title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Do puddles experience tides as well?"
] | [
false
] | Just that. Is one side of the puddle microscopically higher than the other based on where the moon is? | [
"Tidal forces exist everywhere. But it's not going to make much of a difference on a puddle because it's all in pretty much the same place, so it's either low gravity or high gravity. Not like the oceans, where they get low gravity in some areas and high in others so the water moves around. If you looked ",
" clo... | [
"That's what I thought, that one side will be ever so slightly lopsided, like by a single molecule."
] | [
"Technically yes, but not very much.",
"Tides are caused DIFFERENCES in gravity, not the strength of the gravity per se. Gravity becomes weaker as you get farther away from thevsource.",
"The tides occur because the difference in distance from one side of the earth to the other is significant compared to the d... |
[
"How quiet is space?"
] | [
false
] | [deleted] | [
"\"Sound\" in this context is defined as the vibration of air waves (or, more technically, vibration of matter.)",
"Since actual \"space\" has no matter, there's nothing to vibrate, so you have absolutely no sound."
] | [
"So what you are saying is that... \" In space no one can hear you scream\""
] | [
"I think I just derped... Yeah it's a shockwave. It's created by the rebound of the core collapse and moves through the vacuum of space and the ",
"ISM"
] |
[
"For the biology guys: How does the body destroy sickle cells/defective red blood cells?"
] | [
false
] | Or how does it detect their defective nature? Is it by their obscure shape, or by lack of oxygen carrying capacity? Thanks! | [
"Most irregular or damaged blood cells are detected and phagocytized (consumed) by specialized endothelial cells in the spleen. If there are a lot of irregular erythrocytes or if the spleen is damaged, then a high proportion of ",
"Howell-Jolly bodies",
" will be visible in a blood smear stained with Wright's s... | [
"There are a lot of things in biology that are adaptive for one reason and maladaptive for another. Sickle cells are definitely defective at carrying oxygen and not clotting; the only reason the disease still exists in our population is because it's adaptive for exactly one thing, which is resistance to Plasmodium... | [
"Sickle cells are not necessarily defective.",
"In fact, there is considerable evidence that it is a human adaptation in response to the malaria parasite. Sickle cells are more fragile, and they lose structural integrity when plasmodium attempts entry.",
"Source:\nAidoo, M., Terlouw, D. J., Kolczak, M. S., ",
... |
[
"Why do humans sometimes look upwards when trying to think or remember things?"
] | [
false
] | null | [
"Great question, and the answer that usually comes up is ",
": neuro-linguistic programming. Psychologist Paul Bakan proposed the theory in the 1970s that lateral eye movements (LEMs) are automatically triggered by the type of thinking we do. Trying to recall visual imagery, like the layout of a house, fell under... | [
"Very interesting. That also could then be related to why some people turn the radio volume down when trying to spot a house number or street name. It's like some pseudo-subconscious way to lessen external stimuli to better concentration."
] | [
"That's one of the problems with some people with sensory processing disorder like me. It's like the volume of the world is turned to 11. We learn to tune out the sound but sometimes turn down everything so you need to work harder to get our attention. "
] |
[
"Does the universe have a net charge?"
] | [
false
] | Bases have extra electrons and thus a negative charge, while acids have extra protons and thus a positive charge. Thus, if you have more acid than base, you have more protons than electrons and thus a net positive charge. But put that in an even larger amount of base, and then there are more electrons than protons and ... | [
"The fact that gravity dominates over large distances seems to indicate that the net charge is zero or very close to it. Electrostatic interactions are about 10",
" times as strong as gravitational interactions, so if there was a charge imbalance it would change cosmic structure. There are other reasons to believ... | [
"No. There would be enough energy to send particles flying everywhere."
] | [
"I have a question not directly related to OP's question, but I don't want to start a new thread just for it:",
"If a gold atom and an anti-matter iron atom collides, would they annihilate each other and leave behind an iodine atom?"
] |
[
"Why is it possible for people to have the same fingerprints and what is the probability?"
] | [
false
] | null | [
"What is a case of two people having identical fingerprints?"
] | [
"I’m not sure exactly but I remember a while ago reading that someone was getting fingerprinted and he had a 12 point similarity as someone who’s been convicted. "
] | [
"12 matching points does not mean identical. "
] |
[
"Why do cats ''meow''?"
] | [
false
] | Where does it come from? ..And why are they so cute/ appealing when observed by a typical human? Or is there an other reason for cats being a large part of internet-culture? | [
"Apparently, they do it for us.",
"From ",
"ASPCA",
":",
"*The cat’s meow is her way of communicating with people. Cats meow for many reasons—to say hello, to ask for things, and to tell us when something’s wrong. Meowing is an interesting vocalization in that adult cats don’t actually meow at each other, j... | [
"Cats meow to communicate with humans. The sound mimics that of a crying human baby. ",
"http://www.sciencedaily.com/releases/2009/07/090713121348.htm"
] | [
"I recently read an article about how when cats purr and emit the low note we hear, they actually also make a high pitched note at the same time that evokes a very empathetic response in mammals.",
"Clever girl"
] |
[
"Could we ever build an optical/light microscope that could see atoms?"
] | [
false
] | With a big enough lens, could we do this, or would it not be possible? A problem I see with this not working is I assume that atoms aren't much bigger than photons? I don't really know how big photons are, but I assume that if they are at least close to the size of atoms, we wouldn't be able to see anything. Or do I... | [
"This is true for light microscopes, however electron microscopes have become advanced enough to see the silhouettes of multitudes of atoms in materials. This is not to say that you can see the sub-atomic particles inside an atom yet, but rather fairly large clusters of atoms in materials.",
"Still, the question ... | [
"This is true for light microscopes, however electron microscopes have become advanced enough to see the silhouettes of multitudes of atoms in materials. This is not to say that you can see the sub-atomic particles inside an atom yet, but rather fairly large clusters of atoms in materials.",
"Still, the question ... | [
"For a microscope, resolution is limited by the wavelength of light, not the size of the lens.",
"So, you could make a light microscope that could see atoms, if you use light that has very short wavelengths (x-rays). ",
"Current research in this area uses x-rays with very narrow beam size and then scans the ... |
[
"How, and why, do ants make new hills?"
] | [
false
] | I am under the impression that each ant hill have only one queen. Can queen ants give birth to another queen? And why would they leave the hill? | [
"An \"anthill\" is just one extension of an ant hive that reaches the surface. The hills form when dirt is left by the entrance of the hills.",
"https://en.wikipedia.org/wiki/Ant_colony",
"Additionally, some species of ants have more than one queen per colony (polygyne), while others have one per colony (monogy... | [
"If I find an ant say on the second floor of my house and I bring it outside some hundreds of feet away, will the ant survive? Will it be able to find its home?"
] | [
"IMO doubtful, but it might depend on species. The ant would need to find food and water until it could find a scent trail, probably left by a scout from the colony, before being eaten by a predator or succumbing to elements. "
] |
[
"How do researchers tell the difference between the fossils of a small dinosaur species and the fossils of a baby dinosaur?"
] | [
false
] | null | [
"The skeletons of babies and tiny adults of any species look different (in general). Basically, a baby isn’t just a scaled down adult. ",
"For example, we see similar baby vs adult characteristics in chimps and gorillas as we do in humans, due to our close relations. The same can be said for mammals in general. T... | [
"Here’s a fascinating example ",
" of the similarity between chimpanzee and human infants"
] | [
"Thank you!"
] |
[
"Why does a snapping turtle's heart and body continue to function for many hours after death?"
] | [
false
] | A recent catch brought up this question which Google provided no sufficient answers.... upon decapitation, snappers seem immortal. For example, with the heart completely out, it continued to beat for 5 hours on its own. The head continued to bite, and the body would aggressively respond to the cleaning. For example, th... | [
"I know from laboratory experience that amphibians are the same way, as are a lot of other reptiles. And mice to a much smaller degree.",
"The why however is a little outside my area of expertise, I would surmise it has to do with ion concentration in their blood and tissue that promotes heart beat and keeps ner... | [
"I ate it."
] | [
"Why would mammals have such a lower ion concentration?"
] |
[
"If a rocket is tied to a string 1 lightyear long, and I am holding the other end, when will I feel the pull and how far will the rocket be?"
] | [
false
] | Not looking for a numerical answer, more of conceptual answer. Change whatever variables to whatever values to make calculations easier. Rocket is travelling at constant speed, directly away from the holder of the string, string is not stretchable, etc. | [
"If I have a string that's one light-year long...",
"If you had a rod that was one light-year long and pulled it from one end, would the other end move instantly?",
"If an object which has a length supersceding the distance of a light year exists...would moving it in the direction of it is length effect change ... | [
"exactly. Once the rocket reaches 1 light year and the string becomes taut then it will take ",
"1ly / (",
") ",
"amount of time to pull the person holding it along. The rocket will be more than 1ly away."
] | [
"For questions like this, you remove variables like \"movement of the earth\" and whatnot. They complicate the question, and don't really add anything to the answer."
] |
[
"Do DNA tests that aim at finding out information about your ancestry really help in pointing out what ethnic groups you are closely related to?"
] | [
false
] | [deleted] | [
"Yes, they can have pretty high geographic resolution, depending on tons of factors. ",
"This paper",
" is a popular best-case scenario, where genetic markers were used to pinpoint (pure-bred) Europeans more or less ",
"right down to the country",
".",
"However, that specific test you're looking at is pre... | [
"Can they tell where you're from based on mitochondrial DNA? I think I remember seeing (a long time ago in undergrad/high school?) a map of the world that had specific mtDNA genes plotted over it."
] | [
"Only through your maternal lineage. That is, only your mother and your mother's mother and your mother's mother's mother...",
"That's because mitochondria, which have their own little genome, are inherited only from your mother. The opposite is true of the Y chromosome. This leads to interesting results like the... |
[
"Why does dirt stick to my car?"
] | [
false
] | [deleted] | [
"feel I can successfully rule out static electricity, since I drive a '96 Saturn SL2, which has an entirely plastic body",
"Go to a playground with a plastic slide and try dumping sand down the slide, then bringing your finger close to the slide. You will experience a slight electric shock (and people will look a... | [
"So is it always static electricity then? Even in instances such as ",
"this?"
] | [
"That looks like dust settled on the roof of the car then washed onto the sides in a rainstorm. Gravity can also cause dust to settle on cars."
] |
[
"How does light distortion affect calculations of distance between heavenly bodies (in light years)?"
