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[
"Why do carbonated beverages lose carbonation faster when stored at room temperature after opening as opposed to being stored in a refrigerator after opening?"
] |
[
false
] |
[deleted]
|
[
"Gases are more soluble in a liquid at lower temperature, so as the temperature rises, the gas becomes less soluble in the liquid, driving it out of solution.",
"For the record, the inverse is true for solids, they are less soluble in liquids at lower temperatures, so you can dissolve more salt or sugar in a solution by heating it. "
] |
[
"Of course. I'm sure in that case acid-base equilibrium plays a role? "
] |
[
"That is a really good question. Acid base equilibria must play a role, and is probably related but I don't think it's the reason per se. Ammonium carbonate has an endothermic dissolution but again that's related to why but it's not exactly why, as plenty of other salts with endothermic dissolution are more soluble in warm water than cold. I did a few google searches just now trying to learn why but I've come up short.",
"The bottom line is I don't understand the thermodynamics well enough to explain it, but as I work as a chemist, certain things are naturally unforgettable. The fact that chilled water holds more ammonium carbonate than room temp water was one of those things."
] |
[
"Could we make synthetic honey using the same methods bees do but on a larger scale?"
] |
[
false
] |
With the same enzymes and ingredients and stuff, of course. And would it taste the same as real honey?
|
[
"http://en.wikipedia.org/wiki/Nectar#Natural_components_of_nectar",
"it doesn't seem to be so simple",
"some things produced biologically are very difficult to produce in other ways, like silk."
] |
[
"http://en.wikipedia.org/wiki/Nectar#Natural_components_of_nectar",
"it doesn't seem to be so simple",
"some things produced biologically are very difficult to produce in other ways, like silk."
] |
[
"Going off what you have, you also have to take into account of how pollens can affect flavor. Since there is most likely more types of pollen than there are chemicals in nectar, it would be hard to duplicate. ",
"Then there is perhaps the factors of the nectar being inside the bee and the honey comb, which can impart flavors as well."
] |
[
"Is it possible to integrate by parts with more than 2 parts, and if not why not?"
] |
[
false
] | null |
[
"Yeah, you have to iterate the process though. You could try deriving a formula for it using the product rule on 3 terms, like compute (fgh)', manipulate and integrate, but that formula will be messy to deal with.",
"Also it's math, so I mean you can do this yourself. Try integrating x/(1-x",
" by factoring and doing integration by parts (the integral is easy to do direct, it is -1/2ln (1-x",
" )",
"Edit: actually that example may not be doable by parts. Do it in reverse, let f (x)= x e",
" sin (x)",
"Differentiate, you get 3 terms, each of those terms you should be able to compute the integral of by parts. Integration by parts is the \"reverse\" product rule, derivatives of products of functions gives you stuff that you can then integrate by parts. This is a great way to generate practice problems too. "
] |
[
"Any way that we could use it can be reduced to the typical integration by parts. The three-term product rule is (fgh)` = f'gh+fg'h+fgh' So if we have something of the form f'gh, then we could rewrite it as",
"f'gh = (fgh)' - fg'h-fgh' = (fgh)'-f(gh)'",
"Put G(x)=g(x)h(x), then this is just f'G = (fG)'-fG', which is ordinary integration by parts. So it wouldn't be useful thinking of ti in this way. If we have something of the form f'gh+fg'h, then this is just F'h= (Fh)'-Fh', where this is the normal integration by parts with F=f'g. I don't really see when it would be better to use the multi-term formulas, because it's hard to see things like fg'h-fgh'.",
"But let's try to see how it would be used.",
"Let's try to find an antiderivative of ",
". With f(x)=e",
", g(x)=sin(x) and h(x)=cos(x) we have F(x)=f'gh. Using f'gh = (fgh)' - fg'h-fgh' gives",
"F(x) = (d/dx)(e",
"sin(x)cos(x)) - e",
"cos",
"(x)+e",
"sin",
"(x)",
"this is equal to (d/dx)(e",
"sin(x)cos(x)) - e",
"cos(2x). This second term is a slight variation on a ",
"classical one in Integration by Parts",
", and we have that e",
"cos(2x) = (d/dx)(e",
"(2sin(2x)+cos(2x))/5) and so",
"F(x) = (d/dx) (e",
"(sin(x)cos(x) -2sin(2x)/5 - cos(2x)/5))",
"and so G(x) = e",
"(sin(x)cos(x) -2sin(2x)/5 - cos(2x)/5) is an antiderivative of F(x) and we did explicitly use the three-term product rule to do it. So maybe there are places it might come up and not just be reduced to the typical version..."
] |
[
"usually you'll do something like int ugh = int u(gh)\nand then have u as a derivative f' or something like that.",
"keep in mind that the method relies on you knowing how to antiderive some of the factors, so since",
"(fgh)' = f'gh + fg'h + fgh'",
"int f'gh = fgh - int(fg'h) - int(fgh')",
"begs the question whether you are better off doing that.",
"it's really the same as treating gh as a single function:\nint f'gh = fgh - int(f (gh)')"
] |
[
"Does anyone know how long it will be until we lose contact with the Voyager space probe?"
] |
[
false
] |
Does anyone know roughly how long it'll be until we lose contact with Voyager, or at least the distance becomes so great that the time between when it sends the signals and us receiving them makes it useless?
|
[
"At the latest, about 2025. At this point, the on-board power source will have decayed to the point where the probe can no longer operate its instruments. Even if contact could be maintained past here, the probe would be unable to gather any new information to transmit to us, so it's as good as having lost contact in my eyes."
] |
[
"Even if it can only transmit and receive, we can still get time delay ie. distance (and therefore speed), which could give some information about the density of whatever it's passing through... but that's a bit of a stretch.",
"Edit: Actually there are more direct ways of measuring speed via Doppler shift. Some of which might not even need Voyager to be functional at all."
] |
[
"I seriously doubt that it would be possible to detect Voyager with current radar capabilities. Radar detectability goes as 1/r",
" , and from glancing at ",
"this",
" page it seems most of the asteroids we've been able to do radar on are at least hundreds of meters in diameter, and are not more distant than the main asteroid belt about 2-3 AU away. Voyager 1 is ",
"about 123 AU away",
" and is a few meters across."
] |
[
"Creating radio or light waves by spinning a magnet?"
] |
[
false
] |
Maybe my Google is failing me, but something I always wondered. Since radio/light waves are forms of electro-magnetic radiation, is it possible to, for example, create a 500 kHz radio carrier wave by spinning a magnet at 500 thousand RPM? (physics of actually spinning one that fast and keeping it from falling apart aside). Or are radio waves only somewhat related to magnetism? I've always explained radio waves in such terms to people, but got to thinking that I've been giving incorrect information. Thanks.
|
[
"I think you meant 500K RP",
". But setting that aside, if you could \"theoretically\" spin such a magnet, then you would be creating radio waves. Changing magnetic flux produces electric fields. If your movement is sinusoidal, then you will create a similarly varying electric field which is what we call EM radiation.",
"Realistically... you can't spin something that fast - atleast not in any way resembling a classic bar magnet spinning. A 10 cm long magnet spinning at 500kHz would have a tangential velocity approaching 150km/s and would experience around 50 billion Gs near the tip. That's just not something a traditional material can handle.",
"Now, if you start allowing \"magnets\" to be things that don't traditionally look like bar magnets but instead look like tiny subatomic particles, then you'd essentially be explaining the details behind resonant circuits and a quantum mechanical model of electron motion in conductors."
] |
[
"Ok, so if you run a magnet back and forth over a wire at X times per second, you will then cause the wire to emit a radio wave at X Hz then?"
] |
[
"Radio waves have to do with Electro magnetism so spinning a magnet would probably not do much, unless there was a wire near by where the electrons would be affected by the change in magnetic field, and move at the same frequency. ",
"I guess theoretically almost everything is a tiny bit magnetic so you would be creating very very weak electromagnetic waves, but you would need a very strong magnet to achieve any useful radio waves",
"Fun fact if a magnet with a magnet with a 954 meter radius were to spin at 500khz as described, the edge of the magnet would approach the speed of light. :)"
] |
[
"If diamond is the hardest mineral, is it also the most stable to weathering process?"
] |
[
false
] | null |
[
"There are two things to address in the question - what is hardness, and what is weathering?",
"Hardness is simply the ability of a material to resist being scratched. Diamond is currently the hardest known material using this definition, only being able to be scratched by another diamond. This does not mean it isn't easy to break, as anyone with a hammer and a spare diamond could easily illustrate. ",
"Weathering is the breakdown of material, either physically or chemically. Let's consider chemical weathering first. ",
"The majority of chemical weathering at Earth's surface is through interactions with water and substances dissolved in it, but diamond is insoluble and does not react with any common solvents.",
"It has already been mentioned that diamond is a less stable allotrope of carbon than graphite. This is true - the free energy involved in the transition of diamond to graphite is -2.9 KJ mol⁻¹, the negative value shows that graphite is a lower energy state than diamond and so is thermodynamically favourable. So diamond should chemically transform into graphite right? There's just one problem - the ",
"energy barrier",
" required to reach the transition state between diamond and carbon is extremely large, mainly due to the binding energy between carbon atoms in diamond. Without raising the temperature to >2000 K, the natural rate of decay would be a few billion years for a diamond of several grams to convert into graphite. ",
"A review of the phase diagram and transformations for carbon can be found here",
"It would be much quicker to chemically weather diamond by oxidising it. Again this requires elevated temperatures, although not nearly as much as before - around 870-1000 K are the temperatures given in the literature necessary for diamond oxidation in regular air. This could just about be achieved by the hottest forest fires, or a pyroclastic flow. So, the only way to chemically weather a diamond - burn it. ",
"Thinking about physical weathering, diamond can be broken down into smaller pieces by repeated impacts, although I can't find any info on timescales. Research like ",
"this",
" quantifies the erosion of diamond surfaces with sandblasting apparatus, but that gets into much higher windspeeds than would ever be found in nature. Due to the relatively brittle property of diamond particularly along a certain cleavage plane, the best bet for physical weathering would be landslides or if the rock containing the diamond fell a few metres onto rock below. ",
"As we can see it's not easy to weather diamonds at any appreciable rate. Particularly if they sit somewhere undisturbed they could potentially last a couple of billion years, so they must be up there with the most resistant to weathering minerals. ",
"I would say other candidates for most resistant minerals include quartz and zircon. Zircon crystals seem to hang around since whenever they first crystallised from a melt and have been used to provide dates for some of the oldest rocks on Earth as well as being the oldest known examples of minerals, one being dated at 4.4 billion years old in the Jack Hills region of Western Australia. The rock it was in is actually a metamorphosed sandstone, meaning not only did the zircon crystals in it survive the weathering of the original igneous rock they were in, the subsequent transport, deposition and lithification likely at depth to form the sandstone, they also survived the subsequent metamorphism into the currently existing Narryer Gneiss Terrane, which represents the highest grades of metamorphism. There have also been examples of zircon crystals which have been subducted into the mantle and spat out in volcanic eruptions, still remaining largely intact apart from the rims. "
] |
[
"Diamonds also slowly decay to graphite. Graphite is more stable than diamond, so it's structure will slowly become more and more graphite. I don't know if it's THE most stable. It won't be withered away, but it can still break into smaller pieces quite easily."
] |
[
"Doesn't turning a diamond into graphite take billions of years at normal temperatures/pressures? That's insanely slow, even on geological timescales."
] |
[
"Does UVA (long-wave ultraviolet) light behave more like visible light than higher-energy ultraviolet light?"
] |
[
false
] |
It seems to just be an evolutionary accident. UVA light scatters far more easily than visible light (especially in water, so our aquatic ancestors had no need to evolve UVA light receptors). Furthermore, UVA light doesn't stimulate electrons in the way that UVB and UVC light do.
|
[
"All the distinctions along the electromagnetic spectrum are arbitrary. The essential nature or behavior of a photon doesn't depend on its energy.",
"We call visible light \"visible light\" because it's, well, "
] |
[
"All light \"behaves\" the same, the only difference between different parts of the EM spectrum is the wavelength. ",
"UVA is at the lower range of visible light (~300-400 nm) so, if your question actually is \"Is the response of matter to UVA light more similar to visible light than UVB (280-315 nm) or UVC (100-280 nm)?\", then the answer is yes.",
"The reason is that photons of similar wavelengths have similar energy; the farther apart in the spectrum the more energy difference there is. The photon energy determines whether a receptor is triggered, at which depth light is absorbed in a sample and so on."
] |
[
"Okay that's true. My question, though, was really this: could UVA be more appropriately categorized as visible light (we would have to create a new name for the band, of course) if it weren't for this evolutionary accident? ",
"There seem to be non-arbitrary differences between X-rays and gamma rays, between X-rays and Ultraviolet (the minimum energy sufficient to ionize an atom, and also between UV-B and UV-A light (that difference lies on with the minimum that's sufficient to excite an electron to a new energy level). "
] |
[
"If tomorrow I came up with a way to algebraically solve any nth order, nonlinear differential equation, what would we be able to know that we do not now?"
] |
[
false
] | null |
[
"we would know that you have made a mistake, because we have already proven that it is not possible (so as mathematics goes it is a fact now for all time, and will never change).",
"these don't have algebraic solutions:",
"du/dt = u² + t",
"du/dt = u³ + t"
] |
[
"This is a very interesting question with a not very simple answer. The issue is that we can often solve such equations numerically, (at least for small systems), and thus any PARTICULAR (small) system we can also get an accurate number out. However, numerics is a black box, and only answers the exact question asked and not even the slightest bit more. With analytical expressions you gain real understanding, you can clearly see how it behaves in different limits and see the precise relationship between different variables. However, I'm going to ignore cases where numerics is a tool that already works pretty well, as it is difficult to qualify the difference an analytical solution would make (though it would be very nice). Excepting those:",
"So the most immediate benefit would be in large systems, where we can't use numerics. The biggest cases here are in strongly-interacting phenomena, like: ",
"-unconventional superconducting states (we may even be able to build room temperature superconductors if we had an analytical solution for such systems).",
"-exotic magnetic phases, such as spin liquids, which may have applications to quantum computers.\n-any number of macroscopically entangled phases.",
"-Quantum Chromodynamics (QCD) , and we would have a much greater understanding of what's going on inside bound systems of quarks, like protons, neutrons, etc.",
"-etc (stellar/galaxy/galaxy cluster formation, material and band-structure calculations, really all many-body problems)",
"You would also have systems which are known to be chaotic, where we may gain understanding but unfortunately may not help us as much as we'd like because an extreme sensitivity to initial conditions can be a game killer whether we understand why it is true or not. A big ones here might be:",
"-Plasma confinement for nuclear fusion.",
"-Climate models",
"-Predicting the weather",
"-etc. (traffic, fuel logistics, consumer behaviour, the possibilities are endless)"
] |
[
"no, OP claimed ",
" solutions. the source where i got these from said the first one can be solved by airy functions (which are basically integrals of cosines of polynomials) and it said for the second one you can write down a solutions in terms of a power series. "
] |
[
"\"Light from the void\" How do SQUIDs act like turn-table mirrors?"
] |
[
false
] |
I was reading through this article and it mentioned that they used a SQUID to act like a mirror to give virtual photons momentum so that they became real photons. How does this actually work? All they used was a metaphor to describe the process.
|
[
"Correction: tunable mirror*"
] |
[
"You can read the preprint of the actual work on the ",
"arxiv",
". The introductory section describes the device itself:",
"\"[The device is] an open transmission line terminated by a SQUID. The SQUID acts as a parametric inductor whose value can be tuned by applying a magnetic flux through the SQUID loop. When placed at the end of a transmission line, this SQUID can then be used to change the line's boundary condition. The changing inductance can be described as a change in the electrical length of the transmission line and, in fact, provides the same time-dependent boundary condition as the idealized moving mirror.\"",
"In other words, photons coming down the transmission line bounce off the SQUID in a way that depends on the inductance of the SQUID, which can be controlled electrically. When the inductance is changed, the photons behave as if they had to travel different distances before bouncing back (this is due to the changing \"electrical length\" described in the quoted section). So, it is as if the mirror is moving back and forth, and because this is a sort of virtual electrical mirror, the effective velocity is much higher than you could ever get with a physical mirror.",
"I hope that helps explain a bit better what is going on."
] |
[
"Yes it does, thank you."
] |
[
"if you cut someone's lips, and held them closed for an extended period of time, would they heal closed, or just heal normally?"
] |
[
false
] | null |
[
"This question has been asked a few times. I'll summarize the responses. Basically, they would heal together. When you first start the process a blood clot will form bridging the gap between your lips. This clot will be replaced by collagen type III (found in scabs). This collagen will ",
" be replaced by collagen type I (main constituent of scar tissue). This process ",
" if there is adequate blood supply. The entire process would take a week before your lips were stuck together, and close to a month or two for them to be fully healed together. Below are some links to different versions of this questions that have been asked in the past and can provide more information.",
"One",
"Two",
"This one is most similar",
"EDIT: I actually answered the question in the post instead of sending you into the depths of the reddit."
] |
[
"Anecdotes, layman speculation, off-topic jokes, memes or medical advice is my guess."
] |
[
"Anecdotes, layman speculation, off-topic jokes, memes or medical advice is my guess."
] |
[
"Is there a difference in cancer rates between 1st world and 3rd world countries?"
] |
[
false
] |
I know population would make more cases in one area but I want to know based on population if there is a difference in % of people that get cancer in 1st vs 3rd world countries.
|
[
"A major complication in this is that developing countries have significantly higher mortality from diseases that are either eradicated or very easy to treat in developed countries (especially infectious diseases). This means that many people in developing countries die of other diseases before they can get cancer, which predominantly occurs in older adults.",
"The other confounding factor is access to medical care, which impacts the likelihood that somebody with cancer will be diagnosed. Somebody who rarely or never sees a doctor is unlikely to be diagnosed with cancer, because that requires lab and imaging tests that simply aren't available. This makes large-scale data collection nearly impossible, especially in rural areas."
] |
[
"Variations in cancer rates by geography have more to do with local exposure to carcinogens than first-world or third-world status. As an example, gastric cancers are more common in Japan than the US. This is thought to be because of a preponderance of smoked fish in the Japanese diet. Interestingly, if a person of Japanese descent moves to America, their rates of gastric cancer go down to the American background... so this is not likely to be a genetic relationship but an environmental one.",
"Many third-world countries have high smoking rates compared to the US/EU. I would imagine they also have higher rates of squamous cell carcinoma of lung, but that is a guess based on exposure rates rather than geopolitical infrastructure."
] |
[
"The simple answer is yes. Other commenters have explained why so I'll just give you the official figures;\nThere were 268 cases of cancer diagnosed per 100,000 in more developed regions, compared to 148 in less developed regions in 2012.",
"1",
" So thats around 66% more in developed countries, although as ",
"/u/akula457",
" says there are confounding factors"
] |
[
"How legitimate is the technology showcased in this Vice video that transforms CO2 into a carbon-neutral source of fuel for existing vehicles?"
] |
[
false
] |
If it sounds too good to be true, it probably is. But nevertheless, what's your opinion? Do you think this technology is legitimate? If it is, how likely / soon would it be implemented across the world to finally bring greenhouse gas emissions under control? This sounds like a huge turning point in the fight against climate change but I'm very skeptical.
|
[
"Carbon sequestration and the production of artificial fuels are perfectly legitimate. It can be done and it has been done. In fact, producing artificial fuels from atmospheric carbondioxide is, in my opinion, one of the main requirements to significantly affect net carbondioxide emissions across the globe. Because barring an unprecedented breakthrough in battery technology, electric engines are just not going to cut it for many types of vehicles. The energy density of combustible hydrocarbons (fuel) is just that much higher than that of even the best batteries.",
"But (and there's always a \"but\"), the process to capture carbondioxide and to convert it into usable fuels requires a very large amount of energy. So systems like this are only really viable when our electrical grid is supplied by renewable energy, because otherwise any additional energy demand that comes from bringing these carbon sequestration plants online is just going to come from things like coal plants firing up to cover the additional demand. ",
"Right now, the only places where this type of activity is viable are places where there is so much renewable energy production that at times some of that energy is going to waste. Because if I build a wind mill to work alongside an existing coal plant, it's better to use the power from the wind mill to ensure that less coal has to be burned rather than use the wind mill to power a fuel production plant.",
"So while production of artificial fuels is definitely a real thing, it's not a ready-to-go solution. First order of business is to feed the grid with renewables. But once that's taken care of, artificial fuels are an important next step."
] |
[
"What goes up must come down, and you can't get something for nothing. The usual scientist's objection to synthetic fuel technology is \"it's possible but it takes a lot of energy\", which doesn't sound so bad, but that answer obscures the real problem: ",
".",
"So you need a big energy source, and unless you really need hydrocarbon fuel, you'd be better off just using that energy source directly rather than converting it to fuel and back.",
"Now, there are some reasons you need hydrocarbon fuel: it packs a huge amount of energy in a small space, so for vehicles -- airplanes in particular -- it might be worth making. But even then, that's only useful in a world where we have completely gotten rid of all other uses for fossil fuels, and we are so far away from that world that it's not even funny.",
"Making fuel is possible, but it's not the solution to our fossil fuel habit."
] |
[
"Another thing to note is that there is no particular reason to base artificial fuels on carbon / CO2. By using CO2 you first remove CO2 from the air, but by using the fuel you again return the CO2. If you don't base your fuel on carbon you don;t remove any CO2, but you also don't emit any CO2, so the net result is the same.",
"Now when choosing a fuel to artificially produce there are some things to take into consideration (aside from the fact that only a fraction of our power is renewable at this moment)",
"electrochemical cells are much more efficient than combustion engines (less energy wasted as heat)",
"electrochemical cells don't emit CO and NOx (important for cars because theyre in the city and we breathe these toxic compounds).",
"some vehicles can only run combustibles at this moment (planes, rockets, etc)",
"energy density (already explained in your comment)",
"so for example hydrogen (H2) makes sense as artificial fuel because it can be made and used in electrochemical cells, it is made from water which is even easier to get than CO2 and it has a very low weight. The storage/volume is difinitely a problem though.",
"Methanol can also be made/used with electrochemical cells but this is harder than H2 (less efficient). It can also be used in combustion engines and CO2 is quite easy to get. ",
"Ammonia (NH3) is a less known alternative that can also be used in echem cells, N2 / H2O is abundant. Storage is again difficult though due to increased pressure, toxic, corrosive and explosive gas.",
"These are just some well known possibilities, you can think of many others. It shows however that it is not as simple as just taking CO2 and making some random fuel, theres a lot of factors to make it viable. "
] |
[
"Mars, Europa, Titan - what is the most habitable place other than earth in the solar system? Is it realistic that we could colonise it, or find life? And finally, what about Gliese?"
