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[
"Is a difference in pH the only consideration when it comes to an acids ability to dissolve substances?"
] |
[
false
] |
[deleted]
|
[
"No, with aqua regia (\"royal water\"), a 1:3 mixture of nitric acid (HNO3):hydrochloric acid (HCl) being one of the best examples when it comes to dissolving solid Gold (Au). While both of aqua regia's components are strong acids, they are not able to dissolve solid Gold by themselves. The mechanism by which the Gold is dissolved is actually not initiated by the acidity of the aqua regia, but by the strong oxidative properties of the nitric acid, which manages to oxidise (i.e. steal electrons from) barely detectable amounts of Gold which creates a triple positively charged Au",
" ion which in turn can be complexed/dissolved by 4 Cl",
" ions derived from the hydrochloric acid to deliver a soluble [AuCl4]",
" chloroaurate anion. The steady supply of Cl",
" is actually due to chloric acid being a strong acid and hence nearly all of its HCl molecules disscoiate into H",
" and Cl",
" . The formation of this chloroaurate anion is favoured, so the free Au",
" are constantly removed from the equilibrium of the previous reaction, so it doesn't matter that the Au",
" derived by the oxidising reaction at the beginning is only present in miniscule amounts. Note that apart from this special case of dissolving metals like Gold and Platinum, aqua regia isn't a particularly strong acid.",
"\nFun Fact: In \"Octopussy\", James Bond uses aqua regia to escape from an unfortunate situation by dissolving the metal bars of his prison cell. This is slightly far fetched.",
"\nSource: Knowledge from my BioChemistry university lectures and ",
"https://en.wikipedia.org/wiki/Aqua_regia",
". ",
"Another cool example: The reaction of sulphuric acid (H2SO4) with carbohydrates like sugar (or cotton lab coats from my aforementioned Biochemistry studies...): Sulphuric acid is so hygroscopic (i.e. water attracting) that it is able to remove water molecules from carbohydrates (consisting of hydrogen, oxygen and carbon) so that you are left with what is basically pure carbon. This has not a lot to do with sulphuric acid's acidity but is purely based on its love for water. Dissolving sugars in e.g. concentrated chloric acid doesn't do this. Cool video: ",
"https://www.youtube.com/watch?v=poDBrGIyTEk",
". The black stuff coming from the flask is the leftover carbon.",
"\nFun fact here: Because adding water to concentrated sulphuric acid is such a drastic reaction which generates a lot of heat and can hence lead to the acid splashing everywhere, there are proverbs in several language to remind you that you should always add the acid to (a surplus of) water (not vice versa) when diluting it: ",
"edit: Lots of typos, etc."
] |
[
"I just want to add: sulphuric acid's dehydrating ability is related to its acidity. The protonation of hydroxyl functionality creates a water leaving group which readily leaves the molecule. ",
"Hygroscopicity is related to the ability of a substance to absorb water from the vapour phase through incorporation of water within its structure."
] |
[
"Good question! To be honest, I don't know. I'm just a biochemist by training, this is be something an inorganic chemist would know. Both the solubility of KCl and KNO3 are high enough that there shouldn't be any problems getting to similarly high concentrations of NO3",
" and Cl",
" as in classical aqua regia. However, I don't know whether the K",
" might react with the tetrachloroaurate and form a precipitate that might cover the gold and prevent further reaction. But this is purely speculation at this point. "
] |
[
"Dad wants to know - Does the claimed science behind Simple Water Fuel (HHO) produce legitimate results? - xpost from askreddit"
] |
[
false
] |
Hey Reddit. My dad owns an auto repair/body shop and is interested in testing if Simple Water Fuel works to improve car mileage. Judging from the I'm already doubtful. . What I would like explained is just the claimed science behind the product, which is using electrolysis on water and then injecting the results into the engine along with the normal fuel used (gasoline/diesel). Reddit, could you explain if this would result in an increase in gas mileage?
|
[
"This is not absolutely a scam, but it's pretty close. ",
"What they are leaving out is it's a mixture fo hydrogen and oxygen that's being burnt, which is all well and good. But what's being left out is where the hydrogen and oxygen come from and how much energy it takes to accomplish this. If you include this energy the energy consumption of the vehicle doesn't increase, and may even do worse. ",
"Think of it like buying Ultra grade fuel, you get better mileage, but it costs more, so your cost per mile is actually worse, this is the same thing, it works, but it's more expensive than the gas, so what's the point?",
"Also, this isn't a real solution at a large scale, demonstrating a small engine is one thing, doing electrolysis for a car or truck is a completely different thing. Electrolysis to generate hydrogen isn't done at large scale, we do steam reforming of natural gas to do that."
] |
[
"Everything I know about cars comes from watching entirely too much \"Top Gear.\" (I can't help it. James is just so ",
"But with that caveat, my meagre understanding is that gasoline is carefully formulated specifically to ",
" the release of excess hydrogen during combustion, which reduces engine efficiency in some way I couldn't even fake an explanation for.",
"Also? I wouldn't purchase anything from someone who can't spell \"hydrogen.\""
] |
[
"Well i would say it's absolutely a scam, they're selling a product that is physically impossible and making ridiculous claims about how awesome it is.",
"Think about it, if this would truely be working, what would have happened long ago to the world's energy problems?",
"The reason why this isn't working is really very simple: ",
"You can't create something (Like engine power) from nothing (like inert water)",
". To split the water requires energy; and where will that come from? From the fuel.. And with every conversion you LOSE some power (why engines get hot!) so it's actually WORSE.",
"Definitely a scam!"
] |
[
"By what methods do isolated ponds get fish in them?"
] |
[
false
] |
There are a lot of isolated ponds out there with no connection to waterways. Like the ponds here and there on a farm, or the display ponds where I work. They all seem to have fish in them, usually little sunfish, none bigger than a few rare 6-7 inch specimens. How do these fish get to the ponds? I realize there's a variety of methods, probably things like stocking by humans or fish getting washed into a pond by floodwaters. Are there any more exotic or unusual methods?
|
[
"Also migratory birds and waterfowl transfer amphibian and fish eggs. The eggs attach to the legs, down, feathers of the bird and are deposited (washed off) when the bird enters the next water source."
] |
[
"There's the few you mentioned, if it's a display pond, then definitely by human stocking! Flooding is also another common one. You also have to remember that just because a pond isn't connected to a waterway now, doesn't mean it wasn't in the past. It could have been connected for years previously, or again, through a flooding event. Waterways move about a lot when left to nature!",
"There's also rarer methods, such as birds dropping their prey, although the chances of that creating a stable population are rare. "
] |
[
"This one actually seems pretty likely for the specific ponds I'm thinking of, as they're frequented by migratory birds and waterfowl."
] |
[
"Why do meteors get burnt up in the atmosphere and Felix Baumgartner didn't (Red Bull Stratos)?"
] |
[
false
] |
From what I understand, meteors, for the most part, get burnt up and disintegrate from entering the Earth's atmosphere. Felix Baumgartner jumped from 128,100 feet high unharmed.
|
[
"He didn't start at speeds exceeding terminal velocity. ",
"The meteors have great energy and as a result meet a great deal of resistance from the atmosphere that you wouldn't if you started at a low velocity and accelerated due only to gravity."
] |
[
"Atmospheric \"burn up\", what is normally called the ",
", occurs at speeds of Mach 5 or higher. Spacecrafts returning from orbit usually arrive at Mach 23. Meteors can be even faster.",
"Felix Baumgartner merely reached Mach 1."
] |
[
"Kinetic energy scales relative to the square of speed. Baumgartner fell while within the atmosphere, and his speed only got as high as about mach 1.25, reaching a maximum speed of about 377 meters per second. Compare that to a meteor entering the atmosphere at above 11,000 meters per second. The meteor has about 850x as much kinetic energy, which is why it heats up much more."
] |
[
"How does solidifying candy (power to solid) work?"
] |
[
false
] |
Flaired under chemistry as it seems the most relevant to this "food science" question, although physics might also be relevant. There seems to be , and combined to create a solid strip of candy upon being pulled out and exposed to air. What stages/processes might be involved in this, or how does something like this actually work? (E.g. why does it not solidify into a lump when it is already suspended in the solution without being pulled out?)
|
[
"Aha! This was new to me but I figured it out. ",
"Here's",
" a video that shows someone making the candy in more detail. ",
"Here's",
" a web page with an ingredients list in English. And here's an article on gummy chemistry:",
"https://www.sciencedirect.com/science/article/pii/S1878450X13000073",
"The key ingredients are sodium alginate and calcium lactate. Sodium alginate is a chemical derived from brown seaweed. It consists of long chains of sugar-like units, similar to starch, and when dissolved in water it makes the water thick and goopy -- but not solid. The powder you sprinkle on top contains calcium lactate. Calcium causes the alginate to form cross-linking bonds that strengthen the liquid goo into a strong solid gel. It's a bit like the ",
"\"vulcanization\"",
" process used to make hard rubber products from sticky natural rubber.",
"This basic chemistry is used for things like commercial candymaking and \"spherification\" in molecular gastronomy. The reaction isn't new, but the \"gummy fishing\" form factor is."
] |
[
"Yeah, though the chemistry is different. 2-part resin adhesives work by building long chains from small components; alginate gels work by cross-linking pre-existing chains together. It's the difference between making a chain, and making a chain-link fence."
] |
[
"If that is what I think then the powder has gelatin in it to act as a binder. ",
"The powder is carefully placed in the water so that only the outer edge of the powder mass is in contact with the water and forms into relatively rigid cross linked gelatin protein. ",
"As the wire slowly lifts the mass more gelatin is cross linked on exposure to water so you get the string like mass produced. It's the same technique used to ",
"make nylon",
" but with a different feed stock.",
"In other words this is chemistry aided by a very careful lifting technique. Look up the details of gelatin and nylon production to get a really in depth understanding of what is going on."
] |
[
"Are there measurable tides in the hydrocarbon lakes of Saturn's moon Titan?"
] |
[
false
] |
Would these tides be massive due to the intense gravitational attraction of Saturn
|
[
"In that article, the surface they're referring to is the actual, physical surface of Titan. Basically, from gravity measurements, we can tell that the shape of Titan is changes during an orbit, in response to tides. If this result holds up (it may or may not), then it would be good evidence that Titan has a subsurface ocean - since the only way the entire crust could deform would be if it were physically decoupled from the bulk interior.",
"As for the original question, could we measure tides in the lakes? If there are tides, I doubt we could do it with Cassini. Our maps of lakes on the surface are generated from radar imaging, and I doubt we have the resolution or time-series data to see changes over the course of Titan's orbit. Someone correct me if I'm wrong about that though."
] |
[
"Are there measurable tides in the hydrocarbon lakes of Saturn's moon Titan? ",
"Here seems to say yes but I don't understand the details - it apparently says that the \"surface\" of Titan rises and falls, but I don't understand \"surface of what exactly\" they mean. ",
"http://www.nature.com/news/tides-turn-on-titan-1.10917",
" ",
"You might want to make a new post asking for clarification. "
] |
[
"That's kind of what I expected since I could find no data online about it. Thanks."
] |
[
"Is it even possible to successfully send a probe to another star?"
] |
[
false
] |
In Carl Sagan's Pale Blue Dot there's a part where he talks about Voyager 2's flight path as it approached Uranus. Here's the exact quote: JUST BEFORE VOYAGER 2 was to encounter the Uranus system, the mission design had specified a final maneuver, a brief firing of the on-board propulsion system to position the spacecraft correctly so it could thread its way on a preset path among the hurtling moons. But the course correction proved unnecessary. The spacecraft was already within 200 kilometers of its designed trajectory-after a journey along an arcing path 5 billion kilometers long. This is roughly the equivalent of throwing a pin through the eye of a needle 50 kilometers away, or firing your rifle in Washington and hitting the bull's-eye in Dallas. He compares the spacecrafts' trajectory to threading a needle from 50 km, which basically seems impossible. The distance from Earth to Uranus is small compared to the distance of the nearest star. So I'm asking, is it even possible for us to successfully send a probe to another star? If sending a probe by Uranus is like threading a needle from 50 km, then sending one to another star should be like throwing a pin through the eye of a needle on the moon, right? If it's possible to send a probe to another star, then how much more difficult would it be to send one to an exoplanet in another stars system? How about a moon?
|
[
"It's already been done. Or rather, is presently being done. Voyager 1 is on its way to a relatively close encounter — within two light-years — with a star so completely unremarkable it doesn't even have a name, just a catalogue designation. It'll get there in 40,000 years.",
"That's a bit of a cheat, though. Because Voyager is rocketing toward that star at the breakneck speed of twenty kilometers per second … but the star in question is ",
" at over a ",
" kilometers per second. In essence, Voyager is just sitting there at rest, waiting for the star to approach ",
"So yes, if we wanted to we could launch a space probe at a very, very nearby star … say, one about twenty light-years away. It would take about 350,000 years to make the trip. Which is about 35 times longer than all of recorded human history (depending on how strict you are about your definition of \"recorded\")."
] |
[
"It would be difficult, but one advantage is that unlike Uranus, a star has an enormous gravity well that dominates the local region. Once the probe got close enough, it is going to ",
" to fall towards its stellar destination.",
"So it is less of a bullet, and more of a guided missile. "
] |
[
"Voyager will pass within two light-years of said wholly unremarkable star, which is currently 17.6 ly away."
] |
[
"Why are able to clearly see our own thoughts. Even if we have never seen it before, we can always see it in our heads. How?"
] |
[
false
] | null |
[
"Apparently not everyone can:",
"http://boards.straightdope.com/sdmb/archive/index.php/t-310467.html",
"http://ask.metafilter.com/143968/I-cannot-mentally-visualize",
"http://dfan.org/visual.html"
] |
[
"Reading those has only made me paranoid. I'm not sure what \"visualizing\" is supposed to mean anymore.",
"Just to be sure here, imagining a visual image is absolutely nothing like seeing one, right?"
] |
[
"[citation needed] please "
] |
[
"Can prolonged tachycardia cause the heart to be sore?"
] |
[
false
] |
I understand that the heart probably won't hurt after exercise from soreness, but if the heart is beating ~50 bpm faster than normal for multiple day and nights in a row, can that cause the heart to be sore?
|
[
"Sensory nerves innervating cardiac muscle is very different from the sensory nerves that provide sensory information from skeletal muscles (the soreness you're most familiar with after exercising those muscles to exhaustion). The only \"pain\" sensation I'm aware of that cardiac muscle can send is a sensation of pressure/heaviness from cardiac muscle ischemia or hypoperfusion. Any other quality of pain that comes from that region in the chest is most likely not cardiac muscle in nature (like sharp tearing pains from pericarditis or generalized pain/discomfort from esophagus, e.g. heartburn).",
"The long and short of it, cardiac muscles don't have the same sensory nerves as skeletal muscles, so physiologically it may not be possible to feel soreness from cardiac muscle as you do from skeletal muscle."
] |
[
"In short, yes. If your heart is beating too fast to get enough oxygen, lack of oxygen to the heart muscle can definitely cause pain. ",
"Lack of oxygen is called \"ischemia\" and it is very painful. This is what causes the pain of a heart attack. Blood flow to one area of the heart gets blocked, and the lack of oxygen causes the muscle tissue to send pain signals. ",
"If you have a racing heartbeat and chest pain, you should seek medical attention right away. The best option is to call 911 or your local equivalent to get an ambulance. If you absolutely won't take an ambulance then at least have someone drive you to the nearest ER. "
] |
[
"Depends on what causes it - stimulants like cocaine, as well as things like anxiety will cause chest pain. ",
"I’m sure extended (multiple consecutive days) periods of a high heart rate will cause some kind of trauma but this is how all muscles strengthen. ",
"We are endurance animals after all. I’m sure exercise is far better for you due to other benefits. Hormonal, healing, psychological etc. "
] |
[
"I read somewhere that the application of quantum mechanics helped the development of things like tv's and lasers. What are some examples of how quantum mechanics have been used for our modern conveniences?"
] |
[
false
] | null |
[
"Such open-ended questions are better suited for our new-ish sister sub ",
"/r/asksciencediscussion",
". Please consider reposting there instead."
] |
[
"ok I'll post there. Also how can I make the question less open ended? Should I just ask about one specific technology?"
] |
[
"Yes -- asking how a specific thing works is good! You might be able to find an answer to your original question with a simple Google search"
] |
[
"Assuming infinite access to resources, how long could you sustain a sun by e.g throwing vast amounts of hydrogen into it?"
] |
[
false
] |
So assuming you have infinite access to anything what the longest amount of time you could keep a star fusing by throwing things into it (but not doing things like extracting elements e.g iron) before it say eventually collapsed into a black hole. Could you just keep throwing more resources into it by order of magnitude to keep it going forever or, if not would the smallest star possible still fuse longer because a smaller star fuses elements slower and possibly still takes longer to produce elements it cant fuse for energy?
|
[
"It's the latter (sort of). The more massive the star, the more fuel it has to burn, but the faster it will burn through it. So, more massive stars have shorter lifetimes and the least massive stars have the longest lifetimes."
] |
[
"There are a few interesting things about this question.",
"The thought that other commenters have touched on is that adding mass to a star makes it's core higher pressure and temperature so increases the fusion rate. This makes the star brighter but at the expense of longevity so you would have made the Sun last less time. This means that the smaller the star the longer it lives.",
"Another interesting thought that is relevant to any idea of \"refueling\" is that the only the area outside of the Sun's core is convective. This means that there is not a \"dredging up\" of helium ash from the core to the surface and fresh hydrogen from the outer layers to the core. This has the consequence of any new fuel added to the outer atmosphere will never make it into the core and undergo fusion so could not extend the life of the star.",
"You have to increase the mass of a (main sequence) star to around 30% more than the Sun before you make the core convective. At this mass the star's lifetime will be drastically reduced.",
"The problem with these stars is that they have a non-convective outer atmosphere instead. You could take a much smaller star, around 1/3 the mass of the Sun which would have a fully convective atmosphere but such a star would be very dim. For a star that has non convective areas you would hypothetically need to supply the fuel directly to the core of the Star which is, of course, impossible.",
"before it say eventually collapsed into a black hole.",
"One thing people do not often realize about black holes is that a Star will NEVER collapse into a black hole as long as it is undergoing sufficient fusion. ",
"The reason black holes form is because there is insufficient pressure in the core to resist the force of gravity from the stars own weight. When a star is fusing in it's core it is hot, hot gas has a high thermal pressure. Only when the pressure in the core is not provided by thermal pressure and is instead provided by degeneracy pressure is it at risk of collapse and then only if the force of gravity exceeds the degeneracy pressure.",
"The only stars where this can happen are ones where the core is inert either because they have moved into a giant branch and are undergoing fusion only in shells or because they are undergoing no fusion at all (neutrons tars/WD)."
] |
[
"I'm not sure if your response addresses OPs assumption of unlimited hydrogen to keep pumping into the star regardless of size. Can it be kept going, or will fusion break down eventually regardless of available fuel?"
] |
[
"A test for the BRCA gene cost about 4000 USD (according the Fred Hutchinson Cancer Research Center). Sites like 23andMe run genetic tests for as little as 99 USD. What is the difference and is the price discrepancy justifiable?"
] |
[
false
] | null |
[
"The gene-testing field has gone through a lot of upheaval in the last 12 months. The answer to your question is actually one based more on legal restrictions than biological restrictions.",
"As of late last year, 23andMe can no longer do medicine-based analysis of your DNA (only hereditary). Meanwhile, one of the biggest costs of the BRCA test used to be the fact that it was patented by one company (Myriad), so you were required to pay for their service to have the test. Myriad's claim was struck down by the Supreme Court last year. ",
"Wikipedia article",
". The test ",
"is starting to become more affordable now",
".",
"In terms of the actual biology behind it, 23andMe works by analyzing SNPs (pronounced \"snips\"), which stands for \"single nucleotide polymorphisms.\" As a result, you only have to sequence a very short piece of DNA to get a read out of what mutation you have.",
"For BRCA testing there are quite a few different kinds of mutations you would need to sequence, and many of them include rearrangements of large chunks, instead of just single point mutations. If you're feeling up for a scientific read ",
"there's a review here",
". The layperson's summary is essentially that you have to sequence larger portions."
] |
[
"Thank you for such a thorough answer. Much appreciated!"
] |
[
"Thanks! Glad I could help."
] |
[
"Given the observational data available at the time of its acceptance, was geocentrism a valid theory?"
] |
[
false
] |
Of course with today's knowledge we know that it wasn't , but I'm curious to know if the Earth-centric view was one that satisfactorily described the night sky observations during the time of its reign. If there were discrepancies even back then, (i.e. the motion of a particular planet that just didn't quite make sense) how were they reconciled? Were there people who were aware of these problems and made attempts to resolve them or were they swept under the carpet and hoped to be forgotten? Thanks!
|
[
"The main issue was stellar parallax. If the Earth is moving around the sun then the stars should be in slightly different places depending how far away they are. The ancients mentioned this, but could not observe it.",
"The issue is that the parallax is very, very small. It wasn't observed until Bessel I believe in ",
" 1838.",
"Heliocentrism implies stellar parallax, and if the observed parallax is zero, that's a case against it."
] |
[
"Given that the entire point of the model at the time was to predict the position of the planets in the sky - often in order to construct horoscopes - and not to determine their actual position is space, the geocentric theory worked remarkably well for nearly two thousand years.",
"With the geocentric Ptolemaic model, one can accurately predict the positions of Mars, Jupiter, Mercury, Venus, and Saturn - the five planets visible without a telescope - to about as good a resolution as one can get with the naked eye in most circumstances.",
"The heliocentric Copernican model was not any more accurate, or less computationally complex than the Ptolemaic model. It was Kepler who did a first systematic study of which one predicted the position of Mars better, and found that they had similar accuracy.",
"Kepler's geocentric system of elliptical orbits was found to be more accurate, although Kepler had been chastised by his professor for using the principles of terrestrial physics to try to explain the motion of the celestial bodies.",
"A good discussion of the actual history of astronomy in this period which debunks many of the persistent myths - such as the idea of epicycles within epicycles - is ",
"The Book Nobody Read",
" by Owen Gingerich. Unfortunately, I don't know of a good online reference for this topic. "
] |
[
"Heliocentrism implies stellar parallax, and if the observed parallax is zero, that's a case against it.",
"I think that it is worthwhile to note that Tycho Brahe measured the distance to comets using parallax, and because his observations failed to find any stellar parallax as it is insanely tiny, he concluded that a correct theory must be geocentric. Thus he made a model where the Sun orbits the Earth, but everything else orbits the Sun."
