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[
"Why is it whenever I make a root beer float, giant soap like bubbles appear?"
] |
[
false
] |
[deleted]
|
[
"Great question! Have you ever seen what happens when mentos is dropped into a coke? Its the same principle (but usually less messy)! Little air bubbles on the surface (of the ice cream/mentos) act as nucleation sites where CO2 that's dissolved in your root beer rapidly congregate. Water-soluble ingredients in the ice cream change the surface tension of the root beer, trapping formed bubbles in ways it otherwise couldn't."
] |
[
"The reason that you get big, soapy-looking bubbles is because of the thickening ingredients that are used in most ice cream. Typically, you'll find vegetable gums and other thickeners listed among the ingredients. Traditional ice cream formulas contain milk, cream, sugar, and flavorings, and they make less foam."
] |
[
"This being ",
"/r/askscience",
", I did do a quick google search for academic papers on foam formation in ice-cream floats, but surprisingly, I came up empty. Vegetable gums are commonly used for stabilizing foam in foods, though.",
"If you want to go more in-depth on this subject, try a search for \"food foam\" and carrageenan, guar gum, gum arabic, or xanthan gum - lots of great academic papers on foam stability vs concentration, pH, and other factors."
] |
[
"Could an animal evolve to live in space?"
] |
[
false
] |
Besides humans in spacesuits. Could an animal evolve to travel through space, like the Space Whale in Futurama?
|
[
"You may be interested in the ",
"Tardigrade",
":",
"In September 2007, tardigrades were taken into low Earth orbit on the FOTON-M3 mission and for 10 days were exposed to the vacuum of space. After they were returned to Earth, it was discovered that many of them survived and laid eggs that hatched normally.[9][10]",
"My knowledge does not extend much farther beyond the fact that that actually happened. Could an organism evolve to actually live naturally in space? Seems unlikely, but it's pretty much impossible to prove that something can't be done. The major obstacle seems to be that there would be nothing for them to eat. ",
" "
] |
[
"I thought photosynthesis involved using light to break down the CO2, in space it seems that the lack of anything to breakdown would mean photosynthesis would be unnecessary. "
] |
[
"Yeah. You are absolutely right. Complete brain-fart there on my part...."
] |
[
"Does the immune system attack bacteriophages even though they don't pose a threat to human cells?"
] |
[
false
] | null |
[
"It's both. They exist in a symbiosis state with our immune system and mostly reside in the GI tract as microbiome. ",
"However they can leave the GI tract by transcytosis and enter the blood and other organs in the body. But since they can't infect human cells or eukaryotic cells, the immune system do not actively destroy them. They do possess some anti inflammatory properties for reasons that are still unknown. ",
"They can get phagocytosied sometimes by phagocytes as a way to clear phage particles and when there is bacteria infection, they infect the bacteria. This helps the immune system recognise infection sooner. In that case when the immune system attacks the bacteria, they get neutralised as well. ",
"Here are some readings : ",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6356784/",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6956183/"
] |
[
"They do get phagocytosied as I mentioned in my previous reply. Here's a quote from the first paper: ",
"Phagocytosis by immune cells within the liver and spleen seem to be the major process of bacteriophage neutralization within the human body [26,78,80,104,106,107,108]. One should note that phagocytosis allows the removal of phage particles, even when no specific response to bacteriophages has been ",
"It's the reason why I mentioned the answers to your question is both. The phagocytes do clear them of debris but it's not like the immune system seek them out to with the purpose to destroy them. The immune system doesn't recognise phages as foreign objects or see them as dangerous. So unlike an actual bacterial or viral infection, it doesn't recruit the entire immune system."
] |
[
"So the immune system don't bother touching them? I thought the immune system clears blood of debris, such as cell debris, bacteria and whatever else?"
] |
[
"Why can't we see the Andromeda Galaxy?"
] |
[
false
] |
[deleted]
|
[
"Lucky you, here the other day I think I saw the sun"
] |
[
"In a perfectly clear sky with no light pollution you can clearly see the core of Andromeda as a fuzzy smudge. The visible core is smaller than the moon. The outer part of the galaxy is too faint for the naked eye, and you will only be able to capture the full galaxy with a decent telescope and a long exposure."
] |
[
"Padua. It's not really the pollution, it's the atrocious weather."
] |
[
"How harmful is hydraulic fracturing fluid?"
] |
[
false
] |
[deleted]
|
[
"Something that is important to realize is that toxicity depends on concentration so lets say that 5000 gallons of chemicals were dumped 20 miles up stream so that means it will be diluted in millions of gallons of water that means that at worst you could see a few parts per million ... resulting in those chemicals being well below the threshold of being unsafe.",
"Half of the chemicals on the list are non-toxic the other half I believe would be safe at concentrations that could reach you ... if not people within a much closer range of as little as half a mile.",
"Contact your utility or the EPA they both do testing to ensure your safety."
] |
[
"The videos of people being able to light their water on fire isn't from the hydrofrac fluid itself, it's from gas escaping from it's reservoir due to the fractures that are created from hydrofracing. ",
"It can be more dangerous in drier areas where the aquifer is smaller and they tend to be more isolated, so the infiltration of hydrofrac fluid into these smaller reservoirs can be quite harmful. "
] |
[
"Thank you, this is exactly the answer I was expecting. People around here are absolutely freaking out over all of this. There are videos online about people being able to light their water on fire, but nothing has come out yet from people near this incident."
] |
[
"Can one neuron within the human brain have several types of neurotransmitters that binds to it? For instance, can a neuron that usually allows binding by GABA neurotransmitters also allow binding from other types of neurotransmitters, such as NDMA, DA, 5-HT, etc?"
] |
[
false
] | null |
[
"Yes. Neurons can have, for instance, both excitatory and inhibitory inputs, mostly mediated through glutamate and GABA"
] |
[
"There are a large number of examples. In the cerebral cortex, all of them have GABA and glutamate receptors, and generally multiple different types of each. "
] |
[
"Exactly. I'm not sure if your example exists (may or may not, I don't know), but heres one that is fairly common: Cholinergic fibers and adrenergic fibers typically have heteroreceptors for each other in that cholinergic fibers often have presynaptic alpha2-receptors, and adrenergic fibers often have muscarinic receptors on them. ",
"As far as what they are, ",
"receptors are receptors that bind the same chemical that is released from that neuron (so a neuron releases acetylcholine may have a receptor for acetylcholine on the outside of it). ",
"receptors bind something different than what is released from that nerve terminal (as fibers that release ACh may have alpha2-receptors on them that bind norepinephrine). "
] |
[
"What was the diet of early humans? How did they know what foods were safe to eat?"
] |
[
false
] |
What did they survive off of on a daily basis and beyond that how did they know what plants were safe to eat?
|
[
"Australian Aborigines would take the food and hold it against their body for certain amount of time. If there was no negative reaction they would move down the list.",
"Source: Malcolm Douglas"
] |
[
"And they would have an ",
" amount of knowledge of safe edible plants culturally passed on from a time since even before they were humans. Most primates actually ",
" their children what is food and what is not.",
"Coming in contact with completely new potential foodstuff would have been a very rare occasion. Primitive humans travelled slowly and it often took them ages to settle into a completely new biome, more than enough time to try everything they happened upon."
] |
[
"It minimises the risk though. Eventually someone would have to eat it. If they die then they would make a note that that ones not so good for eating. Trial and error, but the knowledge gets passed on until they had enough options to keep fed and taking stupid risks on unknown plants would not be necissary unless they were starving and could not find any safe plants.",
"Even before human testing, watching to see if other animals birds etc. eats the plant would also be a good tip."
] |
[
"Redditors: what are some things you wish they would have mentioned in health class that they didn't?"
] |
[
false
] | null |
[
"I really wish they had mentioned more in sex education than vanilla. It would have helped a bunch to know that my kinks were fairly normal. "
] |
[
"If you can reformulate your question to one of a scientific nature it may be allowed. Personally I think it should be banned as a random survey with no aspect of the scientific method."
] |
[
"Sometimes the vagina can be too tight for penetration"
] |
[
"Does every living thing need to have DNA?"
] |
[
false
] |
With the exception of RNA based "organisms" (like viruses, since they're not really considered alive). Does everything need to have DNA to be alive? Basically if we went to Europa and discovered life, would it be possible for the life that evolved on that planet to be DNA-less? Do we have DNA-less living organisms here on earth?
|
[
"1) It could well be that extraterrestrial life isn't DNA based. But for evolution to happen you need something that encodes information and for complex life you need evolution. So you would need some sort of information storing molecule. Scientist have created artificial DNA alternatives in the lab, so we know that other molecules can accomplish this. There are also ideas about life forms that are not carbon but silicon-based, because silicon also can form quite complex molecules with similar patterns as carbon. For those people have made up systems in which the information isn't stored in the sequence of building blocks but in the spatial pattern, maybe even forming something like human-made computer chips where electrical impulses are generated. You can make up all sorts of systems that should work based on what we know about chemistry, but unless we actually find other life we obviously don't know. ",
"2) All known life forms on earth are based on DNA (plus RNA viruses)"
] |
[
"Based on the definitions of life, all currently known living things have DNA (or RNA that gets converted to DNA at some point of it's life cycle).",
"Now, prions are infectious proteins that can infect, propagate and spread without DNA by converting host proteins into infectious proteins. But, I would not define them as living. And, host DNA is needed to encode the proteins in the first place.",
"And, we don't know about alien life we have yet to discover."
] |
[
"Some viruses. It is still debatable if they count as alive, but I side with the alive crowd.",
"They travel around as encapsulated RNA and infect a cell. Once inside, they are copied as DNA and then encode RNA versions of themselves."
] |
[
"Have flying insects evolved ways to combat spider webs?"
] |
[
false
] |
I noticed a duel of sorts between a moth and a spider just now where I was certain the moth was doomed as it flew into the section where a spider had firmly set up its web, but as it flapped its wings so quickly it tore apart the web, and even sent the spider fleeing. I don't know if this in itself was an adaption to webs, in fact I'd say from an uneducated standpoint that I doubt it... but it did make wonder if there were other insects which had developed natural tools against spider webs.
|
[
"Yes! There are wasps which specialise in preying on spiders. Some even go so far as to kill the spider, then use their web to line their nests. I tried to find something interesting on the ",
" genus, but they're such a bunch of trouble to ID that there's not much written."
] |
[
"According to the ",
"wikipedia article!",
" about them, the sting is ",
"And that's what a human experiences."
] |
[
"Tarantula Hawk. Their sting is so painful it paralyzes tarantulas so they can lay their eggs. Also when they hatch they avoid eating the vital organs so the spider stays alive longer. "
] |
[
"Can children learn musical instruments like languages?"
] |
[
false
] |
[deleted]
|
[
"Language is a specialised function of the brain with dedicated areas. These have probably derived from evolutionary processes because language serves a selective function. In other words, we are predisposed to learn languages, especially during the first years of life.",
"Playing music is different, as we probably have not evolved to do that, albeit it builds on some basic evolved functions like rhythm, auditory discrimination and so on. It is much more of an acquired skill like learning to write or play chess.",
"Most things in life are easier to learn when you're young as the brain is more plastic. I don't think there's anything special about playing music."
] |
[
"Music is practice. The more you practice, the more proficient you are. Thus, anyone can jam a violin…with enough practice. ",
"Some people will have a knack, but those people still need to practice. The person who practices daily for a year, will be better than the person with a knack."
] |
[
"Like many areas its a combination of both natural ability and practice/effort. Some people are very talented but don't put in effort, others are willing to try hard but lack abilities (such as rhythm or pitch awareness). The outstanding ones are those willing to put in the effort who also have at least some raw talent on which to build."
] |
[
"If caffeine antagonizes all adenosine receptors, how can consumption increase activity (A2B receptor)?"
] |
[
false
] |
First of, I am a biomedical student with a great interest in neuroscience and my knowledge is most likely incomplete/imperfect so please correct any mistakes I make: There are 4 adenosine receptors, 3 of which are significantly present in the brain; A1, A2A and A2B. Caffeine antagonizes all of these receptors but only A1 lowers cAMP levels and induce sleep (simply put). A2A decreases dopaminergic activity throughout the CNS, as seen in stimulants higher dopaminergic activity results in increased alertness/focus, but A2A also increases cAMP, so caffeine would lower cAMP levels. Caffeine itself promotes PKA/PKG activty through its phosphodiesterase inhibitor activity, which seems to work against the previously mentioned A2A cAMP interaction. While I can see how the previous system can result in better performance/increased activty, I fail to see how the A2B/caffeine interaction facilitates this: A2B raises cAMP levels, may help with netrin-1 prodution and also raises intracellular calcium levels, antagonizing these systems would decrease cognitive function in most neurons. Is this all just all a matter of which system is stronger or am I seriously missing something here. Many thanks!
|
[
"The most likely answer is what you're suspecting,",
"Is this all just all a matter of which system is stronger or am I seriously missing something here.",
"If you look more closely at the pharmacokinetics of caffeine receptor stimulation/molecular degradation you will most likely find a bottleneck that keeps the stimulant effects active while the rest of your system tries to keep up."
] |
[
"You also need to consider the relative prevalence of each receptor and the strength of each one's effects; there are common and uncommon receptors, and some give stronger responses than others. It would be very, very odd if the final tally somehow ended up with the effects balancing out perfectly.",
"Once you look at that, there's the problem you thought of relating to how the different opposed systems operate: not everything happens instantly, and it's entirely possible for things that appear one way to have different results due to the way the processes occur.",
"P.S. This is true for every chemical you'd be researching that affects the brain, whether it's caffeine or some new antidepressant."
] |
[
"Agreed. I know this isn't very closely related to your question OP, but here's a chart ",
"showing how different Xanthines",
" with VERY similar structures have completely differing effects on biological activity. "
] |
[
"When did the most recent common ancestor of coronaviruses and influenza viruses exist?"
] |
[
false
] |
In some quarters comparisons between covid and the flu have been taken so far as to claim that covid a flu. Such claims seem patently incorrect, as the viruses belong to different taxa - but just how wrong is it? Would it be comparable to claiming that cats are dogs, or more akin to equating cats and nematodes? I'm assuming here that all viruses have a shared ancestry, as it seems to be the case for all organisms conventionally considered alive (bacteria, archaea, eukaryotes). Do we know for sure that this is the case for viruses, or is it possible that they appeared more than once?
|
[
"Coronaviruses and influenza viruses are both members of the ",
"Riboviria",
":",
"RNA viruses that use cognate RNA-dependent RNA polymerases (RdRps) for replication. These viruses are highly diverse genetically, infect a wide range of prokaryotic and eukaryotic hosts, and comprise three classes of Baltimore classification [1]. The available data support, or are compatible with, the conclusion that all these viruses form a monophyletic lineage based on the RdRp palm domains",
"If this is a monophyletic lineage (spelled out in more detail in ",
"Structural Analysis of Monomeric RNA-Dependent Polymerases: Evolutionary and Therapeutic Implications",
") then coronaviruses and influenza viruses do have a common ancestor. (Note that it’s likely that not all viruses are monophyletic, so there may not be any common ancestor for viruses as a group.) However, since coronaviruses are positive-sense RNA and influenza viruses are negative-sense, they must have diverged very early on within that large subgroup. ",
"Working out divergence times for viruses is notoriously hard because of their rapid generation time and (especially with RNA viruses) their rapid mutation rate. Riboviria almost certainly are older than the bacterial/archaea split, and it remains possible that the RNA viruses are older than bacteria. At any rate, hundreds of millions of years at the least, to many billions."
] |
[
"Some viruses probably started as mobile elements from organisms’ genomes, that acquired ways to spread to different organisms. Other viruses probably started as full organisms that gradually become increasingly parasitic, and lost non-essential elements. (Possibly some arose via abiogenesis as free-living mRNA elements.)"
] |
[
"Complicated inferences from the distribution of organisms the various groups of viruses infect."
] |
[
"Why are some viruses deadly?"
] |
[
false
] |
Doesn't it make more sense, evolutionary-wise, for a virus to not kill its host? Wouldn't it be able to spread much better over a longer period of time?
|
[
"Indeed, ebola can cause death within 10 days which makes it a bad propagator of itself (especially in our more sanitary civilized conditions, read ",
" it is a good book); but ebola isn't contagious in the air like a common cold, and needs to kill you to try to spread. It is a trade off, but since said viruses exist, there must be some niche for them"
] |
[
"Viruses interact with the cellular machinery of your body. This is why a virus that is deadly to humans may not affect other animals and vice versa. Really deadly viruses are often viruses that have recently jumped species, or new strains combining a virus that infects one species and a virus that infects another. If these strains kill too quickly, they will often die out quickly, but all of these viruses are likely to be close relatives/ recent mutants of a less deadly virus that is common in a population because it is not very harmful."
] |
[
"You're absolutely right. A virus that kills its host quickly is a crappy virus. If you look at all the most successful viruses, none of them are all that lethal - the common cold, the flu, herpes, chickenpox, HIV, etc. They all have the common trait of being severe enough to cause symptoms, but not dangerous enough in the short term to inhibit their spread.",
"In fact, some of the most successful viruses are those that do nothing at all. Your genome is filled with the remnants of ancient viruses that decided the whole infection thing was overrated, they'll just incorporate themselves into you and let your polymerases do all the hard work. Some of these are transposons, moving around in your genome, occasionally disrupting important genes, but most often doing nothing. Others are just junk DNA that doesn't even bother doing anything at all.",
"Looking at all the super-deadly viruses - Ebola, Hantavirus, smallpox. All of them spell certain death for their host, and none of them are particularly widespread."
] |
[
"Do mosquitoes do anything positive for nature?"
] |
[
false
] |
Because i think they should be eradicated, But i know they probably do something good
|
[
"Well, like with anything, they have a place in their ecosystem. There are things that eat them, and things that compete with them for resources etc, so removing all the mosquitoes could have unpredictable effects on other species in the area.",
" my understanding is that there are lots of species of mosquito in the relevant ecosystems, and only some of those species bite humans. So if we just eliminated those specific species, some scientists think the other species would increase to make up the difference, because of the reduced competition, and the things that eat mosquitoes will just eat them instead, and no real harm would happen.",
"There are actually some ",
"serious attempts to do that getting going right now",
"."
] |
[
"Here you are presenting a ",
": That organisms have a role in nature. Living things aren't here for something, they just are here because the conditions on our environment have led to the development of such creatures.",
"You don't need a role in nature to be part of it. Let me ask you back: ",
" As you can see, this question doesn't make sense; humans don't necessarily have to do something positive (or negative) for nature to be part of it. Should humans be eradicated because of this? You can't argue that because we are humans we shouldn't, if you are arguing that non-positive or negative organisms should be eradicated just because they aren't doing something positive for humans, well, humans should also be eradicated.",
"This is the problem of the ",
" and ",
"."
] |
[
"Thanks"
] |
[
"Why does the sun shine in a \"star\" shape?"
] |
[
false
] |
is what Im talking about. Is it an opticak effect. Is it caused by the lens, the atmosphere, the human eye, the star itself. What goes on here? Thanks smart people.
|
[
"This is caused by the movable aperture blades in a camera lens. ",
"http://www.cameratechnica.com/2011/02/24/how-to-create-and-avoid-starburst-highlights/"
] |
[
"thank you. so do video cameras work the same way?"
] |
[
"Most video cameras use the same kind of 'bladed' set-up to restrict aperture, so yes, it creates the same star shapes in video as in photographs."
] |
[
"How can medication cause side effects that counter effect each other?"
] |
[
false
] |
For example, side effects such as tiredness and fatigue are caused by a medication, but also insomnia or even increased energy. "How is it that medication causes side effects that are opposites of each other?" may be a more appropriate question.
|
[
"When determining side effects for drugs, pharmaceutical companies do a study in which half the people get the drug and half the people get a placebo. If there's a significant difference in the different side effects reported in each group, the company must list that as a side effect, either as a requirement to the FDA or to consumers to avoid lawsuits. Maybe one person suffered insomnia, maybe one person was particularly restless, and these effects may or may not have been caused by the drug, but the company lists them regardless. ",
"Here's a set of industry standards that might be helpful."