] |
[
false
] |
[deleted]
|
[
"Sorry, I just didn't feel like sourcing it. Here you go:",
"liquid water and ice thickness:",
"Schenk, P., Thickness Constraints on the Icy Shells of the Galilean Satellites from a Comparison of Crater Shapes, Nature, Vol. 417, pg. 419-421, 2002",
"Tyler, R., Magnetic remote sensing of Europa’s ocean tides, ICARUS, Vol. 211, Iss. 1, pg. 906-908, 2011",
"Schenk, P., Thickness Constraints on the Icy Shells of the Galilean Satellites from a Comparison of Crater Shapes, Nature, Vol. 417, pg. 419-421, 2002",
"Extremophiles and astrobiology:",
"Ricardo Cavicchioli. Astrobiology. August 2002, 2(3): 281-292. doi:10.1089/153110702762027862.",
"The Cryobot thing:",
"Chumachenko, E.N., et. al., Specific Features of Cryobot Movement in the Ice Structures of Europa, Kosmicheskie Issledovaniy, Vol. 48, No. 6; pg. 568–572, 2010",
"Chela-Flores, J., Kumar, N., Returning to Europa: can traces of surficial life be detected?, International Journal of Astrobiology, Vol. 7, Iss. 3-4, pg. 263-269, 2008",
"Terraforming mars:",
"James M. Graham. Astrobiology. June 2004, 4(2): 168-195. doi:10.1089/153110704323175133.",
"edit: formatting"
] |
[
"There's a lot of debate about this question among planetary geologists. Personally, I think Europa may very well have extant life present on it. Europa is covered in ice, but it is a relatively thin layer (again, some debate here, but it's looking like it's less than twelve km) and it has liquid water underneath it, which would look something like ",
"this",
". Because Europa is large enough to have a differentiated core, it may very well have volcanic vents at the bottom of the global sea, at which life could absolutely grow. In fact, the extremophile bacteria found at the volcanic vents on Earth are some of the most primitive life on Earth, and may be where life originated, which would mean that with a similar situation on Europa, by now multicellular life could even be possible.",
"In terms of exploration, the best way to get below the ice would be a cryobot, which would just essentially be a heated piece of metal that could melt its way through the ice, leaving a probe on the surface to transmit back to Earth.",
"Europa would be much harder to colonize than other planets, however. On that account, I would probably choose Mars. We already have basic plans set out on how to live on Mars. It's similar enough to Earth that with the right technology, terraforming would almost be an easy task."
] |
[
"Another thing to consider is while the surface of Venus is very inhospitable, ",
"a large structure filled with breathable air would actually float in the dense atmosphere",
", and at an altitude of 50km the conditions are very earth-like, with a temperature range of 0-50 degrees C and a pressure of 1 bar."
] |
[
"How much longer does a second last for someone on Earth compared to someone floating in outer space?"
] |
[
false
] |
If I understand it correctly, the fastest you travel through space the slower you travel through time, and time also goes more slowly as the gravitational force acting on you increases. So is it possible to calculate the amount of time dilatation we are undergoing on Earth?
|
[
"The time dilation factor between an observer on earth and one in deep space who is stationary with respect to the sun is tiny. There are three contributing effects:",
"The relativistic time dilation factor is 1+1.55x10",
". The difference in the passage of time due to this factor is almost negligible - ",
"As a fun example on a longer timescale, Einstein's theory of general relativity turned 100 years old last year. For exactly 100 years of earth time there will be 100 years and 25.5 seconds of time passed in the distant frame e."
] |
[
"That's impossible. The reverse works though. For one second for someone not on Earth to be two seconds for someone on Earth, they need to be moving at (√3)/2 c, which is about 87% the speed of light, be in a gravitational field that has that escape velocity, or some combination thereof."
] |
[
"You'd need to be one third the Schwarzschild radius away from the event horizon. At least, if you're using the kind of cheating measuring system that lets you measure the radius of a black hole with distance instead of time. If I'm doing the math right, or rather telling Wolfram Alpha to do the math right, the proper distance to the event horizon is (4 + ln(27))/6 = 1.2160 times the Schwarzschild radius.",
"Edit: That works out to about 14.6 million km away from Sagittarius A* proper distance, or 4 million km coordinate distance."
] |
[
"What do you think is the coolest mystery that science still can't fully explain, and if you're an expert in the field, what's your theory for it?"
] |
[
false
] | null |
[
"You should post this in the suggestion thread for the weekly discussion thread since it is not appropriate in general."
] |
[
"Gotcha. Sorry, I'm a little buzzed and it seemed a good idea at the time."
] |
[
"I think it's a good idea and you should suggest it in this thread: ",
"http://www.reddit.com/r/askscience/comments/wtuk5/weekly_discussion_thread_asking_for_suggestions/"
] |
[
"Can neutrinos pass through neutron stars like they pass through earth?"
] |
[
false
] |
[deleted]
|
[
"The density of a material affects how likely a neutrino is to interact. Neutrinos interact via the weak force, and only the weak force. The weak force is so named because of the relatively weak nature of the force. The interaction is also dependant on neutrino energy. ",
"At energies characteristic of beta decays, the mean free path of a neutrino is such that about half of the neutrinos will decay in about 1.5 lightyears ",
", or 17 lightyears of water. The theoretically much denser neutron star density would therefore contract the mean free path through the star. However, due to the extreme conditions in the local area of that interaction, the interaction is likely discouraged by the effects causing neutron degeneracy to be favored in the first place: if protons and electrons could survive in the core, they would. Instead, the effects of gravity favor denser neutron degenerate matter. The energy of the neutrino likely isn't enough to allow for a neutron-neutrino interaction to form a proton-electron pair."
] |
[
"By exotics, I mean things with charmed, strange, bottom, or top quarks or tau leptons or muons. Things that intrinsically decay, because of mixing through the weak force with lighter states.",
"As for a good book... I dunno... I've just had this stuff thrown at me enough ways, I sort of remember it. Trawl through the internet, and don't be afraid if something doesn't make sense. Do your best to understand it, and ask other people to help explain it."
] |
[
"By exotics, I mean things with charmed, strange, bottom, or top quarks or tau leptons or muons. Things that intrinsically decay, because of mixing through the weak force with lighter states.",
"As for a good book... I dunno... I've just had this stuff thrown at me enough ways, I sort of remember it. Trawl through the internet, and don't be afraid if something doesn't make sense. Do your best to understand it, and ask other people to help explain it."
] |
[
"Do vibrations in a wing affect the way the wing creates lift/downforce?"
] |
[
false
] | null |
[
"If it is more flat on the forward stroke and more vertical on the backwards stroke, it will push the helicopter forward",
"This is not how helicopters gain forward momentum. This kind of cyclic control will roll a hovering helicopter, and only very very negligibly impart any kind of forward momentum."
] |
[
"Seeing as you posted under the Biology heading, I assume you are referring to birds and other flight-capable creatures.",
"If you are referring to the flutter of, say, an eagle's wingtip feathers, the short answer is no. While the angle of attack varies significantly, the flutter is so rapid that it averages out. Additionally, the rest of the wing makes up a large enough and rigid enough body that the flutter effects are minimized.",
"If you're referring to mechanical wings, the answer can be yes, but the vibration itself isn't the cause of the change. It would have to cause a large enough deflection from the intended angle of attack, and the vibration would have to have a long enough period to make a difference.",
"When flying on an airplane, you'll see the wings flex a bit on takeoff or in turbulence. The variation in angle of attack contributes to varied lift, and the plane moves in response. Note that the wings are in fact designed to flex, and the exact movement of the flexing is engineered to minimize the change in angle of attack. ",
"The final type of vibration, which I doubt you're referring to, is flexing of the actual wing which changes the cross section. This would CERTAINLY affect the lift, as the chord and camber define how air flows over the airfoil. Airplane wings NEVER flex in this way as small variations drastically change the flow of air. The deployment of slats and flaps during takeoff and landing are the best example of this."
] |
[
"Hmm actually I didn't even put a heading sorry. I'm speaking more mechanically like on an airplane or race car. But thank you for the answer much appreciated"
] |
[
"Is all history on Earth traveling through space?"
] |
[
false
] |
My understanding is that the further we peer into space, the farther back in time we view, since light from further bodies in space take longer to reach us. And so, with deep space telescopes, we are in effect able to gaze backwards towards the beginnings of the universe. This got me wondering about our own planet. Is everything that ever happened on Earth traveling through space? If we were far enough away from Earth with a strong enough telescope, would we be able to look back in time? If so, one could theoretically witness all sorts of monumental events on Earth...the creation of life, the rise and fall of civilizations, and maybe finally explain to Bill O'Reilly how the moon got there.
|
[
"Not really, no. Inverse-square laws and all that. Light propagates outward in a sphere, and the area of a sphere goes with the square of the radius. So the intensity of light drops with the square of the radius. Before you get very far, in cosmic terms, the light is far too faint to allow anything to be resolved."
] |
[
"As Dimpl3s said, in order to go out far enough to look back at earth, you'd have to overtake the light travelling outwards from Earth and, to steal a phrasing from RobotRollCall, \"faster than light\" is a collection of words that doesn't have any meaning in our universe.",
" supposing there's some Alien intelligence ",
" out there watching towards earth with our hypothetical awesome telescope, they would indeed see all those events.",
"Even more interesting (IMHO) is the fact that our first television broadcasts are, what, 74ish light years away now. Some time very soon Alpha Centauri will get the first episodes of Torchwood and Wolf359 will get the premiere of Mythbusters (if they haven't already, I didn't check to that much precision). :D"
] |
[
"Don't our television broadcasts become so weak after a certain distance of transmission that they are indistinguishable from background noise?"
] |
[
"How does chemotherapy treat tumors without destroying other cells in the body?"
] |
[
false
] |
[deleted]
|
[
"Standard chemo generally tries to target rapidly dividing cells, since cancerous cells tend to undergo a lot of mitosis. They can do this through a number of mechanisms, such as inhibiting DNA synthesis (methotrexate), disrupting DNA (cyclophosphamide), or inhibiting microtubules (paclitaxel). Of course, there are other rapidly dividing cells in the body, and that's where a lot of the toxicity comes in. This is why patients on chemo frequently have abdominal complaints (the epithelial lining of the GI tract is damaged), and cutaneous issues like hair loss. They may also have bone marrow damage leading to immunosuppression.",
"A more targeted approach towards chemotherapy is with the use of biologic molecules such as monoclonal antibodies (rituximab) and receptor antagonists (imatinib). These can more specifically knock out a key component of cancer cells to reduce the side effect profile. However, a real 'magic bullet' has not been developed yet, and even these targeted treatments still can produce adverse effects.",
"Another approach is towards physically targeting chemo to cancer sites. This may be via something like a drug-eluting stent or polymer that releases chemotherapeutic agents local to the cancer, or via conjugated molecules that pair a toxic agent with a homing agent."
] |
[
"Classical chemotherapy such as cisplatin targets rapidly dividing cells. Cancer is a disease characterised by excessively dividing cells, so cancer is hit by chemotherapy. The body remains largely unharmed because most cells in the body actually divide very rarely, if at all. However, those cells that do, are hit just as hard as the cancer. This includes the lining of the intestine, cells in hair follicles and some immune cells, which explains many of the side effects of chemotherapy."
] |
[
"For a variety of reasons, cancer cells are not as efficient as healthy cells at repairing certain types of damage. For example, the vinca alkaloids such as vincristine and vinblastin inhibit microtubule polymerisation, which halts cell division in metaphase. At metaphase, cells have have two sets of chromosomes, no nucleus, and are therefore not viable unless mitosis completes. Cell death follows soon thereafter.",
"As you're aware, an agent like vincristine has significant activity on healthy cells in the bone marrow and gastrointestinal tract, so many of these cells die, but some are able to repair the damage caused by the agent. You've also hit another key point: the side effects of many chemotherapies are very dangerous in the short term. In the long term, chemotherapies that work by causing DNA damage, such as alkylating agents, are also quite carcinogenic in their own right. These drugs may cause rebound malignancies.",
"Sources:",
"http://en.wikipedia.org/wiki/History_of_cancer_chemotherapy",
"http://en.wikipedia.org/wiki/Vincristine",
"http://en.wikipedia.org/wiki/Cisplatin"
] |
[
"When someone has an allergic reaction, such as from being stung by a bee, what exactly is going on?"
] |
[
false
] | null |
[
"This type of allergic reaction is called a type 1 hypersensitivity. To break it down for you, we have 4 main cell types involved and a few main chemical messengers. First the bee venom, or antigens, are captured by antigen presenting cells (dendritic cells). Think of them like the body's surveillance system for foreign substances penetrating the skin. The dendritic cells then present the antigen to a type of T-lymphocytes (TH2 cells). TH2 cells are sort of like the supervisors of all the other white blood cells. They secrete chemical signals, called cytokines, to other cells to let them know what they should be doing and where they should be going. So anyway, after the TH2 cells are presented with the bee venom antigens, they start to secrete one of the cytokines which signals another type of lymphocyte, called a plasma cell, to start making and secreting a bunch of antibody that will be able to later bind specifically to the bee venom antigen. However, before the plasma cells can start making the antibody, they also must have been presented with the antigen. An important point here is that in the case of type 1 hypersensitivity, it is not just any old antibody that is made, it's a specific antibody called IgE. The IgE then coats the outside surface of another white blood cell called mast cells. Mast cells are a special cell filled with little packets of chemicals called histamine and heparin. Think of IgE coated mast cells as little mine fields waiting to burst when a potentially dangerous foreign material gets near them. The IgE now coating their surface can bind to the bee venom antigen when it comes into contact with it. When this happens, the mast cell is activated to degranulate. In other words, it squirts out all its histamine and heparin. These two chemicals cause blood vessels to dilate and become leaky, leading the the swelling and redness you see with a bee sting. The problem with someone with a severe reaction is that their body already has a lot of mast cells with IgE specifically ready to bind to bee venom from previous exposures. When any bit of venom enters the body, mast cells all over the body start to degranulate leading to a lot of dilated leaky bloody vessels and therefore a lot of swelling. Also, when there is enough histamine in circulation, it can cause the airways to constrict. This is why people with severe allergies to bees, or other things, can have extreme difficulty breathing during an episode. Antihistamine drugs, help fight these reactions by blocking the receptors that histamine binds to. However, in severe anaphylactic reactions antihistamines won't get the job done. This is why people with very severe bee allergies often carry epinephrine shots (epi-pens). Epinephrine counteracts the constriction of the airways by binding Beta-2 adrenergic receptors leading to dilation of the airways, and counteracts the leakiness/dilation of the blood vessels by causing them to constrict thru binding alpha-1 adrenergic receptors. This is a detailed, yet still extremely simplified explanation, but I hope it was informative. Source: took veterinary immunology about a year ago. ",
"TLDR: Bee sting allergy = type 1 hypersensitivity"
] |
[
"Bee venom contains proteins, which are foreign to your body. If your immune system recognizes a foreign protein, it can trigger a response to that protein. How the immune system responds will depend on the nature of the foreign protein, the individual's exposure to that protein in the past, their genetics, and many other factors that can affect the resting immune state. ",
"In most cases, the immune response will be harmless, but some individuals can have hypersensitive responses to these foreign proteins, which will trigger autoimmune symptoms like hives or in extreme cases, anaphylaxis. "
] |
[
"I don't think this could have been explained with any more detail. Thanks, very informative!"
] |
[
"Can an archive file be smaller after unpacking?"
] |
[
false
] | null |
[
"Definitely - if you compress data that's totally incompressible. When you compress a file, the archiving program will store metadata (headers) that tell it how to unpack the data. If you can't actually make the data any smaller, then you'll be left with the same size data as before plus the metadata, giving you a bigger file than you started with."
] |
[
"No, they aren't. Mostly files that are coded to be small, so videos, music, images usually aren't compressible.",
"Just imagine that codecs try to make the files as small as possible, so they use basically every compression algorithm available to get the files as small as possible."
] |
[
"They're still almost certainly very compressible, we just don't have the tools yet to do so effectively.",
"Compressibility is, in many ways, the same thing as randomness. See ",
"this layman-readable article",
" by Chaitin, for example. Any time your algorithm can look at data and say \"Hey, that's not gibberish! I can see patterns in that!\", there's going to be a way to compress it. Unfortunately, there are also compressible patterns that no program can identify. Namely, writing a program for optimal compression is (in general) an impossible-to-solve problem (a.k.a. it's at least as hard as the Halting problem).",
"When you have an excellent grasp of the type of data you'll be seeing, you can ",
" write optimal compression algorithms. That's only sometimes. For most real life data, such as videos, music, images, and so on, there are almost certainly still convoluted patterns in the data humans haven't yet discovered that could be used for compression. ",
"One such recently discovered pattern for images is that ",
"certain bit patterns cluster around a Klein bottle",
". Alternatively, SVDs do a suspiciously good job at (noisily) compressing images, meaning that there must be certain patterns in the data that it's picking up on in doing so. It's unfathomable what other types of patterns real images (or other data) may possess. Until we have a firm understanding of exactly what distribution real-life data comes from, we have no reason to believe that our current compression algorithms are even close to optimal.",
"That said, one thing that we do know is uncompressible is truly-random strings. If you pick a uniformly-random string of length 1000000, the odds that you can compress it better than a handful of bits is negligibly small. This basically follows from a pigeonhole principle argument: all data is really just numbers if you read it in binary, and if you find a function from the integers 1...N to integers 1..N (your compression function) without causing any overlaps (because you want to be able to reverse the process) it must be the case that the total amount you decrease some numbers equals the amount you increase the others (as the sum should be N*(N-1)/2 either way). Thus, on average, ",
" compression algorithm that exactly gets you back your original number could not have done any compression at all!"
] |
[
"Is the flu \"more deadly\" this year in the sense that if you contract it, you have a higher chance of dying than in a normal flu season?"
] |
[
false
] |
A friend of mine is over 65 and is concerned about the news reports that this year's flu is "especially deadly". While I understand that the elderly are always at risk, in what way is this year's flu more deadly? Is there something inherent about the flu this year (other than the problems with the vaccine) that makes it worse than other years?
|
[
"The major problem with flu this year is that the vaccine wasn't effective. The yearly vaccine is a combo of three strains of flu experts have predicted will be major that year. If the prediction ends up wrong, an unvaccinated strain can spread. This is most dangerous for older people, who have a higher chance of complications resulting from flu"
] |
[
"I'd like to note that the early reports about the flu vaccine this year being less effective than usual were based on the southern hemisphere flu season. The strains active in Australia during our summer are not the same as the strains that will be active in North America over our winter.",
"According to the ",
"Weekly Flu Surveillance Report from the CDC",
", the main flu type active this year is A(H3N2), with A(H1N1) and B/Yamagata competing for a distant second. For H3N2:",
"159 (99.2%) A(H3N2) viruses tested were well-inhibited (reacting at titers that were within fourfold of the homologous virus titer) by ferret antisera raised against A/Michigan/15/2014 (3C.2a), a cell propagated A/Hong Kong/4801/2014-like reference virus representing the A(H3N2) component of 2017–18 Northern Hemisphere influenza vaccines",
"This means that the vaccine is about as effective as it can be against those viruses. It isn't 100% (because the vaccine doesn't always result in effective immunity), but the virus type is the type we were expecting to see, and the viruses of that type are still shut down by the flu vaccine. Similarly for A(H1N1):",
"and all were antigenically similar (analyzed using HI with ferret antisera) to the reference 6B.1 virus A/Michigan/45/2015, representing the recommended influenza A(H1N1)pdm09 reference virus for the 2017–18 Northern Hemisphere influenza vaccines.",
"B/Yamagata was not protected against by the main flu vaccine (the trivalent vaccine), but there is also a quadrivalent vaccine that is effective against it. B/Yamagata only represents about 10-15% of the positive flu tests from the US this season.",
"B/Victoria was included in the main flu vaccine, however, there was a mutation in that strain this year and about half of the B/Victoria viruses we are seeing have that mutation, and the vaccine is not effective against it. However, B/Victoria only represents about 1-2% of the positive flu tests from the US this season.",
"So still pretty effective, all things considered."
] |
[
"Also very young children."
] |
[
"How violent/rapid was the separation of Pangaea?"
] |
[
false
] |
Hi all, I am wondering how the first few moments would have played out when Pangaea broke up. Was there an almighty quake followed by a dramatic split? Or was it a small split of just a few centimetres that accelerated slowly? Would there have been a point where there was literally a few centimetres separating the continents? Thank you
|
[
"Explained in very simple terms: Look at the Afar region of East Africa as a modern day example. It is a very, very slow process that takes millions and millions of years. There is no ‘crack’ as you might visualize it - it’s more of a slow spreading apart, like taffy getting pulled. Eventually it gets so thin that lava begins to erupt and, because it sits so low, will get filled with water. So no, there is no big crack that separates the plates, and the separation itself was not violent (geologically, at least) or rapid at all."
] |
[
"Continental rift zones exist today and give you a good idea what things would have looked like in the early stages.",
"",
"https://www.nationalgeographic.com/news/2018/04/east-african-great-rift-valley-crack-spd/"
] |
[
"On a sorta side note, the Gulf of California is actually a spreading center right now. The Baja Peninsula is being pushed away from North America and a new “ocean” is being formed."
] |
[
"If I'm playing my music at a volume of 8/10, would that use up my battery faster than if I played the music at 3/10?"
] |
[
false
] |
Does playing something louder use more battery life?
|
[
"It depends largely on the impedance of the headphones. Most headphones designed for portable listening are going to be less than 25 ohms. Headphones with larger drive coils tend to have higher impedance, and will take more power. ",
"But for things like earbuds, the difference between 3/10 and 8/10 will be negligible. The phone is using more power keeping the CPU active while decoding the music than the headphones will ever use."
] |
[
"OP didn't mention a phone or headphones, just loud or not so loud. The answer is yes, louder uses more power. If it's a phone driving headphones, it's probably not a large increase. If it's a battery-powered stereo with speakers, there could be a big difference. "
] |
[
"Because if there is no load connected to the headphone jack, there is no power consumed, besides processing power. The amplifier will pump out audio signals to the jack, but if there is no coil to receive the signal, the signal just remains as a potential charge across the terminals.",
"Unless of course the phone wants to play on the internal speakers. In which case, it will vary from phone to phone."
