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[
"What would happen if I built a transformer where the primary coil was copper and the secondary was antimatter copper?"
] |
[
false
] | null |
[
"Yes, the free charge carriers in the secondary would be positrons. The direction of the current is always the direction of motion of positive charge carrier, so it would behave as expected in both coils."
] |
[
"Ok that's cool. So it would be relatively easy to power antimatter electronics."
] |
[
"The problem is making a device out of antimatter that doesn’t immediately get destroyed by the surrounding matter."
] |
[
"What, How, and Why do I get a heavy, pressing feeling on my chest when I see people get hurt?"
] |
[
false
] |
I can't watch those YouTube "Fail" videos that have people hurting them selves without feeling an uncomfortable heavy feeling on my chest during the moment of impact. What is it? Why does it happen? And is there any explanation as to How I feel seemingly simultaneous pain as someone in a video?
|
[
"OK but what is the mechanism behind it?"
] |
[
"I'm gonna take a shot in the dark and say mirror neurons.\n",
"www.en.wikipedia.org/wiki/mirror_neurons",
"\nThe same reason a smile, yawn or laughter is contagious."
] |
[
"its called empathy. And its all in your head. Its a physical reaction to a stimulus. The stimulus being the visual input and the the reaction is your gut turning or heartbeat racing."
] |
[
"If gold, silver, and other heavy metals were created by supernovae, does that mean that Mars and Venus have a similar distribution of these ores that Earth does?"
] |
[
false
] | null |
[
"MY TIME HAS COME! I am a Geological Engineering Student and am currently studying for an exam on many common ore deposits! ",
"Interestingly enough, ore deposits are considered economic sources of minerals, what this means in the context of this discussion is that ore is not the only place you will find things like gold, silver, copper etc. it is just where you will find them in a concentration great enough to mine them.",
"Mars and Venus definitely do have minerals that would be nice to mine, but ore minerals and more specifically the geological setting and thus the form that the ore minerals appear in on earth are 99% caused by processes that are fairly unique to earth, ie. the large scale tectonics that form things like Volcanic Massive Sulphide deposits (Kidd Creek Mine) only occur on earth as far as we know. So if there are deposits of gold and silver that would be mineable on Mars and Venus, they would likely not appear in geological setting we are familiar with, BUT that doesn't meant that they don't have lots of gold and silver available, they just may not be in high enough concentrations to mine or detec properly ",
"Another part of the answer to this question is that space and the formation of planets doesn't guarantee an equal distribution of all the elements from a super nova explosion and plants thus have a different composition from one another. ",
"Unfortunately the sources I used to answer this question are protected from public distribution by my university so I can't provide a link. If anyone would like to see them, I could upload a PDF somewhere and link it that way. BUT here is the description of the course: ",
"GEOE 362 Resource Engineering",
"\nAn earth-system engineering perspective on the nature and acquisition of energy, mineral and water resources, with particular emphasis on the environment considerations in their extraction, processing, and use. Criteria for designing resource exploration programmes are examined. Practical exercises, projects and seminars (team and individual) deal with these issues, and include the design of risk-management plans, environmental life-cycle assessments, sustainable systems, and ore-reserve estimations. (0/0/12/18/12)",
"GEOL 362",
"\nCharacterization of major ore deposit types using petrological, geochemical and geophysical engineering sciences. Tectonic setting, age, rock composition, geometry, mineralogy and textures, geochemical and geophysical signatures. Metallogenic epochs and provinces. Design and evaluation of ore deposit models and exploration programs, including ore processing and environmental issues. Laboratory work integrates techniques of ore microscopy to determine paragenetic sequences, estimation of ore grade and evaluation of issues related to ore processing and site contamination. (0/9/0/31/14)",
"Sources: Sorry it's messy, I am not a pro formatter on reddit. ",
"My favorite source: ",
"http://gsc.nrcan.gc.ca/mindep/synth_dep/index_e.php",
"Sources I've used in class: ",
"\nBarnes, H. L. (1997). Geochemistry of hydrothermal ore deposits. John Wiley and Sons, Inc. 971 p. (ISBN 0-471-57144X)",
"Cooke, D. and Pongratz, J. (2002). Giant Ore Deposits: Characteristics, genesis and exploration. Codes Special Publication 4., 270 p.",
"Eckstrand, O.R., Sinclair, W.D., Thorpe, R.I. eds. (1996) Geology of Canadian Mineral Deposit Types. Geological Survey of Canada. Geology of Canada, n.8, 640 p. (ISBN 0-660-13136-6)",
"Edwards, R. and Atkinson, K. (1986). Ore Deposit Geology. Chapman and Hall edition, 466p. (ISBN 0-412-24690-2)",
"Evans, A., M. (1996) Ore geology and Industrial minerals: An introduction. Backwell Sciences Ltd., 3e edition. Great Britain, 389 p. (ISBN 0-632-02953-6)",
"Evans, A.M. (editor) (1995) Introduction to Mineral Exploration, Blackwell Sciences Ltd, Great Britain, 396 p. (ISBN 0-632-02427-5)",
"Goldfarb, R.J. and Nielsen, R.L. (editors) (2002) Integrated Methods for Discovery: Global Exploration in the Twenty-first Century, Society of Economic Geologists Special Publication Number 9, Littleton , Colorado, 382 p. (ISBN 1-887483-91-8)",
"Goldfellow, W. (2006). Mineral Deposits of Canada. Geological Association of Canada, Mineral Deposit Division, Special Publication n.5, 1068 p.",
"Guilbert, J.M. and Park, C.F, Jr. (1986) The Geology of Ore Deposits. W. H. Freeman and Company, USA, 985 p. (ISBN 0-7167-1456-6)",
"Hedenquist, J.W., Thompson, J. F.H., Goldfarb, R.J., Richards, J. (2005) Economic Geology One Hundredth Anniversary Volume 1905-2005, Society of Economic Geologists Inc, Littleton,Colorado",
"Kirkham, R.V., Sinclair, W.D., Thorpe, R.I, and Duke, J.M. (1993). Mineral Deposit Modeling. Geological Association of Canada Special Paper n. 40, 798 p. (ISBN= 0-919216-53-6)",
"Moon, C.J., Whateley, M.K.G., Evans, A.M. (2006) Introduction to Mineral Exploration. Blackwell Publishing Ltd., 481 p.",
"Pirajno, F. (1992). Hydrothermal Mineral Deposits: principles and fundamental concepts for the exploration geologists. Springer-Verlag, USA, 709 p. (ISBN 0-387-52517-3).",
"Roberts, R.G. and Sheahan, P. A. (eds.) (1988) Ore Deposit Models. Geoscience Canada, 194 p. (ISBN 0-919216-34-X)",
"Sinclair, A.J., and G.H. Blackwell, 2002, Applied mineral inventory estimation; Cambridge University Press, New York, 381p",
"Stone, J.G. and Dunn, P.G. (1998). Ore Reserve Estimates in the Real World. Society of Economic Geologists, Special Publication n. 3. 160 p.",
"Sheahan, P.A. and Cherry, M. E. (1993) Ore Deposits model, v. II, Geoscience Canada, 154 p. (ISBN= 0-919216-50-1).",
"Whiting, B.H., Hodgson, C.J., Mason, R. (1993) Giant Ore Deposits. Society of Economic Geologist, Special Publication n.2, 404 p.",
"\nCraig, J.R. and Vaughan, D. J. (1994). Ore microscopy and ore petrography. Wiley Interscience, 2nd edition, 434p (ISBN 0-471-55175-9)",
"Ineson, P. R. (1989). Introduction to practical ore microscopy, Longman earth sciences series, 181 p (ISBN 0-582-30140-8)",
"Jones, M.P. (1987) Applied Mineralogy: a quantitative approach. Edited by Graham and Trotman, London, 259 p (ISBN 0 86010 511 3)",
"Marshall, D., Anglin, C.D., Mumin, H. (Eds) (2004). Ore Mineral Atlas. Geological Association of Canada, Mineral Deposit Diviision , ISBN 0-8649-243-9 ",
"Picot, P. and Johan, A. (1982) Atlas of ore minerals. BRGM-Elsevier (ISBN 2-7159-0015-5)",
"Spry, P.G. and Gedlinske, B.L. (1987). Tables of determination of common opaque minerals. Economic Geology Publ. Cia. , 52p.",
":\nCanadian Mineralogist \nCIM Bulletim\nContributions to Mineralogy and Petrology\nEconomic Geology\nExploration and Mining Geology \nGAC and MAC Short Courses series\nGeology\nJournal of Geochemical Exploration\nJournal of Geophysical Exploration\nMineralogical Magazine\nMineralium Deposita\nOre Geology Reviews, SEG Reviews in Economic Geology and Special Publication series"
] |
[
"Yo, this is your TA speaking (Guess who!!! :P). Basically correct, good for you. ",
" Remember to include biogenic processes as well, they're important, and as far as we know unique to earth. Oxygenation of the atmosphere was also an important trigger for a lot of deposition.",
"Hope you did well on your lab exam! I'll be proctoring your final, btw. XD",
"EDIT: For folks who are interested in ore deposits at a bit more of a higher level, ",
"http://gsc.nrcan.gc.ca/mindep/index_e.php",
" is a good source (and Canada has a wide variety, so that's also good!). The sidebar has a lot of information; go to Deposit Synthesis if you like to learn more about different deposits. "
] |
[
"Hey, mining engineer here. A mineral is only considered an ore if it can be mined profitably. As reaching and mining other planets is prohibitively expensive, there is no ore on other planets. Yet."
] |
[
"If you pointed a powerful laser (like the ones the military are using to take down missiles) at a mirror would it burn through the mirror or bounce off it?"
] |
[
false
] | null |
[
"Well, even a really great mirror isn't 100% reflective, so it will always absorb some of the light. If you pump strong enough, yes, you'll start to heat up the mirror faster than it can dissipate the heat and eventually it will melt. ",
"Another thing to consider is that the reflectivity of a surface depends heavily on the wavelength of light. A mirror that might be reflective to visible light, say 99% reflective, might only be 5% reflective to infrared light. So if you were trying to build an anti-missile laser or a laser-proof missile hull, for example, you'd want to take that into account."
] |
[
"Another thing to consider is that the reflectivity of a surface depends heavily on the wavelength of light. A mirror that might be reflective to visible light, say 99% reflective, might only be 5% reflective to infrared light. So if you were trying to build an anti-missile laser or a laser-proof missile hull, for example, you'd want to take that into account.",
"Going a bit further with this, I work with lasers, and you have to select mirrors for not only the wavelength of light, but also the polarization (because the orientation of the electric field changes the reflected light properties). ",
"Breaking a mirror is all about power density. The mirrors used in powerful lasers are usually set up so that the beam is large in diameter when the power or energy is high. Then, the light is focused down and the intensity increases. If you were at the focus of a strong enough laser, there would probably be no mirror in existence that could survive. However, if you were not at the focus, the energy is distributed over a larger area, and the mirror could survive."
] |
[
"Both. If the laser is powerful enough, the energy absorbed by a metallic mirror will burn it, even as a huge amount of energy reflects.",
"In some laser experiments, prisms are used instead of metallic mirrors. They have an advantage of very little absorption (using total internal reflection), but lose about 4% of the energy to reflection when the light enters and leaves the prism."
] |
[
"Can light be caught in orbit?"
] |
[
false
] |
So relativity (or something) states that masses distort spacetime, which in turn allows light to be affected be gravitational fields, despite not having mass. Can light actually orbit a massive enough object? If a beam of light has a gravitational field is it possible for particles of light to orbit each other?
|
[
"If there's a black hole with a certain event horizon radius, there is a circular orbit for light at 1.5 times this radius. It's called the Photon Sphere."
] |
[
"Its mass."
] |
[
"Newtonian physics doesn't cut it, it comes from general relativity.",
"http://en.wikipedia.org/wiki/Photon_sphere"
] |
[
"Do the structures of animal and plant cells evolve over time?"
] |
[
false
] |
I can appreciate how features of animals change over time due to evolutionary mechanisms. Do features of cells that make up organisms change over time, and do they also alter due to similar evolutionary mechanisms at a microscopic level? For example, why did a cell wall form? Do we have an idea of what cells looked like millions of years ago? What will they look like in the future?
|
[
"IIRC, this is also believed to be the same story for chloroplasts in plant cells (or at least similar)."
] |
[
"IIRC, this is also believed to be the same story for chloroplasts in plant cells (or at least similar)."
] |
[
"Yes. In early life on Earth, the genetic material inside of cells was RNA. RNA has a simple single stranded structure and can self replicate (",
"http://www.sciencedaily.com/releases/2009/01/090109173205.htm",
") which made it perfect for basic life forms. The only problem with RNA is that it is a fairly unstable molecule for being the building block of life. So, over time, with modifications to both the nucleotide make-up and monomer structure (along with many other things), a modified form of RNA, known as DNA, was formed. DNA is double stranded and can self-check itself for errors making it a much more stable molecule than RNA. Here are some links if you're interested in the evolution of RNA: ",
"www.nature.com/ncomms/2013/131003/ncomms3494/full/ncomms3494.html",
"\n",
"www.ncbi.nlm.nih.gov/books/NBK6360/"
] |
[
"Looking to fund scientific research, not sure where to start."
] |
[
false
] |
[deleted]
|
[
"A good start",
".",
"It's hard to just give money away, though. You need to be a foundation, if I'm not mistaken. You could donate to a foundation with some stipulations. With that small amount, my recommendation would be for small grants/fellowships/stipends for up-and-coming PhD (or PhD/MD) students working specifically on this problem.",
"From the sounds of it, I'm not sure exactly which fields would study this. A cross between cognitive neuroscience, psychophysics and rat-neuroscience."
] |
[
"start a grant agency... that's how most of the science is financed by now.\nyou can specify general topic of research in your conditions and\napplicants will present their ideas about how they are going to spend your money. then you check their credentials, previous results and consider possible outcome (e.g. how you like their ideas) and with help of some wise people you can decide who do you give your money. plus you get report on how they were spent and you can sometimes even reclaim them if the conditions were not met and decide better next time.",
"just remember - research with no immediate potential outcome might be as important as the so called \"applied research\"... and it possibly needs your help even more."
] |
[
"Are you a researcher yourself or you'd life to fund someone elses venture into it?",
"If the latter, I'd check out your local university and asks around for professors who do neurology research and tell them you have funds which you'd like to apply to that subject. If they themselves aren't doing it, ask if they know any one who is or try contacting another university.",
"Oddly enough the wiki article speaks about the difficulties in research of palinopsia.",
"You could try a science foundation, NSF might be able to point you toward an appropriate group, but I just like universities because I'm biased. "
] |
[
"[URGENT] Can someone please tell me what could have possibly bitten me, as well as what I should do?"
] |
[
false
] | null |
[
"Ask a doctor. Reddit doesn't offer medical advice."
] |
[
"No hard feelings, just playing hall monitor."
] |
[
"It only hurts when I put pressure on it",
"Yeah that reminds me exactly of a mosquito bite. Not saying that it's from a mosquito necessarily (mosquito bites don't normally swell up THAT much), just saying it's probably not serious."
] |
[
"Why does the water in a lake or pond not absorb into the ground below? When I dig a hole and fill it with water, it is absorbed almost immediately."
] |
[
false
] | null |
[
"It does absorb (infiltrate) into the ground below, but at some point that soil is saturated. What stops the water from continuously going down is that there are different types of soil/rock and some are less permeable than others. It usually goes along the line of gravel -> sand -> clay -> rock. Below the permeable soil at some depth (depends on the location) there is usually a practically impermeable bedrock. The water 'pools' in the ground above those impermeable formations.",
"Since it can't go straight down any further, the water in the saturated soil flows downhill just like water on the surface. It looks for places with lower groundwater elevation (or a lower water table). In some cases those places of lower groundwater elevation will intersect with the ground surface and you'll have a spring where water flows downhill and out of the ground (sounds counter intuitive).",
"Here's a cartoon like diagram/animation that's pretty easy to follow",
". In this example you can substitute the river in the picture for a lake or other surface water body.",
"As you mentioned in your post, when you dig a hole and fill it with water, the water infiltrates. If you keep digging in most places you'll dig down to the water table like in the diagram above and you'll have a well.",
"You can find plenty more basic info at the wiki page for ",
"groundwater",
" or by googling some of the terms I used above. I'm happy to answer more questions if you have any.",
"Edit: forgot link"
] |
[
"If you dig a little hole, there's not much groundwater beneath it so any water seeps away quickly. But if you dig a big hole, you'll get down deep enough so the soil is already saturated and is unable to accept any more water.",
"My grandfather bought a farm in the 1950s, and had a government surveyor come out and dig a couple of tanks with a bulldozer. The surveyor surveyed the lay of the land and determined the best places for the tanks so they would get the most runoff. He dug them down about 10 feet deep I guess, and as long as there's enough rain, they keep water year round. They get dry during a prolonged drought, though."
] |
[
"Aside from the usual streams or rivers that feed into a lake or pond there is also ground water seepage into the water body. Also the composition of the benthos (ground) plays a significant factor into the absorption--think porous sandstone vs granite. Also, you're probably only digging a superficial hole that isn't reaching the bedrock. ",
"If you were to analyze the area around the ponds on topographic maps you'll likely find an area around the pond that declines in altitude that feeds into the body of water. "
] |
[
"What exactly makes a person dead?"
] |
[
false
] |
Why wouldn't it possible to bring back someone simply by pumping blood through their bodies? Can't we "restart" the brain?
|
[
"The medical practice has, over time, changed with regards to determination of death. At one time, heart was considered to be the determinant of life or death; now, the brain is. The question of what makes a person dead frequently comes up in the context of organ and tissue donation; see ",
"this summary",
" for some common questions and answers about this (including an overview of the heart death vs brain death issue).",
"To answer your two specific questions: you can't bring someone back by pumping blood through their bodies because what they need is a working brain, and shortly after your heart stops, your brain cells start dying. We currently have next to no ability to repair that type of damage to the brain."
] |
[
"Thank you, I'm just getting into this sub and you not shouting or getting mad really helps. I'll take note for next time! :)"
] |
[
"Your thoughts are factually incorrect. See my reply to the OP for details."
] |
[
"Why has there only been one Big Bang? Or, if there has been more than one, why can't we see any of the other universes?"
] |
[
false
] | null |
[
"The answer to both questions is that if another big bang occurred elsewhere, it's too far away from us to observe, and may be permanently so.",
"Specifically what I mean is that at the very early part of the universe, the universe underwent inflation. It rapidly expanded at a tremendous rate. When inflation ended, things kind of settled down into \"our\" universe. (or our bubble of the universe, or however you wish to define the thing on the whole). ",
"But it could be that inflation stopped at different times in different spaces of the universe. And even fractions of a second between those stops could mean incredibly vast distances given the rate of expansion at that time. So in this model, we occupy a bubble of universe defined by when our inflation ended, and how it ended (technical details beyond that point). Perhaps there are other regions of space that ended just before or after us and ended differently, but they're so far away that light will never reach us from there (due to the ongoing expansion of the universe between). ",
"So the whole thing is a neat... idea, but it's just that. We have no way to say one way or the other, and at the moment, it assumes that inflation can end in different times in different ways. Personally, I'd say that's an assumption unfounded on present data, so it's not a ",
" close-to-scientific description of the world. It could still be true, and that would get us into the philosophy of science that's another discussion."
] |
[
"I don't think many believe in the Big Crunch theory anymore, not since Hubbles initial observations showing presumptive acceleration of galaxies away from one another. This has been basically accepted now.. The further away a galaxy is, the faster it is moving away from us. Why this happens is not fully understood. "
] |
[
"There are plenty of theories in this area, but some scientists believe that the gravity in the universe will stop it's expansion and everything will come back in what's called the big crunch. If you believe this is true then we could be the first or the millionth universe to have existed. ",
"There are multiple theories in this area such as the heat death. I suggest Wikipedia as I find all of\n them very interesting",
"Edit: as to we can't see parallel universes, the accepted ideology is that it's in a different dimension. Not unlike how a square wouldn't be able to see your depth. If your interested in this I recommend reading Flatland by Edwin A Abbot. It really helped me imagine other dimensions"
] |
[
"When eyeballs are donated by an organ donor, does the left eyeball have to be put in the left eye socket of the new body, and vice versa?"
] |
[
false
] | null |
[
"As others have suggested, transplantation of complete, intact eyes is not done because it's not within our current capabilities to reattach all of the nerves.",
"Donor eyes are essentially \"parted out\" for structural elements like the cornea, which can be used to replace deficient parts in the patient's eye."
] |
[
"Not just corneas; sclera is also transplanted, either 1/4, 1/2, or whole globes are used.",
"Source: I work in organ and tissue donation."
] |
[
"Not just corneas; sclera is also transplanted, either 1/4, 1/2, or whole globes are used.",
"Source: I work in organ and tissue donation."
] |
[
"Today's Nobel prize in Physiology or Medicine is on the role of oxygen in cells. The description says the research is important in aiding injuries and understanding cancer. Can someone explain it in a little more detail? Is it also relevant to aerobic exercise?"
] |
[
false
] | null |
[
"William Kaelin, Peter Ratcliffe and Gregg Semenza also won the Lasker for this in 2016.",
"They've independently researched how cells detect and respond to hypoxic conditions. Hypoxia is a state where cells are deprived of oxygen and potentially die.",
"Semenza discovered a protein (HIF-1) which basically the cell uses to (indirectly) promote generation of red blood cell and growth of new blood vessels.",
"Ratcliffe discovered that how much HIF-1 is acting was dependent on oxygen.",
"Kaelin showed how kidney tumours use this mechanism to grow more blood vessels even though they don't need them.",
"Altogether, they uncovered the mechanism that all cells use to detect oxygen, and get more oxygen (in a body) if it looks like they won't have enough. For example, if you have a few cells in your leg that aren't receiving oxygen, they'll use this mechanism to encourage more blood vessel growth and stop that hypoxia.",
"However, if a cancer can mutate in such a way that this mechanism is defective, they can get an improved supply oxygen (from blood), even when they've grown so big they shouldn't be able to get all the oxygen.",
"I basically just summarised ",
"this article",
"31133-3?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0092867416311333%3Fshowall%3Dtrue) from Cell which sums it up well.",
"I don't think there would be any implications for aerobic exercise, at least as far as I can tell.",
"I believe Kaelin, Ratcliffe and Semenza actually made these discoveries in the 90s, and people are only starting to appreciate the significance of their work now."
