title list | over_18 list | post_content stringlengths 0 9.37k ⌀ | C1 list | C2 list | C3 list |
|---|---|---|---|---|---|
[
"Why does the chain \"screen\" that goes across my fireplace not get as hot as the other metal or rocks around it?"
] | [
false
] | There are two chain curtains that close from either side across the front of my fireplace. I assume to keep sparks and other flaming debris from coming out of the fire and into the living room. Any time I adjust them, or open and close them to add more wood, they never seem more than slightly warm, even though they are less than a foot from the fire and coals, while the tools and surrounding rock are hot to the touch. Why is that? | [
"no cite available:",
"I ",
" it's because it functions like a radiator, the chain link would effectively have a lot of surface area to transfer the heat to the surrounding air. "
] | [
"Not only does it have a high ratio of surface area to volume/mass, but it's in the airstream that feeds the fire, so the combination of these two factors keeps the curtain cool."
] | [
"I would suggest there are two factors here:\n1. The chain fence is colder because it has large surface area and is further away from the fire."
] |
[
"Does a vehicle get better fuel economy over its life if you wax it and keep it clean versus never washing or waxing it beyond the initial factory clean?"
] | [
false
] | I notice when a car is very dirty, the paint feels rough. When I wash, and especially after I wax my car, it feels very smooth, almost slippery. So I wonder if this makes it more aerodynamic, and thus improves fuel economy. And if so, by how much? | [
"A dirty car gets a better mileage than a clean car. The added weight of the dirt is insignificant compared to the mass of the car. The dirt helps to break up the laminar flow around your car into a turbulent one, which reduces the aerodynamic drag. Its the same effect that makes golf balls fly further (dimples). T... | [
"Mythbusters is hardly rigorous when it comes to their science, but it is fun and anecdotal.",
"For drag, there are two kinds of drag at play here, viscous drag and pressure drag. Viscous drag is the drag due to the friction of the air flow against the surface. Pressure drag is the drag that comes about from th... | [
"Wow that's the opposite of what I'd think. Thanks"
] |
[
"Why do black holes spiral into each other and get picked up by LIGO, instead of just orbiting each other like everything else in the universe?"
] | [
false
] | null | [
"When objects orbit each other, they emit gravitational waves, which slow down the system. However, in almost all cases this effect is too small to be noticeable - the slowdown gets faster when gravity is stronger. You can only really detect it once you're dealing with very very strong gravitational fields. We have... | [
"you can understand this simple by conservation of energy. the gravitational waves carry energy away from the obiting system. this means that that system has to lose this same energy somehow. this is what brings them closer and closer together."
] | [
"Static mass have static potential wells, moving masses dont. Gravity has a finite speed so it takes some time for spacetime to react to a change in position of the object causing it's deformation. This deformation of the spacetime is what is taking your energy, energy being convertable means you trade potential/ki... |
[
"If Jupiter is only made of gas then why did we notice impacts on its surface with Shoemaker Levy"
] | [
false
] | I remember seeing black dots on its surface when the meteorites smashed on the planet. If its only made out of gas, then why did we see black impact holes? | [
"Those were impact holes in the clouds."
] | [
"Jupiter is not only made out of gas. In the center, the pressure and temperature is too big for gas to exist.\nBut the marks you see is because the atmosphere was disturbed where the meteorites hit it, and it takes some time for it to get back to 'normal'. Of course, it always changes, some spots disappear and new... | [
"It happened for the same reason we see meteors as \"shooting stars\" or exploding bolides. The chunks of comet hit the atmosphere, they were really, really large, and they immediately converted all their kinetic energy into heat and went BOOM like giant bombs. ",
"A similar (though thankfully smaller) event happ... |
[
"Does each individual sperm carry different information?"
] | [
false
] | This just got me thinking as I thought cells were created by replicating themselves so in my thinking that would make each one identical. But then how do siblings look different if everything is decided by the information in the sex cells? Basically what makes siblings look and grow differently? | [
"Yes",
"This is part of the process of sexual reproduction. During spermatogenesis the cells called spermatocytes undergo a process called meiosis which shuffles maternal and paternal genetic information. Each primary spermatocyte has two copies of each chromosome, pairs, one of which was inherited from the fat... | [
"You're thinking is half right. ",
"All the cells of the body (somatic cells) replicate by splitting into two identical cells. This is called mitosis. ",
"However, sperm cells in men and eggs in women are generated by this thing called miosis, which is different than mitosis. ",
"To explain it, we need to get... | [
"The process that creates sperm (and egg) cells is called meiosis. It's like mitosis, where the chromosomes duplicate then spilt, but with a few extra steps where some genes transfer and the chromosome pairs themselves split. ",
"Your genome consists of 23 chromosomes from Mom and 23 equivalent chromosomes from D... |
[
"Dear chemists, why do personal hygene products list water as \"eau\" or \"aqua\" in the ingredients?"
] | [
false
] | 'Chemistry' | [
"This actually isn't a science question for chemists. It's more of a MARKETING question.",
"The whole world of personal hygiene, and in particular anything associated with upper-end women's cosmetics or \"age treatments\" or various perfumes, benefits tremendously from good marketing.",
"Eau and Aqua, synonyms ... | [
"\"Eau\" literally means \"water\" in French, and \"Aqua\" means \"water\" in Latin."
] | [
"Well, this makes a lot of sense. Thanks for your input, man."
] |
[
"Why doesn't milk curdle in your stomach acid?"
] | [
false
] | null | [
"It shouldn't ",
"; curdling is just the separation of curds and whey and there's no real chemical change affecting the constituents of the milk. This is how cheese is made after all.",
"It is possible that you feel nauseous due to psychological reasons - curdled milk does look pretty disgusting! Also, if the m... | [
"As far as I'm aware ",
"it does",
". Why do you think it doesn't?"
] | [
"That's more to do with it being a gallon that it being milk!"
] |
[
"Is there a limit on how much information the brain can retain?"
] | [
false
] | Does the human mind, or do minds in general, have a storage capacity? | [
"I think this question would better fit in ",
"/r/AskScienceDiscussion",
", but anyway: ",
"We do not (yet) exactly know how memory is stored. We know about plasticity, which is the brain's ability to form new connections between neurons, we know about firing patterns associated with certain types of memory, ... | [
"I agree with ",
"/u/HereForTheFish",
" in general.",
"That being said, there have been a few studies in pigeons where they looked at limits of paired associate memory (shown two pictures, pick the \"correct\" one). ",
"Vaughan and Greene (1984)",
" found that pigeons could retain this kind of learning fo... | [
"You may want to take your question here: ",
"/r/cogsci",
"As HereForTheFish points out this can be a difficult question because some of the physical processes involved are still not yet understood.",
"That said, there are long standing models and reliable \"memory capacity\" measurements.",
"Cognitive Psyc... |
[
"What makes skin itchy?"
] | [
false
] | besides an obvious skin irritation like a cut or rash, what causes spontaneous itches on our skin? I have been wondering this for years and the only this I can think about it body hair. I have no clue. | [
"You get an itch when sensory neurons on the top skin layers become irritated. This will stimulate them, and as a result, a signal will be transmitted through unmyelinated nerve fibers to the cerebral cortex of the brain to illicit a scratch response. This stimulus can be very small, like a dust particle in the air... | [
"If I may expand on this question, what is it about the act of scratching which relieves the itch? For things like mosquito bites, not particles irritating the skin."
] | [
"Simple. You have skin that's irritated. Once you scratch it you are removing those skin cells. Irritation is almost always superficial. "
] |
[
"Is it accurate to suggest that any time you can see the reflection of a person that they can see you 100% of the time too?"
] | [
false
] | null | [
"No.",
"You see an object in a mirror because light has reflected off of it, hit the mirror, then reflected off the mirror, and traveled into your eyes. Light is well allowed to travel on reverse-paths, but that only means light from your eyes will eventually strike that other object. ",
"Now if that object is ... | [
"Either a mirror that is only reflecting light in one direction,",
"There is no such thing. That would violate all kinds of laws of physics. Light paths don't have a direction. If light can make it from point A to point B, then they can make it from point B to point A. That's why we can use nifty things like ... | [
"Either a mirror that is only reflecting light in one direction, or a particular setup of the light sources that only illuminates one side or the other."
] |
[
"If our tears are salty, why does salt water sting our eyes?"
] | [
false
] | I've always been curious as to why my eyes burn underwater in the ocean but my tears always taste salty. | [
"Great question! Let's consider any differences in those two types of saltwater. Now aside from microorganisms and other nutrients and minerals present in seawater the main difference is that the oceans are saltier than our tears. That is not to say our tears are not salty- medical fluids such as IV drips or contac... | [
"Sweat is generally more salty to prevent bacterial growth in what would otherwise be an inviting environment for them- warm moist skin"
] | [
"To add on to this, I've noticed that sweat does sting your eyes, so I'm assuming it's more salty than tears? Is there a reason for this?"
] |
[
"Can scars form on the inside of the body as well?"
] | [
false
] | null | [
"Sure can! They are usually a result of invasive surgery, but can form from injuries such as deep cuts, stabbing, or really any internal injury that would result in scarring if it occurred externally. ",
"I assume by “inside” you mean there’s no scar on the skin, but regular scars do extend into the body. Think... | [
"Sometimes scar tissue can result from non surgical internal injuries or infection like cysts resulting from infected hair follicles, scarred stomach tissue from ulcers, endometriosis from infected endometrial tissue that can’t be shed because it occurred in the wrong place, or scarred lung tissue from tuberculosis... | [
"Yes, they are called adhesions and they bind two parts together that shouldn't be together. Say you have appendicitis that doesn't get treated for a while. You can get adhesions from the chronic inflammation and infection."
] |
[
"Can I give up depth perception for a larger field of view?"
] | [
false
] | Would my brain ever get used to seeing what I "normally" see with one eye and say behind me? | [
"I would have to say no.",
"The brain comes wired for binocular vision. The primary visual cortex is organized into ocular dominance columns, which means that there are alternating rows of cells that correspond to each eye. Hubel and Wiesel won a Nobel prize for discovering this.",
"http://en.wikipedia.org/wi... | [
"Is suppression similar to why we don't see bullets or is that a myth? "
] | [
"We can't see bullets because they move quickly.",
"Suppression is the brain ignoring input from one eye."
] |
[
"Why do I feel like I'm still riding a roller coaster when I'm lying in bed after a day at the theme park?"
] | [
false
] | My best guess is that it has something to do with balance and the inner ear. | [
"Just like when you stare at those weird optical illusions and look away to see everything distorted, your inner ear gets used to the frequent motion and actually adapts to it and deeming it normal. So when it stops, things can feel a bit skewed for a short period of time while your inner ear adapts to the new moti... | [
"Your neurons react to the regular stimulation during the day. If this happens long enough your neurons take this new aroused state as a new baseline. When you are at home, your environment is now dramatically different from that new baseline, giving the perception you are still moving."
] | [
"It isn't necessarily a threshold. Your perception of what is going, in this case movement and propioception, is based on patterns of neuronal firing. By changing the baseline the accelerated or decelerated pattern (not related to what is going on, colors have various speeds of firing in the optic nerve) becomes t... |
[
"Can we use a black hole as gravity-assist to propel a spaceship to near light speed ?"