] |
[
"This makes sense as to why they'd list them as side effects. Thanks. Further to this though, I personally have experienced the side effects I listed above, i.e. tiredness & fatigue but unable to sleep at the same time, or shortly after attempting to sleep. Is there an explanation to this? Maybe a biological one? "
] |
[
"I'm not qualified enough to answer that question. Perhaps someone else can jump in. "
] |
[
"Is visible light damaging to your eyes and vision, or just UV?"
] |
[
false
] |
I got some high-powered LED's which emit light within the visible spectrum, and I am wondering, can I do damage with these, or is it just light in the UV range which is actually dangerous?
|
[
"Any light can damage your eyes. But UV has 2 special problems. First, it's higher energy than visible light, and the kind of energy level that organic compounds just love to absorb and subsequently disintegrate or denaturize. Of course, the compounds in your eyes love to absorb visible light as well, that's somewhat important for the whole seeing thing, but for this there are mechanisms in place to get the energy out of the system without damaging anything, to reverse all changes that resulted from the absorption of photons. ",
"The second problem with UV is, we can't see it. If a flash of yellow light comes your way, you might blink and your iris will contract to limit the amount of light that can enter your eye. That doesn't happen with UV, it can just enter your eye unimpeded. You might also just consciously look away from a blinding visible light since you perceive it as uncomfortable, that doesn't happen with UV.",
"And there is a third, somewhat paradoxical thing that is relevant for all eye damage, e.g. visible laser light as well. Your brain is amazingly powerful when it comes to filling in missing information. That means if you suffer a bit of eye damage, you burn a little blind spot into your retina, you won't realize. Your brain will just do a bit more work in the image processing department and you won't even notice a thing. Only once you have accumulated so much eye damage that your brain can no longer fix your vision \"software-side\", you'll notice, and then it's far too late. That's why you should take warnings seriously about not looking directly into the sun or a laser. You might do it and find that you notice no difference. You might think \"I've looked into the sun/a laser 20 times and never did anything happen, guess it's safe or I'm immune\", just to find out at your 21st try that you've ruined your vision forever."
] |
[
"Yes, it can. There are 2 aspects of light that matter for damaging something:",
"see EM spectrum",
"UV light has a short wavelength, and so it has higher energy photons than visible light. UV photons have enough energy to break bonds in DNA, which is why UV can damage tissue and cause cancer. Meanwhile visible light (as well as IR, microwave, radio etc.) can't break those bonds. If you increase the intensity/brightness, i.e. number of photons visible light will still not break those bonds directly because each photon lacks the energy required to do so. However higher intensities of visible light will begin to heat or even burn whatever is absorbing the light so it can still cause damage. Interestingly this explanation, or at least one very similar to it, was first made by Albert Einstein and he eventually won the nobel prize in physics for it (",
"photoelectric effect",
").",
"TLDR: Any type of light can burn/damage your eyes if it's intensity is high enough, UV light (and higher) can also cause additional damage to the DNA directly (making it particularly bad). Don't look into bright lights of any kind if you can help it."
] |
[
"Yes! And even worse, your pupils won’t contract as much either. And this is a bad thing even if you don’t stare into the sun; UV reflected from the environment (esp. water and snow) and scattered by the atmosphere is enough to cause harm over long term in sunny climates. Cheap sunglasses can be actively harmful to your vision!"
] |
[
"What is currently the most dangerous medical threat to humanity?"
] |
[
false
] |
After reading about prion diseases for a while I want to curl up in he fetal position and cry. It's hard to seperate mass media hysteria from scientific knowledge - is there currently a disease or condition that could threaten all of humanity?
|
[
"You must've been reading my comments in that beer thread!",
"Prion diseases are not a dangerous medical threat. So don't worry about them.",
"There are many emerging infectious diseases that scientists worry about. The worst diseases tend to be those that are only recently infectious in humans. Keep in mind, infectious diseases don't really want to kill their host, because they want to stay alive and spread longer. That's why Ebola (a recent jump to humans) is very deadly, but measles (which has been around in humans for a long time) is less-so.",
"Current serious threats in my opinion:",
"This all brings me to my final point..."
] |
[
"Dengue hemorrhagic fever (DHF) is considered to be one of the most dangerous emerging diseases. While it hasn't reached pandemic levels, it certainly has the potential to do so in the future. There are several reasons for this:",
"Dengue is mainly vectored by two different types of mosquitoes, Aedes albopictus and Aedes polynesiensis. Given different behavioral and ecological factors, it could be difficult to control both at the same time.",
"The virus can be transmitted not only horizontally (i.e. from mosquitoes to humans), but also vertically, meaning either transovarially or sexually.",
"Four different strains of the virus exist, some being more pathogenic than others",
"Exposure to one strain followed by exposure of a different strain within five years can lead to severe cases of dengue shock syndrome",
"Increased international travel can spread the virus very quickly. ",
"Poor mosquito management programs in lesser developed areas of the world almost ensure dengue's continued presence.",
"Currently, there is no vaccine or cure"
] |
[
"What do you think about the potential of ",
"Totally Drug Resistant Tuberculosis (TDR-TB)",
"?"
] |
[
"Could loud sounds that cannot be heard by the human ear, from being too low or two high, still cause damage to one's ears?"
] |
[
false
] | null |
[
"Certainly. What we hear as sound is actually vibration caused by kinetic energy. Our hearing range is from 20-20,000 hz but just because we can't hear it doesn't mean it's not there. High energy soundwaves can do more than destroy a person's ear drums, it can kill you.",
"",
"https://www.extremetech.com/extreme/175996-can-a-loud-enough-sound-kill-you",
"",
"For example: 200 decibels of sound pressure at a frequency of 30,000 hertz would be inaudible to humans but highly lethal.",
"",
"See also sonic weapons:",
"",
"https://en.wikipedia.org/wiki/Sonic_weapon"
] |
[
"I'm not sure about sounds above our hearing range but there's been a bit of research into the effects of infrasound (sounds below our hearing range) and prolonged exposure may cause some level of hearing loss but that's not confirmed. There have been some studies showing that infrasound can cause negative emotions in people but again it needs more replication I think."
] |
[
"yes. Sound has two properties of interest in terms of causing damage to the human ear. The first is frequency which determines the pitch of the sound. Humans can hear sounds with a frequency of between 20hz and 20000hz. loud noises in these areas damage the hair cells inside the cone shaped channel in your inner ear called the cochlea. The other property, which is much more impactful is intensity. Intensity is measured in decibels where 0 decibels is the threshold of human hearing, and upwards of 90 decibels it can cause pain. Intensity is unrelated to frequency so you can have a very loud sound that you cannot hear, but would likely be able to feel pressure on you. prolonged exposure to high decibel ultrasound (or infrasound) can lead to a thickening of the tympanic membrane (eardrum) making your ears less sensitive to sound in the future. Actue exposure to high decibel sounds can rupture your eardrum, which causes intense pain and temporary hearing loss."
] |
[
"Has the Copernican Principle been debunked?"
] |
[
false
] |
[deleted]
|
[
"Well, none of those links are working for me, but the cosmological principle has certainly not been debunked (or if it has, it's happened in the last few minutes which is why neither I nor anybody else in my department has heard of it).",
"It's much, much, much more likely that there is a problem with the data from WMAP, or that there's a mere coincidence, than that the Solar System occupies a special place in the universe. This is like that hullabaloo about the neutrinos from CERN that appeared to go faster than light-- remember that? The experiment seemed to indicate that neutrinos were breaking the cosmic speed limit, and the people running the experiment basically asked the physics community to help find their error. The press, of course, went nuts with speculation about ",
" Some months later, it was discovered that there was a faulty cable connection somewhere in the experiment which had thrown off the results. ",
"The last five hundred years of astronomy have consisted of discovery after discovery which indicate that there is absolutely nothing, apart from possibly the presence of life, which makes Earth or the Solar System exceptional. The Sun is a fairly ordinary G-type star, we're finding that planets are extremely common, the Milky Way is a fairly normal, somewhat large barred spiral galaxy, and the Local Group also appears quite ordinary. ",
"I would also like to mention that the cosmologists and I are aware of the illusion of Special Relativity and Universal Inflation. This anomaly is independent of this, as it involves cosmic patterns, not distances.",
"This part is pure and unadulterated bullshit. Special relativity is not an illusion, and neither is inflation or expansion. Whoever's peddling this tripe doesn't understand what they're talking about.",
": ",
"Hansen et al 2012",
" (pdf) argue that Kuiper Belt foregrounds can adequately explain the correlation."
] |
[
"Why would it be shocking if the solar system really ",
" aligned with these background patterns? It has a 1% chance of being within 0.9 degrees of these features. Not cosmically small by any means."
] |
[
"I assumed he was talking about the way inflation makes everything look like its moving away from us.",
"Again, I'm going to assume that by \"cosmic inflation\" you mean expansion, which not only \"makes everything look like it's moving away from us\", it does in fact "
] |
[
"Why is the graph of Water Density vs. Temperature in Celsius a parabola?"
] |
[
false
] |
In my physics class our teacher was talking about finding the equation for water density in relation to degrees Celsius. I looked it up and found the graph, but contrary to what he initially thought, the graph was exponential rather than linear. Why is it that the relationship between the two isn't a linear function?
|
[
"So generally speaking, the graph is parabolic with a local maxima at ~4 C. This is because there are two opposing mechanisms changing the density as we increase temperature.",
"The first is fairly intuitive, the thermal expansion of water with increasing temperature. As we add greater thermal energy to the system, the intermolecular interactions will have a larger mean separation distance between the molecules. So as we heat liquid water, it expands.",
"The other mechanism is not so intuitive. Solid water, ice, is a relatively highly ordered structure, and the greater the order of the structure, the less dense it becomes. This is in contrast to regular liquids, but water expands when it freezes, as the ordered structure can fit fewer molecules per unit volume than the \"chaotic\" liquid. When we heat this structure, say from -10C to -5C, this structure becomes more disordered, allowing for small breakdowns in the lattice which allow tighter packing of molecules, and hence density increases. :) "
] |
[
"The reason why the density of water decreases below 4°C (even if not frozen yet) is that the H2O molecules are asymmetric polar molecules, meaning that the oxygen atom is dragging the electrons of the two hydrogen atoms slightly closer to the oxygen atom. This leaves a \"side\" of the individual molecules slightly positively and the other \"side\" slightly negatively charged. If two of these molecules get close to another with sufficiently low kinetic energy (=temperature) these molecules will form bonds: hydrogen-bonds. (check ",
"http://www1.lsbu.ac.uk/water/images/watere_dimer_2.gif",
" - but imagine it with a lot of molecules)",
"This brings some sort of structure into the liquid. The bonds are stable at a certain distance, which is greater than the average distance of molecules for substances for which hydrogen-bonds do not exist - hence the decreasing density below 4°C. ",
"You touched a truly remarkable part of nature here - this \"anomalous\" behaviour of water keeps the bottom of lakes at 4°C in winter (meaning the lakes don't freeze completely and can support life), lets icebergs swim as well as your beer bottles explode if you keep it in the freezer for too long :-) ",
"There's only a few substances that act in this way, and water is by far the most important for us."
] |
[
"What are the other substances with same behaviour?"
] |
[
"Could you make a star go supernova by throwing planets at it?"
] |
[
false
] | null |
[
"The impact causes the star to go supernova, destroying the entire solar system. Ignoring how you would actually accelerate planets to that speed, is the outcome realistic? would it actually send a star into supernova? ",
"No.",
"If anything, what you're describing would produce two high energy jets of particles streaming from the poles. ",
"The real source of energy of a supernova is gravitational collapse, liberated when the star is actually making the neutron star in the core. There's no reason to think that would happen by shooting some planet-bullets at a star, so no supernova.",
"The ratio of Jupiter's mass to Mars is about 3000. That's a really really enormous relativistic gamma. There should be sufficient momentum for much of this matter to plow right through the star and burst out the other side, like a bullet through a watermelon. And even if it didn't, adding a bunch of particles going at 0.999...99 c just means you're adding heat. It'll serve to make the star swell until it can radiate the extra heat before coming back into hydrostatic equilibrium. "
] |
[
"You shouldn't think of any of this like conventional collisions. You should think of it like particle accelerator collisions. There is so much energy and momentum that they're not just going to hit each other and stop, they're going to produce cascades of particles which are also traveling at a significant fraction of the speed of light. They won't stop and 'release their energy.' All of that energy and momentum will just stream right through the particles going the other direction, causing secondary collisions until they're out of the star. ",
"If they could deposit all their energy in the star, it seems reasonable that the star would become gravitationally unbound, but that's does not a supernova make. Depositing energy in the star will make it puff up, like I said, it becomes more diffuse and that much harder to add more energy to it as the density goes down. "
] |
[
"There should be sufficient momentum for much of this matter to plow right through the star and burst out the other side, like a bullet through a watermelon. ",
"I think the idea is that since these two \"planet-bullets\" are hitting polar opposite ends of the star at the exact same time, they will collide in the middle and release their energy there. ",
"And even if it didn't, adding a bunch of particles going at 0.999...99 c just means you're adding heat. It'll serve to make the star swell until it can radiate the extra heat before coming back into hydrostatic equilibrium.",
"How much energy would actually be delivered to the star assuming that the planets cannot pass through? And would that be significant compared to the stars total output?"
] |
[
"Why do you hear identical notes differently when they are played on different instruments?"
] |
[
false
] |
What accounts for the fact that a flute sounds different than a piano, which sounds different than a guitar (even if they all play the same note)?
|
[
"The note is based on the \"fundamental frequency\" of the sound, which is lowest frequency of the note. From there, you have higher frequency components (often multiples of the fundamental frequency). These higher frequencies are called \"overtones,\" and the relative levels of them determines the timbre, and is largely what makes two instruments playing the same note sound so different."
] |
[
"A simple example of this: vocal formants, the different sounds you can create while singing the same note are dependent upon the resonances of the vocal tract. \"Ah\" \"Eh\" \"EE\" \"Oh\" \"OO\" are all the same pitch but with different peaks in the spectra. Those overtones matter A LOT. "
] |
[
"http://en.wikipedia.org/wiki/Timbre",
"It has to do with the relative ratio of frequencies that are produced when the instrument resonates. For every fundamental frequency that an instrument produces, standing waves are also produced that give the instrument its distinct tone. ",
"Additional info:\n",
"http://en.wikipedia.org/wiki/Standing_wave",
"EDIT: Grammar "
] |
[
"Do all brain-owning animals descend from a common evolutionary ancestor? Or are there animals that developed brains \"independently\" of other species?"
] |
[
false
] |
Forewarning: My science-fu isn't fantastic, so excuse the somewhat informal, "dude, science is awesome" language. Brains are amazing things. It blows my mind (heh) to even think about animals that don't possess them (like jellyfish). Recently, I got to wondering ... do all animals that have brains have them because we all descended from some common species that first possessed a brain? Or were brains developed independently on many separate evolutionary branches?
|
[
"Nearly all metazoans (animals) have nerves (that is, cells with a synaptic junction that can transmit signals from cell to cell via an action potential), with the exception of sponges, an early outgroup on the metazoan tree. So, yes, all extant animals, including all bilaterians (animals with bilateral symmetry, like us), owe their nervous systems to a common evolutionary ancestor.",
"All bilaterians have some kind of brain, even if it is just a cluster of nerve cells (ganglion). From this primitive start, more complex derivatives evolved. Notably, cephalopods (octopus, squid, etc.) and vertebrates have highly developed brains with fairly different architectures that evolved independently."
] |
[
"The answer is that it's sort of complicated. Brains are made of neurons, and basically everything with neurons shared a common ancestor far enough back that had neurons. Many things that don't have brains, like nematode worms with less than 20 neurons, are included in that list, though. As you go up the tree of life, you get more and more complicated clusterings of neurons, and at some point it becomes sort of ambiguous whether or not we're looking at a brain or not. Does a fruit fly have a real \"brain\"? Scientists consider it to be one, but you may not. It certainly reacts to stimuli, and has pre-programmed behaviors, but on some level so do nematode worms. ",
"If you make an arbitrary cut, and say \"does everything with a brain more complicated than a fruit fly share a common ancestor that had at something comparable to a fruit fly brain\", then the answer is basically yes. There are serious differences in how those brains developed, though. A bird brain is significantly different from a mammal brain, because they both diverged at the level of crocodile/reptile brains. The structures that developed after that evolutionary split are markedly different, and represent different solutions to similar problems. They use the same \"tools\", neurons with similar neurotransmitters and genes expressed, but they use different structures to \"wire them up\" to perform tasks.",
"It gets really fascinating when you go to an even earlier evolutionary split, like cephalopods and mammals. Their brains are wildly divergent from our owns. They shared a common ancestor with us that had a sort of brain, but was probably sort of a wormlike animal, probably without a lot of mental capacity. This is an evolutionary split hundreds of millions of years ago, before things like insects even existed. That's probably the best example you can find of a complex brain that developed almost completely independently from the rest of animals with complex brains."
] |
[
"My Marine Biology is weak - can you elaborate or link on how Cephalopod brain architecture is different?"
] |
[
"Do crystal deodorants work?"
] |
[
false
] |
[deleted]
|
[
"I don't know why you'd be surprised that people who insist on using a straight-razor in this day and age might eschew other convenient advances..."
] |
[
"I did some home comparison testing with the crystal deodorant a while back. Crystal on one armpit and conventional on the other. Then crystal vs no deodorant. Repeated for several days with each comparison. \nI found it did provide some protection, but not nearly as good as conventional deodorant. The effect also did not last as long as conventional. By the end of a long hot day there would be little difference between the armpit with the crystal deodorant and the one with no deodorant. "
] |
[
"You can bring an aerosol deodorant in your checked baggage. I do it all the time.",
"What is a \"crystal deoderant\"? A chunk of alum? That'd work, but it's not the best kind of deodorant."
] |
[
"Does Bell's inequality rely on photon polarisation being undefined before measurement rather than simply unknown?"
] |
[
false
] |
My reading of EPR is that simple values such as momentum must have a value even when not measured, which flies against the uncertainty principle and wavelike nature of particles. I've tried reading Bell's papers and subsequent ones and I can't tell whether they rely on the photon having an uncertain polarisation before measurement, but a hidden variable defining the outcome of the measurement, rather than an unknown polarisation before measurement and the outcome of the measurement being probabilistic. Can someone point me to anything that helps me understand this better?
|
[
"When you measure polarisation, the answer is either + or -. If you measure two entangled particles along the same axis, you always get opposite (correlated) answers. If you measure along orthogonal axes (90° apart) you get results that are uncorrelated with each other. Measure with 180° separation and you always get the same (anti-correlated) results.",
"Measure at angles with any other separation, and you get varying amounts of correlation in the results. We know from how the correlation varies with separation angle that it's not possible for the spins at each angle to be pre-determined (unless, somehow, the universe already knew which angles you were going to use to make the measurements)."
] |
[
"I was thinking about photon's though, which are used in most of the tests. The probability of passing a polariser is cos",
" (\\theta), where theta is the angle that light is polarised in.",
"No matter what happens to the other photon, the probability of it passing a polariser is always going to be this cos",
" value, and it seems impossible to make a prediction as to whether it will pass or not. ",
"But the discussions of Bell's like photon tests seem to assume that the outcome of the measurement should be predetermined by a hidden variable. Why is this, if the probability is always cos"
] |
[
"So, to confirm how I understand it, the Bell's test photon synchronicity experiments do not rule out that the pair of photons both have a definite but unknown polarisation before they are detected?",
"Are they simply ruling out a hidden variable that would take away randomness from the measurement?",
"It rules out both (if you add \"local\" to the second statement), and ruling out the latter is actually a much stronger statement.",
"My understanding of the question posed by EPR is that even though you cannot measure both momentum and position at the same time, both must still have real values",
"No they don't. They have a distribution for both."
