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[
"What causes computer screens to have colours more/less visible at extreme viewing angles?"
] |
[
false
] |
[deleted]
|
[
"The way a LCD monitor works is there is a row of lights at the bottom of the screen and a diffuser screen over top to spread the light out. When you view it from an extreme angle you are viewing through more of the diffuser which distorts the color."
] |
[
"Here",
" is a video that explains how an LCD monitor works."
] |
[
"You should specify LCD or CRT."
] |
[
"Will we ever be able to view what happens in other planets at a surface level with a powerful enough telescope?Especially planets that are earth-like/inhabitable."
] |
[
false
] | null |
[
"In theory, yes it's possible. But what do you mean by 'at a surface level'?",
"A group of astronomers recently published a ",
"30 year roadmap for NASA missions",
". In it, they talk about all the amazing science we think we can get in the next 30 years as long as Congress keeps funding us. (If you have time, you should skim the whole thing. It's really fascinating and written at a layperson level.)",
"They also include some really neat missions beyond the 30-year timeline that they call 'visionary', but that are possible with current technology if we had the money and time to develop the technologies further.",
"One of those 'visionary' missions they call the ExoEarth Mapper. They believe it's possible to get 30x30 pixel images of habitable Earth's, that ",
"would look something like this",
".",
"To do it would require a huge investment of resources / a way to get 6-m size telescopes into space much cheaper than we're doing it today. But it's not crazy to imagine this will become possible over time. It would also require space-based visible interferometry to work, which is currently an unproven technology, but in theory possible. We do have visible light interferometers on the ground, so then it's just a matter of setting them up in space in a grid hundreds of kilometers apart instead of the 10 meters apart or whatever we have on the ground...",
"So yes, there's hope that we can map out Earth-like exoplanets and get decent views of them. But given current funding situations and lack of support for space telescopes, I wouldn't bet on it before the year... 2060, just to throw out a number."
] |
[
"Dont you sometimes feel like we were born too late and yet too early to experience some huge breakthrough? ",
" yep there is plenty of extraordinary stuff that happened-is happening during our lives. I just meant things like fusion, interstellar travel or some badass things. But living in a computer age is pretty amazing:) ",
" Thanks to all the people that proved me we live in the amazing era with things unimaginable few decades ago! Also, this is my most upvoted/commented post, so I am happy it could be in ",
"/r/askscience",
". :) ",
" Thank you mysterious stranger for the gold, this is my first one and I will remember it forever! :)"
] |
[
"As someone who is nearly 30, the 2060 number is a tad disappointing. But the thought of having pictures that clear of planets several light years away in my lifetime is amazing. "
] |
[
"How strong would the casing of a nuclear bomb be to hold in a nuclear blast? What would be the effects?"
] |
[
false
] |
How much stronger than steel does the casing have to be to hold in this energy? Could radiation still leak through?
|
[
"I can't answer your question directly, but from the ",
"wikipedia article on underground testing",
" a nuclear bomb causes \"temperatures of several million degrees and pressures of several million atmospheres\" (no exact figures given) and buried in rock will irreversibly strain/deform rock in a radius of around 1km per the cube root of the kiloton yield."
] |
[
"The simplest response to your answer is steel itself can hold in a nuclear blast, and prevent radiation leaks. The micro material properties (atomic constituents, molecular arrangement, etc.) of a nuclear blast \"shield\" are equally as important as the macro structural properties of the shield (thickness, shape, etc.).",
"Imagine a nuclear blast as an immense increase in heat and pressure over a short period of time occurring within an air-tight spherical shield. Now imagine this reaction on a much smaller and less volatile scale - blowing up a rubber party balloon. As you breathe into the balloon, there is an internal increase in pressure and temperature. The more you blow into the balloon, the more the pressure increases until the material reaches its yield stress. When the material begins to yield, it will deform critically until it reaches its critical stress state and breaks. ",
"If you're a human being, there is only so much pressure you can exert into the balloon. If you wanted to prevent yourself from being able to blow up or break the balloon, you would have to increase the strength of the balloon. But how can you do that?",
"In your question, the answer would be as simple as replacing the rubber with something much stronger, like wood or steel. But there are many other ways to made the balloon stronger without replacing material type. For instance, placing one balloon inside another. I guarantee that you won't be able to blow it up. But that's not because you've replaced the shield type, you've just made it thicker. You can also make it weaker by changing the shape of the balloon to a square. There are several means of making a structure stronger or weaker by introducing changes to the object's macro physical properties, without ever touching the material type. While I'm on that note, there are several ways of making the material itself stronger or weaker by simply changing the molecular arrangement (amberlite steel, pearlite steel, etc.)",
"So you can see that this is far from a simple answer, without even considering the magnitude of a nuclear blast. Radiation is a different topic... That depends on radiation resistance of a substance, proximity to the blast, etc. etc. Without knowing shield shape, thickness, or overall dimensions, the answer is anywhere from 0 to the limit of infinity.",
"TL/DR; What is the shape of the shield, are you protecting yourself from the blast, or the blast from you? Changing these properties changes the answer."
] |
[
"Here's my stab at trying to calculate how strong a container would be needed. First off lets make the assumption that due to the fixed nature of our container that the volume in which the explosion would go off would be of a fixed volume additionally due to the fast rate at which the explosion happens and the ridged nature of the container that a relatively small portion of the energy of the explosion will escape the container. So this vessel is roughly isochoric(constant volume). so lets bust out some equations...",
"dU = dQ − dW",
"In this equation dU is the total change in energy, qQ is the change in heat of our system(the bomb and the container) and dW is the work done by the system. I'm using d here to represent the change in the following variable. additionally",
"dW=P * dV",
"here the work done is equal to the pressure of the system times the change in volume but since there is no change in volume dW also equals zero leaving us with this equation....",
"dU = dQ",
"So this means the the energy released by the bomb, dU, is equal to the change in heat to the system, dQ. So this means that all of the energy of the bomb must be converted into heat. so lets estimate how hot our container+bomb system must get. todo that lets look at a more specific formula for the change in heat.",
"dQ = m",
"dT",
"in this equation the change in heat, dQ, is equal to a mass, m, times a constant representing how much energy it takes to heat a gram of your system by one degree(roughly speaking), Cv, times the change in temperatuer dT. so we take this equation and plug it into the equation before to get another equation.",
"dU = m",
"dT",
"So with this equation if we know the energy released by the bomb, dQ, estimate the mass of the bomb + the container (our system), m, and estimate its heat constant, Cv, we should get a rough estimate of how hot our system will get. While I don't have those exact figures, keep in mind even the strongest most thermally resistant materials start to melt at 3695K (tungsten). So thats probably going to put a limit on how hot we can get our sample. Tungsten also has a specific heat capacity of roughly 0.143 Jg−1 K−1 (a very rough estimate due to the fact that Cv will change with changing P). The rest of the numbers you might have to estimate a bit.",
"http://www.kayelaby.npl.co.uk/general_physics/2_3/2_3_6.html",
"http://en.wikipedia.org/wiki/Isochoric_process",
"(I apologize if I fucked anything up its been a while since I've done thermochem)",
"There are a couple other ways your container could work that would break the above equation and reduce the total amount of energy being instantly converted into heat. First would be to dump some of that energy into gravity i.e. bury the bomb underground and force to bomb to lift a couple million tons of rock into the air. Also since we haven't specified how heavy our container must be we can make it absolutely monsterous thus increasing m in the above equation. We can also allow our container to expand although this is probably going to a very limited advantage since our container is going to be so massive. lastly its also possible to use phase change to absorb some of the energy but this effect is going to be very limited due to the shear ammount of energy being released by the bomb.",
"In the end my guess is using gravity is going to be the most reasonable way of absorbing all that energy that fast. so bury your bomb a mile underground and consider a mile wide sphere of rock to be your container, lots of heat absorbing mass that can be thrown into the air and to top it all off rocks are cheap.",
"Digging up some numbers.... wikipedia say the melting point of rock is roughly 700C-1400C, lets use the 700 number as our safe estimate. wikipedia also says the Mk-24 nuclear bomb releases 100 petajoules of energy (1.0 × 10",
" joules), a 25 megaton nuke. bassalt rock has a specific heat capacity of 0.84 kJ/kg K (I'm slightly cheating again). so.....",
"(1.0 × 10",
" j) = (mass of our container+ bomb)* (1.133 kJ/kg/K)*(973.0 K)",
"so m here would be....",
"9.071×10",
" kg (kilograms) = 9.071×10",
" t (metric tons)",
"as a reference ",
"this open put mine contains 86 million tons worth of copper and 256 million tons worth of rock",
". This number seems a bit high so you would probably want to go back through and double check my numbers but to be honest i've never seen a 25 megaton nuke go off so iono....",
"http://en.wikipedia.org/wiki/Nuclear_weapon_yield",
"http://www.engineeringtoolbox.com/specific-heat-solids-d_154.html",
"http://en.wikipedia.org/wiki/Magma",
"....I don't want to work",
"Edit: add more reasonable numbers"
] |
[
"Do insects need to sleep too?"
] |
[
false
] |
As in, does the mosquito that pesters me when I sleep need to sleep as well or do small lifespans of some insects means they die before they need to sleep (if they do sleep).
|
[
"it seems that all animals sleep.",
"here's a good review of the topic of generality of sleep in animals:",
"https://journals.plos.org/plosbiology/article/file?id=10.1371/journal.pbio.0060216&type=printable",
"For a quick review, just read under 'Corollary 1' on the first page.",
"Also, worth reading this abstract from Shaw et al, Science (2000):",
"Drosophila exhibits a circadian rest-activity cycle, but it is not known whether fly rest constitutes sleep or is mere inactivity. It is shown here that, like mammalian sleep, rest in Drosophila is characterized by an increased arousal threshold and is homeostatically regulated independently of the circadian clock. As in mammals, rest is abundant in young flies, is reduced in older flies, and is modulated by stimulants and hypnotics. Several molecular markers modulated by sleep and waking in mammals are modulated by rest and activity in Drosophila, including cytochrome oxidase C, the endoplasmic reticulum chaperone protein BiP, and enzymes implicated in the catabolism of monoamines. Flies lacking one such enzyme, arylalkylamine N-acetyltransferase, show increased rest after rest deprivation. These results implicate the catabolism of monoamines in the regulation of sleep and waking in the fly and suggest that Drosophila may serve as a model system for the genetic dissection of sleep.",
"To sum this up, not only do insects (in this case fruit flies) sleep, their sleep is quite like mammalian sleep, both in overt structure (\"schedule\": they have regular wake/sleep cycles, sleep debt, decline with age, etc) and in its molecular mechanisms; other research (see that first review) has shown that insect 'sleep' has a similar genetic basis and similar neural mechanisms. Sleep seems to be a fundamental feature of any creature that uses neurons to live (i.e. \"animals\")."
] |
[
"Dunno. The results are based on observed behaviour, since we can't ask them and they are generally too small to do an MRI. Perhaps, like many birds and fish, they only rest 1/2 a brain at a time?"
] |
[
"Sleep seems to be a fundamental feature of any creature that uses neurons to live (i.e. \"animals\").",
"I'm nitpicking but not all animals have neurons or even nerves, sponges for example. "
] |
[
"If you were to hang a wrinkled shirt in a wardrobe, would it ever become unwrinkled over time via gravity?"
] |
[
false
] |
[deleted]
|
[
"Fashion Student here.",
"I think it would largely depend on the fabric. For example, if I were to get fabric pleated it would be important for it to be polyester, or have a polyester mix otherwise the pleats would fall out.",
"So, I think that if the shirt is cotton or wool then the creases would eventually disappear, but if it was a poly mix it could be more permanent. "
] |
[
"Polyester is plastic, versus the other two being organic. It becomes significantly more malleable as temperature increases, such as when pleats are being added. It cools and holds the shape given. Polyester also holds its shape more firmly than the other two when at room temperature, which is why the material is often more stiff than organic material. "
] |
[
"I think another way of asking this question is I hang a spring on a planet will it stretch itself eventually. Of course the answer like many questions is it depends...",
"In the case of a spring we should consider how far from equilibrium it is. If you have stretched it just a little bit then internally its not likely to do much. If you have stretched it non-linearly then internal movement of atoms and plastic deformation is likely occurring.",
"So I think that the answer is if the mass of the shirt is enough to stretch the fabric out. It wouldn't fit you anymore but it would get rid of the wrinkles. ",
"Compressing an object seems just the inverse and equally valid. So if I stand an iron rod up on its end it will never really flatten itself out due to just gravity. I can't think of anything very solid that would flatten itself with our gravity. Though the border between solid and liquid could be in play here. "
] |
[
"If animals of the same species talk the same to each other, why did humans have different languages?"
] |
[
false
] | null |
[
"I'm not sure what you mean by \"talk to each other\". Non-human animals can communicate, but they do not have language as formally defined."
] |
[
"Well, I suppose I didn't express myself correctly. For example, you could take a cat from one part of the world and one from the other, they would be able to communicate."
] |
[
"In what way would they be able to communicate? Couldn't humans from different post of the world communicate with signs and gestures?"
] |
[
"Supposing that wealth is redistributed, would inflation still occur even though no wealth is added and why?"
] |
[
false
] | null |
[
"Redistributing wealth could increase the velocity of money (how quickly money changes hands) because poorer people tend to spend their money rather than save it. More and faster spending leads to higher prices.",
"As an aside, poorer people tend to spend a higher proportion of their money on essential goods like food and housing. If you had reverse redistribution of wealth you might see inflation for luxury goods, but luxury goods typically don't enter into the CPI, which measures inflation. "
] |
[
"(Piggybacking for those who are interested, because this is a poorly-understood topic):",
"Taking it a step further, if we ",
" suddenly facing increased inflation, we could keep it under control via monetary policy (raising the federal funds interest rate) to encourage saving. The increase in spending from the poor, who have a higher marginal propensity to spend (mentioned above), would then be somewhat counterbalanced by those who ",
" have disposable income, who would opt to decrease consumption and increase savings, because saving your money is a more attractive option when interest rates are higher.",
"Normally this works in reverse too-- the Fed can decrease interest rates in order to encourage spending over saving, if the economy is depressed; however, the Fed decreased the federal funds rate to 0%-0.25% in late 2008 in response to the financial crisis, and we can't really go lower than 0% on interest rates to stimulate the economy (though there has been some experimentation with negative interest rates in Europe). This limitation is known as the Zero Lower Bound. The Fed does have one other tool, called Quantitative Easing, where they buy up private securities to 1) inject cash into the economy and 2) keep yield rates on those assets as low as possible, to make them less attractive to investors (again, the goal is to discourage saving and increase consumption in a recession). QE has not been very impactful, but it's the best the Fed can do right now, since we're at the Zero Lower Bound and can't realistically lower interest rates anymore--we have more than tripled the monetary base since 2008, but have seen weak growth and very low inflation since. Too low inflation, in fact. The Fed's stated goal is 2% (though some economists are suggesting it should be 4%), and we've been consistently below target the last 8 years-- in short, we'd be very happy to see some modest inflation right about now. It'd be a sign that the economy is heating back up. ",
"When the Fed runs out of options for effective monetary policy, the next best thing to stimulate the economy is fiscal stimulus, which either means 1) tax cuts and/or 2) spending increases from the government. Generally economists prefer to exhaust monetary policy options before turning to fiscal policy because it is less distortionary to markets. Regardless, since interest rates are as low as they can get, it makes sense to borrow money at low rates to stimulate the economy in the short-term, even if we're at a deficit. Most economists agree that concerns about deficit spending and the national debt were harmful to the post-recession recovery. Yes, you want to reign in your debt eventually, but ",
"I think that's all I got for now."
] |
[
"There are things besides total amount of money that affect inflation if that's what you're asking. For example, if you were to redistribute all the USD, then people might be scared you'll pull a stunt like that again and lose their trust in it. They'll start keeping their money in other forms, causing rapid inflation of USD. There's also things like how much money is saved. If there's a recession people will want to save money for in case they lose their job. They'll try harder to earn money and be more resistant to spending it, causing deflation."
] |
[
"Why does the plot of x^x have such a \"weird\" shape around the origin?"
] |
[
false
] |
At a large enough scale it looks rather uniform, like an exponential function, but it has a rather odd shape around the origin that isn't uniform and doesn't seem to make sense. How come it does that? Why, at around 0.4, does it seem to flip the other direction? I mean, I can see by literally multiplying the numbers that "the math checks out," but it just seems odd. Does the number in which it "flips" directions have any significance?
|
[
"The minimum is at 1/e",
". You can show this by taking the derivative of x",
" (it might help to rewrite it as exp(x log x) ) and setting it equal to 0 and solving for x.",
"If we take the convention that 0",
" = 1, and we know that 1",
" = 1, then if the function remains smooth it has to change directions at least once between 0 and 1. When x is negative though it starts doing weird things because it's no longer a purely real function."
] |
[
"Well it's not a convention that 0",
" = 1, but it is true that the limit of x",
" is 1 as x decreases to 0. "
] |
[
"x",
"=e",
", so its behavior mimics xlog(x). (Compare them ",
"here",
".) Below x=1, there is a push-pull between x and log(x). x is positive and wants to go to zero, but log(x) is negative and wants to go to -infinity. Three things can happen: 1.) x wins and the function goes to zero, 2.) log(x) wins and the function goes to -infinity or 3.) They essentially \"balance\" each other out, in which case the function goes to some point between 0 and -infinity. Obviously, from the graph, the first case happens, x wins and the function goes to zero. ",
"This can be understood by knowing that log(x) changes very slowly, even slower than x. Essentially, intuitively, x approaches 0 faster than log(x) approaches -infinity. This can be seen using L'hopital's Rule, which can be applied to xlog(x) at x=0. First write xlog(x)=log(x)/(1/x), and we can find the limit at zero of this by taking derivatives of 1/x and log(x) to get (1/x)/(-1/x",
") = -x, which gives you the limit of 0 at x=0. In general, L'Hopital's rule is here for us to investigate what happens when there is a multiplicative push-pull between two functions."
] |
[
"How can spectroscopy show the Sun is made of hydrogen when the Sun is a plasma"
] |
[
false
] |
How can spectroscopy show the Sun is made of hydrogen when the Sun is a plasma (and is therefore at temperatures high enough to prevent any electrons from falling back into orbit and emitting the characteristic photons)? I understand the Sun's light comes from it's photosphere which has a temperature of about 5777 K but hydrogen is completely ionized at about 5000 K...
|
[
"Thanks, this was the key. Hydrogen doesn't exist solely in the plasma state until 60,000K (though that comes from the same internets that said it's all ionized at 5000K). "
] |
[
"To some extent that depends on what we call the \"surface\" of the sun - being a ball of gas it doesn't have a surface so much as a point at which that gas becomes mostly transparent. So you have light given off at or below this cutoff point which then passes through the transparent gas beyond and produces an absorption spectrum."
] |
[
"Hydrogen is barely ionized at all at 5000 K. Only around 10000 K does hydrogen become overwhelmingly ionized. The Sun's surface temperature is about 5777 K, and the outer layers of the atmosphere are even cooler, so there is plenty of hydrogen absorption in the solar spectrum."
] |
[
"In psychology, what's the relation between priming and availability heuristic?"
] |
[
false
] |
I've been reading Thinking, Fast and slow by Daniel Kahneman. It's an amazing book which does a pretty good job of explaining wide ranging psychological concepts/phenomena in an accessible fashion. But I do sometimes get confused when concepts are laid out separately and no mention of their relation is given. It could be just me for assuming Priming, which I read in the earlier chapters, has anything to do with cognitive biases like Availability heuristic which comes later on. Is there really any relation between the two concepts? thanks!
|
[
"I assume that there could be a relationship between priming and the availability heuristic. I could for example imagine that people can be primed by the news to believe that airplane accidents happen more often as car crashes since the news usually reports on airplane accident quite a lot while they do this less on car crashes. This might lead to people falsely believe that air crashes are more common as car crashes because they can recall stories of airplane crashes more easily as car crashes.",
"If you mean with priming the subconscious influence by for example flashing a soda bottle for a very short time a lot of times during a movie to increase sales probably not since I have read in psychology textbooks and noticed during classes that this research has mostly been debunked.",
"",
"",
"",
""
] |
[
"Thank you for taking time to respond to this old query. Your first paragraph dispelled my doubts. Thank you. "
] |
[
"Thank you for taking time to respond to this old query. Your first paragraph dispelled my doubts. Thank you. "
] |
[
"How much salt would I need to be able to float in my bathtub as if it were the Dead sea, would it work?"
] |
[
false
] |
Can I use kitchen salt? Why would it work? Why wouldn't it work? If the answer to #2 is no, why does it work in the Dead sea?
|
[
"The general rule of thumb for salt water aquariums is 1/2 a cup of salt per gallon. The Dead Sea is 8 times saltier then that so 4 cups per gallon. The average bath tub holds 50 gallons so 200 cups of salt are need. 1 cup of salt weighs approx .6 pounds so you need about 120 pounds of salt. Mix well until all salt is dissolved. Lay back and enjoy your mini Dead Sea. "
] |
[
"Dead sea salinity is 275 g/kg with nominal density of 1.24 kg/l (wikipedia). Average bathtub is about 150 liters.",
"150 liters -> 186 kg of solution -> 51 kg (115 pounds) of salt.",
"Math checks out, yes it would probably work with kitchen salt.",
"EDIT: See answer below, Dead Sea salinity (33.7%) cannot be achieved at sea level (max 30.7%). Maybe somebody else more expert can say if the saturation point at sea level is still enough for similar buoyancy. Also, ",
"temperature",
" (NaCl curve) doesn't seem to have a big effect on solubility, so warm water won't make a big difference."
] |
[
"No, it does not work. See my answer below",
"edit: Copy and paste so you don't have to search for it:",
"The saturation point of NaCl in water is around 5.27M, about 307g/L (I work in a lab) which is 30.7% w/v. The Dead Sea is at 33.7% salinity due to the combination of other salts present such as KCl, MgCl2, and CaCl2. Apparently pressure has nothing to do with it.",
"Second edit: No clue if 30.7% or 27% such as at the Great Salt Lake is \"good enough\" to float in."