] |
[
"Why are paranoid thoughts so common with schizophrenia?"
] |
[
false
] | null |
[
"I am not schizophrenic, but I did have a number of stress induced psychotic episodes, the symptoms of which can be very similar to some schizophrenic patients, and I feel you are missing a crucial part of the explanation.",
"Psychotic symptoms tend to cause your mind to be unable to distinguish between your imagination and reality. When you are suffering psychotic symptoms things that would normally be silly daydreaming or speculative hypothetical situations, become indistinguishable from factual knowledge. It is as if your mind cannot vet the reliability of different assumptions, and simply assumes them all to be equally valid, and the first association which springs to mind becomes your accepted explanation. ",
"This can easily be very confusing. Suppose somebody trying to talk to you reminds you a bit of a famous figure, like the pope. Well, in a psychotic state that may well be perceived as a causative relationship, so you end up simply assuming that there must be a connection. It is not difficult to see how this can rapidly lead to all kinds of delusions and paranoia.",
"The way I describe it is simply that psychosis makes you lose the ability to distinguish between fantasy and reality. As a consequence, if you can imagine something, it may as well be real. "
] |
[
"I'm not sure exactly what question you are asking here. Schizophrenia is characterized by the presence of hallucinations and delusions, as well as meeting criteria for \"negative symptoms\" such as flat or inappropriate affect, reduced speech, inability to feel pleasure, lack of motivation, etc.",
"These hallucinations and delusions often feel foreign and scary to the individual. One of the most common types of delusion is the \"delusion of persecution,\" in which the individual feels that they are being pursued or persecuted by some force because of who they are or what they know. This can cause feelings of intense paranoia as the individual attempts to avoid this persecution. Generally, patients with schizophrenia that includes delusions of persecution are diagnosed with paranoid schizophrenia.",
"So if you're asking about the psychological cause, paranoia is common in schizophrenia because of the symptom of delusions of persecution. ",
"If you are asking about the neurocognitive cause of paranoia, that's a somewhat harder question to answer, because we don't know for sure.",
"There is some evidence that higher levels of the endocannabinoid anandamide in the cerebrospinal fluid may be correlated with paranoid schizophrenia [",
"source",
"]. The study found that levels of anandamide in paranoid schizophrenics were eight times higher than the levels in non-schizophrenic controls. When on anti-psychotic medication (which is know to reduce symptoms of schizophrenia, including delusions of persecution), the disparity in anandamide levels disappears. Keep in mind, this study only finds a ",
" between anandamide levels and paranoid schizophrenia. Correlation is not the same as causation.",
"Another, somewhat older study posits that functional changes in the limbic system and the medial temporal lobe--specifically the left hippocampal formation and the parahippocampal gyrus--may contribute to the positive symptoms (hallucinations and delusions) of schizophrenia, which would in turn lead to paranoia [",
"source",
"]."
] |
[
"This seems like a fun thing to think about and I’ll give it a shot.",
"So, first up Schizophrenia is a syndrome of psychosis. Psychosis is a very broad term which covers a range of phenomenon which result as a problem with ‘reality testing’. As rightly said previously the symptoms of this disorder are broadly lumped into ‘positive’ (things that are added in; perceptual abnormalities, delusions) and ‘negative’ (things that are taken away; poor motivation, blunting of affect). When people are ‘unwell’ they tend to be experiencing predominantly positive symptoms. These can be highly distressing and disruptive for the individual and may lead to hospitalisation. When people are ‘well’ they experience less positive symptoms but may be very disabled by negative symptoms. They may require a great deal of support as, for example, they may not take care their food, finances or personal care.",
"The term 'paranoia' in the psychiatric sense is used to describe interpreting things around you as being related to yourself, i.e. having delusions of self-reference. It may include thoughts of persecution but it does not refer to them exclusively. So delusional thoughts of being monitored and tracked by a shady government organisation which is bent on ruining you by framing you for some heinous crime is a ‘paranoid’, but so too is holding the delusional belief that you are on a special mission to stop terrorism and the strangers on the bus are really fellow agents sending you subtle secret messages by holding their telephones a certain way or glancing at you from time to time.",
"Delusions in general can either be primary or secondary. Secondary delusions follow on from abnormal experiences. If you hear people muttering through the walls, have an uncanny sense of being watched all the time and feel threatened you may conclude that you are being spied on by people who mean you harm. In these cases I find it striking how delusions are really just a rational mind trying to make sense of highly abnormal experiences. These delusions can become highly detailed and complex. They also tend to be very representative of people’s social context. I’m lucky enough to own a copy of a book called ‘Presumed Curable’ which is a set of case studies, accompanied by photographic portraits, of patients admitted to Bethlem Hospital in the late 19th century. Spies of the Kaiser, nobles and religious miracles abound. During the latter half of the 20th century aliens and spacemen hounded our psychotic patients. Now they are increasingly tormented on social media. It’s fascinating how the content of delusional thought shifts over time and across cultures whilst the underlying cognitive errors remain static. Primary delusions are those which appear to just appear, ‘de novo’, without any other apparent psychotic phenomenon driving them.",
"As to why. I’ve got no choice but to be even more reductionist here that I already have been. First up: chemicals. Brain chemicals, neurotransmitters. The neurochemical theories of Schizophrenia are essentially exercises in reverse engineering. This has important implications for proclamations about the aetiology of psychiatric illnesses but also should not lead us, in my view, to dismiss the utility of such drugs. The drugs used to treat the positive symptoms of Schizophrenia are essentially Dopamine blocking agents. Dopamine is the primary inhibitory neurotransmitter in mammals. The first ‘antipsychotic’ developed was Chlorpromazine. This was synthesised in the first half of the 20th century on the back of another drug, Promethazine, which had been developed as an antihistamine. The sedative effects quickly became apparent and these drugs were initially utilised for surgical procedures. Soon they were given to psychotic patients and the effects appeared dramatic to those using them. Remember that up until this point patients were commonly treated (or rather ‘brought under proper control’) with ECT (a safe and effective treatment to this day!), psychosurgery (neither safe nor effective, barbarism), insulin coma therapy (utter madness), seclusion and physical restraint. The Dopamine hypothesis was born. Too much Dopamine made you psychotic, blocking Dopamine made Schizophrenics better, right? The evidence for this hypothesis is really shaky. People really do get better when given antipsychotics (in terms of psychosis anyway) and we know these drugs primarily block Dopamine. We know that if you pump someone full of cocaine their Dopamine levels increase and they can become psychotic. We know that if we treat Parkinson’s patients with Levodopa (a Dopamine precursor which is able to cross the blood-brain barrier) they can become psychotic. Cerebro-spinal fluid examination of psychotic patients shows homovanillic acid (a Dopamine metabolite) levels correlate with the severity of psychosis but not with the psychosis itself. Ropey stuff indeed. Is it likely that the most complex know object in the universe can malfunction? Yes. Is it likely that this is due to one single chemical imbalance? I very much doubt it. Do antipsychotic drugs have utility in the treatment of psychosis? Absolutely, but let us not kid ourselves that we know why that might be. Other neurotransmitters, such as Glutamate, have been the target of antipsychotic drug development but these avenues have not born fruit. How might all this help us answer OP’s question? I personally don’t know enough to join the dots other than to say that positive symptoms in Schizophrenia have been related in functional MRI studies to disorders of the medial prefrontal cortex (executive functioning, attention and theory of mind), amygdala (fear) and hippocampus/para-hippocampal region (memory and spatial awareness) and that signalling problems in these areas probably leads to changes in cognitive processes which end up looking, phenotypically, like psychosis. I’m not trying to be a smart arse, throwing around neuroanatomical jargon here, as my view is that this sort of stuff lends us precious little understanding of what is happening and why.",
"The second way to approach this issue is to look at psychological or cognitive errors. Liddle (1987) proposed three clinical syndromes of Schizophrenia, one of which was that of ‘reality disturbance’. Liddle et al found regional cerebral blood-flow correlates in the left medial temporal lobe and cingulate cortex which led to impairments in an individual’s ability to ‘self-monitor’ and experience delusions and hallucinations. Think of it as the system which ‘tells you’ that your internal monologue is just that, breaks. Random intrusive thoughts become critical ‘third person’ auditory hallucinations (he’s so stupid), thoughts about what you are doing become a ‘running commentary’ (he’s buttering his toast again), intrusive thoughts or thoughts about genuine desires may become ‘command hallucinations’. This may seem more related to the first point about chemicals at first but it is a really important concept. The ability to appropriately self-monitor one’s own thoughts, emotions and bodily sensations is vital if one is to properly make sense of this information. The concepts of ‘self’ and ‘other’ break down in psychosis. Some people speak of their minds becoming porous during psychotic episodes. Humans are already seriously prone to magical thinking, attribution errors and biases. If the areas of the brain which regulate an individual’s ability to monitor their own internal experiences malfunctions and the ability to accurately determine other people’s thoughts, emotions and intent go awry, it seems logical to me that correlates are increasingly perceived as causatives.",
"Sources: Sims’ Symptoms of the Mind, Presumed Curable, Dr Wiki, Shorter Textbook of Psychiatry, talking to lots of psychotic people.",
"TLDR: Fear and pattern recognition are valuable species survival mechanisms the expression of which is mediated by a complex interplay between genome and environment. This can go wrong and lead to an erroneous self-referential thinking style which appears as a paranoid delusion.",
"EDIT - gammar and stuff."
] |
[
"Can we make a super nutrient-dense pill to distribute to people in third world countries?"
] |
[
false
] | null |
[
"we do have these crackers/biscuits that are used already. they come in packs of 2 and have 2300 calories.\n",
"http://en.wikipedia.org/wiki/BP-5_Compact_Food"
] |
[
"Macronutrients (calories) are... big. The best way you can pack them is in fat, at about 600 calories / 100g, and this would still get you at about half a kg (~ a pound) a day - definitely not a pill. Also making a \"complete\" food is expensive. Micronutrients can be packed in a pill, and this is your standard multi-vitamin. Not sure how cheap it can be mass-produced.",
"Fortunately the cheap, large-scale alternative already exists, and this is taking basic staple foods (flour, rice, salt) and fortifying them with the kind of minerals and vitamins that are likely to be missing in a certain population. This is already being done in pretty much every industrial (and probably also developing) nation. ",
"Also the food itself is seldom expensive. Flour for example is very cheap by ton. The problem is the logistic of getting it to people, and occasionally the economic incentives free food creates. ",
"A simplistic example: you have a disaster in a third world country, which makes people unable to harvest and a famine is becoming a real problem. Staple food itself is not a big cost, but transporting and distributing it through the problem area is - whatever caused the people to be unable the harvest (be it conflict or natural disaster) is likely to keep food from getting there in one piece. ",
"Also often you have men with guns who'll demand to do the distributing themselves. Since you want the food to reach the people as fast as possible you'll agree, but then the men with guns will take half the food and sell it (or use it to raise livestock to sell), and use the profits to buy more guns and entrench their position. And of course they won't encourage return to farming, because as long as there are people starving there will be aid coming and they'll get their share. Thus effectively creating a hostage population. This is what economists call \"perverse incentives\" - or getting the opposite of what you intended to happen."
] |
[
"No.",
"The problem isn't micronutrients... the things you'll find in unnecessary-for-american one-a-day type vitamin pills. The bigger problem for starving people is calories, and you can't compress calories much more than say, the calorie density of butter."
] |
[
"How far down the eukaryote tree into unikonts towards animalia do we find fruiting bodies as a form of reproduction?"
] |
[
false
] |
People like to mention that mushrooms are closer related to animals than to plants. While pondering thing, I noted that fruiting is something that both plants and fungi use for propagation. I can't think of a quick or easy way to look this up (having to go into each kingdom, etc.) so was hoping someone here happened to know. So what's the closest organism to an animal that still fruits?
|
[
"The fruiting bodies of fungi and fruit of angiosperms are not homologous structures, they just have similar names. As far as I'm aware, there's nothing more closely related to animals than fungi that has similar structures, though there are other eukaryotes that do this, like ",
"slime molds",
" (amoebozoa), which are more closely related to animals than plants, but still more distant than fungi (",
"source",
")."
] |
[
"I hadn't thought of it being a reuse of the name for a different biological process."
] |
[
"Yeah. I don't even think it would be accurate to describe them as examples of convergent evolution, since they're only very vaguely used for similar functions (i.e., reproduction)."
] |
[
"What exactly happens to metallic objects inside a microwave oven, and why aren't the metallic parts of the microwave itself affected by the phenomenon?"
] |
[
false
] | null |
[
"Imagine that you are pushing somebody on a swing. If you exert enough force you can make the swing go higher and higher, but only if you push at the right times. This means you must be in phase with the swing. Likewise, a microwave produces light waves that are the same frequency as the natural resonance frequency of water. This just means that the water molecules in the food like to jiggle at this frequency. Since the lightwaves are in phase with the water molecules and they exert a force, they make them speed up, heating your food. "
] |
[
"This is a misconception. The frequency of microwave ovens are not near a resonant frequency of water molecules. In essence water can absorb microwave light in the incident frequency range and so it does, so the food gets hotter. There's really nothing more elaborate, no resonant condition, at play."
] |
[
"If you had a sphere in the microwave would it arc?"
] |
[
"Could cancerous cells be useful because of their rate of reproduction?"
] |
[
false
] |
[deleted]
|
[
"I don't know about other purposes, but cancer cells are used for cell research because of their reproductive properties. For example the HeLa cell line (Can someone link toWikipedia, I'm on my phone), which was used not only for cancer research but also to studie the effects of nuclear bombs and to help develop vaccines."
] |
[
"Here's the link",
". ",
"What's more interesting than the cells themselves is the story behind them and their \"creator\", Henrietta Lacks. The family was not informed about the distribution of Lacks' cells. But unlike other cells, they would not die early and would keep reproducing.",
"Radiolab",
" did a segment on them and I think they also interviewed their family - I highly recommend it."
] |
[
"We use multiple myeloma cells to produce monoclonal antibodies. Which are then used in pretty much any sort of immunoassay or immunohistochemistry. These cancerous cells are plasma cells and pump out massive quantities of the exact same antibody. If they are in your body this causes all kinds of problems, but it the proper environment, it is virtually an unlimited supply of the exact same copy of an antibody. This is important when you are looking for an antibody that targets a specific marker, or binds a specific antigen"
] |
[
"Is it possible to \"silence\" a gun like they do in TV/movies?"
] |
[
false
] |
I know a suppressed gun does not sound like most media make it sound. Would it actually be possible to suppress a gunshot to this extent? If so, what would be required?
|
[
"Currently no. In fact, \"silencer\" is the less preferred term to \"suppressor\" because the device only lowers the report by at most 40ish decibels. The use of sub-sonic ammo helps to dampen the sound, but at the cost of bullet speed and accuracy. The most effective suppressors that achieve the most noise reduction to levels comparable to movies (but still much louder) are only good for a few shots. Wikipedia has a pretty comprehensive article on the construction and mechanics of suppressors."
] |
[
"Not sure if the US government didn't supply you with a silencer, or you're a member of the Taliban... "
] |
[
"http://en.wikipedia.org/wiki/Supressor"
] |
[
"Can frame dragging tear a hole in space-time?"
] |
[
false
] |
For example if we had something that spun fast enough rapidly enough (but not enough mass to collapse into a singularity) could it tear a hole? Would the hole be self sustaining or would space fill its self in the way a fluid would? EXAMPLE: Would it be as if you had a drill pressed into a cloth and when you torqued the cloth it rips? or would there just be more space to be pulled in behind the space being torqued? If scenario B is true would the mass of the spinning object increase so high due to the speed of its surface that it would become a massive gravity well?
|
[
"The answer is the same. There's no such thing as a hole in space, nor a hole in time, nor a hole in spacetime.",
"When we say \"the fabric of spacetime,\" that is just a metaphor. It's not really fabric. There isn't a limit to how much it can stretch, and it cannot be pulled apart. It doesn't make even conceptual sense for something like a hole to exist.",
"(For the record, the name \"black hole\" is also a metaphor. It's not an actual hole in anything.)"
] |
[
"I'm desperately waiting for an answer. I'm just so curious about this type of topic. "
] |
[
"No. There is no such thing as a hole in spacetime."
] |
[
"Is pyrolysis of food possible in boiling water under sufficient pressure?"
] |
[
false
] |
At sea level, boiling water will not reach high enough temperatures to cause pyrolysis, but if the boiling is done in a pressure vessel so that the water can reach higher temperatures before boiling, is it possible to char food? How high would that pressure have to be?
|
[
"I'm not completely sure about the chemistry, but for water the maximum temperature at which liquid water may exist is ",
"647K",
" (374 °C; 705 °F), at ",
"minimum pressure 22.064 MPa",
" (3200 psia; 218 atm). ",
"These researchers call 300 °C a low pyrolysis temperature",
" for wood, so it would seem that it would be possible for wood, at least, to char at temperatures attainable by liquid water.",
"Unfortunately, that's not the whole story. As noted by the wood-burners, their samples were first dried in an oven. In the presence of large amounts of water, different chemical reactions take place, generically called hydrolysis. There is apparently a name for this: ",
"hydrous pyrolysis",
". When applied to various organic materials (220-360 ºC and), the products are apparently various alcohols and oils. Their description of the pressure is 'higher than that of saturated steam', so this takes place in liquid water. Is this charring, though? ",
"This patent",
" describes the byproducts as various calcium salts in solution. (Lime was added to aid the reactions.) This doesn't quite sound like charring, but ",
"a similar process applied to turkey offal",
" at lower pressures and temperatures (260 ºC and 600psi) does seem to leave behind carbon char. This process operates at approximately the borderline between liquid and gas, but if I read the chart correctly, does take place in liquid.",
"The last word seems to be apparently ",
"."
] |
[
"To add to this, the type of product obtained depends largely on the catalyst used. If I remember correctly, basic catalysts promote the formation of oils and alcohols, while strong acids promote the formation of solid carbonaceous residue. So:",
"C6H12O6 > 6C + 6H2O",
"Under acidic conditions, and:",
"C6H12O6 > CO2 + \"CxHy\" + \"CxHyOH\"",
"Under basic conditions."
] |
[
"If you put petroleum in a giant industrial steam pressure cooker that's ",
"steam reforming.",
"Under extreme conditions the carbons in hydrocarbons can steal oxygen directly from water. You get carbon monoxide, carbon dioxide, and hydrogen gas. The date of your beef stew is probably roughly similar."
] |
[
"Can a brain ever \"forget\" to wake up?"
] |
[
false
] |
Excluding coma etc. but during the regular sleep cycle
|
[
"As in sleep indefinitely? No. Sleep is homeostatically regulated. In other words, as you spend time awake, you build \"sleep pressure,\" which dissipates as you sleep until it is very low and you awaken. This interacts with the circadian system (24-hour rhythm) as well. The only exception I would mention is Kleine-Levin syndrome, in which people can actually sleep for days at a time. That's more of a pathological process than \"forgetting\" to wake up though."
] |
[
"In other words, as you spend time awake, you build \"sleep pressure,\" which dissipates as you sleep until it is very low and you awaken.",
"Ah okay, thanks. That's one irrational fear off the list."
] |
[
"Insomnia can be affected by the circadian rhythm, but it's not a lack of or diminished rhythm. Insomnia that is limited to difficulty falling asleep, rather than staying asleep, may in some cases be due to a circadian phase delay (i.e., body wants to go to sleep and wake up later than \"normal\" in relation to the local light-dark cycle).",
"I don't know exactly what you mean by oversleeping, so it's hard to answer your question. Some people oversleep, as in sleeping past their alarm, simply due to not allowing themselves time to obtain sufficient sleep. Their body still needs sleep, and so sleep pressure is still high when the alarm goes off. Sleep pressure in this case may manifest in terms of high delta EEG power, sleep inertia, or incomplete awakening while you hit the snooze button. People with pathological oversleeping likely have other causes than simply insufficient sleep opportunity. This may be a sleep disorder such as obstructive sleep apnea, which blocks the natural restorative functions of sleep (try being chocked for a ",
" of 10 seconds at a ",
" frequency of once ",
" twelve minute you are asleep). Sleep pressure never diminishes, and so you get the same problems with trying to awaken. The circadian system does still operate though, even if you have disrupted sleep or even if you are deprived of sleep, so people find themselves becoming more alert during the daytime regardless of the quality or duration of sleep they obtained the night before.",
"A lot of people with insomnia attempt to \"treat\" their insomnia by increasing the amount of time they spend trying to sleep. The problem is that sleep pressure never gets high enough to allow them to fall asleep quickly and stay asleep through the night. Instead, they get little bits of sleep here and there, which continually diminish sleep pressure. Not surprisingly, a common treatment for insomnia involves reducing time spent in bed trying to sleep. This may initially cause a small amount of sleep deprivation, but that's actually good - it's the accumulation of sleep pressure that will be needed to facilitate falling asleep quickly and staying asleep through the night."
] |
[
"Do solar winds create drag?"
] |
[
false
] |
I was watching Spaceballs and after the scene where SB1 passes I got to thinking, would solar winds create any sort of appreciable drag and thus influence the efficieny of travel?
|
[
"Yes, but it is small unless you are either a dust particle or deliberately trying to catch it.",
"The solar wind near Earth is thin (500 atoms per cubic centimeter) but it is traveling away from the sun at 500 km/s. It is also mostly ionized atoms so you can interact with it using an electrostatic spiderweb sail or ",
"tack into the solar wind with a magnetic sail",
".",
"That design study requires 38 tons of superconducting magnetic cable in a 10 km O shape kept below its critical temperature, but it would accelerate at 0.009 m/s",
" - faster than an ion drive without needing any fuel. The field would also deflect the solar wind away from the crew capsule suspended in the center of the ring, greatly reducing radiation dose. If you are near a planet with a magnetic field then you can push off of the planet's field.",
"The limitations are that it won't work well in the outer solar system where there is less wind, it requires slightly better superconductors or a badass cooling system, and you will never know exactly how long it will take to reach your destination because the solar wind is unpredictable. On the other hand, you never run out of fuel and it will outrun almost anything if the wind is favorable. Perfect for bulk shipping and space-hipsters who want something fundamentally different from a rocket."
] |
[
"Yes. Each star has it's own unique stellar wind. We have unfortunately only really been able to study the stellar wind of the one star (the sun)."
] |
[
"Would the size and type of star have any effect on solar wind?"