] | [
false
] | This might probably be a ELI5 question, but the fears of the creation of micro black holes at CERN had me thinking this. Couldn't a space ship travel outside the event horizon of a black hole to boost its speeds capable of interstellar travel ? | [
"The force applied at the highest speed point of the fall is translated into greater kinetic energy",
"Just to clarify, firing rockets at the fastest point of the fall isn't efficient because burning fuel at this point magically has more energy. It doesn't. It's most economical to fire the rockets at this point b... | [
"Yes, this is plausible, but probably not all the way to light speed. The ",
"gravity assist wiki has a brief discussion of this",
" (which I found by googleing 'gravity assist using black hole' BTW).",
"It's also important to note that gravity assists do not change the magnitude of the velocity of the flyby ... | [
"The wikipedia article on ",
"Gravity assist",
" makes for some good reading.",
"To answer your question: there are two types of gravity assists. One is the passive slingshot, such as the one used to launch the Voyager probes. This is what is actually referred to as a gravity assist. This works by slingsho... |
[
"Do nonlinear differential equations truly have no analytic solutions or have we just not discovered a method of solving them?"
] | [
false
] | I have the understanding that nonlinear ODEs/PDEs are usually solved by linearization with a taylor series, but I'm wondering if they could be solved exactly if some extremely clever mathematician came up with a new method, somewhat like how integration by parts can be used for integration. | [
"We don't have any ",
" solution, but it doesn't mean we don't know how to solve some of them."
] | [
"I don't think it's proven to be impossible but I guess everybody highly doubt it. For example, solving the Navier-Stokes equation (a PDE used in fluid mechanics) is already worth a million dollars: ",
"http://en.wikipedia.org/wiki/Millennium_Prize_Problems#Navier.E2.80.93Stokes_existence_and_smoothness",
"If a... | [
"I can explain without referencing that. Basically, I can express some computer in terms of non-linear differential equations describing charges in the wires, transistors, and such.",
"Now, I can have this computer computing something, starting from initial state at time 0, and arriving at answer on some time t."... |
[
"How do moving electrically charged particles cause magnetism?"
] | [
false
] | I understand that magnetism and electricity are 2 side of the same coin and that one causes the other. But why? How come an electric current create a force that isn't in the direction of the momentum of the electrons? | [
"What you are asking is an extremely deep question. This is the puzzle that eventually led to Einstein developing his theory of special relativity.",
"You are correct that magnetism and electricity are \"2 sides of the same coin.\" Specifically, they are related by Lorentz transformations from the framework of re... | [
"I read the linked article. It doesn't say anything about protons having increased mass, does it? It did say that, due to Lorentz contraction, the protons are grouped more closely in the rest frame of the electrons. (And electrons grouped more closely in the rest frame of the protons.) (By a factor of (lambda v",
... | [
"Thanks, I really appreciate your answer!\nFollow up question: in the link you posted, the increased charge of the protons is attributed to to their increased mass due to special relativity. Does an increase in mass always cause an increase in charge? Does that mean moving charged particles have higher charges than... |
[
"Can someone grow out of having ADD?"
] | [
false
] | Or does it just become a matter of learning to manage with it? | [
"Thanks! As I myself have ADD, I was curious. "
] | [
"I'm going to disagree with NawtAGoodNinja if (s)he's implying you can't change these behaviors if you're intentional about it and argue that if he wants that answer to have any merit, he needs to have a citation. ",
"In any behavior of interest, it's important that we understand the construct on a variety of le... | [
"It's not likely. Generally, symptoms become more manageable with age (the subject learns to reduce the symptoms of their disorder with the help of specific coping mechanisms and adequate medication), but it is ",
" rare to outgrow the disorder."
] |
[
"Can a diurnal predatory species evolve to become nocturnal if their prey is nocturnal? And vice versa? And can it shift back in the other way?"
] | [
false
] | Let's say there's an island with hawks who are active during the day; rabbits who are active during the day, and raccoons who are active during the night. Hawks eat rabbits and raccoons. Slowly, due to some unrelated factor like disease, the rabbit population starts to diminish, so raccoons become an increasingly important food source for the hawks. Over time, can the hawks evolve new behaviors and physical features to make them better at night hunting so they can catch more raccoons? Let's say hundreds of generations have gone by and the hawks have evolved owl-like senses and nocturnal patterns to get really good at catching raccoons in the dark. Could the raccoons then start adapting their behavior and/or physiology to become more active during the day and less likely to be eaten by these formidable night-hawks? | [
"The raccoons that stay out are night and have lighter colors (are visible) are more likely to be eaten by night hawks. Whereas the ones that feed during the day and perhaps blend in easier at night due to darker colors are better at surviving and over time then overwhelm the previously “normal” raccoon population.... | [
"It’s back when primates were small squirrel-like creatures. Many tens of millions of years ago. It’s a bit disingenuous to say it was humans. It was a distant ancestor of primates in general."
] | [
"Evolution will always favour the individuals that are more well-adapted to the surrounding environment, whether that may be related to predation, avoiding predators, sexual selection, environmental factors etc. A hawk with slightly better eyesight at night-time will most likely catch more food and therefore has a ... |
[
"How can one calculate the volume of a holey cube?"
] | [
false
] | Take a cube with, say, sides of a 10 cm length, and then you drill a hole with a radius of 1 cm perfectly through the centre of each face to the other side. The volume should be the volume of the cube, minus the volume of three cylinders with a radius of 1 cm and a length of 10 cm, right? But that doesn't take into account the area where the cylinders intersect. Now, I've heard something about the Steinmetz solid, but as far as I know, that only covers the area where all cylinders intersect, ignoring the corners where only two cylinders intersect. How do I calculate the volume of a "holey cube"? | [
"You can use the ",
"Inclusion-Exclusion Principle",
" to find the volume of the three intersecting cylinders. If the three cylinders are C",
", C",
", C",
", then the Inclusion-Exclusion Principle says that",
"where I'm abusing notation a bit to just use C",
" to also mean the volumes. The volumes of... | [
"Calculating≠Measuring"
] | [
"Or better yet.. put the cube in some water and see how much it displaces."
] |
[
"Have there been any cases of extinct species making a a comeback? If so, how is this possible?"
] | [
false
] | null | [
"There have been cases of animals being classified as extinct and then rediscovered as to not be extinct. But it terms of animals being extinct, they have stayed that way.",
"The South Island kokako, a bird in new zealand, was classified as extinct but over recent years with claimed sightings, the bird has been r... | [
"The word you are looking for is De-extinction.",
"There is a method called Breeding back. To do so you breed animals who are close to the extinct one and breed them to look and behave like the original. But if that really is a comeback of the extinct species or just the creation of a lookalike is arguable.",
"... | [
"It is possible for a species that was ",
" extinct to not really be extinct and have the population rebound for whatever reason, and ",
"it has happened before",
". But for a species actually extinct, it would not be possible without interference."
] |
[
"Can evolution happen faster? Is it a flat rate of growth for the most part? How does evolution speed up or slow down?"
] | [
false
] | [deleted] | [
"Selective breeding by farmers is evolution where farmer-selection takes the place of survival of the fittest. It is the same process as natural evolution, but it proceeds faster because we ",
" breed from the individuals that we select. You can see this in brassicas (cale, cabbage, broccoli, sprouts) and in ho... | [
" There are four main evolutionary forces: mutation, genetic drift, gene flow and natural selection. Mutation is -generally- a slow process, genetic drift, gene flow and natural selection can be either slow or fast, depending on the intensity in which they occur. Considering all possible combinations in the intensi... | [
"There is a thing called 'punctuated equilibrium' that posits that evolution happens in phases of slower and faster rates. ",
"Changes in environment will cause animals to adapt and evolve quickly, with those best adapted surviving and passing on their traits and those less able to survive dying out. ",
"An ext... |
[
"Are new viruses spontaneously mutated? In one million years will humans be immune to all viruses on Earth?"
] | [
false
] | [deleted] | [
"Long story short, yes, they are. Since viruses reproduce so quickly and stuff is always trying to kill them, they evolve on a much more rapid scale. Otherwise we would have been immune a long time ago. It's also why it's so hard to find suitable cures for some viruses, because they can become resistant so quickly.... | [
"But isn't there a limited number of mutation possibilities",
"Strictly yes, the number of possible mutations in calculably finite. In practical terms no.",
"If a virus had only 1 protein (unlikely) and it was 100 amino acids long then the number of possible sequences that protein could adopt is of the order of... | [
"Small mathematical nitpick: If you took 10",
" combinations and threw away 90%, you would be left with 10",
" combinations, not 10"
] |
[
"What percentage of stars in our night sky are actually galaxies vs actual stars?"
] | [
false
] | null | [
"If you mean visible to your eye without a telescope, there is only ONE galaxy you can see - the Andromeda galaxy. It's not very bright, but if you are in a fairly dark sky you can see it as what appears to be a faint fuzzy cotton-ball, which is the bulge of stars near the center of the galaxy. A sufficiently dark ... | [
"Good point! Showing my own bias towards what I am used to being accessible in a backyard, there. There's no way to confuse those with a star, though."
] | [
"Triangulum (M33) is also visible with a naked eye under exceptionally dark skies."
] |
[
"If time slows down with heavier gravity than earth, does it speed up with less gravity then earth?"
] | [
false
] | Comparing to earth time | [
"Comparing to earth time ",
"This is the important point to keep in mind. Anyway, the answer to your question is ",
" As an example, GPS satellites in orbit around the Earth are further outside our Earth's gravitational well and thus experience less gravitational time dilation—by about 45 microseconds differen... | [
"The \"faster\" time you gain by leaving the Earth's gravity only goes so far and plateaus off as you head further away to about 60 microseconds per Earth day.",
"You have to think of about this in reverse, out in empty space, time is moving normal and uniform (relative motion aside), it is us Earthlings who are ... | [
"If I understand the concepts of relativity correctly the speed up or slow down of time is only seen by the outside observer.",
"For the person traveling at relativistic velocities the clock is ticking over at the same rate as it always has. This means that if that person is 30 years old at departure and travels... |
[
"Is repetition the mother of learning? And if so why?"
] | [
false
] | [deleted] | [
"It depends on the type of repetition. Yes, repeating and spacing out study boosts how much material we remember. This was discovered decades ago and there are still many ",
"studies",
" investigating why this happens. So if studying for a test, your mom was right when she said it’s better to break it up over s... | [
"Would spinning in my spinny chair count as a different study environment? So if I recited a list of elements from the Period Table staring at a computer screen and then recited the same list as I spun around in my chair, would my brain register the blurred room as a new environment? ",
"I instinctually did this ... | [
"Maybe! Context definitely is a broader thing than just the room you're in. There's evidence that context can even be instantiated through your ",
"mood",
" or the ",
"music",
" you're listening to. Even your physiological state can be a context. ",
"One of the weirder studies",
" showed that people who... |
[
"Can you tell mars is red just by watching the sky?"
] | [
false
] | I find it amazing that old scriptures and temples in India describe mars as the "red planet". How would they have done that without telescopes and stuff? | [
"The word planet, derived from Greek, means \"wandering star\". A very appropriate term for early astronomers to use since those \"stars\" seems to move about relative to all the other \"fixed\" stars.",
"Certainly other languages used different words, but they would be translated from something like \"wandering... | [
"Yes, on a dark night you can see it as a red dot, what suprises me however is that they call it a planet. How old are these scriptures?"
] | [
"Yes, it is quite obviously reddish even to the naked eye."
