title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Will a solder GUN harm magnets, if so how?"
] | [
false
] | I recently took a job helping repair guitar pickups, and our shop installs them with a solder gun. I have seen people say these can harm pickups, but I cannot find any info when I google this. We plan on taking a ceramic magnet to the gun directly and seeing what happens, but can someone explain to me what to expect?... | [
"Heat can damage magnets (or rather, cause them to demagnetize). Soldering guns are ",
" higher wattage than soldering pencils. If the gun is way over-powered for the soldering you're doing, it can cause the work to get hotter than it needs to. Amusingly, a too-small soldering pencil can ",
" cause overheating,... | [
"That statement doesn't actually say anything explicit about the magnetic field being responsible, though it surely implies it. I'm fairly comfortable labeling this idea as folklore, passed from person to person without anything to back it up.",
"I haven't directly measured the magnetic field around the barrel of... | [
"Seymour Duncan had posted an add? about not using soldering gun. I took it as the magnetic field it was letting off would cause damage, not the heat, so this is interesting.",
"Here is the image, and again this comes straight from Seymour Duncan. Here is the quote with it:",
"Tech Tip: When soldering try an... |
[
"Is there any correlation between the regularity and intensity of a womans period and her fertility?"
] | [
false
] | null | [
"It really is a question for a scientist. I'm a woman who used fertility awareness and charting for several years to prevent pregnancy and, while I am now more aware of cervical fluid, cervix position/texture, and ovulation, I don't (and can't, simply from this observation) know if I am differently fertile than oth... | [
"Some of the reasons for more \"intense\" periods (i.e., more cramping, higher blood flow) can cause lower fertility or even infertility. ",
"Endometriosis",
" is one example. ",
"Polycystic ovary syndrome",
" (or PCOS) can also cause irregular cycles as well as painful ovarian cysts. I'm not aware of any s... | [
"IF a woman's period is irregular, this could be a symptom of PCOS, which is linked to infertility or trouble conceiving, depending on the seriousness of the hormonal imbalance. "
] |
[
"Why is it, especially in war movies, said that fixed bayonets are a detriment to accuracy?"
] | [
false
] | So this whole question came to my mind when my friend bought a flintlock rifle, and he wants to get the bayonet for it. I recalled hearing in war movies especially saying that the riflemen should leave off the bayonets as it will make their shots less accurate. Looking it up myself, there doesn't seem to be a consensus... | [
"Bayonets do affect barrel harmonics, but the effect is negligible, especially at the ranges that most firefights take place. They do however make it harder to balance and steady a rifle from most shooting positions, as well as make a rifle much less maneuverable. "
] | [
"its to do with the \"moment\", the further you place a weight from the point of pivot the greater the force.",
"e.g. if our rifle is hand held and we take the point of pivot at the trigger (for simplicity) if weight of the bayonet is multiplied by the barrel length.",
"the longer the barrel therefore the great... | [
"A bayonet will increase both the weight and the moment of inertia of the rifle. More weight will require more strength to hold the rifle and may result in quicker fatigue leading to shaking. A greater moment of inertia will require more torque to move the rifle on target, and as a result less fine motor control ... |
[
"How is gravitational information passed from one object to another?"
] | [
false
] | I understand that gravity moves at the speed of light. I don't understand what is actually moving at this speed. Is it the curvature of space time or is there some type of gravitational particle, like a photon, that is carrying the information? What is actually moving through space that allows object to be affected by ... | [
"This is actually a big debate in modern physics. The standard model, in its current formulation, says there should be a graviton, or quantized excitation in the gravitational field. However, general relativity says that the gravitational \"field\" doesn't really exist, and replaces that notion with space-time curv... | [
"What this means is that quantum physics (on the scale of atoms) suggests that gravity is a particle, or has a particle component. Classical mechanics says that gravity is just the result of mass curving space, so things fall into those curved spaces."
] | [
"No, general relativity doesn't really say that gravitons doesn't exist, no more than classical EM says that photons doesn't exist. GR is just another field theory, although a very non-linear one. The curvature of spacetime, or rather the metric, is just another field, and its quantization leads to gravitons, just ... |
[
"Calculus of Variation beginner question: How do we arrive at the integrand?"
] | [
false
] | [deleted] | [
"And many times that function is replaced by sqrt(1+y'2)",
"The term sqrt(1+y'",
" ) dx represents the infinitesimal distance on the graph of the function y at the point x.",
"(Just approximate the function by its tangent at x and use Pythagorean theorem)",
"So, for example, in all problem where the goal is... | [
"I understood the sqrt(1+y'",
" )dx term. But why is f a function of x, y and (d/dx)y. Why do we need (d/dx)y? Isn't a function f(x,y) sufficient? Why does the (d/dx)y dependency matter and where does it come from?"
] | [
"Because in physics, there are a lot of quantity that depends on the position (x,y) AND the speed dy/dx . For example the total energy of a pendulum."
] |
[
"If you knew all of the dimensions, distances lenses and settings etc, would it ever be feasible to refocus a blurred image?"
] | [
false
] | say you knew exactly how far the camera was from the subject and background etc? | [
"cameras record the intensity of incoming light. that's a scalar. you'd need to measure the direction or phase too. if you had phase/intensity (vector quantity) you could do what you want to do. read about this ",
"http://en.wikipedia.org/wiki/Lytro",
"Edit for clarity"
] | [
"It is possible to get back SOME of the information of a blurred image. If you know the point spread function (blurry image of a single point), it would be possible to perform a deconvolution and get an unblurred image. Unfortunately, some spatial frequency information will have been lost, and since the system is... | [
"http://yuzhikov.com/articles/BlurredImagesRestoration1.htm",
"Above link, guy achieves refocusing of blurred and defocused images.\nWorth a read, provides great info."
] |
[
"Accelerating universal expansion"
] | [
false
] | [deleted] | [
"I think we could safely equate those two. "
] | [
"I think we could safely equate those two. "
] | [
"That doesn't answer the question at all.",
"The Hubble parameter is a measure of the rate of expansion, but not a measure of the acceleration of that expansion. That measurement is called, for historical reasons, the ",
"deceleration parameter",
". ",
"It's a dimensionless number, unlike the Hubble parame... |
[
"Looking for some good introduction to Paleontology books."
] | [
false
] | [deleted] | [
"One I like (I've got an old edition, 1995; there maybe newer) is History of Life by Richard Cowen. I'll ask our paleontologist what book he teaches from and post the title later.",
"EDIT: Bringing Fossils To Life: ",
"An Introduction To Paleobiology",
" by Prothero (expensive text, but perhaps you can find i... | [
"Thanks, I'll look into those! "
] | [
"One other perhaps to consider: The Story of Life by R. Southwood."
] |
[
"why do some things taste better hot while others taste better cold?"
] | [
false
] | not sure if this is the right field. let me know if it's not! | [
"Thermodynamics and, yes, biology. ",
"So, hot food has more energy per molecule than cold food molecules. This means that hot food molecules are moving faster than cold food molecules. Personally, when I eat apple pie, I like it warm. The warmer apple molecules (sugar, fat, Salt) come in contact with taste recep... | [
"if you get your taste receptors (hot coffee scalding) on your tongue, it becomes hard to taste anything afterwards. That's because you destroyed your tools (deformed proteins and cannot do their jobs) "
] | [
"If I had to take a shot in the dark, I'd say it is some sort of learned evolutionary response to food. One example of this would be sweet and sour foods. We associate sour foods with spoiled foods and thus tend to stay away from them. Sweet foods, especially in development, are jammed packed with sugars and are us... |
[
"If fish do grow proportional to their surroundings (i.e. a fish tank), what causes this? And is there any background to suggest why this happens?"
] | [
false
] | null | [
"This is mostly a myth, though there are a few things that contribute to the idea. I'll walk through a sort of hypothetical story that I think explains why this idea is popular.",
"Say you go to a crappy pet store (good ones won't do this) and the sales clerk sees you looking at a ",
"cute baby oscar",
". O... | [
"Fish farming engineer here:\nThere are many water quality parameters that affect growth in one way or another. Before I go into those, we first have to understand the concept of carrying capacity: how much biomass (kilos of fish for example) can a system such as an aquarium can support. ",
"The first parameter a... | [
"Just to add to this, in aquaponics its been demonstrated that even small amounts of ammonia in water will slow growth. And when I mean small something like 2mg per liter amounts. ",
"For reference, in neutral to slightly acid, goldfish can survive in 16 to 18 mg/l but they wont grow much or at all."
] |
[
"What stops an all-male Y-chromosome from being created?"
] | [
false
] | This is just a random thought that came to me during lunch today. We all know that by , having (approximately) a 1:1 sex ratio is the unique equilibrium from a maximize-offspring standpoint for animals that participate in sexual reproduction in a manner similar to humans. However, with a sufficiently large population, ... | [
"However, it seems to me like there's an opportunity for chromosome-level \"cheating\" to go on. Consider a person, Bob, whose Y-chromosome evolved a gene that causes all sperm containing X-chromosomes to become malformed (and thus die off, eventually getting replaced by Y-chromosome sperm).",
"There are ",
"me... | [
"Why, then, do we not see such selfish behavior among the chromosomes themselves?",
"we do.",
"http://www.crick.ac.uk/news/science-news/2012/09/13/sex-chromosome-battle-leads-to-more-female-mice/",
"(though I am not sure if this was the one I read that made me google for it in the surety of finding it)"
] | [
"That's wonderful! Thanks!!"
] |
[
"Scientists think the Earth had 2 periods of time when it was almost completely covered in ice. They only lasted a few million years. Do we have any way of knowing if Europa or Enceladus might be in similar temporary freezes? Or is theirs a clearly permanent state?"
] | [
false
] | null | [
"Oh, man, is this question right up my alley.",
"Europa and Enceladus are definitely in a permanent state. They get so little sunlight that even if you caused them to melt somehow, they'd just freeze right back up again.",
"The \"two-state\" nature of Earth's climate comes about because of the ice albedo feedb... | [
"The Earth gets the right amount of sunlight that when it's covered in water, it absorbs enough sunlight to stay above freezing, and when it's covered in ice, it absorbs little enough sunlight to stay frozen. But if it were closer to the Sun, even an ice-covered Earth would be too hot to be frozen, and so only the... | [
"If all the ice melted completely, ocean salinity levels would be lowered so drastically it would wreck the existing currents as well. Those are a big part of what regulates global temperatures."
] |
[
"Why is light the only thing that travels at the speed of light?"
] | [
false
] | [deleted] | [
"The thing is that the speed of light isn't just some arbitrary speed that light moves at and then nothing can go faster than it. You could say the speed of light (approx. 300,000 km/s) is like a universal \"top speed.\" Anything without mass will travel at that speed, with electromagnetic waves (light) being the p... | [
"Other than every",
" in the electromagnetic spectrum, it is theorized that gravity propagates at the speed of light."
