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[
"What condition does this newborn baby have?"
] |
[
false
] | null |
[
"We have strict guidelines against medical advice which include offering diagnoses. We also cannot speculate based on anecdotal evidence / a single picture."
] |
[
"What are you talking about? I'm just curious what condition this COULD be..."
] |
[
"We try to avoid all posts that require speculation here."
] |
[
"What's the point of recycling biodegradable food waste? If it goes to landfill won't it turn into compost anyway?"
] |
[
false
] |
Seems like a waste of energy to recycle food waste separately. If it goes to landfill am I wrong to think it might even aid the degradation of other less perishable waste like paper and packaging etc. Why, in the UK, is this prioritised over processing batteries separately? Example Camden Council, London:
|
[
"The point of composting is to recover usable biomaterials at the end of the process. Putting it in a traditional dump means it won't be of any use to anyone unless you want to sift through gigantic piles of garbage at a huge expense to collect some in a few years."
] |
[
"Removing and composting biomass to re-use it reduces landfill. Most plastic garbage does not appreciably decompose in a reasonable time - most of it will stay as useless landfill for the foreseeable future. Or until we develop bacteria that can decompose plastics."
] |
[
"Are useable biomaterials at a premium these days? Don't they just use animal waste? I just wonder whether it's worth it really? Separating the waste food plus all the other processing and transportation costs."
] |
[
"Before genes are sequenced, how do scientist make sure they are using the genes from the right organism?"
] |
[
false
] |
As a birthday present I am getting my genes sequenced by a private company. For my sample they send a tube that I have to fill with spit then seal, shake and send back. Once they get my sample how do they make sure that its actually my genes that are sequenced and not some bacteria or other organisms (cow cells from a recent rare steak or something)?
|
[
"The tests use human specific primers/probes for DNA amplification and sequencing, and the sample tube has chemicals that retard bacterial growth. Most of the interference from bacteria is a degradation of human DNA in the sample, it's not really possible to sequence the bacterial genome instead of yours."
] |
[
"As a birthday present I am getting my genes sequenced by a private company.",
"If it cost less than $10,000 then you're probably not. You might be getting genotyped by a SNP array, e.g. 23andMe is one company that does this. The difference is that they just test a fixed set of several million common SNPs (single-nucleotide polymorphisms, i.e. single-base genetic variants), rather than read all the sequence from scratch.",
"This is important because it changes the answer to your question. If they were actually sequencing your genome, what they'd probably do is map each short read (generally it's broken up into chunks of less than 200 bp) to a matching sequence in the reference genome, to figure out where it came from. If it's from some other organism it generally shouldn't map to human (although it might if it's a fairly closely related organism like a cow, due to sequence homology). EDIT: If they wanted, they could try mapping all their reads to the reference genomes for some known potential contaminants, but the human genome is much bigger than bacterial ones, so the vast majority of short human sequences will not exist in any bacterium.",
"On a SNP array, the way that they test each SNP is actually by hybridizing your DNA to a complementary probe that is a couple dozen base pairs long, in order to get some specificity. I haven't followed the microarray literature in a while but it is likely that they choose probe sequences that are unique among multiple known genomes, not just unique within the human genome."
] |
[
"hmm, i'm not sure if there's something that they specifically do but from my own experience in the lab getting my samples sequenced I can tell you the following: the tube they send you is alread sterile and you're going to fill it with your spit so your DNA will probably vastly outnumber the DNA of any errant cells in there. When I used to send my own samples, I sent 10 microlitres of purified bacterial DNA and that seemed to be enough to get a good reading so i imagine a tube full of your spit will also be good enough. They may get some background sequence which is not yours but this will be in the minority compared to how strong the signal from your sequence will be.\nEdit: Yeah, and the blast search as somethingpretentious said! "
] |
[
"What is happening when I push through sleepiness? (x/post from r/answers)"
] |
[
false
] |
Asked this in and was told to bring this here: Just wondering what is happening biologically when I push through a bout of sleepiness. For instance, I take night classes and by about 8pm I'm hit with the drooping eyes and fogginess. But I power through and in about 15 minutes I feel extremely refreshed as if I had actually slept a little bit. What is happening here? How can I feel as if I've gotten any rest at all while through the duration of this mental v. physical battle I am in an extreme haze? Always wondered this. Thanks in advance for any insight!
|
[
"This question is really too personal to answer well. There are many many factors that can result in a temporary reduction in sleepiness. Light has a direct alerting effect. Timing of meals and/or caffeine intake will also affect your sleepiness profile.",
"If we consider the case where all other factors are ostensibly controlled for then there are still a couple of plausible reasons, outlined below. ",
"Typically people think of sleep and wake as whole brain states. However, ",
"recent research",
" shows that parts of the brain can be locally \"asleep\" or \"awake\" when the rest of the brain is awake or asleep, respectively.",
"Local sleep is use-dependent. In other words, brain regions become fatigued from overuse. Constant stimulation of one hand during the day leads to ",
"more intense slow wave sleep in the corresponding region of the somatosensory cortex",
". Conversely, if your arm is immobilized for a day, ",
"the corresponding region of the somatosensory cortex has less intense slow wave sleep",
". ",
"During local sleep, there appears to be ",
"metabolic recovery",
" in these regions. It is therefore plausible that we are able to temporarily rest overworked brain regions by tuning them out when we are otherwise awake. That is still a hypothesis, but it is gaining increasing support.",
"There are two processes that principally regulate sleep: the ",
"sleep homeostatic process",
" and the ",
"circadian process",
". ",
"The homeostatic process is the name we give to the empirical observation that people become increasingly tired the longer they are awake and less tired the longer they are asleep. It is now thought to be due to the accumulation of certain sleep-promoting substances in the brain. These same substances are thought to induce local sleep.",
"The circadian process is due to your body's endogenous circadian clock, which promotes wakefulness during the day and sleep at night.",
"Together, these two processes act in a complementary fashion. Homeostatic sleep pressure is continually increasing across the day. To balance this, the circadian drive for wakefulness also increases across the day, ",
"reaching its peak only a few hours before bedtime",
". This may seem an odd time to have your strongest circadian drive for wakefulness, but it is necessary to fight against the increasing sleep pressure to maintain our long 16-h bout of wakefulness.",
"Consequently, there is a window of time, called the ",
", within which it is very difficult to initiate sleep and where the circadian drive for wakefulness is very strong. For most people, this occurs around the time you are talking about: ~8pm."
] |
[
"How do parts of the brain become \"fatigued?\" Are chemicals used up, or cells or organelles worn out, or what?",
"This is still an open question -- likely, all of the factors you mention are involved to some degree. We know that ",
"ATP levels in the brain decline during wakefulness and surge during sleep",
". We also know that ",
"synapses are pruned during sleep to offset net synaptic growth during wakefulness",
", although there is still ",
"debate over the precise nature of those changes",
".",
"I've also heard it suggested that REM sleep in particular is involved in sort of re-calibrating muscles, and ingraining \"muscle memory.\" Would you agree with this, and if so how does this relate to what you've said already?",
"We know for certain that ",
"sleep is beneficial for the consolidation of various types of memories",
". There have also been some studies purporting to show that particular sleep stages are associated with gains in particular types of memories, insights, or emotional processing. ",
"This",
" is a good, if slightly dated, review.",
"The evidence at this stage is mostly correlational though, i.e., it doesn't prove causality. Performance on various tasks is often correlated with the amounts of each stage of sleep that occurred on the previous night. The problem is that it's difficult to devise an approach that could appropriately test for a causal relationship. Sleep is inherently cyclical, so you cannot independently modify the amount of REM sleep without impacting the structure of sleep as a whole. For example, REM sleep deprivation involves waking participants up every time they enter REM sleep. This has the effect of also fragmenting and reducing the amount of NREM sleep.",
"This has prompted people to look more closely at what the brain is actually doing during these stages of sleep. We are learning more and more about these processes, but it's simply too early to link these findings directly to roles for REM and NREM sleep in consolidation of specific types of memories. It's a question with many extremely astute scientists trying to find an answer, so stay posted on that one!",
"Finally, you talk about accumulating of sleep-promoting substances. What are these, specifically?",
"Specifically, these are known to include adenosine, some cytokines (IL-1 and TNF-alpha), prostaglandin D2, and nitric oxide. ",
"Here",
" is a good review of the topic."
] |
[
"How do parts of the brain become \"fatigued?\" Are chemicals used up, or cells or organelles worn out, or what? ",
"I've also heard it suggested that REM sleep in particular is involved in sort of re-calibrating muscles, and ingraining \"muscle memory.\" Would you agree with this, and if so how does this relate to what you've said already?",
"Finally, you talk about accumulating of sleep-promoting substances. What are these, specifically? I seem to recall reading that adenosine is one (since caffeine is an adenosine antagonist). Would GABA also be included, or is that a more general inhibitory neurotransmitter? Are they all neurotransmitters, or are some hormones, etc.?"
] |
[
"What's wrong with this argument against evolution?"
] |
[
false
] |
: The critical factor in evolutionary change is not actually time. Instead, it’s population size and generational turnover. This is because the requirement is that substantial variability be provided (by population size) and many opportunities for selection to whittle down a generation and act on that variation. This is very important, because it means that what Darwinists claim we can’t see, we actually can see. We can examine what occurs, given a certain amount of evolutionary resources. Malaria has existed on this planet for several millennia, and operates by invading hemoglobin, eating it from the inside out, and destroying it. Its structure is such that it can only survive in very warm climates, however. Given the enormous population of malaria across the planet and the rapid generational turnover- each infected person has billions of malarial organisms that multiply exponentially- malaria Think about that. This is what is supposed to have created the human brain? I suspect there are some fallacies here, or misconceptions about evolution. How would you respond to this person?
|
[
"It's pretty clear that this person doesn't know what they're talking about. \"Malaria\" is a disease, medical conditions can't evolve. The pathogen that causes malaria, and that is capable of evolution is (primarily) Plasmodium falciparum (Plasmodium). Plasmodium doesn't invade hemoglobin, which is a molecule, and hence dozens of orders of magnitude smaller than plasmodium. Plasmodium has a complex life cycle, one stage of which involves living inside red blood cells.",
"",
"Plasmodium has evolved to live within Anopheles mosquitos, and only some of them. In a lot of mosquitos, the host reacts to, and destroys the plasmodium.",
"",
"So the real question is: why have Anopheles mosquitos capable of supporting plasmodium not been able to spread across the globe?",
"",
"So what this authors argument actually boils down to is: If one species is not capable of colonizing the entire earth, then evolution is false. Which is a stupid argument. You might as well argue \"because there aren't polar beers in Africa, evolution is false\". A species is by and large specialized for a specific environment. A species generally, cannot get away with being extremely general, as then in every niche an animal which is perfectly specialized for that niche will perform better, and out compete the general species. So there are mosquitoes that live all over the earth, it's just that the anopheles mosquito is specialized for tropical environments. And a different species is specialized for sub-tropical environments. If an anopheles mosquito formed through mutation that could survive to some extent both in tropical and subtropical environments, it would almost certainly be out-competed by the original anopheles which is specialized for tropical environments and whatever mosquito is specialized for sub-tropical environments."
] |
[
"This is stupid beyond belief.",
"Do you know why there's no malaria in the USA? Because the (precursor of the) CDC ",
"eradicated it in the 1950s",
". That's within living memory. ",
"Malaria used to be a major killer in places like Michigan and Illinois. ",
"Here",
" is a map showing malaria deaths in the US in the 1870s. ",
"The biggest problem with answering these kinds of arguments is that they're so stupid, so ignorant, so bereft of sense, that there's nowhere to start. The small stupidities distract from the larger ones, the little mistakes make it hard to focus on the fact that the big picture is all dingo's kidneys. "
] |
[
"Good answers here but Im just going to correct some other misconceptions. ",
"When it comes down to it, their argument seems to be that because microorganisms can evolve faster (which to be fair is the kernal of truth here) that they should have plenty of time to evolve to be everywhere. Do you see the problem here? Parasites need hosts. Hosts are a limited resource. Parasites need the host to survive for some time so that they can reproduce and spread, so it doesnt benefit them to infect an animal that is already dying from carrying millions of other parasites. So they need to find a niche. If the malaria plasmodium was the only parasite that ever existed it may well have figured out a way to spread in antarctica. But since it is competing with so many other organisms, that alone should make it unsurprising that it does not infect every host in every part of the world.",
"Also, it worth noting that all life came from a common ancestor, relatives of malaria do infect animals in cold regions... they just aren't malaria. If a cold-climate loving malaria did evolve, perhaps it had diverged enough to no longer be called malaria, I suspect the authors of this creationist blog would just argue, but why has the tropical malaria not evolved to infect cold-climate hosts? ",
"Some other points:",
"The malaria parasite doesn't have all that short a generation time, its a few months, not very different to the generation time that the ancestors of humans have had if we go all the way back to the sponge. You'd think they would pick e. coli or something that has a much faster generation time, but then they would have to admit that e. coli is a very adaptable organism....",
"They try to argue that if one lineage is slow evolving (as they argue malaria is) than fast evolving lineages cant exist. This is clearly untrue. Some organisms have not changed all the much over millennia, (say dragonflies, which have been pretty much the same since the start of the Jurassic, and incidentally can have a generation time very close to that of malaria), while others evolved more recently, usually in response to new niches (for example butterflies, which didn't coexist with dinosaurs, evolved to exploit the niche created by the spread of flowering plants)."
] |
[
"If pure energy is a by product of anti matter and matter meeting could we theoretically reverse the process and take pure energy and make it into anti matter and matter?"
] |
[
false
] |
[deleted]
|
[
"There's not such thing as pure energy. It's just not a concept.",
"Matter and anti-matter typically produce high energy photons when they meet. The reverse can happen, for example a gamma ray can interact with a nucleus and produce an electron-positron pair."
] |
[
"Yes, it's called pair production. Check out the beginning of this article:",
"http://astrobites.org/2011/05/21/when-photons-talk-to-each-other/"
] |
[
"Pure energy is not a good phrase, since energy always takes some form. For example, when matter meets antimater, they usually annihilate into photons, which are particles of light. The energy in this case is given by the frequency of the light, or how fast the light wave is oscillating. The higher the frequency, the greater the energy.",
"Another form of energy is kinetic energy, the energy of motion. The faster something is moving, the more kinetic energy it has. The Large Hadron Collider (LHC) at CERN in Geneva, Switzerland regularly converts kinetic energy into matter and antimatter. They take some protons (particles that are inside atomic nuclei), get them moving really fast in opposite directions, and smash them into each other. A lot of different particles can pop out of the collisions, and the energy of motion of the protons is used to make these particles. The particles that pop out are not \"pieces\" of the proton -- they really are particles that have been created from kinetic energy.",
"The reason this is possible is because of Einstein's famous E = mc",
" In this equation, E stands for energy, m stands for mass, and c stands for the speed of light. This equation means that mass is actually just another form energy. The speed of light is there just to tell you ",
" energy is stored in a certain amount of mass. So in LHC collisions, the energy of motion is converted to the energy of the masses of the produced particles.",
"One interesting thing is that virtually every process we know of that can produce new particles always produces matter and antimatter in equal amounts. Yet, the universe, as far as we can tell, is made almost entirely out of matter, with very little antimatter around. Somehow, at some point in the formation of the universe, we ended up with more matter than antimatter, even though we've only ever observed them produced in equal amounts. Nobody thoroughly understands how this happened."
] |
[
"Are man made or artificially triggered earthquakes possible?"
] |
[
false
] |
[deleted]
|
[
"Here",
" is an article on NBC discussing a possible link between sixteen earthquakes in Texas in November and fracking. Fracking, or ",
"hydraulic fracturing",
", is the injection of water in to a wellbore with the intent of creating fractures in rock to extract something, frequently natural gas.",
"And ",
"here",
" is a literature review published in ",
" detailing the ridiculous number of injection-influenced earthquakes and physics behind them."
] |
[
"In theory there are ways to induce earthquakes, changing the stress state or changing pore pressures (which can influence the stress) in an area of the crust near faults or fractures can cause small earthquakes. Earthquakes related to these are almost always byproducts of human activities, e.g., filling reservoirs or pumping fluids into the ground. There are a lot of problems with using this for \"prescribing\" earthquakes. The first problem is that we don't know the details of how to modulate the use of things like fluid injection to cause earthquakes. Even if we did, the chance of producing an earthquake large enough to be meaningful in terms of the stress build up along a fault line is not likely. There are lots of resources online for understanding the relative differences in the amounts of energy released during different magnitude earthquakes, but the key is that it takes a huge number of small earthquakes to equal a single large magnitude event. Finally, the real issue is that even if we knew how to generate a large magnitude earthquake on a fault, it would likely not have the desired effect, i.e., mitigating risk. When an earthquake occurs, it does release stress built up on that fault, but it also loads (adds stress) to other nearby faults. Major fault systems are almost never a single fault, so even if you were able to release stress on the main strand, this could load other faults in the area (including ones we don't know about) and simply move the hazard somewhere else. Best bet is preparedness in areas where seismic risk is high, characterization of faults that could produce an earthquake, and work on early warning systems like the one they are developing in Japan to alert people when an earthquake is first happening."
] |
[
"Well we use earthquake monitoring systems to detect underground atomic detonations. Just like those that occurred when North Korea tested their bomb. So technically that is an earthquake that it is detecting. ",
"It is not beyond the realm of possibilities that a well place nuclear explosive could help a major fault line to slip causing a major earthquake. Only challenge which faults are already on the brink of slipping and only need the push over the edge. "
] |
[
"Waking up in the morning: Why is it that when I sleep outdoors I'm able to wake up bright and early feeling refreshed?"
] |
[
false
] |
Furthermore, why is it that when I sleep for a full 9 hours I still feel crappy when the alarm rings? I know it has to deal with your sleep cycles, but how are these sleep cycles influenced by external factors (light, sound, temperature)? Edit: Thanks for all of the great information! I suffer from sleep phase disruption, which essentially means my circadian rhythm has gone off the deep end. But whenever I sleep outdoors, I find that I fall asleep easily at nightfall and wake up refreshed in the morning. I was just wondering if there was any way to bring whatever factors exist outside into my bedroom.
|
[
"You know, that is very interesting. I'm sure I know the answer:",
"So the pineal gland in your brain is very involved in your circadian rhythm (biological clock), and it produces and secretes melatonin which is a chemical that basically makes you sleepy due to a pathway I won't explain. Anyway you can buy it in the vitamin store to help you sleep.",
"The production of melatonin is stimulated by darkness and inhibited by light. Perhaps you were in more direct sunlight when you woke up since you were outside, and your pineal gland was better able to respond to light, inhibiting the melatonin, thereby bringing you steadily and clearly out of sleep and allowed you to wake up faster (ie start increasing body temperature and blood pressure and levels of the hormones responsible for this).",
"Here's more info on the pineal gland: ",
"http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/otherendo/pineal.html"
] |
[
"You can buy alarm clocks which try and emulate this by having a light that gradually gets brighter until the alarm clock goes off. But how well they work is up for debate.",
"http://www.amazon.co.uk/Philips-HF3485-Wake-up-Light-Playback/dp/B0044YO9BE/ref=dp_ob_title_hpc",
"Is an example of one."
] |
[
"Sleep with the curtains open."
] |
[
"Given sufficient computing power, how accurately could we theoretically predict how an organism would look and act based solely on a genome?"
] |
[
false
] | null |
[
"You're asking if we can predict the phenotype of an organism just from its genome. There are basically 2 ways to go about this. A ",
", from first principles simulation of the genome and its products OR by homology where we would match the genome (information) content to other genomes we know.",
"The homology method would be pretty accurate indeed. This is the core technology which underpins much of modern molecular phylogenetics. If you gave me a genome and an afternoon I could tell you what genus the genome belongs to and from there we could work out which species it is closest too and we could make good first order approximations of the phenotype and appearance of the organism. For eneterobacteria we could tell you quite specifically which biochemical pathways are present or not with very good coverage.",
"For the ",
" simulated method we would do a very, very, very bad job of estimating the phenotype of an organism purely from the information contained in the genome. A genome produces 1000s of products (proteins, mRNAs, tRNAs, snRNAS etc...) these have very, very complex non-linear interactions and only a few of these are well understood across all of life (enterobacteria and experimental mammals have good coverage). Small changes in any of those components can lead to profound changes in phenotype outcome. We also don't have a very thorough understanding of how changes in the genome map to changes in the structures of proteins and RNAs, this means small changes in the genome content are often not well modelled at the protein/RNA structural level (this is the domain of protein engineering)."
] |
[
"This is a very clear and understandable answer, thanks for the detailed response. "
] |
[
"Just to add to this, there is a distributed computing project that uses hundreds of CPU years of computation just to see how a specific protein folds. We are no where near the level of cpu power it would take to create a true simulation that reflects reality."
] |
[
"Why can't we pair a bluetooth device with two others simultaneously ?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"guidelines.",
"You can find the basic answer with a google / wiki search. Please start there and come back with a more specific question.",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"How on earth is my question hypothetical ????"
] |
[
"You're asking about capabilities Bluetooth does not have, thus a hypothetical function & design."
] |
[
"Why is the force of gravity taught as a constant, e.g. -9.8 m/s², when Newton's law depends on the distance?"
] |
[
false
] |
For that matter, wouldn't any inverse-square law force depend on the radius?
|
[
"The -9.8 m/s",
" refers to the acceleration due to gravity near the surface of the Earth, not the acceleration due to gravity in general.",
"In fact this arises from the inverse square law and the fact that the Earth is so much larger than the distances we typically move. The acceleration 9.8 m/s",
" is the value of the expression GM/r",
" where G is the Newtonian gravitational constant 6.67 x 10",
" N m",
"/kg",
", M is the mass of the Earth, and r is the distance to the center of the Earth. Since over typical human scales, our distance to the center of the Earth barely changes (going up or down 100 meters is irrelevant on scale of thousands of kilometers), the acceleration due to gravity near the surface of the Earth is essentially constant."
] |
[
"Calculate the difference in potential at the two points and set that equal to the kinetic energy of the object."
] |
[
"Exactly what my teacher told me a year ago and what we use for solving sums at the high school level. Although the value of g depends on the latitude, the largest difference on the surface on the earth is only 0.05 m/s",
" between the equator and the poles which isn't considered significant enough unless absolutely essential for precise calculations."
] |
[
"If pushed, would a frictionless marble roll across a surface or glide?"
] |
[
false
] | null |
[
"If it was pushed in-line with its center of mass it would glide, and if it was given some torque as it was pushed it would have a rolling component, but it wouldn't roll without slipping, which is what most people mean when they think of rolling."