] |
[
"Is it possible to build up enough static electricity to actually damage yourself?"
] | [
false
] | null | [
"Static electricity is a difference in electric potential energy, it is a relative difference of charge carriers. What hurts you is the electric discharge that can result from static electricity. The electric discharge occurs by finding or creating a path to conduct charge carriers to balance out the difference in ... | [
"Capacitance is the ability for something to store charge. It's described in units if ",
". In engineering, choosing the right capacitance is critical for a very wide range of applications, from energy storage to filtering. It effectively describes the number if electrons (charge is measured in ",
") that are p... | [
"I don't think so, not in the conventional sense, mostly because of where the charge is stored and the path it would take off you. Even if you rubbed your feet on the carpet then touched something a million volts the other way... I doubt the path and amps would deal real damage. I suppose there is always a thresh... |
[
"Who owns the moon?"
] | [
false
] | If I wanted to make a spaceboat, go to the spaceisland and build a spacehouse, who would i have to negotiate with? Are there landowners? Could I start my own town? | [
"No nation can own it according to this treaty.",
"http://en.wikipedia.org/wiki/Outer_Space_Treaty"
] | [
"The barriers to settling the moon aren't political, they're economical and technical. If any nation ever gets close to setting up a colony or gathering resources from the moon, it will probably spark a new legal discussion. In practice it might be similar to how Antarctica is currently administered."
] | [
"Well, I'm talking about the present day. Presumably if there's a time when we have the need and the technology to go to the moon, we'll define the laws about colonization then, but we can only speculate now."
] |
[
"Do we know of any viruses which insert DNA fragments into the human genome?"
] | [
false
] | [deleted] | [
"http://en.wikipedia.org/wiki/Lentivirus",
"Lentiviruses transfer RNA into animals cells. ",
"Agrobacterium can transmit DNA between plant cells and is used very heavily in the production of genetically modified crops/plants, but has also been shown to infect and transmit its T-DNA into the human genome under c... | [
"Many viruses can insert themselves into the human genome. The HIV virus is one of them. Once inserted it becomes inactive until some process activates it, so such endogenous viruses cannot be cured by conventional means."
] | [
"To elaborate on that, as far as I know there is no DNA containing virus that does this. HIV is retrovirus that contains RNA, which is a little bit different and can't be integrated into the genome.",
"So what the virus does about this, it brings along some of its own pre-made proteins that help to convert RNA in... |
[
"Do subatomic particles have an exact mass or ranges of mass?"
] | [
false
] | Nothing is exactly 4 kg in classical physics, there's always a rounding error. Is that true at the subatomic level as well? If so, what is responsible for the variance in masses between different particles of the same category? | [
"Stable particles have an exact mass, unstable particles don't.",
"One form of the uncertainty principle says that the uncertainty in time and in energy (or mass) multiplied together must be above a certain amount. If you are measuring the mass of a particle, you want to maximise the uncertainty in time, so that ... | [
"Excellent answer. Also a note for the OP that these uncertainties you are talking about are ",
" to the quantum particle itself, and do not result from measurement technology (as is the case in classical physics of measuring the exact mass of a 4 kg object). No matter how exact your measurement technology become... | [
"Relativistic mass isn't very useful in any context. Rest mass does not change."
] |
[
"Are all babies female before the third month of pregnancy?"
] | [
false
] | I don't recall where I saw this, but, is that true? For what I can remember, the article said that we are all female until the third month of pregnancy, then, the gender is defined and you become a girl or a boy. | [
"This is one of those pseudo-intellectual misconceptions that can get confusing if not explained properly.",
"A female body is the default early fetal ",
" regardless of what the explicit ",
" is. The distinction is important.",
"Males (XY) have a gene on the Y-chromosome (the SRY gene) which, when activate... | [
"At around 10 weeks ",
"virilization",
" occurs which is the start of sexual differentiation.",
"That said when the egg is fertilized it has either an XY set (male) or XX set (female) so at that moment the baby's gender is determined."
] | [
"Are hermaphrodites the result of SRY gene failing to activate?"
] |
[
"How soon could we overtake the Voyager I probe with modern technologies?"
] | [
false
] | If we were to build a modern probe and launch it in the direction of the Voyager I probe, currently the farthest man made object from earth, how much time would it take to over take it and become the new farthest object. Is this even possible considering the current distance and limitations to our technologies? If so what kind of time scale would we be looking at? If it can not be done what is an estimate before it would be possible? Just some random thoughts i had today.... | [
"I checked, and your numbers are correct, and Im literally in 'holy shit' mode.",
"Once up to speed, 200,000mph for 55,000 hours (or 291 days) would go the 11B miles.",
"So we can make a thing that can catch up to a probe launched some 35 years ago in under 2 years. Mind freaking blown, off to learn about ion e... | [
"I checked, and your numbers are correct, and Im literally in 'holy shit' mode.",
"Once up to speed, 200,000mph for 55,000 hours (or 291 days) would go the 11B miles.",
"So we can make a thing that can catch up to a probe launched some 35 years ago in under 2 years. Mind freaking blown, off to learn about ion e... | [
"Acceleration in space is easier because there are fewer opposing forces to overcome such as a planetary gravity or drag."
] |
[
"How do companies know how many Calories are in food?"
] | [
false
] | It's probably a really simple question, but how do fast food companies know how many calories are in each thing they serve? | [
"Essentially, they burn it.",
"Food calories are a measure of the chemical energy available in the food. Basically, food gives us energy because of the energy in the chemical bonds in the sugars, starches, et cetera, that are present in the food. Subjecting these food substances to exothermic reactions breaks up ... | [
"A quick addition to that is that practically, this method is not done for all foods. They simply know the amount of calories present in a gram of sugars, proteins, fats, etc., and calculate the total calories based off the amount of components present. It's always an average calculation, but the numbers are pretty... | [
"I do want to stress that the answers given so far are right, but ultimately do not answer your question due to the relevance of today. ",
"If you were to do a quick search, you often get the bomb calorie meter used as an explanation so it's easy that it's passed off as the answer.",
"The problem is, and this i... |
[
"How do mRNA vaccines avoid being chopped up by the human body's cell enzymes?"
] | [
false
] | I read this passage in a NYT article: The mRNA molecules our cells make can only survive a matter of minutes. so that the cells can make extra virus proteins and prompt a stronger immune response. But the mRNA can only last for a few days at most before they are destroyed. How does this work? What is it about particular strands of mRNA that makes them accessible for protein production but also prevents them from being destroyed for a while? | [
"Naked RNA would be rapidly degraded by exonucleases before it entered the cell. To prevent this, the mRNA is enclosed in lipid nanoparticles that protect it from extracellular RNAses and also helps it transfect (get into) the cells it needs to enter. mRNA is supposed to come from the nucleus - any mRNA that come... | [
"The difference is the ability to reproduce and spread to other cells. When you say a virus will \"cause the cell to produce something it isn't meant to\", it's not just some arbitrary thing it's producing. By definition, a virus has to get the cell to make more copies of the virus. The vaccines can't do that. They... | [
"Man, if you take a step back and look at this, it's amazing how humans are able to understand our body at the cellular level to basically hack it to develop this immunity to a specific virus. Science rocks!",
"At the same time, its also amazing how some humans would rather believe literally anything else but sci... |
[
"Is the irregular shape of the periodic table caused by imperfect classification or just because that's how the universe is?"
] | [
false
] | It just seems to me that the table should be a perfected organized shape instead of having hydrogen and helium alone at the top and then the Lanthanoids and Actinoids being shown oddly at the bottom | [
"This is more a problem of our way of showing it than nature itself. The sort of odd shape of the table is mostly due to the different electron orbital types that can appear around and atom and what that means for reactivity and such.",
"Also, it is important to note the \"The Periodic Table\" isn't a physical l... | [
"Part of the reason the periodic table is laid out the way it is, is expediency. Strictly speaking if you were to lay out the lower parts of the table following the rules of the upper part of the table, it'd look like this:",
"http://www.chemistryland.com/CHM130W/03-BuildingBlocks/Chaos/PeriodicInnerTrans.jpg",
... | [
"I've read that the elements on the left edge are unstable and the ones on the right edge are stable and as you go from left to right the elements become progressively more stable. Is that wrong?"
] |
[
"What's the easiest way to prove to a layperson that the speed of light is an upper limit for all speeds?"
] | [
false
] | My dad and I got into an argument today about the existence of aliens, and I said that while I think they probably do exist in the universe, I didn't think they'd ever visited here because of how long they'd have to travel. My dad thinks that we just haven't "learned" how to travel faster than light. I have a background in science, and my dad doesn't. While I can try to explain to him that we've done experiments and that the speed of light as an upper limit has been thoroughly established, he's never been exposed to any of that so he just rejects it, saying things like "Well when I was a boy cell phones were a dream, so who knows what we will dream up next?" and that we find errors in scientific findings all the time. Is there any easy-to-explain result that you can use to demonstrate that the speed of light is an upper limit? What I really am looking for I guess is some experimental evidence that relies on the speed of light being an upper limit and comes from an experiment a layperson could understand, or a piece of technology that wouldn't work if the speed of light weren't a limit. Something that demonstrates a real-life consequence of the speed of light, and that he could therefore relate to. | [
"Tell him that he's right in one way (people love to hear that, it makes them way more open to hearing what you have to say), there are theoretical mathematical workarounds to bypass the speed of light, but they're cheats. You simply cannot travel accelerate to the speed of light, because it takes an infinite amou... | [
".99999999999(repeating)c",
"That would be c (0.999(repeating) = 1), and you can't reach that speed."
] | [
"Good catch, I didn't so much meaning repeating forever as for a long time. ",
"1/3,2/3,3/3, blahblahblah. "
] |
[
"Is there an escape velocity for leaving the solar system?"
] | [
false
] | Would an object need to travel faster than a particular velocity in order to leave the suns orbit? Or do I have the concept of escape velocity completely wrong? | [
"Yes, there is. Escape velocity depends on how far you are from the primary - generally the value given is for the surface of the primary. If you are at the distance of the Earth from the sun (1 AU), then you need to recompute this. It's really easy: escape velocity is the velocity that makes the kinetic energy equ... | [
"Not exactly: if a spacecraft is slower than 42 km/s AND is no farther from the sun than 1 AU, then it is trapped. The distance matters. Basically the condition is whether the total energy (kinetic plus potential) is positive or negative. Negative energy means you're bound (your orbit is an ellipse), positive means... | [
"Relevant side note: It is even true that at your current position you need to travel faster than a critical speed in order to escape from the Andromeda Galaxy (a faint fuzzy barely visible in the night sky). You are unlikely to guess this escape velocity correctly: ",
"http://www.science20.com/hammock_physicist/... |
[
"Planks constant states that the position uncertainty of an electron times the momentum uncertainty must be greater than or equal to planks constant divided by two. Why is this? What would happen otherwise, or what is preventing it to happen? Or, how do we know this?"
] | [
false
] | null | [
"You mean the uncertainty principle. It's because position and momentum are incompatible observables in quantum mechanics. The Hermitian operators which represent them don't commute, so they cannot be simultaneously diagonalized. Eigenvectors of one are not eigenvectors of the other.",
"From the postulates of QM,... | [
"Planck's constant is a measurement. There is no way to derive it. The measurements are not done via position and momentum of particles, however, they are done via the energy of photons and similar quantities.",
"Alternatively, you can fix this constant to a specific value to define what a kilogram is, something ... | [
"I do mean the uncertainty principle, thanks! I've been reading about it. But I'm just a layman, so I probably didn't express it well. ",
"You say that \"position and momentum are incompatible in QM\". And I get that. But I don't understand how that relates to H in the equation. ",
"I guess my next question is;... |
[
"Is it possible/practical to harness potential energy given by gravity?"
