in the degree of disruption.",
"A bullet passing through the skull imparts a great deal of its kinetic energy on the substance of the head. Depending on the closeness of the gun, expanding vapors may also accompany the bullet. T... | [
"For a visual on the amount of energy that is imparted into the brain by a bullet, ",
"here's a slow-motion video of a large handgun round (.45 ACP) going into ballistics gel.",
"This is a large rifle round (.308) for comparison.",
"In both of these, note how the \"tissue\" deformation is significantly larger... | [
"It's not always death. Many people have survived being shot through the brain, through surgery similar to what you have described. A very visible example from recent history is Congresswoman Gabrielle Giffords."
] |
[
"Can someone please explain counter-steering?"
] | [
false
] | As per from Thank you. | [
"In short, it comes down to generating the force needed to turn, without generating a torque that will topple you. ",
"The important fact here is that a tire generates force against the ground PERPENDICULAR to the angle that the tire is touching the ground at. With that in mind, realize that the side of the bike... | [
"As a motorcyclist, that isn't what counter-steering is. Counter-steering happens when you're riding any two-wheeled vehicle above a certain speed limit (around 32 km/h or 20 mp/h or so). At these speeds and above, turning the bars right will actually turn the bike ",
" (or rather, 'cause it to lean left, thus ca... | [
"I am both a sometime motorcyclist and, more recently, a mountain biker.",
"Should you apply the rules ",
"/u/kdeff",
" describes? Absolutely.",
"However the force you need to apply to the left handlebar to lean right on a bicycle (mountain or road) is so slight so that it's almost imperceptible. You are ac... |
[
"FAQ Friday: What determines how fast a scent can spread? Find out and ask your questions about smells here!"
] | [
false
] | This week on we're exploring the amazing world of scents and smells! Have you ever wondered: What is a smell? When smelling something, are we inhaling molecules of what we recognize as a scent? How fast can an odor travel? What is the "speed of smell"? If I smell something is it possible to use up all of the scent? Read about these and more in our , or ask your questions here. . | [
"If I am briefly in a room that stinks and I don't want to breathe it - eg a trash room or a recently used restroom - is it better for me to take short shallow breaths or infrequent deep breaths? Should I breathe through my nose or my mouth? If the smell was somehow toxic, is there one breathing pattern that is saf... | [
"How seriously do smell experts take the idea of ",
"quantum olfaction",
"?"
] | [
"Wow! I just casually remembered that this FAQ would be up today, I click on it, and see that the number one comment, unanswered, is addressed by the very first paper I ever had published!",
"As I'd prefer not to throw my full name and publication history up there for all to see, I'll just give you the gist (a s... |
[
"what is the plausibility status of parallel universe/s being the cause of unexplained phenomena attached to dark matter and dark energy?"
] | [
false
] | This is a very unscientific claim, but when watching the miriad documentaries on the subject, it always comes to me the idea of an unseen dimension/universe accounting for gravitational and momentum misteries currently labelled as dark matter or dark energy. Is there any plausibility or actual theory about this? ps . sorry if the wording reads weird, english is not my mother language. | [
"Not really. There are some scientific ideas kinda like what you're proposing, but postulating ",
" just to explain some nonradiating matter and metric expansion is a huge violation of parsimony."
] | [
"The issue isn't scale, the issue is using a more complex explanation when a simpler one suffices. We have pretty good explanations for dark matter, and we have avenues of attack to figure out dark energy significantly less complex than \"so there's a universe which can interact gravitationally with ours except som... | [
"No. Inverse square laws are valid only if gravity propogates through three dimensions; however you add another one, you can't keep that inverse square law valid."
] |
[
"If black is the best absorber of light and white is the worst/most reflective, why are mirrors silvery/grey?"
] | [
false
] | [deleted] | [
"Describing the color of a mirror is a bit as tricky. In most cases we associate the color of an object with the reflection spectrum of that object in the visible range. So for example if you have an object that absorbs all incoming light and reflects very little visible light, we say that it is black. On the other... | [
"Thanks for the informed and elaborate answer.",
"What is spectral dependence?"
] | [
"\"...little spectral dependence...\" meaning the reflection happens substantially equally at all wavelengths. "
] |
[
"Question, may save soldiers lives. How much water would be needed to stop artillery shrapnel / concussion."
] | [
false
] | null | [
"Hey bud, AD Army w/ 2 tours. check DA PAM on survival, i know it gives the thicknessess of different materials to protect against nuclear blast / radiation, it might also give it for fragmentation. Good luck an Give em hell"
] | [
"Bullets directly fired into water very quickly dissapate all of their energy. (within a foot or less). This is also why jugs of water are used as targets.",
"The problem would be that a system such as what you are proposing would only work once, as the water would then leak out."
] | [
"Indirect fire would mean that they're not really having to deal with a constant stream of impact and/or the need for a reusable protection item. They just want a buffer for the one-off round that hits right where their bunk is."
] |
[
"When does the body know to release Insulin?"
] | [
false
] | null | [
"Essentially, the concentration of sugar (glucose) in the blood activates the beta islet cells in the pancreas to release insulin. The more glucose, the more the cells are triggered, releasing more and more insulin. ",
"The mechanism goes: glucose diffuses in to the beta cell, goes through the metabolic process o... | [
"So basically the islets are sitting there hungry and when they get sugar they start doing their job which is to pour insulin into the blood stream.",
"Kind of like a big lock system, the engine of the cell is switching the sluices open by the mechanism of potassium and calcium open the gate."
] | [
"http://www.nature.com/nrendo/journal/v3/n1/images/ncpendmet0368-f1.jpg"
] |
[
"Is it possible to visit a fixed point in space multiple times?"
] | [
false
] | What I mean is it possible with all the planets, solar systems, galaxies and probably the while universe spinning and constantly moving, is it possible to determine exact coordinates in space and then return to those same coordinates again with 100% (or at least 99.9%) accuracy? | [
"There is no objective universal coördinate system with which to ask whether you've \"really\" been to the same place twice; any such statement will necessarily depend on the arbitrary choice of coördinates you assign to spacetime events. As such, it is just as \"correct\" to say that you've ",
" been at a fixed ... | [
"Galaxy positions are typically defined in terms of the Right Ascention (RA) and Declination (DEC), a coordinate system analogous to latitute and longitude (but whose reference zero points are completely different). 3D coordinate systems are worthless due to the immense light travel times involved when talking abou... | [
"Does NASA have any system they use to identify a position in a solar system or galaxy?"
] |
[
"How fast do various microorganisms travel in MPH/KPH? For example, could a flagellated microorganism, if put in water and could only go forward, travel anywhere close to 1 MPH/KPH?"
] | [
false
] | Or simply travel any significant measurable distance? | [
"One of the best studied systems for microbial chemotaxis (motion based on chemical species concentrations) is E. coli. E.coli use flagella to move around, and reach speeds of about 20um/s, which is about 7.2cm/hour. Not very fast by our standards, but pretty fast compared to the length of E. coli (1um). ",
"Chem... | [
"Put in perspective. If the e. Coli travels 20 body lengths per second, that's equivalent to a human swimming at ~80 mph through the water. Not bad."
] | [
"A quick googling (searching for \"speed of microorganisms\") returns this page:",
"http://hypertextbook.com/facts/2000/ElaineKung.shtml",
"The fastest movement they list is 200 µm/s, 200 micrometers per second, which translates to 0.000447387 MPH."
] |
[
"Why can't we apply Hilbert's Hotel paradox to Cantor's diagonal argument?"
] | [
false
] | I've been doing a bit of reading and watching video's about infinity lately and two ideas about infinity really stood out to me: and . For those that don't know about Cantor and Hilbert, Michael from Vsauce does a really great job at explaining these concepts in Now to get to my question, and I hope I can explain it clearly enough: can't we make the real numbers between 0 and 1 countable by applying Hilbert's Hotel paradox to the diagonal argument? If we use Cantor's method of generating random real numbers between 0 and 1 and linking them to whole numbers until infinity we can still create a real number that exists between 0 and 1 that we haven't linked to a whole number yet by using Cantor diagonal method. But can't we treat this new unlinked real number as a new guest like in Hilbert's Hotel Paradox and just shift every randomly generated real number to the next whole number, opening up the whole number '1' for the new unlinked real number? And then we can start the process again by creating another diagonal number with the new set we just created, just to create a new set by shifting everything again and adding the new unlinked real number to 1 again, and then we just repeat this process for infinitely many times so that we link all the real numbers between 0 and 1 to all the whole numbers, making the real numbers between 0 and 1 countably infinite. What is wrong with my logic here? | [
"The process wouldn't be able to generate the real numbers in countably many steps because they are uncountable. You're missing a crucial part of Cantor's argument, it begins with the assumption that you have a one to one correspondence between the real numbers and natural numbers. Then it finds a real number that ... | [
"Cantor assumes that there exists a completed list of real numbers, then finds a number not on that list. You could alter that list to include the new number, but that would contradict it originally being a complete list."
] | [
"More directly giving the fallacy in OP's argument, if the first two numbers in the list are .0000000000000... and .1000000000000000... respectively, OP's process will only ever construct numbers that contain at least one consecutive pair of 1s. However, there are lots (as it turns out, an uncountable collection) o... |
[
"Does sodium pentathol really work as a truth serum? And if so how?"
] | [
false
] | [deleted] | [
"Well, the theory is that it suppresses higher brain functions, sort of kills off your inhibitions to lie. The fact is it is more likely to make you a chatty cathy, but I really doubt its efficacy as a 'truth serum'. It is conceivable though that it could work. In my line of work I routinely administer potent sedat... | [
"Just to cause rapid unconsciousness."