] |
[
"How does mirror matter behave?"
] |
[
false
] |
The standard model is invariant under P-symmetry (reflexion in a mirror). What happens to things like magnetic fields or cross product which have an orientation? How does mirror matter interact with regular matter? I made a much more verbose post basically asking the same question but apparently that's not the appropriate style for this subreddit :)
|
[
"The standard model is invariant under P-symmetry",
"Actually, the weak interaction violates P symmetry maximally. As far as we know so far, all neutrinos, for example, are left-handed. That is, their spin and momentum vectors point in opposite directions. Or, even less jargony, all neutrinos have an intrinsic angular momentum (you can think of this as analogous to the earth spinning on its axis), and if you use your thumb to point in the direction the neutrino is travelling, its spin curls around like the fingers on your left hand.",
"Why we don't observe right-handed neutrinos is a still unanswered question. As far as the standard model says, \"mirror matter\" wouldn't interact with the weak force with normal matter.",
"Most other phenomena are symmetric under parity, though. For example, while the magnetic field has an orientation, so does velocity, and so when you work out the actual motion of a particle (which depends on the cross product of velocity and the magnetic field), it's unchanged under P."
] |
[
"No, sorry, that's not what I'm saying. I was saying that the universe almost has P symmetry, but not quite. If you were somehow able to flip the parity of every particle at once, most phenomena would be the same.",
"If there is mirror matter, it interacts through it's own set of mirror bosons. Bosons are the particles that carry forces, like the photon, gluon, and W/Z. None of these are invariant under P, and so they wouldn't interact with mirror matter. You'd need mirror photons, etc., and the only way mirror matter would interact with normal matter would be some mixing between photons and mirror photons (etc.). That's beyond the standard model and beyond what I really know. I don't do much theory."
] |
[
"Thanks for your answer, it made things clearer. So if I understand, the magnetic field and the cross product orientations are conventions, and if we change both the changes cancel each other in the formulas.",
"I read that the weak interaction is only used in beta decay and in the formation of deuterium. So mirror matter would interact normally with regular matter? It could form chemical bonds, maybe we could also have \"mixed\" heavier atoms?",
"It seems that it would be hard to determine if something is actually made of mirror matter."
] |
[
"Can bacteria survive low temperatures like when frozen into ice-cubes?"
] |
[
false
] |
I have a question about water borne diseases. I am a undergrad student living in New Delhi, India. I don't have much money or a place for a refrigerator so to quench the need of cold drinking water, I buy ice cubes from the market and mix it with the 20-liter mineral water kegs. The purity of the mineral water kegs can be vouched for (well, to a certain degree) but I have no idea as to how good or bad was the quality of water which was frozen into ice cubes. The cubes do not contain any dirt or suspended matter. I was concerned more about the bacterial growth. Can bacteria survive such low temperatures? Maybe they hibernate when the water freezes but come back to live when mixed with the warm mineral water? Should I stop using those ice cubes?
|
[
"Bacteria can survive freezing. We routinely do so in the lab to preserve them over the long term. In those cases, we add some cryo-protectant substances like glycerol, because ice crystals will damage many bacteria, but freezing and thawing is not a reliable way to kill bacterial cells. "
] |
[
"Bacteria can survive, however, you should be fine drinking it unless there is a cholera or some such outbreak. Your immune system is already primed for most bacteria found in the water just due to living there so if you feel sick or there is an outbreak as I said above then stop using the ice but otherwise should be okay. If you really want to avoid the bacteria but want cold water maybe use a cousins' or friend's fridge for storing some boiled or otherwise treated water."
] |
[
"Like superhelical said, microbes can survive freezing. While it is possible that since when water freezes it expands that when the water inside the cell freezes it could lyce the cell, it is not a good way to kill bacteria or other microbes"
] |
[
"I once heard that if you wore glasses that turned your vision upside down for about 3 days and you took it off, you would see the world upside down. Is this even possible?"
] |
[
false
] | null |
[
"Yes. Early psychologist George Stratton wore glasses that turned his vision upside down for 8 days straight. By the third day, he was seeing the world completely as normal -- as if he wasn't wearing the glasses. He could tell things were wrong if he concentrated, but normally scenes appeared completely normal. After he took them off after 8 days, it took a few hours for things to return to normal, in essence he was seeing things upside down.",
"Source with sources: ",
"http://www.madsci.org/posts/archives/mar97/858984531.Ns.r.html",
"edit: alright, I don't normally post to AskScience, I was just suddenly curious and shocked to find a psychology topic I had enough about to track down a source. I hope someone else can provide the answers to the questions below!"
] |
[
"What's the difference?"
] |
[
"Light enters our eyes and should make the world appear upside down",
"You're thinking of the eye as if it were a camera that takes a picture, physically places it somewhere in your head, and then your \"mind's eye\" looks at that. ",
"What's actually happening is that a bunch of cells in your eye are sending signals to your brain, and your brain interprets them. Any inherent orientation exists ",
" in that interpretation. "
] |
[
"A lot of nutritional supplements for someone with a reasonable diet have questionable health benefits. Are there any that have rock solid evidence of benefits?t"
] |
[
false
] | null |
[
"Examine.com has a really extensive list of supplements and their supposed benefits with links to studies. It seems the most proven are creatine, vitamin d, fish oil, and magnesium if there's a deficiency. "
] |
[
"link for the lazy: ",
"Examine.com"
] |
[
"Data is Beautiful",
" has an (in my opinion very neat) interactive data visualization that ranks various supplements by their evidence quality (sources listed and solid) and claimed benefits. \nIt was last updated in 2011 though, I'd also like to hear something else and more recent."
] |
[
"Is it fair to state that the vomeronasal organ is actually an auxiliary olfactory sense organ?"
] |
[
false
] |
I am not a scientist by any means, and am really looking for helpful information on this subject. I am curious as to why Jacobson's organ is specified as an auxiliary olfactory sense organ and am worried that it may be an anthropomorphic statement. I do know that it uses similar (maybe the same) portions of the brain to interpret stimuli, and maybe this is the only criteria necessary to name it auxiliary, but I am curious of the communities opinion on the matter. My main reason for asking is that I am a student of philosophy and understand that the phenomenology of one sense is so drastic from that of another that they cannot be compared from a linguistic perspective and have concerns that this leads us to reduce the possibility of extra sense organs in other animals to human understandable terms.
|
[
"Since no one else has answered yet, I give this a shot.",
"There are three reasons supporting the idea that Jacobson's organ is an auxiliary organ that provides stimuli comparable to smell/olfaction. 1. Jacobson's organ develops from the olfactory placode during embryonic development, so evolutionarily speaking it has recently diverged from the \"main\" olfactory organ. 2. Jacobson's organ is a chemoreceptor. Although this doesn't say anything bout how the stimuli are interpreted by the brain, Jacobson's organ does receive stimuli similar to the main olfactory organ and function in a similar way. i.e. it detects specific chemicals, not physical stimuli like pressure or temperatre. 3. Straight from the OP:",
"it uses similar (maybe the same) portions of the brain to interpret stimuli",
"This is speculation on my part, but that statement leads me to believe that stimuli from Jacobson's organ are interpreted by the brain in a manner similar to what we call smell."
] |
[
"Honestly, it's not my area of expertise, so I don't know what the criteria for an auxiliary sense organ are. I was responding to this statement ",
"the phenomenology of one sense is so drastic from that of another that they cannot be compared from a linguistic perspective",
"Based on the physiology of Jacobson's organ specifically I would predict that it provides feelings that can be described as \"smell\", but with a different range of stimuli (pheremones instead of random volatile chemicals); kind of like how some insects can see \"see\" UV light. ",
"I don't have any specific suggestions for further reading, but the citations on wikipedia are often a good start."
] |
[
"I appreciate the answer. So if I am understanding this correctly we (by we I mean you and the scientific community) don't have a strict list of characteristics for what would constitute an auxiliary sense organ, but rather use what appears to be a property cluster of sorts to verify whether there is novelty in the apparatus and it's corresponding phenomenon. ",
"Again, I appreciate the answer and if you think you may know of somewhere (website/textbook/other subreddit) that may allow me to gain further understanding of this organ or scientific writings on sense organs in particular I would also appreciate it (again I am very weak in the hard sciences, but have an acceptable understanding for a non-scientist)."
] |
[
"Bullet gives opposite reaction on the gun when comes out. Does torch light give opposite reaction when switch on?"
] |
[
false
] |
When the torchlight switches on, the light comes out of it light-speed. So does it give any opposite reaction on the torchlight, like a bullet and gun?
|
[
"Yes, but the effect is vanishingly small. Ultimately, this comes about because light is a carrier of energy and momentum and this holds true whether you're considering the classical or quantum picture. ",
"There's even situations where this is pretty important:",
"\n",
"https://en.wikipedia.org/wiki/Radiation_pressure",
"\nAnd people have even come up with ideas of making spacecraft exploiting this called Solar Sails:",
"\n",
"https://en.wikipedia.org/wiki/Solar_sail",
" "
] |
[
"Yes, light has momentum p=E/c, E energy, c speed of light. My torch lamp has voltage U=4.5V, mass m=0.4kg, battery capacity at most Q=30Ah. So in space I can accelerate my lamp to about v=p/m=E/(mc)=QU/(mc)=4mm/s, which is more than I expected (in case my calculation is correct)."
] |
[
"To follow up on that, assuming this is a typical flashlight with a battery that can power the lightbulb for several hours (let's say 4 hours), that means the actual acceleration felt by the flashlight is approximately 280 nm/s",
" or about 2.8 x 10",
" g's. ",
"Additionally, this is all assuming the flashlight is a) floating freely in space, and b) not rotating at all, so that the acceleration is always in the same direction.",
"Given all that, it's easy to see why this reaction is normally negligible."
] |
[
"What exactly causes the \"seeing stars\" phosphenes?"
] |
[
false
] |
By this, I mean phosphenes that result from standing too quickly, sneezes, low blood pressure and so forth. What's the basic route from one of these events to stimulation of the retinal cells, if that's in fact what's happening?
|
[
"I am not a biologist but from my understanding, it stems from a mixture of 1. a temporary lowering of blood pressure which drains blood from the upper body quickly and 2. the resultant excess of carbon dioxide in the blood stream which impairs the eyeball's oxygen/Co2 pump and so in a sense robs certain rod/cones from functioning properly. ",
"It is always accompanied by lightheadedness which is also a result of a drop in blood pressure."
] |
[
"AndrewKemendo is indeed correct. Standing up too quickly can cause a drop in blood pressure which can stimulate the retinal ganglion cells. There's also a number of other ways this can happen, like rubbing your eyes, and retinal detachment. ",
"However the root cause of all these are essentially identical. The retinal ganglia are stimulated and transmit information towards the visual cortex. The signal becomes large enough that the brain's filter (the thalamus) sends the message to the cortex, and it's registered as a spot of light. Hope that helps :)"
] |
[
"That does help, thank you!"
] |
[
"Do all planets in our solar system revolve on the same plane?"
] |
[
false
] |
Are there any accurate diagrams of the planes that all the planets orbit on? If Earth suddenly changed to let's say to a plane 90° off of its current plane would there be any noticeable differences?
|
[
"Not exactly the same plane, but close to one another. There \"average\" plane of the planets' orbits is pretty close to the orbital plane of Jupiter, usually within a few degrees except for Mercury which is six degrees inclined. This is called the ",
"invariable plane",
"."
] |
[
"A few years ago I programmed a representation of the Solar System in Javascript, you can open it in a webgl-enabled browser (Chrome for example) and is visible here: ",
"http://mgvez.github.io/jsorrery/",
"All the planet's positions and orbits are calculated using data from Nasa JPL, so are accurate, as are the stars positions.",
"If you click and move the mouse, you will be able to turn the system around, and you will see the plane for each planet's orbit. Look at Pluto's, it's not in the same plane as any other."
] |
[
"That's tricky to verify, because we are much better at detecting solar systems where that is the case (e.g. all the planets pass between us and their star). So it appears that other systems orbit in a common plane, but we might not be able to detect it if they didn't.",
"The reason planets tend to orbit in a common plane is because of conservation of angular momentum during their formation. So, we don't expect significant deviations from this."
] |
[
"What's keeping us where we are in the solar system? I mean, I know the gravitational pull of the sun keeps us in orbit, but what keeps us at this distance instead of closer or further away?"
] |
[
false
] |
I mean, the earth has a gravitational pull, and it's keeping us more or less glued to it unless we make a strong enough effort to break free. So why doesn't the sun's pull glue us to it? Why does it pull us close to it but no closer? Why are the really big planets so far back? Wouldn't the mutual pull of larger bodies seem to suggest they should be closer? Is there something pulling from the opposite direction that keeps us suspended in this orbit like one of those things where you can use two magnets to make something hover? And then there's the horizontal (for lack of a better term; I'm sure there is one, I just don't know it) thing. Like... with pictures of the solar system, all the planets save Pluto seem to be on the same plane of orbit. Why is that? Is it just that the pictures are simplified and we really aren't? If not, why is Pluto always shown to have a different orbit? Why don't the planetary orbits in our solar system look more like as opposed to ? TL;DR What keeps us in spot as opposed to spots in relation to the sun? EDIT: Thanks all for your patient explanations as I indulged myself in a fit of "Hey wait a minute... who's driving this thing?!"
|
[
"Drop a ping-pong ball into a martini glass. What keeps it at the bottom?",
"One of the great lessons of science is that every system tends toward its lowest energy state. A ping-pong ball in a martini glass stays where it is because that's its lowest energy state. In order to make the ping-pong ball climb out of the glass, you'd have to inject more energy into the system somehow.",
"One of the ",
" great lessons of science is that, for the most part, energy doesn't just vanish. A system with a given energy will maintain that energy unless some mechanism exists for that energy to be drained away.",
"In the case of the Earth-sun system — which we can consider in isolation, since the effects of the other stuff in the universe is relatively minor and can be rounded down to zero for our purposes — our planet has a certain amount of orbital angular momentum. The sun, in turn, has a certain gravitation. The reason why our planet orbits where and how it does is because that's the stable state of the system. In order for the Earth to move farther away from the sun, it would have to move faster along its orbit, and that energy doesn't just come from nowhere. And in order for the Earth to fall closer to the sun, it would have to move slower along its orbit, and no mechanism exists to drain away that much momentum from our planet in a short amount of time.",
"So the Earth stays more or less where it is, over any reasonable timeline.",
"As for why the planets lie in a plane, that's because the planets are thought to have formed out of a collection of gas and dust that mostly existed in a plane around the sun. As to why the gas and dust occupied a plane, it comes back to conservation of angular momentum. A uniformly distributed dust with some net angular momentum will, under the influence of gravitation, tend to arrange itself into a plane. That's just how all the little interactions between the dust particles end up working out.",
"Once all the stuff around our sun had arranged itself into a mostly-plane, individual densities within that dust began to interact, coagulating into our planets, plus all the asteroids, moons and assorted whatnot that makes up our solar system.",
"Pluto is the odd duck. It's thought that Pluto probably has a distinctly different origin from that of the planets. It's believed to be a Kuiper Belt object; the Kuiper Belt is a ring of stuff too large to be called asteroids and too small to be called planets. It's thought to be left over, basically, from the protoplanetary disc that existed before the planets coagulated out of it. Once, it's thought, the whole solar system was similar to the Kuiper Belt, until such time as gravitational perturbations created areas of density that formed into planets and swept the rest of the space around them clean.",
"It's thought that Neptune perturbed Pluto out of an orbit more customary for a Kuiper Belt object, possibly around the same time in history that Triton got pulled in from the Belt into a stable orbit around Neptune."
] |
[
"Why is the earth traveling at this speed?",
"Because it has no way of getting rid of its momentum. First law of motion, and all that: An object in motion will continue moving at a constant speed and in a straight line unless acted upon by an outside force. No (significant) force opposed the Earth's orbital velocity around the sun.",
"If the earth is a coagulation of space matter, am I right in assuming that it should be expected to continue to grow in size over time?",
"It does. That's what meteors are. It just doesn't happen quickly, on human timescales.",
"Are all the planets orbiting in the same direction?",
"Yes. Retrograde orbits are inherently unstable, for reasons that I don't think I can explain very well without mathematics and pictures."
] |
[
"This awesome little thing here",
" is a good way to get a \"feel\" of what you're asking. ",
"You can adjust their masses and velocities and play around to see what can make a successful orbit! I also shows what happens if you are too slow/small/close and the planet smashes into the star and if you're too fast and fly away!",
"Warning, it can get pretty addictive."
] |
[
"Can someone please explain brain freezes? (Causes, what going on when you are having one, ect.)"
] |
[
false
] |
All I really know is I get one whenever I eat ice cream or a smoothy or something cold. I also know that it can be stopped by putting your tongue to the roof of your mouth. Why does this stop it?
|
[
"It's caused by redditors who don't use the ",
"search function",
". ;) "
] |
[
"For those too lazy to click: ",
"It's referred pain from your palate via the trigeminal nerve. This nerve serves your head, but it passes by the palate. When it senses the constriction of local capillaries caused by the cold, voila, ice cream headache. The brain interprets it as pain from the head due to the function of the nerve. No damage involved.",
"An interesting note. Not all people get brain freeze. This is due to the thickness of said upper palate. A thick upper palate means the capillaries aren't as close to the surface and are therefore not as affected. I'm one of these people. I have only experienced brain freeze once, when I was in subzero temperatures and breathed in through my mouth rapidly."
] |
[
"http://en.wikipedia.org/wiki/Ice-cream_headache#Cause_and_frequency"
] |
[
"Why do streams of ejected liquids break continuous form and lump together into separate projectiles?"
] |
[
false
] |
To elaborate, I mean why does the water from a hose break into pieces as they fall. Or like
|
[
"But this phenomenon is observed in sand which, for all intense and purposes, has no intergranular adhesion ( ",
"source",
" ). Additionally, laminar flow is seen in liquids where no break up of the stream is observed. Whilst surface tensions/ energy will have an effect I think this question fundamentally needs to be answered from a materials flow perspective.",
"Edit: source"
] |
[
"To my knowledge, droplet formation is spontaneous even in laminar liquid threads. (That is, if you're not seeing it, look farther along the thread, because it's kinetically limited.) See ",
"here",
", for example."
] |
[
"I believe its due to the cohesive properties of water molecules. Due to the negative (H) and positive (O) charges of the individual elements that make up water, water is very much attracted to other molecules of water. When water forms a droplet, it is in the lowest energy state. By this, I mean that water molecules 'want' to be surrounded by other water molecules on all sides to resolve the positive and negative charges within each molecule. This is very similar to why when a group of magnets are placed, they clump together. These charges are also what give the water molecule a lot of its unique properties such as adhesion and its ability to dissolve many substances. "
] |
[
"Does the efficiency of a nuclear power plant depend on the level of uranium enrichment? And if so, where is the “sweet spot” of enrichment?"