] |
[
"Location of Atolls, Atlantic Vs Pacific? And several other Atoll related questions"
] |
[
false
] |
Hello I've recently been creating a fantasy map and was looking up Atolls and I've several questions about them. The first, is why are there so few Atolls in the Atlantic (only off the coast of Belize) while the Pacific Ocean and the Indian Ocean are chalk full of them. I presume this is due to lack of Volcanic activity in the Atlantic ocean in area where reefs can form but then that leads to another question about the lack of Volcanic hot-spots in the Atlantic. The second question I have is the removal of the former Island that the coral reef rings around. How does this precisely happen? I recall watching a video where it was stated that the weight of the reef somehow has something to do with it, or is it more to do with Erosion (wouldn't a barrier reef prevent erosion to a degree)? And the last question I have is concerning the make up of islands. Since New Caldonia (>40MYA) is older geologically speaking than Midway Island (27MYA) and the two are completely different (one is an Atoll the other is a proper island). Which is a roundabout way of asking, is the geological makeup of an Atoll more prone to erosion than a "regular" island?
|
[
"The first, is why are there so few Atolls in the Atlantic (only off the coast of Belize) while the Pacific Ocean and the Indian Ocean are chalk full of them. I presume this is due to lack of Volcanic activity in the Atlantic ocean in area where reefs can form but then that leads to another question about the lack of Volcanic hot-spots in the Atlantic.",
"There is volcanism in the Atlantic, but mostly along ",
"mid-ocean ridges",
", specifically the ",
"mid-atlantic ridge",
" and under normal circumstances, mid-ocean ridge volcanism is not productive enough to produce volcanic edifices that reach the surface. As you sort of guess, it comes down to the location of ",
"hotspots",
". While there are ",
"hotspots in the Atlantic",
", the majority of these are relatively minor and not associated with a long-lived ",
"mantle plume",
", e.g. ",
"this figure",
" of plume locations. This is relevant as the production of atolls (more on that in a minute) is especially favored in relation to oceanic islands created by hotspot volcanism as opposed to other mechanisms of creating oceanic islands (e.g. ",
"arc volcanism",
") where the source of melt stays fixed with respect to the volcanic edifice for much longer periods of time. As to why there are few mantle plumes in the Atlantic, this (maybe) related to the location of the plates (and thus the Pacific and Atlantic ocean basins) with respect to the two-antipodal ",
"LLSVPs",
" that hang out around the core-mantle boundary (see also ",
"figure 1 from this paper",
") and may be the source of a lot of long-lived mantle plumes (this is still something people argue about).",
"The second question I have is the removal of the former Island that the coral reef rings around. How does this precisely happen? I recall watching a video where it was stated that the weight of the reef somehow has something to do with it, or is it more to do with Erosion (wouldn't a barrier reef prevent erosion to a degree)?",
"Going back to hotspots, these represent semi-fixed locations (with respect to the moving tectonic plates) of anomalously hot mantle, producing melt that erupts and forms a volcanic island. When a volcanic island is forming over a hotspot two things are happening, (1) it is actively adding mass via continued delivery of melt and eruption of material and/or emplacement of igneous bodies and (2) it, and the portion of lithosphere it is sitting on, are anomalously hot because of the heat added by the injected melt, which means it is thermally buoyant. More broadly, there is a ",
"well known relationship between age of sea floor and it's depth",
". This is because as sea floor age, it cools and becomes more dense and thus sinks, or subsides, because of ",
"isostasy",
". At a hotspot, everything is warm and less dense so the elevation of the surrounding sea floor and the volcano itself are high (relatively). Now, as the plate moves away from the hotspots (remember, the hotspot is basically fixed in the base of the mantle) the source of heat leaves this volcanic island. This means no more mass is added via eruptions/emplacement (and thus erosion can start to dominate), but also the whole things starts to cool, get more dense, and subside. If this island has a coral reef that has established around it, as the entire island subsides, the reef (which is built by ",
"photosynthetic organisms",
") will build upwards to remain in the light (this assumes that the rate of reef building can keep pace with subsidence, if not, the reef will 'drown'). Thus, while erosion of oceanic island does play a role, it's really the thermal subsidence (plus reef building organisms keeping pace to stay alive) that gives you an atoll, as is illustrated in most ",
"schematics of atoll formation",
".",
"And the last question I have is concerning the make up of islands. Since New Caldonia (>40MYA) is older geologically speaking than Midway Island (27MYA) and the two are completely different (one is an Atoll the other is a proper island). Which is a roundabout way of asking, is the geological makeup of an Atoll more prone to erosion than a \"regular\" island?",
"Midway is part of the ",
"Emperor-Hawaii Seamount Chain",
", the result of the movement of the Pacific Plate over a hotspot (currently located under the big island of Hawaii). New Caledonia is not a traditional oceanic island, here's ",
"a paper",
" that gives a bit of geologic history, but in short, New Caledonia is more like a fragment of continental crust that is part of ",
"Zealandia",
", and thus does not have the same change in thermal buoyancy story as a traditional, hotspot related oceanic island."
] |
[
"I want to thank you for your thorough answer, especially with isostasy which was the part I was most confused about (I understood the coral's growing beforehand) and LLSVP. I do have an additional question in regards to what would be a good book to read, that gives similar detail as your answer."
] |
[
"Probably just an introductory geology book would be your best bet. A lot of the details you were asking about are things that would be expounded on more in a plate tectonics text book, but these are usually aimed at students at the end of a BS or in grad school (e.g. the plate tectonics course I teach is a senior level elective and/or a first year grad class) so they might be a bit hard to digest without a more solid background in geology."
] |
[
"How does a bullet-proof vest stop a bullet?"
] |
[
false
] | null |
[
"The fibers that make up a bullet proof vest are very tough. When a projectile impacts the material, instead of cutting through the material or causing it to pull apart, the material stays intact. This unyeilding of the fabric causes the impact force of the projectile to be spread out over a much larger area than just the frontal area of the bullet. ",
"They layer the fabric many times to be sure that most of the layers remain intact. Vests with more layers can generally withstand higher velocity rounds. Some vests are built mainly for handgun rounds, while others can withstand rifle rounds and such. "
] |
[
"It's worth adding that ceramic is not useful for the same reason as kevlar, but for the exact opposite. Ceramic would shatter, but in that collision, energy would go into breaking the ceramic before breaking... you.",
"Some recent ideas tried to use non-newtonian fluids as padding for such a reason. These fluids become like a solid under sudden pressure, and so can also be \"broken\". The difference is that afterward it would return to a fluid, ready to do the same process again. I don't know if this ever managed to pan out as effective or not though."
] |
[
"The bullet only has as much momentum as the person who fired it has",
"You mean after the gunshot. The recoil."
] |
[
"[Physics] Does photoelectric effect experimental techniques destroy materials?"
] |
[
false
] |
[deleted]
|
[
"Outside of testing materials that are known to be sensitive to X-rays (A small and unique subset of materials), XRF spectroscopy is completely non-destructive, so the sample remains physically and chemically unchanged. There are usually more than enough free electrons in the surrounding environment to fill in for any outer shell electrons that may have dropped to the inner shells after emission. You generally do not \"run out\" of electrons. The atoms only remain in a excited state for a fraction of a second before returning to its ground state and emitting a photon. ",
"The X-rays produced typically in ED-XRF systems typically have energies less than 100KeV (in most cases, 50KeV is the max), so they typically are not capable of chemically altering the sample via breaking bonds (outside of certain organic compounds - like DNA) Additionally, The X-rays will also only penetrate so far into the sample, depending on what material it is and what the X-ray energy is (typically only a few microns in metals, maybe a centimeter or so in soil and polymer samples) thus in most cases you will only end up exciting a small portion of your sample on its surface."
] |
[
"You see charging effects in SEM imaging (which usually happens at the same time as an EDS measurement) if the sample is not conductive enough. If the sample is conducive, electrons return to the sample through the grounded stage. "
] |
[
"The Photoelectric effect does ionise materials very effectively. If the material is kept in a circuit then the displaced electrons can be kept in a circuit like an ordinary battery, but if the material is isolated then electrons are often ejected, given that the incident photons have enough energy.",
"As for what happens to the ejected electrons, the electron is usually emitted at a high enough velocity to be considered a Beta",
" Particle, also known as Beta Radiation."
] |
[
"Do the components of a black hole's singularity get \"stuck\" on their own event horizon just like any other matter entering the black hole?"
] |
[
false
] |
Background: User was commenting in the about two black holes colliding, and his main point (best described was that not only should matter approaching a black hole asymptotically slow down to an independent observer as it approaches the event horizon, but the components that initially formed the black hole should as well. If I'm understanding what RobotRollCall correctly, an evenly distributed shell of matter from a collapsing star should naturally act as if all of its mass were at its center singularity. Hence, as the star's matter collapses inward and becomes more evenly distributed, the nature of the gravitation produced by this system should approach that of a black hole. Essentially, there should be an event horizon that forms all the initial mass of the black hole collapses into its singularity (from an independent observer's perspective, of course.) So, my questions are: Is there event horizon that the matter initially forming a black hole asymptotes out to relative to an independent observer? Is that event horizon the same as the black hole's ultimate "mature" event horizon? If that proto-event horizon isn't the same as the event horizon we would observe on a "mature" black hole, does that mean that the event horizons of black holes in general are asymptotically expanding in proportion to our independent observation of the matter constituting their singularity also asymptotically approach an event horizon? The last question is particularly intriguing for me, because if true, it would imply that black hole event horizons change shape over time relative to us as we see their singularity-matter approach a perfectly smeared, even distribution over an event horizon. Then, there would be important considerations involving what happens if an object is approaching a certain event horizon if that event horizon were to change shape.
|
[
"An event horizon is (somewhat unfortunately) defined in a global sense -- by the separation between the region from which light can't escape to infinity and the region where light can escape.",
"As such, the spatial \"shape\" when you slice spacetime into space and time does change over time, for example when a star collapses.",
"The shape itself is not a useful concept, since the geometry is so curved that we can't compare it to a shape in flat space. The shape is also dependent on how you do the slicing into space and time.",
"It doesn't really matter (from an astrophysical standpoint) that observers never \"see\" something fall past the horizon. It's not useful to think of the material as \"living at\" the event horizon -- most people think of the matter as just going inside and then we don't care about what the matter was. The only people who care are quantum information people.",
"EDIT: The fact that the event horizon is based on a global definition is kind of annoying. It means you can't determine where the event horizon is without waiting until the end of the universe. A more handy concept is the apparent horizon, which is the surface where the \"expansion\" of photons is zero. Expansion here is a scalar which measures the divergence of a congruence of null geodesics. If you are interested in the math behind this, read up on the ",
"Raychaudhuri equation",
"."
] |
[
"I don't think it's a useful picture to think of the matter as settling \"onto\" the event horizon. The matter just plunges straight through without a care (the event horizon is a totally regular region of spacetime, with no pathologies).",
"But yes, in some appropriate slicing of spacetime, the event horizon does grow from a point in the middle of the collapsing star, as matter is falling; and this point expands and approaches the asymptotic horizon."
] |
[
"The surface of the event horizon always \"moves at the speed of light\" -- this is by the definition of the event horizon! Since it separates a region where light can escape and light can't escape, the boundary between those two is a light ray that \"marginally\" escapes (or just hovers there).",
"The matter that's falling through is going to start out in homologous free-fall. I expect that quickly it will accelerate to some fraction of the speed of light, but I think that depends on the initial compactness (or density) of the matter. Sorry, I haven't done the calculation!"
] |
[
"Why do we kiss?"
] |
[
false
] |
What's the attraction it kissing. Has it just become a common thing that people do that everyone does it, or is there something to it?
|
[
"To summarize answers from the links people provided:",
"People kiss because social bonding between adults in humans and other social mammals is built off of the same basic neurological and hormonal framework which bonds mother and child (the most \"primitive\" and basic social relationship shared across mammals). Primates often kiss their babies to exchange prechewed food, so this action may have been expanded upon and generalized to adult affiliative behavior. Affiliative behavior in general releases oxytocin and other hormones which promote pair bonding, making it easier for the couple to stick together.",
"People kiss because it allows them to judge the immune system of their prospective mate. MHC complexes play a role in immunity. It is best to get two different sets of MHC genes for maximum diversity in immunity. Human females (maybe males too, not sure if it was tested) have a subconcious ability to detect MHC compatability and prefer potential mates with a good match. This is the \"chemistry\" in kissing.",
"Immunity: Certain diseases can be dangerous to pregnant women or their developing fetus. By kissing early on in the relationship, the male spreads any diseases to the female, allowing her to get over them and build up an immunity before she gets pregnant.",
"And one I didn't see, but should have been on there:\nKissing is a rather complicated social ritual. To do it right you have to have a good sense of social relationships and decent muscle coordination. You have to read your partner's mood and respond to it. Kissing allows you to judge your partner's ability to do these complex cognitive tasks, which are probably somewhat indicative of his or her general ability to succeed in the world.",
"Not all people kiss, but 90% do (aka some cultures don't kiss). This indicates that the behavior is not completely hardwired but can be modified by culture. This probably means that if the culture says kissing is taboo, people won't do it even if there is a biological tendency. If the culture promotes kissing, people will do it more often than expected. ",
"\nThis issue provides an excellent example of proximate vs ultimate causes. ",
"Proximate cause: We kiss because it feels good",
"Proximate cause(mechanism): It feels good because nerves are stimulated and hormones are released",
"Ultimate cause: Nerves are stimulated and hormones are released because of some combination of the reasons mentioned above "
] |
[
"Heh, I'll have to mention that to my prof. I don't know that it has been studied.",
"I will tell you that the birth control pill changes the preference. Women on birth control (and pregnant women, due to the somewhat similar hormonal profile between the two) prefer the smell of t-shirts (I kid you not, that's how they do these studies) worn by men with similar MHC complexes. This threw off the original study before they thought to check for it. It's thought that during pregnancy you might want to be around family (who would have similar MHC complexes) while otherwise you might want to hang around potential mates. Supposedly, women can sometimes find their significant others suddenly not smelling right when they go off the pill to try and get pregnant."
] |
[
"\"Human females (maybe males too, not sure if it was tested) have a subconcious ability to detect MHC compatability and prefer potential mates with a good match. This is the \"chemistry\" in kissing.\"",
"I wonder... does this involve only female / male kissing or does this come into play when lesbian or bisexual women kiss same sex partners?"
] |
[
"Why are anti-parasitics (ie hydroxychloroquine, remdesivir) tested as COVID-19 treatment?"
] |
[
false
] |
Actual effectiveness and politicization aside, why are anti-parasitics being considered as treatment? Is there some mechanism that they have in common? Or are researches just throwing everything at it and seeing what sticks? Edit: I meant Ivermectin not remdesivir... I didn't want to spell it wrong so I copied and pasted from my search history quickly and grabbed the wrong one. I had searched that one to see if it was anti-parasitics too
|
[
"In a basic sense, usually because they’ve been shown in cells or in animal studies to either block binding of a virus to a cellular receptor (zinc for example), inhibit cellular proliferation/ cause cell death (which gives the virus limited resources for infecting new cells and therefore proliferating), and/or it dampens an aspect of the immune response which may be damaging or too taxing to the host organism.",
"It’s important to note that in vitro (cell based) or in vivo (in an organism) study results don’t necessarily correlate to positive or expected outcomes in humans. Cells in a dish don’t always behave exactly how they do in the human body and sometimes in vitro studies that show beneficial results use doses of compounds that are not feasible in humans or animals. Also a compound dosed in a rabbit, rat, mouse or even non human primate study will not necessarily show the same effects in humans as the minute differences in their cellular/immune response may equate to major differences in effects in humans."
] |
[
"Cells in a dish don’t always behave exactly how they do in the human body and sometimes in vitro studies that show beneficial results use doses of compounds that are not feasible in humans or animals.",
"A classic example is that ClF3 is an absolutely awesome in-vitro anti-biotic. You can be 100% sure nothing will survive.",
"Sadly it's not great in-vivo, as it sets the organism on fire.",
"Though to be fair there was a bit of a warning when it set the culture, the culture medium, and the culture flask itself, on fire."
] |
[
"Chlorine trifluoride is ",
"fun stuff",
":",
"It is, of course, extremely toxic, but that’s the least of the problem. It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and ",
", not to mention asbestos, sand, and water-with which it reacts explosively. It can be kept in some of the ordinary structural metals-steel, copper, aluminium, etc.-because of the formation of a thin film of insoluble metal fluoride which protects the bulk of the metal, just as the invisible coat of oxide on aluminium keeps it from burning up in the atmosphere. If, however, this coat is melted or scrubbed off, and has no chance to reform, the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes."
] |
[
"Do photons (ie. light) possess the property of inertia, or inertial mass?"
] |
[
false
] |
It seems surprisingly difficult to find an authoritative (layperson-friendly) answer to this. It's pretty obvious that a hypothetical box of photons will have a greater inertial mass than an identical-but-empty box, but can light be said to have inertia?
|
[
"To talk about photons/light, it is necessary to invoke relativity. We can't use Newtonian mechanics to answer questions about things that move at the speed of light.",
"In relativity, photons are massless particles, where 'mass' is defined to be 'the energy that an object has at rest.' Photons are never at rest, but by carefully considering how the energy of a photon depends on its momentum, one can see that they have no mass. (The argument is roughly that E",
" = m",
" c",
" + p",
" c",
", and photons have E=pc, so they must have m=0.)",
"[Sometimes, especially in older texts, one finds a different definition of mass which increases with speed. This is the 'relativistic mass' which is given by m=E/c",
" or m=m0/sqrt(1-v",
"/c",
"), where m0 is the 'rest mass' discussed above. Using the relativistic mass as what you mean by 'mass' makes certain equations agree with Newtonian mechanics at the cost of hiding what is really going on and making photons more confusing. The modern view is to forget about relativistic mass and always talk about rest mass.]",
"'Inertia' is something that is harder to quantify for a photon. If you just say that inertia is 'resistance to changes in motion' then yes, photons have inertia, because they like to keep moving in straight lines just like massive particles. If you try to define inertia quantitatively, like by inertial mass, then you say it's the resistance to motion for a given force; but F=ma doesn't hold in relativity, so it doesn't follow that photons have no 'inertia' in this sense. Note that physicists never bother saying whether or not something has 'inertia'; they'll just tell you what its mass is. That's the number that matters.",
"By the way, in relativity, systems of multiple particles have a mass that is, in general, not equal to the sum of the masses of the constituents. So a box full of photons does, in fact, have nonzero mass even though each photon is massless."
] |
[
"Alright, that makes the whole 'yes and no' aspect of it clearer. Thank you muchly!"
] |
[
"As an add-on, because photons do have measurable inertia, this exact concept is what propels the various Solar Sail projects going on for next generation spacecraft. The Planetary Society, NASA, ESA, and JAXA all have craft planned or launched to take adfantage of the \"pressure\" from the sunlight! If you've been watching space news recently at all, a rich Russian named Yuri Milner is teaming up with various scientists and businesspeople to send laser-propelled sailcraft to Alpha Centauri! "
] |
[
"How come some illnesses are species-specific?"
] |
[
false
] |
For example, I can't catch kennel cough off of my dog, or FIV (kitty AIDS) from my cat, or shope papilloma virus from a rabbit. Why not? What is it about human cells that makes it so the viruses/bacteria that cause these diseases can't flourish?
|
[
"A great deal of it has to do with the difference in cell machinery. Think of a human cell like a machine, and a cat cell like a similar machine but with different parts. A virus that infects a cat works by using cat specific parts to replicate itself - the whole point of a virus's existence. When that virus comes in contact with a human cell, it is unable to use that cells parts to its advantage, and therefore can't infect it. This is a very simplified explanation",
"More detailed: Human cells are covered with proteins, sugars, and all sorts of markers. So are cat cells. A virus uses receptors to bind to proteins/sugars/etc on the cat cell, and then injects its DNA/RNA into the cat cell. A virus that can infect a cat may not be able to infect a human cell because the markers on a human cell are not similar enough for the virus to bind."
] |
[
"This is correct. Most viruses evolve very closely with their hosts, and as such become dependent on specific host proteins for entry (receptors, as you mentioned), viral replication, and egress. There are a vast variety of species-specific intracellular host proteins, like transcription factors, that are necessary for different viruses. Viruses are not only species specific, but many are tissue specific within a species (e.g. some viruses replicate VERY well in your lung epithelial cells, but cannot replicate in your neurons, due to the vastly different protein repertoire)",
"Viruses that manage to cross species often rely on proteins and structures that are conserved among those species, OR have evolved to infect both species as part of its replication cycle. An example of a virus that this is Eastern Equine Encephalitis virus, an alphavirus which relies on a bird to mosquito replication cycle, with minimal disease in these natural hosts, but when mosquitos infect mammals, like horses, it causes a severe disease. The disease in mammals, however, is a dead end for the virus, as it cannot be passed back to the mosquito to continue the infection cycle."
] |
[
"Thank you. Excellent answer."
] |
[
"How does petrol \"get old\" in a container?"
] |
[
false
] |
Discovered today that petrol, even if it's in a decent container, gets "old" and loses combustability. You can also get additives to prevent this. What's going on and what do the additives do?
|
[
"First of all, some of the more volatile components tend to evaporate over time, unless you have a metal container that is well sealed. This leaves behind the heavier fractions that also tend to have a lower octane rating, and of course have a harder time forming the proper fuel/air ratio in a carburetor.",
"Stale or oxidized gasoline tends to be more of a problem for fuel left in the fuel tank of equipment with small engines, stored for long periods, as the system is not well sealed against oxygen in the air. However many common plastic are permeable to oxygen to some extent, so fuel in plastic containers can be oxidized over time especially if the lid doesn't seal tightly. ",
"When you initially fill the tank, any oxygen that gets in will, over time, oxidize and degrade certain compounds such as toluene, into products that lower the octane rating. Certain iron or manganese compound present in trace amounts may accelerate the oxidation process. This can happen via several reaction mechanisms such as formation of epoxides, aldehydes, Most petrol contains a certain small amount of water. Oxygen and water slowly react to form trace amounts of reactive organic peroxides which cause other degradation reactions.",
"Petrol/gasoline also contains certain amount of unsaturated hydrocabons aka alkenes. Oxygen can catalyze the formation of cross-links between unsaturated compounds. In other words, spontaneous polymerization. This results in the production of solid waxy products \"varnish\" which can clog carb jets and fuel injectors."
] |
[
"Awesome explanation. Thanks so much!"
] |
[
"It is my understanding that the octane rating is raised rather than lowered as the heavy elements are less prone to pre-detonation and thus less volatile. Am I correct in this? Additionally, over time water is drawn in with oxygen further thinning the mix. "
] |
[
"If Satellite TV goes out when it rains, what about 5G \"millimeter wave\"?"