] |
[
"To create force you need a force at a distance. In a frictionless sphere, all force is neccessarily applied normal to the surface, this pointing toward the geometric center of the sphere. To get rotation, you simply need a sphere which has a center of mass that doesn't align to the geometric center. To do that, you need a non-symmetric material density... which I assume is common because of the fancy designs (though perhaps very small, even the colored glass is still glass).",
"Edit: Similarly, with a marble that isn't a perfect sphere, you can apply normal force which isn't at the center of mass. I assume that the design tolerance for geometry is very high though (perhaps the material composition as well, but I'd assume a bit less so)."
] |
[
"Frictionless bodies in a continuous fluid are well described by potential flow. In potential flow, there is no force tangential to the flow (i.e., drag), and, in fact, friction must be accounted for to have a force normal to the flow (i.e., lift). That leads to one of my favorite facts about the world: minimizing drag is very important for airplanes, but eliminating it entirely would make them unable to fly."
] |
[
"Why don't soft drink companies use Oxygen as their fizzing gas?"
] |
[
false
] |
I understand that it would introduce a higher risk of fire, and the possibility of law suits about oxygen poisoning, but it seems as if a drink that made you feel alive and energised would sell very well despite this.
|
[
"Actually at 25oC and 1 atmosphere pressure:",
"Solubility( ",
" 2) = 8.27 mg/l",
"Solubility( ",
" 2) = 1450 mg/l",
"So Carbon Dioxide is ~175 times more soluble than Oxygen at SLC (Standard Laboratory Conditions)"
] |
[
"Who says it would make you feel alive and energized? The body doesn't take in oxygen from the digestive system. The risks associated with the cost, storage, and transportation of oxygen in relation to co2 definitely outweighs any benefit that ingesting oxygenated water might have.",
"Also, CO2 is practical because of its solubility in water. CO2 is more than 3 times as soluble in water as oxygen is. If some company were to try and \"carbonate\" their soda with oxygen, it would take a lot of work to keep that oxygen in there.",
"http://www.ehow.com/about_5439234_oxygenated-drinking-water-pros-cons.html"
] |
[
"Well of cause there are a lot of drinks where the CO2 isn't added but produced as a side product in the production it self (e.g. beer, cider...)\nBut I guess you are going for Coke and other softdrinks, so:",
"I couldn't find a graph showing what my thought was, but I could imagine that the difference in solubility might be a lot bigger for CO2 from let's say 1.5 to 1 bar.",
"So when opening the bottle, and thereby dropping the pressure, there will be more fizz.",
"I can tell you for a fact that you can dissolve like 200 times more CO2 than O2 in water at 20 °C (8 mg/l and around 1700 mg/l)",
"Other than that, Co2 has this slight sour, prickleing taste (O2 hasn't), and it is dissovable enough that a human can taste that too.",
"I hope I could be of help :)"
] |
[
"[Sponsored Content] - How does Quantum Healing regulate our Aura and remove toxins?"
] |
[
false
] |
I know my body is entangled between states of sickness and health, but how do I perturb the Hamiltonian such that I'm more likely to be measured in the healthy state?
|
[
"You should buy this ",
"hexagonal water",
". It heals the Devil away and brings Jesus into your soul."
] |
[
"The basis of Quantum Healing is only recently understood by Western Scientists, while the ancient Chinese understood it for thousands of years. Our Western Scientists have called this the ",
"Delayed Choice Quantum Eraser",
". ",
"We begin by entangling neutrinos and accelerating them faster than the speed of light (as ",
"CERN discovered was possible",
" ). We then pass half of the neutrinos though your body, and measure the health-spin of the other particles. By using a quantum eraser, we are able to erase all of the particles we measure as healthy (since they are entangled, we know all of the ones we measure as spin-healthy, their pair will be measured as spin-sick). Thus, we erase all of the sick neutrinos passing through your body, ensuring you are blasted only with healthy ones. It is important that the neutrinos are superluminal, otherwise the wave-function would collapse before we could erase them. "
] |
[
"Aura's aren't real science. Why is this in ",
"r/askscience",
"?",
"The only thing that's proven to heal your body is ",
"aligning your chakras",
" with chiropathy."
] |
[
"How does the theory of relativity make sense at all?"
] |
[
false
] | null |
[
"See:",
"https://en.wikipedia.org/wiki/Time_dilation"
] |
[
"\"Continuous\" just means that it doesn't have quantized, discrete units. Time being continuous doesn't mean that it can't be relative depending on observer.",
"I recommend you to read one of the many introductory sites about time dilation. Something like ",
"this",
", for example. Or, conversely, what don't you get about ",
"the Wikipedia explanation",
", which derives time dilation from the simple postulate of speed of light being constant in all reference frames?"
] |
[
"\"Continuous\" just means that it doesn't have quantized, discrete units. Time being continuous doesn't mean that it can't be relative depending on observer.",
"I recommend you to read one of the many introductory sites about time dilation. Something like ",
"this",
", for example. Or, conversely, what don't you get about ",
"the Wikipedia explanation",
", which derives time dilation from the simple postulate of speed of light being constant in all reference frames?"
] |
[
"Do sound waves from instruments travel the same in zero G?"
] |
[
false
] | null |
[
"Sound waves are not significantly affected by gravity."
] |
[
"If you mean that you couldn't hear him playing his guitar, it has nothing to do with being in space, just that they haven't recorded it, or haven't put it into the edit.",
"There is no reason why sound would not travel without gravity. Sound is pressure waves in air (or any matter). So as long as you have air between your ear and the source, or physical contact, so that the wave can reach your ear, you will be able to hear something, no matter what the source is.",
"That being said, most places with no (or minimal) gravity don't contain a medium through which sound can travel. i.e if you were out in the middle of space, playing a guitar, you would not be able to hear it."
] |
[
"You say you \"will be able to hear ",
", no matter what the source is.\" Will this sound be distorted or sound clearer/muggy?"
] |
[
"Would a boat float on top of a large ball pit? What are the major factors impacting the question?"
] |
[
false
] | null |
[
"It's not about the relative size of the the objects (quantization). The problem is that the balls have a very low kinetic energy compared to their inter-ball friction. It wouldn't matter if you had an enormous thing the density of air covered in balls, it still would not rise because the apparent viscocity of the balls would be too large. Now if you increased the kinetic energy of the balls by shaking the pit, even a smaller light object would be pushed to the top so long as it's size was larger than the average ball path length or so."
] |
[
"Not in the sense you're thinking. Objects float in liquids because the upward pressure exerted on the submerged portion is greater than the downward pressure + force of gravity. It works out that the amount of fluid displaced must have greater mass than the object in question.",
"This alone would be achieved by any object of less density than the balls, but the object must then be lifted enough to allow more of the fluid to slip underneath and continue to support the object. In the case of the ball pit, the medium consists of \"particles\" several inches in diameter. In water, it's on microscopic scales. If the object were large enough, it might work out, but you're looking at an object that with current materials would collapse under its own weight."
] |
[
"You have to make it really lightweight to have a density lower than the ballpit. You can put it on top and then not move anything around, that will work (unlike with an actual liquid)."
] |
[
"How large if a role does genetics really play in obesity?"
] |
[
false
] | null |
[
"One way scientists can figure out how much effect genetics vs. environment has an affect on a trait is to compare that trait between identical twins (individuals with identical genomes) who were raised in the same household, and identical twins who were raised in separate households. ",
"Scientists in this ",
"study",
" found BMI was 70% correlated male twins and 66% correlated for female twins raised apart. Meanwhile, twins raised together show 74% correlation in BMI for males and 69% correlation for females. ",
"These numbers are specific to this study, but the authors firm take-away is that genetics plays a ",
" role in BMI. "
] |
[
"Although it will be different for each individual, genetics do play a role in obesity to an extent, but calorie intake and exercise will still play a huge role in obesity. The paper below gives an example of how genetics can influence obesity. A certain allele of the FTO gene is implicated in obesity by disrupting a repressor causing IRX3 and IRX5 to be expressed at higher levels causing a shift from energy-dissipating beige adipocytes to energy-storing white adipocytes, with a decrease in mitochondrial thermogenesis and an increase in lipid storage. So the person will burn less fat and instead store it. ",
"https://www.nejm.org/doi/full/10.1056/nejmoa1502214"
] |
[
"I'm actually studying to be a personal trainer and here's a quote from my textbook:",
"\"Even though heredity influences physical fitness and health, everyone can lead a healthy or unhealthy life regardless of genetic makeup. It's not possible to establish the relative portion of an individual's health or fitness that is determined through heredity. Therefore, genetic background neither dooms nor guarantees success in achieving total fitness.\" "
] |
[
"Is it possible for pi to take on different values when moving at a relativistic velocity?"
] |
[
false
] |
In my class on special relativity we never considered rotating objects and it got me thinking. If a disk is rotating at a relativistic velocity, then the outer edge with be Lorentz contracted relative to the centre meaning the circumference of the disk will be less than 2piR. However the disk won't be contracted in the radial direction, which would mean that pi is less than 3.14. I don't see any error in this. Does this make sense? If I'm right, can this happen to other transcendental numbers like e? What would a circle even look like in a rotating reference frame?
|
[
"Pi is defined as the ratio of circumference to diameter of circles in a specific geometry (namely, the Euclidean one). It's not relevant to pi what shenanigans circles may get up to in other geometries. Your circle has a different ratio, possibly, but the connection to pi is flawed.",
"An idealized human has two arms. Some have one. That does not make two sometimes equal to one."
] |
[
"The circumference of a circle rotating with constant angular velocity as measured by a co rotating observer is",
"C' = C/γ",
"Where C is the circumference measured at rest. Straightforward application of Lorentz contraction.",
"The issue is, as you pointed out, the radial direction has no contraction. The resolution to this apparent paradox is that space time is non-Euclidean, in which case this is no longer a paradox. We don't expect the ratio between the circumference and diameter to be the same (or even constant) in non-Euclidean geometry.",
"Also note that the edge of the circle is experiencing a centrifugal acceleration. By the equivalence principle, we know that it's thus the same as an object subject to a gravitational field such that the gravitational acceleration is equal to the centrifugal one. Gravitation causes space time to warp, so we definitely should ",
" a significantly non-Euclidean character, and that's exactly what we get.",
"Edit: math"
] |
[
"C/2γR = pi",
"C is the rest circumference, R is the radius, γ is the Lorentz factor for the tangential velocity component v. More compactly, of course,",
"pi/γ = pi",
"Edit: math."
] |
[
"How do scientists know that ancient hominid fossils are a different species and not just a strange unique example of one individual early man?"
] |
[
false
] |
I am mostly asking about hominid and "early man". I see a ton of diversity these days. How can scientists know that the body types they find, the size of hands, brow, forehead, etc... How can they say "oh that's a different species" and not just "oh this one had strange tall shoulders", you know? I'm talking like a million years ago where the genius homo popped up.
|
[
"It really comes down to process of elimination. Forensic Anthropology Is the study of human skeletal remains. By having a skull/skeleton you can tell a lot of different characteristics in modern humans. Such as ethnicity, gender, age, and even how they died in some cases. The skull is usually the most prominent give away to what type of hominid it was(ie: brain size, brow size, eye shape/front facing, cheek bones, how thick the skull is) Finding tools with the bones gives an indication of brain capacity(which can also indicate what they ate). Sometimes other animal bones are discovered with the hominid remains which gives an indication as to how they died/what they ate/time of existence. Bipedalism is a huge identifying characteristic. Carbon dating the bones helps give a estimated date, how deep the bones were found. Where the bones were found geologically is a big one. You can tell if there were rituals to mourn the dead. All of these combined give you a reasonable hypothesis as to which hominid it could be. ",
"Not having a full skeleton makes it more difficult to narrow down since a lot of these hominids lived at the same time as one another. I’m sure I’m missing some indicators, but these are the most popular because they are the easiest to see. They even use cgi to remake the organism to give a possibility of what it looked like. It’s no easy task to decipher the bones and some don’t fit in. ",
"When new remains are uncovered and brought back to a lab, teams of anthropologist discuss the similarities and differences. They then decide whether it was a certain hominid that has already been discovered or a new one. ",
"I’m not an expert, just someone that is interested anthropology. if someone has a better explanation I would like to be enlightened as well. "
] |
[
"For one thing, we've got hundreds of specimens of varying levels of completeness at this point. For another, the differences in bone structure are much greater than the variation we see within humans today. You don't see many people walking around with brains a third the size of everyone else and jaws protruding almost as much as chimpanzees. These differences are also consistent across different specimens from the same place and time period. It would seem very likely that we've found hundreds of unusual individuals but no normal people, and that their consistently unusual in ways that have changed through time."
] |
[
"We have DNA from Denisovans and that’s the only way we were able to determine that they are a different species, for example.",
"Also your link discusses DNA from African humans. It’s much more challenging to get DNA from Africa than other parts of the world since it’s warmer and there are no glaciers."
] |
[
"I've found what looks to be a glow in the dark microbe in my laundry room. Google hasn't given me any leads."
] |
[
false
] |
[deleted]
|
[
"When you say: \"The place in question has not seen water in months\", do you mean it is as dry as could be or could there be growing a mold.",
"A group of tropical slime molds is known to be bio-luminescent [1]. But without pictures it is very difficult to do anything more than speculate. I am also not to sure about the golden glow.",
"[1] H. Weitz, ",
", FEMS microbiology letters 2001 ",
"PDF link"
] |
[
"Can you link a picture?"
] |
[
"Laundry detergent contains ",
"Optical Brightener",
" agents that phosphor to make clothes look whiter. But they seem to cause more of a bluish glow than a golden glow."
] |
[
"Can scientist predict volcanic activity and why hasn't anything like Pompeii happened recently and how long after an eruption does a place recover?"
] |
[
false
] |
[deleted]
|
[
"Can scientists predict a volcano eruption, and if so how soon can they do it and how?",
"To some degree yes. It isn't perfect, but scientists can monitor pressure changes and earthquakes to tell when a volcanic eruption is imminent. Of course, sometimes they miss something and sometimes they predict an eruption that doesn't happen, but every time they do they understand it better. Volcanoes are typically very well studied, so at this point an unexpected eruption is unlikely.",
"Why has there not been any crazy volcanic activity like what you read about with Pompeii, etc.?",
"There has been. At the moment ",
"Hawaii in in the middle of an eruption",
". Hawaii does benefit from the fact that the area near the active volcano is relatively sparsely populated or else the damage would be much worse. It also benefits from the fact that Kilauea is a very well studied volcano so they knew about the eruption coming and evacuated the area.",
"A more damaging eruption happened a few years ago when ",
"Eyjafjallajökull",
" erupted. The smoke cloud was bad enough that all air traffic in Europe had to be shut down. Again, scientists noted early warning signs and people in the immediate vicinity were able to evacuate so there was little loss of life.",
"A rather famous eruption happened in the continental US in ",
"1980",
". Again, there were signs ahead of time so the loss of life was minimal, but the eruption did cause over a billion dollars in property damage.",
"If you want an example of a recent eruption with large loss of life, you can look at ",
"this eruption in 1985",
" which killed tens of thousands.",
"How long does it take an area to recover/become habitable after a volcanic eruption?",
"It starts happening before the ground finishes cooling. There are several plant species that specialize in taking advantage of land cleared by forest fires. Depending on the type of eruption, a volcano is even better than a forest fire because the ash can make for very fertile soil. It can only take a few years for a forest destoryed by a volcano to return, though there will be definite signs in the species diversity of a recent destruction. Slow lava flows like the Kilaeua eruption take longer because the ground will be covered in rock rather than ash, but there are plants which can take advantage of it. I would expect a couple hundred years before it returns to full forest."
] |
[
"The ",
"Montserrat eruptions",
" starting in 1995 were pretty destructive, but only killed 19 people because they were able to evacuate the island."
] |
[
"1) They can forecast eruptions, not predict them. They can say that an eruption is likely within a certain span of time. For example, the Cascades Volcano Observatory might say that it's a fair bet that in the next 100 years, one of the Cascades in the western United States will erupt. In early May 1980 they were warning that an eruption from St. Helens was likely within weeks. A week ago they were warning that an eruption could occur somewhere in the East Rift Zone on Hawaii within days.",
"2) Vesuvius 79 was a VEI 5 eruption. Those happen almost every decade. They're not exactly common but not rare either, and while notable, they really aren't that big. The reason it killed so many people was proximity and unfamiliarity with the hazard it represented. The same was true for Mt. Pelee 1902; it was weaker than the Vesuvius eruption, but still killed 30,000 people in a similar manner, in a matter of minutes. Again, it wasn't the eruption itself, it was the location of the town and the unfamiliarity with the hazard that enabled so many deaths. These outcomes are unlikely today because that particular hazard is well understood now, and people can be evacuated beforehand.",
"3) Depends on the type of eruption and the cultural factors at work. Lava flows and pyroclastic flow deposits can retain heat for years, but when Goma, DRC was flooded with lava in 2002 some of the affected areas began to be resettled within weeks. This was largely due to the massive population of refugees and the scarcity of space for housing. It is now difficult to see the area of the flow within the city on satellite imagery. Armero, Columbia, which was inundated with mudflows in 1985, has never been rebuilt, despite the relative ease of resettling the floodplain. Often the biggest reason a place might take a while to be resettled is that the eruption persists for decades, as is the case on the island of Montserrat (and as ",
" be the case on the SE coast of Hawaii; the homes currently threatened were built in line with and between vents of a volcano that's been erupting since 1983). And finally, if an island or landmass simply disappears due to an eruption, that's obviously more difficult to recover from."
] |
[
"What does askscience say about the argument presented in this article? Deconstructing Nuclear Experts"
] |
[
false
] | null |
[
"What arguments? It's mostly just a load of mud-slinging. Psychologists aren't scientists. \"Physicists are stupid\" - I mean, seriously. As for the the few-and-far-between things resembling actual relevant information, I'll just comment on that cancer study from \"Lynkoping [sic] University\", about cancer rates in Sweden. Since I know about that particular study. Which is that it's was pretty roundly criticized, including by the Swedish Radiation Safety Authorty (which has been studying the after-effects of Chernobyl very closely). They alleged the cancer cases in the study occurred too soon to be attributable to Chernobyl, and also that the study didn't factor in lifestyle differences. In short, there have been a lot of studies pointing to negligible effects and none supporting that one. ",
"Yet.. the author then concludes from that study that:",
"there was an 11% increase in cancer for every 100kBq/sq metre of contamination. Since the official International Atomic Energy Agency (IAEA) figures for the Fukushima contamination are from 200 to 900kBq.sq metre out to 78km from the site, we can expect between 22% and 90% increases in cancer in people living in these places in the next 10 years. ",
"That's just retarded. Bequerels is the number of decays per second. It makes absolutely ",
" sense to compare health risks on the basis of that without any consideration of which actual isotopes you're talking about. The author doesn't specify, and as far as I know, neither did the IAEA. So why would those numbers be comparable? Also, there's no justification to believe the cancer risk would scale linearly either. That's just a wild guess, and not necessarily a good one, given how complex cancer is.",
"It's just biased propaganda and mudslinging. Even if you're against nuclear power, it should be obvious if you ask me. Although I suppose a site that declares \"Why the Entire Nuclear Industry is Insane, Then, Now and Forever\" right at the top of the page can hardly be expected to provide unbiased information. I mean, if you've already decided that not only is the nuclear industry \"insane\", but that it cannot possibly be otherwise, then you've pretty much precluded any rational debate. "
] |
[
"There are claims that reactor 3 at Fukishima is cracked, that plutonium has been found in the soil, the the spent fuel tanks are exposed to the air and burning, and then there are counter-claims. ",
"Are any of those points in doubt? I think everyone agrees those things have happened, people only differ on their assessment of health impact and on whether nuclear power should be pursued."
] |
[
"The article uses rhetoric that's not credible; however, some of your rhetoric is also suspect:",
"If so then why is no one freaking out about coal power plants",
"This is irrelevant, just a rhetorical diversion. It's like saying, \"why are you upset about this nasty car wreck, when there are other nasty car wrecks?\". It's also suspect because the nuclear industry is in competition with the coal industry.",
"You could step outside tomorrow and die because a meteorite crashed down and hit you. ",
"The meteorite comparison is suspect because there have been at least 3 serious nuclear accidents in my lifetime (Three Mile Island, Chernobyl, & now this), and the first two, at least, had quite serious consequences. We still don't know what the consequences of this disaster are going to be. So, these events aren't so rare as someone being hit by a meteorite.",
"they basically survived a magnitude 9 quake as well as a tsunami",
"No, they didn't. Are you out of your mind?",
"The experts are decided on this issue.",
"Not all experts are in agreement; to say that they are is misleading.",
"So, it would see you also have an agenda. "
] |
[
"I learned in University, that photons are released by electrons that are decreasing in energy. So how do neutron stars emit light?"
] |
[
false
] | null |
[
"Atomic transitions are not the only way that light can be produced. Any particles which interact with the electromagnetic force can emit photons, in various different physical processes."
] |
[
"So specifically for neutron stars, I would assume that the neutrons interacting with the magnetic field of the star causes photons to be emitted? If you wouldn't mind explaining what this process is that'd be helpful."
] |
[
"Neutrons have magnetic dipole moments, so they can undergo electromagnetic interactions that release photons. An example would be a neutron flipping its spin direction in an external magnetic field, and emitting a photon."
] |
[
"If light wasn't dispersed or warped by anything, would our night sky be pure white from the light of every star showing full strength?"
] |
[
false
] |
[deleted]
|
[
"Depending on what you have in mind, these previous discussions might be relevant:",
"http://www.reddit.com/r/askscience/comments/lweu4/why_isnt_the_universe_bright_everywhere_all_the/",
"http://www.reddit.com/r/askscience/comments/elfbc/olbers_paradox_a_thinking_excercise/",
"http://www.reddit.com/r/askscience/comments/k6pdf/why_is_space_black/"
] |
[
"But light ",
" dispersed by something - the inverse square law of propagation. You can't assume that doesn't happen without breaking all sorts of laws of physics/mathematics, at which point the answer you get is meaningless.",
"If light wasn't dispersed, magically, then each star would shine light on you no different than if you were standing an inch away from it. So you would vaporize. But again, a universe like that makes no sense.",
"Other dispersive factors (particles in space, red shift of our expanding universe) are pretty negligible in the strength of a star's brightness, save perhaps for stars in dense nebulae (in which case I can't tell you how their intensity is impacted)."
] |
[
"Cool, I guessed right! No prob :)"
] |
[
"Are there any \"rock-paper-scissors\"-genes?"