] | [
false
] | [deleted] | [
"There are schemes in place that make use of GPE for storage - many smaller hydroschemes consist of two linked storage reservoirs, the upper reservoir can be refilled by pumping the water in the lower reservoir back up.",
"The market price of electricity fluctuates greatly over 24 hrs, typically being cheapest ov... | [
"To clarify this, the only way to practically use gravitational potential energy is if you did not have to expend any/much energy to give your object that potential energy. Hydroelectricity is a great example of this because we, as humans, do not put any effort into 'moving' the water upstream; we simply take advan... | [
"To clarify this, the only way to practically use gravitational potential energy is if you did not have to expend any/much energy to give your object that potential energy. Hydroelectricity is a great example of this because we, as humans, do not put any effort into 'moving' the water upstream; we simply take advan... |
[
"How much radiation does the earth release when it's at equilibrium temperature, relative to the amount of radiation that the earth absorbs?"
] | [
false
] | I'm pretty bad at science and know very little about climate change - but I've been trying, slowly, to learn more about the topic. A few people on Reddit have been telling me about how the earth's equilibrium temperature changes whenever the amount of greenhouse gases in the earth's atmosphere changes. On a very basic level, I understand that the equilibrium temperature of the earth is whatever the earth's temperature is when the amount of radiation emitted by the earth into outer space is equal the amount of radiation absorbed by the earth. I also understand that some of the radiation released by the earth doesn't make it to space (at least, not right away), because it gets trapped in the atmosphere by greenhouse gases. So that would seem to suggest that at any moment, the amount of radiation "released" by the earth's molecules is greater than the amount of radiation "emitted" by the earth into space. And if the earth is at equilibrium temperature, with the amount of radiation emitted equal to the amount of radiation absorbed, then...that would seem to suggest that the earth releases more radiation than it absorbs (because of the transitive property; if radiation emitted is equal to radiation absorbed, and if radiation emitted is less than the total amount of radiation released, then radiation absorbed would also have to be less than the total amount of radiation released). Someone told me though, that the amount of radiation released by an object will always be equal to however much radiation had been absorbed by the object. I only have a very rudimentary understanding of the processes involved - and clearly, I must be thinking about this the wrong way, since the math doesn't seem to work out. Could someone try to clarify this for me? Thanks! :) | [
"Equilibrium temperature is the temperature at which Earth re-emits the same amount of energy as it absorbs. However the equilibrium temperature is not fixed. It depends on a lot of different factors, like for example the reflectivity (albedo) and the emissivity. \nGreenhouse gases indeed increase the equilibrium t... | [
"Equilibrium temperature is the temperature at which Earth re-emits the same amount of energy as it absorbs. However the equilibrium temperature is not fixed. It depends on a lot of different factors, like for example the reflectivity (albedo) and the emissivity. \nGreenhouse gases indeed increase the equilibrium t... | [
"Strictly speaking the amount emitted would be slightly greater than the amount absorbed at equilibrium, due to internal heating. However this is a very small effect."
] |
[
"are there any large systems of planets that orbit a bigger planet rather than a star?"
] | [
false
] | I suppose that would just be a rouge planet with a lot of moons but does it happen often? could you find planets with the size and quantity as the ones in our solar system orbiting one the size of jupiter? or would they all just drift away or crash into eachother or something? (sorry if this is a dumb question) | [
"We have detected some planets around brown dwarfs, which are about 13-75 times the mass of Jupiter, and don't count as stars because they aren't massive enough to produce fusion. This is at the very lower limit of where we can detect planets though, and we've only found a few of these.",
"For rogue planets of Ju... | [
"Is there a reason you would exclude the Jovian system as an example of this? 79 moons orbiting a planet the size of Jupiter would qualify as a large system. Ganymede is bigger than Mercury so would qualify as a planet if it orbited the sun rather than Jupiter. ",
"If you are only interested in exoplanets with... | [
"That's not the reason pluto was declassified as a planet. Pluto is certainly large enough to be rounded by its gravity. Pluto fails the third requirement since it has not cleared the neighborhood of its orbit.",
"The reason Ganymede is not considered a planet is mainly that planets must by definition orbit a sta... |
[
"How to calculate force on a cube with negative pressure?"
] | [
false
] | null | [
"Would I be correct in thinking that taking sea level pressure at 101325 Pa and then taking away my internal pressure of 0.00378 Pa... would that leave me with the N/m2 being exerted on my cube from the outside?",
"Yes, assuming the pressure is constant on the outside of the box. Now just integrate this over the ... | [
"You'd look at the ",
"Knudsen number",
" to decide whether or not fluid mechanics is valid for your situation."
] | [
"You'd look at the ",
"Knudsen number",
" to decide whether or not fluid mechanics is valid for your situation."
] |
[
"Question about black holes / Hawking radiation:"
] | [
false
] | So, I was thinking about black holes today, and had a thought which confused me somewhat. There is a common thought experiment where people ask what would happen if a clock were thrown into a black hole, and it can be shown that, from the perspective of an outside observer, the clock would slow down as it approached the event horizon, never actually reaching it. Presumably, this means that from the clock's 'perspective', time would be passing at a normal rate, but events happening in the rest of the universe would appear to speed up more and more as it approached the black hole, eventually traveling infinitely fast. However, won't this mean that, from an outside perspective, objects would never cross the event horizon in a finite amount of time, and if so, wouldn't that mean that the black hole would decay due to Hawking radiation before the clock ever reached it? If so, does this mean that it is impossible for a black hole to acquire more mass than it started out with? This conclusion doesn't seem right to me, but I'd appreciate it if anybody who knows something about black holes could explain where I have gone wrong in my thinking. | [
"I'm pretty sure it's the other way around. As the clock approaches the event horizon, it experiences time dilation effects, \"stretching\" time in its own reference frame. After it passes the event horizon, it is no longer possible to communicate with the clock (i.e. read the time from it) as the information trans... | [
"Presumably, this means that from the clock's 'perspective', time would be passing at a normal rate, but events happening in the rest of the universe would appear to speed up more and more as it approached the black hole, eventually traveling infinitely fast.",
"That's not actually correct. While events outside "... | [
"Sadly for the poor clock, it reaches the singularity in a finite amount of time, even in its own frame of reference. The slowing down and fading an outside observer can witness is only an effect of photons being unable to escape the event horizon and does note correlate to any kind of time slowing down."
] |
[
"Why don't we ever sneeze while sleeping?"
] | [
false
] | null | [
"When you're awake, allergies, particles etc. can stimulate the nerve cells in your nose. The cells send a signal to the brain and you sneeze to get whatever's causing the stimulation out.",
"When you're asleep, though, much more stimulation is required to initiate a sneeze, due to an inhibitory neurotransmitter ... | [
"anecdotally, my GF wakes up a few times a night to sneeze and goes right back to sleep."
] | [
"I was going to ask the OP how he knows he doesn't sneeze. You'd have to set up a camera/microphone to be sure. Maybe it just doesn't wake you or you don't recall it after falling right back to sleep."
] |
[
"Why is ∞* 0 ≠0"
] | [
false
] | It looks like a simple math. I mean, I know infinity is some number very very big, but regardless of the magnitude of infinity, I would assume if I multiply that number with 0, then I would get 0. | [
"infinity is some number very very big",
"This is the wrong way of looking at things. Infinity ",
" a number - it is a concept used to describe something limitless. ",
"Generally, the instances when infinities are \"part\" of equations are those when you have a function (eg. f(x)), which has parts where cert... | [
"Problem here is that we can ask ourselves multiple questions that all are proper interpretation of 0*infinity:",
"extended real number line",
"cardinal multiplication"
] | [
"Infinity is not a real number, so it can't be treated as such. "
] |
[
"Are mind palaces, like in BBCs Shelock, real? If so how effective are they?"
] | [
false
] | null | [
"Mind palaces are real, though not like the one shown on TV of course. the idea is that we remember locations better than facts, so if we create a location we are familiar with (real or fictional), filled with triggers that links to facts, then we create what is a mind palace. a complicated mind palace takes a lo... | [
"oh for sure, I mean if there are people who can recite pi to the 100,000th digit then a huge mind palace isn't impossible. mind palace is after all a technique/tool, and its potential depends on the user. "
] | [
"It seemed a little crazy to me especially after Season three Episode three where the creepy black mail guy (what ever his name is) has piles of information on hundreds of people stored in his head. Thanks for the response"
] |
[
"I want to understand the difference (and importance of the concept) between impedance (as in \"75 ohm coax wire\") and grade-school resistance (as in \"I = V/R\" and \"P = I squared R\")."
] | [
false
] | I am very comfortable with the concept of grade-school resistance. I tried to read the about impedance, but I think I need a explain-it-like-I'm-five explanation, if anyone would be so kind... | [
"In general, ",
" is the complex (as in 'complex numbers', with a real and imaginary part) form of ",
". Z = R+jX. Z= ",
", R = the (real) ",
" you are familiar with, X= the (imaginary) ",
".",
"This complex ",
" comes in play when describing relations between voltage and current when capacitors and i... | [
"Electrical concepts are usually explained first in terms of direct current because DC is a special case where these concepts are pretty simple (V=IR). You can think of impedance as being composed of two different components. An impedance value holds two pieces of information, resistivity to electrical current, an... | [
"I'll take a stab at this and try to explain it on a simpler level. ",
"/r/ascience",
" engineers, please be kind to me ;)",
"When you get in to impedance you're getting into alternating currents not direct currents more easily solved by Ohm's Law although when you add everything up you still use Ohm's Law.",... |
[
"Would Dinosaurs have been red or white meat?"
] | [
false
] | null | [
"Red vs. white meat is largely a function of how the specific muscles are utilized. The 'red' in red meat is from high amounts of myoglobin for oxygen retention and mitochondria that are used for aerobic respiration and are generally found in higher abundance in slow-twitch muscles that are used for extended period... | [
"Taste in meat is due to so many factors, including presence or absence of different types of fats/oils and whether there's stored glycogen there. Also, since animals do tend to taste differently based on their diet... it is really pretty impossible to know or conjecture. The safe answer would be to say they taste ... | [
"more important, how would it taste ?",
"edit : not sure its possible to begin answering that, not a joke, I am serious"
] |
[
"Why don't scientists clone endangered species as a means to increase their population?"
] | [
false
] | null | [
"One of the most necessary factors in long term species survival is genetic diversity. Cloning would lead to an increase in organisms, however there would be a massive genetic drift toward one genotype (or a few) and increase the likely hood of future offspring having deleterious (harmful) genes or mutations. There... | [
"Species become endangered because they lose their natural habitat, not because they fail to breed. Cloning them would not restore their habitat.",
"Edit: typo."
] | [
"Cloning is not easier than breeding non-clones. Generally, it's harder.",
"Cloning is not done by some scifi replicator, but simply by implanting a zygote into a host-mother's womb and having it grow as normal. To clone, that zygote is prepared by a tricky process of implanting a nucleus into an egg. To non-clon... |
[
"Why was the number 299,792,458 chosen as the definiton of a metre instead of a more rounded off number like 300,000,000?"