] |
[
false
] |
If you follow sites like DSLReports, you may know that Verizon is wanting to use "millimeter wave" and 5G to do home broadband rather than fiber or upgraded DSL (like G.fast). Verizon's 5G broadband uses 28 and 39 GHz bands. It is very well known that Satellite TV , especially because of the use of the Ku-band in the ~12GHz range. Would millimeter wave wireless also go out when it rains because of the use of higher frequencies than Satellite TV?
|
[
"I've never seen satellite go out from rain. I only see it go out from snow after the snow has built up on the dish. The combination of the extra weight on the dish affecit it's focus, and the slight weekening of the signal because of the built up snow. ",
"Soure: Installed satellite for over 5 years. Been on many service calls and the percipitaion itself, while falling, is never the problem. "
] |
[
"the signal does get worse from strong rain (stormy weather, thunder and lightning type strength) to the extent where it may break down completely. weaker signals suffer more of course.. if you have a strong signal you will rarely have problems with it. but for instance when you're in mainland Europe the signal from British satellites will be weak.",
"I'm not sure if it's due to clouds though. ",
"source : have a satellite dish and am somewhat adept layman at things satellite, not just a standard user. "
] |
[
"I have seen them go out when the dish, satellite, and sun are all in a line. The thermal noise from the sun can overwhelm the sat signal."
] |
[
"For feral children/adults, how does their \"inner monologue\" sound when they are thinking? Would it be a visual step by step process instead?"
] |
[
false
] | null |
[
"I don't think that's exactly the same though, because many deaf people know sign language and the structure of language has to affect their \"inner monologue\" in some way versus feral people, who haven't learned language. Is there any validity to that?"
] |
[
"Radiolab did a fascinating story on this (kind of) a while back.",
"http://www.radiolab.org/2010/aug/09/"
] |
[
"Keep in mind this subject is difficult to study and highly debatable. Any research someone presents you with is almost guaranteed to have reasonable arguments against it and in favor of another explanation. I say this only because, as far as psychological concepts are concerned, I see all too often (almost every thread) people presenting an explanation or article that is voted to the top of the thread. That answer often seems to be considered the be-all end-all explanation for many subsequent commenters. When a post concerns psychological complexities you can't find the answer to by Googling it, there will almost never a \"right\" answer that is agreed upon by all the experts in the field."
] |
[
"Which sicknesses have been with humanity the longest?"
] |
[
false
] |
Things like organ failure have been with us since we have had those respective organs; but do we have any idea which bacteria, viruses, pathogens, auto-immune, etc. have been with humanity the longest? I feel like there is more to the question here than I am capable of asking; so please elaborate in your answer.
|
[
"There are a few areas in your second paragraph that are misleading. First \"any particular virus or bacterium -- is quite recent because we can develop defenses against them\" just isn't true. There are many bacteria and viruses that are rather old. Before we eradicated it smallpox was a great example of a virus that had virtually remained unchanged since antiquity. Tuberculosis is another bacteria that until the recent emergence of antibiotic resistance had not changed over time. Even though it may have antibiotic resistance it is still the same pathogen. Possibly the most famous of ancient diseases is Hansen's disease (leprosy). I am not sure if you meant on an individual basis that each time you get an infection it is a new virus or bacterium since it seems like you hinted at that in the last line about flu shots. This also is not necessarily true. The virus that causes the flu is not technically a new virus but rather a new strain of the same virus. The only parts that usually change are the neuraminidase and hemagglutinin. Since they are the primary exposed proteins your immune system uses to recognize the pathogen you need a new shot. I just think that saying it is a new virus is misleading and not necessarily the best way to phrase it."
] |
[
"There are a few areas in your second paragraph that are misleading. First \"any particular virus or bacterium -- is quite recent because we can develop defenses against them\" just isn't true. There are many bacteria and viruses that are rather old. Before we eradicated it smallpox was a great example of a virus that had virtually remained unchanged since antiquity. Tuberculosis is another bacteria that until the recent emergence of antibiotic resistance had not changed over time. Even though it may have antibiotic resistance it is still the same pathogen. Possibly the most famous of ancient diseases is Hansen's disease (leprosy). I am not sure if you meant on an individual basis that each time you get an infection it is a new virus or bacterium since it seems like you hinted at that in the last line about flu shots. This also is not necessarily true. The virus that causes the flu is not technically a new virus but rather a new strain of the same virus. The only parts that usually change are the neuraminidase and hemagglutinin. Since they are the primary exposed proteins your immune system uses to recognize the pathogen you need a new shot. I just think that saying it is a new virus is misleading and not necessarily the best way to phrase it."
] |
[
"I assume you meant not unusual in the third sentence?"
] |
[
"I've heard a lot about String Theory as a 'theory of everything'. What theories haven't I heard about?"
] |
[
false
] | null |
[
"Thousands. There really is a sea of generalizations and alternative theories that can't yet be verified experimentally. For example, my bachelor thesis was (in part) about ",
"f(R) gravity",
", a theory that generalizes our accepted, experimentally verified theory of gravity. You might have heard of ",
"Supersymmetry",
", a further generalization of our Standard model of particle physics.",
": Damn, not sure if I have misinterpeted the question. Neither f(R) gravity nor Supersymmetry are candidates for a theory of everything. I just used them as examples that there is an insane amount of alternate theories you maybe have never heard of."
] |
[
"There isn't really anything else that proposes a ToE. String Theory isn't some crazy invention. If you start with the Standard Model and try to expand it to start including gravity or to unify the Strong interaction with the Electroweak interaction, you inevitably come across failed theory after failed theory after failed theory. String Theory is the simplest approach that unifies gravity and the gauge theories (Strong and Electroweak) without failing other requirements.",
"There are a handful of theories that attempt to quantize gravity and connect it to the standard model, but those aren't ToEs. They are just quantum gravity theories.",
"Here's a rundown.",
"The simplest extension of the SM is supersymmetry. It is a system that identifies bosonic particles to fermionic particles and identifies them as two different aspects of one object. This is a very natural and theoretically satisfying theory that many think will be the next experimentally verified piece of fundamental physics (although many don't.) ",
"Susy has nothing to do with a ToE, however. It simply proposes some new particles (i.e. one that can be identified as a fantastic candidate for dark matter) and can simplify a few mathematical oddities in the standard model.",
"We also have a topic called grand unification. We have a history of finding ways to merge different branches of physics. Starting with electricity and magnetism merging to become electromagnetism, space and time merging to become spacetime under the influence of the equations of electromagnetism, QM and relativity to become quantum field theory. The same principle that defines electromagnetism mathematically also perfectly defines the weak theory and the strong theory. The weak and electromagnetic interactions merge to form the electroweak theory. Grand unification proposes that somehow the Strong and Electroweak theories merge to form a merged one unified interaction that splits into the rest.",
"However, GUTs (grand unified theory) just don't work. I haven't really studied GUTs in any detail, but the most popular version is pretty much excluded because it predicts that Protons decay into other particles. In the history of physics, there has been a grand total of 0 measurements of decaying Protons. This pretty much rules out a simple GUT.",
"Another approach is called supergravity. Supergravity takes supersymmetry and applies a subtle mathematical principle that occurs elsewhere in physics and just so happens to spit out the equations for gravity on top of supersymmetry. However, it requires that the number of dimensions is expanded to 11 and (much worse) it fails completely because the theory is \"non-renormalizable.\" That means that when you try to do calculations with supergravity you find spurious infinities popping up all over the place which, obviously, ruins your ability to calculate anything. IE when trying to make a prediction for the experiments at CERN you find the probabilities are nonsensically infinity.",
"So, no luck yet. We have a maybe result saying that Susy could possibly exist but it hasn't been found and has some other unsatisfying predictions. We have to find a new approach.",
"So we get creative. So we turn to String Theory. Our normal standard model is based off quantum field theory. ",
"Quantum field theory studies the interactions of quantized 1,2 or 4 dimensional fields that are functions of 4 variables on a 4 dimensional spacetime. A natural thing to attempt is to vary some of the these numerical values. ",
"Varying the first values (1,2,4) gives us different particles. The 1 value is, for example, a particle like the Higgs boson. The 2 value could be a neutrino or electron. The 4 value could give us a photon. We've exhaustively studied this variation.",
"Next, we try to vary the next numerical value: the \"4 variables.\" When that value says 1, we are looking at a simple particle theory. This doesn't do anything useful and can be made to be just a more cumbersome version of quantum field theory. Changing that value to 2 gives us strings. When we analyze the theory with the value 2, we miraculously find that it accidentally spits out gravity. With some messaging and adding supersymmetry we find it also spits out the all of our fermions and all of our bosons. However, we find that this theory also fails. That is unless we vary the \"4 dimensional spacetime\" to be 11 dimensional. Now it still provides gravity and all our particles, but it also includes some incredible mathematical niceties that are absent from the standard model which are more complicated to explain.",
"String theory has TONS of problems, but it really is our only approach that unifies everything. Nothing has invalidated String theory while all these other theories have been invalidated. So it's our simplest approach at a unifying theory. I'd say there's still a 50% chance that it's entirely wrong, but there isn't a great competing candidate anyways.",
"I hope this made sense, I probably was just rambling incoherently. But oh well!",
"Also, on a technical note to any string theorists: I didn't study ST, I studied Loop Quantum Gravity and quit before finishing my PhD. Feel free to make corrections as I only have studied ST/SG in my spare time. "
] |
[
"Well, I can try, but I am not very good at it, so I'm sorry in advance. I'm basically answering your question only in the last two paragraphs - all the stuff before is (necessary) prerequisites.",
"One of the most wonderful things you learn very early when studying physics is the ",
"principle of least action",
". Of course you know that if you drop a ball from a certain height, then it falls down to the ground. And in school you learned that in the beginning, the ball had some potential energy and when you drop it, it converts its potential energy into kinetic energy until it lands on the floor and has zero potential and kinetic energy, great.",
"Ever wondered why when you drop a ball, the ball just falls down? Why doesn't it fly around a little bit, maybe hover for a short while and then fall down to the ground? In this scenario, it would have the same potential and kinetic energy in the beginning and in the end. But we don't see that happen, ever. And it's kind of intuitive to say \"well, while it is flying around and hovering, it has different, even more kinetic and potential energy, and this is totally different from just falling straight down\". If we somehow could add up the \"energy balance\", the difference between kinetic energy and potential energy, at any time while the ball is falling, then we would see that the first scenario, where the ball falls straight down, has a much smaller result than the second scenario.",
"This is basically the principle of least action - for some reason, the ball takes the path that minimizes this sum of \"energy balance\", of kinetic and potential energy. And this or a similar principle forms the basis of basically any modern physics theory. You have an action, you can show that this action must fulfill some special things to be minimized, and in the very end this gives you conditions your ball or particle or field must fulfill.",
"The principle of least action is so fundamental that even Einstein himself didn't fully believe in his theory of gravity, general relativity, until a friend of him found a way to derive his very theory through a principle of least action. This friend was Hilbert, and he found the ",
"Einstein-Hilbert-action",
". ",
"As you may have heard, Einsteins theory of gravity states that gravity is caused by spacetime curvature. You can describe spacetime curvature with the Ricci scalar which we simply just call R. The Einstein-Hilbert-action basically is just that - R. Ok, actually it's a bit more, some constants thrown in front of it, but the really interesting part is that you have this Ricci scalar R, you apply some mathematics to it and you get the equations telling you how spacetime is curved by energy and matter.",
"And now, after I explained one of the most wonderful things in such a terrible manner, I can tell you what f(R) gravity is: Instead of your action being just R, as in general relativity, some people asked what if the action is more complex? What if it is R²? Or 1/R? What if the action is some function of R? f(R)? So you can just plug your function f(R) into the action, apply some mathematics to it and you get, again, equations telling your how spacetime is curved. And depending on what function you chose, you get different results. ",
"And now please excuse me as I feel ashamed for this comment. This topic is full of so much wonderful stuff that I just can't properly express. Words are so, so limited compared to thoughts and mathematics...."
] |
[
"Student teacher (physics) with a request"
] |
[
false
] | null |
[
"Can you explain further? I'm not sure for what type of suggestions you're asking. I imagine you want to use a story involving science?",
"Edit: that is a ",
" story, by the way. Bohr was a marvel."
] |
[
"Well I have to tell a story which is somehow connected to the current curriculum (electricity). It must also have some kind of dialogue in it (so I can use different kinds of voices). "
] |
[
"Looks like your post was deleted. I was worried about that, although I must say I disagree with the mods on this one.",
"There must be some stories out there, but my google-fu and recollection fails me. Best of luck!"
] |
[
"If susceptibility testing is already difficult and sometimes highly specific for patients who aren’t immunocompromised, how do doctors select antibiotics and antimicrobials for burn victims and patients who have a severely compromised immune system?"
] |
[
false
] |
Is there a gauntlet of drugs that are used against common skin or nosocomial flora that doctors administer until the skin or immune system can kick back in? For background for anybody reading: We test susceptibility for antibiotics by exposing bacterial cultures to samples of specific antibiotics to see what happens to the bacteria in the plate. When you expose a bacterial colony to an antibiotic it is susceptible to, there will be a reaction that tells us that the doctor can use that antibiotic on a patient to treat an infection. The reason I am asking this question is because I’ve never worked in the ER or burn unit, only small labs. And I’ve seen how in Micro it’s necessary to run multiple tests just to determine the proper antibiotic for a single infection. But for a system wide entry wound like a massive burn, I imagined it must be grueling to find a proper treatment when bacteria come in from every surface possible.
|
[
"Doctors use broad spectrum antibiotics that are active against the bacteria that typically cause an infection in that area.",
"Then based on culture data, they can narrow or broaden their coverage as needed.",
"Susceptibility testing is no different for a competent or immunocompromised patient, because we're testing the bacteria, not the patient."
] |
[
"Cultures help identify the bacteria, which doctors will use to adjust their antibiotics based on which antibiotic typically cover that species.",
"Then susceptibilities help more so that they know for sure which antibiotics should work.",
"It's all important."
] |
[
"For immunocompromised patients, the gauntlet is all the more difficult because the damage can be caused by culture-resistant bacteria or fungi. Burns is different because infections are almost always caused by bacteria which have translocated from the skin.",
"Edit: source in reply comment as the above is oversimplified"
] |
[
"A few questions for aeronautical experts or pilots regarding Colgan air Flight 3407 2009 disaster."
] |
[
false
] |
Looking at the NTSB report and wondering a few things I cannot easily find answers to. Just to satisfy my curiosity: 1- On approach the plane reduced speed from 180 knots to 135 in less than 20 seconds. The flaps were at 5 degrees. There is no indication why the plane lost so much speed so quickly. Any ideas on why that would be? (pilot error, ice buildup, wind conditions etc.) 2- The plane began its stall at 2300 feet and the stick pusher mechanism activated, sending the nose downward. If the pilot had not over-ridden the anti-stall device by pulling the nose upward could the plane have recovered from the stall at that altitude? 3- The co-pilot retracted the flaps and landing gear when the captain attempted to pull out of the stall, did this contribute to the accident in any way? 4 The report says one cause of the accident was "the flight crew’s failure to monitor airspeed in relation to the rising position of the lowspeed cue". What exactly does "rising position of the lowspeed cue" mean in layman's terms?
|
[
"Private pilot here, I haven't read the full NTSB report yet, just my speculations:",
"It is true that that kind of plane does not slow down easily, however with flaps and landing gear down, if the pilot pulls the nose up hard, you can lose that much speed quickly, or if you meet a strong windshear or thunderstorm microburst. ",
"Actually I believe the 2300ft is altitude above sea level, while the ground is about 500ft above sea level, so they only had 1800ft, but still, if proper actions were taken promptly, 1800ft is more than enough to recover from a stall. ",
"Retracting landing gear is the right action, however retracting flaps to 0 degrees immediately in stall recovery is not correct, because stall speed is higher when flaps are up, the correct action should be retracting flaps after the plane has regained positive climb rate. ",
"The \"lowspeed cue\" is just something in the airspeed display, usually looks like a yellow or red vertical bar, when the airspeed slows down, this bar raises up closer to the airspeed indication. "
] |
[
"You did such a great job there is no further need for further comments most likely. Thanks."
] |
[
"naughtius answered everything pretty well satisfactory I think, but if you're interested in seeing a recreation and analysis of the accident, the Canadian documentary series Mayday ",
"did an episode on the crash of Colgan Air 3407",
". Not sure if they video link will work outside Canada or not, though."
] |
[
"How would the BIPM proposed change in the SI units affect the numerical value of the gravitational constant?"
] |
[
false
] |
One consequence is that the numerical value of the Planck constant in the new units will be exact (as will several other physical constants). What impact might this have on the gravitational constant? Will its value be exact as well, or will it still be experimentally determined?
|
[
"The new SI will not have any significant impact on Newton's Gravitational constant G. It will remain an experimental constant. Two things to consider. First unit realizations necessary for G are the kilogram (kg), the meter, and the second. The second and the meter will not change in the new SI, and the kg will change, but only by a very small amount, on the order of 1 part in 10",
" or so. Currently the relative uncertainty in G is fairly large, typically a few parts in 10",
" but discrepancies exist in the data which are 10 times larger. The kg shift will be totally inconsequential. The second thing is that unlike most other fundamental physical constants, there are no practical precision experiments in which G can be determined in combination with any other constant. So even if the other constants shift as a consequence of new SI definitions, G remains unaffected. It remains purely an experimental constant uncoupled from everything else. See ",
"the latest CODATA report",
" for details."
] |
[
"Excellent. Thank you. Since I have you here, maybe you can answer another: in the new SI system, the physical constants are defined explicitly, not the units. The units are then defined as whatever gives those numerical values to those physical constants. The new SI system consists of seven explicit definitions. However, certain units show up in more than one definition (e.g., 'second' shows up in six of them). Does that mean that 'second' is implicitly defined by all six of those principles or is only one responsible for defining 'second'? "
] |
[
"The second will stay as it has been, in terms of the hyperfine Cs 133 transition. Fixing the Planck constant effectively gives you the Kilogram. Fixing e gives you the Coulomb. Fixing k (Boltzmann) gives you the Kelvin. Fixing the Avogadro constant N_A gives you the mole. The meter is unchanged since the speed of light definition is unchanged."
] |
[
"What makes up dust?"
] |
[
false
] |
Do people label any non-homogeneous suspension in air dust, or is there a specific type of dust? Everyone uses the term, but no one clarifies what is contained within it.
|
[
"The common explanation is that dust is mostly dead skin cells, but in abandoned houses, there are layers and layers of dust and no human being has been living there for a very long time, so in this particular case what is dust made up from?"
] |
[
"Mostly dead skin cells."
] |
[
"That only applies to dust found where humans and animals frequent. Dust at a construction site or in a cave is not made of dry skin flakes."
] |
[
"How do hydrogen bombs work and how does the difference in design contribute to it being superior to uranium-based atomic bombs?"
] |
[
false
] | null |
[
"I'd recommend reading up on the ",
"Teller-Ulam design",
".",
"A relatively small (in explosive yield) nuclear device called a \"primary\" is used to generate an extremely high-temperature (hundreds of MegaKelvin) photon gas, which can then be used to implode one or more \"secondary\" stages.",
"The secondary is composed of both fusion and fission fuels. The particular fusion reactions of interest are DT and DD fusion, which both result in a little bit of energy (compared to the relevant fission reactions, which release about ten times more energy per reaction), and more importantly, some high-energy neutrons.",
"Those neutrons can then induce more fission in the fission fuel. So while each of the neutron-generating fusion reactions will directly release a few MeV of energy, they will also introduce another neutron into a supercritical multiplying system of fission reactions. So every fusion neutron has the potential to cause a chain of ",
" fission reactions. And each fission reaction releases around 200 MeV of energy.",
"A common figure you might hear is that adding fusion fuel to an otherwise pure fission device will double the explosive yield (exact numbers depend on the specifics, of course). And for a typical modern nuclear weapon, that's ",
" because the fusion itself directly releases an equal amount of energy as the fission, it's because the high-energy neutrons emitted by the fusion reactions ",
" in the fission fuel.",
"So that's the basic idea. And all modern designs are some variation of this idea. Why is this better? Well as I mentioned, the high-energy neutrons from the fusion reactions allow for more of the fission fuel to be used. Also, the high-energy fusion neutrons can induce fission in nuclides which are fissionable but not fissile (meaning that they have some energy threshold for neutron-induced fission, usually on the order of ~ 1 MeV). So the fission fuel in the secondary can have a lower content of fissile material and still produce the same fission yield. So if you have uranium fission fuel in your secondary, it doesn't have to be enriched as much with uranium-235, for example.",
"So to summarize, you can greatly increase the yield of the weapon, or achieve the same yield with significantly less fissile material."
] |
[
"I would just slightly expand upon this excellent answer to add that fissile material is very, very expensive to produce. In fact, access to sufficient materials is the biggest impediment to building nuclear explosives.",
"Lessening the amount of these special nuclear materials needed to produce the required explosive yield is thus quite desirable."
] |
[
"To further add: pure fission bombs are extremely inefficient. It's estimated that, at best, 1kg of the 65kg of 80% (average) uranium-235 in Little Boy underwent fission. The rest was just scattered into the atmosphere.",
"Fusion increases yeild by increasing efficiency and thus power, and makes the bomb \"cleaner\" as a side effect, as more material will be converted into stable, non-radioactive isotopes than a standard fission bomb that scatters most of its radioactive material without fissioning it."
] |
[
"Assuming our ears and mouths could keep up, how many different conversations could a human brain have at one time?"
] |
[
false
] |
I was watching Futurama's Beast with a Billion Backs and the alien had conversations and experiences with billions of people at the same time. So, assuming that our mouths and ears could handle the physical work, how many conversations, thought processes, etc. could a human brain handle at one time?
|
[
"I struggle mightily with one."
] |
[
"What quality of conversation? How different of a subject matter? There are a LOT of variables that significantly effect this. ",
"Generally, human brains aren't really good at true multitasking, we do more of a fast-switching pseudo-multitasking that degrades with each additional task we take on. "
] |
[
"From my experience most people do, although they don't realize it."
] |
[
"How do they start up a nuclear reactor?"