] |
[
"The overexpression of HIF-1 alpha in cancers is important for a number of reasons.",
"HIF-1 alpha is a transcription factor that increases expression of metabolic enzymes that support aerobic glycolysis and the ",
"Warburg effect",
" .\nThis metabolic switch allows cells to survive in hypoxic conditions and there is good evidence that this switch to glycolysis promotes cancer cell survival in many other ways. ",
"Here",
" is an interesting paper on the role of glycolysis in fuelling calcium pumps. These roles may be important in dense solid tumours such as pancreatic ductal adenocarcinoma (PDAC), the most common form of pancreatic cancer. ",
"Other genes which are influenced by HIF-1 alpha include VEGF and erythropoietin which facilitate angiogenesis. Angiogenesis within the tumour mass can increase the likelihood of cancer cells entering the bloodstream and metastases forming."
] |
[
"And no, improper healing resulting in a cancerous cell is not profound enough. It is like messing up part of a software program that is still trying to run and duplicate itself anyway and it goes rampant. I can go in detail but please tell me that is not what happened. If that is the case give me like 3 days and I ready to win like 20 Nobel prizes you hacks. I love philosophy, you don't want I got. I eat all of science in my free time. Although cancer and evolution is a fun one, it opens the path to some very deliciously dark jokes."
] |
[
"Restoration and Preservation of Very Old Books"
] |
[
false
] |
I just saw an episode of 60 Minutes where they visit the Vatican Library, and they got to see some incredibly old texts, some 600 years old or more. They also showed the restoration area where they work to preserve old texts. NO ONE was wearing gloves to protect these incredibly old books!! Not the librarians, not the reporter they let touch the books, not even the restorers. Are they out of their minds???
|
[
"Old books are likely to have a vellum book block, so the contact is skin-to-skin. Gloves introduce the possibility of of their harboring undetected moisture or contaminants. "
] |
[
"Thats an incredibly well thought out reply, thank you. ",
"In the report they didn't give a sense for how frequently they handled the books but they seemed eager to show them. I got the impression that they might like to show them off more than a few times per century.",
"I'm also still horrified that they let the journalist touch the pages. Speaking as a scientist, no one but someone who I've trained is allowed to handle my samples or my instruments. I can't imagine letting some schmuck handle an irreplacable treasure."
] |
[
"Thats an incredibly well thought out reply, thank you. ",
"In the report they didn't give a sense for how frequently they handled the books but they seemed eager to show them. I got the impression that they might like to show them off more than a few times per century.",
"I'm also still horrified that they let the journalist touch the pages. Speaking as a scientist, no one but someone who I've trained is allowed to handle my samples or my instruments. I can't imagine letting some schmuck handle an irreplacable treasure."
] |
[
"Someone I know is convinced Dinosaurs and Humans existed at the same time, I would like some info on the subject if it's not too much to ask. =)"
] |
[
false
] | null |
[
"See your other thread. Please do not double post."
] |
[
"Yeah well my first post got downvoted, I assume because someone thought I was the one believing it and they had some agenda to fill. "
] |
[
"Google \"carbon 14 dating,\" the \"fossil record,\" and \"James Hutton,\" to start. There is no evidence that dinosaurs and humans existed at the same time, because they did not. Present the evidence in a way that is relatable to your friend."
] |
[
"What would the effects be of receding coastal waterlines on soil fertility?"
] |
[
false
] |
Full disclosure: This is for a D&D campaign and I just want to have some sense of verisimilitude in the setting. Imagine we have some sort of geological event which results in the water level plummeting, say, six feet over 50 years. My interest is specifically in soil fertility in ocean shorelines. It's not clear to me how the salt content of the water would contribute to soil fertility. In freshwater areas, I'd assume the exposed lakebed would be a very good growing medium, but would a seabed be too salty to grow anything? Thanks!
|
[
"Obviously the revealed dry land would be salty. This would decrease depending on the amount of rainfall. Some desert regions have virtually no rain. So the salt would never leach away. ",
"But in high rainfall regions the soil would become fertile. ",
"Sometimes the limiting factor for irrigating crops is the amount of salt left behind when the irrigation water evaporates. Cropland must be rinsed with excess water to remain productive."
] |
[
"Answer depends on local topography.",
"There are examples such as the Netherlands, where roughly 20% of the country is reclaimed from the ocean.",
"Under the sand at your beach can be anything. In some locations such as the LA Basin, what's under the sand is fine sediment from geographical erosion of the mountains. That's pretty good for agriculture. However, other coastlines are sitting on rocks, compressed limestone, bed rock etc which aren't so good for agriculture.",
"Let's say you find an area that isn't just rocks, but what's under the sand is useful soil. Reclaiming that to a useful form doesn't have to take centuries. It's possible to create useful farmland in only a few decades. ",
"First crops are likely to be salt tolerant grasses for grazing animals. Second is forestry products, which can be a simple as firewood for fuel.",
"It will take much longer to get the soil suitable for vegetables or broad acre crops like grains. It requires a sufficient build up of topsoil combined with rainfall/river flow reducing the salt.",
"The bad side of dry or shrinking lake beds is high salinity and/or unproductive clay soils in the immediate area. There are examples where the surrounding area and high salinity is quite toxic to human health, such as the inland Salton Sea (USA) or Aral Sea (central Asia).",
"Easiest local geography to convert to high yield agriculture is near rivers and swamps. Next is high rainfall areas. At the least likely/worst local geography is low rainfall areas which may never support agriculture."
] |
[
"Hey, this is very late, but thank you for the excellent breakdown! I appreciate all the information. It will be very useful for my purposes."
] |
[
"Why aren't watercraft designed to be flexible like fish?"
] |
[
false
] |
I originally posted this question in askreddit and got a whole bunch of nonsense replies but I am extremely curious about this and would love an educated response. From what I've read, Vikings would build linear flex into their Dragonships which enabled them to easily ride over waves. I've searched extensively and I can't find a single example of lateral flex being built into a boat but in my mind it would greatly enhance turning while providing extra stability and possibly could be used for propulsion. Am I wrong? All comments are appreciated, thanks!
|
[
"Because fish are incredibly complex and boats are not.",
"Fish have thousands of muscles which are all delicately and intricately connected in ways that would boggle an engineering team's mind were they to try and reproduce them.",
"That being said we live in an age where you can almost gaurentee sombody is working on something similar. Look up ",
"Nitinol wire",
" and you being to see the potential for artificial muscle."
] |
[
"A lot has to do with the complexity involved in adding a flexible materials. Most ships are built primarily out of steel, if a flexible member was added that would also add a joint. Where two different materials met will have a set of complication that have to be thought out. E.G. The thermal rate of expansion is different which causes the seem to tear apart because one material expands farther than the other. Another complication is how are you going to bind the two materials together? Does welding work? How about riveting or some sort of adhesive. Now extra test have to be run to ensure the binding will last. ",
"Now you may ask, why not just use only a flexible material? Well then you reach the area of tradeoffs between strength and ductility. The more ductile or flexible it is the \"weaker\" it becomes. Meaning it won't be able to support as much. Yes it won't fracture as easily, but it won't be able to hold someone up very easily either. Try standing up in one of those bouncy castle for an extreme example. ",
"Now its not to say the idea is not feasible, but just not very cost effective. All these sorts of flex joints would take new testing and designs which would take a considerable investment. Then another question would be how much benefit would the new ships get from this design? Would it justify the cost? ",
"If you can think of a good way to tackle some of those issues then you might be able to make the concept work. "
] |
[
"First of all, \"flexible like a fish\" is ",
" flexible, to the point of a vessel not being usable any more. Remember, a fish contains mostly muscle which is needed to maintain some shape. If you ever picked up a dead/unconscious fish or animal of any sort (so, one that does not actively maintain shape) you know what I mean. The same would be necessary for a \"flexible as a fish\" ship. You would need huge actuators to shift or maintain shape. These would take up pretty much all of the interior and a huge amount of energy, so the whole point of having that ship would be lost in the first place. You don't need a tanker if you can't fill it with tanks because you need to fill it with \"muscles\".",
"But your Viking ship example makes me think you don't really mean \"flexible like a fish\" but rather \"flexible like a Viking ship\", i.e. to a limited degree, and passive flex instead of active flex?",
"The thing is, the Vikings would have built a lot stiffer boats if they could have done so.",
"For sailing ships, any flex in the hull (or rigging, for that matter) is generally undesirable. Every time the boat flexes in a gust of wind, part of that gust's energy is converted into mechanical energy that gets converted into heat. The energy of the wind makes the boat flex, not go faster. Not good. A similar thing happens when you crash into a wave and flex the hull: you lose some of your propulsion energy to wobble your hull. That is why ",
" modern racing boats (ie the most efficient ones) are built as stiff as humanly possible.",
"The reason why Viking ships (and all other older ships) were very elastic is because the build materials and methods did not allow stiffer ships. Vikings were amazing boat builders for what we know, but with solid wood and iron nails you can only achieve so much high tech, really.",
"The other reason why flexible ships are a downright bad idea is the fact that if a fish changes shape, it does not matter. But imagine your average cruise liner meandered around like that. Your cabin would change shape every few seconds, and doors would only open when ",
" want. Imagine a super tanker with a hull that can be squeezed so the oil squirts out. Imagine a container ship full of square boxes with an irregular shape. Does. Not. Work.",
"edit: I can't grammar...",
"edit 2: a short comment about what you read about \"ships flexing so they can easily ride over waves\". Even the wobbliest viking ship would not have bent so much as to follow the contours of the wave. That is just not possible (mechanically), we are talking about a few inches of flexing over a 20 to 25m long boat here. Still a long way from \"wave shaped\", so whoever told you that misunderstood something ",
"."
] |
[
"Pangaea: How did all the continents end up all crammed together in the first place?"
] |
[
false
] |
It seems really weird to me that all the above‐water landmasses would start out all clustered together on the same side of the planet, instead of more‐or‐less randomly distributed across the earth's like they are now (except, you know, a different more‐or‐less random distribution, presumably). How did they get that way?
|
[
"Well, let’s start at the beginning (of Earth’s history) with probably the least obvious aspect to this whole story - when Earth had accreted and differentiated into a planet with a core, mantle and crust (by about 4.50 billion years ago, probably a smidge before), ",
". ",
"In fact, the original crust was just a cooled version of the (then primitive) mantle, also being fairly uniform in elevation across the world. Today, we have a mantle with a slightly different chemical composition than back then, the main difference being that it is depleted in certain elements because partial melting processes have gradually formed the kinds of crust we have today. Both oceanic crust and continental crust are compositionally different from the mantle - they are more chemically evolved, particularly continental crust which is the result of a higher degree of fractionation. ",
"But let’s not get carried away. Its 4.4 billion years ago and we have a fully formed differentiated planet, Theia has already crashed into the proto-Earth and we now have the Earth and Moon. Volatiles from within the Earth have outgassed and contributed to the oceans and atmosphere. Further water gets delivered to Earth by icy asteroids during the Late Heavy Bombardment. ",
"The interior of the Earth is very hot, and space is very cold. This temperature differential means that the crust is cool and rigid and it fractured in places. Some of these places turn into ",
"spreading ridges",
", where the more fluid (but still solid) mantle below can rise close to the surface, melt due to decompression, and form basalt rock, like the oceanic crust we have today. ",
"So where do continents come in? All that water we mentioned earlier is a key ingredient in the processes at ",
"subduction zones",
", which came some time after spreading ridges, though we’re not exactly sure when. Basically, they sort of close the loop for crust recycling, as this is where oceanic crust returns to the Earth’s mantle. But all that water allows something else - subduction zones are also sites of more crustal production. Water from hydrated oceanic crust makes its way down into the mantle, gets driven off into the overlying mantle wedge, and lowers the melting temperature so that this region of mantle can now partially melt. ",
"Several rounds of this start to produce more chemically evolved crust, that’s right - continental crust. This type of crust is less dense and more buoyant than the basalt produced at spreading ridges, and so it ‘floats’ higher in the mantle than oceanic crust. Buildup of this crust at subduction zones leads to continents; back in the Archean there was a faster production rate for the stable continental interiors often called shields or cratons, than rates of continental crust production today. ",
"Its time to mention another aspect of our now globally recycling plate tectonic system that isn’t immediately obvious: ",
" There are minor exceptions to this rule, though in general, continental crust doesn’t tend to ",
" subducted of kt does get taken down into the mantle at a subduction zone. ",
"What does this mean for the big picture? Well, we have oceanic crust being produced at spreading ridges at a much greater rate than continental crust; and it sort of chugs along like a big conveyor belt underlying the oceans until it reaches a subduction zone where down it goes. This is why we don’t have any oceanic crust older than 300 million years around today, and most is 200 million years old or younger. Continental crust on the other hand, this stuff effectively gets jostled around and repositioned as oceanic crust rejigs the whole picture. The continents slowly grow in size over Earth history and get deformed and weathered away at the edges, continental shelves submerging and re-emerging with the changing volume of water in the ocean basins (ice age = less liquid water to flood the edges of continents), but all in all, the continents remain present. It’s only a matter of time before they come together where oceans between them are subducted. ",
"When this happens in the right way so that all the continental landmasses are pretty much united, we get a supercontinent. Pangea was not the first supercontinent to exist, but only the most recent. This is why we hear so much about it compared to its predecessors - because it’s easier to reconstruct the more recent past. Remember the Earth is about 4.5 billion years old, well Pangea existed from about 0.335 to 0.175 billion years ago - this is completely within the most recent 8% of our planet’s long history."
] |
[
"Thanks. That was very detailed."
] |
[
"I don't think they ",
" all clustered together, but I'm not sure how far back in time geologists can extrapolate. But given that tectonic plates are always moving and they have a a finite surface to move around on, it makes sense that sometimes the continental plates would all be together and other times they would be spread out."
] |
[
"Do Gases experience viscosity?"
] |
[
false
] |
In my chemistry classes we discussed Intermolecular forces and how those effect states of matter. We were told that Intermolecular forces affect viscosity as well. I understand that gases are fast moving therefore have weak IMF. If I was to create a pressurized chamber of a gas so it was condensed and then open the valve would the gas experience viscosity?
|
[
"Yes, ",
"gases have viscosity",
"."
] |
[
"Thank you. "
] |
[
"and the colder they are, the more viscous the are...an aircraft has more lift on a cold day and aerodynamic drag is caused in part by friction induced viscosity. ",
"And if you look at shooting stars, it is due to heat generated friction relating to the viscosity of the gasses."
] |
[
"How can scientists Map our sun?"
] |
[
false
] |
I was reading an article this morning about the solar storm we may experience today as a result of Solar flares. It explained that one of the solar flares happened at "an active region on the Sun known as 1429". That got me thinking...if the sun is just a big molten mass of plasma, how can we map it? How would we know if one sun spot has moved to another place on the sun while the core perhaps rotated differently? Anyhow, just thought I'd ask. Here's a link to the article in case you want to read it yourself. Sorry I can't hyperlink, I'm on my phone.
|
[
"The sun is actually a plasma not a liquid. There is a strong magnetic topology to the sun, which does not vary freely and erratically. The fact that it's a plasma is important because plasmas are generally constrained to move along magnetic field lines. Charged particles feel a force perpendicular to the magnetic fields, so it's hard for them to travel across field lines. Just like the earth, the sun has a magnetic north pole and a south pole. And just like the earth, it has regions where the magnetic field varies from what you'd expect from a simple bar magnet. And lastly, just like the earth, the gross structure of the magnetic field changes over a large time scale. So you can see that we can map out the sun the same way that we can make a magnetic map of the earth.",
"When you see the solar flare occurring, what you're actually seeing is a local bulge of magnetic field lines, and then a sharp breaking event that expels particles. This process is called magnetic reconnection and is a very hot topic in plasma physics. "
] |
[
"It first might help to consider what a sunspot really is. The surface that we see in optical wavelengths of light shows intense and ",
"\"small scale\"",
" convection features called ",
"granulation",
". Sunspots are really regions that are cooler than the surrounding material because surface convection has slowed down, making them appear darker. They're separate from the core of the sun, which rotates faster than the surface anyways.",
"At the surface the sun takes roughly 25 days to rotate once on its axis, and sunspots persist over many days/weeks. There are a cadre of satellites and telescopes on the ground that do nothing but monitor the sun, so now it's quite easy to see a sunspot develop and transit the face of the sun.",
"Large groups of sunspots are given a 4 digit sequential number after they're observed by more than one observatory, and they've been counting since 1972. ",
"The count rolled over 9999 sometime in 2002.",
"Even though it is sometimes featureless in optical wavelengths, ",
"the sun is quite dynamic in almost every other bandpass imaginable.",
" It's easy to watch the sun rotate and say with confidence that you're always watching the same spot or active region.",
"Additionally, there are two satellites called STEREO that watch the sun from two different angles. ",
"Combined with the Earth's view, we have really good coverage over most of the surface of the sun."
] |
[
"I guess what I'm asking is, If the entire surface of the sun is liquid, it must move around freely and irratically. Wouldn't that make it impossible to systematically map out the sun?"
] |
[
"Why it's 0^0 indeterminate?"
] |
[
false
] |
[deleted]
|
[
"Because the function ",
" has different limits as ",
", ",
" → 0, depending on how you take the limit. For example, if you let ",
" = 0 and ",
" → 0 you will get zero, because zero raised to a positive power is zero. But if you let ",
" = 0 and ",
" → 0 you get one, because anything nonzero raised to the power zero is one. For the limit to exist, it has to be independent of such choices.",
"For various reasons it is convenient to choose the latter limit as a convention, which is to say to ",
" 0",
" to be equal to 1. In many applications it turns out that the base is a continuous variable but the exponent is typically restricted to integers, which makes the former limiting case (where ",
" varies) kind of pointless."
] |
[
"Haha ...\"an easy exercise for the reader\". I can't be the only mathematician here that feels the knife to the gut every time it shows up in a textbook. "
] |
[
"Haha ...\"an easy exercise for the reader\". I can't be the only mathematician here that feels the knife to the gut every time it shows up in a textbook. "
] |
[
"Does regular exercise really make you more happy?"
] |
[
false
] |
I have recently read an article that states that 30 minutes af exercise three times a week increase serotonin levels and therefore make a person happier. The article even stated that regular exercise had the same effect as antidepressants. Is this true? and why would 1) regular exercise increase serotonin levels and 2) why would that make a person happier?
|
[
"Additionally, exercise has been shown to raise levels of endogenous cannabinoid compounds in your body. Cannabinoids are the chemicals found in marijuana that contribute to the \"high\" feeling that the drug gives you, and while I'm not sure of their exact mechanism of action in the brain, I'd expect a regular exerciser to have more of them. Some have hypothesized that this natural rewards-for-running system helped encourage humans and their ancestors to become such good distance runners and ensured the survival of our species to this point.\nBut it goes beyond the purely chemical explanations as well--people who exercise regularly are used to doing things that are difficult, they're used to pushing themselves and proving to themselves, on a regular basis, that they can conquer challenges and deal with adversity through willpower, and I'd expect those people to have, on average, a better self-image and higher confidence (both of which contribute to \"happiness\") than those who don't."
] |
[
"Exercise and forced physical labor are not quite the same."
] |
[
"Exercise and forced physical labor are not quite the same."
] |
[
"Can someone explain the difference between triplet oxygen and singlet oxygen?"
