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[
"So I just won ten dollars on a Reddit contest, which science charity should they send it to?"
] |
[
false
] |
I'm only eighteen, and I don't work, so I don't have a Paypal for the guy to give me my reward, so I'll ask him to donate it in my name. Any suggestions for a scientific-research charity?
|
[
"Second prize in a beauty contest?"
] |
[
"I second this fund. Someone gifted me a donation in my name. Apparently they do some great things."
] |
[
"I second this fund. Someone gifted me a donation in my name. Apparently they do some great things."
] |
[
"Why do all organisms want to pass on their genes?"
] |
[
false
] |
We know that the goal of an organism's life is to procreate and pass on their genes to their offspring to increase fitness, but is there a physical explanation as to why organisms feel the need to? (Sorry if this is horribly worded.)
|
[
"Because organisms that don't want to pass on their genes would die out. If all humans suddenly lost the urge to procreate, humanity would be gone in a century. Naturally, it's the surviving organisms that want to pass on their genes that pass on their genes."
] |
[
"Just like mutations that aid in survival become dominant in a population, so do mutations that promote reproduction (because those that reproduce and pass down genes, produce the next generation). If an organism didn't feel the need to pass down their genes, their genetic makeup would end with that generation. "
] |
[
"That actually makes more sense now. Thanks!"
] |
[
"Why do some vaccine injections cause more muscle soreness?"
] |
[
false
] |
In my personal experience, it seems that some shots make me more sore than others. For instance, I recently got my third Gardasil shot two days ago and my arm is still too sore to sleep on. In comparison, I've never felt discomfort after an annual flu shot. In general, why does this happen? I know that variables such as needle gauge, amount of vaccine fluid, muscle tenseness vs. relaxation, injection site, and intramuscular vs. subcutaneous shots play a role -- but how much? Is there something inherent in certain vaccines that makes them more likely to cause muscle soreness than others?
|
[
"This response is a little scattered with correct and incorrect bits weaved together. It's a little hard to break out so I will just try to be general:",
"Inflammation is a mechanism the immune system uses to attempt to ramp up a response to an infection/vaccination as well as attempt to directly clear the infection",
"Inflammation after vaccination can be due to a number of variables, including the formulation of the vaccine and the patient's own immune system. Unfortunately it's not quite as cut-and-dry as \"youve seen the virus before so you get inflammation\". Inflammation occurs regardless of past infections/vaccinations. The DEGREE to which that inflammation occurs may be shaped by the presence of a pre-existing immune response, which I ",
" is what you were getting at but didn't quite have it 100% correct"
] |
[
"Is there something inherent in certain vaccines that makes them more likely to cause muscle soreness than others?",
"Okay so this is the \"key question\" so I'd like to try to focus on addressing this. The short answer is \"yes\" but really, it's far more complicated than a simple yes or no. Inflammation from vaccination can occur to varying degrees for a number of reasons, some of which I will try to get at below:",
"Formulations/Adjuvants - many vaccines include a component known as an adjuvant. An adjuvant in this case (as opposed to the definition of adjuvant as used in cancer therapy) is a compound that serves as a general immune activator. It aids in alerting your immune system to the presence of a foreign protein in your body (in this case the vaccine components) and in doing so it provokes an inflammatory response as inflammation is a major mechanism by which your immune system responds to infection/vaccination. Variations on the type and amount of adjuvant used in a vaccine can influence how much inflammation you notice",
"Pre existing immune responses - as rocmanik mentioned, a pre-existing immune response to the vaccine may also influence the amount of inflammation you feel. for example, if you were ill with Influenza within the last few months and got vaccinated with a Flu vaccine containing the same strain of virus, it is theoretically possible that you would still be generating a strong enough antibody response to clear the vaccine components before your innate immune system was able to generate a significant amount of inflammation. conversely, you could also have a pre-existing response to a vaccine component that could strengthen the inflammatory response to vaccination. so pre-existing responses can actually skew things in either directions, depending on what type of response you have",
"route of administration - intramuscular injections are frequently much larger in volume that intradermal vaccinations. this, coupled with the fact that their administration requires you to penetrate through multiple layers of tissue generally means that intramuscular injections are more painful",
"In your particular case, if I had to take a wild guess (and I do stress the word wild as I have no information on your or your medical history) I would say that the difference you feel in the inflammatory response with the HPV vaccine as opposed to the Influenza vaccine is due in part to the fact that an adjuvant is used for the HPV vaccine but not in the Seasonal Influenza vaccine (in the United States)."
] |
[
"Correct me if I'm wrong but have you ever been sore after getting sick with something like the flu virus? I'm sure the soreness is your immune system inflaming to attack the vaccine. Inflammation causes lots of damage simply due to how it works inside of us. And so people with hyperactive immune systems asthma/allergies are more prone to reacting a little more... Lets say violently towards vaccines sometimes."
] |
[
"Is there any scientific explanation for Déjà vu?"
] |
[
false
] |
Is Déjà vu a chemical reaction in the brain or somehow related to foresight? I ask because I just had an intense bout of it where I was almost certain the same situation had happened previously.
|
[
"I don't think we know, but Daniel Dennett has ",
"a theory",
"."
] |
[
"This question comes up all the time. ",
"Previous threads here",
"."
] |
[
"Confirmation bias. 99% of the time, your dreams don't correlate with any later events, but the 1% of the time that they do, some people assume it's a \"vision\" or \"prediction\" of the future. ",
"In reality, it's just your brain recognising only the dreams that do later have some alignment with what eventually happens."
] |
[
"Why do we feel more 'emotional' when we are inebriated?"
] |
[
false
] | null |
[
"Alcohol impairs activity in the frontal lobe, which is responsible for higher order thinking such as judgment, reasoning, and sociality. Situations that seemed adverse before may no longer appear so, inhibitions are lowered, and the fine-tuned social and emotional cognition we possess becomes less fine-tuned."
] |
[
"Yes and no. It will take away inhibitions. The part that tells you \"don't do that.\" or \"It is a bad idea to call your ex and tell her that you want her back.\" It isn't to say that it changes you as a person, but it can affect your view on what are acceptable and non acceptable actions.",
"I have heard people say such things as, \"People are most honest when they are drunk.\" And I don't believe that to be completely true. On the surface, it might seem that way. But there are PLENTY of thoughts people have that really have no validity once run through the ol' prefrontal cortex which decides if it will be a problem or not. For a morbid example, on suicide assessments if somebody is under the influence of drugs or alcohol that is a big red flag for increased suicide potential, the reason is that with decreased inhibition they might choose to make a decision that if they thought about would decide against.",
"Another reason why it can make you \"moody\" is that alcohol is a central nervous system (CNS) depressant. It DEPRESSES functioning (hence the lowering of inhibitions) and eventually it will depress (stop) functioning of breathing and other important life sustaining systems. Any depressant can have the effect of also lowering mood even further.",
"Hope that helped some."
] |
[
"Very helpful thanks! I actually never thought of the fact that alcohol is a CNS depressant. We are actually busy with the CNS right now in my bio class and specifically neuron firing and the effects of drugs so that's a neat bit more insight that I have there."
] |
[
"How do people get brain tumors if brain cells aren't actively dividing?"
] |
[
false
] |
From my understanding of biology, don't cells become cancerous after a mutation during mitosis? Why then do people get brain tumors if brain cells aren't actively going through mitosis?
|
[
"Brain tumors are generally caused by the small number of dividing cells in the brain -- the most common type of brain tumor is a ",
"glioma",
", which is a tumor derived from glial cells. Unlike neurons, glial cells keep dividing throughout life."
] |
[
"While neurons them selves no longer divide, your brain is composed of multiple other cell types that DO still divide. The cell of interest for most tumors is the Glial cell which is sort of a support cell for neurons. It does things like take up excess neurotransmitter that is released by neurons, keep local pH at acceptable levels, keep salt concentrations at acceptable levels, etc. This cell is not responsible for \"thinking\" so we don't consider it a neuron. ",
"One of the reasons these Glial cells still divide is to make sure that an injury doesn't lead to structural weakness in the brain. For example, let's say someone who isn't wearing a helmet falls of their bike and hits their head hard on the pavement. They hit it so hard that they kill off a bunch of neurons in their right temporal lobe. Well, those neurons that died are eventually going to get cleaned up by macrophage-like cells in the brain, leaving a big void of nothingness, which is fine, except the soft brain would then cave in on itself. Instead, the Glial cells in the area start dividing and fill this void to ensure that the integrity of the brain is retained and there is a place for new axons to form into (and through) in the future. ",
"So it's important that Glial cells are able to divide, but this also means that they are susceptible to malfunctioning in their genetic machinery. Some of these malfunctions can, and do, lead to unchecked cell division--and hence, a tumor."
] |
[
"Does \"glial cell\" refer to a particular cell type, or can it be applied to different kinds of non-neuron brain cells?"
] |
[
"How can we know what the composition of the Earth's core is?"
] |
[
false
] |
I am curios as to how we can define and to what degree of certainty do we know what the elements that compose the Earth's core are.
|
[
"We know the overall density of the Earth because we can observe how it interacts with other bodies (specifically, the Moon). We also know the size of Earth, so we can find it's mean density.",
"The density of samples of the crust and mantle can be measured.",
"By observing how seismic waves behave, we can determine the size of the core, and from the above information, this gives the mean density of the core. The presence of a strong magnetic field suggests it's mostly iron, and we also know iron is very abundant on Earth, and is one of the more abundant heavy elements in our solar system, so iron is a likely candidate. We've found many meteorites composed mostly of an iron-nickel alloy, and since their beginnings are linked to those of Earth, we can infer that Earth's core is likely primarily composed of the same alloy.",
"We can't be 100% certain with the data that we have, especially regarding the exact concentrations of impurities of gold, platinum, etc., but it's highly unlikely that the primary composition we've assumed is incorrect."
] |
[
"Check out this link:",
"http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/waves_and_interior.html",
"About 3/4 down, at P-Waves in Earth, it starts explaining the geometry of how \"shadows\" in P-waves and S-waves and the wavefront velocities reveal the locations of boundaries.",
"TL;DR: Because fluids don't transmit shear waves, we know the outer core is a liquid, and by measuring the speeds and observing zones of no seismic data, we can determine the radii of each layer."
] |
[
"Very interesting.",
"By observing how seismic waves behave, we can determine the size of the core",
"Can you provide more details about this?"
] |
[
"Has the invention of the light bulb lead to any measurable evolutionary changes among moths or other night light-obsessed insects?"
] |
[
false
] |
Full disclosure this was inspired by
|
[
"There does indeed seem to be some research to support this idea! ",
"Altermatt and Ebert 2016",
" conducted a study on ",
"spindle ermine moths",
" to address the question of how light pollution has affected insects. They collected larvae from 10 regions with either high or low light pollution, and raised them all in a common lab environment (so that any differences in behaviour would be more likely to be a result of genetics rather than habituation during their upbringing). And when exposed to lights as adults, the researchers clearly found that moths from darker regions were ",
"more likely to be attracted to lights",
" than those from places with higher light pollution. Though this isn't 100% conclusive, it's reasonably good evidence that there may be selection acting to reduce the strength of phototaxic behaviour in urban moth populations. Also, if you're just generally interested in the impact of light pollution on insects, check out this review paper by ",
"Owens and Lewis 2018",
", though it's more about the effects of artificial light than evolutionary responses to it."
] |
[
"Fair question! The most commonly given explanation I've seen is that moths use celestial objects (such as the moon) as landmarks for navigational purposes, and get confused since artificial lights can easily be as bright or brighter. This reasoning seems to be favoured by Mike Saunders at Penn State (",
"source",
"), who also mentions that this explains why moths tend to circle lights rather than directly fly into them (which seems reasonably sensible, since presumably they are trying to navigate by keeping the normally \"stationary\" moon at a fixed angle). There has been some research which backs this up, such as ",
"Sotthbandhu and Baker 1979",
" and also (the same) ",
"Baker 1987",
", which demonstrated that at least some moths are sensitive to magnetic fields in addition to using visual navigation. For a slightly more recent and broad synthesis of this topic, ",
"Warrant and Dacke 2016",
" looks pretty good too."
] |
[
"What’s the benefit in moths being attracted to light, pre electricity?"
] |
[
"What is the difference between hydrogen and anti hydrogen?"
] |
[
false
] |
How do they vary chemically? Can I drink anti water without it affecting me?
|
[
"Anti-hydrogen is made of an anti-proton and a positron instead of a proton and an electron. If you drank anti-water it would annihilate with the regular matter in your face and, as Randall Monroe puts it \"you would obviously die pretty quickly. You wouldn't really die of anything, in the traditional sense. You would just stop being biology and start being physics.\""
] |
[
"In your mouth"
] |
[
"Using E=mc",
" we get 1.8*10",
" joules for 1g of antimatter annihilating with 1g of matter. That's about 43 kilo tons tnt equivalent."
] |
[
"What are the low level computational operations necessary to perform 1 + 1, or other whole number additions?"
] |
[
false
] |
Assuming you have as much memory space as you need, what does the series of steps boil down to logically to perform this operation on a theoretical computer? I'm guessing there are many ways to do this, but is there a method with the provably least amount of steps that is also capable of arbitrary whole number addition?
|
[
"Whole number addition in computers is taken care of by a circuit known as an ",
"Adder",
". Adders are relatively simple, and come in two types: a half adder, and a full adder.",
"Let's start with a half-adder. The form with the fewest number of logic gates is:",
"S = A ⊕ B\nC = A ∧ B\n",
"This half adder takes two bits as input (A, B), and outputs two bits (S, C), the Sum and Carry values. A truth table for the half adder looks like this:",
"This is equivalent to:",
"0 + 0 = 0\n0 + 1 = 1\n1 + 0 = 0\n1 + 1 = 0 (carry 1)\n",
"A full adder extends the half adder by taking three input values (A, B, Cin), and outputs two values (S, Cout). You can construct one by putting together two half-adders. Algebraically, the full adder can be defined as:",
"S = A ⊕ B ⊕ Cin\nCout = (A ∧ B) + (Cin ∧ (A ⊕ B))\n",
"The truth table for a full adder looks like this:",
"What is the point of a full adder? A full adder taels two values to be added, along with a carry from a previous addition, and outputs a sum bit and a carry bit. Because it takes a carry bit as input (Cin), you can chain a bunch of Full-Adders together to create a multi-bit adder.",
"The (conceptually) simplest version of this is a ",
". This is simply taking a half adder, and then chaining a bunch of full adders to it such that Cout from the previous adder is sent to Cin of the next adder. For a two bit adder",
" it would look something like this:",
"S0 = A0 ⊕ B0\nC0out = A0 ∧ B0\nS1 = A1 ⊕ B1 ⊕ C0out\nC1out = (A1 ∧ B1) + (C0out ∧ (A1 ⊕ B1))\n",
"Here is the truth table (leaving out intermediate results):",
"The above being the equivalent to:",
"0 + 0 = 0\n0 + 1 = 1\n0 + 2 = 2\n0 + 3 = 3\n1 + 0 = 1\n1 + 1 = 2\n1 + 2 = 3\n1 + 3 = 0 (carry 1)\n2 + 0 = 2\n2 + 1 = 3\n2 + 2 = 0 (carry 1)\n2 + 3 = 1 (carry 1)\n3 + 0 = 3\n3 + 1 = 0 (carry 1)\n3 + 2 = 1 (carry 1)\n3 + 3 = 2 (carry 1)\n",
"You can treat the carry bit as a third bit position for the response, in which case anywhere you \"carry 1\" above, you can simply add 4 to get the correct expected value (thus ``2 + 3 = 1 (carry 1) = 5).",
"You can chain as many full adders together as you'd like -- every additional full adder added to the ripple-carry adder doubles the total number of values it can add (an n-bit adder can thus add 2",
" values together).",
"You may find this site very educational",
" -- it allows you to build a half adder and then a full adder using only NAND gates, right in your browser. You can also go much further, towards building an entire CPU using only NAND gates as the basis.",
"I hope this answers your question!",
" -- We can extend this to any number of bits we want, however just going to 3 bits requires a truth table with 64 rows, which is getting a bit big for this post.",
"\n",
" -- Sorry this is a bit ugly looking; Reddit doesn't support subscripts."
] |
[
"To tack on a bit (no pun intended). This is implented in hardware in the processor with a subsystem called an Arithmetic Logic Unit (ALU). ",
"What I mean by that is an N bit adder is implemented by building N full adder stages where the Nth stage is fed by the output bit and carry bit of the N-1th stage, which allows an addition to be performed in a single processor cycle. This is done with individual logic gates built out of NAND logic (as OP described in their link) which uses individual transistors to do so. ",
"When the carry bit of the final stage is 1 it indicates that an overflow has occurred, and the ALU sets its \"status\" register accordingly, alerting the program. In low level programs you can detect the overflow and trigger an error, but most of the time what occurs is called \"wrap around\" where the output is (a +b) mod 2",
" and the program ignores the error. ",
"What's really cool is that signed arithmetic (positive and negative numbers) is implemented with identical hardware, using what's called 2's complement representation of positive and negative numbers. "
] |
[
"It's pretty easy to prove that the half-adder is as efficient as it can possibly be. It's only two logic gates. To be any more efficient, you'd need to be able to do it in a single gate. We know all of the possible gates, so all it requires is seeing that none of them can generate the truth table for the two-gate half adder. I suspect the Full Adder is likewise as efficient as it can get -- here it's just a matter of seeing if you can minimize the algebraic equation that forms a full adder; I don't believe you can.",
"Things get more interesting when we start to chain the full-adders together, as there ",
" ways to improve the runtime efficiency. While ripple-carry adder I described is quite efficient in terms of number of gates, the process of adding an number needs to be clocked in a ripple-carry adder; you can't attempt to add digit k0/k1 until you've added the previous digits, as you need to know the carry. This is where the ",
" comes in -- you have to clock the addition so that you add the digits one at a time, generating the carry value before you can go on to the next digit.",
"There are improvements on this that make for more complex circuits, but more efficient (in terms of runtime). One such improvement is the ",
"Carry-lookahead Adder",
", which attempts to pre-determine whether a group of bit additions will emit a carry bit on the left-hand side. This is quite a bit more complex, but does allow for faster addition by correctly anticipating and propagating carries without having to compute all of the preceding sums in the full adders. This is much more complex than the ripple-carry adder (and I'll admit I don't really understand it myself; it's getting a bit outside my main areas of research and study); if you want the details, read the Wikipedia article linked above.",
"Are there more exotic methods for addition? Probably not for a ",
" computer. Analog computers have a very simple circuit to add two values based on their voltages, however the reason why we don't use these is because it gets very difficult and expensive to build high-speed hardware around analog values, particularly while maintaining high calculation accuracy. We can build digital circuits that are faster, cheaper, and more accurate, which is why most computers are digital, not analog.",
"There are also published algorithms for ",
"quantum addition",
", that are apparently very highly parallelizable. I'll admit here however that quantum computing is well outside my area of study; to date we've only dipped our collective toes into quantum computing, and I understand there are a variety of practical problems that still need to be resolved in order to build a quantum computer of any significant complexity -- if they can't quantum algorithms like his may never truly be practical. The jury is still out on that one."
] |
[
"Do car windscreens absorb a significant amount of UV radiation?"
] |
[
false
] |
[deleted]
|
[
"Side windows are usually plastic and will block UVA but not B.",
"In the US at least side windows are almost always tempered glass. The only exception I can think of is cars with a soft cloth top."
] |
[
"Side windows are usually plastic and will block UVA but not B.",
"In the US at least side windows are almost always tempered glass. The only exception I can think of is cars with a soft cloth top."
] |
[
"Car windshields are typically made from soda-lime based glass, with a plastic (",
"EVA",
", for example) intermediate layer. Soda-lime glass blocks a ",
"pretty good chunk",
" of the ultraviolet spectrum. However, as you can see, the absorption is not quite 100% - and it's a little bit more effective in the UV-B range than in the UV-A range. The intermediate layer of plastic happens to absorb more of the UV-A range, so windshields do a pretty good job with blocking UV. Side windows may not be quite as good.",
"That being said, as you can see from ",
"Figs. 6 and 7",
" and from ",
"this abstract",
", enough UV penetrates the glass so that prolonged exposure can result in a sunburn."
] |
[
"AskScience: Can anyone recommend an insightful intro to Quantum Physics book geared for a social scientist?"
] |
[
false
] |
Consider me fairly well rounded in statistics and methodology. Most of my work has been focused on cognitive correlates of interpersonal trauma. I'm trying to foster an interest in topics outside of my discipline. I feel sheepish to ask for a recommendation regarding the topic: I know a good deal of woo is produced when good intentioned social science people try integrating quantum physics into an explanation. Part of my inquiry here is that some of my colleagues tend to buy into the more Chopra-esque explanations of QP. I'm hoping for a good primer book to help direct them away from that (and to clear up some confusion for myself)
|
[
"What you want to do is find a book on 'Modern physics'. These will be largely devoted to introductory quantum mechanics, and probably only assume that you've had a basic mechanics and a basic E&M course."
] |
[
"E.g. Serway Moses and Moyer."
] |
[
"I really loved QED by Feynman and I'm not a physicist, though I love physics with a passion. The book is fantastic in that you need very little math to enjoy the story. And Feynman is world renowned for his story telling abilities."
] |
[
"Are all prime numbers smaller than the biggest prime number discovered?"
] |
[
false
] |
The record of the biggest prime number is for 2 and was discovered using GIMPS. I want to know if all the smaller prime numbers are discovered, or if are there missing numbers.
|
[
"There are definitely much smaller primes that we don't know about. The first \"gaps\" in our list of primes are ",
" smaller than that, and probably a lot smaller than you might guess. The reason for this is simple: there are just ",
" primes, it's impossible to list them all out.",
"Imagine you wanted to make a list of all primes up to N. ",
"The prime number theorem",
" says there should be about N/log(N) of these. If you were to store a list of these on a computer, each one would require about log_2(N) bits. Conveniently, that cancels out to say that ",
"That means that a list of all prime numbers with 80 digits or less would be about the size of the observable universe (and that's assuming that each \"bit\" is just a single atom). The number 2",
"-1 has over 22,000,000 digits, so we could never get even remotely close to listing out all prime numbers less than it.",
"So how big of a list could we possibly make? A decent order of magnitude estimate for the total number of bits in all computer hard drives in the world is 10",
" bits (i.e. about a ",
"Zettabyte",
"), which is hard upper bound for the largest prime for which we know all lesser primes. As most of humanity's storage space isn't being used to store primes, the largest complete list of primes we could possibly have come up with would be way lower than that. And that's just looking at what it would take to ",
" that list, not even how long it would take to actually calculate all those primes.",
"I don't know exactly when the first \"gap\" in our list of primes numbers is, but I'd be pretty surprised if it's is bigger than 10",
" (one quadrillion) or so, and it honestly could be a lot lower."