] |
[
false
] |
I'm in my last year of high school, and learning about genetics. So far, we've covered dominant and recessive genes, as well as codominance and such. Are there any genes where the alleles dominate each other like in a game of rock-paper-scissors?
|
[
" No, but side-blotched lizards effectively demonstrate the same 'rock, paper, scissor' gene dynamics at the population level.",
"Are there any genes where the alleles dominate each other like in a game of rock-paper-scissors?",
"Hmmm, I have a 'sort of' answer! Though perhaps not mechanistically at the molecular or cellular level, there's certainly one pool of alleles operating in a 'rock, paper, scissors' fashion via behavioural dominance at the level of population genetics in the ",
"side-blotched lizards",
".",
"Side-blotched lizard sex is weird. There are three male 'genders', and two female, with the males grouped into those with ",
"blue, orange and yellow-striped colouration",
" respectively. Orange lizards are large and aggressive, attracting many females by defending territories. Blue lizards are smaller and hold small communal territories, guarding individual females closely. Yellow lizards don't hold their own territories, but pretend to look a bit like females, milling around the edges of the dancefloor and occasionally sneaking in a cheeky bang with a female when the territorial lizards aren't looking.",
"How it works is that, over the course of several generations, when there are more:",
" larger orange lizards physically push blue lizards out of their territories, expanding their domain and mating with more females, thus increasing the number of orange offspring in the population.",
" with more orange lizards, there are more large territories for yellow lizards to exploit. An orange lizard cannot guard his entire territory all of the time, so sneaky yellows are increasingly able to mate more often, increasing their numbers in the population - and decreasing the proportion of orange offspring.",
" now with fewer orange lizards, blues are able to regain their numbers. Blues, who live communally and guard individual females, are better able to protect females from sneaky yellows, thus yellows mate less and the blue population increases.",
"And then rinse-repeat with the orange lizards...",
"So overall, here we have a number of alleles involved in generating the respective orange, yellow and blue phenotypes, exhibiting 'rock, paper, scissor' style dynamics at the population level: blue genes > yellow genes > orange genes > blue genes.",
"However, and here comes the 'sort of', despite exhibiting those dynamics at the population level, the entire system is based upon a single Mendelian factor with three alleles, which operates differently. The orange ",
" allele is dominant over everything, and the ",
" allele is recessive to the ",
" allele. As such, orange lizards have the genotype ",
", ",
", or ",
", yellow lizards have ",
" or ",
", and blue lizards are exclusively recessive with ",
". So it doesn't quite fit your question!",
"Barretto ",
" (2017) have successfully modelled an allele system exhibiting the 'rock, paper, scissors' dynamic, suggesting it's at least theoretically possible, but as far as I'm aware we haven't found it at the gene-level in anything so far, only population genetics. But I could be wrong!",
" ",
" ",
" ",
" ",
" "
] |
[
"Cool question. It could only occur in a multi-allelic locus (in this case, multi means more than two). It is callled circular dominance and is an alternative to hierarchical dominance (also called serial dominance) - where, as you might, expect there is one most dominant allele, followed by an allele that is dominant over all other alleles except the most dominant, followed by an allele that is dominant over all others except the first two, etc. As far as I know (I am an evolutionary geneticist but not entirely comfortable saying I know for sure), circular dominance is purely hypothetical, for example here ",
"https://www.ncbi.nlm.nih.gov/pubmed/28385667/",
". That said, I can imagine a scenario where a multi-allelic locus has incomplete dominance and can by chance appear as having circular dominance, especially if that locus interacts with other loci (a process called epistasis, which is quite common). I do know of an exciting phenotype that has rock-paper-scissor dynamics: side-blotched lizards have three differently collored male morphotypes and they compete with one another and have dominance hierarchies in a rock-paper-scissor type order (also referenced in the paper about circular dominance). I don’t think there is full understanding of the genetics behind this three color morph phenotype. There are also three male mating morphs of the ruff, a bird, which have sort of rock-paper-scissor dominance but in this case the genetic mechanism at play is a large chromosomal inversion (I guess this is where it gets well beyond high school level genetics..). "
] |
[
"Nitpicky point: The morphs are named based on the throat colors. The blotch in the species name is actually a black spot near their armpit.",
"Ahhhh, thanks for the correction! ",
"Why there's no female blue-throat. Any idea why that is?",
"Good question; technically there are! The ",
" allele is floating about happily within female genotypes, but the colouration doesn't really manifest itself as side-blotched lizards are sexually dimorphic, with females (with exception to orange females) displaying muted colouration compared to males, particularly blue. It seems that female colouration is so non-distinct, it's near impossible to distinguish between ",
", ",
" and ",
" females.",
"Furthermore, female phenotypes are categorised differently to males because their sexual behaviours don't split themselves across the three alleles. Unlike males, they aren't governed by a 'rock, paper, scissor' strategy; rather, it's absence or presence of the orange ",
" allele that determines their breeding behaviour - orange females produce lots of small eggs (",
"r-strategy",
"), whilst non-orange females invest heavily in fewer, albeit larger eggs (",
"k-strategy",
").",
"In short; we distinguish females based on their parental strategies, so there's orange, r-strategists and non-orange 'yellow' k-strategists. It just so happens that blue females behave and ",
" look identical to yellow that we just lump 'em in together. Hence only two female forms!",
" ",
" ",
" ",
" "
] |
[
"What exactly happens to a person's behavior after a lobotomy?"
] |
[
false
] |
[deleted]
|
[
"Because a lobotomy is such a crude, destructive procedure, i don’t think there is a single straightforward answer. The tool used for the procedure could potentially cause all different forms of damage to the brain, though it seems it would be primarily the formal lobe that is affected. So it makes sense that we typically associate a lobotomy with reduced intellect and emotion, but those features could be affected in a whole range of ways. ",
"Hopefully someone more qualified comes along with a better answer, but thought I’d throw my $.02 in as a 5th year psych student since nobody else has answered "
] |
[
"I think you've covered it pretty well as to my understanding. Technically lobotomies \"reduced symptoms\" of mental illness but really just in the same way extreme sedation \"treats\" mental illness. Lobotomies also caused epilepsy, problems with inhibition and of course physical issues with the procedure (infection etc)"
] |
[
"It depends on the part of the brain that's removed as well as the age of the person in question. ",
"There's a woman who had her entire right brain hemisphere removed to help with encephalitis (she's now an MS and a speech pathologist)",
". She was young enough (7 years old) when the procedure was performed that you would never know that she only has half a brain now. It also helps that she had her right hemisphere removed instead of her left because the left is more essential for language development, but we can't be sure she wouldn't have been able to bounce back from a left hemispherectomy as well."
] |
[
"What causes musical chills?"
] |
[
false
] |
It seems in particularly emotional or moving parts of music most people tend to get chills throughout their body. What causes this?
|
[
"We have a subreddit for this!",
"http://www.reddit.com/r/frisson",
"Also a good article: ",
"http://arstechnica.com/science/news/2011/01/turns-out-that-music-really-is-intoxicating-after-all.ars"
] |
[
"Thank you!"
] |
[
"This is more related to why music has an emotional impact, but it goes into depth about what specifically causes a physical reaction in the body.",
"http://online.wsj.com/article/SB10001424052970203646004577213010291701378.html?mod=rss_Health"
] |
[
"Why does the hair of some children who were born blonde darken over time?"
] |
[
false
] |
When I was born, I had blonde hair. By the time I was five, my hair had gradually become very dark brown. I've seen this happen with many other children, too. Why was my hair not brown when I was born? What causes this change?
|
[
"Previously asked here ",
"http://www.reddit.com/r/askscience/comments/njgq4/why_was_i_born_with_blonde_hair_that_fell_out_and/",
" ",
"TLDR - different genes are expressed at different stages of one's life and factors such as disease and nutrition can affect gene expression. "
] |
[
"So in theory could you take some sort of pill to change your hair color? "
] |
[
"\"In theory\" is a tricky word here. So far, No, no pills can completely alter your genetic makeup, and this feat will likely be impossible for a while. The pill would need to have things like transcription factors that promote or repress specific gene expression, which will then dictate which proteins are made, where, how much, etc in response to your DNA sequence for an allele (i.e. hair colour). I've read an article about a potential pill that is supposed to target the trichohyalin gene (gene that determines level of curliness in hair), but it's way off in the future, along with other potential breakthroughs like altering skin/eye colour etc. Seems like pretty risky business, considering the complexities of the human genome and even the role of epigenetics on DNA. \nAnyone else have more detail on altering genetic expression via supplements?"
] |
[
"[linguistics] Is there a way to make sense of double negatives not canceling in some languages?"
] |
[
false
] |
I've known people who say things like "I ain't got no smokes", meaning that they DO have no smokes. Several people have told me that this is because a similar construction in Spanish is correct. Whether from Spanish or any other language, is there a way I can parse this so that it doesn't just seem wrong?
|
[
"This is what linguists call ",
". It's not a matter of negatives \"cancelling\" (this isn't math), it's a matter of multiple negatives adding up together to give a stronger, more emphatic, negation. In standard English, we usually use ",
" (and related words) to make our negations more emphatic, as in \"I don't have ",
" smokes\", or \"Things just aren't the same ",
".\""
] |
[
"So, the description they give there is not great. The whole description of how English negations works there is not great. ",
"Let me clear something up, though: negative concord is not a mistake. People who use it are not making mistakes. It's simply how some people talk. It's rule-governed just like the negation system of standard English; just by a somewhat different set of rules, where instead of using words like ",
" or ",
", you use words like ",
" or ",
".",
"Before I say anything else, though, are you looking to distinguish instances where double negatives cancel from instances of bona fide negative concord?"
] |
[
"No, in a sentence like \"I never did anything\" or \"I didn't do anything\", with negator, ",
" is just a ",
"negative polarity item",
". It intensifies the negative meaning. In that context, it doesn't mean \"not none\". What I'm trying to get across is that the only level of structure at which the phrases \"I never did nothing\" and \"I never did anything\" differ is the lexical one (and sociolinguistic, but let's not go there). The two sentences use different words to mean ",
". Otherwise they're structurally identical."
] |
[
"Are all metal elements able to be detected by a metal detector?"
] |
[
false
] |
[deleted]
|
[
"Yes. Nonmagnetic metals aren't detected as easily, but they will detect anything electrically conductive. They create an alternating magnetic field, which will induce a current in a conductor, which produces an opposing magnetic field. The magnetometer sensor can detect the change produced by the induced field. "
] |
[
"This isn't because it didn't detect it, but because most security screening metal detectors have their sensitivity set only to detect relatively large metal objects to avoid getting too many false positives. "
] |
[
"Hello, in answer to your questions :",
"(1) Yes, all transition metals and non-transition metals will be detectable (though metallic Sodium and Lithium would be an incredibly unlikely and unusual occurrence !)",
"(2)Providing the metalloid has a thermally induced electric field, which is very likely, then : yes.",
"(3)Providing you can find unreacted metallic basic/alkali metals in nature, the yes. See point 1.",
"(4)Providing you can find unreacted metallic basic/alkali metals in nature, then yes. See point one. If you are referring to 'basic' as 'unrefined', then yes, with some reservations - see section below.",
"(5)Providing you can find naturally occurring ores of native metal, then yes, but with reservations - see section below.",
"A metal detector does not detect magnetic fields - or else finding metal below the ground would be nearly impossible, and below water almost totally impossible, for the small sizes of metals typically being sought. Instead, most metal detectors actually detect the electric field which forms from the natural flow of the electron 'sea' in metals and metalloids generated by even the slightest temperature gradient.",
"For this reason, even non-ferrous metals, e.g. titanium, can reliably be detected.",
"This is the essential technology used in what are known as MAD (Magnetic Anomaly Detectors - the name itself is a piece of disinformation) booms mounted on naval ASW helicopters and aircraft to detect submerged submarines.",
"During the Cold War, the Soviet Union built the all-Titanium Lyra Class / Alfa Class nuclear attack submarine, able to travel both faster and deeper than competing American, British and French designs. However, despite being non-ferrous in nature, it was instantly detectable by the mis-named MAD boom detectors on ASW aeroplanes thanks to its electrical field.",
"So, providing that the metallic material is able to form a strong electrical field, it will be detectable, even below ground or water."
] |
[
"That little dance your arms do when you slip, is that your body going into autopilot?"
] |
[
false
] |
[deleted]
|
[
"Well yes, since you don't do it voluntarily. It is an instinctive reaction to falling, trying to get a hold on anything that might help stop the falling or, failing that, at least brace the body for impact.",
"I think the evolutionary reason for this is the brain really dislikes hitting the ground, since that tends to incapacitate you quite a lot. It was probably evolutionarily advantageous to risk fracturing your wrists or dislocating a shoulder instead of ending up as a potato wrapped in a bear pelt."
] |
[
"It's actually less of trying to hold on to something or bracing for impact. It has more to do with your body going into autopilot to try to prevent you from losing your balance. You know how when acrobats do the high-wire walking they will sometimes use a really long pole for balance? You arms in this case are basically that pole. Your body uses them to adjust your center of gravity so that you don't lose your balance."
] |
[
"Imagine balancing a broom standing on end in the center of your palm, you have to walk around and always move your hand to keep it in balance. Now, imagine holding a finger out, laying the broom across it with the balance point on your finger. It is much more stable. You don't even have to move to keep it balance. Laying the broom down spreads the weight out, making balance easier to maintain, andddd giving you leverage to move against the mass, in this case your flappy arms. Go Seahawks"
] |
[
"Can anyone provide me with an explanation I can understand about the difference radio active terms?"
] |
[
false
] |
[deleted]
|
[
"Becquerels are a measure of the number of decays occurring. One becquerel is one decay per second. This doesn't necessarily tell you very much about its effects on anything else; it's just a measure of the activity.",
"A rad is 0.01 grays, and usage of rads is generally frowned upon in favour of grays, which are the SI unit. This is a measure of the energy absorbed by a sample of matter from ionising radiation.",
"Sieverts are a measure of the amount of damage done by radiation absorption, and is a function of the amount of energy absorbed (measured in grays) and a weighting function for how much damage is done by the particular type of radiation in question; alpha particles (which are helium nuclei), for example, have a much higher weighting factor than beta particles (which are electrons or positrons)."
] |
[
"Okay. There are different types of ionising radiation - commonly encountered examples include x-rays and gamma rays, beta particles (which are high-energy electrons or positrons released by beta decay), alpha particles (helium nuclei - two protons and two neutrons - released by alpha decay), but any electromagnetically interacting particle with sufficient energy will cause it.",
"Not all types of ionising radiation are equal, however. For the same amount of received energy, i.e. the same measurement in grays, a lot more damage will be done to living tissue by alpha particles than gamma rays, for example. This is what sieverts aim to quantify. "
] |
[
"Okay, So Becquerels are only in reference to the decaying particles per second in the environment. \nRad = 0.01 grays which is a more commonly accepted unit.\nThe last bit about sieverts I don't understand. Can you explain it further? "
] |
[
"Why are there different \"generations\" of cephalosporins?"
] |
[
false
] |
I know that certain generations are slightly better at combating gram-positive or negative bacteria than others, but it seems like plenty of drugs within classes are more efficient with certain types of infections without warranting the strange generational divisions. Why is this the case with cephalosporins?
|
[
"I'm from Europe and as I'm aware different countries will group the generations sometimes a little bit differently BUT:",
"1st Gen: generally cephalosporins with few structural variations except seen on the R group of the C7 position on the ring, these are drugs that will have limited effects against G- and ok range of activities against G+ bacteria but generally aren't as potent as penicillins and may have toxicity problems and may not absorb well through the GI tract. ",
"cefalotin",
"2nd Gen: refer to drugs which have improved activity against G-, usually this is through placing a polar sub(NH2 usually although sometimes CO2H) at the alpha position on the R group at C7. Also, you see a lot more drugs with differing groups at c3 in place of the ester, this is because esterases in the body can metabolize cephalosporins relatively quickly and limit their overall activity by converting them to alcohols (a bad leaving group in terms of the mechanism of action), so we swap in groups like halogens or even amides which won't be as easily metabolized but promote activity too. ",
"cefaclor",
"3rd Gen: A good few of the 2nd gen ones did provide good activities but they still weren't very potent against rougher opportunistic bacteria such as pseudomonas aerugonosa, and some also lacked goof b-lactamase resistance so the R group at C7 was again modified to provide a bit more steric bulk to shield the lactam ring from act by the enzyme, usually some kind oxime residue attached to a heterocycle is used. Furthermore, the H anti to the R residue at 7 is sometimes replaced with a methoxy group to provide additional steric shielding to the ring although results on how great that is vary. 3rd gens tend to have better G- activity as a result of some of the polar subs at on the R group too which inversely means lower G+ activity ",
"cefdaloxime",
".",
"4th Gen: ones that generally have good all round activity, quite good GI tract solubility and can even cross the blood brain barrier, they tend to show zwiterionic subs at c3 and have similar bulky R groups at c7 but tweaked to balance activities between the 2 bacterial classes. ",
"cefozopran",
"Source: ",
"http://en.wikipedia.org/wiki/Cephalosporin",
" and my brain"
] |
[
"Thank you for the rundown! Are their other drugs that are broken up like this? Is \"generation\" a common classification?"
] |
[
"Not really, this is the only group in which the word \"generation\" is commonly used in practice. However many drug classes are modified to lessen side effects or enhance potency. Other drug classes usually get broken into subclasses bases on what makes them different, however it still may have a generation type feel to it. For example the drug class of anti-histamines aka allergy medications. The newer medications are typically referred to as a \"non-drowsy/non-sedating allergy medications\". Some examples are Claritin, Zyrtec and Allegra. Older \"generation\" anti-histamines include Benadryl or Chlortrimeton. Another example is the class of Penicillins which are broken into extended spectrum or narrow spectrum (which can be further subdivided)."
] |
[
"What is quantum gravity?"
] |
[
false
] |
What exactly is it and why is it important?
|
[
"We have quantum field theory, which tells us how very small things behave, and general relativity (gravity), which tells us how very big things behave. These generally don't overlap in scope, because small things are small and big things are big. However, in situations where both gravity and quantum effects are important, neither theory tells the whole story. You need a new theory that combines both to explain what's happening. That's quantum gravity."
] |
[
"Right...but...what exactly does it do?"
] |
[
"Quantum gravity is a theory, not a thing like a photon. It doesn't \"do\" anything in the sense of work. It is an concept, not a physical thing."
] |
[
"When you exercise, does your heart beat harder or just faster?"
] |
[
false
] |
Your muscles need more oxygen so the heart pumps blood through the body at a greater flow rate. I know your heart goes up, but does your heart beat with the same.. effort (there's gotta be a better word)? Or is every beat the same? Edit: Thank you all for your answers and insight!
|
[
"Both. To effectively increase flow throughout the body, both rate & strength need to be increased. Strength is simply how much your heart muscle is contracting... no different than any other muscle in the body.",
"However, it is possible to increase one without the other by targeting different cellular receptors. We have different medications that work by increasing one or the other, or both, administered to heart failure patients."
] |
[
"For those people who like medical terms... ",
"Heart rate --> ",
"chronotropy",
"\nStrength/Contractility --> ",
"inotropy"
] |
[
"Yes, the heart does beat harder. It's called contractility.",
"Cardiac physiology is a complicated concept. It took almost a month of medical school to learn all the details.",
"Wikipedia has a basic introduction",
" which may get you started. Increased calcium levels and adrenaline are the main factors that increase contractility."
] |
[
"How is mechanical energy created from chemical energy in cells?"
] |
[
false
] |
I understand the mechanisms by which ATP creates chemical energy. I can't seem to figure out how the chemical energy from the hydrolysis of the phosphate group is converted into mechanical energy to drive, say, a motor protein. I suppose I've always thought of the energy being released simply as negative ∆G. How is that ∆G converted into directional motion?
|
[
"If you're talking about the muscle sarcomere:",
"The binding of ATP to the myosin crossbridge causes a loss of affinity of myosin for actin leading to dissassociaition. ATP then undergoes hydrolysis to ADP and inorganic Phosphate (ADP + Pi), which once again restores chemical energy back into the system, extending the myosin crossbridge and regaining the affinity for actin.",
"The binding of the myosin crossbridge to actin is responsible for the separation of ADP + Pi from the myosin crossbridge (arguable which step causes which at this point, whether it's the binding that separates the ADP + Pi or visa versa). The stored internal chemical energy from hydrolysis is then dissipated through contraction.",
"I don't know the equivalent biochemical reactions and their energies, but I hope that helped."
] |
[
"As an aside, an even more interesting reaction is electrical energy creating hormonal energy that then creates mechanical energy.",
"Depolarization of a neuronal synapse causes an action potential to propagate down an axon towards the neuromuscular junction. This leads to the release of Acetylcholine into the synaptic cleft and binding to nicotinic receptors which facilitates ligand-gated channels for sodium which further creates another depolarization close to skeletal muscle tissue."
] |
[
"This sliding filament example is a great example of how chemical energy is converted to mechanical energy.",
"I suggest you try thinking of it like this, as I do. It may not be the whole picture but it satisfies some curiousity:",
"All chemical and physical states are merely potential energy. The very configuration of ATP with it's three phosphates has that low delta-G you spoke of, meaning that it is very likely to hydrolyse simply because it could be at a lower potential energy as ADP + Pi. ",
"So, for example, let's say I have a motor protein such as kinesin walking along a microtubule. The ability of this protein to hydrolyse ATP doesn't just cause the ATP change as we so often concentrate on. This reaction also causes a subtle conformational change in the protein itself into a higher energy state. However, unlike how ATP has a chemical path to a lower energy state through hydrolyses, the kinesin has a physical path to a lower energy state through movement. ",
"I should clarify here that the exact step up in potential energy can be different for different proteins. For example, the system can be set up so that the ATP hydrolyses cannot take place without the physical change, thereby coupling the reactions. Or, it could be set up such that the binding of ATP deforms the protein, and phosphorylation simply allows removal of the ATP and cyclic change. There are likely other possibilities along the same lines.",
"It is much easier to think of this as the chemical reaction slightly changing the protein conformation (by protein kinetics), with the result that the new \"lowest energy\" for that protein is through a physical movement. Often this change is achieved through deformation of the ATP binding site or other similar changes.",
"In other words, the ATP doesn't drive the movement like the gas pedal of a car. Rather, the action of ATP is like pulling a bobsled up the hill and then watching it race downward toward lowest energy. "
] |
[
"What could be consequences from the Amazon fires?"