] |
[
false
] |
Context: I was reading a little on the Iran nuclear deal in the news and they mentioned that the deal limited them to a pretty low percentage, but the Iranians had considered making a plant that could produce up to 20% enrichment. A quick google search suggested 80-90% enrichment is needed for weapons.... so what would the higher enriched uranium be good for?
|
[
"The term \"efficiency\" is a loaded word when it comes to engineering, so you'll need to be more specific if this isn't what you're looking for.",
"Typically, when we talk about the efficiency of a power plant we're either talking about (1) the theoretical thermal efficiency expressed as the ",
"Carnot efficiency",
" or (2) the actual measured efficiency.",
"In either case, the level of enrichment does not directly impact the efficiency of the system as a whole. In the first case, the only two relevant factors are the temperature of the \"hot side\" of the power plant (the reactor) and the temperature of the \"cold side\" of the power plant (the temperature of the plant output after all energy extracting steps have finished). Nuclear power plants are not limited by the amount of heat capable of being produced- even lightly enriched uranium produces so much heat that the limiting factor is the plant's ability to moderate heat production and dissipate heat, not the ability to produce heat. (Producing too much heat beyond the ability of the plant to handle it is the worst-case \"melt down\" scenario.)",
"The Carnot efficiency gives us a theoretical upper bound on the efficiency of a plant. It's not the actual efficiency. The actual efficiency is the total amount of energy produced in the reactor compared to the actual amount of energy delivered from the plant. In this case the efficiency only depends on how much nuclear fuel was put in the reactor to start and how much remains when the fuel is removed, but not the actual enrichment level. This is computed through measures such as ",
"burnup",
". ",
"Most civilian power plants run on anywhere from 1% to 5% enriched uranium. But, there are proposals to use up to 20% enriched \"high assay\" uranium. A more highly enriched fuel would allow for smaller nuclear reactors and smaller nuclear fuel assemblies, which has benefits from a design and waste disposal point of view. It also allows for higher levels of burnup, which is the proportion of nuclear fuel that is burned before the fuel is removed from the reactor and replaced, so this allows the reactor to be refueled less often, which is an expensive and time consuming process during which the reactor is not generating power. "
] |
[
"At higher levels you need to refuel the reactor less often. For example US nuclear submarines use highly enriched uranium so they only need to be refueled one every 30 years or so. A civilian reactor on the other hand needs refueling about once a year."
] |
[
"You can engineer nuclear reactors to serve many different kinds of ends. You can make a reactor that uses natural uranium (.7% U-235) fuel, but you require specialized moderators (heavy water or very pure graphite) for that. If you enrich it to 2-5% (\"low enriched uranium,\" or LEU), you can do it with natural water as your moderator, and that has tended to be a pretty nice \"price point\" for many nations that already had access to uranium enrichment technology. (It is worth emphasizing that there are non-technical factors as well. The US encouraged its allies to use enriched fuel because for a long while the US was the only country that was able to sell them enriched fuel. In this way the US kept an eye on the nuclear programs, and kept them somewhat constrained, which was worth something to the US.)",
"Using highly-enriched uranium (HEU) in a reactor is useful if you need it to be very compact, or require less changing between fuel loads. So submarine reactors use weapons-grade uranium as their fuel. But so also do some research or medical isotope production reactors, which are typically very small reactors (compared to power plants) that need large neutron fluxes (to irradiate whatever material will produce the isotope). So MIT's research reactor, for example, uses a small amount of weapons-grade uranium to work, and along with being a research and training reactor, its excess neutrons are used to \"dope\" silicon ingots for the semiconductor industry. Can you design reactors like that which use low-enriched uranium? Yes, but there are always trade offs. Many reactors that used to use HEU have been converted to LEU by changing their internal configurations, in an effort to lower the amount of civilian HEU floating around (for terrorist fears).",
"Anyway. Iran had maintained it wanted to enrich up to 20% because it wants to run a reactor that can make medical isotopes. This made many countries uncomfortable because the jump from 20% to 90% is not as large as it seems (it is less work to go from 20% to 90% than from .7% to 20%). Iran agreed to get rid of much of its uranium already enriched to these levels and roll back some of their other enrichment ambitions as part of the deal. ",
"They are now apparently saying they're going back to the 20% again",
", presumably as a response to the USA essentially tearing up the Iran deal. Again, they are saying it is for a reactor that will produce medical isotopes. "
] |
[
"When we see the dark part of the moon when it's not a full moon is it reflecting mostly starlight or earthlight?"
] |
[
false
] | null |
[
"Mostly Earthlight. Starlight is negligible compared to the brightness of the Earth."
] |
[
"The reason that you can see the dark parts of the moon is that they're lit by the reflected sunlight from the daytime side of the Earth. The city lights are totally negligible.",
"The bright side of the moon is lit by sunlight."
] |
[
"It's called Earthshine.",
"http://en.m.wikipedia.org/wiki/Planet",
"\" Earthshine is reflected earthlight visible on Moon's night side. It is also known as the Moon's ashen glow or as the old Moon in the new Moon's arms.\""
] |
[
"How is an apple a 'false fruit', strawberry a fruit while its seeds are nuts and a cucumber a fruit?"
] |
[
false
] |
We looked into a handbook for biological technical terms and got more questions than answers when we tried looking up 'stawberrry'. Apparently the apple is a false fruit and a cucumber a fruit. Hence the question - why is the categorization so confusing?
|
[
"\"false fruit\" is an old term not really used any more. The term accessory fruit is used instead.",
"These terms are used to outline how the fruit is formed. A cucumber is a true fruit as it is formed from the swelling of the ovary. Strawberries and apples are accessory fruits, which means they are formed from the swelling of other parts of the flower that is not the ovary.",
"However, I don't think this really answers why the terms are confusing... :S "
] |
[
"Wikipedia -- Accessory Fruit",
"A cucumber is a fruit because it is a product of a flower and contains seeds, as are tomatoes, peppers, squash, peas, etc.",
"Intelligence is knowing a tomato is a fruit. Wisdom is knowing not to put it in a fruit salad."
] |
[
"why is the categorization so confusing?",
"Because:",
"A. Scientists are not perfect so while they generally strive to explain their ideas as clearly and simply as they can, they can sometimes fail at that.",
"B. Not all scientists agree on all subjects so some can use a different terminology to others.",
"C. Nature is complicated and extremely variable in its manifestations so it's sometimes impossible to give simple and clearcut descriptions of it.",
"D. Common parlance adds to the confusion by using scientific terms for things they were not intended for by scientists in the first place",
"That said, the definition of what is a fruit and what is not given by ",
"/u/littlewoodenpuppet",
" is spot on. Go by that and no botanist will ever have anything to complain about it."
] |
[
"Are there any meta studies that demonstrate a strong relationship between twice yearly dental cleanings and a decreased risk of cavities?"
] |
[
false
] |
I am on the prowl for some evidence based dentistry. Does anyone have a link to any good research, preferably randomized, controlled trials, that strongly link twice yearly professional cleanings with a decreased risk of cavities or periodontal disease?
|
[
"It could be true as long as you brush & floss your teeth at home, too. I mean, sure, you can go in for a professional cleaning, get the tartar build-up removed, get an air-flow polish etc but it only takes 12-20 days for the dental plaque to mineralize and cause tartar build-up (if you don't brush well) which leads to gingivitis, periodontal pockets, bleeding, tooth mobility etc. \nThere are a lot of studies that show a strong link between brushing and flossing and the use of mouthwash with a decreased risk of cavities and periodontal disease so why not do it at home? Twice a year cleanings are not enough. "
] |
[
"I wasn't hoping to eliminate all dental care save for biannual, professional cleanings. Rather, I was wondering if the professional cleanings themselves have been shown to have any influence on the likelihood of having a healthy mouth years down the road. "
] |
[
"Oh, of course, I know that's not what you meant, but in my experience I have seen people who came in to get professional cleanings because they thought it was enough for them to have a healthy mouth but did not brush nor floss efficiently at home. \nBut getting your teeth scaled and air polished not only removes stains and plaque but also creates a really smooth surface on the tooth which prevents bacteria from attaching to it thus preventing the build up of plaque and cavities. \nSo yes, biannual professional cleanings, flossing and brushing your teeth using an appropriate technique guarantee you a healthy smile :)"
] |
[
"Can anyone elaborate on the Iron-Sulfur World Theory?"
] |
[
false
] |
I am a curriculum writer currently revising a lesson on biomolecules for high school biology. Part of this lesson requires students to analyze and evaluate various theories of how complex biomolecules could have formed on our planet. Students are to examine 3 theories: the Oparin-Haldane hypothesis, the RNA world theory, and the Iron-sulfur world theory. I have plenty of information about the first two, but not quite enough on the last. Can anyone help a writer out? General questions I have: 1. What were the more significant studies done to support/refute this theory? (links to sources that I could read would be awesome) 2. Besides Gunter Wächtershäuser, what other scientists have contributed to the research and from which institutions? 3. What are the most fundamental concepts you think a 9th grader in Texas should understand about this theory?
|
[
"After a brief overview of the theory I have a little insight for #3. The most important aspect (to me) is that it gives a method of concentrating and organizing the cellular machinery. That solves the biggest issue that I've seen with abiogenesis, the argument that it would take billions to trillions of years form anything resembling functional life because of how dilute the compounds necessary for life would have been. The only other reasonable solution I've seen for this problem is the cold RNA world hypothesis.",
"For #1/2: ",
"http://rstb.royalsocietypublishing.org/content/358/1429/59",
"\nalso (slightly less specific but still very important support for the theory) ",
"http://www.sciencedirect.com/science/article/pii/S0016703705007635",
"As much as people hate on wikipedia, it's still a great place to ",
" looking when searching for sources (it took me 30 seconds to go ",
"here",
" and pick out a couples links that didn't have Wächtershäuser in them)"
] |
[
"This is a great question and it truly blows my mind that you're teaching this to high school kids, because I just heard about it my 2nd year into PhD study.",
"Essentially, you won't find a biologist who will say that iron-sulfur chemistry doesn't partially define life on this world. It's an awesome study because it touches on fundamental chemistry and biology at the same time, which can be hard to find.",
"Basically, it must be iron because of the distribution in electron orbitals, and it must be sulfur because of the overlap of sulfur orbitals and iron orbitals.",
"As far as basic concepts go discuss FAD and how it's regeneration requires O2 and how iron can clearly speed up this process. Discuss how many of the molecules in the e- transport chain are heme containing or cytochrome enzymes.",
"In essence; everyone talks about how important oxygen, carbon, and nitrogen are, but life as we know it would not exist without Fe-S chemistry."
] |
[
"Well to be fair, I'm not actually the one teaching it. I was a HS Biology teacher for a time, and now I work for a non-profit group that is creating a comprehensive, online STEM curriculum for classrooms across the state of Texas.",
"The particular lesson-component I'm currently developing involves students researching 3 of the leading theories of the origin of biomolecules, and then moving through 4 separate stations where they explore the structural properties and functions of the 4 biomolecules.",
"And I agree with your position on education, which is why the lessons we develop are very student centered - trying to give kids a hands-on experience to teach them that science is just as much of a skill/methodology as it is interesting facts."
] |
[
"Biologists: Why does lack of oxygen cause necrosis so quickly in brain tissue."
] |
[
false
] |
As title, I looked at the wiki pages on brain death and cell necrosis, but I didn't find an explanation of why lack of oxygen causes cell necrosis as opposed to just temporary lack of functioning until oxygen is returned. I assume it's some kind of damaging by-product of the neurons function, but I'm just guessing here. Follow up question for fun, What kind of time span do other types of cells have for lack of oxygen->necrosis.
|
[
"Your brain cells are some of the most energetically demanding cells in your body, and your brain as a whole accounts for about a quarter of all sugar and oxygen demands throughout your entire body.",
"One reason is the synapse itself, an incredibly complex piece of molecular machinery that is continuously remodeling itself in response to various inputs, that requires that building materials be trafficked down long axons from the cell body.",
"The most susceptible cells to oxygen deprivation in your body are three types of brain cells: level five pyramidal neurons in the cortex, granule cells in the dentate gyrus and purkinje cells in the cerebellum.",
"Other cells are more immune to depleted oxygen supply, but most vital organs will expire quickly. Warm ischemic time should be limited to 30 minutes for a liver transplant and 60 minutes for the kidney and pancreas, meaning they should be removed from the body and chilled to prevent cell death and allow successful transplantation. Similarly, the heart and lungs will not last long without blood flow.",
"Other parts of the body are even more resistant. Structural and connective tissue such as bone, tendons, skin, heart valves and corneas can be harvested successfully within 24 hours of death. "
] |
[
"Without oxygen, the cell cannot create enough ATP to function. There is an anaerobic pathway for making ATP, but neural tissue is too energetically demanding for so little ATP. It has to maintain numerous ion pumps to maintain cell membrane voltage and ion gradients. It has to synthesize a lot of protein and a lot of neurotransmitter. It has to transport materials down axons which may be ",
" long. It has to operate reuptake pumps.",
"With loss of ATP, the ion pumps fail, the gradients equilibrate, protein synthesis fails, calcium influx induces caspase cascades (proteins involved in apoptosis and necrosis), water homeostasis fails and the cell swells from water influx, and death results. The cell may lyse and release free materials into the interstitial space. Dying, necrotic, and lysing cells cause inflammatory responses which can also damage nearby cells."
] |
[
"Thanks for the reply, That helps me narrow down my question. But I still don't understand what happens when there is no oxygen that causes necrosis. I'm trying to understand what actually causes the cell to self destruct rather than wait dormant for more oxygen to arrive. Is it some biological pathway that end up creating a damaging chemical? ",
"I'm an engineering major not a biologist so feel free to give me a lay-persons version.",
"This all stems from me trying to convince someone that brain dead is different from permanent vegetative state, and I wandered off topic when I tried to explain why the brain is dead. I knew that the cells were essentially destroyed, but couldn't explain why."
] |
[
"If someone were sitting in a bathtub full of water, but didn't drink any of the water, would they still become dehydrated?"
] |
[
false
] | null |
[
"Yes. You need to ingest water."
] |
[
"He's 100% right."
] |
[
"Yes. Your skin is not optimized for absorbing water and couldn't possibly keep up with your body's demands. Your kidneys would give out because there wouldn't be enough water to filter with which would cause imbalances in a whole host of things like sodium, potassium, etc."
] |
[
"I have a science degree but I'm not yet prepared to study some areas of physics. What math should I review, and what math should I study to understand the meaning behind quantum equations?"
] |
[
false
] |
[deleted]
|
[
"What areas of physics are you interested in?",
"For undergrad physics (until special relativity and quantum mechanics), linear algebra and differential equations are everywhere. You should also know at least the cool results from multivariable analysis (gauss, stokes, etc), and the theory to solve laplace's and poisson equation."
] |
[
"the topics that will be particularly necessary are matrices (linear algebra) and gradient/curl vector calculus. "
] |
[
"Yes, quantum mechanics at the level of computation is almost completely linear algebra. If you want some more deeper insights, functional analysis will also be required.",
"For magnetism and superconductivity, eventually you'll have to learn some field theory. But once you have the maths for QM/Electrodynamics, it will be easy."
] |
[
"Why can I smell static electricity?"
] |
[
false
] |
Maybe I cant smell static itself, but there is a particular odor I always attribute to static. Am I smelling something else or does the static have an affect on the air creating a unique scent?
|
[
"The most likely source of the smell is from the ozone created by the electrostatic discharge - that is, static shock. When a spark is created between your body and, say, the doorknob, the air molecules along the spark path are ionized. If the spark is strong enough, it can also break some of the molecules apart. In the case of oxygen, which is naturally diatomic (O2), the separated oxygen atoms can join onto other oxygen molecules, creating ozone (O3). Ozone has a pretty characteristic sharp scent."
] |
[
"Yes, nitrogen will also break and form nitrogen oxides. Sorry, I don't have information about the relative rates available. Ozone has a much more pungent smell than nitrous oxide, however."
] |
[
"What about the nitrogen? Does nitrogen react with oxygen to form nitrogen oxides to an extent comparable to ozone formation, or is the N2 molecule too stable for that?"
] |
[
"Do plants die of old age?"
] |
[
false
] |
can plants die of old age? if so how old do they get? Edit: Thanks for the great answers everybody
|
[
"The process you are talking about is ",
"senescence",
", specifically organismal senescence. The whole process of senescence in and of itself is not entirely figured out and there are competing theories for what is actually happening, but we do understand that there are fundamental differences between the processes in most animals and plants.",
"The plant senescence that most people are familiar with is what happens to plants as cold weather onsets: leaves change color, the trees abscise (shed) their leaves, annuals die, and perennials go dormant. All of these processes are not consequential to the age of the cells but rather to environmental cues and the hormonal response to these cues within the plant. This can be easily demonstrated by keeping such plants in a greenhouse over winter - the plants carry on as if nothing has happened, even if cloned plants kept outside senesce.",
"An important consideration is that plants and animals are fundamentally physiologically different. Many plants are modular, meaning that they have discrete levels of tissue organization, but the way that these tissues are assembled do not have specific limits on their number or placement. Or, in other words, most humans are originally genetically destined to have two arms, two legs, and ",
" five digits on each of these limbs, all in a specific arrangement. No such limit exists with the number and placement of the branches of a tree, or the number and placement of the tillers on a crabgrass plant. Another important difference is that most plants have indeterminate growth - they continue to grow throughout their lifetimes, again, unlike most animals, whose growth and development has a finite end. ",
"These two factors have important implications for the way that tissues are differentiated in plants. Plants have meristems, which are the growing points of the plant. These are organized bundles of undifferentiated tissue (think: stem cells) from which new tissues are made. The fact that plants have meristematic tissue has interesting consequences - most plants can be vegetatively propagated or clonally propagated via tissue culture.",
"I know I haven't directly answered your question, mostly because it isn't a simple \"yes\" or \"no\". With modular organisms that can be vegetatively propagated, the question of what is actually a single organism can be complicated in and of itself. I would say with certainty that plants do die of \"old age\", but not in the way we do. Plants don't age like we do because there are fundamental differences in our physiology and how our tissues die and renew themselves. That is all I'm really qualified to say, maybe someone with more expertise on the subject can weigh in. Hopefully what I've shared will at least help you think about the question in a different way."
] |
[
"Yes. ",
"Here is an excellent review article",
" on the basics of plant telomeres and telomerase function in higher plants (using ",
" as the model system.)",
"I don't really feel qualified to explain much past that. I don't work with ",
" or really dicots at all (I'm a grass person), and as such most of my plant physiology for these organisms is limited. I also have only a basic working knowledge of plant genomics and metabolomics, mostly in relation to plant breeding (not so much plant cell function.)"
] |
[
"You are amazing. This is an incredibly specific topic, and in the grand scheme of knowledgeableness, you're probably one of the most informed people in this thread on this topic, and yet, you still have the humbleness to say \"I have a limited understanding\".",
"It is true - \"Education is a progressive discovery of our own ignorance\" (Will Durant)."
] |
[
"Why does hearing your voice played back with a delay essentially nullify your ability to talk?"
] |
[
false
] |
So I came across an app that, when activated, plays back your own voice with a configurable delay. When it's activated your ability to talk is vastly reduced. There was a group of us playing around with the app the other day and while we were all effected to varying degrees one of my friends was the most susceptible. Video here: So my question is, why does this happen? What influences how much you are effected by it? Edit (from a comment below): I found that longer words were harder to say and usually resulted in stuttering. I was reading off my class list and it took me about 10 attempts to get "Microcontrollers" out. It usually came out as "microc-c-c-c-ontrollers" or something thereabout. The only way I could actually say the word was really slowly.
|
[
"I experienced this effect some years ago when playing with some audio software, it's most odd!",
"The best explanation I've sourced is from this patent, ",
"Voice delay feedback apparatus",
".",
"... in order to speak properly humans typically require audio feedback between what they say and how they hear what they say. In other words, in order to speak properly the person speaking must hear what he or she is saying. In the absence of such feedback (such as when a person is deaf), speech becomes difficult. If a device can change such feedback, then it can interfere with normal speech. Such a system could be used as a novelty device in order to observe the reaction of the user's speech to the feedback. Such person speaks as if they were drunk or a stutterer. ",
"I don't know what should influence the difference in degree of effect between people."
] |
[
"This is exactly it. If you pay close attention to what happens under these conditions, you will notice yourself slowing down your speech to \"wait\" for the echo to catch up. In essence, speech isn't just a matter of sending signals from your brain to your mouth and vocal cords - the feedback you get from your auditory system is essential. You listen to yourself to determine whether your vocal tract is working properly. As with any feedback system, disrupting or delaying the feedback will screw things up."
