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[
"Male vs female perceptions of temperature? Why are women always cold?"
] |
[
false
] |
It seems to me that women experience cold differently than men. Is there any truth to this? If so, what causes the differences?
|
[
"http://www.timesonline.co.uk/tol/life_and_style/health/article5106854.ece",
"And women really do feel the cold more than men, but this is because they are better at conserving heat than men. Mark Newton, a scientist at W.L. Gore, the company that makes Gore-Tex, and a researcher at the University of Portsmouth, explains: “Women have a more evenly distributed fat layer and can pull all their blood back to their core organs.”",
"However, this female heating system means that less blood flows to their hands and feet, and as a result they feel cold.",
"While men and women have same average body temperature, their skin is usually colder. Menstrual cycle also changes body temperature. Because female skin is usually little colder than male skin, many women use men as portable heaters at night time. "
] |
[
"how about when you're in bed with a man?"
] |
[
"This does not seem right. Average surface area of human is one point eight square meters. This would mean that blackbody human would have radiative power of over nine hundred watts and would need nineteen thousand kilocalories per day. That's roughly ten times the average human energy consumption. I suspect the reason for this error is the fact that human body temperature is measured from cavities. It's not actual surface temperature. ",
"I'll be damned. Wikipedia article ",
"Blackbody radiation",
" has chapter ",
"Human body emission",
" that has everything. Radiative heat loss with clothes is about hundred watts. "
] |
[
"What material is the smoothest?"
] |
[
false
] |
[deleted]
|
[
"2) Polytetrafluoroethylene aka ",
"Teflon",
" ",
"1) ",
"diamond-like carbon"
] |
[
"Are you referring to non-lubricated surfaces? For dry surfaces, the lowest friction coefficients are BAM (aluminum magnesium boride, .04) PTFE (Teflon, .05), and DLC (diamond-like carbon, .05).",
"If you consider lubrication, though, friction coefficients get much lower. BAM's CoF goes down to .02, and ",
"diamond on diamond with water lubrication can be as low as .001",
"."
] |
[
"In the realm of biologic materials, articular cartilage exhibits a co-efficient of friction of 0.001. [1-3]",
"This is due to a variety of factors. I can go into detail if requested. Just wanted to add that biologic materials also have low coefficients of friction.",
"[1] Linn FC: Lubrication of animal joints. I. The arthrotripsometer.\nJ Bone Joint Surg [Am] 1967; 49: 1079–1098.",
"[2] Unsworth A, Dowson D, Wright V: The frictional behaviour of\nhuman synovial joints. I. Natural joints. Trans Asme Ser F 1975;\n97: 369–376",
"[3] Jin, Z. M., Pickard, J. E., Forster, H., Ingham, E. & Fisher, J. Frictional behaviour of bovine articular cartilage. Biorheology 37, 57–63 (2000)."
] |
[
"How long did it take the last dinosaurs to die out after the Chicxulub impact event? Was it an immediate extinction event? Did it take months or even years?"
] |
[
false
] | null |
[
"It’s not really clear, obviously not all died out, as we see their ancestors of some theropods today (Birds!). Some suggest that the impact was enough to wipe out most beings pretty much immediately, while other theories suggest the earth would have suffered from rising sea levels, climate change ect which would have affected the food chain greatly, as primary producers would have struggled to survive, failing to feed those next in the chain. Leading to the slow death of the mega lizards. They could have lasted for another half a million years, but we will likely never know, because of the signor lipps effect. Our fossil record is so poor and incomplete that an extinct species likely died many Millenia after the most recent fossil we have today. Great example of how poor our record is, is the Coelacanths, which we thought had gone extinct in the creatceous-paleogene event, because that was our most recent fossil on record. However we found them hanging out ALIVE and well on the east coast of Africa in the 30’s!"
] |
[
"The dinosaurs didn't just all drop dead after the impact. ",
"The extinction was quick on a geological timescale, but still took quite a while. It's still a matter of major debate how long. But it was more in the range of several centuries if not a few millennia than just months or years."
] |
[
"The dinosaurs didn't just all drop dead after the impact.",
"Dinosaurs aren't extinct at all. There many, many dinosaurs alive today.",
"Natural History Museum: Why are birds the only surviving dinosaurs."
] |
[
"Face sweats after eating fruit."
] |
[
false
] |
Sometimes my friend says her face gets really hot and clammy when she eats fruit. It almost always happens with apples, but sometimes pears, pineapple, etc. do it too. Why might this be happening? Is it some kind of mild allergic reaction? She doesn't get any other symptoms like hives, pain, swelling that would go along with an allergic reaction. It's nothing that interferes with her life or bothers her, just a lifelong curiosity that she's never been able to figure out.
|
[
"My face does the same thing, my forehead feels like it is getting waxy or something when I eat apples."
] |
[
"Does this only happen with fruit? For myself things such as Skittles and Starbursts also cause it to happen."
] |
[
"I guess one of my first questions would be how often do you eat fruit, does it happen every time, and what does the rest of your diet look like? How often do you eat other things with a lot of sugar or that are high in simple carbohydrates?"
] |
[
"Do warm blooded and cold blooded animals have the same blood?"
] |
[
false
] |
As in, are the blood cells the same in both animals and just act differently or are they differently built all together?
|
[
"Different animals do have different kinds of blood, each species has variations in their blood cells. A particularly striking difference exists in animals with different pigments in their blood. Hemoglobin is what allows our blood cells to carry oxygen, and is also what makes blood bright red. But some other animals use different pigments, leading to blood colors like purple, blue, green, stuff like that. But it isn't really something that decides whether an animal is cold-blooded or not. Different animals just have different metabolisms. Humans are warm-blooded, we feel nice and warm and can deal with much more varied temperatures than, say, my snake. But I eat 3 times a day, while my snake eats a rat once every 2 weeks or so. It's not really something to do with the kind of blood we have, he bleeds red too, it's more just the fact that he doesn't move that much or anything and the materials of his body aren't as finicky as ours, so he doesn't need to produce that much heat to keep himself going, unlike us."
] |
[
"Well, ",
"http://i.imgur.com/cjeW9o9.jpg",
" is a handy little picture to start you off, feel free to utilise Google U. if you want to know a bit more. But if you're asking how to get into it from an academic perspective, I'd probably recommend looking into molecular biology focusing on invertebrates or marine life, that's where you're most likely to encounter them."
] |
[
"This will certainly be a helpful infographic to start from, and I'm saving it to my screensaver rotation. Thank you!"
] |
[
"Would it be possible to see a Star fade away in daylight?"
] |
[
false
] | null |
[
"It could have been an ",
"iridium flare",
" from a satellite, which are very brief, though usually movement is noticeable. If it was already near dawn, though, maybe you only caught the very peak of the flair and didn't have enough of a time baseline to discern movement. Stars don't change brightness on that timescale as a rule since they are too large (light crossing time for the Sun is ~5 seconds, something that size can't vary substantially at faster timescales than that). Things like supernovae that could occasionally (i.e. once every few hundred years) be visible in the daylight last for several days or weeks. Can't be sure from an oral account, but I'd bet on an iridium flare."
] |
[
"Is that possible to see in daylight?",
"I was thinking that, that the light source would be too big to dissapear in a few seconds, which is what made me ponder it.",
"It was about the brightness of an average star on a good clear night, but in the middle of a blue sky."
] |
[
"The brightest ones could be. They can (briefly) reach magnitudes of -10, which is ~100x brighter than Venus. "
] |
[
"Is there a temperature that is too cold for a computer to run?"
] |
[
false
] |
I was just pondering this subject and I couldn't figure out if a computer would shut down, like when it overheats, but due to it being too cold.
|
[
"The chips will have a minimum temperature rating, typically either -25C (248K) or -40C (233K). (As an example, the Intel Atom E3805 is -40C). ",
"But there is an actual threshold below which SiGe (Silicon Germanium) transistors are not viable, which is between 40K and 100K depending on the exact transistor type.",
"The main reason the generic chips from Intel and most other semiconductor vendors is rated only to -40C (233K) is the rated tolerance on various parameters. For example, the Atom E3805 is rated for 1.33GHz at room temperature (298K, 25C), but would probably be derated to maybe 1.1 GHz at -55C. (The exact number is speculation)",
"Also, chips like the Atom E3805 have ceramic capacitors mounted to the die. These caps also have a temperature limit due to their chemical construction and fall off sharply when you get too hot or too cold. This affects the stability of various subsystems in the chip.",
"Interesting link: ",
"http://www.extremetemperatureelectronics.com/"
] |
[
"What exactly is the physical mechanism that prevents operation at low temperatures? With bipolar transistors I'm thinking it's lack of thermal diffusion of charge carriers? What is the mechanism in MOSFETs?",
"EDIT: One reply below has been downvoted a lot, but no-one has explained what is wrong with it. Guys, you're not doing me a favour by just downvoting him without correcting the content. I'm not learning anything here."
] |
[
"Yes there is, and people trying to overclock on liquid nitrogen can hit this limit. It varies by individual processor. Silicon ceases to be semiconducting at -230C, and most processors (Intel 22nm at least) will boot at -140C. "
] |
[
"Can we predict when a gene will be expressed?"
] |
[
false
] |
Genetic modification in the 20th century was a bit of a crapshoot -- literally. You'd put a bunch of DNA on some pellets and shoot them into a plant with an air gun, it's honestly so hilariously basic, it's surprising that it works. That, and Sanford is just a crazy person now. But that's another story. But the genes get inserted pretty randomly, which is weird to me. Do we just practically test the organisms afterwards to see which ones got the insertion right? Or can we predict when or how often a gene will be expressed from its contents and location in the genome? Or do we not know this yet?
|
[
"We can predict whether or not a gene will be expressed based on its promoter and other regulatory regions that control its expression. But we don't need to predict expression as we can just measure RNA levels as ",
"u/jeanmi_bce",
" pointed out.",
"As for gene editing. It used to be more of a random process but methods like ",
"TALENs",
", and ",
"zinc finger editing",
" were developed to help target more specific sequences. Eventually CRISPR would be discovered which is now the gold standard for genome editing. This uses a template against a specific sequence in the genome so we know exactly where genes are inserted (mostly, there can be off-target effects). If we're editing an endogenous gene, we'll know our inserted sequence will be expressed when that gene is normally expressed. ",
"We can also insert a whole new promoter + coding sequence into a ",
"safe harbor locus",
" (an place on a chromosome where we can edit without messing up other genes). Depending on the promoter sequence, the gene will only be expressed in certain conditions. They can be cell type specific (eg only dopaminergic neurons), location specific (eg using the ",
"CRE-loxP system",
"), drug activatable (eg ",
"DREADDs",
"), responsive to certain cellular stimuli (",
"nutrient deprivation",
"), or just always on. ",
"Selecting the right promoter sequence",
" is critical when gene editing to make sure you get proper gene expression in the tissues/cells you're interested in."
] |
[
"Well so you can measure RNA levels. Only genes being expressed will have their RNA present. So we usually run things like qPCR to test genetic expression. And yes modifying the genome (which is not expression) can alter expression of other genes by making them more or less accessible. Think of it like this, your DNA is basically a long series of amino acids, so a bunch of elements all with their own charges and bonds dictating how they fold. That folding is important, it can alter how accessible the gene is to be transcribed and then become a functional protein. As for genetic modification, it isn’t at random. You modify specific place on the chromosomes, adding genes in at specific locations."
] |
[
"Well, when you insert such a big construct such as an entire gene, you might as well introduce a strong promoter or any other regulatory sequence that we know will increase the expression of the adjacent sequence.\nYou pretty much got it right in your question. Insertions are somewhat random and we then select among the successful insertions for the most appropriate candidate to keep. I know it might sounds weird or even dumb not to try harder to engineer the insertions, but remember that keeping it simple is often key to success.\nAnd just as food for thought, nature has proven that semi-random changes coupled with selection produces pretty good results in the long run."
] |
[
"Are there any animals that have adapted to survive better in human made structures to the point where they wouldn't survive in the wild?"
] |
[
false
] | null |
[
"I would say that ",
"purple martins",
" qualify as a non-domesticated species almost entirely dependent on man-made structures. If not the whole species then certainly the eastern subspecies relies on nest boxes. ",
"Purple martins are large swallows that nest in cavities. They nest almost entirely in artificial nest structures in the eastern US, and are pretty much absent from areas where nest boxes aren't provided. ",
"More broadly, humans intensively manage a lot of wild species, propping up low or dropping populations. Of course these are typically due to human activities (habitat destruction, overharvesting). It's not directly a man-made structure, but anything on the IUCN Red List that's ",
"Conservation Dependent",
" or more threatened requires a conservation program. "
] |
[
"Pubic lice, and as TIL has told us many times, they're going extinct because less humans have pubic hair these days."
] |
[
"I think chimney swifts are an even better example - they have only ever occasionally been found to nest in something other than chimneys or similar structures. Where they nested before people in North America built chimneys is probably large hollow trees that mostly dissappeared with the old growth forests of eastern NA)"
] |
[
"Why doesn't Hubble's law imply an accelerating universe?"
] |
[
false
] |
I had been under the impression that Hubble's law described the accelerating expansion of the universe, but it looks like it predates the accelerating universe model by 70 years. Hubble's constant is in units of distance/time/distance. I would expect a non-accelerating expanding universe to have units of distance/time, and an accelerating universe to have units of distance/time/distance (or distance/time/time, but this should essentially be the same thing for light traveling large distances, right?).
|
[
"If the universe was expanding at a constant rate, I would expect to find every galaxy to be moving away from us at roughly the same speed, regardless of their distance.",
"No, Hubble predicts something twice as far away would be receding twice as fast. A linear increase. Actual measurements show far away things receding faster than linear, the deviation is the \"acceleration\". It might be more clear if they called it a ",
"jerk",
"."
] |
[
"If a car is acceleration, you don't measure its speed in length/time",
". It's still length/time, it's just changing value.",
"Is the Hubble constant not a measure of acceleration? Does the constant change over time? If the universe was expanding at a constant rate, I would expect to find every galaxy to be moving away from us at roughly the same speed, regardless of their distance. How can the rate of expansion be constant if further galaxies are moving away faster?"
] |
[
"If a car is acceleration, you don't measure its speed in length/time",
". It's still length/time, it's just changing value.",
"Is the Hubble constant not a measure of acceleration? Does the constant change over time? If the universe was expanding at a constant rate, I would expect to find every galaxy to be moving away from us at roughly the same speed, regardless of their distance. How can the rate of expansion be constant if further galaxies are moving away faster?"
] |
[
"Why do d and especially f orbitals show poor shielding effect?"
] |
[
false
] |
[deleted]
|
[
"You might say that the d and f orbitals are generally less ‘penetrating’ compared to the s and p orbitals; you are less likely to find an electron close to the nucleus for a d or f orbital.",
"Higher orbital angular momenta means that these orbitals have fewer radial nodes. So they typically end up with a large primary radial position where it’s most likely to find the electron. s and p orbitals of the same n, on the other hand, have a greater number of radial peaks of likely probability, with more of these peaks much closer to the nucleus.",
"See ",
"this",
" for more details, in particular point 23 on page 10."
] |
[
"\"create space\"",
"It's not about the electrons having \"space\", it's about shielding the positive nuclear charge. This changes the potential the electrons find themselves in. Electrons that are more likely than other orbitals to be closer to the nucleus will shield the nuclear charge from other orbitals. The s and p orbitals have more peaks in their radial distributions than the d and f orbitals and many of those peaks find themselves closer to the nucleus: thus good shielding.",
"Mercury is liquid in part due to contraction from poor shielding, as discussed, but actually a majority of the contraction of mercury's atomic size ",
"can be attributed to relativistic effects",
". The contraction of mercury's size and orbitals means its 6s electrons are more \"inert\" but it also means mercury is less polarizable. So the intermolecular (inter atomic) interactions (such as Van der Waals forces) are weaker. Thus mercury is a liquid."
] |
[
"Thanks for the answer, that really helped me. I actually asked that to know why is mercury liquid in standard conditions and I found out its mainly because of the poor shielding effect of 5d and 4f. So does it mean that 5d and 4f orbitals have generally less places with high probability (radial nodes), so they can \"create space\" for 6s electrons to be attracted to the nucleus? Or am I mixing things up?"
] |
[
"Is there an evolutionary counterpart to the mantis shrimp that lives on land?"
] |
[
false
] |
After reading the oatmeal comic about the mantis shrimp, I was wondering if there was a counter-creature to the mantis shrimp that lives on land, or even if it would be possible for the mantis shrimp to evolve to be a landed creature. Would it be possible to keep its incredible speed on land?(referring to its supercavitation) I you haven't seen the comic, here it is:
|
[
"You can't get cavitation in a gas. Gasses will always expand to fill the available space, so you can't get bubbles of less-dense gas in the same way bubbles can form in a liquid."
] |
[
"I'd like to piggyback here to ask how much of a difference there is between supercavitation in a liquid and supercavitation in a gas. How much more difficult is it to achieve?",
"Also, could this be applicable in any way to aeronautics, in order to reduce drag?"
] |
[
"you read my mind. I was thinking that the forces underwater would work better because its more dense or something like that."
] |
[
"Why does lighting a match do such a good job of obliterating bad toilet smells?"
] |
[
false
] |
Seriously. Sometimes I even gross myself out, but lighting a match seems to be a miracle cure. Is it that the scent is much stronger than the body odors, or does it somehow neutralize the chemicals that produce the smell? Just something I remembered to wonder this morning.
|
[
"You speak of a couple minutes, but a match only lasts a few seconds; the notion that that's enough to burn off the majority of the sulfurous compounds in the air seems very implausible. Besides, if that were the cause, the same effect should be obtained with any form of open flame, even ordinarily smell-less ones."
] |
[
"You speak of a couple minutes, but a match only lasts a few seconds; the notion that that's enough to burn off the majority of the sulfurous compounds in the air seems very implausible. Besides, if that were the cause, the same effect should be obtained with any form of open flame, even ordinarily smell-less ones."
] |
[
"I'm pretty sure that the smell of the sulphur igniting in the head of the match just overwhelms your sense of smell.",
"\nI know mythbusters did an episode on this, and I remember them disproving the \"burns up the smell\" idea. ",
"Here:",
" ",
"Hydrogen sulfide quickly deadens the sense of smell."
] |
[
"How and Why does the regularization of divergent series work when it comes to Casimir Effect/Physics?"
] |
[
false
] |
Hey. Background on what I know when it comes to this topic: I'm a math boy (if you up during real mathematician hours, smash that like) and at first, series/summation inspired me to learn more math, but lately I just want to learn/comprehend more math so I can apply it to summation (LOL) and in the past I've played with alternating geometric series and used that to assign those special values (Regularizing negative integer values of Dirichlet's Eta function), but just recently i figured out why and how Ramanujan summation works and i was able to directly regularize the divergent series associated with negative integer values of the Zeta function. I am just a clueless bum when it comes to physics, my first course ever was this semester (It was newtonian stuff; no calculus) and I had to drop it because I had a hard time getting a grip on the material. Can someone explain to me how and why does the regularization of divergent series work when it comes to Casimir Effect/Physics? I'm confident with what I know when it comes to the math behind this. I've read an introductory paper about this effect, but it was mainly mathematical and just barely any physics (There was a reference to a vaccum inside a prism and something about the total energy not being equal to zero, but that was like the second page and there was barely any physics after that).
|
[
"I've written about ζ-reg in the Casimir effect ",
"here",
", there are also a few links you could find more useful."