] | [
false
] | So a metre is defined as the distance light travels in 1/299,792,458 of a second, but is there a reason why this particular number is chosen instead of a more "convenient" number? Edit: Typo | [
"The principle was to keep the definition consistent with previous measurements, within their uncertainty. We already had a definition for the metre, just not as precise as the current definition, and we want the new definition to be as consistent as possible, but just easier to measure precisely. Rounding to 300,0... | [
"It'd change the circumference of the Earth by about 30 km, for instance",
"to illustrate the impact, if we built a metal ring with a circumference 30km larger than that of the equator, it's diameter would be ~9km more than that of the earth.",
"that ring would float about 4.5kms above everyone's head."
] | [
"The meter ",
" was defined as 1/10,000,000 the distance from the equator to the North Pole at the longitude of Lyon.",
"Then people figured out that this wasn't a great way of developing a precise unit of length due to difficulty measuring, and the fact that the value might even change due to Earthquakes, and ... |
[
"Why does sodium move inside the membrane during an action potential?"
] | [
false
] | I get that at resting potential, the inside of the membrane is less positive than the outside. Nevertheless, wouldn't potassium cation ion still make the inside of the membrane overall positive? If both the inside and outside of the membrane are overall positively charged, then during depolarization, what is driving Na into moving towards yet another positively charged region? Likewise, what force is causing K to move to the outside of the membrane (which is also positively charged)? Can someone please explain to me the underlying biophysics? | [
"There is a protein integrated into the plasma membrane of cells called the “Na+/K+ transporter”. This protein is constantly using ATP in order to push sodium ions OUTSIDE of the cell. This “Na+/K+ transporter” protein is therefore creating a Na+ ion gradient with a lot of Na+ outside of the cell and very little N... | [
"Also if you’re curious, the reason why there is a transmembrane voltage potential in the first place is because of the K+ ion gradient (maintained by the Na+/K+ Transporter). The K+ ions move outside of the cell down it’s chemical concentration gradient through “K+ leak channels”, and this process is moving positi... | [
"The inside of the cell has negatively charged macromolecules that can't leave the cell, allowing it to have Na+ and K+ ions while still remaining a negative charge. The cell keeps that charge in a few ways, there are ion channels (leak channel) that allow Na+ and K+ into and out of the cell. They follow their conc... |
[
"A health concern is the failing of antibiotics as bacterial become immune to them. Is the same situation true of vaccines or is it not in any way similar?"
] | [
false
] | null | [
"Hi eagle332288 thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the fol... | [
"Medicine"
] | [
"'Medicine'"
] |
[
"Are orbital altitudes correlated to required orbital velocities relative to earth?"
] | [
false
] | So the ISS chills at about 300km above the surface of the earth and travels at about 27000km an hour, how much can that orbital velocity vary? Since the moon does it's thing at 375,000km and travels at 1km a second (3600km an hour?) is it reasonable to assume that the further away a body is, the slower it can/must orbit to stay stable? All those numbers are pretty roundabout and I know all bodies are tugged on by other massive bodies in the solar system, for simplicity I'm curious about earth's gravity taken in isolation (if possible). I also know the moon is slowly drifting away, I'm curious about time spans observable by humans. For fun, what would happen if you appreciably altered the speeds of the ISS and the Moon both faster and slower? | [
"So the ISS chills at about 300km above the surface of the earth and travels at about 27000km an hour, how much can that orbital velocity vary?",
"If the ISS were in a perfectly circular orbit, the velocity would not vary at all. Its orbit isn't perfectly circular, but after a small amount of searching I can't fi... | [
"Orbital speed and altitude are intimately related. For low eccentricity orbits, ",
"v ~ sqrt(m2",
" *G/((m1+m2)/r))",
"So the speed varies inversely with the square root of the semi-major axis.",
"For all non-circular orbits, which is basically all orbits since they all have some eccentricity in real life,... | [
"If you pushed it hard enough, it might escape Earth.",
"Depending on how you pushed it, it could also dip the orbit low enough to burn the ISS up in the atmosphere. This takes much less delta-v (change in velocity, thus requiring less fuel), so it would be a more realistic option for evil geniuses."
] |
[
"Does Compton Scattering produce multiple photons?"
] | [
false
] | Lets say we have a stationary electron with energy E = m c and an incident photon with energy E = hf , where f is the frequency. After the scattering event, the scattered photon will have energy E=hf where f >f and the electron will have energy E=sqrt(m c + p c ) then by conservation of energy we have: hf + m c = hf + sqrt(m c + p c ) My question is that after the collision the electron will have acquired some momentum and if that is the case then its velocity must have changed. Would this not mean that hf + m c > hf + sqrt(m c + p c ) since the electron would have radiated some energy away as it was accelerating and would that acceleration result in more photons? | [
"I like the definition of Compton scattering as seeing a photon + electron in, and then a photon + electron out, which implies that the energy will be conserved. But it's wrong to say that bremssstrahlung doesn't exist in quantum mechanics and has no relevance here. Understanding the effects of bremsstrahlung was i... | [
"Nope. ",
"The actual mechanism behind the scattering event is not actually specified in the usual derivation of Compton scattering. It's treated like a mysterious black box where we simply see one photon and one electron enter the interaction, and a different photon and a different electron leave. To understand ... | [
"The energy of EM radiation decreases like 1/r",
" with distance from the (sufficiently far) source, so the second change should have much less energy than the first. The total energy (in the charges + radiation) will be perfectly conserved of course, so the second wave will have less energy than the original wav... |
[
"If you have a spacecraft that’s designed so it rotates and keeps gravity at 1 g…"
] | [
false
] | ...how fast would the spacecraft be able to go before humans were unable to travel on it? I’m thinking in terms of interstellar travel where we’d need to be on the craft for a long period of time. Similar to how the Earth orbits the Sun at about 108,000 km/h but has enough gravity and rotation (I assume this is the cause) so we don’t feel like we’re going 108,000 km/h. Would the spacecraft be able to travel at 108,000 km/h and beyond if the rotation was enough to keep a constant 1 g? I guess that’s also assuming the spacecraft is able to generate the necessary speed and built to withstand the pressures put upon it. | [
"Unfortunately, you are a bit confused about exactly what kind of conditions are inhospitable. It's not how fast you are going, it's how much you are accelerating. The fact that being in an accelerating frame of reference feels the same as being in a gravitational field is one of the key insights underlying Einst... | [
"It would need to accelerate relatively slowly. Depends on how fast you want to go and how long you're willing to accelerate for. One cute idea from science fiction is to have a spacecraft that accelerates at 1 g for the first half of the journey, then turns around and decelerates at 1 g. Travel aboard such a cr... | [
"so we don’t feel like we’re going 108,000 km/h",
"You never feel speeds. You only feel accelerations.",
"The spacecraft could go any speed you like, so long as it is slower than the speed of light. The rotation which would give you the simulated gravity is entirely separate from the speed the ship travels. ... |
[
"Relativistic effects in gear systems."
] | [
false
] | null | [
"Thanks! I'll do that. I'll crosspost it, and let a mod close it here if they determine that's something that should happen. I'll provide a link here for people to follow."
] | [
"The cross post is ",
"here",
"."
] | [
"A good home for this question would be ",
"/r/AskScienceDiscussion",
"."
] |
[
"What actually causes the internal resistance of a battery?"
] | [
false
] | Batteries have a characteristic which we call internal resistance. I'm an electronic engineer and I understand how this effect manifests itself. It acts like a resistor being in series with the output of the battery, however it is not a "real" resistor but to an engineer it makes our lives easier to think of it that way. I've always thought that the internal resistance was basically due to the battery's limited ability to produce current. i.e. As you try to draw a large current from the battery, the battery struggles and that is analogous to having an increasing series resistance. However, I've been thinking about how batteries can get hot as they discharge. The heat generation is always put down to the current flowing though the internal resistance of the battery which implies that the internal resistance is acting like an ordinary resistor(/conductor). So now I'm confused. Do charges flowing through the electrolyte experience an electrical resistance? Or something similar? Or is it something else entirely? , What actually internal resistance? What is the cause of the heating? | [
"There is in fact an electrical resistance associated with batteries, which causes ohmic heating just like the resistance of any other circuit element. However, it's generally made up of a lot of different components and not only depends on the type of battery, but can change non-linearly with state-of-charge, rate... | [
"There are multiple contributions, including the electrical resistance of the plates, the diffusion process in the electrolyte and the reactions at each plate. Which one dominates can depend on whether you are testing a steady draw or a pulsating draw. The impedance vs. frequency can be used to tease out, to some... | [
"/u/tuctrohs",
" and ",
"/u/almightycuppa",
" both gave correct answers, but maybe failed to directly address your questions, which seem to be more straightforward: ",
"\"What actually IS internal resistance? What is the cause of the heating?\"",
"Generally speaking, the \"origin\" of internal resistance ... |
[
"How the Universe began."
] | [
false
] | I am curious. I guess I am unclear about the space that our universe is expanding into. Since it is expanding then where did this space come from? | [
"Space was, and continues to be created by the expansion/inflation of the Universe after the Big Bang."
] | [
"Thank you all for your responses. It has really helped me understand things a bit better. I still have one question. The simple fact that there was a particle sitting there (before the explosion) means that space has already in existence does it not?"
] | [
"Space itself expands. It needs no medium to expand into because it creates its own. The balloon analogy is used quite often. As the balloon expands, the space between two points on the surface of the balloon continues to increase. You don't need to add anything onto the surface of the balloon, it just expands. ",
... |
[
"I just learned about the MarsOne project, and I was just wondering, what is NASA's take on the matter? Also, is the project a realistic and viable option? What exactly would be necessary for it to be successful?"
] | [
false
] | null | [
"Its a bit vague about the details. The main problem is money."
] | [
"So would NASA be willing to actually contribute to the project. I've heard of NASA wanting to send people to explore Mars, but it seemed like a slower process, you know? It didn't sound like they would just dump people on the planet for the rest of their lives."
] | [
"So would NASA be willing to actually contribute to the project",
"Maybe they would pay for a seat, hard to say.",
"It didn't sound like they would just dump people on the planet for the rest of their lives.",
"That might be the best thing to do. In ten years when my son is an adult I would consider doing som... |
[
"Diffusion: why is it molecule specific?"
] | [
false
] | I was taught in my biology class that if we have add two types of ions with similar with similar charge and size to a water beaker solutions, these ions will distribute uniformly with respect to themselves and NOT with respect to other ions in the solution. That is, say we have Na+ and K+ ions in our solution. After a long amount of time for diffusion to commence, all the Na+ will be uniformly distributed (ignoring the K+), and all the K+ will be uniformly distributed (ignoring the Na+) in the beaker. My question is why is not possible (or is it) that if we look at the beaker after a long time, maybe the left side has a much larger number of K+ ions than the right side, and the right side has a much larger number of Na+ ions than the left side, such that overall the + ion distribution is approximately uniform (as if the Na+ and K+ were just a single type of ion)? | [
"The question you are asking is one of ",
"statistical mechanics",
". This ",
"exemple",
" is very close to what you are asking. ",
"In a nutshell, when your solution has at equilibrium, all configurations of the ions that respects the external conditions (pressure, temperature, etc) are equiprobable (i.e... | [
"What you said makes perfect sense in the one ion case, but I'm still a little hazy on the two ion case. I have one more follow up question that would probably help correct my understanding:",
"Say we have two beakers of water connected with a one-way permeable membrane from beaker A to beaker B. Beaker A has 1M ... | [
"Well, first a little word about solutions. I was careful in my initial post to describe an ",
"ideal solution",
". In an ideal solution, the ions are independent. If the solution is non-ideal, then things can start to get strange. As you correctly start to surmise. ",
"I'll break your exemple into two step.... |
[
"Anyone familiar with GST fusion proteins and how they are prepared?"