] |
[
"What are the mechanics behind some animals having a good sense of smell?"
] |
[
false
] |
There seem to be several measures of a "good sense of smell". Some animals seem to be able to pick out one scent among many others. Other animals, like sharks supposedly smelling blood in water miles away, seem to be able to sense minuscule portions. Do both these capabilities boil down to the same basic functions? What is happening with the olfactory nerves that certain smells (and the chemicals that comprise them) are more noticeable? Perhaps more to the heart of the issue: why is the difference between our sense of smell and another creature's so great?
|
[
"It's generally put down to the size of the olfactory epithelium and the number of active olfactory receptors genes.",
"That is, the amount of tissue within the nose that has cells that express receptors for picking up smells can vary a lot. A human has about 10 cm",
" of olfactory epithelium, a dog can have up to 200 cm",
" [3]. When we looked atand the number of different receptors an animal can express. A human has about 400 different olfactory receptors [1] while dogs have about 850 [2]",
"This means that there is more area for smell molecules to bump into and hence be sensed (as their impact with a receptor is purely probabilistic) which means their can be less molecules in the air (at a lower concentration) and there can still be a good chance for them to bump into a receptor. This means an animal can smell things are lower concentrations.",
"Having more receptors means that an animal would be more likely to be able to tell two different, but similar, compounds apart.",
"[1] Gilad Y, Lancet D (2003). \"Population differences in the human functional olfactory repertoire\". Mol. Biol. Evol. 20 (3): 307–14.",
"[2] Quignon P, Giraud M, Rimbault M, Lavigne P, Tacher S, Morin E, Retout E, Valin AS, Lindblad-Toh K, Nicolas J, Galibert F. (2005) \"The dog and rat olfactory receptor repertoires\". Genome Biol. 2005;6(10):R83.",
"[3] Mark F. Bear, Barry W. Connors, Michael A. Paradiso (2007) Neuroscience: exploring the brain. 3rd Ed. Lippincott Williams and Walker. Phillidelphia"
] |
[
"Thank you"
] |
[
"What have you heard about quantum mechanics in relation so smell? I once remember a guy (spoke on TED) who proposed that smell has many quantum properties? "
] |
[
"How did they come up with expiration dates? Did they try every situation possible? \"Whole milk room temperature, whole milk refrigerated\" and monitored the food? Or did they just estimate it based on the food's composition?"
] |
[
false
] |
And then counted the number of days the food was sitting there? And then how did they know if it went bad? edit: Thanks everyone for the nice answers.
|
[
"Expiration dates are somewhat arbitrary. The dates on packaging is not regulated or tested. Too many variables affect a food's actual quality to just go by the printed date.",
"A good source on how long ",
"a food lasts",
" and, for extremely durable food, look at the ",
"MRE shelf life"
] |
[
"I used to work for a food manufacturer. To measure expiration dates we would take about 10 samples, store it in a fridge or freezer depending on the product, and test it regulary, varying from daily to weekly. We would compare the shelf life test results against the same product specifications used for general quality assurance, and time it takes for the product to not meet the specfication was used as the expiration date."
] |
[
"Amont the many variables that affect such regulations, there are also political reasons. In Greece there was recently a debate about the expiration dates of milk. If kept at 4 days, it would be practically impossible for central european dairy powerhouses such as Austria to export milk to Greece. They made it 7 days, so now there are more exports to Greece and the local industry, which produces at a higher cost, is now facing a crisis. Obviously, noone even dared mention the possible health effects of the new expiration date, because there were no health consequences. It was all about protectionism."
] |
[
"Can the time periods of seasons change?"
] |
[
false
] |
I don't know if I asked this right. What I mean is, can the seasons change over lots of time that our summer months (June, July, and August) could be "winter-y"? And our winters could be hot? Not including global warming as a factor. Just our planet's course through space.
|
[
"That is actually the reason most calendars that depend on the day/night cycle have leap days/weeks/months/years. In short, if we didn't have February 29th every 4 years, yes, we would eventually shift the seasons around the calendar's year.",
"I.e. Earth's orbit around the Sun doesn't take an integer number of days to complete, so any calendar that depends on daylight cycles would fall out of sync exactly like you described, given enough time (how much time would of course depend on the calendar)."
] |
[
"Cleanest perspective I've seen in awhile. How easily we forget that calendars are arbitrary and not an innate measurement.",
"Makes me wonder what else we measure out of convenience that distorts reality."
] |
[
"For one, June, July, and August are winter months in the Southern Hemisphere already. Because of the way we've defined our season, however, our summer will always be relatively warm compared to winter. That said, the lengths and relative intensities of seasons (at least at a specific location) ",
"can change drastically over 100,000 year cycle",
", this likely controlled the frequency of ice ages over the lat 2.5 million years."
] |
[
"How did ancient man get enough salt in their diet?"
] |
[
false
] |
I recently changed my diet to be more sodium free, and found that very few foods actually have a natural source of salt in them, which made me wonder how hunter-gatherers who don't live near the sea (or even do) got enough salt. How did they even know that they needed it?
|
[
"The body only needs sodium ions, not salt in particular. Sodium is found naturally in plenty of foods: eggs, meat, fish, nuts, raw fruits and vegetables. Pretty much every organic food source has some trace of sodium in it, though admittedly not as much as we eat today. ",
"Which is why people have to go on low sodium diets ;)"
] |
[
"You also need chloride, which you can get from a lot of other sources too, so this isn't entirely true.",
"Basically, you need them both, but they don't have to be together as 'salt'."
] |
[
"Ah yes. The original poster seemed to be asking about sodium in particular, but you're definitely right about the chloride too :)"
] |
[
"Would it be possible to power some machine by 'plugging it in' to the body, resulting in no effort calorie loss?"
] |
[
false
] |
My knowledge of weight loss is basically if you consume less energy than you spend, you lose weight. So if you could spend energy on powering some machine with the energy in your body without actually physically turning a turbine or something, could this make it easier to get to a caloric deficit?
|
[
"Some engineers at MIT have been developing a ",
"fuel cell",
" that runs on glucose for powering implanted medical devices. I suppose you could use that technology to simply idle and consume glucose, but if it consumes a significant amount of glucose, it's going to make a significant amount of heat."
] |
[
"How about it channels it into a usb port so you can charge your iphone on the go?"
] |
[
"So can water, you're going to have to qualify that statement. What mechanism does it kill you with?"
] |
[
"Watching the sun from outerspace."
] |
[
false
] |
Well, in a lot of games you can watch the Sun in outerspace. But I was wondering, can you watch the Sun in outerspace without getting blind/eye damage? Because if you look at the sun from Earth your eyes will hurt a lot. EDIT: Sorry for not setting the right Category, I'm not sure where this belongs to.
|
[
"No, looking straight at the sun while in space without shielding would be blinding. In games this is possible because there is generally not a mechanic for retinal damage."
] |
[
"It depends on your distance from the Sun. If you're in Earth orbit, or closer to the Sun than Earth, yes, it will cause damage. Farther from the Sun, somewhere around Jupiter, the intensity falls below the threshold for retinal damage."
] |
[
"Thanks, thats all I needed to know."
] |
[
"Another Special Relativity Question dealing with time."
] |
[
false
] |
[deleted]
|
[
"It was a joke. Settle down."
] |
[
"I won't try to convince you it was a very ",
" joke…"
] |
[
"There have been too many questions on special relativity and time today. This one maxes out our quota. Please hold off on submitting any more questions on special relativity and time until tomorrow when we reopen for business.",
"The answer to your question is no. There are no fixed points in space, all inertial frames are equivalent, and absolutely none of that has anything to do with \"perception.\""
] |
[
"Over what range of frequencies are superconductors impervious to electromagnetic radiation?"
] |
[
false
] |
I'm assuming that due to the Meissner effect that low-frequency radio energy couldn't reach the interior of a hollow superconductor. I'm also guessing that atomic dimensions are too big to counteract radiation on the scale of gamma rays. Could a sort of super-Faraday cage be made of a superconducting shell, and if so, what range of frequencies could it block to what extent?
|
[
"Looking at some papers about a high temperature superconductor, ",
"they are pretty bad at reflecting UV and higher radiation",
" while ",
"it approaches 50%",
" for wavelengths in the millimeter (infrared) range."
] |
[
"It's a complicated subject. The frequency dependent response of superconductors is an important measurement of their microscopic properties. It varies by the pairing mechanism (which determines the symmetry of the order parameter) and by the specifics of the system you're looking at within a particular class. As far as an EMP, you also need to consider the critical current Jc and the critical field Hc: superconductors are 'perfect' conductors and 'perfect' diamagnets up to the point where they're not. They have a certain amount of current they can carry and a certain amount of magnetic field they can withstand. Above these currents and applied fields, they no longer behave 'right'. They are also quite different for AC vs DC applied current/field."
] |
[
"the best materials can deal with around 30T at near 0K?",
"Quite a bit higher than that. The materials I worked on in grad school had ",
"Hc2(T=0) over 30T",
", and those are by no means record holders: optimally underdoped ",
"YBCO",
" has Hc2 so high that ",
"you can't measure it directly.",
"What is the frequency point where superconductors quit blocking radiation?",
"Like I said: it depends.",
"When the wavelength is some small multiple of the crystal unit cell dimension?",
"No, that's much too small. A crystal's unit cell parameters are usually measured in 10's of Angstroms (1Å=10",
"m). That's why you use x-ray crystallography to look at the structure.",
"Is a type I superconductor reflective (perfectly so?) for frequencies below a certain point then suddenly starts being transparent or absorptive in the soft X-ray range?",
"It's perfectly reflective below a certain frequency (and amplitude) but that frequency corresponds to a wavelength much longer than visible light. It would be reflective to radio and maybe to microwave. x-rays are so far beyond that that you can easily use them to look at the microscopic properties of superconductors without worrying about any reflective effect of the 'perfect' conductivity."
] |
[
"Is it possible to rip a black hole into two pieces? How might that happen, and what would happen?"
] |
[
false
] | null |
[
"I must apologise for the terse reply of my fellow panelist but he is correct. ",
"The really important part of the black hole is the singularity at its heart. A singularity is not an object with size in any real sense, so the notion of halving one is tricky.",
"Don't make the mistake of conflating a black hole with its event horizon, this is simply the point-no-of-return boundary that surrounds the singularity (saving the universe from a scandalous glimpse of a naked singularity - my jokey tone is due to this being related to something called the Cosmic Censorship Conjecture). The event horizon is not so much a thing as a condition, so ripping this in half this would also be difficult."
] |
[
"No."
] |
[
"Getting tired of talking about black holes? X)"
] |
[
"CO2 levels above 945ppm, a normal rate in indoor environments, have been shown to reduce cognitive function by 15%. What is the most efficient way CO2 can be removed from indoor air in situations where ventilation is not feasible?"
] |
[
false
] |
Study Referenced: Cognitive function scores were 15% lower for the moderate CO2 day (~ 945 ppm) and 50% lower on the day with CO2 concentrations of ~1,400 ppm than on the two Green+ days (Table 5, dividing the average Green+ estimate by the moderate CO2 and high CO2 estimates, respectively). Are algae scrubbing setups an efficient solution to converting the CO2 in the air into O2? edit: I should clarify that I'm looking at solutions an individual can use in their home.
|
[
"The International Space Station uses ",
" zeolite to scrub CO₂ by ",
" adsorption, and the ",
" zeolite can then be regenerated by heat. The equipment is called the Carbon Dioxide Removal Assembly (CDRA).",
"*edit: zeolite not LiOH per ",
"/u/RuNaa",
"'s comment below."
] |
[
"Houseplants. ",
"https://www.mnn.com/health/healthy-spaces/photos/15-houseplants-for-improving-indoor-air-quality/a-breath-of-fresh-air"
] |
[
"After planting a few succulents in my spiders' enclosures, I didn't some research to see if they could produce enough oxygen to keep a spider alive on their own. During that research, I read that the total decrease in CO2 one can expect from a reasonable number of plants is insignificant. Much less than 1%, if I recall correctly. ",
"It seemed to imply that no viable mass of house plants could possibly compete with the CO2 consumption of an adult human. The article was aimed at criticizing other articles for simply stating that \"plants clean the air because they turn CO2 into oxygen\" without actually doing any math on it. I wish I had time right now to hunt for that article again. Maybe someone can link another reference that did the math. "
] |
[
"Does gravity affect itself?"
] |
[
false
] |
Does gravity have an affect on itself, weaking its external force on other objects?
|
[
"Gravity does self couple. The gravitational field created by mass itself has mass and this changes the gravitational field. This is why the field equations are non-linear."
] |
[
"Einstein's field equations for General relativity, equate the curvature of spacetime (and any gravitational effects) to the energy/momentum density of spacetime. It's a complicated set of equations, but it is fairly easy to see that no, gravity does not self couple."
] |
[
"This is actually a research topic on general relativity (GR) and leads to heated discussions between experts. There is no well defined \"energy\" term for gravity, which means it does not formally appear as a source for itself in the field equations (in technical terms, there is no stress tensor associated with it).",
"Nevertheless, the non-linearity of the equations do make gravity appear as a source for itself in a non-linear wave equation (this is covered, for example in Alcubierre's 3+1 numerical relativity). ",
"The whole viewpoint of gravity as curvature make the definition of \"gravitational energy\" a tricky subject, and hence what it means for it to interact with itself.",
"Technical note: When space is flat \"far away from gravitational sources\" one CAN speak of a GR gravitational energy. Google is your friend."
] |
[
"At what point did Earth become... Earth?"
] |
[
false
] |
What I mean to say is at what point can scientists say that Earth existed? I often hear the number of ~4.5 billion years as the age of our fair planet, but based on the prevailing theory of accretion and protoplanets, at what point did this planet go from being a protoplanet to being Earth? At what point can we say that the planet was no longer forming, and was formed? I hope I'm wording this well enough, but I feel like I often have a hard time articulating this question, and I've yet to receive a thorough, satisfactory answer. Anyone able to shed some light on this for me?
|
[
"It is still \"forming\" as you put it because it has a molten iron core and plate tectonics. If you are talking about habitable to life it would be around 4 billion years ago. \"The name Earth originated from the 8th century Anglo-Saxon word erda, which means ground or soil. In Old English the word became eorthe, then erthe in Middle English. Earth was first used as the name of the planet around 1400."
] |
[
"The formation of Earth refers to getting all the mass that makes up Earth to Earth. It has nothing to do with volcanoes or plate tectonics. It is only a question of the material getting to Earth."
] |
[
"The formation of Earth is a well defined question. Once Earth finished accreting Earth was formed. The fact that heat is left over doesn't affect when Earth formed. It affects Earth today but the formation ended long ago."
] |
[
"How does human muscle fiber compare to that of other animals?"
] |
[
false
] |
Let's say that we are comparing 180 lb. specimens and that all have the same amount of muscle fiber, say roughly 75 lbs. or so. In terms of strength, endurance, explosiveness, etc. how would the muscle in the human compare to other mammals (jungle cat, bear, gorilla, etc.)? Is it pretty much the same stuff or is there a significant difference? Also, how would human muscle compare to things not as closely related i.e. insects, reptiles, birds, fish, etc.
|
[
"I don't know of any specific studies to point you to, but I do remember that one group of scientists had done this study among primates. Turns out a female orangutan (in heat)is pound for pound the strongest primate. They tested using a one-arm pull test. Humans max out at around 200 lbs.-maybe 400 pounds if your a mutant. Female orangutan in heat 1800lbs pulled/dragged with one arm!! ",
"I also remember reading once that dolphin and whale's muscle strength is about the same as a human's - they just have so much more muscle mass that it gives them the power to jump above the water line. "
] |
[
"Thanks!"
] |
[
"I don't know much about the differences in muscle fiber between species, but I'd like to point out that bone/tendon/muscle geometric arrangement accounts for much of the differences in strength between humans and other animals.",
"Compared to most other animals, including our closest primate relatives, human limbs are comparatively long, and our muscles attach closer to our joints, meaning we have less leverage, and therefore less strength, even if our muscles were otherwise exactly identical.",
"The human body evolved more for efficiency and stamina than raw strength"
] |
[
"Why do some animals move in quick bursts (like chickens/small lizards) while others are more deliberate (like humans/bears)?"
] |
[
false
] | null |
[
"The short answer is: smaller animals are more agile, and usually move in quicker bursts, than larger animals, because they have less momentum. A lizard's head/legs/whole body weighs much less than a bear's. Because of this, very little momentum is required to start and stop the movement of the small animal's body.",
"Things at rest tend to stay at rest, and things in motion tend to stay in motion. The more mass a body part or whole body is, the more difficult it is to start movement and stop movement of that body part or body.",
"Edit: as an addition to this, smaller animals usually have more strength per their amount of mass. (Eg. ants being able to lift 1000 times their body weight). Large amounts of (relative) strength and low mass to have to start and stop (low momentum) leads to small animals being quicker than larger ones."
] |
[
"I think we, if we had our same brains, would still move more like a chicken if we were lighter, but that's an interesting question. You are wondering if larger animals are maybe more 'calculating' in their movements, and therefore would use less small, rapid movements because maybe those movements are wasteful?",
"I think it's absolute true that intelligence/psychology will influence how an animal moves. But I believe that if you put any animal, large or small, in a sudden fight or flight situation, the quickness/agility of its movements will be mostly based on its size and muscle-to-weight ratio.",
"That being said, I could be wrong, and would love to hear if you find out something different."
] |
[
"This makes sense, but I’m wondering if there’s a sort of psychological component. As in, if we were much lighter, would we still move like a chicken with out more complex thinking patterns? "
] |
[
"Is it bad to have my laptop resting on my reproductive area while laying in bed?"
] |
[
false
] |
i am in currently in this position as i ask.
|
[
"If you are a male, your most pressing issue would be any heat produced by the laptop. Exposing your scrotum to heat will decrease the viability of your sperm. This affect can last several weeks to several months, depending on how often and the duration that you expose yourself to this additional heat. There are actually methods of birth control that utilize heat to temporarily sterilize men.",
"http://en.wikipedia.org/wiki/Heat-based_contraception",
"Another, though much smaller factor, is potential radio signals emanating from your laptops wireless, bluetooth, cell modem, etc. I believe I read a study that cell phone radiation can slightly decrease sperm motility, though it has no effect on count.",
"Radio Frequency Electromagnetic Radiation (RF-EMR) from GSM (0.9/1.8GHZ) Mobile Phones Induces Oxidative Stress and Reduces Sperm Motility in Rats",
"Male albino Wistar rats (1012 weeks old) were exposed to RF-EMR from an active GSM (0.9/1.8 GHz) mobile phone for 1 hour continuously per day for 28 days. Controls were exposed to a mobile phone without a battery for the same period. The phone was kept in a cage with a wooden bottom in order to address concerns that the effects of exposure to the phone could be due to heat emitted by the phone rather than to RF-EMR alone. Animals were sacrificed 24 hours after the last exposure and tissues of interest were harvested. RESULTS: One hour of exposure to the phone did not significantly change facial temperature in either group of rats. No significant difference was observed in total sperm count between controls and RF-EMR exposed groups. "
] |
[
"Yes. ",
"Its always bad to put a laptop on a fabric surface. Fans blow out hot air and suck in cool air. When your laptop is on your pants its sucks up lint and dirt and this can gunk up your computer, possibly burning out fans and causing damage from overheating (I've seen it happen)."
] |
[
"Just took Fertility, Sterility, and Mammalian Development. It will slightly decrease your sperm count briefly, but there haven't been outcome-based studies that have effectively addressed the actual effects. When sperm are maturing, it happens in the sertoli cell. Heat variance can effect the binding between the sperm and these supportive cells. If the temperature rises too high for a long enough time, the sperm cells will detach prematurely resulting in inviable sperm. Seeing as you make hundreds of thousands per day, though, it probably won't matter much. They've done measurements and biophysical calculations to see how the laptop radiates heat throughout the pelvic area, and they've shown/calculated a significant increase. They've also shown, however, that the mere position of laptop usage (thighs together, testicles entrapped) causes a very similar heat increase. My professor is under the impression that the sitting position probably has a lot more to do with it than the actual laptop usage. ",
"tl;dr Yes, on a small scale, but occasional laptop usage doesn't seem to have any lasting or significant negative effects. ",
"edit: spelling and grammar"
] |
[
"If a Normal Person with a Healthy Weight Started Consuming Only Water and Vitamins, How Long Could They Survive?"
] |
[
false
] |
I saw a video recently that mentioned a ~500 pound man who went over a year without any caloric intake, and consumed only water and vitamins. Under the same conditions, how long could a normal weight human do the same thing? I've always been told that people can go 2 to 3 weeks without food, but usually, that was in the context of surviving in the woods, where one likely wouldn't be receiving the necessary amount of vitamins. Also, what all would start happening to our bodies? And would there be any differences between longevity of males and females?
|
[
"2-3 weeks on the short end. Here's a very long medically supervised fast, described in great detail, which ",
"lasted 382 days (Post Graduate Medical Journal - 1973)",
"."
] |
[
"I would be worried about the health of the intestinal lining and flora. I scanned the study, and didn't see any information about how they reintroduced the subject back to normal food. I would love if a gastroenterologist (or someone who knows) could chime in!"
] |
[
"\"No faecal collections were made, but evacuation was in fact infrequent, there being 37 - 48 days between stools...\""
] |
[
"How do unvaccinated individuals put vaccinated individuals at risk for viruses like Measles?"