] |
[
false
] |
[deleted]
|
[
"The one opportunity for my user name to be relevant.... ",
"I feel I should add something though. ",
"Generating singlet oxygen is more difficult than simply exciting the electron using a photon, as the transition from triplet to singlet state is forbidden (excitation of electronic states is generally achieved through absorption of light). Instead, an intermediary is needed, called a photosensitizer. This absorbs photons, and becomes energetically excited. In this excited state the photosensitizer can transfer energy to the oxygen to generate the singlet state. It is also possible to generate singlet oxygen chemically through the decomposition of hydrogen peroxide with a catalyst. From personal experience I found this is more difficult and more time consuming.",
"Generating the singlet state is useful for a few applications. Singlet oxygen can be be used in chemical reactions in some pretty unique ways to produce chemicals which are either not possible or very difficult to make through normal chemical synthesis. Singlet oxygen is also useful for photodynamic therapy for killing off cancer cells. The photosensitizer is applied specifically to the cancer cells, then light is shone on the area. The singlet oxygen, which kills cells in high enough concentrations, is only generated where the sensitizer is present.",
"The use of singlet oxygen is part of a wider area of chemistry known as photochemistry, which uses light to drive chemical reactions rather than heat, this can have several benefits. Photosynthesis is probably the most obvious example of a photochemical reaction. I will point out that the range of photochemical reactions available in the chemists toolkit is pretty small (including the use of singlet oxygen), so thermal routes will always be more common. "
] |
[
"The diagrams they use are Molecular Orbital diagrams. They display the bonding interactions between the respective orbitals on each species. In short: Molecular Orbital theory pairs the interacting s, p, d, and f orbitals, taking into account orbital symmetries for overlap. Since this is an easy example where both species are the same (dioxygen), all orbitals are symmetrical between s-s and p-p interactions. What we're really looking at is the p-orbital interactions as they are the ones involved in reactivity here. Dioxygen (O2) is a double bond species, which is constituted of one sigma- and one pi-interaction. The p-orbitals contribute each of these: the 3 p-orbitals are px, py and pz, which are all orthogonal to each other (think of the 3D Cartesian axes). The sigma interaction comes from px, and the pi comes from the py and pz (which is why there are two degenerate orbitals for pi). From electron counting, you fill the orbitals with the total number of electrons, pairing from bottom-up, using Pauli's Exclusion Principle and Hund's Rule. Using these same principles explains why a singlet oxygen would be more energetic and therefore more reactive as an unstable species. ",
"We see that triplet oxygen has two unpaired electrons in the antibonding highest occupied molecular orbital (HOMO). Singlet oxygen may or may not have unpaired electrons in the HOMO, but it is defined by having the HOMO electrons in opposite spin (in which case, they are likely to pair and occupy one orbital instead of two) - whereas you see Triplet Oxygen has same spin in the HOMO. This pairing of opposite-spin electrons in singlet oxygen may be what is referred to as the \"same quantum state as most molecules.\"",
"-secret chemist"
] |
[
"Hey. My old adviser would be disappointed that I had to look this up but it's been a while. For a better explanation than wikipedia check: ",
"http://www.healthcare.uiowa.edu/corefacilities/esr/education/2001/1/zhaol-paper1.pdf",
" (no connection at all to me, just cleaner than wikipedia)\nFrom what I can see here and remember, electrons fill orbitals first one per orbital (at a given energy) in the +1/2 spin state, then when those are filled they go back and fill the other 'half' of each orbital with -1/2 spin electrons. This makes the +1/2 spin a lower energy state than a -1/2 spin. The difference between a +1/2 spin and a -1/2 spin in an oxygen molecule is 37 kcal/mol. This energy can be dumped into another molecule to push an electron into an excited state in which it may undergo irreversible chemistry. \nSorry, my quantum mechanics isn't as strong as it should be. Hope this helps a little."
] |
[
"What are some strange things that happen under EXTREME magnetic fields?"
] |
[
false
] |
I was reading about the magnetar SGR 1806-20, which has a magnetic field of 10 Gauss (10 Tesla in intensity) . The article said that if this magnetar were as close as the moon to Earth, it could re-arrange the molecules in your body. What are some other wacky quantum and macroscopic things that happen under these most powerful magnetic fields in the universe? What could happen under even greater strength fields?
|
[
"Many of the things you don't usually consider to be magnetic are actually diamagnetic, which means that any magnetic field will repel them. This effect is usually very weak, but water and graphite are diamagnetic among other things. A sufficiently strong magnetic field would have a repulsive effect on these things. You don't need anywhere near the strength of a magnetar to see these effects though; bismuth is a strong enough diamagnet that it can float suspended between two magnets, and we have electromagnets on earth strong enough to levitate frogs."
] |
[
"Magnetic fields follow an inverse cube law, meaning if you get twice as far away they will be eight times weaker. Even if you have a very powerful magnet, you don't have to move very far away before the field is basically gone. These kinds of fields are usually produced with large machines in a configuration called a Bitter electromagnet. The magnetic field it produces is usually only in a small designated area and an operator would be far enough way that the field would be quite weak. I think you could safely stick your hand in any continuous magnetic field we can produce on Earth as even the strongest is only around 11x more powerful than an MRI machine. Some animals can sense magnetic fields for nagivation and may get disoriented."
] |
[
"Does a powerful electromagnetic field have any measurable biological effect on living organisms; the frogs for example?\nIf so, what kind of precautions shield operators from theoretical magnetic force fields? "
] |
[
"Why are human brains more able to reproduce visual and auditory experiences, but not taste, touch, or smell?"
] |
[
false
] |
The mind is capable of reproducing sensory experiences that it has encountered in the past, such as a music, movie scenes, symbols, or heat. So why is it that when a person thinks about a song or visualizes an object, the mind can reproduce it with great clarity, but when trying to reproduce say a smell, the sensation is more akin to a memory than an actual sensation. I was simply wondering if anyone had a possible neurological explanation for this phenomenon. Does it have to do with the fact that sight and sound are more often used than taste or smell?
|
[
"I'm not sure about everyone else, but I remember tastes, touches, and smells with approximately the same intensity that I remember visual or aural stimuli.",
"Maybe its just harder to put these sensations into words? Its pretty easy to state the lyrics of a song, but harder to describe the bubbly sensation of soda. "
] |
[
"I'm not on my personnal computer but olfactory memory exists in humans. Tast and smell can be remembered and imagined. I don't have access to my databse of articles but here's a ",
"review on the subject",
". I also invite you to read the following ",
"abstract",
" which I think discribes well why we have more difficulties discrbing a smell/taste vs. a sound or a perception.\nI'll try to elaborate more when I get home."
] |
[
"I think that it’s easier to remember because it's easier to narrativize visual and auditory phenomena. It’s just easier to remember stuff when you can make a story out of it. If you were to look at events in isolation, I think most of the advantage would disappear. I, for one, don’t think that there is any significant difference in my recall of a rainbow versus the smell of roses, or the sound of someone’s voice versus the feeling of an ice cube on my skin.",
"If there is a difference, it would likely be because we rely on sight and hearing so much more than the other senses to make our way through the world."
] |
[
"Questions about the first episode of \"Curiosity\" with Steven Hawking."
] |
[
false
] |
Hello everyone! I had a few questions about some of the subject matter in the show and they're pretty specific so a google search didn't really help much. At some point in the show the narrator brings up the point that, at least at the sub-atomic level, it's possible for particles to simply spring into existence for short periods of time. From there the point is made that the universe was, at one point, smaller than a Proton, which allows for the universe to "pop" into existence without violating any natural laws. The first question I have is what exactly is meant by particles "appearing" from nothing. Does that mean that the particles literally create themselves, or were they just not visible to us before and then suddenly spring into the spectrum of our vision? If they do literally create themselves then do we have any clue to how they are able to do so? Also, in the event they don't "create" themselves and they simply pop in and out of our visible spectrum does this mean that they have always existed? My second question involves how these spontaneous appearances lead to a "big bang"? I understand that particles can appear spontaneously, but why would the result of their appearance cause an expansion of such proportions? Technically, we have particles "appearing" all the time at the sub-atomic level, but they don't expand after they appear, they simply dissipate, correct? Was there unique properties in the "first" particle that appeared to cause an expansion? Also, just pure speculation here, but would this be where the idea of a multi-verse came from? The realization that at one time the universe appeared spontaneously on the sub-atomic level, which means that the same event could possibly still be occurring, spawning an infinite number of universes? My last question deals with time. I've always thought of time as a man made construct, but on the other hand I realize that even before man invented the idea of keeping track of time the days still passed with the sun rising and setting every day. This means time exists in a way that is independent from human interaction. However, in the black hole example used in the show they say that if a clock were to be pulled into a black hole it would actually slow down until it finally stops. This either seems really weird to me, or maybe it's simply a bad way to illustrate the point they were trying to make? Would the mechanical mechanisms inside the clock that record a change in time actually slow down upon entering the black hole? If so why would this happen, and if not then I'm obviously grasping the concept of "time" in the wrong way and would appreciate it if anyone could clear up my understanding. In closing I'd just like to thank anyone reading/responding to these questions. I appreciate any insight this community has on the questions, even if currently I'm only capable of understanding a laymans example of what's going on. My current field of study is computer science so I'm a little ways away from my comfort zone asking questions in the field of cosmology. However, after watching this program my "Curiosity" (pun intended :P) really has seemed to have got the best of me and I'm interested in understanding a bit more about the universe, how it works, and how it came to be. With that being said, again thank you for your responses, and also feel free to point out if any of the questions I'm asking don't make sense, aren't relevant, ect. I understand that my ignorance level for this particular field is astoundingly high.
|
[
"The first question I have is what exactly is meant by particles \"appearing\" from nothing. ",
"Particles are states of a field; there's one field for each type of particle. It's possible for a field to jump from its ground state (no particles present at that place) to an excited state (one particle present). That's how, for example, a neutron can decay into a weak boson. Weak bosons are ",
" meaning they have a lot more energy than the neutron can spare. But the weak boson can pop into existence anyway, as long as it decays into an electron-antineutrino pair in a short amount of time. If you want that intermediate boson to stay around, you have to ",
" enough energy into the system for the boson to exist.",
"My second question involves how these spontaneous appearances lead to a \"big bang\"?",
"They don't. Or rather, only quite indirectly. That was probably explained poorly on television — or more likely, just explained ",
" What's applicable here is the idea of ",
" which is really quite a different concept. The idea is that a field can exist in a particular ",
" state for indefinite time, a row of dominoes all balanced on their ends. Left unperturbed, the field will stay that way forever. But it only takes a very tiny perturbation to \"nudge\" the field into a lower-energy state at one point. Once that happens, the change of state radiates outward, just like dominoes knocking each other over.",
"…the same event could possibly still be occurring, spawning an infinite number of universes?",
"Oh heavens no. It's not like that at all.",
"I've always thought of time as a man made construct…",
"It isn't, any more than space is. You can say that ",
" are manmade, but you can also say the same thing about rulers.",
"…something something black hole…",
"Don't worry too much about the details there. Everybody seems to want to use black holes to describe gravitational time dilation, but they shouldn't, because it just overcomplicates things. A clock closer to a source of gravitation will tick more slowly than a clock farther from that source of gravitation. That's all. Nothing weird about it, really."
] |
[
"...what is this supposed to mean?"
] |
[
"Thank you very much for taking the time to respond.",
"You were definitely able to clear some things up, even if at this point I'm not capable of understanding the \"nitty gritty\". You did an excellent job explaining things without without really needing to go there."
] |
[
"Can the human body endure the vacuum of space (given a continuous supply of oxygen)?"
] |
[
false
] | null |
[
"No, ",
" You need a pressurized suit around your body to protect it, not just a scuba tank. ",
"The area around your whole body has to be pressurized for you to breathe properly, so a pressurized tank of air wouldn't work very well. Even if that weren't a problem you would continuously lose moisture as the water from your mucous membranes boiled off into the vacuum. ",
"Finally, when the area around your body isn't pressurized, water vapor bubbles would begin to form causing your body to swell, eventually lead to internal bleeding, and disrupt vital mechanisms in your body. ",
"Here's",
" where I drew the information from and it offers more examples and references. ",
"EDIT: I don't mean to imply that you would die instantly. As my link says (and OP pointed out) you can be exposed to a vacuum for three minutes with relatively minor injury. But 'surviving', as in extended amounts of time unprotected in space, you won't live. ",
"EDIT 2: I did sound really harsh -_-"
] |
[
"I think you came off as a little harsh, our body can endure the vacuum depending on what his question originally was... Which is for how long.",
"I know you posted an example which reading it looks great. However it would be possible, and tests showed that a human can at least survive up to 90 seconds in that type of vacuum. Not a long time, but if there were no suits and my ship was about to explode, and I needed to jump 30 meters to another ship and we only had oxygen tanks.... I'm taking my chances.",
"Actually now that I think about it... Do you have any idea how long a decently sealed mask would hold in the vacuum? Even if it was for 20 seconds, that's enough for my jump."
] |
[
"Oh, I didn't mean to imply that death would be instant or anything. But a human certainly can't 'survive' in a vacuum. Surviving to me implies...I don't know...extended orgy session ",
". ",
"I would totally do a space jump if my craft was on fire or otherwise compromised. "
] |
[
"Why do people feel tired when they overeat?"
] |
[
false
] |
[deleted]
|
[
"Post-prandial somnolence. I know what it's called because I get it good. I dont know the why behind though I am sorry. "
] |
[
"Here's the wiki on ",
"Post-prandial somnolence",
". Seems there are four possible mechanism with either a endocrine (insulin) or neurological source.",
"Good that someone knows the term for it, I always just assumed it had something to do with blood flow to the brain and it is saying that is just a myth. Sometimes it's just a matter of knowing the right terminology and googling/wikiing it, then letting ",
"r/askscience",
" tell you if the results are BS or not! =D"
] |
[
"Insulin",
", baby! Insulin is released when our food is digested and glucose (which is found in pretty much anything carb-y) makes the rounds in our bloodstream. I'm not an expert on what insulin does, but suffice it to say that glucose levels in the bloodstream drop after insulin does its thing.",
"What does glucose have to do with mental fatigue? That's the interesting part! Our ability to ",
"exercise self-control",
" and ",
"engage in mental effort",
" declines as glucose levels drop. After all, the brain is one of the most metabolically expensive parts of the body. The low glucose levels manifest as a feeling of mental fatigue or exhaustion. "
] |
[
"Do different animals see different sized rainbows?"
] |
[
false
] |
We see a rainbow as a spectrum of colour formed by the relative angles of light reflection within drops of water. For those animals that can see different ranges of light (infrared or ultraviolet), am I correct in thinking that their rainbow would be skinnier/fatter and positioned slightly differently? Are there any animals that see both infrared AND ultraviolet, and therefore can see a considerably wider rainbow than we can?
|
[
"We see a rainbow as a spectrum of colour formed by the relative angles of light reflection within drops of water. For those animals that can see different ranges of light (infrared or ultraviolet), am I correct in thinking that their rainbow would be skinnier/fatter and positioned slightly differently? ",
"Yes, if you can't see red (mice), the rainbow would look skinnier. If you could see infrared, then the rainbow would be thicker on that side of the rainbow. ",
"You probably want to read up on ",
"a shrimp",
" that can detect light with 12 color pigments compared to our 3. ",
"This article",
" shows that robins see a wider spectrum than ours, mostly due to greater sensitivity to the short wavelengths."
] |
[
"Let's just say every bumblebee to ever see a rainbow (they see infared) had this reaction ",
"https://www.youtube.com/watch?v=OQSNhk5ICTI"
] |
[
"would the effect droplets of water have on EM be the same through all frequencies?1. "
] |
[
"Why does stirring a soft drink with a wooden chopstick cause it to fizz?"
] |
[
false
] |
[deleted]
|
[
"The key thing to remember with fizzy drinks is that the bubbles don't just naturally form. Bubbles require nucleation sites - imperfections - in order to form around before they rise. A standard glass is of course not a perfectly smooth surface, hence why you see bubbles. Some companies will even specially design glasses to create interesting bubble patterns.",
"The difference between the metal knife and the wooden chopstick, therefore, is that the knife, as stainless steel, is a very smooth surface with little to know points of nucleation. The wooden chopstick however, is, assuming it's unvarnished, particularly rough, providing lots of nucleation sites for bubbles to form. Agitating the drink by stirring it simply dislodges the bubbles, freeing up the sites for more bubbles to form.",
"Apologies for lack of citable sources here, I'm just remembering GCSE science lessons!"
] |
[
"In the simplest terms the wooden chopstick isn't as smooth of a surface as the metal and thus provides nucleation points for the CO2 to drop out of solution and bubble out as gas. ",
"Diet coke and Mentos is a great example of an extreme version of this phenomenon. ",
"http://en.m.wikipedia.org/wiki/Nucleation"
] |
[
"Because science."
] |
[
"What role does electricity play in mental state/memories/maintaining cognitive consistency?"
] |
[
false
] |
So as far as I know, the brain is a network of neural synapses and different processing structures that work together to create the conscious experience. I'm not sure, though, how much of this information is stored physically, for example in the rearrangement of synapses or in the restructuring of the brain. Is any information, for example mental state or memories, simply an abstraction of different electrical states of the brain? What would happen if we were to "zap" the brain and completely reset its electrical state? Would it no longer function? Does an electrical state need to be maintained in the brain at all times, or could we shut off a brain and fire it back up later? If so, what would change? Any memory loss or change in personality? Some of these questions may be impossible to answer I suppose Thank you
|
[
"First, understand that there are no wires in the brain. The most conductive neural materials are still offering a resistance of several KΩ/cm and axons in neurons are over the MΩ/cm. ",
"Sencond, in biology, contrary to a a typical digital circuit, electrical charges will be transported by ions and chemical reactions, not by electrons flowing freely in a conductor. So you will need to define a bit more precisely what you mean by \"reseting\" the electrical state.",
"From what we know, there are two main ways that memory may work: by rearranging neuron connections and by storing charges and neurotransmitters in a synapse (and I seem to recall that at one point it was suspected the geometry of the synapse played a role but I don't know if it has been confirmed or not). So as long as you don't touch it, you should probably be fine, but if a \"reset of the electrical state\" mean that you neutralize ions in synapse and that would almost certainly introduce damages. "
] |
[
"It's true that synapses work on electricity, but it is a slow, chemical process of positively and negatively charged ions floating around in a liquid, rather than the fast transmitting-current-along-wires electricity that most people are familiar with. Intuitions from electronics and computers will not translate well to dealing with the brain.",
"You can temporarily disrupt the function of the brain with a big enough magnetic charge (",
" big) which disrupts the flow of ions, but it will be back to normal as soon as the charge goes away, because nothing gets fried or changed around."
] |
[
"AFAIK, the \"cognitive consistency\" of the brain is a result of its physical structure (synaptic organization) and not its on-going electrical activity. During a seizure, for example, there is widespread, wholly abnormal, electrical activity in the brain, and while there may be disorientation or loss of consciousness during the event, the person recovers their memory and \"self\" after the seizure passes.",
"About the only exception I can think of is short term memory, which may exist as a collective neural firing pattern. If this activity is disrupted before being consolidated into long-term memory, then the associated information would indeed be lost."
] |
[
"Why are we able to get the common cold multiple times in our lifetime? Should the virus not trigger a secondary immune response when it enters our bodies?"
] |
[
false
] | null |
[
"common cold symptoms are created after a viral infection of the upper respiratory system. a memory response will be created for each strain of the virus. if the virus mutates, there is a chance that the secondary response will be either less effective or completely ineffective, leading to the standard primary response, which is weaker and takes longer to work."
] |
[
"Adenovirus, the primary etiologic agent of the \"common cold,\" mutates heavily. When you're a kid, without prior inoculation with any form adenovirus, you get symptoms. If you were inoculated with THE SAME STRAIN, you would see little to no symptoms at all. Because the virus replicates repeatedly as a part of its life cycle, mutations are propagated through the genome in successive generations. These mutations can lead to different gene products/proteins that \"change\" the identity of the virus to your immune system. In the case of adenovirus, these changes are usually that virulent in that they cause similar symptoms to the patient with varying strains of the virus. In other cases (i.e. Avian Influenza), mutations can cause a large increase in pathogenicity to the patient."
] |
[
"You don't get the same 'cold' virus each time. The older you are the less likely you are to get a cold. Once you do reach said old age the effects of a simple 'cold' become far more significant merely due to old age."
] |
[
"Are there any two foods that are safe when eaten separately but dangerous to eat at the same time?"
] |
[
false
] | null |
[
"Grapefruit and lots of things, especially medicine. Serious effects.",
"Antibiotics and birth control pills, not really food, but the combination could cause something that you are obviously trying to prevent.",
" the pamphlet you got with your medicine."
] |
[
"There is a psycadelic mix of plants called ",
"Ayahuasca",
" which contains ",
" vine and a DMT (the psycadelic component) containing plant such as leaves from the ",
" plant. The DMT when consumed alone does not have an effect. It is only when the other plant is added, which contains monoamine oxidase A inhibitors, that the DMT is allowed to pass unmetabolized past the intestinal membranes."
] |
[
"I guess it depends on how willing you are to define alcohol as food, but alcohol consumption temporarily induces the cytochrome enzyme CYP2E1 which is responsible for the metabolism of some of the components of charred or burned food into more toxic compounds(i.e. CYP2E1 is primarily responsible for the metabolism of benzene into carcinogenic benzene epoxide).",
"Its not going to outright kill you, just make the carcinogenic effect of eating charred food worse.",
"edit: oxepine is the correct IUPAC name for benzene epoxide, it is the epoxide tautomer that is reactive that is the reactive and carcinogenic form though."
] |
[
"How do the negative terminals of batteries stay at 0 volts?"
] |
[
false
] |
How can we make batteries that always sit at 0 volts on the negative terminal without accumulating charge at that node?
|
[
"Voltage isn't an instantaneous measurement, you have to measure it relative to something else. The negative terminal doesn't have a voltage of 0, the voltage between the positive and negative terminal is (in new batteries) at 1.5 V. "
] |
[
"The potential can certainly be different. If you use a conventional multimeter, they might equalize quickly though. You can try measuring ground against the + of a battery and then measuring ground against the - of a battery though, or if that's too scary, you can do the experiment with + and - terminals of batteries that aren't otherwise connected."
] |
[
"Say you put 4 batteries in series to get a net 6 V source. The negative terminals can't all be at 0 V."
] |
[
"Do GPS receivers use signals from all GPS systems that are currently operational?"
] |
[
false
] |
For example, if I have an American cell phone and I go to China, would the GPS receiver interpret data from the American global system, the Russian global system, and the Chinese regional system to give me a more accurate signal, or would it only look for American GPS satellites?
|
[
"Depending on the receiver it uses the strongest signal. A majority of Cell phones use public GPS system (now 30 sats) and it is run by the U.S. government. Some vendors GPS receivers like Qualcomm, Broadcom and Exynos support Both US and Russian satellites systems... GLONASS, Galileo, BeiDou and Indian systems are all in deployment and some have commercially available receivers.\nSignal strength determines satellites used, at least 4 or some use upto 12+ if signals or LOS permit. EU system shares US binary offset carrier so they are in distinguishable from each other."
