title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Why does pancreatic cancer have such a low survival rate?"
] | [
false
] | Automod I do not have cancer, I'm not asking for medical advice so backkkkkkkk offf. Alex Trebek just announced he has stage 4 pancreatic cancer thats why I'm asking. | [
"From my very limited knowledge, is that this type of cancer only shows symptoms in late stage. By the time most people search/find it it's to late. A family member had it, it happened to show up in the top corner of a scan while they were looking for something else. 2 other doctors missed it, then one noticed a sp... | [
"Yes, it causes either no symptoms or very nonspecific ones until it's far too late to do anything about it. The pancreas is also a very...\"internal\" organ, and you can't really look at it unless you're doing specialized scans that aren't done routinely."
] | [
"The pancreas releases insulin directly into the bloodstream. When symptoms appears it's usually very far along (stage 4) then cancer cells are already breaking off and spreading into other parts of the body. ",
"It's something like 5% survival rate. My old bosses father died of it. He donates $5 million a year i... |
[
"Could the Huygens probe have contaminated Titan?"
] | [
false
] | null | [
"Hi demojunky73 thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the fol... | [
"Planetary Sci"
] | [
"‘Planetary Sci’"
] |
[
"Why are most of the oldest living people in the world female?"
] | [
false
] | According to most of the oldest living people in the world are female. Why is that the case? | [
"Statistically women tend to live longer than men. This may be due to a number of factors:",
"Up until fairly recently, men tended to work outside the home, while women did not. This put men at greater risk of exposure to work-related injuries and illnesses.",
"Men are more likely to neglect their health and ro... | [
"As ",
"/u/Agnurse",
" mentions, there's a variety of sociological factors that will play a role. But I'd dare to say there's also biological reasons, as the same pattern holds true in most other mammals. For ",
"cats",
", ",
"dogs",
", ",
"monkeys",
", and I could go on.",
"As a general rule of t... | [
"While these would explain why the average woman would live longer than the average man, I would think looking at the just the longest lived list, we're just looking for the outliers. There has to be men that didn't work outside, was conscientious about their health and didn't take risks. No men in the top 50 makes... |
[
"How fast does electricity move?"
] | [
false
] | I just saw that gif of the people lined up, and the guy at the end touched the electric fence and it seemed as though they all were instantly zapped at the same time. If the line were a lot longer would it take more time? | [
"The electrical energy travels at what is called the ",
"propagation velocity",
" Or ",
"this link",
". Typically between 60 to 90% of the speed of light, depending on the cable used.",
"You can use that information with a device called a ",
"time domain reflectometer",
" to find the distance to a cab... | [
"The speed of signal propagation in a metal wire is basically the speed of light divided by (the square root of) some material dielectric permittivity and permeability, which for a metal would be quite close to 1. You can see a table of examples here:",
"https://en.wikipedia.org/wiki/Velocity_factor#Typical_vel... | [
"It almost travels the speed of light so there's no point to try and shock 2 people at different times no matter how far away they are (on earth). It's technically true that they'd be shocked at different times but not practical."
] |
[
"Could the expansion of universe be explained by theory of our universe being inside another as a black hole?"
] | [
false
] | [deleted] | [
"It's a perfectly reasonable theory. However, your problem is that it doesn't actually predict anything, it just describes something that we already know about in a vague way.",
"If you want your theory to be scientific, you need to do more than that. You need to identify some property of the universe that would ... | [
"It's a hypothesis, sure. It's also a theory, by a standard, normal and historical use of the term. But it's not a ",
" theory.",
"I think that accepting the meanings of words but drawing distinctions where necessary is better than trying to enforce rigid redefinitions that aren't even used in a standard way in... | [
"It's a hypothesis, sure. It's also a theory, by a standard, normal and historical use of the term. But it's not a ",
" theory.",
"I think that accepting the meanings of words but drawing distinctions where necessary is better than trying to enforce rigid redefinitions that aren't even used in a standard way in... |
[
"Do animals have a sense of time?"
] | [
false
] | Do they sense a passage of time or do they know if winter months are coming soon? Is the foraging for food just out of instinct or is it because of a sense of passage of time | [
"It's been showcased that orangutans not only plan ahead for the future, but they also communicate it to their peers. It shows evidence that they keep a bit of a schedule for their daily lives.",
"Source",
"If you don't want to read an entire peer reviewed journal on this study, ",
"here",
" is a more strea... | [
"They certainly do have a sense of time, but not necessarily in the way you mean.",
"Animals, including humans, almost all have a sense of time that is described in three scales: millisecond timing, which is largely controlled by the cerebellum and mostly concerned with coordinating movement; interval timing, on ... | [
"So... Does that mean animals also procrastinate?"
] |
[
"If someone listened to the same sound (i.e. a music album) when trying to fall asleep each night over a long period of time would that sound eventually help them fall asleep faster? Conversely would they find it harder to fall asleep if they couldn't listen to it?"
] | [
false
] | null | [
"Interesting question. People find that falling asleep to white noise is easy, because it's the same constant sound and no irregularities. This noise allows a person to be able to shut down their brain and fall asleep faster. If a person substituted this with a music album it would depend on what memories are ass... | [
"I've done that very thing for 6 of the last 10 years. Same album , same volume. IMO it absolutely does help me fall asleep. I stopped for a few years and it didn't keep me from falling asleep. But like turning off the lights it does help me fall asleep faster and sleep better."
] | [
"In terms of classical conditioning, this could more or less work to make you fall asleep faster. This is essentially the same principle used in stimulus control instructions to treat insomnia, but in that case the goal is to associate bed (not music) with sleep. The trick is to avoid associating bed (or music in t... |
[
"What physical property makes certain materials transparent or translucent?"
] | [
false
] | Diamond and graphite are both carbon, yet one is translucent and the other isn't. So are transparency and translucence solely a consequence of molecular structure? Or is there more going on? | [
"Take a clear grocery bag, and stretch it. Starts off transparent, becomes translucent.",
"In this case, some of the tangle of polymer chains that make up the bag line up and the result are these microscopic regions with more crystallinity that scatter light. So the bag looks cloudy and translucent -- still lets ... | [
"Oh, I see. In this case, the distinguishing feature is the electronic band gap of the material, and yes, this strongly depends on the arrangement of atoms. In the case of diamond, the band gap is something around 5 or 6 eV. A photon has to have at least 5eV before it will be absorbed by the diamond. Visible light ... | [
"Here's a great video by Nottingham science: ",
"https://www.youtube.com/watch?v=Omr0JNyDBI0",
"Basically, when a photon hits an opaque material, it uses it's energy to put an electron into it's excited state. By doing that, the photon \"disappears\". When a photon hits a transparent material, it has not enoug... |
[
"Let's say you are being teleported somewhere - Wouldn't you \"die\"?"
] | [
false
] | null | [
"Well, teleportation is magic and you can define your magic to work however you want. If you're talking about quantum teleportation (not magic, a real thing but not what it sounds like) then there is a ",
"theorem",
" that states that you can't create a clone of a quantum state."
] | [
"I just understood it as that teleportation has worked,",
"Where did you get the idea that teleportation in the sense you describe it, \"has worked\"? (or even been attempted?)"
] | [
"I just understood it as that teleportation has worked,",
"Where did you get the idea that teleportation in the sense you describe it, \"has worked\"? (or even been attempted?)"
] |
[
"Why is leukemia contagious between cats but not between humans?"
] | [
false
] | null | [
"It's a feline virus that causes leukemia in cats, and it's the virus that can be transmitted. Leukemia in humans is hereditary and associated with risk factors like radiation exposure but is not related to a transmittable virus."
] | [
"As the others have alluded, there are some cancers that can be caused by a virus. In humans the HPV virus can cause cervical cancer. In other animals other viruses may cause other types of cancers.",
"And since viruses are mostly species-specific, the end result is different types of cancer(really cancer-causing... | [
"It's typically not hereditary. And there are viruses that cause leukemia in humans."
] |
[
"How is velocity measured in space? What is it measured relative to?"
] | [
false
] | null | [
"Usually this is done by the Doppler method. This means that we are measuring the velocity relative to Earth. We then often use models for how Earth and the sun moves to calculate the velocity relative to ",
"local standard of rest",
"."
] | [
"At a more cosmic level, velocities can be measured relative to the comoving zero dipole anisotropy frame of the cosmic microwave background. ",
"So you might be talking about motion relative to a point on the Earth's surface; but that point on the Earth's surface is moving at up to 0.46 km/s relative to the cent... | [
"Interesting, thanks! I've always found it really bizarre when I hear \"the space shuttle travels at <x> miles per hour\"... relative to... the Earth? Which is also moving and is orbiting the Sun? Which is also moving? It all gets very confusing."
] |
[
"When an old star begins fusing Iron it begins \"using\" more energy than it produces. Is the \"used\" energy what builds up to produce super-nova?"
] | [
false
] | I realize there must be enough mass to begin with. But what exactly happens to tip the balances again and set off the explosion? | [
"Iron is the heaviest element a very massive star will produce to gain energy through nuclear fusion so it can withstand the gravitational pull (technically nickel is the heaviest element that still gives off energy in a nuclear fusion process, but for other reasons the star mainly stops at iron). Once the core has... | [
"You can easily google the fission and fusion terms and see that your definition is wrong.",
"The core collapse is also not because of massiveness of the core but because the pressure inside the core drops significantly which causes the collapse."
] | [
"You can easily google the fission and fusion terms and see that your definition is wrong.",
"The core collapse is also not because of massiveness of the core but because the pressure inside the core drops significantly which causes the collapse."
] |
[
"When you feel full after eating, is it because your stomach is literally not able to fit more food or is it just your brain telling you to stop eating?"
] | [
false
] | null | [
"When you start eating and filling up your stomach, your body produces a hormone called leptin that signals to the brain that you’re getting full, reducing your appetite and giving you the feeling of fullness.",
"As you keep eating and your stomach becomes distended as a result of ",
"eating, your body will con... | [
"True! There are other hormones like ghrelin (which stimulates appetite) whose levels decrease during meals, and cholecystokinin (CCK) & glucagon-like-peptide-1 (GLP-1) [which increase after eating] that are also important factors in feeling \"satisfied\" after meals. ",
"Like most functions in our body, even hun... | [
"Leptin is not the main satiety hormone during meals. It's produced by fat cells and works over long periods of time. Other hormones are much more important in the short term. For example - grhelin drops and cck and glp1 increase after eating while leptin remains relatively stable."