] |
[
false
] |
There's an article on the front page about how "anti-vaxxers" have brought back the measles in places like New York City, where outbreaks are now occuring. I understand how these people can catch the virus and spread it amongst other unvaccinated individuals (including toddlers too young to be vaccinated), but the article seems to suggest that these anti-vaxxers are putting us all at risk. How is it that someone who is vaccinated against measles has increased risk under these circumstances?
|
[
"No medication, or vaccine, is 100% effective.",
"A lot of what we consider the effectiveness of vaccines, is that if you can get x% of the population vaccinated, the target disease fails to infect enough hosts to continue to survive, and essentially dies off in that population (or herd).",
"So, even if my vaccine doesn't directly protect me, I'm indirectly protected by being surrounded by people who are immune and who cannot form a part of the pathogen's life cycle.",
"The common nonsense statistic that anti-vax people sprout is that \"there are more cases of measles in vaccinated people than non-vaccinated people\" - an argument which is simply rubbish in every sense. ie. there are many fold times more people vaccinated, so the relative small proportion who remain susceptible to disease numerically outnumber the small number of unvaccinated people who are also unlucky enough to contract a disease despite general herd immunity.",
"Additionally, vaccines tend not to last too long - pertussis, for example, tends to wear off by the time we reach adulthood. This is not a major problem for the adults of the world, as whooping cough is mostly a nasty inconvenience at that stage of life, rather than the life threatening disaster it is in infancy. But a raft of unvaccinated children can produce a reservoir of pertussis hosts, which then infect a bunch of adults who can then go on to infect a bunch of vulnerable groups - such as new born babies and frail elderly.",
"So, in ",
" form, it is all to do with the available reservoir of hosts to be infected, and the herd immunity working to protect the proportion of people for whom the vaccine doesn't directly protect - hence, anti-vax people indirectly (and some would argue directly) threaten the health of everyone else around them."
] |
[
"I think this argument has been turned around. No doctor really cares if a healthy vaccinated adult contracts the measles. What they are concerned is whether infants including infants in utero, young children, or immunocompromised individuals get infected as they are vulnerable.",
"The concern about healthy adults, vaccinated or not, contracting vaccine preventable illnesses is less to do about concern for the healthy adult and more to do with concern that this healthy adult can spread the disease to a vulnerable person. ",
"In all areas of life, in all countries, it is the very young, the very old, and the pregnant that suffer. You get vaccinated for their benefit not for yours. ",
"Addit: and the folks who decline vaccination, they're not taking any risk for themselves. They are risking the wellbeing of infants, children, and pregnant women with whom they have contact. That's why many doctors, rightly or wrongly, think that vaccine refusing people are scum."
] |
[
"I presume you are talking about ",
"this",
" article.",
"The point behind vaccines and getting \"everyone\" vaccinated is to cultivate herd immunity. This is where you have perhaps 80% of the population that will not become sick and spread disease. Vaccines are not 100% effective; depending on the ",
"vaccine",
" you will have probably 50-90% coverage (so like 50 people out of 100 vaccinated will be protected). The goal here is to stop disease from spreading easily so that it will die out. With more and more \"anti-vaxxers,\" you lose the coverage of herd immunity and allow people who are susceptible to become sick and the more people are susceptible, the easier it is to get an \"outbreak.\" Keep in mind, it isn't just people who are anti-vaccine; there will be people who can't get the vaccine due to health issues or allergies to vaccine contents.",
"I'm not sure if I've painted the best picture, but think about it this way, you have a group of 1000 and all of them have been vaccinated against measles. Let's say the vaccine has an 80% efficacy rate and to keep it simple, we won't go into how some people may become infected, but not show disease; either you're protected or you're not. So, an infected person joins this group of 1000; 800 of which are not going to catch or pass on the disease. This means that this 1 would have to come into contact with at least 1/200 of those not protected. At most, you will see 200 people get sick with measles and the rest are fine (that would be a crazy-impressive outbreak, I don't think everyone would get sick, it would be a fraction). ",
"Now think about how many people out of 1000 refuse to get vaccinated or can't. I'm not looking up those numbers because I'm lazy, but let's say only 800/1000 get vaccinated...that means that 640 people are protected and now 460 people are at risk of becoming ill from that one infected person.",
"Getting EVERYONE vaccinated is important. You yourself might not be protected, but it's not completely for personal reasons. It's done for the community."
] |
[
"What do we mean when we refer to the age of the universe?"
] |
[
false
] |
If gravitational time dilation means that the speed of a clock is affected by the mass in the local area of space, then different physical regions of the universe will have different times elapsed since the big bang. The age of the space inhabited by the solar system will be different to that in the intergalactic vacuum. Wouldn't the vacuum observer come up with a different age? What exactly is it that is 13.772 billion years old?
|
[
"The age of the universe is computed in a ",
"comoving reference frame",
", a specific reference frame where the cosmic microwave background is isotropic -- also sometimes called the \"CMB rest frame.\" This frame essentially has the minimum possible proper time elapsed since the CMB. Other reference frames, such as ours here on Earth, will have very slightly longer elapsed time due to both gravitational and velocity-caused time dilation, but that slight increase is well within the error bars of of the calculation (about 21 million years) so it can largely be neglected.",
"By a back of the envelope calculation, the time dilation due to Earth's peculiar velocity would be only about 10,000 years more; I'm not able to do the calculation for gravitational time dilation but I can't imagine it's much larger than that of the peculiar velocity, if it's larger at all. For reference, GPS satellites are also affected by both gravitational and velocity-based time dilation. For a GPS satellite, the gravitational time dilation is about an order of magnitude larger, but GPS satellites are also moving a lot slower relative to Earth than Earth is moving relative to the CMB isotropic frame (3 km/s compared to 370 km/s). A quick Google search suggests that the difference due to gravitational time dilation between the Earth and a position in intergalactic space (out of any significant gravitational potentials) would be about 1 second difference for every 32 years passed -- meaning, over the roughly 13.8 billion years of the universe's history, the difference would be on the order of 14 years or so in total ... much less than the time dilation due to peculiar velocity, and ",
", much less than the error margins on the age of the universe.",
"Hope that helps!"
] |
[
"the time dilation due to Earth's peculiar velocity would be only about 10,000 years ",
"The age of the universe is the CMB frame is the ",
" possible age of the universe. Any observer in motion with respect to the CMB frame will measure that the universe is ",
" younger. In principle, we could imagine some path in spacetime that has arbitrarily large velocity with respect to the CMB frame, and so the age of the universe can be arbitrarily small."
] |
[
"Yeah, you're right, it's my bad. I was too focused on looking at the difference in magnitude of the effects, and not on whether it went one way or the other. I guess I glossed over it since the point I wanted to emphasize was why the difference in magnitude compared to the error bars made compensating for the effect not important, but I should have paid more attention to that aspect and made sure I was keeping the concept straight and using the right language for it, rather than just focusing on the scale and digits. :( Thanks for the correction!"
] |
[
"Why is it so hard to make a vaccine for the Herpes Simplex Virus?"
] |
[
false
] |
[deleted]
|
[
"you can check out ",
"this article",
" which describes the efforts to making a vaccine against Herpes. If you've got a bit more biology under your belt, ",
"this article",
" is about how the herpes virus works, and includes some of the biology of why its hard to make a good vaccine.",
"A couple main points I'll list for brevity, are that 1) we really don't know the mechanisms behind this virus' latency, 2) we don't know a whole lot more about the virus' pathogenicity, 3) we don't know that much about the immune cells' recognition of this virus. ",
"(when I say \"we don't know that much\" I mean \"at the biochemical level, we don't have good molecular targets for drug/vaccine testing\") "
] |
[
"it's pretty high on my list. does that make me selfish?"
] |
[
"thank you!"
] |
[
"Does climate science predict we've warmed the earth in the first place?"
] |
[
false
] |
We hear a lot about temperature reconstruction in the past up to the present. Ostensibly, the temperature has been increasing, and this is often said to be what climate models predicted. But is it? My only evidence for doubting this is this figure: This shows the expected value of total anthropogenic radiative forcing is positive... but the error bars are huge. In fact, the point of 0 is less than 2 standard deviations away from the expected value. That means that there is over a 2% chance that humans have caused no net warming. I'm just eyeballing, and I think it's probably more like 5%. This doesn't change the future predictions. If we continue to emit CO2 then the total forcing will increase dramatically and soon diminish the possibility that we've had zero net warming effect to functionally zero. But the media and scientists keep speaking of climate reconstructions as if it was predicted by science. Isn't this wrong? Isn't it true that science has only predicted a 95% or so chance that we've had a net warming effect in the first place? Have I read the graph wrong? Is this outdated? Notice: if successful I may cross-post this in the future to
|
[
"Those aren't standard deviations, they are 90% confidence intervals. The graph indicates that the available data suggests the total anthropogenic forcing is somewhere between +0.6 and +2.4 W/m",
" with a 10% chance that they lie outside of those values (either above or below)."
] |
[
"I am not an expert in climate science, but I will note that those error bars are not showing standard deviations. They are in fact 90% confidence intervals. See here for the original figure caption:",
"http://www.ipcc.ch/publications_and_data/ar4/wg1/en/tssts-2-5.html"
] |
[
"Ah, that would change things. This is a strange metric though. I'm currently calculating the 90% confidence point to be about 1.16 standard deviations, my work: ",
"http://www.wolframalpha.com/input/?i=solve%28+erf%28x%29%3D0.9+%2Cx%29",
"Then, if we use your numbers of 0.6 and 2.4 we can find how many standard deviations the mean is at. We have the mean at 1.5, and then (1.5-0.6)=1.16 sigma. That gives the standard deviation to be about 0.77, and still comes to the conclusion that 0.0 is almost exactly 2 standard deviations from the mean. It's a small revision, but it still decreases the cumulative probability of net warming being below zero to 2%. But I'm not sure, I think I might have had a problem in my use of the error function here."
] |
[
"Will de-ionized water still heat up in the microwave?"
] |
[
false
] |
[deleted]
|
[
"Yes. The ",
"mechanism for microwaves passing energy to water",
" (",
"dielectric heating",
") does not depend on the ionic strength (salt content) of the water. Salt water or low ",
"TDS",
" water will heat up in a similar fashion."
] |
[
"Microwaves heat water molecules directly.",
"http://en.wikipedia.org/wiki/Microwave_oven",
"Water, fat, and other substances in the food absorb energy from the microwaves in a process called dielectric heating. Many molecules (such as those of water) are electric dipoles, meaning that they have a partial positive charge at one end and a partial negative charge at the other, and therefore rotate as they try to align themselves with the alternating electric field of the microwaves. Rotating molecules hit other molecules and put them into motion, thus dispersing energy. This energy, when dispersed as molecular vibration in solids and liquids (i.e., as both potential energy and kinetic energy of atoms), is heat."
] |
[
"It will heat up. However, be very careful about doing this: there may not be sufficient nucleation sites for the water to ",
", especially with quality smooth glassware and a nonrotating microwave. Much like supercooled liquid water freezing when shaken, superheated water can explosively boil upon the introduction of a fork, spoon, stirring rod. Unlike flash-freezing, the explosion of 100+C water onto your hand is not a pleasant experience."
] |
[
"Can the distribution of protons to neutrons within the nucleus affect the shape of the orbitals, and through that the location of the electrons?"
] |
[
false
] |
If somehow the distribution of the protons & neutrons in the nucleus is such that protons are on the 'right' and the neutrons are on the 'left', wouldn't this create a more positive electrostatic charge towards the right of the atom, so it would be more reasonable to stay electrons are found there, correct? Through this I would assume the shape of electron orbitals are not static in shape, but subject to change depending on the distribution of the protons & neutrons within the nucleus. I'm only an A-level student so if you do know the answer on how I'm mistaken/whether I'm right, please don't use too much scientific jargon.
|
[
"Sort of. The overall structure of electrons around a nucleus is largely determined just by the charge. Quantum mechanics allows us to figure out how the electrons are organized based on the electrostatic attraction.",
"Then there is something called fine structure, where the energy levels of different electron states (3p vs 3d for example) is slightly different due to small factors, including magnetic interaction between the electron and the nucleus, and relativistic effects.",
"Then there are even smaller changes in the energies, and this is called hyperfine structure. This is where effects due to the shape of the nucleus, the individual magnetic moments of the protons and neutrons, and the electric field gradient come into play. The effects you're interested in are hyperfine."
] |
[
"That is really cool, thank you. With that in mind, then, are the effects near negligible? "
] |
[
"Well, it depends how precisely you measure it. Hyperfine transitions are very important for astronomy and also materials science and atomic physics. The second is defined based on a hyperfine transition in cesium."
] |
[
"With the big bang theory of inflation, what caused matter to slow down?"
] |
[
false
] |
So I was reading about how after the big bang . So what caused the expansion to stop after that fraction of a second. That seems like a pretty extreme change in speed especially without friction in space. Was it dark matter? Or if we technically never stopped and the universe is still moving at the same speed, why don't we see drastic gaps between stars getting bigger because I would assume the stars that made it further away from the big bang were moving at a higher rate of speed than the ones who didn't quite make it as far from the point of origin. Also after watching some other documentaries, an expansion that quick would have to move faster than the speed of light, and anything moving faster than the speed of light would actually be going backwards in time... Could time itself be what slowed down matter? Sorry all of this Neil Degrasse Tyson is getting to my head.
|
[
"I'll let actual experts answer your questions, simply wanted to note that this",
"I would assume the stars that made it further away from the big bang were moving at a higher rate of speed than the ones who didn't quite make it as far from the point of origin.",
"is based on an incorrect premise. There is actually no \"point of origin\" for the Big Bang. It is space itself that is expanding, which means that inflation made space itself bigger. One of the common examples given is how the points on a balloon all get further away from each other when the balloon is inflated...you just have a imagine a four-dimensional balloon with galaxies on its \"3D surface\"... :-) Edit: found this ",
"illustration for the balloon analogy",
".",
"Also, if the theory is correct, inflation only lasted for a very short time (a very small fraction of a second). The universe has continued to expand since then, but at a much reduced rate (which is why a distinction is made between \"cosmic inflation\" and \"expansion\")."
] |
[
"You're complaining because we don't yet have a complete theory of what happened 10",
" seconds after the big bang?",
"The theory explains some of the phenomenology, but not all. This is the case with nearly every scientific theory ever invented. Scientific progress involves reducing the unexplained stuff, but I doubt we'll ever see it go to zero. "
] |
[
"So what caused the expansion to stop after that fraction of a second.",
"The expansion didn't stop, only the acceleration. The universe continued to expand.",
" the acceleration started and stopped is not a solved problem. It is postulated that it was caused by a field (similar in many ways to the dark energy that fills the universe now and causes the expansion to accelerate), but the dynamics that started and stopped the exponential expansion is not known.",
"/u/archiesteel",
"'s comment address some of your other questions."
] |
[
"Would dust storms on Mars really be as bad as portrayed in The Martian?"
] |
[
false
] |
I understand the winds get up to ludicrous speeds, but with the air pressure at 0.06 atmospheres would it be as damaging as the book/ movie portrays?
|
[
"No. The most violent windstorm on Mars would feel only as strong as a stiff breeze. That's why, at the climax, it was reasonable for the orbital vehicle to take off with only canvas in place of its armored nose cone. ",
"The author has said in interviews that he knows this was a scientific inaccuracy. He used the sandstorm as a plot device anyway because he wanted a natural reason for the astronauts to be evacuated and separated. "
] |
[
"How is the dust toxic?"
] |
[
"Absolutely not. Even the most 'violent' storms on Mars barely have more push than the force exerted by you exhaling normally. The dust kicked up in these storms however is really bad. It's toxic (so you need to clean your suit before taking it off) and it will get in to ever seam or hole of every machine on mars. "
] |
[
"If Covid-19 mutates to the point that the vaccine will be ineffective, will it be easier to make a new one or it’ll take the same amount of time?"
] |
[
false
] |
[deleted]
|
[
"It took 2 days from obtaining the SARS-CoV-2 genome to formulating the vaccine and less than 4 weeks to manufacture the first batch of vaccines (",
"source",
").",
"If a new variant were to emerge that would require a new vaccine, it would probably be created in a similarly short time. It's the trials that take the bulk of the time."
] |
[
"Similar to the influenza vaccine it's possible that small modifications of existing vaccines could be approved faster."
] |
[
"Also, even if we decided to approve them rapidly, it would still take quite some time to actually manufacture the updated vaccine in sufficient quantities. The current vaccines are able to be rolled out so quickly after approval because they've been manufacturing them for months prior."
] |
[
"Why is the value of e, e?"
] |
[
false
] |
I am talking about the natural constant. I am wondering why e shows up everywhere. Why is it that very different things resemble e? For example, continuous interest has e in its equation while the amount of electrons in a capacitor has a natural logarithm (log base e). Why is this so? I assume e is just a number just like pi is pi because it is.
|
[
"The constant e (",
"Euler's Number",
") has a unique property -- it perfectly represents the rate at which natural systems grow or decay.",
"I might start out periodically increasing a quantity by some ratio, say, 10%, like this:",
"x' = (x+x/n)",
"If n = 10, then x' = x * 1.1. So I have increased the value of x by a desired ratio. But let's say I want to do this repeatedly, like a bank account or the growth of a biological colony. But let's say I would like to make the increase smoother than it would be if I increased the value by 10% per step as in the above example.",
"I realize I can perform the above operation many more times, but each time with a smaller amount of increase. Like this:",
"x' = (x+x/n)",
"This time, I make n a larger number, so the increase more closely resembles a smooth, natural slope such as one might see for a large biological colony.",
"The it occurs to me that there might be a number that summarizes this way of performing the operation,a number that embodies natural growth. I decide to locate it using a limit expression based on the above example:",
"[; \\displaystyle e = \\lim_{n \\rightarrow \\infty} (1+\\frac{1}{n})^n ;]",
"That is e, Euler's number, approximately equal to 2.71828 . This number is uniquely suited to modeling natural growth patterns - compound interest, population growth, any system whose future growth depends on its past growth.",
"The number e also has some surprising properties tied to its unique status. One example is that the derivative of e",
" is e",
" , and the integral of e",
" is e",
" also. This property only holds for this very special number.",
"EDIT: correction"
] |
[
"Small gripe, it's actually Euler's number, not constant. ",
"Euler's constant",
" is an entirely different number."
] |
[
"That's what he said, that's the limit that defines e",
" ",
"lim n->infinity (1 + x / n)",
" = e",
"\n, not e. ",
"e = lim n -> infinity (1 + 1/n)"
] |
[
"Nuclear Bombs dropped in the same location"
] |
[
false
] |
If multiple nuclear bombs (let's say 3) where to be consecutively dropped in the same exact location would the blast radius (or total area destruction)increase. Let's say they were 1 megaton each and dropped, (perhaps, 10 seconds apart) would the blast radius expand? Or would it decrease due to the crater deepening? All factors apply (except radiation/fallout). Also sorry for the excessive use of "Let's Say"
|
[
"I don't know about 10 seconds apart, but the Pacer Project at Los Alamos created designs for a generator that would have been powered by small nuclear weapons detonating repeatedly in an underground chamber. One source claims the final design spec'd 45 minutes between explosions, which sounds a bit fast. AFAIK it was never built due to design difficulties, but it sounded like the cavity was expected to stop expanding after the first few explosions."
] |
[
"If it were physically possible to detonate bombs in the same location in such quick succession, I would imagine the blast radius would increase because you're increasing the pressure in the area, forcing more and more air from the central point. I doubt it would be all that noticeable though, other than having multiple blast waves and such."
] |
[
"Thanks! That clears some things up."
] |
[
"Why are comet trajectories difficult to predict?"
] |
[
false
] |
I've heard it said that comets do exactly what they want...meaing that it is notoriously difficult to forward model their trajectories. Why is it so difficult to measure and predict the orbit of newly discovered comets, given our knowledge of mechanics and our astrometric capabilities?
|
[
"The other issue with comets is they melt. This melting can produce geysers of material which act as a rocket booster changing the comets trajectory."
] |
[
"indeed, although the effect is extremely small, the chaotic nature of the orbit makes it very important."
] |
[
"I would think that the large bodies that affect them would be limited to the Sun, the 8 planets, and a few other largish asteroids and trans-Neptunian objects. Since we know these orbits extremely well, we should be able to do better for short duration events like astroid approaches. I know that > 3 body orbits are impossible to predict over long time scales, but short time scales seems like it should be doable, when only a few things dominate the gravitational pull. What's wrong with my thinking?"
] |
[
"Why do protons not repulse themselves in atom nuclei?"
] |
[
false
] |
As particles with positive charge, they should NOT be aggregated. Why then are atoms (such as, lets say, uranium) posible?
|
[
"Protons ",
" repel each other due to the Coulomb force. However the Coulomb force is not the only force present in nuclei. There is also the residual strong force between nucleons (and the weak force, which has relatively minor effects on the structure of nuclei).",
"The residual strong force is usually attractive, and tends to be much stronger than the Coulomb force."
] |
[
"this webpage has a handy graph explaining just that",
"strong force graph",
" "
] |
[
"One way to think about this is in terms of two major forces acting on protons in a nucleus.",
"The first as you note is electromagnetic repulsion (Coulomb force). Like charges repel like, so positive protons should repel positive protons. Protons ought not like to be next to each other.",
"But the second is the so-called strong force or strong interaction. You can think of this as a force that basically says that at very short ranges, nucleons (which is to say, both protons and neutrons) are strongly attracted to each other. So in this case, protons and neutrons ",
" like to be next to each other — but only at very close distances (but not ",
" close; there is a limit). ",
"So heavy nuclei are possible because they have neutrons in them, which act as a stabilizing force. You'll see from the periodic table that you can't just randomly pile neutrons in and have them be stable. Even uranium, which is ",
" stable (half life in the billions of years) does not have any fully stable isotopes, and indeed, everything heavier than lead is a little bit unstable and may eventually undergo radioactive decay. Uranium-238 has 92 protons and requires 146 neutrons to be as stable as it is. ",
"You might say, what if you just ",
", does it get more stable? For a variety of reasons, no. One interesting consequence of the strong interaction is that it is between individual nucleons, so at some point you'll just overtax its ability. Uranium is just about at the boundary where the strong force can hold the whole thing together, which is why if you jostle a uranium nucleus with a neutron of the right energy, it'll warp just outside of the range of the strong force. When that happens, the Coulomb forces kick in with a vengeance, and treat the nucleus as if it were two highly-positively charged halves. This causes them to repel form each other with tremendous violence, like two cannon-balls. This is nuclear fission, the splitting of the atom. ",
"Similarly, if you think about trying to combine two nuclei, as in nuclear fusion, the major force that's going to be acting on them at most distances is their electromagnetic forces — they're going to repel if you try to put them too close to each other, just like the two positive ends of two magnets do. But if you can get them close enough together than the strong force kicks in (\"beyond the Coulomb barrier\"), then they'll happily merge into one nucleus. This is why nuclear fusion requires ",
" high pressures and/or high temperatures — this overcoming of the Coulomb barrier.",
"The above explanation oversimplifies a lot of complexity but is just meant to give you a little understanding of why understanding these two forces opens up a lot of basic understanding of how nuclei work. There are other things going on in the nuclei, so many caveats included, etc."
