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|---|---|---|---|---|---|
[
"Why did China's recent easing of it's COVID restrictions lead to such a huge explosion in new cases?"
] |
[
false
] | null |
[
"They had an active circulation of a highly contagious variant, in a very dense population in winter with essentially no transmission resistance when they did it.",
"The current Omicron variant is very distant from the initial strain that was the basis for the vaccines, and the Chinese vaccines to begin with had lower efficacy than the mRNA ones used in much of the rest of the world. They tested badly against Omicron when it first emerged and the current variants are even more evasive/ less related. Essentially no Chinese have \"hybrid\" immunity where they were vaccinated and then caught the original Omicron as a virus in the fall of 2021.",
"So there's nothing to slow it down at all, and not much to attenuate the severity."
] |
[
"I can see this thread being locked...",
"Relying on lockdown rather than an immunisation strategy meant that when the restrictions were eased folk started mixing who had no immunity causing a spike in cases.",
"Also, there is a good chance that the numbers before the change in policy were probably optimistic, and were higher than reported, and the spike in cases was not as severe as it appears.",
"Given the somewhat introverted stance of the CCP we'll probably never know the true figures."
] |
[
"Compared to the mRNA vaccines, China’s vaccine (Sinevac) was less effective against the original strain and is almost ineffective against omicron. ",
"The strict isolation and lock-down policies prevented most of the population from getting covid, so there is very little natural immunity. Immunity also wanes very quickly, leaving the majority of the population susceptible to infection. ",
"Omicron, especially the latest strain, is mind-blowingly contagious. The estimated r is around 18, meaning one person on average infects 18 other people. Combined with a short incubation time and an infectious period that starts before symptoms show up, it spreads like a fire through dry forest. ",
"Assuming an r of 18 and an incubation time of 3 days, one sick person can lead to >1.5 million infected people in 2 weeks."
] |
[
"What if there was a place with no Higgs-Boson particles?"
] |
[
false
] |
So my limited understanding of Higgs-Boson, it's theorized as being the particle that gives other particles mass, and that there's a "fog" of Higgs-Boson particles evenly distributed throughout the universe which is why the mass of an object is the same everywhere in the universe. Feel free to correct me if I'm wrong. Now if we assume that Higgs-Boson exists and it's properties are what we currently assume them to be; What would happen in a place with no Higgs-Boson particles? Or on the other hand what would happen if some place had a higher concentration of HB particles? Say could a human still survive there? Or what sort of implications would this have the relativity?
|
[
"You don't need Higgs bosons to have a Higgs field (what you call a \"fog\") any more than you need ripples in order to have a lake. The Higgs field permeates all of space, just like the electromagnetic field, the gravitational field, and so on. There wouldn't be a place where that field doesn't exist. The Higgs bosons - the things we detect in our particle accelerators - are energetic excitations of that field which we can create, say, by colliding particles together at high speeds."
] |
[
"Also the electroweak symmetry would be unbroken. Electromagnetism and the weak force would very obviously be different components of a single force. What this would look like, I'm not sure. At high enough energies (above the ",
") this is the case."
] |
[
"The things we ",
" to detect."
] |
[
"Boiling water in plastic bottle"
] |
[
true
] |
[deleted]
|
[
"It's the ",
"glass transition",
", of PET probably. The change is just the plastic molecules having gained enough freedom of movement from the thermal energy to re-arrange themselves into a more comfortable shape. I doubt it would have any significant impact on the rate at which anything leaches into the liquid, although the heat itself would increase that. ",
"That said, PET isn't presently known to leach anything in harmful quantities. "
] |
[
"Plastic bags, huh? Those would normally be polyethylene, which to my knowledge has never had BPA in it in the first place, or any other additives. Sounds like a marketing gimmick to me. Anyway, BPA is used as a plasticizer; an additive that makes hard plastics soft. Mainly polycarbonate and PVC from what I know, which aren't really used that much for food containers. From what I know, the main concern there was really the existence of polycarbonate baby bottles and toys, and it's been banned for that use in a number of states and places now. (the EU and California at least, I believe)",
"Anyway, as I said, I'd think the bottle here is PET, which to my knowledge hasn't had any BPA in it. But after the whole BPA thing, they've started looking into the possibility of other possibly-harmful residues (rather than additives) in it. "
] |
[
"If you're boiling water in a plastic container, your life is already operating under sub-optimal conditions. For wilderness survival, the short-term exposure to chemical leeching is less dangerous than a bout of protozoal diarrhea. "
] |
[
"What happens to a computer in the gap between between basic theory and a programming language?"
] |
[
false
] |
There is a gap in most of the information I have looked up. They explain the theory really simply, referring to basic "On Off" switches. I understand that part. Then they explain basic programming code. Which I also understand the theory of. But what comes in between? How does a computer get from analyzing milions of zeroes and ones a second to recognizing and forming a command. How does a computer remember what it's supposed to do? What happens in the gap between the time data is read off of a memory chip and the time that the computer recognizes a piece of source code that it can use?
|
[
"But what comes in between? How does a computer get from analyzing milions of zeroes and ones a second to recognizing and forming a command. How does a computer remember what it's supposed to do?",
"Ultimately what it comes down to is, you have your programming \"source code\" which is human-readable, which then gets compiled (or interpreted) into \"machine code\" which is processor-readable.",
"In the machine code, the bytes of data are a ",
" that codes for the series of electrical signals which the processor will interpret as an instruction (as well as at times coding for locations in memory, when an instruction requires it).",
"The processor is ",
" with what is called an \"instruction set\", which includes a mapping of all of the available instructions that the processor can perform, to various sequences of bytes. That's how the processor \"remembers\" what it's supposed to do -- it's actually part of the processor's design."
] |
[
"The gap you described can be broken down into several layers:",
"Programming Language (C, Python, etc)",
"Assembly Language",
"Machine Language",
"Microcode",
"Logic Gates and Flip-Flops (zeros and ones)",
"Transistors and Diodes",
"Electrons and Atoms",
"It may be easier to learn about these concepts starting at top layer and working down to the lower layers one at a time. If you understand a high-level computer programming language such as C or Python well enough to be able to write a simple program (for example, to play tic-tac-toe, or solve a Sudoku puzzle), that perspective may make it easier to understand the significance of Assembly Language, and once you understand Assembly Language, Machine Language is just a short hop from there, and there is something interesting happening at every layer."
] |
[
"I'll try and give a simplistic explanation. Note that I omit a lot of details, and exactly what happens depends on the language used, operating system, processor, etc.",
"First, you write source code in C/C++, or your favorite language. Next, when you compile it, the compiler translates \"source code\" into \"object code\". Each processor has a given set of instructions that it can perform (add, multiply etc), and each instruction has a unique binary representation. So, object code is essentially a whole bunch of these instructions that the processor can understand. The object code is essentially your executable (.exe in windows).",
"Once compiled, the object code is obviously on your hard disk. When you try and run it, it is moved onto RAM, and eventually onto the processor itself. Now, an instruction, say add, triggers the hardware adder on the processor to add two numbers (also pre-loaded onto the processor from RAM). This is where the transistors come in. Once the whole thing is done, the data is moved back from the processor onto RAM, from where the results of your executable are displayed by your operating system."
] |
[
"If I smell something, does that mean I'm taking the smell away?"
] |
[
false
] |
If were to smell a fresh baked loaf of bread, or someone's perfume, would that mean there would be less fragrance for someone else to smell? Would the scent become weaker until there was none left?
|
[
"To set off your sense of smell only takes a few thousand molecules of an odor or fragrance. A loaf of bread or someone's perfume are giving off literally trillions of individual molecules, and refreshing the output of those molecules every second. Your inhaling a few of those molecules is not going to deplete but a minuscule percentage, in effect, having a meaningless depletion of the total. ",
"So go ahead, and sniff that baked bread."
] |
[
"This is the basis of a filtering system, to vastly expand the volume of air in question, if you had a fan pulling the room air through a carbon filter, the carbon will absorb the molecules in the air producing the odor, and reduce the overall amount in the room, much like your nose would, on a much smaller scale.",
"So, yes, but in the case of your nose, not very much at all. "
] |
[
"That is a psychological phenomenon, similar to how your brain can tune out repetitive or monotonous sounds."
] |
[
"Can Someone Please Explain, in Layman's Terms, How Electric Eels Work?"
] |
[
false
] |
I tried reading the Wikipedia article, and frankly, I think it's poorly written. It had a bunch of links to other articles, which in turn link to other articles, and onto others... yadda yadda yadda. And there's a bunch of technical jargon which leaves me like, "I'm not a scientist, so what the fuck do all these words mean?" So could someone please explain, in layman's terms, the following: How are electrical eels (and other electric fish) are able to generate electricity? (I saw something about "organs") Is it enough to kill a human? (I saw this YouTube video where an eel killed a baby alligator, and another lit up a Christmas tree in Japan) Could other animals be genetically modified to do this?
|
[
"This might be better suited to ",
"/r/explainlikeimfive",
" :)"
] |
[
"I'm not among those who downvoted you, but I'll give it a try."
] |
[
"All animal cells have sodium/potassium pumps in their cell membranes. Each time these pump, they move 3 positively charged sodium ions outside the cell, and 2 positively charged potassium ions in. This creates a negative charge inside the cell and a positive charge outside it, and the cell must spend energy to do this because the charges and the ion concentrations want to even themselves out. There's lots of reasons why cells do this, but it's not important for this question. ",
"When the pumps are active, the cell has a \"resting potential\" of about -60 millivolts. When the pumps are deactivated after some sort of trigger, lots of sodium automatically rushes inside the cell in order to equal out the concentration. This brings the cell's charge to about +80 millivolts. ",
"The electrocytes inside electric eels are modified muscle cells with tons of these pumps and arranged somewhat like batteries in a flashlight. The huge number of these cells, arrangement, and the conductivity of water allows them to use this as a weapon. ",
"As for other fish, some other fish use weaker, but similar, electrical organs to communicate, and sharks have electroreceptors in organs called Ampullae of Lorenzini that are able to detect the much smaller electrical activity of regular muscle cells and can find prey with that alone."
] |
[
"What would happen if our Sun was replaced by a 1 solar mass black hole?"
] |
[
false
] |
[deleted]
|
[
"It would get very dark and cold here."
] |
[
"Aside from the loss of heat/light, nothing. We would still be in orbit around it and it would be incredibly tiny. I'm to lazy to compute the size, but you can use this equation if you're interested.",
"http://en.wikipedia.org/wiki/Schwarzschild_radius#Formula_for_the_Schwarzschild_radius"
] |
[
"So the pressures and outward forces of the Sun, like the solar wind, wouldn't be missed? I was thinking that since the Sun pushes things outward and a black hole sucks things in that the planets would either have to compensate by orbiting faster or moving further away, or they would eventually get sucked in. But I'm admittedly a layman with no real knowledge of how it all works."
] |
[
"Why can the sum of two cubes never be prime, but the sum of two squares can?"
] |
[
false
] |
1 is the only number that gives you a prime from what I've found, because 1 + 1 = 2. Im pretty sure the sum of two numbers that are both to an odd power can never be prime, but im not sure. Is there a proof for this?
|
[
"Assuming positive integers",
"a",
" + b",
" = (a + b)(a",
" - ab + b",
" )",
"(a + b) will be a factor of the number, and for positive integers",
"2 <= (a + b) < (a",
" + b",
" )",
"Thus, whatever number you get will always at least have (a + b) as a factor that's not 1 or itself, with 2 as the exception.",
" bad assumption, proof should be fine now."
] |
[
"When n is odd, you can factor the sum explicitly: ",
"a",
"+b",
" = (a+b)sum{k=0,n-1}(-1)",
"a",
"b",
"E.G. a",
"+b",
" = (a+b)(a",
"-a",
"b+a",
"b",
"-a",
"b",
"+a",
"b",
"-ab",
"+b",
")",
"Note the alternating signs force the \"middle\" terms of the product to cancel.",
"So a+b divides a",
"+b",
", and a=b=1 is the only non-trivial case where they are equal (a=0, b>=0; a>=0, b=0; a=-b.)",
"And 2",
"+1",
"=5 is a simple example of the sum of two squares being prime. Note the ",
" of two even powers can be factored in a similar fashion as above, due to the alternating signs involved."
] |
[
"This shows why a sum of cubes cannot be prime. As for why a sum of squares ",
", you could just say that 5=1",
"+2",
" and be done, but this just says ",
" primes can be a sum of square, and not why. The reason why is because sums of squares have really nice divisibility properties. ",
"In particular, we know that if A",
"+B",
" is to be prime, then A and B can share no common factors, otherwise, you could just pull out that common factor. In this case, when A and B share no factors, it follows that any divisor of A",
"+B",
" must also be a sum of squares. This follows because if you can find a factor X of A",
"+B",
" that is not a sum of squares, then you can find a smaller sum of squares a",
"+b",
" and a smaller x that is not a sum of squares that divides it. This process necessarily does not stop, and so it goes down infinitely, when there is not room for it to go down, since you would hit 0 eventually. This is Infinite Descent, and it tells us that sums-of-squares have some nice divisibility properties that we don't see in other things, like sums of cubes. In general, cubes have room to maneuver, to allow for non-sum-of-cube divisors, but squares don't. You actually get more room to maneuver if you even just consider things of the form a",
"+nb",
". If a,b,n don't have any common factors, and a prime divides a",
"+nb",
", then there's no guarantee that p will be of the form a",
"+nb",
". There's actually a whole book devoted to finding ",
"primes of the form x",
"+ny",
", it's actually really good and goese over some pretty advanced number theory in order to answer this question. ",
"So, to find a prime that is a sum of squares, just take any two A and B with no common factors, find A",
"+B",
" and find a prime that divides it, this result says that this prime will be a sum of squares."
] |
[
"has the speed of light always been constant?"
] |
[
false
] | null |
[
"In short, yes. ",
"In not short, there are some more fringe theories coming out of quantum mechanics that posit that the speed of light (or more specifically the speed of causality) has changed slightly over time. However I've never seen anything serious come out of such papers."
] |
[
"Again, my understanding is fairly limited and largely from popular press like a brief history of time and such. So any errors here are all me.",
"In that case please refrain from commenting, especially on very technical topic such as this one. A good rule of thumb is that if you can't provide peer reviewed sources if asked you probably do not have the required expertise to answer the question to the standards of ",
"r/askscience",
"."
] |
[
"Again, my understanding is fairly limited and largely from popular press like a brief history of time and such. So any errors here are all me.",
"In that case please refrain from commenting, especially on very technical topic such as this one. A good rule of thumb is that if you can't provide peer reviewed sources if asked you probably do not have the required expertise to answer the question to the standards of ",
"r/askscience",
"."
] |
[
"Why do some quantities in physics calculations (electricity for example) take on complex values?"
] |
[
false
] |
College student here. I stumbled upon equations in physics on my own that take complex valued quantities. My question is: how can something like electrical impedance or current take on a complex value?
|
[
"It is a mathematical trick -- and a very good and useful one -- to use complex numbers in the situation you describe, AC circuit analysis.",
"The physical current is real, no question about it. But if we embed that current in a complex expression, such that the real current is the real part of that complex expression, a great deal of analysis simplifies, and then, at the end, we can always take any complex expression and extract the real information.",
"The association comes because e",
" has real part cos(a). Derivatives of exponentials are still exponentials, which is a bit easier than dealing with trig functions. In addition, phases are easily encoded. If I want to shift cos(a) to cos(a+k), this corresponds in the complex language to multipying e",
" by e",
". Since capacitors and inductors can produce phase shifts for AC signals, in the complex language, we can handle this by introducing complex impedance."
] |
[
"A lot of things that are formulated in terms of complex numbers can actually be reformulated as two sets of coupled equations. In such case the use of complex numbers is just convenient. The reason it is convenient is that calculus of the complex numbers can actually be a lot more powerful than calculus of the real numbers."
] |
[
"Because integrals in the complex plane are generally zero or take some nice form where you can do things like the Residue theorem. In general contour integration gives your more freedom to deal with messy math. In essence, in the complex plane you have a certain amount of freedom in how an integral is performed and this can be used to \"cookie-cutter\" around things that would blow up in regular integration of the reals.",
"Also, generally the complex component carries some information, be it phase or energy dissipation or what have you. ",
"You also have situations like propagators in quantum field theory where the real line is filled with an infinite number of singularities but you can \"push\" the integral off the real line and do the integral by adding a very small complex number to the equation, doing the integral, and then setting the complex number to zero."
] |
[
"What did I just see? (Biology related)"
] |
[
false
] |
[deleted]
|
[
"I'm not an expert on birds, but I've seen this behavior before and wondered about it. ",
"As a result, I searched around a bit and found it's called the \"spread wing posture\" and is commonly used to thermoregulate (either cool off by pressing the breast into the ground or expose area to sunlight to warm up, depending) or to dry the wings."
] |
[
"Please do not reply as if you give an answer if you don't know the answer. Speculation is not an answer."
] |
[
"Please do not reply as if you give an answer if you don't know the answer. Speculation is not an answer."
] |
[
"What is going on at the atomic level when my skin touches another object? How come we don't fuse with the things we touch?"
] |
[
false
] | null |
[
"When you say why don't we \"fuse\" with the objects we touch, what I would say you are describing can be re-stated as; why don't the molecules that make up our skin form bonds with the molecules that make up the object we are touching? ",
"For the case of your skin touching something that isn't skin - Your skin is made up of complex macromolecules, which are the building blocks for tissues. These include ",
"Proteins",
", ",
"Lipids",
", and ",
"Carbohydrates",
". These are examples of the bio-molecules which make up our bodies. Unless the object you are touching is made up of molecules which can chemically react with the molecules that make us up, there will be no chemical bonds formed - that is there will be no \"fusing\".",
"You could extend your line of reasoning to something like; why, when we touch two pieces of identical wood together, do the molecules in the two pieces of wood react and bond? The pieces of wood are made of the same kind of molecules, which bind to each other to make up each piece of wood. So it stands to reason that the molecules from piece A could bond with molecules in piece B.",
"The reason this doesn't happen (among others I'm sure) is that the ",
"Bond Distance",
" of covalent bonds (the kind which hold most things together) is incredibly small. The surfaces of two pieces of material have to be ",
" smooth to bring individual molecules into these distances. "
] |
[
"Q1: you dont actually ever \"touch\" another object, as in the distance between your skin and the object is 0. the electrons (negative charge) and nuclei (positive charge) of your skin and the object repel each other so strongly that they prevent the distance of closest of approach from reaching zero. afaik this is the primary reason why two objects cant literally reduce the distance between to zero, unless youre talking about like, neutron stars or fusion.",
"So to answer your question, your skin and the object approach each other at some distance X (very very small) and then the nuclei and electron repulsion becomes to great and thats the closest you can get them to be to each other unless you try fusion (you apply a huge amount of pressure and energy and really force them together). this is the major reason why afaik, and i think there are other minor reasons.",
"~~~~~~~~~~~~~~~~~~~~\nA clarification of sorts:",
"your second question asks why your skin and objects dont fuse, this is a different question. your first question asks what happens when two macroscopic objects \"touch\". your second question asks why they dont become the same object (presumably as a result of \"touching\".)",
"~~~~~~~~~~~~~~~~~~~~",
"Q:2 one way for them to become the same object is fusion (you fuse the separate atoms and nuclei together to a single larger atom/nuclei). in most settings, the amount of energy necessary simply isnt there. the second route is chemical bonding (the atoms/nuclei are distinct and separate, but become chained to each other via chemical bonds). The bonds dont form for the same reason. You need to input a sizeable (but much less) amount of energy before bonds form between your skin and object, and that energy (aka Activation Energy) is rarely around. ",
"Moreover, the bonds will form only if they are the most favorable ones to form. It's quite possible that your skin and object wont bond to each other because its more favorable for your skin and object to each bond with air particles or something, if the activation energy was present.",
"im sure someone else can explain this better or correct any mistakes i have put."
] |
[
"In theory, I could see this being possible. Wounds send signals for your cells to migrate to and proliferate at the wound site. Whether or not this would cause the cells of two different people to fuse I am not sure. I do not suspect it would be very successful though, as having another persons skin cells form interactions with yours would likely elicit an ",
"immunogenic response",
"."
] |
[
"If darker colors absorb more heat, why is our skin made to darken when exposed to the sun?"
] |
[
false
] | null |
[
"Because the problem with sunlight is not the heat, but the exposure to UV radiation, which damages skin cells and their DNA, leading to sunburn in the short term, and to melanoma and other problems in the long term. \nMelanin, the pigment responsible for the darkening of the skin, is placed above the DNA of skin cells, protecting it by converting the energy of UV rays - energy that would damage the DNA - into heat. So yes, a little more heat is produced, but that's easily dissipated and won't cause any problem. "
] |
[
"It's complicated. Short answer: not really, as the fact that melanin is dark is probably a byproduct of its qualities and of the necessities of the body, although it does absorb the light that would damage the DNA. It might seem strange, but the long answer explains why.",
"Long answer - it requires a bit of background, so please bear with me for a moment - \nThe color of an object is determined by the fact that it reflects the light of some color while absorbing all other colors. A red objects absorbs all kinds of visible light except red light, and that's why we see it red. Black objects absorb all kind of visible light (that's why they absorb the most heat), while white objects don't absorb any kind of visible light and reflect it all (that's why they absorb the least heat). \nNow, objects are made darker or paler by the fact that they have more or less pigment in them - and thus they have less or more white. A light red t-shirt absorbs less light than a dark red t-shirt because it has less pigment in it to absorb the light, and more white to reflect it, and so it will also absorb less heat. \nMelanin is itself a pigment, and its color is brownish, so, the more melanin there is, the darker brown the object (or person) will appear. The more melanin there is, the more the person is protected against harmful light, so the more you're exposed to that kind of light, the more the body produces melanin, and the darker the person appears. ",
"That's because the light that would damage the DNA and that is absorbed by melanin is UV (ultraviolet) light, which is ",
"outside the spectrum of visible light",
". As it's not visible, even if it's reflected by an object, it doesn't change the color of the object itself. However, as the spectrum of UV light is adjacent to the spectrum of visible light, to ensure the maximum protection to UV light (the maximum absorption of UV light), ",
"melanin also absorbs some of the visible light, making it non-white",
" (wavelength >390 nm is visible light, <390 is UV. the higher the absorbance, the higher the protection).",
"If melanin provided the same absorbance to UV light without absorbing any of the visible light, it would have exactly the same protective effect, without coloring the skin."