] |
[
"One thing that often isn't appreciated is that the \"vacuum fluctuation\" derivation of the Casimir force is actually just a convenient approximation, appropriate in the limit that the fine-structure constant of the walls is infinite. The full derivation involves considering retarded (speed-of-light delayed) van der Waals (dipole-dipole) interactions between the walls. See here: ",
"http://arxiv.org/pdf/hep-th/0503158.pdf",
"I realize that this does not answer your question, but you might find his background text (which is well presented) to be helpful."
] |
[
"The statement \"1+2+3+4+...=-1/12\" should be thought of as the following proposiiton: \"If 1+2+3+4+... could be assigned a number in a meaningful way, then this number has to be -1/12\". We'll let \"meaningful\" be vague, but the only thing that we require is that typical summation manipulations work. In fact, in many of the \"proofs\" of 1+2+3+...=-1/12, they start out by saying \"Assume that 1+2+3+... has some value S\" and then they proceed to show that S needs to be -1/12. No one every proves that it has a value, but if it were to have a value, it would have to be -1/12. ",
"In other words, if we have proved \"If a+b+c+... can be assigned a number in a meaningful way, then that number must be S\" and we encounter the sum a+b+c+... in a context that requires a number to be assigned to it in a meaningful way, then we can forget everything about convergence and assign S to it. Convergence guarantees that we can assign a number to it, but we can assign a number to it without convergence too.",
"It should be noted that there are infinitely many ways that we can look at a sum and it can converge in some and diverge in others. The real numbers aren't special. For instance 1+2+4+8+16+...=-1 converges in the ",
"2-adic Norm",
" but not the real one. Which one is correct? Neither, because no convergence scheme is special.",
"This brings me to physics. In Quantum Field Thoery, when something has a chance of happening, it will. All possible interaction happen simultaneously, and contribute some amount to an interaction. So when trying to figure out an interaction in Quantum Field Theory, you need to sum over an infinite number of possibilities that are all contributing to the interaction. In this context, we are encountering sums that we are already assuming can have a finite number assigned to them. We can check whether or not these sums converge, but that would not be of any help because even if they diverged in the reals there could be some other convergence scheme where they do converge, plus we are already assuming that it does have a finite value, so testing convergence is wasting time.",
"For example, there are interactions that require a finite value for 1+2+3+4+.... I don't need to check whether or not it has a finite value, because I'm assuming that it ",
". Luckily, I have a theorem that tells me that the only meaningful number to assign to is -1/12. So, in this context, I must have 1+2+3+4+...=-1/12. Physics says this sum needs a finite value, and we have a theorem that says there's only one meaningful number that we can assign. Our hands are tied, no need to worry about convergence because we, a priori, are assuming this sum is finite and under this assumption the sum has to be -1/12.",
"(Note that we can't compute these sums in typical ways, because computations assume that we are assigning a value via convergence. But this is limiting, so we have to figure out other ways to determine these numbers.)"
] |
[
"Does the Coastline Paradox actually apply to reality?"
] |
[
false
] |
[deleted]
|
[
"You would in theory, but it doesn't matter. The coastline paradox didn't get its name because of what would hypothetically happen if you measured the coastline sandgrain by sandgrain, it got its name from what happens if you actually measure a coastline using the range of scales that people normally use to map things. ",
"This issue of the difficulty of measuring coastlines has been informally known to mapmakers for ages, but was first rigorously documented by Richardson in \"The Problem of Contiguity: An Appendix to Statistics of Deadly Quarrels\" (1961). ",
"This paper was picked up by Benoit Mandelbrot who applied some \n more mathematics to the problem and popularized it in his paper ",
"How long is the coast of Britain",
". This paper predates Mandelbrot's coinage of the term \"fractal\" by several years and he credits it as being instrumental in helping him develop the idea and make it accessible to a wider audience. The term \"coastline paradox\" does not actually appear in the paper, but it's the clear origin of the concept. ",
"As Mandelbrot writes in his annotations at the end of the paper (which were added later as part of a book, I think). ",
"Fortunately, I stumbled one day upon Richardson’s empirical data on coastline lengths, and recognized instantly that a study of coastlines might lend itself to a ‘‘Trojan horse’’ manoeuver. Indeed, everyone has a knowledge of geography, but no one I knew professionally had a vested professional interest in facts and theories concerning coastlines and relief. The manoeuvre succeeded. Everyone was wonderfully objective and receptive to the seemingly wild idea contained in this paper, and as a result, became more receptive to the use of fractal dimension in fields that really matter to me.",
"Basically, the coastline paradox is called the coastline paradox because the everyday problem of measuring coastlines on maps is something people are familiar with or can easily grasp, and as a result it made it easy to explain the concept of fractals to people (even before the term \"fractal\" had actually been coined). Calling it the fractal paradox wouldn't be helpful because the idea is to help people understand what fractals are in the first place, so you need a relatable comparison."
] |
[
"The most real occurrence of this phenomenon is the border between Portugal and Spain.",
"Spain is much larger than Portugal and their size difference has actually led to them using differently fine grained measurements in their official cards. That lead to Portugal sharing a significantly larger border with Spain that the very same border seen from the much larger Spain."
] |
[
"You have to start fighting Quantum Mechanics around the atomic scale, which means you need to be careful about how you define the border/coast in the first place since everything is probabilistic. In principle if you come up with a definition based on the median border location, it will have a well defined length.",
"Practically, this would be useless because this length would vary rapidly with time. For a coastline, consider the change in length as waves lap up and down, or for a border defined by the midpoint of a river of mountain range, consider the effects of erosion. Both will cause very large changes compared to an atomic scale on a timescale less than a second."
] |
[
"Why do you initially start to feel better when you have radiation sickness?"
] |
[
false
] | null |
[
"Well I'll start it off by saying the initial \"sickness\" is actually your body's immune response. The body is literally trying to repair the damage caused by the radiation. The symptoms felt are how the immune system fights infection and damage. In fact most of the symptoms you feel when you get sick with the flu or common cold are your own body's immune response.",
"However with lethal radiation poisoning, the damage happens too fast and is too extensive. Eventually the immune system is damaged beyond repair as well, so the immune response stops altogether. Thus the patient \"feels better\" but in reality their body is still being shredded by radiation and cascading organ failures."
] |
[
"This was answered nicely by ",
"/u/thetripp",
" in a ",
"post",
" from a while ago.",
"Acute radiation poisoning is the result of damage to very specific cell populations in the body. Radiation is much more lethal in cells that are undergoing cellular division. As a result, the stem cell populations that produce blood cells and intestinal tissue are most sensitive.",
"In short, what happens is that a large dose of radiation can destroy the underlying stem cells of the bone marrow that produce blood cells. Normally, blood cells last about 1 month in circulation before they are removed/replaced. After acute radiation poisoning, no more blood cells are produced, and your blood stops working when existing cells die off. A similar effect occurs in the intestinal lining.",
"So the reason why there is a delay is - it isn't the functional cells that are dying. The cells that replenish the functional cells are the ones damaged most strongly by radiation.",
"As an aside, this is why large doses of radiation are given as a preparatory regimen when someone receives a bone marrow transplant. Patients with cancerous bone marrow come to us, and we give them what would ordinarily be a fatal whole-body dose of radiation. By killing off the entire bone marrow, this destroys the cancer. Then they are implanted with new bone marrow to resume normal blood functions."
] |
[
"No, radiation that kills off your bone marrow is targeted to a specific place in your body. This is just an example of a practical application of radiation poisoning.",
"In actual radiation poisoning, there are pockets of stem cells all over your body that get destroyed. It could be the ones in your bone marrow or it might be the ones hanging out just underneath your skin."
] |
[
"Can oil spills happen naturally?"
] |
[
false
] |
I have always wondered this say there is a large oil reserve under the sea bed is it possible for the ground to break from movements in the earths crust or anything like that and for oil to leak out into the sea?
|
[
"Oil 'spills' would not be the best word for it. There are places on the southern coast of California and in the gulf of Mexico where oil seeps out of the ground, but its often unnoticed and occurs at a very slow rate. Also, this usually isn't pure crude oil, but a mixture of natural gas and other oils. A few species are able to consume the oil as well and live around these places."
] |
[
"Look up La Brea tar pits.",
"These are called oil seeps and they can be seen around lots of oil fields in the world.",
"For example, the Denver-Juelberg basin in Colorado has oil seeps.",
"They are very low flow rate and trickle up through tiny fractures in the rock. Often, this oil has been moving up ground for a thousand years."
] |
[
"A large number of mud volcanoes are present around the globe, both on land and under water. A large percentage of them are present in subduction zones. Many of them leak hydrocarbons. It is entirely possible that a natural oil spill happens due to an abrupt increase in activity of a mud volcano or due to a new rupture or fissure above an oil reserve, but there are no records for something like this as far as I know. With so many satellites around the globe, we will catch the next one when it happens."
] |
[
"Can Solar Panels be charged with Nuclear Radiation?"
] |
[
false
] |
Or is it possible to create equivalent panels which can? Sort of like "nuclear panels"? If so, can they exist now? Wouldn't it be more effecient utility of nuclear energy than boiling water?
|
[
"You can use the decay heat to produce electricity - ",
"radioisotope thermoelectric generators",
" (RTGs) do that.",
"For beta decays you can directly use the radiation and let the electrons fly through a potential difference - ",
"betavoltaics",
".",
"You could in principle let ionizing radiation pass through a material that emits light, and then use the light in a solar cell, but that would be really inefficient.",
"For nuclear reactors the fission produces fast particles somewhere deep inside the reactor - you can't avoid that getting converted to heat, and then your efficiency depends on how well you convert that heat to electricity. Boiling water is very good in that aspect. There are some ideas for alternative reactor geometries but they exist only on paper as far as I know, and they all come with major downsides."
] |
[
"It just has to be higher energy. A gamma photon can produce multiple excitationts in a solar panel, and will still leave on the other side with most of its energy. It would probably give too much energy off on each interaction and result in significant additional kinetic/heat energy. Could make the charge carriers produced energetic enough to produce further pairs on their own. This would imply that if you had an intense enough gamma source to produce noticeable voltage on the panel, it would probably damage it very, very quickly. But either way, not easy to get that kind of intensity with gammas. Just putting it next to an unshielded nuclear reactor wouldn't work."
] |
[
"Band gaps are of electronic nature so they should be in the eV range, just because atomic spectra is in this range."
] |
[
"How can the mass of a blackhole increase its impossible to observe something crossing the event horizon?"
] |
[
false
] |
[deleted]
|
[
"I assume by \" its impossible to observe something crossing the event horizon\" and \"we never see anything entering it\" that you're referring to the idea that it would take an infinite amount of time to observe matter falling to the event horizon.",
"This idea is a misleading simplification. If you naively calculate the time it takes to fall using the Schwarzschild coordinate system you do come up with infinity. But in physics, when your calculations result in an infinity, it's often an indication you need to do something differently. If you choose the ",
"correct coordinate system",
" in which to make your calculations, you'll find that it doesn't actually take infinite time. ",
"[In addition, black holes in the real universe aren't expected to be Schwarzschild black holes, which are spherical, non-rotating, and non-charged. Real black holes are more likely to be rotating and (nearly) non-charged and therefore follow the Kerr metric. But once again, using the ",
"right coordinate system",
", you'll find that it does not take infinite time to cross the event horizon.]"
] |
[
"We can easily observe things falling into a black hole right up until the event horizon. When that happens, we can measure an increase in the gravitational force of the black hole exactly equal to an increase in mass of what just fell in. We still don't know what happens past the event horizon, but the gravitational increase stays put, (with the exception of Hawking radiation, which is a different subject). "
] |
[
"The mass of black hole is predicted using the effects it has on the space around it.For example,it is possible to calculate the mass by observing nearby stars or how the black hole curves the light we observe.\nAlso,sometimes stuff falling into the black hole heats up and starts emitting radiation,so sometimes we actually can see the stuff that falls in."
] |
[
"What percentage of the ocean could we bring to a boil using all the nuclear fuel on earth?"
] |
[
false
] |
If we were to take all of the fissile material on earth (out of all the world's nuclear weapons and power plants and untapped mines), and created a giant nuclear boiler, what percentage of the oceans could we boil away?
|
[
"If you consider ALL uranium (not just that which can be profitably mined), you get some much more interesting numbers. ",
"http://en.wikipedia.org/wiki/Uranium#Biotic_and_abiotic",
"This estimates the total uranium content of the Earth's crust at 2x10",
" kg, giving 1.4x10",
" kg of U-235. ",
"One kilogram of U-235 can theoretically produce 8x10",
" J. ",
"http://en.wikipedia.org/wiki/Uranium#Civilian",
"This gives a total available energy of 1.12x10",
" J. ",
"The world's oceans have a volume of 1.332x10",
" L.",
"http://www.wolframalpha.com/input/?i=volume+of+world%27s+oceans",
"That gives 8.41x10",
" J/L, just over 3.3 times as much energy as is required to boil the water.",
"So about 3.3 world oceans could be boiled."
] |
[
"In a napkin sketch calculation, ll of the uranium readily available, is about 5.4 megatons of Uranium. Of that, 0.7% is fissile uranium, or about 37800 metric tons. That will produce roughly 3x10",
" gigajoules of energy. Boiling water requires 2540 kilojoules per liter.",
"Therefore, you're looking at about 1250 km",
" of water boiled. ",
"The volume of the worlds oceans is approximately 1.3 x 10",
" cubic kilometers. ",
"This is roughly 1 ppm or 1 millionth the volume of the oceans that we could boil with all of the (known and exploitable) uranium on earth. ",
"Also, note that once we boiled it, it would rain back down. "
] |
[
"Aww, we are such puny humans! With all our grandiose dreams and ambitions!",
"What if we include non-fissile uranium, like the stuff that was in the cooling ponds at fukushima that boiled all their water away? I would guess there is a lot of lower grade radioactive materials that give off a lot of heat but aren't used by prissy nuclear reactors."
] |
[
"Would second-generation stars have had planets? Could they concievably have supported life as we know it?"
] |
[
false
] | null |
[
"...aren't we literally orbiting a second generation star?"
] |
[
"To people saying our sun is a second generation star, our sun is actually thought to be a third generation star. Heavier elements weren't produced in the big bang. Population II stars although having low metallicity do have a significant amount. This means there must be a previous generation created with zero metallicity to produce the heavier elements. These Population III stars would be very massive and have a short lifetime finishing with a supernova. They haven't been observed although they are considered as the probable progenitors for long gamma-ray bursts."
] |
[
"No, they're named after the order in which they were discovered, which is the opposite to the order in which they developed, since we had to wait for better telescopes to discover the older ones.",
"Edit: Note that we can't actually see any Population III stars."
] |
[
"Thousands of species are said to have already gone extinct or are going extinct due to human activity. Are there any known species that are currently going extinct unrelated to human activity, and if so how is that measured?"
] |
[
false
] |
[deleted]
|
[
"Secondary question first. Avocados have unusually large seeds. Most mammals cannot carry or swallow a seed so large. The seeds were probably evolved to be spread by giant ground sloths.",
"Giant ground sloths (four tons of armored sloth!) were ",
"probably avocado eaters.",
" The sloths are gone but humans still propagate the seeds.",
"It is suspicious that the sloths and almost all other North American megafauna died off about the time humans arrived. People debate whether to blame human hunters...",
"~~~",
"It is hard to make a species extinct if it is widespread. While armored against every threat in its home habitat, the Pinta Island Galapagos tortoise only ever had one island. If possible spread your species to as many islands as you can so a single disaster such as a volcano or one sailing ship full of hungry humans cannot easily get all of you."
] |
[
"There is no 'should' or 'shouldn't' be when it comes to extinctions, but I assume you meant are there any species that would be extinct if it weren't due to human intervention. We would expect some species to have gone extinct over the past few centuries even if human didn't exist, based on what we know about the extinction rate of species in the past [",
"https://en.wikipedia.org/wiki/Background_extinction_rate",
"]. ",
"Pointing to specific examples is difficult since humans have affected so much of the planet. One possible example of a species caught 'going extinct' could be the ",
"wollemi pine",
". It was a tree thought to be extinct before around 100 were discovered in a gorge (although we don't know how many were previously destroyed by deforestation). Pines such as the Wollemi were much more widepsread until 40 million years ago when the climate of Australia changed. Because of its current limited range it could be easily wiped out in the wild by a single fire. Now the plant has been cultivated and you can buy it in a plant store, so it is unlikely to go extinct. All that being said, you can't truly say a species is going extinct until its extinct, you never know what changes might occur to allow the species to spread again. A fire may have wiped out the remainder, but also, a comet could have hit the planet causing climate change that suited the pine!"
] |
[
"I dont think the Galapagos tortoise is a good example, after all the tortoise did spread to every island of the Galapagos. But they speciated (although thats still debateable) because there was little gene flow between the islands. So its not that the pinta tortoise only had one island, but that they evolved/speciated on that island. ",
"If humans had not come along, the Pinta island tortoises genes may still have existed through occasional gene flow to other islands, even in the case of a volcano wiping out the island."
] |
[
"Can the body create muscle mass from stored fat reserves or can it only create it from ingested protein?"
] |
[
false
] |
If someone's overweight and trains hard and gains muscle mass. Will the muscle mass gained be only from ingested protein via food or have the body been taking stored fat and converting it into muscle mass?
|
[
"While energy from mobilized fat can be used to synthesize fat, and the carbon and hydrogen may contribute to the final product, you can't make protein from fat alone.",
"Nitrogen is needed for protein (as well as traces of sulfur and other elements for some). There is no nitrogen in stored fat, nor is the body able to convert nitrogen gas in the circulatory system to organic nitrogen."
] |
[
"So, no. Basically, mammals have no way of synthesizing new amino acids. They can do various kinds of synthesis to make the carbon skeleton that forms an amino acid, but fundamentally animals have to make use of a transamination reaction to convert this carbon skeleton (an α-keto acid) into an amino acid. That is, they can move the amine group from an existing amino acid to an α-keto acid, but ",
".",
"This means you already cannot synthesize an amino acid from just a nitrogen source (such as ammonia). You need to consume amino acids. \nNitrogen assimilation to form amino acids occurs in plant roots via glutamine synthetase, but animals do NOT produce amino acids this way (glutamine synthetase is only used in some tissues to reduce ammonia concentrations to prevent toxicity). ALL of the amino acids you need eventually come from plants (or fungi and various other microorganisms).",
"In addition, because the transamination reaction involves producing an α-keto acid as a product, it's expensive to synthesize novel amino acids this way. Humans have a certain number of \"non-essential\" amino acids that they can make from de-novo synthesis (involving a transamination reaction). However, this synthesis will produce an &alpha-keto acid, and while in some cases it is easy to get rid of this (alanine transamination produces pyruvate, for example, which you can just chuck into the citric acid cycle), in other cases it is not (imagine phenylalinine), and you have to go through a lot of hassle to get rid of the waste products.",
"Animals that are fed only the essential amino acids therefore do much more poorly than animals that are fed a full complement of amino acids.",
"Long story short: Nitrogen supplements are a waste of time. You are better off just eating protein."