] | [
"Gravity and weak nuclear force, for example, both which are massless, travel at the speed of light.",
"The ",
"weak nuclear force",
" is mediated by ",
"W and Z bosons,",
" which have mass, and therefore move slower than light. The ",
"strong nuclear force",
" is mediated by ",
"gluons",
" which ... |
[
"How did the B vitamins get different numbers and why are there gaps in that numbering system?"
] | [
false
] | null | [
"The basic gist of it is that scientists in the early 1900s identified vitamins, usually by what deficiencies they prevented, and started naming them A,B,C,etc. but as it turns out, the what they originally thought was one vitamin B turned out to be many different compounds so it was split up into B1,2,3,etc. And o... | [
"Things once thought to be vitamins were given numbers in the B-vitamin numbering scheme, but were subsequently discovered to be either not essential for life or manufactured by the body, thus not meeting the two essential qualifiers for a vitamin."
] | [
"Very interesting, thank you!"
] |
[
"Why didn't this guy need a skin graft? He had half his nose removed!"
] | [
true
] | null | [
"Here's your NSFW/NSFL warning everyone.",
"Gagging over here."
] | [
"Apologies, I assumed putting up the red NSFW button would be enough, I now included it in the title."
] | [
"You did fine, I just don't want anybody to be surprised"
] |
[
"Are there invisible free gas giants out there?"
] | [
false
] | During star formation, how likely is it for there to be enough material around to make brown dwarfs or above? Is it possible there are lots of free gas giants because there isn't enough materials to achieve fusion? If there's a 10-Jupiter-mass gas giant 1 light year away, would it be possible to detect? | [
"It seems like you're talking about Sub-Brown Dwarfs. ",
"http://en.wikipedia.org/wiki/Sub-brown_dwarf"
] | [
"Depending on what size you mean, exactly - but there may be a lot of them.",
"http://blogs.discovermagazine.com/badastronomy/2011/05/18/the-galaxy-may-swarm-with-billions-of-wandering-planets/",
"Folks can detect them by staring at a lot of distant stars for a looooong time, then watching a rogue pass in front... | [
"There almost certainly are \"rogue planets\" out there, as such a body would be called. They would be very difficult to difficult to detect, so we don't know how common they would be.",
"http://en.wikipedia.org/wiki/Rogue_planet"
] |
[
"Do plants get sexually transmitted diseases?"
] | [
false
] | The bees sure do get around from flower to flower. It seems like this would be an ideal situation for some virus or bacteria. Are there stds that affect plants? | [
"Or fungus: ",
"anther smut"
] | [
"Strictly speaking, this wouldn't be a sexually transmitted disease, since plants don't reproduce by the sexual reproduction that animals use to procreate (some have flowers with only one 'sex' and some have flowering parts with both 'male' and 'female' structures), and you're right - - bees and other pollinators a... | [
"plants don't reproduce by the sexual reproduction that animals use to procreate",
"Yes, they do. They have different sexual organs than animals (maybe that's what you meant), but even plants with hermaphroditic flowers have sex (often times, with themselves), in the sense that gametes combine to form the next g... |
[
"Why do many hotel and public hot tubs have warnings that say “limit time to 15 minutes for personal safety”? What are the detrimental effects?"
] | [
false
] | null | [
"Just as hypothermia (being too cold) is bad, hyperthermia (being too hot) is bad. The reason for this is the proteins and enzymes in your body are designed to function in a relatively narrow temperature range (aka body temp) before they start to denature, where their shape and functionality can start to change. On... | [
"So is it dangerous for a healthy, fit, individual to stay in a hot tub or bath for a long time? Or is it just a warning that they do for litigation purposes?"
] | [
"A little bit of both, 15 min is probably shorter than necessary for the average person, but for smaller people that might be too long (which is why many places disallow children from the hot tubs). If you notice you feel light headed or tired then you need to get out, as those are the early signs of heat stroke. "... |
[
"Why is geothermal power not a complete no-brainer?"
] | [
false
] | In our recent cultural obsession with "alternative" energy sources, I find myself continuously wondering why geothermal isn't the obvious and easy answer. Sources of heat within the earth are not visible, readily available, and will never end (or at least on a not cosmological time scale). So what exactly is holding th... | [
"Because geothermal isn't available everywhere. This is like complaining about why isn't everyone using hydroelectric dams for all their power.",
"Additionally…",
"Fluids drawn from the deep earth carry a mixture of gases, notably carbon dioxide (CO2), hydrogen sulfide (H2S), methane (CH4), and ammonia (NH3). T... | [
"Came here to say (3). Drilling costs are crazy high. Also, to generalize (5) - most all renewable energy sources are limited to specific geographic areas, often far from where people actually live. Transmission costs are quite expensive, and add transmission losses on top of that, and you see why a coal plant (whi... | [
"Thorium has been discussed before",
"."
] |
[
"If we didn't have planets with rings in our solar system, would we even know it would be possible for planets to have them?"
] | [
false
] | null | [
"It would be known to be possible. Rings can form if a moon orbits inside the planet's ",
"Roche limit",
" and gets torn apart. Tidal forces tearing things apart is important in other aspects of astronomy (e.g. binary stars), so the theory would've been well developed.",
"Someone eventually would've then writ... | [
"Is there anything we think planets could have that does not exist in our solar system?",
"Loads of things actually. But then our solar system only has 8 planets so its not surprising the universe would have tonnes of cool things to discover.",
"There should be:",
"Edit: On a phone. Will try to reference late... | [
"Is there anything we think planets could have that does not exist in our solar system?"
] |
[
"When I'm looking at fire, what exactly am I looking at?"
] | [
false
] | Fire isn't an element. It's not a "material". But it is the result of 2 elements, oxygen and something else, combining. Is not a solid, liquid, or gas. All I understand it to be is "a release of energy from the breaking if chemical bonds". So what makes it visible? And why are some fires different colors, like red, bl... | [
"Essentially you're looking at two different things, one of which depends on the chemical composition of the fuel and another that depends on the temperature of the flame. The first one is the ",
"emission spectrum",
" of the gases produced by the fire after the vaporised fuel reacts with oxygen; these gases, w... | [
"Hard to beat this explanation:\n",
"http://www.youtube.com/watch?v=ITpDrdtGAmo",
"*Edit: As I re-read your question this not exactly what you asked but a great video nevertheless"
] | [
"This video gives an excellent explanation\n",
"https://www.youtube.com/watch?v=5ymAXKXhvHI"
] |
[
"Does a fully electric vehicle get better efficiency in a city or on a highway?"
] | [
false
] | As far as I know, the average vehicle gets better fuel efficiency on the highway as opposed to in a city. Is this the same for fully electric vehicles (such as the Tesla Model S), or do they get more miles per kWh in a city? | [
"Assuming the electric vehicle's motor wasn't excessively inefficient at high speeds, and ignoring air resistance (which depends on the shape of the car), it would be more efficient on the highway.",
"One of the biggest sources of wasted energy during city driving is the constant stopping and starting. Every tim... | [
"There is an optimal speed for any vehicle depending on a range of factors (drag, rolling resistance, engine RPM, weather, road conditions, weight etc). For a Tesla Model S a ",
"constant-speed of ~20 mph",
" will give the best range but that's hard to do because it is too slow for the highway and in the city y... | [
"There is also significantly less energy used when holding still at an intersection or in a queue, since electric motors don't need to idle."
] |
[
"Why does boiling water make patterns in the cup?"
] | [
false
] | Also apologies if the flair isn't suitable | [
"Look's like the water isn't quite boiling. There's no bubbles, but this pattern that you're observing is indicative of temperature gradients in the water. So it can't all be at 100 degrees C yet.",
"The temperature gradients cause gradients in the water density, which in turn cause variations in the refractive i... | [
"closely related, but not quite the same. The cup patterns are caused by variations in density of the water within the cup. Pool reflections are caused by the movement of the surface of the water, both by changing the angle of incidence against the water surface of the incoming light and also varying the depth/th... | [
"Oh, interesting! So it's the same reason why in the summer a pool would have these patterns? I also find it interesting that the water had variations in temperature considering it came out of a kettle that had finished just before I poured it"
] |
[
"For treating near-sightedness, is there any advantage to wearing an underpowered prescription?"
] | [
false
] | I'm pretty severely myopic, and something I've heard several times is that it's advisable to wear a slightly underpowered prescription to prevent your vision from deteriorating further. Is this true? It seems to me that, even if it is, isn't the risk of slightly worsening your vision preferable to worsening your functi... | [
"No it is not true. Vision deterioration does not occur in reaction to your current vision. "
] | [
"Optician for 11 years here: The answer is a resounding NO. The only thing that will come from wearing an under-powered RX is blurry vision."
] | [
"Optometrist: There is some dispute on the issue. In old world monkey studies, under-correction and over-correction both lead to an increase in the development of myopia. (",
"http://www.tutis.ca/NeuroMD/L1Eye/BlurAndEyeGrowth.pdf",
") (first decent source I could find... I'm sure there are better out there)... |
[
"Evolution optimizes physiology based on survivability, and we are always taught about how well adapted many physiologies are. Since evolution is ongoing, what are some examples of current species that suffer from maladaptation?"
] | [
false
] | null | [
"The panda.",
"It's basically a carnivore that eats bamboo, which it can barely digest.",
"they can only mate once a year during a 2 day window.",
"They don't even stay together to raise the babies.",
"Edit: Also, maladapted is not really the right way to think of this. It's not that things adapt badly or i... | [
"Firstly, I don't know but I doubt we actually know the evolutionary history of most animals. We can guess at some, but to be sure is not possible.",
"Second, I doubt the panda was selected for. It was probably just good enough that it was able to survive. Some predecessor became able to eat bamboo, there was a l... | [
"How did the panda get to that point?",
"Is it known what was that made eating bamboo and such a lazy reproduction strategy get selected for?"
] |
[
"Where does the energy for capillary lift come from?"
] | [
false
] | null | [
"Several reasons: the energy of gravity is overcome by the change in chemical action in breaking surface tension; surface tension is energetically expensive, so breaking surface tension releases energy; wetting is endothermic."
] | [
"It's worth pointing out, although the fluid will travel against gravity up the tube - it won't come out of the tube again without expending energy. So it can't be used to do continuous work - it's just a one off release of energy that was already in the system. (Plants constantly evaporate water from their leaves ... | [
"The exposed surface has an energy associated with it. When the water wicks up, the energy difference of the exposed surface to the water coated one provides a capillary force until the mass of water lifted accumulates to an equal gravitational potential to that energy difference."
] |
[
"Do we have any idea what The Great Attractor is or might be?"
