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[
"how do we determine the size of the entire (not just observable) universe?"
] |
[
false
] |
this question was inspired by recent submission to reddit. they list the estimated size of the entire universe to be about 900 Yottameters. How did they come to this number? my best guess is that is has something to do with rate of expansion of the universe. but how can anyone be certain of such a thing? it seems that even throwing out a ballpark number is useless when dealing with such questions. any help?
|
[
"I think that submission is wrong. What it claims is the entire universe at 93 billion light years diameter is actually the observable universe. It claims the observable universe is 14 billion light years, however due to the expansion of space the observable universe is actually around 93 billion light years. ",
"The actual size of the entire universe is not currently known but the best guess is infinite. I think I read somewhere that the lower bound is at least 250 times the size of the observable universe. This size is determined by analyzing the global curvature of spacetime in the observable universe and extrapolating outward. If the global curvature is perfectly flat (which it is currently believed to be) then the entire universe would be infinite."
] |
[
"The paper that produced the ~250 Hubble sphere lower bound can be found ",
"here",
". That paper also shows that a flat universe is more likely than a curved one to have produced the observed data."
] |
[
"In an infinite universe, every finite subset is a small scale. ;)",
"But yeah, I understand that in human terms these are enormous scales."
] |
[
"Do trans people's brains actually resemble the brains of their experienced gender? Where does transexuality come from?"
] |
[
false
] | null |
[
"I posted ",
"this article",
" that was published late last year in a similar thread yesterday. It's a case report of a male with psychosis-induced gender dysphoria. They treated with antipsychotics and resolved the GD.",
"The full paper is fascinating. The man was given constant brain scans during treatment. They linked the GD to the same brain region involved with body identity and body dysmorphic disorder. This doesn't mean that all cases of GD involve this region, but as far as I'm aware this is the only set of with GD/without GD brain scans from the same individual.",
"Grab the full paper from ",
"www.sci-hub.io",
"http://dx.doi.org/10.1007/s10508-015-0660-8"
] |
[
"No. In this case, an individual went to a clinic to get sexual reassignment surgery. They do a full psychological workup beforehand to make sure there are no mental illnesses present that may be altering their decision to transition. They discovered that they had LSD-induced psychosis which was causing the GD, so they treated the psychosis instead of transitioning, and the GD resolved.",
"It's a neat study because of the brain scans they did during treatment. Psychosis-induced GD is not a new phenomenon, but they've never watched the brain for changes before this study AFAIK.",
"Psychosis-induced GD may or may not be similar to genetic GD. We don't know. But this is the only source of information along those lines."
] |
[
"The most concise answer is this: There is some compelling evidence that the brains of trans people \"resemble\" the sex that they identify with, and it's the leading theory for why transexuality exists, but absolutely more research needs to be done. I'm posting some relevant links below:",
"Science journalism:",
"Wall Street Journal: ",
"These neurobiological findings suggest that the APA hasn't gone far enough in changing its categories. The issue isn't that sometimes people believe they are of a different gender than they actually are. Remarkably, instead, it's that sometimes people are born with bodies whose gender is different from what they actually are.",
" (paywalled)",
"New Scientist: ",
"Surprisingly, in each transsexual person’s brain the structure of the white matter in the four regions was halfway between that of the males and females (Journal of Psychiatric Research, DOI: 10.1016/j.jpsychires.2010.11.007). “Their brains are not completely masculinised and not completely feminised, but they still feel female,” says Guillamon.",
"New York Times: ",
"Researchers in the Netherlands have discovered that a region of the hypothalamus, located at the floor of the brain, is about 50 percent larger in men than in women, and almost 60 percent larger in men than in male-to-female transsexuals. If smallness of this brain structure is at all correlated with the feeling of being a woman, the results raise tantalizing possibilities that transsexuals may in a sense be more female than females.",
" (This is from 1995, it was a preliminary study)",
"Research papers (most probably paywalled):",
"http://www.sciencedirect.com/science/article/pii/S0022395610001585#",
"http://link.springer.com/article/10.1007/s10508-011-9805-6",
"http://www.sciencedirect.com/science/article/pii/S1053811909003176",
"http://press.endocrine.org/doi/abs/10.1210/jcem.85.5.6564",
"http://cercor.oxfordjournals.org/content/early/2014/09/12/cercor.bhu194.abstract",
"http://depot.knaw.nl/821/1/15106_285_swaab.pdf"
] |
[
"If gravity acts upon objects with mass, and light is made of photons (no mass), how can gravity 'bend' light?"
] |
[
false
] |
In the example of a black hole, the central mass, or object, exerts so much gravity that it has an escape velocity > c. However, if a photon has no mass, how can gravity affect it? Thanks, askscience!
|
[
"In general relativity, gravitational mass distorts spacetime. Near to very large masses, this distortion gets large. The light is still travelling in a straight line in its local spacetime, it's just that a straight line near to a large mass looks bent from far away. It's like lines of ",
" longitude: they're always straight, and at the equator they are parallel. Despite being straight and parallel, they meet at the poles, because the surface of the earth is not a Euclidean flat surface.",
"Edit: Gah, brain fart... I knew I'd make that mistake somewhere."
] |
[
"In the future you should consult the ",
"FAQ",
" for very commonly asked questions like this one:",
"If light has no mass, how does gravity affect it?",
"Conversely, you should also do a quick search to find ",
"other past threads",
"."
] |
[
"At least in special relativity, there is an ability to calculate invariants, quantities that are fixed across all reference frames. One that comes to mind that would seem to ignore the warping of spacetime is the invariant mass, or the mass of a particle at rest. As for GR invariants (which is really what something invariant under gravity is), I don't know any others off the top of my head. It's hard to think of something not affected by warping spacetime, because most properties of a system depend on spatial separations and temporal evolution, so changing how those two properties relate would seem to affect the evolution of the system."
] |
[
"Why do tortoises live so long compared to other organisms?"
] |
[
false
] | null |
[
"Certain tortoises have negligible senescence...",
"http://en.wikipedia.org/wiki/Negligible_senescence"
] |
[
"Many the same predators that attack water buffalo, zebra, or gazelle, had no problem with going after a human. "
] |
[
"But humans also lack predators.But once a human reaches old age, he is more susceptible to diseases.Why are tortoises more immune to these diseases?"
] |
[
"Why is the skin on your lip different from the rest of your body?"
] |
[
false
] | null |
[
"For the following explanation please have this picture handy: ",
"http://upload.wikimedia.org/wikipedia/commons/2/27/Skin.png",
"It's not actually that different. The skin of the lips, from outside of the mouth to the inside of your mouth, has 3 parts: the pars cutanea (the edge of your lip from outside), the pars intermedia (the red part of your lip, still outside) and the pars mucosa (the part of the lip inside of the mouth).",
"Normal skin in itself has the following structure: the outermost part is called the epidermis and contains interconnected specialized epithelial cells called keratinocytes. Scientifically the epidermis is a squamous (cornified) multi layered epithelium. Several layers compose the epidermis, morphologically the cells become more flat the more outside you are in the skin. This is not important for the explanation, but the layers are the following: stratum basale, stratum spinosum, stratum granulosum, (sometimes) stratum lucidum and the stratum corneum. below the epidermis is the dermis, a connective tissue with more or less disseminated fibroblasts and fibrocytes that produce a very strong network of protein fibers called collagen. The dermis has exactly 2 layers: the stratum papillare and the stratum reticulare.",
"The epidermis and the dermis have an interesting transition into each other, which is apparent in the picture above: the dermis is covered.with so called papilla that stick right into the epidermis. In a cross section the transition between epidermis and dermis looks wave like. At the same time there is a network of blood vessels between the epidermis and dermis called the plexus superficialis, and the plexus superficialis always gives breaches into the papillae. You can sometimes see if you hurt yourself very superficially but it still bleeds, the blood only exits at little dots.",
"How does this relate to the lips? As said, there are 3 distinct parts that gradually change into each other. The pars cutanea is skin exactly like in your face with the same structure and layering, and thus appears like the skin in the rest of your face. the skin of the pars intermedia is about the same with the same structure (a squamous multilayered epithelium with dermis underneath), but a) the epidermis becomes way thinner and b) the papillae stick higher up into the surface. this means that the layers of skin between the outside and the plexus superficialis become thinner and the skin appears redder because the fine network of blood vessels shines through. Then the pars intermedia slowly transitions into the pars mucosa, which is more like the rest of the mucosa inside the mouth: one layer of non-squamous (non-cornified) mucosal epithelium and a bit of connective tissue below. The mucosa is anatomically different from the skin, but because the transition is not acute, but gradual, the red of the lip just kind of goes over into the mucosa.",
"TL;DR your lips appear way redder because the skin is becoming thinner and transitions into the mucosa of the mouth."
] |
[
"Someone also posted on one of the subreddits that the skin on the inside of your mouth is the same as a vagina. Don't quote me yet, I'll hopefully be back with an edit."
] |
[
"I don't have an online source for this, but I remember seeing on the Discovery Channel (take that for what it's worth) that lips evolved at the same time that humans began walking upright and the vagina move forward on the anatomy. This had an effect of you couldn't really see a vagina just from walking behind someone anymore, so lips evolved as sort of an advertisement for the vagina, being that they look sort of similar. "
] |
[
"As there are colours that cannot be distinguished by the colorblind, are there things that only colorblind can see?"
] |
[
false
] |
I hope the question is not too dumb. I just had an idea for a b-day gift for a friend and we're always spoiling him (in a friendly way) cause he's colorblind. I wanted to know whether there are colours that colorblind can distinguish better, so that only he would see an image with those colours... Did I make myself clear? I'm sorry if the question's too dumb. Have a great day! :D
|
[
"It's possibly to make an image that's easier for a colorblind person to see. We had one in a lab I taught on genetics. Basically, you have a scattering of red and green dots that look the same color to someone with red-green colorblindness but very different to someone without. Then you have a slightly darker shaded dots showing a letter or picture. The image pops out to a colorblind person but is obscured (though still visible if you know what you are looking for) to a color vision person. The exact one you use kind of depends on the color blindness variety, but odds are it's red-green and the one below will work.",
"examples:\n",
"http://www.moillusions.com/reverse-color-blindness-test/",
" "
] |
[
" there is a set of colours that would appear to be ",
" to him than the average person... It would depend on exactly what kind of colorblindness he has (there's ",
"quite a few types",
"). Obligatory not-an-expert but I think it's impossible to make an image that would only appear to colorblind people."
] |
[
"Yes-- well, patterns more than colors-- such as certain types of ",
"camouflage",
", which is why in the past ",
"armed forces",
" have actually recruited color-blind men."
] |
[
"Why do our bodies urge us to scratch when in virtually all cases it makes the problem worse?"
] |
[
false
] |
Good examples being eczema, athletes foot, sun burn, etc
|
[
"This guy blogged about that. ",
"http://doctorandy.blogspot.com/2006/05/why-we-scratch.html",
"There's a link in the article to a scientific paper."
] |
[
"I find it contrary to the usual adaptive aspects of evolution.",
"That's the thing though; society can move ",
" faster than evolution can ever keep up with. ",
"Technological progress and the storing and generational transmitting of knowledge, far, far outclasses evolution in providing an organism some fitness advantage.",
"Exhibit A would be that I'm kind of pudgy and not very tall - but a bear isn't going to do shit if I have my .338 lapua rifle and precision machined optics in a tree hundreds of feet away, even though it's possible with ",
" humans could select for more and more body mass and better biting and chewing muscles and sharper teeth. Also we wouldn't really be humans anymore.",
"Also, not only is evolution really ",
", it's also pretty imperfect; from simple allergies to straight up Crohn's disease, the immune system can malfunction and malfunction ",
" when it basically does it's damndest to respond to a threat that isn't even there."
] |
[
"I hope I didn't come across as asserting that, I know our minds and technology far exceed the speed of evolution (I.E wisdom teeth). However, things that cause fits of scratching would seem to be omniscient throughout the history of homosapiens, making it seem that evolution would have \"made it clear\" to not scratch. I find it contrary to the usual adaptive aspects of evolution."
] |
[
"Why makes Endometriosis so hard to diagnose?"
] |
[
false
] |
According to Wikipedia, “Women suffering from endometriosis see an average of seven physicians before receiving a correct diagnosis, with an average delay of 6.7 years between the onset of symptoms and surgically-obtained biopsies, the gold standard for diagnosing the condition. This average delay places endometriosis at the extreme end of diagnostic inefficiency.” What makes Endometriosis so hard to diagnose? Is it purely social factors (“periods are supposed to hurt a little, get over it” etc.) or are there other factors involved that complicate diagnosis?
|
[
"I wrote my thesis partially on this topic. I’m on my phone so don’t have source list handy but can update later if requested.",
"It’s due to a few compounding factors. Chronologically, one of the first delays is that the women themselves don’t know that their periods are particularly bad. A significant number of girls don’t feel comfortable talking about their periods in general, so can’t compare pain levels with friends, and figure that being doubled over in bed for days at a time is normal. This carries through if her mother is the primary source of information, and as endo is often hereditary, is told that this is the expected level of pain.",
"Then, the young woman eventually arrives at the doctor, who also downplays the pain, and the patient normally needs up switching doctor a few times (3 or 4 drs IIRC), until she finds some one to take it seriously. By now she’s 20 or so, and been having awful periods since 14. ",
"Then she arrives at gynaecologist that knows endo when they see it, and gives a provisional diagnoses, but an official one requires surgery, which as other posted have said, can cause potentially a worsening of symptoms.",
"Furthermore, a theory of mine that I explored in my thesis, is that endo was and still is viewed primarily an infertility disease. This means that only when women are thinking about getting pregnant, OR the doctor looks at woman and thinks, you’re about the age/life stage of maybe thinking about starting a family, does endo pop up as a more likely and pertinent diagnosis. As per usual, a woman’s reproductive ability is more cared for than her body or pain itself. ",
"Fortunately, with all the talk in the media and raising awareness, the diagnostic delay in Australia(where I’m from) has reduced significantly in the last 10 years or so. Young women and AFAB people are getting diagnosed in 2-3 years instead of 5-7, which is great.",
"The question is now, what to do with the diagnosis, and more research on more effective treatments than the wildly variable surgeries we use now.",
"Edit adding sources:",
"(Overview of disease) Gupta S, Harlev A, Agarwal A. Endometriosis. Cham: Springer International Publishing;\n2015 2015.",
"Menstrual Taboo and diagnostic delay:",
"Grogan S, Turley E, Cole J. ‘So many women suffer in silence’: a thematic analysis of women’s written accounts of coping with endometriosis. Psychology & Health. 2018;33(11):1364-78. ",
"Seear K. The etiquette of endometriosis: Stigmatisation, menstrual concealment and the diagnostic delay. Social Science & Medicine. 2009;69(8):1220-7.",
"Hudelist G, Fritzer N, Thomas A, Niehues C, Oppelt P, Haas D, et al. Diagnostic delay for endometriosis in Austria and Germany: causes and possible consequences. Hum Reprod. 2012;27(12):3412-6.",
"Fertility being a greater cause for diagnosis/treatment than pain alone:",
"Arruda MS, Petta CA, Abrão MS, Benetti-Pinto CL. Time elapsed from onset of symptoms to diagnosis of endometriosis in a cohort study of Brazilian women. Hum Reprod. 2003;18(4):756-9.",
"Staal AHJ, van der Zanden M, Nap AW. Diagnostic Delay of Endometriosis in the Netherlands. Gynecologic and obstetric investigation. 2016;81(4):321-4.",
"Decreasing time to diagnosis in Australia:"
] |
[
"As someone who is just finishing her PhD on endometriosis, I want to second everything you’ve written and also add that medical sexism has made it so that endometriosis has been misdiagnosed and mistreated for centuries.",
"Endometriosis is commonly misunderstood as a disease of the uterus, but it is actually a full body, systemic, inflammatory disease. The emphasis on “bad periods”, “fertility”, and menstruation has made it easy for the disease to be dismissed alongside other “women’s health” concerns. For decades in the late 20th century, endometriosis was referred to in medical textbooks as a “career woman’s disease” that occurred when women decided to wait to have children to pursue a career. This assumed all patients were white, middle-class, working women, and put the responsibility of the illness on their decision not to have children. This is one example of the long history of patient-blaming around endometriosis. We can see this today in other forms.",
"There is also a massive lack of education and funding for doctors and patients. Proper endometriosis care involves a multidisciplinary team, but most people are only treated by a general ObGyn, even though many of them are not specialized in the disease. This leads to misdiagnosis and lengthens the diagnostic period. Further, pharmaceutical companies fund a lot of the research around endometriosis and this has led to some less than helpful studies, as well as meant that many people are being prescribed pills for endometriosis without never actually being properly diagnosed. ",
"I recommend “Pain and Prejudice” by Gabrielle Jackson and “Doing Harm” by Maya Dusenbery if anyone wants to learn more about medical sexism. There is also a lot of good writing out there on the added stigma around pelvic health, chronic pain, and sexual health."
] |
[
"Did my honours on this and in the process of PhD. It has a huge variety of factors.",
"Firstly, the menstrual education menstruators and non-menstruators receive is often inadequate. It is typically lumped with sex education, stigmatising menstruation. Further, almost no institution-based menstrual education teaches children the symptoms of endometriosis, thus they aren't taught what \"normal\" and \"abnormal\" menstruation looks/feels like.",
"The stigma of menstruation plays a part too. Most young women who experience painful periods are initially told \"just use a hot water bottle\" or take some pain meds. We are taught menstruation is painful, so people put up with it. Some people don't want to talk to their doctor about menstruation.",
"Doctors also play a part. Socially, women's pain is typically dismissed or diminished even by female doctors. This delays interventional action. Some doctors also aren't particularly informed on endometriosis; it is a relatively new publicly known disease. It's also hard to diagnose endometriosis without invasive surgery, which some doctors don't want to do on young women.",
"We also don't really know much about endometriosis in the big scheme of things. There are many theories about what causes endometriosis, and there is currently no treatment. Within the medical community there are still individuals who do not 'believe' in endometriosis.",
"Obviously each of these topics, and more I have left out, are far more complicated than this comment portrays."
] |
[
"Humans are getting taller and taller - will this stop eventually, or will we just keep growing?"
] |
[
false
] | null |
[
"We're getting taller due to cultural factors, not genes. Nutrition plays a huge role in this, such that our gene's expression will result in taller individuals when we eat healthier.",
"Compare North Korea and South Korea for example. NK has shorter and malnourished citizens compared to SK.",
"A google search led me to this source if you're further interested.",
"\n",
"http://www.scientificamerican.com/article.cfm?id=why-are-we-getting-taller"
] |
[
"Most of the reading I've done on this indicates that the maximum potential height for humans in one Earth gravity is about 3 meters. The square cube law (",
"http://en.wikipedia.org/wiki/Square-cube_law",
") basically sates that for every doubling of height, volume (and hence mass) goes up by a factor of 8. Beyond about 3 meters our bones can no-longer support the mass. In addition to that hearts would have enormous difficulty pumping blood the distances required against gravity.",
"The bone and heart issues are why the largest mammals are found in the ocean and not on land. In water the body is supported from all around and can be oriented such that the strain of pumping blood against gravity is minimized. "
] |
[
"That article also states that the age of menarche has also decreased, is this true? I was under the impression that the age of menarche has actually increased."
] |
[
"If vitamins A, E, and K are fat soluble, how do vegetables have such high amounts of them yet so little fat? Where/how do vegetables store these vitamins?"
] |
[
false
] | null |
[
"The terms \"high\" and \"low\" are relative. For example a cup of kale (130g) contains 1300% of your daily value of vitamin K, but that is only 1mg of the vitamin. That same cup contains 0.6g of fat, a relatively low amount compared to fat-rich food, but still a lot of fat to easily dissolve 1mg of vitamin K."
] |
[
"Again, the devil is in the details. They synopsis of an article which is a summary of a scientific study never provides enough details to form far-reaching conclusions about a topic. In this case, the webmd article states:",
"Researchers say this study shows that the minimum amount of fat required for optimal absorption of these nutrients from the salads is more than 6 grams of added fat. But because salads are often consumed with other items that contain fat, the use of a reduced-fat salad dressing may still allow the body to reap the maximum nutritional benefits of fresh vegetables.",
"Two key things here.",
"you need a minimum of 6g fat (which is 10 times what we see in that cup of kale).",
"Perhaps more importantly, nowhere in this article, or the actual scientific article is the hypothesis proved or even really stated that the reason fat is needed is because these nutrients need more fat to be dissolved into. Instead there is a correlation with the amount of nutrients absorbed and the fat content of the meal. There are many hypothesis one could make about why this is the case (the most likely is some combination of the way fat interacts with the digestive system, or with the food itself), but we cannot speak to the validity of each one. ",
"I suggest that you have a look at the ",
"source article",
" which I believe is available for free and see what actual conclusions can be drawn."