] |
[
"Torque on paramagnetic material in a magnetic field"
] | [
false
] | I've come across an equation in a paper about magnetism that isn't derived. I'm trying to figure it out, but haven't found it yet, and it's outside my usual field. It's about how torque is applied by a magnetic field to a paramagnetic fibre. Apparently, the most torque is applied when the fibre is at 45 degrees to the field - the sin(2*theta) term. I'm not sure why that would be, intuitively the torque would be maximum at 90 degrees. Torque=0.5 * mu * V * H * dx * sin(2*theta) where, mu is vacuum permeability V is the volume of the fibre H is the magnetic field intensity dx is the anisotropy of volume susceptibilty theta is the angle between the fibre axis and the magnetic fiield | [
"I'd have to see a diagram, but I guess the force varies as cos(θ), the lever arm as sin(θ), so the torque as sin(θ)cos(θ) = sin(2θ)/2"
] | [
"Ok, I think I got this sussed. Too many years since I did magnetism though.",
"Firstly, your equation for torque is the cross product of magnetic moment and magnetic field.\n",
" (Nm)= ",
" (Am",
" x ",
" (N/Am)",
"Because it's paramagnetic, the susceptibility χ is very small and",
" = μ (1+χ) ",
"... | [
"That would make sense, not sure what you mean about the lever as sin(theta) though...",
"Here's a diagram",
"(Blue is for reference as an axis, the black line is a fibre in the magnetic field caused by the magnets either side)",
"According to the wiki, torque is a cross product of the field and the magnetic ... |
[
"Air and water are both fluids — why are there no birds that fly like fish swim or fish that swim like birds fly?"
] | [
false
] | null | [
"Do you have a source for this?"
] | [
"https://en.m.wikipedia.org/wiki/Atmosphere_of_Earth",
"Air is a gas"
] | [
"Air is not a fluid."
] |
[
"Do people with wider set eyes have better depth perception?"
] | [
false
] | Calling ophthalmic optricians (optometrists) or biologists. Has there been a study on width between the eyes and a correlation with better/worse vision? | [
"Sitting here with me is a device called a stereoscope. This stereoscope contains adjustable mirrors which can be adjusted in such a way that they are effectively setting your line of vision for each eye, outward. As though the eyes are further apart. ",
"There is a point where the brain loses its focus and is... | [
"The ",
"Pseudoscope",
" is nauseating even just reading about it, for some reason."
] | [
"Related: is there a measure of \"depth-perception\"? Would it be related to the standard 20/20 system?"
] |
[
"Microscopy Questions"
] | [
false
] | My apologies, as this is not a traditional askscience post, but I feel that I could reach the most interested parties here. I had a question about a microscope purchase I'm planning on making coming up pretty soon and some other redditors I've contacted have suggested making a general post. I'm doing a project that will involve looking at some slides of stained CNS tissue and blood but mostly looking at fecal samples for parasite loads. Since I'm going to be spending a lot of time doing this (around 500-1000 fecal samples), I was thinking about getting an LCD screen scope instead of the traditional binocular scope. Do any of you have LCD screens experience? If so, any company recommendations? If not, could you recommend a scope in the range of 400-600 dollars? This is an example of the kind of thing I was looking at: but I could go more expensive for a LCD I would. | [
"Well, I forget what brand of scopes I tend to use (inverted and not). But Traditionally we buy the scope, then buy a camera attachment that attaches to a computer. I have seen scopes with LCD controls, but all scopes I have seen with visual displays have an attachable camera. You can scan SO much faster through... | [
"Congrats you made me spill my coffee"
] | [
"Agreed. A good CCD camera on a decent scope will be much more beneficial than having an LCD screen in which you have to scan with. The NIKON COOLSNAP range are pretty decent CCD cameras and a good place to start looking if you are interested."
] |
[
"Why do some fruit juices, take orange juice for example, need to be refrigerated when the orange itself does not need to be?"
] | [
false
] | null | [
"Well an orange's skin secretes oils that have anti-fungal and anti-bacterial properties. An orange with an uncompromised skin will last relatively long. However, the juice and pulp contain no such defenses and certain bacteria and fungi will happily grow on/in it. Refrigeration generally slows down growth and acti... | [
"In addition to the physical barrier the skin provides, the undisturbed cell wall structure of the fruit compartmentalizes the components of the orange that microorganisms would metabolize. Additionally, enzymes that would hasten chemical degradation of the fruit are similarly bound. Once the cell walls are disturb... | [
"Keep in mind that this is only the case if the container of the juice has opened at some point. Leaving it intact keeps the juice inside mostly-sterile, and it's just about as preserved as an unpeeled orange. This is why compromised containers of fruit juices with no preservatives tend to become unsterile and full... |
[
"Are animals' facial expressions representative of their mood or do humans just interpret them that way?"
] | [
false
] | If an animal appears to be smiling, is it actually happy or is it's face just doing that? For some types of expression, I imagine the answer is obviously yes. If a tiger is bearing it's teeth at you and hissing, it is pretty clear that it is demonstrating that it is aggressive. But for expressions like happiness, worry, fear, relaxedness and the like, is that actually how the animal is feeling or do humans just assign human emotions to vaguely similar expressions on animals? | [
"Most animals do actually show facial expressions to indicate their mood however they’re often different than that of humans, for example smiling is not shared by a large group of creatures as the facial structures for animals vary widely so most need to develop different ways since their faces are so different, a ... | [
"There's been a number of articles around lately claiming that dogs evolved eyebrow muscles to better communicate with humans - apparently we liked the more expressive ones better.",
"Animals have body language, and have some very deep-seated yet basic perception around the body language of other animals - someth... | [
"It’s important to note too that facial expressions (specially in animal science) are deemed predictive of a general motivation or tendency to engage in a series of actions. Using this approach, it may be easier to understand the facial expressions of nonhumans that are dissimilar in their look."
] |
[
"Conduction heat transfer to surface from temperature field?"
] | [
false
] | null | [
"Hello,",
"We don't offer schoolwork help here."
] | [
"Who said anything about schoolwork? "
] | [
"The question seems like a homework problem, and you made a brand new account called \"engHelp\" in order to ask it.",
"Is it ",
" schoolwork?"
] |
[
"How would we know if Voyager 1 or 2 crashed into something?"
] | [
false
] | I went to JPL's website, but there is nothing there about the possibility of it happening. Did we just chose a course that at the time looked pretty empty to us? | [
"We're still in contact with both so if that ceased unexpectedly then we'd at least know something went wrong. More than likely it'd have been some kind of failure on one of the crafts but knowing it had crashed into something would be pretty difficult to figure out. Perhaps if part of a spaceship was hit and the t... | [
"Just fyi, traveling at it's current speed it would take Voyager about 76,000 years to reach the nearest star. So they don't have to worry about a trajectory change due to being near a star or black hole. Space really is mind blowingly big!"
] | [
"Perhaps if part of a spaceship was hit and the trajectory changed or it went into some kind of tumble then we might be able to deduce that it was hit.",
"If we're still talking about the Voyagers here, then it is pretty certain we would never be able to ascertain what happened in the case of a fatal collision un... |
[
"Would a relay system of satellites speed up interstellar communication?"
] | [
false
] | If we are trying to talk to an object, let's say 100,000 light years away. We are limited to at most the speed of light let's also say. Would having 100 relay satellites spaced out between us and them, would our transmission would go faster at all? | [
"You can't improve latency (indeed, adding relays will worsen latency). However you can improve bandwidth; a shorter signal path to a relay will have a better signal-to-noise ratio, so you can send at a higher data rate before it becomes unreadable (with each relay applying error-correction codes to restore the mes... | [
"No. Transmission can't go faster than the speed of light. How would the relays improve on that?"
] | [
"Speed, in terms of communication, can refer to one of two things: latency, and bandwidth. Latency is how quickly (time-wise) that information is conveyed, while bandwidth measures how much information is able to be transmitted at once (typically measured in megabytes per second). Bandwidth can always be improve... |
[
"So in spacetime and gravity, time dilation happens. Does space dilation happens too?"
] | [
false
] | Keeping my fingers crossed that this question sees the light of day. Does this question makes any sense? If it doesn't, why it doesn't? If it does, why it does? If the post gets deleted, it's probably the question is ambiguous or retarded. And I'd understand. | [
"Does space dilation happens too?",
"We call this length contraction. If a 1-meter long rod flew past you at 0.99c, it will look about 14 centimeters long. If that rod was made of electrons you'd see a significant magnetic field despite there being none in the rod's reference frame. Gravity will cause space and t... | [
"I think its worth emphasizing to OP that the rod doesn't just ",
" 14 cm long to you, it ",
" 14cm to you. As it flew past you could contain it in a 15cm long box like ",
"this",
". This image is from the wikipedia article on the ",
"ladder paradox",
" which explains the situation well.",
"It probabl... | [
"The sphere would contract in its direction of motion, so it would end up being ellipsoidal. "
] |
[
"What is the largest planet we know? How big can a planet get or is there something restricting it from being Enormous?"
] | [
false
] | [deleted] | [
"Well, they eventually cross over into brown dwarfs. Once they get large enough to begin nuclear fusion, they become stars.",
"Jupiter for, instance, would have to be 80 times more massive than it currently is to initiate hydrogen fusion.",
"Large brown dwarfs can fuse deuterium and tritium, two isotopes of hyd... | [
"It's more than the star forming leads to hydrogen fusion. Once enough matter collects in a single place, it begins to collapse under its own gravity. This heat and pressure becomes so strong that atoms start fusing. At that point, the outward pressure of the fusion fights against the crushing pressure of the stars... | [
"Thoroughly fascinated. I had no effing idea planets can become suns. I thought they were just two different kinds of celestial bodies.",
"Can you explain the hydrogen fusion and how/why that leads to a star forming?"
] |
[
"Why can't you absorb mercury (metal) with a sponge?"
] | [
false
] | [deleted] | [
"When you pick up water with a sponge, some of the water forms very weak chemical connections with the material of the sponge. We say that the sponge is 'wettable' with water.",
"Mercury doesn't have the same chemical properties as water, and won't make the same connections. If you had a sponge made of say, gol... | [
"Cohesion is the intermolecular force between molecules that allows molecules of the same substance to adhere to each other, this creates surface tension. Adhesion is the ability of a liquid to stick to other things, like how that last drop of beer at the bottom never quite makes it to your mouth. Mercury, has a ... | [
"I don't know what would happen.",
"I would guess that it's a mix of the sponge staying squished, and some mercury getting forced into the cells and capillaries of the sponge."
] |
[
"Has a gravitational force been observed between massless particles?"
] | [
false
] | Light is attracted to mass by gravity (black holes, gravitational lensing). Due to Newton's 3rd law (For every action, there is an equal and opposite reaction) the light will assert a force on the mass via gravity. Extending this, is a gravitational force between photons? And is it large enough to be observed? I understand at high energies, pair production will be a factor, but I was thinking about lower energies than this. Additional question: If you shine two lasers of wavelength X metres in parallel, Y metres apart, how long will it before the beams converge due to gravity. I'm not sure about my logic here. Please correct me if I'm wrong. | [
"Extending this, is a gravitational force between photons? ",
"Yes, if they are not perfectly parallel (that also answers your last question).",
"And is it large enough to be observed?",
"Not with today's technology, and not with any planned or even proposed experiment."