] |
[
false
] |
Was looking through YouTube and saw this video Was wondering what exactly is going on in it. What are they starting up? How are they starting it up? Is the blue from the reactor it self or just lights they have?
|
[
"The nuclear fission reaction works by splitting atoms. Typically we use Uranium-235 for most reactors, although Plutonium-239 and Uranium-233 (bred from Thorium-232) can also be used.",
"To split the atom, we provide it with neutrons of the appropriate amount of energy. The atom absorbs the neutron, becomes unstable, and splits. In the process of splitting, it releases heat, radiation, 2-3 smaller atoms, and more neutrons. These extra neutrons can be used to trigger another nuclear reaction. Given the right conditions, these extra neutrons allow the reaction to be self-sustaining.",
"In a nuclear reactor, we want to make sure we control the nuclear reaction. To do that, we use control rods. The control rods absorb neutrons, which inhibits the nuclear reaction. To start up a nuclear reactor, the control rods are removed from the core slowly, until it is observed that the neutron count rate inside the reactor is increasing exponentially with no additional control rod removal. By removing the control rods, we absorb less neutrons in the core, until it reaches a point where the reaction is self sustaining. We can then slowly insert or remove control rods to adjust the number of neutrons in the core, which in turn adjusts our reactor power.",
"In the video you linked, the control rods are being very rapidly removed. That reactor is a test type reactor that goes from fully shut down to maximum power in a fraction of a second. It stays online for about 10-15 seconds, then the control rods are re-inserted to absorb all the neutrons and shut the reaction down.",
"The blue glow you see is called Cherenkov Radiation. This glow is due to the energy which electrons and other particles are emitted from the fuel. As they slow down in the water, they create the blue glow. Because this is a low power test reactor, the blue glow dies pretty quickly after it is shut down. Commercial power reactor fuel can continue to glow for years.",
"Hope this helps!"
] |
[
"In the video link and other material I could find, they talk about pulse lengths much shorter than seconds. I'd be surprised if they weren't using TRIGA fuel and controlling the pulsing with the removal rate of the rods. I've known of several reactors used for neutron research like this one that used TRIGA fuel to get a large and controllable acute neutron dose into samples. "
] |
[
"Looks like they use a special UO2-BeO fuel in the ACRR."
] |
[
"Why Is Summation of Velocity Vectors Valid?"
] |
[
false
] |
I've seen in several Math and Physics texts questions like, "If a boat goes blah blah in still water and is placed in a countervailing current of blah blah, what is the resulting speed?" or "If a plane has mupmup velocity vector and facing a wind vector pumpum, what is the true velocity vector?" and is invariably answered by summing the vectors. Why is this valid? I have absolutely no training in Physics and just a pretty decent understanding of Math. A priori, I would not have thought that the velocity vector would be the simple sum, especially when the mass of one object is substantially greater than the fluid it's pressing against. Is it just that we've empirically found that we get a roughly correct answer by doing this?
|
[
"There is a major assumption that the books should be explicit about, but they often times are not. That assumption is that the airplane/boat is in a steady state. ",
"Most likely what is confusing you is that you are imagining a boat tied to a dock (or something similar) and then becoming untied. Obviously, the boat doesn't instantly start moving at the speed of the river it is in. However, after some amount of time, the boat will be moving at the speed of the river- because it is floating in that water and will begin to be carried with it. An airplane is a little tougher to visualize, because it can't \"hover\" but imagine instead a hot air balloon. If it is tied to the ground, it doesn't start moving at the speed of the wind instantly, but given enough time it will. ",
"So, once the boat or plane has \"settled\" and is moving at this \"steady state\" (no longer accelerating) then the velocity assumptions made are valid. "
] |
[
"That makes a lot more sense, thank you!"
] |
[
"how much training do you have in math? i ask as a way of gauging how to phrase my response to your question (if you still need an answer)"
] |
[
"Will we all eventually be the same skin colour?"
] |
[
false
] |
With humans travelling all over the world very frequently, and other such activities, is it possible that we will all evolve to have the same skin colour?
|
[
"(Not a biologist, am a physicist, took many biology classes while getting various degrees, would invite someone with a biology background to add to this or point out any errors in my understanding)",
"For a long time you would see articles cropping up predicting the end of blue eyes or the end of red hair or other recessive traits based on the fact that they are recessive genes. These articles are all bogus and are a result of a fundamental misunderstanding of genetics. The most basic experiment in combining genes is ",
"Mendel's pea plant experiment",
", and the result of mating two plants with different phenotypes comprised of dominant and recessive genes is offspring that follow a 3:1 ratio of phenotypes, where the 3 will be offspring that inherit dominant genes and the 1 is offspring that inherit completely recessive genes. The conclusion is that recessive genes do not go away over time in populations, because they will be carried by plants with dominant features.",
"Skin color is obviously way more complex than this but in an oversimplified case it follows from this that ultimately recessive genes will continue to exist, and so any parents with some sort of hybrid skin color that is a combination of 2 colors can have children that are completely one color, children that are mixed colors and children that are completely the other color. Other than selective breeding, genocide, or extreme mutations, there is no way to eliminate various skin colors from the gene pool, just as it is with recessive eye and hair color."
] |
[
"Are you sure he's your father?",
"Just kidding. Your father is probably a heterozygous for dark hair and brown eyes (do either of his parents or grandparents have blond hair and/ or blue eyes?) and his recessive alleles were passed on four times. That's pretty incredible. "
] |
[
"What the fuck are you saying? The reason Northern Europeans have a strict immigration policy is because they have welfare systems that they can't afford to strain anymore with the waves of immigrants that come for the social security.",
"\"They don't get a lot of visitors up there\" - What the fuck? Are you 5?",
"\"It would be hard to understand other cultures of you are not exposed to them\" - Europe is one of the biggest melting pot of cultures in the world. Shut the fuck up."
] |
[
"How is it that plastic doesn't occurr naturally in the universe?"
] |
[
false
] |
With the seemingly infinite combinations of elements and conditions, why isn't there a plastic planet?
|
[
"The reason plastic isn't known to be naturally occurring is probably because it's made of a lot of long hydrocarbon chains. The hydrocarbons hold a lot of energy in their bonds. Have you ever burned plastic? Have you seen the energy it releases when it burns? Take another substance made of hydrocarbons: petroleum. It holds a bunch of energy because it is essentially concentrated sunlight, the sunlight energy that dead/decaying animals held when they formed the fossil fuels. ",
"My point is that in order to form these types of bonds and substances, it takes a lot of concentrated energy. And a lot of enegery goes into making plastic. These energy states would be unfavorable in nature considering how high they are. Carbon bonding, like that of every other element, favors neutrality, and so would not opt to form plastics compared to other molecules unless prompted to by a higher energy process."
] |
[
"Well, given this logic, plastic ",
" arised naturally from our hands."
] |
[
"why isn't there a plastic planet?",
"I think we are having a slight misunderstanding in how infinite works.",
"If you put all the parts to say a motorcycle in a box, shook the box up, and opened it expecting to find a motorcycle, it doesn't matter how many times you do it. You aren't ever going to get the torque to securely fasten a bolt using that method, so the thing won't ever come together.",
"It's possible that the conditions that would lead to a plastic planet just never arise for a similar reason, but I am not familiar with that side of it."
] |
[
"Is the size of an anechoic chamber important? How tiny could you make it until it would stop working?"
] |
[
false
] |
I would like to build one myself, maybe even one with the size of a shipping box. would that still work?
|
[
"This is not completely true,because as the chamber gets smaller your body makes up a larger part of the surface inside, leading to more reflections and a less quiet chamber. Soundproofing panels also aren't perfect, they reflect a little bit of sound, and the closer (to you) they are the more of that reflection still hits you. The optimal chamber would be infinitely large , so to not need any walls that can cause reflections.\ntldr: Small anechoic chambers work, but not quite as well as large ones."
] |
[
"It depends on what you are using it for, and what your requirements are.",
"If you want to be measuring in the far field of a source, then you need to be measuring at a distance greater than D",
" / (4 * lambda) where D is the size of your source and lambda is the wavelength of the sound. So your chamber needs to be large enough to accommodate this distance.",
"The amount the chamber attenuates reflected sound energy scales proportional to 1/length",
" of the chamber. Effective design of the walls will cause them to attenuate sound pressure by about 95% immediately, but increasing the path length of the reflected sound helps further attenuate."
] |
[
"That will still work. Anechoic chambers are designed to keep sound from bouncing off the walls, and there's no reason that would be less effective for small rooms. "
] |
[
"When, where, and how did warm-bloodedness evolve?"
] |
[
false
] |
I had a showerthought the other day that the ability to maintain body heat seems like a huge leap forward. How did it spread throughout the world?
|
[
"According to an article in the journal of anatomy on ",
"www.ncbi.nlm.nih.gov/pmc/articles/PMC1328175/?page=1",
" it goes on to say that the creatures who could limit the fluctuation in their body temperature in spite of the variations of the external temperature had the best chance of survival, reproduced more, and developed into warm-bloodedness we know today. It is thought that it developed in terrestrial creatures, as opposed to aquatic creatures because water tends to act as a buffer and holds temperature stability much more than air does. Water will maintain its temperature, whereas air will go from 100 degrees F to below freezing on an average cycle through the year. Water won't act in the same manner. Terrestrial creatures needed some way to develop a buffer for the variation in temperature. "
] |
[
"Marine mammals originated from terrestrial mammals, which are endothermic. Ectothermic species exist in niches where the advantages of ectothermy (eg. lower metabolic requirements) outweigh the disadvantages (eg. reliance on external temperature)."
] |
[
"There ya go! That’s a complete explanation! But just be careful, if your saying the advantages of ectothermy outweigh endothermy than we would likely see most animals be ectothermic in areas where lower metabolic requirements are required ( sloths are a good example, although poor thermoregulators and they have a low metabolic rate, they are still endothermic and equatorial)"
] |
[
"If Uranium-238 decays by alpha emission, does our current science say antiuranium-238 would emit antihelium?"
] |
[
false
] | null |
[
"Yes, it should."
] |
[
"The shortest answer I've ever seen on this sub."
] |
[
"To add more, the strong and electromagnetic forces both behave the same if you exchange all particles with their antiparticles. These are the forces which are relevant to alpha decay.",
"If the question had been about a beta decay instead (the weak force), then there could be small differences."
] |
[
"Is the moon's perigee always during the full moon? If not, why are tides considered to be higher when the moon is full?"
] |
[
false
] |
As per the title. I've read conflicting articles on the subject and was wondering if anyone here has the knowledge to clear this up?
|
[
"No, when the moon is full at perigee it is called a supermoon. The most recent occurrence was on January 30 of this year.",
"Tides are caused by the combined effect of the moon's gravity, the sun's gravity, and the rotation of the earth. The tidal effect is amplified when the sun, earth, and moon are aligned, as they would be during a full moon. "
] |
[
"right, that makes a lot more sense. So a new moon also causes a bigger high tide and its potentially bigger than a full moons tide because the sun and the moon are on the same side of the earth?"
] |
[
"Yes, a new moon works the same way. This link has some good diagrams and explanations: ",
"http://oceanservice.noaa.gov/education/kits/tides/tides06_variations.html"
] |
[
"AskScience AMA Series: Geology and Geosciences"
] |
[
false
] |
We are going to have a joint AMA series today that will span the subjects of Tectonic geology, structural geology, petroleum geology, geochemistry of petroleum and of oceans, geophysics, volcanoes, earth structure, and biogeochemistry (sorry if I've left some out). We will have people contributing from academic backgrounds, and oil-industry backgrounds, so all questions are fair game! I would also like to point out that a few of the mods and some panelists have been invited to contribute to a class-room like blog, where any questions that are received will have an entire blog dedicated to it, explaining the question and hopefully leaving you with more, it is located . It is still in its infancy, but it will take off this week. If any of the panelists are also interested in contributing, please PM me.
|
[
"So, there are a few different types of extensional basins, but we'll go into the most simple one and probably the most prolific mechanisms. Here is a quick reference scheme for an ",
"extensional basin",
"We can take for example the Black Sea. The Black Sea was formed as an extensional basin by the interaction between an oceanic plate, and the angle in which the plate was being subducted under the Eurasian platform. To elaborate, when you have subduction, there is a zone of interaction between the oceanic plate and the continental plate. We'll call this a suture.",
"Depending on the angle of the subduction, it will depend on the subsequent geological formations. If it is a very low angle, it will have a lot of suture area, and thus a lot of friction. This is when you can have mountain building events fairly far from the subduction zone (such is that formed the Rocky Mountains). ",
"If you have a high subduction angle, or if part of the oceanic plate breaks off or rolls back, the suture is strong enough to pull the continental mass along with it, thus causing an area of extension wherever you might have a previous area of weakness. You can see in this picture ",
"here",
" that there is a rift forming behind the volcanic arc and is a direct result of the subducting oceanic plate. ",
"The vacuum that you are speaking of is something called an asthenospheric upwelling, where decompression of the basin draws up the asthenosphere, thus causing a massive amount of heat to be pumped into the basin, and in extreme circumstances, you can have volcanism. "
] |
[
"So, there are a few different types of extensional basins, but we'll go into the most simple one and probably the most prolific mechanisms. Here is a quick reference scheme for an ",
"extensional basin",
"We can take for example the Black Sea. The Black Sea was formed as an extensional basin by the interaction between an oceanic plate, and the angle in which the plate was being subducted under the Eurasian platform. To elaborate, when you have subduction, there is a zone of interaction between the oceanic plate and the continental plate. We'll call this a suture.",
"Depending on the angle of the subduction, it will depend on the subsequent geological formations. If it is a very low angle, it will have a lot of suture area, and thus a lot of friction. This is when you can have mountain building events fairly far from the subduction zone (such is that formed the Rocky Mountains). ",
"If you have a high subduction angle, or if part of the oceanic plate breaks off or rolls back, the suture is strong enough to pull the continental mass along with it, thus causing an area of extension wherever you might have a previous area of weakness. You can see in this picture ",
"here",
" that there is a rift forming behind the volcanic arc and is a direct result of the subducting oceanic plate. ",
"The vacuum that you are speaking of is something called an asthenospheric upwelling, where decompression of the basin draws up the asthenosphere, thus causing a massive amount of heat to be pumped into the basin, and in extreme circumstances, you can have volcanism. "
] |
[
"I'll reply to the second question and hope that other geologists come in and express their opinions on the others: ",
"If I were to do a 30 minute presentation on anything, it would be how mountains and basins are formed. I find it very fascinating that a lot of people (vast majority of people) live, work, play and appreciate geological structures like mountains or valleys, but they never really question why they are there or how old they even are. "
] |
[
"Can neutrinos interact with each other?"
] |
[
false
] |
They barely interact with standard matter.
|
[
"It is expected in the Standard Model that neutrinos interact weakly with each other through the Z boson. However, these interactions are so rare and weak that they have never been observed, and most of the literature I looked through is basically analyzing astrophysical data to see ",
" evidence of their interaction, and using its non-observation to constrain the cross-section for neutrino interaction."
] |
[
"To add to your answer (which is good btw!):",
"The Z boson of the weak force could be produced by a neutrino anti-neutrino interaction, but the \"cross section\" of the interaction would be tiny. Partly because neutrinos have a tiny mass compared to the Z- roughly 11 orders of magnitude different I think? "
] |
[
"If you had a neutrino emission event as strong as a supernova, but without all the other matter, how close would you have to get for it to be essentially opaque to incoming neutrinos due to interactions?"
] |
[
"Do taller / bigger people live shorter lives the way great danes live shorter lives comparative to other dogs?"
] |
[
false
] | null |
[
"Pretty much yes, this is the case WITHIN most species in fact. Interestingly, the opposite is true when comparing ACROSS species, where larger generally means longer life.",
"There are some hints of this being true in humans from the fact that women are smaller and live longer than men. Japanese populations compared to western populations, same deal. Demographic data in humans, when correcting for confounding factors like gender, still supports that smaller size is associated with longer life. There is even evidence that humans with a form of dwarfism called Laron syndrome, which is caused by deficient insulin growth factor (IGF1) and growth hormone (GH) signaling, may age slower than the rest of the population as well.",
"Your dog example is a good one. It turns out that the size differences and corresponding differences in longevity between dog breeds are largely accounted for by differences in IGF1/GH signaling! This pathway is very highly studied in aging research because interventions that reduce signaling through it can robustly increase lifespan in many species from invertebrates to mammals.",
"Sources:",
"Height, body size, and longevity: is smaller better for the humanbody?",
"Growth Hormone Receptor Deficiency Is Associated with a Major Reduction in Pro-Aging Signaling, Cancer, and Diabetes in Humans",
"The Size–Life Span Trade-Off Decomposed:\nWhy Large Dogs Die Young"
] |
[
"Would this suggest that supplements that help produce hgh in weight lifters or other athletes can actually lessen that person's life expectancy? "
] |
[
"It's not rly clear exactly how it works, but it's known that reduced signaling in the IGF/GH axis and other aging interventions (rapamycin, calorie restriction, etc) seem to slow age-associated disease progression across a number of organ systems, extending both average and max lifespan. ",
"There are many other factors in aging as well including differences between species and individuals in a species. In dogs, several diseases of aging are killers in larger vs smaller breeds (cancer, arthritis) but many are also pretty specific to breed (chihuahuas have particularly high rates of cardiac myopathy because they are prone to underlying valve defects). Not positive for great danes specifically , but I don't think heart disease is more of a killer in large dogs than small ones. I would bet gut problems, arthritis, and cancer are up there. ",
"The heart will certainly work harder to pump blood in a larger animal, but its normally equipped to handle this (and remains proportional to size of the animal). The heart also has ways of compensating to meet increasing energy demands , such as adaptive hypertrophy (enlargment) often seen in athletes. Aging, smoking, diet, etc lead to a maladaptive form of hypertrophy that leads to heart disease. Not sure how to relate this to your observation on larger MMA fighters, but I imagine it takes more energy to move the extra weight which could wear them down faster during a fight."
] |
[
"Noob Question about virus, Why there is no vaccine for HIV or any sexually transmitted disease?"
] |
[
false
] | null |
[
"HIV is tricky for many reasons: it infects a part of the immune system responsible for clearing it from the body, it genetically inserts itself into the host cell, and it mutates very rapidly. ",
"This site",
" has a good laymen-level summary of HIV vaccine development.",
"The hepatitis B vaccine and the HPV vaccines are effective vaccines against sexually transmitted diseases."
] |
[
"The coolest thing about the HPV vaccines is that they are also essentially a vaccine against cancer! The Gardasil vaccine protects against strains 6, 11, 16, and 18. The last two of which are responsible for the vast majority of the cases of cervical cancer and anal cancer! HPV can also cause cancers in the vulva, vagina, and oropharynx. ",
"No HPV due to vaccine = much lower risk of cancer!"
] |
[
"Yes. HPV can be spread by men/people without vaginas, so everyone should be getting it"
] |
[
"Just observed a bee chew on wood and took off, why?"
] |
[
false
] |
[deleted]
|
[
"You have probably seen some wasp species, as honeybees don't really collect wood and other bees like carpenter bees may tunnel in wood but don't really collect it and take it somewhere else. But there may also be other solitary bees that do collect wood, that I do not know about. Wasps however, are often seen collecting wood. ",
"Bees and wasps do not have teeth, but they have jaws which are strong (made of the same materials as the insect's exoskeleton) and can cut and chew small pieces of wood. Wasps bring the wood to the nest and chew it to make a paperlike pulp, which they can mold into the nest (hence also the name paper wasps). "
] |
[
"polistes is exactly correct. A variety of wasp species collect small pieces of wood and chew them into pulp which then is built up into a nest. It's similar to the concept of paper mache.",
"If you youtube \"wasps collecting wood\" there are a variety of videos showing and explaining just that. ",
"Way to be observant OP. :)"
] |
[
"In case OP is wondering, this guy is talking about ",
"carpenter bees",
", a type of bee that chews holes into wood to build its nests. They're bigger than your standard bumblebee and have shiny black abdomens, instead of the furry yellow-and-black of a bumblebee. "
] |
[
"Does lead absorb radiation, or deflect it?"
] |
[
false
] |
I've always wondered this. Does lead somehow absorb the radiation from Xrays for example, or does it reflect it back? And if it reflects, is lead the only element capable of reflecting it?
|
[
"The exact interaction that occurs at the atomic level is actually ",
"dependent on the energy of the photons and the atomic number of the shield",
" (for lead Z=82). You can get ",
"Photoelectric interactions",
", ",
"Compton Scattering",
", or ",
"Pair Production",
". ",
"In other words, lower energy photons, up to a few hundred keV, will interact via photoelectric interactions in lead. Above that, you start to get Compton scattering. At really high energies the photons will spontaneously make electron-positron pairs, from which the positrons will interact with other electrons and create characteristic annihilation radiation. ",
" 3 Main mechanisms act to remove the energy of photons in lead, and it depends on their initial energy."
] |
[
"All radiation is basically energy. If it is Photons (ie xray, gamma, microwave range what ever) it is just energy. If it is particle radiation (Betas, Alphas, Neutron) then it is a particle with a very high Kinetic Energy. So basically the shielding material you use for each type is picked based on the type of interaction you want to get to transfer energy. So any shielding exposed to a radiation flux will heat up. And actually the units for radiation (rads/Grays) are based on energy deposition. One Rad is 100 ergs of energy deposited per gram of absorber (= to 0.01 Gy)(Gy is 1 joule per KG). To convert to rem/Sieverts you have to take into account the type of radiation and other biological risk factors since Rem/Sv are measure of biological risk associated with human dose.",
"\nSo the TL;DR is radiation of any type will deposit energy into a shield and heat it up. The amount of heating is dependent on the exposure rate of the radiation field. Which is why many shields designed for high flux applications have a dedicated cooling system."
] |
[
"think of the radiation as light, which is all it really is.",
"Only gamma-radiation is light. Alpha- and beta-radiation is not."
] |
[
"If a baby is born premature 7 months in the pregnancy after a month is it going to be more or less developed than if it was still in the womb?"
] |
[
false
] |
Is it going to be bigger, in terms of body weight and rate of growth? Is it going to be stronger? Will its cognitive development start as if it was born after a complete pregnancy or no? Basically after a month will it be able to react to stimuli as a baby that did 9 months in the womb and then a month out or will it behave as a baby born at 8 months?
|
[
"It probably depends on which outcome you're measuring, but there are likely to be some differences. For things like lung development, they won't get their own surfactant until the roughly equivalent time they would have started to produce it in the womb. For other things, there could be some functional adaptations from the stress of preterm birth to compensate for being out of the womb early.",
"The other main point is that a premature baby is born with gene expression still set to levels of when it was in the womb, so its not really ready to have fully developed antioxidant defenses (to make breathing oxygen less toxic), which is one of the main reasons why premature babies tend to be less healthy later in life than those born at 9 months."