] |
[
"The feedback is not about the skill itself, but about the environment. You have to adjust the way you speak based on the local acoustic environment. If there's a lot of noise, you have to speak louder. If there's a lot of reverberation, you have to speak more slowly. The experiment we're discussing isn't perturbing your ability to speak ",
", it's manipulating the environment in a way that makes your brain try to compensate for the resulting acoustic changes. ",
"It's possible that you could train yourself to ignore those acoustic signals, but then you'd probably sound like a deaf person, and the sound you made wouldn't necessarily be well-correlated to what you intended. As an analogy, imagine playing tennis in the dark. You could learn to do it, but you'd never be a particularly good tennis player."
] |
[
"When they repave a road, where do they send the old asphalt and what is its environmental fate?"
] |
[
false
] | null |
[
"Usually, the asphalt is immediately recycled into the new road surface through the process of ",
"pavement milling",
". If the pavement isn't immediately recycled into the new road surface, it is trucked somewhere and then re-sold as aggregate or as an input to \"new\" pavement.",
"Asphalt is one of the most easily and widely recycled construction materials."
] |
[
"Yep! Asphalt is basically just rocks and glue. With old asphalt, the glue is all dried out, but the rocks are just fine. Crush it up, add glue, asphalt. "
] |
[
"So it just gets broken up and remelted on the spot? That's really cool."
] |
[
"How does hyperparathyroidism and hypercalcemia cause hypomagnesemia?"
] |
[
false
] |
How does hyperparathyroidism and hypercalcemia cause hypomagnesemia? I know it's pretty far-fetched, but I've tried google but to no avail. Yes, I've read my books, but I couldn't wrap my head around the concept. Answers are really appreciated. Thank you!
|
[
"Magnesium is primarily reabsorbed by the thick ascending loop of Henle along with Calcium that occurs along the paracellular route.",
"It is known that hypercalcemia or hypermagnesiemia alone inhibit further reuptake in the kidney. Also, there is some calcium inhibition of magnesium transport as well.",
"Does this help?"
] |
[
"Hyperparathyroism usually causes increase in activity of osteoclast which causes increase breakdown of calcium from bone and lead to increased calcium in plasma resulting in hypercalcemia.",
"The hypercalcemia calcium comperitively inhibits tubular reabsorption of Mg2+, which causes hypomagnesemia."
] |
[
"so calcium and magnesium have competing pathways? or is it a limit with the transporter? "
] |
[
"Is there a fundamental evolutionary explanation for why almost every tract in the CNS crosses to the opposite side?"
] |
[
false
] |
[deleted]
|
[
"One hypothesis looks to the ancestors that first had this feature, the worms.",
"The usefulness of crossing nerves is that an impulse on the left side causes the right to contract, which pulls away from the thing that touched it.",
"Since switching back would be improbable, we appear to be stuck with it."
] |
[
"This is not definitive - but it is suggested it is related to the optic chiasm.",
"Eyesight is the primary tool by which we determine how to interact with the world. We see in stereo, hence nerves from the eyes cross to both sides of the brain. This is the optic chiasm. The information from the eyes is split, and information from the nearside (cloest to the nose) of each eye is sent to the opposing side of the brain. This means that when viewing object from the right, the left side of the brain receives more visual information. In order to make reflex arcs as fast as possible, it is easier to hold motor controls (and everything else) on the same side. Hence the brain controls opposing sides.",
"As i said though, not definitive. Can't be proven as the reason why motor controls are mirrored and there is no reason why nerves could have split information differently."
] |
[
"I've heard that if you get attacked from one side, and get injured on the right side of your head for example, the left brain can still control your right arm to fend off the attack."
] |
[
"Why do blue flames not give off more light than orange flames?"
] |
[
false
] |
I noticed this when was in a mostly pitch black room. My butane torch produces a blue flame that illuminates very little of a reasonably sized room, however if I widen the flow and allow the flame to turn orange the whole room is lit up. From what I've learned blue flame is the hotter of the two. Shouldn't more heat mean more energy, meaning more light?
|
[
"There are a couple of things going on here (such as the \"surface area\" of the flame), but the main thing is how we see light. If we extrapolate your example to even hotter flames that are mostly ultraviolet, the room would go back to appearing dark. Our eyes are evolved to see light based on the Sun's spectrum, which peaks in the yellow-green (meaning the Sun is technically green!) but appears white because its blackbody covers all of the visible spectrum. Simply put, we aren't as good at seeing blue/violet light as we are at seeing orange/yellow light. This is actually the same reason why green lasers of the same power appear brighter than red and violet lasers. Hope that helps!"
] |
[
"Hotter flames produce more light at all wavelengths as black body emitters, so there are no dark flames."
] |
[
"Yes, thank you for the correction. I was thinking just of peak wavelength and not ",
"intensity",
". The laser argument is invalid then, since the flame is at varying intensities. However, the UV flame produced ",
"would not be visible",
", especially if a flame emits mostly in IR and UV like hydrogen, so perhaps flame intensity depends also on the material being combusted and its rate."
] |
[
"After an amputation, whether it be a finger or an arm, how does the body reroute blood flow?"
] |
[
false
] |
Quickly checked wiki for an answer, didn't find much about it. Thanks for your time!
|
[
"Not sure what you mean. When the part is amputated, the surgeon will ligate the arteries going to it and the veins coming out of it. Everything proximal to the amputated part will still have arteries and veins going to it. The heart pumps as it usually does; the baroreceptors will continue to monitor pressure; and the body's circulatory feedback loop will continue to adjust things so that everything still attached gets enough blood. The one difference is that the main arterial branch or branches going to the amputated part is gone, and the main venous tributary or tributaries coming from it are gone."
] |
[
"For me I was taught that the circulatory system is similar to an electrical circuit. So in an electrical circuit if you cut off half of it, the circuit would stop working because it would no longer be closed. Why is it not like that?"
] |
[
"Because it's not just one loop out to the limb and back. Along the way to the end of, say the arm, the brachial artery gives off branches that serve all the structures along the way. Branches for the upper arm muscles, bones, nerves, and skin, then the forearm muscles, bones, nerves, and skin, and so on. And each terminal branch ends in a capillary bed that gets collected in a tiny venous tributary, that joins larger veins on their way out of the arm.",
"So the deal is, it is a circuit, and it does need to be closed. But it's a massively parallel circuit. You can cut off half of a circuit and still have it be closed if there are still operational loops. That's what happens."
] |
[
"Why are ethanol bottles in the chemistry lab labelled 'staining reagent' ?"
] |
[
false
] | null |
[
"I think perhaps your lab in question are using the receptacles of what used to be a staining reagent - which is s chemical used to dye or “stain” microscopic specimens - such as when you will be using an electron microscope and you want to distinguish between two differing tissues, however ethanol is not a staining reagent. It’s a standard laboratory solvent, so I’m assuming either you had a typographical error or your lab is reusing bottles to store their ethanol. "
] |
[
"For gram staining one of the steps is to rinse away excess of the colored staining chemical with ethanol or an ethanol/acetone mixture. This step is usually called decolorizing, and takes only a few drops of the solvent at a time. Are they irrigator bottles or something similar?"
] |
[
"If it's also used as a microbio lab, probably because it's used as a decolorizer for various staining techniques (not limited to gram stain - there's quite a few differential stains that use ethanol to decolorize)"
] |
[
"Why aren't tape worms digested if they live in the digestive track?"
] |
[
false
] |
Meant to say tract instead of track as has been noted in the comments
|
[
"Tapeworms attach themselves to the wall of the small intestine so they can obtain nourishment. The scolex, (the head of the tapeworm) has hooks and suckers which helps the tapeworm to stay attached to the wall lining and to resist the peristalsis action of the intestine (peristalsis is the contractions of the muscles in the intestines which creates wave-like motions, pushing food further down the digestive system). Furthermore, they have a thick tegument, which is a kind of barrier which makes it quite resistant to acids and alkalis.\n(Btw please correct me if I am wrong/missing information. Im only in highschool)"
] |
[
"Most part ot the deconstructive part of the digestion happens in the mouth and stomach, cists traverse this areas protected, then colonized the intestine walls. Intestine walls main function is absortion of lipids and proteins and water from the biological matter that has already passed the stomach, is not a harsh environment to survive in."
] |
[
"That's where the force comes from right?"
] |
[
"Let's just say there is zero friction in our world. Is it possible to pierce with a sharp object? How faster and far would a person slide?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"guidelines.",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"wow they weren't kidding when they said about this subreddit's horrible guidelines"
] |
[
"You are basically asking what would happen if a fundamental law of physics was broken. It is impossible to have a scientifically accurate answer for that."
] |
[
"Toilet Flush -- Is the idea that urine and fecal matter are \"aerosolized\" and spread around the room true?"
] |
[
false
] |
Basically, i've heard it said by many people my entire life that when you flush the toilet whatever is in there ends up turning into vapor and is spread around the room. (Not of it.) Is this true? A moreover, does closing the lid--which has nothing even resembling an airtight seal--alleviate this problem with any significance? What are the health risks?
|
[
"the hazards of urine and fecal matter are greatly over estimated by most people. These things are better thought of as fertilizers than as toxic waste."
] |
[
"A pity, I cannot read ",
"this article",
". Here is quote from the abstract:",
"The studies demonstrate that potentially infectious aerosols may be produced in substantial quantities during flushing. Aerosolization can continue through multiple flushes to expose subsequent toilet users. Some of the aerosols desiccate to become droplet nuclei and remain adrift in the air currents. However, no studies have yet clearly demonstrated or refuted toilet plume-related disease transmission, and the significance of the risk remains largely uncharacterized.",
"So, the answer appears to be yes, some aerosols can be produced, and their associated health risks still need to be further evaluated. Maybe someone can say whether this paper talks about toilet seat covers."
] |
[
"Fecal-oral transmission is a fact of life. Some poopy bacteria are going to end up on the kitchen counter, on your toothbrush, in your nose, and so forth, probably no matter what you do.",
"I'm not suggesting that you stop washing your hands. It's worth fighting the good fight. I'm sure there are a host of papers that explain why it's a good idea to pursue this basic hygienic ritual. ",
"However, we have a lot to learn about why and how people sustain bacterial infections, and these things can't be wholly attributed to the mere discovery of these bugs in the environment. You could culture a few dirty places in your house - kitchen sink and counter, various bathroom sites, the dog's water bowl, your skin - and find MRSA, Legionella, and other nasty bugs. "
] |
[
"How, exactly, do we fall asleep?"
] |
[
false
] |
What is the process going on in our brain? How do we get to that "off" switch?
|
[
"Is NREM 2 the stage where you're paralyzed? I wake up with sleep paralysis quite often. "
] |
[
"Is NREM 2 the stage where you're paralyzed? I wake up with sleep paralysis quite often. "
] |
[
"You're paralyzed during REM to prevent your body from acting out the dreams you have during those stages "
] |
[
"Do space stations lose air from using air locks?"
] |
[
false
] | null |
[
"https://en.wikipedia.org/wiki/Quest_Joint_Airlock",
"https://spaceflight.nasa.gov/shuttle/reference/shutref/structure/airlock.html",
"https://www.nasa.gov/centers/johnson/pdf/123834main_iss_eva_sys_checklist.pdf",
"As part of the depressurisation cycle the ISS quest airlocks use pumps to pump air from the airlock back into the station. The pumps reduce air pressure inside the airlock to 5 psi (34 kPa), 1/3 of that in the station.",
"This reduced pressure is used to test the EVA suits for leaks. The remaining air is vented to space prior to opening the airlock.",
"Ideally you'd want to pump all the air from the airlock into the station, however it is extraordinarily difficult to pump a vacuum to the point where it's just easier and cheaper to ship extra atmospheric gas up to the ISS than try to build, launch, operate and maintain a set of pumps capable of producing a near vacuum.",
"Edit:",
"My description of the procedure isn't correct. See ",
"u/ninelives1",
" post below."
] |
[
"It would cost more to orient the station in such a way to make use of the minuscule thrust than it does to periodically correct orbital degradation/wandering due to airlock decompression. The station is low enough that they have to make fairly frequent corrections anyways."
] |
[
"\"It is possible to calculate the station's drag force from the information in this graph. This is left as an exercise for the reader.\""
] |
[
"How do phased array antennas receive signals?"
] |
[
false
] |
I can understand how a phased array helps direct outgoing radio waves by pointing the major lobe of the transmission towards the "receiver", but how does any sort of flat plate collect incoming radio waves as well as or better than a semi-spherical (?) dish?
|
[
"The simple answer is that a suitably-designed phased array of the same size (same cross-sectional area) as an equivalent dish would be expected to perform approximately ",
" (in terms of directivity and signal-strength). On those basic measures, it can't really perform ",
" than a dish.",
"In a receiver, the signals from the individual array elements are electronically summed (at some stage of the signal processing) with subtle time-delays between the elements in order to \"phase\" the array and create the required directivity. Signals from the wanted direction will sum constructively, while signals from other directions will tend to be non-coherent (at random phases) from the different received elements, and thus average down to a proportionately lower level in the summation.",
"The key advantage of phased-arrays is that the beam-direction can be \"electronically\" steered (i.e. by changing timings in the signal-processing), as opposed to having to physically move a dish. The electronic beam-steering can be essentially instantaneous, whereas the rate at which you can move a dish on motors is limited by physical mass, inertia, motor-power, ... and will be subject to mechanical wear. This high-speed steering is near-essential for tracking low-earth satellites, or military radar, among other applications.",
"There may then be second-order benefits such as physical simplicity, lighter-weight, less wind-loading etc. But if you need super-speed scanning, then moving a physical dish of more than a certain size is simply impractical. Very large dishes are major engineering projects, as the dish needs to retain it's shape to within a fraction of a wavelength (say 1/10th of a wavelength) as the dish is moved and steered. In contrast, a phased array can be fitted on a flat (or even uneven surface/terrain) and \"electronically\" flattened (corrected for physical distortions).",
"A further benefit of phased arrays (for relevant applications) is that you can double up (or triple, or...) in your signal-processing, and then receive from ",
" with the same physical antenna. That's something you simply cannot do with a dish. Again useful for Starlink-type applications where you have multiple low-earth satellites, or military radar when you want to track multiple fast-moving targets.",
"If you have a phased array with a lot of elements then you may be able to control side-lobes better than with a dish, which may be important if you not only want to maximise the signal strength of a wanted signal, but also ",
" or suppress an ",
" signal of the same frequency but coming from a different physical direction.",
"Phased array antenna with many elements are likely to be more expensive than dishes, often considerably so, although the cost of RF electronics is continually falling.",
"(I don't have any first-hand experience with phased-array antenna, but have a lot of experience with signal-processing in other applications, where the underlying reasoning would be similar)"
] |
[
"u/noshowtho",
" If you understand how a phased array can steer its output, then you are well on your way.",
"With a dish setup, all the energy for \"pings\" originates from a relatively concentrated point (which sometimes IS a small phased array) sitting at the focal point of the dish. You probably know that this is why dish systems have some sort of tripod or mechanical arm sitting out front, to hold the transmitter at that point. The transmitter \"lights up\" the dish, and the dish in turn focuses the emitted energy into a beam (with a major lobe). It's just like a flashlight, where the bulb throws off energy that is reflected and focused by the reflector behind it. Just like a flashlight, a dish antenna is aimed at targets by physically moving the dish around, although these days most dishes have a limited ability to do digital steering.",
"When the return signal (energy reflected off the target) comes back, the dish, being large, captures some of that energy and focuses it back on the focal point, onto a receiver sitting there. So the job of the dish is to take very low level energy arriving across a relatively large area and focus it down onto a specific point where the sensor sits. At this point it's operating a little like a telescope.",
"Unlike dish systems that transmit and receive energy from a concentrated point, phased arrays spread the transmit power out over many transmit modules arranged across a flat array. In the dish, the total power level out is the power of the one transmitter. In a phased array, the power out is the sum of the power of all the transmit modules.",
"For transmit, the phased array mimics the function of a dish by controlling the timing (phase) of the energy leaving each transmit module. This opens up all sorts of possibilities for creating different sorts of \"pings\" and avoids a lot of mechanical steering, as the array can be aimed digitally by controlling the energy coming from transmit modules individually.",
"Finally to your question. The return signal coming back to that flat phased array surface is again low level and spread across the entire array surface. But now, instead of a dish \"multiplying\" the intensity by focusing the energy like a telescope, the phased array simply sums the energy received at each receive module across the array surface. And since the returning wave front is captured at many point across the array, the post processing options are many times greater than that of a dish system.",
"The \"better than\" part of your question is significant. Better depends on what one is doing with the antenna system in the first place. Dish systems are relatively cheap, can be relatively simple, and depending on the scenario can outperform even really good phased arrays. But the electronic beam steering, beam forming capabilities, and post processing options for phased arrays make their expense and complexity worth it for many applications."
] |
[
"(Digital) Signal-processing is a very broad field, but very powerful and important in modern communications systems.",
"As examples, you get audio signal-processing for lossy compression (bit-rate-reduction) and echo-cancellation and speech-recognition, and signal processing of radiofrequency signals in any \"digital\"-mode transmitter or receiver such as mobile phone or DAB radio or digital-TV (take a deep breath and look up OFDM :-) ).",
"It's amazing how Fourier transforms invented (or perhaps \"discovered\") by Joseph Fourier 200 years ago are at the heart of so much of modern technology."
] |
[
"What would happen if you were underwater as a tsunami went over you?"
] |
[
false
] | null |
[
"http://www.youtube.com/watch?v=L5IbDi09Yb4"
] |
[
"That was amazing, thank you."
] |
[
"I was wondering about that...But as a surfer, I've dove under 25 foot waves, and it didn't feel like suddenly being 25 feet under.",
"Anybody want to explain the physics of water pressure under a wave?"
] |
[
"If all viruses were effectively eradicated, how would that affect humans, ecosystems and other organisms?"
] |
[
false
] |
I've seen an increasing amount of articles about this miracle cure that could kill any and all viruses. Although I am still very skeptical of the drug's capabilities, what would happen to earth's ecosystems if any and all viruses were removed from the face of our planet? Are there organisms on earth that are mutually dependent on viruses? Could a lack of viruses cause a specific species to overpopulate the planet? After a long time (thousands of years), if all viruses are extinct and humans are still alive, would humans be more sensitive to new diseases?
|
[
"The most abundant form of viruses actually infects bacteria, not humans. Bacterial populations affect every living ecosystem on earth and are a very abundant part of the microenvironments within the soil and within higher order organisms. The impacts of this hypothetical scenario would be large, but it's difficult to say what the specific effects would be since bacteria and viruses cover such a broad, abundant, and diverse category of living organisms. Perhaps bacterial populations will overrun certain higher order organisms, resulting in disruption of certain ecosystems, or perhaps there will be profound environmental changes. It's hard to say.",
"Viruses themselves are very diverse and use different mechanisms to replicate, even if we're only talking about those that affect humans. A simple chemical method of eradicating all viruses is science fiction."
] |
[
"Yeah even the drugs he's talking about (DRACOS) only target specific dual strand rna replicating viruses, not \"all\" in any sense."
] |
[
"Bacteria use viruses as one way to exchange genetic material amongst themselves.",
"I asked this exact same question to a viral expert and they couldn't name any other good examples of any sort of beneficial relationship with viruses, but it may be just because people haven't looked."
] |
[
"When physicists say that the fabric of spacetime will be torn apart if the Big Rip model is true, what does that mean?"