] |
[
"That being the case, why does eating vegetables with a fat source improve absorption of those vitamins if there's already sufficient fat in them to dissolve them? (As per the study discussed in this article ",
"http://www.webmd.com/food-recipes/20040727/fat-helps-vegetables-go-down",
" )"
] |
[
"Where does the carbon come from in 'green steel'?"
] |
[
false
] |
I was reading this morning about green steel production ( ), but I don't understand how fossil fuels can be completely eliminated. As I understand it, renewable sources and hydrogen can be used to heat the furnace, and hydrogen can be used instead of coal to reduce the iron oxide to iron (producing water instead of carbon dioxide). However, steel contains a few percent by mass of carbon, to provide its strength. Where does green steel get that from?
|
[
"The point of \"green steel\" isn't to completely eliminate fossil fuel use, it's to significantly reduce the CO2 output associated with making steel.",
"The traditional way of making iron metal from iron ore is to place it in a blast furnace along with coke (basically purified coal). The coke gives off CO gas, which strips the oxygen out of the iron ore (which is mostly iron oxide) and produces molten iron metal plus an enourmous amount of CO2. That iron then goes though additional processing to adjust its chemistry to match whatever grade or application it's being made into (this may involve tossing in some coal to increase the carbon content of the metal), but the vast majority of the CO2 output comes from the blast furnace step. If you replace the blast furnace burning coal with a different sort of furnace which uses hydrogen gas to strip the oxygen from iron ore, the CO2 output can potentially go down by orders of magnitude.",
"As an aside, although the carbon content in steel ",
" be as high ~1.5%, the vast majority of steel produced has less than half that and many grades of automotive steel which need to be bent and formed into complex shapes may have a carbon content of just a few hundredths of a percent or less. Since the steel in the article you posted is being made in partnership with Volvo, it's very likely that whatever amount of carbon they added in was measured in grams per tonne."
] |
[
"There are many ways of doing that.",
"It's been more than a decade since I learned a bit about metallurgy, so my memory might be a bit foggy on the subject. ",
"But, you can just burn a bit of biomass along side the hydrogen - that way the carbon comes from the fast carbon cycle, and the steel will technically act as a carbon sink. You can also just distill CO2 from the air or produce it via a range of different chemical reactions. And then add that CO2 into the furnace."
] |
[
"You can also just distill CO2 from the air or produce it via a range of different chemical reactions.",
"To add to this, collecting CO2 from an existing chemical plant will use the least energy. Capture from a concentrated point-source emitter uses a fraction of the electricity vs direct air capture with current technology. Usual suspects for CO2 capture - ignoring fossil power stations - would be production of ammonia, ethanol (fermentation), or hydrogen (\"blue\" hydrogen, from fossil methane). ",
"Of those, the raw CO2 stream from ethanol fermentation tends to be the highest purity. That means less energy used for refrigeration/distillation/compression, and less energy use means better economics and lower carbon footprint for obtaining the green CO2.",
"CO2 captured from ethanol fermentation is also attractive because that carbon itself is biogenic. Similar to burning biomass, the green steel would act as a true carbon sink rather than just negating other CO2 emissions."
] |
[
"Who feels the umbilical cord being cut? Mother, child or both?"
] |
[
false
] | null |
[
"Neither, actually.",
"The parenchyma of the umbilical cord is made up of something called ",
"Wharton's jelly",
", it's basically a very thick, mucous-ey substance that provides structural support to the important stuff inside (umbilical arteries and vein). There are no nerves in Wharton's jelly, so no one feels the umbilical cord being cut."
] |
[
"It's attached to the placenta, which comes out shortly after the baby. So they could have left it on and it would have shriveled up and fallen off on it's own. They could have made \"knives\" out of wood, or before that kind of tool-making they could have used sharp rocks or even chewed through it like chimpanzees.",
"It didn't get many answers, but ",
"here's an AskScience post about it",
" from 2 years ago."
] |
[
"Somehow that made me wonder what the early human did with the umbilical cord. Did they cut it? I know that people in the middle ages \"cut it\" with a little string"
] |
[
"Why are we saying that the strong force is the one which maintains the nucleus while it only acts inside hadrons ? Why wouldn't it be the weak force instead ?"
] |
[
false
] | null |
[
"The strong force doesn’t only act inside hadrons, but also ",
" hadrons. This is called the residual strong force, and it’s analogous to intermolecular forces between molecules. The standard electric (Coulomb) force acts inside of a molecule to bind the electrons to the nuclei, but different molecules interact electromagnetically with higher multipoles, so there’s an effective force between them, even though each molecule has zero monopole moment, and the interaction doesn’t look like a Coullmb interaction. These are Van der Waals forces, and the residual strong force is like that, except for the strong force rather than the electromagnetic force.",
"Also, the strong force is not the only force relevant inside nuclei. In order of decreasing strength, the forces present in a general nucleus are: the residual strong force, the electromagnetic force, and the weak force. Gravity is technically present, but totally negligible."
] |
[
"I don't have any other analogy that is simple and sufficiently correct."
] |
[
"Thanks for the answer. Now I understand :). I probably missed the residual force part when I learned about the strong force."
] |
[
"Isn't it not technically correct to say there are four fundamental forces anymore?"
] |
[
false
] |
It seems like there's 6 to me. As far as I know, each boson (group) mediates one force: However, it seems that there are two other groups, the Higgs Boson (the mass interaction? Not sure what to call it), and the X and Y bosons (proton decay, iirc). So are these forces just like the others? If not, why, and if so, why do we still seem to stick to those four as fundamental forces?
|
[
"The Higgs is not the mediator of a \"fundamental\" interaction. The \"four forces\" are gauge interactions, and are mediated by ",
" bosons (the Higgs is a scalar). Gauge theory isn't exactly a trivial subject so it's almost universally omitted in divulgation, but that's basically what is meant by fundamental interaction. The Higgs' coupling to fermions instead is a simple, non gauged, Yukawa coupling.",
"About the X and Y boson, these are hypothetical gauge bosons of most GUT (grand unification theory) proposal. A GUT is a single gauge interaction unifying the electroweak and strong interactions into a single gauge group, not an additional gauge interaction.",
"Finally, it's important to say that the subdivision of the gauge interactions, along with the subsequent \"counting\", it's somewhat arbitrary and at the very least a bit technical. The scheme is as such:",
"This makes four gauge interactions if the criterion is that the generators between two different interactions commute.",
"Now, as a consequence of the Higgs mechanism, there is a certain mixing that happens in the U(1)×SU(2) sector (electroweak). Basically the B and W",
" bosons are mixed into the photon and the Z",
" , while W",
" and W",
" are recombined into the W",
" and W",
" . Note that the total number of gauge bosons hasn't changed! So instead of weak isospin and hypercharge at low energy one usually talks about",
"That's the list that is usually given and it still gives four."
] |
[
"A gauge interaction is related to a symmetry in the physics of (in this case) fields, the symmetry transformation is a gauge transformation and choosing one (set) of the equivalent field configurations is called picking a gauge. I'm not sure how comfortable you are with mathematics so there is little more I can think to say."
] |
[
"In order to describe the excitations (particles) of the gauge fields you need four components (time component + 3 spatial components). This is similar to the description of the momentum in Minkowski space as a four vector (time + 3 x space). Much more importantly, the components of gauge fields transform just like a four vector under Lorentz transformations (e.g. rotations), in addition to the general rules of a field transformation.",
"A scalar field/particle transform differently under Lorentz transformation, i.e., only its argument transforms."
] |
[
"Moderna vs Pfizer/Biontech BNT162b1 vs BNT162b2?"
] |
[
false
] |
There are people that says that the Moderna vaccine should work as well as Pfizer/Biontech because they uses the same spike. Do anyone know how much difference there are between Moderna and BNT162b2 compared to between BNT162b1 and BNT162b2? What was the problem with BNT162b1 that made it fail before phase 3?
|
[
"You don't need to appeal to the fact that the Moderna and Pfizer/BioNTech vaccines both encode the prefusion full-length spike protein to ",
" that they will have equal efficacy, you can just look at the clinical trial results.",
"The results were not meaningfully different, with the Pfizer/BioNTech vaccine ",
"95% effective in preventing symptomatic COVID-19 (CI 90.3 to 97.6)",
" and the ",
"Moderna vaccine 94.1% effective (CI 89.3 to 96.8)",
". ",
"As for the difference between BNT162b1 and b2, the trial for b1 was discontinued because b2 was comparably effective in terms of typical neutralizing titers, with fewer side effects.",
"If b1 were the only option, I have very little doubt it would have gotten an Emergency Use Authorization. But when there's a parallel vaccine candidate that is comparably immunogenic, with fewer and less severe side effects, you focus on that candidate and don't move to a large trial on the one with more side effects."
] |
[
"Why did Pfizer have a significantly stronger CD8 response then?"
] |
[
"We don't know enough about the virus or the immune response to it to answer questions about why some responses differ across vaccine candidate, or even to answer questions about whether it matters at all if there are different immune reaction profiles given that we have observed in large-scale clinical trials that the vaccines provide equivalent protection in the short to medium term."
] |
[
"Are stars getting smaller?"
] |
[
false
] |
Correct me if I am wrong, but stars are born in a nebula, which are the remnants of a supernova? If multiple stars are born in nebulae like in the pillars of creation, then surely an individual star will never be as massive as its parent star?
|
[
"Not all nebulae have to necessarily be supernova remnants. In fact, the supernova remnants are entirely too hot and also posses too much kinetical energy to collaps into a star on its own. Also the total mass expelled in a supernova is entirely too little to form a new star. Of a given gas cloud typically only around 1% ends up in the central mass formed (the new star). ",
"If the shock front of a supernova however came in contact with a preexisting gas cloud it could through local compression very much trigger the gravitational collaps of said cloud.",
"Following that trail of thought, a parent star might trigger the formation of many stars, their mass possibly being a multitude of its own.",
"The first stars ever consisted of hydrogen to a much larger degree then the stars forming today. The stars that are being formed now are enriched in metals because their progenitor gas cloud came in contact with the remnants of a previous star. ",
"The ",
"wikipedia article on star formation",
" really is an excellent read."
] |
[
"No stars are born form massive cold clouds of mostly Hydrogen and Helium. There may be some initial compression from supernovaes or just strong solar winds, but if the cloud is too warm it wont collapse sufficiently to form a star.",
"These clouds tend to be in the 10000s solar mass range, so there is plenty of material to form multiple stars of different size. This comes about from original cloud forming multiple smaller cores that will become the actual star in the end.",
"Where supernovae come in is that they are high mass stars that are short lived so they may go SN while their lower mass siblings are still forming, seeding them with those nice heavy elements (aka humans and polar bears amongst other things :D). Maybe compressing a pocket of gas here and there, on the other hand high mass stars are very good at blowing away gas cutting of supply to other forming stars."
] |
[
"Thanks a lot! That's definitely cleared things up.",
"To follow on, does this mean then, that there is a trend towards heavier element star formation? And the hydrogen they do possess is from the interstellar gas clouds?",
"Does this mean the interstellar gas is being 'used up' in new star formation and thereby there will be fewer stars born and of smaller mass in the distant future?",
"Hopefully I'm making sense."
] |
[
"Why can hyperventilating cause lethal changes in pH?"
] |
[
false
] |
[deleted]
|
[
"It can’t. Hyperventilating will lower your CO2 levels, which will in turn constrict your cerebral arteries and make you pass out. Then when you’re unconscious you’ll stop being a dick and breathe normally. And your blood pH will return to normal. Nothing lethal about it. "
] |
[
"I was gonna chime in as an EMT but this reply sums it up.",
"The only thing I can add is that your breathing is regulated by the Carbonic Drive so as you exhale excess CO2 the need to exhale decreases. So, if you're chilling you breath normally. If you go for a jog, your body starts metabolizing and produces excess of CO2, so you start exhaling to breathe off the excess CO2. When your back in homeostasis your breathing rate returns to normal. People who suffer from chronic diseases like COPD have bad Carbonic drives and they breath based on the Hypoxic drive which is controlled by the amount of oxygen in your body.",
"[Edit] it can be lethal if a chronic condition like COPD. Your brain is suspended in Cerebrospinal Fluid(CF) which is regulated at a specific pH by the aforentioned Carbonic Drive. The more CO2 in your system the lower the pH of the CF fluid. Your brain is very sensitive to changes in it's environment. If the pH is off, too low or too high, your brain stops functioning correctly. With conditions like COPD you're no longer sensitive to the Carbonic Drive, so your body regulates it's pH using the Hypoxic drive. When you hyperventilate you're increasing the pH of the CF fluid, in the case of the Hypoxic Drive, it's slow to react to changes. Because the Hypoxic drive only cares about how much oxygen is is your blood stream you stop breathing once your Hypoxic drive has saturated your body, and the CF, with Oxygen. With the pH high your brain stops functioning correctly and signals stop getting sent to your diaphragm, the muscle you use to breathe... Then you die."
] |
[
"But as you know, as an EMT, that you would never withhold oxygen from a COPD patient in distress. "
] |
[
"Would botulism leave any diagnostic trace a year after someone suffers from it?"
] |
[
false
] |
North Korea claims the American student, Otto Warmbier, had a case of botulism before being sedated and falling into a coma. He is now in a vegetative state. The American doctors examining him stated that they found no evidence of botulism, But it is unclear what exactly they meant by that statement. Botulin, the toxin, would presumably have left the body after 4 or 5 months, no? So of course there would be no "active botulism". So my question is, am I interpreting their statement correctly? It either means everything (he didn't have botulism), or it means nothing (because one wouldn't even expect to observe active botulism after more than a year). Which one is it?
|
[
"Botulinum toxin can cause degradation of the neuromuscular junction, which can be detected on electromyography(EMG) and Nerve Conduction Studies(NCS).",
"The typical findings are as follows:",
"In extremely severe cases of botulism, the neuromuscular junction could be completely degraded leaving the above mentioned findings for a long period of time.",
"Now it's in the realm of possibility that somebody had a case of botulism and developed respiratory compromise leading to anoxic brain injury and coma/vegetative state/unresponsive wakefullness without chronic EMG/NCS changes typical of botulism."
] |
[
"Thanks for the great answer."
] |
[
"The binding of botulinum toxin E is very strong with an unbinding half time of months. This is why injections of botox into facial muscles must be repeated about every 6 months. So very little botox would be found on muscle biopsy but analytical methods are sensitive and a trace might be found still bound to Acetylcholine receptors. Better to look for antibodies in his blood. Poor guy, ruined for stealing a souvenir. But NK is a mad state."
] |
[
"Is it possible for a liquid (or solid) to be lighter than a gas?"
] |
[
false
] |
We know liquids can be heavier (denser) than solids (e.g. ice & water or ). What about gases? Google gives me as the heaviest gas (at room temperature) at 11-13 kg/m and as the lightest liquid at 616 kg/m So it seems unlikely, but can it be done using high pressures/low temperatures/gas mixtures? I'm thinking of a material that is 100% liquid/solid, so party baloons and porous , which are solid objects but gas don't count. I guess that for solids you could cheat by making a ball with a perfect vacuum in it, but does a sufficiently strong and light material exist to build such a ball, so that it won't collapse under air pressure?
|
[
"Yes. Gasses are compressible, so they can have a density that is greater than the usual density at 1 atm pressure. The following website describes how gasses in parts of Jupiters and in stars have densities greater than liquid water.",
"http://www.newton.dep.anl.gov/askasci/chem03/chem03251.htm"
] |
[
"Well, it's not exactly what you're asking, but you can get an aluminum foil boat to float on top of a tank of sulfur hexaflouride, so while the aluminum is still more dense, you can get it to appear lighter due to displacement."
] |
[
"Those are not the droids he's looking for."
] |
[
"Do we expect DNA to be unique to earth?"
] |
[
false
] | null |
[
"I would probably not expect an alien to have DNA exactly like we have it. The exception to this could be the theory of panspermia, if microbial life on earth were somehow dropped here by a comet from somewhere else with life.",
"Assuming life developed completely independently, though, I would not expect DNA as we have it to exist in the aliens. DNA is made of very common elements that should be present throughout the universe, but the unique arrangement of atoms with the exact same 4 bases would almost certainly not occur.",
"The RNA world hypothesis posits that life on earth originally used RNA for its genetic material and enzymatic reactions, and then later developed DNA as a more stable and \"high fidelity\" version of RNA to use as genetic material. There's some evidence to support this, like the catalytic RNA core of the ribosome. ",
"The thing is, there's nothing particularly special about the \"choices\" that were made in RNA and DNA. The four bases we use (adenine, thymine, cytosine, and guanine) aren't the only ones possible or even common. Uracil is used instead of thymine in RNA. Inosine can be substituted in. Methylcytosine is used in DNA for epigenetic marks. All of these probably could have been part of the original \"standard\" for DNA just as easily as our current bases. Evolution tends to be one-way, however, and doesn't really hit on the most optimal solution. It tends to find local optimums, where the first \"good enough\" solution that happens along is optimized and improvised upon. If another organism had started with even a slightly different set of molecules composing the soup out of which they evolved, they are likely to end up with a different version of DNA. It might be mostly similar with slight changes (methyl-C instead of C), or it could be radically different (completely separate bases, different sugar backbone, etc). ",
"It's possible that it would have a similar antiparallel arrangement to DNA, as that does provide a very elegant mechanism for self-replication, but it could be something totally different that we have never imagined."
] |
[
"DNA? maybe, probably not, but there would have to be some kind of hereditary molecule. The fundamental principals of evolution would be expected to hold. "
] |
[
"Put it this way : say you had to pick a molecule other than DNA that could play its role in life. Then around this central choice, there are a whole set of other choices of molecules, systems, and organisation to make a different type of life.",
"It's certainly possible that there are many such choices to be made - that is, many other molecules that could replace DNA. Each of these would have a corresponding system of other molecules to make a living system. These supporting molecules - the metabolism - would have to have complementary properties in order for the whole system to work.",
"However, there are a limited number of properties a molecule can have. Just as you can't replace any metal ion in an enzyme with any other, you can't replace any old part of the metabolic jigsaw with any novel part. Based on the particular choice you made for the 'new-DNA' there may not be enough suitable molecules with complementary properties to form a properly living system.",
"As for your second question : I have no idea, but this is the general problem. Evolution is only ever one side of the coin; the other side is pattern formation in chemical systems. I often see too much emphasis made on how good evolution is at generating novelty without considering the constraints of the underlying physical and chemical system."
] |
[
"Since air condenses to form water on a cold surface, can it condense on the surface of cold water?"
] |
[
false
] |
I am just curious as to whether a solid surface is required for condensation to happen. Also, if it does condense, would there be an increase in volume, or is the rate of evaporation still higher?
|
[
"Condensation is the transition of water from a gaseous to a liquid or solid state, and it doesn't require a surface. ",
"A cloud is a very common form of condensation. A cloud is essentially water droplets that freely float around because warm vapor-bearing air has entered a cold region where the temperature has fallen below the \"dew point\". The water can no longer remain as a vapour and so condenses out into a suspension of tiny tiny droplets. ",
"You often see a surface version of this exact effect on cool mornings over bodies of water or damp valleys where cold air collects. Vapor leaves the surface of the water and immediately condenses out in the cold air into wisps of steam. Fog banks on coastal cities are another example, although a lot bigger. ",
"In this case, the condensed vapour drifts around and may rejoin the body of water, or blow into warmer air where they re-evaporate and disappear. ",
"Finally, ",
"frost crystals can form on lake ice in the right conditions",
". They too are a form of condensation."
] |
[
"I do not believe a solid surface is required for condensation to happen. But, in order for you to observe the condensation taking place you'd need a solid present, or some other calculable amount of water to begin with. You can also think of the surface of a solid becoming wet from condensation. At that time, is the new water forming on the solid itself, or just accumulating to the existing liquid and forming drops? In short: No a solid is not absolutely needed. "
] |
[
"Increase in volume. Condensation is just some vapour turning into liquid. Indeed if hot air containing vapour were cooled by a lake the vapour would condense and form a liquid. ",
"In the above scenario though you would also have to ask how much water would evaporate off the surface from the latent heat of the hotter air. "
] |
[
"Do other languages have a preferred way to order adjectives?"
] |
[
false
] |
I learned recently that in English opinion-size-physical quality-shape-age-colour-origin-material-type-purpose, and would like to learn more about it. Has it always been like this? Is it like this in other cultures? Are there theories as to why this developed?
|
[
"Not to be aggressive but I don't think that's the question.",
"If you say \"a big black and bold guy\" does the adjectives (big black and bold) have a precise order between one another or can they be freely replaced? A bold black and big guy. It's not about the place of the adjectives in the phrase."