] |
[
"Mindboggling as it might seem, but weight loss is mainly through two by products of metabolism, with most of it actually in gaseous form, CO2 and the rest water. I had never thought about it until my friend asked me about weight loss and I had to rethink about fat metabolism. \nthe \nBy increasing muscle mass will actually increase your metabolism overall. The easiest way to do that is to actually lift legs. Your legs are much stronger than your upper body and are more active in your daily activity than your upper body.",
"Source: B.S. Biomedical Engineering~ Systems Physiology class",
"Edit:bad info pointed out by ",
"/u/GeneralRobert"
] |
[
"Can alloys be separated?"
] |
[
false
] |
Can alloy mixtures be split up, back into their elements? Like extracting the carbon from steel, to get pure iron, or separating the copper and tin in bronze? If it can, how does the process work?
|
[
"The process is different for each alloy. Some can be separated when heated by burning off impurities, others can be chemically bonded with elements that naturally disperse like an acid. You would need to google each process individually.",
"The only one I've ever tried first hand was using nitric acid to dissolve gold."
] |
[
"Copper can and is purified using electrolisis, however in metals recycling, copper alloys are often recycled as their alloy, and perhaps some adjustments made during the melt to achieve a desired composition. ",
"Most wire in electronics is tin plated. Rather than purify it when it's recycled, it's melted into a copper tin alloy. "
] |
[
"I though electrolysis only works in ionic compounds, not mixtures. Because the copper in the alloy isn't charged, it won't be attracted to the electrodes?"
] |
[
"Can a cell's proteasomes be turned against the cell?"
] |
[
false
] |
Since a cell's proteasomes identify and destroy what proteins need to be destroyed, could this be hijacked somehow to destroy the cell from the inside?
|
[
"Maybe, but it may not be the best way to do it. A distinct feature of the proteasome is that it has high specificity, meaning that only proteins that are tagged with ubiquitin are recognized and degraded by the proteasome. This specificity requires ATP. So, for destroying the cell, it may not be the most effective system.",
"For large-scale destruction of cellular components, autophagy is a better way to go. It takes up bulk cytoplasmic components (including proteins) and degrades them in lysosomes.",
"In addition, less specific proteases such as calpains might be more effective. This is akin to using nuclear weapons and cluster bombs (calpains/caspases) vs. laser-guided missiles (proteasomes).",
"I'm 5 months late, but I think I can provide some guidance."
] |
[
"I'm currently doing research on the proteasome and searched it on AskScience to see what came up. I found this and you just made my day to think of these things as laser-guided missiles."
] |
[
"I thought my question was dead, but thank you for answering it."
] |
[
"Are there any mammals that do not sleep?"
] |
[
false
] | null |
[
"No. The brain needs rest, and that rest is taken in the form of sleep. Some aquatic mammals are able to use what is called Unihemispheric sleep, where only one half of their brain is asleep at a time - this way, they are still semi-conscious while their brain gets the rest it needs."
] |
[
"Aside from the correct answers on unihemispheric sleep, the mammal that requires the least sleep overall is the giraffe."
] |
[
"Every creature with a brain, needs to sleep. The question being, why do we need to sleep, why not just skip over it ?"
] |
[
"How did scientist know how much protection astronauts needed on first moonwalk?"
] |
[
false
] |
Seems like since there was NO basis for comparison they were kind of just "winging" it. Did they make earlier suits for animals and stuff to see which ones survived? I am just confused how they would know what would allow humans to survive in a place they had never been before?
|
[
"Seems like since there was NO basis for comparison they were kind of just \"winging\" it.",
"How so? We had already performed spacewalks. We know the design requirements which a vacuum poses.",
"Other than lower gravity and somewhat higher ambient radiation, there isn't much difference between a vacuum produce on Earth by evacuating air from a sealed chamber and the vacuum of space present on the Moon."
] |
[
"I mean how did they even know it was a vacuum?",
"Because if space weren't a vacuum, anything orbiting the Earth at high velocities would burn up in short order. But meteors and such don't burn up until they hit Earth's atmosphere, and the probes we had sent up previously confirmed that there was very very little air up above a few hundred miles.",
"As for the Moon, it's fairly easy to show that any atmosphere it ever had will be quickly swept away by the solar wind. The Moon just doesn't have the gravity to hold onto an atmosphere well."
] |
[
"Here's two Wikipedia articles that should keep you busy for a few days:",
"http://en.wikipedia.org/wiki/History_of_spaceflight",
"and",
"http://en.wikipedia.org/wiki/Space_Race",
"The short version: Rockets were developed for military purposes (initially as weapons of terror, then eventually as a delivery vehicle for nuclear weapons). Early space missions were of the \"shoot this collection of sensors into the sky, and see what we find\" variety. A lot of information about the structure of the atmosphere and the conditions of nearby space were determined in this way, long before it was possible to send humans into space."
] |
[
"When I stand up/get up rapidly, and then I get extremely dizzy, almost to a point of passing out - What is that experience/moment called?"
] |
[
false
] | null |
[
"Could be ",
"Orthostatic hypotension",
". "
] |
[
"Likely this!\nHave you had your blood pressure checked?",
"Do you drink enough fluids?",
"Are you on any medications?",
"It may be a good idea to wear a Holter monitor, which could measure and record your BP every hour or so (usually for 24 hours) and see if anything funny is going on. Ask your doctor."
] |
[
"I agree! I think this is it, and I do have a semi-low blood pressure (I recently became a CNA so I had my vitals checked often during class), but I will check on that monitor with my doctor. Thank you!\nEdit: Grammar"
] |
[
"Askreddit didnt seem to interested in this question, trying it here. If it isn't correct place for if I apologize. How should the world mitigate the effects of climate change?"
] |
[
false
] | null |
[
"Just letting you know that your question was caught in the spam filter, and I'm going to leave it there. The reason is that ",
"/r/askscience",
" explicitly avoids questions looking for opinion or speculation, both of which would be required to answer your question. If you wanted to re-word and resubmit (suggestion below), I suppose that would be okay, but climate related questions are a HUGE source of disagreement in the scientific community. While this isn't my area of expertise, past questions about climate change evidence a disagreement about what exactly are the causes of climate change, so I'm fairly certain there is little agreement about the best methods to handle it. That said, if you wanted to resubmit, a better question suited for this subreddit would be something like, ",
"\"Based on current scientific understanding of climate change, what are the leading theories for the most successful methods of mitigating the effects of climate change?\"",
"All the best!"
] |
[
"Thank You! I may do that later on or tomorrow. You have given me some things to think about. "
] |
[
"No problem. If your post doesn't show up in /new within a few minutes, message the mods so one of us can free it from the spam filter. Have a good one."
] |
[
"How do solar panels turn light into energy?"
] |
[
false
] | null |
[
"Solar panels turn light into ",
" That's an important distinction.",
"The short answer is something called the ",
" Put simply, shining light on a particular type of material liberates electrons from the atoms in that material, causing them to move about. Moving electrons is electricity.",
"(Sorry, said \"photoelectric\" originally, should've said \"photovoltaic.\" It's going to be one of those days, apparently.)"
] |
[
"Being light. Light interacts with charged particles; electrons are charged. When an atom absorbs light, the outermost electron bound to that atom gains energy.",
"In some materials, electrons with certain energies are in what's called the ",
" Electrons in the conduction band — that is, electrons with the necessary energy — are free to move around in the material, instead of being tied to a particular atom. The movement of electrons is, again, electricity, and we can do things with it.",
"Imagine being at a stadium during a sporting event. You're sitting there in your seat. You can stand up, you can lean to the right and to the left, but you aren't free to move about really.",
"But if you get up and climb the steps to the landing, you're now free to move unobstructed about the stadium. You can just walk around and around it if you want to, or you can find another empty seat and walk back down the steps to take it."
] |
[
"shining light on a particular type of material liberates electrons from the atoms in that material",
"I guess that's the part I don't understand. What exactly is the light doing that would break the bonds?"
] |
[
"Are there any theories regarding why agriculture (or civilization) emerged independantly multiple times recently?"
] |
[
false
] |
As I understand things, the human species has existed in its modern state for more than 100k years, and for almost all of our history, we've been hunter-gatherers and then suddenly, like a cambrian explosion, settlement and farming emerged a few times almost at once. Is it simply that there hasn't been an epoch more conducive to the prerequisite series of events for these developments than the holocene?
|
[
"David Christian of Big History suggests that it was a result of Earth coming out of the last ice age about 10.000 years ago. Humans for a large part appears to have had all the technologies necessary for agriculture, but simply didn't need to. Increasing in population put pressure on humans to increase the amount of energy extracted from the same area of land. In fact it appears things like living standards and life expectancy went ",
". But those who did go into agriculture started to simply out compete surrounding hunter gathers in shear numbers. When your population density is more than an order of magnitude higher, war becomes almost trivial.",
"The rest is, as we say, history. "
] |
[
"Prior to the last ice age is over ",
"100k years ago",
". We hadn't even left Africa at that point. It's too early in our history. "
] |
[
"Very good question. Unfortunately, the answer is rather complicated. (",
": There were a lot of things happening at the same time. Agriculture is kind of like a symbiotic relationship between plants and humans, and the conditions that allowed this to develop first appear during the Holocene. How this relates to the origins of complex society is even more complicated.)",
"First, you have to understand that when you're talking the origin of 'civilization,' you're really talking about four major changes:",
"You are correct in pointing out that this seems to happen at about 6 different places at the same point in time. (The classical six, in chronological order, are Mesopotamia, Egypt, Peru, India, China, and Mexico.) Unfortunately, these things don't always happen in the same ",
" everywhere. For example, cultures on the coast of Peru c. 3000 - 2,000 BC developed cities with central planning without any agricultural food source. So while we can identify general trends that seem to occur, we can't really reduce it to some kind of formula to produce a civilization. ",
"Not all hunter-gatherers are nomadic. Foragers that make use of maritime or lacustrine resources, for example, may live in permanent settlements along shore lines. Other hunter-gathers are semi-nomadic and have specific places they go to depending on the time of year. Others have migratory patterns that follow specific prey (the cliche example of this is the Lakota of the US great plains who followed American Bison.) All of these patterns can lead to domestication of the food resource in question, but complex society requires that at least some of the population lives in permanent residence at one location. ",
"It is likely not a coincidence that many (although not all) early settled agriculturalists lived in areas where there were lots of resources concentrated in one location (rivers, coastlines, valleys, etc.). It makes sense if you think about it from a cost-benefit framework. If it's easy for you to get all of your resources in one place, it makes sense for you to stay there regularly or exclusively. ",
"Agriculture is about more than just planting. Domestication is an evolutionary change that takes place in plants and animals as a result of humans interfering in the reproductive cycle of the organism. However, this isn't necessarily a conscious process and in some cases seems to happen by accident. The wild precursor of maize (corn), for example, is widely believed to be teosinte. However, teosinte is barely edible in its wild form. It does not appear that the Archaic Period inhabitants of Mexico were planting it as a food source. Instead, its possible the grass simply grew in disturbed environments near campsites and people began collecting it. The other possibility is that people were growing it intentionally but as a supplemental food (i.e., to make beer). Over time people consciously or unconsciously selected those cobs which had larger kernels and more easily removed seed husks. Over time, the plant evolved into maize. ",
"Although we often phrase domestication as something we do to plants, its important to realize that we were also changing in the process. As maize became larger and had a higher caloric yield, people began producing it more. Population went up, and the intensity of farming went up with it. Humans were now interfering in the plant's reproductive cycle to the point where it was dependent on us to reproduce. As a result, it evolved to be more attractive to us. And in response, humans adjusted their culture to make heavier use of it. Since all of this took place over thousands of years, this was not likely something humans set out to do. It just sort of developed as a symbiotic relationship beneficial to both organisms. ",
"Now, as to why this seemed to happen at the same time in multiple places, this ",
" has something to do with the ecological changes that occurred during the Holocene. Warmer climates and the growth of grasslands meant that the conditions necessary for this symbiotic relationship to develop were more common. ",
", we have to be cautious with this interpretation. Its easy for archaeologists to correlate changes in human society with paleoecological changes, but correlation does not imply causation. Some of this may be bias introduced by the fact that paleoecological changes are easier to see than more ephemeral changes in culture, society, and politics. There is likely more to the picture that we're still missing.",
"Now the hard part: how does this tie in to the development of 'civilization?' Most of the \"Old World\" civilizations (like Egypt and Mesopotamia) developed agriculture first, then cities, then social complexity. However, it doesn't look like that pattern is universal. Andean civilizations, for example, developed cities and social complexity first, then agriculture. In Mesoamerica agriculture gets started early, but the domestication process takes a long time. Cities and complex societies develop before the process finishes.",
"Unfortunately, there really ",
" a good explanation for why complex societies developed. We've identified a number of key factors, but a lot of research needs to be done before we can be conclusive about this. Most archaeologists are split between two camps: managerial efficiency (or ",
") models and agency (or ",
") models.",
"These models attempt to explain complex society as part of a system that people buy into. The most famous example of this kind of model is Karl Wittfogel's Hydraulic Hypothesis. Wittfogel hypothesized that complex societies developed in Egypt and Mesopotamia because people needed a central authority to manage irrigation systems. With population increases in these regions there was not enough water for every farmer to use whatever he wanted for his own fields. A kind of 'tragedy of commons' developed, and to combat this people developed centralized institutions that could regulate water consumption. It's fairly well established that ancient Mesopotamian city governments and the Egyptian state did in fact do this, but it's causal importance in their origin has not been established.",
"These models developed as a critique of the top-down character of managerial efficiency models, which don't really explain why an ",
" would want to buy into this. Think about it: if you're John Q. Farmer and a guy comes up to you one day and says you're only allowed to use ",
" amount of water, why would you listen to him? What reason would you have in even acknowledging his authority over you? Agency based models seek to address this by looking at economic and ideological factors in the origin of complex society. These have been gaining lots of ground recently in archaeology, but they currently lack unity.",
"So basically, bottom line: we don't know the exact reasons complex societies developed yet. There are two major theoretical camps, but there are about as many different ideas on this topic as there are archaeologists. "
] |
[
"Why are we unable to unite the theories of quantum mechanics and general relativity?"
] |
[
false
] | null |
[
"It is difficult from a variety of angles. The main fundamental difficulty is that in quantum mechanics particles' positions are defined with respect to some spacetime. In basic quantum mechanics this spacetime is flat, but you can imagine making quantum mechanics work in a curvy spacetime. That's not so hard. But quantum mechanics applies to spacetime itself. Imagine trying to explain the classical double-slit experiment. A single particle approaches the slits, and its wave function interferes with itself past the slits, leading to a pattern on a phosphor screen. But with gravity in the mix, the part of the photon's wave function that went through the left slit, and the part that went through the right slit, each alter spacetime in different ways. So you not only have a quantum superposition of ",
" (as in ordinary QM), but a superposition of positions ",
". The problem then is how do you combine the two incompatible spacetimes in order to calculate a probability. Ordinarily you would add the quantum superpositions and square to get the probability (Born rule). But now you can't simply add the superpositions because they belong to different spacetimes. It's just not an easy problem. Another related but distinct fundamental obstacle is that time in quantum mechanics is treated not as an observable but as some external parameter. This is no good when you are dealing with curvy spacetimes which involve relative time dilations.",
"Another problem (probably the one most often brought up) is related to renormalizeability. This is a fancy way of saying that it is difficult to calculate anything that depends on small-distance behavior, because if you reach a certain energy density you produce a black hole, and a black hole is a necessarily extended object. This means that our tools for calculating the effect of physics at small distances breaks down, because when you look smaller and smaller at a certain point you start producing black holes which are extended and have multipole moments etc and an infinite number of parameters are necessary in order to experimentally constrain the theory. ",
"A related problem is that if quantum mechanics applies to a spacetime that is dynamical (as in General Relativity) then when you try to calculate things that depend on small-distance behavior, you will end up having to understand and compare complicated spacetime topologies, which is a fundamental mathematical obstacle because these topologies are known to be non-classifiable, meaning that you can't compute whether some topologies are equivalent to others.",
"Another problem is that quantum mechanics is fundamentally incompatible with the equivalence principle. This is because the equivalence principle is only true in a locally flat region of spacetime, but quantum mechanical wave functions are necessarily extended objects. This problem is easy to see by just applying the Schrodinger equation to a particle in a gravitational field, and you find the inertial and gravitational masses don't cancel!",
"Another problem is the black hole information problem, basically that a black hole's entropy scales as its area, even though according to quantum mechanics the entropy of a group of particles goes as the volume. So somehow it seems that information is lost when a black hole is formed or when matter falls into a black hole, in contradiction with quantum mechanics.",
"Anyways, as you can see, there are a lot of problems, some of them deep and fundamental. Some deeper framework is needed, such as string theory, in which the two frameworks can coexist in a compatible way. That said, we ",
" do ",
" basic quantum corrections to gravity already in the weak field limit, where we basically treat spacetime as nearly flat, and only consider low-energy/large-distance behavior. "
] |
[
"It is theoretically possible that only one of the two theories needs to be modified in order to accommodate the other, yes. "
] |
[
"It is possible but unlikely that we will ever have a correct theory. It would be difficult to know when you get there, since we will always have some maximum energy level or observational accuracy that is current state of the art, and we wont know what is beyond that until we get there."
] |
[
"Is anything truly random?"
] |
[
false
] |
Like it may SEEM to be unexplainable and random but is everything patterned if you trace it far enough?
|
[
"You are basically describing ",
"Laplace's Demon",
". However quantum physical processes can be completely random. e.g. ",
"radioactive decay",
" is perfectly random. You cannot predict when a particle will decay. You can only give probablities. "
] |
[
"You cannot predict when a particle will decay. You can only give probablities.",
"We can't say that a process is certainly not deterministic just because the best description we have for experimental predictions of that process is stochastic."
] |
[
"There are versions of quantum mechanics where it is deterministic behind the scenes, but in all cases there are events that cannot be predicted without ",
" with perfect knowledge and there's no way to get that knowledge. ",
"In other words, the existence of unpredictable events is a law of physics (and will probably always be), even if there is ultimately something non-random underneath it. These quantum events are as random as anything can be, and they can be used to make cryptography that can never be broken or intercepted. "
] |
[
"Do a baby's nails grow while it is in the womb? Or is that somehow inhibited?"
] |
[
false
] | null |
[
"Yes! and the rate of growth is much faster than adults; the nail beds first appear at 12 weeks gestation and by 20 weeks they can be seen as translucent layer-similar to fetus skin-, the formation of nails is pre-genetically determined and ends 34w for fingernails and 38w for toenails at that time they become hard and slightly sharp, after birth the nails can be trimmed and they grow again as normal."
] |
[
"Sorry, are you saying the nails ",
" growing after 34 (38) weeks and then ",
" growing after birth? What biochemical process triggers nail growth resumption? In particular, is it prompted by actual birth (e.g., the sharp switch over to breathing as method of oxygenation), or is it just timed to about 9 months, so prematurely born babies don't have nail growth for a while?"
] |
[
"Yes, fetuses have nails that begin forming in the end of the first trimester. Fingernails develop earlier than toenails, but by the time a full term baby is born, they have complete nails. In fact, they often need a trim soon after being born! The stage of nail development can sometimes be used to determine how premature a baby is. If you've ever seen a new litter of kittens or puppies you'll notice that they're born with claws just as we're born with nails."
] |
[
"How are food expiration dates determined?"
