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[
"Why do the strong and weak fundamental forces have a limited range?"
] |
[
false
] |
This is something which has bothered me for a while now. I mean, both gravity and electromagnetism (the forces that are more familiar in everyday life) have an unlimited range (e.g. you can feel the gravitational pull of something no matter how far away from it you are), but the strong and weak interactions apparently drop off entirely beyond a range of 10 or 10 meters or so, respectively. Like, if you were to graph the strength of these forces versus distance, would they suddenly drop to zero after you reached a certain point? Or do they just drop off so quickly that we say they're effectively zero after the distance becomes large enough? In other words, how do these forces behave with respect to distance?
|
[
"The strong force range is based on the amount of energy needed to isolate a particle with a bare strong/colour charge.",
"Specifically, the strong force - unlike the other forces - gets stronger with distance. The potential energy stored in a bare colour charge therefore also increases with distance. Eventually, you will have imparted so much energy into separating the particles with strong charge that hadronization occurs - all of that potential energy stored in the system results in the creation of quark-anti-quark pairs that string together the colour charge and neutralize both of them.",
"A good analogy would be what happens when there are two very, very strong electric potential plates in air. The air ends up ionizing (see lightning, for example).",
"Here is a Wikipedia article on Hadronization: ",
"http://en.wikipedia.org/wiki/Hadronization",
"As for the weak force, that is short ranged for a very different reason. The weak force is short ranged because the mediator particles - the W and Z bosons - are both very heavy, and very unstable. They decay rapidly. As a result, their effective range is much shorter.",
"Gravity/EM forces decay as 1/r",
" right? Imagine multiplying an e",
"r/R0",
" to that. 1/r",
" decays pretty fast, but e",
" decays much, much faster! And that e",
" results because the unstable W/Z bosons decay so rapidly."
] |
[
"Two addenda:",
"(1) Massive particles lead to short range forces whether or not they are unstable. (That exponential ignatiusloyola refers to drops off over a distance inversely proportional to that mass.)",
"(2) The explanation by ignatiusloyola addresses why the fundamental strong force is short range. But there is also a residual strong force. The fundamental strong force gets stronger as distances get larger, leading to ",
". Confinement causes quarks (and gluons and antiquarks) to form composite particles, like protons and neutrons, about 10",
" meters in size. It is the residual strong force that binds protons and neutrons together in nuclei (overcoming the electrostatic repulsion of the protons). This force is mediated by particles such as pions; these are massive, and so the residual strong force is short range, dying out rapidly over distances more than that of a nucleus or so."
] |
[
"Anyone who wants a more substantial answer should refer to Zee's Quantum Field Theory in a Nutshell. The calculation that shows massive particles correspond to exponentially decaying forces is one of the first done in that book and can be done with an understanding of undergraduate quantum mechanics and a strong background in calculus (in particular if you can derive the gaussian integral's value, you could probably do it)."
] |
[
"What is the difference between Δ, δ, d and ∂ when used in math and physics?"
] |
[
false
] |
I have never quite understood the difference between Δ, δ, d and ∂ when it comes different equations and formulas. I've understood that has to do with derivatives and infitesimal changes and whatnot, but I would like to get a better understanding of the differences.
|
[
"'",
"' -- means a change in some variable. This makes it a difference operation: ",
".",
"'",
"' -- means an 'infinitesimal' change, or a \"",
"differential form",
".\" It's kind of like a limit as ",
" -> 0, but it is compatible with relative rates or different kinds of limits, so that the notion of a derivative is preserved (in the form dy/dx, for example.)",
"'",
"' -- means a ",
" differential. It's basically the same as ",
", except it also tells you that there are other related variables that are being held constant. In other words, it is never a complete picture. It's typically used in ",
"partial derivatives",
" -- derivatives that are only in one dimension of a larger dimensional space.",
"'",
"' is just a lowercase ",
", and its meaning depends on context. Usually it means an 'infinitesimal' change like ",
", but when you don't want to talk about differential forms or derivatives using the other notations.",
"So, they all mean roughly the same thing by themselves (except for ",
", which is a simple difference.) Together, they help provide a context and subtle details about the problems being addressed. Most of these are a matter of convention."
] |
[
"It's also common to see δ used to refer to a variational derivative."
] |
[
"'∂' can also mean a boundary of an area in topology and this leads to some annoyances in multidimensional calculus if you aren't paying attention to the context. "
] |
[
"Why, and how, does a combination of isopropyl alcohol and salt, plus a lot of shaking, remove the resin tar from the inside of a water pipe?"
] |
[
false
] | null |
[
"Isopropyl alcohol is a good solvent for resin/tar. Salt is not very soluble in the alcohol and acts as a scrubby abrasive that can get into every curve and crevice, while not being hard enough to scratch up the glass. You could use isopropyl alcohol and sand and it would clean great but scratch the glass over time. ",
"Plus the salt easily and cleanly rinses away in water after you're done cleaning (vs something like sugar)."
] |
[
"This is the correct answer. ",
"Just for fun, you can shine up dull coins and metal with vinegar and salt. For the same reasons."
] |
[
"You could use sugar, but if you don't fully rinse it out then the inside of the glass pipe will get sticky and dirty faster. Since salt is not very expensive, there's no reason to use sugar.",
"Some people use rice, which seems like it absorbs some of the tar and is also abrasive. However rice can get stuck in small openings or even just to the inside walls, so I think salt is still a better option."
] |
[
"How far underground do you need to go for the earth's crust to not be affected by seasonal changes in temperature?"
] |
[
false
] |
To put it another way: how deep down should we dig to not be able to tell if it's summer or winter?
|
[
"About 50feet (15meters) down in our latitude.\nIt should be deeper in the north, but might get shallower again when we reach permafrost regions. (i have to think about that!)",
"You wont have to dig at all at the equator for obvious reasons. ",
"source: im a geothermal engineer + ",
"http://www.renewables-made-in-germany.com/en/start/geothermie.html"
] |
[
"visit a salt-mine and be amazed about the relative insignificance of surface-temperatures..."
] |
[
"Yup. You've probably heard of a root cellar. They work on this very idea. They're not often that deep, but as you go further into the ground, the temperatures get more consistent. I'm guessing you didn't grow up in a house with a basement. "
] |
[
"Is there something tangible in the brains of serial killers and the like that separate them from people that can comfortably function within the confines of societal rules?"
] |
[
false
] |
Obviously there are people that murder out of desperation -- I'm excluding them. What makes a mass murderer different neurologically, say, from me who cannot imagine taking another person's life because it just seems ? Doesn't the "triad of sociopathy" (bedwetting, pyromania, cruelty to animals) point to a problem that could maybe be recognized on a cat scan?
|
[
"Doesn't the \"triad of sociopathy\" (bedwetting, pyromania, cruelty to animals) point to a problem that could maybe be recognized on a cat scan?",
"Well, psychopathy couldn't really be seen on a CT scan as that type of neuroimaging has relatively poor ability to visualize the structures of the brain. ",
"However, there is evidence of structural differences on MRI, (which has better ability to visualize the structures of the brain) and on functional MRI which (obviously) looks at the function of the brain. One of the more well replicated findings has been in structural volume differences in the ",
"amygdala",
", a region of the brain known to be associated with the fear response (i.e., psychopaths may not experience fear to the same degree as others). Functional neuroimaging studies have shown differences in neural activation in ",
"frontal and temporal regions",
" of the brain, as well as some studies showing more specific differences in areas of the brain known as the reward circuitry (i.e., differences in behavior needed to produce pleasure/reward feelings). ",
"There's a lot of research being done in this area, and a lot of interesting information is coming out, however we are a LONG way from being able to scan someone's brain and tell that they are or are not a psychopath (though the department of defense is funding this type of research... I may or may not be involved). I'm not sure that thing will ever be possible, but it is something that's being investigated."
] |
[
"do you personally think that it has more to do with nature or nurture?",
"It doesn't matter what I personally think, it matters what the research says. At this point my (somewhat limited) understanding of that literature suggests that both are likely involved, but I don't think enough research has been done to fully understand either, less research has been done on the genetics, however and this is needed before the pathogenesis can fully be understood."
] |
[
"He's also written a book called, The Anatomy of Evil. I daresay the read is better than the watch."
] |
[
"Do colors exists in the real world, or is it something our mind does in response to lights of different wavelengths?"
] |
[
false
] |
[deleted]
|
[
"You can get into semantic arguments about this, but I would say that wavelengths of light are physical phenomena, while colour relates to human perception of that light.",
"A human typically has three colour receptors in their eyes, which cover overlapping bands of wavelengths. We perceive colour by how much each of these three receptors respond to different combinations wavelengths of light. The reason there are three primary colours is because of these three wavelength bands - it's entirely a matter of human biology, and nothing inherent about light.",
"The receptors respond to broad overlapping ranges of wavelengths, so light of one wavelength can tickle more than one receptor. You can \"fake\" light of one wavelength with light of more than one wavelength, if you place things just right so that it excites the receptors in just the same way. For example, if one receptor responded to blue to green, while another responded to green to yellow, then green will excite them both, but if you send a combination of blue and yellow light, then that will also excite them both and look green.",
"So, \"blue and yellow make green\" is more of a statement about human biology than the physics of light. Other animals, and even some humans with slightly different eyesight, will see different colours combine in different ways. So, I would say that yes, colour is somewhat arbitrary, and isn't something inherent in the physics of a particular wavelength.",
"This is why, when telescopes make \"false colour\" images, it's not like they are intentionally making up stuff to look pretty. It actually takes effort and design for a digital camera to produce a colour image that looks like what a human would see, and it's not always perfect (sometimes you actually need to photoshop something to make it look like it actually looked). We can combine telescope data of different wavelengths arbitrarily to make a colour image, because human colour vision is pretty arbitrary to start with."
] |
[
"You can get into semantic arguments about this, but I would say that wavelengths of light are physical phenomena, while colour relates to human perception of that light.",
"This is basically it. To answer the OP's question, wavelengths exist in the real world, and colours are what our brain \"perceives\" in response to light coming through our eyes.",
"I mention this because you sometimes see statements like \"pink isn't a real colour because it doesn't exist on a rainbow\", which is nonsense. Colour is about human vision. If you see something as a distinct colour, it ",
" a distinct colour. "
] |
[
"It's true that each single wavelength of light will be read by your eye/brain as a specific color. But some colors that you perceive don't line up with a single wavelength, only a combination of wavelengths (e.g. magenta). And there are multiple combinations of wavelengths that you will perceive as the same color. A sodium vapor lamp only emits photons very close to 590 nm, but when your monitor tries to show you ",
"what that looks",
" like it emits a combination of longer and shorter wavelength photons (i.e. red and green light) to create the same effect in your brain.",
""
] |
[
"If the Earth's gravity has caused most of the iron on earth to \"sink\" to the core of the Earth because of its mass, would that also mean most of our supply of precious metals like gold, platinum, and uranium are also in the core?"
] |
[
false
] | null |
[
"Density is NOT the only sorting parameter. Chemical affinity/behaviour is also really important.",
"The elements that get concentrated in the core are what we know as siderophile elements; basically they concentrate in iron, and therefore are associated with iron in the differentiation process which separated the layers of Earth. Those elements include gold, copper, iridium, manganese, nickel, platinum and others.",
"Uranium is a great example of an element which is certainly present in the core (and more so the mantle), although not necessarily in high concentrations, but which is concentrated in the crust. ",
"Because Uranium is a large ion element (in fact, one of the 'Large Ion Lithophile Elements', it does not easily get included in mineral structures (it is 'incompatible'). As a result, Uranium is one of the last things to crystallise out of residual melt, meaning it has a higher chance of being incorporated into the last-forming rocks (i.e. it tends to get transported all the way up to the crust along with all the silica and other incompatible elements"
] |
[
"So somewhat the same mechanism, except reversed, as how hydrogen should be nonexistent on earth due to its density(like helium is), but because it forms a dense compounds with carbon/oxygen/etc, we have plenty sitting around?"
] |
[
"Yeah, not a terrible analogy."
] |
[
"Is it possible to create an evolving program?"
] |
[
false
] |
Would it be possible to create a program that evolves by adding a random set of code from a library to its own coding as it duplicates? Essentially creating a simple program with no commands beside mutate, survive, duplicate. (cell.exe) Then create a separate program (darwin.exe) that checks the offspring programs for desired traits, and deletes the undesired traits before the next generation is duplicated. Essentially you'll have created the digital equivalent to a protein and an environment for it to evolve in and eventually you will have lots of completely unpredictable and complex programs. Even AI.
|
[
"Yes indeed, the ",
"Lisp",
" language contains a command to run a list as a program and lisp programs and data are just so lists. Other programming languages contain equivalent evaluation functions.",
"Your idea for a self-evaluating ",
"evolutionary algorithm",
" might run into difficulty because such an algorithm has to include a ",
"fitness function",
" to weed out all of the nonsense results generated by your random mutation. The fitness function is the ",
" equivalent of natural selection and it is responsible for the direction in which the algorithm evolves. You can get evolutionary algorithms to solve almost any problem, but only if you can define and code a relevant fitness function. "
] |
[
"eventually you will have lots of completely unpredictable and complex programs.",
"You were right until you got here.",
"Evolutionary algorithms are not used to create arbitrary programs. You'd quickly end up with far far far far too many programs to simulate and manage. Instead you use it to find a ",
" program that does some specific thing you want. This can be a useful tactic for automated bugfixing but it isn't going to automatically produce some Strong AI."
] |
[
"Almost certainly not. You need selective pressure. In the real world, things that don't reproduce don't pass on their genes. But in this evolutionary system, an algorithm decides what programs should get to \"pass on their genes\". This means you use test cases to see which programs get you closer to your goal and you need a well defined goal.",
"Your system seems to want to just produce programs willy nilly and see what happens. This means either no selective pressure (don't cull any programs) or random selective pressure (choose a random subset each time). The first option produces too many programs and becomes impossible to use. The second option doesn't produce meaningful programs because the enormous majority of randomly generated programs are meaningless.",
"Consider how your system is any different than simply enumerating all possible programs. It really isn't. You are just enumerating them in a weird order. Obviously enumerating all possible programs to see if anything interesting pops up is not feasible, so why should your approach be feasible?"
] |
[
"What is the most recent common ancestor of human and any other currently living animal for which we have physical remains?"
] |
[
false
] |
I am asking because i got asked in a debate about evolution for an example of a fossil of human and chimpanzee common ancestor. I understand that fossilizing is a rather rare event, combined with a chance that it would happen to one of our direct ancestors makes it very unlikely. But can somebody explain better why, if there is none?
|
[
"We don't have fossils of the MRCA, but it's estimated to have occured 5-7 million years ago based on genetic studies.",
"We have three possibilites for MRCA that has fossil remains- ",
"Ardipthecus",
", ",
"Sahelanthropus",
", and ",
"Orronin",
"."
] |
[
"I am assuming that you are talking about MRCA of human and chimpanzee. What about other animals. Is there a fossil about which can be said that it was our ancestor (not necessarily MRCA) and we share it with other animals? "
] |
[
"Tiktalik I think thats how its spelled was one of the first amphibians, but whether we are directly related to any fossilized individual is highly unlikely, however i believe it is reasonable to assume that our direct ancestor would be geneticlly very similar to tiktalik. "
] |
[
"How do we know electrons are negatively charged?"
] |
[
false
] |
And likewise, how do we know that protons are positively charged? And if it was proven that they are charged that particular way, what experiment was used to find this out? I was thinking about this in my chemistry class today and I realised that we were never explained why they were given that charge.
|
[
"It's known they have opposite charge. Which one is called which is an arbitrary convention."
] |
[
"Generally, it doesn't matter at all: it is what physicists call a symmetry (in particular, C-symmetry). You can swap charges between electrons and positrons and noone would bat an eye - every process in the known universe would stay the same, except for a single case: weak interaction, which ",
"violates that symmetry",
"."
] |
[
"The experiment used to identify the charge of the electron and proton were done by J.J. Thompson and Wilhelm Wien in the late 1800s.",
"In short Thompson's ",
"experiment",
" observed the deflection of a cathode ray that s passed through an electric field. The ray's deflection was always towards the cathode (positive charge), thus Thomson determined the cathode ray to be negatively charged. Later the ray a CRT was shown to be a beam of electrons. Thus electrons were known to be negatively charged.",
"Wien was working with an early form of plasma, then called a ",
"canal ray",
", today we would call this a anode ray. Plasma is simply gaseous atoms which have been stripped of electrons and thus positively charged. Wien's ",
"experiment",
" was similar to Thompson, except these particles were repelled by the cathode. Thus these particles (atomic nuclei) were positively charged. ",
"It is pretty fascinating considering how little scientist had to work with back then.",
"It is true that the charge names for electrons (negative) and protons (positive) are arbitrary, and the important note is that they are opposite. "
] |
[
"What factors determine the lifting force of a hot air balloon?"
] |
[
false
] |
Edit: What I should have specified is: how do factors such as lateral surface area of the balloon and volume of the balloon relate mathematically to how fast the balloon rises, or how much buoyant force the balloon has and mathematically how might one calculate the "minimum" volume/lateral surface area or other features to minimize actual surface area (aka: "production costs") of the balloon? Or how much a hot air balloon can lift. In our engineering class, we were challenged in groups to build a balloon out of basically tissue paper and glue that would be able to carry a GoPro to the top of our gym (~170g). As of now, our balloon actually works (yay!) But being high school students we pretty much have no clue how (we aren't aerospace engineers... Yet). Would someone explain how this works? On paper, our balloon has the shape of an upside down square pyramid, if anyone's interested (base ~5m*5m, height ~5m, bottom vertex cut out to fill balloon with). If you'd like more details I can provide them!
|
[
"The reason balloons float in general is the ",
"bouyant force",
". When the balloon as a whole is less dense than the air around it, the air pushes it up with a force equal to the weight of the air the balloon displaces. Helium balloons are lighter than air because helium is a lighter gas than nitrogen and oxygen, which make up the majority of our atmosphere.",
"Hot air balloons are slightly different, because the gas inside them is (mostly) the same mixture as the gas outside. However, the air follows the ",
"ideal gas law",
" pretty closely, so hotter air is less dense than cooler air.",
"The factors that determine the lifting force are the density of the gas in the balloon (determined by the mix of gasses and their temperature and pressure), the size of the balloon, and the weight of the material the balloon is made out of."
] |
[
"Buoyancy force scales with density difference and volume.",
"The lifting force is the difference between the buoyancy force and the weight of the balloon, which depends on how it's made.",
"The terminal velocity of the balloon (rising) is a balance between the lifting force and drag with the air, which scales with the cross-sectional area (as viewed along the direction of motion).",
"The highest buoyancy force/weight will be for spherical or nearly spherical balloons. However, drag will be reduced by making it slightly elliptical."
] |
[
"Thanks to your reply! What I should have specified is: how do factors such as lateral surface area of the balloon and volume of the balloon relate mathematically to how fast the balloon rises, or how buoyant the balloon is and mathematically how might one calculate the \"minimum\" volume/lateral surface area or other features to minimize actual surface area (aka: \"production costs\") of the balloon?"
] |
[
"What is the largest stable molecule known? What molecule has the largest number of unique elements contained within it?"
] |
[
false
] | null |
[
"To answer part of your question, things like proteins, fats, and DNA strands are just very large molecules known as macromolecules. The largest known protein is Titin. It has the chemical formula C169723 H270464 N45688 O52243 S912.",
"Some notably large macromolecules are found in the human genome. The genome contains 3.2 billion base pairs which can be seen ",
"here.",
" That would amount to almost 100 billion atoms!",
"But to answer your question in full, ",
" A flawless diamond is just considered one big molecule! Whenever you have the biggest, you can just make it bigger.",
" For more info, see: ",
"http://www.newton.dep.anl.gov/askasci/chem03/chem03401.htm",
" "
] |
[
"technically speaking, following vulcanization, the rubber in a car tire could be considered a single molecule",
"http://en.wikipedia.org/wiki/Vulcanization"
] |
[
"Considering that the tire rubber has a number of low MW additives (antioxidants, antioxonants...) which are not part of the vulcanization scheme, yes, the rubber of a car-tire is not a single molecule.",
"But at the same time, the concept is correct. There are endless number of very large objects that are crosslinked and have molecular weights that are measured in units of kilograms."
] |
[
"Why can't we continue to bombard fission products with neutrons to end up with products that have shorter half-lives and/ or are less dangerous?"
] |
[
false
] | null |
[
"We can do that."
] |
[
"So why don't we do it all the time?"
] |
[
"It's still in the R&D phase. We can't do it for many kilograms of material yet."
] |
[
"Are humans the only species that (sometimes) feels remorse/empathy when members of other species die/suffer?"