] | [
"An accessible, but somewhat naive, way of motivating the idea is that you can always shift into a reference frame where two parallel beams or photons of light are redshifted arbitrarily close to zero energy. Since spacetime curvature is affected by energy density (and some other factors), then in such reference fr... | [
"Why would there not be a force if they are parallel?"
] |
[
"Is it important for a 14 yr old to study science in school? Why?"
] | [
false
] | null | [
"Initially your first question in your subject seems like it can be answered scientifically, or at least with with some kind of data to support either side.",
"You're second question is more of an opinion. Some individuals will claim that everyone is naturally scientist in some way, that we strive to answer the u... | [
"Is it important for a 14 yr old to study science in school? Why? ",
"The only really objective thing I can say is that obviously not everybody needs to be good at science. Investment bankers don't need to understand vector products and actors don't need to know about meiosis to do their jobs well or lead a ful... | [
"John, you will be delighted to see the non-profit I started - ",
"www.students2science.org"
] |
[
"Are prokaryotes capable of lysing foreign cells?"
] | [
false
] | null | [
"Absolutely, usually via exotoxin secretion into medium or injection into target. For example, streptolycin o is an exotoxin secreted into the medium by Streptococci to lyse erythrocytes, by forming pores in the target cell's membrane."
] | [
"Thank you so much!"
] | [
"Adding on- lysing cells is one way that bacteria can spread in the body. They will use the cell's favorable conditions to grow their numbers, lyse the cell, then find their way into new cells to repeat the process."
] |
[
"During the experiment conducted by Ernest Rutherford in which the nucleus is discovered, an alpha particle is shot at a thin foil strip. An alpha particle is a helium nucleus, so how did they not know the nucleus existed despite being able to isolate one and fire it?"
] | [
false
] | As far as i understand it the gold foil experiment was conducted when the plum pudding model was the accepted theory by the science world, including Rutherford himself. But how can the nucleus not have been discovered before when you consider that the alpha particle is a helium nucleus. How can they not have known what an alpha particle is despite them being able to isolate and ‘fire’ one at the gold foil? | [
"They knew that radioactive materials gave off radiation, but they did not know what that radiation consisted of. There were three types of radiation that were observed: one was charged and heavy (can be stopped by paper), one was charged and light (can be stopped by metal), and one was neutral and light (can only ... | [
"I actually don't know the historical sequence. Apparently for the beta particle it was 1900. With alpha particles it was Rutherford in 1907. However, it wasn't known that ionization involved removing the electrons to leave the much smaller nucleus, because the atomic structure wasn't known."
] | [
"Electrons were already known to have existed, did they know electrons were beta particles at the time or did they, like with the alpha particle, only connect them later?"
] |
[
"[Physics] How does dew form? And also, what exactly does the dew point mean?"
] | [
false
] | I was up early this morning and was looking around my yard. And also looking at the dew, and wondering how it formed, and what the dew point has to do with it. My best idea is that condensation comes down overnight and makes dew stick to everything? At least until the sun comes and "melts it off"? | [
"Air always contains some small amount of water vapor. We generally refer to the amount of water in the air as \"humidity\", generally given as a %. At 100% humidity, by definition, the air is fully saturated and can't hold any more water.",
"It turns out that the colder air is, the less water it can hold. So for... | [
"Air can only hold so much moisture given its temperature, we call this relative humidity. As the temperature drops overnight, the air can no longer hold all that moisture and it condenses on surfaces it touches and it turns to water droplets. There's more science behind it but that's the gist, I work in the humidi... | [
"Thank you for a very detailed answer. \n🇬🇧👍🏻🇬🇧"
] |
[
"If I cuy myself in vacuum, what colour would my blood be?"
] | [
false
] | [deleted] | [
"Normal blood is red: oxygenated blood is brighter red, deoxygenated blood is dark red.",
"So the answer would be red."
] | [
"I don't think \"blue-ish\" is an accurate description of ",
" blood. Venous blood is not blue."
] | [
"Red."
] |
[
"Why is Voltage directly and inversely Proportional to the Current?"
] | [
false
] | V=IR therefore I=V/R. Thus a greater voltage = greater current. However, P=IV therefore I=P/V. This means a greater voltage=smaller current. Why? | [
"Voltage is directly proportional to current when resistance is constant and they're inversely proportional when power is constant. Typically in a circuit voltage will be fairly constant and changing the resistance will change the current causing power to change."
] | [
"Your question has more to do with math than physics.",
"Say you have a function (in this case I) of two independent variables, and you want to see how it \"reacts\" when you change one of them (say V) . This is ",
" defined if you specify which other variable remains constant (in this case either P or R).",
... | [
"In your second equation, greater voltage means smaller current if you keep the power the same.",
"If you increase the voltage and want to keep the power the same, you need to do something to drop the current, which means more resistance."
] |
[
"In fusion reactors, how do they use magnets to control the heat?"
] | [
false
] | null | [
"In a magnetic confinement reactor the magnets are used to confine the plasma. You can use magnetic fields to confine charged particles to some region of space, for example using ",
"magnetic mirrors",
".",
"The reactors are designed with particular geometries and field configurations to trap the hot plasma i... | [
"There is stuff like solar and wind which do turn energy directly into DC electricity. However, they're still a small percentage of the overall generation capacity. There is a way to turn heat directly into electricity but it's not as efficient yet and I have no idea if or when it will be better. If it gets to 40% ... | [
"It should be stated plainly, the magnetic fields created by the superconductive electromagnets do not control the heat, they confine the plasma so it doesn't get too close to the inner surface of the walls which in turn do receive a lot of heat through the vacuum of the chamber, just like we receive heat from the... |
[
"How long would it take for the positions of the stars to appear different from earth?"
] | [
false
] | We are orbiting the sun, and the sun is orbiting the center of the Milky Way along with all of the other stars that we can see from Earth. From my understanding, the constellations/postions of stars that we see on earth have remained the same for thousands of years because the galaxy is so enormous that our point of view really hasn’t changed much. Is my understanding correct? How long would it take for the sun to move far enough that the stars would be in different positions in the night sky? Side question: Is the sun moving quickly or slowly compared to the other stars of the Milky Way? | [
"The Sun seems to be going maybe 10% faster than average, but there's generally a scatter of 10s of km/s between stars on the same rough orbit, so that's not unusual.",
"What you're getting at here is called \"proper motion\". This is the speed in degrees/year that a star appears to move across the sky. Due to pa... | [
"The next north star will be Gamma Cephei in about 4000 AD. Vega won't be the north star until about 13000 AD, and it won't be very precise. Actually Polaris about now is as good as it gets for the north star.",
"https://en.m.wikipedia.org/wiki/Axial_precession",
" has some nice charts."
] | [
"Fantastic answer. Thank you very much."
] |
[
"Does curvature of the universe require an extra dimension to \"curve into\"?"
] | [
false
] | I've been having a Reddit argument with sirbruce in the comments section of some article in , and it's going nowhere ( , and it feels like it's going in circles). Could you guys help out? As far as I can tell, his claim is that it's impossible for the universe to be curved without a dimension to "curve into". My claim is that the extra dimension is either outright unfalsifiable, or its existence is at the very least not proven beyond a reasonable doubt. Can any of you shed some light on this? | [
"I doubt it will get you anywhere — from a quick skim of that exchange, it looks like you're dealing with someone who thinks he has only answers and no questions — but you might consider pointing out that Gravity Probe B parallel-transported a vector around a closed curve and measured a deflection, conclusively pro... | [
"Yeah, sirbruce is completely wrong. It's perfectly possible to have curvature without needing to embed your surface in a higher dimension. Think of a sheet of grid paper lying flat on a table. You then warp the grid lines somehow. The grid is now curved without being embedded in a higher dimension. This is intrins... | [
"That video is rubbish. The book it was created to promote is so fundamentally ",
" that one can't help but wonder if it's not just a big joke. The author is not a physicist, nor a mathematician, nor a person with any particular authority on the subject. He's a musician, and a notorious looney."
] |
[
"Does strength and muscle growth increase more rapidly if you're regrowing muscle to an amount you previously had?"
] | [
false
] | If I had been lifting weights and had increased my lean body mass, but then stopped lifting and my body mass decreased, would I be able to get back to the lean body mass I was at more quickly than the first time? Same with strength. | [
"Um...what?",
"http://en.wikipedia.org/wiki/Myosatellite_cell",
"http://www.nature.com/stemcells/2008/0801/080131/full/stemcells.2008.29.html",
"http://www.unm.edu/~lkravitz/Article%20folder/musclesgrowLK.html",
"http://www.ncbi.nlm.nih.gov/pubmed/18436694",
"From that last study:",
"\"These findings st... | [
"First, your question is VERY vague. If you are 60 and looking to regaing the strength of your 20's, no.",
"Even if you are young, I do not think muscle builds itself any faster just because you \"were that buff\" previously. I remember being a soccer player/cross country runner in high school. Each year, the ... | [
"This is patently false. Muscle cell nuclei might decrease, over time. But they NEVER increase via \"satelite cells\". There are no cells in muscle tissue called \"satelite cells\". ",
"Muscle cells, if you mean skeletal muscle cells, or cardiac muscle cells, do in fact have multiple nuclei. Smooth muscle cel... |
[
"How exactly do antimicrobrial copper alloy surfaces work to kill germs?"
] | [
false
] | null | [
"Ions of copper and zinc have antimicrobial properties. Copper ions specifically disrupts protein structure, and such a lot of membrane proteins and enzymes have their function eliminated. They can also bind lipids causing cells to leak. Copper and zinc also form complexes that can inactivate viruses.",
"Wiki",
... | [
"Awesome, thank you for your explanation. "
] | [
"Interesting read. If copper is so efficient, why not make all water pipes copper?"
] |
[
"As cosmic rays are so powerful, where does the energy go when they hit earth?"
] | [
false
] | [deleted] | [
"When a cosmic ray strikes the atmosphere, it creates a shower of new particles. Its energy is converted to the mass and and kinetic energy of all of these particles. Some of these particles hit the ground and are absorbed by the ground. Some of these particles are unstable and decay into other particles. Scientist... | [
"Here's the incident they were referring to:",
"http://en.wikipedia.org/wiki/Oh-My-God_particle",
"It is an extraordinary amount of energy for such small particles, but on a human scale it's relatively low energy; the Oh My God particle had the kinetic energy of a baseball at 60 mph. But as Chrisbaird mentione... | [
"A few other points that may be helpful to you:",
"Cosmic rays have a wide range of energies. The super-energetic cosmic rays are much rarer than the low-energy rays.",
"Cosmic ray impacts are very common. The lower-energy rays strike each square meter of Earth's atmosphere thousands of times per second. The ve... |
[
"Objects fall into black holes, but an observer falling in would see time slow near infinitely (?) as they approach the horizon. Is this a paradox? Do the two times sync up somehow?"