] | [
false
] | Just finished watching Cosmos, Episode 4. If we're able to see the sun's light before it is actually breaching the horizon because of distortion, couldn't various other types of distortion in the universe totally throw off our calculations of distance to that planet, galaxy, etc.? I imagine it being the same way a stra... | [
"The Sun's light bends around the horizon because of atmospheric refraction. We have a good understanding of how atmospheric refraction affects the apparent position of objects-- we have to, to be able to observe them near the horizon. So this effect can be corrected for. Outside of the atmosphere, there is nothing... | [
"And we are pretty confident we know how to factor that in our calculations? That seems so amazingly difficult to me! "
] | [
"It's only a very small angular deflection. Arcseconds or less, in most cases.",
"The overwhelming majority of things on the sky are exactly where they appear to be."
] |
[
"Why can't you donate blood if you've lived in an area where Chaga's disease occurs for more than five years? Isn't it possible to screen your blood to see if you have it?"
] | [
false
] | I'm interested in donating blood, and have checked my local hospital's website for instructions on how to do so. They have a few guidelines on when one should wait before donating, such as for three weeks after having visited an area where malaria is common, etc. However, it also says that if one has lived in Mexico, S... | [
"Blood donations in all endemic Latin American countries undergo Chagas screening, and testing is expanding in countries, such as France, Spain and the United States, that have significant or growing populations of immigrants from endemic areas.",
"From ",
"Wikipedia.",
"I'm under the impression that they get... | [
"*\"Human American trypanosomiasis, or Chagas disease, has two forms, a trypomastigote found in human blood and an amastigote found in tissues. The acute form usually goes unnoticed and may present as a localized swelling at the site of entry. The chronic form may develop 10 to 20 years after infection.\"......\"Wh... | [
"To make testing more economical in the U.S blood samples from several donors are generally pooled and tested. If one of them fails, than all the samples are discarded. Therefore it makes sense to avoid high risk samples, as it has a high cost. "
] |
[
"How do our bodies produce heat?"
] | [
false
] | null | [
"One of the cooler ways by which is produced in our bodies is oxidative phosphorylation (respiration on a cellular scale kind of) that takes place in the mitochondrial organelle (a tiny little powerhouse that sits in our cells). It uses a long system of enzymes and proteins to make ATP (an energy currency unti in o... | [
"In a really basic sense, by burning our food. It's slower and more controlled than if you tossed some bread into a fire, but your body breaks down the chemical bonds in the food we eat, and some of the converted energy is lost as heat. This heat, being generated in small amounts by all of your cells, is ultimately... | [
"Virtually every chemical reaction that takes place in your body generates a small amount of heat as a by-product. The body has certain biological processes that it can arbitrarily activate just to generate 'waste' heat."
] |
[
"Why do we use nanometers instead of frequency to define the colour of light in photographic colour theory?"
] | [
false
] | Today I had my mind blown when I read that when a light ray travels through a medium of thicker density it slows down. As well it has it's wavelength shorten by a reciprocal amount. But because its frequency does not change, it's colour is unaffected. So in short red, with a wavelength ~700nm would travel through glass... | [
"I don't have an answer, but you have a really good point."
] | [
"Light doesn't ",
" slow down. For the convention of using wavelenght, it's probably some random historical reason. "
] | [
"Yes I know, some say it is absorbed and reignited and others say it bounces around but I get the actual velocity remains the same. The convention refers to the time the light transits. Still stumped though. Needed a quantum physicist to explain this to my little monkey brain. "
] |
[
"What makes sounds of the same frequency sound different to my ear?"
] | [
false
] | If our ears pick up different frequencies and convert them to sounds in our brain, why, for example, would a C note played on a piano sound different than a C played on a guitar? I'm assuming these two notes would contain the same frequencies. | [
"Take a piano for instance. ",
"There's the fundamental vibration of the string (say, 100 Hz for simplicity)",
"There's the overtone series for that string (all vibration modes where the ends are fixed), so 200 Hz, 300 Hz, 400 Hz, etc. Decreasing as you go up.",
"These vibrations (ALL of them, not just the fu... | [
"It's because a \"note\" you identify actually contains much more frequency content than the pure tone at that specific frequency. The amount of other frequency content and the phase relationships between them contribute to the \"timbre\" or overall \"sound\" of the sound."
] | [
"What kinds of other frequency content might contribute to the timbre?"
] |
[
"Why is the visible part of many galaxies flat? What is a dark matter halo and how does it figure into the visible shape of a galaxy?"
] | [
false
] | null | [
"For the same reason planetary systems, rings around and planets and black hole accretion disks are flat. Friction between components brings everything into the same plane eventually, where the plane is determined by the initial angular momentum of the cloud.",
"Dark matter doesn't have interactions that would al... | [
"To expand on that: Any matter system has most likely a total angular momentum (l_tot=0 is just highly unlikely). Any rotation in three dimensions angular momentum can be described by one momentum vector in a specific direction around which the system rotates. Since angular momentum is conserved in all interactio... | [
"The dark matter halo is a big ball-shaped blob of dark matter. The structure is quite simple - it's roughly spherical, but denser in the middle. It might be a bit stretched out into an ellipsoid because of its angular momentum - i.e. it's spinning a little. But the random motions are quite big compared to the rota... |
[
"Happy Pi Day! Come celebrate with us"
] | [
false
] | It's 3/14/15, the Pi Day of the century! Grab a slice of your favorite Pi Day dessert and celebrate with us. We'd like to extend a special thank you to these users for their contributions here today! Here's some reading from to get us started: The symbol π was not known to have been introduced to represent the number u... | [
"Welcome to this thread. You may know me as a Flaired User over at ",
"/r/askhistorians",
" in the History of Mathematics. I'm going to write a short history of Pi in different cultures in Ancient Mathematics. I will go into less detail than some of the Mathematicians posts here, who will explain why certain th... | [
"Alas, much of the world never gets to celebrate Pi Day, because today is 14/3 for us.",
"So how did it come to be that different cultures, even some speaking the same language, write their dates in different orders? And is anyone actually using ",
"ISO 8601",
", the only format that puts all the digits in de... | [
"We could celebrate Pi Approximation Day on 22/7!"
] |
[
"How are satellites launched as not to run into each other?"
] | [
false
] | With Elon Musk wanting to launch 4,000+ satellites into the atmosphere, how are satellites launched so that they don't collide in orbit? Is there any math or timing and angles done to assure that none of the (currently as far as I can find) 2,271 satellites will remain in orbit indefinitely? | [
"There is about 18,000 debris actively tracked by the US military and around 800,000 debris in earth orbit bigger than 1 cm. The surface area of earth is 510 million square kilometers. That means that if all of those debris were to be sprinkled on Earth surface there would be less than 0.2% chance of finding one in... | [
"An interesting case is Geostationary orbit, which is the most constrained orbit that commercial satellites are launched into. To be in geostationary orbit, your satellite must be at a particular distance from the earth, and orbiting precisely in the plane of the equator. You might reasonably-expect that orbit to g... | [
"An interesting case is Geostationary orbit, which is the most constrained orbit that commercial satellites are launched into. To be in geostationary orbit, your satellite must be at a particular distance from the earth, and orbiting precisely in the plane of the equator. You might reasonably-expect that orbit to g... |
[
"Why are there smaller rocky planets closer to the sun and larger gas giants further away from the sun?"
] | [
false
] | [deleted] | [
"Surprised this isn't in the FAQ (paging ",
"/u/Stringoflights",
" I guess).",
"It's essentially due to what we call the 'snow line' (sometimes 'ice line' or other things). This is the point at which in the early solar system the temperature was low enough for water to condense. The early Sun would have heate... | [
"On it!"
] | [
"Such service."
] |
[
"If cameras having more resolution than the human eye are made, could we tell the difference between them and a camera with the exact same resolution as the human eye?"
] | [
false
] | [deleted] | [
"The resolution of a human eye is a lot more complicated than that. They're not like cameras. Each receptor only gives a signal once every second or so, but they don't all do it at once. As such, you can't really say the resolution or the frame rate. To make things worse, the receptors aren't spread out evenly. The... | [
"Look at the sides of your vision. Compare it to the middle of your vision. You can see that you can best see what is right in front of you and the things on the periphery are somewhat unclear and smudged.",
"A camera and an eye work in 2 entirely different ways. A camera provides a ",
" where all points are ex... | [
"Look at the sides of your vision. Compare it to the middle of your vision. You can see that you can best see what is right in front of you and the things on the periphery are somewhat unclear and smudged.",
"A camera and an eye work in 2 entirely different ways. A camera provides a ",
" where all points are ex... |
[
"Thorium Reactors: Snake oil, or a legitimate source of clean energy?"
] | [
false
] | Thorium sounds too good to be true: -No nuclear proliferation issues. -The ability to recycle waste from conventional light water reactors. -Readily available resource that is not concentrated in relatively few countries. | [
"Just to start out, your talk of thorium mixes the reactor type and fuel type. Thorium can be used in many applications, but I believe what you are referring to is LFTR, which is a reactor type that uses thorium as a fertile fuel. I would advise you to understand that those are two different things.",
"With that ... | [
"Thorium can be used as a fuel in almost any type of reactor, however the benefits are hardly worth the cost in most cases. The case where thorium actually makes sense is a special type of reactors, molten salt reactors (MSRs), which are one of the GenIV concepts. The main reason is that in a MSR the fuel processin... | [
"ORNL = Oak Ridge National Lab",
"MSBR = Molten Salt Breeder Reactor",
"TRUs = trans-uranium elements",
"LFTR = liquid fluoride thorium reactor",
"RTG = radio-thermal generator",
"LWR = light water reactor"
] |
[
"What's the deal with lyme disease/chronic lyme and other related diseases (fibromyalgia, Morgellons, etc)?"
] | [
false
] | After doing my own research I'm pretty sure Morgellons is a delusional state, not skin fibers/chemtrails/mutant DNA/etc. Is there ANY evidence to the contrary? Lyme disease is agreed to be an actual condition; what's up with chronic Lyme disease? I just finished watching "Under Our Skin" and was more interested in the ... | [
"I do not believe chronic lyme disease is a real disease. In my opinion, it is the result of inappropriately testing people with ambiguous symptoms for Lyme disease in a shotgun testing approach. The test has lots of false positives, and once that result comes back, patients latch onto the diagnosis, and these da... | [
"I didn't, really. I was asking about 4 different diagnoses that are only very loosely connected. I included fibromyalgia because frankly I'm pretty ignorant about it but the symptoms match many described in \"chronic Lyme disease.\" I didn't mean to offend, I'm sorry."