] |
[
false
] |
I asked this before, but without qualifying "food" and got a whole spectrum of answers. How are food expiration dates calculated? Do two items packaged on the same day received the same date? Why can two different products (companies), with effectively the same ingredients (e.g., salsa) have different dates? Would produce grown in one part of the world have a different expiration than another, i.e., are there environmental differences in inherent in the product(s)? Why do some things take so long to expire (Sriracha!), some things go really fast (milk) and some things expire (honey)?
|
[
"Bacterial counts, color/texture degradation, aroma, and suchlike. Whether or not a product has 'gone bad' is either regulated (in the case of microorganism growth) or arbitrary (in the case of sensory quality). Arbitrary quality thresholds are usually determined by panels of human subjects, to determine when the 'typical consumer' would no longer want to consume the product."
] |
[
"This ",
"USDA page",
" has a wealth of information in this subject.",
"Of note:",
"\"There is no uniform or universally accepted system used for food dating in the United States\""
] |
[
"Check on ",
" every few days? What is being measured? How does one determine \"things are going bad\" over time?"
] |
[
"Why do some words sound so similar in languages that have diverged so long ago?"
] |
[
false
] |
Examples (pronunciation) Mama: Chinese: mama Papa: Chinese: baba Two: Hindi: do French: deux Romani: duj Man: Tamil: manitan French: homme Romani: rrom Chinese: ren Ten: French: dix Hindi: das I found many other examples; mostly in numbers. Is it purely coincidental, or could it be remnants of homosapian's prehistoric language?
|
[
"Mama and papa are probably special cases, being reset each generation because they are some of the first things babies can say (repeated syllables help, a is apparently an easy vowel, the consonants only require control of the lips).",
"As for your other examples, all the languages you mention, except Chinese and Tamil, are ",
"indo-european",
", so they are related. Two of your examples are words for numbers, which typically change much slower than other words.",
"So, those other examples, are they between languages in the same group, e.g. indo-european, or are they between languages that are farther apart?"
] |
[
"Wikipedia ",
"lists Romani as an indo-european language",
", though it is on another branch than any of the others you mentioned. I can't seem to find anything about an indo-european branch, the word indo-european seems to be only used about the whole group and proto-indo-european.",
"Anyway, I don't think it is remnants of the original language, with the simple justification that there are people trying to find that, and they don't seem to be having very much luck. If there were some obvious examples, they would have been found. This is, of course, not a very good argument from a scientific point of view."
] |
[
"Tamil: manitan",
"French: homme",
"Romani: rrom",
"Chinese: ren",
"I mean, I'm no linguist, but how similar are these words really? Maybe the pronunciations are closer but these don't look especially similar.",
"I'm only replying to you so as not to make a top level."
] |
[
"How does time dilation work?"
] |
[
false
] | null |
[
"Ah-ha! This is a fun one to answer. Time dilation occurs because of the principles of special relativity (there's also gravitational time dilation but the principle is similar to what I'll talk about here).",
"So what are the two principles of special relativity?\nthe first is that physics should work the same in every frame of reference. Moving at a different speed shouldn't change the result of an experiment you're carrying with you. ",
"The second principle is that in every possible frame of reference, ",
". ",
"How does this relate to time dilation? We can use a thought experiment to demonstrate its existence. Imagine you have two observers, travelling at some speed ",
" relative to each other. In order to measure time, we need a clock, so one of the two observers is carrying a light clock with him. It works by bouncing a beam of light between two mirrors which have a fixed distance L between them. Since the speed of light is constant, the time taken to travel the distance L always happens in the same time. Simple right? The time taken for the light to travel from one mirror to the other is the tick of our clock. ",
"Now let's think about the other observer. He sees the whole light clock moving at ",
". Because physics works the same in every frame, the photon should still be bouncing between the two mirrors. The difference is that because the mirrors are moving, the photon now has to travel ",
" between bounces. Google brings up lots of diagrams showing this situation, with many looking like ",
"this",
".",
"Now we get to the crux of time dilation. Since the speed of light is constant, but the distance it has to travel is longer for the observer it's moving relative to, the time between each \"tick\" (the photon bouncing off a mirror) is longer for the moving observer! That's time dilation!",
"Now the part that'll really make you scratch your head is the fact that each observer sees the other observer having time dilated! It's not a paradox because time is not an absolute measure but is relative- everything follows its own natural rhythm in its own frame, but the transmission of that information can only travel at the speed of light, leading to distortions in observation like time dilation."
] |
[
"A clock in one inertial frame of reference will tick at a different rate than an identical clock in another inertial frame of reference, or another clock in a stronger or weaker gravitational field."
] |
[
"Objects approaching a black hole get flattened because of ",
"tidal forces",
", not time dilation.",
"If there's anything incorrect in your post, you'll get downvoted. People can't upvote half your post and downvote the other half."
] |
[
"Do all bees belong to a \"nest\"? Are there any bees that live on their own?"
] |
[
false
] | null |
[
"Yes, there are some species of bees which don't form colonies, they are known as ",
"Solitary Bees",
"."
] |
[
"And of bees that do form colonies, all bees have to live in a colony; to my knowledge, there is no species of bees that forms colonies where an individual bee may survive without a colony."
] |
[
"Some bees are called solitary bees and do not live communally, but still build their own nests. ",
"Also, parasitic bees (aka cuckoo bees) do not search for food or build nests on their own. Instead, they use the nests and food of other bees. They can be classified into \"cleptoparasitic bees\" and \"social parasites\". The former attack the nests of solitary bees, hide their eggs in the chambers before the host lay their own and close the chambers."
] |
[
"How can we flip an electric cord plug over in a wall socket? Why don't the different charges fry the electronics?"
] |
[
false
] | null |
[
"This is by virtue of the outlet being wired for alternating current. In AC, the voltage cycles back and forth, and current flow does the same. The connection therefore has no polarity, though one pole is \"live\" side. Conversely, direct current has a high pole and a low pole, and current flows from high to low. If you reverse bias a DC component, you can easily damage it."
] |
[
"In those electric devices where the cord can be flipped, the “direction” of the flow doesn’t matter. Like a lamp, where the electrons simply go in one end and out the other.",
"Where the “direction”does matter, there will be things to help make it work, such as the larger prong on the plug, or some AC-to-DC conversion, where again the “direction” doesn’t matter.",
"In the cases where it does matter, and there aren’t protections, you’ll often get nothing or broken electronics."
] |
[
"In those electric devices where the cord can be flipped, the “direction” of the flow doesn’t matter. Like a lamp,",
"Lamps are one (two prong) thing that can't be flipped. In fact they were the main (possibly only) reason why the outlets have a wider slot. It's so the easy to touch screw base is not connected to the \"live\" wire.",
"Where the “direction”does matter",
"Only for human safety. It doesn't matter for the electrical operation of any device plugged into the outlet.",
"In the cases where it does matter, and there aren’t protections, you’ll often get nothing or broken electronics.",
"DC electronics are behind a bridge rectifier whose inputs can be hooked up to AC supply either way. This isn't \"protection\", it's conversion. So there's no situation where it would result in nothing or broken electronics."
] |
[
"What are gravitational waves and how do they affect objects?"
] |
[
false
] |
[deleted]
|
[
"First, you should feel comfortable going up to your professor and asking these questions!",
"Anyway, it's actually the gravitational potential energy of the system that is converted into gravitational waves. Because the orbit shrinks, the two objects will also orbit around each other more quickly, so the kinetic energy of such a system actually goes up. The underlying mechanism, though, is that any mass curves ",
"spacetime",
", and when two masses are in a binary, you will get ripples in spacetime that look something like ",
"this",
" in 2D. In 3D, it looks more like ",
"this",
" (remember that spacetime is 3 dimensions of space, 1 of time, so it's like that image but with complex time evolution).",
"When a gravitational wave passes perpendicularly through a circular ring of objects, let's say, it will look something like ",
"this",
". In general, it causes lengths to change (the x and y directions get bigger and then smaller in this case). Spacetime stretches and compresses, if you want to think of it like that. It's typically quantified with the strain h ~ ΔL/L, or the change in the length divided by the total length. If you look at the ",
"gravitational wave spectrum",
", you'll see that these numbers are extremely small. NS binaries systems are all the way on the bottom right (NSB), and have a strain around 10",
" That's why projects like LIGO and Virgo are trying to measure changes in distances over a few kilometers to well within the width of a proton. For pulsar timing experiments, the strains are a little higher, but it still means that you're trying to detect the change in distances to pulsars within a few 10s of meters... over a distance of thousands of lightyears.",
"As with anything in GR, there's a time piece to consider because spacetime is one connected object. However, gravitational waves exist in the limit that you are close to a flat spacetime, one in which it looks like an unbent 3D grid, as compared with the first picture I linked, for example. You can write out gravitational waves as a small perturbation on top of this flat spacetime. As I said, h is really small, so this is a small change to flat spacetime. The time piece remains as if it were flat spacetime, so in this approximation, there's no differences in times between both spacetimes. So, it's sort of by construction. The biggest perception in time difference to consider is that since path lengths are changing, the time it takes light to travel over the path changes (because c is constant), so in that sense, measurement times change, but I wouldn't say this is the same thing as a relativistic time correction."
] |
[
"No problem. And sorry, I was just checking, you are of course free to ask questions here. Tell him he should learn more!",
"Short answer: ",
"/u/Fenring",
" gave a very nice and concise answer to your follow-up, so I'll post a link there: ",
"link",
". ",
"Additional stuff: In the case of pulsar timing experiments, this means that we can search for a large supermassive black hole binary emitting what we call continuous gravitational waves. They effect on the arrival time of pulses would look somewhat like a ",
"sinusoid",
" like in the left side of this image, but not quite since it's actually part of a chirped signal. Note that for us, the orbital period should be in years and the amplitude should be a bit larger. This waveform would vary depending on where the source was in the sky but should be correlated in some way, e.g. pulse arrival times from two pulsars in the same direction with respect to us would be heavily correlated. Anyway, because you have a statistical ensemble of these supermassive black hole binaries all over the sky, what you should also be able to detect is from what we call the stochastic background, made up of all of these waves interfering, but should still be heavily correlated in some semi-complicated way. So yes, they definitely do interact with each other."
] |
[
"No problem. And sorry, I was just checking, you are of course free to ask questions here. Tell him he should learn more!",
"Short answer: ",
"/u/Fenring",
" gave a very nice and concise answer to your follow-up, so I'll post a link there: ",
"link",
". ",
"Additional stuff: In the case of pulsar timing experiments, this means that we can search for a large supermassive black hole binary emitting what we call continuous gravitational waves. They effect on the arrival time of pulses would look somewhat like a ",
"sinusoid",
" like in the left side of this image, but not quite since it's actually part of a chirped signal. Note that for us, the orbital period should be in years and the amplitude should be a bit larger. This waveform would vary depending on where the source was in the sky but should be correlated in some way, e.g. pulse arrival times from two pulsars in the same direction with respect to us would be heavily correlated. Anyway, because you have a statistical ensemble of these supermassive black hole binaries all over the sky, what you should also be able to detect is from what we call the stochastic background, made up of all of these waves interfering, but should still be heavily correlated in some semi-complicated way. So yes, they definitely do interact with each other."
] |
[
"If you fill a tire to 30psi of normal air, and an identical tire to 30psi of another gas (say, helium) do they weigh the same?"
] |
[
false
] |
Would the helium compress more due to its lower mass, and end up weighing the same amount?
|
[
"No, assuming they are at the same temperature. In that case, each tire contains an equal number of molecules, but each gas has a different molecular weight. "
] |
[
"No, the helium is still lighter. If you take the ideal gas equation and rearrange it, you get N/V=P/kT. On the left you have the number density, and you can multiply that times the atomic mass to get the mass density."
] |
[
"An equal number of molecules? Fascinating. Thank you!"
] |
[
"Does hearing loss occur largely in a top down fashion? as in you lose the ability to hear high frequencies first?"
] |
[
false
] |
Could you lose hearing of low frequencies too? Low sounds don't seem to hurt my ears as much at higher volumes.
|
[
"High frequency loss is the most common but other patterns occur. ",
"I have low frequency loss; I can hear high frequencies just fine - considering my age - but I don't hear low frequencies well. ",
"I can hear most things just fine, but men who do not enunciate well are very challenging to understand."
] |
[
"Hey, go get a hearing test. They don't cost much and results can be useful for life.",
"Low-frequency hearing loss will be correlated with difficulty hearing conversation in large groups of people, or difficulty hearing in locations with background music. Basically: do have trouble communicating in busy grocery stores or crowded bars?",
"High frequency hearing loss is most common. It's just so happens that most of the damaging sounds in our lives have high frequencies (and the receptors in our ears are most sensitive to those.)",
"Low frequency hearing loss is typically defined as damage in the ability to detect frequencies <2000 Hz. It's typically caused by ",
", which is damage to the hair cells in the inner ear that receive the sounds and convert them to signals that are transmitted by the auditory nerves to the brain.",
"Third type is called a \"",
"cooke bite hearing loss",
".\" It's where you have lower sensitivity for a specific frequency somewhere in the middle. This one is usually hereditary as it can be due to impairment of the cochlear or auditory nerve.",
"It's most frequently age related; next most possible is genetics mixed with environmental damage such as listening to too much heavy bass music (or industrial equipment). It won't affect everyone, but people with relatives who also having low-frequency hearing loss, themselves are more sensitive to also developing environmental caused hearing loww."
] |
[
"I took one maybe 7 years ago in college, but I'm wondering how often I should get checked. I make music for a living."
] |
[
"If we were to bring up a life form from the depth of the Challenger Deep..."
] |
[
false
] |
... would it be able to survive? My understanding is that they evolved to live in those crushing depths, so does that mean that since there is a lot less pressure on the surface it would in a sense fall apart?
|
[
"There are several key effects at play:",
"Gas volume would change going from the deep to the surface so any internal gases, such as within an air bladder in a fish, would cause problems as they expanded at lower pressures.",
"Worse yet gas solubility in liquids, especially water, changes depending on pressure. A given quantity of gas that will be in solution (effectively in liquid form mixed with another liquid) at depth may not be fully soluble at the surface, causing bubbles to form. This is the mechanism that causes \"the bends\" and it's probably the most serious problem to overcome in this case.",
"Also, there is a very much subtler potential problem. Chemical reactivity is dependent on pressure, it's possible that an organism's molecular machinery may not function correctly at lower pressures than its natural habitat. Potentially even a protein's 3-dimensional structure (and thus its chemical properties) could be different at different pressures.",
"In principle, it's possible for an animal to be capable of existing at the surface and at extreme depths, but in general the odds are against it."
] |
[
"I believe death would result from your second point. It would likely be something along the lines of opening a soda bottle but happening inside of each cell. Raising them slowly so as to avoid the \"bends\" may be possible but then the animal would likely die from your 3rd point. "
] |
[
"I think there are many organisms that migrate between tiers of the abyss and can withstand a relatively variable amount of decompression. Whether or not their cells could maintain structural integrity at 1atm would be really cool, but horribly traumatic to observe. Definitely feels like something from my nightmares to \"explode\" on the cellular level, all at once.",
"I also like the question of whether or not the organism would go through the bends like we do as a result of decompression. I think both of you are correct in that there is significantly less free molecular nitogen and oxygen at that high a pressure. So the likelihood of death by nitrogen bubbles is low, but maybe molecular nitrogen would be toxic to a deep sea organism?",
"Very interesting question. "
] |
[
"How can a man survive after cutting off his own arm, while I almost faint from bloodloss after accidently cutting two fingers?"
] |
[
false
] | null |
[
"Human Body"
] |
[
"Human Body"
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
"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."
] |
[
"What is the purpose behind Phillips(cross-head) screw heads? Mechanical efficiency?"
] |
[
false
] |
From an engineering standpoint, why does Phillips even exist? I can't count the number of Phillips I've stripped. I also find myself occasionally cheerfully wishing murder on the inventor.
|
[
"What?!?! Flathead is the absolute worst! Try using a power screwdriver on Flathead. Are you kidding me?"
] |
[
"Created by Henry F. Phillips, the Phillips screw drive was purposely designed to cam out when the screw stalled, to prevent the fastener damaging the work or the head, instead damaging the driver. This was caused by the relative difficulty in building torque limiting into the early drivers.",
"http://en.wikipedia.org/wiki/List_of_screw_drives#Cruciform_types.23Phillips"
] |
[
"Phillips exists as a self-centering screw head with a lock in mechanism. Think about it this way. The production line emerges as a new manufacturing technique. You need a screw head in which a bit can quickly insert itself, lock itself in, not slip out. The bit needs to be center into the head as well, so it rotates with the screw. It also needs to be easily manufacturable. All of these criteria are met by the Phillips.",
"If"
] |
[
"What is the smallest subatomic particle?"
] |
[
false
] |
That atoms are made of electrons, neutrons, and protons. I know that these are made of quarks, leptons, and gauge bosons. But how far does this all go?
|
[
"Electrons aren't ",
" of leptons, they ",
" leptons.",
"If by \"smallest\" you mean \"occupy the least space\", then the answer is \"your question doesn't ",
" make sense\". There are various ways in which we can define the \"size\" of a subatomic particle—de Broglie wavelength, impact parameter, et cetera. For composite particles, like protons and neutrons, there's also things like \"average distance between components\" where \"average\" can take on various meanings ranging from expected value to variance. Then there's always the possibility of defining size in terms of mass.",
"That said, one way to think about the \"size\" of subatomic particles is in whether or not they are composite. Protons and neutrons are made of quarks, for example. In that sense, the \"smallest particles\", being the particles that are, to the best of our knowledge, ",
" composed of \"smaller\" particles, are the leptons (electron, tauon, muon, and their neutrinos), quarks (up, down, top, bottom, strange, charm), and the fundamental bosons (photon, gluons, W and Z, Higgs)."
] |
[
"According to our current best knowledge, quarks and leptons have no substructure. Protons and neutrons are made of quarks; electrons are leptons. The gauge bosons - also apparently without substructure - mediate the forces that hold everything together."
] |
[
"Protons and neutrons are made of quarks, which are fundamental particles. Quarks are bound to one another through the strong force, which is mediated by gluons, which are fundamental particles and a type of gauge boson. Electrons are a type of lepton, and are fundamental particles. They are bound to an atom's nucleus through the electromagnetic force. The electromagnetic force is mediated by photons, which are fundamental particles and a type of gauge boson. "
] |
[
"Are there viruses that target viruses?"
] |
[
false
] |
Given that we have for example phages that specifically target bacteria is there something that is like a virus for virus? Not counting antiviral medication.
|
[
"Kinda but not quite. A virus needs to infect a cell in order to replicate. Another virus can't infect that virus on its own. However sputnik virophages infect cells that a 'helper virus' has already infected and takes over the cell. Kinda comes down to semantics in a way."
] |
[
"A virus will always need a \"living\" host, for its reproduction (e.g. bacteria, plant, animal cells). Viruses are lacking the machinery that is required for the translation of their DNA/RNA and the assembly of their shells, as they are barely more than information in a container."
] |
[
"It's interesting to note that ",
"giant viruses",
" tend to form large and complex viral factories inside their hosts, which are essentially specialized ",
"sub-cellular compartments",
", almost like a cell-within-a-cell, and that ",
"virophages",
" tend to infect these compartments directly and take them over. So it really does look like one virus infecting another virus, more than one virus infecting a cell that just happens to have been infected by a 'helper virus'. But I agree, in the end of the day it does come down to semantics."