] |
[
"What would happen if the moon had a geostationary orbit?"
] |
[
false
] |
Hello! Please let me know if this has already been answered and I'll delete it, but I had a question (Frankly, an idea for a science fiction novel). What would be the effects on the earth if the moon had a geostationary orbit? I'm assuming that it would be at the equator, and closer to earth than it is now, but what other things would happen? Would there be a permanent solar eclipse over an area of the earth? How would tides/gravity be affected? Would it be devastating to us? Alternatively, how small would a moon have to be to not have devastating effects on a planet in geostationary orbit? Any help would be much obliged.
|
[
"This is actually the case for Pluto and Charon: they are tidally locked to each other, so Charon is always in the same place in Pluto's sky and vice versa. The moon is tidally locked to the Earth but the Earth isn't tidally locked to the moon or to the sun. ",
"There could potentially be a solar eclipse every day. It would also mean that there is one place on Earth that is directly beneath the moon. Half the planet would never see it. Tides would be much stronger.",
"A lot of exoplanets are tidally locked to their stars, meaning there is one spot that is right beneath the sun."
] |
[
"Tides would be much stronger",
"Tides happen because the bulge in the oceans rotates with the moon at a different rate than the Earth spins around its axis.",
"With the moon at fixed point there won't be any tides. The sea level will be constant (ignoring the Sun's effects) albeit with a higher sea level at some parts of the planets than others."
] |
[
"This is the definition of tides from wiki:",
"Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth.",
"There won't be any tides (there is no periodic change), but there will be a bulge (as you state it will be stronger)."
] |
[
"Etiology. Isn’t “where to begin” the ultimate question?"
] |
[
false
] | null |
[
"Etiology’s short-comings are “at root”* that we as a species are literally detached from our environment—the natural cycles of our earth and the solar system too have become strangers to us. The origins of change in general then are “ beyond us” & yet the “burden of proof” so near.",
"*pun intended"
] |
[
"medicine"
] |
[
"medicine"
] |
[
"How do far away space probes like New Horizon account for the motion of the Earth and the probe during communications transmission and reception?"
] |
[
false
] |
At over 4 billion miles away, the signal would take 6 hours to reach Earth which would have moved about 389 thousand miles. Does the probe account for this motion and realign its transmission antennas? Edit: Apparently, there would not be too much precise calculations due to the frontal lobe of the signal spreading out enough that as long as the transmission antenna was pointed in the direction of Earth, the signal could be received. Also once a probe is far enough above or below the ecliptic, obstruction would not be a major issue. As for the displacement of the Earth during transmission, it would be minimal given the distance of the probe. Conclusion: I leaned a lot about probe signal transmission and reception. Which was the intent of this post. Thanks ! :)
|
[
"New Horizon and the voyager spacecraft are a few light hours away. The Earth doesn't actually move that much in that time frame. The signals they send out are not collimated that much. Over time they will spread out and cover enough area that antennas on Earth can pick up that signal. \nBoth Voyager probes have left the solar ecliptic, Earth is visible at any given moment. It is not obstructed by either sun nor other planets. "
] |
[
"fyi: the Voyager space craft are about 20 light hours from Earth. New Horizons is about 5.7 light hours from Earth."
] |
[
"The transmission antenna ",
" highly directional, but on the other hand at these distances the beam width may be millions of kilometers and still count as highly directional. But calculating where Earth ",
" be isn't very hard in case it has to be accounted for.",
"One thing that does matter is the Doppler shift caused by relative speed difference. An embarrassing design flaw almost caused the data from the Huygens Titan lander ",
"to be lost in 2004",
"."
] |
[
"Concerning \"germs\" (bacteria, viruses, etc), what is the difference between an immunity developed by an individual, and an immunity inherited via genetics?"
] |
[
false
] | null |
[
"The Europeans had immunity to various diseases because they were exposed to them. It was not 'genetic' in the sense you are using."
] |
[
"The natives were exposed to them and they died en masse. Something is different."
] |
[
"The natives had never been exposed to those diseases or any similar strains of infectious agents. Europeans grew up around those diseases and mutant strains that are less infectious, and were able to develop immunity. "
] |
[
"What's the benefit of slitted pupils?"
] |
[
false
] | null |
[
"Full article",
"Basic summary: slitted pupils allow us not to block out certain wavelengths of light when using a multi-focal lens, meaning that we get more color focus.",
"This",
" article explains it in plain english that, essentially, you get better color vision in low light, which explains our kitties who are crepuscular/nocturnal. "
] |
[
"Hi! This is a scientific subreddit for scientific questions and ONLY scientific anwsers which come ONLY from science. You're most likely being downvoted because you are posting a top-level comment, (a reply directly to the OP), that is off-topic or speculation. Top-level comments in AskScience should only be factual, supported responses to the question asked, or questions seeking clarification. Jokes, off-topic banter, speculation and anecdotes are not appreciated as top level responses, in an attempt to maintain the quality of this subreddit. Just to clarify, the subreddit is called askscience not becouse you ask \"science question\" but becouse you ask the scientific community to anwser your question. To anwser it in a scientific way. For more, see the rules on the sidebar at the right of this page. Thanks!"
] |
[
"Hi! This is a scientific subreddit for scientific questions and ONLY scientific anwsers which come ONLY from science. You're most likely being downvoted because you are posting a top-level comment, (a reply directly to the OP), that is off-topic or speculation. Top-level comments in AskScience should only be factual, supported responses to the question asked, or questions seeking clarification. Jokes, off-topic banter, speculation and anecdotes are not appreciated as top level responses, in an attempt to maintain the quality of this subreddit. Just to clarify, the subreddit is called askscience not becouse you ask \"science question\" but becouse you ask the scientific community to anwser your question. To anwser it in a scientific way. For more, see the rules on the sidebar at the right of this page. Thanks!"
] |
[
"Why does the Earth spin, and why doesn't the moon?"
] |
[
false
] | null |
[
"The moon is ",
"tidally locked",
" to the earth, which doesn't mean it isn't spinning, what it means is that it takes the moon the same amount of time for one rotation as for one orbit. That is why one side always faces the earth.",
"Most of the time, one the smaller object is tidally locked to the body it is orbiting, but sometimes both bodies are locked together - as is the case with Pluto and its moon Charon.",
"(Edit for typo)"
] |
[
"It is a rather complicated thing called ",
"Angular Momentum",
".",
"It is difficult to explain in simple scenario, but as a big ball of gas and rock starts to become more dense through gravity, it generally forms a rotating object. This is due to all the matter coming in with specific trajectories, and this an \"overall average\" trajectory of sorts forms, which means that the object the matter forms ends up carrying all that spin. This was the case with our earth.",
"There is also a ",
"hypothesis that the moon was formed by a huge impact",
" between a young earth and a mars sized body. This would certainly instill a rotation on the resulting bodies. If you read about it, the leading theory is that for the moon to form, it likely impacted at an angle which would also instill a lot of spin."
] |
[
"If it helps, you can also read my ",
"comment",
" in the other thread."
] |
[
"How much radiation would you be exposed to holding weapons-grade plutonium in your hand?"
] |
[
false
] |
In a movie I saw yesterday there were several scenes of the characters holding spheres of weapons-grade plutonium in their bare hands with seemingly no concern for how radioactive it is. My gut says this is a really, really bad idea, but I'm curious just how bad it would be. How much radiation would you be dosed with if you did that in real life?
|
[
"It depends on how much of it you’re holding, and whether or not criticality is reached. The “common” isotopes of plutonium are radioactive to alpha decay, but Pu always comes cladded in other metals, which the alpha particles can’t penetrate. Some fraction of the time, it will undergo spontaneous fission instead, which will also result in the emission of neutrons and gamma rays. These will in general penetrate through the cladding and give you a dose.",
"As long as there is no criticality reached, the dose rate won’t be ",
" high. People can handle amounts on the order of a few kilograms of weapons-grade plutonium (I personally have done so) without receiving a dangerous dose.",
"You don’t just hold bare Pu in your bare hands though, the Pu is cladded with some other metal (like zirconium), and you generally wear gloves when handling it. The gloves are not very heavy-duty, as they’re not used to shield radiation. Instead they’re used to mitigate the spread of radioactive contamination. When you’re done handling the material, your hands will generally be tested for contamination, and once you’ve been given the all-clear, you remove the gloves and dispose of them.",
"So it’s really not as dangerous as you think. The real danger is in criticality accidents, but as long as you’re handling less than the critical mass with your given amount of moderation, then criticality can’t be reached, by definition. A fun fact about it though is that for kilogram amounts of Pu, the cladding actually feels warm to the touch due to the radiation (most of which doesn’t penetrate the cladding)."
] |
[
"For the effects of being exposed to radiation from supercritical plutonium, ",
"see the incidents involving the demon core",
".",
"Note that the plutonium itself in this case is a subcritical mass that went supercritical due to its proximity to neutron reflectors, which probably caused some complacency by the physicists handling the core itself."
] |
[
"Yes, the cladding is due to the chemical properties of plutonium, which are very nasty. It also provides some radiation shielding as a secondary benefit."
] |
[
"Has the universe existed long enough for entire galaxies to have been born and died?"
] |
[
false
] |
Certainly it has happened with stars, but could an entire galaxy have formed and died out in the time since the big bang? I vaguely feel like the universe isn't old enough for that yet, but I'm not an astronomer. (this question inspired by a meme I saw that said "Cthulhu saw galaxies flare into life and fade from view before he put madness in the minds of men")
|
[
"Define died out. Do you mean every star within them gone out? If that's what you mean, then no. All galaxies will invariably contain Red Dwarfs and White Dwarfs. Both stars have live spans that are so massively long, they will not die for what is conceivably, forever.",
" ",
"Red Dwarfs livespans are nearly 1-10 trillion years, ",
"The sun will exist for another 5 billion years by comparison.",
"The entire universe is only 13.75 billion years old.",
"White Dwarfs are theorized to continue shining for a billion billion years.",
" ",
"So do you consider a galaxy to be its parts? If the stars in a galaxy are still alive is the galaxy? Astronomers consider a galaxy dead when they are no longer producing new stars, in which case, yes we have found galaxies that fit that criteria."
] |
[
"Actually yes, in the beginning of the universe the first stars to form where suppermassive, meaning they burned their fuel much faster and living shorter lifes. And what makes a galaxy “alive” is it having constant star formation, but due to this fast fuel burning the gas that composite galaxies and could pottentially become other stars became unable to form those stars as time passed, leaving ellipitcal galaxies with red coloured clouds of sadness.\nBut this is just the way galaxies die from “old age” there are plenty other ways actually."
] |
[
"The scientists studied an image of the oldest light in the universe to confirm its age of 13.8 billion years. This light, the \"afterglow\" of the Big Bang, is known as the cosmic microwave background and marks a time 380,000 years after the universe's birth when protons and electrons joined to form the first atoms."
] |
[
"What kind of an immune system did past species of the genus Homo have?"
] |
[
false
] |
To clarify, I'm not specifying the exact species (e.g homo habilis), because I don't know whether we even have such information. But if we do, any kind of it would be nice to hear. About the immune system: if it is known, how did it differ from the one the humans now have?
|
[
"You can put a boundry on it, at least, by looking at our relatives. ",
"It would be at least as similar as what we see in chimpanzees. There are differences in response, but the overall architecture of the immune system is the same in both chimpanzees and humans. They respond to certain pathogens more, other pathogens less, and other pathogens in different ways."
] |
[
"This is a complete unknown, as no details of any organism's immune system survive in fossils. The best one could do is to assume our ancestors had the immune system characteristics that are shared among the modern Great Apes, but this would of course be just an assumption and not actual information."
] |
[
"Well, that's essentially what I said. My phrase \"complete unknown\" is a bit overstated, but in the realm of human evolution it's alarmingly common for pure speculation to become accepted as unimpeachable fact."
] |
[
"Did CFCs cause the ozone hole over Antarctica? Is the Montreal Protocol making it better?"
] |
[
false
] |
I heard that maybe we got this one wrong. That CFCs aren't directly responsible for the hole in the ozone layer. With some 25 years hindsight what do we know now that we didn't then.
|
[
"NASA has a lot of good ozone hole measurement data here:",
"http://ozonewatch.gsfc.nasa.gov",
"That data shows that the growth of the ozone hole has effectively stopped as a trend (with fluctuations yearly based on other atmospheric conditions).",
"The CFCs already released in the atmosphere will take some time to clear, hence they are still having an effect:",
"\"The manmade chemicals known to destroy ozone are slowly declining because of international action, but there are still large amounts of these chemicals doing damage,\" said James Butler, director of NOAA's Global Monitoring Division in Boulder, Colo.",
"http://www.nasa.gov/topics/earth/features/ozone-2011_prt.htm",
"\"In 2100, CFCs will still be 20 percent more abundant in the atmosphere than they were in 1950. So while it's not getting any worse, it won't get better fast.\"",
"http://www.nasa.gov/topics/earth/features/ozone-aus.html",
"So the official word is still the same, initial estimates for CFC depletion are behind early targets so progress isn't as quick as expected, but observations are consistent with the overall message regarding ozone depletion being caused by CFCs."
] |
[
"This is askscience not askreligion I should be able to question everything. :) Plus there's nothing wrong with seeing if we got it right,",
"But the real reason is the anti-AGW guys are saying we got it wrong. It's nice to see we didn't."
] |
[
"But the real reason is the anti-AGW guys are saying we got it wrong. It's nice to see we didn't.",
"AGW, or anti-AGW, that doesn't matter. Neither of those terms are representative or relevant to the better name of 'climate change.' Tacking on a political connotation to a global environmental issue is not only contributing to political hyperbole but is also producing vehement refusal and/or denial of scientific information by those with opposing political interests. This is not only unhealthy for our country, but for the world as we in the US are not only listening to but coining a term called \"AlGore Warming\" after a politician who, by the way, is NOT a scientist. The polarization of views on this issue stems from fear and misinformation (and boatloads of it), and most importantly climate change is NOT a political issue! Climate change is an issue that can fundamentally change the economical landscape and stability of our future generations. What's worse is that lots of Al Gore's information was without context. There have been times in the past, namely 220 million years ago in the Triassic, when there were NO POLAR ICE CAPS present on the surface of the Earth. I really have a big problem with mixing science and politics, specifically with a politician presenting scientific information that he/she may not understand, nor have context for, in any or all arguments of relevance to the issue. ",
"This isn't about \"saving the Earth.\" It's about saving our own cookies."
] |
[
"How do satellites in Space send signals back to Earth?"
] |
[
false
] |
For example the New Horizons spacecraft that sent pictures from Pluto? How do they get all the way back to earth? I'm guessing it's infrared signals or something but I don't understand at all how stuff like that works.
|
[
"Spacecraft tend to use radiowaves for communication with Earth. New Horizons uses the so-called X-band, which is somewhere between the typical radio frequencies used on Earth and infrared.",
"Because of the distance, at least one side of the communication needs to have a powerful transmitter and a sensitive antenna. On Earth, these are found in the [",
"https://en.wikipedia.org/wiki/NASA_Deep_Space_Network](Deep",
" Space Network). Obviously, engineers will try to optimize the transmitter and antenna on the spacecraft as well, but limitations on size and power consumption are a huge bottleneck there.",
"The further a spacecraft is from Earth, the weaker the signal will become and therefore the data rate has to be reduced. New Horizons was only broadcasting at 1 kbps (1000 bits per second) when it was near Pluto. Another important aspect is the time delay between broadcast and reception: It takes several hours for a signal to travel between Earth and a spacecraft as far away as New Horizons. That means that real-time communication is impossible and any operating instructions sent by the control center have to be carefully planned in advance."
] |
[
"Ahh so it's not so much a direct line as a big transmitter picking up data the Spacecraft has released? ",
"That's how every form of radiocommunication works. One side broadcasts a signal that can be picked up by anyone listening. With the right antenna you can focus the direction of the signal, but given a large enough distance, there's still going to be a large area where it can be picked up. Other transmitters that don't know where their intended recipient(s) is (are), will just send the signal in every direction.",
"Things like encryption are needed to ensure that what you transmit with this signal remains confidential between you and the recipient."
] |
[
"Excellent, I guess I never really thought about it that much but it makes so much sense. Thanks again! "
] |
[
"Is it possible for genotypes to \"converge\" over time, as phenotypes sometimes do in different species?"
] |
[
false
] |
I used to be a docent in a museum, and one of my favorite things to point out on tours was a set of ichthyosaur fossils next to a picture of a dolphin skeleton, showing convergent evolution. I understand convergent evolution on the phenotypic level, but I never really thought about what's going on genetically. After so many random mutations in the genetic code, is it possible for the genotypes of different organisms to "converge" like this over time? Or is that really what underpins convergence on the phenotypic level? Another part to the question: we hear a lot of comparisons of genomes between species, like how we share "X.X%" of our genetic code with bananas, chimpanzees, etc. I was wondering if it's possible for convergence on the genetic level to confuse our phylogenetic analyses in a way that would make us believe two species are more closely related than they truly are.
|
[
"While it would, in theory, be possible, it is extremely unlikely. For a certain phenotype there are loads of different combinations of mutations that could give rise to it. For example, say a certain nutrient needs to be digested more. It could be that the enzyme that digests it is mutated so it's more efficient. It could be that a different gene which upregulates this gene becomes more expressed, or a gene that downregulates it becomes less expressed, etc. ",
"Not to mention that different species have different genes to begin with, so the changes that are necessary will also be different, since even the same mutations have different effects.",
"In fact, this difference in genes is usually what can clue us in to whether a feature evolved before or after a genetic split. If, say, two related species are both poisonous, but the gene(s) for that poison is different (not just the same gene with a couple of mutations) then it is likely that the poison evolved separately in each species, after they split from their last common ancestor."
] |
[
"To expand on this slightly, selection acts on phenotype, not genotype. Similar environmental constraints may drive two organisms to converge on similar phenotypic solutions, but no such pressure acts directly on their genetics."
] |
[
"This is an example of phenotype convergence, so not what the question is about. ",
"It is a very interesting phenomenon though :)"
] |
[
"Do we know the long-term health effects of plant-based meat substitutes yet, like Beyond Meat or Impossible Burger? This trend caught on rather quickly and it makes me worry."
] |
[
false
] |
Not that eating and smoking are the same thing, but we are only just now discovering the long-term effects that vaping can have on the lungs. We know these plant-based meat substitutes are edible and don’t cause immediate issues, but so we know they’re safe if you’re eating them over a period of time. These kinds of developments in food are exciting, but I worry we’re all going to wake up to learn of some nasty side effects or something like that someday. This trend just happened so quickly and it wouldn’t surprise me if this were just another example of people putting money ahead of safety or the common good.
|
[
"The individual ingredients have all been approved for human consumption. As far as I know, only the Impossible Burger actually uses a new ingredient, but they followed all the proper procedures and did the necessary (animal) testing to get it approved before bringing it to market."
] |
[
"I believe they use ",
"leghemoglobin",
", which is similar to heme found in animal red blood cells. It gives the meat an \"iron\" taste. I heard a podcast about it here: ",
"http://freakonomics.com/podcast/meat/"
] |
[
"The ingredients of these burgers are just plant-based products, that people have been eating for a long time. Of course there is a chance that one of the ingredients will be found to have some side effect in the long term, but they aren't more likely to have hidden side effects than meat. The comparison to vaping isn't a good one as we already had good reason to believe vaping would have harmful effects on the lungs before it existed. Ingredient list of both burger below:",
"Beyond burger:",
"Water, Pea Protein Isolate, Expeller-Pressed Canola Oil, Refined Coconut Oil, Contains 2% or less of the following: Cellulose from Bamboo, Methylcellulose, Potato Starch, Natural Flavor, Maltodextrin, Yeast Extract, Salt, Sunflower Oil, Vegetable Glycerin, Dried Yeast, Gum Arabic, Citrus Extract (to protect quality), Ascorbic Acid (to maintain color), Beet Juice Extract (for color), Acetic Acid, Succinic Acid, Modified Food Starch, Annatto (for color).",
"Impossible burger:",
"Water, Soy Protein Concentrate, Coconut Oil, Sunflower Oil, Natural Flavors, 2% or less of: Potato Protein, Methylcellulose, Yeast Extract, Cultured Dextrose, Food Starch Modified, Soy Leghemoglobin, Salt, Soy Protein Isolate, Mixed Tocopherols (Vitamin E), Zinc Gluconate, Thiamine Hydrochloride (Vitamin B1), Sodium Ascorbate (Vitamin C), Niacin, Pyridoxine Hydrochloride (Vitamin B6), Riboflavin (Vitamin B2), Vitamin B12."
] |
[
"Does taking a vitamin D supplement stop natural vitamin D production?"