] | [
"I didn't, really. I was asking about 4 different diagnoses that are only very loosely connected. I included fibromyalgia because frankly I'm pretty ignorant about it but the symptoms match many described in \"chronic Lyme disease.\" I didn't mean to offend, I'm sorry."
] |
[
"Why is water transparent?"
] | [
false
] | What is it about the structure of water that gives it transparent qualities? Do the hydrogen bonds of water contribute to this? In general, I am unclear how a compounds structure of elements translates to the colors is reflect or absorbs and how that relates to being transparent. Thanks! | [
"And also explains why blood looks green when you are 20m under water. It's a scary experience to cut yourself on some coral and start bleeding green when you're not prepared for it.."
] | [
"A compound will only absorb a wavelength of light if there exists ",
" energy level transition that correspond to that range. In the visible spectrum, this corresponds to ",
" - electrons being excited and jumping to a higher orbital. Therefore, the colour of a compound depends largely on the energy level diff... | [
"On a side note, water isn't entirely colorless: pure water is very slightly blue.",
"It is very faint and typically goes unnoticed."
] |
[
"In Quantum Mechanics, do particles act as an observer?"
] | [
false
] | My thinking is, particles have to know each others position to build systems, doesn't this mean they have to have measurement abilities/properties (receiving/sending information)? If it's not the case, how it works on particle scale, and then how these states can make bigger systems without collapsing? If particles ca... | [
"That's not exactly right. It's true that there's nothing special about intelligence, but quantum interactions are different from interactions between a quantum system and the classical environment, which is when the wavefunction collapses, according to the ",
"Born rule",
". "
] | [
"No. Observation, associated with wavefunction collapse or \"state reduction\", is a non-unitary, irreversible process. It happens when a quantum system becomes entangled with a classical environment. On the other hand, the laws that govern the interaction of quantum systems are unitary, which means they are comple... | [
"This depends on your interpretation of quantum mechanics. ",
"Everything from wave function collapse is not a real event. ",
"To measurement ",
" particle interaction(or decoherence).",
"Or there is some yet unknown size at which the wave function collapses.",
"It's honestly a mess. "
] |
[
"If salt (NaCl) dissolves into Na+(aq) + Cl-(aq) then why does salt water still taste like salt?"
] | [
false
] | [deleted] | [
"Because your tongue is wet; you always taste Na+ & CL-."
] | [
"When NaCl hits your tongue, it dissolves into Na+ ions and Cl- ions. Those ions then interact with your taste receptor cells, located in your ",
"taste buds",
". These ionic interactions lead to a depolarization of the taste receptor cell, which eventually leads to the firing of nerve impulses. These impulses ... | [
"Your nose won't dissolve oxygen or ozone into any other compounds, and is able to detect the difference.",
"What 3rdpartyuser is saying is that as soon as the salt (NaCl) touches your tongue it dissolves into its component pieces, as you have mentioned, so we have never actually tasted the compound of sodium chl... |
[
"Are there any anisotropic heat transfer materials?"
] | [
false
] | Have any materials been discovered with the property of directional heat transfer? My question has two parts: Thanks in advance! | [
"Thermal conductivity is a function of",
" phonons",
", and phonons depend upon the molecular arrangement of atoms. So, materials with different arrangements of molecules in different directions, like crystals, will have anisotropic thermal conductivity.",
"Sapphire is one example, but the differences in the... | [
"Many minerals are anisotropic in terms of heat conductance, for example the ",
"olivine",
" group. However, in most cases the variation between axes is minimal.",
"Technically, a material isn't always a thermal insulator or a conductor; its role depends on the thermal conductivity of the surrounding material... | [
"Would microfabricated multilayers of silicon dioxide (or zirconia) and gold (or silver, or copper) count? The difference in effective thermal conductivity would be about two orders of magnitude in the parallel and perpendicular directions of the composite layers."
] |
[
"Why can't I find any video of an actual hologram?"
] | [
false
] | null | [
"Here",
" is a video from the MIT museum."
] | [
"Thanks for the video but I don't understand, are these floating in three dimensional space? Is that what this book is talking about or am I misunderstanding what a hologram is... the book says if you walked around a hologram, you'd see every side of it, like R2D2's famous hologram message. While it looks like the... | [
"They are two-dimensional screens that look like three dimensional images (when suitably lit), which is what holography is. The word literally means drawing the whole, i.e. encoding a 3d image on a 2d screen."
] |
[
"Why can smokers sleep 8 hours without needing to smoke, but why some can't go 2 hours during the day without one?"
] | [
false
] | null | [
"Something worth noting: there are many bodily and hormonal changes that occur during sleep meant to prevent inturruptions. Things like ADH increases to prevent urination, and regulating ghrelin and leptin levels to control hunger.",
"I can't seem to find any good articles for which horomone/bodily change (if any... | [
"chemically, everything a cigarette does to you is inclined to activate and energize through acetylcholine receptor uptake (acting as a neurotransmitter), epinephrine production (kind of a big thing if the goal is to sleep), blood pressure increases, alertness increases, a glucose dump, etc. everything that would b... | [
"The neuroadaptation of nicotine dependence is pretty complex. There's the so-called 'sensitization-homeostasis (SH) model', which states that consumption of nicotine both depresses craving circuits (acutely) and triggers their formation (chronically, Brain Sci. 2012 Oct 17;2(4):523-52.). Cellular mechanisms are de... |
[
"How are the two separate images your eyes see combined to form one image?"
] | [
false
] | [deleted] | [
"That's a complicated question to answer. I'll do my best, but I'm sure there are others more qualified than me.",
"Each of your eyes has a fibrous strand of nerves coming out the back, known as the optical nerve. This contains the image \"information\" out of the eye. However, similar to images off of a digital ... | [
"The first part of the answer to your question is this: Before the optic nerve reaches the visual cortex of your brain, it goes through two other locations. The first, called the ",
"optic chiasm",
", is responsible for converting your vision from two \"cameras\" to two \"fields\". Put simply, the bundles of op... | [
"I went back and checked my copy of \"Sensation & Perception\" (Wolfe and Kluender) and it seems to support my statement that the right visual field is processed by the left LGN, and visa versa.",
"What is true is that the right ",
" field is processed by the right LGN. However, because of the optics in the hum... |
[
"Why is rust red as a powder but gray/silver in bulk (hematite)?"
] | [
false
] | At first I presumed it was because they were polymorphs, but that doesn't seem to be the case. It also doesn't seem to be a result of particle size (i.e. like maybe only nanoscale particles appear red). What's going on here? | [
"I think fully anhydrous iron(III) oxide is black, so when macrocrystalline (as in haematite) it appears silvery. Much like a metal - metal powders are black, but the crystalline material is silvery. It's almost certainly not the same physical phenomenon causing the shininess though.",
"Rust is red, orange, yello... | [
"Huh, I had always assumed it is different forms of rust, like hydrated iron oxide Fe2O3 being red, waterless iron oxide being brown, iron oxide-hydroxide being yellow and Iron II oxide being black.",
"Curious to see if theres something more to it."
] | [
"Iron oxide single crystals (haematite and magnetite) are very noticeably black. They are metallic (electronically) but have very ",
"low density of states at the fermi energy",
". so plasmonic excitations leading to the metallic \"silvery-ness\" are weak and the crystals are only slightly silvery. Being crysta... |
[
"Why are elevators placed at the rear of planes, and not at the front?"
] | [
false
] | null | [
"By placing them at the back (attached to the stabiliser) you get a natural stabilising effect. When flying in a stable cruise, the stabiliser and elevator will be pitched to give a zero moment around the centre of lift (I.e. You fly straight). If you were to pitch down (say because of a change of air pressure), ... | [
"You can do that - when an articulated lifting surface is placed forward of the main wing it’s sometimes called a canard.",
"If I’m remembering correctly such configurations tend to be more maneuverable but less stable because of the way center of lift tends to work out relative to the craft’s CoM in that kind of... | [
"The Wright brothers flyer had its elevator in front of the lifting surfaces. It was a relatively slow aircraft, but as the elevator cut through clean air it would have been very effective. "
] |
[
"Just learned a bit about elements decaying into another elements over time, is it possible that there is something like a timeline that every element is in a different spot of the timeline ? So a mother element decays into every other element over a really long time ?"
] | [
false
] | So what we call different elements are coming from the same element but it is just about where are they in timeline. A better explanation; ....element1 > element2 > rubidium > stronium >element3 > element 4... Is this possible ? | [
"See ",
"decay chains",
".",
"Not every isotope undergoes radioactive decay, so many elements are stable and won't participate in a decay chain (or terminates one). Furthermore, each decay chain doesn't go through every unstable element either - it all depends on the type of decay.",
"If you take into consi... | [
"There's a possibility that protons decay, in which case that would be true. If they don't, then there are certain isotopes which, according to our current understanding of physics, will never decay. There are also some isotopes which theoretically could decay, but have never been observed to. "
] | [
"Thanks a lot!"
] |
[
"Why doesn't fat deposit in feet or hands?"
] | [
false
] | [deleted] | [
"Genetically then is there a functional reason fat doesn't get deposited there? Lack of structures to build that fat? When evolution applied to humans I doubt there were many 400 lb humans too."
] | [
"Genetically then is there a functional reason fat doesn't get deposited there? Lack of structures to build that fat? When evolution applied to humans I doubt there were many 400 lb humans too."
] | [
"Evolution ",
" applies, even to humans. Now that that's cleared up, do not mistake the ability of slight pressure over vast periods of time to cause distinct changes in populations. Whenever the proto-sea-mammals were being \"pushed\" back into the Ocean, its not like all of a sudden a mutation for fully-fledged... |
[
"If a single photon bounces between two perfectly reflective mirrors indefinitely, would the mirrors continually accelerate away from each other? If so, where is that kinetic energy coming from?"
] | [
false
] | I know that radiation pressure is a thing, but I'm fuzzy on the details. Does a photon bouncing between two mirrors (in a vacuum with no significant source of gravity) accelerate them away from each other? If so, the mirrors, in theory, could reach very high velocities relative to one another if given enough time. Wher... | [
"Yes they would accelerate away from each other.",
"As a photon is reflected it undergoes a momentum change from p -> -p . Due to conservation of momentum, this momentum deficit of 2p is transferred to the mirror.",
"Sinc the mirror has finite mass this results in a change of velocity of v=2p/m and a correspond... | [
"What happens to the photon in this scenario? If it's losing frequency and momentum, what happens as frequency and momentum approach 0?"