] |
[
"Why is fictional violence 'fun' but real violence terrifying?"
] |
[
false
] |
People spend hours watching youtube videos of crazy accidents,fights, or explosions, when someone gets injured we tend to laugh at it. However, when it happens for real and is actually experienced, it ends up being horrifying. I'm bringing this to askscience 'cause I presume it's something psychological. So, why do we enjoy fantasy violence but not real violence? Is it like a temporary quench of a need for violence?
|
[
"People, either through observation or cognitive deduction, determine at an early age that fictional violence is incapable of causing tissue injury or end-organ damage."
] |
[
"This may be related to Ramachandran's theory of laughter. We laugh when presented with something that might be harmful but wasn't, in order to alert those around us that the danger is actually safe. As with tickling, we are being attacked but not really.. Or when someone slips on a banana, it's only funny if his brains aren't splattered on the floor. There are neural connections that suggest this phenomenon that R explains in his book The Tell-Tale Brain."
] |
[
"PhD in psychology here. I'm going to start out with the obvious. Fictional violence is not real and we know this, so we know there are no bad consequences, and no reason to be terrified. Just because the audiovisual stimuli bear some resemblance to reality doesn't mean we don't know the difference.",
"Now for the not-as-obvious, but not exactly mind-blowing. Fictional violence is often accompanied by a dramatic element. Either a movie where there is a protagonist that is overcoming obstacles, getting revenge, distributing justice, etc, that we view as positive goals and are very satisfying to see, or a video game, where we get to actually shoot the bad guys ourselves. This kind of activity is fun for similar reasons as why sports are fun. We're trying to accomplish a goal, and succeeding is satisfying. And moderate levels of arousal also produce mild positive affect.",
"If we were watching fictional movies where the good guys get thrashed, it's not fun. If we watch a dramatization of a true story where the good guys get thrashed, it's even less fun and somewhat more scary, because we associate it with the real world consequences. If we're watching video footage of actual events, it's horrifying partly because we feel empathy towards the real person. Empathy activates some of the same negative affect in the brain that happens when bad things happen to ourselves.",
"Why do some people watch videos of real events and laugh, while other people are horrified? Well, first of all if it is someone you know and care about you will be horrified while if it's someone who is acting like a douche, you feel some satisfaction that they \"got theirs\". (I don't know right now if there is research on whether people actually do feel the negative feelings at the same time they feel the positive ones in these circumstances though.)",
"And coming back to the original (obvious) point, if the violence happens next to you in real life, there can be elements that something bad will happen to you, which might make you panic, or you realize that you are responsible for helping someone who just got seriously hurt, and you might not know what to do, which also might make you panic.",
"TL;DR There is no psychological need for violence. 1. we can tell the difference between fiction and reality. 2. Fictional violence is often confounded with something bad happening to someone who \"is bad\", thus it is satisfying to see it happen. 3. real violence is often confounded with other direct and immediate consequences for us, which can result in things like panic that make it seem worse."
] |
[
"Why were animals that lived in the ice age so much larger than the animals of today?"
] |
[
false
] |
I was watching a documentary, and it got me thinking: just why were the giant sloths, wolves, cats, bison, elk etc of the ice age so much larger than their modern counterparts? It it just more efficient for them to be smaller?
|
[
"This is controversial, but I think the evidence is good that the big ones were mostly killed off by humans. Big things tend to reproduce slower, slowly reproducing animals don't respond as well to hunting pressure."
] |
[
"It's a question of the ratio of the envelope (skin) over the volume (internal body). When the ratio is small, you have fewer heat loss because the body is less exposed to the ambient cold air. For a sphere, the ratio goes like 1/r (= area r² / volume r³), so higher sphere radius decrease heat loss. In that way, large animals can keep the heat inside them more efficiently than small animals, in that context."
] |
[
"So as one of the comments mentioned it has to do with surface to volume ratio. When you are a warm blooded animal you are constantly losing heat to your environment. Large animals have a smaller surface to volume ratio than smaller animals and so they are better able to retain their heat and thus they waste less energy trying to keep themselves warm. A perfect example of this is marine mammals. There is a reason that whales, dolphins, and seals are as big as they are and that there are no mammals the size of rabbits and cats that live in the ocean. The sea otter is the notable exception but it has a different method of keeping warm where it uses incredibly dense fur to repel water all together. But if that fur ever gets messed up or the animal cannot keep it well preened then they will freeze to death. When the earth warmed it was no longer necessary for those animals to be so large. Being that big is energetically costly and so evolution favored smaller individuals who required less energetic input. "
] |
[
"How long would it take before the stars in the sky move so much you'd no longer recognize them?"
] |
[
false
] |
I was watching BSG again and at some point in the show they start using constellations to navigate. And I was just wondering how long it would take until the stars move so far that you wouldn't recognize the constellations anymore, or just recognize the night sky in general. So lets say you went to sleep now, how far in the future would you have to wake up before you looked at the sky and didn't recognize anything?
|
[
"It would take a very long time. For reference, the star with the fastest proper motion in our skies (at this time) is Barnard's Star, a small, low-mass red dwarf about 6 light years away in the constellation Ophiuchus, the Snake-holder, just above Scorpio. Relative to us, it moves at about 107 km/s, and it's proper motion is 10.3 arcseconds per year.",
"This means that for that particular star, the \"fastest\" star, it moves about a pinky-width (at arms' length) per 3.5 centuries. Most of the other stars move much, much, much more slowly.",
"Moving sufficiently far to no longer recognize constellations is an arbitrary definition, but you'd expect significant drift in position due to proper motion over a time course of about 100,000 years - even then, most constellations would still be similar to their present configurations, but their shapes would be distorted noticeably from present.",
"There's a longer, more thorough explanation here:\n",
"http://www.fourmilab.ch/yoursky/help/proper.html"
] |
[
"Much longer than a normal human lifetime, at any rate.",
"Many of the bright stars in the sky have proper motions (its apparent angular motion across the sky) ranging from a few milliarcseconds per year (e.g. Rigel) to ~50 milliarcseconds per year (Polaris) to around an arcsecond per year (Sirius). For argument's sake, I'll pretend all the stars move ~100 mas/yr. ",
"The human eye's angular resolution is around ~4 arcminutes (=240 arcsec), so to even have a slightly perceptible change, a star moving at 100 mas/yr would take 2400 years. This would not, however, make a constellation unrecognizable. For that, I'd guesstimate that you'd need stars to move by, say, 2 degrees each. At 100 mas/yr, this would take 72,000 years!",
"Even if the highest proper motion star, Barnard's Star, were visible to the naked eye, its proper motion of ~10 arcsec/year would still require 720 years to move 2 degrees."
] |
[
"I started to come in and say \"not very long, only a few hundred thousand years!\"...I occasionally need to get re-acquainted with what normal people consider a \"long time.\" "
] |
[
"[Quantum Mechanics] What exactly is superposition? What is the mathematical basis? How does it work?"
] |
[
false
] |
I've been looking through the internet and I can't find a source that talks about superposition in the fullest. Let's say we had a Quantum Computer, which worked on qubits. A qubit can have 2 states, a 0 or a 1 when measured. However, before the qubit is measured, it is in a superposition of 0 and 1. Meaning, it's in c*0 + d*1 state, where c and d are coefficients, who when squared should equate to 1. (I'm not too sure why that has to hold either). Also, why is the probability the square of the coefficient? How and why does superposition come for linear systems? I suppose it makes sense that if 6 = 2*3, and 4 = 1*4, then 6 + 4 = (2*3 + 1*4). Is that the basis behind superpositions? And if so, then in Quantum computing, is the idea that when you're trying to find the factor of a very large number the fact that every possibility that makes up the superposition will be calculated at once, and shoot out whether or not it is a factor of the large number? For example, let's say, we want to find the 2 prime factors of 15, it holds that if you find just 1, then you also have the other. Then, if we have a superposition of all the numbers smaller than the square root of 15, we'd have to test 1, 2, and 3. Hence, the answer would be 0 * 1 + 0 * 2 + 1 * 3, because the probability is still 1, but it shows that the coefficient of 3 is 1 because that is what we found, hence our solution will always be 3 when we measure it. Right? Finally, why and how is everything being calculated in parallel and not 1 after the other. How does that happen? As you could see I have a lot of questions about superpositions, and would love a rundown on the entire topic, especially in regards to Quantum Mechanics if examples are used.
|
[
"Let's say we had a Quantum Computer",
"Oh god, let's not. Let's start a hell of a lot simpler than that, especially since quantum computers aren't even known to be ",
" possible.",
"Imagine any situation in which there are only two possible outcomes. Flipping a coin, say. The coin's either gonna come up heads or it's gonna come up tails. There are not other possible options.",
"But if you want to construct a ",
" that describes the behavior of a coin being flipped, you need to deal with the time when the coin's in the air. When it's in the air, it's neither heads-up nor tails-up. But those are the only two possible states for the coin to be in! So how can you describe the coin mathematically when it's in this intermediate, indeterminate state?",
"The answer is that you represent the indeterminate state of the coin as a ",
" of the two possible observable states. When I say \"linear combination\" here, I mean in the sense of a math equation. A linear equation is one that looks like \"x + y.\" The x and the y represent the possible observable states (heads-up and tails-up in this example), and the indeterminate state is a linear combination of them.",
"Why represent the state this way? Because you want to be able to ",
" mathematically, which way the coin's going to fall. Not in any one specific toss of the coin; that's unpredictable. But on the ",
" You want to be able to calculate the ",
" for flipping the coin.",
"We all know, intuitively and 'cause we learned it in school, that there's a 50/50 chance the coin will come up heads, and a 50/50 chance the coin will come up tails. If you want to represent this mathematically, you can say that the state of the coin when it's in the air is 1/√2 x + 1/√2 y, where x represents heads and y represents tails. Why the 1/√2 factors? Because you want the ",
" of that equation to be equal to one. Why? Because that equation tells you the ",
" of the coin coming up ",
" heads ",
" tails. And since it can only come up as one of those two, the probability that it'll be either of them is one.",
"Once you have that equation, you can hit it with a set of mathematical operations that tell you what the probability is of finding the coin in any of its observable states. Of course, in this example we know the answer: It's 50/50 (or 0.5) for heads and 50/50 (or 0.5 again) for tails. But if you ",
" know that, this is the basic mathematical approach you'd use to figure it out.",
"So that's the essence of superposition. It's the idea that when a system is in an indeterminate state, its state can be represented mathematically as a sum of its possible states. The coin is neither heads nor tails when it's in the air, but a combination of both, mathematically speaking. A photon is neither polarized parallel to or perpendicular to an axis, but a combination of both. And so on."
] |
[
"Isn't the idea of superposition that they are in both states at once?",
"We all agree on the math, but we don't all agree on what the math means. You often see people simply stating their interpretation of the math as fact. However, there's a list of different understandings of what's actually going on. ",
"http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics"
] |
[
"It's mostly a philosophical question",
"Consider the instance it's about to pass through the slit(s). Mathematically we say it's a linear combination of it being at left slit and being at right slit. Let's say instead of letting it go through, we measure it. Now we only see it at one of the slits. What happened to the part that was at the other slit? Did it get destroyed? If so, how how did the measurement cause this? We have no good explanation for this(really, we don't, despite what some people think, decoherence doesn't explain it). Maybe it's still there, but in a 'different' universe. That's the many worlds theory. Maybe the universe knew beforehand that we would measure(ie. no free will or CFD).",
"Or maybe it's simply wrong to think of physics as method of picturing reality. Seriously. Just throw out realism in physics. Physics is about a toolbox called math that allows us to predict measurement. It's a bad question to ask anything beyond that. "
] |
[
"Can scaring someone cause them to have a heart-attack?"
] |
[
false
] |
I've always wondered. It can be fun at times... giving people a little fright here and there. But is it harmful? Not specific to heart-attack... but to anything negative at all, really.
|
[
"Technically it can, but their heart has to already be in a very weakened state. The physiological response to fear includes a boost to our cardiovascular system. We need more blood pumped to more places so that we can respond quickly. The reaction can potentially be too much for the heart to handle and result in a heart attack. ",
"In a normal, healthy individual it would be incredibly unlikely. As long as you aren't scaring 80 year olds with bad hearts you should be good."
] |
[
"We had a shooting here on Kauai this week and a witness had a heart attack. He was taken to Oahu and died a day later.",
"http://thegardenisland.com/news/local/kalaheo-shooter-identified-neighbor-dies/article_76d516e4-d55f-11e1-99a1-0019bb2963f4.html"
] |
[
"Gotcha. Advice duly noted. Thanks!"
] |
[
"When standing on Earth, the moon is about as wide as your thumb held at arms length. But pictures of Earth from the moon appear the same size. Why? Shouldn't it be 3.68 times larger?"
] |
[
false
] | null |
[
"If you're on the moon and stick your thumb out then yes, it will look 3.68 times larger."
] |
[
"Pictures can be enlarged, reduced or the camera could have zoomed in to create seemingly different proportions. I'd guess it's difficult to judge who big the Earth would be relative to your thumb from a photograph."
] |
[
"Pictures taken of objects in the sky, whether the Moon from Earth or vice versa are subject to the focal length of the lens used to take the image.",
"Wider focal lengths will cause the objects to appear much smaller in the sky than they do to the naked eye, while longer, or telephoto lenses will cause the objects to appear larger than they do to the naked eye. I suspect cameras used on lunar landing likely utilized somewhat wider 24-35mm lenses opposed to the standard 50mm in order to get wider views of the lunar landscape which would cause Earth in the Moon sky to appear slightly smaller than it did for the astronauts as they stood on the surface."
] |
[
"(Why) is it important, from an evolutionary standpoint, that I look completely unique? Of the billions of other people in the world, no-one else looks like me. Is this an evolutionary advantage, or just a coincidence?"
] |
[
false
] | null |
[
"Your appearance is determined in part by your genetics. So it's not about the advantage conferred by looking different, but, rather, the advantage of sexual reproduction (conferring different genes to progeny) vs. asexual. I recommend reading ",
"this",
" interesting page."
] |
[
"But in the case of many animals, sheep or golden retrievers say, sexual reproduction results in offspring that look almost identical to their parents and siblings. \nEven with genetics is it not possible for me to look almost identical to my father or mother. If so, then what evolutionary advantage is their to me being so distinct in appearance from both of my parents?"
] |
[
"Seemingly almost identical to us because we do not focus on the minute differences. But some farmers can distinguish between their sheep by sight alone. Or a pet owner can distinguish between their dog and someone else's. "
] |
[
"Does the expansion of spacetime allow for a decrease in entropy?"
] |
[
false
] |
It seems to me that an expansion of spacetime allows for an increase of potential energy through the gravitational/electroweak/strong forces without any energy being added to the system thus decreasing entropy. I believe an expansion of volume also decreases entropy because of the addition of possible arrangements correct? If so, doesn't this rule out the heat-death of our universe?
|
[
"Only gravity (and the dark energy, whatever that is) has significant effects on cosmological distance scales, so EM/strong forces are not an important consideration in the expansion. ",
"Also, this is incorrect:",
"an expansion of volume also decreases entropy because of the addition of possible arrangements",
"adding arrangements ",
" the entropy.",
"Nevertheless, the heat death of the universe is an open question. It is not clear that the universe will ever approach thermal equilibrium."
] |
[
"Ok that last line really interests me. If not a heat death do you just mean a citation where temperature extremes are total isolated from each others?"
] |
[
"There are two lines of argument:",
"ekpyrotic (colliding branes) cosmology"
] |
[
"Would be possible to copy the regeneration properties of a fingernail and use them else where?"
] |
[
false
] | null |
[
"Not restricted to humans? Hold on i'll check with my hamster!"
] |
[
";)"
] |
[
"Yeah. I saw the error of my ways. Changed it."
] |
[
"To what extent does the conversion from metal wires to fiber optics mitigate the economic risk from solar storms?"
] |
[
false
] |
My question occurs while reading about the worst solar storm ever recorded, in which telegraph lines generated electrical fires. It seems that perhaps the greatest terrestrial risk from solar storms are very long metal circuits, such as might exist in power or communications lines. However, power cables are, by definition, ready to withstand electrical surges to some extent (although the article discusses the risk to transformers). Does the transition from copper wires to fiber for the world's communication grid help mitigate the extent of disruption a large solar storm would cause?
|
[
"The long haul optical fibers have conductors in them to power the optical amplifiers needed to boost the signal periodically. If the power surge that is induced in the line damages the amplifier systems, game over. Short runs can be just the optical components as the losses are low, and those would be stable in an EM storm but the electronics on the ends would still be sensitive. "
] |
[
"There are power lines that run along to fiber to power the boosters that are spread along the way. 30km gaps between boosters is normal for undersea fiber for example. Gotta get power to the ones in the middle."
] |
[
"There are both conductive and nonconductive types of optical fiber ",
". See ",
"here",
" for some basic information around this.",
"While it's possible for conductive components to transmit current, I'm unclear as to their possible effects on the fiber. Current guidelines (e.g. in the US - Article 770 of the National Electrical Code) permit installation of fiber along with electrical cable, which suggests to me that it's safe under ",
" operation."
] |
[
"What controls the timing of birth in humans? Do conditions in the womb become toxic, driving the birth process?"
] |
[
false
] |
[deleted]
|
[
"I don't know if you find my answer satisfying, but here goes (also sorry for my English). \nAs you (hopefully) know, the mother provides nutrients (glucose, among others) to the baby. At some point, the mother can't provide these nutrients to both herself, and the baby, because the baby is getting too large. This is measured through the glucose levels in the blood of the baby. When this happens, the baby releases stress hormones, and those trigger the birth. "
] |
[
"This may not be a perfect answer, but perhaps it's a start: It is the complete development of the fetus' lungs that is the catalyst in beginning the birthing process. Lungs have a liquid coating called \"surfactant\" to keep themselves from collapsing from their inability to keep air in. This chemical is crucial, and without it, the newborn will suffer Respiratory Distress Syndrome- common in premature babies, but not untreatable. When surfactant is produced (or rather finished being produced), it triggers several biochemical pathways that prepare the mother's body for birth.",
"Edit: words are hard"
] |
[
"Very nice; thanks."
] |
[
"Chemically speaking, is wood similar to the human body?"
] |
[
false
] |
[deleted]
|
[
"Water, carbon and protein are three very different things. Water is a molecule that is present in all known life. It is an excellent universal solvent. Carbon is only present in living material as part of bigger molecules; as far as I know never in it's pure form.\nProteins are a huge class of widely different, complex biochemicals.",
"To answer your question: While both wood and the human body consis of a multitude of living cells, the specific proteins and, of course, the DNA would be quite different. But most importantly wood contains large amounts of a structural material called cellulose, giving it its strength. Humans don't have that. Which is a good thing."
] |
[
"I checked the definition, and you're right. However, substituted hydrocarbons are also counted as organic compounds, so the rest of my answer still holds. Thanks for the rectification."