] | [
false
] | [deleted] | [
"Which part of the preparation are you having trouble with? I haven't actually used GST in particular but it is a similar concept as with any fusion tag. ",
"First step is the molecular cloning - The DNA sequence that encodes the GST tag is known, so you fuse this sequence in-frame with whatever protein you are i... | [
"Usually the tag is already in an expression plasmid. What you do is cut that plasmid and your gene (eg. hp300) separately with a restriction enzyme and you can combine them by mixing and putting in ligase, an enzyme that combines pieces of DNA. You then put your new plasmid with your fusion protein into a host (",... | [
"First off, thank you for responding. We have no textbook and it gets crazy searching online.",
"Anyways, for the first step if I understand correctly, GST tags onto a terminus of a protein (ex/ hp300) which is inoculated into a plasmid. Culture is grown and we have cloned sequences? ",
"I don't think we have t... |
[
"Why does metal turn red when it is heated?"
] | [
false
] | null | [
"Everything glows red when heated to a certain temperature because of blackbody radiation. It's just metal is one of the few things we deal with that doesn't combust or melt before it can get that hot."
] | [
"It's not about how sensitive our eyes are as that they are attuned to the visible spectrum of light. As things get warmer, they release higher energy photons, this is why things get red-hot, red being the lowest energy visible light, before they get white hot."
] | [
"The OP is clearly a layman, and although you have provided a link to technically correct information, the OP is unlikely to learn anything from it. Perhaps explain the content in layman's terms."
] |
[
"Is this statement true? \"as we emit more and more carbon dioxide into our atmosphere, each increment results in less and less warming.\""
] | [
false
] | null | [
"Yes, this is true. If you look at the two formulae in ",
"Wikipedia's entry on radiative forcing",
", you'll see that temperature change varies linearly with radiative forcing, and radiative forcing for carbon dioxide varies logarithmically.",
"That is why climate scientists often speak of change in equilibr... | [
"This would only be a valid argument if you assume that any dangers or issues that can result from increased temperatures increase linearly with rising temperature. It doesn't seem to hold true if you are talking about specific climatic break points, or if the first serious negative impacts occur a comparatively lo... | [
"This is askscience. Every question is asking for a response that is backed up with data and understanding."
] |
[
"Can you measure absolute velocity in space without a frame of reference?"
] | [
false
] | Say you are in a patch of space a few light years across in all 3 dimensions and you have no frame of reference, say for some reason you cannot see any stars, its pitch black. Could you measure your speed? Would it be of experimental interest (say, just to have a lab that is at rest relative to space itself) ? (One method I thought about would be based on the speed of light being constant: Imagine you are in a spaceship. You extend a detector array that includes a highly accurate atomic clock about a light second to your left. You then fire a laser at the thing and see if it hits. If you aim directly at the array and hit, then you are at rest, if not, you need to alter the angle of the laser beam to hit the detector. Based on the distance of the array, the angle on the laser beam and the runtime of the beam, you should be able to calculate your forward motion. You would of course need to have 3 arrays and 3 lasers to accurately dertermine your speed in 3 dimensions.) Edit: Thanks everybody! | [
"No, you can't, because there's no such thing as absolute velocity. The speed of light being constant means it's constant in ",
" reference frames; in general, there is no local experiment you can run to determine any sort of absolute speed."
] | [
"Because the twin in the spaceship ",
". Acceleration isn't relative."
] | [
"Let's say you have several hundred cans of super-magic-rocketfuel. You use one, and discover that it propels you forward at 10% of the speed of light, relative to your friend who was watching.",
"As you make your journey, you use up 200 such cans, and each time you use one, you begin moving faster than before. ... |
[
"How far can a flea see? Does it always know where it's going to land, or does it jump and hope for the best?"
] | [
false
] | null | [
"It would have to be the latter. The insect's size, and thus the size of its eyes, limit the visual resolution that it could have even under ideal conditions. And there's also processing power in the flea's brain - I very much doubt if they have enough neuronal complexity to pick out landing spots, even if they cou... | [
"I would only add that to a flea, his terminal velocity is low enough he never impacts with enough force to damage anything. So jumping into the unknown is not much of a bet for him. "
] | [
"Would size play a factor in what force is needed to cause damage? Is this more related to the strength of the flea's body chemistry? Would a flea the size of a human be able to jump off of a skyscraper and be fine?"
] |
[
"If time slows down in gravitational fields, does it come to a complete stop in singularities?"
] | [
false
] | [deleted] | [
"I just want to tack onto this that singularities aren't thought to be a physical thing, but rather a failure of our model. The fact that our description of black holes contains a singularity at the center doesn't mean we expect an infinitely dense point to lie at the middle, but rather that our description of blac... | [
"We have no idea what happens in singularities. However time does slow down ",
" singularities. If you were to watch someone fall into a black hole from far away, you would see it taking infinite time for the other person to pass through the horizon. In fact, from your perspective, they wouldn't \"pass through\" ... | [
"I want to add on to this, though, that while it takes an infinite time for someone to fall into the event horizon from the perspective of an outside observer, from the perspective of the (spaghettified) observer falling into the black hole, a finite time passes as he crosses the event horizon."
] |
[
"For the economists: beyond ideology, is capitalism a sustainable economic policy?"
] | [
false
] | null | [
"is there a point at which capitalism will cease to be a viable economic policy?",
"Depends on your definition of \"viable\". I would say we passed that point many decades ago.",
"From a more charitable definition, it will happen once the cheap liquid fuel becomes no longer cheap enough, and once the environmen... | [
"It is not sustainable. You hit on precisely the right point - capitalism not only requires continual growth, but continual growth at constantly INCREASING rate. Any time this growth is not met, you get economic collapse. At best this results in a boom-bust cycle.",
"One attempt to provide a framework for a perma... | [
"You're wrong.",
"Technocracy tends toward physics, and views \"left\" \"right\" and everything in between as outdated, obsolete thinking.",
"Socialism is still economically based on the price system, just as far right free market capitalism is. The price system ITSELF is fundamentally flawed. The socialist-cap... |
[
"Why do very few high order derivatives not show up very often in equations of motion?"
] | [
false
] | I’ve seen a lot of equations of motion in terms of velocity and acceleration. But I’ve never seen ones where d x/dt for n > 2 show up or even the n-th integral of x with respect to t ever pop up. This even seems to happen in what I’ve read about quantum mechanics and relativity, (although I haven’t read much about relativity). Why would the laws of physics pretty much limit itself to only using distance, velocity, and acceleration when there’s an infinite amount of higher order derivatives that it could use? | [
"If higher time derivatives would appear anywhere in a fundamental equation it would almost certainly lead to a violation of energy and momentum conservation.",
"The acceleration is linked to a change in kinetic energy (the time derivative of it is m v a), the velocity is what determines the kinetic energy, and t... | [
"The Lagrangian for classical electrodynamics is not of the form \"kinetic energy minus potential energy\". There are terms that are velocity-dependent that mimic the role of a potential in the Lagrangian, but they are not actually potentials. A true potential would have the property that the change in kinetic ener... | [
"There you run into violation of conservation laws as well. You can introduce something like an effective potential in some cases but that doesn't have the same role."
] |
[
"Why do men tend to go bald in the typical horseshoe shaped pattern?"
] | [
false
] | null | [
"Hi, I see many posts have been deleted here so hopefully mine won't be. I'm currently a medical student and I did my senior thesis on male pattern baldness. Essentially, the medical science behind male pattern baldness isn't fully completed. We do know that there is an extremely strong link between the expression ... | [
"Higher levels of 5-alpha reductase are found in the frontal and vertex region of the scalp versus the back and sides. 5-alpha reductase converts testosterone to dihydrotestosterone (DHT), a hormone which causes miniaturization of hair follicles in (mostly genetically) susceptible individuals."
] | [
"Here's something on the subject: ",
"http://www.ncbi.nlm.nih.gov/pubmed/8077349"
] |
[
"Why do free neutrons decay?"
] | [
false
] | [deleted] | [
"They don't decay in the nucleus because decaying in a nucleus would increase the binding energy of the nucleus more than the difference in energy between (a neutron) and (a proton, electron, and antineutrino), which means it is more energetically favorable to stay as a neutron than to decay inside the nucleus.",
... | [
"Because the decay products (a proton, electron, and antineutrino) have less mass (and therefore energy) combined than the neutron did before it decayed."
] | [
"A nucleus is unstable if the product of some reaction (like beta decay) has less mass than the initial state. The mass is determined by how the nucleus is structured. For stable nuclei (again just considering beta decay here), the potential nucleus from a neutron turning into a proton is higher in mass than the in... |
[
"Are supposedly \"habitable\" exoplanets that have 5 times the mass of Earth really habitable?"
] | [
false
] | I just read a new article stating that a habitable exoplanet has been found. However, it states that it has 5 times the mass of Earth. Doesn't that mean that it will have 5 times as much gravity? It seems like that would make the planet inhabitable, having the much gravity. Am I wrong? | [
"Habitable usually means that the surface could support liquid water (assuming the atmosphere is right for that). In terms of mass and gravity, a planet 5 times the mass of Earth would actually probably have surface gravity closer to twice that of Earth, because the greater radius of the planet reduces the gravita... | [
"Okay so, ignoring all the constants involved to simplify the math (justifiable), and assuming the exoplanet is the same density as earth (not necessarily justifiable, but it simplifies the comparison), start by considering the classical form of the gravitational interaction: ",
"F = (mass1 * mass2) / (distance ... | [
"Keep in mind that the size of the planet has an effect on surface gravity. Just because it has 5 times the mass doesn't necessarily mean it has 5x the surface gravity. "
] |
[
"What makes a caterpillar become a moth or butterfly?"
] | [
false
] | null | [
"First, the caterpillar digests itself, releasing enzymes to dissolve all of its tissues. If you were to cut open a cocoon or chrysalis at just the right time, caterpillar soup would ooze out. But the contents of the pupa are not entirely an amorphous mess. Certain highly organized groups of cells known as imaginal... | [
"A caterpillar doesn’t choose so to speak. A moth and a butterfly are two different species. However, both species go through a similar process of metamorphosis. This is where they cocoon and after a few days or so emerge as a butterfly, or a moth. But one can’t just become the other."
] | [
"I never knew I wanted to know this, until now!",
"Thanks for the research!"
] |
[
"Why aren't there animals today that are as large as dinosaurs were?"
] | [
false
] | null | [
"A lot of today's animals are larger than dinosaurs. An African elephant is larger than the majority of the dinosaurs that ever lived.",
"Dinosaurs ",
" bigger for a number of reasons:"
] | [
"Makes sense, thanks!"