] |
[
false
] |
Apparently some people have been burning the Amazon forest for weeks now. What will or could happen if they keep burning it?
|
[
"An excellent response. I'll just add to it that there is a current theory that of the Amazon loses as much as 5% more of its 1970 area it will cause a cascade effect which will result in the Amazon drying up and converting to a desert savanna. In other words, if too much more of the Amazon is destroyed the rainforest may never come back. ",
"https://news.mongabay.com/2018/03/amazon-forest-to-savannah-tipping-point-could-be-far-closer-than-thought-commentary/",
" ",
"Currently the Amazon rainforest loses roughly 1% every 3 years, mostly to slash and burn agriculture used to feed cattle and supply palm oil. This 1% every 3 years is a slowdown from the rates before 2006."
] |
[
"I cross-post this from a similar question on ",
"/askscience",
":",
"\nPartial deforestation of the Amazon and elsewhere has probably already ",
"altered rain patters across the world",
" and made the Amazonia more vulnerable to stress (such as wild fires). ",
"Climate change beyond two degrees is expected to further push Amazonia beyond its tipping point",
". If this happens, it would result in the release of huge amounts of CO2 that easily could ",
"cascade into a series of global events",
" that would be highly unfavourable for humanity, a state referred to as 'Hothouse Earth'. This would include average temperatures 4-5°C higher than pre-industrial temperatures, and sea level 10-60 m higher than today."
] |
[
"average temperatures 4-5°C higher than pre-industrial temperatures",
"Is this even survivable?"
] |
[
"Is there a good \"do it yourself\" method to view the Venus transit safely?"
] |
[
false
] |
I'd like to see the transit, but don't have glasses or know how to acquire them. What can I use?
|
[
"Welding mask lens. Shade 14.",
"Welding shop: Maybe $15 for a pack of 3."
] |
[
"In addition to the direct observation methods listed above, you can also make a pinhole viewer very easily.",
"What you need:",
"Cut a small (2\") hole in the center of one of the opaque squares. Tape a small piece of foil over this new hole. Poke a very small hole with the nail in the aluminum foil.",
"Now, standing with your back to the sun, hold both squares up so that the sun shines through the hole of the modified one onto the unmodified one.",
"You can make a more sophisticate set up (making a box so the contraption would be mostly dark, etc), but this is probably one of the simplest ways to view the transit. Substitute material as needed, but try to make sure you have a mostly circular 'pinhole'. Also, the 'squares' don't need to be square."
] |
[
"All welding masks ",
" to block UV, since the whole point is to protect your eye from the UV light coming from a welding spark."
] |
[
"Apparently our eyebrows are there to protect debris from falling into our eyes. Why/how would natural selection favor eyebrows, could they really save lives or make humans more likely to reproduce? Same goes for other seemingly insignificant parts of organisms."
] |
[
false
] |
[deleted]
|
[
"Iggy Pop once shaved his eyebrows before a concert because he thought it would look cool. Not long into the show, sweat was pouring down his face, blinding him and causing so much pain he almost had to stop the show. Afterwards his eyes were very swollen.",
"Now imagine you're a bald ape without claws, fangs, or any other shit to work with other than a pointy stick. You spend your day in the sun, hunting, running etc. naturally you sweat. I'm guessing your odds of throwing a spear and defending yourself go down with sweat in your eyes."
] |
[
"So in short you're saying \"eyebrows are not insignificant.\" OK, so he picked a bad example, but I think his question still stands unanswered. "
] |
[
"They also play a key role in communicating with other humans"
] |
[
"Is there a cure or just a way to manage PTSD?"
] |
[
false
] |
Ive been told that people can manage PTSD but cant actually heal it. I just want to know if this is true or if it is curable. If it is curable, how is it possible? If it's not, why not? I couldn't find anything about this in the research I did.
|
[
"It depends on what you mean by \"cure\". That's not a term that's typically used in mental health treatment. What we can talk about though is response (meaningful reduction in symptoms), remission (defined by symptoms below a meaningful threshold) and no longer meeting diagnostic criteria.",
"What's particularly notable about PTSD is that there is a trauma involved, something that happened to a person that was quite terrible. The past will never change and will always be something that is unpleasant, sad, etc. What can change are intrusive symptoms (nightmares, intrusive memories, cued emotional/physiological reactions), avoidance (of memories, thoughts, feelings, people, places, situations), arousal symptoms (insomnia, hypervigilance, concentration problems, hyperstartle, irritability), and negative emotional/cognitive changes (emotional numbing, excessive blame, negative beliefs about the world). Those sorts of symptoms are quite normal in the immediate aftermath of a trauma, but there is a natural course of recovery over time such that the majority of people (>80%, even combat veterans) will not develop PTSD. ",
"A meta-analysis found that over time (mean of 40 months across studies included in this analysis, covering >80,000 people), almost half of people with PTSD will no longer meeting criteria for diagnosis of PTSD",
". ",
"Sidebar: something else important to know is that PTSD is just one way a person can react to a trauma. Some people develop depression (low mood, lack of interest, poor sleep, appetite disturbances) or generalized anxiety disorder (difficulty to control worry about many different areas of life). These can also co-occur with PTSD. A helpful differential question is how to the memories come back - in PTSD they can come up intrusively when not desired and the person will try to push them away. A person with depression may ruminate on them (rather than push them away) and think about what they did wrong. A person with GAD may worry about all of the \"what if\" situations about what else could have gone wrong, again not trying to push the memory away. These are all negative reactions to traumatic experiences, but they do not all fit with a diagnosis of PTSD, no matter how much that term gets carelessly tossed around and no matter how much a person may want to have a diagnosis of PTSD (strange, but true).",
"Two main things keep people stuck, preventing natural recovery. The first is avoidance of memories, people, places, situations, etc. that ",
" dangerous but are objectively safe. As an analogy, if you took a child to the beach and the child got hit by a wave and was very upset, they would not want to ever go back. As long as they stay away, they won't have that extreme distress, ",
" they will maintain a strong fear of the breach. Avoidance is very effective for managing fear and anxiety in the short term, but that fear will not go away as long as a person continues to avoid these things. So targeting avoidance is a main goal of trauma-focused therapies. Unhelpful beliefs about the self and the world can also keep a person stuck, preventing their recovery. These beliefs may include feelings of guilt or responsibility that are disproportionate to actual responsibility, belief that you are incompetent (thinking you can't do anything will keep you from doing just about everything), belief that the world is dangerous (of course there's danger, but this can be terrifically amplified in PTSD), etc.",
"The problem is when those PTSD symptoms prevent the person from living the life they want to live. If everything feels dangerous, you may avoid driving, crowds, etc. and your world becomes smaller and smaller. If you're distrustful and irritable you may push people away.",
"What effective treatments do is help a person to reduce their symptoms by targeting avoidance and/or unhelpful thoughts and beliefs. By doing so, things that are objectively safe can feel less dangerous, helping you re-calibrate fear, so that you can go to the grocery story, go to the gym, go to dinner or concerts with your SO, attend your children's soccer games, and live the life you want to be able to live.",
"We have several time-limited psychological treatments that have years, even decades, of evidence showing they reduce PTSD symptoms, with followup studies showing these reductions can last for years. ",
"Here's a figure showing the proportion of patients who meet diagnostic criteria for PTSD from pre- to post-treatment and the 5 years later",
" (",
"ref",
")."
] |
[
"Posttraumatic stress disorder as we currently understand it is a suite of symptoms related to extreme anxiety and distress, catalyzed by a single traumatic event or a series of traumas. These occur because the individual is unable to cope in a healthy way with the trauma(s) they have experienced. ",
"Most current accepted therapeutic techniques focus on initial symptom management--helping the client reduce instances of panic attacks and dissociations (commonly called 'flashbacks'), and be able to cope with these symptoms in the moment if they do occur. Once the client is more confident in their ability to handle the symptoms, the therapy moves toward gaining understanding and acceptance of the trauma, thereby removing the triggers for the symptoms. ",
"You may note that these are all geared toward management. Even in the most wildly successful scenario, the individual may come to a place of perfect acceptance and ability to cope, but may still very well experience rare panic attacks and exhibit hypervigilance. The current goal of PTSD therapy is reducing the frequency of these attacks as much as possible by giving the client the tools they need to cope with them as needed. Now, this can mean that the individual experiences the symptoms so rarely that they no longer qualify for diagnosis, but the symptoms ",
" recur.",
"Part of the problem with 'curing' PTSD--or any mental disorder, really--is that the experience of these disorders is quite subjective. With respect to PTSD, we term the individual's ability to avoid traumatic victimization as 'resilience.' All things being equal other than resilience, two people that experience the same traumatic event may react very differently--one may develop PTSD while the other is perfectly fine. This means the experience of PTSD is unique to the individual that suffers from it; the symptoms follow a recognizable pattern, certainly, but each individual will have different reactions, even to the same trauma. This makes it difficult to develop a global treatment style that is effective for all people, much less to find a cure.",
"That being said, as mentioned elsewhere in this thread, psychiatrists and psychologists are constantly researching new methods of treatment for PTSD to find the most effective ones. Research into utilizing MDMA as a prescription drug while providing concurrent therapy has yielded very promising results, but we're still years away from perfecting this method. Even then, it faces several legal hurdles, MDMA being illegal in most countries. EMDR therapy has also shown promising results, though it remains controversial due to the replication crisis in psychological research."
] |
[
"EMDR therapy has also shown promising results, though it remains controversial due to the replication crisis in psychological research.",
"EMDR has a ",
" of replication over decades. There's certainly controversy around it including post-hoc explanations for its mechanism of action and studies showing that one of its key components (eye movements) is inert. For those reasons, I'm a stronger supporter of ",
"I'm surprised that you'd mention EMDR and MDMA therapy, but not PE and CPT."
] |
[
"Regular pentagons tile in spherical space. There are 15 known irregular pentagons that tile in flat space. Is it true that *any* pentagon will tile in some space with homogeneous curvature?"
] |
[
false
] | null |
[
"for the purposes of tiling, aren't polygons defined in terms of the relationships between their various angles? A regular pentagon in some arbitrary space would be a 5-sided polygon whose internal angles are all equal. ",
"At least, defined thus, is it true that any 5-sided polygon will tile in some space with homogeneous curvature? I don't think the question depends on my defining 'regular pentagon' in flat space and referring to it tiling in spherical space."
] |
[
"What a shape is depends not only on its side lengths and internal angles, but also on the space it's embedded in. It wouldn't be correct to say that a regular pentagon in spherical geometry is the same shape as a regular pentagon in Euclidean geometry, because they have different internal angles. It's obvious enough in the case of regular polygons that they are \"similar\" (in the colloquial sense, not in the geometric similarity sense), but there's no immediate generalisation for arbitrary polygons.",
"For this reason, it's not a valid question to ask whether a specific polygon that you defined using X geometry will tile in Y geometry. (Substitute any two of Euclidean/spherical/hyperbolic for X and Y.)"
] |
[
"You can regularly tile the sphere with 4, 8, or 20 geodesic triangles. Since the tilings have 3, 4, and 5 triangles meeting at a point respectively, it's clear that the vertex angles of the geodesic triangles in the different tilings must be different.",
"What's a \"space with homogeneous curvature\"?"
] |
[
"Should I rush to re-open a closing door or should I just open a closed one?"
] |
[
false
] |
In a food court, there are 4 adjacent self closing doors. I have noticed that people run to re-open a closing door behind someone who had just went through. I think the intuition is that a half open door is easier to open than a closed one. But the physics in my head seems to think that opening a closed door uses less energy. But when I work it out on paper, it seems to give me equivalent efficiency (equal efforts) for both situations. Here is my breakdown Situation 1 - Closing door: One must first do work in order to bring the closing door to rest before doing the work to reopen it into the open configuration. Situation 2 - Closed door: Work must be done to bring the stationary door into motion and into the open configuration. The assumption I made in my personal calculations is that the open configuration is twice the angle at which the closing door is brought to rest. So... is it equal? My mind's telling me no. But the maths... The maths it telling me yeaaah.
|
[
"Buildings are slightly positively pressurized, the additional pressure on the door can make an inward swinging door more difficult to open, initially, before the \"seal\" is broken. A reasonable target is 0.02in-wc, which is about 0.0007psi. While this is a small number, over a large exterior door it can be a few lbs of pressure holding the door shut (assuming an inward swinging door)."
] |
[
"When OP said",
"One must first do work in order to bring the closing door to rest before doing the work to reopen it into the open configuration.",
"I think he meant",
"the force/momentum of the door as it is closing. This force must be overcome in order for the door to rotate the other direction."
] |
[
"Note that these assumption are not valid for all doors",
"Yeah, I don't think that's a good model. The mechanisms that close a door have a spring component, but they also have a piston whose job it is to prevent the door from moving too fast at any point. It can be roughly modelled as the force it provides being proportional to the velocity of the door. This is why closing doors accelerate until they are mostly closed then seem to \"bounce\" on the air, then close again at a slower speed. So the equation for the force on the door has a \"kx\" for the spring position and a \"lv\" for the piston velocity."
] |
[
"In this gif for what reason do the gas bubbles sink?"
] |
[
false
] |
Here's the . I imagine if it went on longer the bubbles would rise but I can't imagine any reason they seem to sink unless the perspective is skewed and the gun is pointed more downward than I think.
|
[
"Keep in mind the huge bubble that comes out when the gun is fired is very hot. It's cooled nearly immediately, greatly reducing the volume of gas. ",
"What you see going downward is the particulate/smoke from the explosive in the ammunition, which is sinking in the water as one would expect. Toward the end of the gif you can see the few bubbles that went with the smoke separate from it and start traveling upwards."
] |
[
"Most of that bubble isn't bubble at all, it's ",
"cavitation",
" caused by the bullet exploding out of the gun creating a momentary vacuum in the water. It collapses right after and dissipates. "
] |
[
"What you see going downward is the particulate/smoke from the explosive in the ammunition",
"I really don't think it's that easy. I see the following:",
"After the bullet leaves the barrel, the porpelling gases form a bubble in front of the gun. The gases compress (like you said) but also mix with the water to form a mixture of fine gas bubbles. But this is happening AS the bubble is collapsing. And the bubble, collapses from the top to bottom. This creates a net impulse downwards that is carried by the gas/water mixture.",
"This is only natural because ... think of it: The bubble presses away water in all directions (almost) an equal distance away because pressure from the water is equal in all directions. However, the water pushed up is gaining potential energy, and the water pushed down is losing potential energy. After the gas compresses and mixes with the water, this energy has to go somewhere. This is why the mixture of gas and water is moving downwards.",
"As tombleyboo points out (and of course he is perfectly right)",
"unfortunately the part about water being pushed up and down is wrong. Where does the pushed-down water go? the bottom of the pool is solid, the only way for the water below the bubble to go down is if it displaces other water, in the end, wherever you displace water, you're pushing some water up. Another way to say this is that the bubble experiences pressure from all sides, above and below very nearly equally.",
"This just reinforces my point.",
"Of course this is just a rough description of what's happening. We completely ignore that the bubble is not a sphere for many reasons. Also the gas/water mix is flowing downwards AND forwards. The forwards movement is from the bullet and the gas ... at least I think it is ... please correct me.",
"What you see going downward is the particulate/smoke from the explosive in the ammunition, which is sinking in the water as one would expect.",
"Both smoke and particulate would actually suspend in water as their surface to weight ratio would not let them sink ... right?",
"/edit for clarity",
"/edit another one for the correction from tombleyboo"
] |
[
"Is Marinol less medically useful/potent than \"medical marijuana? Why do I never hear about it?"
] |
[
false
] | null |
[
"Marinol is synthetic THC. Medical marijuana differs because there's many different cannabinoids that work in conjunction with THC in ways we don't fully understand to produce the desired therapeutic effect.",
"I hope this analogy works. Lets say milk is illegal, but pure caesin (protein in milk) isn't. You want to bulk up, but drinking a protein shake of caesin isn't going to be as nutritionally fulfilling as milk is."
] |
[
"Good answer. ",
"Cannabidiol",
", for example, has been shown to ",
"work as an anti-psychotic",
" (pdf file)."
] |
[
"I think there's a few good answers to this. As a caveat, I've not used marinol in any of my patients, nor have I ever had it myself. I haven't used marijuana either, because it's illegal, and I like having a medical license.",
"Like ",
"hullabazhu",
" pointed out, there is more than just one active chemical in marijuana, whereas in marinol, there is just one. This causes somewhat different effects physiologically.",
"However, just because there is only one chemical involved doesn't mean that it has no effect. The drug company chose that chemical for a reason. There are many ",
"studies",
" examining marinol (aka dronabinol). A ",
"search",
" of pubmed for \"dronabinol\" gives 166, which admittedly includes some that are only tangentially related, but does include quite a few useful studies.",
"With that said, there is no reason to suspect that just because a medication is widespread, that it will be widely known. Compare how many high school students know about the drugs Coreg, Lisinopril, and Keppra with how many know about \"medical marijuana\". These are widely used drugs, but really only the people who need to use them are aware of them (in general).",
"There is a large part of culture that is VERY excited about marijuana, and enjoys using it recreationally. I think that this plays into why so many people are interested in medical marijuana. The reason is (in my opinion), that some see medical marijuana as \"one step closer\" to legalizing it for recreational use, some are just interested in an \"edgy\" topic, and some like the idea of a \"natural\" medicine (and dislikes \"big pharma\").",
"Taking all of this together, I suspect that marinol has a similar effect on many conditions to what \"raw\" marijuana has, with some differences. However, the perception of many in the \"mainstream\" medical community of the drug is less than favorable (with the perception of medical marijuana even less favorable), and certainly less favorable than the opiates and opioids (which, by the way are chemically similar to ",
"heroin",
"...). In contrast, the perception of marijuana in the \"medical marijuana community\" is highly favorable, and since it is much simpler (and probably more profitable) to use whole marijuana, there is no real reason to use Marinol."
] |
[
"How can volcanoes form where there are no plate boundaries?"
] |
[
false
] |
In high school I've learned that volcanoes form on plate boundaries which I understand. But what I've been thinking about is how can volcanoes form where there are no plate boundaries. The main example I'm oging to use is in Edinburgh, where the Edinburgh castle is build ontop of an extinct volcanoe. How did that volcanoe form if there are no plate boundaries in Scotland?
|
[
"Couple of options:",
"1) ",
"Hotspot volcanism",
" where volcanoes erupt above a localized zone of anomalously hot mantle. These are most likely related to ",
"mantle plumes",
", but a few holdouts still argue for alternative mechanisms. Regardless, hotspots can occur near plate boundaries (e.g. Iceland) or in the middle of plates (e.g. Hawaii).",
"2) Plate boundaries are a bit more diffuse than many people realize. There can be a lot of activity even relatively far away from the formal plate boundaries. As an example, the formal plate boundary between ",
"Arabia and Eurasia",
" is in northern Iraq, but there is extensive volcanism throughout eastern Turkey, Georgia, Armenia, Azerbaijan, and into Russia (in some cases 1000+ kms from the plate boundary) that is associated with the collision between Arabia and Eurasia.",
"3) Just because something isn't a plate boundary now, doesn't mean it wasn't a plate boundary in the past. This is the relevant answer for your example question. Specifically, Edinburgh castle is ",
"built on top of 400-300 million year old volcanics",
". At this time, this portion of Scotland was along a plate boundary, e.g. ",
"the Devonian period of Scotland",
"."
] |
[
"This",
" write up does a pretty thorough job of going through some of the arguments. The short version is that it's complicated and arguably the simple vision of plumes that appear in intro textbooks probably don't exist. The question as to whether something functionally like a plume but a bit more messy exists is still pretty hotly debated (and it seems like every time it appears to have settled back down, some new observation reignites the debate)."
] |
[
"Re: 1, how do the holdouts still manage to hold out in this? I was under the impression that in at least the case of Hawaii mantle plumes were pretty decisively supported. Since the whole motivation for alternatives was to simplify the model, that would seem to kill that motivation.",
"What am I missing?"
] |
[
"What is PWM and why is it used in driving an inductive load?"
] |
[
false
] | null |
[
"I worked with pwm drives for many years. They are used to drive inductive loads as a way to vary both voltage frequency and current seen by the load. ",
"They are basically just used with 3 phase motors so I will talk about them. In a regular off the line start, a 3 phase motor will typically produce 150% full load torque and 200 to 1200!% in full load amps, these large moments of inrush power can be hard on electrical equipment and mechanical equipment. ",
"Older soft starters were developed to cut voltage at startup to cut current and torque. Cutting the voltage 50% will cut current 50% and torque 25%. These are affective in decreasing starting stresses, but offer no speed control.",
"The theory behind basic PWM drives is to operate a motor on a linear volt per hertz ratio. So if there was a motor which operated at 120 v at 60hz. The PWM drive will adjust the linear adjustment to 2v per hertz. This will produce 100% of rated torque at any rpm it is adjusted to.",
"PWM drives can be further expanded into advanced open and closed loop VFD drives which can offer speeds from 0 to 400hz, and torque ratings of more than 100 percent down to zero speed."
] |
[
"Pulse Width Modulation is used because it is an efficient way of synthesizing a variable voltage to a load.",
"PWM amplifier transistors act as switches, they are either 'on' or 'off'. When 'on' there is very little voltage across the switch and a lot of current through it. When 'off' there is a lot of voltage across the switch but very little current through it. The semiconductor 'switches' dissipate little power while the load is delivered a lot of voltage and current. PWM amplifier efficiency routinely exceeds 95%.",
"High-power PWM amplifiers are usually 'H-bridges'. The letter 'H' has a horizontal bar with a vertical bar above and below at each end of the horizontal bar. The horizontal bar is the motor coil (mostly inductive with some resistance) and each vertical bar is a semiconductor 'switch'.",
"The top two switches connect to a positive voltage, the bottom two switches connect to ground. That is 4 'on/off' switches. Let's call them UL (upper left), LL (lower left), UR (upper right) and LR (lower right).",
"The law of switching an H-bridge is \"only 1 switch at a time can be 'on' at each end of load\".",
"Now let's use the H-bridge. The simplest is turn UL and LR 'on' for a short while, then turn them 'off' and turn UR and LL 'on' for a short while. Repeat the process.",
"Usually this is done 20,000 times a second. A 50% PWM duty cycle has each switch-pair 'on' for 25 microseconds and 'off' for 25 microseconds. If you did that and used 100V for the positive voltage, the coil would 'see' a 20kHz squarewave voltage across it with an amplitude of +/-100 volts. The DC voltage component is zero at a 50% duty cycle and the current in an ideal inductance would have zero net change.",
"Changing the duty cycle changes the DC voltage component across the inductive load and that determines the rate and direction of current change. Using feedback then allows controlling the magnitude of current in an inductance (motor) as well. Now you have all the components necessary to make motor current proportional to a command input.",
"I am a EE and I design servomotor and microstepping drives for a living. "
] |
[
"(I'll try to tackle this one, even though I'm still learning myself) Pulse Width Modulation is the process of changing a waveform's duty cycle. The periodic signal you get from a function generator is typically 50% by default, but that can be modified. A 10% duty cycle would be a signal that's on 10% of the period. PWM is used with various DC-DC converters, which consist of a voltage or current controlled switch, diodes, capacitors, inductors and resistors to either step up or step down the input voltage. DC motors are generally modeled as an inductive load, and PWM would function as speed control for the motor."