] |
[
"All living things consist for a huge part out of water and hydrocarbons. Hydrocarbons are molecules which consist out of a backbone of carbon atoms, with hydrogen atoms, or sometimes other elements such as nitrogen or oxygen, attached to it. These molecules can range from very simple (such as gasoline) to highly complex (such as DNA) and from very small (such as natural gas) to very large (such as plastics). Because of the fact that these hydrocarbons make up a huge part of all living things, we call them organic compounds. They are literally everywhere around us, from oil, to wood, to sugar, our own bodies. Organic compounds are everywhere. VERY crudely, one could say that everything that isn't water, a mineral or a metal, is made up of hydrocarbons.",
"So, in some sense, one could say that wood is similar to the human body, but because of the huge amount of hydrocarbons, and the infinite ways of putting them together, they are still very much different.",
"I hope this answers your question. If not, let me know."
] |
[
"How does adding chemicals to gold make it purer in the refining process?"
] |
[
false
] |
I understand that when gold is made into jewelry, it is made into alloys with other metals to make it more durable and cost effective, but I don’t understand how the added chemicals during the smelting process make the gold more pure. Wouldn’t adding stuff to it make it less pure, rather than the opposite?
|
[
"Let's say you have a mixture of gold and some element, Q. Q likes to be alloyed with gold, but it likes to bind with X even better. So, when you melt the gold, you sprinkle in a little X into the liquid. The X binds with the Q, turning it solid (we've chosen X carefully so this happens), and it either floats to the top or sinks to the bottom. We now have no more Q in our gold."
] |
[
"Yep, same sort of idea. You'll find the same technique with people casting iron/steel and aluminum, too."
] |
[
"Ok. So that’s like making cheese, and you’re skimming the excess off the top before continuing, right? I’ve seen videos, and all I’ve seen is the extra stuff being added before it all goes into the crucible. Then it all gets brought to a molten state. I never see the removal of the impurities, just the forming of the gold ingots."
] |
[
"If the Moon orbits Earth and Earth orbits the Sun, what does the Sun orbit?"
] |
[
false
] | null |
[
"The Sun orbits the galaxy. So it doesn't exactly orbit one thing, but rather the combined mass of the other stuff in the galaxy makes it follow a path that takes around 250 million years to complete one orbit.",
"The Sun's temperature is determined by its own heat production, since any other stars are many light-years away."
] |
[
"The Sun orbits the galactic center along with pretty much everything else in the galaxy. In turn the Milky Way is gravitationally bound (not to be confused with orbit however) to other large structures in the Local Group. In turn these are gravitationally bound to enormous structures formed from groups of galaxies, and these in turn form enormous filaments and voids throughout the universe."
] |
[
"sun orbits the center of the Milky Way galaxy called Sagittarius A*",
"Not quite. While we orbit the region where Sag A* happens to be, the black hole itself has almost no significant gravitational influence on the Sun because of the distance. It's more accurate to say the Sun orbits the center of mass for the entire galaxy (which is centered roughly in the region known as Sagittarius A, which includes the black hole Sagittarius A*).",
"To put in perspective, the Sun dominates the gravity of the Solar System because it's about 99.7% of the Solar System's mass. Meanwhile, as massive as it is, Sag A* only accounts for about 0.04% of the Milky Way's mass - pretty insignificant to anything not near it. Because gravity drops at the square of the distance, Alpha Centauri actually exerts roughly ten times the gravitational influence on the Sun than Sag A* does due to it being 1/7500th the distance even though it's also a mere 1/2000000th the mass."
] |
[
"Is all oil and natural gas from dead organisms?"
] |
[
false
] |
[deleted]
|
[
"For the title question, yes, on Earth naturally occurring oil and natural gas is derived from organisms, mostly marine microorganisms. There are countless resources online that describe the formation of petroleum in detail, e.g. the one ",
"wikipedia",
" isn't a bad place to start.",
"With regards to the Titan aspect, here is a slightly modified version of a previous answer to a similar question:",
"Despite the buzzy headlines, Titan does not have 'oil', it has relatively simple hydrocarbons, mostly methane (the simplest hydrocarbon with a single carbon atom) but with also slightly longer chain hydrocarbons like ethane (2 carbons) and propane (3 carbons), e.g. ",
"the Lake section of the Wikipedia article on Titan",
". In comparison, ",
"oil",
" on Earth is a mix of a variety of relatively complex hydrocarbons, which also does occur with things like methane, i.e. ",
"natural gas",
".",
"When the compounds on Titan are described as 'organic', it is being used in the chemistry sense, i.e. ",
"a compound that contains carbon",
", as opposed to being the products of life. I'm not a chemist, so I'll avoid going too far afield from things I know well, but simple hydrocarbons, like those found on Titan, do not require life to form. In general, organic compounds (again, in the chemistry sense) are pretty common in extraterrestrial materials, e.g. in ",
"carbonaceous chondrites",
" and even in ",
"cosmic dust",
"."
] |
[
"Fuel is burned in periodic little explosions inside cylinders which move pistons down. That motion is converted into rotary motion and that turns the wheels."
] |
[
"Petroleum is refined into gasoline, which in the right conditions is explosively combustive. Those explosions are used to propel pistons. The pistons are connected to a crankshaft which converts that energy into circular motion, which ultimately turns the vehicle's wheels.",
"Petroleum can also be refined into diesel fuel. I don't know much about how diesel engines work but they also involve setting the fuel on fire and using the resulting gas expansion to get energy to turn wheels."
] |
[
"Is there such a thing as a \"fourth generation quarks or leptons?\""
] |
[
false
] |
Are they possible to make and just have extremely short lifespans or is the third generation of top quarks, bottom quarks, taus and tau neutrinos has heavy as quarks and leptons can possibly get?
|
[
"A simple, fourth generation of fermions with the same couplings as the first three generations is ruled out by the Higgs boson coupling measurements: ",
"https://arxiv.org/abs/1204.1252",
"There are ideas that there could be a fourth \"vector-like\" generation of fermions. These would then have equal couplings for the left- and right-handed fermions and do not couple to the Higgs in the same way as the usual fermions. These are being searched for quite actively, with current mass limits in the order of 1 TeV (see for example ",
"https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CombinedSummaryPlots/EXOTICS/ATLAS_VLQ_TT_step4/ATLAS_VLQ_TT_step4.png",
"). As far as I remember several models predict vector-like \"top\" quarks (i.e. charge +2/3 VLQs which mix mostly with top quarks) in the mass range of 1-2 TeV, to which the LHC should be sensitive in a few years."
] |
[
"There is no experimental evidence for them but nothing in the standard model prevents there from being more than three generations.",
"It is, perhaps, interesting to point out that three generations of quarks might be required for life to exist! The CKM matrix which describes the way in which mass and weak eigenstates mix is an n x n unitary matrix.",
"\nYou can show that n has to be at least 3 to allow for a (physically significant) complex phase in this matrix. A complex phase here is then responsible for CP violation in the standard model, without which you don't get more matter than anti-matter and you don't have universe suitable for life!"
] |
[
"Could you (or anyone else reading this) expand on the way this potential \"vector-like\" generation of fermions would couple differently to the Higgs, relative to how the presently existing generations couple? "
] |
[
"Do pheromone colognes like Pherlure or PherX actually contain pheromones and do those colognes actually work?"
] |
[
false
] |
[deleted]
|
[
"Chemist here. If it attracts poontang or just makes you more confident so you pick up more 'tang, I say it has served its purpose. ",
"The scientist in me, however, is tempted to call bullshit. Show me proof.",
"PS: I've always wanted to incorporate the word \"poontang\" into a scientific discussion."
] |
[
"As our smelling abilities are not as acute as most animals, we cannot smell pheromones per se. But there's some reaction to the pheromone molecules, at the olfactive cell level, that is known to trigger some hormonal responses. So, the best those products could achieve would be some sort of unconscious response that could lead to some willingness to interact, but it's something that's not really established, and it's comprehensible, given the complexity of human mating.",
" It's probably best if you seek some other alternatives to those colognes. "
] |
[
"So far, all the tests have been inconclusive. I remember reading multiple studies and the results varied massively, inferring theirs no correlation between the pheromones and the \"Picking up\".",
"Also: I'm sure a biologist and chemist will come by soon to expand more on why it shouldn't work (pheromones in cologne reacting to humans, that is)."
] |
[
"Is it possible to un-polarize polarized light?"
] |
[
false
] |
And if so, what applications might this have?
|
[
"You're doing the maths right, but interpreting them wrong. To understand how the polarization of light really works you have to dive into the quantum mechanics of the spin state of an individual photon. When you do that, you'll find that in fact no, it is not possible to ",
" the spin state of a photon. Which makes sense, once you understand that it's not possible for anything about a photon to change, due to the proper time along a null geodesic being zero. A photon exists only for a single instant, so of course it can't change.",
"Just as an aside, classical optics is pretty much the best example I can think of of a model that's absolutely, unequivocally wrong, but that we keep around anyway for practical reasons."
] |
[
"In optical measurement instruments, a \"diffuser\" is sometimes inserted into the light path; think a rough piece of aluminum or some such. This has the explicit goal to get rid of the polarization in the incoming light (to be more exact: to have all possible polarizations represented equally).",
"This is done because e.g. optical sensor response may be highly polarization-dependent, and you want to make sure that does not affect your measurement.",
"(Disclaimer: I' a humble software guy, but I have worked in a project where an optical remote sensing instrument was calibrated)."
] |
[
"This is wrong. Polarizers do change the light.",
"For instance, lets start with unpolarized light and pass it through a polarizer so that it comes out linearly polarized in the x direction. Then we can pass it through a linear polarizer with a transmission access at 45 degrees. Now our light is polarized at 45 degrees to our origin (and with some reduced brightness). Next we apply a linear polarizer with a y transmission axis. The component along y is kept and we have linearly polarized light in the y direction. Now if we had left the 45 degree polarizer out of the process, we would have lost all light with the y-axis polarizer. Thus the 45 degree polarizer ",
" the light and did not simple pick out suitable photons because by that logic they should have disapeared at the y-polarizer.",
"You can try this yourself real easy using ",
"Jones calculus",
", I started with (1, 0) light and applied the 3rd and then 2nd Jones Matrices. Even more interesting is creating circularly and elliptically polarized light from linearly polarized light."
] |
[
"Is the assignment, positive and negative, to the charges completely arbitrary? Or is there an actual mathematical significance for doing so."
] |
[
false
] | null |
[
"Completely arbitrary."
] |
[
"Ben Franklin coined positive, negative, charge, and battery with relation to electricity.",
"He discovered that there were two types of charges, positive and negative. He did not know whether negative or positive charges were transferred, so he guessed - positive. He was wrong, but only by chance (and if he was right, it would have been by chance as well). So it is arbitrary."
] |
[
"It's arbitrary what's negative/positive, but the fact there are two types of opposing charges that repel/attract the way they do is not."
] |
[
"How does altitude of detonation of a nuclear bomb affect the “fallout area?”"
] |
[
false
] |
When a nuclear bomb is detonated, the surrounding air is almost instantly heated and rises rapidly. Various debris, gasses, and radioactive material are brought up with this air, and a repeated heating and cooling process occurs that forms the infamous mushroom cloud. The cloud, however, will reach a maximum height when the pressure at the top of the cloud is equal to the atmospheric pressure at that height. The cloud will then move in a generally lateral direction. If a nuclear weapon is detonated at a higher altitude than anticipated, say, in the accidental premature detonation of a warhead, how would the area the nuclear fallout covers be affected? Would the cloud move laterally for a longer distance? If so, how would the radiation levels on the ground be affected? Sorry for my insufficient vernacular; I’m just a high school student who likes to read Wikipedia.
|
[
"In general, the main concern regarding fallout and detonation height is how much dirt and debris is sucked up in to the radioactive fireball. This will determine how much, and when, the radioactive material in the cloud \"falls out\" to the ground. ",
"If you detonate a bomb sufficiently high (a multiple of the maximum radius of the fireball), pretty much no heavy material ends up in the fireball (because the fireball has just vaporized all of the bomb material). This means that the cloud stays light for a longer period of time, and radioactive material does not start falling out for days or weeks. This means, in turn, that the area underneath that cloud is very large (the cloud has dispersed), so no particular area gets a very high concentration of material. It also means that the worst of the fission products have decayed prior to falling to the ground. From a military perspective this is consider a \"negligible fallout\" situation. (There are still a few ways that fallout can happen, such as if the cloud happens, through atmospheric conditions, to \"rain out\" early.)",
"If you detonate a bomb on the ground, the fireball sucks up macroscopic bits of ground material (i.e., the size of sand). The fission products adhere to these, and these materials \"fall out\" of the cloud within hours. This results in relatively heavy contamination immediately downwind of the detonation (\"local fallout\") by materials that are still very radioactive. This is the fallout that people generally worry about, because the concentrations and radioactivity can be high enough to be very acutely dangerous for several days or even weeks, depending on the initial amount of radioactivity present (which varies with the type of bomb, type of surface detonated upon, etc.). ",
"In between these two extremes there is a gradation of situations in which the total radioactivity deposited as local fallout decreases with altitude, as you move between the \"surface\" case and the \"too high for local fallout\" case. ",
"This is the only case where detonation at different altitudes should play a major role in fallout dispersal. If you are detonating a bomb high enough that the wind at different altitudes is going to be significantly different, then you're likely already at an altitude where local fallout is not going to be a big issue, except for cases with the largest multi-megaton bombs. In any case, by detonating it higher, you always are going to lose total fallout deposited, so any possible increase in area affected is going to also be exposed to less contamination, not more."
] |
[
"This is an awesome explanation. Thank you!"
] |
[
"No problem. ",
"NUKEMAP",
", as an aside, takes altitude into account when it calculates fallout. So you can play with it, if you want. It uses a scaling rule, derived from government publications, that reduces the intensity of the bomb as a factor of height of burst in between the two extremes of HOB = 0 and HOB = negligible fallout.",
"Looking at Glasstone and Dolan's ",
"Effects of Nuclear Weapons",
" (1977), they say (on page 71) that the maximum height of burst in which you are expected to have non-negligible local fallout is 180 x W",
" feet, where W is the yield of the weapon in kilotons. So for a 20 kiloton weapon, that would be 596 feet; for a 20 megaton weapon, it is 9455 feet."
] |
[
"Do shirts shrink due to being washed in hot water or due to being dried in a hot air dryer? Why?"
] |
[
false
] |
Title is all that is necessary.
|
[
"Textile Engineer here (yes, there is such a thing):",
"\nMost the clothes that shrinks is cotton. The reason cotton shrinks (normally in the dryer, but some in the washer) is because the heat of the dryer adds energy to the polymer chains. This will return the amorphous regions of the polymer chains to their natural, unaligned state.",
"\nWhen textiles are dyed, they are normally under a good deal of tension, so when heat is applied, the amorphous regions somewhat align. The heat of the dryer counteracts this. ",
"On a related note, the reason steam and heat helps get rid of wrinkles is because weak hydrogen bonds are formed between different polymer chains. The heat and steam break these bonds, allow the fabric to return to its natural, unwrinkled state."
] |
[
"This will return the amorphous regions of the polymer chains to their natural, unaligned state.",
"This is worded a little confusingly. Do you mean the induced crystalline regions will return to their natural amorphous state when heated?",
"...so when heat is applied, the amorphous regions somewhat align. The heat of the dryer counteracts this.",
"Again, this wording is a little confusing. Care to elaborate?"
] |
[
"My understanding of the process is somewhat similar to dirtay's, except I view it from a polymer scientist's point of view so I have different language.",
"Its not that the cellulose chains crystallize. But there is (and I hesitate to use this terminology because its ",
" scientifically but is able to provide you with a reasonable intuitive understanding of the process) a large amount of free volume between the chains because of the treatment process of cotton. When you add water and heat, you induce a great deal of chain mobility that results in shrinkage. This is a purely entropic phenomenon -- shrink wrap does this for the same reason.",
"For ironing, what you're doing is heating the cellulose through its ",
"brittle to ductile transition",
" (the article is for metals but it applies to polymers too...) so that the chains can rearrange and get rid of those annoying wrinkles. The water lowers the temperature of this transition, which is why you use it on cotton which (so Google tells me) has a relatively high BTD temperature."
] |
[
"How can neutrinos change flavor?"
] |
[
false
] |
How can neutrinos change flavor? Doesn't that mean they must be changing mass? Where does the extra mass come from?
|
[
"How can neutrinos change flavor? Doesn't that mean they must be changing mass? Where does the extra mass come from?",
"The neutrino flavors don't have definite masses, and the neutrino masses aren't attributed to definite flavors.",
"Mass and flavor are incompatible observables for neutrinos, just like position and momentum are incompatible observables for all particles in quantum mechanics. A particle with a definite position doesn't have a definite momentum, and a neutrino with a definite mass doesn't have a definite flavor.",
"When a neutrino is produced in some weak interaction, it has a definite flavor. But that means that it's got a superposition of different masses.",
"So as the state evolves with time, the probability of detecting it in a given flavor oscillates with time.",
"Here",
" is an explanation and some math to show how it works."
] |
[
"I was under the impression that a neutrino is made of types of waves. The phase of the waves determines the flavor of neutrino. Is that inaccurate?"
] |
[
"It might be accurate in some particular sense but is misleading, and I've never heard that description before.",
"I think what's meant by \"being made of waves\" here is the following:",
"Suppose I have an apparatus to measure the flavor of a neutrino in some particular mass eigenstate. The chance of measuring one of the three flavor eigenstates oscillates like a sine or cosine wave, and the cosine or sine wave for each of the flavors has a different amplitude. This oscillation is \"wave-like,\" in that it oscillates the same way that the electric field carried by an electromagnetic field will oscillate. Indeed, the phase of the wave at some particular point in space and moment of time is what determines the odds of being in a specific flavor state. This is something of a guess as to what was meant by whoever gave you that explanation."
] |
[
"Why are there so few neurons in the Cerebral Corex, compared to the number in the Cerebellum?"
] |
[
false
] |
I have searched for answers online but haven't found anything satisfactory. From what I know, there are ~69 billion neurons in the Cerebellum, and ~16 billion in the Cerebral Cortex. This seems strange, considering the fact that the Cerebrum accounts for roughly 85% of brain mass. . Is 16 billion a rather low number in comparison or am I over this?
|
[
"Just a med student here. Id like to point out, that the number of neurons doesnt equal the number of synapses (connections). Those are responsible for the amount of information the brain holds. Neuron bodies are just something that connects them together and produce building blocks for them. So to my understanding, cerebral cortex may have much less neurons if they interconnect more.",
"Also, 50 billion of cerebellar neurons are ",
"the smallest neurons in human body"
] |
[
"I don't think we yet understand how exactly the cerebellum processes information but you have to consider how vast amount of stuff it has to do. It controls the movement of your body, it learns the movement patterns and how to reproduce and adapt them in different situations. When you learn to walk, it is actually cerebellum that learns to walk, when you learn to throw, it is cerebellum that learns to throw. It has to control thousands of little parameters according to information from thousands of sources in an extremely precise way. ",
"About the mass thing: most of the brain mass is fat that is used as an insulator around axons. Cerebellum is small and very tightly packed so there is less fat there than there is in cerebrum where the connections are longer.",
"Someone already stated that it is actually the connections that matter and the cells themselves are there to support the connections. This is both true and not true. A machine learning neural network model is often a good analogy of the brain. More neurons in a layer does not equate better processing but you still need enough neurons. Just connecting everything everywhere does not do anything. ",
"We are still mostly limited in studying what happens when cerebellum receives damage so it is really hard to get full picture of what happens there."