] |
[
"If you are asking about navigation GPS, then there are 24 Earth orbiting satellites, plus an extra three for back up and the constellation can support up to 30 satellites. The constellation is arranged so that the satellites provide maximum coverage all over the globe. So wherever you are in the world, your phone or navigation device will detect these satellites. ",
"The satellites are arranged so that at least 4 of these are \"visible\" (can be detected) by the phone. Your accurate signal depends on visibility of these satellites as they measure the distance between the satellite and phone to determine your location. ",
"As for communication like phone call, mobile phones use line-of-sight communication to the base station beyond which most of it is wired communication. ",
"I hope this helps : )"
] |
[
"Your cell phone most likely does not have the technology, or antenna specs to be able to pick up multiple constellations. The constellations below have different communication standards, and operate at different frequencies. There are receivers in development with this capability.",
"http://www.sage.unsw.edu.au/snap/publications/rizos_2008a.pdf",
"your phone is not one of them :)",
"The GPS Sats are well spread across the band of the globe. Up north, you can get spotty with ranging because of the low azimuth angles on the horizon. Other constellations have better satellite spread up north. Satellite spread is what gets you the best fix, and GPS was made for worldwide acquisition in the denser populated areas. Our military uses this stuff in the middle east, the satellites have good reception everywhere to give our military this advantage."
] |
[
"How can gravity be geometry in GR if..?"
] |
[
false
] |
Hi, I'm trying to understand how can gravity be actually just geometry in General Relativity. For example, imagine that the geometry of space-time is like the surface of an apple. Locally, you see that parallel straight lines don't intersect immediately, but in the end they actually may because the apple's surface is curved. And also the straight line can intersect with itself. I do get that. What I don't get with that example is that if you follow a straight line in the apple, it doesn't matter how fast you travel through that straight line, the path will be the same... but that doesn't happen with gravity: an object will follow a different path if he changes its velocity. I guess the answer is in the metrics of the system, like what is called proper time in special relativity: ds = -dt + dx + dy + dz So instead of using just distance as a measure in spacetime I should use proper time/distance. Am I right?
|
[
"So instead of using just distance as a measure in spacetime I should use proper time/distance",
"That's it. It's a 4-dimensional geometry we're moving through. If I'm moving in a straight line, or falling straight down onto the Moon, I'm following the same path in space (just a straight line), but I have a different path in ",
", because the time I reach each point in space is different between the two scenarios."
] |
[
"Okay thanks, I think I get it :)"
] |
[
"I want to add that, in relativity, your \"speed\" in the full spacetime sense is actually always ",
", the speed of light. Adding to your speed (in just the space sense) takes away from your movement through time. So, for a given path through spacetime in the general relativistic picture, there's actually only one physically relevant spacetime \"speed\" that you're moving along that path, and you can't travel that path faster or slower."
] |
[
"Why do we still use bike and car tires that can lose air?"
] |
[
false
] |
It seems like by now we would have come up with a solution that doesn't allow for car and bike tires to deflate and have to be refilled - is there a practical reason that something completely air tight and factor inflated isn't a good idea? Is it simply easier, or to make it possible to repair a flat?
|
[
"Rubber tires can never be perfectly air-tight, although a fully sealed rubber time could get quite close.",
"More importantly, what would you do about temperature changes then? Or punctured tires? How would you calibrate these necessarily pre-pressurized tires, if they will be mounted on a wide range of vehicles with different weights? How would you get them on or off of the rims, since they are already pressurized?",
"Given that tire pressure is not a universal constant, but changes due to things like temperature and load, it's quite useful to have pressure be adjustable. Plus, there are more practical challenges with the manufacture and assembly of some sort of permanent solution. You effectively need to either replace tires and rims every time, or develop a new standardized system of rims that have removable, permanently inflated tires.",
"Alternatively, you're looking for tires that are not inflated at all. There are many examples of this idea, and they have improved greatly, but there are still a number of drawbacks, including (currently) higher cost, lower lifetime, generally a significant weight increase, reduced shock absorption, and some others. That being said, this is sort of the direction tires could very well head in the coming years/decades, but it's not yet good enough and cheap enough for wider adoption."
] |
[
"Have you pushed a stroller with completely rubber tires vs ones that inflate? Once I pushed a stroller with inflated tires and saw how much easier it was, I was hooked. Solid tires would be miserable in terms of shock absorption."
] |
[
"Thanks for the thorough answer!"
] |
[
"Why do we get hot under pressure / when embarrassed?"
] |
[
false
] | null |
[
"Fight or flight instinct. Whenever you're in a stressful situation (and being embarrassed does count) you start releasing a lot of adrenaline, causing your heart to pump faster, which means increased blood flow. More blood flow means you feel hotter. The increased blood flow is also why you blush when embarrassed. "
] |
[
"...but why is that our physiological response? Is it because the rapid blood flow to the areas are necessary in some way?"
] |
[
"The heat is actually just the increased blood flow to the skin's superficial plexi, which occurs when the arterioles expand and allow more blood to flow near the surface. There is no increase in cell activity near the surface leading to heat."
] |
[
"Do we currently have a good explanation as to why the layers of the retina are inverted from what we would expect?"
] |
[
false
] |
From my understanding in my neurobiology course, the layers of the retina are not arraigned to best "capture" the light. The cones and rod cells are farthest away from the vitreous body instead of being the closest, and the light has to penetrate the ganglion and bipolar cells to order to strike the photo-receptive cells. Do we have an hypothesis at the moment as to why the layers are inverted? Does it serve to protect the cones and rods from infection, or is the clarity "good enough" and the change in developmental process large enough that a natural reversal is unlikely?
|
[
"An even bigger issue is that the optic nerve and blood vessels attach to the front of the retina, blocking a significant portion of it. My understanding is that there's no good reason for any of this and you're correct with your \"good enough\" explanation, but I'll leave that to someone who knows more about it..."
] |
[
"The explanation we learned was evolution: photoreceptors came first and then more complex circuitry was added later. It turns out, cephalopods ",
"have stuff in the \"sensible\" order",
" and vertebrates do not. It's less of a big deal than you might think: a thin layer of tissue is mostly transparent - that's why you have to stain it to see anything under a microscope."
] |
[
"I don't think we know for sure, but ",
"here's",
" an interesting theory.",
"Essentially, they believe that for small-eyed animals, an inverted configuration would save space by maximizing the amount of cells between the lens and the photoreceptors (a space called the vitreous humor that would otherwise be filled with only fluid).",
"Just a thought."
] |
[
"If I can’t touch anything how am I able to push things?"
] |
[
false
] | null |
[
"Electrons in your hand repel electrons in the object and transmit the force from your hand to the objet."
] |
[
"But how do they transmit force if they’re not touching? "
] |
[
"Force can be transmitted at a distance, when you jump you are not connected to the Earth but you still feel it's attraction. Similarly electromagnetic forces act at a distance. "
] |
[
"Is Helium-3 a viable fuel source?"
] |
[
false
] |
I had the TV show Ancient Aliens playing for background noise while studying for finals (so I feel less lonely after being secluded in room 8+ hours). But the show claimed that a single space shuttle filled with Helium-3 could power all the U.S.’s power needs for a year. Is this even remotely true? If so, how feasible would it be to utilize this fuel source/ how realistic is it’s possible use? ( did a brief google search and all I really got was Helium-3’s use in nuclear fusion)
|
[
"That would perhaps have a semblance of truth if we had working fusion power plants, but we don't. The ones that do exist, which don't produce more energy than they consume, use deuterium and tritium as their reactants and not helium-3.",
"One would need about 20 tons of helium 3 per year in order to power the United States (calculations based on energy yield per fusion reaction and some assumptions about power efficiency). The space shuttle is not huge, the cabin is about 75 cubic meters which would only be a few kilograms of helium at normal pressure, so you would have to jack the pressure pretty high to get a few tons.",
"Helium 3 right now is extremely important for low-temperature physics, and very hard to get."
] |
[
"There’s a lot of 3He on the Moon, but there’s also a lot of ",
" on the Moon. That is, you need to process a ridiculous amount of regolith in order to extract industrially relevant amounts of 3He. You need a trillion-dollar infrastructure on the Moon ",
" helium mining can become a trillion-dollar industry."
] |
[
"There’s a lot of 3He on the Moon, but there’s also a lot of ",
" on the Moon. That is, you need to process a ridiculous amount of regolith in order to extract industrially relevant amounts of 3He. You need a trillion-dollar infrastructure on the Moon ",
" helium mining can become a trillion-dollar industry."
] |
[
"Do we know when voyager 1 will fall into the gravity of another star?"
] |
[
false
] | null |
[
"Now that NASA's Voyager 1 probe has left the solar system, its next big spaceflight milestone comes with the flyby of another star — in 40,000 years.",
"Voyager 1 entered interstellar space in August 2012, nearly 35 years after blasting off, scientists announced Sept. 12. As it leaves our solar system behind, the robotic spacecraft is streaking toward an encounter with a star called AC +79 3888, which lies 17.6 light-years from Earth.",
"According to NASA, \"In about 40,000 years, Voyager 1 will drift within 1.6 light-years (9.3 trillion miles) of AC+79 3888, a star in the constellation of Camelopardalis which is heading toward the constellation Ophiuchus.\" ",
"Is this what you were asking or if when Voyager will be trapped by another star's gravity?"
] |
[
"it should be noted that voyager has \"left\" the solar system many times. this is due to the loose definition of solar system and interstellar space.",
"In that case voyager hasn't even passed through the oort cloud yet and won't for thousands of years.",
"edit: ",
"relevant XKCD"
] |
[
"Well Voyager left several times our solar system. It's way you you define our solar system. I read somewhere it will take significant more time to actually leave the gravity influence of the sun. That would be the point it leaves our solar system for the last time."
] |
[
"What determines the \"warm-bloodedness\" of a creature?"
] |
[
false
] |
I know that warm-blooded animals generate heat through internal metabolic processes while cold-blooded animals have to rely on external heat sources. But why do they have to do that? What mechanisms do they lack that would have allowed them to be warm-blooded?
|
[
"This question relies on the assumption that being warm blooded is better, and cold blooded animals are lacking something. Evolving to be warm or cold blooded is simply an adaptation to the environment. ",
"Being cold blooded is advantageous in some environments like deserts where animals get the heat they need from the sun. It saves them a LOT of energy not having to make their own body heat, and so they don’t have to eat as much to maintain their bodies. This makes food scarcity much less of a problem than it is for warm blooded animals."
] |
[
"Temperature is the most obvious regulatiom but think wider. All our body cells perform complex biochemical reaction at astounding speeds to keep us alive and healthy.",
"But reactions have many variables to them: temperature and pH being just a few of them. For example, many reactions are dependent on enzymes, efficient biocatalysts. But enzymes and other proteins have certain operating temperatures. All our cellular machinery is fine tuned to work at this specific temperature at peak efficiency.",
"This is why maintaining a stable core temperature and pH are so important: they let biochemistry happen reliably and constantly regardless of outside conditions.",
"However energetically expensive, it is a major evolutionary advantage in a wide range of situations."
] |
[
"Both endothermy (warm-bloodedness) and ectothermy (cold-bloodedness) are successful biological strategies. Like a lot of things in life, it's about trade-offs. ",
"Endotherms spend energy in order to maintain a stable internal environment (aka homeostasis). This means we warm blooded animals have specific and narrow ranges of conditions that our bodies spend lots of energy maintaining. so we maintain a specific temperature, specific salt concentration, specific pH, etc, no matter what the conditions are outside our bodies. So we spend ",
" to regulate our metabolism.",
"Ecotherms allow their internal conditions to vary with the variance of their environment. So if it's hot outside, the cold blooded animal gets hot too. If it's cold outside, they get cold too. They don't have the same homeostatic mechanisms that endotherms have, which means they spend less energy at rest because there is less to maintain. Ectotherms ultimately use their ",
" to regulate their metabolisms. (I'm cold--> go somewhere warm). ",
"The trade-off is energy. Consider an endotherm and an ectotherm of the same size.. the warm-blooded animal has 10X the maximal metabolic rate as the cold-blooded animal. This is called aerobic scope. The warm-blooded animal also spends 10X as much energy as the cold-blooded animal under normal resting conditions. It's like comparing a gas-guzzling hum-V to a honda civic: the hum-V has a much higher energy demand when it's idling, so it burns a lot more fuel compared to the honda civic, which has lesser demands and burns a lot less fuel when idling. Along with that, the hum-V can ",
" a lot more energy when it needs to compared to the civic: it can accelerate faster, it has more power, etc. The hum-V in the scenario is the endotherm, the civic is the ectotherm. ",
"So having warm blood is expensive in term of energy, but it means the endotherm is capable of spending a lot of energy when it needs to and it can maintain that energy expenditure for a long time (a deer can run fast for a long time). Ecotherms spend far less energy when resting (aka idling), and they also have much lower capacity for energy expenditure (a crocodile can move quickly, but it tires quickly and cannot maintain prolonged energy expenditure). ",
"biology! <3"
] |
[
"Is there an exact point when we evolve into another species?"
] |
[
false
] |
[deleted]
|
[
"There is no exact point. Look up \"ring species\" to read about a case where this transition happens through space rather than time."
] |
[
"To get at the reason why there doesn't have to be an exact point, you have to understand that species are somewhat fuzzy concepts. They aren't like, say, buckets, where you can be in bucket A or bucket B but never kind of in both. As hybrids like mules demonstrate, you can be 50% one species and 50% the other (and to further complicate it, sometimes the hybrids become their own species). So while you can ususally say for certain that most members of species A are in species A, there are often boundary areas where any definition of the line between A and B is arbitrary. Because any point you place down has to be arbitrary, it's better not to think of their being an exact point."
] |
[
"As has already been stated, no, there is no specific point at which it happens. This sort of question has been discussed a few times on this board before, so in case you're interested in more extensive discussion, I'm attaching two of my previous responses. I know there are more out there in the archive, but these are the first two I managed to track down. Follow up questions also welcome.",
"http://www.reddit.com/r/askscience/comments/idcpv/are_we_exactly_as_intelligent_as_the_first_homo/",
"http://www.reddit.com/r/askscience/comments/jp273/are_there_any_theories_about_or_is_it_likely_that/c2dy6oq"
] |
[
"Do tumors cut off their own blood supply with their uncontrolled growth?"
] |
[
false
] |
If so, how do they survive and continue growing? If not, how do the cancerous tissues manage to stay connected to the circulatory system despite their chaotic growth?
|
[
"Sometimes, yes. Rapidly growing tumors often display central necrosis, indicating the growth rate outpaced angiogenensis (formation of new blood vessels). Many tumors produce and secrete growth factors (VEGF, EGF, among others) to help counteract this. Some therapies are aimed at blocking these growth factors or their receptors, however individual chemotherapeutic agents are rarely used as monotherapy."
] |
[
"No, the reverse happens actually... Inhibition of tumor angiogenesis is a current target for drug therapies... If you can inhibit signaling for more blood flow, then you can basically starve the tumor of blood and the nutrients it needs to grow/propagate "
] |
[
"Its been a long time since I have had to think about this in medical school... If I remember correctly, the cells releases growth factors informing close by vessels that they need more nutrients... If I remember correctly VEGF is the big factor that is studied and serves as the signaling molecule... Though I could be wrong and surely there is more than one signaling molecule involved... The other thing that always caused me dissonance, was how do the newly developed arterial vessels link back with the venus supply. ",
"The body can handle necrosis \"just fine\" under most circumstances... Its happening all the time in your body. I say \"just fine\" because it can be ugly and painful, but the body is able to deal with it under normal circumstances. "
] |
[
"Does Large Hadron Collider need re-calibration after redefinition of SI units?"
] |
[
false
] |
How are measurements in different detectors over at LHC connected to the current values of speed of light, kilogram, etc? Would redefinition of SI units need updates in other kinds of measuring devices in science laboratories across the world?
|
[
"No. The new unit is defined to be mathematically identical to the old one, and all measurement devices on the planet are still as correct today as they were last week.",
"We've just gone from having a very accurate experiment whose results depend on the size of the kilogram to having the kilogram depend on the results of that very accurate experiment. Since that experiment is more reliable and repeatable than putting the old platinum cylinder kilogram on a scale, it's an improvement for the future, but it doesn't make any practical difference today."
] |
[
"Not exactly. The kilogram used to be \"the mass of a lump of Platinum in a vault in Paris,\" but now it's \"a unversal constant multiplied by a certain number, which is equal to the mass of a lump of Platinum in Paris on <whatever day the decision was made official>.\" That doesn't make any real difference now, or for the average measurer, but in 100 years the mass of that lump of Platinum will have changed (as it has in the past) but the Kilogram will have not. It's more future-proofing than some sort of revolutionary change - still important, but not quite as impressive in the short term."
] |
[
"Good question! I don't know. My guess is that a cylinder is especially easy to shape using a lathe. Lathes are easy to build and very accurate, while shaping a perfect cube requires a mill which is more complicated and difficult to align. Also, when an object is handled, bumps and scrapes tend to cause the most damage at at the edges and corners, and a cylinder has fewer of those.",
"If anyone knows much about the design and construction of the prototype kilogram, I'd love to learn more!"
] |
[
"How would vibrating at the speed of light affect the flow of time?"
] |
[
false
] |
[deleted]
|
[
"No, things can't vibrate at the speed of light."
] |
[
"I'm trying to understand what 'vibrate at the speed of light' even means. When I think of vibrations I think of some kind of frequency."
] |
[
"It's not possible to vibrate at the speed of light. However... taking that and setting it aside, time would flow for the people aboard a ship in such a way that it's speed would resemble a sine wave. \nLike any ship traveling at light speed, there'd be \"no running\" signs all over. lol (for reasons I'm too high to get into right now)"
] |
[
"Do bacteria develop resistances to the soaps we use?"
] |
[
false
] |
I hear a lot about super bugs and their greater resistance to antibiotics. I do wonder though if bacteria could resist the hand soaps we use daily and if there are any documented cases about it. If they don't develop a resistance, then why not?
|
[
"Hand soaps are surfactants, they work by making the surface they're applied to too \"slippery\" for germs and particles to stick to. This is why the proper way to wash your hands is to soap up to a lather, then rinse away the lather down your hands to your fingertips and off, rather than just washing it away.",
"In reality I suppose they could develop a resistance to this, but it's probably less likely than something that attempts to destroy the germs."
] |
[
"/u/milkysniper",
" is correct, it's unlikely that bacteria will develop major \"resistance\" to soaps. Some bacteria have the ability to cling to surfaces using pili and other attachment methods, so I suppose that is a form of resistance. But these aren't formed via the evolutionary process with soaps as pressure, at least I've never heard of it. Most forms of resistance just happen to exist in the bacterial attachment method. A good example (although it's fungal) is Athlete's foot, and how it is \"resistant\" to soaps. It doesn't break down the soap, as soap is only used for mechanical removal, but it's attachment to skin prevents removal by soap. ",
"You may be referring to the antibiotics in some soap, in which case, yes, bacteria can become resistant to antibiotic soap. "
] |
[
"Just to add, your hands and the rest of your body is always coated with a layer of oil which you secrete. Soaps are lipophilic and hydrophilic, and wash away part of that layer. Generally speaking bacteria go with it, along with some of your epidermis (which is dead anyway). It's pretty hard to evolve a resistance to having your entire world (and it is that when you're microscopic) washed away with you in it."
] |
[
"Apart from obvious cost-reasons, why didnt we build the LIGO-observatory in space? Wouldn't the accuracy be greatly enhanced by avoiding all disturbances on the earth?"
] |
[
false
] | null |
[
"LISA"
] |
[
"Aside from cost reasons, LIGO is 4,000 meters long on each arm. To do this in space, we would need to send up multiple satellites for each arm, and be able to control their distances from each other extremely precisely. Right now, there are plans to build a space-based observatory, but there are some technologies we need to test first before trying to put up a full-scale version."
] |
[
"Adding to this, the current space-based detectors that are proposed (e.g. eLISA) would be complementary to LIGO rather than replacing LIGO. ",
"See this chart",
" and compare the curves for eLISA and LIGO (there is a button to add LISA to the chart too). They would be designed to detect different types of events. ",
"So it is a good idea to build a space detector, but the different engineering challenges mean that it would have its own niche separate from LIGO's niche."
] |
[
"Are time and gravity inversely proportional?"
] |
[
false
] |
[deleted]
|
[
"None of this has anything to do with quantum physics. Let's get that out of the way right up front.",
"Every particle in the universe is in motion all the time. That motion includes a spatial component ",
" As you sit there reading this, you are in motion toward the future.",
"Massive bodies curve spacetime. That's basically impossible to visualize without resorting either to complex mathematics or fundamentally flawed metaphors, so I won't bother encouraging you to try. Just accept it as an axiom: Massive bodies curve spacetime.",
"In the reference frame of an observer at rest relative to the moving body — that is, Isaac Newton sitting under his tree — the motion of a freely falling body — that is, the apple — is tilted such that it gains a spatial component. In the reference frame of the freely falling body — again, the apple — no motion through space is apparent. All motion appears to be directed toward the future, and the falling body perceives itself to be at rest. But to the stationary observer — Newton — the falling body's intrinsic motion toward the future includes a spatial component of motion. This is all because of the curvature of spacetime around massive bodies.",
"Apples fall from trees because their future points toward the ground."
] |
[
"None of this has anything to do with quantum physics. Let's get that out of the way right up front.",
"Every particle in the universe is in motion all the time. That motion includes a spatial component ",
" As you sit there reading this, you are in motion toward the future.",
"Massive bodies curve spacetime. That's basically impossible to visualize without resorting either to complex mathematics or fundamentally flawed metaphors, so I won't bother encouraging you to try. Just accept it as an axiom: Massive bodies curve spacetime.",
"In the reference frame of an observer at rest relative to the moving body — that is, Isaac Newton sitting under his tree — the motion of a freely falling body — that is, the apple — is tilted such that it gains a spatial component. In the reference frame of the freely falling body — again, the apple — no motion through space is apparent. All motion appears to be directed toward the future, and the falling body perceives itself to be at rest. But to the stationary observer — Newton — the falling body's intrinsic motion toward the future includes a spatial component of motion. This is all because of the curvature of spacetime around massive bodies.",
"Apples fall from trees because their future points toward the ground."