] | [
false
] | If from the observers view they never fall in, and perhaps that is an incorrect statement, how do the two views of the event match up? | [
"The visible light you are observing coming from the man as he approaches the event horizon would get stretched out into longer and longer wavelengths, first going through infrared and then into the other non-visible wavelengths beyond, by the intense gravity of the black hole. This continues until none of it is le... | [
"For the one falling, time wouldn't change except the rest of the universe would move in time faster and faster.",
"For someone on Earth, the man falling into the black hole would go slower until, on the event Horizon, he would stop and fade away redshifting"
] | [
"\"Fade away redshifting\"?"
] |
[
"In western countries, life expectancy is around 80 years. I'm 25, so on average, I have 55 years to go. But in the past 50 years life expectancy has gone up 10 years. Assuming it will do so for the next 50 years as well, what is my life expectancy?"
] | [
false
] | null | [
"Cannot tell if this is a trick question or not? ",
"Your new life expectancy is 91... right?"
] | [
"It's what I would guess. But I got a weird feeling that the math is trickier than that. I'm assuming that 80 is the age people die on average ",
". ",
"So mine would be 90, as you pointed out. But is it really? Or am I missing something?"
] | [
"The math does get \"trickier\" but it also gets trivial.",
"In 50 years the life expectancy will be 90, you will be 75. In 15 years after that, life expectancy will be 93, you will be 90. In the 3 years after that, the life expectancy will be 93 + 3/5. Etc. Just a case of diminishing returns.",
"Also this is p... |
[
"Could there theoretically be an infinite number of elements?"
] | [
false
] | Since an element is determined by the number of protons it has, could you theoretically just keep adding protons and forming new elements infinitely? | [
"I've answered this ",
"once before",
"The answer is no.",
"\"could you theoretically just keep adding protons and forming new elements infinitely?\"",
"No, not forever.",
"What causes a nucleus to continue existing is its stability. There are certain shapes such as the 4 nucleons of Helium that are parti... | [
"No, 155 is the largest possible.",
"But your basic point of some elements being more stable than others is correct. It has been theorised that there are so called '",
"islands of stability",
"' of element numbers where elements will be less unstable. There's a ",
"cool picture here"
] | [
"Is it possible that there would be a gap making structures like 155, 156, 157 etc. impossible, but the structure for 1037 would be stable enough to exist, or is it a steady decrease in stability?",
"(Atomic numbers just an example, not sure if 1037 is significant)"
] |
[
"How deep into the ocean will the impacts of a hurricane be felt?"
] | [
false
] | I was watching the forecast of Florence and though about how deep a submarine would need to be to not be effected. | [
"Three times the effective wave height.",
"The magnitude of water movement underneath a wave tails of quite rapidly with depth. Once you are about three times the wave height (trough to crest) below the surface, the movement is barely noticeable.",
"\"Effective wave height\" is the average height of the biggest... | [
"We're gonna need a rag-tag group of young marine biologists, a small fishing boat, and a Vice reporter."
] | [
"Very interesting, thank you!"
] |
[
"Are light and other small wavelength electromagnetic waves simply caused by the drop in energy levels by an individual electron? If yes, how are ~2 km wavelength radio waves made?"
] | [
false
] | [deleted] | [
"Good answer. Just wanted to add that other wavelengths of light, even visible and x-rays, can be created by similar methods (accelerating electrons). This is how synchrotrons produce light for experimental research."
] | [
"How are they ",
" made?",
"When humans make them, we do it by taking a big long metal wire and making the electrons jiggle back and forth. The change in the electric field only moves at the speed of light, so we make different wavelengths by jiggling the electrons faster for shorter wavelengths and slower for ... | [
"The simple answer is that it means that charged particles interact with photons. Photons are electromagnetic waves (oscillating electric and magnetic fields)."
] |
[
"How do we know pi is never-ending and non-repeating if we're still in the middle of calculating it?"
] | [
false
] | Note: Pointing out that we're not literally in the middle of calculating pi shows not your understanding of the concept of infinity, but your enthusiasm for pedantry. | [
"I've posted this ",
"earlier",
" to a similar question about why is pi irrational.",
"Why is pi irrational? Its not the easiest thing to prove but is has been done. A simpler proof is why sqrt(2) ~ 1.414 ... is irrational. First, you assume sqrt(2) rational. That means there is some fraction sqrt(2) = x/y wh... | [
"This is correct. The answer is that pi is irrational, so it cannot be written as a ratio of integers, i.e. p/q for some integers p and q. If pi's decimal expansion terminated or repeated, then it would necessarily be a ratio of integers.",
"There is one minor thing I'd like to point out about your answer though,... | [
"This is why Physicists and Mathematicians never remain friends for long."
] |
[
"What causes sufferers of dyslexia to perceive words as jumbled up?"
] | [
false
] | null | [
"They don't see words \"jumbled up\". People with this kind of dyslexia can't supress the mechanism which normally alows us to see objects as the same regardless of their orientation. As the result, some letters look almost identical to each other, such as n vs u, m vs w or b/p/q/d. Specially designed fonts where t... | [
"Do dyslexics exist in places where the alphabet has no such sets of congruent letters?"
] | [
"However, there is something called ",
"visual stress",
", which isn't recognised as a disorder, but is being studied, where words can appear distorted and jumbled. "
] |
[
"If atoms are 99% 'empty space', how big would the universe be if we compressed every atom down to it's most space efficient arrangement, essentially leaving no space between particles?"
] | [
false
] | Or our observable universe, whatever is easy to speculate on... My thoughts were that perhaps the universe would become small enough to resemble what was present before the big bang, and the expansion between everything has just taken a very slow and long time (the rate at which our universe is expanding now?) and appears to have "exploded", hence the Big Bang... | [
"The \"atoms are 99% empty space\" thing is a big misconception. Particles do not have \"size\" as we typically think of it. An electron in an atom is a \"wave of probability\" and does not have a specific \"size\" or \"location\", these properties don't make much sense quantum mechanically. In fact ",
"these hea... | [
"Quantum Mechanics never fails to blow my mind over and over again. Thanks for the reply."
] | [
"So density is mass/volume or volume = mass/density. Our mass is 10",
" and our density is 8x10",
" if we divide 10",
" by neutron density, we get a volume of 1.25x10",
" m",
"Taking the cube root, we get a box with side length 500 million kilometers, or about 3 times the distance between the earth and th... |
[
"Is noise a way to release energy?"
] | [
false
] | Let's take a car accident. When those two cars crash, the energy is released via crumpling the car, breaking headlights and being metal. Talking about energy, what part is lost by noise in a car crash? Does noise take up energy? I hope this is clear. And if it does take energy to make crashing noises, then is it possible to have crash crashes release the entire energy via noise? | [
"Noise (sound) is actually pressure waves and pressure waves are moving air. The air that is moving after the crash (the sound waves) was not moving before the crash so some of the energy was definitely spent on making the sound you hear. I can't imagine any way to direct all of that energy to moving only the air... | [
"Yes, you're on point. I was wondering more along the lines of whether it's possible to have two objects collide with each other, but instead of damaging the two items, the sound created through the collision is enough to dispel the force. But that's very likely... impossible."
] | [
"Well, if we imagine a car that is infinitely rigid and impervious to damage, most of the energy probably ",
" be dissipated as sound. But, I think you actually want the car to crumple, or at least \"spring\" a little (or, maybe, a lot) so that you, the passenger, gradually decelerate. If you're inside a car mo... |
[
"Do we know the \"universal common ancestor\"?"
] | [
false
] | So we were learning about phylogeny trees and wanted to know if we traced waaaaay back, if we could find a common ancestor. My Bio prof said yes but he didnt know what it is or if it has been done. | [
"so have we pretty much ruled out that its possible life could have sprung up independently of one another in different parts of the Earth, and therefore two branches could not share a common ancestor at all? "
] | [
"so have we pretty much ruled out that its possible life could have sprung up independently of one another in different parts of the Earth, and therefore two branches could not share a common ancestor at all? "
] | [
"Not entirely correct. Viruses depend on cells (prokaryote & eukaryote) to replicate. So viruses are most likely younger than the first cell. Even in evolution 'simpler' isn't always 'older'.",
"Viruses could be escaped transposons, for instance."
] |
[
"Is there objective evidence for our mind's \"inner world\" of experiences?"
] | [
false
] | Aside from our own individual, personal, experiences, do we have any scientific evidence for the existence of conscious experience? I know we can tell if someone is conscious by looking at their brain with various tools, but do we have anything, other than anecdotal evidence, to suggest that such brain signals correspond to an inner, subjective experience? I feel sure there must be something as it's such a basic thing to know about, but can't think what. | [
"No, there is no way to infer or measure consciousness.",
"An EEG will show you electrical activity in the brain. An fMRI will show you blood flow in the brain. A PET will show you sugar metabolism.",
"In all of these modalities, there are ",
" of consciousness - patterns which are associated with consciousne... | [
"As well you should. We don't even have even good ",
" as to how brain circuitry creates conscious experience. ",
"For more, but from the philosophy of mind side of the story, look into the mind body problem, David Chalmers and the Hard Problem of consciousness, etc."
] | [
"Thankyou very much for this reply. I find this gap in our knowledge and/or ability astounding."
] |
[
"What mutualistic organisms could I pair with a bonsai tree?"
] | [
false
] | I've just recently bought a bonsai tree and wondered if I could have some kinda fungus growing around it or even some insect of some sort. Such as moss. | [
"Micorrhiza Fungi is great for bonsai trees. HOWEVER: spores are species specific, your bonsai will probably 'find' its species specific fungus on its own. You're better off ensuring the soil is good, and adding trace elements to it. \n",
"http://bonsaistudygroup.com/general-discussion/myconox-mycorrhizal-fungi/"... | [
"Don't know why the down vote.... ",
" regularly appears in flowerpots, and small mushrooms growing with a bonsai tree look very artistic.",
"http://www.mushroomexpert.com/leucocoprinus_birnbaumii.html"
] | [
"Don't know why the down vote.... ",
" regularly appears in flowerpots, and small mushrooms growing with a bonsai tree look very artistic.",
"http://www.mushroomexpert.com/leucocoprinus_birnbaumii.html"
] |
[
"Will a heavier object absorb more momentum than a light one? Or is there no difference at all?"
] | [
false
] | [deleted] | [
"no. both energy and momentum must be conserved. if you take the equations for those and apply them to a 2 body system, you can show a proof of the variable transfer of energy mathematically ",
"here",
"to summarize, a small object hits a big object, it gets bounced away, keeping some of its initial energy.",
... | [
"thanks a lot!",
"Then what I need to know is just how much of that kinetic energy that is transfered, and what factors that determines it.",
"EDIT: Very nice explanation, it's just as I hypothesized. :)"
] | [
"thanks a lot!",
"Then what I need to know is just how much of that kinetic energy that is transfered, and what factors that determines it.",
"EDIT: Very nice explanation, it's just as I hypothesized. :)"
] |
[
"Is it true you should put both feet together and hop away from a downed power line?"