] | [
"Things would change when you reach wavelengths comparable to the separation between mirrors. You certainly can not use the tennis ball bouncing off the wall approach. You would need a new way to carry out your calculations (proper QM).",
"In fact, to look at a particular example, when the wavelength is twice the... |
[
"How does hashing work?"
] | [
false
] | So i just calculated that 1 kb data has so many possible permutations, that you would need to reuse every SHA-512 81351712473709768731270537754804570854718677526374656556827099078453655249183513967370837200474504180985168034891530712241198603273685958563940205636396467367223546345381006686686417664027889082824824040056... | [
"As you correctly found out, even within a relatively small set of data, you will find a lot of collisions. The point however is that, for a hash function that is well-designed, it is impossible to quickly calculate which two strings collide. So for a given string of 1 kb, you know that there exist a large number o... | [
"Even pigeons understand the ",
"pigeonhole principle",
"."
] | [
"I'm not sure if I understand you correctly, but you might be confusing ",
" and ",
". Both are desirable properties of hash functions.",
" says that given the output of the hash function, you cannot (easily) get the input back. ",
" says that you cannot (easily) find two different inputs that result in the... |
[
"Where does the water vapor in electronic cigarettes come from? (The ingredients do not list water)"
] | [
false
] | I was looking at the ingredients on a pack of Fin Electronic Cigarette refills and I noticed an auspicious lack of the key ingredient that is advertised, Water. I went back to check the packaging to make sure that it specifically stated "Water Vapor" and it does. Do any of the chemicals listed contain a water molecule ... | [
"Yes, I've listed those compounds in the original post. The marketing on the product claims that what is produced is water vapor. My question is, where does that water vapor come from, as \"water\" is not one of the ingredients listed."
] | [
"Yes, I've listed those compounds in the original post. The marketing on the product claims that what is produced is water vapor. My question is, where does that water vapor come from, as \"water\" is not one of the ingredients listed."
] | [
"\"FIN electronic cigarettes are smoke free. FIN e-cigarettes produce vapor, not smoke. Though it looks like smoke, ",
" disappears in seconds.\" -- ",
"www.fincigs.com",
"It doesn't say \"water vapor\", it says \"vapor\". The propylene glycol is an inert liquid base (in a lot of things) with flavors in it. I... |
[
"If graphene is a single layer of carbon atoms, how would it conduct electricity?"
] | [
false
] | Essentially asking the mechanics of how graphene conducts electricity. Is it possible to make a super durable/malleable wire/“tape” that can conduct electricity for a cheap price?Any research papers I can dive into too? | [
"It’s graphene’s structure that makes it conducive. A given carbon atom shares sigma-bonds with 3 other carbon atoms in the same layer, and pi-bonds with the adjacent layers. This pi-bond (actually pi-band) enables free electron movement, and hence electronic properties (namely conductivity). ",
"When you get dow... | [
"The sticky tape method for single-layer graphene production must be near the top of the list of mundane solutions to high-tech problems. Right there with the almost pedestrian bottle of hydrogen gas that serves as the proton source for the LHC."
] | [
"It would be possible to create such a tape, but graphene would be a rather bad choice for it. Graphene may be a very strong material, but it still is only 1 atom thick so it is very easy to damage. You can bend it quite well without damaging but it won't be very reliable. Also, the electrical resistance will be hi... |
[
"Why can't nuclear waste just be ground up and diluted in sand?"
] | [
false
] | E.g. to the original levels uranium was found in its ore? Or is waste more radioactive than unused isotopes? | [
"The waste is more radioactive than the unused isotopes. The half life of uranium-235 is 700 million years. The waste tends to include elements with half lives of hundreds or thousands of years. After tens of thousands years it will pretty much all be gone, but until then it will be much more radioactive than urani... | [
"Put it into RTGs for they rest of there hot lives. Idk how much power it would output but it's better than putting them in the grounf"
] | [
"I would suspect, since this isn't done now, that the available heat is low enough to not justify the construction of a device capable of harvesting that energy. Most likely due to the requirement that said system would still have keep the radioactive isotopes isolated from anything they could harm. We could also... |
[
"How does relatively long range wireless electricity transfer work?"
] | [
false
] | A recent experiment at Mitsubishi heavy industries in Kobe, Japan managed to transfer 10 kW 500 m wirelessly. What is the science behind this accomplishment and how feasible is it for practical use? Does the transmitter send waves in all directions equally, and all that does not hit the receiver is lost? What degree of... | [
"Using microwaves, not radio frequencies. Microwaves are relatively coherent. Since the intended use is for transmission of power to and from space, geostationary orbit, there is some spreading that could be a problem. Back in the day when the L5 society was promoting this for solar power satellites we were expecti... | [
"So you are looking at Tesla's work versus microwave transmission of power. Tesla wanted to avoid building transmission lines on the ground so his work was for broadcast, non-focused power distribution. This suffers from inverse square losses with distance. The Japanese are investigating for solar power satellite g... | [
"One of my assumptions was that in order to complete the circuit you need to have a conductive ground and air which the antenna with a large metal ball (or torus) will be suspended to receive the transmitted energy and use the ground to complete the circuit? Just off the top of my head, It's been a while since I to... |
[
"Does the hippocampus effectively fluctuate?"
] | [
false
] | This study shows that the hippocampus is shrunk by shooter games, but grown by platformer games. Are these circumstances highly unique, or do different circumstances just cause the hippocampus to fluctuate in size? | [
"I think the important thing here (which is mentioned in one of the comments on the linked thread) is that brain change correlates with the individual approach of the gamer in navigating a task or objective — not necessarily the type of game they play. FPS games tend not to require a lot of memory skills (at least ... | [
"My current understanding is that our brain’s structures are like muscles, where they grow “stronger” (and probably bigger) when we use them a lot and they likewise weaken and grow smaller when we don’t use them as much.",
"This is very much NOT how the brain works. Your brain only decreases in number of neurons ... | [
"I stand corrected, thanks for the revision! I shouldn’t write about things that I’m in the process of learning lol ^",
"I’d read about neurogenesis and stem cells a few months ago — does that tie into those exceptions you talked about with the hippocampus? I remember it was one of the structures mentioned in the... |
[
"inspired by GI joe. What size would an object need to be in order to be dropped from space and hit the earth with the same energy as a nuclear bomb?"
] | [
false
] | I understand that different materials would affect this scenario. From the looks of the movie, lets assume the object is pure steel. though I would like to know the difference in size for different materials. | [
"Your question is a bit ambiguous: nuclear bomb yields vary greatly, and \"dropped from space\" does not define a precise altitude. So first, we'd need to define \"dropped from space.\" Let's assume this means freefall from Low Earth Orbit. I'll use the orbit of the ISS as the height from which the object is dro... | [
"A couple of answers have already done the math on how much kinetic energy an object would have if dropped from a very high altitude. It's worth emphasizing that this intuitive idea really doesn't work, though. If the rods are sitting up there waiting to be \"dropped\", then by definition, they're in orbit. Releasi... | [
"USAF looked into it, labeling the idea ",
"Project Thor",
". They described a 20' long by 1' wide tungsten rod, which would impact at Mach 10 with an impact energy of about 11.5 tons TNT"
] |
[
"If fats have twice the energy density of sugar, does eating the same calorie surplus in fat cause you to gain half as much weight?"
] | [
false
] | I've always heard calories in, calories out. But calories are a unit of energy, not weight. If I eat 1000 more calories than I take in in fat, I'll have 111 extra grams to burn off. If I eat 1000 more calories than I take in in sugar, I'll have 250 extra grams to burn off. Is this true? If so, it seems to contradi... | [
"calories are a measure of the energy in food. energy in food is either used or stored (As fat). ",
"the weight, or mass, of food has little to do with weight gain/loss because it includes things that cannot be absorbed by the body. only the absorbable energy counts toward calorie count. ",
"essentially... | [
"I still don't really understand. Let's say John ate 10 grams of pure fat over his calorie limit for dinner. After his body burns the energy for the day, he weighs 10 grams more.",
"\nNow suppose John ate 22.5 grams of pure sugar over his calorie limit. After his body burns the energy for the day, he weigh... | [
"In the second scenario, John converts the extra 22.5g of sugar into ~10g of fat for long-term storage.",
"This is a simplification of course, but essentially what's going on."
] |
[
"Can being around crazy people make a sane person crazy?"
] | [
false
] | The phrase "you're driving me crazy" got me thinking about this. Is there any evidence to suggest that being around individuals with mental health/emotional health issues can rub off on an otherwise mentally stable individual? Can someone develop a disorder simply by being exposed to it for long periods of time? | [
"Well, it's an interesting question. In the most basic sense, no, a mental illness cannot \"catch\" over time. Psychiatric nurses do not develop schizophrenia after hanging out with schizophrenics all day. Kids sitting next to their ADHD best friend at school don't get ADHD. ",
"But in a more complicated sense,... | [
"In regard to your last paragraph: I've just watched a Horizon documentary on murders / psychopaths and it basically said that the psychopaths found to have faults, among other things, within the cortex of their brain and also this warrior gene but what actually ended making them turn to killing, was a traumatic ch... | [
"right, yes. Intersectionality of many factors is the name of the game in psychology."
] |
[
"What is the substance that makes aging lunchmeat slimy?"
] | [
false
] | Pretty self-explanatory. As lunchmeat ages in my fridge, it gets slimier. Why? What is that slime? And how long is it still ok to eat? | [
"There are two different reasons why lunchmeat might be slimy/shiny.",
"One is harmless-ish. First, it has to be ",
"one of the industrially cured or brined meats",
", like ham, turkey or roast beef, because it's that juice seeping out and congealing over time that's creating the oily sheen. Second, the lunch... | [
"\"across the grain\" Only in solid muscle products. Almost all deli-meat is made by packing smaller chunks of muscles in a large casing and cooking it; similar to sausage making only the meat isn't ground. Grain will be in multiple directions.",
"\"Slime-formers\" is what we call the mostly harmless things that ... | [
"A note to our readers:",
"Please remember that we prohibit medical and food-safety advice on ",
"/r/askscience",
", as well as anecdotes.",
"If you came here to post about how someone should or shouldn't eat whatever kind of meat product, please don't hit save.",
"If you came here to post about your luck... |
[
"Does light have zero velocity when it is in contact with the surface it reflects off of?"