] |
[
"Skin pigmentation isn't about dealing with heat, it's about avoiding the harmful effects of ultraviolet radiation from the sun. Melanin is good at absorbing UV, and thus preventing it from penetrating to deeper skin layers and causing second-degree burns and cancer. In places where it isn't really bright all the time, lighter skin makes it easier for people to synthesize vitamin D using sunlight. Lighting changes throughout the year though, so the tanning response is the bodies way of balancing vitamin D production with UV protection. ",
"Skin color isn't a much of a player as far as body heat is concerned. We have sweat to deal with that. "
] |
[
"Why does stainless steel have a higher density than carbon steel?"
] |
[
false
] |
[deleted]
|
[
"I'm going to wager that the chromium fits into the spaces between the iron atoms. So you're left with a crystal structure of slightly greater volume, and substantially more atoms. Hope that makes sense."
] |
[
"When you alloy two materials, the alloy's density will not normally just be an average of the alloying materials. This is because the alloy's crystal structure (here it is crystal structure for the metals) is altered by containing the two materials.",
"To give a simple example: \nImagine a large box filled with bowling balls. Bowling balls are far more dense than packing peanuts. But if you add packing peanuts to the box, the overall density of the box will increase because the peanuts will be mostly filling in spaces between the bowling balls.",
"Obviously what is happening between Iron, Carbon, and Chromium is much more complicated than the analogy given above - but the principle is similar - the 'packing efficiency' (or more correctly the crystal structure) is changed by having different sized atoms being placed together."
] |
[
"Plain iron, the dominate metal in steels, usually exists as a body centered cubic crystal arrangment (it can also exist as a face centered cubic). When the iron is alloyed with other metals (and carbon), the inclusions are typically found along interstitial sites in the crystal structure. As a result, more atoms can be found int he same space as plain iron crystal. ",
"For stainless steels, more alloying agents are used, such as Chromium and Nickel, and these tend to occupy more of the interstitial sites int he crystal lattice than simple carbon steel."
] |
[
"Could a powerful enough magnet pull apart the Earth?"
] |
[
false
] |
I'm writing a Sci-Fi, and I'm wondering if its plausible or possible that if something gigantic and magnetic could pull apart the Earth.
|
[
"Since the earth is a magnet itself, if you have a very powerful (and I mean insanely powerful) magnet you might be able to twist the earth axis. Any magnet will align itself to the local magnetic field, but as far as I can imagine, no magnet will be torn apart. So that part is not possible.\nBut tilting the earth on its axis will cause some interesting effects on earth (tidal waves, permanent night on one side, permanent day on the other, you're the writer so you can probably think of some more). However, from a technological perspective, based on current technology this huge magnet could not be build in a million years. But it's scifi, so who cares.",
"In comment to what I have seen below:",
"There is no negative or positive magnet. All magnets have a negative and a positive pole, but if you would cut it in half, you have two magnets with a positive and a negative pole each (so four poles).",
"A huge magnetic field would not kill humans directly: you can lie safely in a MRI, whose magnetic field is enormous. Apart from metal objects flying through the air, humans are safe. Also, I don't believe humans have a magnetic field to speak of, so they would not be pulled into space, unless they are in a car for instance."
] |
[
"If you're writing sci-fi about very strong magnets, then you may be interested in ",
"this",
"."
] |
[
"How to Destroy the Earth"
] |
[
"By what mechanism is silver (and other heavy metals supposedly) antimicrobial?"
] |
[
false
] |
Bonus Question: If silver is in fact antimicrobial and can kill off infections like MRSA and VRE can/will those organisms eventually develop a resistance to it as they have antibiotics?
|
[
"It is called oligodynamic effect (",
"wiki",
") and the exact mechanism is not completely understood AFAIK, but these metals are wide ranged catalysts, meaning they could easily push an otherwise stable protein over the treshold of some reaction that would denature it. This is most likely the effect. "
] |
[
"A catalyst is a substance, a presence of which will lower the activation energy of a chemical reaction. In example, hydrogen and oxygen will not condense to water unless heated/ignited to a high temperature. If platinum is present, however, the reaction will take place at almost room temperature (very usefull to prevent hydrogen buildup and potential explosion). ",
"Another example is the characteristic smell of coins, this is actually the smell of decayed organic compounds on your skin that are otherwise stable but the metals in the coins katalyze the reactions with oxygen and so on so they change and can be smelled.",
"Something similar is happening to certain proteins when in contact with certain metals. Silver atoms may interfere with a reaction and cause - if nothing else - a change in the 3d shape of the protein which usually has significant consequences further down the chain."
] |
[
"heavy metals interrupt disulfide bridges in proteins. This causes deformation in 3D shape and ultimately ceases function of proteins"
] |
[
"How are anti-quarks created?"
] |
[
false
] |
Using an anti-proton in this situation I assume that an anti-proton is made up from anti-quarks to give us the negative charge. However, I can't find a direct answer as to how those anti-quarks come about. The only thing I have found so far is that when you separate two quarks from one another (assuming they're paired some how) the energy required to do this creates two more, one quark and one anti-quark. Is this sort of correct or am I on the wrong path? Thanks
|
[
"Ah ok, cheers :) That was easy."
] |
[
"Ah ok, cheers :) That was easy."
] |
[
"Due to anti-matter being difficult to contain?"
] |
[
"Can I \"distill\" my fermented alcohol by adding molecular sieves?"
] |
[
false
] | null |
[
"You can certainly use 3a molecular sieves to dehydrate alcohol for consumption, as long as they are food grade. It's not used in large consumer alcohol operations because it would be so expensive. That's not the only reason you distill alcohols, though. There are plenty of higher-molecular weight fermentation byproducts that you can remove by distillation that molecular sieves won't catch. ",
"One caveat is that, depending on the source, you may need to activate your sieves before use, and that requires them to be baked at several hundred degrees for several hours to dehydrate.",
"Drying alcohols with magnesium sulfate is not a good idea. You end up with goop that's almost impossible to filter."
] |
[
"Well, I suppose I chose the wrong word, concentrate would probably be more along the lines of what I was thinking, therein the higher weight stuff I don't necessarily mind, as I want to keep as much of everything else as possible but just remove the aqueous part to make it higher proof. My thoughts were that the [home] distillation process would lose a lot of the volatiles when clearing of the methanol, so using something like this would give a fresher taste, all conjecture but I think I may try it."
] |
[
"im pretty sure any form of distilling is illegal without the proper permits. by the way, you can just use ice to freeze the water and remove it by hand."
] |
[
"What is the series for the number of faces if you have a cube with a slightly smaller cube attached to each face, and a small cube attached to each one of those faces, etc.. to infinity?"
] |
[
false
] |
I start out with a cube. That's 6 sides. If I put cubes on those 6 sides, then only 5 faces of each of those cubes would be showing because the attachment point is a hidden side. If I kept repeating this trend, what does the series look like for the number of faces? I feel like this is a simple math problem but I just can't figure it out.
|
[
"Let's write a[n] for the number of sides of this solid after n iterations, so a[1] = 6, a[2] = 36, etc.",
"We can write down a recurrence relation",
"a[n] = 6(1 + 5/6 a[n-1]) .",
"This is because on each of the 6 sides of the cube we're putting a smaller copy of the previous iteration with only 5 out of the 6 sides (plus the 1 side of the large cube we're attaching it to).",
"Solving this recurrence relation",
" gives the formula",
"a[n] = 3/2 (5",
" - 1)",
"with first few terms",
"6, 36, 186, 936, 4686, ... ."
] |
[
"The first few terms of the series are:",
"6 + 30 + 150 + 750 + ...",
"r > 1, so the series diverges to infinity. If we were looking at the surface area, then you might get a convergent series if the extra cubes are small enough."
] |
[
"Your question doesn't agree with your subject line. If you're attaching \"slightly smaller\" cubes, then you won't be hiding the face they attach to- in that case, do you want to define \"face\" as being \"face of the new polyhedron\" or visible cube-faces\"?",
"Secondly, a series may not be the easiest way to think of \"number of faces visible after n iterations\". Indeed, if we assume that every attachment is such that it completely hides the previous faces, then pursuing a series representation would probably lead you to some kind of telescoping series; moreover, it would diverge (since the only cubes that could completely cover their attaching points have to be larger than or the same size as the original cube). If I assume that every cube is the same size as the original cube, then this is what the construction looks like (after 3 steps):\n",
"http://i.imgur.com/O9mAW71.png",
"If you wanted the sequence of numbers F",
" where the nth number was the number of visible faces after n steps of this process (step 0 being the basic cube), then the answer is F",
" = 12n",
" + 12n + 6 = 6(2n",
" + 2n + 1) = 6(1+ 4(n(n + 1) / 2) = 6 * (1 + 4 * (sum of all integers from 0 to n)). I'll pause here if you want to figure out for yourself why this is the formula.",
"We can take advantage of a particular feature of this problem: no face is \"in the shade\" of another face. Put simply, all the faces that 'face' a certain direction (there's an orientation here, so the front 'faces' a different way than the back does) are all visible from that direction.\n",
"http://i.imgur.com/IDlzQEG.png",
"\nThus, if I look at this construction from any of the six axes the original cube was built on, I will be looking at exactly all the faces that point that direction. This explains the 6-fold factor; since there are 6 axes, I need only count up how many faces point in a certain direction and then multiply by 6 to get the answer.",
"Now the question is simpler: if I hold the construction in front of me so that my line of sight is along one of these axes, how many faces do I see?",
"Well, if I consider the face right in the middle to be special, I can then take advantage of the 4-fold symmetry around a particular axis. \n",
"http://i.imgur.com/kUPg2r6.png",
"\nLooking at the problem this way, I see that the answer is the familiar triangular number sequence; that is, the sum of all integers from 0 up to n.",
"Hope that helps.\nedit: fixed a sign error"
] |
[
"Why does the light from the moon not scatter and become blue upon entering Earth's atmosphere."
] |
[
false
] | null |
[
"A Full Moon is about half a million times dimmer than the Sun. As a result, the \"blue sky\" caused by the full Moon is similarly half a million times dimmer than the \"blue sky\" caused by the Sun.",
"The effect is still somewhat noticeable to the unaided eye, though. If you're in a place with dark skies when the Full Moon is out, take note of the faintest star you can see. If you look again a couple weeks later when the Moon isn't up, the skies will have improved quite a bit - you'll be able to see fainter stars. Similarly, the Milky Way looks washed out when viewed during a Full Moon, even if you're looking at the opposite part of the sky.",
"Astronomers are aware of this effect, and the scheduling of telescope time happens accordingly. If you're observing very faint objects like distant galaxies that require incredibly dark skies to get the best signal-to-noise, you'll likely be awarded \"dark time\", which are times that the Moon isn't up. If you observe bright objects like planets in our solar system when sky brightness isn't such an issue, you'll likely be awarded \"bright time\", which are times when the Moon is up.",
": It does, it's just dim."
] |
[
"It does.",
"When it's low to the horizon, it's yellow - just like the sun. When it's high in the sky, the moon's light is distinctly blue. (Tough the moon itself is not - just as the sun is not.)"
] |
[
"It is it's just very dim. Take ",
"this image",
" for example. It's a long exposure during a full moon. Since the shutter on the camera was open for several seconds (possibly a couple minutes), it was able to collect more light that the moon was giving off. In a camera this makes the image appear brighter and, as you can see, the sky is still as blue as it would be on a normal day."
] |
[
"What are the causes of friction at the atomic level?"
] |
[
false
] |
Since atoms never actually come into contact, but are repelled by their electrons, it would seem like there shouldn't be any friction at all. It seems like contact should behave like a maglev train system. This obviously isn't the case, so what's going on?
|
[
"What's going on is that the molecular maglev train is constantly running into bumps on the road.",
"If you take two surfaces in contact with each other, generally you're not talking about two atomically flat surfaces. As you can see from for example ",
"this",
" image of a razor blade, most materials more closely resemble sanding paper than a pristine skating ring on a molecular scale. Even though the atoms repel each other, they don't repel each other nearly enough to overcome the surface roughness."
] |
[
"The negatively-charged electrons do repel each other. However, the electromagnetic force scales weakly with distance (relative to some other fundamental forces), which means that even far away from each other, two electric charges will still interact with each other.",
"Put most simply, the electrons in one molecule can be attracted to the nuclei in a different molecule--not necessarily enough for the two molecules to form a chemical bond and become a single new molecule, but enough that the energy of the system is lower if they are closer together. (Remember, all systems are trying to move to the lowest energy possible.)",
"The ways in which electrons and nuclei can become pretty complicated, and so you get all sorts of differently behaving interactions that can lead to friction."
] |
[
"So really the question is, how does an inelastic process come about in a material? How does kinetic energy dissipate?",
"I think what happens during a frictional process is you excite electrons when the materials are brought close together. For this to be a reversible process, the electrons would have to stay excited until the materials separate. But instead of remaining excited, the excited electrons can decay by creating phonons (lattice vibrations) (it can also lead to the excitation of other electrons, but this is generally thought of as an energy-conserving process -- and there are other more exotic ways for electrons to decay, but that's not important to think about for now). If phonons are created, they transfer energy away from the site of contact, turn into other phonons, and when the whole lattice is vibrating in different ways, this is what we think about when we say that friction heats up a material.",
"I saw a paper a couple years ago (link below) where they claimed that increasing the interaction strength between electrons and phonons (lattice vibrations) is what led to increased friction. They measured two very similar samples (one-layer and two-layer graphene), measured the strength of the interaction through electronic bandstructure measurements, and the strength of the frictional force by dragging a tip across the samples. I'm not sure if I personally believe the study, but it seems plausible and was published in a very well-regarded journal. It's also a very recent study, and I'm not sure if there's a more developed explanation behind it or a more extensive literature because I don't study friction myself, I came across the paper for other reasons. Here's the link: ",
"http://pubman.mpdl.mpg.de/pubman/item/escidoc:736279:1/component/escidoc:736278/429425.pdf"
] |
[
"Why does superconductivity occur in certain materials at low temperatures?"
] |
[
false
] | null |
[
"The key behind superconductivity is an attractive interaction between electrons, leading to bound states called Cooper pairs. In fact, if you have a metal and introduce a net attractive interaction between the electrons, a transition to superconductivity is inevitable. For \"conventional\" superconductors, you can get an effective attractive interaction by considering the interaction of electrons with the positive nuclei in a material. The cartoon picture is that an electron whisks through the lattice at a fairly high speed (typical speeds of 10",
" m/s), and the positively-charged lattice will contract towards the electron. Then electron zips off, but another electron now sees a bunch of nuclei that have been compressed to look like a bit of positive charge, so the second electron is attracted to where the first electron just was. However, in order for this to work, we need to have low temperatures, since at high temperature the nuclei will be wobbling about randomly so they won't be able to be pulled into a nice little region of positive charge to attract the second electron.",
"(Realizing bound states of electrons for the high-temperature superconductors is a super controversial matter - they are not metals and their transition temperature is way too high to be due to the above lattice effect. Hopefully I can uncontroversially state that the interaction is definitely due to magnetic interactions, but you can't throw a stone at a condensed matter conference without hitting a new theory for how this is supposed to work.)",
"Once you have bound states of electrons, superconductivity occurs because of the large energy cost of exciting your system: you need to break the pair apart. Now, if you consider a fluid of Cooper pairs moving with some velocity in a certain direction, when they impact an impurity they must create an excitation in the opposite direction to slow the fluid down. BUT, you must conserve momentum and energy (or at least give energy off to the environment) when describing the creation of the excitation + slowing down of the whole fluid. It turns out that as long as the electrical current isn't too fast, there's simply no way to do this, and the current flows forever. Essentially the same description is why superfluids will flow forever, although superfluids do have low-energy states, just \"not enough\" in a certain precise sense."
] |
[
"To add to this in light of OP's question, the strength of the effective attractive interaction between the electrons is quantified by an energy scale, let's call it ",
" This can be converted to a temperature by dividing by the Boltzmann constant:",
"_B = 1.3806488(13)×10",
" J⋅K−1",
"to give the approximate critical temperature ",
"_c = ",
" / ",
"_B.",
"This will (roughly) be the temperature where superconductivity is lost, because thermal fluctuations can rip the bound electrons apart. Since the attractive interaction is very weak, superconductivity generally happens at very low temperatures. Recently, there was a report on superconductivity in hydrogen-sulfide under (ultrahigh) pressure at more than 200K. One of the reasons that this works is that the binding energy (called \"electron-phonon interaction\") is relatively strong."
] |
[
"I have a question since it is sort of relevent. Has there been an example of super conductivity with + ions?"
] |
[
"Are there any pets which age at the same rate as humans?"
] |
[
false
] |
Basically is there a pet that would age at the same rate as their human owner, I know most smaller animals age at a much faster rate and one of our 'years' can equal several of theirs.
|
[
"African Gray Parrots",
" have an average lifespan of 50 years and a maximum known lifespan of 60 years. Not quite the same rate as a person, but longer than the scant ten to twenty year lifespan of dogs and cats."
] |
[
"I have a parrot that was born in the same year as I. ",
"They",
" live 80 years."
] |
[
"Fascinating, thanks very much. "
] |
[
"Would handling Martian soil be harmful to humans if we were to ever come into contact with it?"
] |
[
false
] |
I was reading that Martian soil was found to contain perchlorates and other chemistry which is not to friendly to organic matter. If we ever did send humans to Mars would the soil and rocks be considered hazardous to handle with bare hands?
|
[
"Not really. ",
"Almost entirely normal, everyday rocks",
" just like on Earth, just with a lot more iron oxide. Harmful chemicals are found in ",
" small quantities. Although the abundance of atmospheric dust may be harmful to human lungs."
] |
[
"Dust gets everywhere. If you go outside, it will coat your spacesuit, and get into the air when you re-enter. This is an especially serious challenge for future long-term lunar colonies, as the complete lack of atmosphere there means the dust is unweathered and sharp, and could potentially cause ",
"serious lung damage",
"."
] |
[
"Dust gets everywhere. If you go outside, it will coat your spacesuit, and get into the air when you re-enter. This is an especially serious challenge for future long-term lunar colonies, as the complete lack of atmosphere there means the dust is unweathered and sharp, and could potentially cause ",
"serious lung damage",
"."
] |
[
"Is the principle behind radiowaves inside coaxial cables and visible light inside optical cables the same?"
] |
[
false
] |
Is the principle behind radiowaves inside coaxial cables and visible light inside optical cables the same? The glass in optical cables is transparent for light in and arroud the visible spectrum. Is coaxial cables of aluminium and copper "transparent" for electromagnetic waves in the 30-1000Mhz range in the same sense? Also does the shielding on coax cables reflect and contain the radiowaves in the same sense as different types of glass keeps light contained in optical cables? I know this probably isnt exactly the same principle since the wavelengths are orders of magnutide different, but how close?
|
[
"The fundamental equations dictating how electromagnetic waves behave (Maxwell's equations/QED) are the same in both cases, since radio waves and light waves are both electromagnetic waves. But the exact mechanisms at work are different because they materials are engineered differently on purpose.",
"An EM waveguide is any system that will contain and guide electromagnetic waves. Coaxial cables and optical fibers are both waveguides. To guide waves, you need reflective walls to continually reflect the waves and contain them in the waveguide. ",
"A coaxial cable accomplishes reflection though the simple reflective property of good metals. In a coaxial cable, most of the wave is not traveling inside the metal, but is rather traveling in the space between the metal. The EM wave keeps bouncing between the metal core and the metal shielding. A fiber optic cable accomplishes reflection through the principle of total internal reflection. When one dielectric material (i.e. insulator) is placed against another dielectric material of a different index of refraction, for certain angles the light will be completely reflected off the interface. ",
"You could in principle create a coaxial metal cable that guides visible light (kind of like a kaleidoscope), but the surface roughness and energy absorption of metals is much more of a problem for the shorter wavelength of visible light, so the visible light signal would not make it very far down such a cable. You could also in principle create a fiber-optic cable that guides radio waves, but the cable would have to have a large diameter and use non-standard materials to actually work decently. "
] |
[
"Coaxial fiber exists",
", the core isn't metal though. It's usually a cylinder of a different type of material or a hollow cylinder. These types of fiber are designed for things like maintaining polarization."
] |
[
"What you linked to are photonic crystal optical fibers, which are not conductive coaxial cables at all. Photonic crystal fibers are just like regular optical fibers except you use the photonic crystal effect to get reflection at the edges of the core region instead of the effect of total internal reflection. "
] |
[
"Would a \"still suit\" from Dune actually work?"
] |
[
false
] | null |
[
"The suit would indeed kill you through heatstroke very quickly. The book tries to explain it away by saying the first layer is porous, allowing sweat to evaporate off of the skin. And then the secondary layers of the suit recapture that evaporated sweat. But this is completely ignoring the first law of thermodynamics (conservation of energy.) ",
"The reason evaporating sweat cools you is that as the sweat evaporates, the evaporation process consumes thermal energy from your body to convert the sweat to vapor, which then carries this thermal energy away from your body, cooling you. But if this vapor is then recaptured by a suit and pumped back to you to drink, that thermal energy is still there in the water, it never magically disappears after it evaporated. In fact if the suit somehow converts this vapor back to liquid for you to drink, it would first have to remove thermal energy from it, essentially heating up the suit (and the person inside) even more. "
] |
[
"I haven't read Dune in about 15 years but I remember them talking about how the suit is powered by pumps that you work just by walking. One of the characters even says that the boots can't be too tight because then the pumps won't work at full efficiency. Could it be possible to use this energy to convert the water vapor back to liquid without overheating?"
] |
[
"I always imagined the surface layer of a still suit works like high efficiency heat exchanger, meaning the surface would be quite hot, hotter than the desert air, comparative to the layer touching the skin. Meaning you don't actually sweat that much in a still suit, its practically AC'd.",
"We would be incapable of creating one with current technologies, but explaining it plausibly in sci-fi is more than possible, we already have some very small, very efficient heat exchangers, in a few hundred years, a still suit may be a possibility, the heat exchange membrane just has to be malleable, and very thin, and these 'heel pumps' would have to provide almost 100% power conversion, and I would also put forth that in a real life application, the surface of the still suit could also provide solar power.",
"Just give us another few hundred years of miniaturization and power conversion breakthroughs."
] |
[
"What does it actually mean to “burn fat” during exercise?"