] |
[
"Was Einstein truly an unmatched genius, or was he just in the right place at the right time?"
] |
[
false
] | null |
[
"Can't he be both?",
"Einstein was unquestionably a genius. Even in an era of many new discoveries, his own work was both visionary and profound, and extended through many different areas of science; the 'scientific career' section on his ",
"wikipedia page",
" is quite amazing. But at the same time, it was tremendously deep - he didn't just think up the core idea of relativity, for instance, but invented an entire new notation for describing reality and was involved in really understanding many of the iconic discoveries that we take for granted.",
"But as well as this, to do all that he did when he did it could certainly be said to be somewhat due to luck. If he hadn't made his discoveries, others would have done soon enough, just as many were heavily involved at the same time.",
"is there any evidence that the scientists currently working at CERN or on quantum physics/computing are less intelligent than he was? What would it take for a modern day scientist to be declared the next-level Einstein?",
"Well, for a start, it's hard to define intelligence in a useful way. I expect there have been lots of people of similar intelligence by any measure, but in this sense perhaps Einstein really does benefit from his being around at the right time, with the right attitude.",
"I think it's fair to say that a large part of Einstein's continuing fame in popular culture is that he was involved in amazing things that really entered the public consciousness, with which even a layman could grasp in general terms the astounding changes in our understanding. With things like ",
"early tests of general relativity",
", he could literally stand up and say that everyone in the past had been wrong. Nowadays there are problems that are just as hard and complicated, but not on the kind of relatively everyday scale that people can relate to.",
"Overall, I think it's dangerous to suggest he's an ",
" genius, but that any real comparison is at best very difficult. Physics has benefited from a great many amazing minds in the last few decades, and perhaps many of them have just as good exposure in the physics community where the depth and importance of their ideas are understood. But Einstein's particular influence happened to extend into areas that really entered the public imagination, so he gets far more exposure there than just about anyone else. Even then, scientists like Stephen Hawking have their own strong public image, and it comes back to the question of how exactly you compare greatness...if you really can at all."
] |
[
"Well, with quantum mechanics (Planck, Bohr, de Broglie, Heisenberg, Schrödinger, Dirac, ",
") I think it's safe to say we've probably got people of equal stature/ability now, and that some of them were just in the right place at the right time, and Einstein was too, to some extent.",
"When it comes to Einstein's most important work, I think a lot of it would've been found out within a fairly short time-frame. Specifically his famous 1905 works on special relativity, brownian motion and the photoelectric effect. With SR specifically, Poincaré and Lorentz were clearly on the right track, even if Einstein provided the final (and most difficult) piece of the puzzle.",
"I think ",
" Relativity was a rather singular achievement though. There's some dispute about whether Hilbert might've come up with the specific field equations first, but the general idea/approach was indisputedly Einstein's. As far as I know, the only one working on anything similar was ",
"Nordström",
", for which he really deserves to be much more well-known than he is. It seems much harder to say if and when we'd have figured out GR without Einstein.",
"But the problems facing fundamental theoretical physics are rather different than in Einstein's day. In 1900 they knew about atoms, but they didn't understand how they 'worked'. Chemistry and physics were not unified. There were plenty of easily-observable everyday phenomena where the fundamental underlying physics was unknown. ",
"The situation is different now. The underlying physical theory required to explain all everyday phenomena (and quite a few exotic ones), to observable accuracy, is known (or believed to be). There's simply less that's likely to require a new theory to explain. While reconciling GR and QM is the next 'logical' step towards a unified theory of physics, there isn't a lot to test it against."
] |
[
"Within a six month stretch in 1905, at the age of 26, while working as a patent clerk, ",
"he wrote four groundbreaking papers",
": ",
"Photoelectric effect",
", ",
"Brownian Motion",
", ",
"Special Relativity",
", and ",
"Energy/Matter Equivalence, E=mc",
" ",
". ",
"He was undoubtedly a genius. ",
"If anything, you could argue that he was in the ",
" place (the patent office) to be doing this level of work. How many patent clerks have repeated his level of production since? Personally, I don't think it matters much where someone of Einstein's abilities works; the cream tends to rise to the top. "
] |
[
"How do medications cause you to gain or lose weight as a side effect?"
] |
[
false
] |
If you eat exactly the same on and off a medication could it make you gain or lose weight? (Not just water weight, but actual weight in the long term.) I thought weight was just the difference between calories in and calories out, so I don't understand how this happens, but I've definitely gained weight from medications. Do these meds actually just affect appetite and make you eat more? Or does it affect your metabolism and make you burn fewer calories or something? Finally, what stuff in medications lead to side effects that involve weight gain?
|
[
"Some antidepressants are associated with weight gain due to increased appetite, or similarly changing a person's taste perception. Other drugs might affect how efficiently you burn calories, some might affect how your body actually absorbs nutrients from the food you eat, or how your body makes and stores fat. ",
"The human body is very complicated. Not every drug works the same way. You'd have to have a particular drug in mind to get more than a superficial answer"
] |
[
"Anti-psychotics frequently have weight-gain associated as a side-effect and olanzapine is no exception. There are a number of plausible mechanisms but if anyone has shown a demonstrable one outside of simple increased appetite then I am unaware of the study. There are treatment options but again, I don't know of any that counteract olanzapine specifically rather than weight-gain/Diabetes generally."
] |
[
"What about Zyprexa? It's notorious for making people gain something like 30 pounds in a month."
] |
[
"Does deeper sleep during thunderstorms relate biologically to a decrease in predator activity?"
] |
[
false
] | null |
[
"Here",
" is the link that got me thinking about this.",
"edit: I meant to link to ",
"this reddit post",
" but copied the wrong link."
] |
[
"Dr. Ralph Pascualy is the medical director of Northwest Hospital Sleep Center in Seattle. He explained to me that the brain naturally craves sensory input. That's why people in sensory depravation tanks hallucinate; robbed of any stimulus, the brain creates its own. During sleep in a quiet night, any random noise, whether a passing truck or a creaking floorboard, is likely to activate the restless brain, waking you up. Constant white noise, he told me, \"gives the brain a tonic signal that dampens its own internal systems.\"",
"Lifted from ",
"White Noise and Your Brain",
".",
"This article gives an explanation for how such noises aid sleep but doesn't mention a biological basis. I wasn't able to find anything relating to my question on a search. I did find that some animals hunt more in the rain, such as coyotes. Searching also showed we may be sleepier during storms because of a lack of sunlight and vitamin d production. The coyote information suggests it's not related to predatory activity, but I haven't found anything that specifically answers my original question."
] |
[
"Continuous pink noise has not ever been shown in any rigorous manner to improve sleep quality."
] |
[
"Do solar flares affect the human brain?"
] |
[
false
] |
Recently I’ve been reading about solar flares, how they impact the Earths magnetosphere, etc, and I’ve been wondering if they affect the human brain, as our brains are made up of neurons pulsing electricity between themselves. Is there ANY correlation between solar activity and the human brain?
|
[
"In principle, electromagnetic fields can influence the brain noticeably, if strong enough. This is used in ",
"Transcranial magnetic stimulation",
"(TMS) or ",
"Transcranial direct-current stimulation",
".",
"The biggest solar storm that got measured was in 1859, the so called Carrington Event with 1760nanoTesla (=0.0017mT). Tesla is the unit of the magnetic flux density (~magnetic field strength).",
"For comparisons Magnetic Resonance Imaging(MRI) uses typically 3000mT, as does TMS. But it can lead to minor effects, and with some machines up to 7000mT people report problem, e.g. headaches.",
"The biggest effect on human in big solar flares is not the effect on the brain due to EM fields, but the particle radiation that affects the whole body."
] |
[
"I worked with high-field NMR magnets. Even while crawling around below 18 to 20T magnets, I never felt anything."
] |
[
"The change in the magnetic field is much more important than the absolute strength, you are right. That's why TMS has a much bigger effect than MRI, as the first uses a pulse, where as the later has an almost constant field but the same field strength."
] |
[
"Is \"crowd wisdom\" effective for anything other than trivial questions?"
] |
[
false
] |
If, for example, several hundred people are asked to guess how many pennies are in a jar and their answers are averaged out the result will be very close to the actual number of pennies. However, I read an article recently in which a computer scientist analysed global news reports over the last several years and plotted where these reports guessed Bin Laden was hiding. It turns out that the news articles clustered on area of 200km radius which included abbottabad. ( ) I think the computer scientist was probably just lucky in this case, but it did get me wondering whether there are any real examples of this kind of effect. Does anyone know if there are any well established or proven examples of non trivial crowd wisdom like the Bin Laden example above?
|
[
"As someone in a hard science field, I think it should be noted that the wisdom of crowds is mainly applicable in areas where everyone is equally expert (guessing number of pennies in a jar). If you're asking people what the best grand unified theory of physics is, there's no point to asking a crowd, obviously. I've seen too many askreddit questions with 200 horribly wrong answers to trust the wisdom of crowds on anything that isn't solvable by intuition alone. "
] |
[
"Yes I understand this perfectly (I am a physicist!). What I would like to know is if there have been studies which test crowd wisdom in more esoteric areas, such as future predictions, maybe the stock market or race horse betting, that sort of thing. "
] |
[
"Yes I understand this perfectly (I am a physicist!). What I would like to know is if there have been studies which test crowd wisdom in more esoteric areas, such as future predictions, maybe the stock market or race horse betting, that sort of thing. "
] |
[
"Would the heat from a hot water tank sanitize most human pathogens?"
] |
[
false
] |
Our city is under a boiled water advisory right now and I'm wondering if it's better to use the hot water from the tank for basic cleaning (washing dishes etc). I took a temperature reading and our hot water is running at 58 C - 60 C ( . Assuming a hot water tank is set at 70 C is that high enough to kill most human pathogens or at least inhibit them so they are no a sufficiently large population to cause problems? More generally is properly heated hot water more or less sanitized than cold water?
|
[
"Microbiologist here. ",
" ",
"If you're going to be eating off of something within ~24 hours of washing it in this water, boil it first. Most organisms will be dead after 24 hours due to lack of nutrition, so if you're waiting that long then it shouldn't be an issue. If you have small children, elderly family, or a pregnant woman in the house you ",
" to make sure that the water and all of the dishes/whatever are clean and sterile. Most of the severe bacterial infections affect those groups. I actually got an E.coli infection a few weeks after starting at my current lab, it was the worst four days of my life. I would recommend that you boil your water regardless of situation because bacterial infections suck and I personally wouldn't want you or anyone to go through that. The other post is correct also, the 70C should kill most salmonella or E.coli and things like that (they are really wimpy around heat, you really need to get up to boiling temperatures to kill the really nasty stuff like the Clostridium or Bacillus. "
] |
[
"Why does it take longer at 138°C?",
"EDIT: It appears that 138°C for 2 seconds is for ultra-pasturization which is a different standard. Also, is this table for milk or water and are they different? "
] |
[
"Funny story, I didn't. I was working with ~30 different strains of E.coli of a particularly deadly nature so I was freaking out when the hospital told me that it was E.coli. After the CDC investigation though it the strain I got didn't match any of the ones I had been working with. Turned out that I got it from a local eatery."
] |
[
"I am in my second year of a four year science degree. I have to pick my speciality soon,i am most interested in biology,what will make me the most employable?"
] |
[
false
] | null |
[
"askscience is for specific science questions; you should try ",
"/r/askacademia",
" or ",
"/r/biology"
] |
[
"Either a medical degree or a Ph.D in some molecular/chemical/engineering specialty. (Definitely don't stop with a BS; the long-term career prospects of bachelor's level biologists are below those of art history majors.)"
] |
[
"Is an M.Sc. a bad option ? I just don't want to spend another 4 years at college :(, or an MBA ? Get a job working for a biochemistry company ? Understanding business and science ? "
] |
[
"When does an object reach maximum velocity after an impact?"
] |
[
false
] |
I'll make the question a bit more specific and I'll try to stick to one single problem, but I will see how it goes because I think different situations could produce different answers. So I got into an argument with a friend about when does a puck reach maximum velocity after a shot. I was confident that it's right at the moment of a shot and then the friction and air resistance (and maybe some other forces?) makes the puck loose speed. Right? It sounds very logical and probably is true, but we both like to look at the world from its smallest possible parts to the largest. Well, this is where my friend confused me. And this is where I will also branch out the question because I feel these two situations could have different answers. The first situation would be a normal hockey shot. Puck which is not moving comes in contact with a fast-moving stick. Stick is pushing the puck for a while and then leaves the stick. And as soon as it does it starts losing speed. I feel like that's correct. But what if we look at the time frame from when the stick first touched the puck? The second situation is a bit more trivial. What if the stick did not do the "pushing" motion. What if it was truly a hit where as soon as the stick hit the puck it stopped. (I now feel like this is a really trivial action) When does the puck reach max velocity? I thought this wouldn't be different than the first problem. But wouldn't that mean that the puck went from 0m/s to its max velocity instantaneously making the acceleration of the puck infinite? I can see two outcomes of this. Eather I was not aware that acceleration can actually be infinite at a single point or "instantaneously" is not a term in physics and the puck takes time to reach max velocity. Which one is it? So... To sum up my questions. What happens in a normal hockey shot? Stick hits the puck, the stick loses some minimal amount of speed to gradually start accelerating the puck and the puck reaches the max velocity right at the end of the shot. (Correct? Any details to add?) How trivial is the second situation? What exactly makes it trivial? And what happens in this trivial or similar, more possible, situation? Extra... Because I think the forces in action could be more visible in the world with two heavier, more friction receiving and, in this context, more flexible objects - when does a stopped vehicle reach maximum velocity after it gets hit by another vehicle? P.S. Extra street cred for videos explaining this or tbh any interesting physics videos. +1 for great, basic quantum mechanics explanation videos. If you feel like you could write a book about this - please do!
|
[
"Wow, that's a long question. But I'm going to take a shot (pun intendend) at answering it, because there's a little mind-bending realization about how the world works, in there.",
"Your question is about forces and accelerations. But first, let's just look at forces. One of the first things we learn in physics is that when you set a mass on a table, it doesn't accelerate because the net force is zero. Gravity is pulling it down, but there's an exactly balancing upward force from the table, called the \"normal force\", because it acts in a direction perpendicular (\"normal\") to the table's surface.",
"How in the world does the table know exactly how much upward force to apply, to exactly counteract gravity? The answer is that the table is actually just like a spring. Imagine setting that weight on a spring, instead. The spring compresses until F_spring = -kx (where k is the spring constant, ie a thing that depends on the stiffness of the spring, and x is the deflection of the spring) exactly balances gravity. Well, the table itself, no matter what it is made of - wood, steel, granite, whatever - is just a very stiff spring. You put a weight on it, and it deflects a little, until F_spring balances gravity.",
"That is, there is no material in existence that is truly completely 100% rigid. Everything deflects, bends, distorts a little when you push on it. When you walk across a floor, even a stone floor, the stone is just barely deforming as you step on it. The world is, at some level, all squishy.",
"Now, to get to your question about a hockey puck and a hockey stick (which are both squishy), we need to introduce another important idea. Objects accelerate when a force is applied to them. You don't, however, apply that force \"instantaneously\". In fact, the change in momentum of the object (delta_p) is given by delta_p = force x time. If you want to give something (a hockey puck) momentum, you have to apply a force over some time.",
"(Note for aficionados: if you want to talk about the change in energy of the puck, you have to think about force applied over a distance, because the work is the force times the distance over which it's applied.)",
"Well, here's where the springy-ness of the stick and puck come into play. If you hit a hockey puck with a stick, they deform so that they stay in contact for a while. The stick applies a force to the puck for a period of time, even in the hardest slapshot. See ",
"this video here",
" (esp at 22 seconds) that shows them being in contact for a long time, or ",
"this video here",
" that shows a baseball deforming at it's hit by a bat.",
"So, stop thinking about \"instantaneous\", and instead think about \"how long\" the force is applied, and everything should make sense."
] |
[
"This. ",
"Also, the puck will reach maximum velocity at some time during the push from the stick. As the puck moves away from the stick, the force it feels will start to decrease. At some point the force of the stick will become balanced with air resistance and friction. This means the cceleration will be at zero. At this instant the puck is moving the fastest."
] |
[
"And also to add to the excellent explanation given by ",
"u/pfisico",
" , this universe has an absolute speed limit. Although it is called the \"speed of light\" because it is the speed at which massless particles like photons (which make up light) travel, a better term for it is the \"speed of causality\". ",
"This is the speed limit of cause and effect. Other than the weirdness of quantum entanglement, all objects that have mass cannot interact with another faster than this speed, and this is true down to the individual atoms of an object like a hockey stick and puck. ",
"So when a hockey stick \"hits\" a puck. The atoms where the puck is initially contacted detect this hit first. This impact cannot be transmitted to the atoms at the \"front\" of the puck faster than the speed of light (in fact it will be much slower - depending on the bonds between the atoms in the puck) So the \"front\" of the puck doesn't know the \"back\" of the puck has been hit for a brief period. (explains the deflection)",
"For any object with mass, things cannot happen instantaneously because no information can travel faster than the speed of light."
] |
[
"What happens to all of the microorganisms which we are constantly inhaling?"
] |
[
false
] |
There are millions of bacteria, fungal spores, and other microscopic organisms that are in the air we inhale constantly. So what happens to them and us when we inhale them?
|
[
"Depends on their size. Some are trapped in the nasopharyngeal (nose and mouth) region where they are then swallowed and the stomach acid takes care of them. Then some are deposited in the upper airways where the mucociliary escalator sweeps them out of the lung and again they are swallowed, and the ones that bypass this are usually engulfed by macrophages, or absorbed via pinocytosis and again, swept out of the lung and swallowed for excretion, or taken in the blood to the liver where it becomes mixed in bile and is then swept out in the poop. The body is quite an amazing filter actually. "
] |
[
"Mucus is the major mechanism of trapping microbes that we inhale. It has even been shown that some polymers in mucus aid in preventing bacterial biofilm formation.",
"There is a little review on that ",
"here",
".",
"Other means are cilia in the lungs that aid in sweeping the bacteria away. These are considered natural barriers. The innate immune system would fight off any microbes that got past these defenses. "
] |
[
"It's not 100% efficient, especially when viruses and bacteria replicate faster than they are destroyed. There's a lot of biology and chemistry that goes into answering your question properly, so for pollution I'll briefly answer. The composition of the pollution plays a huge role. Metals can dissolve, complex gas mixtures can cause construction of the airways and blood vessels, and many other outcomes. There is an entire division of toxicology devoted to this question. If you google health effects of PM 2.5 you will be overwhelmed with data. "
] |
[
"If I take ice II at 500MPa and -80°C, and reduce the pressure to 100kPa, will the ice reorganise itself into ice I? Does it need to be melted in order to transition between its solid phases?"
] |
[
false
] |
Do any of the solid phases of ice form a stable configuration that can be taken out of its usual temperature-pressure boundaries once formed?
|
[
"I don't know about ice specifically, but for other materials, phase changes between different solid phases certainly does take place. For example the changes between the different phases in steel is used in order to create the desired microstructure to give the desired bulk physical properties for particular applications of steel."
] |
[
"True, a solid is also not really solid as we think of them mostly. Solid doesn’t mean it doesn’t move. All atoms move constantly as heat is actually the vibration of an atom. The difference is there are forces between atoms and if those forces are stronger then the vibration of the atom they win. For example metal atoms have a strong bond between them so you need a lot of heat (= vibration, speed of the atom) before they can break that bond to go to liquid and same happens to go from liquid to gas phase. \nAn example I know from work is an aluminium milling block. They are casted but due to the cooling the alloy elements are mostly in the sides of the block instead of nicely divided in the block so we heated those blocks back up till close to melting temperature for hours to days to let those elements diffuse through the block"
] |
[
"The short answer is yes. The reason is what we call \"thermodynamics vs kinetics.\" ",
"Thermodynamics describe the arrangement of matter with the lowest free energy. Given enough time, this is what we expect the matter to do.",
"Whether the matter in your system can actually rearrange itself into that configuration quickly is the subject of kinetics. For many kinds of materials, there is some sort of energy barrier involved in rearranging things. To get to a low state you have to go through a higher energy state first. This may be the hump to move an atom from one crystal site to a neighboring site, or it may be nucleating a new phase (making a bunch of high energy surfaces). The terms usually associated with these \"humps\" are activation energy and activation volume.",
"Generally, temperature gives atoms the energy to get over humps. Things are jiggling around, and occasionally they will bounce violently enough to make it over the hump. Making it hotter means you give it more energy to get over that hump, and so things can rearrange faster. Making it colder makes it less likely to get over a hump, so it rearranges slower. Increasing pressure increases the energy required for a given activation volume (e.g. squeezing an atom through a gap), and so on.",
"So, metastability (the ability to keep a configuration that is not thermodynamically optimal) depends on a variety of things like",
"Materials with strong bonds (e.g. ceramics, which can often melt at thousands of degrees Celsius) can have large humps, and thus retain metastable phases at room temperature or even elevated temperature. Other materials might need to be kept very cold to preserve metastable phases. Technically just about everything has at least ",
" metastability. This can be good or bad depending on what your goals are."
] |
[
"Do hearts vary a lot among vertebrates?"
] |
[
false
] |
I learned recently that mammalian four-chambered hearts are more efficient than reptilian three-chambered hearts. Are mammals special as far as hearts go?
|
[
"Fav animal fact. Amphibians have a two chambered heart as larvae, then when they hit metamorphosis ,it changes to 3 chambers. All while pumping happily away. did i mention then most species move from being an obligate herbivore to obligate carnivore at the same time and gut track totally rearranges, oh and they suddenly grow lungs."
] |
[
"Some. ",
"Amphibians and reptiles have 3 chambers with the exception of crodilians which have something closer to a mammalian 4 chamber setup. ",
"Birds the general structure is very similar to mammals, but tends to be larger relative to body size and a bit more efficient to deal with the oxygen demands of flight. Dinosaurs share a lot of circulatory features with birds and are related to crocodilians so it's commonly thought they likely had four chambered hearts and many or all may have been homeothermic like birds and mammals.",
"Fish have four chambered hearts. ",
"Cold blooded creatures just don't need the long term efficiency mammals, birds and most fish do, they're all about efficiency with occasional bursts of action followed by long recovery periods.",
"Birds need more power by weight, so theirs are set up a little differently than mammals. Among a group, mammals or birds or whatever there are some differences in trends based on size but the general structure is the same."