] | [
false
] | So light as we know it, moves at 3*10 m/s (if i remember right) and it can be reflected off of a surface. So say your light hits a mirror. Does the light that is hitting the mirror have no velocity or does it move at the speed of light always even if it changes direction? I might be stepping on sensitive ground by comp... | [
"I might be stepping on sensitive ground by comparing a photon to a tennis ball but, when you throw a tennis ball on the floor and it bounces back there is a point where it has no velocity. Do photons experience the same slowing that the tennis ball does?",
"No. The light never slows down or actually reverses dir... | [
"This is fully incorrect and exactly why I wrote my comment above, The notion of a bare photon traveling through a material is simply not valid. Remember, materials are made up of charged particles which will get pushed around by the EM fields of the optical signal. This means that you can not have a photon pass... | [
"This is fully incorrect and exactly why I wrote my comment above, The notion of a bare photon traveling through a material is simply not valid. Remember, materials are made up of charged particles which will get pushed around by the EM fields of the optical signal. This means that you can not have a photon pass... |
[
"If you boiled salt water then collected the steam vapor could you healthily drink it?"
] | [
false
] | [deleted] | [
"Yes, in fact this is the most commonly used method for water desalination and is practiced on industrial scales, especially in places like the Middle East, where water reserves are very scarce.\nThe most common way that desalination is carried out industrially is via what is called flash distillation. The basic sc... | [
"Brine (salt water) is an aqueous solution, not a suspension (solid-liquid mixture)."
] | [
"Is this only possible on a very small scale?",
"Reverse osmosis is very common in large scale desalination plants. From what I understand, it's gaining ground and is being used in most new construction."
] |
[
"Open source MRI scans?"
] | [
false
] | null | [
"Okay, so license them under creative commons under the most permissive terms possible. People can then do pretty much whatever they want. "
] | [
"Thing is, as much as I applaud you for wanting to do this, no researchers have absolutely no access to such data",
"What about computer science students working on CV algorithms, or bedroom hackers who have a slight interest in human biology? Data being available may well cause talented and dedicated individuals... | [
"You're absolutely right, didn't think of this when typing my reply. I only saw my own use case."
] |
[
"How do surgeons place back organs like intestines?"
] | [
false
] | I have seen in some films and series how they take the intestines out of the chest and move them but I have never seen how they put them back. Is there any way of doing it or do they just place them back and they recover their shape by themselves? | [
"While some movies show the intestines as a totally untethered tube that could spill out, they're actually loosely attached by mesentery, a sort of fatty sheet with intestine running along the free edge. You can't completely pull them out; it's actually fairly tricky at times to work around them in place. (As a med... | [
"Surgeon here. Obviously, this is a simplified explanation.",
"Regarding the bowel specifically, the small bowel is composed of three portions. The duodenum, the jejunum, and the ileum. This in turn connects to the colon, which can be subdivided into the ascending, transverse, descending, and sigmoid. This th... | [
"Thank you very much! I didn't knew they were attached I thought they were a free tube that floated inside the abdomen. "
] |
[
"New Biology student here. At what point do cells \"start up\" and perform the functions for which they were created?"
] | [
false
] | With white blood cells for example. When does it go from being freshly created by the body to doing its particular job. Is there some sort of activation period for cells? Is the process different for each cell type? Thanks! Thanks for the replies! It seems that this is quite a bit more complicated then I previously tho... | [
"\"White blood cell\" is a broad category. What do you mean in particular? Monocytes? Leukocytes? Neutrophils? Most of these things respond to particular cellular contexts. Monocytes might differentiate into a macrophage after they have incorporated into a particular tissue (based on signals from the local environm... | [
"It's more of a spectrum of processes - there's certain functions at certain points in the cell. Most cells do not have an 'off' or 'dormant state,' unless it's specifically something that benefits them (say, for defense reasons in the case of bacteria). To get you started, for eukaryotic cells you should look i... | [
"Cell function is controlled through activation of certain genes. Housekeeper genes (ones that essentially keep the cell ticking) are always on, other cell functions can be controlled through various stimuli, leading to a change in gene expression. "
] |
[
"Is there a detectable change in the brain when a person consciously takes control of their breathing or blinking?"
] | [
false
] | [deleted] | [
"Breathing is usually controlled on the ",
"brainstem level",
" automatically. If you do it voluntarily, it's controlled by the ",
"cortex",
". So if you put a person in an fMRI machine and told them to start breathing consciously, you should see the motor strip in the frontal lobe light up, where prevously... | [
"Yeah - it's super rare. You'd need a tracheostomy and to be hooked up to a ventilator at night."
] | [
"Does this mean they would require some kind of mask for sleeping, or what happens there?"
] |
[
"How did sexual organs evolve from the cellular stage to humans?"
] | [
false
] | I always wondered how genitalia developed as it is now. Did it start out like a tail or slowly extend out from the base to develop as a penis? Or what? | [
"This page has a lot on the general concepts;",
"http://en.wikipedia.org/wiki/Evolution_of_sexual_reproduction",
"And here is something specific to the evolution of the penis but mainly as it pertains to the shape;",
"http://www.scientificamerican.com/article.cfm?id=secrets-of-the-phallus",
"This is interes... | [
"awesome, thank you so much"
] | [
"I suggest watching the whole series, but CDK007 on youtube made a great series on abiogenesis leading to the origin of the brain.",
"Origin of sexual reproduction",
"If you do watch the whole series he even notes what data it is based on, and for the abiogenesis portion is our best theories on the subject, we ... |
[
"Are lasers (when viewed as radio antennas) subject to the antenna reciprocity principle?"
] | [
false
] | Since lasers emit electromagnetic radiation, are they subject to the reciprocity principle? I know that the principle is only for (electromagnetically) linear antennas, but I am not sure if a laser is linear. The second question then pops up, as lasers are based on diodes, are diodes subject to the reciprocity prinicpl... | [
"The laser diode as a whole cannot be thought of as an antenna by itself, It can be thought of as an array of phased antennas made up of the excited atoms.",
"The individual atom harmonic structure follows reciprocity only up to the point that photon in is the same as photon out in a time reversed format, This is... | [
"Lasers are usually rather non-linear and dissipative, but that doesn't mean you can't build a time-reversed \"laser\".\nHere is a description of a \"coherent absorber\" that is basically laser in reverse:\n",
"http://link.aps.org/doi/10.1103/Physics.3.61",
"I believe this has been actually demonstrated as well... | [
"Good explanation! So what it boils down to is that the processes in the laser are not reversible (because of the phonon emission), so it is definitely not reciproce."
] |
[
"physics question regarding air resistance and velocity."
] | [
false
] | If I am traveling in a car at 10 kmh and a bird flying next to the car at the same speed merges through the open window, what will happen to the birds speed/ velocity? | [
"What you are not considering is that, in order to fly, air has to move above the wings of the bird. Since the bird would be at rest relative to the air in the car, it would either drop as a stone or have to accelerate in order to keep flying.",
"So, the fact that the bird would accelerate does not primarily have... | [
"Nothing. The bird will be carrying the same amount of momentum when it enters the car. However, if the bird were to fly in the back window and flap it's wings really fast and then fly out the front, it would gain more velocity than it otherwise would've because the air resistance in the car would be lower because ... | [
"Yes, you are right. I did not take lift into account.... what I meant to say is that the bird would be carrying the same amount of momentum... not that it would still be able to fly."
] |
[
"Does a constant loud noise at frequencies of sound that you cannot hear still damage your ears/overall hearing?"
] | [
false
] | For example after a certain age, most people will lose the ability to hear above say 15 kHz. If a speaker is playing a constant 18 kHz sound at 100 decibels, even if you can't hear it, will it be damaging to you? | [
"Ultrasonic noise exposure does indeed cause hearing loss. The literature is somewhat sparse and ",
"this",
" is a review on the topic. The catch: the exposure must have a very high intensity or occur over a very long period of time. This is likely due to the fact that noise induced hearing loss is a function o... | [
"Yep. But what a lot of hearing aid users report, especially with more severe hearing loss, is that amplified sounds become uncomfortable before they're audible sometimes. The intensity threshold for pain or discomfort doesn't change when hearing threshold increases due to hearing loss. This is why many users have ... | [
"What if someone is hard of hearing and can only hear loud noises? Could those loud noises, which sound normal to the person, cause hearing damage?"
] |
[
"Can lasers travel extreme distances in space without degradation?"
] | [
false
] | If so, it seems to me their uses could include communication and propulsion. Is this plausible? | [
"The biggest problem is divergence. When you shine a laser across a room, 1 mrad of divergence (1 part per thousand) seems pretty small, but when you shine a laser 250,000 miles onto the moon, the spot is 250 miles across. "
] | [
"It's caused by diffraction, which is a fundamental limit of optical systems. The effect is smaller for shorter wavelengths or a larger aperture (the gap, lens or mirror from which the beam leaves the source), but it can never be eliminated. You can do stuff like diverging the beam and reflecting it off a really la... | [
"thanks, makes sense. Is divergence something with the potential to be significantly improved?"
] |
[
"Is there a limit to how many times paper can be recycled before it no longer resembles paper? What is the environmental impact of all the additional resources (e.g. water, transportation to the recycling plant) needed to recycle paper versus making paper from scratch?"
] | [
false
] | This question came to me while thinking of all the gift wrapping and unwrapping that will take place today. A lot of gift wrap is now made of recycled paper and also encourages you to recycle it once it's served its purpose. But can this paper be recycled and reused indefinitely, or at some point will the original mate... | [
"Melting glass takes less energy than melting the raw material. ",
"http://wwf.panda.org/about_our_earth/teacher_resources/project_ideas/recycling_glass.cfm/"
] | [
"You can recycle paper a limited amount of times:",
"“How many times can a piece of paper be recycled?",
"Five or six times, on average. At a recycling plant, paper is heated and chopped into tiny bits to make a pulp. During that process, each of the long fibers that characterize virgin paper has an approximate... | [
"Actually we are running out of sand suitable for a lot of purposes including making glass. Recycled glass called cullet is used even in the manufacturing of new glass.",
"Many third world countries are having a problem with illegal sand mining. Much of it going to first world countries for construction. ",
"s... |
[
"How does the upward force decide if an object floats or not?"