] |
[
"French is fun, because adjectives have both an order as well as a location (before ",
" after the noun). ",
"If a word is short or has one of the qualities beauty-age-goodness-size, it goes in front of the noun, otherwise it goes after the noun. ",
"As for multi-adjective ordering, the more \"relevant\" an adjective is to the noun (which is obviously context dependant on the point being made by the speaker), the closer to the noun it is. The French equivalent of \"big beautiful dog loyal brown\" places the emphasis on beautiful and loyal. There are obviously more rules because French is a proud language of how it flows, introducing complicated structure rules.",
"Origin, material, and purpose usually are last because they are often expressed with preposition phrases. Quantity is always first."
] |
[
"has one of the qualities beauty-age-goodness-size",
"...but only for the basic adjectives with these meanings, such as ",
", ",
", ",
" and ",
". Others, such as ",
", ",
", ",
" and ",
" come after the noun."
] |
[
"Does turning the sound off with a handheld like a Nintendo DS use less battery life?"
] |
[
false
] |
And if yes, does it really make a big difference?
|
[
"Short Answer: Yes it will save some battery power, but no it will not make a big difference.",
"Longer Answer: A lot of handhelds have piezoelectric speakers which don't draw much power ~0.1A or 100mA at full power. The DS has a 850mAh battery, meaning you could run the speaker at full power for 8.5 hours. It's rare though that speakers ever draw full power (I'd guess at normal listening it'd be about 30mA but i've never measured it). It is usually the screen that drains the power the quickest, or more specifically the backlight of the screen, so turning down the brightness will increase battery life much more than the turning down the speakers."
] |
[
"Got any sources on that?"
] |
[
"If you have an android phone, you can go to Settings->Battery and it will tell you what parts of your phone have been drawing the most power. In this way you can determine (at least assuming you have an android phone) what's eating up the battery for your particular usage pattern. For what it's worth, the screen is always at the top of my list, usually by a wide margin."
] |
[
"Why does the moon rotate at that perfect rate so we only see 1 side?"
] |
[
false
] |
I want to know if it has anything to do with the theory that the moon broke off of the earth as a result of a meteor/comet, or is just random chance.
|
[
"It's called tidal locking and is quite common. Initially the moon was rotating faster, but as it flexed from tidal forces from the Earth, it acted as a frictional brake and slowed down the moon's spin to the point where the lunar day and lunar month are the same length. Eventually the Earth's spin will slow down enough so only one side of the Earth will face the moon.",
"http://en.wikipedia.org/wiki/Tidal_locking"
] |
[
"Eventually the Earth's spin will slow down enough so only one side of the Earth will face the moon.",
"Only if given enough time, but long before that the sun would have destroyed them both, unless future humans can save them in some way. The moon receding and the oceans evaporating will also hinder this process."
] |
[
"For clarity: Earth's gravity is slightly stronger on the near side ",
" than it is on the far side. There's a bit of gravity variation throughout the earth, but that's not what we're talking about here."
] |
[
"Why are particles the size they are and not any other? Why can't there be protons the size of a peanut. What is the underlying mechanic that forces a particle to become a particular size when it is created?"
] |
[
false
] |
Something I've thought about a while. Are all protons exactly the same size and why? If it is somehow related to the forces they have then what prevents the forces on another proton to not become "bigger" in scale compared to other protons? Why do all the particles share the same "rules" they act on?
|
[
"Rather than asking, \"Why are protons (and other subatomic particles) so much smaller than us?\" we should ask, \"Why are we so much bigger than protons?\" The answer is very simple: we need to be made up of a huge number of them to have the complexity that we do. \"Big\" and \"small\" are relative terms. On the scale of elementary particles and their interactions, we're freaking gigantic, but if we were much smaller, we couldn't be made up of all of the complex molecules necessary to make us.",
"Protons are all identical because they're made up of the same elementary particles: quarks (two ",
" and one ",
" to be specific). In our current understanding, elementary particles like quarks, electrons and such don't really have a size. Whether or not they are truly points or have some intrinsic size is actually one of the big open questions in physics right now. Composite particles (like protons, neutrons, atoms, and on up) have their size set by the nature of the forces binding their constituent particles together."
] |
[
"Protons are the size of protons because of the forces that dominate in the micro world. In the macro world, gravity is the king, whereas in the microscopic world there are different \"rules\". These rules are weak nuclear forces, strong nuclear forces, and electromagnetic forces. These 3 forces and the gravity force are the 4 forces that describe our macro and micro worlds and how they interact. ",
"Infact one of the biggest questions in science right now is to determine how all 4 forces live together. It is described as the Theory of Everything and is one of the hottest topics in science. "
] |
[
"Because it wouldn't be a proton anymore if it did."
] |
[
"Why does your mouth get all cold when you drink water after eating a mint?"
] |
[
false
] |
[deleted]
|
[
"Because chemicals in the mint change the behaviour of the proteins in your mouth that sense cold. These proteins/ion channels (primarily one called TRPM8) normally are activated when you mouth gets down to around 12 degrees. However, methnol directly activates these channels, causing your mouth to seem cold. It also makes the channels more sensitive to cold, meaning that they open at warmer temperatures than normal.",
"This is also exactly what happens with chillis/capsaicin but just in the other direction. Capsaicin makes heat sensing channels more sensitive to heat, meaning the open at closer to body temperature."
] |
[
"I doubt it. Different neurons code for the different sensations. So you would end up with a combination of the two. Which I'm sure would just feel very strange."
] |
[
"Yes and no. Capsaicin can be inflammatory for sure. Pepper spray down the throat can cause enough inflammation to cause difficulty breathing, and there's potential for damage to the corneas as well as mild damage to epithelial cells that heals fairly quickly. (",
"http://iovs.arvojournals.org/article.aspx?articleid=2123766",
")",
"At the concentrations you're eating, you're fine. If you have pre-existing sensitivity to inflammation - for example, if you have inflammatory bowel disease - capsaicins ",
" be contraindicated, as the slight inflammation can trigger a bigger feedback loop, resulting in a relapse. But that damage is basically a result of your autoimmunity, not of the trigger itself."
] |
[
"if a woman uses birth control that also stops her her period, does it actually stop the body from releasing its monthly egg and if not, what happens to the egg without the period?"
] |
[
false
] |
[deleted]
|
[
"Most pills (I assume you mean the pill) contain an estrogen and a progestogen, which together suppress these things called 'gonadotropins'. There are two big gonadotropins that the pill is meant to deal with: Follicle-Stimulating Hormone (FSH) and human Lutenizing Hormone (LH). They both get downregulated by the pill, but have different effects that together stop ovulation. Normally in ovulation, FSH stimulates the growth of a 'follicle' on a woman's ovary that contains an egg cell, which then gets released when an LH surge occurs, popping the follicle and releasing the ovule. Without FSH and LH, the follicle doesn't grow and doesn't pop, so the woman never ovulates. The egg cell stays in the ovary. Hope that helps!"
] |
[
"You may also be interested to know that there are hundreds of eggs that never ovulate, even in women who do not take birth control!"
] |
[
"You may also be interested to know that there are hundreds of eggs that never ovulate, even in women who do not take birth control!"
] |
[
"If a pipeline is developed to pump sea water into the desert, would that create a natural precipitation system and irrigate the surrounding land?"
] |
[
false
] | null |
[
"There was a project the British were considering back in the early 1900's called the Qattara Depression project. The idea was to create canals to allow water to flow downhill into a huge area of the Sahara that is below sea level. They would create an inland saltwater lake, and generate hydroelectricity along the canals. ",
"Fishing, transportation and water supply would be revolutionised and it would bring industry to some of the poorest parts of the world. Eventually the lake would turn hypersaline due to evaporation but it would last for a while. It was also believed it would improve the climate of Europe, and turn the surrounding areas into Savannah. "
] |
[
"Qattara Depression project",
"Here's",
" the Wikipedia article if anyone's interested. Cool topic!"
] |
[
"Holy crap, I was reading on that and while they're still pushing for the idea, in the 1950s they wanted to use nuclear bombs to dread the canal... INSANE!",
"\"The core problem of the entire project was the water supply to the depression. Calculations showed that digging a canal or tunnel would be too expensive. Bassler decided to use nuclear explosions to excavate the canal. Exactly 213 boreholes would each have a nuclear explosive charge of 1.5 megatons. Every one of these bombs would have an explosive yield one hundred times that of the atomic bomb of Hiroshima. This fit within the Atoms for Peace program proposed by President Dwight Eisenhower in 1953.\""
] |
[
"How do power companies measure how much electricity you've used?"
] |
[
false
] |
[deleted]
|
[
"The meter on the outside of your house. They used to be analog and a meter reader would come to your house each month to record how many kwh you've used and reset it. Now they are largely digital and the company does all of that remotely. "
] |
[
"The old spinny disc meters worked by diverting a small amount of the power being used (~2 Watts) into spinning said disc. Since the power diverted is proportional to the power being delivered, you can track how much energy is being consumed by counting revolutions of the disc, which is what the dials above the disc count. An employee from the power company would come along monthly and record the dials and then subtract the new reading from last month's reading to get the total consumption.",
"Modern meters are electronic and measure the power by measuring both the voltage and current using a known reference resistance and voltage, then multiplying them together to get the power, and then re-sampling it at fixed intervals to get the energy, which is what you're actually buying from electric company (kWh is a unit of energy, not power)."
] |
[
"It actually depends on where you are.",
"Some power companies use monthly estimates based on the type of accomodation you live in along with ambient conditions and time of year, and correct any offset when they send out personnel to verify these meters.",
"These days, power meters are digital and are capable of \"talking\" back to the grid over the powerlines."
] |
[
"Is there a positive correlation between age at which mating occurs and length of life in humans?"
] |
[
false
] |
There was a study done on fruit flies in the 1970s that got the flies to live "significantly longer" within 12 generations. I was wondering: (1) what "significantly longer" means, especially in terms of proportionality, and (2) have we been seeing these effects in humans? Has the experiment been performed on any other animal species?
|
[
"The effect on female fruit flies is significant. Virgin females live about twice as long as those raised with males. Very generally, female fruit flies are on the losing side of the battle of the sexes. They devote a HUGE chunk of their energy and resources toward reproduction when they've mated.",
"I'm not aware of any similar data in humans, and would be quite surprised if any significant effect were found. The two systems just aren't very comparable in this respect."
] |
[
"It has nothing to do with genes. It's simply that reproduction is really really hard on female flies. They lay eggs nearly constantly from mating until death. That's a huge amount of energy expended and wear and tear on the body. Nothing more deeply significant than that. "
] |
[
"Is this expressed genetically??",
"Meaning, is the scientist, in effect, putting artificial evolutionary pressure on the group to live longer?"
] |
[
"Does this hadith below have any scientific meaning or importance?"
] |
[
false
] | null |
[
"Nope"
] |
[
"So it's fake?"
] |
[
"I don't know what you are referring to by \"it\" and what you mean by \"fake\", but nothing like that that happens during intercourse has any impact on the appearance of the child."
] |
[
"Why doesn't lightning occur in fog?"
] |
[
false
] |
The way I understand is that fog is basically just clouds on the ground, so why so we have lightening in the up top clouds and not the down below clouds?
|
[
"Thunderstorms are the result of convective activity - i.e., rapidly rising and falling air due to differences in temperature and moisture content in a parcel of air relative to the air around it. This strong vertical motion leads to a separation of charges within the cloud; lightning is the result of this charge separation (similar to static electricity). ",
"Unlike thunderstorms, fog is the result of a very stable air layer. There's very little or no vertical and horizontal motion - even a wind of just 1-2 m/s is enough to prevent fog from developing. With no motion, there's no charge separation and thus none of the precursors for lightning exist. "
] |
[
"Or between cloud and ground. Although the majority are inter cloud discharges."
] |
[
"Interestingly enough I believe that ",
" the voltage difference needed to break the thin layer of non-conductive air and discharge would be orders of magnitude smaller than that needed for a cloud to earth discharge. In the latter case, the insulating layer of air is a few kilometers thick (and certainly much less than the few dozen meters for most fogs)."
] |
[
"What would happen if you submerged your hand in Mercury?"
] |
[
false
] |
Mercury is dense. Ignoring the poisonous vapors causing brain damage, could one submerge their hand into Mercury?
|
[
" I've put a finger in mercury before. I made sure there weren't any nicks or cuts in my skin and did it quickly. Obviously I wasn't trying to breathe any vapors in. It feels \"heavy\", it was hard to sink my finger into it. The liquid seemed like it was squeezing my finger from all directions. Really, it didn't feel liquid like at all just because people are use to putting their finger in water, which is 13.5 times less dense. After that was done I washed my hands right away. It would have been pretty easy to submerge my whole hand, I just would have had to put quite a bit of my own weight on it.",
" Couldn't one find the downward force necessary to submerge a hand by using Archimede's Principle? The buoyant force is equal to the weight of liquid displaced. This is equal to the density of the liquid, multiplied by both the acceleration due to gravity and the volume of the object being submerged: F= (density of mercury)(volume of fist)(9.8m/s",
" )",
"If the density of mercury is 13.53g/cm",
" = 1,353kg/m",
" , the volume of your fist is approximated by a sphere with a radius of 30cm = 0.03m, then to total mass of mercury displaced is 5.10kg. This would be the same as about 11 lb-force on earth, assuming gravity was 9.8m/s",
" ."
] |
[
"When you say \"Mercury,\" at first I thought you meant the planet. Chemical names don't need to be capitalized.",
"The vapour pressure of mercury actually isn't high. The main danger comes from contact. Yes, one can submerge their hands into mercury - in fact, back in the days, miners did gold extractions with mercury bare-handed."
] |
[
"Ignoring all bad effects and such, yeah, you could, but you'd have to force your hand in.",
"Mercury, at 13.5g/cm",
" is so much more dense than I, that it would only take 6154 cm",
" of it, to equal my weight (or six liter).",
"I'm absolutely horrible at eyeballing, but I'd say that my skinny arm is about six liters.",
"That would mean that it would take all of my bodyweight to push my arm, up to the shoulder, into a canister of mercury.",
"This answer does not take into account the compressibility of mercury or of my arm (ouch).",
"Also, if balance was not a problem, you could do a handstand in mercury."
] |
[
"What is the surface area and volume of a Proton, Neutron and electron?"
] |
[
false
] | null |
[
"Well, we know there's three so-called \"valence\" quarks, the quarks that determine the properties of protons and neutrons and all other baryons. But there's also gluons and all the interactions of the strong force that come with them. So think about a proton or neutron. They have about 940 MeV/c",
" in mass, but the 3 quarks that make them up are each only about 3 MeV/c",
" in mass. The overwhelming ",
" of the proton is really just the strong force interactions between quarks. And the strong force manifests itself in a ",
" number of massless gluons, and things like \"sea quarks,\" quark anti-quark pairs arising from virtual processes. (To be specific, they only truly \"exist\" when we go to measure them, and by measuring them, give them sufficient energy for them to become \"real\"). We describe these various contributing factors as \"parton distribution functions\" or pdfs. And we say that at some fraction of the proton's momentum ",
", there is some probability for a particle to be carrying that momentum fraction. At high momentum fraction, the function is dominated by up and down quarks, but at low momentum fraction, there's a divergent (appears to go to infinity) number of gluons. There may be a level of saturation of course, where the number of gluons being created is balanced by number of gluons being destroyed. We're presently probing that physics."
] |
[
"To begin we need to separate the subatomic particles into two classes, Composite Particles, and elementary particles. ",
"The electron is an elementary particle and pjfoster is correct that the electron size really cant be determined. This is because the mass of an electron is so small that the electron exhibits substantial wave-like characteristics. And, it doesn't really make sense to talk about the SA or volume of a wave. For more info see the wiki page on wave-particle duality",
"Protons and Neutrons however are heavy enough that they exhibit mainly particle characteristics. While pfoster is again correct that none of the particles have well defined sizes there are values that can be obtained related to size. For example, a charge distribution map of a proton reveals that 99% of the charge density lies within a 0.8775fm radius. Converting this to volume gives us 2.83 x 10",
" L. Really small! Hope that helps.",
"And as a side note, the electron definitely exists, they just cant be described by properties such as surface area and volume. "
] |
[
"Although in reality they're a blob of quarks and gluons, and when you count up all the quarks you'll find that there are two more up quarks than anti-up quarks and one more down than anti-down. Strange and anti-strange are in equal numbers."
] |
[
"Is there a mathematical definition of a chaotic system?"
] |
[
false
] |
I know the general definition of chaotic system is a system where very small changes in the initial conditions creates extremely large changes in the end result. (Like dropping a double pendulum). I was just wondering if there is a mathematical standard for determining whether a system is chaotic.
|
[
"The definition of chaos is still sort of in the works, in terms of a precise, abstract definition but there are a few things that characterize it. One of them is the Lyapunov exponent that was already mentioned, which is a measure of how fast nearby initial conditions diverge as they evolve. This is a measure of the sensitivity to initial conditions, which is one of the hallmarks of chaos.\nA chaotic can seem to behave randomly, in that it is very unpredictable, but the behaviour is generally not random, and subject to some well-behaved governing dynamic. Chaotic systems are often deterministic or stochastic (deterministic with a random component), but generally not fully random.",
"Additionally, chaotic systems must be bounded. This makes sense from a real-world perspective, but it allows stipulation of another condition, ",
"mixing",
"). In conjunction with the lyapunov exponent, which is a measure of the exponential rate of divergence of nearby initial conditions, mixing implies that nearby points in the phase space of the system will diverge rapidly, but will reconverge and end up passing nearby to each other arbitarily often in the future evolution of the system.",
"A great, and relatively simple, example that encompasses all of the above characteristics is the ",
"Baker's map",
", named not after a person but for its \"stretch and fold\" mixing dynamics, which are reminiscent of a baker's method of folding pastries. ",
"e: the study of chaotic systems and their characteristics is a very deep field of study, and I've just scratched the surface. The wiki article linked to elsewhere in this thread has a good list of characteristic dynamics, but a rigorous definition of chaos is still in the works (as far as I know)"
] |
[
"Thanks! Answered my question perfectly."
] |
[
"Thanks! Answered my question perfectly."
] |
[
"Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology"
] |
[
false
] | null |
[
"Is true that the monolith discovered in Utah was not man made? If so how was it formed?"
] |
[
"Do to a bot glitch, this was posted twice. This is the thread that was removed, so I am letting you know you should ask your question in the main post.",
"Sorry!",
"https://www.reddit.com/r/askscience/comments/k0tnr1/ask_anything_wednesday_biology_chemistry/"
] |
[
"The field of psychology has taken some serious hits lately regarding made-up study data and false research, which has led to questions about the entire field's validity. What is the psychology field in general doing to address these problems and concerns?"
] |
[
"Do furry pet owners experience respiratory problems at a higher rate than non-pet owners, due to hair/dander in the home?"
] |
[
false
] |
I appreciate there would be a lot of confounding variables in any such study, but have any attempts been made to measure?
|
[
"Asthma, allergic rhinitis, and eczema are all statistically more prevalent in children of households with animals present than without",
". This was a hospital-based study that looked at Qatari children, so the mix of animals (cats, goats, birds) weren't exactly the same mix as you'd find in, say, the USA, but the statistical significance was ",
" strong (p=0.008 to p=0.0001)",
"This study of Dutch children",
" was a little more interesting, as it looked at both ",
" and ",
" pet ownership (dogs, cats, rodents, or birds). People who have always had pets (and still do) were actually the ",
", followed by people who had never had pets. So if you stopped reading the paper there, you might think \"oh, maybe having pets is actually ",
" for your respiratory health!\" But the researchers also asked about respiratory symptoms (asthma, coughing, wheezing, etc.) in people who ",
" to have pets but no longer have pets...and often, those households no longer have pets ",
" the children had developed respiratory issues. And some of the people who ",
" had pets made that choice precisely because they had pre-existing respiratory issues that they did not want to aggravate. So it's not enough to look just at who currently has animals, because people change their behavior over time, and sometimes in response to the very variables you're trying to study.",
"In short, yes, it appears that living with animals (especially cats) increases the risk of developing respiratory symptoms like asthma, allergies, wheezing, etc...and that those symptoms persist at a higher rate than experienced by non-animal-owners even if the household goes animal-free."
] |
[
"\"sometimes in response to the very variables you're trying to study.\"",
"We run into this a lot in economics. Economics is particularly fun because you have to predict how people may respond to your study, further adding issues."