] | [
false
] | [deleted] | [
"The so-called Great Attractor is (in my opinion) somewhat overrated. It is simply an over-density of matter (galaxies, etc.) of a type that appears to be very common in the universe. In the early days of cosmology, when we could only detect very nearby galaxies, structures like the Great Attractor were thought t... | [
"To get collapse into a black hole, you need a strong gravitational field that will \"pull everything in\". Because the universe was very homogeneous and isotropic early on, gravity pretty much cancels out everywhere."
] | [
"The reason why the universe didn't collapse into a black hole despite its enormous density at early times was that the expansion rate back then was also enormous. If the expansion rate were significantly smaller for the same density, then the universe would have collapsed, possibly into a black hole. ",
"The q... |
[
"Why can't we access information that arrived at our senses during sleep?"
] | [
false
] | Maybe it seems like a strange question, but for example, why can't I remember everything that my ears heard during sleep? They are still technically functioning...converting waves into electrical pulses and sending that information along. Where does it go? And it seems like...however the system works...there are certai... | [
"There are two main reasons.",
"There is some modulation of sensory input during sleep (by the thalamus for example), which causes some incoming information to be filtered out. The exact way in which this modulation occurs is not fully understood. Nevertheless, sounds still reach the brain during sleep and some p... | [
"Your #1 is interesting and makes me want to try hacking my skill development.",
"Your #2 suggests that maybe you hear everything during sleep, but simply forget (or rather you never wrote it to memory in the first place). I know you didn't say that specifically, but it's an interesting idea. Maybe the machinery ... | [
"This is incorrect. All senses can awaken a person who is sleeping."
] |
[
"In a system of objects without velocity (In space) can we move the center of mass without outside forces?"
] | [
false
] | null | [
"No, this is the whole point of Newton's 1st law: an object at rest will stay at rest unless acted on by outside forces."
] | [
"Photons still have energy, so if you're going to be emitting radiation then you need to be calculating the center of energy density of the system."
] | [
"Conservation of momentum dictates that you cannot accelerate the center of mass of a system without outside influence.",
"If you use some internal energy source to make a rocket and shoot particles away at high velocity, those particles are still part of the system and as a result the center of mass of the syste... |
[
"Why are galaxies shaped like discs, instead of orbs?"
] | [
false
] | I have a very elementary understanding of cosmology, so please bear with me. Why do so many galactic structures end up in a disc shape? Edit: Thanks again, askscience. I really appreciate your input. You are growing my understanding of the universe. | [
"Well, there are many parts to a galaxy, so I'll talk about a few of them. The disk, is the big flat part of the galaxy. This is probably formed because there was some initial angular momentum in the galaxy, or gravitational potential energy was converted into angular momentum. ",
"So I'll diverge to answer yo... | [
"Meh. I'd like an answer from someone with a more relevant area of study."
] | [
"Actually galaxies come in all shapes (Disks, orbs and irregulars)"
] |
[
"Are newscientist.com, physorg.com, sciencedaily.com, dailygalaxy.com and popsci.com good quality sources for science news?"
] | [
false
] | [deleted] | [
"It really depends on whether you are a scientist or a layman. Most scientists regard the journals Science (sciencemag.org) and Nature (nature.com) as being the big dogs and as such follow their news feeds. ",
"They are general interest journals and as such have news on all aspects of science, in fact many of the... | [
"I'd definitely say no to newscientist and physorg, though I don't know the others well enough. I'd stick to Scientific American, Physics Today, etc... The New York Times's science section generally does a good job, unless Dennis Overbye is writing the article."
] | [
"I like sciencedaily.com. They include journal references, have a lot of news in a wide variety of fields, and rarely write anything boneheaded. ",
"The only downside I find is that they're not very consistent with the amount of scientific education needed to understand an article... even inside one article you ... |
[
"Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology"
] | [
false
] | Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! ... | [
"So, it seems that it is unlikely for the common flu (by which I assume you are referring to seasonal flu viruses that already infect humans) to cause pandemics (to which I assume you are referring with \"kill us all\"). According to ",
"the CDC's website on pandemic flu",
":",
"An influenza pandemic can occu... | [
"Why open bodies(fresh), both human and animal, disgust most people and cause them to feel nausea or even vomit?"
] | [
"Have you heard of Gestalt processing? The whole idea behind a colorblindness test is that an overall pattern emerges from the individual shapes, visible only by color contrast between them. The brain will use one of ",
"a number of rules to group",
" small figures into larger ones. The simpler the larger patte... |
[
"For cell phones, is there an audio volume at which the built-in speaker and the Bluetooth connection would use the same amount of power? And does Bluetooth power consumption vary with distance?"
] | [
false
] | The built-in speaker uses more power as the volume goes up, but the power used to transmit to a Bluetooth device doesn't change with volume. So is Bluetooth the most power-efficient choice at all volume levels, or do they intersect at some point (considering just the phone's battery, not the power source required for t... | [
"I've looked around, and there's currently no information on how these correlate with each-other. At least, not directly.",
"I did, however, stumble across this:\n",
"http://www.clearevo.com/ecodroidlink/bluetooth_vs_wifi_on_android_battery_consumption/",
"This seems like it would be a good baseline. With onl... | [
"Bluetooth power consumption should be about the same at all distances.",
"With respect I do not believe what you wrote to be accurate:\n",
"https://en.wikipedia.org/wiki/Near-far_problem",
"In addition variable gains do exist and being in which bluetooth is packet based and quite capable of running tcp, retr... | [
"Actually retransmissions do not add that much. Bluetooth works much like all mobile technology, with a heavy dose of forward error correction.",
"If outage occurs, aka if the snr drops below the SNR threshold for fec, the channel is tested before retransmision occurs. Honestly there is no point in doing anything... |
[
"Are there known \"evolutionary valleys?\" Suboptimal traits that, once evolved, remain for long periods of time because, despite being suboptimal, selection pressure still pushes deviations back towards the trait?"
] | [
false
] | null | [
"You (probably) have two right inside your own face. Specifically in your eyes.",
"The light sensing cells in your retina have a detecting end and a nerve connection end. The end where the nerve comes out is facing inward, meaning all the nerves need to come together into a single point in the retina to connect t... | [
"This is one of those interesting aspects of biology with deeper layers that are quite fascinating. The flaw is a trade off that enabled a much bigger advantage. ",
"Nerves at the front allowed the development of a lot of blood flow at the rear of the eye, which (amongst other advantages), gave increased cooling ... | [
"There's a nerve circuit in Giraffes that does a 15 foot detour from the brain down into the chest cavity, then back up the neck to the larynx, mere inches from the starting point. An unfortunate but logical result of evolutionary pressure that resulted in Giraffes becoming long necked over time.",
"The Recurrent... |
[
"Will the Cosmic Microwave Background Radiation turn to Radiowaves as the universe further expands?"
] | [
false
] | I always wondered why the light of the CMBR, that has been increasing in wavelength since it's formation, hasn't moved even farther to the low energy part of the EM spectrum in the last 14 billion years. As the universe is still expanding this eventually has to happen, right? How long would it take until we classified... | [
"The CMB is the most perfect blackbody ever measured and this implies that some amount of the photons from the epoch of recombination are low-frequency radio photons now. We call it the cosmic microwave background because the bulk of the radiation is in microwaves. In fact, ",
"microwaves",
" are quite arguably... | [
"Thank you, especially for calculating the value. "
] | [
"Some on-topic comments from Lawrence Krauss' ",
":",
"...[A]s the universe expands ever faster in the future, the temperature of the CMBR will fall. When the presently observable universe is about 100 times larger than it is now, the temperature of the CMBR will have fallen by a factor of 100, and its intensit... |
[
"What is the difference between a flame temperature and a similar temperature with no flame?"
] | [
false
] | What is the difference between an open flame and straight temperature? Why can I light gasoline with an open flame that's less hot than a cigarette ember? The ember goes out but the flame ignites the gas. | [
"Sometimes because of how fast heat dissipates above a flame, we forget how hot they really are.",
"Let's use methane, because I know the numbers for that and not gasoline. A methane flame will have a temperature of somewhere around 3500 F (the adiabatic flame temperature, for a stoichiometric methane/air ratio).... | [
"paper may ignite at 451 F or so, but I think that it burns (ie the flame) much hotter than that. I don't have numbers, but knowing that it's a partial plasma, that the flame is black body carbon well into the yellow... (edit, here's ",
"wiki",
" that says flames are ~1000-2000 F) and please try to be a bit mor... | [
"paper may ignite at 451 F or so, but I think that it burns (ie the flame) much hotter than that. I don't have numbers, but knowing that it's a partial plasma, that the flame is black body carbon well into the yellow... (edit, here's ",
"wiki",
" that says flames are ~1000-2000 F) and please try to be a bit mor... |
[
"Why can't we see well underwater? What is different about the eyes of aquatic animals?"
] | [
false
] | null | [
"The key difference is in the lens of the eye that handles focusing the image onto the retina. When focusing, the \"work\" is done as light transitions from one material to another, as the index of refraction changes, which causes the light to bend.",
"Outside the water, this is (roughly) air -> lens -> vitreous... | [
"In theory with a sufficiently extreme myopia this could be possible, but I suspect it would need to be so extreme that I doubt it could happen."
] | [
"Be merciful if this is a dumb question, but does this mean that someone with the \"right\" bad vision or eye abnormality could theoretically be able to see better underwater?"
] |
[
"According to a post in TIL time on the edge of a black hole travels half as fast as time on earth, what would happen if people in a spaceship on the edge were in realtime communication with people on Earth?"
] | [
false
] | I can't wrap my head around this, it could be a 5 minute conversation for those in the spaceship but last ten minutes for the people on Earth, even though it's the exact same thing happening on both ends | [
"Stargate SG1: \"A Matter of Time\" S02E15."
] | [
"Well, there isn't really a such thing as a \"realtime communication\", since you can't transmit information at faster than light speed. In order for some people near a black hole to have a conversation with people on Earth, they'd have to send out some sort of signal that would travel to Earth at light speed at b... | [
"It wouldn't be the same thing on both ends. The people closer to the black hole would experience the people on earth as moving in fast forward. And the earth people would experience the black hole people to go in slowmo.",
"There was a nice Stargate episode covering this scenario, refreshingly accurately, too."
... |
[
"Rutherford Gold foil experiment"
] | [
false
] | If it was done with any metal other than gold, how would results change? | [
"The result would stay pretty much the same. Most alpha particles pass through and some are scattered.",
"The reason for gold was, that very thin sheets of gold are readily available."
] | [
"But wouldn't the denser nucleus of gold vs lighter nucleus of Silver make a difference in angle of scattering?",
"So results wont be same? Isn't it?"
] | [
"The details of scattering would differ, but the conclusion- that atoms contain a nucleus- would be the same."
] |
[
"If I want to make a smart heating element without the use of a micro controller, does a thermistor with a negative k connected to a nichrome heating element work?"