] | [
"I think he worded that poorly. Probably more, kills off your inhibitions towards telling the truth, or your reasoning on keeping up a lie."
] |
[
"Is every trait of every animal a result of evolution?"
] | [
false
] | Since every animal evolved from single celled organisms, it makes sense (to me) that each trait or characteristic came about because of evolution or natural selection. For example I presume I have two kidneys because it's more efficient than one big kidney (if one should die). Surely the fact that I have two kidneys is because my one-kidney'd ancestors died out due to natural selection? But then things like wings throws this idea out the window and the steps between a wingless animal and an animal capable of flight / freefall. Surely until the wing could actually do anything, it was just a hindrance and of no evolutionary benefit? What I want to know is if everything about every animal from the colour of my hair to the shape of my toes is 100% down to evolution and natural selection. If a trait wasn't caused by evolution, how and why does that animal have that trait? I hope my question makes sense and I'd love to hear what you thought about it. Thanks | [
"Technically, yes - every trait of every animal is a \"result\" of evolution.",
"Every lineage of organisms has been evolving for about 3.5 billion years.",
"The characteristics of human beings are the result of 3.5 billion years of evolution. (Of that species and its ancestors.)",
"The... | [
"The newer traits that pop up and are selected are kind of random. So while some that stay are likely due to natural selection (color of certain animals, for example), not all were necessarily selected for. ",
"For example, let's say you have lots of fur and that works well because the environment is cold. Howeve... | [
"Fun facts: \n- A trait (like 3 eyes) that comes about as a result of selection for another trait is a \"spandrel\".\n- If it used to serve a role but no longer does, it's a \"vestigiality\"\n- If its a throwback to an ancestral trait, its an \"atavism\""
] |
[
"What's outside the spectrum of EM radiation?"
] | [
false
] | Are there waves with a lower frequecy than radio, or higher frequency than gamma? If so, what makes them different than EM radiation? Is it possible that there are wavelengths that are light-years across? | [
"What happens when you move towards infinite on either end? "
] | [
"What happens when you move towards infinite on either end? "
] | [
"To expand on this, if you change your reference frame light can redshift or blueshift. If there was a minimum possible wavelength, that would imply that if there's light with that wavelength you can't change your reference frame to blueshift it more. Likewise, if there were a maximum wavelength you wouldn't be abl... |
[
"Fluid Mechanics: Is it possible to determine the viscosity of a Non-Newtonian fluid by sending it through a pipe?"
] | [
false
] | Say you have a Non-Newtonian fluid flowing through a straight pipe. You have a pump in one end and you can measure flow and pressure at both ends of the pipe. Would it be possible to determine the viscosity of the fluid? What properties of the fluid and pipe would you need to know (density, temperature, friction?)? I'm thinking it would be impossible, but I can't seem to put it into words. | [
"First of all, for a non-Newtonian fluid the viscosity isn't constant, but changes with the shear rate.",
"The only way I could see that you could do this would be if you know (or assume) that your non-Newtonian fluid is a ",
"power-law fluid",
". By testing different pipe sizes and pressure gradients, you s... | [
"What if we had a Newtonian fluid though, and that I just wanted to see a trend (lets say that the temperature and flow is constant)? \nWould it be possible to use pressure at the inlet and outlet, along with the flow rate to find the viscosity of the fluid?"
] | [
"Sure, that's simplicity itself. You just keep the Reynolds number below 2000 so that you have laminar flow, and use the ",
"Hagen-Poiseuille Equation",
". Knowing the flow rate and pressure gradient, then you solve for the only remaining unknown, the viscosity."
] |
[
"What effects do the solar cycle have on Earth's temperature?"
] | [
false
] | We currently experiencing a "solar minimum" meaning there is less electromagnetic activity and fewer sunspots. We are also experiencing record setting high temperatures do to high levels of green house gases in the atmosphere. Will the next solar cycle exacerbate the greenhouse effect, or have some other effect? | [
"The sun does get slightly brighter at the peak of each solar cycle, but the climate effect is very small compared to greenhouse gases.",
"The sun gets brighter and dimmer on a fairly regular 11-year cycle. This changes the amount of sunlight absorbed by the Earth by about 0.25 watts per square meter, about 0.1%... | [
"The sun gets brighter and dimmer on a fairly regular 11-year cycle. This changes the amount of sunlight absorbed by the Earth by about 0.25 watts per square meter, about 0.1% of the total absorbed. In comparison, greenhouse gases like CO2 have increased the energy input by about 3 watts per square meter since 1880... | [
"Half that change, I gave the full range, not the amplitude."
] |
[
"How I calculate the velocity of the water inside of a pipe through the pressure and the area?"
] | [
false
] | null | [
"It's often treated as ",
"Poiseuille flow",
"."
] | [
"You should post the exact question on ",
"/r/AskPhysics",
", you'll get good answers there."
] | [
"The problem is we don't have the volumetric flow rate. Actually the purpose of finding the velocity is to find the volumetric flow rate.",
"Edit: ΔP isn't avaliable as well."
] |
[
"Can /r/askscience help explain basic lightning to me? (link to a reddit comment that sparked this inside)"
] | [
false
] | I don't feel like I'm getting the complete picture here: | [
"The same convection based process that forms hail also helps build up electric charge separation in thunderclouds. This creates a voltage (electrical potential difference) between the cloud and the ground, much like a capacitor. The air between is an insulator but when the voltage builds up high enough insulators ... | [
"Once a lightning channel is established through all of the small ionized paths (the dart leader process) that same channel is often used to multiple discharges. Initially there is one large pocket of charge in the cloud that creates the first discharge, then you get discharge channels reaching further into the clo... | [
"Yup. I assume that there are multiple \"pockets\" of charge in the clouds, when one of them comes into contact with the ground that changes the electric potential of the former pocket, encouraging a lightning bolt that connects another pocket to the discharged pocket and the ground."
] |
[
"Is it possible for a paper airplane to hover between two fans?"
] | [
false
] | This clip has been making the rounds lately, showing a paper airplane hovering between two desk fans: Would it actually do that? And if so, how? | [
"It doesn't seem possible for the paper airplane in that clip to hover as it does. The fans both seem to be pointing and blowing turbulent air at the airplane. A fan (approximately) generates a vortex tube, which can also be considered a turbulent jet (a tube whose surface supports a velocity jump). When two of the... | [
"I don't know if it is relevant, but in the MoMa entrance, there is an ",
"installation where a strip stays around air flowing between two fans",
"."
] | [
"Art layman here. I have seen it first hand and unfortunately, there are two extremely thin wires going from one fan to the other keeping the strip from flying off. Nothing more than an optical illusion. So... sorry, but no."
] |
[
"Why do we windmill our arms when we lose our balance?"
] | [
false
] | null | [
"Conservation of angular momentum. If you're standing on the edge of a platform, your angular momentum is zero. If you start wheeling your arms in a clockwise fashion, your trunk will have to start turning in a counterclockwise fashion so that the total angular momentum of your body is still zero. This is what you ... | [
"Exactly correct, except:",
"Dragsters popping a wheelie aren't a good example of conservation of angular momentum because they are in contact with the ground; there is an actual torque applied to the body of the car from the traction force being not in line with the center of mass (the traction is in line with t... | [
"This is true. But then again, so is the case of someone wheeling their arms, because there is torque applied at the shoes, pretty much analogous to what's happening with the dragster."
] |
[
"As there are robotic limbs that can be controlled by the brain, is it possible in many years from now, for brains to be in essence a CPU for a whole mechanical robotic body?"
] | [
false
] | [deleted] | [
"Brains already are \"CPUs\" for a \"mechanical body\". The mechanical body just happens to be squishy, fleshy and often times smelly.",
"But, I believe you're asking if either a) we can slowly replace our bodies piece by piece until we are made of circuits and metal/fibers/plastics and leave the brain (much like... | [
"I think it's ridiculous to imagine that our medicine and technology won't have advanced sufficiently to allow such a thing in a hundred, a thousand, or even a million years in the future.",
"What's to say we'll even be around in 1000 or 1 Million years? It's silly to conjecture that far. In a reasonable time fra... | [
"In addition to this, we haven't actually solved the brain>computer interface issue yet. Yes, we can control robotic limbs \"with our brains\" but really, we're controlling the robotic limbs \"with part of our brain that has a slightly higher electrical potential in an area while we think really damn hard on movin... |
[
"How does the Earth's outgoing radiation attain equilibrium with incoming radiation?"