] |
[
false
] |
[deleted]
|
[
"Probably not. Consider that vitamin D3 comes from 7-dehydrocholesterol. The sun turns 7-dehydrocholesterol into vitamin D3, but 7-dehydrocholesterol is also converted into cholesterol. All cells must produce cholesterol, as it is an integral part of the cell membrane. Any feedback regulation that would inhibit 7-dehydrocholesterol would also inhibit cholesterol formation in the cell.",
"However, vitamin D3 is not the active form of vitamin D. There are two more hydroxylation steps, one in the liver and one predominantly in the kidneys. The active form activates an enzyme that deactivates the active form molecule, essentially creating a negative feedback loop."
] |
[
"The process that creates vitamin D also creates another important (by-)product. Thus stopping this process just because your body does not need more vitamin D would be detrimental and is thus unlikely."
] |
[
"Can you explain again, like I'm 5?"
] |
[
"Coded Aperture Imaging - It can be used to localize Gamma Ray Bursts, but can it be applied to Medical Imaging?"
] |
[
false
] |
I recently learned about coded aperture (CA) imaging, which is a technique used in some survey sattelites to identify the location of high-energy photon events (such as gamma ray bursts). Directionality is usually established in visible light images through various optics techniques, such as focusing light using a parabolic mirror. It is very difficult to focus x-rays and gamma rays, so if one of these is detected it becomes difficult to identify where it came from. My understanding of CA comes entirely from (a good read for anyone that wants to learn more). A semi-transparent grid, with some unique pattern, is placed over the detector. By analyzing the shadow that is cast on the detector by the grid, one can determine what direction the gamma rays are coming from. I see how this would work for a distant point source of gamma rays, such as a gamma-ray burst in a far away galaxy. However, I'm wondering if this could be applied to medical imaging. Specifically, most photon-based scanning systems suffer degradation of their image when the x-rays scatter within a patient's body. The assumption is that the photon travels along a straight line from the source to detector, and if the direction of the photon changes through scatter this assumption is broken. So my question is, could CA imaging be used to determine which parts of the signal are coming from off-axis (scattered) directions? In other words, in , could a coded-aperture imaging system separate the green photons from the red ones? It seems like normal coded-aperture reconstruction might not work in a scenario where the important signal has to do with attenuation through a large object before detection.
|
[
"The true difference between x-rays and gamma rays isn't their energy, but their origin. X-rays are defined as photons that originate from electrons, and gamma rays originate from the nucleus. Thus, for medical imaging, the difference becomes a bit meaningless. For instance, you can have a ~30 keV \"gamma ray\" which comes from the decay of I-131, or a 20 MeV \"x-ray\" generated by bombarding a tungsten target with an energetic electron.",
"Regardless, there are plenty of applications of high-energy photons to medical imaging (here I define high energy as > 100 keV, where Compton scatter dominates photoelectric absorption). SPECT, for instance, typically uses gamma ray sources with energies above 200 keV ",
" for the reason you mentioned - they are able to escape the body without interacting. PET scans are based on annihilation photons, with energy 511 keV.",
"Other times we use high energies because it is convenient, not necessarily because the image quality is better. For instance, megavoltage CT using a radiation therapy accelerator."
] |
[
"I don't see a use for coded aperture imaging in medicine. The main reason is that there is no reason to use coded aperture for any kind of radiation except for gamma-rays. And gamma-rays will make for an extremely poor medical imaging technology. X-rays are used for medical imaging because human soft tissue is transparent to x-rays while bones are opaque so you can effectively image the inside of humans. Gamma-rays have a higher energy than x-rays so they are more penetrating than x-rays which means that all human tissue is transparent to gamma-rays. So it will be much more difficult to image the humans with gamma-rays.",
"In addition, the gamma-rays that are absorbed by humans are much more damaging to human tissue than x-rays so they are much more damaging. So since gamma-rays are unsuited for medical imaging and coded aperture imaging is only necessary for gamma-rays, I don't see any reason to adopt it."
] |
[
"Well, that is the nuclear physics definition of the difference between a gamma-ray and an x-ray. The astronomy definition is that x-rays can be imaged with glancing incidence telescopes while a gamma-ray is anything above that limit (about 15 keV). In astronomy, x-ray atomic transitions and nuclear are rarely seen so the difference comes from the instrument used to detect it. ",
"When I said that gamma-rays wouldn't be useful I guess I was only thinking of projection radiography and had not considered imaging where the patient ingests radioactive material and is then imaged by a ring of detectors around them. Unfortunately, I don't see how a coded aperture can help this type of imaging either. SPECT and PET scans work by putting the photon detectors really close to the body and creating an image based on which detector is hit. A coded aperture telescope creates an image of a gamma-ray source by assuming that the source is far away. I guess the math could be modified to work for an object close to it but you would get a better image by losing the aperture and just putting the sensors as close to the object as possible. In addition, PET scans use time of flight to make a 3d image, adding an aperture would just decrease the number of pairs that you could use for timing. "
] |
[
"Is there a chemical or other fire type which does not require oxygen?"
] |
[
false
] |
Edit: on earth.
|
[
"Yes but you generally need a very strong oxidizers such as chlorine trifluoride. Since fire is just rapid oxidation it can theoretically happen with any oxidizer but realistally it is rare. Also some metals will catch fire with CO2 rather than atmospheric oxygen but that technically has oxygen it it."
] |
[
"Chlorine is a common oxidizer for fire. There is a classic demonstration of ",
"acetylene burning in chlorine",
". I have done this one myself. It is really fun to watch. (but the gases are quite toxic)",
"http://chemed.chem.purdue.edu/demos/main_pages/24.10.html"
] |
[
"What you see as fire is a type of oxidation. While Earth with more oxygen than it should have thanks to plants and algae, most flames you see oxygen is the oxidizer. A simple example you can look up a demonstration of from the Royal Society of Chemistry public lecture \"Fire and Flames\" which is on YouTube, is combustion of hydrogen gas in an atmosphere of chlorine. In an oxygen atmosphere this burns rapidly and typically explodes and forms water. In the chlorine case it is similar except it forms hydrogen chloride, which if dissolved in water is hydrochloric acid."
] |
[
"Question about the distribution of human vision quality."
] |
[
false
] |
So I was wondering, are there any studies done on the distributions of prescriptions of people. I'm sure that there has to be, if we study trends in vision quality and stuff, but I just can't seem to find any results. I'm curious what average human eyesight is, and how varied it is. Does it end up being very bi-modal: either good or bad, associated with some genetic switch or something, or is it smooth throughout? Also: How does this stack up for people from other places in the world, what do these curves look based on demographics essentially? And, I know there are a lot of various types of problems, and ways to parameterize vision, so I guess im curious how all of these evolve across the spectrum for people. I tried searching for all of this, but didn't really find any good results. Thanks for any help!
|
[
"There's a journal called Opthalmic Epidemiology; you might be able to find something there."
] |
[
"Yeah a search for \"Ophthalmic Epidemiology distribution myopia\" seemed to turn up some stuff. I'm not in the field at all, but maybe something like this is relevant: ",
"http://shileyeye.ucsd.edu/eyemobile/RefErrinLowIncCh.pdf"
] |
[
"I found ",
"this",
" article (1974, but free to access) that did a survey of Egyptians' visual acuity. Page 250 has a table with distributions by acuity using a Snellen chart (they use the metric form of 20/20, which is 6/6)."
] |
[
"Why does the the cosmic background radiation have a uniform temperature of 2.7 K?"
] |
[
false
] |
I know that light is red shifted by traveling over cosmological distances, and the CMB was hotter and bluer in the past. What I don't understand is how it stays in thermal equilibrium as the universe expands. Does the light it come to an equilibrium temperature by interacting with matter? Does redshift change the wavelength distribution of light in such a way that it stays in thermal equilibrium?
|
[
"The light is redshifted not because it has traveled, but because the universe has expanded.",
"In the early universe, the photons were in thermal equilibrium with matter. When the universe was about 375000 years old, atoms formed, and the light ",
", meaning that, generally speaking, it was no longer regularly interacting with other things.",
"At that time, the light was in thermal equilibrium at a temperature of 3000K. As the universe expanded, as you suspected, the redshift keeps the spectrum a thermal spectrum, just at gradually lower temperatures."
] |
[
"Generally, in an expanding universe, a thermal distribution of blackbody radiation stays thermal, which was shown by Tolman in the 1930s.",
"So the photons got into equilibrium when they and matter were all interacting. Then the photons decoupled and were locked into a thermal distribution. The expansion of the universe has the net effect on such a distribution of keeping it thermal and lowering the temperature.",
"This page",
" from NASA might be helpful. "
] |
[
"Just to elaborate on ",
"/u/fishify",
"'s great answer, a thermal spectrum of light has the following energy distribution function:",
"f(E) ~ 1 / (e",
" - 1)",
"where T is the temperature, k is Boltzmann's constant, and E is the energy of a photon (light particle). As the universe expands, the energy redshifts, scaling inversely with the size of the universe. Because every photon redshifts the same way, this is equivalent to a thermal distribution where the temperature is redshifted.",
"One interesting thing is that this is only true because photons are massless. If photons had mass, then their energy would not simply redshift, because the mc",
" contribution to their energy does not redshift. So the above argument would break down, meaning that we would be unable to describe the cosmic background radiation as a thermal distribution with some temperature. The reason this matters is that, similar to the cosmic microwave background (CMB), there is also a cosmic neutrino background (CNB). Like the CMB, the CNB was initially a thermal distribution described by a temperature. But because neutrinos have mass, the redshifted distribution is no longer a thermal distribution. Unlike the CMB photons, cosmic neutrinos are not in thermal equilibrium."
] |
[
"Posting this here in the hopes a marine biologist or someone knowledgable can answer this. (x-posted from r/AskReddit originally from r/Pics)"
] |
[
false
] |
[deleted]
|
[
"I think in fact, the correct term is 'squid giant axon,' which clarifies its meaning quite a bit."
] |
[
"Fish are jawed vertebrates. They have myelinated axons as well!",
"EDIT: ",
"You might find this interesting"
] |
[
"Just to clarify (because I once had this misconception), when we say ",
"giant squid axon",
", one should read it as \"giant\" squid axon, not \"giant squid\" axon. It is a large axon from a certain type of normal-sized squid, ",
" a normal axon from a giant squid. Although that would be awesome."
] |
[
"Has modern medicine influenced natural selection at all?"
] |
[
false
] | null |
[
"Most evolution and human disease doesn't quite work that way. Most genetic diseases are either multigenic or recessive.",
"Let's start with recessive genes. Take an example cystic fibrosis. Among those of European descent, the carrier rate (one copy of the mutation) for the cystic fibrosis mutation is around 1 in 25. This allele is in equilibrium in this population, so we could use Hardy-Weinberg:\np",
" + 2pq + q",
" = 1 and p+q = 1",
"Where p is the frequency of the normal allele and q is the frequency of the mutated allele. 2pq is 1/25 which is the frequency of individuals with one copy of the mutated allele and one copy of the nonmutated allele. Solving for q",
" we get around 1/2400, which is close enough to the disease incidence in caucasians. Source is ",
"this calculator",
" with plug-and-chug because I'm lazy and don't want to do the quadratic equation this AM.",
"In short, 1/25 people have a copy of the CF mutation. Half of the time they pass that on to their offspring. These individuals don't have a negative fitness and thus evolution (and modern medicine) doesn't touch them. It has been proposed that these carrier individuals may actually have a positive fitness in some situations. ",
"Modern medicine helps out the 1/2400 babies that are born with CF, helping them survive to reproduction. Obviously, even though all of their gametes contain the mutation, this is dwarfed by the mutations supplied by half of the gametes of the much more numerous carriers.",
"The same is probably true of multigenic traits. Imagine that you need 3 relatively common alleles to cause a heart condition. The event of getting all 3 is quite rare. The number of carriers with 1 or 2 of these alleles would dwarf the number of people with 3 alleles that modern medicine is helping out.",
"For rare dominant traits, which like achondroplasia and Marfan disease, are usually ",
" mutations, I do think that modern medicine may play a role in selecting. For these, new mutation was the only source for alleles, providing that affected individuals would not survive until reproduction (which however isn't the case for achondroplasia and Marfan disease). Modern medicine now allows less negative fitness and more survival to reproduction, and could in theory alter allele frequency and natural selection."
] |
[
"so, just to clarify, even though the genes are getting passed on because these people are now able to live, it doesnt necessarily increase the amount of genetic defects because the gene pool is so large. kinda like putting a needle in a haystack, yeah, the needle is there, but youre not likely to get stuck? "
] |
[
"Yes I think that's mostly true but I got it a bit wrong. But as marblar pointed out, over the long run, modern medicine could affect disease frequency because you are lowering the negative selection coefficient in a formula called the mutation-selection balance. New mutations arise spontaneously. If these are bad, they exit the gene pool. The frequency of that mutation is determined by the balance of new mutations and how quickly they exit. There is a formula that describes this called the ",
"mutation-selection balance",
". ",
"This assumes a bunch of things which may not all be correct for the particular example I described, cystic fibrosis (the frequency is quite high, higher than we would expect, and maybe it is because carriers of the mutation have advantages). For a \"normal\" recessive disease, though, if you were able to reduce the negative-selection ",
" value in the mutation-selection balance (1 would imply all die before mating age, the lower the number the more survive), it could be a way to change the allele frequency over many generations.",
"I have never heard of this being reported. But it is certainly possible."
] |
[
"Last year, CERN released 300 terabytes of Large Hadron Collider data. Why does particle physics use so much data?"
] |
[
false
] |
[deleted]
|
[
"To give an example of just one small part of ATLAS (which is only one of several detectors): The Pixel Detector consists of 1744 modules arranged in cylindrical layers around one of the collision points. Each of those modules contains 47,000 pixels (so 80 million total). The beams are manipulated so that they collide with each other 40 million times a second, so all 80 million pixels must be read 40 million times a second. ",
"Most of these readings are actually analyzed and thrown away in hardware, then there is a large computing cluster that does more analysis and discards even more data, but even after all that they store upwards of 100 megabytes per second while the beam is active.",
"This is all needed because we are looking for very rare particles, and we want to observe them many times in order for our measurements to gain sufficient statistical certainty. Having lots of pixels in the detector means their track can be observed more closely, which gives information as to their mass and charge."
] |
[
"I'm not sure about the Hadron, but I used to work in X-ray crystallography which is kind of similar in terms of data collection. In our systems we would mount a single crystal which held an unknown protein. The sample would be mounted on something that rotated 360 degrees while an x-ray beam was shot at it and a detector collected the scatter of xrays that were emitted from the crystal. Each image was around 16Mb. Imagine the amount of data collected when the collection is set up to take one image every half of a degree for 360 degrees. They do this every few days for an entire year...that is a shit ton of data that takes massive clustered servers to process.",
"I'd imagine that since the Hadron has mere nanoseconds to collect the data they have a massive number of very high resolution detectors \"watching\" the reaction."
] |
[
"All of the pixels are not collecting or being exposed to data 100% of the time."
] |
[
"How does quantum field theory explain spin?"
] |
[
false
] |
I have tried to find the answer to this online, but I can't seem to find a satisfying answer.
|
[
"I'm not saying that your historical overview of the Dirac equation is incorrect, I'm saying that attributing spin to relativity is incorrect. Spin is a consequence of rotational invariance. You can have relativistic particles with or without spin, and non-relativistic particles with or without spin. ",
"Relativity is a red herring in answering OP's question, but it's one which is used a lot in pedagogy because the Dirac equation is taught in a historical rather than correct manner."
] |
[
"I'm not saying that your historical overview of the Dirac equation is incorrect, I'm saying that attributing spin to relativity is incorrect. Spin is a consequence of rotational invariance. You can have relativistic particles with or without spin, and non-relativistic particles with or without spin. ",
"Relativity is a red herring in answering OP's question, but it's one which is used a lot in pedagogy because the Dirac equation is taught in a historical rather than correct manner."
] |
[
"Spin arises in non-relativistic quantum mechanics, so this answer is not correct. "
] |
[
"When someone is critically injured, does keeping him/her awake & alert really help prevent death? If so, why?"
] |
[
false
] |
Is it just a psychological reaction by others that sleeping is like death, so preventing sleep will prevent death? Or is there a medical basis - perhaps being awake improves vital signs over being asleep?
|
[
"No. In fact, the critically ill are often medically sedated for a number of reasons, depending on the specific circumstances. "
] |
[
"This has been asked before if you want to do a search.",
"The answers from EMTs were along the lines that it's much easier to assess and ask questions of conscious patients."
] |
[
"Actually the person is periodically awoken to assess for things that wouldn't be noticed in a sleeping patient - blurred vision, impaired speech, dizziness, nonreactive pupils, headache, confusion etc. ",
"A person may initially present with a brain bleed or swelling that has no symptoms and without a scan you won't know how serious it is. If there is something to worry about, in most cases symptoms will begin to appear after time as intra-cranial pressure increases / damage spreads / cells die / etc. If this starts to happen to want to catch it as early as possible. ",
"There's nothing wrong with sleeping other than it can prevent you from catching these things."
] |
[
"Do people with better reaction times experience the passage of time slower?"
] |
[
false
] | null |
[
"That's a great question. Although, this doesn't answer your question directly, there was an experiment performed asking a similar question.",
"When jumping off a building / bungee jumping, time feels to be moving slower. The hypothesis for this experiment was that you would be able to read a number flashed at you that would otherwise be too fast to read.",
"The result of the experiment was no, your reaction speed (or at least your eye/brain's ability to see something quick) does not improve.",
"http://www.pbs.org/wgbh/nova/body/profile-david-eagleman.html"
] |
[
"Bah, beat me too it. ",
"Here",
" is the study.",
"This",
" article is a pretty good description of different ways our perception of time changes. "
] |
[
"I'd like to know how you would measure how people experience the passage of time (not aimed at OP)?"
] |
[
"Does the ISS need course corrections due to people moving around inside, and if so how frequently does it happen?"
] |
[
false
] | null |
[
"There a couple important points to make here. Absent of external factors, there is nothing you can do on the inside of closed vessel in space that will result in any long-term change in the velocity. Essentially, momentum conservation means that you pushing off the wall at some point is exactly cancelled by you running into the opposite wall later. However, in a non-uniform gravitational field this needn't necessarily be the case. That being said, anything the astronauts do will we dwarfed by the fact that the ISS is not high enough to be completely outside the influence of the atmosphere. The height of the ISS is constantly decreasing due to drag: ",
"https://www.heavens-above.com/IssHeight.aspx",
". Corrections are regularly done every month or so."
] |
[
"No. The people moving around inside will not change the location of the ",
"center of mass",
" of the system: the weighted-average position of the station and its contents will be unaffected.",
"We can even do the math! There are ",
"6 astronauts",
" on the ISS right now, with a total mass of about 400 kg. The ISS has a mass of ",
"400,000 kg",
", and is about 70 meters long. If everybody on the ISS moved from the front to the back, the ISS would move from back to front by about 70 m * (400/400,000) = ",
"."
] |
[
"No. Astronauts inside or otherwise attached to the ISS must obey Conservation of Momentum and thus any motion (i.e. linear or angular momentum) imparted on the ISS by an astronaut will be cancelled out a short time later when the astronaut must impart an opposite force on the ISS to stop their original motion."
] |
[
"If a sealed jar of air was brought up to low Earth orbit and opened, would the air eventually fall back into the atmosphere?"
] |
[
false
] |
[deleted]
|
[
"The only thing that keeps our atmosphere from blowing away with the solar winds, aside from gravity's contribution, is our magnetic field. It blocks the solar winds.",
"An excellent refutation of this idea is the planet Venus, which has a thicker atmosphere than Earth's with no magnetic field. Mass of the Earth and consequently it's gravity is what protects our atmosphere."
] |
[
"Venus has a strong ionosphere and an induced magnetosphere protecting its atmosphere. "
] |
[
"Nope, just in front of the bow shock if we are considering the magnetic field, and the bow shock is 90,000 km from the surface, or about a fifth of the way to the moon. "
] |
[
"Which side tips?"
] |
[
false
] |
I have found following image on some image board and it got me thinking. For the sake of this question lets asume that the scale would be level with the balls removed e.g. there is same amount of water, the beaks are identical, and the scale is level on it's own. My idea: The buoyancy of ping-pong ball won't affect the equilibrium. Because it's one system, the forces will equal out (same idea as helicopter flying inside a closed cube). The beak with steel ball should be pushed down, because of Archimedes law. That's because the steel ball is not attached to the scales. On the other hand mass of the ping pong ball will be affected by gravity and thus pulling the lever down. So in the end I think that the right part with steel ball will tip, because the buoyancy force will be bigger than the gravitational pull on the ping-pong. Are my conclusions correct?
|
[
"Since the steel ball is suspended, its mass does not affect the system. ",
" It's suspended, but some of its weight is supported by the water. In fact, it adds a force exactly equal to the weight of the water it displaces. This can be seen by noting that the force it exerts on the string is reduced by exactly that much once the ball is lowered into the water.",
"Imagine replacing the steel ball with a ball that is exactly as dense as water. It will suspend in the water and won't exert any force on the string. Thus, it adds exactly its weight to the beaker.",
"Now imagine replacing the steel ball with a ball that is less dense than water. It will float and add exactly its weight to the beaker.",
"Why would the steel ball impose less force than these two instances with lighter balls?",
"So the left beaker is supporting: (weight of water)+(weight of ping pong ball)",
"\nand the right beaker is supporting: (weight of water)+(weight of water displaced by steel ball)",
"Edit: critical typo"
] |
[
"Since the steel ball is suspended, its mass does not affect the system. ",
" It's suspended, but some of its weight is supported by the water. In fact, it adds a force exactly equal to the weight of the water it displaces. This can be seen by noting that the force it exerts on the string is reduced by exactly that much once the ball is lowered into the water.",
"Imagine replacing the steel ball with a ball that is exactly as dense as water. It will suspend in the water and won't exert any force on the string. Thus, it adds exactly its weight to the beaker.",
"Now imagine replacing the steel ball with a ball that is less dense than water. It will float and add exactly its weight to the beaker.",
"Why would the steel ball impose less force than these two instances with lighter balls?",
"So the left beaker is supporting: (weight of water)+(weight of ping pong ball)",
"\nand the right beaker is supporting: (weight of water)+(weight of water displaced by steel ball)",
"Edit: critical typo"
] |
[
"One slight correction: the buoyancy of the ping pong ball does not affect the weight of the left side.",
"As far as gravity is concerned, that string in the left beaker is irrelevant (other than it's weight of course, let's assume the string itself is weightless). The weight of the left side, regardless of what is happening internally in the jar, must be the weight of the ball plus water (plus beaker plus string if we want to include those). The left beaker would weigh the same amount if you cut the string and the ball was floating on the surface of the water.",
"A simpler way to think about this is to assume the masses of the ping pong ball and the strings are zero. Both sides have the same beaker+water mass, and the right side has a metal ball as well. Since the weight of the metal ball is only partially supported by the string, it's going to contribute to the weight of the right side and therefore the right side will be heavier."