] | [
false
] | I'm reading off of some websites, I do not know very much about circuitry besides basics I learned in AP physics. It seems if I connect a power source to a thermistor, when the water is cold, the resistance goes down, and more current flows to the heating element which gets hotter, and when it gets hotter, the resistan... | [
"I suppose you could it that way but you have to consider the huge amount of current you want to pass though that resistor, effectively the same as though the heating element? So the resistor will burn quickly i fear. But if you use the resistor as the heating element you just have to find one with the right charac... | [
"Since I've heard the term 'smart heating element' a few times lately, I'm just going to link ",
"here",
", skipping to where thermistors are used."
] | [
"So, what you're referring to is oscillation, and it's what can happen if there's a delay between the heating and the sensor detecting that the temperature has gone up. Whether it can happen with something as rudimentary as a thermistor and a heater, I am not sure off the top of my head, but it's dependent on the ... |
[
"Why do some people sneeze when they look at the sun?"
] | [
false
] | null | [
"Genetics! Photic sneeze reflex occurs in around a quarter of the population, and thought to be autosomal dominant. In fact, it is listed in ",
"disease databases",
" as \"ACHOO (Autosomal-dominant Compelling Helio-Ophthalmic Outburst) syndrome\".",
"A ",
"recent published study",
" found genetic variants... | [
"Thank you for the answer!"
] | [
"This question ",
"was asked yesterday",
", so you may want to check that thread. "
] |
[
"Does light actually travel at \"the speed of light\" in a vacuum, or do interactions with virtual particles slow the light down?"
] | [
false
] | I have only a rudimentary understanding of physics, but I gather that photons traveling through matter will be delayed as a result of interactions with the particles that make up the matter, effectively slowing down the light wave. I also understand that empty space isn't really empty, but is full of virtual particles... | [
"It isn't obvious at all that photons shouldn't acquire an effective mass from quantum corrections.",
"However, it is found in quantum field theory that the mass of the photon is protected from any quantum correction by gauge invariance. This is a nontrivial result."
] | [
"Regardless of quantum effects, electromagnetic radiation follows time-like curves in General Relativity. This is due to the fact that the electromagnetic field has energy and thus is affected by gravity. The effect is so small as to be essentially unmeasurable.",
"But classically (since GR is a classical theory)... | [
"The OP is asking about quantum corrections to the photon propagator. Definitely empty space is not empty and is not obvious that a photon should still travel at c after considering higher-order QED corrections to the photon propagator."
] |
[
"Why did my oven safe PYREX glass shatter after cooling down?"
] | [
false
] | PYREX glass exploded after cooling down on top of my oven. We baked two baked potatoes at 425 degrees for one hour. Took it out of the oven and let it cool for 10 minutes. We finished eating about 10 minutes later and we heard a loud glass explosion. The Pyrex pan had shattered. The glass by this point was just warm. D... | [
"Yup, your \"Pyrex\" isn't really Pyrex. Traditionally, the Pyrex brand meant borosilicate glass-ware, which has tremendous stability against being subjected to temperature extremes. It's the same stuff a lot of lab ware is made out of. In 1998 Corning stopped making Pyrex cookware and instead spun off a subsidiary... | [
"According to ",
"this image",
", you could check the logo."
] | [
"Because pyrex no longer uses borosilicate glass. They use tempered soda lime glass instead. Go with arcuisine or something like that."
] |
[
"At what rate does water freeze? As in, when the portion of water reaches freezing temperature, does it freeze in an instant in its entirety, or does it start a discrete point and progress through the entire portion of water? If so, at what speed?"
] | [
false
] | null | [
"People have already posted about supercooling water below freezing.",
"I'll just point out that in normal freezing, when ice is formed the latent heat is released into the surrounding water, so the remaining water is raised to above freezing point. ",
"Therefore the water can only freeze as fast as quickly as ... | [
"water doesn't freeze immediately it needs something to bind to like an imperfection in the water (like a mineral) and then each molecule can attach to the next frozen one in line. you can actually 'super cool' water and get it to be liquid at below freezing temps but it has to be very pure water. Veretasium on you... | [
"Would that mean if you had absolutely pure water (not sure that's even possible), then it would never freeze or about what temperature would freeze it?",
"Edit for purity"
] |
[
"How does dew happen? And what exactly is meant by the \"dew point\"?"
] | [
false
] | How does the dew point change from day to day and why is it included in the weather reports? | [
"This will be a simplified explanation... The dew point is the air temperature where condensation will occur. It happens when warm moist air comes in contact with surfaces that have been cooled, typically by the cooler air overnight. Similar to the condensation that occurs on the outside of a cold soda can on a hot... | [
"Water condenses when the force of attraction between water molecules exceeds the kinetic energy of said molecules. This is a function of temperature. So It's true that other gaseous components don't directly contribute to condensation/vaporization.. However, during a diabetic processes the vapor may do work on th... | [
"Air can hold water. It can hold less water when it's cold. Overnight, it gets cold. So if there's enough water in the atmosphere, the air can't hold it anymore when it gets cold at night, and some of it comes out (aka \"condenses\").",
"Dew point is the temperature where water will start coming out of the air (d... |
[
"How do vegetables such as onions, potatoes, and garlic sprout long after harvest?"
] | [
false
] | [deleted] | [
"Yep, they're still alive!",
"A potato, carrot or beetroot is essentially a storage container for the plant. Take the carrot - it's a biannual, meaning it has a two-year life cycle where the plant spends the first year of its life gathering energy and nutrients, and the second year spending its stores on reproduc... | [
"You're right, it's not at all a hard and fast rule. My point was merely that a tuber is very well-adapted for regrowing the rest of a plant's body."
] | [
"and a leaf can't easily regrow a whole plant",
"I have an objection to this part. There are many plants where a leaf can easily regenerate the entire thing because putting roots down is trivial."
] |
[
"What thermal insulating material does a soldering iron use to not melt the plastic handle it is attached to?"
] | [
false
] | Today I took apart an old soldering iron out of curiosity. I noticed that there was a white powdery substance inside the metal heating element. I figured this must be some sort of thermal insulator because when I turned the iron on I was able to touch the back end with out getting burned. My question is, does anyone kn... | [
"Ceramic. Same stuff they use on the space shuttle to keep it from burning up on re-entry.",
"http://en.wikipedia.org/wiki/Ceramic"
] | [
"Thanks for your reply Kirmz. Do you know if it's a proprietary blend of ceramic? or could I literally crush a ceramic pot and use that powder to reduce heat transfer?"
] | [
"Ceramic (the word) refers to a class of materials with similar properties. Wikipedia - A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. It is likely a very common substance, at least in a soldering iron. ",
"In short, you could literally crush a ceramic pot a... |
[
"Why does the lifetime of a battery decrease over time?"
] | [
false
] | null | [
"I think you're referring to rechargeable batteries, like phone batteries, right? Basically energy of a battery is stored in the chemicals that are at the two ends of the battery. The chemicals at the cathode (positive terminal) want electrons more than the chemicals at the anode (negative terminal). The difference... | [
"In general the reason is the same reason that a car engine wears down, runs less and less smoothly, and produces less torque while consuming more fuel.",
"That is, entropy. Without outside intervention, forces such as friction, thermal expansion, or corrosion will cause parts of any system to wear down and opera... | [
"First of all, the cathode is the negative terminal, the ions attracted to the cathode are called cations however, they are positive ions. The electrolyte in a battery is generally homogenous. The life of a battery is limited by this homogenous material's ability to sustain free ions and the electrodes ability to r... |
[
"Why do depolarizing neuromuscular blockers like succinylcholine cause flaccid paralysis?"
] | [
false
] | Why is it that sustained depolarization doesn't come with sustained contraction? I remember in a lab stimulating a frog leg with electrodes and it was able to maintain contraction for minutes as long as the depolarizing potential was applied. Why does succinylcholine allow relaxation with depolarization? | [
"The succinylcholine-treated cell is maintained in something called the absolute refractory period, which prevents it from firing a second time. In the case of electrical stimulation, the cells are actually pulse-firing, rather than maintaining a single continuous action potential. PKThunder7 gave a great descrip... | [
"Anesthesiologist here. After IV administration of \"sux,\" there is a period of fasciculations lasting 5-10 seconds, followed by flaccidity lasting 5-10 minutes. The fasciculations can be prevented by prior administration of a nondepolarizing neuromuscukar blocker such as pancuronium, rocuronium, etc (10% of a typ... | [
"I am following up on the statement by ",
"/u/Cum_on_doorknob",
" that \"so if the cell is depolarized in a continuous state then it can't repolarize\" which is entirely accurate. You then asked why, if the cell is still depolarized, can it not fire an action potential. This is because of how the channels that ... |
[
"Potentially NSFW question, but this subreddit is one of the few with a mature attitude."
] | [
true
] | I'm not trying to make a sexual joke at all in this post, I'm simply curious. If women use penis size as an arbiter for who to mate with, evolutionarily speaking, has the average penis size increased over the years? | [
"Your appear to be assuming that women make their choices based on penis size alone, but if you consider it, they often don't know the penis size until their mate has been chosen. Women look for other signs in a mate including making judgements about a mates ability to give them healthy children (the potential mate... | [
"Sexual selection is a huge area of research in biology, and there are a lot of interesting popular-biology books on it. Check out the ",
"wiki",
" page. Also from the sexual selection page on ",
"humans",
", \"Anthropologists believe that 'male genitalia ...represent a critical target of sexual selection.'... | [
"You need to provide sources. I've also read about the \"penis plunger\" idea, but what I read was that it was mostly inconclusive and likely not the reason. Actually, I believe this was something I watched on PBS now that I think about it. But in any case, that's what I remember. We're both speaking in anecdotes r... |
[
"How do those little winter birds, like chickadees, not freeze to death, and, if they are just little well-insulated furnaces, where does all their energy come from, just seeds?"
] | [
false
] | null | [
"rete mirabilis"
] | [
"Adding onto that, seeds are incredibly calorie dense when compared against stuff like fruits and veggies. I know with Parrots that most birds well risk obesity on a seed diet and do better with fruit, veggies, pellets, etc. "
] | [
"Adding on to that - pipefitter here. Always fascinated when nature designs it better than we could. I've installed a lot of heat exchanging type systems and they're a direct rip-off of the veinous systems of cold-climate waterfowl. Limited knowledge so correct me if I'm wrong."
] |
[
"Are black holes really holes or just compact spheres?"
] | [
false
] | null | [
"Under just general relativity, they are mathematical points. No width, depth, or height. Not holes or spheres. Although the event horizon (point of no return for light) is a sphere around it.",
"That said, they may not be exactly mathematical points under a theory of quantum gravity. But we don't even have a... | [
"They aren't really \"holes\". When we talk about the shape of a black hole, we usually mean the shape of its ",
" - the boundary beyond which nothing can escape. These are spherical, so to an external observer, a black hole looks like a sphere.",
"You might argue that the ",
" is the more fundamental \"black... | [
"As to their shape, I tend to imagine that the super massive, often small center of a black hole is spinning at some exceedingly ridiculous rate which I would like to believe is spherical with slight deformation due to angular momentum.. but I dont think there is much of a tangible grasp of matter at that density/m... |
[
"why do bug bites itch?"