] |
[
"I see that in a lot of my children clients who were born premature. Many of them end up with Retinopathy of prematurity, which often causes vision loss. I didn't know it was a gene expression thing that made the oxygen less toxic, though. ",
"https://en.wikipedia.org/wiki/Retinopathy_of_prematurity"
] |
[
"It's very possible, neonates inside mom don't have any where near as much to worry about. All they need to do is grow and move. Being early baby would need to stress about learning to eat early, his body has to process food now, he has to breath on his own, he is interacting with people, and lights are bright. All of this too early makes development a bit slower, it's stressful! This doesn't always mean baby will go on to have any deficits or that he is weaker. He will just need a little more time because when a full term baby is 2 months old he has actually existed for 11 months, where a baby who was born 2 months early maybe 2 months old, but has only had 9 months of existing and developing!"
] |
[
"Do the good bacteria in probiotic drinks and yogurts multiply as time passes? If so, does that mean we should wait as soo as possible before consuming them to get the most of it?"
] |
[
false
] | null |
[
"Nah, they are freeze-dried (that's what turns them into powder) until they are consumed. In fact, the bacterial count goes down, not up, so theoretically it would be better to start using them earlier rather than later. "
] |
[
"Bacteria can survive freeze drying and will be 'reactivated' upon rehydration (though the process will kill at least some of them off). ",
"As to why they won't multiply particularly well, these strains are happiest at roughly body temperature. That means all their enzymes and biological processes work best at around that temperature. When the product is chilled, these processes don't work very well so they either can't replicate at all or can only do so relatively slowly. That's why milk takes a while to go off in the fridge, but maybe only a few hours sat out on the counter (for example)."
] |
[
"It doesn't kill them. It puts them in a dormant state until they reach the body. It's a lot like when able bacteria form endospores due to lack of nutrients. They stop metabolic function, but stay alive. "
] |
[
"I've never been able to swallow pills. Does crushing or chewing pills make them less effective than those swallowed whole?"
] |
[
false
] |
[deleted]
|
[
" It can be incredibly dangerous to modify the delivery system of certain medications and it's very important to discuss this with your pharmacist and physician. "
] |
[
"(LAYMAN)",
"It depends on the pill. When it matters, the instructions that come with the medication will usually specify \"do not cut or crush\".",
"The reason it sometimes matters is some pills have special coatings that cause them to be released at a given rate or at a specific part of your digestive system. For example, I used to take ",
"a pill",
" that was coated to stay intact in the stomach and then later release when it hit the less acidic pH of the gut, where it was essentially a topical (rather than systemic) medication. Crushing it would have defeated this coating.",
"Protip I used to use to help my kid take pills: wrap it in a piece of a fruit rollup and wet it a bit. It will be sweet and slippery and go down like a charm."
] |
[
"Pills are formulated to be taken whole and complex compositions ensure release of active components where it is supposed to be.",
"OP I'm assuming that you are young (16-21), you should very much get over your aversion of swallowing pills because over the long term you will have to take many. Swallow with a gulp of water or milk, if you can't handle that then swallow with bread or food-which is how animals are often coaxed into it.",
"Edit: I don't mean to compare the OP to an animal, I'm offering the most plausible way to someone who has difficulty swallowing pills to do it. My parents made me start swallowing pills with food and told me that it works for everyone, and gave the example of animals to show how broad and effective it was. I did not mean it to be demeaning, I'm sorry if you took it that way."
] |
[
"How do I calculate how a branch bends under its own weight?"
] |
[
false
] | null |
[
"You are asking how straight segments bend with the caveat that they can't bend. This question is fundamentally flawed.",
"If you want to know how an object bends under its own weight, I suggest reading a text on elastics. A typical first chapter will describe 1-dimensional elastics and should derive an equation for the shape of a thin rod with a given load that bends under its own weight. The problem is a boundary value problem: you declare whether the item is fixed at one end or both, declare the load, and then find the shape."
] |
[
"As I said, \"bending joints\".\nAlso, \"find the shape\" implies that you're suggesting a method for finding curving segments, which I have made incredibly clear is not what I want.",
"It's like you didn't even read what I said."
] |
[
"I did read your post. I addressed the fundamental flaw in my very first sentence. If only portions of your rod are deformable, then the same reference I gave can explain how to handle that, a suggestion implied by the second part of what I wrote.",
"Cheers."
] |
[
"If a plane flies along a great circle - does it turn?"
] |
[
false
] |
If a plane is flying between 2 points along the path of a great circle, is actually flying a "straight" line between the two points, which looks curved on a projection of the globe on a 2D surface; or would the pilot actually need turn the plane in flight to follow the curve? I'm pretty sure it's the former.
|
[
"Straight, although in reality the plane is turning \"down\" the whole time. :)",
"(And let's not get started about the rotation and motion of the earth, since I assume you're talking about a case where we ignore those.)",
"But really, the equator and lines of longitude both form great circles, and on some map projections those are curved, and on some they're not. "
] |
[
"That is true if you do not care where you end up. Unless your destination is the antipode, the three points (start, end, and center of the earth) have exactly one plane that includes all three."
] |
[
"Thanks. Thought so but wasn't sure. "
] |
[
"How did the horseshoe crab, a living fossil, survive ocean acidification of the climate event known as, Paleocene-Eocene Thermal Maximum (PETM), a period that exhibited large amounts of carbon, which occurred 56-58 million years ago?"
] |
[
false
] |
The Paleocene-Eocene Thermal Maximum (PETM) is studied to draw corollaries to modern day global warming. The horseshoe crab has fossils dating back 450 million years ago.
|
[
"Horseshoe crabs are pretty tough, they made it through the end-Permian extinction and the K-T extinction that wiped out the dinosaurs. They are apparently quite capable of continuing to form shell even in acidified oceans (which isn't too surprising, lots of arthropods form hard shells in fresh water environments that are much more acidic than the ocean will ever be). Arthropod shells are made mostly of chitin, not calcium carbonate, so they are less sensitive."
] |
[
"The main distinction is that carbon dioxide levels are rising at least 5 times faster today than 55 million years ago. As a result ocean acidification is rising 10 times faster, and projected to reach much higher levels than at any time in the last 65 million years. As catastrophic as PETM was for bottom feeders, there was more time for life to adapt to changes back then compared to today.",
"Also ocean pH varies by location, so maybe, and this is speculation in relation to the horseshoe crab specifically, although documented behaviour in terms of evolutionary population migration, maybe localized pockets of populations were able to survive and then repopulate when conditions changed for the better. "
] |
[
"Just as a general point, the term \"living fossil\" is a bit misleading. All it means is that a living species looks very similar to fossils, but it doesn't mean that living species has remained completely unchanged for millions of years. Natural selection will always apply so the horseshoe crab could have gone through many adaptations that didn't change its physical appearance and we wouldn't be able to tell this from fossils. "
] |
[
"AskScience AMA Series: We are women scientists from the Homeward Bound expedition, recently returned from the inaugural voyage to Antarctica! Ask us anything!"
] |
[
false
] |
Hello ! is a ground‐breaking leadership, strategic and science initiative and outreach for women, set against the backdrop of Antarctica. The initiative aims to heighten the influence and impact of women with a science background in order to influence policy and decision making as it shapes our planet. The inaugural 2016 voyage took place from 2 - 21 December 2016 and was the largest‐ever female expedition to Antarctica. We care about science, the concerns of others, and we think science can unite us towards seeing and managing the planet as our global home. Answering questions today are 5 participants from the inaugural Homeward Bound expedition: Heidi is an environmental scientist, an explorer, and a science communicator, sharing her passion for science with others. She is an , Colorado. She studies how environmental changes affect mountain watersheds and Arctic systems and their link to our well-being. and featured in the , including the . Find her on social media and Medium.com @heidimountains. is a current PhD student in the program at the University of Minnesota, researching the intersection between climate change, biodiversity conservation, and women's justice. She holds a Bachelor's degree in environmental policy from St. Olaf College and a Masters in Biodiversity, Conservation, and Management from the University of Oxford. Previously, Ms. Christianson worked in the U.S. House of Representatives writing and advising on energy and environmental legislation, for Ocean Conservancy advocating for science-based marine policy, and held the position of Vice President of , a non-profit organization working to empower women to become leaders in the environmental field. A 2016 Homeward Bound participant, Ms. Christianson was enthralled by Antarctica, and inspired by the 75 other women striving to create a global network of female change-makers. is a penguin expert, TED speaker, and author of the award-winning book, . She lectures internationally about penguins, and is a sought-out expert on radio and TV, including and CNN. A participant on the inaugural Homeward Bound expedition, she returns to Antarctica next year as a . A four-times TEDx speaker, about saving 40,000 penguins from an oil spill can be viewed on TED.com. She is on Facebook, Twitter, and LinkedIn as The Penguin Lady. is an evolutionary biologist and recently submitted her PhD thesis to the at in Townsville, Australia. Her research questioned what constitutes a species, highlighting the importance of animal behavior to the outcomes of hybridization, a common and significant evolutionary phenomena where closely related species interbreed. on coral reef fish using behavior and genetic tools provides novel insights into the ecology and evolution of species. She is passionate about the marine environment, women in science, and diving. She joined the Homeward Bound network in 2016 to build future collaborations and learn within a program aimed to elevate each woman's leadership abilities and capacity to influence in the future. This was highlighted in an article written for . Connect with her on twitter at @AshtonGainsford. , is a climate scientist with specific research interests in climate variability and change, alpine hydrometeorology and Antarctic meteorology and climatology. She works for (a government-owned renewable energy company operating in Australia's alpine region), and specialises in understanding weather and climate processes that effect water resources in the Australian Alps. Johanna maintains an affiliation with the following her PhD on Antarctic meteorology and climatology. She wants to live in a world where quality science is used to make more informed decisions in the way this planet is managed. She thinks Homeward Bound is a pretty inspiring initiative to help get more women to the decision-making table. See for her publications, or find her on twitter @johspeirs.
|
[
"Antarctica was beyond what I expected in so many ways. This coming from a person who thought it would be Greenland-like just icier. I've spent whole summers in Greenland studying polar deserts and their response to climate change. So how is Antarctica different? I knew there would be very few plants - just two species of flowering plants, mosses and algae. As we approached for our first landing, the ground was a fluorescent green; it almost seemed lit up from underneath. Moss, I thought? And why so much of it? We landed and I went to see what made the earth so green. The answer was not what I expected. It was algae, an incredibly thin layer and underneath was penguin poo. Penguins feed in the sea, and through their poo transfer nutrients to the land. These are the nutrients needed to sustain the growth of algae on young, nitrogen-poor soils. From a distance, the hills looked covered in plants like an alpine meadow. This now has me wondering how they look from space, can satellites see the 'green'? The icebergs were the other big surprise. Their size was truly massive, especially as one considers the depth they go beneath the sea given the mass above. Their shapes were like the mesas of the US desert SW near where I live. Anne took incredible photos. See if she'll post a few...I think we can post photos on an AMA."
] |
[
"We all know science isn't really about preconceived notions but were there any discoveries or experiences that went against what you'd expected to see, or anything that went beyond what would be expected?"
] |
[
"How cold is it there really? This may seem like a childish question but hear me out. I live in Pennsylvania and it gets pretty cold here. Like face-hurting wind cold. And I'm pretty sure it's gets colder in other parts of America but I can barely handle here. Was it the type of cold that made you immediately regret the decision, or was it something you knew you could handle? "
] |
[
"How can an object have zero net torque, yet be able to turn?"
] |
[
false
] | null |
[
"So I am not sure if I am interpreting your question correctly. Do you mean how can an object that is rotating have zero net torque?",
"The answer is constant angular velocity. Torque is a force applied across a distance (the cross product of force and distance). Force is mass x acceleration, and acceleration is the rate of change of velocity. So putting that all together we have:",
"torque = mass x rate of change of velocity x radius from point of contact to point of rotation .",
"If your angular velocity is constant (the rate of change of angular velocity is 0), you can be turning but have no net torque. A soon you speed up, slow down, or change radius, however, a torque is exerted due to change in momentum. "
] |
[
"Roughly speaking, you can think of torque as the angular analogue of force. ",
"Translating your question into linear mechanics, it is equivalent to asking",
"\"How can an object have zero net force, yet be able to move?\" ",
"The answer is that it is already moving. ",
"Now, it's possible that you're asking a slightly different question, in reference to angular momentum being stored in e.g. a magnetic field. Here is a paper related to that: ",
"http://www.ate.uni-duisburg-essen.de/data/postgraduate_lecture/AJP_2009_Griffiths.pdf"
] |
[
"Are you asking how to change direction in space while maintaining zero total angular momentum? (This is not exactly what you asked, but it's a pretty common question, so I'm wondering if it's what you meant.) It is possible to do this within a closed system---that is, without using rockets. ",
"This article",
" explains how."
] |
[
"Can two people repopulate the Earth?"
] |
[
false
] |
Would it be possible for a single male and female to slowly repopulate the Earth? (disregarding some catastrophic event).
|
[
"You asked if it is possible. Perhaps, but it is very unlikely. A breeding population of two humans would lead to genetic problems, which would very likely lead to a high rate of mortality for offspring for many generations. A lack of genetic diversity could also lead to the population being susceptible to disease, which could wipe it out very quickly. ",
"A good followup question would be the minimum number of humans that would constitute viable population. According to ",
"a paper from the Key Centre for Biodiversity and Bioresources",
", a minimum viable population is defined as one with a 99% probability of persistence after 40 generations. They calculated the mean estimate of MVP to be 7316 and the median estimate to be 5816 for vertebrates in general. This might be a bit lower for humans, and these numbers could vary greatly depending on the genetic diversity of the initial population and the environmental conditions those humans might face. "
] |
[
"It's important to remember that minimum viable populations* and inbreeding depression are not hard limits, they just make it more difficult for populations to become established. Two people could most certainly repopulate the planet. Islands have frequently been colonized by animals with populations this small. Heck, practically every golden hamster in captivity today is descended from a single pregnant female. ",
"It all comes down to whether the two and their children have the resources to survive most of the time and themselves have many children, plus a bit of luck in the genetics department (recessive deleterious alleles being few enough that not ",
" offspring die) and some random chance (eg, the woman doesn't die in childbirth the first time).",
"*check the definition for what a minimum viable population is: 99% chance of survival for 40 generations. It's more of a \"minimum sure-thing\" population"
] |
[
"That isn't ",
" we have genetic disorders. (I'm not being snarky, but) the reason we have genetic disorders is because of genetic maladies, or genes that do things that we deem less than ideal (sickle cell, for instance). ",
"Can some of the disorders be traced to that bottleneck? It's possible. Some are likely newer occurrence or entirely random. Not all genetic maladies are hereditary, some occur as random chance. "
] |
[
"How is a mental illness defined and differentiated from the \"normal\" spectrum of behavior?"
] |
[
false
] |
[deleted]
|
[
"1.) Yes and no. A lot of what might be classified or termed \"normal behavior\" is (not surprisingly) subjective, and is really influenced by cultural norms. And this really coincides with question 2.",
"2.) For something to be considered a mental illness it would need to be defined under the Diagnostic and Statistical Manual of Mental Disorders, or DSM. ",
"APA DSM",
"\nTo cut through all the fluff it basically boils down to a specific set of behaviors, and whether those behaviors are severe enough to affect one's functioning. ",
"To expand, some symptoms and illnesses are much easier to recognize diagnose: say auditory hallucinations in a schizoaffective patient. Whereas some can be much harder to diagnose--say loss of interest in depression; where other confounding symptoms would be taken into account(such as appetite, mood, sleep disturbances) and length of time experiencing them. And again, separating somebody with major depressive disorder from someone with bipolar because of the existence of a manic state.",
"3.) From a biomedical standpoint, much the same way as any other illness--through research and real world experience--though defining the illnesses is done in the DSM by professionals(and is subject to change by new knowledge and practitioner feedback). And the same with pharmacological treatments: through research and by accident."
] |
[
"To give you the short answer, if the behavior causes a severe disruption of the person's Occupational, Interpersonal, or Leisure activities, the person has a good chance to get a diagnosis. We call it the OIL, and we check a person's OIL."
] |
[
"Abnormal behavior would generally be considered behavior that lies on the far ends of the Bell curve for a given population (I say this just to give you a picture of what abnormality is - I do not intend to say that all abnormal behavior is statistically at the ends of the bell curve, though it often is). Mental illnesses are often extreme forms of normal (i.e. common) human experience. For example, it's obviously very normal to be sad sometimes and happy sometimes. But when that sadness doesn't lift for months and you spend most of your time crying in bed, or your elation last for weeks and causes you to act impulsively without regard for the consequences, you would likely be diagnosed with some form of depression or mania, respectively, or both (bipolar).",
"However, as mentioned in other comments, this is largely in respect to cultural norms. In Western society, a person who sees spirits constantly or communicates with the dead would likely be considered to be \"crazy\" (most likely a psychotic disorder like schizophrenia). However, New Age circles might consider this person gifted, and other cultures might consider this person to be a medicine man. In these contexts, the behavior is acceptable and would not be defined as mental illness - it may even be encouraged.",
"A large part of what goes into a person being considered mentally ill is their level of functioning. Someone with bipolar might become hypomanic, which is a milder form of mania. While mania is usually incredibly frightening and has severe consequences (sexual promiscuity, running up credit card bills, extreme volatility, etc.), hypomania can sometimes manifest as self-confidence, a sense of focus, increased creativity and sociability - generally good things in our society. The person's level of functioning might actually increase temporarily. In bipolar disorders, however, there is a downswing into depression which may or may not show outward signs of impaired functioning. Millions of people with depression (whether related to bipolar or not) seem completely \"normal\" - they smile and laugh, show up to work, and no one can tell how much they are hurting. So even though they still appear to be functioning well, things are still very much out of whack cognitively and emotionally. Determining one's overall level of functioning is an incredibly important area of discernment for therapists.",
"In America, most therapists use the DSM-IV-TR as their guidebook for determining whether or not to diagnose a client with a mental illness. This manual is published by the American Psychiatric Association and dictates what symptomology is required for a person to have a diagnosis. The criteria for diagnosis is very cut and dry, which in my opinion is one of its weakest points. For example, suppose someone has been having hallucinations and delusions that have persisted for a several months, but is still able to function relatively well in social and occupational environments. This person would not be diagnosed with schizophrenia under the DSM, because impaired functioning is a diagnostic criteria for schizophrenia. The person might be instead diagnosed with schizophreniform disorder. This is incredibly important, as an official diagnosis plays a crucial role in determining which medicines can be administered and what insurance companies will pay for.",
"I personally am largely against the concept of abnormality, as the word lends itself to stigmatization and because mental anomalies, even if rare, are still a part of human experience and have been for thousands of years, and are thus \"normal\" in their own right. The next edition of the DSM is supposed to be coming out next year, and I hear that they are moving towards a more spectrum-oriented method of diagnosis.",
"Edit: Added a couple words and fixed some grammar."
] |
[
"Why is cancer often \"delayed\"?"
] |
[
false
] |
I recently watched and realized that cancer tends to manifest well after exposure to certain substances. This is true with many things, such as smoking, drug use, sunburns, etc. My understanding is that cancer is a mutation of cells often caused by an outside source such as chemicals or radiation. In this woman's case, shouldn't cancer have manifested shortly after exposure to burn pits? Why did it take so long, and why does this often seem to be the case regardless of the initial cause?
|
[
"DNA for Cell replication is happening all the time, and mutations are pretty normal. There are actually a bunch of different kinds of mutations, most of them are relatively harmless. But when you get damaged DNA via viruses, radiation, burns etc. It greatly increases the chances of more mutations happening as cells replicate, thus increasing the chances massively of one of the mutations leading to cancer cuz there’s so many more happening… at least that’s how I understand it. Replication still needs to happen and will happen, but stuff like large exposure to radiation makes cancer pretty much guaranteed at some point cuz of the damaged DNA."
] |
[
"This is a simplified view (I don't know the details either), but the transition from normal to cancerous flesh has several steps and takes time. Several ",
"biological capabilities are acquired",
" Nor is it inevitable: some heavy smokers live for an annoyingly long time. (Annoying to me, not them.) Why? Our cells have several layers of defence against cancer built into them, and if even one of those layers holds, the cancer can be suppressed."
] |
[
"The details will depend on the type of cancer and exposure, but the very general answer is that cancer requires multiple \"hits\", or damages/alterations to DNA, to occur. The initial exposure is just one \"hit\", and then repeated exposures, or just spontaneous mutations accumulating slowly over time, are needed to develop cancer."
] |
[
"Are huge Saharan features caused by erosion?"
] |
[
false
] |
When looking at a detailed globe, there are some huge structures that look like the remnants of ancient water or ice erosion, but could also be an illusion of rock formation. A very clear example of this is a 700km by 500km "fan" straddling the Chad-Libya border. Most of Mauritania looks like it is "flowing" west to the Atlantic, and there is a large parenthesis shape ")" covering most of Saudi Arabia. What are these structures? Do they have a name?
|
[
"Other commenters are talking about sand dunes but I don't think that's quite what you're asking about. While it's true that sand sculps much of the topography of the Sahara you asked about the really big stuff- and I think I'll just address them individually. But first, let me mention that \"ancient\" water erosion last happened only a few thousand years ago and comes and goes in the Milankovitch cycles- in geologic terms, water actively sculpts the Sahara.",
"On to the features you mentioned.",
"The big \"fan\" of gray rock is a plateau called the Tibesti mountains. The uplift was formed by volcanic activity and active lava flows started around 30 million years ago- the dark rock is basalt. You can zoom in on the map and see the volcanic craters. Some of the peaks top 11,000 feet in altitude!",
"Moving to Mauritania- you're correct in identifying that the landscape seems to \"flow\" to the ocean- this is simply the prevailing winds moving sand around. Much of that sand comes from more eastern parts of the Sahara and some of it goes all the way to the Amazon, where it serves to help fertilize the rainforest. (Bonus: the ",
"Richat Structure",
" is in Mauritania and is one of the most striking things in the Sahara)",
"The structure in Saudi Arabia is formed similarly. The actual geology making the ridges is different layers of rock being compressed by tectonic activity- but what these mountains lead to is some fairly odd wind patterns. ",
"This map",
" shows how wind sweeps down the crescent, and, as you might imagine, takes a lot of sand with it that fills up the basins.",
"Hopefully this sheds some light on your question!"