] |
[
false
] |
I understand that the body can use carbs and/or fat as an energy source during exercise, in differing proportions depending on intensity, but what does “burning fat” during exercise actually mean, and how is it different to actually losing fat? If you do a long, low intensity workout where your body predominantly uses fat as its fuel source, will your body fat percentage be lower when you’re done? Is your body burning fat for fuel the same thing as when it loses fat due to a calorie deficit?
|
[
"The short answer to all your questions is, yes. Adipocytes (fat cells) store energy in large lipid droplets that are encased in their own single-layer phospholipid membrane. People tend to describe lypolysis (the breakdown of of fat) as though it doesn't happen until your body has completely exhausted all blood sugar and stored carbohydrates. That's probably (I'm saying probably because I didn't look this part up, but I'm pretty confident) not true, it's more like you are using all forms of energy all the time, but you may increase or decrease the retrieval of different energy stores depending on your metabolic needs. ",
"Lipids tend to be stored as triglycerides (larger, more complex lipids) and then are broken down into free fatty acids (smaller, simpler lipids) and transported out of adipocytes in a few different ways. Some are carried by proteins, some are carried by small vesicles. It probably depends on the pathway that is being used/what process has led to lypolysis. ",
"Different signals that induce lipolysis are going to come from fasting, growth, stress, and disfunction of things like the thyroid. All the pathways lead to some amount of stored lipids leaving adipocytes in one way or another. For different people these processes may be more or less efficient. There are a lot of steps in signaling lypolysis and if any of them are impaired, it will be harder to release stored lipids. ",
"I imagine that you have a balance of storing and releasing lipids that is constantly happening. If you expend more energy than you consume, the balance will shift towards fat loss. When this happens, your fat cells essentially shrink as their droplets become depleted. Since you are (again, educated assumption) constantly breaking down and replacing lipids, the effects of the shift won't be noticeable immediately after initiation. But if you keep the balance of fat loss and production on the loss end, you will eventually lose enough lipid mass that you see a difference. ",
"So, even though the signaling that leads to \"burning fat\" may be somewhat different during exercise or fasting, the end result for your fat cells is more or less the same. Following exercise, depending on how efficiently you can signal for lypolysis, you may have a minute net loss of lipids in your fat cells. But they have to be further broken down and the byproducts have to leave your body at a higher rate than you generate new lipids for you to notice a loss of body fat.",
"I hope this helps!"
] |
[
"One thing I find really cool about weight loss is how the mass actually leaves the body. I don't remember the exact process, but ultimately it is mostly excreted via your lungs - all that carbon and oxygen is breathed out as carbon dioxide.",
"If my memory serves me correctly, when you want to know how many calories a person is burning--and to measure it ",
", instead of just estimating by their level of activity--you do it by measuring how much carbon dioxide they produce. Metabolism ",
" combustion."
] |
[
"I think the reason people talk about the body using up all its carbs before starting to munch on fat reserves is that sugar is the \"fast\" energy source. It is the easiest energy source for the body to use, because:\n- it requires little to no processing/metabolism/breaking down before its chemical energy can be accessed, as it is a fairly simple molecule.\n- it is stored primarily in the liver and in muscle cells, so it is always immediately accessible during the initial period of exercise.\n- It is water-soluble, so readily dissolves into blood and is easy to transport around the body.",
"Fats are far more complex molecules than a sugar like glucose. They are made of the same atoms as sugars (C,H,O), so fat can be processed into sugar to replenish depleted reserves, but this requires a level of energy investment before the energy payoff is reached.",
"For the above reasons, I think it's pretty fair to assume that carbs and sugars will be used preferentially over fats and proteins, simply because of their ease of use and accessibility.",
"One thing I find really cool about weight loss is how the mass actually leaves the body. I don't remember the exact process, but ultimately it is mostly excreted via your lungs - all that carbon and oxygen is breathed out as carbon dioxide."
] |
[
"I am drinking a glass of water and my lips keep getting shocked when I take a sip. What's going on here?"
] |
[
false
] |
I am drinking from a plastic cup and got the water out of a cooler at a coffee shop. When i use a straw I don't get shocked, but almost every time I sip straight from the cup I get what feels to be an electric shock on my lips. Why this is?
|
[
"The straw is an electrical insulator. Unplug the glass."
] |
[
"Try it with your finger instead of your lips. Same result?"
] |
[
"I don't have the cup anymore to try this with but judging by the way it was behaving I believe that it would have the same reaction as it did with my lips."
] |
[
"I have a question about the Twin Paradox."
] |
[
false
] | null |
[
"My question is, it possible for the space traveler to control his flight in a way, be it speed, flight time or distance traveled, to return to Earth at a predetermined future time.",
"What?",
"The space traveller can ",
" return to Earth at some future time.",
"And yes, by adjusting speed, flight time or distance traveled, can select some particular future time. "
] |
[
"This is wrong, the time difference occurs due to being at high speed and relativity, nothing to do with inertial reference."
] |
[
"Presumably, yes. Knowing that the time dilation (to use science fiction terminology) would be proportional and thus calculable from the speed of travel (and time spent traveling at that speed), yes, one could plan a trip that would return them to Earth at a specific time."
] |
[
"Did the worms that used to bore into the hulls of ships face a decline in population as humans transitioned to using materials other than wood to build their vessels?"
] |
[
false
] |
Reading by Colin Woodard. Woodard frequently mentions that, in the Age of Sail, ships would have to frequently be careened so that their crews could clear the hull of barnacles and other sea life that damaged the hull. One such organism is a worm that would bore holes into the wood of the hull and cause the ship's structural integrity to weaken. Since humans have transitioned to using metal and fiberglass to construct ships and boats, have these worms declined in population? Or would these same worms also act as parasites to other marine organisms?
|
[
"The amount of wood in ships at any time in history would be dwarfed my the amount of wood that has fallen into the ocean due to storms and gradual erosion of riverbanks and coastlines. The worms did fine before wooden ships and fine afterwards"
] |
[
"I don’t know how one defines “sizable” but as a reference point here’s a photo from Rialto Beach in Washington a few months ago. Each of those logs is an enormous tree. We saw logs that were 10-15’ in diameter and hundreds of feet long (big Douglas firs) and this driftwood covered multiple miles of beach up there on the Olympic peninsula. ",
"https://i.imgur.com/AkTJy11.jpg",
"This is just one place on earth. Just imagine the amount of wood washed out to sea each year. I’m with the top commenter that for every capital ship built there was likely many, many thousands of times more driftwood washed out to sea (the entire boreal forests of the northern hemisphere, the Amazon, south east asian tropical forests, Patagonia, etc…). Shipbuilding would barely make a dent imo."
] |
[
" or shipworm, is essentially ",
"today at it's highest population in history",
". It is an invasive species that displaces native wood-eating species.",
"There were a few population spikes in the 1930's, 1950's, but the entire range has spread since then. For instance, it was first detected in Oregon in 1988, it went away, then it came back in only 2000!",
"While you may think the wooden sailing ships hull is a lot of wood, there is way more wood in fixed structures such as piers, as well as natural forests such as mangroves.",
"Shipworm also gets transported in modern ships hull water."
] |
[
"Is it possible for a solar system to have two planets of the same size within the habitable (Goldilocks) zone?"
] |
[
false
] |
I’m reading some science fiction where two earth-like planets of the same size are only slightly outside of each other’s orbit, and have similar orbital periods. So similar life forms move back and forth between each planet. I wasn’t sure if this is possible. Would the two planets just collide?
|
[
"Its absolutely possible to have two earth sized planets in the habital zone, but they need to be in stable orbits, meaning that theyd need to be a minimum distance apart, or gravitational interactions would eject one body, cause their orbits to become unstable over time, or tear them apart."
] |
[
"Sure, take a look at Trappist-1, google yields a good overview.",
"Super tiny system, all those worlds are at less than half the orbital height of mercury and there are three similar sized ones in super close proximity in the habitable band.",
"The why of not colliding is called 'orbital resonance'. I recommend wiki, i'd only confuse you, but it explains why pluto never hits neptune"
] |
[
"Given how vague the habitable zone is then yes. In the Solar system you can argue that Earth Venus and Mars are all in the habitable zone. You can also argue that Io and Europa are in the habitable zone. For these planets (and moons) you can also argue some of them out of the habitable zone. ",
"The habitable zone is basically a term used to get the media excited but really is too vague to be of much use (although astronomers still like to throw it around).",
"But the essence of your question is could two planets be close enough to harbour similar enough conditions to house life that is somewhat similar. Yes! Mars, Venus and Earth could have all been quite similar. Or better yet a double planet (which Earth is not far from being). These are all in stable orbits on human timescales."
] |
[
"If we observe a single atom as it heats up, is it possible to tell what state it is in and whether or not it is changing state, or is there no difference at all?"
] |
[
false
] |
I understand that the state of an object has to do with the bonds between atoms and their potential energy, but this is all between atoms. Are there any differences in the way an individual atom behaves in different states?
|
[
"The concepts of temperature and chemical phase (e.g. solid, liquid, gas) do not apply to a single atom. Rather, they describe how multiple atoms are interacting with each other. In a loose sense, temperature is a measure of the average random kinetic energy of the atoms relative to each other. The \"average\" part of this description is important because it allows temperature to be linked to descriptions of heat flow. If you just have one atom, you can choose a reference frame where it has no kinetic energy, and so the temperature of an atom does not make sense. Additionally, even if you forced some property of the atom to represent the temperature of the atom, it would not be linked properly to concepts of heat flow. Once you are looking at the level of a single isolated atom, you have to describe how energy comes and goes using the exchange/creation/annihilation of quantum particles, not using thermodynamics.",
"Also, the chemical phase is a description of how atoms are to bonded to each other and therefore requires many atoms. A handful of carbon atoms bonded together by stable bonds makes solid graphite or diamond. A handful of carbon atoms bonded together by ever-changing bonds makes liquid carbon. A handful of carbon atoms that are not bonded but do collide into each other makes carbon gas. A single carbon atom is just a single carbon atom. It is not a solid, liquid, or gas. If I extract a carbon atom from a diamond and extract a different carbon atom from a carbon gas, being careful to hold everything constant, the two carbon atoms are chemically identical. ",
"A single atom can have its electrons excited to different energy level. However, this is a completely different concept from a chemical phase of matter."
] |
[
"You are correct in that the thermodynamic state is characterized by the inter-atomic interactions of a collection of matter. But an isolated single molecule can reasonably be considered to be in the gas state for temperatures far enough away from absolute zero. Gas behavior is extrapolated from the summation of a number of isolated atoms bouncing around in empty space bumping into one another and any container walls (The Kinetic Theory of Gases). The case described is one where P approaches 0 and V approaches infinity for an ideal monatomic gas.",
"As for observable behavior changes, you are unlikely to see anything. You could theoretically measure the Kinetic Energy of the atom and extrapolate a temperature where \nKinetic Energy = 1/2",
"v",
" = 3/2",
"T"
] |
[
"Not sure what you mean by \"state\" in the context of a single atom. If you add energy to a single atom, all you can say is that it's flying around more quickly (or, depending on the energy involved, that its electrons are in higher energy levels). The latter can lead to emission of electromagnetic radiation - visible light, as in the yellow color of excited sodium atoms in a flame, or even higher-energy stuff."
] |
[
"Light Reflection : To maximize bedroom light, do I turn the bathroom light on or close the bathroom door? [w/ Diagram]"
] |
[
false
] |
(All the walls and doors are painted off-white) I've been wondering about this for a while. I like my bedroom to be really bright when I'm reading at my desk. I have a few lamps and an overhead light that I turn on. Now, if I want to maximize the brightness in my bedroom, which should I do: (1) turn on the bathroom lights and open the bathroom door; or (2) close the bathroom door? Obviously it isn't going to make a lot of difference either way, but I've become really curious about how the problem could be solved using science+math.
|
[
"Well, this is a problem that can only really be solved by experiment! Especially since we have no idea about a lot of the factors involved (the exact geometry of the rooms, the exact optical properties of the paint/wallpaper, etc etc). ",
"The simplest way to measure I can think of would be to use my DSLR with a set exposure time and just take pictures of my desk with the door open and then closed, since that's a fairly objective way to measure how bright it is. ",
"If you don't have a DSLR, have fun, come up with your own experiment. Isolate what you're trying to measure as best you can and have at it!"
] |
[
"yeah, this is a cool idea. If you have a light meter, it might also be possible to simply place it on your desk, record the lux, and then repeat that with the bathroom door open and see if you observe any difference in light intensity."
] |
[
"try putting mirrors behind both your 55w bulbs, and one on the bathroom door, leaving it open. this will maximize your lighting. "
] |
[
"If your car is on a steep hill or towing something heavy and you push on the gas pedal but the car doesn't move, where is the energy going?"
] |
[
false
] |
[deleted]
|
[
"If he has an automatic transmission, a large deal of the energy would go into heating up the torque converter."
] |
[
"This situation is very much like pushing on a wall with a firehose. If the wall does not move, all the energy stays in the water as it splashes about and knocks other things over. In the situation with the truck, all the energy goes into heating up: gasses exiting your tailpipe, the engine, and the transmission."
] |
[
"The torque converter, mostly. The torque converter in your car translates the spinning of the crankshaft, which is what your engine spins, to the driveshaft, which is what spins the wheels",
". The torque converter is filled with fluid, so what happens is that the crankshaft spins the fluid, and then the fluid spins the driveshaft.",
"Since it's not a direct connection, the crankshaft can spin without causing the driveshaft to spin. That's what happens when you're stopped: the crankshaft is still spinning, but all it's doing is swirling around the fluid in the torque converter. The fluid swirling isn't powerful enough to move the driveshaft, so the car just sits in place.",
"This all applies to automatics, of course. Manuals have a clutch, which directly connects the camshaft to the driveshaft when disengaged. If you're flooring a standard gearbox and the wheels aren't moving, you're converting gas straight into heat and probably blowing your engine/transmission up."
] |
[
"What is it about eukaryotic cytoplasm that requires mRNA to be capped and tailed vs. a prokaryotic cytoplasm which does not have such protection?"
] |
[
false
] |
[deleted]
|
[
"Good question. It's not that the eukaroytic cytoplasm is more or less toxic to mRNA -- it turns out that getting mRNA from genome to ribosome can be quite a feat no matter how you slice it -- it has more to do with the nature of eukaryotic and procaryotic cells themselves. 5' capping is a handy way for a eukaryotic cell to mark a transcript as a mature, ready-to-export-out-of-the-nucleus mRNA. A protein called RNA polymerase II (RNAPII) makes mRNA. ",
" RNAs made by RNAPII get capped, so only mRNA and another class of RNA that RNAPII makes called miRNA get 5' caps (this is ensured by the capping enzyme ",
"attaching",
" itself to RNA Polymerase II. As RNAPII churns it's way through a gene, capping enzyme jumps to the still elongating RNA and caps it while its 3' end is still attached to RNAPII. It's crazy). ",
"In a eukaroytic cell, for an mRNA to get translated, it has to exit the nucleus and go to the cytoplasm, where all the ribosomes are. An uncapped mRNA doesn't exit the nucleus, because mRNA exit is facilitated by the reasonably named ",
"cap-binding complex",
". This complex of proteins binds to 5' caps, and in turn, interacts with the nuclear pore, facilitating the transport of the mRNA out of the nucleus. ",
"In bacteria, which don't have compartmentalized organelles, none of that needs to happen. In bacteria, mRNA can get translated ",
", which is also kinda bananas. I will point out, however, that poly-adenylation, the process of adding a bunch of As to the end of mRNA transcripts, is another mark of a mature transcript in eukaryotes and protects mRNAs from degradation in the cytoplasm. In bacteria, poly-adenylation also occurs ",
", actually targeting mRNA for ",
"degradation",
". Totally bananas. ",
"You might be thinking, \"",
"/u/dazosan",
", lots of RNAs need to get transported out of the nucleus in eukaryotes that aren't mRNAs, like ribosomal RNA or transfer RNA. If they don't get 5' capped, how they get to the cytoplasm?\" First off, that's another good question. I bet you're very smart and good looking in real life. Ribosomal RNAs associate with ribosomal proteins inside the nucleus. Those ribosomal proteins, carrying rRNAs, are recognized by shuttling proteins called nuclear export factors and can then get transported ",
"out",
". ",
"Before writing this I was not familiar with how tRNAs get exported. After about 15 minutes of background reading, my quick-and-dirty grasp of a decades old field is \"haha we don't know.\" That's not strictly true, we know some things. A common export pathway for proteins, called the Ran pathway, appears to be involved. Similar to rRNA, tRNAs associate with particular proteins that themselves can get exported to the nucleus, carrying tRNA with it. This a class of proteins that for some reason is called importins. However, the importin that appears to be important for tRNA export is way more reasonably named ",
"exportin-t",
". This protein appears to recognize structural elements unique to mature tRNAs, whereupon it binds to that tRNA and, in conjunction with the Ran pathway, transports it out. ",
"I say \"haha we don't know\" because if you take a yeast cell and remove its copy of exportin-t, it lives. It's not super happy or anything, but it lives. So yeast have some other way of getting their tRNAs out of the nucleus, and obviously there's something we don't know about how it all works. ",
"I pulled a lot of this from ",
"this",
" review, which should be free; I found it very informative. Hope that helps. ",
"This is a total aside but if you have any interest in molecular biology, the body of work describing the co-transcriptional processing of mRNA (stuff happening to RNA while it's still being transcribed, like the process of capping I described above) are, in my opinion, some of the most elegant basic research done in recent memory. You know how mathematicians are always going on and on like the pricks they are about mathematical beauty? This is biological beauty. "
] |
[
"Mitochondrial genetics is, I think, a kind of bizarro world where things tend to resemble nuclear genetics in some ways, but in other ways are totally off-the-wall. I don't want to write another wall of text, so I'll just bottom-line some stuff. ",
"Mitochondrial RNA doesn't need to get transported, so there's no 5' capping. There are no introns or UTRs. However, mt-mRNA does get poly-adenylated, though apparently it's for the purpose of creating stop codons on transcripts and not for pro- or anti-proteolytic reasons. Why would a transcript need to get an after-market stop codon? Well, apparently when a gene gets transcribed, ",
". After that, what I assume has to be a monstrous nascent transcript gets processed down to the coding region. Also apparently when that transcript gets processed, some of the liberated regions of RNA become functional mt-tRNAs. ",
"It gets weirder from there. ",
"Here's",
" one review. ",
"Here's",
" another. It gets really weird. So hold on to your butt. "
] |
[
"All true. I would like to add that the 5' cap is necessary for recognition by the ribosome and binding by the EIF4E binding protein in order to initiate translation. The 3' polyadenylated tail is necessary for transcriptional termination of mRNA, and the cap and tail bind together to make the mRNA circular in the cytoplasm. This confers resistance to ribonucleases that degrade immature mRNA in the cytoplasm and this is able to modulate the transient existence of individual genes at the post-transcriptional level of regulation. Finally, mRNA circularization allows eukaryotic ribosomes to have high processivity because the ribosomal subunits do not have to travel all the way back across the length of the transcript to start the translation process again. "
] |
[
"Why is fire red/orange?"
] |
[
false
] |
Why is fire red/ orange? Does it have something to do with the makeup of the materials that are combusting? I know that some gases, when burning, come off as blue or even clear at the base then turn to the stereotypical red/orange. Any input is appreciated
|
[
"Yes but that's not all. This is true for example why Sodium ions color a flame orange, or barium does a greenish color.",
"Flames can also get colors by not fully burned material in the air which emits light based on it's temperature (Incandescence), just like a light bulp does. Because of this you can often estimate the temperature of a flame by it's color, red is cold, blue is hot."
] |
[
"Yes but that's not all. This is true for example why Sodium ions color a flame orange, or barium does a greenish color.",
"Flames can also get colors by not fully burned material in the air which emits light based on it's temperature (Incandescence), just like a light bulp does. Because of this you can often estimate the temperature of a flame by it's color, red is cold, blue is hot."
] |
[
"To expand on this, incandescence is the dominant mode of light emission in most everyday flames (e.g. candle, campfire, car exploding on TV). The dominant source of incandescent light is soot particles, which reach high temperatures in the flame and emit (typically) red/orange light. Soot is excess unburned carbon, so it forms when there is too much fuel present. If no soot forms, then incandescence will be negligible. Thus, the color of fuel lean hydrocarbon flames (e.g. a gas stove) is blue, as a result of high energy electrons relaxing. The blue color is largely a result of this occurring in the CH radical, an intermediate species formed during the combustion of methane/natural gas. ",
"It is important to note that flame color is a function of both the fuel and the combustion conditions. For example, a candle flame may be blue at the base but orange at the top because there is not time for soot to form at the base, but plenty of soot forms by the top of the flame. ",
"More info: ",
"http://doctorbrookschemistry.net/topics/chemistry-of-fire/"
] |
[
"Do humans share a similar brain \"wrinkle\" pattern, or is it like fingerprints where each person comes out with a distinct pattern?"
] |
[
false
] |
So I was reading 'The Dragons of Eden' by Carl Sagan, a book in which he devotes a lot of time studying the evolution of brains. The random thought presented in the title of this post popped up as I was reading but I haven't been able to find an answer with my google-fu. Thanks in advanced!
|
[
"The wrinkles are called \"sulci\" and the ridges of brain are called \"gyri\" (see top image ",
"here",
"). The folds are similar between human brains and each have specific functions. For instance halfway back on the brain from side to side is the central sulcus. In front of that is the precentral gyrus which is where the commands to move various parts of the body come from. Behind it is the post-central gyrus which receives all the touch sensation from the body. "
] |
[
"Exactly, it increases surface area of the cerebral cortex, which is where our \"higher functions\" take place. This is most pronounced in humans; if you look at say, a sheep or rat's brain they will be much smoother."
] |
[
"Because of the architecture of the brain. Have a look at ",
"this cross section",
". The cortex is the grey edge around the outside. Grey matter is what does the processing because it has many neuron cell bodies in it in a particular arrangement. Inside that is white matter which contains axons which transmit signals to other parts of the brain. The large surface means you can map more functions onto that processing area. Someone better versed in neuroscience and the various layers of cortex could probably tell you more."
] |
[
"Why do like charges repel and opposite charges attract?"
] |
[
false
] |
I'm also asking the question from a physics point of view (QED) despite the chem tag
|
[
"This answer is circular. One state is stable relative to another because work can be done by going from one to the other. Work can be done because of the force acting to draw the system towards a lower potential energy. Potiential energy and conservative forces are different ways of expressing the same concept, so explaining one from the other isn't satisfactory.",
"As to the question: the electrostatic forces emerge from the QED description of how charges interact with the electromagnetic field by absorbing and emitting virtual photons. If you calculate the total energy of the field with a few different configurations of charges (somewhat easier said than done) you'll find that this energy becomes lower when opposite charges are separated and like charges are not. You could map out a potential landscape on the space of charge configurations, from which the forces could be derived."