] |
[
false
] | null |
[
"Lots of other animals appear to mourn their dead, especially primates. ",
"Here's a video",
" of a chimpanzee mother that is clearly upset that her child is dead. And ",
"a mother elephant",
" tries to save her baby calf and appears to be showing what we would call empathy. ",
"I think people seriously underestimate the intelligence/emotional capacity of animals. ",
"Edit: I saw that you clarified what you meant under Fluffeh's post but I'll leave the links anyway because I think they're interesting. As for your question, I'm not completely sure but I do have the anecdotal evidence that I've had dogs that clearly understood that I was in pain, both physical and emotional. I wouldn't be surprised if there were some (limited) emotional understanding between different species of mammals. "
] |
[
"Koko & All Ball",
" is one instance that spring to mind. Then in relation to Ryguythescienceguy's point about dogs and man there is, for example, the case of ",
"Greyfriars Bobby",
". Both pretty anecdotal though."
] |
[
"The key point here is appear. Female chimpanzees and some monkeys (such as geladas) are known to carry around dead infants - in some cases for days, well after the body has begun to decay. At the same time, anecdotes (which do not count as evidence) of primates helping injured or sick group members besides their immediate kin are rare. It is very hard to extrapolate any animal behaviour to emotional drives or state of mind. We do know that many primates are able to deceive, which means they do have some ability to predict or understand what another might be thinking. This is theory of mind, and likely underpins human sympathy and empathy. Numerous studies show that children do not develop this capacity until well into the toddler years."
] |
[
"Is biological evolution driven by isolation?"
] |
[
false
] | null |
[
"[biological] evolution is driven by isolation",
"If by isolation they mean gene flow, then yes it has an effect; though, it's certainly not the only factor. You also have to take into account a number of other variables, including selection, population size, genetic drift, mutation rates, etc."
] |
[
"To me, that sounds like an attempt to use population genetics to justify a personal political/cultural view. ",
"That being said, it ignores the fact that migration is an important source of variation. It can introduce novel alleles that could be beneficial for the recipient population (and vice versa), ones that would otherwise have to arise via mutation, which is far less likely. "
] |
[
"I hesitate to give a definitive answer because - as I mentioned earlier - there are many variables that must be considered. If we make assumptions regarding these factors (e.g., no stochastic events, which can have a huge effect on small populations, etc), then it would boil down to time frame. In the short term, beneficial alleles would propagate quickly. However, since the population is isolated and we're assuming no other outside forces, the only source of variation is via mutation (and since there are few individuals, that source is inherently limited by both numbers and time). While a more beneficial allele may arise eventually, it is more likely that it would be introduced from some outside population."
] |
[
"I've heard multiple times recently that our classic model of the atom isn't actually what atoms look like, what exactly do people mean by this? What do atoms (really) look like?"
] |
[
false
] |
[deleted]
|
[
"Typically this stems from a model of the atom depicting electrons as inhabiting a distinct path around the nucleus. This is not the case. Electrons do not follow a path, or even move in a way you and I would be familiar with. Rather the electrons can be modeled in terms of probability. A model which captures some of this (better than the classical model) would be to delineate an 'electron cloud' or a region in which the electron is likely to be found with x probability."
] |
[
"In addition to probability of where it is, depending on the energy level of the electron, it will follow a different probability cloud pattern than those with different energy levels. So say, you have an atom of lead, those electrons which are housed in the lowest energy level (or on average closest to the nucleus, form a pretty neat little shell around the nucleus. But some of the other, higher energy, electrons, have very weird shaped probability patterns. View more about it here: ",
"https://www.khanacademy.org/science/chemistry/orbitals-and-electrons/v/more-on-orbitals-and-electron-configuration",
"Also, in terms of scale, realize that the nucleus is on the order of hundreds of thousands of time smaller than that of the \"size\" of the atom as a whole. And the size of an electron is tens to hundreds of times smaller than the nucleus. For scale, on a Hydrogen atom, if the single proton was the size of the sun, the electron would be roughly the size of Jupiter and orbiting about 5 times as far from the sun as Neptune is."
] |
[
"A proton is made of three quarks, with charges 2/3, 2/3, and -1/3. These quarks are pretty tiny, much closer to electron mass than proton mass. The proton gets the bulk of its mass from the gluon binding energy that keeps the quarks together. So the electron does have more 'oomph', but not by too much. "
] |
[
"How did monkeys get to the New World?"
] |
[
false
] | null |
[
"Primatologist/biologist here. Rafting is the most currently plausible theory, as /avec_aspartame stated. Here is something to think about if this sounds implausible: All Platyrrhines (new word monkeys) are monophyletic. This means that they all share a common genetic ancestor, and the extant evidence points to ~35 million years ago. What can be inferred from this is that a single, ancestral population arrived in the \"New World\" and that all subsequent extant NWM species are derived from this common ancestral species. The prevailing theory is that a large storm probably swept trees or vegetation containing this ancestral population into the ocean, and it drifted to South America, where the ancestral population took root, spread, and diverged into many species over millions of years. ",
"Other theories have been advanced, including via land bridges across the South Atlantic (purely speculative) and the Bering Sea (plausible... this land bridge was open at various times through history depending on sea level... but a lack of fossil evidence as well as the climate data makes this unlikely). ",
"Lemurs, primates endemic to Madagascar (the group I study), arrived there in a similar manner. We know this because lemurs, like NWM, are monophyletic, and Madagascar has not been connected to the mainland since long before primates evolved. ",
"See: Molecular clocks keep dispersal hypotheses afloat: evidence for trans-Atlantic rafting by rodents. Journal of Biogepgraphy.",
"Diane L. Rowe1,2,*,\nKatherine A. Dunn3,\nRonald M. Adkins4 and\nRodney L. Honeycut\n",
"The tempo and mode of New World monkey evolution and biogeography in the context of phylogenomic analysis. Molecular Phylogenetics and Evolution. ",
"Natalie M. Jameson Kieslinga,\nSoojin V. Yib,\nKe Xub,\nF. Gianluca Speronec,\nDerek E. Wildman\n"
] |
[
"It's worth noting that the Atlantic was somewhat narrower 35 million years ago. Still wide, but not ",
" wide."
] |
[
"Probably through a rafting event. During strong storms and floods, large sections of wetlands can be ripped free and set adrift. Under favourable conditions, such rafts can cross more than a thousand miles of ocean. ",
"South America and Africa were ~1,000 kilometres (600 miles) closer than they are today. Sea levels were also lower which may have exposed islands in between the continents to break up a long journey into smaller steps. It's plausible that such events were responsible for the introduction of not only old world monkeys, but rodents as well. ",
"If this seems really unlikely, keep in mind we have millions of years to work with and a successful crossing only needs to happen once. ",
"edit: source is my memory of Dawkin's Ancestor's Tale."
] |
[
"How do network lines carry more than one signal?"
] |
[
false
] |
My basic understanding of the internet is as follows: information is broken down by the client into bytes and put in packets with an address, then sent onto the wires transferring them. The server reads the wire and finds the packet, looks where it's supposed to go, then puts it on the proper wire and the end client reads the wire and finds the packet there, unpacks it, and the message has been transmitted. But surely there can't be a direct line from every single network connected to the internet straight to an ISP's servers. They must be combined somehow, but then how can all of the packets be sent to where they need to go? If they go one after another, the network gets backed up with traffic, each client waiting to see a packet for them on the wire. If they all go at once, they surely just blend into noise, as there's no good way to tell which bit belongs to which packet. Is this not how information is transmitted over the internet? If it is, how big of a problem was this to early designers of the internet, and how was/is it solved?
|
[
"My basic understanding of the internet is as follows: information is broken down by the client into bytes and put in packets with an address, then sent onto the wires transferring them.\nThe server reads the wire and finds the packet, looks where it's supposed to go, then puts it on the proper wire and the end client reads the wire and finds the packet there, unpacks it, and the message has been transmitted.",
"That's a pretty good high-level overview.",
"surely there can't be a direct line from every single network connected to the internet straight to an ISP's servers",
"Indeed, that would be too expensive.",
"Instead, we organise our hosts into smaller networks. The gateway to those networks is a ",
"; the router knows the networks (",
") it serves and it can route (IP) packets to. Subnet information is part of the IP address, and can be ",
"determined",
" by looking only at it.",
"The routing process is thus organised; each router knows ",
" to forward packets that are destined for any given subnet. The processes by which routers acquire this information can be either a static configuration (aka. \"static routes\") or dynamic ",
"cooperation",
" with other routers.",
"They must be combined somehow, but then how can all of the packets be sent to where they need to go?",
"Each host and routers, as described, only needs to know where to send packets for a given IP subnet. If you're using a DSL router, for instance, it knows to forward all packets destined to your internal subnet to the local devices connected to it (your WiFi clients, desktop PC, etc.), and all the rest to a ",
", which is typically one of your ISP's routers.",
"If they go one after another, the network gets backed up with traffic, each client waiting to see a packet for them on the wire.",
"Physical links are mostly parallel; multiple symbols of a packet are coded and transmitted over the channel. You can look up the term (signal) 'modulation' if you want to find out exactly how bits in a packet end up encoded as symbols on a wire.",
"You're right that multiple packets can't be transmitted simultaneously. [1] Forwarding a packet at a router will necessarily incur a delay for the packets that follow. The sum total of these processing and forwarding delays between two end hosts on the internet make up their connection ",
".",
"how big of a problem was this to early designers of the internet, and how was/is it solved?",
"Historically speaking, I don't know. There was a lot of work gone into the development of the ",
"Internet Protocol",
", and at the same time it was designed to be as simple as possible. Once it went into effect and deployment of higher-level facilities happened, the characteristics of internet traffic started to shape the characteristics of our networks. Today, a large amount of research is dedicated into modelling traffic patterns and understanding their effects, in order to reliably evaluate network protocols in our deployments. It is , therefore, an ongoing process. From this process we attempt to extract simulations which we can use to evaluate potential replacements, and so forth.",
"On the other side of the IP coin is the stack of protocols and processes used to encode information on a physical medium. These are also in constant flux and development as we develop faster transmission media, like fiber optics. Here we have a different set of problems like how to conserve power, how to synchronise data transmission between two unsynchronised endpoints, how to best take advantage of the channel bandwidth and minimise noise, how to perform error detection (& possibly recovery), and so forth.",
"Hope this helps, even if it seems a bit vague. Ask away if you want more detail on something.",
"[1] Well, ",
". There are cases where packets are just dumped into a stream, which is then transmitted without consideration to packet boundaries. So, ",
" might be transmitted simultaneously over a given wire."
] |
[
"What you're missing is that there's usually not a direct connection to a physical server, packets on the Internet often go through over a dozen ",
".",
"Each router is basically a special purpose computer system which has several physical jacks for connecting network cables. The router matches the address in the packet against a table which can be programmed by the network administrator. Based on the contents of the packet and its programming, the router will send the packet out over another jack.",
"So the Internet isn't a bunch of dedicated lines directly connecting clients and servers, it's a connected graph of nodes and links. Nodes with a single link represent endpoints such as clients or servers -- those are the systems most people use every day. Nodes with multiple links are routers. Routers tie multiple other systems together -- a router may simply transmit packets between endpoint systems directly connected to it, or it may forward a packet to a second router. The second router may forward the packet to a third router, and the third to a fourth, and so on until it finally ends up at its destination.",
"If they go one after another, the network gets backed up with traffic, each client waiting to see a packet for them on the wire",
"This is why packets are small. A 1500 byte packet is 12000 bits, at 1,000,000,000 bits per second (most wired networking equipment manufactured in the last decade is at least this fast), you can send 83,000 full sized packets per second.",
"One critically important, fundamental design choice of the Internet is that ",
". If some router's link becomes overloaded and outgoing packets start to queue (or if a customer's traffic exceeds the bandwidth they're paying for), the router may drop packets. It's the responsibility of endpoints to notice that packets are being dropped and handle it accordingly.",
"The TCP protocol (used by most applications, including webpages) builds a ",
" delivery on top of an unreliable network that may potentially reorder packets. TCP adds ",
" in a packet's data field, the receiver can detect a missing packet and request re-transmission of the lost packet(s). When a sender's notified their packets are being lost, it will immediately decrease its transmission rate. When all packets arrive in a timely manner, the sender will slowly ramp-up its transmission rate and the number of simultaneous packets allowed to be \"in-flight\". So the application data packets themselves continuously probe the network conditions and allow the transmission speed to self-balance to use most of the available bandwidth while avoiding congestion.",
"If they all go at once, they surely just blend into noise, as there's no good way to tell which bit belongs to which packet",
"As long as you have a device which can cause bits to travel over a link, Internet protocols (TCP, IP) don't really \"care\" about how the bits are physically transmitted. The link can physically consist of wires, or radio signals (wifi), or fiber optics, or telephone lines (DSL or old-school dialup modems). Some of these allow physical means to transmit multiple bits at once -- for example using different frequencies of light or sound."
] |
[
"Ignoramus checking in. Is 'mulitiplexing' still used? Idle curiosity."
] |
[
"Can animals really predict disaster ahead?"
] |
[
false
] |
[deleted]
|
[
"The seizure sniffing dogs are a legit thing. They're a form of service animal that are ",
" highly trained. I saw one assisting his \"owner\" (for lack of a better word in this context). About a minute before the guy started to seize, the dog did something (I didn't notice the signal, but apparently the guy did) to indicate that the seizure was about to start, the guy let me know what was about to happen and took a moment to roll his wheelchair over to an area with low foot traffic. The dog then kept guard on him for about a minute and a half while the seizure was happening, picked up the guy's dropped water bottle and put it back in his lap and gently nuzzled his hand once the seizure was ending. So, yeah, anecdotal, but totally legit.",
"As for animals detecting earthquakes, there was a really interesting segment on River Monsters where a Japanese scientist was studying the Nomazu catfish for signs of responses preceding earthquakes. Apparently, they will swim away from the bottom of the lake preceding an earthquake. I'm not sure how scientifically accurate the study was, as the fish were in tanks, but the implication and (presented) evidence seemed pretty strong to me."
] |
[
"It's a numbers game. Let's say you have 1000 pet owners in a town. Every day, 10 random pets are going to behave oddly for some reason - not important which. The owners most likely will shrug or maybe tell their friends about it over dinner. ",
"Now let's say we have an earthquake. Of those 10 pet owners maybe 2 will understand statistics and 3 won't care, but it's a fair bet you'll have 5 people telling everybody who'll listen that \"The morning before the earthquake my cat just couldn't sit still! I have no idea what got into her, she must have sensed the earthquake coming.\""
] |
[
"This paper studied a case where a number of toads left their breeding pond for higher ground a day before an earthquake. ",
"It suggest that they were able to sense the release of certain ions from the rock below and move away from the pond before the water became potentially toxic due to a change in PH as a result of the earthquake. ",
"Granted they based this study off one abnormal mass movement of toads and that is simply not enough to definitely prove anything, their explanation and resulting research into the subject provides some interesting methods by which animals could sense an impending earthquake. ",
"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3138006/pdf/ijerph-08-01936.pdf"
] |
[
"What is the rate of formation for Uranium 235 in relation to Uranium 238 and how do we know?"
] |
[
false
] |
In supernovae, where Uranium 235 and Uranium 238 are formed, how much Uranium 238 is formed in relation to Uranium 235? And More importantly, how do we know why this is the case? As far as I know: When working out the age of the earth you have to know what the rate of formation are for the different nuclear isotopes so that you can use their different rate of decay to calculate the age of the earth.
|
[
"The ratio of production of U-235 to U-238 in supernovae is roughly 1.65:1, however, this isn't relevant to radiometric dating.",
"Radiometric dating works through processes that cause elemental separation which then makes it possible to measure the amount of time since that separation occurred. In the case of Uranium dating the basic mineralogical mechanism is, usually, the formation of zircon (Zirconium silicate). Due to the chemical properties of zircon crystals they have a tendency to allow the incorporation of Uranium and Thorium while rejecting the incorporation of Lead. However, Uranium and Thorium will decay ",
" Lead over time. If you then crack open a zircon crystal and measure it's contents of certain Uranium/Thorium/Lead isotopes very accurately then by measuring their ratios we can estimate the amount of time since the zircon was formed (since it excluded Lead, essentially)."
] |
[
"Thanks. "
] |
[
"If you happen to know I'd still like to know how we came up with the 1.65/1 ratio."
] |
[
"Schrödinger's Wave Equation"
] |
[
false
] | null |
[
"Well, we must be a bit careful with the word \"derivation\" in this case. Obviously, one can't truly derive the Schrodinger equation from classical physics. Some extra axioms and ansatzes have to be put in, but there are many equivalent sets of axioms that will define quantum mechanics - even proposing the Schrodinger equation itself and going from there is a valid ansatz. It's like F=ma: we tend to think of it as a definion, like an ansatz, but we could derive it from something else if we have some other ansatz.",
"Anyway, it seems to me like that's why there aren't necessarily any good and satisfying derivations of the Schrodinger equation. But I do like the \"derivation\" outlined in the first 70 or so pages of Sakurai's \"Modern Quantum Mechanics\", which is one of the more popular QM books at the graduate level. It's very well-reasoned, I think, and talks about \"deriving\" the Schrodinger equation from considering the time evolution of state vectors under the influence of the given Hamiltonian. I think it should be accessible to anyone who has been through the first few chapters of Griffiths, especially since it attempts to build QM from the ground up using a very reasonable set of axioms.",
"If you're considering grad school in physics, you might as well buy this book. It's probably the most popular grad QM book (although Shankar's book seems to be gaining on it), and most people really like the first half or so of the book that was written by Sakurai himself. (He died while writing the book, and the rest of it was pulled together from his notes by someone else.) And, well, if you're not ready to buy a copy, there are internet means of obtaining it - say, in a large torrented cache of physics books that may or may not have been floating around the interwebs for many years."
] |
[
"There's a nice little derivation on page 94 in Townsend's QM book (I hope ",
"this link works",
"), which just uses the ideas that the Hamiltonian should generate time translations, and time evolution should be unitary."
] |
[
"I was mainly referring to the derivation from the de Broglie wave equation which Schrödinger originally did. But I heard there are flaws with Schrödinger's original paper, and apparently no translations, so I was wondering what the best derivation of it is from established theory prior to it. I guess proof might have been a better term to use.",
"I tried reading a derivation through a thought experiment in Introduction to Quantum Mechanics by Wittke J. P. and Dicke Robert H., bu it was a bit convoluted in its style of writing, being from 40 or so years ago. So I was trying to find out if there are any better derivations, otherwise my knowledge of quantum mechanics will likely remain largely procedural."
] |
[
"Is there a cause for the orientation of an accretion disc around a black hole?"
] |
[
false
] |
[deleted]
|
[
"There are two common situations. First, a stellar mass black hole in a binary star system. Second, a supermassive black hole in a galaxy's center.",
"You never really have a free-floating stellar mass black hole with an accretion disk -- the density of gas in the interstellar medium is just too low for that to happen.",
"So, the first situation. In a binary system, if there is an accretion disk, it's because the donor star is \"overflowing its Roche lobe\" and gas is flowing onto the black hole. There is a region about the black hole where the force of gravity is basically dominated by the black hole; and there is a region about the ordinary star where the force of gravity is basically dominated by the ordinary star. Roughly, those two regions are the Roche lobes of each of the bodies (not exactly, but roughly).",
"When an ordinary star is done burning Hydrogen in its core, it will expand (for technical reasons) and often times its outer layers (the envelope) will overflow its Roche lobe.",
"When this happens, the direction that it falls onto the black hole is controlled by the orbital angular momentum of the binary. The accretion disk will end up with the same plane as the orbital plane of the binary.",
"As for supermassive black holes, I am not sure if there is a good way to understand the orientation of the accretion disk. I have never seen that explained.",
"I will say, though, that ",
" close to the black hole, the disk may align with the spin of the black hole. This is due to the \"dragging of inertial frames\". I will try to remember the name of this effect. It's not globally important, though -- only in the innermost few gravitational radii about the black hole.",
"EDIT: Super important edit. The mechanism I mentioned above is called the Bardeen-Petterson effect. It turns out that there is a torque on the black hole from this effect, which then causes the black hole to align with the accretion disk.",
"EDIT 2: Here is an ",
"abstract",
" for the paper on disk-spin alignment."
] |
[
"Wow! That was really helpful. Thank you!"
] |
[
"You're welcome! :) Glad to have shared something I learned."
] |
[
"Is there any truth to the practice of Acupuncture?"
] |
[
false
] | null |
[
"This is a blog run by Dr's, medical scientists, etc.. check out some of their articles on acupuncture. ",
"Science Based Medicine"
] |
[
"May be asking to get downvoted, but also why religion made it this far."
] |
[
"So doesn't work whatsoever, how has it lasted this long in a modern setting?"