] |
[
"Could you try rephrasing the question? Gravity is a force and time is a unit of measurement. There isn't really an \"inversely proportional\" relationship here."
] |
[
"What would fire look like under a microscope?"
] |
[
false
] | null |
[
"Fire would still look like a fire.",
"In essence, a fire is the light that's being given off as molecules are reacting in some type of combustion. Molecules are (typically) smaller than the wavelength of light, so at best you'd just see a \"large flame\" under the microscope objective."
] |
[
"I am no expert however I can google like a mofo. ",
"Fire is light, heat and a flame so you'd have to use a spectroscope to get any real information.",
"Until an actual answer from someone comes along check out this awesome site and its awesome explanation on how one would look at fire under a 'microscope'.",
"http://spectroscopyonline.findanalytichem.com/spectroscopy/article/articleDetail.jsp?id=436813",
"PS: The article is, unless I'm mistaken, an answer to your question!"
] |
[
"Depending on the objective and depth of field it will just look like a bright light... or a blurry bright light."
] |
[
"Why is it called \"mononucleosis\"? Do not most cells have a single nucleus?"
] |
[
false
] | null |
[
"Leukocytes come in all shapes and sizes. Lymphocytes and macrophage / monocytes (which are referred to as mononuclear cells) do have a single unsegmented nucleus but granulocytes (Neutrophils, basophils and eosinophils) AKA PMNLs have what looks like multiple smaller nuclei nuclei joined by thing \"strings\" under a light microscope. PMNL stands for\"Polymorphonuclear leukocytes\" meaning that they have nuclei that are segmented (Especially for neutrophils) or lobulated."
] |
[
"According to a well-referenced wikipedia entry (",
"https://en.wikipedia.org/wiki/Infectious_mononucleosis#History):",
" \"The word mononucleosis has several senses. It can refer to any monocytosis (excessive numbers of circulating monocytes), but today it usually is used in its narrower sense of infectious mononucleosis, which is caused by EBV and of which monocytosis is a finding.",
"The term \"infectious mononucleosis\" was coined in 1920 by Thomas Peck Sprunt and Frank Alexander Evans in a classic clinical description of the disease published in the Bulletin of the Johns Hopkins Hospital, entitled \"Mononuclear leukocytosis in reaction to acute infection (infectious mononucleosis)\".\"",
"EDIT: So mononuclear means the cell contains one rounded nucleus, which you correctly identified. Leukocytosis is when the circulating levels of white blood cells are elevated above normal levels i.e. reacting to something. "
] |
[
"My question really is, though, what makes \"mononuclear\" significant? The vast majority of cells have one nucleus, right? Do leukocytes tend to have multiple nuclei?",
"Aha! The ",
"WP article on leukocytes",
" indicates that most of them have multi-lobed nuclei, and are not considered to be mononuclear.",
"Thanks! Your answer got me most of the way there."
] |
[
"How did the trait in which dead bees emit a scent that warns other bees of danger survive and make its way into the population when this trait does not aide the individual bee before reproduction?"
] |
[
false
] |
More generally how do genetic traits that occur after the point of reproduction survive and enter the main population if there is no mechanism (i.e. natural selection) to ensure its survival? Also, since this is a trait that benefits others and not the individual, how do such traits that only contribute to the welfare of others not the individual survive?
|
[
"The bees that the dead bee saves are genetically very closely related to the dead bee. Helping your close relations helps your own genes. Hence people are prepared to do a lot for close family.",
"It's called ",
"Kin Selection",
".",
"The fun thing about that is that it's mathematical, we know the formula that evolutionary psychology is optimising on. People should be prepared to die to save more than two siblings, more than four nephews, or more than 8 cousins. It sounds horrible but that's the calculation we're effectively doing."
] |
[
"The worker bees don't mate in general - only the queen does with her male drones. As this would obv benefit the queen via hive defence, it still makes sense under natural selection."
] |
[
"Evolution in some parts of the insect world works pretty differently than it does with the kinds of sexual reproduction we humans are more familiar with.",
"The bee reproductive model involves ",
"haploid sex determination",
" in which different 'genders' within the colony have different numbers of chromosomes. The queen has the full set of 32 chromosomes, and is the only one able to lay eggs. Each egg contains half of her genetic material, and when unfertilized will hatch into a \"male\" drone (with 16 chromosomes). The \"female\" worker bees hatch from fertilized eggs and have a full set of 32 chromosomes (half of the queen's genetic material recombined into 16 chromosomes, plus the full 16 chromosomes from a haploid drone which came from the queen as well), but are unable to lay additional eggs of their own in most species. Thus every individual bee is some form of a 'partial clone' of the queen. ",
"In this example I'm going to simplify all of the genetics of the queen into 5 ",
"loci",
") on each of two chromosomes, where the number represents the loci and the upper/lower case letter represents the particular allele occupying that loci (each allele is a possible expression of each gene). I'm calling these ChromosomeQ and ChromosomeD to represent the fact that one came from the former queen, the other from a drone:",
"Queen:",
"ChromosomeQ: 1A, 2B, 3c, 4d, 5e",
"ChromosomeD: 1A, 2b, 3c, 4D, 5E",
"When she gives birth to a male drone egg, he will only get one chromosome, which will be a shuffled combination of her two chromosomes. For example:",
"Drone: DChromosomeQ: 1A, 2b, 3c, 4d, 5e",
"In this example, loci 1 and 3 could have come from either, but we know loci 2 came from ChromosomeD and loci 4 and 5 came from ChromosomeQ. Since he only has code from the queen, he only has a DChromosomeQ. On the other hand, when the queen gives birth to a female worker bee, half of it's code will come from her directly (shuffled up the same way it did for the drone) and the other half will be a direct copy of whichever drone fertilized the egg. Here's an example of a potential female worker bee which came from the queen and the drone above:",
"Female Worker bee:",
"FChromosomeQ: 1A, 2B, 3c, 4D, 5e",
"FChromosomeD: 1A, 2b, 3c, 4d, 5e",
"(note, FChromosomeD is an exact copy of DChromosomeQ, while FChromosomeQ is one of many possible outcomes of the queens DNA being shuffled)",
"The point of this exercise is to show that every bee in the hive inevitably shares the queen's genetic code, though it will not be in the same proportions, allowing for multiple allele expressions. In this way they are all \"partial clones\" of the queen. (technically not true, as some of the drones fertilizing new eggs will have come from the old queen. Queens live several years, while workers and drones only live 4-7 months, so as long as no new queens are fertilized during this period the hive's genetic pool will reduce down to only that of the current queen.)",
"In this model, it is appropriate to say that the hive as a whole operates as a distinct \"evolutionary unit\", since it collectively shares one set of DNA and reproduces, survives and evolves as a cohesive unit. With respect to analyzing the pressures of natural selection on bees, it is more appropriate to think of the individual workers and drones as components of a larger organism, the hive. The genetic code which causes these individual bees to emit dying warning pheromones is something which provides advantage to this \"hive organism\" as a whole.",
"The queen is the genetic core of the hive, and new queens are created by selectively raising a tiny fraction of the female worker bee larvae with a special type of food called \"royal jelly.\" Without this jelly they would hatch as normal female worker bees, but with the jelly they develop into \"virgin queens.\" Only a small fraction of these virgin queen larvae survive, since as soon as they hatch they kill their potential competition (any other virgin queen larvae they detect). These virgin queens will then either break off from the hive and take a swarm with them to go create a new hive, or they will supercede the existing queen and take over the existing hive (if the current queen is old and no longer able to carry out her duties, the drones will kill her).",
"In this way, bee hive reproduction has some characteristics of asexual reproduction (one hive splitting into two, all genetic code of the second hive coming from the first) and some characteristics of sexual reproduction, since the genes are internally \"shuffled\" through the 16 chromosome haploid drone / 32 chromosome queen process. This means that the genetic code of the new queen (and thus, the new hive) will descend from the code of the old queen, though in different proportions and potentially with different alleles being expressed. For instance, the female worker bee we created in the example above could be raised as a virgin queen, and go to create her new hive with slightly different genetics than her mother. In that example, the female we created was identical to the queen except for the 5th loci, where she had homogeneous expression of 'e', rather than the heterogeneous e/E mix of her mother. This shuffling is important because it promotes faster bee evolution, both through swarming and splitting a hive, or by replacing queens of a current hive. If this new e/e expression is more successful then the e/E expression, the new hive will flourish (all male drones coming from the new queen will have the 5e allele. If this is a good allele, this hive will do better than one where half of the males are 5e and half are 5E).",
": Explanation of genetics in bee hives. It's very different than with standard sexual reproduction between individual male/female mates, and it's mechanisms readily encourage these sorts of group selection characteristics."
] |
[
"Why do green screens have to be green? Would they work with any other colour?"
] |
[
false
] | null |
[
"Green is often ideal, as it's far from human skin color, the sky, and most other things that might be on screen. In post production any similar color on screen might be erased by accident.",
"Green is normal but blue is also often used if it makes more sense for the situation. Also rarely red can be used, but it's hard to isolate it from skin tone."
] |
[
"The process is called \"chroma key compositing\" and the chroma key doesn't need to be green. Green and blue are the most common chroma keys but any color can work. However, there are drawbacks to certain colors depending on what is in your shot. For example a blue chroma key would work poorly outside where the compositing might replace part of the sky."
] |
[
"The green of the greenscreen only would interfere with grass and trees shot in the physically same location as the screen. You can replace the greenscreen with anything you like and that \"background\" source would be independent of the color of the screen.",
"You'd only have to worry about green grass your subject is standing on with the greenscreen behind them."
] |
[
"Can someone please explain to me what this is on the weather map and how it formed like this?"
] |
[
false
] |
[deleted]
|
[
"I see the radar site!",
"Weather radar sometimes misbehaves with cloud formations too close to the system. I'd bet good money this station's radar data comes from a site in Aberdeen."
] |
[
"Are cloud locations triangulated? If so it's possible one station dropped out, meaning that range was only plotted from the remaining station, leading to a circle."
] |
[
"A radar glitch is much more likely than the large government conspiracy HAARP. I'm not sure if you got lost, or if you thought this was ",
"/r/conspiracy",
", but this is actually ",
"/r/askscience",
", where evidence actually matters. "
] |
[
"If the lungs in land vertebrates evolved from the gas bladder, what did the gills evolve into?"
] |
[
false
] | null |
[
"Ah, the interesting thing is the gas bladder evolved from lungs! Early bony fish lived in fresh waters that were often low in oxygen. They commonly gulped air into their digestive tracts to absorb some oxygen through their gut. Pouch a bit off the digestive tract and you get a primitive lung. It seems that getting oxygen, not buoyancy, drove this adaptation in the first place. Proper gas bladders only show up in a particular lineage of bony fish that appeared later on and then diversified to give rise to most of the fish in the world today. Many earlier branching groups of fish like lungfish, bichirs, and bowfin still rely quite a bit on air breathing in some situations. ",
"Doesn't exactly answer your question, but I thought it was worth bringing up."
] |
[
"fish and land vertebrates both have pharyngeal arches (which become gill arches in fish) and pharyngeal pouches (which become the gills themselves in fish) during development",
"the gill arches have more or less become ",
"neck cartilage and bits of head bones",
", and the pharyngeal pouches turn into... well, ",
"a bunch of things",
"#Specific_pouches)"
] |
[
"Teleosts, which are a particular branch of them"
] |
[
"How does salt water oral rinses increase mouth pH?"
] |
[
false
] |
Several online resources describing the benefits of oral salt water rinses mention the increase of salivary pH (more alkaline) as the means to inhibiting/slowing bacterial growth. However these sources do not describe the chemistry of how salt water increases oral pH. NaCl doesn’t change the pH of water so is it reacting with something else in the mouth to neutralize acids?
|
[
"Adding table salt probably isn't making your mouth more alkaline, but what is happening is that rinsing your mouth with water will help to remove acid build up from bacteria. This is likely what is raising the pH of your saliva. Highly saline water does make a good mouth wash, but the salt itself is probably not raising the pH.",
"Edit: The salt does indirectly increase the pH overt time by helping to kill bacteria in your mouth. The fewer the bacteria, the fewer acids produced."
] |
[
"I guess it’s a bit of a positive feedback loop then. Kills bacteria > less acid produced > less acidic environment less favorable for bacteria."
] |
[
"Haha yeah googling didn’t really get me anywhere either. I think osmosis/hydration might play a role. Salt rinses are supposed to be isotonic to slightly hypertonic. So in the theory it would dilute or draw water out to hydrate tissue surfaces more than plain water? But yeah, it’s all conjecture here, haha. ",
"Yeah baking soda rinse would make much more sense. I did find a study testing baking soda to increase salivary pH on google scholar."
] |
[
"Why are so many tornadoes occurring in the United States?"
] |
[
false
] | null |
[
"There aren't. The current count is on pace for a relatively normal total. This is the first year in a while that there have been F5's however...and they've been unfortunately placed",
"http://en.wikipedia.org/wiki/Tornadoes_of_2008#United_States_yearly_total",
"http://en.wikipedia.org/wiki/Tornadoes_of_2009#United_States_yearly_total",
"http://en.wikipedia.org/wiki/Tornadoes_of_2010#United_States_yearly_total",
"http://en.wikipedia.org/wiki/Tornadoes_of_2011#United_States_yearly_total"
] |
[
"If you mean \"...compared to the rest of the world\", then the answer is that the US has ",
" had more tornadoes then anywhere else in the world, it's completely normal. We're the lucky nation with the ideal conditions.",
"http://en.wikipedia.org/wiki/Tornadoes_in_the_United_States",
" "
] |
[
"As someone who has grown up in tornado alley, I would anecdotally occur. ",
"There seems to be a bit more media coverage than usual. Natural disasters are the big topic right now because the news has nothing more interesting to talk about. ",
"It sucks, but if it was a year from now (US election season), you'd probably hear a lot less about the recent disasters. "
] |
[
"Could this solar flare potentially destroy the earth?"
] |
[
false
] |
[deleted]
|
[
"I visited NOAA's space weather prediction center last month and wrote a ",
"brief article",
" about this if you're looking to find out more. ",
"The upshot - yes a huge storm could seriously harm the electrical grid and communications network if we are not prepared for it. It could not \"wipe out\" countries or directly physically harm anyone on the Earth's surface though."
] |
[
"Probably not, although some damage has been done in the past they were by MUCH larger flares (this isn't even an X-class flare).",
"Also you should note that the majority of damage will be in things like transformers on the grid rather than in electronics.",
"This is because the flare knocks the earths magnetic field, this changing magnetic field induces a current in the earths crust, this gives a potential difference across anything grounded perhaps on the order of a few volts per km.",
"This is a problem for the grid because if you have a 50km separation between transformers (earthing points) you may suddenly have a 25-100V induced current in your transformer central iron core, this knocks everything out of phase which makes the transformer generate a huge amount of excess heat.",
"On the opposite size scale your home electronics sizes are small, sizes between earthed points are small so the induced currents are small. Also the 25V isn't actually that much and most stuff can cope with it.",
"So any damage is done is to large scale grid structures it depends on many things such as the conductivity of the ground, the latitude of the locale and the rate of change of the earth's magnetic field."
] |
[
"I stumbled upon this article, saying that ... \"reach earth, and ruin all our electrical devices and potentially wipe out whole countries\"",
"All I see is that \"The CME is expected to deliver a glancing blow to Earth's magnetic field on Dec. 28th at 1200 UT\"",
"Ignore it. Nothing to see here. Happens all the time.",
"The 2012 Mayan alignment thing isn't anything to worry about either."
] |
[
"Is there such thing as Zero Point Energy?"
] |
[
false
] |
Is Zero Point energy the same as energy of the vacuum? Could zero-point energy be used to power humanity if the right technology was developed? Is there such a thing, even theoretically?
|
[
"Is Zero Point energy the same as energy of the vacuum?",
"Yes. It's the energy present in some quantum system when it's in its lowest-energy state.",
"Could zero-point energy be used to power humanity if the right technology was developed? Is there such a thing, even theoretically?",
"Not even theoretically, no. ZPE is ",
" the lowest possible energy the system can have. You can't get any energy out of something which already has the lowest possible energy."
] |
[
"That is entirely consistent with what I said."
] |
[
"Yes, and if you calculate the energy of a ball on the ground compared to the centre of the earth, you get a pretty large number. Still doesn't help you get any energy out of it whatsoever if it's already on the ground and can't go any lower. "
] |
[
"What does it mean that \"the electromagnetic force is carried by photons\"?"
] |
[
false
] |
[deleted]
|
[
"Virtual photons don’t literally exist. They are just mathematical things that show up in certain calculation schemes in quantum field theory.",
"To say that the photon is the “force carrier” for the electromagnetic force means that charged particles interact with the electromagnetic field, and excitations of the electromagnetic field are quantized particles called photons.",
"Mathematically, the interactions between charged particles can be made to look like one charged particle exciting the photon field at some point in spacetime, then that photon propagating to another point in spacetime, being destroyed, and the four-momenta of the two charged particles ending up different than they were at the beginning. This would correspond to a tree-level Feynman diagram, and to get the total amplitude of the process, you’d sum the contributions of all possible Feynman diagrams that link the same initial and final states. This is how calculations are done in perturbation theory.",
"However there are other ways of doing the same calculation, in which there never is any “virtual photon” being exchanged. And sometimes, when interactions are strong, perturbation theory doesn’t even work. So virtual particles should not be taken as physical things that literally exist. They are just a mathematical artifact of perturbation theory. What’s physical are the incoming and outgoing “asymptotic states”, not the intermediate “virtual particle” states."
] |
[
"So these \"states\" are the evolving quantum states in the process of observation/measurement/interaction? ",
"The state at t = -∞ is the initial state. It's whatever state you prepare the system in. For example, an electron moving towards another electron with a momentum of 5 GeV/c.",
"The state at t = ∞ is what you're left with at the end of the process. This is what you'd physically detect.",
"What kind of t durations are we talking about here? [-∞, ∞] is a big range.",
"It's not literally infinite time, but after some finite amount of time, the interactions between the particles becomes negligible, and the state of the system is no long affected by the interaction. Saying that it's at infinite time just means that it's after the interaction process is over.",
"edit: I finally figured out the \"incoming and outgoing\" states are the same as the initial and final states you previously mentioned.",
"Yes."
] |
[
"They are the states of the system at times t = -∞ and t = ∞. In other words, they're states that are actually observable."
] |
[
"Why does a major fall (say, 20ft) hurt less when you land with forward momentum on wheels (skates, skateboard) than with no forward momentum (in shoes) if horizontal and vertical motion are independent?"
] |
[
false
] |
Confusing question, but I'll try to explain a little better. In a physics class I took years ago, I was taught that horizontal and vertical motion are independent vectors and therefore don't affect each other. However, I used to skate, and noticed that jumping from a height with forward motion on skates hurt much less than jumping straight down from the same height in shoes, despite supposedly hitting the ground with the same amount of force (and not rolling my body or anything to minimize that force). Do the turning wheels somehow mitigate the impact force, or is there something else going on?
|
[
"This doesn't work. Ski jumping ramps are sloped downwards, such that ski jumpers do not land on a horizontal plane but with a downward slope (as seen ",
"here",
"). This slope is basically the same as the velocity of the ski jumper such that there is almost no ",
". \nThe vertical movement is slowed down, due to the ramp. This has nothing to do with the horizontal velocity and thus does not answer OPs question. If a ski jumper would land on a horizontal plane, he would die - regardless of his horizontal velocity."
] |
[
"It's not the fall, but the sharp stop at the end that hurts.",
"If you jump forward onto a downward ramp, then - from your perspective - the ground is dropping away from you. That means that the relative speed that you hit the ground with is smaller. Hitting a downward ramp 'on the run' can work in a similar fashion.",
"Skateboards (and to a lesser degree roller skates) can also act as a cushion to spread out the impact over time, which makes the stop less sharp."
] |
[
"I don't see a reason why the horizontal velocity should have an impact on how much a fall hurts; especially when you have wheels on your feet.",
"The only reason I can think of is that you land differently. Maybe you bend your knees more and your body is not upright, thus is able to buffer the fall better. If you jump with a straight spine and locked knees, you'll hurt yourself whether you're on wheels moving forward or not.",
"So your understanding that the velocities are independent is correct, and the reason for the difference in the two cases has to be looked for elsewhere."
] |
[
"Which journal should I submit my paper?"
] |
[
false
] | null |
[
"This is an interesting question, but not really appropriate for ",
"/r/askscience",
". I would recommend ",
"/r/physics",
" or ",
"/r/asksciencediscussion",
"."
] |
[
"This isn't the right sub for this question. Talk to your mentor. You can try ",
"/r/askacademia",
" or a similar sub"
] |
[
"Thanks a lot for the heads up. I'll try those subs."
] |
[
"Do larger blacks holes have a stronger gravitational pull? Could a larger black hole suck mass off of a smaller one, similar to what a black hole does to a star? Could an infinitely powerful bomb magically placed at the center of a black hole disperse it?"
] |
[
false
] |
Sorry for all of the questions!
|
[
"Time.",
"It will eventually lose mass due to Hawking radiation, but it'll take quite a bit of time."
] |
[
"The bomb in the black hole would have no effect other than adding to it's total mass. Once the bomb passes the event horizon, the total mass + energy of the bomb is now a part of the black hole and indistinguishable from it. An infinitely powerful bomb would create an infinitely massive black hole."