] |
[
"Ah, I didn't realise they could vary in size, that's interesting. Thanks for the information.",
"I've become quite interested in this topic recently but I know it's like spitting into the ocean when it comes to such a huge and complex topic like neuroscience."
] |
[
"Where can I learn about the genetic differences and similarity between fruit?"
] |
[
false
] |
How much has the genetic sequencing of all the different types of fruit helped to understand their relationships? Where can I learn about it and find out things for myself? Although I wouldn't know what to do with it I also wonder if all the DNA data is online?
|
[
"This won't exactly give you the spelled-out relationship of two fruits, but nonetheless: Check out ",
"TimeTree",
". It takes any two organisms and estimates how long ago their phylogenetic lineage split - i.e. when they had their last common ancestor.",
"For example:",
"Strawberries and Durian evolved in different lineages since around 100 million years ago",
"Strawberries and ",
" split 1.5 billion years ago",
"Nice phylogenetic trees can also be found at ",
"the Hillis Lab",
"."
] |
[
"One of the most interesting courses I ever took was on economic botany. We discussed the relationships between many of the fruits and vegetables that we normally eat. ",
"Did you know, for example, that broccoli, cauliflower, brussels sprouts, cabbage, kale, collard greens, and kohlrabi are all the same species?",
"The professor who taught the course also wrote the book, if you're interested in learning more. Otherwise, I'd go on Wikipedia (or their taxonomy site) and notice the taxonomy of the fruits you're curious about. That way you can get an idea of how closely they're related.",
"Here's the book:\n",
"http://www.amazon.com/Economic-Botany-Plants-our-World/dp/0072909382"
] |
[
"Timetree is pretty cool, there's also this resource for phylogenetic trees: ",
"http://tolweb.org/tree/",
"Hillis is a pretty amazing researcher, and he helped write the book on molecular systematics (",
"literally",
")."
] |
[
"What types of particles can I detect using a homemade cloud chamber?"
] |
[
false
] |
This video claims you can see subatomic particles at home. Does that method really work? And what kinds of particles can I see? Thank you!
|
[
"Yup those are real! ",
"They're very simple cloud chambers.",
"As a rule of thumb most incident rays are protons, however, you don't see these on the ground, they generally interact with the atmosphere ",
"producing a whole zoo of particles.",
" ",
"An indiscriminate detector will see mostly electron, muon and gamma activity, but not all detectors are equal. A cloud chamber will generally not register gamma radiation as the tracks they produce are much weaker, but you may see gamma scattering where a track spawns into existence inside the detector when a gamma photon hard scattered. Among the signals, you'll also more rarely see hadronic shower products like charged pions and kaons, but you'd need a magnetic field to differentiate them.",
"Edit: Some more info, ",
"http://hyperphysics.phy-astr.gsu.edu/hbase/particles/cloud.html",
" ",
"http://astronomy.nmsu.edu/tharriso/ast536/ast536week10.html",
" ",
"http://hyperphysics.phy-astr.gsu.edu/hbase/astro/cosmic.html"
] |
[
"Your local supermarket might have some. Publix usually has it, but if you're not in the south I don't have a good answer."
] |
[
"Where does one get dry ice? I used to live in Japan and you could get it anywhere there. Where does one get it in the U.S.? "
] |
[
"Determining the Product of Exponentials Formulation for the kinematics of a robot"
] |
[
false
] |
I'm just starting out in robotics and am doing some self study... I'm trying to figure out how the Product of Exponentials Formulation works when describing the kinematics of a robot. [1] Here's a link to a free text book by Murray that describes it... mostly. Ok, sort of. Chapter 3, around page 80 or so, begins to describe it. What I'm trying to figure out is how the matrices described on page 89 are constructed. That is to say, epsi_i*theta_i matrices. I understand, or at least I think I do, where the psi term comes from but I'm not seeing how those matrices are put together. Any help would be appreciated. Thanks.
|
[
"I'm not sure if this should be tagged as Engineering or Mathematics... so, please let me know.\nThanks."
] |
[
"I suspect that ",
"this",
" is the book to which you're referring. At the very least, it has matrix exponentials on page 89. If so, I'd first like to point out that those are xis, not epsilons.",
"Now, if that is the book about which you're talking, I'm not sure where your confusion comes from. The basic definition for their hat-notation is introduced on page 26 and indicates the linear operator associated with the cross product",
"hat(xi)v = xi cross v",
"for all v. Once you have a coördinate system in place, you can write this operator as a matrix. They elaborate on this throughout the intervening text as necessary to handle more information. In particular, page 70 defines the relevant meaning of hat(xi) for the matrices in which you're interested. The xi_i themselves are defined on page 88; they are given as vectors in ",
", which (as clarified on page 70) is to be interpreted as a pair of vectors in ",
", one of which produces a map according to the above hat-notation; i.e., as the axis of rotation. The thetas are just ordinary real scalars, and you just take the matrix exponential of xi_i*theta_i."
] |
[
"Yes. That's helpful. Thank you. I'm trying to use the Euler Angles on page 31. I think I understand how to set up the first three columns of the rotation matrices.",
"\nMy next question is about the fourth column, the translational components. I'm having some trouble seeing how to \"add\" the components from successive joints together properly...",
"\nFor instance, I see the examples for the SCARA robot (although eventually I really want to also make sure I understand that Stanford Arm, especially how the third, prismatic, joint affects things). Is there a good example of how the Elbow Manipulator is determined? I see the next example, but I'm looking for something that has the steps shown and not just the end result."
] |
[
"So how do you evolve from 44 chromosomes from 42 chromosomes?"
] |
[
false
] |
I understand, from listening to one of Ken Miller's talks, that our 2nd chromosome is actually the result of the fusion of two chromosomes, found in related species. But how could such a thing spread. I can envision such a fusion taking place, and producing a viable offspring. But how does such a mutant find a compatible mate?
|
[
"But how does such a mutant find a compatible mate?",
"Chromosome number doesn't really matter much when finding a mate. Your ",
" have to line up, and while having the same number of chromosomes helps, it doesn't really matter if they're fused together.",
"That is: I can line up these two just fine:",
"ABC DEF GHI JKL",
"ABC DEF GHI JKL",
"If I fuse the middle two, they can still line up:",
"ABC DEFGHI JKL",
"ABC DEF GHI JKL"
] |
[
"Could you go into a bit more detail about how genes \"line up\"? That whatever process it is by which genes line up isn't affected by the fusing of two chromosomes into one sounds fascinating."
] |
[
"Should this be a not-uncommon occurrence, then? Do we know of species (hopefully mamallian, or at least non-insect) in which differing numbers of chromosomes is just a common variation across the species?"
] |
[
"Is there a limit to the size of rocky planets?"
] |
[
false
] | null |
[
"There is a fundamental limit on the ",
" of rocky planets based on how material compresses. When I say \"size\" I mean how much ",
" the planet takes up, as measured by the planet's radius or diameter. See ",
"Figure 4 from S. Seager et al. 2007, Ap.J. 669, 1279",
". After a point, adding more mass would cause the radius, the ",
", to ",
". So, while a rocky planet could theoretically be as ",
" as Jupiter, it size cannot be as large as Jupiter's size. The maximum ",
" of a planet of Earth-like composition (red dashed lines in the figure) is a little more than 3 Earth radii. (For reference, 1 Jupiter radius is 11.2 Earth radii.)",
"As iorgfeflkd mentioned, additionally there is a practical limit to a rocky planet's mass based on the fact that during planet formation a large rocky body will gravitationally collect gas from the proto-planetary nebula."
] |
[
"Yes but it isn't precisely known what the limit is. Above a certain size, it will be massive enough to attract interplanetary gas and become a gas giant. This is thought to occur around 7 Earth masses."
] |
[
"what if it is so far away from everything else that it is large but, effectively, has \"no\" gravitational pull or influence on gas?",
"Is there a point that it becomes so large that it would collapse on itself? I imagine it would depend on the density. If it was a giant, jupiter sized ball of talcum powder vs. a giant, jupiter sized ball of led"
] |
[
"If you placed a plant or tree in an airtight container, would it remain preserved like a human body?"
] |
[
false
] |
Was thinking about this last night. My instinct tells me yes, but my friend seemed convinced that it wouldn't be the case. Assume no sunlight is reaching the plant.
|
[
"What do you mean \"preserved\"? Certainly an airtight (and thus, maybe more importantly, watertight) container would slow decay, but neither a human body nor a plant would be completely preserved. Sequestering anything that dies from the natural elements (fresh air, moisture, other organisms) will likely slow decomposition, but I believe it takes pretty tightly constrained conditions to ensure full preservation,"
] |
[
"Well, I know that I have a distant aunt that was buried in a fully air-tight glass coffin. She died in the 50's I believe, and my family has a mausoleum. You could go and see the body and it is exactly as it lied when she died. I was just wondering if sequestering a plant in an airtight glass container with no sunlight would have a similar effect, or if plants don't apply to this principal. "
] |
[
"If this is the case then it is unlikely she was just placed in an airtight coffin. She would have gone through an embalming process which preserved her body. Even this is not perfect and she will not be looking so great in another 50 years or so."
] |
[
"What are researchers and scientists primarily doing on Antarctic missions? What have been the most significant discoveries or advancements from this study?"
] |
[
false
] | null |
[
"One of the most historically significant discoveries made in Antarctica was the work of Joseph Farman (and many others after him) on the ozone hole over Antarctica and its relationship to CFCs. Farman begin collecting ozone readings in Antarctica in 1957, although his work was largely dismissed by the scientific community at the time. It wasn't until 1974, when two American scientists showed that CFCs could destroy ozone in the stratosphere that anyone begin paying attention and a dangerous ozone hole was theorized. In 1985, Farman and colleagues published a paper in Nature showing that ozone levels over the Antarctic had decreased by 40% since 1975, and that the ozone hole was a very real problem. The discoveries of Farman, and many others over the years, lead to the Montreal Protocol, an international treaty intended to phase out the use of ozone-depleting industrial compounds. The Montreal Protocol was signed by 24 countries in 1987, and has been signed by more than 200 today. The story that begins with Farman's work in Antarctica and ends with the Montreal Protocol, which has effectively eliminated CFCs and stopped the expansion of the ozone hole, is one of the greatest success stories in the history of modern science. "
] |
[
"There's really a myriad of different research projects being carried out there, from biological surveys on and in ice, to sub-ice hydrological mappings. One big thing is Paleo climate and Paleo biology (scientists drill into the ice to look at chemicals and life forms that got trapped in it thousands of years ago).",
"Currently physical oceanographers and geochemists are measuring the effects of recent changes in atmosphere, ice and ocean and how the entire system reacts to bounce back into balance. I.e. glacial melt water, co2 and others are being poured into the ocean through ice and atmosphere, changing ocean mixing patterns and many things more. We want to know whether these factors will decrease zooplankton (base of trophic chain in the sea) production, or maybe accelerate ocean acidification, etc. "
] |
[
"One of the other things that is done in Antarctica is the Meteorite Search. Antarctica doesn't likely get any more meteorites than anywhere else int he world, but because it's largely white, and meteorites are largely dark, they become much easier to find.",
"Yet another research project going on in Antarctica is the \"Ice Cube\" neutrino observatory. Basically, they've taken a 1km cube of ice and filled it with photomultiplier tubes, and look for the flashes that come from neutrinos interacting with the ice."
] |
[
"Is it possible for plants/fungi or other organisms lacking brains to have a sense of consciousness?"
] |
[
false
] |
My friends were having a debate about being vegan. One of them was saying based on animals having consciousness we shouldn't infringe on the rights of animals because they have consciousness. Then my friend decided to play devil's advocate, he said plants have a type of plant intelligence and awareness and therefore perhaps a certain level of conscientious. Maybe individual plants were apart of a larger conscientious. He's also said what's to say these fungal/plant root networks are communicating to each other and other species in a way that was maybe meaningful. Saying that perhaps individual organisms are really just individual connections contributing to a distributed consciousness, like individual brain cells in a brain. I'm a laymen who couldn't begin to argue. We saw a TED presentation talking about plant intelligence that was suggesting it was was possible. edit: This is the TED presentation that I watched that inspired this my friend to play devil's advocate.
|
[
"Nobody has the foggiest idea what \"consciousness\" means."
] |
[
"Short answer: When it comes to questions about consciousness, the answer is usually \"who the hell knows?\"",
"I typed up a rambling conjecture for a \"long answer,\" but realized halfway in it was much more suited to Philosophy or ",
"/r/PhilosophyofScience",
". In the case of plants, the answer is almost certainly \"no.\" If there is anything that could be called a consciousness, it would have to be contained in chemical and hormonal information transfer. If you're really interested in the topic, you may want to check out Douglas Hofstadter's work, specifically ",
" and ",
"."
] |
[
"Define consciousness. "
] |
[
"How do astronomers decide what star systems to search for potentially habitable planets?"
] |
[
false
] | null |
[
"Well, I'm not sure they rule out any stars, but our detection abilities are still limited.",
"So",
"An earth like planet isn't going to make much wobble or block much light from it's parent star. Our best bet is from smaller dimmer stars for the search for earthlike worlds.",
"Additionally, Earth only became \"habitable\" several hundred million years after it's formation. (now limited down to perhaps a couple hundred million) so obviously looking at planets orbiting stars that have life-spans numbering only 10 million years would be futile. ",
"Finally, planets sufficiently dense enough to form large rocky worlds like Earth would most likely form around population I stars. "
] |
[
"I daresay they might also start with the closest stars and work their way out."
] |
[
"The other answers here are a bit incomplete. What stars are observed depends on the telescope used. Some exoplanet searches focus on the brightest stars (in apparent magnitude) because those are easier for followup research, but the chances of finding a planet are lower because of the small number of such stars; others (like the Kepler mission) just look at relatively dense regions of the galaxy because they are more interested in large-number statistics. Yet other planet finding missions look for planets around low-mass stars because potentially habitable planets will be located closer to the star and are thus easier to study (although there is some debate about the actual habitability of the habitable zone around those stars; but that is another issue)."
] |
[
"How did bees evolve to have stingers?"
] |
[
false
] |
I doubt many predators are eliminated this way. Bees have exoskeletons so I would expect that they wouldn't be able to use them against other bumblebees, and they are social animals. I know that humans know to avoid bees, but are there other animals that know to avoid them? I just can't see how they are helpful.
|
[
"Stingers are present in large groups within the suborder Apocrita, including many social and solitary wasps, and also many ants. Basically the stinger is a modified form of the ovipositor (egg laying organ, which also means that only females have stingers) and may or may not have venom. Stingers are used for both offense and defense in predatory wasps and ants (such as paralyzing the prey). So basically you could say that the ancestor of bees already had a stinger.",
"Bees also have much use for a stinger in their defense against predators such as wasps and hornets. Their ",
"barbed stingers",
" are especially useful for that as it is easier to penetrate the exoskeleton that way. The stinger also does not break off and kill the bee, this only happens when the skin of the victim is very thick, such as in mammals. "
] |
[
"They can use their stingers against smaller predators like wasps. And exoskeletons can be penetrated at the joints quite easily, and are far less likely to kill the attacking bee in the process as opposed to e.g. human skin.",
"Being a social animal does not mean that they are peaceful and never fight. It just means they cooperate more than they try to kill/displace each other as individuals - only social animals wage wars against other groups of the same species."
] |
[
"Stingers can be used in defense of a hive. All it takes for some bumbling animal is to get stung trying to attack a hive, and maybe it will avoid hives next time it finds them. It is an evolutionary positive to have defense or hives would be eaten for their honey more often. If the hive survives, so does the queen/drones, so it can pass on stinging to the next generation.",
"Also note that worker bees die when they deliver a sting. This would not likely evolve for a sexual creature for if it dies, it loses its chance to mate. But for defending the queen, it is fine for some workers to be lost because they don't impact the queen's breeding."
] |
[
"If a picture is taken of a regular mirror from the nonreflective side of a two-way mirror, what would the picture show?"
] |
[
false
] |
I've searched for the answer but never found it
|
[
"Your question was a little confusing for me, so here's a quick diagram to help me clear it up. Hopefully I got it right! ",
"Observer -> ",
"One-way mirror",
" -> Mirror",
"You would observe an effect similar to the ",
"infinity mirror",
" mentioned above. The mirror would display an effect similar to what you get when ",
"two mirrors face each other",
" (basically itself ad infinitum), but the image would get dimmer and dimmer towards the center. This is because every time the one-way mirror reflects the mirror, only a percentage of light is reflected."
] |
[
"Also, the image you see would get greener and greener as it recedes \"away\" from you. Mirrors have an imperceptible green tint that is amplified by the repeated reflection. Even if you used two regular mirrors and could somehow see inside, the gradual dimming and greening effect would still be there. Mirrors aren't perfect reflectors."
] |
[
"It would show two mirrors reflecting each other's image into infinity. "
] |
[
"What will happen if a UTI goes untreated?"
] |
[
false
] |
[deleted]
|
[
"First what is a urinary tract infection (UTI). A UTI is essentially just inflammation of the urinary lining in response to an infection. When detecting a UTI we generally are looking for two things: bacteriuria (the presence of bacteria in the urine which generally does not have detectable bacteria) and pyuria (signs of inflammation). Bacteriuria can be present without a UTI. This occurs in colonization (having bacteria on the bladder lining). ",
"It is hard to look at your question using recent data because, most often, people are treated when diagnosed. There have been some studies looking at bacteriuria in women and have shown that it will go away without treatment in 60% of women within a month. In one series of 45 women left untreated, all but 2 were able to clear their bacteria by six months. Interestingly, this same study found that treating with antibiotics did little to prevent the recurrence of UTIs. ",
"So, why treat? One is to provide expeditious symptomatic recovery. Additionally, there are some bad outcomes that can result from a UTI. One is pyelonephritis (infection of the kidney). Generally, urine from the bladder does not go back to the kidney, so infection should not spread in most cases. A couple of conditions make it more likely to spread and as a result require more aggressive treatment. One is pregnancy, women with untreated bacteria in their urine have greatly increased rates of pyelonephritis. The other is vesico-ureteral reflux (VUR), a condition in some children which results in the passage of urine from the bladder up to the kidney. ",
"Another concern is sepsis. Sepsis is an over-response to infection. Older patients are much more at risk of this and are also more at risk of having bacteria from a urinary tract infection pass into their blood (bacteremia). ",
"A final concern is that chronic urinary tract infection may be a potential risk factor for bladder cancer, though this link is not well established in the general case."