] | [
"Well, the ",
"largest animal ever to have existed",
" is still around today. Here are some size ",
"comparisons",
".",
"But, I'd say land animals aren't that big now because (a) it isn't advantageous to be that size in the current environment and/or (b) it just hasn't come up in all the random mutations ... |
[
"Are there any downsides to camouflage?"
] | [
false
] | Animals that are cryptically colored can hide from predators. This seems too perfect. Is there any trade off that the prey may face? | [
"Camouflage that is ideally suited to one environment will stick out like a sore thumb in different areas and may end up reducing the effective range of that particular animal."
] | [
"Mating.\nThis is like the biggest point.\nDon't get eaten, but still be seen by the girls :)",
"Since most animals don't have a opposable thumb, they have a hard time filling out their online-dating-profiles.",
"But seriously, that is the biggest problem, that the females are mostly attracted by coulerful male... | [
"Camouflage is considered a primary defense mechanism as opposed to a secondary defense mechanism (ex: when a lizard severs its tail to get away) or a tertiary mechanism (emetics, some sort of toxin). However, organisms can't afford to maximize all three of these types of defense mechanisms. An organism that is cry... |
[
"Because violet light is closer to UV and X-ray light than the other colors, is violet light at all more likely to give someone cancer?"
] | [
false
] | null | [
"The key to understanding the damage caused by photon radiation (light and electromagnetic radiation) is whether or not it is capable of creating ionization when it impacts another material. Ionization is when an electron is stripped from an atom, which causes it to become charged and reactive, and possible to brea... | [
"Blue/violet light can cause some damage, particularly to the retina of the eye:",
"http://en.wikipedia.org/wiki/High-energy_visible_light#Blue-light_hazard",
"There are also some studies showing Mitochondrial DNA damage from blue light:",
"http://www.jbc.org/content/280/22/21061.full"
] | [
"UV light isn't ionizing radiation either.",
"The process by which UV light causes cancer is not through ionization, but through chemical creations.",
"Ultraviolet light can cause burns to skin[8] and cataracts to the eyes.[8] Ultraviolet is classified into near, medium and far UV according to energy, where nea... |
[
"what is karposa sarcoma when related to a person with aids? what percent of people survive?"
] | [
false
] | null | [
"Kaposi's sarcoma is a systemic disease that presents with a very specific appearance on the skin and mucus membranes of affected individuals. It is caused by a different virus than the HIV virus. The virus is not typically capable of creating symptoms in an individual who is not immuno-compromised, so this is wh... | [
"The causative virus is human herpes virus 8. It can rarely cause Kaposi's in people without HIV, typically in people from Greece or Turkey, but the vast majority of cases are seen in HIV patients or organ transplant recipients. In many HIV patients it is an incidental finding of little importance that won't greatl... | [
"All good additive information, I don't follow it a ton, but I see it from time to time."
] |
[
"Are all forces just interactions between fields?"
] | [
false
] | null | [
"I was trying to say that there always are different formulations of what is happenning. The key point is that in the gauge theory you have a particle which mediates the force, in the other case the change of spacetime results in the change of motion."
] | [
"Field theory is just our way to describe what is happening around us. It certainly is not the only wayy to describe nature, but most of the time it is the easiest and has the most predictive power.An example for a description without (gauge) fields can be general relativity. You can either formulate everything in ... | [
"In both cases it is a field theory, just not expressed in a lagrangian formalism."
] |
[
"Why do Newton's corrections to critical pressure and temperature exist for hydrogen and helium?"
] | [
false
] | In my chemical engineering book, we are told to adjust the critical pressure and temperature of hydrogen and helium by 8K and 8 atm when calculating reduced pressure and temperature. Why? Why are the actual values 8K and 8 atm lower? why not just define them as the corrected value? | [
"Someone else may have to correct me on this, but I believe this is related to the Joule-Thomson effect, where helium and hydrogen have anomalous behavior, being very much non-ideal gases.",
"I don't remember enough about the topic offhand to go into it in detail, but I'd read up on the ",
"Joule-Thomson Coeffi... | [
"http://pubs.acs.org/doi/abs/10.1021/ie50523a054?journalCode=iechad",
"This should explain it. So the critical temperature and pressure are not incorrect. However when using critical temperature and pressure in reduced P & T calculations, the resulting relationship between compressibility factor and reduced press... | [
"I don't think they're non ideal",
"This is wrong. Hydrogen and Helium can often by ",
" as ideal gasses, but they do not always behave as such. ",
"In the case of the Joule-Thomson effect, the individual gas particles are interacting with one another, so they are definitely ",
" behaving like an ideal gas.... |
[
"When stirring a liquid clockwise in a glass, how does the liquid move with the straw?"
] | [
false
] | [deleted] | [
"Friction and especially friction because water tend to pull itself once in motion (which is why it clumps into drops). Essentially what is happening is the friction between the straw and objects causes them to move, and the friction with the glass causes it to slow. If the centripetal force is high enough, the wat... | [
"Water polarity has nothing to do here. It's all friction.",
"Do a quick wikipedia search on Dynamic Viscosity if you're interested :) there you'll find insight in the relationship between movement and friction in layers of liquids.",
"The concept is quite weird though. It's counter-intuitive, at first, to thin... | [
"Due to molecular forces between the solid and the fluid, fluids almost always closely obey a 'no-slip' condition near a boundary, meaning that the fluid is moving at exactly the same velocity as the solid right at the interface. You can look at this video for a demonstration:",
"https://www.youtube.com/watch?v=c... |
[
"pregnancy/cancer test for males: why is checking for cancer by looking for levels of 'Human chorionic gonadotropin' not a regular test?"
] | [
false
] | somebody had a male friend who used a pregnancy test which became positive, the community told him to go to doctor to check for cancer, he has a small tumour on one testicle. Turns out that levels can come from cancer. Why is this not a standard tool for diagnostic medicine? (I hope this does not stray too close to giving out medical advice) | [
"Just typed this out elsewhere to kind of the same question:",
"This is completely true and yet it does not at all mean that this is a good way of detecting cancer in men.",
"In medicine, a test is not only graded on how sensitive it is (how likely you are to have cancer and for the test to come back positive) ... | [
"Keeping in mind that HCG (and other tumor markers) can be used to aid in diagnosis and then be tested to obtain a baseline for subsequent monitoring of progression of disease, treatment response and for recurrence. So it isn't that the test is completely ignored.",
"But yes, for the most part tumor markers and s... | [
"Imagine you have a test that has 100% sensitivity, but is only 75% specific. ",
"Now lets for argument's sake assume incidence rate of actual cancer is exactly 5%.",
"If you test 100 people. you will get 5 TRUE positives. and ~25 ",
" Positives. If you test 1000 people, you'll get 50 TRUE positives and 250 "... |
[
"Would a child reach adult intelligence in time if their growth was halted?"
] | [
false
] | If a 3 year old child stayed the same physically for 30 years, would they reach the intelligence of an adult? How much is growth versus learning? | [
"The brain goes through a profound pruning stage during adolescence, and certain brain areas undergo different stages of maturation at different stages of childhood, adolescence, and young adulthood. If those developmental processes were halted, the child would definitely never have an 'adult' brain/mind; however,... | [
"By definition, if a child stayed 3 years old for 30 years their brain would remain the same and therefore would be incapable of the kinds of things older children are normally able to do. If you're asking how much can a 3 year old learn, without the constraints of time, then there would only me marginal improvemen... | [
"What do you mean by \"stayed physically the same?\" If taken literally and fully down to the last atom, obviously not, because the structure of the brain would be exactly the same."
] |
[
"Why do we define the imaginary unit as the square root of -1 and not as another undefined quantity?"
] | [
false
] | What's so special about -1? Why don't we use ln(-1) or 1/0 or anything else? | [
"This is kind of like asking why we define \"2\" as the \"first integer after 1\" instead of \"cos(pi/3)\". The symbol \"2\" is just a picture that we assign to the first integer after 1 for convenience, if we assigned this picture to something else, then we'd have a different object. ",
"\"i\" is just a picture ... | [
"Most highschools are only concerned with computing real roots of polynomials, getting into the real \"meat\" of algebra would fly over >99.99% of high schoolers heads"
] | [
"As someone who has taught college algebra, if my students were remotely interested in learning why things worked, I'd love to talk about that with them in my office hours. In class, there's only a short amount of time to cover a lot of things.",
"I personally try to show the derivation of the quadratic formula, ... |
[
"Can lithium float on tungsten hexafluoride?"
] | [
false
] | [deleted] | [
"No! At least not at atmospheric pressure... ",
"",
"The density of lithium is 534 g/L and the density of tungsten hexafluoride is 12.4 g/L. If you could compress a liter of WF6 to 41 atm or so, and it survived and behaved like an ideal gas and didn't undergo a phase change you might be able to."
] | [
"You could answer your own question with a few seconds googling.",
"Lithium has a density of 534 grams per liter.",
"Tungsten hexaflouride has a density of 12.4 grams per liter as a gas.",
"Lithium is 40 and a bit times as dense. So...No."
] | [
"Sorry haha, i was given false information."
] |
[
"During astronomical night, how much solar radiation reaches the ground?"
] | [
false
] | On a moonless clear night (Sun is below 18° below the horizon and Moon is too dim / too deep below the horizon to cause any effect on the dark night sky), how much solar radiation (including IR, visible and UV) still reaches the ground? | [
"Almost none. The main causes for ",
" (rather than starlight) to reach the ground in true nighttime would be reflection off planets -- especially Venus and Jupiter -- and the zodiacal light, which is sunlight reflecting off dust grains in the solar system.",
"If I'm doing the math right, the largest contribut... | [
"Is it really solar radiation if there’s absorption and re-emission?"
] | [
"Don't neglect airglow from upper atmospheric oxygen & nitrogen molecules recombining from nitrous oxide NO back to O² & N² following a full day of absorbing solar UV"
] |
[
"How do cells in the body become determined and organized correctly?"
] | [
false
] | Apologies if this has been asked before, I searched here and at sciencefaqs and nothing popped up. I'm having trouble understanding the nature of cell determination in the body. My understanding of this is from high school biology so it's patchy at best, but from a single undetermined cell develops a set of different cells. How does the body organise cells in the correct areas, why doesn't a heart tissue cell grow in the liver or on the skin for example? Also, what stops skin cells from spreading into other areas. When the fetus is developing when does cell organisation begin? Is it gradual or instantaneous? Sorry if this is obvious or poorly worded. | [
"http://www.reddit.com/r/askscience/comments/g7p8i/how_do_cells_know_their_location_in_the_body/",
"I liked this answer from user mamaBiskothu",
"Imagine a bunch of kids playing some role-playing game. At least in my country the way it goes is that we just kinda decide who's going to be who, and we start the ga... | [
"Thanks for this! I read through the whole thread and that was the exemplary answer for me as well. It's really fascinating."
] | [
"I will leave it to someone more well versed in developmental biology (it was never my strong point) to attempt a succinct answer, but in the mean time I think reading up on Hox genes is what you're going to want to do:",
"http://en.wikipedia.org/wiki/Hox_genes",
"http://www.nature.com/scitable/topicpage/hox-ge... |
[
"With all the advantages Solar Sails have over Fuel, why aren’t they being utilized more?"