] |
[
"What makes your steering wheel \"level out\" when you press the accelerator?"
] |
[
false
] |
Ever since I started driving I noticed that if you're turning and you accelerate after completing most of the turn, the steering wheel will go back to being straight without you having to rotate it yourself. Why is this?
|
[
"Caster causes a self-centering force."
] |
[
"yes, but i've noticed it in my all wheel drive cars as well"
] |
[
"yes, but i've noticed it in my all wheel drive cars as well"
] |
[
"Why do some chemical reactions need catalysts (such as potassium permanganate), and what does the catalyst do if it is not used up?"
] |
[
false
] |
[deleted]
|
[
"Catalysts do take part in the reaction if you consider the mechanism, or overall sequence of steps, involved in a reaction instead of just the overall reaction. Any reaction that involves 3 or more reactant molecules (even if some of them are of the same type) proceeds via a multistep mechanism. A catalyst is a reactant in an early step in the mechanism, but a product in a later step of the mechanism. So on our macroscopic scale, it appears that the catalyst was not involved in the reaction because it can be recovered at the end of the reaction. Some reactions can get from the reactants to the products via several pathways. A catalyst will be a reactant which allows a pathway which has a lower activation energy than the pathways which were available without the catalyst. So at a given temperature, more molecules have enough energy to transform from reactants to products and the overall reaction proceeds at a faster rate.\nedit: Potassium permanganate is not a true catalyst for the decomposition of H2O2. They react together to make O2, MnO2, KOH and H2O. The potassium permanganate cannot be recovered."
] |
[
"In general when we write out a chemical reaction, we are writing a very brief summary. Most reactions have very many steps required for the reactants to become the products, often involving multiple intermediate structures. If a reaction does not occur spontaneously very quickly, it is often because one (or more) of these intermediates has a higher energy level than the reactants, meaning that energy has to be added to the system in order for the reaction to proceed. In an overall ensamble of molecules, some naturally will have more kinetic energy, and will be able to participate in those reactions, going to completion, while other will not. That difference between the reactant energy and the highest energy intermediate is called activation energy, and more molecules will be able to achieve that extra energy at higher temperatures, hence why reactions occur faster at higher temp.",
"Now a catalyst is basically something that stabilizes that high energy intermediate. It does not end up donating or accepting any electrons from the reactants or products, but will lower the overall energy of the intermediate by interacting with it. Thus the catalyst lowers the activation energy and allows molecules to more easily undergo the reaction thus speeding up the reaction rate. ",
"In the case of KMnO4 and H2O2, the potassium does not do anything. The permanganate actually is not a catalyst either but participates in the reaction. The permanganate is reduced to +2 oxidation state from +7 in the ion while the oxygen in the peroxide is oxidized.",
"In many organic reactions, you can often have metals serve as catalysts because they chelate well to certain residues and can stabilize them. All of life depends on the ability of some amino acids in proteins to stabilize intermediates given a certain 3-D organization. These proteins are called enzymes."
] |
[
"interesting!! thanks for the detailed response."
] |
[
"In a packed grocery store with long cashier lines, is it better to choose one at random?"
] |
[
false
] |
So I got stuck today for 20 minutes in a cashier line, and it got me thinking about the optimal way to choose a line. Whenever a customer had finished shopping he would run through all the lines to find the shortest one. But here I was thinking, if every customer before me has searched for the better line, then the lines are more or less equally long. So the best option would be just to pick the nearest line and not bother looking for anything better. So I know this obviously has been thought about someone before. And while I know a little about game theory, I have no idea how I would search for such a concept. Does anyone have somewhere to lead me to? Could anyone explain under what area of economics/mathematics this would fall into?
|
[
"Personally I evaluate the amount of products in each persons cart, I'd rather get in the line with five lightly loaded carts than two heavily loaded ones. Also I've found that younger to middle aged (20-35) cashiers seem to be a bit faster. Several elderly persons in a line are usually a red flag as they tend to write checks which increases the wait time."
] |
[
"When you pick a line, you have to wait until all the people who were on the line before have finished. How much that takes depends on how many people are on the line and the products they have. Thus, if you choose the line which takes less time, you will wait less. That's it. Your initial intuition was right.",
"It is true that, since all people will think like you, the lines will ",
" to get similar, but they won't always be, because the amount of people who enter the lines and their amount of groceries are both random. You can't control what the others will do, so you can only look out for yourself. Since you can only estimate the duration of each line, there will be times where you won't be able to tell which one is best, and you'll have to choose at random, but other than that, just look for the best line.",
"It would get way more interesting if you could make everyone follow a certain strategy: then maybe another strategy could lead to better result, but I don't think so. That would be modeled with some kind of stochastic process, but I don't know a lot about that."
] |
[
"5 lightly loaded carts means 5 payment exchanges, increasing the odds of a check or somebody deciding to wait until presented with the total before fumbling through a cavernous bag for a purse/wallet. "
] |
[
"What is the math behind the microgravity on the ISS?"
] |
[
false
] |
I've read that the reason astronauts are weightless on the ISS is because the centrifugal force is equal to gravity. Can anyone do the math to back this up?
|
[
"Gravity is fictitious too! ",
"Sorry for the lame humor, just want to point out that \"fictitious\" doesn't mean \"non-existent\", it means ",
"\"dependent on your frame of reference\"",
". Specifically, inertial versus non-inertial.",
"However, whether your frame of reference includes fictitious forces or not, you get the correct answer as long as you include (or exclude) all of the appropriate fictitious forces for the frame of reference you choose."
] |
[
"1.Set coordinate system to earth",
"2.Idealize the ISS as a point mass, neglect friction and gravitational influences of other planets, approximate that the orbit of the mass is a perfect circle around earth",
"3.The tangential speed of the mass is kinematically preset",
"4.Cut the mass free and draw in all forces (D'Alembert's principle)",
"5.Gravitationforce points to earth, fictitious force points exactly the opposite way",
"6.Set up the dynamic equilibrium F_g - ma = 0",
"7.F_g is the gravitaional force F_g = G",
"m2)/r²",
"8.Rearrange \"ma\" with the centripetal force formula, ma = mw²r , while w is the angular velocity",
"9.This equation must be correct to achieve microgravity",
"G",
"m1 = v²r",
"G: Gravitationconstant, m1: Mass of earth, r: gap between mass and middlepoint of earth, v: tangential speed, w: angular speed",
"Edit:typos, oh and btw, centrifugal force is not a real force, its actually the fictitious force"
] |
[
"That is an equivalent way to say the same thing. From a fixed reference frame, they're accelerating towards Earth. From a rotating reference frame, gravity and centrifugal force are cancelling out."
] |
[
"I'm getting a lot of conflicting answers. Are there any real benefits of drinking alkaline water?"
] |
[
false
] | null |
[
"Everything I have ever seen besides the propaganda, indicates that it is a bunch of new age bull. ",
"http://www.chem1.com/CQ/ionbunk.html",
"http://message.snopes.com/showthread.php?t=13815",
"http://www.apswater.com/article.asp?id=198&title=Alkaline_Water_Hoax_-_It_Is_Simple_Science",
"."
] |
[
"Your body has natural pH buffers. You can't improve that or change how they function. "
] |
[
"No. The pH of the water you're drinking is not important so long as it is neither too high nor too low, which would cause ulcers. The stomach makes short work of any alkalinity in the water and takes it to a pH of about ~2 (depending on what you just ate or drank). It then enters your intestine where it goes up to 7...and then 8. This is all very carefully controlled since digestive enzymes do not work outside of a very small pH range. Thus, there are safe guards against the consumption of acidic or alkaline foods.",
"That said, there may be benefits in drinking water that is high in magnesium or calcium (which are usually presented as carbonates) but this would be insignificant since a healthy diet contains these minerals aplenty. "
] |
[
"My apartment offers free water but not electricity. Would it be possible to use the water to generate enough power for my apartment? (eg. bathtub water wheel)"
] |
[
false
] |
I have a pretty standard one-bedroom apartment and would need to power a refrigerator, 3 room lights, a laptop and other standard appliances. Is there any shot I could harness the power provided by the free water to meet my electricity needs or is it simply not enough energy? Also, of course the apartment would probably catch on and kick me out if I was running water 24 hours a day, so lets ignore that reality.
|
[
"Let's say you're using your bathtub. I looked it up, bathtubs put out about 4 gallons per minute. 4 gallons of water is 15 kg. I think this is higher than reality, but let's say the water falls 2 feet from the faucet to the ground. The potential energy then is m*g*h, so the amount of potential energy over a minute is 15*9.8*0.66 = 98 J. Watts are J/s, so divide that by 60 and you get 1.6 W. Thus, your bathtub can produce about 1.5 W. So no, you won't come close to powering your house, sorry. "
] |
[
"Typical residential water pressure is about 3 to 5 ATM and typical flow rate inside a residential home is somewhere around 10-15 gal/min, about 38-57 l/min. This is assuming you could source the water from the pipes rather than a faucet. The flow from a faucet will be much less, maybe 1 to 3 gal/min. ",
"Multiply pressure and flow rate numbers and you get watts. This equates to about 190-500 watts. ",
"This could potentially power part of your apartment, but this is a real Scumbag Steve move. If you are getting 15gal/min, in 24 hours that is 21.6 thousand gallons of potable water. A typical shower head is 2gal/min and if your shower lasts 10 minutes, that water you use in one day to power your apartment is enough for almost 3 years of showers. ",
"Now lets calculate cost, even though you are not paying for it. ",
"San Francisco water rate",
" is based on 100cu ft units, which is 748.1 gal. The first 3 units is $3.90 ea, and each additional is $5.20. This is $146.24 for just the water. ",
"Now lets find the cost they'll charge for sewer. The sewer flow is assumed to be 90% of the water use, so 19440 gal in this case. The sewer rate is $7.52 for the first 3 and $10.03 for each additional. This cost is $253.11. ",
"Total cost to for one day of water to power your apartment: $399.35",
"Edit: According to this ",
"blog",
", this guy uses between 6 and 10 kWh per day in his apartment. I do not remember my electrical rate but lets say it's 13-18 cents per kWh, typical US rates. Even if you use 10kWh @ 18 cents, this is $1.80 only. If you generate 500W for 24 hours, you generate 12kWh for $399.35. From the electrical grid the cost for the same amount is $2.16. This is an astronomical cost to the proprietor for you to save so little.",
"I do not know what your lease or rental agreement is like, but this is not normal usage and your landlord might not only be able to kick you out, but they may be able to come after you for the cost of your shenanigans."
] |
[
"Houses have pressure regulators. This is why if you live far below the water tower, water still doesn't explode out of the faucet. Regardless- we know the gallons per minute of most bathtubs, and how many gpm it puts out is determined by the pressure, so we are taking all of that into account. "
] |
[
"Do taller and shorter people have higher and lower heart rates than people with average heights?"
] |
[
false
] |
It's late (as of typing this) and I'm wondering stuff.. Also I guess an extension of the question is "Are taller people more susceptible to high blood pressure?"
|
[
"Cardiac tissue is post-mitotic (the cells can no longer divide) there are other organs like this (brain) but the main problem with people who get extremely tall like pituitary-giants is that while the rest of their body keeps growing their heart reaches a maximum size relatively early in development. Their hearts are the same size as someone who could be up to two feet shorter but this cardiac tissue now has the job of pumping blood through a much greater volume of systemic tissue.",
"So, yes those who are unusually tall are also unusually susceptible to hypertension and cardiac problems."
] |
[
"Working at a hospital for quite a while I can say that generally heart rate differs from patient to patient depending on their level of activity. Someone who does a good amount of aerobic activities and exercises will generally have a lower heart rate than someone who doesn't. The normal heart rate being 60bpm-100bpm, the people that exercise more might float around 45bpm(lowest ive seen for a normal heart rate) to 60bpm. I haven't seen any heart rate patterns concerning only the height of a patient, although there are many factors that can dictate a persons heart rate, including just your own bodies adaptation. So I cant say that height has any play in heart rate as I've seen both short people with low and high heart rates, and very tall people with low and high heart rates. Its more based on their genetics, body adaptations, any conditions they may have, and their lifestyles."
] |
[
"Thank you for your answer. I learned from it."
] |
[
"Is molecular movement really random?"
] |
[
false
] |
[deleted]
|
[
"The motion of atoms in many situations can be described classically, in which case it is indeed deterministic. However, it may still be ",
", meaning a small difference in initial conditions will cause a very different result as time goes on, making it impractical to predict the precise paths of a large number of atoms.",
"Quantum mechanics, on the other hand, is generally believed to be truly random. If quantum mechanics is significant in determining the motion of a particle, you can't prescribe one set path it will take. There is no way to predict, for example, the position of an election bound to a nucleus other than as a probability distribution function."
] |
[
"Classical mechanics is not ",
" deterministic, but many classical systems are. Classical collisions between particles are deterministic."
] |
[
"Classical mechanics is not deterministic",
". In addition to that, while quantum mechanics is not deterministic, it is unitary, unlike classical mechanics. Unitarity means that you can always run the system in reverse and get back to the initial state. Unitarity is not guaranteed in classical mechanics (though we usually assume that all cases in which unitarity fails in classical mechanics are pathological, although to my knowledge this has not been proven), while it is guaranteed in quantum mechanics."
] |
[
"Why are there no CMYK colored Pen sets?"
] |
[
false
] |
Hi, In subtractive color / printing yan, agenta, ellow and blac are used to create all colors on a white background. These colors act as a filter to the colors in ambient light and thus the correct CMYK filter combination shows the desired color. Why isn’t CMYK a readily available combination for pigment colors such as pens, paint and the like?
|
[
"It seems like your theory is if someone had these four colors they could create any color they want on paper.",
"The problem is, to create a certain color, you would need the ability to very precisely deposit an exact ratio of the necessary base colors. Pens allow ink to flow at a generally consistent rate. You can’t control that rate, so the ratio would essentially always be 1:1, 1:1:1, or 1:1:1:1.",
"With paint, these systems are in place at paint stores. A base white has specific amounts of various tints added to reach the desired color. Frequently using a scant few drops of certain tints to achieve the final color."
] |
[
"https://www.amazon.com.au/Set-Primary-Ecoline-Liquid-Watercolour/dp/B07C5QBS59",
" ",
"https://www.amazon.com.au/Holbein-Artists-Gouache-Primary-Mixing/dp/B001GQ37TI"
] |
[
"They can be mixed. I said \"You would have to mix and dilute the inks before drawing with them. \". Unless you want highly saturated color, of course."
] |
[
"Do I understand correctly that what we call color \"green\" is actually two different things?"
] |
[
false
] |
One is the light with wavelength corresponding to green, and the other one is mixture of wavelengths corresponding to yellow and blue. Then on the other hand, there may be some other colors that if you mix them you get green. Perhaps all those pairs of colors which are equidistant from green on the color spectrum.
|
[
"Colour is entirely a product of perception. You can have a photon of one wavelength, or photons with a mixture of wavelengths, activating the receptors in your eye that lead to the perception of \"green.\" In that sense, the colour green is only one thing."
] |
[
"So you're referring to two different things. Green light is green light, and it spans a well-defined range of wavelengths of light. However, you're talking about combining colors to get green.",
"So the color of the light we see depends on ",
" we combine the colors. If we were to take a blue light and a yellow light and shine them onto the same surface, we'd probably see a white light. This is called ",
"\"additive color.\"",
"If instead we take ",
" instead, we get the more well-known ",
"\"subtractive color\"",
". The mechanism is pretty much what GLaDOSexe describes in another comment: dyes remove (well, absorb) certain colors of light and what we see is what they let reflect back. Therefore, blue and yellow dyes together remove the spectra of light to leave what we see in the range of the \"green\" wavelengths.",
"You should consider reading the Color Physiology section here.",
" "
] |
[
"\"The reason that you see yellow and blue in the first place is because each paint reflects light of those colors. Anything that's blue is absorbing the orange light, and anything yellow is absorbing indigo light. When you mix yellow and blue, they absorb all visible colors except for green\"",
"Just what a quick Google search told me."
] |
[
"What do ants do at night? Sleep?"
] |
[
false
] |
I don't know what is the correct flair to use.
|
[
"Ant colonies are like human cities. And just as human endeavour continues 'round the clock, so does the activity of the humble ant colony. The bulk occurance of human activity however skews sharply towards daylight hours, with only a fraction of the population engaging in e.g. night-shifts, or panicked essay-crisis all-nighters (preach!). Is there a similar circadian skew in ant activity?",
"Well, it partly depends entirely on the species, and partly what they're doing.",
"When it comes to foraging, most ant species forage 24/7. Some species however, many living in hot and/or humid environments (such as ",
", a desert harvester ant), are often more active outside the nest during the cooler hours of evening and night [1]. In contrast, others prefer the day and sometimes indeed even specialise in high temperature activity. Saharan silver ants (",
") make a living primarily snatching other animals that succumb to the high daytime temperatures of the desert. As the early afternoon develops and temperatures approach their height, ant-nomming predators scuttle off to seek shade thereby presenting a short window of opportunity where the proverbial dinner table is open to plunder. Silver ants scoot out at the ant top speed record (~2.2mph, equivalent to you running ~447mph) to grab anything and everything they can before continuously rising temperatures make it too hot (>53°C) for even the ant to handle (check out ",
"this clip from BBC's ",
") [2]. Their whole shtick kinda' reminds me of the ",
"'bio-robots' at Chernobyl",
". Yeesh!",
"Circadian-associated foraging aside, are there any other day/night differences in ant activity? Well, not really. The overwhelming bulk of most ant activity takes place at all times: cleaning, rearing young, tending to the queen etc. As such, ants generally don't have a circadian-associated sleep cycle. Oh, and speaking of sleep, yes, they do! One study demonstrated fire ant (",
") workers cumulatively 'sleep' approximately ~4 hours a day over an average of ~253 microepisodes, each episode just over a minute long [3]. Queen ants 'sleep' almost twice as long (around ~9.4 hours), over ~92 'sleep' batches each ~6 mins long. They do this at fairly regular intervals 24/7, with no skew towards any particular time of day.",
" though some species forage outside at different times, the overwhelming majority of ant activity, particularly inside the colony, takes place 'round the clock. Ants do sleep, but in regular short batches all day/night long.",
"[1] ",
"Hunt, G.L. (1977) Low Preferred Foraging Temperatures and Nocturnal Foraging in a Desert Harvester Ant. ",
". 111 (979), 589-591",
"[2] ",
"Wehner, R., Marsh, A.C. & Wehner, S. (1992) Desert ants on a thermal tightrope. ",
". 357",
"[3] ",
"Cassill, D.L., Brown, S., Swick, D. & Yanev, G. (2009) Polyphasic Wake/Sleep Episodes in the Fire Ant, Solenopsis Invicta. ",
". 22 (4), 313-323"
] |
[
"Thanks this is fascinating."
] |
[
"Do they have a spot where they go to sleep or do they just sort of drop down somewhere and the others crawl over them?"
] |
[
"If going at the speed of sound creates a sonic boom, then hypothetically, if a light source was accelerated to the speed of light, would there be a big \"light wave\"?"
] |
[
false
] | null |
[
"So, we can't answer the question of \"what happens if a light source is traveling at the speed of light\" because things with mass can't travel at the speed of light, and the equations that would answer this question \"blow up\" at the speed of light, but there are two things which are related to this question which you may find interesting. ",
"If an object was heading towards you at a very high speed, the light would blue shift ",
"as it underwent the Doppler Effect",
". So, what that means is whatever frequency of light the light source is emitting, it will be a higher frequency when it comes to you. And depending on the speed, this shift can be dramatic. A light emitting visible light could be blue shifted all the way to gamma radiation, so a \"safe\" light bulb could emit cancer causing radiation if the light bulb was moving towards you fast enough.",
"(On a side note, the more famous version of this is red-shifting- which is what happens when objects are moving away from you. Looking around and seeing that on average galaxies are moving away from us, was the first indication what the universe was expanding)",
"The idea perhaps even more in line with your question is ",
"Cherenkov radiation",
". This is caused when a charged particle (like an electron) travels though a medium faster than the phase velocity of light ",
" (So, there is a speed of light, c, which is the speed of light in a vacuum. However, a light way will propagate through a material slower than c, and some materials that can be significantly slower than c). As the charged particle moves through the material, it polarizes the material- and since an accelerating charge emits radiation, this will cause light to shine. If the particle is traveling slower than the speed of light in that material, then this light source will appear spherical. However, if it is going faster than the speed of light in that material, much like a sonic boom, the emitted light \"builds up\" on the front of the charged particle, much like how sound builds up on the front of a supersonic jet."
] |
[
"While slow-light jocks can do some crazy things in the lab, for most solid and liquid materials it’s 20-50% slower. The ratio of light speed on vacuum to light speed in the material is the ",
"index of refraction"
] |
[
"and some materials that can be significantly slower than c",
"How significant are we talking here? Orders of magnitude?"
] |
[
"If spacetime \"isn't a thing\", but just defined by the distances between events, how can it be curved?"
] |
[
false
] |
This has been bothering me for a while. It comes up a lot that it's incorrect to talk about the "fabric of spacetime", and I've heard it said many times on this forum that space and time aren't actual physical things. If this is the case, then how does it make sense to talk about spacetime being curved? If it's not a real thing, but only exists conceptually when measuring the distances between physical phenomena, then how does it make sense to talk about gravity being the curvature of this thing that "doesn't really exist"? To my simpleton mind it seems like there are two options to describe the situation of two objects coming closer together due to gravity: The objects are directly interacting with one another (with a force as Newton thought). The objects aren't directly interacting but are embedded in some "medium" that is affected by their presence in some way which eventually changes their orientation with respect to one another. But if there is no medium, what is actually being affected by the objects' presence? Please someone help me.
|
[
"there are no absolute measurements of distance and time. There are only measurements relative to some observer. This observer may be moving relative to another observer, or may be near the presence of energy (maybe in the form of mass). The way in which these measurements vary with observer location is ",
" by the mathematics of curved geometries. It doesn't mean that it's a thing to be curved or warped, just how the mathematics of it all works out. "
] |
[
"http://www.reddit.com/r/askscience/comments/itehf/can_someone_explain_the_curvature_of_space_time/",
"Basically, the curvature of spacetime isn't the kind of curvature that things have. It's a specific mathematical kind of curvature, which is just a property of the way that different points in space are connected."