] |
[
"Not really. Adding mass/energy just increases the black hole's lifespan a lot, by reducing the intensity of Hawking radiation it emits.",
"If the black hole is rotating (and real black holes should rotate), it has something called an ergosphere, which extends beyond the event horizon, a region in which objects are forced to rotate along with the black hole regardless of their velocity.",
"This means you can theoretically \"gain\" kinetic energy from the rotating black hole, and if you can \"transport\" this energy outside the ergosphere, you have taken energy from the black hole. The Penrose process describes such a mechanism.",
"However, since a rotating black hole's energy is the sum of its rotational energies and its mass, and you'd be taking energy from the first component alone, this mechanism wouldn't allow the \"draining\" of the black hole other than to make it stop spinning; you'd be left with a non-rotating massive black hole which you again can't do anything about."
] |
[
"The pill is 99% effective. What happens to that 1% fetus when the woman doesn't realize she's pregnant and continues taking them?"
] |
[
false
] |
Would she have a miscarriage? Would the baby have birth defects or anything? What about the mother? Any adverse effects for her (aside from pregnancy)?
|
[
"Nothing much. There're some small/weak studies showing (sometimes disputed) associations with various pregnancy complications:",
"This case-control study",
" reports:",
"Maternal OC use during the first 3 months of pregnancy was associated with an increased odds ratio for 2 of 32 birth defects: hypoplastic left heart syndrome (adjusted odds ratio = 2.3 [95% confidence interval = 1.3-4.3) and gastroschisis (1.8 [1.3-2.7]).",
"This cohort study",
" reports:",
"Oral contraceptive use within 30 days prior to the last menstrual period was associated with increased risks of very low birth weight (OR: 3.24, 95% CI: 1.18, 8.92), low birth weight (OR: 1.93, 95% CI: 1.17, 3.20), and preterm birth (OR: 1.61, 95% CI: 1.01, 2.55); however, oral contraceptive use 31-90 days prior to the last menstrual period did not increase the risk of low birth weight or preterm birth.",
"This case-control study",
" looked at associations with congenital urinary tract anomalies (CUTAs):",
"OC use after conception was associated with a 4.8-fold increased risk of having a baby with a CUTA [odds ratio (OR) = 4.8, 95% confidence interval (CI), 1.6-14.1) relative to no contraception at or after conception. The risk seemed to increase with increasing duration of OC use after their last menstruation: OR = 8.0 for women with longer than 4 weeks duration of use. "
] |
[
"It also helps to understand the mechanism by which hormonal BC works.",
"I can understand the chain of thoughts. Hormonal BC prevents pregnancy. If pregnancy does occur, wouldn't that preventive thing kick in? And then >Would she have a miscarriage? Would the baby have birth defects or anything?",
"But hormonal BC is not an ",
"abortifacient",
". Hormonal BC works by preventing pregnancy and implantation. The most common types of hormonal BC is the pill, which is estrogen/progestin combined. Progestin is not progesterone, but it is a synthetic progesterone with similar effects.",
"Female fertility is cyclical and female hormone levels are cyclical. You get see this by looking. Here is a ",
"lovely image showing the female cycle",
". See the ovulation? That's the release of the egg, and for a woman to get pregnant, she needs to ovulate. Also, see those peaks that happen before and during ovulation? Those peaks in hormones are what causes ovulation. The ovaries produce more and more estrogen. Estrogen has a ",
"positive feedback on the pituitary in the hypothalamic-pituitary-gondal axis",
" so the pituitary makes more LH and FSH, and these in turn stimulate the ovaries to make more estradial which stimulates more LH and FSH and on and on and it's basically a biological circlejerk. The circlejerk is broken when ovulation occurs. The build up of LH and FSH is what stimulates an egg to be released. After that all the peaks come crashing down.",
"In their place, progesterone begins to rise. Progesterone, unlike estrogen, has a negative feedback on the pituitary, and so the LH and FSH levels stay lower. No ovulation. No egg, no pregnancy. Basically, there's a time in a fertile woman's cycle when she is naturally infertile. That's when progesterone is high. ",
"BC exploits this infertile period. Hormonal BC just sort of... extends this phase (sorry if that's not very science-y) by introducing progesterone like negative feedback by using progestin in the pill.",
"In fact, progesterone is a normal part of a pregnant woman's hormone... slurry I guess (it is late, that is close enough). ",
"You can see here.",
" And progestin is at least occasionally used to prevent miscarriages (Loose, Davis S.; Stancel, George M. (2006). \"Estrogens and Progestins\". In Brunton, Laurence L.; Lazo, John S.; Parker, Keith L. (eds.). Goodman & Gilman's The Pharmacological Basis of Therapeutics (11th ed.). New York: McGraw-Hill. pp. 1541–71.)",
"tl;dr Hormonal BC prevents pregnancy by making a woman not ovulate using the a synthetic version of a hormone that pregnant women naturally produce. This does not mean one way or the other about the effects using the pill would have on the pregnancy though.",
"Source: my notes from my behavioral endocrinology course, also wikipedia. Much apologies if this is not helpful, or scientifically unsound- it has been a couple years."
] |
[
"Looking at wiki, for perfect use it says it is 99.7% effective and clarified this mean 99.",
"7 percent of women using it will not get pregnant during the first year of use."
] |
[
"[Physics] Why is for example Lithium more electropositive than Potassium?"
] |
[
false
] |
Seing as they both lack the same amount of electrons.
|
[
"Just to clarify, electropositivity is the opposite of electronegativity. So since lithium is more electronegative, it is less electropositive. "
] |
[
"Lithium is not more electropositive than potassium. Lithium has an electronegativity of 0.98, and potassium has one of 0.82. The reason for this is because potassium has more electrons, and they shield the pull of the nucleus from the valence electron, meaning that it is held more loosely than lithium's valence electron. "
] |
[
"I'd rather put it like Ihmes: the valence electron is on average further away from the nucleus in the larger atom, so the electrostatic energy is larger, which makes it easier to strip away the electron. In both cases, the valence electron \"sees\" one positive unshielded charge in the nucleus."
] |
[
"Where is the force from a jet engine realised?"
] |
[
false
] |
I can see how I can analyse a jet engine as a system and get gas going one way so thrust in another but where does the 'force' actually manifest itself? Basically what needs to be built rigid? The combustion chambers don't look it and the rear end is probably drag. Obviously on a turbofan (a turboprop in a pipe) it is on the impeller but is this true of non-bypass engines?
|
[
"I still can't quite get a good grip of the forces. Maybe you can sketch a free body diagram of the nozzle?"
] |
[
"Depends on the type of jet engine. A turbine is basically a mechanical device that converts moving fluids to rotary motion, slowing the fluid in the process.",
"Turbofan thrust comes mostly from the large intake fan being driven by jet exhaust. The ratio depends on how much of the jet thrust energy is used by the turbine. Turbofans have a slower jet exhaust velocity and produces less noise. If all jet energy is used, then it becomes a turboprop.",
"Turbojet thrust is from the high velocity jet exhaust. The turbine captures only enough energy to drive the compressor and the rest of the energy produced is high velocity exhaust."
] |
[
"Depends on the type of jet engine. A turbine is basically a mechanical device that converts moving fluids to rotary motion, slowing the fluid in the process.",
"Turbofan thrust comes mostly from the large intake fan being driven by jet exhaust. The ratio depends on how much of the jet thrust energy is used by the turbine. Turbofans have a slower jet exhaust velocity and produces less noise. If all jet energy is used, then it becomes a turboprop.",
"Turbojet thrust is from the high velocity jet exhaust. The turbine captures only enough energy to drive the compressor and the rest of the energy produced is high velocity exhaust."
] |
[
"[physics]Why is the base unit of Mass Kilogramm and not simply Gramm?"
] |
[
false
] |
[deleted]
|
[
"The meter ",
" the base SI unit for length, however it is now defined as a fraction of c.",
"http://physics.nist.gov/cuu/Units/units.html",
"\n",
"http://en.wikipedia.org/wiki/SI_base_unit"
] |
[
"It's for practical reasons. A kilogram is defined as the mass of an object - the International Prototype Kilogram (IPK) - and the gram was deemed to small to make or use accurately. When they decided to create the IPK, they couldn't very well redefine the gram as it already was in use and had a definition: 1g = 1cm",
" of water at freezing (if you live in the US, you know how hard it is to make people switch methods of measurement). In order to keep things fairly consistant but move to the IPK method of definition (as opposed to the water weight method), the kilogram was defined as the standard and a platinum-iridium kilogram was created. "
] |
[
"Not in any commonly-accepted scientific use, no. Although \"megagrams\" isn't common either. It's a \"tonne\". (which is an SI-sanctioned synonym) "
] |
[
"Question about supposed link of vaccination and autism."
] |
[
false
] |
What would be the effects (if any) of delaying all vaccinations by 12 months? I ask this because if there weren't any harmful effects, why not have doctors delay all infant vaccinations by 12 months and see if the average age of children developing autism changes at all? I think it would prove conclusively one way or another. What do you think?
|
[
"There ",
"is no",
" \"supposed link\". The study that showed otherwise was based on falsified data and its author was found guilty of scientific misconduct."
] |
[
"http://phys.org/news/2011-01-autism-vaccine-fraud-journal.html",
"http://www.cnn.com/2011/HEALTH/01/05/autism.vaccines/index.html",
"http://www.msnbc.msn.com/id/40951375/ns/health-childrens_health/t/autism-vaccine-fraud-leaves-lot-mistrust-mop/",
"http://www.sciencefriday.com/blog/2011/01/the-great-autism-vaccine-fraud/"
] |
[
"delaying vaccinations by 12 months puts infants at risk for serious, life-threatening infections for 10 months longer than they have to be (most vaccinations start at 2 months of age)",
"There is NO. LINK. between autism and vaccination. Wakefield falsified his data, the paper was retracted by the journal and he is BARRED from practicing medicine again"
] |
[
"What causes the Casimir effect?"
] |
[
false
] | null |
[
"The vacuum fluctuations are a fundamental feature of the universe. They aren't really \"caused\" by anything. All of our quantum theories contain these fluctuations in various forms. Do you have a background in quantum mechanics? If so, I can give you some more detail. But the long and the short of it is that nobody knows ",
" the universe does that."
] |
[
"Ripples in the various fields that occasionally and temporarily line up to resemble a more permanent oscillation.",
"This is a nice explanation below.",
"http://profmattstrassler.com/articles-and-posts/particle-physics-basics/virtual-particles-what-are-they/"
] |
[
"As someone already pointed out, no one exactly knows ",
" this happens, but perhaps I can help you understand it a bit better.",
"I'm sure you're familiar with the Heisenberg's uncertainty principle [;\\Delta x \\Delta p \\ge \\frac{\\hbar}{2};] ",
"Another variation of this principle also exists:",
"[;\\Delta E \\Delta t \\ge \\frac{\\hbar}{2};] ",
"This ultimately means that a particle-antiparticle pair can be created out of nothing, if they \"borrow\" some energy [;\\Delta E;] for their creation and then \"return\" it via annihilation in some short time [;\\Delta t;]. Larger ammounts of borrowed energy mean shorter return times. This is why these fluctuations zero out at long time intervals and become visible at short time intervals.",
"But the point of the Casimir effect is that the vacuum expectation energy is not zero and that the energy fluctuates around this value. ",
"/u/Quoonit",
" stated that when two surfaces are broung together, the vacuum energy has to obey boundary conditions, as he described. This causes that not all modes are possible which results as different average vacuum energies between the surfaces and outside. This difference can be seen as a force that pushes the surfaces together, kind of like an example of an act of lower pressure. So if the average energy was zero or if there were no fluctuations, no energy difference would occur.",
"Here",
" is a nice image that shows how not all modes of vacuum fluctuations are possible in between two surfaces"
] |
[
"Why does a fan lower air temperature when you are adding kinetic energy into a system?"
] |
[
false
] |
I was thinking about this today when I was in my room. A fan is designed to be a mechanical machine that takes electrical energy and transforms into kinetic energy by moving the air molecules that come into contact with fan blades. Why does this increase in kinetic energy not translate into higher temperatures? (Ex. Wind chill factor) Edit: words
|
[
"Short answer: it does.",
"A fan not only adds extra motion to the air causing it to increase in temperature, but it also takes external energy and converts it to waste heat while moving the fan blades.",
"As a result, running a fan in a sealed room will increase air temperature.",
"The OTHER things the fan does, however, are:",
"a) it moves cooler air past your skin, enabling your body to transmit waste energy to air molecules which are then pushed out of the way and replaced with less energetic air molecules that can take up more of your waste heat. Because of this, the moving air feels cool to your skin, even though on a whole, it is warmer.",
"b) fans force airflow through an open system, such that you can pull cooler air from other places in your house to the rooms that are warmer by shoving all the hot air in the opposite direction."
] |
[
"A couple of points...",
"First, the average speed of a molecule in a gas is way higher than you think. If you do the calculation for nitrogen at room temperature, you'll find that the average molecular speed is ~500 m/s. However, the molecules will be moving in all different directions. All the fan does is cause a slight net movement in one direction, but it's going to do very little to change either the kinetic energy distribution or the temperature.",
"Second, if it's strong enough, the flow of air will heat up whatever it hits. The skins of aircraft get hotter the faster the aircraft is moving.",
"Third, as others have mentioned, you feel cooler when a fan blows on you because it enhances both the rate of heat flow and evaporation from your skin."
] |
[
"It doesn't lower air temperature and does, ultimately, make a closed system warmer.",
"However, in terms of personal comfort, it's not really relevant what the total effect is on temperature. A human body will warm up and humidify the air around it, so a fan that blows away that bubble of warm, wet air will make you feel cooler. "
] |
[
"Which part of speech is the most numerous? (prepositions, nouns, verbs, adjectives, adverbs, etc.)"
] |
[
false
] | null |
[
"Nouns are easily the most numerous. Nouns include the proper names of everything and everyone. They are often created to describe newly discovered objects. There are hundreds-of-thousands of last names in English alone."
] |
[
"It should be pointed out that OP's question only really makes sense on a language-specific basis (or maybe family-specific basis), since there is no crosslinguistically valid definition of what a \"noun\", a \"verb\" or an \"adjective\" entails. So comparing English parts of speech with Inuktitut parts of speech.",
"Also, if one were to meaningfully answer this question, one would have to account for derivation. Adverbs can be derived from adjectives, adjectives from nouns, etc. "
] |
[
"Most numerous could mean in the lexicon, or it could mean in terms of actual words uttered. I don't know if nouns are most numerous in the second sense, though it's plausible they are. If not nouns then adjectives or verbs."
] |
[
"How do humans determine the location of sounds?"
] |
[
false
] |
Is it based solely on differences in amplitude between the ears, or are we able to detect the minor delay as well?
|
[
"Like with depth perception in vision, we unconsciously fuse multiple direction cues. We can detect the amplitude difference and the delay, but my understanding is that a lot of it is (as ",
"/u/HorsefuckerJim",
" says in more detail) that the shape of our outer ear (the pinna) alters the sound differently depending on the direction it arrives from. We ",
" build up a mental model of where things are and use that to resolve ambiguities — we don't perceive each sound by itself, but at least partly based on our expectations and understanding of our environment.",
"The Wikipedia article on sound localization",
" goes into detail about many different mechanisms."
] |
[
"It's based on the difference in timing between each ear (interaural time difference or ITD) and a difference between the sound's frequency (pitch) and amplitude (loudness) between each ear (interaural level difference or ILD). Your ears can scrutinize ITD to microseconds. ILD is also super precise but I'm not sure of a good way to explain it in layman's terms. ",
"Your ears pick up the sound -> Sound waves in air are converted to fluid waves in your ear -> Fluids bend special receptor cells in your ear -> Which cells are bent and to what degree encodes details about the sound (pitch, loudness, etc.) -> Action potential to brain -> Superior olivary nucleus in your brain stem receives this info from both ears and compares ITD. Inferior colliculus in the midbrain does the same but with ILD. In both parts of the brain, certain neurons favor one ear. Based on how many \"left ear\" neurons vs \"right ear\" neurons are activated and some other brain magic -> More neural processing"
] |
[
"This is the main factor. Other people are talking about ear shape and other factors, but as someone who is now deaf in one ear and can very rarely tell where sounds are coming from, the differences between the left and right ears is by far the most important factor for determining the direction of sound."
] |
[
"Why do we laugh when being tickled when it actually pisses us off?"
] |
[
false
] |
from .
|
[
"Tickling behavior has been discussed by a lot of biologists. See, e.g. ",
"this article",
". The upshot seems to be that it is an evolved set of instincts to learn/teach what areas are vulnerable and should therefore be protected. Thus, you can't (normally) tickle yourself and all but the least inhibited individuals would not tickle strangers. Moreover, it has a heavy social component. There was some view that tickling was an essentially interpersonal behavior but this has been disconfirmed by the fact that people respond to tickling very similarly when they think a person or a machine is doing it. Here's a ",
"source which also surveys a bit of related literature",
"(pdf) It seems that in that context it also has some amount of dominance issues; someone tickling is making the instinctive point that they are dominant and can easily access one's vulnerable areas (this is probably part of why being repeatedly tickled can be unpleasant). This is similar to how in many other species play fighting even at a young age does result in actual dominance hierarchies. And in fact one sees similar behavior including \"laughter\" like behavior in other social mammals. See e.g. ",
"this paper discussing similar behavior in rats",
"(pdf). "
] |
[
"all but the most inhibited individuals would not tickle strangers",
"Could you elaborate on this please? It seems counterintuitive, since I would expect the least inhibited people to do this."
] |
[
"Yes, it is called I need to proofread more before hitting \"save\". That should be least inhibited individuals. Thanks for catching that. "
] |
[
"Is it possible to construct a radially magnetized sphere?"
] |
[
false
] |
Consider a product like which is an arc-segment magnet, with one pole on the inside, and the other on the outside. Is there a way to produce a solid sphere in this configuration? Would it behave like some sort of simulated monopole with one pole all over its surface and the other at its center? Would it be at risk from fracturing/exploding from the magnetic pressure of the pole constrained at the center? Or is this all just a fool's errand?
|
[
"The second of ",
"Maxwell's equations",
" which is known as ",
"Gauss's law for magnetism",
" states that the divergence of a magnetic field is zero.",
"This means that if you imagine a sphere that encloses your \"simulated monopole\" and you sum up the magnetic field lines exiting over the entire surface, the value of this sum must be zero. So Maxwells equations say that your \"simulated monopole\" is impossible in the same way as a real monopole.",
"The simple explanation of why monopoles do not exist is that unlike electric field lines, magnetic field lines always form loops and do not have a net divergence from any given \"magnetic charge\".(see ",
"here",
") So given this constraint, your \"simulated monopole\" with radial symmetry would have to have magnetic field lines that point outward with radial symmetry but also point inward with radial symmetry, which is the same as saying zero magnetic field.",
"Monopoles could exist, but they would have to be due to a \"magnetic charge\" type entity, such that the divergence of the magnetic field is nonzero for points on the \"magnetic charge.\" Vector calculus shows that it is not possible to create a \"simulated monopole\" by rearranging materials that produce magnetic fields with zero divergence. You either have this \"magnetic charge\" entity or you don't.",
"This is a classical argument, but as far as I understand this argument correct without dependence on an explanation of magnetic materials on a quantum scale."
] |
[
"This is the right way to think about it. If you could perfectly make that sphere, you'd have a magnetic monopole.",
"So you can't make that sphere have a perfectly radial field. Even in the link posted, those magnets do not have truly radially outward fields. If you carefully measured the field around that circular configuration, you will see the field flip direction periodically, showing that the field is made up of higher-order multipole moments (and no monopole ones)"
] |
[
"If you could perfectly make that sphere, you'd have a magnetic monopole.",
"I'm not sure I like the above sentence. It might imply that we're just talking about manufacturing issues, if you read it a certain way.",
"I can't make a radially magnetized sphere as a neodymium magnet, or even a section of a sphere, because of how difficult it is to shape this hard, brittle material, and to control the magnetization direction this way. There's huge manufacturing challenges. But let's ignore all that.",
"One question I often hear is, \"What if you put two half spheres together? Would that be like a monopole?\" I like this example, because the answer is illustrative and points to the practical result.",
"Let's assume for a minute that I could make a half sphere that's perfectly, radially magnetized (I can't). Alone, the magnetic field lines would flow out of the north pole (the outer surface) and around to go into the south pole (the interior surface). Now imagine taking 2 of these and smooshing them together, despite any repelling force. What do you get?",
"If you look at the magnetic field, it still flows out of the north pole, but it flows back in at the intersection of the two magnets. It flows back in at that equator-like line that goes around your sphere, where the 2 magnets meet.",
"In practical terms, what does this look like? Imagine that you have an ",
"electronic pole identifier",
" that can tell you the direction of the magnetic field. As you point it around the surface of these spheres, it will look like a north pole all around the outside surface. Right at the intersection of the two, however, the field will \"flow\" back in, and look like a south pole.",
"If you go back to the perfectly (!) homogenous, one-piece, radially magnetized sphere, the story is still the same. It doesn't have an obvious, equator-like fault line, but the magnetic filed is still going to flow back in somewhere. Maybe it's evenly distributed around the surface, but it's still getting in there. You might have to look at the microscopic level, if it squeezes in between magnetic domains."
] |
[
"If we threw a clock into outer space, at what point would it stop showing us the \"right\" time when viewed through a telescope?"