] |
[
"There are certainly smaller primes that have not been discovered. Mersenne Primes (the primes that GIMPS finds) are a very special case of primes that follow a specific rule (a factor of 2",
" -1) - but not all primes (big or small) follow this rule. ",
"There are known non-Mersenne Primes amongst the ten largest primes which are relatively ‘close’ in size to the largest known prime. "
] |
[
"You can store the primes much more efficiently. You don't have to store every single bit of its binary representation, it is sufficient to store e.g. the difference to the previous prime plus absolute numbers once in a while. And you don't have to store the last bit ever because it is always 1 (apart from the first prime).",
"Fair point, but this doesn't save as much as you might expect. There are still N/log(N) primes that you have to list, so even in the unrealistic best case scenario where you only need one bit per prime, that would only improve things by a factor of log(N). For N = 10",
", that's about 50. More realistically, I'd expect this to save you about an order of magnitude.",
"Primality checks for 22-digit numbers are done in something like a millisecond even for difficult numbers and on home computers, you could do tens of billions of them per computer per year, and even more on more powerful systems.",
"True, but the limiting factor here isn't the time to test each prime, it's the number of primes to test. There are about 2*10",
" primes less than 10",
". If you could test 10 billion (= 10",
") of them a year, it would take you 20 billion years to do all of them. This is also ignoring the time spend testing composite numbers, which would often be faster than testing prime numbers, but probably wouldn't be negligible.",
"Now, you could speed that up quite a bit by doing it on a super computer or using a bunch of computers, but almost certainly not by enough to make testing everything up to 10",
" feasible. (This is all under the assumption that we aren't devoting a significant fraction of humanity's total computing resources to this, as I'm trying to figure out what's likely to have actually been done.)",
"Also just to point this out, the best primality testing algorithms we have are actually ",
", in that they have a small chance of giving an incorrect result. That's fine for everyday life, but not if you want to make a list of all primes with 100% accuracy. Fortunately the ",
"BPSW test",
" is deterministic for numbers less than 2",
", so this probably wouldn't be an issue for the range of primes we care about here though.",
"I will concede that listing all of the primes up to a quadrillion might be a bit more feasible than I'd initially estimated. That's about 3*10",
" primes and a 100 terabyte file (which could probably be compressed to 10 Tb, by the method you describe), so it would probably take a significant amount of time on a super computer, but I could imagine that someone's done that. I could even believe someone's gone an order of magnitude or two farther, but that feels close to the practical limit.",
"I would be interested to know if someone actually knows what the record is. "
] |
[
"Which way should a fan face to get more fresh air into a room?"
] |
[
false
] |
I live in a studio apartment with only one window. If I want to increase ventilation and the amount of fresh air, which direction should the fan face? I've heard arguments for both into the apartment and towards the window, can anybody help? Bonus meme: I have a vent in my bathroom, would permanently keeping this on improve the ventilation or make it worse?
|
[
"Keeping the vent on in your bathroom, and placing the fan infront or in your window to blow fresh air into the apartment will provide maximum fresh air replenishment. The bathroom will be venting stale air from inside your apartment to the outdoors, while the fan will be sucking fresh air from outside and blowing it into your apartment."
] |
[
"I'll just add another option. Instead of blowing air out or sucking air in, another option is to blow air parallel to the window, the idea being that turbulence with the window will bring in fresh air while also circulating that air into the room."
] |
[
"Understood and appreciated. Thank you very much! "
] |
[
"What is the next likely leap forward in computing?"
] |
[
false
] |
I have heard that computers are reaching their a physical constraint in how fast they go so what is are the potential technologies for the next big breakthrough? I am computer illiterate but have heard about quantum computers, and other potential technologies involving bioligical elements... How far away are we from realising any of these technologies?
|
[
"The physical constraints have more or less pretty much been encountered as you said. ",
"Not that this is what you asked, but the nature of the problem is that the circuitry making up CPUs has gotten so small that the \"wires\" and \"rubber/insulator\" that consitute the circuit are each no thicker than a few nanometers. At scales this small the strange world of quantum mechanics comes in and while quantum mechanics is not my field of expertise, a person once explained it to me as the following (though he might have been over-simplifying):",
"\nAtoms have various energy levels in which electrons are spinning around the nucleus. These various energy levels are in turn at varying distances away from the nucleus. Due to quantum mechanics there is no real \"transition\" between these distances. Given enough energy, the electron in a lower energy level will simply hop the distance to the higher energy level without really travelling through the intermediate space. As such, if the thickness of the \"wire\" is narrower than the distance of the energy levels, electrons can simply leap across the \"rubber/resistor\" resulting in current leakage completely negating the purpose of the circuit.",
"Current efforts at improving computing besides big paradigm shifts like quantim or biologic computing include:\n1) Algorithm optimization - i.e. using our brains to instruct computers to do things much more efficiently, freeing up resources to allow the computer to do more with the same or less amount of circuitry\n2) Multiple Cores - basically shoving multiple computers into one device. Again though, this relies on humans writing programs that lend themselves to parallel tasks."
] |
[
"\"next likely leap\"",
"Many many processor cores in a single chip.",
"Recently 1 core was the only affordable option; and highly parallel chips were rather inflexible and could only do one thing well (say, GPUs, or hardware video chips), or were extremely hard to program (DSPs with odd-sized registers and tricky memory management; Playstation 3's Core processor).",
"Now 4 core CPUs are cheap and 8 core CPUs are common; and GPUs capable of doing hundreds of operations in parallel are now becoming easier and easier to program each month as the tools improve.",
"I think it's safe to say that the next leap will be very programmable massively parallel logic in a single chip."
] |
[
"Also, if I understand correctly, the electron acts as a wave, a higher energy results in a larger wave length and the size of this wave length is what limits the distance to the nucleus. Therefore it isn't the the electrons \"Magically\" jump to a new location without traveling in between but rather the wave becomes larger. <--(I'm not a scientist and this is likely missing important info)",
"EDIT: Struk out my nonsense"
] |
[
"So, the Oort Cloud... Is there any hard evidence?"
] |
[
false
] |
Every time I read something about comets they always mention the Oort Cloud. Looking into the subject, I can never find anything about it that doesn't seem like speculation. Yes, they seem to be very well thought out theories, but nothing seems to imply any hard evidence to its existence. It seems like an awful lot of extrapolation when, as far as I can find out, the only info we have is essentially, "There are comets, therefore. . ."
|
[
"Well, when we look at comets, we find many comets that are long term periodic comets. These comets take thousands of years to orbit and go very far out beyond what we conventionally think of as our solar system. However, they are still a 'part' of our solar system as they're gravitationally bound to the sun.",
"I will contrast this with there are some comets that we know AREN'T a part of our solar system, they're basically just passing through. So there's two different populations of comets (periodic and nonperodic) and only one group implies an Oort Cloud.",
"The reason it does provide evidence for the Oort Cloud is that when we look at periodic comets, we see something a bit unusual. If comets were simply coming from the disk that the planets formed out of, then you'd expect to see that comets tend to have orbits that are in the same plane as the solar system. Instead, however, we find that periodic comets are coming into the solar system from all directions, and that indicates that the comets form a uniform population around our solar system, rather than being juts constrained to the plane that the planets (and the asteroids) are found in."
] |
[
"At this point, the idea of the Oort Cloud fits the facts, and is the simplest explanation that we have that fits the facts.",
"- If we discover that this idea doesn't really fit the facts, or if we come up with a simpler explanation that fits the facts, then we'll use ",
" explanation instead. ",
"http://en.wikipedia.org/wiki/Oort_cloud",
" ",
"http://www.britannica.com/EBchecked/topic/424706/Ockhams-razor",
" - "
] |
[
"But what facts? Other than just seeing long- period comets, what about them leads to these conclusions? Every other sentence in the Wikipedia article starts with, \"it is believed...\" or \"scientists think...\" and other vague language. As far as I can tell, and admittedly I'm no astrophysicist, what's to say comets aren't coming from just general debris from interstellar space and not some localized cloud?",
"I'm not trying to deny it as bad science or anything, I'm just trying to understand the logic applied."
] |
[
"Why do some animals (like certain reptiles) grow until death while others stop growing fairly early in life?"
] |
[
false
] |
[deleted]
|
[
"This isn't my area, but here goes:",
"Think of a housecat and a lion. Both require pretty much the same kind of diet, the lion just needs a lot ",
" Why? Because the lion is much bigger, it burns more energy just walking around and existing. This is referred to as the basal metabolic rate (BMR), and is literally the number of calories an organism expends just keeping itself functioning while laying around doing nothing all day. In general, bigger organisms have higher BMRs because they have more cells, organs, etc. that need fuel and maintenance. The upshot of this is that while a bigger creature is probably going to have an easier time killing its dinner, it's also much more likely to starve to death during lean times. ",
"Now, replace that housecat with a crocodile and compare it to the lion. Again, pretty much the same nutritional requirements. However, the lion is warm blooded, meaning that it burns energy just to keep its body at a specific temperature where its cells and enzymes work best. Meanwhile, the crocodile just doesn't care. It lets its body temperature be the same as its surroundings, and while it might be a bit more energetic in the heat than in the cold, in general its body functions about as well in both cases (up to a point, but more on that in a minute). Because of this, a crocodile's BMR might be a mere fraction of that for a lion less than half its weight. All its energy is going toward movement and growth, with none wasted on regulating its body temp. ",
"But then why aren't big cats and primates and whales all cold-blooded, too? Wouldn't that make more sense from an energy perspective? Yes, except the enzymes and related chemical reactions that make cells go work best within a pretty narrow band of temperatures. Cold-blooded creatures make do in warm regions because it gets hot enough often enough for them to be active and feed themselves, but outside of those environments they'd be little more than a cold lunch for their warm-blooded relatives who are, though less efficient, much more versatile."
] |
[
"The gist is that it would be evolutionary suicide for warm blooded animals to keep growing- getting enough food to keep up with their energy requirements would be an enormous challenge. So they were probably selected against this when they diverged from reptiles. Reptiles don't care- constantly increasing size means they'll be able to catch bigger prey and possibly conserve heat better while keeping energy requirements low. I'm no zoologist/evolutionary biologist but I can see that this trait may actually be encouraged in reptiles. "
] |
[
"The gist is that it would be evolutionary suicide for warm blooded animals to keep growing- getting enough food to keep up with their energy requirements would be an enormous challenge. So they were probably selected against this when they diverged from reptiles. Reptiles don't care- constantly increasing size means they'll be able to catch bigger prey and possibly conserve heat better while keeping energy requirements low. I'm no zoologist/evolutionary biologist but I can see that this trait may actually be encouraged in reptiles. "
] |
[
"I'm not sure where to ask this but: what are some theories that were widely accepted by the scientific comunity but have since been proven false?"
] |
[
false
] | null |
[
"I forgot to add that they had to be proved under what we today would call rigorous testing of some sort. Not necessarily intense but at least following the scientific method. I think these examples are more things people would infer because they seemed obvious."
] |
[
"Caloric theory",
" was a remarkably successful and fairly long lived but mostly wrong theory of heat.",
"I think geocentric theory is a decent candidate as well. It might have been the obvious inference, but the theory was carefully thought out, was and is capable of very accurate astronomic predictions, and originally matched observations better than heliocentric theories (E.g., heliocentrism predicted stellar parallax, which was not observable. Turned out this was because stars are a wee bit further away than anybody thought reasonable, but at the time it was strong evidence against a moving earth.)."
] |
[
"Thanks. Geocentric theory is close to what I was looking for."
] |
[
"Is there any reason Death Valley happens to be both one of the lowest and hottest points on earth, or is this just a coincidence?"
] |
[
false
] | null |
[
"Okay important:",
"It ",
" the hottest. In summer, it has record high temperatures. In winter, even the nearby Sonoran desert will be warmer than Death Valley.",
"The high temperature is due to a combination of the low elevation (higher atmospheric pressure) and extremely dry conditions allowing for high insolation (\"insolation\" being sunlight)."
] |
[
"Hello, friendly neighborhood geologist here. Death Valley never has been a sea. Its so low because its an example of a pull-apart basin. It happens to be caught between two fault zones that have a bend in them and as they slip, the part in the middle gets dropped down. Since the inception of the faults responsible, Death Valley hasn't had any connection to the sea. It has some sea floor rocks around it, but those are several hundred million years old.",
"I'll let an atmospheric scientist comment on the climate, but DV's depth arose from tectonics."
] |
[
"Hello, friendly neighborhood geologist here. Death Valley never has been a sea. Its so low because its an example of a pull-apart basin. It happens to be caught between two fault zones that have a bend in them and as they slip, the part in the middle gets dropped down. Since the inception of the faults responsible, Death Valley hasn't had any connection to the sea. It has some sea floor rocks around it, but those are several hundred million years old.",
"I'll let an atmospheric scientist comment on the climate, but DV's depth arose from tectonics."
] |
[
"How were steam tables generated experimentally?"
] |
[
false
] |
Specifically, how were properties of water/steam like internal energy, enthalpy, and entropy determined (or confirmed) experimentally?
|
[
"Enthalpy, entropy and internal energy are derived from first principles using the laws of thermodynamics and the definition of these terms.",
"The constants in each case for example the specifix heat capacity is determined experimentally. Using the equations and imperial data you get the desired value.",
"Am I being too vague? Should I give an example? "
] |
[
"Some of the experimental methods are covered in ",
"Tables of the Properties of Saturated Steam and Other Vapors",
"."
] |
[
"Yes please"
] |
[
"How is toothpaste sweet and 'good' for our teeth?"
] |
[
false
] |
[deleted]
|
[
"Toothpaste uses non-cariogenic sweeteners (usually xylitol or other sugar alcohols) to provide a sweet taste without contributing to tooth decay, even if you were to smear it on your teeth and leave it there."
] |
[
"Toothpaste, above all over reasons, is an abrasive that is easily washed away after application.",
"The toothpaste is just there to help clean gunk and buildup off your teeth and just under/around the surface of your gums. By removing these off the surface, you stop tooth decay. Toothpaste also has a few ingredients to help with sanitation, as well as floride for protecting and reinforcing enamel.",
"It is crucial that you rinse your month after brushing so that you can eject all remaining gunk/bacteria/sweeteners and chemicals from the toothpaste."
] |
[
"you do not want to leave you teeth exposed to those for any significant amount of time. You will end up with spots on your teeth."
] |
[
"Does gravitational time dilation cause Mercury to travel through time slower than Earth?"
] |
[
false
] |
Mercury is close enough to the sun to experience relativity effects. Gravitational time dilation is a phenomenon of General Relativity where time passes more slowly for something close to a source of gravity, compare to something more distant from that source of gravity. Does it follow that Mercury is travelling through time more slowly than, say Venus or Earth? And, in general, that planets orbiting very close to their stars are in fact experiencing time more slowly than planets further out?
|
[
"Yes. The equation for gravitational time dilation is ",
"To = Tf(sqrt(1-2GM/(rc",
" ). To is time viewed from mercury, and Tf is time viewed from outside of the gravitational field. ",
"So therefore 1 hour to an outside observer is equal to (3600sqrt(1-2G(1.989E30 )/(5.7909E10 c",
" ))=3599.99991 seconds on mercury. On Earth, one hour to an outside observer is 3599.99997 seconds. This does not take into account mercury's relative movement through space relative to earth though. Gravitational time dilation is usually not very prominent unless near an extremely high density object such as a black hole. "
] |
[
"what's the follow-up question?"
] |
[
"Would time dilation have an effect on how a star ages from our frame of reference?",
"Do the nuclear reactions in the core happen significantly slower than a similar nuclear reaction on earth?",
"Does a massive star age slower than a smaller star due to time dilation?"
] |
[
"Why is the Milky Way a [barred] spiral galaxy?"
] |
[
false
] |
I know that galaxies are created in a process having something to do with lots of dust coming together in one way or another to form stars. It seems, though, that such a collection of dust and gas would tend to form a blob, perhaps in the same manner as a very large dust bunny. asked this question, but didn't receive any answers. says that gases collapse into a disk because that minimizes the energy configuration; why is this needed though? says that the spiral arms are likely not actually groups of stars, but merely passing waves, similar to a traffic jam. Why does this traffic jam exist? Why is it jammed in such a pattern, forming arms?
|
[
"It seems, though, that such a collection of dust and gas would tend to form a blob, perhaps in the same manner as a very large dust bunny.",
"The thing is that gas is collisional, so it won't remain in a diffuse blob indefinitely-- it will collapse, and as it collapses, it will pick up rotation, and as it rotates, it is forced to flatten out into a disk.",
"As for density waves, well, they're a dynamic effect that occurs in a system like a galaxy disk. The pattern stays because it is created by the orbits of the stars."
] |
[
"The simplest answer to this question is: energy. Any system must conserve angular momentum, but \"wants\" to get to a low energy state, by dissipating the energy into heat. The the case of orbital systems, the way to do this is put as much angular momentum momentum in the smallest amount of matter, thus shoving that matter way, way far out of the system and allowing the rest to drain toward the center. ",
"Both spiral density waves and bars are mechanisms for the outward transport of angular momentum, putting the system into a more energetically favorable configuration. It's sort of like asking why streams exist -- waters wants to get downhill, and streams are a way of doing this. As my flair-having compatriots have said, the exact mechanics of it are pretty complex and stiff under rather active discussion (the last major bar conference was two weeks ago in Spain). "
] |
[
"I'll break your question up a bit.",
"So, imagine we start as a big blob of gas. These gas particles have all sorts of large random velocities, and these big velocities keep them in orbit around the centre-of-mass of the big blob of gas.",
"Now, these gas particles have all sorts of velocities, so they're going to bump into each other from time to time. These aren't \"elastic\" collisions - some of the kinetic energy is lost in the collision. This energy is used up by shunting an electron into a higher energy shell. The electron will then drop back down to neutral, and spit out a photon of light. Because the gas is very transparent, this photon flies out of the giant blob of gas. So we now have less energy than before.",
"This keeps on happening, and the gas keeps on losing kinetic energy. Because the particles are moving slower, they start to \"fall\" inwards. However, there's a limit to how much energy you can lose. Every collision must conserve angular momentum, which means that you'll always have a little bit of kinetic energy left, just enough to keep your angular momentum.",
"So finally, you end up with a situation where you have the lowest amount of kinetic energy possible while still holding onto your angular momentum. Here, basically all of your kinetic energy must be in circular motion. So you end up with a nice flat disc, because any vertical motion is kinetic energy that can be \"burned up\".",
"To understand this fully really requires a grad-level understanding of collisionless mechanics, but I'll try to sum it up for you.",
"In a galaxy you have all sorts of \"forces\" going on. You have gravity, which likes to make things clump together, but you also have \"velocity dispersion\", which is the fact that stars have different speeds and hence tend to drift away from each other, and also \"differential rotation\", which is the fact that the inner parts of the galaxy complete an orbit faster than the outer bits, so anything that tries to clump will get stretched out into a spirally shape.",
"These can combine in interesting ways to create a \"resonance\", a large-scale stable structure like a bar or spiral arms."
] |
[
"Why are different brain structures associated with different functions?"
] |
[
false
] |
I’m starting my PhD in clinical psychology studying neuropsychology this fall and I’ve been getting interested in learning some functional neuroanatomy before I begin. One thing I’ve found particularly difficult to wrap my head around is the functions of brain structures in relation to each other, something I know is not unique to me. That being the case, I was wondering if anyone could explain to me the WHY of neuroanatomical function. WHY is the hippocampus so associated with memory? Is it something unique to its place in the brain, it’s connections, or it’s unique physiology? Or broca and wernicke’s areas, WHY do they perform their unique functions in speech? Again is there something about the unique connectivity between brain regions that allows for this specificity of function or is it something else?
|
[
"Is it something unique to its place in the brain, it’s connections, or it’s unique physiology?",
"All three.",
"its place in the brain",
"The brain was built up piece by piece over the course of evolution, and the oldest structures are typically involved in basic physiological processes, such as the regulation of heart rate and breathing. The most recent structures (like the neocortex) are typically involved in higher-order cognitive processes necessary to animals with complex problem solving ability.",
"it’s connections",
"This is important, too. The most obvious examples are the primary sensory areas, which receive input from our sense organs. The optic nerve passes through the thalamus to the occipital cortex, and the primary function of the early occipital cortex is to process visual signals. A region which did not have relatively direct access to this information would not be well suited to the task. Conversely, it would be poorly suited to something like object recognition, because this requires a great deal of highly processed information not only about the visual scene, but about semantic information related to the object (you can recognize an object as a cup even if you've never seen that particular kind of cup before, because you understand the ",
" of a cup, and certain objects have physical forms that clearly allow them to fulfill that function), and past experiences with the object (i.e. memory). This requires the synthesis of many different kinds of information, and so requires ",
" to that information, through connections to other regions.",
"or it’s unique physiology?",
"Yes. Different parts of the brain differ in the in their neuronal (and glial!) makeup. A particularly well understood example would be the striatum; part of the basal ganglia. The striatum receives input from nearly the entirety of the cortex, does \"something\" with it, and then sends projections back to the cortex through the thalamus. This makes it extraordinary well suited to influencing cortical information processing, and indeed the striatum is involved in nearly every function you can name. Some of the most important of these are reinforcement learning and motor control. ",
"As a ",
" coarse description, the striatum has multiple pathways back to the cortex, through which it can exhibit either inhibitory or excitatory control. This function is especially important in motor control, as it allows for the voluntary initiation or inhibition of movement, and disorders of this system (e.g. Parkinson's) often result in either tremors or the inability to smoothly initiate movement. The neurons projecting to these different pathways are strongly modulated by dopamine, and yet the ",
" in which they are modulated depends on the specific subtype of dopamine receptor possessed by the neuron. These pathways differ the relative concentrations of different receptor types, which allows them to be modulated differently by dopamine. Dopamine itself is provided to the striatum by another set of structures containing primarily dopamine producing neurons, and these neurons fire as learning signals that tune the activity of the striatum based on the outcomes of past actions.",
"As a nearly opposite example, the cerebellum is an example of a region with almost completely uniform structure. The neuronal makeup of the cerebellum doesn't really vary across the cerebellar cortex, even though it it is densely connected with most of the cortex. In the context of motor control, the cerebellum is pretty clearly established to function as a state estimator -- that is, it receives copies of motor commands from the cortex, and then generates a prediction about the state of the body after the command has been executed. This is then compared to sense data to detect errors in the intended state of the body. Now, the cerebellum is also involved in, well, everything else. And so the fact that its neuronal structure is so uniform has led to the influential idea that its ",
" vis a vis the rest of the cortex should be fairly similar, and so it has been suggested that the cerebellum is really just a generalized prediction machine.",
"Speaking to your examples (e.g. speech), it's generally impossible to say ",
" a specific region has a specific function, especially in the case of the neocortex, where many regions are densely connected association regions involved in multiple poorly defined functions. In most cases, we can't even unambiguously ",
" the function of these regions (Broca's area is a particularly good example of this, as even its popular role in speech production is debated), let alone start asking how its particular pattern of connection or neuronal makeup support that function. So I suppose that answer to your question is \"all three are clearly important, but in the case of most specific regions, we don't really know\"."