] | [
false
] | I was once told that if a power line falls down near you, you should put your feet together and hop away, rather than walking. Something about how the way the power spreads out as it goes into the ground, if you walked, there would be enough voltage difference between your back foot and your front foot to electrocute you. Is this true or BS? Anyone care to estimate what kind of voltage differential there could be between your feet in that situation? | [
"To electrocute you a current would need to flow through your body. If the voltage difference is between your feet the current would need to flow up one leg and down the other, but if there is \"electricity\" in the ground already why would it bother to flow through you in the first place? If the ground is already ... | [
"Electricity always follows the shortest path",
"No, it follows the path of least resistance.",
"Well, technically, the current flowing through each path is dependent on each path's resistance - a lower resistance path with have a proportionally higher current flowing through that path."
] | [
"The reason is to prevent current from going higher up into your body. Electricity always follows the shortest path (ok, it is actually more complicated than that, but as a simplification...). If it has the option to travel up one foot, through your ankles, into the other foot, and back down, it will do that rather... |
[
"Is Adenovirus \"escape\" from the lysosome into the cytosol species specific?"
] | [
false
] | [deleted] | [
"Apparently I didn't do a good job explaining the hypothetical scenario, both people who responded misunderstood what I meant lol"
] | [
"Apparently I didn't do a good job explaining the hypothetical scenario, both people who responded misunderstood what I meant lol"
] | [
"Here's a better scenario. If you enclosed adenovirus into an artificial membrane vesicle that you produced in a lab, then acidified the vesicle, would it fuse to the vesicle membrane and release its naked DNA into the outside solution?"
] |
[
"If there are 11 dimensions, is the magnitude of the \"eleven-velocity\" still c?"
] | [
false
] | As I understand it, the magnitude of the spacetime four-velocity is constant, c. If there are additional dimensions, do they extend the concept of four-velocity, and is the magnitude of the resulting "n-velocity" still c? If so, if an observer were to have a large velocity in one of the higher dimensions, could he or she experience time-dilation while still remaining stationary in regular space? | [
"Yes, it's exactly the same (with the same value of c) but the Lorentz indices go from 0 to 10 instead of 0 to 3. And yes, I believe it would mean that. The problem is you can't just accelerate in the transverse dimensions because of momentum conservation. Moreover, because the extra dimensions must be compactified... | [
"is it possible (but unlikely) that we're all traveling at a non-zero velocity around one of the compact dimensions?",
"To answer this question, you need to specify an additional piece of information: relative to ",
"? There are no absolute velocities, so any non-zero velocity must be in reference to some oth... | [
"Thanks! I hadn't considered the momentum being quantized due to the compactness of the extra dimensions.",
"Along these lines, is it possible (but unlikely) that we're all traveling at a non-zero velocity around one of the compact dimensions? If so, what would the consequences be if one could stop (barring the q... |
[
"If you entangle 2 particles, then put one in a black hole, then look at the other one : information coming out of a black hole?"
] | [
false
] | null | [
"The general understanding of entanglement has nothing at all to do with particles \"communicating\" information between them",
". In the interpretations of quantum mechanics where they ",
" communicate, it's faster than light communication anyway, so there's no real reason to believe a black hole would hinder ... | [
"I have two marbles; one red and one blue, and I tell you their colors.",
"I give you a red marble but I never actually show you the blue one. But, from the information that you derive from the red marble, you can make reasonable assumptions about the other one. For instance, if the one you have in your hand is... | [
"the results of my measurement. You need to know if I measure \"spin up\" or \"spin down\" for example. If we both agree ahead of time what we're measuring, then we send no information at all.",
"Let's be more specific. I prepare two entangled spin 1/2 particles. We both agree on what our x,y,z axes are, and we a... |
[
"Is it possible to accurately predict the magnitude of an earthquake by measuring the waves in backyard pools?"
] | [
false
] | null | [
"In Medieval times, especially in Asia, pots of water were buried near walls and checked for ripples, not for earthquakes, but to detect if someone was trying to tunnel under the wall. They could even triangulate where the tunneler was using 2 or more pots.",
"What you're asking is possible, but not feasible. Y... | [
"What about from multiple pools around the affected area?"
] | [
"I mean, maybe with a lot of effort? At the simplest level, if you replace pools with ",
"seismometers",
", this is basically what we do to locate and measure the magnitude of earthquakes in the first place. For the use of pools, to get in the right ball park, you would need to know a variety of things. You wou... |
[
"Is there currently a widely accepted theory in Biology that describes how prokaryotic cells became eukaryotic cells?"
] | [
false
] | Bacteria seem to be able to adapt to their environments so well that that there doesn't seem to be any adaptive advantage to complexity, and there doesn't appear to be much in the way of proto-eukaryotic intermediaries that you would expect if natural selection were at work. So what gives? Is there an established theory in biology that explains this? | [
"Yes - it is called the ",
"Endosymbiotic theory",
". Essentially the belief is that a prokaryotic cell engulfed another prokaryotic cell (Theories differ exactly on what these cells were but I believe generally the cell that was engulfed was particularly good at energy production) and that this turned into a s... | [
"Piggybacking this. One of the main reasons this is well-accepted is that a cell's mitochondria has completely separate different DNA than the cell's nucleus. In human sexual reproduction, DNA is taking from nuclei of both parents and not the mitochondria. As a result, you actually have the same mitochondrial DNA a... | [
"Prokaryote is a general term that describes any organism without a nucleus (or other membrane-bound organelles), so whether or not it was identical with any living prokaryote, there must have been a prokaryote (or two) that gave rise to all eukaryotes by endosymbiosis with mitochondria and/or the development of a ... |
[
"Do babies that are born via C-section have a lower immune system versus babies that are born vaginally?"
] | [
false
] | From what I understand is babies born vaginally have bacterial flora introduced into their system when travelling down the vaginal canal. Because babies born via C-section are not exposed to this bacteria does it mean that they start out with an immune system that is not as strong? If so are there treatments that babies undergo to give them a boost? | [
"Yes.",
"C-section increaes the risk of developing type 1 diabetes by 20%.",
"It also increases the risk of asthma by the same amount.",
"It is possible (although unproven) that this is due to the lack of exposure to maternal commensal bacteria. The above studies are meta-analyses so are relatively more trust... | [
"I'm not sure what point you think I was making? I don't know what the mechanism is, but I don't see how it's a stretch to consider it possible that diabetes has a link to microbiotic exposure at birth. The researchers in the diabetes meta-analysis mentioned that their results couldn't be explained by known confoun... | [
"There is some ",
" data",
" on this practice, colloquially known as \"seeding\". I would not recommend it without much more evidence, the potential for contamination from things like faecal matter and normal vaginal infections would be a huge risk factor in this sort of thing. "
] |
[
"Brazilian president suggested that someone should start working on a way to storage the wind, as we do to the water, for later use to generate energy. It's possible ?"
] | [
false
] | null | [
"It's possible. There is a utility down south that put aircompressors on their towers and corked a cave to store the compressed air. Then they added an airturbine to the front of one of their steam turbines and use the compressed air to drive the generator when there is enough wind. When there isn't they use the bo... | [
"You can also use the energy generated to pump water to an uphill reservoir and then use it later to turn a turbine, or spin up a large low-friction flywheel. Hydrogen and normal batteries also work."
] | [
"It's called ",
"compressed air energy storage",
" and it is awesome.",
"Even when not dealing with somewhat unpredictable sources such as wind or solar, there's this problem where it takes several minutes to turn on a big natural gas turbine to keep up with everyone deciding to turn on the lights at once. Ha... |
[
"Is there any wind on the moon?, even a negligible amount"
] | [
false
] | So, The moon has an atmosphere nothing like the one on earth obviously, but a thin layer of gases that are “attached” to the moon through gravity barring any space weather, impacts and the like. My question is with the extreme temperature changes between the light and dark side of the moon would it not generate wind? I’m not talking about let’s build a windmill wind more something detectable with modern instruments, even theoretically. Or is the density/pressure just too low for the effect to take place? | [
"The “atmosphere” of the moon is a surface boundary exosphere. This means molecules are ejected from the surface (by various processes), fly on a ballistic arc, then hit the surface again with almost no chance of encountering another molecule on the way.",
"Without interaction between molecules, the atmosphere do... | [
"I don’t believe there is a high enough density of molecules in the “air” on the moon to produce the same thing we call wind on earth. Sure, they’re going to move around a bit, but they’re unlikely to collide with each other often enough to create a detectable trend of common movement, aka wind."
] | [
"Thanks, I thought this might be case. But just could rule out a small boundary layer that moves very very slightly. We'll explained my good man"
] |
[
"Question about an imgur photo of a torn pectoral."
] | [
false
] | Some of you may have seen image of a torn pectoral on imgur. What is the reason for the regular patterning of the bruise? | [
"To me it looked like he had bandages on it while the bruise formed. I can't answer your question, but when I had seriously major bruising you could see lines from my bandages, ice packs, tape and clothing. I guess I should add that you could only see those imprints in the very shallow bruising; all deep bruises pr... | [
"This.",
"The recommended treatment for muscle tears is ",
"ice and light compression",
" to minimize swelling (bleeding into the muscle and surrounding tissue. ",
"Taping perpendicular to the grain",
" is also recommended."
] | [
"This is not a full answer to your question, but it might be worth noticing that the pectoralis major is not a continuous, flat muscle, rather it connects in bands, as can be seen in these photos:",
"anatomy - edit: look at mc2222's link, mine didn't work apparently",
"body builder"
] |
[
"What are itches, and why do they occur?"
] | [
false
] | My arm itches... but why? | [
"Some foreign body (an antigen) is activating cells on your skin (IgE antibodies probably) to cause your mast cells to degranulate releasing histamine, causing inflammation and release of bradykinins which cause pain and itching"
] | [
"Are there not other causes? I've heard of menopausal women having the feeling of bugs crawling on there skin. ",
"I personally have chronic exzema, and I wonder, other then the raw irritated skin, why I itch. I know part of it has to do with antihistamines, but there has to be more to it."
] | [
"I am not sure about menopausal women and the cause. However, I know that methamphetamine addicts itch their skin to a bleeding rubble because it 'itches.' This is due to the deposition of crystal pyproducts (and other chemicals) of meth into the dermal layers and sweat gland pores - which many people say is becau... |
[
"How random are genetic mutations?"
] | [
false
] | I know that when an offspring appears (for let's say ... a mammal species), it's genes are a random combination of it's parent's genes. Q1: Do we know what determines which genes will be active or inactive? Q2: Is the process following a limited set of rules? Q3: What factors influence the process? | [
"I wouldn't say mutations are 100% random. There are certainly several specific defined mechanisms for mutations that will have a bias for certain sequences or locations or mutation type. For instance, damage from UV radiation occurs when you have adjacent thymine bases, spontaneous mutations have a couple of commo... | [
"I talked about actual genetic mutations in my reply to another comment, but I figured I'd try to address your specific questions.",
"1) We have some idea, but the process is incredibly complicated. There are a ton of regulatory processes that control gene expression (whether or not genes are active) ranging from... | [
"Unfortunately not true for translocations and rearrangements. They're highly biased and we're just beginning to learn why."