] |
[
"If this is the case, then how does it make sense to talk about spacetime being curved?",
"Geometry, is the answer. It's not really possible to elaborate on that ",
" without equations, which I'm loathe to try to typeset, but suffice to say that curvature is a property of geometry, and we're defining geometry here as the relationship between neighboring points in spacetime.",
"As for your two alternative ideas, they're both legitimate in that they're ideas physicists have studied ",
" in decades and centuries past. It's just that it's known that neither of those descriptions adequately describes ",
" of the various gravitational phenomena we observe. Using either of those conceits you can construct a theory of gravity that works ",
" but if you want to explain ",
" you have to look to general relativity."
] |
[
"Is it negative to expose yourself to bacteria/fungi/etc?"
] |
[
false
] |
[deleted]
|
[
"Most bacteria on fruit is the 'good' kind that won't hurt you. That's not the reason you are supposed to wash them though. You wash them to get the pesticides off. "
] |
[
"I'd say as far as fruit and what not goes, you're OK. An immune boost if nothing else. ",
"As far as meat, however, lots of weird stuff can happen when parasites enter the picture. Read about neurocysticercosis if you want a neat little picture. ",
"Also there is such a thing as an infective dose, which varies from organism to organism (both in terms of invaders and defenders). So you may be introducing yourself to pathogens but simply not enough for them to establish. Your immune cells that are your first line of defense are wiping them out before they can get established, but if you get a large enough dosage, the pathogens would overwhelm the initial response and have a chance to set up shop to where actual damage could be done. ",
"Ultimately I'd say why chance it? I'm not saying be hyper-germophobic or anything but doing simple stuff to reduce your chances of infection, like washing your fruit or waiting until the meat is at least partially cooked to taste it, is never a bad thing. An ounce of prevention and all that good stuff. "
] |
[
"Despite the best efforts of factory farms, not all chicken is a writhing mass of salmonella. You've been lucky enough not have ingested enough.",
"For fruit, I'd be more concerned about pesticide."
] |
[
"If I stood in an empty field away from civilization, would I be able to hear an earthquake?"
] |
[
false
] |
Every video of an earthquake that I've ever watched is shot inside or near buildings/civilization and the accompanying sounds are much like what you'd expect: Glass shattering, people screaming, etc. Would an earthquake make any sound that I could perceive if it happened right below me? What might that sound like?
|
[
"You might. As you've correctly surmised, teasing out what if any sound produced during an earthquake is generated by the seismic waves as opposed to cultural items (i.e. buildings, etc) breaking is difficult. The USGS has a ",
"discussion of reported sounds that occurred along with earthquakes",
". The sound as described is basically a booming noise, not unlike a sonic boom from an aircraft, though it's unclear if it would be as loud as one produced by an airplane. As referenced in the USGS page, some ",
"experiments have been run",
" to try to determine what might be producing the sounds associated with earthquakes. Based on the timing of when they occur, it seems that the p-wave, the first wave to arrive after an earthquake, has the potential to generate a sound. S-waves, though stronger and usually responsible for most of the damage in an earthquake likely vibrate at too slow a frequency to produce a sound audible to humans (this is the explanation offered by those who conducted the experiment)."
] |
[
"You would, provided it's above a certain strength. Depending of what substrate you are on (rock vs mud), you would probably heard anything above 5.5 to 6.0. From previous experience, it sounds like a deep bass rumbling/growling.",
"You might yet still hear peripheral noise from trees falling and/or shaking, or perhaps landslides."
] |
[
"I think the other two posters pretty much covered it, but I wanted to add something that I think about often: since the slowest seismic wave, the Rayleigh wave, travels about ten times faster than the speed of sound, it's pretty much impossible to \"hear\" an earthquake coming. By the time you can hear it, it's here!"
] |
[
"How does the remaining area of a regular polygon with an incircle change as you increase the number of sides?"
] |
[
false
] |
If I have an incircle of an equilateral triangle with radius r there will be a certain amount of area outside of the circle but inside the triangle. If I take the same circle and create a square around it so that it is the incircle of the square there are now four areas outside of the circle that are smaller than the three left in the triangle. Does the remaining area have any relationship with the area of the triangle? Does the relationship continue with polygons of increasing side #?
|
[
"If we are inscribing the circle, which has radius R, then the ",
"apothem",
" of the polygon is R. The ",
"area of a regular n-gon with apothem R",
" is nR",
"tan(pi/n). The area of the circle is pi*R",
". So the area of what is leftover is",
"There isn't, then, any \"nice\" relationships between the areas for different n, aside from the fact that they are all described by this function. Though, the fact that you can approximate the area of a circle using regular polygons is equivalent to the statement that the limit of A(n) at n=infty is 0, which is equivalent to the limit of xtan(pi/x) at x=infty being pi, which is equivalent to the limit of sin(x)/x at x=0 being 1."
] |
[
"Okay then, thanks! So as the equation approaches infinity the remaining area does reach 0, right? Since then you would be ever-approaching a circle."
] |
[
"Yes. You can see the graph ",
"here",
"."
] |
[
"What would happen if you built a bridge around the earth and broke all of the legs simultaneously? would it remain floating?"
] |
[
false
] |
assuming it is evenly distributed so that one part isn't heavier than the other would it just float there since it's being pulled equally from all parts? ignore the viability of building such a bridge, i'm more interested on how the physics aspect works.
|
[
"It's in unstable equilibrium. If a part is tiny bit closer to the Earth, it will be attracted more strongly and will fall. The opposite side, attracted less strongly, will rise."
] |
[
"In an idealized setting, where the bridge and the pull of gravity is perfectly symmetric, it would indeed stay floating. But this state is known as an \"unstable equilibrium\" because the tiniest deviations from symmetry, which always exist in the real world, would cause the bridge to fall in one direction or another.",
"The situation is similar to standing a sheet of paper on one of its edges. If the paper were perfectly flat, it would stay standing, but in reality it always ends up bending and falling to one side or the other."
] |
[
"If done in real life no it would not, or at least not for long.",
"But:",
"Presuming a simplified earth with equal gravity and no other forces such as wind or snow.\nPresuming the bridge type is able to withstand the pressures from \"holding itself up\".",
"Then yes, the bridge would remain \"floating\". "
] |
[
"How do blood clots form?"
] |
[
false
] |
What's the process. What's the material. How it's done.
|
[
"Let's start with what a blood clot is; a blood clot, or Thrombus is a sort of plug or patch that stops bleeding, and it's composed of two things; Platelets, and Fibrin. Platelets a normal component of the blood, along with White Blood cells and Red Blood cells. Like red blood cells, they lack a nucleus; they're more or less cytoplasma fragments. ",
"When you get injured enough to clot, the inner surface of the blood vessel is disrupted, exposing a layer called the collagen; with receptors on the surface of the platelet, the platelets adhere to this layer, and change shape as well as excrete hormones and other chemical messengers. These chemicals activate more platelets, and together the whole thing starts to bind itself together out of platelets. ",
"Once this platelet plug is formed, the next step is the depositing of fibrin onto the clot. Fibrin is a protein, and, as the name implies, is fibrous. It's tough and insoluble, and it gives the clot a lot of strength. ",
"Eventually, the clot is reabsorbed by the body. ",
"This is, of course, a simplification of a biological process that's rather complicated."
] |
[
"I'm a bit sleepy and will give a more detailed answer in the morning but your body has a specific set of steps (a cascade) that it goes through to stop bleeding and start the healing process. Hemophiliacs are deficient in one or more of these steps so the chain is incomplete, and there is a serious risk of death from even a minor cut. On the bright side, quick clot was created by isolating the proteins involved in the clot-forming process, with the main downside that clotting is very exothermic-patients can get serious burns while the quick clot powder takes effect (within your body it is more regulated)\nLinks for hemophilia and quick clot\n",
"http://www.nhlbi.nih.gov/health/health-topics/topics/hemophilia/",
"\n",
"http://www.amazon.com/gp/aw/d/B001BCNTHC?pc_redir=1401018386&robot_redir=1"
] |
[
"The process of blood clotting is triggered whenever flowing blood is exposed to certain substances. There are many different such substances, which are called thrombogenic because they promote formation of thrombus (another name for a clot). Many thrombogenic substances are located in the skin or in blood vessel walls. Normally safely separated from flowing blood, their contact with blood usually means the blood vessel wall is ruptured and bleeding. Examples of these thrombogenic substances are tissue factor, collagen, and von Willebrand factor.",
"Blood clots may also form when blood fails to flow properly. Atrial fibrillation is an abnormal heart rhythm in which blood pools in the heart, potentially forming blood clots. If a blood clot dislodges and travels to the brain, it can cause a stroke. Prolonged immobilization can reduce blood flow in the legs, increasing the risk for blood clots in leg veins (deep venous thrombosis, or DVT)."
] |
[
"How does dehydration cause edema?"
] |
[
false
] |
so, as far as i know, dehydration means lower blood volume, which means lower blood pressure, while edema is mostly caused by high blood pressure in the veins.
|
[
"It’s more rehydrating after being dehydrated that can cause edema than being dehydrated itself. The body tries to pull too much water back into your cells when you take in water after being dehydrated which can result in swelling and, in more serious cases cells bursting."
] |
[
"Edema can be caused by lots of things. Dehydration doesn't cause edema, but it's possible for some other underlying problem to cause both. For example you could have an electrolyte imbalance. ",
"It's also possible for edema to cause a kind of dehydration. If fluid is collecting in your tissues as edema, that means it is leaving your bloodstream, so there's less water available in your bloodstream to support your bodily functions. For example this can happen to burn patients, as their blood vessels are damaged and become \"leaky.\""
] |
[
"Thanks!"
] |
[
"Does the presence of a measurement device alone effect particle behaviour in quantum physics experiments?"
] |
[
false
] |
This question is coming from someone with no understanding of quantum physics other than youtube videos, but say you were to place a camera that was not on in the experiment, how would that affect things, etc.?
|
[
"You might have the idea that \"observation\" somehow collapses quantum wavefunctions. In reality, it's actually interactions with a macroscopic object that cause the wavefunction to become decoherent - essentially to collapse. ",
"So it doesn't matter if the camera is on or off, as long as it's interacting with the quantum system, it'll \"observe\" the state."
] |
[
"IANAQP but my understanding is that if you measure something then you have extracted some energy from that system, in the form of light, electric potential, etc. so that means that the system is different. In the macroscopic environment you can usually get away with some kind of measurement (energy extraction) that doesn't matter. It's not the case in quantum physics."
] |
[
"Let me be very careful, because this is the step that sends people into crackpot-ism more quickly than anything else. We create a fundamentally different path for the light (or whatever) to travel through by putting a detector there. The type of experiment we perform will select what result we get. But this has ",
" to do with our consciousness or \"special observer\" status or any such mystical hokum. We merely have made two different experiments that test for two different things. If there was an asteroid out there somewhere that for whatever reason had two very tiny slits carved into it, light would still interfere through them. And if it also, more implausibly had some crystal grow over one slit and it would act as a which slit detector, the light would cease to interfere in that manner. Because they're just very different systems for the light to pass through."
] |
[
"How does the heat produced in a reaction affect the rate of that reaction?"
] |
[
false
] |
For example, in chemistry, we were discussing reaction constants and my teacher said that the constant only applied at a certain temperature. My friend asked then, how do reactions that feature change in heat over time affect the reaction constant?
|
[
"The formula that relates reaction rate constant with temperature is the ",
"Arrhenius equation",
". As temperature goes up, the rate of reaction increases.",
"Note that this is purely in terms of the rate constants (i.e., kinetics). Temperature can also affect the thermodynamics of the reaction - for example, increasing temperature in an exothermic reaction can shift the equilibrium towards the reactant, such that the reaction is no longer favourable."
] |
[
"Like the other two said, the Arrhenius equation for the rate constant changes with temperature. However, in most real reactions, the change in temperature is also dependent on the rate of reaction, in addition to the heat capacity and heat of reaction, which are also dependent on temperature. So all of these factors come together to really complicate how the reaction gets affected.",
"And this doesn't even take into account exo-/endo- thermic reactions, and whether the reaction temperature is above, at, or below the \"optimal\" temperature for the reaction. Just taking the Arrhenius equation as the sole factor, gives us \"Hotter is faster\", which generally works. But when running an endothermic reaction above the optimum temp, lowering the temp would increase the rate of the reaction. "
] |
[
"oh okay thanks!"
] |
[
"If antimatter and matter destroy eachother on contact, how can lasers be used to suspend antimatter with out it being destroyed?"
] |
[
false
] | null |
[
"Antiparticles can't annihilate with photons, if that's what you're getting at."
] |
[
"A particle can only annihilate with its own antiparticle. And photons are their own antiparticles. So if you're storing anti-atoms in a trap, you can shoot photons at them, and there won't be any annihilation."
] |
[
"Oh neat I thought they could annihilate with any form of matter, interesting to know that it's only there own antiparticle. Thank you"
] |
[
"How does white protective suits, goggles and blue gloves protect you from radiation?"
] |
[
false
] |
I was reading this article when I began to wonder about this question, but I have pondered this previously.
|
[
"It's mostly so you don't touch or breathe the radioactive stuff directly, and so you don't take them home with you later either.",
"Most shirts are enough to stop alpha and beta radiation. Some suits that are lined with dense materials can stop some gamma radiation as well."
] |
[
"Exactly this. While some sorts of radtion (gamma, beta) can easily pass through your suit, it is not a good idea to have things like radioactive dust on your clothes. The suit makes sure that once you take it off, and leave the \"danger zone\" (or whatever), you leave behind any radioactive things that may have attached themselves to you.",
"Alpha radiation however, has such a large interaction cross section, that it won't even make it through your skin or your suit. However, if it gets into your nose/throat/ears/eyes/gonads(for women) (basically any soft tissue that is not protected by your skin) the results are catastrophic. While alpha emitters are a not so scary compared to others in the lab, I would much rather swallow a beta/gamma than an alpha. You'd be dead mighty quick...",
"EDIT: Scratch that...I don't want to swallow ",
" type of emitter"
] |
[
"The terms are actually archaic, but stick with us all the same. Gamma rays are just really high energy photons. Light. Beta rays are electrons or positrons, but generally electrons (usually the positron kind is Beta",
" ). Alpha rays are He",
" nuclei. ",
"Nuclei decay by alpha decay or beta decay to become new, more stable nuclei. But any time a particle has excess energy it may emit a gamma ray. So often times alpha and beta radiation is accompanied by gamma radiation. Furthermore, one of the beta decay processes absorbs an electron from the inner shell of the atom, and an electron from the outer shell may fall in to that gap, and that process also releases a gamma. ",
"Anyways, the stopping is somewhat determined by mass. Alphas, being a helium nucleus, are about 8000 times heavier than betas. They're stopped by pretty much anything. Paper. ",
" an alpha source is dangerous though, since you don't have your skin to protect you from internal radiation. Betas are light. But they're charged, so a reasonable amount of matter will stop them. I have a sweet pair of polycarbonate goggles I got when I worked with a beta source this summer. But they could penetrate your unprotected body. So the full body coverage goes a long way there. Gammas are light. Very high energy light. It can penetrate through a lot of matter, so your protection is to put as much mass between you and the source. That's what lead is used for. It's cheap and has a high density. If you're building a structure, concrete is cheaper, you just need thicker walls.",
"With any nuclear reactor there are going to be a lot of decay products from the fuel, each decaying further by whatever means it finds energetically favorable. So yes, there's going to be a blend of radioactivity. But if you just have a single isotope that only has one step in its decay chain, (as you might in a lab) then you can limit the type of radiation."
] |
[
"Why is it that when I chew gum for a long time, at one time it stops being chewy and elastic and becomes a granular, fibrous lump that's much softer? This transition happens pretty rapidly, in maybe a couple of seconds."
] |
[
false
] |
Anyone else know what I mean? Or do I have messed up oral chemistry? Either way, can anyone explain?
|
[
"I've once read this somewhere and it had to do with components leaving the ",
"Gum-Base",
" just like the favor leaves the gum.",
"\nI don't see how this could happen in a moment, and from my own experience I don't recognize such rapidness in the change."
] |
[
"It could have something to do with the biochemistry of your saliva. Saliva natually contains enzymes that break down whatever we are trying to eat. Gum is one of those things that is extremely tough for our repitoire of enzymes(or even stomach acid) to break down.",
"As far as your case goes, you might just have some enzymes that convert/dissolve the elastic components of gum more quickly than other people. Volume of saliva production could be an important factor as well. ",
"Honestly, there are lots of scientific standpoints that could point to the right answer. Regardless, very interesting question!"
] |
[
"Happens to me too. It becomes less cohesive as well. It becomes very sticky but tends to separate very easily. I've noticed that it seems to be certain brands that will do this as well. For me, the main offender is Juicy Fruit."
] |
[
"How do astronomers determine the radius of the moon?"
] |
[
false
] | null |
[
"From basics, we can determine how far away the Moon is by knowing how big the Earth is and then timing the progress of the Earth's shadow on the Moon during a Lunar eclipse.",
"https://www.universetoday.com/91120/do-it-yourself-guide-to-measuring-the-moons-distance/",
"Since we can measure the Moons apparent size in the sky, once we know how far away it is we can use basic trigonometry to determine it's actual size.",
"Nowadays we can use use lasers to determine the distance to moon very accurately thanks to reflectors left on the Lunar surface as part of the Apollo program."
] |
[
"Lasers, you shoot them at the moon and catch the reflection. Measure the round trip time gives you the height to your spacecraft.",
"Do that often enough to cover the whole surface and the average is your lunar mean diameter."
] |
[
"You can determine it by knowing how far away it is and by how big it looks."
] |
[
"What is the oldest known biological ancestor we have, and do we have a name for it?"
] |
[
false
] |
For example, we know more recent ancestors like Homo Habilis and Homo Erectus, but what's the oldest known ancestor? Something with fins? Some kind of bacteria? Who is our oldest relative?
|
[
"There is the Last Universal Ancestor, which is the organism all extant life evolved and branched from. It was probably bacteria-like. Or are you looking for a more specific answer?"
] |
[
"Check out this website if you want to trace your ancestry (roughly) back to the last universal common ancestor: ",
"http://tolweb.org/tree/"
] |
[
"I'm just taking the best knowledge I have, someone with a better education/knowledge of these things might be able to answer it better.",
"The oldest known ancestor to humans is ",
"Sahelanthropus tchadensis",
", an extinct hominid dated to roughly 7 million years. It is possibly one of the first species to arise after the division of ",
"Chimpanzees and Humans",
" ",
"The skull which they found had structural features different of that found in later hominins. The Sahelanthropus had a flatter face, u-shaped dental arcade, small canines, an anterior foramen magnum, and heavy brow ridges. ",
"Because no postcranial bones have been found (bones located below the skull), we can't determine if it was bipedal (walking on two feet), but we can roughly guess based on the position of the foramen magnum.",
"Sahelanthropus tchadensis is the oldest known ancestor to modern humans",
", but if you wanted to go back further, finding out would be extremely difficult. I personally don't know, (being a high school student), but perhaps other reddit users more advanced in those particular fields can further the details I put forward and add more."
] |
[
"If waves can be disrupted through destructive interference, and light travels in waves... Why can't we disrupt light?"
] |
[
false
] |
I used to work with communications equipment in my last job. One of the things you could do to radio waves was broadcast at the inverse frequency to disrupt the signal. You can do similar things with sound, Wi-Fi etc. But why can't we do this with light? Is it possible?
|
[
"In theory we can, visible light works almost in the same ways as radio waves. In practice it's more tricky, since we would have to precisely match all the frequencies and since they can be quite chaotic from every day sources, it's really hard. But in a lab under controlled settings it's just as with the radio waves, all you need to do is send a light pulse of the same wavelength and 180° off phase. "
] |
[
"I can't think of any direct applications involving of disrupting all light from a source, it's just to much work for blocking out some light. But we can use the interference effect of light for many different things, for example shining laser through a lattice or crystal and by looking at the subsequent interfere pattern we will get information about the crystal structure etc. See for example the double slit experiment to understand the basic concepts and then think that different configurations of the slits would give ut different patterns. "
] |
[
"Well thanks for answerimg my question. Enjoy gold"
] |
[
"Are there any species of biota native to North America that are invasive or destructive in other parts of the world?"
] |
[
false
] |
I live in the Appalachian mountains and kudzu is a real problem in my neck of the woods/world. I was just wondering if any native North American species caused problems elsewhere in the world.
|
[
"Nessie doesn't mention ",
"Muskrats",
", which are a big problem in the Netherlands because they damage our dikes. We spent about 30 million euro each year trying to exterminate them (and failing miserably)."
] |
[
"Bass and American crayfish in Japan. ",
"Here's the full list for Japan:",
"http://www.nies.go.jp/biodiversity/invasive/index_en.html",
"Cane toad in Australia",
"http://en.wikipedia.org/wiki/Cane_toad",
"Grey squirrel in the U.K. ",
"Here's a roundup of 10 species from National Geographic",
"http://www.necis.net/intro-to-invasive-species/what-we-know/ten-invasive-species-that-the-united-states-exported/"
] |
[
"Another example is black cherry in Europe."
] |
[
"How close could a person get to the sun before they burned up completely?"
] |
[
false
] | null |
[
"Without the protection of the Earth's atmosphere, you would burn up right here. This is a big problem on the space station, where ",
"the sun heats the facing side to 250 F (120 C)",
". So the distance to which you can approach the sun is a function of your ability to mitigate the radiation. I know that's not a satisfying answer, but there you go. Soft, squishy human beings aren't build for it."
] |
[
"Yes, I watched this based on recommendation on AskScience too. Some parts are not really accurate, the director took some 'artistic liberties'. Satisfying nonetheless."
] |
[
"Yes, I watched this based on recommendation on AskScience too. Some parts are not really accurate, the director took some 'artistic liberties'. Satisfying nonetheless."
] |
[
"Can long term sleep deprivation cause any permanent damage?"
] |
[
false
] |
[deleted]
|
[
"Is it possible that I've sustained any permanent damage?",
"The more common long-term sequelae of chronic sleep deprivation are hypertension and other cardiovascular issues. Since I'm not a cardiologist, I won't go into more specifics, but the heart is shown to take a lot of stress from not going into rest mode. As for the brain, it's really tough to say as there really isn't a lot of ",
" research in humans with a good sample size that controls well for confounds. We do know that chronic sleep deprivation is associated with cerebrovascular disease (problems with the blood vessels in the brain) and generalized brain atrophy (shrinking), however that's over MANY years and is typically seen more in middle aged persons. We also don't know if sleep deprivation at younger ages, followed by good sleep as an adult, will show these problems or if it's only sleep deprivation in middle age that causes the problems, so it's tough to say. Therefore, without knowing specifics about you (which I don't want to know because then it would be medical advice) I can't say if there's any permanent damage, go talk to your doctor about that.",
"Tl;DR It's possible, yes, though given the demographics of the average redditor, not extremely likely. "
] |
[
"I've been told by a psychologist that a few days without sleep and you start risking psychosis. While that psychosis may not be permanent, it could start a big snowball of problems."