] |
[
false
] |
Could someone elucidate the idea of spacetime getting ripped apart by accelerating expansion? What would be the physical description of this scenario? Does this mean that time itself would cease to exist? I know that there are certain fields inherent to space, such as quantum and Higgs. What would cause these fields to be destroyed instead of just stretched out?
|
[
"Technically, it means that the scale factor becomes infinite in finite time. The scale factor describes the expansion of the universe. Right now, the scale factor is 1 by definition. There was a time where it was 0.5. Pick two arbitrary distant galaxies. Their distance was only half of what it is now at that time.",
"Similarly, there will be a time where their distance will be twice of what it is now.",
"When the scale factor becomes infinite, strange things happen. Observers will be causally separated. Eventually, atoms will be torn apart and even the confinement of quarks will be broken up. Then it's the end of everything."
] |
[
"An exponential function doesn't blow up in finite time, but another type of function might. The typical accelerated expansion (dark energy dominated era of the universe with an exponential scale factor) isn't a big rip.",
"https://en.wikipedia.org/wiki/Scale_factor_(cosmology)"
] |
[
"You're simply confusing expansion happening forever and the acceleration of that expansion increasing exponentially. Let's say I have a magic balloon that is capable of being blown up at a steady rate forever without popping, that's expansion. Yet if I blow it up faster and faster then at some future point it won't be able to handle how quickly I blow it up and it pops, that's accelerating expansion. That's where your confusion lies. If expansion occurs forever without accelerating exponentially then we could experience a Heat Death instead of a Big Rip. Right now we don't know the exact nature of dark energy so that's why we have these different scenarios."
] |
[
"Why do most humans have negative associations with harmless spiders and bugs, while very neutral or even positive associations with deadly mammalian predators (bears, lions, wolves)?"
] |
[
false
] | null |
[
"Bears and wolves actually leave humans alone for the most part. They won't come into our camps and attack our tribes. And the fear of insects is largely cultural rather than an evolved trait. Many cultures do not think about insects as we do. Many places simply see them as a food source, as you or I might see a shrimp."
] |
[
"It might be a form of xenophobia. "
] |
[
"I think it's a cultural thing. A lot of cultures aren't creeped out by spiders. Instead, THEY EATUM UP. Also, there is a stronger relation between bears/pups with humans than there is between a wasp and a human. More relatable I guess. "
] |
[
"Do black holes preserve the appearance of their supernovae?"
] |
[
false
] |
I saw a documentary and it began explaining that black holes would essentially suck in the supernova at the point of collapse but to the outside universe all we would see is the supernova before it actually collapsed since we cannot see beyond the event horizon. My question is, would all the black holes in the universe still be showing the supernovae before collapse, including the light they gave off?
|
[
"From the perspective of an external observer things that approach the event horizon never reach it. That is true. However the light emitted is redshifted (to that same observer) more and more as the object approaches the event horizon. This means you can't \"see\" it as it won't be in the visible spectrum. Also even if you looked at the correct wavelength the luminosity would be incredibly small."
] |
[
"Thank you for your response!"
] |
[
"So if you were to watch someone fly a space ship into a black hole, they would sort of fade out reddish until you couldn't see them anymore, but never look like they reach the black hole?"
] |
[
"How strong are the magnetic fields around power lines?"
] |
[
false
] |
Curious for above ground, underground, and long transmission lines. Also if its possible to provide a comparison of power to something else, I'd be much appreciated.
|
[
"The formula for the strength of the magnetic field is proportional to the current and inversely proportional to the distance.",
"The maximum power generation capacity of, for instance, Big Bend Power station near Tampa is 1.73GW. Big Bend is a large coal-fired plant. Assuming a 110kV transmission line, the current output next to the power plant is 15,730 Amps. Assuming you were standing 15m away from this power line:",
"B = mu_0 * 15730A / (2",
"15m) = 20mT (milliteslas)",
"For comparison: 5mT is the field strength of a typical refridgerator magnet\n1.25T is the field strength at the surface of a rare earth magnet. ",
"Most power plants (1) don't operate at capacity, and (2) have multiple transmission lines, so this would certainly be a rare event for even this strong of a magnetic field."
] |
[
"110KV line-to-line 3 phase would only be 9080 Amps."
] |
[
"At the power plant I used to work at, it was pretty intense. The 345,000 volt lines that were 30 foot above ground would induce a voltage in the ground. At about a two foot distance you could pick up a one thousand volt potential differance."
] |
[
"Can everyone in the world share in the modern standard of living?"
] |
[
false
] |
[deleted]
|
[
"According to a mathematical model by Hulett in 1970 if everyone in the world had the same standard of living as people in the US the resources of Earth could support about 1 billion global population.",
"So it depends on what you mean by standard of living. (As Cam-ille said)"
] |
[
"Economics graduate here. Actually, a fair wage is a very controversial concept. What in the United States is considered a fair wage, may considerably exceed a fair wage in India, for instance.",
"Taking that into account, there is a common misconception that the wealth of some can only be sustained if some other people are poor. In a fair market, your wage will be equal to the value of what you produce, the fact that there is poor people is because they don't have the opportunity to produce valuable goods or services, not because everybody is taking advantage of them. ",
"As an economy develops, its citizen become more skilled and educated, so they are capable of producing more valuable goods, which in turn provide them a better wage."
] |
[
"they don't have the opportunity to produce valuable goods or service...",
"hold on a sec - everything we have pretty much comes from these 1$/day countries. Even our apple iphones - those are pretty valued in our economy, yet I am sure the people who make them are not paid \"fair wage\". So I disagree, they are being taken advantage of, if we paid them \"fair wage\" my iphone would cost way more - which people here would not be willing to pay.",
"You are basically saying that desk jobs are more valued in this economy then all the market goods that are produced."
] |
[
"Was potassium-40 always present on the surface of the earth? Would it have been a part of the human diet before mined fertilizers/nutrients were used in agriculture?"
] |
[
false
] |
[deleted]
|
[
"Yes and yes.",
"It's got a billion year half-life. Suffice to say it's had time to get distributed around.",
"Edit: Also, why do you ask? Because that sounds like a bogus argument invented by someone who went out looking for reasons why fertilizers are bad. With a half-life ",
" long, it's in no way a health risk at the concentrations at which it occurs in food, soil and rock.",
"If you're worried about radioisotope health risks, I'd suggest you start by getting your house checked for radon. "
] |
[
"Yes, on both counts. Potassium-40 is naturally occurring, therefore it's always been there. Your body needs certain amount of potassium to live, and potassium-40 is a portion (albeit small) of all the potassium available. You will likely have potassium-40 in your body regardless of what you eat, or where that food comes from. This is part of the natural background radiation we observe."
] |
[
"Potassium-40 is an extremely long-lived isotope (with a half-life of over a billion years). It was likely produced in the supernova that seeded and helped trigger the formation of our solar system about 5 billion years ago and has decayed to a slightly lower level since. Similarly, U-235 was produced by the same supernova (and was once nearly as prevalent as U-238) but has decayed since then to almost trace quantities."
] |
[
"Could a torpedo break the speed of sound of water, while travelling through it? What would happen?"
] |
[
false
] |
[deleted]
|
[
"This is mildly wrong in several places.",
"First and foremost: it would not be the same. ",
"You are correct that the speed of sound is infinite in an incompressible material. There is, in fact, no such thing as an incompressible material. It is a rather useful idealization engineers can use for certain situations which is very accurate when used properly.",
"Air is incompressible if you're talking about flows < Mach 0.3 or so.",
"When travelling quite fast in water you get ",
"http://en.wikipedia.org/wiki/Cavitation",
" . This is much different than the behavior in air and would make 'breaking the sound barrier' in water very much more complicated."
] |
[
"It would be the same. Shockwaves et al. The speed of sound is in fact a measure (well sort of) of the compressibility of a medium. In a truly incompressible medium, speed of sound is infinity.",
"So a torpedo breaking the speed of sound would cause a very similar reaction as in air. The answer is similar for your second question as well.",
"Though, the shockwave might decay sooner due to the higher viscosity of water. This is something I'm not fully sure of...",
"Also, of course, the drag of the torpedo is much, much higher and the speed of sound is also much, much higher, so getting to the supersonic region would be pretty much impossible.",
" Speed of sound is infinity in incompressible medium. There are no shockwaves in incompressible flow."
] |
[
"Oh nice :) I actually researched cavitation for quite a bit when I was getting my MS, but it completely slipped my mind when replying to this question!",
"So cavitation would prevent the onset of supersonic flow itself?",
"EDIT: Some googling reveals that shock waves in water are indeed, different from shock waves in air...They do exist though. Cool :)"
] |
[
"What would it feel like to be in a motionless spacecraft hovering above the earth (not orbiting)?"
] |
[
false
] |
If weightlessness is a product of freefalling to earth like the astronauts and cosmonauts on the International Space Station experience as they orbit the earth, then what would it feel like to if the ISS was not in an orbit but able to stay at a fixed altitude above earth? Would you be able to stand? How much gravity would you experience? What if you were at the altitude of the moon (without the moon's gravity interfering)? Also is there a curtain altitude away from earth that you could become weightless without actually orbiting earth?
|
[
"It would be the same as what you already feel. You're rotating with the Earth because the Earth is spinning, but this is way slower than orbital speed, and only makes a small difference. There's no big difference between standing in a building that's stationary on the surface, and standing on a floating rocket platform that's stationary to the surface. You feel \"weight\", because you can feel the floor supporting you against gravity.",
"Gravity does get weaker as you get further away, but at the altitude of the ISS it's only like 10% weaker than it is on the surface. The ISS - and many other satellites - are in \"low earth orbit\", and are basically still in the upper atmosphere. This is why the ISS needs a little boost now and again to stop it falling to the ground, and why the (controversial) Starlink satellites will deorbit themselves eventually.",
"The strength of gravity from a spherical object is proportional to 1/(distance)",
", where the distance is measured from the centre of mass. We are currently one \"Earth radius\" (about 6370 km) away from the centre. If you're one more \"Earth radius\" away (~13000 km from the centre), gravity is 1/4 as strong. For a sense of scale, the Moon is about 60 Earth radii away.",
"Classically, the Earth's gravity never actually goes to zero at any distance. Instead, its gravity just ends up getting so weak that nearby objects are much more important. Escape velocities and orbital velocities also just become very small. At a distance of 1 AU - the distance from the Earth to the Sun - orbital speed is about 180 km/h, and if you're going faster than that, you won't fall down to Earth. As the planets orbit the Sun at many kilometres ",
", they can mostly ignore the Earth's gravity on that scale."
] |
[
"Imagine getting on a hot air balloon that is sitting on the ground. Would you still fill gravity when you are standing in the basket? Now imagine it takes off, and it hovers a few feet off the ground, would you feel gravity then? Then it slowly gains altitude, and lets say there is no wind, so it \"hovers\" above the same spot. It goes up hundreds, then thousands of feet to the height of planes. You'd still feel gravity, much like when you are in a plane, right?",
"Gravity drops off slowly (1/distance^2 as someone pointed out in another answer), so it takes a while for you to feel any dip in gravity, but eventually you will."
] |
[
"It's from the center of mass (of the Earth). That means if you go to an altitude equal to the radius of the Earth (6300 km), you'd feel 1/4 the normal gravity. By my quick calculations, if you go up about 1000 km, you'd feel around 75% normal gravity."
] |
[
"Cells -->Tissue...When?"
] |
[
false
] |
How many cells congregated together does it take before we say they have created "tissue". How many are needed / at what point do they start to actually function as muscle, bone, an organ, brain structures/spinal cord, etc., rather than just existing as a collection of cells. What causes them to take on and start performing that tissue's function rather than just existing and living as independent cells?
|
[
"Tissue is not simply defined as a certain number of cells. Rather, it is cells that have adopted a certain organized architecture; the cells take on a structure consistent with their function. Cells have ",
"polarity",
" and specialized roles depending on their position -- ",
"check out how detailed* structure can get",
". In addition, tissue is made up of more than cells in that it also contains connective layers (i.e. \"matrix\" - made of proteins and fluid).",
"Take a look at this experiment done in a culture dish",
". The researchers placed a bunch of cells (HUVEC) down on a matrix-coated surface and waited. After six hours, you can see the cells have organized into a mesh-like structure, almost as if they are trying to surround something. It turns out that HUVEC cells are like cells that make blood vessels (the tubes that carry out blood). Those gaps the cells are surrounding are the cells attempting to make such tubes -- so the cells know to organize themselves into tissue. Breast cells in ",
"\"3D cell culture\"",
" can do something similar -- start adopting architecture reminiscent of how those cells would organize in breast tissue. These are very simplified examples, but they illustrate the first point pretty well.",
"Essentially, from the moment a sperm meets an egg and an embryo forms, a complex pattern of cell division and organization starts to get played out. This involves gradients of chemicals and cells communicating to each other about their orientation relative to each other. For instance, a cell can know if it is facing the \"back\" of another cell or the \"front.\" As you go on, cells \"differentiate\" from early embryo cells to more specialized cells -- like a kidney cell. Layers upon layers of specialization. From that, you get these intricate architectures. And when enough architecture develops, you end up with mature tissues and organs. It's basically a function of distance and communication all the way back to the embryo. Amazing stuff, developmental biology. ",
"It's difficult to point out exactly when they start functioning as, say, a mature organ. But typical development patterns are well known for* many organisms and you can look up when we expect* a healthy fetus to start developing different structures, etc."
] |
[
"Answers so far have been great, thanks very much, everyone. ",
"I think what I'm wondering is, at what point / why would you look at a collection of like cells and no longer say \"There is a bunch/group/formation of [HUVEC / breast / kidney] cells starting to gather and organize.\", but instead say \"There is [blood vessel / breast / kidney] tissue\". ",
"I could very well be wrong, but I don't imagine that we have [whatever kind of] tissue when we have two of the same kind of cells connected together and interacting. Or ten. Or ten thousand. I'm sure it's not just based on a number of cells, as that seems too arbitrary and that it doesn't consider all the nuance you mentioned above.",
"So if you're looking at video of that example you linked above, from the start, it's a bunch of cells; but at some point, you scientists are going to say it's tissue. What would be your trigger for identifying what you have in the culture dish as tissue? Or am I asking a question for which there's not any more specific answer?"
] |
[
"Cells in a culture dish are not usually identified as tissue. In fact, we would normally discuss tissue in the context of living systems. There are perhaps some exceptions, as always. For example, scientists are now growing muscle in culture -- so called synthetic ",
" meat",
" -- which might be described as muscle tissue in a lab. ",
"I suppose the exact cell/tissue border is not sharp but rather fuzzy. Some of the thresholds you have to cross along the transition are: ",
"Organization, wherein cells form rudimentary patterns such as the HUVEC pattern above. This need not be a circular form, but could simply be striation or a brick-wall pattern.",
"Polarity, wherein cells have a specific directionality and sense it. So for the HUVEC example, a cell must know which way the interior of the tube (lumen) is and which side of itself is facing away or is flush against another cell.",
"Macro structure, where organizational complexity increases and three dimensional structures start to appear. ",
"Interaction with other tissue types, wherein tissues will embed themselves within or come into contact with other tissue such as connective tissue (of which collagen is a component). We would expect to see nearby blood vessels supplying the tissue with nutrients and other features of organ-level organization. ",
"Adoption of function, wherein organization and individual cellular function becomes coordinated between the constituent cells. This can be as simple as forming a water-tight barrier or as complicated as absorption of nutrients like in our guts. Sometimes adoption of function also means that cells will differentiate and become specialized for a given task -- so no longer are we dealing with every cell being the same as every other (stems cells can be in a different place than the \"worker\" cells for every tissue, for example). ",
"All these together lay the seed work for organ formation, which is multiple tissue types (connective, nerve, muscle, etc.) all working in conjunction. At this point, a collection of cells is recognizable as tissue in my opinion. But this is a very, very basic summary because I don't want to get confusing. "
] |
[
"How deep could humans make it into the Earth's crust?"
] |
[
false
] |
How deep could we possibly make it into the earth before pressure or heat destroys the materials we used to get there and us with it? Edit: follow up question, what technology could we develop in the next 50 years to see us be able to go farther into the earth.
|
[
"Most geologists will tell you that the ",
"Kola Superdeep Borehole",
" is the deepest in the world though technically there are a couple oil wells that have gone a bit deeper. The Kola borehole seems to be about the limit with current technology. Drill bits frequently need to be replaced and once they got to a certain depth (I'm not sure exactly what depth it was) they found that the hole would close up as soon as they pulled out the drill to change out the bit. ",
"This is due to the increasing temperatures and pressures, as you descend into the the crust rocks and minerals start to act like toothpaste rather than solid materials. It's worth considering that the borehole itself is only about a foot in diameter.",
"The deepest mine where people can actually descend to the bottom of is the ",
"TauTona Mine",
" in South Africa which is 3.9 km deep.",
"There probably are several places on Earth where the crust is thick enough to drill even further down before heat and pressure become too much of an issue but without game-changing technological advances it's unlikely we'll get much deeper."
] |
[
"You're welcome. As for exploring deeper down, I believe there was a proposed design for a laser drill that would melt the rock around it and form a strengthened tunnel as it went. It's all pretty theoretical at this point and I don't know of plans to build one."
] |
[
"This is exactly what I was looking for in an answer, thanks so much friend. I need to add a follow up question of what technology could we develop in the next 50 years to see us be able to go farther into the earth. "
] |
[
"If humans can get extra chromosomes, can other creatures get extra ones too?"
] |
[
false
] |
[deleted]
|
[
"This chimp was born with an extra chromosome",
", but he was not mentaly defective. ",
"He had some human-like characteristic, like walking upright and straight face. He also seemed more interested in mating with humans than monkeys. His is not a happy story, but at least he died in pace and quiet."
] |
[
"Yes this would be absolutely possible though I'm not aware of any specific syndromes in animals. ",
"It is important to note though that the issue with Down Syndrome is not necessarily an extra chromosomes. The extra copies of the DNA, throwing off the genetic balance in the genome, is the issues. This can happen from an extra chromosome or from extra DNA getting stuck onto the tail of an existing chromosomes (",
"Robertsonian Translocation",
"). ",
"If you look at XYY for example there are few problems despite the presence of the extra chromosome (obligatory reference to the fact that ",
"XXY",
" is over represented in the prison population) "
] |
[
"Insects certainly can have extra chromosomes, but the effect isn't always going to be the same. In drosophila, for example, the ratio of X to autosomes (non-sex genes) determine whether the fly is male or female (though the Y gene is necessary for sperm development).",
"With normal flies it works out fine: you have the autosomes from mom and the autosomes from dad (so you have 2A). Then if they have XX they're a girl (2A:2X is a 1:1 ratio), and if they have XY they're a boy (2A:1X is a 2:1 ratio). However, we can alter their DNA to produce a fly with XXY sex chromosome, which will develop as female (2A:2X so the Y is irrelevant). You can go pretty deep down the rabbit hole with them, but this is just kind of a precursor.",
"Wikipedia link",
"Basically you can have extra chromosomes, but they will have different effects based on the species and the chromosome."
] |
[
"What makes the electronic configurations of transition metals so unique?"