] | [
false
] | Science has always been a difficult subject for me to understand, and I lack much of an education in even basic physics - which means that my decision to try and learn the science behind climate change through the internet was probably a bad idea, haha. One concept that's been explained to me by several people is that if the Earth had no greenhouse gases, the amount of radiation emitted by the Earth's surface would be in equilibrium with the amount of radiation absorbed by the Earth. But because the Earth's atmosphere have greenhouse gases, most radiation emitted by the Earth's "surface" can't escape into space. And so, instead, there's an altitude in the atmosphere called the "effective emission height", at which outgoing radiation is equal to incoming radiation. In order for the effective emission height to actually emit as much radiation as the Earth absorbs, it has to have a temperature of 255.20 K, which is known as the Earth's equilibrium temperature. But currently, the Earth's effective emission height is only 255.04 K, which means that the amount of radiation emitted from that altitude is actually somewhat less than the amount of radiation absorbed by the Earth. This is why the Earth's average temperatures are currently increasing, and the Earth's temperatures will continue to increase until the effective emission height warms up to the equilibrium temperature. Because the amount of radiation absorbed by the Earth currently exceeds the amount of radiation emitted by the Earth, the amount of thermal energy present on Earth is increasing. Some of this additional thermal energy remains around the Earth's surface, increasing surface temperatures, and some of this additional thermal energy is making its way up through the atmosphere, increasing temperatures at higher altitudes. Once enough thermal energy is added to the Earth to warm the effective emission height's temperature to 255.20 K, the Earth will regain equilibrium and stop warming - so long as the amount of greenhouse gases in the atmosphere doesn't increase (and obviously, the amount of greenhouse gases in the atmosphere increasing, which shifts the effective emission height to a higher, colder temperature, and so we're unlikely to attain equilibrium anytime soon). Or at least...that's how I understood what was told to me. But it's now starting to seem like I'm not putting this together properly. I was recently talking with someone who seems to have a very strong physics background. Early in our conversation, this person said: What happens as the land and oceans get warmer? They will emit more thermal radiation, which will raise the temperature at the emission height until it balances the equilibrium temperature. When this happens, the planet won't be banking thermal energy any more, and and the global mean surface temperature will stop rising. This to match-up with what I just summarized. But later in our conversation, this person said: The Earth doesn't gain equilibrium by using thermal energy to warm the air at a certain height. That's not how any of this works. When I pointed out that this second statement seems to contradict the first and asked for clarification, this person replied that they were unable to explain the distinction between their two statements, because my background in physics wasn't strong enough (and again, it's quite true that I barely understand any basic physics, aside from a scattering of things that have been explained to me on Reddit over the last few months). The person also recommended that I watch , paying special attention to the part about the "adiabatic lapse rate". So I watched the video and pointed out that the instructor makes the following two statements: You heat up the ground. The ground starts transferring that energy back up, some of it through convection, some of it through radiation, some of it through the water cycle. So basically the energy starts working its way up through the atmosphere. Eventually you reach a point where you're high enough in the atmosphere, there's little enough of that gas above your head, the infrared radiation can just escape out there into space...so this is the level of the atmosphere that you have to heat up to that minus eighteen degrees centigrade, in order to get the balance between the energy coming out and the energy coming in. Both of those quotes seem to support my initial understanding of the concepts, and also seem to line up with this person's first statement that I quoted. But when I asked the person again if they could clarify their second statement, they said that they couldn't. They also said: Of course the air at the emission height will have to get warmer before equilibrium is reached. If you want to take that super-literally, then yes, this happens by thermal energy being added to the air. That is literally a thing that happens. What I'm saying is that this completely misses the point of what is involved in equilibrium being reached. I have absolutely no idea what this person is trying to communicate to me, so I thought I'd start a new thread and see if someone else is following what the person is saying. Can anyone with a firm grasp on this topic understand what it is that I'm missing? Thanks! | [
"I don't know if the effective emission height really helps you understand the mechanism at work.",
"The equilibrium condition means that the Earth has to radiate the same amount of energy away that it receives from the sun. This always has to be true- if we radiated significantly less energy than the sun imparts... | [
"Right, the Earth's actual temperature is not constant. And neither is solar irradiance, which are the two big assumptions in the above analysis. ",
"If the Earth's temperature is constant for any length of time then it will be in total equilibrium. The amount of energy emitted will be exactly equal to the amount... | [
"If only it were that simple: ",
"https://andthentheresphysics.wordpress.com/2014/03/05/effective-emission-height/",
"If this model is correct, then the effective emission height rises, but the temperature at the effective emission height does not.",
"Edit: or more specifically, the temperature at every heigh... |
[
"Is it true that when astronouts return they are a couple of inches taller thanks to the effects of zero g on their spinal discs?"
] | [
false
] | null | [
"No. They're taller in space because the cartilage in their spines acts as a spring. In space, there's no gravitational pressure compressing it, so they're taller. As soon as they're back in a normal gravity environment they re-compress."
] | [
"Do they re-compress instantly, or how long does this take?"
] | [
"After getting a good nights sleep, you are a tiny bit taller, as lying horizontal gives those discs a chance to expand. beeblebroxh2g2 comment is correct, but I disagree with his \"no\"... sounds like he confirmed it. It takes time for those discs to re-compress."
] |
[
"If you freeze blood, how long will the DNA in the blood maintain its integrity?"
] | [
false
] | null | [
". DNA on it’s own is a relatively stable molecule owing to the double helix and (in eukaryotes) chromatin structures. A pure, dry DNA sample with no contaminants will survive for quite a while at room temperature and in fact this is how DNA is typically shipped in the mail. However long term DNA preservation is no... | [
"Red blood cells do not contain any DNA,",
"Unless you're a bird, reptile, amphibian, etc. Or you have a strongly regenerative anemia with some residual DNA in it ;)"
] | [
"Almost indefinitely. Source: I pull DNA from ages old blood samples regularly. ",
"Scientists have had very good luck pulling DNA from mammoths frozen in the tundra - you can read \"Bring back the King\" if you have any interest in that sort of stuff. ",
"DNA itself is very hardy. We pulled DNA from a deca... |
[
"When laying a new undersea cable with a plow, how do they not accidentally dig up an old cable that needs to be crossed over?"
] | [
false
] | (Don't judge that it is quora). They mention that they bury the cables under the sea bed around a meter using a . Looking at a of where cables are buried, they obviously criss cross at certain points. How does the plow avoid digging up other cables? | [
"Existing cables are shown on our charts so we stop ploughing 500m before the cable and fly the plough over it till 500m after. From that point we continue ploughing the new cable in. A followup vessel will come along and use a trenching ROV to jet in the cable for the 1 km that is exposed. A guard vessel will usua... | [
"Usually the path and margins on each side that the cable will be layed will be surveyed.",
"\nFYI, There’s thousands of miles of old analog cables that crisscross every body of water imaginable. Sometimes that gets snagged and has to be cut.",
"\nIt’s the live fiber optic cables that belong to someone else y... | [
"Only military cables are secret. In general we want everyone to be aware of the cable location so they don't accidentally drop an anchor in the wrong place. Governments now recognize the importance and vulnerability of subsea cables. Check out ",
"https://www.iscpc.org/"
] |
[
"Why are so many people scared of- or disgusted by spiders? Is it cultural, or is this 'disgust' found in many cultures?"
] | [
false
] | null | [
"It's found in many cultures, but to my knowledge the only animal universally feared by humans is snakes (see ",
"Human Universals",
"). Some cultures make a practice of eating tarantulas, which even their children will fearlessly capture.",
"This, coupled with the fact that any parent of a young child is aw... | [
"About what country/area of the world are you speaking?"
] | [
"Given that small arthropods such as insects and spiders may carry diseases or be venomous, it doesn't seem like a big stretch to assume that people have simply been teaching their kids (even if unconsciously) to avoid them for many thousands of years.",
"In my country, killing a spider is bad luck; having a spid... |
[
"Mixing different temperature liquids, differently"
] | [
false
] | I have 2 cups, one of just boiled water, and one of room temp (cool) water. If I pour one cup into the other, which results in the cooler mixture? hot into cold, cold into hot, no difference | [
"Water has a high heat capacity. If you mixed boiling water with room temperature water then you'd just end up with water with a temperature somewhere in between 100°C and 25°C. The order in which you mix the liquids shouldn't matter. "
] | [
"It should not make a difference HOWEVER practical factors like heat exchange with the room and splashing will cause a difference that depends on the mixing and measuring procedure used.",
"There is a \"correct\" way order to add them, but that's to stop you splashing yourself with boiling water."
] | [
"shouldn't matter.",
"hmmm, I'm going to try and test this and video it.\nMy common sense says you're right."
] |
[
"Would the altitude of a (American) football stadium make a difference in the distance of a kick/pass?"
] | [
false
] | Question came up while watching the Denver Broncos and St. Louis Rams game, curiosity got the best of me so I decided to ask you guys/gals. | [
"Yes, it will. The higher altitude will have a thinner atmosphere and there will be less wind resistance against the ball. ",
"One quick way you could check this would be to see if there are more touchbacks kicked in Denver than in other stadiums. If you look at NFL stats Denver has lead the league in touchback... | [
"Yes, Balls in Denver/Phoenix do travel slightly higher and farther in the thinner air, but the effect is negligible. Far more important is the high altitude effect on the endurance of the players, which gives the home team a distinct advantage (as they are acclimated)"
] | [
".",
"I worked this out a while back on a question on home runs at Coors field. The answer is yes, although the effect is a lot more pronounced in baseball where you're dealing generally longer distances (400 ft home run versus maybe a 50 yard football pass.) Let me work it out for you here:",
"Say you throw a ... |
[
"Is there a satellite that provides a live feed of the earth?"
] | [
false
] | null | [
"Like, is there a satellite for public use where if I drove my car in front of my house, I could see my own house or car? "
] | [
"No unless by accident a satelite happens to line up"
] | [
"You can find the answer with a simple google search / on wiki. Please start there and come back with a more specific question."
] |
[
"While whatching a time lapse from the ISS, I noticed distinctive green lightning from the south part of México. Could someone explain?"