] |
[
"There are the psychological issues as mentioned below. Also, you would be exhausted and, in the long term, risk passing out or collapsing from said exhaustion. There is the possibility of injuring yourself some way there. Mental functions such as the ability to make sound, logical decisions also take a dive when you are sleep deprived, which could also lead to some form of injury, severe or not.",
"tl;dr The sleep deprivation itself is not likely to, but while you are sleep deprived there is a much greater risk of something happening that could permanently damage you."
] |
[
"If there are magnetic field lines are there gravitational field lines also?"
] |
[
false
] |
If there are what is the significance of them and how do field lines relate to the waves in electromagnetic and gravitational fields?
|
[
"Yes. Similar to how magnetic field lines give some indication of which way a dipole will orient at that location and how strongly, and electric field lines indicate the direction of force a positive charge would experience, gravitational field lines indicate the strength of gravitational force a mass would experience at a particular location. ",
"In the case of the Earth, these gravitational field lines would point towards the center of the Earth, and converge(indicating more force) as a mass moves toward the surface.",
"Keep in mind these field lines are just visual depictions of the field. They aren't \"real\" in the way gravity is real, just representations. "
] |
[
"Iron filings act as little magnets themselves, so they tend to repel each other. This effect isn't as strong as that of the main magnet. In this way, the filings line up with the field and separate from each other to create the lines. Gravity, on the other hand, clearly does not produce this effect.",
"Although, as ",
"/u/Pajamawolf",
" noted, magnetic field lines are a visualization of the field, and the actual shape of the field is smooth. You could easily draw gravitational field lines, and they would look like the field lines of a negative point charge.",
"The way electric field lines are drawn is by figuring out what would happen to a tiny positive charge when placed into the field. This is why negative charges have field lines pointing in and positive charges have field lines pointing out. Magnets work similarly. A magnet is a dipole, meaning it has one of each \"charge\". The field lines go out from the \"positive\" end and into the \"negative\" end. (Note that north and south are not positive and negative, but are analogous.)"
] |
[
"You can easily see gravitational field lines in the same sense that you can see magnetic field lines!",
"Simple hold a rock on a piece of string and it will point straight down. That's the gravitational field line!"
] |
[
"So I know about the colors of urine (dark means dehydrated), but what does cloudy mean?"
] |
[
false
] |
My only thought on this is when it happened my previous meal was a bag of pretzels, but this has occurred before in a morning urination. Is it just my body expelling excess salt?
|
[
"Cloudiness is caused by proteins, crystals, or cells in the urine, which are all normal. Cloudy urine isn't pathologic in itself. It also depends on ",
" cloudy it is, which you can't tell by looking at it in the toilet. When we look at it in the lab, there are 4 grades of turbidity: Clear, hazy, cloudy, and turbid. If all the urinalysis tests are normal, the only time we worry about it is if it comes up turbid.",
"TL;DR It's normal."
] |
[
"There are specific grades of cloudiness:",
"This is done with a well mixed specimen, in a clear container that is of a specific size, and is viewed against a white background with text, grid, or a series of lines.",
"The cloudiness is not specifically related to diet. Contamination from the environment can also cause cloudiness. You can't tell what specifically is in your urine without urine testing. Some specimens look ",
" cloudy, but when we mix them they turn out to be pretty clear. I know that's counter-intuitive but it does happen. The same with color. ",
"If you have a persistent change in your \"normal urine\" then yes you should see your doctor. However, if you pee cloudy once in a while, it is generally nothing exciting.",
"They don't pay the nice lab folks at the hospital the amount of money they do if you could. Trust me on that, hospitals hate spending money. "
] |
[
"There are specific grades of cloudiness:",
"This is done with a well mixed specimen, in a clear container that is of a specific size, and is viewed against a white background with text, grid, or a series of lines.",
"The cloudiness is not specifically related to diet. Contamination from the environment can also cause cloudiness. You can't tell what specifically is in your urine without urine testing. Some specimens look ",
" cloudy, but when we mix them they turn out to be pretty clear. I know that's counter-intuitive but it does happen. The same with color. ",
"If you have a persistent change in your \"normal urine\" then yes you should see your doctor. However, if you pee cloudy once in a while, it is generally nothing exciting.",
"They don't pay the nice lab folks at the hospital the amount of money they do if you could. Trust me on that, hospitals hate spending money. "
] |
[
"How is there economies of scale with both diminishing costs and returns?"
] |
[
false
] |
If both marginal costs and returns go down as output increases, how can we have a lower marginal cost per unit of production?
|
[
"Since you haven't yet gotten an answer, I'll respond even though this is outside my main area of study.",
"Economies of scale and diminishing costs happen in different regions of production quantity. For a very simplified model, ",
"see here",
". Increasing output from Q to Q2 causes the average cost to drop, which we call \"Economies of Scale\". Increasing output past Q2 causes the average cost to rise, which we call \"Diminishing Returns\"."
] |
[
"I hope I understand your question properly. But I hope this answers it. I'll try to keep it as simplistic as possible.",
"Marginal cost, aka the cost of producing one more unit decreases with an increase of production. But at the same time the supply of the product increases and causes the price of the units down. This has an effect on the marginal return.",
"The marginal cost (MC) is not affected by the revenue, as the MC is the actual cost occurred for producing one more unit. Basically, the MC is the cost of production, and does not take into account the profit margin of the sold unit. Hence the MC decreases with the scale of the production even though the margin per sold unit decreases due to increased supply.",
"It is important to note, that MC will not decrease indefinitely. This can easily be exemplified as follows: When the production increases beyond the supply of say local resources, the business will need to source resources for a higher cost from say further away which drives up costs. "
] |
[
"Oh, thanks a lot."
] |
[
"Have the effects of hallucinogens on comatose patients been studied?"
] |
[
false
] |
[deleted]
|
[
"Not something that is going to happen. There are numerous restrictions on human testing, and with comatose patients there isn't any way of getting them to sign a waiver after the coma has happened, and even if they did prior to the incident the family could push for power of attorney and put a stop to it."
] |
[
"And yet at the same time the Milgram experiment, as with the Stanford Prison experiment, were incredibly useful in exploring human nature and opened up a whole new world of thinking and are still being discussed as relevent so many years later. Research ethics are absolutely important, and protecting the experimental participants from psychological harm is the ultimate in import. However, the potential for harm must be weighed against the potential for the expansion of human understanding. ",
"I feel very strongly that IRB's have become overly restrictive, especially given the incredibly low rate of development of things such as PTSD as a result of trauma. I haven't seen any follow up studies done on the subject, but it would be very interesting to see how many of the Milgram participants experienced long term psychological harm as a result of the experiment. It well may be that the concern over harm is greatly overestimated and the participants are quite well adjusted later in life. One could even argue knowing their capacity to do harm when blindly following a leader would allow them a type of self actualization and independent nature that few humans ever reach. My point is that, particularly with medical testing, I feel there are times when our desire to protect from potential harm impedes our ability to make breakthroughs in medical science. ",
"Now, I don't think that giving hallucinogens to patients in a vegetative state is a good idea, nor do I see any way in which it would produce positive outcomes, but that isn't the point. Look at the breakthrough that was stumbled upon regarding Ambien and it's ability to restore function in patients following stroke, even those in a persistent vegetative state. The knowledge is there, we have seen it work time after time, but IRB's continually block the proposed research because of informed consent issues. There are many potentially greatly beneficial experiments that have been or will be blocked by IRB's, or even worse never proposed because having your research proposal rejected by iRB can he damaging to a career. Anyway, just having a rant"
] |
[
"Ethics in research is important. Consider the Milgram experiment and then think of how you'd feel if you were convinced to torture a person until they died."
] |
[
"Why don't the bubbles (head) created when pouring a beer dissolve quickly like bubbles produced when pouring pop?"
] |
[
false
] |
If you pour a carbonated drink straight down (Pepsi, let's say), it bubbles up at the top, but these bubbles quickly melt away. A beer's head however dissolves much slower. Why is this? Similarly, when you pour pepsi onto ice cream in a glass when making an ice cream float, the bubbles don't melt away at all, why is this?
|
[
"Beer, unlike soda, contains a melange of proteins from the grains and the yeast. Many of these proteins are amphipathic (i.e. they have sections that are hydrophilic, and sections that are hydrophobic, similar to soap), and, similarly to soap, these proteins help to stabilize gas bubbles. (I hope that someone can elaborate on the mechanism by which this happens, as I can't)"
] |
[
"To add changing the cereals used in the beer will actually change the properties of those bubbles. Beer is, in the simple case, made with partially germinated, roasted barely; adding 10% wheat will actually cause bubble retention. "
] |
[
"Because of the proteins and additives, beer has a much higher surface tension than water or soda. The higher surface tension stabilizes the bubbles in the foam for longer lasting head. A common additive to stabilize head is ",
"aliginate",
".",
"Here's a good explanation of the relationship between surface tension and foam stability:\n",
"http://www.aem.umn.edu/people/faculty/joseph/archive/docs/understandfoams.pdf",
"If you want something a little less in-depth, here's a layman explanation of what's happening in the bubble film:\n",
"http://www.exploratorium.edu/ronh/bubbles/soap.html"
] |
[
"If chips are square why are they produced in circular discs?"
] |
[
false
] |
See this video for an example: it just seems like wasted material to me, but they are engineers so they must have a good reason.
|
[
"Silicon crystals are produced in a process where they are continuously rotated and grow outward radially. It produces ingots like ",
"this",
", which are then sawed into the circular disks. As far as I know there is no process for growing similar quality crystals with a square cross section."
] |
[
"This is indeed correct. Also, the silicon can be reused I believe so it's not like the extra goes to waste. In any case, it is purely because the processes used to make the 'pure' silicon do not produce square results."
] |
[
"When you grow silicon crystals, they are grown on cylindrical pullers known as the Czochralski process. The cylinder is then cut into slices (like pepperoni from a sausage).",
"There are also efficiencies in the lithography tools for using circles rather than squares with edges. Think the way CDs or Vinyl Records are designed."
] |
[
"Why are humans good at dealing with ambiguity as opposed to say, a computer program?"
] |
[
false
] |
I think we could build a program that would understand ambiguity if we were to do something like build a database of every ambiguous statement we could think of, then define all possible meanings, then ask a program to choose the best based on the circumstances. Is that the same way we deal with ambiguity, just on a much more complex basis? Or is there something that makes us able to deal with it that no sort of computer logic will ever be able to match?
|
[
"Ambiguous reasoning can easily be programmed. Look into ",
"fuzzy logic",
". One commonly-used idea is to represent beliefs with probabilities. The field of machine learning, the most popular subfield of AI today, is based around this concept. ",
"As a simple example, every time you use a credit card a program runs that tries to predict if the transaction is fraudulent or not. The program will return a number from 0 to 1, where 1 means it is positive it is fraud and 0 means it's positive it's not. The program is operating on ambiguity when it returns non-0 and non-1 scores, as it will almost always do. "
] |
[
"it just matches what is written. ",
"it does a lot more than that, including deciphering what you ",
" to search for from what you ",
" search for"
] |
[
"I think you're getting into trouble with \"ambiguity.\" If something is ambiguous it has multiple possible meanings, and you need some mechanism for sorting out which meaning(s) are required. To do this you'll need to bring in additional information not specified in the original ambiguous reference (if they told you what meaning they meant, it wouldn't be ambiguous now would it?)",
"Now machines are perfectly good at this, that's what Google and wolfram alpha are doing, but they have two problems:",
"1) Humans have orders of magnitude more information about how the world works. ",
"Some people will disagree with me (",
"Minsky",
" won't). \"Google has scads more data than you! It's read far more books.\" Fine, granted. Google cannot throw a ball, it has no physics engine, and it certainly doesn't have a physics engine as good as mine which I learned via years of interaction with real physical systems (think how many frictional coefficients I've learned!) Google has never flirted with a girl, and lacks my practice at reading tone of voice or body language. Siri can barely understand the words that I'm saying let alone the tone of frustration in my voice. All these things are learnable, it's not that I have magic human juice, it's just that you're comparing my expertise in many broad domains to, say, googles expertise in hyperlink analysis. If the ambiguity cannot be captured by hyperlinks, I'm probably going to do better.",
"2) Humans have multiple algorithms.",
"Most machine learning systems are using a single algorithm to try to capture everything about the world. Sometimes there are more efficient specialized algorithms to capture certain sub-domains. Humans have lots of different brains systems specialized for different sub-domains, so they can do a parallels search for different possible meanings. It's not fair to compare google's algorithm to my brain if, my brain has google and wolfram alpha and google image search etc. etc. "
] |
[
"Is the boundary between X-Ray radiation and Gamma Ray radiation a \"change of phase\" like with liquids and solids?"
] |
[
false
] | null |
[
"No. The electromagnetic spectrum is a continuum - our names for the different parts are just where we happen to place distinctions based on observed phenomena. For instance, \"visible light\" is called that because our eyes are able to respond to it. ",
"X-rays and gamma rays even have different distinctions based on what field you are in. In astronomy, x-rays are any photon than can be focused using a grazing incidence telescope, and gamma rays are those whose energy is too high to focus. In physics, x-rays are photons that originate from motion of electrons or other charged particles, and gamma rays are photons from the decay of unstable nuclei. In this definition, x-rays can actually have much higher energies than gamma rays because we can accelerate electrons to such high speeds."
] |
[
"Historically x-rays emerged from x-ray tubes and gamma rays from radiactive decay and the radiation from the tube had a lower energy.",
"Today this is not generally the case and you can have X-rays (from accelrators) with higher energy than low energy gamme rays. However, both are photons of a certain frequency. The energy distribution of the source might vary quite a bit but the radiation is not qualitatively different ",
"."
] |
[
"No. There is just a continuum of frequencies, and we by convention decide to call electromagnetic waves with certain frequencies ",
" and others ",
" (and still others ",
" and ",
" and so on)."
] |
[
"Have we identified any objects at a fixed point in space that are not moving, relative to the universe?"
] |
[
false
] | null |
[
"Hi Indisputable1 thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"Please flair my query 'Astronomy'. Thanks. "
] |
[
"Please re-read the instructions in the post above for how to add flair.",
"This is a common question. Try searching for something like \"universe stationary\". Unfortunately, because of the high volume, a lot of great questions and answers can get buried quite quickly. The searchbar can be a great way of exploring ",
"/r/askscience",
" and we encourage everyone to use it before posting."
] |
[
"If you become Paraplegic, would it make sense to amputate the limbs you have no feeling?"
] |
[
false
] | null |
[
"Why would you do that? Besides the risk of surgery, what if a repair treatment or assistive device is developed why would enable use of those limbs?"
] |
[
"Aside from a medical reason would it be reasonable to remove unusable legs for example, if it offered increased mobility by way of weight reduction? The ballpark estimate seems to be roughly a third of body mass is the legs, so could that be an advantage to the person not having to carry that weight in/out of wheelchairs, vehicles, etc... Or do they serve a purpose such as helping with seated balance or play an integral role in blood flow? This assumes the person has emotionally accepted removing the legs of course.",
"If the weight reduction and lack of risk of clots/bedsores etc... could be seen as benefits, would they even come close to balancing out the risk of surgery? I've never heard of this choice being made but I have had the same thought as the OP asked."
] |
[
"Many paraplegics or quadraplegics retain at least some feeling in their legs, and amputating them, as mingy pointed out, completely removes the chance we can develop treatments for spinal cord injury in future.",
"The blood clot issues are not severe in healthy indivudals, and can be relatively simply combated if necessary. There's also a fair bit more stigma going around without legs than with non-functional legs, since we're sticking with that. They also can retain some feeling in their legs, it's not so simple as \"they don't move so you can't feel them at all.\" Referred movements and balance etc can still, to a degree be achieved, depending on the individual.",
"It makes some sense that weight reduction could make life in a chair simpler, but it really won't. How high up the leg do you cut? If you leave the stump too high, they're going to get compression sores on it from the chair, not to mention it's still a risky majory vascular surgery. Afterall, the femur is the largest bone in the body.",
"More amputees every year are finding ways to be active, and build that upper body strength, and while I by no means work with a great deal, I've yet to hear of one who'd rather not have their legs than have them. Just because men have erectile dysfunction doesn't mean they want the penis removed just to make pants fit better, after all. It seems counterintuitive or ridiculous to state that, but really, we could easily leave a functional stoma for the bladder, it's not a dissimiliar proposition."
] |
[
"How can (relatively) slow evolving human immune systems keep up with very fast evolving bacteria?"
] |
[
false
] |
If the generation length ratio of bacteria to humans is something like 20 minutes:20 years, why can't bacteria just outrun the immune system recognition mechanisms, or destruction mechanisms?
|
[
"There are two reasons for this, related to the innate and adaptive immune system.",
"First of all, the innate immune system has, throughout evolution, been tailored to recognise invariant structures on the surface of bacteria. The reason these structures are invariant is because they are essential to the bacteria's survival, e.g. certain peptidoglycans. This means bacteria can be recognised on the basis of their defining characteristics. However, not all the bacterium's characteristics are predefined, and some bacteria can camouflage these invariant ones, which brings us to our next point.",
"The second reason has to do with that our immune system is not pre-defined, and goes down deeper than our \"standard\" genome. B- and T-cells are able to randomly combine certain pieces of DNA in our genome, in a process known as VDJ recombination. This essentially yields a \"randomised\" gene, which codes for an equally random protein. These proteins essentially recognise every possible structure that there is to be found. To prevent our immune system from attacking structures in our own body, there is a round of selection that kills cells that recognise those endogenous structures. This way, 'foreign' structures (i.e., whatever isn't supposed to be there) are recognised for elimination from the human body.",
"You might wonder, how come we don't instantly fight off any infection then? The answer is simple; because usually, only one or very few cells exist that recognise the structure present on the bacterium/virus. When an infection is detected, these cells are stimulated to divide and proliferate, a process which obviously takes time. ",
"Hence, while bacteria may evolve quickly during a few generations, we can adapt quickly ",
" a generation.",
"Obviously this is a boiled down version of the truth, and there are many more intricacies which finetune our immune response to a given pathogen. But this should give you an idea of an answer to your question. Feel free to ask on though!",
"Edit: clarity and some more info",
"Edit 2: spelling."
] |
[
"It always amuses me that the tl;dr of immunology is basically brute forcing antigen recognition. "
] |
[
"It's not brute forcing at all! It's totally spray and pray. We don't know what the enemy is going to look like next? Let's make antibodies for ALL THEM BITCHES POSSIBLE. Then when we find one that matches, we's gonna make a clone army! "
] |
[
"As space is a vacuum and laden with radiation bombardment, would a body on the moon decay, or last \"for ever\"?"
] |
[
false
] |
I mean, on a rather atmosphere-less body such as the moon or an asteroid, would they essentially be there for eternity (in regards to human timescale). I assume eventually they would freeze and break up due to either, a lot of little collisions over time, or a (few) big collision(s)... but would any anaerobic bacteria be able to decompose it at all?
|
[
"Aerobic bacteria still require air, they just don't require oxygen. In space, you would decay not from rotting but desiccation coupled with extreme temperature shifts. You'd dry out complete, and your remains would be in an environment that shifted between extremely hot and extremely cold. By extremely, I mean extremely, super duper hot and cold. In space you're exposed to ",
" sunlight, so all of the energy that's normally refracted through the atmosphere hits you directly, leading to temperatures in excess of 250 degrees F (120C) and as low as -380F and -230C! "
] |
[
"Ah thank you. I forgot about the intense temperature shifts. I guess in my mind I was imagining the body was positioned in such a place say, as the northern or southern pole craters on the moon. The ones that have recently been found to hold a LOT of frozen water (as they never get sun light).",
"In the aforementioned circumstance, is the timeline relatively fast where desiccation would make the body brittle enough to... \"evaporate\" or something?"
] |
[
"Desecration happens regardless of exposure to sunlight. The lack of atmosphere is so... Vacuume-y that the liquid sucks right out of your body and.... Disperses into the lack of atmosphere. "
] |
[
"mirror puzzle"
] |
[
false
] |
Why is it that when you look into a mirror, right and left appear interchanged, but up and down do not?
|
[
"Feynman explains: ",
"http://www.youtube.com/watch?v=msN87y-iEx0"
] |
[
"Mirrors really reflect ",
". You looking in the mirror is the same as looking at another person who is facing you; their right hand is opposite your left hand (and their left hand is opposite your right hand), but your head is opposite their head (and your feet are opposite their feet)."
] |
[
"You looking in the mirror is the same as looking at another person who is facing you;",
"Not quite. Looking in the mirror is the same as looking at another person who is facing away from you, but has been \"turned inside-out\" (or frontside-back, to be more accurate).",
"their right hand is opposite your left hand",
"Their left had is opposite your left hand. The hand is just \"inverted\", which makes it resemble a right hand.",
"The reason that left and right appear to be reversed is because we have no concept of flipping \"frontside-back\". When you look in the reflection in the mirror, you intuitively think of how you could rotate (instead of the appropriate motion of \"inverting\") yourself to match their position and, since humans are bilaterally-symmetrical, the only possibility is to turn 180 degrees on the vertical axis. Thus left and right appear to be reversed.",
"Some hypothetical creature who is symmetrical on the horizontal axis would see mirrors as flipping top and bottom."
] |
[
"Prompted by the question about stars on the front page today, I'm wondering, is it possible for there to be a solar system with only planets? I.e., all planets in the system orbit around a much larger planet at the center?"
] |
[
false
] | null |
[
"It's possible, but it does depend on what you mean by \"planet\" for the thing in the center. If a star forms with less than about 80 times the mass of Jupiter, it won't have enough pressure to ignite the fusion of hydrogen to helium in its core. This fusion is the source of almost all of the light emitted by stars like our Sun. These \"failed stars\" are called ",
".",
"Brown dwarfs can be found on their own, as companions orbiting larger stars, or even as the central object ",
"surrounded by planets",
". Whether a brown dwarf is a star, a planet, or another category of thing altogether is a matter of definition on which people disagree, and it's pretty central to your question.",
"For some people, a brown dwarf below 13 Jupiter masses - the threshold below which it can't burn deuterium - is a planet, so if planets form around such a light brown dwarf (and there's nothing wrong with this in principle), that'd be a positive answer to your question. But other people say the difference between a star and a planet is based not on mass but on formation - that stars form from the collapse of a cloud of gas, while planets are what form from the disks of matter that surround those newborn stars - and so if a brown dwarf forms the way a star did, it's not a planet. With that definition, of course, it's much harder to have a planet at the center of a system, because presumably it would have formed the way stars do."