] |
[
"Thank you, yes, those are the some of features I was asking about. ",
"The Tibesti uplift is now clear to me. There are smaller NE-SE striations across, for example, The ",
"Eye of the Desert hiking area",
" which appears to be a much older outflow cone. The more I look at this, it is very complex interaction between underlying geology and weathering. ",
"The wind map of the Saudi Peninsula exactly predicts (informs) the giant features there. ",
"I now see the scope of my original question was hard to articulate. I was once smacked in the face with \"scale invariance\" when hiking on ",
"Mount Lemmon",
". From a distance it stands like a monolithic sky-island but gets ever more complex as you twist your way into it. All that was for a feature only a fraction of the size of ",
"Emi Koussi",
" which itself is an outcropping of the Tibesti range which is beside the larger feature that first caught my eye."
] |
[
"Technically yes, mainly wind erosion and sand in the wind sandblasting hard rock away. But we have to remember that erosion can technically build structures as well because that eroded material has to go somewhere. It doesn’t disappear. These structures could be caused by erosion of large rock, or they could be caused by eroded material depositing in one place over hundreds to thousands of years. Lastly it’s proven that wind can build structures out of eroded material as how wind creates giant crescent dunes in deserts. Structures made by wind."
] |
[
"Are software systems on Voyager I or other older spacecraft upgraded or improved?"
] |
[
false
] |
As we upgrade our technology and infrastructure in the IT world we have to flash new firmware, upgrade software/hardware, and/or perform maintenance on systems to keep them up-to-date and running smoothly. As technology improves are organizations like NASA actively making software changes on a spacecraft like Voyager I, potentially adding features or improving existing processes?
|
[
"In the 19",
"80's the Galileo probe had it's image software updated to allow for image compression. This resulted in the ability to transmit significantly more images using the limited bandwith available.\nTo illustrate how dangerous interplanetary software updates are here are two cases where it went wrong:",
"The Viking Mars probe was accidentally broken after a software update to correct a battery charging issue caused the antenna array to stop working.\nRussia's Phobos 1 probe was also broken after a software update caused the attitude thrusters to go wrong."
] |
[
"They can be, but you don't want to go messing around with the systems more than you absolutely need to. If you put the wrong firmware on a server's motherboard and you need to pull the CMOS battery then you can do that relatively easily—it's a headache but it'll just cost you your afternoon and, in the worst case, that motherboard; you're out a few hundred dollars. If you pull a similar move with a space system then you've ended a multi-million to multi-billion dollar project.",
"This",
" article in Wired mentions upgrading old Fortran libraries to C as the probe has gone through its life. "
] |
[
"\"If it ain't broke, don't fix it\". Especially when it is Billions of miles from Earth and you can't \"unfix\" it."
] |
[
"Is it true that concussions and even subconcussive impacts kill neurons?"
] |
[
false
] |
I’ve gotten a lot of mixed info on this. I heard you don’t even need to get a concussion for an impact to damage your brain and kill neurons, is this true?
|
[
"You've probably gotten a lot of mixed info because there is a ",
" of mixed info out there. ",
"This paper",
" would be a good read if you want a detailed and relatively recent description of what we currently understand about concussions.",
"But, in brief, after a (mild) concussion, the changes in brain function are less a result of structural damage to the brain, and more a result of widespread short-term neuron malfunctioning. ",
"The initial impact throws off the balance of potassium in the brain",
", which causes a bunch of excititory neurotransmitters to get released, which causes a whole cascade of problems that looks a lot like when the brain runs out of oxygen. During this \"energy crisis\", blood supply is actually ",
" to the brain, and neurons have to slow down and take their time to pull themselves back together. Nearly all neurons recover, but ",
"a few stragglers might actually die",
". But the neurons that die weren't necessarily killed during the impact, just pushed too hard during the neurochemical aftermath.",
"Other neurons may end up permanently injured (this time as a direct result of the impact) ",
"like when an axon gets overstreched",
" (or snaps completely). The neurons don't ",
", but the damaged axons don't work right, and may never actually heal.",
"However, during the \"energy crisis\", ",
"the recovering neurons are especially vulnerable",
". A second trauma (like, say, a second concussion) before neurons are completely healed could kill a whole lot of neurons that would have otherwise made a full recovery."
] |
[
"What about when there are no symptoms? Like in a subconcussive impact. "
] |
[
"Well, if somebody's not showing symptoms, then what they skipped was the depolarization/overfiring/potassium everywhere/\"energy crisis\" part that makes it a concussion. However, the axon damage part (stretching/snapping) could ",
" still be happening. Even something as (seemingly) non-traumatic as ",
"heading a football can cause significant axon damage",
", especially if the small impacts get repeated many times.",
"That axon damage doesn't meany any neurons died, but it does mean that neurons were disconnected from one another, which is...also not great. Repeated across enough axons and you get measurable impacts on overall brain function."
] |
[
"In what manner does antimatter-matter annihilation release energy?"
] |
[
false
] |
Can we please consider positron/electron annihilation and proton/antiproton annihilation and their preferences to producing massive particles and massless particles? Production of massive particles aside would the reaction produce two photons of opposite momentum and equal energy or maybe a spectrum of photons mostly gamma rays? How would the spectrum of photons look like in relation to the type of particle/antiparticle interaction?
|
[
"Typically, when a positron and an electron annihilate, two photons are produced, each with an energy of 511 keV, the mass of the electron (times c",
" ). ",
"If the particles had significant kinetic energy before annihilating, the photons can have more energy, or other particles can be created if the electrons were going close to the speed of light.",
"Here is a spectrum from positronium decay, which looks like a smeared peak at 511 keV",
"http://www.stolaf.edu/academics/positron/gas_analysis.htm",
"I'll try to find better spectra."
] |
[
"The other comment already addressed the energy issue. ",
"All products in annihilation reactions will have the same quantities as the original pair i.e. All quantities are conserved. "
] |
[
"Cool, thanks for finding the link for me. ",
"So I got a follow up question. What's up with the photons to the left of the 511keV part of the spectrum? Think it could be that say there is a significant difference in kinetic energy/momentum that you'd get say one photon of 510keV and another of say 514keV to make up for the momentum in one direction and the kinetic energy?"
] |
[
"Could an infinite sequence of random digits contain all the digits of Pi?"
] |
[
false
] |
It's a common thing to look up phone numbers in pi, and it's a common saying that every Shakespeare ever written is encoded in pi somewhere, but would it be possible for every digit of pi to appear in a random sequence of numbers? Similarly this could apply to any non terminating, non repeating sequence like e, phi, sqrt(2) I suppose. If not, what prohibits this? I guess a more abstract way of putting it is: Can an infinite sequence appear entirely inside another sequence?
|
[
"It's a common thing to look up phone numbers in pi, and it's a common saying that every Shakespeare ever written is encoded in pi somewhere, ",
"I just want to note this this is commonly believed, but as yet unproven. A infinite decimal in which every possible digit sequence appears ",
" is called a ",
"\"normal number\"",
". It has ",
"not been proven that pi is a normal number",
". It's expected to be, but no one has shown a mathematical proof that pi does contain every possible sequence of digits. "
] |
[
"It's any ",
" sequence of digits."
] |
[
"Sure. Take 1 + π/10 = 1.314159265359...",
"or 138.594859 + π/10",
" = 138.594859314159265359...",
"etc.",
"Further, since the decimal exansion of π is non-terminating, you can't ever have a number of the form",
"some_digits,π,some_more_digits\n",
"so those are really the only options for realizing this."
] |
[
"Is the \"red-ness\" of hemoglobin somehow connected to its function?"
] |
[
false
] |
The color of blood is so impressive, is it only coincidence or somehow relevant for its function?
|
[
"It’s because of the iron. Red blood cells need iron to make haemoglobin and myoglobin in order to transport oxygen to various parts of the body. ",
"This isn’t the only way to achieve this though which is why horseshoe crabs have blue blood. In their case they use haemocyanin instead which uses copper which makes their blood blue."
] |
[
"And the red-ness of (iron based) blood is actually connected to the amount of oxygen it carries. Blood full of fresh oxygen is bright red and blood carrying back CO2 to the lungs, so it can be breathed out, is a much darker red."
] |
[
"I'm pretty sure it's because you don't have elemental iron in your blood, which is the form that iron bars are made from. Rather, you have ferrous iron oxide in your hemoglobin, which is a dark red color (the color of rust, because it is rust)."
] |
[
"Do black holes have entropy?"
] |
[
false
] |
[deleted]
|
[
"Yes, the entropy of a black hole is kA/4L",
" where A is the surface area of the black hole, k is Boltzmann's constant and L is the plank length. "
] |
[
"Just wanted to emphasize that entropy proportional to surface area is the only sensible answer. The inside of a black hole is inaccessible and so, in order to conserve entropy, whatever entropy a black hole has must manifest on the surface."
] |
[
"Yeah, it's the surface area of the event horizon."
] |
[
"If you include something made up into a story (of a real event) and tell it again and again, will other people who were part of it actually start to believe your version?"
] |
[
false
] |
I guess you'd probably have to tell the story again and again? And wasn't there something about telling stories that would make you believe that you were part of it, even if you weren't, if told often enough? Edit: Everyone, thank you so much! Your answers helped a lot!
|
[
"When you remember something, you aren't actually accessing some sort of data bank pertaining to that event. You're actually recreating the event from concepts within your brain that have strong connections to it. Pretty much every time you remember something, it changes, even if just slightly. So, yes, reinforce one version of a story enough and even people who were part of the story might start to remember false details."
] |
[
"The research on this kind of thing is pretty famous, and is in large part thanks to Dr. Elizabeth Loftus (et al., of course). Her research focussed a lot on how you can alter memories with language use and how fallible eye witness testimony is because we don't actually store things very well at the time (and so anything you didn't store you basically make up on the spot under pressure, without realizing it, and then start to believe it). ",
"A quick google scholar search reveals some of her greatest hits: \n",
"Heres ",
"a study that showed you can influence people to remember objects they didn't see in the first place, ",
"another",
" that demonstrated memories being altered by how people were asked about them, A ",
"cool one",
" about childhood \"memories\" seeming more likely if you imagine them first, and a ",
"personal favorite",
", what amounts to a discussion on whether repressed memory is really a thing. ",
"I just thought you might like to know about those since they seem relevant to your question!",
"Or, Tl;dr version: yes."
] |
[
"When you remember something, you aren't actually accessing some sort of data bank pertaining to that event. You're actually recreating the event from concepts within your brain that have strong connections to it. ",
"That's actually extremely terrifying. Do you have a source for it?, because I'd like to read more."
] |
[
"Why is hair loss so symmetrical?"
] |
[
false
] |
Gentlemen of advanced age always seem to have very symmetrical balding patterns. Why is it so?
|
[
"Androgenic alopecia is thought to be caused by abundance of sex hormone (DHT) in predisposed scalps. While different distribution patterns do exist, it would be far more surprising if the pattern were not bilateral, since that would suggest a non-random distribution of hormone in the affected tissue.",
"That said, there are certainly differences in the two major patterns of androgenic alopecia as evidenced by efficacy of Minoxidil (trade name rogaine). Rogaine is only useful for vertex baldness (think monks). As you might imagine, baldness is a perennial hot topic for drug companies and dermatologists, so expect more information in the future.",
"I'm new here, so let me know if I can clarify anything.",
"*As an aside, if you do see a lateralized alopecia, that's a good indication that something else is afoot. And if you see a well-defined shape, you should immediately think about trichotillomania."
] |
[
"No problem. Front to back is the other big one. Blanking on a neater name for it."
] |
[
"Thanks so much! So if vertex balding is the monk style pattern, what is the other type of androgonic alopecia that Rogaine is not effective on?"
] |
[
"Hey /r/AskScience, can I get some ideas on chemistry-related cookie designs?"
] |
[
false
] |
[deleted]
|
[
"These!"
] |
[
"How about Schrödinger's Cookies? You could bake cat-shaped cookies and put it them little cardboard boxes."
] |
[
"And the cookies may or may not be in the box!"
] |
[
"How does convection fit into the behavior of Brownian motion? Doesn't the observation of convection contradict the Brownian motion?"
] |
[
false
] |
I've got a contradiction in my understandings of convection and Brownian motion. It seems to me that the assertion that gas molecules would be statistically unbiased in their direction (Brownian motion) fails to explain the macroscopic behavior of unbounded lighter molecules. For instance: why does a flame point upwards? I understand that heated gases are less dense than colder gases, of similar chemical composition, but why don't they just expand in all directions? Doesn't the Brownian model require hotter molecules to just vibrate faster, but still move in an unbiased direction? I can see why helium in a balloon would rise in an air atmosphere. Basically the pressure differential between the top and bottom of the balloon results in a net upwards force on the balloon which is lighter than the net hydrostatic pressure difference across the height of the vessel. This behavior of rising lighter gases goes funny when the container disappears and the molecules are allowed to diffuse. Can a heat and mass transfer professor help me with this conundrum?
|
[
"You can still have biased brownian motion. For instance, something that feels a potential in one direction but is free to diffuse in the other two directions (what you're talking about), or a brownian particle that is still under a central force (this is how optical tweezers work). Or a simple example, a small bead inside a fluid filled straw less then twice the diameter of the bead, which only diffuses along the axis of the tube."
] |
[
"Gravity. As represented in the ",
"Rayleigh Number",
". A flame in gravity raises upward. A flame in microgravity or less actually forms a ",
"ball",
" as you thought it would."
] |
[
"I'm not meaning to criticize Rayleigh's work. It does fail to explain the behavior at a particle level though. I am aware that there are many macroscopic models which predict the bulk behavior of gases. My boggle is that the only microscopic model that I know of (Brownian motion) fails to explain a lot of macroscopic behaviors. I'm hoping to reconcile a particle explanation of behavior with macroscopic observations."
] |
[
"Why, after Hurricane Katrina, were large masses of trees planted near the mouth of the Mississippi River?"
] |
[
false
] |
I've heard bits and pieces of a story that, after Hurricane Katrina devastated much of the southern states of the US, thousands of acres of trees and/or shrubs were planted near the mouth of the Mississippi river. I can't seem to be able to find much information.
|
[
"Trees have roots that hold the soil around them which stops wetland loss. Wetlands act as a buffer to storm surge during hurricanes. In addition, trees would poke up through the storm surge during a hurricane and knock down waves. Those waves could be breaking over the levees. "
] |
[
"The Mississippi River Delta has seen alarming amounts of wetland loss in part due to sediment deprivation (resulting in subsidence), saline intrusion and land development projects. The reason this is so important is because for every ~3.4 miles of coastal wetland a storm must pass over, storm surge is diminished by one foot. Hurricane Katrina served as a reminder for just how important this ecosystem is and spawned many projects to revitalize their coastal ecosystem. Unfortunately at this point it may be too little too late. "
] |
[
"The Louisiana coast line currently loses roughly a football field of land per hour without the assistance of hurricanes."
] |
[
"Why do retroviruses have to go through reverse transcriptase to create mRNA?"
] |
[
false
] |
Retroviruses are a class VI virus. Their genome is positive single strand RNA (+ssRNA). mRNA is also +ssRNA. Class IV viruses are also +ssRNA and are used directly as mRNA. Whereas Retroviruses have to be converted to a double stranded DNA intermediate via reverse transcriptase and then the +mRNA is transcribed from the dsDNA. Why couldn't retroviruses be used directly as +mRNA? , class IV and class VI viruses circled in red
|
[
"The simple explanation is they evolved that way. We don't know enough about viruses to justify how they evolved (heck, we don't even know if they're even ",
").",
"Class IV viruses do not incorporate their genome into the host DNA. Like you said, they transcribe directly as mRNA into protein. This means that they ",
" be less infectious, even if they directly infect the host. Retroviruses, on the other hand, are able to churn out more copies of mRNA because they incorporate themselves into the host genome.",
"Why did they evolve separately? Nobody knows for sure."
] |
[
"It's just so weird. They are both +ssRNA, so what makes them different? Oh and my professor explicitly said that viruses are NOT alive but he also included the loophole \"at least not for the purposes of this class.\" It's just odd to claim they aren't alive, what makes them less alive than a bacteria? They evolve, they respond to stimulus in a way, they have genetic info. "
] |
[
"There's an ongoing debate on whether or not they're alive. Your professor is right though: it's much more useful to say they're non-living for the purposes of your class. Saying that viruses are alive conjures up the debate and so it's not really useful to discuss.",
"You're implying in your statements that evolution has a purpose. That is also a topic of debate right there. Right now, we just don't know enough about viruses to justify why they evolved the way they are."
] |
[
"Are there any major cases of speciation/evolution in invasive species that we know of?"
] |
[
false
] |
Are any invasive species known to have diverged substantially from original populations after years of isolation? Obviously evolution is ongoing and continuous but what about obvious physical differences that are already the result of a species being relocated by humans?
|
[
"I am not sure if you find it a \"major case\", but just in a few decades the Spanish slug(invasive land slug in much of Europe) have changed colour quite dramatically here in Denmark. When it first invaded in the late 90's it was ",
"bright orange",
", but just over the last 15-20 years it has changed to a more ",
"darker brown",
". I believe it was partly due to interbreeding with other local species, but nonetheless it is impressive to me that such a distinct difference have happened in my lifetime(despite my molluscophobia :P).",
"",
""
] |
[
"Interesting! That's exactly the sort of thing I was looking for. "
] |
[
"Commenting to hear others' input, but it would seem that to be an invasive species would mean being introduced to an area with less stressors than the native environment--they thrive in the new environment as-is without pressure thereby lessening the likelihood of \"quick\" speciation."
] |
[
"My 6 year old friend wants to know: If you split one atom how big would the explosion be?"
] |
[
false
] | null |
[
"202.5 megaelectronvolts, or about 4.32x10",
" kg of dynamite. That is on the order of a millionth of a millionth of a millionth of a kilogram of dynamite. (This calculation assumes that the atom is U-235, which is the most common nuclear fuel)"
] |
[
"Thanks. I'll tell him \"So small you can't see it or hear it but big enough to split the atom next to it.\" Would this be correct? Would the explosion be big enough to split several more atoms? How many?"
] |
[
"Yes! That is exactly how atomic bombs work. The first explosion triggers 2-3 more and so on until all the atoms have been split."
] |
[
"Does everyone's intestines fold the same way?"
] |
[
false
] |
From dietary images to textbooks, I've seen the internal organ diagram with the big jumble of intestines. But is it random? Do intestines just kinda, grow, or is there a specific way they grow?
|
[
"The intestines don't grow the same way for everyone. The large intestine has a pretty specific schematic to it so that is pretty constant in everyone; however, there are many minor differences and a few major ones. The small intestines are what are really variable. ",
"When it comes to abdominal surgeries, you can take out the small intestines and basically just throw em back in. As long as you aren't damaging anything, it doesn't matter the exact position they end up in.",
"EDIT: my wording may be a bit inaccurate. You can't actually \"take out\" the small intestines from the body unless you want to cut them out. The small intestines are connected to the posterior abdominal wall by connective tissue known as mesentery. The mesentery has blood vessels and nerves running through it. If you move aside the small intestines you can see the mesentery coming off of them. "
] |
[
"I guess I should have been more accurate with how I described it. The small intestines are connected by mesentery to the posterior abdominal wall. The mesentery is where all the blood vessels to and from the small intestine travel through. If you move aside the small intestines, you can see the mesentery coming off of them.",
"In front of the small intestines, there are no connections. There is, however, a layer of connective tissue known as the greater omentum. It is made of visceral peritoneum. It is commonly referred to as a drape, and that is basically what it is. "
] |
[
"..like stuffing a sleeping bag back into the pouch?"
] |
[
"Is there such a thing as objective reality?"
] |
[
false
] |
I know it's a vague question. But I have friends that postulate that everything is subjective, and when I bring up the laws of science they find a way to weasel out of it, mostly because I'm not knowledgeable enough to arrest them on their mistakes. Are they right? And if not, how can I make a better argument for my case?
|
[
"Oh I see; Well ",
"Asimov",
" had a nice answer to this.",
"My answer to him was, \"John, when people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together.\""
] |
[
"No one actually believes that reality is subjective.",
"Even the most ardent sophist looks both ways before crossing the road. This is because they believe in the objective reality of oncoming traffic."
] |
[
"There are no experiments right now that suggest otherwise. Measurable results appear to be independent of the observer's consciousness."
] |
[
"Why is processed sugar bad for you if your body breaks down food into sugars cells use to power your body?"
] |
[
false
] | null |
[
"There are two general reasons why: refined (i.e. purified) sugar does not have other nutrients that come in healthy food, and it means that you're consuming a lot of sugar in a short time.",
"The first part is I guess pretty easy to understand. Refined sugar is empty calories - it replaces other important nutrients such as proteins and minerals. Some amino acids, which make up proteins, can be synthesized using sugar as one of the substrates, however it's not very efficient. In general though your body needs a lot of different nutritients to function properly.",
"The second part is much more complex. Ingesting a lot of sugar at the same time means that your blood sugar level will get high. To get the sugar from the blood inside the cells, your pancreas releases a hormone called insulin, however it takes some time for this to happen, so the insulin level is not immediately adjusted. Of course when the high amount of sugar gets inside your cells, they have to do something with it, and often it gets transformed into fat to store the energy. ",
"The form of sugar usually found in blood - glucose - is a very important source of energy for all of your cells however, like every single substance, it is bad in excess. Glucose and other sugars have a property that allows them to bind to amine groups, such as the ones that are often found in proteins. This can cause the protein in question to stop functioning properly, as they were evolved over millions of years of humans eating fruit, not candy.",
"So if you regularly consume large amounts of refined sugar, you regularly give your body big spikes of insulin, which may cause some of your cells to stop reacting to it as strongly as they're supposed to. This is how you develop type II diabetes. Now your pancreas is even less capable of controling the sugar level in your blood. If you continue with the same unhealthy diet, your future does not look bright. The cells that form the lining of small blood vessels don't rely on insulin to absorb the sugar, so they grow too big, and eventually these blood vessels start bursting. This is bad because the small blood vessels often supply important stuff, such as nerves. So you get blind (",
"diabetic retinopathy",
"), your feet (sometimes also hands) get insensitive and can get ulcers, which may lead to gangrene because you didn't notice, since you didn't feel it, and it was healing very slowly, because the blood vessels there were already screwed up (",
"diabetic foot",
") etc. Diabetes can also lead to heart attack or stroke.",
"So, like, it's a good idea to put some thought into how much sugar you consume, especially in the form of sweetened drinks, because they're not filling your stomach, and thus you feel like you ate nothing even though they usually contain a really big amount of sugar. Also eat polysaccharides, they release sugar much more slowly, so you don't get that big spike of insulin."