] | [
false
] | null | [
"Deploying a piece of foil a few tens of microns thick spanning kilometers while in 0g is not easy. Even deploying cables is hard. I don't think anything longer than a few tens of meters have been deployed in space (",
", see comment below).",
"They are also not that interesting when you are in Earth orbit beca... | [
"Whats not the same? All I commented on was the statement:",
"I don't think anything longer than a few tens of meters have been deployed in space",
"We have. The shuttle deployed a cable 20km long with a satellite on the end of it.",
"The reason for the deployment isn't relevant to the length."
] | [
"Ah, i missed the part about not even deploying cables in space. I thought we were talking about solar sails, and read your link and was confused. I'm sorry."
] |
[
"Would running with or against the rotation of an artificial gravity ring in space significantly change the effect it had on you?"
] | [
false
] | If this was the case could you completely negate the affect of gravity by sprinting against the rotation resulting in the situation where you were floating in place as the ring was rotating without you. | [
"Yes, you can change the effects of the \"effective gravity\" force by running with/against the rotation of the ring. Whether or not it's a significant effect depends on the ratio of your running speed to the linear speed of rotation of the ring. If the rotation of the ring is fast compared to your running speed, y... | [
"Astronauts running around the \"ring\" in Skylab. The station is not spinning.",
"https://www.youtube.com/watch?v=S_p7LiyOUx0"
] | [
"Also, astronauts demonstrating running around the inside of a circular portion of the space station. Even though the station was in zero-g, they were able to generate enough centripetal force to get the traction needed."
] |
[
"Are we the only animal to have deciduous (baby) teeth, and what is their function?"
] | [
false
] | [deleted] | [
"No, all mammals have deciduous teeth. ",
"Pic",
". Except for elephants and manatees, who replace teeth often, mammals are \"diphyodont\"- have 2 sets of teeth. Other species have several sets of teeth (fish, reptiles) and are called \"polyphyodont\".",
"The function? Teeth don't really grow in size and an i... | [
"Not sure about the function, but I can confirm dogs and cats have them too."
] | [
"Good post...Just some more details to follow up:",
"The basic tooth plan for other vertebrates is a bunch of simple teeth constantly falling out and being replaced. Mammals have complexly shaped teeth which have to fit together closely to work right. In order for this precision fit to happen, teeth can't be co... |
[
"Why doesn’t anybody want to find more stable isotopes of existing elements?"
] | [
false
] | With all the talk about discovering new elements, other elements are just left behind. Take astatine, for example. While it theoretically has a stable isotope, it’s still heavier than any isotope discovered or created. It’ll surely be easier to add more neutrons to astatine than try to make element 119 or 120. With the many, possibly unique properties of the those near the end of the periodic table, it seems like a no-brainer to try and look into those as well as discovering new ones. | [
"We are very interested in discovering new elements, and new isotopes of already-discovered elements. And people are actively working on doing this in labs all over the world, every day.",
"However, it's unlikely that there are any yet undiscovered nuclides which will be stable."
] | [
"Take astatine, for example. While it theoretically has a stable isotope",
"Where did you get that from?",
"We are discovering new isotopes of known elements frequently, they just don't get any attention in the popular press. For elements up to uranium we know all the isotopes near the stable region already. Th... | [
"Bismuth-209 is marked as stable in the graph, but it decays by alpha emission with a half-life of 20.1 exayears. I'm very angry about this oversight.",
"Edit: The half-life was even longer than I remembered!"
] |
[
"What is Quantum Computer? How do they work? What are the differences between that at the computer I'm asking this question from?"
] | [
false
] | And anything else interesting about the field. Thanks in advance! (Just noticed the small derp in my first question and the larger derp in my last. I'm a tired man.) | [
"A quantum computer uses the key concepts of quantum mechanics—superposition and entanglement—to solve some problems more efficiently than a classical computer.",
"At the heart of it, you have quantum (as opposed to classical) bits, which can be realized in many different physical architectures, such as photons, ... | [
"D-Wave is using superconducting circuits using hundreds of qbits to do quantum annealing, which isn't general quantum computation but it is still pretty impressive and useful.",
"They can help with stuff like pattern recognition, protein folding, traveling salesman problems and the like and are quickly scaling u... | [
" explains how they work very well. I have done several research papers on the topic, and the main difference that a user would notice is the speed. A quantum computer is not a linear speed increase, it is exponential. For example, since every qubit exists in both states simultaneously, the equivalent amount of bin... |
[
"If alcohol is so deadly to bacteria, why is it safe for humans to come into contact with?"
] | [
false
] | I have been told alcohol is such a effective disinfectant because it is too powerful for things like antibiotic resistance to apply. If it is do deadly to bacteria, why can I pour rubbing alcohol on my arm and not observe any harmful effects (not even minor skin irritation)? | [
"Alcohol (whether isopropanol or ethanol) will kill almost any cell it comes in contact with. It does this by dissolving the cell membranes which are made of lipids that are not soluble in water, but very soluble in alcohols. It is exactly the same for bacteria and for our cells if the cells are exposed. The factor... | [
"Part of the issue missing from the other responses thus far is what percentage alcohol are we talking about? If I'm working in lab, 70% ethanol is generally considered sufficient to decontaminate a surface. Many hand sanitizers have less than that. And much of what you drink is also less than that. So while yo... | [
"Actually, alcohol is a common irritant in many acne medications. Also, aftershave with alcohol tends to dry the skin out and cause irritation. I am not an expert in cellular biology, but these seem to indicate that, in fact, alcohol does have harmful effects on human skin."
] |
[
"Why are there holes in the ozone layer, as opposed to the ozone redistributing itself around the layer to be equally thin everywhere?"
] | [
false
] | null | [
"This is due to a polar vortex, a rotating low pressure zone above both the north and south poles, that minimizes the air exchange above these regions. The vortex limits the inflow of ozone to the depleted regions. The polar vortex above Antarctica is typically stronger than the one above the arctic, hence the oz... | [
"To be specific, it is because the chemistry that depletes the ozone occurs on the surfaces of tiny ice crystals that only form in high enough concentrations at the altitude of the ozone layer during the late winter and early spring at the center of the polar vortex. In areas outside the center of the vortex the ic... | [
"Looks like the above was not completely accurate. The chemicals condense on the polar ice clouds, but are not active until they are activate by the return of sunlight in the late winter/early spring. The clouds act as traps, gathering the chemicals into high concentrations. Then, when the sun strikes the cloud, th... |
[
"Does a volcano erupting reduce the pressure in other nearby volcanos, or is each magma pocket independent?"
] | [
false
] | null | [
"The majority of volcanoes have independent magma chambers. Usually when magma finds it's way to the surface it's only going to form one volcano, not two.",
"If you've got linked magma chambers then you get what's called a volcano complex. Or a complex volcano. It's kindof a matter of if you want to think of it ... | [
"Thank you for taking the time to answer. I was curious if the magma was a planet-wide pressure system, and if a bit of that pressure was released, it could lower the chance of a volcano erupting on the other side of the world, or at least other volcanos on the fault line (forgive me if that sounds dumb.) It seems... | [
"Reduce may not be the correct word but if you say alter, you’re more on the right track. Take the case of Iceland where Eyjafjallajökull and nearby Katla are independent from each other but have a tendency to erupt within a geologically short time of each other. Katla’s magma chamber is still connected to the co... |
[
"Synthesizing an Acid Halide from an Alcohol"
] | [
false
] | I took an Organic Chemistry midterm today, and did some really funky stuff on a multi-step synthesis problem. I got myself in a situation where in one of the steps I needed to create an acid halide/Ester (Cl-C=O-Oet) from an alcohol (I am guessing methanol, but any alcohol under 4 carbons would work) as one of the steps. Is this even possible???? I missed these points, but I have the feeling that it is possible to do so I am trying to figure out how I can defend myself and get back my A in the class...so far no luck. | [
"You can make ethyl chloroformate. May I ask how you backed yourself into this corner?"
] | [
"Well, if you wanted to start with ethanol, we need to oxidize it a lot to get there. First we could oxidize to the aldehyde using either PCC or a Swern oxidation. Then you could do a Baeyer-Villager oxidation to make the formate. Then KMnO4 oxidation to get the acid, followed by chloride substitution with thionyl ... | [
"Why not just react ethanol with phosgene/triphosgene to give you ethyl chloroformate in a single step?"
] |
[
"Do non-humans exhibit signs of autism/autism spectrum disorders?"
] | [
false
] | [deleted] | [
"I can't answer your question in full. But what I do know is that we regularly create ASD type symptoms in animals for testing/research purposes. So broadly, yes, artificially altered animals can exhibit signs of autism. If you are asking if it is observed to occur naturally, then I am unsure. As a neurologist I ca... | [
"Building off of this, we use animal models that share certain behavioral traits with ASD (altered sociability, stereotypic behaviors, altered communication). But no, the animals aren't said to have autism, as that's anthropomorphizing, but we'll refer to them as a model of autism due to the behavioral phenotype a... | [
"This is a good question and well-worded. Had you asked \"do animals get autism\" there would be no way to answer because an autism diagnosis must be based on human frame of reference. That seems obvious, but it's key to recognize there can never be an autistic animal. As soon as the symptoms leave human context, i... |
[
"Is there an explanation as to why I've dreamt the same dream, with me dying in that dream, 3 times within the past 3 years?"
] | [
false
] | null | [
"Hi ",
" thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the followin... | [
"We can't speculate about this here."
] | [
"Where should I post this? And what does it mean to flair a post?"
] |
[
"In the event of a large scale nuclear war, involving two super powers like the U.S. and Russia, how long would it take for survivors in underground shelters to be able to repopulate the earth?"
] | [
false
] | Basically, I'm interested in how long it would take for the Earth to be habitable to survivors again. I would really appreciate any information you guys can have! | [
"I think you're over estimating the impacts of nuclear fallout. Even if the whole world was targeted, there would be lots of survivors."
] | [
"I do not know why you are being downvoted. Life on earth has survived SIX major extinction already and our nukes now are CLEANER then the ones we dropped on japan"
] | [
"Your figure is dramatically exaggerated. There was nowhere near 1,000,000 deaths from the Chernobyl accident."
] |
[
"Would the DNA taken from my red beard hairs be the same as that from my majority black beard hairs? If so, what makes the red hair red?"
] | [
false
] | My beard consists of 4 or 5 red beard hairs. What is the science behind those hairs? | [
"Gene expression. Just like the DNA sequence in your nerve cells is identical to the DNA sequence in your skin cells, the thing that differs is gene expression. ",
"All the steps of protein synthesis can be regulated to alter gene expression and even rate of protein breakdown can be regulated to alter phenotype. ... | [
"That's so interesting. I've never thought of it like that. I guess my question then is at what level is this change occurring?",
"I don't know very much about biology, so I apologize for asking really basic/dumb questions in advance. The difference between cells becoming skin or hair probably takes place at an e... | [
"The DNA is the instructions on what every kind of cell in the body does. When cells are created, only a small subset of these instructions are actually used by the cell. Small proteins determine which bits get used"
] |
[
"Homosexuality and genetics."
] | [
false
] | null | [
"This question has been addressed several times, please use the search function."
] | [
"Thank you. I found a lot about the genetic side. Has there been anything on the behavioral side? This post is stemming from a discussion when we realized all of our gay friends have rough childhoods (various abuse, absentee fathers). Is there any research correlating abuse to homosexual tendencies? "
] | [
"It's out of my field, but there may have been comments related to it in the history of /AskScience, maybe search some more, if you can't find anything, feel free to post a question, and mention that you did a search, it will help us mods approve the question."
] |
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