] |
[
false
] |
Current undergrad here taking a level 1000 course. (By unique I meant that I'm unable to grasp what's going on microscopically.. :( ) According to the one electron system approximation/model, the 4s atomic orbitals have a lower energy levels, translating into stability for the system and thus getting filled first. This leads to (n)s subshells being filled first, before moving into (n-1)d subshells. Traditionally, this would be that the electrons in the d subshells are of higher energy levels, and thus would be favorably removed when ionization occurs, yet this is not the case for transition metals e.g: This question then extends to Nickel, which has electronic configuration: Is there an explanation for what is occurring here? I have done some reading which shows plots of energy levels of 4s and 3d subshells, indicating a crossover at around Z=21 (which is Sc), from thereupon which the 3d orbital has lower energy than the 4s orbital with an increasing energy gap. What is the significance of the gap here? I have slight exposure to Schrodinger's equations and energy level calculations, but is there an explanation besides the math which would help my understanding? Thanks in advance!
|
[
"The problem is that the Aufbau principle is only a rule of thumb and holds mostly for neutral atoms. Even there it cannot predict the electronic configurations of all the elements correctly (e.g., Cr = [Ar] 4s1 3d5 instead of 4s2 3d4, or Cu = [Ar] 4s1 3d10 instead of 4s2 3d9).",
"This is because the Aufbau principle assumes that electrons are all in distinct atomic orbitals with now interaction between them. The further you go down the periodic table, the more electrons are you adding, and the worse these approximations will get. ",
"In general you have to consider many different terms to the total energy of an electronic configuration. The essential ones are: (there may be even more, these are the essential ones I learned in university):",
"Now, for most elements the orbital energy is much larger in comparison to the repulsion and exchange energy and the Aufbau principle holds. However, for the first row transition metals the orbital energy difference between the 4s and 3d orbitals is very small, as you found out yourself, and is dependent on the exact configuration of the nucleus. This is why every atomic configuration has the be analysed on its own. For Cr and Cu it just happens that the energy gained from promoting a 4s electron into the 3d orbital (higher exchange and lower repulsion energy) is larger than the difference in orbital energy between the two, resulting in a net energy gain, and therefore in their electronic configurations given above.",
"Now, for ions it gets even more complicated. You are right: starting from K you first fill the lower energy 4s orbitals, followed by the 3d orbitals. However, there is no reason to believe that upon ionizing an atom the same rule can just be followed backwards to find the electronic configuration. Ca+ must not automatically have the same electronic configuration as K, because their number of protons and neutrons is different. For most ions the electronic configuration will indeed be the same, as it is for Ca+ and K btw., but for the first row transition elements it is not, because of the very small energy difference between 4s and 3d orbitals.",
"Sc+ (you wrote Sr, but I assume from the context you mean Sc) does not lose the 3d electron, because the energy gained (repulsion energy, exchange energy, etc.) of having one 4s and one 3d electron is larger than the difference in orbital energy. Note: The same is not true for Ca = [Ar] 4s2, just because the different nucleus. Sc2+ has actually the configuration [Ar] 4s0 3d1, which shows that for Sc2+ the 3d orbital is actually lower in energy than the 4s. Electron-electron repulsion in the tight 3d orbitals is responsible for the fact that for Sc+ and Sc the 4s levels are filled next instead of adding electrons to the 3d shells.",
"See ",
"http://www.rsc.org/eic/2013/11/aufbau-electron-configuration",
" and the references given there for a more detailed discussion about this topic."
] |
[
"Exchange energy: The exchange energy is a quantum mechanical effect between electrons with the same spin in degenerate orbitals. The exchange energy lowers the total energy of the electronic configuration and is the reason why electrons in degenerate orbitals have aligned spins.",
"I've never quite grasped this before, but by what process can electrons of a certain spin change their spin to match the other electrons in degenerate orbitals? For example this happens in transitions such as excitation to singlet oxygen from triplet oxygen.",
"Sorry for the slight change in topic OP."
] |
[
"Spin-orbit coupling is what allows singlet to triplet and triplet to singlet transitions to occur. This type of transition is called intersystem crossing. There are other types of angular momentum coupling, but spin-orbit coupling is usually the dominant effect in molecules."
] |
[
"Why does our throat \"tighten\" when we're at the edge of tears?"
] |
[
false
] |
I'm sure I'm not the only one who has this, when about to cry (and I do mean sob) my throat will tighten sometimes to a painful extent. Why does that happen? Is there any use to it or is it just a thing that happens? EDIT: Didn't know if I should tag this as biology or medicine.
|
[
"It's called the globus sensation which has associations with hypertonicity of the UES, the upper esophageal sphincter, as well as GERD. The purpose of the UES is to keep food in and air out. Stress, can cause the UES to tighten, the exact etiology of that action isn't known, but there is an association with stress and rapid breathing and losing your lunch, both things the UES interacts with."
] |
[
"It's not just the UES though. If it was just the UES, there would be no associated voice changes during those emotional moments. Globus sensation can occur in the absence of emotion and is just a general medical term for when patients complain of feeling a more chronic \"lump in the throat\" feeling. (I am a speech pathologist working at an ear, nose, and throat group)."
] |
[
"The sources I found say that it is caused by your glottis expanding. The glottis is the opening that allows air to pass through to the lungs and the size of it is controlled by your vocal chords. The glottis also closes when we swallow. When you try to \"swallow back\" your tears, you feel a \"lump in your throat\" because your vocal chords are both trying to close the glottis to swallow and keep it open to allow the increased oxygen flow. ",
"Doctor Oz - Source",
",\n",
"Source",
", ",
"Reddit - same question 3 years ago",
"It also happens with anxiety attacks and other stressful situations."
] |
[
"How much CO^2 do volcanoes spew out when extremely active and does that have any effect on climate change?"
] |
[
false
] |
After reading the entries in AskScience 2012 awards I found myself wondering how much of an effect an erupting volcano would have on our climate (indirectly). I'm assuming me have mounds of data on Mt. St. Helens, if possible compare the amount of CO that the volcano spewed into the air compared to the annual amount that say America does. Is it possible a string of bad volcanoes could send us further and faster into climate change? I can only hope this isn't a completely stupid question. I have so many thoughts but am horrible with putting them into words. Thank you in advance.
|
[
"There is a pretty good article by the USGS ",
"here",
".",
"In short, a volcano's effects last only few years. With a large enough eruption, the sulfur aerosols can reduce global temperatures 1-2 degrees. From the article... for CO2, Human activities are responsible for about 35 billion metric tons (gigatons) of CO2 emissions in 2010. An amount of CO2 that dwarfs the annual CO2 emissions of all the world’s degassing subaerial and submarine volcanoes. "
] |
[
"Possibly, yes. If I recall correctly there have been documented instances of limited cooling happening with exceptionally large eruptions. But again, it's temporary and would not significantly affect long term climate patterns ."
] |
[
"The Siberian Traps flood basalt eruptions has been proposed as a possible factor contributing to the end Permian mass extinction. CO2 emissions from the eruption are linked to the spike in global temperature at the Permo-Triassic boundary.",
"A lot of great material ",
"here",
" from MIT. "
] |
[
"Are there strains of HIV that aren’t detectable by modern testing?"
] |
[
false
] |
(Edited to meet guidelines) Hello all, Are there any cases where an individual might test negative (outside of the window period) using HIV RNA PCR & antibody/antigen testing despite actually being positive? Is it possible that someone might have some weird/rare mutation that causes the HIV RNA PCR test to not detect any HIV despite it being present? If so, would that mutation also impact the HIV antibodies to where they are also not detectable? Thank you for your time.
|
[
"The tests don’t look for single places; they check for a wide range of HIV components, and HIV effects. For a virus to avoid all the components that are tested for, it would no longer be a functional HIV."
] |
[
"The term you're looking for is \"False Negative\" which is where someone is infected, but the test says no infection. ",
"This is very possible inside the window (which is why you get tested multiple times if you have a significant concern). ",
"Outside of the window, it's really unlikely. As in probability says you're more likely to get hit by lightning. ",
"Further reading: ",
"https://www.aidsmap.com/about-hiv/false-negative-results-hiv-tests"
] |
[
"To build on this excellent answer, the 4th generation HIV tests have an incredibly low rate of false negative as well. Something in the range of less than 0.001% of the time. And as this poster said, if you're outside of the window period, chances are astronomically small of having a false negative, but the 4th gen test also includes the p24 antigen, and lowers the chances of having a false negative test."
] |
[
"What causes one to vomit during/after strenuous exercise?"
] |
[
false
] | null |
[
"While this is specific to one case, they do go over some broader statistics, tragically without isolating a root cause. ",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4027831/",
"It seems that fasting and dehydration are major factors according to a ",
" study out of Nagoya in Japan. ",
"https://www.sciencedirect.com/science/article/abs/pii/S019566630090391X?via%3Dihub",
"The best answers I'm aware of that don't involve those factors are a matter of altered blood flow due to demands of the limbs, chest, back and abdominal wall, buildup of lactate, and possibly hyperthermia."
] |
[
"While your muscles are working harder during strenuous exercise, blood flows away from your midsection or deep organs toward superficial muscles/skin (O2/temperature). Just like in flight/fight stress response, digestion comes to a halt. If your stomach is very full, but not digesting it can feel uncomfortable or nauseating. Every body is different but most people avoid exercising on a full stomach of heavy foods. ",
"Marathon runners eating those energy goo things during races is slightly different because (hopefully) their stomach isn't extremely full and sugars begin digestion in the mouth. Those 'energy' things have a high glycemic index [broken down for simple sugars extremely quickly/easily] and spike blood glucose levels. ",
"I hope this helps! Stay hydrated everyone and don't push yourself too hard-exercise science undergrad student"
] |
[
"I have always wondered if it has something to do with the body “shutting down” digestion processes to divert all energy to the exercise."
] |
[
"Why does fruit get sweeter (or more flavorful) as it ripens?"
] |
[
false
] |
I can't explain why I want to know the answer to this but... I want to know the answer to this. Reddit? I'm sure there's something you know here. I'm counting all fruits here, even the perennial last kids chosen for te team, avocados and tomatoes.
|
[
"tldr: starch (unripe storage form of sugar) is broken down to it's basic units, which are typically things that taste good to us.",
"slightly longer version:\n",
"http://www.ccmr.cornell.edu/education/ask/index.html?quid=1174"
] |
[
"If you're asking \"why\", it is because fruit seeds are better spread by getting eaten, so making them taste better is a good way of encouraging that. If the seeds weren't transported by the process of digestion, the trees would spread slower and compete with themselves, as the seeds would end up near the original tree. I believe (I'm not 100% sure on this) that the digestive precess also helps the seeds germinate.",
"http://en.wikipedia.org/wiki/Fruit#Seed_dissemination",
"If you are asking \"how\", apfejes has already covered that below."
] |
[
"Thanks!"
] |
[
"Burning Methane question (about the arctic methane)"
] |
[
false
] |
Hello all i know next to nothing about chemistry just read this article about a huge Methane deposit that is going to release sometime in the future and its impact Question is why can't they just burn it? i think it creates co2 / h2o when burned, but wouldn't the released co2 be less damaging? (probably wrong i know nothing) just curious as to the result of burning it would it explode? thanks :) downvote if its a stupid question just curious about it, seen videos of methane lakes burning and what not pretty interesting
|
[
"The nature article is ",
"here",
" for anybody who is interested.",
"It's likely to be hard to just burn the methane because the release won't happen in one place. It will be spread out in the form of plumes of bubbles scattered over thousands of square miles. And that's an area that gets seasonal sea ice cover, so you would have to build and remove your infrastructure to do the burning every year.",
"Furthermore, nobody is going to pay you to burn that methane. "
] |
[
"Did you even read the article? Using the numbers you provided that would be a 5 times increase in the amount of methane in the atmosphere. That seems like a huge deal. ",
"According to the EPA: ",
"Pound for pound, the comparative impact of CH4 on climate change is over 20 times greater than CO2 over a 100-year period.",
"I had trouble finding an exact number but globally humans seem to emit 35 billion tons of CO2 every year. The article says the arctic could emit 50 billion tons of methane. That is equivalent to 1 trillion tons of CO2 (50 billion * 20) which is 28 years of CO2 emissions. "
] |
[
"I'm not here to argue the merits of anthropogenic global warming. No matter where you stand it could still increase atmospheric methane by 5 times and according to your number it would release 1.25 times the total yearly CO2 output. If you believe in global warming this will have a huge impact (equivalent of 30 years of warming) and if you don't the huge increase in methane will still have some sort of impact. "
] |
[
"Dry Shampoo: How does it work?"
] |
[
false
] |
So short answer is that my roommate is pretty much telling us that dry shampoo doesn't actually clean the cat. He says the dirt molecules that were there before are still there. All the dry shampoo is doing is sanitizing the cat and making it smell delightful. So my question; is he right, and is the dry Shampoo just moving stuff around without actually doing anything? Or is the dry shampoo actually cleaning the cat? Thanks again in advance for taking the time to consider my question. tl;dr Friend says dry shampoo isn't actually cleaning the cat other than "maybe" sanitizing the cat and making the cat smell nice. I say it's cleaning the cat. Please help.
|
[
"Dry shampoo is baby powder/corn starch mixed with some fragrance. It just soaks up the oil in your hair. "
] |
[
"Ok, so it pretty much doesn't actually get rid of the stuff, right? So if you use it, you would still have to scrub pretty decently to get rid of the filth right?"
] |
[
"It soaks up the oil and makes your hair less shiny... But you also now have hair with an extra thing (dry shampoo) in it. It's exactly like putting face powder on oily skin. Not quite the same as washing."
] |
[
"Why does a near-light-speed astronaut age slower than the earth, and not vice-versa?"
] |
[
false
] |
According to the theory of relativity, the faster something travels, the slower time moves for it. So, if an astronaut leaves earth and travels close to the speed of light, he will feel like 2 years have passed on his journey, but when he returns to earth, 40 years will have passed (or whatever). However, from the astronaut's point of view, isn't he staying still and everything else moving? There is no Ultimate Reference Point in the universe by which all speeds are measured. Objects' velocities are measured relative to other objects. Why doesn't the Earth's time move slower than the astronaut's, so that 40 years pass for him but only 2 for the earth?
|
[
"When the astronaut turns and returns to Earth, his reference frame changes. This isn't relative. Both observers will agree that the astronaut is the one who changed reference frames. "
] |
[
"No. All velocities are relative. That postulate - that the laws of physics are the same for all inertial reference frames - is really the basis upon which special relativity is built.",
"Honestly, I wouldn't take what ",
"/u/NilacTheGrim",
" is saying too literally. I've never seen that explanation before, and it doesn't really make sense - it seems to invoke absolute measures of velocities. The correct answer to your question was given by ",
"/u/I_Cant_Logoff",
" ."
] |
[
"Both observers travel through spacetime. You can trace out the \"length\" of their path through spacetime. When the astronaut is leaving earth, you're right. Both observers can be viewed to be stationary and everything is nice and relative. ",
"To each observer, his own path in spacetime during this scenario is straight and only in the time direction. The other guy's path is on a diagonal. The image is the same for both observers. ",
"When the astronaut turns to return, his spacetime path is no longer straight. The spacetime paths from the perspective of both observers are no longer the same. "
] |
[
"Why does herpes only appear in the mouth region and the genital region?"
] |
[
false
] |
[deleted]
|
[
"You're asking specifically about \"herpes simplex I\" and \"herpes simplex II\"; as other answers point out there are several other herpes viruses (a total of 8 known for humans alone) that specialize in different regions of the body/different tissues.",
"As part of HSV I and II's lifestyle, they set up latent infection in neurons. They infect a superficial part of the skin, then track up the neurons to the body of the neuron -- the ganglion -- where they shut down most of their protein expression and basically hide out for years or decades.",
"Every so often, they reactivate, sending down new viruses to the region of the body that the ganglion innervates. That part of the body now can shed new virus and infect a new host.",
"HSV I has a strong preference for setting up latency in the trigeminal ganglion, which innervates the mouth. HSV II prefers the lumbar sacral ganglion, which innervates the genital region. (Probably \"prefers\" means more about the ability to reactivate from the particular ganglia, though I don't think the details are understood.)",
"Both these viruses can and do infect other parts of the body besides the mouth and genitals; HSV II is above the waist and HSV I below it in a significant minority of cases. As well, for example, HSV I can cause recurrent eye infections."
] |
[
"Herpes viruses",
" can express anywhere on the body. For example, varicella (chickenpox) is a herpes virus. ",
"Herpes Simplex",
" (STD herpes) generally are present in mucous epithelium, which is most commonly found around the mouth and genitals. However, it can also effect the eye. Other herpes viruses can affect different cell types. "
] |
[
"This extends to Herpes relatives like chicken pox. When the virus reactivates as Shingles, any involvement with the eyes is considered very serious. Vision can be affected, sometimes permanently. Antivirals are usually prescribed to limit the damage."
] |
[
"Does 0.9c appear the same to all observers?"
] |
[
false
] |
We all know that the speed of light appears the same to all observers, regardless of reference frame. However, if you were to say an object is traveling at 0.9c (or any other fraction of c for that matter), would it appear the same to all observers? Or is what appears to be 0.9c to one observer 0.5c to another?
|
[
"No. In the object's rest frame is appears at rest. In any other reference frame it can be at any speed. Only in one specific frame will it appear that speed.",
"You are currently going at 90% the speed of light in some reference frame, does it feel special?"
] |
[
"that may not be that impressive",
"Well, it's still impressive in ",
" reference frame where such speed requires a great amount of energy to accomplish. The matter is slightly complicated also because those protons are experiencing centripetal acceleration as well, keeping them on the track--acceleration is ",
" relative. ",
"And this is possible because there are an infinite set of values between 99.9%c and c.",
"I'm not sure what your saying here, there are also an infinite number of distances between me and my front door, but that isn't too important."
] |
[
"I think you're missing the point, which is that all inertial rest frames are equally valid."
] |
[
"How does a food processor keep bacteria out of packaged goods?"
] |
[
false
] |
I understand that "cold pasteurization" is used at packaging plants. The website indicates it is used for fruit, poultry and seasonings. What about diary products like packaged sliced cheese? Those packages will keep for a long time if they are not opened. And it seems that if any bacteria were present in a sealed container it could possibly create a serious contamination? I can't believe plants use a universal positive airflow with no dust in it. How does it work?
|
[
"For Dairy, it depends on the product. In the US just about all dairy products are pasteurized which is rapidly heating the milk before processing to kill bacteria while minimally affecting flavor. Also preservatives are often used. Note that one of the most common preservatives is salt. Food processors also use techniques to keep bacteria out of containers including autoclaving glass bottles. ",
"If for something like sliced cheese there was bacteria in the vacuum sealed package, the bacteria wouldn't be able to colonize or grow because of a lack of oxygen. ",
"You should note the packaged military MREs (Meals Ready to Eat) often have shelf lives of 2-3 years. This is because they have preservatives, are pasteurized, and are irradiated. "
] |
[
"re: vacuum sealing. thanks, does that include anaerobic bacteria in sealed plastic packages?"
] |
[
"If anaerobic bacteria were on the surface or inside the object being vacuum sealed (which is unlikely). Also many bacteria need specific environments to grow. "
] |
[
"Tired of glasses - really. How safe would Lasik be considered, in general?"
] |
[
false
] | null |
[
"someone please answer this. i could also benefit"
] |
[
"Lasik is as safe as the person operating the machine. I had a long talk with my optometrist about it and essentially, there are people who are valid candidates for Lasik and people who aren't. You need to find a doctor who isn't just trying to get as many people through as possible. Someone who knows the machine (preferably owns the machine where it isn't leased out by a company) and won't be afraid to turn you away. ",
"With the right doctor, your risk will be extremely minimal. "
] |
[
"ok, full disclosure. ",
"i work in neurology/neurophysiology field.",
"people who own the EMG/NCV machines seem to do many many more studies than the guys who don't. the guys who \"rent out\" time from the hospital or the neurodiagnostic lab.",
"the reason being that the guys who own the machine get money every time it is turned on. from the patien. they get what is called the \"technical component\" as well as the professional componenet.",
"the technical is usually about 9/10ths more than the professional.",
"\\the guys who rent time just get the professional component, so they don't do the proceedure unless it is needed. \nthe difference is 300 dollars if you own it, 30 dollars if you don't in neurophysiology.",
"most who don't need the proceedure, don't get it fi the guy doesn't own the machine, if the guy owns the machine, the person gets the proceedure often even if he doesn't need it.",
"is opthamology different?"
] |
[
"What effect does the moon's gravitational pull have on dry land (as compared to the tide for water)?"