] |
[
"Just commenting to expand on fish hearts; they are four chambered but not the same way as in mammals. As they only have a singular vascular circuit (no lungs), the chambers are all one after another, instead of 2 atriums and 2 ventricles separated by a septum."
] |
[
"Why is the sound quality for AM and FM radio so different?"
] |
[
false
] | null |
[
"A radio works by decoding a known carrier wave (the frequency you tune in on), AM modifies the amplitude (hight/strength of the waves) and Fm the frequency. As can be seen ",
"here",
"Now the amplitude weakens when the signal travels from far away, producing static. \nThe other method however does not look at the amplitude but at the frequency that doesn't change, causing far less static. ",
"Edit: \nOh and FM radios can keep tuned in on their frequency because they have e 150kHz bandwidth, meaning that the station frequency can go 75kHz in both ways (which is a lot), AM stations only get 10kHz."
] |
[
"The bandwidth would probably be the main reason why they sound so different. This is a technical limitation of AM. You'd think since only the amplitude of the wave is being changed, it would be a very narrow spike on the spectrum. But in reality, it ends up having two sidebands each with the bandwidth of the original signal. If you were to have a 150KHz bandwidth signal modulated on AM, you'd end up with the carrier spike and 2 150KHz sidebands, taking up 300KHz of spectrum. FM, on the other hand, only takes up 150KHz for a 150KHz signal.",
"AM was also put into use when radio receivers were primitive and speakers were tinny and badly amplified. There was probably little to no benefit transmitting higher bandwidth audio at that time, and the standard just stuck."
] |
[
"The bandwidth of AM commercial radio is not a technical limit, it is a political one having to do with dividing up the scarce spectrum at those low frequencies. An AM channel occupies about twice its audio band width in the radio spectrum, plus some margin to separate the stations. It is technically feasible to have dual channel 44kHz stations in the AM band (CD quality sound with a powerful enough station), but each one of those takes up a minimum of 176kHz, more like 200-250 kHz if you include the need to separate the stations. So you could fit like 3 stations in the whole band.",
"FM stations have broader bandwidth,but that is because there is more band up there -- FM commercial stations are at 100 MHz, AM stations are at 1MHz. "
] |
[
"When the human body is starving, which minerals and vitamins are depleted first?"
] |
[
false
] |
And which ones last the longest?
|
[
"Fat stores are not depleted within days. I'm sorry but that is completely incorrect. A healthy adult man of 70 kg and 20% bodyfat has 14 kg of adipose tissue - or 98 000 kcal. This will last him around 40 days, given a metabolic rate of 2500 kcal/day.",
"You are also mistaken about ketosis and muscle wasting. Muscle wasting is a product of prolonged gluconeogenesis. Ketosis supplements gluconeogenesis in order to keep glucose levels sufficiently high. Now, the substrates for gluconeogenesis is glycerol, lactate - but most of all - amino acids. This means that gluconeogenesis pretty much always means breakdown of proteins.",
"And gluconeogenesis actually starts as soon as the glycogen is consumed - long before ketosis kicks in. So just letting your glycogen run out means protein breakdown. It has nothing to do with ketosis.",
"Now, is protein breakdown the same as \"muscle wasting\"? Not necessarily. Your body has a lot of excess protein besides muscle tissue - more than you think. Substantial muscle wasting will only occur once fat reserves are almost completely depleted.",
"This, of course, makes great evolutionary sense. Imagine a hunter-gatherer who is starving. If his body was to use the protein is his muscles as a fuel source before the fat was gone, he would lose his ability to gather new food. He would die in a cave, a paralyzed heap of bones and fat.",
"Source: I'm a medical student, 3rd year"
] |
[
"The short answer would be that the water-soluble vitamins would be depleted first. They would be constantly loss due to production of sweat and urine. Fat-soluble vitamins (A, D, E, K) would be depleted next. These would also be the ones that \"last the longest\" so to speak, because it takes a relatively long (days) amount of time to metabolize fat stores in a starvation situation.",
"Minerals are tricky to answer. Most minerals are required in trace amounts by the body, so any loss is negligible. The bigger concern in a starvation situation would be vitamin loss. ",
"As an aside, when one is starving, the first thing that gets used for energy are glycogen stores. These are depleted within hours. After that, fat stores (containing vitamins A, D, E, and K) are used. These are depleted within days. During this time, ketosis occurs, because your body wants to spare muscle from breakdown. Once ketosis reaches its maximum level and the body sees that this isn't enough, then muscle wasting will occur. Once muscle wasting occurs you would have a loss of all manner of minerals (copper, iron, etc). ",
"Further reading: ",
"https://en.wikipedia.org/wiki/Starvation",
"If you would like to know what exactly we've got inside us, and in what amounts, take a look at this: ",
"https://upload.wikimedia.org/wikipedia/commons/c/cb/Blood_values_sorted_by_mass_and_molar_concentration.png",
"- ice "
] |
[
"The best source I could find about it",
"The reason you won't find detailed studies about this is because they would be entirely unethical to enact. You can't just starve people in unhealthy way to see what happens, the only way you could get these results is to sample a series of sufficiently malnourished people, say in a famine situation, and see what their levels of vitamins and minerals were and ask them how long they had gone without food. However, you would have no original base line and the only one available would be after they got back to a healthy weight, which may not have been similar to their start point.",
"Even in the case of studying weight loss you would do it in a way that supplements all the required vitamins, minerals, essential amino acids and fatty acids in a way that stops depletion to an unhealthy level occurring. "
] |
[
"Are tropical storms more frequent and powerful now then they were 50 or 100 years ago?"
] |
[
false
] |
How have the predictions of climate scientists done so far? What were the predictions? What is the most reliable data?
|
[
"“\nExisting records of past Atlantic tropical storm or hurricane numbers (1878 to present) in fact do show a pronounced upward trend, which is also correlated with rising SSTs (e.g., see blue curve in Fig. 4 or Vecchi and Knutson 2008). However, the density of reporting ship traffic over the Atlantic was relatively sparse during the early decades of this record, such that if storms from the modern era (post 1965) had hypothetically occurred during those earlier decades, a substantial number of storms would likely not have been directly observed by the ship-based “observing network of opportunity.” We find that, after adjusting for such an estimated number of missing storms, there remains just a small nominally positive upward trend in tropical storm occurrence from 1878-2006. Statistical tests indicate that this trend is\nnot significantly distinguishable from zero (Figure 2).”",
"https://www.gfdl.noaa.gov/global-warming-and-hurricanes/"
] |
[
"Note however, from the same source, that: \"A review of existing studies, including the ones cited above, lead us to conclude that: ",
".\"",
"",
"The basic physical of why hurricanes get stronger with warming was developed in the 1980s and is well understood. However, we just don't have enough observations to decidedly validate the predictions yet, because they are just so infrequent and year-to-year variability is so large."
] |
[
"Kerry Emanuel at MIT has researched and this question systematically, using historical data. His results show a correlation between ocean temperatures and intensity. This result is obvious given that the thermodynamic efficiency of the systems are proportional to the difference between the surface and stratospheric temperatures. With a warming ocean and enhanced greenhouse gases, the surface temperatures go up and stratospheric temperature decrease, enhancing the heat gradient in the atmospheric column. What's not as well constrained are the effects of shifting wind patterns due to climate change. These can impact hurricane formation.",
"Most of the current research predicts GW will increase the number of intense storms but not the overall number storms. A cursory look at statistics going back a few decades is striking in terms of the number of records broken with respect to intensity, barometric pressure, rainfall totals, accumulated cyclone energy (ACE) and duration of peak intensity for individual storms. Also, interesting is the location of many storms occurring in areas where they are usually rare. With respect to basic physics and meteorology it is expected that GW will increase storm intensities and rainfall amounts. However hurricane formation depends on other factors such as lack of wind sheer, lack of dry air masses and conditions which may be enhanced or diminished by GW."
] |
[
"Can light traveling in opposite directions interfere?"
] |
[
false
] | null |
[
"Yes, absolutely. If you had two plane waves moving in opposite directions then there would be periodic times when the fields were zero everywhere. The wonderful thing about waves, though, is that if you had, say, two wave packets moving in opposite directions, once they were finished \"touching each other\", they would continue on as if nothing had happened. "
] |
[
"Thank you. So if you had, let's say, two beams of monochromatic light aimed at each other such that the the fields canceled along both beams, what would happen to the energy of the light, since it must be conserved. "
] |
[
"That's exactly the right question to ask. Good catch. I think I was just ",
" to say what I said. It can't be the case that the fields are everywhere zero for exactly the reason you bring up. The waves will still interfere. But I was wrong to say that it would be totally destructive like that. "
] |
[
"How do fish get into a lake when there's no river/sea connected to it?"
] |
[
false
] |
And do fish that are in landlocked lakes speciate? Shouldn't each landlocked lake have its own species of fish? EDIT: Thanks for the responses!
|
[
"One theory is that some species of fish have sticky eggs which can be dispersed when they adhere to an animal's fur, feet, or feathers. The eggs will then drop when they are rubbed off or perhaps the eggs become less sticky as they age.",
"Another theory is that fish eggs may be a bit more robust than we expect them to be and may be able to pass through a duck's digestive system and still be viable.",
"http://www.researchgate.net/post/Is_there_scientific_proof_that_water_fowl_can_transport_fish_eggs_from_one_water_body_to_an_other",
"The discussion on that page includes several links to journal articles discussing the viability of various water fauna through waterfowl digestive tracks."
] |
[
"Alot of lakes that have fish in them that arn't connected to a river or ocean could be planted their by the city/states fish and game. Or it is possible that thousands of years ago it was connected but over time water levels have dropped cause it to be disconnected. "
] |
[
"Around these parts (Southern Manitoba) a lot of lakes and even recent human-made lakes (like stone quarries) have been populated by flood conditions.",
"Also for non-fish, ",
"many seeds and invertebrates have been shown survive passage of a birds digestive system",
". "
] |
[
"Why does \"nothing\" sound the way it does?"
] |
[
false
] | null |
[
"Probably ",
"tinnitus",
". Its pretty crazy how different quiet in your bed at night vs real quiet is. If you ever have the chance to sit in an anechoic chamber you'd be surprised how loud the sound of blood flowing through your body is. "
] |
[
"blood flowing through your ears and/or the hairs in your inner ear subtly changing positions. "
] |
[
"Are you referring to your ears ",
"ringing",
"?"
] |
[
"What causes magnetism?"
] |
[
false
] |
What is it about certain objects that causes it to be magnetic? Is it the electron configuration? Is it the overall structure of the atom? Or is it something completely unrelated to its chemical makeup?
|
[
"It's a combination of the structure/makeup of the atom itself and the crystal structure (how the atoms arrange into a molecule). It comes mostly from the Pauli Exclusion Principle.",
"I'll focus solely on ferromagnetism. There's a few other types that behave differently (paramagnetism and antiferromagnetism), but the idea is the same with some details changed. So the first thing the atom needs to have is an unpaired electron. This is because every fundamental particle has a property called spin, which is a magnetic moment. Electrons have spin. Electrons are effectively tiny magnets in that they produce their own magnetic field where 'north' is the direction of their spin (I think it's north not south but it's not super important)",
"If you know some chemistry then you know that 'paired' electrons are ones that fit in the same orbital with opposite spins. Helium has 2 electrons in the same orbital (The 1s orbital) with opposite spins. These spins add and cancel. So helium has 0 net spin from its electrons. But many atoms have lots of unpaired electrons. Carbon famously has 4, which is why it can form so many bonds.",
"Following ",
"Hund's Rules",
", all the unpaired electrons have spin in the same direction. So those spins add to a larger net spin. So every atom makes a stronger net magnetic field. We can see that our ideal magnetic material would have a good amount of unpaired electrons. Iron has 4. A noble gas (no unpaired electrons) will never be magnetic in its usual state.",
"The next bit comes from the Pauli exclusion principle. When the atoms bond, the electrons are prevented from being in the same orbital unless they have opposing spins. The other option is for them to be in different orbitals (and therefore further apart) but with parallel spins. This is a direct result of the Pauli Exclusion principle if you're not familiar with it.",
"Electrons repel each other because they're both negatively charged. So the further apart they are, the lower energy that state is, and the more likely for the electrons to be in that configuration. This is the gist of the exchange interaction: parallel spins have lower energy due to constraints from the Pauli Exclusion principle and the fact that electrons repel.",
"The exchange interaction is competing against the \"dipole-dipole interaction,\" which is just the interaction you get by considering all your electrons as magnets. If you take two magnets and put them right next to each other, the lowest energy for them is antiparallel, or pointing in different directions. This is in direct opposition with the exchange interaction. Materials where the exchange interaction wins by a large amount end up having all the spins aligned in one direction. Remember that spins are tiny magnets, so if we have all of them pointing in one direction, they add up to a much larger magnetic field. These are our ferromagnets. In Iron, the exchange interaction is around 1000 times stronger than the dipole-dipole interaction. In most materials you never get this sort of alignment, because the exchange interaction doesn't dominate as much. Whether or not the exchange interaction dominates depends on the exact structure of the bonds in the crystal, because a change in the bonds changes how far or close the electrons can be. There are even elements that have both magnetic and non-magnetic structures like ",
"Austenite",
" which is a different structure of Iron."
] |
[
"Macroscopic magnetism (like the magnetic field of something you can stick to the fridge) is due to a large number of microscopic magnetic moments that are aligned. Each microscopic magnetic moment is due to the spin of the electrons in an atom or compound. Spin is an intrinsic property of electrons that basically makes them act like very tiny magnetic dipoles that can either point up or down. When the electronic orbitals of an atom are all filled, each electron is paired with another electron that has opposite spin and the magnetic moment is cancelled out. When the orbitals are not filled, there are unpaired electrons whose spins contribute to the overall magnetic moment of the atom. The more unpaired electrons, the larger the magnetic moment.",
"Any element or compound with a nonzero magnetic moment exhibits some kind of magnetism. Permanent magnets (the ones you put on the fridge) are ferromagnets, which are a special type of material that not only have nonzero magnetic moments, but whose moments tend to align with their neighbors and add up to a macroscopic magnetic field even when there's no other magnetic field around. Other magnetic materials that respond to an external magnetic field but don't keep it when it's taken away are either paramagnetic or diamagnetic, meaning their moments tend to align or anti-align with an external field."
] |
[
"if you look at the (not well known) structure of neutrons stars, they're not 100% neutrons."
] |
[
"Can water freeze under tremendous pressure, like at the bottom of the ocean?"
] |
[
false
] |
Why isn't the water at the bottom of the ocean frozen?
|
[
"The pressure at the bottom of the ocean isn't high enough, but yes, water will change to ice if you increase the pressure sufficiently. It's not the same phase as the ice you're familiar with. There are actually many known phases of ice, which occur under different temperature and pressure conditions. Wikipedia has some ",
"more information",
", including a diagram of the temperature/pressure regions different ice phases occur at.",
"The pressure at the deepest point in the ocean is ",
"a little over 1000 atmospheres",
". From that diagram, it would have to be around 10,000 atmospheres for ice to form."
] |
[
"I am an oceanographer, the way water works is the most dense water is super cold, super salty water, this water is on the bottom of the ocean.\n",
"http://www.cgrer.uiowa.edu/people/carmichael/atmos_course/ATMOS_PROJ_98/mapeter/4_atlanticmasses.gif",
"\nIs an example of the water in the Atlantic ocean. The very salt water created by ice freezing in the Antartic and thus salt being left behind in the water as the ice freezes, makes super cold, super salty water that sinks. If that makes sense. ",
"http://www.hurricanescience.org/images/hss/TSD_depth.sm.jpg",
" explains this concept as well (the ocean is layered in patterns of saltiness and temperature variably. "
] |
[
"Examine ",
"this phase diagram",
".",
"At the ",
"Mariana Trench",
", the pressure is 1086 bars, and the temperature is 1 - 4°C. You'll notice in the phase diagram that for ice to begin to form at those temperatures, the pressure needs to be around 600 MPa, while the pressure of 1086 bars translate to 108.6 MPa."
] |
[
"Many questions about recent /r/science posts about our universe being inside a black hole."
] |
[
false
] |
My questions come from this article/thread: but I've read others. Questions: 1) Does anyone know how seriously the science community is taking these kinds of theories (the media is never realistic about this). 2) I'm confused about how the influx of matter into a black hole corresponds to the arrow of time for the universe inside. Am I to understand that for every particle that falls into a black hole, a clock ticks forward one nanosecond in the contained universe? Is the converse true? Black holes decay by emitting Hawking radiation. Will this make time move backwards in the contained universe? 2) What happens when a black hole disappears altogether due to Hawking radiation? Does its contained universe end? 3) Are the timescales between parent and child universes comparable? That is, can a child universe live for eternity, while its parent's black hole only lives for a few billion years? 4) Is the total energy of the parent and child universes comparable? If not, is there any correspondence between the total energy of the child universe and the total amount of mass that fell into the parent's black hole? 5) Is there any correspondence between the laws of physics of the parent and child? I am quite certain that my questions are full of naive assumptions, so somebody please tell me what's what.
|
[
"That topic was posted in ",
"/r/science",
", which has very different standards from ",
"/r/askscience",
" and can't deliver reliable answers."
] |
[
"1) Not very. It's mostly just that one guy working on it. It's a cool story, so they picked up on it.",
"2) The arrow of time markers shouldn't be viewed as something causative: time doesn't advance because of entropy increasing or the universe expanding. Rather, they're ways to figure out which way is which. It's similar to losing your bearings while scuba diving, and watching the bubbles to figure out which way is up.",
"2B) I'm not sure this is fully understood, but by the time it gets small enough for that to happen it is emitting high energy gamma radiation. In reality black holes are colder than the cosmic microwave background so they won't have a net loss of energy.",
"3-5 I have to do more research and I'm not on a computer with journal access right now."
] |
[
"This is true, although I am thankful that OP has given me a chance to appreciate the source, as I missed it the first time around on my news feed."
] |
[
"Is there a theoretical limit on the wavelength of radio waves?"
] |
[
false
] |
I apologize if this is a stupid or obvious question, but in textbooks it always says that radio-waves are defined as the electromagnetic radiation with a wavelength between approximately 1m and 1km. Although this does say 'approximately' and may differ by a factor of 10 or so, but is there any theoretical limit on the wavelength of electromagnetic radiation and if not what source emit radio-waves with such large wavelengths?
|
[
"waves that act like light",
"They don't \"act like\" light, they ",
" light. \"Radio waves\" are merely a subset of electromagnetic waves, no different physically from other wavelengths such as visible light and (on the other end of the spectrum) gamma rays. (I'm sure you know this, but I don't want OP to get confused)",
"Technically there is no upper limit to wavelength, but as you say, detecting them gets harder the longer the wavelength gets. There's also a practical limit: ",
"the atmosphere blocks radio waves",
" with wavelengths much longer than 10 meters."
] |
[
"waves that act like light",
"They don't \"act like\" light, they ",
" light. \"Radio waves\" are merely a subset of electromagnetic waves, no different physically from other wavelengths such as visible light and (on the other end of the spectrum) gamma rays. (I'm sure you know this, but I don't want OP to get confused)",
"Technically there is no upper limit to wavelength, but as you say, detecting them gets harder the longer the wavelength gets. There's also a practical limit: ",
"the atmosphere blocks radio waves",
" with wavelengths much longer than 10 meters."
] |
[
"There's no maximum frequency or wavelength for an electromagnetic wave. The idea of splitting up the EM spectrum and calling different ranges of frequencies by different names is a human construct to make things easier. I suppose there's a maximum wavelength where something will be called a \"radio\" wave, but if you increase the wavelength even more it will just be called something else instead."
] |
[
"Animals can survive on \"pet food\" indefinitely. Is there a \"human food\" equivalent?"
] |
[
false
] |
To reiterate in a more complete way: Is there any food (man made or not) that, like the food we give our pets, could potentially have everything we need for us not to have any diet-related problems? - that is, it would have all the nutrients we need, and close to the amounts that are nowadays deemed as healthy. And if there isn't, why aren't we making one? Or are we?
|
[
"Well, first off, most pet foods claim to be perfectly engineered for the dietary requirements of the animal at hand, but that is a questionable assertion. Grain-based cat food is the biggest offender, which is why now you have diabetes in domestic cats. You take one of the most perfect carnivores that nature ever devised and feed him grains (essentially bird food). Felines are designed for a high protein, low carbohydrate intake. If you screw that up, and give them a moderate protein, high carbohydrate intake, it is no surprise when some of them develop glucose-tolerance-related health problems (such as diabetes). Example source ",
"on feeding cats too much carbohydrate",
".",
"Now... on to perfect human food. Native Americans used to grind up meat and mix it with fat in something called Pemmican. It sometimes even contained some organ meat (liver has Vitamin C in it!). They could survive months on it. It contained basically all the vitamins and minerals a person needs to be happy and healthy. That being said, Vilhjalmur Stefansson proved one can live for a very long time on an all-meat diet. He had lived with the Eskimos and noticed they had very little access to fruits and vegetables. In fact, they subsisted on an all-meat diet for 6 to 9 months at a time, with no ill health effects. He went on to prove this is possible by subjecting himself to a year-long experiment where he and a colleague ate nothing but meat (with a little bit of liver thrown in occasionally) for a year-long experiment, under medical supervision, at NYs Bellevue Hospital. Stefansson emerged from the experiment perfectly healthy and with no signs of scurvy, calcium deficiency, or any other health problems. He ate only whatever he liked, as long as it was classified as meat. Some examples of what he ate daily include: steaks, chops, brains fried in bacon fat, boiled short-ribs, chicken, fish, liver and bacon. (Note the liver again! This is important as lighty-cooked liver contains enough vitamin C to fight off scurvy).",
"So, it appears, as long as you are also eating a bit of liver (not too much though!), and mostly muscle tissue and fat, then there you have your perfect human food. Which stands to reason. We are pretty good carnivores, and meat contains everything we are made of! ",
"Source on Stefansson experiment",
".",
"Note that Stefansson went on to eat NOTHING but meat for 10 years and he developed no health problems whatsoever and was in fine health. So the Eskimos and Stefansson could very well have discovered perfect human food. Meat! (With some organs thrown in)."
] |
[
"Rob Rheinhart invented Soylent, which is supposed to essentially be a replacement for meals. It is a powder which you mix with water to form a drink. The cost is advertised to be ~$3/meal.",
"I am a bit skeptical as to the health aspects of relying on such a drink for sustainment. There have been claims that there are high levels of heavy metals present in these drinks."
] |
[
"That's interesting! Have any studies since corroborated Stefansson's results?"