] |
[
"Older theories of planetary formation?"
] |
[
false
] |
I just finished reading the 1979 SciFi book (Piers Anthony). It's a good read, if a bit convoluted. Anyway, covered within the book was a theory of planetary formation wherein the gas giants were formed from what sounded more or less like "black dwarfs" -- burned out stellar remains, which were captured by our protosun. While this is certainly not the current model (Wikipedia seems to indicate the as the most accepted model right now), was it ever seriously considered? My core question is, was this guy just making up stuff for his novel, or was this a serious model of solar system formation prior to our current understanding of stellar evolution (with the three endpoints being a white dwarf, neutron star, or black hole, if I've read correctly)?
|
[
"I know that prior to the discovery of fusion, it was thought that the mechanism of the sun's heat was Kelvin-Helmholtz contraction, which gave it about an 8 million year lifespan. (while this is the established mechanism of formation, it ends when fusion starts and there is a new hydrostatic equilibrium)"
] |
[
"I don't think this idea was ever seriously considered. The closest thing to it is the theory that the gas giants formed by ",
"disk instability leading to localized gas collapse",
", as opposed to starting with massive cores and capturing gases (as described in this ",
"pdf",
")."
] |
[
"I remember an old theory of planetary formation I was taught in undergrad. Basically it went that planets form when two stars pass close enough to one another that a significant amount of mass is pulled between them and meets in the middle where it condenses into a planet which begins to orbit one of them."
] |
[
"Is the total amount of water on (and in) earth (within the atmosphere) a constant amount or does it vary?"
] |
[
false
] |
I always wondered this because I would like to think that there is some kind of balance where all the watermolecules on the earth added up will end up in one big total number. That number would include all the molecules captured in ice, rain, air, earth itself and so on. Given the climate changes we see happening all around us could this total number (‘balance’ if you like) be influenced by human intervention to gain beneficial improvements for a sustainable future?
|
[
"As recently as a few years ago (2014), announcements were being made about ",
"huge quantities of water",
" on Earth that were previously unknown. ",
"To answer your question in the strict context of climate change, however, we need to consider how of the water we know about actually participates meaningfully in the Earth's climate. The water referred to in the above link is unlikely to play a role, as regardless of the quantity, it is too deep in the Earth to affect the surface. ",
"However human intervention has, in certain places, brought in to play water that are not really supposed to be in play. In Libya, parts of the American midwest, and other places around the world, huge quantities of ground water from deep, ancient reservoirs have been tapped and used for agriculture and other types of human consumption. These source, often called \"fossil water\" or \"paleowater\" have often been in place for millenia, are effectively sealed off, and not replenished via recharging from surface sources. Their use is generally NOT sustainable. But in the short term, they provide crucial benefits where other water resources are severely lacking or nonexistent. I consider myself environmentally conscious. But after learning about the various facets of the matter, I have a really hard time coming down 100% against their use. I'd like to know what others think."
] |
[
"I don't know the relative magnitude of these effects, but they won't balance exactly. So yes, the amount of water close to the surface (and also on Earth in total) changes."
] |
[
"It varies.",
"2·H2O -->->-<-<-- H3O(+) + OH(-)",
"The arrows are for dynamic equilibrium.",
"K=1 meaning that it's forward and reverse reactions are equally likely to occur.. This means that your water is going to dissociate into hydronium (or simply a single proton but I like hydronium much better in theory for my chemical computations) and hydroxide ions which are going to associate into water molecules. This is highly pH (or pOH or current or whatever you use) dependant.",
"Think fission and fission, also. We try to have cold fusion to get the large energy out but it's not feasible however it is possible. This would change how many water molecules there are but it would not change how much matter there is on Earth.",
"That's a different story."
] |
[
"How do you measure the weight of matter that weighs less than air. For example, how much does a tonne of helium weigh?"
] |
[
false
] | null |
[
"1 tonne....\nBut to actually be helpful, usually for fluids (gases and liquids) we simply multiply their density by their volume to obtain their mass\nBut now you're just asking how we find the density",
"The first way that comes to my mind would be to turn a graduated cylinder upsides down and blow some helium into it, however much water it displaced would be proportional to its mass. Since we can measure the volume in the graduated cylinder, there's our density!"
] |
[
"It does not weigh one tonne because weight is a measure of force not mass. It's weight would be about -70,000 N within air. ",
"-p_h=0.18\n-p_a=1.28\n-\\DeltaM=M_h-M_a=1000(1-1.28/0.18)\\approx 7,000\n-g\\DeltaM \\approx 70,000"
] |
[
"First things first, a tonne of Helium would weigh a tonne, because a tonne is a unit of weight.",
"I think you're getting confused between mass and weight, they are not the same thing.",
"The mass of something doesn't depend on the medium it's in. Mass is a measure of how much matter something is made up of, so for a mass of helium you would just have to know how many atoms of helium there are and multiply that by its atomic mass.",
"Weight is a measure of the strength of a gravitational field on a given mass, so the stronger the field, or the more massive the object, the more weight it has. You would weigh less on the moon than you do on earth (because the moon is less massive and therefore has a weaker gravitational pull), but you would be just as massive in both places."
] |
[
"If heat kills bacteria, why can't you simply reheat all food, no matter how old?"
] |
[
false
] |
If heat kills bacteria, then why are there so many guidelines for food safety? Couldn't you just reheat any food and kill that bacteria? (obv this might impact taste, but it seems simpler than the complex food safety laws)
|
[
"Sufficient heat will kill live bacteria, sterilizing the food as far as infection risk, however many food-borne pathogens create toxins as part of their metabolism and those toxins will remain even after killing the bacteria. ",
"For example, the bacteria ",
" produces botulinum toxin which is capable of blocking the release of acetylcholine, functioning as a neurotoxin [",
"Nigam & Nigam, 2010",
"].",
"Similarly, ",
" is capable of causing infectious disease, but also may produce Shiga toxin, which can halt protein synthesis, killing or damaging cells even in the absence of live bacteria [",
"Pacheco & Sperandio",
"]"
] |
[
"Also important, even if the toxin isn't particularly dangerous, it can still make your food taste pretty awful. "
] |
[
"Both botulinum toxin and shiga toxins are easily destroyed by heat. ",
"However certain strains of E.coli produce a group of \"Heat-stable Enterotoxins.\"",
"Certain strains of Staphylococcus, for example MRSA, produce a heat stable toxin. Staphylococcus spcs. don't grow easily under refrigeration or under acidic conditions. Therefore staphylococcal food poisoning tends to be occur in certain foods that are kept for several days at room temperature, but don't have excess acidity."
] |
[
"Is the distribution of isotopes the same on other planets as it is on Earth?"
] |
[
false
] |
For example, on earth about 75% of Cl has atomic mass of 35, with the other 25% having atomic mass 37, is this distribution the same is space?
|
[
"Stars and Supernovae are the sites of nuclear reactions that consume/create isotopes, so other solar systems almost certainly have different ratios of the things.",
"As for planets in the same solar system, I don't know but I guess it should be sort of the same. (Although an important caveat is that one should keep in mind that concentrations of elements in a planet vary a lot from the crust to the core and I'm thinking \"on the average\")"
] |
[
"Not exactly the same, no, but there very interesting similarities and trends. A full answer to this question would be quite involved, so I'll just point out a few aspects of it.",
"The various isotopes are made in \"nucleosynthesis\" processes. There are a few major ones which produce most of the material in the universe: ",
"you can read about them here",
". ",
"For example there is the ",
" process",
", which slowly builds up heavy nuclei in giant stars. While every such star is a bit different than every other one, the physics behind the process is the same, and the ratios of the isotopes produced during the process is rather consistent each time it happens.",
"We can do spectroscopy on the light of other stars and see what their composition is of various elements, and we can pick out elements that we expect to be produced only in one process. We can do this for multiple stars and compare. For example, here are the ",
" process abundances for three stars",
". They have been intentionally offset in that figure so you can see them separately. The lines represent the abundances in our solar system (re-drawn for each star), and the dots are measurements of some of the elements for the three stars. You can see the consistency is impressive.",
"So these various nucleosynthesis events are happening all the time, filling galaxies with this material. Solar systems then form from this material, from a combination of multiple nucleosynthesis events. The amounts from each process varies from solar system to solar system, so there will be some isotope ratios that can be different because the two isotopes are made in different processes. However, for ratios of isotopes mainly produced in the same process, the ratios will be rather consistent."
] |
[
"The ratio of the various isotopes is slightly, but measurably, different between Earth/Moon, Mars, and asteroids, etc. Page down a couple times and the following link should prove to be interesting. ",
"http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=2398",
"When the Apollo astronauts brought back samples from the Moon, many were surprised that the Moon's isotope ratios were basically identical to those of the Earth. ",
"http://en.wikipedia.org/wiki/Giant_impact_hypothesis#Evidence"
] |
[
"When we say that a rotating gyroscope's axis is 'fixed', it is fixed relatively to what?"
] |
[
false
] |
[deleted]
|
[
"gyroscopes seem to violate the laws of relativity of frames of reference",
"This applies to linear motion, not to rotational motion. There is no \"absolute zero velocity\", you can always pick another inertial reference frame to change the observed velocity of all objects.",
"But there is an \"absolute zero\" for angular velocity. Any object in uniform circular motion (eg an atom of the gyroscope) experiences an acceleration that grows with the square of angular velocity. Only at zero angular velocity does that acceleration go to zero."
] |
[
"Apply newtons laws and see that they dont line up with reality unless you introduce fictitious forces arising from your rotating frame. If they do work okay without them, your frame isnt rotating"
] |
[
"A zero rotational frame is a rotational frame in which a light beam never makes a spiral, no matter how you orient the beam."
] |
[
"As we age, do our organs lose transplant value? If they do, are there any with more longevity? Like, a 70 year old heart might not be desirable, but maybe kidneys or something else retain some value despite age?"
] |
[
false
] | null |
[
"Short answer yes, they basically retain their age. ",
"That is why there is a large shortage of donated organs even though old people die all the time. You can not transplant a 80 year old kidney in a 20 year old. If we could do that, organs would be a dime a dozen. ",
"You can of course transplant a young organ in an old body, but that would be a waste of usable life span for the organ. So organ donation list systems matches people both on age as well as compatability and need. ",
"As a result, if you go to the transplant ward anywhere you will see older people getting transplanted rather quickly. While younger patients has to wait longer. ",
"In general, both organ and recipient should be within 10 years of each other. ",
"On the other hand, tissues for transplant are not as restricted as organs. So it wouldn’t matter if you get old skin (which will be processed to become acellular dermal matrix) or an older cornea."
] |
[
"Lung/heart units are the worst organs as far as degeneration, then small bowel, then livers then kidneys are more resilient IIRC from my transplant rotation ",
"Skin is not transplanted directly as skin. Instead the cells are stripped out and the underlying tissue matrix is used for tissue re-enforcement. So thin and weak skin has it uses (such as a hiatal hernia repair) while stronger skin is used for abdominal wall reconstruction. ",
"When a person needs actual skin, his own skin is usually grafted from one part of the body to the other. It can be stretched if a lot of skin is needed. ",
"Corneas depends more on the underlying collagen matrix which (like skin) doesn’t degenerate easily."
] |
[
"That's interesting. It makes sense, but I had no idea. Does it apply to all organs? I mean, I've heard things about the amazing resilience of livers, does a liver hold up better than a lung?",
"Also, I'm kind of surprised by the idea that skin and corneas would hold up, since they seem to visibly degenerate to the point that they wouldn't be compatible, in comparison to their younger counterparts."
] |
[
"Hey /r/askscience, I'm having a hard time understanding how force carrier particles (gluons, etc.) work, can you help me clarify?"
] |
[
false
] |
First of all, I am having a very hard time understanding how a particle travelling between two points (such as a gluon or a graviton) can transmit a force that has the effect of "pulling" the objects together or closer, as is apparently done by the Strong force and Gravity? Secondly, I am wondering if the force carriers of the EM field are the photons? And if Gravitons are the force carriers of gravity and the curving of space time? And last I have what might seem as a bit odd question. How can gravity pull on photons if photons are massless particles that are moving in the speed of light, just as gravitons are. In another perspective my question is like this; If I am driving my bike trying to push my friend who is also biking. We are driving at the same speed. How can I (Graviton) catch up with my friend (the Photon) and push him? I know Gravitons are a theoratical particle, put my question on how gravity can influence light still stands.
|
[
"There is a general miscommunication between experts and lay people that leads to your confusion. That miscommunication is the couching of forces in terms of \"virtual particles.\" This is misleading on a number of fronts, but I'll just say that \"virtual particles\" are the result of a mathematical tool, and not a fundamental description of reality. The fundamental description of reality is: things (described by quantum fields) attract and repel from other things. It is misleading to think that this is \"caused by\" exchanging photons or other force carriers. It is more accurate to simply say that the EM field is associated with the force between electrically charged particles, and photons are ripples in the EM field. Similarly for the other forces. Now, to answer your other questions:",
"I am wondering if the force carriers of the EM field are the photons? And if Gravitons are the force carriers of gravity and the curving of space time?",
"Yes in the language of gauge theory the \"force carriers\" of the EM field are photons, and gravitons are the force carriers of gravity and the curving of space time. A caveat to the latter is that we don't have an agreed-upon theory of quantum gravity, and it may not turn out to be a gauge theory; nonetheless in any such theory it is likely that what you say about gravitons is essentially true.",
"And last I have what might seem as a bit odd question. How can gravity pull on photons if photons are massless particles that are moving in the speed of light, just as gravitons are. In another perspective my question is like this; If I am driving my bike trying to push my friend who is also biking. We are driving at the same speed. How can I (Graviton) catch up with my friend (the Photon) and push him?",
"This misunderstanding is one and the same as what I addressed in my first paragraph. Gravitons are not literally sent out from the sun (for example) and \"catch up with photons\" and hit them in such a way that the photon is pulled toward the sun. The more simple and correct statement is simply that photons interact gravitationally. One way of ",
" this gravitational interaction involves summing over un-physical graviton exchanges. But this should not be taken literally."
] |
[
"Yes you are confused due to poor pedagogy (this is a frequent confusion). The Casimir effect is evidence for the existence of quantum fields that fill the vacuum of space. It is evidence for this vacuum having physical properties. The Casimir effect can be calculated without ever talking about \"virtual particles\", although if one wants to quickly explain why the Casimir effect exists to someone who doesn't know quantum field theory, it is easiest to lazily explain it by talking about virtual particles. "
] |
[
"Lowly undergrad here. You say that virtual particle exchange is 'unphysical' and should not be taken literally. It had been my understanding that the Casimir effect proved that these virtual particles do exist and are a physical effect, not just a mathematical description or am I confused?"
] |
[
"How far back can we successfully recover DNA?"
] |
[
false
] |
With the new , I often wonder if scientist have ever found a way to really mine DNA from amber or some other source. I remember reading in the past there's a finite limit no matter how ideal the conditions. DNA has a half-life of several hundred to 500 years? As of today, are there any new innovations which could push the envelope? I'm only getting older and I need to clone my reclassified Brontosaurus today!
|
[
"Depends what you mean by recover. ",
"This",
" happened last year - it was still fully functioning. As for recovery of DNA from organisms no longer living - much much older - ",
"See here",
". "
] |
[
"Really cool, scary, but cool. Yea, so here's the ",
"half life excerpt",
", but a few years prior, ",
"they did find soft tissue in a T-Rex bone",
". Scientist were able to ",
"sequence the soft tissue samples",
". Apparently, if there's enough ",
"Iron content",
" in the dino's body, it can help to preserve the soft tissue. I take it there are some flaws in this DNA half-life theory? I might have hope after all."
] |
[
"Well according to the article they sequenced the protein rather than the DNA, though even that is really really impressive. "
] |
[
"Does temperature affect how sound travels?"
] |
[
false
] |
I feel like I hear things more clearly on a cold winter night.
|
[
"Sound travels faster in warm air, because soundspeed (c) is given by:",
"c=√(ΥRT/m)",
"Where Υ, R, and m are the ratio of specific heat for air, universal gas constant, and molar mass of air, respectively. And T is the absolute temperature. Because R is a constant and both Υ and m are determined by the gas, sound speed only really depends on temperature for our purposes.",
"That said, this doesn't explain why you can hear more clearly on a cold winter night. Since speed doesn't change the clarity of a sound.",
"There are a few reasons why sound on a cold day seems clearer. One of the biggest reason is that is less noise on a winter night. Less animals running around making sounds, fewer people out driving their cars or walking around, fewer leaves rustling on trees, etc. This makes sounds clearer because we are always listening to sounds in comparison to the noise around them, and less noise means a higher signal-to-noise ratio means that the sounds we do hear seem more distinct.",
"Another big reason has to do with temperature inversions. Normally, the air closer to the ground is warmer than the air higher up. This means that the sound speed near the ground is faster than the sound speed in the air above, which causes sound to bend upward (because snell's law says that waves tend to bend towards regions of lower propagation speed). In the winter, however, it's much more common to get regions of cold air near the ground that gradually get warmer as you elevate. This causes sound to refract downward, to carry further, and focus on listeners near the ground (near the ground meaning human height). This also happens over lakes, and is part of why sound carries so well over bodies of water.",
"The last big reason that I can think of also has to do with noise, but is specific to there being a layer of snow on the ground. Snow is a righteous absorber of sound, because it's porous, tortuous, and a good thermal insulator. It can also get pretty thick. With all of these things put together, sound that hits a bank of freshly fallen snow tends to not escape and gets converted to heat. Because so much of the noise we hear is reflected off of the ground and other objects, covering everything in snow means that noise levels are decreased. When listening to a nearby source directly, however, a higher proportion of the sound you hear comes directly from the source, avoiding the absorbing snow.",
"Hopefully that answers your question! Enjoy listening closely to the sound (or lack thereof) of winter!"
] |
[
"That's actually a misconception about sound. the sound speed I gave was specifically for gases, but a more general form is given by c=sqrt(B/rho) where B is the bulk modulus (stiffness) and rho is density.",
"In other words, density actually causes sound speed to ",
", not increase.",
"The real reason why liquids have higher speeds than gases, and solids are even higher, is that they are so much stiffer that it more than makes up for the increased density. Water is 1000 times denser than air, but it's also 10000 times stiffer, which results in the sound speed increasing overall.",
"The effects of density are more clear when looking at the same states of matter. Helium has a higher speed than air, because it's light. Sulfur hexaflouride is slower, because it's heavy. The bulk module of all of these gases are the same, so it's very clear how sound speed is impacted in this case."
] |
[
"Yeah, it travels faster in warmer air. An empirical formula is v=331+0.6T with v in m/s and T in degrees Celsius."
] |
[
"How is Gravitational Potential Energy Stored?"
] |
[
false
] |
[deleted]
|
[
"The potential energy is not stored in the object, it's stored in the gravitational field. ",
"On a separate note, I may be being stupid here but does applying a force not require energy.",
"Applying a force doesn't require energy, energy is required only when that force is applied through some distance. That means energy is not required for the ground to provide the normal reaction force.",
"when the ground provides a reactive force equal and opposite to weight",
"The normal reaction force from the ground does not form an action-reaction pair with the weight as per Newton's third law. The normal reaction force is the reaction force of the contact force from the object resting on the ground. ",
"The reaction force of weight acts on the Earth and is the \"weight\" of the Earth under the object's gravitational field."
] |
[
"because if force carrying particles are needed, then it requires energy",
"You need to elaborate on this, because it seems like you have a misconception of what force carrying particles are."
] |
[
"because if force carrying particles are needed, then it requires energy",
"You need to elaborate on this, because it seems like you have a misconception of what force carrying particles are."
] |
[
"Circular weather pattern around large cities only at night."
] |
[
false
] |
Hey AskScience. I recently started the night shift in a NOC and in monitoring the weather I've noticed that as night falls across the US, strange circular formations crop up over many large cities, especially in the midwest. Here's a national radar image from a few minutes ago, from radar.weather.gov: None of my colleagues know what causes this either. A search of the reddits reveal a few similar questions over the last year but no answers, just speculation. My colleagues and I have speculated that it's caused by an increase in humidity at night, but that doesn't really explain why it's primary located around high-population areas. Is this an actual meteorological phenomenon or is it the result of some fundamental issue with current radar technology (considering weather radars tend to be located in high-pop areas)? If anyone knows about weather radar tech or meteorology, if you could help us satisfy our curiosity we'd really appreciate it!
|
[
"UPDATE!",
"A colleague with superior google skills figured it out.",
"It's caused by many nocturnal species of birds that tend to migrate southward behind cold fronts. Their nocturnal migration appears around radar locations as a circular formation with radars that are behind a cold front showing larger, darker formations (because the most dense area of the migration is right behind the leading edge of the cold front).",
"This is in line with the map image because a) there is a cold front moving across the US, and b) the darkest spots are right behind the cold front.",
"The effect is also visible when there are no large cold fronts (and appears the same way), but is not as heavy as when there is a notable cold front.",
"You can see a detailed explanation from last month here: ",
"http://metabunk.org/threads/753-Circle-Sweeps-HAARP-Rings-and-Scalar-Squares-are-Often-From-the-Birds",
"It is a forum thread but it seems to have good info."