] |
[
"Magnetic Molecules?"
] |
[
false
] |
Magnetic materials have magnetic properties creating a north and south pole, correct? And, if you break a magnet in half, it makes two magnetics, each with their own north and south poles, right? And this just keeps going for any number of breaks you make? What about down to the molecular level? If I separate a single molecule of a magnetic material, would it still have a north and south pole?
|
[
"This isn't actually fully known, and it's quite relevant as hard drive bits become smaller and smaller. At IBM they showed that magnetic domains could form in clusters of just 12 atoms: ",
"http://www.research.ibm.com/articles/madewithatoms.shtml#fbid=81IDhyf7B9w"
] |
[
"Probably, yes. If you get down to it, the reasons things are magnetic is because of rotating charges. A single rotating charge (like an electron) will produce a magnetic field with both north and south pole.\nNow there may be some exotic monopole out there, but it certainly isn't well known- and you won't get it by splitting magnets apart!"
] |
[
"That makes sense. I wasn't sure if the magnetic fields were created by subatomic particles or the interactions therein, so that's good to know."
] |
[
"Is there any research to verify the existence of the \"Ben Franklin effect?\""
] |
[
false
] |
The is a popular trope on the internet but is there any actual research that verifies this as an actual phenomenon or is this more of a popular idea?
|
[
"There's definitely research to support aspects of this effect. For instance, lots of research has demonstrated the ",
"foot-in-the-door effect",
", wherein you are more likely to do a bigger favor for someone if you have already agreed to do a smaller one. ",
"As mentioned by another comment in this thread, social psychologists explain this behavior with Cognitive Dissonance Theory. Cognitive Dissonance occurs when there is a discrepancy between two beliefs that you hold, or between a belief and your actions, etc. For example, if I claim to believe it's important to recycle, but I throw my soup can from lunch in the trash can and my friend calls me a hypocrite (this may or may not be a real life example), I am now experiencing cognitive dissonance, which is uncomfortable. I can rectify this by changing my belief (\"this soup can isn't really that important to the environment\") or my behavior (stop being lazy and recycle the can). ",
"So, in the case of doing a favor for someone, you infer from your own actions that doing a favor for this person must be important, or something that you value (in other words, the action affects your beliefs or self-perception), and then you are more likely to do another favor because not doing so may cause dissonance with the belief that doing the favor is important, or that you value being kind to others.",
"There is much evidence for cognitive dissonance theory in this sort of context, but it should also be noted that it can be highly influenced by the context. A lot of these studies have the participant engage in a behavior that they don't have very strong beliefs or reasons for (such as selecting a product from a list of products), so they are more likely to form beliefs based on their behaviors than vice versa. ",
"For example, if I asked you to tell me how to get to the store and you complied, then I asked you for a ride to the store, you would probably not give me the ride because, despite the belief that helping people is good, you also already believe that strangers asking for rides is creepy, and that would probably win out.",
"Festinger, Leon. \"Cognitive dissonance theory.\" R. West and LH Turner, Introducing communication Theory Analysis and Application 4 (2010): 112-128."
] |
[
"It is mentioned in ",
"59 seconds",
", which is fully sourced, so there must be. I don't have my copy here, I will try and remember to post a source when I get home."
] |
[
"What is the connection between these two? ",
"Please avoid posting links without explanation / answering the question."
] |
[
"If I'm stranded on an island, how long can I live off of a diet consisting of only coconuts?"
] |
[
false
] |
I know coconuts are very healthy, but how long can I live off an indefinite amount of only coconuts. Assume no fresh water is readily available outside of the coconuts so all you have is coconut meat and milk. How long do I have?
|
[
"Coconuts are a pretty complete protein source and are a good source of fats and carbohydrates as well. However, they are severely lacking in Vitamins A, K, B6, and B12. Deficiencies in these vitamins can cause ",
"pernicious",
" or ",
"microcytic",
" anemia, ",
"loss of ability to fight infections",
", and ",
"increased bruising/bleeding",
".",
"I don't have the medical knowledge to know how long it would take for any one of these issues to become fatal but I would imagine vitamin B6 and B12 deficiencies would take hold the quickest because they are water-soluble vitamins and therefore there would be no excess stored in your body fat to use when your diet was lacking."
] |
[
"Actually the body stores B12 to prepare for long periods of going without it, so some people have ingested no B12 for 5-7 years before symptoms developed. I'm not sure if the same is true for B6...."
] |
[
"Pernicious anemia isn't caused by B12 deficiency. It's an autoimmune process against parietal cells and intrinsic factor, which is required for absorption of B12. Pernicious anemia results in B12 deficiency, not the other way around.",
"B12 deficiency causes megaloblastic anemia (macrocytic not microcytic). B12 is stored 50% in the liver, and the liver stores can last 3-5 years, so it would take quite a while to become deficient. Folate causes a similar picture of anemia (without peripheral neuropathy), and the stores for folate are only ~4 months. ",
"When someone shows up with macrocytic anemia, we check serum / RBC folate and serum B12 levels."
] |
[
"Could a zombie virus be created? Also, could a zombie run purely on brain function like it is potrayed in the movies/television?"
] |
[
false
] |
[deleted]
|
[
"Not to mention zombies would be extremely easy to kill, probably easier to kill than a healthy human considering the wear and tear it has to suffer. "
] |
[
"There are several known diseases/parasites that cause major behavioral changes in hosts.",
"Rabies",
" makes hosts more aggressive, allowing the virus to be transferred through saliva during a bite.",
"The ",
"lancet liver fluke",
" causes host ants to put themselves in great danger of being eaten by grazing animals. (The life cycle travels from ant to grazing animal to snail and back to ant.)",
"This parasite",
" does something similar with its host fish.",
"This only answers part of your question, but I hope it helps."
] |
[
"Rabies often don't make humans aggressive though."
] |
[
"Will a black-painted surface cool faster or slower at night compared to a white surface?"
] |
[
false
] |
I know sunlight is better absorbed by black surfaces, and they warm up faster and hotter in the daytime. But what effect (if any) would color have on nighttime cooling?
|
[
"Radiation emitted by an object in this case, the so-called blackbody radiation, depends only on the temperature of the object. ",
"It doesn't ",
" depend on the temperature - it also depends on the emissivity, which is very important in the case of discussing an exterior coating of paint.",
"White paint is usually made with titanium dioxide as a pigment, which has an emissivity very close to one for wavelengths around 10 microns, where room temperature objects emit most of their IR radiation. Black paint's emissivity around these wavelengths varies depending on the pigment used (such as carbon black), but generally won't have quite the emissivity that white paint does.",
"As a result, white-painted objects will generally cool down slightly faster than black-painted objects."
] |
[
"If you look up Emissivity on Wikipedia, you will see that color is not a good indication of ability to absorb or radiate infrared radiation, but, yes different materials do \"cool\" or emit \"heat\" at different rates. Here's an excerpt...",
"With the exception of bare, polished metals, the appearance of a surface to the eye is not a good guide to emissivities near room temperature. Thus white paint absorbs very little visible light. However, at an infrared wavelength of 10x10<{−6} meters, paint absorbs light very well, and has a high emissivity. Similarly, pure water absorbs very little visible light, but water is nonetheless a strong infrared absorber and has a correspondingly high emissivity."
] |
[
"As ",
"u/Astromike23",
" mentions, there is a difference. An object radiates energy proportional to the blackbody spectrum times the absorption spectrum, as described by ",
"Kirchhoff's Law",
". ",
"Black paint and white paint are tricky because at normal temperatures the blackbody curve peaks in the infrared. White paint usually absorbs very well there (it is \"black\" in the infrared), while black paint scatters IR a bit. So the white object cools faster.",
"However, metallic surfaces reflect IR light very well. So a metallic surface will radiate less heat than a black or a white object. You can take advantage of this a little by wrapping an object in a ",
"mylar blanket",
". ",
"The last thing to keep in mind is that on earth, cooling happens primarily by convection of air in contact with the object surface. So changing the emissivity can lower the radiative heat loss, but this has a small effect on the total heat loss. If you were in the vacuum of space, on the other hand, radiative heat loss would be the primary source of cooling. For satellites, ",
"multiple mylar layers",
" provides very good insulation."
] |
[
"Do earthquakes affect the planet's orbit?"
] |
[
false
] |
Wouldn't Newton's third law suggest that no amount of planetary wriggling could cause it to move in space?
|
[
"If you mean \"Can an earthquake change Earth's orbit around the sun,\" the answer is a flat-out, resounding \"No.\" It would take either a collision with another planetary-scale body of similar mass, or a massive rocket engine firing from the surface.",
"However...an earthquake ",
" (and even ",
", in the recent past) change the speed of Earth's ",
" much like an ice skater pulling in her arms can speed up in a spin. ",
"It works on the exact same principle: mass is redistributed either closer to the Earth's center, speeding up the rotation very slightly, or farther away from the center, slowing it down very slightly.",
"The Tohoku earthquake in 2011 that caused the tsunami that resulted in Fukushima melting down shortened the length of a day by 1.8 millionths of a second. ",
"Relevant link."
] |
[
"You're right in saying that Newton's third law suggests this. Newton's first law is more useful in this case: an object stays at rest/in motion unless acted on by an ",
" force. They leave external out most of the time. Since earthquakes are internal to Earth, they cannot cause the orbit to shift."
] |
[
"Just to clarify a part of this. You do not need a collision to alter Earths orbit around the Sun. This happens naturally and all the time by gravitational interactions (such as resonances and tidal effects)."
] |
[
"How exactly does this screwdriver trick work?"
] |
[
false
] |
It looks fake, but I hear that many other mechainc have done the same thing. Anybody know how it happens?
|
[
"This is an example of the ",
"Coandă effect",
". Basically, the air flow tends to be attracted to nearby objects, and vice versa. It's a bit hard to explain, but the change in momentum of the air stream bending around the cylinder (screwdriver) balances the momentum of the object in the air stream, causing it to hover.",
"Unfortunately, it's a bit of an abstract concept, and my google-fu is failing me right now for a proper diagram."
] |
[
"It uses the ",
"Coandâ effect",
". A jet of air is attracted to nearby surfaces, and tends to follow the shape of the surface. ",
"In the screwdriver trick, the air follows the curved top of the screwdriver, being diverted in a downwards direction. Since the air is \"expelled\" downwards, it imparts an upwards force on the screwdriver. ",
"I'm going out on a limb here, but I think this is also helped by ",
"Bernoulli's principle",
", that states that \"an increase in the speed of the fluid occurs simultaneously with a decrease in pressure\".",
"Edit: I didn't actually see the gif (it won't work on my mobile device), but I'm assuming the screwdriver is suspended by a stream of compressed air. "
] |
[
"Never seen this before, but it doesn't look fake to me. It looks like he's shooting compressed air at just the right angle on the molded handle to both keep it spinning and balance it. Basically like spinning a basketball on your fingertip, but with the added element of the angle of the handle and the weight distribution of the screwdriver."
] |
[
"Just had an idea for a night readable e-ink reader (without a standard backlight or lighted cover)."
] |
[
false
] |
So, a while ago I bought my wife a Kindle 3G. She loves it and I think it's pretty cool as well. I bought the lighted leather cover, and it works great, but I was wondering about the ability of having the text be illuminated internally - not with a backlight per se, but somehow lit without using a light shining on the surface. I also bought a sample kit of glow paint from glownation.com. One of the colors/phosphors is called "Super Phos Green". That stuff glows for hours. Like 12 hours. When I wake up in the morning, the jar is still glowing from the night before. It is faint, but it is glowing still. Anyway, I was thinking, what if the e-ink spheres were composed of black/phosphor. The phosphor side would have a slight greenish-yellow cast, but not terrible. The e-reader would have two modes; day and night. Day mode would be normal - white page and black text. Night mode would be inverted - black pages and white/phosphor text. The way it would work is that the e-reader - when switched to night mode - would temporarily transition to an all black screen, exposing the white/phosphor side to the LED backlight. The LED backlight would temporarily turn on and charge the phosphor, then turn off. The screen would then go to the inverted text mode, and the text would glow green. At each page turn, the screen would transition through an all black screen for just a second before going to the next page and the LED backlight would come on and recharge the phosphor. I guess the LED backlight would deplete the battery more than normal mode, but less than using an LED light that has to be continuously on to read. Anyway, what do you guys think? I tried to post this to but apparently no text posts are allowed. That's cool.
|
[
"I assume there would be mechanical difficulties with combining screen types that way. But in theory, yes, it can be done."
] |
[
"I think this is a great idea, though you are probaly not the first one to think about it, it's highly likely very impractical to make. "
] |
[
"Yeah, I just had to get it out in case I forgot it. "
] |
[
"Viral spread in marine environment?"
] |
[
false
] |
How do viruses spread in marine environments? After reading about the morbillivirus causing the increase in dolphin beachings and deaths, I was wondering how a virus like this might spread in a marine environment.
|
[
"Understanding aquatic disease is in three steps: 1) you have to have an environment suitable for the pathogen, 2)you have to have a susceptible, compromised/stressed individual, 3) you need the right pathogen. When all three are positive, then disease is highly likely. If one is negative, then you have a very low possibility.",
"When it comes to pathogens in general in the aquatic environment, the water itself tends to be the transmitter: that is the media/mode by which contact with may result in the transmission of pathogen to the host. Like the common cold be can be transmitted through the air, many pathogens can be transmitted by water.",
"What we worry about in the realm of viral outbreaks in oceans for stocks of fish, whale, and other resources is how that virus exactly transmits itself. You can't treat the organism without acknowledging the pathogen's mode of transmission. Most of the time, we think of horizontal spreading of viruses: that is direct contact between infected individuals or the media that is occupied by a pathogen. Basically: organism-to-organism whether directly (touch) or indirectly (touching the transmitting material). There can be also vertical spreading (from mother to daughter/son).",
"Many disease causing pathogens are found in the soils more so than the water column. This is because eventually diseases in the water column have to fall because they are particles and are subject to Stokes' Law. The only way to counteract this and remain in the water column is to be buoyant in some capacity (have a vacuole or something). Or, it divides fast enough to infect carriers.",
"Carriers are disease vectors such as little fish, inverts, or other plankters that can carry the disease itself, but don't necessarily become affected by it. When an organism eats a carrier, or comes into contact with the carrier in a way that's similar to how a remora attaches to a shark, then it can be sick.",
"Finally, diseases and carriers of disease in the oceans move about with the help of vector dynamics (movements of carriers) and the currents/tides themselves (physical moving of pathogenic particles). Pathogens can be killed in bad environments by chance so this is one reason why you may see local diseases. Other reasons are that there are no individuals to infect so there's no chance for the disease to occur. However it can still persist there in the carriers. And further, other areas may aggravate the occurrences of viral disease so that it may be even more devastating than the source area of the disease.",
"Simply put, viral dynamics in water are not too dissimilar than viruses in air media."
] |
[
"Multiplicity of infection is an important concept to this as well. ",
"One virus is not likely to cause an infection due to probability of it infecting, not being killed by innate immune response, and not being cleared too quickly before enough virus are produced. So just because 1 particle is floating around doesn't mean it will cause disease and concepts like proximity are very important. ",
"A lot of disease transfer in aquatic environments is the same as terrestrial and usually from food sources and contact when enough virus particles are exposed. "
] |
[
"One lesser appreciated role of viruses in the ocean is the Microbial loop. Basically, bacteria are constantly uptaking carbon and being killed by viruses in the open ocean. Quite a lot of material gets cycled through this loop over and over again, occasionally getting diverted up the food chain to copepods and fish and whales and things.",
"There are a ",
" of viruses in the ocean...by abundance, 95% of all nucleic acid containing objects, by biomass, about 5% (meaning they probably outmass all the eukaryotic life in the oceans...the other 90-odd% is bacteria).",
"http://www.nature.com/nrmicro/journal/v5/n10/fig_tab/nrmicro1750_F1.html"
] |
[
"What do we know about employee self-management and work motivation?"
] |
[
false
] |
I can find a lot on how self-management or employee participation in decision-making in private firms affect productivity and health, but are there any studies that have attempted to measure how the motivation to work is affected by less hierarchical organization structures? Also, what do we know (from experiments or otherwise) about the general effect on taking part in decision making and how that affects your willingness/motivation to participate in what that decision resulted in? Finally, is there any concept similar to "framing" that can be applied to this? That is, does the illusion of being part of a decision work almost as well as actual involvement?
|
[
"Take this post with a grain of salt, I don't keep up with the latest research in I/O psychology. With that said;",
"There's been ",
"some research",
" suggesting that employee participation ",
" significantly alter motivation - the \"Moderators\" subheading of the paper I've linked to discusses the studies in question.",
"Apparently, when an employee is not involved in a decision ",
" the reasons for that decision are not adequately explained, then ",
" when motivation and performance suffer. So in regards to your final question, there's presumably no need for an 'illusion' of being part of a decision - as long as the reasoning behind the decision is given."
] |
[
"There's also a ",
"neat animation",
" done of the same guy's talk"
] |
[
"There's a neat TED talk on why incentives don't work.",
"Link"
] |
[
"Do other elements naturally occur in multiple configurations in their pure form, the way carbon does?"
] |
[
false
] |
Do other elements naturally occur in multiple configurations, the way carbon does? Not just phases. Pure, solid arbon naturally occurs as and graphite, for example. I realise it bonds more generously than most elements, but do are any others diverse like this?
|
[
"do you mean like allotropes?",
"Carbon can have several allotropes including buckyballs, graphite, and diamond, and more. ",
"http://en.wikipedia.org/wiki/Allotropes_of_carbon",
"Other elements can exhibit allotropy",
"http://en.wikipedia.org/wiki/Allotropy"
] |
[
"Almost all elements can take on a variety of configurations of pure elemental forms. (Perhaps the Noble Gases are an exception, as they're unable to form bonds under common conditions.) Elements like phosphorus and sulfur take on many structures, but you might not encounter them every day. A better example would be oxygen: both diatomic oxygen gas, as well as triatomic ozone, are stable at standard conditions.\n(As a side note, there are also many more allotropes if you consider those that will only remain stable at nonstandard conditions.)\nAllotropes of carbon are most commonly used to demonstrate the phenomenon because there are several with which the average person will be familiar. (And because the energetics of switching between allotropes makes the majority of carbon allotropes quite stable and slow to interconvert.)"
] |
[
"Exactly what I was looking for, thanks! I appreciate the links."
] |
[
"Before methods of starting a fire were discovered, was the only source of fire from lightning?"
] |
[
false
] |
thoughts?
|
[
"You mean the only human-used source, or only source in nature?",
"Lava occasionally starts brushfires."
] |
[
"http://en.wikipedia.org/wiki/Andamanese_people#Culture",
"\nPeople in the Andaman Islands kept fire going from lightning for thousands of years."
] |
[
"Natural things that can start a fire:",
"Lightning is by far the most common."
] |
[
"What happens to ants and their nest when it rains?"
] |
[
false
] | null |
[
"Water diffuses into the soil. Nest tunnels are surrounded by soil, so as water moves down through the soil, even if it drips into a chamber/tunnel, it will eventually hit soil again and diffuse. If the water table rises it can flood the deepest tunnels, however, ant nests are usually quite large and have plenty of space for ants to evacuate to closer to the surface.",
"If the nest were to flood more completely, many ant species can remain submerged for hours, other species will evacuate to the surface and move nests"
] |
[
"Some various articles about different aspects of my explanation, nothing incredibly specific, really.",
"http://link.springer.com/article/10.1007/BF02223951#page-1",
"\n",
"http://web.archive.org/web/20060524210928/http://wwwrcamnl.wr.usgs.gov/uzf/unsatflow.html",
"\n",
"http://link.springer.com/article/10.1007/BF00377268#page-1",
"\n",
"http://psyche.entclub.org/96/96-239.html",
" << Seems to be down at the moment.\n",
"http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3032.2005.00492.x/abstract;jsessionid=AC46B5FA91FD9C5F5FFA61B219DF7E72.f01t02?deniedAccessCustomisedMessage=&userIsAuthenticated=false",
"Journey to the Ants and The Ants by E.O. Wilson/Holldobler provides a much fuller description. Can't remember which one specifically, but both are worth the read."
] |
[
"Fire ants create a float simply by linking their bodies together. The raft floats on the surface until the waters recede. Here are a couple of pictures.",
"Raft",
" floating in the water. ",
"Bridge",
" across two land areas. ",
"Pressed",
" down to show how buoyant the float actually is.",
"Not all species are like this, but I think their response is very interesting. "
] |
[
"How complete is our knowledge of any particular single cell? Can we build an atom-for-atom model of a living cell?"