] |
[
false
] |
Okay, don't even totally know what I'm asking so bear with me here: We put an atomic†, never-running-out-of-batteries clock into outer space, maybe not even going at a speed fast enough to noticeably dilate time††, and we let it go for a long long time. When we look through a telescope at things very far away, we're technically looking . So when/where would that clock stop showing the same time as earth clocks? Or, rather, what would it show? † does that make a difference? †† is that even possible? Hopefully that question makes sense. I'm excited for the answers. Thanks! Edit: spelling and notes. Edit 2: Awesome answers guys! and thank you. In the light of day, I feel silly about how simple the answer is. I think I meant to ask more about what would happen while i was viewing the clock, but I think I figured out (with the help of you guys and a few other physics friends) that if the clock is moving away from me at a constant speed, the length of time that lapses between Space Clock's seconds will increase. ...exponentially? I think originally I wanted to know what time looked like over time, but these answers and discussions have been enjoyable.
|
[
"It depends on what you're sensitive to measuring on Earth. Let's say you moved it slowly enough to avoid the effects of special relativity and let's ignore the effects of gravitational time dilation for the moment too. Now let's say I can measure time to a precision with an atomic clock, which from ",
"wikipedia",
" says roughly 1 nanosecond (that's also what ",
"this",
" page seems to verify if I read that correctly). You want to convert the lookback time of this clock to your clock into a distance. Well, light travels at roughly 1 foot / nanosecond. So, your answer just considering lookback time: 1 foot (~0.3 m).",
"This may seem puzzling to you, since that means if I put an atomic clock 1 foot from you, it would be 1 ns off. This doesn't seem like a very good clock except for the fact that all atomic clocks are shifted to the same time standard which takes into account the position on the Earth, etc. This is pretty messy business. If you're interested, start ",
"here",
". You can keep defining more precise time standards until you're measuring the deviations from a perfect sphere in the case of the Earth, or the slight effects of gravity from the various Solar System bodies.",
"EDIT: Typo."
] |
[
"At the most basic, the clock will be behind based on its distance from you. If it's one light-year away, it will be a year behind. If it's a light-minute away, it will be a minute behind, simply because it takes that long for the light to reach you. This ignores any relativistic effects, but I think it's what you're asking."
] |
[
"Actually, atomic clocks are typically quite good for keeping time standards, unless you need some ridiculous precision. They rely on keeping good measurements of a natural process, so aren't really Earth-centric in that sense. It's when you want to start comparing atomic clocks that things get tricky but since you're typically comparing them on or around Earth, this is quite fine. ",
"In reality, the better your clock is at measuring, the shorter the distance would be in your problem. Really, you can't get past the fact that the speed of light is finite, so that everywhere you look in the Universe appears \"in the past\" to you so to speak."
] |
[
"How did we adopt standard rendering settings such as 1080p resolution, 30-60 fps, 60-144 hz refresh rate, etc.?"
] |
[
false
] |
I'm curious as to how we came up with these standard values that most screen manufacturers, game creators, video rendering programs have adopted, etc. have adopted.
|
[
"The standard TV refresh rates - 50Hz in former \"PAL\" countries, 60Hz in former \"NTSC\" countries - came about largely because they matched the frequency of the alternating current used in the countries that developed them, although NTSC later screwed this up and has annoyed a generation of broadcast engineers by dropping it to 59.94Hz when they introduced colour."
] |
[
"It's not technically NTSC, as that is purely an analogue system (as is PAL), but we (former broadcast engineer, sort of, current video enthusiast) still call any video which is 704/720x480 @ 23.976/29.97fps (interlaced or not) \"NTSC\". Sometimes it's used to refer only to the framerate, even if the video itself is HD."
] |
[
"I don't pretend to know how over-the-air digital works, so I have to ask if we are still broadcasting NTSC encoded digitally and still have that grandfathered in, or if we are using more modern codecs now?"
] |
[
"Friend has been working in the schools chem lab for years & still has no idea what this thing is for. Anyone?"
] |
[
false
] | null |
[
"Looks like an adaptor for vacuum evaporation that has an adapter to prevent any solutes from getting sucked up as well. "
] |
[
"I believe it is a cold finger. ",
"http://en.wikipedia.org/wiki/Cold_finger"
] |
[
"It's kinda hard to tell what it is from the picture. Can you get a better picture of it without so much glare/blurriness? ",
"From what's there in the picture, the best I can guess is some strange kind of distillation head or, if that tube on the bottom is sealed, the top half of a sublimator."
] |
[
"How does the mRNA from the new vaccines enter our cells?"
] |
[
false
] |
From what I understand most vaccines use a “vector” to deliver the payload to our cells, in order to trigger the immune response. But with these new mRNA vaccines there appears to be no vector. They just inject mRNA into the body directly and our cells just “slurp it up” somehow?
|
[
"But the RNA vaccines don't work like that, the idea of inject the RNA is for your own body to produce the spike protein"
] |
[
"But the RNA vaccines don't work like that, the idea of inject the RNA is for your own body to produce the spike protein"
] |
[
"The mRNA is packaged inside ",
"liposomes",
" or ",
"micelles",
" (not sure which), which are little (~50x smaller than a cell) packets of cell wall without any receptors. Basically fancy soap bubbles. There are a bunch of them naturally in your blood stream doing various things, and they are capable of merging with a cell in the same way that two soap bubbles can merge.",
"Viruses typically need receptors because the process of merging like this is pretty slow- cell walls are naturally repelled from each other. The success of a virus depends on its ability to outrace the immune system's ability to remove it- plain liposomes will get removed by the liver and any macrophages floating around. A virus that only reproduces like this will not be a very dangerous infection unless your immune system is really compromised. ",
"The mRNA vaccines don't need to worry about outracing your immune system. When a virus is introduced to your body, there may be a very small number of infectious agents, and they have a very small number of chances to reproduce. A vaccine doesn't have that problem since you can just increase the dose. As long as ",
" mRNA gets into some cells, they'll start producing spike protein which will train the immune system."
] |
[
"Is freezing point elevation possible?"
] |
[
false
] | null |
[
"Substitution of heavier isotopes will result in a higher freezing point. For example, you'll get roughly +0.04 °C elevation in the freezing point of water for every mole % increase of Deuterium. Freezing point elevations in other isotopomers, however, are generally smaller."
] |
[
"Surprisingly, yes. In nanopores, phase behaviour of compounds are changed. In most cases, the freezing point will be decreased, but if the correct pore diameter and size is used, the freezing point will instead increase, as reported in this article by Kaneko et al.",
"Kaneko, K.; Watanabe, A.; Iiyama, T.; Radhakrishan, R.; Gubbins, K. E., A remarkable elevation of freezing temperature of CCl4 in graphitic micropores. Journal of Physical Chemistry B 1999, 103 (34), 7061-7063.",
"This is most likely not applicable in larger volumes of liquid where the colligative properties of a mixture will lead to freezing point decrease. However, when studying a phase diagram for most compounds (baring water which is special), you can see that the freezing point will increase under pressure as the solid form takes up less space than the liquid."
] |
[
"Awesome. Just awesome. Thank you. "
] |
[
"What are the magnetic properties of light?"
] |
[
false
] |
Light is part of the electromagnetic spectrum, it's more common to think of light's electric properties, what's magnetic about light? How strong and useful are the magnetic properties?
|
[
"Light, in terms of how you wish to discuss it, exists in its wave form as orthogonal waves of electric and magnetic fields--fields is the important aspect. It doesn't exhibit magnetism in the sense of a traditional bar magnet--in fact, it doesn't really exhibit magnetism as we think of it in terms of classical physics at all. There's no magnetism at all, it's just a manifestation of EM radiation. "
] |
[
"Well after doing my own research, ",
"light does of some magnetic properties.",
" and I was looking more along the lines of the power of it's magnetic field."
] |
[
"Light is a traveling oscillation in the electromagnetic field. This means it does have a magnetic component, so it can influence charges like a magnet would. Light waves look like ",
"this",
"—the magnetic field component is shown in blue.",
"It's not so much that light has magnetic properties. It's more than oscillations in the magnetic field are half of what light actually is! However, magnetic fields are generally much weaker than electric fields (glossing over some details), so you wouldn't tend to notice this as much as the electric field component.",
"As to that article…the effect they're talking about is interesting, but very poorly-described. Don't take any of the article's language at face value. For instance:",
"Light, like all other physical forces, has electric and magnetic effects.",
"I don't even know where to begin correcting that sentence!"
] |
[
"Is cold water detergent really worth the expense?"
] |
[
false
] | null |
[
"Here's a NY Times article talking about the introduction of cold water detergents. Not exactly what you are asking about, but relevant. The first paragraph is a good summary of the article:\n",
"http://www.nytimes.com/2011/09/17/business/cold-water-detergents-get-a-chilly-reception.html?pagewanted=all&_r=0",
"Newly formulated laundry detergents can wash most clothes perfectly well in cold water, manufacturers say, but customers are stubbornly refusing to turn down the temperature. Although some of these detergents have been available for several years, customers cling to mom’s age-old advice that hot water washes best — squandering energy and contributing to greenhouse gas emissions."
] |
[
"Sorry, but you completely messed up the terminology there.\n\"Soap\" is a general term for mixtures of fatty acid salts which can function as surfactants. Metal ions in hard water will form precipitates with soaps, but this is not an intended function. For this reason detergents, the stuff you use to wash your clothes, does not contain any soap. Instead it contains a different surfactant, ",
"alkylbenzenesulfonate",
". Also detergent contains a large amount of \"builders\", which are used to soften the water through ion exchange.",
"TLDR: soap != detergent"
] |
[
"The idea of \"soap\", is to soften the water - remove metallic ions; it also degreases. I always wash-up using cold water and still get good results; it's just unpleasant to my hands on a cold day. It would seem, cold water detergent, could be a marketing ploy."
] |
[
"Is eating a raw diet the healthiest method of sustinence?"
] |
[
false
] |
Aka a largely vegan diet? I've heard this argument a great deal from vegans. As well as the argument that "we aren't supposed to eat meat" I.e. "Meat eating is unnatural".
|
[
"A very apt example is the vitamin B12 (cobalamin), of critical importance to the survival of almost every kind of human cell, that is only found in sufficient amounts in non-vegetarian food (read: meat).",
"This is the death knell of the idea that eating meat is \"unnatural.\" Without the ability to artificially purify/create Vitamin B-12 and fortify vegetarian diets with it, which is a capability that has only existed for about 90 years, not eating meat causes megaloblastic anemia, and ultimately irreversible spinal cord degeneration and death if untreated. The ability to survive off of vegetables is a modern luxury."
] |
[
"To elaborate on this, our metabolism on a cellular level reflects our omnivorous role in nature. There are many fats, vitamins and other micronutrients that are essential to our survival that we can't synthesize even if we have the necessary ingredients.",
"There hasn't been any evolutionary pressure for human cells to develop ways to make these compounds because we have successfully relied on eating other animals and plants that can synthesize them. A very apt example is the vitamin B12 (cobalamin), of critical importance to the survival of almost ",
" kind of human cell, that is only found in sufficient amounts in non-vegetarian food (read: meat)."
] |
[
"To elaborate on this, our metabolism on a cellular level reflects our omnivorous role in nature. There are many fats, vitamins and other micronutrients that are essential to our survival that we can't synthesize even if we have the necessary ingredients.",
"There hasn't been any evolutionary pressure for human cells to develop ways to make these compounds because we have successfully relied on eating other animals and plants that can synthesize them. A very apt example is the vitamin B12 (cobalamin), of critical importance to the survival of almost ",
" kind of human cell, that is only found in sufficient amounts in non-vegetarian food (read: meat)."
] |
[
"I know that computers use base 2, we use base 10 and base 12 would be more useful. But are there other (non-primitive) ways to count things other than \"base x\"?"
] |
[
false
] |
[deleted]
|
[
"The most important way is ",
"Continued Fractions",
". These are much better than any base, in terms of accuracy, but are not convenient to do arithmetic with.",
"A sequence [a",
",a",
",...] is the continued fraction expansion of a number x if x=a",
"+1/(a",
"+1/(a",
"+... For instance, the continued fraction expansion of pi is [3,7,15,1,292,1,1,1,2,1,3,...], so if we want to get an approximation for pi, we just plug some number of these into this pattern. So",
"pi ~ 3",
"pi ~ 3+1/7 = 22/7",
"pi ~ 3+1/(7+1/15) = 3+15/106 = 333/106",
"pi ~ 3+1/(7+1/(15+1/1)) = 3+1/(7+1/16) = 3+16/113 = 355/113",
"etc",
"If you do this infinitely, you'll get pi exactly. Each of these is a pretty good approximation for pi, the last one being accurate to 6 digits. Continued fractions ",
" converge to the number they represent ",
" than decimals. Much faster.",
"They have some other interesting properties. It's relatively well known that a number is ",
" if it's decimal expansion eventually starts repeating a pattern. Even if that pattern is just zeros (which means it ends). If we look at the continued fraction expansion of a rational number, it will always terminate. That is, it always just ends in zeros. We can view this as saying \"The continued fraction expansion of any number that is a root to an equation of the form Ax-B=0 terminates, where A and B are integers.\" So what are the numbers that have ",
" continued fraction expansion? It's all ",
" numbers. That is, the numbers whose continued fraction expansion eventually repeats a pattern are exactly the numbers that are solutions to equations like Ax",
"+Bx+C=0. How they eventually repeat only depends on the discriminant B",
"-4AC. ",
"For example, the Golden Ratio has continued fraction expansion [1,1,1,1,...]. The square root of 2 has continued fraction expansion [1,2,2,2,2,2,...]. ",
"To see how this might work, notice that the golden ratio is the largest root of x",
"-x-1=0. This means that x = 1+1/x. Plugging x=1+1/x into the second x gives x=1+1/(1+1/x). Plugging x=1+1/x into the second x of ",
" gives x=1+1/(1+1/(1+1/x))). Continuing this forever gives x=1+1/(1+1/(1+1/(1+1/(..., which is the continued fraction [1,1,1,...]. In fact, since small denominators make for larger values compared to large denominators, and these denominators are all 1s, the Golden Ratio (and it's relatives) has the ",
" converging continued fraction expansion of any real number. In this way, some might say that the Golden Ratio is the ",
" irrational number.",
"EDIT: Contrast this to decimal expansions of numbers. A sequence a",
"a",
"a",
"... of numbers with 0<=a",
"<9 is the decimal expansion of the number ",
"For example, if n=0 and a",
"=3, a",
"=1, a",
"=4, a",
"=1,... then we get the decimal expansion for pi:",
"Which we usually just write as 3.1415... to save space. When we write any decimal expansion we are always implicitly writing a sum like this, and it is these sums that make our addition, multiplication and division algorithms work as they do. We can only get one decimal for each term in the sequence a",
", by definition. Since continued fractions don't have this limitation, you almost always get many decimal places for every term. This means that they converge faster."
] |
[
"There's Roman numerals, although that's very similar to base ten. There's also ",
"mixed radix",
" numeral systems. For example, there's 24 hours in a day, 60 minutes in an hour, 60 seconds in a minute, and 1000 milliseconds in a second. So if you say something takes 3 hours, 12 minutes, 26 seconds and 412 milliseconds, you're not using any one particular base."
] |
[
"This doesnt really answer the question of OP. The continiued fraction of a natural number n is just the number itself. Thats not really another way for \"counting\"."
] |
[
"Do vitamin supplements provide health benefits or am I just paying for expensive urine?"
] |
[
false
] | null |
[
"Let me know if I'm just misunderstanding your post; but isn't the gist of it: \"Healthy adults don't need multivitamins because they don't cure cancer or prevent heart disease.\" If that is it, then I don't think its answering OP's question or addressing the reason most people take vitamins. I was under the impression that people take vitamins to use their disposable income on something that keeps their coats shiny and their vitamin C up on days when they maybe drink less than the recommended dosage of OJ - not to cure their cancer or keep them alive."
] |
[
"The current consensus is that healthy individuals do not need any regular micronutrient supplementation. For example, ",
"this large RCT published in JAMA",
" looked at cancer rates in male physicians over 50, and found a small (8%) reduction in overall cancer rates, without significant reductions in specific individual cancers. There was also no reduction in cancer mortality. ",
"The same study",
" found no significant effects on cardiovascular events, cardiovascular mortality, or total mortality in 10 years of follow-up. ",
"Similar cohort studies in postmenopausal women",
" also found no significant benefit to cancer rates, cardiovascular disease, or total mortality. ",
"This study of 13,000 French men and women",
" found no effect on overall cancer risk, with a slight decrease (31%) in cancer risk in men, without any effect on cardiovascular disease. ",
"Another study of 35,000 Swedish women",
" found a small (19%) increase in risk of breast cancer associated with multivitamin use, while also finding a small (27%) decrease in new heart attack rates.",
"Large cohort studies",
" and ",
"meta-analyses",
" have repeatedly demonstrated no benefit in all-cause mortality. ",
"There are some clear roles for vitamin supplementation (eg folic acid for women who may become pregnant, or supplementation for specific deficiencies), but on the whole it is not recommended that healthy individuals take multivitamins. Admittedly these studies are unable to identify benefits that take longer to develop (follow-up period for these studies is usually around 10 years), but as it stands there is no good evidence to recommend regular MVI use in healthy individuals given the conflicting data on specific health benefits and the unequivocal data showing no mortality benefit. "
] |
[
"Pharmacist here: \nTLDR Version: Vitamins A,D,E,K are fat soluable vitamins and can be harmful if taken is excess as they are not excreted in the urine. Vitamin D supplementation is the new craze at the moment, but levels need to be monitored with blood draws so see your doctor before starting supplimentation. ",
"Water soluable vitamins (every other vitamin) are mostly a waste unless your diet is terrible."
] |
[
"How can lasers cool something to near absolute zero?"
] |
[
false
] |
[deleted]
|
[
"The easiest method to explain and I believe one of the earliest is Doppler cooling. The Doppler effect as it relates to light basically means that if you're moving towards a light source the light will be blueshifted, meaning it has a shorter wavelength and a higher energy, and if you're moving away it will be redshifted, having a longer wavelength and lower energy.",
"To cool atoms using the Doppler effect, you use a laser that has a photon energy slightly lower than the energy needed to excite a certain state in the atom. If an atom is moving away from or perpendicular to the laser, the energy of the photons will not be enough to excite the atom so they will not interact. However, if an atom is moving towards the laser, the photons will be blueshifted, giving them enough energy to be absorbed and excite an electron to a higher state. By conservation of momentum, the atom now has its initial momentum minus the momentum of the photon it absorbed (since the atom and photon are moving in opposite directions), meaning it has slowed down. The excited atom will then release another photon as its electron returns to the ground state, which will change its momentum again, but the direction of emission is random, so on average an atom will lose momentum equal to that of the incident photons."
] |
[
"So collisions can be considered perfectly elastic?"
] |
[
"Ah, this is really interesting.",
"First of all, atoms absorb and emit electromagnetic waves, i.e. light of specific, quantized, frequency (or wave length). Second, light carries momentum. Meaning it pushes on stuff it hits.",
"Big contribution to the temperature of atoms is their movement in space. And you use laser to suppress that movement and consequently cool them. How? By using lasers which have frequency tuned little bit ",
" \n lower than frequency which is absorbed by atoms. That way only atoms which move towards laser can absorb light because they see frequency shifted up because of ",
"Doppler effect",
". And since light has momentum atom is pushed the other way it was moving causing it to slow down.",
"Atom that absorbed photon is now in excited state and must return to its ground state by emitting photon which could be a problem because emitted photon would push in opposite direction. However, emission is in random direction so it averages out to zero after a while."
] |
[
"Why do Iron fillings highlight the field lines of a magnet?"
] |
[
false
] |
I understand that there is a magnetic field surrounding a bar magnet and they make a torus shape. And that the iron filings are showing that when we sprinkle them over the top. But why do the iron filings display them as lines? I thought they would be a somewhat smooth distribution. Is it some sort of frictional mechanism with the filings and the paper maybe?
|
[
"The \"lines\" are a result of the filings, and not discrete magnetic lines.",
"The filings are not round but small strips, and when subject to a magnetic field become magnetically attracted to each other, end to end, forming the lines.",
"Each filing more strongly attracts to the end of other filings than to the sides of other filings, so you don't get a smooth gradient."
] |
[
"That makes sense, thank you"
] |
[
"The iron filings become tiny little magnets in the presence of the field. One end is drawn towards each magnetic pole. The net result of the two attractions and two repulsions present results in the filings pointing in the direction of the magnetic field lines."
] |
[
"I am about to attend my first scientific conference. What should I expect, and what should I do to get the most of it?"
] |
[
false
] |
I'm an undergrad who is really interested in research, and I'll be going to this year's SFN. I'm not presenting a poster, but I just wanted to see and learn from all the other work being presented. I don't know quite what to expect at a conference. Any advice for me from those who have experienced it all? Also, I'd love to hear if any of you will be at SfN.
|
[
"First and foremost, chill out!! These things are very relaxing and a very good chance to network while at the local bar. ",
"My best advice; Talk to lots of people at the poster sessions, even if it isn't your field, people are very open, friendly and more than willing to discuss there work with you, even if you are just an undergrad and don't really understand it, it gives them practise discussing there work (and more often, passes time). If you can, try remember names, say hello when you see people you have spoken to and they will remember who you are. Get to know who the big-wigs are in the field and talk to their PhD students, chances are the big-wigs are near by and will enter the conversation. If you are looking for something more, like a PhD position from a lab which is going to be there, do your background on what the lab's current topics are, who there competitors are and which direction the field is going in. When speaking to someone presenting a poster (generally a PhD student or new Post-Doc), drop that you are interested in their lab and they will prob introduce you to the Prof whom you can have an open discussion with. ",
"I have presented at many conferences and this has been done to me, and I have done it many times. Nobody is going to judge your academic ability, just try have a general grasp of current topics.",
"You will enjoy it!!"
] |
[
"Go through all the listings beforehand and highlight all the talks you want to attend. They usually are clumped by symposium so that will make it easy. For smaller conferences, the best talks tend to clump towards the beginning of the week in my experience. Carry a notebook for notes and contact info of interesting people. If there are no very interesting and germane talks you want to see, find an interesting symposium and sit in there. This is how you discover interesting new sub-fields and shake up your thinking.",
"During poster sessions, obviously check out the poster listings you find interesting. Poster sessions, since they are closer to 1-1 interaction are a great way to find out about other research groups you might want to work for if you are looking for a postdoc/grad program. You can ask what the group dynamic/PI is like and get a contact in that group."