] |
[
"This is not the only reason. If you look at a specific radar image from NOAA, youll see from the debug info that the radars go into \"clear air\" mode overnight, making them more sensitive to reflections. Sorry that I can't get you a link, because I'm on my phone. But this combined with your info (as well as insects, bats and such) create the rings which are centered around the radar site."
] |
[
"I've heard of this sort of thing referred to as a \"bird-burst\". It's surprising to see them happening over so many regions simultaneously."
] |
[
"If I drive my car at a constant velocity, then take a turn around a corner, I feel the force of acceleration. Assuming that the earth is traveling a constant velocity (universe expanding etc.) and yet it \"turns\" around the sun, why don't we feel this acceleration?"
] |
[
false
] | null |
[
"EDIT: Whoops, my bad. Thanks for all the comments below me. Earth is in free-fall around the Sun, so there is no centrifugal force because you are ",
" in free-fall around the Sun and glued to Earth by its gravity. ",
" if you're on the side of Earth that faces towards or away from the Sun, you will get very slight tidal forces directed away from the center of the Earth because you're moving faster or slower than what a freefall orbit would be at that point in orbit around the Sun. I have no idea how strong they are, but these tidal forces are negligible compared to the Moon's gravitational pull. The Moon is strong enough enough to cause the ocean tides twice a day."
] |
[
"What? There is certainly acceleration in orbit; it's just that the ",
" acceleration is that due to gravity."
] |
[
"See ",
"proper acceleration",
". An object in freefall does not undergo any proper acceleration - which is a sufficient answer to why one doesn't feel any acceleration."
] |
[
"If there is an Earth-like moon orbiting a gas giant in the habitable zone, would we be able to find it?"
] |
[
false
] | null |
[
"There are several projects currently trying to find large moons orbiting planets discovered by the Kepler mission. They're trying to discover the moons similar to the one used to discover the planets – the transit method. When the planet appears to pass in front of its star, we see a decrease in the amount of light that reaches us from the star due to the occultation, and we can infer properties about the planet from the amount and rate of dimming. ",
"If a moon was orbiting a transiting planet, we would see an increase in the amount of dimming, and the rate of dimming would change depending on where the moon was in its orbit around its planet.",
"One project working specifically on finding habitable exomoons, called ",
"HEK",
", keeps an accessible ",
"Twitter account",
" you can watch for news. Just recently they ",
"released some completeness statistics",
" that answer your question. At present, they're sensitive enough to find about 50% of the moons roughly a few times the size of Earth for the 60 planets they've studied, and they've not yet detected any moons. "
] |
[
"Right now, it could mean either. I would say that their sample size is a bit too small to say that there aren't any, but it would suggest that either: (1) not all planets that could host habitable exomoons actually host exomoons or (2) if they do, they're typically smaller than Earth."
] |
[
"Does that mean they might be too small to detect? Or that there isn't any? "
] |
[
"How/Why did it snow in the Sahara Desert just very recently?"
] |
[
false
] |
I've seen the same pictures on a lot of different media that it has snowed on the Sahara Desert ( ) and that it hasn't snowed in about 40 years. So, how did this happen and why?
|
[
"Hi, I am a german meteorologist with not much experience in forecasting weather in desserts or in Africa (mainly not that exciting anyways), but the main reason is explainable. Obviously it's true, that weather is weather as the others wrote, but of course there is also a scientific reason. This explanation is based on scientific facts, but not on research I did.\nOn both hemispheres you have strong temperature differences due to different radiation inputs. The meridional temperature gradient is strongest in the so called \"frontal zone\". This frontal zone can be imagined as a border between cold polar air and warm equatorial air. It goes around the world in a wave pattern, which effects the weather in the midlatitudes strongly. Because of the wave pattern (which is based on the fact that the atmosphere tries to balance the temperature/energy differences between the north and the south) you find colder than average temperatures if cold air pushes south to you or the other way around. If the amplitudes of these waves get too big, they can break and cause even more unusual temperatures in certain regions. A wave of cold air pushing south is called \"trough\" and is generally also associated with a low pressure system, which can cause air to rise and clouds and precipitation to form. So what happened is that one of these waves (they can reach pretty far south on the northern hemisphere in winter) had a big amplitude reaching up to northern Africa, in which a low pressure system was embedded, broke. So the conditions for very rare conditions observations were given. Also, in the night, it's often pretty cold in desserts anyways, but sure, precipitation is rare. Need to get back to work now, just ask if I did not explain something sufficiently. Will come back here later."
] |
[
"A desert is a large continuously-dry place, and therefore hostile to - and generally barren of - most life. \nBut \"dry\" desert terrain can include never-melting ice / snow. For example: Antarctica, with its massive blizzards and snowfalls is also a desert - its bitter-cold, dry interior is loaded with snow - most of which never receives enough heat to melt into liquid-water (which is essential to most animal and plant life).",
"\nThe Sahara (whose name, BTW, is the Arabic word for desert) can also receive occasional snowfalls; these are too rare however - and change to melt-water and evaporate too rapidly to flow.",
"\n\"In between\" the extreme desert examples cited above would fall the desert areas of Nevada. They receive very little water - not enough to sustain widespread, lush life, but just enough for scrub brush and other hardy plants (and small critters) to live."
] |
[
"So what happened is that one of these waves (they can reach pretty far south on the northern hemisphere in winter) ",
"This is the really important bit. We tend to think of the idealized planetary-scale circulation in terms of Hadley cells: warm air rising at the equator, moving towards the poles aloft, falling somewhere around +/- 30 degrees latitude, and returning to the equator closer to the surface.",
"This cycle tends to produce rain over the equator as the air initially rises, removing most of that air's moisture in the process. By the time it descends around +/- 30 degrees, the air is very dry, which explains why you see lots of deserts at those latitudes (Kalahari, American Southwest, Australian Outback, Sahara, etc).",
"Outside of this low-latitude tropical circulation, weather at mid-latitudes tends to be more wave-driven. As mentioned, cold troughs of the wave produce precipitation and warm ridges produce warm clear days. The generation of these waves are mostly caused by the inherent instability of the jet streams.",
"Now, that's all an idealized view. In reality, the point in the Hadley cell where the air returning from the deserts comes together and rises again (the so-called Intertropical Convergence Zone, ITCZ) doesn't usually happen exactly at the equator. A lot of research in the 70s and 80s showed the ITCZ migrates quite a bit depending on the season - in general it tends to follow the Summer sun, since that's where sunlight is greatest at any time and will generate the most lifting potential. ",
"So, right now (Winter in the Northern Hemisphere, Summer in the Southern Hemisphere), the ITCZ is quite a bit south of the equator. This tends to pull those mid-latitude waves with it, too, so the cold/warm front weather we usually only see at higher latitudes has a much better chance of making it equatorward down to the regions that are normally deserts in the Northern Hemisphere, occasionally even producing things like snow in the Sahara."
] |
[
"why are most consumer drugs dosages in two pill form?"
] |
[
false
] |
every painkiller type dose is 2 every anti-gas pill, anti-diarrheal, anti-histamine etc. why wouldn't they just put the same amount of medication in one pill? is because then the pills would be too large to swallow, or the body will absorb it better if the medication came from more than one source? or is it a marketing thing, so that when you buy a pack of 30 caplets, you think that you're getting twice the amount than you really are, 15 doses?
|
[
"This is not the correct answer, the OP is wondering why dosage is often \"2 pills\" that are taken simultaneously."
] |
[
"IAMA uh person. ",
"why wouldn't they just put the same amount of medication in one pill?",
"Diphenhydramine is a common anti-histamine. It comes in 25mg doses in most OTC preparations. When it's combined with acetaminophen it's generic name is ",
". A tylenol PM pill contains 25mg of diphenhydramine and 500mg of acetaminophen.)",
"The recommended dosage for ",
" is usually two caps (50mg of diphenhydramine and 1g of acetaminophen) but some people may not need nor want to take that much of it. By offering a lower amount of the drug per pill it allows people to properly regulate their dose. ",
"You can take more if you need more but not many people want to bother/guess cutting a pill in half to get the medication they need/want. ",
"And exposure of surface area helps break down pills from what I understand so more pills may be more logical for certain drugs."
] |
[
"Metabolic half-life. In order to maintain levels of a drug in the body at a certain (medicinally effective) level, dosing must be repeated at specific intervals in order to achieve the desired benefit of a drugs. Taking too much would accrue side effects. "
] |
[
"Can bugs get fat?"
] |
[
false
] | null |
[
"Recent studies in fruit flies (",
") have found that individuals with mutant forms of an intracellular calcium signaling channel (Inositol 1,4,5-trisphosphate receptor) have significantly altered lipid homeostasis, leading to the storage of excess triglycerides and, ultimately, obesity given a normal diet",
"Subramanian ",
" 2013. Altered lipid homeostasis in Drosophila InsP3 receptor mutants leads to obesity and hyperphagia. Disease Models & Mechanisms, 6: 734-744.",
"Subramanian ",
" 2013. Loss of IP3 receptor function in neuropeptide secreting neurons leads to obesity in adult Drosophila. BMC Neuroscience. "
] |
[
"Fruit flies are commonly used as model organisms for complex eukaryotic processes (even for human systems). In that regard, it would not be surprising if similar biochemical pathways are present in other insects, though it would be unwise to assume so based on a handful of studies on one type of organism, especially such a highly derived one (as compared to more primitive insects). "
] |
[
"So would these findings be applicable to all insects?"
] |
[
"Is it theoretically possible for a planet to have a figure eight orbit around twin stars?"
] |
[
false
] | null |
[
"It would be thoroughly unlikely, because the orbiting planet would act on both the stars, a little bit, and the stars would act on each other. That instability in multiple degrees would probably cause the orbits to decay into each other, and then your figure-8 wouldn’t be.",
"Under ",
" conditions... maybe."
] |
[
"Well let’s get real, statistically, every configuration is possible with near infinite opportunities"
] |
[
"Most configurations of the 3 problem body are non-periodic. However, some periodic configurations exist, and one of them follows an 8 figure (although it is not exactly the one you are thinking about). You can find more ",
"here",
", along with a nice animated gif."
] |
[
"The half-life of Beryllium-6 is ~5 zeptoseconds. How were we able to determine such a miniscule time?"
] |
[
false
] |
. To put this into perspective, in that time, . To put into perspective, the empirical atomic radius of a hydrogen atom is . How were we able to determine a half-life that is so short, it could be considered small even at an atomic scale?
|
[
"This is more of a particle physics question. You have to remember Heisenberg's Uncertainty principle. Not the position and momentum one, but the uncertainty in energy and time",
"(delta E)(delta t) >= hbar/2",
"The reaction they did was probably this",
" Li + ",
" He -> ",
" H + ",
" Be",
"and the Be-6 would decay to 2 protons and a He-4 nucleus",
"So what they would do would bombard a sample of Li-6 with He-3 of different energies and watch what comes out the other side. When you hit just the right energy, you will have a resonant peak because the cross section will increase meaning the reaction is much more likely to occur. And they observe more H-3 (or tritons). The width of that peak tells you how long lived the isotope is. If it is very narrow (delta E is small) you have a long half life (delta t is big). However if you have a very wide peak (delta E is large), then you have a very short half life. ",
"If you look you'll see the half-life is also given as 0.092 MeV which if you divide hbar by that, you get around 10",
" seconds.",
"http://en.wikipedia.org/wiki/Isotopes_of_beryllium",
"Phys Rev (150) 836 (1966) - Magnetic Analysis of the Li6(He3,t)Be6 Reaction",
"Phys Rev C (66) 047603 (2002) - 6Be and 8C Level widths"
] |
[
"/u/FoolishChemist",
" answered it correctly. It has too short of a half-life to measure using conventional methods."
] |
[
"I wonder if this is how they do it.",
"I wouldn't imagine so. I can certainly see it for long half-lives where you can take a large sample, observe it for a length of time and extrapolate from there.",
"Going the other way seems like a trick though. It's not like you'll have a large sample at any given time and the parent isotopes of my example (Boron-7 and Carbon-8) have similarly tiny half-lives (and no known parents).",
"I suppose you can fuse the atoms, but I feel you'd need a tremendous quantity of them to make a calculation that resulted in a time so small."
] |
[
"Are we humans really that much more intelligent than other species? How much of our perceived intelligence can be attributed to inherited knowledge and experience?"
] |
[
false
] |
I'm not sure how one would go about measuring something like this or if it's really comparing apples to oranges, but it is something that intrigues me. Certain animals certainly can, at the very least, appear to be highly intelligent but the best cases always seem to involve human training. It's obviously taken us a long time to get where we are today as a species but I get the feeling that our perceived dominance over all other life in terms of intelligence can be largely attributed to a very small number of traits - sort of like the total being more than the sum of the parts. This makes me think that certain animals, such as Dolphins or Elephants given a few hundred thousand years or so (just as we have had) could possibly rival us if only they had an effective means of writing (hands/opposable thumbs) because I think the recording of information for future generations is the biggest contributing factor to our intelligence. Here's some more anecdotal evidence - from time to time (actually pretty damn regularly) we all do stupid things. When I really think about what it is that I know and consider myself intelligent for I cannot attribute to myself and are all things that I have learned from other peoples trials and tribulations. TLDR; Are we really that intelligent? or just standing on the shoulders of giants?
|
[
"Humans had fully-developed language long, long before the first writing system was invented. Writing arose around 3000-6500 BCE, depending on what you count as a writing system, whereas the estimates for the emergence of spoken language range anywhere from 50,000 to 2-3 million years ago. ",
"Presumably, we have had oral histories and passed-on knowledge for as long as we have had ",
" sort of language system. The nature of the beginning of human language is hotly debated, but it's very likely that modern language was preceded by a less complex language system. Even a very simple system that simply assigned abstract names to concrete objects would have the potential to be passed on from generation to generation. ",
"Anyway, returning to your question, this means that it's not the development of ",
" that is really crucial to differentiating humans and other \"intelligent\" animals. It's the emergence of a language faculty in general that allows for a massive transfer of world-knowledge from generation to generation, and thus for the accumulation of large amounts of societal knowledge. ",
"In terms of their anatomy, Dolphins and Apes could easily develop language. Apes could develop a sign language. Dolphins could communicate via sonar/echolocation. As far as we can tell, they don't. That's not to say that they don't communicate at all, but they don't seem to have the cognitive ability to learn and use a truly functional, powerful language to pass on the knowledge they gain. Humans have this cognitive ability, and that's why we see a steady increase of societal knowledge. Writing systems and later printing, and then electronic information storage have made us even more able to store and pass on knowledge, but the key mechanism that differentiates us from apes and dolophins is the fundamental cognitive ability to use complex (recursive, hierarchical, symbolic) language. ",
"Some say this ability emerged simply because humans were \"smart\" in other ways, and then they (relatively) suddenly figured out that they could make a language. I think a somewhat more common assumption is that once the first leap was made (maybe just particular phonetic grunts abstractly associated with concrete referents), language ability was ",
" by natural selection. Maybe at first, some individuals were more able to memorize lots of sound combinations, which helped them communicate with their tribe (and other tribes), which helped them survive. Anyway, you get the idea, this would mean that the human brain was developing under selectional pressures to have a specific ability to use this proto-language. By the time you get to modern man, you have an animal that learns vastly complex language systems with apparent ease very early in its life, if exposed to the proper input. ",
"But regardless of its origins, our ability to use language in the ways that we do is the reason we have a \"cultural heritage\", and the reason we are able to \"stand on the shoulders of giants\" (of course for science, writing was quite helpful indeed..). "
] |
[
"Great post. How long is it thought to have taken between the emergence of \"identifying grunts\" and simply naming things to the emergence of spoken logic? Example, not merely having a name for herd of caribou, but being able to tell your children that the caribou will return once it gets warmer."
] |
[
"My understanding is that we really aren't that much smarter. We have just enough of an edge in being able to teach, learn, read, and things like that. This lets us build up knowledge beyond what can be learned and memorized by a person in their lifetime. And the amount of new knowledge that can be generated is based on the amount of knowledge we already have, in other words we see exponential growth.",
"It might be that other animals are on such an exponential track, but they are in the negative arguments still. So even if they continue for a hundred years, they might not make much progress."
] |
[
"What sorts of things exist between the Galaxies in intergalactic space?"
] |
[
false
] |
Do planets exist there? Is there dark matter there? Are there black holes there? I am really interested in what things we have observed and what things are predicted to exist there.
|
[
"Nothing much. A hydrogen atom every cubic meter or so. It's really quite boring for the most part.",
"Here and there you'll find some rogue stars. There are three main ways that a star can get ejected out into intergalactic space. ",
"Hypervelocity stars",
" are stars which are thought to be ejected by 3-body interactions with a central supermassive black hole and shot out of the galaxy at tremendous speeds (up to ~1000 km/s). ",
"Some supernovae are asymmetric, which means that if the supernova produces a neutron star it can have a very considerable kick, up to 1500 km/s in the case of a neutron star ",
"RX J0822-4300",
".",
"Finally, and perhaps most commonly, stars can be stripped from a galaxy during interactions between two or more galaxies. Tidal forces during a merger or interaction create long structures known as tidal tails (for example in the merger known as ",
"The Mice",
"), and some of the material in these tidal tails can escape the gravity of the galaxies. ",
"However, intergalactic space is still ",
" sparse."
] |
[
"Approximately one hydrogen atom per cubic meter.",
"There are ",
"occasional stars",
" that have been ejected from their home galaxies. How stars do this is ",
"not fully understood",
". ",
"Any planets hypervelocity stars once had are probably moving at a significant percentage of the speed of light, but on a different trajectory. ",
"More",
". It's a bit cold and lonely out there though with an average effective temperature of 2.7 K, but on the positive side a planet is unusually roomy for a no-fare intergalactic starship.",
"Other than that it's pretty empty. There are very rare ",
"mysterious blobs",
" of dark matter, detectable only through their gravitational lensing of objects behind them. This lends a lot of support to the idea that dark matter is a thing and not just a flaw in our theories of gravity. There's also some regular dark matter halo for a good ways around every galaxy."
] |
[
"Nothing much. A hydrogen atom every cubic meter or so. It's really quite boring for the most part.",
"Well... the ",
" is very low, but it looks like almost half of the baryonic mass of the universe is in this hot intergalactic medium."
] |
[
"Do new social insects learn from their peers or is their complex behavior mostly or entirely genetic?"
] |
[
false
] |
[deleted]
|
[
"Queen Mary University of London has done such studies, showing that worker bees learn from observing other worker bees:",
"Real paper: ",
"http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002564",
"Associative Mechanisms Allow for Social Learning and Cultural Transmission of String Pulling in an Insect",
"...",
"Here, we first show that bumblebees can be trained to pull a string to access a reward, but most could not learn on their own. Naïve bees learned how to pull strings by observing trained demonstrators from a distance. Learning the behavior through observation relied on bees paying attention to both the string and the position of the trained demonstrator bee while pulling the string. We then tested whether bees could pass this information to others during a semi-natural situation involving several colonies. We found that ",
" even after the initial demonstrator was no longer available. These results suggest that learning a nonnatural task in bumblebees can spread culturally through populations.",
"Fluff article on the same paper with a video: ",
"https://www.reuters.com/article/us-science-bees/brainy-bees-learn-how-to-pull-strings-to-get-what-they-want-idUSKCN124233"
] |
[
"I don't know about any purposeful experiments like that, but most ants, wasps and termites have their colonies started by a single queen (that is, the swarming behavior of bees is unusual) and newly hatched workers probably can't learn any complex behaviors (especially related to the outside activities) from the queen."
] |
[
"I don't know about any purposeful experiments like that, but most ants, wasps and termites have their colonies started by a single queen (that is, the swarming behavior of bees is unusual) and newly hatched workers probably can't learn any complex behaviors (especially related to the outside activities) from the queen."
] |
[
"Why are there only small dinosaurs such as Chickens,Ducks and Geese the only one left?"
] |
[
false
] |
Why didn't the dangerous live? or did the these Birds evolve from dangerous to harmless?
|
[
"Worth noting that the oxygen hypothesis for mage fauna is not at all supported by what little evidence we have."
] |
[
"Worth noting that the oxygen hypothesis for mage fauna is not at all supported by what little evidence we have."