] |
[
"Why do our attempt to find life on other planets focus primarily on the existence of water?"
] |
[
false
] |
Why is that all searches for life on foreign planets are focused on the existence (current, past or future) of water? Yeah, life on our planet is dependent on water, but couldn't other forms of yet discovered life be equally dependent on something else, ANYTHING or NOTHING else? Only thing that I can think of is that water is the only know support for life, so might as well focus our efforts on that. But I'm sure someone has given this more though and will have a better answer.
|
[
"Because that is the only sort of life we have any concept of.. ",
"looking for something we know nothing about is very hard. ",
"at least with water dependent life we have some sort of frame of reference from which to base our searches. "
] |
[
"Because for chemicals to interact they need to be able to move around one another. This rules out solids as they don't move, and this rules out gases as in them particles just shoot around rarely hitting each other. So we know life requires some sort of liquid.",
"Water is the best bet for finding life since its molecules are very small. There are some other theoretical possibilities, but water remains the most likely.",
"Additionally, water is incredibly abundant. Hydrogen is the most common element, and oxygen isn't too far away from it."
] |
[
"Because searching for theoretical forms of life is just a wild goose chase. I'm pretty sure if we discover a form of life that doesn't depend on water, it won't be an intentional discovery; it'll catch us by surprise."
] |
[
"What is the mechanism that allow dolphins and whales to stay underwater for such a long time?"
] |
[
false
] | null |
[
"They have a high concentration of oxygen binding myoglobin, far more than any humans. Therefore they can store more oxygen for use and as they dive deep down and they cover their blowholes to keep water from getting in to their lungs."
] |
[
"Could we, using genetic engineering or some drug simply increase the amount of oxygen binding myoglobin in our blood and be able to hold our breath for minutes under water or is it more complicated than that / would cause deadly side effects. ",
"I know that in cycling they use blood doping and EPO to increase the amount of oxygen they can carry in their blood and so increase their aerobic threshold but there are supposedly dangerous potential risks caused by this related to blood clots. But that makes sense when you are making the blood \"thicker\" if you simply increased the carrying capacity of a single red blood cell would that carry the same risk?"
] |
[
"When myoglobin is broken down it is filtered by our kidneys. If you were to suddenly increase that amount I imagine you would overwhelm your kidney and cause kidney failure",
"Edit: also as you take in more oxygen, you’re gonna create more carbon dioxide that your lungs have to get rid of. It would overwhelm your lungs and cause its own set of problems. "
] |
[
"If you were to lie in a pool of white blood cells, would it heal cuts and wounds on the surface of the skin?"
] |
[
false
] | null |
[
"White blood cells",
" would only disinfect your wounds as they act against foreign materia. If it was instead a pool of stem cells, then that could accelerate your healing a tiny bit, by entering your bloodstream through cuts."
] |
[
"I used to know this, but I am really rusty on biology these days. What is it inside your body that heals wounds? As I remember the red blood cells clot the wound to stop bleeding and infection, and then the white blood cells do the healing. I know that the body has very few naturally occurring adult stem cells, but does it use them to heal wounds?"
] |
[
"Red blood cells don't really contribute to clotting, it's a feature of other stuff that forms in the blood plasma (fibrin for example)."
] |
[
"How can old films be re-released in higher and higher resolutions a technology of displays progress?"
] |
[
false
] | null |
[
"Photographic film works by having tiny photosensitive crystals suspended in a gelatin emulsion. When light hits the crystal, it causes a chemical change, and developing chemicals later preserve that change so that you can see it in the negative. The crystals are referred to as \"grains\" and speed of the film (indicated by the ISO number) refers to how large the grain is. Larger grains are more sensitive to light, but they are easier to see when enlarged. In older movies, you can sometimes see this graininess during night scenes or other low-light situations (though movies that have been digitally converted usually help remove this noise from the picture).",
"The film grain size is ultimately what limits how much a film image can be enlarged, though digital post-processing to remove noise can increase it further. There's no hard equivalency between film resolution and digital resolution, but in photography circles, 35mm ISO 100 film is commonly held to be roughly equivalent to 24MP digital camera. An 8K display is equivalent to 33 MP, so I would think that 4K would be approaching the limit of 35mm film conversion in absence of more advanced digital post-processing techniques."
] |
[
"Film doesn't have a characteristic resolution the same way that digital images do, film has \"grain\" which depends on about a zillion factors. A typical 35mm shot (what a lot of films and tv shows were shot on) will have a grain that corresponds to something between 4 and 20 megapixels of resolution, with the typical break between \"good and poor\" shots falling somewhere in the 10-12 megapixel range. In the absolute best case scenario a 35mm shot could have over 100 megapixels of effective resolution, but in practice that level only occurs with still photographs shot on the right film in perfect conditions.",
"In short, when digitizing motion pictures shot on 35mm stock you'd expect diminishing returns to start at resolutions of around 12 megapixels and you'll hit a pretty hard plateau at about 20 megapixels. (It should be noted that the mechanism of projecting a widescreen shot onto 35mm will also affect the effective resolution, potentially in important ways.) 4k is 6-9 megapixels depending on your definitions (UHD vs. DCI 4k full-frame). So that's already pretty close to the limits of 35mm film. You're going to hit the limit of 35mm prints at around 5k resolution (20 megapixels), in comparison 8k is 35+ megapixels.",
"Larger film formats are, of course, higher resolution. 70mm film has 4x the resolution of 35mm film (2x2), which translates to up to 80 megapixels per frame, pushing things into the 8-10k digital resolution range.",
"There are likely plenty of films that weren't intentionally shot to be exceptionally crisp for which even 1080p might be pushing the boundaries of the detail in the print. 4k is probably a reasonably good match for what almost all 35mm prints are capable of, especially if the end goal is viewing rather than archival storage. For exceptional film formats and projection technologies such as IMAX, CinemaScope, 70mm, etc. 8k is probably a pretty good fit though not necessarily sufficient to exhaust the underlying film's level of detail (for reference, an 8k projection onto an IMAX sized screen has ~3mm wide pixels)."
] |
[
"So film is kinda strange. Theoretically really high quality 35mm should have the same resolution as an 87 MegaPixle image (Depending on who's metrics you use). As with anything, the reality is... well... complicated.",
"Movies are not always shot in ideal conditions, lighting, apertures, Cameras ect. This often results in film needing to get \"Pushed\" or \"pulled\" durring the development process to produce a good image, and this can effect the quality of what the film actually captured, along with how well the Camera operators maintained focus and a bunch of other factors. So that really crazy number of 87MP could be more like 15 if the conditions did not lend them selves for a good shot or the processing was not perfect.",
"Putting that next to the standards you listed\n3840 x 2160 is 4k UHD - (8.3 Mega Pixels)\n7680 × 4320 8K UHD - (33.2 Mega Pixles)",
"it's clear that film still has some legs left in it. It should also be noted that not all movies are shot on 35mm, many films are shot on 16mm, in part due to its \"look\". ",
"IMDB Films shot on 16mm",
" You may have noticed a trend.",
"Outside of Hollywood productions with large budgets and a director whos going for \"A look\", film is dead. Much of it in part due to the fact that the effective resolutions it brings is not that much better than current digital cinema cameras. Yes, we will see older Star Wars films getting scanned and put out at 4k and 8k thats a given. The truth is, at some point the juice is just not worth the squeeze. Processing film, particularly scanning and correcting it is a lot of work. At some point its easier to take your 4k scan, upscale it to 8k and run a full set of optimized filters to sharpen and kick up the the image quality. "
] |
[
"What are the most \"intelligent\" asexually reproducing species?"
] |
[
false
] |
Among the asexually reproducing species of life on Earth, do any have a brain and nervous system, etc? Of those, which are the most intelligent? (As agreed upon by scientists) (Also allowed are species which have both asexual and sexual reproduction, but I don't know much about these)
|
[
"Parthenogenesis is a form of asexual reproduction that has been documented in turkey, condors, and quail, so one of them. If you restrict the query to animals who reproduce ~primarily~ asexually though, it's probably stick insects or thrips.",
"I'm just getting this from the Wikipedia article on asexual reproduction, if you'd like to read it for yourself - until checking it I would have said whiptail lizards."
] |
[
"Asexual reproduction is not incest at all. The problem with incest is that it can expose recessive homozygous combinations (e.g. from heterozygotic parents) that can be deleterious. But asexual reproduction won't do this as the offspring is the same as the parent."
] |
[
"It actually does allow for variation, but at a much slower rate. Asexual offspring will still experience transcription errors and other random mutations. Naturally this is less of an issue for organisms that reproduce at a high rate than it would be for complex organisms."
] |
[
"Compared to say, 60 years ago, how harmful are todays cigarettes?"
] |
[
false
] |
Are they about the same, worse, or better? I'm almost sure the answer is worse but I'm looking for some concrete justification. Would a heavy smoker fare better today or in the 1940's?
|
[
"Would a heavy smoker fare better today or in the 1940's?",
"Today, for at least two reasons. First, health care is better; there are more treatment options for emphysema, lung cancer, COPD, etc today than there were 70 years ago.",
"Second, filters didn't become widely used until ~1950s, and these did help. But then again, there are filterless cigarettes still on the market. And you can always hand-roll. There was also the introduction of the \"light\" cigarette, in which less smoke was inhaled on each drag. ",
"As for the rest....I think it will vary, but I don't think there's any way to be sure. Cigarette manufacturers have changed their blends over the years. Different tobaccos, different additives, different processing techniques, etc. Some probably made them marginally more healthy and some probably made them less healthy.",
"But they have always been tight-lipped about this stuff, so you don't know what all is in there for certain, and you don't know what all ",
" in there 70 years ago, and you don't know for sure what each of those things are going to do to you."
] |
[
"Well back then it was mostly tobacco. We know for a fact they add many chemicals and fillers now as compared to the 60s. The amount of actual tobacco leaf used is half what it was in the 60s, the rest is fillers of some sort. ",
"[1]",
"Also those \"safer\" Cellulose acetate filters were known to cause damage to lungs. They didn't release any of those reports until 1999.",
"We know that they were willing to introduce addictive chemicals in order to increase sales so who know what else they have been willing to add. Also the carcinogenic nature I believe depends on the brand and which chemicals they add. (But then again who knows at all what was in stuff before the 40s, like even look at early Coke products)"
] |
[
"I'd like to point out that there is a persistent myth in our culture that additives in cigarettes make them significantly more dangerous. At the end of the day, you're breathing in a bunch of smoke, and that is incredibly bad for you. An additive can only have a minimal positive or negative effect."
] |
[
"Why do people die of starvation without using up all their bodies' fat reserves first?"
] |
[
false
] |
I've read that the human body starts breaking down proteins for energy after some time during starvation even when there is still fat left that the body could have utilized to make energy. Why is that so? Also, is it possible for a person to survive on just his fat reserves for a long period of time if he can't find anything to eat?
|
[
"Your body requires more than just fat and protein to survive, and this long list includes your vitamins and minerals that keep your inner machinery working. Not enough vitamin C? Scurvy! No vitamin A in your diet? Keratomalacia!Lacking vitamin B12? Say hello to atrophic gastritis.",
"Again, you can't survive on just fat alone."
] |
[
"Don't forget sodium and potassium just to move the muscles with the \"sodioum/potassium pump\". If muscles lack the energy to move then the heart can't pump blood."
] |
[
"Your body still needs a base amount of energy to break down the fats. Once it runs out, its out. People usually succumb to dehaydration before they actually starve to death, so to say. Without water, your body cannot do anything. "
] |
[
"How does a neutron star generate a magnetic field if it is composed entirely of neutrons?"
] |
[
false
] | null |
[
"Mostly because it's not composed ",
" of neutrons - just nearly so. ",
"The very outer layers of a neutron star are \"normal\" matter (as normal as 1,000,000 K matter can be, that is) and probably consist of a very dense fluid of nuclei and electrons. This layer is conductive, and so combined with the very fast rotation of the neutron star as a whole, can generate quite a whomping magnetic field.",
"Farther inside, as the pressure increases, we find a higher density of neutrons as degeneracy pressure fuses more and more electrons and protons. But still, there are some particles with electric charge to be found, and so a source for a magnetic field.",
"Even in the very center of a neutron star we're not completely sure what we'll find; but if there are free charged particles forming any kind of fluid, then again a magnetic field can form."
] |
[
"Of course, all stars are made of subatomic particles, when you get down to it. But what happens in a neutron star is that the protons and electrons - which normally make up atoms - get essentially \"smashed\" together by the extreme gravity. As it turns out, when you combine a proton and electron under the correct extreme conditions, you get a neutron! The result is that the atoms that make up a star can, under the right conditions, start to \"melt\" together into neutrons. Eventually most of the star turns to neutrons -- after releasing a lot of energy :) -- and we have a \"",
"neutron star",
"\". ",
"Some theories allow even a neutron star to further collapse into a ",
"quark star.",
" I should stress that these are hypotheses, and we don't really quite know what happens under such conditions. "
] |
[
"I am no expert on neutron stars, but I figured I would point out that neutrons, while electrically neutral, ",
" have magnetic moment.",
"The overall charge of the neutron is zero, but it made out of charged particles, their charged just cancel. The distribution of charged particles within the neutron create a magnetic moment."
] |
[
"Why are UHF TV antennas (almost) always loop antennas, vs. VHF antennas which are usually whip antennas?"
] |
[
false
] | null |
[
"The length of an antenna is related to the wavelength of the signal it is meant to receive, typically some fraction (1/2 or 1/4). UHF wavelengths are less than a meter, so loop antennas (antennae?) work fine. VHF wavelengths are longer, 1m - 10m, so they need longer antennas.",
"There is math involved, so someone else will have to get into that."
] |
[
"It's my understanding that Loop antennas come in two main varieties; self-resonant large-loops where the circumference of the loop is roughly the same size as the wavelength, therefore works better on the high-frequency/short-wavelength bands (so the physical size of the antenna doesn't end up too large) whereas small-loops (which use magnetism to modify the 'length' of the antenna electrically) are not great for transmission and because of this, they're usually used for receiving-only, and at low-frequency/high-wavelength bands where the inefficiency and lossiness aren't a big deal and in fact, it can help by cutting down on noise interference."
] |
[
"It also has to do with wave propagation and reflection. If you are trying to get UHF frequencies from a single distant tower, a \"beam\" design will still be your best bet. VHF antennas were essentially a beam design. Reflection was a major issue with VHF frequencies. Al loop antenna on UHF is much more forgiving regarding positioning. ",
"A bowtie reflector can also be very effective at longer range UHF reception but they are also pretty directional.",
"https://www.solidsignal.com/xtreme-signal-8-bay-bowtie-outdoor-hdtv-antenna-65-mile-vhf-uhf-hdb8x?utm_source=google&utm_medium=cse&utm_term=HDB8X&gclid=EAIaIQobChMI88Pi9dSE9gIVn8mUCR0XKgu-EAYYAiABEgJ4zPD_BwE",
"This is an example of a multi bowtie reflector, for when you are a long distance from transmitters that are not close to the same direction from the receiver."
] |
[
"Is washing your hands with warm water really better than with cold water?"
] |
[
false
] |
I get that boiling water will kill plenty of germs, but I’m not sold on warm water. What’s the deal?
|
[
"In a ",
"2005 report in the Journal of Occupational and Environmental Medicine",
", scientists with the Joint Bank Group/Fund Health Services Department pointed out that in studies in which subjects had their hands contaminated, and then were instructed to wash and rinse with soap for 25 seconds using water with temperatures ranging from 40 degrees Fahrenheit to 120 degrees, the various temperatures had “no effect on transient or resident bacterial reduction.”",
"They found no evidence that hot water had any benefit, and noted that it might increase the “irritant capacity” of some soaps, causing contact dermatitis. “Temperature of water used for hand washing should not be guided by antibacterial effects but comfort,” they wrote, “which is in the tepid to warm temperature range. The usage of tepid water instead of hot water also has economic benefits.",
"TL;DR: Hot water for hand washing has not been proved to remove germs better than cold water."
] |
[
"Warmer water is better at breaking-down the dirt or grease on your skin, but isn’t shown to have any effect on the bacteria. The quality of the soap and the hand-washing technique are themselves the biggest contributing factors."
] |
[
"If removing caustic chemicals, however most substances exhibit greater solubility in water with higher temperatures , thus removing greasy residue better with soap."
] |
[
"is there a limit on how far back in time we can see with a telescope?"
] |
[
false
] |
I've heard about how the JWST allows us to see things that happened close to the start of the universe. I sort of understand how this works, but I was wondering if there is any sort of theoretical limit on how long ago something could have happened that we could see with the telescope? Are there things that are just gone from our ability to observe, or will we be able to see further back by looking in the right places with more and more powerful telescopes?
|
[
"There is a limit. As the early universe was opaque, ",
"we can't see past a redshift of ~1100",
"."
] |
[
"As further context, JWST won't see anything farther than redshift ~10 because that's when the first galaxies formed. If you want to look farther than that, you need to be searching for the kind of light that was produced or scattered at earlier times, which includes radio waves (from the 21-cm atomic transition of neutral hydrogen) or microwave radiation (from the cosmic microwave background)."
] |
[
"There is essentially no light at infrared or shorter wavelengths that was sourced much earlier than 13 billion years ago, because such light is produced inside galaxies. At earlier times, there were no galaxies.",
"The time period between last scattering (at an age of about 350 thousand years) and the formation of the first galaxies (at an age of about 500 million years, but this is pretty uncertain) is called the \"dark ages\". There was a lot of hydrogen, so efforts to study this epoch basically amount to using radio telescopes to look for ",
"a hydrogen spectral emission line",
".",
"Edit: was careless with my numbers, fixed"
] |
[
"Does having exercised in early life have an effect on losing weight later on?"
] |
[
false
] |
Suppose there are two people at an equal level of fitness, but one has never done sports and the other has had lots of exercise in his youth. Does the person with experience in sports get fit faster?
|
[
"This is wrong. Your muscles contain no memory at all and that is just marketing/laymans terms of something already completely understood.",
"Muscle memory is attributed to the strengthening of neural pathways in the brain that govern the exercise youre doing. Do it often enough, and you brain has to spend less and less resources \"activating\" this pathway as it fines tunes out \"errors\" associated with the task.",
"The easiest way to understand this is thinking about kicking a ball. There are hundreds of different ways to hold the ball with your hand, kick it with your foot. Any combination of these actions uses different muscles each time and the muscles dont coordinate themselves, the brain does."
] |
[
"To answer your question OP, yes the person who has done physical activity in their youth will have a slight advantage, why? Because their brain has to spend less time forming new pathways, essentially increasing their efficiency (gains from the workout) from the start.",
"Someone who has never worked out before will have to learn to coordinate their bodies consciously to effectively do a compound movement such as benching or deadlifting. This is called learning form and is an essential part to any physical activity, learning how to maximise your output from a set input. A person who has done physical activity before will have to spend less time maximising their efficiency as their brain already has the pathways, it just has to learn to refind them again.",
"Edit: This is all assuming these two individuals are starting from scratch after a hiatus. If these two individuals have already been working out for a substantial amount of time, then no, their previous experiences have no effect."
] |
[
"Thank you for the correction. "
] |
[
"Can you have a coefficient of friction greater than 1?"
] |
[
false
] |
My physics teacher said it does exist but I just cannot wrap my head around it. Wouldn't that mean the frictional force is greater than the applied force (assuming its on a flat surface)? So when you push it it would move toward you? I just need some help understanding this.
|
[
"Yes, it is possible for a coefficient of friction to be greater than 1. One particular example is rubber on rubber, which, according to ",
"this",
", has a static coefficient of friction of 1.16.",
"The idea behind static friction is that in order to get an object moving, the force ",
" that you exert on it must be at least ",
" times the normal force, assuming that the direction of the force is parallel to the surface the object is resting on. A coefficient of friction greater than 1 just means that the amount of force you need is greater in magnitude than the force of gravity pressing the object against the surface."
] |
[
"It can be greater than 1. The thing you misunderstand here is that the coefficient of friction is the ratio of the NORMAL force (or in the simplest case, weight) to the frictional force. For example, say a box sitting on the ground is pushed at a constant speed, and that the coefficient of friction is 1. In this case, the force required to push it is equal to its weight. Now let's say you put sand paper on the bottom and the coefficient changes to 2. It would then be twice as hard to push it as it would be to lift it.",
"Here, have a link to my favorite physics site: ",
"http://hyperphysics.phy-astr.gsu.edu/hbase/frict.html#coe"
] |
[
"Thanks! My teach failed to mention that it mean less than or equal! It all makes sense now."
] |
[
"Why is consuming cow milk more popular than milk from other animals?"
] |
[
false
] | null |
[
"Several reasons. ",
"One is that there is a very limited range of animals that produce milk of a texture and flavor that is widely appealing. A lot of animals have thick or strongly flavored milk, but cows milk has a similar fat content to human milk (whole milk is around 4% fat) so it seems \"right\" to us.",
"Generally humans only like milk from grazers. These animals turn a plentiful inedible resource (grass and scrub) into an edible resource (milk), have nice-sized nipples for milking, tend to be relatively docile, and generally have mild flavored milk (grass doesn't impart any strong or gross flavors on milk).",
"Another reason is simply that cows are highly productive compared to other animals. You can get a lot of milk from a cow. ",
"Sheep milk is too fatty to drink straight, and goats milk is quite strong (they eat all sorts of plants that nobody else will) and can't easily be made into butter (it doesn't separate well). Cows were the critters we brought with us in our travels. Once they became established, people developed a preference for cows milk over the small handful of alternatives. "
] |
[
"In theory probably yes. It wouldn't taste exactly like cows milk, but it would not have the same bitter compounds from all the weird things goats eat. ",
"In practice, good luck stopping goats from eating everything in sight."
] |
[
"Does this mean then that, if you had goats that only grazed on grass, you would end up with a milder goats milk compared to how it typically tastes?"
] |
[
"Has the earth's gravity increased in any significant manner since the emergence of life?"
] |
[
false
] |
I've always assumed that the earth's mass (and by extension gravity) has remained fairly stable through out its history. But I realised maybe I'm wrong, the earth is constantly catching space rocks which could've added mass to the earth, also the earth's rotation is slowing down so surely that'd increase the gravity at the equator.
|
[
"The short answer is no, there has been no substantial change. The mass of the earth is on the order of 10",
" kg, so for even a 1% change in gravitation potential you would need a change in the mass on the order of 10",
" kg, which is a ",
" amount of matter and far more (in my estimation) than catching space debris could produce.",
"About the slowing of the earth's rotation, that might technically affect gravitational forces at the equator (or, more precisely, net acceleration at the equator), but this effect is negligible compared to the acceleration due to gravity. Thus a change in the earth's rotation rate wouldn't produce a noticeable change in the weight of a given mass at the equator."