] |
[
"Spending even a short amount of time in complete silence of the Anechoic Chamber at Orefield Labs causes people to experience a good deal of emotional discomfort. Why don't deaf people experience this same discomfort?"
] | [
false
] | null | [
"According to this article:",
"http://www.dailymail.co.uk/sciencetech/article-2124581/The-worlds-quietest-place-chamber-Orfield-Laboratories.html",
"It's not so much the silence that makes people uncomfortable, but that when you're in such a quiet room your ears begin to adapt to the silence and start becoming ... | [
"Hi! I can answer this, as I have one at my place of work and used one extensively at university. ",
"Many people don't like the sensation because the lack of near and far field reflections almost tricks your brain into thinking everything is in close proximity. ",
"Being in an anechoic room with another person... | [
"Can anyone explain why this is such an unnerving and unpleasant experience in practice? I read this description and I think it would be incredible to hear my body working with that level of acuity."
] |
[
"A doctor told me once you attempt suicide, the same meds (SSRIs/SNRIs) don't work as effectively - why?"
] | [
false
] | As far as I understand it, SNRIs and SSRIs just tell the brain the produce more serotonin, or rather, they delay the nerve that says "Hey, stop making serotonin!". Obviously in the case of SNRIs that's also norepinephrine. So, why would the brain react differently post-suicide attempt? Even if the neural pathways change, it should still be the same nerve that controls serotonin, right? TO CLARIFY: I am not asking what happens with the drug if you tried to kill yourself by overdosing on an SSRI, but by other means. The doctor I was speaking to mentioned that after every suicide attempt, the efficiency of the same dosage of an anti-depressant is no longer as effective, and often medicines have to be switched. | [
"What exactly did the doctor say?",
"My guess is he meant to say that a suicide attempt is a sign they aren't working effectively, or is a side effect that would be contraindicative.",
"Also, if this is about ",
" treatment, please consult a professional, and not the internet, for your medical advice."
] | [
"Edit: There was some confusion about what OP was actually asking, and my original answer (which I've left below) was answering the question as though OP was asking if an overdose on SSRI/SNRI would have an effect on the medication. As for the actual question ",
"that after every suicide attempt, the efficiency... | [
"It's not a nerve but an enzyme. Anyway, yes, they should work the same. I have not heard anything like that before, and I have used SSRIs."
] |
[
"A question about black holes, and I promise I'm not high."
] | [
false
] | I realize that this will probably sound like wallbanger moon logic, but here goes anyway: As I understand it, the distance from the event horizon to the center of a black hole is greater than the diameter of the event horizon itself, and this distortion is created by the superdensity of the matter of whatever initially created the black hole. The actual matter of a black hole exists in a kind of spatial asymptote. My question is this: Would it be possible for a chunk of matter to have sufficient density to hide itself in a spatial distortion crossing over the threshold into planet-eating singularity territory? In other words, could an object's density create a spatial bubble exactly equal to the physical volume of the hypothetical object without creating the discontinuity of an asymptote? I fully accept that the only dense thing here might be me, and that the very nature of this question might well belie a vast and embarrassing misunderstanding of singularities, gravity, or even basic arithmetic. I promise that the reasoning underlying the question was not induced by recreational chemicals. In my defense, questions about black holes and spatial distortions will, by their very nature, tend to sound drug-induced. | [
"Its ok...we all want a ...Tardis..."
] | [
"General Relativity has at its heart the \"Einstein Field Equations\". Essentially: the curvature of space-time is equal to the stress energy tensor; curvature equals stuff making curvature. Now usually, we start with the stress-energy tensor, maybe throw in the information about a star, and see what curvature resu... | [
"Are you asking if it's possible for an object to be (at least marginally) bigger on the inside?"
] |
[
"Is it possible that not only space is expanding, but time as well?"
] | [
false
] | Could you provide reasons or sources, if you think just space is expanding and time is unable to? Related questions: | [
"Similar questions have come up previously. ",
"Here is a link to one such post",
" and ",
"here is a link to one of my several responses",
". I offer a response that shows you some of the math behind the question, and the top response by ",
"/u/adamsolomon",
" offers a less mathy explanation. Take your... | [
" here I was going to give a reply, and you go ahead and just link to me making the same reply someplace else! :P"
] | [
"Proper coordinates consists of proper spatial coordinates to measure distance and so-called cosmological time to measure time. The proper distance between two galaxies at a given time is the distance measured between those galaxies using rulers ",
" and you always use the same rulers. So as space expands, you ne... |
[
"Is it possible that life could exist in currently inhabitable places in space? (details inside)"
] | [
false
] | Scientists make predictions on the probability of life relative to what homo sapiens and other animals that survive on Earth need to survive. Is it possible that other life, if present, could survive using different techniques such as using elements that are abundantly available to them instead of oxygen to respire and provide energy to themselves (if they require it)? Would something be able to adapt to their surroundings if it were extremely dark and cold and instead of oxygen, use something that was more abundant in their position in the universe? | [
"Yes this is completely possible. NASA has considered Arsenic-based life. ",
"Also search \"Extremophiles\" on Google."
] | [
"There are lots of examples of bacteria and archeae that have extremely diverse ways of gaining energy.",
"There are examples of bacteria that don't need oxygen or light for energy gain. Some bacteria such as ",
"Acidothiobacillus",
" gain their energy from redox reactions using metal ores in rocks. There are... | [
"First problem, \"life\" and \"consciousness\" are currently not defined. We don't understand what consciousness is, and we haven't yet agreed on what is alive and what is not alive. ",
"A computer program can pass tests used to define 'life' and can pass self-awareness tests of Artificial Natural Intelligence re... |
[
"Why do the electrons in the double-slit experiment behave differently when observed?"
] | [
false
] | Doesn't seem to make sense but there has to be a reason for everything. For those who don't know these may give more information: Electron is observed: No wave pattern Electron isn't observed: Creates wave pattern By the way what is the definition of a particle and a wave? | [
"figure that out and the next Nobel Prize is yours"
] | [
"This also leads to my friend's favourite quantum algorithm: to factorize N, pick some random numbers. If numbers are correct, return the result. Otherwise, destroy the universe"
] | [
"Observation is not important. Interacting with any other particle is what prevents interference patterns. Loosely speaking, if the photon can go along the left slit and hit the back plate or go via the right slit and hit the back plate in the same place ",
" then we get interference patterns. If the photon tweak... |
[
"Physiologically speaking, how do animals like the arctic fox and arctic hare change their fur color?"
] | [
false
] | It is well known that some mammals change their fur color over the course of a year due to seasonal variation. What is the physiological mechanism that allows them to do so? Is it light dependent? Temperature dependent? Edit: Added more specificity to the question. | [
"Hi and thanks,",
"I am actually referring to how they adjust their camouflage scheme and fur colors relative to seasonal variation. That is, how is it that an arctic fox can produce white fur during the winter when there is snow on the ground and produce brown/tan fur during the summer?"
] | [
"Hi and thanks,",
"I am actually referring to how they adjust their camouflage scheme and fur colors relative to seasonal variation. That is, how is it that an arctic fox can produce white fur during the winter when there is snow on the ground and produce brown/tan fur during the summer?"
] | [
"Ammount of daylight dependent.",
"Many mammals change the outer layer of fur seasonaly. Mostly to adapt thermally and sometimes, like you point out, to change the camo. You can see that even cats are more fluffy during winter. ",
"In most cases this is due to hormonal change triggered by the pineal gland based... |
[
"Why do neutrons tend to interact more readily with light nuclei rather than heavy ones (i.e., why is water a better neutron shield than lead)?"
] | [
false
] | null | [
"It's not because they necessarily \"interact more readily\", it's just that the kinematics is more favorable when they do interact.",
"If you want to slow something down, you want to take as much kinetic energy away from it as possible with each collision, and simple kinematics shows that the optimal way to do t... | [
"Surprisingly, water is 14x denser than liquid hydrogen. The bonding angle of the H-O-H makes the O slightly positive and the H slightly negative which then tends to attract another H from the other H-O-H and holds it closer (surface tension). Even at cryogenic level water will have more H than liquid H."
] | [
"Liquid hydrogen is awkward to work with and water has a higher density of hydrogen atoms."
] |
[
"How do governments tell the difference between nuclear launches and peaceful space missions?"
] | [
false
] | This has two parts: 1) Governments monitor the launch of nuclear missiles. But there are rockets being shot into space all the time. How do they know that those rockets aren't carrying nuclear weapons. 2) Satellites are shot into space regularly. How do we know that they aren't hiding nuclear weapons? | [
"A computer glitch back in the 80s ",
"nearly started World War III",
", which was only prevented when a Soviet officer remembered exactly this. A Russian early warning system reported an American missile launch. The official policy was that any such warning had to be immediately reported up the chain of comm... | [
"You would think that telemetry would tell you soon enough. Barring that, it makes almost no sense for a nuclear power to start an attack with a single missile. You should start worrying when you see hundreds of 'satellites' being launched at once."
] | [
"Well it depends where. If you're launching by a commercial provider, SpaceX, Arianespace or something like that, then it's unlikely you could do this \"illegaly\", because of all the tests payloads have to take. Everything is measured, so you can't really smuggle anything apart from what's in the specs (even chang... |
[
"Why when we get vaccinated our children don't inherit the immunity?"
] | [
false
] | null | [
"The genetics provide the blueprint for the immune system, but you get vaccinated against things you're not naturally immune to. ",
"A vaccination teaches your body how to respond and fight off an illness, but it doesn't alter your DNA. "
] | [
"When you talk about genetically modifying humans you get into a very messy area of ethics, whatever the reason. It intertwines the ethics of biology, sociology, and philosophy.",
"Aside from that, we can't get everyone to agree on GMO vegetables. GMO humans aren't anywhere close to being a serious talking point... | [
"By next step I assume you mean \"step we've achieved but haven't legalized for obvious reasons\"."
] |
[
"Are oceans caustic and not acidic? Does the pH level ever go below 7.0?"
] | [
false
] | Some say elevated levels of carbon dioxide strive to cause seawater to be acidic, is this true? | [
"The pre-industrial pH of the ocean ",
"was 8.179 (see the chart)",
" so the ",
"process of acidification",
" (or see the ",
"NOAA",
" for an even simpler take on the process) is moving the average ocean pH closer to a neutral pH as opposed to crossing into being truly acidic. The current average pH is ... | [
"As ",
"/u/CrustalTrudger",
" says, ocean acidification simply refers to the reduction in ocean pH as opposed to the pH falling below 7. It's important to understand that the pH does not have to fall below 7 to have major consequences for marine life. For calcifying organisms, for example, the key parameter is ... | [
"To be clear, in your last sentence, did you mean: CO2 emissions are beneficial ",
", rather than harmful?"
] |
[
"Is it possible for a planet to have a breathable atmosphere without organic life feeding it?"