] |
[
"And now the big question, what is spin? Or should I make a whole new post about it? "
] |
[
"A really technical answer is that for any force mediated by a spin-1 particle, like charges will repel while opposite charges will attract. This fact can be proved in quantum field theory. Electric forces are mediated by photons, which are spin 1, so like electric charges repel and opposite electric charges attract.",
"Similarly it can be proved that for forces mediated by spin-0 or spin-2 particles, like charges attract while opposite charges repel. Gravity can be modeled as being mediated by a spin-2 particle, the graviton. The \"charge\" for gravity is mass, and all masses are positive, so all masses attract gravitationally."
] |
[
"Who came up with the Order of operations like multiplication bevore substraction/addiditon? And why does it make sense?"
] |
[
false
] |
2+3*4 = 14 and not 20. Who came up with it it, why does it make sense? I never really asked that question, always accepted it as a fact, but lately I've been asking that questions. Why is 20 wrong? Who says?
|
[
"PEDMAS and heuristics like it convey the idea of unsaid parenthesis sets we've decided not to write to save ink and space. ",
"(2+3)*4 is 20 ",
"2+(3*4) is 14 ",
"If everyone in the room agrees to follow a certain order of operation convention, you can skip writing parenthesis, if not, make sure to write them or you'll write ambiguous equations with no solution."
] |
[
"BEDMAS/BODMAS/PEMDAS or whichever acronym you decide to use are not hard, set rules of mathematics; rather, they're designed to provide a common format for incompletely notated equations.",
"For example:",
"2+3*4 = 14",
"and ",
"2+3*4 = 20",
"are both correct equations. It is only because the equation is not fully specified (by parentheses) that we can come to inconsistent answers. If we were to follow the standard order of operations, we assume something along the lines of 2+3*4 = ( 2 + ( 3 * 4 ) ) = 14",
"https://en.wikipedia.org/wiki/Order_of_operations",
"Venturing into speculation here, but I would guess that our current order of operations is decided by the complexity of operations: more complex operations are capable of being expressed as multiple simpler operations. ",
"For example, 3",
" = 3 x 3 x 3 x 3",
"and 3 x 3 = 3 + 3 + 3",
"and 3 + 3 = 3 + 1 + 1 + 1",
"and 3 = 0 + 1 + 1 + 1",
"Therefore, given that we should evaluate more fully specified operations first, we arrive at this order of operations:",
"Parentheses (Specified order of operations)",
"Exponentials (Sequential multiplication/division)",
"Multiplication/Division (Sequential addition/subtraction)",
"Addition/Subtraction (Sequential incrementation/decrementation)",
"Or PEMDAS. Note that incrementation/decrementation, as the most basic operations, are not generally given their own operator symbol. "
] |
[
"It is worth mentioning that there are other conventions. So-called ",
"Polish notation",
" and its cousin ",
"reverse Polish notation",
" are designed so that there is no need for parentheses ever."
] |
[
"How are we able to find planets light years away but are still finding dwarf planets at the edge of our solar system?"
] |
[
false
] |
I just saw a post where a new dwarf planet was found at the edge of our solar system. Should we not have found all these by now since they are closer and we are finding planets light years away. Is it not easier to find these closer celestial bodies?
|
[
"Planets far away from our solar system are usually not found directly but rather indirectly. They are found by calculating the periodic dimming of the light of the star they are orbiting. When a planet travels better us and the star, we can measure the drop in it's brightness and estimate the size of the planet. The time taken to cross the star gives us it's speed and thereby it's distance from it's star. The planets in our solar system however need to be found either by direct observation it by the gravitational influence it has on other known objects this is a very hard process as planets are not self luminous and hard to spot even with the modern technology"
] |
[
"For a couple of reasons.",
"They can have a measurable influence on the star or the starlight we receive: While they orbit the star the star also moves a bit as reaction, this can be measurable. Alternatively the planet might pass our line of sight and block parts of the starlight for a while. Most planets are found via one of these two effects. Both don't apply to dwarf planets far away from the Sun.",
"Even for direct images: For exoplanets we know where to look, close to stars. For dwarf planets in our solar system we do not, they could be anywhere.",
"As a simplified description we have two types of telescopes. Precision telescopes like Hubble can detect extremely faint objects - but they can only look at a tiny region in the sky at a time, there is no way to scan the whole sky that way. Survey telescopes can scan larger parts of the sky but they are way less sensitive, dim objects (such as dwarf planets far away) can escape detection. They also look similar to stars, it can be difficult to recognize them as dwarf planets.",
"Last but not least don't forget that we don't have a complete list of either. We have found a few thousand exoplanets but our galaxy has hundreds of billions. We have found several dwarf planets but our solar system has many more."
] |
[
"I think planets that are light years away are found by their association with a nearby star. Local dwarf planets are more difficult to find because they are relatively solitary; even though they are orbiting our sun, from the earth's perspective they are in the blackness of space instead of circling a star. "
] |
[
"Skin Color question"
] |
[
false
] |
I have always understood that it is predicted that human beings first developed out of Africa (Fertile Crescent, Mesopotamia, Etc) and I was wondering what gave the rise to skin color? Did the changing skin color help is adapt to new weather patterns throughout the ages, and is that why Nordic people have lighter skin (colder weathers) and why people closer to the equator developed darker skin? Also, if it was just a tan, there would be no genetic modification (would there?) so there was no chance of passing on your "modified" skin color through reproduction, and therefore what caused distinct skin colors? I hope my question is properly constructed and that you understand what I mean. Thank you askReddit :) Thank you for the overwhelming response. It had really bugged me for a bit to figure out how it had all occurred. That you cited everything has given me a little bit of reading material and I'm enjoying every little bit of it. Thanks once again Wow, this blew up! Thanks everyone for your responses! It is helping me to understand the issue greatly, I just expected a simple answers. You guys are too good<3
|
[
"It is simple natural selection, maximizing the amount of vitamin D synthesized, and minimizing any potential damage to the DNA in the basal layer of skin cells. For example, in Africa, there is incredible amounts of ultraviolet light, so African natives have been selected for very dark skin. The large amount of melanin doesn't prevent vitamin D synthesis because there is so much UV. However, if you head North, there is not enough UV to synthesize adequate vitamin D and all kinds of birth defects result from people with darker skin. Thus, in the Northern climates, lighter skin was selected for this maximize/minimize relationship."
] |
[
"Great question. The fact is Inuit people are lighter in skin than their ancestors but only slightly. This is because they get their vitamin D and folic acid from fatty rich sea food diets, so the selection pressure for lighter skin is far less as there is not nearly as high a requirement for the ultraviolet catalyzed vitamin synthesis pathways."
] |
[
"Why then do people in the far North (I'm thinking about natives I've seen in the Canadian north) have dark skin as well?"
] |
[
"Why does metal sometimes look so rough and \"powdery\" on the inside when it breaks?"
] |
[
false
] |
I noticed this most recently on this corkscrew/bottle opener that snapped. I would have expected it to be smoother and more shiny, even if not quite as much so as the polished surface.
|
[
"Metals are crystalline, but the metals we work with typically are not in the form of nice chunky crystals but are composed of many many small crystal grains. When a metal piece breaks, the exact surface of separation will propagate randomly between these grains which results in the rough surface."
] |
[
"Hey there! What you've just described is called intergranular fracture, and is distinct from microvoid coalescence, which is what is causing the particular texture that OP is showing. Intergranular fracture is more common with high strength steels, and results in crystal facets being shown on the fracture surface via a mechanism that you described above quite well."
] |
[
"A metalugusit will have a better answer I just beat and weld on the stuff occasionally. Cast metals have a granular crytaline structure as it's a one and done process where molten metal is poured into a form or mould. Processes steel goes through a series of processes involving heat and pressure to refine the crystalline structure to a degree where it's practicaly invisible to the naked eye. ",
"Sort of like building a sandcastle out of damp course sand vs very fine plaster sand. The fine sand will hold its shape much better and be stronger than the course sand castle."
] |
[
"[Neuroscience] Is there a difference in language comprehension depending on which ear we listen with?"
] |
[
false
] |
Both Broca's and Wernicke's Areas are on the left hemisphere of the brain, so is there any detectable difference in our ability to comprehend language depending on which ear hears the words? I imagine any differences must be slight, but do any exist? Also, follow up question: What about people who have had their corpus callosum severed, and thus don't have as much communication between hemispheres of the brain? What happens with language comprehension then?
|
[
"Yes, differences in comprehension do exist if you isolate the message to one ear. In right handed people and most lefties, verbal information entering the right ear (which sends signals to the left hemisphere) is more easily processed than information entering only the left ear. ",
"If you cut the corpus callosum, then language information entering the ",
" ear is not processed for verbal meaning. Interestingly, because the left hemisphere is usually responsible for speech production as well, the ability for the right hemisphere to communicate its thoughts and feelings are extremely limited when you cut the corpus callosum. It is fair to say that split-brain patients have two independent brains. One that can speak and respond to the spoken word of others (left), and another one that is mute and unable to verbally communicate because it no longer has the ability to utilize Broca's area.",
"Here is one article that talks about the lateralization of language in the brain, but there is a lot of information about lateralization and split brain patients out there. ",
"Friederici, A. D., & Alter, K. (2004). Lateralization of auditory language functions: A dynamic dual pathway model. Brain And Language, 89(2), 267-276. doi:10.1016/S0093-934X(03)00351-1",
"EDIT: I should add that the effect sizes are small with regard to which ear is \"better\" at processing the meaning of spoken words as long as the brain is intact. Information entering the left ear is still adequately processed in Wernicke's area, but the information will be of slightly lower quality. "
] |
[
"Aren't people who get their corpus callosum cut abnormal in the first place though? How generalizable are results from experiments conducted on people with ",
" otherwise untreatable severe seizures?"
] |
[
"Thank you for clarifying! I'm not sure where I got the schizophrenia thing from, now that I'm trying to look it up. I think I may have learned at some point that schizophrenics have an abnormal corpus colossum and then got that mixed up with the seizure treatment and lobotomy as you say."
] |
[
"Why is a real string pitch depending on the wave amplitude?"
] |
[
false
] |
When you pick a string on, say, a guitar, with exaggerated force, you may notice a higher pitch, then rapidly decreasing to the expected one when the wave amplitude decreases. This pitch shift is especially noticeable on the lower strings (where larger amplitudes are possible). What is the physical phenomenon leading to this? How can one express this dependence between pitch and amplitude mathematically? Edit: This is not about higher harmonics. There is a small but perceptible shift of the fundamental towards higher frequencies. My guess is that the deformation applied to the string increases the tension, which in turn increases the wave frequency. Is this a possible explanation?
|
[
"Because the tension in the string is a function of the amplitude. This is because the tension is nonlinear with amplitude. As the string is moved further from the relaxed center position, the tension increases. Tension is part of the equations describing the frequency. That is why in stringed instruments they have screw string tension adjusters.",
"https://en.wikipedia.org/wiki/String_vibration"
] |
[
"Tension is nonlinear with amplitude, but itnis more of a \"state\" and not a property. The core of the nonlinearities lies in material properties that change with deformation amplitude."
] |
[
"The tension in a string - or any vibrating metal - depends on many properties including stiffness of a material: how much it deforms under a given pressure. Anther factor pertinent to your question is the shape (cross sectional area for a string) of the metal/string.",
"For small amplitude oscillation, these properties are all considered constant. But as you increase the amplitude, the material properties can change; most commonly the stiffness changes; and the cross sectional area decreases around the middle of the wire as it is extended a large amount.",
"If these properties changed but remained constant at their new values, we would just hear a new frequency (pitch) when the string was plucked. But, as the oscillation amplitude decreases, the material properties go back toward their original values and the pich goes back to normal.",
"Thunking about even further, the frequency of oscillation actually changes each oscillation (at high amplitudes): When a string vibrates, it oscillates between its neutral position and the positive/negative peaks. the instant the string is in its neutral state, the material properties are their nominal value; but when the cable extends fully, the stuffness and shape are different. This would manifest itself in a non-constant damped natural frequency (at high amplitudes); a nonlinear phenomenon; which would change to a constant damped natural frequency when the amplitude of oscillation has decayed to lower levels. You may be able to hear this distortion at high amplitudes, but it would be hard because there are already multiple frequencies excited when you pluck a string.",
"Edit: To address the \"mathematical\" question; all these properties (shape, stiffness, etc) are considered the \"constants\" in the equations for small amplitude oscilation. When derived, equations describing these oscillations take the form of linear differential equations. \n When large amplitudes are at play, these all change with amplitude; forming nonlinear differential equations when analyzed. Needless to say, the latter are a hell of a lot harder to analyze."
] |
[
"If some animals can emit light, can they emit other forms of electromagnetic radiation in useful ways (obviously, excluding infrared as escaped heat)?"
] |
[
false
] | null |
[
"So there's a lot going on here. I'm a physicist, not a biologist, so I'm going to talk mostly about the physics involved.",
"Visible light is very useful as a sensory medium because the spectrum of the sun peaks in the visible region. So the world is nice and bright in those wavelengths, at least during the day. This is why animal eyes have generally evolved to make use of those wavelengths. I know a few animals such as birds and some insects extend that range a little into the UV beyond what humans can perceive, but they don't go very far, because there's not much point having a sense organ sensitive to wavelengths that aren't commonly found in on Earth. Similarly with anything beyond short infrared. There are some species such as pit vipers who have infrared sensory organs to detect body heat of prey, but nothing detects microwaves or radio.",
"There's a physical problem on the long wavelength end. To detect a given wavelength, your detector needs to be at least roughly the same size. Even if there were natural radio waves bright enough to be useful, no animal would be able to see them without a detector the size of an aerial, or a satellite dish.",
"There's another physical problem too, in that microwaves, radio waves, x-rays, and gamma rays all pass through our bodies. If your body can't ",
" a photon passing through it, it basically can't detect it.",
"Putting all this together explains why living beings can sense visible light and almost nothing else. We can feel the warmth of infrared, but because of the longer wavelength it doesn't have the fine resolution of visible light. So those pit vipers can detect roughly where a warm prey animal is, but they can't resolve it with any detail.",
"If animals can't ",
" any given wavelength, then there's not much point being able to emit it, even if it were physically possible. A lot of wavelengths simply can't be generated by an organic being - radio for example takes a large transmitter, and is most efficiently built of metal. X-rays require too much energy input, and are dangerous besides.",
"I'm fairly certain no organisms emit anything other than visible light, or possibly near UV/IR (as well as the thermal IR you mentioned). And I hope what I said explains why."
] |
[
"There's another physical problem that you didn't mention, which is that UV light tends to damage cells. Our biology usually tends to block UV instead of using it, because the biological cost of using it isn't paid back. But some hunting birds have developed regenerating retinas so that they can see the reflections of UV light from rodent piss."
] |
[
"Insects can see UV too, right? What do they do, uh, have disposable eyes? Or do they grow back? Or are they less prone to damage?"
] |
[
"Weird visual/ auditive effect when I watch TV or the computer screen too long."
] |
[
false
] | null |
[
"Do you have a sensitivity to light and sound?"
] |
[
"Nothing apart from this phenomenon."
] |
[
"\"The longer I keep the effect up the larger, louder and faster everything seems.\"",
"Does that mean you control the effect? I don't know what it's called or what it means, but I've had the same experience a few times too..."
] |
[
"If you clear your nose often will your nose run more in the long term?"
] |
[
false
] |
I.E Does your brain compensate for an abnormal mucus loss?
|
[
"Wow, not much traffic on this question. I'll try to throw my (lightly researched) 2 cents in.",
"This",
" and ",
"this",
" will tell you how mucus generally helps keep the nasal and airway tissues from drying out, among other things (trapping irritants and such). Obviously this doesn't tell you whether blowing it all out will spur ",
" mucus production. Hopefully a proper scientist and/or physician can comment on that. Just keep in mind that, like many things in your body, it serves a purpose of sorts.",
"Additionally, if there is actual concern about blowing your nose too much (which there should be, since it can be a symptom of various ailments), you may want to look into ",
"nasal irrigation",
" as an alternative since it apparently alleviates excess nasal mucus without some of the shitty side-effects of blowing your nose all the time."
] |
[
"I think the interesting thing would be the brain's response (if any) to the dry nasal passages. I would like to assume it just results in more mucus produced, because that feels accurate in an anecdotal sense... but yeah, if somebody could science this up it would be helpful."
] |
[
"oh yeah not really looking for medical advice. Was interested to know how the brain deals with this particular situation. Kinda like the brain getting used to paracetamol you know?\ncheers though man!"
] |
[
"When someone has some kind of head trauma what is it about keeping them awake that can keep them alive; and vice versa?"
] |
[
false
] | null |
[
"It doesn't keep them alive as such. If I understand it correctly when you are awake and the trauma worsens you will immediately see it by changing in person's behavior and will be able to do something about it. If you are asleep nobody would notice anything."
] |
[
"There isn't anything. That's a myth that you need to keep people awake after a head trauma. There's nothing about falling asleep or unconscious that will cause more damage to the person than would otherwise be caused by the injury. You can see how the belief would arise though, the patients people were able to keep awake likely had a more mild injury then those who they weren't able to. So, people started associating retaining consciousness with better outcomes, but to say it is necessary to keep people awake is sort of reversing the cause and effect. People who are able to stay awake are more likely to have better courses than those who aren't. It isn't the keeping them awake what is doing it. "
] |
[
"To add to this, sometimes it’s actually ",
" for people to be unconscious with head injuries. Which is one reason why medically induced comas are a thing."
] |
[
"'Planetary Sci.' Why are the Pacific and Atlantic sea levels different if they are all connected? The difference between the two at opposite ends of the Panama canal can be as much as 20 feet."
] |
[
false
] | null |
[
"It's all about ",
"currents",
". Currents run east to west on both sides of the Panama Canal, so the water piles up on the east side and is pulled away on the west side. "
] |
[
"Wouldn't it also have to do with global tides as lunar gravity pulls more water towards it?"
] |
[
"But if you dug a canal straight through, what would happen ?"
] |
[
"Why is it better to wait until food cools down before refrigerating it?"
] |
[
false
] |
Why not just put food in the fridge straight away after it's been cooked (unless you intend to eat it all)? If you leave it out to cool down first, one might concur that this would give germs more time to multiply on the food.
|
[
"In most cases it isn't better to let it cool down. ",
"Here",
" is a paper which looked at hygiene practices and compared to reccomendations. Here is a relevant section:",
"Putting warm food in the\nrefrigerator increases energy consumption and causes\ncondensation inside the refrigerator. However, the food\ncools more quickly this way, thus limiting microbial\ngrowth. Currently, the World Health Organization (WHO)\nand AFSSA recommend that perishable foods\nshould not be left for more than 2 h at ambient temperature\nand that when a large quantity of a dish has been prepared,\nit should be divided into smaller portions so it can cool\nmore quickly.... Therefore, it is essential to substitute\nthe usual recommendation to avoid putting warm or\nhot food in the refrigerator with the above WHO recommendation.",
"While it may not be a good idea to put a large boiling pot of soup straight in the fridge, as it can raise the temperature of the fridge, for most foods the safest thing is to put it in the fridge fairly promptly, and before it gets down to the ",
"'danger zone'",
") of 60C. In the case of the big pot of soup, just portion is out before putting it in the fridge so that it will cool more rapidly."
] |
[
"What do you mean you don’t reach 140 significantly faster? The rate of heat transfer by convection is directly proportional to the difference in temperature of an objects surface and its environment. The fridge has a lower environmental temperature and heat transfer will occur more rapidly as a result. The fridge will then expel the excess heat it takes from the food and exchange it through its built in heat exchanger to maintain its operational temperature setting."
] |
[
"What do you mean you don’t reach 140 significantly faster? The rate of heat transfer by convection is directly proportional to the difference in temperature of an objects surface and its environment. The fridge has a lower environmental temperature and heat transfer will occur more rapidly as a result. The fridge will then expel the excess heat it takes from the food and exchange it through its built in heat exchanger to maintain its operational temperature setting."
] |
[
"What kind of DNA damage is not fixable by the cell?"
] |
[
false
] |
if any?
|
[
"I think that the ability to repair DNA damage is a function of enzyme availability.",
"If there is more damage than available enzymes there will be portions that will remain unrepaired. ",
"Other than that I think that only particular cell states will determine the unrepairability of DNA, like senescence or apoptosis."
] |
[
"Thanks for your response!",
"Because you hit on the root of my question (senescence) I have a two forked response. When you say if there are not enough enzymes then damage will remain, does that mean injecting enzymes will solve the issue? I'm not suggesting that's simple (is it?) because each cell would need their own, but would dumping an excess of enzymes actually fix it?",
"Secondly, you said that's not the case in cases of apoptosis and senescence, well I was reading how senescence occurs and it says that it happens when telomeres shorten and other cases of irreparable DNA damage. So the question I really wanted to ask is, what non-telomeric damage is irreparable that leads to senescence?"
] |
[
"Regarding the first question, a lot of DNA damage repair events are replication dependent, so unless you de-senesce a cell there will still be areas of the DNA left unrepaired. ( I am going to post this and go back to the second question, I totally forgot what it was)",
"I'll be back!",
"Hmm the non telomeric dependent mechanisms can be induced by double strand breaks, by chromatin deacethylation, and ATM and p53 induction.",
"Oh and I forgot to mention, one of the steps in apoptosis is DNA laddering, so the DNA is literally broken into really small fragments, believe me it is really hard to recover from that."
] |
[
"Is it possible that a good portion of the cancer today was caused by all the radioactive products created for the public back in the 50's?"
] |
[
false
] |
I had a thought the other day when I was reading an article on Cracked about all the radioactive products. And, I know radiation causes DNA damage so I put 2 and 2 together...is there any connection between the DNA damage over 50 years ago and cancer today?
|
[
"I dont have the fancy flair on Askscience, but I have worked as a biostatistician and the more likely \"cause\" of the increase in cancers is extended length of life from other medical care and better diagnostic equipment. I have actually worked on data for these types of arguments.",
"Our life expectancy is very high compared to even the 1940s and 50s...we are talking almost 10 years, on average, longer than just 60 years ago. ",
"Many people just died before the chance to be killed by cancer and the medical field has become much more effective at finding cancer. This means a larger pool of people that will develop it and more doctors that know what they are looking for with reporting mechanisms to track it.",
"It is very likely that there are too many data inconsistencies to say \"cancer has increased\", because there are just too many medical changes and medical advancements in diagnostics and treatment of other diseases to ever say that the rate is \"higher\" from any cause.",
"TL;DR People are dying of cancer because they aren't dying as often from other things and diagnostic advances are finding cancer that was impossible to diagnose previously, causing a spike in cancer rates.",
"http://www.nationmaster.com/graph/hea_dea_fro_can-health-death-from-cancer"
] |
[
"Great post. One thing worth reiterating is that cancer risk becomes much higher the older you get. This is supported by numerous theories of carcinogenesis. In the DNA mutation model, a cell becomes cancerous when it accumulates several (~7-10) mutations in a handful of traits that control cell division - ",
"the hallmarks of cancer",
". In this way, old age increases the risk of cancer because there is more time for these mutations to accumulate.",
"In the evolutionary model, cancer that strikes after a person has passed reproductive viability exerts very weak selective pressures on our cancer defenses. In other words, evolution/natural selection can only improve our defenses against cancer at ages where we can reproduce. With almost no way to pass on genes after we become sterile, there is no pressure to select those with better defenses against cancer in old age.",
"So this is why we see higher rates of cancer as other areas of medicine improve."