] |
[
"Just pulling this out of my bum, but I would presume after a disaster like this there is far less food to go around. Smaller creatures need to eat less to survive so they manage to hang in there while the big creatures and predators no longer have the resources (food/prey) available to sustain themselves."
] |
[
"Can you miss something by a molecule?"
] |
[
false
] |
As in, if I was bowling could I miss hitting a pin by a molecule?
|
[
"I don't know about bowling, but there's a technique called non-contact atomic force microscope where you move a probe very near to, but not touching, a surface and the wigglings of the probe tell you about the surface, without touching it."
] |
[
"First off, a molecule isn't a unit of distance. However, if we talk about the size of a specific molecule, then yes. You can miss something by the length of one molecule.",
"If the molecule was a piece of stretched out DNA (a few feet) it's easy to miss a bowling ball by a few feet.",
"If the molecule was a long carbon chain (a few nanometers), it's possible that as the bowling ball passed by the pin the shortest distance between the two could have been a few nanometers.",
"On length scales smaller than this, things get a bit hazy. It depends upon how you define \"miss.\" For example, most people would consider hitting the pin as \"not missing.\" Some people would consider the ball kissing the pin, but not knocking it over as \"not missing.\" Other people would consider it \"hitting, but not knocking over.\"",
"Now, let's push that further. How do you define \"hitting?\" If the bowling ball molecule impart a force on the pin, does that count? It counts to me! Well, even at a few feet away these forces exist, but are negligible enough that they don't overcome things like friction forces keeping the pin in place. At a pin-ball separation somewhere between a few meters and a few negative nanometers (basically, the ball has to hit the the pin head on just a little bit), there is point where the pin will get knocked over. But in terms of the math that describes the situation, there's nothing special about the knock over point from any other point (hitting the pin head on or being a foot away). ",
"If there is a separation distance smaller than the size of a hydrogen molecule (two protons, two electrons, which is the smallest molecule) at which the ball doesn't knock over the pin, then it's interesting to note that you can miss a bowling pin by LESS than a molecule.",
"But really it's all wave functions and you're part of the pin and the ball and jessica alba and your dead great grandpa and it's all just stuff. Ha ha!"
] |
[
"What if the bowling pin was composed of a single cross-linked polymer? Then it might be argued as a 'huge molecule'..."
] |
[
"How long would it take for the water in a toilet bowl to fully evaporate?"
] |
[
false
] | null |
[
"That depends on a boatload of factors. Atmospheric pressure, temperature, humidity...",
"It could take anywhere from a few days to a few months, and possibly never happen if the humidity was high enough."
] |
[
"So assuming houston's current weather (85.6°F, 29.85 in Hg, 72% humidity), how long would it take?"
] |
[
"I hate these responses in askscience. Instead of addressing anything about the poster's question just ask for detail upon detail upon detail. Make some reasonable assumptions and give an order of magnitude answer. "
] |
[
"Would it be possible to create a virus that transmits like Ebola, yet has the same pathology as AIDS?"
] |
[
false
] |
I've always wondered why is that the deadliest viruses have the most optimal routes of transmission, while the slow developing viruses like AIDS mostly spread through sexual contact and blood transfusion. Would it be possible to create a deadly combination of Ebola and AIDS using current technology? If not, is it even theoretically possible?
|
[
"That's exactly what you want us to think..."
] |
[
"I don't think you need to make Ebola any more dangerous. From what I know about Ebola, the major reason that it hasn't killed everyone yet is it is just too virulent. You can't infect that many other people if you die in 2 weeks."
] |
[
"Explain your belief that ebola has the most optimal route of transmission. Isn't the goal of the virus to spread its genetic information? Symptoms are just the result of a host trying to eliminate the invader or enhance transmission but they are secondary to the goal of replication. ",
"Hiv infects more people than ebola ever will. Flu infects more than hiv. Jc virus infects nearly all humans. Transposons present in all humans may be viruses that lost the ability to spread on their own. I'd argue they have the most optimal route of transmission, not ebola. "
] |
[
"Why does extreme velocity and extreme mass create relativistic effects?"
] |
[
false
] |
Is there a connection between higher velocities and high mass objects?
|
[
"It doesn't. The universe is relativistic (at least to an insane degree of accuracy). The real question is why do slow speeds and low velocities give the approximation to relativity they do. This is due to Taylor expansion basically.",
"As for relation between mass and velocity. This depends on your perspective. An old interpretation of relativity would call m/(1-v",
" /c",
" ). Nowadays it is more common to call the mass m and consider the \"gamma factor\" to be a separate thing which happens to be approximately 1 at low speeds.",
"edit: To clarify, relativistic effects are there at all speeds and masses, just they are too small to notice."
] |
[
"To expand on this: our intuition is shaped by our environment and we, in terms of the totality of our species history, have lived exclusively in the realm of unnoticeable relativity. This means that classical Newtonian physics is \"normal\" to us. This does not make relativistic deviations unusual, rather it just makes them outside of our \"normal\" experience. Essentially, to view all phenomena that deviate from our \"normal\" as being modifications on our \"normal\" is looking at things the wrong way round, it is far more probable that our \"normal\" is modification of more general phenomena. In other words: as far as a general description of nature is concerned, its far more likely that our \"normal\" is in fact a set of weird unusual phenomena deviating from \"universe normal\". It's us who are weird, not relativity."
] |
[
"Special relativistic effects can occur totally independent of the effects of general relativity (essentially we can always choose a small region of space to governed only be special relativity). Special relativistic effects occur because of large speeds, obviously large speeds are easier to achieve with small mass (think momentum formula), so these effects are more likely to occur in small mass systems rather than large ones. This doesn't preclude these effects from occurring in large mass systems but you can already see that relativity creates no special connection between these two scales. Of course the same principles (that light has a finite, invariant speed and the laws of physics are the same to all inertial observers) are what connect the relativistic effects associated with large mass and large velocity which is why these scales might seem connected."
] |
[
"How do: planetary, interstellar, and intergalactic space relate and differ?"
] |
[
false
] |
[deleted]
|
[
"Hi there,",
"There are actually differences between these because you're right, space is a vacuum, but it's not a ",
" vacuum. The vacuum part starts around 100km up from Earth, but there's still quite a bit of atmospheric particles as well as particles from the sun in our Solar System, and this is enough to create drag on satellites as they orbit Earth for example.",
"When you start going outside the Solar System though things get a little closer to a vacuum. As a rule of thumb, there is one atom per cubic meter of interstellar space, and one atom in 10 cubic meters per intergalactic space. So basically, less and less random atoms the further you get from the \"stuff\" in the universe, which is more or less what you'd expect.",
"Hope that answers your question!"
] |
[
"Pretty much- how much a radio signal scatters over a certain distance is determined by the number of electrons in its path. "
] |
[
"The reason we see expansion between galaxies, but not planets and stars, is that galaxies are not usually gravitationally bound to one another (exception, galactic clusters). Everything within a galaxy is gravitationally bound together, so as space expands, the galaxy stays the same. If you separated all the components of a galaxy to the point where they were no longer bound together, then they too would expand away from each other with the expansion."
] |
[
"What causes hair loss from eating disorders?"
] |
[
false
] |
Is it a high stress level? Or lack of nutrients or something
|
[
"Malnourishment.",
"When a person’s body is malnourished, such as during an eating disorder, the protein stores in their body become depleted. When this occurs, the body has to make sure that it takes care of essential functions (such as organ function and retaining muscle tissue) above all else. Our hair, which is made up of a protein called keratin, is not as essential to our body’s functioning. So, hair growth stops so the body can focus on keeping that person alive.",
"Depending on a person’s age, genetic makeup, and other developmental factors, regular hair growth will most likely return to normal after a person maintains nutritional stabilization for six months or more."
] |
[
"This is true, though there's more to it than just not having protein—a protein-sparing severely hypocaloric period can still involve the same abundant hair shedding, as can non-nutritional events.",
"The term for the whole thing has a name that sounds like it came out of Harry Potter: ",
"Telogen Effluvium",
".",
"Hair growth is a long, cyclical process with three described phases:",
"In normal situations, the balance of these phases keeps the number of active follicles on your head within a fairly steady range (note: length of hair isn't the same thing!). But a lot of things, starvation included, screw up the normal signalling. Anagen stops early and follicles go straight to telogen, meaning you lose years of hair growth progress and start shedding very quickly.",
"As for exactly what mechanisms are involved in the signalling, I believe it's not entirely understood. We know that things like pregnancy and male hypergonadism (high testosterone) can be linked to alterations to phases, meaning sex hormones have direct or indirect influence, and we also know that extreme physiological or psychological stress can cause effluvium, too, meaning something like cortisol could play a role. Drugs like minoxidil and finasteride have effects on follicles, too, so hair growth clearly responds to a lot of things."
] |
[
"Why does the body target hair on the head and not the bodily hair on the rest of the body. Agreed that there are more hair on the head compared to other parts, but does it also mean that bodily hair is lesser/weaker source of protein compared to hair on the head?"
] |
[
"Suppose I have a balloon filled with Deuterium. How often should I expect quantum tunneling or lucky collisions to merge two of the nuclei into a helium nucleus?"
] |
[
false
] | null |
[
"So you're asking for the rate of DD fusion reactions at room temperature and atmospheric pressure? Very, very low."
] |
[
"Any idea how low? Are we talking weeks or Gigayears per?"
] |
[
"If you take the S-factor at zero energy to be around 50 keV b, and the Gamow factor to be around 1 MeV, I get a cross section in barns which is so small that my phone calculator calls it zero.",
"Not to mention that under these conditions, you wouldn't have free deuterons but rather D",
" molecules."
] |
[
"Why did they put speakers on the Mars Curiosity? Surely not just for will.i.am?"
] |
[
false
] |
[deleted]
|
[
"I don't think Curiosity has any speakers - it's just going to stream the audio back to Earth.",
"http://www.space.com/17320-mars-rover-will-i-am-song-broadcast.html",
"A lot of news sources are saying it will be played through speakers but it might have just been a misunderstanding that was propagated."
] |
[
"\"Though Curiosity has no speakers, it will transmit the song via radio waves back to Earth to be received at 1 p.m. PDT (4 p.m. EDT)\" good call sir"
] |
[
"Basically because they decided there probably wasn't anything worth hearing.",
"http://www.reddit.com/r/IAmA/comments/ybmmh/we_are_engineers_and_scientists_on_the_mars/c5u3d45"
] |
[
"Can medicine really be injected into the body as shown in the movies, just stab the syringe into a fleshy area and inject the medicine, instead of searching for a vein like how the regular doctors do it ?"
] |
[
false
] |
[deleted]
|
[
"Many medications are given intramuscularly, meaning they are injected directly into muscle tissue. Most vaccines are given this way. More care is taken than just stabbing the patient because the proper location and depth reduces pain at the injection site, but in principle it could just be a fast stick. This is what epipens do, you press them firmly against a fleshy part of your leg and they push the needle in for you."
] |
[
"You usually inject something into a vein when you want a very fast delivery of the substance all over the body or at least to a part of the body that is reached by blood. For example in a hospital setting for rapid relief of severe pain, morphine may be injected into a vein as it can then reach certain areas of the brain in a matter of seconds or minutes.",
"It also depends on how fast the particular substance can reach the desired areas if injected 'randomly' (usually in a large muscle).",
"Other medicines may actually be deadly or at the very least harmful if injected into a vein instead of let's say into a muscle. For example some steroids have to be injected deep into a muscle so that they are released slowly into the bloodstream."
] |
[
"There's also subcutaneous injections, which are put into the layer directly below the dermis. It all depends on how quickly you want the drug absorbed and how it interacts with the body."
] |
[
"Digestion/Absorption of Pills: Does Size Matter?"
] |
[
false
] | null |
[
"The ",
"placebo effect",
" is a powerful one. In many cases, the more involved / invasive placebo elicits a bigger effect than smaller ones. So the bigger pill is more effective, based on placebo effects alone, than the small pill.",
"Unless the two pills have different designs (one for continuous release, for example), the difference is likely psychological."
] |
[
"Amount of food matters - especially for large, polar drugs. If you have lots of food in your stomach, the stomach will spend some time churning its contents before food is passed onto the intestine - this is called gastric emptying. Many drugs don't cross cell membranes well, so they're not absorbed very much in the stomach; instead they're absorbed in the intestine. So delaying how fast the drug gets to the intestine would certainly affect how quickly it reaches your blood stream.",
"Some drugs also cannot be taken with certain types of food - some antibiotics and grapefruit, for example."
] |
[
"Amount of food matters - especially for large, polar drugs. If you have lots of food in your stomach, the stomach will spend some time churning its contents before food is passed onto the intestine - this is called gastric emptying. Many drugs don't cross cell membranes well, so they're not absorbed very much in the stomach; instead they're absorbed in the intestine. So delaying how fast the drug gets to the intestine would certainly affect how quickly it reaches your blood stream.",
"Some drugs also cannot be taken with certain types of food - some antibiotics and grapefruit, for example."
] |
[
"When a song gets \"stuck in your head,\" what part of your brain is doing the singing?"
] |
[
false
] |
Sometimes I realize that a song has been "playing" in my head for a while, without me actually consciously thinking about it or even noticing it. Then my normal thoughts are interrupted when I realize I'm "hearing" this song in my head. I feel like this must be similar to when you actively start thinking about something else while reading, but you actually keep reading. Then you reread the paragraph a few times before you actually get your conscious mind back on the words in front of you. Is this another "type" of conscious thought that also happens in the same area of the brain as my thoughts that sit on the surface? Or is it some kind of unconscious thought that happens elsewhere?
|
[
"Thoughts related to interpreting and producing language are in ",
"Wernicke's area",
" and ",
"Broca's area",
" respectively. They are tightly linked but reside in two different lobes of the brain (frontal and auditory cortex-fissure between temporal and parietal). Language interpretation (what is being activated when you listen to and/or \"get music stuck in your head\") is located in that fissure I mentioned within the auditory cortex.",
"Most cognitive, effortful thought takes place in the frontal lobe. Language interpretation is not primarily occurring in that lobe. Things like memory associations, etc, are happening there- but not pure interpretation. Both regions can activate simultaneously. That's how you get that dual effect of thinking ",
" getting a song stuck in your head. ",
"EDIT: Wanted to note, my background is in experimental psychology, so this isn't my specialty, but it's the best I can remember from my grad classes in bio and cognitive psychology."
] |
[
"meditation"
] |
[
"i think that's probably more of a cerebellar or motor area phenomenon. As in, you are doing the motor movements required to move your eyes pretty much automatically but your left hemisphere isn't really processing the information.",
"Audition is produced in the temporal lobes (specifically heschl's gyrus) and memory is reconstructed in the right frontal lobe, so i imagine that it is a combination of the two. When you picture something in your head the area of your brain that gets activated is the same as the ones that are aroused when you actually look at something."
] |
[
"Why are species with dark fur or skin located in warm climate and species with light fur or skin in cold climate? Shouldn't It be the opposite ?"
] |
[
false
] |
Think a bear or a wolf (or a human but I don’t want to trigger any knee jerk reaction). According to physic a light surface reflects energy and a dark surface absorbs it. Seems to me that a species with dark fur or skin would be better equip to absorb solar energy and remain warm in a cold climate. On the other hand a species with a light skin would be able to better equip to regulate its temperature. It the reason why we tend to dress in white in warm climate. Evolution seems to have taken the opposite direction. Why is that?
|
[
"Because the fur colors didn't evolve to increase the animal's temperature, but instead to reduce their visability. If they need to be warmer the coat can get thicker, but nothing's gonna help a black fox hide on an Arctic tundra. So the animals who had some mutated fur color could hide better and had a better chance of passing on their genes."
] |
[
"It's not reflected, it goes right through. If you look at your skin color, for example, it's not the sort of brilliant white that's actually reflecting a huge proportion of light."
] |
[
"I'm totally ripping this off of the cosmos but... typically in colder climates there is snow. And simply put a brown bear is easier to See by prey in a snowy environment. So over time A mutation happens in a brown bears DNA that causes it to have white fur instead. This gives the bear an advantage in a snowy environment by providing camouflage and this is easier to catch prey and survive and mate. I hope all this make sense"
] |
[
"Does anyone know if a handy online database of online tutorials to brush up on science ?"
] |
[
false
] | null |
[
"For maths and to a certain degree science, ",
"Khan Academy",
" is the ultimate source. It has a plethora of videos covering almost all imaginable subjects and a really good regimen of online training exercises for maths.",
"Absolutely worth for as well beginners as the more experienced!"
] |
[
"khanacademy.org",
" Go there now, seriously.",
"Perfect for this. You are going to really like it. Lots of subjects.",
"EDIT: Also, there was a list created by reddit for online learning ",
"HERE"
] |
[
"Oh man, this is precisely what I was looking for. I knew it existed just didn't know the name !"
] |
[
"Why does corn pop and can you pop anything else?"
] |
[
false
] |
What makes corn kernels pop into popcorn when cooked on the stove? Can you pop other seeds or is there something special about the physiology of corn kernels?
|
[
"It's a sudden evaporation of the moisture inside the kernel.",
"I'm certain that it works with wheat and rice as well, as the result is sold as cereal, probably other grains too."
] |
[
"You can pop ",
"amaranth",
" "
] |
[
"Green coffee beans have two stages of \"pop\" when they are roasted, referred to as first and second \"crack\"."
] |
[
"Is voyeurism a purely human phenomenon?"
] |
[
false
] |
Or do animals like watching other animals bang? Does it have the same physiological effect on them? On a related note, are there Instances of paraphilia in the animal kingdom, like necrophilia or pedophilia? Or are those also purely human?
|
[
"This is practically a FAQ here.",
"Animal porn was discussed in quite a bit of detail in ",
"this question from 2 weeks ago",
"Monkeys ... value pornographic material ... showing young male pandas \"panda pornography\" is widely credited with a recent population boom among pandas in zoos",
"And around the same time there were many comments about ",
"non-mammalian masturbation",
", that even answers your paraphilia / necrophilia question:",
"... More interestingly from a Cog Sci perspective (and disgustingly from a NSFL perspective) they also caught male penguins engaging in violent gang rapes of female penguins, in some instances even leaving the females deformed and/or dead... \n... trout fake orgasm .... turtles rampant masturbators ....One can easily get insects like bees to \"mate\" with an inanimate fake bee,",
"Wikipedia has a good page on ",
"animal sexual behavior",
" too."
] |
[
"Well, the need/desire for privacy during sexual activity is considered a fairly unique human trait. I'm pretty sure it was mentioned in [this video])",
"http://www.youtube.com/watch?v=LOY3QH_jOtE&feature=player_detailpage#t=5033s",
"). That would seem to rule out any ",
" thrill associated with watching sexual activity, which seems to be a big part of human voyeuristic tendencies. "
] |
[
"Is that a universal human trait; or a result of some religious / cultural training?"
] |
[
"If you place water and an ice cube in a cup so that the cup is entirely full to the brim, what happens to the level of water as the ice melts?"
] |
[
false
] | null |
[
"assuming the ice is floating, and not pushed down under the surface, the volume of the ice that is under the surface is the same as the volume of liquid water that has the same mass as the entire ice cube (This is Archimedes' Principle). as the ice melts, its volume will decrease both above and below the surface of the water. When melting is complete, the ice will have reduced in volume to be exactly equal to the volume of water it had been displacing. The peaks of ice over the brim will go away, but the water level will not change."
] |
[
"assuming the ice is floating, and not pushed down under the surface, the volume of the ice that is under the surface is the same as the volume of liquid water that has the same mass as the entire ice cube (This is Archimedes' Principle). as the ice melts, its volume will decrease both above and below the surface of the water. When melting is complete, the ice will have reduced in volume to be exactly equal to the volume of water it had been displacing. The peaks of ice over the brim will go away, but the water level will not change."
] |
[
"He's talking about the volume of water that makes up that ice when frozen is exactly the same as the volume of water that the ice displaces. A bouyant object displaces the volume of water that matches its own weight. An ice cube therefore displaces the same weight in water - and therefore, the same ",
" when it melts.",
"The water level will not change. The \"extra volume\" of the ice you're thinking of is the bit of ice that peaks above the water level."
] |
[
"What happens to the areas of the brain involved in language production and recognition in the non-dominant hemisphere when language becomes lateralised to a specific hemisphere?"