] | [
false
] | Different from the orange and yellow artificial lightning from the world at large and nothing to do (I think) with the northern lights, which are also featured on the video. It appears to be the only place on earh with this kind of luminosity. [0:26-0:30]. | [
"I noticed that before and wondered the same thing. The only possible explanations that come to mind are: There is some thin aerosol or cloud layer there, that has unusual spectral extinction (meaning, it preferentially scatters or absorbs all but the green light); or there is something particular about those light... | [
"I can't see it, but judging from the video the lightning you're talking about at that time is mostly occurring in semitranslucent clouds over large cities. The most obvious answer would be the blue light from the lightning flashes is additively combining with scattered yellow light from the sodium D line at 589nm ... | [
"If it's something related to the light sources, some more info should be somewhere on the Internet. If it isn't, perhaps the phenomenon should be observable in another time lapse (in another region, maybe). Yeah, I vote for more observation, that would discard some of the options given. Thanks for the response."
... |
[
"Since light is also a wave, can you use light to cancel out light as you can do with sound in noise-canceling headphones?"
] | [
false
] | null | [
"Sound is propegated by a mechanism of pressurization/rarefaction of air. The frequency of these cycles, or \"vibrations\" create sound, higher the frequency, higher the tone of sound created. By feeding a signal identical to the original, but 180 degrees out of phase, you can cancel the original. This is known (wi... | [
"Yes absolutely. This is an entire branch of optics called interferometry which deals with the wave interference of light. It is very often used in advanced and precision measurement techniques. LIGO uses interferometry to measure differences in distance smaller then 10",
" meters.",
"Interference is a property... | [
"The magic happens because the fields pick up a minus signs on reflection only in certain places (it depends on the index of refraction of the materials on either side of the bounce)."
] |
[
"How can antimatter annihilation release so much energy?"
] | [
false
] | [deleted] | [
"The famous equation, E=mc",
" is called the ",
"mass-energy equivalence",
" relation. This means that mass has a certain amount of energy, so no energy is lost in the conversion (see more ",
"here",
"). The ",
"full equation",
" relates the total energy to both the rest mass and the momentum."
] | [
"You can also use energy to create mass. One anti particle and one normal particle will be created. It is strange then that the universe have more normal matter than anti matter, wouldnt this imply the creation of the universe created mass out of thin air, violating the rule?"
] | [
"Definitely right. Mass-energy should only be considered \"potential energy\" in a very casual linguistic sense (\"mass has the ",
" to be converted into energy\"). Kind of in the same way that we can consider Chemical energy to be the \"potential\" for a chemical to release energy due to a reaction."
] |
[
"Why does intense physical activity make you want to vomit?"
] | [
false
] | null | [
"The best theories about this are:",
"Exercise shunts blood flow to the skeletal muscles and away from the intestines. This causes peristalsis (the wavelike movement of your intestines) to decrease/stop and the food won't progress. This will cause nausea/vomiting if you have recently eaten or drunk too much. H... | [
"Two quick reasons, though there are additional factors:",
"Build up of lactic acid due to anerobic processes causes acidification of the blood. Acidification of the blood triggers receptors that lead to nausea.",
"The sympathetic system halts digestive processes while performing intense physical activity. "
] | [
"Its been a while, but I believe you're correct with the lactic acidosis, at least that's what I learned in my systems physiology class. I believe it affects the Area postrema of the brain stem which controls vomiting once the buffering in your blood can no longer keep pH balanced at the systemic level. "
] |
[
"If I were a photon and I could see, what would I see?"
] | [
false
] | [deleted] | [
"You would see nothing. Though there is technically no inertial frame moving at the speed of light, as you approach the speed of light your clock slows relative to others. In the limit, your clock wouldn't tick at all so to you, in a way, no time would ever pass between being absorbed and being emitted. You can't s... | [
"The problem is that one of the postulates of relativity says that all photons travel at the speed of light, c, regardless of the reference frame. That means that even if you are moving away from me at c/2, and I shoot a laser beam at you, we will both see the photons of the beam travel from you to me at a speed e... | [
"So... if I understand this correctly... by physics, a photon is technically blind because within the context of the photon, time has stopped and therefore light that I would see can't be seen because that would be a function of time? Or would everything be seen at once kind of like a bright light that never goes a... |
[
"In the most scientifical way, how likely is it to have a zombie outbreak."
] | [
false
] | null | [
"Anything transmitted solely by bites should be relatively easy to deal with. An epidemic of biting attacks would be noticed, and quarantine procedures would be fairly straightforward. It would be stopped quite quickly."
] | [
"Well, not unless you were going to anyway. I think you're ok. "
] | [
"How much something like that spreads depends on the incubation period. If it is minutes or hours from the bite until the person becomes a zombie, it won't spread as well as if it takes several days, because people won't be able to travel as far carrying it. Epidemics where people are killed very fast tend to run t... |
[
"Are there enough nuclear weapons on the planet to kill every human?"
] | [
false
] | null | [
"[Citation needed]",
"The wikipedia article",
" (from which you can follow links to more credible sources if you like) isn't at all so certain about what would happen. In any case, it seems quite unlikely that a nuclear winter would kill every human being. An average temperature drop of -20 C (which is at the e... | [
"For reference:",
"According to the Ploughshares Fund's ",
"Nuclear Stockpile Report",
", there are approximately 19,000 nuclear bombs worldwide (including 10,000 in Russia and 8,000 in the U.S.).",
"And the most powerful American bomb (Castle Bravo) has a payload equivalent to 15,000 kilotons of TNT, while... | [
"There is enough potential nuclear destructive power to alter the environment for the entire planet by blocking out the sun with dust and radioactive fallout, so that anyone who does not have a special, protected long term shelter with years of supplies would not be able to survive. The radioactive fallout would o... |
[
"If elephants had gone extinct before humans came about, and we had never found mammoth remains with soft tissue intact, would we have known that they had trunks through their skeletons alone?"
] | [
false
] | Is it possible that many of the extinct animals we know of only through fossils could have had bizarre appendages? | [
"Trunks do leave visible attachment marks for muscles, ligaments, & such on the skull. However, from osteological correlates alone, it would be impossible to infer exactly what the trunk looks like. In what is perhaps a \"reverse-application\" of this line of reasoning, ",
"trunks can be rejected for sauropod din... | [
"Wow. What a crazy amount of research on this exact topic. Thanks."
] | [
"Except for the fact that we have fossilized webs preserved in amber, so we actually do know about ancient spiderwebs. ",
"Edit: fixing autocorrect"
] |
[
"Why does cold water seem to quench your thirst better than warm water?"
] | [
false
] | null | [
"I seem to recall this question popping up here not so long ago. Even without feeling really hot, a normal healthy amount of human warmth may still drive a little bit of sweat production. In its own small way, a chilled beverage may reduce this warmth and inhibit sweating. The end result is a sense of less need ... | [
"The body handles excess heat through perspiration, which has the side effect of using up the water in the body. Cold water not only replenishes the body's store of water, it also cools it down directly. When you drink water, you get a positive feedback both from thirst satiation and the presence of a cooler substa... | [
"Frequently when you are thirsty it is in some party due to your body attempting to cool down. It could be via sweating out breathing hard. Either way your if your body temperature us high then bringing it down with cold water will bring a feeling of refreshment. Warm water might end up raising your body temperatur... |
[
"Was there any reason for the dial up modem tone that we heard back in the 90s?"
] | [
false
] | That Dial-Up tone you hear whenever you wanted to connect back to the internet. It was a series of very memorable ... noises... so to speak. Was there any significance to this like what those sounds meant? I'm asking this because I remembered there was a period of time we could NOT connect at all and the tones kept replaying in a loop. | [
"Because dial up modems were trying to send digital information over a network made to carry human voice conversations, the modems would have to speak our language to make use of it. That noise you're hearing is the modem dialing into your ISP and then starting a connection. That noise is literally played over the ... | [
"That's right, the data in a dial up connection is sent over the phone line as sound essentially. You'll hear that same kind of sound if you've ever tried calling someone while they were sending a fax. "
] | [
"Also, that ksssssshhhhhh PANG PANG PANG ksssssssssshhhh sound was the modems figuring out what protocol versions were supported. If the other modem didn't respond correctly, it could back down to a slower connection. ",
"I used to leave my modem volume up so that I could disconnect and reconnect if I didn't ge... |
[
"Why do certain foods, notably meats and cheeses, taste differently depending on how finely they're cut or shredded?"
] | [
false
] | null | [
"They dont necessarily taste differently, but you experience them differently. ",
"A small piece of cheese that you can easily chew and taste and swallow would be experienced alot better than an entire cheese wheel that gets all cloggy and hard to chew and swallow."
] | [
"Increased surface area means more interaction with your taste buds. A big chunk of cheese has to be chewed. This turns the once flat piece of cheese into small curdles or chunks. That takes a flat piece with a lot of surface area and changes it to small sphere-ish things with a much smaller surface area to interac... | [
"I’m not an expert, but my take is that exposed meats/cheese oxidize. When meats/cheeses oxidize their flavor profiles will usually change along with the amount of oxidation that has occurred; this is where the gamey flavor of lamb comes from for example. So different ways of cutting meats/cheeses will expose diffe... |
[
"Can you actually gain weight from just a few meals?"
] | [
false
] | [deleted] | [
"People will say that a particular meal caused them to \"gain five pounds\" or that they gained x pounds over the weekend. The scale may actually register a weight gain, but it might not be permanent. They may still be digesting an unusually large meal. The entirety of the meal is still inside them and hasn't be... | [
"What I meant is that you can gain more weight than you eat, if you include the effect of water loading. For each gram of carbohydrate, you store around 3 grams of water. You can gain alot of weight simply by storing water from eating a lot of excess carbohydrates."
] | [
"You are neglecting water."
] |
[
"Why do we say electrons in a metal move around with velocities determined by kT instead of the Fermi level?"