] |
[
"Since no one else has offered an answer yet, here's my take on it.",
"Speaking generically: A structure in the brain functions the way it does according to 3 main criteria.",
"Regarding the location of different structures, that appears to be mainly related to how far back they evolved. Like the basic functions that keep us alive are regulated in the deepest, oldest parts of the brain. Emotions are mediated in the intermediate layers. Logical thought is in the frontal cortex, in the newest part of the brain. But there are interesting counter-examples. The pineal gland helps to regulate the sleep/wake cycle. It is located behind the eyes, which means that daylight can stimulate it, which is why exposure to bright lights at night can interfere with sleep.",
"You were probably looking for a more specific answer. Here's the thing. We DON'T know more than we DO know about why the brain is the way it is. So we put together the bits and pieces we do know and make some guesses. Then we keep revising those guesses as new data dribbles in.",
"But it's been several years since I was in grad school, so maybe they have better answers now."
] |
[
"Or broca and wernicke’s areas, WHY do they perform their unique functions in speech? Again is there something about the unique connectivity between brain regions that allows for this specificity of function or is it something else?",
"Wernicke's is right around the primary and secondary auditory cortex, where you hear sounds and parse them for meaning, while broca's is neighboring the primary motor cortex, just to the south of it. Particularly the tongue and mouth control parts of the motor cortex, they're right down near broca's. There's also a big pathway, a highway of axons, between broca's and wernicke's called the arcuate fasciculus, it connects the two areas quite well. Knock this out and you'll get conduction aphasia. So in a way yes, there is now a unique structure between the two that allows them to function optimally for language.",
"Do you think there would be a better spot for them? ",
"Don't read too much into the WHY, evolution can be messy and often goes with a 'good enough for now, or good enough given the other things we have to work around' approach (don't get me started on the cranial nerves, what a mess). But it does makes sense as to how the two main language centers would be where they are. It would be the most efficient spots for them given the input (sound) and output (mouth and tongue movement)"
] |
[
"Why does increasing the brightness of your phone while it is in the sun make it easier to see since it is already very bright outside?"
] |
[
false
] | null |
[
"What you see is determined by what light enters your eyes (duh). If the light of the sun is brighter than the light of your phone, you'll only see reflected sunlight from your phone. If you turn up the brightness on your phone, its light will be brighter than the reflected sunlight, and you will see your screen."
] |
[
"The issue is contrast. Phone screens are usually light-emitting. Shining light on them lightens the black, but doesn't brighten the colors, so the the black-to-color contrast is reduced.",
"There are also rare \"electronic paper\" or Mirasol (IMOD) microelectromechanical screens that are not light-emitting, but light-reflecting. In their case, shining light on them brightens the colors more than the black, so the contrast is increased. The original Amazon Kindle had an electronic paper screen, and Mirasol screens are also in the market, but are not commonly used."
] |
[
"Your eyes work over an amazing range of lighting conditions by varying the size of your pupil to control the amount of light entering the eye. It's an amazingly broad range... from tiny amounts of light reflected from the moon (less than millionths of candellas per square meter), to the brightest sunniest days (more than millions of candellas per square meter). At night, with a simple 20W bulb or similar you still see things 'brightly' even though there's 1000ths or less of the amount of light as during a sunny day due to this dynamic brightness control.",
"So, the relative brightness of your screen and the reflected light from the sun matters. If the sunshine is bright, your pupils will have shrunk to keep perceptual brightness \"about right\", but that means that much less of the light from the screen gets into your eye, and so it appears darker. Cover the phone in shadow, reduce the amount of light reflected from the sun (the 'average' brightness), your pupils will dilate a little and the phone screen will appear brighter.",
"A lot of TVs, monitors and phone displays include a photo-sensor to automatically increase or decrease the display brightness as the background lighting intensity changes to adjust the 'perceptual' brightness of the screen as they're moved, and as they lighting changes through the day.",
"This is also how projectors, LCD screens and the like make \"black\" on non-black surfaces. If you look at a completely black LCD monitor in the dark, you'll see some light from the backlight leak through, and the darker the room you're in the brighter it will appear. But when the display is showing bright colours, those same pixels leaking the same amount of light from the backlight look as black as can be.",
"(edited: me do English good.)"
] |
[
"Do synthetic neurotransmitters exist?"
] |
[
false
] |
And if they are why don't you hear more about them being used as treatment? For example if Alzheimer's is caused (or can be caused) by a lack of acetylcholine, would it be feasible to make a synthetic in order to treat it?
|
[
"You have you to remember that neurotransmitters are just soluable signalling molecules. Serotonin, for instance, can be easily classified as a hormone. Estrogen is a steroid. I think if you adjust your concept of what defines a signalling molecule, you'll find that many drugs are in fact \"synthetic\" neurotransmitters.",
"Synthetic receptors (RASSLs, DREADDs, etc.), now that's something much more novel and something to think about..."
] |
[
"its never usually as simple as 'we just need more neurotransmitters'",
"some examples though, not cures but they are helpful:",
"l-dopa for parkinsons which gets converted to dopamine",
"acetylcholine precursors for alz(cdp-choline, alpha-gpc)",
"mao-b inhibitors slow down the body from breaking down dopamine (deprenyl)",
"mao-a inhibitors slow down breaking down of serotonin (moclobemide) ",
"ssris stop serotonin from being taken back into the cell",
"dopamine reuptake inhibitors do similar for dopamine",
"same for acetylcholine(huperzine, galantamine, )",
"dopamine-type agonists which mimic dopamine (pramipexole)",
"acetylcholine-type receptor(nicotinic) agonists (nicotine)",
"serotonin 1a agonist (buspar)",
"serotonin 2c agonist (locaserin, weightloss)",
"afaik, plain neurotransmitters don't cross the blood brain barrier(they won't reach the brain)"
] |
[
"There's no need to synthesize artificial ones as we can actually synthesize the real thing. For example, common neurotransmitters, like glutamate and acetylcholine, are easily available from the chemical company Sigma-Aldrich. They have modified variants of these transmitters too, but no one calls them \"artificial transmitters\".",
"It seems to me that you have a misconception about Alzheimer's by saying it's the lacking of a transmitter. The lacking of a transmitter indeed can lead to neurodegeneration. But Alzheimer's is usually much more complicated than that. Please try to read on Google about amyloid precursor protein (APP), presenilins 1 and 2, and accumulation of Tau proteins (these are some of the most famous molecules that are involved in Alzheimer's), then you'll start to understand why we still don't have a cure for it yet. The fact is, we still don't understand the ultimate cause and the detailed progression of the disease. ",
"Showering the brain with neurotransmitters would not help as it would only lead to seizure..."
] |
[
"When research shows some people share 2-4% of their DNA with Neanderthals, what DNA are they talking about?"
] |
[
false
] |
I read in an article recently that some people share 2-4% of their DNA with Neanderthals. However, we also share loads of DNA (>95% IIRC) with less similar species such as Chimpanzees. So, when we say we share 2-4% of DNA with Neanderthals, is that only some part of our DNA that is measured separately, like repetitive sequences?
|
[
"Here's a simple analogy. Suppose almost everyone in your family was Icelandic, except that one of your great-grandparents was Nigerian. Your DNA would be 87.5% Icelandic, 12.5% Nigerian. ",
". However, those populations have accumulated mutations that make parts of their DNA distinct. So when someone says you are 12.5% Nigerian, what they mean is that 12.5% of your DNA is inherited from a Nigerian ancestor and contains mutations that originated in Nigeria. The actual sequence difference between you and a person of purely Icelandic descent will be much, much smaller than 12.5%: it will be a tiny fraction of one per cent.",
"Likewise, when someone says your DNA is 3% Neanderthal, they mean that 3% of your DNA consists of chunks that are traceable to Neanderthal ancestors. ",
". The sequence difference between you and a hypothetical person with no Neanderthal ancestry will be much, much smaller than 3%."
] |
[
"Aah, so it's kinda like how we share \"50%\" of DNA with either parent even though a lot of the DNA is the same, it's just that certain DNA that makes us different from one another is 50% from either parent?"
] |
[
"Yes, more or less. You're much more than 50% identical to either parent, in terms of sequence content. But roughly half of your DNA will be inherited from each and will be characterized by SNVs (as well as other variants) associated with that particular parent."
] |
[
"Why is a detached, insulated but non-heated garage warmer than outside during winter?"
] |
[
false
] |
[deleted]
|
[
"There could be tons of factors influencing this. Firstly, even if completely insulated (and ignoring the sun) you should expect the temp to average out to the same daily average as outside, but with smaller extremes. This means if you have a high of +5C during the day and low of -25C at night you would maybe expect the garage to swing from -5C to -15C. This might make the garage feel much warmer at certain times of the day, namely the morning.",
"After that things will get too complicated to give you a straight answer. ",
"Are you parking a car that is ever driven in there? Each time you drive and park inside you bring in a ton of heat with the warm car, and lots of that will stay inside the garage if well insulated. ",
"Do you have windows? The greenhouse effect will warm the inside considerably compared to outside where the warm gas isn't trapped near the ground.",
"What is the ground temp and how much thermal mass is in there? Cold snaps take a long time to cool the ground, you might be still feeling warmth from the foundation and ground from months ago.",
"Electronics, lights, tools, etc? All of these will put off lots of heat.",
"In your garage a lot? Even your own body puts off quite a bit of heat.",
"Lots of wind outside? The interior of the garage is protected from moving cold air which will take away much more heat than stationary air.",
"Snow outside? It will serve to cool the outside air by absorbing energy to melt and reflecting sunlight, but it might actually further insulate the inside of your garage like a blanket on top (but is balanced by how much the incoming solar energy would warm your garage if it didn't reflect off the snow).",
"I'm sure I am missing some potential contributors, but all of these things might serve to minimally warm your garage compared to the outside temp and could explain the temperature discrepancy you are seeing."
] |
[
"if completely insulated (and ignoring the sun) you should expect the temp to average out to the same daily average as outside, but with smaller extremes.",
"If completely insulated, the temp will be the ",
" average.",
"This is the famous Wine Cellar problem, a pretty popular partial differential form in the realm of heat transfer problems. Like the name suggests, it can be used to model the temperature in a wine cellar as a function of depth in the ground. It also works well for modeling temperature fluctuations and lag in any partially insulated enclosure, and explains why caves always maintain the same temperature as the yearly average outside.",
"The solution takes the form of a decaying, phase-offset sinusoid, and follows the general pattern that:",
"For complete insulation, the temperature is just the yearly average outside temperature with no fluctuations.",
"As insulation decreases, you start getting seasonal temperature fluctuations, but with a time lag of a couple months (e.g. the hottest time might be in September).",
"As insulation decreases further, the size of the fluctuations increase and the time lag decrease.",
"As insulation continues to decrease, eventually there's almost no seasonal lag, and the temperature is just the daily average.",
"With even less insulation, you now start to get daily fluctuations, but now with a time lag of several hours (e.g. max temp might occur at 6 PM). A lot of houses are found in this realm.",
"As you go to zero insulation, daily fluctuations increase and the time lag decreases until the temperature is the same as the outside temperature."
] |
[
"I would imagine the ground would be not much less than 0C if the air temp is not consistently under 0C for less than 2 months (canadian intuition)."
] |
[
"Do metal bonds make pure chemical compounds or mixtures?"
] |
[
false
] |
Say bronze, witch is an alloy between tin and copper. Is bronze then a mixture like chocolate is a mixture or is it a pure compound like salt or CO.
|
[
"I'm not sure how in-depth a response you want, but:",
"Things like bronze are a mixture of pure elements, at least one being a metal. As the materials don't bond together to make a compound, alloys are really much closer to a mixture. (Although producing an alloy of two metals can produce vastly different physical properties than those of the original elements)",
"I'm sure someone will jump in soon with a more detailed response."
] |
[
"Bronze is a mixture. It's not possible to have a single molecule of bronze (as it is for CO). There is no crystal structure for bronze (as there is for salt). However, the tin and copper atoms are bonded to each other by metallic bonding."
] |
[
"would for example an iron bar be one really big molecule with just lots of iron atoms in it or something else? "
] |
[
"Is it possible to determine the composition of a new molecule using spectroscopy?"
] |
[
false
] |
[deleted]
|
[
"Theoretically I think you could determine the spectrum of a molecule based on physics, though this would be incredibly difficult. I don't think this works the other way around though, ie determining the molecule by the spectrum.",
"It would be more likely that we could just compare it to known molecules and look for a match. "
] |
[
"There are efforts to identify the specific chemical formulas of the Polycyclic Aromatic Hydrocarbons that are identified in molecular clouds in space from their spectral lines."
] |
[
"In principle, it's not out of the realm of possibility. Practically speaking, astrochemistry has both observational and laboratory components. Being able to pin down unique spectral signatures in the laboratory benefits future observational efforts. "
] |
[
"What is the purpose of LPS-stimulated cytokine release?"
] |
[
false
] |
I'm curious as to what specific research questions are satisfied with LPS-stimulated cytokine release through use of whole blood, as opposed to running high sensitivity ELISA kits on blood plasma.
|
[
"It's usually just a gross measure of activation. It can tell you how many monocytes or dendritic cells are present (they are some of the primary cells expressing the receptor for LPS; TLR4) but also how the cells are communicating. For example, LPS will stimulate IL-12 production which can promote T or NK cell expression of IFNg, if that doesn't happen it could tell you that T or NK cell function is screwed up. Also note that measuring some factors in whole blood is very very tough---specifically some of the proteins expressed downstream of LPS activation. IL-12 for instance is a heterodimer consisting of two parts---measuring the in tact cytokine as opposed to each individual part is very very hard. "
] |
[
"The questions are different-- LPS would tell you how the cells in blood are responding to an inflammatory stimulus, whole blood plasma would tell you what has already been produced and is floating around in the blood. Depends on the question you want to ask. Based on your interest in the inflammatory response I'd guess the LPS would be better since the ELISA is only going to tell you what's already present so unless you're looking at stress hormones or something like that (which you might expect to be altered by a behavioral intervention) you probably wouldn't see much. Especially if these people aren't sick in some way and are otherwise healthy. "
] |
[
"Thanks for the informative response!",
"What about the distinction between LPS stimulated cytokine release vs your typical high sensitivity ELISA via plasma? Is there a clear demarcation as to when one is indicated vs the other? I'm basically looking into a project that would assess an individual's inflammatory response to a fear task, and the whether a two-week behavioral intervention would regulate that inflammatory response over time.",
"I've been under the impression that plasma ELISA would make the most sense here, but a lab within our department is using the whole blood cytokine release approach so I wasn't sure if this should be considered. "
] |
[
"Why is it that when sleeping, we can regulate our temperature by having one foot in or out of the duvet?"
] |
[
false
] |
When I get hot at night, if I leave one foot out of the duvet I feel as if my temperature is much more comfortable, likewise if I'm cold I'll pull it in. Generally I'll always sleep with one foot out however, it seems 'optimal'. I know many other people do this and experience this too, so what's the science behind it - do our feet have a certain control over how hot or cold the rest of our body feels? Or is it all in the mind?
|
[
"Under a heavy blanket that allows little heat to escape, one can feel overheated because we are constantly producing heat as a byproduct of reactions going on in our cells. Leaving one foot out of the duvet allows heat to escape. ",
"Thermoregulation mechanisms include the rerouting of blood flow to superficial or deep vessels; superficial blood vessels (close to the skin) allow heat to escape more readily (this is why your skin appears red when you're too warm) whereas deep vessels conserve heat (your body tissue acts to insulate and keep heat in). ",
"When you leave your foot out of the covers, it will become colder than the rest of your body, so the blood entering your foot will be considerably warmer. This acts to warm your foot, and if you're overheating it will increase the escape of heat from your body. ",
"The foot has no control over thermoregulation, this is regulated by a control centre in the brain (including the hypothalamus). ",
"Wikipedia has an article on homeostasis and a section on temperature: ",
"http://en.wikipedia.org/wiki/Human_homeostasis#Temperature",
" "
] |
[
"Yes, but to a lesser extent. Humans experience greater heat loss per unit surface area from their feet than from hands. This has been attributed to vasoconstrictor tone of vessels in the leg, different vascularization between the hands and feet, and morphological differences (size, shape, insulation etc.). This paper suggests that, perhaps, \"cold feet\" could be the result of bipedalism:\n",
"http://onlinelibrary.wiley.com/doi/10.1002/ajpa.1330320203/abstract"
] |
[
"Awesome explanation, thanks. So potentially the same effect could be had by sticking an arm out perhaps?"
] |
[
"Timeline of a viral infection of one cell?"
] |
[
false
] |
As I understand, a virus spike protein latches to the cell receptor. The viral RNA (or DNA, not sure) gets inside and starts instructing the cell to produce more viruse copies. Eventually, the cell bursts and releases the virus copies. My question is how long does each step take? Is it super quick like 10 seconds or super long like 10 minutes or more?
|
[
"Different families of viruses have different proteins and different mechanisms of infection; you’re correct that coronaviruses have a spike protein on their surface to attach to a host receptor. Viruses can have DNA and/or RNA, also dependent on the virus. Answering your question, the replication timeline also varies by virus, but an example of the influenza virus takes around 6 hours from entry into a host cell to shedding new viruses. Source: ",
"https://www.euro.who.int/en/health-topics/communicable-diseases/influenza/data-and-statistics/virology-of-human-influenza"
] |
[
"This is a great question and one I actually had to do a bit of research on.",
"At least for adenoviruses, it varies cell to cell--time from when the virus contacts the cell to when it starts replicating ranged from 10 minutes to 4 hours in ",
"this experiment",
". From then, there was another hour or two from when the virus starts replicating until it actually lyses the cell."
] |
[
"It depends on both the virus and the cell but in general in on the scale of hours. Different viruses go about this differently too. For example Herpes viruses (like HSV or chickenpox) might infect a nerve cell and do nothing for decades before becoming active again while Norovirus might bud off a cell a few hours after entering and rapidly cause symptoms. ",
"Viruses can use either RNA or DNA for their genome and it can be single or double stranded (half the ladder or all of it). There are then many different ways viruses can reproduce within the cell, ways they can take over the cell and hid from its internal defenses (cells will shut down protein production and/or destroy themselves if they realize they have a virus). For example, Coronaviruses make bubbles within the cell in which they make more coronaviruses. Then to leave the virus can either lyse the cell or bud off from the cell membrane."
] |
[
"Do NSAIDs help soft tissue injuries heal?"
] |
[
false
] |
A medical student that I know was the opinion that NSAIDs should be taken in the case of soft tissue injuries and that these help them to heal faster. If I look this up, most of the advice available on the internetz is actually to the contrary - inflammation is necessary for injuries to heal, and anti-inflammatories can slow down the healing process. Which of these answers is true? The information seems pretty contradictory and the studies admit to a need for more investigation, there doesn't seem to be any consensus.
|
[
"Top answer is misinformed. First and foremost, nsaids are not linked to injury through swelling by “bleeding.” when nsaids are linked to greater injury the mechanisms are super complicated because inflammation is super complicated. It typically involves misbehavior of specific group of cells, not bleeding. ",
"The answer to your question is its still unclear. Studies and meta analyses are super mixed. There are studies showing high dose nsaids post surgery help but long term is bad, and there are studies in animals showing acute nsaid use is bad and late phase healing they’re good. What we do know, flat out, is that certain subtypes of inflammation lead to scarring and improper cell regeneration which NSAIDS can help fix but also that NSAIDS can interfere in healing through other mechanisms not completely understood ",
"Overall clinical consensus is that pain management, especially in physical injury, encourages early mobility which is usually better than sitting on ur ass. The classic treatment of ibuprofen and cold therapy is not completely based in science",
"Source: I study inflammation and endothelial repair",
"Edit: People are asking about how to reduce inflammation. the number one source of inflammation in the modern world is being overweight. Don’t be overweight, exercise outdoors and eat leafy greens. I cannot overstate how powerful these life practices are.",
"Edit 2: exercise outdoors so you get exercise + vitamin d and lower stress. The outdoors and all its microbes are fucking magical for our immune system. Just try to avoid bird shit and bat ridden caves lol they nasty (from an immunology perspective)"
] |
[
"I'm a doctor and just want to reinforce what you said here. This is the best answer. I think it's a VERY important point that, for most injuries, encouraging early mobility is a huge part of healing. In general, less pain and swelling leads to more movement which leads to enhanced healing. All else being equal, NSAIDs may cause some harm through the potential mechanisms mentioned, but moderate use of NSAIDs to enhance mobility through the recovery period is generally, IMO, a good idea."
] |
[
"They CAN help under certain situations. During the acute phase of the injury they can actually do some damage by increasing bleeding/swelling. This is why anytime someone is going in for a surgery or procedure the doctors want you off of NSAIDS. ",
"But they can help in the chronic phase of injury by reducing pain and some inflammation. In the chronic phase returning the injured body part to more normal function is the goal. For example, with a sprained ankle, after a week-ish (depending on severity) getting the ankle working again is important but pain and leftover swelling can inhibit that function. NSAIDS can reduce that pain which reduces the inhibition of the body to use the ankle.",
"Source: PhD in rehabilitation science. I didn't study NSAIDS specifically but studied tissue repair and the like. The current science might differ a bit but this is the general clinical understanding."
] |
[
"Would an 'alien' have the same senses we do?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"You say this is speculative but it's not. Well a little. But I just want to know if you need all 5 senses that we have to have a super-being like humans, or if others can be used or less. Do you know of a better way to word this?"
] |
[
"I don't know what you mean by superbeing. We have way more than 5 senses. Nonhuman animals have plenty of senses that we don't like echolocation, sensitivity to magnetic fields, sensitivity to electrical currents, etc."
] |
[
"Why do some people have higher body temperature than others? (I think my SO is the Human Torch)"
] |
[
false
] |
Is my girlfriend secretly a member of the Fantastic Four? My girlfriend and I (I'm a girl too) are almost the same height and weight, have similar diet (but she exercises much more than I do) and yet she burns up in the middle of the night enough to wake me up (and I'm a heavy sleeper!). She isn't sick or anything, because I ask her if she feels feverish but she tells me that she feels absolutely normal. Even in the middle of the day, I would hug her and it's like hugging an oven! Sometimes she would also be completely red all over.
|
[
"Thyroid disorders and diabetes can affect body temperature. The Fahrenheit scale was supposed to have been defined such that 100ºF was body temperature, but Dr. Fahrenheit picked a bad subject for calibration."
] |
[
"I would like to know more about this as well. My normal temperature is about .6 degrees above the average. Girls I've been with have definitely noticed that I can heat a football stadium while in a coma."
] |
[
"[[citation needed]]"
] |
[
"How does the SARS 2 virus infect a cell via ACE2?"