] |
[
false
] |
I'm currently studying lateralisation that occurs in the brain during human development for a university subject. I understand that approximately 70% of all people, regardless of handedness, have speech lateralised to the left hemisphere of the brain, specifically in Broca's and Wernicke's areas. From what I understand, during development we have the capacity to develop speech in the left or right hemisphere as these areas are symmetrical and non-lateralised. What happens to these areas in the non-dominant hemisphere when language becomes localised to one hemisphere? Do other functions arise in the other hemisphere where Broca's and Wernicke's areas would have arisen? Are these areas still loosely involved in speech or do they control something completely different?
|
[
"Might be slightly askew to your question but... Right Hemisphere is involved with the discrimination, repetition, and production of linguistic and emotional prosody (essentially the \"rhythm\" of language i.e. how it is said) as well as comprehension of emotional processing. Linguistic prosody is stress on words eg. rising pitch when asking a question, while emotional prosody relates more to mood (happy/angry/scared/etc). ",
"Interestingly, the amygdala is involved in the processing of fear while the basal ganglia and/or the frontal-subcortical pathway promotes salience of information and the associative functions in the cortex. Their involvement in processing speech is essentially that it looks at the emotional salience (fear/anger/urgency) of the message in conjunction with the environmental salience (dangerous situation) and puts that information together to make a decision about the speech. ",
"TL;DR - Right hemisphere processes prosody of speech."
] |
[
"We think singing can be produced from right-lateralized regions, ",
"as demonstrated here",
".",
"Some of it stays as related to speech - there's some arguments in the rehab literature for the involvement of the right for speech recovery (and also for inhibition of the right). The right region tend to be geographically smaller, so the nearby cortical function suck up some of the space."
] |
[
"There is no distinct Brocca or Wernicke \"area\" on the opposite hemisphere perse - that I can see in the literature (please correct me if this is not the case). By rhythm of language I am referring to how it is said e.g. think about how you ask the same question when you are angry in comparison to when you are happy. Rhyming itself should be thought of a type of speaking and its production is more left lateralised because it is assimilating phonological/semantic information in addition to prosodic information "
] |
[
"Does the way that parents treat their child really determine how the child turns out?"
] |
[
false
] |
When kids grow up, the way they turn out (e.g. slacker or hard-working, disciplined or not) is usually attributed to the way their parents bring them up (i.e. nature vs nurture and all that). But now that we know so much more about the inner workings of the brain and genetics, can we really still calim that? Wouldn't the personality type and character traits be mainly determined by the genotype and neurochemistry, and not the parental upbringing? Is there any data on that?
|
[
"This work highlights a much more powerful influence from genetics:\n",
"http://www.sciencedaily.com/releases/2012/05/120516115903.htm?utm_source=rss&utm_medium=rss&utm_campaign=character-traits-determined-genetically-genes-may-hold-the-key-to-a-life-of-success-study-suggests"
] |
[
"Nice find! Thanks!"
] |
[
"The answer is yes. I remember reading a wonderful article about this a few years ago and here it is.\n",
"http://ehp.niehs.nih.gov/1307892/",
"\nThe topic you are dipping into is called 'Behavioral Epigenetics', and is concerned with how DNA is modified through methylation, etc. by things such as early life stress and maternal care and touch. There is alot of info on it online that can be verified through Wiley Online Library. Hope this helps."
] |
[
"Has the invention of shoes changed the anatomy of human feet?"
] |
[
false
] | null |
[
"Short answer, no.",
"\nFull foot covering shoes are a relatively new thing, only being around for the last 1000 years or so, and before that any type of footwear was usually sandals or similar or just went barefoot. Once you go barefoot awhile your skin thickens to the point you can walk over stones without an issue."
] |
[
"What about things like flat feet or bunions? Do shoes increase their incidence?"
] |
[
"What about things like flat feet or bunions? Do shoes increase their incidence?"
] |
[
"Why don't we circulate ATP in our blood?"
] |
[
false
] |
It seems to me that all the conversions between ATP and carbohydrates (the light independent reactions of photosynthesis) and then back again (respiration) must result in a huge loss of energy overall. Why do organisms bother?
|
[
"http://employees.csbsju.edu/hjakubowski/classes/ch331/oxphos/olcouplingoxphos.html",
"It's actually fairly stable. It is kinetically unfavorable for it to convert to ADP and it only does so normally with the aid of enzymes."
] |
[
"ATP is very ",
"ionized",
" because of it's phosphate groups, and therefore doesn't travel through cell walls readily. You'd need a transport mechanism which would probably have to be active because of the rate ATP is utilized (facilitated diffusion would be slow without a lot of proteins, and increasing the number of proteins to speed it up is also not energetically favorable unless you had some sort of key like there is with insulin and glucose transporters). ",
"Another problem then becomes potential shortage in various regions, which could rapidly lead to cell death. An interruption in flow would be catastrophic. Something like cardiac arrest could be potentially (near) instantly fatal.",
"From an energetics standpoint it just makes sense to store things near where you use them, which is inside the cell relatively near the mitochondria."
] |
[
"ATP has a half-life of about ",
"1 second in blood",
", mostly because of hydrolyzing enzymes. It is a potent signaling molecule in the vasculature and nervous system as well. ",
"You might envision an arrangement where this isn't the case, and ATP is supplied from a central organ to other parts of the body. It would likely be more inefficient, especially in cases where the ATP use varies. It makes sense to have the control of ATP production being extremely local to its use, and the transport and storage being in more energy dense molecules like glucose and glycogen. "
] |
[
"Why are some grapes sweet and some sour/bitter on the same cluster?"
] |
[
false
] | null |
[
"Veraison",
" happens in cultivated fruits as well as wild plants. Each grape on a cluster could be at a different level of ",
"ripeness",
"--with the sweeter ones being more ripe."
] |
[
"Veraison",
" happens in cultivated fruits as well as wild plants. Each grape on a cluster could be at a different level of ",
"ripeness",
"--with the sweeter ones being more ripe."
] |
[
"Thanks for the response!"
] |
[
"Why is a tesseract depicted the way it is?"
] |
[
false
] |
A few guys at work were talking about Interstellar, and we started talking about all those 'funny physics' - relativity, time dilation, black holes, and, of course, the tesseract. One of them didn't really understand the whole tesseract thing. I understand the challenges and concept behind depicting four dimensional space in a 3D universe, so I tried to explain it to him. This is how I explained it (which may or may not be accurate, it'd be nice to be corrected): I took a piece of paper and drew some grid lines on it. I told him to imagine that this was space. I put a point in the middle and said that we have a light source there, and we flash it. Then, at the first set of grid lines, I drew a circle originating from the point and said that this was one light-second. Then I did it for two light-seconds and three light-seconds. Three concentric rings outwards. "Now," I said, "we have space as two dimensions - left / right, and up / down. If we add time as a third dimension - upwards - and we draw our light rings, what do we get?" Then I drew the . We've now depicted space and time as a 3D object... sort of. I then explained where our comprehension ends: light doesn't travel in two dimensions, it travels in three. In order to understand time from the third dimension, you have to add a fourth, but we're locked in the fourth dimension, unable to move forwards and backwards, only able to experience it at the present. I then more or less paraphrased Carl Sagan's piece on the tesseract, explaining with the flatlanders and how they can only comprehend their own two dimensions, and that while we can project a three dimensional object into their dimension, it will appear 'off'. A 3D cube has perfect right angles and equal sides, but a 2D representation of a 3D cube has all sorts of funny angles and sides of different lengths. Then I drew a tesseract and said that the tesseract, if we made it a 3D model, is a box within a box with the verticies connected. That box is what a fourth dimensional object looks like projected into three dimensional space. Then he asked something along the lines of 'how do we know that's what that represents', and honestly I found myself unable to answer that. I went around looking for Youtube videos where it gets explained better, but honestly, I really don't see anything. The tesseract just "is" depicted as it is, because that's how it's going to be. So, a little help? I'm not sure how to categorize this. I could be astronomy, but not really. It could be physics, but hell, even our understanding of physics doesn't completely work at this level. So let's call it math, because math is what all science boils down to anyway.
|
[
"I don't know anything about Interstellar so I don't know if I'm missing some important sci-fi context, but as far as why a tesseract is often drawn as a cube-with-a-cube it's fairly straightforward.",
"Start with a point. This is your 0-cube.",
"To go up a dimension, add another 0-cube parallel to the first one and connect the corresponding endpoints. Most of that is pretty meaningless when we're really just talking about points in 1 dimension, so what I actually mean is just draw another point and connect them. Now you have a simple line segment. This is your 1-cube.",
"To go up a dimension, add another 1-cube parallel (as in parallel lines) to the first one and connect the corresponding endpoints. What I mean by corresponding is if your first line segment is AB, and the second is A'B' then connect A-A' and B-B' so that you end up with a square instead of two triangles. Now you have a square. This is your 2-cube.",
"To go up a dimension, add another 2-cube parallel (as in parallel planes) to the first one and connect the corresponding endpoints. You should have a standard 3 dimensional box, which is your 3-cube.",
"To go up a dimension, add another 3-cube parallel to the first one and connect the corresponding endpoints. What does \"parallel\" mean in 4 dimensions? We don't really know because we're trapped in 3-dimensions, so often the easiest way to draw it is simply to draw one cube inside the other so that the corners are easy to connect. But this isn't strictly necessary, you can also draw two boxes next to each other on the page or some other configuration so long as you connect the correct vertices to each other.",
"Angle and length will not be preserved, just like drawing a 3d box doesn't really preserve right angles or edge lengths (on the page), but that can't be helped. Anyway whatever you draw is your 4-cube, a tesseract.",
"This is obviously not any kind of formal proof but I get the impression you wanted more of an intuitive explanation that it wasn't just pulled out of somebody's ass so I hope this construction helps.",
"The wikipedia pages for ",
"Tesseract",
" and ",
"Hypercube",
" contain more (obviously) but in particular there are some animated .gifs of tesseracts which might help."
] |
[
"I think what you're asking is, \"how do we know that a tesseract projected into 3-D space looks like a cube within a cube.\" ",
"tl;dr: projection into spaces of lower dimensionality is a coordinate transformation that maps the 4D coordinates of a tesseract's vertices to some 3D coordinates in 3D space. Those 3D coordinates sometimes lie on the vertices of two nested cubes. It's a linear algebra problem. ",
"You're correct to categorize this as a math question. But I think this problem is a neat example of how astronomy and math complement one another. With telescopes we can peer into the farthest corners of the universe. Mathematics allows us to see beyond what's observable through the eyepiece, and extends our gaze in directions a telescope can't point. ",
"The topic in mathematics that addressed your question is called geometric transformations. Geometric transformations take as inputs the coordinates of some point or set of points, and return as outputs those points' corresponding new coordinates. A simple example of a geometric transformation could be a rotation, where some points in space are all rotated by some angle about some axis. ",
"Another way to think of geometric transformations is that they describe a correspondence between the coordinates of points measured in one coordinate system to the coordinates of the same points measured in a different coordinate system. Using rotation as an example again, if you measured the coordinates of some points in space using a coordinate system that was anchored to your body, and then you rotated your body by some angle, the coordinates of the points measured in your rotated coordinate system will be different than in your original coordinate system, even though the points themselves didn't move. ",
"Importantly, different types of transformations have different properties. Some transformations, such as rotations, preserve lengths, angles between vectors, and parallel relationships (these are called \"similarity transformations\"). This means that rotating a square, for instance, always results in another square. ",
"Some transformations, called \"affine transforms,\" preserve parallel relationships between lines but not the angles between them or their lengths. For example, an affine transformation will always transform a square into a parallelogram, but not necessarily into another square or rectangle. ",
"The types of transformations that concern a tesseract's projection into 3d space are called projective transformations. Projective transformations give a correspondence between coordinates in a space of some dimensionality to the coordinates of those points in some lower-dimensional space. Cameras provide a common example of projective transformations, where points in 3D space are projected onto a 2D camera sensor or film sheet. An important and relevant property of projective transformations is that they map straight lines to straight lines, but do not preserve lengths, angles between lines, or parallel relationships, so squares map to arbitrary quadrilaterals. This means that photographing (or projecting from 3D to 2D) a cube, whose sides are squares, will result in a 2D image of adjacent quadrilaterals. The precise shapes of those quadrilaterals are described mathematically by the coordinates of their vertices within the 2D plane of the camera sensor, and those 2D coordinates are themselves given by their coordinates in 3D space after having undergone a projective transformation. ",
"Most importantly, there are some orientations of a cube in 3D space whose projective image appears to be a square (e.g, a head-on view). If the cube has transparent sides, then its projection would actually look like a smaller square (the image of the rear face) inside of a larger square (the image of the front face). Again, the coordinates of these vertices are determine by (1) the coordinates in 3D space and (2) the projective transformation itself. ",
"This analogy is exactly extensible to projecting 4D (or higher) shapes into 3D space. A 4D cube (a tesseract) is defined by the coordinates of its vertices in 4D space. A projective transformation into 3D space of those 4D coordinates results in a new set of 3D coordinates. For some orientations of the vertices of a tesseract, its corresponding 3D points will lie on the vertices of two nested cubes. This is how we know that a tesseract projected into 3D space looks the way it does; the answer is \"where its vertices project to from 4D to 3D.\" ",
"Incidentally, the actual mechanics of transformations in mathematics are performed by multiplying vectors (the points' coordinates) by matrices (the transformations themselves). To find the coordinates of points in 3D space projected onto a 2D image, you multiply the original coordinate vector by a matrix that describes the specifics of the projection. ",
"A few weeks ago someone on reddit asked about the applications of linear algebra; this is one of them. "
] |
[
"Right. When we draw a 3D cube on paper, we're typically drawing it with perspective scaling, where the parts father away are shrunk closer to the center of view, because objects father away reflect/emit less light that hits your retina than closer objects.",
"If we drew an orthogonally aligned 3D cube on paper in orthographic (no perspective and the cube is axis aligned with the world/paper's x, y and z), it would be that we would see a square.",
"So if you drew a representation of an axis aligned 4D cube in 3D space without perspective, it would seem as though you were looking at a 3D cube. The end which is farther away would appear to overlap the end which is closer."
] |
[
"Scientists of r/askscience, what are some glaring scientific inaccuracies that everyone understands to be the truth?"
] |
[
false
] | null |
[
"That glass flows at room temperature. "
] |
[
"The big bang was not a bang, nor was it an explosion."
] |
[
"This question is probably more suited to ",
"/r/AskScienceDiscussion"
] |
[
"Hi Askscience! Got some questions on black holes!"
] |
[
false
] |
Hi guys! I'm 15 years old and I'm stupid compared to alot of you, lets start of by saying sorry for my not-so-good english. Ok, 1st question is: As of what I've understood, a black holes is practically the closest thing to nothing as it gets, yet it has an incredibly large mass. How is this possible? If a black isn't "nothing" as i claimed, what is it then? I've maybe misunderstood the word "singularity" (told you, I'm stupid). How large is a black hole actually? Like a football field or? (I'm talking about the actual black hole, so the event horizon is not included). I've read somewhere, that if you got into the event horizon, there is no way back, not even with a magical engine, which can go to whatever speed, because when you get into the event horizon, you won't be able to see anything, and you won't be able to come, because there is something called "spacetime" (i will go to Wiki about spacetime, so don't bother about me not knowing what it is). So my question is, how can this be true, because if you look from outside, you could imagine the core of the Earth being the singularity, and the rest the event horizon the outer parts of the Earth, or am i wrong? Thanks for reading, now, enlighten me! :p
|
[
"1 A black hole is an object so dense that the escape velocity exceeds the speed of light. Since nothing can travel faster than the speed of light, things can only fall into it; they'll never be escape. This concept applies to light, too. Light is affected by gravity, see. This is part of the theory of special relativity, and we can observe the bending of light around objects with a lot of mass (see ",
").",
"2 Black holes are formed when massive stars, with more than around 10 times the mass of the sun collapse on themselves. They fuse hydrogen into helium, and then at their cores, they fuse helium. This process produces a pressure that pushes outwards, and normally balances with gravity. It takes a lot more energy to fuse heavier elements, so when the helium starts to get used up, there's not enough pressure to keep the star from collapsing. All the mass of the star falls inwards, and if the density becomes high enough for the escape velocity to exceed the speed of light, then none of it can escape again. In the cases where the density ",
", the mass will essentially bounce back outwards, as a supernova.",
"...so, this brings us to the size of the black hole. We can calculate this by using the total mass of the star that formed it. For example, if you had a black hole with the mass of our own sun (impossible, but let's calculate it anyway), we'd get a radius of just 3km. Tiny, right? You really do need a lot of mass crammed into a small space to have a powerful enough gravitational pull to make a black hole.",
"3 The event horizon is defined as the point at which the escape velocity is greater than the speed of light. This basically means that the gravitational pull is so huge, not even light can escape. Since we know nothing can travel faster than light, you wouldn't be able to escape with even the fastest spaceship. You'd still be able to see a few things, but you wouldn't be able to get ",
".",
"Escape velocity is more or less the property by which we define a black hole, really; it's an object so dense that light cannot escape it."
] |
[
"Basically it's a region in which any path something can take leads towards the center. From the outside, this has the appearance of the thing being black, because light can't escape.",
"Usually a few kilometers across, except for the supermassive ones at the centers of galaxies, which are billions of times that size.",
"That is correct. I don't really understand your Earth analogy."
] |
[
"We can do quantum field theory in curved spacetime, but I don't know that anyone has every worked out the dynamics of even a free field for the interior of a black hole."
] |
[
"In regards to superposition, why does observing an object cause it to leave the state of superposition?"
] |
[
false
] |
I just finished reading THE CODE BOOK which dives into quantum encryption, superposition, Schrodinger's cat ETC as well as what I could find with a brief google expedition. If anyone out there could take the time to explain it to me I would be ever grateful :)
|
[
"When a quantum object interacts with another object (the \"observer\"), its quantum state becomes entangled with that other object. This is a more complicated situation than the simple superposition it was in before, so phenomena such as interference are modified, and may disappear."
] |
[
"Why does the act of just looking at something cause an interaction though? Does our field of vision shoot particles or something? "
] |
[
"It has nothing to do with us looking. It has to do with the light that bounces off the object, that might or might not enter our eyes. If we close our eyes, the entanglement (of object with photon) still happens."
] |
[
"How will/Can wide-spread use of wind energy negatively effect the environment/world?"
] |
[
false
] | null |
[
"First off, I just want to make it clear that ",
" was a miserable failure from a scientific standpoint. I know you said you were aware it's just a movie, but I just want to be clear. Nothing in that turd of a film should be taken seriously. ",
"That aside, the actual question you are posing has been a topic of recent (brief) debate. The threat posed by removing wind-energy from the atmosphere is infinitesimally small for two reasons. (1) The amount of wind power extracted from the system is practically nothing compared to the amount of energy in the system to begin with; sort of like asking if we affect the sea level by putting boats in the water. (2) The energy is being removed at surface level where the wind comes into contact with objects anyway, and you might as well be concerned with whether we are pushing the climate over-the-edge by erecting tall buildings for the wind to collide with. ",
"There was an article recently about how wind turbines raise the average nighttime temperature in their vicinity that got some play in the media, because it was misinterpreted as saying that the turbines were contributing to global warming. In reality, at night a cool layer of air forms near the ground with warmer air above it, and a turbine merely has the effect of mixing that cool layer with the warm air above it, raising the surface temperature through minor redistribution rather than actually heating anything."
] |
[
"Another issue that we're seeing in Nevada is that it disturbs Sage Grouse (if you don't know about the shitstorm surrounding sage grouse, look it up) and can interfere with migration of many animals. Turbines frighten them quite a bit. ",
"Source: I work for NDOW. "
] |
[
"Ok. I have time now. ",
"Sage grouse may kinda maybe be endangered, but not listed. So anything that may hurt them (or hurt them more, depending on your views) causes a great clusterfluck. All sorts of projects are going on to preserve their habitats, and turbines interfere with that. "
] |
[
"Why isn't nuclear physics considered to be chemistry?"
] |
[
false
] | null |
[
"Chemistry is primarily concerned with things at the atomic or molecular level. Nuclear physics is concerned with the nucleus itself. There is a whole branch of chemistry called \"nuclear chemistry\", and what they do is essentially identical to what nuclear physicists do."
] |
[
"why is the subject matter of physics so broad, and why isn't chemistry physics?",
"Well, you could say that chemistry ",
" physics. The goal of physics is to understand the natural world. Nature doesn't care how humans decide to divide up the sciences.",
"why was there a need to distinguish between the to when there is so much cross over?",
"This is more a historical question than anything. And one that I don't know the answer to."
] |
[
"Chemistry is mainly concerned with the electron interactions between various atoms. Anything more fundamental is more physics than chemistry."
] |
[
"How fast would a dyson ring/sphere have to rotate to maintain constant 1g?"