] |
[
"I think the down votes are because your point is misleading in the extreme and therefore bad science. Did you bother to check how much polonium is in a pack of cigarettes? Is it enough to matter? I did.",
"A cigarette contains about .04 picocuries of polonium-210. The maximum safe level is about 30 nanocuries. So you would have to smoke on the order of 10",
" cigarettes to reach danger levels. You would have to smoke more than ten packs a day and still take over a year to smoke that many. Given that it has a half-life of less than five months, the chances of ingesting enough polonium-210 via cigarettes alone is small.",
"Sources:",
"http://www.nytimes.com/2006/12/01/opinion/01proctor.html",
"http://en.wikipedia.org/wiki/Polonium"
] |
[
"When we get sick with the common cold, what is actually happening to cause the symptoms?"
] |
[
false
] |
ie. Why does swallowing become painful? Why does our nose end up getting blocked? (And why only one nostril?). etc
|
[
"The virus doesn't, rather your own body causes this as part of it's attempts to fight off the infection. Almost all symptoms of an infection result from your own body's attempt to fight it off. It's unpleasant, but biologically preferable to death.",
"I'm not qualified to properly explain the specifics."
] |
[
"Common cold is usually caused by a viral infection. The viruses cause inflammation of the nasal mucous membrane with swelling of the membrane and outpouring of mucous , thereby reducing the calibre of the passage and blocked nose. If the pharynx at the back of the throat is inflamed and congested, the nerves carrying pain fibres in that area are stimulated to give a painful swallowing."
] |
[
"That makes sense, as a follow up question:",
"Why does the virus cause the mucous membrane to become inflamed?"
] |
[
"Ask Anything Wednesday - Engineering, Mathematics, Computer Science"
] |
[
false
] |
Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away!
|
[
"There are multiple problems with computers right now:",
"So we have a limit to transistor amount and frequencies. AMD currently circumvents the transistor limit by glueing multiple dies on one chip on their Workstation and server cpus and is researching how to do that with their gpus aswell. Chiplets bring another set of issues with them, but no hard limits like with single die cpus"
] |
[
"How fast are we approaching what's physically possible with computer systems? Gpu's and Cpus's are steadily getting better and better and smaller and smaller, but I'm sure that similar to cars, were going to hit a brick wall at some point where you physically can't cram anymore inside a space without significant technological advancement.",
"Cars were rapidly evolving similar to computers but have now slowed on advancements because we're reaching the bounds of what's possible. How soon is that gonna happen to computers, do you think it ever will happen? "
] |
[
"What, physically, are the defects you mentioned in your second point? Are they something that will eventually be (mostly) eliminated as the tech matures? To what extent are they feasibly avoidable?"
] |
[
"How can our bowels selectively pass either gaseous or solid/liquid contents?"
] |
[
false
] |
How do muscle contractions selectively act on gasses as opposed to more substantial contents? Is this similar to how one can burp without expelling gastric juices? I apologize for the shitty question, but not for the pun.
|
[
"To move fecal matter you use persistaltic muscle contractions in your intestines, for gas these movements are either minimized or not present-releasing gas compared to a solid is much easier. The body has many sphincters, which is something that just constricts an opening. For a sphincter to pass gas it doesn't need to open as wide for a solid or liquid. You can imagine that when you burp the gas already wants to move to a space with more equal pressure so your body doesn't need to force it much, just give it a place to go. The majority of these muscles aren't under your conscious control (some are, most aren't)."
] |
[
"Moreso mechano/stretch receptors in your rectum and anal sphincters that signal whether or not you need to poop or pass gas. Funnily enough, it gets tripped up from time to time, which is why people tend to have accidents. You also tend to pee a bit when you defecate because your urinary system uses the same receptors, but the anal ones are so much more powerful. You will be less likely to poop when you pee for this reason."
] |
[
"Moreso mechano/stretch receptors in your rectum and anal sphincters that signal whether or not you need to poop or pass gas. Funnily enough, it gets tripped up from time to time, which is why people tend to have accidents. You also tend to pee a bit when you defecate because your urinary system uses the same receptors, but the anal ones are so much more powerful. You will be less likely to poop when you pee for this reason."
] |
[
"Thought problem: looking into a mirror"
] |
[
false
] |
I came up with a little thought experiment the other day. Lets assume you have a perfectly circular mirror (a mirror that reflects back an identical and completely undistorted image), and you looked directly at it. If you then spun this mirror very fast (lets say 1/10, 1/2 or even 99.99% the speed of light) what would you see? Would your image looked skewed or exactly the same?
|
[
"There is no evidence to assert this claim. It is highly possible that the image might be skewed at speeds around .9999C because locally the atoms have a tangential velocity. Electrons in the atoms of the mirror absorb and re-emit the photons. There has to be something deeper happening than ",
".",
"While normally a mirror at .9999C would have far too much energy to hold together as a mirror, let's say we have devised a way for it to stay whole and the property of reflecting to remain possible.",
"I'm NOT a physicist ",
" You're talking about a property of quantum electrodynamics at relativistic speeds. I'm not equipped to give a very reliable answer.",
"I hope a real physicist ",
" can shed some light on this interesting thought experiment."
] |
[
"I think one problem that this thought experiment describes is the problem we have resolving relativity with quantum phenomena.",
"Doubtful. In this case, gravitational effects shouldn't be considered for simplicity's sake. Quantum mechanics can be used with special relativity without the problems encountered with general relativity."
] |
[
"Since it takes a nonzero time for the photon to be absorbed by the material and then reemitted wouldn't the mirror have shifted a bit in that time (assuming we can spin it arbitrarily close to ",
")?"
] |
[
"Does thinking really hard use measurably more calories?"
] |
[
false
] |
[deleted]
|
[
"Depends what you mean by thinking really hard.",
"Your brain is functioning at all times in some manner or another. I'm assuming you're referring to higher functioning in the sense of thoughts and images and sounds being relived through memory, the issue with that is we don't exactly understand how that comes about. Amongst the types of cells in the brain we have not yet been able to explain higher functioning. ",
"What is thinking really hard? Is it dwelling? Is it anxiety? Well anxiety can potentially cause palpitations by increasing activation of the sympathetic (flight/flight) nervous system but even then it won't really be an increase in energy expenditure significant to a 2000 calorie diet. The brain has a balance between the sympathetic and parasympathetic system, when you're resting you have increased blood flow to digestive tract, but during times of stress it diverts to muscles and the heart to prepare you for danger, but the blood flow to the brain is always reasonably constant, the fMRI just maps the regional variations in uptake throughout the brain.",
"TL:DR We don't really know the anatomy or physiology of thinking to be able to answer that question, but considering haemo-dynamics (Brain bloody supply constant during times of rest and activity).",
"Edit: I'd like to point out the percentage of blood going to the brain is always constant, it does receive more blood during times of activity because your heart is pumping faster but that's not really relevant to togomogo's question."
] |
[
"Depends what you mean by thinking really hard.",
"How about \"flow\" or intense concentration? Like when doing a math exam.",
"Also, is it possible that amount of blood flow is somewhat beside the point? Are there differences in the brain's utilization of blood glucose, e.g. measured as ",
"? Mind you I'm somewhat of a layman, but genuinely curious."
] |
[
"One anecdotal story is not science, sorry. See sidebar note on \"free of anecdotes\"",
"Also, just to napkin sketch losing \"a couple of pounds\" in a weekend is ~7000 calories over (2) 12-hour days, or 300 calories per hour. This is not a totally unreasonable amount of energy to expend (comparable to brisk walking), but it's far more likely that he lost water weight due to a change in habit.",
"Edit: I did find a source that claims chess grandmasters could be burning as much as 7000 calories a day thinking: ",
"http://news.stanford.edu/news/2009/june17/classday-061709.html",
" but those aren't cited statements."
] |
[
"Genome wide association studies and SNP data interpretation."
] |
[
false
] |
Genome wide association studies use SNP data from the entire genome sequence of study participants to identify particular SNPs that are strongly associated with a disease state (in my example study Type II Diabetes and triglyceride levels). Those SNPs can be used to identify nearby genes that are likely associated with the disease. This is because it is not likely that there will be recombination between the nearest gene and the SNP. What I don't understand is why there are SNPs located within the gene and between the gene and the SNP that was associated with the disease that are not associated with the disease. How can one SNP be associated with a particular allele of a gene that causes disease, while the intervening SNPs are not associated with the disease? The introduction of the concept of haplotypes and their association to SNPs further complicates my understanding of SNP association to gene alleles. How can one haplotype be associated with a disease and the SNP alleles within that haplotype not be associated? An example for those of you that have institutional access: More clarification: I assume at one point there was a haplotype containing the first mutant allele of a gene that contributes to disease and specific alleles at the surrounding SNP loci. What genetic events could occur that would alter the surrounding SNPs such that an SNP 2kb downstream would be associated with the disease while the intervening SNPs are not?
|
[
"This is largely a question of statistical power. Consider the following three SNPs. SNP X/x causes the disease if you have allele x. SNP Z/z was found to be linked to the disease. SNP Y/y occurs between SNPs X/x and Z/z, but was not found to be linked to the disease. There are four haplotypes: XYZ occurs in 93% of individuals, XyZ occurs in 2% of individuals, XYz occurs in 4% of individuals, and xYz occurs in 1% of individuals. Only haplotype xYz causes disease, because it's the only one with allele x. Note that these four haplotypes could form without any recombination occurring. Technically SNP Y/y is correlated with the disease, but you would need an extremely large sample size to infer that, because the probability of having allele x if you have allele Y (1.02%) is not much different from the probability of having allele x if you have allele y (0%). In contrast, SNP Z/z is strongly correlated with the disease, because the probability of having allele x if you have allele Z (0%) is very different from the probability of having allele x if you have allele z (20%).\nEdit: These individuals are haploid in this example. The same idea applies to diploid species like humans."
] |
[
"Thanks for that! I always wondered the same thing as OP."
] |
[
"Thanks, but how do the intervening SNPs (in your example SNP Y/y) arise? The only scenario I can think of is that SNPs that are correlated with disease arose from a point mutation shortly after the disease allele of the gene they are associated with was created, such that the associated SNP allele traveled with almost all of the disease allele of the gene.",
" A bit of clarification:",
"If you look at the study I referenced, they show the 6 SNP loci that were associated with type II Diabetes and Triglyceride conc. and their surrounding 100k bp. The R",
" value is the y-axis and the x-axis is the location (in bp). They mark the nearest gene on the x-axis. There are numerous SNP loci that were assayed and have R",
" values less than 0.1 located between the significant loci and the gene. This is what confuses me. How are those SNPs insignificant while a more distant SNP is an almost perfect predictor of disease?"
] |
[
"If we're creating so much carbon dioxide, what keeps us from creating a photosynthesis machine to get rid of it?"
] |
[
false
] |
This is a question that's been bugging me for awhile. Maybe the science is too technical and we're not there yet, but I'd like to know whats keeping us from doing it. If you look at a basic for photosynthesis, it shows if we take some carbon dioxide + water + sun = oxygen and sugar. Why can't we do the same thing and start pulling carbon dioxide out of the air ourselves? Thanks!
|
[
"Considering the amount of energy involved, it would be far more efficient to simply plant more trees. As a bonus, you mitigate problems with soil erosion, ecosystem destruction, etc."
] |
[
"This is a relatively old ",
"article",
" but it explains the difficulties involved in creating artificial photosynthesis. "
] |
[
"Leaves on trees are green because that is the part of the spectrum that has the largest intensity from the sun's radiation. Unfortunately, that part of the spectrum is the least efficient portion to convert to energy. Think of it like you are in a dry climate and you want to store water in your house from a rare rainstorm. You need buckets that can collect a lot of water, but you also need some way of transporting it to storage. Unfortunately, often a good transportation unit isn't a good storage unit. Often with solar power, we run into the difficulty of transporting it.",
"There is a lot of work right now being done on trying to get algae to convert CO2 and light to biofuels, but as stated before the efficiency isn't very high and so it is often not cost-effective. Even so, algae is getting its use. At my university, the heat plant pumps all of its outtake lines though large vats of algae, which remove a good portion of the carbon dioxide.",
"So maybe there are bio-mimicking pathways to use enzymes to perform CO2 catalysis efficiently. Biology is very complex and so finding those efficient pathways is very difficult. It's also very rewarding: major findings toward transport of energy often get into Science and Nature."
] |
[
"Is it possible to harvest electrical energy from plants?"
] |
[
false
] |
Aside from the obvious potato or lemon batteries, but for the possibility to harvest electricity from an oak tree and how much could it generate?
|
[
"A lot of people seem to not properly understand how these batteries work. The lemon or potato don't actually \"have electricity\" in them. Rather their \"juices\" act as electrolytes that allow for the transfer/flow of electrons from the zinc-copper diodes* that are needed for these to work. You can actually replace the lemon, lemon juice or potato with brine.",
"*These are commonly used for these home made batteries since they are easily obtainable, but others can be used.",
"EDIT: I just realize this sounds a bit snarky. I'm not criticizing your question, just trying to clarify a common misconception."
] |
[
"Burn plant matter as fuel for a generator. ",
"Anything that can burn can be used to generate electricity. "
] |
[
"Lemon batteries can generate voltages of about 0.9V. ",
"According to Guinness, the highest voltage ever recorded from a potato battery (which consisted of 1,000 potatoes) was 538.1V",
"http://www.guinnessworldrecords.com/records-7000/highest-voltage-from-a-potato-battery/",
"These voltages are very low. It would not be economically efficient to power anything this way."
] |
[
"When did life evolve sleep?"
] |
[
false
] |
As a secondary question, which modern animals don't sleep? Why?
|
[
"This is kind of a weird question to ask, since it all comes down to how you define sleep. Most organisms, including unicellular organisms like bacteria, show a 24-hour cycle of rest and activity. These 24-hour cycles are driven by some sort of internal circadian rhythm, and their purpose is to address both external factors (you should behave differently when it's day vs. night) and internal factors (lots of internal rhythms need to be timed specifically). So, in a way, you could call these cycles of rest and activity \"sleep,\" and claim that sleep evolved extremely early, as early as the first unicellular organism. However, that's losing sight of some of the intricacies of sleep, and it's worth exploring further what exactly we mean when we say \"sleep.\"",
"Before we can talk about when sleep evolved, we need to discuss what exactly it means for an animal to be sleeping. Humans have broadly 6 stages of being awake-- waking, drowsy, stage 1 sleep, stage 2 sleep, stage 3 sleep, stage 4 sleep, and REM sleep. For each stage of sleep, an EEG will show a distinct signal. However, EEG measures activity produced by the neocortex, and you immediately run into a problem since not all animals have a neocortex, and so not all brains are capable of generating EEGs specific to sleep stages. Thus, sleep researchers have come up with 6 criteria used to define sleep. They are:",
"The animal needs to be in a state of immobility with reduced sensory responsiveness that they can quickly exit out of. The caveat of being able to quickly leave is important because it excludes things like hibernation and being in a coma.",
"The animal needs to have increased arousal thresholds (needs more noise to be woken) and needs to have decreased responsiveness to external stimulation",
"All animals in the species need to have somewhat similar postures when they sleep and need to sleep in somewhat similar places",
"Animals have specific behaviors before sleeping. These are thinks like circling territory, yawning, or \"making the bed\"",
"A circadian rhythm needs to exist and last around 24 hours.",
"To quote another redditor, \"A state that is homeostatically regulated, meaning that if the organism is prevented from entering that state, they will later attempt to catch up on the state (if given the opportunity). There may also be commensurate deficits in behavior until homeostasis is restored.\"",
"So using these 6 criteria, plus distinctive EEG signatures, let's look across the animal kingdom and see who sleeps.",
"All mammals definitely sleep. When mammals are sleep deprived, they sleep more the next night. In humans, for example, pulling an all nighter will result in more stage 3+4 sleep the next night. Certain other mammals like rodents, cats, dogs, and monkeys fulfill all 6 behavioral criteria and show distinct non-REM (stages 1-4) and REM EEG patterns. All known mammals show REM sleep of some kind.",
"Birds are pretty similar to mammals in sleep EEG-- they show both REM and non-REM EEG patterns when they're inactive, and they have specific sleep postures. When birds experience REM, they also show rapid eye movements and experience muscle paralysis, just like we do, although their REM sleep is extremely brief (only 10 seconds or so). Some people have theorized that birds actually have more lengthy REM cycles, but only at the level of the brainstem, not the cortex. Broadly, birds fulfill all 6 of the behavioral criteria that I mentioned, but there are differences when compared to mammals. For example, birds don't \"catch up on sleep.\" When you disrupt mammalian sleep, they'll get more sleep the night after. When birds are migrating, their overall sleep is reduced by 70%, but we don't see any signs of sleep rebound or reduction in cognitive abilities.",
"We don't know much about how reptiles and amphibians sleep. Back in the 60s, people noted sleep-like states in frogs and toads, which show \"sleep behaviors,\" have higher arousal thresholds, and some studies talk about how they have signatures of non-REM EEG. We do know that reptiles show some elements of the 6 criteria I listed. Turtles will show rest periods that are accompanied by decreased sensitivity to stimuli, and there's pretty good evidence that they experience rebound sleep. Lizards and crocodiles show something like non-REM EEG when they were resting. There's very little evidence suggesting, however, that reptiles exhibit REM at all.",
"Most bony fish exhibit resting states that fulfill the 6 criteria I listed. Many fish show reduced respiration and increased response thresholds at night. Some fish also have sleep-specific postures. The wrasses will lie on their side on the sand at night, partially buried, and often in groups. Some species float in open water. Fish in coral reefs will retreat into small holes in the coral when they rest. Zebrafish have been shown to respond to sleep deprivation by getting more \"sleep\" the next day, suggesting some sort of homeostatic sleep rebound. There's no evidence that fish have non-REM or REM like brain patterns, but that's probably because their brains are too simple",
"Invertebrates are by far the most diverse group I'm talking about here, but we don't really know much about how they sleep. Many invertebrate species fulfill some of the criteria listed. Squids and octopi will show increased arousal thresholds with narrowed pupils and colour changes during rest phases. Insects will show periods of reduced sensory response in a 24 hour day. Bees show increased responsiveness to visual stimuli and less at night, as well as show some signs of sleep rebound. ",
"So, to finally answer your question, when did sleep evolve? It looks like sleep evolved along with the first animals, but it's easy to refute this. The fact of the matter is that very few animals fulfill all 6 of the behavioral criteria I listed. Other people say that you should measure sleep defined on EEG alone. If you try to define sleep by EEG alone, then invertebrates don't sleep at all, and sleep evolved with the vertebrates.",
"However, if you exclude species that don't show a very clear EEG, then you'd exclude all the fish and amphibians.",
"If you exclude species that don't engage in REM sleep, you'd exclude most reptiles.",
"If you exclude species that have non-REM but don't show clear REM or have very brief REM, then you'd exclude birds.",
"And now you're left with only species that show clear nonREM + REM cycles, and we only have mammals left, but then we run into the problem of defined sleep based on what ",
" do.",
"So when did sleep evolve? With the first microorganisms... or with the evolution of class Mammalia, depending on what exactly you define sleep to be."
] |
[
"Just to add to the invertebrate section, at least one ",
"jellyfish species",
" is thought to sleep (arguably), despite not having a brain (it uses a nerve net). It definitely fulfills criteria 1, 2, 5, and 6, and it's not clear 3 and 4 could possibly apply to a species that basically has one posture and one behavior.",
"Primary source: ",
"https://www.sciencedirect.com/science/article/pii/S0960982217310230?via%3Dihub",
"Secondary summary: ",
"https://www.theatlantic.com/science/archive/2017/09/even-jellyfish-sleep/540432/"
] |
[
"I'm not sure that's a change of concept so much as a change of how information is indexed."
] |
[
"How do emotions trigger tears?"
] |
[
false
] |
I know that stimulants and irritants can stimulate the tear ducts to secrete fluid, but how do emotions do the same thing?
|
[
"Your body produces different types of tears. The ones that irritants make aren't the same as the ones that you create through emotional response.",
"Emotional tears contain prolactin, corticotropin, Leu-enkephalin, and trace elements that are not found in reflex tears (which are 98 percent water). These hormones play a role in stress reactions, and excreting them may improve mood and allow dopamine levels to rise."
] |
[
"where would that 98 percent of water come from?"
] |
[
"They all come from the same place, the lacrimal glands and the conjunctiva perform active excretion. These glands are able to formulate various concentrations of substances as needed for lubrication, removing irritants, or discharging abundant proteins."
] |
[
"Knowing that water expands when either boiling or freezing, is there a temperature at which it takes up as little volume as possible?"
] |
[
false
] |
[deleted]
|
[
"+4C.",
"Above that, it expands with heat. Below that, it expands as it starts to form into crystal lattices."
] |
[
"Just want to add that this assumes standard pressure (as does the OP's question)"
] |
[
"Assuming you're talking about its liquid form, 4C or 39F. At this temperature water has the highest density, and since d=m/V, the volume will be the smallest."
] |
[
"What is so special about \"prime numbers\"?"
] |
[
false
] |
I understand prime numbers and pseudo-prime numbers have applications in cryptography, precisely because it is difficult to determine what a particular unknown number's factors are, if any. However, what is really so fundamentally special about prime numbers? There seems to be an air of mystery around them, and I'd genuinely like to understand this. Thanks!
|
[
"Prime numbers are special because they form a sort of basis for natural numbers: you can describe all natural numbers by their decomposition into prime factors (eg: 15 = 3 * 5). This decomposition is unique, and importantly for the cryptography application, is very hard to find for big numbers (you pretty much have to try all of the primes one by one)"
] |
[
"There are a -lot- of primes. For example, we can approximate the number of primes smaller than n by n/ln(n). RSA public keys are typically at least 1024 bits large. Making some gross approximations (2",
" ~ 10",
" we get there should be about 2*10",
" primes or roughly 2",
" primes. ",
"So even if you had a lookup table of all known primes, you'd 'reduced' the amount of work required by ~2",
" That's great... but doesn't help one bit. "
] |
[
"For example - we can take two large primes, say 100 digits each, and multiply them. The number we get from this can be the public key --- or what people use to encrypt their messages. They can encrypt in such a way that to decrypt, one would require the two original primes we used to create the key. Since they are so hard to find, we have a secure system that would take ages to crack."