] |
[
"and that those symptoms persist at a higher rate than experienced by non-animal-owners even if the household goes animal-free.",
"Is it a causal link? Or is it because non-animal-owners are a mix of people with and without respiratory issues at approximately population-average proportion and people who'd gone animal-free are more likely to have pre-existing respiratory issues?"
] |
[
"Has there ever been more living beings in the planet than right now or is this the period that’s seen the most life?"
] |
[
false
] |
Is it even possible to answer this question?
|
[
"Count bacteria, ignore animals, plants and similar large living beings because their number is negligible anyway. But I would be surprised if we know the number of bacteria today or in the past well enough to make any useful estimate."
] |
[
"I took a course in geology, where the teacher showed a slide of the populations of living beings over time. Aside from several population extinctions, life has always come back stronger over time. At this point, however, we are in the beginning of another extinction. ",
"https://en.m.wikipedia.org/wiki/Holocene_extinction"
] |
[
"Correct me if I'm wrong, but the data you saw was probably number of species, not number of individuals. Total population of all individuals of all species would be really hard to estimate and also not very meaningful--e.g., an individual whale has much more ecological importance than an individual krill."
] |
[
"In batteries, does the metal matter?"
] |
[
false
] |
I'm looking at the galvanic cell, here: And as near as I can tell, the electron flow is from the anode metal to the cathode's . It's just a redox reaction directed through a wire. So the zinc sulfate should be interchangeable with other electrolytes, and the copper metal should be interchangeable with other metals, without altering the overall voltage. Is there any reason this shouldn't be the case? Edit: I replaced the two and am getting 2.26V of current, but the light bulb isn't lighting up. What gives?
|
[
"I replaced the two and am getting 2.26V of current, but the light bulb isn't lighting up. What gives?",
"The choice of metals and electrolyte determines your voltage, but the current is largely determined by the surface area of the metals in contact with the electrolyte. If you are using small beakers it is unlikely that you will be able to draw anywhere near enough current to light a regular bulb. ",
"Try using a red LED, it should light up if you can get around 2-3V. You may have to hook up two cells in series."
] |
[
"Replacing the zinc sulfate with another electrolyte will shift the equilibrium of the oxidation of zinc toward its ion (Le Chatelier's principle). Changing the copper metal is a bit different. The reduction of the Cu",
" ion is energetically favorable, whereas the reduction of another metal such as Na",
" is not. You could change metals, but the voltage would be different."
] |
[
"So replacing the zinc sulfate should speed it up then, yes? Because I'm looking at it here- I replaced the zinc sulfate with sodium sulfate- and absolutely nothing is happening. Voltmeter says no current is flowing.",
"In the left beaker I have zinc metal in sodium sulfate (1M), in the right beaker I have copper metal in copper sulfate (1M), in the middle I have a strip of dialysis tubing with 5M sodium chloride and an overhand knot tied in each end. I'm running wires with alligator clips from the strips of metal, to a light bulb, and back. The wires and the light bulb work, I've tested them with a D cell (1.5V?).",
"What's going wrong?",
"edit: voltmeter seems to say I'm getting 1.16V of current between 'em. But the bulb ain't lightin'."
] |
[
"If I am riding in a bus traveling 60 mph, and I throw a ball 30 mph from the front the bus to the back of the bus, what exactly is happening? Is the ball moving, or is the bus accelerating away from the ball at 30 mph?"
] |
[
false
] | null |
[
"The people in the bus will see the ball travelling at 30 mph backwards. That is, until it hits the floor or the back of the bus.",
"Someone standing on the side of the road, looking into the bus as the ball is being thrown will see the ball travelling 30 mph forward, in the direction that the bus is going, but at half the speed.",
"Someone sitting on the ball, will see the bus move forward around it at a speed of 30 mph. He will see the observer next to the road move backwards at 30 mph."
] |
[
"To add to the current top responses, I want to refer to the \"or is the bus accelerating away?\" part. In the frame of reference of the ball, the bus is ",
" away from the ball at 30mph, but not ",
". That is a common source of confusion that I wanted to highlight: things are moving, in this frame of reference it's the bus at 30mph. Since 1) acceleration is the rate of change of velocity, and 2) velocity is constant at 30mph, then there is no change = no acceleration.",
"For this situation one can consider multiple frames of reference, leading to multiple velocities, but will never get non-zero acceleration. This is a result of the Newton's first law - once you have finished the throw (the ball is no longer being pushed by your hand, just flying along the bus), there are no longer any forces in this system, and thus there can be no acceleration happening."
] |
[
"Everything is based on the reference frame of the observer. In this case the speeds can be added linearly, based on the observer. An observer outside will see the ball will see the ball moving forward at 30 mph (and the bus at 60 mph)",
"An observer on the bus will observe the ball to be moving backwards at 30 mph.",
"And the ball will observe the bus and its occupants moving forward at 30 mph, and an external stationary observer to be moving backwards at 30 mph. "
] |
[
"When talking about the electromagnetic field and the different frequencies, what exactly is the medium that is vibrating?"
] |
[
false
] |
As I understand it, the different in visible light and radio waves is the difference in frequencies or vibrational speeds. What is vibrating? Since these things can travel through a vacuum, I assume that it isn't matter, right?
|
[
"This was the question that drove people to assume the existence of 'luminiferous ether' (literally, light bearing background substance) in the 19th century. Wikipedia actually has a ",
"pretty decent discussion",
" of the history of the idea and how it was abandoned.",
"What you're doing is assuming that because the same mathematics applies to electromagnetism and waves in media, there should be deeper analogies between them. But let's look at how we actually interact with both situations. For waves in a medium, such as water, we can see the height of the water throughout and find that the height obeys a wave equation.",
"But what about electromagnetism? Fundamentally, all of electromagnetism is about the fact that when I wiggle a charged particle over here, a charged particle over there wiggles as well. That's it. But when we carefully map out how the wiggles work, we find that the most convenient way to keep track of it is to invent something we call the electromagnetic field that obeys wave equations. But we must not confuse our bookkeeping device with displacements of some medium that we observe."
] |
[
"There is no medium vibrating. In a plane wave at a particular fixed point in space, for instance, the electric field will have the form ",
"(t) = ",
" cos(2πf t). So the frequency f describes (via f = 1/T) the period of the electric field oscillation from ",
" to -",
" and back to ",
"."
] |
[
"I really don't understand what you are trying to ask. The wave is an oscillation of the electric and magnetic fields. I explained this in the top-level response."
] |
[
"Do humans have any adaptations specifically for combat?"
] |
[
false
] | null |
[
"While humans are not as strong or fast as other large animals, there is one physical adaptation that humans have developed better than any other animal: long distance running. No other animal has the long distance capacity that humans have, and it's widely theorized that a big part of human development and success was due to this. Ancient humans would just follow prey for hours, or days, and wait for them to get tired to go in for the kill.",
"For a really great scholarly paper about it, check out ",
"this link",
"."
] |
[
"Our brains let us develop weapons and build defenses. We are also great long distance runners who can work as a team to track and literally run after prey until they die of exhaustion"
] |
[
"Biological anthropology minor here (majoring in Paleo, so it's kind of legit, I suppose.) Not only are we adapted for running/long-distance walking, but the way our shoulders are canted allows us to throw things, which is quite useful in a fight. The acetabulum (sort of ball-and-socket joint) of the shoulder blade is facing more laterally than up than it would be in our arboreal deep ancestors; this allows us to manipulate objects in front of our faces rather than over our heads."
] |
[
"\"Solar wind induced magnetic field around the unmagnetized Earth\" - Why would this not work on mars? Or would it work if the atmosphere would be more dense?"
] |
[
false
] | null |
[
"I really wish people would stop trotting this factoid out.",
"IT'S NOT TRUE.",
"Titan is far smaller and less massive than Mars, yet has an atmosphere thicker than our own. That alone disproves the idea that Mars is too small to hold an atmosphere. ",
"There is no simple answer to why Mars has a thin atmosphere. It's a complex interplay of solar wind dissociation, photochemistry, sputtering, mineralogical cycles, greenhouse feedback effects and probably much more."
] |
[
"Correct - the solar wind ionizes the upper layers of the atmosphere, which protects lower layers from large amounts of radiation. This only works if your atmosphere is dense enough to begin with that the ions are likely to form a consistent barrier to radiation."
] |
[
"Yeah, I see this around a lot so it's not surprising it gets repeated. There's a nice plot that gives an insight here ",
"http://abyss.uoregon.edu/~js/ast121/lectures/lec14.html",
". You can see that in terms of Temp vs. Gaseous escape velocity, Mars isn't far away from Venus. It can easily retain a CO2 atmosphere against thermal escape, and could hold onto an Earth-like Nitrogen/Oxygen atmosphere. It's just below water vapour, but the bigger problem is the photo-dissociation of water vapour, which leaves you with hydrogen (which easily escapes), and Oxygen radicals, which rapidly react with anything they come into contact with, including the surface, meaning the oxygen drops out of the atmosphere into other chemicals on the ground."
] |
[
"Why do people with tourettes disease never yell nice things?"
] |
[
false
] | null |
[
"Hello, I have Tourette's with coprolalia. (Incidentally, the majority of words or phrases that I do say aren't yelled.)",
"Two of my less offensive articulate tics have been \"I love you\" and \"I miss you.\" Still, not the most comfortable things to say to the stranger next to you on public transit. ",
"Tics can change over time. I love you appeared over the summer this year. I miss you appeared just after my grandfather passed in early 2010. Yes I think that's related.",
"My most recent phrases: \"Shut up. That's right. That's what I said.\" (Or any combination thereof, sometimes \"Fuck your mom, that's right, that's what I said.\") \"How's your mama?\" had been prevalent recently, only being replaced by Fuck your mom, a phrase of which I am less fond.",
"To answer your question more directly: There have been studies done on the matter. Long story short, swearing activates different areas of the brain than do nonswear words and can cause relief of stress and/or pain. I'll be back to post a link.",
"\nEdit: And I'm back. ",
"Abstract from university's website.",
"\nThis isn't quite the link I was looking for. I vaguely recall one done with MRI scans.",
"\nSomehow this stress-relief thing may be related to TS. The fact that the words have different psychoneuroimmunological responsibilities is probably the reason they're more commonly ticced. "
] |
[
"As a general rule, don't confuse the way a movie portrays a disorder with the actual disorder."
] |
[
"Don't get tourette's confused with coprolalia (yelling out swear words/inappropriate shit). The latter is independant of but can be a symptom of the former."
] |
[
"Is there any physical limit to the Periodic Table? Or could we theoretically just keep fusing elements together to make heavier ones?"
] |
[
false
] |
My basic understanding is that heavier elements are typically made when 2+ lighter elements are fused together (e.g. inside of stars, or synthetically in a lab). If there were no technological restrictions, is there any limit to how high the periodic table could go? I found an article on that might contain some sort of answer, but I didn't really follow it. Thanks!
|
[
"\"My basic understanding is that heavier elements are typically made when 2+ lighter elements are fused together\"",
"Absolutely right.",
"\"could we theoretically just keep fusing elements together to make heavier ones?\"",
"No, not indefinitely.",
"What causes a nucleus to continue existing is its stability. There are certain shapes such as the 4 nucleons of Helium that are particularly stable, and a C12 nucleus can be thought of as being similar to three He nuclei fused together.",
"With very large atoms such as U 238, their nucleus tends to be unstable. As you get to larger and larger artificial elements that you see being added to the bottom right of the periodic table, then you will find that they are very unstable and some half a half life of seconds or less. ",
"Making heavier and heavier atoms increases instability in an analogous way that piling building blocks to make a taller and taller tower would also increase instability."
] |
[
"The physical limit would be at the proton drip line, when it is just impossible to bind another proton."
] |
[
"It's 3:00am here and I have no idea why I'm still up, but here is something that might help answer your question. I'm too tired to try to explain it though... ",
"http://en.wikipedia.org/wiki/Periodic_table#Future_and_end_of_the_periodic_table"
] |
[
"What does it mean for a unit of light to have a certain wavelength?"
] |
[
false
] |
[deleted]
|
[
"A good rule of thumb is that ",
". This means that any interaction with matter - absorption and emission - must occur in discrete chunks of energy which we call photons.",
"When we say light is an electromagnetic wave - we mean that it is a change in the electric and magnetic fields that move through space together. When you see those pictures of light represented as a wave, it's typically a drawing of how strong the ",
" of the light is, as it moves through space. At one point it's very strong, at another point it's very weak, and so on (in a sinusoidal/wavey pattern). The photons don't \"bob\" or \"swing back and forth\" - remember, photons are simply a name we give to the fact that light is emitted or absorbed in discrete chunks.",
"One wavelength is simply the distance between regions of high electric field (or high magnetic field). To give a more broad definition, it is the distance it takes the EM wave to begin to repeat itself."
] |
[
"Light is an electromagnetic wave, and if you were to watch the electric field as it passes by you'd expect to see the field oscillate at the frequency of the light wave. For example if you put an antenna there, the light may cause an AC current in the wire at that frequency. The wavelength is how far the light travels during this period of repetition. That's what light is, it's ripples in the electric and magnetic fields that spread out into space. ",
"Photons also have polarization that defines what direction the fields are varying in, it will be perpendicular to the direction the photon travels so there are essentially two polarizations: horizontal and vertical. And you'd expect a straight antenna to mostly absorb the polarization that aligns with the wire. This is how some polarizing filters work, a network of parallel \"wires\" (or other structures) that absorbs the field oscillations along that direction, while not affecting light of the other polarization."
] |
[
"i`m no scientist, but all photonic radiation (radio, light, uv, etc) is self propagating Electro-Magnetic radiation. i capitalize to emphasize that it is actually both fluctuations in the electric field and the magnetic field at right angles to each other. since an electric field will induce an magnetic field (at right angles) and vice verca, this is the self propagating part, and the wavelength is (i think) easier to visualize as the frequency of these oscillation. ",
"so no, wavelength is not photons moving up and down, it is how long (well, how far at the speed of light) it takes for the EM wave to complete 1 cycle.",
"obviously, this doesn",
"t tell you how a photon IS related to wavelength, as i",
"m sure it does, but i am also sure i dont know that answer at all.",
"here is the wikipedia page, which has a good drawing of the 2 fields at right angles to each other. ",
"http://en.wikipedia.org/wiki/Electromagnetic_radiation"
] |
[
"What is the evolutionary 'purpose' of flies, fleas and cockroaches?"
] |
[
false
] | null |
[
"You misunderstand evolution. It doesn't create things it needs. Things are created randomly, and if they survive and prosper, they survive and prosper.",
"They have no purpose, they have features which randomly allowed them to prosper."
] |
[
"OK, I understand this better than the first comment from Osymandius - I do understand evolution, I suppose it sounds like my question is coming from an 'intelligent design' standpoint, which is NOT my intent! ",
"Basically, while being annoyed by these creatures I often ask myself 'what the hell do they do but annoy people?' and yes it is just survival for us all. Sorry for the silly question! (from a scientific standpoint) :)"
] |
[
"OK - how about the question I maybe should have asked: if these creatures (flies, mosquitos, cockroaches, fleas) didn't exist, would there be any detriment to ecosystems anywhere? "
] |
[
"In the context of the Earth's climate changing drastically on its own over time, why is the current climate change bad?"
] |
[
false
] |
[deleted]
|
[
"Change is disruptive. Was the ice age bad? Not from our historical perspective, but for the species and societies wiped out, it was. Even those who managed to adapt found it a challenge. When you've built up a massive amount of infrastructure, it's potentially much worse. Sure, we have more mobility now, but dealing with millions of refugees from Bangladesh isn't a trivial issue. Moving croplands northward is expensive, and politically complex.",
"Think about what relatively minor or localized events or shifts have done to Detroit or New Orleans or the area around the Aral Sea. Can we deal with these things effectively? Surely we can. ",
" we? No. Now imagine dealing with them on a global scale."
] |
[
"First, it’s good to see someone asking sharp questions about climate change without getting all conspiracy-ish.",
"a climate that's good for people to live in",
"Yes, but ",
". In the short term, people might like it if it were sunny and room temperature everywhere. In the long term, a climate that’s good for people to live in is one where, for example, resources are sustainable. In other words, human comfort depends strongly on the stability of many parts of the rest of the ecosystem.",
"it's not really what the movement to stop climate change makes itself out to be.",
"I disagree. I think this is the stated goal of many of the movements (plural) toward limiting anthropogenic climate change.",
"Opposition to “environmentalism” sometimes takes what seems to me to be a very dated, Rachel-Carson–era approach where the topics of discussion are things like beauty, biological toxins, and “nature” as the constitutive other. This is a straw man, at least of my position. Modern environmentalism is about things like ecological stability, pollutants which are beneficial at certain ",
"levels",
", and figuring out how to set up incentives that won’t lead to floods, famines, and wars."
] |
[
"Then couldn't you justify stopping the Earth's natural climate change if it happened to be heating up independent of human activity?"
] |
[
"How recently did we discover/understand evaporation?"
] |
[
false
] |
Were people 10,000 years ago like, "Yo, Where did my water go?" What theories did we have about evaporation before we knew what was actually happening?
|
[
"There's evidence of large organised Salt production facilities dating back 5000 years or more. The easiest method for salt generation in Ancient cultures would have been to flood salt flats with water, dam them and wait for the water to evaporate.",
"Evaporation needs to be well understood (i.e. what environmental conditions it works in) to exploit this.",
"Presumably Evaporation was understood on a 'cottage industry' level WELL before this, as methods tend to develop and mature over time."
] |
[
"I feel it would have been for a long time. Easily 100,000 years. Considering there would have been a clear observational understanding that water that was dripped on hot surfaces first makes them wet, then steam/water vapour would come off and eventually wet spot would dry. I also feel that people for a long time would understand that in cold moist air areas, water would stay in a cup to stay a long time, and opposite to that in hot climates that water left in the sun would \"go away\" quicker they would put two and two together easily. Likely they would also understand that clouds were water because when a fog would roll in things would get wet. So, in our current stage of evolution ",
"we migrated out of Africa 50 - up to 100K years ago",
". That means that our capacity for thinking and interpreting our world is essentially similar to what is was then (minus a bit because of nutrition and disease). Of course, at that time we wouldn't know on a micro level what was going on, but we would understand on a macro observational level and likely that steam was water going away, and that water just left out would go away similarly. We are very good at finding cause and effect relationships and so we would have likely observed the mechanics of water and vapour early on, given how vital it is to our survival. Likely even Neanderthals would understand too."
] |
[
"I'm not so sure about that. It's not just the brain and nutrition. We grow up with the expectation that everything has a scientific explanation today.",
"See the history of ",
"spontaneous generation",
" of life for example. Mice forming from wheat. An absurd idea today, but it was taken seriously for a long time."
] |
[
"Would this matter to energy converter work in principle?"
] |
[
false
] | null |
[
"Yup. Some people have thought of it too (though there's variations). It's really sci-fi-ish, but there's nothing wrong with it theoretically and is in fact maximally efficient."
] |
[
"Give it a charge and hold it in an electric field? It would be safest to do it out in space and if anything goes wrong it could be towed away from Earth."
] |
[
"How do you keep the BH in place?"
] |
[
"Hypothetically, an electron can travel infinitely far from its nucleus, right? If so, what is the furthest we've ever measured?"
] |
[
false
] |
Of course it would be rare for the electron to fall outside its cloud but it happens, right?
|
[
"An atom with an electron orbiting really far from the nucleus is called a ",
".",
"It can be as far as a millimeter: ",
"http://prl.aps.org/abstract/PRL/v100/i24/e243004"
] |
[
"Let's look at the ground state of the hydrogen atom. When we solve Schrodinger's equation, we discover that the probability density for the electron goes like a decaying exponential, in the characteristic size of the atom, that is\nP(r) ~ e",
"r/a0",
" \nwhere a0 turns out to be about 1/2 an Angstrom,",
"We can then calculate the probability of finding an electron at any point beyond some position, r' by integrating this probability density function in spherical coordinates. Turns out that the probability of finding an electron for a Bohr atom ground state, anyway outside a radius of a is",
"P(a) = e",
" (2a (a+1) +1)",
"which, once we get out to about 5xa0, or 2.5 angstroms, the probability is already 0.2%, at 10xa0, or 5 angstroms it's at 5x10",
" % at 100*a0 or 50 angstroms it's at 10",
" %. You get the picture. So, try as hard as you might, you're not going to find electrons very far away from nuclei"
] |
[
"Electrons can be liberated from their atom and go completely free, then their distance from the atom is of no particular interest since they aren't orbiting it.",
"If you're asking what the largest observed orbit of an electron is, you'd have to wait for a bit for an answer.."