] |
[
false
] | null |
[
". Also equivalent to ",
".",
"\n∴",
" = ",
" = 14 * 10",
" m",
"\n",
" = 9.81 m/s",
"\n",
" = 117,192 m/s ",
" ",
"This last bit is quite important, since the constant acceleration towards the Sun will negate part of this effect - which is the reason anything in orbit feels as if there is no gravity. "
] |
[
"The acceleration is due to the centripetal force on the objects attached to the inner surface. Therefore, it's given by ",
"*",
" , where ",
" is the radius of the ring and ",
" is its angular speed. Since ",
" = 1.39x10",
" m, and ",
" = 9.81 m s",
" , it results ",
" = 8.39x10",
" rad s",
" . This means the ring completes a full turn every 20.8 h, and the speed of a point on the surface is about 117 km h",
" ."
] |
[
"thank you for a great answer. i was thinking about an inner and an outer disk, where one is in a \"classical\" orbit at 308,709 m/s and another spinning faster so it's inhabitants would have \"gravity\". Adding all the accuracy i could conjure, the outer ring would have to be spinning at 425,575 m/s for a g."
] |
[
"Does it seem like there is a gap between published research findings and actual implementation of findings (if applicable)?"
] |
[
false
] | null |
[
"I work in a field where this issue is turned on its head, but extremely relevant. Scientists often use a \"bad\" numerical technique for their given problem because they haven't read the literature or aren't sufficiently knowledgeable about computers or mathematics to make an informed decision. Oftentimes, a mature, robust numerical library will be overlooked in a project for which it is aptly suited because the PI has no idea that it's now 2012 and BLAS isn't the only show in town.",
"Economy usually rectifies this issue, albeit slowly. A technique will become available and remain widely ignored until an already-notable researcher decides to hop on it and apply it to ",
", ",
" problems with some sort of ",
" behind them. I believe this is the same in the medical community.",
"I'm always left wondering how quickly brand-new techniques percolate down to scientists (and whether they apply them in the domain for which they are intended) and, even worse, the medical field. I know in the mid 00s there was a fertile collaboration between geophysicists and medical researchers in employing a novel solution to the tomography problem (and some other new machinery) to come up with a cool way of screening for breast cancer.",
"Hopeful note: science is becoming more interdisciplinary, so maybe the presence of more scientific polyglots in academia and industry will help cross-pollination."
] |
[
"I'm sure there are other reasons beyond my purview, but sometimes it just comes down to funding (especially in medicine). The cost of bringing a technology or product to market is much more than that of discovering a new gene/reaction/effect in the lab. ",
"Even if an experimental research team seems like it has done \"a lot\" of testing, it is still not approaching the amount of costs that are incurred by product companies through animal/human trials, drug/tech interaction trials, FDA certification, etc. ",
"Finding someone to foot the bill that brings your discovery to market can be very frustrating and disheartening, especially when you consider that there may be powerful players in business who would be hurt by your new discovery. "
] |
[
"I know that in certain fields, alternative energy being a good example, announced 'breakthroughs' tend to be one dimensional. So, for example, nearly every day there is a breakthrough in battery chemistry, solar panel development, etc., etc.. The problem is these breakthroughs relate to a specific thing: how fast a battery charges, how efficient the solar cell is, and so on. Now, it turns out that real life is more complicated: a fast charging battery is nice, but not so much if it costs 10x, or lasts half as long, or can only deliver a small current, for example. ",
"The headlines, which tend to get circulated, especially on the web, tend to not address real world considerations. Indeed, the science itself may not have been concerned with commercial factors. A scientist may figure its his job to show how nanotubes can be used, and somebody else's job to figure out how to make them cheaply."
] |
[
"do quantum mechanics disprove the consapte of CAUSALITY?"
] |
[
false
] | null |
[
"I like the book ",
" by Shankar."
] |
[
"No, QM does not say anything against causality."
] |
[
"can you recomand any book/article"
] |
[
"Why do earthquakes take place at a focus/epicenter instead of a plane or line?"
] |
[
false
] |
Paleo major in college, I just never got this. Why is the eq starting at a point instead of a plane? Wouldn’t the earthquake move the whole block along the fault plane?
|
[
"This question gets asked fairly often, e.g. the ",
"FAQ on it",
", or ",
"this answer",
" or ",
"this one",
".",
"In short, earthquakes do represent rupture (i.e. slip) of a portion of a fault plane. The hypocenter represents the point on the fault plane where the rupture starts, and the epicenter is the projection of the hypocenter to the surface (An important clarification is that hypocenters/epicenters often do not correspond to the center of a rupture, i.e. the location with maximum slip.). The area of the fault plane that ruptures relates to the magnitude of the earthquake (more area = higher magnitude), but ruptures are still finite, i.e. they typically do not rupture an entire fault plane (though this will depend on the size of the fault plane, so we need to be careful with blanket statements). As to why ruptures have finite areas as opposed to always rupturing the entire fault plane, we can think about this in terms of energy and/or balance of forces. A rupture happens when the accumulated strain overcomes the frictional strength of a fault plane in a spot (the hypocenter). The release of this strain, i.e. the slip, actually adds strain to neighboring areas on the fault plane and if that added strain overcomes the strength of the next neighboring bit, the rupture will continue to propagate (i.e. the next bit slips which strains the next bit, etc). As the edge of the rupture spreads out, the \"energy\" is being spread over an increasingly large perimeter so the amount of slip that happens in the next neighbor decreases until the rupture eventually terminates, i.e. the little bit of slip that happens is not enough to push the next neighboring bit past the frictional strength. While not 100% applicable, we can apply a lot of the principles of ",
"fracture mechanics",
" to think about rupture propagation.",
"Thus, we can think about the different ways an earthquake might be represented on a map, and these could be (and are, depending on the purpose) as a point (i.e. epicenter representing the start of the rupture), a line (representing the extent of the fault that ruptures in 2D or the extent of surface rupture), or a polygon (representing the actual patch of the fault that ruptures that could be viewed in a 3D perspective or projected up to the surface of the Earth)."
] |
[
"Just to add. The hypocenter is relatively easy to locate by triangulating based on the arrival times of the first seismic waves at different seismometers. It takes more work to establish how the rupture propagated in the fault plane after that.",
"For small earthquakes, the length of the rupture is comparable to or less than the error bars on the hypocenter location anyway which are usually a few kilometres. Based on the data at the end of this paper, it looks like an earthquake below magnitude 6 will usually rupture well under 10 km in length.",
"https://www.researchgate.net/publication/281433403_Statistical_Relations_Among_Earthquake_Magnitude_Surface_Rupture_Length_and_Surface_Fault_Displacement#pf9"
] |
[
"Yes, and while automation of routines has really sped up the calculations of the details of the rupture, it's still the difference between having a location for an epicenter literally seconds after the first seismic waves arrive at a few seismometers to several hours (or longer) for enough data to be collected, shared, and processed across seismometer networks for the estimations of the rupture patch, etc."
] |
[
"Why does it feel like the body is more prone to pain and why does the body also magnify pain in colder environments?"
] |
[
false
] | null |
[
"not a medical specialist makes you a laymen, no laymen speculation"
] |
[
"not a medical specialist makes you a laymen, no laymen speculation"
] |
[
"Yes. A lack of understanding of common knowledge 'facts' can lead to wildly inaccurate extrapolations which, although occasionally correct, mostly serve to confuse and to spread misinformation."
] |
[
"can I see the past if i travel any amount of light years instantaneously?"
] |
[
false
] | null |
[
"Yup. The only hiccup is, of course, the ability to transverse such a distance. "
] |
[
"And of course, the ability to see things in detail from such great distances, which we also cannot do well.",
"According to the Rayleigh Criterion, you'd need a telescope that has a lens with about a 20-light-year diameter to be able to view a 2 m dinosaur from 65 million light years distance."
] |
[
"This and the fact that when you arrive, you'd be viewing the past at a great distance. Look at the stars at night. They are tens, hundreds, and millions of years old when the light hits your eye."
] |
[
"Can two ions with the same number of electrons have different electron configurations?"
] |
[
false
] |
I thought you could have two different electron configurations even if the number of electrons are the same...
|
[
"Yes they can. Electron configurations can change if the electrons are excited. ",
"Another instance is when a transition metal forms a ligand, the d orbital can spit. Sort of like this:",
"http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch12/graphics/12_17.gif",
"Depending on the gap between the two split levels, the electrons will fill the orbital differently. They can either fill all the orbitals as if they were at the same energy level, or they can fill in the bottom ones first, then the top.",
"This is a very basic overview, and I think mostly correct. I did research in undergrad on molecules that experienced this type of d-orbital splitting, but I'm a bit rusty. You can read more about this splitting here: ",
"http://en.wikipedia.org/wiki/Crystal_field_theory"
] |
[
"It's possible if electrons are excited by light. In an Li+ ion, for example, the usual electronic configuration would be 1S2, but it is possible (but highly unlikely) that light would promote one of those elections to the 2S orbital, giving a configuration of 1S1 2S1.",
"It is also possible if the 'ion' is part of a larger complex. A complexed ion has orbital mixing. This means that some orbitals are stabilised and others destabilised relative to the isolated ions orbitals. Metal centres in complexes aren't, however, really ions.",
"For an isolated ion, I'm pretty sure the answer is no."
] |
[
"The ground state is the configuration with the lowest energy. You may have degenerate ground states in which different \"micro\"-configurations all possess the same energy, but you couldn't tell these apart from the outside because, well, they're degenerate.",
"Actually, for different electronic configurations you don't even need ions. The ",
"oxygen molecule",
" is in a triplet configuration in the ground state (left), and there are two excited singlet states (middle and right)."
] |
[
"What is the Delta variants mortality?"
] |
[
false
] |
I’m seeing 10,000 new cases a day in the UK and no increase in the death rate. Is there good data on the mortality of the delta variant?
|
[
"A number of factors to consider here:\n1. There will be a delay from new case reporting to hospital admissions to ICU admissions to mortality. Death is a trailing indicator!\n2. A large proportion of the UKs population that is most vulnerable have already been vaccinated, meaning that even if they are infected, they are now less likely to require hospital admission, ICU admission, or to die\n3. The remaining population that hasn’t been vaccinated are younger and healthier (due to vaccine priority for older and more vulnerable populations) so they are less likely to be hospitalized or die.",
"I’ll grab you the data points when I’m off mobile but the question has some suggested answers, but these explanations above are probably more impactful to the observation you’ve made above.",
"Edit to add there is no great quality study that I can find that answers your question. A study looking at this question for Alpha is found here:",
"https://www.bmj.com/content/372/bmj.n579",
"But I’ve not found something of comparable quality for Delta. May simply be too soon to have the data."
] |
[
"I have no data on the mortality rate, but the \"no increase in death rate\" is likely because the cases only started climbing a few weeks ago. The death rate increase (if it happens) typically lags 2-4 weeks behind."
] |
[
"In the Public Health Scotland/EAVE II study, Cox proportional hazard regression was used to estimate risk factors for the time from test to hospitalisation among individuals who tested positive. Hospitalisation with COVID-19 was defined as any admission within 14 days of a positive test or where there was a positive test within 2 days of admission. The model was adjusted for age and days from 1 April 2021 as spline terms together with number of co morbid conditions, gender and vaccination status. Vaccination status was determined at the data of the PCR test. Individuals who tested positive from 1 April 2021 onwards (until 14 June 2021) were included in this analysis. There was an increased hazard ratio of hospitalisation for those who were S-gene positive compared with those with S gene target failure (1.8, 95% 1.4 to 2.3)",
"The previous variant, Alpha / B.1.1.7 / Kent, has a mutation (deletion at 69/70) that results in a false negative for the S-Spike gene in TaqPath PCR machine. This is known a S-gene dropout. The new Delta variant lacks this mutation so it is S-gene positive. That allows health authorities in the UK to track the growth in cases without needing to do full genetic sequencing.",
"In Scotland they are seeing people who test S-Spike gene positive (Delta) are about 1.8 times more likely to end up in hospital compared to S gene failure (Alpha). ",
"This is circumstantial evidence that the Delta variant might cause more severe COVID-19 symptoms than the Alpha variant. If this is the case, it might be due to the P681R mutation, that may boost cell-level infectivity.",
"https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment\\_data/file/994839/Variants\\_of\\_Concern\\_VOC\\_Technical\\_Briefing\\_16.pdf"
] |
[
"How come sewage is so filthy?"
] |
[
false
] |
[deleted]
|
[
"Soap doesn't magically \"clean\" something. It solubilizes whatever you don't want - grease, stains, etc. - and ",
" wash it out.",
"If your plate is dirty, does it magically get clean when you dump detergent on it and let it sit? No! You need to ",
" to get rid of it. All the stuff you don't want leaves the plate and goes down the sink."
] |
[
"I know, but what about the water that goes down the drain? Or is it just basically a poo water solution?"
] |
[
"What about it? It's a solution consisting of everything you dump down the drain."
] |
[
"How is the suffix of an element determined?"
] |
[
false
] |
I woke up with this weird question on my mind for some reason. You have some elements ending in "gen" IE: Oxygen, Hydrogren, and some ending in "ium" IE: Cadmium, Helium, Francium. How are these suffixes determined?
|
[
"Well \"gen\" is ",
" greek for maker, or generator, the word \"Hydrogen\" literally means \"Water Maker\", whereas Oxygen (somewhat misnamed) means \"Sharp (Acid) Maker\"",
"Not too sure what \"Ium\" means, but ^ is where the gen comes from!",
"Hope that helps :)"
] |
[
"Wiktionary says it's from Greek:\n",
"http://en.wiktionary.org/wiki/hydrogen",
"\nBut there's also the word \"genus\" in Latin which can mean birth.",
"The -ium/-um is from Latin (Ferrum is Iron for example). The latin names for hydrogen and oxygen are hydrogenium and oxygenium"
] |
[
"There really isn't much of a rhyme or reason behind it. Since the majority of the elements were discovered a long time ago their names have been assigned by their discoverers without too much consideration. Check the wiki on ",
"chemical elements name etymology",
" for more info. I can't remember where I read it, but these days they try to name things so they end in '-ium', which is why the lanthanides, actinides, all of period 7 and half of period 6 end that way, because they were discovered later and have been subject to this rule. "
] |
[
"Could the number of dimensions be infinite?"
] |
[
false
] |
I'm only of a casual understanding of all of this, so, you know, laugh away. I'm working off of the . We operate spatially in dimensions 1, 2, and 3, moving along 4. If you combine all of space (1,2,3) into a given point, then you can treat dimensions 4, 5, and 6 as if they are spatial, right? If matter is built from something which signifies information, then perhaps a point in dimensions 4,5,6 behaves like a point in dimensions 1,2,3. Perhaps the fundamental building-block of our universe is a point representing dimensions -2, -1, and 0, just as all of our spatial reality forms a building-block in dimensions 4,5,6. Perhaps this proceeds infinitely in both directions, or perhaps it loops in on itself. Any meat on that bone? EDIT: After watching , I see now that I am retarded.
|
[
"The ten dimensions video is ",
" but pseudo-science. It has ",
" to do with reality.",
"Edit: we just had ",
"this discussion",
" a few days ago about it."
] |
[
"Sorry, Maybe I was too harsh. I really, truly didn't intend to embarrass. I'm just more frustrated with the people making these videos and presenting them as fact. Before I learned physics, I would have easily bought into something like this myself. If you take a bunch of fancy words that sound technical, you can create a very \"correct sounding\" piece of work that has nothing to do with reality. ",
"Edit: And I can't just go on youtube and tell everyone the video is just some guy talking out his ass. Die-hard cranks will yell about me trying to suppress the truth, others will think I'm trolling, or won't understand that I know a bit about what I'm talking. Or ultimately, most likely, my comment would be drowned in a sea of \"OMG MIND=BLOWN\" comments. Again, it really isn't your fault, or even the other people watching that feel like they've learned something profound. People are truly and rightly interested in how the universe \"works.\" It's a real fucking shame that other people take advantage of that. "
] |
[
"You weren't nearly harsh enough. I agree that Jan shouldn't be embarrassed, but that video and the accompanying book are a con job of the worst kind."
] |
[
"Why do the „warm“ and „cold“ seasons happen a bit later than the „bright“ and „dark“ seasons?"
] |
[
false
] |
21st of June is the day with the most sun hours, 21st of December the one with the least. So why do the really hot days occur in July and August, and the coldest ones usually in January and February? (I live in Germany, if that matters)
|
[
"Sunlight heats a place up ",
", it doesn't make it instantly become warm. June 21 or thereabouts is when we in the northern hemisphere get the most sun, so it's also the time when our regions heat up the fastest, but that's not the same as saying that's when they have the max temperature. That only happens after weeks and months of sustained warming up, even if, at that time, there's slightly less sunlight than earlier.",
"It's mostly the same reason why it's not warmest at noon and it's not coldest at midnight. It's also why, if you turn off the heating in your house, it doesn't get cold immediately.",
"For a perfectly sinusoidal heat flow / temperature relationship you would expect the point of maximal and minimal temperature to be exactly halfway between the point of maximal and minimal heating, so the warmest day of the year in the north would be in mid-september, and the coldest time of day would be at 06:00. In reality it happens a bit before that."
] |
[
"For a perfectly sinusoidal heat flow / temperature relationship you would expect the point of maximal and minimal temperature to be exactly halfway between the point maximal and minimal heating",
"I'm not sure this is true. If the earth's temperature on the timespan of a year behaves something like an LTI system (and I don't see why it wouldn't), then a sinusoidal input (sunlight) would cause a sinusoidal output, but the phase shift may not be 90°."
] |
[
"Right. I had a straight up differential equation in mind: dTemp/dt = Light."
] |
[
"Why do most Mandarins have 11 segments?"
] |
[
false
] |
I've been counting them for a while, and some have twelve, some have 10, but the majority have 11. Why such a strange number?
|
[
"The segments of the fruit are derived from carpels which are a part of the flower, so they will usually come in multiples of 3, 4, or 5. The carpel is part of the female reproductive organs and contains the ovules. So each segment will have seeds and the number of different segments will help with seed dispersal, etc. ",
"But it's important to note some things. First is that developmental errors happen and can produce carpels in strange numbers. The second is that citrus fruit is almost never grown from seed. It's propagated by cutting a stem from a tree and grafting it onto a new plant. And they decide which stems to use based on the fruit. ",
"So with your mandarins, what would have happened is that there was some mistake that caused a strange number of segments, and there was also some change that made a more desirable fruit. That could be thinner skin, more sugars, any number of things really. The important thing is that for some reason it co-occurred with the strange number of segments. ",
"So when that fruit was propagated it was propagated for the positive changes, but it brought along the weird number of segments. And every mandarin has been propagated from that fruit, so the mandarins have the strange segment configuration. "
] |
[
"I'm afraid that question exceeds my botanical knowledge. I'm more of an insect kind of biologist. I just happen to know a bit about the citrus because I used to live next to the ",
"National Clonal Germplasm Repository for Citrus & Dates.",
" ",
"Which is probably the world's premier citrus repository. In addition to research plots for I don't even know how many projects, it has two specimens each of over 1,000 varieties of citrus. "
] |
[
"Is the stamen on a flower segmented by number of carpels? Is it possible to fertilize only some of the carpels and get oranges of reduced numbers of segments?"
] |
[
"Why do your lungs get sharp pains when you go running in colder (possibly drier) weather?"
] |
[
false
] |
I've lived in Florida most of my life and I noticed that when I run in cold weather (it is also drier) I experience sharp pains in my lungs which I do not experience when running in warmer, more humid weather. I have heard others with this complaint and have been told that it does not affect everyone. I have also been told it may have something to do with the cold air interacting with phlegm lining your throat. Can askscience help?
|
[
"Your upper airway exists to moisten, warm, and filter air. When you are breathing harder, the air spends less time becoming moist and warm in your upper airway before it proceeds down into your more sensitive lower airways. This causes discomfort. However, if this pain is accompanied by shortness of breath or any abnormal lung sounds, it may be a more serious condition."
] |
[
"It depends where the pains are, and how long you've been running. Cold weather can induce asthma, and also causes the mucociliary function of the respiratory tract to decrease. Pain can be a sign of vaso occlusion (if the pain is unilateral), maybe it would help if you described it more. It could also just be that if you come from a warm environment and go into a cold one with increased ventilation demand, the cold air is decreasing compliance of the alveoli as they get smaller (temperature volume laws). "
] |
[
"My best differential would be that the air makes your alveoli less compliant then. When you breathe in too much, you are expanding them past where they want to go, and feeling pain as a result of the increased intrapleural pressure caused by the cold air. Still, I'd see a PCP about it if it's bothering you"
] |
[
"*Nuclear Engineers* Why did Fukushima melt down if the loss of cooling water should actually kill the reaction?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):"
] |
[
"The flawed premise is that the Fukushima reactors melted down due to an uncontrolled chain reaction, when in reality they were SCRAMmed immediately after the earthquake (which was long before the tsunami arrived).",
"The issue is that the cores continue to produce decay heat even after the chain reaction is stopped. This is just due to the radioactive decay of the fission products, and not due to more fission occurring. So the absence of moderator, which is used to control the rate of fission reactions, is not relevant to the decay heat."