] |
[
false
] |
This is something I've been wondering about for a while, ever since almost the beginning of this pandemic, actually. ACE2, as the name implies, is an ngiotensin onverting nzyme. Its purpose appears to be that it sits on (or well, in, but one part sticks out above and one below) the cell membrane so that when molecules of the aforementioned angiotensin happen by and join with the enzyme head sticking out of the cell, they have a piece cut, converting them from one form to another. Yet here's the thing. This protein also seems somehow to be able to serve as the entry point for the SARS 2 virus that causes COVID-19, when the much larger spike protein attaches to it. But that is very strange, because based on the "part description" above it seems to have nothing to do with transportation, yet apparently once the virus attaches there, the cell initiates an active transport process (endocytosis) in response that brings the virus in. Why, and how, does that happen? How can, and why would, a protein that is supposed to simply function as processing enzyme be able to do this "double duty" as a signal that something is to be brought from the outside of the cell to the inside? Is it that the virus's binding damages the protein or else causes it to malfunction in some way, and then the cell recognizes that damage and so tries to retrieve it for repair or replacement, and in doing so, the whole virus gets pulled in along with it?
|
[
"It binds with the ACE2 receptor to enter the host cell. The S protein is primed by serine protease TMPRSS2, which release the S protein subunit S2 to fuse the viral and cellular membrane. Then the viral genes enter into the cell and reproduce more viruses (",
"source",
")."
] |
[
"I actually did not know that. I would add then that binding to a surface protein can correctly position another entry method since binding to the protein fixes the orientation and position relative to the target cell, allowing a built in transport mechanism to do its thing.",
"I actually never delved too far into bacteriaphage and HIV but I know they attach externally to deliver their contents.",
"I imagine relatively soon sars2 will join them in the textbooks as one of our more well studied and understood viral species for future BS holders to half remember and forget about a few years out of school."
] |
[
"The simplest way to address this topic is to tale about a more commonly targeted receptor: glucose. Every cell needs glucose, so if a virus needs bait to get into the cell, they can attach a glucose molecule to a stick and when the cell goes to bring in the glucose the virus comes with it. Sugars are commonly available components and is not too complicated to come up with a structure with a sugar at the end of a stick by random mutation and then have that shape and corresponding genetic material be successful and get passed down.",
"Underlying this mechanism is \"receptor mediated endocytosis.\" The way the body gets things from point A to point B is bonkers, instead of having some guaranteed mechanism, everything just gets released into the bloodstream where it randomly bumps into different cells until one of them happens to bump a protein that it slots into. ACE is one of those signaling molecules that controls heart a lung function. E.G. certain heart and lung calls have ACE receptors, and other cells do not. This defines the specific cells most effected by a virus that uses ACE as its lure. Every cell has a multitude of receptors that help them perform their functions.",
"So how does a virus end up using ACE specifically? It could be random. ACE is a relatively simple molecule and randomly assembling part or the whole of it by chance is possible. There could be a transcription error where host DNA doesn't detach properly from viral DNA and the gene got added in in some ancestor virus. It could be a coincidence and a reactive part of the virus might happen to bind to ACE irreversibly if is present or something else if it is not",
"Someone more informed about sars-cov2 specifically might know specifically, but that generally how any virus might end up with a particular receptor."
] |
[
"How big can a cube get before gravity would collapse it into a sphere?"
] |
[
false
] | null |
[
"If you look at asteroids. After a few miles across they start to appear more and more spherical. But i think your question depends on the rigidity and density of the cube. That I can’t answer but my guess is a hundred or so miles across before bending or collapsing into more sphere like. "
] |
[
"This depends on the composition of the object. What you're asking is about ",
"hydrostatic equilibrium",
". If the cube was made of ice, a diameter of 400km or so seems to be the lower limit. Ice needs less mass to reach hydrostatic equilibrium than rock. For example, the icy Saturnian moon Mimas has an equilibrium shape (not necessarily in hydrostatic equilibrium) with a diameter of 397 km, while the largest object not in hyrdostatic equilibrium is ",
"Iapetus",
" with a diameter of 1470 km."
] |
[
"But Iapetus is 80% ice so you'd think it would be in equilibrium too?"
] |
[
"How reliable is the act of testing/comparing isotope fingerprints in a living organism against those fingerprints in lead in ammunition?"
] |
[
false
] |
one of the quotes from the article: In a study led by Finklestein’s team at UC Santa Cruz, the source of the lead poisoning was traced back to ammunition via isotope testing. Whereas captive condors have lead isotope “fingerprints” which match that of background environmental lead in California, the wild condors have been found to have an isotope fingerprint which matches that of lead ammunition. How reliable is the act of testing/comparing isotope fingerprints taken from living organisms against lead in ammunition?
|
[
"The problem with this study is that they did not test other environmental factors that may cause lead exposure. In effect, they skewed the study for a political agenda...",
"See the post here made by indgosky",
"Plain and Simple -- It is a Propaganda Piece",
"Hunting with lead over water has been banned in the state for a very long time, and hunting varmints (anything that you'd leave the carcass) with lead has also been banned.",
"And yet the numbers get worse? Do you actually believe the condors are digging in the ground, and finding old lead, and eating it because it looks tastier than all the carrion and human food waste that's available by the roadsides and in dumps?",
"This article fails to mention two other sources of information on the subject...",
"In one, the lead that's still in circulation, which the birds are managing to ingest, is from landfills -- human garbage including batteries and such -- which has ZERO to do with hunting.",
"In the other -- and this was admitted by a game officer of the state, in a talk he gave -- the people charged with saving the condors were providing food for them to ensure they had the best chances possible. Since food is expensive, they looked for sources of free food. Local cattle farmers offered up their stillborn calves, which the preservationists readily and happily accepted. Nobody questioned why the calves were stillborn. Turns out the mother cows (and their fetuses) had severe lead poisoning from eating things off the ground around the farms. Again having basically ZERO to do with hunting and lead ammo.",
"This whole sack of condor shit is just a (typical of commiefornia) smoke screen and a lie -- a convenient tool in the anti-gun, anti-hunting agenda that so many coastal californian's share.",
"I wouldn't even wipe my ass with this bought-and-paid-for \"study\"."
] |
[
"Until someone else answers you, I'll offer what I found.",
"Determination of isotopes is very well understood. It is how radiocarbon dating works.",
"I do not know how lead melted down for ammunition would differ from any other form. [",
"http://en.wikipedia.org/wiki/Lead#Isotopes](Wikipedia)",
" says that the \"amounts of [each isotope] in nature depend also on other elements' presence, the isotopic composition of natural lead varies by sample: in particular, the relative amount of lead-206 varies between 20.84% and 27.78%\"",
"My take on this is that the samples original geographic area could be determined, but not whether or not it was once formed into ammunition. If a company is known to use lead from a certain mine, that narrows things down. However, Wikipedia also says that about half of the lead produced is recycled. "
] |
[
"This article has slightly more of the science: ",
"http://www.biologicaldiversity.org/species/birds/California_condor/pdfs/Condor-Lead-Science.pdf",
"In short:",
"Isotopic analysis of lead in the blood of pre-release and free-flying condors in California \nstrongly supports the link between lead ammunition and lead exposure. Lead isotope ratios \nhave been used for over 25 years to trace source(s) of environmental lead exposure. The use of \nlead isotope ratios for evaluating lead exposure is based on the natural existence of lead in four \nstable isotopes. The natural relative abundances of these isotopes often varies across different \nlead-containing industrial products (e.g., leaded paint or ammunition) because lead used in \nmaking those products comes from different sources of lead. Lead isotopic ratios in lead-exposed \nanimals are like fingerprints that can be traced back to a particular source of lead exposure.",
"\nIndeed, lead isotopes offer the most accurate way to trace the sources of elevated lead exposures, \nand they have been used to trace the sources and pathways of lead exposure in humans, as well as \nin wildlife such as California condors.",
"\nChurch et al. (2006)",
"evaluated the sources of elevated lead exposure in California condors based \non: (i) knowledge of the plausible sources of lead exposure to the condor, including lead \nconcentrations; (ii) the quantified isotopic ratios of those plausible lead sources within that \nenvironment; and, (iii) information about behavioral habits, as well as an evaluation of viable \npathways of exposure to the organism. This study clearly shows that pre-release condors have an \nisotopic signature that is significantly different from lead in free-flying condors in central \nCalifornia, whereas the blood lead isotopic signature of the majority of free-flying condors ",
"approached or matched the isotopic signature of lead ammunition collected from the condors’ \ncentral California range. Lead ammunition is, therefore, the principal, and only plausible, \ndocumented source of lead exposure in condors. The Church et al. (2006) study underwent \nrigorous scientific peer review in the publication process for Environmental Science and \nTechnology. This publication is an American Chemical Society journal and one of the top-ranked \nscientific journals in the areas of environmental chemistry and environmental toxicology",
"Here's the actual article, with all its data: ",
"http://www.peregrinefund.org/docs/pdf/research-library/2006/2006-Church-lead.pdf"
] |
[
"How is shocked quartz considered evidence of mass extinctions?"
] |
[
false
] |
The Permian-Triassic extinction is what I have in mind here. According to what I've found from google searching this extinction event, shocked quartz discovered in Australia and Antarctica are huge indicators that it was caused by a meteor impact. How are deformed rocks that indicative of something like this? Is there more convincing evidence (fossil record) that I haven't found? Thanks in advance for any help!
|
[
"A couple of things:",
"The Permo-Triassic extinction is a fact, we do not need shocked quartz to postulate it's existance. We lost in excess of 90% of marine species at that time (source 1: (",
"https://194.44.198.33/faculty/geology/phis_geo/fourman/library-Earth/New-library/How%20to%20kill%20(almost)%20all%20life%20the%20end-Permian%20extinction%20event.pdf",
"), ",
"source 2",
", ",
"source 3",
"). ",
"But what we ",
" is a mechanism to account for why and how it happened. What processes led to that extinction? Our understanding of mass extinctions has grown quite a lot in the last 25 years, and we've found several factors (glaciations, ocean acidification, loss of continental margins, etc.) which can play a role. One of them is large impacts.",
"So, one of the questions abouth the P-T event is whether there was a large impact associated with it. Since 2/3 of Earth is ocean, odds are we would have no trace of the crater caused by such an event, so we look for mineralogic indicators. There are a few of these, and shocked quartz is one of the most important. At this point, it is important to stress that \"shocked quartz\" in not mere deformed quartz (which is omnipresent). Shocked quartz is a very specific type of deformed quartz, formed at ultra-high pressures but relatively low temperatures. It is not formed at depth, but can only be the result of shock-induced metamorphism in near surface conditions such as meteor impacts of nuclear testing sites. It can also be accompanied by 2 high pressure / medium temperature quartz polymorphs: coesite and stishovite. You can find a primer on shocked quartz ",
"here",
". It is Worth pointing out that shocked quartz has been found at the PT-boundary; so have ",
"fullerenes",
" which also suggest a high pressure lowish temp event.",
"The advantage of shocked quartz and high pressure quartz polymorphs is that they can scatter in the ejecta of a large impact and, since they preserve well (quartz is quartz after all, tough mineral) be recognised thousands of kilometers from the crater in ejecta layers. They thus can provide solid evidence for a large impact in a usefull way with the help of a favorable geochronological setting.",
"Now, the PT-extinction was the largest extinction event we know of. Life as we know it, or at least creatures some degree of complexity, came within a hairs-breadth of dissapearing without issue. Current understanding is that it was an extraordinary event where several factors cumulated on top of one another and competed with one another, leading to a collapse in biodiversity (",
"review",
"). Amongst the assorted smoking guns we've found: loss of platforms through continental convergence, ocean acidification (possibly caused by volcanism), climate change, and a major impact. Assessing the relative contribution of each one of these factors and others is a difficult task and the subject of considerable reasearch."
] |
[
"It's worth adding that one of the other principal candidates for a cause for the P/Tr extinction is the eruption of the Siberian Traps through large deposits of carbonate. The PNAS paper that ",
"/u/Gargatua13013",
" linked to as a review of biodiversity collapse is critical of this hypothesis (or at least critical of a volcanic cause), but later work has made the Siberian Traps a strong contender as the primary driver for the extinction event, ",
"e.g. this review paper from a few years ago",
". "
] |
[
"There is a lot of sourced data in the reply I gave, you may have a look at the first 3 sources which are general papers on the event.",
"The evidence we have for the extinction event comes from counting the species on either side of the PT-boundary. We see through direct observation a loss of in excess of 90% of marine species and 70% of land vertebrates in a geological eyeblink. It's quite a direct exercise, essentially we've compiled lists of the fauna we observe bed by bed across the horizon and we see that the PT-horizon was the site of a stupefying loss of biodiversity at this one moment in time. The PT extinction is an observed fact, not a hypothesis.",
"You can find sources documenting and commenting on that loss in biodiversity here:",
"http://www.sciencemag.org/content/206/4415/217.short",
"http://www.sciencedirect.com/science/article/pii/0031018273900114",
"http://palaios.sepmonline.org/content/16/1/95.short",
"https://194.44.198.33/faculty/geology/phis_geo/fourman/library-Earth/New-library/How%20to%20kill%20(almost)%20all%20life%20the%20end-Permian%20extinction%20event.pdf",
"http://www.cornellcollege.edu/geology/courses/Greenstein/paleo/Permo_Tr.pdf",
"http://www.jstor.org/stable/2400143?seq=1#page_scan_tab_contents",
"Where shocked quartz comes in is in looking for evidence for the possibility that one of the mechanisms we have seen in other extinctions also participated in this one. We ",
" there was an extinction. What we ",
" know is the relative importance of the mechanisms which may have caused it."
] |
[
"Is salt sterile?"
] |
[
false
] |
All I know is that salt has a way of drying out and preserving things from bacteria and the like. So, is the surface of salt itself free of any bacteria?
|
[
"I'm sure the surface of salt is devoid of free-living bacteria, but there are many other forms of life to consider when thinking of sterility. Spores, viruses, prions, etc... could all live on the surface of a salt crystal."
] |
[
"You are correct in your assessment of life, but it should be noted that sterilization is more broadly defined than that. To offer a more thorough explanation for anyone who might not understand. ",
"Life is defined in biology as anything which satisfies most or all of the these states:",
"Homeostasis: Regulation of the internal environment to maintain a constant state; for example, electrolyte concentration or sweating to reduce temperature.",
"Organization: Being structurally composed of one or more cells — the basic units of life.",
"Metabolism: Transformation of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.",
"Growth: Maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter.",
"Adaptation: The ability to change over time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's heredity, diet, and external factors.",
"Response to stimuli: A response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is often expressed by motion; for example, the leaves of a plant turning toward the sun (phototropism), and chemotaxis.",
"Reproduction: The ability to produce new individual organisms, either asexually from a single parent organism, or sexually from two parent organisms.",
"Viruses are nothing but capsules of RNA and do not maintain an internal environment, are not composed of cells, do not metabolize, do not grow, do not show any response to stimuli, and cannot reproduce sexually or asexually with their same species. For this reason they are considered replicators, and not life.",
"Likewise prions are simply misfolded proteins (according to current theories which are still under active debate) that through some action cause other proteins of that same type to become malformed and misfolded within an organism. Prions are no more alive than any other strand of protein would be and satisfy none of the descriptors for life. ",
"Sterilization however is defined as ",
"a term referring to any process that eliminates (removes) or kills all forms of microbial life, including transmissible agents (such as fungi, bacteria, viruses, spore forms, etc.) present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media.",
" Because both prions and viruses are considered infectious agents, any surface, compound or fluid containing them cannot be described as sterile. "
] |
[
"As I have said previously, your perspective is a valid one and viruses straddle the edge of what is life and what is not. It was ultimately decided that they are not alive and nobody here has the authority or means to change that definition. It is simply a definition though, and it changes nothing in regards to the behavior or study of viruses. ",
"It's frustrating to have to end the debate there by simply saying that \"it was decided that it was one way therefore that's the way it is\", but it is at its core an argument over semantics. ",
"French Nobel laureate André Lwoff once said:",
"“Whether or not viruses should be regarded as \norganisms is a matter of taste.”",
"And I think for the time being that is how it will remain. "
] |
[
"Could the universe be full of intelligent life but the closest civilization to us is just too far away to see?"
] |
[
false
] | null |
[
"Thousands of years ahead? Try billions of years.",
"A solar system capable of supporting life needs to be formed from the material from a dead star. Most stars last for several billion years, but really massive stars can have lifespans of only a few million years. The universe had 9 billion years to develop before our sun came along. Our sun has been here for a bit over 4.5 billion years (just a little older than the Earth). Our sun is believed to have formed partly from the remnants of a nearby supernova. This may have been due to the explosion of a short-lived massive star. The oldest star we know of was born when the universe was around half a billion years old, and the Milky Way galaxy has been around for about the same amount of time. It is reasonable to assume that it is possible for a new solar system to form out of the residue within a similar time frame. That leaves us with 8 billion years for a really massive star to form, go through its entire life, and end with a supernova. That's entirely possible, because as I said, really massive stars can have lifespans as short as a few million years. The bigger the star, the shorter it's life.",
"It took our solar system 4.5 billion years to form intelligent life, but even there, there's some leeway. It took Earth 800 million years, but it's conceivable that some other planet, with slightly different conditions could develop life a hundred million years or so quicker. Once the first cells formed, it took about 2 and a half billion to 3 billion years before multicellular organisms appeared. I don't know much about the biology, or the probabilities of it happening, but is it not possible that this could have happened on another planet maybe half a billion, or even a billion years quicker? Mammals lived under the dinosaurs for almost 150 million years. Imagine if the dinosaurs went extinct 100 million years sooner? A 3 billion year old planet could possibly reach our level.",
"There's so much leeway here. There's no reason a species of our technology level could not have existed 5 billion years ago, more than 5 billion light years away, and we just can't see it yet."
] |
[
"There's no reason a species of our technology level could not have existed 5 billion years ago",
"I guess academically I knew this, but seeing it explicitly written and then considering it is overwhelming."
] |
[
"I think if you haven't managed intergalactic colonization and domination after 5 billion years it's safe to say your species hasn't really been trying."
] |
[
"Is storing nuclear waste substantially more dangerous from storing mercury?"
] |
[
false
] | null |
[
"Nuclear waste is much more dangerous than elemental mercury. That being said, yes, people are very ignorant and overly afraid of nuclear waste storage."
] |
[
"Nuclear waste is much more dangerous than elemental mercury.",
"How do you quantify that? As a totally uninformed guess, I would think that more health damage is being done by mercury than by nuclear waste, if you sum it up.",
"Also, nuclear waste has the nice property that you can detect it trivially with a Geiger counter, which is a very nice property for a poisonous substance to have. Mercury does not that a similar trivial detection method. So to ask the rhetorical question: why are people panicking over nuclear waste, and not mercury?"
] |
[
"Why would you think that? What is that assumption based on?",
"Nuclear waste is a highly radioactive cocktail of many elements and compounds, some of which are very toxic to humans."
] |
[
"Do protons and neutrons also have probability clouds?"
] |
[
false
] |
And any other particle for that matter
|
[
"There's uncertainty in position and momentum for all particles, so yes. My modern physics professor had an assignment where you calculate the uncertainty in position of a Buick. It's just that the probability cloud for a Buick is so small that it's silly to even think about."
] |
[
"So basically it's a normal physics question."
] |
[
"It's one of those ridiculous exponential answers, where the answer is so large (or in this case, small) that it outnumbers the atoms in the universe."
] |
[
"Is it more economical to fly against the rotation of the earth on its axis?"
] |
[
false
] |
Let's say you're in the middle of USA and you want to fly exactly to the other side of the earth. Would it take less gas flying against the rotation of the earth? Why/why not? I can't seem to wrap my head around this topic.
|
[
"You might be thinking that you would have to fly less if the Earth was moving underneath you while you are flying towards a location, and that thought is correct: when planning flight routes airlines take into account the rotation of the Earth.",
"For most practical reasons though, the effect is completely negated by strong high-level winds at the cruising altitude of most airlines. At the latitude of the US the dominant wind direction is from west to east, which means it would take a lot of extra gas to fly into the wind. Depending on where you start it would be faster to go the other way, but really it would be fastest to go over the North pole."
] |
[
"Thank you for the explanation. :)"
] |
[
"I want to understand the first part, having to do with rotation. Since the plane starts with the same velocity of the Earth, how could rotation make a difference?",
"If I'm on top of a train going 20 mph and leap forward five feet, then jump with the same strength in the other direction, wouldn't I go five feet again?"
] |
[
"Why do bubbles form on the walls of a water bottle when you first fill it up?"
] |
[
false
] |
When I fill up my water bottle, there's a ton of bubbles and they all seem to stick to the walls of the water bottle. I assume they are air that is trapped as the water is being poured, and they eventually dissipate. Why are they so attracted to the wals of the water bottle though? Thanks!
|
[
"They form around ",
"nucleation sites",
". ",
"There was a show about that reaction you get from adding Mentos to Coke (Mythbusters? I can't remember) explaining it quite nicely."
] |
[
"The plastic bottle isn't perfectly smooth. There are microscopic pockets of air along the walls of the bottle. As bubbles form, they attract each other, Sort of like watching water roll down the window on a rainy day. So the question isn't necessarily why the are attracted to the walls, but what keeps the air in place along the walls of the bottle."
] |
[
"What kind of water are you talking about? tap water drinking distilled? \nTap water has carbonic acid, that is just CO2 that is dissolved in the water. If you de-gas the water there may be less bubbles. The porous inside of your water bottle (presumably plastic) is allowing the dissolved gasses to attach to the walls, release the water molecule and then let the gas buildup. The gas bubbles that are stuck to the walls need to 1) get big enough to escape the walls or 2) receive a large enough shock to get them to release on their own."
] |
[
"Why does the chloralkali process with graphite anodes create furans (dioxin-like)?"
] |
[
false
] |
Are dioxin like furans (PCDF) formed if saltwater comes in contact with electricity and steel like in a phone charger or computer port? Are they formed in school experiments with electrolysis of brine?
|
[
"I’m a Chemical Engineer with years of chlorine and reactive metal experience. ",
"In general, chlorine being formed at the graphite anode corrodes the anode. The corrosion products are “chlorocarbons”. The most abundant product is carbon tetrachloride. ",
"The whole range of saturated chlorocarbons is formed. The higher the molecular weight the smaller the quantity. ",
"For this reason most chlorine makers use dimensionally stable anodes. (Not graphite). ",
"Makers of reactive metals (lithium, sodium, potassium, and near reactive metal magnesium) still use carbon anodes that generate chlorocarbons. ",
"Since brine is used in chlorine production, in theory carbon anodes in sea water should make chlorocarbons. But I’ve got no experience trying it."
] |
[
"Thanks. Will any chlorine, carbon and anode combo make furans though? Is there something unique about the graphite, like the aromatic structure, required for PAH and then PCDF formation?"
] |
[
"Most of my work was in the 400-1000 C range. Any water was interstitial water in the salt crystal. I never found Furans. Did make a bunch of phosgene. But furans are pretty volatile and flammable. ",
"Carbon tetrachloride was in the 50 ppm range. Aromatics were primarily hexachlorobenzene (ppb levels). Roughly each carbon reduced the likelihood exponentially. ",
"We used graphite because it could withstand the operating temperatures and coincident current density (crazy amperes). Graphite quality mattered. Nongraphitized carbon would degrade rapidly. ",
"Standard chlorine production runs much cooler with brine. Electrolyzed water is a byproduct. Outputs are chlorine, sodium hydroxide, and hydrogen. Carbon tetrachloride was a big concern. I imagine there were many other byproducts, maybe furans. But any paper I’ve read focused on carbon tetrachloride. Carbon tet makes the chlorine unsellable. So virtually all chlorine production in North America uses dimensionally stable anodes. These are carbon free."