] | [
false
] | So if there's a box in let's say water, there is an upward force working up on it (archimedes principle). What my book doesn't explain, are the other pressures acting on the box. I know there's the atmoshperic pressure which is distributed through the water/liquid, but it's the same in all directions so we don't have t... | [
"The buoyant force is ultimately due to the pressure forces acting on the object.",
"The forces relevant to whether an object is buoyant or not are the ",
"buoyant force and the gravitational force",
".",
"If the weight of the object is larger than the weight of the fluid that it displaces, it will sink. If... | [
"One thing to point out- whether or not an object floats does not depend on the strength of gravity. An object that floats on the Earth will both float on the Moon and on Jupiter. Because while you can say it's the weight of the object and weight of the fluid it displaces, since weight is just g*m, then 'g' will ca... | [
"I know there's the atmoshperic pressure which is distributed through the water/liquid, but it's the same in all directions so we don't have to count it.",
"Atmospheric pressure still has a pressure gradient, that's why helium balloons float (and everything weighs a little bit more in a vacuum).",
"The mechanis... |
[
"How long does alcohol consumption evidence stay in your system?"
] | [
false
] | null | [
"We can't advise you about this here."
] | [
"Where should I ask instead, I just figured this would give me the best results. I'm sorry! "
] | [
"You could try ",
"/r/answers",
"."
] |
[
"In a planetary model of an atom, electrons orbit the protons and neutrons. Why don't the electrons get attracted to the protons?"
] | [
false
] | null | [
"The electrons ",
" attracted to the proton, that's why they orbit around it."
] | [
"I see. Is something preventing them from going right next to the proton?"
] | [
"Just like planets orbiting around the sun, their angular momentum is conserved."
] |
[
"Do stars ever die \"quietly\"? What would be left over if one did?"
] | [
false
] | I always hear about stars dying in gigantic explosions or collapsing in some way, but do they ever just... fizzle out? Does all the material get fused into some non reactive substance like iron, leaving a huge lump of metal? Can that turn into a planet? | [
"The quietest star deaths would be those of red dwarfs. They will just shrink into white dwarfs without going through the red giant phase first.",
"However, since red dwarfs are so long-lived, this has never happened yet. The Universe is still too young."
] | [
"I believe most stars die quietly, actually.",
"http://en.wikipedia.org/wiki/Star#Collapse"
] | [
"That fucking amazes me, that the universe is too young for a red dwarf to shrink into a white dark."
] |
[
"Why do sleepers and rails from the railway track need to be removed and replaced with new ones?"
] | [
false
] | null | [
"On the other side of the pond, we call “sleepers” “railroad ties.” And even though railroad ties are soaked in a preservative such as creosote, they will degrade. As do the rails. Wear and tear, basically, just as highways do."
] | [
" railroad ties get soaked in creosote. Concrete ties don’t need it."
] | [
"Thank you for explaining that. I thought \"sleepers and rails\" meant \"sleeper cars and rails\". In other words, that they were replacing both the train rails and a bunch of the cars, probably to conform to some new standard or law. "
] |
[
"With a near-perfect fiber optic cable, how far can you transmit the data?"
] | [
false
] | [deleted] | [
"It depends on the rate of energy loss, which is dependent on the material. This is a complex concept as the transmission of light is not the only criterion here. We have to consider signal-to-noise ratio, so one would have to decide what SNR is the lower threshold...",
"It's similar to asking \"how much power ca... | [
"If by 100% perfect you mean total internal reflection at any angle, you'll still hit a problem with evanescent waves. This is a property of internal reflection in which part of your wave travels ",
" the boundary of your cable. Keep i mind that light is only an electromagnetic wave. When evanescence occurs, the ... | [
"Hence the question, how far can you transmit the data?"
] |
[
"How seseriously is Bret Weinstein's Reserve Capacity Hypotheses taken by the scientific community?"
] | [
false
] | In his recent appearance on the , Bret Weinstein brought up his Reserve Capacity Hypotheses which, roughly said, implies that a particular strain of lab mice that are used for testing pharmaceuticals have been inadvertently bred with abnormally long telomeres. And that this, in practice, leads to unreliable data on tox... | [
"The entire field of biogerontology is not taken very seriously. It is populated by eccentric researchers (like Aubrey de Grey), mostly in private labs, funded by millionaires who seek immortality. It overlaps with the cryonics community.",
"Bret Weinstein argues that laboratory mice have long telomeres, which co... | [
"It’s also worth pointing out this isn’t some new, shocking finding. It’s been known for decades that lab mice have long telomeres, compared to humans and to wild mice. Here’s a review from 1997 ",
"Mouse Models for the Study of Telomerase",
", here’s a study from 2000 ",
"Wild-derived inbred mouse strains ha... | [
"Seems unlikely. ",
"For what it’s worth, I was peripherally involved in the early telomerase work done by one of Grieder’s competitors (I’m acknowledged in their papers but not an author) and everything I heard about her was that she was very generous with her time and credit."
] |
[
"Some questions on the nature of the stellar and interstellar environment."
] | [
false
] | Thank you for your time! | [
"The front of the bow shock is whichever direction the interstellar wind is coming from, not whichever direction the Sun is traveling. If the Sun is traveling one direction around the galaxy, and the background interstellar material is traveling in the same direction but faster, then the bow shock's leading edge wi... | [
"Charged particles will definitely behave ",
" differently, yes. They'll be affected by electromagnetic fields in ways uncharged matter won't."
] | [
"Stellar aurora certain exists, but it'd be hard to detect, because it's just light-emitting plasma like the rest of the solar atmosphere, but way dimmer. Also, since the radiating material would be the solar atmosphere itself, it would look exactly like normal emissions from the sun. You'd expect then that solar a... |
[
"What exactly allows clouds to form and grow, instead of the condensed water just immediately falling back down as light rain?"
] | [
false
] | null | [
"Most of the time, the droplets of water that make up a cloud are really, really, small. That means that they have a large surface area compared to their mass, which results in the tiny amount of energy they get from gravity acting on their tiny amount of mass being almost completely negated by air resistance. Once... | [
"Very small cloud droplets stay suspended in the air. Since they have such small mass, the force of gravity on them is insignificant compared to the forces generated by rising air currents, turbulence, and Brownian motion."
] | [
"Look up something called 'dew point temperature'.",
"I only understand it very basically but if the temperature of the Air falls to the dew point clouds begin to form because the water vapour in the air condenses.",
"Until that point the air is not saturated and so can hold moisture in it in the form of gas wi... |
[
"Do insects have pain receptors?"
] | [
false
] | null | [
"We know that insects can avoid injuries, and sense most potential sources of damage. The best studied nociceptor is the Drosophila nociceptor TRPA1, which is pretty closely related a gene in mammals which has an identical function. It senses pressure and heat, and reacts to the chemicals which make peppers hot (ca... | [
"on the behavioral side, drosophila (and bees, and probably many/most other insects) can be trained in an aversive conditioning paradigm (where they learn to associate a shock with a particular odor or other stimulus). doesn't mean they feel \"pain\" per se, but it is suggestive.."
] | [
"Yeah exactly, not so much “pain” per se. It’s like signal receptor to let the insect be aware to injury. Doesn’t feel the pain, but it’s definitely tracking it just lost a leg from you swatting it. "
] |
[
"Why can't the photoelectric effect be explained in terms of classical physics?"
] | [
false
] | As far as I understand, the classical physics should predict that the energy of the electrons increases with the intensity of th light. Could someone explain why, exactly, it would predict that? | [
"Hmm, that makes sense, but why does light have to be particles for the frequency to have effect? Isn't frequency something inherent to waves in the first place?"
] | [
"So would it be correct to say that light is neither particle, nor wave, but rather something completely different that in some situations follows the mathematics of waves, and in others the mathematics of particles? Because as a particle, light wouldn't display a diffraction pattern, would it?"
] | [
"The fact that light is emitted in discreet packets of energy was already known at the time. Plank figured it out as a solution to the ultraviolet catastrophe, and came up with a formula for the energy of each packet based on the frequency of the light involved (Plank's Law). But still everyone assumed what you are... |
[
"Are there any remnants of planets in our solar system that existed before our sun?"
] | [
false
] | How would we know, and how big can they be? How many solar births and deaths have they been through? | [
"Our solar system is a third-generation system, seeded with the heavy elements left over from the previous two generations of stars.",
"Some of that material may well have been part of second-generation planets at some point in its history (there were no first-generation planets), but if you're asking if there ar... | [
"Any ideas what that possible second generation of planets might have looked like? "
] | [
"If we assume that our discoveries of planets around other stars has sampled second, third, maybe even fourth generation stars, then the planets would probably have resembled something like our own system, with perhaps a mix of rocky and gassy planets. ",
"That said though, our current findings are that our solar... |
[
"Is it more environmentally friendly to wash your dishes? Or use paper plates instead? What is the real carbon footprint left by wasted water, vs paper plates?"
] | [
false
] | I am very confused and don't have the education to back any legit answer. I understand the variables. Let's ballpark it Edit: let's compare two regions, and a generic paper plates company, Dixie for instance, and water located near a river. So plentiful water. | [
"Tl; dr: Paper plates are an environmental nightmare! You can't even compare them, by far.",
"Anyway... First thing I want to make it clear that it isn't that meaningful to compare water carbon footprint. In some regions water delivery might even come without carbon footprint at all and even generating a little b... | [
"I've wondered about this too and I found it very hard to find good information. It undoubtedly depends on where you live because the relative costs of water and trash removal vary so much depending where you live. I think in water-scarce regions of Arizona, Nevada and Southern California, there is a decent argum... | [
"Yes, if all the data about the energy usage and footprints of all the suppliers in the chain were were collected in one place and you had access you could figure out relative costs. But it also depends on the specifics of the question. What do you want to optimize? Carbon footprint, Utility costs, Water usage, ... |
[
"How do we avoid confusing sunspots (starspots?) and planets in other solar systems?"
] | [
false
] | How do we determine the difference between a planet that obscures part of the light of a star, vs that star's natural sunspot cycle? | [
"Sunspots are visible for half of the rotation period with slowly changing intensity in that time, planets make a well-defined dip in the intensity for a short part of their period."
] | [
"Observation of multiple transits. A planet will have a consistent orbit and size so we can expect to see a consistent periodic change in intensity from the star. Sunspots are more ephemeral in nature. Someone with more direct knowledge can step in and correct me but I believed Kepler initially required three tra... | [
"Sunspots generally take much longer than a planet to traverse the star. So while a large sunspot might masquerade as a planet in terms of the percent drop in brightness that a planet would make, it would be easily identified as non planetary due to the variability and duration of the light from the star."
] |
[
"How do germs/bacteria travel exactly?"