] |
[
"Why is it that when you're in a \"dark\" room and you focus on a really dark spot, everything, even light, will start to fade away?"
] |
[
false
] |
I know I probably didn't make any sense since it's hard to explain but imagine being in a dark room with nothing but a little red LED light in the center of the room, if you focus on a dark corner you can see how this light will fade away into darkness. Why is that?
|
[
"What you describe is an example of Sensory Adaptation. Through the process of sensory adaptation, our sensory systems become less sensitive to constant, unchanging stimuli. ",
"In your scenario, if your eyes remain motionless, what little light is present will continually stimulate the same retinal photoreceptors at the same level. Sensory adaptation reduces our awareness of such a constant stimulus. In the case, the dim light will seem to fade. But twitch your eyes just a bit and the perception is restored.",
"Your other senses exhibit similar adaptations. You may smell a pungent aroma upon entering a room, but remain there and soon you may be entirely unaware of it. When you wear a new wristwatch or ring, you may at first be aware of the sensation of pressure on your skin, but after a while you no longer notice it."
] |
[
"Yes. The photopsins in your cone receptors photobleach when stimulated and take time to regenerate. So, if the same cones keep receiving the same light signal, the photopsins will bleach out faster than they can regenerate and that part of your eye becomes more and more insensitive to that color. When the image shifts to a greyscale image, since that part of your eye cannot see the color that was overstimulated before very well, the white light looks like the opposite color, so long as you hold your gaze fixed on the image. Eventually, the photopsins regenerate and your color sensitivity returns. This isn't a big problem normally since you move your eyes around a lot and the color of light that falls on any part of your retina changes frequently."
] |
[
"Is this the same concept that’s in play when you stare at those inverted color images for x amount of seconds and then look away to see the image in color? "
] |
[
"What would modern cars look/perform like if occupant safety was not a design factor?"
] |
[
false
] | null |
[
"How do I move it?"
] |
[
"A good home for this question is ",
"/r/AskScienceDiscussion",
"."
] |
[
"Just make a new post."
] |
[
"Do animals ever get zapped by \"static shock\" in non-human made environments? Or is getting that static shock a byproduct of human engineering?"
] |
[
false
] |
It seems like all the times that I've ever gotten a static shock, I was in a human made environment where there was carpet, or a car, or a door knob. Now, I'm not saying that animals could never get a static shock, I know it's just the passing of electrons, but I'm wondering, are there are any natural environments that are conducive to creating that build up? EDIT: So I'm still a little confused as the "of course it happens" posts often are not taking into account man-made fibres and contexts. It looks like it might happen more often in winter since it is drier, and would be more likely if the animal was not touching the ground (so in a tree with lots of sap and resin maybe?), however since most animals are touching the ground a lot, the build up necessary wouldn't happen nearly as often.
|
[
"Furry animals in dry environments generate static electricity all the time. Pet an outdoor cat in winter, and you'll hear the crackling."
] |
[
"Unless anyone came up with a specific example, then I'd say no. ",
"For a static shock to occur, two materials on opposite ends of the ",
"triboelectric series",
". need to come into contact. Most biological environments are made up of materials on the positive end of the triboelectric series (air, skin, hair etc..) while most of the materials on the negative end are man made (such as plastic and vinyl).",
"Interestingly, there are examples of naturally occurring substances on the negative end and these include rubber and resin. So maybe that mosquito inside the amber of John Hammond's walking stick had a nasty shock before he died."
] |
[
"Good call on the amber. Around 600 BCE, in Greece, a mathematician named Thales discovered that amber rubbed with animal fur attracted light objects. This was the first known discovery of static electricity. "
] |
[
"Who is the human holotype?"
] |
[
false
] |
Is there a specimen of Homo Sapiens that was used when it was formally described?
|
[
"QI did a section on this: ",
"http://www.youtube.com/watch?v=xpRksEo4Q8k",
"To summarize:",
"Edward Drinker Cope was going to be, but then they found he had syphilis ",
"http://en.wikipedia.org/wiki/Edward_Drinker_Cope",
"Currently, there is no human holotype."
] |
[
"I bet Marsh was ",
" when he found out they were planning on using Cope"
] |
[
"No. Or not when I last checked. The person who described humans (or something) WAS going to be it, but it was found he had syphillis or something "
] |
[
"Why is there a limit to how far back humans can remember?"
] |
[
false
] |
For example, why can't we remember learning to walk, or speak, or virtually any of the first few years of our lives? Does it have something to do with incomplete neurological development?
|
[
"The lack of the proper use of the word 'you' makes it extremely hard to take you seriously. :( other than that, your response sounds valid to me."
] |
[
"Well memories are basically reinforced neural pathways that are maintained so that u can replay the same sequence again. This is useful because it allows u to remember where u stored the milk, or where u can go buy bread. Stuff like that is used every day, so you reinforce it more and more by playing the sequence again and again. Your hippocampus (the part responsible for allocating memory essentially) gets better at reinforcing important stuff as u go along, so at first it doesn't really reinforce anything because everything is new. In addition, anything you did reinforce at that age either got offloaded to the cerebellum as a critical motor skill (e.g. walking. You don't need to remember how u learned to do that, u just need to be able to do it) or was reassigned to something more important - like words and vocabulary. Language is hard. You can only maintain a certain number of pathways so the hippocampus only retains those you use on a regular basis, or which seemed particularly important at the time when they happened. We remember a lot of stuff just because we were focused on it at the time or because it stood out as an unusual and novel event."
] |
[
"As with most things neurological, we don't really have a clear understanding of the limits of neural circuits, and guessing why something evolved over time to be the way it is usually leads to either an unsatisfying level of generalization, or unscientific speculation. That being said, you might be surprised to know that some people can remember just about everything. It is a condition called ",
"hyperthymesia",
". So, while it seems that the brain is capable of such a feat, reading about the difficulties faced by these individuals can help you see why it might sometimes be better to forget."
] |
[
"Any update on theories on how will universe end?"
] |
[
false
] |
In an "askreddit" thread on what will happen after death, someone did post an insightful quote on how our atoms will be here forever, and this leads me to reflect on the few theories I did read here and around the internet on the end of the Universe, mostly about the so called "heat death". When looking around in this sub, I did realize that the few threads on the matter are few years old, and I was wondering if more recent studies did change our perspective, or maybe made more solid one of the few theories. Thanks for any reply.
|
[
"Since the accelerating expansion of the universe was first discovered in the late 90s, we've really just got more and more precise in measuring this acceleration of the universe - there's no indication that it isn't actually accelerating. So the \"heat death\" is just being increasingly confirmed.",
"The current biggest controversy is that some methods show the Hubble constant is 68 km/s/Mpc, while others show the Hubble constant is 73 km/s/Mpc. So it's not that there are major arguments about the fundamentals of whether the universe is accelerating - we are arguing about factors of less than 10%."
] |
[
"\"ruled out\" would be difficult to say with certainty, but it does appear vanishingly unlikely. dark energy appears to be a constant energy ",
" of space itself. therefore, as the universe expands, there is more space, and with it there is more dark energy. if dark energy weren't created out of nothing, the density would decrease as space expanded, and there's no evidence indicating that the density can decrease.",
"thus, as dark energy increases, the expansion will accelerate faster and faster in a feedback loop.",
"having said all that, to my knowledge we still have no idea why the original inflation period ended, so there must be ",
" built-in mechanism to slow the expansion of the universe under some conditions, and it's possible that such a reversal could happen again."
] |
[
"Wikipedia has the \"",
"Timeline of the far future",
"\" article which covers many of the possible scenarios and the time when they might occur if our predictions are correct."
] |
[
"Why do meteors burn up on entry into the atmosphere?"
] |
[
false
] | null |
[
"Friction",
" and compression both play a part. As the atmsopheric particles interact with the surface of the meteorite heat is produced. The more particles interact, the higher the friction. Rub your hands together. Now increase the rate or force of the rubbing - you'll notice your hands get hotter quicker. Same process.",
"However, the atmosphere in front of the meteorite is subject to massive compression. You compress a gas and you heat it up (feel a stirrup or hand pump next time you use one to inflate a tyre). That builds up huge amounts of heat at the head of the meterorite",
"Because the meteorite is a good thermal insulator the heat builds up rapidly at the surface and triggers melting."
] |
[
"Atmospheric friction is just a simplification for the general public view. (air have v. little fiction)",
"Compression following the gas law is what actually heats up anything travelling through a gas at speed."
] |
[
"Sorry to reply to a 6 day old comment, but I figured the subreddit was flooded with meteor questions around now, and this question seems the closest to mine:",
"I understand why things heat up and burn up when entering the Earth's atmosphere, but what is the mechanism behind their exploding before impact? (That is what happened here, yes?)"
] |
[
"Is it theoretically possible for chimerism to occur between identical twins?"
] |
[
false
] |
, though I'm not sure whether it would be this or . If something like this did happen, would we even be able to tell since the embryos had identical DNA? Edit: The way I worded the title may be confusing. I meant, "Can a pair of identical twins become a chimera?" And would you even be able to tell if they did?
|
[
"You would not be able to tell the difference between them if there were. By definition, a mosaic is comprised of two ",
" genotypes. So the situation you describe wouldn't be mosaicism or chimerism, and we wouldn't know if they existed, due to their genetic compatibility."
] |
[
"This would be mosaicism. Mosaics come from one zygote, as is the case with monozygotic (identical) twins. Fraternal twins could be chimeras, although the odds of that happening would be much smaller likely than mosaic monozygotic twins. And ",
"yes",
" it has happened. They can test via blood sampling."
] |
[
"I don't think that's quite what I meant. The article you linked talks about a pair of twins that each had mosaicism; I meant a single person who was a chimera of identical twins. Or does chimerism have to occur before the zygote starts dividing?"
] |
[
"When scientists refer to \"information\" as in \"can information be lost in a black hole,\" what is the information?"
] |
[
false
] |
[deleted]
|
[
"quantum numbers. For instance, there's a thing called lepton number. When a neutron decays to a proton it emits an electron and anti-electron neutrino. Why anti? Because you get a +1 lepton number from the electron and a -1 lepton number from the anti-neutrino. And since you had no leptons to begin with +1-1=0 so lepton number has been conserved throughout the decay."
] |
[
"evaporation was the resolution. See we used to think that all of that information was just trapped in the black hole. But now it seems more like evaporation releases the information back into the universe. So to continue with my example, when an electron \"falls in\" its lepton number is recorded on the event horizon. When the black hole evaporates an electron via Hawking radiation, that lepton number is free to leave the black hole. So the lepton number was never truly lost. Just delayed.",
"In fact, RobotRollCall is trying out a new explanation of black holes that I really quite enjoy. You could think of this delayed information as just a really really slow scattering. As the electron passes through the region of the black hole it takes so long to complete the process that trillions of years or more could pass to complete that motion."
] |
[
"It is literally information, as in Shannon information. ",
"All information is physical, i.e. it must be encoded in something, for example the switching state of a transistor, or even just as lines on a sheet of paper.",
"What remains is to figure out how much information can possibly be carried by a given system. This has been answered. A two-level quantum system (a ",
"), for example, can carry exactly one classical bit of information.",
"A common example for the black hole information paradox you describe is the following: Consider two entangled photons. They carry two bits if information, which are fully encoded in the correlations between the two photons, not in the individual photons (this is a key property of entanglement). If you now send one photon into a black hole, it \"disappears\". The second photon is now left in a completely mixed state, and thus carries zero bits of information. The (largely unresolved) question is: where did the 2 bits of information go?"
] |
[
"Where/How do we get birthmarks?"
] |
[
false
] |
[deleted]
|
[
"We don't know why birthmarks occur. There are two types. Pigmented birthmarks are caused by an excess of skin pigment in the area while vascular birthmarks are caused by blood vessels clustering up. Vascular birthmarks are not hereditary, it's just an imbalance. Pigmented are not necessarily genetic but the condition that causes them to occur may be. "
] |
[
"Developmentally, they can be explained by clonal colonies of cells. A patch of cells early in the embryo over express pigment. Later all the cells from this line will express the excess pigment too because something is causing the gene to be up regulated. This could be a minor mutation, or some environmental compound that acts to increase expression of pigment for one reason or another. This is called ",
"phenocopy",
". Like king1037 said, this is why the condition that causes it is most likely genetic, but the marks themselves are not necessarily part of the \"usual\" development plan. "
] |
[
"I find this amazeing that we do not know why they occur. are you talking in a evolutionary why extent like why would our ancestors have had them or what there.left over from. or are you talking like what use they could of served? "
] |
[
"If the Earth is 4.5 billion years old, shouldn't the oceans have higher salt content?"
] |
[
false
] |
I understand that the salt content in the ocean is caused by mineral run-off, volcanic explosions, and hydrothermal vents on the ocean floor, and that there's evidence that the current salinity of our oceans was about the same a billion years ago. I've heard those in favor of a younger earth state that the salinity of the oceans is proof that the earth is much younger. I don't know enough about this, and am curious. I've done a few searches on Google, but everything I've found so far is coming from the Creationist standpoint. Would you mind offering some clarity for me, ? : You're the best, . Thank you very much for your input so far. I'm reading and learning as we go.
|
[
"Salts do enter and form in the ocean, but they also leave it.",
"The two major processes capable of removing significant amounts of salt from the ocean are the formation of ",
"evaporites",
" (rocks that form when restricted, salty water evaporates) and the sequestration of ",
"brine",
" as groundwater on the continents. It's actually been proposed that the early ocean was saltier than today (maybe up to twice as salty). Salt was removed from the oceans over geologic time as the Earth cooled and the continents grew, providing more space favorable for salt/evaporite deposition and the formation of saline groundwater. It's been argued that modern-day salinity wasn't reached until relatively recently, perhaps playing a role in the origin and radiation of animal life (known as the Cambrian Explosion).",
"Overall, it's an interesting problem that isn't quite resolved. Try ",
"Knauth 2005",
" for more information. "
] |
[
"Ocean salinity",
"Ocean salinity has been stable for billions of years, most likely as a consequence of a chemical/tectonic system which removes as much salt as is deposited; for instance, sodium and chloride sinks include evaporite deposits, pore water burial, and reactions with seafloor basalts.[11] Following the ocean's formation, sodium no longer leached from the ocean floor, but instead was captured in sedimentary layers covering the ocean bed. Plate tectonics possibly forces salt under the continental land masses, where it slowly leaches again to the surface."
] |
[
"As described by D8M900 and wiki-linked by stubob, the salinity of the ocean has been (relatively) stable for a long time. This is due to the cyclical nature of the addition and removal processes, which is intuitively obvious when you consider these processes have had plenty of time to equilibrate.",
"Truth be told, what we really know is the ratios of the ",
"conservative major ions in seawater",
" have existed in the same ratio to each other for this time period. The overall salinity changes with the addition/removal of water based on glacial cycles.",
"That said, we are still learning the finer points of those processes. For example, it was not until relatively recently we learned the removal of Mg of seawater was dominated by ",
"hydrothermal circulation",
"."
] |
[
"Do the contents of our blood have any affect on mosquitos after they drink it? Do drunk people make drunk mosquitos?"
] |
[
false
] | null |
[
"I think the answer is, \"",
"we don't know",
",\" but it seems that mosquitoes are more attracted to drunk people, than sober people, and according to the article I linked fruit flies do get drunk, but have a high tolerance. ",
"Same article also says, \"Any liquid other than blood is diverted first to a separate digestive pouch where enzymes break it down. So it is likely the alcohol is neutralised before it hits the insect’s nervous system.\""
] |
[
"Remember than even an extremely drunk person won’t have a blood alcohol content of more than about 0.20-0.30%. You could drink a nearly infinite amount of 0.2% alcohol solution without becoming intoxicated yourself."
] |
[
"Train of thought?"
] |
[
"Does a satellite orbiting earth cast a shadow on the earth's surface?"
] |
[
false
] | null |
[
"More specifically, the umbra cone of the satellite falls far short of the earth's surface, while the penumbra is too subtle to discern with the naked eye."
] |
[
"The shadow does not reach the earth's surface.",
"A shadow is not actually straight lines from an object down to the surface, it is actually slightly angled (the sun is much bigger than any object on or near earth, or earth for that matter). These angles are small because the sun is very far away.",
"It is quite easy to understand though, anything that does not entirely block the sun (for at least one point on the surface of earth) does not make a shadow. So anything that is either small or far away.",
"That does not mean that the sattelite does not obstruct the light flow. it just does not cause a shadow.",
"http://en.wikipedia.org/wiki/Umbra"
] |
[
"Imagine yourself on Earth with a satellite between you and the Sun. You are not in the shadow, because the satellite is too small. "
] |
[
"Do hot objects experience time differently than cooler objects?"
] |
[
false
] |
Temperature corresponds to the average kinetic energy of an object's molecular particles. Objects with more kinetic energy experience time "slower" than objects with less. Do hot objects experience time "slower" than cold objects (assuming both objects are made of the same material, and have the same mass)?
|
[
"You would have to own an extremely accurate scale.",
"You can do the calcs with iron, with those numbers. I'm too lazy but the steps would be, figure out the amount of heat required, in joules, to change the temperature or 1 kg iron (easy formula). Convert that to MeV. Use 931.5 MeV/ 1 Atomic Mass Unit."
] |
[
"No. Hotter objects are more massive, but time does not ",
" slow down with increased energy/mass.",
"All goes back to E=mc",
" If energy increases, the mass does as well. But, in order for time to dilate a formula is used:",
"Δt'=γΔt,",
"where gamma is the Lorentz factor, and t is time. The prime indicates a different reference frame. The differences in reference frames is created by a difference in velocities, v. The slower time in one frame is caused by the gamma. The gammas formula depends on velocity, v. As the velocity goes up, gamma gets bigger, and the dilation does too. Notice that the velocity has nothing to do with the mass or energy though.",
"Therefore, as an object gets hotter, it becomes more \"massive\", but it does not experience time at a different rate, unless it is moving faster.",
"The only instance I can think of where a particle moves faster as it gets hotter would be in a gas molecule or plasma. This would experience time slower as it got hotter. Other phases of matter would not be able to achieve the speeds necessary to enter relativistic frames."
] |
[
"Got curious.",
"5.563×10",
" kg (kilograms)",
"Would be somewhere around the mass change."
] |
[
"Question about anti matter-matter annihilation?"
] |
[
false
] |
Does anti matter annihilate with any matter or just with its exact opposite? As in, would antihydrogen be safe in containment of pure carbon for example and only annihilate with hydrogen or does it react to everything? If it does annihilate with all normal matter, what would happen if we pushed antihydrogen to say uranium (or any other really heavy element)?
|
[
"Does anti matter annihilate with any matter or just with its exact opposite?",
"Just its exact opposite. An antiproton and an electron do not annihilate each other, for example.",
"As in, would antihydrogen be safe in containment of pure carbon for example and only annihilate with hydrogen or does it react to everything? ",
"The anithydrogen would not be safe in carbon, because atoms are made up of protons, neutrons, and electrons, while anti-atoms are made of antiprotons, antineutrons, and positrons (antielectrons). So antihydrogen in the presence of any ordinary matter would annihilate, as the constituents of the antihydrogen (antiproton and positron) would encounter constituents in the ordinary matter that they'd annihilate with.",
"If it does annihilate with all normal matter, what would happen if we pushed antihydrogen to say uranium (or any other really heavy element)?",
"The basic principle is unchanged, whether you are using light elements or heavy elements."
] |
[
"Matter/anti-matter annihilation reactions are best understood in the context of laws of conservation. There are many well known laws, such as conservation of momentum, conservation of mass/energy, conservation of charge, etc. There are some other laws that are less well known such as conservation of lepton number, and other quantum-mechanical conservation laws. These are the things that prevent ordinary matter from just disappearing into a puff of photons. An electron can't decay into something else on its own because it is bound by conservation of charge and lepton number. A muon is also a charged lepton but it ",
" decay because it has a lot more mass (aka energy) than the electron, so it can simply emit a muon-neutrino(which keeps the \"muon-ness\" balanced, lepton-number wise) and an anti-electron-neutrino (likewise for \"electron-ness\") and then \"turning into\" an electron (this is a gross simplification of course), with energy to spare. The electron is the lightest charged particle so it can't do that, it's trapped in being an electron. Similarly, a proton is bound by similar conservation constraints and can't simply decay into something else.",
"In general, there are a variety of different possible particle reactions when you have a certain set of particles interacting together. Of course, all of those reactions are constrained by conservation laws. However, an interesting thing happens when two related kinds of particles react together. Every particle has a corresponding particle with otherwise opposite \"quantum numbers\" (like charge, \"electron-ness\", spin, etc.). Call this relationship whatever you like, call the opposite quantum number particles \"mirror particles\", if you like. But something interesting happens with reactions between a particle and its mirror version. Because the mirror particle has opposite quantum numbers, all of the quantum numbers are balanced at zero. That means it's possible to have a particle reaction that retains none of the original components in the reaction products. You don't need to maintain electron-ness, or muon-ness, or proton-ness, or electric charge, or what-have-you because all of that is net zero between both particles. So you basically have a reaction that nets out to just being an amount of energy and momentum to play with, and you can have reactions that \"get rid of\" the original constituents and end up with completely different other particles or \"pure energy\" (i.e. photons) as the products. And for various reasons those types of reactions are generally fairly favorable, so they are very likely to occur.",
"So you can have reactions between a particle and its mirror particle which \"annihilate\" both original particles. And this is why we talk about annihilation reactions and we refer to these \"mirror\" type particles as \"anti-matter\".",
"OK, so all of that is a bit of a digression to the main question here, which is about atoms and anti-atoms. Atoms are composed of only a handful of sub-atomic components: electrons, protons, and neutrons. An anti-atom would similar be composed of only a handful of anti-matter equivalents of those components: positrons, anti-protons, and anti-neutrons. If you have an atom of anti-Hydrogen which interacts with an atom of Carbon the anti-Hydrogen's positron will annihilate with one of the Carbon atom's electrons, then the anti-Hydrogen's nucleus (an anti-proton) will be electrostatically attracted to the Carbon's nucleus where it will annihilate with one of the protons there."