] |
[
"If I remember correctly, in our solar system only the largest gaseous giants actually radiate more energy than they receive from the sun, so that effect wouldn't be a likely mechanism for mass loss on the earth. Even if it were however, tiny amounts of mass convert to huge amounts of energy, so converting the energy lost by radiation into a mass via E=mc",
" would probably give you a negligible change in mass anyway."
] |
[
"The Earth loses about 3 kg of atmosphere a second, or about 31,000 tons a year. ",
"http://www.reddit.com/r/AskReddit/comments/150srk/is_any_matter_from_our_atmosphere_gases_for/",
"It gains about 40,000 tons a year from space dust and meteorites. ",
"http://www.bbc.co.uk/news/magazine-16787636",
"In terms of how the Earth's acceleration due to gravity and centripetal force, you may find the following interesting. Keep in mind that the Earth spun faster in the past as the tides are slowing it's rotation down. ",
"http://en.wikipedia.org/wiki/Gravity_of_Earth",
" ",
"http://www.bbc.co.uk/news/magazine-16787636"
] |
[
"Why does most trees have dark bark, but trees like Birch have \"white\" bark? What's the benefit for the Birch tree? Does it effect the tree differently?"
] |
[
false
] | null |
[
"In Aspens the bark is white because it has chloroplasts embedded in it (sometimes you can see a green or brownish tinge if you look at it up close), and photosynthesis occurs in the bark during winter, helping it survive. In most trees the outer layer of bark is dead tissue called rhytidome which helps protects the trees from herbivorous animals, but is less suitable for gas exchange, and allowing in light.",
"source: Berveiller, D. & Damesin, D. Interspecific variability of stem photosynthesis among tree species. Tree Physiology 27, 53-61 (2007)"
] |
[
"In birch (not aspens) the bark is flaky and constantly shed. Combined with potent chemical defenses, this makes it very difficult for insects and rot to attack the tree.",
"It is ",
"speculated",
" that the white color and insulation help keep trees from warming up in the winter. Freezing and staying frozen is better than freezing and thawing repeatedly."
] |
[
"Wow. Is that why birch bark is a good fire starter?"
] |
[
"Does it take more energy for an mp3 player to play music at a loud volume, or is the volume independent of battery life?"
] |
[
false
] | null |
[
"It does draw more power to have higher volume - there is a relationship between sound intensity and energy. However, things like the LCD screen on the device draw so much more power that the difference should be negligible."
] |
[
"Louder draws more power, however when you're talking something just powering earbuds I'd be surprised if it had a measurable difference (Think of the energy require to make the thudding bass in a car, for example. This is why they have multiple amplifiers)"
] |
[
"Yes, they will use more power driving the speakers in your headphones if turned up. The output is pretty small though. I think w're talking about anywhere between 1 and 10mw. I think your typical mp3 decoder is going to use around 40-100mw of power and you're also looking at the display driver, storage system (lots of power if its a physical hard drive not flash), non-decoding CPU, etc. I'd think that the % of power used by the headphone amp is a very, very small percentage of system power. Maybe so little as to be negligible. "
] |
[
"What's the margin of error for atomic clocks?"
] |
[
false
] | null |
[
"The ",
"NIST-F1 caesium clock",
" is accurate to 1.5e-15 (1 second in 20 million years). Recently, a German group built a clock based on Ytterbium transitions which ",
"is accurate to 3.2e-18",
", or about 1 second in 10 billion years! "
] |
[
"How is the accuracy measured? "
] |
[
"That's a question which is very specific to the implementation. Uncertainties from different sources can be added/multiplied/exponentiated/etc in ",
"well-defined mathematical ways",
". The final uncertainty value for an experiment like this (and in fact, most reported uncertainties in science) is a combination of uncertainties from various aspects of the experiment (for example, in the PRL paper, ion temperature uncertainties, quantum projection noise, timing uncertainties for the free evolution period, etc.) If you're curious about this specific experiment, it's described in pages 2-4 of the paper, which is mirrored on ",
"arXiv",
"."
] |
[
"Earthquakes and Tsunami's speeding up or slowing down time?"
] |
[
false
] |
I was in my stellar galactic astronomy class today and my professor asked me a puzzling question. He had recently attended a meeting of sorts on the recent disasters in Japan. One of his colleagues had made a comment about how the earthquakes made the day shorter by a microscopic amount and would then in turn make her age faster. His question was as follows: If the earthquakes did shorten the day would it make a person younger, older, or equal out. In other words would the day being shorter have any visible effect whatsoever or would the shift be so minimal there would be nothing to observe. I hope I was clear enough. If not I will attempt to elaborate. I am new to actually posting on reddit. So I am not sure whether or not I have to designate this post to a physics or astronomy section. I am in every sense of the word, a newbie. I appreciate you all for taking the time to consider this question.
|
[
"I can say with confidence that the earthquake did not speed up or slow down time.",
"Technically there would be an imperceptibly small time dilation, since it changed the speed of rotation of earth (and thus the people on it)."
] |
[
"This question has a few implications. I'll do my best to address them.",
"1) The Earth circles the sun in 365.24 days. If the day were shortened, that would mean that there would suddenly be more days in the year because a revolution still takes a fixed amount of time.\n2) if you live a fixed amount of time, say 77 years exactly, and the day is shortened by a small amount, you should experience more days of life, but the same amount of time... except...\n3) Circadian rhythms don't change too much. Your own biology ",
" shorten your life to a fixed number of days, but this seems very unlikely.",
"TL;DR: You will live the exact same number of years, but experience more days."
] |
[
"http://www.space.com/11115-japan-earthquake-shortened-earth-days.html",
" it is estimated that 1.6 microseconds were taken from each day, due to the shift in earth’s orbit/mass distrubution. For somebody on the planet this change would go unseen. For satellites and GPS timings this may be more important (not a physicist)."
] |
[
"Biology: My question is about deep ocean ecology. Are there places in the deep ocean that humans can't submerge into?"
] |
[
false
] |
I remember watching a documentary where an exploration team was unable to pass through a certain area of the ocean. It looked like an ocean within the ocean. So my question is what are these places and does anyone know what documentary that was? Cheers!
|
[
"My guess is you saw something like ",
"this",
", where salt water and fresh water meet but don't mix underwater.",
"The reason divers avoid entering the more dense salt water that makes the \"rivers\" is because they have to carefully calculate ",
"their buoyancy",
" to set up their gear (mainly their weights).",
"Physically it's probably possible to enter water like that, but it would take very careful preperation and support."
] |
[
"Wow! Yeah it looked similar to this! The only difference was that it was in the ocean. I'm sure though something similar to this occurs in the ocean. Thanks for answering! "
] |
[
"The same sort of thing... \"rivers\" of denser water... does ",
"happen in the ocean",
", but there it's caused by vast temperature differences that haven't equalized yet, as ocean currents mix colder and warmer waters together. So that might have been it."
] |
[
"When you drink cold water, heat from the body is transferred to warm the water to your core temperature. So, how much 32 degrees F water do I have to drink throughout the day to burn, say 500 calories?"
] |
[
false
] | null |
[
"One calorie raises the temperature of one gram of water by one K. So, each gram of 0°C water would take 37 cal to heat up. 500/37 gives 13,5 g. ",
"Now, keep in mind that what is colloquially called \"calorie\" when it comes to food is actually a kilocalorie. Carbohydrates yield roughly 4 kcal/g. So, to compensate the body temperature loss from ingesting 13,5 g of freezing water, you would need 0,125 g of sugar.",
"This is not going to work out as a diet..."
] |
[
"I would like to point out that the kilocalorie type of Calorie is always capitalized to differentiate it from actual calories."
] |
[
"Thanks for the info - I am not a native english speaker, so that one was new to me. "
] |
[
"When you have mono-zygotic twins, are the chromosomes from one or both parents coded to replicate prior to conception? Basically, is there anything that signals the zygote to split, surely there should be 46 chromosomes for both fetuses?"
] |
[
false
] |
[deleted]
|
[
"No. The zygote divides into 2 then 4 cells and so on. Eventually, the cells will start to differentiate, but if the zygote separates into two at this very early stage, each one just goes 'huh', and develops into a new individual. Nothing amazing needs to occur - just that physical split. "
] |
[
"Exactly. ",
" cell in your body (barring mistakes) has all 46 chromosomes. A developing embryo is no different. As a zygote begins to become an embryo, it divides many times, replicating its chromosomes for each division. The only difference for identical twins is that the early embryo breaks in two parts, which then each become an individual."
] |
[
"I was thinking more along the lines of DNA. Basically, do people that have mono-zygotic twins on the DNA level does something say (loosely speaking) \"hey we need double everything b/c we are going to split\" or does the splitting just happen, like \"oh shit, replicate\"? What I am trying to get at how do the gametes know there will be twins."
] |
[
"I saw massive spider web \"structures\". Does anyone know why they would do this?"
] |
[
false
] |
[deleted]
|
[
"Did you actually see any spiders? It's far more likely that this was the work of some species of caterpillar. Here in Maine they are an invasive species and will cover tons of trees and bushes, killing them, as well as being highly allergenic due to their little spines that come off regularly."
] |
[
"Although most social spider colonies remain relatively small, they will sometimes form massive webs like this. The answer to the evolutionary \"why\" question is that larger groups are more effective and efficient at capturing large prey than a single individual (see ",
"this article",
"). A web of this size may be prompted by favorable weather and prey conditions, but is probably not sustainable. The aforementioned web in Texas in 2007 was formed by a large group of social spiders."
] |
[
"On the east coast a number of years back we had a problem with some sort of caterpillar. They left giant white constructions on every tree you could find. Maybe that's what you're thinking of? I think they called it a gypsy moth."
] |
[
"What happens to fat cells as fat is metabolized?"
] |
[
false
] |
Is fat metabolism basically just a point in time process, or does it kick off a process of longer changes to the fat cells? What is that process and how long does it take? This question comes from a thought I had on a 6 hour bike ride yesterday.
|
[
"The fat cells (adipocytes) undergo very little changes when fat is used in metabolism, other than decreasing in volume. DNA modifications such as methylation/demethylation and histone remodeling may be long-term effects of fat loss by adipocytes, but this is unclear at this time.",
"A skinny person and a fat person have the same number of adipocytes. They are like trash bags; when empty they are flat and take up little space, but they have enormous storage capacity. When a person loses fat, the triacylglycerides (TAGs), or fat molecules, are clipped into 2-carbon pieces which then are used in the citric acid cycle (Kreb's). Fat is eventually breathed out as CO2. The adipocyte trash bags are emptied and thus take up less volume."
] |
[
"So if someone were to have liposuction and reduced the number of fat cells in the body what is the effect on the number of adipocytes long term? Does this have a lasting effect on how fat the person can get from that point on? I'm genuinely curious, not asking for a recommendation on surgery."
] |
[
"No, not to any real extent. Adipocytes are basically cell membranes, with a smushed nucleus to one side, and the rest of the cytoplasmic space is filled with fat molecules. ",
"Here",
" is a light microscope pictures of adipocytes stained with hematoxylin and eosin stain, which stains DNA. ",
"Some transciption and metabolism is happening inside the adipocytes, but they [do not typically divide when full](Lefterova, MI et al. (2009) New developments in adipogenesis. Trends in Endocrinology and Metabolism 20:107-114]).",
"edit: can't fix link format"
] |
[
"How do satellites in space protect their electronics from all the different types of Electromagnetic waves they are exposed to?"
] |
[
false
] |
[deleted]
|
[
"They are made inside metal enclosures, so they do have some inherent protection as the body of the satellite itself provides some protection. That being said, they are still vulnerable to em interference. During solar storms they can be disrupted or even destroyed. Another example of a satellite being destroyed by electromagnetic pulse is the time the United States nuked the first British satellite*.",
"*Source: ",
"https://www.google.com/amp/s/www.wearethemighty.com/articles/britain-nuke-satellite/amp"
] |
[
"One of the biggest sources of damage to satellites is electrostatic discharges. Not direct EM waves. The solar wind, protons and electrons, causes charges to build up on insulation surfaces. The potential builds up until it arcs over surfaces or even out to free space. This causes high surge currents in the satellite wiring. With nanosecond rise times. Damaging electronics. There are multiple ways they try to address this. "
] |
[
"With difficulty. ",
"Usually the electronics are in a sealed metal box. ",
"But then you have to still deal with rejecting unwanted signals on any connections into the box.",
"And, if you are a a responsible space citizen, you do your utmost to prevent to you box of tricks radiating unwanted EMI."
] |
[
"What happens when a newer fossil of unknown species is found in an older rock strata?"
] |
[
false
] |
Lets say a new cretaceous dinosaur species is living near the bank of a river, The river is continuously eroding the rock on which the cretaceous dinosaur stands on exposing triassic rocks, the cretaceous dinosaur dies near the exposed triassic rocks and gets buried and fossilized. We humans then find this fossil of new cretaceous dinosaur along with the triassic rocks and triassic fossils, So how do we avoid not misjudging that the Dinosaur is triassic or the Sedimentary rocks surrounding it are Cretaceous? Other than absolute dating methods.
|
[
"In this scenario, the remains of the Cretaceous dinosaur, if it was preserved as a fossil, would be within Cretaceous rocks sitting unconformably on top of Triassic rocks, i.e., the \"gets buried and fossilized\" part implies that the sediment burying the dinosaur is Cretaceous in age. So the fossil would not be \"along with Triassic rocks\", but rather directly above Triassic rocks and perhaps with clasts of Triassic rocks within the basal layer of the Cretaceous rock, i.e., you've basically described a textbook ",
"disconformity",
".",
"In detail, recognizing that the rocks hosting the dinosaur are Cretaceous and not Triassic (and restricting ourselves to things other than absolute dating as you mention, as this would be a clear way of assessing this assuming there was material amenable to these methods), would rely on additional context. In terms of the biostratigraphy, Triassic fossils (that had weathered out and been deposited in the Cretaceous) would be recognizable as such and distinguishable from Cretaceous fossils in a few ways; 1) they would not be in \"life position\" as they had obviously at least been eroded and likely transported from their original position, 2) they might be encased in a clast of rock within the larger deposit, or 3) they would show signs of being transported significant distance (i.e., they would have different ",
"taphonomic",
" characteristics than Cretaceous fossils within the Cretaceous rock, which may have also been transported, but only once). Presumably also within the Cretaceous rocks, even if the dinosaur itself is a new, previously unrecognized species, it would be fossilized with other known Cretaceous organisms (and especially microflora and fauna, like fossil pollen, i.e., it's exceedingly unlikely that if the conditions were favorable for fossilization, you would only end up with one single organism fossilized) that would indicate that the host sediments were deposited during the Cretaceous, not the Triassic. ",
"In addition to biostratigraphic observations, there would likely be sedimentological indications of an erosional unconformity, like the possible clasts of Triassic rocks within the basal layer of the Cretaceous rocks, but also \"topography\" on the contact, i.e., preserved channel cuts, etc given the description of the environment. Even if we assume that the source for the Cretaceous sediment is exclusively Triassic sedimentary rock, an additional cycle of weathering, erosion, transport, and deposition, would likely change the sedimentological character (e.g., grain size, mineralogy, sorting, etc) such that the Triassic and Cretaceous sediments (and later rocks) might look relatively distinct. Essentially, all of the above is a large part of learning to do geology in the field, i.e., becoming attuned to the clues that rock A and rock B might be a different age and separated by a contact based on a variety of (mostly) field observations. ",
"A final point might be, but definitely expanding into areas I'm less familiar with as primarily a geologist as opposed to a verterbate paleobiologist, is that the difference between Triassic dinosaurs and Cretaceous dinosaurs is relatively large given the amount of geologic time (i.e., we've skipped the entire Jurassic, a period of ~55 million years, to say nothing of where in either the Triassic or Cretaceous are juxtaposed across this unconformity, i.e., a lot of evolution happens in that amount of time), so even without all of the above, someone who specializes in dinosaurs and knows the history of the development of different features, etc, would likely be able to quickly hypothesize that the Cretaceous dinosaur was not Triassic in age, and specifically younger. A panelist more in the paleobiology side of things like ",
"u/StringOfLights",
" might be able to more fully comment on that aspect of the question."
] |
[
"Thank you so much for the extremely detailed answer. It answered my question in both practical sense and also in the sense that my curiosity wanted it to be answered in.",
"I would like to let you know that you are sort of a celebrity among my 5 close friends here in India who also study Geology with me for being the person who always answers questions very precisely on the ",
"r/askscience",
" 's Earth science related question. Thank you so much for doing what you do! It is always and will always be appreciated. 🙏🏻"
] |
[
"As Crustal says, you don't really get fossils incorporated into ",
" rocks, because for various reasons you can see the difference between the new rock layer with the fossil and the older rock layer beneath it.",
"What ",
" sometimes happen, though, is a fossil incorporated into a newer rock strata. Imagine your scenario, but instead the dinosaur dies and gets buried in a cretaceous strata, and then a few million years pass and the rock erodes during the Paleocene. The dinosaur fossil tumbles out and gets buried in some sand which then becomes a Paleocene rock layer. It's actually ",
" a Paleocene layer and a part of it, unlike the case where it's simply lying on top of a Triassic layer. These are called remanié fossils and can be tricky to identify...although sometimes it's obvious that they were fossilized in a different sort of rock than they are found in."
] |
[
"If a particle needs to be massless to travel at the speed of light, does that mean that tachyons need to have negative mass?"
] |
[
false
] | null |
[
"Damn you, Rene Descartes, and your condescending terminology!",
"For real though, ",
"/u/tanzmeister",
", famous French mathematician Decartes essentially had the same this-is-nonsense notion as you for these complex numbers and started snidely calling them \"imaginary\" numbers, and the name stuck. It's a bit of a shame we haven't tailored our terminology over the years."
] |
[
"Damn you, Rene Descartes, and your condescending terminology!",
"For real though, ",
"/u/tanzmeister",
", famous French mathematician Decartes essentially had the same this-is-nonsense notion as you for these complex numbers and started snidely calling them \"imaginary\" numbers, and the name stuck. It's a bit of a shame we haven't tailored our terminology over the years."
] |
[
"Damn you, Rene Descartes, and your condescending terminology!",
"For real though, ",
"/u/tanzmeister",
", famous French mathematician Decartes essentially had the same this-is-nonsense notion as you for these complex numbers and started snidely calling them \"imaginary\" numbers, and the name stuck. It's a bit of a shame we haven't tailored our terminology over the years."
] |
[
"Can you ferment avocados?"
] |
[
false
] |
Can you ferment avocados and make an alcoholic beverage from them? Would it taste good enough to drink?
|
[
"Found ",
"this",
" for ya, hope it helps?"
] |
[
"It looks like a ",
"few",
" different ",
"homebrewers",
" have at least attempted to make beer with avocados. They both posted a while ago; you could try and contact them to see if they had any luck. Aside the relatively large amount of oils, an avocado wouldn't be too much different from any other fruit that is added to beer all the time."
] |
[
"It's the fat and oil that makes it not very feasible as a fermentable fruit. The yeast won't metabolize fat, so it would sit there on top starving anything of oxygen."
] |
[
"Why do you see countershading in some land mammals, when it seems to serve no purpose?"
] |
[
false
] |
I get why there is countershading in sea animals, the light color blending in with the lighter water above; the dark color with the darker water below. Why though, do so many land mammals have white bellies? Is this perhaps an evolutionary remnant? You see it with all sorts of land animals, but not all either. Horses for example do not, rabbits and deer do. So why do some land animals have white bellies and others don't? EDIT: The animals selected were the first I could think of, and not the only ones in question. TLDR: Great article posted by fellow redditor: ( ) which provides some cool data on the topic.
|
[
"Countershading can still serve a purpose on land just like in the sea or air. It's not quite as effective, but it still helps to break the outline, which is the most important part of camouflage."
] |
[
"I expect it's an energy saving response. The belly of some animals will be white, and therefore unpigmented because, not only is it rarely seen (i.e rodents, mustelids etc.), it is rarely in contact with the sun.",
"How is light-colored belly fur an energy-saving response?",
"If it's an energy-saving response, then all animals should have light-colored bellies, not just deer, rabbits, and field mice. ",
"Among mustelids, the long-tailed weasel only has a light-colored belly in summer coat, and the wolverine has, not a light-colored belly, but light-colored lateral stripes.",
"Among rodents, neither the Norway rat nor the black rat have light-colored bellies.",
"Moose do not have light-colored bellies. Neither do elk, who actually are light on top and darker underneath."
] |
[
"I expect it's an energy saving response. The belly of some animals will be white, and therefore unpigmented because, not only is it rarely seen (i.e rodents, mustelids etc.), it is rarely in contact with the sun.",
"How is light-colored belly fur an energy-saving response?",
"If it's an energy-saving response, then all animals should have light-colored bellies, not just deer, rabbits, and field mice. ",
"Among mustelids, the long-tailed weasel only has a light-colored belly in summer coat, and the wolverine has, not a light-colored belly, but light-colored lateral stripes.",
"Among rodents, neither the Norway rat nor the black rat have light-colored bellies.",
"Moose do not have light-colored bellies. Neither do elk, who actually are light on top and darker underneath."
] |
[
"What is physically changing in my computer when I overclock my CPU?"
] |
[
false
] |
I can vaguely picture information being stored in ram, and how different states in a semiconductor move information through logic gates... But when I change the clock speed on my CPU, what is actually happening? I know digital watches have a quartz crystal in them that vibrates at a very specific frequency.... But how is that modulated, and what is actually physically controlling my CPUs clock speed?
|
[
"There are frequency divider circuits using something called a T flip-flop, which toggles whenever the clock goes high. ",
"More complicated than that. Only the early processors divided the Crystal. Like dividing 4 MHz to 1 Mhz. But in today's world of gigahertz clocks, where there are no GHz crystals, They take a low frequency crystal of usually 33 or 66 Mhz and use an internal ",
"phase lock loop circuit",
" to multiply it up to the multi GHz range. So overclocking is just a matter of reprogramming the divide by N part of the PLL to get higher clock frequencies."