] | [
false
] | It's all over solid state text books that the velocity of electrons in a metal (assume no applied field) is something like root(kT/m) (I don't care about the 2's and/or 3's that I'm missing). This perspective makes sense because it's sort of the amount of energy an electron might get from the thermal bath it's sitting in. But also, from QM, if we keep adding fermions (electrons in this case) to the metal, they'll occupy higher and higher energy states. Even at T = 0, the electrons will have nonzero energy, in particular, electrons at the top will be at the Fermi energy. In this case, the thermal velocity would be zero, but the Fermi velocity can get up near a percent of the speed of light (graphene for example). Clearly this is a huge discrepancy. So, why do we say electron speed is governed by kT instead of the Fermi level? It’s a quantum vs classical issue as pointed out. Dense systems of electrons should go by Fermi energy, sparse systems can use kT. | [
"They're both sort of right. In solid state physics it's important to remember we can't actually solve for the electron's motion. There are 10",
" electrons interacting with eachother and 10",
" nuclei. The 2- body problem is classical is hard enough. So every thing is an approximation. You use the simplest one... | [
"Thank you."
] | [
"The 2- body problem is classical is hard enough.",
"The 2-body problem is trivial. It's the 3-body problem that is so difficult."
] |
[
"Anyone have a conceptual explanation of how fission and fusion works?"
] | [
false
] | null | [
"There is no simple answer or “conceptual” picture. There is a complicated balance of forcing which determine the binding energy of any give nucleus. It just turns out that if you plot BE/A versus A for nuclides near stability, it peaks at nickel-62."
] | [
"Well concepts and visualization work great in introductory physics, but quantum systems are non-intuitive, and not easily visualized."
] | [
"There are lots of different theories of nuclear structure that you could apply to model nickel-62. Most of them are quantum theories (the main exception being the liquid drop model). And in quantum mechanics, you describe things with quantum state vectors."
] |
[
"How does drinking water clear the bad stuff out of our bodies?"
] | [
false
] | Does distilled VS stilled water make a difference? How does it help our skin? Just curious how it actually works inside of our bodies. Always heard that drinking water can flush all the bad stuff out. Esp after a greasy, fat meal. | [
"Always heard that drinking water can flush all the bad stuff out",
"Pop culture has endless theories on how things work, probably because most people don't care to actually learn the biology or realize that biochem processes are exceedingly complex and try to simplify the knowledge."
] | [
"I don't have any opinion on the pancreatitis, but asking for medical advice on Reddit is even in a best case scenario a waste of time. Go see a real doctor, or at the very least (if you don't have access to healthcare) find a reasonably trustworthy source. This could be a good place to start:",
"http://www.webmd... | [
"I've been drinking 1 USgal/day for a few months because I have pancreas issues. (Chronic Pancreatitis) which is miserable. It just seemed intuitive. So I'm wasting my time?"
] |
[
"In regards to \"nitrogen narcosis\", how does the gas we inhale while diving suddenly become narcotic to us at great depths?"
] | [
false
] | null | [
"You need to understand a little about how SCUBA works. You can snorkel at the surface, right? What if you had a 12 foot snorkel, would it work? No, but why? Because the weight of 12 feet of water is squeezing you body. You don't feel it because hey we are made out of water. However, it's more weight than your lun... | [
"Most gasses are lipid-soluble, meaning that they can diffuse into fats, which includes cell membranes. At standard pressure, the amount that dissolves into tissue is negligible, but at higher partial pressures that amount increases and eventually it's enough to interfere with the chemical signaling of nerve cells... | [
"This is spot on the answer i have been searching for. Thank you!"
] |
[
"How long does tap water need to be boiled for or kept at boil in order to sterilise it?"
] | [
false
] | Looking around online and I can't find any sources or scientific information on how long water needs to be boiled for in order to sterilise it. I'm seeing between 1 and 10 minutes? | [
"For clarification, the process you're referring to (Pasteurization) kills a large number of bacteria but absolutely does ",
" sterilize the milk. ",
"Here's an interesting document",
" that shows how many bacteria are allowable in milk products (TL;DR: a lot, as long as they aren't pathogens)."
] | [
"For clarification, the process you're referring to (Pasteurization) kills a large number of bacteria but absolutely does ",
" sterilize the milk. ",
"Here's an interesting document",
" that shows how many bacteria are allowable in milk products (TL;DR: a lot, as long as they aren't pathogens)."
] | [
"Depends on what the water contains. To kill most of living bacteria you do not even need to boil it. If it contains spores, it's the best autoclave it (~121 degrees C) for 10 min, but it reqiures equipment. When you don't have an autoclave, you can go old school and use tyndallization method.\n",
"http://en.wiki... |
[
"How do transitions lenses work?"
] | [
false
] | null | [
"I am an optician and sell them every day but still had to goto web search to get the scientific terms for it.",
"Old glass photochromic lenses were embedded with silver chloride. Here you can see what happens to raw silver chloride when exposed UV light.",
"http://en.wikipedia.org/wiki/File:Decomposition_of_Si... | [
"Well, silver chloride decomposes, naphthopyran only changes its shape (photoisomerization being the fancy word for 'changing shape due to light). ",
"If I'm interpreting it correctly, the UV light is absorbed by the double bond between carbon atoms seen opposite oxygen in the ring. This excites the electrons in ... | [
"The auto-darkening welding helmets I've seen are electrically powered LCD screens. Usually a small solar panel keeps it charged (it requires very little power). It uses a common photocell to determine whether to switch to \"dark\" or \"light\" mode. There's a dial adjustment for that."
] |
[
"Where was all of the condensed matter prior to the big bang?"
] | [
false
] | This has always bothered me, and has made more than one science teachers angry at me when I asked it. But seriously, the big bang theory seems to never address this, or more likely I've never heard an actual explanation. If there was no galaxy prior to the big bang, then where was all the matter that caused the big bang? | [
"The equations describing the space-like separation between points in the standard cosmological model have a singularity at a finite time in the past (t = 0). Our best model right now says that at all times ",
" that time (t > 0), the universe was infinite, but ",
" that time the distance between any two points... | [
"i don't think you know how science works.",
"theories are more than just \"i have an idea\".",
"We can observe evidence for the big bang, that we can demonstrate and view over and over again.",
"It's not the same as, \"3 children saw the virgin mary appear, what a miracle, god exists!\"."
] | [
"God isn't even an hypothesis, since it isn't based in any reliable observations whatsoever. "
] |
[
"Is donated blood cleaned in any way to prevent the spread of disease?"
] | [
false
] | I was watching Blade and that scene where he fell into a pool full of blood and healed himself and it got me thinking. Aren't blood transfusions from multiple donors? Meaning you'd get every single virus they carried combined? | [
"Blood is transfused (out of the donor and into the recipient) by the unit and each unit of blood is only from a single person. Also, it is all screened, in high income countries, anyhow, for a range of infectious disease including (These are what the Red Cross check for, other organizations test for other diseases... | [
"Just an FYI for those who have never donated, in addition to testing, you answer ~50 questions relating to possible disease exposure, and talk about these with someone. Temperature, blood pressure, pulse, iron are also tested pre-donation to make sure everything's normal. I guess you could lie on the questions, bu... | [
"If you know you're going into surgery where you might need a transfusion, you and your family members and friends can donate blood ahead of time and they will set it aside for you, so only your blood will be put back into you.",
"In the United States, you used to be able to sell your blood if you were a rare blo... |
[
"Why does it take so long to develop aids from a HIV infection?"
] | [
false
] | [deleted] | [
"That's an excellent question, and, to the best of my knowledge, we really don't know. The problem is, although we know that HIV causes AIDS, we don't know exactly ",
" it causes AIDS. Or rather, we know the proximate cause -a massive reduction in the numbers of a very important type of immune cell, known as ",
... | [
"Well, clearly it does something like that in some way, directly or indirectly, but it's highly unlikely that it does so \"on purpose,\" so to speak. Those T-cells are its food, it would go directly against the interests of the virus to inhibit production of said food. ",
"Fortunately for HIV (but unfortunately f... | [
"Well, clearly it does something like that in some way, directly or indirectly, but it's highly unlikely that it does so \"on purpose,\" so to speak. Those T-cells are its food, it would go directly against the interests of the virus to inhibit production of said food. ",
"Fortunately for HIV (but unfortunately f... |
[
"Is it possible to quantify an emotion?"
] | [
false
] | [deleted] | [
"Sure, they just handed out surveys during my morning transit commute. On a scale of 1-5, How satisfied are you with the cleanliness of your train?",
"Replace \"satisfied\" with \"happy\" and congratulations, you've just quantified my happiness!",
"Edit: To all the downvoters, poll questions such as the exampl... | [
"You are right. Concerning the pain scales, they often set a certain range where in people can place a dot relatively to the minimum and the maximum. People answer these on intuition."
] | [
"Whereas surveys do contain specific questions for the patient to self-evaluate, they are most frequently accompanied by an array of other questions that address the point obliquely. The overall panel of questions are then used to generate a score that may not match what the patient self-evaluates as. i.e. a patien... |
[
"Why is the twin paradox asymmetrical?"