] |
[
"How do gravitational slingshots work?"
] |
[
false
] |
In order for the Voyager 1 space probe to escape the suns gravity it had to slingshot around Jupiter and Saturn. What happens when the probe slingshots around a planet? Where does the added velocity and energy come from?
|
[
"The added energy is coming from the motion of the planet. As the planet is in motion, it is easy to show that the time spent approaching the planet can be greater than the time spent leaving. Net result is a greater velocity to the spaceship. The planet slows down by a relative amount based on mass."
] |
[
"Let's say you're behind the wheel of a truck stopped at a red light, and a kid tosses a (perfectly elastic) rubber bouncy-ball at you at 30 mph. What do you see? Well you'll see a bouncy-ball coming at you at 30 mph, then bouncing off and flying away at 30 mph. Good. Easy. ",
"Now say you're chugging along the road at 50 mph and again the kid tosses the ball at you at 30 mph. What do you see? First of all, you'll see a bouncy ball coming at you at 80 mph. Now, we know that the laws of physics are the same for everyone moving along at a constant velocity (i.e., in an inertial reference frame). So, if we say the ball doesn't budge the truck in any noticeable way, then a (perfectly elastic) rubber bouncy-ball coming at you at 80 mph will bounce off at 80 mph. ",
"What does this look like from the street: a ball flying away at 80 mph relative to a truck that itself is moving at 50 mph? The ball will appear to be screaming at 130 mph! ",
"Of course the ball is moving at a different speed than it did before, i.e. it has a different energy and momentum. Where else would it have come from if not from the truck? These quantities relate to the mass and velocity of an object as p=mv and K=m v",
" / 2, that is, they are proportional to mass. So, for an object with a huge mass, a tiny change in velocity can go a long way... i.e. the truck can give up a bit of energy and momentum and barely feel a bump, while the ball (with a relatively tiny mass) will get a huge boost to its velocity. ",
"This is the basis for a gravitational slingshot. ",
"In the reference frame of the sun, say a satellite is moving at velocity V almost head-on to Saturn, which is orbiting at U. A Saturnian will see the satellite flying at her planet at (U+V), swing around, and fly off at (U+V). So from the sun, the satellite will be flung at velocity (U+V) relative to Saturn, which itself is moving at U. The velocity of the satellite will be 2U + V. Slingshotting gives the satellite a boost by twice the speed of the planet!",
"Edit: Looks like I had some serious cryptomnesia... I was looking at the ",
"Gravitational Slingshot",
" wikipedia article a few weeks ago, so I apparently rehashed a similar example, with the same velocities and everything."
] |
[
"The added velocity comes from the planet. You have to come from the \"backside\" of the planet, that is, the side opposite the direction of its velocity vector. As you approach the planet, it's pulling you toward it, increasing your velocity in that direction. If you get your timing and distance right, you'll be flung out away from the planet at a higher speed, and the planet will slow down a tiny amount, proportional to your mass over the planet's mass. If the planets weren't moving, you wouldn't get this effect.",
"Here's an explanation with more mathematics",
"."
] |
[
"If visible light is photons, then is all electromagnetic radiation photons? If so, why does its wavelength give the photons certain properties (e.x. harmful to humans, visible, can pass through matter)?"
] |
[
false
] | null |
[
"I'm not sure I'd say that gamma is the highest - that would seem to imply that there is a highest energy, which doesn't make sense. ",
"A better way to say it is that we usually use the name \"gamma rays\" to describe photons with frequency equal or greater than 10 exahertz, and that we don't have any higher classifications. "
] |
[
"Yeah that mostly covers my question. Thanks for taking the time to write that out!"
] |
[
"Yeah that mostly covers my question. Thanks for taking the time to write that out!"
] |
[
"Why is calcium a metal? Why does it seem to have so few obviously metallic properties?"
] |
[
false
] | null |
[
"Calcium the element is a metal and has all the properties of one this is what it looks like ",
"http://f.tqn.com/y/chemistry/1/L/w/3/1/Calcium_1.jpg",
"\nThe calcium you're probably talking about are compounds like calcium carbonate or whatever large compounds it makes in our bodies."
] |
[
"https://en.wikipedia.org/wiki/Calcium#/media/File:Calcium_unter_Argon_Schutzgasatmosph%C3%A4re.jpg",
"Even a better representation of what metallic calcium looks like."
] |
[
"Metal is just a classification based on chemical and physical properties. The reason that calcium (and magnesium and beryllium and other alkaline earth metals as well as alkali metals like cesium) are different is because in pure form, they are very reactive due to only having 1 or 2 electrons in their valence shells. ",
"(properties of metals means that they are, for example, ductile, conductive of heat and electricity, and shiny, which metals in these groups tend to have)."
] |
[
"Why is \"hydrogen carbonate\" also called \"bicarbonate\"?"
] |
[
false
] |
I don't know if it's a stupid question, and I haven't been able to really find this since the keywords bring up so many other things about the bicarbonate ion and whatnot, but what is "bi-" about bicarbonate? -- meaning, since as far as I know, "bi-" means/implies both, or two, so I'm getting lost where that name would come from and/or how it's tied to "hydrogen carbonate" (though I understand how it is hydrogen carbonate since it's HCO3)
|
[
"Bicarbonate is a historical name, and the official name is now hydrogen carbonate. Historical names are hard habits to break though, and continue to be used in many cases. The Bi doesn't mean two in this sense, in chemistry, two is represented with Di, as in dihydrogen. The bi refers more to the fact that's it's an intermediate in certain reactions with two steps. Again, it's a historical name, and wasn't properly named by the system we use now.",
"Another example of historical names would be ferrous and ferric, which are now represented with Roman numerals, iron(II), iron(III). "
] |
[
"That makes sense. and also something like oil of vitriol as a historic name for sulfuric acid. But, yeah, I was confused since I knew that \"di\" is two, so why would \"bi\" be used, but this helps!"
] |
[
"Historical names can be a pain to deal with, like acetylene for instance, which is a common chemical. The Ene ending indicates a double bond now days, but acetylene has a triple bond, and it doesn't have an acetyl group and it's official name is ethyne now. So in some cases it can even be deliberately misleading which is a headache."
] |
[
"Is the lift force generated by a wing greater than the resulting drag force?"
] |
[
false
] |
[deleted]
|
[
"No, I would not describe it as a mechanical advantage. A wing is not multiplying your force input.",
"You have an engine which is pushing the airplane forward, powered by fuel. You have gravity pulling the airplane towards the ground. As the airplanes moves forward, the reactionary forces on the wing will be pointing up and back. You can take the component of this force and call it the lift and drag forces. When the lift component exceeds the weight, you will take off. When the drag forces equals your thrust force, you will stop accelerating."
] |
[
"No, I would not describe it as a mechanical advantage. A wing is not multiplying your force input.",
"You have an engine which is pushing the airplane forward, powered by fuel. You have gravity pulling the airplane towards the ground. As the airplanes moves forward, the reactionary forces on the wing will be pointing up and back. You can take the component of this force and call it the lift and drag forces. When the lift component exceeds the weight, you will take off. When the drag forces equals your thrust force, you will stop accelerating."
] |
[
"Yeah, typical lift to drag ratio of an airplane is something like 15-20. You can imagine for the wing itself it is even larger since the fuselage, landing gear, etc isn't built to generate lift."
] |
[
"Why was the 2009 H1N1 pandemic less deadly than the H1N1 pandemic in 1918? Was it a less dangerous disease, or did we just have better medicine?"
] |
[
false
] | null |
[
"In addition to what others already wrote, it's also worth pointing out that the 1918 H1N1 virus was a very different one than the 2009 H1N1 virus. ",
"The HxNx classification system is fairly coarse and is based on two surface proteins of the viruses, but doesn't take other differences into account."
] |
[
"I'm reading a scientific review about it that says \"Many data from that era [1918] suggest that almost all deaths resulted from secondary bacterial bronchopneumonia\" and also \"[1918] featured an enormous and ",
" mortality in healthy young adults.\" ",
"They don't mention anything about malnourishment or WWI.",
"https://pubmed.ncbi.nlm.nih.gov/20048675/",
"Schoenbaum et al 1996 propose that older people were spared due to prior immunization in earlier pandemic (1889-1893).",
"So to answer OPs question, the 1918 flu was definitely more deadly than the 2009 flu. But there is no consensus or strong evidence as to why young people died at such a high rate"
] |
[
"Probably a combination of factors. In 1918 at the end of WW1 there was widespread malnutrition, soldiers with gas damage to their lungs, and generally less sanitary living conditions that may have affected people's immune function and made the pandemic more deadly. They didn't have specific medical resources like automated ventilators that can save some flu patients, and hospitals in general weren't as good at keeping people alive as they are today. No antibiotics to treat secondary infections, either. ",
"One final factor is population genetics. The 1918 flu was very widespread, affecting about one third of the world's population. Any individuals who had a genetic susceptibility to H1N1 that made the disease more deadly for them would have died at a higher rate, and so less likely to have descendants living in 2009 that inherited their susceptibility."
] |
[
"Can wormholes be used for long distance communication?"
] |
[
false
] | null |
[
"Such hypothetical / speculative / open-ended questions are better suited for our sister-sub ",
"/r/asksciencediscussion",
". Please post there instead."
] |
[
"Already removed"
] |
[
"Sounds good, I reposed this over there. ",
"https://www.reddit.com/r/AskScienceDiscussion/comments/b4zrp6/can_wormholes_be_used_for_long_distance/",
"",
"Shall I delete this thread?",
""
] |
[
"Why is symmetry attractive?"
] |
[
false
] |
AFAIK, one of the features that best predict if someone is thought of as attractive regardless of things like cultural background is symmetry of the face. I think this holds true not only for humans but also for animals. A typical handwavy explanation for this is that this is an indicator of 'good genes'. But what does that mean exactly? And why are good genes making symmetric faces? Or Is there another explanation?
|
[
"Symmetry is a signal for fitness, as you suggest",
". This link should provide a great starting point.",
"Fluctuating asymmetries (FAs) are nondirectional (random) deviations from perfect symmetry in bilaterally paired traits. In nonhuman animals, FA in body traits reflects developmental instability (inability to withstand stress during development), increasing with inbreeding, homozygosity, parasite load, poor nutrition, and pollution (Møller & Swaddle 1997, Parsons 1990, Polak 2003). In humans, body FA increases with inbreeding, premature birth, psychosis, and mental retardation (Livshits & Kobylianski 1991). If similar relationships exist for facial FA, then it could signal mate quality",
"\nAverageness and symmetry are both attractive in male and female faces, with\nmedium to large effect sizes in all cases. Sexual dimorphism is also attractive.\nFemininity is attractive in female faces and is preferred to averageness. Masculinity\nis also attractive in male faces, although the effect is smaller than for female faces,\nand average traits also contribute (independently) to male attractiveness. Reported\npreferences for feminized male faces appear to be an artifact of using sex continua\nthat do not adequately capture sexual dimorphism. Preferences for averageness,\nsymmetry, and femininity generalize across race of face. It remains to be seen\nwhether the masculinity preference generalizes across race. Finally, note that if\naveraged composites of male faces fail to display typical levels of masculinity, as\nsuggested above, then the conclusion that averageness is attractive in male faces\nmust rest primarily on the data from real faces.",
"Symmetrical faces are also easier to process, which \"feels\" \"good\"",
" both in quotes because they're rather abstract. This could help explain some of what's left, and could be a next step to read for you.",
"2 EDITS for formatting and spelling"
] |
[
"Those are some interesting resources, especially the first one. Especially when they point out that several 'disadvantages' like psychosis are correlated with asymmetric faces, so there seems to be some truth to this signaling some favorable genes. The mechanisms would be interesting of course"
] |
[
"Because our DNA basically maps both sides as the same thing, but reflected (excluding some internal structures), if it's not matching or almost matching, there's a possibility of genetic or other health problems. Which an organism looking to continue their species would like to avoid (on an instinctual level)"
] |
[
"What are examples of physical processes that involve wave function collapse?"
] |
[
false
] |
I learned in an intro quantum mechanics course that taking measurements on quantum particles results in a collapse of their wave functions to a narrow spike, and that the measured quantity assumes a definite value after the measurement. Can anyone give me some examples of these types of measurements? The professor and text were exceedingly vague on this.
|
[
"The professor and text were exceedingly vague on this.",
"They're vague, and frustratingly so as I recall, because they don't know. They may have an opinion, like ",
"/u/RetraRoyale",
", who doesn't think it's a physical process, but there's no broad consensus in the field anyone can point to you to. It's known as the ",
"measurement problem.",
". You get into the entire debate about Schrodinger's cat and all that. It's either a complete waste of time or the most important question in all of physics, depending on which physicist you ask. "
] |
[
"It's not an opinion. It's a fact.",
"Absolutely not. Decoherence is a physical process. Objective collapse theories have their share of proponents. You should not insist something as fact when there is widespread disagreement with your \"fact\".",
"It doesn't matter. Science is not done by majority vote or democratic process.",
"That's certainly true. however, we are not doing science right now. We are communicating with the public. When doing that, it is reasonable to present the varied opinions of the field rather than present your personal view as fact. No matter how convinced you may be of it. A bit of humility wouldn't hurt. ",
"The measurement problem has nothing to do with wave function collapse or even measurement.",
"The measurement problem in quantum mechanics is the problem of how (or whether) wavefunction collapse occurs.",
"It is that many experiments and their measurements show that no \"realistic\" physical model can be applied to whatever is happening to a particle before it is measured.",
"Delayed choice? Is that what you're talking about? I hate to question your creditionals, but do you have any reason to think those experiments rule out an objective reality prior to measurement - beyond pop sci articles that is?"
] |
[
"Imagine that you've got a model universe with a car driving down a highway. You predict what it is going to do: keep going straight. Now someone comes along and tells you that your model is wrong: the world is not that simple. In actuality, there's a big block of concrete in the middle of the road. So you rehash your prediction, and now it says that there's a big puff of dust and smoke in the road and a mashed up car.",
"That's basically how wave-function collapse works. It's not a 'physical' process. It's what happens when you take a simple wave-function in a simple universe and you 'update it' to account for the fact that the universe is not as simple as you assumed because there are actually other particles around, interacting with the things you're trying to model.",
"Wave-function collapse is a method for modeling the transition between the \"I can use a simple wave-function to model this particle\" and the \"I have to use a complicated wave-function to model all these interactions\" assumptions. So it applies anywhere you have interacting particles and a wave-function which is not sophisticated enough to model the whole of the universe. (I.e., pretty much every real-world interaction.)"
] |
[
"At what evolutionary distance can two animals no longer reproduce?"
] |
[
false
] |
You can mate within the same species like breeding dogs. However, we cannot mate with monkeys despite sharing a common ancestor. My question is as follows: Say animal A is geographically separated and some because animal B and the others become animal C. At what point are B and C too different to reproduce with each other? From my understanding it is when they are of a different genus. What change in them (genetically or otherwise) marks that point or becomes formidable enough for the DNA not to mix? I'm not a science major and I've tried to word this as well as I can. I hope I've at least gotten the main question across properly.
|
[
"Essentially a single major change (say a chromosome splitting) could be enough the separate a group of individuals in a small number of generations; on the the other hand thousands of (functional) single nucleotide polymorphisms might not be enough -- it all depends on what the genes actually do, how it affects the body and behavior of the species, etc.",
"Part of the issue is the well-definedness of \"evolutionary distance\". The other is what you mean by \"no longer reproduce\". Horses and donkeys can reproduce but the offspring are not fertile. There is a similar situation with dogs and jackals, but it can take more generations for the fertility line to terminate.",
"I presume that what you are really asking is \"how much change is required for speciation\", and this is a very complex question. Take a look at ",
"ring species",
" to see just how so."
] |
[
"There's a lot to consider here. First is that we can't really look at \"evolutionary distance\" in terms of any meaningful units. This is because the \"distance\" in question isn't just gene frequencies. ",
"Also keep in mind that \"species\" is not a well-defined word. Sometimes we designate species based on morphological characteristics (the way they look or even behave), sometimes its based on whether the ",
" produce fertile offspring and sometimes its based on whether they ",
" produce fertile offspring in the wild. ",
"So taking this into consideration, there are multiple axes upon which we can measure \"distance\". ",
"Gene frequencies may stay similar in general but behavioural isolation may occur. So species may adopt mating or courtship behaviours that are so different from their former relatives that no mating occurs. Alternately slight changes in DNA may lead to changes in outward appearance which prevent members of one group from wanting to mate with members from the other. You can change only a few genes and have an organism look significantly different.",
"The opposite scenario would be that many genes change and the two organisms - despite being able to mate - cannot create a viable embryo or the offspring they do create is not capable of procreating.",
"Thus we can have two groups that are quite similar genetically but they can't mate because the genes or behaviours on which they differ are ",
" to producing fertile offspring. We can also have groups that appear to be quite different but they retain key genes that allow them to produce fertile offspring. ",
"I realize this is a borderline non-answer but understand that when we differentiate species we do so on a sort of continuum that involves multiple factors, not just genetic difference. ",
"What change in them (genetically or otherwise) marks that point or becomes formidable enough for the DNA not to mix?",
"For some specific examples this article (",
"Reproductive isolation",
") should cover everything. ",
"Pre-zygotic barriers",
" prevent zygotes from even forming. ",
"Post-zygotic barriers",
" affect the viability of the zygote after it has formed. The ",
"section on genetics",
" may be a little in depth but it goes over some of the actual mechanisms through which these barriers operate."
] |
[
"no, a common genus has absolutely nothing to do with this. This ability doesn't really have anything to do with anything as far as classification goes. The process of turning a fertilized egg into an animal that can live is extremely complicated and involves the use of millions of genes. If these particular genes are similar enough, than a mule type thing might be able to be created. There are also a bunch of genes involved in the making protein coverings for sex cells to reject sex cells of the wrong species, which have to also just happen to have not changed that much. That's really all that can be said about that. ",
"We have a different number of chromosomes than chimps, which may have something to do with the lack of a humanzee. "
] |
[
"What occupies most of the space of an atom?"
] |
[
false
] |
[deleted]
|
[
"The electrons orbit the atom at various radii. This conglomerate of the electrons orbiting the nucleus is commonly know as the \"electron cloud\" and that is the majority of the space an atom occupies."
] |
[
"They can be treated as such - that's what a wavefunction is."
] |
[
"The wavefunction can tell you the probability density of finding an electron over a defined space - and your electron orbital is usually defined as \"the volume in which there is 95% chance of finding the electron.\" Until a measurement is made (i.e. an interaction occurs, thus the ",
"wavefunction collapses",
"), the electron can be said to occupy all of its possible positions.",
"In chemistry, this isn't ",
" big of a concern - most of chemistry is satisfied with knowing that an electron exists in a given orbital. However, there ",
" real, tangible consequences of quantum mechanical behaviour of the electron through space - ",
"van der Waals forces",
" is an example.",
"In trying to define the position of an electron, you're also faced with the ",
"uncertainty principle",
". So the end result is that the electron does in fact exist in the entire orbital."
] |
[
"Why is the Ohio River considered a tributary to the Mississippi River and not the other way around?"
] |
[
false
] |
If a tributary is a river that flows into a larger one shouldn't the Ohio river be considered the main river/source?
|
[
"Generally, the definition of which stream is a ",
"main stem or trunk",
" stream vs which is a ",
"tributary",
" is not always consistent, or rather, there are a few different properties of a river network that are used to distinguish trunks and tributaries. If you're starting from scratch, the definition of which stream upstream of a confluence is the main stem from sort of empirical measure, it may be based on the stream with (1) the larger drainage area (i.e. the surface area of the ",
"drainage basin",
"), (2) the larger ",
"discharge",
", (3) the higher ",
"stream order",
" (though this can also be ambiguous, and is the least so when using shreve ordering), or (4) the longest river distance to its source (and while some of these might give you the same answer, many times they will not). However, in the case of the Ohio vs Mississippi (or the Mississippi vs several of its tributaries), I think the answer comes down to history more than anything else (i.e. what we describe as the main stem of the Mississippi and the various tributaries were named as such before we had clear measures of the properties listed before), but someone with more of a background in the history of exploration of the US might be able to provide more insight."