] |
[
"how can you tell direction in outer space?"
] |
[
false
] |
I was just thinking about how if youre on earth you can head in one direction and end up back where you started. also our compass only has 2-axis. if you were in outer space you'd have a lot more possiblities for direction. Say you have a friend on mars, how the hell do you give them directions back to earth (keep in mind they could be on any side of the planet so telling them to start head towards the stars wouldn't help.)
|
[
"You need to establish a coordinate system. When you talk with your frind on mars about directions, it would be a good idea to take the sun as the center of a ",
"spherical coordinate system",
". Then you can tell him to fly towards a point in that coordinate system."
] |
[
"This is the best answer I have read so far:",
"There's nothing special about directions in space as such (maybe if you get into general relativity but I don't suppose you meant that). Mars is right in the direction where it seems to be. What I think you're asking is how the orbits work. That is, if you are on the Moon and want to go to Mars, with a spaceship that's at least somewhat realistic, then you of course don't point your ship towards Mars and just go.\nYou might be thinking that things in space go in a straight line so to get from A to B, you just point to B and go. And that's true if there's nothing else in space but everything in the solar system is in a big gravity field. So things don't go at all in straight lines, they go in what are called conic sections[1] . There are three kinds of conic sections, ellipse (the circle is a special case of this), hyperbola and parabola. An object that's escaping the system is either on a parabolic (if exactly at the escape velocity) or a hyperbolic trajectory (if greater than the escape velocity). Everything else is in an elliptic orbit and we'll focus mostly on them now. An important thing to keep in mind is that if you don't use your engines or get close to another planet or moon or get inside the atmosphere of something, then you will stay in the same orbit forever. It doesn't spiral down to the object you're orbiting. It doesn't circularise itself. After a full orbit you return to the same spot you left from and at the same speed.\nOrbits have a couple important properties. First the eccentricity[2] . This means how circular the orbit is. Eccentricity 0 means that the orbit is perfectly circular, values between 0 and 1 mean more and more elliptic orbits as the eccentricity gets closer to 1. Eccentricity 1 is a parabolic orbit and values higher than 1 are hyperbolic.\nThe other important thing is altitude, or radius. If the orbit is perfectly circular then altitude is clear. If it's an ellipse then the altitude will vary at different points of the orbit and it's better to use something else. One way is to specify the radius at the lowest and highest point, called the periapsis and apoapsis[3] , respectively. Or names such as apogee and perigee are used if you're on Earth orbit, or aphelion and perihelion on Solar orbit or a whole lot of other stuff for other planets but they all mean the same thing. Another way to specify the same thing is to use the semi-major axis[4] . It is the \"radius\" of the ellipse at the most elongated point. Note that it's measured to the middle of the ellipse, not to the central body you're orbiting. In essence this is a number that roughly describes the radius of an elliptic orbit. For a circular orbit it is the actual radius.\nThere are other things too that relate to how the orbit is aligned three-dimensionally. Like is it an orbit that goes over the poles or one that goes along the equator and such things. But we best keep things two dimensional for now so we don't need them.\nAnd when thinking of moving around in the solar system, or just between the Earth and the Moon, or even just between different Earth orbits, don't think at all about going in a straight line or maintaining your velocity or in what direction the gravity is and how it'll affect your velocity. Just think what your orbit is, that is the eccentricity (how elliptic it is) and what the altitude is. And of course, where on the ellipse you are now. Your velocity, both direction and magnitude, are fully determined by your orbit and your location in it. An object on a specific orbit always has the same velocity at the same point regardless of the mass of the object or anything else (it does depend on the mass of the central body though). Or when you intend to change orbits think of it the other way round, how your changed velocity will determine your future orbit.\nSo let's start with a circular orbit around the Earth. You make some kind of a change in your velocity by using your engines. The orbit you get to will be one that goes through the point where you used your engines. That should be intuitive since your current location must of course be a point of the orbit. So if you want to get to an orbit that doesn't intersect your current orbit, then you will necessarily have to do at least two engine burns. First to get to a temporary orbit that intersects your current orbit and the target orbit, this is called a transfer orbit. And then a second engine burn at the intersection of the transfer orbit and the target orbit to get to the target orbit.\nSo let's say we want to get from a low Earth orbit to a geostationary orbit which is a much higher orbit. They are both circular and of course do not intersect. In general circular orbits of different radius can naturally never intersect. First we want to turn our low circular orbit into an elliptic orbit that will intersect the higher geostationary orbit. To do this we accelerate along our orbital motion. That means tangential to the circle. Or parallel to the surface of Earth. You'll get a long way by just accelerating along the motion (prograde) or opposite the motion (retrograde) and never accelerating in any other direction. Accelerating prograde will always increase the altitude at the opposite side of the planet. In other words it increases the semi-major axis and in this case it also increases the eccentricity, that is makes the orbit more elliptic. We should burn the engines until the altitude of the orbit at the opposite side is just at the height of geostationary orbit, anything that intersects the geostationary orbit would get us there but any more is a waste of fuel. After that we just wait until we move along the orbit to that point, that is the point where our transfer orbit and the geostationary orbit intersect. There we'll do another engine burn to turn our transfer orbit into the desired geostationary orbit. This will again be prograde (along the orbital motion) increasing our speed and again raising the altitude at the opposite side of the planet. Again the semi-major axis is increasing but now the eccentricity is decreasing and our orbit is becoming more circular. When the altitude at the opposite side is also at the geostationary orbit altitude, we will be done and are on a circular geostationary orbit.\nWhat we just did is a Hohmann transfer[5] and it's the basic building block of all orbital transfers. You can drop your orbit by doing the opposite, first burn retrograde (against the motion to deccelerate) and then again retrograde at the opposite side. To get to the Moon you do pretty much the same thing but raise the orbital altitude all the way to the orbit of the Moon and just time it so that the Moon is there when you get close to its orbit. Only thing that'll be a bit different is that the gravity of the Moon will become significant at some point and you need to start thinking in terms of orbiting the Moon and not the Earth. Or to get to the Mars it's again the same thing but now we're orbiting the Sun and not the Earth. So you have to accelerate along the orbit around the Sun to raise your solar orbital altitude. You should try to do this when your orbit around the Earth goes the same direction to take advantages of your orbital speed around the Earth.\nIf you want to get an intuition about orbits in a fun way, I highly recommend trying the Kerbal space program[6] game.",
"http://www.reddit.com/r/askscience/comments/vmjok/how_do_directions_work_in_space/c55si1n"
] |
[
"It sounds to me like you know better (\"a lot of wasted energy\")... ",
"For the OP's sake, and anyone else wondering... No. It isn't a straight shot. When you leave one planet you orbit around the Sun. So your path to get from one planet to another involves you working your way around the Sun. On top of that, the planets are moving. Just like shooting a moving target with an arrow, you don't aim right at the target or it won't be there when the arrow arrives.",
"You ",
" technically take a straight path. But, yes, the energy requirements to do such a thing are absurd."
] |
[
"How vaccines work, specifically why do we need boosters?"
] |
[
false
] |
[deleted]
|
[
"They are basically an incomplete tutorial for your body to store on how to deal with a certain issue , it is complete enough for your cells to get the basic idea and instructions on how to deal with the issue but it is incomplete enough to never allow your cells to learn how to fully utilize the powers of the instructions! "
] |
[
"You can think of antibodies as an ",
". When the arrest warrant is released, it calls in the law enforcement to take out the bad guy. The antibodies \"tag\" the pathogen in the body, which then calls in other immune cells (law enforcement) to kill it.",
"When we receive vaccines, what are trying to do is make the body produce antibodies (aka arrest warrants). The antigens in the vaccines convert ",
" B-cells into ",
" B-cells. Once we have the memory B-cells ready, the memory B-cells then convert into ",
". The plasma cells are what makes the antibodies. ",
"Plasma cells can live up to days, weeks, months, etc. but the point is that the plasma cells go away after a certain period of time. What remains in the body is the memory B-cells - it will always remain in your body. Next time the pathogen enters your body, your memory B-cell can quickly turn into many plasma cells, to release those antibodies. The reason why we need boosters is to stimulate B-cells to convert into plasma cells so that it can produce antibodies. "
] |
[
"Maybe this ",
"graph",
" will help. The first exposure causes plasma cells and antibodies to be made; the second exposure causes even a stronger response with longer-lived plasma cells and antibodies with higher affinity. ",
"As to why some vaccines require boosters and some don't I'm not really sure. I'm under the impression that vaccines that are live-attenuated do not require boosters, but the conjugate vaccines do. "
] |
[
"If you touch a live wire at a rate equals to the line frequency (i.e. 50 Hz) such that the touching is synchronizeed with zero crossings, will you be conducting electricity?"
] |
[
false
] | null |
[
"If you have an load and you connect it to AC for very brief periods of time during which the voltage across the leads is zero, no current will flow. Your body would not be able to achieve that type of precision of movement, but an electrical component like an IGBT or MOSFET could."
] |
[
"Electronics can quite easily and do match this frequency.\nThis is done to reduce switch-on currents - basically the load \nis turned on at the zero crossing, this results in a steady rise of the current instead of a steep step, which causes noise in the power grid."
] |
[
"To answer your question in different terms, voltage is also referred to as potential. Just as an object on the ground has no potential energy, an electrical wire with no voltage has no potential. So at 0 volts there is no potential and therefore you would not conduct electricity. You would have to be really accurate to match the frequency so I don't recommend trying it."
] |
[
"Is it possible to set up a series of mirrors to reflect light in a long enough path so that a person can visibly notice a difference from the point the light is turned on, until the end of the path?"
] |
[
false
] |
I always wondered if you had a source of direct light (a laser or something similar) and set up a series of probably thousands (or more) mirrors, could you tell the difference from when the light is turned on? As in, when the light is turned on, is there a distinguishable difference in time until the light reaches the last mirror? I would think that this is theoretically possible since light has a finite speed. I guess another way to phrase this would be: If the path is long enough, is it possible to see the light travel from point A to point B?
|
[
"...meaning it effectively \"goes slower\". The distinction is real but not relevant to the current discussion, Captain Pedant."
] |
[
"Yes, but not very easily. You would need to run the light through a fiber optic cable wrapped 8 times around the planet to get a delay of a single second. "
] |
[
"Yes. A good example is bouncing a laser off of reflectors left by the Apollo astronauts on the moon. It takes the light about 2 seconds to reach the Moon and 2 seconds to come back for a round trip of 4 seconds.",
"One of the earlier experiments to determine the speed of light involved sending a flash through a rapidly spinning wheel with tiny slits cut in it and bouncing it off a mirror several miles away. By the time the light returns and comes back through the slitted wheel the wheel has had a chance to turn every so slightly and the returning light will come through a different slit than the one it left from."
] |
[
"In a post-collapse scenario, would most nuclear reactors eventually melt down?"
] |
[
false
] |
I'm imagining a scenario where suddenly, all nuclear engineers have disappeared and there is no longer anyone who can man the reactors. I understand many Gen III and later reactors have passive safety systems, but I believe most operating reactors lack these systems. Does this mean a likely nuclear catastrophe at most operating sites? Even if a meltdown was avoided, would the spent fuel pools pose a serious risk? Thank you.
|
[
"In the normal likely collapse, the grid would go first. The reactors would 'trip' because there would be nothing to absorb the power. Excess heat would dump into a suppression chamber or condenser until the core cooled. The unit would then wait indefinitely until capable people could repair the grid and restart the reactor. With failing security, terrorists, robbers, or superstitious people might try to compromise the integrity of the installation. "
] |
[
"The key thing is you need manual action to cool the reactor down to cold shutdown (mode 4 for BWRs and 5 for pwrs). ECCS and safety systems do not accomplish vessel cool down automatically. And as you've said, once you lose active cooling it's only a matter of time before the vessel boils again. Even years later. "
] |
[
"Rcic/HPCI in bwr designs and turbine driven aux feedwater in most PWR designs utilize steam to drive injection systems. These systems use steam from the reactor/steam generator (bwr/PWR respectively) along with dc battery power for valve control. For pwr plants, I believe the turbine driven aux feed pump (tdafp) exhausts its steam to atmosphere. It can do this because it uses non radioactive steam, but it means you are limited on how much clean water inventory you have available. Additionally you have limits based on how long your decay heat supports natural core circulation. ",
"BWRs on the other hand discharge their steam to the suppression pool. Once the suppression pool heats up, containment pressures increase, which causes reactor pressure to increase, and causes rcic to have to inject against greater reactor pressure. Eventually pump flow is so low that the pump can no longer cool itself sufficiently and the pump fails. This is most likely what happened with Fukushima unit 2s RCIC system based on available reports and data, over 6 hours reactor pressure increased past 1100 psi (nominal is around 1000), and rcic flow tapered off until the pump failed. ",
"In both cases, without electricity or auxiliary systems, your turbine driven cooling pumps will fail. ",
"Im working on a rcic control system redesign right now and would be willing to discuss if you have any specific questions. For Fukushima data, I don't have access to my links right now, but it is linked off of the nuclear engineering forums on physicsforums.com and comes from the \"national diet of Japan\" report in the appendices. I will try to locate the source (on my iPhone so difficult)"
] |
[
"Do electrons still bounce around inside superconductors?"
] |
[
false
] |
I know that in a regular conductor the electrons you push in at one at one end are not the same electrons you get out the other end. They can bounce between atoms within the conductor for thousands (millions?) of years before finally making it out the other end. Does that behaviour still apply in superconductors, or are the electrons able to travel directly from one end of the conductor to the other, without all that bouncing around?
|
[
"Yes, they still bounce around, but they do it as ",
"Cooper Pairs,",
" trading a metal-lattice Phonon (quantum of thermal vibration) as they go.",
"In resistive metals a moving electron does work upon the crystal lattice and slows down, while the lattice then radiates away vibrations as heat. In other words, electrical resistance is a sort of \"electron friction.\"",
"Semi-classical ELI5 version: in superconductors, one electron slows down and generates a heat vibration, while a nearby electron absorbs it again and speeds up. The second electron swallowed the entire thermal vibration, with none escaping. So, on average the population of electrons isn't being slowed, even though it's still generating lattice vibrations. Or, imagine two electrons connected by a spring, and \"inchworming\" their way along, where all the heat-vibrations stay in the connecting spring and aren't radiated away to the environment."
] |
[
"So do these Cooper Pairs bounce into and interact with other Cooper Pairs, like single electrons in a non-superconductive material, or do they simply \"inchworm\" through the entire material pair by pair?"
] |
[
"Ok. So the first thing you should realize is that electrons are indistinguishable. We have no way of knowing if the electrons you push in at one end are the same electrons that you get out the other end, and it isn't even a meaningful question since electrons are indistinguishable.",
"But this picture of electrons bouncing around and moving slowly is more or less correct on average -- the average drift velocity of an electron is much slower than its instantaneous velocity due to scattering.",
"Superconducting electrons do not scatter. Or at least, not significantly. If you start current flowing through a superconducting ring, it will keep flowing for millions of years or until a trucking strike prevents you from receiving your monthly shipment of liquid nitrogen/helium to keep it cold.",
"Having said this, at finite temperatures only a fraction of the electrons in a material will be in the superconducting state. These will naturally dominate transport, but realize that there is a fraction of normal-state remaining. The fraction of remaining normal state continues to decrease with temperature."
] |
[
"Did early humans organize into family units like modern humans do?"
] |
[
false
] |
Did early humans have families like what we know now? with parents and children living as a group?
|
[
"The only real answer is that we can't really know. ",
"Kinship",
" structures range wildly all over the world. The only thing one could say with any amount of confidence is that that children were taken care of to some degree, but by who we have no idea."
] |
[
"Yep. The short answer is: \"we don't know\".",
"Based on archaeological evidence, the size of a typical \"band\" of people, a group of humans who foraged a territory together, varied significantly. Some bands were as small as 4-6 people. Others were as big as 100 people or more. It probably depended upon what they were eating, and what kind of hunting or foraging was available. People who mostly hunted/trapped small game and foraged in a resource-poor territory tended to live in small bands. Groups that occupied rich coastal communities lived in larger bands.",
"It's tempting to assume that a small band of 4-6 people probably consisted of a nuclear family - a couple and their children, with perhaps a grandparent or two tagging along. If this were true, you could possibly extrapolate that to larger groups and say they were groups of such nuclear families living together.",
"However, we have no way to prove this, so the answer remains \"we don't know, we can only guess\"."
] |
[
"From various lines of evidence, we know that species as early as Homo heidelbergensis hunted in packs. This suggests a strong social structure, possibly comprised of at least one \"family\", although not necessarily a traditional modern family. If so, and if you consider H. heidelbergensis to be an ancestor of H. sapiens, then the earliest H. sapiens would recognize an organized family unit. I know that this is a lot of speculation on my part, and for that I apologize. As Ckoo said, we don't know for sure."
] |
[
"How long will it tale geologic processes to erode Mount Rushmore?"
] |
[
false
] |
I'm not sure what type of rock the mountain is made of but how long will it take for the faces to become unrecognizable as an unnatural modification to the landscape?
|
[
"I ask this because I feel in 50 to 100 thousand years our written history mat be lost, but the mountain will still exist. How will it but interpreted."
] |
[
"The mountain is granite, which is pretty tough. according to the ",
"National Park Service",
", it is eroding at the rate of one inch per 10,000 years. So, they should still be recognizable for a long time yet."
] |
[
"That number is waaaay too low. That erosion rate would assume that in the entirety of earth history (4,500,000,000 years) you could erode just 11.43 km of granite.",
"While that erosion rate may be true of this particular window in time, over a period of 10,000 years the climate and environment can vary considerably. In a glacial period, for example, that erosion rate might easily be measured in meters per century. Similarly, a simple increase in rainfall could increase that 1 inch per 10 kyr value by an order of magnitude or more. ",
"Vegetation growth can easily speed erosion, and with cliffs the far more important issue is episodic collapse; while the weather might only shave off a few microns a year, every few centuries or millenia the cliffs fail through fracture and can lose tens of meters in a few seconds."
] |
[
"How much would it take to throw the earth out of a safe orbit?"
] |
[
false
] |
[deleted]
|
[
"anything big enough to significantly alter our orbit would be big enough to kill every last one of us. ",
"And that line about if we were ten feet closer/farther is utter nonsense. "
] |
[
"Correct, and correct.",
"Impact of a comet weighing 0.0000001 times the Earth's mass would kill all of us, while barely altering the planet's orbit."
] |
[
"A rogue planet passing near Earth would alter our orbit without killing everyone."
] |
[
"Why can our eyes precisely lock onto objects, but can't smoothly scroll across a landscape?"
] |
[
false
] | null |
[
"Eye movement is controlled by a couple different mechanisms that are essentially reflex mediated. The first is saccadic movement. This is the fast, voluntary movement you use to 'lock onto' an object. Saccades can rotate the eye up to 500",
" per second. The movement of the eye is so fast that there is a phenomenon called saccadic masking where the brain ignores visual input during the saccade to avoid blurring of the vision during eye movement. Yes, you go temporarily blind when you move your eyes with saccadic motion. Saccades are controlled by the frontal eye fields and the superior colliculus allowing for fixation of the eyes on a point. ",
"The next type of reflex/eye movement is called smooth pursuit. The exact neuronal circuitry for this is still up for debate, but we do know that the cerebral cortex, cerebelleum, and superior colliculus are involved. This eye movement allows you to track a moving object without the need for saccades. This reflex also requires input from the pre-frontal cortex, and is often suppressed under the effects of alcohol. This is why a sobriety test involves tracking a finger across the visual field; under the influence of alcohol the brain cannot perform smooth pursuit so the brain resorts to saccades, resulting in what looks like nystagmus. ",
"The next type of eye reflex is the vestibular-occular reflex. This mechanism takes orientation/acceleration input from the inner ear and processes the data so that as your head moves, your eyes move in the opposite direction. This is why your vision doesn't jump around when you walk or move. You can try it by nodding your head up and down: your head moves, but your eyes move opposite, so the resulting visual image appears stationary. It even works with eyes closed.",
"So in summary, there are three main control mechanisms for eye movement, saccades, smooth pursuit, and the vestibulo-occular reflex. Saccades allow for precise fixation, smooth pursuit allows for tracking a moving object, and the V-O reflex reduces signal noise from head movement. ",
"E: Thanks for the gold, really cool. I just got home and saw this, I'll try answer the unanswered questions.",
"Just a couple points of clarification: saccadic masking takes the blur out and replaces it with the end image after the saccade. You don't actually go blind, your brain still 'sees something'. This is why if you saccade onto the second hand of a clock it can seem to pause longer than a second. Apologies for the unclear wording above. And to everyone asking about 'why' vs 'how' these reflexes work/exist I'll just leave you with the words of ",
"Richard Feynman",
". "
] |
[
"The first is saccadic movement. This is the fast, voluntary movement you use to 'lock onto' an object.",
"Interestingly, saccadic movement is a fine motor skill that can be trained. Educators are increasingly looking into the impact of saccadic movement on reading, such as:",
"Background. Eye movements are necessary for the physical act of reading and have been shown to relate to underlying cognitive and visuoattentional processes during reading. The purpose of this study was to determine the effect of saccadic training using the King-Devick remediation software on reading fluency. Methods. In this prospective, single-blinded, randomized, crossover trial, a cohort of elementary students received standardized reading fluency testing pre- and posttreatment. Treatment consisted of in-school training 20 minutes per day, 3 days per week for 6 weeks. Results. The treatment group had significantly higher reading fluency scores after treatment (P < .001), and posttreatment scores were significantly higher than the control group (P < .005). Conclusion. Saccadic training can significantly improve reading fluency. We hypothesize that this improvement in reading fluency is a result of rigorous practice of eye movements and shifting visuospatial attention, which are vital to the act of reading.",
"The present study examined thevisual scanning hypothesis, which suggests that fluent oculomotor control is an important component underlying the predictive relationship between Rapid Automatized Naming (RAN) tasks and reading ability. Our approach was to isolate components of saccadic planning, articulation, and lexical retrieval in 3 modified RAN tasks. We analyzed 2 samples of undergraduate readers (ages 17–27). We evaluated the incremental contributions of these components and found that saccadic planning to nonlinguistic stimuli alone explained roughly one third of the variance that conventional RAN tasks explained in eye movements registered during text reading for comprehension. We conclude that the well-established predictive role of RAN for reading performance is in part due to the individual ability to coordinate rapid sequential eye movements to visual nonlinguistic stimuli.",
"We review the literature on children’s vs. adults’ eye movements during reading. We test two theories of these differences using a model of eye-movement control. Our simulations suggest that linguistic proficiency accounts for these differences. Our conclusion is discussed in relation to development, aging, and reading skill. "
] |
[
"I would add to this that smooth pursuit is usually difficult to do without a target. Normally, we do not need to slowly scan over a static scene. We can get more information from a static scene by making saccadic movements and getting disparate parts of the scene to fall on the fovea. However, smooth pursuit can be trained, and you can learn to smoothly move your eyes across a static scene / without a target to track. ",
"The exception to this is what happens when a moving objects disappears (e.g. goes behind an occluding surface). In that case, we are able to smoothly move our eyes along the extrapolated trajectory of the object, even though there is no longer a target there. However, eye velocity gradually slows down and you often have to make a big saccade to the object when it reappears (or else, if you can expect where it will reappear, you make a big saccade to that location and wait for it to appear there; that is, you either saccade too late (catch-up) or too early). This effect increases with the time that an object remains invisible.",
"In addition, even when tracking moving objects with smooth pursuit, we are looking slightly behind the object and often have to make \"catch up\" saccades to jump our eyes forward along the trajectory. ",
"Edit: see below for a longer discussion of some of these points + citations and demos."