] | [
false
] | We've heard it a million times, every time relativity is discussed: a twin goes out of the earth for a trip at near-light speeds, and when the ship comes back, the twin in question is much younger than their earthly sibling. The part that confuses me is this: according to classical mechanic laws, a person standing on a train going 50 m/s forward is equivalent to the whole world going 50 m/s in the opposite direction, depending on the frame of reference. So what would happen if instead of the twin in the spaceship accelerating forward, the entire earth (or universe) accelerated in the opposite direction, then accelerated back to the original position, with the spaceship remaining stationary? I mean, theoretically it should be indistinguishable, right? | [
"This is the whole \"paradox\" in the twin paradox. The resolution to be paradox is the fact that the motion of the twins is ",
" symmetric. In order for the twins to meet up at the end of the experiment, at least one of them must accelerate, and therefore ",
" in order to turn around.",
"In the standard form... | [
"Ah, the clever topological twist to the twin paradox.",
"The resolution of the paradox in that scenario is that special relativity is ",
" with the topology you proposed. A flat torus of characteristic length L is constructed by the identifications:",
"t ~ t\nx ~ x + L\ny ~ y + L\nz ~ z + L\n",
"(The ident... | [
"What you have described is the paradox. One would naively think they should be equivalent and they both give different answers.",
"The ",
"wikipedia article",
" gives a good explanation of the resolution."
] |
[
"If the speed of light is the maximum speed an object can move then isn't there a maximum temperature?"
] | [
false
] | From my limited experience I understand that heat comes from particles moving and bumping into each other. The faster the particles the higher the temperature. So since particles are moving arent they bound by the speed of light? And if that's true isn't there a maximum temperature since the particle speed is limited? Or maybe i'm just confused... | [
"Temperature is technically defined as the amount of internal energy/entropy of the system. Now let's just ignore entropy for the moment, as that's a much larger discussion. In the non-relativistic picture you are correct in saying that energy and velocity appear to be linked in a simple manner. E=0.5 mv",
" . Bu... | [
"Agreed. Been on here for hours. I feel like a dumbass, but I enjoy learning these things. "
] | [
"the energy going into mass is a largely outdated concept. What is true is that for massive particles, p=mv is only the low-speed limit of the fuller definition of momentum, p=gamma*mv. Somebody decided to smush gamma*m together and call it a \"relativistic\" mass. But that doesn't ",
" anything physically. It's ... |
[
"Why does albino specimens have red eyes?"
] | [
false
] | I just saw a video of an albino owl and was amazed at the red color of the eyes. Why is it that albino specimen have red eyes? Can you have the mutation of discolored / white body without also mutating the color of the eyes? | [
"The melanin in the eyes are responsible for iris color. Without that melanin present, all that is visible are the veins at the back of the eye, giving it a red appearance. ",
"It's the same reason we get red eye in photos with the flash on: the light passes through the iris and bounces off of the blood vessels a... | [
"To elaborate on sharltocopes answer, Albinos suffer from improper pigment production. This results in an inability to produce pigment in both skin/fur/scales and eyes. So the eyes are red for the same reason that the skin is white. No pigment. "
] | [
"You can also have an animal that has a more specific pigment deficiency instead of albinism (total and complete lack of pigment production), which would make certain body parts, like fur, white without affecting others, like eye color. A blanket term for such animals would be \"leucistic\"."
] |
[
"is one divided by infinity zero?"
] | [
false
] | My mom posed this question to me and I don't know the answer. I would think it would be zero. | [
"For most practical purposes, yes. But the question itself is a bit improper.",
"The term 'infinity' is usually used as part of a limit as a shorthand for a less intuitive formal definition. We can readily say that limit (x->inf) 1/x =0. However, this is just shorthand for saying, \"for all epsilon greater tha... | [
"If you're a scientist, 1/∞ = invent renormalization groups."
] | [
"Infinity isn't a number, but usually when you see it in the context given folk really mean the limit of the expression as the quantity grows without bound. In that case, yes, the limit of 1/n as n grows without bound is 0."
] |
[
"What exactly is aliasing, and what does a nyquist frequency have to do with it?"
] | [
false
] | null | [
"In digital systems which interact with the physical world there are always three stages: signal acquisition, signal processing, and signal output. Signal acquisition is the use of sensors (microphones, cameras, accelerometers, etc.) to obtain a digital representation of a signal of interest, which you then process... | [
"if you picture a sinusoid: you need to catch all the valleys and peaks to get what's going on.",
" what I needed to understand. Thank you hexphreak. "
] | [
"You might find the explanation in the second video ",
"here",
" very enlightening. The first video is also very good."
] |
[
"Having some problems understanding Torque Scientifically. Can someone explain to me how the relationship between lever length and force works?"
] | [
false
] | So we all know that trying to tighten with a bolt with your bare hand is MUCH harder than with a wrench, and it is NOT due to grip. But scientifically, why does this work? tl;dr, if I had a kilometer long indestructible rod, I could probably lift an elephant (or maybe elephants) easily. Why? | [
"Ok. Torque is basically the rotational version of work and Work = Force * Distance. So you can increase work by increasing either force or distance. Same thing with torque. You can increase torque by increasing the force applied ",
" increasing the distance that force is acting through.",
"When you're turn... | [
"Wait, wait! So the work to push the lever, say 30 degrees from the middle vs from the end of the rod is the same? So basically it's like lifting up a huge box of weighs as opposed to picking up the weights one by one? ",
"In other words, it's easier to do but requires the same total work? "
] | [
"It might be easier to think of it \"backwards.\"",
"When you apply force at the end of the wrench, it moves through a certain angle. You exert X amount of work pushing the end of the handle and every part of the wrench is moving through that same angle. As you get closer to the bolt, the actual \"straight line... |
[
"How does signaling through a cable work (e.g, USB)? How can they obtain such high speeds with such great accuracy?"
] | [
false
] | USB 3.0 can transfer up to 5 Gigabits per second, that's 5 billion bits per second. I understand USB works by essentially signaling 0s and 1s through a cable (two cables if we want to get fancy and talk about redundancy/noise cancelling). But I cannot comprehend how a wire can send 5 billion electrical pulses so accurately for such a sustained amount of time? How does it synchronize itself? What if the signal "hiccups" and lags for a nanosecond, then wouldn't the subsequent bit be misrepresented and all the following bits would be incorrectly shifted? If it uses quartz, quartz's frequency is only 32768 Hz, a far cry from 5 billion. Even if we can upscale the signal of quartz by multiplying it by a factor, wouldn't it then be inaccurate overtime? This is only USB. I understand that fiber optics nowadays can obtain rates in the hundreds of terabytes! Wow! TL;DR: 1. How can cables signal bits so fast and accurately? 2. How do we synchronize / error check the signal to make sure there are no hiccups along the way? 3. Is there a theoretical physical limit to how fast we can make these things? | [
"2. How do we synchronize / error check the signal to make sure there are no hiccups along the way?",
"When there's no dedicated clock line in the wire, signals are usually encoded such that there are guaranteed signal edges every now and then for synchronization (so that e.g. a series of all 0s isn't just a flat... | [
"There will always be a chance of a bit error. That fact is simply unavoidable.",
"Let me start by answering how we signal though a cable (wired) or wireless medium.",
"When you boil it all down, we transfer digital information consisting of bits that are either 1's or 0's. We can modulate the data which will e... | [
"How does it synchronize itself? What if the signal \"hiccups\" and lags for a nanosecond, then wouldn't the subsequent bit be misrepresented and all the following bits would be incorrectly shifted? If it uses quartz, quartz's frequency is only 32768 Hz, a far cry from 5 billion. Even if we can upscale the signal o... |
[
"What is happening on the cellular level when second degree burns occur, and why can't the body fully heal them?"
] | [
false
] | And why does a burn continue to feel warm for hours after it occurs? Surely it isn't storing heat for so long? | [
"The distinction between the various ",
"degrees of burns is based on the depth of the burn",
".",
"First degree burns are epidermal burns - i.e. they only involve the outermost layer of the skin. Because the underlying dermis is undamaged, they quickly look red (from capillary dilation), and heal readily as... | [
"If the fluids in blisters is from the capillaries, then why doesn't it look like blood? And do blisters help the healing process, or are they just a by-product of the damaged skin? ",
"And why is the body, still having the DNA that tells it how to make things, unable to replicate the same structure and fully hea... | [
"This paper",
" gives a good description of how the different components of your cells are impacted in a burn. The authors use mathematical modeling to describe the thermodynamics (reaction to heat) of different molecules in a cell (proteins, lipids, carbohydrates, nucleic acids, and subgroups thereof). As ",
"... |
[
"Which DNA, nuclear or mitochondrial, is more abundant in a human body? Has the total quantity been measured or is it only estimated?"
] | [
false
] | Mitochondrial DNA is rather small compared with nuclear DNA but there can be up to 1,500 mitochondria in a cell. Their number also varies in tissues and nuclear DNA is absent from red blood cells for instances. Perhaps some other cellular organelles have also some DNA. | [
"So far, DNA has only been identified within the nucleus and mitochondria. The human genome consists of 23 pairs of chromosomes within the nucleus that contain a total of ~6 billion base pairs. Mitochondria can have a range of 1-15 molecules of DNA where each molecule consists of ~16500 base pairs in any given huma... | [
"A human cell averages ",
"100 mitochondria",
", and each mitochondria averages 5 mt genomes (each 16569 bp in length). Thus a cell averages just over 8 million bps of mtDNA. ",
"A diploid human nuclear genome (present in nearly every human cell) contains around 6 billion bps (slightly less in males; slightly... | [
"What about bacterial DNA?"
] |
[
"If Dissociative Identity Disorder arises during early life when major skills are learned, could one personality learn a skill while another has no clue about it?"