] | [
false
] | If I drop food on the floor, there's no way I'm eating that food. However, if I place a plate of food on the floor, I'd still eat the food off that plate. Do germs and/or bacteria manifest only on whatever it comes in direct contact with, or will it spread around (in my example, around the plate and onto the food)? | [
"It all depends, most pathogenic bacteria live in a water environment so they'd have to some kind of direct contact to that to spread. This is why the CDC always preaches to clean up raw chicken juice while cooking and to properly wash your hands after using the toilet.",
"Other bacteria can float in the air, lik... | [
"PHealthy gives a good practical explanation of how bacteria spread, but we can get down and dirty. The topic is called Bacterial Locomotion and Signal Transduction (",
"BLaST",
") if you want to look up more research.",
"",
"proton motor",
"endoflagella",
"hook on to surfaces and pull them around.",
... | [
"This is a good overview. Just to expand on some points. ",
"Bacterial flagella are not really like eukaryotic flagella at all, apart from looking somewhat similar. There are also archaea (the third domain of life besides bacteria and eukaryota with with they are more closely related), which have a third kind of... |
[
"What happens to electrons during a voltage drop and how can electrons move when the voltage is 0 at the end of a circuit?"
] | [
false
] | From what I understand, volts in a battery is the difference in electric potential between the negative and the positive terminal. Voltage drops each time current pass a resistor. The voltage across a circuit connected to a battery reaches zero at the end of a circuit. I have 3 questions: What happens to the electrons ... | [
"/u/Naf623",
"'s answer is correct, but I'll explain it a bit differently. \"Voltage\" is really a measure of the potential energy that belongs to a charged particle because of its position in an electric field. ",
"As a rough analogy, charge moves through an electric field in the same way mass moves through a ... | [
"I know this is 4 months old, but wow. Your gravity analogy just blew this wide open for me. ",
"I've been reading a ton of different things on basic electronics, trying to understand how voltage drop = energy = getting work done. I just couldn't make any sense of it. When the electron must still keep moving at t... | [
"Does that make sense?"
] |
[
"How does solid matter stay in the together if it is being spun? Shouldn't relativistic effects tear all matter apart?"
] | [
false
] | Obviously, matter doesn't get torn apart when it moves. So I know there is some effect keeping it together. But this is the scenario I imagine: An armature of solid metal, with one end mounted on an axle so it can spin, similar to a clock dial. Set the arm in motion, and the center will be travelling at a slower rat... | [
"You should read up about the ",
"Ehrenfest paradox",
". It is indeed true that if you spin solid objects fast enough they do indeed have to deform, eventually falling apart."
] | [
"The question sounded like it was talking about it being at the wrong ",
". If it's at the wrong place, then it will be pulled forward into the right place. This is what allows you to rotate the object in the first place instead of it just breaking under the slightest torque."
] | [
"Indeed. I think the key point for OP to understand is that no material is completely rigid. Anytime you accelerate anything the stuff you push has to transmit that force along the object. So if you spin a clock dial, actually you are very slightly bending the dial. It's like a spring, except it is a ",
" stiff s... |
[
"On a thermodynamic level, how is it possible that both nuclear fusion and fission release energy?"
] | [
false
] | I know fission involves splitting atomic nuclei. Splitting a larger nucleus into smaller nuclei I think would be entropically favorable and would have a negative deltaG. So it follows that fission would release energy. Following that logic in reverse would imply fusion would not release energy at all and actually be en... | [
"The nuclei that release energy upon fusing (light nuclei like hydrogen and helium) are not of the same type as those that release energy upon splitting (heavy nuclei like uranium).",
"If an uranium nucleus splits into a krypton and a barium nucleus (and some neutrons which carry some kinetic energy) for instance... | [
"This is covered in our ",
"nuclear and atomic physics FAQ",
"."
] | [
"All of the less stable isotopes release energy when they migrate towards Nickel. Nickel",
" is the most stable element in the universe, the ",
"highest binding energy per nucleon",
" of any element. (People think it's Fe",
" but it's not. It's just that Fe",
" is the last element on the way to Nickel",... |
[
"Does the weight of an object vary with the rotational speed of the planet?"
] | [
false
] | I'm assuming the centripetal force would reduce the effect of gravity on the surface...... | [
"Yes. This comes from two non-independent effects: the centrifugal force itself, and the change in the planet's shape due to the rotation, that makes gravity stronger at the poles and weaker at the equator. The case of the Earth is discussed ",
"here",
"."
] | [
"In addition to the two relevant effects iorgfeflkd mentioned, there is also a tiny effect from the increased energy content of the planet, which slightly increases its mass. That's roughly a one part in a trillion effect for Earth."
] | [
"Technically, the weight of the object is the force due only to gravitation, so it would not be reduced by increasing rotational speed. In fact, the mass of the body would be slightly increased by the increased rotational energy, actually increasing the weight of the object."
] |
[
"If light can only move at the speed of light (and doesn't accelerate), then how does it reflect off of things? Wouldn't the velocity momentarily go to 0 and then accelerate back?"
] | [
false
] | So right according to Intermediate Value Theorem wouldn't light have to momentarily accelerate to the speed of light when it is reflected? If so, what is this force on it (because force cause accelerations, right?). I bet it has something to do with how it doesn't really have mass. I feel like there is a ridiculously o... | [
"There is \"a ridiculously obvious reason for this:\" light is a wave. Your question could just as well apply to the waves in your bathtub that reflect off the walls of the tub. In your bathtub when you see a ripple moving left or right, the water itself that the wave is made of is not moving left or right. It is s... | [
"How is it we can predict the reflective angle with regard to the incident angle? Why isn't the photon emitted in a random direction when energy is lost from the electron? "
] | [
"A simplified explanation:",
"The direction of a single emitted photon actually is random and can't really be determined. However, there is an overall probability distribution that allows us to predict where most of the photons will be emitted over time. Lasers can therefor emit huge ensemble of photons correlate... |
[
"Can a virus alter the genome of a mature organism?"
] | [
false
] | I read that an endogenous retrovirus can change the genome of an organism by infecting germ cells. Could a virus change the entire genome of a mature organism too or does it only work with germ cells? | [
"Viruses change the genome of bacteria all the time. It's driving force for evolution. ",
"Multicellular organisms are obviously a different bag. But strictly speaking, in high enough titres, a virus could plausible infect all cells before the organism was dead..."
] | [
"Well, here's the general operating procedure for a virus:\n1. infect the cells with your DNA/RNA\n2. Use the native cell replication machinery to "
] | [
"sorry..",
"use the native cell machinery to incorporate your DNA into the genome or translate your RNA into proteins and replicated your RNA",
"With the DNA present in the genome it will be transcribed + translated.",
"The virus has now hijacked the cell and is making large numbers of protein sheaths. Then,... |
[
"When an electrical signal is at the junction of a bifurcated wire, how can it \"figure out\" the path of least resistance before traveling it?"
] | [
false
] | null | [
"An electrical signal takes ",
" paths, in proportion to the conductance (inverse of resistance) of each path."
] | [
"Imagine you have two drains in your sink, one of which is clogged with a big, nasty hairball and one that isn't. How does the water figure out to (mostly) take the clear drain.",
"The answer is that the wire/drain is already full of electrons/water which upon reaching the resistance/blockage transmit it's presen... | [
"Because the wires are already full of electrons before the signal gets there. If one has less resistance, there will be less resistance to the signal right at the junction, and the signal will go to that one."
] |
[
"How do bird lungs work?"
] | [
false
] | I stumbled upon the Wikipedia article about bird anatomy ( ) and am excited to see that bird lungs are really different than how mammal lungs work (which seem simpler to me and I think I roughly understand.) I am trying to understand what's going on here but am having some trouble. Specifically, there is a caption on t... | [
"Here, try ",
"this",
" diagram instead of the one on the wikipedia page. The bird breathes in air, which goes to the farthest air sacs. It breathes out, and air travels through the lungs. It breathes in again, filling that rear set of air sacs once more while the first breath enters the air sacs nearest the mo... | [
"Amazing! Thanks so much. It reminds me of a car engine or something similar."
] | [
"This really is neato."
] |
[
"If antimatter exists, would it be theoretically possible for an antihuman to exist?"
] | [
false
] | null | [
"Antimatter and matter behave in very similar ways. Most of the interactions relevant for forming atoms and human bodies are due to the strong and electromagnetic forces, which work the same way for matter and antimatter (the weak force doesn't)."
] | [
"Yes, it's possible."
] | [
"What would an antihuman be like? would an antihuman look different at all? would an antihuman consider us to be antihumans? "
] |
[
"Is there any connection between Information Entropy and Thermodynamic Entropy?"
] | [
false
] | I've been reading a lot about information theory lately and it is really interesting. But many of the equations I've seen remind me of physics so I'm curious:Is there any connection between Information Entropy and Thermodynamic Entropy or any other physical quantities? I'm somewhat familiar with digital physics, and I'... | [
"The two things are related, but not exactly the same. The total information content of a closed system is constant, which is not true for entropy in thermodynamics. My preferred way of looking at it is to say that the thermodynamic entropy is the amount of information of a system that's hidden in the microscopic ... | [
"I recently read a great comment (which I can't find) about how ",
"Huffman coding",
" works. It is directly related to Information Entropy.",
"I will try to explain the basics here.",
"Imagine you have a text file with 4 letters in it. In a straightforward approach you can give each letter a code from 00 t... | [
"Interesting post, but I'm not sure I understand the exact physical connection you're making here. As I mention in my answer, the information to fully describe a system does not change over time, whereas thermodynamic entropy can. When you say \"need less information (per symbol) to describe it.\" what type of desc... |
[
"Why is nuclear power in France have a 40% share of energy consumption yet a 76.3% share of energy production?"
] | [
false
] | [deleted] | [
"The nations of Europe are trading electricity with each other. In fact most of continental Europe shares one synchronized power grid, so Hungary may very well order some nuclear electricity in France when their production is short."
] | [
"maybe, some 36.3% of that capacity is used for export, government, and/o industry? It may be that the number you reference is consumer or household consumption? ",
"Do you have context? i don't know your source."
] | [
"France actually load follows with their nuclear plants. They are the first to do regular real time load following. ",
"We do load following at a handful of us plants too. It’s uncommon but it’s not hard to do. I’ve had to answer load follow orders before. It’s easy. "
] |
[
"Why do animals eyes reflect light when humans don't?"
] | [
false
] | Was driving home in the dark, saw two bright spots staring back at me about a foot off the ground. As I got close I saw it was a woman walking her dog. I know this also happens with other critters such as raccoons and possums as well, but why? | [
"Its from the Tapetum Lucidum. Its an extra layer in the eye of nocturnal animals that reflects photons so the eye can capture more. It's not in us because on bright sunny days where we are our most active, the last thing you want is more light in your eyes. ",
"edit: spelling"
] | [
"we dissected a cow eye once, and let me tell you, the layer is absolutely beautiful, It has this amazing colorful sheen."