] | [
false
] | Ok so I did a bunch of yardwork without applying some bug spray first and I have a ton of bites. My question is why do bug bites itch? Wouldn't it be more advantageous for the host to never even know you were there? I am curious why they itch both as a literal means such as what chemicals etc... and what is the adva... | [
"Bug bites itch because while the mosquito is sticking its strawlike needle mouth (or it's proboscis, if you want the actual term) into your skin, looking for a blood source, they inject some of their saliva. Their saliva acts as an anticoagulant so they can get liquid blood without any clots. In the saliva, ther... | [
"You must also consider the opposite possibility, that humans developed an allergic reaction to the mosquito saliva as an advantage. There are many diseases carried by mosquitoes so any evolutionary change that caused humans to avoid mosquito areas would be (possibly) re-inforced. "
] | [
"Is there research showing what percentage of the population is non-reactive to the saliva? I haven't noticed a mosquito bite in years, and I spend a lot of time outside in areas where mosquitoes are common (and my friends and family get eaten up)."
] |
[
"Do we just not have the technology do bring something down to a temperature of 0°K, or is it a matter of scientific impossibility?"
] | [
false
] | null | [
"It would be a violation of the Third Law of Thermodynamics. "
] | [
"This is wrong. First, ",
" the energetic degrees of freedom are ultimately included in heat, not just kinetic energy. Second, temperature is ",
" defined in terms of motion, and 0 K doesn't imply zero motion. Quantum zero-point vibrations mean that things are not stationary at 0 K, not that you can't reach 0K ... | [
"Absolute zero is considered a theoretical construct only and is impossibly to reach. Heat is really just motion on a molecular level, particles jostle about. Cooling implies removing this energy and slowing them down. But since particles naturally have some vibration they are never stopped entirely which is what y... |
[
"Does the Brachistochrone answer work horizontally?"
] | [
false
] | null | [
"The brachistochrone solves the problem of finding the path which minimizes the time for a particle to travel from point A to point B under gravity alone. Gravity does not act horizontally. The comic has nothing to do with the brachistrochrone problem."
] | [
"The solution applies to a constant downward force. Detailed solutions are readily available; the Wikipedia article has two full solutions. All of the required assumptions are stated (e.g., uniform gravity, no friction, etc.)."
] | [
"I see. That's solved then, and my mistake, but does it apply for other forces? Is there an equivalent problem for say, magnetism?"
] |
[
"Why are mesh elements in Finite Element Analysis tools like COMSOL or Synopsis triangular?"
] | [
false
] | Is there a reason why they can't be squares for example? | [
"The more fundamental issue is that any mesh can be triangulated, but only some meshes can be turned into quads. Start by imagining any arbitrary mesh described by vertices, edges connecting those vertices and faces connecting those edges. Every face must contain 3 or more co-planar vertices. Any face with 5 or mor... | [
"They can be squares. I've previously used Abaqus and you can define roughly what shape you'd like. It can depend on the geometry of the part your meshing. Some geometries call for triangles, some squares or a mixture of the two."
] | [
"The reason triangles are more commonly used is because quads limit your solver to very simple geometries i.e. pretty much only containing 90 degree angles.",
"This isn't entirely true. You can make quads with any arbitrary angle, and a robust solver will be able to handle quads with any arbitrary angle. There ar... |
[
"What describes a collision in which a moving object imparts all of its kinetic energy to another resting object?"
] | [
false
] | I am imagining something like a bullet hitting a body and then the bullet being stuck inside the body, this in contrast to a ball hitting a body and then the ball flying off into another direction. What is the physical property that lets the bullet end up without any kinetic energy after collision? | [
"There really is no simple description for an effect like that. In your example of a bullet hitting a body, you can't treat the body as one solid object. It's actually the bullet impacting a dozen or more smaller parts (bones, organs, fluids, etc). The energy gets released by several mechanisms (note, not strictly ... | [
"Read those two Wikipedia Articles for further information",
"Elastic Collision",
"Inelastic Collision",
" ",
"In elastic collisions, the kinetic energy is conserved, whereas during inelastic collisions the amount of kinetic energy changes.",
"The only collision where one object transfers all of its own k... | [
"The only collision where one object transfers all of its own kinetic energy to another is a head on fully elastic collision of two object of the same mass.",
"Doesn't that go against my own example of a bullet entering a body and then stopping inside the body? All of the bullet's kinetic energy was transferred e... |
[
"Why aren't herbivores capable of digesting meat?"
] | [
false
] | Even when deer raid bird nests for calcium, they just spit out all the baby bird meat | [
"If you look at the digestive system of a ruminant, like a cow for instance, it's set up much more differently than an omnivore's or a carnivore's. Since most animals cannot produce cellulose-degrading enzymes, much of the digestion in the digestive system of a cow is actually done by microbes, and the cow extracts... | [
"Their evolution has adapted them to deal with more plants than meat, this progressed into being herbivores."
] | [
"How do you know deer raid bird nests for calcium, and spit out baby bird meat?"
] |
[
"Does a perfectly black object exists ?"
] | [
false
] | With the obvious exception of black holes. I was wondering if there was an object, or matter, or anything, that would absorb every single visible wavelength, making it appear truly black. | [
"Absorbing all wavelengths is not the same as being black. Some of the objects that work best as approximations of black bodies (which means an object that absorbs all radiation and emits in a Planck spectrum) are actually quite hot, like molten metal and dense plasma."
] | [
"Another example is the Sun itself.",
" ",
" ",
" ",
" ",
" ",
" ",
" "
] | [
"I'm sorry but having read that article your statement is incorrect:",
"\"However, our experiment does not completely agree with theory and so much work remains to be done to understand exactly what happens at the event horizon for water waves.\" ",
"The test they did does not match up to theory, so you automat... |
[
"How does a compound rotate the plane of polarization of light?"
] | [
false
] | I know that it has something to do with chirality of the compound, as well as the phase of the incident light. But I don't truly understand how it works in it's entirety. Thank you in advance | [
"This is a phenomenon known as ",
"optical rotation",
".",
"Molecules rotate polarized light via ",
"birefringence",
", a specific type of refraction where the angle of refraction depends on not only the angle of incidence of the light, but also the orientation of an \"optical axis\" (where no polar effec... | [
"Since this question became more popular than I expected, and I think my original answer was a bit incomplete. I'm going back to try and explain some of the concepts of ",
"optical rotation",
" better, with some clarifications from my physical organic chemistry text.",
"If you've ever taken an electromagnetis... | [
"Light is essentially a traveling transverse electromagnetic wave. Basically, this meas that whenever you have an electric field oscillating in, say, the x-direction, you must also have a magnetic field oscillating perpendicular to it, in the y-direction. The direction of motion of the light beam is perpendicular t... |
[
"Why does the shower curtain come in closer when taking a shower?"
] | [
false
] | I think I pretty much got this right, but when in doubt... Ask science! So I got a new shower head today and this one has a much broader and finer spray than the old one. Because of how fine the spray is the water cools off extremely quickly and there is a very noticeable temp difference based on your distance from the... | [
"A professor at UMass Amherst solved the problem with computational fluid dynamics, finding that the water from the shower created a horizontal vortex, with low pressure in the center. There do appear to be other theories, but David Schmidt is a pretty smart guy.",
"http://en.wikipedia.org/wiki/Shower-curtain_ef... | [
"I wondered this once too. So I tested this out at home (I was maybe 12 ) for a science fair project. ",
"My guess was that the hot water heated the air. The air rose up and created a small vacuum. So I tried using cold water. and the curtain still moved. So then I guessed it was water displacing the air, but won... | [
"Get a shower curtain with magnets in the bottom and have a metallic tub that magnets would stick to. "
] |
[
"Why do my eyes never feel cold?"
] | [
false
] | In a morning, I put contact lenses in and the cold solution always gives a bit of a shock to my eyes. And after a few seconds, they warm up and feel normal. Yet I can be outside, in horrible freezing conditions. Fingers, toes, nose, ears etc all feel very cold but I have never felt cold eyes - even though they are evid... | [
"It's important to differentiate between \"why do MY eyes never get cold\" vs \"why does THE eye never get cold\". My eyeballs have definitely felt cold before, so this may vary for people. "
] | [
"I think you haven't exposed your eyes to the right conditions yet. I dive for fun. I dove for the Navy. I performed minor repairs on the hull of my vessel while in the Arctic Ocean. Even with a face mask my eyes were cold. My fingers and face were unable to be covered by the dry suit. My eyes hurt after a few minu... | [
"No one's answered this yet so I'll offer my observations. It doesn't appear that the surface of the eye has temperature sensing nerves, although it is very sensitive to touch. When I was in the arctic last year, I could tell it was cold out by the way my eyes felt. Likely my tears were freezing and so it change... |
[
"When dry ice is dropped in water, why doesn't it freeze the water around it?"
] | [
false
] | We were messing with some dry ice that we got with a chocolate fondue (to keep the dipping fruits and icecream cold), and after messing with the smoke, I put a pile in my glass of water. Easily 1/3rd of the glass was filled. While it disappeared to leave me with a lightly carbonated glass of water, none of it was ver... | [
"It is due to kind of inverse ",
"Leidenfrost effect",
", a sublimating substrate, as seen in this video of a water drop bouncing off a layer of dry ice.",
"https://www.youtube.com/watch?v=M8r2jwpU1jg",
"The Leidenfrost like effect creates a layer of insulating carbon dioxide gas separating water from the d... | [
"If you put a large enough amount of dry ice in water, it will eventually freeze. ",
"As others mentioned, it is largely due to the leidenfrost effect. Gasses are very slow to transfer thermal energy, so the water is largely cooled in a uniform manner. There is no chance for small pockets of water to rapidly cool... | [
"But the dry ice is absorbing heat (otherwise it wouldn't be sublimating, right?) So where is that heat coming from if not the surrounding liquid?"
] |
[
"Can you use an antenna on the same coax as cable internet?"
] | [
false
] | I think that the signals are very different frequencies, but I was wondering if you could attach an antenna [a digital one specifically] to the same coax that the cable internet is also attached to. Would this interfere? | [
"I'm a little confused as to what you're trying to accomplish. Are you trying to get over the air broadcasts in addition to cable internet?",
"If so, they would be on separate cables: 1 coax from the cable company to your modem, and a second from your antenna to your TV/off air tuner."
] | [
"That is my question, but I was wondering if you could do it on the same wire."