] |
[
"in feynman diagrams antiparticles are displayed as going back in time.",
"from wikipedia:\" Feynman used Ernst Stueckelberg's interpretation of the positron as if it were an electron moving backward in time.[2] Thus, antiparticles are represented as moving backward along the time axis in Feynman diagrams.\"",
"and in the pictured one the timeaxis is from left to right."
] |
[
"Can someone explain to me what makes a good or bad nucleophile for SN 2 and SN 1 reactions?"
] |
[
false
] |
I know that it affected by the strength of it being a base, but I'm still confused by knowing exactly how to figure it out. Being in a summer class my professor flew through it and didn't explain it that well.
|
[
"Try ",
"this Wikipedia article",
" for some help.",
"Basically, the rate of the reaction is only affected by the nucleophile in the SN2 case, assuming high enough nucleophile concentration. How easily that nucleophile can donate its electrons to the central carbon determine how fast the reaction proceeds. The list of factors that affect this are the following: steric hindrance, solvent, and leaving group.",
"Steric hindrance is basically how much \"room\" there is for the nucleophile to attack the substrate. If either is too bulky, it can't happen quickly.",
"The solvent can potentially protonate the nucleophile and prevent it from donating its electrons, so a nonprotic solvent is usually used.",
"The leaving group on the substrate should ideally be stable enough to take the two electrons with it. Larger or resonance-stabilized leaving groups are usually preferred.",
"Once you've gotten past all that, you should look at how \"basic\" the nucleophile is for a measure of how well it can donate those electrons to the substrate.",
"The above shouldn't be confused with the SN1 reaction, which doesn't depend much on the nucleophile strength."
] |
[
"There are four factors that affect nucleophilicity for an SN2 reaction:",
"1) Bases are better than conjugate acids (another way of saying negative > neutral > positive). The justification is that negatively charged atoms will have higher starting energy and the transition state will have lower energy.",
"2) The less electronegative atoms make better nucleophiles when moving along a row (C > N > O). Remember, being a nucleophile is all about sharing your electrons. If you are more electronegative, you don't want to share your electrons, thus you don't want react.",
"3) The larger atoms are better nucleophiles (down a column I > Br > Cl). Larger atoms have less hold on their valence electrons and are better able to freely donate them.",
"4) The less steric hinderance on the nucleophile, the better. Nucleophiles attack alpha-carbons. The alpha carbon has a lot of other carbons blocking the way. A small nucleophile is less likely to bump (interact) the other carbons in the electrophile when reacting. This will lower the energy of the transition state and make the reaction proceed easier. A bulky nucleophile will get \"blocked\" by the neighboring carbons of the electrophile and have difficulty reacting.",
"To answer your second question:",
"You need to think of E1, E2, Sn1 and Sn2 as only three reactions: Sn2, E2 and Sn1/E1. Sn1/E1 are very similar reactions. The first step of both is the spontaneous loss of the leaving group to form a carbocation. For both these reactions, this is the rate-determining step. Because every subsequent reaction is easier than the loss of the leaving group, it is impossible for the molecules to \"pick\" between going Sn1 or E1. So they will go both. It is also important to remember that in an Sn1/E1 reaction, the solvent is playing three roles: It is the solvent dissolve the electrophile; it is the nucleophile or base to attack the carbocation once it has been formed; and it acts as a base to remove excess protons (H+) to provide your neutral product.",
"The first thing you should do is identify the alpha-carbon. If it's methyl (CH3-I for example) it's automatically SN2 and you are done. If it's tertiary ((CH3)3C-I for example) it's never going to be SN2. ",
"If it's primary (CH3-CH2-I), your next step is to identify the nucleophile (see above). If your nucleophile is neutral it's Sn2 (since a neutral nucleophile is not strong enough to do an E2 reaction). If your nucleophile is negatively charged it could be either E2 or Sn2. We can distinguish between them by identifying whether or not the nucleophile is a strong base (NaH for example) or a bulky base (KOtBu for example). If it's a strong or bulky base it will go E2. If it's a weaker base it will go Sn2 (weaker bases have nitrogen, carbon, OH-).",
"If the alpha-carbon is secondary, you still have to identify the nucleophile. The same rules as above apply for negatively charged nucleophiles (strong and/or bulky = E2, weaker = Sn2). However, if you have a neutral nucleophile, the reaction will likely proceed Sn1/E1, since it is possible for a stable carbocation to form.",
"Lastly, if the alpha-carbon is tertiary, it can't be SN2. If it's a negatively charged nucleophile it's E2 and if it's a neutral nucleophile it's Sn1/E1.",
"This is a lot of information condensed into one post. Feel free to ask if you are still confused."
] |
[
"Okay let me breakdown those 4 types of mechanisms for you clearly and concisely side by side, for reference.",
"Elimination-1 means only one thing happens at a time. First we will have our leaving group bounce, and then our nucleophile will attack the vacant spot in a second step. E-1 reactions are supported by good leaving groups, stable charged intermediates, polar and aprotic solvents (to stabilize the charged intermediate), and weak nucleophiles. Look for E-1 when you have a tertiary carbocation intermediate and a leaving group that is very easy to pull off!",
"SN-1 likes the same setup as E-1, which can be tricky. The difference will be largely with the subtrates! A smaller and stronger nucleophile and weak base will lead to Sn-1 over E-1, relative to the big, bulky, weak nucleophiles, but stronger bases that favor E-1. Otherwise, they are identical. Remember! Because there is a true carbocation intermediate, there will be a racemized product.",
"Now SN-2 reactions happen in one step, two things at once, your LG bounces and your Nuc attacks. This will be favored by good LGs, polar, aprotic solvents, strong! and small nucleophiles but weak bases, and easy access to backside attack on the reactive carbon. You can separate this from SN-1 by 1) there is an inversion of the carbon center and 2) an SN-1 Nuc is weak (though stronger than an E-1), while an SN-2 Nuc is quite potent.",
"Last is E-2. E-2s take even more severe conditions than SN-2! Your LG will leave while a Hydrogen is pulled off from a Carbon simultaneously. How do we know E-2 over SN-2? Big and bulky stuff can't eliminate by SN-2! Also E-2 are really high energy as well, so higher temp suggest E-2. Really strong base but a weak nucleophile points to E-2. ",
"If you can get all this stuff, E1cb is cake.",
"Msg if you need anymore help!"
] |
[
"Is it possible to massively accelerate the growth rate of plants?"
] |
[
false
] |
[deleted]
|
[
"It depends on how much you mean by \"massively\". You can get a plant to grow many times faster than typical by giving it lots of light of the proper spectrum, nutrients of the right types, CO2 supplementation, and hormones, such as gibberellins.",
"Mind you, making a plant grow faster is a lot more tricky than just \"add gibberellins.\""
] |
[
"Thank you for your answer! As a follow-up, what do these factors influence in the plant that makes it grow more quickly?"
] |
[
"Well, what most of the factors do is remove natural bottlenecks that slow plant growth.",
"If you have a ton of light, then you are limited by the ability of the plant to take up nitrogen and other nutrients. If you have an optimized system that allows the maximum possible uptake of nutrients, then CO2 concentration in the air becomes a bottleneck.",
"Hormones will alter plant cell division and growth, but as far as I know there arn't any really good tricks that don't have bad side effects on the plant. "
] |
[
"RIP Kepler Megathread"
] |
[
false
] |
After decades of planning and a long nine years in space, NASA is retiring the Kepler Space Telescope as it has run out of the fuel it needs to continue science operations.We now know the Galaxy to be filled with planets, many more planets existing than stars, and many very different from what we see in our own Solar System. And so, sadly we all must say goodbye to this incredibly successful and fantastic mission and telescope. If you have questions about the mission or the science, ask them here!
|
[
"Oh man. The gap between this and James Webb (which appears to be launching in about a year, and that is a fact that appears to remain true independent of what year you're reading this in) is gonna kill me. Bye little buddy. Anybody close to this project have any cool science/mission facts they could share that aren't available through the links in the OP?"
] |
[
"We now know the Galaxy to be filled with planets, many more planets existing than stars, and many very different from what we see in our own Solar System.",
"I know this will be somewhat subjective, but what do you think is the strangest, most unexpected planet that we have discovered?"
] |
[
"I've got two that I'll suggest as strangest objects, though neither fits into the 'planet' category neatly from Kepler discoveries. The former.... could be tied to planets, and the latter may be the remnants of a former planet. More broadly, the goal of Kepler was primarily to understand planet frequency, especially of earth-like planets around sun-like stars. The next missions up are TESS (currently in space taking data) which is looking for bright stars that have planets around them, and then the James Webb Space Telescope is supposed to launch in 2021 and will be a great instrument for observing those planets. The importance of bright stars is that usually we're observing the star to get information about the planet, so the brighter the star, the easier it is to get those observations.",
"On to the weird stuff:",
"\nThe first is ",
"KIC 8462852",
", or Boyajian's star. Weird enough system that it has its own subreddit at ",
"r/KIC8462852",
", the star shows dramatic and somewhat unpredictable dimming events. I think the best guess at the moment is that this is caused by a swarm of comets, but it's been pretty contentious. ",
"Object number two was somewhat suspected as a possibility (enough that they searched for it), and is ",
"WD 1145+017",
". In this case, the host star is a white dwarf, sort of the small remnants of a star after nuclear fusion has ended, resulting in the mass of a star compressed down to the size of the earth. Orbiting around that white dwarf is an object about 1000 km in size (about double the size of the largest object in our solar system's asteroid belt), which is currently being broken down into smaller pieces. There looks to be several smaller pieces also in orbit, all being vaporized by the star that they're orbiting once about every 4-5 hours. The largest of these objects (WD 1147+017 b) is expected to last another couple hundred million years before it's fully destroyed.",
"Other people may have their own favs, but that's been the two I think have been most interesting that came from Kepler. Beyond just Kepler discoveries, honestly the most unexpected was the first Hot Jupiter. It wasn't generally thought that you'd find Jupiter-mass planets orbiting in closer than Mercury's orbit (Mercury's orbit is about 3 months, and the Hot Jupiters are on orbits of a few days)"
] |
[
"Why do things look darker when they get wet?"
] |
[
false
] |
Pavement, hair, clothes, everything!
|
[
"Reflection and absorption. When you see something, you're sensing the light that has reflected off of that thing. ",
"When it's dry, a portion of the light that strikes your target is absorbed by it and the rest is reflected. When there is a layer of water (or oil, laquer, etc) the same thing happens BUT some of the reflected light is reflected back by the surface of the coating.",
"This actually loops over and over again, though there is a diminishing result. You can sometimes see interference patterns because of this behavior, too. With the right materials choices you can intentiinal reduce the ammount of light reflected back and make... Anti-reflective coatings."
] |
[
"The reason materials often look darker when wet is that there is decreased back-scattering of light towards the observer.",
"Materials such as clothing and paper and made of fibers with air spaces in between (pavement also has an irregular surface with many air spaces). According to Fresnel's equations, at each material-air interface, reflection occurs. These equations state that the amount of reflection depends on the relative refractive indices of the substances at the interface; a greater difference results in more reflection. Since there are myriad such interfaces, and the fibers/micro-crystals are not perfectly ordered, diffuse reflection occurs. This reflected/back-scattered light makes the object appear bright, since it is sent back towards the observer.",
"However, when the material is wet, the air-material interface is replaced by a water-material interface. Since the refractive indices are closer for the water-material pair than air-material pair, according to Fresnel's equations, less light is reflected at each interface. Thus, the object appears darker, since more light is transmitted and less is back-scattered towards the observer. This phenomenon is also why it is easier to see through wet paper or clothing. ",
"Edit: clarified Fresnel's equations"
] |
[
"You seem to be neglecting transmitted light. If all the light was either absorbed or reflected, then it would not be possible to see diffuse light through a dry sheet of paper or what's underneath a wet t-shirt."
] |
[
"Do people with similar kinds of synesthesia have similar kinds of synesthetic associations?"
] |
[
false
] |
[deleted]
|
[
"Us non-synesthetes for the most part see the same colors in the same places, and agree on high and low pitched sounds, etc.",
"We're taught that a particular wave-length of light corresponds to a particular colour. The way that those wave lengths are given off by objects doesn't change because of the person looking at it."
] |
[
"Yes, yes ",
"beetle in the box",
". Still, we don't ",
" the wavelengths, we see the signal the eye gives the brain in response to those wavelengths. And you could say we don't see the signal either, we \"see\" whatever the furthest thing back in the causal chain is that the brain does in response to receiving that signal. And some colorblind people won't share our agreement about which colors are which.",
"And people with sound/musical key synesthesia \"see\" what their brain does in response to hearing a certain musical key. Yet in Oliver Sacks' book, people with the same kind of synesthesia, despite agreeing on which colors are which disagree about which key has which color, or which note has which color. But I wonder if there's any underlying agreement or symmetry to their experiences, as in the symmetry of people who happen to find \"green\" in all the same places, or the broader symmetry between a colorblind and non-colorblind person who can at least overlap in agreement on which things are green and which are brown."
] |
[
"So I have grapheme->color, grapheme->personality and space sequence synesthesias. I just found out this year that these were even a thing - always thought it was my imagination that likes 'a' to be yellow. They are sort of embarrassing to describe so I barely even talk about the grapheme->color, and almost never talk about the other types.",
"But I've been fascinated by it and have been occasionally exploring research conducted and observing my own syns. It turns out that I have the projector grapheme->color, as opposed to the associator. Associators sense or feel the color of the character internal to their mind's eye. Projectors literally see the color on the character externally. You can have a mix of both, but my projection definitely dominates.",
"There is more to my discoveries but to somewhat answer your questions, I definitely have noticed some patterns in the color assignments. My color assignments have little or nothing to do with the sequence of the characters. So far, it appears that they are based on the shape of the characters. Note that no two characters are the same exact color. They are always at least shades apart.",
"Example 1: My only two green characters are '3' and 'E'. Notice how they are almost the same character only 180 degrees different.",
"Example 2: '6' and '9' are both yellow. '9' has more orange in it though. 'a' is yellow and 'd' is orange, which lowercase versions are similarly shaped. And lowercase 'd' is similar to an upside down '9'. Also 'b' which is a mirror of 'd', is brown which is different than yellow and orange, but in the same family.",
"Example 3: 'r' and '5' are my only two red characters. 'r' looks like it can fit into the top part of '5'. 'k' is pink and notice how close it resembles the uppercase 'R'.",
"Example 4: '4' is baby blue and 't' is a dark dark blue.",
"None of these are perfect associations and it might seem like it's stretching in some cases, but there are patterns there. Ask me any questions."
] |
[
"Does letting a phone battery die completely before charging help improve battery life?"
] |
[
false
] |
It seems occasionally my phone will start to get a terrible battery life, lasting less than 12 hours, but if I run the battery to zero and let it charge to 100%, the phone seems to last a whole day again. Is this a real effect? If it isn't, why would it seem like a real effect?
|
[
"Resetting the charging circuit has been covered here. However, you should avoid fully discharging a lithium-ion cell as much as possible.",
"The rate at which a lithium-ion cell is damaged varies based on how far the cell is from its nominal voltage (~3.7V). The voltage limits for your device are chosen to balance the total cycles, and the capacity available. The deeper you discharge the cells the quicker it will die. So if you are looking to conserve your cells life, it is best to only partially discharge the battery between recharges, 40-70% Depth of Discharge results in a pretty good balance. ",
"Battery University is typically a good resource for lithium-ion related questions:",
"\n",
"They cover best practices and reference the calibration charge here",
" "
] |
[
"I thought modem batteries had safety measures in place to keep from ever fully discharging. "
] |
[
"ya but due to internal resistance they will self-discharge.",
"The cut off is to stop the terminals from providing current if the voltage is too low (to save space for self-discharge)."
] |
[
"My physics textbook says that small redshifts of galaxies are due to their velocities relative to us, while large redshifts would be caused by expanding space stretching wavelengths. Is it really necessary to make a distinction like this, and can redshift be explained through a particle model?"
] |
[
false
] |
Thanks in advance!
|
[
"No it does not. (The other poster is very very wrong) The expanding space solution does not apply for gravitationally bound systems. Here's a look at the concept: ",
"http://arxiv.org/abs/0809.4573"
] |
[
"It is indeed necessary to separate the two kinds of redshift. They are actually physically very different. The relative velocity redshift occurs immediately - someone at rest with respect to us who was right next to the galaxy would see the exact same redshift as we see.",
"The cosmological redshift is much more gradual and occurs only over very long distances. It depends strongly on how far away you are from the object (ie, the same light beam has different redshifts at different points on its trajectory) and it doesn't depend on an object's peculiar velocity. Two objects that are 10 billion light years away and are travelling at 0.8c with respect to eachother have the same cosmological redshift. So you can see that the physics behind the two redshifts is completely different, even though mathematically they can just be added to produce the total redshift.",
"Redshift is inherently a wave effect, and it is not useful to think of light as a particle when explaining it. It is important to remember that in quantum field theory the basic entity is the field (which can have waves in it) and the particles that appear are just excitations of that field. Especially with massless bosons like photons (where there is no extra energy cost to exciting an extra photon or making one disappear) it is rarely useful to think in terms of particles when trying to understand the dynamics of the quantum field."
] |
[
"Since the relative velocities of other galaxies are proportional to the distance between us and them (",
"Hubble's Law",
"), the redshift of the nearby galaxies are much smaller than that of far away ones. Therefore, the redshift of nearby galaxies could be regarded as a redshift due to the recession of the light source.",
"However, in reality, the galaxies don't really recede from us (if we neglect the actual velocities of galaxies moving through space, which are negligible for galaxies far away). Instead, the expansion of space between the galaxies cause the relevant redshift."
] |
[
"Can anything be said in every language?"
] |
[
false
] |
I know some languages don’t express certain words or concepts. Like English borrowed “rendezvous” among very many others because there isn’t a good substitute. And some languages lack certain color words. And there are probably many more examples. But other than maybe “yes”, “no”, and greeting (and even then I can’t be sure if that’s true), is there any concept that’s universal among languages? If so, what/why?
|
[
"I listened to a podcast awhile ago about the most universal word understood among languages both now an early precursors to modern language. The word they came up with was \"mama\" and thought it was at least partly due to human vocal development. Basically, mama is one of the earliest sounds a baby can make, so we as humans have universally adopted it as the word for mother."
] |
[
"There are certainly words that don't have a 1 to 1 translation. The German \"waldeinsamkeit\" is the experience of being alone in the woods. English doesn't have one word for that, but clearly I can convey the meaning. I would argue rendezvous is is just a specific type of secret-ish meeting. Agglutinative languages like Inuktikut Throw out the concept of word boundaries and can say anything in one \"word\". Languages evolve to communicate the human experience. If a language is introduced to one word that expresses a more complex concept they can just snag it into their own vocabulary. It simply wouldn't make sense for a language to have never evolved a way to express a certain concept."
] |
[
"English has a way to express \"rendezvous\" without using that word, though:",
"a meeting at an agreed time and place, typically between two people.",
"You could just say that whole thing every time you would say \"a rendezvous\", if you happened to not know that word, or had a weird thing against French loanwords. You could even go further and replace a lot of those words with longer explanations, too.",
"So, to answer your question: yes. You can express anything with a surprisingly small well-chosen vocabulary, and I'd argue that a suitable set of words exists in some form in every language. (Toki Pona is the usual extreme example of this - it includes 120 words and forms every other concept with those and imported proper nouns.)",
"Side note: ",
"there are languages without \"yes\" and \"no\", too."
] |
[
"Why are download and upload speeds in average internet connections so radically different?"
] |
[
false
] | null |
[
"Simply because most ISPs limit your upload speed to a fraction of your download speed as a cost-saving measure.",
"The idea from the ISPs side is that most of what users want to do is download (streaming music, video, visit web pages, etc.), so they go cheap and limit your upload speed so they don't need as much infrastructure to handle upload traffic. It also discourages people from running their own servers.",
"That's not a technical limitation. Find an ISP that provides symmetric upload and download speeds, and you won't see much of a difference."
] |
[
"That depends. For the most part, your ISPs equipment will be full duplex; any given router or server at your ISP should be able to run the same aggregate speed in either direction.",
"However, just like you get asymmetric speeds from your ISP, your ISP also buys their capacity from an upstream provider, and they may have a Service Level Agreement (SLA) that specifies a different upload speed versus download speed.",
"There are other issues, however. The International standard for data over cable service is DOCSIS (Data Over Cable Service Interface Specification). The latest standard, DOCSIS 3.1, specifies a maximum theoretical speed rate of 10Gbps downstream, and 1Gbps upstream. If you use cable-based Internet, your modem is most likely a DOCSIS compliant modem. Currently, all released DOCSIS specifications are asymmetrical, with slower upload than download. Your ISP technically ",
" provide symmetric speeds, however they can only do that by artificially capping the download speed to match the upload speed (that is, they'd have to slow down your downloads).",
"The good news is that CableLabs (which develops the DOCSIS standard) has announced DOCSIS 3.1 Full Duplex, which will provide maximum download ",
" upload rates of 10Gbps in each direction. I suspect it will be a few years before we see this available for residential installations, and even when it does I suspect cable providers will not offer the full theoretical speeds to residential customers. Note as well that it is expected the maximum speeds can only be achieved if you have ",
"; having cable TV service over the same cable will by necessity reduce the available bandwidth.",
"The situation is similar for DSL (Digital Subscriber Loop/Line). There are a number of DSL standards, but in terms of upload/download symmetry the two major standard sets are ",
" DSL (SDSL), and ",
" DSL (ADSL). Most residential providers provide ADSL, as it requires less infrastructure and targets what most consumers want (download speed over upload speed). As these standards are often built into the modems themselves, like cable it's a bit more than just \"flipping a switch\". Like cable ISPs, DSL based ISPs will be using servers and routers than can handle full speed full duplex operations, however the interconnects between the ISP and the customer relies on a standard that provides asymmetric speeds, so that part would need to be upgraded (and as that \"part\" includes every customers modem, this can be a big task)."
] |
[
"Historically, high speed Internet via T1, T3, OC5, etc. Was the same bandwidth up and down. Early cable used the cable wire for down and the slower telephone wire for up, so there was a discrepancy there in the early days. Then along cane DSL which got T1 speeds over twisted pair phone cables — with a catch. To increase the downstream speed, they sacrificed some of the upstream speed, because it was all about pulses travelling down the same lines — they couldn’t travel both directions at once.",
"These days, DSL is the only technology still used that has this limitation; but the overall speeds are generally high enough that from a technical standpoint, there’s not really any reason to do this for most subscriptions.",
"However, continuing to suppress upstream speeds lets the ISPs differentiate levels of service. They traditionally only provide high upstream speeds to business customers, and keep all the consumer speeds throttled in gradiation. This way they can drive demand, make more money, and not upgrade all their equipment as often."