] |
[
"Many researchers have mapped the geomorphology of the Mississippi & Ohio River Basins. Roger T Saucier is considered to have the most accurate model(1974, 1982 multiple pubs), but these are largely based on the work of Fisk from 1944. Because I’m away from my books right now, this will largely recount these from memory.",
"Approximately 50,000 years bp, the Ohio River flowed from its headwaters to the gulf, while the Mississippi River flowed from its headwaters to near where modern day Arkansas Post is. The course of the channel was west of the loess capped Crowley’s Ridge formation in southeast Missouri and northeast Arkansas. The modern day lower White River channel and Cache River represent this flow. ",
"Due to meltwash, The Mississippi began migrating east, forming the modern L’Anguille River, which cut the ridge. By 30,000–18,000 bp (can’t remember exact date), the Mississippi had abandoned the L’Anguille and was now confined east of Crowley’s Ridge. Eventually, within the past 500 years, the Mississippi was near to its modern course. As it migrated East it formed the St Francis, Little, and Tyronza rivers. While it migrated East, it is largely viewed as having cut off the Ohio and overtaking its course. ",
"I can’t remember the exact names of the articles but Fisk’s maps are beautiful. I’d be happy to have them printed and framed. Saucier’s refines Fisk’s guesses and makes it a little more useful, but LiDAR often finds that Fisk was pretty accurate."
] |
[
"Thanks! I have the plates digitized and on my computer for GIS purposes, but my article is at the office."
] |
[
"Big Bang question."
] |
[
false
] |
[deleted]
|
[
"Is the big bang proven science?",
"There is no such thing as \"proven science\". Scientific theories are all subject to disproof with new evidence, and there are no \"proven theories\" in science. If a theory were ever to be declared \"proven\", in that moment it would leave the domain of science, and enter philosophy.",
"This scientific precept was best expressed by John Stuart Mill, who said, “No amount of observations of white swans can allow the inference that all swans are white, but the observation of a single black swan is sufficient to refute that conclusion.\" ",
"Is there science that explains the origins of the. Universe?",
"There is a theory called the Big Bang, which at the moment is the best-supported theory about the beginning of the universe. The evidence for this theory is excellent, and many new observations continue to clarify the basis for this theory.",
"Nevertheless, the Big Bang theory is a scientific theory, which means it is open to revision or falsification by new evidence. This is the single most important thing to understand about science -- there are no truths, no proofs.",
"EDIT: typo"
] |
[
"No, we don't know anything about what was before the Big Bang and the Big Bang theory makes no attempts to explain this; it only explains the conditions of the early universe. In fact, it is actually impossible to see further back than ~400,000 years because the universe was opaque to EM radiation up to then, as photons were absorbed a very short time after emission. However, there is what's known as the cosmic neutrino background which if we could collect data on would allow us to measure back to a few seconds after the big bang, up to which time the universe was effectively opaque to neutrinos; it's very difficult to test this hypothesis though because neutrinos interact so rarely with matter and thus are difficult to detect. Huge, complicated detectors need to be constructed to even detect a few neutrino-matter interactions."
] |
[
"The evidence that there was a big bang at the beginning of the universe is extremely compelling.",
"We see the afterglow of the big bang in the cosmic microwave background. This is probably the best direct evidence.",
"We measure that the universe is expanding directly. This is pretty direct evidence.",
"The arrangement of galaxies follows a pattern predicted by the theory of Baryon Acoustic Oscillations, which suggests that the universe was much hotter and denser in the past. This is pretty good evidence.",
"The relative abundances of Hydrogen, Helium, and (almost) Lithium are what is predicted by Big Bang Nucleosynthesis - although heavier elements are produced in stars at later times, the abundances of elements is what you would predict it to be if there was a big bang.",
"There are probably more, if you like, but that's probably a good start."
] |
[
"Can motion of planets produce sound ?"
] |
[
false
] | null |
[
"This is a deceptively difficult question to answer because it hinges on how you define sound and gets into a philosophical debate about cause in a complex system. I'm going to define sound as sound waves that exist on a human or \"larger than human\" scale. Sound that theoretically could exist at an immeasurable scale is going to be ignored for simplicity.",
"Does planetary motion produce sound in space? Generally no, because there is insufficient matter for sound waves to meaningfully propagate. If a planet were to pass through a sufficiently dense medium, both rotation and motion would produce sound but only within the medium and planet itself. Imagine the sound caused by moving into another planet.",
"Most things on a planet are moving or rotating at the same speed and there will be no sound produced from motion on the planet itself as a consequence. When things are not moving at the same speed as the planet, there is sound produced. However, attributing this to planetary motion is not standard, and here's why. If a planet were completely stationary and never rotating to observers at various distances from the planet, there would still be sound produced if things on the surface moved at different speeds relative to the planet. We tend to attribute these sounds to the object not going along with planetary motion rather than to planetary motion itself.",
"There are all kinds of potential pedantic arguments here. Even simple ones, like how on earth weather patterns and tides are impacted significantly by rotation and clearly produce sound. ",
"It's fairly safe to say \"no\" in response to the question \"Does planetary motion produce sound?\". However, you asked \"Can motion of planets produce sound?\" and the answer is it can happen. If we limited the problem to constant velocity, in a perfect vacuum, with no other bodies, and with a uniform density planet then the answer is no."
] |
[
"Replace planet with any arbitrary object and you get an equally deceptively question. I don't think this question make sense at all."
] |
[
"Usually when people ask it about a planet they mean is there is a distinctive \"planet motion\" sound.",
"The question makes sense to ask with the context of moving things frequently producing sound on earth."
] |
[
"Is mass directly proportional to inertia?"
] |
[
false
] | null |
[
"\"Inertia\" by itself doesn't have a mathematical expression, so it wouldn't be precise to say yes, but Newton's second law states that F = ma, where F is force, m is inertial mass, and a is acceleration...so if you're talking about inertia as a resistance to acceleration, then yes, it's proportional. (So doubling the mass of an object subjected to a given force will half its acceleration.)",
"Of course, this isn't so straightforward when discussing rotation, where moment of inertia is more relevant than actual mass."
] |
[
"Of course, this isn't so straightforward when discussing rotation, where moment of inertia is more relevant than actual mass.",
"But it still remains essentially true, since you can deconstruct the rotational inertia of an object and explain it solely in terms of 'regular' linear inertia of the components of the rotating object. Rotational inertia isn't really a different phenomenon, it is a mathematical tool used to simplify calculations.",
"I also think that it's valid to equate inertia and mass. Inertia is the resistance of an object to changes in velocity, which is exactly the function of the mass in Newton's second law. If we ever figure out why inertial and gravitational mass are equivalent (or if we determine that they are ",
" actually equivalent), then there may be a reason to separate the two, in which case the ",
" in F = ma should be called inertia, whereas the ",
" in gravitational equations like the law of universal gravitation should be called mass (essentially the gravitational 'charge')."
] |
[
"Adding onto this, I find it useful to view inertia as a resistance to a change of state of an object. ",
"In mechanics, an object with no external forces will maintain some constant velocity and direction. Now when a force is applied to change the velocity or direction, mass (inertia) is the resistance to that change.",
"In EM, if an emf is applied to a circuit that follows V=IR, then V is the applied \"force,\" resistance is like an intertial analog, and I, current, is the resulting \"acceleration.\" Thus a higher resistance, or \"intertia,\" the lower the resulting change of state (current)."
] |
[
"Why does stress lead to us sleeping badly? It would seem evolutionary advantageous to be able to recharge peacefully during times of stress"
] |
[
false
] | null |
[
"Stress hormones are released by the body when it perceives that it is in danger or has to mobilize extra resources in order to succeed. When you see it like this, you can realize why being more sleepy is disadvantageous. Stressful situations call on us to mobilize everything and be in fighting condition to address the issue that's causing us to be stressed, rest becomes a secondary priority then."
] |
[
"Yes, but why are they being released when we are in no immediate danger and try to relax? Is it just a loop in the brain that keeps running for a while after the original \"stress impulse\"? "
] |
[
"Because your body doesn't think it isn't \"in danger\". Your body operates primitively and isn't designed to handle modern day stresses that can't necessarily be faced directly. "
] |
[
"Is the gravity of Ceres strong enough to allow for walking or running?"
] |
[
false
] |
Given Ceres' extremely low mass, would it feel more like Zero-G, or would the gravity "keep you grounded", so to speak?
|
[
"Ceres has just under 3% of Earth's gravity, at about 0.27m/s².",
"This means if you weigh 200 pounds on Earth, you would weigh 6 lbs. on Ceres.\nWalking would be very difficult, nearly impossible unless you moved at about a snail's pace. Running could have an equivalent if you leaned forwards until you were nearly lying down in a push-up position, then diving forwards horizontal to the surface. Doing this would be probably the most efficient way of getting around, but stopping could be difficult. Unless you were very gentle about it, you would slide and tumble for a long time from a very strong forward lunge.",
"If you're thinking about performing a spacewalk on Ceres, for many practical purposes it need to be treated the same as if it were in complete free-fall like in orbit. Being able to stop is dependent on friction, and friction is dependent on gravity. If you started to tumble down a slope, no matter how hard you try to grab stuff or bury your arm into the soil, you might keep rolling until you reached the lowest nearby elevation. And that could be dangerously far from where you first fell."
] |
[
"Not really, according to ",
"wikipedia",
", the escape velocity of Ceres is 500m/s. However you could jump about 35 times higher than on earth."
] |
[
"You'd actually take off and land with the similar velocity as you would on earth. It just takes gravity longer to slow you down and then speed you back up.",
": misunderstood your question, sorry. No, I don't think terminal velocity is a meaningful term on Ceres. You'd keep accelerating until impact."
] |
[
"Where do photons, gluons, w and z bosons come from?"
] |
[
false
] | null |
[
"What do you mean \"come from\"? They're fundamental field excitations. Imagine the skin of a drum. Now you strike the skin, and it begins vibrating. Particles are like that vibration, ",
"they're \"excited states\" of fields that permeate and make up the entire universe",
"."
] |
[
"the quark is itself an excitation of the quark field, and has properties of \"color charge\" in addition to electric charge. And like the electric charge excites the electromagnetic (photon) field, the \"color charge\" excites the strong (gluon) field(s)."
] |
[
"well the photon is absorbed (destroyed) when the electron gains energy, and created when an electron loses it (among other processes). It's the other processes you need to think about really when you talk about gluons. All of these particles carry momentum away from some fundamental fermion(s) and give it to some other fundamental fermion(s). The gluon carries momentum and color charge between quarks and acts in such a way to keep the quarks bound together in \"hadrons\" (of which the protons and neutrons are examples).",
"Here's our sciencefaq on fundamental particles"
] |
[
"How can both black holes and gravitons exist?"
] |
[
false
] |
If gravity is carried by particles that move at the speed of light, how is it possible for a black hole to transmit gravitational effects to outside its own event horizon?
|
[
"Actually it's not necessary to think about gravitons (quanta of the gravitational field) in order to have this question-- the same applies to the classical gravitational field and gravitational waves, the latter of which are how changes in the former propagate, and do so at the speed of light. As a star collapses, matter at the center is getting denser and denser, which is making the gravitational field inside the star stronger. These changes in the field propagate outward from the center of the star to the stellar interior at the speed of light, and continue to do so during the collapse, continually modifying the field. Eventually, the star may collapse inside its own Schwartzschild radius. After that point, the gravitational field outside that radius is mostly unchanging and is a solution to the vacuum Einstein equations (essentially vacuum because the matter density is small away from the singularity.) The black hole doesn't have to transmit any more effects: the state of the field (classically, the geometry of the spacetime) is to a first approximation quiescent, and test particles move in that field along the geodesics. ",
"In other words, the motion of test particles is affected locally by the state of the gravitational field, which was generated dynamically by stellar collapse and experienced changes that propagated through it at the speed of light during that volatile time. The test particles aren't actively interacting with the singularity and aren't sensitive to any dynamical processes still ongoing inside the horizon, due to the presence of the horizon."
] |
[
"It's a bit of a misnomer to say that forces are \"carried\" by particles. It's not as if the electric force works by two charges shooting photons at each other, for example.",
"A black hole forms from a collapsing star. That star had a gravitational field, and that gravitational field won't disappear simply because the matter sourcing it moves behind an event horizon. Mass has to be conserved, and angular momentum and so on. The gravitational field \"knows\" how strong to be.",
"What gravitons - or, ignoring quantum mechanics, gravitational waves - do is communicate ",
" in the gravitational field. But for a field that's already there, like the gravitational field of a black hole, it will just sit there in perpetuity, constantly gravitating."
] |
[
"That's not true. The Casimir effect and virtual particles are very seperate from gravity."
] |
[
"Whats the difference between moving your arm, and thinking about moving your arm? How does your body differentiate the two?"
] |
[
false
] |
I was lying in bed and this is all I can think about. Tagged as neuro because I think it is? I honestly have no clue if its neuro or bio.
|
[
"There is a fair amount of evidence from fMRI, PET and EEG studies that show involvement of the primary motor cortex in motor imagery tasks. I've performed a bunch of experiments with EEG motor potentials during ballistic movements (they evoke sharp, strong and easy to detect signals in the EEG), and I've even been involved in a brain-computer interface experiment which pretty successfully detects motor imagery so motor imagery is definitely activating very similar regions to what an actual movement activates.",
"So, looking at the evolution of scalp potentials over time around the time of a ballistic movement, there's a clear bilateral activation of frontal areas up to one second /before/ movement (the (in)famous bereitschaftpotential) that \"travels\" towards the back of the head as motor planning takes place and gives way to motor execution and, later, the evaluation of visual and proprioceptive feedback from the execution of the movement. At some point, the cortex will \"assemble\" a motor command which then is, possibly, \"filtered\" through lower structures and the cerebellum (which seems to play a prominent role in error processing and correction), to be then sent through the wires in the spine to respective muscles.",
"As far as I know from reading, experiments and the wisdom of my superiors, motor imagery pretty much runs the same \"program\" up to a point, but the motor command is never sent. Some groups have reported interesting results on motor imagery for motor learning (ie. training), showing that rehearsing, or \"visualizing\" a movement, seems to have effects closely resembling actual training to some extent. Of course it will never be as efficient as actual training with feedback, but it does inform us somehow.",
"Since motor imagery is usually dependent on visualizing the movement (more or less vividly), there is some speculation that mirror neurons are more involved than pathways and cells more related to actual movement, but it's all speculation at this point. ",
"So in short, the difference is relatively small, as the brain still has to compute the movement, predict the outcome, and \"imagine\" the results. A lot of the chips and wires used will be the same as the ones used in actually moving, but we can consciously suppress the motor output, so in a sense, the body doesn't have to differentiate anything, because nothing really leaves the brain. ",
"I just woke up so I might not make sense, I can dig up some interesting sources later if there's more interest.",
"src: Msc biomedical engineering, 2+ years working on eeg, motor learning, bci, reflexes, electrical stimulation etc. ",
"edit: holy crap that's a lot of questions in the comments! I'll do my best to try and answer as much as i can, thanks for the interest"
] |
[
"I'd suggest that you ",
" reacting to a changing environment or stimulus. It's just that the changes/stimulus come from your internal landscape and not from the exterior one. "
] |
[
"I'd suggest that you ",
" reacting to a changing environment or stimulus. It's just that the changes/stimulus come from your internal landscape and not from the exterior one. "
] |
[
"If sentient marine life were to evolve, say, on another planet, would they be able to advance as far technologically as humans?"
] |
[
false
] |
This question occurred to me when I was reading a post awhile ago about how dolphins are now considered more intelligent than chimpanzees. It doesn't seem inconceivable that on another planet that marine life could evolve to have human level intelligence, but would their aquatic environment stifle technological innovation? Shelter wouldn't be necessary, nor would the wheel, and fire, along with the advances that implement it such as metalwork would be impossible, so would the species be able to advance beyond the the tribal stage of our stone age ancestors? It's an interesting topic to me. Tl;dr How far could sentient marine life advance technologically?
|
[
"Availability of high-density energy sources would be key. Is this an aquatic planet, or are there land masses, covered with plants?",
"If it's a pure ocean planet, it would be damn difficult. You'd be limited to hydrogen reduction of metals, and cold welding. No smelting (I don't think you could build protective suits to deal with hot vents and lava).",
"Consider a rocket. How would you build a large chemical rocket underwater, or on top of a water ocean? Getting the fuel? Launching it?",
"Extremely difficult. I won't say impossible, but aquatic sentients on a wet planet would be a handicap from hell."
] |
[
"I've thought about this concept as well. I'm not sure how much of our technology they might be able to create but there might very well be some technology that we haven't even conceived of that only an aquatic species would invent, or at least that would come naturally to an aquatic species that wouldn't to us. Fun stuff to think about."
] |
[
"Actually, there are ",
"several correct plurals of 'octopus'",
", including that one. At least if you go by the Merriam-Webster definition. "
] |
[
"In this video of a car on two wheels, why do the wheels in the air stop spinning. At least one should be powered by the engine, right?"
] |
[
false
] | null |
[
"This is not accurate at all.",
"All cars have differentials. Most have open differentials, which allow the outside wheel to travel faster than the inside wheel. Open differentials have the disadvantage of sending power to the wheel with LESS grip (which is a side effect of allowing the outside wheel to spin faster than the inside wheel in a turn.)",
"In theory if the car in the video was RWD or FWD with an open differential, the wheel in the air should get most of the power and be spinning (very few differentials are capable of sending 100% of the power to one side at a time.)",
"LIMITED Slip Differentials on the other hand send power to the wheel with MORE grip (more resistance), so that your available traction is maximized. In theory a FWD or RWD set up with a limited slip differential would allow the ground contacting wheel to continue to get most of the power. However, as I said before, few types of differentials allow for 100% of the power to be transferred, so the raised wheels should still be getting SOME power. But as we can see in the video, they are getting none.",
"Looking at the Wikipedia for the Toyota FJ Cruiser",
" (the vehicle used in the video), we can see that there are RWD, part-time 4WD and full-time 4WD (aka AWD) which uses TORSEN differentials to split up the power. I'm guessing this is PROBABLY a full-time 4WD model which features the 3 TORSEN differentials.",
"I initially thought maybe the traction control system was using the brakes to stop power transfer to the raised wheels, but you can see in the video that the wheels move when one of the guys puts his foot on them, etc. So the brakes are not being used.",
"Instead, I think this is a case where these are high quality TORSEN diffs capable of actually transferring 100% of power to the wheel with traction.",
"Source: see wikipedia articles on differentials and drivetrains. This is basic stuff for anyone who loves cars."
] |
[
"This is not accurate at all.",
"All cars have differentials. Most have open differentials, which allow the outside wheel to travel faster than the inside wheel. Open differentials have the disadvantage of sending power to the wheel with LESS grip (which is a side effect of allowing the outside wheel to spin faster than the inside wheel in a turn.)",
"In theory if the car in the video was RWD or FWD with an open differential, the wheel in the air should get most of the power and be spinning (very few differentials are capable of sending 100% of the power to one side at a time.)",
"LIMITED Slip Differentials on the other hand send power to the wheel with MORE grip (more resistance), so that your available traction is maximized. In theory a FWD or RWD set up with a limited slip differential would allow the ground contacting wheel to continue to get most of the power. However, as I said before, few types of differentials allow for 100% of the power to be transferred, so the raised wheels should still be getting SOME power. But as we can see in the video, they are getting none.",
"Looking at the Wikipedia for the Toyota FJ Cruiser",
" (the vehicle used in the video), we can see that there are RWD, part-time 4WD and full-time 4WD (aka AWD) which uses TORSEN differentials to split up the power. I'm guessing this is PROBABLY a full-time 4WD model which features the 3 TORSEN differentials.",
"I initially thought maybe the traction control system was using the brakes to stop power transfer to the raised wheels, but you can see in the video that the wheels move when one of the guys puts his foot on them, etc. So the brakes are not being used.",
"Instead, I think this is a case where these are high quality TORSEN diffs capable of actually transferring 100% of power to the wheel with traction.",
"Source: see wikipedia articles on differentials and drivetrains. This is basic stuff for anyone who loves cars."
] |
[
"This is due to the axle setup on the FJ Cruiser, which uses an open differential with ATRAC to provide traction to tires on the ground.",
"On an open differential, the car will transfer the most torque to the wheel that experiences the least resistance. This is disadvantageous for a car like an FJ Cruiser that is designed for offroad use. For instance, if one wheel were in mud and the other on pavement, the tire in the mud would spin freely because it experiences the least resistance. What Toyota does to combat this is called ATRAC, active traction control. Here, the car senses when a wheel is spinning freely and the ATRAC system is activated. The car will then apply the brakes to the spinning wheel and divert the power to the opposite wheel. ",
"So in the video, the car is flipped onto it's outside tires and the cars ATRAC system halts the rear tire that is in the air from spinning and diverts the power to the wheel in contact with the ground. The front wheel, however, continues to spin after being tipped. I'd assume this is because the car is not in 4WD, which would make the front axle freely open and deactivate the ATRAC.",
"Edit: I was totally wrong in original posting. FJ cruiser does not have limited slip dif, but instead uses ATRAC to create a \"locked\" dif instead. "
] |
[
"Why aren't we using hydrogen instead of fossil fuels?"