] |
[
"The crystal always oscillates at the same frequency like you said. There are frequency divider circuits using something called a T flip-flop, which toggles whenever the clock goes high. ",
"If you put one T flip-flop behind another one, you get something that toggles every other clock cycle. Through careful combination of these, you can multiply and divide the output clock as much as you want. "
] |
[
"To add to that, something I didn’t understand about PLLs when I first heard about them is they use a voltage controlled oscillator to increase the clock frequency. So one might use a 10MHz clock to adjust a VCO to 100MHz by dividing the VCO by 10, and comparing the frequencies of the two clocks. Then you go on and use the 100MHz clock to drive your logic. "
] |
[
"Does radio sound have a 'quality'?"
] |
[
false
] |
We're used to MP3's being in 320kbps or 128kbps. Analagous to that, does broadcasted radio sound have a quality?
|
[
"Yes.\nFor an analogue wave transmission you have bandwidth and signal-to-noise ratio. Bandwidth in analog signals is similar to sampling frequency of a digital sound. For example, FM channels have allocated bandwidth of 200 KHz, which is plenty to fit a 20 KHz sound wave. That's also why you are able to transmit stereo FM sounds. Though, 200 KHz bandwidth is also made that big to minimise cross-talk between neighboring stations.",
"Signal to noise ratio is more like the audio bit depth. Higher S/N values mean that sound wave gets way above noise floor, which makes it sound better. ",
"Keep in mind that the comparisons above aren't direct divisions of each other and I just used them as an example since you seem to be a birr more familiar with digital audio encodings."
] |
[
"If it deviates more than +/- 75kHz it is exceeds FCC limits. Analog TV was +/- 25kHz. "
] |
[
"I think you mean bitdepth as the analogous digital counter part the SNR. Bitrate is a depends on both the sampling frequency and bitdepth. ",
"Given he knows mp3 files quality by bitrate, I guess it would be good to note how those make up bitrate. Sampling frequency is how many times each second the sound is measured, bitdepth is how many bits are used to give a value to this measurement. So say you sample at 44 kHz with 16-bit depth (near enough what a CD is), you'd get a bitrate of 688 kb/s. Obviously higher than even high quality 320 kb/s mp3, but mp3 are a compressed audio file. Bitrate of a compressed file is partly indicative sampling frequency and bitdepth of the original uncompressed, but that's usually the same for two different mp3s and the bitrate is determined by how much compression was done, which doesn't really have an analog counterpart. ",
"Also, for FM radio I'm pretty sure they are usually 500 kHz bandwidth or more for stations. Frequency modulation is very bandwidth inefficient. Even though the stereo audio signal may only be 40 kHz (actually think it ~50 kHz for stereo FM radio), the bandwidth usage is technically infinite. In practise the far away frequencies make little impact, so we can lose them and cut it to some bandwidth and still get the original sound more or less. Though the bandwidth is still much larger than the audio signal. The bandwidth by Carson's rule is 2 (75 kHz + 50 kHz) = 250 kHz, where 75 kHz is the frequency deviation of the FM. That's more than this 200 kHz bandwidth you are stating. "
] |
[
"When I breathe casually, why does my stomach move in and out. But when I breathe deeply my chest expands?"
] |
[
false
] |
[deleted]
|
[
"When you inhale normally, your diaphragm drops displacing the contents of the abdominal cavity. When you do a forced inhalation, you utilize your external intercostals and other accessory muscles, allowing for further expansion of your chest cavity until your inspiratory reserve capacity. "
] |
[
"My fault, continue posting identical answers. I guess we don't capitalize here either, as long as we are telling others what to do. "
] |
[
"My fault, continue posting identical answers. I guess we don't capitalize here either, as long as we are telling others what to do. "
] |
[
"Why are there tigers in Primorye and historically throughout Siberia, but none in the similar ecosystem of Alaska?"
] |
[
false
] |
Was there something that prevented the migration of Siberian tigers across the land bridge between Asia and the New World?
|
[
"But Beringia may have been reasonably temperate and populated by big mammals. I don't think climate should be considered the main factor. \nSource: ",
"http://www.beringia.com/research/beringia_flora.html"
] |
[
"There were a number of large cats that formerly inhabited North America, such as the American Lion: ",
"http://en.wikipedia.org/wiki/American_lion",
" And the Saber-toothed cat: ",
"http://en.wikipedia.org/wiki/Saber-toothed_cat",
"The only species to survive in North America into modern times is the Cougar. ",
"http://en.wikipedia.org/wiki/Cougar"
] |
[
"Thank you for the response. I was aware of the fact that The Americas were inhabited by large cats in prehistoric times. My question is, \"why did they survive in Asia and not in the New World?\""
] |
[
"Why do dogs like to lick my face and hands?"
] |
[
false
] |
Is this common to any other animals besides dogs? Is it a socio-behavioral thing? Do they expect something particular in return? These are just a few general question I was curious about.
|
[
"There are a number of reasons dogs lick. ",
"That is how the mother communicates with her puppies, how she gets them to start breathing and how she cleans them when they are born. You’ll find the puppies (both feral and domestic) will lick around the mother’s mouth...this is just instinct.",
"It’s also sort of a submissive gesture — the more subordinate members of a pack will lick the more dominant members as recognition which promotes peace.",
"Dogs also lick because they like the taste of an owner’s salty skin. ",
"Dogs use licking to explore their environment. ",
"Mostly, with domestic dogs, it's a sign of affection. It's their way of interacting with you whether it be a way to get your attention or share in your emotional state. You have to be careful with encouraging this type of licking. Allowing it too much can lead to compulsive licking which is not so good. You may have to train them out of this.",
"If licking is a chronic problem you can play tricks to get them to stop over time like ignoring it or just leaving the room when he starts.",
"This type of thing happens in most of the other animals of the canidae family. I don't really know about animals outside that tree."
] |
[
"Ugh. My 1.5 year old dog is a compulsive licker. Terribly difficult to train out of. "
] |
[
"Long and preachy, but this is the trainer coming out so bear with me. ",
"It takes discipline on your part, and even then it is indeed very hard to train since it's something that is rooted in their instinctual habits. ",
"For chewers there is this bitter apple spray that you can get at pet stores which makes it taste terrible but most likely you don't want to spray that on yourself. ",
"The best thing you can do is engage in both positive and negative responses. If you get up and leave the room every time they lick this would constitute the negative response. A good rule is that it take 5,000 repetitions for them to train out of the habit but since it's instinctual it may take more. ",
"The positive responses take more work but IMHO is much more effective and satisfying. Dogs are social and want to be part of your life so I feel negative responses are alienating to them which you should strive to avoid. A couple things to try:",
"Just remember he wants to make you happy. It's up to you to teach him how to do that."
] |
[
"I'm new to the idea of emergence..."
] |
[
false
] |
So I'm new to the topic of emergence and I'm looking for the scientific perspective of it. I recently came across the idea that if a phenomenon is 'emergent' from other phenomena that it supervenes upon - such as laws of social systems emerging from the laws of physics - that it isn't possible to describe the higher phenomena in terms of the lower. IOW it's meaningless to talk about the laws of economics in terms of the laws of physics. TL;DR Is it possible, even if only theoretically, to describe the complexities of, say, two governments interacting in terms of subatomic particles and their interactions?
|
[
"I think a better term is \"derivative reality.\" (imo) We know the vast majority of day-to-day physics really well. Does that mean we can solve quantum mechanics ",
" for the interaction between two atoms to make a molecule? No. So we make some assumptions for some simple systems, and maybe we can do those... but usually the next step is to make a large body of assumptions about binding energies and orbital shapes and call this body of assumptions \"Chemistry.\" It makes the problem easier and allows us to answer many questions with enough precision to be useful. ",
"Chemists in turn, specifically biochemists, may be looking at specific molecules within a cell, but rarely do they try to model the molecular interaction of every molecule in an entire body. So a ",
" set of assumptions are made regarding chemistry, and we call that biology. ",
"More assumptions about biology lead to a model of how the brain works (psychology), and assumptions about psychology give rise to sociology.....",
"So back to my original hypothesis. Derivative reality is a term describing a reality that is derived from another field. Almost always by making a lot of assumptions and simplifications from that more general field. Thus Biology is a derivative of Chemistry is a derivative of Physics is a derivative of Philosophy and Math. (though the last step may be contentious) But the point is that each is still valid, and we know we ",
" be able to explain it from the more general field but no one wants to invest the time in solving the horrendous transitions. So long as each field justifies it theory from data, they are a \"scientific\" one."
] |
[
"but it's not the electrons neutrons and protons that have color. It is the light they emit or reflect that does. And that light, in a way, doesn't care about the arrangement of those various particles. I mean, I understand what you're saying, but I'm trying to encourage the thought that you haven't really created something \"new\" just by arranging things in a certain way. ",
"Let's take a simpler example. A lone proton will (according to our best data) never decay. But put that proton in a nucleus with too many other protons, and it will. Is this an emergent phenomenon? I argue no: see the proton always has the capacity to decay, it's in the nature of the proton itself. The problem is that it is energetically unfavorable to do so. However, when you have the binding energy of the whole nucleus, it can become energetically favorable. No \"new\" physics happens. ",
"Furthermore, let's consider gold nanoparticles. They're reddish-purple when they're in solution. But stick enough of them together and they look... well... golden. What gives? In the first case, quantum mechanical effects are very large, so it changes what types of light the nanoparticles can absorb. In the second case the quantum mechanical effects that give rise to the red-purple particles are drowned-out by what we might consider \"classical\" mechanics. But classical mechanics isn't an emergent property of quantum mechanics, it's just a simplification. We see that the quantum-allowed energy levels become ",
" close together, that we just go ahead and allow electrons to occupy any energy in a given band. But it's only a simplification of a tremendously hard quantum mechanics problem. "
] |
[
"I think it's a concept that becomes quickly misappropriated. I mean, this is why I wanted to encourage you to think along these other lines. If I say that biology is somehow \"emergent\" from physics, that life is something that can't be quantified in terms of particles and forces, then people take this quickly to mean that there must be some sort of soul.",
"But when you reframe the transition and linkages between sciences as derivative reality, then you can see a bit more closely what is meant by the several sciences. Chemistry is the physics of electrons orbiting atoms, or as the kind of mediating particle of chemical bonds. Biology is the chemistry of ",
" complex chemical systems that tend to reproduce themselves.",
"But let's look historically for a moment too. Each of the several fields developed without knowing that these linkages would exist. Biologists believed in some \"living force\" that was present in living things and not inanimate objects. Chemists were studying the transition between several \"elements\" or compounds. Physics was largely about rolling balls down slopes. As each field learned more and more, we ",
" that each was a derivative reality of the ",
" more general. ",
"We could very easily imagine a sci-fi/fantasy universe where the stuff making up people was somehow ",
" different than the stuff making up animals, and all of that different than rocks. But we discovered that our universe ",
" this. (barring any future discovery for the moment) We discovered that chemistry can be described by a connection to a specific branch of physics. We discovered that biology can be described by a connection to a specific branch of chemistry. This leads me to strongly believe that there isn't any ",
" effect, merely specific instantiations of a more general theory, simplified to make the math go from entirely unreasonable to... usable. ",
" ambiguous language."
] |
[
"Is there a way to safely dispose of nuclear weapons?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):"
] |
[
"Can I ask how it is fundamentally flawed?"
] |
[
"and we can't destroy them. ",
"What makes you think that we can't disassemble them?",
"Why can't we dispose of them outside of earth's orbit?",
"We could, if we wanted to dispose of them, but that would not be cost-effective at all. They can just be disassembled on Earth.",
"Would they be able to survive leaving the atmosphere without detonating?",
"They have to, by design because ballistic missiles travel through space.",
"Even if they are stable enough to handle leaving earth's atmosphere - could we even detonate them in space?",
"They've been detonated in space, and you can find videos of it on YouTube.",
"Is cost even a factor at this point?",
"Yes."
] |
[
"Can we think of a Black Hole as just a really really dense planetary body?"
] |
[
false
] |
I read this and I think it helped explain black holes to me better than I ever understood them, but I want to make sure I have it right. A black Hole is just a body that is so dense that nothing can reach an escape velocity to leave the body. So any body with escape velocity greater than C would be a black hole (assuming that C is the maximum velocity of any object in the current universe). As the mass of the body increases the event horizon expands because the area in which the escape velocity is greater than C expands. At the middle of the black hole though there is still a tangible mass even if its a Million solar masses in a body the size of a basketball (not saying this is the accurate size), correct? Thanks for any answers
|
[
"A black Hole is just a body that is so dense that nothing can reach an escape velocity to leave the body. So any body with escape velocity greater than C would be a black hole (assuming that C is the maximum velocity of any object in the current universe). ",
"It's actually quite a bit more complicated than that. First, note that just having an escape velocity equal to the speed of light wouldn't prevent anything from escaping; objects can quite easily leave a planet without ever reaching escape velocity by providing a continuous thrust. A better characterization would be that the acceleration required to increase your distance from a black hole is infinite at the horizon. As for definitions, a black hole is a defined, roughly, as region of space such that any physically realizable path originating inside that region can never lead outside that region.",
"At the middle of the black hole though there is still a tangible mass even if its a Million solar masses in a body the size of a basketball (not saying this is the accurate size), correct?",
"Not according to the general theory of relativity. In relativity, the black hole \"mass\" is just a property of the spacetime; there's no \"object\" of ",
" size inside the black hole. For a collapsing star black hole, the collapsing mass passes through the event horizon and then ceases to exist upon reaching the singularity; an imprint of that matter's mass, charge, and angular momentum is left behind in the spacetime curvature, but the \"stuff\" is just gone.",
"Now, we have to mention that we know the general theory of relativity isn't the whole story. There is very good reason to believe that new physics takes over in the region around the singularity, and it's entirely possible that some as-of-yet unidentified effect prevents the formation of a singularity. Unfortunately, we lack proper models—and experimental and observational data to confirm them—to determine whether or not that's the case."
] |
[
"Newp.",
"It's not just the case that you can't escape a black hole once you cross the event horizon: it is impossible to do anything except fall inwards towards the central point. It is literally impossible for any force to hold you up. So all the mass just collapses into a single point."
] |
[
"Not really. A ",
"neutron star",
" is a very dense object, so dense that its gravity will bend light when you stand on it, allowing you to see way past the horizon. (And also be crushed to a horrible, horrible death.)",
"A black hole is mostly just empty. As far as we know, all the matter in the black hole is collapsed into a single point. The event horizon marks the boundary where light (and information) can no longer escape. It's of course more dramatic than this, as others have pointed out, once inside the event horizon, the singularity is in your future, no matter what direction you try to travel in. No matter which way you boost, every movement brings you closer to the singularity. But \"between\" the singularity and the event horizon, there isn't really anything. Being just inside the event horizon of a supermassive black hole would not really be all that uncomfortable."
] |
[
"What is a moving node in wave mechanics?"
] |
[
false
] | null |
[
"A node is just where the oscillatory function goes to zero. Those points can be stationary or moving."
] |
[
"Thank you."
] |
[
"May I ask if a moving node would in turn do something to a mass in an optical or acustic tweezer setup?"
] |
[
"Is it possible to create a superconductor that works at room temperature?"
] |
[
false
] | null |
[
"The short answer is that we don't know. We do not understand the mechanism that causes high temperature superconductivity (and we aren't even certain it is the same mechanism in all materials). Since we don't understand high temperature superconductivity theoretically, there is no way for us to predict an upper bound on the critical temperature.",
"There has been, and continues to be lots of experimental research devoted to developing higher and higher temperature superconductors, but currently the highest temperature superconductivity has been achieved at is around 130 K (still quite a ways from room temperature). "
] |
[
"Here I go diving into the details, but whether room temperature superconductivity leads to a technical revolution will depend a lot on the kind of progress made in vortex pinning between now and then. High temperature type II superconductors won't be that useful if vortices are continuously dissipating energy. Also, even if some material managed to sneak it's critical temperature above room temperature, it's critical field at that temp might be so small that wifi or the like could quench it.",
"My understanding is that it's primarily cost (growth is hard!) and poor mechanical properties (ceramics are brittle!) that are keeping current high temperature superconductors from seeing wider use. Liquid nitrogen cooling is actually relatively cheap and easy by comparison."
] |
[
"And if you were to discover a good way to make room-temperature superconductors you'd revolutionise experimental physics, medical imaging, computing, and possibly even fusion power. It would be an enormous technological advance, because a lot of the difficulty with these things comes from the extreme cooling current superconductor-based technologies need."
] |
[
"How can the transfer of photons between a positively charged particle and a negetively charged particle make them attract each other ?"
] |
[
false
] |
[deleted]
|
[
"There is no transfer of photons."
] |
[
"Actually, ",
" photons are transferred, which is just a common but misleading way of saying that static/pseudo-statc electromagnetic fields emanate from charges and exert forces. A real photon is an asymptotically free oscillation in the electromagnetic field. All other forms of the electromagnetic field; static fields as well as near-fields; exist physically just fine without being photons."
] |
[
"Yes, the electromagnetic force is carried by the quantized electromagnetic field as described by QED field theory. In a particle physics context, we refer to the QED field as a collection of photons, but that does not mean that we always have real photons."
] |
[
"What is the origin of the quadratic formula?"
] |
[
false
] |
I used to know this back when I did honours maths in the Irish version of high school, but I can't remember anymore, it is my favourite formula in applied maths so I thought I might ask the hyper intelligent mathematicians of r science to impart the knowledge.
|
[
"Do you mean historically or a proof?",
"Historically, the Babylonians had some concept of the problem (~2000BC) and the ancient Greeks (~300BC) were able to generalize and find solutions geometrically (when they made sense). Between 0-1000 AD, many Indian mathematicians worked with it, and eventually lead to a purely algebraic proof requiring no geometry but it still only found the positive solution. It wasn't until the 1500s that it took the shape we know today. ",
"See Here",
".",
"As for proofs, there are many. But first we need to know what the problem is. If we have an equation like 2x+3=0, then there is only one vale for x where this is true: x=-3/2. If I plug in x=1, I get 5=0, which is false, by 2(-3/2)+3=0 is true, and this is the only such number. In general, the solution to ax+b=0 is x=-b/a. This gives a formula to solve any equation of the form ax+b=0.",
"But we can look at higher order problems. What is the solution to x",
"-6x+5=0? Turns out there are exactly two values for x that make this true, x=5 and x=1, so these are the solutions. Given an arbitrary quadratic equation, ax",
"+bx+c=0, can we find a formula for x that gives all the solutions? ",
"The answer is \"Yes\", and the solution is:",
"Where the + gives one solution and the - gives the other.",
"In what follows, since reddit is not the best at math formatting, I'm going to do a little trick to make things easier. If x is a solution to ax",
"+bx+c=0, with a not zero, then I can divide through by a and get x",
"+Bx+C=0 where B=b/a and C=c/a. The solutions to ax",
"+bx+c=0 and x",
"+Bx+C=0 will always be the same, because we can get from one to another by multiplying zero by a number. So I'm going to find solutions to x",
"+Bx+C=0 and to recover the full equation, all you need to do is replace B=b/a and C=c/a.",
"For the first proof, note that we can use square roots to very easily solve the equation (x-H)",
"-K=0. Moving the K to the other side, we have (x-H)",
"=K and so x-H=±√K and so the general solution is ",
"x=H±√K",
"Can we take the equation x",
"+Bx+C=0 and turn it into something that looks like (x-H)",
"-K=0? If we can, then we can solve the equation. That is, given B and C, I want to find some H and K so that ",
"as polynomials. To help figure this out, let's expand (x-H)",
"-K. This will give x",
"-2Hx+H",
"-K. This means that we need",
"Two polynomials being equal is the same thing as all the coefficients being the same. The coefficients for x",
" are already the same. We need B=-2H for the x coefficients to be the same, and we need C=H",
"-K for the constant terms to be the same. Since we know B and C and are trying to figure out what H and K need to be, the two equations",
"give us a way to do this. Solving the first gives H=-B/2. Plugging this into the second gives C=-K+B",
"/4 and so we need K=-C+B",
"/4. That is, we have",
"Plugging this into the equation x",
"+Bx+C = (x-H)",
"-K gives",
"So we need to solve",
"Doing this the same way we did for (x-H)",
"-K=0, or just using the solution formula x=H±√K we get",
"x = (-B±√(B",
"-4C))/2",
"This is the method of Completing the Square, and is what is generally taught in a typical classroom setting.",
"Completing the Square is not my favorite proof. Here is my favorite:",
"Let's pretend that we already have the solutions to x",
"+Bx+C=0. Let's say that they are x=R and x=S, just as placeholder labels. This means that R",
"+BR+C=0 and S",
"+BS+C=0, and there are no other solutions. Since they are roots, this will mean that we have",
"Expanding the right side, gives x",
"-(R+S)x+RS. You can check that plugging in x=R and x=S will give zero. This means that we have",
"and so B=-(R+S) and C=RS. If you remember how to factor quadratics, this is why you have to find two numbers that add up to B and multiply to C in order to factor. These are Viete's equations;",
"B=-(R+S)",
"C=RS",
"We have two equations in two unknowns (R and S), can we find their solution? We cannot use typical, linear methods, because C=RS is not linear, so we have to get more creative. ",
"What I'm going to do is turn the problem of trying to find two numbers, R and S, into a problem of only finding ",
" number. Set D=R-S. If R and S are both real numbers and R is bigger than S, then D is the distance between R and S. So we can think of D as being the distance between the two roots. I claim that if we can find D, then the equation B=-(R+S) will allow us to find R and S. This is because R=D+S and plugging this into B=-(R+S) gives",
"Solving -B=D+2S for S then gives",
"Since R=D+S, I can plug in this expression for S into this and get R=D+(-B-D)/2, which is",
"So if I can find the distance D, then we'll have that x=(-B±D)/2 are the solutions to x",
"+Bx+C=0. Now I just need to find one number.",
"To find D I'm going to do a trick. We know that D=R-S, but I want to use the fact that B=-(R+S) and C=RS to rewrite D. As it stands now, we can't do this, but if I look at D",
" I'll have",
"We can do a little bit here and we see that 2RS=2C, so what we have is D",
"=R",
"+S",
"-2C. We just have to deal with R",
"+S",
". Let's see what happens when we square B=-(R+S): We'll have",
"So what we have is B",
"=R",
"+S",
"+2C. Moving the 2C over gives",
"This means that D",
" = R",
"+S",
"-2C = B",
"-2C-2C = B",
"-4C, or",
"But we need D. (There is one issue about this, there are ",
" numbers whose square is B",
"-4C, which one is D? It turns out, it doesn't matter, because if √(B",
"-4C) is one square root, then -√(B",
"-4C) is the other. If we choose the wrong one, then we have just switched R and S, so no big deal.) Taking the square root then gives D=√(B",
"-4C). The solutions are then",
"R = (-B+√(B",
"-4C))/2",
"S= (-B-√(B",
"-4C))/2",
"Overall, this proof has a lot more interesting and big ideas going into it than Completing the Square. If you want to solve cubic and quartic equations in a systematic way, you would generalize this method rather than completing the square."