] |
[
"Processed sugars get absorbed quickly in the small intestines and are sent to the liver to be transformed in fat. The amount of energy is so high that the body does't use it immediately, so it stores it instead of eliminating it. ",
"To do so, the pancreas releases a large amount of insulin to process all that sugar. That puts a strain on the pancreas. Repeat cycles will end up damaging your pancreas and liver leading to diabetes and fatty liver. ",
"Then comes the damage to your intestinal flora. As the energy is absorbed in the small intestine, the flora that lives in the large intestines will starve without sugar contained in fibrous foods (fruits and vegetables) and other nutrients. That end up releasing toxins in the blood stream.",
"Processed sugar is really bad for you."
] |
[
"Sorry? Can you provide some evidence for this please"
] |
[
"At what age* do human babies start having their own bacteria in their stomachs? (*while in the mother's womb itself or after birth)"
] |
[
false
] |
The good bacteria that help digest stuff that is..
|
[
"Initial colonization occurs at birth; prior to birth, they are sterile. In the first few weeks and months the intestinal ecosystem gradually shifts from what was acquired from the mother at birth to one that is more adapted to digestion."
] |
[
"They aren't. They are transferred from mother's vagina (in case of vaginal delivery) and skin (through post-delivery skin contact), and then later also from everything that the baby sticks inside their mouth. ",
"The bacteria that live in your intestine aren't special intestine-only bacteria. They live in all sorts of other places on you and in the environment. What's special about them in the intestine is a) the nutrient mixture they have access to (from what you eat and drink) b) the communication they have with the rest of your body (by excreting chemicals into your intestine that can enter your body and regulate different biological processes) and c) the exact mixture of the different bacterial species (which is partly due to the nutrients)."
] |
[
"Like the answer you got, they are sterile before birth and then acquire their bacteria at and after birth. And this can actually become a problem with C-sections because we are finding that, believe it or not, bacteria from the mother's vagina actually ends up being important for the baby to encounter upon birth. Google \"C-section gut bacteria\" and you'll find a few articles on it."
] |
[
"If oral steroids such as prednisone and dexamethasone are immunosuppressants, why are they effective in treating Covid? I would presume you want your immune system in tip top shape, no?"
] |
[
false
] | null |
[
"From the ",
"NIH",
": “Patients with severe COVID-19 can develop a systemic inflammatory response that can lead to lung injury and multisystem organ dysfunction. It has been proposed that the potent anti-inflammatory effects of corticosteroids might prevent or mitigate these deleterious effects.”",
"For more information, here is a link to the ",
"RECOVERY trial",
" (dexamethasone use in covid). The ",
"NIH treatment guidelines",
" have additional info (and summarize the RECOVERY trial nicely). Dexamethasone has been shown to be effective previously in non-covid ARDS but not viral pneumonia (though this is controversial). It’s important to note that the trial showed no benefit to patients not receiving supplemental oxygen, and the greatest benefit was to patients requiring ventilation. Additional studies on other steroids have mostly not demonstrated efficacy."
] |
[
"One thing I haven’t seen mentioned here in the replies yet is that Covid has different phases, and you give different treatments during different phases. ",
"Here’s a tweet by infection disease expert Daniel Griffin that shows the basics of these stages and what treatment you’d use during them. ",
"https://twitter.com/DanielGriffinMD/status/1323418530780532738?s=20",
"As you can see, the viral phase of the disease-before your immune system mounts a strong defense- is only the first few days. You would NOT want to give steroids during this time, basically for the reasons you gave in your OP. This is when it’s effective to give treatments like remdesivir and monoclonal antibodies. ",
"After the viral phase is past all the symptoms are caused by your immune system freaking out, and the virus is pretty much gone. That’s why steroids are safe and effective during this time."
] |
[
"This was probably already mentioned, but the immunosuppressive effect of glucocorticoids is dose dependent. Typically doses of 20mg/day for 3 weeks or longer is considered “high dose” and would start having impacts. ",
"Short course bursts really hit inflammation with very very little immune system change."
] |
[
"What exactly is a \"field\"?"
] |
[
false
] |
So, while reading about quantum physics, in all of its confusing mumbo-jumbo, I have come across the term 'field' often, like the electron 'field', or the higgs 'field', and various particles are simply excitations of these 'fields'. What exactly does this mean? What are these fields? Is it related to the theory that says that the universe exists in eleven(?) dimensions. The way I visualize it, it is similar to sticking your finger into a two dimensional world/plane. All that would appear in the world would be a small circle made out of a cross-section of my finger. In my mind, the small circle that my finger makes would represent an excitation in the 'field', and the 'field' would be either my finger or the entire 'third dimension'. Though this visualization seems like it would only work in accordance with the 'eleven dimension' theory. So what exactly are these fields? Is my visualization accurate? If not, what might be a better one? thanks in advance
|
[
"It's simpler than all that. A field is something that has a value at every point in space. For example, if you consider the surface of a body of water, at each point the water has some temperature, so you could call the temperature field the temperature at each point on the water."
] |
[
"Well you can consider things like an electric field or a magnetic field or a gravitational field, they can extend indefinitely. Instead of considering the electric field of a single object, you can consider the magnitude of ",
" electric field throughout the entire universe.",
"Quantum fields are a bit more complicated. If you consider like a vibrating string, there are different levels that it can be vibrating at different levels (like ",
"this",
") and an excitation would be when it goes from the lowest level to a higher one. Except instead of an actual spring it could be like the density of air in a box or whatever.",
"In quantum field theory, the lowest level of a field is a vacuum, and the first excitation is a particle."
] |
[
"A field is a function of space and time, as would be written f(t,x,y,z,) typically, that has a defined value for each point; that value might be zero however.",
"We could define the wind direction and speed as a vector field on the earth. Temperature distribution and elevation serve as good examples of scalar fields."
] |
[
"What are the ways to measure very high level of radiation?"
] |
[
false
] |
What are the ways that very high levels (Chernobyl, 20,000+ ) are measured? Is it a matter of Geiger counter being able to sample at a very high frequency or there is some other type of sensors that are being used for those kind of levels? Edit: I realize how Geiger counters work, so I was wondering if it is simply an issue of electronics to register that high of CPM count. Well that and some insane shielding to be able to work in that kind of field.
|
[
"In some cases, detector size is reduced to ensure fewer overall photon interactions occur in the detector volume. This can also reduce the clearance time for space charge effects, allowing another interaction to be detected. ",
"In other cases, alternative detector types are used (semiconductors) which can be manufactured with very small depletion regions (active detector volume) that limit the total number of interactions or have increased charge carrier collections speeds.",
"Or, the detector (gas filled) is operated in a different bias voltage regime or operated in current mode. Both of these have the effect of either shortening the instrument ‘dead time’ between voltage pulses or ignoring pulse height completely and simply measuring overall current (ion chamber). ",
"I would assume (having never looked into this) that 1980’s era instruments detecting dose rates that high were Ion Chambers. ",
"Modern Semiconductor diode detectors can be purchased “off the shelf” in reactor operating environments to reliably detect dose rates as high as 3 million rad/h (30,000 Sv/h)."
] |
[
"Perfect! Thank you for the reply. Tried to google this for a while to no avail."
] |
[
"You can also increase distance since the radiation generally drop with the square of the distance (for small sources).",
"Could of course be confusing if there are many sources around as in the chernobyl case."
] |
[
"What effect does the lack of gravity in space have on astronauts' digestive systems?"
] |
[
false
] | null |
[
"Gravity doesn't really play much of a role in our digestive system. There are a series of muscles that line every part of our digestive track (from throat to anus) that push the food towards the next stage in the system. You could technically eat, swallow, and digest all your food while hanging upside down.",
"edit- ",
"Peristalsis",
" is the term I'm talking about."
] |
[
" How does digestion change while astronauts are in space?"
] |
[
"What about balance? I used to have nightmares as a kid (I used to get dizzy, and I HATED IT) that I'd be in space and just be stuck in extreme dizziness. My head spins just thinking about it..."
] |
[
"Is eating a venomous creature as deadly as being bit by a venomous creature?"
] |
[
false
] |
It would still have venom sacs filled with the toxin right? Would your digestive system care or just take it like a boss?
|
[
"It's important to note that venom != poison. Venom is dangerous intravenously, and poison is generally absorbed through through tissues. For instance, you are safe to drink most animals' venom, excepting those animals which don't produce their own venom, but rather \"steal\" a poisonous toxin from another creature. An example of this would be certain species within the genus ",
"Rhabdophis",
" of snakes, which are, in fact, poisonous."
] |
[
"Not that simple. You can drink rattle snake venom. It's chemically similar to egg whites. By that same token, injecting yourself with egg whites is a bad idea.",
"I don't know what other venoms are nontoxic when ingested, but I'm sure there are others. ",
"Also you would have to deliberately leave the venom glands in the animal if you're assuming it's dead. So... Why?"
] |
[
"Absolutely not the same thing. A protien based venom can be digested by your digestive system. Most snake venom, for example, contains a mix of peptide and related toxins, and also neurotoxins. I'm not sure if the neurotoxins would still take effect."
] |
[
"How are drugs such as cancer drugs delivered to specific cells within the body?"
] |
[
false
] |
How are drugs or biological cargo delivered artificially throughout the body? How do they target specific cells rather then all cells?
|
[
"This is one of the biggest challenges in drug research. Most drugs ",
" have targeted delivery - the drug is distributed evenly throughout the body (with certain limitations, such as the blood brain barrier preventing certain compounds from crossing) - but they target specific ",
", so that they can only act where those receptors are present. This is a big problem for cancer drugs, which commonly act on rapidly-dividing cells without much discrimination - this is the reason for side effects of chemotherapy.",
"There are a number of current strategies in this area - for example, one can design a ",
"prodrug",
" that gets metabolized into the active ingredient by enzymes that are prevalent at the site of action. Another approach abuses the fact that cancer cells are more \"leaky\" - they have vasculature with bigger pores. So an example would be using a ",
"nanoparticle",
" of sufficient size as a carrier for drugs such that it's too big to diffuse through the capillaries of normal cells, while it's small enough to pass into cancer cells.",
"You can also utilize the fact that certain surface receptors are more prevalent at the site of action, so drug carriers with the ligand will localize in the site of action. An example would be using ",
"folate receptors to target cancer cells",
".",
"It's a very broad field with numerous approaches. Note that in each of these approaches, there still isn't really preferential \"delivery\" - that is, it's not like an UPS driver delivering a package to a single address. Drugs are still distributed throughout the body."
] |
[
"but they target specific receptors, so that they can only act where those receptors are present. ",
"This. One of the current strategies drug companies are investigating is the development of an effective antibody-drug conjugate. ",
"Antibodies are immunoglobulin that are an innate part of the immune system. By design, their function is to recognize and bind to a target of interest. When you get an infection, they go after the foreign antigens and help your body fight off the infection. In such circumstances they sometimes go after your own infected/abnormal cells to your benefit (but sometimes for ill in the case of auto-immune diseases).",
"Antibody-drug conjugates are supposed to achieve more precise targeting of therapeutic agents by linking them to antibodies that will only recognize cancerous cells. This way, rather than flooding the entire body upon administration, the drug ends up being concentrated right where it is needed. Relatively speaking, a lesser dose of what is usually a very toxic compound will have the same anti-cancer potency.",
"Clinical trials were still ongoing when I was working at a major drug company a few years ago. I don't think any has made it onto the market yet. Someone better informed than I am, please correct me."
] |
[
"Actually antibodies are part of the adaptive immune system because they are produced in response to an antigen. I'm not familiar with this technology but how will the drug (which I assume is conjugated to the FC portion of the antibody) actually detach and cross the membrane of the target cell?"
] |
[
"Why certain chemicals are cancerogenic?"
] |
[
false
] |
What is the chemical mechanism of cancerogenesis caused by cancerogenic chemicals and why many of aromatic compounds fall in this class?
|
[
"There is no single mechanism of oncogenesis. Cancer is simply cumulative DNA damage, and anything that causes DNA damage can (with enough time) cause cancer. There are many mechanisms that are involved in DNA replication and repair, and so there are also many possible mechanisms that lead to DNA damage.",
"That said, aromatic organic compounds usually have low boiling points and therefore easily get into your lungs, which are less well protected than your skin. This means that they more easily get into your body and therefore can cause more damage than similar quantities of other compounds."
] |
[
"Carcinogenic is the term you're looking for. And aromatic compounds are carcinogenic because they have a higher likelihood of mutations because that aromatic ring looks similar to some dna molecules. They get incorporated into the dna. Low amounts of mutation can be taken care of by natural mechanisms but the propensity of mutation specifically mutation in molecules necessary to make and keep those natural mechanisms working is a problem."
] |
[
"Not exactly accurate, although I think it's mostly mis-phrasing; they don't get incorporated into the DNA per se and most aromatic compounds are not really that similar to nucleotides either.",
"The aromatic compounds, due to their electron makeup that makes them aromatic (delocalized electrons) are largely flat. Literally, geometrically flat, with the nuclei of the component atoms lying in one plane.",
"This means they can slide in between base pairs in DNA and royally mess up stuff during enzymatic processing of DNA, causing a variety of processes that lead to changes in the sequence and thus, mutations, which can cause various pathways to be disrupted if the gene's product is non-functional.",
"There are also different mechanisms: ",
"Some chemicals may facilitate normally rare switches between the DNA base pairs' forms from the 'classical' ones to alternative ones which pair with different base pairs, causing them to be recognized as a mismatch and replaced by a nucleotide that 'fits' the new pair, again causing a sequence change that might be disruptive.",
"Yet others are chemicals which ARE in fact similar enough to bases (base analogs) to be used instead of the proper ones, but again cause cellular error detection and repair mechanisms to replace the offending pair with something less problematic, again leading to a mutation which may lead to oncogenesis."
] |
[
"Does light exert a gravitational pull?"
] |
[
false
] |
I know light can be affected by gravity (ie curve around black holes and such) but could sufficiently large amounts of light energy exert a gravitational force on things? E=mc 2 and all that?
|
[
"Yes; you might find the idea of the ",
"kugelblitz",
" intriguing. Generally there will be a gravitational attraction between any two things for which the system as a whole possesses ",
"invariant mass",
", and note that Newton's 3rd law (1) implies that if a massive object exerts a force on light, the light in turn must exert a force on the massive object.",
"(1) Technically Newton's 3rd law is a complicated subject matter in general relativity, but let's put that aside. "
] |
[
"\"",
"Wheeler's Geon",
"\" is a proposed particle composed of nothing but light, with high enough energy density to bend its own light into a loop."
] |
[
"From a Newtonian standpoint, there is no universal speed limit and no reason light must travel at C. But even if you assume light always travels at C, that doesn't prevent gravity from bending the direction of light at eg 9.8 m/s",
" (though in GR it is twice the Newtonian value)... "
] |
[
"Possibly stupid question but how do we know some ancient civilisations believed in the afterlife vs writing about it for entertainment like we have for books/movies?"
] |
[
false
] | null |
[
"Because we often have records indicating they did.",
"You can find records or accounts of punishiments being carried out against non-believers in most ancient societies.",
"Not to mention people didn't create complex rituals off of fictional characters until Star Trek conventions were a thing."
] |
[
"didn't create complex rituals off of fictional characters until Star Trek conventions were a thing.",
"Lord of the Rings?"
] |
[
"I'm talking about something resembling religious services. There are many fictional stores in history that weren't treated as truth. The Journey to the West for example."
] |
[
"How did we prove that elementary particles are indivisible and how indisputable is that proof?"
] |
[
false
] | null |
[
"First thing to understand is, that there can be no such proof. Apart from the impossibility of having indisputable proofs in science in general, we can only have more or less usefull transient models, whose limits of applicability are just yet to be found.",
"What we can find out is whether there are additional degrees of freedom at the energy scale we are investigating. In a sense, what we call particles are abstractions we use to make sense of the world, they are in a sense intellectual and somewhat arbitrary constructs used to describe and predict systems, but ultimately you could probably reformulate all of physics with other sets of properties wrapping them up into different \"fundamental\" units and have perfectly good and usefull models.",
"Now what I mean by energy scale dependence is the following:",
"If you look at objects using light in the visible range your resolution is limited to 100s of nanometers and since energy and length are inversly proportional, at that scale you cannot see atoms and the processes that govern them. The world to you at that energy scale consists of cells, organelles, metallic grains, fibers... that sort of thing. Once you use higher energy light or sensors that are much more sensitive to magnetic/electric fields or do certain elastic and inealstic scattering experiments you will become aware of the fact that atoms have electrons and nuclei. It is in fact by doing deep inealstic scattering experiments, shooting stuff at other stuff and analysing how they scatter off of each other, that we confirmed what theoretical physicists had predicted decades prior: protons and neutrons consist of quarks.",
"You could say, the more energy we put in ever smaller spaces, the better our particle \"microscope\" becomes.",
"So what we consider \"fundamental\" is more a reflection of the energy scale we can probe at the moment rather than some fundamental truth about nature. In the String Theoretic framework the fundamental objects are strings, which are many orders of magnitude smaller than quarks, but that means to test if those are \"there\" we need experiments that use way higher energies, in fact given current technology, we would need a particle accelerator the size of the solar system if we wanted to probe that scale."
] |
[
"It’s also important to note, in addition to this excellent response that in quantum physics, shorter wavelengths means more energy and thus there comes a point where the technology we use to interact with the particles is too strong not to alter the particle in fundamental ways. Furthermore we then get into the energy scale where Heisenberg’s work comes into the picture and that there is a physical barrier that forbids exactness in measurements at this level. Of course it’s always plausible that elementary particles aren’t fundamental because every model previous to the standard model was thought to be fundamental at the time, however our current understanding dictates that they ",
" be the fundamental particles of the universe."
] |
[
"Yes, but as ",
"u/Badger_Wadger_420",
" pointed out, the Heisenberg uncertainity makes the whole picture much more complicated. In high energy regimes you have production of particles from the vacuum that make it hard to have a \"clean\" view of what is going on, the LHC needs to filter out a lot of irrelevant soup of particles that are created from the collision energy of the protons. On the other hand according to current understanding there are limits of how much energy you can put in a volume of space, i.e. how high we can make energy density, before the region collapses to a black hole. Obviously in that regime, about the Planck energy, observations become quite hard, black holes being very shy about their nature and all that. While almost certainly this is not the end of the road theoretically it may present a practical limit to what we can reasonably probe and hence call fundamental building blocks. We will need a theory of quantum gravity to make predictions about the physics beyond that and new ways to do experiments will have to be designed aswell."
] |
[
"why is it that an impact to the testes results in a delayed pain?"
] |
[
false
] | null |
[
"I would suggest that the interpretation of the experience as painful is a mental process and takes time. If the experience is a major trauma, shock can delay the onset of pain for a good deal more than a few seconds.",
"Or, because all your brain power is in denail - 'OH SHIT THAT DID NOT JUST HAPPEN!', before it moves on to actually checking to see if it did, indeed, happen. Then the pain registers."
] |
[
"I've had that happen but with my finger. It got shut in a door and the door locked. I started to walk away but I was caught on something and only then I realized what the hell just happened."
] |
[
"Probably has to do with the fact a lot of the nerves involved in a man's junk actually lie within the upper abdomen. Like a shark's testes are somewhat located near the middle lower part of its ribcage. For some reason evolution decided to move our junk down and outside of our body so the nerves are still in our abdomen and elongated more therefore possibly causing that brief delay. "
] |
[
"How sanitary are public pools, really?"
] |
[
false
] |
Is chlorine effective enough to keep them clean?
|
[
"Depends on your definition of clean. Is there piss in there ? Yes. Peoples skin ? Yes. Would you get sick drinking the water ? Most likely not but it's not recommended."
] |
[
"pH is 0",
"I sure hope not."
] |
[
"Chlorine in pools is not effective at eliminating ",
" species. These little Apicomplexan protozoans cause diarrhea, among other unpleasant symptoms, and can be lethal in immunocompromised individuals. A lot of attention was drawn to Cryptosporidiosis (infection with ",
" species) when the AIDS pandemic broke in the United States, as immunocompromised adults are especially susceptible to deadly infections.",
"So, if you're not immunocompromised, I wouldn't worry about it, but just know that chlorine doesn't do an excellent job of killing them. And, since they're fecal-borne, if someone with an infection takes a dip in the pool, he/she could be introducing up to 1,000,000 infective oocysts per GRAM of feces clinging to his/her nasty ass. "
] |
[
"Gambler's fallacy"
] |
[
false
] |
[deleted]
|
[
"Coin flips are independent events. A run of heads will not change the probability of subsequent flips.",
"The somewhat-intuitive ",
" line of reasoning goes something like this: \"I just got 10 heads in a row. The probability of 11 heads in a row is astronomically small, so the next coin toss is more likely to be tails.\"",
"The ",
" line of reasoning is: \"I just got 10 heads in a row. The probability of 11 heads in a row is exactly the same as the probability of getting 10 heads followed by tails, and is indeed equal to the probability of ",
", so the next toss still has a 50/50 chance of being either heads or tails.\""
] |
[
"Don't know why you're getting downvoted.",
"AnteChronos's comment is completely accurate, if you don't account for any of the variables that do exist, however minute they are.",
"There are so many variables that actually affect the outcome of a coin toss. The odds are never ",
" 50/50."
] |
[
"You're correct. The probabilities are independent for each new trial. ",
"Here's an analogy that might help.",
"You're going to flip a coin four times. There are 16 possible outcomes, each with equal probabilities. If you wrote each possible outcome on a piece of paper, you'd only have one piece of paper that said TTTT, so a 1/16 probability of four tails in a row. There's a 15/16 probably of not having four tails in a row.",
"If you flip the coin and get tails, you can immediately throw away the papers that had you getting heads on the first toss. That's 8 paperss gone, 8 remaining. 1/8 probability of TTTT, 7/8 probability of not having four tails in a row,",
"If you do it again, and get tails again, you're down to 4 papers, because you throw away the 4 that had tails then heads. You're left with a 1/4 probability of four tails, 3/4 probability of not 4 tails.",
"If you do it a third time, and get tails, you can throw away the TTHx papers, leaving you with only two papers - TTTH and TTTT. 50% probability of getting heads, 50% of tails. Completely independent from the first trials.",
"You only had a two in sixteen chance of getting three tails in a row in the first place, so even though you only had a one in sixteen chance of getting four tails in a row, the final coin toss is still a 50/50 probability."
] |
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