] |
[
"Others have great points.",
"I would add: get the agenda and plan to see talks that are interesting to you and relevant to your ambitions. Ask people for cards, or where to e-mail for a pre-print and then FOLLOW UP.",
"Try to attend any cocktail sessions or other social events. Professors are most honest and useful with a bit of alcohol in them.",
"If anything really grips you, and you want to do research, look for ways to connect ideas or extend them - that is a decent way to get started in research."
] |
[
"How does gravity work?"
] |
[
false
] |
Why are objects with mass attracted to each other? And how can the universe expand infinitely if all objects with mass are attracted to each other? (After reading the wikipedia page on I think I understand the answer to the second question... At least a very basic level.)
|
[
"Objects with mass are attracted to each other because mass curves spacetime. The ",
"Einstein Field Equations",
" describe this. These equations are, basically:",
"Curvature = Matter",
"So, if you've got two masses, they both cause space time to curve. This causes the masses to move towards each other. You can try to think of lots of visualisations of this (masses on rubber sheets, etc) but they all tend to contain at least one oversimplification. The important thing is that some kind of ",
" is what gives rise to the phenomenon we see as massive objects attracting each other. "
] |
[
"The Einstein equations are the central results of general relativity, which is a ",
" field theory. The graviton is a hypothetical particle which would enable us to model gravity using ",
" field theory, which is the framework with with we model all other physical phenomena. But, for various reasons, this framework is somewhat difficult to use for gravity, so for the moment general relativity is formulated without considering quantum mechanics, so without the idea of the graviton. "
] |
[
" isn't really within the scope of physics, as far as we know. ",
" is explained by ",
"general relativity"
] |
[
"How do we know what happened during Big Bang Nucleosynthesis?"
] |
[
false
] |
I know that we use the modern day elemental abundances (mostly of H, D, He-3, He-4, and Li-7), baryon-photon ratio, and cross section to determine the conditions during BBN, but how exactly does all of this tie in? Is there one singular formula like those posed in that ties all of these together? Also, can we use these data to extrapolate into the future? It would be great if you're as specific as possible.
|
[
"Hi again. There is no simple formula to extract the ratios of these elements, it depends on detailed knowledge of the level structure and interaction crossections of these nuclei, particularly with lithium, which has the most complicated structure, being the largest.",
"If you're referring to equation 1 from αβγ, it is not as simple as it seems. All of nuclear physics known and unknown is hidden in the sigma terms. It is also overly simplistic in that it treats nuclei as a 1-dimensional family (mass number) rather than 2-dimensional (proton and neutron numbers). αβγ, while an important paper in history, is not a good source of information for nucleosynthesis.",
"The conditions of the universe now can be extrapolated back to the big bang with the help of the ",
"FRW equations"
] |
[
"So regardless of accuracy, how could I use aby to extrapolate backwards? "
] |
[
"I don't know if I can explain it better than they do. They use the crossections (sigmas) they cite and find what conditions during BBN give the closest fit to the abundances we see now."
] |
[
"Will releasing store-bought Preying Mantises into my garden unbalance its ecosystem?"
] |
[
false
] |
My girlfriend works at a garden center that just started selling these little pods full of Mantis eggs, about 300 eggs per pod. You're supposed to release the eggs into the garden, and when they hatch after a few weeks, the little guys are supposed to descend upon the bugs in the garden like the black wing of death, devouring everything they can find. I'm thinking this is great, Praying Mantises are awesome, and they're eat all the pests attacking the plants, but won't they kill all the beneficial insects too? Bees and butterflies and so on? Will this ultimately be creating a much more severe problem than it's meant to fix?
|
[
"One problem is outbreeding depression. You would be modifying the resident gene pool with potentially foreign genes. the other possibility is that you could be introducing non-native mantises, and they may be an invasive species at you location."
] |
[
"Yeah. You should probably not do that. They'll kill pretty much everything, and moving species around in general is almost never a good idea unless you're a conservation biologist and you really know what you're doing (and even then, it's hard to do without screwing up ecosystems)."
] |
[
"Could you explain what outbreeding depressing is?"
] |
[
"Are there organisms with multiple brains?"
] |
[
false
] |
I am excluding symbiotic units for this question. And I'm also specifying only brains grown through cell differentiation, not through the assimilation of a foreign organism. And, if they exist, what are they? Thanks.
|
[
"You don't have multiple brains, but you do have spinal cord ganglia - clusters of nerves - able to process simple information and take independent action such as moving limbs away from pain without the delay of sending the message up and down your spinal cord.",
"Biologists say humans have a high degree of cephalization. Information processing and sensory equipment is concentrated in one region - a \"head,\" and you have a centralized mass of fused ganglia crammed close enough to rapidly trade information called a brain. ",
"Evolving a brain allows for more sophisticated and faster processing. Many creatures such as flatworms are less cephalized than humans and are less bothered by losing their heads. They say two heads are better than one but evolution has never gone in that direction."
] |
[
"An octopus has a decentralised nervous system meaning that most of its neurons are actually in its arms, rather than the brain. With eight arms and a central brain, some people say that an octopus has \"nine brains.\" This is a bit flashy for my taste but depends on your definition of a brain.",
"Also strangely their throat (or throat equivalent) runs straight through the central brain, so if they eat something a bit too sharp, it can damage nervous tissue. ",
"In early vertebrate evolution, before a true 'brain' emerged, there may have been two nervous control systems. One controlling the eyes and one controlling the mouth (this would have been very early on in evolutionary history, pre-Cambrian I think). Eventually the two would have fused together, to get the brain we have today.",
"Read Other Minds by Peter Godfrey-Smith if you like this stuff :)"
] |
[
"Octopus. If learnt that from \"finding dory\"",
"https://apnews.com/article/ri-state-wire-octopuses-ma-state-wire-ba6e3fa5bb804565b9d6d666b6d40a73#:~:text=The%20giant%20Pacific%20octopus%20has,making%20reality%20stranger%20than%20fiction.&text=A%20central%20brain%20controls%20the,that%20biologists%20say%20controls%20movement.&text=Two%20hearts%20pump%20blood%20to%20the%20gills",
"."
] |
[
"Why are the furthest 4 planets gas giants, but the closest 4 are rocky? Do gas giants always form farther away from stars?"
] |
[
false
] | null |
[
"As I recall from my recent-ish astronomy course, the outer gas giant planets are beyond the ",
"frost line",
". This means that in early planetary formation, the planets that had begun to coalesce beyond the frost line were able to take in icy compounds and combine them with the planets, which was an enormous help in gaining enough matter to gravitationally bind gasses to the core. The inner planets didn't have the advantage of being able to \"gather\" its local water and integrate it into its planet, so they couldn't gain enough mass to become large enough to gather any respectable amount of gas like the gas giants.",
"This is of course just our current understanding of the ",
"evolution of the solar system",
". I should also point out that the article on the frost line notes:",
"However, gas giant planets have been found inside the frost line around several other stars (so-called hot Jupiters). They are thought to have formed outside the frost line, and later migrated inwards to their current positions.",
"Although I do not believe we have any definitive evidence for a \"migration\"."
] |
[
"Due to the centripetal forces acting on he spinning disk, those particles with less mass feel greater acceleration, thus moving away from the star much faster. As you can guess, this separates the disk into a dense, rocky center and a light, gassy outer ring.",
"Incorrect. All objects will feel the same acceleration in the same gravitational field. If what you're saying is true, you and I would be flung into the outer solar system because we feel a weaker acceleration towards the Sun than the Earth does. A bowling ball would fall faster than an apple when dropped at the same time.",
"From a mathematical perspective, this is because ",
"F=m1a",
" and ",
"F=Gm1m2/r^2",
". ",
"m1a = Gm1m2/r^2",
" -> ",
"a = Gm2/r^2",
". Acceleration is independent of mass of the falling object.",
"The real reason is because lighter particles are more influenced by ",
"radiation pressure",
" than heavier elements. Radiation pressure is independent of the mass of the particle being influenced, only to its cross section.",
"Also, heavier elements clump up into objects of varying size. Helium is always a gas, which is swept away by radiation pressure. Hydrogen typically ends up as molecular hydrogen, which is swept away by radiation pressure, or methane in the presence of carbon, which is swept away by radiation pressure, or water in the presence of oxygen, which is often swept away by radiation pressure depending on its state. Once you get rid of all the helium and most of the hydrogen, you end up with Earth."
] |
[
"The reason why gas giants form farther away from their host star then rocky planets, is that they need to be far enough away from their host star so that the temperature is low enough for compounds such as ammonia, water and methane to condense into solid grains(about 150 kelvin/-123 degrees celcius). The distance from the star where this is possible, is called \"the frost line\". Inside of the frostline, hydrogen compounds such as water, ammonia and methane remain in a gaseous state, and are therefore unable to form solid grains, wich are necessary for further accretion to occur. However, since metals and rocks have a much higher boiling point, they are able to stay in a solid state inside this frostline, therefor creating solid grains of rock/metal which can accrete into planets. Here is a link for more details: ",
"http://lasp.colorado.edu/education/outerplanets/solsys_planets.php",
"Also, rock and metals are more common near the star, and lighter elements are more common farther away. I am not sure why this is, but my guess is that during the supernova of the previous star, the lighter elements(with lower mass) accelerated more then the heavier elements(with more mass), and thus trowing them farther out into space. "
] |
[
"How much could the largest gorillas bench press?"
] |
[
false
] | null |
[
"Good ole ",
"wikipedia",
" archived discussion says that this has never been really truly studied. there is a neat factoid near the bottom of the article that says the Guiness Book of world records recorded a chimp did a 600lb deadlift. they extrapolate that to a gorilla being able to lift maybe 1200 lbs. "
] |
[
"The Straight Dope",
" has an old article on how a 165 pound chimp once yanked on a dynamometer to the tune of 847 pounds with one hand, and a 135-pound female pulled 1260 pounds. It notes chimps have deadlifted 600 pounds without problems.",
"It then suggests a mature male gorilla \"could probably heft an 1,800-pound weight and not think twice about it.\""
] |
[
"For context, the current deadlift world record is 460,4 kg (1015 lbs).",
"http://en.wikipedia.org/wiki/Deadlift#World_records"
] |
[
"What happens to a candle's wax as it burns? Why does it slowly disappear until there's none left at the end?"
] |
[
false
] | null |
[
"It oxidizes, as burning is a combustion reaction. The carbon compounds in the material break apart whilst reacting with the oxygen to form carbon dioxide, energy and byproducts (depending on the specific compounds, greatly simplified). The energy is the heat and light from the fire (mostly), the carbon dioxide is the gas (again, mostly, there are also carbon particles, carbon monoxide, unburned carbon dioxide and fumes, etc.) Since the compounds make up the wax and the compounds are being broken down into gas, eventually, all the wax has turned into gas and soot (the candle has been completely burned) and there is therefore no more wax."
] |
[
"For the same reason as gasoline in your engine slowly disappears until there's nothing left. Or, if you stop eating, the fat & muscles in your body disappear until there's less of you left.",
"Generally, as with all oxidizable fuels, the oxidation (aka burning) of the fuel produces gasses (exhaust) + energy. The fuel itself disappears and its mass goes into the gasses of the exhaust (usually CO2 + water + other exhaust gasses).",
"You, your car, and a candle burn your fuels and dump the products into the atmosphere. As you do this, you get energy, and the fuel itself seems to disappear. Really the fuel is converted to gas and it ends up in the atmosphere as new different (often simpler and less energetic) chemicals such as water, CO2, etc."
] |
[
"The wax melts to form a pool around the wick. The hot wax rises to the surface. Wax as a liquid flows up the wick from capillary actions just as paper towels sop up oil. In the wick the wax turns mostly to gas which is oxidized and burns initially with a blue almost invisible flame. The orange and red flames are heated soot and poorly burnt wax."
] |
[
"How are there fish in dune pools/lagoons (ephemeral pools?) like those in North East Brazil?"
] |
[
false
] |
In Super/natural on Disney +, episode 6 titled “impossible journeys” a slider turtle finds pools of water that form in the desert after rain. My question is, how are there fish in these pools if there was no water before it rained?
|
[
"There are studies that suggest that mallard ducks are the cause.",
"Mallards consume large amounts of eggs from fish that have entered spawning season, most of which are excreted within an hour. In an experiment where about 500 eggs were fed, it is said that 3 eggs finally hatched.",
"If a mallard duck defecates after an hour, it can travel about 60 km, and if it defecates after 4-6 hours, it can travel 360 km.",
"A low probability shouldn't be a problem, as carp lay 1.5 million eggs and Prussian crucian carp 400,000 eggs at a time.",
"Proceedings of National Academy of Sciences(PNAS), DOI: 10.1073/pnas.2004805117"
] |
[
"I haven't see the episode in question, however the most likely option for fish in ephermial pools is annual killifish. These fish live in temporary pools of water, lay their eggs on the bottom of these pools, and the eggs survive drying out and hatch when the next rain falls. There are many groups of annual killifish living in South America, so some of those were likely the fish you were seeing. ",
"Fish also get stranded in pools when rivers flood due to rain and then recede, but that may not apply to the situation you are talking about."
] |
[
"Killifish in general are pretty incredible and I’m surprised more people aren’t aware of them, there are also some species that can tolerate high salinity and very low oxygen conditions, and one species (the mangrove killifish, Kryptolebius marmoratus) can even survive for weeks at a time as an adult inside tree hollows or rotting logs out of water (so long as conditions remain humid), actually altering its metabolic processes (such that nitrogenous wastes are excreted through its skin rather than exhaled through its gills, and water for breathing its stored in its closed gills) to do so. ",
"Mangrove killifish can also tolerate salinity of up to 68% (for comparison, the ocean averages 3.5%) and water temperatures up to 38 °C (100 °F), and they’re one of the few examples of a vertebrate with an androdioecious sexual biology (meaning most of them are simultaneous hermaphrodites, but some males also exist), and I think the only known example of a vertebrate where hermaphroditic individuals can self-fertilize."
] |
[
"Do the Halal and Kosher methods of animal slaughter increase or reduce the suffering of the animals (in comparison with stunning/conventional slaughter)?"
] |
[
false
] |
Is there any difference between the theory of the technique and it's actual practice (i.e. in theory it's better for the animals but in practice, X has to happen which is worse for the animal)?
|
[
"I raise hogs and have slaughtered them myself and seen how the pros slaughter cattle, both kosher and otherwise.",
"My opinion is that the slaughter is the ",
" important part of what differentiates an ethical operation from an inhumane one. As long as we're not talking about a psychopath deliberately torturing an animal to death, the last few seconds/minutes of its life are going to be roughly the same in any efficient operation. What matters is the six months leading up to that final step."
] |
[
"To be honest, they come to approximately the same thing, especially for the animal in question. Both involve some suffering, and theres no way for us to accurate distinguish which is more or less.",
"Howerver, the halal and kosher slaughter method has less to do with being humane and more to do with cleanliness. By cutting the major blood vessels, you prevent accidental damage to organs that contain less savory bits. It also avoids contaminating the meat with fecal matter. While not necessary germane in modern times, back in the day it was important."
] |
[
"Since we are mostly talking about large mammals here, consider this: ",
"If you cut off blood supply to the brain, how long before unconsciouness comes about? If I recall its 10-15 seconds usually. This is what is happening under the Halal/Kosher slaughter methods. These methods also do not cut the brain stem so the momentary struggle is observable when their throat is slit.",
"The captive bolt method (CBM) strikes the brain and typically induces unconsciousness nearly instantly, however the heart is still beating just like in Halal/Kosher. This typically also induces paralysis instantly, which makes the process ",
" more humane.",
"Both methods have their failure modes. I have a hard time consdering one method superior to the other with respect to physiology and humane treatment, but that is just my opinion. I would say anyone concerned about the humane treatment of animals ought to avoid slaughter outright."
] |
[
"How did the first replicating RNA or DNA begin to result in organelles with functions?"
] |
[
false
] | null |
[
"At least some organelles seem to be the result of endosymbiosis - i.e. they were formerly independent life forms which became symbiotic with other life forms (like our ancestors). ",
"Mitochondria, which are in every cell in your body keeping you alive, in particular are thought to have originated in this way. ",
"- ",
"http://en.wikipedia.org/wiki/Endosymbiotic_theory",
" - ",
"- ",
"http://en.wikipedia.org/wiki/Endosymbiosis",
" -",
"- ",
"http://en.wikipedia.org/wiki/Organelle",
" - ",
"- ",
"http://en.wikipedia.org/wiki/Mitochondrion",
" - "
] |
[
"But how did the nucleus, chloroplasts, and all the other internal structures form? And how did mitosis code for itself? "
] |
[
"RNA itself is really versatile. It can act as an enzyme, and is used in ribosomes (which are pretty much the 'factories' that assemble proteins from amino acids). So after RNA does its thing you end up with proteins, which can be both structural and functional, and used in the organelles that you mentioned.",
"As for the organelles themselves, I believe their borders are defined phospholipid membranes, like most cells. These membranes kind of spontaneously form in water. Phospholipids are composed of one water-loving and one water-hating side, and the most energy stable form they can take is a double layered round shape that we see in cells.",
"Not entirely sure how these different processes came together to form the first tiny organelles, but it isn't to hard to imagine lucky coincidences and chance happenings (the type that litter evolutionary history, really) bringing them together."
] |
[
"Does string theory describe any actions or phenomena that occur in the hidden extra dimensions?"
] |
[
false
] |
Descriptions of string theory indicate various versions of theory require 6, 7, 10 or 11 dimensions whereas we only perceive 3, or 4 dimensions if you count time as one. The fact that we can't see or sense these dimensions is explained by suggestions that they are "compact" or curled up in tiny closed loops. Do any of the string theories describe forces or particles that transmit or translate through these hidden dimensions to create effects we can see and measure in the 3/4 visible dimensions? For example, particle quantum entanglement is bit of mystery in our current physics, especially the apparent "instaneous" communication of the quantum state information between entangled particles when one particle is measured. Do any of the string theories suggest the channel of communication between distantly separated entangled particles could be communicated through these hidden dimensions? Are there any other examples of forces or fields in the standard model that string theory says is operating through these dimensions?
|
[
"Small correction: superstrings are all in 10D. M-theory is in 11D, but it's not a string theory (it has no strings, so...). When going from superstrings to us, we compactify 10 - 4 = 6 dimensions (typically on a Calabi-Yau). When going from M to us, we compactify 11 - 4 = 7 dimensions.",
"Yes, all sorts of wacky stuff can happen in string theory in the extra dimensions. Strings (let's call them F-strings) can move in ",
" wrap around the extra dimensions, D-branes can do the same but in much more complex ways, and also form-fields can \"flow\" through the small dimension (this is called flux). All of these elements will affect 4D physics in complex ways. This is a ",
" subject and I don't think I can fit all of those things together in a reddit comment.",
"About entanglement... good question. Entanglement is a prediction of quantum mechanics and since string theory is naturally a quantum theory, then intuitively it shouldn't really provide a \"mechanism\" for entanglement or quantum phenomena. Certainly extra dimensions in particular have nothing to do with it (since, for example, you can entangle two strings in 10 large dimensions), but it's possible there is a connection, or even a duality of sort, between quantum mechanics and the geometry of spacetime. Susskind and co. have conjectured (ER=EPR) that suitably entangled groups of particles seem, in some sense, to be literally connected by a (non traversable) wormhole or wormhole-like structure, meaning that this geometrical feature could be an equivalent expression of the entanglement. It would be cool if it was found that there is a complete mapping between geometry and quantum mechanics.",
"We already know strings create spacetime, though it's not known how to formulate it. You usually put strings in a background \"stage\", but (once provided with quantum mechanics) the strings feature a graviton state which can equivalently be reinterpreted as curvature of the background spacetime - they're complementary pictures. It's sensible therefore to deduce that the background was not really necessary to begin with. That's why strings are background-independent (contrary to what some people claim). Given that quantum mechanics is similarly a \"background\", or an axiom, for strings it would be interesting if the same could be done to quantum mechanics, giving it an equivalent description in terms of geometry.",
"However, all of this is strictly conjectural."
] |
[
"Hey thanks for a very informative response. Wonder if you can give some sources or search terms for some of the cross-dimensional dynamics you reference in your 2nd paragraph. To paraphrase \"Starship Troopers\", I'd like to know more. ",
"Also, same question in reference to Susskind, et al with regards to suitably entangled particles seeming to be connected by wormhole like structures. Is this a purely theoretical example? Or, alternatively, is there an actual observed phenomenon where a connection through extradimensional wormholes connections is one explanation? If the latter, can you provide more detail on that observation?"
] |
[
"You can read about the attempted search for experimental evidence for extra dimensions ",
"here",
"."
] |
[
"Are electric water cookers made out of plastic a health risk?"
] |
[
false
] |
I was always told as a child to avoid putting boiling water or very hot food into any sort of plastic container, based on the idea that toxins from the plastic would enter the food/drink and be bad for you. This has led to me having a general aversion to things like plastic cups for hot drinks (I a country where they serve boiling-hot tea in plastic cups all the time) and things like electric kettles made of plastic. But since these kettles are specifically manufactured to be in contact with boiling water that is then consumed, I would think that a sort of plastic would be used that is safe, and doesn't release any dangerous substances into the water. Is this the case? Is there any evidence to suggest that an electric kettle made out of metal would be a "healthier" choice?
|
[
"That's why I'm asking ",
"r/askscience",
", and not ",
"r/askreddit",
" or ",
"r/answers",
". "
] |
[
"I am far too much of a coffee snob to use a plastic drip coffee maker anyway ;)",
"Stainless stovetop espresso makers or glass/stainless french presses are easy to come by"
] |
[
"I am far too much of a coffee snob to use a plastic drip coffee maker anyway ;)",
"Stainless stovetop espresso makers or glass/stainless french presses are easy to come by"
] |
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