] | [
false
] | Say a child develops DID before they reach kindergarten or so. If one personality is dominant during the time the child learns to read and write, would the other personality(s) know how to read/write? Or are knowledge and skill sets entirely compartmentalized? | [
"In short, yes. Sorry for how delayed this response is. I have DID. An example that relates to what you are asking about: I used to be quite good at viola. Haven't played in a couple years. However, I played in a quartet with three of my cousins at my grandfather's funeral a couple days ago. I and one of my alters ... | [
"In some people they do. I get the impression that Guardian ages with me, but Little One and Melody are stuck at their particular ages.",
"And yeah, that's pretty much what it is like! Some people have a literal \"head space\" that helps them to with communicating between alters, etc. If such exists with my alter... | [
"Interesting. So the alters, as you say, are aware of what's going on and can take over at any time if need be? Is there any dominant alter generally agreed upon by all?",
"And does that mean that Hollywood's version of DID where a person can not even realize that they have it actually not exist? Or is that just ... |
[
"Does any organism's hair, other than humans, go white with age?"
] | [
false
] | I was looking at my dog and though to my self "I've never seen a pets hair grow white when it got older". Does this phenomenon only occur in humans? | [
"Sure, ",
"gorillas",
" and ",
"golden retrievers",
" both have fur that lightens as they age"
] | [
"it's fairly obvious on black labradors' muzzle, here's a ",
"young one",
" and an ",
"older one"
] | [
"Thus the term \"silverback gorilla\" for describing a older, male gorilla."
] |
[
"Are Wormholes a proven fact?"
] | [
false
] | I ask this in the light of Interstellar. I know black holes are a thing, like we have seen it happen and I've heard about wormholes my whole life and how they can bend time and space. But is that actually true? Or are just we still trying to get hard proof (I know we've never actually sent anything through what could be considered a 'wormhole')? | [
"Wormholes are purely theoretical at this point. We have no reason to believe they exist outside that the mathematics supports them under very particular circumstances."
] | [
"I thought so. Thank you for clarifying. "
] | [
"It should also be noted that even though there are theoretical models in which you can get wormholes, there are lots of problems with such models. Despite the possibility that comes up when you naïvely do the mathematics, many physicists believe that these objects are non-physical and could not occur in nature—the... |
[
"Can the air become so humid a human can be hydrated from it alone?"
] | [
false
] | null | [
"Or would you drown?"
] | [
"To really make sure it stays put, the partial pressure of water in air needs to be equal to the vapor pressure of water in your body.",
"Relative humidity is the ratio between the partial pressure of water vapor in the air and the vapor pressure of liquid water at that temperature.",
"If it is 37 Celsius outsi... | [
"So then another question would be, do you have to ingest water to hydrate? Or can you just absorb it from the atmosphere. If you can absorb it through the air, then there's probably a point of humidity where you start absorbing enough water, and then another point where you start drowning, and then if the drowning... |
[
"If I'm in polluted air or there's an awful smell, is it better to breathe through my nose or my mouth, to have as few molecules reach my lungs as possible?"
] | [
false
] | null | [
"It honestly depends on what is in the air. Is is particles or chemicals? For larger particles (think dust) , breathing slowly through your nose would be best. Your nose is built as a rough filter. ",
"For a chemical, think paint thinner or another solvent, it wouldn't matter. You need specialty air filters to re... | [
"For respirators, you would still need the correct cartridge for protection. ",
"More importantly: An old gas mask may not provide protection against anything especially if the cartridge has been opened for a while, more than about 30 days. The cartridge is often filled with charcoal and that stuff is always abso... | [
"I worked with respirators for a while, where exactly did you get the 30 days rule? As far as I know the charcoal is just fine unless some adsorbents are getting through it in high concentrations, such as chemicals which undergo physisorption (for chemical sorption, which is necessary to remove volatile chemicals w... |
[
"Why is it that a bad night of sleep makes my *everything* hurt?"
] | [
false
] | [deleted] | [
"yeah, my google-fu failed me too. I thought about that, but even if I spend 8 hours in bed, just laying there, still sore when I get out of bed with the alarm if i didn't fall asleep.",
"Thanks for trying though!"
] | [
"Hmmm... What about the possibility of your brain only starting the repairing when it's on autopilot? Aka just your subconscious working."
] | [
"Hmmm, I tried googling it, but I didn't find anything pertinent in 50 seconds, so my guess is that your body goes into a full on repair mode while you sleep so your muscles can regrow, joints can relax, etc. and when you don't get enough sleep, the process isn't completely finished and it still hurts. Kind of like... |
[
"How is it that electromagnetic waves can travel through space without needing a medium? If they are able to do so because they are also particles, then why describe them as waves at all?"
] | [
false
] | null | [
"We know we can feel electric forces and magnetic forces at a distance. The concept of a field is the classical way to explain how these forces can work, since we need some way of describing the rules for how much force you feel as you move relative to a magnet or charge. ",
"Now, if someone moves a magnet or a c... | [
"Electric and magnetic fields oscillate perpendicular to each other at the point where they meet they push each other and hence propagate without any mediums need.",
"Even in a \"perfect vacuum\", i.e. barring quantum fluctuations, all fields are present. Their field values just are zero, corresponding to no part... | [
"In fields, a wave is a technical abstraction of a probability distribution.",
"You're thinking of wave ",
". A wave ",
" in quantum mechanics is a quantity that when squared gives you a probability distribution.",
"a ",
" is a change in amplitude of a particular field. In a water wave, the amplitude of... |
[
"How can gravitational waves be measured using light (optical path distance), when the space itself (including the light) is stretched?"
] | [
false
] | I'm sure I'm missing something here. It seems like you're measuring the length of some line of space with a rubbery ruler. When the space is stretched, the ruler is also stretched, so you're not able to actually tell the space is any bigger... Does it even make sense to talk about space being stretched? What is the space being stretched relative to? | [
"A beam is split into two beams that run orthogonally to each other (at 90 degrees), to a separate mirror and back. If the beams combine and cancel each other out, the two distances are the same.",
"Any variation in the distance causes the waves to not completely cancel out, and the resultant signal is a candida... | [
"You're absolutely right about rulers stretching with space - by itself, a single ruler could never measure any distortion in space, for the reasons you mention.",
"The trick to making such a measurement is to compare two different rulers in areas of space with different amounts of stretching. This is what LIGO ... | [
"The speed of light is the same in all reference frames. So if you sit at the laser beam junction, the time it takes for light to travel to the mirror actually depends on how stretched or squeezed the distance is. "
] |
[
"How does fluoride ion (HF acid) hydrolyze amides and esters, why is it so corrosive?"
] | [
false
] | [deleted] | [
"Shamefully you stumped me and I had to go look in Housecroft and Sharpe to figure it out! You probably know most of this, but to reiterate...",
"The Pka value for HF, as you rightly say, is high(ish), suggesting low dissociation in aqueous solution. The reasons for this are two-fold:",
"A good spontaneous reac... | [
"Thanks for your reply! The problem is with the convention that we have set up. It isn't that HF is a weak acid, it's that it is a weak acid IN WATER. Because we have used water as our standard we also have large entropic effects to consider, it magnifies the entropic cost of making the resulting F- ion, which real... | [
"Thanks for your reply! The problem is with the convention that we have set up. It isn't that HF is a weak acid, it's that it is a weak acid IN WATER. Because we have used water as our standard we also have large entropic effects to consider, it magnifies the entropic cost of making the resulting F- ion, which real... |
[
"If a 10w LED can output the same amount of light as a 100w incandescent, where does the added energy output from the 100w bulb go? Heat? If the full answer is that the additional 90w is output as heat, then is that output at the same efficiency as if you had a 90w electric heater?"
] | [
false
] | The bulb obviously wasn't made to emit heat, it was made to emit light, but the heater was made with the sole intention of outputting heat. So, does the efficiency of both match? | [
"The extra power is definitely lost as heat. And the resulting heat would be produced as efficiently as that produced by a resistive electrical heater.",
"Now... that's not the only type of home heating, and there are some complications as well. A heat pump will warm a house more than twice as much for the same... | [
"Not exactly. Incandescent bulbs put out two types of heat, local convective heat within the bulb which is what makes it hot to the touch, and infrared much like a heating element. Infrared is radient heat and is more desired than convection as a heating source. \nMore to the point: The latent heat of lighting isn'... | [
"Even a heater will not be 100% efficient because there might be sound or light or other energy released.",
"For example, your toaster might hum as the resistive elements heat up. This is sound energy which is not going to toast your bread. You can also see the elements, which is infrared, not all of which is goi... |
[
"How do plants like lemon trees and chilli bushes hope to spread their seeds and multiply?"
] | [
false
] | I ask because I was under the impression that that plants evolved fruit to be appealing to animals who would consume them and the seeds within. However with really bitter fruits like lemon and the spicy chilli, how in nature would these plants get animals to eat their seeds? | [
"Capsaicin does not affect birds. Hotness in Capsicum plants actually helps them spread their seeds because it makes them unpleasant for mammals, but still tasty for birds.",
"Moreover, you should keep in mind that the fruits you bring up are human-made cultivars, and they are often very different from their wild... | [
"The biggest thing that has changed by human cultivation of chili peppers is size. The wild varieties are small, blueberry-sized fruits and tend to be pretty spicy, encouraging distribution by birds. Over time humans have bred chili peppers to have less heat and be much larger than their original fruits."
] | [
"This is tangentially related to this discussion, but it's a cool thought I read in a book about foraging for wild edibles once.",
"The very first chapter, the author spoke about how people tend to think of wild plants as \"poisonous\" or \"not poisonous,\" but that distinction appears silly when we look at domes... |
[
"Are there illnesses for which bloodletting actually improves a person's condition?"