] |
[
"Ok thanks for that. My question was still valid however, in the last part I asked “Or is even a dead reactor still hot enough to warrant continued cooling and can still lead to a meltdown?”. Which you just confirmed to be true, which makes it inappropriate to remove my post, as my premise wasn’t completely flawed."
] |
[
"Are breathing exercises generally useful or harmful ? In what context ?"
] |
[
false
] |
Hello ! I would like the post to stay focused on respiration exercises, rather than practice that include, among other things, monitoring of your respiration. I tried to search for the benefits of respiration exercise, and didn't find much that was scientifically backed, actually I even found some website saying it was a bad idea. So, are breathing exercises useful ? harmful ? In what context ? Edit : Would like more focus on the "are breathing exercise " part.
|
[
"Could someone who knows more also comment on the notion that deep abdominal breathing stimulates the vagus nerve, which causes relaxation? I've heard this from multiple sources, but nothing I'd consider truly trustworthy, but I haven't been able to find anything debunking it either."
] |
[
"Because they're still under the placebo effect of the doctor telling them it can still work, even though they're not under the placebo effect that the sugar pill is an actual drug."
] |
[
"Any support for this ?"
] |
[
"What causes light to be emitted as one of the results of friction?"
] |
[
false
] |
[deleted]
|
[
"It has to do with ",
"Black-body radiation",
".",
"All matter emits electromagnetic radiation when it has a temperature above absolute zero. The radiation represents a conversion of a body's thermal energy into electromagnetic energy, and is therefore called thermal radiation.",
"Black-body radiation becomes a visible glow of light if the temperature of the object is high enough. The Draper point is the temperature at which all solids glow a dim red, about 798 K"
] |
[
"That is not equal to black body radiation.",
"Black body radiation originates from vibrations of the charges."
] |
[
"Agreed. Light can be emitted through changes in electron states, but this is not thermal black body radiation. An accelerating charge produces light, thus vibrating atoms will do that."
] |
[
"Does high cortisol in the body, or a stronger than average cortisol response to external stressors, equate to a person being generally more stressed out? In other words, stress 'causes' cortisol, but does cortisol cause stress?"
] |
[
false
] |
We know that external stressors and/or stress generally result in a statistically significant cortisol response. Has the opposite connection been shown to hold statistical significance? In other words, stress 'causes' cortisol, but does cortisol cause stress? I'm asking this because I've come across studies in the past about this and general comparisons of stress in urban and rural populations. For example, I quickly found comparing rural and urban upbringings. I'm not well-versed enough to know whether this or other studies on cortisol and cortisol responses directly claim or show that more cortisol equals more stress.
|
[
"Both. Cortisol is a sign of how aroused the hypothalamus-pituitary-adrenal axis is, which is a central part of the body’s response to chronic stress. But at the same time, neurons in the cortical and limbic structures express corticotropin releasing hormone receptors that act in a kind of feed-forward dynamic, to mediate a behavioral aspect of the stress response. ",
"Not only do these exert a direct effect on behavior, they also alter the expression of housekeeping and neurotrophic genes in many neurons. This can act in maladaptive ways. For example, chronic stress-hormone exposure antagonizes the expression of BDNF receptor, which is necessary for adult neurogenesis in the hippocampus. These changes can manifest long-term as an anxiety/depression syndrome. ",
"The long-term dysregulation of stress-hormone levels in this feed-forward mechanism is implicated in the withdrawal syndromes for drugs like alcohol, which can be seen as a kind of maladaptive chronic-stress response precipitated by not drinking. ",
"One of the hypotheses for the way antidepressant drugs like SSRIs work is that the increased serotonin signaling they produce causes gene-expression changes that oppose what the stress hormones do. Essentially, they help to reverse the cellular and behavioral aspects of the stress-hormone induced responses in the brain. "
] |
[
"Cortisol is a hormone that does a lot of things in the body. It is a glucocorticoid and is involved in the regulation of blood glucose. This hormone has been linked to behavioral and cortical arousal (increased levels of hormone lead to increased arousal). One of the main factors in waking from sleep is the secretion of cortisol, which is essentially off while asleep. ",
"During an acute stressor there is a surge of hormones involved in the fight or flight response. Adrenalin (epinephrine), noradrenaline (norepinephrine), and cortisol comes in later because it is synthesized de not and that takes a bit of time. This response essentially prepares your body by orchestrating changes in function that allow for fast, powerful, and somewhat prolonged physical activity. Cortisol helps by causing a sharp rise in blood sugar through it's glucocorticoid effects. ",
"Corticotropin releasing hormone is what causes the release of cortisol. As another comment mentioned, research has shown that CRH has direct effects on behavior and neural activity. Conditions like PTSD have shown elevated levels of CRH but not cortisol, suggesting this hormone but not cortisol itself is related to the hypervigilence and anxiety in this condition. ",
"The big issues come from chronic stress and stressors. The chronic, high level, release of cortisol actually seems to damage the feedback loop for cortisol release. So, stress leads to more stress, to more stress, etc. This is strongly linked to depression and anxiety. "
] |
[
"What’s your source on stress inhibiting adult neurogenesis? I swear I read a paper on that exact topic but I don’t remember where. "
] |
[
"As a method for speciation how does \"Oceanic Dispersal\" really work (considering how much ingenuity it takes for humans to survive long periods on rafts)?"
] |
[
false
] |
[deleted]
|
[
"You're right, it's a tough question. But the first thing to remember is that millions of years ago, Africa and South America were actually in contact, then split from tectonic movements and have been diverging ever since. So it may not have been several months. It could have been weeks or even days, depending when and where the dispersal event occurred.",
"Sure, that journey is hard, and not many creatures can survive a week without water. But what if the primates were really fortunate, and the vegetative raft contained some fruiting trees? Just a bit of this fruit in the midst of a raft could sustain a few individuals. There could be other ways the journey was aided as well...other animals that died first and could be eaten, lucky arrangements of large leaves to catch rainwater, etc. Yes, I'm speculating here, but it's very clear that this event ",
" happen, even if we don't know ",
".",
"So it's certainly not a common matter. Not everything can be coconut trees (the undisputed kings of worldwide oceanic dispersal). But these events are rare, as you would expect. We can be very confident that it did happen, though ... morphological and molecular data on this is conclusive - they are distant cousins and more closely related to each other than anything else in South America is related to the New World Monkeys. If primates did NOT travel from Africa to South America after the continents split, then something very much more improbable happened, something like magic or alien tampering or something for which there is zero evidence, because New World Primates clearly did not evolve from anything else living in South America before they showed up.",
"Edit: It is possible that the alternative was a land bridge, instead of an oceanic raft."
] |
[
"Look at ",
"this frame",
" from ",
"this graphic",
" and tell me that Africa and South America were one land mass 40 million years ago, when New World Monkeys diverged from Old World primates. "
] |
[
"Nah, I got the time frame wrong."
] |
[
"Why is epinephrine used to treat severe allergic reactions?"
] |
[
false
] | null |
[
"Epinephrine is a catacholamine that stimulates the sympathetic receivers (beta 2) in the upper and lower airways, bronchials and bronchi to dilate. During an allergic reaction there is swelling, narrowing and possible obstruction of the airways. In a severe allergic reaction there also is a possibility of arterial dilation and a drop in blood pressure. Epinephrine also stimulates sympathetic (Alpha) receivers in the arteries to make them constrict, thus raising the blood pressure."
] |
[
"Great explanation, but it's *catecholamine and *bronchioles. "
] |
[
"It also stimulates beta 1 which increases chronotropy (rate) and inotropy (force) of heart contractions which increases cardiac output. That, combined with the vasoconstriction from alpha 1, helps to maintain blood pressure."
] |
[
"Japan has smoking population that is about 1/3 of its total population. How do the they have the second longest life expectancy in the world, when so many people smoke?"
] |
[
false
] | null |
[
"Epidemiologist here. Just wanted to raise a key point I haven't seen the responses thus far. ",
"It takes a long time for smoking to induce lung cancer. ",
"Peak rates of smoking in a population result in peak lung cancer rates decades (~30 years) later. ",
"For example, lung cancer incidence in Canadian men peaked only recently, even though smoking rates peaked decades ago. Women's cancer rates continue to increase because women in much of the western world took up smoking later than men. We predict rates will start to decline soon, reflecting the widespread quitting of smoking that began some 20-35 years ago.",
"Since smoking became widespread in Asian countries long after the West, we expect that the major bulge of lung cancer incidence and mortality is yet to come. But it will come. ",
"A couple of relevant articles:\n",
"http://www.bmj.com/content/321/7257/323",
"http://med.stanford.edu/biostatistics/abstract/RobertProctor_paper1.pdf",
"tl;dr Soon",
"EDIT: since the comment took off (thanks for the gold!) some additional stuff:",
"Smoking causes illness and death through a variety of conditions, not just lung cancer. I didn't mean to suggest that smoking's effects on mortality/ life expectancy are only caused by lung cancer. I used lung cancer in my comment because it tracks so well with smoking and has a pretty clear lag. Other conditions like COPD (aka emphysema), heart disease, stroke etc are also linked to smoking and ",
" be affected by lags since they often appear later in life.",
"Second, lots of the other comments below respond to the paradox assumed in the question with other cool hypotheses related to diet, tea, alcohol, artifacts in life expectancy calculation, genetics etc. Since many of these things could be true simultaneously, how do we figure it out?",
"It's hard to figure anything out when all we know is the exposure and outcome rates for populations/countries/regions as a whole. It's called an ecological comparison, and it's tricky as hell,\nthough often a good starting point.",
"Ideally, an epidemiologist would have access to data on each Japanese person. And each American person. And each Danish person. All the way down. If we know about exposures (smoking, diet, etc) and outcomes (cancer, CVD, overall mortality, etc) for each individual, we can make some much more robust conclusions about trends at the population level and their causes. And then identify targets for treatment and (even better) prevention. And this is what is happening, but it takes time. ",
"Please, if you are ever asked if an epidemiologist can access your health records for research, please say yes. And please support initiatives to give researchers greater access (after ethics review) to population health data that currently just sits in a figurative drawer but could help us so much.",
"Edit 2: thanks to ",
"u/skakaiser",
" for linking this great paper on smoking prevalence in Japan that shows smoking has already declined and lung cancer rates are following with the multi decade lag.\n",
"http://www.who.int/bulletin/volumes/91/5/12-108092/en/"
] |
[
"Do you have a source for that claim that 1/3 are smokers? Seems a little high to me. Or possibly out of date. When I moved to Japan (1996) it seemed like the whole country was one large smoking section but there has been a sharp decline in smokers in the past decade or so. In 1996 I didn't think it was odd to find people smoking in an office of any kind, but these days there are a lot more places that are smoke free. There are fewer people smoking now, but perhaps also smokers smoke less due to more smoke-free offices/spaces than before. Part of that was a bit cultural seismic shift I believe, but also due to an increase in anti-smoking ads (or actually mind-your-manners ads) and getting a bit stricter about not selling to minors. I quit smoking around 1999 but friends tell me that vending machines (some? all?) require a majority card to buy cigarettes now. ",
"One more thing - when you conflate \"x% of the population are smokers\" and \"why do they live so long\" you are implicitly assuming that lung cancer etc is equally determined by all levels of smoking. Is that the case? I thought heavier smokers were more likely to get a smoking-related disease than light smokers. That isn't captures in a \"percentage of the population\" statistic. ",
"I did a google search - according to Japan Tabacco, in the summer of 2012, 21.1% of adults were smokers. ",
"SOURCE:\n",
"https://www.jt.com/investors/media/press_releases/2012/0730_01.html"
] |
[
"Your question is related to what is called the \"Japanese lung cancer paradox\". This is based on the observation that Japanese men smoke more than American men, but have much lower rates of lung cancer. ",
"The exact cause is not known. Speculation includes: \" more toxic cigarette formulation of American manufactured cigarettes as evidenced by higher concentrations of tobacco-specific nitrosamines in both tobacco and mainstream smoke, the much wider use of activated charcoal in the filters of Japanese than in American cigarettes, as well as documented differences in genetic susceptibility and lifestyle factors other than smoking.\"",
"See: ",
"http://www.ncbi.nlm.nih.gov/pubmed/11700268",
" for more information."
] |
[
"I remember in school we had a PTC test (taste test for Phenylthiocarbamide)... Is this why certain foods, such as coriander, are so distasteful to certain people"
] |
[
false
] |
(I remember hearing people talk about how they would rather eat dirt than have coriander on there food and there are multiple sites on the internet dedicated to the dislike of coriander)
|
[
"The ability to taste PTC and a dislike of coriander/cilantro are not controlled by the same genes, as far as we know. This is a qualified answer, because there doesn't seem to be a lot of work on why coriander is disliked. The ability to taste PTC is caused by the TAS2R38 receptor (see ",
"Wikipedia",
"). The only work I can find on the genetics of coriander sensing comes from ",
"Lilli Mauer's 2011 Master thesis",
". The abstracts states that mutations in the OR4N5 olfactory receptor or the TAS2R1 taste receptor might be associated, in Caucasians. There is, so far, one paper published on that work: ",
"Mauer and El-Sohemy, ",
" 2012,1:8",
". This paper states that \"genetic factors associated with cilantro preference have yet been identified\"."
] |
[
"thank you for this, in follow up, is it theorized that taste preferences in general are due to individuals mutations of specific receptors?"
] |
[
"I'm by no means an expert in the genetics of taste perception or taste preference. I just happen to have read about the genetics that affect how people perceive the flavor of coriander.",
"Taste perception (which we were talking about with PTC and coriander) is different from taste preference (what flavors you like). You can try the 2007 review ",
" (",
"MC Neurosci. 2007; 8(Suppl 3): S3.",
") for an over view of how the genetic components of taste and taste preference are figured out.",
"The gist from the review that the frequency that someone eats something, or how much of something someone eats, is controlled by many different genes. But components of a taste are detected by specific receptors."
] |
[
"If global warming ramps up C02 in the atmosphere, wouldn't that potentially cause plants to grow bigger and faster as it got worse?"
] |
[
false
] |
I could be completely wrong in my understanding, but from what I assume we are really just worried about our liveable conditions in the environment. When plant life will, like they always have, thrive on warmer temperatures and increased C02 in the atmosphere. It could eventually pan out that we will find it difficult to live in new evolutions in climate change. But from what I gather this only means other organisms will have a better chance to thrive. Kind of like mother natures way of forcing us to stay in-doors, because we couldn't play with the rest of the kids nicely.
|
[
"While this is partly correct, I would like to point out that this does not really paint the whole picture and leaves out important caveats. This is because CO2 is not a limiting resource for most plants. Nutrients in the soil (like phosphorous or nitrogen) or even water availability limit how much plants grow in a natural environment. We can artificially make plants grow more or bigger in greenhouses or by fertilizing them but we cannot do this on a scale that would offset carbon production by humans. "
] |
[
"One might ",
" plants to do better in higher CO2 concentrations, but realistically only plants where CO2 is the limiting nutrient will have any significant short-term improvement due to increasing CO2 levels. And while this question is ongoing and still very much being studied, it looks like CO2 is only rarely the limiting nutrient in plants. Or, in other words, plants already tend to get all the CO2 they need. As jamesj points out, the level of CO2 necessary to see a response in plant growth in the short term is extremely high.",
"Now in the long run, higher CO2 concentrations may very well make some mutations advantageous and plants may adapt to take advantage of it - but that would require CO2 levels remain elevated for quite some time, when realistically the majority of CO2 only stays in the atmosphere for less than a thousand years, and humans aren't going to be able to sustain modern CO2 emissions without some major technological breakthroughs (which would probably involve removing CO2 from the atmosphere in the first place).",
"Whether warmer temperatures helps plants depends. More than temperature, precipitation is the important factor here. Which is why you can get incredibly high biomass in rainforests in relatively cool climates (temperate rainforests). If future climate change involves higher temperatures ",
" higher precipitation in most areas, then one might expect plants to eventually do well (even if the plants that do well replace the native plants in a region). If future climate change involves higher temperatures and lower precipitation in most areas, then one might expect plants to do very poorly.",
"But arguably, all this is still missing the most important point.",
" human-caused climate change eventually turns the planet into something more suitable for plant and/or animal life, the process of shifting climates will still result in the pre-mature deaths of countless trillions of animals and plants. Yes, the planet will go on supporting life after humans do whatever we are going to do with it, but that doesn't there won't be associated suffering and loss due to human activity. ",
"The human organism will be quite capable of surviving any projected degree of climate change, but the socioeconomic impacts of climate change will cause an unknowable amount of damage to the human species.",
"So it's less like:",
"mother natures way of forcing us to stay in-doors, because we couldn't play with the rest of the kids nicely.",
"And more like:",
"we're the schoolyard bully, and we killed 50% of the other school children in the playground, and injured ourselves in the process. We end up re-taking third grade while a new batch of students arrives and mother nature crosses her fingers that we don't do it all over again."
] |
[
"While carbon dioxide isn't usually a problem, there's a reason C4 and CAM plants exist - carbon dioxide is collected by opening the stomata, resulting in water loss. So a higher concentration of CO2 would result in faster acquisition of required carbon, with corresponding lower water loss.",
"Of course, this would mostly be of concern to plants in arid environments - which are probably going to become a lot hotter and quite possibly more arid as a result of climate change. Obviously, this will result in less water availability and more evaporation while the stomata are open. So I wouldn't expect any increased viability for the plant."
] |
[
"Can someone identify this old circuit diagram I found in a book from 1931?"
] |
[
false
] |
I found this paper folded up in a book called "Frieder Im Thuringer Wald" with a copyright date of 1931. I'm not sure if the book and the paper with the circuit diagram are related, but they both seem pretty old and fragile. I'm curious as to what the circuit diagram might be. Thanks for your help.
|
[
"Well first, you're holding it upside down.",
"Using the orientation you took it at, bottom appears to be a radio receiver, three stage tube amplifier. The others looks like alternative amplifier designs and seem half drawn out. It's not a crystal radio, I don't see a crystal.",
"Looks a whole lot like this 3 tube radio"
] |
[
"Yea, someone else said it was upside down as well. I took the pic with that orientation because when the paper is flipped over, the stationary is right side up.But, thanks for the info."
] |
[
"That makes a lot more sense. I didn't recognize the vacuum tubes!"
] |
[
"How would donut shaped planets work?"
] |
[
false
] |
Hello, I'm in fifth grade and like to learn about planets. I have questions about the possibility of donut shaped planets. If Earth were a donut shape, would the atmosphere be the same shape, with a hole in the middle? Or would it be like a jelly donut without a hole? How would the gravity of donut Earth be different than our Earth? How would it affect the moon's orbit? Thank you. :)
|
[
"I've saved a few sources on donut-shaped planets. (The mathematical word for a donut shape is ",
", by the way. The adjective form of that is ",
" ",
". And if you're interested, the branch of mathematics that deals with neat shapes like this is called topology.)",
"Here's a video",
" that discusses rotation, gravity, seasonal variance, climate/weather, and other subjects. It was based on ",
"this blog post",
" that has a bit more information.",
"This page",
" has more information on torus gravity, but it's kind of mathematically dense. (I'm in my 20s and I don't understand half of it myself.)"
] |
[
"This reply is a pretty good start. Going to be a while before you can deal with the math. Maybe get a teacher to help you with the higher end portions.",
"Good question by the way. Not many think about things like that."
] |
[
"If you look at the formula F = GMm/d",
" it's not actually the center of mass. That's only an approximation. For a donut, you'll still be pulled toward the 'ground' because the gravitational force on your side of the donut is far stronger than the gravitational force from the other side of the donut."
] |
[
"How do the same cacti appear in widely separated deserts all over the world?"
] |
[
false
] |
[deleted]
|
[
"There is only one species of cactus that is native to the Old World (and also the New World), ",
" (aka Mistletoe Cactus). It is thought that the seeds were probably distributed to the Old World within the past couple thousand years by migratory birds. The other species of cactus you see outside of the Americas were all introduced by humans."
] |
[
"There's also the \"all deserts are the American southwest\" issue which crops up in movies and so forth. The planet has a wee bit more biodiversity than you'd assume from what shows up on the television."
] |
[
"There seems to be a common misconception that you can go to the Sahara and see saguaros everywhere."
] |
[
"Does the concept of DL³ exist. Why does it or why doesn't it, and if it doesn't exist, what would make it possible to exist?"
] |
[
false
] | null |
[
"What is DL",
" ?"
] |
[
"Cubic Decilitre"
] |
[
"A decilitre is already cubic."
] |
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