] |
[
false
] |
I was reading an article about aging that mentioned a class of proteins who's function in cells is still unknown. This surprised me as I had kinda assumed that we had a pretty perfect knowledge of the structure and function of at least some cells. I had believed that we could break out the little plastic atom sets and build an exact model of a cell, if we wished to. Is this not so?
|
[
"Yeah we are constantly trying to solve more structures and new things are being added to the ",
"protein data bank",
" all the time. It's hard to make a prediction about when something like this would be available though. A lot depends on how accurate you want the model to be. Take a quick look at how resolution works ",
"here",
". ",
"We have atomic level models of many viruses. They are much much easier to do for several reasons, 1 is that your typical virus is much much much smaller than your average cell. In addition viruses tend to be made up of a very small number repeating protein units. So once you have the structure of 1 unit and how it connects to the others you essentially know the whole thing.",
"I'm honestly not sure if we will ever be able to create an atomic resolution model of something like an e.coli cell. At least not any time soon. I don't think a method of taking all the known structures and combining them into a final model would ever work, and even if you got it right you would never know that you weren't missing things. ",
"Ultimately you would need a method to take an atomic resolution image of an individual cell. I honestly can't see that happening in the next hundred years...maybe not ever. "
] |
[
"We can get close to replicating large scale function of simple cellular organisms. Stanford had a project a couple of years ago simulating a single cell of ",
" but this is largely a simulation of intracellular activity. It took around 1GB of data for a single cell, and took around 12h to simulate one replication cycle.",
"In reality, it's far more complicated. A lot of what cellular organisms do is communicate with their environment. We are not yet at the stage where we can incorporate multi-cellular interactions (which are still applicable to individual cells, as they effect gene function).",
"To simulate an atom-by-atom approach is currently far beyond our computational capacity."
] |
[
"There are several technical problems. A cell contains an incredible number of atoms, so even if you do (relatively) simple classical Newtonian mechanics you would need a fearsomely powerful array of computers to process all the interactions. Such simulations are called molecular dynamics simulations and even simulating boxes as small as (10 nm)",
" is computationally challenging for long simulation times. ",
"These simulations usually use discrete time steps in the 10",
" s range, which is necessary to resolve the thermal motion at these energy scales correctly. So to get to a second, you need to calculate 10",
" (1 000 000 000 000 000) update cycles. At each cycle, you need, in principle, to calculate the interaction of each atom with each other, so if you have n atoms, each time step needs n(n-1) ~ n",
" evaluations of some force potential (this can be optimized somewhat by disregarding atoms that are very far away, but the problem still scales at least linearly with the number of atoms and this so-called cut-off is problematic for long-range forces). That is a lot of processor cycles.",
"Even if you have a sufficiently powerful computer, there's still the problem that classical dynamics isn't really correct. While it provides surprisingly good results, these are usually the result of effective force fields that are calculated in a previous step with a quantum mechanical simulation. You need to perform this calculation for all the molecules in your cell, which is very challenging as well. The resulting effective potentials usually also don't capture all of the characteristics of your system, so they are only good in some calcultions but not in others, and it's not always clear if they work or not. It also requires a lot of knowledge about the molecules, at the very least their structure formula and the structure they commonly have in a cell.",
"That being said, chemical reactions, which are a big part of what a cell is about, are not even covered by this. These would have to be calculated in a sort of intermediate quantum chemistry step or every possible chemical reaction would have to be pre-calculated. ",
"So, all in all, we are still a long way away from being able to calculate something as large as a cell. Simulation techniques and hardware are always progressing, however, so if you ask the question again in 20 years time, we may already be able to simulate at least parts of a cell and will probably be a lot closer to a full one. 20 years ago, probably nobody would have been able to simulate even a single fairly simple protein, which we are now able to do fairly well."
] |
[
"If we could theoretically break the speed of light, would we create a 'light boom' just as we have sonic booms with sound?"
] |
[
false
] |
[deleted]
|
[
"In media such as water where the speed of visible light is less than its speed in a vacuum, charged particles moving faster than the local speed of light will produce a cone of radiation called Cerenkov radiation, which gives nuclear reactors their characteristic blue glow."
] |
[
"What makes the visible light slower",
"The current best-accepted explanation goes something like this: light traveling in a medium couples to vibrational modes (and other types of excitation modes) within the medium, and ceases to be a massless photon but rather becomes a type of particle called a ",
"polariton",
". Polaritons are massive, and thus they travel slower than the speed of light in vacuum.",
"The former best-accepted explanation was that photons are repeatedly absorbed and emitted by particles in the medium, thus briefly slowing them down on their journey. However this explanation is unsatisfactory because different materials have discrete absorption and emission spectra, therefore only some wavelengths should be slowed, but in experiments this is not the case, so that explanation is lacking.",
"Hope that helps!",
"Edit: autocorrect; but really, \"automistake\" is more accurate"
] |
[
"What makes the visible light slower",
"The current best-accepted explanation goes something like this: light traveling in a medium couples to vibrational modes (and other types of excitation modes) within the medium, and ceases to be a massless photon but rather becomes a type of particle called a ",
"polariton",
". Polaritons are massive, and thus they travel slower than the speed of light in vacuum.",
"The former best-accepted explanation was that photons are repeatedly absorbed and emitted by particles in the medium, thus briefly slowing them down on their journey. However this explanation is unsatisfactory because different materials have discrete absorption and emission spectra, therefore only some wavelengths should be slowed, but in experiments this is not the case, so that explanation is lacking.",
"Hope that helps!",
"Edit: autocorrect; but really, \"automistake\" is more accurate"
] |
[
"how would Proton decay work?"
] |
[
false
] |
I've read that proton decay is handled by x and y bosons, but I don't get how. They have color charge and weak isospin so I assume they act on a single quark, bu what happens to the other quarks, and why can the x and y decay into two quarks despite only having one color charge?
|
[
"The X and Y bosons you speak of are part of a Grand Unified Theory (GUT). We have no evidence that they exist, and experimental data shows that the proton is stable on timescales exceeding the age of the Universe, so no one has ever witnessed one decay.",
"That being said, many theoretical physicists consider GUTs because they're aesthetically pleasing and have a lot of symmetry, and there are a couple good reasons that they should exist at very high energy scales, so it's not entirely out of the question.",
"In the simplest GUT: ",
"SU(5)",
", there are 24 force-carrying particles. Because of the massive amounts of symmetry in the theory, quarks and leptons are interchangeable if the symmetry is unbroken. Unfortunately (or maybe fortunately), the symmetry ",
" broken, and several things happen:",
"1) 12 of the 24 force-carrying particles become the ones we know about today (gluons, W's, Z, photon), and the rest are known as the X and Y. They are superheavy and don't interact often.",
"2) The quarks and leptons are no longer the same, and now behave as different particles (quarks now have color, whereas leptons don't, for example). However, because of the previous symmetry, they still couple to the X and Y bosons.",
"Now because the quarks and leptons couple to the X and Y, it is possible to change a quark into a lepton if it interacts with one of these bosons. In a proton, you have several quarks, and during this hypothetical decay, two of the quarks merge together to become a virtual X/Y, which then quickly turns into a quark and a lepton. So now instead of 3 quarks, you have 2 quarks and a lepton, which quickly rearrange themselves into a meson (quark-antiquark bound state) and a free lepton (in a way that conserves charge, color, spin, etc.). The reason this would be possible is because the meson-lepton final state has a lower mass than the proton. Even though the intermediate X/Y is ",
" heavier than the proton, it can exist for a short time because... quantum mechanics says so. So now your proton is gone, and you have a lepton and a meson (which itself quickly decays to other leptons). The proton has decayed.",
"That's the gist of it. Proton decay is also possible in supersymmetry (if you include baryon-violating interactions), but instead of X/Y bosons it's the squarks that mediate the decay. People impose something known as R-parity in order to get around this."
] |
[
"From that perspective it is, but i wanted to emphasise the point that it is a highly non-trivial process to get rid of proton decay in susy models. It actually gets worse if you include other problems like the mu-problem. Additionally you can potetially run into problems with cosmological history because of domain walls or other things.",
"I get annoyed when people say \"just introduce R-parity and you dont have to worry about proton decay\"."
] |
[
"That's the gist of it. Proton decay is also possible in supersymmetry (if you include baryon-violating interactions), but instead of X/Y bosons it's the squarks that mediate the decay. People impose something known as R-parity in order to get around this.",
"People all the time say that R-parity is enough to prevent proton decay in supersymmetric models, but unfortunatly this is not true. You still will have dim-5 operators mediating proton deccay. There ae ways around this by imposing discrete symmetries (like \"matter hexiality\"), but these may have other prolems. For example if you want to have a discrete symmetry preventing proton decay and also commuting with a SO(10) GUT the discete symmetry is unique !"
] |
[
"How does a virion assemble itself so perfectly in an infected cell?"
] |
[
false
] | null |
[
"The first thing to know is that almost all viruses are actually very bad at assembly. There are two ways to measure the quantity of virus in a sample: you can do qPCR - a way to quantify how much of a specific sequence there is (in this case you’re quantifying viral genome copies) and you can do a plaque assay - a way to see how many infectious particles there are. ",
"The first method (number of viral genomes) usually gives a result 100x higher than the second. This is a gross generalization of course but in general it holds true. What all this means is that for every active, working virus, there are 99 shitty ones. Some of these are bad mutations that make it ineffective, and some of these are poor assembly. The virus doesn’t have to be perfect, the strategy is to just make a lot and enough will work out. ",
"As for the ones that do it right, it’s all about the viral proteins and how they all fit together. Imagine a soccer ball disassembled into the individual pieces, except when two pieces that are meant to go together touch sides they kinda stick together. Now all the pieces are floating around in a small space, thousands of them. Pretty quickly you’re gonna start getting soccer balls out of that soup. That’s how the coat, or capsid forms. The viral genome and other proteins get in there because they stick to the inside of the soccer ball as it forms up."
] |
[
"Oh thanks for your input! Is it possible for viruses to accidentally pick off certain parts from the host? And in a way mutate because of this?"
] |
[
"Non-enveloped viruses vary, some have a tiny capsid that don’t allow for any extra cargo but it’s very very hard to rule out that a host protein or two hitch a ride. Enveloped viruses typically pick up a bunch of host proteins in the tegumen - the space between the lipid membrane and the capsid - and carry those with them. Also the membrane itself, often taken from the endoplasmic reticulum, will have host proteins embedded in it. ",
"These proteins can have an impact on what happens upon infection. There are multiple examples of this, the one that comes to mind is two reports in Science about virus picking up inflammatory second messenger molecules called cGAMP and packing it in its virions. Upon infection of a naive cell the cGAMP immediately activates its antiviral response. ",
"But taking on extra protein cargo isn’t the same as mutation. The viral genome is what it is, and mutation rate is only affected by its replication machinery and host defenses (part of antiviral defense are enzymes that severely mess up RNA transcripts, this is technically mutation but they produce nonsense, viruses that have undergone that kind of editing will be dead). ",
"Finally, stepping away from the kinds of viruses I think you’re asking about, there IS genetic transfer in a way between virus and host. There are a number of genes in the human genome that originate with endogenous retroviruses (parasitic elements that are permanent components of our genome) and have been repurposed to serve essential functions for us. There are also viruses that encode malicious versions of key host proteins, a phenomenon called viral mimicry. I have no idea if these are thought to have been picked up from the host or if they evolved naturally in the virus. My moneys on the second idea. the chances of such a thing happening are infinitesimal, but viral reproduction rate is really really high. Over 1000s of years of infecting an animal, a virus can easily develop all the machinery it needs."
] |
[
"How does antibody treatment work with COVID-19?"
] |
[
false
] |
My issue is the following: IV administered IgG mixture does seem to work in animal models and in patients. The question really is: does it work on the lung surface? If it does, how? Any papers I have seen suggested that very little IgG reaches the mucosal surface, as the FcnR transport "outside" is not very effective; IgAs use a different mechanism to reach the surface. Yet it seems like IgG based treatments work. Do they work by limiting the viral replication outside the lung, leaving the lungs "undefended"? Wouldn't this cause serious problems with inflammation in the lungs? The other idea I can think of is that when these are administered, the integrity of the lung tissue is already compromised, so the IgGs can reach the mucosal membrane reasonably well - but this would mean the treatment is not useful as a preventive measure in mild cases when the patient is in a high-risk group. Since I cannot find any papers discussing the mechanism of IgG therapy within the lungs I thought I would ask here. EDIT: Thank you all for the answers, but the strange thing is that none of the responses here actually addressed my question: namely how does IgG reach the mucosal surface -if it ever does in a meaningful way. Back in my PhD we did some experiments of FcnR mediated IgG transport with intestinal lining -mucosal surface but not lung- and our results were sub 1%, so this is why I am curious how IgG treatments work.
|
[
"IgA is only one layer of defense. It is important in the initial acquisition of an infection because of its action at mucosal surfaces. Although IgG isn't as good at getting to mucosal surfaces, it plays a role in preventing the virus from further replicating and spreading. It is even present in mucosal linings to some extent and helps activate immune cells that line the lung's air sacs (alveolar macrophages);",
"",
"IgG is generally a much more powerful activator of the immune system than IgA.",
"",
"Also, IgA's shelf life in the body is only a few days and IgG is a few weeks.",
"",
"Info on IgG in respiratory tract",
"https://www.mayoclinicproceedings.org/article/S0025-6196(12)64949-0/fulltext",
"64949-0/fulltext)"
] |
[
"It’s a common misconception that the IVIG is used to fight the virus.",
"IVIG attaches to virus particles throughout the body, which reduces the amount of virus the body’s own immune system sees. This then has a major role in downregulating the strength of the body’s immune response.",
"In conditions of hyperinflammatory response, such as the way the immune system goes nuts in the lungs of Covid patients, the theory is that turning the volume of that response down will improve health outcomes.",
"There’s not great evidence for IVIG in Covid, although it is being tried.",
"Source: am doctor, have prescribed it."
] |
[
"a bunch of things point to fake poster with no history and something being off. a physician would normally say physician rather than doctor and would not say «prescribed it». The descriptions are simplified and inaccurate with weak theories put in as facts. ",
"source: am physician scientist, two immunology publications in Nature, have not provided ivig to any of my patients (yet) ...."
] |
[
"What is this perfect arc of discolored peel from stem to navel on my orange?"
] |
[
false
] |
I bought a bag of navel oranges, and one of them has a . The discolored area starts as a narrow arc at the stem of the orange, broadens over the meridian, and ends at a wider arc around the navel. I think it's too precise to be dyed. Why did it grow that way?
|
[
" Citrus fruits are segmented on the inside. Those segments develop from a part of the flower called the carpel. Part of the carpel is the ovary (female reproductive bit). The ovary wall is what actually forms the rind of this fruit. The rind is actually made up of the same number of segments as the inner fruit but the rind grows together.",
" I think one carpel of the original flower had some kind of defect that caused the discoloration. The discoloration is in a perfect band because it represents only one ovary wall section. If this is correct, when you peel your fruit there should be a fleshy fruit segment that lines up pretty well with the discolored rind."
] |
[
"Thank you!",
"I peeled across the band. ",
"Close-up shot",
". It turns out the discolored skin represents ",
" of a segment. One edge lines up with the segment edge, the other lines up (only roughly) with a fiber wandering roughly down the middle of the segment.",
"But the flesh of the segment itself looks normal."
] |
[
"I've done some poking around the internet and I can't find an explanation for only half of segment having the weird rind. I'm not surprised that the flesh seems normal as it is derived from a different part of the flower. For a better explanation of the 1/2 colored thing, we'll just have to wait for a botanist. (I'm am a biologist but my expertise is more animal based.)"
] |
[
"How does a single vibrating paper cone produce a sound in which one can distinguish multiple tones of distinct timbre?"
] |
[
false
] |
I know that a quality sound system is comprised of multiple speakers which reproduce tones of different pitch but how is it possible to (imperfectly) reproduces that full range of sounds with a single vibrating membrane, or a single, continuous wavy groove on a vinyl platter?
|
[
"Picture that you have a sine wave on a graph. Now, add another one at half the frequency:",
"f(x)=sin(x)+sin(x/2)",
"The graph of that function is what the waveform would look like for 2 tones played at the same time, with one being twice the pitch of the other. I just used sine because it's convenient; the waves that you add together can be any kind of sound wave. The structures in your inner ear are actually constructed to separate the tones apart again, providing your brain information on specific frequencies of sound."
] |
[
"The way speakers handle pitches is by vibrating at certain frequences. The faster it vibrates the higher the pitch.",
"A subwoofer cone can vibrate quite slowly. But the lowest frequency audible to a human is about 20Hz if iirc. The highest freq. we can hear is about 20.000 Hz, but this usually lowers as you get older.",
"You can certainly produce a cone that is able to cover that spectrum of frequencies, but it is preferable to separate the tweet from the sub to get a better soundscape.\nYou must just make sure that the material of the cone is able to withstand oscillating back and forth from 20 to 20.000 times per second.\nAnd make sure that it can take sudden changes etc."
] |
[
"As you know, sound is comprised of sound waves, which can be thought of differences the density of air travelling in a direction. Objects can emit sound by vibrating - the vibration causes the air above it to compress, increasing the density, and a sound wave is created. The pitch or frequency of the sound depends on the amount of waves per time period (eg. the number of waves reaching your ear every second). As the frequency increases (more waves per second), the pitch increase.",
"Any object that can vibrate can emit sound at any frequency - it just depends on how fast you vibrate it. A paper cone can be made to vibrate at different speeds, changing the frequency of sound produced. Likewise, on a vinyl platter, increasing the amount of waves in your grove over a certain distance will increase the amount of times the needle vibrates each second, which (after turning it into an electric signal to send to the speakers where it converts back to movement again) increases the frequency of sound produced.",
"The reason your quality sound system has multiple speakers is because different materials and different shapes of objects are better (or worse) at vibrating at different frequencies. Thus, when you make a sound system, you choose different speakers for different parts of the frequency range because they are better at vibrating at those frequencies.",
"A paper cone can do an ok job of vibrating in the acoustic range (ie the range of pitch that is audible to humans). However, paper isn't very rigid, and therefore different parts of the paper could start flapping around or vibrating at different frequencies - creating imperfect sound. "
] |
[
"whats the difference nutritionally between concentrated and not from concentrate fruit juice?"
] |
[
false
] | null |
[
"Concentrated fruit juice started as normal juice, was somewhat dehydrated (into a thick liquid), and was later reconstituted with water. This is done because concentrate stores for longer and ships more easily. Not-from-concentrate has been in its juice form the entire time. If you have ever seen the cans/tubes of frozen juice that you add water to, that is fruit juice concentrate.",
"Nutritionally there shouldn't be a big difference if the final product is just concentrate + water, but some people think that re-concentrated juice tastes different or has a different texture, it is certainly more \"processed\" (but that's an ill-defined buzz word that doesn't necessarily mean less healthy), and it has likely had a longer shelf life."
] |
[
"It's also worth noting that fruit juice, concentrated or not, has very little nutritional value, and is basically just sugar water. Most of the good stuff in fruit is in the pulp."
] |
[
"To be fair, by far the most necessary nutrient is calories. Micronutrients are an absolutely tiny proportion of your food. It's not at all strange that also in OJ, micronutrients only represent a tiny fraction of the product."
] |
[
"The lights turned off when I touched the light-bulb with a wet finger - why is that?"
] |
[
false
] |
So I was trying something random/weird. After washing my hands, I touched the light-bulb in the bathroom with my wet index-finger. Then, suddenly and silently, the lights went off. It's this type - .
|
[
"I have an explanation for you. I think your bulb isn't completely screwed in, so it barely makes contact. When you touched it, you may have moved the bulb enough that it broke the connection, thus turning it off. I think your finger being wet was just coincidental."
] |
[
"Is it possible the bulb was barely screwed in? ",
"Many times when people install light bulbs with the switch on, they stop turning when the bulb lights up. But this doesn't get the bulb screwed in tightly, so bumping or touching the bulb can make it appear to go out when it actually just disrupts the connection."
] |
[
"This seems like a coincidence to me. Did the bulb work afterward? Did all the other lights also turn off?"
] |
[
"A question about ice interact with water."
] |
[
false
] |
If you have one Cubic meter of ice at -10°C and one Cubic meter with water at 10°C. If These two blocks interact with eachother will the ice gain more ice or will the water gain more water? (There is no other considerations)
|
[
"The math is easier if you use mass instead of volume. but to estimate...",
"according to this site:\n",
"http://www.school-for-champions.com/SCIENCE/heat_ice_steam.htm",
"the specific heat of water is 1.0 cal/g degree C",
"the specific heat of ice is .5 cal/g degree C",
"for 100 grams of ice changing temperature from -10 to -0 C you would absorb 500 cal.",
"for 100 grams of water changing from 10 to 0 C you would release 1000 cal.",
"since we know a binary solution of water and ice will reach equilibrium at 0C assuming no heat interaction with its environment.",
"we can say that the ice will melt a little in order to absorb the addition heat released by the water. ",
"You picked volumes so we would have to compare our estimate against that ",
"a cubic meter is 100",
" cubic centimeters.",
"the density of pure water is 1 g/cm",
"the density of ice (nominal) is 0.9167 g/cm",
"so a cubic meter of water should weigh 1000 kg ",
"and a cubic meter of ice should weigh 916.7 kg",
"if we plug that back into the original equation, the heat lost by cooling the water would be 10,000,000 cal",
"the heat absorbed by the ice coming up in temp would be 4583500 cal",
"so we would still need to absorb 5416500 additional cal through melting.",
"the heat of fusion of water is ~ 80 cal/g ",
"http://en.wikipedia.org/wiki/Enthalpy_of_fusion",
"which means we would need to melt ~67706 g or 67.7 kg of ice.",
"so your block of ice would shrink by ~73858 cc and weigh ~849 kg after the two combined.",
"and the water and the block of ice would both be ~0 degree C",
"note: i did not check my math."
] |
[
"Not even close. You neglected the heat of fusion (the energy needed to break apart the ice lattice to make water), which is 334 J/g."
] |
[
"Not even close. You neglected the heat of fusion (the energy needed to break apart the ice lattice to make water), which is 334 J/g."