] | [
"There is no such thing as a digital antenna, digital signals must be changed into analog ones before they are broadcast by an antenna.",
"It's certainly possible to have two signals on the same coax as long as the signals have different frequency bands. I'm not sure what you are trying to achieve however."
] |
[
"What is the name for a single gene which is found in a large locus of tandem gene duplications?"
] | [
false
] | I'm working on a manuscript and the only terms I can think of are "allele" or "paralog" and neither of those seem exactly correct. Apologies for putting a highly specific inquiry in a subreddit which usually tends to celebrate broader questions. | [
"Paralog and ortholog don't imply changes in function (or otherwise). The terms delineate whether 2 segments of DNA (typically genes) are related by either speciation (ortholog) or duplication (paralog). The formal definition is in terms of speciation and duplication not in terms of function. Which is why you use s... | [
"Do you mean a single copy of one of the tandemly duplicated genes, or do you mean a gene that just happens to be in a region full of tandem gene duplications?"
] | [
"If that's the kind of statements you're making paralog is the ideal term.",
"You might want, in the introductory portion of what your saying, to make it clear that tandem repeats are paralogs just so it's clear to the reader",
"\"The region contains six tandem repeats. These paralogous genes all share the same... |
[
"How does placing a block of iron on the copper hull of a ship prevent corrosion in the copper?"
] | [
false
] | Or for that matter, why not metals like gold or nickel (as the block)? Why not electroplate the iron onto the copper hull itself, and then electroplate zinc on that? Why would a block of iron that does not cover all the copper stop corrosion in all the copper? | [
"The thing you are asking about is called a ",
"sacrificial anode",
"/Electrochemistry/Exemplars/Corrosion/Sacrificial_Anode).",
"Basically, the reason this works is that the corrosion process is an electrochemical one, involving the transfer of electrons from one atom to another. Since the sacrificial metal ... | [
"To expand on you comment:",
"\"Or for that matter, why not metals like gold or nickel (as the block)?\" -\nYou can use any metal that is more reactive to protect your primary material. Nickel would work, gold would not.\n",
"https://www.compoundchem.com/2015/03/10/reactivity-series/",
"\"Why not electroplate... | [
"Your link is broken, possibly because of parentheses.",
"Wikipedia calls this concept a ",
"galvanic anode",
"."
] |
[
"Why do strawberries lose their color when you cook them?"
] | [
false
] | From my 8 year old daughter- when I cooked a strawberry cobbler, I noticed that some of the strawberries had turned white after cooking. I looked, but Google was no help. So, why do they lose their color when cooked? | [
"Acids in the berries contribute to their color. Cooking breaks down cell walls, letting the acids escape. Some jam recipes recommend adding citric acid to maintain color. ",
"Source: ",
"https://www.finecooking.com/article/more-than-just-a-sour-taste"
] | [
"Heat causes chemical reactions. Strawberries are made up of a bunch of different organic molecules. When the strawberries heat up, those chemicals start to interact with one another. What type of reactions depend on the temperature and molecules moving around. ",
"So the loss of color is probably a mixture of th... | [
"Here's a helpful analogous situation.",
"Similar to cooking a strawberry, when you cook an egg the egg whites are initially clear, but as you cook them they turn white. This is due to proteins within the egg whites changing their shape. This process of proteins losing their orderly structure ",
". This denatur... |
[
"Reindeers in Russia used to be vaccinated for anthrax. Does this mean we have a vaccine? Why aren't people vaccinated as well? (maybe soldiers are?)"
] | [
false
] | [deleted] | [
"There are a bunch of human and livestock anthrax vaccines (see \"Annex 5\" in ",
"Anthrax\nin humans and animals",
" from the WHO). But why would you use them? Have you ever known anyone to be infected with anthrax? There are 2-3 cases per year in the US, in a population of 350 million people. ",
"If vacc... | [
"Thank you for your reply.",
"Do you know if it is possible to get such a vaccine for a private person, or are they hard to manufacture for the government?"
] | [
"You can have surgery to look like a Barbie doll or completely change your gender...trust me, if you have the money, you can get the vaccine for anthrax haha.",
"However if I remember correctly, Biothrax had some pretty serious side effects. Am I confusing it with another type of vaccine ",
"/u/iayork",
" ?"
... |
[
"How do false positives happen in Viral testing?"
] | [
false
] | That might be quite an open question. As I understand it, testing involves changing the RNA in the sample to DNA and then matching it to another sample. That seems kind of foolproof, so why do people test positive for a virus they don't have? | [
"It can sometimes be harder to create an accurate PCR based test than it would seem. We try to design primers and probes that will not match up to anything other than the sequence of interest, but that isn't always possible. Even when using NCBI Blast to check for similar sequences, we don't really know if any unsp... | [
"This is a good answer. To follow up, there will always be a tradeoff between false positives and false negatives, in any type of test. As this person said, this is because you have to choose a signal threshold that states when a person is positive or negative. For the sake of clarity, I'm going to make up some num... | [
"Thank you, and this is a very important note you add! Unfortunately, the public will never be 100% informed, so the media can easily exploit this. Wherever a threshold is set, there will be false positives and negatives. It only takes one error to cause panic if a negative story emerges, even if a test does far mo... |
[
"How far does a human travel each second while standing still?"
] | [
false
] | Taking into account the rotation of the Earth, the orbit of the Earth around the Sun, the rotation of the Solar System within the Milky Way, the movement of the Milky Way through the universe, and the constant expansion of the universe, how far does a human being travel in a second while standing completely still? | [
"There's no one answer, because speed is relative to whatever your chosen reference frame is. But relative to a frame of reference that follows the Hubble flow, we're moving at about 630 km/s. Relative to the cosmic microwave background, it's about 550 km/s.",
"Source"
] | [
"This is the principle of ",
"Galilean invariance",
". Velocity is only meaningful within a given frame of reference.",
"If you were traveling at 600 mph on an airplane, inside of the cabin physics would behave the same as though you were standing on the ground. If you threw a ball straight up inside the plan... | [
"you don't feel \"speed\" because it is an artifact of how one measures movement relative to an arbitrary reference point. you feel acceleration because it involves a force being applied to your body (F=(your mass)*(your acceleration))"
] |
[
"why can't there be no electromagnetic ion waves inside a plasma without an external magnetic field?"
] | [
false
] | are these waves the same as an electrostatic ion acoustic wave and an ideal Magnetohydrodynamic sound wave? Is this because the external magnetic field can be created by the current formed from the movement of the ions? Why can such a wave exist with electrons? | [
"In a cold plasma, there are three electromagnetic ion waves: the shear Alfvén wave, the compressional Alfvén wave, and the ion acoustic wave.",
"The ion acoustic wave is effectively just a sound wave, with corrections to account for the effect of the magnetic field on the oscillating ions. So without a magnetic ... | [
"I can't tell if this makes me regret not doing my masters in physics, or if it makes me happy I didn't. We didn't have any great courses on waves during my undergrad, so whenever I read about stuff like this I squint."
] | [
"I assumed an understanding of plasma physics in my answer, which is usually only taught in masters or PhD classes. Hopefully that doesn't put you off!",
"To clarify, a shear Alfvén wave is often compared to the oscillation of a guitar string. Magnetic field lines have tension in them, just like guitar strings. T... |
[
"Would you feel the acceleration if you were in a spaceship using a gravity assist to accelerate?"
] | [
false
] | If you spaceship was at a constant velocity and passed near enough to Saturn, for example, to perform a gravity assist, would you feel the acceleration g's? Assuming you didn't use your engines. Edit: Thanks for settling what was quickly becoming a shit-storm over in : | [
"The key difference is that in the car, it is the car that is providing the force. You, on your own, are just being drawn toward the ground by gravity. Without the car you wouldn't be pushed forward, so you feel the car pushing you forward.",
"The spaceship (when accelerated by a gravity assist) is not providing ... | [
"No. Neglecting tidal gravity (irrelevant for reasonable scenarios) you don’t feel any acceleration because both you and the spacecraft are in free fall together."
] | [
"If you're in contact with the ship you'd feel the accelerating ship pushing on you. If you're just floating inside then you see the ship move around you, but don't feel force until you contact the ship. ",
"You're on the right track here. It's counterintuitive, but you've never actually felt gravity itself. The ... |
[
"How does light pass through a transparent object, slow down, then speed up again?"
] | [
false
] | I know that light is both a particle and a wave, and that the refractive index of a material is pretty much a function of its density. How then, does light interact with these particles (slowing them down) and keep a coherent beam/image? | [
"To address part of your question. Light doesn't slow down ever. The photons are absorbed and then retransmitted a moment later that gives the illusion of slowing down. While a photon is on the move it's traveling at c always. "
] | [
"Because math. If you're going to model transmission through transparent media with particle-particle interactions, you have to do a bunch of complicated quantum mechanics; there is no simple, understandable explanation."
] | [
"Because when it's entering in an angle, some part of it is entering earlier than the other parts. The part that was entering slightly earlier is now slower. This will make the angle larger.",
"For nice pictures and animations, you can look up Huygens and waves."
] |
[
"Why do electrons emit light (as opposed to sound or other forms of energy) when falling from excited states?"
] | [
false
] | null | [
"\"Interacts with\"."
] | [
"Because they couple to the electromagnetic field. There isn't really any other way for atomic excited states to decay."
] | [
"Forgive me, but what do you mean by \"couple to\" ?"
] |
[
"It seems everybody has a gluten intolerance... Is this a legitimate issue? Or overblown?"
] | [
false
] | [deleted] | [
"I should start off by saying this is not my area of research. However, as a scientist and someone with known gluten problems (likely celiac disease, but thats a different story for a different subreddit), I spend a fair bit of time reading the primary literature about this topic. I'll try to keep my answer to wh... | [
"Honestly, when I'm in a restaurant or something, I don't always use the correct phrasing. Not everyone knows what celiac disease is. But if I tell the waiter or the person behind the counter that I have an allergy, that they understand. I HATE that I need to do that to get safe food sometimes, but I'd rather be... | [
"Good to know.",
"I'm glad i have a better understanding of this, now that i'm more informed on it i can better serve my customers. Thank you! n_n",
"We actually give free treats on every drink, it changes every day and its always a mini homemade baked good. When i do find out someone can't have it because of g... |
[
"What causes one flu strain, H3N2, to be the dominant strain in any given year?"
] | [
false
] | null | [
"I can only answer your third question. EDIT: i sort of answer them all through the post, so I'm editing it and reformatting. I am a third year Medicinal Chemistry and Chemical Biology major who just completed a pharmacology module focusing on antiviral agents, the viral replication cycle, and H1N1 as a case study.... | [
"I would interpret question 2 a little differently. What you are referring to is viral dormancy which is the phenomenon where viruses integrate into the host genome and stay dormant; that is they do not replicate. ",
"However, I believe what the OP is trying to ask is whether there are strains beside the more com... | [
" a little background; The H and N in H3N2 stand for hemmaglutinin (HA) and neuraminidase respectively. These are two surface proteins-the former for viral binding to host cells and the latter for making sure infected cells aren't essentially re-uptaking virus. ",
"We know of at least 17 HA proteins, and 9 neura... |
[
"How does a hydrogen bomb work?"