] |
[
"When I look at a star, what exactly am I seeing?"
] |
[
false
] |
By my understanding, they are basically all like our sun, albeit in different stages, but am I seeing them in the past?
|
[
"The most common type of stars are red dwarves (M type stars). However they are smaller than our Sun (~0.1 to ~0.5 solar mass) and much dimmer. Therefore many of them are not easy to spot with a naked eye unless they are fairly close. More massive K stars and even more massive G stars (like out Sun) are less common, but much brighter and therefore more easily seen on the night sky. Bigger, brighter stars are even more rare, but again much brighter and therefore you will see even those very far away. So really its a big zoo of various types of stars. You'll see stars at all stages of their evolution.",
"Technically speaking anything you look at is an image from the past, even your own reflection in the mirror. Looking at the Sun, you are seeing it as it was ~8 minutes in the past. If you look at Polaris (Northern Star) you're seeing it as it was ~434 years ago. So yes, few of the stars you see in the night sky may not even be there any more. "
] |
[
"Therefore many of them are not easy to spot with a naked eye unless they are fairly close.",
"Actually, none of them is visible to the naked eye under normal conditions. There is one star called ",
"Lacaille 8760",
" which might be visible to some observers under the most perfect conditions (age less than 30, absolutely no light pollution, perfect clearness, high inclination). This star is also extraordinary massive for a red dwarf, with about 60% of the sun's mass. "
] |
[
"There's different types of stars, but yes. Our sun is a star.",
"As for the time delay; the stars you see in the sky are so far away that it takes tremendous amounts of time for their light to reach earth. ",
"If i remember correctly, light travels 186k miles per second. So a star being as close as 10 lightyears away is an incredible distance and the light you see has actually been on its way here for 10 years."
] |
[
"A question about radiation in space"
] |
[
false
] |
After reading several articles about the amount of radiation astronauts would absorb on a two-year trip to Mars I wonder, what would happen if either the ship or the astronauts themselves were surrounded by a pocket of water on their journey?
|
[
"The halving mass of lead is 12 g/cm",
" and the halving mass of of water is 18 g/cm",
" so it makes more sense to use lead shielding. However, since you need to take along a supply of water, it might as well be used in addition to the lead assuming the cost of an envelope type container doesn't out weight the value of the additional shielding."
] |
[
"This was actually being considered as it would definitely be effective. While it may not be feasible to cover the entire ship with water (too heavy) it is currently being researched if it can be used to protect astronauts when they spacewalk.",
"Meaning, they wanna put water in the spacesuits."
] |
[
"Any amount of extra material is generally helpful, unless that material tends to stop incident radiation by giving off more dangerous forms of radiation. Then the issue becomes cost. So, somehow getting a layer of water between various layers of the craft's superstructure would help (maybe melt off a chunk of comet?), but the cost of getting Earth water into space isn't worth the fuel. If the Moon or some in-orbit source of water was available, then it'd be much more feasible."
] |
[
"Why would the immune system attack the eyes, if it knew they were there?"
] |
[
false
] | null |
[
"There are organs in our body that are immunologically isolated from the bloodstream:",
"Why wouldn't lymphocytes react to everything in our body? Well, during childhood, T lymphocytes are trained in the thymus and are exposed to basically*** all the self antigens that the blood touches. If no antigens specific to the eye are in the bloodstream at that moment, T lymphocytes won't be tested and rejected for a self-host reaction.",
"Edit for ***: ",
"/u/CD11cCD103",
" has a comment explaining better how all the self antigens reach the thymus. It's not that the blood carries bits and pieces of everything towards the thymus, but that some \"nanny\" cells of the thymus can express antigens of anything during the T lymphocytes maturation process."
] |
[
"Could we theoretically train our own immune system on these things as children? Kind of like a reverse vaccine?"
] |
[
"I guess it could theoretically be possible, but might require extensive treatment (multiple doses at different intervals) while also having the risk of making the patient (which would be an infant!) non reactive to some real non self antigens (prone to infections).",
"I sincerely don't know, but would love to research this when I have more time!"
] |
[
"Why does the integral of 1/x result in a logarithm? Also, why does logarithm have base e?"
] |
[
false
] |
I think it seems too beautiful and amazing that this is just a coincidence that the integral of 1/x results in a logarithm (much less for that logarithm to have a base of one of the most useful numbers in mathematics, e) for it to just be coincidence. Can someone come up with a proof, or at least a logical argument, for why this is the case?
|
[
"The function 'log(x)' (here I mean natural logarithm) is usually defined as the integral of 1/t from 1 to x. You can prove that the integral has the properties you'd expect out of a logarithm, if that makes you feel better. Try it yourself, first show that log(1/x)=-log(x) by using the definition (set the upper bound of integration to 1/x, and use the substitution u=tx), then show using the fact you just showed that log(xy)=log(x)+log(y) (set the upper bound of integration to xy, use substitution u=t/x). log(1)=0 is pretty straight forward",
"For showing that the base of log(x) is e, i.e. that log(e",
") = x, or alternatively that log(x) is the inverse function of e we can just suppose that we have some inverse function for log(x) and show that the function is e",
". Let u(x) be such that log(u(x)) = x",
"Taking derivatives of both sides and with the chain rule you get: 1/u(x)*u'(x)=1 meaning u'(x)=u(x), note also that log(u(0))=0 (meaning u(0)=1), this is a differential equation with a unique solution u(x) = e",
"."
] |
[
"The function 'log(x)' (here I mean natural logarithm) is usually defined as the integral of 1/t from 1 to x",
"This is the first time I hear it defined that way... I usually hear it defined as the inverse of the exponential function e",
" and then it's trivial to show that d/dx log(x) = 1/x using the \"inverse\" rule for derivatives, and then you use the Fundamental Theorem of Calculus."
] |
[
"Explicitly, log(x)=integral of dt/t for t=1 to t=x. By the Fundamental Theorem of Calculus, this is true because the derivative of log(x) is 1/x (and log(1)=0). You can prove this through the equation e",
"=x. Setting y=log(x) and implicitly differentiating e",
"=x with respect to x, we get, through the chain rule, y'e",
"=1. But since e",
"=x, it follows that y'x=1 and therefore (d/dx)logx=1/x. If the base is not e is this, say we have y=log",
"x and a",
"=x, then because the derivative of a",
" is log(a)a",
", we'll get log(a)y'x=1. e is when this constant goes away.",
"In this way, then, it is because (d/dx)e",
"=e",
". This actually implies that if we have any equation of the form e",
"=f(x), then we'll get that y'=f'(x)/f(x). This is, in fact, called the ",
"Logarithmic Derivative",
", as y=log(f(x)), it's a pretty important concept.",
"There are some more intuitive reasons why this should be true. Note that an antiderivative of x",
" is x",
"/(n+1). If n=-1, then this obviously doesn't work, since the denominator becomes zero. But if that wasn't a problem, then it makes it seem like the function f(x)=x",
" should be related to a logarithm. Of course, this isn't the case, since x",
"=1, but, in a way, the logarithm behaves kinda like an \"infinitesimal power\" of x. ",
" But, you'll note that if you take any positive power s, no matter how small, then x",
"<log(x)<x",
" for large enough x. So the lognkinda plays the part of the missing power that's too small to actually be a power. ",
"Another thing we can do is look at how the integrals behave. You can use u-substitution to show that if F(x)=integral of dt/t from t=1 to t=x, then F(xy)=F(x)+F(y), so it changes multiplication into addition which is a defining characteristic of logarithms, so it must be a logarithm. This has to do with the fact that a u-substitution of the form u=ty satisfies dx/x=du/u. In this way, the term dx/x ican be seen as a way to look at multiplicative properties of functions."
] |
[
"Recently, it has been speculated that gravity causes wave function collapse and that entanglement causes gravity - are these two ideas compatible?"
] |
[
false
] |
I may be misunderstanding the point of these two articles but those were the ideas I took from them: "But the incompatibility of general relativity and quantum mechanics itself suggests that gravity might behave differently. One compelling idea is that gravity could act as a sort of inescapable background noise that collapses superpositions. “While you can get rid of air molecules and electromagnetic radiation, you can’t screen out gravity,” said Miles Blencowe, a professor of physics at Dartmouth College. “My view is that gravity is sort of like the fundamental, unavoidable, last-resort environment.”" "Using holographic duality, Sonner derived the entangled quarks, and found that what emerged was a wormhole connecting the two, implying that the creation of quarks simultaneously creates a wormhole. More fundamentally, the results suggest that gravity may, in fact, emerge from entanglement. What’s more, the geometry, or bending, of the universe as described by classical gravity, may be a consequence of entanglement, such as that between pairs of particles strung together by tunneling wormholes." Assuming I didn't misunderstand the articles, are these two ideas compatible, or must one be wrong for the other to be right?
|
[
"The second paper is about a parallel between pairs of entangled quarks and wormholes, not quarks being held together in hadrons."
] |
[
"I didn't carefully read the articles you linked to but the idea that gravity causes wavefunction collapse is not that new actually, and has been championed by Roger Penrose, and bears his name: ",
"Penrose Interpretation",
"Regarding wormholes connecting quarks... that sounds really bizarre, and I'm surprised to see the article in the mit.edu domain, and certainly surprised to see Susskind's name dropped in there. The overwhelmingly likelihood is that ",
"gluons",
" exist and that they hold quarks together via exchange forces. There is empirical evidence for the existence of gluons, they have been experimentally observed.",
"I don't think either of the ideas are well enough developed to be able to say whether they are compatible or not. These are early theoretical directions for further investigation and as yet physicists don't know enough about spacetime behavior at the smallest scales to able to make that conclusion."
] |
[
"There is empirical evidence for the existence of gluons, they have been experimentally observed.",
"Well, ",
" have not been experimentally observed. Only effects that so far can only be explained by the existance of gluons (such as jets of hadrons during hadron collisions) have been observed. That ",
" count as empirical evidence for the existance of gluons, but it's (strong) indirect evidence, not direct."
] |
[
"Is there ANY scientific evidence to suggest that you can influence the probability of your offspring being a particular gender?"
] |
[
false
] |
[deleted]
|
[
"If your old wives' tale involves ultracentrifugation of a semen sample to separate sperm by the mass difference between the X and Y chromosomes, then there might be something to it.",
"EDIT: That's the way it's often done for the livestock industry and perhaps some humans - that or sorting the cells with a fluorescent dye attached to an antibody that specifically binds one sex chromosome or the other. If there were a simpler way, you'd better believe they'd be all over that."
] |
[
"I believe they're using a flow cytometer (reviewed ",
"here",
", ",
"here",
") these days. Reportedly it's 90% effective and has been successfully applied to cattle, sheep, pigs, horses, elk, domestic cat, domestic dog, some wild cats, sika deer, swamp buffalo, and probably others by now. ",
"This paper",
" reports that it's being used in humans now - primarily in the context of IVF, and sometimes to prevent X-linked diseases. ",
"See Fig 3 of the first paper for a diagram of a patented sperm-sorting \"Cytonozzle\" used to sort cattle sperm."
] |
[
"The 'X'. It's not just an arbitrary choice of letter; they look like their shapes. The 'Y' is missing most of one arm."
] |
[
"Could Dzhanibekov effect be at play in causing the periodic reversal of Earth's magnetic field?"
] |
[
false
] |
I'm not sure if this is a silly question or not: This video has been posted to Reddit a few times now demonstrating the Dzhanibekov effect, which causes rotating objects in space to "flip" weirdly on one of the axes of rotation... My question is, could this effect be responsible for the periodic reversal of Earth's magnetic field? If so, what would the implications be for the actual observed "flipping" process?
|
[
"No. The ",
"'Dzhanibekov effect'",
" requires three distinct principal moments of inertia, whereas the inner earth should be symmetric about the Earth's rotational axis. In simpler terms, that effect only works for strangely-shaped objects."
] |
[
"The earth's magnetic field is generated by small electrical currents in the liquid outer core which are generating small magnetic fields. These magnetic fields are aligned due to the Coriolis effect from the earth's rotation. Having a solid metal core in the middle of the liquid outer core causes little variations in the way the magnetic field is aligned and causes the magnetic poles to migrate slightly. Models of the earth's magnetic field do produce reversals at what seems to be fairly random intervals and is likely due to having a solid inner core that interferes with the eddy currents in the liquid outer core that generate the magnetic field. ",
"The moment of inertia of the earth is pretty well understood and can be derived using calculus. It doesn't have anything to do with earth's magnetic field, however."
] |
[
"How much do we actually know vs. assume about the moments of inertia for the [mass?] that's generating our magnetic field? Is it conceivable that it ",
" have multiple moments of inertia?"
] |
[
"If somone gets the COVID-19 vaccine, would the PCR test come back positive in the weeks to follow?"
] |
[
false
] | null |
[
"The RT-PCR test looks for the presence of certain RNA sequences, and will only give a result if those exact sequences are present. From a quick look at the COVID virus genome, neither of the regions used in the official CDC test are in the spike protein, which is the part of the virus used in the front-runner vaccines.",
"So in theory, an mRNA vaccine could be detected by a PCR test (the vaccine itself, not the body's response), but the PCR test used in the US at least is testing the wrong parts of the virus for that to happen."
] |
[
"No, the mRNA used for the vaccine is not the same region of the viral genome that the PCR test detects.",
"The vaccine codes for the spike protein, and the PCR tests usually use primers that bind to the region of the genome encoding the nucleocapsid."
] |
[
"And he said detectable \"in the weeks to follow\", to my understanding the mRNA from the vaccine is degraded in the body within hours (or days?), but the antibodies persist. So there would be no detectable mRNA even a few days after getting a vaccine."
] |
[
"Does the moon have a different apparent vertical orientation in the two hemispheres?"
] |
[
false
] |
Put plainly, would the moon appear upside down to me if I went to Argentina or Australia (I live in the U.S.)? Edit: Thanks so much everyone! This was probably the most mind-blowing fact I've learned in a long, long time.
|
[
"Take it to the extreme and its easier to visualize.",
"If you stand on the North pole and the moon is on the horizon, imagine a big A on the surface of the moon, right side up.",
"TIME IS FROZEN FOR THIS ILLUSTRATION (the moon does not move, only you)",
"Now travel south toward the mooon. The farther south you go, the higher in the sky the moon is, until at the equator it would be directly over head. ",
"Now up until this point the \"A\" on the moon is right side up, just higher and higher to your orientation of the ground. Once it reaches directly over head you no longer have a clear reference point of \"this is right side up, this is up side down\" All directions are up and down.",
"Now as you head farther south into the southern hemisphere the moon is now getting closer and closer to the opposite horizon. So technically it is \"behind you\" meaning you have to turn around from the direction you are walking to see it, and the \"A\" is also now upside down from that horizon. (but, funny enough, if you are walking south and lean back like a limbo and look back upside down the \"A\" will be \"right side up\" but the horizon will be upside down)",
"So that is why it looks upside down. ",
"The moon itself doesn't move, rather your orientation to a horizon does. Instead of looking to the \"southern horizon\" you are now looking to the \"northern horizon\" which is an opposite direction (making the moon looked flipped)"
] |
[
"Yes. Yes I suppose it would appear \"upside down\" in the southern hemisphere (assuming you are from the northern hemisphere). Wow. I never thought about that. "
] |
[
"Yep, it looks like ",
"this",
". I've submitted a few moon pics to reddit in the past and always get the \"upside-down\" comments. I live in New Zealand but that pic was taken in Australia."
] |
[
"Whenever matter/antimatter annihilation is mentioned it's almost always hydrogen/anti-hydrogen. What would happen if it were not the same (anti)elements interacting?"
] |
[
false
] |
Say, if you had an atom of anti-hydrogen come into contact with a gold atom, would you get a platinum atom and a lot of energy, or would something else occur? Further along those lines, what if the anti-hydrogen reacted with a radioactive element, such as uranium?
|
[
"But atoms aren't individual particles. I think he's asking if nuclei can partially annihilate. "
] |
[
"Particles only annihilate with their own antiparticles.",
"So an electron and a positron can annihilate, but an electron and an antiproton can't."
] |
[
"Yes, they can."
] |
[
"Why does it happen and what is happening when you get a ringing randomly in your ear?"
] |
[
false
] | null |
[
"Sounds like you're referring to ",
"tinnitus",
". ",
", according to Marion and Cevette. It may be defined as any sensation of sound for which there is no source outside the individual. ",
" (nonvibratory and vibratory, in the terminology of Fowler). The tonal type is by far the more common and is what is meant when the unqualified term tinnitus is used. It is also called subjective tinnitus, because it can be heard only by the patient. The nontonal form is sometimes objective, in the sense that under certain conditions the tinnitus can be heard by the examiner as well as by the patient.",
"Nontonal tinnitus is caused not by nerve abnormalities but by actual sounds created in the head (hence, objective). They can be due to muscle contractions or blood flow sounds, which may be caused by abnormalities in blood vessels or changes in intracranial pressure, among other things.",
"These head noises are ",
" and are conducted to the inner ear through the various hard or soft structures or the fluid or gaseous media of the body. They are ",
" but have their origin in the contraction of muscles of the eustachian tube, middle ear (stapedius, tensor tympani), palate (palatal myoclonus), or pharynx (muscles of deglutition), or in vascular structures near the ear. One of the most common forms of subjective tinnitus is a self-audible bruit, the source of which is the turbulent flow of blood in the large vessels of the neck or in an arteriovenous malformation or glomus jugulare tumor. ",
"Tonal tinnitus results form dysfunction of either the eardrum, the bones of the middle ear, the inner ear, or the nerve that relays signal to the brain. The exact mechanism is still unclear. Many things can contribute to this (medications, sound exposure, infections, etc).",
"Under ideal acoustic circumstances (in a soundproof room having an ambient noise level of 18 dB or less), ",
" (\"physiologic tinnitus\"). The ambient noise level in ordinary living conditions usually exceeds 35 dB and is of sufficient intensity to mask physiologic tinnitus. Tinnitus because of disease of the middle ear and auditory neural mechanisms may also be masked by environmental noise and hence becomes troublesome only in quiet surroundings—at night, in the country, etc.",
"Most often, subjective tinnitus signifies a ",
". As already remarked, a majority of patients who complain of persistent tinnitus have some degree of deafness as well. Tinnitus that is localized to one ear and is described as having a tonal character (such as a ringing, bell-like, or like a high and steady musical tone) is particularly likely to be associated with impairment of cochlear or neural function.",
"The ",
". One supposition attributes tinnitus to an overactivity or disinhibition of hair cells adjacent to a part of the cochlea that has been injured. Another postulates a decoupling of hair cells from the tectorial membrane. Yet another theory is based on the finding of an abnormal discharge pattern of afferent neurons, attributed to ephaptic transmission between nerve fibers that have been damaged by vascular compression (Møller). "
] |
[
"Well, I don't think he was referring to a constant tinnitus. I experience what I believe OP does often enough, that my ear suddenly starts to ring -- tonally -- at arbitrary times. Not always, just now and then, and with unchanged ambient noise."
] |
[
"So are you saying, let's give a scenario I'm out target shooting with a .44 magnum when I shoot that gun and the after effect is my ears ringing this is because my body had a sudden change in pressure waves that affected the blood flow and everything else you explained? Or is it just be cause of the loud noise and pressure on the eardrum?"
] |
[
"What makes MIG/TIG weld fumes so dangerous?"
] |
[
false
] |
Weld fumes are really dangerous, causing bronchitis or lung cancer over a long period of time if inhaled, but what I don't understand is how steel and argon can have a reaction that creates something so toxic when both aren't used up in a reaction and both aren't toxic to begin with. What's in weld fumes that make them so toxic and how does it get there?
|
[
"When you say \"steel and argon aren't toxic\", you are mistaken. Toxicity depends on not just what you get into your body, but on how you get it in, and how much you get. ",
"An excellent example of this is mercury. You can swallow small to moderate quantities of liquid mercury with no harm. But even a small amount of inhaled mercury vapors is neurotoxic.",
"So, returning to your question: sure, steel is not harmful when swallowed, but pretty much all metals and alloys are toxic when they are inhaled as vapors or fine dust. In short, this is because they damage cells in your lungs, which then leads to a variety of problems, including lung inflammation, asthma, and lung cancer."
] |
[
"Mercury, consisting of unionized mercury atoms, first crosses into your blood (from your lungs) and then into your brain. In the brain, it is ionized; normally, this would make it easier to excrete it (because ionized mercury can bind to other compounds and that makes it easier for your body to get rid of it); unfortunately, ionized mercury is unable to cross back into blood from your brain, so it gets stuck in your brain cells, accumulates in there, and causes damage."
] |
[
"Asbestos would*?"
] |
[
"How do radio antennas work?"