] | [
false
] | For example, here on earth the atmosphere, as I understand, is partially sustained by plants that take in CO² and emit O². When I used to play Spore (I understand its a game), you would have to place plants and animals in order to sustain the "terrascore" of the planet. Does this have truth in real life, or could there possibly be a planet that we could live on that is completely barren? | [
"Oxygen can also be generated from water by ionizing radiation. The term \"ionizing\" says it all: it can excite electrons causing them to escape their orbits and leave an ion behind. If this happens to an electron participating in a chemical bond, the molecule may be broken into free radicals or even lone atoms. S... | [
"Oxygen is very reactive. I would imagine it would burn faster than it can be produced by ions."
] | [
"You're right, but that only happens if there is something on the surface it can react with. On an icy surface like Europa, it just can't.",
"Fun fact: the external surfaces of spacecraft are usually aluminium or glass fiber (beta cloth) to avoid reacting with the atomic oxygen of Low Earth Orbit. They can resist... |
[
"How much genetic variation is there in a single person?"
] | [
false
] | Among a single person, comparing 2 random cells, how much variation can you expect in their genomes? Over time mutations and such are bound to happen, but I’m not finding any results for how frequently there may be variation. edit: I’ve time-> Over time | [
"That is all true in theory. But in practice, there is always mutation. Always. The replication machinery is not even close to perfect, error rates are as high as 1 per 100 nucleotides (the A, T, C, G). With ~3 billion nucleotides in the genome you can expect up to 30 million errors (mutations) per replication. Tha... | [
"Great question! Your DNA is broadly divided into exons, introns, and intergenic regions. Exons code for proteins. That is, the DNA will at some point be transcribed into messenger RNA and that mRNA will be translated into proteins that \"do stuff\". This is the classical purpose of DNA as the generic code. But tha... | [
"All the cells in a human body have identical genomes with the same DNA combination. Each cell has all the information to reproduce the entire organism.",
"Two sets (alleles) of each gene is required to express a character. One half comes from the mother, the egg, (secondary oocyte) and the other set, sperm, f... |
[
"Is there any publicly available database that has collected a lot of raw data but no one put the effort to analyze or summarize the result?"
] | [
false
] | null | [
"Hi, this is a better question for our sister subreddit ",
"/r/AskScienceDiscussion",
". Our panelists have flair there, too, but the conversation is more open-ended. Also, the short answer is that yes, there are tons of databases out there, and some have lots of unanalyzed data. Feel free to post over on ",
... | [
"Thanks for the recommendation, I will post it there : )"
] | [
"Cool, you're all set."
] |
[
"Can stars/sky in a photograph give us the location from where the photograph was taken? If so, how does it work?"
] | [
false
] | I've seen this happen in movies/TV many times. Also someone was talking about it(confused celestial coordinates with coordinates on earth) in today. Feel free to go deep about it in your answers if you want. Edit: A lot of you were confused...Assume that the photographs have timestamps and the angle of the photo with respect to the horizon. Thanks!! | [
"3) what time it was (hence the importance of clocks that stay accurate on a moving ship).",
"Interestingly, this importance is what lead to the first determination of the speed of light.",
"When Jupiter's moons were discovered, they were found to keep very stable orbits, and it was suggested that their transit... | [
"Generally speaking, it's not possible to do that from just a photograph of the sky, though I might be misunderstanding the question. (Maybe link the ",
"/r/space",
" discussion?) The issue here is that astronomical objects are really far away, so everyone on Earth is essentially seeing them from the same angle... | [
"They don't directly; instead, by consulting a table of them which was previously calculated, you could (if the speed of light were infinite) use them to determine what time it was precisely. An accurate time reference relative to another location is what gives you your longitude.",
"For example, suppose a star ... |
[
"Wouldn't it make sense for airplane manufacturers to make the wheels spin either with a motor or the wind before a landing to preserve tires?"
] | [
false
] | null | [
"Not worth the extra weight and complexity. Tires are relatively cheap and have to be replaced regularly anyways.",
"There were some tests done with an Airbus airliner a few years back where they put electric motors in some of the wheels so the jet could taxi using just using its APU providing electric power. The... | [
"There were some tests done with an Airbus airliner a few years back where they put electric motors in some of the wheels so the jet could taxi using just using its APU providing electric power. The idea behind it was to save fuel when taxiing by not having to have the engines running (and burning fuel), especially... | [
"It was done by L-3 partnering with Lufthansa, they provided the aircraft. The system worked, it was not flight tested and so after the tests it was removed and jet was returned to regular service.",
"If you do some searching, Honeywell and Safran are planning on testing a flight-worthy electric taxi prototype on... |
[
"Are humans the only animals that cry?"
] | [
false
] | (And by cry, I mean shed tears when you get upset.) Anyway, what a maudlin question! But I am a bit curious about it nonetheless! The topic came up in a discussion with my girlfriend, where she claimed that dogs don't cry. Now since she's a vet I'm inclined to believe her, but that brings up a bigger question: What animals besides humans cry? After thinking about it for a bit, I can't really come up with any examples -- but maybe I just don't know enough. So : What is the deal? Are there other animals that cry or not? | [
"Crocodiles cry, but it's a way of getting rid of excess salt. "
] | [
"Elephants cry, but I think that's it. No one knows exactly why humans cry, so we've no idea why other animals don't. It ",
" have something to do with being able to use tears on bare skin to signal distress to others. Or it may not. "
] | [
"While evolution can be a good explanation for things it's important not to just jump to the most convenient explanation."
] |
[
"Why and how does inbreeding create genetic defects?"
] | [
false
] | null | [
"Inbreeding doesn't create genetic defects, it increases the [frequency of homozygosity] within a population.",
"You have a whole heck of a lot of genes, and you have two copies of nearly all of those. One copy is from your mother and one from your father (except in the case of mitochondrial DNA, which is always ... | [
"In simplest terms, nasty genetic traits are pretty much always recessive (a dominant trait that causes serious defects would just die out). In a suitably diverse population, it is rare for people with the same recessive gene to meet and produce offspring.",
"When close relations breed, they are more likely to sh... | [
"Say your grandfather had mutation in a gene (XXm). It's no problem, happens all the time and goes unnoticed for generations because you only have one mutated gene (Xm) and the other normal gene (X) still functions perfectly. Goes unnoticed that is until that fateful day when a baby is born with the same mutation i... |
[
"Why would some peppers evolve to be difficult to eat?"
] | [
false
] | Doesn't that defeat the purpose of fruit style seed dispersion? | [
"Peppers want birds to eat their seeds (since they don't digest them, and just defecate them at some distance), and not mammals (who would digest them.)",
"That's why some peppers produce capsaicin, which is an irritant for mammals, but not for birds."
] | [
"\"Difficult to eat\" meaning \"spicy\"? ",
"Capsaicin ... is the active component of chili peppers, which are plants belonging to the genus ",
" [peppers]. It is an irritant for mammals, including humans ...",
"http://en.wikipedia.org/wiki/Capsaicin",
"The situation is entirely different for birds. While m... | [
"I would like to hope that you posted that link as a way to say that this is an easy question to answer by a simple Google search, but all it really does is make you look like an ass."
] |
[
"Is there any difference between getting your vitamins from a multivitamin rather than a food source?"
] | [
false
] | null | [
"To clarify, there are two types, water soluble and fat soluble. Excess of water soluble vitamins will just pass through the body, but excess of fat soluble vitamins will be absorbed from the body and may cause issues. That's why those ridiculous 1000% DV Vitamin C tablets don't hurt you... 900% DV of vitamin C end... | [
"This is correct, but in my opinion what OP wanted to know is, Are vitamins from food \"healthier\" than \"synthetic, unnatural\" multivitamins as a lot of people think, and the answer is no, they are chemically the same, but vitamin supplements have disadvantages such as hypervitaminosis and some vitamins work bet... | [
"yes, you can overdose vitamins if you take them from multivitamin etc, or taking it in pure form.\nAlso some vitamins work better if other ingredients are present."
] |
[
"Does science acknowledge a limit to what we as a species can mentally comprehend ?"
] | [
false
] | Is there a theory, idea, or acknowledgment that the human brain has limits on just how complex, complicated, etc... of an idea it can comprehend, and work with ? I'm kind of wondering as we continue to advance at such a fast pace into advanced physics like string theory, quantum physics, and all that stuff if we will eventually hit a wall simply because our brains have physical limitations on what they're able to process, and effectively work with. | [
"The catch with string theory and/or quantum physics is not that we can't describe or articulate and thus understand it on a language basis.",
"That quantum objects are at multiple places both vibrating and resting at the same time just contradicts the logic we as a lifeform have been trained over the centuries."... | [
"There's an interesting idea called \"cognitive closure\" that you might find illuminating. It posits that there are certain things that cannot possibly be understood by the mind because of the intrinsic way the mind works."
] | [
"Well there are limits to working memory: ",
"http://en.wikipedia.org/wiki/Working_memory#Capacity",
" ... we can hold something like 7 items in our conscious mind at one time, and can't work on tasks that require more than that.",
"However we are able to split tasks up into sub-tasks to a large extent to kee... |
[
"How does an electron absorb energy from a photon in a solar cell?"
] | [
false
] | When an electron and a photon interact to raise the energy level of the electron, what happens? How is energy transfered from the photon to an electron? Is this some passing of quarks? | [
"Quarks are not involved. Atoms are made of electrically charged particles (nucleus and electrons), so they interact with external electromagnetic fields.",
"A photon is an excitation of the electromagnetic field. An atom and the EM field can exchange energy, momentum, angular momentum, etc. by creating or destro... | [
"A solar cell is a semiconductor diode. The light may excite an electron in the covalent bonds to the conduction band (this is the internal photoelectric effect), leaving a hole in the valence band. If this happens near the junction between p- and n-type semiconductor, the electron and the hole are pulled apart by ... | [
"It is related to the ",
"photoelectric effect",
" (for which Einstein was granted his Nobel prize) and is related to the particle like nature of light. Basically a photon comes along and \"bounces\" an electron out of its orbit. A photon is pure energy, so all that energy is absorbed directly by the electron... |
[
"What is happening when I zip a file?"
] | [
false
] | I would imagine it depends on the type of information being compressed, but I'm not sure. | [
"Here's a good example of lossless compression.",
"http://en.wikipedia.org/wiki/Huffman_coding",
"In this case what happens is that you analyze the uncompressed file and essentially create an encoding scheme such that from a smaller file you can recreate the original given instructions, which can be read at the... | [
"You use lossy encoding in \"analog\" files (for lack of a better word—obviously they're still stored digitally) like audio, video, and photos, because the lossy compression algorithm can lead to much smaller file sizes by stripping away near-imperceptible content in these types of media.",
"For example, an .mp3 ... | [
"For example, it would be easier to have MS Word open a .doc file than have it extract a .doc file from a .zip file.",
"Actually, newer MS Office applications use OpenXML file format, represented by extensions ending with \"x\" (docx, xlsx, etc), which are in fact just zipped XML files."