] |
[
false
] |
It's my understanding that hydrogen can be produced by electrolysis using sea water. Why aren't we using solar panels, wind, whatever green energy is available to start mass producing hydrogen? It just seems to me that hydrogen is the best energy storage system out there. Clean and green. I understand there are some hurdles, such as transportation requires putting it under pressure, but we do that with natural gas anyway... doesn't seem like a deal-breaker. I want to thank everyone here for their input. I've read every reply, and believe it or not you've all given me of material to ponder and think about. I've already started watching TED talks about energy and batteries, lol! Special shoutout to and for your engaging, thought-provoking replies. Thank you all :)
|
[
"You touched on a few of the main problems. ",
"It's not an energy source, it's an energy storage medium and competes with batteries more than with fossil fuels ",
"It has a very low energy density and must be compressed to extreme pressures to get a decent amount into a reasonable volume. This takes a lot of energy to do- much more than natural gas due to the lower molecular weight ",
"Solar and wind capacity isn't enough yet to produce near enough energy to do that"
] |
[
"Regards point 2 - to add to the fun, hydrogen is a slipperly little bugger and won't stay in the tank long - the small size of the molecule mean that it can make it's way through seals, or, iirc, tank walls, more easily than just about anything else."
] |
[
"The third issue is that Hydrogen causes a lot of metals to become brittle (Hydrogen Embrittlement). Not what you really want in a pressure vessel."
] |
[
"Is there a way to accurately tell how much pain someone is in?"
] |
[
false
] |
I know that in hospitals, the 1-10 scale is used for pain, but knowing that there are pain receptors, is it possible for there to be a definite number or percentage of pain someone is in?
|
[
"Ooh! I actually worked on this many years ago! ",
"At least based on the massive pile of patient records I analyzed, there were no statistically significant correlations between vitals and either patient or nurse-estimated pain levels. ",
"Someone may have done a more thorough study since then, but we never even published our results because the PI didn't think a negative result would make for a good paper."
] |
[
"This. I love objective measurements as much as the next person, but when someone tells you they're suffering, all you can do is choose whether you believe them. Also why pain must always be evaluated relative to individual baselines."
] |
[
"If I remember correctly, while there are pain receptors and we can measure the significance of brain activity, the concept of pain itself is relative to the person experiencing it.",
"In other words, it scales differently for everyone. What could be painful for one person, could be considered a mild discomfort to another.",
"Despite this, I think at best we could theoretically measure the amount of pain sensations that are detected by nerves, but I don't think it would directly correlate to how the brain ultimately processes them."
] |
[
"Where does science stand on Time?"
] |
[
false
] | null |
[
"Yikes. Need to add flair! I’m very Joanna at the moment!",
"My flair..."
] |
[
"Yikes. Need to add flair! I’m very Joanna at the moment!",
"My flair..."
] |
[
"Yikes. Need to add flair! I’m very Joanna at the moment!",
"My flair..."
] |
[
"Prisms split white light into it's component colours, based on wavelength. Why?"
] |
[
false
] | null |
[
"The property of prisms that allow them to spectrally resolve light is that the glass they are composed of is dispersive. Specifically, the real component of the refractive index of glass decreases slowly as you pass through the visible spectrum towards longer wavelengths as shown ",
"here",
". Snell's law, states that at any interface, the angle of incidence (relative to the normal), ti, and the angle of refraction (tr) are related by ti/tr=n2/n1, where n1 and n2 are the refractive indices of the materials on the two sides of the interface. Because the refractive index varies as a function of wavelength means that light will then be refracted at different angles depending on its color so the initial beam will spread in the prism. Finally, when the light exits the prism on the other side, the glass has a different slope, such that you spread the light once more by color via the exact same effect (if the two sides were parallel, the difference in refraction at each interface would cancel out exactly producing no net resolution of light, which is why a slab of glass doesn't act the same way as a prism).",
"Now let's talk about why glass is dispersive in the first place. The reason is that the real and imaginary parts of the refractive index are related to each other. The imaginary part of the refractive index is zero, except in areas where electronic transitions are possible, where it peaks. In contrast the real part of the refractive index is equal to 1 far away from any electronic transitions, but rises above 1 as you approach (in the frequency domain) an electronic transition, then falls under one as you pass the transition, and then asymptotically goes towards 1 on both sides. The behavior of the real and imaginary indices near a transition is ",
"shown here",
". Quantum mechanically, the origin of both effects is that far from an electronic transition, light can still interact with matter via a second order interaction, which as shown by second order perturbation theory means that the transition must be mediated by a real electronic transition, such that this second order interaction is stronger the closer you are in energy to the real electronic transition. Ultimately it is this second order interaction that makes the real part of the refractive index deviate from 1 far away from an electronic resonance. ",
"To put the two pictures together, in the case of glass, as you go from blue to red and into the infrared, you are moving away from the electronic transitions of glass which lie in the UV, and so you are in the regime shown in the picture above where you are moving towards away from the electronic transition to lower energies, so the real part of the refractive index is slowly falling. This regime is called \"normal\" dispersion. "
] |
[
"Light waves are slowed in glass because they interact with the electrons in the material. In glass the electrons have particular 'natural vibration modes', and so like moving at some frequencies more than others. So the effect that the electrons have on light changes depending on the frequency of that light, which ends up meaning that the speed of that light in the material will be different for the different frequencies. This leads to the different frequencies (i.e. colors) being bent at different angles."
] |
[
"Light waves are slowed in glass because they interact with the electrons in the material. In glass the electrons have particular 'natural vibration modes', and so like moving at some frequencies more than others. So the effect that the electrons have on light changes depending on the frequency of that light, which ends up meaning that the speed of that light in the material will be different for the different frequencies. This leads to the different frequencies (i.e. colors) being bent at different angles."
] |
[
"What makes the spark mechanism in a safety lighter work?"
] |
[
false
] |
Have you ever taken apart one of those long safety lighters, inside there is a button with wires running to it, which generates a spark when the button's pressed down. How does this work? I've searched for this before, but I've never found out how it actually works. I couldn't find a picture of what I'm talking about... am I the only one that's taken one of these apart?
|
[
"The spark mechanism contains a piezo-electric crystal. This is a material that builds up an electric charge when pressure is applied. You pressing the button provides the pressure, and the wires direct the spark to the fuel source.",
"Further reading;",
"piezo-ignition",
"video explanation"
] |
[
"It's not effectively a battery, so you're phrasing the question incorrectly. The crystal doesn't really \"wear out\" , but it could break (shatter or something) or the mechanical parts could fail which would result in the lighter or ignition failing."
] |
[
"It's not effectively a battery, so you're phrasing the question incorrectly. The crystal doesn't really \"wear out\" , but it could break (shatter or something) or the mechanical parts could fail which would result in the lighter or ignition failing."
] |
[
"How exactly does fluticasone nasal spray work?"
] |
[
false
] |
The stuff immediately makes my allergy symptoms go away. I know it’s a corticosteroid but I can’t find an actual breakdown of what it’s doing once inhaled.
|
[
"From the package insert:",
"Fluticasone propionate is a synthetic trifluorinated corticosteroid with anti-inflammatory activity. Fluticasone propionate has been shown in vitro to exhibit a binding affinity for the human glucocorticoid receptor that is 18 times that of dexamethasone, almost twice that of beclomethasone-17- monopropionate (BMP), the active metabolite of beclomethasone dipropionate, and over 3 times that of budesonide. Data from the McKenzie vasoconstrictor assay in man are consistent with these results. The clinical significance of these findings is unknown.",
"The precise mechanism through which fluticasone propionate affects rhinitis symptoms is not known. Corticosteroids have been shown to have a wide range of effects on multiple cell types (e.g., mast cells, eosinophils, neutrophils, macrophages, lymphocytes) and mediators (e.g., histamine, eicosanoids, leukotrienes, cytokines) involved in inflammation. In 7 trials in adults, Fluticasone Propionate Nasal Spray has decreased nasal mucosal eosinophils in 66% of patients (35% for placebo) and basophils in 39% of patients (28% for placebo). The direct relationship of these findings to long-term symptom relief is not known."
] |
[
"Well its a great starting off point. It's probably not the most cutting edge or in depth info you can get, but its well tested. "
] |
[
"Thanks friend; guess I should have held onto that, huh? Haha "
] |
[
"Is it true that an albatross is able to fly for 5 years without landing?"
] |
[
false
] |
[deleted]
|
[
"That is truly amazing. I can't even fly while I'm awake.",
"Piggybacking on the original question, can birds go for an extremely long time without eating/drinking? ",
"Edit: typo thanks IamaLlamaAma"
] |
[
"I guess that's a typo but a funny one. Sleeping while awake would be quite exceptional."
] |
[
"According to this ",
"article",
", Albatross is able to sleep while it flies by locking the shoulders."
] |
[
"What does the claim that our Universe is a hologram mean?"
] |
[
false
] |
I was watching a "Through The Wormhole with Morgan Freeman" episode in which they talk about how our reality is a holographic projection from the edges of the Universe. There's also a book I have yet to finish, called "The Holographic Universe" by Michael Talbot; the book mentions Karl Pribram and David Bohm, and their ideas are touched upon . What does this mean, and why is this important?
|
[
"It is a very rough description of something called the holographic principle, you shouldn't take it too seriously.",
"Basically, the holographic principle states that sometimes physics in some space can be described by a theory that lives in the boundary of that space. For example, the entropy of a black hole is determined by its surface area alone.",
"However, if the episode claimed that the whole universe is a hologram they were most likely referring to the AdS/CFT correspondence, which is an equivalence between a certain class of gravitational theories defined in a particular space and another class of theories defined on the \"boundary\" of that space.",
"edit: if anyone wants me to expand on any of this just let me know. I didn't know how detailed of an answer you wanted so I just kept it short."
] |
[
"Ok, basically the way it works is that we have two different theories that yield the same physics. So any question you might have about the one theory could in principle be answered by a calculation in the other theory.",
"In this particular case the two theories are string theory or supergravity defined on \"anti de Sitter space,\" which is basically an n-dimensional generalization of a hyperbola, and a \"conformal field theory\" (a quantum field theory invariant under conformal transformations) defined on the boundary of the anti de Sitter space. So, because all of the physics of the ads theory is described by a lower dimensional theory we say that it is like the theory is a hologram.",
"However, it is important to realize that in this description neither of the two theories is more fundamental than the other. So, it doesn't make sense to say that the universe is \"really\" a hologram. One could just as easily say that the boundary theory is \"really\" a higher dimensional gravitational theory."
] |
[
"I didn't mean to put you on the defensive - I'm just saying that using acronyms makes it somewhat harder to research the terms."
] |
[
"I'm looking out my window at a half-orange, half-green tree at the moment. Why isn't the entire tree orange?"
] |
[
false
] |
The tree's leaves are split down the middle in color. South side is orange while the north side is green. Why does this happen? Is it sunlight? Winds? Temperature on one side?
|
[
"Pictures might help here.",
"edit: Not trying to be facetious, I'm serious. Take a picture and post it up. Do you mean the leaves themselves are split in color, or the entire tree itself is split in half by color?"
] |
[
"The tree's leaves are split down the middle in color."
] |
[
"My apologies, man. ",
"Here's an example.",
"Half the tree has the red-orange thing happening with its leaves and the other half is still green foliage from summer. "
] |
[
"Can't the Japanese just drop some concrete on the reactor like it was done on Chernobyl?"
] |
[
false
] |
The macho (and probably dumb solution): "Let's just drop a ****load of concrete on this baby and call it a day?"
|
[
"Well you know, concrete will melt too, and if they haven't sufficiently cooled the core down, it will just melt. Secondly, the core is still inside the primary containment. The Soviet RBMK reactors like in Chernobyl are built completely different. The limited containment that was at Chernobyl was destroyed during the failure and spread the core all over the place."
] |
[
"No, they've been pumping seawater into them which writes them off completely apparently. The main reason is probably to do with getting it under control first - they might seal them off in this way eventually."
] |
[
"Not to be too much of a debbie downer, but the whole concrete phase of Chernobyl happened ",
" the entire reactor had exploded in a violent fashion.",
"By the time the fire fighters were on scene at chernobyl, there was no reaction left, nothing really melting down. Just fires and smoldering wreckage. ",
"That does not appear to have happened at any of the Japanese reactors, which means there is a big emphasis now on making sure it continues to not happen. Pouring concrete on it at this point, were it even possible, would encase the nuclear fuel - which would then either melt through everything or violently explode.",
"The fuel produces heat very differently from a fire. If you put a pot or water on a fire, its \"fuel\" - which is something combustible and air - gets limited, and it is quickly burned through and the reaction (which is a fire) extinguished.",
"With nuclear fuel, the reaction is occurring on an atomic level within the fuel rods. When they got hot, they need to be cooled down, or else the reaction can get worse/hotter and thus more difficult to contain and more likely to cause other explosions. If you encased the nuclear fuel, you wouldn't be cutting off any of its supply. ",
"The control rods helped by limiting the reaction, but the \"decay heat\" of the separated fuel rods is still substantial enough to cause all kinds of meltdown like damage.",
"Still, the simplest and most direct answer is that events in Chernobyl proceded much more quickly, much more violently, and were more or less concluded by the time recovery efforts were made.",
"Also worth pointing out were the massive casualties associated with anyone involved in the emergency response to Chernobyl, including the construction of its concrete tomb. It's not a decision without costs, even if it gets to that point. "
] |
[
"Does the size of boobs increase the probability of breast cancer?"
] |
[
false
] |
The last year around December, my Mom went to do some exams about breast cancer (everything went ok), she told me that she had to put her boobs in a machine, then the machine squeezed her boobs a little and a big needle pierce her and left inside a titanium chip or something like that. When I imagined this I thought: "ok, with medium and big boobs they can do this, but what if the woman has small boobs or practically no boobs at all?". Then I remembered that any picture of a woman that got affected by breast cancer and survived always has medium/big boobs and I never heard/saw of a woman with small boobs survive cancer. This may sound stupid, but I'm truly curious about this
|
[
"If they used the titanium clip then It’s likely she had a biopsy. This means they basically removed a small amount of her breast tissue (if this was the case you probably had to wait for lab results?). As a side note the titanium clip is almost certainly used as a marker. If the sample turned out to require surgical removal the surgeon would use the marker to show them where to cut.",
"Like most cancers the causes of breast cancer are almost certainly an interplay of multiple factors. It’s probably not a very satisfying answer but I guess the right one is that it depends. Breasts vary not only in size but also in density which is a more important risk factor than size. People with large breasts may have increased risk of cancer due to the increased number of cells which can potentially be mutated. BUT a woman with smaller but more dense breasts would have even more cells than a woman who has large breasts of average density.",
"Genome wide association studies are a type of research that compares the genome of groups of people. By comparing the genomes of women with breast cancer with each other as well as to those without it you can identify POSSIBLE genes associated with the disease. Interestingly these studies found that SNPs in some genes associated with larger breasts can also increase cancer risk. While interesting it’s important to note that this is not proof of a causal relationship."
] |
[
"Most breast cancer are carcinomas, which means they start in epithelial cells. Fat cells are called adopocytes.",
"Breast cancer is not \"the mutation of fat cells\"."
] |
[
"Most breast cancer are carcinomas, which means they start in epithelial cells. Fat cells are called adopocytes.",
"Breast cancer is not \"the mutation of fat cells\"."
] |
[
"How do mirrors reflect light from a quantum perspective?"
] |
[
false
] |
In particular, if a photon hits a flat mirror, it is reflected at the same angle, correct? If photons are absorbed then re emitted by the mirror, how is the angle preserved? Also, is it reflected by the surface only or also by atoms deeper inside?
|
[
"Here is a nice explanation",
" from ",
"r/askscience",
".",
"tl;dr:\nFrom a particle perspective, we add up all of the possible paths the photon can take, and they almost all cancel out, leaving only the angle that obeys the law of reflection.",
"From a wave perspective, the surface acts like a ",
"diffraction grating",
". The interference pattern from this grating results in a wave obeying the law of reflection.",
"As for your other question, the light does penetrate the surface and interact with the underlying atoms. Even if the metal were a perfect conductor, an ",
"evanescent field",
" would reach a few tens of nanometers into the surface. For real metals, the wave actually propagates a through a few layers of atoms before it's completely absorbed or reflected. This is called the ",
"penetration depth",
"."
] |
[
"Everything is ultimately quantum in Nature, so it's quite accurate as far as we know. There's no macroscopic scale in which quantum physics stops applying.",
"In fact, good ol' macroscopic classical physics is founded on a stationary action principle (Lagrangian/Hamiltonian mechanics), which is taken as sort of a given truth. ",
"However, the principle emerges naturally from the quantum superposition of different possible paths, as discovered by Feynman after following the tracks of some musings by Dirac.",
"You simply compute a probability amplitude for each path you can possibly imagine from some starting point and time leading to some final position and time, even the ones violating classical laws (these laws all emerge from the action you use), then add them all up. These probability amplitudes are just a complex number related to the probability of measuring some physical system in a given state (say, finding a ball on the floor after you drop it).",
"The phase of each probability amplitude is directly proportional to the classical action divided by Planck's constant. This is where both classical and quantum perspectives connect.",
"The probability amplitudes add up near the classical path, just like explained above, since there's very little change between the phases there. Those complex numbers \"point\" in the same direction. And since Planck's constant is so tiny, any deviation from the classical path results in a HUGE change in the phase angle. This means anything far from that path is pretty much a bunch of random probability amplitudes, which add up to nothing on average: destructive interference.",
"The result is that the path where there's the least amount of change in action is the path that ends up being most probable, by a HUGE margin for macroscopic systems. This is what we observe classically, and it works all the way to single particles. Quantum field theory is basically this sort of thing. You just model the action accounting for all interactions between the fields.",
"Now, bear in mind, none of this has anything to say about interpretations of quantum mechanics, like Everett's Many Worlds. This is a direct result of Feynman's Path Integral formulation of quantum mechanics, which is mathematically equivalent to any other and compatible to whatever interpretation you want."
] |
[
"That explanation makes it sound like all of reality is one giant interferometer. How accurate is that statement?"
] |
[
"If someone licked the inside of a dirty toilet how sick would you get? Asking for a friend."
] |
[
false
] | null |
[
"We can't comment on personal anecdotes / isolated incidents without resorting to speculation which we try to avoid."
] |
[
"Let’s speculate. I’m fine with that. I know this isn’t webmd "
] |
[
"We don't allow such posts on this sub. Try another. You can use ",
"/r/findareddit",
" for help in finding an appropriate sub."
] |
[
"Is there a scientific reason for hiccups?"
] |
[
false
] |
I just had the hiccups for about 15 minutes and I cannot think of one reason as to why this would be vital for human survival.
|
[
"The process that causes hiccups is the same that allows tad poles and lung fish to be able to breathe both in air and water. So there is a chance it is a vestigial character left over from evolution"
] |
[
"Do you know of any studies looking into this characteristic of hiccups?"
] |
[
"Going on right now? Not that I know of, bu there was an article is Science Magazine or Scientific American that was talking about it. I'll try and dig through the ones and work and try to find it. Might be available online somewhere",
"EDIT: Here is a post from Scientific American, though it isn't a study. ",
"http://www.scientificamerican.com/article.cfm?id=what-causes-hiccups",
"Another from BBC news ",
"http://news.bbc.co.uk/2/hi/health/2730251.stm"
] |
[
"Is Muscle Atrophy in Zero-G caused by the lack of gravity, or the lack of activity while in gravity?"
] |
[
false
] | null |
[
"It's from the lack of gravity mainly, but they two ideas almost go hand in hand: the presence of gravity requires more force from a muscle to move a limb, and thus, in zero gravity, when a muscle does not have to work as hard to move a limb, it atrophies."
] |
[
"Yes. Also, in null gravity your slow-twitch oxidative muscle fibers convert to fast-twitch glycolytic. One speculation as to why this happens is that weight bearing muscles are virtually all slow-twitch (high fatigue threshold). This is important because we don't want to get tired just stand or sitting up. Now when you decrease or eliminate force, as in outer space or a cast, these muscles convert temporarily because of lack of usage. "
] |
[
"To rephrase my question; does the pull of gravity alone fight muscle atrophy, or does one need to move for gravity to be effective?"
] |
[
"How fast do plants make oxygen?"