] | [
"For anyone who's ",
"curious",
". And yes it's quite a lovely sight. More so than you'd expect to see in the eye of a dead animal. ",
"Chicken ovaries are pretty wild too. "
] |
[
"How would big gravitational waves affect Earth from up close?"
] | [
false
] | If there were two supermassive blackholes colliding near Earth, would they affect the hypothetical orbit of Earth (considering that it would be different with 2 black holes closeby)? Would things start flying away and off of Earth? | [
"If the two supermassive black holes were near enough to the Earth to affect the orbit, we would basically just be in orbit of those black holes and you wouldn't even be concerned about the gravitational waves.",
"Gravitational waves from supermassive black hole binaries will emit typically very low frequency gra... | [
"We ran some back-of-the-envelope calculations before announcing the GW150914 detection, and at the point where tidal forces started to have a smaller effect than the gravitational waves, it would feel similar to standing in front of a loud subwoofer at a concert. ",
"So yeah, if you want to feel a stronger effec... | [
"I really like that comparison; I'll make sure to use that in the future!"
] |
[
"If you were standing on any other planet besides earth in space, and threw a ball, would it still fall accordingly as a parabola?"
] | [
false
] | [deleted] | [
"on earth the trajectory of any object thrown can be represented by a parabola but would the same thing happen on Mars?",
"Yes. ",
"I suspect gravity has something to do with it ",
"It has ",
" to do with it. :)",
"Objects fall in parabolas relative to the \"flat\" surface of the earth because of differin... | [
"one other thought to add, the trajectory will be slightly offset due to air resistance. On planets with more air resistance relative to the downward force o gravity, the trajectory could change to a detectable level. "
] | [
"one other thought to add, the trajectory will be slightly offset due to air resistance. On planets with more air resistance relative to the downward force o gravity, the trajectory could change to a detectable level. "
] |
[
"Can water evaporate below its boiling point?"
] | [
false
] | null | [
"Yes, water evaporates in “normal” conditions. Put a cup of water somewhere and leave it for a while, you can see it"
] | [
"Thermal equilibrium doesn’t mean that every individual microscopic member of the fluid has the same energy. They have a spread of energies and occasionally there will be a water molecule with quite a large energy at the surface of the water which can then break free"
] | [
"You’re welcome"
] |
[
"What determines the pitch of feedback?"
] | [
false
] | More specifically, if one has a system of microphone + speakers at a certain separation, amplification small enough to cause feedback, what would determine the frequency (or pitch) of the feedback noise? Also, if the separation between speakers and microphone were not small enough to cause feedback, but were large enou... | [
"Every amplifier amplifies certain frequencies better than others. Every speaker emits certain frequencies better than others. Every microphone picks up certain frequencies better than others. Feedback will tend towards the frequency that optimizes those things."
] | [
"the pitch frequency of of the feed back is one over the time it takes the sound to complete one circuit. So basically the speed of sound divided by the distance between the speaker and the microphone."
] | [
"I just did some science, and I don't think this is right. I figured I could have some geeky fun by finding the frequency of feedback with my computer two distances away from a speaker to determine the speed of sound. I found that even walking from right next to the speaker to pretty far from the speaker, the pitch... |
[
"Can cordyceps infect humans?"
] | [
false
] | [deleted] | [
"Toxoplasmosis"
] | [
"Syphilis",
"Edit: some with neurosyphilis become disinhibited and may become more promiscuous.",
"Double edit: ",
"Rabies",
"!"
] | [
"ha ha ha, don't worry fellow human friend, cordyceps can't infect us humans, cordyceps is our friend!"
] |
[
"Are there scientific research fusion centers?"
] | [
false
] | In the military we have what are known as Intelligence or Operational Fusion Nodes where analysts and decision makers are funneled intelligence and operational data. The analysts give background or significance, correlations and add anything that might link different events or indicate upcoming developments or actions ... | [
"I came here thinking about actual fusion and wanted to mention things like the National Ignition Facility...",
"As a whole, science is becoming extremely interdisciplinary, and there are many scientists that are trying to bridge the gaps between different fields, or using discoveries in another field to apply to... | [
"there are many scientists that are trying to bridge the gaps between different fields",
"It always seems ad-hoc however. Most of the researchers and docs I know just read on their own different things which they have stumbled upon in the past that is applicable. There seems to be no organization guiding their ha... | [
"Well that is the unfortunate nature of science and the massive degree of specialization. You really can only read things relevant to your research and your field. It would be grossly inefficient to try to follow on all sorts of research. Me reading some ecology study of the effect of pesticides on XYZ has absolute... |
[
"Will the Higgs Field lead to further understanding of the speed of light? If not, what might?"
] | [
false
] | null | [
"The speed of light is pretty well understood. Is there a reason you think it isn't?"
] | [
"We already understand the speed of light just fine. In terms of light, we can understand the speed in terms of Maxwell's equations, although that's not fundamental (after all, things like gluons and gravitational waves travel at the exact same speed, and they have no idea about Maxwell's equations).",
"What the ... | [
"Could it perhaps offer a way to prove that the mass of a photon is indeed 0?"
] |
[
"Time dilation paradox?"
] | [
false
] | null | [
"You are describing ",
"length contraction",
". There is no paradox."
] | [
"That's what I figured. But I'm not sure how to interpret that. Length contraction says the observer should be seeing a compressed length. Not a larger one. "
] | [
"The pilot does see a contracted length."
] |
[
"Do antibodies stay with you for life?"
] | [
false
] | Do antibodies stay with you for life both naturally acquired through getting sick and through vaccines? If they don't why is this? | [
"Antibodies themselves have very short half lives. Our acquisition of immunity or tolerance to an antigen comes through memory B cells which produce antibodies. Compared to effector cells of our immune system, the memory cells, as their name suggests, have very long lifetimes.",
"Let's say you get a meningitis C ... | [
"A couple of weeks"
] | [
"What about the antibodies that are circulating the body? How long do they last?"
] |
[
"How many people would have to point a laser pointer at the moon simultaneously for the lasers to be visible? Is it possible?"
] | [
false
] | If it wouldn't be possible then what limitations do we face? | [
" - how much does a laser disperse on its way to the moon?",
"A household laser beam pointed at the moon will have expanded to somewhere between 10s to many 100s of miles in diameter by the time it gets to the moon (depending on the quality of the laser, the latter being most household varieties). ",
"Assume a ... | [
"To add on to part (1):",
"The divergence of high-quality laser beams is commonly less than 1 milliradian",
". Assume theta=1 milliradian divergence at D=384 000 km, you would expect a point like beam to grow to a size D tan theta ~ D theta ~ 384km."
] | [
"For whoever wants to add to this:",
"To follow this up, you need to figure out how much of the moon must be lit up (in area) to be visible to your eyes (given the previous answer on this, would that area be enough?), you can assume total darkness around yourself and that the moon is not lit (for the sake of eye ... |
[
"Can dissolving a solid into a liquid decrease its volume?"
] | [
false
] | We've been learning about partial molar volumes of solutions, and I was wondering if the same effect could be achieved with a liquid and a solid. Assuming, the solid is completely soluble in the liquid, wouldn't the interactions in the resulting solution be the same as if you had combined two solutions? | [
"Yup! I just found a ",
"simple experimental protocol",
" that looks at how the volume of a solution decreases when you add sodium chloride. ",
"The key is something you mention - the interactions between water molecules ",
" when you dissolve something in it. By adding salt, some of the distance between wa... | [
"Um, no? Anything you add to it takes a piece of that 100%, so you wouldn't be able to go over 100%.",
"Suppose you add 1 mL of some kind of salt into 100 mL of ethanol and get 97 mL of solution, like he said. That's 100 mL of ethanol per 97 mL of solution, which is roughly 103.1% alcohol by volume. Personally I'... | [
"Saltwater is more dense than freshwater, so yes. "
] |
[
"[Paleontology] How often are the skeletons of Dinosaurs seen in museums composed from bones of more than one individual?"
] | [
false
] | I know that almost all skeletons and "bones" in museums are actually castings, however I was wondering how many individual complete skeletons of larger dinosaurs actually ever fossilised, leading me to think that most museum skeletons are the result of many individuals' bones as that allows us to have at least an idea ... | [
"So....plane boring regular ole geologist here, firstly your mostly correct. It’s not most but I would say all the skeleton constructions you see are castings, since actual rock is too heavy and delicate to display. Granted I haven’t visited every natural history museum on earth but it’s a fair assumption. Fossils ... | [
"I remember going to the natural history museum in Chicago and it was a slightly big deal that the t -rex (I think) was the largest from one animal, or something along those lines. My point is that they are probably mostly a composite skeleton. Interested to hear someone with more knowledge, though"
] | [
"Um, what?",
"Are you asking why don’t they display the animal with muscle/skin?",
"Well they (museums) do, but the skeletons are still molds from ",
" so they represent a fossil someplace, usually...or it’s a approximation if that bone (ribs usually look like ribs, especially from the same animal....if they ... |
[
"Why doesn't the pudendal nerve carry parasympathetic fibres?"
] | [
false
] | The pudendal nerve arises from S2, S3 and S4 but it apparently only carries afferent and efferent sympathetic fibres - not parasympathetic. I thought parasympathetic outflow was craniosacral so how do nerves from S2, S3, S4 not carry parasympathetic fibres via the pudendal?? Thanks in advance! | [
"Parasympathetics in the pelvis are carried on pelvic splanchnic nerves. These nerves arise from ventral rami of the S2-S4 spinal nerves (cell bodies located in sacral ventral horns), as does the pudendal. However the parasympathetics take their own path and branch on pelvic splanchnic nerves, through the inferior ... | [
"The pudendal nerve carries fibers that originate in the ventral horn (somatomotor) and dorsal root ganglia (somatosensory) of the S2-S4 spinal levels. It picks up post-ganglionic sympathetic fibers from the sacral sympathetic trunk. Pre-ganglionic sympathetic fibers originate in the lateral horns of L1-L2 spinal l... | [
"I thought the parasympathetic was cranio-sacral and the sympathetic was thoraco-lumbar. So why does the pudendal nerve, arising from the sacral section, exclude parasympathetic fibres? Or does it arise from the lumbar section and enter through the sacral foramen to be called a 'sacral nerve'?"
] |
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