] |
[
"It really depends on a complex interplay between the bacteria causing the infection and the person it is infecting.",
"An otherwise healthy person stands a very good chance of eventually clearing the infection on their own, though it would likely be uncomfortable until the infection was resolved.",
"Someone who is not so healthy (i.e. has diabetes, is immunosuppressed, or has a urinary tract that doesn't behave normally - think enlarged prostate causing urinary retention) may not do so well for a number of reasons. Their normal defensive mechanisms don't work well. The man with an enlarged prostate who cannot fully empty his bladder is unable then to fully flush the bacteria out. The person who is taking drugs to suppress their immune system doesn't have the vigorous response needed to clear the infection.",
"The passage of urine is not necessarily as one way as we would like to think, and some people can have \"reflux\" of the urine from the bladder up towards the kidneys. It isn't all-or-none, it's just that a certain amount of urine will make it back up to the kidney and then back down. Probably all of us have some degree, however mild or infrequent, of reflux at some point in our lives.",
"This reflux means that the bacteria in the bladder can be carried to the kidneys. There's also the fact that some of the buggers have flagella, which makes them able to move and thereby assist in their own transport back to the kidneys. This kidney infection (pyelonephritis) then can cause fever, back pain, nausea, and vomiting. Sometimes this arouses the immune system well enough that the infection will stop here, though you will be bad sick for a few days while you get better.",
"Without an adequate immune response, this can cause an abscess in or around the kidney, which you may or may not wall off and take care of that way. More likely than that, however, is that you'll get bacteria entering the bloodstream from the kidneys (because the kidneys are there to filter the blood, and it's not much for the bacteria to gain access through the filters). Should that happen, you'll likely start to become quite ill with something called sepsis.",
"At that point, a nasty fight ensues, and some of the body's own reactions to the infection can be harmful. Chief among this is widespread dilation of the blood vessels. This happens because when you have a localized infection (say an infected cut on your hand), you want the blood vessels in that area to dilate and allow more blood to flow to the area to deliver more infection fighting capacity. But, when the infection is \"everywhere\" because it's mixing throughout the bloodstream, the dilation happens in widespread fashion.",
"This can lead to profoundly low blood pressure, which in turn deprives organs of the blood supply they need to function properly, and then you start to see bad things like kidney failure, liver dysfunction, heart dysfunction, etc. Think of it as tying tourniquets around the various organs' blood supplies, and you get the picture. This cascade then leads to more organ dysfunction in a dismaying downwards spiral, and without aggressive treatment, will often result in demise. That's not to say that people in the course of human history haven't gotten better on their own (my dad survived typhus in Burma without antibiotics but was sick for weeks), but the survival rate in full-blown sepsis is extremely low.",
"I should say a couple of things about that sepsis explanation. The actual sepsis cascade is vastly more complex than I've made it out to be, but that is a generally acceptable lay explanation for it. I will also say that other infections such as pneumonia or skin infections can and do lead down the same pathway - in other words, it isn't just kidney infections that cause sepsis.",
"TL;DR - UTI's don't always kill you, you can fight them off yourself some of the time. Sometimes you don't and you die. The less healthy you are, the less likely you'll cure yourself."
] |
[
"This is an awesome answer. I'm especially happy to see that you included the concern that we are over treating UTIs. Even many practicing physicians are actually under the impression that most UTIs will become a kidney infection if left untreated.",
"I would add that sepsis from a urinary tract infection is usually due to kidney infection."
] |
[
"(How) do we know that other observed galaxies aren't made of antimatter?"
] |
[
false
] |
Given that we're really only looking at electromagnetic signatures when we image other galaxies, couldn't a significant portion of them be made of antimatter without being close enough to ordinary matter galaxies to decompose?
|
[
"While space is relatively sparse of matter, it is still not empty. At the border of any region of space dominated by antimatter, we would expect to see extremely energetic collisions between its content and matter from outside."
] |
[
"To back up your assertion, the ",
"Alpha Magnetic Spectrometer",
", launched in 2011, would have been able to detect if there were any such antimatter galaxies in the observable universe, and as of yet it has not. So the odds of there being antimatter galaxies ",
" in our observable universe are very low."
] |
[
"In the milky way it seems density is on the order of 1 Hydrogen atom /cm",
" I would think that would be lower in the space between galaxies. That seems like a pretty weak signal compared to the stars in the galaxy."
] |
[
"Is lens blurring related to uncertainty principle?"
] |
[
false
] |
Taking a very specific example of bokeh, does the disk-of-confusion form because you can't (don't) exactly know the location of the point light source that made that disk?
|
[
"Those features are out of focus because the light rays from each point in the field were not focused to a point in the image plane. This does not have anything to do with the uncertainty principle.",
"The diffraction limit of light and the resolution limit of a lens does have to do with the uncertainty principle, but that does not apply to that example."
] |
[
"Personally I find this ",
"picture",
" a perfect explanation of what \"out of focus\" means."
] |
[
"The uncertainty principle has to do with the fact that observing tiny particles by ",
" messes with their behavior and collapses their waveform. These lens effects have nothing to with a quantum mechanical function."
] |
[
"Is the concept of a \"multiverse\" falsifiable and scientific?"
] |
[
false
] |
Within the context of science, we cannot say there is a "god" because that would not be falsifiable. If we claim there is no god, and then find a way to prove god's existence scientifically, then we can falsify the theory that there is no god. Does this apply to the multiverse? If we claim there is one universe and suddenly find evidence of another universe, we can falsify that statement. So why is the "multiverse" reported as a sound scientific thing?
|
[
"The answer depends on what you mean by \"multiverse.\" To my knowledge there two main distinct uses of this word in science and popular science.",
"The first refers to the many worlds interpretation of quantum mechanics, which, like all other interpretations of quantum mechanics, is currently not falsifiable. However, it may be possible that advances in our theoretical understanding of theories ",
" quantum mechanics will allow falsifiability of QM interpretations.",
"The second refers to causally disconnected regions of space time, usually formed shortly after the big bang due to inflation. I'm not an expert here, so I'm not certain whether or not we can find evidence as to whether or not these things exist. If such evidence does exist however, I would suspect that it would be equivalent to finding evidence for the different inflationary models."
] |
[
"Well there's also the third kind where there are actually multiple universes, but not as part of the many-world interpretation of QM or as distant regions caused by inflation. I think it's part of M-theory as 3D branes."
] |
[
"The first refers to the many worlds interpretation of quantum mechanics, which, like all other interpretations of quantum mechanics, is currently not falsifiable.",
"I think Sean Caroll makes a great point in his recent blog post on the MWI. It clearly ",
" falsifiable. Just show an objective collapse of a wave function. It just hasn't been falsified. That's not the same as being unfalsifiable. Several interpretations make different experimental predictions. The MWI clearly states there is no wave function collapse so the experimental observation of such a collapse would falsify it. ",
"http://www.preposterousuniverse.com/blog/2014/06/30/why-the-many-worlds-formulation-of-quantum-mechanics-is-probably-correct/"
] |
[
"Why and how does light propagates as a \"sphere\"?"
] |
[
false
] |
Don't know if the question is clear enough, so let me try to explain. Let's imagine a balloon with a lot of dots painted on it (a finite amount). When I inflate it, the dots are going to be more and more spaced. Why doesn't this happen to light?
|
[
"This has more to do with what your source is doing. A laser doesn't propagate outward as a sphere.",
"Spherical propagation, more fundamentally, this is a statement of flux in a 3 spatial dimensional universe. If you look at something like Gauss's law, often factors of 4pi appear, because when we're talking about \"conserved\" quantities, the total flux must be captured across the surface of a sphere in 3D, the surface area of a sphere is 4piR",
" ",
"In short, if you're casting a net on a school of fish and you close the net, the number of fish (or energy) needs to be conserved within the volume. If the fish are small and can leave through the holes in the net, then the surface of the net has to describe completely the flux of fish through that surface--because we're not creating or annihilating any fish here."
] |
[
"It does, actually. The intensity of the light diminishes more and more as you get further out from the source."
] |
[
"Going back to OP's analogy, in some cases it's as though all the dots on the balloon are within a microscopic distance of each other. When you inflate it, they'll still be further apart, but just because of how they started they won't be ",
" apart."
] |
[
"Are pessimists less likely to be affected by placebos?"
] |
[
false
] | null |
[
"in short, ",
"yes",
". It should be noted, though, that not all of the placebo effect is \"mind over matter\" and \"expectation of results\". It has a number of components (some of which come from the physician/researcher, not the patient/subject) and would be better described as \"non-specific effects\".",
"Here's an article",
" by the great Steven Novella, who has written about and discussed placebos to great length."
] |
[
"Also worth reading about is the ",
"nocebo effect",
", which is when the patient is harmed by his belief that the medication will do him harm."
] |
[
"That is correct. Thank you for helping to clarify. "
] |
[
"Why is it that when a person gets kidney stones, he/she has a risk of getting stones again?"
] |
[
false
] |
From what I understand, those who got kidney stones have a high chance of getting it again. Is there a difference in the risk of getting stones before that person got the stone?
|
[
"One interesting reason is that the crystalline formations of minerals can be \"contagious\" - i.e, as a crystal starts forming, more and more oxylate gets \"locked\" into position and forms a bigger stone. When it finally breaks off, some might be left behind, serving as the \"seed\" for the next stone.",
"Since the conditions that gave rise to the first stone probably haven't changed, the second one is an inevitability.",
"Drink more water! That means more dilute urine and less free-floating calcium oxylate."
] |
[
"There will be certain conditions that led to the original stones formation. So if those conditions continue, there will be a high probability of it resulting in more stones forming. If you want to stop further stones, you need to work out what was causing them and try to change things."
] |
[
"Really depends on the cause of the stone. Contrary to popular belief there are many different types of kidney stones. For some it could be a malfunctioning endocrine system, for some it’s diet, for some processing of certain foods isn’t happening. There are even cases of people who take a certain antibiotic and consume certain food preservatives causes stone to form. The recurrence is dependent on the cause."
] |
[
"In a molecule like Formaldehyde, the Carbon is said to be sp2 hybridized. Is the oxygen also sp2 hybridized? or does the C-O sigma bond occur between an sp2 lobe from C and a horizontal p lobe from O?"
] |
[
false
] |
[deleted]
|
[
"It's not justification, it's a way to determine hybridisation because for most molecules, VSEPR predicts configurations and shapes that have been experimentally confirmed. "
] |
[
"The oxygen in formaldehyde is sp2 hybridised. A good way to determine hybridisation in general is to look at the prediction made by VSEPR. In this case, the oxygen has three equivalent orbitals in a trigonal planar structure, two of which contain lone pairs. This structure is only possible with sp2 hybridisation. "
] |
[
"in my experience, VSEPR is a much simpler model than orbital hybridization and should not be used as a justification for orbital hybrids.",
"as an example, vsepr model predicts that any 4 electron group atom should have an sp3 hybridization, but atoms with lone pair electrons deviate from this model. VSEPR doesn't explain why, it just simply notes that things like the oxygen in water tend to have compressed bond angles. The reasoning would seemingly be that the oxygens unhybridized electrons are forcing the bonded electrons away from their standard 109.5* angles."
] |
[
"What is the \"I don't care\" medicine they give you before a surgery? Is it usually the same thing or does it depend on the anesthesiologist?"
] |
[
false
] |
[deleted]
|
[
"I worked in a hospital pharmacy for awhile. Versed, or midazolam, is a common benzodiazepine given before surgery or intubation. Also could be fentanyl, the two are often used simultaneously."
] |
[
"usually the agent that is used to actually put you to sleep is an inhaled drug like isoflurane. the above drugs are used to prevent pain and reduce anxiety."
] |
[
"Versed. Causes temporary amnesia."
] |
[
"Is there an inverse placebo effect? I.E. a patient's disbelief in drug efficacy can literally make a drug less effective?"
] |
[
false
] |
Is there such a thing as an inverse of the placebo effect? How extensively has this been studied? What I'm asking is how much people's negative expectations can actually the efficacy of a drug. And if there's a term for this. I'm asking about the nocebo effect, in which people report negative effects from an inert substance. I know that negative attitudes can impact overall treatment outcomes, but how extensively has this been studied at the drug level? For example, say Drug X reduces blood pressure in the general population. Is there any evidence that people who think, "Drugs don't work on me," will not see this same reduction? (My example focuses on blood pressure because it is objectively measurable. I don't doubt that this happens for more subjective problems, like pain management.)
|
[
"Um, if most of your answer is correct, it should be summarized as \"No, definitely not.\" You answered the OP's question as no, but said it was \"yes\" in the first sentence."
] |
[
"Yes, absolutely.* In addition to positive and negative expectations, a placebo can be affected by zero expectation. If you give someone a real placebo and tell them so, and they believe you, they will experience no effect. If you give them a real drug, tell them it's a placebo, and they believe you, the effect they receive will be entirely dependent on the drug itself.",
"The control group and active group should each have a representative sample of the population. One would expect some will experience no placebo effect. But it's impossible to really tell who does or does not.",
"* I'm editing this post to say that the answer to this question depends on what the questioner is specifically asking. If they're asking whether or not someone not experiencing the placebo effect would have less efficacy from a drug than someone who was experiencing the placebo effect, the answer is obviously yes. This is why double blind trials are needed. Presumably the same number of people will be effected by placebo, lack of placebo, or nocebo effects as in the control group."
] |
[
"Any source on this?"
] |
[
"What is the risk for developing long term effects or other severe side effects from COVID 19?"
] |
[
false
] |
From what i understand long covid seems a really important issue but the coverage on it seems to have dropped the last few months. Also i dont understand why the odds of getting myocarditis from the mRna vaccine gets so much coverage especially to young people but the odds of getting myocarditis from covid is never mentioned. Isnt this "unfair" to the vaccine ?
|
[
"It seems that about 30% of those who get light cases of covid 19 become long haulers to some extent. I don’t understand why people don’t get the vax and think they will be fine if they get it. That’s close enough to 1 in 3 people that I got the vax as soon as I could. ",
"But humans are terrible at estimating risk."
] |
[
"The vaccine isn't even approved yet, there are reasons to be skeptical of taking it. I'd also like to know where this 30% number comes from and if it includes possible issues cause by experimental medical treatments."
] |
[
"The 30% number is reported in many places, including the CDC. It seems to be pretty world wide. It’s typically people who got a lighter case, most often didn’t spend any time in the hospital or had any real treatment, other than the basics to reduce symptoms. ",
"Some of the long haul symptoms are reduced/damaged lungs, damaged heart, reduced kidney function, reduced or missing erections, chronic and debilitating fatigue, loss of taste or smell, often for months.",
"None of this is something I wanted any part of so I vaccinated as soon as I was eligible."
] |
[
"Can substances be dissolved in a gas?"
] |
[
false
] | null |
[
"Supercritical fluids aren't gases..."
] |
[
"The answer is no. Gasses cannot dissolve substances because solvation involves intermolecular interactions and these are practically non-existent in the gas phase short of the occasional bumping into each other.",
"Someone pointed out super critical carbon dioxide which is interesting to think about. If you think about a gas... it expands to fill the volume of the container. If you think about a supercritical fluid... it also expands to fill the volume of the container. ",
"So what is the defining difference? Aside from supercritical fluids being much more dense, they can dissolve things. The phase is sufficiently dense that the particles are no longer completely non-interacting. Note that this is different from an aerosol with is a solid suspension in a gas.",
"So if a 'gas' is dissolving things, it is not a gas by definition. :)"
] |
[
"Would it still have the invisibleness of a gas?"
] |
[
"If the reason testicles are kept outside the body is that sperm can't survive at the body's internal temperature of 37C/98F, why do people who live in places where the ambient temperature is routinely higher than that have no trouble breeding?"
] |
[
false
] | null |
[
"At an ambient temperature higher than body temperature, and at 100% humidity, there would be no evaporative effect. So sweat would only cause dehydration. A person would require some external cooling source to survive and/or cool their nuts.",
"Edit: getting a lot in my inbox. What about this place? What about that place?",
"\n100% humidity I said. If you have that ",
" body temp air, you and the nuts will eventually overheat, and die. But luckily, you don't often get those conditions on earth. Saunas? If at 100% humidity, you're slowly overheating. Hot tubs? Are you submerged? And breathing overheated air? You're overheating."
] |
[
"Is there a limit where the sack can't regulate the temperature?"
] |
[
"A person would require some external cooling source to [..] cool their nuts.",
"I am now eager to rig such a contraption using parts procured from the local PC hardware shop's watercooling section... With a working prototype I'll throw a kickstarter to tempt punters into the new comforts of desk jockeying !",
"More seriously, to build up on your answer, suitability to human life is indeed function of both temperature and humidity - the combination of those two factors is the ",
"heat index",
" : at 100% humidity 32°C is great danger whereas at 40% humidity the same threat is only equaled around 42°C"
] |
[
"Since gunpowder burns well and quickly, is it technically high in calories?"
] |
[
false
] | null |
[
"This depends on your definition of high calorie content and what you are comparing it to. A calorie is 4.184J. According to Wikipedia, gunpowder contains 3 MJ/kg. ",
"For comparison animal and plant fat contains 38 MJ/kg and carbohydrates are 17 MJ/kg.",
"Check out the table of common energy storage materials here: ",
"http://en.wikipedia.org/wiki/Energy_density"
] |
[
"It is not that high in calories probably less than sugar. It is just that it is able to release all of it's energy very fast. This is an Energy versus Energy/Time situation. Gasoline has about as much energy as its equivalent weight in fire wood but gasoline burns faster than fire wood."
] |
[
"The term you might be looking for is ",
"energy density",
". For comparison you can also look at the ",
"energy densities of food",
". For the record - MJ/kg is equivalent to kJ/g."
] |
[
"Is there a conceivable way to diffuse sound in outdoor venues that hasn't been manufactured yet?"
] |
[
false
] | null |
[
"You may have noticed that major highways near residential areas typically have some form of concrete wall between the road and the buildings. The purpose is to reflect car noise. ",
"As a side note unrelated to your question, I have spent much more than 30 minutes in an anechoic chamber and noticed no unbearable effects."
] |
[
"You'd probably have better luck having monitors using noise-cancelling tech to broadcast the counter-signal of the concert, cancelling the soundwaves for anyone outside the concert while not effecting those inside the radius of outward facing speakers.",
"Though in all honesty this would be prohibitively expensive, and it probably wouldn't work all that well what with other structures around reflecting the noise all over."
] |
[
"I did notice that. Maybe they are too expensive for small venues?? And municipal building guidelines ",
" be prohibitive for big walls."
] |
[
"I have a glass of water, and I want to cool it with ice as fast as possible. Should I use crushed ice or regular cubes? Why?"
] |
[
false
] |
[deleted]
|
[
"Crushed ice will have a larger surface area to volume ratio, so it will cool your water more quickly with an equivalent amount of ice."
] |
[
"To add to that, stirring the water will ensure that you don't get a buffer-zone of chilled water around the ice-cubes. (though convection will also make movement in the water, stirring is more efficient)"
] |
[
"Although by stirring you'll be putting more kinetic energy into the system. So just stir slowly"
] |
[
"Does the dark side of the Moon overall receive more light than the light side?"
] |
[
false
] | null |
[
"By a very very small amount (about 0.5%), because when there is a new moon and the far side is illuminated, it is closer to the sun than when there is a full moon and the near side is illuminated."
] |
[
"But on the other hand, during a new moon, the near side is receiving light reflected from the entire Earth, which has a much higher albedo than the moon. Isn't that a larger difference? (especially because the far side does ",
" get this benefit during Full Moon)",
"Then there's also lunar ecplises, which only affect the near side, but only for a couple of hours twice a year maximum."
] |
[
"No, with the small exception of lunar eclipses."
] |
[
"Does the oxygen from water oxygenated the blood just like oxygen from the air does?"
] |
[
false
] | null |
[
"A flair is used to categorize a post into one of the categories shown in the message above. There are also instructions for how to add flair."
] |
[
"Hi Johanakerblom thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
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"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
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" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"what are flairs and how do i use them?"
] |
[
"Is .3 [recurring] times 3 equal to .9 [recurring]?"
] |
[
false
] | null |
[
"Yes. (1/3)*3 = 1."
] |
[
".333...=1/3",
".999...=1"
] |
[
".333...=1/3",
".999...=1"
] |
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