] | [
false
] | In the modern practice of medicine, are there genuine applications in which bloodletting is still regarded an effective treatment or even the most effective method of treatment? | [
"Bloodletting is used today in the treatment of a few diseases, including hemochromatosis and polycythemia; however, these rare diseases were unknown and undiagnosable before the advent of scientific medicine. It is practiced by specifically trained practitioners in hospitals, using modern techniques, and is also k... | [
"In addition to the haemochromatosis mentioned here, bloodletting is also an effective, but seldom used treatment for one more condition. In heart failure with acute intravascular volume overload, the quickest way to relieve this is by letting a few hundred ml of blood. But normally diuretics and CPAP carry the pat... | [
"Do you consider injury as a type of illness? \nBloodletting with leeches is sometimes used in treatment of replantation of digits after accidental amputation. ",
"Caution, some explicit photos of severe hand wounds in the article:\n",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4082525/"
] |
[
"How do the doctors figure out a prescription for baby glasses?"
] | [
false
] | I've seen a lot of videos of babies getting glasses. How do the doctors figure out what prescription the baby needs? As an adult, there's a lot of guess and check in getting my prescription right, and they need continuous feedback from me. Is it a less exact prescription for babies? I know the machines they use before the guess-and-check get the prescription somewhere close. | [
"There is a machine that can actually get your prescription exact, it shines a light in and measures how it comes out, they tend to not use it on adults because with feedback it's easier to use the current method.",
"There is also a form, wherein you use special cards to attract their attention, with smaller and ... | [
"I've never heard of the brain wave machine, but autorefractors that measure how infrared light is focused on the retina as the eye looks at an image are common. They're often used for adults, too (this is the machine that you look into with the picture of a hot air balloon or house at the end of a road that goes i... | [
"Just curious where you got this information. A baby brain wave machine for eye testing? 🤔"
] |
[
"If C is the fastest speed an object can travel, how fast are objects going relative to each other if they accelerate at .999 C in opposite directions?"
] | [
false
] | [deleted] | [
"I'll answer this for two objects moving at a velocity of 0.999 * c ; object's can't accelerate at a speed, since acceleration is a rate of change in speed. The velocity addition formula for relativistic speeds is: ",
"s = (v + u) / (1 + (v*",
"u/c",
"For objects moving towards one another. Notice that, for l... | [
"To clarify, that velocity transform equation can be found in any intro university physics textbook, and is a result of Einstein's special relativity."
] | [
"For the powers, you have to put what you want to become superscripted in parenthesis. like this ",
"(v*u/c^(2))",
", which displays like this: (v*",
"u/c",
")",
"If you don't, it displays like this (v*",
"u/c",
" with the closing parenthesis also superscripted, because markdown ends the superscript o... |
[
"If you were to throw a paper airplane in a vacuum would it fly or fall?"
] | [
false
] | Would if fall straight down because of gravity? Or in space would it just float there where there is no gravity? | [
"It would trace part of a parabola"
] | [
"what these people are trying to say to you is that throwing a paper airplane in a vacuum would be exactly like throwing a tiny ball in a vacuum."
] | [
"Apollo 15 Hammer and Feather Drop"
] |
[
"If the Earth had 2 moons."
] | [
false
] | null | [
"Here's a collection of relevant AskScience posts (in no particular order):",
"How would multiple moons affect a planet's tides?",
"If Earth had a second moon, how would it affect the tides?",
"Pretend we have a second moon, basically identical to our current one, orbiting perfectly on the opposite side of th... | [
"The entire approach to coastal living would have to change, this is assuming that the the new, second moon, is in addition to our current moon. If our current moon were split in two it would depend on their distance from the Earth. The second moon would have to be further out so as not to be pulled into the clos... | [
"In a situation like that would you see towns like New Orleans and Copenhagen get flooded?"
] |
[
"What do you use to de-ice your -80C fridge? (X-post from r/biology)"
] | [
false
] | I used to use a hammer and the dinky scrapper that comes with the freezer, but is there a better way? What are some lab hacks that you use to keep your freezer from icing over? Our lab only has one -80C freezer. So it's not feasible to transfer the stuff to a second freezer and defrost. :( | [
"Eeee, don't use a hammer and scraper, it's way to easy to rupture a coil.\nI'll sometimes scrap areas where I know there are no cooling coils, but I never hammer. You don't want a shelf size piece of ice to suddenly move and kink something.",
"Looking over the ",
"r/biology",
" thread, I agree with everyone ... | [
"we just had an issue with ours where ice had collected between the rubber gasket (think that's what it's called) and the frame so the door wasn't closing properly and we never got to -80C. the fridge guys came and looked and advised that you should defrost EVERY YEAR to prevent issues. also said once you see act... | [
"haha. i think those were troll posts. But I'm still thinking of just using a scraper and occasional hammering instead of moving everything."
] |
[
"Why do the stars appear fixed?"
] | [
false
] | In other words, I would think a bunch of unrelated stars at all sorts of distances (~4 to 8,000 LY for eye-visible stars) might change position relative to each other on a nightly basis. Are we in some sort of larger reference frame all together moving around the galaxy? | [
"The stars appear fixed because humans don't live very long and distances involved are mindbogglingly huge. When traveling along the highway, the median speeds by, the telephone poles move more slowly and the distant mountains hardly move at all—now consider the stars lightyears away. Those stars are indeed going a... | [
"Most of the stars we are noticing are much bigger than the sun and not very close. Those stars are in our galaxy and relatively close, like in our arm of the galaxy. Like our sun they're shifting about relative to us and the stars near them. The reason they appear fixed is that their vast distance from us mostly ... | [
"The yearly motion of Earth around the sun changes the apparent relative positions of nearby stars in the sky by a very small but measurable amount. This ",
"parallax",
" effect can be used to measure the stars' distances. It's completely indistinguishable to an unaided eye though."
] |
[
"Are there some good alternative explanations or hypotheses in place of the dark matter theory?"
] | [
false
] | The fact that something like dark matter exists in such a large quantity that is yet undetectable seems less likely to me than an alternative explanation like, maybe the laws of physics act differently in space in different places or this extra mass I see made up of a bunch of tiny black holes everywhere | [
"The fact that something like dark matter exists in such a large quantity that is yet undetectable",
"Dark matter is not undetectable, or we wouldn't know about it. Multiple ways of detecting it all give the same results. We see the gravitational influence of dark matter on the motion of stars in galaxies, in t... | [
"Sure, tons. Everything from MaCHOs (numerous rogue planets, brown dwarfs, or black holes) to gas clouds to modified gravitational mechanics.",
"The thing you have to understand about the dark matter theory (i.e. cold dark matter in the form of WIMPs) is that it is the survivor. Every time scientists have conduct... | [
"/u/fishify",
" gave an excellent response, but perhaps didn't really answer your question. The answer is \"yes\", there are alternatives. The most common is MONDs (Modified Netwonian Dynamics), which basically suggests that maybe the behaviour of gravity is a little different at very small accelerations:",
"... |
[
"When comparing the costs of developping, maintaining and operating reusable launch systems with those of single-use systems, are reusable systems worth the effort and if so to what extent?"
] | [
false
] | Not too sure if the tag should be Planetary Science or Economics | [
"http://www.zmescience.com/space/spacex-reusable-rocket-100-times-cheaper-0432423/",
"According to SpaceX’s Elon Musk, $200,000 in fuel and oxygen make up just 0.35% of his firm’s launch costs. The rest is in their $56.5 million Falcon 9 rocket."
] | [
"To expand on this: rocket flight is ",
" rough on the rocket, so with past+current technology, even if we do recover the rocket, we need to spend huge amounts of money banging it back into shape, replacing tons of components, running diagnostics on all the parts, etc., before its next flight. The space shuttle, ... | [
"Sure, but, ironically, with cheap lift comes the ability to lift ",
", making it cost-effective to attempt efforts in space that may lead to sustainability and a future in which we don't have to lift everything the astronauts need to survive. ",
"You make SpaceX sound like a marginal proposition, and that m... |
[
"Does there exist an animal with naturally polarized vision?"
] | [
false
] | [deleted] | [
"Some cephalopods can distinguish light polarization, although the purpose of this ability is not quite clear",
"This is not quite the same thing that happens in polarizing sunglasses, though. The sunglasses block all light except that which has a particular polarization. The cephalopod eyes do not block any ligh... | [
"Many arthropods, including most flying insects, are able to detect polarized light. ",
"In insects, there are usually two or three ocelli on the 'forehead' of the insect, in between the compound eyes. These are sensitive to polarized light, and are thought to be involved in navigation and predator detection. ... | [
"Humans ",
"can detect",
" polarized light too, though the effect is weak and probably doesn't serve any evolutionary purpose."
] |
[
"How did Mars get sand dunes?"
] | [
false
] | posting here from seeing the image on Just wondering.. I thought it was through erosion? Water, and lots of it? Or are there other ways? | [
"Mars has an atmosphere, and therefore wind, just like Earth does. This wind carries sand particles, and these can, under the right conditions, form dunes. This image ",
"http://earthsci.org/education/teacher/basicgeol/windes/winddepos.gif",
" somewhat shows the process, in that a natural barrier (e.g. a rock) ... | [
"Erosion can happen via wind.",
"Think monument valley (",
"http://parkerlab.bio.uci.edu/pictures/photography%20pictures/2009_09_14_Monument%20Vly_SELECT/IMG_3402_tweak.jpg",
").",
"IF Mars had water in the past, some erosion may have happened via water as well. "
] | [
"It is due to the wind, although the very weak atmosphere changes the physics a bit compared to dunes on earth. Can't find a peer reviewed link, but ",
"here is a nice discussion",
" from a radio interview."
] |
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