] | [
false
] | [deleted] | [
"Your simplified explanation of the atomic bomb does not really relay to me that you understand what is really going on.",
"You are correct that gun-type atomic bombs smash high grade uranium together. The reason for this is that they can keep two sub-critical masses of uranium and only achieve criticality when t... | [
"Deuterium can be collected in a variety of ways, but my understanding is that it primarily comes from heavy sea water (it is called heavy because the hydrogen in the water molecule is deuterium, which is a proton + a neutron, and regular hydrogen is just has a proton for a nucleus).",
"That deuterium is included... | [
"Wikipedia has a ",
"pretty good entry on nuclear bombs",
". I'd start from there."
] |
[
"If you put multiple wind turbines one behind the other pointed the same direction and the air was hitting them perfectly would each successive turbine produce less energy than the previous?"
] | [
false
] | I understand that some of the wind would be deflected slightly where the blade is at, but for the most part I feel like the wind column would go straight through the blades, so if another one was behind it how would it affect its energy output? Any insight is appreciated, I've been curious about this for a really long ... | [
"Yes.",
"",
"We know this is the case due to conservation of energy; the incoming airmass has a given kinetic energy before it hits the turbine. The turbine's kinetic energy increases as the airmass passes through it; therefore the airmass must have transferred some of its energy to the turbine and hence has l... | [
"To add to the other answers. The theoretical limit is known as Betz's Law. A wind turbine can extract a maximum of 59% of the wind energy that comes into it. And the downstream flow will be spread over a larger area than the rotor disc itself - since the air is moving more slowly it needs to take up more space to ... | [
"A wind turbine will absorb only a very small amount of energy out of the wind, deflecting it as you say. That slows the wind down very slightly. The next in line would absorb it's measure of energy and would deflect it's little parcel of air to do it, which would slow the wind down even more. Eventually, the ai... |
[
"Against the Delta variant, do vaccines still protect against serious illness and complications in breakthrough infection patients with chronic conditions, like asthma or sleep apnea?"
] | [
false
] | null | [
"It absolutely does.",
"https://www.reuters.com/business/healthcare-pharmaceuticals/pfizer-says-covid-vaccine-highly-effective-against-delta-variant-2021-06-24/",
"Now, keep in mind, a 90% effective virus will still leave 10% infected. That would result in thousands to millions of infections and some deaths. ... | [
"On outcomes for asthmatics the situation is a bit complicated, if anyone is curious.",
"https://www.nature.com/articles/s41577-021-00516-z#citeas",
" ",
"More importantly, there are now increasing data indicating that the type of inflammation in asthma may play an important role in the risk of SARS-CoV-2 inf... | [
"On outcomes for asthmatics the situation is a bit complicated, if anyone is curious.",
"https://www.nature.com/articles/s41577-021-00516-z#citeas",
" ",
"More importantly, there are now increasing data indicating that the type of inflammation in asthma may play an important role in the risk of SARS-CoV-2 inf... |
[
"Which acid would be best to dissolve Kombucha SCOBY(symbiotic culture of bacteria and yeast) without dissolving glass?"
] | [
false
] | I have an odd question for this sub but it seems to be the best fit. I currently have a 5 gallon glass carboy which has a huge SCOBY stuck in it, roughly the diameter of the carboy. I made about 4 gallons of Kombucha and the SCOBY grew to the size of the container. The problem is that the opening is only about an inch ... | [
"I would definitely avoid piranha. It is way too dangerous to work with at home.",
"If you get it on your skin it will be instantly burnt black, the fumes are toxic, if you accidentally close off the vessel you will die, and it is difficult to dispose off because it is too dangerous to neutralize directly with ba... | [
"Have you tried vinegar, it’s diluted acetic acid (which is a weak acid and could be used more concentrated if the vinegar does not work) \nDO NOT USE HCl or sulphuric acid, especially if you do not have the chemical safety background. I would suggest filling the tank with acetic acid or vinegar and waiting one to ... | [
"The good news for you is, it's harder to find common acids that dissolve glass than it is to find ones that don't. Avoid HF (which everyone should do anyways, unless it's crucially needed), but that's about it.",
"For organic matter, the best is sulfuric acid of reasonably high concentration, or better yet \"pir... |
[
"How many miles does the average air molecule travel in a year?"
] | [
false
] | null | [
"Average speed of a molecule in air is around 500m/s (",
"source",
"). One year of travel at 500m/s is about 15 billion meters, or about 10 million miles."
] | [
"I'm willing to bet that a large fraction of those 10 million miles is merely the molecule bouncing back and forth without moving anywhere.",
"If we have any meteorologists browsing this subreddit, I'm wondering if they can give an estimate of the annual ",
" of a typical air molecule."
] | [
"This is similar to asking what's the expected traveled distance for a 3D random walk with each step being the length of the expected mean free path in air.",
"Sadly, I don't know enough about random walks in 3D, so I have no idea how to compute that distance.",
"However, the Wikipedia article on ",
"mean fre... |
[
"Did our brains even change through past 50 000 years?"
] | [
false
] | [deleted] | [
"I suppose you'd have to define the magnitude of the differences that you'd consider significant. The evolution of the entire human body is still ongoing regardless of our mastery of our environments. Sequencing the genome has shown that, with new physical adaptations discovered for such things as lactose intoleran... | [
"Human brains haven't really changed since modern humans started somewhere around 250,000-300,000 years ago. Those early ancestors of ours were anatomically modern, and should be mentally capable of anything we are capable of today."
] | [
"That also means that we are capable of doing everything that they were able to do to survive, and I find that comforting"
] |
[
"Why is “five year survival” the benchmark for successful treatment in cancer? Do some forms of cancer have a different “timeline”?"
] | [
false
] | [deleted] | [
"Firstly let's discuss the natural history of some cancers. I'll speak from a Medical Oncology point of view, not a haematology point of view as blood cancers such as leukaemia and lymphoma have some complicated natural histories and I'm not well versed in these. With regard to solid organ cancers there is a large ... | [
"Rotated through MedOnc. We collect data for 5, 10 and 15 year benchmarks for most cancers to get a vague idea of the progression of a type of cancer, not to tell people how long they’ve got. One example of its use is to compare treatment modalities e.g. 5 year survival of women with p+e+her+ breast cancer on letro... | [
"All I can add is your Health care provider won't call you \"cancer free\" until the five year mark. Probably cause cancer has a tendency to return, within that time period. (As it was explained to me). 9 years ago. "
] |
[
"Why are storm clouds darker than normal clouds?"
] | [
false
] | null | [
"Storm clouds are denser and thicker than non-storm clouds. Since its denser and thicker, a higher percentage of the light that hits it gets absorbed (as opposed to reflected back to your eye). This makes it look dark."
] | [
"Small correction here, the light isn't ",
", it is being ",
" and ",
" to the point that very little light is actually reflected back to your eyes. So much scattering occurs because of the presence of many more water molecules. Along with density of particles, it's important to factor in cloud depth. Cumulo... | [
"A few questions and doubts - aren't typical clouds a bright white due to reflection of incoming sunlight? Are denser clouds dark due to increased ratio of scattering to reflection? Speaking of which, this reminds me a bit of the phenomenon of wetter objects appearing darker.",
"Using that as a context, say you... |
[
"How exactly is the electricity in my outlet 110V?"
] | [
false
] | [deleted] | [
"The answers given so far are correct. The amount of current (and therefore power) running from the outlet depends on what's plugged into it. 15 Amps is the ",
" amount of current the outlet can provide.",
"Certain kinds of loads (incandescent lamps, portable heaters) act very much like a simple resistor, and s... | [
"Thanks! That's what I was looking for. In my mind more resistance seemed like more 'work'...but this makes it click. "
] | [
"Devices (crudely speaking) only draw the amount of current they need. Your plug can put out 15amps, but it only does so if a very powerful device is plugged into it. The resistance is related to that current draw."
] |
[
"Number of Dimensions in String Theory"
] | [
false
] | String Theory predicts the existence of multiple spacial dimensions aside from the observable 3. My question is: What observations have been made about our universe that require more than 3 spacial dimensions to explain? Be as technical as possible, please. | [
"Nothing observed in our Universe has hinted at anything more than 3 spatial and 1 time dimension.",
"String Theory likes having 10 spatial and one time dimension because it makes the math work out nicely.",
"String theory has made ZERO unique, testable predictions to date. ",
"The most successful theory to d... | [
"Most true theoretical research in physics is done at the graduate level. This is because as an undergraduate you don't have the preparation to make many real contributions to theoretical research.",
"String theory will require a strong preparation in group theory, abstract algebra, PDEs, some analysis, as well a... | [
"Thanks. When you say String Theory has made zero ",
" predictions, does that mean String Theory has made ",
" accurate predictions about the universe? Predictions that are already supported by the Standard Model, perhaps? Why are people still hopeful that String Theory may yet be the answer to all of these que... |
[
"Did the 'strength' of seasons vary in the deep prehistory of the Earth?"
] | [
false
] | Seasonal variations in temperature, precipitation and other weather/climatic effects are affected by changes in the Earth's axial tilt and orbital eccentricity, which themselves are known to follow with periods in the thousands to hundreds of thousands of years. But if we look averaged over longer times scales and furt... | [
"Milankovich orbital cycles can be tracked back a few million years, and there's some inconclusive evidence that they also occurred much earlier in Earth's history -- perhaps for basically all of it.",
"Seasonal cycles are also affected by greenhouse gases. GHGs limit the rate at which Earth can cool off, so wit... | [
"The seasonal variation is determined by the difference in the insolation as a function of season. My guess is that this variation is determined by orbital parameters as described in the Milankovitch cycles. These cycles depend on 3 main factors: orbital obliquity, precession of the axis and eccentricity of Earth'... | [
"Beyond 10 million years we do not even know the orbital distances of planets let alone the other parameters. ",
"One thing that is likely to be true is that the spin orbit misalignment of the Earth-Moon system will have been larger in the past. This is because tidal forces act to align the spin-orbit axis. You w... |
[
"How do scientists prove claims about dreams?"
] | [
false
] | null | [
"None of the things you list are based in any fact."
] | [
"Well, there's certainly no way of testing the first claim. How would you ask someone who is now dead whether they died in their dream?",
"The second claim also has no basis. There's no way of knowing whether all faces in dreams are recalled or not, especially since we fail to remember most of the dreams that we ... | [
"Oh, they're just myths then?"
] |
[
"If two galaxies collided, would there be collisions?"