] |
[
"When deep in thought, why do you \"space out\" and can't focus on things even right in front of you?"
] |
[
false
] | null |
[
"Attention is a finite resource. When you are devoting a lot of attention to a thought, you aren't as aware of your sensory perceptions. There are a number of what are called executive functions (",
"http://en.wikipedia.org/wiki/Executive_functions",
") that help to manage your attention and other cognitive resources. When you are working in a noisy environment, for example, EF can help you \"tune out\" the noise and focus. Likewise, if you are deep in though, you don't have resources available to attend to other things. Since our attention and cognitive resources are finite, this is a good thing, since otherwise you would just be overwhelmed by the stimuli in the world all the time."
] |
[
"is ADHD when people lack a lot of these functions?"
] |
[
"I love that psychologists use the term Flow. It's so simple.",
"Flow happens when a person is immersed in something they are skilled in but are still challenged by, such as creating something with your hands, playing music, or solving a problem. Religious activities, create flow as well. ",
"\"In every given moment, there is a great deal of information made available to each individual. Psychologists have found that one's mind can attend to only a certain amount of information at a time. According to Mihaly's 1956 study, that number is about 126 bits of information per second. That may seem like a large number (and a lot of information), but simple daily tasks take quite a lot of information. Just having a conversation takes about 40 bits of information per second; that's 1/3 of one's capacity.[6] That is why when having a conversation one cannot focus as much attention on other things.\"",
"http://en.wikipedia.org/wiki/Flow_(psychology)"
] |
[
"Would a poke with the same force as a punch do more damage?"
] |
[
false
] |
This question is assuming I won't break my finger/hand performing the poke. Mainly, I have no idea what determines how much harm an impact causes to a person.
|
[
"There are two major components of \"punching damage\", aka blunt force trauma: Acceleration and compression, which also corresponds to two types of transfers of kinetic energy: elastic collision and in-elastic collision respectively.",
"Compression is when you absorb impact energy in an inelastic collision. This is what causes bruises and it can in serious cases deform hollow organs and lead to ruptures.",
"Acceleration is when the impact energy transfers to you in an elastic collision, making you accelerate and experience massive g-forces during a short period of time. This is what \"knocks you out\", and is generally the more dangerous of the two.",
"If the poke and the punch had the same kinetic energy (same speed and weight behind the punch) the poke would be more dangerous in terms of \"compression damage\", as the impact area would be smaller. But the \"acceleration damage\" would be more severe, as your fingers in a poke would probably compress on impact, thus making some of the impact energy go to compressive damage to ",
" fingers.",
"TL;DR: If you aim for a soft-spot such as the throat or the eye, the poke would do more damage. If you aim for a harder part such as the forehead, you'd do better with a punch.",
"EDIT: Typo."
] |
[
"Easy way to visualize this is to go to extremes. Imagine a 20 lb weight falling on your stomach that is in the shape of a barbell weight. Then imagine the same 20 lb weight with a spike on the bottom of it falling towards your stomach. The less like a spike, the less chance of penetration."
] |
[
"What baalak and ronin1066 said, and also what you said - you have to make sure your don't break or jam your fingers. For that reason these types of fists are best reserved for certain types of targets, like around the neck down to just above the sternum, or possibly the temple, sometimes the ribs if you know what you're doing.",
"Also, there are other fists, like Leopard, which ",
"is formed by folding the first two joints of the fingers",
". This is handy for a direct muscle blow, and also neck blows. It gives a couple of inches of extra reach over a regular fist, has a small surface area like a poke, but is a little safer for your digits. Hit somebody in the pec with a leopard fist when they're advancing on you, it'll stun them momentarily at least."
] |
[
"Relationship between most favorable energy states on a chemical and quantum level. What are the implications for origin of life?"
] |
[
false
] |
Hi, as far as I understand, chemical reactions occur because the atoms "prefer" to be in a lower state, energetically. Why is that so on a quantum level? Also, if all chemical reactions are trying to sustain the lowest energy state, then would that mean that DNA, is doing that as a macromolecule? (And its current incredibly complex mechanisms are just functions of fighting entropy.) If I sound like I'm confusing things, please correct me. I'm a biology major in college, and most of what I know about quantum physics is stuff I read up on my own. These are just questions that I came up with when working on my philosophy of existence paper. If there is any relevant work on this it would be awesome to have a few examples. Thank you!
|
[
"I think you trying to connect a lot of disparate ideas in a way that is entirely unnatural.",
"Systems tend to follow the course of lowest action, and minimize energy state for conservation of energy reasons. On the other hand, if there is enough energy present (for example from thermal fluctuations), you can sample higher energy states. This is why we have population distributions between many quantum states. However, as you move to larger systems quantum effects become unnoticeable, and instead we move towards continuum mechanics (as you have relatively infinite quantum states for the range of energies at play). While we can recover macroscopic properties from quantum systems using statistical thermodynamics, it's often times better to address these types of systems using more appropriate models. While many macroscopic systems may appear to follow entropic trends, once you've moved to a certain scale, your no longer working with the definition of entropy as intended (possible distributions of states), as the number of quantum states available is essentially enumerable. For this reason, \"the clothes scattered over a dorm room analogy\" doesn't really work in a meaningful way as an entropic explanation, as the possibility of scattered states is essentially infinite, so a shoe in one corner versus the other is making essentially no difference.",
"As we move to DNA, sure you can talk about the organization and folding of DNA in terms of energy minimization, but this doesn't relate to composition, as this is governed by enzyme mechanics. So, while the enzymes locally minimize the energy of the system when they catalyze the formation of DNA, the composition is a large stretch away from a more global minimization. In fact, most biology depends on far from equilibrium systems being maintained. ",
"So, while you might be able to conceptually make the jump from small molecules to a larger system of complex organism, and observe similar patterns and trends, no good mathematical model actually links these systems, so they are essentially independent. While some models are similiar in the pattern they form, the mathematical assumptions going into the model are going to be different, even if this is just in the form of inputs, meaning that the two systems cannot be directly compared.",
"TL-DR: While these systems may seem to follow similar trends/ patterns, they essentially are different, or at least no proven link exists."
] |
[
"What I'm trying to say is that while the quantum mechanics may be negligible on a macro scale, weren't they the basis for all of atomic bonding in the first place? ",
"On the scale of an atom aren't the quantum mechanics fairly important? \n(The orbital theory of the atom and hybridization states.) ",
"The first building blocks were likely formed under more extreme conditions that allowed for nucleotides to form naturally. \nWouldn't this nucleotide (a pretty small molecule) formation follow the laws of binding that are the result of quantum mechanics of electron movement? \nThen the entire genetic code is a slow accumulation of these nucleotides coming together to be an energetically stable state. The molecules that by chance found themselves within a membrane would then have a micro environment in which the reactions can occur, and necessary (yet accidental) pathways to keep those building blocks stable be the one that would \"survive\" and continue to what we have as early life?"
] |
[
"why are you wanting to bring quantum into this? Why not use a more traditional chemical approach?",
"Sure, you can talk about quantum mechanics in a DNA context, but things get needless complicated almost instantly. One analogy would be trying to swat a fly. Sure, I can talk about getting rid of a fly using a lazer targeted cruise missile with a nuclear payload. It would be very efficient at doing the job, and would certainly kill the fly. But it would be a lot of effort to construct a nuclear weapon just to swat my fly, while on the other hand I could use a more appropriate tool such as a fly swatter. Sure, I have not completely obliterated the fly, but I've saved myself a lot of effort in the process.",
"Using quantum mechanics to describe the genetic code is similar. Sure I can get the job done this way, but it's probably not worth it to go through that effort for this particular fly.",
"Additionally, your adding this natural selection bent of survival which I don't think is wholly appropriate in this context."
] |
[
"Are people with higher IQ more suscetible to depression?"
] |
[
false
] | null |
[
"Just looking at raw correlations, higher intelligence would seem to be associated with a lower overall risk of mental illness. ",
"Lower IQ score was associated with increased risk for schizophrenia, severe depression, and other nonaffective psychoses, but not bipolar disorder.\" ",
"[1]",
"Lower childhood IQ predicted significantly increased risk of a diagnosis of schizophrenia spectrum disorder, major depression, or any anxiety disorder in adulthood. ",
"[2]",
"IQ scores were inversely related to the risk of total psychiatric illness, with the highest levels apparent in the lowest scoring IQ group ",
"[3]",
"There's a problem with taking these correlations at face value to mean high intelligence is a direct protective factor against mental illness: high intelligence is correlated with socioeconomic status, which is in turn correlated with... almost everything, as ",
"this study",
" points out. The first two studies above did not attempt to correct for socio-economic status and the last study only controlled for the parents' status.",
"a higher pre-morbid IQ was associated with less CES-depression, less sleep difficulty, and better SF-12 mental health status at age 50. In contrast, a higher pre-morbid intelligence was associated with higher rates of a lifetime diagnosis of depression. [...] Adjusting for adult SES [socioeconomic status] led to substantial attenuation of IQ's association with CES-depression, sleep difficulty, and SF-12 mental health, but it amplified the effect size of the association with a diagnosis of depression.",
"But again, this isn't enough evidence to conclude that high intelligence ",
" depression. It may be that intelligent people are both more aware of the symptoms of depression and have the resources to seek treatment.",
"It is possible that more intelligent Americans are motivated to strategically get a diagnosis of depression if they experience symptoms of psychological distress, even if they are not actually depressed, because it would allow them to get insurance coverage for treatment, which they might think they would benefit from",
"Based on these sources, it seems like there's not enough evidence for or against high intelligence correlating one way or another with depression."
] |
[
"From the opposite direction, low IQ correlates with early lead exposure, fetal alcohol spectrum disorder and a diverse range of congenital defects which all broadly adversely affect cognitive functions, including emotional regulation."
] |
[
"In a way. Mostly what I hear of is kids with high IQs end up having so much pressure put on them that they “burn out” and become depressed due to feeling like their letting everyone down. ",
"But otherwise i wouldn’t say their more susceptible just because of their higher IQ. It has a lot more to do with the brain chemistry and make up."
] |
[
"How does the immune system manifest itself at the mouth level?"
] |
[
false
] |
There are no white blood cells to fight off oral bacteria, so is there any antibacterial secretion in saliva?
|
[
"There are ",
"IgA",
" antibodies that line the mucosal layer of the mouth. This, along with ",
"lysozyme, lactoferrin, and peroxidase",
" are the primary molecules involved in the mouth's immune system.",
"When this system doesn't work properly, such as those with HIV/AIDs or people who take corticosteroids, flora in the mouth can take over. One of the most common infections is ",
"oral thrush",
" or candidiasis. When the mouth's immune system isn't in full function, this yeast will begin to take over and may spread to other places in the body. Source: I work with Candida"
] |
[
"And don't underestimate the mechanical cleansing provided by tongue, chewing, and swallowing. That helps to eliminate many microbes by sending them to the gastrointestinal tract. It is often forgotten that immunity is very much a numbers game, and diluting the contents of the oral cavity by continuous salivation and periodical chewing does a lot of the work!"
] |
[
"is there any antibacterial secretion in saliva?",
"Yup.",
"You produce lysozyme, an enzyme that targets the peptidoglycan layer in bacterial cell walls, immunoglobulin A, lactoferrin, and a few other proteins that have antibacterial as well as antiviral and antifungal properties."
] |
[
"Is it possible to have two different dreams in the different hemispheres of the brain?"
] |
[
false
] | null |
[
"Yes and no. I'll start off with why not. The two hemispheres of the brain are connected at numerous points, notably through the corpus callosum, anterior commissure, and hippocampal commissure. The dense connections between the two hemispheres makes it almost impossible for something (real or imagined) to affect one and not the other. This effectively eliminates the possibility of a dream occurring in one hemisphere exclusively. The notable exception to this is \"split-brain\" patients, who have had their corpus callosum severed. I haven't seen any studies of dreaming in split brain patients (they may be out their), but I would presume that ",
"PGO waves",
" (which are thought by many to be the ",
"neural correlate",
" of dreaming) would occur somewhat independently in the two hemispheres, so you could effectively say they are \"dreaming\" independently. The reason I say \"somewhat independently\" is because of possible residual connections left in the corpus callosum or other inter-hemispheric fiber tracts, which would allow information to flow between the hemispheres.",
"edit:spelling + grammar"
] |
[
"I agree that due to the myriad connections between the two hemispheres, the idea of dreaming different simultaneous dreams in each hemisphere is far-fetched. ",
"As for split-brain patients, remember that the brainstem is not separated in a split-brain patient, so the origin of PGO waves, the pons, is connected as normal. The \"G\" part of PGO, the geniculate, is part of the thalamus, which is rarely separated in the surgery (although there are some patients who had the massa intermedia cut -- those are the fibers that connect the thalamus. This was much more common in the early days of the surgery; later it became more common to cut only the fibers of the corpus callosum that were necessary to stop the spread of the seizures, so partial callosotomy became the norm. I don't think any of the original complete commisurotomy patients are still surviving at this point.) The O, the occipital lobes, are indeed separated in almost all such patients, and separate sensory experiences are known to occur. ",
"However, while PGO waves may have a role to play in dreaming, I do not think you will find any neuroscientist who believes them to constitute the neural correlate of dreaming on their own. If anything, they may provide the cortex with some \"random\" sensory activity which it can then go about interpreting. The question of whether each hemisphere can construct its own narrative out of those sensory experiences is a very interesting question that is not easy to answer. "
] |
[
"As we don't know what dreams are, it would be difficult to say - however I suppose people suffering from \"multiple personality disorder\" logically might indeed suffer from this syndrome. However we don't really know exactly what part of the brain it is that creates dreams, all we can do is watch people who are dreaming and see where their brain lights up using Functional Magnetic Resonance Imaging. Scientists are also studying Brain waves with the hope of interpreting dreams using a computer."
] |
[
"How do black holes get larger?"
] |
[
false
] |
When an object moves towards the event horizon of a black hole, it experiences increasing time dilation from our perspective. If it takes an infinite amount of time for matter to "cross" the event horizon then how can a black hole grow in size in any meaningful time period? Wouldn't all the new matter just run into the old matter outside the event horizon as it hits slower and slower time "areas"?
|
[
"The cores of black holes are, essentially, raw energy (sort of like the Big-Bang's theoretical singularity) held in place by seemingly impossible gravity wells",
"It's probably best to not talk about the nature of the singularity because we literally dont have models for it without quantum gravity. Suffice it to say that the interior of a black hole is an extremely exotic place we can't describe with our current knowledge.",
"Polar ejections of black holes are material in its orbit getting ejected, to be clear! It's like how orbital paths can result in an object getting flung out of orbit only way bore dramatic and cool."
] |
[
"The cores of black holes are, essentially, raw energy (sort of like the Big-Bang's theoretical singularity) held in place by seemingly impossible gravity wells",
"It's probably best to not talk about the nature of the singularity because we literally dont have models for it without quantum gravity. Suffice it to say that the interior of a black hole is an extremely exotic place we can't describe with our current knowledge.",
"Polar ejections of black holes are material in its orbit getting ejected, to be clear! It's like how orbital paths can result in an object getting flung out of orbit only way bore dramatic and cool."
] |
[
"Quasars man. One of the many things that could end all life as we know it with absolutely 0 warning. "
] |
[
"How is sea level and elevation determined?"
] |
[
false
] |
[deleted]
|
[
"It's pretty far from trivial actually, if you get right down to it. Let's start with ",
"this picture",
". All the features are of course exaggerated but it illustrates several interesting points. ",
"First the dashed green line (labelled 2). It's the reference ellipsoid. A kind of simple mathematical model for the shape of the Earth. Basically what you get if you take a perfect sphere and then squish it a bit so that the equator becomes wider than the polar great circles. It's a very rough shape for what you might call the shape of the Earth but there really hasn't been any effort to match it with local features like mountains.",
"Next look at the plumb lines (labelled 3). Think of having a stick in the ground and then a string tied to the top end with a weight at the end of the string. The plumb line is the line defined by the dangling string. So it is the direction gravity pulls the weight at the end of the string. In the picture the plumb lines are dangling at the end of spokes and the spokes go to the centre of Earth, you can see this because the spokes are at a right angle to the ellipsoid (well that's not exact, because the ellipsoid isn't a perfect sphere but close enough). But the plumb lines, the dangling string and weight, might point to a different direction. That means that the local gravity does not necessarily point to the centre of the Earth. Near mountains the mountain's gravity is significant enough to be measured and gravity points a bit towards the mountain. (See ",
"Schiehallion experiment",
", an 18th century experiment that tried to measure the mass of the Earth by measuring the gravity caused by a mountian.)",
"Then finally the geoid, or equipotential surface, (labelled 5). Note how the sea level is exactly at the equipotential surface. It's basically a surface where the gravitational potential is the same everywhere. Water tends to flow to a lower potential energy which of course means that if we ignore tides and waves and such, the water level settles at equal potential level. Of course there are many such equipotential surfaces, one for every potential energy value, where the water ends up depends on how much water there is. It goes to the lowest one where all the water can fit. The point however is that it's at one equipotential surface.",
"Also note how the plumb lines are always at a right angle relative to the equipotential surface. The local gravity is at a right angle to the equipotential surface (strictly speaking, not necessarily the same equipotential surface the oceans follow but one that crosses the local point at its altitude). Another way to think of this, what's level ground, it's when a ball will not roll on its own or water will not flow in any direction. What direction is the gravity pointing at on level ground, it's pointing down at a right angle to the ground. If it wasn't and was pointing a bit to some direction, the ball or water would move in that direction.",
"Gravitational potential energy is a mathematical concept that only depends on the mass distribution of the planet and where you are. The value of potential energy can be calculated even inside Earth. So you can figure out where the equipotential surface the oceans follow would be even inside a mountain, even though you don't actually have an ocean there. Thus the sea level can be extended inland as well.",
"The shape of the geoid, the equipotential surface, has been determined by accurately measuring the gravitational force experienced by orbiting satellites. Through these measurements, several different models for the geoid have been done, improving in accuracy over the years. For example, GPS devices use one such model to correct the initial values that are based on the simple ellipsoid to get a more accurate reading. ",
"Here",
"'s an image illustrating how the EGM96 geoid model differs from the reference ellipsoid."
] |
[
"There's more than one way. The easiest is air pressure. But other more sophisticated methods involve using GPS to tell you how high you are from the reference ellipsoid, or if you want even more accuracy, the height from the geoid. But (consumer) GPS units don't have geoid data built in to them, so you'd have to take your GPS data to a computer with geoid data."
] |
[
"It's a really good question; I do know it's based on atmospheric pressure, although I have no clue on the formula used to get the Worldwide Mean Value."
] |
[
"Does widespread immunity decrease virus mutation rates?"
] |
[
false
] |
With ongoing news about mutations to the covid-19 virus (and potential impacts to vaccine programs) I'm curious what the relationship between the level of population immunity and mutation rate is. It would stand to reason that lower infection rates -> fewer opportunities for mutation -> greater long term vaccine efficacy; but of course what's intuitive isn't always right. Are we in a race to get ahead of mutations, or does it not really matter?
|
[
"Iirc the logic you stated is correct. Because the virus does not transmit as readily it does not have as much opportunity to mutate as it doesn't get exposed to as much in the few hosts it has. This isn't to say that it can't mutate, just that the likelihood of it doing so is lower."
] |
[
"It would stand to reason that lower infection rates -> fewer opportunities for mutation -> greater long term vaccine efficacy",
"Generally, yes. To make things worse, if you have many vaccinated people getting exposed to the disease then mutations that avoid the vaccination or make it less effective are heavily favored. Ideally you would like to get cases down before starting a vaccination campaign, which is then used to keep the cases down only."
] |
[
"Your logic is correct! Fewer bodies infected with the virus leaves fewer opportunities for the virus to go through its replication cycle and thus, fewer opportunities to mutate. However, mutations could still arise in one or two infected people, because viruses are so tiny and create hundreds of thousands of progeny within a host they infect, so the opportunities with one infections are still present, but far fewer mutations will be selected for when there are dramatically less infections."
] |
[
"Is indefinite and undefined the same thing mathematically?"
] |
[
false
] |
As in an indefinite amount of times or an undefined amount of times?
|
[
"Do you mean indefinite integral? That's the only indefinite math term I can think of. In either case, indefinite and undefined are two different things. If you meant indefinite number in the linguistic sense: an indefinite number is one that is simply vague or undefined, such as a bunch of chips. There is a real and definite amount of chips, but the amount in a bunch isn't known or stated. ",
"An undefined number mathematically is one that \"doesn't make sense,\" it can't exist. The most familiar is probably dividing by 0.",
"You can think of division as asking \"how many equal parts can I make the numerator, or top number, into to get the bottom number(the denominator? Lets take 5/3. We have five things, and want to make 3 equal groups. we end up with one and 2 thirds things, in ",
" groups. So, how can we ever chop something up to get ",
"? If we have ",
" we can't chop it it and get nothing, can we? That question is asking for something impossible, an undefined number."
] |
[
"Yeah that's a good way of looking at it, but if you can't chop it and get nothing how can we chop it and get less than nothing? e.g. 4 / -2 = -2"
] |
[
"think about it in terms of physical objects if the intangible concepts are confusing.",
"if you are trying to send gallons of water down a pipe (for some random reason) between people, from me to you is positive, and from you to me is negative (from my perspective). say i need to send you 10 gallons of water divided once. (10/1) you would get 10 gallons of water.",
"now say you needed to split the water evenly within your house, to the kitchen and the bathroom. now its (10/2) each separate pipe to each room gets 5 gallons. ",
"now think you have to send me 10 gallons of water to my house instead. the current is negative, the opposite of me sending you water. (10/1)",
"under the same scenario as before, if i had to split up the current to 2 different rooms, itd be (-10/2) once again. each room technically getting a negative of 5 gallons. ",
"if it helps, you can reverse the signs for either case, whichever makes more sense "
] |
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