] |
[
false
] |
I have been wondering this for a few months now, I know that RSSI (Receiver Signal Strength Index) is a range of voltage. Does this mean that when an antenna is subjected to a radio wave it always applies a voltage to the receiver? Another part of this question is how do transmitter antennas work, I know that P=V*I but when the ground and center (of the coax) are not touching how does current flow through the coax? (or is the current just super small because of the resistance of the air between the two "wires".
|
[
"RSSI is a measurement in dBm typically. (where 0dB is 1mW of power) a receiver will always be subject to an input voltage/current from the antenna, but unless there is a specific signal it will be at background noise levels, usually around -80+ dBm.",
"current flows due to the characteristic impedance of the cable, impedance being the ac equivalent to resistance. a transmitters antenna then operates by being tuned to the transmit frequency wavelength. typically they are tuned to multiples of a 1/4 wavelength. by not being earthed, the signal flows down the copper of the antenna, and then reflects back towards the tx output. if you imagine your transmission as a sine wave, by tuning the length to a multiple of 1/4 wavelength, the signal returning to the source will be 0dB. "
] |
[
"First: In high-frequency you cannot think about voltage and current like in the DC case. P = V*I is not necessarily correct. The thing is that electric signals move with light speed which requires extended calculations at higher frequencies, in the air but also in any conductor. Simply because the signal is too slow to be regarded as constant over space.",
"The antenna usually radiates an electric field which continuously alternates with a magnetic field as described by the Maxwells equations (and the boundary conditions thereof, material constans etc.). These calculations today are mostly done by computers figuring out how to make an antenna good numerically, its nearly impossible to solve the maxwell eqs analytically.",
"Now for the antenna to work you need some signal source, an amplifier, perhaps a wire and the antenna itself. The signal source sends out a signal, like a voltage pike or similar. It travels through the electronics and hits the antenna. In the antenna now there is an electric field building up because of the signal (physics does not allow otherwise) and the antenna directs the field to the desired direction. (The details are all in very complex math.) In fact: also at any part of the device there will always be a little e-field dispatching from the line with the signal, usually this is undesired. The antenna now is simply built to create the e-field on purpose. Also not all of the signals power get sent into space. There are amplifier losses, line losses, and you have to double check your line lengths for not canceling out the signal.",
"It all boils down to the Maxwell equations which state that moving charges induce a magnetic field which creates an electric field which induces a magnetic field etc... The antenna simply allows this process to be very efficient where you would not normally want to have this.",
"Of course you can describe the antenna with various figures like the RSSI, the ERP, the directivity, the radiation resistivity, the gain, and most important the radiation pattern.",
"Source: I have an exam about this stuff in about 3 weeks. (2nd year electrical engineer BSc)"
] |
[
"The signal source sends out a signal, like a voltage pike or similar.",
"By this you mean voltage spike?",
"Another question: how does this transmit information, I can understand if the receiver voltage is equal or proportionate to the Tx. voltage."
] |
[
"In lab testing with animals, how do you know when they are experiencing an invisible symptom?"
] |
[
false
] |
I was researching tinnitus as I have Meniere’s and saw that there was testing on lab rats with medication to see if they have more or less tinnitus. How do they know a rat is experiencing that at all? How can you tell if it’s better or worse for them? Adding link per request:
|
[
"If this is peer reviewed paper then they should definitely report the methods for determining improvements in outcomes. ",
"Most likely though they expose both treament groups to a stimulus and see which one responds to it. ",
"Maybe they found out the frequency at which tinnitus occurs and then play similar sounds so that only rats with improved outcomes can hear the sound. This all just a guess though, you should let us know what paper you're talking about."
] |
[
"Link to research attached to main post."
] |
[
"From the paper:",
"Acoustic trauma caused a significant increase in the auditory brainstem response (ABR) thresholds in the exposed animals",
"...",
"Hearing levels were measured using auditory brainstem response (ABR) thresholds in both the ears of exposed and sham animals before the acoustic trauma, in both the ears of the exposed animals immediately after the acoustic trauma, in the ipsilateral ear of all exposed animals and in both ears of selected sham animals at the conclusion of the study. ",
"...",
"One month later, the animals were tested for the behavioral signs of tinnitus using a conditioned lick suppression paradigm",
"https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0166346",
"They basically train the rats to lick when they hear certain sounds. So you give them tinnitus, then see if they lick. Then you do your study and see if they stop licking (against the control group which gets nothing and should continue licking).",
"They also put electrodes into the nerve regions of the rats that produce hearing and measure electrical signals directly.",
"So generally if you are interested in this, the way to do it is to first read the abstract again, then look in the \"methods\" section. If you don't understand anything in the methods section, crack open google and plug the thing you don't understand in. I had never heard of a lick suppression paradigm before so I plugged it into google and it spat out the second paper for me. I then read the abstract of the PLOS paper. If I hadn't understood the abstract, I would have read the methods of the new paper. Keep repeating until you arrive at something you understand (and when it gets basic/common enough it'll spit a wikipedia article out at you). This is the very basic google-recursion algorithm I use for a new area for getting a 3 minute grasp on a topic, although if you don't have a background it'll take you longer."
] |
[
"Why does mint make your mouth cold?"
] |
[
false
] |
I'm talking about when you chew minty gum or eat a mint, and drink water or breathe. I'm not sure how to explain it other than your mouth going cold.
|
[
"Menthol is used as a mint flavoring. It activates nerve receptors that detect cold."
] |
[
"Yes, your mouth actually \"thinks\" it's about 4 degrees (Celsius) than it really is. It doesn't just feel \"like\" cold - it actually feels cold! Pretty nifty! ",
"Compare this with capsaicin, which activate pain receptors. It doesn't just sting \"like\" pain - it's actual pain!",
"The intensity for both is largely the concentration of the relevant molecule in the solution, and how thoroughly they're distributed in your mouth."
] |
[
"It's a trick of the receptors, from the menthol in the mint. Even though the air you breath in isn't cold, its colder than your mouth already is so your nerves are tricked into thinking its a lot colder than it really is. ",
"Check this out: ",
"http://www.thenakedscientists.com/HTML/articles/article/dalyacolumn5.htm/"
] |
[
"When you delete something where does it go?"
] |
[
false
] | null |
[
"Why ",
" it simply vanish?",
"(In practice, most computer systems don't actually do anything with the data when you delete it; they just tell other programs they're allowed to write over it. But writing over it ",
" just make the data vanish.)"
] |
[
"The data is never deleted from the disk, their entries are deleted from the \"",
"file index",
"\" so that they can be overwritten."
] |
[
"Data on hard drives is represented by 1's and 0's. All grouped data (files), are accompanied by a delete flag. For data in use, this is set to 0, so that it won't be overwritten. When you delete something, in almost all cases, the only thing that happens is changing this flag to 1, which is simply indicating that the data that this flag accompanies can be overwritten.",
"This is why data-recovery often works. When you delete something, it is not really deleted until it is overwritten by other data. So as long as it is still there, it can be recovered."
] |
[
"Are there people who exist on the opposite end of the spectrum from sociopathy- i.e. an \"anti-sociopath\" or a hyper-empathic individual?"
] |
[
false
] |
There's so much written about sociopathic and psychopathic people, but is there any information on the existence of people who are their opposite? In other words, someone possessing such an overdeveloped conscience, empathy, and a sense of the rights of others that it could possibly be considered debilitating or even a personality disorder?
|
[
"The closest condition that I can think of like this is called Williams syndrome (",
"http://en.wikipedia.org/wiki/Williams_syndrome",
"). People who have it tend to be overly trusting, cheerful and friendly. They also have a distinctive appearance and some negative physiological symptoms. However, I believe that being tooooo trusting can lead to a few problems."
] |
[
"This is going to sound mean, but most people only ever see the people with Down's syndrome that are allowed to go outside; they keep the rest locked up because they are a potential threat to either themselves or their environment. It's probably this type of selective exposure that accounts for the cheerful stereotype."
] |
[
"Maybe not exactly what you're looking for since this isn't exactly a disorder - but have you read about ",
"highly sensitive persons",
"? "
] |
[
"I've heard it said that there are some foods that require more energy to digest than they provide as energy to the body. True?"
] |
[
false
] |
I have heard it said that there are some foods that require more energy to eat and digest than they provide in terms of food energy to the human body. Celery is one example I distinctly remember as being part of this. Is this true or even nearly so? If I crashed on the Desert Island of Celery, would I be doomed?
|
[
"Upvoting because the link is good and should be seen, but your conclusion about it is wrong... try reading things you link.",
"Basically, negative calorie foods are a myth."
] |
[
"From the article:",
"Celery, a commonly cited negative calorie food, actually requires only about 10% of its food energy content to be digested (due to the thermic effect)."
] |
[
"This is a common claim made by various dieting websites, although it is assumed to be incorrect - there's no scientific evidence to suggest it to be true but at the same time it hasn't been specifically studied.",
"One of the reasons for the claim is sometimes confusion between calories burnt by thermic effect and resting metabolic rate.",
"If you have a RMR of 2000 calories, you would burn one calorie every 43.2 seconds. According to ",
"this",
" a medium stick of celery has 6 calories, so if you took 4 and a half minutes to eat it then technically you would have burnt more calories than in the celery, before taking into account thermic effect, but you'd have burnt those calories anyway, they have nothing to do with eating the celery.",
"Generally the thermic effect is about 10% of the food but it varies widely depending on what food it is and on the individual eating it.",
"Water has no calories to begin with but does require energy to digest. Cold water needs to be heated up by your body which requires more calories and will in theory also be absorbed slower (so warmer water will hydrate you faster)."
] |
[
"Would be able to see a inside of a 3d egg if we were looking at it from the 4th dimension?"
] |
[
false
] |
[deleted]
|
[
"If it is a purely 3 dimensional object in 4 dimensional space, then yes.",
"Of course there are no 4 dimensional eyes in this universe, but for the sake of argument, let's consider that you are able to \"see\" point P from your perspective if there is a straight line from you to P that passes into no solid object between you and P. Then we can call any point in 4d space (x,y,z,w) and place the 3d object at (x,y,z,0). Then all of the solid objects that could obstruct your view have coordinates (x,y,z,0), and for every such point there is a straight line along the w axis, (x,y,z,t) (t from -infinity to infinity) that passes through that point without hitting any solid object except at the one point t=0, so every point in the object is visible.",
"There are other ways of extending an object to higher dimensions, though. For example, you can have a 2D circle that you extend to 3 dimensions by making it an infinite cylinder. If you extend your \"egg\" infinitely along the w-axis, it will still have an inside and an outside in 4 dimensions."
] |
[
"What they said. You might read \"Flatland\" by Abbot (it's public domain).",
"But yeah, to a 4D actor your insides are just as reachable as your outsides. Just like you can lift a pencil off the \"Start\" of a line maze and just make an X on the finish, ignoring any intervening lines. Another interesting ability such a beastie would have is that they could rotate something such that it flips its chirality, or 'handedness'. They could pick you up, flip you around, and put you back with your body being a mirror image of itself. (You'd probably die though - lots of biology depends on the handedness of molecules)."
] |
[
"Obviously this is getting very hypothetical, but the body mainly depends on the chirality of molecules inside it relative to other molecules inside it. So you probably wouldn't die until you tried to eat something. As long as you could find mirror food though, you should be ok.",
"The only reason I qualify all of that is because apparently the weak force of particle physics is not mirror symmetric, and I'm not knowledgeable enough about that to say it couldn't have an effect."
] |
[
"Why is bisexuality so rare?"
] |
[
false
] |
I understand the evolutionary principles that have been used to explain how "gay genes" can be permitted to exist in a species that reproduces via sexual reproduction - concepts such as the kin selection theory and other such societal/community factors. I can accept that heterosexuality may be the most numerous category in a population that is in equilibrium. However, I cannot think of a good reason why homosexuality should be the next biggest group, above bisexuals. Evolutionarily speaking, shouldn't bisexuality be more prolific than homosexuality? If you consider hetero-, homo- and bi- as the three majority sexual preferences, don't bisexuals hold more cards than homosexuals (and possibly even heterosexuals). What is it that determines the relatively small proportion of bisexuals? My ideas: (these are just vague thoughts, please don't criticize me for being shallow or narrow-minded. I'm certainly not suggesting (as per point #3) that I think bisexuals are the violent, antisocial type)
|
[
"From anecdote from people I know I think 2 is more likely, but even more likely than that is that sexuality is probably a ",
"bimodal distribution",
". Two peaks at the edges, but blending to some continuum between. Bisexual leaning heterosexual etc. There's also some suggestions that the distributions are different between the genders, with females tending to more occupy the continuum and men to be more polarized. But I don't know the factors that lead to that situation."
] |
[
"Sexuality is a psychosocial characteristic at least as much as it is a biological one. Our designations of strait, gay, and bi are not universal. I wouldn't spend to much time looking for the genetic basis of sexuality then I would looking for the genetic basis of sports preferences. I'm sure there out there, but there not what's driving the phenomena. I'd recommend \"The Accidental Mind if you're looking for more material on the subject."
] |
[
"Layman speculating.",
"I wouldn't spend to much time looking for the genetic basis of sexuality then I would looking for the genetic basis of sports preferences.",
"Except that sexual orientation has obvious evolutionary ramifications. From a simplistic perspective you would expect that any genetic causes for homosexuality would have been removed long ago from the gene pool, and even if some environmental factors are at play you would still see genetic adaptations to minimize homosexuality... and yet it is rather prevalent.",
"One purely conjectural hypothesis I have about how homosexuality could be supported by natural selection is that perhaps sisters of homosexual men have more offspring than average, to the point where it compensates the lack of offspring of their brothers. Vice versa for brothers of lesbians. On the other hand I imagine that an idea as obvious as this has already been put to test and discarded."
] |
[
"Why is it that the neutron to proton ratio decreased as the universe cooled down in the early universe?"
] |
[
false
] | null |
[
"Two reasons.",
"The neutron is slightly more massive than the proton, which means that in equilibrium, one expects more protons than neutrons by a factor of e",
"Once neutrons and protons fall out of equilibrium (which is basically when all the electrons and positrons annihilate, leaving behind about 1 electron for every 10",
" electron/positron pairs), then neutrons will decay from being 1/6 of the nucleons to being 1/8 (this happens during the first 3 minutes of the universe). At that point, virtually all of the neutrons ended up in He4, which explains why Helium is 25% of the universe by mass (matter is 1/4 helium and helium is 1/2 neutrons)."
] |
[
"I do not know if this explains everything, but neutrons decay into protons."
] |
[
"excuse the syntax, but I think the question is still clear"
] |
[
"How do things like Bop It manage to generate pseudorandom numbers?"
] |
[
false
] |
In a normal computer, random numbers are generated by using various data and manipulating them until you get a single number, right? So how come a Bop it, or any other single-serving machine like that, which contains no data at the time of it being turned on, manage to create a random number that is different every time? Wouldn't it be always the same value, which would generate a predictable second value, and a predictable third and so on?
|
[
"A very common way to generate random numbers in a small embedded device like that is to have a fairly fast free-running counter. When the device receives some input (like the player pressing the start button) the counter is read and that can provide a dozen or so bits of entropy, which is plenty to make a game like Bop It random. (If it needed more, it could read the counter every time you activate one of the thingies on the game, and accumulate entropy.) It probably uses this entropy to seed a simple PRNG like a LFSR.",
"Building a reasonably-good hardware random number source is not hard, but it would add a few cents or tens of cents to the toy's cost, and at the volumes those things are made that's a significant price. The free-running-counter approach can usually be implemented very cheaply."
] |
[
"Like ",
"/u/manlymann",
" said twice, it's using a pseudorandom number generator to generate the values. Most likely, it's generating numbers between 0 and either 2",
" - 1 or 2",
" - 1 , and using the remainder of that number divided by k (where k is the number of distinct bop it actions) to figure out the next move.",
"As you pointed out, the process of generating random numbers from previous ones is entirely deterministic. How does bop-it initialize the (pseudo)random sequence, then? I have two guesses",
"Since bop-it has a time aspect, it has a piece of hardware can keep track of time. I wouldn't be at all surprised if it kept track of time even when off, since these pieces are so mass produced that it would probably be cheaper to install one of these than to install a piece of hardware that ",
" keep track of time while off. When it's turned on, it uses the time as the initial seed for the RNG and works from there.",
"It has a very small amount of memory to store the previous state of the RNG while off. When you turn it on, it simply returns the RNG to the previous configuration and starts from there.",
"Interestingly, in both cases, it's likely that bop-it is actually draining your battery a bit when off as volatile memory (memory that gets erased when it loses power) is much cheaper than non-volatile (fun fact: the various Nintendo cartridges used to have built-in watch-like batteries to keep your saves intact!). Thankfully, the amount of battery power consumed in either case is even less than what a typical watch battery provides, and your AAs can handle the tiny amount of power consumption with ease."
] |
[
"rand()",
" isn't magic, you have to seed it with something random enough so you don't start off with a small number of possible prng states. The real question is where is the device pulling entropy from so you don't have the same sequence every time."
] |
[
"If you are knocked out and fall into water, would you unconsciously hold your breath or take in a big gulp of water?"
] |
[
false
] | null |
[
"The slightly circular answer is \"it depends if you're breathing spontaneously or not.\" If unconscious and breathing on your own outside of water, you'll breathe in water. (Even conscious drowning people may not be able to hold their breath to the point of unconsciousness; involuntary breathing may take over, filling the lungs with water.) If unconscious and not breathing spontaneously, you won't breathe in water either.",
"The difference will come down to how you became unconscious, and the effect on the respiratory centers in your brainstem and pons. Generally, assessing for breathing is one of the most important parts of assessing unconscious people, because failing to breathe is not compatible with staying alive for all that long."
] |
[
"Humans have a dive reflex that is activated by cold water on the face (trigeminal nerve). Regardless of whether one is conscious or unconscious, the dive reflex would be activated. This would stop a person from breathing in/out, slow heart rate, slow peripheral blood flow to ensure that oxygen was able to get to the brain and essential organs. ",
"However, the dive reflex only lasts until the need for oxygen becomes too much. So, as long as a person was still breathing when they entered the water - assuming their breathing or nervous system wasn't disturbed by being knocked unconscious - then the dive reflex would still likely apply (I'm not sure its ethical to try this out though!) "
] |
[
"Ahh thank you. Never heard of this reflex before "
] |
[
"Is there any substance to the no-shampoo movement?"
] |
[
false
] |
I'm always frustrated when looking up anything about cosmetics or health/fitness; there are so many fads and so much woo that often turn out to be baseless. That said, the idea of no-poo or poo-minimal life is intriguing to me. I wash/condition daily and my straight hair is usually getting uncomfortably greasy by the end of the day. One of the main postulations of the no-poo movement is that the removal of oil from your skin daily (by using shampoo), causes your glands to produce more oil to compensate. No-poo pushers claim that, after a break-in period, you'll stop producing so much oil, and your body with take care of itself naturally. I figure we must have not used shampoo in the past. Were we all just going around with greasy, crappy hair? Is that why our forefathers wore wigs? Anyhoo, I think I'm going to give the baking soda/vinegar a try for a while and see if I can't ease into no shampoo. That is, unless it's wholly refuted here.
|
[
"As far as I know, I'm the only panelist with shampoo \"specialty\" and I have to admit that my background provides absolutely no guidance. I've messaged some biology panelists to see if they know something about the sebacious glands which oil up hair. If there is a feedback loop, the theory may have some credence to it, but I have no way to know how.",
"EDIT: I've looked into this a little bit further. The whole baking soda/vinegar think smells funny to me (no...not a pun). Based on what I can determine, you're washing your hair with vinegar and then conditioning it with the baking soda. This is, seriously, exactly what shampoo and conditioner do (and no, its not because of some acid/base thing...). ",
"So, until a biologist shows up, I'm going to maintain my skepticism of hippy-woo."
] |
[
"Based on what I can determine, you're washing your hair with vinegar and then conditioning it with the baking soda.",
"It's the other way around.",
"This is, seriously, exactly what shampoo and conditioner do (and no, its not because of some acid/base thing...).",
"The principle is the same although baking soda is supposedly less aggressive than sulfates used in shampoos. And ACV is mostly used to neutralize the drying effect of sodium bicarbonate; its use isn't necessary, it's just recommended for people whose scalp seems dry after being washed with baking soda."
] |
[
"Well I'll take a crack at this, dermatology isn't my specialty, but I spend a lot of time with dogs and cats, so I know my fair share.",
"Their claim about the oil production is true. Sebaceous glands will produce less oil when the body's natural balance system realizes what is going on. So if you were really willing to try and take this approach, I'd suggest a couple days where that girl you're interested in won't be around. ",
"My roommate in college showered everyday, but only used shampoo and conditioner every 4th day, and her hair looked beautiful. This may be anecdotal evidence, but will suffice nevertheless.",
"In regards to eaglefalconn's discussion of the chemicals they suggest to use, the main difference they're trying to make is that the baking soda and vinegar are less harsh. Whether this is true or not, I do not know. "
] |
[
"If a human pants (like a dog) will they actually cool themselves down?"
] |
[
false
] | null |
[
"If you move air over a body part with a rich blood supply, like the tongue, you will lose heat through convection. However, a dog is obviously going to be better adapted for this, and more efficient."
] |
[
"It would work, but there are more effective ways. ",
"But you would get acidosis pretty fast from unnecessary hyperventilation and your head would hurt. Try it. "
] |
[
"This is correct more specifically as long as the air temperature is lower than that of the body energy in the form of heat will be transferred to the air (by convection and conduction) which you then breathe out."
] |
[
"Can someone explain how lipoedema can grow without the required energy intake?"
] |
[
false
] |
I have recently discovered and at first dismissed it as "yet another excuse for fatties to fat", but the NHS page says it doesn't improve with dieting? if we simplify TDEE to: (base energy to survive) + (base energy to power daily activity) then in a patient with lipoedema it would be: ( + ) + (the energy to sustain the edema)? So if that's the case, during an energy deficit (diet) something has to give, I mean, you can't create energy from nothing. Yet I see no symptoms relating to organ failure so I can only assume that the people afflicted are just permanently exhausted? am I missing something obvious? EDIT:Formatting
|
[
"I'm not a lipoedema expert, but your question seems somewhat obvious when we look at other cellular growth or metabolic abnormalities. You can't diet cancers away either."
] |
[
"I think my question was poorly phrased, I mean, theoretically ",
" has to give, so does it affect organ function or just general energy levels? I mean, a cancerous tumor of that size would RUIN a person, but people with lipoedema seem to (from what I read) get by absolutely fine."
] |
[
"The problem with cancer is that they can impede with normal organ functions. ",
"There are massive benign tumours as well. Furthermore, I think the enlarged fat cells aren't particularly dense and the way they distribute appear to be further away from important places (the organs).",
"If I understand your question correct, you're asking whether lipoedema is essentially parts of the body's fat tissue gone out of control and decided to take a larger share of the body's energy input to keep itself growing?"
] |
[
"Do obesity rates drop during economic recession?"
] |
[
false
] | null |
[
"It's the opposite, according to science daily. Obesity rising makes more sense because food that's bad for you is cheaper than food that's good for you. That, plus the rise in depression and comfort eating makes for a perfect storm for obesity.",
"https://www.sciencedaily.com/releases/2018/03/180301094841.htm#:~:text=Summary%3A,according%20to%20a%20new%20study",
"."
] |
[
"Science Daily just reposted a press release of peer-reviewed work. Here's the press release and research they are talking about: ",
"https://www.city.ac.uk/news-and-events/news/2018/03/2008-great-recession-led-to-increase-in-obesity-diabetes-and-mental-health-issues-says-study",
"https://www.sciencedirect.com/science/article/abs/pii/S0277953617307402?via%3Dihub"
] |
[
"It's also cheaper to stay home and sit on the couch than it is to drive to destinations and engage in fun outdoor activities."
] |
[
"Is it possible to burn a high calorie food to get water hot enough to smelt metal?"
] |
[
false
] |
As I've always been told, a calorie is the unit of energy required to heat up a kilogram of water 1 degree Celsius. I know that may not be a lot, but if Epic Meal Time burned their 100,000 calorie burger and was somehow able to contain all of the heat, could they get water hot enough to smelt metal?
|
[
"You gotta think of the heat equation:\ndQ= m Cp dT",
"Where dQ is a change in heat, m is a mass of the thing you're heating, Cp is the thing's specific heat (mostly constant and specific to the material), and dT is the change in temperature.",
"You might realize from this equation that if you have a massless enough piece of metal and you put enough heat into it, you can change the temperature enough to cause it to melt.",
"But, you wouldn't get water hot enough to smelt metal, because it turns into gas at 100C. (Ignoring Pressure)"
] |
[
"Someone created a torch for cutting metal using oxygen and bacon.",
"Here's the ",
"link"
] |
[
"So technically its possible but it would require something other than water? So a furnace of some sort could be heated?"