] |
[
"Why are our fingerprints spirals?"
] |
[
false
] | null |
[
"No one can answer that because No one knows about regularity of fingerprints, because fingerprints are not genetic. All of your finger and toe prints are formed when you’re rubbing the inside of the amniotic sac."
] |
[
"The number you present in your argument is binary",
"As the base wasn't specified, it could be in any base, including base 10. As such, it is an example of a repeating number which doesn't contain every possible number."
] |
[
"The number you present in your argument is binary",
"As the base wasn't specified, it could be in any base, including base 10. As such, it is an example of a repeating number which doesn't contain every possible number."
] |
[
"Does the DNA scramble randomly?"
] |
[
false
] |
[deleted]
|
[
"Yes, this phenomenon is known as ",
"genetic recombination",
" and is quite common - and is arguably the biggest contributor to genetic diversity in offspring. Many mechanisms exist for genetic recombination, including what others have mentioned about homologous recombination of sister chromatids known as ",
"chromosomal crossover",
". This primarily occurs during meiosis in eukaryotes. Homologous recombination is also a major pathway in error-free DNA repair in all domains of life, and is incredibly interesting. ",
"Additionally, other forms of genetic shuffling exist, like ",
"transposable elements",
". These were also mentioned below, and basically are ways for DNA to be incorporated into plasmids and chromosomes.",
"Now for your last word of your question - randomly. There are, unfortunately, different degrees of \"randomness\" associated with genetic shuffling. For example, in homologous recombination / chromosomal crossover, the \"random\" would refer to ",
" and ",
" the chromosomal crossovers occur. While the exact location and frequency of crossover is relatively random (which is good, since this leads to evolutionary diversity), as soon as a chromosome begins the process of crossing over, however, there's only one place it can go: to a homologous chromosome.",
"As far as transposable elements are concerned, these are much more random in terms of where they'll insert into the genome, and while many people believe they ",
" insert into \"junk\" DNA known as introns, this isn't quite the case. They most likely ",
" insert everywhere into the genome, it's just that the only cells that ",
" this genetic scrambling are those who carry transposable elements not inserted into essential genes. These transposable elements are useful tools in molecular biology for random mutagenesis of host genomes for knock-out and gene deletion studies."
] |
[
"Well, it's 'random' and it isn't. There is a random shuffle between chromosomes, and also somewhat with chromosomes during crossovers. But, depending how close certain gene loci are together, they will more often be associated with each other. and genes on a certain chromosome, will nearly always (barring weird reciprocal translocations) be on the same chromosome. "
] |
[
"Well, it's 'random' and it isn't. There is a random shuffle between chromosomes, and also somewhat with chromosomes during crossovers. But, depending how close certain gene loci are together, they will more often be associated with each other. and genes on a certain chromosome, will nearly always (barring weird reciprocal translocations) be on the same chromosome. "
] |
[
"How far can a smell travel? Are there ways to figure out where a smell will/is going? Do different odors travel farther?"
] |
[
false
] |
[deleted]
|
[
"The inner workings and sensitivity of the olfactory system are beyond me, but \"smells\" and how they travel basically works as follows:",
"Odor compounds are given off by something - bottle of perfume, skunk, rosemary chicken cooking in the oven. What you're smelling are various molecules that your olfactory system picks up as having an odor. (That's a biology question and I'm an engineer.)",
"At the micro-scale, those molecules are randomly whizzing around, bumping into other molecules, via a process known as Brownian Diffusion. It's all random. However, because there is a large quantity of odiforous compounds near the source, when they randomly move, the macro-scale result is that the smell emanates outward from the source, ideally in a spherical direction. This diffusion will be constrained by the geometry of the system (perfume has to escape through the neck of the bottle, skunk spray tends to diffuse upward/outward and not so much into the ground.) This will be proportional to the initial concentration (the greater mass of odor compound at the source, the greater concentration you'll see with distance) and temperature (at higher temperature, molecules in the gas have more energy and whiz around further/faster), and inversely related to the size/mass of the compound (smaller molecules travel further/faster than heavier ones).",
"Layered on top of this process is going to be the bulk movement and turbulence in the atmosphere. A person walking through a room, past an open bottle of perfume, is going to create turbulence that will allow the perfume to travel faster than it would normally by diffusion alone. If the wind is blowing west, the smell goes west. The whole process is termed dispersion there are lots of models for how pollutants in the atmosphere disperse based upon microscale diffusion and macro-scale advection. The ",
"wikipedia article on air pollutant modeling",
" shows a classic picture of how pollutants (which smells can be certainly classified as) disperse.",
"How far a smell can travel is tricky. Certainly odiferous molecules can travel very far. However, for your nose to detect them, there is a threshold concentration below which they no longer smell. (Some compounds stop smelling above a certain concentration; essentially overwhelming your nose. A good example is hydrogen sulfide.) So as the smell is spreading outward, blowing down wind, the concentration is slowly decreasing and at some point, undetectable by your nose.",
"The smell is smoke is going to be incomplete products of combustion (assuming the smoke is from a fire, rather than some chemical smoke grenade). The actual smoke is soot and vaporous by-products.",
"Smells stick to people via sorption. The surface - your skin, hair, woolen sweater - interacts with the odiferous molecule through some sort of physicochemical means - hydrogen bonding, van der Waals interaction, etc. - and temporarily forms a bond with the molecule. Your hair and clothes tend to smell much more than skin does, because there's a lot more surface area to volume in your clothing and hair than your skin (also clothing and hair is permeable, air can flow easily through it, whereas skin really isn't), so as the smoke from the fire blows past you, it blows past and through a lot of hair/clothing surface area and has a lot of opportunities to stick.",
"As \"smell\" really is your nose picking up chemicals in the air, and the chemicals in the air are randomly whizzing around there physically aren't layers to a smell, just different concentrations that your nose picks up on with different degrees of sensitivity. One caveat, is that molecules that are heavier than air will tend to sink over time and accumulate near the ground, while molecules that are lighter than air will rise (lighter can also be due to density differences - smoke from a fire tends to rise at least until is cools and then would fall.)",
"Again, this is all from the perspective of an environmental engineer, and how a generic chemical would travel through the air."
] |
[
"Also, does odor displace air, or does it infect it and change it? How does it spread on the molecular level? "
] |
[
"A smell can travel at least several kilometers. Look up \"The Tacoma aroma\"."
] |
[
"If a 9 hours sleeper sleeps 7 hours a night, are the effect the same as when a 8 hour sleeper gets 6 hours?"
] |
[
false
] | null |
[
"When it comes to sleep, \"we don't really know\" is usually the best answer.",
"It was only recently that it was discovered that our bodies clean the fluid around our brain during sleep. This may or may not be the primary reason for sleep.",
"In terms of time, we don't really know. Because we don't know what drives sleep we can't control the variables. Without controlling those variables an experiment of two identical 9 hour sleepers, having them sleep 7 hours, the result between the two would likely be different."
] |
[
"Thought sounds pretty interesting. Can you dig up a source for the fluid-cleaning during sleep? I'd love to read more about that."
] |
[
"I actually worked on a study relevant to this! The project itself studied the effects of minor sleep loss (3 hours per night for a week) on speech processing in adults, using EEG event related potentials to speech sounds. The analysis mainly showed that speech processing under minor sleep deprivation involved an increased activation of the prefrontal cortex. However, during the analysis I also took a look at whether or not baseline sleep affected the results. I don't recall which post-hoc test I used, or the exact p value, but the relationship was not statistically significant, p lying well above .05.",
"Conclusion: No statistical difference in prefrontal cortex activity evoked by speech sounds between subjects varying in baseline sleep. Put simply, at least in this specific scenario, the effects of a 9 hour sleeper losing (in the studies case three) hours of sleep is not statistically different from an 8 hour sleeper losing the same amount."
] |
[
"Has a virus ever been cured with medication? If no, why not?"
] |
[
false
] |
[deleted]
|
[
"-- Are immunizations possible for bacterial infections? If no, why not?",
"Yes, the anthrax vaccine for example.",
"-- Why are bacterial infections curable with medication, and virus infections not curable, or more difficult to treat?",
"Bacteria are sperate organisms with their own metabolisms and their cells are very different than ours. Antibiotics work by targeting metabolic pathways that aren't present or are very different than human ones.",
"Viruses work by taking over your cells to create more viruses. creating antivirals is difficult because you have to find something that will stop the virus from replicating, but wont poison you."
] |
[
"this would be depending on what you consider acceptable as \"cure\"",
"There is quite the assortment of antiviral drugs out there.",
"One of the most commonly known ones (thanks birdflu) would be Oseltamivir or more commonly known as Tamiflu. (on a side note H1N1 seems to be resistant against it by know).",
"its used in the treatment for influenza A & B its not super effective but it seems to cut down the avg. healing time by about a day.",
"I'm just gonna link the Wikipedia page for ",
"Antiviral Drugs",
" here",
"list several actual drugs and also gives an entry level of info on why antiviral drugs are so hard to come by.",
"The shortest answer is given by Wiki in the first paragraph as to \"why not\" : \"Unlike most antibiotics, antiviral drugs do not destroy their target pathogen; instead they inhibit their development.\"",
"as to vaccines for bacteria, take your pick you probably have had a couple of these depending on where you're from and if you got all your shots etc.",
"a couple Bacteria that can be vaccinated against:",
"Tuberculosis; Diphtheria; Tetanus; Pertussis (whooping cough); Haemophilus influenzae A & B; Cholera (though thats a bit hit & miss the currently available one is about 50:50); Typhoid",
"The WHO suggests that you should be vaccinated against: diphtheria, tetanus, pertussis, hepatitis B (virus) and Hib"
] |
[
"Thanks!"
] |
[
"About Einstein-Rosen-Bridges and thermodynamics..."
] |
[
false
] |
I read an article about in which was stated, that a "white hole" can seemingly "ignore" the laws of thermodynamics. How is that possible I always thought, laws of physics have to be universial, which ultimately is a criterion to be a law of physics. Does anyone have any explanation for this?
|
[
"One of the main problems in theoretical physics in the 1970s was the black hole entropy problem, where black holes would seemingly violate the second law of thermodynamics if they had no entropy. To solve this problem, Hawking and Bekenstein conjectured that black hole entropy was proportional to the surface area of their event horizons. However, this would put black holes at an entropically maximized state; they have the highest entropy that can be put in a fixed volume. Hence, the falling of an object into a black hole would no longer violate the Second Law of Thermodynamics. However, if a white hole is a black hole working in reverse; hence it would always violate the second law of thermodynamics by decreasing universal entropy.",
"There are a couple of solutions to this potential problem; the first is that white holes may actually be even theoretically impossible due to thermodynamics. The second, put forth by Hawking, was that because a black hole emits thermal radiation (Hawking radiation), it can be in thermal equilibrium with a gas - thus, its time reversal must be itself since a equilibrium is T-symmetric. Thus, Hawking radiation from a black hole would be white hole emission. ",
"Complicating all of this is the potentiality that the Second Law of Thermodynamics is only a statistical law, not a real law of nature. Recently, there have been papers published that have indicated that the Second Law of Thermodynamics can be violated on short timescales:",
"http://prl.aps.org/abstract/PRL/v89/i5/e050601",
"Lastly, the article mentions that a white hole could be a perpetual motion machine of the second kind; this is one that converts all of the heat obtained from a reservoir into useful work, violating the second law of thermodynamics."
] |
[
"Thank you for that detailed answer could you specify what ",
"a perpetual motion machine of the second kind",
"means?"
] |
[
"It is a machine that would be able to take in heat and convert it all to work, thus violating the second law. For example. it would be able to take in steam at 500 K, then release it at 0 K after extracting all heat from it to do useful work. This is impossible."
] |
[
"Correlation between countries age gap indicative of Prosperity?"
] |
[
false
] |
Countries that have a higher median age tend to prosper more than countries that have a lower median age.
|
[
"Two things I'd consider is that as education improves people tend to have fewer babies and they have them later. This effects the median age. Also developed nations tend to have longer life expectancies also effecting the age distribution."
] |
[
"An interesting idea, but I believe your premise to be flawed. I'll present several cases at the end to show that there is a not a substantial correlation between age and GDP. As you will be able to see, there are a great many other factors which determine a state's economy (area of country, size of workforce, industrialization, primary industries, history, etc). Here are the figures; especially note places like India, where the median age is only 26 but the GDP is approaching two trillion dollars, while the GDP of Slovakia is only around one hundred billion with a median age is over 35."
] |
[
"Correlation vs. Causation. It's the bane of every stats and econ major. Combine them, and you get econometrics!",
"In actuality, this is how economists measure things. Regression analysis gives you hard data on whether certain variables are correlated.(assuming you set up the regression correctly with good data.)",
"So! Here's what you do. Go buy a copy of stata. Read the instructions. And input your data!",
"And then see if you get any statistically significant results.",
"But if I had to take a guess (and this is really naughty of me ... this is how you get into all sorts of trouble) I'd say that the causation is that developed countries have more political stability and have invested more in healthcare than non-developed countries. And better education.",
"So if I had to choose, I'd say Higher GDP/capita => Higher media age. And that's just a correlation at best. The causality of all the data is too much to make such a sweeping statement.",
"I can already think of a ton of reasons why this hypothesis is so short sighted..."
] |
[
"How are Carbon Nanotubes made into useful things?"
] |
[
false
] |
So from my understanding carbon nanotubes look like a black powder to the naked eye. How is this turned into string, or rope. How would this be made into a surface like the body of some future car. I don't understand how these microscopic tubes in powder form are made into anything at all. By the way I watched this: Which explained how the powder itself is made pretty well but not how it is made into an end product.
|
[
"In a lot of cases they're added to traditional carbon fiber composites, such as ",
"this",
" bike frame. "
] |
[
"I'd take that application with a grain of salt. To get the strength-to-weight ratio they cite in comparison to normal carbon fiber you'd need continuous carbon nanotubes acting like the continuous fibers of typical carbon fiber. It's an apples to oranges comparison. Carbon nanotubes right now are similar to composite 'whisker' which is used as a high strength, low weight filler material similar to glass microbeads.",
"There's been some research into aligning these 'whiskers' so they act more like continuous fibers that have made some improvements but to my knowledge it's still being studied academically -- not something I expect to see in production. And ",
"This image of theirs",
" makes it looks like they're just mixing the whiskers in with the resin. This cuts down on weight and improves stiffness but shouldn't be expected to improve strength appreciably. The conventional carbon fiber is still the load-bearing mechanism."
] |
[
"Caveat: I'm not a materials expert and not necessarily up to date on the latest in carbon nanotubes. Materials to me are only as good as they are macroscopically useful.",
"How is this turned into string, or rope.",
"Currently, it isn't. At least the last time I read up on what's been going on with carbon nanotubes. The holy grail of nanotubes is a process by which you could grow long strands of the stuff -- like long enough that you could see the length with the naked eye. Because then you could reap some major theoretical benefits. ",
"They're being used (I'm honestly uncertain to how much benefit) as a filler material. This has been common practice for some time with glass microbeads. We have some of this stuff in bags in the lab I work in. The 'beads' are so small that all together the material looks like a white liquid. You can slosh it around in the bag. It's extremely stiff and worth mixing into resins if you need some additional stiffness and need to lose some weight due to resin. ",
"Generally, however, adding these sorts of filler materials tends to increase stiffness but also make the resin more brittle which can reduce damage tolerance and thus fatigue life. "
] |
[
"Is it possible to develop a biological tolerance to allergens via medicine and/or continuous exposure?"
] |
[
false
] |
Also, is it possible to become immune to certain allergens as a result of this?
|
[
"It is also possible to become more allergic to something after repeated exposure. In the medical field, this often happens with latex gloves."
] |
[
"Short and sweet: Yes, but not always. Works for some and not others."
] |
[
"Not necessarily, I don't think there's a ",
" hereditary component to allergies, most of it is environmental and dependent on habits though we still don't have a full understanding of what these cues are.."
] |
[
"Why do pipes sometimes \"resonate\" and create a loud hum when I turn on the faucet a certain way?"
] |
[
false
] |
I can't really think of any mechanism that would cause this, but fluid dynamics are not my strong point.
|
[
"A direct application of my thesis work?",
"I'm going to have to email this thread to my mom who can never understand what I do.",
"Anyway....",
"When water forms a free surface, waves form on the surface due to a combination of ",
"Rayleigh instabilities",
" and ",
"Helmholtz instabilities",
" (depending on the speed of the fluid). These instabilities ultimately cause the fluid cylinder to break up into droplets.",
"However, since every action has an equal but opposite reaction, these instabilities do not only act downstream of the fluid (away from the faucet), but also toward the faucet. A series of compression waves comes back to the faucet and causes it to vibrate.",
"Normally a facet is well attached to the sink and these vibrations are dissipated without any further effect. However, if the faucet is loose, the facet can transmit these vibrations to the pipes. If the frequency happens to be a resonant frequency for the length and rigidity of pipe, the vibrations build up in magnitude to create the effect you describe. This is why it only happens when the faucet is open a certain amount - you have to find that resonant frequency."
] |
[
"Fascinating! Thank you. :)"
] |
[
"Possibly - if it does it when the valve is just cracked it's probably the water slugging. Basically the pressure builds up, a slug of fluid shoots out, the pressure drops and the valve slams shut, then the cycle repeats itself over and over. "
] |
[
"Why does coming into contact with a dangerous substance like di-methyl-mercury kill you?"
] |
[
false
] | null |
[
"Elemental mercury is toxic but what makes mercury compounds such as dimethlymercury so toxic is that it can easily pass through latex or pvc gloves and the human skin. Once it finds its way into the body it will pass the blood-brain barrier. It's not sure how this happens but its presumed because it forms a complex with the amino acid cysteine.",
"Inside the brain is where the dimethylmercury does the damage. It's a neurotoxin so it intervenes with the exchange of neurotransmitters between synapses of neurons. This means that a lot of impuls exchanges to neurons of muscles get disturbed. The human body can actually break these compounds down but this happens very slowly so the mercury can accumulate very easily. It doesn't help either that a small dose of dimethylmercury like 0,1 mL is lethal.",
"The chemical side of this all is a treatment for mercury poisoning. Chelation therapy is used for poisoning of heavy metal like mercury. The patient is treated with EDTA (ethlyene diamine tetra-acetetic acid). This compounds forms a complex with the mercury compounds. The complex itself is harmless and leaves the body through the urinary tract.",
"A very interesting yet tragic case to show how dangerous dimethylmercury is, is the death of professor Karen Wetterhahn. She spilled a drop of dimethylmercury on her latex gloves, that found its way into her body. Half a year later she was brain dead due to the damage the compound caused to her nervous system."
] |
[
"It varies from chemical to chemical. Methyl mercury kills partly because it's fat soluble so it can cross into the brain tissue and cause symptoms akin to cerebral palsy. That's not the only effect. Other poisons may affect transmission of nerve signals, prevent oxygen transport to cells or cause paralysis."
] |
[
"Would chelation work when the mercury has already penetrated the blood brain barrier?"
] |
[
"How exactly is the second based on the hyperfine structure of the Caesium atom?"
] |
[
false
] |
I know its based on the electromagnetic transitions in its hyperfine structure, but I have no idea what that means. I've clicked through the different wiki article explaining both, and I just can't quite model it out in my head. Any help would be appreciated! I would also have to think it would be possible to base our second on something else (a comparable vibration/transition of the Hydrogen atom maybe?), and I don't know why we wouldn't outside of it being impractical or incompatible with our current conception of the traditional second. Not sure about any of that, but intensely interested in any responses.
|
[
"Hyperfine structure is really simple to understand. You have a nucleus, which has charge and spin. It therefore acts like a little bar magnet aligned along the spin axis. Similarly, the electron has a charge and spin. It also then has a magnetic field. These two magnetic dipole moments are in a lower energy state when the two spins are anti-aligned rather than aligned, just like two bar magnets will stick together one way but repel the other way.",
"To define the second based on this standard, you say \"the second is the length of time corresponding to X periods of the radiation from this transition\". You then implement this definition by measuring the frequency of the transition very very precisely. When the second is properly calibrated in whatever timing divice is involved in your frequency measurement, 1 second/X = f. If you get too large or two small an answer you adjust the calibration accordingly.",
"I would also have to think it would be possible to base our second on something else (a comparable vibration/transition of the Hydrogen atom maybe?)",
"Sure. It just turns out that this particular hyperfine splitting in Cs is in the microwave (wavelength ~ 3cm) which makes it really good to work with in human scale experiments. It's also easier to find, trap and cool than hydrogen. It's just a choice of convenience really."
] |
[
"Hey there, I worked for NIST for a while (though not in the Time and Frequency division). They're the people that build and maintain the standard atomic clock(s).",
"It's just a choice of convenience really.",
"It's more than ",
" convenience. You can define the second in a ton of different ways. All you need is some kind of repetitive event (let's call it Event X). Then every time the event happens, you say, \"ok, Event X just happened, that means Time Unit Y has passed.\" The more frequently Event X happens, the shorter time periods you can measure. You also want the time intervals between the events to be as similar to eachother as possible. That's called the precision of the clock. So ideally, you want a very fast and very precise clock. For example, the time between different waves hitting the beach is periodic, but it's not very precise. And further, the time it takes the moon to go from new to full and back is very precise, but not very fast. So neither of those are good choices. Note that if you're trying to synchronize events that happen more frequently than Event X, you are basically screwed until you can figure out a faster clock (maybe you don't need it to be as precise).",
"For a long time, we used pendulums swinging back and forth, then gears and springs, then quartz crystals, then cesium atoms. The different sources of noise in each system (i.e. fluctuations in the signal that are beyond our control) limit the precision. It just so happens that the cesium clock is insanely precise (to within one second in a billion years or something) while also being very fast, on human time scales (billions of cycles per second). There are rubidium clocks the size of a grain of rice that are ",
" this good, and there is active research into getting even ",
" precision from other elements.",
"Hopefully that answers the more philosophical part of your question. The technical stuff about quantum mechanics is beyond me."
] |
[
"The frequency of the photon it emits is how many times it oscillates per unit time. If you define that unit time as ~1/86400 of Earth's rotation, then the frequency is 9.2 billion whatever times per second. If you make the second longer then the frequency is higher.",
"Given that a Hz is 1 per second, you can say \"how long should we make the second so that this transition has a frequency of 9.2GHz?\""
] |
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