] |
[
"Wouldn't that make the planets in the OPs question moons?"
] |
[
"They're moons because they orbit a planet."
] |
[
"Why do we prefer muscles for vaccine injection?"
] |
[
false
] | null |
[
"Firstly, intramuscular and subcutaneous injections are not only easier on the patient but also on the trained professional. They're easier to administer and patients are often frightened of intravenous injections.",
"Secondly, antigen-presenting cells (e.g., dendritic cells) aren't just present in blood but are largely found in tissue as well. They take up the antigen and process it for presentation to lymphocytes in lymph nodes. So, the vaccine doesn't necessarily have to enter systemic circulation and distribute throughout the body to be able to be picked up by antigen-presenting cells for developing an adaptive immune response.",
"Thirdly, an intravenous bolus is administered virtually instantaneously into the blood, whereas intramuscular/subcutaneous routes can form a slow-releasing 'depot', which in-turn minimizes adverse events. A recent example is the Pfizer vaccine. A study conducted on mice found that, when injected intravenously, rapid onset myopericarditis was observed unlike the intramuscular route (",
"source",
"). This is because an intravenous bolus is administered rapidly into circulation, where it distributes throughout the body and triggers an inflammatory response, ",
" in the heart. An intramuscular depot is more localized and slow-releasing, in contrast. Another study found that intravenous typhoid vaccine is associated with cardiomegaly (enlarged heart). ",
"source"
] |
[
"The muscles and/or subcutaneous fat can act as an easy \"deposition\" site for the injection. There is a lot of room to accept the injection bolus. Also, as opposed to direct injection into the blood stream, the immune reaction can be slower, more tempered, and cause fewer adverse reactions. Thirdly, it's easier to administer and causes less pain."
] |
[
"To top off what everyone else has written The intramuscular route optimises the immunogenicity of the vaccine and minimises adverse reactions at the injection site. ",
"Injecting a vaccine into the layer of subcutaneous fat, where poor vascularity may result in slow mobilisation and processing of antigen, is a cause of vaccine failure. Compared with intramuscular administration, subcutaneous injection of hepatitis B vaccine for example leads to significantly lower seroconversion rates and more rapid decay of antibody response.",
"Traditionally the buttocks were thought to be an appropriate site for vaccination, but the layers of fat do not contain the appropriate cells that are necessary to initiate the immune response (phagocytic or antigen-presenting cells). The antigen may also take longer to reach the circulation after being deposited in fat, leading to a delay in processing by macrophages and eventually presentation to the T and B cells that are involved in the immune response. In addition, antigens may be denatured by enzymes if they remain in fat for hours or days. ",
"Serious reactions to intramuscular injections are rarer than in subcutaneous fat. Muscle is probably spared the harmful effects of substances injected into it because of its abundant blood supply. Adipose tissue, having much poorer drainage channels, retains injected material for much longer and is therefore also more susceptible to its adverse effects. In the case of vaccines in which the antigen is adsorbed to an aluminium salt adjuvant—such as those for hepatitis A, hepatitis B, and diphtheria, tetanus, and pertussis vaccines—the intramuscular route is strongly preferred because superficial administration leads to an increased incidence of local reactions such as irritation, inflammation, granuloma formation, and necrosis"
] |
[
"If light moves at the same speed in all inertial reference frames, why does it get red/blue-shifted when you get closer to light speed?"
] |
[
false
] |
I was playing around with and , and both included redshift. If light always moves at c relative to you, wouldn't the color stay the same?
|
[
"The redshift/blueshift is a result of the perceived frequency of the light wave changing when switching inertial frames. How do you measure frequency? You count a certain number N of cycles of the wave and divide by the time T over which you observed those cycles.",
"Okay, now suppose an inertial observer is traveling away from at some speed and emitting photons. What does he see the frequency as? He measures it to be N/T, and he measures the time T with a clock in his own frame. What happens if you observe the same N cycles? You measure those same N cycles as coming over a time S. Now since the emitter is moving away from you, S is larger than T just from considerations related to the classical Doppler effect. But, as you know, time also gets dilated, so that ",
" time T measured in the frame of the emitter is necessarily longer in your frame. These effects combine. The main effect is ",
". So you think the frequency is N/S, which is smaller than N/T. The frequency has decreased; the light wave is redshifted.",
"So redshift/blueshift is ultimately a byproduct of time dilation. (A better way to understand it is actually to view the energy and momentum of the photon as components of a so-called ",
". When switching inertial frames, this momentum vector transforms just like the position 4-vector. Whereas we get time dilation for the position 4-vector, we get an analogous result for the momentum vector, which also mixes the components in such a way to cause the frequency to change.)"
] |
[
"Smart people,tell me if I'm right.",
"It's called The Doppler effect.Say you're moving to an object at a very fast speed,the wavelengths will compress,making the object appear more red.",
"The inverse is true,when you move away from an object at a very fast speed,the wavelengths will stretch,making the object appear blue-er.",
"This is how scientist determine if solar bodies are moving away from us,or towards us.",
"And keep in mind,you will either have to be 1.Travelling extremely fast or\n2.The object you're moving away from/towards is relatively large (in astrological scale)"
] |
[
"Imagine that you're in a spaceship and traveling at half the speed of light (0.5c)",
"If you were to fire an object backwards at three quarters light speed and then look behind you, you'd see that object moving away from you at 0.75c. That's your relative velocity.",
"But an outside observer would see the object moving at only 0.25c because the object was slowed by your high initial velocity in the other direction.",
"Light doesn't work that way. Light always moves at the speed of light even if it's being emitted by a moving object.",
"If you were instead shooting a laser beam backwards from your half light speed ship the laser beam would be shooting backwards at 1c, even though your ship is moving. Because of this movement, the wavelength of the light becomes 'stretched'.",
"It's called the Doppler effect, and we can see it in everyday life when dealing with sound. Sound is similar to light in that it will move at a constant speed regardless of the speed of the object emitting it. ",
"Here's an animation of sound waves coming from a moving car.",
" You can see that even though the wavelength of the sound waves as they're being emitted doesn't change, because of the car's movement, the waves in front are compressed closer together while those behind are stretched farther apart.",
"With sounds, shorter wavelength means higher pitch. While longer wavelength means lower pitch. Watch ",
"any video of a train passing by",
" to see (or rather, hear) this in effect in action. As the train approaches the whistle is higher pitched, and once it passes the pitch immediately drops.",
"The whistle didn't actually change. It's just that since the source of the sound changed from moving towards the observer to moving away the doppler effect changed from compressing the sound waves to stretching them.",
"Light works the same way, but with color. An object moving towards an observer has the wavelength of light it emits compressed, and so that light will become more blue. And an object moving away has wavelength stretched and so it becomes more red."
] |
[
"If I bury my dog in just a burlap sack, why doesn't the ground sink in six months later, after she has decomposed?"
] |
[
false
] |
[deleted]
|
[
"It does, if the body is big enough. Google \"grave site ground settling\" for some info."
] |
[
"Because they would decompose and become the soil, no?"
] |
[
"because as the body decomposes and as invasive organisms digest it, their waste takes the place of the displaced soil. "
] |
[
"Can you explain me \"hyperbolic trigonometric functions\" and how can they be of use?"
] |
[
false
] | null |
[
"For example, the formula for the ",
"composition of velocities",
" in special relativity :",
"s = (u+v)/(1+(uv/c",
")",
"can be understood as a hyperbolic trigonometric ",
"identity",
" :",
"tanh(a+b)=(tanh(a)+tanh(b))/(1+tanh(a)tanh(b))"
] |
[
"Hyperbolic trig functions are very much an analogue of the 'traditional' trig functions. If we look at the definition of the 2 normal trig functions:\n cos(x) = (e",
" + e",
")/2\n sin(x) = (e",
" - e",
")/2i, \nwhere i is a solution of y",
" + 1 = 0.\nWe can compare these to the hyperbolic trig functions:\n cosh(x) = (e",
" + e",
" )/2\n sinh(x) = (e",
" - e",
" )/2\nSo the hyperbolics seem like a 'non-complex number' form of the standard trig functions. This makes sense in practice. One of the main uses of trig functions is of solutions to differential equations; the equation x'' + x = 0 (that of simple harmonic motion, SHM) has as its solutions Acos(x) + Bsin(x), with A,B constants. We expect the graph of a particle undergoing SHM to be look like a wave; sin and cos do also, so the solutions kind of make sense.\nIf we look at the corresponding equation x'' - x = 0, this has solutions Ce",
" + De",
" with C,D constants. But we can rewrite this as C'cosh(x) + D'sinh(x), so we see immediately there is some symmetry going on in the answers to the two equations.\nExponentials crop up a lot as solutions to differential equations; it's very useful having a shorthand of cosh and sinh to rewrite them, as there are loads of easy-to-remember manipulation rules for hyperbolic trig functions, which saves a lot of time compared to just dealing with the exponentials."
] |
[
"Beyond looking at Euler's identity and solutions of ODEs there's other properties that the hyperbolic trigonometric functions have with the trigonometric functions.",
"Sinh is odd like sine (sinh(-x) = (e",
" - e",
" )/2 = -(e",
" - e",
" )/2 = -sinh(x)",
"And cosh is even like cosine (cosh(-x)=cosh(x) )",
"This is related, but the Taylor expansion of sinh and cosh around zero contain odd and even powers of x respectively, like sine and cosine. Which tells you that very close to zero sinh(x) ~ x and cosh(x) ~ 1",
"You can define a function tanh(x) = sinh(x)/cosh(x) , the function is bounded on the real numbers and tanh(x)~x very close to 0. This makes it easy to analyze it's behaviour as x->0 and x->infinity, which makes it nice for physical applications where usually you want certain physical properties to be bounded and you want 'nice' asymptotic behaviour to make analysis generally easier (at least when you're doing initial tests of a model). IIRC some simplified water wave models the phase speed of the wave end up being a hyperbolic tangent function.",
"Notice that as tan(x) is actually unbounded on finite intervals the tangent and hyperbolic tangent are quite different in this respect. Also hyperbolic sine and cosine are unbounded as x->+/-infinity where as sine and cosine are bounded."
] |
[
"Why is a long chain hydrocarbon from crude oil less useful than a polymer thousands of carbons long?"
] |
[
false
] |
[deleted]
|
[
"long chain polymers, when manufactured, tend to have known structures and can be made in batches where those structures are relatively consistent.",
"long chain hydrocarbons are just single molecules that are long chains. Unlike polymers, they're not made up from a single small repeating unit, and when pulled from fossil fuels, are often a horrible mix of who-knows-what.",
"If you could pull straight octane or straight dodecane or whatever from the ground, I don't think we'd bother cracking fossil fuels. However, what you get from the ground is a random mix, and thus there aren't too many (chemical) uses for a material that is composed of millions of different molecules."
] |
[
"Not all polymers are made from a single repeat unit, many have 2 or 3 monomers to make up the chain, allowing for very specific design of the polymer made. ",
"Also, on top of this, we can funtionalise the polymer chain to be better at the desired task, such as making it have lots of trifluoro-methane end units to make it very hydrophobic etc.",
"And you can to an extent get octane/dodecane from the crude with a fractional distillation. It will give some other fractions with similar boiling points, but can be easier and more efficient that cracking and resynthesising the desired product."
] |
[
"What's so useful about the heaviest fractions (longest chains) in crude oil? It's asphalt, not plastic."
] |
[
"Needing input on how to make this better/more accessible to people with little experience with Science."
] |
[
false
] | null |
[
"to be honest, It runs long. It's a little repetitious. I would try to trim about... 1 quarter to a third of the runtime out. Start with your conclusion. Then justify it. This is the best approach to public presentation I find. People get bogged down in detail and by the time you get to the conclusion, they're bored or tired.",
"Science is ___. Cat example (which was good, esp. the unnecessary data). evidence stuff. ",
"Another thing that is super useful the line between data points is much closer to scientific \"law\" and the big picture is much closer to \"theory\" than the public generally believes. Laws are simplified relationships between small amounts of data. Theories are ensembles of data that create a larger story.",
"Finally, Skip the religious stuff. I agree with you completely, but it ",
" turn off viewers. Leave it implied with \"no individual or organization\"",
"edit: ignore the runtime arguments. I think if you rearranged the discussion and had a little bit more focus on the \"what is science\" aspect, it would improve the pacing."
] |
[
"Obviously there are spelling errors in a couple of places which need fixing, but anything else that could be done to make this more appealing or interesting?"
] |
[
"Looks good! I think the one thing I'd do is add a little bit about how the rules also allow experts in different fields to trust information and work on their own area of expertise (Eg. if neuroscientists had different rules of proof to psychologists they couldn't use each other's work). "
] |
[
"Is \"String Theory\" even a theory? Should it better be called \"String Philosophy\"?"
] |
[
false
] |
This is not trolling, but a serious question. Does it have any experimental predictions that can be used to verify / falsify it? My understanding is that with the landscape scenario there are at least 10 possible vacua (initial conditions) for potential universes and the anthropic principle is used to explain ours. Is this really a physical theory, or more a philosophical theory since it doesn't appear testable?
|
[
"It's absolutely a theory. ",
"It's not impossible to test ",
". It's just impossible with our current technology. ",
"It would be testable directly if we could build a particle accelerator about 10",
" times more powerful than the LHC. Such an accelerator would have to be about the size of the galaxy.",
"It could also probably be tested directly if we could do experiments near the event horizon of a black hole.",
"Even though we're not going to be able to do those experiments any time soon, there's evidence that we may be able to observe one aspect of string theory, known as the AdS/CFT correspondence, at very ",
" energies. This theory may be able to explain phenomena such as high temperature superconductivity.",
"The landscape problem (the issue of having so many possible vacua) is a problem because we don't have a method of matching a vacuum at high energy to it's low energy limit. If such a method is found, then we would very likely be able to make predictions that would be testable at much lower energies. ",
"String theory is a very rigorous and well developed ",
" theory. The big question is, \"is it a theory that describes ",
" Universe?\"",
"So yes, string theory is much more than a simple \"philosophy.\""
] |
[
"String theory would be better described as a general mathematical approach. One can talk about a string theory in the sense that one can talk about a quantum field theory, and in my limited understanding a string theory is somewhat of a natural generalization of a quantum field theory.",
"You could make the same criticism of quantum field theory, as one could set up countless field theories with multiple symmetries and interactions, but in the case of QFT we currently have the standard model, which for all of its warts describes all current data very well.",
"String theory is also on very solid mathematical footing and several results of interest to the mathematical community have developed from it. If history is any guide, all interesting mathematics eventually finds an application, and so I would be shocked if nobody ever finds systems that could not at least be effectively described by string theory in approximation. ",
"Currently there are a great many theories floating around as everyone knows that the standard model must disintegrate at very high energies, and yet there have been no experimental signals to date that would allow theorists to differentiate between models. Hopefully the LHC will collect enough terascale data by 2014 to merit an observation of new physics.",
"From my experimental perspective, the string theory 'debate' is little more than typical quibbling between theorists over whose approach will eventually win out and why. In the end, the data will decide what approaches are best. The only difference between this debate and previous ones is that the current theoretical squabbles are sometimes taking place on internet blogs, with the resulting emotions, flamewars, trolling, etc. The end result of this is that to an outside observer the physics community might appear to be in crisis, while in reality 99% of the participants are too busy tweaking their experiments and developing mathematical tools to care about the blogs."
] |
[
"Pretty much any collider can get particles moving so fast that the difference between them is negligible if you just compare speeds alone, as they can only asymptotically approach the speed of light.",
"There is no limit on the amount of ",
" a particle could have though, and this is the critical number for the power of an accelerator."
] |
[
"\"earth/ground\" node in electrical circuits, how does it work?"
] |
[
false
] |
I can’t get my head around earth/ground in electrical circuits, from what I understand the Earth itself is a reservoir of free electrons and it was used as a return pathway in single phase power transmission systems back in the days, but how? And from where these electrons come from? The earth consists of rocks and dirt which they have a very high resistance to the flow of electrons, how can it be treated as a current carrier? The “ground node” as we refer to it is just a metallic rod/mesh buried in the ground
|
[
"\"Reservoir of free electrons\" is probably a misnomer. Circuits are based on electrons flowing, not free charges. Separated charges are extremely uncommon.",
"You are also correct that the ground is resistive: typically 10 - 1000 ohm*m, compared with 10",
" ohm-meters that is typical for metals.",
"However, it isn't a total insulator. The ground is big, so the ",
"cross sectional area",
" is typically big, and it is significantly more conductive than the common insulators, like rubber (10",
" ohms) or glass (10",
" ohms). In fact, the earth is about as conductive as undoped silicon (~10 ohm-m). Which isn't actually ",
"a coincidence",
".",
"On the upside, the ground is super big - approximately earth-sized, in fact. The ground can conduct electrons just like any other circuit element, it just happens to be a bit bulkier than most circuit components. Plus, no one really cares if you accidentally melt the ground (unless you managed to melt a whole lot of it, I guess).",
"As for why it is an easy source for electrons - the earth has a lot of capacitance. Because it is big. There is a limit to how quickly you can push charge in or out of the earth because it is so resistive, but pushing some current into it is unlikely to change the earth's average voltage by much. ",
"You can easily substitute for the earth with a really, really big capacitor. That is what mobile devices typically do. But big capacitors are expensive and heavy, so using cheats (like using the planet) can be effective cost-saving solutions."
] |
[
"I'm not perfectly certain, to be honest. It takes at least ",
"20 ms",
" for any electrical signal to propagate through the earth, so in many situations where you need a large ground, including radio waves, lightning strikes, and power surges, you can't treat the earth as a static component - it will take a while for the entire earth to come to equilibrium with your circuit.",
"Furthermore, the earth's soil is not actually isolated because it interacts with stuff like the oceans, the atmosphere, and the mantle. These are all much bigger than anything we humans do, so it is difficult to say how far a human-generated signal really travels. Looking at some papers I could find, like ",
"this one",
", it looks like any human-generated EM wave dies out pretty quickly (within a few miles). That is still far enough that we can use ",
"ground penetrating radar",
" to study soil and water deposits.",
"So the best answer I can give you is that the earth probably is earth-sized (in the sense that the earth is completely connected) but anything you do to the earth electrically is too small to notice from far away (the same way jumping on the earth doesn't really shake the whole planet).",
"Most of the time it doesn't matter because for just about any practical purpose the earth may as well be infinite."
] |
[
"Circuit ground is a ",
" convenient approximation, much like the old joke about modeling a cow like a sphere or cylinder for heat transfer analysis. The reality is that there isn't any such thing as zero potential. Voltage is a statement about the difference in electric potential between different places, equal to the path integral of the electric field along a path between the places being considered. Labeling a particular node on a circuit diagram as \"ground\" establishes a global reference for all potentials to be measured relative to.",
"Buildings have a safety ground network that is intended to keep all bare metal conductors at the same potential. This includes pipes, steel beams, structural cable, server cabinet parts, etc. That network is bonded to earth in exactly once place with a no-kidding copper rod sunk into the dirt. Thus, for that building, ground is the potential of the dirt at the location of that copper rod. The ground potential of one building is not necessarily equal to the ground at another building - current flow through the dirt between them does produce a voltage between them (say, due to a nearby lightning strike).",
"A key feature of the building's safety ground network is that it is ",
" used as the normal return path for electric loads. Instead, the neutral wires of AC power systems are bonded to that ground network at exactly one place, near the source transformer for that power system. So, sometimes you'll see the neutral wire referred to as the \"return\" wire, even though it nominally has the same potential as the ground network. The reason is that the neutral wire (and the ground network!) have impedance. Return current through one portion of the network really does change the local voltage of that wire with respect to other paths that don't have current flowing through them. In fact, the neutral wire is insulated just like any of the hot wires. Usually, this difference doesn't matter. But consider the case where the building's (complex) ground network is used as the return instead. Now different pieces of exposed bare metal have a different potential to each other, based on their relative impedance. During extreme transients like short circuits, that potential can be fatal."
] |
[
"Do arterial blockages get diagnosed regularly before symptoms?"
] |
[
false
] |
I realise it’s probably a selection bias at play but I seem to regularly hear stories where someone who was otherwise healthy and led a healthy lifestyle dropping dead from a heart attack with no prior symptoms. Are there non Invasive diagnostic tools available that can pick up any issues with a regular GP check up or do you generally just go to hospital after you have symptoms?
|
[
"Exercise stress testing or cardiac CT angiogram can be used as screening tools to help prevent a potential myocardial infarction. Echocardiograms can evaluate for valvular heart disease. \nRisk factor modifications controlling BP, diet exercise, keeping cholesterol in check are preventative medicine strategies to minimize cardiac issues."
] |
[
"We don't do exercise stress testing or CT scans on asymptomatic people to prevent MI. The obstruction has to be pretty advanced anyway for exercise stress testing to show restricted flow."
] |
[
"No. There are different types of arterial blockages but I'll talk about 3 common ones: coronary artery disease, carotid artery disease, and peripheral arterial disease.",
"For coronary artery disease, this is when there is atherosclerotic blockage in your coronary arteries, or the arteries that directly supply your heart muscle. Your heart is a very active muscle/pump and therefore needs a constant blood supply. Without adequate blood, the muscle starts to die = myocardial infarction = heart attack. This happens when your arteries are very clogged. To diagnose it, we do coronary catheterization, which can also be therapeutic. In milder cases, deploying a stent will relieve the obstruction. In more severe cases (there are defined criteria), the patient will require a CABG to bypass the obstruction. Since coronary catheterizations are invasive, we generally don't do it for asymptomatic people. Now, there is newer technology using CT scans to image the coronaries but to my knowledge, that is also not used on a large scale to diagnose asymptomatic people. ",
"For carotid artery disease, we typically don't catch those until they become symptomatic, at which point the obstruction is causing problems. In other words, we don't screen for this. Once it's symptomatic, treatment depends on the degree of obstruction and patient-specific risk factors but can include endarterectomy. ",
"For peripheral arterial disease, this is one that gets diagnosed when patients develop claudication symptoms in the lower extremities. Usually an ABI is done at that point where the systolic BP is measured at the ankle and at the arm and the ratio between the two is determined. That is diagnostic of PAD. We don't routinely do this for asymptomatic people because it would likely be normal until the obstruction is pretty advanced."
] |
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