] |
[
"AskScience AMA Series: We are researchers studying biological rhythms and we want to 'lock the clock' to permanently end daylight saving time - ask us anything!"
] |
[
false
] |
We are from the Society for Research on Biological Rhythms ( ), an organization of international scientists, clinicians, and industry experts who promote basic and applied research in all aspects of biological rhythms. We are dedicated to advancing rigorous, peer-reviewed science and evidence-based policies related to sleep and circadian biology. Daylight saving time (DST) in the USA ends this weekend and we support the campaign to permanently end DST for better health. You can read more about this in our position paper titled " " that was published in the Journal of Biological Rhythms earlier this year. Our team for today is: You can also find us on Twitter at . We will be online at 3pm ET (19 UT) on Friday November 1st to answer your questions. Ask us anything! Thank you to everyone who participated! We were not able to answer every question, but were happy to see so much interest and many insightful questions! For more information, go to our website (srbr.org) or follow us on twitter (@SRBR_Outreach, or any of our individual twitter handles shown above). Sincerely, SRBR Outreach (Laura, Louise, Jonathan, Emily, Allison, and Céline)
|
[
"I'll bite. While I'm not a fan of having to change the clock twice a year, how much of an impact does it really have on one's health? A great number of people travel to different time zones multiple times per year (or week even). Given that a traveler's Circadian rhythm can adjust to large changes in time zone (say Europe to US or even SE Asia to US) fairly quickly, how much of an impact does +/- 1 hr 2x/yr really make?"
] |
[
"What test cases have you studied? I'm from Western Australia where it's been trialled a couple of times and rejected at referendum each time, but we're treated like Luddites by East-coasters.",
"This makes me wonder: are there geographic arguments for and against? In Perth WA, the summer afternoons can be brutally hot through to 5 or 6pm standard time, I've always thought this played against implementing DST. Also possibly ",
"longitude relative to the 'natural' timezone (not specific to Perth)?"
] |
[
"What's the best advice you can give someone to maintain a healthy circadian rhythm? What exactly is a good rhythm?",
"Should one:\nUse blue light blockers at a certain time?\nWake up at the same time? \nEat breakfast at the same time?"
] |
[
"If I cross my eyes, do I risk the chance of getting a lazy eye?"
] |
[
false
] |
EDIT: Yes, I suppose I am referring to strabismus, not amblyopia
|
[
"if you're talking about strabismus i believe there is a possibility. while vergence is a natural visual reflex, strabismus can be the result of physical as well as neurological dysfunction. while it is highly unlikely that constantly engaging in vergence (crossing eyes) will result in cranial nerve damage, damage of the extraocular muscles such as the medial rectus muscle can result in \"lazy eye\". this can be corrected with surgery and should be as soon as possible to prevent cortical remapping.\nand just so you know, i am quite drunk at 2 am so i don't know how reliable this response may be but i am a physiology major."
] |
[
"Edit; no.",
"Theoretically, its possible.\nHere's why.\nLazy eye is caused by an imbalance in the strength of opposite muscles that hold your eye in place. (There's actually more to this I believe, but lets just assume that there is one muscle that pulls left, one that pulls right, one for top, one for pulling to bottom). \nNow, a healthy non-lazy eye will have muscles that depending on where you want to see will strengthen/relax. If your eye wants to see left, the left pulling muscle will pull harder than the one that pulls the right pulling muscle, etc. Now, muscles will get stronger the more you exercise them, and the muscles that pull the eyes are no exception.",
"I have a lazy eye, where my inner muscle is stronger than my outer muscle. I went to a doctor and asked if there are any exercises that I can do, and he said 'unless you can look left with your left eye and right with your right eye at the same time, no'. He also said that if my outer muscle was stronger than my inner one then I could do the exercises (by crossing my eyes).",
"I actually used to play computer games like... 12-15 hrs a day. Although doctors say playing computer games cant cause this... I did play games a LOT... and even though you look left and right on your screen, its still not enough to exercise the outer muscle (unless you play on a huge screen from few feet away). I doubt my doctors knew how much I played daily, and I'm sure there were no studies done with people who stared at the center of the monitor 10+ hrs a day daily for years. This is still just a theory I thought of, but for some reason I can't think of this as a just a coincidence.",
"Edit: Spelling mistake // Changed last paragraph a bit"
] |
[
"Just to clarify: \"Lazy eye\" refers specifically to amblyopia, which is a developmental disorder of vision and, while related to strabismus (which some of you seem to mean), is NOT the same thing. Children who have strabismus as they grow up can develop amblyopia because the double vision resulting from strabismus causes the developing vision tracts to \"ignore\" visual input from one eye, causing decreased vision in that one eye. This is why childhood strabismus must be corrected quickly before amblyopia develops, and this is why before the surgery is done, the child is treated by covering the \"normal\" eye with an eyepatch, in order to let the visual tracts in the \"abnormal\" eye develop. While strabismus can be corrected through surgical intervention on the extraocular muscle, amblyopia has nothing to do with the extraocular muscles and can develop without the presence of strabismus; for example, if a kid just went around closing one of his eyes and only using one eye for most of his life, he would also develop amblyopia. It is, essentially, a problem with the brain, not the eye itself. \"Lazy eye\" is used by laymen to describe strabismus, but it is, in medical and scientific terms, incorrect.",
"tl;dr: Strabismus != \"lazy eye\"; amblyopia == \"lazy eye\""
] |
[
"Should doctors be allowed to prescribe placebos?"
] |
[
false
] | null |
[
"Whether something should or shouldn't be done is not a science question. Please post to a different sub"
] |
[
"What subs do you recommend?"
] |
[
"Perhaps an ethics or philosophy or medical sub"
] |
[
"A dirty filter is better than a clean filter?"
] |
[
false
] |
I replaced the air intake filter in my car this past weekend and it reminded me of something my boss said last spring. We were having pollen issues in our lab, and he made a comment how a dirty filter should function better than a clean filter. It sort of made sense, but is this true? It makes me think of like a packed bed--a thicker bed will be a thicker filter so a dirty filter will be better. Why do we change filters then? Just to get rid of stale smells? Does it actually help?
|
[
"As the filter clogs, the HVAC system must work harder to push less and less air through the filter. As this progresses, eventually the system will not be able to provide the minimum CFM it was designed to. This means if your lab was designed as a negative or positive pressure system, it may no longer be. Also, dust and other contaminants may not be removed from the air effectively since the reduced air flow will allow them to stay suspended. This would mean pollen is left to drift around the lab.",
"Also as the filter clogs, the air as it seeks the path of least resistance may end up traveling around the filter or through leaks in the duct work bypassing the filter all together. ",
"The reason we change filters is that the filters are designed to remove dust down to a certain micron whether they are packed with dust or not. So if you need to remove a certain size of contaminants you pick the filter that provides that fresh out of the box, not the one that needs to collect dust for a month before it does so. And since they are designed for a certain performance level, as the dust collects it reduces the airflow through them. ",
"So as the filters clog you may get better filtration but it is unquantifiable while also straining the HVAC system. If your boss is having pollen issues in the lab, he should switch to higher performance filters with either a smaller micron pore size, higher CFM or talk to maintenance about the HVAC system. The proper solution to his problem would be to replace the filters with small micron pore size and more often since the higher CFM of the system would remove the pollen from the air faster. Leaving dirty filters in place will only make the pollen problem worse. "
] |
[
"I don't know. I suspect that it isn't cleaner, because now theres increased pressure on the filter, and you're forcing the impurities through it. But I don't have any actual evidence of this."
] |
[
"The problem is that as it gets dirty, the filter gets obstructed, and its harder to get air through it."
] |
[
"When a clock is so accurate that it \"only loses one second in X billion years,\" or something, how can we possibly know that? What do we compare it to?"
] |
[
false
] |
It used to be that to gauge the accuracy of a clock, you'd compare it to the position of the sun in the sky. But we've since learned that the Earth's rotation is always slowing, so that's not terribly accurate. And now that we have atomic clocks and a second isn't even as 1/86400th of a day anymore, how do we know how accurate any given atomic clock is? Do you compare it to an even more accurate atomic clock? And how accurate is that one? And so on...
|
[
"We know the definition of the second as \"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.\"",
"If we state that a clock only loses, say, one second in a billion years, it means it measures each of its seconds as the equivalent length of approximately 9192631769.9999999999999999683119 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. (I used a value of 24 hours in the day, and 365.25 days in the year to calculate that number, which aren't accurate but whatever.) ",
"They lose time because they don't keep seconds as accurately as the definition of the second implies."
] |
[
"That would leave a problem considering the meter is defined as the distance light travels in X amount of time."
] |
[
"First:",
"Atomic clocks work by getting a cesium-133 gas, cooling it to near absolute zero (0K), and placing the gas in an adjustable microwave cavity. The microwave cavity is tuned to emit electromagnetic radiation (light) at the precise frequency corresponding the ground-state transition of Cs-133. (You tune it by change the microwave frequency slightly, until the amplitude is maximized--which will occur at the transition frequency). Once you tune your microwave cavity to emit radiation at the precise frequency (9 192 631 770 Hz), you have an electronic circuit count the number of microwave oscillations and after every 9192631770 oscillations you have a second. ",
"Now how can you get errors? You could calculate what you expect from known sources of error, or measure them by comparing multiple clocks. If you have a clock that has an accuracy of 1 in 10",
" (or lose one second in about 3 million years), and over the course of a day one clock measured 794243384928000 and another measured 794243384928008, then these clocks agree to about 1 in 10",
"For known sources of error, you could check ",
"here's one from around the time the stanadrd was being adopted",
".",
"But I'll sum this up to a layman. First note the transition doesn't occur at exactly 9192631770.0000 Hz in all cases, but has some line width (e.g., each Cs133 atom will transition between say 9192631770. +/- 0.1 Hz (not actual error; didn't look up). Generally this effect isn't that bad, because if you look at enough transitions this will average out. Second, there are effects that could cause the center of the frequency to shift (or equivalently make the distribution become assymetric). Roughly, the Zeeman and Stark effect say that quantum mechanical transition frequencies change in the presence of magnetic/electric fields, so this must be accounted for -- especially as your microwave cavity provides an electromagnetic field. Third, the line may not have actually shifted, but you may slightly mistune your microwave cavity (e.g., there is a background transition you measure) causing you to slightly miscount. Overall these effects are quite small but the size of them can be estimated.",
"Note above, I assumed we have some alternative definition of the second (and also Hz) that isn't based on the oscillations of Cs133 to avoid irrelevant complications. This is analogous to how if someone questions whether the speed of light changes throughout the universe, its simpler to talk about it if you define the meter in terms of something other than c (otherwise you have to talk about alpha changing)."
] |
[
"Why aren't we trying to colonize Venus? Why is Mars such the hot-shot?"
] |
[
false
] | null |
[
"I assumed that when you said colonization and contrasted with Mars, you meant on the surface"
] |
[
"Such open-ended questions are better suited for our new-ish sister sub ",
"/r/asksciencediscussion",
". Please consider reposting there instead.",
"However, the answer to your question is likely the fact that the surface temperature of Venus is ~850° F."
] |
[
"Why the surface? What's the temperature of the Venusian atmosphere at one bar? "
] |
[
"esophageal cancer"
] |
[
false
] |
Whats going in in the countries highlighted red here thats causing esophageal cancer to be so prevalent?, or are these places that don't have treatments?
|
[
"It is really hard to say. There are a lot of regional differences between cancer prevalence that we don't full understand, such as the high incidence of prostate cancer in the US. ",
"Wikipedia lists several risk factors for esophageal cancer. ",
"http://en.wikipedia.org/wiki/Esophageal_cancer#Increased_risk"
] |
[
"The \"classic\" med school answer for the elevation in esophageal cancer in those Middle Eastern countries is the increased intake of hot beverages such as teas. Whether or not this is the case or if there are other factors that may increase the incidence I'm unsure.",
"Link to Pubmed abstract on this topic."
] |
[
"Here's similar maps for smoking in males\n",
"http://upload.wikimedia.org/wikipedia/commons/1/1b/Male_Smoking_by_Country.png",
"and females\n",
"http://upload.wikimedia.org/wikipedia/commons/2/2a/Female_Smoking_by_Country.png",
"It doesn't exactly correlate."
] |
[
"Why doesn't dust fly off of a fan?"
] |
[
false
] |
Whether it is a cieling fan or a dust seems to always accumulate on EACH side (front/back) and edge. How come it doesn't fly off of the blades when they are spinning?
|
[
"Some does; however dust can have a charge, such as a static charge in which it sticks to another charged surface. Since ceiling fans are spinning they accumlate a static charge through friction with the air, and attract dust.",
"The static charge attraction is stronger than the centripetal force.",
"As another user pointed out laminar flow is another contributing factor as the closer you get to the fan blades the less flow is occurring. Dye to this as I pointed it the only force really acting on moving the dust off the fan is centripetal force which is overcome by static charge."
] |
[
"This is correct but I would restate it this way: The fan drags the (very near) air around with it; the region where this occurs is the ",
"Boundary Layer"
] |
[
"This is correct but I would restate it this way: The fan drags the (very near) air around with it; the region where this occurs is the ",
"Boundary Layer"
] |
[
"Can ethylene glycol stop an alcohol overdose?"
] |
[
false
] |
[deleted]
|
[
"No. Ethylene glycol is much more ",
"toxic",
" than ethanol. Ethanol, in fact, is the treatment for glycol poisoning. "
] |
[
"if i'm not mistaken i believe ethanol is also used to treat methanol poisoning."
] |
[
"That too. Same enzyme competition. "
] |
[
"Since star's are formed by gathering gas, will Jupiter or Saturn ever become stars?"
] |
[
false
] |
I got thinking about this, and couldn't find anything after a search. As in the title, since they are gas planets then are they still gathering gas and could they eventually (in the very distant future) become stars themselves?
|
[
"Stars aren't formed by just gathering gas, stars are formed by a collapsing gas cloud. That's a significant difference, because the first one implies stars could grow just by collecting stuff, whereas the second says, that a given mass just contracts to a smaller volume. ",
"Stars after formation emit stellar winds, blowing out all remainder out of their system, making further growing impossible. Only stuff gathering ",
" powerful stellar winds emerge contributes to the size of the star, i.e. stuff that was falling towards the center of the star's progenitor (a so called proto star). ",
"Material that doesn't do so but enters an orbit forms planetesimals, which have a limited time to gather material from the proplanetary disk, before all the light stuff gets blown out by the star. That's actually one of the reasons why you have rocky planets close to the sun: the solar wind and high temperatures evaporated the light elements like hydrogen and helium, and only the gas giants had more times because it is cooler out there and the solar wind had to spread over an bigger area, losing much of its power. ",
"After a star's formation, no more material can enter the system in form of gas, because the stellar wind which moves outward deflects all incoming interstellar gas, rendering planetary growing via that way impossible. Only collecting gas from the star itself or via collisions could let a planet grow. However the amount of gas from the solar wind is way too small to make any noticable difference. Collisions also can't contribute much more, as Jupiter mass is roughly 3 times higher than the mass of all other planets together. ",
"To create a brown dwarf, a substellar object that is capable of fusing deuterium for a very limited amount of time, you need at least 13 jovian masses. The smallest star requires already 75-80 jovian masses (not exactly known yet). ",
"So no, the planets are never gonna ignite and form stars, except you find another 75 jupiters to collide with our own in literally cosmological timescales. "
] |
[
"Would the star, before it collapses in on it's self and ignites look like a gas giant planet (only on a much larger scale) ? ",
"In short, no.",
"Star formation starts out with an pretty ordinary gas cloud, mainly made from hydrogen and helium and a small percentage of heavier elements. In these gas clouds, you have one or more of denser areas, for example after the shockwave of a nearby supernova hit a part of that gas cloud. ",
"Denser areas have a higher gravitational pull, because there is more matter in them and these pull cause the other material to fall to this point, which then becomes even denser and so on. As the material falls toward this center, potential energy is transformed in kinetic energy, which is then converted into heat when particles collide ",
" the center. The process is similar to an air pump, material that is compressed becomes warmer. ",
"Material always emits radiation based on its temperature, called ",
"Blackbody radiation",
". The hotter it is, the bluer it becomes, it's the exact same reason why heated metal becomes red, orange, yellow and white with increasing temperature. ",
"Long before the outer rim has a particular shape, the inside is already much hotter than the surface of a star. From outside you would still see some kind of gas cloud, while from the inside you would still see the infalling gas onto a hot bright center, seemingly looking like a star, but not yet in a stable phase of hydrogen fusion. ",
"so the sun sort of preserves how the planets were formed and protects them from stuff from outer space ",
"Yeah, but only against gaseous particles. Heavy objects like comets or bigger or radiation still enters the solar system undisturbed. "
] |
[
"Very interesting and informative, thanks! Here's a question then : Would the star, before it collapses in on it's self and ignites look like a gas giant planet (only on a much larger scale) ? ",
"Very interesting about the solar winds, so the sun sort of preserves how the planets were formed and protects them from stuff from outer space "
] |
[
"What is the most up to date scientific opinion on water fluoridation? If you can cite sources that would be much appreciated."
] |
[
false
] |
Title. My father is trying to convince me that it is horrible because he saw it on Dr. Mercola's website but I believe that to be unreliable. Anything that shows Dr. Mercola is an unreliable source is also welcome, again sources appreciated.
|
[
"Here",
" is the CDC's site about water flouridation studies by the National Academy of Sciences.",
"Here",
" is another site that specifically addresses some of the conspiracy theories and internet propaganda surrounding Flouridation."
] |
[
"For anyone not wanting to click the link, fluoridation is considered a good thing at the concentrations which its normally added to drinking supplies."
] |
[
"The latest scientific studies into the matter concluded that there is no clear link between fluoridated water and reduction in cavities. Another recent study linked fluoridation to higher rates of ADHD. A Harvard study from last year also found significant evidence that fluoride \"may adversely affect cognitive development in children.\"",
"http://truthinmedia.com/new-study-says-water-fluoridation-does-not-reduce-cavities/",
"http://www.newsweek.com/water-fluoridation-linked-higher-adhd-rates-312748?piano_d=1",
"http://www.newsweek.com/fluoridation-may-not-prevent-cavities-huge-study-shows-348251",
"http://www.hsph.harvard.edu/news/features/fluoride-childrens-health-grandjean-choi/"
] |
[
"How long would days be if the earth was twice as big? does the mass of the earth affect the rotation on its axis? and would the extra mass make its orbit around the sun longer or shorter?"
] |
[
false
] |
I have only been able to find videos about what would happen on earth is the planet got bigger. Like gravity is twice as strong, bigger and hotter core, bone density would evolve to be bigger. But I haven't been able to find anything on what happens in the solar system if that were to happen.
|
[
"There is no correlation between planet size/mass and rotation rate, there are a multitude of factors that determine how fast a planet rotates, but the mass isn't one of them.",
" For instance, Venus (almost the same size and mass as Earth) has a rotation period of 243 days, where Jupiter's is only 9 hours 55 minutes."
] |
[
"Similarly, the orbit wouldn't change at all. Our orbit has more to do with the sun's mass than ours.",
"What would change is how other things moved because of us. The moon would have to move more quickly to stay in orbit, giving us a shorter month, or it would have to be further away (making it smaller in the sky, and preventing solar eclipses)."
] |
[
"Always found it crazy that we're perfectly timed to get a proper solar eclipse. It won't always be this way, but we get to experience it."
] |
[
"Is it possible to weld under liquid gasoline?"
] |
[
false
] |
I am familiar with welding the outside of containers with fuel in them by using inert gas, however in one of my class's at college this idea of welding under liquid gasoline became a heated debate. Scenario: Liquid gasoline in a steel bucket thick enough so that welding through the bottom is impossible, and enough gasoline so that you are never near the surface of the fuel. My understanding of it is that it would be possible as long as the welding stayed in complete liquid, away from the surface where oxygen and fumes are present. However I have had many classmates argue that it would not be possible. Anyone know if it would be possible or not?
|
[
"An experiment is in order... "
] |
[
"Got it. I'm not sure that I have any evidence per se, but you're missing a leg of the fire triangle. You have to have an oxidizer in order to have fire. If you are submerged and using a welding technique that does not involve the introduction of oxygen to the welding site, the conditions to cause an explosion simply don't exist."
] |
[
"Sure thing. ",
"Here you go",
" "
] |
[
"Where do the bacteria responsible for armpit and foot odor come from?"
] |
[
false
] |
Symbiotic bacteria like E. Coli comes us from eating food that contains them, but what about the bacteria on the skin of our armpits and feet? These bacteria eat our sweat and produce that smelly odor we all hate. This used to be helpful when humans lived in the wild amongst other predators and the smell can help put off their appetite and save our lives, but nowadays the smell just becomes an annoyance. Remedies like apple cider vinegar's acidic properties seem to be somewhat effective in killing these bacteria on our odorous regions, but the bacteria always seem to revive after a while. Is this because they aren't being completely eradicated and simply repopulate? Do we "contract" more of them by touching clothing? Does the human body produce more of them? Where do they come from and how did they get on our body in the first place?
|
[
"These bacteria have lived on us our entire lives. As a baby passes through the birth canal, the newborn’s skin is colonized by the local bacteria and fungi. For C-section babies, the same thing happens the first time someone touches them. There is an entire biome on a human’s skin, and various changes to the person or environment can alter that. The composition of microbes on various parts of the body differs based on the excretions put out by the local glands."
] |
[
"I'd like to add that the reason one starts to small is because they're able to multiple in much greater numbers under those conditions."
] |
[
"What would happen if a person didnt do anything to get dirty but never washed in their entire life. Would this bacteria become visible and what would the person look like if it did?"
] |
[
"Since O2 is slightly heavier than N2, why doesn't the oxygen in the air sink to the floor?"
] |
[
false
] |
[deleted]
|
[
"The gases in the ocean are dissolved in the water. The random molecular movement in the water wiggles them around too much for them to be able to separate.",
"To be technical, in deltaG = deltaH - T*deltaS, the temperature is great enough that the entropy term is weighted largely enough that the entropy change that would occur from the separation of gases is much more significant than the energy change, so it doesn't happen."
] |
[
"Lemme ask if this is an appropriate analogy?",
"You have a jar filled with mixed multicolored sand. Even though the red sand is ground of the densest mineral represented, it would take too much energy to move the rest of the sand out of the way relative to their respective densities, so they stay fairly evenly distributed?"
] |
[
"Not exactly. It's not that there isn't enough energy to separate them, it's that it would decrease the entropy of the system too much, and the 2nd law of thermodynamics says that it is hard to decrease entropy."
] |
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