] |
[
"When I look at, for example, the north star, how many photons are hitting my retina every second?"
] | [
false
] | null | [
"First you would need to find the factor that the sun's apparent magnitude is brighter than Polaris given by the equation (x=mf-mb) and (v=2.512",
" Which will get you 2.99x10",
"Now here comes the tricky part of your question. The sun produces billions upon billions (sagans) of photons which are spread out acr... | [
"443,341.8 photons per second",
"Maybe relevant: I think I recall that the human eye can detect as few as 5 photons per second, but I can't find a source anymore. Can a specialist drop in and clarify?"
] | [
"It depends - if you mean the maximum sensitivity of our photodetector cells in the eye, then rod photoreceptors are capable of detecting individual photons no worries. If you mean how many until we ",
" that we have detected light, then it's around 9 in less than 100 ms. This difference is due to filtering by th... |
[
"What exactly does a blast cap do?"
] | [
false
] | From what I hear large explosions can be pretty difficult to detonate (such as C4). I hear physical force, raising temperature and a flame doesn't set it off (although I may have heard wrong). What does a blasting cap do to make something detonate? | [
"Most military (safe to carry) explosives are very hard to actually get to explode. This makes them safe to carry and store. A blasting cap is a small explosive device (won't be devastating if it goes off) kept separate until it's placed with the primary explosive, like C4. ",
"That way there's almost no risk of... | [
"The blasting cap is a primary explosive, the stable explosive is a secondary."
] | [
"A blasting cap is a small sensitive primary explosive device generally used to detonate a larger, more powerful and less sensitive secondary explosive such as TNT, dynamite, or plastic explosive.",
"Blasting caps come in a variety of types, including non-electric caps, electric caps, and fuse caps",
"From the ... |
[
"Can k (the curvature of spacetime) be complex?"
] | [
false
] | So in our cosmology lectures we've looked at k from a basic "if it's positive, it does this, if it's zero it does that, if it's negative it does this other thing" point-of-view,with the lecturer saying that a full General Relativity treatment of k will be left till the fourth year. So I'm wondering; can k be complex/imaginary? Is that a thing which can happen, perhaps when doing the full GR treatment of it? If so, what would the physical meaning of such a value be? | [
"The parameter k shows up only in maximally symmetric spaces, but the curvature is always real-valued in GR. General Relativity is basically differencial geometry in a space with a lorentzian metric. The metric only has real-valued entries and thus the Riemannian curvature tensor also is real-valued (it can be cons... | [
"No. k cannot be complex because of how k is defined. The spatial curvature parameter comes about because the \"boundedness\" of an object can be described using a coordinate system that has too many variables--in that not every variable can be treated and independently varying. Take the cartesian equation for a sp... | [
"The short answer is that the curvature is real-valued in general relativity.",
"In more details, the curvature \"k\" used in cosmology is directly related to what is called the \"Ricci tensor\" in general relativity, which is a local measure of how strongly curved spacetime is.\nThe Ricci tensor is itself obtain... |
[
"What are common applications of usage of the world's most powerful supercomputers?"
] | [
false
] | null | [
"There are dozens of applications that really require computing at these scales. I know that protein modelling is one of the heaviest applications but I'm sure someone else here can explain that better. Hopefully someone familiar with geodynamics can chip in too, because those models have to execute some extremely ... | [
"I would imagine you're asking what they're used for, as opposed to specific software names. But weather forecasting, quantum computing, simulations on things like weapons testing, black holes, medical simulations on protein folding etc. If you want specific software you can see a sampling here: ",
"https://www.o... | [
"Wow, that's extremely interesting. Can you give me anymore information about the epidemiological models?"
] |
[
"Does the casimir effect become weaker over time?"
] | [
false
] | null | [
"No"
] | [
"Then stonger? Or is it a constant?"
] | [
"The pressure depends exclusively on the separation between the plates, nothing more."
] |
[
"The retina is \"inside-out,\" at least in humans. Are there any species in which this is not true?"
] | [
false
] | The human retina is considered "inside-out", with the photoreceptors positioned behind the bipolar and retinal ganglion cells. Is this feature conserved across all species with eyes, or are there any known species in which this is not true? | [
"It is not true in octopus. I think that applies for all cephalopod molluscs, but I'm not sure..."
] | [
"Octopus",
"."
] | [
"This \"insideoutness\" is what causes animals to have blind spots.",
"Cephalopod eyes are the right way around; no blind spot.",
"Here's a vid which explains it, as well as teaching you a neat thing to do with your eye"
] |
[
"Can a household fan function as a generator?"
] | [
false
] | If I put my fan in a breezy window and plug it in, can it generate a few milliwatts? Should I sign up for net metering? | [
"Your fan is most likely using an induction motor, according to ",
"wikipedia",
" these need to be spun quite fast in order to generate electricity (that page gives 1800 rpm as a typical speed). Given this requirement, you're not going to get electricity generated with any reasonable wind."
] | [
"However, if the fan was wired up to it's own circuit (separate from the utilities) and you don't specifically need 60 Hz alternating current, the fan would still provide a current but at a lower frequency if the fan was turning slower."
] | [
"Most generators are this way. The wind turbines actually have transmissions that turn the relatively slowly rotating blades, into high rpm rotation for the generator. "
] |
[
"Are all nuclei arranged the same way?"
] | [
false
] | I understand that neutrons help hold protons together because they have the strong force and exert no electromagnetic repulsion, but it seems to me that would mean there's an optimal packing arrangement of the neutrons in relation to the protons (if you had two protons and a neutron, it would make more sense to put the neutron in the middle rather than the outside). So if I was looking at 10 atoms of carbon, would the arrangement of protons and neutrons be the same in each nucleus? I know that some unstable atoms can have multiple decay modes; is this caused by the nucleus occasionally being "packed" a different way? | [
"Thinking about protons and neutrons like little balls will only get you so far, the reality is more complicated. You can consider the proton and neutron wavefunctions (similar to how electron wavefunctions are considered in atomic physics), and the energy levels that are occupied by particles (the way that atomic ... | [
"This is a great explanation."
] | [
"This is a complicated problem, but two nuclei with the same number of protons and neutrons in the same quantum state (i.e. the ground state, or an isomer, or any of the excited states) will have the nucleons arranged in exactly the same way (by which I mean they will have the same many body wave functions). You ca... |
[
"Why do unhealthy foods taste so much better?"
] | [
false
] | null | [
"In the natural world there wasn't any food with the kind of densities of salt sugar and fats that you get in a big mac. So if we found something that was calorie dense/salty/sweet etc. it would be a rare treat and good for our system (as they are rare). As a result we learned to like these the most.",
"Now comme... | [
"our problem is too much of a good thing"
] | [
"\"bad for you\" foods are usually energy-dense. In the natural world, energy-dense foods are rare, and you need all the energy you can get, so it makes sense for you to really like eating energy-dense food.",
"Nowadays, energy-dense food is everywhere, and we don't exercise as much, so your body stores that unu... |
[
"How true is Ohm's law?"
] | [
false
] | I've almost never got a perfect straight line while plotting a V/I graph even under lab conditions. | [
"Ohm's Law is not a law derivable from Maxwell's equations, but rather just a description of how many materials behave, derived directly from experiment only. (There is some justification for it though from an atomic perspective.) All materials will disobey Ohm's Law past their dielectric breakpoint. There are also... | [
"That helps. Thank you."
] | [
"Remember that real world materials almost never behave 'perfectly', there are manufacturing tolerances as well as all the other effects such as inductance, capacitance, temperature induced changes,etc,etc.",
"Things like Ohms law are totally correct for ideal components, and are close enough to be useful as long... |
[
"Why did the black death just stop?"
] | [
false
] | I know there are still a handful of cases that happen each year, but for the most part the plague just seemed to disappear. Why hasn't this also happened with other diseases like the common cold? | [
"Improved hygiene and sanitation conditions probably helped out immensely with reducing disease spread. Moreover not everyone would die of the plague, ",
"especially those with mutation that makes them immune against HIV (a very small population)",
".",
"The cold virus also mutates at a much faster rate than ... | [
"Just to be pedantic, the plack plague, ",
", is actually a bacterium.\nCCR5 is present in several immune cells and ",
" presumably uses it as help to enter macrophages, but it is not perfectly understood."
] | [
"This doesn't answer the question at all. Antibiotics were discovered som 600 years after the black plague ended."
] |
[
"To what degree are increases in cancer and terminal illness related to living longer?"
] | [
false
] | null | [
"Too a large degree:",
"\"The total number of cancers is projected to increase by 45% from 2010 to 2030, driven largely by the growing number of older adults. By 2030, an estimated 70% of all cancers will occur among adults aged ≥65 years.\"",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4544764/",
"Cancer r... | [
"The longer you live, the more time you have to accumulate damage to your DNA that will eventually lead to cancer. A study in 2015 reported that a large portion of cancers can potentially be attributed to \"bad luck\", they found a very linear relationship between cancer type and stem cell division for that cell ty... | [
"There's a direct correlation; most cancers are a disease of age due to the time it takes to acquire the mutations necessary for transformation. This can be influenced by environmental factors, genetic factors and just plain bad luck also. Indeed the mean age of diagnosis varies for different cancers, however you ... |
[
"During Polymerase Chain Reaction, Why does Taq polymerase only extend the primer-DNA hybrid upto 1.5 kilo base pairs and not beyond that?"
] | [
false
] | null | [
"Processivity has to do with the likelihood of the polymerase falling off the DNA. In cells there is a protein called the clamp which literally clamps around the DNA and anchors the polymerase to the DNA. This increases processivity enormously. Its not included in the PCR design because its an extra step that is ha... | [
"PCR can also extend far beyond 1.5 KBP, it depends on the specific enzymes and reaction conditions but 1.5 KBP sounds like a limit placed by extension step timing on the thermocycler. We usually quote a 1 kbp/min line, but it can vary pretty heavily just based on something like GC content of the desired product."
... | [
"Thanks"
] |
[
"I understand how visible light images are captured with a lens and 2D array of sensors, but not sure how radio telescopes create images. Is it just a single radiowave-sensitive sensor that is scanned across the sky to form a 2D image?"
] | [
false
] | null | [
"Typically, yes, a radio telescope has just one \"pixel\" which it needs to scan across the sky to get an image. There's no fundamental reason you couldn't have more than one pixel though - just shove more of those radio sensitive receivers into the focal plane. The trick is that those radio sensitive pixels can be... | [
"Radio interferometry. Imagine you have multiple radio telescopes, 1000 kilometers away. Depending on where the signal is coming from, it will reach one of the telescopes a bit earlier. You can use the time difference to work out the angle from which the signal is coming from.",
"Now, using complicated math you c... | [
"In most cases yes. I don't know of any single radio telescope (as opposed to arrays) that can take a \"snapshot\" image.",
"For good efficiency the receiving element of the antenna - the wire that connects to the receiver circuitry - needs to be comparable in size to the wavelength. For typical radio astronomy b... |
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