] |
[
false
] |
Sig Factors are probably surface area, environmental conditions effecting respiratory rate but how many moles of oxygen does a typical plant cell produce in a day? what about a bkade of grass? A 4 ft plant?
|
[
"This is a very (very) common misconception. I mean i've seen several lecturers make this slip. The O2 doesn't come from CO2 with the carbon ripped off. The oxygen actually comes from water - the plant uses light to split a molecule of H2O (called hydrolysis) to release hydrogen ions and oxygen - the oxygen diffuses away - the hydrogen ions reduce a molecule called NAPD to NADPH2, which are used in a process called the Calvin cycle. ",
"This cycle is where the CO2 molecules are brought in, and eventually they - both the carbon and oxygen - end up in carbohydrates - (the C6H12O6 part of the equation). The enzyme which actually takes gaseous CO2 and turns it into an actual intermediate molecule is called RuBisCO.",
"So plants only produce oxygen when they are splitting water - and they can only do that when light is present, whereas plants don't need light to respire - and that's lucky, because they need to do that 24/7 just like us, and hence are always releasing CO2. "
] |
[
"This is a copypaste of what I have written to somebody else. I hope it might help you:",
"Let me calculate this for you:",
"Some papers say a beech tree absorbs about 6kg of CO2 per day.",
"The mass of our substance divided by its molar mass gives us the amount of particles:",
"6000g/(44.01g/mol)=n=136.330mol",
"This is the amount of CO2 molecules contained in 6kg CO2.",
"Under normal conditions 1mol of gas is equal to 22.4 litres.",
"136.330*22.4l=3053.8 litres",
"So one tree roughly \"inhales\" about 3 cubic metres of CO2.",
"Since the equation (6CO2 + 6H2O = C6H12O6 + 6O2) tells us that the amount of molecules is exhaled (6O2) as inhaled (6CO2).",
"This only counts for the number of molecules exchanged and the overall volume exchanged.",
"If you consider the difference in mass you can see:",
"3.0538m^ 3",
"m^ -3=6,05kg for the mass of CO2 (consider rounding errors with my iPhone)",
"versus",
"3.0538m^ 3",
"m^ -3=4,36kg for the mass of O2. "
] |
[
"Just going to point out that converting into volumes is an unnecessary step. From the equation you can see that there is a 1:1 ratio of carbon dioxide taken and oxygen produced. So there are 136.33 mol of oxygen produced which you can multiply that by the molar mass to get your 4.36 kg of oxygen."
] |
[
"If you lay or sit in a position that causes a limb to \"go to sleep,\" would you then be able to amputate that limb painlessly?"
] |
[
false
] | null |
[
"Extremely unlikely. Parasthesia is usually caused by reduced circulation; reducing circulation enough to inhibit nerve responses would cause both tissue damage and significant pain of its own accord. "
] |
[
"To add to this question, when a limb wakes up (like an arm or hand), what is actually happening when I feel the electric pins and needle sensation that can come on very strongly as the limb wakes up?"
] |
[
"If you're looking to amputate your own limbs please do consider seeking a medical professional, if not I would suggest any cryogenic fluid, such as liquid nitrogen."
] |
[
"Do wasps have a positive net effect on polination?"
] |
[
false
] |
[deleted]
|
[
"Tl:dr: Yes, of course they do.",
"Wasps perform numerous important ecological functions and reducing their numbers is an awful idea. \"Honeybees\" are technically a domesticated animal, and in the US, are actually considered to be a ",
"problem",
" when they become feral. There are thousands of plant species pollenated only by wasps and thousands more that bees won't touch at all. ",
"Honeybees being \"the most important pollenator\" is something of a myth, and they are actually completely irrelevant in the ecology of many habitats that they did not occupy before humans brought them there. They are however great at pollenating human agricultural products, and unfortunately, a lot of ",
"invasive plants.",
".",
"The beekeeper you spoke to is just mad about their hives being atracked, wasps will attack bees but they are also important pollenators. My landlord keeps bees on the property and I grow a lot of native (New England) plants. The Honeybees ignore certain plants that wasps, native bees, flies, and ants pollenate, and the Honeybees are the only thing really fixated on the European plants in my herb garden like Lavender and Basil."
] |
[
"In the U.S. except in rare occasions wasps are not a significant killer of honey bee. Those rare occasions are typically late fall when everything has stopped blooming and certain wasps, yellow jackets in the southern U.S., attempt to rob hives. They can in that circumstance kill a lot of bees even destroy a hive but its not common enough that isnt causing a pollination problem, largely because when it happens pollination is done for the year. If there was still pollination going on the wasps would find other food and not have to go after honey bee stores.",
"Yes wasps are important pollinators. Some ",
"fruits rely totally on wasps for pollination",
". The minor damage a few wasp species do do to honey bees is vastly outweighed by the tens of thousands of wasp species that will never harm a bee.",
"They are also important at controlling other insect pests we don't want. While adult wasps need carbohydrates; nectar or honey for energy, larva wasps need protein. This protein comes from other creatures the adults kill and bring back to feed the larva. There are tens of thousands of wasp species and each predates on different species but in large part they go after other insects, eliminating caterpillars that eat our crops.",
"I am a beekeeper."
] |
[
"My garden is almost exclusively pollinated by wasps. I value them more than bees. ",
"The bee keeper is mad becsue HE loses money when a wasp comes and kills the invasive (honey bee imports) bees. It has nothing to do with protecting bees, that's his lively hood. He wants to kill wasps who are a major player in the ecosystem so he doesn't lose his money, not because he's saving the earth."
] |
[
"What are some evolutionary explanations for homosexuality?"
] |
[
false
] |
[deleted]
|
[
"Well, if I may take a stab at clarifying your question, I think what you're really trying to ask is \"why hasn't natural selection removed a trait that seems to make animals not want to reproduce?\"",
"In order for a trait to be subject to natural selection in the first place, there need to be different versions of it, the version you get needs to be determined genetically, and which version you get has to change your chance of having offspring.",
"It's actually not clear whether those requirements are met for sexual orientation. People have looked for a genetic link and essentially not found it. There was a study that reported a genetic marker that was significantly more common in gay men than you'd expect by chance. However, further research failed to reproduce the connection, and at any rate it would only have explained a fraction of cases even if it were true. ",
"more",
"In fact, there are interesting lines of evidence that suggest homosexuality may be \"inborn\" but not actually genetic - instead, a product of the prenatal environment. ",
"example",
"But even if homosexuality were caused by a single locus with straightforward Mendelian genetics, it still might not be selected against. A couple of mechanisms are suggested by a nowhere-near-conclusive piece of evidence: one study found that female relatives of homosexual men on their mother's side tend to have more offspring, i.e. ",
"genetic fitness",
"). The totally speculative hypothesis is that an allele of some gene on the X chromosome might somehow increase fitness when present in a woman (and perhaps only when present in one copy, not two), but cause homosexuality in men (who only have one ",
"X chromosome",
" and it's always from the mother). There could actually be selection ",
" this allele if the fitness gain in women more than offsets the speculated loss in men, especially if the ",
"penetrance",
" (unfortunate word) is low, i.e. the allele only makes men marginally likely to be homosexual. ",
"more",
"And another explanation for the same data is the \"gay uncle\" hypothesis, where that allele actually doesn't have to do anything interesting in females, but having a homosexual male relative in the family increases fitness for the members who do reproduce. Thus, even though the allele that's causing the fitness boost is only definitely present in an individual who's not reproducing, it's statistically likely the same allele will also be present in the beneficiaries, an example of what is maybe best understood as ",
"kin selection",
" even if that term is problematic. ",
"so much more",
"Of course, all of this is assuming homosexual individuals reproduce less, which we shouldn't take for granted now, let alone over the course of evolutionary history, most of which did not contain LGBT subcultures."
] |
[
"Great answer, very well put.\nMy "
] |
[
"This needs to be FAQd cause its asked every week"
] |
[
"If I stopped wearing my glasses, would my eyesight revert back to normal? If I had never gotten glasses as a kid, would my eyesight be fine as an adult?"
] |
[
false
] | null |
[
"No. Although your eyeball shape does continue to change as you age, so it's possible that a mild myopia or hyperopia will correct itself... but it's not ",
" you didn't wear glasses."
] |
[
"So then is there any way your vision could be made worse by glasses?"
] |
[
"I'm not aware of any evidence supporting this. Although if you wear the incorrect prescription, it can give you headaches. "
] |
[
"Why doesn't mold start growing on food immediately?"
] |
[
false
] |
Why does it take 1-2 weeks sometimes for bread to start to mold? Or several days for food to start molding in my fridge? What is the mold "waiting" for?
|
[
"It does. The mould you see is typically the fruiting body and spores. They are darker to protect them from damage due to UV light The mould has been growing for quite some time before you start to see the effects visually. Prior to that it's simply not visible to your eye the same way bacteria is not visible on your countertop. "
] |
[
"It really isn't a bad thing though, just a common misconception that really ought to be corrected. ",
"We tend to like to pretend that our world is clean and sterile when it most certainly is not. The fault is not with the world for being what it is but with us for pretending it is something else. A little mold (or bacteria, fecal matter or anything else really) isn't going to hurt you."
] |
[
"It really isn't a bad thing though, just a common misconception that really ought to be corrected. ",
"We tend to like to pretend that our world is clean and sterile when it most certainly is not. The fault is not with the world for being what it is but with us for pretending it is something else. A little mold (or bacteria, fecal matter or anything else really) isn't going to hurt you."
] |
[
"How do electrical signals instigate contraction in muscles?"
] |
[
false
] |
What is the mechanism behind the contraction of voluntary muscles due to electrical signals being sent from the brain? Does the same mechanism apply to involuntary (smooth, cardiac) muscles?
|
[
"A signal travels down the membrane of a muscle cell until it reaches membrane-bound calcium channels, which are stimulated by the electrical signal to transport calcium into the cell. The calcium further stimulates ryanodine receptors on the sacroplasmic reticulum to causes release of even more calcium ions into the cell. The contraction of the muscle fibers inside the cell is dependent on calcium.",
"See ",
"here for cardiac muscle summary",
" and ",
"here for skeletal muscle summary",
"."
] |
[
"It's all about ATP binding. ",
"Here",
" is a link that explains the role of ATP and calcium ions in muscle contraction and explains how the nervous system is responsible for ATP actuation."
] |
[
"the motor neuron descends directly from your brain in the case of your fingers",
"Are you saying there are only Upper Motor Neurons supplying the radial, median and ulnar nerves? I've never heard of that, could you explain please?"
] |
[
"Why don't they launch space bound rockets out of tube like bullets from a barrel of a gun?"
] |
[
false
] | null |
[
"A gun barrel serves as a means to influence control over direction of a bullet's travel ( though it also keeps the explosive forces concentrated behind the projectile)",
"Because the rocket is capable of being steered and carries it's own gunpowder, firing it through a tube is simply not required."
] |
[
"Because it would not have any benefit.",
"The difference is that a bullet is pushed by an explosion next to it and pushed out by the expansion. A rocket is pushing itself away by pushing out the exhaust of the burned fuel.",
"So you don't need to direct the push, since it is inside the rocket anyways."
] |
[
"If you actually could impart enough energy into the space bound rocket to reach orbit, depending on the length of the tube you would have to impart such strong g forces on it that you would kill anyone inside and likely also destroy any sensitive equipment.",
"So it needs to be a slow and steady push, with a gradual acceleration that astronauts can remain conscious through.",
"Now, if we build a tube that reaches from the ground all the way into low orbit, we could use that tube to launch rockets into space with much less energy required. That would be sort of like the space elevator that people have envisioned."
] |
[
"Does the hydrophobicity of an objects surface affect the bouyancy of the object?"
] |
[
false
] |
Will one of two objects break the surface tension of water quicker if the only difference between them is their surface texture? Will one of the two sink faster afterwards?
|
[
"No. hydrophobicity doesn't have any effect at the macro (i.e. large) scale. Years ago there was a youtube video that showed people running on water because they wore waterproof shoes. It was a total hoax, but for months afterwards people were asking \"what if's\" about hydrophobic materials. ",
"At insect size surface tension has some meaningful effects and then you might see a difference for hydrophobic materials. But anything larger, no. "
] |
[
"What if a speed boat had rainex? Could gliding easier provide more lift with increased speed and aerodynamics? "
] |
[
"The boat still has to physically push the water out of the way to move forward. It’s the water’s inertia more than surface friction that slows the boat down."
] |
[
"Does modern firefighting equipment have preventive measures for extreme cold conditions?"
] |
[
false
] |
I was reading an article about the in NYC which was left to burn since the firefighters equipment froze during the blaze. I realize hydrant lines are pressurized, but would they still be likely to freeze under extreme conditions?
|
[
"In a word, yes. ",
"We have a more scientific understanding of how to prevent things from freezing today than we did in 1912. For example, on a cold day we never shut the hose off entirely once it's been charged - we'll keep the water moving. Moving water is harder to freeze. A fire on a day when the temperature is -20, however, will be a difficult one to deal with no matter how much scientific trickery we employ. Remember that all the water you're throwing in to the building is finding its way out of the building and freezing."
] |
[
"In areas where freezing is likely there are dry hydrants which don't hold water in them. The water supply is under ground and is accessed by opening a valve on the hydrant. A dry hydrant looks like what you're familiar with as a fire hydrant."
] |
[
"Thats a dry barrel hydrant, a dry hydrant is actually something slightly different. The dry barrel has the valve at the main located below the frost line. Turn the nut at the top, it spins a long shaft, and opens the valve below. This shaft can and does snap from time to time. When the valve is closed, it opens drains at the bottom of the barrel allowing it to drain into the surrounding earth, usually gravel drainage support. ",
"A dry hydrant is unpressurized, there's no valve, and the engine has to draft water under suction from a fixed source, not a pressurized main."
] |
[
"Does the sport you play while going through puberty affect your body type for the rest of your life?"
] |
[
false
] |
My brothers and I pretty much grew up the same height and weight at our respective ages through our childhood. We all played soccer pretty much everyday for years but I was the only one who ended up quitting soccer in order to wrestle around the time of puberty. Years later my brothers are both still pretty skinny and lean where as I am a bit more thick with muscle. I am wondering whether wrestling during puberty changed the way my body developed as oppose to the way it would have if i played soccer
|
[
"The book, \"The Sports Gene\" touches on this quite a bit. Your genetics play a the part in how these differentials occur. You may have received the gene for larger muscle growth and due to the type of training you may have received in wrestling your body may have had the ability to express that gene, more so then when you were playing soccer. I will have to find the source but it has been found that bulky muscle, generally those preferred in power sports such as wrestling are majorly built up of fast twitch muscle fiber. Your brother may carry this same gene and may have just as much fast twitch muscle fiber that has been expressed, he may not. Its hard to say unless someone could sequence and compare your genomes to determine certain factors that may have contributed to the difference in your ability to build muscle. "
] |
[
"While this may not apply to you and your brother, I want to point out a common fallacy that I think is relevant here. With competitive athletics, there is often the notion that the sport produces the body type that you have. Runners have small frames because they're runners, swimmers have wide shoulders because they swim, dancers are more flexible because they dance, etc. While those sports certainly enhance those traits, it is also very likely that the athletes always had those traits and they were naturally more advanced, which caused them to excel, earn praise, and continue on with the sport. The ones left at the \"top\" are typically the ones who are the best and it's impossible to say how their initial body type combined with their training to make them who they are.",
"Nassim Taleb brings this up with the example of the Russian Gulag in his book The Black Swan (correct me if it's another book). The myth was that the Gulag \"produced\" men with extraordinary strength and of an unusually hard demeanor. In reality, that strength and demeanor was likely required to survive at the labor camp and they exhibited those traits more than most people before. The average person would die and the camp merely killed off the weak and allowed the super fit to survive, thus making the cohort of survivors only contain extremely fit people."
] |
[
"Unfortunately its not so simple. We currently dont have an extremely good understanding of what genes cause what results because often it is an accumulation of different genes that cause a certain result. Scientists are constantly working to understand certain genes and work out how they express themselves but this complicated interplay between genes is something that changes from person to person. In david epsteins book he talks about the natural and artificial selection of athletes with preferential attributes but there is a lot more that goes into building athletes then simple physical attributes, such as aerobic trainability and baseline or even the amount of blood in a persons body."
] |
[
"What is the current scientific consensus on Genetically Modified Organism (GMOs) in our food?"
] |
[
false
] |
I'm currently doing a research paper on GMOs and I'm having trouble gathering a clear scientific consensus.
|
[
"The safety of currently used GM crops is clear.",
"US National Academies of Sciences stated: \"To date, no adverse health effects attributed to genetic engineering have been documented in the human population.\"",
"\"A 2008 review published by the Royal Society of Medicine noted that GM foods have been eaten by millions of people worldwide for over 15 years, with no reports of ill effects.\"",
"Current traits have had a general net benefit to the environment. They decrease insecticide use, and replace more harmful herbicides. They also help promote no-till agriculture which conserves soil.",
"\"Planting glyphosate-tolerant corn and soybean and using glyphosate in lieu of some residual herbicides (alachlor, atrazine, linuron, and metribuzin) should reduce the impact of the production of these cros on surface water quality.\" ",
"\"Replacing these herbicides (atrazine and alachor) with glyphosate and glufosinate can reduce the occurrence of dissolved herbicide concentrations in runoff exceeding drinking water standards.\"",
"\"Effects of glyphosate on contamination of soil, water, and air are minimal, compared to some of the herbicides that they replace. No risks have been found with food or feed safety or nutritional value in products from currently available GRCs. Glyphosate-resistant crops have promoted the adoption of reduced- or no-tillage agriculture in the USA and Argentina, providing a substantial environmental benefit.\"",
"\"Studies have shown that these Bt crops can be successfully deployed in agriculture, which has led to a decrease in pesticide usage, and that they are environmentally benign.\"",
"\"over 4 million smallholders have been able to increase yield per hectare, and reduce pesticide costs, time spent spraying dangerous pesticides, and illnesses due to pesticide poisoning.\"",
"There are very real risks however. Some non-target insects have been affected through loss of habitat.",
"Milkweed loss in agricultural fields because of herbicide use: effect on the monarch butterfly population",
"There is also the risk and the emergence of resistance.",
" Though, this isn't any different from other types of biotechnology, like antibiotics or antiretrovirals. ",
"Overall in my opinion, a very large benefit to the environment and the farmer and the consumer. There are very real risks, but thus far any negative impact has been minimal. "
] |
[
"Absence of evidence (in your comment) is not evidence of absence in the real world. Here are some I found with just a few minutes in Google Scholar, etc.:",
"Only one of those addresses safety, and that article is written by an author known for using misleading statistics",
"Multiple independent investigations including those conducted by the ",
"European Food Safety Agency",
" and ",
"Food Safety Agency of Australia and New Zealand",
" have found his results from 2007 to be the result of poor statistics, either due to incompetence or intentional deception.",
"Similarly, his 2009 paper was investigated and debunked as not representative of fact by the ",
"EFSA",
" and ",
"FSANZ",
". That is not even to mention what the FDA says about it...",
"The review uses these two papers as the basis for its flawed conclusion.",
"But we must look beyond the peer reviewed literature to get a full picture of the harm caused by GMO agriculture",
"That is not how science works...",
"The safety of currently used GM crops is far from clear.",
"Talk is cheap. Show me the peer reviewed science."
] |
[
"\"GMOs are totally safe\" ",
"Never said that.",
"I have said, that current evidence clearly supports safety.",
"But, as some of the peer reviewed links that I offer show, there is clear evidence that GMO crops are not safe based on a reasonable definition of \"safety\".",
"You haven't shown any such links.",
"This is the response of someone who is trapped in the 'logic' that anyone who opposes their agenda must be incompetent or a liar.",
"Did you read the links from the Eurpean Food Safety Agency or the Food Standards of Australia and New Zealand?",
"Of course not, because you don't care about the scientific method. You only care about your ideology.",
"Another article which references primary sources is",
"Then link the primary sources, instead of linking someone telling you what to think.",
"Also, should I even mention the irony of linking to Tom Philpott, an industry propagandist if there ever was one?",
"The Bt toxin showed up in 93 percent of pregnant women and 80 percent of their fetuses. It was also present in 69 percent of non-pregnant women in the study.",
"Further highlighting your complete ignorance of this subject.",
"If you actually read the scientific paper (which you didn't) and actually understood what they were measuring (which you don't), you would see that this is not a safety issue.",
"The paper took blood samples and was measuring peptide fragments, not full peptides. 5-10aa breakdown products of a protein. You could conduct that same study on any protein eaten by humans and find the exact same result.",
"Any reasonable person should be highly concerned about that",
"And any person who actually has an education in biology could see you are full of shit.",
"Everyone is free to judge the peer reviewed papers and credible sources I have supplied and compare ",
"Should be easy. You have yet to cite a single credible study that shows harm."
] |
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