] |
[
false
] |
Is there any measurable or significant effect on dry land like the rides? I read an article about that moon of Jupiter that is stretched and compressed so intensely that its surface pops like a zit I was just wondering what it would be like for there to be a moon but no oceans, what effect would there be if any at all?
|
[
"Yes, there is a similar tide for the solid Earth, usually called the ",
"Earth tide",
", though the ",
"magnitudes are small, amounting to a few to 10s of cm of vertical change",
" compared to the tides in the ocean. The magnitudes are such that it's not something you're going to notice without instrumentation, but they are definitely significant and measurable. The Earth tide also needs be corrected for (or considered) in lots of applications, e.g. ",
"measuring water levels in aquifers with pressure transducers",
", ",
"measuring gravitational acceleration",
", ",
"measuring positions/elevations with GPS",
", ",
"high precision instruments / facilities that stretch over very long distances like the CERN",
", and more."
] |
[
"Thank you! Lots of neat stuff to dive into"
] |
[
"I'm not sure, maybe I'm telling you something you already know -- and if so, I apologize.",
"But to me your question implies a common misconception about why the rather small tidal forces (in regards to earth) of the moon/sun create such noticeably big bulges of water on earth. The reason is not because the moon \"pulls the water to itself\". While that force does exist, it is rather miniscule (~1/10^7 of g). If it were not, you would just float away into space when the moon was above you. The bulges in the oceans are instead created because ~71% of earths surface is covered by oceans and all that water \"pushes on itself\" in the directions towards and away from the moon. So it's really more like a \"hydraulic pump\" than the water being pulled. The same forces act on the continents but because",
"a) there is so much less connected material, there is less rock \"pushing on itself\"",
"and",
"b) rock makes for bad hydraulic material because it is so much more stress-resistant",
"Now in your hypothetical of there being no water, a) would not apply which would definitely make Earth Tides more noticeable but because of b) they would still be nowhere near the same result as our water-tides.",
"P.S.: My all-time favourite video explaining tides: ",
"https://www.youtube.com/watch?v=pwChk4S99i4"
] |
[
"Have we observed any effects on the Earth related to our position in our galactic orbit?"
] |
[
false
] | null |
[
"So 240 million years = 1 Galactic year.",
"The earth is only about 8 Galactic years old.",
"Man is only a Galactic day or so old."
] |
[
"The earth takes about 240 million years to orbit the galaxy so nothing has been directly observed over the span of civilization. Ice ages however are thought to be influenced by our position in the galaxy and the resultant changes in cosmic ray flux."
] |
[
"More like 13.5 Galactic years.",
"If we divide 240 million years by 365, a Galactic \"day\" would be 650,000 years. IIRC our species is around 200,000 years old, so not even a day old in Galactic term."
] |
[
"Is it impossible to gain weight without consuming carbohydrates (without your body producing insulin)?"
] |
[
false
] |
I recently finished an interesting book, "Good Calories, Bad Calories" by Gary Taubes. While the book has several big flaws, overall it is very valuable as it shows how many current nutritional/medical "facts" are not based on good science. In the book one of Taubes's main assertions is that it's impossible to gain weight if we eat no carbohydrates. Since insulin is the only hormone that facilitates fat deposition into adipose tissue, if we remove insulin, then we cannot have any more fat stored in the body. I guess it would just all be excreted as waste. The book goes into the fat storage/mobilization cycle in great detail. Several researchers are quoted, basically saying that insulin is what causes fat to be stored. So, my question to any biologists, nutritionists, or doctors, is insulin really the only hormone that causes fat to be stored? If so, does it follow that it's impossible to gain weight eating only protein and fat (if I got it right, then if the body doesn't take in carbs, it won't release insulin)?
|
[
"Insulin secretion is not only carbohydrate dependent. Fat in the intestinal lumen induces secretion of hormones (GLP1, GLP2, GIP, Neurotensin, PYY), and at least some of these stimulate insuline secretion. ",
"If you block all insulin secretion, it is true that you would lose weight (like type 1 diabetics). If you only impair insulin secretion and/or sensitivity, you could still gain weight (type 2 diabetics). "
] |
[
"I don't think you will get a definitive answer here.",
"However, there are a few things to consider.",
"First, it's not just glucose that stimulates insulin secretion. It's also stimulated (to a lesser degree) by fats, and probably proteins.",
"Second, insulin isn't the only thing that promotes fat storage in fat cells. Acylation Stimulating Protein (ASP) secreted by the fat cells themselves can also promote the storage of fats, in ways that may completely bypass the insulin mechanism. ",
"This paper",
" goes into more detail about ASP. There are probably other agents and mechanisms too that are involved in weight gain, we don't know them all.",
"It's certainly possible to gain weight without consuming carbohydrates. Inuit people traditionally ate no carbs, and while they weren't exactly what you would call obese, they certainly had fairly thick subcutaneous fat to insulate them and serve as energy storage for lean times. Many people on low carb diets, such as Atkins, also know it's possible to gain weight on the diet IF you eat excessively. If you just keep stuffing your face with fats, regardless of hunger or satiety, you will probably gain weight, even on no carbs.",
"More broadly, you can look at it this way. Proteins come with a sort of built-in \"hard limit\". You cannot survive on proteins alone, no matter how much you eat. This is because there's a limit to how much digestive enzymes your liver can produce and how much urea your kidneys can excrete. Beyond that, even if you gorge on proteins, you will starve because your body won't be able to use them. I suspect that there's a lot of individual variation and genetics involved, but at a rough guess I think 1000-1500 calories per day from proteins is about what you can usefully extract.",
"So you have to make up the shortfall with carbs or fats, neither of which has such a limitation. Carbs, very obviously, stimulate the secretion of large amounts of insulin. Even more so if they are refined sugars or starch. Insulin is well known to cause the conversion and storage of fats. So gaining weight is very very easy on a high carb diet.",
"In comparison, it's harder to gain weight if you substitute the carbs with fats, because the insulin levels aren't as high. Anyone who has done keto and monitored blood glucose knows that it falls after you've been on keto a while. This has a very direct correlation with insulin levels, which are also correspondingly lower. Also, protein + fats give you a greater feeling of fullness and satiety than carbs, specially refined sugars and starches. So you tend to not get hungry as often.",
"I think that's basically what it comes down to. You can gain weight whether you're on keto or not. You can lose weight whether you're on keto or not. However, the protein+fat diet is somewhat less fattening than the protein+carb+fat diet, mostly because of reduced insulin levels, but also perhaps because it makes you less hungry."
] |
[
"People say that because his views are contrary to mainstream opinions. However, his books are well-written, and more importantly, he cites peer-reviewed literature extensively throughout them.",
"Unfortunately in science there can be bias against new information that conflicts with previously-held longstanding beliefs. I see that a lot in my work."
] |
[
"For someone who needs to consume more calories than average, like an olympic swimmer, do they still need to stay within the daily recommended saturated fat, fat, cholesterol, etc limits? Or does the ratio increase based on overall caloric consumption."
] |
[
false
] |
Title basically says it all. For example, does a weight lifter need to get the extra calories from protein or could he also increase fat/ cholesterol intake without getting fatter or raising his bad cholesterol and/or lowering good.
|
[
"Consuming fat does NOT make you fat. Consumption of excess calories causes the body to store them long term as fat via lipogenesis. ",
"That said, breaking down fats for energy is a more difficult process for the body than dealing with carbohydrates. A person engaged in strenuous exercise could certainly increase their fat intake a decent amount with few adverse effects, provided they don't exceed their caloric needs."
] |
[
"Normally diets are broken down into macro nutrient ratios. Macro nutrients (fat, protein, and carbohydrates) are all parts of a healthy diet and take up a certain amount of your diet (like 40% protein, 40% carbs, 20% fat). If your calorie consumption has to increase to match physical activity, then so do your overall macro nutrients. An extra 500 or so calories in your diet should be broken down into macro nutrient ratios."
] |
[
"I've heard that one in that case would not ",
" to stay within the recommended amount, but it is prefared to do so (and instead increase protein and carb intake). Further on the person continued and claimed that the percentage system (f.ex. 40-40-20% named earlier) was outdated. Can't find the source though."
] |
[
"Genesis of elements in a nuclear explosion"
] |
[
false
] |
I know that essentially all elements in the universe heavier than hydrogen are the product of runaway fusion in supernovae. I also know that a nuclear explosion produces radioisotopes from neutron absorption, but are there measurable amounts of elements heavier than lithium created when a hydrogen fusion bomb explodes, perhaps from fusion of the heavier elements in the structural parts of the bomb? If not, is it just that the density is too low or is there something else going on?
|
[
"I know that essentially all elements in the universe heavier than hydrogen are the product of runaway fusion in supernovae",
"This isn't quite correct. In the first few minutes after the Big Bang, hydrogen and helium form in copious quantities (about 3/4 hydrogen, 1/4 helium), along with tiny amounts of lithium and beryllium.",
"In stars, fusion produces elements up to iron, without need of a supernova. Supernovae are responsible for all the elements beyond iron, as well as important contributions for elements from magnesium to iron.",
"I know this doesn't answer your question about thermonuclear bombs. That is a bit more complicated, because a hydrogen bomb is not simply a fusion bomb; the fusion reaction is initiated by a fission bomb (and the full process actually has more than just a fission and fusion stage), so there are all sorts of products from the explosion. I think your question is do you see fusion processes going up the periodic table, and while that seems unlikely to me (the explosion quickly causes everything to separate), I am not an expert on these weapons."
] |
[
"Stellar nucleosynthesis is only the majority up to sodium. Past that, the majority of the atoms in the universe are from supernovae nucleosynthesis.",
"As far as fission products, the fissile chain is fairly easy to follow. Pu-239 -> U-235 + He-4 -> Th-231 + He-4 -> Pa-231 -> 227 Ac (+ He-4) ... -> Pb-207. It's easy to follow, and it stops at lead. That makes it easy to correct for."
] |
[
"Past that, the majority of the atoms in the universe are from supernovae nucleosynthesis.",
"Not quite correct. About half is created in the ",
"s-process",
" in giant stars. Some is created in the ",
"rp-process",
" in thermonuclear flashes on neutron stars. The other half is made in the ",
"r-process",
" which ",
" be in core-collapse supernovae, but that is not a certainty. It may be in neutron star collisions or some other events involving neutron stars.",
"As for your original question, I am not a weapons expert, so I hesitate to answer the fusion question. I will point out that even in hydrogen bombs, the majority of the energy released tends to be from fission of uranium, ",
"with the fusion acting primarily as a neutron source.",
" Given all that fission, including ",
"ternary fission",
", I would be surprised if what you are looking for would be detectable."
] |
[
"Why do clothes feel crunchy when you air dry them, but soft out of the dryer?"
] |
[
false
] | null |
[
"Tap water has minerals dispersed in it in solution. When it dries on a line the fibers/threads stiffen because the clothing is not moving much, and the threads retain their shape as the water evaporates and leaves the minerals behind, while in a tumbling dryer the threads are constantly crunched and tugged and squeezed so they cannot stiffen in this way. "
] |
[
"i'd say even then tumble drying will be softer as the fabric fibres are massaged while drying, and won't stick together.. kinda like how wet pieces of paper stick together if they dry while touching.. water allows the little hairs on the fibres to tangle and hold like velcro, whereas agitation while drying breaks these holds"
] |
[
"So if you were to use distilled water for washing your clothing, air dried clothing would come out the same as dryer-ed clothing?"
] |
[
"If an electron is knocked out from the L shell of an iron atom, leaving behind a vacancy, or hole, from what energy shells can an electron make a transition to fill the hole and emit an L X ray?"
] |
[
false
] | null |
[
"An electron from any orbital which can make the transition without violating conservation laws. Using the electric dipole approximation, it would have to come from another orbital with opposite parity, and the angular momenta of the initial and final states should differ by 0 or 1."
] |
[
"What"
] |
[
"What is the context for the question?"
] |
[
"Proof the moon affects the tides?"
] |
[
false
] |
My brother and I were having a few drinks and chatting, when he started talking about gravity. Mind you neither of us are very scientifically literate but I'm smart enough to know not to talk out of my ass when I don't know something. He went on to try and tell me that there's no way the tides are caused by the moon because the worlds oceans contain more mass than the moon. I have a feeling he's mistaken. Is there something I can show him or is he right?
|
[
"The mass of all the world's oceans is less than ",
"2%",
" of the mass of the moon. The moon is not a lightweight and has a significant gravitational effect on the Earth.",
"Now in a simple water-world model, the tides would look like ",
"this.",
" However, the Earth has continents which get in the way and even the surface gravity depends on where you are. The tides on Earth are much more complicated and look like ",
"this.",
"The Sun causes tides too which superimpose themselves onto the moon's tides which are larger, that added with the continents and other Earthly quirks ",
" the tides in many places, so that high tide might not occur when the moon is directly above or below. However, here's a picture from ",
"Maine",
" where the position of the moon follows the tides like clockwork."
] |
[
"The bulge on the far side is ",
" caused by inertia. It is caused by the gravitational gradient. This is a common misconception that makes it into elementary textbooks and popular science descriptions.",
"The textbook \"Planetary Sciences\" by de Pater and Lissauer devotes Chapter 2.6.1 to a mathematical derivation of tidal forces and tidal bulging. No where does inertia enter the picture. The equations and the effects are wholly gravitational."
] |
[
"Why is there a bulge on the other side of the Earth?",
"I've read ",
"http://en.wikipedia.org/wiki/Tide#Forces",
", but still not sure about how the Moon is supposed to weaken local gravity on the other side?"
] |
[
"Why do we, in the United States, use the metric system with respect to energy consumption?"
] |
[
false
] | null |
[
"The reason for this is that there are no U.S. customary units for \nElectric current, Resistance, Potential Difference, or charge, simply because the ability to measure these has only really been around since the world switched over to metric. (The metric system was put into use in most european nations around the early 1800s). Most of the measurements and laws came about after that, for example: ",
"George Ohm",
" (a German scientist) published Ohm's law in 1820.",
"It's a semi complicated issue, I recommend you read ",
"wikipedia's",
" article for some more information."
] |
[
"The real question is why don't you use the metric system for everything else? "
] |
[
"1 watt = volt * amp = ohms * amps",
" = volts",
" / ohms",
"it all ties together!"
] |
[
"How big could insects and arachnids get?"
] |
[
false
] |
[deleted]
|
[
"Within the fossil record there's evidence for dragonflies with up to 70cm wingspans in the carboniferous (",
"http://deepblue.lib.umich.edu/bitstream/2027.42/62968/1/375117a0.pdf",
"). This is inferred to be related to an uptick in oxygen concentrations, as one of the limits for invertebrates is their respiratory system - many of the smaller arthropods relying on diffusion. That in turn puts limits on how big they can get (through how thick their body walls can get).",
"That's about the limit of my knowledge in the area though :D"
] |
[
"It depends on oxygen concentrations in the atmosphere. The higher the concentration the bigger they can get, hence having larger insects back in times when it's generally thought these concentrations were higher.",
"As to a theoretical maximum I'm unsure, and at higher levels of oxygen concentration you would probably have more variables to consider (such as what other concentrations said insect needed in the atmosphere and how that would effect food sources and such)."
] |
[
"Higher concentration of oxygen in the past lead to bigger insects; many insects grew larger due to diffusive oxygen intake. This means oxygen was easily supplied to tissue even though their surface area was greater. However, the growth of insects can not carry on ",
". Take spiders for example; the design of their respiratory system and circulatory system would limit their size. I believe the following to be true but have no supporting evidence, that the biomechanics would start to fail at some critical mass. Spider legs would be unable to support to the body at some large size.",
"Here is a study on beatles\n",
"http://www.sciencedaily.com/releases/2007/08/070810194908.htm"
] |
[
"Why are some cancers incurable?"
] |
[
false
] |
Chemotherapy of course has its own drawbacks, but I can't understand how some types of cancers aren't completely eliminated by aggressive chemotherapy. I'm not talking about returning cancer but rather about cancers that can't "go away" in the first place.
|
[
"Immunotherapy for renal cancer was only developed 20 years ago. without that I would be dead now.",
"Chemotherapy is not universal. It only works on some cancers. Cancer is not one disease. It is hundreds of diseases.",
"Radiation treatment is fairly universal but it has dangerous side effects when used on some tumours."
] |
[
"Because some cancers don’t respond to chemotherapy drugs, each of which target different proteins mostly in fast-dividing cells. If a particular cancer (or group of cancers) doesn’t have those proteins, then it won’t respond to chemotherapy."
] |
[
"Because hitting every cell of a specific type is hard with how our bodies process things. Chemo is just poison that you try to outlast compared to every cell of cancer. Sometimes one survives or resists and comes back.",
"To really cure cancer, we need to develop cancer specific killing or removal methods, currently they just try to kill all sorts of things and hope for the best"
] |
[
"According to Maxwell's theory of Electromagnetism, visible light is a combination of fluctuating Electric and Magnetic fields. So why don't we see a compass needle being deflected in the presence of, say, a light bulb?"
] |
[
false
] | null |
[
"The fluctuating magnetic field associated with visible light is fluctuating very very quickly. It's reversing directions 100's of trillions of times per second. The needle of a compass simply has too much mass to respond quickly enough to such a fast variation in magnetic field. And if it did, it would be changing trillions of times too fast for your eye to observe it."
] |
[
"Besides the speed and low intensity of the perturbations, light from normal light bulbs is not polarised, so the orientation of the magnetic field in each wave is random and tends to cancel out with another wave."
] |
[
"The oscillation might be only billions (or 100's of millions) of times faster than a high speed camera can see, rather than trillions. It's still absurdly faster than any available technology can respond to."
] |
[
"If quantum effects reign supreme in the microscopic world and relativistic effects dominate the macroscopic world, at what level of scale do the two compete with one another for dominance?"
] |
[
false
] |
Why is it that I am a collection of atoms where each follow quantum rules, yet the me as a whole does not suffer quantum effects (being at two places at the same time, entangled with some other macroscopic object, etc.)
|
[
"Quantum physics is intrinsically probabilistic. That means, the outcome of quantum mechanical experiments can only be predicted using probabilities. ",
"Due to this inherently probabilistic character, quantum mechanical effects get \"averaged\" away in macroscopic ensembles. ",
"The ",
"Ehrenfest Theorem ",
"states roughly, that the expectation value of quantum mechanical processes has to converge towards the classical value for many particles. ",
"Relativistic effects, on the other hand, are not probabilistic. Thus they are relevant in the macroscopic ",
" the microscopic realm.",
"\nGeneral relativistic effects are more obvious in cosmic scales, simply because gravity prevails macroscopically over the other interactions. However, special relativity is extremely relevant for quantum mechanics. ",
"Without relativistic corrections, most of quantum mechanics will yield catastrophic predictions for most experiments."
] |
[
"Well, not ",
" quantum mechanical effects.",
"Superconductivity and topological insulators are both intrinsically quantum effects which nevertheless manifest on the macroscale. Quantum mechanics isn't just about the probabilities; sometimes the form of the wavefunction, and they symmetries of the system, are relevant as well."
] |
[
"Why is it that I am a collection of atoms where each follow quantum rules, yet the me as a whole does not suffer quantum effects (being at two places at the same time, entangled with some other macroscopic object, etc.) ",
"A tossed coin has a 50% chance to land on tails and 50% chance to land on heads. The more times you toss the coin, the closer the distribution of heads and tails is to 50%. The larger the sample size, the smaller the chance to end up with statistical anomalies. ",
"Just like the coin toss example, quantum mechanics are probabilistic. When the sample size is small, ie. one electron, it is possible to encounter entangled particles, quantum tunneling and other such phenomena. When the sample size is very large, which would be the case in a collection of atoms such as you, the chances of rare quantum phenomena happening to every particle approaches infinitesimal. ",
"Throwing one coin will get you a 100% rate of either tails or heads, but if the sample size is one million coins, you would never get there. ",
"I'm sorry if this doesn't go to the point, but I think it might make it easier to understand."
] |
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