] |
[
"I was indeed referring to the proof, however the history is interesting and appreciated. Alot of forgotten terms that i need to relearn there with your proof's, even though you already have simplified it down. But thank you for feeding my curiosity. "
] |
[
"It's derived by factoring through completing the square, there was a slicker method but I forgot it now.",
"This is worked through step by step: ",
"http://m.wikihow.com/Derive-the-Quadratic-Formula"
] |
[
"A question about cooling atoms..."
] |
[
false
] |
I didn't really want to start a new thread with this question, however the right comment to ask hasn't come up. Following the link about "atomtronics" it mentioned about cooling atoms using lasers. I have seen and heard about this quite a few times however still not sure about how this works. I believe they managed to create the first Bose-Einstein condensate by using a method of cooling Rubidium atoms with lasers. Now my primitive mind assumes that firing lasers at something would provide more energy to whatever it hits and therefore not cool it. Anyone care to clarify if you have a spare moment? Thanks
|
[
"It's a process that takes advantage of both relativity and quantum mechanics.",
"Atoms can only absorb photons of specific energies; that's the quantum-mechanical part. If you shine light at a material, photons that can be absorbed will be, putting the atoms that absorb them into an excited state. An atom in an excited state will quickly emit another photon of the same energy but in a random direction, giving itself a little \"kick\" of momentum. This is how light heats things up.",
"But if you're very, very careful about which frequency of light you use, you can arrange it such that only atoms moving ",
" the source of the light will absorb photons. This is due to relativity; since the speed of light is the same in all reference frames, light that's emitted from a source moving toward you — or, equivalently, that's emitted while you're moving toward its source — will have a higher energy in your reference frame. The light that's emitted by the laser is of the wrong frequency for absorption in the reference frame of the laser itself, but atoms that are moving toward the laser are in a different reference frame, so the photons have enough energy to be absorbed by those atoms but not by atoms moving parallel to or away from the laser.",
"Since only atoms that move toward the laser can absorb the photons, only those atoms go into an excited state and get little \"kicks\" of momentum. Since the little \"kicks\" are in a totally random direction, more atoms are slowed by this process than are speeded up. So the net result is that the average kinetic energy of the system goes down, which is equivalent to a reduction in temperature."
] |
[
"There are several methods of laser cooling, the most widely used is called Doppler cooling, which uses the Doppler shift to its advantage.",
"An atom can only absorb discrete energies. Two lasers are pointed at each other, with the atom in the middle. The energy of the lasers are set so that if the atom moves to either direction, the Doppler shift makes it more likely that the atom will absorb from the laser it is moving ",
". Since it absorbs more photons from that direction (and radiates uniformly into all directions), it gradually slows down from because it has absorbed the momentum from the photons.",
"When the atom is \"at rest\" then it will absorb equally from both, and stay at rest (in a statistical sense, because it can only absorb one photon at a time)."
] |
[
"It's actually pretty neato. You need to know the energy levels of the element you want to cool. Then you tune your laser to ",
" a little ",
" the frequency that would excite an atom in its ground state to some higher state. Then you shoot that laser on there from all six directions. The thing is now that only those atoms absorb one of the laser photons if they move slightly ",
" the laser because of the doppler shift. If a photon that doesn't have the right frequency to lift the atom from one energy level to another hits the atom, nothing happens, because photons can only be absorbed as a whole, energy levels are discrete and energy must be conserved. And the doppler shift makes sure that the photons have the right frequency, since we tuned the laser just so.",
"And if one of the atoms absorb a photon, they are slowed down, because they gain the momentum of the photon, and the photon always carries negative momentum with respect to the absorbing atom. So they lose kinetic energy which is nothing but temperature on a microscopic scale. Of course, the atom is now excited and will soon emit a photon again. But unlike the absorption, the direction of emission is random, so it all equals out."
] |
[
"Does pilot wave theory work with experimental results of (delayed choice) quantum erasers?"
] |
[
false
] |
[deleted]
|
[
"s types, those who just can't get around the philosophical matter of wtf QM is saying, and people outside of QM. I think the vast majority of physicists are still (professionally) \"Shut up and calculate\" types; the question of an ontol",
"Very interesting. Would you be able to also explain how, in the model of pilot waves, these experiments are explained because I can't see it yet. I personally have no problem with the Copenhagen interpretation whatsoever but I was wondering if the pilot wave theory has merit or potential to take over at some point. "
] |
[
"There is no science in this. The different interpretations make no difference to any predictions of the theory."
] |
[
"Yes, it does (by getting rid of locality and adding a deterministic, FTL, universally present \"Pilot Wave\"); the the reason that theory isn't quite dead is that it still manages to make the same predictions as QM. The reason that nobody cares who isn't a devotee is that it's not much of a theory... just another Interpretation in different clothes. It makes no new predictions, offers no new insights which aren't ontological. ",
"The thing you have to remember is that this is an issue that mostly appeals to wingnuts, religious types, those who just can't get around the philosophical matter of wtf QM is saying, and people outside of QM. I think the vast majority of physicists are still (professionally) \"Shut up and calculate\" types; the question of an ontology for QM isn't as interesting as the actual physics. "
] |
[
"Why do I get a static shock from everything this time of year?"
] |
[
false
] |
Every time I touch something metal, something touching metal (I just got a shock from touching my damn taquitos in the oven) or people, I get a shock. Why does this happen and is there anything I can do about this?
|
[
"Get an ionizer. I run a commercial 3M ionizer. You can measure static energy in the air with a multimeter.. Point the ionizer at it, and you can watch the voltage drop. "
] |
[
"I've been thinking of it as the worst super power ever. My archnemesis is the door knob on my back door. Earlier, that thing shocked me so hard that I heard it. "
] |
[
"I've been thinking of it as the worst super power ever. My archnemesis is the door knob on my back door. Earlier, that thing shocked me so hard that I heard it. "
] |
[
"If an atom's electrons zip around at high speeds, what do they look like when two atoms form a covalent bond?"
] |
[
false
] |
Hi, I've been teaching myself chemistry in my spare time recently, and in general I understand bonds and that electrostatic charges cause them to form. But they're tricky to visualize. Diagrams and models are of course static, whereas in reality electrons are jumping all over the place. So, say I've got NH3. Normally, the electron(s) of each atom are zipping around the nucleus -- but what happens when the atoms bond? Do they continue zipping around the nucleus of both atoms? Or do they kind of hover in between (as diagrams would imply)?
|
[
"...the electrons interfere with each other in such a way that they resolve to a lower energy state upon bonding. If they are behaving as standing waves, then they must be undergoing destructive interference to acquire this lower energy state.",
"This is wrong. Let's first approach this using molecular orbital theory and the linear combination of atomic orbitals. Electrons are standing waves which are contained with atomic orbitals in the free atoms. Upon combining, the wave functions which represent the electrons combine linearly. In other words, we have, say, 2 1s orbitals (for 2 Hydrogen atoms). When they combine, they form 2 molecular orbitals (One in which the wave functions of the two electrons add, and one in which the two electrons subtract). In this model, if ever we mix two atomic orbitals (Or any two orbitals, atomic, metallic, organometallic, etc.), we get out both a higher energy and a lower energy orbital (Bonding and antibonding molecular orbitals). These new orbitals extend well beyond the atoms from which the atomic orbitals originate and actually delocalize over some part of the molecule. This is the only place relevant to this discussion where we have \"constructive\" and \"destructive\" interference of wave functions, if you want to call it that. The electrons then fill the bonding orbital which is lower in energy and we are happy. This is the stabilizing effect. One can also argue that the delocalization of the electron across several nuclei that are all positively charged is also a stabilizing effect.",
"Now let's approach it from a physical point of view. Total electron energy is equal to their kinetic energy plus their potential energy. In order to reduce its energy, we need to reduce these two. An electron that sees two nuclei (Such as when it is located between the two) has a lower potential energy since it is closer to the positively charged protons. Kinetic energy is somewhat harder to explain, but it also does drop when you form a bond (It certainly doesn't increase, and that should be enough for this argument). Thus, when forming a bond, the electrons lose total energy and the system becomes more stable. "
] |
[
"When you form a bond, the behavior of the electrons don't really change per say. They are still very much moving around just like on a single atom. But what changes is where it is doing the zipping. In a molecular orbital, the electrons are either zipping around multiple atoms or primarily hanging around in between the atoms. It depends on the type of bond. A sigma bond typically has the largest density in between both atoms while pi bonds and conjugated structures has a large density around the atoms. "
] |
[
"Isn't the model of \"electrons zipping around\" a classical interpretation of what is really more of a probabilistic quantum distribution? "
] |
[
"Is it possible to harness the Earth's magnetic field for flight with a strong enough and self stabilizing electromagnet?"
] |
[
false
] |
[deleted]
|
[
"For flight...very unlikely. The Earth's magnetic field is something like 30 to 60 microteslas at the surface of the Earth (depending on your latitude), which is minuscule. For reference, the superconducting electromagnets used to control the proton beam at the LHC are on the order of 10 Teslas...so about a million times stronger. And those take CRAZY amounts of power and resources to operate, plus they're pretty massive.",
"But sure, just for kicks, let's work this out to see what it would take, in as simple a way as possible (everyone, please let me know when I make assumptions or mistakes that are inaccurate!). First, let's start with the general principle here. Magnetic fields exert forces when there are charged objects moving through them (there is of course a lot of nuance to that statement, but for simplicity let's just take it at face value), and the force is always perpendicular to both the field, and the motion of the object. So, in the case of a flying object, we need the force to point AWAY from the Earth, to counter gravity.",
"Problem is, this force would just keep it in the air, it wouldn't propel it forward. In fact, the object would already HAVE to be moving forward for it to work in the first place. So an object will still need some form of propulsion, like a propellor or jet engine. All the magnetic field would do is keep it up...which is what wings on planes already manage to do quite well. So why would we try to do this? Well, one reason I can think of is to reduce the aerodynamic profile of the object, and thus reduce drag. But I'll get to why that also is unlikely to really matter.",
"So back to this force idea. Let's say we're travelling east along the equator (a simple case, since now the Earth's magnetic field is pointing more or less due north, though the field is weaker), and we want our object stay in the air due to this magnetic force (we'll give it the more accepted term and call it the Lorentz force). Basically, it is a product of the charge, the velocity it is moving at, and the strength of the magnetic field it is moving through. And the direction of the force comes from applying a cross-product (I'm not sure what your math/physics background is, but google the 'right hand rule' for a visual). So q x v x B. For an object moving as fast as a Boeing 747 (roughly 900 km/h, or 250 m/s), our force is q x 250 x 0.00003. So q is going to have to be big, but how big?",
"Let's stick with the 747 idea, and basically say our object has the same mass. The new 747-8 has a maximum takeoff mass of about 440,000 kg, but we'll assume we're not at the maximum, and we'll just round it to 400,000 (again, for simplicity). This is important because we need to know the gravitational force that our Lorentz force has to counter. So 400,000 x 9.81 (acceleration due to gravity, where Newton's second law is applied), is 3,924,000 Newtons. Which is a hell of a lot of Newtons. So, equating this to our Lorentz force equation about to solve for q (the charge), q has to be 0.5232 gigacoulombs. That is...immense. I mean, that is so unbelievably big it's ridiculous. There are probably BIG ramifications to this.",
"So first, to apply this charge to our object (no idea how we would...), let's say we had a metal frame, with the charge evenly distributed. Also, it has to hold a lot of people, like a 747 (let's say 300 people), so it has to be fairly big. In fact, let's make it simple and say it's a sphere (which is REALLY bad for aerodynamic drag). Working this out on paper with the idea of packing these people like cattle, I'd say at minimum we'd need a 10 m radius sphere. The biggest problem here, I'm going to guess, is that we've exceeded breakdown voltage of the surrounding air. Look at take-off for example. Let's say this big sphere is about 3 meters above the ground (landing gear). Assuming the ground is...well...grounded, that means we have a voltage difference between the sphere and the ground of about 1 x 10",
" volts. Yikes. The breakdown voltage in dry air is 33 kV/cm, or 9.9 MV over the distance between the sphere and the ground. We've exceeded that...by a lot. So we are going to get one HELL of a spark, that will completely ionize the air under the sphere, probably heating it up to a plasma and in turn melting the sphere and everyone inside it. So that sucks.",
"What if we somehow get it up to altitude? So at 30,000 feet (9000 meters), the voltage difference (I'm skipping a lot of details here, but I think the main idea still holds) could only be as high as 27 gigavolts. We still exceed that by a TON. So...this is not a very good idea, basically. It would look pretty spectacular, but the result would not be altogether pleasant.",
"On a happier note, we are starting to use the earth's magnetic field for propulsion in space. It's called a ",
"tether",
", and at the moment it's mostly experimental. But it relies on the idea of using a current (and the surrounding plasma in Earth's orbit) to interact with the magnetic field and drive the tether forward. It's a very small force, and very limited in where it can be applied, but still cool. I think it's one of the most promising ideas for how to effectively deorbit satellites when their lifetimes are up.",
"Damn that was long, and sorry for all the wild simplifications. But basically, this is why we still use planes with wings.",
"EDIT: I didn't address the electromagnet idea because I don't think even the concept would work; the earth's magnetic field would just align the magnet to its direction (slowly...), but not actually cause it to lift or move. And applying a current would also be implausible, as any setup would necessarily involve a current LOOP, which would have zero net force exerted upon it by the Earth's magnetic field, no matter the size of the loop or current. Unless it's a GIGANTIC loop that is anchored say in the middle of the US, and spins in the Earth's field such that it could deliver people from one coast to the other...but that's just being silly."
] |
[
"There's no need to point out someone's lack of understanding, if they understood the concept in the first place they wouldn't need to ask about it."
] |
[
"q has to be 0.5232 gigacoulombs. That is...immense. I mean, that is so unbelievably big it's ridiculous. There are probably BIG ramifications to this.",
"The biggest rammification would be that, in the case of positive charge, which is easier to get by in larger quantities than negative charge (electrons will just \"vapour\" away if the electrostatic potantial exceeds their exit work) you'd end up with a Coloumb explosion, i.e. disintegration of matter on the molecular level, due to the electrostatic force; namely the positive charges of nuclei no longer shielded from each other by the electron hulls (of those electrons being stripped away) and also due to loss of chemical bonding."
] |
[
"Is there a reason, from like... a linguistics standpoint, that people say \"like\" so much?"
] |
[
false
] |
Maybe this is a dumb question, but I was thinking about this earlier when I caught myself saying "like" numerous times in a conversation. I've always kind of noticed that a lot of people, including myself, do this. Then I thought why on Earth would that be a thing? Why the word "like"? Do other languages besides English have any similar quirk?
|
[
"Generally \"like\" is used as a linguistic filler, which indicates the person is thinking about what to say next. Previously, people seemed to use \"um\" and \"ah\", but we seem to have moved away from that to using terms such as \"like\" or \"actually\".",
"As a poor French speaker, I tend to need fillers all the time, and have taken to saying \"tu vois (you see)\" - I'm not sure how well this would go down with native French speakers!"
] |
[
"In Mandarin they say 那个 all the time. (Sounds like \"negga\", btw.)",
"Without any solid evidence I would hazard a guess that it's almost 100% cultural. No-one I know outside of a certain social sphere uses \"like\" in the way you're describing. I'm strongly of the opinion it's a learned cultural behavioir. "
] |
[
"I'm not sure 'like' means exactly the same thing as 'um' or 'ah'. 'like' in its \"filler\" usage has a softening effect, because it has the effect of making the speaker seem less articulate, more casual, it can be used to make criticism less harsh. Compare",
"You're like such a hypochondriac",
"You're um such a hypochondriac",
"You're ah such a hypochondriac",
"With 'like', the criticism stands, but sounds somewhat less harsh than without 'like'. With 'um' or 'ah', it sounds more like the speaker paused while she searched for something to say or for the right word. ",
"Words that fill pauses like 'um' and 'ah' are used so the speaker is able to pause, but signal to her interlocutors that she wants to \"hold the floor\", meaning she doesn't want anyone else to jump in and start talking before she finishes. "
] |
[
"How strong of a magnetic field is required to rip iron particles from the bloodstream?"
] |
[
false
] |
This occurred to me after reading AMA about a man who had magnets implanted in his fingers and his concern about taking a MRI. Not sure if its even possible, but what a old 4T MRI machine can do.
|
[
"That depends entirely on the hemoglobin state. Deoxyhemoglobin is usually paramagnetic. ",
"To answer the OP's question though (and this has been asked before): You cannot do this with a magnetic field strength that's anywhere near what we can create. You'd be talking about something like hundreds of thousands of Teslas."
] |
[
"Hemoglobin (iron containing protein in blood) is slightly ",
"diamagnetic",
", and would be repulsed, not attracted to a magnetic field."
] |
[
"You can read ",
"all the previous questions here",
". The short answer is that the iron in your blood is not ferromagnetic, thus won't be attracted like the metal objects you see in the video."
] |
[
"What's between protons/neutrons and electrons?"
] |
[
false
] | null |
[
"There isn’t anything “between” them. Their wavefunctions all overlap somewhat in space."
] |
[
"Electrons in s orbitals have a nonzero probability of being in the nucleus."
] |
[
"Electrons in s orbitals have a nonzero probability of being in the nucleus."
] |
[
"How exactly do we get used to capsaicin?"
] |
[
false
] |
A few years ago, my idea of spicy was something along the lines of cayenne pepper sauce. As I'm typing this, I'm enjoying a cheese sandwich spiced up with a Madame Jeanette chutney. What happened to my body to allow me to sit through this sandwich with enjoyment rather than burning screams of agony?
|
[
"Another tangential question: if you hold water in your mouth when your tongue is burning from spice, the burn is completely gone. But as soon as you swallow the water the burn comes back. What's going on here?"
] |
[
"Chilli (capsaicin) is detected by the capsaicin-receptor (TRPV1) on the surfaces of heat-sensing pain fibres. ",
"Science doesn't completely understand the process of habituation (tolerance) to capsaicin exposure - but it is thought to be because of down regulation of the receptor (i.e. reduction in the numbers of receptors .: harder to activate and hence you can tolerate more curry).",
"A signaling pathway such as calmodulin and the decrease of PIP2 have been linked in desensitization of TRPV1 but its very much a \"hot\" (haha!) topic at the moment as several pain drugs are targeting this receptor and its pathways; but are being held back by its role in thermal regulation."
] |
[
"afaik it is oil-soluble, so the milk helps because it contains a lot of fats"
] |
[
"Why is hot chocolate powder still dry when it comes out on the spoon?"
] |
[
false
] |
A cup of hot chocolate and a spoon with HC on it , dip it in and its dry about 70% of the time.
|
[
"When you stick the loaded spoon in the cup of milk/water, the surface layer is dampened, then keeps more moisture from migrating to the center of the spoonful of powder because the powder particles on the surface have become stuck together, and the gaps between the particles is too small to let water through.",
"This happens with many things, from baking to mixing concrete."
] |
[
"Is there a way to minimize it? It's frustrating."
] |
[
"Well, with hot chocolate...adding the powder to hot milk or water by pouring it in (slowly...not all at once), then stirring, works best for me. You will still have some clumps, but the heat will melt/help dissolve the clumps. And keep stirring, as the agitation action of stirring also helps break up the clumps."
] |
[
"Does Teleporation violate the 3rd law of thermodynamics?"
] |
[
false
] |
I am FAIL and meant the because I forgot they start at zero. If teleportation over practical distances (football field or a mile) with larger masses (like a human or a truck) is possible, then does one of these have to be true? I hear about small "quantum sized" objects being teleported small distances in sensational news headlines, but I don't really know anything about it. My question is worded awkardly because I don't know how to address IF it's possible/already kinda happening.
|
[
"Who claimed you could do that without expending energy?"
] |
[
"Quantum teleportation is ",
" actual teleportation, and it's very frustrating that newspeople won't make the distinction. Quantum teleportation involves transporting the state of one system onto another; it's an interesting phenomenon in and of itself, but it's not the same thing as transporting matter.",
"But you're correct about your question. Any method of teleportation would have to either violate the second law of thermodynamics or explain why you can't teleport something up a very high potential energy well to create energy."
] |
[
"Why would it violate ",
" law of thermodynamics?"
] |
[
"If the speed of sound in fresh water is nearly 1500 m/s, why do the ripples on a pond travel so slowly?"
] |
[
false
] |
Are they fundamentally different types of wave?
|
[
"Yeah they are different types of wave. Sound waves are ",
"compression waves",
", whereas ripples are ",
"displacement waves",
", (more specifically ",
"gravity-capillary waves",
").\nSound relies effectively on the mechanical properties of water (I am in no way an expert on that), whereas ripples rely on gravity and surface tension."
] |
[
"this is also why when there is an earthquake, the p-waves (or compression waves) are detected first, and the s-waves are detected second. It's just a difference in the way the energy is propagated. "
] |
[
"If you're interested here's another type of wave, soliton, that travels at less than 1 feet/s:",
"http://www.youtube.com/watch?v=PyjwZ39EDmw"
] |
[
"The owners of WannaCry attack can withdraw the bitcoin money without being tracked by police? How?"
] |
[
false
] | null |
[
"There is no way to match a Bitcoin address to a person. It's not like an IP address that is assigned based on your location. However, there is a public record of every Bitcoin transaction, and if the attackers tried to directly sell the bitcoins for real money, then the exchange they use has information about who owned that address. The way people obscure this is by doing \"Bitcoin mixing\", where the bitcoins they stole are shuffled around via another party. The attackers will send a mixer their stolen coins, and then the mixer, after some delay in time, will send the attackers the coins from somebody else, to a new address they specify. If the mixer is trustworthy, he will then delete the record of the attackers' new Bitcoin address and no one will ever know who got the coins. "
] |
[
"But someone ends up with the stolen bitcoins, and the authorities could chase them. Don't people who use mixers worry they could end up with \"hot\" bitcoins in this way?"
] |
[
"The coins could potentially be confiscated without charging the owner with a crime. This is what happens to people who unwittingly buy stolen goods from someone, if the police track the goods to them. A lot would depend though on where the mixer resides, and if the country they are in has any laws in place regulating bitcoins as a valuable asset or not."
] |
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