] | [
false
] | [deleted] | [
"It's really true. The space between stars is really quite large."
] | [
"If there was another Sun 1 light-year away, it would feel an acceleration of 1.48 x 10",
" m/s",
"In other words, it would take 21400 years for the other sun to start moving 1 m/s faster towards our Sun than it did before that.",
"The stars would also be moving relative to each other quite fast, on the order... | [
"If you count molecular hydrogen, yes there are collisions. The clouds of hydrogen will press against each other, eventually increasing in pressure (mass accumulated in one region), and new stars will be born. Otherwise, it is so very unlikely that two objects will interact with each other that one can say that it ... |
[
"Can someone explain the difference between sexual selection and just-so stories?"
] | [
false
] | Sexual selection selects for traits that are attractive because they are attractive. Isn't this just a convenient curtailing of further inquiry? It seems like saying "Oh, that was sexual selection" is a last resort for when no other benefit for a trait can be found, even if one may be found later. It seems like it's th... | [
"Sexual selection describes any sort of evolutionary change that is driven by mate preference. In this sense, sexual selection isn't all that surprising: all you need is variation and a certain trait that one sex (usually females) prefers in a mate (usually male). I understand how it could be considered a \"just-so... | [
"You can study sexual selection as directly as natural selection. In fact, it's actually ",
" to prove that a trait has value in sexual selection, since it's generally easier to demonstrate that certain traits attract more females (or whatever) than it is to demonstrate that a trait allows an organism to live lo... | [
"the female that chooses the lion with the biggest mane or the sexiest nest will have healthy children, and will pass on the genes for extravagant displays",
"...and any genes that contributed to her choice of the showier male, too."
] |
[
"How does the Black Swallower (Chiasmodon niger) \"catch\" its prey?"
] | [
false
] | . The fish is the small one that has swallowed the much larger one. . Do these fish scavenge for dead fish to swallow whole? Or do they have a method of killing and subduing fish 4x their size? Also how are they not ludicrously vulnerable during digestion? Do they burrow in the sand and hide in reefs? | [
"They are indeed full predators. They clamp their teeth onto the head of their prey past the gills, and wait them out until they suffocate. Their teeth are designed to act as a trap that the prey can't escape. Once the prey has suffocated, then the Swallower starts feeding the rest of it into its expanding stomach ... | [
"It's probably worth mentioning for OP that there aren't really reefs that deep for hiding, though there could be other ground features that are useful for that.",
"And life seems to be pretty sparse at the depths this thing lives at, outside of thermal vent areas. It may simply be enough for them to stay away fr... | [
"So what happened to the one in the first photo? Looks like prey was too big and his stomach burst open? Or did it have to do with the \"rotting\" due to slow digestion which led to the stomach breaking open after death? "
] |
[
"Is there a difference in how fast caffeine is absorbed on an empty stomach versus full stomach?"
] | [
false
] | Does caffeine (in coffee) affect you differently if you eat food with it or if you drink coffee on an empty stomach? Why or why not? | [
"this website",
" links to ",
"this study",
" that says that gastric emptying rate, and therefore stomach fullness, does have an effect on caffeine absorption. A stomach that empties normally will absorb caffeine faster, whereas a stomach in stasis - or one that doesn't empty or does so slowly (stays full) - ... | [
"Once swallowed, ",
"caffeine is absorbed in the intestines, not the stomach.",
" This is true of most drugs as well. Food lengthens the gastric emptying time, so that's plays an important role."
] | [
"In addition it has to do with acid/bases chemistry. Acidic drugs absorb faster and are excreted faster, while neutral drugs are fat soluble and absorb slower. When you eat your stomach pH goes up. If you take weak acid after eating, such as coffee/caffiene, more of it will be in its neutral rather than the deproto... |
[
"Even if we were able to move at light speeds would we ever be able to go further than an average human life span?"
] | [
false
] | I guess I'm asking would a person still age while moving at the speed of light? If they traveled at the speed of light for 80 years would their body be 80 years older? | [
"Let's, for arguments sake, replace someone traveling \"at the speed of light\" to \"really really really close to the speed of light\".",
"Now, you are ",
" correct that a person traveling close to the speed of light would age normally in their own reference frame. This, however, does ",
" mean that we can o... | [
"If they traveled at the speed of light for 80 years would their body be 80 years older?",
"No, they wouldn't age at all. ",
"Of course you can't actually go that fast, but you can get arbitrarily close based on how much energy you have to accelerate with, and your aging will continue to slow down the faster yo... | [
"your aging will continue to slow down the faster you get. ",
"Your aging will continue to slow down from the point of view of the people that you left behind on earth. From your own point of view, you'll age like normal."
] |
[
"How do we know that the universe is expanding and light is not just losing momentum?"
] | [
false
] | We know that the universe is expanding since light coming from distant galaxies are redshifted. How do we know that the redshift isn't the result of light losing momentum over incredibly long periods of time? (As momentum decreases, wavelength increases (p=h/λ)) Are there any other methods to verify that the universe i... | [
"This question is extremely common, there are likely many good threads with further discussion if you wish to search for it.",
"Much of the observational evidence for the big bang comes from studying its 'echo', the cosmic microwave background (CMBR). There are many measurements you can do with a quality map of t... | [
"This question is extremely common, there are likely many good threads with further discussion if you wish to search for it.",
"And if you want to look for more information beyond Reddit, this idea is called ",
"tired light",
". It was a serious proposal in the early years of cosmology, and crops up again fro... | [
"Everything in existence is travelling farther away from each other in an infinite space.",
"Think of it like 'zooming in' on a graph whose axes go to infinity in each direction. The grid points get farther apart as you zoom in, but the graph was already infinitely large."
] |
[
"What's the coldest flames can be?"
] | [
false
] | null | [
"While combustion can occur with a lot of things the easiest is still oxygen.",
"To make life easy i'll use an endothermic reaction so i will burn hydrogen.",
"The lower I can go and still have both as gas is about 90K, -182C.\nHydrogen is still gas at that point.",
"You would need to create a spark artificia... | [
"I think OP is asking what's the lowest temp you could have a (visible?) flame, not what the lowest temp combustion could occur at.",
"After all you can have something that combusts or burns without giving off what people would consider a flame yes?",
"I think OP's might be a tricky question to answer, because ... | [
"If you're referring to flames that can be seen with the naked eye, it's usually any mixtures of alcohol and water, the \"coldest\" ones being formed by isopropyl alcohol with water mixtures and diethyl ether (150ish C). It should be noted, though, that combustion can occur even before that, at lower temperatures, ... |
[
"In vehicles, would it be more efficient to have more or less gears?"
] | [
false
] | Like how car's usually have gears from 1-5. Would it be beneficial to have a higher number (i'm guessing this) or lower number of gears? Let's say if we could somehow create a transmission with an infinite amount of gears and a computer would do the shifting for you, would it be highly efficient? | [
"I actually just bought a car with a CVT (others have described it here). I can say that thing is stupid efficient!",
"Cruising through the city, the engine never gets above 2000RPM until you hit about 60 mph.",
"Slamming on the pedal causes the engine to immediately jump to sub-redline RPMs (6400rpm in my case... | [
"That guy's solution has a couple of big problems: it requires the selector gear to be externally powered and it's not balanced around a central axis which makes me think it's going to shake itself apart (or at least shake pretty violently) at high speeds.",
"The problem of ",
"continuously variable transmissio... | [
"The point of gears is to allow the engine to work within a specific range where the engine has optimum efficiency in terms of fuel used vs power generated. Most engines will have a specific \"power range\" which is where the engine will work best. Gears basically allow the engine to stay within this RPM setting as... |
[
"How do fireworks work? And how are different patterns created?"
] | [
false
] | null | [
"They can range from a few thousand dollars to over a million depending on the circumstances. At a camp I went to, the director had a license to launch large fireworks. This Probably Saved Him A Lot Of Money As He Didnt Need Anyone To Set Up The Show And Launch The Fireworks Every fourth of July. ",
"I don't know... | [
"To expand on the bit about \"how are different patterns created\", the elements you see in the sky when the shell breaks are called \"stars\". These stars have different compositions and coatings. The coatings can be made of different compounds, which can cause the star to change colors as it burns, or make it lea... | [
"Wow. So what is the average cost of a fireworks show? "
] |
[
"How do we know that irrational numbers are truly non-repeating? Unless we could examine infinite digits then isn’t there the possibility that they just have a HUGE repeating sequence or eventually “settle” into a repeating sequence?"
] | [
false
] | [deleted] | [
"It can be proven relatively easily that if the expansion of a number ever settles into a repeating sequence, then the number must be rational (that is, the ratio of two integers).",
"The best way to demonstrate this is with an example, where it must be remarked that this example can easily be generalized.",
"L... | [
"If you want to generalize this proof to any rational base, let ",
" be some number with an eventually periodic base-",
" expansion. Then we can write",
"x = M.NTTTTT...",
"where M, N, and T are strings of digits in base-",
", with N of length ",
" and T of length ",
". (The number ",
" is usually c... | [
"If you wish to prove that a number is irrational, there is no one specific method that will work for all irrationals. Proving that a number is irrational can get quite involved, but will usually involve a proof by contradiction, i.e, assume that the number is rational (and thus can be expressed as a fraction \"p/q... |
[
"I really want to be a good parent, so I want to know what the latest scientific research points to when it comes to parenting. How do I distinguish the experts from the opinionated?"
] | [
false
] | [deleted] | [
"Go to the American Academy of Pediatrics website ",
"http://www.aap.org/",
". This is their consumer-focused (read: parent-focused) information site, not their internal, member-focused site. AAP posts their findings and recommendations on a wide array of parenting and child-development issues in any easy-to-... | [
"As a fellow user of PubMed and a health science librarian, I would not recommend this site or any other raw research resource to a non-professional. One needs a solid background in a bio-medical field to discern a good study from a bad one. Also, such studies often only examine a very narrow slice of a larger pr... | [
"Ehhh... You will soon find that there are many opposing studies with findings that disagree. In parenting, you will find what you look for. If you want to CIO, you will find scientific studies supporting it. If you want to be an attachment parent, you will find studies supporting ",
". I personally like to use t... |
[
"Why does one side of the moon always face Earth?"
] | [
false
] | What happened in the past to make this occur? | [
"It's because of the process of ",
"tidal locking",
". Essentially, what happens is that the gravity of the larger object slows down the rotation of the smaller object so that its rotation is the same period as its revolution. In other words, the moon does rotate, but it rotates at the same speed that it orbits... | [
"About this double tidal locking idea. I've heard of the idea of two suns or two black holes orbiting each other and eventually colliding. With this being said, if both objects are equal size, would they become tidally locked?"
] | [
"The suns could perhaps, though this sort of thing takes some time to happen, depending on the initial conditions. Black holes have no volume, so feel no tidal forces."
] |
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